PROPIONATE INHIBITS INCORPORATION OF COLONIC [1,2-C-13]ACETATE INTO PLASMA-LIPIDS IN HUMANS

Acetate and propionate, produced during colonic fermentation of unabso rbed carbohydrate, may influence systemic lipid metabolism. As a preli minary study to see whether colonic acetate is incorporated into plasm a lipids and whether propionate inhibits this process, 5 healthy males were studied after fasting overnight. They were given, in random orde r, 12.5 mmol (1.05 g) [1,2-C-13] sodium acetate by intravenous or rect al infusion, and the rectal infusion was given with or without 6 mmol (0.58 g) sodium propionate. Two hours after rectal acetate, C-13 recov eries in plasma cholesterol (0.59 +/- 0.22%) and triglycerides (1.24 /- 0.69%) were significantly greater than after intravenous acetate (0 .09 +/- 0.12% and 0.29 +/- 0.18%, respectively). Addition of propionat e reduced C-13 recovery in triglycerides (0.19 +/- 0.06%, P = 0.024) c ompared with rectal acetate alone, but the effect on cholesterol (0.26 +/- 0.05%) was not significant. These data suggest that incorporation of colonic acetate into plasma triglycerides is inhibited by propiona te. Further studies are required to quantify the effects of colonic ac etate and propionate on lipid synthesis.