P-31-NUCLEAR MAGNETIC-RESONANCE STUDIES OF BIOENERGETIC CHANGES IN SKELETAL-MUSCLE IN MALNOURISHED HUMAN ADULTS

In previous studies,both animals and malnourished children receiving 2 5% of the protein-energy intake of a control group, resulting in a 25% weight loss, had lower ratios of phosphocreatine to beta-ATP and of p hosphocreatine to inorganic phosphorus, higher free ADP concentrations , and lower free energy of ATP hydrolysis than the control group. Ther efore, the effect of malnutrition on muscle energetics in adult humans was examined by using P-31-nuclear magnetic resonance spectroscopy in malnourished patients with a mean body mass index (BMI; in kg/m(2)) o f 16.4 compared with healthy control subjects with a significantly hig her body mass index of 24.5 (P < 0.005). The mean (+/- SEM) ratio of p hosphocreatine (PCr) to ATP in the malnourished patients was 2.28 +/- 0.27, which was significantly lower than the ratio of 3.1 +/- 0.15 in control subjects (P < 0.02). The ratio of inorganic phosphorus (Pi) to ATP in malnourished patients was 0.33 +/- 0.04, which was significant ly lower than the ratio of 0.48 +/- 0.03 in control subjects (P < 0.02 ), but the ratio of PCr to Pi was not significantly different from tha t in control subjects. There was a significant correlation between BMI and the ratio of PCr to ATP (P < 0.01) and of Pi to ATP (P < 0.01). T hese data suggest that progressive loss of BMI is associated with a re lative loss of muscle creatine and phosphorus in relation to ATP. The findings were unlikely to have been due only to atrophy of fast-twitch fibers because such atrophy would have altered the ratio of PCr to Pi .