Monday, February 18, 2008

Fatter and Sicker: Obesity weakens Immunity

This paper reminds me of an old joke: when a patient, having received a dubious diagnosis, asks for a second opinion, the doctor replies 'you're also ugly'. But seriously, folks, this paper suggests that the rise of obesity in the US could have unanticipated consequences for infectious disease. To test the effect of obesity on immunity, Amar and colleagues infected fat or lean mice with Porphyromonas gingivalis, a bacterium that causes gum disease. Mice fed with high fat food for 4 months weighed about 30% more than the mice on normal chow.
They found that mice with diet-induced obesity (DIO) suffered a greater loss of alveolar (gum) bone than did lean mice. P. gingivalis infection induced less inflammatory cytokine release in DIO mice than in lean mice. Macrophages cultured from DIO mice showed significantly reduced activation by LPS of the intracellular signaling molecule NF-kappaB (a chromosome immunoprecipitation is shown, from Fig. 8). Oddly, C-reactive protein, a marker of inflammation, is reported elevated in the bloodstream of obese humans. Do you have a 'second opinion'?
Amar et al., Diet-induced obesity in mice causes changes in immune responses and bone loss manifested by bacterial challenge. Proc Natl Acad Sci U S A. 2007 Dec 18;104(51):20466-71.

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