Growth/differentiation factor 15 causes TGFß-activated kinase 1-dependent muscle atrophy in pulmonary arterial hypertension.

INTRODUCTION: Skeletal muscle dysfunction is a clinically important complication of pulmonary arterial hypertension (PAH). Growth/differentiation factor 15 (GDF-15), a prognostic marker in PAH, has been associated with muscle loss in other conditions. We aimed to define the associations of GDF-15 and muscle wasting in PAH, to assess its utility as a biomarker of muscle loss and to investigate its downstream signalling pathway as a therapeutic target. METHODS: GDF-15 levels and measures of muscle size and strength were analysed in the monocrotaline (MCT) rat, Sugen/hypoxia mouse and in 30 patients with PAH. In C2C12 myotubes the downstream targets of GDF-15 were identified. The pathway elucidated was then antagonised in vivo. RESULTS: Circulating GDF-15 levels correlated with tibialis anterior (TA) muscle fibre diameter in the MCT rat (Pearson r=-0.61, p=0.003). In patients with PAH, plasma GDF-15 levels of <564 pg/L predicted those with preserved muscle strength with a sensitivity and specificity of ≥80%. In vitro GDF-15 stimulated an increase in phosphorylation of TGFß-activated kinase 1 (TAK1). Antagonising TAK1, with 5(Z)-7-oxozeaenol, in vitro and in vivo led to an increase in fibre diameter and a reduction in mRNA expression of atrogin-1 in both C2C12 cells and in the TA of animals who continued to grow. Circulating GDF-15 levels were also reduced in those animals which responded to treatment. CONCLUSIONS: Circulating GDF-15 is a biomarker of muscle loss in PAH that is responsive to treatment. TAK1 inhibition shows promise as a method by which muscle atrophy may be directly prevented in PAH. TRIAL REGISTRATION NUMBER: NCT01847716; Results.

Bosentan in pulmonary hypertension associated with fibrotic idiopathic interstitial pneumonia.

RATIONALE: Pulmonary hypertension (PH) associated with fibrotic idiopathic interstitial pneumonia (IIP; idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia) confers important additional morbidity and mortality. OBJECTIVES: To evaluate the safety and clinical efficacy of the dual endothelin-1 receptor antagonist bosentan in this patient group. METHODS: In a randomized, double-blind, placebo-controlled study, 60 patients with fibrotic IIP and right heart catheter confirmed PH were randomized 2:1 to bosentan (n = 40) or placebo (n = 20). The primary study endpoint was a fall from baseline pulmonary vascular resistance index (PVRi) of 20% or more over 16 weeks. MEASUREMENTS AND MAIN RESULTS: Sixty patients (42 men; mean age, 66.6 ± 9.2 yr), with a mean pulmonary artery pressure of 36.0 (± 8.9) mm Hg, PVRi 13.0 (± 6.7) Wood Units/m(2) and reduced cardiac index of 2.21 (± 0.5) L/min/m(2) were recruited to the study. Accounting for deaths and withdrawals, paired right heart catheter data were available for analysis in 39 patients (bosentan = 25, placebo = 14). No difference in the primary outcome was detected, with seven (28.0%) patients receiving bosentan, and four (28.6%) receiving placebo achieving a reduction in PVRi of greater than or equal to 20% (P = 0.97) at 16 weeks. There was no change in functional capacity or symptoms between the two groups at 16 weeks, nor any difference in rates of serious adverse events or deaths (three deaths in each group). CONCLUSIONS: This study shows no difference in invasive pulmonary hemodynamics, functional capacity, or symptoms between the bosentan and placebo groups over 16 weeks. Our data do not support the use of the dual endothelin-1 receptor antagonist, bosentan, in patients with PH and fibrotic IIP. Clinical trial registered with www.clinicaltrials.gov (NCT 00637065).

The use of sildenafil to treat pulmonary hypertension associated with interstitial lung disease.

BACKGROUND AND OBJECTIVE: Limited data suggest a benefit following sildenafil treatment in patients with pulmonary hypertension (PH) and interstitial lung disease (ILD). The role of sildenafil in the management of PH in ILD is not clear. We report our experience of ILD patients with PH after 6-month sildenafil therapy. METHODS: We reviewed 15 patients (mean age 55 ± 15 years; 8 men) with ILD (mean FVC 52.6 ± 15.4%) and PH (mean right ventricular systolic pressure 73.8 ± 17.8 mm Hg). Median brain natriuretic peptide: 37 (5-452) pmol/L; mean 6MWD: 156 ± 101 m. RESULTS: Following 6-month treatment with sildenafil, brain natriuretic peptide levels were lower (n = 12, P = 0.03), 6MWD was higher (n = 6, P < 0.05), but no change in right ventricular systolic pressure (n = 11) was demonstrated. CONCLUSIONS: Our observations suggest that sildenafil may be useful in the management of PH in ILD. Controlled trials are warranted before therapeutic recommendations can be made.

Disease targeting therapies in patients with Eisenmenger syndrome: response to treatment and long-term efficiency.

OBJECTIVES: To examine long-term efficacy of disease targeting therapies (DTT) in patients with Eisenmenger syndrome. METHODS: All adult patients with Eisenmenger syndrome treated with DTT at our institution were included. Functional class (FC), oxygen saturation and 6-minute walk test distance (6 MWTd) were analysed retrospectively. RESULTS: Between 2002 and 2010, 79 Eisenmenger patients (21 males, 16 with Down syndrome) aged 34 ± 10 years (range 17-68 years) were included. Median follow-up was 3.3 years (range 0.2 to 8.9 years). 6 MWTd increased early after initiation of DTT, with a plateau after approximately 3 years and no obvious trend towards a deterioration on average during longer-term follow-up. Two patients died during follow-up and escalation of treatment was required in 18 patients after a median period of 2.5 years. Escalation of therapy was also associated with an increase in 6 MWTd. In addition, FC improved on DTT and oxygen saturation, increased, both at rest and peak exercise. This effect was more pronounced in the patients with the lowest baseline oxygen saturation at rest. CONCLUSIONS: Long-term DTT is safe and improves objective exercise capacity and subjective symptoms. Response to DTT was typically observed early after initiation of DTT and was, on average, maintained longer-term. However, 1 in 5 patients required escalation of DTT, with time, due to symptomatic deterioration and this was associated with an afresh improvement in 6 MWTd.