Akio Maekawa

Dietary fiber suppresses elevation of uric acid and urea nitrogen concentrations in serum of rats with renal dysfunction induced by dietary adenine.

This study was conducted to examine the effects of several kinds of dietary fiber (DF) with different physical properties on the elevation of uric acid and urea nitrogen concentrations in serum of rats induced by dietary adenine. DF decreased an uptake of 14C-labeled adenine in the rat jejunum in vitro, but the reduction varied with the physical property of DF. Male Wistar rats (3 weeks old) were fed a diet with or without a 0.4% adenine and a 5% DF (cellulose, chitin, chitosan, or xanthan gum) for 20 days. Feeding of adenine in the fiber-free group elevated the concentrations of uric acid, creatinine, and urea nitrogen in serum, but decreased the excretions of these compounds into urine and increased the amounts of 2,8-dihydroxyadenine (2,8-DHA) in kidney and urine. The test DF was found to suppress the elevation of uric acid, creatinine, and urea nitrogen concentrations in serum induced by dietary adenine, and to mitigate the decreased excretions of these compounds into urine and the increased retention of 2,8-DHA in kidney and urine. This phenomenon was remarkable in the xanthan gum group. These results suggest that DF suppresses the elevation of uric acid and urea nitrogen concentrations in serum by attenuating the absorption of dietary adenine.

Vitamin B-12-Deficiency Affects Immunoglobulin Production and Cytokine Levels in Mice

To clarify the role of B-12 in the immunological function, serum C3, IgM, IgG, IgE contents, splenocytes expression of CD4, CD8, and CD4 positive intracellular IFN-gamma and IL-4 were examined in B-12-deficient mice, and the effect of the administration of CH3-B-12 was also studied. Serum C3, IgM and IgG contents were lower in B-12-deficient mice than in the control mice. On the other hand, serum IgE content was significantly higher in B-12-deficient mice, and the value in CH3-B-12 administered mice, administered CH3-B-12 to B-12-deficient mice for 48 h before the end of feeding period, showed a tendency to recovery. CD4+CD8- cells and CD4+CD8-/CD4-CD8+ ratio in splenocytes were significantly higher in B-12-deficient mice than in control mice. CD4+IFN-gamma+ cells was significantly lower in B-12-deficient mice than in control mice, and CD4+IL-4+ was significantly higher in B-12-deficient mice than in control mice. These results suggest that B-12-deficiency causes CD4+CD8-T cells shift from the T helper type 1 to the T helper type 2, which participate in the IgE production and elevates CD4+CD8-/CD4-CD8+ ratio. Thus, B-12 plays a role in maintaining the immune function in mice.

Effects of a Partially Hydrolyzed Curdlan on Serum and Hepatic Cholesterol Concentration, and Cecal Fermentation in Rats

A significant reduction was observed for serum and hepatic cholesterol concentrations in the rats fed diet containing a 5% partially hydrolyzed curdlan (PHCD), whereas only the hepatic cholesterol concentration was decreased in the curdlan (CD)-fed rats. The cecal contents in the CD group contained a significantly larger amount of short-chain fatty acids, but not those in the PHCD group. CD, but not PHCD, significantly increased the population of cecal bifidobacteria. From the in vitro fermentation test with cecal contents from cellulose powder (CP) and CD-fed rats, PHCD proved to be easily fermented by both cecal contents; incidentally CD was more susceptible to the cecal contents from CD-fed rats than to those from CP-fed rats. These results suggest that PHCD is involved in the modulation of lipid metabolism and intestinal microflora through a different manner from the native CD in rats.