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1.  Long-Term Effects of Bariatric Surgery on Meal Disposal and β-Cell Function in Diabetic and Nondiabetic Patients 
Diabetes  2013;62(11):3709-3717.
Gastric bypass surgery leads to marked improvements in glucose tolerance and insulin sensitivity in obese type 2 diabetes (T2D); the impact on glucose fluxes in response to a physiological stimulus, such as a mixed meal test (MTT), has not been determined. We administered an MTT to 12 obese T2D patients and 15 obese nondiabetic (ND) subjects before and 1 year after surgery (10 T2D and 11 ND) using the double-tracer technique and modeling of β-cell function. In both groups postsurgery, tracer-derived appearance of oral glucose was biphasic, a rapid increase followed by a sharp drop, a pattern that was mirrored by postprandial glucose levels and insulin secretion. In diabetic patients, surgery lowered fasting and postprandial glucose levels, peripheral insulin sensitivity increased in proportion to weight loss (∼30%), and β-cell glucose sensitivity doubled but did not normalize (compared with 21 nonsurgical obese and lean controls). Endogenous glucose production, however, was less suppressed during the MMT as the combined result of a relative hyperglucagonemia and the rapid fall in plasma glucose and insulin levels. We conclude that in T2D, bypass surgery changes the postprandial response to a dumping-like pattern and improves glucose tolerance, β-cell function, and peripheral insulin sensitivity but worsens endogenous glucose output in response to a physiological stimulus.
doi:10.2337/db13-0321
PMCID: PMC3806605  PMID: 23835342
2.  Prediction of Diabetes Based on Baseline Metabolic Characteristics in Individuals at High Risk 
Diabetes Care  2013;36(11):3607-3612.
OBJECTIVE
Individuals with impaired glucose tolerance (IGT) are at high risk for developing type 2 diabetes mellitus (T2DM). We examined which characteristics at baseline predicted the development of T2DM versus maintenance of IGT or conversion to normal glucose tolerance.
RESEARCH DESIGN AND METHODS
We studied 228 subjects at high risk with IGT who received treatment with placebo in ACT NOW and who underwent baseline anthropometric measures and oral glucose tolerance test (OGTT) at baseline and after a mean follow-up of 2.4 years.
RESULTS
In a univariate analysis, 45 of 228 (19.7%) IGT individuals developed diabetes. After adjusting for age, sex, and center, increased fasting plasma glucose, 2-h plasma glucose, ∆G0–120 during OGTT, HbA1c, adipocyte insulin resistance index, ln fasting plasma insulin, and ln ∆I0–120, as well as family history of diabetes and presence of metabolic syndrome, were associated with increased risk of diabetes. At baseline, higher insulin secretion (ln [∆I0–120/∆G0–120]) during the OGTT was associated with decreased risk of diabetes. Higher β-cell function (insulin secretion/insulin resistance or disposition index; ln [∆I0–120/∆G0–120 × Matsuda index of insulin sensitivity]; odds ratio 0.11; P < 0.0001) was the variable most closely associated with reduced risk of diabetes.
CONCLUSIONS
In a stepwise multiple-variable analysis, only HbA1c and β-cell function (ln insulin secretion/insulin resistance index) predicted the development of diabetes (r = 0.49; P < 0.0001).
doi:10.2337/dc13-0520
PMCID: PMC3816921  PMID: 24062330
3.  Prevention of Diabetes With Pioglitazone in ACT NOW 
Diabetes  2013;62(11):3920-3926.
We examined the metabolic characteristics that attend the development of type 2 diabetes (T2DM) in 441 impaired glucose tolerance (IGT) subjects who participated in the ACT NOW Study and had complete end-of-study metabolic measurements. Subjects were randomized to receive pioglitazone (PGZ; 45 mg/day) or placebo and were observed for a median of 2.4 years. Indices of insulin sensitivity (Matsuda index [MI]), insulin secretion (IS)/insulin resistance (IR; ΔI0–120/ΔG0–120, ΔIS rate [ISR]0–120/ΔG0–120), and β-cell function (ΔI/ΔG × MI and ΔISR/ΔG × MI) were calculated from plasma glucose, insulin, and C-peptide concentrations during oral glucose tolerance tests at baseline and study end. Diabetes developed in 45 placebo-treated vs. 15 PGZ-treated subjects (odds ratio [OR] 0.28 [95% CI 0.15–0.49]; P < 0.0001); 48% of PGZ-treated subjects reverted to normal glucose tolerance (NGT) versus 28% of placebo-treated subjects (P < 0.005). Higher final glucose tolerance status (NGT > IGT > T2DM) was associated with improvements in insulin sensitivity (OR 0.61 [95% CI 0.54–0.80]), IS (OR 0.61 [95% CI 0.50–0.75]), and β-cell function (ln IS/IR index and ln ISR/IR index) (OR 0.26 [95% CI 0.19–0.37]; all P < 0.0001). Of the factors measured, improved β-cell function was most closely associated with final glucose tolerance status.
doi:10.2337/db13-0265
PMCID: PMC3806596  PMID: 23863810
4.  Circulating Lysophosphatidylcholines Are Markers of a Metabolically Benign Nonalcoholic Fatty Liver 
Diabetes Care  2013;36(8):2331-2338.
OBJECTIVE
Nonalcoholic fatty liver (NAFL) is thought to contribute to insulin resistance and its metabolic complications. However, some individuals with NAFL remain insulin sensitive. Mechanisms involved in the susceptibility to develop insulin resistance in humans with NAFL are largely unknown. We investigated circulating markers and mechanisms of a metabolically benign and malignant NAFL by applying a metabolomic approach.
RESEARCH DESIGN AND METHODS
A total of 265 metabolites were analyzed before and after a 9-month lifestyle intervention in plasma from 20 insulin-sensitive and 20 insulin-resistant subjects with NAFL. The relevant plasma metabolites were then tested for relationships with insulin sensitivity in 17 subjects without NAFL and in plasma from 29 subjects with liver tissue samples.
RESULTS
The best separation of the insulin-sensitive from the insulin-resistant NAFL group was achieved by a metabolite pattern including the branched-chain amino acids leucine and isoleucine, ornithine, the acylcarnitines C3:0-, C16:0-, and C18:0-carnitine, and lysophosphatidylcholine (lyso-PC) C16:0 (area under the ROC curve, 0.77 [P = 0.00023] at baseline and 0.80 [P = 0.000019] at follow-up). Among the individual metabolites, predominantly higher levels of lyso-PC C16:0, both at baseline (P = 0.0039) and at follow-up (P = 0.001), were found in the insulin-sensitive compared with the insulin-resistant subjects. In the non-NAFL groups, no differences in lyso-PC C16:0 levels were found between the insulin-sensitive and insulin-resistant subjects, and these relationships were replicated in plasma from subjects with liver tissue samples.
CONCLUSIONS
From a plasma metabolomic pattern, particularly lyso-PCs are able to separate metabolically benign from malignant NAFL in humans and may highlight important pathways in the pathogenesis of fatty liver–induced insulin resistance.
doi:10.2337/dc12-1760
PMCID: PMC3714475  PMID: 23514731
5.  HCC Development Is Associated to Peripheral Insulin Resistance in a Mouse Model of NASH 
PLoS ONE  2014;9(5):e97136.
NAFLD is the most common liver disease worldwide but it is the potential evolution to NASH and eventually to hepatocellular carcinoma (HCC), even in the absence of cirrhosis, that makes NAFLD of such clinical importance. Aim: we aimed to create a mouse model reproducing the pathological spectrum of NAFLD and to investigate the role of possible co-factors in promoting HCC. Methods: mice were treated with a choline-deficient L-amino-acid-defined-diet (CDAA) or its control (CSAA diet) and subjected to a low-dose i.p. injection of CCl4 or vehicle. Insulin resistance was measured by the euglycemic-hyperinsulinemic clamp method. Steatosis, fibrosis and HCC were evaluated by histological and molecular analysis. Results: CDAA-treated mice showed peripheral insulin resistance at 1 month. At 1–3 months, extensive steatosis and fibrosis were observed in CDAA and CDAA+CCl4 groups. At 6 months, equal increase in steatosis and fibrosis was observed between the two groups, together with the appearance of tumor. At 9 months of treatment, the 100% of CDAA+CCl4 treated mice revealed tumor versus 40% of CDAA mice. Insulin-like Growth Factor-2 (IGF-2) and Osteopontin (SPP-1) were increased in CDAA mice versus CSAA. Furthermore, Immunostaining for p-AKT, p-c-Myc and Glypican-3 revealed increased positivity in the tumors. Conclusions: the CDAA model promotes the development of HCC from NAFLD-NASH in the presence of insulin resistance but in the absence of cirrhosis. Since this condition is increasingly recognized in humans, our study provides a model that may help understanding mechanisms of carcinogenesis in NAFLD.
doi:10.1371/journal.pone.0097136
PMCID: PMC4031080  PMID: 24853141
6.  Comparison of Liver Fat Indices for the Diagnosis of Hepatic Steatosis and Insulin Resistance 
PLoS ONE  2014;9(4):e94059.
Context
Hepatic steatosis, defined as increased hepatocellular lipid content (HCL), associates with visceral obesity and glucose intolerance. As exact HCL quantification by 1H-magnetic resonance spectroscopy (1H-MRS) is not generally available, various clinical indices are increasingly used to predict steatosis.
Objective
The purpose of this study was to test the accuracy of NAFLD liver fat score (NAFLD-LFS), hepatic steatosis index (HSI) and fatty liver index (FLI) against 1H-MRS and their relationships with insulin sensitivity and secretion.
Design, Setting and Participants
Ninety-two non-diabetic, predominantly non-obese humans underwent clinical examination, 1H-MRS and an oral glucose tolerance test (OGTT) to calculate insulin sensitivity and β-cell function. Accuracy of indices was assessed from the area under the receiver operating characteristic curve (AROC).
Results
Median HCL was 2.49% (0.62;4.23) and correlated with parameters of glycemia across all subjects. NAFLD-LFS, FLI and HSI yielded AROCs of 0.70, 0.72, and 0.79, respectively, and related positively to HCL, insulin resistance, fasting and post-load β-cell function normalized for insulin resistance. Upon adjustment for age, sex and HCL, regression analysis revealed that NAFLD-LFS, FLI and HSI still independently associated with both insulin sensitivity and β-cell function.
Conclusion
The tested indices offer modest efficacy to detect steatosis and cannot substitute for fat quantification by 1H-MRS. However, all indices might serve as surrogate parameters for liver fat content and also as rough clinical estimates of abnormal insulin sensitivity and secretion. Further validation in larger collectives such as epidemiological studies is needed.
doi:10.1371/journal.pone.0094059
PMCID: PMC3986069  PMID: 24732091
7.  The Ontogeny of the Endocrine Pancreas in the Fetal/Newborn Baboon 
The Journal of endocrinology  2012;214(3):289-299.
Background
Erratic regulation of glucose metabolism including hyperglycemia is a common condition of premature infants and is associated with increased morbidity and mortality.
Objective
To examine histological and ultra-structural differences in the endocrine pancreas in fetal (throughout gestation) and neonatal baboons.
Methods
Twelve fetal baboons were delivered at 125 days (d) gestational age (GA), 140dGA, or 175dGA. Eight animals were delivered at term (185dGA); half were fed for 5d. Seventy-three non-diabetic adult baboons were used for comparison. Pancreatic tissue was studied utilizing light microscopy, confocal imaging and electron microscopy.
Results
The fetal and neonatal endocrine pancreas islet architecture became more organized as GA advanced. The percent areas of α-β-δ-cell type were similar within each fetal and newborn GA (NS), but were higher than the adults (P<0.05) regardless of GA. The ratio of β-cells within the islet (whole and core) increased with gestation (P<0.01). Neonatal baboons who survived for 5 days (feeding), had a 2.5-fold increase in pancreas weight compared to their counterparts euthanized at birth (P=0.01). Endocrine cells were found amongst exocrine ductal and acinar cells in 125,140 and 175dGA fetuses. Subpopulation of cells that co-expressed trypsin and glucagon/insulin show the presence of cells with mixed endo-exocrine lineage in fetuses.
Conclusions
The fetal endocrine pancreas has no prevalence of a of α-β-δ-cell type with larger endocrine cell percent areas than adults. Cells with mixed endocrine/exocrine phenotype occur during fetal development. Developmental differences may play a role in glucose homeostasis during the neonatal period and may have long term implications.
doi:10.1530/JOE-12-0070
PMCID: PMC3686495  PMID: 22723715
Insulin; glucagon; fetus; islet cells; primates
8.  Non-Alcoholic Fatty Liver Disease (NAFLD) and Its Connection with Insulin Resistance, Dyslipidemia, Atherosclerosis and Coronary Heart Disease 
Nutrients  2013;5(5):1544-1560.
Non-alcoholic fatty liver disease is marked by hepatic fat accumulation not due to alcohol abuse. Several studies have demonstrated that NAFLD is associated with insulin resistance leading to a resistance in the antilipolytic effect of insulin in the adipose tissue with an increase of free fatty acids (FFAs). The increase of FFAs induces mitochondrial dysfunction and development of lipotoxicity. Moreover, in subjects with NAFLD, ectopic fat also accumulates as cardiac and pancreatic fat. In this review we analyzed the mechanisms that relate NAFLD with metabolic syndrome and dyslipidemia and its association with the development and progression of cardiovascular disease.
doi:10.3390/nu5051544
PMCID: PMC3708335  PMID: 23666091
non-alcoholic fatty liver(NAFLD); steatosis; visceral fat; lipotoxicity; insulin resistance; free fatty acids; dyslipidemia; cardiometabolic risk
9.  Glucokinase links Krüppel-like factor 6 to the regulation of hepatic insulin sensitivity in non-alcoholic fatty liver disease 
Hepatology (Baltimore, Md.)  2012;55(4):1083-1093.
The polymorphism, KLF6-IVS1-27A, in the Krüppel-like factor 6 (KLF6) transcription factor gene enhances its splicing into antagonistic isoforms and is associated with delayed histological progression of non-alcoholic fatty liver disease (NAFLD). To explore a potential role for KLF6 in the development of insulin resistance, central to NAFLD pathogenesis, we genotyped KLF6-IVS1-27 in healthy subjects and assayed fasting plasma glucose (FPG) and insulin sensitivities. Furthermore, we quantified mRNA expression of KLF6 and glucokinase (GCK), as an important mediator of insulin sensitivity, in human livers and in liver tissues derived from a murine Klf6 knockdown model (DeltaKlf6). Klf6 overexpression studies in a mouse hepatocyte line were utilized to mechanistically link KLF6 with Gck promoter activity.
Results
KLF6-IVS1-27Gwt (ie., less KLF6 splicing) was associated with stepwise increases in FPG and insulin and reduced hepatic insulin sensitivity. KLF6 binds to the liver-specific Gck promoter and activates a GCK promoter-reporter, identifying GCK as a KLF6 direct transcriptional target. Accordingly, in DeltaKlf6 hepatocytes, Gck expression was reduced and stable transfection of Klf6 led to upregulation of Gck. GCK and KLF6 mRNAs correlate directly in human NAFLD tissues and immunohistochemistry studies confirm falling levels of both KLF6 and GCK in fat laden hepatocytes. In contrast to full length KLF6, splice variant KLF6-SV1 increases in NAFLD hepatocytes and inversely correlates with glucokinase regulatory protein, which negatively regulates GCK activity.
Conclusion
KLF6 regulation of GCK contributes to the development of hepatic insulin resistance. The KLF6-IVS1-27A polymorphism, which generates more KLF6-SV1, combats this, lowering hepatic insulin resistance and blood glucose.
doi:10.1002/hep.24793
PMCID: PMC3295906  PMID: 22095588
Krüppel-like Factor 6; non-alcoholic fatty liver disease; hepatic insulin sensitivity; insulin resistance; glucokinase
10.  Gastric bypass and banding equally improve insulin sensitivity and β cell function 
The Journal of Clinical Investigation  2012;122(12):4667-4674.
Bariatric surgery in obese patients is a highly effective method of preventing or resolving type 2 diabetes mellitus (T2DM); however, the remission rate is not the same among different surgical procedures. We compared the effects of 20% weight loss induced by laparoscopic adjustable gastric banding (LAGB) or Roux-en-Y gastric bypass (RYGB) surgery on the metabolic response to a mixed meal, insulin sensitivity, and β cell function in nondiabetic obese adults. The metabolic response to meal ingestion was markedly different after RYGB than after LAGB surgery, manifested by rapid delivery of ingested glucose into the systemic circulation, by an increase in the dynamic insulin secretion rate, and by large, early postprandial increases in plasma glucose, insulin, and glucagon-like peptide–1 concentrations in the RYGB group. However, the improvement in oral glucose tolerance, insulin sensitivity, and overall β cell function after weight loss were not different between surgical groups. Additionally, both surgical procedures resulted in a similar decrease in adipose tissue markers of inflammation. We conclude that marked weight loss itself is primarily responsible for the therapeutic effects of RYGB and LAGB on insulin sensitivity, β cell function, and oral glucose tolerance in nondiabetic obese adults.
doi:10.1172/JCI64895
PMCID: PMC3512168  PMID: 23187122
11.  Liver Enzymes Are Associated With Hepatic Insulin Resistance, Insulin Secretion, and Glucagon Concentration in Healthy Men and Women 
Diabetes  2011;60(6):1660-1667.
OBJECTIVE
The pathophysiological mechanisms to explain the association between risk of type 2 diabetes and elevated concentrations of γ-glutamyltransferase (GGT) and alanineaminotransferase (ALT) remain poorly characterized. We explored the association of liver enzymes with peripheral and hepatic insulin resistance, insulin secretion, insulin clearance, and glucagon concentration.
RESEARCH DESIGN AND METHODS
We studied 1,309 nondiabetic individuals from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study; all had a euglycemic-hyperinsulinemic clamp and an oral glucose tolerance test (OGTT) with assessment of insulin secretion and hepatic insulin extraction. The hepatic insulin resistance index was calculated in 393 individuals.
RESULTS
In both men and women, plasma concentrations of GGT and ALT were inversely related with insulin sensitivity (M/I) (all P < 0.01). Likewise, the hepatic insulin resistance index was positively correlated with both GGT (r = 0.37, P < 0.0001, men; r = 0.36, P < 0.0001, women) and ALT (r = 0.25, P = 0.0005, men; r = 0.18, P = 0.01, women). These associations persisted in multivariable models. Increased GGT and ALT were significantly associated with higher insulin secretion rates and with both reduced endogenous clearance of insulin and hepatic insulin extraction during the OGTT (P = 0.0005 in men; P = 0.003 in women). Plasma fasting glucagon levels increased over ALT quartiles (men, quartile 4 vs. quartile 1 11.2 ± 5.1 vs. 9.3 ± 3.8 pmol/L, respectively, P = 0.0002; women, 9.0 ± 4.3 vs. 7.6 ± 3.1, P = 0.001).
CONCLUSIONS
In healthy individuals, increased GGT and ALT were biomarkers of both systemic and hepatic insulin resistance with concomitant increased insulin secretion and decreased hepatic insulin clearance. The novel finding of a positive correlation between ALT and fasting glucagon level concentrations warrants confirmation in type 2 diabetes.
doi:10.2337/db10-1806
PMCID: PMC3114399  PMID: 21521874
12.  Fatty Liver Index Predicts Further Metabolic Deteriorations in Women with Previous Gestational Diabetes 
PLoS ONE  2012;7(2):e32710.
Background and Aims
Determinants of fatty liver (FL) might be predictive for further deterioration in insulin resistance (IR) in women with previous gestational diabetes (pGDM). The aim was to evaluate the association between pGDM, FL and future manifestation of type 2 diabetes (T2DM) by a detailed pathophysiological characterization early after pregnancy.
Methods
68 pGDM and 29 healthy controls were included 3–6 months after delivery and underwent specific metabolic assessments: status of IR was determined via oral- and intravenous-glucose-tolerance-tests with analysis of proinflammatory factors and kinetics of free-fatty-acids (FFA). According to the fatty-liver-index (FLI), pGDMs were categorized into three groups with low (FLI≤20), intermediate (20
Results
FL was strongly associated with IR in pGDM. pGDM with FLI≥60 showed significantly increased interleukin-6, plasminogen-activator-inhibitor-1, tissue-plasminogen-activator, fibrinogen and increased ultrasensitive-C-reactive-protein compared to the low risk group (FLI≤20). Analysis of FFA indicated a less pronounced decrease of plasma FFA levels during the oral-glucose-tolerance-test in subjects with FLI≥60. History of GDM plus FLI≥60 conferred a high risk for the manifestation of diabetes over 10 years of observation as compared to pGDMs with FLI≤20 (HR:7.85, Cl:2.02–30.5, p = 0.003).
Conclusion
FL is closely linked to GDM, especially to IR and inflammation. Most interestingly, subjects with the highest FLI values showed significant alterations in FFA kinetics and a higher risk to develop T2DM in future.
doi:10.1371/journal.pone.0032710
PMCID: PMC3290578  PMID: 22393439
Clinical Endocrinology  2010;73(3):339-345.
Summary
Objectives
By using tracer techniques, we explored the metabolic mechanisms by which pioglitazone treatment for 16 weeks improves oral glucose tolerance in patients with type 2 diabetes when compared to subjects without diabetes.
Methods
In all subjects, before and after treatment, we measured rates of tissue glucose clearance (MCR), oral glucose appearance (RaO) and endogenous glucose production (EGP) during a (4-h) double tracer oral glucose tolerance test (OGTT) (1-14C-glucose orally and 3-3H-glucose intravenously). Basal hepatic insulin resistance index (HepIR) was calculated as EGPxFPI. β-cell function was assessed as the incremental ratio of insulin to glucose (ΔI/ΔG) during the OGTT.
Results
Pioglitazone decreased fasting plasma glucose concentration (10·5 ± 0·7 to 7·8 ± 0·6 mM, P < 0·0003) and HbA1c (9·7 ± 0·7 to 7·5 ± 0·5%, P < 0·003) despite increased body weight and no change in plasma insulin concentrations. This was determined by a decrease both in fasting EGP (20·0 ± 1·1 to 17·3 ± 0·8 μmol/kgffm min, P < 0·005) and HepIR (from 8194 declined by 49% to 3989, P < 0·002). During the OGTT, total glucose Ra during the 0- to 120-min time period following glucose ingestion decreased significantly because of a reduction in EGP. During the 0- to 240-min time period, pioglitazone caused only a modest increase in MCR (P < 0·07) but markedly increased ΔI/ΔG (P = 0·003). The decrease in 2h-postprandial hyperglycaemia correlated closely with the increase in ΔI/ΔG (r = −0·76, P = 0·004) and tissue clearance (r = −0·74, P = 0·006) and with the decrease in HepIR (r = 0·62, P = 0·006).
Conclusions
In diabetic subjects with poor glycaemic control, pioglitazone improves oral glucose tolerance mainly by enhancing the suppression of EGP and improving β-cell function.
doi:10.1111/j.1365-2265.2010.03811.x
PMCID: PMC3265037  PMID: 20455891
PLoS ONE  2011;6(11):e27617.
Non-Alcoholic fatty liver disease (NAFLD) is characterized by accumulation of triglycerides (TG) in hepatocytes, which may also trigger cirrhosis. The mechanisms of NAFLD are not fully understood, but insulin resistance has been proposed as a key determinant.
Aims
To determine the TG content and long chain fatty acyl CoA composition profile in liver from obese non-diabetic insulin resistant (IR) and lean insulin sensitive (IS) baboons in relation with hepatic and peripheral insulin sensitivity.
Methods
Twenty baboons with varying grades of adiposity were studied. Hepatic (liver) and peripheral (mainly muscle) insulin sensitivity was measured with a euglycemic clamp and QUICKI. Liver biopsies were performed at baseline for TG content and LCFA profile by mass spectrometry, and histological analysis. Findings were correlated with clinical and biochemical markers of adiposity and insulin resistance.
Results
Obese IR baboons had elevated liver TG content compared to IS. Furthermore, the concentration of unsaturated (LC-UFA) was greater than saturated (LC-SFA) fatty acyl CoA in the liver. Interestingly, LC-FA UFA and SFA correlated with waist, BMI, insulin, NEFA, TG, QUICKI, but not M/I. Histological findings of NAFLD ranging from focal to diffuse hepatic steatosis were found in obese IR baboons.
Conclusion
Liver TG content is closely related with both hepatic and peripheral IR, whereas liver LC-UFA and LC-SFA are closely related only with hepatic IR in non-human primates. Mechanisms leading to the accumulation of TG, LC-UFA and an altered UFA: LC-SFA ratio may play an important role in the pathophysiology of fatty liver disease in humans.
doi:10.1371/journal.pone.0027617
PMCID: PMC3220682  PMID: 22125617
Objective
We sought to determine the effect of daily soy supplementation on abdominal fat, glucose metabolism, and circulating inflammatory markers and adipokines in obese, postmenopausal Caucasian and African American women.
Study Design
In a double-blinded controlled trial, 39 postmenopausal women were randomized to soy supplementation or to a casein placebo without isoflavones. Thirty-three completed the study and were analyzed. At baseline and at 3 months, glucose disposal and insulin secretion were measured using hyperglycemic clamps, body composition and body fat distribution were measured by CT scan and DXA, and serum levels of CRP, IL-6, TNF-α, leptin, and adiponectin were measured by immunoassay.
Results
Soy supplementation reduced total and subcutaneous abdominal fat, and IL-6. No difference between groups was noted for glucose metabolism, CRP, TNF-α, leptin, or adiponectin.
Conclusion(s)
Soy supplementation reduced abdominal fat in obese postmenopausal women. Caucasians primarily lost subcutaneous and total abdominal fat, and African Americans primarily lost total body fat.
doi:10.1016/j.ajog.2010.02.058
PMCID: PMC3206645  PMID: 20435291
Menopause; obesity; soy; isoflavones; body composition; body fat distribution; race; insulin secretion; glucose metabolism
Diabetes Care  2010;33(11):2327-2332.
OBJECTIVE
Dicarboxylic acids are natural products with the potential of being an alternate dietary source of energy. We aimed to evaluate the effect of sebacic acid (a 10-carbon dicarboxylic acid; C10) ingestion on postprandial glycemia and glucose rate of appearance (Ra) in healthy and type 2 diabetic subjects. Furthermore, the effect of C10 on insulin-mediated glucose uptake and on GLUT4 expression was assessed in L6 muscle cells in vitro.
RESEARCH DESIGN AND METHODS
Subjects ingested a mixed meal (50% carbohydrates, 15% proteins, and 35% lipids) containing 0 g (control) or 10 g C10 in addition to the meal or 23 g C10 as a substitute of fats.
RESULTS
In type 2 diabetic subjects, the incremental glucose area under the curve (AUC) decreased by 42% (P < 0.05) and 70% (P < 0.05) in the 10 g C10 and 23 g C10 groups, respectively. At the largest amounts used, C10 reduced the glucose AUC in healthy volunteers also. When fats were substituted with 23 g C10, AUC of Ra was significantly reduced on the order of 18% (P < 0.05) in both healthy and diabetic subjects. The insulin-dependent glucose uptake by L6 cells was increased in the presence of C10 (38.7 ± 10.3 vs. 11.4 ± 5.4%; P = 0.026). This increase was associated with a 1.7-fold raise of GLUT4.
CONCLUSIONS
Sebacic acid significantly reduced hyperglycemia after a meal in type 2 diabetic subjects. This beneficial effect was associated with a reduction in glucose Ra, probably due to lowered hepatic glucose output and increased peripheral glucose disposal.
doi:10.2337/dc10-0663
PMCID: PMC2963488  PMID: 20724647
Hypertension  2009;53(3):508-515.
Obesity-associated inflammation causes insulin resistance. Obese adipose tissue displays hypertrophied adipocytes and increased expression of the cannabinoid-1 receptor. Cobalt protoporphyrin (CoPP) increases heme oxygenase-1 (HO-1) activity, increasing adiponectin and reducing inflammatory cytokines. We hypothesize that CoPP administration to Zucker diabetic fat (ZDF) rats would improve insulin sensitivity and remodel adipose tissue. Twelve-week-old Zucker lean and ZDF rats were divided into 4 groups: Zucker lean, Zucker lean–CoPP, ZDF, and ZDF–CoPP. Control groups received vehicle and treatment groups received CoPP (2 mg/kg body weight) once weekly for 6 weeks. Serum insulin levels and glucose response to insulin injection were measured. At 18 weeks of age, rats were euthanized, and aorta, kidney, and subcutaneous and visceral adipose tissues were harvested. HO-1 expression was measured by Western blot analysis and HO-1 activity by serum carbon monoxide content. Adipocyte size and cannabinoid-1 expression were measured. Adipose tissue volumes were determined using MRI. CoPP significantly increased HO-1 activity, phosphorylated AKT and phosphorylated AMP kinase, and serum adiponectin in ZDF rats. HO-1 induction improved hyperinsulinemia and insulin sensitivity in ZDF rats. Subcutaneous and visceral adipose tissue volumes were significantly decreased in ZDF rats. Adipocyte size and cannabinoid-1 expression were both significantly reduced in ZDF–CoPP rats in subcutaneous and visceral adipose tissues. This study demonstrates that HO-1 induction improves insulin sensitivity, downregulates the peripheral endocannabinoid system, reduces adipose tissue volume, and causes adipose tissue remodeling in a model of obesity-induced insulin resistance. These findings suggest HO-1 as a potential therapeutic target for obesity and its associated health risks.
doi:10.1161/HYPERTENSIONAHA.108.124701
PMCID: PMC2745551  PMID: 19171794
insulin resistance; heme oxygenase-1; adiponectin; adiposity; endocannabinoid; pAMPK
Journal of Lipid Research  2009;50(7):1293-1304.
We examined mechanisms by which L-4F reduces obesity and diabetes in obese (ob) diabetic mice. We hypothesized that L-4F reduces adiposity via increased pAMPK, pAKT, HO-1, and increased insulin receptor phosphorylation in ob mice. Obese and lean mice were divided into five groups: lean, lean-L-4F-treated, ob, ob-L-4F-treated, and ob-L-4F-LY294002. Food intake, insulin, glucose adipocyte stem cells, pAMPK, pAKT, CB1, and insulin receptor phosphorylation were determined. Subcutaneous (SAT) and visceral adipose tissue (VAT) were determined by MRI and hepatic lipid content by magnetic resonance spectroscopy. SAT and VAT volumes decreased in ob-L-4F-treated animals compared with control. L-4F treatment decreased hepatic lipid content and increased the numbers of small adipocytes (P < 0.05) and phosphorylation of insulin receptors. L-4F decreased CB1 in SAT and VAT and increased pAKT and pAMPK in endothelium. L-4F-mediated improvement in endothelium was prevented by LY294002. Inhibition of pAKT and pAMPK by LY294002 was associated with an increase in glucose levels. Upregulation of HO-1 by L-4F produced adipose remodeling and increased the number of small differentiated adipocytes. The anti-obesity effects of L-4F are manifested by a decrease in visceral fat content with reciprocal increases in adiponectin, pAMPK, pAKT, and phosphorylation of insulin receptors with improved insulin sensitivity.
doi:10.1194/jlr.M800610-JLR200
PMCID: PMC2694329  PMID: 19224872
diabetes; adiponectin; adiposity; apolipoprotein A-I; heme oxygenase-1; insulin receptor; insulin sensitivity; obesity; endothelial dysfunction
Background
Non-human primates are valuable models for the study of insulin resistance and human obesity. In baboons, insulin sensitivity levels can be evaluated directly with the euglycemic clamp and is highly predicted by adiposity, metabolic markers of obesity and impaired glucose metabolism (i.e. percent body fat by DXA and HbA1c). However, a simple method to screen and identify obese insulin resistant baboons for inclusion in interventional studies is not available.
Methods
We studied a population of twenty baboons with the euglycemic clamp technique to characterize a population of obese nondiabetic, insulin resistant baboons, and used a multivariate linear regression analysis (adjusted for gender) to test different predictive models of insulin sensitivity (insulin-stimulated glucose uptake = Rd) using abdominal circumference and fasting plasma insulin. Alternatively, we tested in a separate baboon population (n = 159), a simpler model based on body weight and fasting plasma glucose to predict the whole-body insulin sensitivity (Rd/SSPI) derived from the clamp.
Results
In the first model, abdominal circumference explained 59% of total insulin mediated glucose uptake (Rd). A second model, which included fasting plasma insulin (log transformed) and abdominal circumference, explained 64% of Rd. Finally, the model using body weight and fasting plasma glucose explained 51% of Rd/SSPI. Interestingly, we found that percent body fat was directly correlated with the adipocyte insulin resistance index (r = 0.755, p < 0.0001).
Conclusion
In baboons, simple morphometric measurements of adiposity/obesity, (i.e. abdominal circumference), plus baseline markers of glucose/lipid metabolism, (i.e. fasting plasma glucose and insulin) provide a feasible method to screen and identify overweight/obese insulin resistant baboons for inclusion in interventional studies aimed to study human obesity, insulin resistance and type 2 diabetes mellitus.
doi:10.1186/1475-2840-8-22
PMCID: PMC2674590  PMID: 19389241
Fertility and sterility  2007;88(6):1609-1617.
Objective:
To determine if a supplement of soy protein improves body composition, body fat distribution, and glucose and insulin metabolism in non-diabetic postmenopausal women compared to an isocaloric casein placebo.
Design:
Randomized, double-blind, placebo-controlled 3-month trial
Setting:
Clinical Research Center
Patients:
15 postmenopausal women
Interventions:
CT scans at L4/L5, dual energy x-ray absorptiometry (DXA), hyperglycemic clamps
Main outcome measures:
Total fat, total abdominal fat, visceral fat, subcutaneous abdominal fat, and insulin secretion.
Results:
Weight by DXA did not change between groups (+1.38 ± 2.02 kg for placebo vs. +0.756 ± 1.32 kg for soy, p=0.48, means ± S.D.). Total and subcutaneous abdominal fat increased more in the placebo compared to the soy group (for differences between groups in total abdominal fat: +38.62 ± 22.84 cm2 for placebo vs. −11.86 ± 31.48 cm2 for soy, p=0.005; subcutaneous abdominal fat: +22.91 ± 28.58 cm2 for placebo vs. −14.73 ± 22.26 cm2 for soy, p=0.013). Insulin secretion, visceral fat, total body fat, and lean mass did not differ between groups. Isoflavone levels increased more in the soy group.
Conclusion:
A daily supplement of soy protein prevents the increase in subcutaneous and total abdominal fat observed with an isocaloric casein placebo in postmenopausal women.
doi:10.1016/j.fertnstert.2007.01.061
PMCID: PMC2200634  PMID: 17412329
soy; isoflavones; menopause; body composition; insulin secretion

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