title: Macrophage TNF-alpha contributes to insulin resistance and hepatic steatosis in diet-induced obesity.
abstract: Obesity is commonly associated with development of insulin resistance and systemic evidence of inflammation. Macrophages contribute to inflammatory amplification in obesity and may contribute directly to insulin resistance and the development of nonalcoholic fatty liver disease through the production of inflammatory cytokines, including tumor necrosis factor (TNF)-alpha. To test this hypothesis, we transplanted male wild-type (WT) and TNF-alpha deficient (KO) mice with either TNF-alpha-sufficient (TNF-alpha(+/+)) or TNF-alpha-deficient (TNF-alpha(-/-)) bone marrow. After consuming a high-fat diet for 26 wk, metabolic and morphometric characteristics of the animals were analyzed. While there were no differences in terms of relative weight gain, body composition analysis yielded a lower relative adipose and higher relative lean mass in mice lacking TNF-alpha, which was partially explained by reduced epididymal fat pad and liver weight. TNF-alpha(-/-) -->KO mice exhibited enhanced insulin sensitivity compared with that observed in TNF-alpha(+/+)-->KO mice; remarkably, no protection against insulin resistance was provided by transplanting TNF-alpha(-/-) bone marrow in WT mice compared with TNF-alpha(+/+)-->WT. The preserved insulin sensitivity seen in TNF-alpha(-/-)-->KO mice provided protection against the development of hepatic steatosis. Taken together, these data indicate that macrophage-derived TNF-alpha contributes to the pattern and extent of fat accumulation and insulin resistance in diet-induced obesity; however, this contribution is negligible in the presence of host-derived TNF-alpha.
authors.affiliation: Departments of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Bart M
authors.initials: BM
authors.lastname: De Taeye
authors.forename: Tatiana
authors.initials: T
authors.lastname: Novitskaya
authors.forename: Owen P
authors.initials: OP
authors.lastname: McGuinness
authors.forename: Linda
authors.initials: L
authors.lastname: Gleaves
authors.forename: Mousumi
authors.initials: M
authors.lastname: Medda
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Covington
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Vaughan
mesh_terms: D000818:Animals; D004041:Dietary Fats; D005234:Fatty Liver / Q000378:metabolism*; D007333:Insulin Resistance; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009765:Obesity / Q000139:chemically induced / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D004041:Dietary Fats; D014409:Tumor Necrosis Factor-alpha