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OBJECTIVE--Insulin resistance in skeletal muscle is an early phenomenon in the pathogenesis of type 2 diabetes. Studies of insulin resistance usually are highly focused. However, approaches that give a more global picture of abnormalities in insulin resistance are useful in pointing out new directions for research. In previous studies, gene expression analyses show a coordinated pattern of reduction in nuclear-encoded mitochondrial gene expression in insulin resistance. However, changes in mRNA levels may not predict changes in protein abundance. An approach to identify global protein abundance changes involving the use of proteomics was used here. RESEARCH DESIGN AND METHODS--Muscle biopsies were obtained basally from lean, obese, and type 2 diabetic volunteers (n = 8 each); glucose clamps were used to assess insulin sensitivity. Muscle protein was subjected to mass spectrometry-based quantification using normalized spectral abundance factors. RESULTS--Of 1,218 proteins assigned, 400 were present in at least haft of all subjects. Of these, 92 were altered by a factor of 2 in insulin resistance, and of those, 15 were significantly increased or decreased by ANOVA (P < 0.05). Analysis of protein sets revealed patterns of decreased abundance in mitochondrial proteins and altered abundance of proteins involved with cytoskeletal structure (desmin and alpha actinin-2 both decreased), chaperone function (TCP-1 subunits increased), and proteasome subunits (increased). CONCLUSIONS--The results confirm the reduction in mitochondrial proteins in insulin-resistant muscle and suggest that changes in muscle structure, protein degradation, and folding also characterize insulin resistance. Diabetes 59:33-42, 2010 [ABSTRACT FROM AUTHOR]

It has been proposed that obesity and type 2 diabetes (T2D) are state of chronic low grade inflammation that elevates activity of proinflammatory/stress-signaling pathways. NFκB signaling pathway may play a role in the pathogenesis of insulin resistance associated with obesity and T2D. Local lipid infusion and diet-induced obesity studies show changes in the inhibitor of κB (IκB)/NFκB signaling pathway. Despite these observations, the effect of obesity per se on the activity of IκB/NF κB pathways in skeletal muscle remains unclear. Therefore, we studied the relationship between % body fat and the (IκB)/NF κB inflammation signaling pathway in skeletal muscle from 25 non-diabetic volunteers with a wide range of adiposity but similar BMI. Subjects were divided into two groups, low body fat (LBF, < 30% body fat, n=14, 3F/11 M, 25±1% fat, BMI=29±1, 35±3 yr) and high body fat group (HBF, > 30% body fat, n=11, 6F/5M, 40±2% fat [P<0.01], BMI=31±2 [P=NS], 40±3 yr [P=NS]). Insulin sensitivity was determined by euglycemic clamp (80 mU-m sup -2]min[sup -1]); IκBα, Phospho-IκB α IκB β, NF κB p50, and NF κB p65 protein were determined by immunoblot analysis. Insulin-stimulated glucose disposal was greater in LBF than HBF (5.90.4 vs 3.7 0.4 mg⋅kg[sup -1]⋅min[sup -1], P<0.01) despite similar BMI. Muscle from subjects with HBF was characterized by a 13.0±0.1 % decrease in IκBα (P < 0.001) and 15.4±0.1% increase (P < 0.03) in phospho- IκBα protein abundance, indicating activation of the IκB/NF κB pathway. IκBα (r = -0.74, P < 0.000l) and IκBα (r = -0.49, P < 0.02) protein abundance inversely correlated with % body fat while phospho- IκBα protein abundance directly correlated with % body fat (r = 0.55, P < 0.01). In summary, increased % body fat is associated with activation of IκB/NF κB signaling in skeletal muscle independent of BMI. [ABSTRACT FROM AUTHOR]