Seiho Mizusawa

Association of the rs738409 polymorphism in PNPLA3 with liver damage and the development of nonalcoholic fatty liver disease

BackgroundIn a genome-wide association scan, the single-nucleotide polymorphism (SNP) rs738409 in the patatin-like phospholipase 3 gene (PNPLA3) was strongly associated with increased liver fat content. We investigated whether this SNP is associated with the occurrence and progression of nonalcoholic fatty liver disease (NAFLD) in the Japanese population.MethodsSNP rs738409 was genotyped by the Taqman assay in 253 patients with NAFLD (189 with nonalcoholic steatohepatitis [NASH] and 64 with simple steatosis) and 578 control subjects. All patients with NAFLD underwent liver biopsy. Control subjects had no metabolic disorders. For a case-control study, the χ2-test (additive model) was performed. Odds ratios (ORs) were adjusted for age, gender, and body mass index (BMI) by using multiple logistic regression analysis with genotypes (additive model), age, gender, and BMI as the independent variables. Multiple linear regression analysis was performed to test the independent effect of risk allele on clinical parameters while considering the effects of other variables (age, gender, and BMI), which were assumed to be independent of the effect of the SNP.ResultsThe risk allele (G-allele) frequency of rs738409 was 0.44 in the control subjects and 0.60 in patients with NAFLD; this shows a strong association with NAFLD (additive model, P = 9.4 × 10-10). The OR (95% confidence interval) adjusted for age, gender, and BMI was 1.73 (1.25-2.38). Multiple linear regression analysis indicated that the G-allele of rs738409 was significantly associated with increases in aspartate transaminase (AST) (P = 0.00013), alanine transaminase (ALT) (P = 9.1 × 10-6), and ferritin levels (P = 0.014), and the fibrosis stage (P = 0.011) in the patients with NAFLD, even after adjustment for age, gender, and BMI. The steatosis grade was not associated with rs738409.ConclusionsWe found that in the Japanese population, individuals harboring the G-allele of rs738409 were susceptible to NAFLD, and that rs738409 was associated with plasma levels of ALT, AST, and ferritin, and the histological fibrosis stage. Our study suggests that PNPLA3 may be involved in the progression of fibrosis in NAFLD.

Association of variations in the FTO , SCG3 and MTMR9 genes with metabolic syndrome in a Japanese population

Metabolic syndrome is defined as a cluster of multiple risk factors, including central obesity, dyslipidemia, hypertension and impaired glucose tolerance, that increase cardiovascular disease morbidity and mortality. Genetic factors are important in the development of metabolic syndrome, as are environmental factors. However, the genetic background of metabolic syndrome is not yet fully clarified. There is evidence that obesity and obesity-related phenotypes are associated with variations in several genes, including NEGR1, SEC16B, TMEM18, ETV5, GNPDA2, BDNF, MTCH2, SH2B1, FTO, MAF, MC4R, KCTD15, SCG3, MTMR9, TFAP2B, MSRA, LYPLAL1, GCKR and FADS1. To investigate the relationship between metabolic syndrome and variations in these genes in the Japanese population, we genotyped 33 single-nucleotide polymorphisms (SNPs) in 19 genes from 1096 patients with metabolic syndrome and 581 control individuals who had no risk factors for metabolic syndrome. Four SNPs in the FTO gene were significantly related to metabolic syndrome: rs9939609 (P=0.00013), rs8050136 (P=0.00011), rs1558902 (P=6.6 × 10−5) and rs1421085 (P=7.4 × 10−5). rs3764220 in the SCG3 gene (P=0.0010) and rs2293855 in the MTMR9 gene (P=0.0015) were also significantly associated with metabolic syndrome. SNPs in the FTO, SCG3 and MTMR9 genes had no SNP × SNP epistatic effects on metabolic syndrome. Our data suggest that genetic variations in the FTO, SCG3 and MTMR9 genes independently influence the risk of metabolic syndrome.

Genetic variations in the CYP17A1 and NT5C2 genes are associated with a reduction in visceral and subcutaneous fat areas in Japanese women

Visceral fat accumulation has an important role in increasing the morbidity and mortality rates, by increasing the risk of developing several metabolic disorders, such as type 2 diabetes, dyslipidemia and hypertension. New genetic loci that are associated with increased systolic and diastolic blood pressures have been identified by genome-wide association studies in Caucasian populations. This study investigates whether single nucleotide polymorphisms (SNPs) that confer susceptibility to high blood pressure are also associated with visceral fat obesity. We genotyped 1279 Japanese subjects (556 men and 723 women) who underwent computed tomography for measuring the visceral fat area (VFA) and subcutaneous fat area (SFA) at the following SNPs: FGF5 rs16998073, CACNB2 rs11014166, C10orf107 rs1530440, CYP17A1 rs1004467, NT5C2 rs11191548, PLEKHA7 rs381815, ATP2B1 rs2681472 and rs2681492, ARID3B rs6495112, CSK rs1378942, PLCD3 rs12946454, and ZNF652 rs16948048. In an additive model, risk alleles of the CYP17A1 rs1004467 and NT5C2 rs11191548 were found to be significantly associated with reduced SFA (P=0.00011 and 0.0016, respectively). When the analysis was performed separately in men and women, significant associations of rs1004467 (additive model) and rs11191548 (recessive model) with reduced VFA (P=0.0018 and 0.0022, respectively) and SFA (P=0.00039 and 0.00059, respectively) were observed in women, but not in men. Our results suggest that polymorphisms in the CYP17A1 and NT5C2 genes influence a reduction in both visceral and subcutaneous fat mass in Japanese women.

Association between type 2 diabetes genetic susceptibility loci and visceral and subcutaneous fat area as determined by computed tomography

Visceral fat accumulation has an important role in the development of several metabolic disorders, such as type 2 diabetes, dyslipidemia and hypertension. New genetic loci that contribute to the development of type 2 diabetes have been identified by genome-wide association studies. To examine the association of type 2 diabetes susceptibility loci and visceral fat accumulation, we genotyped 1279 Japanese subjects (556 men and 723 women), who underwent computed tomography for measurements of visceral fat area (VFA) and subcutaneous fat area (SFA) for the following single-nucleotide polymorphisms (SNPs): NOTCH2 rs10923931, THADA rs7578597, PPARG rs1801282, ADAMTS9 rs4607103, IGF2BP2 rs1470579, VEGFA rs9472138, JAZF1 rs864745, CDKN2A/CDKN2B rs564398 and rs10811661, HHEX rs1111875 and rs5015480, TCF7L2 rs7901695, KCNQ1 rs2237892, KCNJ11 rs5215 and rs5219, EXT2 rs1113132, rs11037909, and rs3740878, MTNR1B rs10830963, DCD rs1153188, TSPAN8/LGR5 rs7961581, and FTO rs8050136 and rs9939609. None of the above SNPs were significantly associated with VFA. The FTO rs8050136 and rs9939609 risk alleles exhibited significant associations with body mass index (BMI; P=0.00088 and P=0.0010, respectively) and SFA (P=0.00013 and P=0.00017, respectively). No other SNPs were significantly associated with BMI or SFA. Our results suggest that two SNPs in the FTO gene are associated with subcutaneous fat accumulation. The contributions of other SNPs are inconclusive because of a limitation of the sample power.

Computed tomography analysis of the association between the SH2B1 rs7498665 single-nucleotide polymorphism and visceral fat area

Visceral fat accumulation has an important role in increasing morbidity and mortality rate by increasing the risk of developing several metabolic disorders, such as type 2 diabetes, dyslipidemia and hypertension. New genetic loci that contribute to the development of obesity have been identified by genome-wide association studies in Caucasian populations. We genotyped 1279 Japanese subjects (556 men and 723 women), who underwent computed tomography (CT) for measuring visceral fat area (VFA) and subcutaneous fat area (SFA), for the following single-nucleotide polymorphisms (SNPs): NEGR1 rs2815752, SEC16B rs10913469, TMEM18 rs6548238, ETV5 rs7647305, GNPDA2 rs10938397, BDNF rs6265 and rs925946, MTCH2 rs10838738, SH2B1 rs7498665, MAF rs1424233, and KCTD15 rs29941 and rs11084753. In the additive model, none of the SNPs were significantly associated with body mass index (BMI). The SH2B1 rs7498665 risk allele was found to be significantly associated with VFA (P=0.00047) but not with BMI or SFA. When the analysis was performed in men and women separately, no significant associations with VFA were observed (P=0.0099 in men and P=0.022 in women). None of the other SNPs were significantly associated with SFA. Our results suggest that there is a VFA-specific genetic factor and that a polymorphism in the SH2B1 gene influences the risk of visceral fat accumulation.

Targeted next-generation sequencing and fine linkage disequilibrium mapping reveals association of PNPLA3 and PARVB with the severity of nonalcoholic fatty liver disease

The genomic regions containing PNPLA3, SAMM50 and PARVB are susceptibility loci for the development and progression of nonalcoholic fatty liver disease (NAFLD). In order to search for all common variations in this region, we amplified the genomic DNA of 28 NAFLD patients by long-range PCR, covering the entire susceptibility region and sequenced the DNA using indexed multiplex next-generation sequencing. We found 329 variations, including four novel variations. Fine mapping of variations including insertion/deletions was performed for 540 NAFLD patients (488 with nonalcoholic steatohepatitis (NASH) and 52 with simple steatosis) and 1012 control subjects. HaploView analysis showed that linkage disequilibrium (LD) block 1 and 2 occurred in PNPLA3, block 3 in SAMM50 and block 4 in PARVB. Variations in LD blocks 1–4 were significantly associated with NAFLD as compared with control subjects (P<1 × 10−8). Variations in LD block 2 were significantly associated with the NAFLD activity score (NAS), aspartate aminotransferase and alanine aminotransferase. Variations in LD block 1 were significantly associated with the fibrosis stage. The strongest associations were observed for variations in LD block 4, with NASH as compared with simple steatosis (P=7.1 × 10−6) and NAS (P=3.4 × 10−6). Our results suggested that variations, including insertion/deletions, in PARVB, as well as those in PNPLA3, are important in the progression of NAFLD.

Development of a simple genotyping method for the HLA-A*31:01-tagging SNP in Japanese

AIM To construct a simple, low-cost typing method for the surrogate marker of HLA-A*31:01, a risk factor for carbamazepine (CBZ) related Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). MATERIALS & METHODS DNAs from Japanese SJS/TEN patients were used for genotyping and developing the assay. RESULTS HLA-A*31:01 was confirmed to be significantly associated with definite/probable cases of CBZ-related SJS/TEN (p = 0.0040). Three single nucleotide polymorphisms, rs1150738, rs3869066 and rs259945, were in absolute linkage disequilibrium with HLA-A*31:01 in 210 Japanese SJS/TEN patients. Robust genotyping of rs3869066 in ZNRD1-AS1 was developed using polymerase chain reaction-restriction fragment length polymorphism assays. CONCLUSION Single nucleotide polymorphism genotyping is less time consuming and cheaper than conventional HLA typing, and would be useful for identifying Japanese patients at risk of CBZ-related SJS/TEN.