Amino acid homeostasis is a target of metformin therapy.

OBJECTIVE: Unexplained changes in regulation of branched chain amino acids (BCAA) during diabetes therapy with metformin have been known for years. Here we have investigated mechanisms underlying this effect. METHODS: We used cellular approaches, including single gene/protein measurements, as well as systems-level proteomics. Findings were then cross-validated with electronic health records and other data from human material. RESULTS: In cell studies, we observed diminished uptake/incorporation of amino acids following metformin treatment of liver cells and cardiac myocytes. Supplementation of media with amino acids attenuated known effects of the drug, including on glucose production, providing a possible explanation for discrepancies between effective doses in vivo and in vitro observed in most studies. Data-Independent Acquisition proteomics identified that SNAT2, which mediates tertiary control of BCAA uptake, was the most strongly suppressed amino acid transporter in liver cells following metformin treatment. Other transporters were affected to a lesser extent. In humans, metformin attenuated increased risk of left ventricular hypertrophy due to the AA allele of KLF15, which is an inducer of BCAA catabolism. In plasma from a double-blind placebo-controlled trial in nondiabetic heart failure (trial registration: NCT00473876), metformin caused selective accumulation of plasma BCAA and glutamine, consistent with the effects in cells. CONCLUSIONS: Metformin restricts tertiary control of BCAA cellular uptake. We conclude that modulation of amino acid homeostasis contributes to therapeutic actions of the drug.

Sexual dimorphism in selenium deficiency is associated with metabolic syndrome and prevalence of heart disease.

BACKGROUND: Serum selenium levels have been associated with the incidence of heart failure (HF) and signs of the metabolic syndrome. In addition, notable differences have been reported between males and females in food intake and micronutrient metabolism, possibly explaining different health outcomes. OBJECTIVE: Our objective was to elucidate sex-specific, cross-sectional phenotypic differences in the association of serum selenium concentrations with parameters of metabolic syndrome and HF. METHODS: We investigated data from individuals from a community-based cohort (PREVEND; N = 4288) and heart failure cohort (BIOSTAT-CHF; N = 1994). In both populations, cross-sectional analyses were performed for potential interaction (p < 0.1) between sex and serum selenium with overlapping signs and clinical parameters of the metabolic syndrome and HF. RESULTS: Baseline selenium levels of the total cohort were similar between PREVEND (85.7 µg/L) and BIOSTAT-CHF (89.1 µg/L). Females with lower selenium levels had a higher BMI and increased prevalence of diabetes than females with higher selenium, in both PREVEND (pinteraction < 0.001; pinteraction = 0.040, resp.) and BIOSTAT-CHF (pinteraction = 0.021; pinteraction = 0.024, resp.), while opposite associations were observed for males. Additionally, in females, but not in males, lower selenium was associated with a higher prevalence of myocardial infarction (MI) in PREVEND (pinteraction = 0.021) and BIOSTAT-CHF (pinteraction = 0.084). CONCLUSION: Lower selenium was associated with a higher BMI and increased prevalence of diabetes in females, opposite to males, and was also associated with more MI in females. Interventional studies are needed to validate this observation.

Selenium and outcome in heart failure.

AIMS: Severe deficiency of the essential trace element selenium can cause myocardial dysfunction although the mechanism at cellular level is uncertain. Whether, in clinical practice, moderate selenium deficiency is associated with worse symptoms and outcome in patients with heart failure is unknown. METHODS AND RESULTS: BIOSTAT-CHF is a multinational, prospective, observational cohort study that enrolled patients with worsening heart failure. Serum concentrations of selenium were measured by inductively coupled plasma mass spectrometry. Primary endpoint was a composite of all-cause mortality and hospitalization for heart failure; secondary endpoint was all-cause mortality. To investigate potential mechanisms by which selenium deficiency might affect prognosis, human cardiomyocytes were cultured in absence of selenium, and mitochondrial function and oxidative stress were assessed. Serum selenium concentration (deficiency) was <70 µg/L in 485 (20.4%) patients, who were older, more often women, had worse New York Heart Association class, more severe signs and symptoms of heart failure and poorer exercise capacity (6-min walking test) and quality of life (Kansas City Cardiomyopathy Questionnaire). Selenium deficiency was associated with higher rates of the primary endpoint [hazard ratio (HR) 1.23; 95% confidence interval (CI) 1.06-1.42] and all-cause mortality (HR 1.52; 95% CI 1.26-1.86). In cultured human cardiomyocytes, selenium deprivation impaired mitochondrial function and oxidative phosphorylation, and increased intracellular reactive oxygen species levels. CONCLUSIONS: Selenium deficiency in heart failure patients is independently associated with impaired exercise tolerance and a 50% higher mortality rate, and impaired mitochondrial function in vitro, in human cardiomyocytes. Clinical trials are needed to investigate the effect of selenium supplements in patients with heart failure, especially if they have low plasma concentrations of selenium.

The effects and costs of home-based rehabilitation for heart failure with reduced ejection fraction: The REACH-HF multicentre randomized controlled trial.

BACKGROUND: Cardiac rehabilitation improves health-related quality of life (HRQoL) and reduces hospitalizations in patients with heart failure, but international uptake of cardiac rehabilitation for heart failure remains low. DESIGN AND METHODS: The aim of this multicentre randomized trial was to compare the REACH-HF (Rehabilitation EnAblement in CHronicHeart Failure) intervention, a facilitated self-care and home-based cardiac rehabilitation programme to usual care for adults with heart failure with reduced ejection fraction (HFrEF). The study primary hypothesis was that the addition of the REACH-HF intervention to usual care would improve disease-specific HRQoL (Minnesota Living with Heart Failure questionnaire (MLHFQ)) at 12 months compared with usual care alone. RESULTS: The study recruited 216 participants, predominantly men (78%), with an average age of 70 years and mean left ventricular ejection fraction of 34%. Overall, 185 (86%) participants provided data for the primary outcome. At 12 months, there was a significant and clinically meaningful between-group difference in the MLHFQ score of -5.7 points (95% confidence interval -10.6 to -0.7) in favour of the REACH-HF intervention group ( p = 0.025). With the exception of patient self-care ( p < 0.001) there was no significant difference in other secondary outcomes, including clinical events ( p > 0.05) at follow-up compared with usual care. The mean cost of the REACH-HF intervention was £418 per participant. CONCLUSIONS: The novel REACH-HF home-based facilitated intervention for HFrEF was clinically superior in disease-specific HRQoL at 12 months and offers an affordable alternative to traditional centre-based programmes to address current low cardiac rehabilitation uptake rates for heart failure.

A systems BIOlogy Study to TAilored Treatment in Chronic Heart Failure: rationale, design, and baseline characteristics of BIOSTAT-CHF.

AIMS: Despite major improvements in pharmacological and device treatments, heart failure remains a syndrome with high morbidity and mortality, poor quality of life, and high health-care costs. Given the extensive heterogeneity among patients with heart failure, substantial differences in the response to therapy can be expected. We hypothesize that individualized therapy is an essential next step to improve outcomes in patients with heart failure. METHODS: The BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF) included 2516 patients with worsening signs and/or symptoms of heart failure from 11 European countries, who were considered to be on suboptimal medical treatment. Another 1738 patients from Scotland were included in a validation cohort. Overall, both patient cohorts were well matched. The majority of patients were hospitalized for acute heart failure, and the remainder presented with worsening signs and/or symptoms of heart failure at outpatient clinics. Approximately half of the patients were in New York Heart Association class III, and 7% vs 34% of patients of the index vs validation cohort had heart failure with preserved ejection fraction. According to study design, all patients used diuretics, but owing to the inclusion criteria of both cohorts, patients were not on optimal, evidence-based medical therapy. In the follow-up phase, uptitration to guideline-recommended doses was encouraged. CONCLUSION: By using a novel systems biology approach, incorporating demographics, biomarkers, genome-wide analysis, and proteomics, a model that predicts response to therapy will be developed, which should be instrumental in developing alternative therapies for patients with suboptimal response to currently recommended therapies and thus further improve care for patients with heart failure.

Allopurinol reduces left ventricular mass in patients with type 2 diabetes and left ventricular hypertrophy.

OBJECTIVES: This study sought to ascertain whether high-dose allopurinol causes regression of left ventricular mass (LVM) in patients with type 2 diabetes mellitus (T2DM). BACKGROUND: Left ventricular hypertrophy (LVH) is common in T2DM and contributes to patients' high cardiovascular (CV) event rate. Oxidative stress (OS) has been implicated in LVH development, and allopurinol has been previously shown to reduce vascular OS. We therefore investigated whether allopurinol causes regression of LVH in patients with T2DM. METHODS: We conducted a randomized, double-blind, placebo-controlled study of 66 optimally-treated T2DM patients with echocardiographic evidence of LVH. Allopurinol, 600 mg/day, or placebo was given over the study period of 9 months. The primary outcome was reduction in LVM as calculated by cardiac magnetic resonance imaging at baseline and at 9 months' follow-up. Secondary endpoints were change in flow-mediated dilation and augmentation index. RESULTS: Allopurinol significantly reduced absolute LVM (-2.65 ± 5.91 g vs. placebo group +1.21 ± 5.10 g [p = 0.012]) and LVM indexed to body surface area (-1.32 ± 2.84 g/m(2) vs. placebo group +0.65 ± 3.07 g/m(2) [p = 0.017]). No significant changes were seen in either flow-mediated dilation or augmentation index. CONCLUSIONS: Allopurinol causes regression of LVM in patients with T2DM and LVH. Regression of LVH has been shown previously to improve CV mortality and morbidity. Therefore, allopurinol therapy may become useful to reduce CV events in T2DM patients with LVH. (Allopurinol in Patients with Diabetes and LVH; UKCRN 8766).

Effects of vitamin D supplementation on markers of vascular function after myocardial infarction--a randomised controlled trial.

BACKGROUND: Low vitamin D levels are common, and are associated with a higher incidence of future vascular events. We tested whether vitamin D supplementation could improve endothelial function and other markers of vascular function in patients with a history of myocardial infarction. METHODS: Parallel group, placebo-controlled, double-blind randomised trial. Patients with a history of myocardial infarction were randomised to receive 100,000 units of oral vitamin D3 or placebo at baseline, 2 months and 4 months. Outcomes were measured at baseline, 2 and 6 months. Reactive hyperaemia index on fingertip plethysmography was the primary outcome. Secondary outcome measures included blood pressure, cholesterol, C-reactive protein, von Willebrand factor, tumour necrosis factor alpha, E-selectin, B-type natriuretic peptide, thrombomodulin and 25-hydroxyvitamin D levels. RESULTS: 75 patients were randomised, mean age 66 years. 74/75 (99%) completed 6 month follow-up. 25 hydroxyvitamin D levels increased in the intervention group relative to placebo (+13 vs +1 nmol/L, p=0.04). There was no between-group difference in change in reactive hyperaemia index between baseline and 6 months (-0.18 vs -0.07, p=0.40). Of the secondary outcomes, only C-reactive protein showed a significant decline in the intervention arm relative to placebo at 6 months (-1.3 vs 2.0mg/L, p=0.03). Systolic blood pressure (+1.4 vs +2.3 mmHg, p=0.79), diastolic blood pressure (+2.0 vs +0.8 mmHg, p=0.54) and total cholesterol (+0.26 vs +0.24 mmol/L, p=0.88) showed no between-group difference at 6 months. CONCLUSIONS: Supplementation with vitamin D did not improve markers of vascular function in patients with a history of myocardial infarction.

Mechanistic insights into the therapeutic use of high-dose allopurinol in angina pectoris.

OBJECTIVES: The aim of this study was to evaluate the effect of high-dose allopurinol on vascular oxidative stress (OS) and endothelial function in subjects with stable coronary artery disease (CAD). BACKGROUND: Allopurinol, a xanthine oxidase inhibitor, prolongs the time to chest pain during exercise in angina. We sought to ascertain whether allopurinol also improves endothelial dysfunction in optimally treated CAD patients, because such an effect might be of value to reduce future cardiovascular mortality. The mechanism of the anti-ischemic effect of allopurinol could be related to its reducing xanthine oxidase-induced OS, and our second aim was to see whether allopurinol really does reduce vascular tissue OS in CAD patients. METHODS: A randomized, double-blind, placebo-controlled, crossover study was conducted in 80 patients with CAD, comparing allopurinol (600 mg/day) with placebo. Endothelial function was assessed by forearm venous occlusion plethysmography, flow-mediated dilation, and pulse wave analysis. Vascular OS was assessed by intra-arterial co-infusion of vitamin C and acetylcholine. RESULTS: Compared with placebo, allopurinol significantly improved endothelium-dependent vasodilation, by both forearm venous occlusion plethysmography (93 ± 67% vs. 145 ± 106%, p = 0.006) and flow-mediated dilation (4.2 ± 1.8% vs. 5.4 ± 1.7%, p < 0.001). Vascular oxidative stress was completely abolished by allopurinol. Central augmentation index improved significantly with allopurinol (2.6 ± 7.0%, p < 0.001) but not with placebo. CONCLUSIONS: Our study demonstrates that, in optimally treated CAD patients, high-dose allopurinol profoundly reduces vascular tissue OS and improves 3 different measures of vascular/endothelial dysfunction. The former effect on OS might underpin the anti-ischemic effect of allopurinol in CAD. Both effects (on OS and endothelial dysfunction) increase the likelihood that high-dose allopurinol might reduce future cardiovascular mortality in CAD, over and above existing optimum therapy. (Exploring the therapeutic potential of xanthine oxidase inhibitor allopurinol in angina; ISRCTN15253766).

Selective low-level leg muscle training alleviates dyspnea in patients with heart failure.

OBJECTIVES: The purpose of this study was to demonstrate in patients with moderate to severe heart failure that exertional dyspnea can be alleviated by improving muscle function. BACKGROUND: Dyspnea is a frequent limiting symptom in patients with chronic heart failure (CHF). This sensation may originate from activation of receptors in the musculature rather than the lung. METHODS: To investigate whether dyspnea could be alleviated by selective changes in leg muscle function, we performed isolated lower-limb training in 17 patients with severe CHF. Eight patients learned guided imagery relaxation techniques and served as an active control group. Exercise training consisted of three months of low-level bicycle and treadmill exercise such that minute ventilation was <25 l/min. Leg calisthenics were also performed. Maximal and submaximal exercise performance, respiratory and quadriceps muscle strength and endurance and quality-of-life and dyspnea scales were measured before and after each intervention. Metabolic stress testing (VO(2)), pulmonary function tests and isokinetic strength testing were also performed. RESULTS: In the active control group, no changes in leg muscle function, pulmonary function, maximal and submaximal exercise performance or quality-of-life questionnaires were observed. In the training group, peak torque of leg flexors (pre: 39 +/- 15 ft-lb; post: 50 +/- 13 ft-lb; p < 0.002) increased and the fatigue ratio decreased, indicating improved strength and endurance of the leg muscles. Maximal inspiratory and expiratory mouth pressures and maximum voluntary ventilation were unchanged. Peak VO(2) was increased (pre:12 +/- 2.2 ml/kg/min; post: 14 +/- 2.6 ml/kg/min) as well as the duration of exercise at 70% peak VO(2) increased (pre: 11.5 +/- 3.1 min; post: 21.5 +/- 5.4 min; p < 0.003). Perceived dyspnea during the submaximal testing was decreased. Minnesota Living with Heart Failure Score, Guyatt Dyspnea Scale, and the Transitional Dyspnea Index were all improved with training (all p < 0.05). CONCLUSIONS: We concluded that improvement of limb muscle function alleviates dyspnea and improves exercise performance in patients with CHF.