Abstract:
The time course for the reversal of the adaptive increase in pyruvate dehydrogenase
kinase (PDK) activity following a 6d high fat diet (HP: 4.2 ± 0.2 % carbohydrate;
75.6 ± 0.4 % fat; 19.5 ± 0.8 % protein) was investigated in human skeletal muscle
(vastus lateralis). HF feeding increased PDK activity by 44% (from 0.081 ± 0.025
min"' to 0.247 ± 0.025 mm\p < 0.05). Following carbohydrate re-feeding, (88%
carbohydrate; 5% fat; 7% protein), PDK activity had returned to baseline (0.111 ±
0.014 min"') within 3h of re-feeding. The active fraction of pyruvate dehydrognease
(PDHa) was depressed following 6d of the HF diet (from 0.89 ± 0.21 mmol/min/kg
WW to 0.32 ± 0.05 mmol/min/kg ww,p <0.05) and increased to pre-HF levels by 45
min of post re-feeding (0.74 ±0.19 mmol/min/kg ww) and remained elevated for 3h.
Western blotting analysis of the PDK isoforms, PDK4 and PDK2, revealed a 31%
increase in PDK4 protein content following the HF diet, with no change in PDK2
protein. This adaptive increase in PDK4 protein content was reversed with
carbohydrate re-feeding. It was concluded that the adaptive up-regulation in PDK
activity and PDK4 protein content was fiilly reversed by 3h following carbohydrate
re-feeding.
