Beta blocker effects on plasma homocysteine levels in patients with hypertension

Homocysteine as a Predictor of Paroxysmal Atrial Fibrillation-Related Events: A Scoping Review of the Literature

High levels of homocysteine (Hcy) have been linked with adverse cardiovascular outcomes, such as arrhythmias and stroke. In the context of paroxysmal atrial fibrillation (PAF), hyperhomocysteinemia has been demonstrated to be an independent predictor of future events. The aim of this report was to address the potential value of Hcy levels in predicting future paroxysms of atrial fibrillation (AF), as well as to identify the potential mechanisms of action. We searched PubMed and the Cochrane Database on 16 January 2022. Keywords used were homocysteine or hyperhomocysteinemia paired with a total of 67 different keywords or phrases that have been implicated with the pathogenesis of AF. We included primary reports of clinical and non-clinical data in the English language, as well as systematic reviews with or without meta-analyses. We placed no time constraints on our search strategy, which yielded 3748 results. Following title review, 3293 reports were excluded and 455 reports were used for title and abstract review, after which 109 reports were finally used for full-text review. Our review indicates that Hcy levels seem to hold a predictive value in PAF. Herein, potential mechanisms of action are presented and special considerations are made for clinically relevant diagnostic procedures that could complement plasma levels in the prediction of future PAF events. Finally, gaps of evidence are identified and considerations for future clinical trial design are presented.

Metoprolol and Nebivolol Prevent the Decline of the Redox Status of Low-Molecular-Weight Aminothiols in Blood Plasma of Rats During Acute Cerebral Ischemia

Cerebral ischemia has previously been shown to cause a systemic decrease in levels of the reduced forms of low-molecular-weight aminothiols [cysteine (Cys), homocysteine (Hcy), and glutathione (GSH)] in blood plasma. In this study, we examined the effect of beta-adrenergic receptor (β-AR) antagonists metoprolol (Met) and nebivolol (Neb) on the redox status of these aminothiols during acute cerebral ischemia in rats. We used a model of global cerebral ischemia (bilateral occlusion of common carotid arteries with hypotension lasting for 10 minutes). The antagonists were injected 1 hour before surgery. Total and reduced Cys, Hcy, and GSH levels were measured 40 minutes after the start of reperfusion. Neb (0.4 and 4 mg/kg) and Met (8 and 40 mg/kg) treatment increased the levels of reduced aminothiols and the global methylation index in the hippocampus. The treatments also prevented any decrease in reduced aminothiol levels in blood plasma during ischemia. Although both of these drugs eliminated delayed postischemic hypoperfusion, only Neb reduced neuronal damage in the hippocampus. The results indicate an essential role of β1-AR blockage in the maintenance of redox homeostasis of aminothiols in the plasma and brain during acute cerebral ischemia.

An association of serum ALT with elevated blood pressure in senior adults: a case-control study

Hypertension is a major risk factor for cardiovascular diseases in China; hence, identifying good serum markers might provide cost benefits in terms of reducing morbidity rates. In this population-based case-control study, participants were recruited from five districts in Hunan province, and 416 cases were matched with an equal number of controls. Markers related to elevated blood pressure were assessed: Body Mass Index, total cholesterol, triglycerides, fasting blood glucose, and creatinine. Three potential serum markers homocysteine (HCY), C-reactive protein (CRP), and alanine aminotransferase (ALT) were dichotomized as normal or high level. Binary logistic regression was used to determine odds ratios (ORs) and 95% confidence intervals (CIs). The findings showed that ALT is a powerful serum marker for predicting high risk of high blood pressure with OR = 2.94, 95% CI (1.44-6.02), while there were no significant differences between cases and controls for HCY and CRP. Additionally, it seems likely that high concentrations of HCY conferred a protective effect against elevated blood pressure. When adjusted for sex, ORs for hypertensive females were nearly five times higher than for hypertensive males (OR = 4.34, 95% CI = 1.17-16.04). The study strongly supports findings showing ALT is a potential indicator for patients with hypertension.

Elevation in Total Homocysteine Levels in Chinese Patients With Essential Hypertension Treated With Antihypertensive Benazepril

OBJECTIVE

To investigate the effect of benazepril on plasma homocysteine (Hcy) levels and to analyze the correlation between the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and changes in Hcy levels in response to benazepril.

METHODS

A total of 231 patients with mild to moderate essential hypertension were enrolled, and benazepril was orally administered at a dose of 10 mg/d for 2 weeks. Plasma Hcy levels were measured by high-performance liquid chromatography at baseline and after 2 weeks of treatment. Genotyping of the MTHFR C677T polymorphism was performed by TaqMan probe technique.

RESULTS

There was no significant change in Hcy level after benazepril treatment for 2 weeks (P = .97). However, stratified by baseline Hcy levels, the patients with baseline Hcy <10 μmol/L had a significant increase in plasma Hcy levels (P = .003). The results from the multivariable linear regression analysis demonstrated a significant correlation between baseline Hcy levels and the changes in Hcy levels found in both the unadjusted (P = .002) and the adjusted model (P = .004). Strikingly, we found no significant effect modification by the MTHFR C677T polymorphism on the Hcy changes after benazepril treatment. There were also no statistically significant interactions of gene and environment factors (ie, gene smoking and drinking) on the changes in Hcy levels after benazepril treatment.

CONCLUSION

Benazepril may cause an increase in plasma Hcy levels among patients with hypertension with low baseline Hcy levels, while effect modification by MTHFR C677T genotypes on the changes in Hcy levels in response to benazepril was not significant among patients with essential hypertension.

Homocysteine as a risk factor for hypertension: a 2-year follow-up study

Homocysteine (Hcy) is regarded as a risk factor for hypertension, but research on the causal relationship between Hcy and hypertension is limited. In the present study, we prospectively tracked the blood pressure progression of a normotensive population with different Hcy levels over a 2-year period. The incidence of hypertension with increasing Hcy quartiles produced an approximately U-shaped curve, with significance in males. Compared with the third quartile, the risk of hypertension in the first and second quartiles was increased by 1.55 (95% confidence interval [CI] 1.154–2.081) fold and 1.501 (95% CI 1.119–2.013) fold, respectively, with the increase being more significant in males. In conclusion, Hcy is related to hypertension incidence with the results approximating an U-shaped curve. Low Hcy levels might also increase the risk of hypertension.

Effect of enalapril on plasma homocysteine levels in patients with essential hypertension

OBJECTIVE

To investigate the effect of enalapril on plasma homocysteine (Hcy) levels and the association of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with the changes of Hcy levels in response to enalapril among patients with essential hypertension.

METHODS

A total of 130 patients with mild-to-moderate essential hypertension were enrolled and enalapril was orally administered at a dose of 10 mg/d for eight weeks. Plasma Hcy levels were measured by denaturing high-performance liquid chromatography (DHPLC) at baseline and after eight weeks of treatment. Genotyping of MTHFR C677T polymorphism was performed by TaqMan probe technique.

RESULTS

Compared with baseline, plasma Hcy levels did not change significantly after eight weeks (P=0.81). Stratified by baseline Hcy levels, a significant increase in plasma Hcy levels (P=0.02) among those with Hcy <10 micromol/L was observed, in contrast to no significant changes in plasma Hcy levels (P=0.54) among those with Hcy > or =10 micromol/L. No significant association was observed between MTHFR C677T polymorphism and changes in Hcy levels in response to enalapril.

CONCLUSIONS

Enalapril may cause an increase in plasma Hcy levels among the hypertensives with low baseline Hcy levels. There was no significant association between MTHFR C677T genotypes and changes in Hcy levels in response to enalapril among subjects with essential hypertension.

Postgraduate Symposium The MTHFR C677T polymorphism, B-vitamins and blood pressure

High blood pressure (BP) and elevated homocysteine are reported as independent risk factors for CVD and stroke in particular. The main genetic determinant of homocysteine concentrations is homozygosity (TT genotype) for the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, typically found in approximately 10% of Western populations. The B-vitamins folate, vitamin B12and vitamin B6are the main nutritional determinants of homocysteine, with riboflavin more recently identified as a potent modulator specifically in individuals with the TT genotype. Although observational studies have reported associations between homocysteine and BP, B-vitamin intervention studies have shown little or no BP response despite decreases in homocysteine. Such studies, however, have not considered the MTHFR C677T polymorphism, which has been shown to be associated with BP. It has been shown for the first time that riboflavin is an important determinant of BP specifically in individuals with the TT genotype. Research generally suggests that 24 h ambulatory BP monitoring provides a more accurate measure of BP than casual measurements and its use in future studies may also provide important insights into the relationship between the MTHFR polymorphism and BP. Further research is also required to investigate the association between specific B-vitamins and BP in individuals with different MTHFR genotypes in order to confirm whether any genetic predisposition to hypertension is correctable by B-vitamin intervention. The present review will investigate the evidence linking the MTHFR C677T polymorphism to BP and the potential modulating role of B-vitamins.

Practical management of dyslipidemia with elevated lipoprotein(a)

OBJECTIVE

To report a case and describe a practical approach to treating dyslipidemia in a very-high-risk patient with elevated lipoprotein(a) [Lp(a)].

SETTING

Pharmacist-managed lipid clinic, from November 2006 to July 2007.

PATIENT DESCRIPTION

A 50-year-old white woman with a recent history of multiple myocardial infarctions presented for management of dyslipidemia.

CASE SUMMARY

At baseline, the patient had elevated low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), total cholesterol (TC), and Lp(a) (306 nmol/L) levels and low high-density lipoprotein cholesterol (HDL-C) levels. Early initiation of combination therapy with a statin and niacin extended release (ER) titration was started. After 3 months, despite progressive weight gain caused by dietary indiscretion, LDL-C decreased by 24% and TG and TC levels reached goal. Lp(a) levels did not change. Niacin ER titration continued, pravastatin was maximized, and ezetimibe 10 mg daily was started. Despite dramatic 9-month weight gain (68 lb total), LDL-C and HDL-C reached goal and Lp(a) levels decreased by 33% (204 nmol/L) after niacin ER maximization.

RESULTS

Lp(a) is an emerging risk factor in cardiovascular disease (CVD). Elevated Lp(a) (>30 mg/dL) has been implicated as both an independent and an additive risk factor for CVD and stroke, particularly in women. In this case, the patient did not reach the optimal goal (<30 mg/dL) but did experience more than 30% reduction in Lp(a) levels. Although multiple factors, including subclinical hypothyroidism, hormonal changes, and renal disease, increase Lp(a) levels, few beneficial treatment options exist (i.e., estrogen and niacin). Although the exact mechanism of action is unknown, niacin ER has been documented to reduce Lp(a) by 36% to 38%. Some effect of ezetimibe on Lp(a) in this patient cannot be ruled out.

CONCLUSION

This case illustrates a practical use of currently available therapy options to address Lp(a) as a secondary cardiovascular risk factor. Niacin is a preferred option for Lp(a) lowering in very-high-risk patients with coronary heart disease and dyslipidemia. The importance of moderate reductions in Lp(a) is not known.