Enterobacter cloacae administration induces hepatic damage and subcutaneous fat accumulation in high-fat diet fed mice.
Keskitalo A, Munukka E, Toivonen R, Hollmén M, Kainulainen H, Huovinen P, Jalkanen S, Pekkala S
PLoS One. 2018. doi: 10.1371/journal.pone.0198262
COMMENT: Several studies have reported associations between gut microbiota composition and obesity; obese individuals seem to have reduced gut microbiota diversity compared to lean individuals, and the abundance of specific microbial taxa, functional genes, as well as metabolic activities differ significantly between the obese and lean individuals. In addition, gut microbes have been shown to participate in the regulation of host lipogenesis and fat storage.
Family Enterobacteriaceae and especially Enterobacter cloacae strain B29 have been previously linked to obesity and hepatic damage. The underlying mechanisms, however, remain unclear.
In this article Keskitalo et al. examined the effects of E. cloacae subsp. cloacae (ATCC® 13047™) administration on host metabolism of mice fed with high-fat diet (HFD). Their results show that E. cloacae administration increased subcutaneous fat mass and the relative proportion of hypertrophic adipocytes. Both subcutaneous and visceral fat had signs of decreased insulin signaling and elevated lipolysis that was reflected in higher serum glycerol levels. In addition, E. cloacae -treated mice had significantly higher hepatic AST and AST/ALT ratio, and their liver histology indicated fibrosis, demonstrating that E. cloacae subsp. cloacae administration promotes hepatic damage in HFD fed mice.
The results also suggest that E. cloacae administration, accompanied by HFD, has activated the intestinal defense mechanisms. However, as the gut microbiota composition was not analyzed, it cannot be concluded whether this activation was a direct consequence of E. cloacae colonization or arose from more complex chances in gut microbiota. Furthermore, only female mice were analyzed in this study. Previous studies have shown that both gut microbiota composition and immunity are, to some extent, sex-dependent, and thus the findings presented in this study might not be seen in male mice.