Postprandial Lipids Levels And Their Relationships With Carotid Artery Intima-media Thickness In Metabolic Syndrome

Objective:The present study is to observe lipoprotein and free fatty acid changes after a fatty tolerant test(FTT),and evaluate the characteristics of lipoprotein,free fatty acid metabolic in patients with metabolic syndrome(MS).We also discussed the relationship with the levels of postprandial lipoprotein,the insulin resistance and the carotid artery intima-media thickness (IMT).Materials and Methods:91 subjects of metabolic syndrome were divided into two groups: normal-fasting triglyceridemia(TG)group(MS₁,n=42)and hypertriglyceridemia(HTG)group (MS₂,n=49).47 normal subjects served as controls.The FTT was carried out in the three groups, fasting TG(TG0h),TG2h,TG4h,TG6h were taken as the index of response of TG after test of fat loading.At the same time glucose(GLU),total cholesterol(TC),high density lipoprotein (HDL-C),lower density lipoprotein(LDL-C),free fatty acid(FFA)and insulin(INS)were measured.We also counted body mass index(BMI)and homeostasis model assessment-insulin resistance(HOMA-IR).The carotid artery intima-media thickness(IMT)was measured using echography.Results:1.Comparison of postprandial lipid metabolism status in three groupsâ‘ Postprandial triglyceride concentrationPostprandial TG concentrations of the three groups are all raised.The TG peak time was all approximate 4 hour in three groups.We also observed that the level of TG at fasting and 6 hour after meal was similar in the control(p＞0.05),but the TG levels at 6 hour were significantly higher than the fasting levels in MS₁ and MS₂ groups(p＜0.01).The 2,4,6 hour after meal levels of TG were much higher in metabolic syndrome(MS₁,MS₂)than the control.The TG area under curve(TG-AUC)and TG peak response(TG-PR) were significantly higher in MS₁ and MS₂ groups than control,but no significantly difference was found between them(p＞0.05).Spearman rank correlation analysis shows that the TG-AUC and TG-PR were positively correlated with the TG concentration at 4 hour after the fat meal(r=0.799,p＜0.01;r=0.721, p＜0.01). â‘¡Postprandial free fatty acidWe observed that the level of FFA was slight decrease at 2 hour after fatty tolerant test in control,and the respond curve is smooth.But in metabolic syndrome(MS₁,MS₂)groups,the FFA levels progressively increased after the meal and reach at peak at 4 hour,and the FFA levels at 2,4,6 hour were significantly higher than the fasting levels(p＜0.05,p＜0.01).The fasting and 2,4,6 hours after meal levels of FFA were much higher in metabolic syndrome(MS₁,MS₂)groups than the control(p＜0.01).The FFA area under curve(FFA-AUC) and FFA peak response(FFA-PR)were significantly higher in MS₁ and MS₂ group(p＜0.01), while MS₂ group was much higher than MS₁(p＜0.05).Spearman rank correlation analysis shows that the FFA-AUC and FFA-PR were positively correlated with the FFA concentration at 4 hour after the fat meal.(r=0.923,p＜0.01;r=0.897, p＜0.01).â‘¢Postprandial HDL-C,TC and LDL-CIn the MS₁ and MS₂ group the HDL-C levels were both decreased at 2,4,6 hours after fat meal(p＜0.05).The HDL-C concentrations in MS₁ and MS₂ were both lower before and after the fatty tolerant test than the control,no significantly difference was found between the MS₁ group and MS₂ group(p＞0.05).But we found that the TC,LDL-C levels has no significantly changes after fat meal(p＞0.05).2.Comparison of insulin resistance index of three groupsThe HOMA-IR of MS₁ group and MS₂ group were significantly higher than those of the control(p＜0.05,p＜0.01),furthermore the HOMA-IR of MS₂ group was significantly higher than those of MS₁ group(p＜0.05).3.Comparison of carotid artery IMT and the detection rate of the carotid artery IMTThe carotid artery IMT of the control,MS₁ and MS₂ group were 0.86±0.19mm, 1.08±0.18mm and 1.11±0.15mm respectively.The absolute value of carotid artery IMT in both of the MS₁ and MS₂ group were significantly higher than that of the control(P＜0.05),no significantly difference was found between the MS₁ and MS₂ group(P＞0.05).Three groups detection rate of the carotid artery IMT were 40.43%,69.05%,79.59%.The detection rate of the carotid artery IMT in MS₁ and MS₂ group were both significantly higher than thus in the control, but in MS₁ and MS₂ group it was similar.4.Spearman rank correlation analysis shows that TG-AUC and TG-PR were both significant associated with FFA-AUC,FFA-PR,FFA4h,INS-AUC and HOMA-IR in metabolic syndrome group(p＜0.01),and had no relationship with GLU-AUC and fasting HDL-C.FFA-AUC and FFA-PR were both significant associated with INS-AUC and HOMA-IR in metabolic syndrome group(p＜0.01),and had no relationship with GLU-AUC and fasting HDL-C. 5.In the stepwise regression about carotid artery IMT and its relative factors,taken fasting glucose,fasting lipids,age,sex,smoking,BMI,WHR,SBP,DBP,HOMA-IR,TG-AUC and FFA-AUC as variables,TG-AUC and BMI were positively correlated with carotid artery IMT. When replace TG-AUC and FFA-AUC with TG-PR and FFA-PR,TG-PR and BMI were positively correlated with carotid artery IMT.Conclusion:1.The postprandial dyslipidemia usually appears before fasting dyslipidemia in patients with metabolic syndrome.It is necessary to measure fasting TG level and 4 hour TG level to see if the triglyceride metabolism is abnormal.The FTT is easy,cheap,and sensitivity,which can be accepted by patients,so it can be regarded as a good method to evaluated the postprandial lipids.2.There was severe and belated lipids dysfunction,especially in the postprandial status in metabolic syndrome.The concentration of TG and FFA at 4 hour after the FTT has the best correlation ship with the TG-AUC and FFA-AUC,so we can detect the concentration of TG and FFA at 4 hour to make the test easy.3.The suppressive ability to FFA of insulin is decreased in MS,and in thus patients,the postprandial FFA significantly increase and the clearance rate is prolonged,which is highly associated to postprandial TG respond.4.BMI,TG-PR,TG-AUC were independently and significantly correlated with carotid artery IMT.Which suggest that obesity,postprandial hypertriglyceridemia and triglycerio rich lipoprotein may independent predictors of atherosclerosis in early time,which partially explain the increased incidence of cardiovascular diseases.