Improvement of insulin resistance by Chlorella in fructose-rich chow-fed rats

Chlorella is a type of unicellular fresh water algae. In an attempt to develop new agents for handling insulin resistance, Chlorella was employed to screen the effect on insulin resistance in rats induced by fructose-rich chow. A single oral administration of Chlorella for 90 min decreased the plasma glucose in a dose-dependent manner in rats receiving 4-week fructose-rich chow. In addition, chronic treatment with Chlorella for 15 days also lowered plasma glucose in the same manner. Then, the insulin action on glucose disposal rate was measured using the glucose-insulin index, values of the areas under the curves of glucose and insulin during the intraperitoneal glucose tolerance test (IPGTT). Oral administration (three times daily for 5 days) of Chlorella to rats receiving 4 weeks of fructose-rich chow abolished the elevated value of the glucose-insulin index, indicating that Chlorella has an ability to improve insulin resistance. An increase of insulin sensitivity by Chlorella was further evaluated using the plasma glucose lowering action of exogenous insulin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Oral administration of Chlorella three times daily to STZ-diabetic rats increased the response to exogenous insulin 15 days later. The obtained results suggest that oral administration of Chlorella has the ability to improve insulin sensitivity, which may be used as an adjuvant therapy for patients with insulin resistance.