Abstract
It remains unclear whether sickle cell trait (SCT) should be considered a risk factor during intense physical activity. By triggering the polymerization-sickling-vaso-occlusion cascade, lactate accumulation-associated acidosis in response to high-intensity exercise is believed to be one of the causes of complications. However, our understanding of lactate metabolism in response to high-intensity exercise in SCT carriers is incomplete. Thirty male SCT carriers (n = 15) and healthy subjects (n = 15) with and without α-thalassemia performed a 2-min high-intensity exercise. Blood and muscle lactate concentrations were measured at exercise completion. Time courses of blood lactate and glucose concentrations were followed during the subsequent recovery. Additional biochemical analyses were performed on biopsies of the vastus lateralis muscle. SCT was associated with lower blood and muscle lactate concentrations in response to the short high-intensity exercise. Compared to controls, the muscle content among SCT carriers of lactate transporter MCT4 and β2-adrenergic receptor were higher and lower, respectively. During recovery, the lactate removal ability was higher in SCT carriers. In the present study, no effect of α-thalassemia was observed. The lower blood and muscle lactate accumulations in SCT carriers may, to some extent, act as protective mechanisms: (i) against exercise-related acidosis and subsequent sickling, that may explain the relatively rare complications observed in exercising SCT carriers; and (ii) against the deleterious effects of intracellular lactate and associated acidosis on muscle function, that might explain the elevated presence of SCT carriers among the best sprinters.
Highlights
Disagreement exists about whether sickle cell trait (SCT) carriage should be considered a benign condition or a risk factor during intense physical activity [1,2,3,4,5,6]
The anthropometric, physiological and hematological characteristics of the subjects are reported in Table 1 [21]
The two groups of subjects were matched in terms of age, body mass, maximal heart rate, exercise capacity and daily energy expenditure, suggesting that the groups were homogenous regarding physical characteristics and fitness
Summary
Disagreement exists about whether sickle cell trait (SCT) carriage should be considered a benign condition or a risk factor during intense physical activity [1,2,3,4,5,6]. SCT a risk factor is based on the fact that during high-intensity exercise, SCT carriers are prone to hemorheological disturbances (augmented blood viscosity, decreased red blood cell deformability and increased endothelial activation), intravascular coagulation and sickling [7,8,9,10,11]. SCT as a risk factor becomes important when intense exercise is performed at altitude, and is associated with dehydration or hyperthermia. In such circumstances, serious complications (such as heat stroke, hyperkalemia, hematuria, pulmonary edema, cardiac arrhythmias and ischemia, splenic infarction, renal failure, myalgias, vasoocclusion crisis (VOC) and fulminant rhabdomyolysis) have been reported, which can lead to sudden death [3,5,12,13,14,15,16]. The main reason for this is that acidosis decreases, by the Bohr effect, the affinity of hemoglobin (Hb) for oxygen, releasing it early in the microcirculation so that HbS polymerization, and sickling, is favored [18]
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