Independent effects of protein and fibre sources on glucose and cholesterol metabolism in the rat

Abstract

Casein and soy protein were used in combination with wheat bran and oat bran in four balanced diets to verify the effects of protein and fibre sources on various parameters of glucose and cholesterol metabolism in the rat. Fifteen animals were fed each diet for two weeks, under a dephased light/dark cycle. On day 15, blood samples were collected in the portal vein and abdominal aorta and liver was excised in fasted (09:00 h) and fed rats(12:00 h and 16:00 h) from each group. The animals fed casein had significantly higher total plasma cholesterol levels at all sampling times, higher HDL-cholesterol values at 12:00 h and higher hepatic cholesterol concentrations at 12:00 h and 16:00 h, as compared to those fed soy protein. Systemic glycemia at 09:00 h and 12:00 h and insulin levels at 12:00 h were also highest in casein fed groups. As regards fibre sources, wheat bran feeding induced lower portal and systemic glycemia at 12:00 than did oat bran feeding. Oat bran diet groups had the lowest HDL-cholesterol levels and the highest hepatic cholesterol concentrations at 09:00 h. No interaction between dietary protein source and fibre source was evidenced by ANOVA on any of the parameters tested. Thus, these nutrients fed simultaneously seem to exert independent and mostly distinct effects on glucose and cholesterol metabolism.