Pulmonary Arterial Hypertension Improvement With Nutrition and Exercise (PHINE) A Randomized Controlled Trial

Pulmonary arterial hypertension (PAH) leads to premature death as a consequence of increased pulmonary vascular resistance and right heart failure. PAH-targeted therapies developed over the past 20 years target excessive vasoconstriction. However, the pathobiology of PAH is more complicated, and includes dysregulated vascular cell proliferation, cellular metabolic abnormalities, and inflammation. Even with modern PAH therapies, current outcomes remain poor, with an estimated 3-year survival rate of only 55%. Thus, there is a clear need for more effective therapies, based on better understanding of the pathobiology of the disease.

Insulin resistance has emerged as a potential new mechanism in PAH. Animal models of insulin resistance are associated with PAH, which reverses with the administration of insulin sensitizing drugs. Over the past decade there has been an epidemiologic shift in PAH, where the disease is increasingly observed in older, obese, and diabetic subjects. Low levels of high-density lipoprotein cholesterol in PAH, a feature of insulin resistance, have been observed and found to be a strong independent predictor of PAH mortality. Elevated glycosylated hemoglobin (HbA1c) also correlates with PAH diagnosis and severity. As measured by the OGTT, idiopathic PAH patients have not only insulin resistance, but also an inability to mount an appropriate insulin response to a glucose challenge. These data point to dysfunction in the pancreatic beta cells of PAH patients. It is known that an exercise and low glycemic index diet intervention improves insulin sensitivity in pre-diabetic subjects.