The Association Of The Common Gene Mutations In Lipoprotein Lipase With Type 2 Diabetes Mellitus

Objective: Type 2 diabetes mellitus (Type 2 DM) is a multifactory disease. Eventhough the manifestation of Type 2 DM clearly has a genetic component, the etiology of this is largely unknown. In Type 2 DM and other insulin-resistant conditions, postprandial hyperglyceridaemia and low HDL are important lipid metabolic perturbations. Moreover, a strong correlation between Type 2 DM and adiposity ^ CAD> hypertension indicats contribution from a dyslipidemic state. This implies that genes involved in lipid metabolism might be relevant candidates of a common disorder. Lipoprotein lipase (LPL) is a rate-limiting enzyme in lipid metabolism, which plays a key role in lipoprotein metabolism by catalyzing the hydrolysis of triglycerides of very low density lipoprotein (VLDL) and chylomicrons (CM), and the gene coding for LPL is therefore a candidate gene in Type 2 DM. Recently, a number of more common coding mutations in the LPL have been described, which found to influence plasma lipid. Two of these, Asp9Asn and Asn291Ser, have been described to have small deleterious effects on plasma high-density lipoprotein(HDL) cholesterol and TG, and another, Ser447Ter is reported by some investigators to underlie higher HDL cholesterol levels and lower TG , thus would represent a beneficial genetic variant in lipoprotein metabolism. However, little is know about their effects on the plasma lipoprotein metabolism of Type 2 DM. The purpose of the present study is to unravel the association between the three common gene mutations in the LPL gene and the lipid metabolic perturbations in Type 2 DM and to explore the relationship between the three common gene mutations in the LPL gene and Type 2 DM and it' scomplications.Methods: The study population consisted of 102 patients of Type 2 DM who had been admitted to the first affiliated hospital of Zhengzhou University and 113 control subjects. All subjects enrolled in the study were Chinese Han nationality and except other endocrine disease, treatment with lipid-lowing or betablocking agents. There were no significant different in sex and age between the two groups. Subjects were drawn 3ml blood before breakfast and the genome DNA were extracted by classic SDS-proteinase K-hydroxybenzene-chloroform methods from the blood. Through PCR amplification, electrophoresis on 2% agarose gel, and EB-staining, we observed and analysed the specific segments of Asp9Asn> Asn291Ser and Ser447Ter using DNA Marker pBR322 DNA/Ztei/RI(HaeIII). And then, the segments went on being digested with restriction endonuclear enzyme Taq I, Rsa I and Hinf-I respectively. Finally, the digested segments were analysed through 6%~ 10% non-denaturation polyacrylamide gel.All the analyses were performed with the SPSS 11.0 statistical analysis package. A chi-square test was performed to assess whether the observed genotype frequencies were in Hardy-Weinberg equilibrium. Data on age and lipid levels were analyzed by the unpaired Student' s t test. The frequencies of the alleles and the relations of genotype between the study groups were analyzed by constructing 2*2 and 2*3 contingency tables followed by chi-square analysis. A P value < 0.05 was considered significant.Results: Type 2 DM patients had significantly lower HDL and higher TG> LDL> ApoB and Lp(a) than controls. Asp9Asn and Asn291Ser variants were not found either in 102 NIDDM patients or in 113 controls. As for the Ser447Ter mutation, the frequency of the Ter447 allele and Ser447Ter genotype were lower in cases than controls. The differences were very close to the significant level (P =0.065 and P =0.057). In control group, there were trend to lower TG and higher HDL in carriers of the Ser447Ter mutation. In NIDDM patients group, the level of plasma TG was also obviously lower in carriers of the Ser447Ter mutation than in non-carriers (P=0.032). Furthermore, the beneficial effects of Ser447Ter mutation on plasma lipids could beseen in either sex. In the three genetic variants of LPL, the frequency of A allel in the Asp9Asn mutation and G allele in the...