Abnormalities of muscle metabolism and histology in malnourished patients awaiting surgery: Effects of a course of intravenous nutrition

Abstract

Abstract Malnourished surgical patients have metabolic and functional abnormalities of skeletal muscle and it has been suggested that these are due to reduced activities of glycolytic enzymes associated with abnormalities of muscle fibres. We have measured the activities of four key enzymes of glucose utilization and the size and distribution of muscle fibre types in vastus lateralis biopsies from 14 undernourished patients awaiting surgery (mean weight loss 24 ± 10 per cent). These results were compared with those from 14 normally nourished controls, comparable in age, sex, race and habitual activity. Fructose bisphosphatase activity was reduced in undernourished patients by 44 per cent (P < 0·01), phosphofructokinase by 40 per cent (P = 0·005) and hexokinase by 37 per cent (P < 0·001). Both fibre types were smaller in patients than controls (area I, 41·4 μm2 × 10−2 ± 0·4 vs. 73·3 μm2 × 10−2 ± 0·6, P < 0·001; area II, 27·7 μm2 × 10−2 ± 0·4 vs. 72·5 μm2 × 10−2 ± 0·5, P < 0·001), and there was a smaller proportional number of type II fibres in patients (35 per cent vs. 65 per cent, P < 0·01). This loss of type II fibre numbers and preferential type II atrophy may account for the enzyme depression associated with it and could produce the syndrome of impaired glucose tolerance, muscle weakness and fatigue seen in undernourished patients. In a subgroup of 11 patients, biopsy was repeated after 14 days of intravenous nutrition. Only phosphofructokinase activity rose significantly (19·62 ± 1·85 to 30·74 ± 2·99 μmol min−1 g−1, P < 0·01) and both type II fibre size (40·6 ± 18·5 to 47·4 μm2 ± 20·3 × 10−2, P < 0·05) and number (42 per cent ± 6 to 56 per cent ± 5, P < 0·05) also rose. Intravenous nutrition may therefore increase maximum glycolytic rate and improve muscle function in undernourished surgical patients.