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1.  Adiponectin may modify the risk of Barrett’s esophagus in patients with gastroesophageal reflux disease 
Background & Aims
Abdominal obesity and increasing body mass index are risk factors for esophageal adenocarcinoma and its main precursor, Barrett’s esophagus; however, there are no known biological mechanisms for these associations or regarding why only some patients with gastroesophageal reflux disease develop Barrett’s esophagus. We evaluated the association between Barrett’s esophagus and multimers of an adipose-associated hormone, adiponectin.
Methods
We conducted a case-control study evaluating the associations between adiponectin (total, high molecular weight, and low/medium molecular weight) and Barrett’s esophagus within the Kaiser Permanente Northern California population. Patients with a new diagnosis of Barrett’s esophagus (cases) were matched to patients with gastroesophageal reflux disease (GERD) without Barrett’s esophagus and to population controls.
Results
Complete serologic and epidemiologic data were available for 284 cases, 294 GERD controls, and 285 population controls. Increasing adiponectin levels were a risk factor for Barrett’s esophagus among patients with gastroesophageal reflux disease (total adiponectin fourth vs. first quartile odds ratio [OR]=1.96; 95% confidence interval (CI) 1.17–3.27; high molecular weight adiponectin OR=1.65; 95% CI 1.00–2.73; low/medium molecular weight adiponectin OR=2.18; 95% CI 1.33–3.56, but not compared with population controls. The associations were significantly stronger among patients reporting frequent GERD symptoms and among smokers (p-values interaction <0.01).
Conclusion
Adiponectin levels are positively associated with the risk of Barrett’s esophagus among patients with GERD and among smokers, but not among population controls without GERD symptoms. Higher adiponectin concentrations may either independently contribute to the aberrant healing of esophageal injury into Barrett’s esophagus or be a marker for other factors.
doi:10.1016/j.cgh.2015.01.009
PMCID: PMC4515407  PMID: 25632808
esophageal adenocarcinoma; adiponectin; BMI; Barrett’s esophagus; adipokines
2.  Linkage and association analysis of circulating vitamin D and parathyroid hormone identifies novel loci in Alaska Native Yup’ik people 
Genes & Nutrition  2016;11:23.
Background
Vitamin D deficiency is a well-documented public health issue with both genetic and environmental determinants. Populations living at far northern latitudes are vulnerable to vitamin D deficiency and its health sequelae, although consumption of traditional native dietary pattern rich in fish and marine mammals may buffer the effects of reduced sunlight exposure. To date, few studies have investigated the genetics of vitamin D metabolism in circumpolar populations or considered genediet interactions with fish and n-3 fatty acid intake.
Methods
We searched for genomic regions exhibiting linkage and association with circulating levels of vitamin D and parathyroid hormone (PTH) in 982 Yup’ik individuals from the Center for Alaska Native Health Research Study. We also investigated potential interactions between genetic variants and a biomarker of traditional dietary intake, the δ15N value.
Results
We identified several novel regions linked with circulating vitamin D and PTH as well as replicated a previous linkage finding on 2p16.2 for vitamin D. Bioinformatic analysis revealed multiple candidate genes for both PTH and vitamin D, including CUBN, MGAT3, and NFKBIA. Targeted association analysis identified NEBL as a candidate gene for vitamin D and FNDC3B for PTH. We observed significant associations between a variant in MXD1 and vitamin D only when an interaction with the δ15N value was included. Finally, we integrated pathway level information to illustrate the biological validity of the proposed candidate genes.
Conclusion
We provide evidence of linkage between several biologically plausible genomic regions and vitamin D metabolism in a circumpolar population. Additionally, these findings suggest that a traditional dietary pattern may modulate genetic effects on circulating vitamin D.
Electronic supplementary material
The online version of this article (doi:10.1186/s12263-016-0538-y) contains supplementary material, which is available to authorized users.
doi:10.1186/s12263-016-0538-y
PMCID: PMC4971612  PMID: 27579147
Alaska Native; Vitamin D; Linkage; n-3 fatty acids; Parathyroid hormone
3.  Linkage and association analysis of obesity traits reveals novel loci and interactions with dietary n-3 fatty acids in an Alaska Native (Yup’ik) population 
Objective
To identify novel genetic markers of obesity-related traits and to identify gene-diet interactions with n-3 polyunsaturated fatty acid (n-3 PUFA) intake in Yup’ik people.
Material and Methods
We measured body composition, plasma adipokines and ghrelin in 982 participants enrolled in the Center for Alaska Native Health Research (CANHR) Study. We conducted a genome-wide SNP linkage scan and targeted association analysis, fitting additional models to investigate putative gene-diet interactions. Finally, we performed bioinformatic analysis to uncover likely candidate genes within the identified linkage peaks.
Results
We observed evidence of linkage for all obesity-related traits, replicating previous results and identifying novel regions of interest for adiponectin (10q26.13-2) and thigh circumference (8q21.11-13). Bioinformatic analysis revealed DOCK1, PTPRE (10q26.13-2) and FABP4 (8q21.11-13) as putative candidate genes in the newly identified regions. Targeted SNP analysis under the linkage peaks identified associations between three SNPs and obesity-related traits: rs1007750 on chromosome 8 and thigh circumference (P=0.0005), rs878953 on chromosome 5 and thigh skinfold (P=0.0004), and rs1596854 on chromosome 11 for waist circumference (P=0.0003). Finally, we showed that n-3 PUFA modified the association between obesity related traits and two additional variants (rs2048417 on chromosome 3 for adiponectin, P for interaction=0.0006 and rs730414 on chromosome 11 for percentage body fat, P for interaction=0.0004).
Conclusions
This study presents evidence of novel genomic regions and gene-diet interactions that may contribute to the pathophysiology of obesity-related traits among Yup’ik people.
doi:10.1016/j.metabol.2015.02.008
PMCID: PMC4408244  PMID: 25772781
Alaska Native; linkage; obesity; n-3 fatty acids
4.  Increased Soluble Leptin Receptor Levels in Morbidly Obese Patients With Insulin Resistance and Nonalcoholic Fatty Liver disease 
Obesity (Silver Spring, Md.)  2010;18(12):2268-2273.
The adipocyte hormone, leptin has been demonstrated to have profibrogenic actions in vitro and in animal models. However, no correlation was found between plasma leptin levels and fibrosis stage in humans. Thus, our aim was to study whether soluble leptin receptor (SLR) or free leptin index (FLI; calculated as the ratio of leptin to SLR), may correlate better with the features of metabolic syndrome and with the histological grade and stage of nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). We studied a population (n = 104) of morbidly obese patients undergoing bariatric surgery. Data including BMI, type 2 diabetes mellitus, hypertension, and hyperlipidemia were obtained. Plasma fasting leptin and SLR, fasting glucose and insulin were measured, and homeostasis model of assessment insulin resistance (HOMAIR) index and FLI were calculated. All patients had intraoperative liver biopsies. Leptin levels correlated with the BMI. The multiple regression analysis indicated that increasing HOMA and decreasing FLI were predictors of steatosis in the liver (P < 0.0003). SLR levels were positively correlated with the presence of diabetes mellitus and the stage of fibrosis. In conclusion, increased SLR levels in morbidly obese patients with diabetes are correlated with the stage of liver fibrosis, and may reflect progressive liver disease.
doi:10.1038/oby.2010.95
PMCID: PMC4820322  PMID: 20448542
5.  Differential Responses of Plasma Adropin Concentrations To Dietary Glucose or Fructose Consumption In Humans 
Scientific Reports  2015;5:14691.
Adropin is a peptide hormone encoded by the Energy Homeostasis Associated (ENHO) gene whose physiological role in humans remains incompletely defined. Here we investigated the impact of dietary interventions that affect systemic glucose and lipid metabolism on plasma adropin concentrations in humans. Consumption of glucose or fructose as 25% of daily energy requirements (E) differentially affected plasma adropin concentrations (P < 0.005) irrespective of duration, sex or age. Glucose consumption reduced plasma adropin from 3.55 ± 0.26 to 3.28 ± 0.23 ng/ml (N = 42). Fructose consumption increased plasma adropin from 3.63 ± 0.29 to 3.93 ± 0.34 ng/ml (N = 45). Consumption of high fructose corn syrup (HFCS) as 25% E had no effect (3.43 ± 0.32 versus 3.39 ± 0.24 ng/ml, N = 26). Overall, the effect of glucose, HFCS and fructose on circulating adropin concentrations were similar to those observed on postprandial plasma triglyceride concentrations. Furthermore, increases in plasma adropin levels with fructose intake were most robust in individuals exhibiting hypertriglyceridemia. Individuals with low plasma adropin concentrations also exhibited rapid increases in plasma levels following consumption of breakfasts supplemented with lipids. These are the first results linking plasma adropin levels with dietary sugar intake in humans, with the impact of fructose consumption linked to systemic triglyceride metabolism. In addition, dietary fat intake may also increase circulating adropin concentrations.
doi:10.1038/srep14691
PMCID: PMC4592955  PMID: 26435060
6.  Deterioration of plasticity and metabolic homeostasis in the brain of the UCD-T2DM rat model of naturally occurring type-2 diabetes 
Biochimica et biophysica acta  2014;1842(9):1313-1323.
The rising prevalence of type-2 diabetes (T2DM) is becoming a pressing issue based on emerging reports that T2DM can also adversely impact mental health. We have utilized the UCD-T2DM rat model in which the onset of T2DM develops spontaneously across time and can serve to understand the pathophysiology of diabetes in humans. An increased insulin resistance index and plasma glucose levels manifested the onset of T2DM. There was a decrease in hippocampal insulin receptor (InR) signaling in the hippocampus, which correlated with peripheral insulin resistance index along the course of diabetes onset (r=−0.56, p< 0.01). T2DM increased the hippocampal levels of 4-hydroxynonenal (4-HNE; a marker of lipid peroxidation) in inverse proportion to the changes in the mitochondrial regulator PGC-1α. Disrupted energy homeostasis was further manifested by a concurrent reduction in energy metabolic markers, including TFAM, SIRT1, and AMPK phosphorylation. In addition, T2DM influenced brain plasticity as evidenced by a significant reduction of BDNF-TrkB signaling. These results suggest that the pathology of T2DM in the brain involves a progressive and coordinated disruption of insulin signaling, and energy homeostasis, with profound consequences for brain function and plasticity. All the described consequences of T2DM were attenuated by treatment with the glucagon-like peptide-1 receptor agonist, liraglutide. Similar results to those of liraglutide were obtained by exposing T2DM rats to a food energy restricted diet, which suggest that normalization of brain energy metabolism is a crucial factor to counteract central insulin sensitivity and synaptic plasticity associated with T2DM.
doi:10.1016/j.bbadis.2014.05.007
PMCID: PMC4372388  PMID: 24840661
Energy homeostasis; Dietary energy restriction; Insulin signaling; Liraglutide; Plasticity; Type-2 diabetes
7.  Fructose consumption: potential mechanisms for its effects to increase visceral adiposity and induce dyslipidemia and insulin resistance 
Current opinion in lipidology  2008;19(1):16-24.
Purpose of review
Based on interim results from an ongoing study, we have reported that consumption of a high-fructose diet, but not a high-glucose diet, promotes the development of three of the pathological characteristics associated with metabolic syndrome: visceral adiposity, dyslipidemia, and insulin resistance. From these results and a review of the current literature, we present two potential sequences of events by which fructose consumption may contribute to metabolic syndrome.
Recent findings
The earliest metabolic perturbation resulting from fructose consumption is postprandial hypertriglyceridemia, which may increase visceral adipose deposition. Visceral adiposity contributes to hepatic triglyceride accumulation, novel protein kinase C activation, and hepatic insulin resistance by increasing the portal delivery of free fatty acids to the liver. With insulin resistance, VLDL production is upregulated and this, along with systemic free fatty acids, increase lipid delivery to muscle. It is also possible that fructose initiates hepatic insulin resistance independently of visceral adiposity and free fatty acid delivery. By providing substrate for hepatic lipogenesis, fructose may result in a direct lipid overload that leads to triglyceride accumulation, novel protein kinase C activation, and hepatic insulin resistance.
Summary
Our investigation and future studies of the effects of fructose consumption may help to clarify the sequence of events leading to development of metabolic syndrome.
doi:10.1097/MOL.0b013e3282f2b24a
PMCID: PMC4151171  PMID: 18196982
dyslipidemia; free fatty acids; fructose consumption; hepatic steatosis; insulin resistance; metabolic syndrome
8.  Administration of pioglitazone alone or with alogliptin delays diabetes onset in UCD-T2DM rats 
The Journal of endocrinology  2014;221(1):133-144.
There is a need to identify strategies for type 2 diabetes prevention. Therefore, we investigated the efficacy of pioglitazone and alogliptin alone and in combination to prevent type 2 diabetes onset in UCD-T2DM rats, a model of polygenic obese type 2 diabetes. At 2 months of age, rats were divided into four groups: control, alogliptin (20 mg/kg per day), pioglitazone (2.5 mg/kg per day), and alogliptin+pioglitazone. Non-fasting blood glucose was measured weekly to determine diabetes onset. Pioglitazone alone and in combination with alogliptin lead to a 5-month delay in diabetes onset despite promoting increased food intake and body weight (BW). Alogliptin alone did not delay diabetes onset or affect food intake or BW relative to controls. Fasting plasma glucose, insulin, and lipid concentrations were lower and adiponectin concentrations were threefold higher in groups treated with pioglitazone. All treatment groups demonstrated improvements in glucose tolerance and insulin secretion during an oral glucose tolerance test with an additive improvement observed with alogliptin+pioglitazone. Islet histology revealed an improvement of islet morphology in all treatment groups compared with control. Pioglitazone treatment also resulted in increased expression of markers of mitochondrial biogenesis in brown adipose tissue and white adipose tissue, with mild elevations observed in animals treated with alogliptin alone. Pioglitazone markedly delays the onset of type 2 diabetes in UCD-T2DM rats through improvements of glucose tolerance, insulin sensitivity, islet function, and markers of adipose mitochondrial biogenesis; however, addition of alogliptin at a dose of 20 mg/kg per day to pioglitazone treatment does not enhance the prevention/delay of diabetes onset.
doi:10.1530/JOE-13-0601
PMCID: PMC4457365  PMID: 24627447
Pioglitazone; type 2 diabetes; alogliptin; islet
9.  CDKAL1 and HHEX are associated with type-2 diabetes-related traits among Yup’ik people 
Journal of diabetes  2013;6(3):251-259.
Background:
Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with type-2 diabetes (T2D), mainly among individuals of European ancestry. We examined the frequency of these SNPs and their association with T2D-related traits in an Alaska Native study population with a historically low prevalence of T2D. We also investigated whether dietary characteristics that may protect against T2D, such as n-3 polyunsaturated fatty acid (n-3 PUFA) intake, modify these associations.
Methods:
In 1,144 Yup’ik people, we examined 17 SNPs repeatedly identified in GWAS for individual and cumulative associations with T2D-related traits. Cumulative associations were evaluated using a genetic risk score (GRS) calculated by summing risk alleles. Associations were tested for interactions with sex, BMI, and n-3 PUFA intake.
Results:
The rs7754840 SNP in CDKAL1 is significantly associated with HbA1c (p=0.00091). The rs5015480 SNP near HHEX is significantly associated (in opposite direction to that in Europeans) with a combined fasting glucose (FG) and HbA1c measure (p=0.00046) and with HOMA-B (p=0.0014). The GRS is significantly associated with FG and combined FG & HbA1c only when the HHEX SNP is dropped from the GRS. Associations are not modified by BMI or n-3 PUFA intake.
Conclusion:
Our results highlight the potential importance of CDKAL1 and HHEX in glucose homeostasis in this Alaska Native population with a low prevalence of T2D, and suggest that these loci should be examined in greater detail in this population.
doi:10.1111/1753-0407.12093
PMCID: PMC3964139  PMID: 24112421
Alaska Native; CANHR; type-2 diabetes SNPs; glycemic traits
10.  Clinical Research Strategies for Fructose Metabolism12 
Advances in Nutrition  2014;5(3):248-259.
Fructose and simple sugars are a substantial part of the western diet, and their influence on human health remains controversial. Clinical studies in fructose nutrition have proven very difficult to conduct and interpret. NIH and USDA sponsored a workshop on 13–14 November 2012, “Research Strategies for Fructose Metabolism,” to identify important scientific questions and parameters to be considered while designing clinical studies. Research is needed to ascertain whether there is an obesogenic role for fructose-containing sugars via effects on eating behavior and energy balance and whether there is a dose threshold beyond which these sugars promote progression toward diabetes and liver and cardiovascular disease, especially in susceptible populations. Studies tend to fall into 2 categories, and design criteria for each are described. Mechanistic studies are meant to validate observations made in animals or to elucidate the pathways of fructose metabolism in humans. These highly controlled studies often compare the pure monosaccharides glucose and fructose. Other studies are focused on clinically significant disease outcomes or health behaviors attributable to amounts of fructose-containing sugars typically found in the American diet. These are designed to test hypotheses generated from short-term mechanistic or epidemiologic studies and provide data for health policy. Discussion brought out the opinion that, although many mechanistic questions concerning the metabolism of monosaccharide sugars in humans remain to be addressed experimentally in small highly controlled studies, health outcomes research meant to inform health policy should use large, long-term studies using combinations of sugars found in the typical American diet rather than pure fructose or glucose.
doi:10.3945/an.113.005249
PMCID: PMC4013177  PMID: 24829471
11.  Associations of ghrelin with eating behaviors, stress, metabolic factors, and telomere length among overweight and obese women: Preliminary evidence of attenuated ghrelin effects in obesity? 
Appetite  2014;76:84-94.
Ghrelin regulates homeostatic food intake, hedonic eating, and is a mediator in the stress response. In addition, ghrelin has metabolic, cardiovascular, and anti-aging effects. This cross-sectional study examined associations between total plasma ghrelin, caloric intake based on 3 day diet diaries, hedonic eating attitudes, stress-related and metabolic factors, and leukocyte telomere length in overweight (n=25) and obese women (n=22). We hypothesized associations between total plasma ghrelin and eating behaviors, stress, metabolic, cardiovascular, and cell aging factors among overweight women, but not among obese women due to lower circulating ghrelin levels and/or central resistance to ghrelin. Confirming previous studies demonstrating lowered plasma ghrelin in obesity, ghrelin levels were lower in the obese compared with overweight women. Among the overweight, ghrelin was positively correlated with caloric intake, giving in to cravings for highly palatable foods, and a flatter diurnal cortisol slope across 3 days. These relationships were non-significant among the obese group. Among overweight women, ghrelin was negatively correlated with insulin resistance, systolic blood pressure, and heart rate, and positively correlated with telomere length. Among the obese subjects, plasma ghrelin concentrations were negatively correlated with insulin resistance, but were not significantly correlated with blood pressure, heart rate or telomere length. Total plasma ghrelin and its associations with food intake, hedonic eating, and stress are decreased in obesity, providing evidence consistent with the theory that central resistance to ghrelin develops in obesity and ghrelin’s function in appetite regulation may have evolved to prevent starvation in food scarcity rather than cope with modern food excess. Furthermore, ghrelin is associated with metabolic and cardiovascular health, and may have anti-aging effects, but these effects may be attenuated in obesity.
doi:10.1016/j.appet.2014.01.011
PMCID: PMC4170078  PMID: 24462487
12.  Alterations in intervertebral disc composition, matrix homeostasis and biomechanical behavior in the UCD-T2DM rat model of type 2 diabetes 
Type 2 diabetes (T2D) adversely affects many tissues, and the greater incidence of discogenic low back pain among diabetic patients suggests that the intervertebral disc is affected too. Using a rat model of polygenic obese T2D, we demonstrate that diabetes compromises several aspects of disc composition, matrix homeostasis and biomechanical behavior. Coccygeal motion segments were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days). Findings indicated that diabetes but not obesity reduced disc glycosaminoglycan and water contents, and these degenerative changes correlated with increased vertebral endplate thickness and decreased endplate porosity, and with higher levels of the advanced glycation end-product (AGE) pentosidine. Consistent with their diminished glycosaminoglycan and water contents and their higher AGE levels, discs from diabetic rats were stiffer and exhibited less creep when compressed. At the matrix level, elevated expression of hypoxia-inducible genes and catabolic markers in the discs from diabetic rats coincided with increased oxidative stress and greater interactions between AGEs and one of their receptors (RAGE). Taken together, these findings indicate that endplate sclerosis, increased oxidative stress and AGE/RAGE-mediated interactions could be important factors for explaining the greater incidence of disc pathology in T2D.
doi:10.1002/jor.22807
PMCID: PMC4408867  PMID: 25641259
intervertebral disc degeneration; type 2 diabetes; vertebral endplate; advanced glycation end-products; pentosidine
13.  Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high fructose corn syrup 
Our laboratory has investigated two hypotheses regarding the effects of fructose consumption: 1) The endocrine effects of fructose consumption favor a positive energy balance, and 2) Fructose consumption promotes the development of an atherogenic lipid profile. In previous short- and long-term studies, we demonstrated that consumption of fructose-sweetened beverages with 3 meals results in lower 24-hour plasma concentrations of glucose, insulin, and leptin in humans compared with consumption of glucose-sweetened beverages. We have also tested whether prolonged consumption of high-fructose diets could lead to increased caloric intake or decreased energy expenditure, thereby contributing to weight gain and obesity. Results from a study conducted in rhesus monkeys produced equivocal results. Carefully controlled and adequately powered long-term studies are needed to address these hypotheses. In both short- and long-term studies we demonstrated that consumption of fructose-sweetened beverages substantially increases postprandial triacylglycerol concentrations compared with glucose-sweetened beverages. In the long-term studies, apolipoproteinB concentrations were also increased in subjects consuming fructose, but not those consuming glucose. Data from a short-term study comparing consumption of beverages sweetened with fructose, glucose, high fructose corn syrup (HFCS) and sucrose, suggest that HFCS and sucrose increase postprandial triacylglycerol to an extent comparable to that induced by 100% fructose alone. Increased consumption of fructose-sweetened beverages along with increased prevalence of obesity, metabolic syndrome, and type 2 diabetes underscore the importance of investigating the metabolic consequences fructose consumption in carefully controlled experiments.
doi:10.3945/ajcn.2008.25825D
PMCID: PMC3037017  PMID: 19064538
Fructose; glucose; insulin; leptin; lipids; triacylglycerol; apolipoprotein-B
14.  Twenty-four Hour Endocrine and Metabolic Profiles Following Consumption of High Fructose Corn Syrup-, Sucrose- Fructose-, and Glucose-Sweetened Beverages with Meals 
Background
We have reported that compared with glucose-sweetened beverages, consuming fructose-sweetened beverages with meals results in lower 24-h circulating glucose, insulin and leptin concentrations, and elevated triacylglycerol (TG). However, pure fructose and glucose are not commonly used as sweeteners. High fructose corn syrup (HFCS) has replaced sucrose as the predominant sweetener in beverages in the U.S.
Objective
We compared the metabolic/endocrine effects of HFCS with sucrose, and in a subset of subjects with pure fructose and glucose.
Design
34 men and women consumed 3 isocaloric meals with either sucrose- or HFCS-sweetened beverages, and blood samples were collected over 24 hours. Eight of the male subjects were also studied when fructose- or glucose-sweetened beverages were consumed.
Results
In 34 subjects, 24-h glucose, insulin, leptin, ghrelin and TG profiles were similar between days that sucrose or HFCS were consumed. Postprandial TG excursions after HFCS or sucrose were larger in men than women. In the men in whom the effects of 4 sweeteners were compared, the 24-h glucose and insulin responses induced by HFCS and sucrose were intermediate between the lower responses during consumption of fructose and the higher responses during glucose. Unexpectedly, postprandial TG profiles after HFCS or sucrose were not intermediate, but comparably high as after pure fructose.
Conclusions
Sucrose and HFCS do not have substantially different short-term endocrine/metabolic effects. In male subjects, short-term consumption of sucrose and HFCS resulted in postprandial TG responses comparable to those induced by fructose.
PMCID: PMC3037416  PMID: 18469239
glucose; fructose; high fructose corn syrup; sucrose; insulin; leptin; ghrelin; triacylglycerol; free fatty acids; postprandial hypertriacylglycerolemia; humans
15.  Changes in Post-prandial Glucose and Pancreatic Hormones, and Steady-State Insulin and Free Fatty Acids after Gastric Bypass Surgery 
Background
Changes in the multiple mechanisms that regulate glucose metabolism after gastric bypass (RYGB) are still being unveiled.
Objective
To compare the changes of glucose and pancreatic hormones [C-peptide, glucagon and pancreatic polypeptide (PP)] during a meal test (MTT) and steady-state insulin and free fatty acid (FFA) concentrations during euglycemic–hyperinsulinemic clamp 14 days and 6 months after RYGB in morbidly obese non-diabetic patients.
Setting
Academic Medical Center, United States.
Methods
Two groups were studied at baseline and at 14 days: RYGB followed by caloric restriction (RYGB, n=12) or equivalent caloric restriction alone (Diet, n=10), to control for energy intake and weight loss. The RYGB group was studied again at 6 months, to assess the changes after substantial weight loss. During MTT we determined the early and overall changes in glucose and pancreatic hormone concentrations, and during the clamp we assessed steady-state insulin and FFA concentrations.
Results
After 14 days, RYGB subjects had enhanced post-prandial glucose, C-peptide and glucagon responses and decreased post-prandial PP concentrations. Steady-state insulin concentrations were decreased at 14 days only in RYGB subjects, and FFA increased in both groups. Six months after RYGB and substantial weight loss, the decrease in insulin concentrations during clamp persisted, and there were further changes in post-prandial glucose and glucagon responses. FFA concentrations during clamp were significantly lower at 6 months, relative to pre-surgical values.
Conclusions
RYGB produces, in morbidly obese non-diabetic patients, early changes in post-meal glucose, C-peptide, glucagon and PP responses, and appears to enhance insulin clearance early after RYGB and improve insulin sensitivity in adipose tissue at 6 months post-surgery. The early changes cannot be explained by caloric restriction alone.
doi:10.1016/j.soard.2013.07.010
PMCID: PMC3896512  PMID: 24209879
Gastric bypass; gut hormones; incretins; insulin resistance; free fatty acids; insulin clearance; hyperinsulinemic euglycemic clamp; bariatric surgery; C-peptide; glucagon; glucose; type 2 diabetes
16.  Adverse metabolic effects of dietary fructose: Results from recent epidemiological, clinical, and mechanistic studies 
Current opinion in lipidology  2013;24(3):198-206.
Purpose of review
The effects of dietary sugar on risk factors and processes associated with metabolic disease remains a controversial topic, with recent reviews of the available evidence arriving at widely discrepant conclusions.
Recent findings
There are many recently published epidemiological studies that provide evidence that sugar consumption is associated with metabolic disease. Three recent clinical studies, which investigated the effects of consuming relevant doses of sucrose or high fructose corn syrup along with ad libitum diets, provide evidence that consumption of these sugars increase risk factors for cardiovascular disease (CVD) and metabolic syndrome. Mechanistic studies suggest that these effects result from the rapid hepatic metabolism of fructose catalyzed by fructokinase C, which generates substrate for de novo lipogenesis and leads to increased uric acid levels. Recent clinical studies investigating the effects of consuming less sugar, via educational interventions or by substitution of sugar-sweetened beverages for non-calorically sweetened beverages, provide evidence that such strategies have beneficial effects on risk factors for metabolic disease or on BMI in children.
Summary
The accumulating epidemiological evidence, direct clinical evidence, and the evidence suggesting plausible mechanisms support a role for sugar in the epidemics of metabolic syndrome, CVD and type 2 diabetes.
doi:10.1097/MOL.0b013e3283613bca
PMCID: PMC4251462  PMID: 23594708
Fructose; sucrose; high fructose corn syrup; sugar; metabolic disease
17.  Low Prepregnancy Adiponectin Concentrations Are Associated With a Marked Increase in Risk for Development of Gestational Diabetes Mellitus 
Diabetes Care  2013;36(12):3930-3937.
OBJECTIVE
To examine whether circulating total and high–molecular weight (HMW) adiponectin concentrations, measured before pregnancy, are associated with subsequent risk of gestational diabetes mellitus (GDM).
RESEARCH DESIGN AND METHODS
This was a nested case-control study among women who participated in the Kaiser Permanente Northern California Multiphasic Health Check-up exam (1984–1996) with a serum sample obtained and who had a subsequent pregnancy (1984–2009). Eligible women were free of recognized diabetes. Case subjects were the 256 women who developed GDM. Two control subjects were selected for each case and matched for year of blood draw, age at exam, age at pregnancy, and number of intervening pregnancies.
RESULTS
Compared with the highest quartile of adiponectin, the risk of GDM increased with decreasing quartile (odds ratio [OR] 1.5 [95% CI 0.7–2.9], 3.7 [1.9–7.2], and 5.2 [2.6–10.1]; Ptrend <0.001) after adjustment for family history of diabetes, BMI, parity, race/ethnicity, cigarette smoking, and glucose and insulin concentrations. Similar estimates were observed for HMW (Ptrend <0.001). The combined effects of having total adiponectin levels below the median (<10.29 mg/mL) and being overweight or obese (BMI ≥25.0 kg/m2) were associated with a sevenfold increased risk of GDM compared with normal-weight women with adiponectin levels above the median (OR 6.7 [95% CI 3.6–12.5]).
CONCLUSIONS
Prepregnancy low adiponectin concentrations, a marker of decreased insulin sensitivity and altered adipocyte endocrine function, is associated with reduced glucose tolerance during pregnancy and may identify women at high risk for GDM to target for early intervention.
doi:10.2337/dc13-0389
PMCID: PMC3836148  PMID: 23990523
18.  Maternal ileal interpostion surgery confers metabolic improvements to offspring independent of effects on maternal body weight in UCD-T2DM rats 
Obesity surgery  2013;23(12):10.1007/s11695-013-1076-y.
Introduction
Increasing numbers of people are undergoing bariatric surgery, of which approximately half are women in their child-bearing years. However, information on the long-term effects of maternal bariatric surgery in their children is lacking. Furthermore, since bariatric surgery is performed to reduce body weight, clinical studies have not been able to differentiate between benefits to the child due to maternal body weight loss versus other maternal postoperative metabolic changes. Therefore, we used the UCD-T2DM rat model of type 2 diabetes to test the hypothesis that maternal ileal interposition (IT) surgery would confer beneficial metabolic effects in offspring, independent of effects on maternal body weight.
Materials and Methods
IT surgery was performed on 2-month old prediabetic female UCD-T2DM rats. Females were bred 3 weeks after surgery and male pups were studied longitudinally.
Results
Maternal IT surgery resulted in decreased body weight in offspring compared with sham offspring (P<0.05). IT offspring exhibited improvements of glucose-stimulated insulin secretion and nutrient-stimulated GLP-2 secretion (P<0.05). Fasting plasma unconjugated bile acid concentrations were 4-fold lower in IT offspring compared with sham offspring at two months of age (P<0.001).
Conclusion
Overall, maternal IT surgery confers modest improvements of body weight and improves insulin secretion and nutrient-stimulated GLP-2 secretion in offspring in the UCD-T2DM rat model of type 2 diabetes, indicating that this is a useful model for investigating the weight-independent metabolic effects of maternal bariatric surgery.
doi:10.1007/s11695-013-1076-y
PMCID: PMC3855031  PMID: 24036841
19.  The good, the bad, and the unknown: Fructose and FGF21☆ 
Molecular Metabolism  2014;4(1):1-2.
doi:10.1016/j.molmet.2014.11.002
PMCID: PMC4314528  PMID: 25685684
20.  Evidence for novel genetic loci associated with metabolic traits in Yup’ik people 
Objectives:
To identify genomic regions associated with fasting plasma lipid profiles, insulin, glucose, and glycosylated hemoglobin in a Yup’ik study population, and to evaluate whether the observed associations between genetic factors and metabolic traits were modified by dietary intake of marine derived omega-3 polyunsaturated acids (n-3 PUFA).
Methods:
A genome-wide linkage scan was conducted among 982 participants of the Center for Alaska Native Health Research study. n-3 PUFA intake was estimated using the nitrogen stable isotope ratio (δ15N) of erythrocytes. All genotyped SNPs located within genomic regions with LOD scores > 2 were subsequently tested for individual SNP associations with metabolic traits using linear models that account for familial correlation as well as age, sex, community group and n-3 PUFA intake. Separate linear models were fit to evaluate interactions between the genotype of interest and n-3 PUFA intake.
Results:
We identified several chromosomal regions linked to serum apolipoprotein A2, high density lipoprotein-, low density lipoprotein-, and total cholesterol, insulin, and glycosylated hemoglobin. Genetic variants found to be associated with total cholesterol mapped to a region containing previously validated lipid loci on chromosome 19, and additional novel peaks of biological interest were identified at 11q12.2-11q13.2. We did not observe any significant interactions between n-3 PUFA intake, genotypes, and metabolic traits.
Conclusions:
We have completed a whole genome linkage scan for metabolic traits in Native Alaskans, confirming previously identified loci, and offering preliminary evidence of novel loci implicated in chronic disease pathogenesis in this population.
doi:10.1002/ajhb.22429
PMCID: PMC3785243  PMID: 23907821
Alaska Native; metabolism; multi-point linkage genome scan
21.  Leptin concentrations in response to acute stress predict subsequent intake of comfort foods 
Physiology & behavior  2012;107(1):34-39.
Both animals and humans show a tendency toward eating more “comfort food” (high fat, sweet food) after acute stress. Such stress eating may be contributing to the obesity epidemic, and it is important to understand the underlying psychobiological mechanisms. Prior investigations have studied what makes individuals eat more after stress; this study investigates what might make individuals eat less. Leptin has been shown to increase following a laboratory stressor, and is known to affect eating behavior. This study examined whether leptin reactivity accounts for individual differences in stress eating. To test this, we exposed forty women to standardized acute psychological laboratory stress (Trier Social Stress Test) while blood was sampled repeatedly for measurements of plasma leptin. We then measured food intake after the stressor in 29 of these women. Increasing leptin during the stressor predicted lower intake of comfort food. These initial findings suggest that acute changes in leptin may be one of the factors modulating down the consumption of comfort food following stress.
doi:10.1016/j.physbeh.2012.04.021
PMCID: PMC3409346  PMID: 22579988
22.  Isotopic estimates of sugar intake are related to chronic disease risk factors but not obesity in an Alaska Native (Yup’ik) study population 
Background
Sugar intake may be causally associated with chronic disease risk, either directly or by contributing to obesity. However, evidence from observational studies is mixed, in part due to the error and bias inherent in self-reported measures of sugar intake. Objective biomarkers may clarify the relationship between sugar intake and chronic disease risk. We have recently validated a biomarker of sugar intake in an Alaska Native (Yup’ik) study population that incorporates red blood cell carbon and nitrogen isotope ratios in a predictive model.
Objective
This study tested associations of isotopic estimates of sugar intake with BMI, waist circumference (WC), and a broad array of other physiological and biochemical measures of chronic disease risk in Yup’ik people.
Subjects/Methods
In a cross-sectional sample of 1076 Yup’ik people, multiple linear regression was used to examine associations of sugar intake with BMI, WC and other chronic disease risk factors.
Results
Isotopic estimates of sugar intake were not associated with BMI (P = 0.50) or WC (P = 0.85). They were positively associated with blood pressure, triglycerides, and leptin, and inversely associated with total-, HDL- and LDL-cholesterol and adiponectin.
Conclusions
Isotopic estimates of sugar intake were not associated with obesity, but were adversely associated with other chronic disease risk factors in this Yup’ik study population. This first use of stable isotope markers of sugar intake may influence recommendations for sugar intake by Yup’ik people; however, longitudinal studies are required to understand associations with chronic disease incidence.
doi:10.1038/ejcn.2013.230
PMCID: PMC3947290  PMID: 24219893
Isotopes; carbon; Isotopes; nitrogen; Chronic disease; Risk factors; Caloric sweeteners
23.  Effects of Sugar-sweetened Beverages on plasma Acylation Stimulating Protein, Leptin & Adiponectin and Metabolic Parameters 
Obesity (Silver Spring, Md.)  2013;21(12):10.1002/oby.20437.
Objective
We determined the effects of fructose and glucose consumption on plasma acylation stimulating protein (ASP), adiponectin, and leptin concentrations relative to energy intake, body weight, adiposity, circulating triglycerides, and insulin sensitivity.
Design and Methods
32 overweight/obese adults consumed glucose- or fructose-sweetened beverages (25% energy requirement) with their ad libitum diets for 8 weeks, followed by sweetened beverage consumption for 2 weeks with a standardized, energy-balanced diet. Plasma variables were measured at baseline, 2, 8 and 10 weeks, and body adiposity and insulin sensitivity at baseline and 10 weeks.
Results
Fasting and postprandial ASP concentrations increased at 2 and/or 8 weeks. ASP increases correlated with changes in late-evening triglyceride concentrations. At 10 weeks, fasting adiponectin levels decreased in both groups, and decreases were inversely associated with baseline intra-abdominal fat volume. Sugar consumption increased fasting leptin concentrations; increases were associated with body weight changes. 24-h leptin profiles increased during glucose consumption and decreased during fructose consumption. These changes correlated with changes of 24-h insulin levels.
Conclusions
The consumption of fructose and glucose beverages induced changes in plasma concentrations of ASP, adiponectin and leptin. Further study is required to determine if these changes contribute to the metabolic dysfunction observed during fructose consumption.
doi:10.1002/oby.20437
PMCID: PMC3732502  PMID: 23512943
fructose; glucose; obesity; acylation stimulating protein; leptin; adiponectin
24.  Chronic Administration of the Glucagon-Like Peptide-1 Analog, Liraglutide, Delays the Onset of Diabetes and Lowers Triglycerides in UCD-T2DM Rats 
Diabetes  2010;59(10):2653-2661.
OBJECTIVE
The efficacy of liraglutide, a human glucagon-like peptide-1 (GLP-1) analog, to prevent or delay diabetes in UCD-T2DM rats, a model of polygenic obese type 2 diabetes, was investigated.
RESEARCH DESIGN AND METHODS
At 2 months of age, male rats were divided into three groups: control, food-restricted, and liraglutide. Animals received liraglutide (0.2 mg/kg s.c.) or vehicle injections twice daily. Restricted rats were food restricted to equalize body weights to liraglutide-treated rats. Half of the animals were followed until diabetes onset, whereas the other half of the animals were killed at 6.5 months of age for tissue collection.
RESULTS
Before diabetes onset energy intake, body weight, adiposity, and liver triglyceride content were higher in control animals compared with restricted and liraglutide-treated rats. Energy-restricted animals had lower food intake than liraglutide-treated animals to maintain the same body weights, suggesting that liraglutide increases energy expenditure. Liraglutide treatment delayed diabetes onset by 4.1 ± 0.8 months compared with control (P < 0.0001) and by 1.3 ± 0.8 months compared with restricted animals (P < 0.05). Up to 6 months of age, energy restriction and liraglutide treatment lowered fasting plasma glucose and A1C concentrations compared with control animals. In contrast, liraglutide-treated animals exhibited lower fasting plasma insulin, glucagon, and triglycerides compared with both control and restricted animals. Furthermore, energy-restricted and liraglutide-treated animals exhibited more normal islet morphology.
CONCLUSIONS
Liraglutide treatment delays the development of diabetes in UCD-T2DM rats by reducing energy intake and body weight, and by improving insulin sensitivity, improving lipid profiles, and maintaining islet morphology.
doi:10.2337/db09-1564
PMCID: PMC3279561  PMID: 20622169
25.  Ileal Interposition Surgery Improves Glucose and Lipid Metabolism and Delays Diabetes Onset in the UCD-T2DM Rat 
Gastroenterology  2010;138(7):2437-2446.e1.
Background & Aims
Bariatric surgery has been shown to reverse type 2 diabetes, however the mechanisms by which this occurs remain undefined. Ileal interposition (IT) is a surgical model that isolates the effects of increasing the delivery of unabsorbed nutrients to the lower gastrointestinal tract. In this study we investigated the effects of IT surgery on glucose tolerance and diabetes onset in UCD-T2DM rats, a polygenic obese animal model of type 2 diabetes.
Methods
IT or sham surgery was performed on 4 month old male UCD-T2DM rats. All animals underwent an oral glucose tolerance test (OGTT). A subset was euthanized 2 months after surgery for tissue analyses. The remainder was followed until diabetes onset and underwent an oral fat tolerance test (OFTT).
Results
IT surgery delayed diabetes onset by 120 ± 49 days compared with sham surgery (P< 0.05) without a difference in body weight. During OGTT, IT-operated animals exhibited lower plasma glucose excursions (P< 0.05), improved early insulin secretion (P< 0.01) and 3-fold larger plasma GLP-17–36 excursions (P< 0.001) and no difference in GIP responses compared with sham-operated animals. Total plasma PYY excursions during the OFTT were 3-fold larger in IT-operated animals (P< 0.01). IT-operated animals exhibited lower adiposity (P< 0.05), smaller adipocyte size (P< 0.05), 25% less ectopic lipid deposition, lower circulating lipids and greater pancreatic insulin content compared with sham-operated animals (P< 0.05).
Conclusions
IT surgery delays the onset of diabetes in UCD-T2DM rats which may be related to increased nutrient-stimulated secretion of GLP-17–36 and PYY and improvements of insulin sensitivity, β-cell function and lipid metabolism.
doi:10.1053/j.gastro.2010.03.005
PMCID: PMC2883638  PMID: 20226188
Bariatric surgery; diabetes prevention; glucagon-like peptide-1; peptide-YY

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