Measurement of changes in CO2 generated from propionate in Caenorhabditis elegans using novel 13CO2 gas analysis.

Caenorhabditis elegans contains two pathways for propionate metabolism, the vitamin B12-dependent and shunt pathways, which are similar to those in humans. In this study, we monitored the changes in propionate metabolism in the whole body of C. elegans using novel 13CO2 gas analysis. We measured the increase in 13CO2 excreted in the air after administering [1-13C]-labeled propionate ([13C]propionate) to the worms. The 13CO2 generated from [13C]propionate in C. elegans increased in a dose-dependent manner, reaching a maximum at 48 h. Enhanced expression of propionate metabolism-related genes was observed after administration of propionate. Knockdown of mmcm-1, which encodes the rate-limiting enzyme of the propionate metabolism, using RNAi reduced 13CO2 excretion. Thus, 13CO2 gas analysis could be confirmed 13CO2 excretion associated with changes in the metabolism of [13C]propionate in nematodes. This analysis can contribute to further understanding of the physiological effects of short-chain fatty acids.

Dietary daidzein decreases food intake accompanied with delayed gastric emptying in ovariectomized rats.

We previously found that equol, a metabolite of intestinal bacterial conversion from soy isoflavone daidzein, has female-specific anorectic effects. In the present study, we used seven-week-old female ovariectomized (OVX) Sprague Dawley rats to test the hypothesis that the anorectic effect of dietary daidzein may be attributed to delayed gastric emptying. Results suggest that dietary daidzein delays gastric emptying and that it has an anorectic effect with residual gastric contents, but not without gastric contents. Dietary equol significantly decreased daily food intake in the OVX rats without sleeve gastrectomy, but not in those with sleeve gastrectomy, suggesting that the accumulation of food in the stomach is required for the anorectic effect of equol to occur. These results support the hypothesis that the anorectic effect of dietary daidzein is attributed to delayed gastric emptying.

Body heat responsive gelation of methylcellulose formulation containing betaine.

We examined a methylcellulose (MC) formulation that gels at body temperature for enteral alimentation. Betaine was found to have a lowering effect on the gelation temperature of the MC solution. The thermal gelation temperature of a body heat-responsive (BHR) gelling MC formulation, consisting of 2% MC, 15% glucose, 1.2% sodium citrate, and 3.5% betaine mixture, was approximately 32 °C, indicating that it could gel in response to body heat. Glucose release from the BHR gels was delayed at 37 °C in an in vitro study. In rats, oral administration of BHR gelling MC formulation delayed an increase in blood glucose and appearance of 13CO2 in expired air in a 13C-acetate breath test in comparison with the control. These results suggested that the BHR gelling MC formulation was gelled in the stomach and delayed gastric emptying after oral administration and glucose in the gels was absorbed slowly.

Degradation of pectin in the caecum contributes to bioavailability of iron in rats.

The present study was designed to investigate the effect of pectin on Fe bioavailability in ileorectomised rats or caecectomised rats. In Expt 1, rats were divided into the following two groups: ileorectomised rats fed a fibre-free diet (FF diet) and ileorectomised rats fed a FF diet supplemented with 5 % (w/w) pectin (pectin diet). Apparent Fe absorption in ileorectomised rats fed the pectin diet was significantly lower compared with ileorectomised rats fed the FF diet. In Expt 2, caecectomised rats and sham-operated rats were given one of the following diets for 3 weeks: diet containing ferrous iron (FeII diet), diet containing pectin at 50 g/kg diet (pectin diet) and diet containing a mixture of FeII and product prepared by the enzymatic degradation of pectin (FeII-OGA diet), which were presumed to be oligomers of galacturonic acid. The Fe content of these diets was 7·6, 8·1 and 7·7 mg/kg diet, respectively. The bioavailability of Fe in rats fed the FeII diet was not affected by caecectomy. In contrast, in rats fed the pectin diet, where Fe bound to pectin was the only Fe source, Hb gain and Hb regeneration efficiency were significantly decreased by caecectomy. The bioavailability of Fe from the FeII-OGA complex was not affected by caecectomy. These results suggest that Fe in pectin might be released by microbial degradation and subsequently made available for absorption in the large intestine, although pectin might decrease Fe absorption in the small intestine.

Iron bound to pectin is utilised by rats.

In the present in vitro study, the effects of pH and ionic strength on the release of iron from pectin and the ability of pectin to reduce ferric iron to ferrous iron were examined. The bioavailability of Fe bound to pectin was evaluated in rats. The amount of Fe released from pectin was at a maximum at pH 2·0 and decreased as the pH value increased. At pH 2·0, the amount of Fe released from pectin increased as the ion length increased; at pH 5·0, ion length had no effect on pectin release. Pectin effectively reduced Fe from the ferric form to the ferrous form. In rats fed a pectin diet, where Fe bound to pectin was the only Fe source, the final Hb concentration using diets containing 4·4-5·7, 7·2 or 11·5 mg Fe/kg diet was equal to the concentration in rats fed diets containing 4·5, 7·6 or 13·5 mg ferrous iron/kg diet, respectively. Hb regeneration efficiencies in rats fed pectin diets were significantly different from rats fed a diet containing 13·5 mg ferrous iron/kg diet. In rats fed a diet with or without pectin, where ferric iron was the only Fe source, pectin increased the final Hb concentration. These results suggest that Fe bound to pectin is utilised by rats.