Low molecular weight chitosan prevents the progression of low dose streptozotocin-induced slowly progressive diabetes mellitus in mice

The present study was designed to clarify the effect of low molecular weigh t (LMW) chitosan (chitosan lactate, average MW: 20000) on the progression o f slowly progressive non-insulin-dependent diabetes mellitus (NIDDM) induce d by a single i.p. injection of low dose (100 mg/kg) streptozotocin (STZ) t o 8-week-old male ICR mice. The non-fasting serum glucose levels of STZ-tre ated control mice continued to rise throughout the experimental period unti l 23 weeks after STZ treatment. The 0.2% or 0.8% chitosan (water solution), given as drinking water from prediabetic stage (2 weeks after STZ treatmen t), markedly prevented the time course-related rise of serum glucose levels of diabetic mice. In addition, the reduction of relative numbers of insuli n-immunoreactive cells (beta -cells) in the islets of diabetic mice at 24 w eeks after STZ treatment was markedly prevented by 0.2% or 0.8% chitosan ad ministration. However, the progression of hyperglycemia in diabetic mice wa s not affected by 0.2% glucosamine, a monosaccharide of chitosan. The gluco se levels of normal mice were not affected by 0.8% chitosan administration. When 0.2% chitosan administration was stopped at 20 weeks, these animals h ad still maintained significantly lower serum glucose levels, compared to c ontrol animals, even at 5 weeks after stopping the administration. These re sults indicate that LMW chitosan prevents the progression of low dose STZ-i nduced slowly progressive NIDDM.