Expression patterns of hepatic genes involved in lipid metabolism in cows with subclinical or clinical ketosis

摘要

Dairy cows with ketosis are characterized by highblood concentrations of ketone bodies and hepatic lipidmetabolism disorder. The discrepancies in the abundanceof mRNA encoding a variety of hepatic candidategenes in varying degrees of ketotic cows representspecific responses of the liver to the challenge of fattyacids and ketone bodies. Importantly, the expressiondisorder of hepatic genes involved in lipid metabolismplays a promoting role in the onset and progressionof ketosis. Thus, the aim of this study was to investigatethe expression patterns of genes involved inthe hepatic fatty acids uptake, transport, activation,β-oxidation, synthesis, and esterification in the cowswith subclinical ketosis (SCK) or clinical ketosis (CK).Twenty-four cows were selected into control [n = 8,β-hydroxybutyrate (BHB) ≤0.6 mM], SCK (n = 8, 3.0> BHB ≥ 1.2 mM), and CK (n = 8, BHB ≥3.0 mM)groups according to the blood BHB concentration andclinical symptoms. The accumulation of hepatic lipid, asindicated by triglycerides (TG) contents and Oil Red Oand hematoxylin and eosin staining, was pronouncedlyexacerbated in the tCK group compared with the controland SCK groups. The hepatic mRNA expression offatty acids transport and activation genes, liver fattyacid-binding protein (FABP1) and long-chain acyl-CoAsynthetase 1 (ACSL1), were both significantly higher inthe SCK and CK groups than in the control group. Theexpression levels of peroxisome proliferator-activatedreceptor α (PPARA) and its target genes, carnitinepalmitoyltransferase 1A (CPT1A) and carnitine palmitoyltransferase2 (CPT2), were significantly elevated inthe SCK group but reduced in the CK group comparedwith control group. Furthermore, the gene expressionlevel of sterol regulatory element-binding protein 1(SREBP1) and the protein expression level of sterolregulatory element-binding protein 1c and its targetgenes acetyl-CoA carboxylase 1 (ACC1), fatty acidsynthase (FAS), and stearoyl-CoA desaturase-1 (SCD1)and TG synthesis genes diacylglycerol acyltransferase 1(DGAT1) and diacylglycerol acyltransferase 2 (DGAT2)were significantly higher in the CK group relative to thecontrol group. In short, the present data indicated thathepatic fatty acids uptake, transport, and activationare significantly increased in cows with SCK and CK,hepatic fatty acids β-oxidation is significantly increasedin SCK cows but markedly decreased in CK cows, andhepatic fatty acids and TG synthesis are significantlyincreased in CK cows, thereby inducing hepatic steatosisin CK cows.