Gene expression in skeletal muscle biopsies from people with type 2 diabetes and relatives: differential regulation of insulin signaling pathways.

BACKGROUND: Gene expression alterations have previously been associated with type 2 diabetes, however whether these changes are primary causes or secondary effects of type 2 diabetes is not known. As healthy first degree relatives of people with type 2 diabetes have an increased risk of developing type 2 diabetes, they provide a good model in the search for primary causes of the disease. METHODS/PRINCIPAL FINDINGS: We determined gene expression profiles in skeletal muscle biopsies from Caucasian males with type 2 diabetes, healthy first degree relatives, and healthy controls. Gene expression was measured using Affymetrix Human Genome U133 Plus 2.0 Arrays covering the entire human genome. These arrays have not previously been used for this type of study. We show for the first time that genes involved in insulin signaling are significantly upregulated in first degree relatives and significantly downregulated in people with type 2 diabetes. On the individual gene level, 11 genes showed altered expression levels in first degree relatives compared to controls, among others KIF1B and GDF8 (myostatin). LDHB was found to have a decreased expression in both groups compared to controls. CONCLUSIONS/SIGNIFICANCE: We hypothesize that increased expression of insulin signaling molecules in first degree relatives of people with type 2 diabetes, work in concert with increased levels of insulin as a compensatory mechanism, counter-acting otherwise reduced insulin signaling activity, protecting these individuals from severe insulin resistance. This compensation is lost in people with type 2 diabetes where expression of insulin signaling molecules is reduced.

Metabolic and vascular effects of tumor necrosis factor-alpha blockade with etanercept in obese patients with type 2 diabetes.

OBJECTIVE: The pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) impairs insulin action in insulin-sensitive tissues, such as fat, muscle and endothelium, and causes endothelial dysfunction. We hypothesized that TNF-alpha blockade with etanercept could reverse vascular and metabolic insulin resistance. METHOD AND RESULTS: Twenty obese patients with type 2 diabetes were randomized to etanercept treatment (25 mg subcutaneously twice weekly for 4 weeks) or used as controls in an open parallel study. Forearm blood flow and glucose uptake were measured during intra-arterial infusions of serotonin, sodium nitroprusside and insulin co-infused with serotonin. Beta-cell function was assessed with oral and intra-venous glucose tolerance tests and whole-body insulin sensitivity by hyperinsulinemic euglycemic clamps. Plasma levels of C-reactive protein and interleukin-6 decreased significantly with etanercept (C-reactive protein from 9.9 +/- 3.1 to 4.8 +/- 1.4 mg l(-1), p = 0.04; interleukin-6 from 3.1 +/- 0.4 to 1.9 +/- 0.2 ng l(-1), p = 0.03). Vasodilatory responses to serotonin and sodium nitroprusside infusions remained unchanged. Insulin effect on vasodilatation and on whole-body and forearm glucose uptake remained unchanged as well. Beta-cell function tended to improve. CONCLUSION: Although short-term etanercept treatment had a significant beneficial effect on systemic inflammatory markers, no improvement of vascular or metabolic insulin sensitivity was observed.