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Hyperleptinemia without obesity in male mice lacking androgen receptor in adipose tissue.

ABSTRACT: Insulin resistance occurs through an inadequate response to insulin by insulin target organs such as liver, muscle, and adipose tissue with consequent insufficient glucose uptake. In previous studies we demonstrated that whole body androgen receptor (AR) knockout (AR(-/y)) mice develop obesity and exhibit insulin and leptin resistance at advanced age. By examining adipose tissue-specific AR knockout (A-AR(-/y)) mice, we found A-AR(-/y) mice were hyperleptinemic but showed no leptin resistance, although body weight and adiposity index of A-AR(-/y) mice were identical with those of male wild-type control mice. Hypotriglyceridemia and hypocholesterolemia found in nonobese A-AR(-/y) mice suggested a beneficial effect of high leptin levels independent of fat deposition. Further examination showed that androgen-AR signaling in adipose tissue plays a direct regulatory role in leptin expression via enhanced estrogen receptor transactivation activity due to elevated intraadipose estrogens. The present study in A-AR(-/y) mice suggests a differential tissue-specific role of AR in energy balance control in males.

SUBMITTER: Yu IC

PROVIDER: S-EPMC2329275 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Hyperleptinemia without obesity in male mice lacking androgen receptor in adipose tissue.

Yu I-Chen IC Lin Hung-Yun HY Liu Ning-Chun NC Wang Ruey-Shen RS Sparks Janet D JD Yeh Shuyuan S Chang Chawnshang C

Endocrinology 20080214 5

Insulin resistance occurs through an inadequate response to insulin by insulin target organs such as liver, muscle, and adipose tissue with consequent insufficient glucose uptake. In previous studies we demonstrated that whole body androgen receptor (AR) knockout (AR(-/y)) mice develop obesity and exhibit insulin and leptin resistance at advanced age. By examining adipose tissue-specific AR knockout (A-AR(-/y)) mice, we found A-AR(-/y) mice were hyperleptinemic but showed no leptin resistance, a ...[more]

PMID: 18276764

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Project description:Introduction: Obesity and related metabolic disturbances are frequently related to modern lifestyle and are characterized by excessive fructose intake. Visceral adipose tissue (VAT) inflammation has a central role in the development of insulin resistance, type 2 diabetes (T2D), and metabolic syndrome. Since sex-related differences in susceptibility and progression of metabolic disorders are not yet fully understood, our aim was to examine inflammation and insulin signaling in VAT of fructose-fed female and male adult rats. Methods: We analyzed effects of 9-week 10% fructose-enriched diet on energy intake, VAT mass and histology, and systemic insulin sensitivity. VAT insulin signaling and markers of VAT inflammation, and antioxidative defense status were also evaluated. Results: The fructose diet had no effect on VAT mass and systemic insulin signaling in the female and male rats, while it raised plasma uric acid, increased PPARγ level in the VAT, and initiated the development of a distinctive population of small adipocytes in the females. Also, adipose tissue insulin resistance, evidenced by increased PTP1B and insulin receptor substrate 1 (IRS1) inhibitory phosphorylation and decreased Akt activity, was detected. In addition, fructose stimulated the nuclear accumulation of NFκB, increased expression of proinflammatory cytokines (IL-1β, IL-6, and TNFα), and protein level of macrophage marker F4/80, superoxide dismutase 1, and glutathione reductase. In contrast to the females, the fructose diet had no effect on plasma uric acid and VAT inflammation in the male rats, but less prominent alterations in VAT insulin signaling were observed. Conclusion: Even though dietary fructose did not elicit changes in energy intake and led to obesity in the females, it initiated the proliferation of small-sized adipocytes capable of storing fats further. In contrast to the males, this state of VAT was accompanied with enhanced inflammation, which most likely contributed to the development of insulin resistance. The observed distinction could possibly originate from sex-related differences in uric acid metabolism. Our results suggest that VAT inflammation could precede obesity and start even before the measurable increase in VAT mass, making it a silent risk factor for the development of T2D. Our results emphasize that adipose tissue dysfunction, rather than its simple enlargement, could significantly contribute to the onset and development of obesity and related metabolic disorders.

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Hyperleptinemia without obesity in male mice lacking androgen receptor in adipose tissue.

Publications

Hyperleptinemia without obesity in male mice lacking androgen receptor in adipose tissue.

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