紫檀芪對於生理時鐘混亂合併高脂飲食誘導肥胖的預防效果

Abstract

生理時鐘會隨著日夜週期，調控生物體內的代謝及生理反應，以適應環境變化。除了中樞生理時鐘之外，體內的腸道菌叢也會根據晝夜節律與攝食時機，而產生相對應的節律變化。當外部的環境因子破壞內在生理時鐘的同步性，就會造成生理時鐘紊亂，並導致廣泛的疾病發生，主要是肥胖、代謝症候群、心血管疾病、腸道菌相混亂等。紫檀芪 pterostilbene (PSB) 為白藜蘆醇的雙甲氧基類似物，多存在於藍莓、葡萄中，在先前的研究中已被證實具有抗肥胖、抗發炎、調節腸道菌相的功效。近年來也被發現可調節小鼠因睡眠剝奪產生的生理變化，但其對於改善時差所致肥胖之功效仍未知。因此，本研究擬透過飲食中 PSB 的介入，以改善生理時鐘紊亂合併高脂飲食所致的肥胖為首要切入方向，進一步達到調節腸道菌相的功效，作為主要實驗目標。根據實驗結果指出，PSB 可顯著降低小鼠的體重、內臟脂肪及腹股溝脂肪重量。經切片染色結果顯示，PSB 可減緩肝臟脂質蓄積，並抑制脂肪細胞增大。血清生化數值方面，PSB 可降低 ZT18 的血膽固醇濃度，減緩瘦素阻抗。而以抗肥胖的機制而言，PSB 可透過改善 SIRT1，及棕色化作用轉錄因子 PPARγ 及 C/EBPβ 之節律，達到促進生熱作用的效果。在生理時鐘調控的部分，PSB 則是透過重塑腹股溝脂肪中 CLOCK 蛋白的節律，以及肝臟中 clock、bmal1 與 rev-erbα的mRNA 表現節律，達到改善代謝混亂的效果。腸道菌相的分析結果顯示，PSB 在高脂飲食合併時差誘導肥胖之小鼠體內，可增加腸道菌相的物種多樣性，也可顯著提高小鼠於 ZT0 的益生菌 Bifidobacterium 豐度、降低病原菌以及與肥胖高度相關的 Erysipelotrichaceae 豐度。而透過 KEGG 路徑分析可知，PSB 可能透過抑制能量代謝路徑以預防肥胖。綜合上述，PSB 對於改善生理時鐘紊亂、以及其所導致的肥胖與代謝異常，具有相當之潛力。

Circadian clock in mammals rhythmically regulates metabolic and physiological processes to adapt the environment. Besides, our gut microbiota fluctuation follows the circadian rhythm and feeding-fasting schedules. Chronic disruption of circadian rhythm may result in adverse health effects, such as obesity, gut dysbiosis, and metabolic disoreder. Therefore, understanding the role of gut microbiome alterations in response to circadian misalignment may provide new opportunities to combat the increasing prevalence of chronic diseases. Pterostilbene (PSB) is a methoxylated analog of resveratrol identified in blueberries, and it has attracted attention because of its microbial regulative ability and anti-obesity effect, especially thermogenesis enhancement. PSB has been previously found to restore rhythms of circadian clock genes in sleep restriction mice, however, the effect of PSB on improving jetlag induced obesity is still scarce. For reasons outlined above, a chronic jet lag model along with high-fat diet feeding to induce obesity in mice model was designed, and the study aimed to investigate the metabolic regulating effect of PSB. Our results showed that PSB could significantly reduce the body weight, visceral fat and inguinal fat weight induced by jetlag in high-fat diet feeding group. The adipocyte hypertrophy and lipid accumulation in liver could also be prevented by PSB. On the other hand, PSB could improve serum cholesterol, combat leptin resistance in mice. We subsequently investigated the related molecular mechanism and found out that PSB could restore the rhythmicity of thermogenesis, clock related protein expression in beige adipose tissue, and also circadian gene expression rhythm in liver. Furthermore, the results of microbiota 16s rDNA analysis suggested that PSB could elevate the microbiota diversity and the abundance of Bifidobacterium, decrease the abundance of obesity-related microbiome such as Erysipelotrichaceae. In addition, energy metabolism functional prediction was altered by PSB based on KEGG pathway analysis. In sum, these scientific evidences demonstrate that PSB can potentially modulate the gut microbial composition and prevent the metabolic disorder caused by circadian misalignment exacerbated obesity.