Effects Of DG On Fat Metabolism Of SD Rats And Its Mechanisms

Diacylglycerol(DG), which consists of 1, 3-DG and 1, 2(2, 3)-DG, comprisesup to 2-10％of glycerides in common plantderived edible fats and oils. It isreported in recent studies that food containing DG oil can reduce fasting serumtriacylglycerol, suppress postprandial increases in serum triacylglycerol level,prevent the accumulation of body fat in animals and humans, compared with theconsumption of triacylglycerol (TG).Fatty acid synthase(FAS) and acetyl-CoA carboxylase(ACC) are two keyenzymes during fatty acid synthase in liver tissue. FAS and ACC can have effecton lipid metabolism through the regulation of fatty acid synthesis. Central foodintake regulation involves complex relations of neuropeptides, monoamines, andother brain messengers at various levels in the nerve system. In the hypothalamus(the main center of food regulation), the neuropeptides agouti-related peptide (AgRP), neuropeptide Y (NPY) and the neuropeptide precursorpro-opiomelanocortin (POMC) are implicated in the regulation of energyhomeostasis.Our experiment is about the effects of DG on fat metabolism of SD rats.Through the observation of changes in body weigt, serum lipids, expression ofacetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) mRNA in hepartissue, the expression of neuropeptide Y (NPY), agouti-related peptide (AgRP)and precursor pro-opiomelanocortin (POMC) mRNA in the hypothalamus, weinvestigated the possible mechanisms of the effects of DG on lipid metabolism.This study will provide experimental basement for further understanding themolecul mechanisms of antiobesity of DG.MethodsMale Sprague-Dawley rats were randomly selected and given free access todiets of 5％(wt) triacylglycerol (control group), 20％(wt) TG or 20％(wt) DGdiets for 10 weeks. At the end of the experiment, the rats were sacrificed, the ratioof lipids to body weight were calculated, and the serum glucose, serum lipids,serum insulin, serum leptin were measured. Reverse transcriptase-polymerasechain reaction (RT-PCR) was used for measuring the expression of acetyl-CoAcarboxylase (ACC) and fatty acid synthase (FAS) mRNA in hepar tissue, and theexpression of neuropeptide Y (NPY), agouti-related peptide (AgRP) and precursorpro-opiomelanocortin (POMC) mRNA in the hypothalamus.Results(1) Body weight and body fat content: The TG group had a significantlymore body weight gain and abdominal adipose tissue weight gain than the controlgroup (P＜0.05). No significant differences of final body weight, body-weight gain and abdominal adipose tissue weight gain were observed among rats in the controlgroup and DG group after 10 weeks. DG group had lower abdominal adiposetissue increase and ratio of abdominal adipose tissue weight to body weightcompared with TG group (P＜0.05).(2) The effect of different diets on the blood parameters: serum glucose levelwas higher in the TG group compared with the control group (p＜0.05), but therewas no significant difference between the DG and TG group for this parameter.Total triacylglycerol and serum leptin concentration were higher in the TG groupthan the DG and control groups, and there was no significant difference betweenthe DG and control groups. However, there was no significant difference in totalcholesterol and insulin among the three groups.(3) The effects of DG on ACC and FAS expression in hepar tissue:Theexpression of ACC and FAS mRNA levels in hepar tissue were down-regulated inDG group compared with TG group(P＜0.05). But there was no significantdifference between the DG and control groups.(4) The effects of DG on hypothalamic NPY, AGRP and POMC expression:The NPY and AgRP mRNA levels were significantly higher in the TG group thanin the control or DG group. The NPY mRNA level in the TG and DG groupsincreased by 130.1％and 44.0％compared with the control group, respectively. Inrelation to the control group, the levels of AgRP mRNA were 25.5％higher in theTG groups, whereas there was no significant difference between the DG andcontrol groups. The POMC expression was decreased in the TG and DG groupscompared with the control group (38.77％and 29.84％respectively, Fig. 2C), butthere was no significant difference between the DG and TG groups. ConclusionsThese suggest that the changes in body weight and serum lipids level mayimpart its effect on lipid metabolism partly through altering the expression of thegenes associated with improved fat metablisim, appetite control and energybalance. Hower, DG exerts its effects by multipule not single mechanism.Therefore, it is necessary to make further study to elucidate the mechanism ofDG's effects.