The Role And Mechanism Of Trivalent Chromium In Lipid Metabolism In Saccharomyces Cerevisiae

With the rapid development of the world economy,great changes have taken place in people's dietary habit and lifestyle.Overweight and obesity has become increasingly prominent.Obesity not only affects the lives of people,but also is the main cause of many chronic diseases,such as diabetes,cardiovascular disease and cancer.The prevention and solution of obesity is the focus of current research.Chromium is an essential mineral that appears to have a beneficial role in the regulation of glucose and lipid metabolism.Although studies have shown that trivalent chromium has the function of regulating lipid metabolism,the molecular mechanisms have not been clearly clarified.In this paper,the molecular mechanisms of chromium on lipid metabolism were investigated in Saccharomyces cerevisiae.First of all,the model of lipid accumulation was constructed in yeast cells treated by oleic acid.The addition of chromium to the yeast model showed that chromium could distinctly alleviate lipid accumulation treated by oleic acid.Our data indicated that chromium could effectively reduce fatty acids uptake and synthesis of TAG,decreased the number of lipid droplet and regulated the proportion of fatty acids in yeast cells.Chromium could also inhibit the lipid peroxidation induced by excessive oleic acid.Secondly,the effect of chromium on the contents of seven essential metal ions,including K,Ca,Na,Mg,Zn,Fe and Cr,were detected by ICP-AES.The data showed that chromium could significantly reduce the content of iron in the yeast cells treated by oleic acid.Chromium could be transported into yeast cell by iron transport receptor(Fet4p),and reduced iron uptake by decreasing the expression of iron transport receptor(Fet3p and Fet4p)and iron-dependent transcriptional activator(Aft1p and Aft2p).The mRNA level of Olelp,a fatty acid desaturase regulated the fatty acid composition,was up-regulated because of down-regulation of iron.Then,we screened the genes related to lipid metabolism by spotting assay and RT-qPCR.These data showed that chromium could decrease mRNA levels of genes of FAs uptake(FAA1 and FAA3)and TAG synthesis(DGA1,PAH1 and LRO1).Meanwhile,we found that chromium could regulate DGA1 transcription through HSF1 transcription factor by EGFP reporter gene assay.Finally,we conducted a conservative verification on the effect of chromium in SMMC-7721 cells,and found that chromium can also reduce the mRNA levels of fatty acid uptake related genes(ACSL1 and ACSL3)and triglyceride synthesis gene(DGAT2),leading to the reduction of fatty acid uptake and TAG synthesis.Our data reveal the important role and regulatory mechanism of chromium ion on lipid metabolism in yeast cells.These results provide a theoretical basis for chromium ion to alleviate obesity,and provide an important reference for the development of chromium dietary supplements.