Plasma-Derived microRNAs Are Influenced by Acute and Chronic Exercise in Patients With Heart Failure With Reduced Ejection Fraction

Background: Exercise training improves VO₂peak in heart failure with reduced ejection fraction (HFrEF), but the effect is highly variable as it is dependent on peripheral adaptations. We evaluated changes in plasma-derived miRNAs by acute and chronic exercise to investigate whether these can mechanistically be involved in the variability of exercise-induced adaptations.

Methods: Twenty-five male HFrEF patients (left ventricular ejection fraction < 40%, New York Heart Association class ≥ II) participated in a 15-week combined strength and aerobic training program. The effect of training on plasma miRNA levels was compared to 21 male age-matched sedentary HFrEF controls. Additionally, the effect of a single acute exercise bout on plasma miRNA levels was assessed. Levels of 5 miRNAs involved in pathways relevant for exercise adaptation (miR-23a, miR-140, miR-146a, miR-191, and miR-210) were quantified using RT-qPCR and correlated with cardiopulmonary exercise test (CPET), echocardiographic, vascular function, and muscle strength variables.

Results: Expression levels of miR-146a decreased with training compared to controls. Acute exercise resulted in a decrease in miR-191 before, but not after training. Baseline miR-23a predicted change in VO₂peak independent of age and left ventricular ejection fraction (LVEF). Baseline miR-140 was independently correlated with change in load at the respiratory compensation point and change in body mass index, and baseline miR-146a with change in left ventricular mass index.

Conclusion: Plasma-derived miRNAs may reflect the underlying mechanisms of exercise-induced adaptation. In HFrEF patients, baseline miR-23a predicted VO₂peak response to training. Several miRNAs were influenced by acute or repeated exercise. These findings warrant exploration in larger patient populations and further mechanistic in vitro studies on their molecular involvement.

Diet-dependent entropic assessment of athletes' lifespan

Life expectancies of the athletes depend on the sports they are doing. The entropic age concept, which was found successful in the previous nutrition studies, will be employed to assess the relation between the athletes' longevity and nutrition. Depending on their caloric needs, diets are designed for each group of athletes based on the most recent guidelines while they are pursuing their careers and for the post-retirement period, and then the metabolic entropy generation was worked out for each group. Their expected lifespans, based on attaining the lifespan entropy limit, were calculated. Thermodynamic assessment appeared to be in agreement with the observations. There may be a significant improvement in the athletes' longevity if they shift to a retirement diet after the age of 50. The expected average longevity for male athletes was 56 years for cyclists, 66 years for weightlifters, 75 years for rugby players and 92 years for golfers. If they should start consuming the retirement diet after 50 years of age, the longevity of the cyclists may increase for 7 years, and those of weightlifters, rugby players and golfers may increase for 22, 30 and 8 years, respectively.

Evidence of a double anaerobic threshold in healthy subjects

AIMS

The anaerobic threshold (AT) is an important cardiopulmonary exercise test (CPET) parameter both in healthy and in patients. It is normally determined with three approaches: V-slope method, ventilatory equivalent method, and end-tidal method. The finding of different AT values with these methods is only anecdotic. We defined the presence of a double threshold (DT) when a ΔVO2 > 15 mL/min was observed between the V-slope method (met AT) and the other two methods (vent AT). The aim was to identify whether there is a DT in healthy subjects.

METHODS AND RESULTS

We retrospectively analysed 476 healthy subjects who performed CPET in our laboratory between 2009 and 2018. We identified 51 subjects with a DT (11% of cases). Cardiopulmonary exercise test data at rest and during the exercise were not different in subjects with DT compared to those without. Met AT always preceded vent AT. Compared to subjects without DT, those with DT showed at met AT lower carbon dioxide output (VCO2), end-tidal carbon dioxide tension (PetCO2) and respiratory exchange ratio (RER), and higher ventilatory equivalent for carbon dioxide (VE/VCO2). Compared to met AT, vent AT showed a higher oxygen uptake (VO2), VCO2, ventilation, respiratory rate, RER, work rate, and PetCO2 but a lower VE/VCO2 and end-tidal oxygen tension. Finally, subjects with DT showed a higher VO2 increase during the isocapnic buffering period.

CONCLUSION

Double threshold was present in healthy subjects. The presence of DT does not influence peak exercise performance, but it is associated with a delayed before acidosis-induced hyperventilation.

Isocapnic buffering period: From physiology to clinics

Background

During cardiopulmonary exercise test, the isocapnic buffering period ranges between anaerobic threshold (AT) and respiratory compensation point (RCP). We investigated whether oxygen uptake (VO2) increase during the isocapnic buffering period (ΔVO2AT-RCP) is related to heart failure severity and prognosis.

Methods

We retrospectively analysed reduced ejection fraction heart failure patients who attained RCP at cardiopulmonary exercise test. The study endpoint was the composite of cardiovascular mortality and urgent heart transplantation/left ventricular assist device implantation. Hazard ratio was assessed to identify the increase of risk associated with ΔVO2AT-RCP (below and above the median of ΔVO2AT-RCP).

Results

AT and RCP were both identified in 782 (39.2%) out of 1995 reduced ejection fraction heart failure cases. Left ventricular ejection fraction and peak VO2 were 33 ± 9% and 16.5 ± 4.5 mL/kg per min (61 ± 16% of predicted value), suggesting moderate heart failure. At five years, endpoint did not vary between patients below and above the median ΔVO2AT-RCP (3.85 mL/min per kg (25–75th interquartile range = 2.69–5.46)). ΔVO2AT-RCP correlated with several parameters associated to heart failure prognosis, such as peak VO2, VE/VCO2 slope, brain natriuretic peptide and left ventricular ejection fraction. The ΔVO2AT-RCP value was associated with prognosis at univariate but not at multivariable analysis, where only VE/VCO2 slope endured.

Conclusion

ΔVO2AT-RCP correlates with several parameters linked to heart failure severity. Isocapnic buffering period stratifies heart failure patients, but not more than other prognostic indices.