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1.  A Prevalent Variant in PPP1R3A Impairs Glycogen Synthesis and Reduces Muscle Glycogen Content in Humans and Mice 
PLoS Medicine  2008;5(1):e27.
Background
Stored glycogen is an important source of energy for skeletal muscle. Human genetic disorders primarily affecting skeletal muscle glycogen turnover are well-recognised, but rare. We previously reported that a frameshift/premature stop mutation in PPP1R3A, the gene encoding RGL, a key regulator of muscle glycogen metabolism, was present in 1.36% of participants from a population of white individuals in the UK. However, the functional implications of the mutation were not known. The objective of this study was to characterise the molecular and physiological consequences of this genetic variant.
Methods and Findings
In this study we found a similar prevalence of the variant in an independent UK white population of 744 participants (1.46%) and, using in vivo 13C magnetic resonance spectroscopy studies, demonstrate that human carriers (n = 6) of the variant have low basal (65% lower, p = 0.002) and postprandial muscle glycogen levels. Mice engineered to express the equivalent mutation had similarly decreased muscle glycogen levels (40% lower in heterozygous knock-in mice, p < 0.05). In muscle tissue from these mice, failure of the truncated mutant to bind glycogen and colocalize with glycogen synthase (GS) decreased GS and increased glycogen phosphorylase activity states, which account for the decreased glycogen content.
Conclusions
Thus, PPP1R3A C1984ΔAG (stop codon 668) is, to our knowledge, the first prevalent mutation described that directly impairs glycogen synthesis and decreases glycogen levels in human skeletal muscle. The fact that it is present in ∼1 in 70 UK whites increases the potential biomedical relevance of these observations.
Stephen O'Rahilly and colleagues describe the effect of a mutation inPPP1R3A, present in 1.36% of participants from one UK population, that directly impairs glycogen synthesis and decreases glycogen levels in human skeletal muscle.
Editors' Summary
Background.
The human body gets the energy it needs for day-to-day living from food in a process called metabolism. However, not all the energy released by metabolism is used immediately. Some is stored in skeletal muscles as glycogen, a glucose polymer that is used during high intensity exercise. After eating, chemicals in the digestive system release glucose (a type of sugar) from food into the bloodstream where it triggers insulin release from the pancreas. Insulin instructs muscle, liver and fat cells to remove glucose from the bloodstream to keep the amount of sugar in the blood at a safe level. The cells use the glucose immediately as fuel or convert it into glycogen or fat for storage. Glycogen turnover (the depletion and replacement of glycogen stores) is tightly controlled by glycogen synthase and glycogen phosphorylase, enzymes that make and destroy glycogen, respectively. A third enzyme called protein phosphatase 1 promotes net glycogen synthesis by activating glycogen synthase and inactivating glycogen phosphorylase. The activity of protein phosphatase 1 is regulated by a family of “targeting subunits.” In muscle, one of these targeting subunits, called RGL, facilitates protein phosphatase 1 action on glycogen synthase and glycogen phosphorylase.
Why Was This Study Done?
Several known human genetic disorders affect the breakdown of muscle glycogen but few genetic changes (mutations) have been found that decrease the synthesis of muscle glycogen. Researchers are interested in discovering mutations that affect glycogen turnover and other aspects of metabolism because some of these may be involved in the development of diabetes, an important metabolic disorder characterized by high blood sugar levels. In this study, the researchers have investigated how a recently identified mutation in PPP1R3A, the gene that encodes RGL, affects glycogen synthesis. This mutation—PPP1R3A FS—was previously found in 1.36% of a UK white population. It causes the production of a short version of RGL that lacks the part of the molecule that tethers RGL to a cellular structure called the sarcoplasmic reticulum but leaves its glycogen binding domain intact.
What Did the Researchers Do and Find?
To confirm that PPP1R3A FS is a common mutation in the UK white population, the researchers sequenced the gene in 744 healthy adults enrolled in the Oxford Biobank (which hopes to uncover metabolically important genetic variations by monitoring the health of a large number of 30- to 50-year-old people from whom DNA has been collected). 1.46% of these people had the PPP1R3A FS mutation. To examine glycogen storage in carriers of the mutation, the researchers used a technique called in vivo 13C magnetic resonance spectroscopy. Basal muscle glycogen levels and those reached after a meal were lower in these individuals than in people without the mutation but their blood sugar and insulin levels were normal. Finally, to examine how the mutation reduces muscle glycogen, the researchers made mice carrying the PPP1R3A FS mutation. Like the human carriers, these mice had less glycogen than normal in their muscles. Unexpectedly, in biochemical experiments the truncated RGL protein made by the mutant mice did not bind to glycogen or co-localize with glycogen synthase. This lack of binding decreased the activity of glycogen synthase and increased the activity of glycogen phosphorylase, thus decreasing muscle glycogen.
What Do These Findings Mean?
These findings identify the PPP1R3A FS mutation as the first prevalent mutation known to impair glycogen synthesis and to decrease glycogen levels in human skeletal muscles. They also confirm that this mutation is very common in UK whites. Although these human carriers do not report any exercise intolerance, detailed studies are needed to test whether the mutation has any effect on skeletal muscle performance. In addition, suggest the researchers, the mutation might be involved in the development of type 2 diabetes. Impaired insulin-stimulated glycogen synthesis, which is a feature of insulin-resistant muscle and liver cells, is thought to be a key event in the development of type 2 diabetes. Although some previous results indicate that the PPP1R3A FS mutations can sometimes predispose people to develop insulin resistance, only a large population-based study in multiple ethnic groups will reveal whether the PPP1R3A FS mutation has an important impact on the development of type 2 diabetes.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050027.
Wikipedia has pages on metabolism and on glycogen (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
The MedlinePlus encyclopedia provides information about diabetes (in English and Spanish)
The UK Biobank is looking for genetic variations among human populations that are associated with metabolic and other disorders
Web sites are available with brief descriptions of the research programs of Stephen O'Rahilly and Anna DePaoli-Roach
doi:10.1371/journal.pmed.0050027
PMCID: PMC2214798  PMID: 18232732
2.  Prevalence and clinical characteristics of lower limb atherosclerotic lesions in newly diagnosed patients with ketosis-onset diabetes: a cross-sectional study 
Background
The clinical features of atherosclerotic lesions in ketosis-onset diabetes are largely absent. We aimed to compare the characteristics of lower limb atherosclerotic lesions among type 1, ketosis-onset and non-ketotic type 2 diabetes.
Methods
A cross-sectional study was performed in newly diagnosed Chinese patients with diabetes, including 53 type 1 diabetics with positive islet-associated autoantibodies, 208 ketosis-onset diabetics without islet-associated autoantibodies, and 215 non-ketotic type 2 diabetics. Sixty-two subjects without diabetes were used as control. Femoral intima-media thickness (FIMT), lower limb atherosclerotic plaque and stenosis were evaluated and compared among the four groups based on ultrasonography. The risk factors associated with lower limb atherosclerotic plaque were evaluated via binary logistic regression in patients with diabetes.
Results
After adjusting for age and sex, the prevalence of lower limb plaque in the patients with ketosis-onset diabetes (47.6%) was significantly higher than in the control subjects (25.8%, p = 0.013), and showed a higher trend compared with the patients with type 1 diabetes (39.6%, p = 0.072), but no difference was observed in comparison to the patients with non-ketotic type 2 diabetes (62.3%, p = 0.859). The mean FIMT in the ketosis-onset diabetics (0.73 ± 0.17 mm) was markedly greater than that in the control subjects (0.69 ± 0.13 mm, p = 0.045) after controlling for age and sex, but no significant differences were found between the ketosis-onset diabetics and the type 1 diabetics (0.71 ± 0.16 mm, p = 0.373), and the non-ketotic type 2 diabetics (0.80 ± 0.22 mm, p = 0.280), respectively. Age and FIMT were independent risk factors for the presence of lower limb plaque in both the ketosis-onset and non-ketotic type 2 diabetic patients, while sex and age in the type 1 diabetic patients.
Conclusions
The prevalence and risk of lower limb atherosclerotic plaque in the ketosis-onset diabetes were remarkably higher than in the control subjects without diabetes. The features and risk factors of lower limb atherosclerotic lesions in the ketosis-onset diabetes resembled those in the non-ketotic type 2 diabetes, but different from those in the type 1 diabetes. Our findings provide further evidences to support the classification of ketosis-onset diabetes as a subtype of type 2 diabetes rather than idiopathic type 1 diabetes.
doi:10.1186/1758-5996-6-71
PMCID: PMC4054910  PMID: 24926320
Type 1 diabetes; Ketosis-onset diabetes; Type 2 diabetes; Lower limb arteries; Atherosclerosis
3.  Reproducibility and Absolute Quantification of Muscle Glycogen in Patients with Glycogen Storage Disease by 13C NMR Spectroscopy at 7 Tesla 
PLoS ONE  2014;9(10):e108706.
Carbon-13 magnetic resonance spectroscopy (13C MRS) offers a noninvasive method to assess glycogen levels in skeletal muscle and to identify excess glycogen accumulation in patients with glycogen storage disease (GSD). Despite the clinical potential of the method, it is currently not widely used for diagnosis or for follow-up of treatment. While it is possible to perform acceptable 13C MRS at lower fields, the low natural abundance of 13C and the inherently low signal-to-noise ratio of 13C MRS makes it desirable to utilize the advantage of increased signal strength offered by ultra-high fields for more accurate measurements. Concomitant with this advantage, however, ultra-high fields present unique technical challenges that need to be addressed when studying glycogen. In particular, the question of measurement reproducibility needs to be answered so as to give investigators insight into meaningful inter-subject glycogen differences. We measured muscle glycogen levels in vivo in the calf muscle in three patients with McArdle disease (MD), one patient with phosphofructokinase deficiency (PFKD) and four healthy controls by performing 13C MRS at 7T. Absolute quantification of the MRS signal was achieved by using a reference phantom with known concentration of metabolites. Muscle glycogen concentration was increased in GSD patients (31.5±2.9 g/kg w. w.) compared with controls (12.4±2.2 g/kg w. w.). In three GSD patients glycogen was also determined biochemically in muscle homogenates from needle biopsies and showed a similar 2.5-fold increase in muscle glycogen concentration in GSD patients compared with controls. Repeated inter-subject glycogen measurements yield a coefficient of variability of 5.18%, while repeated phantom measurements yield a lower 3.2% system variability. We conclude that noninvasive ultra-high field 13C MRS provides a valuable, highly reproducible tool for quantitative assessment of glycogen levels in health and disease.
doi:10.1371/journal.pone.0108706
PMCID: PMC4189928  PMID: 25296331
4.  Ketosis Onset Type 2 Diabetes Had Better Islet β-Cell Function and More Serious Insulin Resistance 
Journal of Diabetes Research  2014;2014:510643.
Diabetic ketosis had been identified as a characteristic of type 1 diabetes mellitus (T1DM), but now emerging evidence has identified that they were diagnosed as T2DM after long time follow up. This case control study was aimed at comparing the clinical characteristic, β-cell function, and insulin resistance of ketosis and nonketotic onset T2DM and providing evidence for treatment selection. 140 cases of newly diagnosed T2DM patients were divided into ketosis (62 cases) and nonketotic onset group (78 cases). After correction of hyperglycemia and ketosis with insulin therapy, plasma C-peptide concentrations were measured at 0, 0.5, 1, 2, and 3 hours after 75 g glucose oral administration. Area under the curve (AUC) of C-peptide was calculated. Homoeostasis model assessment was used to estimate basal β-cell function (HOMA-β) and insulin resistance (HOMA-IR). Our results showed that ketosis onset group had higher prevalence of nonalcoholic fatty liver disease (NAFLD) than nonketotic group (P = 0.04). Ketosis onset group had increased plasma C-peptide levels at 0 h, 0.5 h, and 3 h and higher AUC0–0.5, AUC0–1, AUC0–3 (P < 0.05). Moreover, this group also had higher HOMA-β and HOMA-IR than nonketotic group (P < 0.05). From these data, we concluded that ketosis onset T2DM had better islet β-cell function and more serious insulin resistance than nonketotic onset T2DM.
doi:10.1155/2014/510643
PMCID: PMC4009153  PMID: 24829925
5.  Ultrasonic assessment of exercise-induced change in skeletal muscle glycogen content 
Background
Ultrasound imaging is a valuable tool in exercise and sport science research, and has been used to visualize and track real-time movement of muscles and tendons, estimate hydration status in body tissues, and most recently, quantify skeletal muscle glycogen content. In this validation study, direct glycogen quantification from pre-and post-exercise muscle biopsy samples was compared with glycogen content estimates made through a portable, diagnostic high-frequency ultrasound and cloud-based software system (MuscleSound®, Denver, CO).
Methods
Well-trained cyclists (N = 20, age 38.4 ± 6.0 y, 351 ± 57.6 wattsmax) participated in a 75-km cycling time trial on their own bicycles using CompuTrainer Pro Model 8001 trainers (RacerMate, Seattle, WA). Muscle biopsy samples and ultrasound measurements were acquired pre- and post-exercise. Specific locations on the vastus lateralis were marked, and a trained technician used a 12 MHz linear transducer and a standard diagnostic high resolution GE LOGIQ-e ultrasound machine (GE Healthcare, Milwaukee, WI) to make three ultrasound measurements. Ultrasound images were pre-processed to isolate the muscle area under analysis, with the mean pixel intensity averaged from the three scans and scaled (0 to 100 scale) to create the glycogen score. Pre- and post-exercise muscle biopsy samples were acquired at the vastus lateralis location (2 cm apart) using the suction-modified percutaneous needle biopsy procedure, and analyzed for glycogen content.
Results
The 20 cyclists completed the 75-km cycling time trial in 168 ± 26.0 minutes at a power output of 193 ± 57.8 watts (54.2 ± 9.6% wattsmax). Muscle glycogen decreased 77.2 ± 17.4%, with an absolute change of 71.4 ± 23.1 mmol glycogen per kilogram of muscle. The MuscleSound® change score at the vastus lateralis site correlated highly with change in measured muscle glycogen content (R = 0.92, P < 0.001).
Conclusions
MuscleSound® change scores acquired from an average of three ultrasound scans at the vastus lateralis site correlated significantly with change in vastus lateralis muscle glycogen content. These data support the use of the MuscleSound® system for accurately and non-invasively estimating exercise-induced decreases in vastus lateralis skeletal muscle glycogen content.
doi:10.1186/s13102-015-0003-z
PMCID: PMC4406335  PMID: 25905021
Cycling; Muscle biopsy; Vastus lateralis; Skeletal muscle; Sonography
6.  Interactions of Fat and Carbohydrate Metabolism—New Aspects and Therapies 
NO one has so far produced anything approaching a clear picture of either fat or carbohydrate metabolism and the interactions of the two are still more involved and elusive although they clearly exist. Plants and animals build up reserves of fat from carbohydrate, but the reverse process (fat into carbohydrate), proved in plant seeds, is still unproven in animals, although theoretically possible.
In normal human metabolism fat-carbohydrate interactions are almost hidden. The disturbances shown in the metabolism of a diabetic seem to give us the clearest indications of these interactions. Either carbohydrate or fat can be used as the main source of body fuel, but their metabolic course is very different, both as regards chemistry and function. It is only whep carbohydrate is not available, either in starvation or severe diabetes, that fat provides the fuel of the body; this contrast is also manifest in the blood and internal organs, especially the liver. Under the commonest normal conditions of diet carbohydrate is predominantly and preferentially used for metabolism. The liver is rich in glycogen, poor in fat; the blood fat is minimal and ketone bodies, although perhaps present in small amount in the blood at most times, are absent on common tests. As soon as carbohydrate is insufficiently available for the needs of metabolism, depot fat flows to the liver and is there catabolized to ketone bodies which recent proof has shown to be burned peripherally in the muscles independent of carbohydrate metabolism. This is a normal process, harmful only in diabetes, and especially harmful when it occurs suddenly, e.g. when insulin is cut off from a fat diabetic dog or human patient. A diabetic supports with ease a prolonged severe ketosis but suffers from one of sudden onset, although of milder severity. Insulin in the diabetic and sugar in the starved switches metabolism from fat to carbohydrate usage very quickly and ketonuria usually disappears in three to six hours.
“Diabetic obesity” is very common and is often seen in the earliest stages and again after insulin treatment. It seems probable that hyperglycæmia causes this obesity and this has been clearly established by observations on an unusual case of lipæmia, diabetes and lipodystrophy.
Lipæcmia may occur in two opposite phases of metabolism, one anabolic—when fat is on its way to storage, the other catabolic—when it is flowing from stores to the liver. The latter is the usual condition obvious in disease.
Work has also been done which suggests that other lipotropic factors—choline, lipocaic, &c., exert an influence on carbohydrate-fat balance, more specifically the glycogen-fat balance in the liver.
In America attention has been drawn to the frequent and persistenzt occurrence of fatty enlargement of the liver in diabetic children. The author has seen many diabetic children (usually in a state of chronic ketosis) with enlarged livers, but such enlargement has rapidly disappeared with better management of the diabetes. Only two out of some 500 diabetic children have clearly shown the unmistakable syndrome of “hepatomegalic dwarfism ”. In these two cases choline and lipocaic were given over prolonged periods without any effect: the liver, however, of one of these cases has since become normal by the addition of zinc protamine insulin.
PMCID: PMC1998199  PMID: 19992415
7.  Prevalence and clinical characteristics of carotid atherosclerosis in newly diagnosed patients with ketosis-onset diabetes: a cross-sectional study 
Background
The features of carotid atherosclerosis in ketosis-onset diabetes have not been investigated. Our aim was to evaluate the prevalence and clinical characteristics of carotid atherosclerosis in newly diagnosed Chinese diabetic patients with ketosis but without islet-associated autoantibodies.
Methods
In total, 423 newly diagnosed Chinese patients with diabetes including 208 ketosis-onset diabetics without islet-associated autoantibodies, 215 non-ketotic type 2 diabetics and 79 control subjects without diabetes were studied. Carotid atherosclerosis was defined as the presence of atherosclerotic plaques in any of the carotid vessel segments. Carotid intima-media thickness (CIMT), carotid atherosclerotic plaque formation and stenosis were assessed and compared among the three groups based on Doppler ultrasound examination. The clinical features of carotid atherosclerotic lesions were analysed, and the risk factors associated with carotid atherosclerosis were evaluated using binary logistic regression in patients with diabetes.
Results
The prevalence of carotid atherosclerosis was significantly higher in the ketosis-onset diabetic group (30.80%) than in the control group (15.2%, p=0.020) after adjusting for age- and sex-related differences, but no significant difference was observed in comparison to the non-ketotic diabetic group (35.8%, p=0.487). The mean CIMT of the ketosis-onset diabetics (0.70±0.20 mm) was markedly higher than that of the control subjects (0.57±0.08 mm, p<0.001), but no significant difference was found compared with the non-ketotic type 2 diabetics (0.73±0.19 mm, p=0.582) after controlling for differences in age and sex. In both the ketosis-onset and the non-ketotic diabetes, the prevalence of carotid atherosclerosis was markedly increased with age (both p<0.001) after controlling for sex, but no sex difference was observed (p=0.479 and p=0.707, respectively) after controlling for age. In the ketosis-onset diabetics, the presence of carotid atherosclerosis was significantly associated with age, hypertension, low-density lipoprotein cholesterol and mean CIMT.
Conclusions
The prevalence and risk of carotid atherosclerosis were significantly higher in the ketosis-onset diabetics than in the control subjects but similar to that in the non-ketotic type 2 diabetics. The characteristics of carotid atherosclerotic lesions in the ketosis-onset diabetics resembled those in the non-ketotic type 2 diabetics. Our findings support the classification of ketosis-onset diabetes as a subtype of type 2 diabetes.
doi:10.1186/1475-2840-12-18
PMCID: PMC3583071  PMID: 23324539
Ketosis-prone diabetes; Type 2 diabetes; Atherosclerosis; Carotid arteries; Epidemiology
8.  Effects of Intravenous Glucose Load on Insulin Secretion in Patients With Ketosis-Prone Diabetes During Near-Normoglycemia Remission 
Diabetes Care  2010;33(4):854-860.
OBJECTIVE
Most patients with ketosis-prone type 2 diabetes (KPD) discontinue insulin therapy and remain in near-normoglycemic remission. The aim of this study was to determine the effect of glucotoxicity on β-cell function during remission in obese patients with KPD.
RESEARCH DESIGN AND METHODS
Age- and BMI-matched obese African Americans with a history of KPD (n = 8), severe hyperglycemia but without ketosis (ketosis-resistant type 2 diabetes, n = 7), and obese control subjects (n = 13) underwent intravenous infusion of 10% dextrose at a rate of 200 mg per m2/min for 20 h. β-Cell function was assessed by changes in insulin and C-peptide concentrations during dextrose infusion and by changes in acute insulin response (AIR) and first-phase insulin release (FPIR) to arginine stimulation before and after dextrose infusion.
RESULTS
The mean ± SD time to discontinue insulin therapy was 7.1 ± 1.7 weeks in KPD and 9.6 ± 2.3 weeks in ketosis-resistant type 2 diabetes (NS). During a 20-h dextrose infusion, changes in insulin, C-peptide, and the C-peptide–to–glucose ratio were similar among diabetic and control groups. During dextrose infusion, subjects with ketosis-resistant type 2 diabetes had greater areas under the curve for blood glucose than subjects with KPD and control subjects (P < 0.05). The AIR and FPIR to arginine stimulation as well as glucose potentiation to arginine assessed before and after dextrose infusion were not different among the study groups.
CONCLUSIONS
Near-normoglycemia remission in obese African American patients with KPD and ketosis-resistant type 2 diabetes is associated with a remarkable recovery in basal and stimulated insulin secretion. At near-normoglycemia remission, patients with KPD displayed a pattern of insulin secretion similar to that of patients with ketosis-resistant type 2 diabetes and obese nondiabetic subjects.
doi:10.2337/dc09-1687
PMCID: PMC2845041  PMID: 20067967
9.  Noninvasive Measurements of Glycogen in Perfused Mouse Livers Using Chemical Exchange Saturation Transfer NMR and Comparison to 13C NMR Spectroscopy 
Analytical Chemistry  2015;87(11):5824-5830.
Liver glycogen represents an important physiological form of energy storage. It plays a key role in the regulation of blood glucose concentrations, and dysregulations in hepatic glycogen metabolism are linked to many diseases including diabetes and insulin resistance. In this work, we develop, optimize, and validate a noninvasive protocol to measure glycogen levels in isolated perfused mouse livers using chemical exchange saturation transfer (CEST) NMR spectroscopy. Model glycogen solutions were used to determine optimal saturation pulse parameters which were then applied to intact perfused mouse livers of varying glycogen content. Glycogen measurements from serially acquired CEST Z-spectra of livers were compared with measurements from interleaved natural abundance 13C NMR spectra. Experimental data revealed that CEST-based glycogen measurements were highly correlated with 13C NMR glycogen spectra. Monte Carlo simulations were then used to investigate the inherent (i.e., signal-to-noise-based) errors in the quantification of glycogen with each technique. This revealed that CEST was intrinsically more precise than 13C NMR, although in practice may be prone to other errors induced by variations in experimental conditions. We also observed that the CEST signal from glycogen in liver was significantly less than that observed from identical amounts in solution. Our results demonstrate that CEST provides an accurate, precise, and readily accessible method to noninvasively measure liver glycogen levels and their changes. Furthermore, this technique can be used to map glycogen distributions via conventional proton magnetic resonance imaging, a capability universally available on clinical and preclinical magnetic resonance imaging (MRI) scanners vs 13C detection, which is limited to a small fraction of clinical-scale MRI scanners.
doi:10.1021/acs.analchem.5b01296
PMCID: PMC4920106  PMID: 25946616
10.  Adipose tissue glycogen accumulation is associated with obesity-linked inflammation in humans 
Molecular Metabolism  2015;5(1):5-18.
Objective
Glycogen metabolism has emerged as a mediator in the control of energy homeostasis and studies in murine models reveal that adipose tissue might contain glycogen stores. Here we investigated the physio(patho)logical role of glycogen in human adipose tissue in the context of obesity and insulin resistance.
Methods
We studied glucose metabolic flux of hypoxic human adipoctyes by nuclear magnetic resonance and mass spectrometry-based metabolic approaches. Glycogen synthesis and glycogen content in response to hypoxia was analyzed in human adipocytes and macrophages. To explore the metabolic effects of enforced glycogen deposition in adipocytes and macrophages, we overexpressed PTG, the only glycogen-associated regulatory subunit (PP1-GTS) reported in murine adipocytes. Adipose tissue gene expression analysis was performed on wild type and homozygous PTG KO male mice. Finally, glycogen metabolism gene expression and glycogen accumulation was analyzed in adipose tissue, mature adipocytes and resident macrophages from lean and obese subjects with different degrees of insulin resistance in 2 independent cohorts.
Results
We show that hypoxia modulates glucose metabolic flux in human adipocytes and macrophages and promotes glycogenesis. Enforced glycogen deposition by overexpression of PTG re-orients adipocyte secretion to a pro-inflammatory response linked to insulin resistance and monocyte/lymphocyte migration. Furthermore, glycogen accumulation is associated with inhibition of mTORC1 signaling and increased basal autophagy flux, correlating with greater leptin release in glycogen-loaded adipocytes. PTG-KO mice have reduced expression of key inflammatory genes in adipose tissue and PTG overexpression in M0 macrophages induces a pro-inflammatory and glycolytic M1 phenotype. Increased glycogen synthase expression correlates with glycogen deposition in subcutaneous adipose tissue of obese patients. Glycogen content in subcutaneous mature adipocytes is associated with BMI and leptin expression.
Conclusion
Our data establish glycogen mishandling in adipose tissue as a potential key feature of inflammatory-related metabolic stress in human obesity.
Highlights
•Hypoxia redirects extracellular glucose to glycogen synthesis in human adipocytes.•Glycogen modifies the endocrine function of adipocytes and induces insulin resistance.•Glycogen stimulates leptin secretion through an autophagy-dependent mechanism.•Enforced glycogen accumulation in macrophages promotes M1 polarization.•Obesity is associated with higher GS expression and glycogen stores in adipose tissue.
doi:10.1016/j.molmet.2015.10.001
PMCID: PMC4703799  PMID: 26844203
Glycogen; Adipocyte; Macrophage; Autophagy; Obesity; Insulin resistance
11.  Mechanism of liver glycogen repletion in vivo by nuclear magnetic resonance spectroscopy. 
Journal of Clinical Investigation  1985;76(3):1229-1236.
In order to quantitate the pathways by which liver glycogen is repleted, we administered [1-13C]glucose by gavage into awake 24-h fasted rats and examined the labeling pattern of 13C in hepatic glycogen. Two doses of [1-13C]glucose, 1 and 6 mg/g body wt, were given to examine whether differences in the plasma glucose concentration altered the metabolic pathways via which liver glycogen was replenished. After 1 and 3 h (high-dose group) and after 1 and 2 h (low-dose group), the animals were anesthetized and the liver was quickly freeze-clamped. Liver glycogen was extracted and the purified glycogen hydrolyzed to glucose with amyloglucosidase. The distribution of the 13C-label was subsequently determined by 13C-nuclear magnetic resonance spectroscopy. The percent 13C enrichment of the glucosyl units in glycogen was: 15.1 +/- 0.8%(C-1), 1.5 +/- 0.1%(C-2), 1.2 +/- 0.1%(C-3), 1.1 +/- 0.1%(C-4), 1.6 +/- 0.1%(C-5), and 2.2 +/- 0.1%(C-6) for the high-dose study (n = 4, at 3 h); 16.5 +/- 0.5%(C-1), 2.0 +/- 0.1%(C-2), 1.3 +/- 0.1%(C-3), 1.1 +/- 0.1%(C-4), 2.2 +/- 0.1%(C-5), and 2.4 +/- 0.1%(C-6) in the low-dose study (n = 4, at 2 h). The average 13C-enrichment of C-1 glucose in the portal vein was found to be 43 +/- 1 and 40 +/- 2% in the high- and low-dose groups, respectively. Therefore, the amount of glycogen that was synthesized from the direct pathway (i.e., glucose----glucose-6-phosphate----glucose-1-phosphate----UDP-glucose---- glycogen) was calculated to be 31 and 36% in the high- and low-dose groups, respectively. The 13C-enrichments of portal vein lactate and alanine were 14 and 14%, respectively, in the high-dose group and 11 and 8%, respectively, in the low-dose group. From these enrichments, the minimum contribution of these gluconeogenic precursors to glycogen repletion can be calculated to be 7 and 20% in the high- and low-dose groups, respectively. The maximum contribution of glucose recycling at the triose isomerase step to glycogen synthesis (i.e., glucose----triose-phosphates----glycogen) was estimated to be 3 and 1% in the high- and low-dose groups, respectively. In conclusion, our results demonstrate that (a) only one-third of liver glycogen repletion occurs via the direct conversion of glucose to glycogen, and that (b) only a very small amount of glycogen synthesis can be accounted for by the conversion of glucose to triose phosphates and back to glycogen; this suggests that futile cycling between fructose-6-phosphate and fructose-1,6-diphosphate under these conditions is minimal. Our results also show that (c) alanine and lactate account for a minimum of between 7 and 20% of the glycogen synthesized, and that (d) the three pathways through which the labeled flux is measured account for a total of only 50% of the total glycogen synthesized. These results suggest that either there is a sizeable amount of glycogen synthesis via pathway(s) that were not examined in the present experiment or that there is a much greater dilution of labeled alanine/lactate in the oxaloacetate pool than previously appreciated, or some combination of these two explanations.
PMCID: PMC424028  PMID: 4044833
12.  The Role of Skeletal Muscle Glycogen Breakdown for Regulation of Insulin Sensitivity by Exercise 
Glycogen is the storage form of carbohydrates in mammals. In humans the majority of glycogen is stored in skeletal muscles (∼500 g) and the liver (∼100 g). Food is supplied in larger meals, but the blood glucose concentration has to be kept within narrow limits to survive and stay healthy. Therefore, the body has to cope with periods of excess carbohydrates and periods without supplementation. Healthy persons remove blood glucose rapidly when glucose is in excess, but insulin-stimulated glucose disposal is reduced in insulin resistant and type 2 diabetic subjects. During a hyperinsulinemic euglycemic clamp, 70–90% of glucose disposal will be stored as muscle glycogen in healthy subjects. The glycogen stores in skeletal muscles are limited because an efficient feedback-mediated inhibition of glycogen synthase prevents accumulation. De novo lipid synthesis can contribute to glucose disposal when glycogen stores are filled. Exercise physiologists normally consider glycogen’s main function as energy substrate. Glycogen is the main energy substrate during exercise intensity above 70% of maximal oxygen uptake (Vo2max⁡) and fatigue develops when the glycogen stores are depleted in the active muscles. After exercise, the rate of glycogen synthesis is increased to replete glycogen stores, and blood glucose is the substrate. Indeed insulin-stimulated glucose uptake and glycogen synthesis is elevated after exercise, which, from an evolutional point of view, will favor glycogen repletion and preparation for new “fight or flight” events. In the modern society, the reduced glycogen stores in skeletal muscles after exercise allows carbohydrates to be stored as muscle glycogen and prevents that glucose is channeled to de novo lipid synthesis, which over time will causes ectopic fat accumulation and insulin resistance. The reduction of skeletal muscle glycogen after exercise allows a healthy storage of carbohydrates after meals and prevents development of type 2 diabetes.
doi:10.3389/fphys.2011.00112
PMCID: PMC3248697  PMID: 22232606
glycogen phosphorylase; glycogen synthase; exercise; type 2 diabetes; insulin resistance; exercise; de novo lipogenesis
13.  Abnormalities in Glycogen Metabolism in a Patient with Alpers’ Syndrome Presenting with Hypoglycemia 
JIMD Reports  2013;14:29-35.
Intermittent hypoglycemia has been described in association with Alpers’ syndrome, a disorder caused by mutations in the mitochondrial DNA polymerase gamma gene. In some patients hypoglycemia may define the initial disease presentation well before the onset of the classical Alpers’ triad of psychomotor retardation, intractable seizures, and liver failure. Correlating with the genotype, POLG pathogenicity is a result of increased mitochondrial DNA mutability, and mitochondrial DNA depletion resulting in energy deficient states. Hypoglycemia therefore could be secondary to any metabolic pathway affected by ATP deficiency. Although it has been speculated that hypoglycemia is due to secondary fatty acid oxidation defects or abnormal gluconeogenesis, the exact underlying etiology is still unclear. Here we present detailed studies on carbohydrate metabolism in an Alpers’ patient who presented initially exclusively with intermittent episodes of hypoglycemia and ketosis. Our results do not support a defect in gluconeogenesis or fatty acid oxidation as the cause of hypoglycemia. In contrast, studies performed on liver biopsy suggested abnormal glycogenolysis. This is shown via decreased activities of glycogen brancher and debrancher enzymes with normal glycogen structure and increased glycogen on histology of the liver specimen. To our knowledge, this is the first report documenting abnormalities in glycogen metabolism in a patient with Alpers’ syndrome.
doi:10.1007/8904_2013_280
PMCID: PMC4213341  PMID: 24272679
14.  Ketosis-Onset Diabetes and Ketosis-Prone Diabetes: Same or Not? 
Objective. To compare clinical characteristics, immunological markers, and β-cell functions of 4 subgroups (“Aβ” classification system) of ketosis-onset diabetes and ketosis prone diabetes patients without known diabetes, presenting with ketosis or diabetic ketoacidosis (DKA) and admitted to our department from March 2011 to December 2011 in China, with 50 healthy persons as control group. Results. β-cell functional reserve was preserved in 63.52% of patients. In almost each subgroup (except A−  β− subgroup of ketosis prone group), male patients were more than female ones. The age of the majority of patients in ketosis prone group was older than that of ketosis-onset group, except A−  β− subgroup of ketosis prone group. The durations from the patient first time ketosis or DKA onset to admitting to the hospital have significant difference, which were much longer for the ketosis prone group except the A+ β+ subgroup. BMI has no significant difference among subgroups. FPG of ketosis prone group was lower than that of A−  β+ subgroup and A+ β+ subgroup in ketosis-onset group. A−  β− subgroup and A+ β+ subgroup of ketosis prone group have lower HbA1c than ketosis-onset group. Conclusions. Ketosis-onset diabetes and ketosis prone diabetes do not absolutely have the same clinical characteristics. Each subgroup shows different specialty.
doi:10.1155/2013/821403
PMCID: PMC3655588  PMID: 23710177
15.  Characteristics of Type 2 Diabetes with Ketosis in Baoshan, Yunnan of China 
Journal of Diabetes Research  2016;2016:7854294.
Objectives. The study provided data to demonstrate the characteristics of type 2 diabetes (T2D) with ketosis in rural parts of south-west border of China in order to help health professionals with optimizing diabetic care. Methods. All hospitalized adult diabetic patients consecutively between January 2011 and July 2015 in Baoshan People's Hospital, Yunnan province of China, were evaluated. T2D with ketosis, ordinary T2D (without ketosis), and type 1 diabetes (T1D) patients were analyzed according to the clinical and biochemical parameters and chronic complications in these subjects. Results. The prevalence of T2D with ketosis was 12% in the whole study subjects. Overweight and obese patients were predominant (49.1%) in T2D patients with ketosis. The mean HbA1c (13.3 ± 3.1%, P = 0.01), fasting plasma glucose (16.9 ± 6 mmol/L, P < 0.0001), and plasma triglyceride (4.0 ± 4.0 mmol/L, P < 0.0001) in T2D patients with ketosis were significantly higher than ordinary T2D patients without ketosis. Infections were the most common inducements in T2D patients with ketosis. Chronic complications including peripheral neuropathy (34.9%), retinopathy (12.7%), diabetic foot (18.1%), and persistent microalbuminuria (11.7%) were common in T2D patients with ketosis. Conclusions. This study indicated the poor glycemic control in diabetic patients in rural areas of south-west part of China. More efforts were urgently required to popularize public health education and improve medical quality in diabetic treatment in these regions.
doi:10.1155/2016/7854294
PMCID: PMC4736950  PMID: 26881259
16.  Endoscopic ultrasound-guided sampling of solid pancreatic masses: 22-gauge aspiration versus 25-gauge biopsy needles 
BMC Gastroenterology  2015;15:122.
Background
Biopsy needles have recently been developed to obtain both cytological and histological specimens during endoscopic ultrasound (EUS). We conducted this study to compare 22-gauge (G) fine needle aspiration (FNA) needles, which have been the most frequently used, and new 25G fine needle biopsy (FNB) needles for EUS-guided sampling of solid pancreatic masses.
Methods
We conducted a retrospective cohort study of all EUS-guided sampling performed between June 2010 and October 2013. During the study period, 76 patients with pancreatic masses underwent EUS-guided sampling with a 22G FNA needle (n = 38) or a 25G FNB needle (n = 38) for diagnosis. An on-site cytopathologist was not present during the procedure. Technical success, the number of needle passes, cytological diagnostic accuracy, cytological sample quality (conventional smear and liquid-based preparation), histological diagnostic accuracy, and complications were reviewed and compared.
Results
There were no significant differences in technical success (100 % for both), the mean number of needle passes (5.05 vs. 5.55, P = 0.132), or complications (0 % for both) between the 22G FNA group and the 25G FNB group. The 22G FNA and 25G FNB groups exhibited comparable outcomes with respect to cytological diagnostic accuracy (97.4 % vs. 89.5 %, P = 0.358) and histological diagnostic accuracy (34.2 % vs. 52.6 %, P = 0.105). In the cytological sample quality analysis, the 25G FNB group exhibited higher scores for the amount of diagnostic cellular material present (22G FNA: 0.92 vs. 25G FNB: 1.32, P = 0.030) and the retention of appropriate architecture (22G FNA: 0.97 vs. 25G FNB: 1.42, P = 0.010) in the liquid-based preparation. The 25G FNB group showed a better histological diagnostic yield for specific tumor discrimination compared with the 22G FNA group (60 % vs. 32.4 %, P = 0.018).
Conclusions
Use of the 25G FNB needle was technically feasible, safe, efficient, and comparable to use of the standard 22G FNA needle in patients with solid pancreatic masses in the absence of an on-site cytopathologist. The cytological sample quality in the liquid-based preparation and the histological diagnostic yield for specific tumor discrimination of EUS-guided sampling using a 25G FNB needle were significantly higher than those using a 22G FNA needle.
doi:10.1186/s12876-015-0352-9
PMCID: PMC4589185  PMID: 26419845
Endoscopic ultrasound; EUS-guided fine needle aspiration; Pancreatic mass
17.  Characterization and pathogenesis of anemia in glycogen storage disease type Ia and Ib 
Purpose
The aim of this study was to characterize the frequency and causes of anemia in glycogen storage disease type I.
Methods
Hematologic data and iron studies were available from 202 subjects (163 with glycogen storage disease Ia and 39 with glycogen storage disease Ib). Anemia was defined as hemoglobin concentrations less than the 5th percentile for age and gender; severe anemia was defined as presence of a hemoglobin <10 g/dl.
Results
In glycogen storage disease Ia, 68/163 patients were anemic at their last follow-up. Preadolescent patients tended to have milder anemia secondary to iron deficiency, but anemia of chronic disease predominated in adults. Severe anemia was present in 8/163 patients, of whom 75% had hepatic adenomas. The anemia improved or resolved in all 10 subjects who underwent resection of liver lesions. Anemia was present in 72% of patients with glycogen storage disease Ib, and severe anemia occurred in 16/39 patients. Anemia in patients with glycogen storage disease Ib was associated with exacerbations of glycogen storage disease enterocolitis, and there was a significant correlation between C-reactive protein and hemoglobin levels (P = 0.036).
Conclusion
Anemia is a common manifestation of both glycogen storage disease Ia and Ib, although the pathophysiology appears to be different between these conditions. Those with severe anemia and glycogen storage disease Ia likely have hepatic adenomas, whereas glycogen storage disease enterocolitis should be considered in those with glycogen storage disease Ib.
doi:10.1038/gim.2012.41
PMCID: PMC3808879  PMID: 22678084
anemia; glycogen storage disease I; hepcidin; inflammatory bowel disease; iron
18.  A metabolic link between mitochondrial ATP synthesis and liver glycogen metabolism: NMR study in rats re-fed with butyrate and/or glucose 
Background
Butyrate, end-product of intestinal fermentation, is known to impair oxidative phosphorylation in rat liver and could disturb glycogen synthesis depending on the ATP supplied by mitochondrial oxidative phosphorylation and cytosolic glycolysis.
Methods
In 48 hr-fasting rats, hepatic changes of glycogen and total ATP contents and unidirectional flux of mitochondrial ATP synthesis were evaluated by ex vivo 31P NMR immediately after perfusion and isolation of liver, from 0 to 10 hours after force-feeding with (butyrate 1.90 mg + glucose 14.0 mg.g-1 body weight) or isocaloric glucose (18.2 mg.g-1 bw); measurements reflected in vivo situation at each time of liver excision. The contribution of energetic metabolism to glycogen metabolism was estimated.
Results
A net linear flux of glycogen synthesis (~11.10 ± 0.60 μmol glucosyl units.h-1.g-1 liver wet weight) occurred until the 6th hr post-feeding in both groups, whereas butyrate delayed it until the 8th hr. A linear correlation between total ATP and glycogen contents was obtained (r2 = 0.99) only during net glycogen synthesis. Mitochondrial ATP turnover, calculated after specific inhibition of glycolysis, was stable (~0.70 ± 0.25 μmol.min-1.g-1 liver ww) during the first two hr whatever the force-feeding, and increased transiently about two-fold at the 3rd hr in glucose. Butyrate delayed the transient increase (1.80 ± 0.33 μmol.min-1.g-1 liver ww) to the 6th hr post-feeding. Net glycogenolysis always appeared after the 8th hr, whereas flux of mitochondrial ATP synthesis returned to near basal level (0.91 ± 0.19 μmol.min-1.g-1 liver ww).
Conclusion
In liver from 48 hr-starved rats, the energy need for net glycogen synthesis from exogenous glucose corresponds to ~50% of basal mitochondrial ATP turnover. The evidence of a late and transient increase in mitochondrial ATP turnover reflects an energetic need, probably linked to a glycogen cycling. Butyrate, known to reduce oxidative phosphorylation yield and to induce a glucose-sparing effect, delayed the transient increase in mitochondrial ATP turnover and hence energy contribution to glycogen metabolism.
doi:10.1186/1743-7075-8-38
PMCID: PMC3141389  PMID: 21676253
19.  Predominant role of gluconeogenesis in the hepatic glycogen repletion of diabetic rats. 
Liver glycogen formation can occur via the direct (glucose----glucose-6-phosphate----glycogen) or indirect (glucose----C3 compounds----glucose-6-phosphate----glycogen) pathways. In the present study we have examined the effect of hyperglycemia on the pathways of hepatic glycogenesis, estimated from liver uridine diphosphoglucose (UDPglucose) specific activities, and on peripheral (muscle) glucose metabolism in awake, unstressed control and 90% pancreatectomized, diabetic rats. Under identical conditions of hyperinsulinemia (approximately 550 microU/ml), 2-h euglycemic (6 mM) and hyperglycemic (+5.5 mM and +11 mM) clamp studies were performed in combination with [3-3H,U-14C]glucose, [6-3H,U-14C]glucose, or [3-3H]glucose and [U-14C]lactate infusions under postabsorptive conditions. Total body glucose uptake and muscle glycogen synthesis were decreased in diabetic vs. control rats during all the clamp studies, whereas glycolytic rates were similar. By contrast, hyperglycemia determined similar rates of liver glycogen synthesis in both groups. Nevertheless, in diabetic rats, the contribution of the direct pathway to hepatic glycogen repletion was severely decreased, whereas the indirect pathway was markedly increased. After hyperglycemia, hepatic glucose-6-phosphate concentrations were increased in both groups, whereas UDPglucose concentrations were reduced only in the control group. These results indicate that in the diabetic state, under hyperinsulinemic conditions, hyperglycemia normally stimulates liver glycogen synthesis through a marked increase in the indirect pathway, which in turn may compensate for the reduction in the direct pathway. The increase in the hepatic concentrations of both glucose-6-phosphate and UDPglucose suggests the presence, in this diabetic rat model, of a compensatory "push" mechanism for liver glycogen repletion.
PMCID: PMC442816  PMID: 1530852
20.  4-Hydroxyisoleucine improves hepatic insulin resistance by restoring glycogen synthesis in vitro  
Introduction/Aims: Hydroxyisoleucine (4-HIL), derived from fenugreek seeds, improves insulin resistance in 3T3-L1 adipocytes and L6 myotubes. However, the effects of 4-HIL on liver glycogen synthesis and hepatic insulin resistance have not been described. The aim of this study was to investigate the effects of 4-HIL on glycogen synthesis in a tumor necrosis factor-α (TNF-α)-induced insulin resistance model using HepG2 cells. Materials and methods: HepG2 cells were divided into eight groups: control; TNF-α; and 5, 10, or 20 μM 4-HIL without or with TNF-α. Glycogen and protein expression were evaluated using a glycogen assay kit and western blotting, respectively. Results: Glycogen levels did not differ between the 4-HIL groups and control (P>0.05), but were decreased significantly in the TNF-α group (P<0.05), indicating the establishment of insulin-resistant HepG2 cells. Adding 20 μM 4-HIL to TNF-α-treated cells increased glycogen levels (P<0.05). Relative to the control group, the P-IRS-1/IRS-1 and P-JNK/JNK ratios were increased (P<0.001) in the TNF-α group, whereas the P-AKT/AKT and P-GSK/GSK ratios were decreased (P<0.001). When 20 μM 4-HIL was added to TNF-α-treated cells, the P-IRS-1/IRS-1 and P-JNK/JNK ratios decreased (P<0.001 and P<0.05, respectively), whereas the P-AKT/AKT and P-GSK/GSK ratios increased (P<0.05 and P<0.001). Conclusions: 4-HIL directly or indirectly reversed TNF-α reduced glycogen levels by inhibiting JNK and IRS-1 (Ser307) phosphorylation and increasing AKT (Ser473) and GSK-3 phosphorylation. These findings demonstrate that 4-HIL modulates hepatic insulin resistance at the molecular level, and suggest that it is a novel potential therapeutic agent for the treatment of insulin resistance in patients with diabetes.
PMCID: PMC4537988  PMID: 26309514
Fenugreek; JNK signaling pathway; insulin resistance; 3T3-L1 adipocytes; L6 myotubes
21.  Splanchnic and leg exchange of glucose, amino acids, and free fatty acids during exercise in diabetes mellitus. 
Journal of Clinical Investigation  1975;55(6):1303-1314.
The influence of exercise on leg and splanchnic exchange of substrates was examined in eight insulin-dependent diabetics 24 h after withdrawal of insulin and in eight healthy controls studied at rest and after 40 min of bicycle ergometer exercise at 55-60% of maximal capacity. In four of the diabetic subjects, basal arterial ketone acid levels were 3-4 mmol/ liter (ketotic diabetics) and in the remainder, below 1 mmol/liter (nonketotic diabetics). ,ree fatty acid (FFA) turnover and regional exchange were evaluated with 14-C- labeled oleic acid. Leg uptake of blood glucose rose 13-18 fold during exercise in both the diabetics and controls and accounted for a similar proportion of the total oxygen uptake by leg muscles (25-28%) in the two groups. In contrast, leg uptake of FFA corresponded to 39% of leg oxygen consumption in the diabetic group but only 27% in controls. Systemic turnover of oleic acid was similar in the two groups. Splanchnic glucose output increased during exercise 3-4 fold above resting levels in both groups. In the diabetics, splanchnic uptake of lactate, pyruvate, glycerol, and glycogenic amino acids rose more than twofold above resting levels and was fourfold greater than in exercising controls. Total precursor uptake could account for 30% of the splanchnic glucose output in the diabetic group. In contrast, in the controls, total splanchnic uptake of glucose precursors was no greater during exercise than in the resting state and could account for no more than 11% of splanchnic glucose output. The augmented precursor uptake during exercise in the diabetics was a consequence of increased splanchnic fractional extraction as well as increased peripheral production of gluconeogenic substrates. The arterial glucagon concentration was unchanged by exercise in both groups, but was higher in the diabetics. In the diabetic subjects with ketosis in the resting state, exercise elicited a rise in arterial glucose and FFA, an augmented splanchnic uptake of FFA, and a 2-3 fold increase in splanchnic output of 3-hydroxybutyrate. Uptake of 3-hydroxybutyrate by the exercising leg rose more rapidly than splanchnic production, resulting in a fall in arterial levels of 3-hydroxybutyrate. It is concluded that (a) glucose uptake by exercising muscle in hyperglycemic diabetics is no different from that of controls; (b) splanchnic glucose output rises during exercise to a similar extent in diabetics and controls, while uptake of gluconeogenic substrates is markedly higher in diabetics and accounts for a greater proportion of total splanchnic glucose output; (c) exercise in diabetic patients with mild ketosis is associated with a rise in blood glucose and FFA levels as well as augmented splanchnic production and peripheral uptake of ketone bodies.
PMCID: PMC301886  PMID: 1133176
22.  Lack of Lipotoxicity Effect on β-Cell Dysfunction in Ketosis-Prone Type 2 Diabetes 
Diabetes Care  2009;33(3):626-631.
OBJECTIVE
Over half of newly diagnosed obese African Americans with diabetic ketoacidosis (DKA) discontinue insulin therapy and go through a period of near-normoglycemia remission. This subtype of diabetes is known as ketosis-prone type 2 diabetes (KPDM).
RESEARCH DESIGN AND METHODS
To investigate the role of lipotoxicity on β-cell function, eight obese African Americans with KPDM, eight obese subjects with type 2 diabetes with severe hyperglycemia without ketosis (ketosis-resistant type 2 diabetes), and nine nondiabetic obese control subjects underwent intravenous infusion of 20% intralipid at 40 ml/h for 48 h. β-Cell function was assessed by changes in insulin and C-peptide concentration during infusions and by changes in acute insulin response to arginine stimulation (AIRarg) before and after lipid infusion.
RESULTS
The mean time to discontinue insulin therapy was 11.0 ± 8.0 weeks in KPDM and 9.6 ± 2.2 weeks in ketosis-resistant type 2 diabetes (P = NS). At remission, KPDM and ketosis-resistant type 2 diabetes had similar glucose (94 ± 14 vs. 109 ± 20 mg/dl), A1C (5.7 ± 0.4 vs. 6.3 ± 1.1%), and baseline AIRarg response (34.8 ± 30 vs. 64 ± 69 μU/ml). P = NS despite a fourfold increase in free fatty acid (FFA) levels (0.4 ± 0.3 to 1.8 ± 1.1 mmol/l, P < 0.01) during the 48-h intralipid infusion; the response to AIRarg stimulation, as well as changes in insulin and C-peptide levels, were similar among obese patients with KPDM, patients with ketosis-resistant type 2 diabetes, and nondiabetic control subjects.
CONCLUSIONS
Near-normoglycemia remission in obese African American patients with KPDM and ketosis-resistant type 2 diabetes is associated with a remarkable recovery in basal and stimulated insulin secretion. A high FFA level by intralipid infusion for 48 h was not associated with β-cell decompensation (lipotoxicity) in KPDM patients.
doi:10.2337/dc09-1369
PMCID: PMC2827521  PMID: 20028938
23.  Mechanism of Antidiabetic Action of Compound GII Purified from Fenugreek (Trigonella foenum graecum) Seeds 
To study the mechanism of action of water soluble compound GII purified from fenugreek (Trigonella foenum graecum) seeds which was shown earlier to have antidiabetic effect in the subdiabetic, moderately and severely diabetic rabbits. In rabbits (1–1.5 kg bw) diabetes was induced by intravenous injection of 80 mg/kg bw of alloxan. They were fed with GII at a dose of 50 mg/kg bw daily once in the morning for 15 days in the subdiabetic and moderately diabetic and 30 days in the severely diabetic rabbits. Serum total cholesterol (TC), triglycerides (TG), LDL + VLDL cholesterol [(LDL + VLDL)C], HDL cholesterol [(HDL)C], total tissue lipids, glycogen and enzymes of carbohydrate metabolism (glycolysis, gluconeogenesis, polyol pathway) hexokinase, glucokinase, pyruvate kinase, malic enzyme, glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, aldose reductase and sorbitol dehydrogenase and antioxidant enzymes glutathione peroxidase, glutathione reductase and superoxide dismutase were estimated. Liver and kidney function parameters were also estimated. Treatment with GII for 15 days in the subdiabetic and moderately diabetic rabbits and for 30 days in the severely diabetic rabbits (i) decreased the elevated lipids TC, TG, (LDL + VLDL)C and increased the decreased (HDL)C, (ii) decreased the elevated liver and heart total lipids, TC and TG, (iii) increased the decreased liver and muscle glycogen, (iv) increased the decreased hexokinase, glucokinase, pyruvate kinase, malic enzyme, glucose-6-phosphate dehydrogenase, superoxide dismutase, glutathione peroxidase, (v) decreased the increased glucose-6-phosphatase, sorbitol dehydrogenase, aldose reductase. Results thus show that treatment with GII compound purified from fenugreek seeds for 15 days in the subdiabetic and moderately diabetic and 30 days in the severely diabetic rabbits corrects the altered serum lipids, tissue lipids, glycogen, enzymes of glycolysis, gluconeogenesis, glycogen metabolism, polyol pathway and antioxidant enzymes. Histopathological abnormalities (fatty infiltration and other cellular changes) seen in the pancreas, liver, heart and kidneys were repaired after treatment with GII. In fact partially damaged pancreas was repaired. Liver and kidney function test results were normal in the GII treated animals indicating that GII treatment is safe and free from any side effects.
doi:10.1007/s12291-011-0150-2
PMCID: PMC3210251  PMID: 23024468
GII from fenugreek seeds; Mechanism of action; Serum and tissue lipids; Glycogen; Glycolysis; Gluconeogenesis; Antioxidant enzymes
24.  GLYCOGEN SYNTHESIS FROM URIDINE DIPHOSPHATE GLUCOSE  
The distribution in liver cell fractions of UDPG-glycogen transferase has been studied. In fasting animals which have been refed 6 hours before sacrifice, the distribution of the enzyme in the various cell fractions can be correlated with the glycogen content of each fraction. A purified glycogen fraction has been prepared by differential centrifugation in sucrose gradients. This glycogen fraction contains vesicular structures which resemble those seen in association with glycogen deposits in the intact liver cell. In addition, the glycogen pellet contains UDPG-glycogen transferase in high specific activity. Subfractionation of the glycogen pellet separates the majority of vesicular elements from the bulk of transferase activity and glycogen. The evidence presented suggests that the presence of UPDG-glycogen transferase in the glycogen pellet is to be attributed to its binding to glycogen rather than to its association with the structural elements found in the glycogen fraction.
PMCID: PMC2225075  PMID: 13764028
25.  Non-invasive measurement of brain glycogen by NMR spectroscopy and its application to the study of brain metabolism 
Journal of neuroscience research  2011;89(12):1905-1912.
Glycogen is the reservoir for glucose in the brain. Beyond the general agreement that glycogen serves as an energy source in the central nervous system, its exact role in brain energy metabolism has yet to be elucidated. Experiments performed in cell and tissue culture and animals have shown that glycogen content is affected by several factors including glucose, insulin, neurotransmitters, and neuronal activation. The study of in vivo glycogen metabolism has been hindered by the inability to measure glycogen non-invasively, but in the past several years, the development of a non-invasive localized 13C nuclear magnetic resonance (NMR) spectroscopy method has enabled the study of glycogen metabolism in the conscious human. With this technique, 13C-glucose is administered intravenously and its incorporation into and wash-out from brain glycogen is tracked. One application of this method has been to the study of brain glycogen metabolism in humans during hypoglycemia: data have shown that mobilization of brain glycogen is augmented during hypoglycemia and, after a single episode of hypoglycemia, glycogen synthesis rate is increased, suggesting that glycogen stores rebound to levels greater than baseline. Such studies suggest glycogen may serve as a potential energy reservoir in hypoglycemia and may participate in the brain's adaptation to recurrent hypoglycemia and eventual development of hypoglycemia unawareness. Beyond this focused area of study, 13C NMR spectroscopy has a broad potential for application in the study of brain glycogen metabolism and carries the promise of a better understanding of the role of brain glycogen in diabetes and other conditions.
doi:10.1002/jnr.22703
PMCID: PMC3189435  PMID: 21732401
Brain glycogen; 13C NMR spectroscopy; in vivo glycogen measurement

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