Contribution of visceral fat mass to the insulin resistance of aging.
ABSTRACT Recent studies have shown that central obesity (increased waist to hip ratio [WHR]) is related to insulin resistance and aging. Furthermore, in central-obesity states, the intraabdominal fat (IAF) depot has been postulated to contribute most to the development of insulin resistance. Therefore, the observed insulin resistance of aging may be related more to changes in body composition than to aging per se. The purpose of this study was to explore the association of IAF with age and insulin sensitivity (SI) after controlling for obesity. We examined 60 healthy nondiabetic subjects (normal 75-g oral glucose tolerance test, aged 23 to 83, 15 men and 45 women). We chose subjects so that those < or = 125% and greater than 125% of ideal body weight were equally represented in each age decade. We quantified total and subcutaneous abdominal fat and IAF at the umbilicus using a validated magnetic resonance imaging (MRI) scanning technique and determined SI using a modified minimal model. IAF correlated significantly with age (r = .49, P = .0001) in the group as a whole, as well as in men (r = .58, P = .022) and women (r = .48, P = .0008) separately. In all subjects, SI was significantly related to IAF (r = -.50, P < .0001) but was not related to age (r = .00, P = .98). In multivariate analysis for various combinations of age, sex, and measures of fat distribution, WHR accounted for 28% and IAF for 51% of the variance in SI, whereas age, sex, and interactions of age and sex accounted for only 1%.(ABSTRACT TRUNCATED AT 250 WORDS)
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ABSTRACT: Adipose tissue (AT) depots are heterogeneous in terms of morphology and adipocyte metabolism. Adiponectin, one of the most abundant adipokines, is known for its insulin sensitising effects and its role in glucose and lipid metabolism. Very little is known about the presence of adiponectin protein in visceral (vc) and subcutaneous (sc) AT depots. We assessed serum adiponectin and adiponectin protein concentrations and the molecular weight forms in vc (mesenterial, omental and retroperitoneal) and sc (sternum, tail-head and withers) AT of primiparous dairy cows during early lactation. Primiparous German Holstein cows (n = 25) were divided into a control (CON) and a conjugated linoleic acid (CLA) group. From day 1 of lactation until slaughter, CLA cows were fed 100 g of a CLA supplement/d (about 6% of cis-9, trans-11 and trans-10, cis-12 isomers each), whereas the CON cows received 100 g of a fatty acid mixture/d instead of CLA. Blood samples from all animals were collected from 3 wk before calving until slaughter on day 1 (n = 5, CON cows), 42 (n = 5 each of CON and CLA cows) and 105 (n = 5 each of CON and CLA cows) of lactation when samples from different AT depots were obtained. Adiponectin was measured in serum and tissue by ELISA. In all AT depots adiponectin concentrations were lowest on day 1 compared to day 42 and day 105, and circulating adiponectin reached a nadir around parturition. Retroperitoneal AT had the lowest adiponectin concentrations, however, when taking total depot mass into consideration, the portion of circulating adiponectin was higher in vc than sc AT. Serum adiponectin was positively correlated with adiponectin protein concentrations but not with the mRNA abundance in all fat depots. The CLA supplementation did not affect adiponectin concentrations in AT depots. Furthermore, inverse associations between circulating adiponectin and measures of body condition (empty body weight, back fat thickness and vc AT mass) were observed. In all AT depots at each time, adiponectin was present as high (about 300 kDa) and medium (about 150 kDa) molecular weight complexes similar to that of the blood serum. These data suggest differential contribution of AT depots to circulating adiponectin.Domestic animal endocrinology 12/2013; DOI:10.1016/j.domaniend.2013.12.001 · 1.78 Impact Factor
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ABSTRACT: A semi-purified fraction isolated from Cistanches Herba (HCF1), was previously found to induce mitochondrial uncoupling in H9c2 cells and in rat hearts. We therefore hypothesized that HCF1 would produce weight loss effect against a high fat diet (HFD)-induced obesity. To test this hypothesis, a mouse model of HFD-induced obesity was established and the effects of HCF1 on normal diet (ND)-fed and HFD-fed mice were examined. In the study, long term HCF1 treatment produced weight reduction effect against HFD-induced obesity in male and female mice. The HCF1-induced weight loss was associated with improved insulin sensitivity in HFD-fed animals. To understand the action mechanism underlying the weight reduction effect afforded by HCF1, its effects on mitochondrial uncoupling was examined. A comparative study with cholestyramine (CT), a bile acid sequestrant, was also conducted. The findings demonstrated that HCF1-induced weight loss was likely mediated by the increase in energy consumption, probably via the induction of mitochondrial uncoupling in mouse skeletal muscle. Thus, our findings suggest the potential use of HCF1 to prevent obesity and the associated health consequences such as diabetes, cardiovascular diseases and metabolic syndrome.Journal of Functional Foods 09/2014; 10:292–304. DOI:10.1016/j.jff.2014.06.019 · 4.48 Impact Factor