The impact of exogenous ketone body suppletion on energy and pH balance in skeletal muscle during exercise in chronic heart failure patients: a prospective randomized double-blind cross-over study

Abstract Background Heart Failure (HF) is characterized by impediments in exercise capacity. Disruptions in the energy metabolism of skeletal muscle contribute to this condition. Pre-clinical and clinical evidence showed that reductions in carbohydrate and FA metabolism in HF may be partially overcome by a compensatory increase in ketone body oxidation and suggest that suppletion of ketone bodies (KB) may improve energy metabolism in HF. Purpose We tested the effect of exogenous KB suppletion on energy and pH balance during cycling exercise using 31P Magnetic Resonance (MR) Spectroscopy of the exercising quadriceps muscle in patients with HF. Methods In a randomized, double-blind, placebo-controlled cross-over study, 14 stable HF patients with reduced ejection fraction and diminished exercise capacity underwent maximal exercise testing in a MR scanner fitted with a cycling ergometer after KB or placebo treatment. Phosphocreatine (PCr) and inorganic phosphate (Pi) resonance amplitudes and frequencies were measured continuously in the quadriceps muscle during rest, exercise and recovery using in-vivo 31P MR spectroscopy (Figure 1). Results Patients had a median age of 66 [53 – 75] years, were 14% female, had a median LVEF of 37% [27 – 40] and circulating NT-pro BNP levels of 411 [182 – 946] pg/mL. Peak oxygen uptake (VO2) was 18.2 [15.2 – 20.3] ml/kg/min, which is 68% [62 – 78%] of predicted. After treatment, exercise performance in terms of cycling duration and workload were comparable between treatment arms (Figure 2). Quadriceps acidification during exercise was larger after KB suppletion compared to placebo (ΔpH: -0.2 [-0.3 - -0.1] vs -0.1 [-0.3 - -0.1] respectively; p=0.041) while quadriceps energy depletion during exercise was not altered by treatment (ΔPi/PCr 0.77 [0.55 – 2.51] vs 0.66 [0.46 – 0.81] respectively; p=0.087). Post-exercise mitochondrial oxidative function was similar between treatment arms (KB: PCr resynthesis rate 48 sec [25 – 59] versus placebo: 42 sec [36 – 63]; p=0.767). Conclusions Ketone body suppletion increased acidification and did not improve energy balance in skeletal muscle during exercise or mitochondrial function during recovery in patients with chronic HF. These results question the value of ketone bodies as treatment to boost muscular energy metabolism during exercise in HF.31P MRS Spectrum during exercise in HFExercise and energy parameters