Effect Of Α-Lipoic Acid On Liver Lipid Metabolism In Rats And Its Mechanism

Abnormal fat metabolism refers to abnormalities in the absorption,decomposition,and transportation of lipids in the body.It is caused by a combination of multiple factors,such as genes,diet,drugs,etc.,which can lead to a variety of diseases in humans and animals.Fatty liver is induced by imbalance between fatty acid uptake and fatty acid oxidation and output.Alpha lipoic acid(ALA)has become a common ingredient in multivitamin formulas,anti-aging supplements and pet foods.It has the effects of scavenging free radicals,chelating metals and restoring intracellular glutathione levels.Studies have shown that α-lipoic acid could alleviate liver fat deposition,and its mechanism of action remains to be further studied.Therefore,this experiment aims to reveal the effects of α-lipoic acid on rat growth performance,biochemical indicators,blood routine and liver lipid metabolism,and to explore its regulatory mechanism.1 The effect of dietary α-lipoic acid on growth performance,biochemical indexes and blood routine of ratsIn the experiment,24 Sprague-Dawley male rats with similar body weight and 6～8weeks old were randomly divided into two groups,the control group(basal diet)and the α-lipoic acid group(basal diet added with 0.2% α-lipoic acid).The body weight and feed intake were recorded during the 5-week trail.At the end of experiment,whole blood and plasma samples were taken when the two groups of rats were anesthetized,and the liver,kidney,spleen and heart were weighed and recorded,and to analyze organ index.The results showed that dietary addition of α-lipoic acid had no significant effect on body weight and feed intake(P>0.05),nor did it have a significant effect on the net weight of liver,spleen,heart and kidney(P>0.05).α-lipoic acid addition extremely increased the liver index(P<0.05),but had no significant effect on other organ indexes.Plasma biochemical results showed that dietary supplementation of α-lipoic acid significantly increased the content of glutamate(AST)and alanine aminotransferase(ALT)in plasma(P<0.05),but greatly reduced the ratio of AST/ALT(P<0.05)).At the same time,it was found that the plasma triglyceride(TG)content of the α-lipoic acid group was significantly lower than that of the control group(P<0.05).The other biochemical indicators such as total cholesterol(TC),high-density lipoprotein(HDLC),low-density lipoprotein(LDL-C)and glucose(GLU)had no significant difference between two groups(P>0.05).The results of routine blood analysis showed that α-lipoic acid had no significant effect on red blood cell(RBC),hemoglobin(HGB),hematocrit(HCT),mean red blood cell volume(MCV),mean red blood cell hemoglobin content(MCH),mean red blood cell hemoglobin concentration(MCHC),coefficient of variation of red blood cell distribution width(RDW-CV),red blood cell distribution density(RDW-SD),platelet count(PLT),mean platelet volume(MPV),platelet distribution width(PDW),platelet packed volume(PCT),white blood cell(WBC)),neutrophils(Neu),lymphocytes(Lym),monocytes(Mon)and eosinophils(Eos).2 Effect of dietary supplementation of α-lipoic acid on liver lipid metabolism in ratsOil red staining,real-time fluorescence quantitative PCR and western blot were used to detect changes in liver lipid content,gene expression related to lipid synthesis,transport and release in rats.Oil red staining results showed that dietary supplementation of α-lipoic acid could markedly reduce the number of liver lipid droplets.Corresponding to the oil red results,liver TG content also lowered in rats fed to α-lipoic acid.PCR results showed that α-lipoic acid supplementation greatly reduced lipid-related gene stearoyl-Co A desaturase(SCD)expression(P<0.05),but markedly up-regulated the sterol regulatory element binding protein-1(SREBP-1)and adipose triglyceride lipase(ATGL)expression(P<0.05).Western blot analysis found that the protein expression of fatty acid synthase(FASN)and fatty acid binding protein 1(FABP1)was greatly down-regulated(P<0.05),while the phosphorylated hormonesensitive triglyceride(p-HSL)was significantly up-regulated(P<0.05)in rats treated by α-lipoic acid.3 The effect mechanism of dietary supplementation of α-lipoic acid on liver lipid metabolism in ratsMicroRNAs(MiRNAs)are small non-codingRNAs,which inhibit target mRNAs through cleavage or translation,and participate in a variety of metabolic pathways in the body.Small-RNA sequencing analysis was used to screen differential miRNAs expression in rat liver.The sequencing results showed that dietary supplementation ofα-lipoic acid greatly up-regulated 8 miRNAs(rno-miR-200a-5P,rno-miR-3548,rnomiR-429,rno-miR-29c-5p,rno-miR-27a-3p,rno-miR-182,rno-miR-150-5p,and rnomiR-21-5p)(P<0.05),but significantly down-regulated 11 miRNAs(rno-miR-582-3P,rno-miR-451-5p,rno-miR-9a-3p,rno-miR-9a-5p,rno-miR-7b,rno-miR-124-3p,rnomiR-9b-3p,rno-miR582-5p,rno-miR-190b-5p,rno-miR-28-3p,and rno-miR-802-5p)(P<0.05).Immediately,rno-miR-3548,rno-miR-182,and rno-miR-27a-3p were predicted to have binding sites,which could bind with Fasn’s 3’UTR.Co-transfection Fasn 3’UTR dual luciferase reporter and the mimics of the above three miRNAs,it was found that miR-3548 mimic can markedly reduce the fluorescence intensity of fireflies.Moreover,con-transfection Fasn 3’UTR mutation luciferase reporter and miR-3548 mimic,it was found that the decrease of fluorescence intensity was significantly alleviated.In summary,dietary supplementation of α-lipoic acid could reduce liver lipid deposition by down-regulating the expression of FASN and FABP1 protein and upregulating the expression of p-HSL.At the meanwhile,it was found that the inhibition of FASN expression was partly mediated by increasing the level of miR-3548 in rat liver.