Visceral Fat Adipokine Secretion Is Associated With Systemic Inflammation in Obese Humans

TLDR

Excess visceral fat is linked to noninfectious inflammation, yet its causal role in metabolic disease remains uncertain. The study aimed to test whether visceral fat secretes inflammatory adipokines into portal blood by measuring arteriovenous differences in 25 severely obese patients undergoing gastric bypass. Researchers obtained portal vein and radial artery blood samples during surgery to quantify adipokine concentration differences across visceral fat. Portal vein IL‑6 was about 50 % higher than radial artery and correlated with systemic CRP, leptin was ~20 % lower, while other adipokines were unchanged, indicating visceral fat is a key IL‑6 source linked to systemic inflammation in abdominal obesity.

Abstract

Although excess visceral fat is associated with noninfectious inflammation, it is not clear whether visceral fat is simply associated with or actually causes metabolic disease in humans. To evaluate the hypothesis that visceral fat promotes systemic inflammation by secreting inflammatory adipokines into the portal circulation that drains visceral fat, we determined adipokine arteriovenous concentration differences across visceral fat, by obtaining portal vein and radial artery blood samples, in 25 extremely obese subjects (mean ± SD BMI 54.7 ± 12.6 kg/m2) during gastric bypass surgery at Barnes-Jewish Hospital in St. Louis, Missouri. Mean plasma interleukin (IL)-6 concentration was ∼50% greater in the portal vein than in the radial artery in obese subjects (P = 0.007). Portal vein IL-6 concentration correlated directly with systemic C-reactive protein concentrations (r = 0.544, P = 0.005). Mean plasma leptin concentration was ∼20% lower in the portal vein than in the radial artery in obese subjects (P = 0.0002). Plasma tumor necrosis factor-α, resistin, macrophage chemoattractant protein-1, and adiponectin concentrations were similar in the portal vein and radial artery in obese subjects. These data suggest that visceral fat is an important site for IL-6 secretion and provide a potential mechanistic link between visceral fat and systemic inflammation in people with abdominal obesity.