Is obesity an inflammatory disease?

Abstract

Background: Most obese individuals have elevated concentrations of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), markers of inflammation closely associated with diabetes, hypertension, and stroke.

Hypothesis: Obesity is a low-grade inflammatory disease, and Roux-en-Y gastric bypass (RYGB) reduces biochemical markers of inflammation and modifies gene expression in hypothalamic food intake/energy-related nuclei and subcutaneous abdominal fat (SAF).

Methods: Obesity was induced in 24 3-week-old Sprague Dawley pups fed a high-energy diet (HED). Three groups (n = 8/group) were studied: RYGB, sham-operated pair-fed, and sham-operated ad libitum HED. Controls were nonobese rats fed chow (n = 6). Rats were killed 10 days after operation, and blood was collected to measure corticosterone and SAF and mesenteric fat to measure IL-6, TNF-alpha, and corticosterone. Total mRNA from arcuate nucleus and SAF purified for gene expression profiling. Data were analyzed with analysis of variance, Mann-Whitney test, and t test.

Results: Before operation, the body weight of the obese groups was 493 +/- 7 g and control = 394 +/- 12g. The 10-day postoperative weight was RYGB = 417 +/- 21 g, pair-fed = 436 +/- 14 g, and ad libitum HED = 484 +/- 15 g. Mesenteric and SAF weight decreased in RYGB. Mesenteric/SAF ratio of IL-6, TNF-alpha, corticosterone, and gene profiling showed decrease of inflammation after RYGB.

Conclusions: Gastric bypass reduces biochemical markers of inflammation, suggesting that obesity is an inflammatory condition.