생체시계가 대사기능에 미치는 영향에 관한 연구

Abstract

In mammals, the suprachiamatic nucleus (SCN) of the anterior hypothalamus acts as master circadian rhythm generator, which regulates the molecular organizations of clock oscillations residing in peripheral organs. Molecular circadian clock organization have evolved to adapt day and night environmental changes and to regulate daily physiological occurrences. And one of the important roles of circadian clock is to control daily metabolism in molecular and in systemic levels. 5-AMP activated protein kinase, AMPK, is known as the key cellular energy sensor, which interacts with circadian clock to maintain cellular energetic status. AMPK is involved with various metabolic functions, such as glycolysis, gluconeogenesis and lipid metabolism. Therefore, AMPK has been a key target for developing therapeutic agents to treat metabolic disorders. Metformin is known as the first-in class therapeutic choice for treatment of type 2 diabetes. It has been used since early 1950s, and growing mechanistic studies have identified AMPK as key modulating factor by metformin to decrease hyperglycemia and increase insulin sensitivity. Here, following the previous results of metformins effects on circadian oscillation, I have investigated effects metformin-derived novel chemical compound, H271, on circadian clock. Compared to metformin, I was able to find HL271 was much more potent on AMPK phosphorylation. Under ~1000x lower dosage concentration, HL271 displayed similar molecular effects as compared to metformin. HL271, also modulated molecular circadian clock by increasing degradation rates of PER2 and CYR1 and shortening of Per2 expression dose-dependently. Interestingly, HL271 did not appear to lower blood glucose level as compared to metformin, and the difference of physiological outcome demonstrated that HL271 may act differently in systemic level. Omega-3 fatty acids (FA) are known as essential fatty acids, which mammals require for normal development. Although omega-3 FA is known to elicit health benefits such as improved inflammatory system and, retinal- and neural development, there are paucity of studies regarding the effects of omega-3 FA on circadian clock. By utilizing a unique omega-3 FA animal model, fat-1 transgenic mouse, which converts omega-6 FA to omega-3 FA endogenously, I have investigated effects of omega-3 FA on circadian oscillation. By cross-breeding fat-1 TG mouse with Per2::luc KI mouse and created fat-1/Per2::luc mouse. Fat-1/Per2:luc mouse displayed enhanced Per2 expression in the peripheral tissues, including liver, kidney and submandibular gland. In Fat-1 TG mouse, clock mRNA levels were elevated in liver and kidney, however, clock gene expression in the hypothalamus only displayed shifting of period. Molecular analysis revealed that in Fat-1 TG mouse, the core clock gene, BMAL1 was highly sumoylated and ubiquitinated eliciting enhanced proteosomal-mediated degradation and protein turnover. In accordance with the alteration of clock oscillation in the SCN, Fat-1 TG mouse displayed elongated period during free-running activities in constant darkness (DD) condition. Therefore in the present study, I investigated effects of omega-3 FA on circadian clock system and provided evidence for role of omega-3 FA on molecular circadian clock oscillation, and illustrated possible benefits of omega-3 FA influencing pronounced circadian oscillation which may yield longer life