Casein-rich diet reduces intestinal glucagon-like peptide 1 and may prevent hypoglycemia by increasing plasma glucose in rats

摘要

The aim of this study was to explore, in normal rats, the effects upon selected metabolic and hormonal variables of both the rapid intake or long-term administration of a diet containing 1.3% protein (wt/wt; control diet) and enriched with 40% (wt/wt)casein. The response to the intake of the control and casein diet was examined in meal-trained rats given access to these diets for 15 minutes, A glucose tolerance test involving the intragastric administration of glucose (1.2 mg/g body weight) was performed in overnight fasted rats otherwise given free access to the control or casein diet for 19 to 36 days,. In meal-trained rats, the secretory response of insulin-producing cells, as judged from the increment of the paired plasma insulin/glucose ratio,was higher in the rats exposed to the casein, as compared with control diet, despite a higher integrated plasma glucose incremental area in the latter case. After intragastric administration of glucose to overnight fasted rats otherwise maintained for 19 and .36 days on either control or casein diet, the integrated values over 120 minutes for both plasma glucose and insulin concentrations were higher, however, in the casein than in the control group, without significant difference in the integrated value for the paired insulin/glucose ratio. Likewise, neither the basal plasma glucagon-like peptide 1 concentration nor the incremental area above such a basal value was significantly different in the 2 groups of rats. The gain in body weight over 50 daysof observation, as well as the insulin content of the pancreas at day 50, were also comparable in the 2 groups of rats. The intestinal glucagon-like peptide 1 content was lower, however, in the casein than in the control group. These findings are consistent with the insulinotropic action of amino acids and with the role of some of them as gluconeogenic precursors. Advantage could conceivably be taken of such an approach to prevent hypoglycemia in selected situations.