Aim: 

Metabolic Syndrome (MS) is associated with obesity, and involves risk factors for type II diabetes mellitus and arteriosclerosis, due in part to inflammatory processes. Indeed, obesity is regarded as a "low grade inflammatory process" in which macrophages may play an important role. Since exercise (which also modulates the inflammatory response) has been reported to be beneficial for obese people, the aims of this investigation were: (1) to evaluate differences between obese Zucker rats (a good experimental animal model to study MS) and control (Lean) rats in the number and interleukin (IL)-1b (a pro-inflammatory cytokine) producing capacity of peritoneal macrophages, and (2) to evaluate the effects of an exercise training protocol (running on a treadmill for 35 minutes at 35 cm/sec, 5 days per week, for 16 weeks) and an acute bout of exercise on macrophages in the obese rats.

Methods: 

IL-1b production (measured by ELISA) was evaluated in the supernatant of macrophages cultured (37°C, 5% CO₂, and 100% RH) for 24 hours both in the presence (activated macrophages) and in absence of lipopolysaccharide (LPS).

Results: 

Although the obese rats presented fewer peritoneal macrophages than non-obese rats, non-activated macrophages from obese rats released higher concentrations of IL-1b. However, IL-1b production by activated macrophages was greater in non-obese rats. In addition, LPS-activated macrophages from obese rats increased the release of IL-1b in response to both the acute exercise and the exercise training protocol.

Conclusion: 

It is concluded that obese Zucker rats have an impaired inflammatory macrophage response. In addition, exercise training improves the lowered LPS-induced release of IL-1b in macrophages of obese rats.

This work was partially supported by grants PRI 06A172 (Junta de Extremadura) and GRU08039, and by a studentship from the Junta de Extremadura, Spain.