Progressive Insulin Resistance Research Articles

SAT-299 Chronic Treatment Of Juvenile Hypothalamic Pomc-deficient Mice With RM-493 Prevents The Development Of Obesity

Arc-Pomc knockout mice have a disruption of the two neural enhancers for the Pomc (proopiomelanocortin) gene, resulting in selective loss of Pomc gene expression in the arcuate nucleus of the hypothalamus. This gene targeting strategy leaves pituitary Pomc expression unaffected. These mice are hyperphagic starting at weaning, and develop progressive obesity, infertility and insulin resistance over their lifetime. RM-493 (setmelanotide) is a melanocortin-4 receptor agonist that has shown promise in treating humans with Pomc null mutations. In this preclinical study, we investigated the effects of chronic RM-493 treatment using subcutaneously implanted osmotic minipumps in two groups of male mice: Arc-Pomc knockout mice, fed regular chow throughout the study period, and their wildtype counterparts, fed a 45% high-fat diet. Each of these groups of mice was randomized into three treatment cohorts at weaning: one that was given RM-493 throughout the entire study period (4–24 weeks of age, “RM-493” group), one that was given RM-493 only for the first 4 weeks of the study (4–8 weeks of age, “switch” group) and then switched to vehicle, and one cohort that received vehicle for the entire study (“vehicle” group). We serially measured body weight, food intake, body composition, glucose tolerance, insulin tolerance, and several measures of metabolism using the Comprehensive Lab Animal Monitoring System, including oxygen consumption, energy expenditure, ambulatory activity and lipid and glucose oxidation.Among other results, at the end of the study (24 weeks of age), Arc-Pomc knockout mice in the RM-493 group weighed significantly less than either the switch or vehicle groups (p<0.05). Arc-Pomc knockout mice on RM-493 also had higher energy expenditure when compared to the switch and vehicle groups (p<0.05). In addition, RM-493 improved the glucose-insulin index for Arc-Pomc knockout mice (p<0.05). According to our preliminary results, wildtype mice on high-fat diet, treated chronically with RM-493, did not differ in any of these measurements from their switch and vehicle groups.We conclude that the obesity syndrome caused by a loss of hypothalamic Pomc expression was completely blocked by RM-493 treatment started before the onset of obesity, with no apparent desensitization to the drug’s action over 20 weeks. However, the beneficial effects of a single month’s treatment were steadily reversed within one month after switching to vehicle treatment. In contrast to the dramatic effects of RM-493 in the genetic obesity syndrome, at this time, there does not appear to be any phenotypic changes in wild-type mice with RM-493 administration on the development of obesity or secondary metabolic disruptions in response to high-fat diet consumption.

Insulin Sensitivity and Insulin Secretion Estimated by Homeostatic Model Assessment (HOMA) in Gestational Diabetes Mellitus

Background: Progressive insulin resistance (IR) is an important pathophysiologic mechanism of gestational diabetes mellitus (GDM). Homeostatic model assessment (HOMA) is commonly used as a parameter of the severity of insulin resistance. Aims: To determine indices of insulin resistance (IR) and β-cell function in gestational diabetes mellitus (GDM). Methods: This cross sectional study was conducted from March 2017 to September 2018 at Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh. The study was performed with 41 GDM and equal number of pregnant women with normal glucose tolerance (NGT) diagnosed on basis of WHO criterion-2013 during 24 - 40 weeks of gestation. Serum glucose was measured by glucose oxidase method and fasting serum insulin was measured by chemiluminescent immunoassay. Equations of homeostatic model assessment (HOMA) were used to calculate insulin indices like-insulin resistance (HOMA-IR), β-cell function (HOMA-B) and insulin sensitivity (HOMA-%S). Data were analyzed and compared by statistical tests. Results: A total of eighty-two (82) subjects [41 women with GDM (age: 28.29 ± 3.79 years, BMI: 27.16 ± 4.13 kg/m2) and 41 women with NGT (age: 26.22 ± 5.13 years, BMI: 25.27 ± 3.01 kg/m2)] were included in this study. It was observed that GDM women were significantly older (p = 0.041) and had significantly higher BMI (p = 0.020) than pregnant women with NGT. The GDM group had significantly higher IR as indicated by higher fasting insulin value [GDM vs. NGT; 10.19 (7.71 - 13.34) vs. 6.88 (5.88 - 8.47) μIU/ml, median (IQR); p = 0.001] and HOMA-IR [GDM vs. NGT; 2.31 (1.73 - 3.15) vs. 1.42 (1.15 - 1.76), median (IQR); p β-cell secretory capacity [GDM vs. NGT; HOMA-B: 112.63 (83.52 - 143.93) vs. 128.60 (108.77 - 157.58), median (IQR); p = 0.04] and low insulin sensitivity [GDM vs. NGT; HOMA-%S: 43.29 (31.77 - 57.98) vs. 70.42 (56.86 - 86.59), median (IQR); p < 0.001]. Conclusions: GDM is associated with both insulin resistance and inadequate insulin secretion.

In Human and Mouse Spino-Cerebellar Tissue, Ataxin-2 Expansion Affects Ceramide-Sphingomyelin Metabolism.

Ataxin-2 (human gene symbol ATXN2) acts during stress responses, modulating mRNA translation and nutrient metabolism. Ataxin-2 knockout mice exhibit progressive obesity, dyslipidemia, and insulin resistance. Conversely, the progressive ATXN2 gain of function due to the fact of polyglutamine (polyQ) expansions leads to a dominantly inherited neurodegenerative process named spinocerebellar ataxia type 2 (SCA2) with early adipose tissue loss and late muscle atrophy. We tried to understand lipid dysregulation in a SCA2 patient brain and in an authentic mouse model. Thin layer chromatography of a patient cerebellum was compared to the lipid metabolome of Atxn2-CAG100-Knockin (KIN) mouse spinocerebellar tissue. The human pathology caused deficits of sulfatide, galactosylceramide, cholesterol, C22/24-sphingomyelin, and gangliosides GM1a/GD1b despite quite normal levels of C18-sphingomyelin. Cerebellum and spinal cord from the KIN mouse showed a consistent decrease of various ceramides with a significant elevation of sphingosine in the more severely affected spinal cord. Deficiency of C24/26-sphingomyelins contrasted with excess C18/20-sphingomyelin. Spinocerebellar expression profiling revealed consistent reductions of CERS protein isoforms, Sptlc2 and Smpd3, but upregulation of Cers2 mRNA, as prominent anomalies in the ceramide–sphingosine metabolism. Reduction of Asah2 mRNA correlated to deficient S1P levels. In addition, downregulations for the elongase Elovl1, Elovl4, Elovl5 mRNAs and ELOVL4 protein explain the deficit of very long-chain sphingomyelin. Reduced ASMase protein levels correlated to the accumulation of long-chain sphingomyelin. Overall, a deficit of myelin lipids was prominent in SCA2 nervous tissue at prefinal stage and not compensated by transcriptional adaptation of several metabolic enzymes. Myelination is controlled by mTORC1 signals; thus, our human and murine observations are in agreement with the known role of ATXN2 yeast, nematode, and mouse orthologs as mTORC1 inhibitors and autophagy promoters.

MondoA drives muscle lipid accumulation and insulin resistance.

Obesity-related insulin resistance is associated with intramyocellular lipid accumulation in skeletal muscle. We hypothesized that in contrast to current dogma, this linkage is related to an upstream mechanism that coordinately regulates both processes. We demonstrate that the muscle-enriched transcription factor MondoA is glucose/fructose responsive in human skeletal myotubes and directs the transcription of genes in cellular metabolic pathways involved in diversion of energy substrate from a catabolic fate into nutrient storage pathways including fatty acid desaturation and elongation, triacylglyeride (TAG) biosynthesis, glycogen storage, and hexosamine biosynthesis. MondoA also reduces myocyte glucose uptake by suppressing insulin signaling. Mice with muscle-specific MondoA deficiency were partially protected from insulin resistance and muscle TAG accumulation in the context of diet-induced obesity. These results identify MondoA as a nutrient-regulated transcription factor that under normal physiological conditions serves a dynamic checkpoint function to prevent excess energy substrate flux into muscle catabolic pathways when myocyte nutrient balance is positive. However, in conditions of chronic caloric excess, this mechanism becomes persistently activated leading to progressive myocyte lipid storage and insulin resistance.

Dynamics of carbohydrate metabolism in pregnant women with different prepregnancy weight

Objective: to determine the carbohydrate metabolism in pregnant women with different prepregnancy weight depending on gestational weight gain (GWG).Material and methods. There were studied 163 pregnant women: 97 (59.5%) with normal prepregnancy weight, 18 (11.0%) — insufficient and 48 (29.4%) — overweight and obesity. The recommended GWG was diagnosed in 56 (34.4%), insufficient in 33 (20.2%), and excessive in 74 (45.4%) patients. Anthropometry was performed in each trimester of pregnancy, the weight gain, the percentage of body fat mass and the carbohydrate profile (fasting glucoseand insulin levels, HOMO-IR index) were diagnosed. Statistical analyses were carried out using Statistical program "Statistica 6.0".Results. In pregnant women with normal prepregnancy weight, recommended and insufficient GWG normal insulin sensitivity was diagnosed, excessive weight gain led to progressive hyperinsulinemia and insulin resistance. In women with insufficient weight carbohydrate status did not differ significantly from women of normal weight. Pregnancy in overweight and obese women was characterized by the carbohydrate metabolism stress from the early terms, but hyperglycemia occured only in excessive GWG patients, indicating the development of metabolic decompensation.Conclusions. Changes in carbohydrate metabolism during pregnancy are determined by the GWG level. The prepregnancy weight is an aggravating factor, but not the main one.

Obeticholic acid ameliorates dyslipidemia but not glucose tolerance in mouse model of gestational diabetes.

Metabolism alters markedly with advancing gestation, characterized by progressive insulin resistance, dyslipidemia, and raised serum bile acids. The nuclear receptor farnesoid X receptor (FXR) has an integral role in bile acid homeostasis and modulates glucose and lipid metabolism. FXR is known to be functionally suppressed in pregnancy. The FXR agonist, obeticholic acid (OCA), improves insulin sensitivity in patients with type 2 diabetes with nonalcoholic fatty liver disease. We therefore hypothesized that OCA treatment during pregnancy could improve disease severity in a mouse model of gestational diabetes mellitus (GDM). C57BL/6J mice were fed a high-fat diet (HFD; 60% kcal from fat) for 4 wk before and throughout pregnancy to induce GDM. The impact of the diet supplemented with 0.03% OCA throughout pregnancy was studied. Pregnant HFD-fed mice displayed insulin resistance and dyslipidemia. OCA significantly reduced plasma cholesterol concentrations in nonpregnant and pregnant HFD-fed mice (by 22.4%, P < 0.05 and 36.4%, P < 0.001, respectively) and reduced the impact of pregnancy on insulin resistance but did not change glucose tolerance. In nonpregnant HFD-fed mice, OCA ameliorated weight gain, reduced mRNA expression of inflammatory markers in white adipose tissue, and reduced plasma glucagon-like peptide 1 concentrations (by 62.7%, P < 0.01). However, these effects were not evident in pregnant mice. OCA administration can normalize plasma cholesterol levels in a mouse model of GDM. However, the absence of several of the effects of OCA in pregnant mice indicates that the agonistic action of OCA is not sufficient to overcome many metabolic consequences of the pregnancy-associated reduction in FXR activity.

Concentric and Eccentric Endurance Exercise Reverse Hallmarks of T-Cell Senescence in Pre-diabetic Subjects.

The peripheral T-cell pool undergoes a striking age associated remodeling which is accelerated by progressive insulin resistance. Exercise training is known to delay several aspects of T-cell senescence. The purpose of the current study was to investigate the effect of 3 weeks regular concentric or eccentric endurance exercise training on the composition of the T-cell compartment in pre-diabetic subjects. Sixteen male older adults with impaired glucose tolerance were recruited and performed either concentric exercise (CE) or eccentric exercise (EE) walking 3 times a week for 3 weeks. Fasting venous blood sampling was performed before training and after the training intervention. Various T-cell subpopulations were analyzed by flow cytometry. We did not find significant time × group effects (interaction) but found several significant time effects for cell type ratios and cell subsets proportions. There was an increase of the CD4+/CD8+ (0.55 ± 0.85%; p = 0.033) and CD4+/CD3+ ratio (5.63 ± 8.44%; p = 0.018) and a decrease of the CD8+/CD3+ ratio (-0.95 ± 1.64%; p = 0.049) after training. We found proportional increases of CD4+/CCR7+/CD45RO+ central memory cells (5.02 ± 7.68%; p = 0.030), naïve CD8+/CCR7+/CD45RO- (3.00 ± 6.68%; p = 0.047) and CD8+/CCR7+/CD45RO+ central memory cells (3.01 ± 3.70%; p = 0.009), while proportions of CD4+/CCR7-/CD45RO- TEMRA cells (-2.17 ± 4.66%; p = 0.012), CD8+/CCR7-/CD45RO- TEMRA cells (-5.11 ± 7.02%; p = 0.018) and CD16+ cells (-4.67 ± 6.45%; p = 0.016) decreased after training. 3 weeks of either CE or EE were effective in reversing hallmarks of T-cell senescence in pre-diabetic subjects. It is suggested that exercise stimulates production and mobilization of naïve T-cells, while differentiated TEMRA cells might disappear by apoptosis.

HDAC3 inhibition prevents blood-brain barrier permeability through Nrf2 activation in type 2 diabetes male mice

BackgroundType 2 diabetes mellitus (T2DM) is a chronic metabolic dysfunction characterized by progressive insulin resistance and hyperglycaemia. Increased blood-brain barrier (BBB) permeability is a critical neurovascular complication of T2DM that adversely affects the central nervous system homeostasis and function. Histone deacetylase 3 (HDAC3) has been reported to be elevated in T2DM animals and may promote neuroinflammation; however, its involvement in the BBB permeability of T2DM has not been investigated. In this study, we tested our hypothesis that HDAC3 expression and activity are increased in the T2DM mouse brain. Inhibition of HDAC3 may ameliorate T2DM-induced BBB permeability through Nrf2 activation.MethodsT2DM (db/db, leptin receptor-deficient), genetic non-hyperglycemic control (db/+), and wild-type male mice at the age of 16 weeks were used in this study. HDAC3 expression and activity, Nrf2 activation, and BBB permeability and junction protein expression were examined. The effects of HDAC3 activity on BBB permeability were tested using highly selective HDAC3 inhibitor RGFP966. In primary cultured human brain microvascular endothelial cells (HBMEC), hyperglycemia (25 mM glucose) plus interleukin 1 beta (20 ng/ml) (HG-IL1β) served as T2DM insult in vitro. The effects of HDAC3 on transendothelial permeability were investigated by FITC-Dextran leakage and trans-endothelial electrical resistance, and the underlying molecular mechanisms were investigated using Western blot, q-PCR, co-immunoprecipitation, and immunocytochemistry for junction protein expression, miR-200a/Keap1/Nrf2 pathway regulation.ResultsHDAC3 expression and activity were significantly increased in the hippocampus and cortex of db/db mice. Specific HDAC3 inhibition significantly ameliorated BBB permeability and junction protein downregulation in db/db mice. In cultured HBMEC, HG-IL1β insult significantly increased transendothelial permeability and reduced junction protein expression. HDAC3 inhibition significantly attenuated the transendothelial permeability and junction protein downregulation. Moreover, we demonstrated the underlying mechanism was at least in part attributed by HDAC3 inhibition-mediated miR-200a/Keap1/Nrf2 signaling pathway and downstream targeting junction protein expression in T2DM db/db mice.ConclusionsOur experimental results show that HDAC3 might be a new therapeutic target for BBB damage in T2DM.

Lipotoxicity reduces β cell survival through islet stellate cell activation regulated by lipid metabolism-related molecules

BackgroundIslet stellate cells (ISCs) activation is mainly associated with islet fibrosis, which contributes to the progression of type 2 diabetes. However, the molecular mechanism underlying this process is not fully understood. MethodsIn order to investigate this process the current study examined ectopic fat accumulation in rats with high-fat diet (HFD) induced obesity. Levels of lipotoxicity-induced ISC activation and islet function were assessed via intraperitoneal glucose and insulin tolerance tests, and immunohistochemistry. The expression of lipid metabolism- and ISC activation-related markers was evaluated in cultured ISCs treated with palmitic acid (PA) using quantitative PCR and western blotting. We also overexpressed sterol regulatory element-binding protein (SREBP)-1c in ISCs by lentiviral transduction, and assessed the effects on insulin release in co-cultures with isolated rat islets. ResultsHFD increased body weight and ectopic fat accumulation in pancreatic islets. Lipotoxicity caused progressive glucose intolerance and insulin resistance, upregulated α-smooth muscle actin, and stimulated the secretion of extracellular matrix. Lipotoxicity reduced the expression of lipid metabolism-related molecules in ISCs treated with PA, especially SREBP-1c. Overexpression of SREBP-1c in ISCs improved islet viability and insulin secretion in co-cultures. ConclucionsThese results indicate that lipotoxicity-induced ISC activation alters islet function via regulation of lipid metabolism, suggesting that therapeutic strategies targeting activated ISC may be an effective treatment for prevention of ISC activation-associated islet dysfunction.

Hepatoprotective Effects of a Ruthenium(II) Schiff Base Complex in Rats with Diet-Induced Prediabetes

Progressive insulin resistance in a prediabetic state has been reported to be the predominant causative factor for the development of nonalcoholic fatty liver disease. The combination of dietary modification and pharmacotherapy has been recommended to manage diabetic liver complications. However, poor patient compliance and toxicity of current drug therapy on liver function still results; thus, newer alternative drugs are required. This study sought to investigate the hepatoprotective effects of the ruthenium(II) Schiff base complex in the presence and absence of dietary intervention in a diet-induced pre-diabetic rat model. Prediabetic rats were randomly allocated to respective treatment groups. The ruthenium-based compound (15 mg/kg) was administered to the prediabetic rats in both the presence and absence of dietary intervention once a day every third day for 12 weeks. The administration of the ruthenium compound in both the presence and absence of dietary intervention resulted in the restoration of liver and body weights. This treatment also reduced liver damage enzyme biomarkers, bilirubin, and sterol regulatory element binding protein 1c concentrations in the plasma. The ruthenium(II) complex showed beneficial effects as it ameliorated and prevented the progression of diabetes-related liver derangements while eliminating the hepatotoxicity associated with the use of metal compounds. However, further studies are still required to further determine the physiological mechanisms behind this effect.

Temporal immmunometabolic profiling of adipose tissue in HFD-induced obesity: manifestations of mast cells in fibrosis and senescence.

Chronic low-grade inflammation/meta-inflammation in adipose tissue leads to obesity-associated metabolic complications. Despite growing understanding, the roles of immune cell subsets, their interrelationship, and chronological events leading to progression of obesity-associated insulin resistance (IR) remains unclear. We carried out temporal immunometabolic profiling of adipose tissue from C57BL/6 mice fed a high-fat diet (HFD) for 4, 8, 12, 16, and 20 weeks. We used clodronate sodium liposomes (CLODs) to deplete macrophages and disodium cromoglycate sodium liposomes (DSCGs) to stabilize mast cells. In the temporal HFD settings, mice showed progressive glucose intolerance, insulin resistance, and adipose tissue senescence. Histochemistry analysis of epididymal white adipose tissue (eWAT) using picro-sirius red and Masson's trichrome staining showed extensive collagen deposition in the 16th and 20th weeks. Flow cytometry analysis of the stromal vascular fraction (SVF) from eWAT revealed T-cell subsets as early-phase components and pro-inflammatory macrophages, as well as mast cells as the later phase components during obesity progression. In our therapeutic strategies, macrophage depletion by CLOD and mast stabilization by DSCG attenuated obesity, adipose tissue fibrosis, and improved whole-body glucose homeostasis. In addition, mast cell stabilization also attenuated senescence (p53 and X-gal staining) in eWAT, signifying the role of mast cells over macrophages during obesity. New-generation mast cell stabilizers can be exploited for the treatment of obesity-associated metabolic complications.

Hepatic Insulin Signaling Regulates Hepatokines to Coordinate Energy Expenditure and Weight Gain through Irs2 in Sim1 Neurons

Insulin resistance is the underlying cause of type 2 diabetes; however, insulin resistance might also be a feed-back mechanism to protect cells and tissues from acute effects of over nutrition. Based upon our results with LDKO (hepatic specific Irs1L/LIrs2L/L CreAlbumin) mice, we found that hepatic insulin resistance elevated systemic oxygen consumption and energy expenditure, which was associated with a dramatic reduction of the RER (respiratory exchange ratio) and resistance to diet-induced obesity. Deletion of hepatic FoxO1 in LDKO-mice restored energy homeostasis and oxygen consumption, and increased the RER into the normal range. Contrary to the progressive peripheral insulin resistance of the LDKO-mice, Irs2 expression and insulin sensitivity increased in the PVH (paraventricular nucleus of hypothalamus). Interestingly, deletion of Irs2 in the PVH (Irs2L/L-mice intercrossed with CreSim1-mice) increased body weight and promoted obesity. To identify the molecular cross-talk between liver and brain, we used a neuronal cell line to screen for the effects of hepatokines that were dysregulated in LDKO-mice—but normalized in LTKO-mice. Among these dysregulated hepatokines, excess circulating NTF3 and GPX3 led to increased Irs2 expression and insulin sensitivity in neurons. Thus, our study suggests that hepatic FoxO1-dependent hepatokines—NTF3 or GPX3—modulate systemic energy expenditure and body weight through Irs2 expression in the PVH. Disclosure R. Tao: None. K.D. Copps: None. O. Stoehr: None. M.F. White: Advisory Panel; Self; Housey Pharmaceutical Research Laboratories.

Duodenal-Jejunal Bypass Surgery Reverses Diabetic Phenotype and Reduces Obesity in db/db Mice.

Type 2 diabetes mellitus (T2DM), a complex metabolic disorder typically accompanying weight gain, is associated with progressive β-cell failure and insulin resistance. Bariatric surgery ameliorates glucose tolerance and provides a near-perfect treatment. Duodenal-jejunal bypass (DJB) is an experimental procedure and has been studied in several rat models, but its influence in db/db mice, a transgenic model of T2DM, remains unclear. To investigate the effectiveness of DJB in db/db mice, we performed the surgery and evaluated metabolism improvement. Results showed that mice in DJB group weighed remarkably less than sham group two weeks after surgery. Compared to the preoperative level, postoperative fasting blood glucose (FBG) was dramatically reduced. Statistical analysis revealed that changes in body weight and FBG were significantly correlated. Besides, DJB surgery altered plasma insulin level with approximate 40% reduction. Thus, for the first time we proved that DJB can achieve rapid therapeutic effect in transgenic db/db mice with severe T2DM as well as obesity. In addition, decreased insulin level reflected better insulin sensitivity induced by DJB. In conclusion, our study demonstrates that DJB surgery may be a potentially effective way to treat obesity-associated T2DM.

Abstract 228: FADS2 Regulates Cardiometabolic Risk Phenotypes in Mice

Single nucleotide polymorphisms of the FADS2 gene associate with cardiometabolic risk in humans. Additionally, serum fatty acid profiles reflecting hepatic hyperactivity of the FADS2 gene product, delta-6 desaturase (D6D), correspond to cardiometabolic syndrome (CMS) phenotypes in humans and animal models. D6D catalyzes rate-limiting steps in essential polyunsaturated fatty acid (PUFA) metabolism, but its role in the pathogenesis of CMS has not been defined. In the present study, we employed pharmacological and genetic gain- and loss-of-function approaches to investigate the links between D6D activity and CMS phenotypes in mice. Transgenic overexpression (TG) of FADS2 in normal (FVB) mice modestly increases hepatic D6D protein expression and serum PUFA product/precursor ratios reflecting greater enzyme activity in vivo . FADS2 TG mice develop a mild, but progressive obesity and insulin resistance with age compared to WT mice, as well as elevated serum triglycerides and LDL/HDL and hepatic macrophage infiltration, but not hepatic steatosis. Global FADS2 ablation prevents obesity/insulin resistance and hyperlipidemia induced by high-fat feeding in C57Bl/6J mice, but promotes severe hepatic steatosis. Pharmacological D6D inhibition in vivo with SC-26196 (100 mpk 4-8 weeks) ameliorates hepatic inflammation and glucose intolerance in FADS2 TG mice and leptin-deficient ( ob ) mice, and prevents severe hyperlipidemia and atherosclerosis in ldlr -/- mice fed an atherogenic diet; despite augmenting hepatic steatosis in all cases. Tissue phospholipid analyses across these models revealed consistent positive relationships between D6D activity, pro-inflammatory eicosanoid accumulation, and a higher phosphatdiylcholine/phosphatidylethanolamine (PC/PE) ratio previously linked to increased hepatic VLDL synthesis and release. These studies establish an important role of D6D activity in the development of CMS and inflammation, and reveal novels links with tissue phospholipid class distribution and metabolism relevant to the development an atherogenic serum lipid profile, hepatic lipid homeostasis, and perhaps other aspects of cardiovascular risk currently under investigation in our laboratory.

Exercise initiated after the onset of insulin resistance improves trabecular microarchitecture and cortical bone biomechanics of the tibia in hyperphagic Otsuka Long Evans Tokushima Fatty rats

The present study extends our previous findings that exercise, which prevents the onset of insulin resistance and type 2 diabetes (T2D), also prevents the detrimental effects of T2D on whole-bone and tissue-level strength. Our objective was to determine whether exercise improves bone's structural and material properties if insulin resistance is already present in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. The OLETF rat is hyperphagic due to a loss-of-function mutation in cholecystokinin-1 receptor (CCK-1 receptor), which leads to progressive obesity, insulin resistance and T2D after the majority of skeletal growth is complete. Because exercise reduces body mass, which is a significant determinant of bone strength, we used a body-mass-matched caloric-restricted control to isolate body-mass-independent effects of exercise on bone. Eight-wk old, male OLETF rats were fed ad libitum until onset of hyperglycemia (20weeks of age), at which time they were randomly assigned to three groups: ad libitum fed, sedentary (O-SED); ad libitum fed, treadmill running (O-EX); or, sedentary, mild caloric restriction to match body mass of O-EX (O-CR). Long-Evans Tokushima Otsuka rats served as the normophagic, normoglycemic controls (L-SED). At 32weeks of age, O-SED rats had T2D as evidenced by hyperglycemia and a significant reduction in fasting insulin compared to OLETFs at 20weeks of age. O-SED rats also had reduced total body bone mineral content (BMC), increased C-terminal telopeptide of type I collagen (CTx)/tartrate resistant acid phosphatase isoform 5b (TRAP5b), decreased N-terminal propeptide of type I procollagen (P1NP), reduced percent cancellous bone volume (BV/TV), trabecular number (Tb.N) and increased trabecular separation (Tb.Sp) and structural model index (SMI) of the proximal tibia compared to L-SED. T2D also adversely affected biomechanical properties of the tibial diaphysis, and serum sclerostin was increased and β-catenin, runt-related transcription factor 2 (Runx2) and insulin-like growth factor-I (IGF-I) protein expression in bone were reduced in O-SED vs. L-SED. O-EX or O-CR had greater total body bone mineral density (BMD) and BMC, and BV/TV, Tb.N, Tb.Sp, and SMI compared to O-SED. O-EX had lower CTx and CR greater P1NP relative to O-SED. O-EX, not O-CR, had greater cortical thickness and area, and improved whole-bone and tissue-level biomechanical properties associated with a 4-fold increase in cortical bone β-catenin protein expression vs. O-SED. In summary, EX or CR initiated after the onset of insulin resistance preserved cancellous bone volume and structure, and EX elicited additional benefits in cortical bone.

Cortisol dysregulation: the bidirectional link between stress, depression, and type 2 diabetes mellitus.

Controversy exists over the role of stress and depression in the pathophysiology of type 2 diabetes mellitus. Depression has been shown to increase the risk for progressive insulin resistance and incident type 2 diabetes mellitus in multiple studies, whereas the association of stress with diabetes is less clear, owing to differences in study designs and in forms and ascertainment of stress. The biological systems involved in adaptation that mediate the link between stress and physiological functions include the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous and immune systems. The HPA axis is a tightly regulated system that represents one of the body's mechanisms for responding to acute and chronic stress. Depression is associated with cross-sectional and longitudinal alterations in the diurnal cortisol curve, including a blunted cortisol awakening response and flattening of the diurnal cortisol curve. Flattening of the diurnal cortisol curve is also associated with insulin resistance and type 2 diabetes mellitus. In this article, we review and summarize the evidence supporting HPA axis dysregulation as an important biological link between stress, depression, and type 2 diabetes mellitus.

FADS2 Over expression Promotes Metabolic Syndrome in Mice: Influence of Maternal Dietary Polyunsaturated Fatty Acid Composition

Accumulating evidence from human and animal studies indicates that risk of developing metabolic syndrome (MSx) is strongly influenced by maternal genotype and the nutritional environment encountered during fetal and early postnatal development. In addition to the well‐established effects of over nutrition, the fatty acid composition of the diet, particularly the n6:n3 polyunsaturated fatty acid (PUFA) ratio, has been postulated to play an important role in the development of MSx. However, results from dietary PUFA intervention studies on metabolic health have been inconsistent, perhaps in part due to individual and population differences in endogenous PUFA metabolism. Indeed, common FADS2 haplotypes and elevated serum indices of PUFA metabolism by its gene product, delta‐6 desaturase (D6D), also predict obesity and MSx in children and adult populations, though any causal relationship remains to be established. To directly investigate the effect of FADS2 expression on metabolic phenotype, we generated mice with global transgenic over expression of FADS2 (CMV promoter), backcrossed for 8 generations on a FVB background. FADS2‐tg mice exhibit elevated serum and tissue PUFA product/precursor ratios reflective of systemic D6D hyperactivity similar to those associated with FADS2 haplotypes and cardiometabolic risk in epidemiological studies. When maintained on a standard chow diet (Harlan 2918; 18% Kcals Fat), FADS2‐tg mice develop progressive obesity, glucose intolerance, insulin resistance and hyperlipidemia beginning at 1–2 months of age compared to age‐matched FVB wild‐type (WT) mice on the same chow diet. Importantly, linoleic acid (18:2n6) represents the majority (91%) of PUFA in 2918 chow, generating a dietary n6:n3 PUFA ratio of &gt;10:1, similar to the modern “western” diet. Based on clinical evidence for potentially beneficial effects of perinatal n3‐PUFA supplementation on infant metabolic status, we tested the hypothesis that reducing this ratio to ~3:1 in the maternal diet of FADS2‐tg mice would attenuate development of MSx in her offspring. FADS2‐tg females were fed 2918 chow supplemented with 2% flaxseed oil (providing ~1% w/w n3 α‐linolenic acid; ALA) beginning 2 weeks prior to pairing with a WT male until litters were weaned. Offspring were maintained on the standard 2918 chow diet after weaning, and compared to litters from the same mother without ALA supplementation. Interestingly, maternal ALA supplementation significantly normalized weight gain and glucose tolerance to near WT levels in male, but not female, offspring for up to 2 months post weaning on the chow diet. Food intake was similar across groups, actually trending higher in the offspring from the ALA supplemented pregnancy. Taken together, these studies suggest a causal link between FADS2 expression and the development of MSx, and reveal sex‐specific benefits of prenatal n3‐PUFA supplementation in this context. The cellular mechanisms responsible for MSx induced by FADS2 over expression, and its suppression by maternal ALA supplementation, are currently being investigated in our laboratory.Support or Funding InformationSupported by grants from the USDA and Colorado Agricultural Experimental Station to AJC.

Implication of the myokine irisin in maternal energy homeostasis in pregnancies with abnormal fetal growth

Objective: To prospectively investigate maternal concentrations of the myokine irisin in large for gestational age (LGA) and intrauterine growth restricted (IUGR) versus appropriate for gestational age (AGA) normal pregnancies and associate them with various perinatal parameters.Methods: Plasma irisin and insulin concentrations were measured by enzyme-linked immunosorbent assay (ELISA) and immunoradiometric assay (IRMA), respectively, in a cohort of 80 mothers delivering LGA (n = 30), IUGR (n = 30) and AGA (n = 20) singleton full-term infants.Results: Maternal irisin concentrations were similar among LGA, IUGR and AGA groups and did not correlate with respective insulin ones or maternal body mass index. In a combined group, maternal irisin concentrations decreased with advancing gestational age (p < 0.001) and were lower in multi-, compared to nulliparous women (p = 0.004). In the IUGR group, maternal irisin concentrations were higher in cases of smoking (p = 0.006).Conclusions: Irisin may not be differentially regulated in insulin resistance-associated pregnancy disorders resulting in fetal macrosomia and IUGR. Maternal irisin down-regulation with advancing gestation could possibly contribute to the observed maternal fat accumulation and progressive insulin resistance towards term. Similarly, lower maternal irisin concentrations in multiparous women may reflect the documented positive association between parity and fat deposition. Irisin up-regulation in cases of smoking may indicate the need for enhanced oxygen consumption to maintain energy production under conditions of hypoxia.

Gelam Honey Attenuates the Oxidative Stress-Induced Inflammatory Pathways in Pancreatic Hamster Cells.

Purpose. Type 2 diabetes consists of progressive hyperglycemia and insulin resistance, which could result from glucose toxicity, inflammatory cytokines, and oxidative stress. In the present study we investigated the effect of Gelam honey and quercetin on the oxidative stress-induced inflammatory pathways and the proinflammatory cytokines. Methods. HIT-T15 cells were cultured and preincubated with the extract of Gelam honey (20, 40, 60, and 80 μg/mL), as well as quercetin (20, 40, 60, and 80 μM), prior to stimulation by 20 and 50 mM glucose. Results. HIT-T15 cells cultured under hyperglycemic condition showed a significant increase in the inflammatory pathways by phosphorylating JNK, IKK-β, and IRS-1 at Ser307 (p < 0.05). There was a significant decrease in the phosphorylation of Akt at Ser473 (p < 0.05). Pretreatment with Gelam honey and quercetin reduced the expression of phosphorylated JNK, IKK-β, and IRS-1, thereby significantly reducing the expression of proinflammatory cytokines like TNF-α, IL-6, and IL-1β (p < 0.05). At the same time there was a significant increase in the phosphorylated Akt showing the protective effects against inflammation and insulin resistance (p < 0.05). In conclusion, our data suggest the potential use of the extract from Gelam honey and quercetin in modulating the inflammation induced insulin signaling pathways.

The ΔF508 Mutation in the Cystic Fibrosis Transmembrane Conductance Regulator Is Associated With Progressive Insulin Resistance and Decreased Functional β-Cell Mass in Mice.

Cystic fibrosis (CF) is the result of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF-related diabetes affects 50% of adult CF patients. How CFTR deficiency predisposes to diabetes is unknown. Herein, we examined the impact of the most frequent cftr mutation in humans, deletion of phenylalanine at position 508 (ΔF508), on glucose homeostasis in mice. We compared ΔF508 mutant mice with wild-type (WT) littermates. Twelve-week-old male ΔF508 mutants had lower body weight, improved oral glucose tolerance, and a trend toward higher insulin tolerance. Glucose-induced insulin secretion was slightly diminished in ΔF508 mutant islets, due to reduced insulin content, but ΔF508 mutant islets were not more sensitive to proinflammatory cytokines than WT islets. Hyperglycemic clamps confirmed an increase in insulin sensitivity with normal β-cell function in 12- and 18-week-old ΔF508 mutants. In contrast, 24-week-old ΔF508 mutants exhibited insulin resistance and reduced β-cell function. β-Cell mass was unaffected at 11 weeks of age but was significantly lower in ΔF508 mutants versus controls at 24 weeks. This was not associated with gross pancreatic pathology. We conclude that the ΔF508 CFTR mutation does not lead to an intrinsic β-cell secretory defect but is associated with insulin resistance and a β-cell mass deficit in aging mutants.