Cellularity and adipogenic profile of the abdominal subcutaneous adipose tissue from obese adolescents: association with insulin resistance and hepatic steatosis.

Description

The objective of this paper was to investigate the distribution of adipose cell size, the estimated total number of adipose cells and the expression of adipogenic genes in subcutaneous adipose tissue in 2 groups of obese adolescents with marked differences in the proportion of intra-abdominal (visceral) to subcutaneous abdominal fat. For that purpose, a total of 38 adolescents with similar degrees of obesity underwent a subcutaneous periumbilical adipose tissue biopsy and were divided into 2 groups: high vs. low ratio of intra-abdominal to intra-abdominal + subcutaneous fat [IAAT/(IAAT+SAT)]. Data revealed that obese adolescents with a high IAAT/(IAAT+SAT) ratio had impaired adipogenesis/lipogenesis as assessed by gene expression and a low proportion of large adipose cells and high peak cell diameter. Accordingly, subjects with a high ratio had a tendency towards higher plasma levels of free fatty acids and triglycerides and significantly greater quantities of liver fat. These findings suggest that impairment in adipose cell differentiation is characterized by impaired lipogenesis and relative reduction in the proportion of large adipose cells, but hypertrophy of the largest cells. The subsequent decreased ability to store triglycerides in subcutaneous adipose tissue may be responsible for the development of liver steatosis and insulin resistance. In their editorial comment, Kim SH and Reaven G reported the interesting mechanism this article put forward to explain the link between obesity and insulin resistance. However, they underlined some limitations such as the absence of differences in insulin sensitivity between obese adolescents with high and low intra-abdominal fat proportion and the misinterpretation of the racial differences between the 2 groups.