Taurine improves insulin sensitivity in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous type 2 diabetes.
BACKGROUND
Taurine, a potent antioxidant, has been reported to improve streptozotocin-induced diabetes mellitus, in which the development of diabetes results from an attack by oxygen free radicals on pancreatic beta cells. However, taurine also increases the excretion of cholesterol via conversion to bile acid and would be expected to improve insulin resistance.


OBJECTIVE
The effects of taurine on insulin sensitivity were examined in a model rat of insulin resistance and type 2 diabetes-the Otsuka Long-Evans Tokushima Fatty (OLETF) rat.


METHODS
Male OLETF rats were divided into 2 groups at the age of 16 wk: a taurine-supplemented group and an unsupplemented group. As a nondiabetic control, Long-Evans-Tokushima-Otsuka rats were used. An oral-glucose-tolerance test and hyperinsulinemic euglycemic clamp were performed at the ages of 23 and 25 wk.


RESULTS
The OLETF rats had hyperglycemia and insulin resistance and they had a greater accumulation of abdominal fat than did control rats. Abdominal fat accumulation, hyperglycemia, and insulin resistance were significantly lower in the taurine-supplemented group than in the unsupplemented group. Serum and liver concentrations of triacylglycerol and cholesterol were significantly higher in the OLETF rats than in the control rats and were significantly lower in the taurine-supplemented group than in the unsupplemented group, presumably because of the increased secretion of cholesterol into bile acid. Taurine-supplemented rats also showed higher nitric oxide secretion, evidenced by increased urinary excretion of nitrite.


CONCLUSIONS
Taurine effectively improves metabolism in OLETF rats by decreasing serum cholesterol and triacylglycerol, presumably via increased secretion of cholesterol into bile acid and decreased production of cholesterol because of increased nitric oxide production.
Nakaya
Y
Y
Department of Nutrition, Tokushima University, School of Medicine, Tokushima, Japan. nakaya@nutr.med.tokushima-u.ac.jp
Minami
A
A
Harada
N
N
Sakamoto
S
S
Niwa
Y
Y
Ohnaka
M
M
D000273:Adipose Tissue / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D001806:Blood Urea Nitrogen; D001835:Body Weight / Q000187:drug effects; D002784:Cholesterol / Q000097:blood*; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy*; D004195:Disease Models, Animal; D015309:Glucose Clamp Technique; D006949:Hyperlipidemias / Q000188:drug therapy; D007333:Insulin Resistance; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis; D051381:Rats; D020334:Rats, Inbred OLETF; D013654:Taurine / Q000627:therapeutic use*
D013654:Taurine; D009569:Nitric Oxide; D002784:Cholesterol