Heart failure (HF) is epidemic with aging and prevalence of HF is steadily increasing as the population of older adults expands. Despite the fact that age always stands out as a leading risk factor for HF incidence as well as for poor HF prognosis, few HF trials focus specifically on aging physiology as a key determinant of the disease, and/or on the utility of targeting mechanisms associated with aging as beneficial therapeutic targets. Consistently, HF trials have tended to focus primarily on central mechanisms of cardiac pumping dysfunction despite the fact that HF-outcomes are strongly related to functional decrements that are largely mediated by peripheral manifestations of the disease, and which are particularly interrelated with aging physiology. HF-related skeletal muscle myopathy is a manifestation of HF that diminishes physical function, and which is likely exacerbated by sarcopenia, vascular stiffening, and other aspects of aging such that exercise intolerance is disproportionate among older HF populations as well as its insidious clinical implications. In a pilot investigation, the investigators will study older (age ≥70 years) adults, including patients with HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF) and age-matched healthy controls, to study benefits of nitrite therapy (in addition to established standards of HF care) to improve physical function. In this pilot analysis the investigators will focus on the utility of daily nitrite supplements to moderate aerobic (maximal and submaximal) and strength (maximal, endurance, and power) indices as well as underlying skeletal muscle mechanisms (skeletal muscle mitochondrial performance, gene expression, and capillarity).
Atrophy of type 1 skeletal muscle myocytes is associated with HFrEF and HFpEF. Multiple studies of normal aging have also demonstrated typical atrophy of type 2 skeletal muscle fibers. Consistently, older adults are compromised by cumulative atrophy risks, with studies showing losses of lean body mass as well as intrinsic skeletal muscle weakening, increased interstitial fat, and increased inflammation, with associated functional decrements and fatigue. While aerobic and strength exercise training may be used to modify such HF-related muscle patterns, deconditioning remains pervasive among older HF patients, and efforts to promote exercise interventions are typically confounded by comorbidity (e.g. arthritis, peripheral arterial disease, diabetes, depression), geriatric syndromes (e.g., falls, frailty, incontinence, dementia, poor sleep, malnutrition, auditory and vision impairments), as well as pain, anxiety, and logistic limitations. Even major exercise-training trials that provided strong reinforcements to ensure requisite behavioral changes yielded only poor exercise adherence. There is high conceptual rationale for a therapy that intrinsically improves skeletal muscle performance in HF as a vital means to improve physical function and moderate effects of disease itself as well as to frailties and enfeeblement associated with the disease. This will potentially improve efficacy and quality of care, and also potentially mitigate the skyrocketing costs associated with aggregate HF management.
Studies have demonstrated nitrate therapy increases adenosine triphospate (ATP) synthesis in skeletal muscle mitochondria concomitant with reduced whole-body oxygen cost during steady state exercise. Our own work has demonstrated safety and efficacy of an FDA-IND approved sodium nitrite (10 mg) capsule, and its utility to upregulate the SIRT3-AMP pathway of skeletal muscle of younger HF patients. It now seems exceptionally logical and opportune to apply these insights to older HF patients and to delineate mechanisms of disease and aging that respond to nitrite therapy.
Overall aims:
1. To demonstrate that oral nitrite pills provide skeletal muscle physiological benefit in old HFrEF and HFpEF patients:
* To show that oral supplements are manifest as increased plasma nitrite.
* To show that increased plasma nitrite is associated with improved skeletal muscle (mitochondrial respirometry) and platelet (Seahorse XF) metabolism.
* To demonstrate that improved metabolism is associated with shifts in skeletal muscle anabolic gene expression (Fibronectin type III domain-containing protein 5 \[FNDC5\], peroxisome proliferator-activated receptor-γ coactivator \[PGC1α\], Sirtuin 3) as well as reduced catabolic gene expression (ubiquitin, muscle RING-Finger Protein \[MuRF\], Atrogin1\]) and inflammation (Tumor necrosis factor alpha \[TNFα\], Interleukin 1beta (IL-1β), Interleukin six (IL-6).
2. To demonstrate that improved skeletal physiology achieved using oral nitrate pills is associated with improved clinical indices in old HFrEF and HFpEF patients:
* To show that oral nitrite supplements increase efficiency of work, i.e., reduced oxygen uptake (VO2) required for the same work intensity.
