Association Of Haptoglobin With Diabetic Macroangiopathy In Chinese Type 2 Diabetes Patients

Type 2 diabetes mellitus（T2DM）is a group of chronic comprehensive diseases characterized by hyperglycemia.The macrovascular disease caused by T2DM is an important cause of disability and death in diabetic patients.Therefore,the investigation of the etiology in macrovascular disease is imminent.Haptoglobin（Hp）is an acidic glycoprotein widely distributed in human serum.Its main function is to eliminate the oxidative damage of blood vessels and organs induced by free haemoglobin.There existed copy number variations（Copy number variation,CNV）in the coding gene of Hp,mainly constitutes three common genotypes of Hp 1-1,Hp 1-2 and Hp 2-2.Previous studies have shown that Hp gene CNV and serum Hp levels are associated with T2DM macrovascular disease,but the causal relationship has not been clarified.Therefore,this study genetically investigates the association between Hp and diabetic macroangiopathy in Chinese patients with T2DM from three aspects as following.1.Association between haptoglobin gene polymorphism and diabetic macroangiopathy in Chinese T2DM patientsThis study aimed to investigate the association between Hp gene polymorphism,including Hp gene CNV and single nucleotide polymorphism（SNP）rs2000999,and diabetic macroangiopathy in Chinese T2DM patients.We enrolled 5687 patients with T2DM in total.According to the inclusion criteria of macrovascular disease,they were divided into macrovascular disease group and control group.The Hp gene CNV and SNP rs2000999 were genotyped in all the subjects.The results showed that Hp gene CNV was significantly associated with susceptibility to diabetic macroangiopathy（P=0.0410）,especially carotid atherosclerosis（P=0.0202）.However,there was no significant association between SNP rs2000999 and diabetic macroangiopathy susceptibility（P=0.6109）.2.Mendelian randomization analysis to assess a causal effect of serum haptoglobin on macroangiopathy in Chinese T2DM patientsThis study aimed to apply Mendelian randomized analysis to investigate a causal effect of serum Hp on macroangiopathy using Hp gene CNV as an intermediate variable.The study enrolled 935 patients with T2DM,including 500 patients with diabetic macroangiopathy and 435 controls,and all the participants were subjected to detect CNV mutations in Hp gene.Serum Hp concentration and serum oxidative stress marker8-hydroxy-2’-deoxyguanosine（8-OHdG）levels were determined.The Hp gene CNV was significantly associated with Hp serum levels(β1±SE=0.1662±0.014,P=3.55×10^-31);Hp serum levels were significantly associated with susceptibility to diabetic macroangiopathy（OR2=2.123,95%CI=1.098-4.102,P=0.0252）;Hp gene CNV was significantly associated with diabetic macroangiopathy（OR3=1.357,95%CI=1.025-1.798,P=0.0329）;The predicted effect between Hp gene CNV and diabetic macroangiopathy was calculated as OR4=1.130,which is also bigger than 1 as OR3.We concluded that there is a causal association between serum Hp and diabetic macroangiopathy.In addition,we also found that Hp gene CNV（P=0.0001）and serum levels（P=0.0084）were associated with serum 8-OHdG levels.3.Targeted metabolomics study on the relationship between serum haptoglobin and carotid atherosclerosisWe investigated a metabolic profile associated with serum Hp and carotid atherosclerosis related parameters via a targeted metabolomics approach to provide insight into potential mechanisms between serum Hp and diabetic macroangiopathy.A number of 120 T2DM patients were enrolled.Serum Hp levels were measured in all the subjects.AbsoluteIDQTM p180 kit was used to detect metabolites.The carnitine metabolite C16-OH,phosphatidylcholine metabolite PC ae C32:2 and five metabolite ratios of aliphatic amino acid to metabolite PC ae C32:2 were found to be significantly correlated with carotid atherosclerosis related parameters,blood lipids and serum Hp levels（P<0.05）.In summary,our study revealed a significant correlation of Hp gene polymorphism and diabetic macroangiopathy in Chinese T2DM patients,and then by using Hp gene CNV as an intermediate variable,we found a causal effect of serum Hp on diabetic macroangiopathy through Mendelian randomized analysis.Furthermore,a targeted metabolomics approach was launched to reveal the possible intrinsic mechanisms between serum haptoglobin and carotid arterial functions.