Circadian Regulation of Apolipoprotein in Brain: Implications for Lipid Metabolism and Diseases

Abstract

The circadian clock is a 24-hour cycle within the body that regulates various factors, including sleep, body temperature, and hormone secretion. It allows the body to adjust to the light and dark cycle. Disruptions to the circadian rhythm are important risk factors for many diseases, including neurodegenerative illnesses. The central clock is controlled by the clock genes in the suprachiasmatic nucleus (SCN) of the brain, and one of the main functions of the circadian clock is to regulate lipid metabolism. There has been a lack of investigation on the circadian regulation of lipid metabolism-related apolipoprotein genes in the brain; thus, this study sought to summarize the rhythmic expression of clock genes and lipid metabolism-related apolipoprotein genes within the SCN of Mus musculus. Out of the 20 apolipoprotein genes that were studied by the published database, all 9 genes were highly expressed in the SCN. Most of the 6 genes showed rhythmic expression in the brain of mice, suggesting that the master clock might regulate them. The results, therefore, reveal a potential target for preventing and treating circadian disorders. We summarized most studies of lipid-related apolipoprotein genes within limited locations of the SCN and brain to further understand how disordered cerebral lipid metabolism causes multiple brain diseases and disorders. We reviewed recent studies, determined the unexplored questions, and identified a potential direction for further research.

Rhythmic variation in proteomics: challenges and opportunities for statistical power and biomarker identification

“…For example, CFH within the complement cascade has been iden fied as a biomarker of Alzheimer's, 36,37 , as have the fibrinolysis pathway proteins FGA and FGB, 38,39 and indeed as has AZGP1. 40 Three apolipoproteins were also iden fied as rhythmic; the genes governing the expression of many of this family of proteins have previously been demonstrated to show rhythmic expression 41 and these results are also consistent with lipid metabolism more broadly having a circadian component; 42 40 Apolipoproteins have also been directly linked to Alzheimer's disease; especially with regard to APOE4. 43,44 It should be noted that in some cases, where rhythmic proteins are iden fied as biomarkers of a condi on, there is a risk that they are in fact biomarkers of generic circadian dysregula on, and are not specific to the disease in ques on.…”