**6.3. G protein-coupled receptors**

It has been well-established that probiotic bacteria exert benecial effects on the intestine especially the antimicrobial property by producing organic acids or regulating the organic acid-producing flora [93]. It has been also reported that GPR41 and GPR43 can be activated by short-chain fatty acids(SCFAs)[101]. Thus, it is possible that probiotic may affect GPRs through production of SCFAs in gut. However, this relationship among these have not yet been well-established. Study performed in Gpr41-deficient mice under germ free or conventional environment revealed that present of microflora was associated with harvest of short-chain fatty acids from the diet which control the degree of adiposity [102].

By our knowledge, only one study has investigated the effect of prebiotic which can specifically increase intestinal probiotic bifidobacteria on GPR43 expression through modified lipid profile [103]. Using a high-fat fed rodent model, the authors studied the effects of prebiotic on changes of microflora, adipose fatty acid profile and receptors expression. High fat diet is able to increase GPR43 and TLR4 expression as well as PPAR-γ expression due to oleic acid and α-linolenic acid production, while prebiotic decreases GPR43 and TLR4 overexpression.
