Cafestol, a Bioactive Substance in Coffee, Stimulates Insulin Secretion and Increases Glucose Uptake in Muscle Cells: Studies in Vitro

Diet and exercise intervention can delay or prevent development of type-2-diabetes (T2D), and high habitual coffee consumption is associated with reduced risk of developing T2D. This study aimed to test whether selected bioactive substances in coffee acutely and/or chronically increase insulin secretion from β-cells and improve insulin sensitivity in skeletal muscle cells. Insulin secretion from INS-1E rat insulinoma cells was measured after acute (1-h) and long-term (72-h) incubation with bioactive substances from coffee. Additionally, we measured uptake of radioactive glucose in human skeletal muscle cells (SkMC) after incubation with cafestol. Cafestol at 10–8 and 10–6 M acutely increased insulin secretion by 12% (p < 0.05) and 16% (p < 0.001), respectively. Long-term exposure to 10–10 and 10–8 M cafestol increased insulin secretion by 34% (p < 0.001) and 68% (p < 0.001), respectively. Caffeic acid also increased insulin secretion acutely and chronically. Chlorogenic acid, trigonelline, oxokahweol, and secoisolariciresinol did not significantly alter insulin secretion acutely. Glucose uptake in SkMC was significantly enhanced by 8% (p < 0.001) in the presence of 10–8 M cafestol. This newly demonstrated dual action of cafestol suggests that cafestol may contribute to the preventive effects on T2D in coffee drinkers and be of therapeutic interest.