益生菌降胆固醇功能研究进展

本文对益生菌在动物及人体上的降胆固醇功能及可能机理进行了综述。益生菌是一类能够对人体健康起到促进作用的活体微生物。现已发现某些乳杆菌、双歧杆菌和肠球菌属的一些菌株具有降低血清胆固醇水平的能力。由于实验动物和人体在生理学上存在差异,因此同一菌株在实验动物和人体上获得的结论可能不同。关于益生菌降胆固醇功能的机理,研究者提出了不同的假说。这些假说包括:(1)益生菌将胆固醇吸收至细胞膜或细胞质中;(2)益生菌将胆固醇吸附到细胞表面;(3)胆固醇和游离胆盐在酸性环境下发生共沉淀;(4)结合胆盐被益生菌的胆盐水解酶水解成了游离胆盐,后者具有较低的溶解度,不易被肠道回收;(5)胆酸被益生菌的荚膜胞外多糖黏附到了细胞表面;(6)益生菌发酵肠道食源性未消化的碳水化合物产生丙酸,后者能够抑制肝脏胆固醇的生物合成,从而导致血清胆固醇水平降低;(7)益生菌通过下调NPC1L1蛋白基因表达来降低小肠细胞对胆固醇的吸收;(8)益生菌抑制胆固醇乳化胶束的形成。这些假说将为我们认识益生菌的降胆固醇机制及潜在降胆固醇功能菌株的筛选提供了依据。

Cholesterol-lowering effects of probiotics-A review

Abstract: We reviewed existing literature concerning the effects of probiotics on serum cholesterol levels in animals and humans, with particular attention to the possible mechanisms of their action. Probiotics are live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host. One specific benefit that has been reported is that certain probiotic strains (e.g. lactobacilli, bifidobacteria and enterococci) can lower serum cholesterol levels. However, conclusions regarding such hypocholesterollemic effects can vary from studies on animals and humans due to differences in their physiology. As for the cholesterol-lowering mechanisms, different hypotheses have been proposed, including: (I) cholesterol is absorbed into the cellular membrane or cytoplasm; (II) cholesterol is bound to the cellular surface; (III) cholesterol is co-precipitated with free bile acids; (IV) conjugated bile acids were hydrolyzed by probiotics and the resulting free bile acids are more likely than are conjugated ones to be excreted from the body; (V) free bile acids were bound to the cellular surface by capsule exocellular polysaccharides produced by probiotics; (VI) food-derived indigestible carbohydrates were fermented by probiotics to produce propanoic acid in the gut, which can then decrease systemic levels of serum cholesterol by inhibiting hepatic cholesterol synthesis; (VII) a reduction in cholesterol absorption by probiotics through the down-regulation of NPC1L1 gene expression of cells; and (VIII) cholesterol micelle is disrupted by probiotics. The future research is needed to further confirm these hypotheses.