Endocrine Abstracts

Our group has recently shown that interleukin-6 (IL-6) gene knockout mice develop mature onset obesity, and that IL-6 treatment enhances oxygen consumption in resting rodents via an effect on the CNS. Moreover, IL-6 is produced and released in large quantities from skeletal muscle during exercise. We have now investigated the effects of IL-6 deficiency during exercise in IL-6 gene knockout mice.
Male 4-5 months-old IL-6 gene knockout mice on C57BL/6 background (n=6) and littermate wild-type mice (n=6) were exercised on a treadmill. In one protocol, the mice run at a fixed speed of 10 m/min with an inclination of 0, 10, or 20 degrees, and the energy expenditure was measured as oxygen consumption (VO2) with indirect calorimetry. To investigate endurance capacity a protocol with increasing speed at 10 degree inclination was used.
The IL-6 knockout mice reached significantly lower VO2-levels at 10 and 20 degree inclinations compared to the wild-type mice and seemed to have diminished endurance capacity, as only 5/6 (33 %) were still running after 25 min vs.5/6 (83 %) were running in the wild-type group. During the endurance test, the IL-6 concentration in serum increased in the wild-type mice, but were undetectable in the IL-6 knock-out mice.
In summary, the release of endogenous IL-6 from skeletal muscle during exercise may be of importance for exercise induced increase in energy expenditure as well as for endurance.