Endocrine Abstracts

Adiponectin is an adipocyte derived-hormone, associated with insulin sensitivity and a lower risk of atherosclerosis. As central rather than gluteo-femoral fat is known to increase the risk of type 2 diabetes (T2DM) and cardiovascular disease we investigated the mRNA and protein expression of adiponectin in human adipose tissue depots. RNA and protein was extracted using a cohort of 46 human adipose tissue samples (non-diabetic (ND) (age: (mean plus/minus SD) 44.33 plus/minus 12.4; BMI 28.3 plus/minus 6.0): 21 abdominal subcutaneous, 13 omentum, 6 thigh; T2DM subjects (age: 66.6 plus/minus 7.5; BMI 28.9 plus/minus 3.17; abdominal subcutaneous 6; thigh 3). Quantitative PCR and Western analysis was used to assess the expression of adiponectin. This study determined a significant reduction in adiponectin protein expression in diabetic abdominal subcutaneous adipose tissue (Abd Sc AT) compared with Abd Sc AT obtained from NDs (0.36 plus/minus 0.15; p<0.0001, n=4). In addition, adiponectin protein expression in non-diabetic omental Abd AT was lower (0.25 plus/minus 0.16; p<0.0001, n=6) when compared with both thigh and Abd Sc AT. Further our ex vivo studies determined that an increase in BMI was associated with lower adiponectin protein expression in ND Abd Sc AT (BMI: 23.4 plus/minus 1.55 Vs BMI: 34.6 plus/minus 4.4 = 0.25 plus/minus 0.04; p<0.0001); a finding in agreement with previous in vivo serum studies. The mRNA studies correlated with our protein expression data. In summary, this study indicates that adiponectin mRNA and protein expression in non-diabetic subjects remains high in Abd Sc AT, including thigh, while diabetic status or BMI reduces adiponectin protein expression. Omental fat however expresses little adiponectin. In conclusion, in non-diabetic subjects, Sc fat expresses more adiponectin compared with fat from T2DM subjects, in whom this protective factor appears to be reduced. The reduced expression of adiponectin in fat depots from obese & T2DM patients may result in the observed decrease in circulating adiponectin levels observed by previous in vivo studies.