Cafestol increases serum cholesterol levels in apolipoprotein E*3-Leiden transgenic mice by suppression of bile acid synthesis

Cafestol, a diterpene present in unfiltered coffee, potently increases seru m cholesterol levels in humans. So far, no suitable animal model has been f ound to study the biochemical background of this effect. We determined the effect of cafestol on serum cholesterol and triglycerides in different mous e strains and subsequently studied its mechanism of action in apolipoprotei n (apo) E*3-Leiden transgenic mice. ApoE*3-Leiden, heterozygous low density lipoprotein-receptor (LDLR+/-) knockout, or wild-type (WT) C57BL/6 mice we re fed a high- (0.05% wt/wt) or a low- (0.01% wt/wt) cafestol diet or a pla cebo diet for 8 weeks. Standardized to energy intake, these amounts are equ al to 40, 8, or 0 cups of unfiltered coffee per 10 MJ per day in humans. In apoE*3-Leiden mice, serum cholesterol was statistically significantly incr eased by 33% on the low- and by 61% on the high-cafestol diet. In LDLR+/- a nd WT mice, the increases were 20% and 24%, respectively, on the low-cafest ol diet and 55% and 46%, respectively, on the high-cafestol diet. These inc reases were mainly due to a rise in very low density lipoprotein (VLDL) and intermediate density lipoprotein cholesterol in all 3 mouse strains. To in vestigate the mechanism of this effect, apoE*3-Leiden mice were fed a high- cafestol or a placebo diet for 3 weeks. Cafestol suppressed enzyme activity and mRNA levels of cholesterol 7 alpha-hydroxylase by 57% and 58%, respect ively. mRNA levels of enzymes involved in the alternate pathway of bile aci d synthesis, ie, sterol 27-hydroxylase and oxysterol 7 alpha-hydroxylase, w ere reduced by 32% and 48%, respectively. The total fecal bile acid output was decreased by 41%. Cafestol did not affect hepatic free and esterified c holesterol, but it decreased LDLR mRNA levels by 37%. The VLDL apoB and tri glyceride production rates, as measured after Triton injection, were 2-fold decreased by cafestol, indicating that the number of particles secreted ha d declined and that there was no change in the amount of triglycerides pres ent in the VLDL particle during cafestol treatment. However, the VLDL parti cles contained a 4-times higher amount of cholesteryl esters, resulting in a net 2-fold increased secretion of cholesteryl esters. The decrease in tri glyceride production was the result of a reduction in hepatic triglyceride content by 52%. In conclusion, cafestol increases serum cholesterol levels in apoE*3-Leiden mice by suppression of the major regulatory enzymes in the bile acid synthesis pathways, leading to decreased LDLR mRNA levels and in creased secretion of hepatic cholesterol esters, We suggest that suppressio n of bile acid synthesis may provide an explanation for the cholesterol-rai sing effect of cafestol in humans.