Suppression of diabetes in non-obese diabetic (NOD) mice by oral administration of water-soluble and alkali-soluble polysaccharide conjugates prepared from green tea

Water-soluble tea polysaccharide conjugates (TPC-W) and alkali-soluble tea polysaccharide conjugates (TPC-A) were extracted from green tea by hot and alkali water respectively. Physicochemical properties of TPC-W and TPC-A were analyzed. Non-obese diabetic (NOD) mice were used to evaluate antidiabetic bioactivities of TPC-W and TPC-A. The daily oral administration of 150 mg kg−1 TPC-W can significantly decrease the level of blood glucose in NOD mice. The anti-glutamic acid decarboxylase (GAD) antibody level in NOD mice treated with 150 mg kg−1 TPC-W decreased 27% (P < 0.05). To the end of trial, only 2 out of 10 mice in NOD groups treated with TPC-W or TPC-A exhibited diabetic symptoms compared with model control group, in which 7 of 10 mice developed diabetes. The result of organ index showed that both TPC-W and TPC-A can protect thymus from shriveling to some extent. In sum, our studies demonstrated that both TPC-W and TPC-A can suppress spontaneous diabetes mellitus in NOD mice.