Elucidating the Modulatory Activity of Probiotic Bifidobacterium Longum Towards Enterocytic Fasting Induced Adipocyte Factor (FIAF), A Regulator of Fat Storage
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Gut bacteria have been shown to influence diet-related obesity, mediated in part via intestinal FIAF, a circulating lipoprotein lipase inhibitor that modulates fat-storage in the adipose tissue. Probiotic bacteria and probiotic-derived bioactive compounds with stimulatory activity towards intestinal FIAF may thus serve a protective function against diet-related obesity. We have previously shown that secreted factors from Bifidobacterium longum (B. longum), a resident member of the human gut and a probiotic, significantly increased the levels of FIAF secreted from enterocytes in vitro. The objective of this study was a preliminary characterization of the secreted bioactive compounds from B. longum responsible for the observed increases in enterocytic FIAF levels. Our experiments revealed that the modulatory factors were produced by B. longum primarily during exponential phase and caused a concentration-dependent increase in FIAF-secretion. Potent increases in FIAF levels were produced by fractions of molecular weight >50kDa isolated from B. longum cell free supernatants. Heat-treatment did not impact their ability to increase FIAF levels but freeze-thaw lead to loss of modulatory activity. Trypsin- or pepsin-treatment of cell free supernatants also led to loss of FIAF-increasing ability, suggesting that the modulatory factors may be secreted B. longum proteins.