Dataset Information

Loss-of-function mutation in myostatin reduces tumor necrosis factor alpha production and protects liver against obesity-induced insulin resistance.

ABSTRACT:

Objective

Insulin resistance develops in tandem with obesity. Ablating myostatin (Mstn) prevents obesity, so we investigated if Mstn deficiency could improve insulin sensitivity. A loss-of-function mutation (Mstn(Ln)) in either one or both alleles of the Mstn gene shows how Mstn deficiency protects whole-body insulin sensitivity.

Research design and methods

Mstn(Ln/Ln) mice were weaned onto a high-fat diet (HFD) or standard diet. HFD-fed Mstn(Ln/Ln) mice exhibited high lean, low-fat body compositions compared with wild types. Wild-type and heterozygous and homozygous mutant mice were bled to determine basal levels of insulin, glucose, and homeostasis model assessment of insulin resistance. To evaluate postprandial insulin sensitivity between animals of a similar size, glucose and insulin tolerance tests and hyperinsulinemic-euglycemic clamp studies were performed with heterozygous and homozygous mutant mice. Quantitative RT-PCR quantified TNF proportional, variant, IL-6, IL-1beta, F4/80, GPR43, and CD36 expression in muscle, fat, and liver. Histological analysis measured hepatosteatosis.

Results

Homozygous mutants were glucose tolerant and protected against overall insulin resistance compared with heterozygous mice. Hyperinsulinemic-euglycemic clamp studies revealed a dramatically improved glucose infusion rate, glucose disposal rate, and hepatic glucose production in 11-month-old Mstn(Ln/Ln) mice on an HFD. Improvements to muscle and liver insulin sensitivity (approximately 200-400%) correlated with 50-75% decreased tumor necrosis factor (TNF)alpha production and coincided with severe Mstn deficiency. Hepatosteatosis appeared to be ameliorated. Short-term treatment of Mstn(Ln/Ln) mice with recombinant Mstn led to increased plasma TNFalpha and insulin resistance.

Conclusions

We find that severe Mstn deficiency caused by Ln (lean) mutations in HFD-fed mice protects muscle and liver against obesity-induced insulin resistance.

SUBMITTER: Wilkes JJ

PROVIDER: S-EPMC2671051 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Publications

Loss-of-function mutation in myostatin reduces tumor necrosis factor alpha production and protects liver against obesity-induced insulin resistance.

Wilkes Jason J JJ Lloyd David J DJ Gekakis Nick N

Diabetes 20090210 5

<h4>Objective</h4>Insulin resistance develops in tandem with obesity. Ablating myostatin (Mstn) prevents obesity, so we investigated if Mstn deficiency could improve insulin sensitivity. A loss-of-function mutation (Mstn(Ln)) in either one or both alleles of the Mstn gene shows how Mstn deficiency protects whole-body insulin sensitivity.<h4>Research design and methods</h4>Mstn(Ln/Ln) mice were weaned onto a high-fat diet (HFD) or standard diet. HFD-fed Mstn(Ln/Ln) mice exhibited high lean, low-f ...[more]

PMID: 19208906

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Project description:Obesity is often associated with insulin resistance, low-grade systemic inflammation, and reduced plasma adiponectin. Inflammation is also increased in adipose tissue, but it is not clear whether the reductions of adiponectin levels are related to dysregulation of insulin activity and/or increased proinflammatory mediators. In this study, we investigated the interactions of insulin, tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) in the regulation of adiponectin production using in vivo and in vitro approaches. Plasma adiponectin and parameters of insulin resistance and inflammation were assessed in a cohort of lean and obese insulin-resistant subjects. In addition, the effect of insulin was examined in vivo using the hyperinsulinemic-euglycemic clamp, and in adipose tissue (AT) cultures. Compared with lean subjects, the levels of total adiponectin, and especially the high-molecular-weight (HMW) isomer, were abnormally low in obese insulin-resistant subjects. The hyperinsulinemic clamp data confirmed the insulin-resistant state in the obese patients and showed that insulin infusion significantly increased the plasma adiponectin in lean but not obese subjects (P < 0.01). Similarly, insulin increased total adiponectin release from AT explants of lean and not obese subjects. Moreover, expression and secretion of TNF-α and IL-6 increased significantly in AT of obese subjects and were negatively associated with expression and secretion of adiponectin. In 3T3-L1 and human adipocyte cultures, insulin strongly enhanced adiponectin expression (2-fold) and secretion (3-fold). TNF-α, and not IL-6, strongly opposed the stimulatory effects of insulin. Intriguingly, the inhibitory effect of TNF-α was especially directed toward the HMW isomer of adiponectin. In conclusion, these studies show that insulin upregulates adiponectin expression and release, and that TNF-α opposes the stimulatory effects of insulin. A combination of insulin resistance and increased TNF-α production could explain the decline of adiponectin levels and alterations of isomer composition in plasma of obese insulin-resistant subjects.

Dataset Information

Loss-of-function mutation in myostatin reduces tumor necrosis factor alpha production and protects liver against obesity-induced insulin resistance.

Objective

Research design and methods

Results

Conclusions

Publications

Loss-of-function mutation in myostatin reduces tumor necrosis factor alpha production and protects liver against obesity-induced insulin resistance.

Similar Datasets

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