Free advanced glycation end product distribution in blood components and the effect of genetic polymorphisms.

One hypothesis regarding the cause of diabetic complications is that advanced glycation end products (AGEs) bind to the AGE receptor and induce changes in gene expression. However, what AGEs exist in vivo and how individual AGEs are produced and impact body metabolic process to cause diabetes complications are not understood. We developed a new precise method to measure AGEs using LC-MS/MS with a new column and measured 7 free AGEs, including N(6)-carboxymethyllysine (CML), N(6)-(1-carboxyethyl)-l-lysine (CEL) and N5-(5-hydro-5-methyl-4-imidazolon-2-yl)L-ornithine (MG-H1), in human blood components. Blood was obtained from 9 people, and free AGEs were measured in individual blood components with LC-MS/MS before and after a meal. Free CML and CEL were abundant in erythrocytes, with 92% of free CML and 85% of free CEL localized in erythrocytes. In contrast, 60% of free MG-H1 was distributed in the serum. After the meal, free serum MG-H1 increased, but CML and CEL did not. CML and CEL are mainly distributed in erythrocytes and were not affected by the meal, indicating that they are produced in vivo. However, the main source of MG-H1 is the meal. The effect of genetic polymorphisms on AGEs was also investigated. Low activity type aldehyde dehydrogenase 2 (ALDH2) increased the CML concentration in the blood. This is the first observation that shows that the metabolic process of CML and CEL is different from that of MG-H1 and the effect of ALDH2 SNPs on CML.

Efficacy of habitual exercise for improving lipid profiles depends on the PPRAγ genotype in Japanese males.

Peroxisome proliferator-activated receptor gamma (PPARγ) responds to thiazolidinedione derivatives, which are ligands of PPARγ, and affects insulin resistance. Recently, a PPARγ study reported that in high-fat-diet-induced obesity, the phosphorylation of PPARγ prevented the transcription of specific PPARγ targets that have anti-obesity effects. We previously reported that genetic variants of the fatty acid desaturase were associated with plasma lipid profiles and could contribute to dyslipidemia in Japanese males. The aim of this study was to investigate the anti-obesity effects of PPARγ variants on lipid profiles. One hundred and thirty-eight (138) Japanese males participated in the study. Their serum lipid markers and the fatty acid composition of their red blood cell (RBC) membranes were determined. The stearoyl-CoA desaturase 1 (SCD1) indices were represented as the fatty acid product : precursor ratios. The participants were genotyped for the single-nucleotide polymorphism rs2938392 in the PPARγ gene. The participants' fitness habits were also surveyed by questionnaire. The effects of habitual exercise on the measured lipid parameters were compared in each genotype group. No association between the genotypes in the PPARγ gene and the biochemical data was found. However, the serum triglyceride levels and the SCD1 indices in RBC membranes were significantly higher in the participants who carried the major rs2938392 allele (A/A) and did not habitually exercise than in those who did exercise. These findings indicate that the risk for detrimental lipid profiles in the absence of habitual exercise depends on the PPARγ genotype in Japanese males.

Genetic variants of the fatty acid desaturase gene cluster are associated with plasma LDL cholesterol levels in Japanese males.

Fatty acid (FA) compositions in tissues are related to metabolic disorders, and consequently the appropriate management of underlying FA compositions in tissues is considered to be important. However, the relationship among the serum lipid profiles, the FA composition of the red blood cell (RBC) membranes and genetic variations in the fatty acid desaturase (FADS) genes in Japanese men is unclear. In this study, the subjects recruited were 137 Japanese men, 40 to 60 y old, who had a regular health checkup. Their serum lipid profile and the relative FA composition of the RBC membranes were measured. They were genotyped for the single nucleotide polymorphisms (SNPs) rs174553, rs174546, rs99780 and rs174583 in FADS gene. Multiple regression analysis was conducted to detect the relationship among hyperlipidemia, the FA composition of the RBC and the FADS genotypes. As a result, the homozygous genotype for the minor alleles in rs174553, rs174546, rs99780 were found to be associated with lower low-density lipoprotein cholesterol (LDL-C) levels and a lower LDL-C/total-cholesterol ratio. The homozygous genotype for the minor alleles reduced the risk of high LDL-C level (R2=0.50, ß=-0.20, p=0.009), whereas, the arachidonic acid (AA) levels in the carriers of the homozygous genotype for the minor alleles tended to be lower compared with the carriers of the major alleles. However, no significant differences were observed in any FA level among the three genotypes for four SNPs. These results indicate that the appropriate management of serum LDL-C levels depending on genetic predisposition in FADS genotypes should be encouraged.