Project description:Global transcript profiling to identify differentially expressed skeletal muscle genes in insulin resistance, a major risk factor for Type II (non-insulin-dependent) diabetes mellitus. Compared gene expression profiles of skeletal muscle tissues from 18 insulin-sensitive versus 17 insulin-resistant equally obese, non-diabetic Pima Indians. Keywords: other
Project description:Endurance exercise training has been shown to decrease whole-body and skeletal muscle insulin resistance and increase glucose tolerance in conditions of both pre-diabetes and overt type 2 diabetes. However, the adaptive responses in skeletal muscle at the molecular and genetic level for these beneficial effects of exercise training have not been clearly established in an animal model of pre-diabetes. The present study identifies alterations in skeletal muscle gene expression that occur with exercise training in pre-diabetic, insulin-resistant obese Zucker (fa/fa) rats and insulin-sensitive lean Zucker (Fa/-) rats. Treadmill running for up to 4 weeks caused significant enhancements of glucose tolerance as assessed by the integrated area under the curve for glucose (AUCg) during an oral glucose tolerance test in both lean and obese animals. Using microarray analysis, a set of only 12 genes was identified as both significantly altered (>1.5-fold change relative to sedentary controls; p<0.05) and significantly correlated (p<0.05) with the AUCg. Two of these genes, peroxisome proliferator-activated receptor-g coactivator 1a (PGC-1a) and the z-isoform of protein kinase C (PKC-z), have known involvement in the regulation of skeletal muscle glucose transport. We confirmed that protein expression levels of PGC-1a and PKC-z were positively correlated with the mRNA expression levels for these two genes. Overall, this study has identified a limited number of genes in soleus muscle of lean and obese Zucker rats that are associated with decreased insulin resistance and increase glucose tolerance following endurance exercise training. These findings could guide the development of pharmaceutical M-^Sexercise mimeticsM-^T in the treatment of insulin-resistant, pre-diabetic or overtly type 2 diabetic individuals.
Project description:5 arrays from obese insulin-resistant and lean insulin-sensitive females adipose tissue at fasting and after 3h hyperinsulinemia 5 arrays from obese insulin-resistant and lean insulin-sensitive females adipose tissue at fasting and after 3h hyperinsulinemia FIR x 5, FIS x 5, HIR x 5, HIS x 5 F=fasting, H=hyperinsulinemia, IR=Insulin-resistant, IS=Insulin-sensitive (FIR, FIS, HIR, HIS)
Project description:We characterized the insulin sensitivity and multi-tissue gene expression profiles of lean and insulin resistant, obese Zucker rats untreated or treated with one of four PPARγ ligands (pioglitazone, rosiglitazone, troglitazone, and AG035029). We analyzed the transcriptional profiles of adipose tissue, skeletal muscle, and liver from the rats and determined whether ligand insulin-sensitizing potency was related to ligand-induced alteration of functional pathways. Ligand treatments improved insulin sensitivity in obese rats, albeit to varying degrees. Male Zucker fatty (fa/fa) and lean (fa/+) rats (Charles River, Wilmington, MA) were received at 6 weeks of age. Fatty rats were weight-matched upon arrival and randomly divided into one of five experimental groups. The fatty rat groups varied by the type of chow they were fed - normal chow alone or with a PPARγ ligand admixture: normal chow (fatty control, FC), rosiglitazone-treated (Rosi), pioglitazone-treated (Pio), troglitazone-treated (Tro), or AG035029-treated (AG). Lean control (LC) rats were all fed normal chow. Rats groups were maintained on the diets for 21 days. Adipose tissue (epididymal), skeletal muscle (gastrocnemius), and liver were harvested from lean (LC) and insulin resistant, obese Zucker rats untreated (FC) or treated with one of four PPARγ ligands (pioglitazone [Pio], rosiglitazone [Rosi], troglitazone [Tro], and AG035029 [AG]).
Project description:Purpose. Insulin resistant muscle is resistant to gene expression changes induced by acute exercise. This study was undertaken to identify transcription factors that differentially respond to exercise in insulin resistance. Candidate transcription factors were identified from analysis of 5’-untranslated regions (5’-UTRs) of exercise responsive genes and from analysis of the 5’-UTRs of genes coding for proteins that differ in abundance in insulin resistance. Research design and methods. Muscle biopsies were obtained from lean and obese subjects before and after a single exercise bout. Euglycemic glucose clamps assessed insulin sensitivity. Global proteomics analysis identified differentially abundant proteins. The 5’-UTRs of genes coding for significant proteins were subjected to transcription factor enrichment analysis to identify candidate transcription factors. Q-rt-PCR to determine expression of candidate transcription factors was performed on RNA from resting and post-exercise muscle biopsies; immunoblots quantified protein abundance. Results. Obese subjects were insulin resistant compared to lean but performed exercise at the same intensity. Proteins involved in mitochondrial function, protein targeting and translation, and metabolism were among those significantly different between the groups. Transcription factor enrichment analysis of genes coding for these proteins revealed new candidate transcription factors. Q-rt-PCR analysis of RNA and immunoblot analysis from pre- and post-exercise muscle biopsies revealed several transcription and growth factors that had altered responses to exercise in insulin resistant subjects. Conclusions. These results confirm findings of an association between insulin sensitivity and transcription factor mRNA response to exercise and extend these results to show that obesity also may be a sufficient prerequisite for exercise resistance. Analysis of the muscle proteome together with determination of effects of exercise on expression of transcription factors suggests that abnormal responses of transcription factors to exercise may be responsible for differences in protein abundances in insulin resistant muscle.
Project description:We have carried out whole-genome expression profiling of whole blood from obese subjects, defined as obese diet-sensitive and obese diet-resistant, and well matched lean individuals. The diet-sensitive or diet-resistant status refers to the different rates of weight loss observed in the two groups on a low-calorie diet regimen. Bioinformatic analysis revealed alterations in transcription in key pathways that are consistent with impaired capacity for fatty acid oxidation driven mitochondrial ATP synthesis in obese subjects who are resistant to weight loss. A total of 80 samples are analyzed. This consists of 20 lean subjects studied at one timepoint and 20 obese subjects (10 diet-sensitive and 10 diet-resistant) studied at 3 timepoints during caloric restriction (day of entry into program, week 3 into the program and week 6 into the program)
Project description:Skeletal muscle (rectus femoris) gene expression was analyzed from diet-resistant and diet-sensitive obese women undergoing clinically supervised weight-loss at a weight management clinic The goal of the study was to characterize global gene expression profiles in skeletal muscle from obese women, prior to their participation in a clinically supervised, low-calorie diet, weight management program. Following entry into the weight-loss program, subjects can be categorized as being 'diet-sensitive' or 'diet-resistant' depending on the rates of weight loss achieved. In the current study, we selected an equal number of diet-sensitive and diet-resistant subjects for comparative expression profiling
Project description:Skeletal muscle insulin resistance, an early metabolic defect in the pathogenesis of type 2 diabetes, may be a cause or consequence of altered protein expressions profiles. Proteomics technology offers enormous promise to investigate molecular mechanisms underlying pathologies, however, the analysis of skeletal muscle is challenging. Using a state-of-the-art mass spectrometry (MS) based workflow, we performed a global proteomics analysis of skeletal muscle from leptin-deficient, obese, type 2 diabetic (ob/ob) and lean mice, identifying more than 6,000 proteins with 118 proteins differentially regulated in obesity. This included protein kinases, phosphatases, and secreted and fiber type associated proteins. Enzymes involved in lipid metabolism in skeletal muscle from ob/ob mice were increased, providing evidence against reduced fatty acid oxidation in lipid-induced insulin resistance. Mitochondrial and peroxisomal proteins, as well as components of pyruvate and lactate metabolism were likewise increased. Finally, the skeletal muscle proteome from ob/ob mice displayed a shift towards the ‘slow fiber type’. This detailed characterization of obese rodent models of type 2 diabetes demonstrates an efficient workflow for skeletal muscle proteomics, which may easily be adapted to other complex tissues.
Project description:High-fat diet (HFD) decreases insulin sensitivity. How high-fat diet causes insulin resistance is largely unknown. Here, we show that lean mice become insulin resistant after being administered exosomes isolated from the feces of obese mice fed a high-fat diet (HFD) or from human type II diabetic patients with diabetes. HFD altered the lipid composition of exosomes from predominantly PE in exosomes from lean animals (L-Exo) to PC in exosomes from obese animals (H-Exo). Mechanistically, we show that intestinal H-Exo is taken up by macrophages and hepatocytes, leading to inhibition of the insulin signaling pathway. Moreover, exosome-derived PC binds to and activates AhR, leading to inhibition of the expression of genes essential for activation of the insulin signaling pathway, including IRS-2, and its downstream genes PI3K and Akt. Together, our results reveal HFD-induced exosomes as potential contributors to the development of insulin resistance. Intestinal exosomes thus have potential as broad therapeutic targets.