Total homocysteine is associated with nephropathy in non-insulin-dependent diabetes mellitus

Angiotensin-converting-enzyme inhibitors and angiotensin receptor blockers for preventing the progression of diabetic kidney disease

BACKGROUND

Guidelines suggest that adults with diabetes and kidney disease receive treatment with angiotensin-converting-enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB). This is an update of a Cochrane review published in 2006.

OBJECTIVES

We compared the efficacy and safety of ACEi and ARB therapy (either as monotherapy or in combination) on cardiovascular and kidney outcomes in adults with diabetes and kidney disease.

SEARCH METHODS

We searched the Cochrane Kidney and Transplants Register of Studies to 17 March 2024 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included studies evaluating ACEi or ARB alone or in combination, compared to each other, placebo or no treatment in people with diabetes and kidney disease.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias and extracted data. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

One hundred and nine studies (28,341 randomised participants) were eligible for inclusion. Overall, the risk of bias was high. Compared to placebo or no treatment, ACEi may make little or no difference to all-cause death (24 studies, 7413 participants: RR 0.91, 95% CI 0.73 to 1.15; I2 = 23%; low certainty) and with similar withdrawals from treatment (7 studies, 5306 participants: RR 1.03, 95% CI 0.90 to 1.19; I2 = 0%; low certainty). ACEi may prevent kidney failure (8 studies, 6643 participants: RR 0.61, 95% CI 0.39 to 0.94; I2 = 0%; low certainty). Compared to placebo or no treatment, ARB may make little or no difference to all-cause death (11 studies, 4260 participants: RR 0.99, 95% CI 0.85 to 1.16; I2 = 0%; low certainty). ARB have uncertain effects on withdrawal from treatment (3 studies, 721 participants: RR 0.85, 95% CI 0.58 to 1.26; I2 = 2%; low certainty) and cardiovascular death (6 studies, 878 participants: RR 3.36, 95% CI 0.93 to 12.07; low certainty). ARB may prevent kidney failure (3 studies, 3227 participants: RR 0.82, 95% CI 0.72 to 0.94; I2 = 0%; low certainty), doubling of serum creatinine (SCr) (4 studies, 3280 participants: RR 0.84, 95% CI 0.72 to 0.97; I2 = 32%; low certainty), and the progression from microalbuminuria to macroalbuminuria (5 studies, 815 participants: RR 0.44, 95% CI 0.23 to 0.85; I2 = 74%; low certainty). Compared to ACEi, ARB had uncertain effects on all-cause death (15 studies, 1739 participants: RR 1.13, 95% CI 0.68 to 1.88; I2 = 0%; low certainty), withdrawal from treatment (6 studies, 612 participants: RR 0.91, 95% CI 0.65 to 1.28; I2 = 0%; low certainty), cardiovascular death (13 studies, 1606 participants: RR 1.15, 95% CI 0.45 to 2.98; I2 = 0%; low certainty), kidney failure (3 studies, 837 participants: RR 0.56, 95% CI 0.29 to 1.07; I2 = 0%; low certainty), and doubling of SCr (2 studies, 767 participants: RR 0.88, 95% CI 0.52 to 1.48; I2 = 0%; low certainty). Compared to ACEi plus ARB, ACEi alone has uncertain effects on all-cause death (6 studies, 1166 participants: RR 1.08, 95% CI 0.49 to 2.40; I2 = 20%; low certainty), withdrawal from treatment (2 studies, 172 participants: RR 0.78, 95% CI 0.33 to 1.86; I2 = 0%; low certainty), cardiovascular death (4 studies, 994 participants: RR 3.02, 95% CI 0.61 to 14.85; low certainty), kidney failure (3 studies, 880 participants: RR 1.36, 95% CI 0.79 to 2.32; I2 = 0%; low certainty), and doubling of SCr (2 studies, 813 participants: RR 1.14, 95% CI 0.70 to 1.85; I2 = 0%; low certainty). Compared to ACEi plus ARB, ARB alone has uncertain effects on all-cause death (7 studies, 2607 participants: RR 1.02, 95% CI 0.76 to 1.37; I2 = 0%; low certainty), withdrawn from treatment (3 studies, 1615 participants: RR 0.81, 95% CI 0.53 to 1.24; I2 = 0%; low certainty), cardiovascular death (4 studies, 992 participants: RR 3.03, 95% CI 0.62 to 14.93; low certainty), kidney failure (4 studies, 2321 participants: RR 1.15, 95% CI 0.67 to 1.95; I2 = 29%; low certainty), and doubling of SCr (3 studies, 2252 participants: RR 1.18, 95% CI 0.85 to 1.64; I2 = 0%; low certainty). Comparative effects of different ACEi or ARB and low-dose versus high-dose ARB were rarely evaluated. No study compared different doses of ACEi. Adverse events of ACEi and ARB were rarely reported.

AUTHORS' CONCLUSIONS

ACEi or ARB may make little or no difference to all-cause and cardiovascular death compared to placebo or no treatment in people with diabetes and kidney disease but may prevent kidney failure. ARB may prevent the doubling of SCr and the progression from microalbuminuria to macroalbuminuria compared with a placebo or no treatment. Despite the international guidelines suggesting not combining ACEi and ARB treatment, the effects of ACEi or ARB monotherapy compared to dual therapy have not been adequately assessed. The limited data availability and the low quality of the included studies prevented the assessment of the benefits and harms of ACEi or ARB in people with diabetes and kidney disease. Low and very low certainty evidence indicates that it is possible that further studies might provide different results.

Meta-analysis of Serum Vitamin B12 Levels and Diabetic Retinopathy in Type 2 Diabetes

BACKGROUND

Previous studies have shown an association between low serum vitamin B12 levels and the risk of diabetic retinopathy (DR) in type 2 diabetes, but the conclusions from various studies were inconsistent. Therefore, we collected relevant data from various databases to perform a meta-analysis and address the inconsistencies in these studies.

METHODS

We searched PubMed, Embase, Cochrane Library, CNKI, Wanfang and CQVIP for eligible studies published up to April 10, 2022, and performed a meta-analysis using Stata software to assess the association between serum vitamin B12 levels and DR.

RESULTS

A total of 15 studies were included in this meta-analysis. Statistical analysis showed that serum vitamin B12 levels were significantly reduced in patients with type 2 diabetic retinopathy ,WMD 95% CI = -68.91 (-76.76, -61.06) (p <0.00001, I² = 88.30%). In subgroup analyses by ethnicity, an association between low serum vitamin B12 levels and DR risk was found in East Asian, South Asian and mixed populations, but not in Caucasian populations.

CONCLUSIONS

This meta-analysis analyzed vitamin B12 in patients with type 2 diabetic retinopathy and emphasized the importance of monitoring serum vitamin B12 levels in patients with type 2 diabetic retinopathy, but this meta-analysis still has deficiencies and limitations, and more clinical studies are needed to confirm this conclusion in the future.

Involvements of Hyperhomocysteinemia in Neurological Disorders

Homocysteine (HCY), a physiological amino acid formed when proteins break down, leads to a pathological condition called hyperhomocysteinemia (HHCY), when it is over a definite limit. It is well known that an increase in HCY levels in blood, can contribute to arterial damage and several cardiovascular disease, but the knowledge about the relationship between HCY and brain disorders is very poor. Recent studies demonstrated that an alteration in HCY metabolism or a deficiency in folate or vitamin B12 can cause altered methylation and/or redox potentials, that leads to a modification on calcium influx in cells, or into an accumulation in amyloid and/or tau protein involving a cascade of events that culminate in apoptosis, and, in the worst conditions, neuronal death. The present review will thus summarize how much is known about the possible role of HHCY in neurodegenerative disease.

Plasma cystathionine and risk of acute myocardial infarction among patients with coronary heart disease: Results from two independent cohorts

BACKGROUND

Cystathionine is a thio-ether and a metabolite formed from homocysteine during transsulfuration. Elevated plasma cystathionine levels are reported in patients with cardiovascular disease; however prospective relationships with acute myocardial infarction (AMI) are unknown. We investigated associations between plasma cystathionine and AMI among patients with suspected and/or verified coronary heart disease (CHD).

METHODS

Subjects from two independent cohort studies, the Western Norway Coronary Angiography Cohort (WECAC) (3033 patients with stable angina pectoris; 263 events within 4.8 years of median follow-up) and the Norwegian Vitamin Trial (NORVIT) (3670 patients with AMI; 683 events within 3.2 years of median follow-up) were included.

RESULTS

In both cohorts, plasma cystathionine was associated with several traditional CHD risk factors (P < 0.001). Comparing the cystathionine quartile 4 to 1, age and gender adjusted hazard ratios (95% confidence intervals) for AMI were 2.08 (1.43-3.03) and 1.41 (1.12-1.76) in WECAC and NORVIT, respectively. Additional adjustment for traditional risk factors slightly attenuated the risk estimates, which were generally stronger in both cohorts among non-smokers, patients with higher age, and lower BMI or PLP status (P-interaction ≤ 0.04). Risk associations also tended to be stronger in patients not treated with B-vitamins. Additionally, in a subset of 80 WECAC patients, plasma cystathionine associated strongly negatively with glutathione, an important antioxidant and positively with lanthionine, a marker of H₂S production (P < 0.001).

CONCLUSIONS

Plasma cystathionine is associated with increased risk of AMI among patients with either suspected or verified coronary heart disease, and is possibly related to altered redox homeostasis.

Serum folate, vitamin B12 levels and diabetic peripheral neuropathy in type 2 diabetes: A meta-analysis

The association between serum folate and vitamin B12 levels and the risk of diabetic peripheral neuropathy (DPN) remains unclear. This meta-analysis included 16 studies of serum folate levels (1190 cases and 1501 controls) and 18 studies of serum vitamin B12 levels (1239 cases and 1562 controls) in patients with type 2 diabetes mellitus (T2DM). Reduced serum levels of folate and vitamin B12 were found in patients with T2DM and DPN compared with patients with T2DM but without DPN; weighted mean difference (WMD) = -1.64 (95% confidence interval [CI] = -2.46, -0.81) and WMD = -70.86 (95% CI = -101.55, -40.17), respectively. A subgroup analysis confirmed these associations in the Chinese population, but not in the Caucasian and mixed populations. In conclusion, these findings support the need for further controlled studies in defined patient populations and the importance of monitoring serum folate and vitamin B12 levels in patients with T2DM.

Diabetic neuropathy is not associated with homocysteine, folate, vitamin B12 levels, and MTHFR C677T mutation in type 2 diabetic outpatients taking metformin

BACKGROUND

Hyperhomocysteinemia and vitamin B12 deficiency may be involved in the development of diabetic peripheral neuropathy (DPN). Metformin therapy may reduce vitamin B12 plasma levels, thus contributing to DPN.

AIM AND METHODS

The purposes of this cross-sectional study were to assess (1) the potential associations of DPN with serum levels of homocysteine (tHcy), B-vitamins, and/or the common methylenetetrahydrofolate reductase (MTHFR) C677T mutation; (2) the influence of chronic treatment with metformin on tHcy and B-vitamins concentrations and, finally, (3) to evaluate whether, by this influence, metformin is a risk factor for DPN in a group of type 2 diabetic outpatients.

RESULTS

Our data showed that fasting tHcy, folate, and vitamin B12 levels and the MTHFR C677T genotype distribution were comparable between subjects with (n = 79, 30 %) and without DPN (n = 184, 70 %). Metformin-treated subjects (n = 124, 47 %) showed significantly lower levels of vitamin B12 (P < 0.001), but the prevalence of DPN was not different when compared to those not treated with this drug (33 vs. 27 %, P = NS). At univariate regression analysis, DPN was associated with age, duration of diabetes, HbA1c, creatinine levels, and the presence of coronary heart disease (CHD), and negatively with HDL-C concentrations (P < 0.05 all), but at multivariate regression analysis, high creatinine levels (P = 0.06), low HDL-C levels (P = 0.013), and a higher prevalence of CHD (P = 0.001) were the only variables independently associated with DPN in this population.

CONCLUSIONS

In conclusion, in these type 2 diabetic outpatients circulating levels of tHcy, folate, and the MTHFR C677T mutation are not associated with DPN, which was predicted by creatinine levels, CHD, and dyslipidemia. Metformin therapy is associated with a mild vitamin B12 level reduction, but not with DPN.

Relationship between homocysteine level and diabetic retinopathy: a systematic review and meta-analysis

Background

The relationship between homocysteine (Hcy) and diabetic retinopathy (DR) remains unclear to date. Therefore, a systematic review and meta-analysis was performed on the relationship between Hcy level and DR.

Methods

Studies were identified by searching PubMed, Embase, and Web of Science databases until 5 May, 2014.

Results

A total of 31 studies involving 6,394 participants were included in the meta-analysis. After pooling the data from each included study, the blood Hcy concentration in the DR group was observed to be higher than that in the control group [WMD = 2.55; 95% confidence interval (CI), 1.70–3.40], and diabetes mellitus (DM) patients with hyperhomocysteinemia were at a risk for DR [odds ratio (OR) = 1.93; 95% CI, 1.46–2.53]. Considering the different DM types, hyperhomocysteinemia in T1DM (OR = 1.83, 95% CI, 1.28–2.62) was associated with DR rather than in T2DM (OR = 1.59, 95% CI, 0.72–3.51). Considerable statistical heterogeneity in the overall summary estimates was partly explained by the geographical differences.

Conclusions

Results from this current meta-analysis indicate that hyperhomocysteinemia is a risk factor for DR, especially proliferative DR. Differences between geographical regions were observed in the relationship between hyperhomocysteinemia with T1DM risk. Given the heterogeneous results, the relationship between high Hcy and DR needs further investigation.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_167

Association between homocysteine status and the risk of nephropathy in type 2 diabetes mellitus

BACKGROUND

It is well documented that hyperhomocysteinemia induces renal injury. However, the association between homocysteine level and type 2 diabetic nephropathy (T2DN) remains elusive.

METHODS

We evaluated the alteration of plasma level of homocysteine in T2DN patients with macroalbuminuria or microalbuminuria compared with type 2 diabetes mellitus (T2DM) controls without albuminuria by performing a meta-analysis. We searched the PubMed, Embase and Cochrane databases from January 1990 to October 2013 to identify studies that met predefined criteria.

RESULTS

Seven studies were included in this investigation. T2DN patients with macroalbuminuria demonstrated a significantly higher level of plasma homocysteine than T2DM without albuminuria (4 studies, random effects SMD: 1.66, 95% CI: 0.46 to 2.87, P=0.007) and T2DN with microalbuminuria (3 studies, random effects SMD: 0.99, 95% CI: 0.62 to 1.36, P<0.001). T2DN patients with microalbuminuria demonstrated significantly higher level of plasma homocysteine than T2DM without albuminuria (6 studies, random effects SMD: 1.29, 95%. CI: 0.59 to 2, P<0.001). Exclusion of any single study had little impact on the pooled SMDs. No evidence of publication bias was observed.

CONCLUSIONS

Our findings indicate that the status of plasma homocysteine is associated with both the risk and severity of nephropathy in T2DM. Frequent monitoring and early intervention should be recommended.

Association of MTHFR C677T and A1298C gene polymorphisms with hypertension

OBJECTIVES

To check for the association of genetic polymorphisms related to the methylenetetrahydrofolate reductase (MTHFR) gene namely C677T and A1298C with hypertension in Saudi affected subjects from Qassim region.

SUBJECTS AND METHODS

Participants included 123 Saudi hypertensive cases (83 males and 40 females) in addition to 250 (142 males and 108 females) unrelated healthy controls from the same locality. Their age mean ±SD was 50.93 ± 15.43 years. For all subjects, DNA was extracted followed by real-time PCR amplifications for characterization of genotypes and alleles related to MTHFR C677T and A1298C gene polymorphisms

RESULTS

Total cases showed significantly higher carriage rate for the mutant allele 677T compared to controls (40.7% vs. 26%, OR=1.9, 95% CI= 1.2-3.1) with a lower frequency of the wild type 677CC genotype (59.3% vs. 74%, p=0.004). The same was observed among cases-subgroups of hypertension associated with obesity with a notably higher odds ratio (OR=2.6, 95% CI=1.3-5.01, p=0.004). Total cases showed also significantly higher frequency of mutant 1298 C allele carriage rate compared to controls (59.3% vs. 42.4%, OR=1.98, 95% CI= 1.3-3.1) with a lower frequency of the normal AA genotype (40.7% vs. 57.6%, p=0.003). The same was observed among cases-subgroups of hypertension associated with both diabetes and obesity and among cases of hypertension with obesity, also with higher odds ratio (OR=2.6 and 2.2 respectively).

CONCLUSION

This work showed that genetic polymorphisms related to the MTHFR gene are associated with the risk of hypertension particularly when accompanied with obesity and diabetes among Saudi subjects.

Antihypertensive agents for preventing diabetic kidney disease

BACKGROUND

Various blood pressure-lowering agents, and particularly inhibitors of the renin-angiotensin system (RAS), are widely used for people with diabetes to prevent the onset of diabetic kidney disease (DKD) and adverse cardiovascular outcomes. This is an update of a Cochrane review first published in 2003 and updated in 2005.

OBJECTIVES

This systematic review aimed to assess the benefits and harms of blood pressure lowering agents in people with diabetes mellitus and a normal amount of albumin in the urine (normoalbuminuria).

SEARCH METHODS

In January 2011 we searched the Cochrane Renal Group's Specialised Register through contact with the Trials Search Co-ordinator.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any antihypertensive agent with placebo or another agent in hypertensive or normotensive patients with diabetes and no kidney disease (albumin excretion rate < 30 mg/d) were included.

DATA COLLECTION AND ANALYSIS

Two investigators independently extracted data on kidney and other patient-relevant outcomes (all-cause mortality and serious cardiovascular events), and assessed study quality. Analysis was by a random effects model was applied to analyse results which were expressed as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

We identified 26 studies that enrolling 61,264 participants. Angiotensin-converting enzyme inhibitors (ACEi) reduced the risk of new onset of microalbuminuria, macroalbuminuria or both when compared to placebo (8 studies, 11,906 patients: RR 0.71, 95% CI 0.56 to 0.89), with similar benefits in people with and without hypertension (P = 0.74), and when compared to calcium channel blockers (5 studies, 1253 participants: RR 0.60, 95% CI 0.42 to 0.85). ACEi reduced the risk of death when compared to placebo (6 studies, 11,350 participants: RR 0.84, 95% CI 0.73 to 0.97). No effect was observed for angiotensin receptor blockers (ARB) when compared to placebo for new microalbuminuria, macroalbuminuria or both (5 studies, 7653 participants: RR 0.90, 95% CI 0.68 to 1.19) or death (5 studies, 7653 participants: RR 1.12, 95% CI 0.88 to 1.41); however, meta-regression suggested possible benefits from ARB for preventing kidney disease in high risk patients. There was a trend towards benefit from use of combined ACEi and ARB for prevention of DKD compared with ACEi alone (2 studies, 4171 participants: RR 0.88, 95% CI 0.78 to 1.00).The risk of cough was significantly increased with ACEi when compared to placebo (6 studies, 11,791 patients: RR 1.84, 95% CI 1.24 to 2.72), however there was no significant difference in the risk of headache or hyperkalaemia. There was no significant difference in the risk of cough, headache or hyperkalaemia when ARB was to placebo. On average risk of bias was judged to be either low (27% to 69%) or unclear (i.e. no information available) (8% to 73%). Blinding of participants, incomplete outcome data and selective reporting were judged to be high in 23%, 31% and 31% of studies, respectively.

AUTHORS' CONCLUSIONS

ACEi were found to prevent new onset DKD and death in normoalbuminuric people with diabetes, and could therefore be used in this population. More data are needed to clarify the role of ARB and other drug classes in preventing DKD.

Acute hyperhomocysteinaemia blunts endothelial dependent and endothelial independent vasodilatation in diabetic patients

The aim of this study was to investigate the effects of acute, methionine-induced hyperhomocysteinaemia on endothelial function of skin microcirculation in diabetic compared with non-diabetic persons. Endothelial- and non-endothelial-dependent vasodilatation of the skin microcirculation were evaluated in 20 persons with type 2 diabetes (59.95+/-2.36 years old) and 24 age- and gender-matched controls using laser Doppler flowmetry, during fasting and four hours after 0.1 g/kg methionine-induced acute hyperhomocysteinaemia. Methionine loading caused a comparable increase of homocysteine in the two groups. Four hours after induction of acute hyperhomocysteinaemia, endothelial-dependent vasodilatation (acetylcholine effect) was lower in the diabetic patients compared with the controls ([mean+/-SEM] 8.09+/-1.18-fold increase in diabetic patients vs. 11.11+/-1.33-fold increase in controls, p=0.027). The same was observed for the endothelial-independent vasodilatation (sodium-nitroprusside effect, 7.55+/-0.80-fold increase in the diabetic patients vs. 12.19+/-1.26-fold increase in controls, p=0.008). Acute hyperhomocysteinaemia causes a decreased response of both endothelial-dependent and endothelial-independent vasodilatation of the skin microcirculation in diabetic compared with non-diabetic persons. These alterations might contribute to the vascular complications of hyperhomocysteinaemia in diabetes, and especially the microvascular ones.

Factors associated with serum total homocysteine level in type 2 diabetes

OBJECTIVES

The aim of this study was to investigate the determinants of serum total homocysteine level (tHcy) in patients with type 2 diabetes mellitus (DM) according to sex.

METHODS

A total of 1,276 Japanese, diabetics (n = 280) with a control group of non-diabetics (n = 996), were enrolled into the study from 2003 to 2005. This cross-sectional study was conducted for all the subjects, using personal data regarding clinical characteristics and lifestyle. Multiple regression analysis was performed to analyze the association of tHcy with selected factors.

RESULTS

In diabetic subjects, estimated glomerular filtration rate (eGFR) and serum creatinine levels (Cre), even those within the normal range, were strongly associated with tHcy after adjustment in both sexes; the standardized partial regression coefficient of eGFR for tHcy was -0.251, (p = 0.001) in diabetic men and -0.523, (p < 0.001) in diabetic women. Furthermore, the eGFR of the diabetics, except patients with nephropathy, also had significant association with tHcy in both sexes. Fasting plasma glucose levels and serum triglyceride levels were strongly associated with tHcy in diabetic men only. HbA1c was also associated with tHcy in diabetic men only, though not as significantly. Age and presence of hypertension were significantly associated with tHcy in women.

CONCLUSIONS

This study suggests that there are some differences in the factors associated with tHcy between diabetics and non-diabetics, and between the sexes. There is, therefore, circumstantial evidence that elevated tHcy should be evaluated clinically. Because tHcy was strongly associated with eGFR and Cre, even within the normal ranges, tHcy may have important implications regarding the microangiopathy of the kidney and atherosclerosis.

Homocysteine and diabetic retinopathy

OBJECTIVE

Homocysteine is an emerging risk factor for cardiovascular and nondiabetic ocular vaso-occlusive diseases. However, studies of the relationship between homocysteine and diabetic retinopathy have reported inconsistent results. The purpose of this study was to evaluate the relationship between plasma total homocysteine concentration and diabetic retinopathy.

RESEARCH DESIGN AND METHODS

We assessed the homocysteine-retinopathy relationship in 168 men and women with type 2 diabetes in a community-based, cross-sectional study. We photodocumented diabetic retinopathy status and measured plasma total homocysteine concentration using a commercial fluorescence polarization immunoassay enzymatic kit. Data for selected clinical/demographic variables and established risk factors for diabetic retinopathy were obtained from fasting blood samples and an interviewer-assisted lifestyle questionnaire.

RESULTS

A higher mean plasma total homocysteine concentration was observed in diabetic individuals with retinopathy than in those without retinopathy (11.5 mumol/l [95% CI 10.4-12.5] vs. 9.6 mumol/l [9.1-10.2], P = 0.001). Furthermore, the relationship between homocysteine and diabetic retinopathy was not explained by renal dysfunction and was independent of the other major risk factors for diabetic retinopathy (duration of diabetes, A1C, and systolic blood pressure) and determinants of higher homocysteine concentrations (age, sex, and red cell folate) (odds ratio 1.20 [95% CI 1.023-1.41], P = 0.024).

CONCLUSIONS

Plasma total homocysteine concentration may be a useful biomarker and/or a novel risk factor for increased risk of diabetic retinopathy in people with type 2 diabetes.

Appropriate blood pressure control in hypertensive and normotensive type 2 diabetes mellitus: a summary of the ABCD trial

The hypertensive and normotensive Appropriate Blood Pressure Control in Diabetes (ABCD) studies were prospective, randomized, interventional clinical trials with 5 years of follow-up that examined the role of intensive versus standard blood pressure control in a total of 950 patients with type 2 diabetes mellitus. In the hypertensive ABCD study, a significant decrease in mortality was detected in the intensive blood pressure control group when compared with the standard blood pressure control group. There was also a marked reduction in the incidence of myocardial infarction when patients were randomly assigned to initial antihypertensive therapy with angiotensin-converting-enzyme inhibition rather than calcium channel blockade. The results of the normotensive ABCD study included associations between intensive blood pressure control and significant slowing of the progression of nephropathy (as assessed by urinary albumin excretion) and retinopathy, and fewer strokes. In both the hypertensive and normotensive studies, mean renal function (as assessed by 24 h creatinine clearance) remained stable during 5 years of either intensive or standard blood pressure intervention in patients with normoalbuminuria (<30 mg/24 h) or microalbuminuria (30-300 mg/24 h) at baseline. By contrast, the rate of creatinine clearance in patients with overt diabetic nephropathy (>300 mg/24 h; albuminuria) at baseline decreased by an average of 5 ml/min/year in spite of either intensive or standard blood pressure control. Analysis of the results of 5 years of follow-up revealed a highly significant correlation of all-cause and cardiovascular mortality with left ventricular mass and severity of albuminuria.

Methylenetetrahydrofolate reductase gene polymorphism, homocysteine and risk of macroangiopathy in Type 2 diabetes mellitus

OBJECTIVE

A polymorphism in the gene for methylenetetrahydrofolate reductase (MTHFR) has been reported to be associated with hyperhomocysteinemia and risk for atherosclerotic vascular diseases. In this case-control study, we examined the distribution of the MTHFR genotypes in the Chinese population and clarified the relationship between the gene polymorphism for MTHFR and macroangiopathy in Chinese Type 2 diabetes mellitus.

METHODS

Two hundred and sixteen unrelated patients with Type 2 diabetes mellitus, 112 of whom had macroangiopathy, and 114 healthy control subjects, were recruited. The MTHFR C677T genotype was analyzed by polymerase chain reaction-restriction fragment length polymorphism. 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 31.1%. The genotype distribution did not differ between control subjects and Type 2 diabetic patients (chi2=3.03, p=0.220). Genotypic analysis revealed that the MTHFR genotype was different between diabetic patients with and without macroangiopathy (chi2=12.42, p=0.002). Type 2 diabetic patients with macroangiopathy displayed a greater prevalence of T allele than Type 2 diabetic patients without macroangiopathy (44.6 vs 29.3%; chi2=10.82, p=0.001). The odds ratio for macroangiopathy in Type 2 diabetic patients in presence of T allele was 1.94 [confidence interval (CI) 95%: 1.31-2.89]. 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 could constitute a useful predictive marker for macroangiopathy in Chinese Type 2 diabetic patients.

Mild hyperhomocysteinemia and the common C677T polymorphism of methylene tetrahydrofolate reductase gene are not associated with the metabolic syndrome in Type 2 diabetes

A moderate increase of total homocysteine (tHcy) plasma levels seems to increase cardiovascular disease (CVD) risk in Type 2 diabetic subjects, but its relationship with diabetes and insulin-resistance is still controversial. We examined whether mild hyperhomocysteinemia and its major genetic determinant would cluster with the metabolic syndrome (MS) in Type 2 diabetes. One hundred Type 2 diabetic subjects with and without MS were enrolled in the study. Fasting tHcy, vitamin B12, and folate plasma levels, insulin-resistance [assessed by homeostasis model assessment, (HOMAIR)] and the methylene tetrahydrofolate reductase (MTHFR) C677T genotype were assessed in all the participants. Geometric mean tHcy concentration and the prevalence of mild hyperhomocysteinemia, as commonly defined by tHcy >/=15 micromol/l, were comparable in diabetic subjects with and without MS, even after adjustment for age, sex, vitamin B12, folate and creatinine levels. In both groups, the MTHFR C677T genotype distribution was not significantly different from the Hardy-Weinberg equilibrium, with a TT homozygous frequency of 21% in subjects with and 18% in those without the syndrome (p=ns). tHcy plasma levels and the degree of insulin-resistance did not differ across MTHFR genotypes in both groups, even after multivariable adjustment. Overall, tHcy significantly correlated with creatinine (r=0.25; p=0.009) and trygliceride concentrations (r=0.24; p=0.02), but not with HOMAIR. At multivariate analysis, only creatinine was significantly correlated with tHcy levels (beta=0.42; p=0.001). In conclusion, hyperhomocysteinemia and the common C677T variant of MTHFR gene are not associated with MS in Type 2 diabetic subjects.

Homocysteine and vascular disease in diabetes: a double hit?

Cardiovascular disease is a major problem in diabetes, and risk factors presumably unrelated to diabetes, such as hyperhomocysteinaemia, may be related to the development of cardiovascular complications in diabetic individuals. Plasma homocysteine levels are usually normal in diabetes, although both lower and higher levels have been reported. Homocysteine levels in diabetes are modulated by hyperfiltration and renal dysfunction, as well as low folate status. Insulin resistance does not appear to be a major determinant of plasma homocysteine level. Hyperhomocysteinaemia has been associated with microalbuminuria and retinopathy in type 1 and type 2 diabetes. In patients with type 2 diabetes, plasma homocysteine concentration is a significant predictor of cardiovascular events and death. This relation seems to be stronger in subjects with diabetes than without. The underlying pathophysiological mechanism of this increased vascular risk remains unexplained, but may be related to worsening of endothelial dysfunction and/or structural vessel properties induced by oxidative stress. Because homocysteine and diabetes have apparent synergistic detrimental vascular effects, patients with diabetes are candidates for screening and treatment with folic acid until the results of ongoing clinical trials are available.

Plasma homocysteine and microvascular and macrovascular complications in type 1 diabetes: a cross-sectional nested case-control study

OBJECTIVES

To examine the independent relationship between plasma total homocysteine (tHcy) and microvascular and macrovascular complications.

DESIGN

We performed a cross-sectional nested case-control study from the EURODIAB Prospective Complications Study.

SETTING

A hospital-based multicentre study at 24 centres in 13 European countries.

SUBJECTS

A total of 533 type 1 diabetic patients, diagnosed at <36 years of age. Cases (n=359) were defined as those with one or more complications of diabetes and control subjects (n=174) were all those with no evidence of any complication. Main outcome measures. Retinopathy, albumin excretion rate (AER), glomerular filtration rate (GFR) estimated by Cockcroft-Gault formula, hypertension and cardiovascular disease (CVD) were assessed.

RESULTS

In unadjusted models, tHcy (per 5 micromol L(-1)) was significantly associated with nonproliferative retinopathy (OR=1.45, 95% CI: 1.10-1.91), proliferative retinopathy (OR=1.74, 95% CI: 1.34-2.27), macroalbuminuria (OR=1.90, 95% CI: 1.49-2.42), hypertension (OR=2.23, 95% CI: 1.69-2.93) and CVD (OR=1.59, 95% CI: 1.18-2.14). In multivariate models, tHcy was significantly related to macroalbuminuria (OR=1.66, 95% CI: 1.24-2.24) and hypertension (OR=1.57, 95% CI: 1.19-2.07), independent of age, sex, diabetes duration, GFR, microvascular and macrovascular complications and cardiovascular risk factors. There was a significant relationship between tHcy and decreased GFR, independent of established risk factors. The relationship between tHcy and retinopathy was not independent of albuminuria or GFR. The initial positive relationship with CVD was explained by cardiovascular risk factors.

CONCLUSION

In this large study of European type 1 diabetic subjects, increased concentrations of tHcy were independently related to macroalbuminuria, renal function and hypertension, which suggests that tHcy might play an important role in the pathogenesis of vascular complications in type 1 diabetes.

Age and kidney function are the primary correlates of fasting plasma total homocysteine levels in non-diabetic and diabetic adults. Results from the 1999-2002 National Health and Nutrition Examination Survey

Background

Plasma total homocysteine (tHcy) is commonly elevated in persons with diabetes. This may be due to effects of insulin and/or glucose and/or metabolic control on the metabolism or plasma levels of tHcy. This study examined the effects of fasting plasma glucose status on fasting tHcy levels among adults without diabetes, and diabetes per se among adults with a self-report history of diabetes.

Methods

Analysis of data on adults (≥ 20y) who had fasted at least 8 hours, from the National Health and Nutrition Examination Survey (1999–2000 and 2001–2002). Subjects with no self-report history of diabetes were grouped according to fasting plasma glucose status as normal (< 100 mg/dL = NFG, n = 2,244), impaired (≥ 100 < 126 mg/dL = IFG, n = 1,108), or a provisional diagnosis of diabetes (≥ 126 mg/dL = DFG, n = 133). Subjects with a self-report history of diabetes (n = 275) were examined separately.

Results

Fasting tHcy was higher (Ps < 0.01) among non-diabetic subjects with DFG and IFG, compared to NFG (median [95% confidence interval] = 8.6 [8.0–9.2], 8.3 [8.1–8.5], and 7.4 [7.3–7.5] μmol/L, respectively). Diabetic subjects had levels similar to non-diabetic subjects with DFG and IFG (8.3 [7.9–8.6] μmol/L). Age and estimated creatinine clearance were strong correlates of fasting tHcy among non-diabetic subjects (r = 0.38 to 0.44 and r = -0.35 to -0.46, respectively) and diabetic subjects (r = 0.41 and r = -0.46, respectively) (Ps < 0.001), while fasting glucose and glycohemoglobin (HbA_1c) were weaker (but still significant) correlates of tHcy in non-diabetic and diabetic subjects. Fasting glucose status was not a significant independent predictor of fasting tHcy levels in non-diabetic subjects, and HbA_1c was not a significant independent predictor of tHcy in diabetic subjects (Ps > 0.05).

Conclusion

Fasting tHcy levels are elevated among non-diabetic adults with elevated fasting glucose levels, compared to persons with normal fasting glucose levels, and among diabetic adults. However, elevations in fasting tHcy appear to be mediated primarily by age and kidney function, and not by measures of glucose metabolism.

Diabetes mellitus, hyperhomocystinemia and atherosclerotic vascular disease in Taiwanese chronic hemodialysis patients: a retrospective study

AIM

Diabetic patients with hemodialysis (HD) have a high mortality rate from atherosclerotic vascular disease (ASVD). However, the extent of the role of hyperhomocystinemia as a risk factor of ASVD is uncertain in diabetic HD patients. We investigated whether there was an association with ASVD events in diabetics and non-diabetics where these were chronic hyperhomocystinemia HD patients.

METHODS

Two hundred patients undergoing HD were included in the study. About 50% of the patients had diabetes mellitus (DM). They had predialysis blood work performed for total homocysteine. A history of DM was elicited using information from the patients' questionnaires and verified by careful inpatient and outpatient chart review.

RESULTS

A total of 196 patients had hyperhomocystinemia and were enrolled this study. Mean homocysteine concentration was 29.7 +/- 6.6 micromol/L overall. DM was present in 50.0% of patients. The mean homocysteine concentration was 29.4 +/- 9.5 micromol/L and 29.9 +/- 9.7 micromol/L in diabetic HD patients (n=98) and non-diabetic HD patients (n=98), respectively (P=0.71). There was no association with hyperhomocystinemia between diabetic and non-diabetic in chronic HD patients. There were significant differences including age, sex, HDL cholesterol, triglycerides, hypertension, smoking, serum creatinine, dialysis duration and glucose intolerance in the two groups (P<0.05). There were also significant differences in ASVD (P=0.0027) and CVD (P=0.0017) between diabetics and non-diabetics in cases of chronic hyperhomocystinemia HD patients. The adjusted odds ratio for ASVD was 3.02 (95%CI, 1.63 to 5.59) for those subjects with a DM in the highest quartile compared with the lowest 3 quartiles.

CONCLUSIONS

There were associations with ASVD and CVD in diabetics and non-diabetics in cases of chronic hyperhomocystinemia HD patients. There was no association with hyperhomocystinemia between diabetic and non-diabetic in Taiwanese chronic HD patients. This study found that the presence of DM and advanced age were the major determinants for ASVD events in chronic HD patients, rather than the levels of homocysteine.

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.

Total homocysteine levels relation with chronic complications of diabetes, body composition, and other cardiovascular risk factors in a population of patients with diabetes mellitus type 2

OBJECTIVE

The significance of hyperhomocysteinemia in type 2 diabetes is further complicated by the multiple ways of considering impaired renal function and vitamin status. The aim of our study was to analyze the relationship between total homocysteine (tHcy) in a population of type 2 diabetic patients and chronic complications. We also analyzed the relationship between tHcy and the body composition of these patients and other cardiovascular risk factors.

DESIGN

In a cross-sectional study, a total of 155 patients with diabetes mellitus attending in our diabetes service (90 females/65 males) were enrolled in a consecutive way.

MATERIAL AND METHODS

All enrolled patients underwent the following examinations: (i) biochemical cardiovascular risk factors including total cholesterol, triglyceride, lipoprotein (a), low-density lipoprotein (LDL-cholesterol), high-density lipoprotein (HDL-cholesterol), glucose, HbA(1c), fibrinogen, homocysteine, vitamin B12, folate, and microalbuminuria; and (ii) fat mass assessed by body mass index, weight, percentage of fat mass, and tricipital skinfold.

RESULTS

Patients were divided in two groups (Group I: tHcy> or =15 micromol/l; Group II: tHcy<15 micromol/l). Smoking habit was similar in both groups. A prevalence of cerebrovascular accident was present in 3.3% in the total group. This prevalence was not different in both groups (7.4% vs. 2.3%; ns) (OR 3.3; 95% CI 0.49-19.68). The prevalence of coronary heart disease in the total group was 5.8% without statistical differences between groups (3.5% vs. 6.3%; ns) (OR 0.57; 95% CI 0.065-4.53). Concerning macrovascular complications, only peripheral vascular disease prevalence was higher in Group I (16% vs. 3.1%; P<0.05; OR 5.33; 95% CI 1.18-21.5). A prevalence of nephropathy was higher in Group I (93.3% vs. 12.8%; P<0.05; OR 7.15; 95% CI 2.9-17.9). No statistical differences were detected in prevalence of retinopathy (global group 41.9%) (42.5% vs. 40.9%; ns) (OR 1.75; 95% CI 0.78-3.9). Also, peripheral neuropathy was similar in both groups (7.1% vs. 6.5%; ns) (OR 1.1; 95% CI 0.15-8.2). No correlation was detected among homocysteine and anthropometric parameters (body mass index, weight, percentage of fat mass, fat mass, and tricipital skinfold). Elevated levels of fibrinogen, lipoprotein (a), microalbuminuria, and blood pressure were detected in Group I.

CONCLUSION

The present study shows that elevation of plasma tHcy levels in type 2 diabetic patients is associated with a higher prevalence of peripheral arteriopathy and nephropathy. Our data suggest that hyperhomocysteinemia is not associated with fat mass but it is associated with high levels of fibrinogen, lipoprotein (a), microalbuminuria, and blood pressure levels.

Single nucleotide polymorphism in CTH associated with variation in plasma homocysteine concentration

Plasma total homocysteine (tHcy) concentration, an independent risk factor of atherosclerosis, has numerous genetic and environmental determinants. While the thermolabile polymorphism in MTHFR encoding methylenetetrahydrofolate reductase is the best-studied genetic factor associated with variation in plasma tHCy, other candidate genes are being evaluated. Recently, we discovered that cystathioninuria was caused by mutations in the CTH gene encoding cystathionine gamma-lyase, an enzyme that converts cystathionine to cysteine in the trans-sulfuration pathway. We also identified a common single nucleotide polymorphism (SNP), namely c.1364G>T (S403I) in exon 12 of CTH. In the current analysis, we studied the association of genotypes of this SNP with plasma tHcy concentrations in 496 Caucasian subjects. CTH 1364T/T homozygotes had significantly higher mean plasma tHcy concentration than subjects with other genotypes, and the effect sizes of CTH and MTHFR genotypes were similar. The findings suggest that common variation in CTH may be a determinant of plasma tHcy concentrations.

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.

Correlates of total homocysteine plasma concentration in type 2 diabetes

BACKGROUND

Although well-defined in the general population, correlates of total homocysteine (tHcy) plasma concentration have not been sufficiently evaluated in diabetes. We investigated factors potentially associated with tHcy concentration in a cohort of type 2 diabetic subjects.

MATERIALS AND METHODS

The common methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism, fasting tHcy, vitamin B12 and folate plasma levels were assessed in 312 diabetic subjects, whose clinical, metabolic and lifestyle information was also available.

RESULTS

The MTHFR genotype distribution was comparable to the Hardy-Weinberg equilibrium, with an overall TT homozygous frequency of 22%. Fasting tHcy concentration was significantly higher in men than in women (P < 0.001). Multivariate-adjusted tHcy concentration was significantly different across the quartiles of age (P < 0.001), folate (P = 0.01), vitamin B12 (P = 0.03), creatinine concentrations (P = 0.001) and smoking (P = 0.02). Overall, significant trends were noted for creatinine clearance (P for trend = 0.02) and systolic blood pressure (BP) (unadjusted P for trend = 0.01), whereas no differences were noted according to BMI, diastolic BP, presence of hypertension, and diabetes-related variables, such as diabetes duration, fasting glucose and glycated haemoglobin concentrations, current treatment and diabetes long-term complications. Total homocysteine levels significantly correlated with age, systolic BP, vitamin B12, creatinine and creatinine clearance, but only age, creatinine, folate and vitamin B12 levels were independently associated with tHcy concentration in stepwise regression analysis.

CONCLUSIONS

Age, creatinine, folate, vitamin B12, and to a minor extent, sex, smoking, TT genotype and systolic BP were significantly associated with Hcy plasma concentration in type 2 diabetes, whereas no significant associations were noted with diabetes-related variables.

Homocisteína en el paciente con diabetes mellitus

Homocysteine is a sulphur aminoacid with a free thiol group which is not present in dietary protein. This aminoacid is a secondary f methionine by-product from cysteine metabolism. The pathogenic mechanisms of homocysteine in vascular damage have not been clarified. At present, it is no possible to develop an atherogenic and thrombogenic hypothesis. Yet high levels of homocysteine can cause endothelial damage, with increased thrombosis and atherosclerosis. Hyperhomocysteinemia has been reported in patients with diabetes mellitus type 1 and type 2; the prevalence and secondary cardiovascular risk is higher in patients with diabetes type 2 than those with diabetes type 1. In patients with diabetes mellitus type 1, microvascular and macrovascular complications and neuropathy are found to be increased in those with hyperhomocysteinemia. In patients with diabetes mellitus type 2, the relationship between hyperhomocysteinemia, macrovascular complications and renal disease is unclear; however, a higher prevalence of macrovascular complications in diabetic patients with hyperhomocisteinemia is associated with a higher prevalence of renal disease. Moreover, patients with hyperhomocysteinemia have hypertension and dyslipemia. Multivariate regression analyses have shown an independent relationship between homocysteine and macrovascular complications. The relationship between retinopathy and homocysteine has not been clarified. In summary, hyperhomocysteinemia could be a risk factor accounting for chronic complications in diabetic patients. Nevertheless, it is necesary to perform more prospective and intervention studies to clarify the independent risk of homocysteine and thus assay alternative treatments.

Variation in plasma cystathionine and its relation to changes in plasma concentrations of homocysteine and methionine in healthy subjects during a 24-h observation period

BACKGROUND

Plasma cystathionine measurement may be a useful complement to total homocysteine measurement in the assessment of B vitamin status. Information on the within-person variation in cystathionine is currently sparse.

OBJECTIVE

The goal was to study the daily variation in plasma cystathionine concentrations in healthy subjects.

DESIGN

Twelve subjects (aged 22-29 y) were followed for 24 h. During the observation period, the subjects received a breakfast (containing 15-18 g protein) at 0900 and a beef dinner (containing approximately 50 g protein) at 1500. Multiple blood samples for metabolite analyses were collected during the day, and a final sample was obtained the next morning. The results are expressed as medians and interquartile ranges.

RESULTS

All subjects had normal fasting cystathionine concentrations [0.120 (0.100-0.160) micro mol/L]. Cystathionine concentrations increased significantly after breakfast, reached a maximum after 4 h of 142.4% (100.0-170.3%) of the fasting concentration, and then declined to fasting concentrations before dinner. After dinner, plasma cystathionine started to increase within 0.5 h and reached a maximum after 6 h [281.3% (194.1-351.4%) of the concentration measured before dinner]. The changes in plasma methionine and total homocysteine concentrations during the day were less pronounced.

CONCLUSION

Food intake, even of foods with low protein content, causes an increase in plasma cystathionine concentrations that is more pronounced than the concomitant changes in total homocysteine and methionine. In studies including plasma cystathionine measurement, blood sampling in the fasting state should be considered.

Relation between total homocysteine levels and beer intake in patients with diabetes mellitus Type 2

BACKGROUND/AIM

The evaluation of the significance of hyperhomocysteinemia in type 2 diabetes is further complicated by the multiple ways of considering impaired renal function, vitamin status, and lifestyle. The aim of our study was to investigate the relation between macro- and micronutrient intakes and homocysteine levels in a population having diabetes type 2.

METHODS

A total of 155 patients with diabetes mellitus type 2 attending our Diabetes Service (90 females and 65 males) were enrolled in a consecutive way. All patients underwent determination of fasting blood homocysteine, glycated hemoglobin, glucose, vitamin B(12), and folate levels. Microalbuminuria was evaluated on the basis of a 24-hour urine. The patients were instructed to keep 3-day written food records incorporating the use of food scales and models to enhance portion size accuracy. Alcohol drinking, physical activity, and smoking habits were also registered.

RESULTS

The mean homocysteine levels were 10.5 +/- 4.3 micromol/l. The mean glucose and Hb A(Ic) levels were 9.5 +/- 3 mmol/l and 7.8 +/- 1.4%, respectively. The vitamin status was normal: 592.6 +/- 522 pg/ml vitamin B(12) and 10.5 +/- 5.5 ng/ml folic acid. Mean microalbuminuria was 81.7 +/- 238 mg/day. The calorie intakes were normal (carbohydrates 43%, proteins 23.8%, and lipids 33.1%). A decrease in daily intakes of vitamins (A, B(1), D, and E) and trace elements (Zn, Mg, Se, and Ca) was detected. High daily intakes were detected for protein, P, and vitamins C, B(12), K and P 29.7% of the patients drank beer and 18% other alcoholic beverages. 11.7% of the patients smoked, and 77.7% maintained daily physical activity (mean/day 25.7 +/- 20.9 min). Only protein (g/day; r = 0.25; p < 0.005) and beer (ml/day; r = -0.46; p < 0.05) correlated with the total homocysteine levels. The daily intakes of vitamin B(12) and folic acid were inversely correlated with the total homocysteine levels: r = -0.29; p < 0.05) and (r = -0.12; p < 0.05), respectively. Physical activity and smoking habits were not correlated. In the multivariate analysis with a dependent variable (total homocysteine) adjusted for age, sex, microalbuminuria, and nutrient intakes (proteins, folic acid, and vitamin B(12)) and beer remained in the model.

CONCLUSION

The present study shows that protein intake and beer could modify the levels of total homocysteine in patients with diabetes type 2.

Genomic basis of cystathioninuria (MIM 219500) revealed by multiple mutations in cystathionine gamma-lyase (CTH)

Hereditary cystathioninuria (MIM 219500) is presumed to be caused by deficiency of the activity of cystathionine gamma-lyase (cystathionase; CTH EC 4.4.1.1), which is normally required for the conversion of methionine into cysteine. To date, no mutations have been described among patients with cystathioninuria. From genomic DNA, we sequenced CTH in four unrelated probands with cystathioninuria. We found two nonsense mutations, namely exon 8 c.940-941delCT and exon 11 c.1220delC, and two missense mutations, namely exon 2 c.356C>T (T67I) and exon 7 c.874C>G (Q240E). All affected subjects were either simple homozygotes or compound heterozygotes. A common non-synonymous single nucleotide polymorphism in exon 12, namely c.1364G>T (S403I), was also identified and characterized in four ethnic groups. The reagents described in this report make the molecular diagnosis of cystathioninuria possible, allowing for studies of phenotype-genotype correlation. Also, the availability of a common non-synonymous SNP can allow for testing of association of the CTH gene with biochemical traits affected by trans-sulfuration, such as plasma concentrations of homocysteine or even cystathionine itself, in addition to more downstream clinical phenotypes, such as vascular disease.

Progression of diabetic nephropathy: role of plasma homocysteine and plasminogen activator inhibitor-1

Among patients with diabetic nephropathy, the decline in glomerular filtration rate (GFR) varies substantially, ranging from 2 to 20 mL/min per year. Identification of predictors of progression in diabetic nephropathy is important. Plasma total homocysteine (tHcy) rises with urinary albumin excretion rate in diabetes, and plasminogen activator inhibitor-1 (PAI-1) has been correlated with increased matrix accumulation in various glomerulopathies. In this prospective observational cohort study, we evaluated the importance of baseline tHcy and PAI-1 as predictors of the rate of decline in GFR. Baseline tHcy and PAI-1 were measured in 157 type 1 diabetic patients with diabetic nephropathy (92 men; mean age, 41 +/- 10 years; mean diabetes duration, 27 +/- 8 years; median GFR, 80 mL/min/1.73 m(2) [range, 23 to 143 mL/min/1.73 m(2)]). Hereafter, GFR was measured yearly with a plasma clearance technique for at least 3 years (median, 7 years [range, 3.0 to 8.3 years]). The mean rate of decline in GFR was 3.7 +/- 0.3 mL/min per year. A linear regression analysis revealed a borderline significant relationship between rate of decline in GFR and tHcy (P = 0.069) and PAI-1 (P = 0.087). Analysis of the rate of decline in GFR and tertiles of tHcy and PAI-1 revealed that increasing levels of tHcy were correlated with a significantly faster decline in GFR (P = 0.025), whereas increasing levels of PAI-1 were not. After adjustment for other well-established risk factors for progression of nephropathy in a multiple linear regression analysis, however, neither tHcy levels nor PAI-1 levels were independent predictors of rate of decline in GFR.

The relationship among homocysteine, creatinine clearance, and albuminuria in patients with type 2 diabetes

OBJECTIVE

Although it is accepted that elevated plasma homocysteine (tHcy) levels occur in end-stage renal disease and type 2 diabetes, the changes with milder renal dysfunction (e.g., microalbuminuria) are less clearly established. This study explores the relationship among tHcy, creatinine clearance (Ccr), and albumin excretion rate (AER) in a population with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 260 patients with type 2 diabetes were screened in our outpatient clinic during 10 months. Fasting blood samples were collected, and AER was calculated from an overnight timed urine sample. Ccr was calculated using the Cockroft-Gault formula.

RESULTS

A total of 198 subjects (76%) had normoalbuminuria (<20 microg/min), 50 subjects (19%) had microalbuminuria (20-200 microg/min), and 12 subjects (5%) had macroalbuminuria (>or=200 microg/min). Those with microalbuminuria had higher levels of tHcy than those with normoalbuminuria (13.2 +/- 7.8 vs. 11.3 +/- 4.6 micromol/l, P < 0.05). Patients were then subdivided based on low Ccr (<80 ml x min(-1) x 1.73 m(-2)) and normal Ccr (>or=80 x min(-1) x 1.73 m(-2)). None of the patients with macroalbuminuria had normal Ccr. In those with normoalbuminuria, tHcy levels were higher than in those with low Ccr than in those with normal Ccr (12.0 +/- 4.6 vs. 10.0 +/- 4.4 micromol/l, P < 0.01). The same was found for those with microalbuminuria (low Ccr versus normal Ccr: 14.6 +/- 9.0 vs. 10.2 +/- 2.8 micromol/l, P < 0.02). For normal Ccr, tHcy was similar irrespective of AER (normoalbuminuria versus microalbuminuria: 10.0 +/- 4.4 vs. 10.2 +/- 2.8 micromol/l, NS). For low Ccr, tHcy was higher in those with microalbuminuria versus normoalbuminuria (14.6 +/- 9.0 vs. 12.0 +/- 4.6 micromol/l, P = 0.01). Using multivariate regression, Ccr, but neither AER nor the presence of albuminuria, was an independent predictor of tHcy.

CONCLUSIONS

These data strongly suggest that in patients with type 2 diabetes, the relationship between plasma tHcy and AER is largely due to associated changes in renal function, as defined by Ccr.

Vitamin B12 metabolism after urinary diversion with a Kock ileal reservoir

OBJECTIVE

To elucidate the influence of construction of a Kock reservoir for urinary diversion using 70 cm of the distal ileum on vitamin B12 metabolism.

MATERIAL AND METHODS

Blood samples for determination of cobalamin concentrations were drawn up to 18 years after construction of a Kock reservoir in 97 patients. Preoperative values were obtained in 20 of these patients. Pre- and postoperative Schilling tests and analyses of methylmalonic acid and homocysteine concentrations were performed in subgroups.

RESULTS

The operation did not induce a significant decrease in cobalamin uptake as reflected in the pre- and postoperatively performed Schilling tests. No significant decline in cobalamin concentration postoperatively was noted. The value of analysis of methylmalonic acid and homocysteine concentrations in finding patients with cobalamin deficiency is limited by the fact that kidney function influences the results. Ten per cent of the patients did develop true cobalamin deficiency. A postoperative vitamin B12 value below 200 pmol/l indicates a 50% risk of later cobalamin deficiency.

CONCLUSIONS

The construction of a Kock reservoir does not per se cause cobalamin deficiency. Substitution should be instituted at a postoperative concentration below 200 pmol/l.

Methylenetetrahydrofolate reductase polymorphism, type II diabetes mellitus, coronary artery disease, and essential hypertension in the Czech population

Increased plasma concentrations of homocysteine have been found in patients with coronary artery disease (CAD) and essential hypertension (EH) and in patients with diabetic complications. The 677C/T methylenetetrahydrofolate reductase (MTHFR) gene polymorphism is related to the MTHFR enzyme activity and to the plasma homocysteine concentration. This study was designed to investigate an association of this polymorphism with CAD, EH, and type II diabetes mellitus in the Czech population. The MTHFR genotypes were assessed by the polymerase chain reaction-based methodology in a sample of 1199 unrelated Caucasian subjects with CAD, EH, type II diabetes, or a combination of these diseases, and in healthy subjects. Allele frequencies of the MTHFR polymorphism differed considerably between women with and without type II diabetes mellitus (P = 0.00069), with a higher frequency of the C allele in the diabetic women. In addition, the MTHFR T allele frequency was significantly higher in normotensive subjects with CAD compared with normotensive subjects without this disease (P = 0.020). Both associations were confirmed by multiple logistic regressions. In conclusion, while the C allele of the 677C/T MTHFR polymorphism is associated with type II diabetes mellitus in women, the T allele is associated with CAD only in normotensive subjects of Czech origin.

Homocysteine and endogenous markers of renal function in type 2 diabetic patients without coronary heart disease

The aim of this study was to assess parameters of renal function and other determinants of plasma homocysteine in type 2 diabetic patients without coronary heart disease (CHD). Fasting plasma homocysteine, serum cystatin C and serum creatinine were determined in 183 (75 men, 108 women) Type 2 diabetic patients without clinical evidence of CHD. Creatinine clearance was calculated and parameters such as blood pressure, body mass index (BMI), and glycated haemoglobin (HbA(1c)) were assessed. The urine albumin:creatinine ratio was used to classify patients as normo-, micro- or macroalbuminuric. One hundred and ten patients were normoalbuminuric, 67 patients were microalbuminuric and six patients were macroalbuminuric. There was no statistically significant difference in plasma homocysteine concentration between patients with normoalbuminuria and microalbuminuria. There was a trend towards increasing plasma homocysteine with decreasing glomerular filtration rate (GFR) (r=-0.46; P<0.0001). There was statistically significant correlation between plasma homocysteine and age (r=0.37), serum cystatin C (r=0.47), and serum creatinine (r=0.56). Plasma homocysteine concentration was significantly higher in patients with BMI<30 kg/m(2) and showed significant inverse correlation with weight (r=-0.16; P=0.03) and body mass index (r=-0.24; P=0.001). Homocysteine and serum creatinine were significantly higher in males than females and higher in smokers than non smokers but was not associated with glycemic control and duration of diabetes. In conclusion, elevated homocysteine concentration in patients with type 2 DM without CHD is related to age, gender, smoking, BMI and GFR. Follow up studies will provide further information on the association between hyperhomocysteinemia and the development of cardiovascular disease.

The association between two common mutations C677T and A1298C in human methylenetetrahydrofolate reductase gene and the risk for diabetic nephropathy in type II diabetic patients

Mutations of the methylenetetrahydrofolate reductase (MTHFR) gene have been shown to be associated with a predisposition to developing diabetic nephropathy (DN) in specific populations. The frequency of two MTHFR mutations, a recently described mutation in the human MTHFR gene A1298C and C677T, whose association with DN is already known, was determined in an Israeli Jewish population with type 2 diabetes mellitus (DM). Both A1298C and C677T are highly prevalent in the diabetic population with allele frequencies of 0.35 and 0.36, respectively. The genotype frequency and allele frequency for these two polymorphisms in patients who are normoalbuminuric (n = 55) were compared with those of patients who had either micro- or macroalbuminuria (n = 43). For both polymorphisms, there were no significant differences in either the genotype distribution or allele frequency in patients with or without DN. However, in patients with serum folate <15.4 nmol/L, there was a greater incidence of DN in those patients who were homozygous or heterozygous for the C677T mutation. For the A1298C mutation, there is evidence suggesting that the homozygous state may be protective in patients with low-normal serum folate. Folate supplementation in diabetic patients with the C677T mutation and low-normal serum folate may prevent the onset or retard the progression of DN.