EFFECTS OF DIETARY PROPIONATE ON HEPATIC GLUCOSE-PRODUCTION, WHOLE-BODY GLUCOSE-UTILIZATION, CARBOHYDRATE AND LIPID-METABOLISM IN NORMAL RATS

Increased intake of dietary fibres is associated with several benefici al effects on carbohydrate and lipid metabolism. The colonic fermentat ion of dietary fibres produces short-chain fatty acids (SCFA; acetate, propionate and butyrate), Some authors have suggested that SCFA could be partly responsible for the effects of dietary fibres. The purpose of the present study was to test the effects of one of the SCFA, propi onate. The effects of moderate amounts of dietary propionate on insuli n sensitivity and hepatic glucose production were studied in male Spra gue-Dawley rats. Two groups of twenty-one adult rats were fed for 3 we eks on a diet containing 78 g propionate/kg (P) or 78 g/kg of a poorly fermentable cellulose (control group; C). Feed intake, body weight, f asting plasma glucose, insulin, free fatty acids, alanine, lactate, gl ycerol and beta-hydroxybutyrate levels were measured weekly in anaesth etized rats. At the end of the feeding period basal hepatic glucose pr oduction (BHGP) was measured with a primed continuous infusion of [3-H -3]glucose and the in vivo insulin sensitivity in rats was quantified by the euglycaemic-hyperinsulinaemic clamp technique (0.6 and 2 U/kg p er h). At that time fasting plasma glucose measured in anaesthetized r ats was significantly lower in group P than in group C: 7.7 (SE 0.2) v . 8.5 (SE 0.2) mmol/l respectively (P < 0.002); plasma insulin levels were not significantly different. Neither the BHGP (mg/min per kg; C 1 4.8 (SE 1.3), P 15.1 (SE 1.3); n 7, not significant) nor the basal met abolic clearance (ml/min per kg; 8.9 (SE 0.8) v. 9.9 (SE 1.1); not sig nificant) were different between treatments. Hepatic glucose productio n and glucose utilization at the two insulin concentrations (approxima tely 500 and 1500 mU/l respectively, n 7) did not differ significantly between the two groups. These results show that dietary propionate ch ronically ingested by normal rats could decrease fasting glycaemia, bu t from our findings, no effect on hepatic glucose production and whole -body glucose utilization could be clearly demonstrated.