Metabolic diseases,including obesity and diabetes,etc.,are a spectrum of life-threatening diseases,in which metabolic dysfunction is a hallmark.It is in urgent need of new insights for the prevention and treatment of the diseases.Circadian rhythm is fundamental in health and wellbeing.Research on circadian rhythm has shed light on metabolic homeostasis,thereby giving birth to a new direction,named circadian metabolism.Here,we summarize recent advances in circadian metabolism regarding organelle regulation,inter-and intra-organ crosstalk of circadian clocks,as well as molecular mechanisms of time-restricted eating,and propose circadian communication across the hierarchy of central and peripheral clocks as a key concept for understanding the temporal regulation of metabolism.The underlying mechanisms on circadian communication should shed light on precision medicine in a temporal resolution and provide guidelines on when to eat and when to exercise for the prevention of metabolic diseases.

Objective To explore whether hepatocyte Perilipin-2(Plin2)is involved in the development of fatty liver related to comparative gene identification-58(CGI-58)deficiency mice and compare the effects of Plin2 and Plin3 on lipid droplet formation and lipid accumulation.Methods Based on CGI-58Flox/Flox mice as animal model,the adeno-associated viruses targeting mouse liver,CGI-58 knockout and Plini2 knockdown were achieved by co-expression Cre protein and micro-RNA targeting Plin2(Mi-KD).Then CGI-58 deficiency mice were used as control(NC)to detect the differences in metabolic phenotype and liver pathology.AML-12 mouse hepatocytes were used as cellular model and interfered with siRNA to achieve Plin2/Plin3 knockdown in AML-12 cells.Lipid droplet formation and lipid accumulation were compared with Bodipy staining and enzyme colorimetry in basal condition or lipid-overloaded condition(OA inducement)after Plin2/Plin3 knockdown.Results Plin2 knockdown(Mi-KD)reduced PLIN2 protein level by＞99％in mouse livers.Mi-KD decreased hepatomegaly(P=0.019 5)and liver injury(P=0.000 4),while reduced the histological NAS score(P=0.000 2)and hepatic triglyceride content(P=0.016 6)in the CGI-58 deficiency female mice.Mi-KD prevented microvesicular hepatic steatosis in the CGI-58 deficient female mice.Plin3 knockdown significantly reduced the triglyceride content in basal condition of hepatocytes(P=0.001 4),and Plin2 knockdown just showed a decreased trend.Plin2 or Plin3 knockdown significantly reduced the triglyceride content separately in lipid-overloaded hepatocytes(P＜0.05).Conclusion Hepatocyte Plin2 is essential in the development of microvesicular hepatic steatosis caused by CGI-58 deficiency.Both Plin2 and Plin3 are involved in lipid droplet formation and lipid accumulation in hepatocytes,and Plin3 shows a stronger effect.