Glucose Metabolism In Obesity Research Articles

CerS6-dependent ceramide synthesis in hypothalamic neurons promotes ER/mitochondrial stress and impairs glucose homeostasis in obese mice

Dysregulation of hypothalamic ceramides has been associated with disrupted neuronal pathways in control of energy and glucose homeostasis. However, the specific ceramide species promoting neuronal lipotoxicity in obesity have remained obscure. Here, we find increased expression of the C16:0 ceramide-producing ceramide synthase (CerS)6 in cultured hypothalamic neurons exposed to palmitate in vitro and in the hypothalamus of obese mice. Conditional deletion of CerS6 in hypothalamic neurons attenuates high-fat diet (HFD)-dependent weight gain and improves glucose metabolism. Specifically, CerS6 deficiency in neurons expressing pro-opiomelanocortin (POMC) or steroidogenic factor 1 (SF-1) alters feeding behavior and alleviates the adverse metabolic effects of HFD feeding on insulin sensitivity and glucose tolerance. POMC-expressing cell-selective deletion of CerS6 prevents the diet-induced alterations of mitochondrial morphology and improves cellular leptin sensitivity. Our experiments reveal functions of CerS6-derived ceramides in hypothalamic lipotoxicity, altered mitochondrial dynamics, and ER/mitochondrial stress in the deregulation of food intake and glucose metabolism in obesity.

Albumin Deficiency Reduces Hepatic Steatosis and Improves Glucose Metabolism in a Mouse Model of Diet-Induced Obesity.

Serum albumin facilitates the transport of free fatty acids (FFAs) from adipose tissue to other organs. It was not known if impeding this process could protect from hepatic steatosis and metabolic dysfunction in obesity. We tested whether albumin knockout (Alb-/-) mice would exhibit a reduction in plasma FFA concentration, reduced hepatic lipid accumulation, and improved glucoregulation as compared to wild-type (WT) mice. Male homozygous albumin knockout mice (Alb-/-) and WT controls were fed a low-fat diet (LFD) or high-fat diet (HFD). Alb-/- mice exhibited a similar body weight gain and body composition as WT on both diets. Despite HFD-induced obesity, Alb-/- mice were protected from various comorbidities. Compared to WT mice on the HFD, Alb-/- exhibited lower plasma FFA levels, lower blood glucose levels during glucose tolerance and insulin tolerance tests, and lower hepatic steatosis and inflammation. Alb-/- mice on HFD also exhibited elevated expression of multiple genes in the liver and adipose tissues, such as peroxisome proliferator-activated receptor α in both tissues, as well as glucose transporter-4 and adiponectin in adipose tissues. The results indicate that albumin's FFA transport function may be involved in the development of hepatic lipid accumulation and dysregulated glucose metabolism in obesity.

Orexin receptors 1 and 2 in serotonergic neurons differentially regulate peripheral glucose metabolism in obesity

The wake-active orexin system plays a central role in the dynamic regulation of glucose homeostasis. Here we show orexin receptor type 1 and 2 are predominantly expressed in dorsal raphe nucleus-dorsal and -ventral, respectively. Serotonergic neurons in ventral median raphe nucleus and raphe pallidus selectively express orexin receptor type 1. Inactivation of orexin receptor type 1 in serotonin transporter-expressing cells of mice reduced insulin sensitivity in diet-induced obesity, mainly by decreasing glucose utilization in brown adipose tissue and skeletal muscle. Selective inactivation of orexin receptor type 2 improved glucose tolerance and insulin sensitivity in obese mice, mainly through a decrease in hepatic gluconeogenesis. Optogenetic activation of orexin neurons in lateral hypothalamus or orexinergic fibers innervating raphe pallidus impaired or improved glucose tolerance, respectively. Collectively, the present study assigns orexin signaling in serotonergic neurons critical, yet differential orexin receptor type 1- and 2-dependent functions in the regulation of systemic glucose homeostasis.

Gut Microbiota of Chinese Obese Children and Adolescents With and Without Insulin Resistance.

ObjectiveThe intestinal flora of gut microbiota in obese Chinese children and adolescents with and without insulin resistance (IR) was analyzed, as well as associations between the gut microbiota and two serum cytokines related to glucose metabolism, adropin and angiopoietin-like 4 (ANGPTL4).MethodsClinical data, fecal bacterial composition, glucose-related hormones, and serum adipokines (adropin and ANGPTL4) were analyzed in 65 Chinese children with exogenous obesity. The composition of the gut microbiota was determined by 16S rRNA-based metagenomics and IR was calculated using the homeostasis model assessment (HOMA).ResultsThe 65 obese subjects were divided into two groups: insulin sensitive (IS) (n=40, 57.5% males) or IR (n=25, 60% males). Principal coordinates analysis revealed that the gut microbiota samples from the IS group clustered together and separated partly from the IR group (p=0.008). By Mann-Whitney U-test, at a phylum level, a reduction of Firmicutes and an increase of Bacteroidetes in the IR subjects was observed. LEfSe analysis revealed that IS subject, when compared to their IR counterparts, harbored members of the order Coriobacteriales, Turicibacterales, Pasteurellales and family Turicibacteraceae, that were significantly more abundant. In contrast, the IR subjects had members of family Peptococcaceae that were significantly more prevalent than the IS subjects (all p<0.05). Spearman’s correlation analysis revealed that serum ANGPTL4 was positively associated with genus Bacteroides, Butyricimonas, and Alistipes, and adropin was positively associated with genus Anaerostipes and Alistipes, and negatively associated with genus Blautia (all p<0.05).ConclusionIn obese children, the gut microbiome in IR subjects was significantly discordant from the IS subjects, and the abundance of some metabolism-related bacteria correlated with the serum concentrations of adropin and ANGPTL4. These observations infer that the gut microbiota may be involved in the regulation of glucose metabolism in obesity.

Exercise retards ongoing adipose tissue fibrosis in diet-induced obese mice.

Exercise has been recommended as an important strategy to improve glucose metabolism in obesity. Adipose tissue fibrosis is associated with inflammation and is implicated in glucose metabolism disturbance and insulin resistance in obesity. However, the effect of exercise on the progression of adipose tissue fibrosis is still unknown. The aim of the present study was to investigate whether exercise retarded the progression of adipose tissue fibrosis and ameliorated glucose homeostasis in diet-induced obese mice. To do so, obesity and adipose tissue fibrosis in mice were induced by high-fat diet feeding for 12 weeks and the mice subsequently received high-fat diet and exercise intervention for another 12 weeks. Exercise alleviated high-fat diet-induced glucose intolerance and insulin resistance. Continued high-fat diet feeding exacerbated collagen deposition and further increased fibrosis-related gene expression in adipose tissue. Exercise attenuated or reversed these changes. Additionally, PPARγ, which has been shown to inhibit adipose tissue fibrosis, was observed to be increased following exercise. Moreover, exercise decreased the expression of HIF-1α in adipose fibrosis, and adipose tissue inflammation was inhibited. In conclusion, our data indicate that exercise attenuates and even reverses the progression of adipose tissue fibrosis, providing a plausible mechanism for its beneficial effects on glucose metabolism in obesity.

Insulin-Stimulated Muscle Glucose Uptake and Insulin Signaling in Lean and Obese Humans.

Skeletal muscle is the primary site for insulin-stimulated glucose disposal, and muscle insulin resistance is central to abnormal glucose metabolism in obesity. Whether muscle insulin signaling to the level of Akt/AS160 is intact in insulin-resistant obese humans is controversial. We defined a linear range of insulin-stimulated systemic and leg glucose uptake in 14 obese and 14 nonobese volunteers using a 2-step insulin clamp (Protocol 1) and then examined the obesity-related defects in muscle insulin action in 16 nonobese and 25 obese male and female volunteers matched for fitness using a 1-step, hyperinsulinemic, euglycemic clamp coupled with muscle biopsies (Protocol 2). Insulin-stimulated glucose disposal (Si) was reduced by > 60% (P < 0.0001) in the obese group in Protocol 2; however, the phosphorylation of Akt and its downstream effector AS160 were not different between nonobese and obese groups. The increase in phosphorylation of Akt2 in response to insulin was positively correlated with Si for both the nonobese (r = 0.53, P = 0.03) and the obese (r = 0.55, P = 0.01) groups. Total muscle GLUT4 protein was 17% less (P < 0.05) in obese subjects. We suggest that reduced muscle glucose uptake in obesity is not due to defects in the insulin signaling pathway at the level of Akt/AS160, which suggests there remain significant gaps in our knowledge of muscle insulin resistance in obesity. Our data imply that models of acute lipotoxicity do not replicate the pathophysiology of obesity.

187-OR: Gut Microbiota Regulate Pancreatic Growth, Exocrine Function, and Gut Hormones

Growing evidence suggests a link between alterations in gut microbiota, diabetes, and metabolic syndrome. We recently showed that treatment with antibiotics to alter gut microbiota could improve insulin signaling and glucose metabolism in obesity- and diabetes-prone C57BL/6J mice on high-fat diet (HFD). This occurred in part through changing metabolite composition in plasma and decreasing adipose tissue inflammation. We also showed that these changes could be induced in germ-free mice by transferring the gut microbiota. It is known that diabetes is associated with exocrine pancreatic dysfunction, and diseases of the exocrine pancreas can be associated with diabetes. To explore the role of gut microbiota on host pancreatic exocrine function and its crosstalk with the endocrine system, mice were given either normal chow or HFD, or HFD and treatment with vancomycin or metronidazole. As expected, HFD alone produced signs of metabolic syndrome but also increased total pancreas weight by ~20%, an amount that could not be explained by islet hyperplasia. Analysis of the fecal proteome of these mice identified 138 host proteins of which 32 changed with either HFD or antibiotic treatment. Notably, the most significantly changed proteins by diet and altered microbiome were pancreatic enzymes: amylase, lipase and elastase. Furthermore, the plasma levels of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) levels were decreased, while glucose-dependent insulinotropic peptide (GIP) was increased by the HFD. These alterations of pancreas growth, acinar cell hyperplasia, exocrine pancreas function, and hormone secretion were reversed by antibiotic treatment of the host. These changes could also be reproduced in germ free mice by transfer of gut microbiota. Together, these data indicate that gut microbiota can regulate pancreatic growth and both exocrine and endocrine function. Better understanding pancreas-gut microbiome crosstalk can help us develop probiotics to cure pancreas dysfunction in diabetes. Disclosure E. Altindis: None. M. Soto: Employee; Self; LNC Therapeutics. Other Relationship; Self; biomeostasis. L. Orliaguet: None. Q. Huang: None. C. Cederquist: None. E. Dirice: None. S. Fujisaka: None. J. Hu: None. R. Kulkarni: None. C. Kahn: Advisory Panel; Self; MedImmune. Board Member; Self; Kaleido Biosciences. Consultant; Self; AntriaBio, Inc., Cobalt Therapeutics, Flagship Pioneering. Research Support; Self; Alnylam. Funding National Institutes of Health

STUDY OF RELATIONSHIP BETWEEN THE PROTEIN OXIDATION MARKERS AND ADIPOKINES IN OBESE TYPE 2 DIABETIC PATIENTS

Objective: This study was done to explore the correlation if any, between obesity markers adiponectin, leptin, and protein oxidative stress (OS) status in obese with and without type 2 diabetic mellitus (T2DM) patients.&#x0D; Methods: In the present study, 30 healthy subjects, 30 obese non-diabetics, and 30 obese T2DM patients were enrolled. Protein OS parameters such as advanced oxidation of protein products (AOPPs) and protein carbonyl (PC) were estimated. Serum leptin, adiponectin, and insulin levels were measured by ELISA.&#x0D; Results: The AOPP, PC, leptin, leptin adiponectin ratio (LAR), insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) levels were significantly higher in obese non-diabetic and obese T2DM as compared to healthy control (p&lt;0.001). However, serum adiponectin levels were significantly lower in obese non-diabetic and obese T2DM as compared to control (p&lt;0.001). HOMA-IR and LAR both the index of IR were increased in obese non-diabetic and obese T2DM. Positive correlations were observed for AOPP with body mass index, PC in obese non-diabetic and with fasting blood glucose, postprandial blood glucose, HOMA-IR, and PC in obese T2DM. A negative correlation was found between PC and adiponectin in obese non-diabetic and obese T2DM. A significant inverse correlation was obtained between leptin and adiponectin in obese T2DM only.&#x0D; Conclusion: The present study suggested that increased protein OS, hyperinsulinemia, and hyperleptinemia may lead to hypoadiponectinemia in obese with and without T2DM. Moreover, determination of protein oxidation markers can be useful for monitoring the dysregulation of adipokines and glucose metabolism in obesity and T2DM.

Erythropoietin and long-acting erythropoiesis stimulating agent ameliorate non-alcoholic fatty liver disease by increasing lipolysis and decreasing lipogenesis via EPOR/STAT pathway

Erythropoietin (EPO) has been reported to exert a beneficial effect on glucose metabolism in obesity. However, the effect of EPO on lipid metabolism and non-alcoholic fatty liver disease (NAFLD) was unclear. Furthermore, the effect of long acting erythropoiesis stimulating agents (ESA) on metabolism has not been poorly understood. The objective of this study was to investigate the effect of EPO and long acting ESA on NAFLD and lipid metabolism. We administered EPO and darbepoetin alpha (DEPO), a long acting ESA, by intraperitoneally injection for 4 weeks to mice with high-fat-diet (HFD)-induced obesity. EPO and DEPO treatment reduced body weight, ameliorated glucose tolerance and insulin resistance, and prevented lipid accumulation in liver and white adipose tissue (WAT). Administration of EPO and DEPO suppressed lipid synthesis-related protein in liver, including sterol regulatory element-binding protein 1 (SREBP-1), acetyl-CoA carboxylase (ACC1) and fatty acid synthase (FAS). EPO and DEPO also increased lipolysis protein in visceral WAT, including hormone-sensitive lipase (HSL), atni-adipose triglyceride lipase (ATGL). EPO and DEPO increased phosphorylation signal transducer and activator of transcription 3 (STAT3) and STAT5, transcriptional factors with crucial roles of lipid metabolism. These data suggest that EPO and DEPO ameliorated NAFLD by improving lipid metabolism via EPO/EPOR-induced STAT3 and STAT5 activation. EPO and DEPO may be a therapeutic option for NAFLD.

(-)-Epigallocatechin-3-gallate (EGCG) inhibits starch digestion and improves glucose homeostasis through direct or indirect activation of PXR/CAR-mediated phase II metabolism in diabetic mice.

As a major component of green tea, (-)-epigallocatechin-3-gallate (EGCG) has attracted interest from scientists owing to its potential to combat a variety of human diseases including abnormal glucose metabolism in obesity and diabetes. This study aims to (1) evaluate the molecular mechanism of EGCG in starch digestion before EGCG absorption; (2) investigate the link between PXR/CAR-mediated phase II metabolism and glucose homeostasis after EGCG is transported to small intestine and liver. EGCG suppressed starch hydrolysis both in vitro and in vivo. Molecular simulation results demonstrated that EGCG could bind to the active site of α-amylase and α-glucosidase, acting as an inhibitor. In addition, the anti-diabetic action of EGCG was investigated in high fat diet and STZ-induced type 2 diabetes. EGCG improved glucose homeostasis and inhibited the process of gluconeogenesis (PEPCK and G-6-Pase) and lipogenesis (SREBP-1C, FAS and ACC1) in the liver. Meanwhile, EGCG treatment activated PXR/CAR, accompanied by upgrading PXR/CAR-mediated phase II drug metabolism enzyme expression in small intestine and liver, involving SULT1A1, UGT1A1 and SULT2B1b. Dietary polyphenol EGCG could serve as a promising PXR/CAR activator and therapeutic intervention in diabetes.

OP-29 - Brain glucose metabolism in obesity

OP-29 - Brain glucose metabolism in obesity

Antibiotic effects on gut microbiota and metabolism are host dependent.

Interactions of diet, gut microbiota, and host genetics play important roles in the development of obesity and insulin resistance. Here, we have investigated the molecular links between gut microbiota, insulin resistance, and glucose metabolism in 3 inbred mouse strains with differing susceptibilities to metabolic syndrome using diet and antibiotic treatment. Antibiotic treatment altered intestinal microbiota, decreased tissue inflammation, improved insulin signaling in basal and stimulated states, and improved glucose metabolism in obesity- and diabetes-prone C57BL/6J mice on a high-fat diet (HFD). Many of these changes were reproduced by the transfer of gut microbiota from antibiotic-treated donors to germ-free or germ-depleted mice. These physiological changes closely correlated with changes in serum bile acids and levels of the antiinflammatory bile acid receptor Takeda G protein-coupled receptor 5 (TGR5) and were partially recapitulated by treatment with a TGR5 agonist. In contrast, antibiotic treatment of HFD-fed, obesity-resistant 129S1 and obesity-prone 129S6 mice did not improve metabolism, despite changes in microbiota and bile acids. These mice also failed to show a reduction in inflammatory gene expression in response to the TGR5 agonist. Thus, changes in bile acid and inflammatory signaling, insulin resistance, and glucose metabolism driven by an HFD can be modified by antibiotic-induced changes in gut microbiota; however, these effects depend on important interactions with the host's genetic background and inflammatory potential.

A high fat diet induces sex-specific differences in hepatic lipid metabolism and nitrite/nitrate in rats

Men and women differ substantially with regard to the severity of insulin resistance (IR) but the underlying mechanism(s) of how this occurs is poorly characterized. We investigated whether a high fat (HF) diet resulted in sex-specific differences in nitrite/nitrate production and lipid metabolism and whether these variances may contribute to altered obesity-induced IR.Male and female Wistar rats were fed a standard laboratory diet or a HF diet for 10 weeks. The level of plasma nitrite/nitrate, as well as free fatty acid (FFA), in both plasma and liver lysates were assessed. The levels of inducible nitric oxide (NO) synthase (iNOS), p65 subunit of NFκB, total and phosphorylated forms of Akt, mTOR and PDK-1 in lysates, and the levels of glucose transporter 2 (Glut-2) and fatty acid translocase/cluster of differentiation 36 (FAT/CD36) in plasma membrane fractions of liver were assessed.HF-fed male rats exhibited a significant increase in plasma nitrite/nitrate, and hepatic FFA and FAT/CD36 levels compared with controls. They also displayed a relative decrease in iNOS and Glut-2 levels in the liver. Phosphorylation of Akt (at Ser473 and Thr308), mTOR and PDK-1 was also reduced. HF-fed female rats exhibited increased levels of NFκB-p65 in liver compared with controls, while levels of Glut-2, FAT/CD36 and Akt phosphorylation at Thr308 and PDK-1 were decreased.Our results reveal that altered lipid and glucose metabolism in obesity, lead to altered iNOS expression and nitrite/nitrate production. It is likely that this mechanism contributes to sex-specific differences in the development of IR.

Failure of hyperglycemia and hyperinsulinemia to compensate for impaired metabolic response to an oral glucose load

ObjectiveTo evaluate whether the augmented insulin and glucose response to a glucose challenge is sufficient to compensate for defects in glucose utilization in obesity and type 2 diabetes, using a breath test measurement of integrated glucose metabolism. MethodsNon-obese, obese normoglycemic and obese type 2 diabetic subjects were studied on 2 consecutive days. A 75g oral glucose load spiked with 13C-glucose was administered, measuring exhaled breath 13CO2 as an integrated measure of glucose metabolism and oxidation. A hyperinsulinemic euglycemic clamp was performed, measuring whole body glucose disposal rate. Body composition was measured by DEXA. Multivariable analyses were performed to evaluate the determinants of the breath 13CO2. ResultsBreath 13CO2 was reduced in obese and type 2 diabetic subjects despite hyperglycemia and hyperinsulinemia. The primary determinants of breath response were lean mass, fat mass, fasting FFA concentrations, and OGTT glucose excursion. Multiple approaches to analysis showed that hyperglycemia and hyperinsulinemia were not sufficient to compensate for the defect in glucose metabolism in obesity and diabetes. ConclusionsAugmented insulin and glucose responses during an OGTT are not sufficient to overcome the underlying defects in glucose metabolism in obesity and diabetes.

Oral salmon calcitonin enhances insulin action and glucose metabolism in diet-induced obese streptozotocin-diabetic rats

We previously reported that oral delivery of salmon calcitonin (sCT) improved energy and glucose homeostasis and attenuated diabetic progression in animal models of diet-induced obesity (DIO) and type 2 diabetes, although the glucoregulatory mode of action was not fully elucidated. In the present study we hypothesized that oral sCT as pharmacological intervention 1) exerted anti-hyperglycemic efficacy, and 2) enhanced insulin action in DIO-streptozotocin (DIO-STZ) diabetic rats. Diabetic hyperglycemia was induced in male selectively bred DIO rats by a single low dose (30mg/kg) injection of STZ. Oral sCT by gavage was delivered as once-daily administration with lead-in (2mg/kg) and maintenance (0.5mg/kg) dose of oral sCT for a total of 21 days. Food intake, body weight, blood glucose, HbA1c, glucose and insulin tolerance test, and parameters of insulin sensitivity were investigated. Plasma glucoregulatory hormones and pancreatic insulin content were analyzed. Oral sCT treatment induced a pronounced anorectic action during the 7 days lead-in period and markedly reduced food intake and body weight in conjunction with improved glucose homeostasis. During the maintenance period, oral sCT normalized food intake and attenuated weight loss, albeit sustained glycemic control by reducing fasting blood glucose and HbA1c levels compared to those of vehicle-treated rats at the end of study. Notably, plasma levels of insulin, glucagon, leptin and adiponectin were unaltered, albeit insulin action was enhanced in conjunction with protection of pancreatic insulin content. The results of the present study indicate that oral sCT exerts a novel insulin-sensitizing effect to improve glucose metabolism in obesity and type 2 diabetes.

Advanced oxidation protein products in obese women: its relation to insulin resistance and resistin

Obesity is a major risk factor for insulin resistance and type 2 diabetes mellitus (T2DM). Resistin, an adipocyte-secreted hormone, is thought to take a part in the development of insulin resistance and T2DM. The aim of this study was to characterise the changes in circulating levels of resistin and proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 in diabetic and prediabetic obese patients and to explore their relationship to insulin resistance. Attempts were also made to see whether resistin levels are related to the degree of oxidative stress, as determined by the measurement of advanced oxidation protein products (AOPPs). The study groups consisted of obese diabetic (BMI: 30-42 kg/m(2), n=28) and prediabetic (BMI: 29-41 kg/m(2), n=23) women. Fourteen healthy women, with BMI in the range 21.5-25.5 kg/m(2), were taken as controls. Serum levels of TNF-a, IL-6, resistin, glucose, insulin and AOPPs were measured. Insulin resistance was calculated by the homeostasis model assessment (HOMA-IR). Diabetic and prediabetic obese patients had increases in serum resistin and TNF-alpha levels (P<0.01 and P<0.001, respectively). IL-6 levels in diabetic patients were significantly higher than in prediabetics (P<0.05). AOPP levels were also significantly higher in diabetics than prediabetics and controls (P<0.05 and P<0.001, respectively); and positively correlated with blood glucose. Insulin was significantly associated with circulating resistin and TNF-alpha. The development of insulin resistance may contribute to the elevation of circulating resistin or vice versa. Determination of AOPPs may be helpful for monitoring the impaired glucose metabolism in obesity.

Abnormal Lipid and Glucose Metabolism in Obesity: Implications for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease represents a spectrum of histopathologic abnormalities, the prevalence of which may be as high as 24% of the population of the United States. Nonalcoholic fatty liver disease will play a major role in the science and practice of gastroenterology in the near future. The fundamental derangement in nonalcoholic fatty liver disease is insulin resistance, a key component of the metabolic syndrome, which includes type 2 diabetes mellitus, hypertriglyceridemia, essential hypertension, low circulating high-density lipoprotein, and obesity. The natural history of fatty liver disease is not always benign, and causality for cirrhosis and chronic liver disease is well-founded in the literature. Treatment strategies are limited and, at present, are primarily focused on weight loss and use of insulin sensitizing agents, including the thiazolidenediones. Recent data clearly implicate hepatic insulin resistance as a culprit in accumulation of free fatty acids as triglycerides in hepatocytes. Hepatic insulin resistance is clearly exacerbated by systemic insulin resistance and impaired handling by skeletal muscle and adipose tissue of both glucose and free fatty acids. The key consequence of hepatic insulin resistance, impaired hepatocyte insulin signal transduction, results in adverse cellular and molecular changes exacerbating hepatocyte triglyceride storage. Cytokines secreted by white adipose tissue, adipokines, have emerged as key players in glucose and fat metabolism previously thought controlled largely by insulin. Modulation of adipokines may aid in further understanding of the pathophysiology and treatment of nonalcoholic fatty liver disease.

Regarding “Selection and Recall Bias in a Case–Control Study of Lifetime Alcohol Intake and Breast Cancer Risk”

We previously reported that oral delivery of salmon calcitonin (sCT) improved energy and glucose homeostasis and attenuated diabetic progression in animal models of diet-induced obesity (DIO) and type 2 diabetes, although the glucoregulatory mode of action was not fully elucidated. In the present study we hypothesized that oral sCT as pharmacological intervention 1) exerted anti-hyperglycemic efficacy, and 2) enhanced insulin action in DIO-streptozotocin (DIO-STZ) diabetic rats. Diabetic hyperglycemia was induced in male selectively bred DIO rats by a single low dose (30 mg/kg) injection of STZ. Oral sCT by gavage was delivered as once-daily administration with lead-in (2 mg/kg) and maintenance (0.5 mg/kg) dose of oral sCT for a total of 21 days. Food intake, body weight, blood glucose, HbA1c, glucose and insulin tolerance test, and parameters of insulin sensitivity were investigated. Plasma glucoregulatory hormones and pancreatic insulin content were analyzed. Oral sCT treatment induced a pronounced anorectic action during the 7 days lead-in period and markedly reduced food intake and body weight in conjunction with improved glucose homeostasis. During the maintenance period, oral sCT normalized food intake and attenuated weight loss, albeit sustained glycemic control by reducing fasting blood glucose and HbA1c levels compared to those of vehicle-treated rats at the end of study. Notably, plasma levels of insulin, glucagon, leptin and adiponectin were unaltered, albeit insulin action was enhanced in conjunction with protection of pancreatic insulin content. The results of the present study indicate that oral sCT exerts a novel insulin-sensitizing effect to improve glucose metabolism in obesity and type 2 diabetes.

Are we closer to finding the treatment for type 2 diabetes mellitus in morbid obesity? Are the incretins the key to success?

Morbid obesity is a serious health problem associated with disease and mortality. One such disease is non-insulin-dependent diabetes mellitus (NIDDM). Approximately 95% of American diabetics have NIDDM. One of the major causes for type 2 diabetes is obesity. The improvement of diabetes with weight control is not in the earliest description of the disease. However, dietary control of NIDDM is often disappointing. Diet can improve glucose metabolism in obesity, but the improvement usually represents only a portion or a brief return to euglycemia, even when patients appear to be compliant. In contrast, reversal of NIDDM has been much more successfully achieved after bariatric surgery. Intra-abdominal fat deposition is associated with increased plasma concentration of free fatty acids, which reduce insulin sensitivity at both muscular and hepatic sites. The progression of diabetes is heralded by the inability of the beta-cells to maintain their previously high rate of insulin secretion in response to glucose, in the face of insulin resistance. The propensity to develop type 2 diabetes may be genetically determined or triggered by environmental factors. The connection between diabetes and obesity represents a continuum that progresses through different phases in which defective insulin action is the principal problem. At this point, we are unable to correlate the different findings of the many questions that arise, such as: 1) Does the decrease in sensitivity to insulin result from rearrangement of the insulin receptor? 2) Is weight loss the trigger for decrease of insulin resistance? 3) Is rearrangement of part of the intestine a mechanism to trigger the secretion of hormones (incretins) that help in insulin response? 4) Which mechanism controls the insulin resistance? The goal of this paper is to review literature on incretins and address the role of incretins after bariatric surgery. We know very little about the action of incretins in diabetes. We will assess the interaction between the secretion of incretins and bariatric surgery for the cure of diabetes.

Relation of abdominal and thigh adipose tissue distribution to serum lipids and glucose metabolism in obese males.

Spin-echo magnetic resonance imaging (MRI) and postprocessing for fat quantification were used to examine the relationship of abdominal and thigh adipose-tissue distribution to serum lipids and glucose metabolism in obesity. Thirteen simple obese male patients and 12 non-obese male volunteers were examined by MRI, blood pressure, and fasting blood sample levels of serum lipids, glucose, immunoreactive insulin, c-peptide, HbA1C and hematocrit. Correlations of thigh visceral and subcutaneous fat areas to serum lipid levels were generally similar, but marked differences were found between relationships of thigh versus abdominal fat areas to serum lipid levels. In addition, diastolic blood pressure was significantly correlated with the fat area, especially with the abdominal visceral fat area (r=0.51, p<0.01), but not with abdominal subcutaneous fat area. The thigh muscle area was highly and inversely correlated with c-peptide (r=-0.72, p<0.01) and systolic blood pressure (r=-0.65). Differences in correlations between visceral and subcutaneous fat areas in the abdomen to metabolic parameters were found between abdominal visceral fat areas and HbA1C and between the abdominal subcutaneous fat areas and HbA1C. These findings suggest that the character of regional fat could be heterogeneous with respect to lipid and glucose metabolism and blood pressure levels in obese males.