Feeding a Low Energy Diet and Refeeding a Control Diet Affect Glycolysis Differently in the Slow- and Fast-Twitch Muscles of Adult Male Wistar Rats

What is it about?

Thirty adult male Wistar rats were randomly assigned to receive one of two isovolemic and micronutrient-complete liquid diets, a control (CN) energy-complete diet for 10 d or a diet 80% lower in energy (HYPO) for 7 d producing a 20% loss of initial weight. Rats were refed an energy-complete diet for 1 or 4 d (RE1, RE4). Glycolytic metabolites were measured in electrically stimulated slow and fast twitch muscles that were freeze-clamped with liquid nitrogen in mid contraction. We found, 1) a lower fructose-1,6-bisphosphate (F-1,6-P2)/fructose-6-phosphate (F-6-P) ratio; 2) a greater glucose-6-phosphate (G-6-P)/lactate ratio; 3) a lower lactate/glycogen ratio; and 4) lower lactate concentration. Four days of refeeding normalized the F-1,6-P2/F-6-P ratio, but did not improve the lactate/glycogen or the G-6-P/lactate ratios. We conclude that undernutrition compromises glycolysis only in slow-twitch muscles and that 4 d of refeeding restores phosphofructokinase activity.

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Why is it important?

Slow-twitch muscles are the significant muscle fibers on which recovering patients depend on for normal ambulation. This research clearly shows that the slow-twitch glycolytic cycle in muscles are very vulnerable to malnutrition. There is a clear decrease in glycolytic activity during periods of chronic malnutrition but that recovery of glycolysis occurs rapidly with refeeding and precedes compositional changes

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