饲料中添加胆酸钠对大口黑鲈生长及糖代谢的影响

为探究胆酸(Cholic acid, CA)作为饲料添加剂对大口黑鲈(Micropterus salmoides)生长及糖代谢的影响, 实验以饲料中添加300 mg/kg胆酸钠(Sodium cholate, CAS)作为胆酸钠组, 以不添加胆酸钠作为对照组。在饲养8周后, 分析胆酸钠对大口黑鲈生长性能、肠道菌群、糖代谢及与糖代谢相关酶的活性和基因表达的影响。结果显示: 与对照组相比, 胆酸钠组中大口黑鲈的生长指数和体成分的变化均没有显著差异; 胆酸钠组中大口黑鲈的肠道菌群组成无显著差异; 胆酸钠组中肝糖原含量和肝中糖原合成酶(Glycogen synthase, GCS)的活性显著增加, 肝中糖原分解酶糖原磷酸化酶a(Glycogen phosphorylase a, GPa)活性无显著变化, 而胆酸钠组中肌糖原含量、肌肉GCS与GPa的活性无显著差异; 胆酸钠显著促进肝中糖异生途径中果糖-1,6-二磷酸酶(Fructose-1,6-bisphosphatase, FBPase)和葡萄糖-6-磷酸酶(Glucose-6-phosphatase, G6Pase)基因的表达; 胆酸钠显著降低肝中糖酵解基因丙酮酸激酶(Pyruvate kinase, PK)和肌肉中己糖激酶(Hexokinase, HK)基因的表达; 同时, 研究还发现饲料中胆酸钠的添加可以显著降低肝中胆汁酸受体法尼醇受体(Farnesoid X receptor, FXR)基因的表达量, 而不改变肠道FXR的表达量。研究表明: 在饲料中添加300 mg/kg胆酸钠可以促进大口黑鲈肝脏糖异生, 抑制肝脏和肌肉糖酵解, 并促进鱼体肝糖原的合成。这些糖代谢的变化与肠道菌群没有直接关系, 但可能与肝中FXR的表达量降低有关。

EFFECTS OF SODIUM CHOLATE ON GROWTH AND GLUCOSE METABOLISM OF LARGEMOUTH BASS (MICROPTERUS SALMOIDES)

Cholic acid (CA) is the main bile acid (BAs) in fish. To explore the effects of cholic acid on the growth and glucose metabolism of largemouth bass (Micropterus salmoides), we formulated an experimental diet by adding 300 mg/kg sodium cholate (CAS) in the control diet for an 8-week trial before analyzing the effects of CAS on the growth, intestinal microbiota, gene expression of glucose metabolism and bile acid receptor Farnesoid X receptor (FXR) of largemouth bass. The results showed that CAS had no significant effects in the growth index, including weight gain rate (WGR), condition factor (CF), carcass ratio (CR), viscerosomatic index (VSI), hepatosomatic index (HSI) and mesenteric fat index (MFI). CAS also did not affect the body composition including moisture, crude protein, crude lipid and crude ash of the largemouth bass, and it did not regulate the intestinal microbiota of the largemouth bass. Sodium cholate promoted glycogen synthesis and activity of glycogen synthase (GCS) in liver but not in the muscle without impacting the activity of glycogen phosphorylase a (GPa) in the liver. Sodium cholate significantly promoted the expression of fructose-1,6-bisphosphatase (FBPase), glucose-6-phosphatase (G6Pase), and pyruvate kinase (PK) in liver, and it significantly decreased hexokinase (HK) genes in muscle. Moreover, sodium cholate significantly inhibited the expression of the bile acid receptor Farnesoid X receptor (FXR) in the liver, without changing the expression of intestinal FXR. These results suggest that 300 mg/kg CAS did not affect growth and body index of largemouth bass, and that CAS may regulate glucose metabolism via liver FXR expression.