The bioavailability of α- and β-carotene is affected by gut microflora in the rat

Abstract

The present study examined whether the intestinal microflora could affect the bioavailability and vitamin A activity of dietary aand b-carotene in the rat. In the first set of experiments, we used conventional, germ-free (axenic), and human-flora-associated (heteroxenic) rats. In a second series, conventional rats were treated with either an antibiotic mixture or a potent inhibitor of gastric secretion (Omeprazole). All animals were first depleted of vitamin A over 4 weeks and then were fed on a sterilized diet supplemented with 14 mg b-carotene and 3 mg a-carotene/kg for 2 weeks. In both experiments, a reduction in the intestinal microflora resulted in an increased storage of b-carotene, a-carotene and vitamin A in the liver. Neither the nature of the metabolism of the intestinal microflora (aerobic or anaerobic) nor treatment with omeprazole, to modify intestinal pH, induced a significant effect on the measured variables. When incubated with 15 mol b-carotene/l for 72 h, neither the anaerobic nor the aerobic sub-fractions obtained from rat or human faeces contributed to b-carotene degradation or to vitamin A synthesis. These findings suggest that reduction in gut microflora results in a better utilization of aand b-carotene by rats, although bacteria do not have a direct effect on the bioavailability of these pigments.

Domestic cats convert [2H8]‐β‐carotene to [2H4]‐retinol following a single oral dose

“…However, other investigators have also noted low and variable recoveries of BC in faeces after a single oral dose in other species (Lederman et al., 1998; Ho et al., 2009). BC may also be destroyed in the GI tract by chemical and microbial degradation, decreasing faecal excretion (Yeum and Russell, 2002); for example, it was shown that BC excretion was higher in germ‐free rats compared with those with normal intestinal microflora (Grolier et al., 1998).…”

Meeting the Vitamin A Requirement: The Efficacy and Importance ofβ-Carotene in Animal Species

“…It has also been shown that plant lipoxygenases present in feed plants could quickly destroy BC and lutein in vitro in bovine rumen fluid [72]. In addition, bioavailability of BC was higher in germ-free rats compared to those with normal gut microflora [73]. …”

“…However, cattle and their close relatives appear to be unique among the species of the family Bovidae, many of whom have been designated nonaccumulators of carotenoids despite consuming moderate to high dietary levels (see “other Artiodactyla”). BC can be destroyed by rumen bacteria [72] and lipoxygenases present in some forage plants [73], and these factors may contribute to variability of responses to BC consumed by cattle and other herbivores.…”

Investigation of endogenous metabolic changes in the urine of pseudo germ-free rats using a metabolomic approach

“…Additionally, antibiotic treatment is a very simple method used to determine the impact of the gut microflora on drug metabolism [28,29,[35][36][37]. Thus, the analysis of metabolic profiles for antibiotic-treated animals might be valuable, to understand the gut microflora's role in host physiology and metabolism.…”