Coffee intake down-regulates the hepatic gene expression of peroxisome proliferator-activated receptor gamma in C57BL/6J mice fed a high-fat diet

Several lines of evidence, including those from epidemiological studies, have suggested that coffee intake reduces the risks of diabetes and obesity, although the detailed mechanisms of such effects are not clearly understood. The present study was conducted to examine the effects of three types of coffee (caffeinated, decaffeinated, and green unroasted coffee) on the livers of C57BL/6J mice fed a high-fat diet, and to elucidate the detailed physiological responses to coffee intake by analysing the data obtained from a transcriptomic analysis using DNA microarrays. The results showed that the three types of coffee suppressed the weight gain and fat accumulation induced by a high-fat diet. A remarkable finding was a down-regulation of PPARγ and related molecules. Furthermore, the protein levels of hepatic peroxisome proliferator-activated receptor gamma (PPARγ) were revealed by Western blot analysis to be lower in all of the coffee-fed groups compared to the high-fat group. Since overexpression of PPARγ in the liver has been implicated in adipogenic hepatic steatosis, we hypothesised that the alterations in PPARγ and its target molecules, which play pivotal roles in adipogenic hepatic steatosis, might be involved in the anti-obesity effect of coffee.