Protective effects of dietary 1,5-anhydro-D-glucitol as a blood glucose regulator in diabetes and metabolic syndrome.

1,5-Anhydro-D-glucitol (1,5-AG) is fairly widespread in food products. It is also one of the major polyols in the human body, and its concentration is homeostatically regulated. We report here on the beneficial effects of 1,5-AG in preventing hyperglycemia and its role in improving metabolic syndrome. The findings revealed that it does not affect blood glucose levels itself under normal conditions but clearly has a suppressive effect on the levels of dietary sugars, such as glucose, maltose, and sucrose. A long-term administration study revealed that feeding db/db diabetic mice 3% 1,5-AG for 8 weeks significantly decreased blood glucose levels compared to untreated mice (339 ± 30 versus 438 ± 34 mg/dL; p < 0.05). Furthermore, this treatment also significantly suppressed serum cholesterol levels (110.2 ± 18.0 versus 168.4 ± 9.8 mg/dL; p < 0.01). 1,5-AG did not inhibit intestinal α-glucosidase activities but regulated liver glucose levels via affecting both the glycogenolysis and gluconeogenesis pathways. Furthermore, the oral administration of 1,5-AG significantly increased urinary glucose excretion in hyperglycemic conditions. These results clearly suggest that dietary 1,5-AG acts as a modulator of glucose levels in hyperglycemia. 1,5-AG therefore represents a new class of promising functional sweeteners, where the daily consumption of 1,5-AG with meals could inhibit the progress of hyperglycemia and metabolic syndrome.