Food & Function：壳寡糖对小鼠非酒精性脂肪肝的改善作用及机制

     广东药科大学郭姣、苏政权教授团队在Food & Function发表题目为“Ameliorating the effect and mechanism of chitosan oligosaccharide on nonalcoholic fatty liver disease in mice”研究论文（壳寡糖对小鼠非酒精性脂肪肝的改善作用及机制）。

摘要：

      此前的研究发现，壳寡糖（COST）可以缓解非酒精性脂肪肝（NAFLD）患者的临床症状。 我们打算用不同浓度的COST对高脂肪饮食诱发的NAFLD小鼠进行干预。 通过生理生化指标观察COST对NAFLD模型小鼠的基本作用。 采用16S rRNA测序技术分析肠道微生物群，进一步分析短链脂肪酸（SCFA）含量。采用Western blot和RT-PCR检测COST对NAFLD小鼠肝脏PI3K/AKT/mTOR信号通路的影响。 结果发现，COST高剂量组可减轻NAFLD小鼠体重，改善血脂异常，减轻肝脏病变，且COST对NAFLD小鼠有治疗作用。 16S rRNA 测序分析表明，COST 可以增加 NAFLD 小鼠肠道微生物群的多样性。NAFLD 小鼠中 SCFA 的下调被逆转。 WB和RT-PCR结果显示PI3K/AKT/mTOR信号通路参与NAFLD小鼠的发生发展。 COST 通过抑制肝脏 DNL 改善 NAFLD 小鼠的肝脏脂质代谢。COST可增加产热蛋白、UCP1和PGC-1α基因的表达；PI3K/AKT/mTOR信号通路在蛋白质和基因水平上受到抑制。本研究揭示，COST通过肠道微生物群和SCFAs调节脂质毒性引起的相关炎症因子的表达，改善HFD诱导的NAFLD小鼠的肝脏脂质代谢，为开发有效、低毒的治疗NAFLD药物奠定了基础。

研究结果：

3.1 COST可改善NAFLD小鼠的症状

Fig. 1 Average weekly food intake (a) and weight gain (b) in NAFLD mice. COST affected insulin (c) and fasting blood glucose levels (d), area under glucose curve (e) and serum glucose curve of the oral glucose tolerance test (f). COST affected serum levels of FFA (g), TG (h), TC (h), LDL-C (h) and HDL-C (h) in each group. COST affected serum levels of TNF-α, IL-1β, IL-6 and IL-10 in each group (i). Influence of COST on the serum antioxidant function indices CAT and T-AOC of mice in each group (j). At the end of the experiment, serum LPS histogram of mice in each group and HE staining of ileal and colon sections of mice (k) (200×, scale 50 μ.). (n = 6, mean ± SEM. Note: Compared with model group, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.)

3.2.COST可改善NAFLD小鼠的肝损伤，调节肝脏脂质代谢紊乱

Fig. 2 COST affected the changes of serum liver function indices AST and ALT in each group (a) (n = 6, mean ± SEM). Direct morphology and pathological section of livers of mice in each group after COST administration (b) (n = 6, 200×, scale 50 μ. mean ± SEM). COST affected the levels of TG, TC, HDL-C and LDL-C in the livers of mice in each group (c) (n = 6, mean ± SEM). Effect of COST on the expression of SREBP-1c, ACC, FAS and SCD-1 proteins in livers of mice in the NAFLD group (d) (n = 3, mean ± SEM). Effect of COST on the relative expression levels of TNF-α, IL-6, IL-1β and IL-10 genes in the livers of mice in the NAFLD group (e) (n = 6, mean ± SEM). (Note: compared with the model group, *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.)

3.3.COST可改变NAFLD患者的脂肪比例，促进褐色脂肪脂质氧化，提高脂质代谢水平

Fig. 3 COST affected the adipose tissue proportion, brown adipose tissue coefficient, epididymal white adipose tissue coefficient, perirenal white adipose tissue coefficient and subcutaneous white adipose tissue coefficient in each group (a) (n = 6, mean ± SEM). H&E staining of brown adipose tissue (b), epididymal white adipose tissue (c), perirenal white adipose tissue (d), and subcutaneous white adipose tissue (e) after COST treatment. (200×, scale 50 μ.) (n = 6, mean ± SEM). Effect of COST on UCP1 and PGC-1α (f–h) protein levels (n = 3, mean ± SEM) and gene level expression (i and j) in the brown fat of mice in the NAFLD group (n = 6, mean ± SEM). (Note: Compared with the model group, *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.)

3.4.COST给药可改变NAFLD小鼠肠道微生物群的组成，并提高肠道微生物群多样性

Fig. 4 Venn diagram of the OTU sequence of each group after the experiment (a). Analysis diagram of the α diversity index of each group after the experiment, dilution curve (b), observed species index (c), ACE index (c), Chao1 index (c), Shannon index (c), and Simpson index (c). Analysis of β diversity in each group after the experiment (d). The relative abundance of the top 10 species at phylum (e), species (f) and genus (g) levels, the relative abundance graph of Akkermansia, Ligilactobacillus and Desulfovibrio predominant flora (h), and the ratio of Firmicutes to Bacteroidetes (i). (n = 6, mean ± SEM. Note: Compared with the model group, *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.)

3.5.COST给药可以增加优势细菌的丰度，并可能逆转NAFLD小鼠SCFA降解的趋势

Fig. 5 Histogram of the LDA effect values of each group (a) and taxonomic branch diagram (b) of each group after the experiment. Short-chain fatty acids in each group after the experiment (c). (n = 6, mean ± SEM. Note: compared with the model group, *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.)

3.6.COST干预可抑制PI3K/AKT/mTOR信号通路，提高NAFLD肝脏的脂质代谢水平

Fig. 6 Effect of COST on PI3K/Akt/mTOR signaling pathway protein expression in NAFLD mice (a) (n = 3, mean ± SEM). Effect of COST on PI3K/Akt/mTOR mRNA expression in NAFLD mice (b) (n = 6, mean ± SEM). (Note: compared with the model group, *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.)

原文链接：

DOI https://doi.org/10.1039/D3FO03745B