[Effects of high protein feeding on blood glucose and blood lipids in healthy rats].

Objective: To investigate the effects of high-protein diets from different sources, under isocaloric conditions, on the blood glucose and lipid profiles in healthy rats.

Methods: Ninety Wistar rats were randomly divided into nine groups, receiving diets with varying protein sources and protein energy ratios: a control group, casein groups were fed casein at protein energy ratios of 15%(C15), 30%(C30), 40%(C40) and 50%(C50), while the soy protein groups were fed soy protein at equivalent energy ratios(S15, S30, S40 and S50) for 12 weeks. The rats were observed during the experiment and weighed weekly, blood samples were collected at the midpoint and endpoint of the experiment, and serum was analyzed for determination of fasting blood glucose(FBG), glycated serum protein(GSP), high-density lipoprotein cholesterol(HDL-C), low-density lipoprotein cholesterol(LDL-C), free fatty acids(FFA), total cholesterol(TC), and triglyceride(TG). At the endpoint, an oral glucose tolerance test(OGTT) was performed.

Results: Energy intake was comparable across all groups. However, the S50 group exhibited a significant reduction in final body weight compared to the control group(P=0.03). At the midpoint(week 6), FBG was significantly elevated in the C40 and C50(P<0.01), while LDL-C in the C50 showed a significant reduction(P=0.02). Additionally, FFA was notably lower in both the C50 and S50(P<0.05). By the end of the study(week 12), FBG was significantly higher in the S40 and S50(P<0.05), though no significant differences were observed in GSP, OGTT, HDL-C, TC, or TG among groups.

Conclusion: Under isocaloric conditions, short-term(6 weeks) high-protein intake(protein energy ratio≥40%) reduced LDL-C, FFA, and TG levels in healthy rats, TC and TG were generally lower in the soy protein groups than in the casein groups. Fasting glucose was impaired by high-protein intake(protein energy ratio≥40%), high soy protein intakes induced a later increase in glucose than the high casein groups.