Gene expression in adipose tissue linked with metabolic traits
MedWire News: Dutch researchers have identified a number of genes that are differentially expressed in subcutaneous and visceral adipose tissue (SAT/VAT), and are associated with blood lipid levels.
They say that the new information could lead to the development of alternative strategies for the management of obesity and dyslipidemia.
Marten Hofker (University Medical Center Groningen, The Netherlands) and team sought to identify genes expressed in SAT and VAT and to compare gene expression between the two fat depots.
In all, 75 morbidly obese individuals with a body mass index >35 kg/m2 were genotyped and had blood samples analyzed for lipid and cardiometabolic parameters. Twenty-five individuals had Type 2 diabetes and 41 had nonalcoholic steatohepatitis.
Hofker and team found that a "remarkably large" number of genes (n=138) had a more than 10-fold higher expression in VAT than in SAT, whereas only 20 genes were upregulated by more than 10-fold in SAT than in VAT.
Genes that were more than 10-fold upregulated in both VAT and SAT were involved in cell structure, cell motility, and the metabolism of lipids, fatty acids, and steroids.
Importantly, the expression levels of many individual genes were strongly correlated with metabolic traits. For example, leptin mRNA levels in VAT were highly correlated with body mass index, while the expression of CD68, CD300A, and SREBF1 were significantly correlated with plasma levels of high-density lipoprotein (HDL) cholesterol.
The team then looked for associations between "modules" of co-expressed genes and specific metabolic traits.
In SAT, three modules were inversely associated with HDL cholesterol levels and a fourth module was inversely associated with both plasma glucose and plasma triglyceride levels. These modules were "markedly enriched" in immune and metabolic genes, say the researchers.
In VAT, one module was inversely associated with both BMI and insulin, and another was positively associated with plasma glucose. The latter was enriched in inflammatory genes and showed a marked overlap in gene content with the SAT modules related to HDL.
"This underlines both the singular importance of these genes for lipid and glucose metabolism and the specific roles of these two fat depots in this respect," the team concludes.
The study is published in the open-access journal BMC Medical Genomics.
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By Joanna Lyford