Circulating fasting total BA was not associated with obesity .
FGF19 was inversely and faecal BA excretion was positively associated with obesity .
Roux-en-Y gastric bypass ( RYGB ) and sleeve gastrectomy ( SG )  modulated BA metabolism , ie , increased BA and FGF19 .
Our results indicate that BA metabolism is altered in obesity .
Circulating bile acids in healthy adults respond differently to a dietary pattern characterized by whole grains, legumes and fruits and vegetables compared to a diet high in refined grains and added sugars: A randomized, controlled, crossover feeding study.
OBJECTIVE The effects of diets high in refined grains on biliary and colonic bile acids have been investigated extensively . However , the effects of diets high in whole versus refined grains on circulating bile acids , which can influence glucose homeostasis and inflammation through activation of farnesoid X receptor ( FXR ) and G protein-coupled bile acid receptor 1 ( TGR5 ) , have not been studied . MATERIAL S AND METHODS We conducted a secondary analysis from a r and omized controlled crossover feeding trial ( NCT00622661 ) in 80 healthy adults ( 40 women/40 men , age 18 - 45 years ) from the greater Seattle Area , half of which were normal weight ( BMI 18.5 - 25.0 kg/m2 ) and half overweight to obese ( BMI 28.0 - 39.9 kg/m2 ) . Participants consumed two four-week controlled diets in r and omized order : 1 ) a whole grain diet ( WG diet ) , design ed to be low in glycemic load ( GL ) , high in whole grains , legumes , and fruits and vegetables , and 2 ) a refined grain diet ( RG diet ) , design ed to be high GL , high in refined grains and added sugars , separated by a four-week washout period . Quantitative targeted analysis of 55 bile acid species in fasting plasma was performed using liquid chromatography t and em mass spectrometry . Concentrations of glucose , insulin , and CRP were measured in fasting serum . Linear mixed models were used to test the effects of diet on bile acid concentrations , and determine the association between plasma bile acid concentrations and HOMA-IR and CRP . Benjamini-Hochberg false discovery rate ( FDR ) < 0.05 was used to control for multiple testing . RESULTS A total of 29 plasma bile acids were reliably detected and retained for analysis . Taurolithocholic acid ( TLCA ) , taurocholic acid ( TCA ) and glycocholic acid ( GCA ) were statistically significantly higher after the WG compared to the RG diet ( FDR < 0.05 ) . There were no significant differences by BMI or sex . When evaluating the association of bile acids and HOMA-IR , GCA , taurochenodeoxycholic acid , ursodeoxycholic acid ( UDCA ) , 5β‑cholanic acid‑3β,12α‑diol , 5‑cholanic acid‑3β‑ol , and glycodeoxycholic acid ( GDCA ) were statistically significantly positively associated with HOMA-IR individually , and as a group , total , 12α‑hydroxylated , primary and secondary bile acids were also significant ( FDR < 0.05 ) . When stratifying by BMI , chenodeoxycholic acid ( CDCA ) , cholic acid ( CA ) , UDCA , 5β-cholanic acid-3β , deoxycholic acid , and total , 12α-hydroxylated , primary and secondary bile acid groups were significantly positively associated with HOMA-IR among overweight to obese individuals ( FDR < 0.05 ) . When stratifying by sex , GCA , CDCA , TCA , CA , UDCA , GDCA , glycolithocholic acid ( GLCA ) , total , primary , 12α‑hydroxylated , and glycine-conjugated bile acids were significantly associated with HOMA-IR among women , and CDCA , GDCA , and GLCA were significantly associated among men ( FDR < 0.05 ) . There were no significant associations between bile acids and CRP . CONCLUSIONS Diets with comparable macronutrient and energy composition , but differing in carbohydrate source , affected fasting plasma bile acids differently . Specifically , a diet characterized by whole grains , legumes , and fruits and vegetables compared to a diet high in refined grains and added sugars led to modest increases in concentrations of TLCA , TCA and GCA , lig and s for FXR and TGR5 , which may have beneficial effects on glucose homeostasis
Circulating fasting total BA was not associated with obesity .
FGF19 was inversely and faecal BA excretion was positively associated with obesity .
Roux-en-Y gastric bypass ( RYGB ) and sleeve gastrectomy ( SG )  modulated BA metabolism , ie , increased BA and FGF19 .
Our results indicate that BA metabolism is altered in obesity .