Decreased plasma insulin but normal glucagon in rats fed low protein diets

Plasma glucagon and insulin were determined in rats fed three diets, one control and two low protein (LP 1 & LP 2). In LP 1, the protein omitted was replaced by carbohydrate while in LP 2, fat and alpha-cellulose replaced the omitted protein. Among rats fed LP diets ad libitum, food consumption decreased and body weight loss occurred. In order to separate the effects of reduced food intake and weight loss from the effects of LP diet alone, paired feeding and paired weight experiments were conducted. In another experiment, ingestion of a LP diet for 8 to 10 days was followed by refeeding the control diet for 5 days. The results demonstrate that plasma insulin was reduced in LP rats compared to the full-fed controls and pair-fed controls, the lowest levels being observed in rats fed LP 2 diet. Furthermore, the paired feeding experiment revealed that the diminished food consumption plays no significant role in lowering plasma insulin in LP rats. The refeeding experiment showed that the decline in plasma insulin in LP rats is a transient phenomenon and the plasma insulin promptly reverts to normal upon resumption of feeding the control diet. Plasma glucagon was unaltered throughout these dietary manipulations.