| Summary: | 碩士 === 國立陽明大學 === 醫學生物技術暨檢驗學系 === 107 === Obesity is a major global health issue, which increases the risk of metabolic diseases such as type 2 diabetes mellitus, cardiovascular diseases, and other metabolic syndrome. Mitochondrial dysfunction reduced mitochondrial mass and ATP production and increased reactive oxygen species production would eventually lead to insulin resistance and metabolic disorders. Our previous studies demonstrate that full-length PINK1 (full length-PINK1, f-PINK1) is cleaved by mitochondrial inner membrane-located presenilin-associated rhomboid-like protein (PARL) to become small PINK1 fragment (s-PINK1), and then released to the cytoplasm during adipocyte differentiation. PARL silencing aborts adipogenesis by inhibiting the expression of peroxisome proliferator-activated receptor gamma (PPARγ), a critical transcription factor for adipocytes differentiation. In addition, expression of hepatic lipogenic enzymes is altered by PARL knockdown, suggesting PARL may mediate lipid metabolism in both hepatocytes and adipocytes. Therefore, we speculated that PARL may have potential to become a therapeutic target by mediating obesity and lipid metabolism. In this context, the present study aimed to explore the effects of PARL knockdown on lipid metabolism by using 3T3-L1 cells and diet-induced obese (DIO) and genetically deficient obese (Leptin145E/145E, 145E) mice. In the in vitro study, expression of hormone-sensitive lipase (HSL) and fatty acid binding protein (FABP4) as well as intracellular lipid contents were slightly decreased in mature adipocytes despite the efficacy of PARL knockdown (KD) was not as expected. In animal study, the data shows that the expression of mitochondrial autophagy-related protein DJ-1 was decreased in potential preventive strategy in eWAT-specific PARL KD HFD mice. In animal model for evaluating the potential therapeutic efficacy of PARL KD in HFD mice, both body weight gain and eWAT ratio were slightly decreased, while the expression of PARL,Parkin and DJ-1 were increased. Besides, adipose DJ-1 and FABP4 were slightly decreased in 145E mice with eWAT-specific PARL KD. Collectively, although PARL is not efficiently inhibited as expected, the expression of lipid metabolism-related proteins HSL, FABP4 and amounts of lipid droplets were slightly decreased in mature adipocytes. Likewise, the physiological and biochemical parameters of DIO and 145E mice are not significantly improved by directly delivering PARL shRNA into eWAT. Nevertheless, the mitochondrial autophagy-related DJ-1 protein was still affected, which awaits further study to uncover the underlying mechanism. Hopefully, our findings provide clues and information for developing novel therapeutic strategies for the management of obesity, and metabolic abnormalities.
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