Extrahepatic morbidity and mortality of chronic hepatitis C

Chronic hepatitis C virus (HCV) infection is associated with several extrahepatic manifestations. Patients with HCV may develop mixed cryoglobulinemia and its sequelae, ranging from cutaneous and visceral vasculitis to glomerulonephritis and B-cell non-Hodgkin lymphoma. HCV-infected patients have increased rates of insulin resistance, diabetes, and atherosclerosis, which may lead to increased cardiovascular morbidity and mortality. Neurological manifestations of HCV infection include fatigue and cognitive impairment. The mechanisms causing the extrahepatic effects of HCV infection are likely multifactorial and may include endocrine effects, HCV replication in extrahepatic cells, or a heightened immune reaction with systemic effects. Successful eradication of HCV with interferon alfa and ribavirin was shown to improve some of these extrahepatic effects; sustained virological response is associated with resolution of complications of cryoglobulinemia, reduced levels of insulin resistance, reduced incidence of diabetes and stroke, and improved fatigue and cognitive functioning. The availability of new interferon-free, well-tolerated anti-HCV treatment regimens is broadening the spectrum of patients available for therapy, including those in whom interferon was contraindicated, and will likely result in greater improvements in the extrahepatic manifestations of HCV. If these regimens are shown to confer significant benefit in the metabolic, cardiovascular, or neuropsychiatric conditions associated with HCV infection, extrahepatic manifestations of HCV may become a major indication for treatment even in the absence of liver disease.

Dairy consumption, cardiovascular risk factors and inflammation in elderly subjects

BACKGROUND

Previous epidemiological studies of dairy product consumption and health outcomes have reported mixed findings. Despite increasing in life expectancy, scarce data are available in this field in elderly individuals. We tested the hypothesis that greater dairy intake is associated with lower high sensitive C-reactive protein (hs-CRP) level and better lipid profile and glycemic control.

METHODS

This cross-sectional study was undertaken on 107 elderly individuals who aged 60-78 years. Usual dietary intakes were assessed by means of a validated food frequency questionnaire (FFQ). Anthropometric measures and biochemical markers were determined using standard protocols.

RESULTS

The reported mean ± standard deviation (SD) of daily intake of dairy products and age were 588.02 ± 418.88 g/d and 63.22 ± 6.92 years, respectively. After control for demographic characteristics and dietary intakes, dairy consumption was not significantly related to the increased risk of insulin resistance [Odds ratio (OR): 2.19, 95% confidence interval (CI): 0.54, 8.86; P = 0.520] and elevated hs-CRP (OR: 1.54, 95% CI: 0.37, 6.35; P = 0.550). Participants in the top tertile of dairy had greater, but statistically not a significant risk of elevated triglyceride (TG), total cholesterol and low-density lipoprotein cholesterol (LDL-C). No significant relations were seen for hs-CRP, insulin resistance and lipid profile across tertiles of dairy products.

CONCLUSION

In this elderly population, total dairy consumption was not associated with inflammatory biomarkers levels and other cardiometabolic risk factors.

Fitness Level is Associated with Sex-Specific Regional Fat Differences in Normal Weight Young Adults

OBJECTIVES

To characterize regional body composition and insulin sensitivity differences between young adults who were normal weight with either high or low fitness determined by VO₂ peak. We hypothesized that higher fitness levels would be associated with reduced visceral fat (VAT) and improved insulin sensitivity.

DESIGN

A cross-sectional comparison of normal weight males and females with high or low fitness matched on age and sex.

METHODS

A total of 38 (20M/18F) individuals were recruited for this study. Thirty-two young adults (18M/14F) were matched on age (mean 22.5 ± 3 yrs.) and BMI (22.4 ± 2.4 kg/m²) and sex and classified by high or low fitness based on VO₂ peak difference (≥ 8ml/kg/min). Total and regional body composition, including VAT, was measured by Dual Energy X-Ray Absorptiometry (DXA). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. An analysis of variance compared regional body composition and insulin sensitivity between high and low fitness young adults with a normal BMI.

RESULTS

Higher fitness was associated with significantly lower percent body fat, lower android fat mass and higher insulin sensitivity in males (-7.2%, P<0.001; -0.5kg, P=0.048; 5.6mg/kg (FFM)/min, p=0.002). In females, higher fitness was associated with significantly lower percent body fat, lower leg fat but no difference in insulin sensitivity (-6.7%, P=0.001; -2.7kg, P<0.001; 2.5 mg/kg(FFM)/min, P=0.40). No differences in VAT were observed between high and low fitness groups. Interestingly in females, there was no difference in total lean mass, trunk lean mass or leg lean mass (P=0.59, P=0.17, P=0.99).

CONCLUSION

Higher fitness does not influence VAT in normal weight individuals. Sex influenced regional fat and insulin sensitivity differences between high fitness and low fitness groups.

The metabolic syndrome and inflammation: role of insulin resistance and increased adiposity

OBJECTIVES

We sought to determine the role of obesity and insulin resistance (IR) in the pathogenesis of inflammation in metabolic syndrome (MetS).

METHODS

Our study included 100 patients with MetS and 100 age and gender matched control patients who attended a tertiary care laboratory in Rawalpindi, Pakistan. Anthropometric data was obtained including height and weight to calculate body mass index. A record of patient's blood pressure (BP), waist circumference (WC) and hip circumference (HC) was made. Biochemical analysis included measurements of fasting glucose, triglycerides (TG), high-density lipoprotein cholesterol (HDL-c), insulin, and high-sensitivity C reactive protein (hsCRP). IR was determined by the homeostasis mode assessment insulin resistance (HOMA-IR) method.

RESULTS

The levels of hs-CRP were found to be elevated in all patients with MetS where it correlated significantly with all its components including measures of obesity, fasting insulin and glucose levels, IR, TG and HDL-c. However, on linear regression analysis only WC, fasting insulin, and HOMA-IR remained significantly correlated with hs-CRP.

CONCLUSION

MetS is a condition characterized by chronic low-grade inflammation, which arises because of increased abdominal adiposity and IR. Large multicenter studies are needed to gain insight into its pathogenesis and derive treatment strategies.

Relation of Osteoprotegerin, Visfatin and Ghrelin to Metabolic Syndrome in Type 2 Diabetic Patients

BACKGROUND

It is now realized that insulin resistance plays a principal role in initiating the pathologic manifestations of the metabolic syndrome (MetS).

OBJECTIVES

The aim of this study was to assess the possible role of osteoprotegerin, visfatin and ghrelin in the pathogenesis of MetS among type 2 diabetes mellitus (T2DM).

DESIGN AND METHODS

Serum blood samples were obtained from 116 subjects (39 T2DM; 48 T2DM with MetS; 29 healthy controls). Glycemic status and lipid profile were assessed by enzymatic method. Osteoprotegerin, visfatin, ghrelin and insulin were measured by ELISA method.

RESULTS

Osteoprotegerin and visfatin were significantly higher, while ghrelin was significantly lower in diabetic patients compared to healthy control group (p<0.05). Moreover, Osteoprotegerin and visfatin showed significant higher levels in T2DM patients with MetS than those without MetS (p<0.05). The best cut-off values for the investigated markers were determined by ROC curve. Osteoprotegerin (1.06 ng/mL), visfatin (32.27 ng/mL) and ghrelin (33.65 pg/mL) presented sensitivity of 76%, 92% and 39.1%; respectively and specificity of 41%, 69.2% and 62.9%; respectively, in predicting MetS among T2DM. Among the investigated parameters, Visfatin was the one which predicts MetS among diabetic patients [AUC=0.88, p<0.05].

CONCLUSION

Osteoprotegerin, visfatin and ghrelin might be implicated in the pathogenesis of diabetes. Moreover, osteoprotegerin and visfatin may have additional potential role in the development of the metabolic syndrome. Visfatin was superior among studied parameters in predicting MetS among T2DM.

Nox2 mediates skeletal muscle insulin resistance induced by a high fat diet

Inflammation and oxidative stress through the production of reactive oxygen species (ROS) are consistently associated with metabolic syndrome/type 2 diabetes. Although the role of Nox2, a major ROS-generating enzyme, is well described in host defense and inflammation, little is known about its potential role in insulin resistance in skeletal muscle. Insulin resistance induced by a high fat diet was mitigated in Nox2-null mice compared with wild-type mice after 3 or 9 months on the diet. High fat feeding increased Nox2 expression, superoxide production, and impaired insulin signaling in skeletal muscle tissue of wild-type mice but not in Nox2-null mice. Exposure of C2C12 cultured myotubes to either high glucose concentration, palmitate, or H2O2 decreases insulin-induced Akt phosphorylation and glucose uptake. Pretreatment with catalase abrogated these effects, indicating a key role for H2O2 in mediating insulin resistance. Down-regulation of Nox2 in C2C12 cells by shRNA prevented insulin resistance induced by high glucose or palmitate but not H2O2. These data indicate that increased production of ROS in insulin resistance induced by high glucose in skeletal muscle cells is a consequence of Nox2 activation. This is the first report to show that Nox2 is a key mediator of insulin resistance in skeletal muscle.

Opposite cross-talk by oleate and palmitate on insulin signaling in hepatocytes through macrophage activation

Chronic low grade inflammation in adipose tissue during obesity is associated with an impairment of the insulin signaling cascade. In this study, we have evaluated the impact of palmitate or oleate overload of macrophage/Kupffer cells in triggering stress-mediated signaling pathways, in lipoapoptosis, and in the cross-talk with insulin signaling in hepatocytes. RAW 264.7 macrophages or Kupffer cells were stimulated with oleate or palmitate, and levels of M1/M2 polarization markers and the lipidomic profile of eicosanoids were analyzed. Whereas proinflammatory cytokines and total eicosanoids were elevated in macrophages/Kupffer cells stimulated with palmitate, enhanced arginase 1 and lower leukotriene B4 (LTB4) levels were detected in macrophages stimulated with oleate. When hepatocytes were pretreated with conditioned medium (CM) from RAW 264.7 or Kupffer cells loaded with palmitate (CM-P), phosphorylation of stress kinases and endoplasmic reticulum stress signaling was increased, insulin signaling was impaired, and lipoapoptosis was detected. Conversely, enhanced insulin receptor-mediated signaling and reduced levels of the phosphatases protein tyrosine phosphatase 1B (PTP1B) and phosphatase and tensin homolog (PTEN) were found in hepatocytes treated with CM from macrophages stimulated with oleate (CM-O). Supplementation of CM-O with LTB4 suppressed insulin sensitization and increased PTP1B and PTEN. Furthermore, LTB4 decreased insulin receptor tyrosine phosphorylation in hepatocytes, activated the NFκB pathway, and up-regulated PTP1B and PTEN, these effects being mediated by LTB4 receptor BTL1. In conclusion, oleate and palmitate elicit an opposite cross-talk between macrophages/Kupffer cells and hepatocytes. Whereas CM-P interferes at the early steps of insulin signaling, CM-O increases insulin sensitization, possibly by reducing LTB4.

Increasing adipocyte lipoprotein lipase improves glucose metabolism in high fat diet-induced obesity

Lipid accumulation in liver and skeletal muscle contributes to co-morbidities associated with diabetes and obesity. We made a transgenic mouse in which the adiponectin (Adipoq) promoter drives expression of lipoprotein lipase (LPL) in adipocytes to potentially increase adipose tissue lipid storage. These mice (Adipoq-LPL) have improved glucose and insulin tolerance as well as increased energy expenditure when challenged with a high fat diet (HFD). To identify the mechanism(s) involved, we determined whether the Adipoq-LPL mice diverted dietary lipid to adipose tissue to reduce peripheral lipotoxicity, but we found no evidence for this. Instead, characterization of the adipose tissue of the male mice after HFD challenge revealed that the mRNA levels of peroxisome proliferator-activated receptor-γ (PPARγ) and a number of PPARγ-regulated genes were higher in the epididymal fat pads of Adipoq-LPL mice than control mice. This included adiponectin, whose mRNA levels were increased, leading to increased adiponectin serum levels in the Adipoq-LPL mice. In many respects, the adipose phenotype of these animals resembles thiazolidinedione treatment except for one important difference, the Adipoq-LPL mice did not gain more fat mass on HFD than control mice and did not have increased expression of genes in adipose such as glycerol kinase, which are induced by high affinity PPAR agonists. Rather, there was selective induction of PPARγ-regulated genes such as adiponectin in the adipose of the Adipoq-LPL mice, suggesting that increasing adipose tissue LPL improves glucose metabolism in diet-induced obesity by improving the adipose tissue phenotype. Adipoq-LPL mice also have increased energy expenditure.

Carrageenan Inhibits Insulin Signaling through GRB10-mediated Decrease in Tyr(P)-IRS1 and through Inflammation-induced Increase in Ser(P)307-IRS1

Inflammation induced by exposure to the common food additive carrageenan leads to insulin resistance by increase in Ser(P)(307)-insulin receptor substrate 1 (IRS1) and subsequent decline in the insulin-stimulated increase in Ser(P)(473)-AKT. Inhibition of carrageenan-induced inflammation reversed the increase in Ser(P)(307)-IRS1 but did not completely reverse the carrageenan-induced decline in Ser(P)(473)-AKT. To identify the additional mechanism responsible for the decrease in Ser(P)(473)-AKT, studies were performed in human HepG2 cells and in C57BL/6J mice. Following carrageenan, expression of GRB10 (growth factor receptor-bound 10 protein), an adaptor protein that binds to the insulin receptor and inhibits insulin signaling, increased significantly. GRB10 silencing blocked the carrageenan-induced reduction of the insulin-stimulated increase in Tyr(P)-IRS1 and partially reversed the decline in Ser(P)(473)-AKT. The combination of GRB10 silencing with BCL10 silencing and the reactive oxygen species inhibitor Tempol completely reversed the decline in Ser(P)(473)-AKT. After carrageenan, GRB10 promoter activity was enhanced because of activation by GATA2. A direct correlation between Ser(P)(473)-AKT and Ser(P)(401)-GATA2 was evident, and inhibition of AKT phosphorylation by the PI3K inhibitor LY294002 blocked Ser(401)-GATA2 phosphorylation and the increase in GRB10 expression. Studies indicated that carrageenan inhibited insulin signaling by two mechanisms: through the inflammation-mediated increase in Ser(P)(307)-IRS1, a negative regulator of insulin signaling, and through a transcriptional mechanism leading to increase in GRB10 expression and GRB10-inhibition of Tyr(P)-IRS1, a positive regulator of insulin signaling. These mechanisms converge to inhibit the insulin-induced increase in Ser(P)(473)-AKT. They provide internal feedback, mediated by Ser(P)(473)-AKT, Ser(P)(401)-GATA2, and nuclear GATA2, which links the opposing effects of serine and tyrosine phosphorylations of IRS1 and can modulate insulin responsiveness.

Spirituality moderates the relationship of psychosocial stress to metabolic risk factors among Afro-Caribbean immigrants in the US Virgin Islands

OBJECTIVE

Spirituality may contribute to the health advantage of foreign-born blacks compared to United States (US)-born blacks. The objective of this study was to test the hypothesis that spirituality attenuates the association of psychosocial stress to stress-associated metabolic risk factors among foreign-born Caribbean blacks living in a US jurisdiction.

METHODS

Data on demographic factors, anthropometric measurements (height, weight and waist), fasting glucose and insulin, lifestyle behaviors (smoking and alcohol use), psychosocial stress and spirituality were collected from a population-based sample of 319 Afro-Caribbean immigrants, ages 20 and older, who were recruited between 1995 and 2000 in the Virgin Islands of the United States (USVI). Glucose and insulin measurements were used to estimate insulin resistance by the homeostasis model assessment (HOMA-IR) method. Participants were classified into three levels of spirituality, "low", "medium" and "high" based on the distribution of spirituality scores. Stepwise regression analyses were used to identify the significant predictors of waist circumference and HOMA-IR within each level of spirituality.

RESULTS

The predictors of waist circumference and HOMA-IR varied across the levels of spirituality. Psychosocial stress was an independent predictor of waist and HOMA-IR only among participants with a low level of spirituality.

CONCLUSION

Spirituality appears to attenuate the association of psychosocial stress to waist circumference and insulin resistance among Afro-Caribbean immigrants in the USVI.

Selective insulin resistance in adipocytes

Aside from glucose metabolism, insulin regulates a variety of pathways in peripheral tissues. Under insulin-resistant conditions, it is well known that insulin-stimulated glucose uptake is impaired, and many studies attribute this to a defect in Akt signaling. Here we make use of several insulin resistance models, including insulin-resistant 3T3-L1 adipocytes and fat explants prepared from high fat-fed C57BL/6J and ob/ob mice, to comprehensively distinguish defective from unaffected aspects of insulin signaling and its downstream consequences in adipocytes. Defective regulation of glucose uptake was observed in all models of insulin resistance, whereas other major actions of insulin such as protein synthesis and anti-lipolysis were normal. This defect corresponded to a reduction in the maximum response to insulin. The pattern of change observed for phosphorylation in the Akt pathway was inconsistent with a simple defect at the level of Akt. The only Akt substrate that showed consistently reduced phosphorylation was the RabGAP AS160 that regulates GLUT4 translocation. We conclude that insulin resistance in adipose tissue is highly selective for glucose metabolism and likely involves a defect in one of the components regulating GLUT4 translocation to the cell surface in response to insulin.

A comprehensive review of metabolic syndrome affecting erectile dysfunction

INTRODUCTION

Metabolic syndrome (MetS) is the most important public health issue threatening the health of men and women all over the world. Its current prevalence (i.e., approximately 30%) is continuously increasing. MetS by itself is considered a risk factor for erectile dysfunction (ED).

AIM

To focus on the definition epidemiology, pathogenesis, and possible mechanistic links between MetS and ED in order to provide guidelines for treating such individuals.

METHODS

The search strategies yielded total records screened from PubMed.

MAIN OUTCOME MEASURES

Regardless of the definition, MetS consists of insulin resistance, hypertension, dyslipidemia, and obesity. MetS is not an end disease but is a disorder of energy utilization and storage.

RESULTS

The prevalence of ED in patients with MetS is almost twice than in those without MetS, and about 40% of patients with ED have MetS. An important mechanism linking MetS and ED is hypogonadism.

CONCLUSIONS

Recognizing through ED, underlying conditions such as hypogonadism, diabetes and MetS might be a useful motivation for men to improve their health-related choices. The clinical management of MetS can be done by therapeutic interventions that include lifestyle modifications, hormone replacement alone or in combination with phosphodiesterase 5 inhibitors, and other pharmacological treatments.

Integrin α1-null mice exhibit improved fatty liver when fed a high fat diet despite severe hepatic insulin resistance

Hepatic insulin resistance is associated with increased collagen. Integrin α1β1 is a collagen-binding receptor expressed on hepatocytes. Here, we show that expression of the α1 subunit is increased in hepatocytes isolated from high fat (HF)-fed mice. To determine whether the integrin α1 subunit protects against impairments in hepatic glucose metabolism, we analyzed glucose tolerance and insulin sensitivity in HF-fed integrin α1-null (itga1(-/-)) and wild-type (itga1(+/+)) littermates. Using the insulin clamp, we found that insulin-stimulated hepatic glucose production was suppressed by ∼50% in HF-fed itga1(+/+) mice. In contrast, it was not suppressed in HF-fed itga1(-/-) mice, indicating severe hepatic insulin resistance. This was associated with decreased hepatic insulin signaling in HF-fed itga1(-/-) mice. Interestingly, hepatic triglyceride and diglyceride contents were normalized to chow-fed levels in HF-fed itga1(-/-) mice. This indicates that hepatic steatosis is dissociated from insulin resistance in HF-fed itga1(-/-) mice. The decrease in hepatic lipid accumulation in HF-fed itga1(-/-) mice was associated with altered free fatty acid metabolism. These studies establish a role for integrin signaling in facilitating hepatic insulin action while promoting lipid accumulation in mice challenged with a HF diet.

Reduced CD300LG mRNA tissue expression, increased intramyocellular lipid content and impaired glucose metabolism in healthy male carriers of Arg82Cys in CD300LG: a novel genometabolic cross-link between CD300LG and common metabolic phenotypes

BACKGROUND

CD300LG rs72836561 (c.313C>T, p.Arg82Cys) has in genetic-epidemiological studies been associated with the lipoprotein abnormalities of the metabolic syndrome. CD300LG belongs to the CD300-family of membrane-bound molecules which have the ability to recognize and interact with extracellular lipids. We tested whether this specific polymorphism results in abnormal lipid accumulation in skeletal muscle and liver and other indices of metabolic dysfunction.

METHODS

40 healthy men with a mean age of 55 years were characterized metabolically including assessment of insulin sensitivity by the hyperinsulinemic euglycemic clamp, intrahepatic lipid content (IHLC) and intramyocellular lipid content (IMCL) by MR spectroscopy, and β-cell function by an intravenous glucose tolerance test. Changes in insulin signaling and CD300LG mRNA expression were determined by western blotting and quantitative PCR in muscle and adipose tissue.

RESULTS

Compared with the 20 controls (CC carriers), the 20 CT carriers (polymorphism carriers) had higher IMCL (p=0.045), a reduced fasting forearm glucose uptake (p=0.011), a trend toward lower M-values during the clamp; 6.0 mg/kg/min vs 7.1 (p=0.10), and higher IHLC (p=0.10). CT carriers had lower CD300LG mRNA expression and CD300LG expression in muscle correlated with IMCL (β=-0.35, p=0.046), forearm glucose uptake (β=0.37, p=0.03), and tended to correlate with the M-value (β=0.33, p=0.06), independently of CD300LG genotype. β-cell function was unaffected.

CONCLUSIONS

The CD300LG polymorphism was associated with decreased CD300LG mRNA expression in muscle and adipose tissue, increased IMCL, and abnormalities of glucose metabolism. CD300LG mRNA levels correlated with IMCL and forearm glucose uptake. These findings link a specific CD300LG polymorphism with features of the metabolic syndrome suggesting a role for CD300LG in the regulation of common metabolic traits.

TRIAL REGISTRATION NUMBER

NCT01571609.

Initiation of human regular U-500 insulin use is associated with improved glycemic control: a real-world US cohort study

AIM

Describe the characteristics of patients initiating human regular U-500 insulin (U-500R) and their subsequent glycemic control in a real-world setting.

METHODS

US Humedica electronic health record system data (July 2007-September 2011) were used to identify patients with diabetes aged ≥18 years with ≥1 records for U-500R prescriptions, 6 months of preindex data, 12 months following first use of U-500R, and at least one glycated hemoglobin (HbA1c) value in both preindex and postindex periods. Paired t tests were used to measure the change in HbA1c from preindex to postindex periods (last or most recent values) and hypoglycemia.

RESULTS

Among patients initiating U-500R (N=445), 96.9% had type 2 diabetes with mean age 57 years and mean body mass index 40.4 kg/m(2). Postindex prescriptions were written for U-500R alone (47.0%, group A) and concomitant U-500R/U-100 insulins (53.0%, group B). Concomitant oral antihyperglycemic agents (AHAs) and non-insulin injectable AHAs were used by 43.4% and 14.6% of patients, respectively. Following initiation of U-500R, mean HbA1c improved 0.68% in all patients (p<0.0001 compared with baseline), but the decrease in HbA1c did not differ significantly between groups (A: 0.78%; B: 0.60%). Overall, hypoglycemic events, largely captured in the outpatient setting, increased in incidence from 6.7% to 11.9% (p≤0.0001) and from 0.23 to 0.39 events/patient/year, an increase of 0.16 (p=0.003), from preindex to postindex.

CONCLUSIONS

This real-world outcomes analysis demonstrates that U-500R initiation is associated with a clinically meaningful improvement in glycemic control over the subsequent 12-month period with modest increase in incidence and rate of hypoglycemia.

Effect of a 1-week, eucaloric, moderately high-fat diet on peripheral insulin sensitivity in healthy premenopausal women

OBJECTIVES

To determine whether a weight-maintaining, moderate (50%) high-fat diet is deleterious to insulin sensitivity in healthy premenopausal women.

DESIGN/SETTING/PARTICIPANTS

23 African-American and non-Hispanic white, healthy, overweight, and obese premenopausal women recruited in New York City, USA, fed either a eucaloric, 1-week long high-fat (50% of total Kcal from fat) diet or a eucaloric, 1-week long low-fat (30% of total Kcal from fat) diet, assigned in a randomized crossover design.

MAIN OUTCOME MEASURES

Peripheral insulin sensitivity and metabolic flexibility during a euglycemic hyperinsulinemic (80 mU/m(2)/min) clamp measured during the follicular phase of the menstrual cycle, at the end of each diet period.

RESULTS

Peripheral insulin sensitivity (mg kg/fat-free mass/min (µU/mL)×10(-1)) was not decreased after the high-fat diet vs the low-fat diet (0.09±0.01 vs 0.08±0.01, p=0.09, respectively) in the combined group of African-American and white women, with no significant diet by race interaction (p=0.6). Metabolic flexibility (change in substrate utilization, ΔNPRQ, in response to insulin during the clamp) was similarly unaltered by the diet (0.12±0.01 vs 0.11, p=0.48, for the high-fat diet vs the low-fat diet, respectively) in the combined group of women, with no significant diet by race interaction (p=0.9). African-American women had a lower insulin clearance compared with the white women, regardless of the diet (p<0.05).

CONCLUSIONS

We conclude that a short term (1 week), moderate (50%), eucaloric high-fat diet does not lower peripheral insulin sensitivity in healthy, overweight and obese premenopausal women.

Effect of Vitamin D Supplementation on Glucose Control and Inflammatory Response in Type II Diabetes: A Double Blind, Randomized Clinical Trial

BACKGROUND

Diabetes mellitus (DM) and vitamin D deficiency are major health concerns around the world. Evidence suggests a possible role of vitamin D in improvement of insulin secretion and sensitivity.

OBJECTIVES

We assessed whether vitamin D supplementation could be used in vitamin D deficient-type II diabetes to improve glucose metabolism, components of metabolic syndrome (MetS) and specific inflammatory biomarkers.

PATIENTS AND METHODS

A double blind, randomized clinical trial was conducted in King Khalid University Hospital, Saudi Arabia to evaluate the effect of cholecalciferol supplementation on glycemic control, MetS components and specific inflammatory biomarkers including tumor necrosis factor-alpha (TNF-α), Interleukin (IL-6), leptin, adiponectin and vascular cell adhesion molecule-1 (VCAM-1). Twenty-two patients with type II diabetes with insulin resistance, glycated hemoglobin (HbA1c) ≥ 6 (42 mmol/mol) and serum 25(OH)D < 50 nmol/L were randomized using a computer program to receive either supplementation with cholecalciferol (5000 IU/day) or placebo for 12 weeks. The primary outcome was change in HbA1c levels from baseline.

RESULTS

Median [IQR] 25(OH)D levels increased significantly in the vitamin D group as 58.1 [48, 67.3] nmol/L (P = 0.002). There was no significant difference in the change of HbA1c between the groups (P = 0.5) with a decrease of -0.1% [-1, 0.5] in the vitamin D group and an increase of 0.15% [0.1, 0.2] in the placebo group. A significant improvement was observed in the homeostasis model of assessment of β-cell activity (HOMA-%B) (P = 0.03) with vitamin D supplementation compared to baseline.

CONCLUSIONS

Vitamin D repletion for 12 weeks increased serum vitamin D concentrations and improved β-cell activity in vitamin D-deficient type II diabetes with no significant changes in HbA1c or insulin sensitivity.

The threshold value of homeostasis model assessment for insulin resistance in Qazvin Metabolic Diseases Study (QMDS): assessment of metabolic syndrome

BACKGROUND

The homeostasis model assessment of insulin resistance (HOMA-IR) is a useful model for application at large epidemiologic studies. The aim of this study was to determine the HOMA cut off values to identify insulin resistance (IR) and metabolic syndrome (MS) in Qazvin, central Iran.

METHODS

Overall, 480 men and 502 women aged 20-72 yr attended in this cross sectional study from September 2010 to April 2011. The diagnostic criteria proposed by national cholesterol education program third adult treatment panel (ATPIII), International Diabetes Federation (IDF) and new Joint Interim Societies (JIS); were applied to define MS. Lower limit of the top quintile of HOMA values in normal subjects was considered as the threshold of IR. The receiver operating characteristic (ROC) curves of HOMA for MS diagnosis were depicted. The optimal cut point to determine MS was assessed by maximum Youden index and the shortest distance from the point (0, 1) on the ROC curve.

RESULTS

The threshold of HOMA for IR was 2.48. Fifty one percent of the subjects were insulin resistant. The cut point for diagnosis of JIS, IDF, ATP III and Persian IDF defined MS was 2.92, 2.91, 2.49 and 3.21, respectively. Sensitivity and specificity of ATP III defined MS to diagnose IR was 33.95% and 84.78%, of IDF defined MS was 39.13%, 81.29% and of JIS defined MS was 43.77% and 78.11% and of Persian IDF defined MS was 27.32% and 88.76%, in that order.

CONCLUSIONS

The high prevalence of IR in the present study warns about the future burden of type 2 diabetes. Only the ATP III criteria introduced more specific cut point for putative manifestations of IR.

The effect of macrobiotic Ma-Pi 2 diet on systemic inflammation in patients with type 2 diabetes: a post hoc analysis of the MADIAB trial

INTRODUCTION

Current guidelines for the management of type 2 diabetes (T2D) emphasize diet as essential therapy. However, the effect of diet on systemic inflammation remains unclear. We investigated the effects of consuming a macrobiotic Ma-Pi 2 diet versus a standard recommended diet (control diet) on markers of inflammation in patients with T2D.

METHODS

This was a post hoc analysis of the MADIAB trial, a 21-day randomized controlled trial conducted in 51 patients (25 males and 26 females) with T2D. Patients were randomized 1:1 to the Ma-Pi 2 macrobiotic diet or a control diet based on dietary guidelines for T2D. Biological antioxidant potential of plasma and circulating levels of high-sensitivity C reactive protein, interleukin-6, tumor necrosis factor-α, and insulin-like growth factor-1 were assessed.

RESULTS

After 21 days on the Ma-Pi 2 or control diet, markers of inflammation were reduced in both groups. The antioxidant potential of plasma improved significantly in the Ma-Pi group. A significant reduction in insulin growth factor-1 was observed in the Ma-Pi group versus control group (p<0.001).

CONCLUSIONS

Findings of this post hoc analysis demonstrated that the Ma-Pi 2 diet is a safe dietary strategy to reduce levels of the markers of insulin resistance and inflammation, compared with baseline values, in the short term. Furthermore, the Ma-Pi 2 diet was superior to the control diet in reducing insulin growth factor-1 and may be beneficial for patients with T2D.

TRIAL REGISTRATION NUMBER

Current Controlled Trials ISRCTN10467793.

Insulin regulates nitric oxide production in the kidney collecting duct cells

The kidney is an important organ for arterial blood pressure (BP) maintenance. Reduced NO generation in the kidney is associated with hypertension in insulin resistance. NO is a critical regulator of vascular tone; however, whether insulin regulates NO production in the renal inner medullary collecting duct (IMCD), the segment with the greatest enzymatic activity for NO production in kidney, is not clear. Using an NO-sensitive 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) fluorescent dye, we found that insulin increased NO production in mouse IMCD cells (mIMCD) in a time- and dose-dependent manner. A concomitant dose-dependent increase in the NO metabolite (NOx) was also observed in the medium from insulin-stimulated cells. NO production peaked in mIMCD cells at a dose of 100 nm insulin with simultaneously increased NOx levels in the medium. At this dose, insulin significantly increased p-eNOS(Ser1177) levels in mIMCD cells. Pretreatment of cells with a PI 3-kinase inhibitor or insulin receptor silencing with RNA interference abolished these effects of insulin, whereas insulin-like growth factor-1 receptor (IGF-1R) silencing had no effect. We also showed that chronic insulin infusion to normal C57BL/6J mice resulted in increased endothelial NOS (eNOS) protein levels and NO production in the inner medulla. However, insulin-infused IRKO mice, with targeted deletion of insulin receptor from tubule epithelial cells of the kidney, had ∼50% reduced eNOS protein levels in their inner medulla along with a significant rise in BP relative to WT littermates. We have previously reported increased baseline BP and reduced urine NOx in IRKO mice. Thus, reduced insulin receptor signaling in IMCD could contribute to hypertension in the insulin-resistant state.

Inhibited insulin signaling in mouse hepatocytes is associated with increased phosphatidic acid but not diacylglycerol

Although an elevated triacylglycerol content in non-adipose tissues is often associated with insulin resistance, the mechanistic relationship remains unclear. The data support roles for intermediates in the glycerol-3-phosphate pathway of triacylglycerol synthesis: diacylglycerol (DAG), which may cause insulin resistance in liver by activating PKCϵ, and phosphatidic acid (PA), which inhibits insulin action in hepatocytes by disrupting the assembly of mTOR and rictor. To determine whether increases in DAG and PA impair insulin signaling when produced by pathways other than that of de novo synthesis, we examined primary mouse hepatocytes after enzymatically manipulating the cellular content of DAG or PA. Overexpressing phospholipase D1 or phospholipase D2 inhibited insulin signaling and was accompanied by an elevated cellular content of total PA, without a change in total DAG. Overexpression of diacylglycerol kinase-θ inhibited insulin signaling and was accompanied by an elevated cellular content of total PA and a decreased cellular content of total DAG. Overexpressing glycerol-3-phosphate acyltransferase-1 or -4 inhibited insulin signaling and increased the cellular content of both PA and DAG. Insulin signaling impairment caused by overexpression of phospholipase D1/D2 or diacylglycerol kinase-θ was always accompanied by disassociation of mTOR/rictor and reduction of mTORC2 kinase activity. However, although the protein ratio of membrane to cytosolic PKCϵ increased, PKC activity itself was unaltered. These data suggest that PA, but not DAG, is associated with impaired insulin action in mouse hepatocytes.

Adipocyte-specific disruption of fat-specific protein 27 causes hepatosteatosis and insulin resistance in high-fat diet-fed mice

White adipose tissue (WAT) functions as an energy reservoir where excess circulating fatty acids are transported to WAT, converted to triglycerides, and stored as unilocular lipid droplets. Fat-specific protein 27 (FSP27, CIDEC in humans) is a lipid-coating protein highly expressed in mature white adipocytes that contributes to unilocular lipid droplet formation. However, the influence of FSP27 in adipose tissue on whole-body energy homeostasis remains unclear. Mice with adipocyte-specific disruption of the Fsp27 gene (Fsp27(ΔAd)) were generated using an aP2-Cre transgene with the Cre/LoxP system. Upon high-fat diet feeding, Fsp27(ΔAd) mice were resistant to weight gain. In the small WAT of these mice, small adipocytes containing multilocular lipid droplets were dispersed. The expression levels of the genes associated with mitochondrial abundance and brown adipocyte identity were increased, and basal lipolytic activities were significantly augmented in adipocytes isolated from Fsp27(ΔAd) mice compared with the Fsp27(F/F) counterparts. The impaired fat-storing function in Fsp27(ΔAd) adipocytes and the resultant lipid overflow from WAT led to marked hepatosteatosis, dyslipidemia, and systemic insulin resistance in high-fat diet-treated Fsp27(ΔAd) mice. These results demonstrate a critical role for FSP27 in the storage of excess fat in WAT with minimizing ectopic fat accumulation that causes insulin-resistant diabetes and non-alcoholic fatty liver disease. This mouse model may be useful for understanding the significance of fat-storing properties of white adipocytes and the role of local FSP27 in whole-body metabolism and estimating the pathogenesis of human partial lipodystrophy caused by CIDEC mutations.

Are women with polycystic ovarian syndrome at a high risk of non-alcoholic Fatty liver disease; a meta-analysis

CONTEXT

Insulin resistance is a hallmark of metabolic syndrome (MS). It has been proposed that both polycystic ovarian syndrome (PCOS) and nonalcoholic fatty liver disease (NAFLD) are correlated with Insulin resistance. Therefore, PCOS and NAFLD can be attributed with insulin resistance and therefore MS. The aim of this meta-analysis was to determine whether PCOS patients are at a high risk of NAFLD.

EVIDENCE ACQUISITION

Google scholar, Scopus, ISI Web of Science, Embase, MEDLINE, and some Iranian databases such as scientific information database (SID), IranMedex, and MagIran were searched to identify relevant studies. We included all papers regardless of their language from January 1985 to June 2013. By using data on prevalence of NAFLD in patients with and without PCOS, odds ratio (OR) with 95% confidence intervals (CIs) were calculated in each study. Chi-squared test was used to assess heterogeneity between studies.

RESULTS

We finally included seven eligible studies. According to chi-squared test, there was a significant heterogeneity (73.6%) between studies (P = 0.001). NAFLD prevalence was significantly higher in patients with PCOS compared to healthy control, with an overall OR of 3.93 (95% CI: 2.17, 7.11).There was no significant publication bias based on Begg's and Egger's tests.

CONCLUSIONS

According to the results of this meta-analysis, there was a high risk of NAFLD in women with PCOS. We suggest evaluating patients with PCOS regarding NAFLD.

Multiple tissue-specific roles for the O-GlcNAc post-translational modification in the induction of and complications arising from type II diabetes

In this minireview, we will highlight work in the last 30 years that has clearly demonstrated that the O-GlcNAc modification is nutrient-responsive and plays multiple roles in metabolic regulation of signaling and gene expression. Further, we will examine recent studies that have investigated the impact of O-GlcNAc in a variety of glucose- and insulin-responsive tissues and the roles attributed to O-GlcNAc in the induction of insulin resistance and glucose toxicity, the hallmarks of type II diabetes mellitus. We will also summarize potential causal roles for the O-GlcNAc modification in complications associated with diabetes.

A single mechanism can explain network-wide insulin resistance in adipocytes from obese patients with type 2 diabetes

The response to insulin is impaired in type 2 diabetes. Much information is available about insulin signaling, but understanding of the cellular mechanisms causing impaired signaling and insulin resistance is hampered by fragmented data, mainly obtained from different cell lines and animals. We have collected quantitative and systems-wide dynamic data on insulin signaling in primary adipocytes and compared cells isolated from healthy and diabetic individuals. Mathematical modeling and experimental verification identified mechanisms of insulin control of the MAPKs ERK1/2. We found that in human adipocytes, insulin stimulates phosphorylation of the ribosomal protein S6 and hence protein synthesis about equally via ERK1/2 and mTORC1. Using mathematical modeling, we examined the signaling network as a whole and show that a single mechanism can explain the insulin resistance of type 2 diabetes throughout the network, involving signaling both through IRS1, PKB, and mTOR and via ERK1/2 to the nuclear transcription factor Elk1. The most important part of the insulin resistance mechanism is an attenuated feedback from the protein kinase mTORC1 to IRS1, which spreads signal attenuation to all parts of the insulin signaling network. Experimental inhibition of mTORC1 using rapamycin in adipocytes from non-diabetic individuals induced and thus confirmed the predicted network-wide insulin resistance.

Impact of ENPP1 K121Q on change of insulin resistance after web-based intervention in Korean men with diabetes and impaired fasting glucose

Ectoenzyme nucleotide pyrophosphate phosphodiesterase 1 (ENPP1) gene has been studied in relation to type 2 diabetes mellitus (T2DM) and insulin resistance (IR). We hypothesized that the difference in genotype may be one of the factors that affect the outcome of intervention. We genotyped 448 men with fasting glucose≥5.6 mM/L, including 371 in subjects with K allele (KK) (69 control group [CG]; and 302 intervention group [IG]) and 77 in subjects with Q allele (KQ+QQ) (13 CG and 64 IG). The web-based intervention based on a lifestyle modification was delivered by e-mail once a month for 10 months. In the KK, IG demonstrated significantly decreased levels of fasting serum insulin (FSI) as compared to CG and homeostasis model of assessment of insulin resistance (HOMA-IR). In the KQ+QQ IG group, hemoglobin A1c (HbA1c), FSI and HOMA-IR were significantly decreased, and showed further reduction in the HOMA-IR than KQ+QQ CG. After analysis of covariance, K121Q did significantly influence the change of HbA1c in CG after appropriate adjustment. In a multivariate model, BMI change predicted HOMA-IR change (adjusted β=0.801; P=0.022) in KK IG subjects with T2DM. ENPP1 K121Q did not influence the change in IR. However, individuals with T2DM carrying the K121 variant are very responsive to the effect of BMI reduction on HOMA-IR.

Anti-hyperglycemic and insulin sensitizer effects of turmeric and its principle constituent curcumin

CONTEXT

Turmeric is obtained from the plant Curcuma longa L; its major constituent, curcumin, is a polyphenol with multiple effects which can modulate some signaling pathways.

EVIDENCE ACQUISITION

Insulin resistance is a major risk factor for chronic diseases such as type 2 diabetes, atherosclerotic, metabolic syndrome and cardiovascular disease. In addition, Insulin resistance in peripheral tissue is one of the most important reasons of hyperglycemia which can cause global or systemic effects. The present study reviewed studies published in PubMed from 1998 to 2013, indicating the role of curcumin in attenuation of many pathophysiological processes involved in development and progression of hyperglycemia and insulin resistance.

RESULTS

Curcumin can reduce blood glucose level by reducing the hepatic glucose production, suppression of hyperglycemia-induced inflammatory state, stimulation of glucose uptake by up-regulation of GLUT4, GLUT2 and GLUT3 genes expressions, activation of AMP kinase, promoting the PPAR ligand-binding activity, stimulation of insulin secretion from pancreatic tissues, improvement in pancreatic cell function, and reduction of insulin resistance.

CONCLUSIONS

Curcumin has antihyperglycemic and insulin sensitizer effects. Thereby, more studies evaluating the effects of curcumin on hyperglycemic state and insulin resistance in related disorders such as diabetes are recommended.

Relationship between serum levels of fetuin-A with apo-A1, apo-B100, body composition and insulin resistance in patients with type 2 diabetes

BACKGROUND

Some results exist on fetuin-A as marker for vascular disease in type 2diabetes. We examined the relationship between serum fetuin-A with some factors, in patients with type 2 diabetes mellitus (T2DM).

METHODS

From October 2012 to June 2013, a total of 131 T2DM patients were recruited and evaluated for various parameters including HOMA-IR, Apo-A1, Apo-B100, body fat percentage and waist circumference. Serum fetuin-A levels were measured by enzyme-linkedimmunosorbent assay (ELISA), and Serum glucose with a Cobas MIRA analyzer by enzymatic method. Apo-B100 and apo-A1 were measured by immunoturbidimetry with a Cobas MIRA analyzer. HOMA-IR was calculated by the following formula: [fasting insulin (uIU/mL) × fasting blood glucose (mmol/L)]/22.5.

RESULTS

The mean levels of HOMA-IR were significantly increased progressively across fetuin-A tertiles (p for trend=0.04) in women but not men. Fetuin-A had just a significant positive correlation with Apo- A1(r=0.22, p=0.02).

CONCLUSION

This present study showed that levels of serum fetuin-A are significantly associated with insulin resistance in women with T2DM.

Inhibiting monoacylglycerol acyltransferase 1 ameliorates hepatic metabolic abnormalities but not inflammation and injury in mice

Abnormalities in hepatic lipid metabolism and insulin action are believed to play a critical role in the etiology of nonalcoholic steatohepatitis. Monoacylglycerol acyltransferase (MGAT) enzymes convert monoacylglycerol to diacylglycerol, which is the penultimate step in one pathway for triacylglycerol synthesis. Hepatic expression of Mogat1, which encodes an MGAT enzyme, is increased in the livers of mice with hepatic steatosis, and knocking down Mogat1 improves glucose metabolism and hepatic insulin signaling, but whether increased MGAT activity plays a role in the etiology of nonalcoholic steatohepatitis is unclear. To examine this issue, mice were placed on a diet containing high levels of trans fatty acids, fructose, and cholesterol (HTF-C diet) or a low fat control diet for 4 weeks. Mice were injected with antisense oligonucleotides (ASOs) to knockdown Mogat1 or a scrambled ASO control for 12 weeks while remaining on diet. The HTF-C diet caused glucose intolerance, hepatic steatosis, and induced hepatic gene expression markers of inflammation, macrophage infiltration, and stellate cell activation. Mogat1 ASO treatment, which suppressed Mogat1 expression in liver and adipose tissue, attenuated weight gain, improved glucose tolerance, improved hepatic insulin signaling, and decreased hepatic triacylglycerol content compared with control ASO-treated mice on HTF-C chow. However, Mogat1 ASO treatment did not reduce hepatic diacylglycerol, cholesterol, or free fatty acid content; improve histologic measures of liver injury; or reduce expression of markers of stellate cell activation, liver inflammation, and injury. In conclusion, inhibition of hepatic Mogat1 in HTF-C diet-fed mice improves hepatic metabolic abnormalities without attenuating liver inflammation and injury.

Essential role of protein-tyrosine phosphatase 1B in the modulation of insulin signaling by acetaminophen in hepatocytes

Many drugs are associated with the development of glucose intolerance or deterioration in glycemic control in patients with pre-existing diabetes. We have evaluated the cross-talk between signaling pathways activated by acetaminophen (APAP) and insulin signaling in hepatocytes with or without expression of the protein-tyrosine phosphatase 1B (PTP1B) and in wild-type and PTP1B-deficient mice chronically treated with APAP. Human primary hepatocytes, Huh7 hepatoma cells with silenced PTP1B, mouse hepatocytes from wild-type and PTP1B-deficient mice, and a mouse model of chronic APAP treatment were used to examine the mechanisms involving PTP1B in the effects of APAP on glucose homeostasis and hepatic insulin signaling. In APAP-treated human hepatocytes at concentrations that did not induce death, phosphorylation of JNK and PTP1B expression and enzymatic activity were increased. APAP pretreatment inhibited activation of the early steps of insulin signaling and decreased Akt phosphorylation. The effects of APAP in insulin signaling were prevented by suramin, a PTP1B inhibitor, or rosiglitazone that decreased PTP1B levels. Likewise, PTP1B deficiency in human or mouse hepatocytes protected against APAP-mediated impairment in insulin signaling. These signaling pathways were modulated in mice with chronic APAP treatment, resulting in protection against APAP-mediated hepatic insulin resistance and alterations in islet alpha/beta cell ratio in PTP1B(-/-) mice. Our results demonstrate negative cross-talk between signaling pathways triggered by APAP and insulin signaling in hepatocytes, which is in part mediated by PTP1B. Moreover, our in vivo data suggest that chronic use of APAP may be associated with insulin resistance in the liver.

Effect of therapeutic dose of vitamin d on serum adiponectin and glycemia in vitamin d-insufficient or deficient type 2 diabetic patients

Background:

Lower vitamin D status has been reported in diabetic patients. Serum 25-hydroxyvitamin D and adiponectin were inversely associated with type 2 diabetes and insulin resistance. Vitamin D may involve in regulation of the adiponectin levels, which is directly related to insulin sensitivity.

Objectives:

The aim of this study was to investigate the effect of therapeutic dose of vitamin D on serum adiponectin and insulin resistance in vitamin D-insufficient or deficient type 2 diabetic patients.

Materials and Methods:

This double-blind, randomized, clinical trial was conducted on 81 type 2 diabetic patients with vitamin D level of 10-30 ng/mL. Intervention was 50000 IU vitamin D or placebo once a week for 8 weeks. At the beginning and end of the study, blood samples were collected after 12 hours of fasting and serum glucose, insulin, 25-hydroxyvitamin D, and adiponectin were measured. Insulin resistance was calculated by homeostasis model assessment (HOMA-IR).

Results:

After 8-week intervention, serum 25-hydroxyvitamin D significantly increased and reached the normal levels in patients receiving vitamin D (P < 0.001) and the levels of fasting serum glucose, insulin, and HOMA-IR were significantly decreased (P = 0.04, 0.02 and 0.007, respectively). No significant changes were observed in these levels in the placebo group. Significant differences were observed in mean changes in the above-mentioned variables between the two groups (P = 0.01, 0.04 and 0.006, respectively). No significant changes were found in serum adiponectin in the vitamin D and placebo groups (P = 0.83).

Conclusions:

Therapeutic dose of vitamin D can improve vitamin D status and glycemic indicators. But it seems that an 8-week intervention period was not sufficient to reveal the possible effects of vitamin D on serum adiponectin levels.

Requirements for pseudosubstrate arginine residues during autoinhibition and phosphatidylinositol 3,4,5-(PO₄)₃-dependent activation of atypical PKC

Atypical PKC (aPKC) isoforms are activated by the phosphatidylinositol 3-kinase product phosphatidylinositol 3,4,5-(PO4)3 (PIP3). How PIP3 activates aPKC is unknown. Although Akt activation involves PIP3 binding to basic residues in the Akt pleckstrin homology domain, aPKCs lack this domain. Here we examined the role of basic arginine residues common to aPKC pseudosubstrate sequences. Replacement of all five (or certain) arginine residues in the pseudosubstrate sequence of PKC-ι by site-directed mutagenesis led to constitutive activation and unresponsiveness to PIP3 in vitro or insulin in vivo. However, with the addition of the exogenous arginine-containing pseudosubstrate tridecapeptide to inhibit this constitutively active PKC-ι, PIP3-activating effects were restored. A similar restoration of responsiveness to PIP3 was seen when exogenous pseudosubstrate was used to inhibit mouse liver PKC-λ/ζ maximally activated by insulin or ceramide and a truncated, constitutively active PKC-ζ mutant lacking all regulatory domain elements and containing "activating" glutamate residues at loop and autophosphorylation sites (Δ1-247/T410E/T560E-PKC-ζ). NMR studies suggest that PIP3 binds directly to the pseudosubstrate. The ability of PIP3 to counteract the inhibitory effects of the exogenous pseudosubstrate suggests that basic residues in the pseudosubstrate sequence are required for maintaining aPKCs in an inactive state and are targeted by PIP3 for displacement from the substrate-binding site during kinase activation.

Chrysin and luteolin alleviate vascular complications associated with insulin resistance mainly through PPAR-γ activation

Chrysin and luteolin are two flavonoids with Peroxisome proliferators-activated receptor γ (PPAR-γ) stimulating activity. Here, we investigated the protective effect of chrysin and luteolin from vascular complications associated with insulin resistance (IR). IR was induced in rats by drinking fructose for 12 weeks while chrysin and luteolin were given for 6 weeks with or without PPAR-γ antagonist, bisphenol A diglycidyl ether (BADGE). Then, blood pressure (BP) was recorded and serum levels of glucose, insulin, advanced glycation end products (AGEs) and lipids were measured. Concentration response curves for phenylephrine (PE), KCl, and acetylcholine (ACh) were obtained in thoracic aorta rings. Aortic reactive oxygen species (ROS) and nitric oxide (NO) generation were also studied. Chrysin and luteolin significantly alleviated systolic BP elevations caused by IR, while the co-administration of BADGE prevented chrysin alleviation. Although, neither chrysin nor luteolin affected ACh impaired vasodilatation, they both alleviated exaggerated vasoconstrictions to PE and KCl in IR animals. In addition, incubation of the aorta from IR animals with chrysin or luteolin prevented exaggerated vasoconstrictions to PE and KCl. On the other hand, co-administration of BADGE or co-incubation with GW9662, the selective PPAR-γ antagonist, prevented chrysin alleviation. Both chrysin and luteolin inhibited the developed hyperinsulinemia and increases in serum AGEs, lipids while, BADGE reduced the effect of chrysin on hyperinsulinemia and dyslipidemia. Chrysin and luteolin markedly inhibited elevated NO and ROS in IR aortae while BADGE did not change their effect on NO and ROS. In conclusion, chrysin and luteolin alleviate vascular complications associated with IR mainly through PPAR-γ dependent pathways.

Body composition in adults with newly diagnosed type 2 diabetes: effects of metformin

Background

The aim of this study was to measure the body composition in adults with newly diagnosed type 2 diabetes mellitus and to explore the effect of metformin therapy on the various components of body composition, insulin sensitivity, and glucose homeostasis.

Methods

This was an observational study consisted of 51 newly diagnosed people with type 2 diabetes on 1000 mg metformin twice daily for 6 months. The body composition of each subject was measured by dual energy X-ray absorptiometry at enrollment and 24 weeks after metformin mono-therapy. Sarcopenia was defined and compared based on the ratio of appendicular skeletal muscle and height squared, skeletal muscle index and residual methods.

Homeostasis model assessment-insulin resistance and Quantitative Insulin Sensitivity Check Index were used for estimating insulin sensitivity. The level of physical activity was assessed using self-administered International physical Activity questionnaire.

Results

Forty one subjects (80.4%) completed the study. The mean age of the participants was 52.67 ± 10.43 years. Metformin treatment was associated with a significant decrease in total fat mass (−1.6 kg, P = 0.000). By week 24, the lean to fat ratio increased (P = 0.04) with men showing greater significant changes. Twenty percent of the female participants were detected to have sarcopenia.

In addition, there was a significant improvement of glucose homeostasis and insulin sensitivity.

Conclusions

Metformin therapy results in significant improvement in body composition and insulin sensitivity of adults with newly diagnosed type 2 diabetes. Furthermore, sarcopenia begins in women with diabetes much earlier than expected as an age related phenomenon.

Insulin resistance in pulmonary arterial hypertension, is it a novel disease modifier?

Background:

Recent studies have introduced glucose intolerance and insulin resistance (IR) as novel risk factors in patients with pulmonary arterial hypertension (PAH).

Objectives:

We aimed to investigate the prevalence of glucose intolerance and IR in patients with PAH and their correlation with functional capacity and prognostic factors.

Patients and Methods:

Sixty-nine patients with pulmonary arterial hypertension (class I Pulmonary hypertension in accordance with updated clinical classification of pulmonary hypertension) scheduled for right heart catheterization were enrolled. FBS, HbA1c, lipid profile, pro –BNP and hs-CRP were measured along with a 6-minute walk test (6-MWT) and obtaining demographic, functional and hemodynamic data. Fasting triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C) was used as a surrogate of insulin sensitivity. Using published criteria, HbA1c ≤ 5.9% defined as normal, 6.0-6.4% as glucose intolerance, and ≥ 6.5% as diabetes. All patients were followed for a year regarding development of any cardiovascular event (mortality and/or hospitalization).

Results:

In total, 76.8% of patients were female: 61% of them had idiopathic PAH, 33% Eisenmenger syndrome, and 6% PAH secondary to a connective tissue disease. With respect to TG/HDL-C, 43.5% of patients had IR and 47.8% of patients had HbA1c > 6. There was no difference between IR and insulin sensitive (IS) group or glucose intolerance and sensitive group regarding NYHA class, 6MWT, Pro BNP, hs-CRP and hemodynamic data and there was no correlation between IR or glucose intolerance and any event.

Conclusions:

Unrecognized glucose intolerance and IR are common in PAH. However, further studies are needed to show whether glucose or insulin dysregulation plays any role in PAH pathogenesis or it is secondary to advanced PAH.

Insulin resistance and its correlation with risk factors for developing diabetes mellitus in 100 omani medical students

OBJECTIVES

The aim of this study was to assess the prevalence of insulin resistance (IR) in healthy young Omanis and relate this with their body mass index (BMI) and family history (FH) of diabetes mellitus (DM).

METHODS

This study was conducted between May 2009 and February 2010 at Sultan Qaboos University, Muscat, Oman. A detailed questionnaire was completed by 50 male and 50 female medical students between 20-25 years old. Fasting blood samples were obtained for serum glucose and insulin measurements. IR was calculated using the homeostasis model assessment-estimated insulin resistance (HOMA-IR) formula (fasting insulin x fasting glucose/22.5) and a value above 2.5 was considered elevated. The results were analysed using the Statistical Package for the Social Sciences (SPSS).

RESULTS

PARTICIPANTS WERE CLASSIFIED INTO THE FOLLOWING BMI CATEGORIES: 59% were normal (18.5-24.9 kg/m(2)), 26% were overweight or obese (>24.9 kg/m(2)) and 15% were underweight (<18.5 kg/m(2)). A FH of DM was present in 74%. The HOMA-IR index was elevated in 16% and was directly correlated to the BMI (P = 0.003). There was no correlation between IR and a positive FH of DM.

CONCLUSION

There is a high prevalence of IR (16%) and obesity (26%) in healthy young Omani medical students. Counselling is recommended for all overweight and obese individuals in an attempt to prevent or delay the onset of DM in the future.

Epicardial adiposity in children with obesity and metabolic syndrome

OBJECTIVE

Obesity increases cardiac diseases by increasing tendency to atherosclerosis. Our aim was to define epicardial adipose tissue thickness, and its related factors in obese children.

METHODS

Total of 94 patients were divided into obesity with metabolic syndrome (MS) (n=30), obesity without MS (n=33), and control (n=31) groups. Auxological values with fasting glucose, fasting insulin, alanine transaminase, serum lipid levels, and high sensitive C-reactive protein levels were evaluated. Epicardial adipose tissue thickness, interventricular septum thickness and left ventricular mass were measured by echocardiography.

FINDINGS

Weight, body mass index, waist circumference, insulin, alanine transaminase, and high sensitive C-reactive protein values were markedly higher in obesity group when compared with controls (P<0.001). Epicardial adipose tissue thickness was 0.64±0.23 cm in obesity with MS; 0.60±0.20 cm in obesity without MS, and 0.27±0.12 cm in control group (P<0.001). Interventricular septum thickness and left ventricular mass values were markedly high in obesity without MS group (P<0.001 and P=0.002).

CONCLUSION

Our study has indicated that obesity has unfavorable effects on heart starting in the adolescence.

Pioglitazone normalizes insulin signaling in the diabetic rat retina through reduction in tumor necrosis factor α and suppressor of cytokine signaling 3

Dysfunctional insulin signaling is a key component of type 2 diabetes. Little is understood of the effects of systemic diabetes on retinal insulin signaling. A number of agents are used to treat patients with type 2 diabetes to normalize glucose levels and improve insulin signaling; however, little has been done to investigate the effects of these agents on retinal insulin signal transduction. We hypothesized that pioglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) agonist, would normalize retinal insulin signal transduction through reduced tumor necrosis factor α (TNFα) and suppressor of cytokine signaling 3 (SOCS3) activities in whole retina and retinal endothelial cells (REC) and Müller cells. To test this hypothesis, we used the BBZDR/Wor type 2 diabetic rat model, as well as REC and Müller cells cultured in normoglycemia and hyperglycemic conditions, to investigate the effects of pioglitazone on TNFα, SOCS3, and downstream insulin signal transduction proteins. We also evaluated pioglitazone's effects on retinal function using electroretinogram and markers of apoptosis. Data demonstrate that 2 months of pioglitazone significantly increased electroretinogram amplitudes in type 2 diabetic obese rats, which was associated with improved insulin receptor activation. These changes occurred in both REC and Müller cells treated with pioglitazone, suggesting that these two cell types are key to insulin resistance in the retina. Taken together, these data provide evidence of impaired insulin signaling in type 2 diabetes rats, which was improved by increasing PPARγ activity. Further investigations of PPARγ actions in the retina may provide improved treatment options.

Elevated brachial-ankle pulse wave velocity is independently associated with microalbuminuria in a rural population

Microalbuminuria is a marker of generalized endothelial dysfunction resulting from arterial stiffness or insulin resistance, and brachial-ankle pulse wave velocity (baPWV) is a good measure of arterial stiffness. We aimed to investigate whether elevated baPWV is independently associated with microalbuminuria. This study included 1,648 individuals aged over 40 who participated in the baseline Multi-Rural Cohort Study conducted in Korean rural communities between 2005 and 2006. Participants were classified into less than 30 mg/g as normoalbuminuria or 30-300 mg/g as microalbuminuriausing urinary albumin creatinine ratio (UACR). The median and Q1-Q3 baPWV values were significantly higher in the microalbuminuric group both in men (1,538, 1,370-1,777 cm/s vs. 1,776, 1,552-2,027 cm/s, P < 0.001) and women (1,461, 1,271-1,687 cm/s vs. 1,645, 1,473-1,915 cm/s, P < 0.001). BaPWV was independently associated with microalbuminuria in both genders after adjusting for pulse rate; fasting blood glucose; triglyceride; homeostatic model assessment insulin resistance (HOMAIR) and, history of hypertension and diabetes. Fasting blood sugar and HOMAIR were judged as having nothing to do with multicolinearity (r = 0.532, P < 0.001). Elevated baPWV was independently associated with microalbuminuria regardless of insulin resistance among rural subjects over 40 yr.

Mitochondrial complex I deficiency enhances skeletal myogenesis but impairs insulin signaling through SIRT1 inactivation

To address whether mitochondrial biogenesis is essential for skeletal myogenesis, C2C12 myogenesis was investigated after knockdown of NADH dehydrogenase (ubiquintone) flavoprotein 1 (NDUFV1), which is an oxidative phosphorylation complex I subunit that is the first subunit to accept electrons from NADH. The NDUFVI knockdown enhanced C2C12 myogenesis by decreasing the NAD(+)/NADH ratio and subsequently inactivating SIRT1 and SIRT1 activators (pyruvate, SRT1720, and resveratrol) abolished the NDUFV1 knockdown-induced myogenesis enhancement. However, the insulin-elicited activation of insulin receptor β (IRβ) and insulin receptor substrate-1 (IRS-1) was reduced with elevated levels of protein-tyrosine phosphatase 1B after NDUFV1 knockdown in C2C12 myotubes. The NDUFV1 knockdown-induced blockage of insulin signaling was released by protein-tyrosine phosphatase 1B knockdown in C2C12 myotubes, and we found that NDUFV1 or SIRT1 knockdown did not affect mitochondria biogenesis during C2C12 myogenesis. Based on these data, we can conclude that complex I dysfunction-induced SIRT1 inactivation leads to myogenesis enhancement but blocks insulin signaling without affecting mitochondria biogenesis.

Effects of Resistance versus Endurance Training on Plasma Lipocalin-2 in Young Men

PURPOSE

Lipocalin-2 (Lcn2) has been recognized as an adipocyte-derived acute phase protein that is positively correlated with obesity, insulin resistance, type 2 diabetes, and cardiovascular disease. The effects of resistance and endurance training (RT vs. ET) on plasma lipocalin-2 are still unclear. Therefore, the purpose of this study was to examine the effects of RT vs. ET on plasma lipocalin-2 in young men.

METHODS

Twenty nine healthy and sedentary young men (age, 21-29 years) participated in this study. The subjects were randomly assigned to RT group (n=9), ET group (n=10) or control group (n=10). The experimental groups performed either RT or ET, 3 days a week for 8 weeks. The endurance training program included continuous running at an intensity corresponding to 65-80% of maximal heart rate, while resistance training consisted of 2-4 sets of circuit weight training for 8 stations and at an intensity corresponding to 65-80% of 1-RM in each station.

RESULTS

No significant changes in the body mass, BMI, body fat percentage and WHR were found after the RT and ET. The results showed that Lcn2 decreased after RT and ET compared with the control group (P<0.05). High sensitivity C-reactive protein (hs-CRP) and insulin resistance determined by HOMA-IR, did not change in the RT and ET compared with the control group.

CONCLUSION

Lcn2 decreases after 8 weeks RT and ET, but this improvement was not accompanied by decreased hs-CRP and insulin resistance in healthy and sedentary young men.

Association of inflammatory sialoproteins, lipid peroxides and serum magnesium levels with cardiometabolic risk factors in obese children of South Indian population

The Incidence of childhood obesity and metabolic syndrome is increasing even in rural and semi-urban regions of India. Adipose tissue mass secretes several inflammatory proteins, which could potentially alter the metabolic processes, leading to several complications at the later stages of life. With limited studies on protein bound sialic acid (PBSA) as a marker of oxidative stress mediated inflammation in obese children, this study was aimed to assess and correlate PBSA with lipid peroxidation and other cardiometabolic risk factors like Insulin Resistance (IR), serum magnesium, and high sensitive C reactive Protein (hsCRP) levels in order to provide an insight into the degree of systemic inflammation and oxidative stress. This study included 62 obese children (≥95% percentile of the CDC chart) and 60 non obese controls. This study documents significant higher levels of PBSA, IR, Malondialdehyde (MDA), hsCRP and uric acid in obese children (p<0.001). PBSA was associated with IR, hsCRP, uric acid, hypomagnesaemia. Higher degrees of oxidative stress, Insulin resistance and low serum magnesium levels were noted in obese children. PBSA and hsCRP levels were elevated and were associated with Insulin resistance in obese children of South Indian population.

Co-activation of nuclear factor-κB and myocardin/serum response factor conveys the hypertrophy signal of high insulin levels in cardiac myoblasts

Hyperinsulinemia contributes to cardiac hypertrophy and heart failure in patients with the metabolic syndrome and type 2 diabetes. Here, high circulating levels of tumor necrosis factor (TNF)-α may synergize with insulin in signaling inflammation and cardiac hypertrophy. We tested whether high insulin affects activation of TNF-α-induced NF-κB and myocardin/serum response factor (SRF) to convey hypertrophy signaling in cardiac myoblasts. In canine cardiac myoblasts, treatment with high insulin (10(-8) to 10(-7) m) for 0-24 h increased insulin receptor substrate (IRS)-1 phosphorylation at Ser-307, decreased protein levels of chaperone-associated ubiquitin (Ub) E3 ligase C terminus of heat shock protein 70-interacting protein (CHIP), increased SRF activity, as well as β-myosin heavy chain (MHC) and myocardin expressions. Here siRNAs to myocardin or NF-κB, as well as CHIP overexpression prevented (while siRNA-mediated CHIP disruption potentiated) high insulin-induced SR element (SRE) activation and β-MHC expression. Insulin markedly potentiated TNF-α-induced NF-κB activation. Compared with insulin alone, insulin+TNF-α increased SRF/SRE binding and β-MHC expression, which was reversed by the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) and by NF-κB silencing. In the hearts of db/db diabetic mice, in which Akt phosphorylation was decreased, p38MAPK, Akt1, and IRS-1 phosphorylation at Ser-307 were increased, together with myocardin expression as well as SRE and NF-κB activities. In response to high insulin, cardiac myoblasts increase the expression or the promyogenic transcription factors myocardin/SRF in a CHIP-dependent manner. Insulin potentiates TNF-α in inducing NF-κB and SRF/SRE activities. In hyperinsulinemic states, myocardin may act as a nuclear effector of insulin, promoting cardiac hypertrophy.

Insulin resistance is an independent predictor of severe lower urinary tract symptoms and of erectile dysfunction: results from a cross-sectional study

INTRODUCTION

Several studies have linked the association between lower urinary tract symptoms (LUTS), erectile dysfunction (ED), and the presence of insulin resistance (IR) due to an underlined metabolic syndrome (MetS).

AIM

This study aims to determine the relationship between IR, sexual function, and LUTS and to demonstrate the ability of IR in predicting ED and severe LUTS.

METHODS

Between January 2008 to January 2013, 544 consecutive patients with benign prostatic hyperplasia-related LUTS were enrolled. LUTS and sexual function of the patients were evaluated by the International Index of Erectile Function (IIEF) and the International Prostate Symptom Score (IPSS). MetS was defined by the International Diabetes Federation. IR was defined as a homeostasis model assessment (HOMA) index of 3 or greater.

MAIN OUTCOME MEASURES

Uni- and multivariate logistic regression analysis was performed to assess significant predictors of severe LUTS (IPSS ≥ 20) and ED (IIEF-Erectile Function [IIEF-EF] <26), including MetS component, prostate volume, prostate-specific antigen, total testosterone, and HOMA index.

RESULTS

IR patients resulted in higher values of IPSS (19.0 vs. 15.0; P<0.01), IPSS-storage (6.0 vs. 5.0; P<0.01), IPSS-voiding (12.0 vs. 9.0; P<0.01), total prostate volume (54.8 vs. 36.5; P<0.01), and lower values of IIEF-EF (17.0 vs. 20.0; P<0.01), IIEF-Intercourse Satisfaction (3.0 vs. 10.0; P<0.01), IIEF-Orgasmic Function (8.0 vs. 9.0; P<0.01), IIEF-Overall Satisfaction (6.0 vs. 8.0; P<0.01), and total testosterone (3.83 vs. 4.44; P<0.01). IR was demonstrated to be a strong predictor of ED (IIEF-EF <26) (odds ratio [OR] =6.20, P<0.01) after adjusting for confounding factors. Finally, IR was also an independent predictor of severe LUTS (IPSS ≥ 20) (OR=2.0, P<0.01) after adjusting for confounding factors.

CONCLUSIONS

IR patients are at high risk of having severe LUTS and contemporary sexual dysfunctions. We strongly suggest to prevent LUTS and ED by reducing insulin resistance.

Involvement of insulin resistance in the protective effect of metformin against alcoholic liver injury

BACKGROUND

Alcoholic liver disease (ALD) continues to be a major cause of morbidity worldwide. The exact mechanisms for ALD pathogenesis are not fully understood. There is currently no known available drug for ALD. Previous studies have suggested that ethanol (EtOH)-induced hepatic insulin resistance, through the inhibition of adenosine monophosphate-activated protein kinase (AMPK) and the expression of adiponectin as well as downstream enzymes, contribute to the development of ALD. This study was to determine the effects of EtOH on AMPK activity as well as the protective effect of metformin.

METHODS

Forty male Wistar rats weighing 200 ± 20 g were randomized into 4 groups (n = 10) as follows: A = control group-rats received rodent chow; B = control + metformin group-rats received metformin (200 mg/kg/d intragastrically [IG]) at 21:00; C = EtOH group-rats were gavaged with alcohol of gradually increasing concentrations (30 to 60%, 5 to 9 g/kg/d) twice a day (9:00 and 16:00); D = EtOH + metformin group-rats received the same amount of EtOH as the rats in group C, and in addition received metformin (200 mg/kg/d IG) at 21:00. After 16 weeks, blood and liver samples were collected for further study.

RESULTS

Chronic EtOH consumption led to liver injury both histologically and biochemically accompanied by insulin resistance, reduced AMPK activity, and dysregulation of downstream enzymes. Decreased levels of circulating adiponectin and decreased expression of proliferator-activated receptor gamma coactivator-1α (PGC-1α) and peroxisome proliferator-activated receptors-α (PPAR-α) in the hepatic tissue were observed. Treatment with metformin attenuated the severity of liver injury, restored AMPK activity and normalized the expression of acetyl-CoA carboxylase and fatty acid synthase. In addition, metformin also increased the circulating adiponectin and liver adiponectin receptor 2 expression. Furthermore, PGC-1α and PPAR-α activities were also restored.

CONCLUSIONS

EtOH exposure induces hepatic insulin resistance. Metformin improved insulin resistance and reversed liver injury through the activation of AMPK and normalized adiponectin signaling making metformin a promising drug for the treatment of ALD.

Metabolic syndrome, insulin resistance and Fatty liver in obese Iranian children

BACKGROUND

Obesity is a global epidemic and its morbidities such as metabolic syndrome, insulin resistance, and fatty liver leads to a spectrum of psycho-social and medical consequences.

OBJECTIVES

The objective of this study was to investigate the prevalence of fatty liver in obese Iranian children and its' association with metabolic syndrome and insulin resistance.

PATIENTS AND METHODS

102 obese Iranian children, referred to pediatric clinics from March 2011 to March 2012, were enrolled in this cross-sectional study. All the patients were visited by a pediatric endocrinologist, a pediatric gastroenterologist and an expert radiologist in the evaluation of fatty liver grading.

RESULTS

The grade of fatty liver was higher in older children (P = 0.001). It was also more in taller and heavier children (P = 0.000). The more the BMI was, the more the fatty liver grade was (P = 0.002). Severity of fatty liver according to liver sonography in patient had a positive relationship with waist circumference, hip circumference, serum TG, serum FBS, serum fasting insulin, serum ALT, systolic blood pressure and HOMA index and had a negative correlation with the level of alkaline phosphatase. Severity of fatty liver also had a close relationship with the presence of acanthosis nigricans and HOMA index.

CONCLUSIONS

Prevalence of fatty liver is high in our obese children. It was associated with criteria of metabolic syndrome and insulin resistance, so visceral fat may participate in the pathogenesis of the metabolic syndrome or merely serve as a marker of increased risk for the metabolic complications of obesity.

Effects of Aerobic Exercise on Serum Retinol Binding Protein4, Insulin Resistance and Blood Lipids in Obese Women

BACKGROUND

Retinol binding protein4 (RBP4) is a type of adipokine which transports vitamin A to serum. RBP4 could be a bridge between obesity and insulin resistance. This study aimed to investigate the effects of aerobic exercises on RBP4 serum's concentration and metabolic syndrome risk factors in obese women.

METHODS

Twenty obese women with body max index 35.81±3.67Kg/m2, fat percentage 43.98±4.02, and waist to hip ratio 1.03±0.05 were included and were randomly assigned to experimental and control groups. The experimental group received aerobic exercises for a period of 12 weeks each three sessions on treadmill workout. The treadmill speed were based on a 60-65 and 80-85 maximal heart rate percentage and duration of 15-20 and 45-50 minutes, at the beginning and the end of exercise, respectively. Body composition, serum glucose, insulin, TG, LDL-C, HDL-C, total cholesterol, and RBP4, were measured in both groups before and after the treatment by ELISA method. Insulin resistance was measured by HOMA-IR. To compare within group differences and between group comparisons t-correlated and t-independent tests were used, respectively.

RESULTS

After 12 week aerobic exercises; weight, fat percentage, WHR, and BMI in the experimental group was significantly decreased (P<0.05). RBP4, insulin, insulin resistance, TG and HDL-C had significant differences between two groups. The cholesterol level, LDL-C and glucose did not have any significant changes.

CONCLUSION

The aerobic exercises can decrease body composition, insulin resistance, TG, and RBP4, so it can be beneficial for obese women's health, because it.

Myeloid cell-specific disruption of Period1 and Period2 exacerbates diet-induced inflammation and insulin resistance

The circadian clockworks gate macrophage inflammatory responses. Given the association between clock dysregulation and metabolic disorders, we conducted experiments to determine the extent to which over-nutrition modulates macrophage clock function and whether macrophage circadian dysregulation is a key factor linking over-nutrition to macrophage proinflammatory activation, adipose tissue inflammation, and systemic insulin resistance. Our results demonstrate that 1) macrophages from high fat diet-fed mice are marked by dysregulation of the molecular clockworks in conjunction with increased proinflammatory activation, 2) global disruption of the clock genes Period1 (Per1) and Per2 recapitulates this amplified macrophage proinflammatory activation, 3) adoptive transfer of Per1/2-disrupted bone marrow cells into wild-type mice potentiates high fat diet-induced adipose and liver tissue inflammation and systemic insulin resistance, and 4) Per1/2-disrupted macrophages similarly exacerbate inflammatory responses and decrease insulin sensitivity in co-cultured adipocytes in vitro. Furthermore, PPARγ levels are decreased in Per1/2-disrupted macrophages and PPARγ2 overexpression ameliorates Per1/2 disruption-associated macrophage proinflammatory activation, suggesting that this transcription factor may link the molecular clockworks to signaling pathways regulating macrophage polarization. Thus, macrophage circadian clock dysregulation is a key process in the physiological cascade by which diet-induced obesity triggers macrophage proinflammatory activation, adipose tissue inflammation, and insulin resistance.

Indomethacin treatment prevents high fat diet-induced obesity and insulin resistance but not glucose intolerance in C57BL/6J mice

Chronic low grade inflammation is closely linked to obesity-associated insulin resistance. To examine how administration of the anti-inflammatory compound indomethacin, a general cyclooxygenase inhibitor, affected obesity development and insulin sensitivity, we fed obesity-prone male C57BL/6J mice a high fat/high sucrose (HF/HS) diet or a regular diet supplemented or not with indomethacin (±INDO) for 7 weeks. Development of obesity, insulin resistance, and glucose intolerance was monitored, and the effect of indomethacin on glucose-stimulated insulin secretion (GSIS) was measured in vivo and in vitro using MIN6 β-cells. We found that supplementation with indomethacin prevented HF/HS-induced obesity and diet-induced changes in systemic insulin sensitivity. Thus, HF/HS+INDO-fed mice remained insulin-sensitive. However, mice fed HF/HS+INDO exhibited pronounced glucose intolerance. Hepatic glucose output was significantly increased. Indomethacin had no effect on adipose tissue mass, glucose tolerance, or GSIS when included in a regular diet. Indomethacin administration to obese mice did not reduce adipose tissue mass, and the compensatory increase in GSIS observed in obese mice was not affected by treatment with indomethacin. We demonstrate that indomethacin did not inhibit GSIS per se, but activation of GPR40 in the presence of indomethacin inhibited glucose-dependent insulin secretion in MIN6 cells. We conclude that constitutive high hepatic glucose output combined with impaired GSIS in response to activation of GPR40-dependent signaling in the HF/HS+INDO-fed mice contributed to the impaired glucose clearance during a glucose challenge and that the resulting lower levels of plasma insulin prevented the obesogenic action of the HF/HS diet.