An LMNA variant is associated with dyslipidemia and insulin resistance in the Japanese

Nuclear lamins A and C are encoded by LMNA and are present in terminally differentiated cells. Rare mutations in LMNA were shown to cause familial partial lipodystrophy, a syndrome characterized by regional loss of adipose tissue, glucose intolerance, and dyslipidemia, making LMNA a candidate gene for insulin-resistant diabetes. The aim of this study was to investigate whether genetic variation in LMNA can influence the risk of type 2 diabetes in a Japanese cohort. First, we performed mutational screening of LMNA by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequence analysis in 8 insulin-resistant males with acanthosis nigricans who were not lipodystrophic. One known single nucleotide polymorphism, 1908C/T, was found in exon 10. We subsequently screened samples of 171 nondiabetic and 164 type 2 diabetic male subjects for the presence of the 1908C/T polymorphism by PCR-restriction fragment length polymorphism (RFLP). The frequency of subjects with the 1908T allele tended to be higher in the diabetic group than in the nondiabetic group; however, the difference was not significant (43.9% v 32.2%) (P =.084). Carriers of the 1908T allele, both among diabetics and nondiabetics, showed significantly higher fasting insulin, triglycerides (TG), total cholesterol (TC), and lower high-density lipoprotein-cholesterol (HDL-C) levels than those of the 1908C/C subjects. These results suggest the LMNA 1908C/T single nucleotide polymorphism (SNP) is not associated with the prevalence of type 2 diabetes, although it may be a factor predisposing to insulin resistance and dyslipidemia in some Japanese.     

2型糖尿病肾病亚甲基四氢叶酸还原酶基因多态性研究

目的探讨亚甲基四氢叶酸还原酶(methylenetetrahydrofolate     

Association of the C825T polymorphism of the G-protein beta3 subunit gene with hypertension, obesity, hyperlipidemia, insulin resistance, diabetes, diabetic complications, and diabetic therapies among Japanese

A C825T polymorphism of the gene encoding the G-protein beta3 subunit (GNB3) is associated with increased intracellular signal transduction. We know that this C825T polymorphism may influence hypertension and obesity. In whites, the C825T polymorphism has been reported to induce hypertension, obesity, and diabetic nephropathy. Thus, we investigated how genetic variation in the GNB3 gene is associated with hypertension, obesity, insulin resistance, diabetes, diabetic complications, and diabetic therapies in 427 Japanese subjects with type 2 diabetes mellitus and in 368 Japanese subjects who underwent general health examinations. The frequency of the GNB3 gene polymorphism was 0.48 and 0.47 in subjects with diabetes and in those who had general health examinations, respectively. The amount of hyperlipidemia of the CT allele was significantly lower than the amount in the CC allele in the Japanese subjects with diabetes. Our results suggest that the C825T polymorphism influences lipid metabolism and is not associated with hypertension, obesity, insulin resistance, diabetes, diabetic complications, or diabetic therapies.     

The C825T polymorphism in the human G-protein β3 subunit gene is not associated with diabetic nephropathy in Type I diabetes mellitus

Summary In Type I (insulin-dependent) diabetes mellitus a genetic predisposition exists to nephropathy and is related to parental hypertension. Enhanced G-protein activation, a cellular phenotype observed in cultured cells from patients with essential hypertension, was recently documented in Type I diabetic subjects with nephropathy. This enhanced G-protein activation has been associated with a genetic variant in the G-protein β3 subunit, GNB3. A C→T polymorphism at position 825 in exon 10 is associated with G-protein activation, the T allele associated with enhanced activity. Furthermore the T allele was observed more frequently in a group with essential hypertension. In this report we have analysed the role of the C825T polymorphism in the predisposition to diabetic nephropathy in Type I diabetes. We have investigated the frequency of this polymorphism in a large case-control study and found no association of the T allele with diabetic nephropathy. Specifically carriage of the T allele as CT or TT was observed in 49 % of 200 Type I diabetic control subjects with normoalbuminuria (diabetes duration 24 years) compared with 53 % of 216 Type I diabetic subjects with nephropathy (overt proteinuria or end-stage renal failure). Within this group we have also examined the inheritance of C825T alleles in a family study and found no evidence for excess transmission of the T allele to Type I diabetic offspring with nephropathy (T allele transmitted to 51 % of nephropathy offspring, C allele transmitted to 49 % of nephropathy offspring, p = 0.79). In none of the Type I diabetic datasets examined was there any effect of genotype on variation in systolic or diastolic blood pressure. In conclusion we can find no evidence for the C825T polymorphism of the β3 G-protein subunit as a major gene in the susceptibility to diabetic nephropathy in Type I diabetes. [Diabetologia (1998) 41: 1304–1308] Received: 27 April 1998 and in revised form: 9 July 1998     

Common genomic variation in LMNA modulates indexes of obesity in Inuit

We discovered that rare mutations in LMNA, which encodes lamins A and C, underlie autosomal dominant Dunnigan-type familial partial lipodystrophy. Because familial partial lipodystrophy is an extreme example of genetically disturbed adipocyte differentiation, it is possible that common variation in LMNA is associated with obesity-related phenotypes. We subsequently discovered a common single nucleotide polymorphism (SNP) in LMNA, namely 1908C/T, which was associated with obesity-related traits in Canadian Oji-Cree. We now report association of this LMNA SNP with anthropometric indexes in 186 nondiabetic Canadian Inuit. We found that physical indexes of obesity, such as body mass index, waist circumference, waist to hip circumference ratio, subscapular skinfold thickness, and subscapular to triceps skinfold thickness ratio were each significantly higher among Inuit subjects with the LMNA 1908T allele than in subjects with the 1908C/1908C genotype. For each significantly associated obesity-related trait, the LMNA 1908C/T SNP genotype accounted for between approximately 10--100% of the attributable variation. The results indicate that common genetic variation in LMNA is an important determinant of obesity-related quantitative traits.     

The association between end-stage diabetic nephropathy and methylenetetrahydrofolate reductase genotype with macroangiopathy in type 2 diabetes mellitus.

The T/T genotype of the methylenetetrahydrofolate reductase C677 T gene polymorphism is associated with elevated homocysteine levels and presumably with increased atherosclerotic risk. We evaluated the interaction between this gene polymorphism and end-stage diabetic nephropathy on the observed prevalence of macroangiopathy in type 2 diabetes mellitus. The methylenetetrahydrofolate reductase 677 C/T genotypes were determined in 174 type 2 diabetic patients: 80 with and 94 without renal failure due to diabetic nephropathy. In the patients with renal failure, the T/T genotype and T allele were significantly associated with macroangiopathy (T/T; 31 % vs. 2 %, P = 0.0001 T allele; 59 % vs. 29 %, P = 0.00014), whereas the associations were not significant in the patients without renal failure. In the multiple logistic regression analysis, age (10 years OR 4.05 [1.79 - 9.31], P < 0.0005) and 677 T allele (6.84 [2.12 - 22.05], P = 0.0013) were significantly associated with macroangiopathy in the patients with renal failure. In conclusion, this study demonstrated that the 677 T/T genotype and T allele of MTHFR were significantly associated with macroangiopathy in type 2 diabetic patients with renal failure. The MTHFR 677 T allele, together with renal dysfunction due to diabetic nephropathy, could be a strong risk factor for atherosclerotic disease.     

亚甲基四氢叶酸还原酶基因多态性与糖尿病微血管并发症相关性研究

目的：探讨亚甲基四氢叶酸还原酶(MTHFR)基因多态性与中国人2型糖尿病微血管并发症的关系。方法：运用PCR—RFLP检测263例中国人(206例为2型糖尿病，其中148例合并肾病或视网膜病变，57例为正常对照组)MTHFR基因C677T位碱其突变，比较各组间等位基因频率和基因型频率。结果：(1)同时合并肾病和视网膜病变的2型糖尿病组与无微血管并发症的2型糖尿病组及正常对照组相比，TT基因型频率显著增加，突变等位基因T频率也明显升高。(2)2型糖尿病合并肾病组TT基因型频率及T等位基因频率明显高于不伴有肾病的2型糖尿病组及正常对照组。(3)2型糖尿病合并视网膜病组与无视网膜病的2型糖尿病及正常对照组相比，TT基因型频率及T等位基因频率明显升高。结论：MTHFR基因C677T碱基突变是促进中国人2型糖尿病患者并发微血管并发症的危险因子，突变T等位基因是糖尿病微血管并发症的易感基因。     

亚甲基四氢叶酸还原酶基因多态性与糖尿病肾病相关性研究

目的：研究亚甲基四氢叶酸还原酶（MTHFR）基因多态性与2型糖尿病肾病的关系。方法：运用聚合酶链反应－限制性片段长度多态性技术（PCR－RFLP）检测85例2型糖尿病患者（其中39例伴糖尿病肾病）及57例正常对照组MTHFR C677T基因型,采用高效液相色谱法测定血浆同型半胱酸水平。结果：糖尿病肾病组MTHFR基因TT纯合基因型,CT杂合基因型及T等位基因频率（分别为38．21％,51．28％,53．85％）均明显高于糖尿病不伴肾病组（分别为19．57％,28．26％,33．70％）及正常对照组（分别为17．54％,28．07％,31．58）,基因型和等位基因频率分布差异均有统计学意义（P＜0．05）,而MTHFR基因该多态性在不伴肾病组与正常对照组之间差异无显著性（P＞0．05）,T等位基因与糖尿病肾病的发生密切相关（OR＝2．30,95％可信区间;1．24－4．26）。糖尿病肾病组,糖尿病不伴肾病组及正常对照组中,MTHFR基因有C677T突变者血浆同型半胱氨酸水平均显著高于无基因突变者。结论：MTHFR基因C677T位碱基突变致血浆同型半胱氨酸水平高是糖尿病肾病发病的重要遗传因素。     

The relationship of the methylenetetrahydrofolate reductase C677T gene polymorphism in Turkish type 2 diabetic patients with and without nephropathy

BACKGROUND: Poor glycaemic control, hypertension and duration of diabetes are risk factors for the development of diabetic nephropathy, but there may be genetic factors. Recently, a common C to T mutation at nucleotide position 677 of the MTHFR gene (MTHFR677C > T) has been reported to be correlated with hyperhomocysteinemia and the severity of coronary artery disease as macroangiopathy. We aim to investigate Turkish type 2 diabetic patients with/without diabetic nephropathy and healthy group and examine the contribution of the MTHFR gene polymorphism to the development of diabetic nephropathy. METHODS: DNA was extracted from peripheral leukocytes of the subjects. Genotyping of the MTHFR C677T polymorphism for all individuals was performed by melting curve analysis of the generated amplicons after real-time online PCR. RESULTS: This genotype distribution did not differ between control subjects and type 2 diabetic patients in which 6.8% were TT, 43.7% were CT and 49.5% were CC (chi2 = 0.201, p > 0.05). The frequency of the mutant T allele was 23.4% in diabetic patients with nephropathy versus 33.0% in those without nephropathy. The genotype frequencies were TT, 2.1%; CT, 46.6%; CC, 55.3% in diabetic patients with nephropathy versus TT, 10.7%; CT, 44.6%; CC, 44.6% in those without nephropathy. CONCLUSIONS: The MTHFR genotype and allele frequencies were not different between diabetic patients with and without nephropathy (chi2 = 3, 386, p > 0.005; chi2 = 2.320, p > 0.005, respectively). Therefore, we conclude that the MTHFR gene polymorphism is not associated with the development of diabetic nephropathy in Turkish type 2 diabetic patients.     

白介素18基因型及血清水平与2型糖尿病肾病的相关性

目的研究白介素18（IL-18）基因型及血清水平与2型糖尿病肾病（DN）的关系。方法采用聚合酶链反应-限制性片段长度多态性（PCR-RFLP）技术,检测360例2型糖尿病患者（160例伴DN）及180名正常对照组的IL-18的基因多态性,同时采用酶联免疫吸附试验（ELISA）检测血清IL-18水平。结果与对照组比较,糖尿病肾病组血清IL-18水平显著高于对照组（P〈0．01）。IL-18基因-137G／C多态性在两组人群中的分布差异有统计学意义（P〈0．05）,携带-137C等位基因的糖尿病肾病患者血清IL-18水平显著高于不携带者（P〈0．05）。结论IL-18基因-137G／C多态性与DN的发病可能具有相关性,其中C等位基因可能是DN发病的遗传易感基因;携带C等位基因的个体可能通过促进IL-18的高度表达进而增加了DN的发病风险。     

Aldosterone synthase (CYP11B2) -344T/C polymorphism is not associated with the initiation and progression of diabetic nephropathy in Caucasian Type 1 diabetic patients.

AIMS: Aldosterone is one of the main effectors of the renin-angiotensin-aldosterone system regulating blood pressure. Previous studies have shown that the aldosterone synthase promoter polymorphism -344T/C influences aldosterone levels and is associated with hypertension, a risk factor for the initiation and progression of diabetic nephropathy. Therefore, we investigated whether the -344T/C polymorphism is associated with the development and progression of diabetic nephropathy in Type 1 diabetes mellitus. METHODS: The -344T/C polymorphism was determined using standard PCR techniques in 422 Type 1 diabetic patients with overt diabetic nephropathy [mean age 43 years (SD 11)], and in 479 patients with persistent normoalbuminuria and long-standing Type 1 diabetes [age 47 years (SD 12), duration of diabetes 27 years (SD 10)]. Furthermore, we genotyped 163 Type 1 diabetic patients with overt diabetic nephropathy treated with angiotensis-converting enzyme inhibitors (ACE-I). These patients were followed for a median of 6 years (range 3-14), with nine measurements (range 3-29) of glomerular filtration rate (GFR), and had a decline in GFR of 3.1 (-3.2; 23.7) ml/min per year. RESULTS: There was no significant difference between cases and controls in either genotype distributions (cases TT 0.33, TC 0.48, CC 0.19; controls TT 0.32, TC 0.48, CC 0.20) or allele frequencies (cases T/C 0.57/0.43; controls T/C 0.56/0.44). Furthermore, a genotype-phenotype interaction analysis in the normoalbuminuric patients revealed no differences in sex distribution, age, duration of diabetes, blood pressure, HbA(1c,) or urinary albumin excretion rate across genotypes. In the observational follow-up study, the rate of decline in GFR did not differ between groups of patients with different -344T/C genotype (P = 0.41). However, the T-allele made a statistically significant contribution to both systolic and diastolic pressure during follow-up (P = 0.006 and 0.032, respectively). CONCLUSIONS: The -344T/C polymorphism of the aldosterone synthase gene is not associated with initiation or progression of diabetic nephropathy in Caucasian Type 1 diabetic patients, but modulates blood pressure variation.     

内皮细胞型一氧化氮合酶基因多态性与糖尿病肾病的相关性研究

目的：探讨内皮细胞型一氧化氮合酶（eNOS)基因第7外显子894G→T点突变,及其第4内含子的1个27bp的插入／缺失（a/b)多态性,与2型糖尿病肾病（DN）之间的关系。方法：894G→T点突变采用聚合酶链反应限制性片段长度多态性（PCR－RFLP）技术,27bp的a/b多态性采用聚合酶链反应结合4％琼脂糖凝胶电泳分离技术。比较各组间的等位基因频率与基因型频率。结果：（1）早期糖尿病肾病组（DN^ 组）T等位基因及TG基因型频率显著高于糖尿病非肾病患者（DN^-组,P＜0．05）。（2）DN^ 组a等位基因及ab基因型频率显著高于DN^-组（P＜0．05）。（3）DN^ 组的TGab基因型频率亦显著高于DN^-组（P＜0．05）。（4）糖基化血红蛋白（GHbA1c),收缩压（SBP）,总胆固醇（TC）,eNOS基因第7外显子894G→T基因点突变及第4内含子a/b多态性均属糖尿病肾病的独立危险因素。结论：糖尿病患者eNOS基因第7外显子T等位基因及第4内含子a等位基因与DN^ 的发生密切相关,两种等位基因同时存在者,DN^ 发病风险更高。     

No association between MTHFR gene polymorphism and diabetic nephropathy in Japanese type II diabetic patients with proliferative diabetic retinopathy

The development of diabetic nephropathy shows marked variation among individuals. Not only hyperglycemia, but also genetic factors may contribute to the development of diabetic nephropathy. Methylenetetrahydrofolate reductase (MTHFR) is involved in remethylation of homocysteine to methionine. Decreased activity of MTHFR which can result in hyperhomocysteinemia may lead to cerebrovascular disease and coronary artery disease. Recently, a common C to T mutation at nucleotide position 677 of the MTHFR gene (MTHFR677C>T) has been reported to be correlated with hyperhomocysteinemia and the severity of coronary artery disease as macroangiopathy. In the present study, we recruited 173 of Japanese type II diabetic patients with proliferative diabetic retinopathy who would be exposed to long-term hyperglycemia, and examined the contribution of the MTHFR gene polymorphism to the development of diabetic nephropathy as microangiopathy. The frequency of the mutated allele was 43.3% in patients with nephropathy (n = 105) versus 41.9% in those without nephropathy (n = 68). The genotype frequencies were +/+, 16.2%; +/−, 54.3%; −/−, 29.5% in patients with nephropathy versus +/+, 13.2%; +/−, 57.4%; −/−, 29.4% in those without nephropathy (+ indicates the presence of the mutation). The MTHFR genotype and allele frequencies were not significantly different between patients with and without nephropathy. Therefore, we conclude that the MTHFR gene polymorphism is not associated with the development of diabetic nephropathy in Japanese type II diabetic patients.     

Aldose reductase gene polymorphism is associated with progression of diabetic nephropathy in Japanese patients with type 1 diabetes mellitus

Aim: The objective of this study was to investigate cross-sectionally and longitudinally whether polymorphism of the (A-C)n dinucleotide repeat sequence of the aldose reductase ( AR ) gene may modulate risk for diabetic nephropathy or retinopathy in Japanese patients with type 1 diabetes.
Methods: We obtained DNA samples from 101 patients followed up after the onset of type 1 diabetes and analysed a (A-C)n dinucleotide repeat polymorphic marker in the AR gene by polymerase chain reaction (PCR) method.
Results: Ten alleles ranging from Z−10 (128 bp) to Z+8 (146 bp) in repeat number were identified. In cross-sectional studies, the prevalence of the Z+2 allele was higher than that of any other allele in patients with diabetic nephropathy (37.5% of patients in a microalbuminuria group, and 41.7% of those in a macroalbuminuria group including patients with chronic renal failure and maintenance haemodialysis treatment). Prevalence of the Z+2 allele was not increased in patients with diabetic retinopathy. In longitudinal Kaplan–Meier plots, the cumulative incidence of nephropathy was significantly associated with homozygosity for the Z+2 allele (log rank test, p = 0.031); respective prevalence of nephropathy after diabetes durations of 10 and 15 years was 42.9% and 100% in Z+2 homozygotes ( n  = 8), 17.6% and 27.4% in Z+2 heterozygotes ( n  = 44), and 6.1% and 17.4% in patients without the Z+2 allele ( n  = 49). However, occurrence of retinopathy was not influenced by the Z+2 allele (log rank test, p = 0.926).
Conclusions: Homozygosity for the Z+2 allele was associated with accelerated early progression of diabetic nephropathy in Japanese type 1 diabetic patients.     

RAGE基因启动区-429T/C多态与2型糖尿病肾病相关

采用PCR RFLP法对 3 98例 2型糖尿病 (DM )患者和 2 12名正常对照者 (NC) ,进行晚期糖化终末产物受体 (RAGE)基因启动区 -4 2 9T/C多态基因型检测。比较 2型DM合并或未合并肾病组以及NC组间 -4 2 9T/C多态的基因型频率和等位基因频率。结果提示 ,-4 2 9T/C多态与 2型DM肾病的进展有关 ,C等位基因可能是中国人 2型DM临床肾病的保护因素。     

Genetic polymorphism of methylenetetrahydrofolate reductase as a risk factor for diabetic nephropathy in Chinese type 2 diabetic patients

OBJECTIVE: Genetic predisposition has been implicated in diabetic nephropathy (DN). The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, may play a role in the development of not only vascular disease but also diabetic microangiopathies. In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and diabetic nephropathy. METHODS: 220 unrelated patients with type 2 diabetes mellitus and 130 controls were recruited. The MTHFR genotype was analyzed by PCR followed by HinfI digestion. Plasma total homocysteine levels were measured using high-performance liquid chromatography (HPLC) with fluorescence detection. RESULTS: In 130 healthy control subjects, the frequency of the mutant T allele was 30.0%, comparable to that of a Hong Kong (Chinese) population. The distribution of the three genotypes was as follows: TT genotype, 16.9%; CT genotype, 26.2%; and CC genotype, 56.9%. This genotype distribution did not differ between control subjects and type 2 diabetic patients in which 19.1% were TT, 34.5% were CT and 46.4% were CC (2=3.85, P>0.05). The frequency of the mutant T allele was 42.3% in diabetic patients with nephropathy (n=124) versus 28.6% in those without nephropathy (n=96). The genotype frequencies were TT, 21.0%; CT, 42.7%; CC, 36.3% in diabetic patients with nephropathy versus TT, 16.7%; CT, 23.9%; CC, 59.4% in those without nephropathy. The MTHFR genotype and allele frequencies were different between diabetic patients with and without nephropathy (chi2=12.27, P<0.005; chi2=8.77, P<0.005, respectively). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype. CONCLUSIONS: The C677T mutation of MTHFR gene is common in the Chinese population. MTHFR C677T gene polymorphism associated with a predisposition to increased plasma homocysteine levels may represent a genetic risk factor for diabetic nephropathy in Chinese type 2 diabetic patients.     

Polymorphism of the solute carrier family 12 (sodium/chloride transporters) member 3, SLC12A3, gene at exon 23 (+78G/A: Arg913Gln) is associated with elevation of urinary albumin excretion in Japanese patients with type 2 diabetes: a 10-year longitudinal study

Aims/hypothesis We have shown previously that the SLC12A3 +78G/A polymorphism in exon 23 (Arg913Gln) was a new candidate for conferring susceptibility to diabetic nephropathy. The aim of this study was to confirm the effect of this polymorphism on the elevation of urinary albumin excretion in type 2 diabetic patients.Methods We retrospectively studied 264 Japanese patients with type 2 diabetes over a ten-year period. The subjects were classified into two groups: (1) persistent normoalbuminuria or microalbuminuria, or improvement from microalbuminuria to normoalbuminuria (group N); and (2) progression from normoalbuminuria to microalbuminuria or overt proteinuria, or progression from microalbuminuria to overt proteinuria (group P). They were assessed for association with the +78G/A polymorphism.Results The frequency of the +78A allele was significantly higher in group N than in group P (10% vs 1%, p=0.021). By logistic regression analysis and discriminant analysis, the substituted allele was shown to be an independent factor correlating negatively to the elevation of albumin excretion (p=0.043 and 0.022, respectively).Conclusions/interpretation The SLC12A3 +78A(+) genotype may have a protective effect against the development and/or progression of diabetic nephropathy in Japanese type 2 diabetic patients.     

Genetic variation in thrombin-activatable fibrinolysis inhibitor is associated with the risk of diabetic nephropathy

Diabetic nephropathy is a kidney disease or damage that results as a complication of diabetes, especially Type 2 diabetes, while albuminuria is an early marker for diabetic nephropathy as it can predict cardiovascular events and mortality in diabetic patients. A potent inhibitor of fibrinolysis, the thrombin-activatable fibrinolysis inhibitor (TAFI) has been isolated and characterized from human plasma. We investigated the associations of the activity-related variants in the TAFI coding gene (505A/G,1040C/T) with the risk of diabetic nephropathy by examining 297samples including 140 health controls and 157 confirmed diabetic nephropathy patients. Diabetic nephropathy grades were further categorized by the urine albumin excretion (UAE)-to-creatinine ratios (ACR). We found little difference that was statistically significant in terms of 505A/G among patients and controls. While at 1040C/T, the detected frequency for the T allele in the group of diabetic nephropathy patients was significantly smaller than that of the control group (15.6% vs 25.7%, respectively; p<0.05). This was due to the relative decrease of T/T homozygotes in the patients (p<0.05, 95% odds ratio 0.28, confidence interval 0.11-0.70). Surprisingly, the difference was only observed with initial diabetic nephropathy stages. This study clearly indicates that, at 1040C/T, the frequency for the T allele is strongly associated with increased risk for diabetic nephropathy in a subset of the general population, implying that the T allele confers protection against the onset of diabetic nephropathy only in homozygosity and may function as a recessive trait.     

The Val81 missense mutation of the melanocortin 3 receptor gene, but not the 1908c/T nucleotide polymorphism in lamin A/C gene, is associated with hyperleptinemia and hyperinsulinemia in obese Greek caucasians

Obesity-related phenotypes have been linked to human chromosomes 1q21 and 20q13, regions where the lamin A/C gene (LMNA) and the melanocortin 3 receptor gene (MC3R) map, respectively. Recently, a common single nucleotide polymorphism (SNP) in LMNA (1908C/T) was associated with plasma leptin and obesity indices in aboriginal Canadians, but these associations have not yet been explored in other populations. In contrast, no significant associations of MC3R variants with obesity have been detected, although a significant association with hyperinsulinemia has been reported in Caucasian populations. We investigated the associations between the LMNA 1908C/T variant and the 241G/A variant of the MC3R gene (Val81Ile missense mutation) and body composition, as well as plasma leptin and insulin levels, in two samples of unrelated healthy Greek subjects. A group of 112 young nonobese subjects, and a group of 116 adult women with a body mass index (BMI) ranging from 23.2 to 47.7 kg/m2 were studied cross-sectionally. We found no significant association of the LMNA 1908C/T and a borderline significant association of MC3R 241G/A SNPs with body composition variables, in the entire study sample. However, unlike the LMNA 1908C/T genetic variation, the MC3R 241G/A genetic variation was significantly associated with hyperleptinemia and huperinsulinemia in obese subjects, and there was evidence of interaction between this polymorphism and fat mass or BMI in predicting hyperinsulinemia. Our results suggest that the LMNA 1908C-->T substitution and the Val81Ile mutation of the MC3R gene are unlikely to be major predictors of body composition in Greek Caucasians, but the latter genetic variation may predispose obese subjects to develop insulin and leptin resistance. Future studies are needed to confirm these data and assess whether individuals carrying this mutation are more resistant to weight-reducing and insulin-sensitizing treatments.     

Putative role of polymorphisms in UCP1-3 genes for diabetic nephropathy

Increased production of reactive oxygen species (ROS) has been suggested as a cause of diabetic complications. Uncoupling proteins (UCPs) have been ascribed a role in reducing the formation of ROS, and genetic variation in genes encoding for UCPs could thus be putative candidate genes for diabetic nephropathy. To test this hypothesis we searched for association between the A-->G (-3862) variant in UCP1, the insertion/deletion (I/D) polymorphism in exon 8 in UCP2, and the C-->T (-55) polymorphism in UCP3 and diabetic nephropathy in 218 diabetic patients with normal urinary albumin excretion rate (AER), 216 with micro- or macroalbuminuria, and in 106 control subjects without a family history of diabetes. We did not find any association between the different polymorphisms and diabetic nephropathy, nor did we observe any difference in AER among carriers of different UCP1-3 genotypes. We could, however, confirm the reported association between BMI and the UCP3 -55 C-->T polymorphism; patients carrying the T allele had higher BMI than patients homozygous for the C allele (26.4+/-4.2 vs. 25.3+/-4.3 kg/m(2); P=.01). We conclude that studied polymorphisms in the UCP1-3 genes do not play a major role in the development of micro- or macroalbuminuria in Scandinavian diabetic patients.