Per2 Deletion Aggravates Fasting-induced Metabolic Changes in Hepatic Sulfur Containing Substances = Per2 결핍 시 절식에 의해 유도된 간의 황함유 아미노산 대사 변화의 악화

다국어 초록 (Multilingual Abstract)

Short-term fasting of mice involves systemic metabolic remodeling, which has a significant effect on the level of endogenous metabolites. In particular, hepatic lipid accumulation is known to be a representative phenomenon of metabolic adaptation to fasting. Period circadian clock 2 (Per2), known as clock gene, plays a central role in the circadian rhythm to maintain metabolic homeostasis. Sulfur-containing amino acids and metabolites are essential to maintain antioxidant activity and biological function. This study was conducted to examine the effect of Per2 deletion on metabolic changes of sulfur-containing substances in the liver of 24 hours fasted mice. No change in the level of hepatic methionine and cysteine was observed, and that a significant decrease in S-adenosylmethionine (SAM) and glutathione was induced in the liver of wild-type mice after 24 hours fasting. Notably, Per2 deletion significantly aggravated the decrease in SAM and triglyceride accumulation observed in the liver of 24 hours fasted mice. SAM to S-adenosylhomocysteine ratio, an indicator of transmethylation activity, was significantly decreased in the liver of Per2-/- mice compared with that of wild-type mice, which induces the downregulation of expression of phosphatidylethanolamine N-methyltransferase to synthesize phosphatidylcholine. This led to a decrease triglyceride in the serum. Lipid accumulation in the liver increased, which could also be confirmed by Perilipin 2. These results suggest that the decreased export of free fatty acids could contribute to higher lipid accumulation in the liver of Per2-/- mice than that of wild-type mice after 24 hours fasting.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1. Circadian rhythms 1
• 1.2. Short-term fasting 5
• 1.3. Sulfur amino acid metabolism 8
• 1.4. Purpose of this study 10
• 2. Material and Method 11
• 2.1. Experimental animals 11
• 2.2. Determination of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) 11
• 2.3. Determination of SAM and SAH 12
• 2.4. Ultra-high-performance liquid chromatography triple quadrupole mass spectrometry analysis 12
• 2.5. Immunoblotting analysis 13
• 2.6. Determination of triglyceride 14
• 2.7. Statistical analysis 14
• 3. Results 15
• 3.1. Phenotype 15
• 3.2. Liver function 17
• 3.3. Concentrations of hepatic cysteine, glutathione, and taurine 19
• 3.4. Hepatic enzyme associated with glutathione and taurine synthesis 21
• 3.5. Concentrations of hepatic methionine, SAM, SAH, and homocysteine 23
• 3.6. Hepatic enzyme associated with methionine, SAM, SAH, and homocysteine synthesis 25
• 3.7. Hepatic enzyme associated with SAM consumption 27
• 3.8. Concentrations of hepatic lipid accumulation 29
• 3.9. Hepatic enzyme associated with lipid accumulation 31
• 4. Discussion 33
• 5. References 37
• 6. Korean abstract 45