Cytoprotective agent in Lactobacillus bulgaricus extracts.

Adenosine 5'-diphosphoribose (ADP-ribose) has been identified as a significant contributor to the anti-cytotoxic activity of Lactobacillus bulgaricus extracts. Although the biological activities associated with the administration of probiotic bacteria and components thereof are sometimes attributed to the peptidoglycans that comprise a substantial portion of the Gram-positive bacterial cell wall, we found that the beta-nicotine adenine dinucleotide (NAD) hydrolysis product ADP-ribose was a significant contributor to the observed anti-cytotoxicity in our L. bulgaricus extracts. The ADP-ribose was isolated, identified, and quantitated by high performance liquid chromatography (HPLC) and by nuclear magnetic resonance (NMR) spectroscopy. ADP-ribose levels as low as 5 mg/L exhibited a measurable inhibition of tumor necrosis factor alpha (TNF-alpha) mediated cytotoxicity in an in vitro cell assay, whereas the ADP-ribose content of the L. bulgaricus extracts often exceeded 5 mg/g dry weight.

Yeast extract stimulates glucose metabolism and inhibits lipolysis in rat adipocytes in vitro.

Foods contain bioactive components that contribute to optimal health. Food-grade yeast may contain components that enhance cellular glucose metabolism. We tested the effect of brewer's yeast (Saccharomyces cerevisiae) extract (YE), in vitro on rat fat cell glucose transport, glucose metabolism to lipid, and lipolysis. YE was fractionated by reverse-phase chromatography on a C18 open column using ammonium acetate (0.05 mol/L, pH 5.8), with acetonitrile (40%) elution solvent into fraction 1 (Fx1), fraction 2 (Fx2) and fraction 3 (Fx3). Isolated rat adipocytes were preincubated with insulin (51 pmol/L), YE (10 mg/L) or both; transport of U-(14)C-glucose was measured. Adipocytes were incubated with insulin and YE fractions (10 mg/L); glucose metabolism to lipid was measured by incorporation of U-(14)C-glucose into total lipids. Lipolysis was measured by glycerol release. Insulin stimulated glucose transport to sevenfold the basal value (P < 0.05). YE did not affect glucose transport. Insulin stimulated glucose metabolism to 2.6-fold the basal value (P < 0.001); YE stimulated glucose metabolism 14% (P < 0.005). YE potentiated the action of insulin 30% (P < 0.002). YE Fx2 and Fx3 stimulated glucose metabolism 25-40% (P < 0.05). Insulin inhibited lipolysis 47% (P < 0.001). YE alone inhibited lipolysis 63% (P < 0.001). YE and insulin inhibited lipolysis 81% (P < 0.001). Fractions of YE inhibited lipolysis in the presence of insulin (P < 0.05); the order of potency was Fx2 = Fx3 >> Fx1. A novel yeast extract (YE) and its fractions affect pathways of adipocyte metabolism differentially. YE and its fractions are good candidates for in vivo study.