Abstract
BackgroundMice lacking Receptor-interacting protein 140 (RIP140) have reduced body fat which at least partly is mediated through increased lipid and glucose metabolism in adipose tissue. In humans, RIP140 is lower expressed in visceral white adipose tissue (WAT) of obese versus lean subjects. We investigated the role of RIP140 in human subcutaneous WAT, which is the major fat depot of the body.MethodsMessenger RNA levels of RIP140 were measured in samples of subcutaneous WAT from women with a wide variation in BMI and in different human WAT preparations. RIP140 mRNA was knocked down with siRNA in in vitro differentiated adipocytes and the impact on glucose transport and mRNA levels of target genes determined.ResultsRIP140 mRNA levels in subcutaneous WAT were decreased among obese compared to lean women and increased by weight-loss, but did not associate with mitochondrial DNA copy number. RIP140 expression increased during adipocyte differentiation in vitro and was higher in isolated adipocytes compared to corresponding pieces of WAT. Knock down of RIP140 increased basal glucose transport and mRNA levels of glucose transporter 4 and uncoupling protein-1.ConclusionsHuman RIP140 inhibits glucose uptake and the expression of genes promoting energy expenditure in the same fashion as the murine orthologue. Increased levels of human RIP140 in subcutaneous WAT of lean subjects may contribute to economize on energy stores. By contrast, the function and expression pattern does not support that RIP140 regulate human obesity.
Highlights
Mice lacking Receptor-interacting protein 140 (RIP140) have reduced body fat which at least partly is mediated through increased lipid and glucose metabolism in adipose tissue
Subcutaneous white adipose tissue (WAT) RIP140 mRNA levels are inversely correlated to obesity We first assessed abdominal subcutaneous WAT RIP140 mRNA levels in relationship to adiposity
Levels of RIP140 mRNA were lower in visceral as compared to subcutaneous WAT, and this was due to a difference in lean subjects only (Figure 1A)
Summary
Mice lacking Receptor-interacting protein 140 (RIP140) have reduced body fat which at least partly is mediated through increased lipid and glucose metabolism in adipose tissue. RIP140 is lower expressed in visceral white adipose tissue (WAT) of obese versus lean subjects. Receptor-interacting protein 140 (RIP140) is a nuclear receptor corepressor that in mice is expressed in several organs; the mRNA levels in white adipose tissue (WAT) are higher than in other metabolically active tissues, such as brown adipose tissue (BAT), muscle, and liver [3,4,5]. The physiological function of RIP140 has been tested in RIP140 knock out (RIPKO) mice. These mice have a reduced body weight and body fat content, when compared to wild-type (WT) mice [3].
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