Mitochondria undergo architectural/functional changes in response to metabolic inputs. How this process is regulated in physiological feeding/fasting states remains unclear.
Researchers show that mitochondrial dynamics (notably fission and mitophagy) and biogenesis are transcriptional targets of the circadian regulator Bmal1 in mouse liver and exhibit a metabolic rhythm in sync with diurnal bioenergetic demands.
Bmal1 loss-of-function causes swollen mitochondria incapable of adapting to different nutrient conditions accompanied by diminished respiration and elevated oxidative stress.
Consequently, liver-specific Bmal1 knockout (LBmal1KO) mice accumulate oxidative damage and develop hepatic insulin resistance.
Restoration of hepatic Bmal1 activities in high-fat-fed mice improves metabolic outcomes, whereas expression of Fis1, a fission protein that promotes quality control, rescues morphological/metabolic defects of LBmal1KO mitochondria.
Interestingly, Bmal1 homolog AHA-1 in C. elegans retains the ability to modulate oxidative metabolism and lifespan despite lacking circadian regulation.
These results suggest clock genes are evolutionarily conserved energetics regulators.