Physiological Effects of Nondialyzable Melanoidin in Rats

The absorption and excretion of melanoidins, a mixture of the low- and high-molecular weight components (LMM and HMM), and the LMM component prepared from a l-lysine^d-glucose system, at pH 7.4 and 9.0, respectively, and the effects of these melanoidins on cholesterol metabolism were examined in rats. Weanling male rats of the Wistar strain weighing about 50 g were fed diets containing 10% casein (10C) with 3% of a melanoidin or 25% casein (25C) with 4% of the melanoidin for 12 weeks, and the 25C diet including 3% of the melanoidin or LMM for 8 weeks. The growth and organ weights of the melanoidin-supplied groups were not different from those of the control ones. In rats given the melanoidin diets with both protein levels, the kidneys became dark brownish due to the accumulation of the melanoidin, though the accumulated amount was extremely small (nearly 0.5 mg/g wet kidney), and gel filtration chromatography of a water extract of the kidneys on Sephadex G-75 showed that the deposited melanoidin was the LMM component. Most of the ingested melanoidin, however, was excreted in the feces, and on comparison of the gel chromatographic patterns, the melanoidin groups were found to have more fecal LMM than the control ones. When rats were provided with LMM, HMM increased in their feces. The addition of melanoidin suppressed the level of plasma total cholesterol and elevated the fecal excretion of total lipids and total cholesterol. The urinary contents of protein and total creatinine did not differ from those in the control groups.