Increasing homocysteine levels and diabetic autonomic neuropathy

Fiber selectivity of peripheral neuropathy in patients with Parkinson's disease

OBJECTIVE

To determine the function of each type of peripheral nerve fiber and investigate the possible role of levodopa (LD) in peripheral neuropathy (PN) in Parkinson's disease (PD) patients.

METHODS

We enrolled 60 patients with idiopathic PD. All PD patients were divided into three groups: levodopa exposure >3 years (LELD), levodopa exposure ≤3 years (SELD) and de novo patients with PD (NOLD). The current perception threshold (CPT), which was measured by Neurometer at 2000, 250 and 5 Hz, the level of homocysteine, Vitamin B12 and folic acid in plasma, were compared with those of sex- and age-matched healthy controls (HCs).

RESULTS

Current perception threshold was higher at 250 Hz (p < .05) and 5 Hz (p < .05) in the LELD group than the NOLD, SELD, and control group. CPT was lower at 5 Hz in the NOLD than in the HCs group (p < .05). The CPT of the more affected side of PD patients was positively correlated with H-Y stage at 5 Hz current stimulation (r = .42, p = .01). Multivariate logistic regression analysis showed that elevated homocysteine levels were the risk factor of sensory nerve injury in PD patients (p < .01). Serum homocysteine levels were positively correlated with levodopa (LD) daily dose, LD equivalent daily dose, and LD cumulative lifetime dose (p < .05).

CONCLUSIONS

Peripheral neuropathy in PD patients can occur in the early stage of PD exhibiting as hyperesthesia and is fiber selectivity, especially for Aδ and C nerve fibers. PN in PD patients is related to PD itself and long-term LD exposure. Elevated plasma homocysteine is a risk factor for PN in PD patients.

Relationship of Homocysteine With Gender, Blood Pressure, Body Mass Index, Hemoglobin A1c, and the Duration of Diabetes Mellitus Type 2

Introduction Increased levels of homocysteine (Hcy) may lead to endothelial damage and increase the risk of cardiovascular and renal malfunction. The current study aimed to evaluate the association of serum Hcy levels with gender, body mass index (BMI), duration of diabetes mellitus type 2 (DMT2), hemoglobin A1c (HbA1c), and blood pressure (BP).  Methodology  A prospective observational study was conducted at Hayatabad Medical Complex in Peshawar, Pakistan in the department of endocrinology from June 2020 to June 2021. All patients with diagnosed DMT2 above the age of 18 years were included in the study. Individuals with unconfirmed diagnoses with ages over 75 years were excluded from the study. All data including the patient's age, gender, and medical history were recorded. Height and weight were used to calculate the BMI. BP was examined thrice and a mean value was recorded for each patient. For laboratory investigation, a vial of 3 ml blood was extracted keeping sterile and aseptic conditions by a trained nurse. The sample was sent for the determination of HbA1c and serum Hcy levels. Measurement of serum Hcy was done by chemiluminescent microparticle immunoassay. All data were documented by the researchers on a predefined pro forma.  Results A total of 188 patients with DMT2 were included in the study with a mean age ± SD of 54.65 ± 8.42 years. Normal (<15 micromoles per liter [mcmol/l]) serum Hcy levels were reported in 75 (39.89%) individuals, while in 47 (41.59%) individuals, there was severe (>100 mcmol/l) hyperhomocysteinemia. More than half of the patients, i.e. 157 (83.52%), had HbA1c of greater than 7%, which indicated poor glycemic control. The study revealed that the majority of the female patients, i.e. 37 (78.72%), had severe hyperhomocysteinemia (p<0.0001). Similarly, there was a direct correlation between HbA1c levels and serum Hcy. Severe hyperhomocysteinemia was found in over 80% of the patients with poor glycemic control, i.e. HbA1c >7% (p<0.0001). Furthermore, the duration of DMT2 and hypertension were both significantly associated with increased levels of Hcy with p-values of <0.0001 and <0.0001, respectively. However, no association was found between hyperhomocysteinemia and BMI.  Conclusion The study revealed that increased levels of serum Hcy were associated with female gender, poor glycemic control (HbA1c >7%), BP, and duration of DMT2. However, the study failed to find an association between serum Hcy and BMI. It is recommended that patients with poor glycemic control or those with the duration of DMT2 of more than five years must be regularly checked for hyperhomocysteinemia and renal function tests.  Large-scale and multi-center studies are required in order to determine the validity of these findings. The current study suggests that patients with diabetes mellitus and hypertension are likely to have increased levels of Hcy and, therefore, must be regularly screened for hyperhomocysteinemia.

Homocysteine and diabetes: Role in macrovascular and microvascular complications

Diabetes mellitus (DM) can lead to the development of macro- and microvascular complications. Homocysteine (Hcy) may play a role in the development of cardiovascular (CV) diseases (CVDs). The role of Hcy in the development of the vascular complications associated with DM is not clearly defined. Despite a strong initial assumption regarding the importance of Hcy in DM and its complications, over time "enthusiasm has waned" because several studies showed unconvincing and occasionally contradictory results. A universal conclusion is not easy to draw given the diversity of studies (e.g. number of patients, design, folic acid and vitamin B status, ethnic differences, genetic background). For some complications, most results encourages further investigation. Impaired renal function is a major independent determinant of high total Hcy (tHcy) levels. However, the role of hyperhomocysteinaemia (HHcy) in the development of diabetic kidney disease (DKD) has yet to be determined. Hcy-lowering therapies can significantly decrease Hcy levels but their effects on CVD risk reduction are conflicting. Further studies are needed to determine the influence of Hcy-lowering therapy on CVD risk reduction, especially in patients with DM.

An update on vitamin D and B deficiency in the pathogenesis and treatment of diabetic neuropathy: a narrative review

Diabetic peripheral neuropathy (DPN) is highly prevalent and affects up to 50% of patients with diabetes. Painful neuropathic symptoms may occur in a third of patients with diabetes and is a major cause of sleep disturbance, morbidity and poor quality of life. Effective treatment of DPN remains a major challenge as current therapeutic options have a number of undesirable side effects and only provide a partial response to neuropathic pain. Furthermore, there are a lack of treatments that modulate the natural history of DPN. A growing body of evidence suggests that vitamin B and vitamin D may have analgesic effects and neuroprotective benefits in DPN. This narrative review explores the role of these vitamins in DPN. Given their limited side effects, further mechanistic studies and good quality randomized controlled trials of their putative analgesic ability are required to define the role of vitamin B and D in DPN.

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.

Identifying Common Genetic Risk Factors of Diabetic Neuropathies

Type 2 diabetes mellitus (T2DM) is a global public health problem of epidemic proportions, with 60-70% of affected individuals suffering from associated neurovascular complications that act on multiple organ systems. The most common and clinically significant neuropathies of T2DM include uremic neuropathy, peripheral neuropathy, and cardiac autonomic neuropathy. These conditions seriously impact an individual's quality of life and significantly increase the risk of morbidity and mortality. Although advances in gene sequencing technologies have identified several genetic variants that may regulate the development and progression of T2DM, little is known about whether or not the variants are involved in disease progression and how these genetic variants are associated with diabetic neuropathy specifically. Significant missing heritability data and complex disease etiologies remain to be explained. This article is the first to provide a review of the genetic risk variants implicated in the diabetic neuropathies and to highlight potential commonalities. We thereby aim to contribute to the creation of a genetic-metabolic model that will help to elucidate the cause of diabetic neuropathies, evaluate a patient's risk profile, and ultimately facilitate preventative and targeted treatment for the individual.

Hyperhomocysteinemia and neurologic disorders: a review

Homocysteine (Hcy) is a sulfur-containing amino acid that is generated during methionine metabolism. It has a physiologic role in DNA metabolism via methylation, a process governed by the presentation of folate, and vitamins B6 and B12. Physiologic Hcy levels are determined primarily by dietary intake and vitamin status. Elevated plasma levels of Hcy (eHcy) can be caused by deficiency of either vitamin B12 or folate, or a combination thereof. Certain genetic factors also cause eHcy, such as C667T substitution of the gene encoding methylenetetrahydrofolate reductase. eHcy has been observed in several medical conditions, such as cardiovascular disorders, atherosclerosis, myocardial infarction, stroke, minimal cognitive impairment, dementia, Parkinson's disease, multiple sclerosis, epilepsy, and eclampsia. There is evidence from laboratory and clinical studies that Hcy, and especially eHcy, exerts direct toxic effects on both the vascular and nervous systems. This article provides a review of the current literature on the possible roles of eHcy relevant to various neurologic disorders.

Physical activity, glycemic control, and diabetic peripheral neuropathy: a national sample

To determine if physical activity and/or blood glycohemoglobin (HbA1c) are associated with the prevalence of peripheral neuropathy (PN) in a representative population of diabetics. Three hundred thirty-nine diabetic participants (40-85 yrs) taking part in 2003-2004 National Health and Nutrition Examination Survey were studied. Participants were defined as having peripheral neuropathy if examination determined ≥1 insensate area in either foot. Moderate-to-vigorous physical activity (MVPA) was objectively-measured using accelerometry. After adjustments, MVPA was not significantly associated with PN (OR=1.16; 95% CI: 0.48-2.78), nor was HbA1c (OR=0.55; 95% CI: 0.28-1.04). However, there was evidence of statistical interaction (OR=0.24; 95% CI: 0.06-0.87) between MVPA and HbA1c status, showing that diabetics engaging in higher levels of MVPA and having normal HgbA1c levels were less likely to have PN than what would be expected based on the individual effects of MVPA and HbA1c alone. Although MVPA was not directly associated with PN, these findings suggest that proper physical activity, coupled with good glycemic control, is associated with less neuropathy. Future longitudinal studies are required to evaluate whether physical activity and improved glycemic control may help prevent or slow the progression of diabetic end-organ damage, particularly diabetic neuropathy.

[Correlation between plasma concentrations of homocysteine and diabetic polyneuropathy evaluated with the Semmes-Weinstein monofilament test in patients with type 2 diabetes mellitus]

BACKGROUND AND OBJECTIVE

Few modifiable risk factors are known to be associated with the presence and progression of diabetic polyneuropathy (DPN).

MATERIAL AND METHOD

We have analyzed in 405 type 2 diabetic (T2DM) subjects (169 women) the association of plasma homocysteine with the presence of DPN measured with the Semmes-Weinstein (SW) monofilament test. A score below 4 was considered an altered SW monofilament test. Plasma homocysteine, vitamin B12 and folic acid were measured using standard procedures (ELISA).

RESULTS

Patients with T2DM with altered SW test have significantly higher age, evolution of disease, HbA1c and lower creatinine clearance values. In addition, plasma homocysteine values were independently and significantly higher in T2DM with DPN measured as altered SW test (13.64 ± 4.93 vs. 12.22 ± 4.48 μmol/l, P<.01) with similar vitamin B12 and folic acid values comparing the 2 groups.

CONCLUSION

Plasma homocysteine and HbA1c values are the 2 modifiable biological factors associated with the presence of DPN evaluated as an altered SW monofilament test in T2DM subjects.

Plasma homocysteine levels are independently associated with the severity of peripheral polyneuropathy in type 2 diabetic subjects

Peripheral polyneuropathy (PN) is a frequent complication of diabetes. However, mechanisms underlying the development of PN are multifactorial and not well understood. Our aim was to examine the association of plasma homocysteine (Hcy) with the prevalence and grade of peripheral PN in patients with type 2 diabetes (T2DM). We studied a cohort of 196 subjects with T2DM classified according to the grade of PN (Neuropathy Disability Score, NDS). Subjects with the highest grade of PN were older and had significantly increased levels of creatinine, microalbuminuria, HbA1c, and plasma Hcy compared to the other two groups. The differences in plasma Hcy values were maintained after correcting for confounding factors. Plasma Hcy, HbA1c, duration of diabetes, and age were predictors of the grade of PN. In conclusion, for each increase of 1 µmol in plasma Hcy there was a 23% increase of the risk of diabetic PN evaluated by NDS. Moreover, the grade of PN was predicted by plasma Hcy and HbA1c values, age and duration of diabetes. Further prospective studies should be conducted to confirm the association of plasma Hcy levels with the grade of PN in subjects with T2DM.

Associations between plasma homocysteine levels, aortic stiffness and wave reflection in patients with arterial hypertension, isolated office hypertension and normotensive controls

The aim of this study was to evaluate any possible association of homocysteine with arterial stiffness indices in patients with essential arterial hypertension (AH), isolated office hypertension (IOH) and normotensive controls. The final cohort comprised 231 normotensives (NTs, 119 males), 480 patients with IOH (196 males) and 1188 patients with essential AH (713 males). All patients were screened for plasma homocysteine levels and lipidaemic profile and underwent aortic compliance and wave reflection assessment by using carotid-femoral pulse wave velocity (PWVc-f) and aortic augmentation index corrected for heart rate (AIx) accordingly. In the total population, stepwise multiple linear regression analysis showed that homocysteine levels remained a significant determinant of PWV (beta (SE): 0.056 (0.007), P<0.001) and AIx (beta (SE): 0.236 (0.052), P<0.001) independently of the traditional factors affecting arterial stiffness and wave reflection. When the three groups were examined separately, homocysteine levels remained an independent determinant of PWFc-f in all groups (NT: beta (SE): 0.070 (0.022), P=0.002; IOH: beta (SE): 0.109 (0.015), P<0.001; AH: beta (SE): 0.040 (0.009), P<0.001). However, homocysteine levels remained an independent determinant of AIx only in the IOH and AH, but not in the NT group (IOH: beta (SE): 0.302 (0.124), P=0.015; AH: beta (SE): 0.183 (0.057), P=0.001; NT: beta (SE): 0.308 (0.240), P=0.200). This study points to an independent relationship between circulating homocysteine levels, aortic compliance and wave reflection.

Correlations between homocysteine levels and atherosclerosis in Japanese type 2 diabetic patients

Elevated total plasma homocysteine (tHcy) level and aortic stiffness are associated with high mortality in type 2 diabetic patients. We tested the hypothesis that tHcy correlates with aortic stiffness and insulin resistance in type 2 diabetic patients. The study consisted of 40 Japanese patients with type 2 diabetes mellitus and high tHcy levels (mean age +/- SD, 57 +/- 7 years) and a control group of 45 age-matched patients with normal tHcy levels (mean age +/- SD, 57 +/- 6 years). Brachial-ankle pulse wave velocity (BaPWV) was measured by an automatic oscillometric method. Brachial-ankle pulse wave velocity was used as an index of atherosclerosis. Body mass index values (P < .05), waist circumferences (P < .05), and the waist-to-hip ratios (P < .05) were larger in the high-tHcy group than in the normal-tHcy group. The BaPWV was higher in the high-tHcy group than in the normal-tHcy group (P < .0001). Fasting plasma glucose (P < .005) and insulin concentrations (P < .0001), and the homeostasis model assessment (HOMA) index (P < .0001) were higher in the high-tHcy group than in the normal-tHcy group. Multiple regression analysis showed that tHcy levels were independently predicted by BaPWV and the HOMA index. In conclusion, our results indicate that the elevated level of tHcy in Japanese patients with type 2 diabetes mellitus is characterized by increased aortic stiffness and insulin resistance, and that the BaPWV and the HOMA index are independent predictors of tHcy.

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.

The association of homocysteine and related factors to brachial artery diameter and flow-mediated dilation

Brachial artery flow-mediated dilation (BAFMD) has been proposed as a measurement of the degree and severity of cardiovascular disease. The purpose of this study was to (1) evaluate the associations between BAFMD and homocysteine, folate, vitamin B(12), vitamin B(6); (2) examine the influence of 5,10-methylenetetrahydrofolate reductase (MTHFR) genotypes on homocysteine levels and BAFMD; and (3) evaluate the effect of homocysteine on the baseline diameter of the vessel vs BAFMD. A total of 174 healthy research subjects were examined for BAFMD, homocysteine, folate, vitamin B(12), vitamin B(6), and MTHFR genotype, nucleotide 677 C-->T. The data indicated a significant inverse correlation between homocysteine and BAFMD (r = -0.1763, P = .02). There was a significant difference in BAFMD between MTHFR genotype groups (P = .01) (T/T vs C/C, P = .042; C/C vs C/T, P = .13; T/T vs C/T, P = .003). Homocysteine was significantly associated with the baseline brachial artery diameter (r = 0.1878, P = .013). The data confirmed a significant inverse correlation between baseline diameter and BAFMD (r = -0.3321, P = .0001). Regression analysis indicated that the MTHFR genotype, homocysteine, and age were significant predictors of BAFMD (P = .0001, r(2) = 0.118). When the baseline brachial diameter was incorporated into the model, the effect of homocysteine on BAFMD disappeared. The present data indicate an association between homocysteine and BAFMD and reduced BAFMD in individuals with the MTHFR nucleotide 677 T/T genotype, despite similar blood values for folate and homocysteine. Finally, the data suggest that the effect of homocysteine on vascular reactivity is in part a consequence of its influence on baseline brachial artery diameter.

Homocysteine levels are associated with the results of 123I-metaiodobenzylguanidine myocardial scintigraphy in type 2 diabetic patients

PURPOSE

Elevated total plasma homocysteine (tHcy) levels and cardiovascular autonomic dysfunction are associated with a high mortality in type 2 diabetic patients. We tested the hypothesis that hyperhomocysteinemia is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients not receiving insulin treatment.

METHODS

The study group consisted of 17 type 2 diabetic patients with high tHcy levels (>15 mmol/l, age 58+/-5 years, high tHcy group). The control group consisted of 23 age-matched type 2 diabetic patients with normal tHcy levels (<or=15 mmol/l, age 58+/-9 years, normal tHcy group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy.

RESULTS

Early and delayed (123)I-MIBG myocardial uptake values were lower (p<0.005 and p<0.01, respectively) and the percent washout rate of (123)I-MIBG was higher (p<0.001) in the high tHcy group than in the normal tHcy group. The fasting plasma insulin concentrations (p<0.0001) and the homeostasis model assessment (HOMA) index values (p<0.0001) were higher in the high tHcy group than in the normal tHcy group. Multiple regression analysis revealed that the level of tHcy was independently predicted by the HOMA index values and the myocardial uptake of (123)I-MIBG at the delayed phase.

CONCLUSION

Our results demonstrate that high levels of tHcy are associated with depressed cardiovascular autonomic function and insulin resistance in patients with type 2 diabetes mellitus.

Adjuvant strategies for prevention of glomerulosclerosis

The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.

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.

Homocysteine levels are not associated with cardiovascular autonomic function in elderly Caucasian subjects without or with type 2 diabetes mellitus: the Hoorn Study

OBJECTIVE

Homocysteine and cardiovascular autonomic function are both predictors of cardiovascular disease and death, particularly in patients with diabetes. The mechanism by which homocysteine causes disease is unknown. The objective of our study was to determine whether hyperhomocysteinaemia is associated with impaired cardiovascular autonomic function in an age-, sex-, and glucose tolerance-stratified sample of an elderly Caucasian population.

METHODS

We studied 609 subjects, 252 with normal glucose metabolism, 173 with impaired glucose metabolism, and 184 with type 2 diabetes. Cardiac cycle duration (RR interval) and continuous finger arterial pressure were measured under three conditions: during (i) spontaneous breathing, (ii) six deep breaths over 1 min, and (iii) an active change in position from lying to standing. From these readings, 10 parameters of autonomic function were assessed (three Ewing tests, six heart rate variability tests and one test of baroreflex sensitivity). These 10 measurements were summarized in a single cardiovascular autonomic dysfunction score (CADS).

RESULTS

Comparing values of autonomic function measures in the lowest versus the highest quartile of homocysteine revealed no significant association between homocysteine level and autonomic function in the whole study group, nor in the individual glucose tolerance groups. Multiple adjustment for age, sex, waist-to-hip ratio, serum creatinine, use of antihypertensives and fasting insulin, confirmed this result. We found no evidence of effect modification of glucose tolerance status on the association between homocysteine and autonomic dysfunction (P for interaction for CADS = 0.79).

CONCLUSIONS

There is no evidence for an association between homocysteine levels and cardiovascular autonomic function in either diabetic or nondiabetic subjects. Cardiovascular autonomic dysfunction does not help explain why hyperhomocysteinaemia is related to cardiovascular mortality.