Association of I27L Polymorphism of Hepatocyte Nuclear Factor-1α Gene with High-Density Lipoprotein Cholesterol Level
The serum level of high-density lipoprotein cholesterol (HDL-c), which protects against the development of atherosclerosis, is under genetic control. However, the genetic components responsible for the serum HDL-c level are yet to be determined. A recent knockout mouse study demonstrated that hepatocyte nuclear factor-1 alpha (HNF-1 alpha) is an essential transcriptional regulator of HDL-c metabolism. In this study, the association of an HNF-1 alpha gene polymorphism, isoleucine (Ile) 27 leucine (Leu), with lipid parameters, in particular with serum HDL-c level, was studied in 356 unrelated Japanese men. Though no significant difference was observed in total cholesterol and triglyceride levels among the three genotypes, the serum HDL-c level was significantly associated with the genotype (P < 0.01, trend test). Subjects with the Ile/Ile genotype had low serum HDL-c levels, and those with the Leu/Leu genotype had high serum HDL-c levels. These results demonstrate that the HNF-1 alpha gene locus is associated with serum HDL-c level and suggest that the Ile27 allele is a risk marker for atherosclerosis.
Available from: Kazuko Nakagawa
- "The present results are similar to previous findings that the 27L variant is associated with higher HDL cholesterol levels in healthy Japanese individuals  and with lower triglyceride levels in Brazilian subjects with T2DM . The 27L and 487N variants have also been reported to be associated with lower levels of C-reactive protein (CRP) and/or ␥-glutamyl transferase (GGT) . "
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The common variants p.I27L (rs1169288), p.A98V (rs1800574) and p.S487N (rs2464196) of the hepatocyte nuclear factor 1-α (HNF1A) gene have been inconsistently associated with impaired glucose tolerance and/or an increased risk of type 2 diabetes mellitus (T2DM). The present study aimed to investigate whether these associations are affected by weight.
A cross-sectional analysis was conducted among 861 Japanese subjects (males: 65.5%; 61.8±12.3years) attending a health-screening programme. Interactive effects between HNF1A variants and weight status on risk of T2DM or dysglycaemic status were determined.
The 27L variant carriers were at higher risk of T2DM and dysglycaemic status than non-carriers, but only in normal-weight subjects [odds ratio (OR): 2.04, P=0.03 and OR: 2.56, P=0.01, respectively]. An interactive effect of the p.I27L (rs1169288) variant and weight status on the risk of dysglycaemic status was found (P=0.04). Age, but not body mass index (BMI), was a risk factor for dysglycaemic status in the 27L carriers (OR: 1.05, P=0.0003), whereas BMI was a risk factor in non-carriers (OR: 1.23, P=0.008). No carriers of 98V were identified, and 487N was not associated with either T2DM or dysglycaemic status in our study population.
These findings suggest that the HNF1A p.I27L (rs1169288) variant may be a significant risk factor of T2DM in normal-weight subjects and that earlier inconsistent results may have been due, in part, to subjects' weight status. Further investigations in larger cohorts are needed to verify these findings.
Available from: Fernando M.A. Giuffrida
- "Our findings for I27L and hypertriglyceridemia are analogous to data previously reported for HDL , which is in accordance to a known pathophysiological connection  between both lipid subtypes. Among the different cardiovascular risk factors with a well-studied association to I27L [9-11], none of them occurred consistently, however they showed a common trend of protective effect upon MS and IR associated traits in non-diabetic individuals. These effects have not been similarly demonstrated in diabetic patients, but a subsequent publication showing subjects from the Botnia study to be more insulin-sensitive in presence of I27L  supports this hypothesis. "
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ABSTRACT: Type 2 diabetes mellitus (T2DM) is a genetically heterogeneous disease, hepatocyte nuclear factor-1 homeobox A (HNF1A) single-nucleotide polymorphisms (SNPs) playing a minor role in its pathogenesis. HNF1A is a frequent cause of monogenic diabetes, albeit with early-onset. Some uncommon subgroups like late-onset autosomal dominant diabetes mellitus (LOADDM) may present peculiar inheritance patterns with a stronger familial component. This study aims to investigate the relationship of HNF1A SNPs with cardiovascular risk factors in this group, as well as to characterize them in contrast with classical T2DM (CT2DM).
eighteen LOADDM (age at onset > 40 y.o.; diabetes in 3 contiguous generations, uniparental lineage) along with 48 CT2DM patients and 42 normoglycemic controls (N group) have been evaluated for cardiovascular risk factors and SNPs of HNF1A.
LOADDM showed significantly higher frequencies of SNPs A98V (22.2% vs 2.1%, p = 0.02) and S487N (72.2% vs 43.8%, p = 0.049) of HNF1A compared to CT2DM. I27L did not show significant difference (66.7% vs 45.8%), but associated with lower risk of hypertriglyceridemia (OR 0.16, 95% CI 0.04-0.65, p = 0.01). "Protective effect" was independent from other well-known predictive risk factors for hypertriglyceridemia, such as waist circumference (OR 1.09 per 1 cm increase, p = 0.01) and HDL (OR 0.01 per 1 mmol/l, p = 0.005), after logistic regression.
Late onset autosomal dominant diabetes mellitus is clinically indistinguishable from classical type 2 diabetes individuals. However, LOADDM group is enriched for common HNF1A polymorphisms A98V and S487N. I27L showed "protective effect" upon hypertriglyceridemia in this sample of individuals, suggesting a role for HNF1A on diabetic individuals' lipid profile. These data contribute to the understanding of the complex interactions between genes, hyperglycemia and cardiovascular risk factors development in type 2 diabetes mellitus.
Available from: ahajournals.org
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ABSTRACT: Plasma high-density lipoprotein cholesterol (HDL-C) concentrations are genetically determined to a great extent, and quantitative trait locus (QTL) analysis has been used to identify chromosomal regions containing genes regulating HDL-C levels. We discuss new genes found to participate in HDL metabolism. We also summarize 37 mouse and 30 human QTLs for plasma HDL-C levels, finding that all but three of the mouse QTLs have been confirmed by a second cross or a homologous human QTL, that the mouse QTL map is almost saturated because 92% of recently reported QTLs are repeats of those already found, and that 28 of the 30 human QTLs are located in regions homologous to mouse QTLs. This high degree of concordance between mouse and human QTLs suggests that the underlying genes may be the same. Strategies to more rapidly identify genes underlying mouse and human QTLs for HDL-C include focusing on the mouse and using mouse-human homologies, combining crosses, and haplotyping to narrow the region. Sequence analysis and expression studies can distinguish candidate genes consistent across multiple mouse crosses, and testing the candidate genes in human association studies can provide additional evidence for the candidacy of a gene. Together these strategies can accelerate the pace of finding genes that regulate HDL.
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