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Effects of Megestrol Acetate on Circulating Interleukin-15 and Interleukin-18 Concentrations in Healthy Elderly Men

¹ Nutrition, Metabolism, and Exercise Laboratory, Donald W. Reynolds Center on Aging, University of Arkansas for Medical Sciences, and Geriatric Research, Education and Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock.
² Wastl Human Performance Laboratory, Department of Health, Kinesiology, and Leisure Studies, Purdue University, West Lafayette, Indiana.

Address correspondence to Charles P. Lambert, PhD, Nutrition, Metabolism, and Exercise Laboratory, Donald W. Reynolds Center on Aging, University of Arkansas for Medical Sciences, Little Rock, AR 72205. E-mail: lambertcharlesp{at}uams.edu

Background. Interleukin-15 (IL-15) and interleukin-18 (IL-18) are potential regulators of body composition in humans. The authors previously reported that megestrol acetate ingestion causes a large accumulation of adipose tissue and reduces muscle mass. Therefore, the purpose of this investigation was to evaluate the effects of megestrol acetate ingestion on circulating IL-15 and IL-18 concentrations in healthy elderly men.

Methods. All participants received 800 mg of megestrol acetate per day during this 12-week study. Megestrol acetate was combined with testosterone injections (100mg/week), placebo injections, resistance training, or resistance training and testosterone. Resting IL-15 and IL-18 concentrations were measured by enzyme-linked immunosorbent assay at week 0 (pre), week 6 (mid), and week 12 (post).

Results. The time effect for IL-15 was significant (p =.0008), with the mid and post values being significantly greater than the pre value. The change in IL-15 concentration was not significantly related to the change in muscle mass (r = –.31; p >.05), nor was it related to the change in fat mass (r =.17; p >.05). Differences among groups or over time were not significant for IL-18, nor were correlations between pre body weight and pre IL-18 (r = –.03), pre fat mass and pre IL-18 (r =.14), or the change in fat mass and the change in IL-18 (r = –.07).

Conclusions. IL-15 was increased as a result of megestrol acetate ingestion; however, megestrol acetate did not affect circulating IL-18 concentrations, and the change in IL-18 did not correlate with any body composition variables.