Starch synthase IIIa and starch branching enzyme IIb-deficient mutant rice line ameliorates pancreatic insulin secretion in rats: screening and evaluating mutant rice lines with antidiabetic functionalities.

Diabetes mellitus is a metabolic disease spreading worldwide that has been reported to worsen the development and progression of other diseases (cancer, vascular diseases and dementia). To establish functional rice lines with anti-postprandial hyperglycaemic effects, we developed mutant rice lines, which lack one or two gene(s) related to starch synthesis, and evaluated their effects. Powder of mutant rice lines or other grains was loaded to rats fasted overnight (oral grain powder loading test). Incremental area under time-concentration curves (iAUC) were calculated with monitored blood glucose levels. Rice lines with anti-postprandial hyperglycaemic effects were separated by cluster analysis with calculated iAUC. A double mutant rice #4019 (starch synthase IIIa (ss3a)/branching enzyme IIb (be2b)), one of the screened mutant rice lines, was fed to Goto-Kakizaki (GK) rats, an animal model for type 2 diabetes, for 5 weeks. Plasma levels of C-peptide, a marker of pancreatic insulin secretion, were measured with ELISA. For in vitro study, a rat pancreatic cell line was cultured with a medium containing rat serum which was sampled from rats fed #4019 diet for 2 d. After 24-h of incubation, an insulin secretion test was performed. Through the oral rice powder loading test, seven rice lines were identified as antidiabetic rice lines. The intake of #4019 diet increased plasma C-peptide levels of GK rats. This result was also observed in vitro. In rat serum added to cell medium, ornithine was significantly increased by the intake of #4019. In conclusion, the mutant rice #4019 promoted pancreatic insulin secretion via elevation of serum ornithine levels.

Hemodialysis with a new single stable bicarbonate dialysate.

A specified stable bicarbonate/glycylglycine dialysate for hemodialysis (HD) analogous to those introduced by us for continuous ambulatory peritoneal dialysis (CAPD) is described. HD with this single dialysate is simple, easy, safe and of reasonable cost. Results obtained from 6 HD patients proved its superiority against acetate dialysate. Bicarbonate/glycylglycine dialysate is also more stable, harmless and easier to use than bicarbonate dialysate prepared on-line.

Small intestinal absorption of glycine and glycyl-glycine in patients with chronic renal failure.

Intestinal absorption of glycine and glycyl-glycine was studied in 9 patients with chronic renal insufficiency (mean creatinine clearance 9 ml/min) and 7 healthy controls. After an oral load of the amino acid or dipeptide, plasma alpha-amino nitrogen (alpha-NH2N) was measured repeatedly for two hours and the area under curve (AUC) was calculated using the trapezoidal rule. In uremic patients, plasma alpha-NH2N was significantly lower after glycine than after glycyl-glycine at 30, 45 and 60 min and also AUC was smaller after the amino acid indicating a reduced total uptake. One patient with severe, terminal uremia had a flat curve after glycine administration. In control subjects, plasma levels were lower after glycine than after glycyl-glycine at 30 min but AUC did not differ between the amino acid and the dipeptide. Generally these results agree with those in earlier studies of non-uremic man showing that, in small intestine, dipeptides are taken up better and by a different mechanism than amino acids.