No abstract

Although epidemiological data have indicated that a strong negative association exists between coffee consumption and the prevalence of obesity-associated diseases, the molecular mechanisms by which coffee intake prevents obesity-associated diseases has not yet been elucidated. In this study, we found that coffee intake significantly suppressed high-fat diet (HFD)-induced metabolic alternations such as increases in body weight and the accumulation of adipose tissue, and up-regulation of glucose, free fatty acid, total cholesterol and insulin levels in the blood. We also found that coffee extract significantly inhibited adipogenesis in 3T3-L1 preadipocytes. In the early phase of adipogenesis, 3T3-L1 cells treated with coffee extract displayed the retardation of cell cycle entry into the G2/M phase called as mitotic clonal expansion (MCE). Coffee extract also inhibited the activation of CCAAT/enhancer-binding protein β (C/EBPβ) by preventing its phosphorylation by ERK. Furthermore, the coffee extract suppressed the adipogenesis-related events such as MCE and C/EBPβ activation through the down-regulation of insulin receptor substrate 1 (IRS1). The stability of the IRS1 protein was markedly decreased by the treatment with coffee extract due to proteasomal degradation. These results have revealed an anti-adipogenic function for coffee intake and identified IRS1 as a novel target for coffee extract in adipogenesis.

Coffee is a complex mixture of many bioactive compounds possessing anti-inflammatory properties. However, the mechanisms by which coffee exerts anti-inflammatory effects remains unclear and the active ingredients have not yet been identified. In this study, we found that coffee extract at more than 2.5%(v/v) significantly inhibited LPS-induced inflammatory responses in RAW264.7 cells and that antiinflammatory activity of coffee required the roasting process. Interestingly, we identified pyrocatechol, a degradation product derived from chlorogenic acid during roasting, as the active ingredient exhibiting anti-inflammatory activity in coffee. HPLC analysis showed that 124 μM pyrocatechol was included in 100% (v/v) roasted coffee. A treatment with 5%(v/v) coffee extract and more than 2.5 μM pyrocatechol inhibited the LPS-induced activation of NF-κB and also significantly activated Nrf2, which acts as a negative regulator in LPS-induced inflammation. Furthermore, intake of 60% (v/v) coffee extract and 74.4 μM pyrocatechol, which is the concentration equal to contained in 60% (v/v) coffee, markedly inhibited the LPS-induced inflammatory responses in mice. Collectively, these results demonstrated that pyrocatechol, which was formed by the roasting of coffee green beans, is one of the ingredients contributing to the anti-inflammatory activity of coffee.

No abstract

Recent epidemiological studies showed that coffee consumption is associated with a lower risk of type 2 diabetes, presumably due to suppression of excess fat accumulation in adipocytes. However, the mechanism underlying the effect of coffee on adipocyte differentiation has not been well documented. To elucidate the mechanism, we investigated the effect of coffee on the differentiation of mouse preadipocyte 3T3-L1 cells. Coffee reduced the accumulation of lipids during adipocytic differentiation of 3T3-L1 cells. At 5% coffee, the accumulation of lipids decreased to half that of the control. Coffee also inhibited the expression of the peroxisome proliferator-activated receptor γ (PPARγ), a transcription factor controlling the differentiation of adipocytes. Furthermore, coffee reduced the expression of other differentiation marker genes, aP2, adiponectin, CCAAT-enhancer-binding protein α (C/EBPα), glucose transporter 4 (GLUT4), and lipoprotein lipase (LPL), during adipocyte differentiation. Major bioactive constituents in coffee extracts, such as caffeine, trigonelline, chlorogenic acid, and caffeic acid, showed no effect on PPARγ gene expression. The inhibitory activity was produced by the roasting of the coffee beans.