The role of adipose tissue and lipotoxicity in the pathogenesis of type 2 diabetes

Overexpression of IL-10 in C2D macrophages promotes a macrophage phenotypic switch in adipose tissue environments

Adipose tissue macrophages are a heterogeneous collection of classically activated (M1) and alternatively activated (M2) macrophages. Interleukin 10 (IL-10) is an anti-inflammatory cytokine, secreted by a variety of cell types including M2 macrophages. We generated a macrophage cell line stably overexpressing IL-10 (C2D-IL10) and analyzed the C2D-IL10 cells for several macrophage markers after exposure to adipocytes compared to C2D cells transfected with an empty vector (C2D-vector). C2D-IL10 macrophage cells expressed more CD206 when co-cultured with adipocytes than C2D-vector cells; while the co-cultured cell mixture also expressed higher levels of Il4, Il10, Il1β and Tnf. Since regular C2D cells traffic to adipose tissue after adoptive transfer, we explored the impact of constitutive IL-10 expression on C2D-IL10 macrophages in adipose tissue in vivo. Adipose tissue-isolated C2D-IL10 cells increased the percentage of CD206(+), CD301(+), CD11c(-)CD206(+) (M2) and CD11c(+)CD206(+) (M1b) on their cell surface, compared to isolated C2D-vector cells. These data suggest that the expression of IL-10 remains stable, alters the C2D-IL10 macrophage cell surface phenotype and may play a role in regulating macrophage interactions with the adipose tissue.

Additional effect of diabetes mellitus type 2 on the risk of coronary artery disease: role of serum adiponectin

Background:

Adiponectin, an adipocyte-derived hormone, is implicated in diabetes mellitus type 2 and atherosclerosis. The study was designed to investigate whether serum adiponectin levels in patients with both coronary artery disease (CAD) and diabetes mellitus type 2 (T2DM) are lower than in patients with CAD alone and control subjects.

Objectives:

In this present study, we measured serum adiponectin levels in consecutive CAD patients with and without T2DM and investigated whether decreased adiponectin is associated with risk factors of CAD.

Materials and Methods:

The study included 198 subjects, 138 patients with CAD (72 of whom had both CAD and T2DM), and 60 control subjects. We measured serum adiponectin, interleukin-6 (IL-6) and insulin by ELISA. In addition, Lipid profile, glucose and anthropometrical measurements were performed in all subjects.

Results:

The results revealed significant difference in serum adiponectin levels between patients with CAD+T2DM and patients with CAD alone (3.80 ± 1.52 vs. 5.25 ± 2.35, P = 0.007), between patients with CAD and control (5.25 ± 2.35 vs. 7.04 ± 3.32, P = 0.001), and between patients with CAD + T2DM and control (3.80 ± 1.52 vs. 7.04 ± 3.32, P < 0.001). Serum adiponectin level was significantly higher in women in contrast to men (5.97 ± 3.15 vs. 4.62 ± 2.81 µg/ml, P = 0.002). Serum adiponectin levels were correlated significantly with insulin (r = -0.178, P = 0.013), total cholesterol (r = -0.313, P < 0.001), low density lipoprotein (r = -0.154, P = 0.016), body mass index (r = -0.171, P = 0.016), glucose (r = -0.202, P = 0.006), HOMA-IR (r= -0.251, P = 0.001), and IL-6 levels (r = -0.321, P = 0.001). Adiponectin was correlated positively only with high density lipoprotein (r = 0.389, P < 0.001).

Conclusions:

It is speculated that increased insulin resistance and increase in other adipokines such as IL-6 may contribute to the decreased serum levels of adiponectin in patients with both CAD and T2DM.

Safety and efficacy of sitagliptin in combination with transient continuous subcutaneous insulin infusion (CSII) therapy in patients with newly diagnosed type 2 diabetes

Sitagliptin was used as monotherapy or in combination with metformin, thiazolidinedione or sulfonylurea. It is not clear whether effects are enhanced or unique when in combination with transient continuous subcutaneous insulin infusion (CSII) therapy. The aim of this study was to assess the safety and efficacy of sitagliptin in combination with transient CSII therapy in patients with newly diagnosed type 2 diabetes. Eighty patients with newly diagnosed type 2 diabetes from July 2011 to May 2013 were recruited into the study. These patients were randomly divided into a CSII monotherapy group (group A, n = 40) or a sitagliptin in combination with CSII therapy group (group B, n = 40) and received insulin intensive therapy. Treatments were maintained for 2 weeks. 75g oral glucose tolerance test (OGTT) was performed before and after treatments, and the levels of glucose, insulin and C-peptide were examined. The results indicated that, compared with CSII therapy group, the level of plasma glucose significantly decreased, the levels of insulin and C-peptide strikingly increased and homeostasis model assessment for beta-cell function (HOMA-β) and Insulinogenic index (Ins index) were improved in the group of sitagliptin in combination with CSII therapy. Above all, the incidence of hypoglycemia was lower, insulin doses were less and the rate of recovery to normal glucose tolerance (NGT) or impaired glucose tolerance (IGT) determined by 75gOGTT was higher in the latter. So, Sitagliptin in combination with CSII therapy can be a new safe and effective therapy in patients with newly diagnosed type 2diabetes.

Downregulation of Bcl-2 expression by miR-34a mediates palmitate-induced Min6 cells apoptosis

Recent studies have demonstrated that the expression of miR-34a is significantly upregulated and associated with cell apoptosis in pancreatic β -cell treated with palmitate. Nevertheless, the underlying detailed mechanism is largely unknown. Here, we showed that miR-34a was significantly induced in Min6 pancreatic β -cell upon palmitate treatment. Elevated miR-34a promoted Min6 cell apoptosis. Intriguingly, ectopic expression of miR-34a lowered the expression of Bcl-2, an antiapoptotic protein. Luciferase reporter assay indicated the direct interaction of miR-34a with the Bcl-2 3'-UTR. Moreover, downregulated expression of Bcl-2 induced by palmitate could be restored by inhibition of miR-34a. We conclude that direct suppression of Bcl-2 by miR-34a accounts for palmitate-induced increased apoptosis rate in pancreatic β -cell.

Macrophage infiltration and stress-signaling in omental and subcutaneous adipose tissue in diabetic pregnancies

OBJECTIVE

To examine if, as in obesity, pregnancies complicated by gestational diabetes mellitus (GDM) exhibit increased macrophage infiltration and activated MAP-kinases in omental adipose tissue.

METHODS

Paired omental (OM) and abdominal subcutaneous (SC) fat samples were collected from 11 GDM and 20 normal pregnancies during cesarean delivery. Tissues were stained to detect macrophages, and analyzed to assess MAP-kinases.

RESULTS

OM had higher macrophage counts than SC in GDM (6.10 ± 2.20 versus 2.53 ± 1.45, p = 0.04), but not in normal pregnancies (p = 0.346). GDM pregnancies had more macrophages than normal pregnancies in OM (6.10 ± 2.20 versus 1.29 ± 0.55, p = 0.01), while only a trend was observed in SC fat (p = 0.08). Significant correlation (R = 0.619, p = 0.005) was observed between OM-macrophage infiltration and insulin resistance. Using multivariate analysis, only obesity independently associated with GDM. Expression of total p38MAP-kinase was higher in OM versus SC in both normal and GDM pregnancies, without significant differences between these groups. However, expression of activated p-p38MAP-kinase, and its upstream kinase MKK4, was comparable between fat depots.

CONCLUSION

GDM pregnancies demonstrate increased macrophage infiltration to OM fat, correlating with higher insulin resistance. As in non-pregnant-patients obesity and OM macrophage infiltration may be on the same causal pathway, leading to GDM. Yet, this occurs without activation of p38MAP-kinase signaling.

Pectinase-Processed Ginseng Radix (GINST) Ameliorates Hyperglycemia and Hyperlipidemia in High Fat Diet-Fed ICR Mice

To develop a ginseng product possessing an efficacy for diabetes, ginseng radix ethanol extract was treated with pectinase and obtained the GINST. In the present study, we evaluate the beneficial effect of GINST on high fat diet (HFD)-induced hyper-glycemia and hyperlipidemia and action mechanism(s) in ICR mice. The mice were randomly divided into five groups: regular diet group (RD), high fat diet group (HFD), HFD plus GINST at 75 mg/kg (GINST75), 150 mg/kg (GINST150), and 300 mg/kg (GINST300). Oral glucose tolerance test reveals that GINST improves the glucose tolerance after glucose challenge. Fasting plasma glucose and insulin levels were decreased by 4.3% and 4.2% in GINST75, 10.9% and 20.0% in GINST150, and 19.6% and 20.9% in GINST300 compared to those in HFD control group. Insulin resistance indices were also markedly decreased by 8.2% in GINST75, 28.7% in GINST150, and 36.4% in GINST300, compared to the HFD control group. Plasma triglyceride, total cholesterol and non-esterified fatty acid levels in the GINST300 group were decreased by 13.5%, 22.7% and 24.1%, respectively, compared to those in HFD control group. Enlarged adipocytes of HFD control group were markedly decreased in GINST-treated groups, and shrunken islets of HFD control mice were brought back to near normal shape in GINST300 group. Furthermore, GINST enhanced phosphorylation of AMP-activated protein kinase (AMPK) and glucose transporter 4 (GLUT4). In summary, GINST prevents HFD-induced hyperglycemia and hyperlipidemia through reducing insulin resistance via activating AMPK-GLUT4 pathways, and could be a potential therapeutic agent for type 2 diabetes.

Association between protein signals and type 2 diabetes incidence

Understanding early determinants of type 2 diabetes is essential for refining disease prevention strategies. Proteomic technology may provide a useful approach to identify novel protein patterns potentially related to pathophysiological changes that lead up to diabetes. In this study, we sought to identify protein signals that are associated with diabetes incidence in a middle-aged population. Serum samples from 519 participants in a nested case-control selection (167 cases and 352 age-, sex- and BMI-matched normoglycemic control subjects, median follow-up 14.0 years) within the Whitehall-II cohort were analyzed by linear matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Nine protein peaks were found to be associated with incident diabetes. Rate ratios for high peak intensity ranged between 0.4 (95% CI, 0.2-0.8) and 4.0 (95% CI, 1.7-9.2) and were robust to adjustment for main potential confounders, including obesity, lipids and C-reactive protein. The proteins associated with these peaks may reflect diabetes pathogenesis. Our study exemplifies the utility of an approach that combines proteomic and epidemiological data.

Identification of regulatory elements that control PPARγ expression in adipocyte progenitors

Adipose tissue renewal and obesity-driven expansion of fat cell number are dependent on proliferation and differentiation of adipose progenitors that reside in the vasculature that develops in coordination with adipose depots. The transcriptional events that regulate commitment of progenitors to the adipose lineage are poorly understood. Because expression of the nuclear receptor PPARγ defines the adipose lineage, isolation of elements that control PPARγ expression in adipose precursors may lead to discovery of transcriptional regulators of early adipocyte determination. Here, we describe the identification and validation in transgenic mice of 5 highly conserved non-coding sequences from the PPARγ locus that can drive expression of a reporter gene in a manner that recapitulates the tissue-specific pattern of PPARγ expression. Surprisingly, these 5 elements appear to control PPARγ expression in adipocyte precursors that are associated with the vasculature of adipose depots, but not in mature adipocytes. Characterization of these five PPARγ regulatory sequences may enable isolation of the transcription factors that bind these cis elements and provide insight into the molecular regulation of adipose tissue expansion in normal and pathological states.

Nonalcoholic fatty liver disease: current issues and novel treatment approaches

Nonalcoholic fatty liver disease (NAFLD) is considered the most common liver disorder in the Western world. It is commonly associated with insulin resistance, obesity, dyslipidaemia, type 2 diabetes mellitus (T2DM) and cardiovascular disease. Nonalcoholic steatohepatitis (NASH) is characterized by steatosis with necroinflammation and eventual fibrosis, which can lead to end-stage liver disease and hepatocellular carcinoma. Its pathogenesis is complex, and involves a state of 'lipotoxicity' in which insulin resistance, with increased free fatty acid release from adipose tissue to the liver, play a key role in the onset of a 'lipotoxic liver disease' and its progression to NASH. The diagnosis of NASH is challenging, as most affected patients are symptom free and the role of routine screening is not clearly established. A complete medical history is important to rule out other causes of fatty liver disease (alcohol abuse, medications, other). Plasma aminotransferase levels and liver ultrasound are helpful in the diagnosis of NAFLD/NASH, but a liver biopsy is often required for a definitive diagnosis. However, there is an active search for plasma biomarkers and imaging techniques that may non-invasively aid in the diagnosis. The treatment of NASH requires a multifaceted approach. The goal is to reverse obesity-associated lipotoxicity and insulin resistance via lifestyle intervention. Although there is no pharmacological agent approved for the treatment of NAFLD, vitamin E (in patients without T2DM) and the thiazolidinedione pioglitazone (in patients with and without T2DM) have shown the most consistent results in randomized controlled trials. This review concentrates on our current understanding of the disease, with a focus on the existing therapeutic approaches and potential future pharmacological developments for NAFLD and NASH.

MicroRNAs as pharmacological targets in diabetes

Diabetes is characterized by high levels of blood glucose due to either the loss of insulin-producing beta-cells in the pancreas, leading to a deficiency of insulin in type 1 diabetes, or due to increased insulin resistance, leading to reduced insulin sensitivity and productivity in type 2 diabetes. There is an increasing need for new options to treat diabetes, especially type 2 diabetes at its early stages due to an ineffective control of its development in patients. Recently, a novel class of small noncoding RNAs, termed microRNAs (miRNAs), is found to play a key role as important transcriptional and posttranscriptional inhibitors of gene expression in fine-tuning the target messenger RNAs (mRNAs). miRNAs are implicated in the pathogenesis of diabetes and have become an intriguing target for therapeutic intervention. This review focuses on the dysregulated miRNAs discovered in various diabetic models and addresses the potential for miRNAs to be therapeutic targets in the treatment of diabetes.

Obesity, immunomodulation and chronic kidney disease

Obesity-induced inflammation is associated with numerous pathologies and is an independent risk factor of chronic kidney disease (CKD). The prevalence of CKD is escalating and current therapeutic strategies are seriously lacking in efficacy, and immunomodulation has been suggested as a potential new therapeutic approach. Indeed, specialized pro-resolving mediators (SPMs), such as lipoxins (LXs), resolvins and protectins, have demonstrated protection in adipose inflammation, restoring insulin sensitivity and adiponectin production, while modulating leukocyte infiltration and promoting resolution in visceral adipose tissue. Furthermore, SPMs display direct renoprotective effect. Thus we review current evidence of immunomodulation as a potential strategy to subvert obesity-related CKD.

Abdominal adiposity largely explains associations between insulin resistance, hyperglycemia and subclinical atherosclerosis: the NEO study

OBJECTIVE

The relative importance of insulin resistance and hyperglycemia to the development of atherosclerosis remains unclear. Furthermore, adiposity may be responsible for observed associations. Our aim was to study the relative contributions of adiposity, insulin resistance and hyperglycemia to subclinical atherosclerosis.

METHODS

In this cross-sectional analysis of the Netherlands Epidemiology of Obesity (NEO) study, a cohort of persons of 45-65 years, BMI, waist circumference (WC), fasting glucose (FPG), HbA1c and insulin concentrations were measured and the revised HOMA-IR was calculated. The carotid Intima-Media Thickness (cIMT) was measured by ultrasound. We performed linear regression analyses between standardized values of FPG, HbA1c, HOMA-IR, BMI, WC with cIMT, and subsequently included age, sex, ethnicity, education and smoking, HOMA-IR, HbA1c and FPG, BMI and WC in the models.

RESULTS

After exclusion of participants with glucose lowering therapy (n = 356) or missing data (n = 252), this analysis included 6065 participants, 43% men, and mean (SD) cIMT of 616 (92) μm. Differences in cIMT (95% CI) per SD were: FPG: 16 (10,21); HbA1c: 12 (7,16); HOMA-IR: 11 (6,16) μm. These associations attenuated after adjustments, and attenuated most strongly after adjustment for WC. Differences in cIMT (95% CI) per SD in the full model were: FPG: 4 (0,7); HbA1c: 2 (-1,5); HOMA-IR: 0 (-3,3); BMI 16 (13,19); WC: 18 (14,21) μm.

CONCLUSION

In middle-aged individuals, we observed similar contributions of insulin resistance and hyperglycemia to subclinical atherosclerosis. These contributions were largely explained by abdominal adiposity, emphasizing the importance of weight management.

Nonalcoholic Fatty liver disease, diabetes mellitus and cardiovascular disease: newer data

Nonalcoholic fatty liver disease (NAFLD) is the most common, chronic liver disease worldwide. Within this spectrum, steatosis alone is apparently benign, while nonalcoholic steatohepatitis may progress to cirrhosis and hepatocellular carcinoma. NAFLD is strongly associated with obesity, dyslipidemia, type 2 diabetes mellitus, and cardiovascular disease. The pathogenesis of hepatic steatosis is not clearly known, but its main characteristics are considered insulin resistance, mitochondrial dysfunction, increased free fatty acids reflux from adipose tissue to the liver, hepatocyte lipotoxicity, stimulation of chronic necroinflammation, and fibrogenic response. With recent advances in technology, advanced imaging techniques provide important information for diagnosis. There is a significant research effort in developing noninvasive monitoring of disease progression to fibrosis and response to therapy with potential novel biomarkers, in order to facilitate diagnosis for the detection of advanced cirrhosis and to minimize the need of liver biopsy. The identification of NAFLD should be sought as part of the routine assessment of type 2 diabetics, as sought the microvascular complications and cardiovascular disease, because it is essential for the early diagnosis and proper intervention. Diet, exercise training, and weight loss provide significant clinical benefits and must be considered of first line for treating NAFLD.

Effect of Lactobacillus gasseri BNR17 on Overweight and Obese Adults: A Randomized, Double-Blind Clinical Trial

Background

Lactobacillus gasseri BNR17 is a type of probiotic strain isolated from human breast milk. A study was reported regarding the fact that BNR17 was an inhibitor of obesity and diabetic activities in the human body through previous animal experiments. This study was furthered to investigate the effect of BNR17, a probiotic strain isolated from human breast milk, on obese and overweight adults.

Methods

Sixty-two obese volunteers aged 19 to 60 with body mass index ≥ 23 kg/m² and fasting blood sugar ≥ 100 mg/dL participated in a placebo controlled, randomized, and double-blind trial. For 12 weeks, 57 participants were given either placebo or BNR17 and were tested by measuring body fat, body weight, various biochemical parameters, vital signs, and computed tomography at the start of the study and at weeks 4, 8, and 12. The subjects assumed usual daily activities without having to make behavioral or dietary modifications during the course of the study.

Results

At the 12th week, a slight reduction in body weight was noted in the BNR17 group, but there were no significant weight changes between groups. Decrease of waist and hip circumferences in the BNR17 group was more pronounced than those in the placebo group. The two groups had no special or severe adverse reactions.

Conclusion

Despite there being no change in behavior or diet, administration of only the supplement of BNR17 reduced weight and waist and hip circumference. However, there were no significant differences between the two groups. These findings warrant a subsequent longer-term prospective clinical investigation with a large population.

Antihyperlipidaemic and antioxidant effect of the total flavonoids in Selaginella tamariscina (Beauv.) Spring in diabetic mice

Objectives

To investigate the antidiabetic, antihyperlipidaemic and antioxidant activity of total flavonoids in Selaginella tamariscina (Beauv.) Spring (TFST) in a mouse model of diabetes.

Methods

Normal mice, mice fed with a high-fat emulsion diet and streptozotocin (STZ)-induced diabetic mice were treated with TFST for 6 weeks. Serum glucose, insulin and lipid, hepatic steatosis, production of the protein visfatin and antioxidant indices were evaluated.

Key findings

TFST significantly decreased the concentration of fasting blood glucose, total cholesterol, triglycerides and low-density-lipoprotein cholesterol, while it increased the levels of insulin and high-density-lipoprotein cholesterol in diabetic mice. TFST also improved the results of the oral glucose tolerance test to a certain degree. Furthermore, both the free fatty acid levels in the liver and hepatic steatosis were ameliorated by TFST treatment. These changes may be be associated with decreased production of visfatin. Administration of TFST also significantly decreased the levels of malondialdehyde, nitric oxide and inducible nitric oxide synthase and increased the content of glutathione and the activity of superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase in the liver. No change in blood glucose levels were observed in the normal mice treated with TFST.

Conclusions

TFST showed an excellent effect in reducing the high blood glucose level but had no effect on normal blood glucose level. The antidiabetic activity of TFST could be explained by its antioxidant and antihyperlipidaemic activity, which finally elevated the insulin sensitivity of liver.

Oxidative stress associated to dysfunctional adipose tissue: a potential link between obesity, type 2 diabetes mellitus and breast cancer

Diabetes mellitus and breast cancer are two important health problems. Type 2 diabetes (T2DM) and obesity are closely linked with both being associated with breast cancer. Despite abundant epidemiological data, there is no definitive evidence regarding the mechanisms responsible for this association. The proposed mechanisms by which diabetes affects breast cancer risk and prognosis are the same as the mechanisms hypothesised for the contribution of obesity to breast cancer risk. The obesity-induced inflammation promoted by adipose tissue dysfunction is a key feature, which is thought to be an important link between obesity and cancer. Inflammation induces an increase in free radicals and subsequently promotes oxidative stress, which may create a microenvironment favourable to the tumor development in obese persons. Oxidative stress is also proposed as the link between obesity and diabetes mellitus. Therefore, obesity-related oxidative stress could be a direct cause of neoplastic transformation associated with obesity and T2DM in breast cancer cells. This review is focused on the role of obesity-related oxidative stress in the context of chronic inflammation, on the time of breast cancer onset and progression, which provide targets for preventive and therapeutic strategies in the fields of diabetes and obesity-related breast cancer.

Chronic alcohol exposure disturbs lipid homeostasis at the adipose tissue-liver axis in mice: analysis of triacylglycerols using high-resolution mass spectrometry in combination with in vivo metabolite deuterium labeling

A method of employing high-resolution mass spectrometry in combination with in vivo metabolite deuterium labeling was developed in this study to investigate the effects of alcohol exposure on lipid homeostasis at the white adipose tissue (WAT)-liver axis in a mouse model of alcoholic fatty liver. In order to differentiate the liver lipids synthesized from the fatty acids that were transported back from adipose tissue and the lipids synthesized from other sources of fatty acids, a two-stage mouse feeding experiment was performed to incorporate deuterium into metabolites. Hepatic lipids extracted from mouse liver, epididymal white adipose tissue (eWAT) and subcutaneous white adipose tissue (sWAT) were analyzed. It was found that 13 and 10 triacylglycerols (TGs) incorporated with a certain number of deuterium were significantly increased in alcohol induced fatty liver at two and four weeks of alcohol feeding periods, respectively. The concentration changes of these TGs ranged from 1.7 to 6.3-fold increase. A total of 14 deuterated TGs were significantly decreased in both eWAT and sWAT at the two and four weeks and the fold-change ranged from 0.19 to 0.77. The increase of deuterium incorporated TGs in alcohol-induced fatty liver and their decrease in both eWAT and sWAT indicate that alcohol exposure induces hepatic influx of fatty acids which are released from WATs. The results of time course analysis further indicate a mechanistic link between adipose fat loss and hepatic fat gain in alcoholic fatty liver.

Investigation of the Protective Effects of Phlorizin on Diabetic Cardiomyopathy in db/db Mice by Quantitative Proteomics

Patients with diabetes often develop hypertension and atherosclerosis leading to cardiovascular disease. However, some diabetic patients develop heart failure without hypertension and coronary artery disease, a process termed diabetic cardiomyopathy. Phlorizin has been reported to be effective as an antioxidant in treating diabetes mellitus, but little is known about its cardioprotective effects on diabetic cardiomyopathy. In this study, we investigated the role of phlorizin in preventing diabetic cardiomyopathy in db/db mice. We found that phlorizin significantly decreased body weight gain and the levels of serum fasting blood glucose (FBG), triglycerides (TG), total cholesterol (TC), and advanced glycation end products (AGEs). Morphologic observations showed that normal myocardial structure was better preserved after phlorizin treatment. Using isobaric tag for relative and absolute quantitation (iTRAQ) proteomics, we identified differentially expressed proteins involved in cardiac lipid metabolism, mitochondrial function, and cardiomyopathy, suggesting that phlorizin may prevent the development of diabetic cardiomyopathy by regulating the expression of key proteins in these processes. We used ingenuity pathway analysis (IPA) to generate an interaction network to map the pathways containing these proteins. Our findings provide important information about the mechanism of diabetic cardiomyopathy and also suggest that phlorizin may be a novel therapeutic approach for the treatment of diabetic cardiomyopathy.

Differentially expressed genes in adipocytokine signaling pathway of adipose tissue in pregnancy

Objective

To profile the differential gene expression of the KEGG Adipocytokine Signaling pathway in omental compared to subcutaneous tissue in normal pregnancy.

Study Design

Subjects included 14 nonobese, normal glucose tolerant, healthy pregnant women. Matched omental and subcutaneous tissue were obtained at elective cesarean delivery. Gene expression was evaluated using microarray and validated by RT-PCR. Differential gene expression was defined as ≥1.5 fold increase at p < 0.05.

Results

Six genes were significantly downregulated with two upregulated genes in omental tissue. Downregulation of Adiponectin and Insulin Receptor substrate, key genes mediating insulin sensitivity, were observed with borderline upregulation of GLUT-1. There were downregulations of CD36 and acyl-CoA Synthetase Long-chain Family Member 1which are genes involved in fatty acid uptake and activation. There was a novel expression of Carnitine palmitoyltransferase 1C.

Conclusion

Differential gene expression of Adipocytokine Signaling Pathway in omental relative to subcutaneous adipose tissue in normal pregnancy suggests a pattern of insulin resistance, hyperlipidemia, and inflammation.

Doxorubicin treatment inhibits PPARγ and may induce lipotoxicity by mimicking a type 2 diabetes-like condition in rodent models

Doxorubicin-treated animals show elevated serum triglyceride and blood glucose levels. Adipocytes play an important role in buffering blood glucose and lipids. A raise in serum lipid level triggers adipogenesis in order to increase the lipid absorption capacity of adipose tissue. Doxorubicin inhibits adipogenesis through the down-regulation of PPARγ, a crucial component of the lipid metabolic pathway which controls the expression of glucose and fatty acid transporters. Doxorubicin-mediated down-regulation of PPARγ inhibits blood glucose and lipid clearance thereby causing hyperglycemia and hyperlipidemia resulting in lipotoxicity, glucotoxicity, inflammation and insulin resistance. Therefore we hypothesize that doxorubicin treatment could mimic a type 2 diabetic condition.

The association of baseline adipocytokine levels with glycemic progression in nondiabetic Korean adults in 4 years of follow-up

AIMS

Low-grade inflammation and lipotoxicity contribute to insulin resistance and islet secretory dysfunction that lead to insulin deficiency. We analyzed the associations of several adipocytokines measured at baseline with glycemic progression in non-diabetic Korean subjects after a 4-year follow-up.

METHODS

In 479 non-diabetic Korean subjects who underwent medical screening in 2003, serum tumor necrosis factor (TNF)-α, interleukin (IL)-6, retinol-binding protein (RBP)-4, monocyte chemoattractant protein (MCP)-1, visfatin and fatty acid-binding protein (FABP)-4 were measured at baseline. After 4 years, changes in glycemia were assessed.

RESULTS

Among the subjects, 79.2% maintained their baseline glycemic status, 14.6% progressed to worse glycemic status (impaired fasting glucose (IFG) to diabetes, normoglycemia to IFG or normoglycemia to diabetes) and 5.8% regressed to normoglycemia after 4 years. Baseline TNF-α and FABP4 showed the highest values in the progression group. In the logistic regression analyses with glycemic progression as the dependent variable and TNF-α and FABP4 as independent variables in separate models, TNF-α and FABP4 individually predicted glycemic progression after adjustment for confounding variables. When both adipocytokines were included in the same model, only FABP4 significantly predicted glycemic progression after 4 years.

CONCLUSIONS

TNF-α and FABP4 were significant predictors for glycemic progression in 4 years, with FABP4 being the stronger predictor.

Effect of bromocriptine-QR (a quick-release formulation of bromocriptine mesylate) on major adverse cardiovascular events in type 2 diabetes subjects

BACKGROUND

Bromocriptine-QR (a quick-release formulation of bromocriptine mesylate), a dopamine D2 receptor agonist, is a US Food and Drug Administrration-approved treatment for type 2 diabetes mellitus (T2DM). A 3070-subject randomized trial demonstrated a significant, 40% reduction in relative risk among bromocriptine-QR-treated subjects in a prespecified composite cardiovascular (CV) end point that included ischemic-related (myocardial infarction and stroke) and nonischemic-related (hospitalization for unstable angina, congestive heart failure [CHF], or revascularization surgery) end points, but did not include cardiovascular death as a component of this composite. The present investigation was undertaken to more critically evaluate the impact of bromocriptine-QR on cardiovascular outcomes in this study subject population by (1) including CV death in the above-described original composite analysis and then stratifying this new analysis on the basis of multiple demographic subgroups and (2) analyzing the influence of this intervention on only the "hard" CV end points of myocardial infarction, stroke, and CV death (major adverse cardiovascular events [MACEs]).

METHODS AND RESULTS

Three thousand seventy T2DM subjects on stable doses of ≤2 antidiabetes medications (including insulin) with HbA1c ≤10.0 (average baseline HbA1c=7.0) were randomized 2:1 to bromocriptine-QR (1.6 to 4.8 mg/day) or placebo for a 52-week treatment period. Subjects with heart failure (New York Heart Classes I and II) and precedent myocardial infarction or revascularization surgery were allowed to participate in the trial. Study outcomes included time to first event for each of the 2 CV composite end points described above. The relative risk comparing bromocriptine-QR with the control for the cardiovascular outcomes was estimated as a hazard ratio with 95% confidence interval on the basis of Cox proportional hazards regression. The statistical significance of any between-group difference in the cumulative percentage of CV events over time (derived from a Kaplan-Meier curve) was determined by a log-rank test on the intention-to-treat population. Study subjects were in reasonable metabolic control, with an average baseline HbA1c of 7.0±1.1, blood pressure of 128/76±14/9, and total and LDL cholesterol of 179±42 and 98±32, respectively, with 88%, 77%, and 69% of subjects being treated with antidiabetic, antihypertensive, and antihyperlipidemic agents, respectively. Ninety-one percent of the expected person-year outcome ascertainment was obtained in this study. Respecting the CV-inclusive composite cardiovascular end point, there were 39 events (1.9%) among 2054 bromocriptine-QR-treated subjects versus 33 events (3.2%) among 1016 placebo subjects, yielding a significant, 39% reduction in relative risk in this end point with bromocriptine-QR exposure (P=0.0346; log-rank test) that was not influenced by age, sex, race, body mass index, duration of diabetes, or preexisting cardiovascular disease. In addition, regarding the MACE end point, there were 14 events (0.7%) among 2054 bromocriptine-QR-treated subjects and 15 events (1.5%) among 1016 placebo-treated subjects, yielding a significant, 52% reduction in relative risk in this end point with bromocriptine-QR exposure (P<0.05; log-rank test).

CONCLUSIONS

These findings reaffirm and extend the original observation of relative risk reduction in cardiovascular adverse events among type 2 diabetes subjects treated with bromocriptine-QR and suggest that further investigation into this impact of bromocriptine-QR is warranted.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov. Unique Identifier: NCT00377676.

Resolution of inflammation: therapeutic potential of pro-resolving lipids in type 2 diabetes mellitus and associated renal complications

The role of inflammation in the pathogenesis of type 2 diabetes mellitus (T2DM) and its associated complications is increasingly recognized. The resolution of inflammation is actively regulated by endogenously produced lipid mediators such as lipoxins, resolvins, protectins, and maresins. Here we review the potential role of these lipid mediators in diabetes-associated pathologies, specifically focusing on adipose inflammation and diabetic kidney disease, i.e., diabetic nephropathy (DN). DN is one of the major complications of T2DM and we propose that pro-resolving lipid mediators may have therapeutic potential in this context. Adipose inflammation is also an important component of T2DM-associated insulin resistance and altered adipokine secretion. Promoting the resolution of adipose inflammation would therefore likely be a beneficial therapeutic approach in T2DM.

Seeking the source of adipocytes in adult white adipose tissues

Adipocyte progenitors are thought to play a fundamental role in white adipose tissue (WAT) plasticity, which enables dynamic modulation of WAT metabolic and cellular characteristics in response to various stimuli. In general, two main strategies have been used to identify adipocyte progenitor cells: fluorescence-activated cell sorting (FACS)-based prospective analysis and lineage tracing. Although FACS-isolation is highly useful in defining multipotential stem cell populations for in vitro analysis and transplantation, lineage tracing is essential to identify endogenous progenitors that do, in fact, differentiate into adipocytes in vivo. Our recent lineage tracing studies have shown that cells expressing the surface marker platelet-derived growth factor receptor α (PDGFRα) give rise to white and brown adipocytes in adult WAT, depending on inductive cues. PDGFRα⁺ cells are a subpopulation of those expressing CD34 and Sca1, and have unique morphology whereby long dendritic processes contact numerous cell types in the microenvironment. The significant contribution of PDGFRα⁺ cells to browning and hyperplastic expansion of WAT leads us to propose that PDGFRα⁺ cells are remodeling stem cells in adult WAT. Application of advanced imaging technology and genetic tools to this progenitor population will allow greater understanding of cellular plasticity in adipose tissue.

Association of Alanine Aminotransferase Levels (ALT) with the Hepatic Insulin Resistance Index (HIRI): a cross-sectional study

BACKGROUND

The association between serum alanine aminotransferase (ALT) levels and hepatic insulin resistance (IR) has been evaluated with the hyperinsulinemic-euglycemic clamp. However, there is no information about the association of ALT with the Hepatic Insulin Resistance Index (HIRI). The aim of this study was to evaluate the association between serum ALT levels and HIRI in subjects with differing degrees of impaired glucose metabolism.

METHODS

This cross-sectional study included subjects that had an indication for testing for type 2 diabetes mellitus (T2DM) with an oral glucose tolerance test (OGTT). Clinical and biochemical evaluations were carried out including serum ALT level quantification. HIRI was calculated for each participant. Correlation analyses and lineal regression models were used to evaluate the association between ALT levels and HIRI.

RESULTS

A total of 324 subjects (37.6% male) were included. The mean age was 40.4 ± 14.3 years and the mean body mass index (BMI) was 32.0 ± 7.3 kg/m2. Individuals were divided into 1 of 5 groups: without metabolic abnormalities (n = 113, 34.8%); with the metabolic syndrome (MetS, n = 179, 55.2%), impaired fasting glucose (IFG, n = 85, 26.2%); impaired glucose tolerance (IGT, n = 91, 28.0%), and T2DM (n = 23, 7.0%). The ALT (p < 0.001) and HOMA2-IR (p < 0.001) values progressively increased with HIRI quartiles, while ISI-Matsuda (p < 0.001) progressively decreased. After adjustment for sex, age, and BMI, we identified a significant correlation between HIRI and ALT in persons with the MetS (r = 0.22, p = 0.003), IFG (r = 0.33, p < 0.001), IGT (r = 0.37, p < 0.001), and T2DM (r = 0.72, p < 0.001). Lineal regression analysis adjusting for age, HDL-C, TG and waist circumference (WC) showed an independent association between ALT and HIRI in subjects with the MetS (beta = 0.07, p = 0.01), IFG (beta = 0.10, p = 0.02), IGT (beta = 0.09, p = 0.007), and T2DM (beta = 0.31, p = 0.003). This association was not identified in subjects without metabolic abnormalities.

CONCLUSIONS

ALT levels are independently associated with HIRI in subjects with the MetS, IFG, IGT, and T2DM. The ALT value in these subjects may be an indirect parameter to evaluate hepatic IR.

β-cell function preservation after 3.5 years of intensive diabetes therapy

OBJECTIVE

To assess β-cell function preservation after 3.5 years of intensive therapy with insulin plus metformin (INS group) versus triple oral therapy (TOT group) with metformin, glyburide, and pioglitazone.

RESEARCH DESIGN AND METHODS

This was a randomized trial of 58 patients with treatment-naïve newly diagnosed type 2 diabetes. All patients were treated with insulin and metformin for a 3-month lead-in period followed by random assignment to the INS or TOT group. β-Cell function was assessed using a mixed-meal challenge test at randomization and 6, 12, 18, 30, and 42 months. Analyses were intention to treat and performed with repeated-measures models.

RESULTS

Completion rates at 3.5 years were 83% in the insulin group and 72% in the TOT group, with good compliance in both groups (87 ± 20% in the INS group vs. 90 ± 15% in the TOT group). β-Cell function was preserved at 3.5 years after diagnosis, with no significant change from baseline or difference between the two groups as measured by area under the curve (AUC) of C-peptide (P = 0.14) or the ratio of C-peptide to glucose AUC (P = 0.7). Excellent glycemic control was maintained in both groups (end-of-study HbA(1c) 6.35 ± 0.84% in the INS group vs. 6.59 ± 1.94% in the TOT group). Weight increased in both groups over time (from 102.2 ± 24.9 kg to 106.2 ± 31.7 kg in the INS group and from 100.9 ± 23.0 kg to 110.5 ± 31.8 kg in the TOT group), with no significant difference between groups (P = 0.35). Hypoglycemic events decreased significantly over time (P = 0.01) but did not differ between groups (P = 0.83).

CONCLUSIONS

β-Cell function can be preserved for at least 3.5 years with early and intensive therapy for type 2 diabetes with either insulin plus metformin or triple oral therapy after an initial 3-month insulin-based treatment period.

Activation of pregnane X receptor by pregnenolone 16 α-carbonitrile prevents high-fat diet-induced obesity in AKR/J mice

Pregnane X receptor (PXR) is known to function as a xenobiotic sensor to regulate xenobiotic metabolism through selective transcription of genes responsible for maintaining physiological homeostasis. Here we report that the activation of PXR by pregnenolone 16α-carbonitrile (PCN) in AKR/J mice can prevent the development of high-fat diet-induced obesity and insulin resistance. The beneficial effects of PCN treatment are seen with reduced lipogenesis and gluconeogenesis in the liver, and lack of hepatic accumulation of lipid and lipid storage in the adipose tissues. RT-PCR analysis of genes involved in gluconeogenesis, lipid metabolism and energy homeostasis reveal that PCN treatment on high-fat diet-fed mice reduces expression in the liver of G6Pase, Pepck, Cyp7a1, Cd36, L-Fabp, Srebp, and Fas genes and slightly enhances expression of Cyp27a1 and Abca1 genes. RT-PCR analysis of genes involved in adipocyte differentiation and lipid metabolism in white adipose tissue show that PCN treatment reduces expression of Pparγ2, Acc1, Cd36, but increases expression of Cpt1b and Pparα genes in mice fed with high-fat diet. Similarly, PCN treatment of animals on high-fat diet increases expression in brown adipose tissue of Pparα, Hsl, Cpt1b, and Cd36 genes, but reduces expression of Acc1 and Scd-1 genes. PXR activation by PCN in high-fat diet fed mice also increases expression of genes involved in thermogenesis in brown adipose tissue including Dio2, Pgc-1α, Pgc-1β, Cidea, and Ucp-3. These results verify the important function of PXR in lipid and energy metabolism and suggest that PXR represents a novel therapeutic target for prevention and treatment of obesity and insulin resistance.

Lipoxin A4 attenuates adipose inflammation

Aging and adiposity are associated with chronic low-grade inflammation, which underlies the development of obesity-associated complications, including type 2 diabetes mellitus (T2DM). The mechanisms underlying adipose inflammation may include macrophage infiltration and activation, which, in turn, affect insulin sensitivity of adipocytes. There is a growing appreciation that specific lipid mediators (including lipoxins, resolvins, and protectins) can promote the resolution of inflammation. Here, we investigated the effect of lipoxin A4 (LXA4), the predominant endogenously generated lipoxin, on adipose tissue inflammation. Using adipose tissue explants from perigonadal depots of aging female C57BL/6J mice (Animalia, Chordata, Mus musculus) as a model of age-associated adipose inflammation, we report that LXA4 (1 nM) attenuates adipose inflammation, decreasing IL-6 and increasing IL-10 expression (P<0.05). The altered cytokine milieu correlated with increased GLUT-4 and IRS-1 expression, suggesting improved insulin sensitivity. Further investigations revealed the ability of LXA4 to rescue macrophage-induced desensitization to insulin-stimulated signaling and glucose uptake in cultured adipocytes, using vehicle-stimulated cells as controls. This was associated with preservation of Akt activation and reduced secretion of proinflammatory cytokines, including TNF-α. We therefore propose that LXA4 may represent a potentially useful and novel therapeutic strategy to subvert adipose inflammation and insulin resistance, key components of T2DM.

mTOR signaling in growth control and disease

The mechanistic target of rapamycin (mTOR) signaling pathway senses and integrates a variety of environmental cues to regulate organismal growth and homeostasis. The pathway regulates many major cellular processes and is implicated in an increasing number of pathological conditions, including cancer, obesity, type 2 diabetes, and neurodegeneration. Here, we review recent advances in our understanding of the mTOR pathway and its role in health, disease, and aging. We further discuss pharmacological approaches to treat human pathologies linked to mTOR deregulation.

Physical training prevents body weight gain but does not modify adipose tissue gene expression

The relationship of body weight (BW) with white adipose tissue (WAT) mass and WAT gene expression pattern was investigated in mice submitted to physical training (PT). Adult male C57BL/6 mice were submitted to two 1.5-h daily swimming sessions (T, N = 18), 5 days/week for 4 weeks or maintained sedentary (S, N = 15). Citrate synthase activity increased significantly in the T group (P < 0.05). S mice had a substantial weight gain compared to T mice (4.06 ± 0.43 vs 0.38 ± 0.28 g, P < 0.01). WAT mass, adipocyte size, and the weights of gastrocnemius and soleus muscles, lung, kidney, and adrenal gland were not different. Liver and heart were larger and the spleen was smaller in T compared to S mice (P < 0.05). Food intake was higher in T than S mice (4.7 ± 0.2 vs 4.0 ± 0.3 g/animal, P < 0.05) but oxygen consumption at rest did not differ between groups. T animals showed higher serum leptin concentration compared to S animals (6.37 ± 0.5 vs 3.11 ± 0.12 ng/mL). WAT gene expression pattern obtained by transcription factor adipocyte determination and differentiation-dependent factor 1, fatty acid synthase, malic enzyme, hormone-sensitive lipase, adipocyte lipid binding protein, leptin, and adiponectin did not differ significantly between groups. Collectively, our results showed that PT prevents BW gain and maintains WAT mass due to an increase in food intake and unchanged resting metabolic rate. These responses are closely related to unchanged WAT gene expression patterns.

Genetic and environmental factors associated with type 2 diabetes and diabetic vascular complications

Faced with a global epidemic of type 2 diabetes (T2D), it is critical that researchers improve our understanding of the pathogenesis of T2D and related vascular complications. These findings may ultimately lead to novel treatment options for disease prevention or delaying progression. Two major paradigms jointly underlie the development of T2D and related coronary artery disease, diabetic nephropathy, and diabetic retinopathy. These paradigms include the genetic risk variants and behavioral/environmental factors. This article systematically reviews the literature supporting genetic determinants in the pathogenesis of T2D and diabetic vasculopathy, and the functional implications of these gene variants on the regulation of beta-cell function and glucose homeostasis. We update the discovery of diabetes and diabetic vasculopathy risk variants, and describe the genetic technologies that have uncovered them. Also, genomic linkage between obesity and T2D is discussed. There is a complementary role for behavioral and environmental factors modulating the genetic susceptibility and diabetes risk. Epidemiological and clinical data demonstrating the effects of behavioral and novel environmental exposures on disease expression are reviewed. Finally, a succinct overview of recent landmark clinical trials addressing glycemic control and its impact on rates of vascular complications is presented. It is expected that novel strategies to exploit the gene- and exposure-related underpinnings of T2D will soon result.

Macrophage-specific transgenic expression of cholesteryl ester hydrolase attenuates hepatic lipid accumulation and also improves glucose tolerance in ob/ob mice

Cellular cholesterol homeostasis is increasingly being recognized as an important determinant of the inflammatory status of macrophages, and a decrease in cellular cholesterol levels polarizes macrophages toward an anti-inflammatory or M2 phenotype. Cholesteryl ester hydrolase (CEH) catalyzes the hydrolysis of stored intracellular cholesteryl esters (CE) and thereby enhances free cholesterol efflux and reduces cellular CE content. We have reported earlier reduced atherosclerosis as well as lesion necrosis and improved insulin sensitivity (due to decreased adipose tissue inflammation) in macrophage-specific CEH transgenic (CEHTg) mice in the LDLR(-/-) background. In the present study, we examined the effects of reduced intracellular accumulation of CE in CEHTg macrophages in an established diabetic mouse model, namely the leptin-deficient ob/ob mouse. Macrophage-specific transgenic expression of CEH improved glucose tolerance in ob/ob-CEHTg mice significantly compared with ob/ob nontransgenic littermates, but with no apparent change in macrophage infiltration into the adipose tissue. However, there was a significant decrease in hepatic lipid accumulation in ob/ob-CEHTg mice. Consistently, decreased [(14)C]acetate incorporation into total lipids and triglycerides was noted in precision-cut liver slices from ob/ob-CEHTg mice. In the primary hepatocyte-macrophage coculture system, macrophages from CEHTg mice significantly reduced the incorporation of [(14)C]acetate into triglycerides in hepatocytes, indicating a direct effect of macrophages on hepatocyte triglyceride biosynthesis. Kupffer cells isolated from ob/ob-CEHTg mice were polarized toward an anti-inflammatory M2 (Ly6C(lo)) phenotype. Taken together, these studies demonstrate that transgenic overexpression of CEH in macrophages polarizes hepatic macrophages (Kupffer cells) to an anti-inflammatory M2 phenotype that attenuates hepatic lipid synthesis and accumulation.

Effect of adipose tissue insulin resistance on metabolic parameters and liver histology in obese patients with nonalcoholic fatty liver disease

The role of adipose tissue insulin resistance in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) remains unclear. To evaluate this, we measured in 207 patients with NAFLD (age = 51 ± 1, body mass index = 34.1 ± 0.3 kg/m(2) ) and 22 controls without NAFLD (no NAFLD) adipose tissue insulin resistance by means of a validated index (Adipo-IR(i) = plasma free fatty acids [FFA] x insulin [FPI] concentration) and as the suppression of plasma FFA during an oral glucose tolerance test and by a low-dose insulin infusion. We also explored the relationship between adipose tissue insulin resistance with metabolic and histological parameters by dividing them based on quartiles of adipose tissue insulin resistance (Adipo-IR(i) quartiles: Q1 = more sensitive; Q4 = more insulin resistant). Hepatic insulin resistance, measured as an index derived from endogenous glucose production x FPI (HIRi), and muscle insulin sensitivity, were assessed during a euglycemic insulin clamp with 3-[(3) H] glucose. Liver fat was measured by magnetic resonance imaging and spectroscopy, and a liver biopsy was performed to assess liver histology. Compared to patients without steatosis, patients with NAFLD were insulin resistant at the level of adipose tissue, liver, and skeletal muscle and had higher plasma aspartate aminotransferase and alanine aminotransferase, triglycerides, and lower high-density lipoprotein cholesterol and adiponectin levels (all P < 0.01). Metabolic parameters, hepatic insulin resistance, and liver fibrosis (but not necroinflammation) deteriorated as quartiles of adipose tissue insulin resistance worsened (all P < 0.01).

CONCLUSION

Adipose tissue insulin resistance plays a key role in the development of metabolic and histological abnormalities of obese patients with NAFLD. Treatment strategies targeting adipose tissue insulin resistance (e.g., weight loss and thiazolidinediones) may be of value in this population.

Abundance of circulating preadipocyte factor 1 in early life

OBJECTIVE

Soluble preadipocyte factor 1 (Pref-1) inhibits adipocyte differentiation. We tested whether circulating levels of soluble Pref-1 are higher in smaller fetuses.

RESEARCH DESIGN AND METHODS

We performed longitudinal assessments of circulating Pref-1 in infants born appropriate for gestational age (AGA) or small for gestational age (SGA) and also in late-gestational women and in newborns on days 2 and 3.

RESULTS

At birth, Pref-1 levels were ~100-fold higher than in adults, being in SGA fetuses ~50% higher than in AGA fetuses. By age 4 months, Pref-1 had reached near-adult levels and the original AGA versus SGA difference had disappeared. Pref-1 levels were low in late-gestational women and were still elevated in newborns.

CONCLUSIONS

Pref-1 is abundantly present in the fetus, is higher in SGA than in AGA fetuses, and is likely to be of fetal origin. We speculate that Pref-1 in early life contributes to variation in postnatal adipocyte numbers, in the subsequent expandability of adipose tissue, and thus in the susceptibility to diabetes in later life.

Role of obesity and lipotoxicity in the development of nonalcoholic steatohepatitis: pathophysiology and clinical implications

As obesity reaches epidemic proportions, nonalcoholic fatty liver disease (NAFLD) is becoming a frequent cause of patient referral to gastroenterologists. There is a close link between dysfunctional adipose tissue in NAFLD and common conditions such as metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. This review focuses on the pathophysiology of interactions between adipose tissue and target organs in obesity and the resulting clinical implications for the management of nonalcoholic steatohepatitis. The release of fatty acids from dysfunctional and insulin-resistant adipocytes results in lipotoxicity, caused by the accumulation of triglyceride-derived toxic metabolites in ectopic tissues (liver, muscle, pancreatic beta cells) and subsequent activation of inflammatory pathways, cellular dysfunction, and lipoapoptosis. The cross talk between dysfunctional adipocytes and the liver involves multiple cell populations, including macrophages and other immune cells, that in concert promote the development of lipotoxic liver disease, a term that more accurately describes the pathophysiology of nonalcoholic steatohepatitis. At the clinical level, adipose tissue insulin resistance contributes to type 2 diabetes mellitus and cardiovascular disease. Treatments that rescue the liver from lipotoxicity by restoring adipose tissue insulin sensitivity (eg, significant weight loss, exercise, thiazolidinediones) or preventing activation of inflammatory pathways and oxidative stress (ie, vitamin E, thiazolidinediones) hold promise in the treatment of NAFLD, although their long-term safety and efficacy remain to be established. Better understanding of pathways that link dysregulated adipose tissue, metabolic dysfunction, and liver lipotoxicity will result in improvements in the clinical management of these challenging patients.

Prevalence of prediabetes and diabetes and metabolic profile of patients with nonalcoholic fatty liver disease (NAFLD)

OBJECTIVE

Prediabetes and type 2 diabetes mellitus (T2DM) are believed to be common and associated with a worse metabolic profile in patients with nonalcoholic fatty liver disease (NAFLD). However, no previous study has systematically screened this population.

RESEARCH DESIGN AND METHODS

We studied the prevalence and the metabolic impact of prediabetes and T2DM in 118 patients with NAFLD. The control group comprised 20 subjects without NAFLD matched for age, sex, and adiposity. We measured 1) plasma glucose, insulin, and free fatty acid (FFA) concentration during an oral glucose tolerance test; 2) liver fat by magnetic resonance spectroscopy (MRS); 3) liver and muscle insulin sensitivity (euglycemic insulin clamp with 3-[(3)H]glucose); and 4) indexes of insulin resistance (IR) at the level of the liver (HIR(i)= endogenous glucose production × fasting plasma insulin [FPI]) and adipose tissue (Adipo-IR(i)= fasting FFA × FPI).

RESULTS

Prediabetes and T2DM was present in 85% versus 30% in controls (P < 0.0001), all unaware of having abnormal glucose metabolism. NAFLD patients were IR at the level of the adipose tissue, liver, and muscle (all P < 0.01-0.001). Muscle and liver insulin sensitivity were impaired in patients with NAFLD to a similar degree, whether they had prediabetes or T2DM. Only adipose tissue IR worsened in T2DM and correlated with the severity of muscle (r = 0.34; P < 0.001) and hepatic (r = 0.57; P < 0.0001) IR and steatosis by MRS (r = 0.35; P < 0.0001).

CONCLUSIONS

Patients with NAFLD may benefit from early screening for T2DM, because the prevalence of abnormal glucose metabolism is much higher than previously appreciated. Regardless of glucose tolerance status, severe IR is common. In patients with T2DM, adipose tissue IR appears to play a major role in the severity of NAFLD.

Pre-diabetes, metabolic syndrome, and cardiovascular risk

Pre-diabetes represents an elevation of plasma glucose above the normal range but below that of clinical diabetes. Pre-diabetes can be identified as either impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). The latter is detected by oral glucose tolerance testing. Both IFG and IGT are risk factors for type 2 diabetes, and risk is even greater when IFG and IGT occur together. Pre-diabetes commonly associates with the metabolic syndrome. Both in turn are closely associated with obesity. The mechanisms whereby obesity predisposes to pre-diabetes and metabolic syndrome are incompletely understood but likely have a common metabolic soil. Insulin resistance is a common factor; systemic inflammation engendered by obesity may be another. Pre-diabetes has only a minor impact on microvascular disease; glucose-lowering drugs can delay conversion to diabetes, but whether in the long run the drug approach will delay development of microvascular disease is in dispute. To date, the drug approach to prevention of microvascular disease starting with pre-diabetes has not been evaluated. Pre-diabetes carries some predictive power for macrovascular disease, but most of this association appears to be mediated through the metabolic syndrome. The preferred clinical approach to cardiovascular prevention is to treat all the metabolic risk factors. For both pre-diabetes and metabolic syndrome, the desirable approach is lifestyle intervention, especially weight reduction and physical activity. When drug therapy is contemplated and when the metabolic syndrome is present, the primary consideration is prevention of cardiovascular disease. The major targets are elevations of cholesterol and blood pressure.

Endoplasmic reticulum (ER) stress in cumulus-oocyte complexes impairs pentraxin-3 secretion, mitochondrial membrane potential (DeltaPsi m), and embryo development

Fatty acids such as palmitic acid at high levels are known to induce endoplasmic reticulum (ER) stress and lipotoxicity in numerous cell types and thereby contribute to cellular dysfunctions in obesity. To understand the impact of high fatty acids on oocytes, ER stress and lipotoxicity were induced in mouse cumulus-oocyte complexes during in vitro maturation using the ER Ca(2+) channel blocker thapsigargin or high physiological levels of palmitic acid; both of which significantly induced ER stress marker genes (Atf4, Atf6, Xbp1s, and Hspa5) and inositol-requiring protein-1α phosphorylation, demonstrating an ER stress response that was reversible with the ER stress inhibitor salubrinal. Assessment of pentraxin-3, an extracellular matrix protein essential for fertilization, by immunocytochemistry and Western blotting showed dramatically impaired secretion concurrent with ER stress. Mitochondrial activity in oocytes was assessed by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide staining of inner mitochondrial membrane potential, and oocytes matured in thapsigargin or high-dose palmitic acid had significantly reduced mitochondrial activity, reduced in vitro fertilization rates, and were slower to develop to blastocysts. The deficiencies in protein secretion, mitochondrial activity, and oocyte developmental competence were each normalized by salubrinal, demonstrating that ER stress is a key mechanism mediating fatty acid-induced defects in oocyte developmental potential.

Effects of a combination of oral anti-diabetes drugs with basal insulin therapy on β-cell function and glycaemic control in patients with newly diagnosed type 2 diabetes

BACKGROUND

Oral anti-diabetes drugs plus basal insulin (OAD + insulin) therapy in patients with newly diagnosed type 2 diabetes might improve β-cell function and result in extended glycaemic remission. This randomised trial compared the effect on β-cell function and diabetes remission rate between oral drug alone or with addition of basal insulin.

METHODS

One hundred and twenty-nine patients, aged 35-50 years, were enrolled between June 2005 and June 2009. For initial correction of hyperglycaemia, patients with fasting plasma glucose ≥9.0 mmol/L and HbA(1c) ≥ 9.0%, were randomly assigned to therapy with oral drugs + insulin or oral drugs alone. Treatment was stopped after normoglycaemia was maintained for 3 months. Patients were then followed-up with diet and physical exercise. Blood glucose, HbA(1c) and insulin were measured prior to treatment and at 1-year follow-up.

RESULTS

More patients achieved target glycaemic control in the oral drugs + insulin group [98.3% (58 of 59)] in less time [(10.4 ± 2.5) days] than those in the oral drug group [95.7% (67 of 70) and (12.4 ± 3.4) days]. At 1-year follow-up, more patients maintained target glycaemia without any drugs in the oral drug + insulin group than in the oral drug group [37.9% (22 of 58) vs 20.9% (14 of 67)]. Both treatments improved homeostasis model assessment-β (HOMA-β) and homeostasis model assessment-insulin resistance (HOMA-IR) significantly. They had similar effects on insulin resistance [lg(HOMA-IR): (0.50 ± 0.09) vs (0.48 ± 0.09), p = 0.23]. However, oral drugs + insulin could recover β-cell function much more than OAD alone could [lg(HOMA-β): (2.17 ± 0.14) vs (2.11 ± 0.13), p = 0.03].

CONCLUSION

In newly diagnosed type 2 diabetes, therapy with oral drugs + insulin has had favourable outcomes on recovery and maintenance of β-cell function and protracted glycaemic remission compared with treatment with oral drugs alone.

Activation of peroxisome proliferator-activated receptor-γ by rosiglitazone improves lipid homeostasis at the adipose tissue-liver axis in ethanol-fed mice

The development of alcohol-induced fatty liver is associated with a reduction of white adipose tissue (WAT). Peroxisome proliferator-activated receptor (PPAR)-γ prominently distributes in the WAT and plays a crucial role in maintaining adiposity. The present study investigated the effects of PPAR-γ activation by rosiglitazone on lipid homeostasis at the adipose tissue-liver axis. Adult C57BL/6 male mice were pair fed liquid diet containing ethanol or isocaloric maltose dextrin for 8 wk with or without rosiglitazone supplementation to ethanol-fed mice for the last 3 wk. Ethanol exposure downregulated adipose PPAR-γ gene and reduced the WAT mass in association with induction of inflammation, which was attenuated by rosiglitazone. Ethanol exposure stimulated lipolysis but reduced fatty acid uptake capacity in association with dysregulation of lipid metabolism genes. Rosiglitazone normalized adipose gene expression and corrected ethanol-induced lipid dyshomeostasis. Ethanol exposure induced steatosis and upregulated inflammatory genes in the liver, which were attenuated by rosiglitazone. Hepatic peroxisomal fatty acid β-oxidation was suppressed by ethanol in associated with inhibition of acyl-coenzyme A oxidase 1. Rosiglitazone elevated plasma adiponectin level and normalized peroxisomal fatty acid β-oxidation rate. However, rosiglitazone did not affect ethanol-reduced very low-density lipoprotein secretion from the liver. These results demonstrated that activation of PPAR-γ by rosiglitazone reverses ethanol-induced adipose dysfunction and lipid dyshomeostasis at the WAT-liver axis, thereby abrogating alcoholic fatty liver.

Perinatal iron deficiency combined with a high-fat diet causes obesity and cardiovascular dysregulation

Consumption of a high-fat Western diet (WD) and the resultant obesity is linked to a number of chronic pathologies, including cardiovascular dysregulation. The purpose of the present study was to determine whether perinatal iron deficiency (PID) added to the consumption of a WD would precipitate an obese phenotype with exacerbated metabolic and cardiovascular outcomes in adult offspring. Female Sprague Dawley rats were fed either a control (225 mg/kg Fe) or an iron-restricted diet (3-10 mg/kg Fe) prior to and throughout gestation. At birth, all dams were fed an iron-replete diet. At weaning, offspring were fed a normal diet or WD for up to 21 wk. Hemodynamics and locomotor activity were assessed by radiotelemetry starting at 15 wk of age. Iron restriction during pregnancy caused severe anemia in dams and offspring, resulting in 15% lower birth weights in the offspring. PID offspring fed the WD had greater caloric intake and exhibited reduced locomotor activity compared with their normal diet-fed littermates; no such effects were observed in normal iron control offspring. Despite having a similar effect on serum lipid profiles, consumption of the WD had a greater impact on body weight in the PID group, and this weight gain was due largely to visceral adipose tissue accumulation. A significant correlation between visceral adipose tissue weight and mean arterial pressure was observed in the PID offspring but not in controls. These observations demonstrate that PID predisposes offspring to an enhanced response to WD characterized by increased fat accumulation and cardiovascular dysregulation.

Characterization of the lipid droplet proteome of a clonal insulin-producing β-cell line (INS-1 832/13)

Lipids are known to play a crucial role both in the normal control of insulin release and in the deterioration of β-cell function, as observed in type 2 diabetes. Despite this established dual role of lipids, little is known about lipid storage and handling in β-cells. Here, we isolated lipid droplets from oleate-incubated INS-1 832/13 cells and characterized the lipid droplet proteome. In a total of four rounds of droplet isolation and proteomic analysis by HPLC-MS/MS, we identified 96 proteins that were specific to droplets. The proteins fall into six categories based on function or previously observed localization: metabolism, endoplasmic reticulum/ribosomes, mitochondria, vesicle formation and transport, signaling, and miscellaneous. The protein profile reinforces the emerging picture of the lipid droplet as an active and dynamic organelle involved in lipid homeostasis and intracellular trafficking. Proteins belonging to the category mitochondria were highly represented, suggesting that the β-cell mitochondria and lipid droplets form a metabolic unit of potential relevance for insulin secretion.

Adipocyte NCoR knockout decreases PPARγ phosphorylation and enhances PPARγ activity and insulin sensitivity

Insulin resistance, tissue inflammation, and adipose tissue dysfunction are features of obesity and Type 2 diabetes. We generated adipocyte-specific Nuclear Receptor Corepressor (NCoR) knockout (AKO) mice to investigate the function of NCoR in adipocyte biology, glucose and insulin homeostasis. Despite increased obesity, glucose tolerance was improved in AKO mice, and clamp studies demonstrated enhanced insulin sensitivity in liver, muscle, and fat. Adipose tissue macrophage infiltration and inflammation were also decreased. PPARγ response genes were upregulated in adipose tissue from AKO mice and CDK5-mediated PPARγ ser-273 phosphorylation was reduced, creating a constitutively active PPARγ state. This identifies NCoR as an adaptor protein that enhances the ability of CDK5 to associate with and phosphorylate PPARγ. The dominant function of adipocyte NCoR is to transrepress PPARγ and promote PPARγ ser-273 phosphorylation, such that NCoR deletion leads to adipogenesis, reduced inflammation, and enhanced systemic insulin sensitivity, phenocopying the TZD-treated state.

Chronic alcohol exposure stimulates adipose tissue lipolysis in mice: role of reverse triglyceride transport in the pathogenesis of alcoholic steatosis

Alcohol consumption induces liver steatosis; therefore, this study investigated the possible role of adipose tissue dysfunction in the pathogenesis of alcoholic steatosis. Mice were pair-fed an alcohol or control liquid diet for 8 weeks to evaluate the alcohol effects on lipid metabolism at the adipose tissue-liver axis. Chronic alcohol exposure reduced adipose tissue mass and adipocyte size. Fatty acid release from adipose tissue explants was significantly increased in alcohol-fed mice in association with the activation of adipose triglyceride lipase and hormone-sensitive lipase. Alcohol exposure induced insulin intolerance and inactivated adipose protein phosphatase 1 in association with the up-regulation of phosphatase and tensin homolog (PTEN) and suppressor of cytokine signaling 3 (SOCS3). Alcohol exposure up-regulated fatty acid transport proteins and caused lipid accumulation in the liver. To define the mechanistic link between adipose triglyceride loss and hepatic triglyceride gain, mice were first administered heavy water for 5 weeks to label adipose triglycerides with deuterium, and then pair-fed alcohol or control diet for 2 weeks. Deposition of deuterium-labeled adipose triglycerides in the liver was analyzed using Fourier transform ion cyclotron mass spectrometry. Alcohol exposure increased more than a dozen deuterium-labeled triglyceride molecules in the liver by up to 6.3-fold. These data demonstrate for the first time that adipose triglycerides due to alcohol-induced hyperlipolysis are reverse transported and deposited in the liver.

Perinephric and epididymal fat affect hepatic metabolism in rats

The present study examined whether the perinephric and epididymal visceral fat (PEVF) depot under short-term excess nutrient protected the liver by trapping nutrient-derived nonesterified free fatty acids (NEFAs) or had deleterious effects on hepatic triglycerides (TGs) accumulation and insulin resistance due to adipokine secretion. Young rats pre-emptively underwent surgical PEVF removal or sham operations and were fed with either high-fat diet (HFD) (PEVF-HFD) or regular chow (RC) (PEVF-RC) for 3 days. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. Liver TG, serum NEFA, and fat-derived adipokines were assessed. Insulin and lipogenesis signaling were assessed by western blots. Pre-emptive PEVF removal significantly decreases insulin-induced suppression of hepatic glucose production (HGP) both in RC and in HFD-fed rats. In accordance with the clamp results, hepatic TG accumulation is also significantly reduced by PEVF excision both in RC and HFD-fed rats. These results are further validated by insulin signaling results, which show that pre-emptive PEVF removal increases phosphorylation of hepatic Akt, irrespective of diet. Notably, high levels of serum leptin induced by HFD are significantly reduced by pre-emptive PEVF excision. Additionally, expression of lipogenic enzyme p-acetyl-CoA-carboxylase, denoting reduced lipogenesis, is increased in the PEVF-HFD rats. In conclusion, PEVF has a deleterious effect on the liver as a source of insulin resistance-inducing adipokines irrespective of diet, and does not serve as a buffer for excess nutrients.

CD36 genetics and the metabolic complications of obesity

PURPOSE OF REVIEW

The review summarizes our current understanding of the function of the fatty acid translocase, CD36, in lipid metabolism with an emphasis on the influence of CD36 genetic variants and their potential contribution to obesity-related complications.

RECENT FINDINGS

Studies in rodents implicate CD36 in a number of metabolic pathways with relevance to obesity and its associated complications. These include pathways related to fat utilization such as taste perception, intake, intestinal processing, and storage in adipose tissue. Dysfunction in these pathways, coupled with the ability of CD36 to transduce intracellular signals that initiate inflammation in response to excess fat supply, promotes metabolic pathology. In the last few years, the relevance of discoveries in rodents to humans has been highlighted by genetic studies, which identified common CD36 variants that influence circulating lipid levels and cardiometabolic phenotypes.

SUMMARY

Recent genetic studies suggest that CD36 plays an important role in lipid metabolism in humans and may be involved in obesity-related complications. These findings may accelerate the translation of CD36 metabolic functions determined in rodents to humans. Importantly, these studies highlight the potential utility of assessing CD36 expression and common single-nucleotide polymorphism genotypes.

Unmet needs in Hispanic/Latino patients with type 2 diabetes mellitus

In the United States, the prevalence of adults who are overweight or obese is higher in Hispanics/Latinos compared with non-Hispanic whites. In addition, data from the National Health and Nutrition Examination Survey (NHANES) indicate that the prevalence of type 2 diabetes mellitus is consistently greater in racial/ethnic minority groups, such as Hispanics/Latinos, compared with non-Hispanic whites. In fact, data from the Centers for Disease Control and Prevention (CDC) from 2007 to 2009 suggest that the prevalence of type 2 diabetes is almost twice as high in Hispanics/Latinos compared with non-Hispanic whites (11.8% vs. 7.1%, respectively). Although genetics plays a role in the increased prevalence of type 2 diabetes in Hispanics/Latinos, cultural and environmental factors also contribute. In addition to the increased prevalence of type 2 diabetes in Hispanics/Latinos, evidence suggests that the patients in this population are often undertreated and, therefore, less likely to achieve control of their glucose, blood pressure, and lipid levels. Because individuals with type 2 diabetes have a 2- to 4-fold increased risk of cardiovascular disease compared with individuals with normal glucose levels, there is consensus that targeting environmental factors, particularly the development of obesity at an early age, is the most cost-effective approach to prevent the development of type 2 diabetes and its broad spectrum of complications, including cardiovascular disease. Cultural and socioeconomic barriers, such as language, cost, and access to goods and services, must be overcome to improve management of type 2 diabetes in this high-risk population. By increasing healthcare provider awareness and the availability of programs tailored to Hispanic/Latino individuals, the current treatment gap among ethnic minorities in the United States will progressively narrow, and eventually, disappear.

An Endocrine Perspective of Nonalcoholic Fatty Liver Disease (NAFLD)

Endocrinologists are encountering patients with obesity-related complications such as metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) on a daily basis. Nonalcoholic fatty liver disease (NAFLD) is a liver condition characterized by insulin resistance, hepatic steatosis and frequently T2DM. This is now the most common chronic liver condition in adults and is present in the majority of obese subjects. Liver fat accumulation may range from simple steatosis to severe steatohepatitis with hepatocyte necroinflammation (or nonalcoholic steatohepatitis [NASH]). Although the natural history is incompletely understood, NAFLD may lead to serious medical consequences ranging from cirrhosis and hepatocellular carcinoma to earlier onset of T2DM and cardiovascular disease (CVD). The diagnosis of NAFLD may be challenging because signs and symptoms are frequently absent or nonspecific, and thus easily missed. Liver aminotransferases may be helpful if elevated, but most times are normal in the presence of the disease. Liver imaging may assist in the diagnosis (ultrasound or MRI and spectroscopy) but a definitive diagnosis of NASH still requires a liver biopsy. This may change in the near future as novel biomarkers become available. Treatment of NAFLD includes aggressive management of associated cardiovascular risk factors and many times control of T2DM. Pioglitazone and vitamin E appear promising for patients with NASH, although long-term studies are unavailable. In summary, this review hopes to address the common clinical dilemmas that endocrinologists face in the diagnosis and management of NAFLD and increase awareness of a potentially serious medical condition.

Going out of the brain: non-nervous system physiological and pathological functions of Cdk5

Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase that is mostly active in the nervous system, where it regulates several processes such as neuronal migration, actin and microtubule dynamics, axonal guidance, and synaptic plasticity, among other processes. In addition to these known functions, in the past few years, novel roles for Cdk5 outside of the nervous system have been proposed. These include roles in gene transcription, vesicular transport, apoptosis, cell adhesion, and migration in many cell types and tissues such as pancreatic cells, muscle cells, neutrophils, and others. In this review, we will summarize the recently studied non-neuronal functions of Cdk5, with a thorough analysis of the biological consequences of these novel roles.