Effect of propionate on fatty acid and cholesterol synthesis and on acetate metabolism in isolated rat hepatocytes

Abstract

In the present study the actual role of propionic acid in the control of fatty acid and cholesterol synthesis was investigated in isolated liver cells from fed rats maintained in the presence of near-physiological concentrations of glucose, glutamine and acetate. Using 3H2O for lipid labelling, propionate appears as an effective inhibitor of fatty acid synthesis and to a lesser extent of cholesterol synthesis, even at the lowest concentration used (0·6 mmol/l). Butyrate is a potent activator of both synthetic pathways, and the activating effect was not counteracted by propionate. Using 1-[14C]acetate, it was observed that propionate at a moderate concentration, or 1 mmol oleate/l, are both very effective inhibitors of 14C incorporation into fatty acid and cholesterol. This incorporation was drastically inhibited when propionate and oleate were present together in the incubation medium. The net utilization of acetate by rat hepatocytes was impaired by propionate, in contrast to oleate. 1-[14C]butyrate was utilized at a high rate for fatty acid synthesis, but to a lesser extent for cholesterol synthesis; both processes were unaffected by propionate. Intracellular citrate concentration was not markedly depressed by propionate, whereas it was strongly elevated by butyrate. In conclusion, propionate may represent an effective inhibitor of lipid synthesis when acetate is a major source of acetyl-CoA, a situation which is encountered with diets rich in readily-fermentable fibres. The present findings also suggest that propionate may be effective at concentrations close to values measured in vivo in the portal vein.

Effects of Dietary Addition of a Low-Pectin Apple Fibre Preparation on Rats

“…[Fung et al, 2012]. Moreover, acetate and propionate which are also signifi cantly increased in the present study can differentially infl uence fat metabolism; acetate seems to promote lipogenesis in the liver, whereas propionate has been reported to inhibit this process [Nishina & Freedland, 1990;Demigné et al, 1995], however, there are strong evidences suggesting that the inhibitory effect of propionate is rather unlikely [Illman et al, 1988]. In the present study, the intensifi cation of SCFA synthesis in group A resulted in just slightly lowered pH value of the caecal digesta and signifi cantly lowered pH of the colon digesta.…”

Comparative gastrointestinal and plasma cholesterol responses of rats fed on cholesterol-free diets supplemented with guar gum and sodium alginate

“…There is no doubt that increased consumption of fermentable NSP has been associated with increased caecal production of SCFA, and higher concentrations of SCFA, including propionate, in portal blood (Goodlad & Mathers, 1990). However, the reported effects of increased propionate availability on blood cholesterol concentrations or on hepatic cholesterol synthesis rate are not consistent (Chen et al 1984;Illman et al 1988;Venter et al 1990;Todesco et al 1991;Beaulieu & McBurney, 1992;Demigne  et al 1995;Lin et al 1995;Hara et al 1998). This apparent inconsistency, coupled with apparent variations in response between human and rat hepatocytes in vitro (Lin et al 1995), casts some doubt on the primary role of propionate in reducing plasma cholesterol concentrations.…”

Production performance of pigs reared in different systems and fed increased energy content diets with or without green alfalfa

“…HDL and LDL levels), it could be assumed that feeding regime (diet with increased ME content from rapeseed oil supplementation and green alfalfa forage addition) and rearing conditions (with access to outdoor runs) might improve the dietetic value of meat. Demigne et al (1995) stated that there is dependence between a cholesterol production in animals` livers and the dietetic value of pork.…”