Changes in Bile Acid Subtypes and Improvements in Lipid Metabolism and Atherosclerotic Cardiovascular Disease Risk: The POUNDS Lost trial.

BACKGROUND: Distinct circulating bile acid (BA) subtypes may play roles in regulating lipid homeostasis and atherosclerosis.

OBJECTIVES: We investigated whether changes in circulating BA subtypes induced by weight-loss dietary interventions were associated with improved lipid profiles and atherosclerotic cardiovascular disease (ASCVD) risk estimates.

METHODS: This study included adults with overweight or obesity (n=536) who participated in a randomized weight-loss diet intervention trial. Circulating primary and secondary unconjugated BAs and their taurine-/glycine-conjugates were measured at baseline and 6 months after weight-loss diet interventions. The ASCVD risk estimates were calculated by the validated equations.

RESULTS: At baseline, higher levels of specific BA subtypes were related to higher levels of atherogenic VLDL lipid subtypes and ASCVD risk estimates. Weight-loss diet-induced decreases in primary BAs were related to larger reductions of triglycerides and total cholesterol (every 1-SD decrease of glycocholate, glycochenodeoxycholate, or taurochenodeoxycholate was related to β [SE] -3.3 [1.3], -3.4 [1.3], or -3.8 [1.3] mg/dl, respectively; P <0.05 for all). Greater decreases in specific secondary BA subtypes were also associated with improved lipid metabolism at 6 months; there was β -4.0 [1.1] mg/dl per 1-SD decrease of glycoursodeoxycholate (P=0.003) for changes in LDL cholesterol. We found significant interactions (P <0.05) between dietary fat intake and changes in BA subtypes on changes in ASCVD risk estimates; decreases in primary and secondary BAs (such as conjugated cholate or deoxycholate) were significantly associated with improved ASCVD risk after consuming a high-fat diet but not after a low-fat diet.

CONCLUSIONS: Decreases in distinct BA subtypes were associated with improved lipid profiles and ASCVD risk estimates, highlighting the importance of changes in circulating BA subtypes as significant factors linked to improved lipid metabolism and ASCVD risk estimates in response to weight-loss dietary interventions. Habitual dietary fat intake may modify the associations of changes in BAs with ASCVD risk.