In this study, senescent-prone rats were subjected to melatonin between 1 and 10 months of age and their brains investigated for signs of mitochondrial aging. The very promising result for those currently supplementing or planning to supplement with melatonin was that Melatonin administration between 1 and 10 months of age completely prevented the mitochondrial impairment, [...]

This study in the Journal of Pineal Research shows that melatonin has a variety of interesting and potentially beneficial effects regarding the modulation of mitochondrial metabolism.

Melatonin protects the mitochondria from oxidative damage reducing oxygen consumption, membrane potential, and superoxide anion production.
J Pineal Res. 2008 Nov 19; PMID: 19054298
Lopez A, Garcia JA, Escames G, Venegas C, [...]