Role of protein and fiber-source nature on glucose metabolism in rats.

Casein, beef protein, and soy protein were used in combination with oat bran and wheat bran in six balanced diets to verify the verify the effects of protein and fiber-source nature on glucose metabolism in rats, according to a 3 x 2 factorial arrangement. Fifteen animals were fed each diet for 26 days. On day 27, blood samples were drawn from the portal vein and abdominal aorta, and liver was excised in fasted (0830) and fed (1130 and 1430) rats from each group. Wheat-bran feeding induced lower portal glycemia at 1130 (p < 0.01) and 1430 (p < 0.02) and lower portoaortic differences in glycemia at 1130 (p < 0.01) than did oat bran feeding. Animals fed beef protein had a higher insulin-glucagon ratio at 0830 (p < 0.05) and higher arterial lactate concentrations at 1430 (p < 0.04) than those fed casein. Also, groups of rats fed animal proteins tended to have higher total hepatic glycogen stores at 1430 (p < 0.08) than those fed soy protein. Furthermore, at 1130, an interaction between dietary fiber and animal protein nature was evidenced on arterial insulin concentrations (p < 0.05), indicating that casein and beef protein seem to react differently when combined with different fiber sources. These results confirm that fiber-source nature affects the appearance in circulation of glucose in the postprandial period. In addition, this work indicates that protein and fiber-source nature interact to modulate some aspects of glucose systemic utilization.