Pyruvate dehydrogenase (PDH) plays an important role in regulating carbohydrate metabolism in skeletal muscle. PDH is activated by
PDH phosphatase (PDP) and deactivated by
PDH kinase (PDK).
Obesity has a large negative impact on skeletal muscle carbohydrate metabolism, whereas
endurance training has been shown to improve regulatory control of skeletal muscle carbohydrate metabolism, more so when coupled with
obesity. A majority of this literature has focused on PDK, with little information available on PDP. To determine the relative role of PDP in regulating skeletal muscle PDH activity with
obesity and
endurance training, obese and lean Zucker rats remained sedentary or were endurance trained (1 h/day, 5 days/wk) for a period of 8 wk. Soleus, red gastrocnemius, (RG), and white gastrocnemius (WG) muscles were sampled after the training period. The main findings were 1)
obesity resulted in a 46% decrease in PDP activity expressed per milligram extracted
mitochondrial protein only in RG, while PDP
isoform content was unchanged; 2) 8 wk of
endurance training led to a significant 1.4-2.2-fold increase in PDP activity of all muscle examined from obese rats, and the concomitant increase in PDP1
protein was only seen in soleus and RG; 3) 8 wk of
endurance training led to a trending 1.4-2.2-fold increase in PDP activity of all muscle examined from obese rats, and the concomitant increase in PDP1
protein was only seen in soleus and RG; and 4) PDP2
protein content was not affected by
obesity or training. These results suggest that decreased PDP activity in oxidative skeletal muscles may play a role in the impairment of carbohydrate metabolism in obese rats, which is reversible with
endurance training.