Data_Sheet_1_Grape Polyphenols Attenuate Diet-Induced Obesity and Hepatic Steatosis in Mice in Association With Reduced Butyrate and Increased Markers of Intestinal Carbohydrate Oxidation.pdf

A Western Diet (WD) low in fiber but high in fats and sugars contributes to obesity and non-alcoholic fatty liver disease (NAFLD). Supplementation with grape polyphenols (GPs) rich in B-type proanthocyanidins (PACs) can attenuate symptoms of cardiometabolic disease and alter the gut microbiota and its metabolites. We hypothesized that GP-mediated metabolic improvements would correlate with altered microbial metabolites such as short chain fatty acids (SCFAs). To more closely mimic a WD, C57BL/6J male mice were fed a low-fiber diet high in sucrose and butterfat along with 20% sucrose water to represent sugary beverages. This WD was supplemented with 1% GPs (WD-GP) to investigate the impact of GPs on energy balance, SCFA profile, and intestinal metabolism. Compared to WD-fed mice, the WD-GP group had higher lean mass along with lower fat mass, body weight, and hepatic steatosis despite consuming more calories from sucrose water. Indirect and direct calorimetry revealed that reduced adiposity in GP-supplemented mice was likely due to their greater energy expenditure, which resulted in lower energy efficiency compared to WD-fed mice. GP-supplemented mice had higher abundance of Akkermansia muciniphila, a gut microbe reported to increase energy expenditure. Short chain fatty acid measurements in colon content revealed that GP-supplemented mice had lower concentrations of butyrate, a major energy substrate of the distal intestine, and reduced valerate, a putrefactive SCFA. GP-supplementation also resulted in a lower acetate:propionate ratio suggesting reduced hepatic lipogenesis. Considering the higher sucrose consumption and reduced butyrate levels in GP-supplemented mice, we hypothesized that enterocytes would metabolize glucose and fructose as a replacement energy source. Ileal mRNA levels of glucose transporter-2 (GLUT2, SLC2A2) were increased indicating higher glucose and fructose uptake. Expression of ketohexokinase (KHK) was increased in ileum tissue suggesting increased fructolysis. A GP-induced increase in intestinal carbohydrate oxidation was supported by: (1) increased gene expression of duodenal pyruvate dehydrogenase (PDH), (2) a decreased ratio of lactate dehydrogenase a (LDHa): LDHb in jejunum and colon tissues, and (3) decreased duodenal and colonic lactate concentrations. These data indicate that GPs protect against WD-induced obesity and hepatic steatosis by diminishing portal delivery of lipogenic butyrate and sugars due to their increased intestinal utilization.

高糖高脂、低纤维的西方饮食（Western Diet, WD）可诱发肥胖与非酒精性脂肪性肝病（non-alcoholic fatty liver disease, NAFLD）。补充富含B型原花青素（B-type proanthocyanidins, PACs）的葡萄多酚（grape polyphenols, GPs），可缓解心血管代谢疾病症状，并调控肠道菌群及其代谢产物。本研究提出假设：葡萄多酚介导的代谢改善，与肠道菌群代谢产物（如短链脂肪酸（short chain fatty acids, SCFAs））的变化密切相关。为更贴近真实西方饮食模型，本研究选用C57BL/6J雄性小鼠，喂食蔗糖与乳脂含量较高的低纤维饲料，并辅以20%蔗糖水以模拟含糖饮料。该西方饮食模型额外补充1%葡萄多酚（WD-GP组），用以探究葡萄多酚对能量平衡、短链脂肪酸谱及肠道代谢的影响。与仅喂食西方饮食的小鼠相比，WD-GP组小鼠的瘦体重更高，体脂、体重及肝脂肪变性程度更低，尽管其从蔗糖水中摄入的热量更高。间接与直接测热法结果显示，补充葡萄多酚的小鼠脂肪沉积更少，这可能源于其更高的能量消耗，故而相较于西方饮食组小鼠，其能量利用效率更低。补充葡萄多酚的小鼠肠道内嗜黏蛋白阿克曼氏菌（Akkermansia muciniphila）丰度更高，该菌群已被报道可提升能量消耗。结肠内容物的短链脂肪酸检测结果显示，补充葡萄多酚的小鼠体内丁酸（远端肠道的主要能量底物）浓度更低，同时腐败性短链脂肪酸戊酸的含量也有所降低。此外，葡萄多酚补充使乙酸与丙酸的比值降低，提示肝脏脂肪生成作用减弱。鉴于补充葡萄多酚的小鼠蔗糖摄入量更高但丁酸水平更低，本研究假设肠上皮细胞会将葡萄糖与果糖作为替代能量来源。回肠组织中葡萄糖转运蛋白2（glucose transporter-2, GLUT2, SLC2A2）的mRNA水平升高，表明其对葡萄糖与果糖的摄取能力增强。回肠组织中酮己糖激酶（ketohexokinase, KHK）的表达上调，提示果糖分解代谢增强。以下证据支持葡萄多酚诱导的肠道碳水化合物氧化增加：（1）十二指肠丙酮酸脱氢酶（pyruvate dehydrogenase, PDH）的基因表达上调；（2）空肠与结肠组织中乳酸脱氢酶a（lactate dehydrogenase a, LDHa）与LDHb的比值降低；（3）十二指肠与结肠的乳酸浓度降低。综上，本研究数据表明，葡萄多酚可通过增强肠道对生脂性丁酸与糖类的利用，减少其门静脉输送，从而抵御西方饮食诱导的肥胖与肝脂肪变性。