Effects of the Chinese medicine TSJN on insulin resistance and hypertension in fructose-fed rats

The aim of this study was to determine the effect of Tang-Shen-Jiao-Nang (T SJN), a Chinese medicine used to treat diabetes mellitus, on insulin resist ance and hypertension in fructose-fed rats (FFR). Six-week-old male Sprague -Dawley rats were fed either normal rat chow (control) or a fructose-rich c how (FFR) for 6 wk. For the last 2 or 4 wk of a 6-wk period of either diet, the rats were treated by gavage with gum arabic solution as a vehicle (con trol or FFR) or TSJN (800 mg/kg/d; FFR+TS), and then we performed the eugly cemic hyperinsulinemic glucose clamp technique to estimate insulin sensitiv ity. Systolic blood pressure was measured weekly for 6 wk. At the end of th e glucose clamp, the soleus muscle was dissected out for determination of m uscle fiber composition by ATPase methods. Systolic blood pressure was elev ated at 2 wk after the start of the fructose-rich chow feeding and persiste d thereafter throughout the study. Systolic blood pressure during the gluco se clamp in the FFR group was significantly higher than that in the control group. Although there was no effect on systolic blood pressure in rats treated wit h TSJN for the last 2 wk of their 6-wk diet, those treated with TSJN for th e last 4 wk of their 6-wk diet had lower systolic blood pressure than did t he rats in the FFR group. The average rate of glucose infusion during the g lucose clamp, as a measure of insulin sensitivity (M value), was significan tly lower in the FFR than in the controls (10.9 +/- 0.6 and 15.4 +/- 0.4, m g/kg/min, for FFR and controls, respectively; p < 0.01). Treatment with TSJ N for 2 wk significantly improved the M value compared to that of the contr ol level (15.1 +/- 0.5 mg/kg/min). The composite ratio of type I fibers in the soleus muscle was significantly decreased in the FFR compared to contro ls (75.0 +/- 1.7 and 81.7 +/- 1.5%, for FFR and controls, respectively; p < 0.01), and treatment with TSJN for 2 wk led to a recovery composite ratio of type I fiber to the same level as that of the control group (78.7 +/- 1. 7% in FFR+TS). The M value was significantly correlated with the compositio ns of type I and type II fibers (for type I fibers, r = 0.45, p < 0.01, for type II fibers, r = -0.44, p < 0.05). These results suggest that the Chine se medicine TSJN may improve insulin resistance, lower the systolic blood p ressure, and modulate muscle fiber composition in hypertensive and insulin- resistant fructose-fed rats. (Hypertens Res 2000; 23: 101-101).