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Cancer patients undergoing chemotherapy often experience anorexia and weight loss that substantially deteriorates overall health, reduces treatment tolerance and quality of life, and worsens oncologic outcomes. There are currently few effective therapeutic options to mitigate these side effects. The central melanocortin system, which plays a pivotal role in regulating appetite and energy homeostasis, presents a logical target for treating anorexia and weight loss. In this preclinical study, we evaluated the efficacy of TCMCB07, a synthetic antagonist of the melanocortin-4 receptor, in mitigating anorexia and weight loss in several rat models of chemotherapy: cisplatin, 5-fluorouracil, cyclophosphamide, vincristine, doxorubicin, and a combination of irinotecan and 5-fluorouracil. Our results indicate that peripheral administration of TCMCB07 improved appetite, stabilized body weight, preserved fat and heart mass, and slightly protected lean mass after multiple cycles of chemotherapy. Furthermore, combining TCMCB07 with a growth differentiation factor 15 antibody enhanced treatment effectiveness. Similar effects from TCMCB07 treatment were observed in a rat tumor model following combination chemotherapy. No notable adverse effects nor increased chemotherapy-related toxicities were observed with TCMCB07 treatment. These findings suggest that peripheral administration of TCMCB07 holds promise as a therapeutic approach for alleviating chemotherapy-induced anorexia and weight loss, potentially benefiting numerous patients undergoing chemotherapy. [ABSTRACT FROM AUTHOR]

Cachexia, a devastating wasting syndrome characterized by severe weight loss with specific losses of muscle and adipose tissue, is driven by reduced food intake, increased energy expenditure, excess catabolism, and inflammation. Cachexia is associated with poor prognosis and high mortality and frequently occurs in patients with cancer, chronic kidney disease, infection, and many other illnesses. There is no effective treatment for this condition. Hypothalamic melanocortins have a potent and long-lasting inhibitory effect on feeding and anabolism, and pathophysiological processes increase melanocortin signaling tone, leading to anorexia, metabolic changes, and eventual cachexia. We used 3 rat models of anorexia and cachexia (LPS, methylcholanthrene sarcoma, and 5/6 subtotal nephrectomy) to evaluate efficacy of TCMCB07, a synthetic antagonist of the melanocortin-4 receptor. Our data show that peripheral treatment using TCMCB07 with intraperitoneal, subcutaneous, and oral administration increased food intake and body weight and preserved fat mass and lean mass during cachexia and LPS-induced anorexia. Furthermore, administration of TCMCB07 diminished hypothalamic inflammatory gene expression in cancer cachexia. These results suggest that peripheral TCMCB07 treatment effectively inhibits central melanocortin signaling and therefore stimulates appetite and enhances anabolism, indicating that TCMCB07 is a promising drug candidate for treating cachexia. [ABSTRACT FROM AUTHOR]

In response to illness, animals subvert normal homeostasis and divert their energy utilization to fight infection. An important and unexplored feature of this response is the suppression of physical activity and foraging behavior in the setting of negative energy balance. Inflammatory signaling in the hypothalamus mediates the febrile and anorectic responses to disease, but the mechanism by which locomotor activity (LMA) is suppressed has not been described. Lateral hypothalamic orexin (Ox) neurons link energy status with LMA, and deficiencies in Ox signaling lead to hypoactivity and hypophagia. In the present work, we examine the effect of endotoxin-induced inflammation on Ox neuron biology and LMA in rats. Our results demonstrate a vital role for diminished Ox signaling in mediating inflammation-induced lethargy. This work defines a specific population of inflammation-sensitive, arousal-associated Ox neurons and identifies a proximal neural target for inflammatory signaling to Ox neurons, while eliminating several others. [ABSTRACT FROM AUTHOR]

Skeletal muscle mitochondrial dysfunction and insulin resistance occur in chronic kidney disease. Ghrelin is a gastric hormone previously shown to enhance muscle mitochondrial enzyme activities and AKT-mediated insulin signaling independent of food intake in healthy rats. Here we determined the impact of ghrelin treatment on anorexia, skeletal muscle mitochondrial oxidative capacity, AKT phosphorylation as a measure of insulin signaling, and lean body mass in a rat model of chronic kidney disease. Ghrelin infusion promoted higher food intake and lean body mass. Further, although muscle mitochondrial enzyme activities were low in the rats with CKD (chronic kidney disease), they normalized with ghrelin treatment, a change that was consistent with the increase in the transcript levels of regulators of mitochondrial biogenesis and lipid metabolism. This was associated with a lower muscle triglyceride content and higher AKT phosphorylation. Pair-feeding showed that mitochondrial effects of ghrelin are independent of changes in food intake, whereas combined ghrelin treatment and higher food intake were needed to enhance AKT phosphorylation. Thus, ghrelin-induced muscle mitochondrial changes and lower tissue triglycerides could favor insulin action and muscle anabolism in the presence of improvement in food intake. Our study shows that combined effects of ghrelin on appetite and muscle mitochondria improve muscle metabolic and nutritional alterations in chronic kidney disease. This could have potential beneficial impact on patient morbidity and survival. [ABSTRACT FROM AUTHOR]

Signaling via the type 4-melanocortin receptor (MC4R) is an important determinant of body weight in mice and humans, where loss of function mutations lead to significant obesity. Humans with mutations in the MC4R experience an increase in lean mass. However, the simultaneous accrual of fat mass in such individuals may contribute to this effect via mechanical loading. We therefore examined the relationship of fat mass and lean mass in mice lacking the type-4 melanocortin receptor (MC4RKO). We demonstrate that MC4RKO mice display increased lean body mass. Further, this is not dependent on changes in adipose mass, as MC4RKO mice possess more lean body mass than diet-induced obese (DIO) wild type mice with equivalent fat mass. To examine potential sources of the increased lean mass in MC4RKO mice, bone mass and strength were examined in MC4RKO mice. Both parameters increase with age in MC4RKO mice, which likely contributes to increases in lean body mass. We functionally characterized the increased lean mass in MC4RKO mice by examining their capacity for treadmill running. MC4R deficiency results in a decrease in exercise performance. No changes in the ratio of oxidative to glycolytic fibers were seen, however MC4RKO mice demonstrate a significantly reduced heart rate, which may underlie their impaired exercise performance. The reduced exercise capacity we report in the MC4RKO mouse has potential clinical ramifications, as efforts to control body weight in humans with melanocortin deficiency may be ineffective due to poor tolerance for physical activity. [ABSTRACT FROM AUTHOR]