Fasting serum bile acid (BA) composition in healthy people is still unknown: only recently an adequate technology to measure in the same sample both free and conjugated BAs has been developed. Aim of this study was to evaluate serum BA levels and composition in healthy subjects. Methods: 30 healthy young subjects (15 females and 15 males) [no gallstone disease, no abnormal liver tests, no liver steatosis on ultrasonography; mean age 26.5±0.8 (range 22−40 yrs)] were selected. A blood sample was taken in the morning after a standardized overnight fasting period (8 hours). Serum samples, diluted 1:6 (v/v) with NaOH 0.1N and heated to 64ºC for 30 minute, were loaded on conditioned cartridge and washed with 10 ml of water. The cartridge was eluted with 5 ml of methyl alcohol; the eluate was dried under vacuum and then reconstituted with the mobile phase (70:30 v/v ammonium acetate buffer/acetonitrile) and injected into HPLC-ESI-MS instrument. The recovery of each BA ranged from 80% to 96% and accordingly corrected. Results: Total serum BA levels were 3.65±0.40 mmol/L (male:4.2±0.7; female:3.1±0.4 mmol/L, p = ns); total cholate levels were 0.65±0.11 mmol/L (M:0.79±0.18; F: 0.52±0.13 mmol/L, p = ns); total chenodeoxycholate levels were 1.7±0.2 mmol/L (M: 2.0±0.32; F: 1.4±0.24 mmol/L, p = ns); total deoxycholate levels were 0.8±0.13 mmol/L (M: 0.9±0.24; F: 0.72±0.10 mmol/L, p = ns); total lithocholate levels were below the detectability threshold; total ursodeoxycholate levels were 0.51±0.03 mmol/L (M: 0.55±0.051; F: 0.50±0.05 mmol/L, p = ns). Free BA levels were 1.9±0.3 mmol/L (male: 2.4±0.5; female: 1.4±0.19 mmol/L, p = ns); total glycoconjugate levels were 1.5±0.14 mmol/L (M: 1.7±0.18; F: 1.32±0.22 mmol/L, p = ns); total tauroconjugate levels were 0.29±0.05 mmol/L (M: 0.17±0.03; F: 0.41±0.09 mmol/L, p = 0.02). Conclusions: Free and glycoconjugated BAs undergo passive diffusion and facilitated transport along the entire small intestine, accounting for their higher fractional serum level. Tauroconjugated BAs absorption occurs only in the distal ileum through an active transport system, and their hepatic uptake is extremely efficient, accounting for their lower spill into the systemic circulation; their higher levels in females suggest a pivotal role of oestrogens in the modulation of the transport systems involved in Bas enterohepatic circulation.

HIGH FREE AND GLYCOCONJUGATED AND LOW TAUROCONJUGATED BA LEVELS IN SERUM ARE THE MIRROR OF INTESTINAL EVENTS AND HEPATIC UPTAKE

BUONFIGLIOLI, FEDERICA;AZZAROLI, FRANCESCO;MONTAGNANI, MARCO;SIMONI, PATRIZIA;RASPANTI, MARIA ELENA;LISOTTI, ANDREA;LODATO, FRANCESCA;COLECCHIA, ANTONIO;FESTI, DAVIDE;RODA, ALDO;RODA, ENRICO;MAZZELLA, GIUSEPPE
2009

Abstract

Fasting serum bile acid (BA) composition in healthy people is still unknown: only recently an adequate technology to measure in the same sample both free and conjugated BAs has been developed. Aim of this study was to evaluate serum BA levels and composition in healthy subjects. Methods: 30 healthy young subjects (15 females and 15 males) [no gallstone disease, no abnormal liver tests, no liver steatosis on ultrasonography; mean age 26.5±0.8 (range 22−40 yrs)] were selected. A blood sample was taken in the morning after a standardized overnight fasting period (8 hours). Serum samples, diluted 1:6 (v/v) with NaOH 0.1N and heated to 64ºC for 30 minute, were loaded on conditioned cartridge and washed with 10 ml of water. The cartridge was eluted with 5 ml of methyl alcohol; the eluate was dried under vacuum and then reconstituted with the mobile phase (70:30 v/v ammonium acetate buffer/acetonitrile) and injected into HPLC-ESI-MS instrument. The recovery of each BA ranged from 80% to 96% and accordingly corrected. Results: Total serum BA levels were 3.65±0.40 mmol/L (male:4.2±0.7; female:3.1±0.4 mmol/L, p = ns); total cholate levels were 0.65±0.11 mmol/L (M:0.79±0.18; F: 0.52±0.13 mmol/L, p = ns); total chenodeoxycholate levels were 1.7±0.2 mmol/L (M: 2.0±0.32; F: 1.4±0.24 mmol/L, p = ns); total deoxycholate levels were 0.8±0.13 mmol/L (M: 0.9±0.24; F: 0.72±0.10 mmol/L, p = ns); total lithocholate levels were below the detectability threshold; total ursodeoxycholate levels were 0.51±0.03 mmol/L (M: 0.55±0.051; F: 0.50±0.05 mmol/L, p = ns). Free BA levels were 1.9±0.3 mmol/L (male: 2.4±0.5; female: 1.4±0.19 mmol/L, p = ns); total glycoconjugate levels were 1.5±0.14 mmol/L (M: 1.7±0.18; F: 1.32±0.22 mmol/L, p = ns); total tauroconjugate levels were 0.29±0.05 mmol/L (M: 0.17±0.03; F: 0.41±0.09 mmol/L, p = 0.02). Conclusions: Free and glycoconjugated BAs undergo passive diffusion and facilitated transport along the entire small intestine, accounting for their higher fractional serum level. Tauroconjugated BAs absorption occurs only in the distal ileum through an active transport system, and their hepatic uptake is extremely efficient, accounting for their lower spill into the systemic circulation; their higher levels in females suggest a pivotal role of oestrogens in the modulation of the transport systems involved in Bas enterohepatic circulation.
2009
258
Buonfiglioli f; Azzaroli F; Montagnani M;Simoni P; Locatelli M; Raspanti ME; Lisotti A; Lodato F; Alessandrelli F; Colecchia A; Festi D; Roda A; Roda E; Mazzella G
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/76323
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