We have established a new differential assay method for cathepsin L-type proteinases using specific inhibitors, E-64 for all cysteine proteinases, CA-074 for cathepsin B, and PLCPI for cathepsin L-type proteinases with Z-Phe-Arg-MCA as the substrate. The value of cathepsin B calculated by this method did not coincide with value assayed directly in terms of the hydrolysis of Z-Arg-Arg-MCA, a specific substrate for cathepsin B. The activities of cathepsin L-type proteinases, cathepsins B and J in rat liver and kidney were assayed at the same time using this new assay method as a representative example.

Summary Ample evidence indicates that a high-protein/low-carbohydrate diet increases glucose energy expenditure and is beneficial in patients with type-2 diabetes mellitus (T2DM). The present study was designed to investigate the effects of l-tryptophan in T2DM. Blood glucose was measured by the glucose dehydrogenase assay and serum insulin was measured with ELISA in both normal and hereditary T2DM rats after oral glucose administration with or without l-d-tryptophan and tryptamine. The effect of tryptophan on glucose absorption was examined in the small intestine of rats using the everted-sac method. Glucose incorporation in adipocytes was assayed with [ 3 H]-2-deoxy-d-glucose using a liquid scintillation counter. Indirect computer-regulated respiratory gas-assay calorimetry was applied to assay energy expenditure in rats. l-Tryptophan suppressed both serum glucose and insulin levels after oral glucose administration and inhibited glucose absorption from the intestine. Tryptamine, but not l-tryptophan, enhanced insulin-stimulated [ 3 H]-glucose incorporation into differentiated adipocytes. l-Tryptophan increased glucose-associated energy expenditure in rats in vivo. l-Tryptophan-rich chow consumed from a young age preserved the secretion of insulin and delayed the progression of T2DM in hereditary diabetic rats. The results suggested that l-tryptophan suppresses the elevation of blood glucose and lessens the burden associated with insulin secretion from b-cells.

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When mice were placed on diets extreme deficient in vitamin B6, ovalbumin-dependent antibody productions (IgE, IgG1, IgG2a) were significantly suppressed, and alanine aminotransferase activity in the liver was also significantly decreased. In the case of pyridoxine excess (6 mg% = about ten times standard amount) in a 70% casein diet, ovalbumin-dependent antibody productions were also considerably suppressed. These responses were weaker in a low casein (5%) or normal casein (20%) diet than in a 70% casein diet. The administration of high doses of pyridoxine (6 mg%) resulted in the suppression of hepatic cathepsin B activity. Therefore, we conclude that ovalbumin-dependent antibody productions (IgG1, IgE) were suppressed by pyridoxine excess diet (6 mg%), because hepatic cathepsin B activity was suppressed by the excess pyridoxine in diet.

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