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Insulin resistance - Top 30 Publications

Association between sleep timing, obesity, diabetes: the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) cohort study: Sleep timing, obesity, and diabetes.

Recent studies implicate inadequate sleep duration and quality in metabolic disease. Fewer studies have examined the timing of sleep, which may be important because of its potential impact on circadian rhythms of metabolic function. We examined the association between sleep timing and metabolic risk among Hispanic/Latino adults.

Sleep Duration and Cardiometabolic Risk Among Chinese School-aged Children: Do Adipokines Play a Mediating Role?

To assess the associations between sleep duration and cardiometabolic risk factors in Chinese school-aged children and to explore the possible mediating role of adipokines.

Insulin and diet-induced changes in the ubiquitin-modified proteome of rat liver.

Ubiquitin is a crucial post-translational modification regulating numerous cellular processes, but its role in metabolic disease is not well characterized. In this study, we identified the in vivo ubiquitin-modified proteome in rat liver and determined changes in this ubiquitome under acute insulin stimulation and high-fat and sucrose diet-induced insulin resistance. We identified 1267 ubiquitinated proteins in rat liver across diet and insulin-stimulated conditions, with 882 proteins common to all conditions. KEGG pathway analysis of these proteins identified enrichment of metabolic pathways, TCA cycle, glycolysis/gluconeogenesis, fatty acid metabolism, and carbon metabolism, with similar pathways altered by diet and insulin resistance. Thus, the rat liver ubiquitome is sensitive to diet and insulin stimulation and this is perturbed in insulin resistance.

Cross-talk between insulin signaling and GPCRs.

Diabetes is a major risk factor for the development of heart failure. One of the hallmarks of diabetes is insulin resistance associated with hyperinsulinemia. The literature shows that insulin and adrenergic signaling is intimately linked to each other; however, whether and how insulin may modulate cardiac adrenergic signaling and cardiac function remains unknown. Notably, recent studies have revealed that insulin receptor and β2 adrenergic receptor (β2AR) forms a membrane complex in animal hearts, bringing together the direct contact between two receptor signaling systems, and forming an integrated and dynamic network. Moreover, insulin can drive cardiac adrenergic desensitization via PKA and GRK phosphorylation of the β2AR, which compromises adrenergic regulation of cardiac contractile function. In this review, we will explore the current state of knowledge linking insulin and GPCR signaling, especially βAR signaling in the heart, with emphasis on molecular insights regarding its role in diabetic cardiomyopathy (DCM).

Fish oil supplementation inhibits endoplasmic reticulum stress and improves insulin resistance: involvement of AMP-activated protein kinase.

The beneficial effects of fish oil consumption on glucose metabolism have been generally reported. However, the mechanism underlying the fish oil-induced protective effects against insulin resistance remains unclear. Endoplasmic reticulum (ER) stress is recognized as an important contributor to insulin resistance. The aim of this study is to evaluate whether fish oil supplementation reduces ER stress and ameliorates insulin resistance in diet-induced obese mice, and to investigate the molecular mechanism of fish oil-induced benefits on ER stress. C57BL/6J mice were fed one of the following diets for 12 weeks: the low-fat diet (LFD), the high-fat diet (HFD) or the fish oil-supplemented high-fat diet (FOD). Fish oil supplementation led to lower blood glucose, better glucose tolerance and improved insulin sensitivity in high-fat diet-induced obese mice. Importantly, fish oil administration inhibited high-fat feeding-induced ER stress and reduced adipose tissue dysfunction. The fish oil-induced improvements were accompanied by the elevation of phosphorylated AMP-activated protein kinase (AMPK) expression in white adipose tissue. Correspondingly, the results of in vitro experiments showed that docosahexaenoic acid (DHA), the main n-3 polyunsaturated fatty acid (PUFA) in the fish oil used in the study, led to a dose-dependent increase in AMPK phosphorylation and suppressed palmitic acid (PA)-triggered ER stress in differentiated 3T3-L1 adipocytes. Furthermore, AMPK inhibitor (compound C) treatment largely blocked the effects of DHA to inhibit PA-induced ER stress. Our data indicate that n-3 PUFAs suppress ER stress in adipocytes through AMPK activation, and may thereby exert protective effects against high-fat feeding-induced adipose tissue dysfunction and insulin resistance.

Regulation of hepatic lipogenesis by the zinc finger protein Zbtb20.

Hepatic de novo lipogenesis (DNL) converts carbohydrates into triglycerides and is known to influence systemic lipid homoeostasis. Here, we demonstrate that the zinc finger protein Zbtb20 is required for DNL. Mice lacking Zbtb20 in the liver exhibit hypolipidemia and reduced levels of liver triglycerides, along with impaired hepatic lipogenesis. The expression of genes involved in glycolysis and DNL, including that of two ChREBP isoforms, is decreased in livers of knockout mice. Zbtb20 binds to and enhances the activity of the ChREBP-α promoter, suggesting that altered metabolic gene expression is mainly driven by ChREBP. In addition, ChREBP-β overexpression largely restores hepatic expression of genes involved in glucose and lipid metabolism, and increases plasma and liver triglyceride levels in knockout mice. Finally, we show that Zbtb20 ablation protects from diet-induced liver steatosis and improves hepatic insulin resistance. We suggest ZBTB20 is an essential regulator of hepatic lipogenesis and may be a therapeutic target for the treatment of fatty liver disease.

Pharmacological inhibition of adipose triglyceride lipase corrects high-fat diet-induced insulin resistance and hepatosteatosis in mice.

Elevated circulating fatty acids (FAs) contribute to the development of obesity-associated metabolic complications such as insulin resistance (IR) and non-alcoholic fatty liver disease (NAFLD). Hence, reducing adipose tissue lipolysis to diminish the mobilization of FAs and lower their respective plasma concentrations represents a potential treatment strategy to counteract obesity-associated disorders. Here we show that specific inhibition of adipose triglyceride lipase (Atgl) with the chemical inhibitor, Atglistatin, effectively reduces adipose tissue lipolysis, weight gain, IR and NAFLD in mice fed a high-fat diet. Importantly, even long-term treatment does not lead to lipid accumulation in ectopic tissues such as the skeletal muscle or heart. Thus, the severe cardiac steatosis and cardiomyopathy that is observed in genetic models of Atgl deficiency does not occur in Atglistatin-treated mice. Our data validate the pharmacological inhibition of Atgl as a potentially powerful therapeutic strategy to treat obesity and associated metabolic disorders.

Health benefits and consequences of the Eastern Orthodox fasting in monks of Mount Athos: a cross-sectional study.

Greek Orthodox fasting (OF), which involves 180-200 days of fasting per year, is dictated by the Christian Orthodox religion. For the first time, this cross-sectional study examines the characteristics and the effects of OF on anthropometry, cardiometabolic markers and calcium homeostasis in Athonian monks (AMs).

Role of the Cytokine-like Hormone Leptin in Muscle-bone Crosstalk with Aging.

The cytokine-like hormone leptin is a classic adipokine that is secreted by adipocytes, increases with weight gain, and decreases with weight loss. Additional studies have, however, shown that leptin is also produced by skeletal muscle, and leptin receptors are abundant in both skeletal muscle and bone-derived mesenchymal (stromal) stem cells. These findings suggest that leptin may play an important role in muscle-bone crosstalk. Leptin treatment in vitro increases the expression of myogenic genes in primary myoblasts, and leptin treatment in vivo increases the expression of microRNAs involved in myogenesis. Bone marrow adipogenesis is associated with low bone mass in humans and rodents, and leptin can reduce marrow adipogenesis centrally through its receptors in the hypothalamus as well as directly via its receptors in bone marrow stem cells. Yet, central leptin resistance can increase with age, and low circulating levels of leptin have been observed among the frail elderly. Thus, aging appears to significantly alter leptin-mediated crosstalk among various organs and tissues. Aging is associated with bone loss and muscle atrophy, contributing to frailty, postural instability, and the incidence of falls. Therapeutic interventions such as protein and amino acid supplementation that can increase muscle mass and muscle-derived leptin may have multiple benefits for the elderly that can potentially reduce the incidence of falls and fractures.

Deletion of Macrophage Mineralocorticoid Receptor Protects Hepatic Steatosis and Insulin Resistance through ERα/HGF/MET Pathway.

Although the importance of macrophages in nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) has been recognized, it remains elusive how macrophages impact hepatocytes. Mineralocorticoid receptor (MR) has been implied to play important roles in NAFLD and T2DM. However, cellular and molecular mechanisms are largely unknown. Here we report that myeloid MR knockout (MRKO) improves glucose intolerance, insulin resistance, and hepatic steatosis in obese mice. Estrogen signaling is sufficient and necessary for such improvements. Hepatic gene and protein expression suggests that MRKO reduces hepatic lipogenesis and lipid storage. In the presence of estrogen, MRKO in macrophages decreases lipid accumulation and increases insulin sensitivity of hepatocytes through hepatic-growth-factor (HGF)/Met signaling. MR directly regulates estrogen receptor 1 (Esr1, encoding ERα) in macrophages. Knockdown of hepatic Met eliminates the beneficial effects of MRKO in female obese mice. These findings identify a novel MR/ERα/HGF/Met pathway that conveys metabolic signaling from macrophages to hepatocytes in hepatic steatosis and insulin resistance, and provide potential new therapeutic strategies for NAFLD and T2DM.

Extended multiplexing of TMT labeling reveals age and high fat diet specific proteome changes in mouse epididymal adipose tissue.

The lack of high-throughput methods to analyze the adipose tissue protein composition limits our understanding of the protein networks responsible for age and diet related metabolic response. We have developed an approach using multiple-dimension liquid chromatography tandem mass spectrometry and extended multiplexing (24 biological samples) with TMT labeling to analyze proteomes of epididymal adipose tissues isolated from mice fed either low or high fat diet for a short or a long-term, and from mice that aged on low vs. high fat diets. The peripheral metabolic health (as measured by body weight, adiposity, plasma fasting glucose, insulin, triglycerides, total cholesterol levels, and glucose and insulin tolerance tests) deteriorated with diet and advancing age, with long-term high fat diet exposure being the worst. In response to short-term high fat diet, 43 proteins representing lipid metabolism (e.g., AACS, ACOX1, ACLY) and red-ox pathways (e.g., CPD2, CYP2E, SOD3) were significantly altered (FDR < 10%). Long-term high fat diet significantly altered 55 proteins associated with immune response (e.g., IGTB2, IFIT3, LGALS1) and rennin angiotensin system (e.g. ENPEP, CMA1, CPA3, ANPEP). Age-related changes on low fat diet significantly altered only 18 proteins representing mainly urea cycle (e.g., OTC, ARG1, CPS1), and amino acid biosynthesis (e.g., GMT, AKR1C6). Surprisingly, high fat diet driven age-related changes culminated with alterations in 155 proteins involving primarily the urea cycle (e.g., ARG1, CPS1), immune response/complement activation (e.g., C3, C4b, C8, C9, CFB, CFH, FGA), extracellular remodeling (e.g., EFEMP1, FBN1, FBN2, LTBP4, FERMT2, ECM1, EMILIN2, ITIH3) and apoptosis (e.g., YAP1, HIP1, NDRG1, PRKCD, MUL1) pathways. Using our adipose tissue tailored approach we have identified both age-related and high fat diet specific proteomic signatures highlighting a pronounced involvement of arginine metabolism in response to advancing age, and branched chain amino acid metabolism in early response to high fat feeding. Data are available via ProteomeXchange with identifier PXD005953.

Response to Comment on Inzucchi et al. Pioglitazone Prevents Diabetes in Patients With Insulin Resistance and Cerebrovascular Disease. Diabetes Care 2016;39:1684-1692.

Comment on Inzucchi et al. Pioglitazone Prevents Diabetes in Patients With Insulin Resistance and Cerebrovascular Disease. Diabetes Care 2016;39:1684-1692.

Overactivation of the endocannabinoid system alters the anti-lipolytic action of insulin in mouse adipose tissue.

Evidence has accumulated that obesity-related metabolic dysregulation is associated with overactivation of the endocannabinoid system (ECS), which involves cannabinoid receptor 1 (CB1R), in peripheral tissues, including adipose tissue (AT). The functional consequences of CB1R activation on AT metabolism remain unclear. Since excess fat mobilization is considered an important primary event contributing to the onset of insulin resistance, we combined in vivo and in vitro experiments to investigate whether activation of ECS could alter the lipolytic rate. For this purpose, the appearance of plasma glycerol was measured in wild-type and CB1R(-/-) mice after acute anandamide administration or inhibition of endocannabinoid degradation by JZL195. Additional experiments were conducted on rat AT explants to evaluate the direct consequences of ECS activation on glycerol release and signaling pathways. Treatments stimulated glycerol release in mice fasted for 6 h and injected with glucose but not in 24-h fasted mice or in CB1R(-/-) suggesting that the effect was dependent on plasma insulin levels and mediated by CB1R. We concomitantly observed that Akt cascade activity was decreased, indicating an alteration of the anti-lipolytic action of insulin. Similar results were obtained with tissue explants exposed to anandamide, thus identifying CB1R of AT as a major target. This study indicates the existence of a functional interaction between CB1R and lipolysis regulation in AT. Further investigation is needed to test whether the elevation of ECS tone encountered in obesity is associated with excess fat mobilization contributing to ectopic fat deposition and related metabolic disorders.

The potential role of follicle-stimulating hormone in the cardiovascular, metabolic, skeletal, and cognitive effects associated with androgen deprivation therapy.

To explore how follicle-stimulating hormone (FSH) may contribute to cardiovascular, metabolic, skeletal, and cognitive events in men treated for prostate cancer, with various forms of androgen deprivation therapy (ADT).

Erectile dysfunction in patients with nonalcoholic fatty liver disease.

There is a lack of studies on erectile dysfunction (ED) in patients diagnosed with nonalcoholic fatty liver disease (NAFLD). The present study aimed to estimate the prevalence of ED in patients with NAFLD and to determine the independent predictors of ED in these patients.

Physicochemical properties and antidiabetic effects of a polysaccharide from corn silk in high-fat diet and streptozotocin-induced diabetic mice.

This study aimed to investigate the physicochemical properties and antidiabetic effects of a polysaccharide obtained from corn silk (PCS2). PCS2 was isolated and the physicochemical properties were characterized. The hypoglycemic effects were determined using the high-fat diet and streptozocin induced type 2 diabetic mellitus (T2DM) insulin resistance mice. The results showed that PCS2 was a heteropolysaccharide with the average molecular weight of 45.5kDa. PCS2 was composed of d-galactose, d-mannose, d-(+)-glucose, d-(+)-xylose, l-arabinose and l-rhamnose. PCS2 treatment significantly reduced the body weight loss, decreased blood glucose and serum insulin levels, and improved glucose intolerance (P<0.05). The levels of serum lipid profile were regulated and the levels of glycated serum protein, non-esterified fatty acid were decreased significantly (P<0.01). The activities of superoxide dismutase, glutathione peroxidase and catalase were notably improved (P<0.05). PCS2 also exerted cytoprotective action from histopathological observation. These results suggested that PCS2 could be a good candidate of functional food or medicine for T2DM treatment.

Is metabolic dysregulation associated with antidepressant response in depressed women in climacteric treated with individualized homeopathic medicines or fluoxetine? The HOMDEP-MENOP Study.

Climacteric is associated with both depression and metabolic dysregulation. Scarce evidence suggests that metabolic dysregulation may predict poor response to conventional antidepressants. Response to depression treatment has not been studied in homeopathic medicine. The aim of this study was to investigate the prevalence of metabolic disorders in depressed climacteric women treated with homeopathic medicines, fluoxetine or placebo, and if these alterations have any association with response to depression treatment.

Blood Pressure and Metabolic Changes After 3-Month CPAP Therapy in a Very Elderly Obese with Severe Obstructive Sleep Apnea: A Case Report and Review of the Literature.

Age is one of the main risk factor for the presence of obstructive sleep apnea (OSA). This syndrome is associated with hypertension, cardiovascular disease, cognitive impairment and metabolic abnormalities, such as type 2 diabetes. Continuous positive airway pressure (CPAP) represents the gold standard therapy, but its benefit is still to be determined in very elderly. We report the blood pressure and metabolic changes in a very elderly obese with severe OSA after 3-month CPAP therapy. We have evaluated a very elderly obese male affected by severe symptomatic OSA, poor controlled nocturnal hypertension and insulin resistance. After 3-month CPAP therapy, without any changes in drug therapy, we observed a normalization of circadian blood pressure (BP) pattern, an improved insulin sensitivity, together with a reduced resting energy expenditure, despite no significant change in weight. This case report shows the benefits of OSA treatment with CPAP, not only on BP profile, but also on metabolic parameters in a very elderly, a particular type of patient in which scientific evidence is still scant. Further studies are needed to better investigate the relationship between OSA, CPAP therapy and energy expenditure not only in adults but also in elderly patients.

Enzymes involved in branched-chain amino acid metabolism in humans.

Branched-chain amino acids (leucine, isoleucine and valine) are structurally related to branched-chain fatty acids. Leucine is 2-amino-4-methyl-pentanoic acid, isoleucine is 2-amino-3-methyl-pentanoic acid, and valine is 2-amino-3-methyl-butanoic acid. Similar to fatty acid oxidation, leucine and isoleucine produce acetyl-coA. Additionally, leucine generates acetoacetate and isoleucine yields propionyl-coA. Valine oxidation produces propionyl-coA, which is converted into methylmalonyl-coA and succinyl-coA. Branched-chain aminotransferase catalyzes the first reaction in the catabolic pathway of branched-chain amino acids, a reversible transamination that converts branched-chain amino acids into branched-chain ketoacids. Simultaneously, glutamate is converted in 2-ketoglutarate. The branched-chain ketoacid dehydrogenase complex catalyzes the irreversible oxidative decarboxylation of branched-chain ketoacids to produce branched-chain acyl-coA intermediates, which then follow separate catabolic pathways. Human tissue distribution and function of most of the enzymes involved in branched-chain amino acid catabolism is unknown. Congenital deficiencies of the enzymes involved in branched-chain amino acid metabolism are generally rare disorders. Some of them are associated with reduced pyruvate dehydrogenase complex activity and respiratory chain dysfunction that may contribute to their clinical phenotype. The biochemical phenotype is characterized by accumulation of the substrate to the deficient enzyme and its carnitine and/or glycine derivatives. It was established at the beginning of the twentieth century that the plasma level of the branched-chain amino acids is increased in conditions associated with insulin resistance such as obesity and diabetes mellitus. However, the potential clinical relevance of this elevation is uncertain.

Effects of Metreleptin in Pediatric Patients with Lipodystrophy.

Lipodystrophy syndromes are rare disorders of deficient adipose tissue. Metreleptin, a human analog of leptin, improved metabolic abnormalities in mixed cohorts of leptin-deficient children and adults with lipodystrophy.

Gestational Protein Restriction impairs Glucose Disposal in the Gastrocnemius muscles of Female Rats.

Gestational low protein (LP) diet causes hyperglycemia and insulin resistance in adult offspring but the mechanism is not clearly understood. In this study, we explored the role of insulin signaling in gastrocnemius muscles of gestational LP exposed female offspring. Pregnant rats were fed control (20% protein) or isocaloric LP (6%) diet from gestational day 4 until delivery. Normal diet was given to mothers after delivery and to pups after weaning until necropsy. Offspring were euthanized at 4 months and gastrocnemius muscles were treated with insulin ex vivo for 30 min. mRNA and protein levels of molecules involved in insulin signaling were assessed at 4 months. LP females were smaller at birth but showed rapid catch up growth by 4 weeks. Glucose tolerance test in LP offspring at 3 months showed elevated serum glucose levels (p<0.01; glycemia ΔAUC 342±28 in LP vs.155±23 in controls, mmol/L*120min) without any change in insulin levels. In gastrocnemius muscles, LP rats showed reduced tyrosine phosphorylation of IRS-1 upon insulin stimulation due to the overexpression of tyrosine phosphatase SHP-2 however, serine phosphorylation was unaffected. Further, insulin induced phosphorylation of Akt, GSK-3α and GSK-3β were diminished in LP rats and they displayed an increased basal phosphorylation (inactive form) of glycogen synthase. Our study shows that gestational protein restriction causes peripheral insulin resistance by a series of phosphorylation defects in skeletal muscle in a mechanism involving IRS1, SHP-2, Akt, GSK-3 and GS causing dysfunctional GSK-3 signaling and increased stored glycogen leading to distorted glucose homeostasis.

Substrate Metabolism and Insulin Sensitivity During Fasting in Obese Human Subjects: Impact of GH Blockade.

Insulin resistance and metabolic inflexibility are features of obesity and are amplified by fasting. GH secretion increases during fasting and GH causes insulin resistance.

Hepatic Insulin Resistance and Altered Gluconeogenic Pathway in Premature Baboons.

Premature infants have altered glucose regulation early in life and increased risk for diabetes in adulthood. Although prematurity leads to an increased risk of diabetes and metabolic syndrome in adult life, the role of hepatic glucose regulation and adaptation to an early extra-uterine environment in preterm infants remain unknown. The purpose of this study was to investigate developmental differences in glucose metabolism, hepatic protein content and gene expression of key insulin signaling/gluconeogenic molecules. Fetal baboons were delivered at 67%, 75%, and term gestational age and sacrificed at birth. Neonatal baboons were delivered prematurely (67% gestation) and survived for 2 weeks, and compared to similar postnatal term animals and underwent serial hyperinsulinemic-euglycemic clamp studies. Premature baboons had decreased endogenous glucose production compared to term animals. Consistent with these results, the gluconeogenic molecule, PEPCK mRNA, was decreased in preterm baboons compared to terms. Hepatic insulin signaling was altered by preterm birth as evidenced by decreased insulin receptor (IR)-β, p85 subunit of PI3K, phosphorylated IRS-1, and Akt-1 under insulin stimulated conditions. Furthermore, preterm baboons failed to have the normal increase in GSK-3 from fetal to postnatal life. The blunted responses in hepatic insulin signaling may contribute to the hyperglycemia of prematurity, while impaired endogenous glucose production leads to hypoglycemia of prematurity.

Autotaxin is Regulated by Glucose and Insulin in Adipocytes.

Autotaxin (ATX) is an adipokine that generates the bioactive lipid, lysophosphatidic acid. Despite recent studies implicating adipose-derived ATX in metabolic disorders including obesity and insulin resistance, the nutritional and hormonal regulation of ATX in adipocytes remains unclear. The present study examined the regulation of ATX in adipocytes by glucose and insulin and the role of ATX in adipocyte metabolism. Induction of insulin resistance in adipocytes with high glucose and insulin concentrations increased ATX secretion, whereas co-incubation with the insulin sensitizer, rosiglitazone, prevented this response. Moreover, glucose independently increased ATX mRNA, protein, and activity in a time- and concentration-dependent manner. Glucose also acutely upregulated secreted ATX activity in subcutaneous adipose tissue explants. Insulin elicited a bi-phasic response. Acute insulin stimulation increased ATX activity in a PI3Kinase-dependent and mTORC1-independent manner, whereas chronic insulin stimulation decreased ATX mRNA, protein, and activity. To examine the metabolic role of ATX in 3T3-L1 adipocytes, we incubated cells with the ATX inhibitor, PF-8380, for 24 h. While ATX inhibition increased the expression of peroxisome proliferator-activated receptor γ (PPARγ) and its downstream targets, insulin signaling and mitochondrial respiration were unaffected. However, ATX inhibition enhanced mitochondrial H2O2 production. Taken together, this study suggests that ATX secretion from adipocytes is differentially regulated by glucose and insulin. This study also suggests that inhibition of autocrine/paracrine ATX-LPA signaling does not influence insulin signaling or mitochondrial respiration, but increases reactive oxygen species production in adipocytes.

Separating the Anti-Inflammatory and Diabetogenic Effects of Glucocorticoids through LXRβ Antagonism.

Synthetic glucocorticoids (GCs) including dexamethasone (DEX) are powerful anti-inflammatory drugs. Long-term use of GCs, however, can result in metabolic side effects such as hyperglycemia, hepatosteatosis, and insulin resistance. The glucocorticoid receptor (GR) and liver X receptors (LXRα and LXRβ) regulate overlapping genes involved in gluconeogenesis and inflammation. We have previously shown that Lxrβ-/- mice are resistant to the diabetogenic effects of DEX, but still sensitive to its immunosuppressive actions. To determine whether this finding could be exploited for therapeutic intervention, we treated mice with GSK2033, a pan-LXR antagonist, alone or in combination with DEX. Herein, we report that GSK2033 suppressed GC-induced gluconeogenic gene expression without affecting immune responsive GR target genes. The suppressive effect of GSK2033 on DEX-induced gluconeogenic genes was specific to LXRβ, liver cell autonomous and occurred in a target gene specific manner. Compared to DEX treatment alone, the co-administration of GSK2033 with DEX decreased the recruitment of GR and its accessory factors MED1 and C/EBPβ to the Pepck promoter. Interestingly, GSK2033 had no effect on DEX-mediated suppression of inflammatory genes expressed in the liver or in mouse primary macrophages stimulated with LPS. In conclusion, our study provides evidence that the gluconeogenic and immunosuppressive actions of GR activation can be mechanistically dissociated by pharmacological antagonism of LXRβ. Treatment with an LXRβ antagonist could allow the safer use of existing glucocorticoid drugs in patients requiring chronic dosing of anti-inflammatory agents for the treatment of diseases such as rheumatoid arthritis and inflammatory bowel disease.

Bone turnover is suppressed in insulin resistance, independent of adiposity.

The contribution of insulin resistance vs. adiposity to bone mineral density (BMD), bone turnover and fractures in humans remains unclear.

Whole-body vibration mimics the metabolic effects of exercise in male leptin receptor deficient mice.

Whole-body vibration has gained attention as a potential exercise mimetic, but direct comparisons with the metabolic effects of exercise are scarce. To determine whether whole-body vibration recapitulates the metabolic and osteogenic effects of physical activity, we exposed male wildtype (Wt) and leptin receptor deficient (db/db) mice to daily treadmill exercise or whole-body vibration for three months. Body weights were analyzed and compared with Wt and db/db mice that remained sedentary. Glucose and insulin tolerance testing revealed comparable attenuation of hyperglycemia and insulin resistance in db/db mice following treadmill exercise or whole-body vibration. Both interventions reduced body weight in db/db mice and normalized muscle fiber diameter. Treadmill exercise and whole-body vibration also attenuated adipocyte hypertrophy in visceral adipose tissue and reduced hepatic lipid content in db/db mice. Although the effects of leptin receptor deficiency on cortical bone structure were not eliminated by either intervention, exercise and whole-body vibration increased circulating levels of osteocalcin in db/db mice. In the context of increased serum osteocalcin, the modest effects of TE and WBV on bone geometry, mineralization, and biomechanics may reflect subtle increases in osteoblast activity in multiple areas of the skeleton. Taken together, these observations indicate that whole-body vibration recapitulates the effects of exercise on metabolism in type 2 diabetes.

Chronic intranasal insulin does not affect hepatic lipids, but lowers circulating BCAAs in healthy male subjects.

Non-alcoholic fatty liver disease and elevated circulating branched-chain amino acids (BCAAs) are common characteristics of obesity and type 2 diabetes. In rodents, brain insulin signaling controls both hepatic triglyceride secretion and BCAA catabolism. Whether brain insulin signaling controls similar metabolic pathways in humans is unknown.

Assisted reproductive technologies predispose to insulin resistance and obesity in male mice challenged with a high fat diet.

ART alters glucose homeostasis in mice and humans, but the underlying mechanisms are incompletely understood. ART induces endothelial dysfunction and arterial hypertension by epigenetic alteration of the eNOS gene. In eNOS deficient mice, insulin resistance is related to impaired insulin stimulation of muscle blood flow and substrate delivery and defective intrinsic skeletal muscle glucose uptake. We, therefore, assessed glucose tolerance, insulin sensitivity (euglycemic clamp), insulin stimulation of muscle blood flow in vivo and muscle glucose uptake in vitro in male ART and control mice fed a normal chow (NC) or challenged with a high fat diet (HFD) during 8 weeks. Glucose tolerance and insulin-sensitivity were similar in NC-fed animals. When challenged with HFD, however, ART mice developed exaggerated obesity, fasting hyperinsulinemia and hyperglycemia and a 20% lower insulin-stimulated glucose utilization than control mice (steady state GIR, 51.3±7.3 vs. 64.0±10.8 mg/kg • min, P=0.012). ART-induced insulin resistance was associated with defective insulin stimulation of muscle blood flow, whereas intrinsic skeletal muscle glucose uptake was normal. In conclusion, ART-induced endothelial dysfunction, when challenged with a metabolic stress facilitates glucose intolerance and insulin-resistance. Similar mechanisms may contribute to ART-induced alterations of the metabolic phenotype in humans.