Protein energy ratio as a critical factor in determining growth & glycogen content of muscles in rats

Effect of protein deficiency, which was produced in rats either by feeding low protein diet (8% protein) ad libitum (PD) or by restricting the amount of diet containing 15 per cent protein (protein calorie deficiency; PCD) on the growth in terms of muscle weight, length, cross-sectional area, protein and glycogen content was studied in extensor digitorum longus (EDL), medial gastrocnemius (MG) and plantaris (PL) muscles in rat. Because of decreased total calorie intake, PCD group exhibited higher value for protein/total calorie consumption. Excepting glycogen concentration, the retardation of growth in terms of all parameters studied was less in the PCD group. Glycogen concentration (mg/g muscle weight) in the PCD group was 3.0 +/- 0.3 in EDL and 2.6 +/- 0.3 in PL, whereas the values in PD group were 1.0 +/- 0.1 in EDL and 1.1 +/- 0.2 in PL respectively. This glycogen sparing effect was not evident in MG of PCD group possibly due to the greater number of glycolytic fibres. It is suggested that lesser retardation of growth of muscles and glycogen sparing effect in PCD group, could be due to altered metabolic changes resulting in enhanced gluconeogenesis.