Lore Metz | PubMed Health

PubMed2005

Endurance training increases lactate transport in male Zucker fa/fa rats.

The purpose of this study was to investigate the effect of endurance training (10 weeks) on previously reported alterations of lactate exchange in obese Zucker fa/fa rats. We used sarcolemmal vesicles to measure lactate transport capacity in control sedentary rats, Zucker (fa/fa), and endurance trained Zucker (fa/fa) rats. Monocarboxylate transporter (MCT) 1 and 4 content was measured in sarcolemmal vesicles and skeletal muscle. Training increased citrate synthase activity in soleus and in red tibialis anterior, and improved insulin sensitivity measured by intraperitoneal glucose tolerance test. Endurance training increased lactate influx in sarcolemmal vesicles at 1 mM of external lactate concentration and increased MCT1 expression on sarcolemmal vesicles. Furthermore, muscular lactate level was significantly decreased after training in red tibialis anterior and extensor digitorum longus. This study shows that endurance training improves impairment of lactate transport capacity that is found in insulin resistance state like obesity and type 2 diabetes.

Amino Acid Sequence↗

PubMed2005

Relationship between blood lactate concentration and substrate utilization during exercise in type 2 diabetic postmenopausal women.

Increased blood lactate concentration and alterations of substrate utilization have been shown to be partly involved in development of insulin resistance in obese and type 2 diabetic patients. As blood represents the first great distribution space and participates to lactate exchange in whole body, we investigated lactate transport in red blood cells at rest and the potential relationships between elevated blood lactate and substrate utilization in 7 obese controls and 7 obese type 2 diabetic postmenopausal women during an incremental exercise test. Blood samples were collected at rest, 30%, 50%, and 60% of maximal power and at 8 and 20 minutes of recovery time. Baseline lactatemia and its increase during exercise were higher in the diabetic group (P < .05). We found a negative correlation between basal and 30% maximal power lactatemia and 2 indexes of substrate utilization (crossover point: r = -0.79, r = -0.82 and maximal lipid oxidation point: r = -0.83, r = -0.80; P < .05) in diabetic group only. Furthermore, there were positive correlations between the affinity constant, maximal velocity transport, and basal lactate level in diabetic subjects (r = 0.91 and r = 0.73, respectively; P < .05). These results show that the elevation of blood lactate is associated with a greater carbohydrate oxidation in type 2 diabetes, but the mechanisms underlying the alteration of substrate utilization need to be clarified. Furthermore, increased lactate levels cannot be explained by alterations of lactate transport in red blood cells, but it could affect monocarboxylate transporter 1 properties.

Diabetes Mellitus, Type 2↗