SRA gene knockout protects against diet-induced obesity and improves glucose tolerance.

We have recently shown that the non-coding RNA, steroid receptor RNA activator (SRA), functions as a transcriptional coactivator of PPARγ and promotes adipocyte differentiation in vitro. To assess SRA function in vivo, we have generated a whole mouse Sra1 gene knock-out (SRA(-/-)). Here, we show that the Sra1 gene is an important regulator of adipose tissue mass and function. SRA is expressed at a higher level in adipose tissue than other organs in wild type mice. SRA(-/-) mice are resistant to high fat diet-induced obesity, with decreased fat mass and increased lean content. This lean phenotype of SRA(-/-) mice is associated with decreased expression of a subset of adipocyte marker genes and reduced plasma TNFα levels. The SRA(-/-) mice are more insulin sensitive, as evidenced by reduced fasting insulin, and lower blood glucoses in response to IP glucose and insulin. In addition, the livers of SRA(-/-) mice have fewer lipid droplets after high fat diet feeding, and the expression of lipogenesis-associated genes is decreased. To our knowledge, these data are the first to indicate a functional role for SRA in adipose tissue biology and glucose homeostasis in vivo.