2型糖尿病颈动脉内中膜厚度与亚甲基四氢叶酸还原酶基因C677T多态性及血浆同型半胱氨酸水平的关系

目的探讨亚甲基四氢叶酸还原酶（MTHFR）基因C677T多态性及同型半胱氨酸水平与早期2型糖尿病（T2DM）颈动脉内中膜厚度（IMT）的关系及影响因素。方法测定T2DM患者及对照组（NC）颈动脉IMT,分为糖尿病无内中膜增厚组（DM1）和糖尿病合并内中膜增厚组（DM2）。用PCR—RFLP检测MTHFR基因C677T多态性。结果DM。组MTHFR C677T基因TT基因型频率与NC组比较明显增高（40．4％ vs 17．3％,P〈0．01）,与DM1组比较明显增高（40．4% vs 17．9％,P〈0．01）,DM1组与NC组比较无统计学差异（17．9％ vs 17．3％,P〉0．05）。T等位基因频率DMz组与NC组比较明显增高（57．0％ vs 33．7％,P〈0．01）,与DM1组比较明显增高（57．0％ vs 42．9％,P〈0．01）,差异有统计学意义。结论高同型半胱氨酸血症、T等位基因是早期糖尿病患者颈动脉内中膜增厚的危险因素之一,血浆同型半胱氨酸水平与MTHFR C677T基因多态性有关。     

甲烯四氢叶酸还原酶基因多态性与糖尿病大血管病变的关系研究

目的探讨甲烯四氢叶酸还原酶(MTHFR)基因C677T位碱基突变与2型糖尿病患者同型半胱氨酸(Hcy)水平和糖尿病大血管病变的关系。方法将患者分为对照组、糖尿病颈动脉内中膜厚度(IMT)正常组、糖尿病IMT增厚组。应用酶联免疫法测定Hcy水平,采用多聚酶链反应-限制性内切酶片段长度多态性技术(PCR-RFLP)检测MTHFRC677T基因型,用高分辨彩色多普勒检查颈动脉内中膜厚度(IMT)。结果糖尿病IMT增厚组MTHFR基因的TT基因型和T等位基因频率显著增高,与糖尿病IMT正常组及对照组存在统计学差异(P<0.05)。对照组与糖尿病IMT正常组之间T等位基因频率无统计学差异。MTHFR基因突变者血浆Hcy增高。糖尿病组MTHFR基因突变者IMT值明显高于无基因突变者。结论糖尿病IMT增厚组T等位基因频率增高。MTHFR基因C677T点突变组血浆Hcy水平升高,颈动脉IMT增厚。推测MTHFR基因C677T点突变可能是糖尿病合并大血管病变发病的重要遗传因素。     

MTHFR基因多肽性及血浆同型半胱氨酸水平与老年人脑卒中发病的关系

目的：探讨N^5，N^10-亚甲基四氢叶酸还原酶（MTHFR）基因C677T位点突变和血浆总同型半胱氨酸（tHcy）水平升高是否增加中国老年人群脑卒中的危险。方法：对1002例经头颅CT确诊的老年（〉60岁）脑卒中患者和948例非卒中对照者，采用多聚酶链反应．限制性内切酶片段长度多态性技术（PCR-RFLP）检测MTHFR C667T基因型，用高效液相色谱法测定血浆总同型半胱氨酸水平，同时所有研究对象记录其病史，体检等临床资料及吸烟，饮酒等流行病学资料。结果：脑卒中患者MTHFR基因纯合子突变（TT）和杂合子突变（CT）发生率（69．4％）明显高于对照组（64．3％，P=0．016），卒中组T等位基因频率（45．8％）也高于对照组（42．4％，P=0．032）；脑卒中患者血浆总同型半胱氨酸水平及异常检出率和中、重度增高率亦明显高于对照组（P〈0．001），且MTHFR基因TT型〉CT型〉CC型（P〈0．001）。Logistic回归分析结果显示：在调整传统危险因素后，升高的tHey水平和CT和TT基因型仍与脑卒中发病的有关，且血浆同型半胱氨酸水平越高发生脑卒中的危险性越大。结论：高同型半胱氨酸血症是中国老年人脑卒中发病的一个独立危险因素，而MTHFR基因C677T位点突变可能是其发病的重要遗传因素。     

急性脑梗死患者MTHFR基因多态性与血浆同型半胱氨酸水平的关系

目的 探讨急性脑梗死（ACI）患者N5,N10-亚甲四氢叶酸还原酶（MTHFR）基因多态性与血浆同型半胱氨酸（Hcy）水平的关系.方法 采用多聚酶链反应2-限制性内切酶片段长度多态性技术（PCR2-RFLP）检测48例ACI患者MTHFR基因C677T位点多态性,同时测定血浆总Hcy及血清叶酸、维生素B12、尿酸（UA）.结果 ACI患者MTHFR基因T/T型频率为35.43％,T/C型频率为56.32％,C/C型频率为8.25％;T等位基因频率为63.59％,C等位基因频率为36.41％.MTHFR基因T/T型ACI患者血浆Hcy显著高于其他两型,T/C型与C/C型血浆Hcy水平较比较无显著差异.Hcy中度与轻度增高者MTHFR基因分布比较,P≤0.05.3组基因型间叶酸、维生素B12及UA水平均无显著差异.结论 ACI患者MTHFR基因C677T突变与Hcy水平显著相关,MTHFR基因纯合突变可能是引起高Hcy的一个重要遗传因素.     

类风湿关节炎合并心血管病变患者血清同型半胱氨酸水平及其与亚甲基四氢叶酸还原酶基因多态性的关系

目的检测类风湿关节炎（RA）患者血清同型半胱氨酸水平和亚甲基四氢叶酸还原酶（MTHFR）基因单核苷酸多态性,分析其在RA合并心血管病变患者中的作用。方法收集183例RA患者,分为合并心血管病变组和无心血管病变组,同时选取50名我院健康体检者作为对照组。采用实时荧光定量聚合酶链反应方法测定RA患者和对照组的MTHFR基因rs1801133C／T（677）和rs1801131A／C（1298）2个位点的基因单核苷酸多态性;ELISA法检测3组受试者血清同型半胱氨酸水平。结果①183例RA患者心血管病变发生率约为29．0％,其中合并心血管病变组同型半胱氨酸水平明显高于无心血管病变组（P〈0．001）。②677TT基因型组血清同型半胱氨酸水平高于CC及CT组（P〈0．05）。③RA患者血清同型半胱氨酸水平与心血管事件呈正相关。结论RA合并心血管病变患者血清同型半胱氨酸水平明显高于RA无心血病变组及正常对照组,其水平增高可能与MTHFR677C／T基因多态性有关。血清同型半胱氨酸水平升高可作为RA患者发生心血管事件的预测指标。     

亚甲基四氢叶酸还原酶基因多态性与原发性高血压患者合并冠心病的相关性研究

目的探讨N5,10-亚甲基四氢叶酸还原酶(MTHFR)C677T位点突变与河南豫北地区原发性高血压及其合并冠心病发病的关系。方法选择原发性高血压患者405例为高血压组,高血压合并冠心病患者400例为冠心病组,健康体检者400例为对照组。对3组MTHFR基因C677T多态性进行基因分型。结果冠心病组T等位基因频率和TT基因型频率明显高于高血压组和对照组(P<0.05)。冠心病组TT基因型患者TC和血浆同型半胱氨酸水平明显高于CC+CT基因型(P<0.05)。结论 MTHFR基因C677T多态性与原发性高血压患者冠心病的发生相关。     

血浆同型半胱氨酸及其相关酶基因多态性与Alzheimer病的关系

目的探讨同型半胱氨酸（homocysteine,Hey）及其相关酶5,10亚甲基四氢叶酸还原酶（methylenetetrahydrofolate reductase,MTHFR）的基因多态性与阿尔茨海默病（Alzheimer$disease,AD）的关系。方法对68例AD患者和68例健康对照组采用循环酶法测定血浆Hcy水平;多聚酶链反应-限制性片段长度多态性（PCR—RFLP）方法检测MTHFR基因C677T的多态性。结果AD患者血浆Hcy水平13．92&#177;5．513μmoL／L显著高于健康对照组10．83&#177;3．800μmol／L;MTHFRC677T各基因型总体分布在两组之间差异有显著性,其中C／T基因型在AD组中所占比例（64．71％）显著高于对照组（42．65％）。结论血浆高Hcy水平可能参与AD的发生发展;MTHFR基因C677T突变导致的基因多态性可能参与了AD的遗传机制;山西汉族人血浆高Hcy水平在很大程度上与遗传有一定关系。     

MTHFR基因多态性与冠心病的关系

目的研究天津地区人群N^5,N^10-亚甲基四氢叶酸还原酶（MTHFR）基因C677T多态性与冠心病的关系。方法应用聚合酶链反应（PCR）技术和限制性酶切片段长度多态性（RFLP）分析技术检测50例冠心病患者（冠心病组）和50例正常人（对照组）的MTHFR基因C677T多态性,应用高效液相色谱法测定血浆同型半胱氨酸（Hcy）水平,采用125I标记放免法测定血清叶酸浓度。结果1.冠心病组与对照组MTHFR基因频率分布不同（P〈0.05）,对照组CC型、TC型、TT型基因频率分别为52.0%,28.0%,20.0%,冠心病组分别为26.0%,44.0%,30.0%。冠心病组T等位基因频率为52.0%,C等位基因频率为48.0%,与对照组比较有显著性差异（P〈0.05）。2.两组的TT基因型者血浆Hcy浓度均明显高于CC和TC基因型者（P〈0.05）,而后两者间无显著性差异（P〉0.05）。3.冠心病组Hcy浓度高于照组（P〈0.05）,两组叶酸水平无显著性差异（P〉0.05）,血浆Hcy浓度与叶酸水平呈显著负相关（r分别为-0.617和-0.588,P〈0.05）。结论MTHFR基因C677T点突变与冠心病发病密切相关,MTHFR基因纯合突变是引起高Hcy血症的一个重要的遗传因素。     

MTHFR基因多态性及血浆同型半胱氨酸与老年脑梗死的相关性研究

目的探讨N5，N10亚甲基四氢叶酸还原酶（MTHFR）基因多态性及血浆同型半胱氨酸（Hcy）与老年脑梗死的相关性。方法应用高效液相色谱法和多聚酶链反应限制性内切酶片段长度多态性技术检测并比较了102例老年脑梗死患者（脑梗死组）和100例健康老年人（对照组）的血浆Hcy浓度及MTHFR基因型。结果两组MTHFR677位点基因型分布和各等位基因频率比较均有统计学差异（P均〈0．05）；脑梗死组T等位基因频率及血浆Hcy浓度高于对照组（P均〈0．05）。结论MTHFR基因突变可导致血浆Hcy浓度升高，高Hcy浓度及MTHFR基因T型均为老年脑梗死的高危因素。     

5,10-亚甲基四氢叶酸还原酶C677T基因多态性与老年单纯收缩期高血压的相关性研究

目的探讨5,10-亚甲基四氢叶酸还原酶(MTHFR)C677T基因多态性与老年单纯收缩期高血压(ISH)发病的相关性。方法入选220例年龄≥60岁ISH患者为ISH组,选择同期体检无高血压老年人群128例为对照组。检测入选者MTHFR C677T基因多态性及血浆同型半胱氨酸水平。结果ISH组T等位基因频率高于对照组(51.8%vs 37.5%,χ~2=13.33,P=0.000),C等位基因频率低于对照组(48.2%vs 62.5%,χ~2=13.33,P=0.000);CC基因型分布低于对照组(20.5%vs 40.6%,χ~2=16.38,P=0.000),CT基因型分布高于对照组(55.5%vs43.8%,χ~2=4.44,P=0.035);血浆同型半胱氨酸水平均高于对照组(13.35μmol/L vs 11.75μmol/L,P=0.01)。logistic回归分析显示,MTHFR C677T基因型(OR=1.910,95%CI:1.356~2.690,P=0.00)、同型半胱氨酸水平(OR=1.084,95%CI:1.031~1.140,P=0.02)、血尿酸水平(OR=1.004,95%CI:1.001~1.006,P=0.01)为老年ISH患病的独立预测因素。结论 MTHFR C677T基因多态性及血浆同型半胱氨酸水平是老年ISH发病的独立危险因素。     

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.     

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     

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。     

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.     

Methylenetetrahydrofolate reductase polymorphism associated with susceptibility to coronary heart disease in Chinese type 2 diabetic patients

OBJECTIVE: Epidemiological studies have identified hyperhomocyst(e)inemia as an independent risk factor for atherosclerosis. The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, might play a role in the development of coronary heart disease (CHD). In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and CHD in Chinese type 2 diabetic patients. METHODS: Two hundred and twenty-eight unrelated patients with type 2 diabetes mellitus (126 with coronary heart disease) and 114 healthy control subjects 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 114 healthy control subjects, the frequency of the mutant T allele was 38.0%, comparable to that of a Hong Kong (Chinese) population. The genotype distribution did not differ between control subjects and type 2 diabetic patients (chi(2) = 3.67, P > 0.05). Genotypic analysis revealed that type 2 diabetic patients with CHD displayed a greater prevalence of T allele (45.2%) than type 2 diabetic patients without CHD (30.4%) (chi(2) = 8.72, P < 0.005). The odds ratio for CHD in type 2 diabetic patients in presence of T allele was 1.89 (CI 95%, 1.24-2.88). The MTHFR genotype were different between diabetic patients with and without CHD (chi(2) = 11.98, P < 0.005). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype or CC plus 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 could constitute a useful predictive marker for CHD in Chinese type 2 diabetic patients.     

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.     

MTHFR C677T and A1298C gene polymorphisms and hyperhomocysteinemia as risk factors of diabetic nephropathy in type 2 diabetes patients

Point mutations in methylenetetrahydrofolate reductase (MTHFR) and hyperhomocysteinemia were implicated in the pathogenesis of diabetic nephropathy (DN) in many ethnic groups. This study addressed the association of C677T and A1298C single nucleotide polymorphisms (SNPs) of MTHFR gene with DN in Tunisian type 2 diabetes (T2DM) patients. Study subjects comprised 93 DN patients, 267 patients with normoalbuminuria, and 400 control subjects. C677T and A1298C genotypes were determined by PCR-RFLP analysis, and homocysteine levels were measured by ELISA. A1298C and C677T were highly prevalent among T2DM patients, with allele frequencies of 0.26 and 0.36, respectively. Higher mutant 677T allele and 677C/T and 677T/T genotypes of C677T SNP, but not A1298C SNP, together with 677C/1298A, 677C/1298C, and 677T/1298A haplotypes were seen in DN patients compared to normoalbuminuric patients, (p<0.001). Plasma homocysteine was positively associated with MTHFR 677T/T genotype among the three groups, and was significantly elevated in double heterozygous DN patients but not in normoalbuminuric patients or controls. Logistic regression analysis with DN as dependent variable showed that homocysteine (OR, 1.153) and MTHFR 677T/T (OR, 9.799) were the only variables associated with DN, after adjusting for possible confounding variables. C677T, but not A1298C, SNP, is a risk factor for DN, presumably acting by elevating homocysteine levels.     

Thermolabile methylenetetrahydrofolate reductase enzyme genotype is frequent in type 2 diabetic patients with normal fasting homocysteine levels

OBJECTIVE: To investigate the plasma homocysteine concentrations with regard to nutritional, metabolic and genetic factors and to find out the frequency and impact of thermolabile methylenetetrahydrofolate reductase (T-MTHFR) polymorphism in patients with type 2 diabetes mellitus. DESIGN: A cross-sectional study. SUBJECTS: A total of 94 subjects with type 2 diabetes mellitus and 91 healthy age- and sex-matched nonsmoking volunteers were recruited. MAIN OUTCOME MEASURES: Age, sex, duration and complications of diabetes mellitus, metabolic variables, fasting plasma homocysteine levels, and presence of T-MTHFR polymorphism were evaluated for all participants. Presence of T-MTHFR polymorphism was analysed to define any possible role in diabetes progress, complications and metabolic milieu. RESULTS: Fasting homocysteine levels were similar in diabetic patients and controls. Prevalence of homozygous polymorphism of thermolabile MTHFR gene (TT) was encountered more frequently in patients with diabetes mellitus than the healthy controls (P = 0.004). Subgrouping of the patients with respect to MTHFR genotype revealed similar metabolic variables and frequency of chronic complications of diabetes mellitus in groups. Patients with TT genotype revealed longer diabetes duration when compared with the patients having heterozygous mutation of thermolabile MTHFR or normal homozygous MTHFR genotypes (P = 0.046). CONCLUSIONS: Type 2 diabetic patients have similar fasting plasma homocysteine levels with that of age- and sex-matched healthy people. There is no correlation between diabetic complications and this amino acid metabolite. On the contrary, thermolabile variant of MTHFR genotype is found to be more frequent in diabetic patients especially in those who have experienced a longer duration of disease.     

Association between plasma homocysteine concentrations and asymptomatic cerebral infarction or leukoaraiosis in elderly diabetic patients

Background: The purpose of the present study was to investigate the possible contribution of plasma homocysteine to asymptomatic cerebral infarction (CI) or leukoaraiosis. Methods: The relationship between plasma homocysteine concentrations and cerebral lesions was investigated in 233 elderly diabetic patients (mean age: 74 years) who were divided into three groups based on the neurological and brain MR findings: asymptomatic cerebral infarction (CI), symptomatic CI, and a control group with no evidence of cerebrovascular disease. Plasma total homocysteine concentrations were measured by high‐performance liquid chromatography. The C677T polymorphism in the methylene tetrahydrofolate reductase (MTHFR) gene was assessed by PCR‐RFLP. The total score of T2 high‐intensity lesions on the brain MR images was summed from the focal T2 high‐intensity scores in 24 areas of the brain. Results: Diabetic patients with asymptomatic or symptomatic CI had significantly higher homocysteine concentrations in plasma than the control group. The plasma homocysteine concentration was more strongly associated with the presence and number of small infarctions or infarction of the putamen, which may explain the association between increased plasma homocysteine concentrations and asymptomatic CI in elderly diabetic patients. In the diabetic patients, high plasma homocysteine concentrations were also significantly associated with high scores of total T2 high‐intensity lesions or focal T2 high‐intensity scores in some periventricular regions. Although there was no significant relationship between the MTHFR TT genotype and CI, a significant association was found between the MTHFR TT genotype and total T2 high‐intensity scores. Conclusion: An elevated plasma homocysteine concentration is independently associated with asymptomatic CI and T2 high‐intensity lesions on brain MR images in elderly patients with diabetes mellitus. The association between the MTHFR TT genotype and periventricular T2 high‐intensity lesions, but not with CI, suggests an important effect of C677T MTHFR gene mutation on leukoaraiosis, independent of hyperhomocysteinemia in elderly diabetic patients.