Metabolic, endocrine, haemodynamic and pulmonary responses to different types of exercise in individuals with normal or reduced liver function

Abstract

The liver is central to the metabolic response to exercise but measurements of effects of reduced liver function on the physiological adaptation to exercise are scarce. We investigated metabolic, endocrine, pulmonary and haemodynamic responses to exercise in 15 healthy untrained controls (Co) and in 30 subjects with reduced liver function (i.e. liver cirrhosis, Ci). The following protocols were used: protocol 1 maximal oxygen uptake $\dot V{\text{O}}_{{\text{2max}}}$ and anaerobic threshold (AT), protocol 2 stepwise increases in exercise intensity from 0 to 40% $\dot V{\text{O}}_{{\text{2max}}}$ giving steady-stage conditions, protocol 3 1 h exercise at 20% $\dot V{\text{O}}_{{\text{2max}}}$. Muscle glycogen content was determined in 15 Ci. Spirometry was essentially normal in Ci. Result: protocol 1 Ci had impaired $\dot V{\text{O}}_{{\text{2max}}}$ and reduced AT (P < 0.05). Basal plasma concentrations of insulin, glucagon, growth hormone and adrenaline were increased in Ci (P < 0.05); cortisol was normal. During exercise, only glucagon remained different between groups. In protocol 2 Ci had decreased resting respiratory exchange ratio (RQ: p < 0.05) associated with increased plasma concentrations of free fatty acids and glycerol. They had disproportionately enhanced lipolysis and RQ. heart rate (+ 24%), ventilation (+ 28%), thermal effects of exercise (+ 31%) and intrapulmonary shunt volume (+ 76%), which accounted for 11.7 (SD 3.0) or 7.4 (SD 0.9%) of cardiac output during exercise in Ci and Co, respectively (P < 0.05 for all the differences reported). The metabolic effects of Ci were independent of the clinical and nutritional state of the patients. In protocol 3 muscle glycogen content was highly variable in Ci, but mean values were normal [16.9 (SD 8.9) μmol·g⁻¹ wet mass]. Glycogen content positively correlated with resting and exercise-induced RQ, but negatively correlated with the exercise-induced alterations in plasma glucose concentration. From these results we concluded that with reduced liver function $\dot V{\text{O}}_{{\text{2max}}}$, and AT are reduced, but metabolic, pulmonary and haemodynamic reponses per unit power output are enhanced. Muscle glycogen content would seem to contribute to the metabolic response, but its mobilization to be limited in individuals with reduced liver function.