Energy and macronutrient restriction regulate bile acid homeostasis.
Level 5 - mechanism / opinion, no new human data
Animal study in male mice (CEBM Level 5).
PubMed 37925090 · doi:10.1016/j.jnutbio.2023.109517
What was done
Male mice were subjected to various restrictive dietary regimens, including caloric restriction (CR), intermittent fasting, a fasting-mimicking diet, overnight fasting, a low-carbohydrate diet, and a ketogenic diet. Investigators measured bile acid (BA) concentrations across liver, plasma, intestinal mucosa (ileum), and feces, along with hepatic and ileal expression of BA synthesis enzymes (CYP7A1, Cyp27a1, Bal) and regulatory/transport factors (Shp, Ntcp, and ileal BA transporters).
What was found
The abstract reports directional findings without numerical values: - Caloric restriction increased liver and plasma BA concentrations, decreased fecal BA concentrations, and elevated ileal mucosal BA levels. - In CR mice, hepatic Shp expression was reduced, while CYP7A1 (protein and mRNA), Cyp27a1, Bal, Ntcp, and ileal BA transporter expression were elevated. - Intermittent fasting and fasting-mimicking diets similarly increased liver and ileal BA concentrations, whereas overnight fasting had negligible effect. - Low-carbohydrate and ketogenic diets increased BA concentrations in the liver but not in the intestine.
Why it matters
The study shows that carbohydrate restriction alone can stimulate hepatic bile acid synthesis, but sustained energy restriction is necessary to increase intestinal bile acid concentration and uptake.
Limits
The study was conducted only in male mice, precluding direct extrapolation to human metabolism or female physiology. The abstract provides no sample sizes (n), quantitative values, effect sizes, or statistical metrics. The functional or long-term clinical consequences of these changes were not assessed.
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- supports Time-restricted feeding upregulates a liver enzyme that converts cholesterol into bile acids, reducing liver cholesterol and increasing bile acid production.