OPA1 and obesity due to melanocortin 4 receptor deficiency: Though the precise molecular mechanisms through which melatonin regulates OPA1 and DRP1 protein levels were beyond the scope of this study, our findings provide preliminary insight into the role of melatonin in the regulation of BAT mitochondrial fission-fusion, which may play a key role in the deregulation of BAT thermogenic function in obesity and consequently could be novel future therapeutic targets.