Genetic and pharmacologic blockade of central melanocortin signaling attenuates cardiac cachexia in rodent models of heart failure

Abstract

The central melanocortin system plays a key role in the regulation of food intake and energy homeostasis. We investigated whether genetic or pharmacologic blockade of central melanocortin signaling attenuates cardiac cachexia in mice and rats with heart failure. Permanent ligation of the left coronary artery (myocardial infarction (MI)) or sham operation was performed in wild-type (WT) or melanocortin-4 receptor (MC4R) knockout mice. Eight weeks after surgery, WT-Sham mice had significant increases in lean body mass (LBM; P<0.05) and fat mass (P<0.05), whereas WT-MI did not gain significant amounts of LBM or fat mass. Resting basal metabolic rate (BMR) was significantly lower in WT-Sham mice compared to WT-MI mice (P<0.001). In contrast, both MC4-Sham and MC4-MI mice gained significant amounts of LBM (P<0.05) and fat mass (P<0.05) over the study period. There was no significant difference in the BMR between MC4-Sham and MC4-MI mice. In the second experiment, rats received aortic bands or sham operations, and after recovery received i.c.v. injections of either artificial cerebrospinal fluid (aCSF) or the melanocortin antagonist agouti-related protein (AGRP) for 2 weeks. Banded rats receiving AGRP gained significant amount of LBM (P<0.05) and fat mass (P<0.05) over the treatment period, whereas banded rats receiving aCSF did not gain significant amounts of LBM or fat mass. These results demonstrated that genetic and pharmacologic blockade of melanocortin signaling attenuated the metabolic manifestations of cardiac cachexia in murine and rat models of heart failure.

Figure 1

Survival to the end of the 8-week study period after myocardial infarction. WT-Sham, 19 of 21 survived; MC4-Sham, 17 of 20 survived; WT-MI, 14 of 34 survived; MC4-MI, 11 of 19 survived. *P<0·001 versus WT-Sham and MC4-Sham mice.

Figure 2

MC4RKO mice resist cardiac cachexia and increase LBM accumulation after myocardial infarction. Data are mean±s.e.m. ***P<0·001 versus WT-MI.

Figure 3

MC4RKO resist an increase in energy expenditure in response to CHF. Basal oxygen consumption during the light phase (0900–1700 h) is increased in WT-MI mice (n=15) compared with WT-Sham mice (n=19). Basal oxygen consumption is not increased in MC4-MI mice (n=8) compared with MC4-Sham mice (n=10). Data are mean±s.e.m. ^aP<0·001 versus WT-MI, ^bP<0·05 versus WT-Sham.

Figure 4

Effect of AGRP versus aCSF administration on the accumulation of LBM in sham-operated and aortic-banded rats. Data are mean±s.e.m. *P<0·05 versus Band-aCSF; **P<0·01 versus Band-aCSF; ***P<0·001 versus Band-aCSF.