Potential linkages between circadian rhythm and membrane lipids: timekeeper and bilayer

Membrane lipids play significant roles in cellular functions, including those controlled by circadian machinery (e.g., membrane transport). Membranes have been overlooked during the investigation of circadian mechanisms. The findings of previous studies suggest that membrane action potentials and phospholipid composition exhibit daily oscillations, which involve changes in fatty acid saturation and chain length, and are subjected to fatty chain remodeling. Thus, it is possible that membranes are affected by oscillatory output rhythms from cellular autonomous clocks. The regulation of lipid chain length and degree of unsaturation, along with resulting changes in membrane lipid polymorphic properties, may serve as the basis of an important mechanism that mediates the circadian regulation of various membrane-associated processes. However, direct evidence indicating that membrane lipid oscillations are part of the circadian machinery has yet to be reported. This review updates the current understanding of potential connections between the membrane bilayer and the circadian clock, with important implications for circadian rhythm disorders and related chronic diseases, such as obesity, diabetes, and cardiovascular disease.