Activities of hexokinase, phosphofructokinase, fructose bisphosphatase and 2-oxoglutarate dehydrogenase in muscle of normal subjects and very ill surgical patients

The measurement of enzyme activities in the resting human polymorphonuclear leukocyte--critical estimate of a method

As a system for study, the isolated human polymorphonuclear leukocyte combines the advantages of a quasi-non-invasive preparation with a nearly complete complement of enzymes of carbohydrate and energy metabolism. However, small sample volumes and, in some cases, very low enzyme activities make high demands on sample processing, storage, and performance of continuous measurements, if the enzyme activities are to be measured with acceptable reproducibility. In the presented study several aspects of homogenization, storage, and continuous measurement were scrutinized, to identify critical steps and consider ways of optimizing the method. Polymorphonuclear leukocytes were separated from the blood of healthy subjects by sedimentation and density gradient centrifugation. After ultrasonic homogenization, 13 enzymes of glycolysis and gluconeogenesis, the tricarboxylic acid cycle, and glycogen metabolism were determined photometrically. The variation of several conditions showed: 1. The duration of exposure to ultrasound for the homogenization of polymorphonuclear leukocytes has no influence over a wide range of time. 2. Addition of the detergents Triton X-100 and deoxycholic acid, as well as the SH-group protector dithiothreitol, to the homogenizing medium increased the measured activities of only a few enzymes. 3. Considerable inaccuracy was encountered when the suspension was divided into parts for homogenization with different additives; such splitting of the suspension should therefore be performed only when necessary, as in the determination of reference values (e.g. protein or DNA content of the cell suspension). 4. Twenty four-fold determination of enzyme activities from one homogenate resulted in precisions between 4.5% (citrate synthase) and 14.4% (transketolase), which is satisfactory for the low activities (as low as 1 U/l) in the homogenate. 5. The reproducibility of enzyme activities, measured in homogenates of polymorphonuclear leukocytes from different blood samples drawn simultaneously, was only slightly worse than that of the continuous measurement method itself. Thus, the precision of the measurement of enzyme activity seems to be the main determinant of the overall method. In conclusion, the described procedure of separation, homogenization, and enzyme measurement in human polymorphonuclear leukocyte meets the requirements of biochemical or clinical trials and can be recommended for clinical metabolic studies.

Contrasting action of short- and long-term adrenaline infusion on dog skeletal muscle glucose metabolism

There are important differences between the short- and long-term effects of adrenaline on determinants of glucose tolerance. To assess this metabolic adaptation at tissue level, the present study examined the effect of acute and prolonged in vivo elevation of adrenaline on glycogen metabolism and glycolysis in skeletal muscle. Adrenaline (50 ng.kg-1.min-1) was infused for 2 h or 74 h and the results compared with 1 h 0.9% NaCl infusion in six trained dogs. Muscle glycogen content was reduced by long-term adrenaline (161 +/- 17 vs NaCl 250 +/- 24 mumol/g dry weight; p less than 0.05) but not short-term adrenaline (233 +/- 21) indicating a sustained effect of adrenaline on glycogen metabolism. Acutely, glycogen synthase I was reduced (short-term adrenaline 12 +/- 6 vs NaCl 22 +/- 7 mumol glycosyl units.g-1.min-1; p less than 0.05) but returned to normal with prolonged adrenaline infusion (20 +/- 5). In contrast, Km for glycogen phosphorylase alpha was not changed acutely (short-term adrenaline 31 +/- 6 vs NaCl 27 +/- 7 mmol/l inorganic phosphate) but was reduced during long-term infusion (19 +/- 4; p less than 0.05 vs short-term adrenaline). Thus, with short- and long-term adrenaline infusion, there were different enzyme changes, although likely to promote glycogenolysis in both cases. In the glycolytic pathway the substrates glucose 6-phosphate and fructose 6-phosphate did not change significantly and hexokinase was not inhibited. Acutely, phosphofructokinase had reduced Vmax (short-term adrenaline 34 +/- 6 vs NaCl 44 +/- 5 U/g; p less than 0.05) but was still above the maximal operating rate in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intravenous nutrition on nutrition and function in acute attacks of inflammatory bowel disease

The effect of IV nutrition on protein nutriture and physiological function in 19 patients who were clinically malnourished and had acute exacerbations of inflammatory bowel disease was studied. Total body protein, plasma proteins, respiratory muscle function, and skeletal muscle function were measured at the commencement of a 14-day course of IV nutrition and 7 and 14 days later. Final measurements were made after recovery approximately 200 days later. Compared with a group of matched controls, the patients had lost approximately 35% of their body protein stores with accompanying physiological impairments of 20%-40%. After 4 days of IV nutrition, there were improvements in all the physiological measurements (approximately 12%) but no significant change in total body protein. During convalescence, there were further improvements in physiological function, which were accompanied by an increase in body stores of protein. We conclude that there is an early and rapid improvement in physiological function with IV nutrition in patients hospitalised for exacerbations of inflammatory bowel disease even though this is not accompanied by significant protein gain. Later during anabolic recovery, physiological improvements occur in association with repletion of total body protein. Short courses of IV nutrition in these patients prevent protein loss and result in significant improvements in skeletal muscle function and respiratory muscle function.

Skeletal muscle enzyme activities and metabolic substrates during exercise in patients with postoperative fatigue

Subjective fatigue was quantified before and 20 days after uncomplicated elective abdominal surgery in 12 patients and compared with changes in heart rate, enzyme activities and skeletal muscle substrates before and after bicycle exercise for 10 min at 65 per cent of patients' preoperative maximum work capacity. Fatigue increased from a mean(s.e.m.) preoperative level of 2.5(0.5) arbitrary units to 4.6(0.5) on postoperative day 20 (P less than 0.01). Body-weight, triceps skinfold thickness and arm circumference decreased postoperatively (P less than 0.02). Postoperative values of muscle enzyme activities indicative of oxidative phosphorylation capacity (citrate synthase and 3-OH-acyl coenzyme A dehydrogenase) were lower than preoperative values (P less than 0.05). Lactate dehydrogenase was unaltered and resting values of muscle glycogen and adenosine triphosphate were higher after operation (P less than 0.05). In response to exercise, heart rate, muscle glucose, glucose-6-phosphate and lactate increased (P less than 0.05), while muscle glycogen and creatine phosphate decreased (P less than 0.05). Increase in postoperative fatigue correlated with the increase in heart rate (P less than 0.05), while no significant correlations were found between fatigue and muscle parameters. Our results suggest that lack of exercise and malnutrition may be of importance in the decrease in work capacity and in fatigue after operation.

Abnormal muscle fructose bisphosphatase activity in malnourished cancer patients

Malnourished patients without cancer have abnormal glucose metabolism, low activities of the key enzymes of glycolysis in muscle, and abnormal muscle fiber-type distribution. Malnutrition in cancer is also associated with altered glucose metabolism, and therefore muscle enzyme activities and fiber types were measured in 17 malnourished patients with gastrointestinal cancer (weight loss, 18.1% +/- 7.9 SD). These patients were matched with 17 depleted noncancer patients (weight loss, 22.8% +/- 10.25 SD) and 17 normal controls. Results of in vitro measurement of the maximal activity of phosphofructokinase (PFK), hexokinase (HK), and oxogluterate dehydrogenase (OGD) were similar in both undernourished groups and lower than that of normal controls. Both groups also had reduced Type II fiber size and number. The activity of fructose bisphosphatase (FBP) was significantly higher in cancer patients (0.62 mu ml min-1 g +/- 0.26 SD) than in noncancer patients (0.39 +/- 0.15), but similar to that in controls (0.65 +/- 0.29). As FBP is involved in substrate cycling, inappropriately high activity reflects an inability to adapt to malnutrition that could lead to high rates of cycling and wasteful energy expenditure at times of maximal activation of the cycle.

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

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 less than 0.01), phosphofructokinase by 40 per cent (P = 0.005) and hexokinase by 37 per cent (P less than 0.001). Both fibre types were smaller in patients than controls (area I, 41.4 micron2 X 10(-2) +/- 0.4 vs. 73.3 micron2 X 10(-2) +/- 0.6, less than 0.001; area II, 27.7 micron2 X 10(-2) +/- 0.4 vs. 72.5 micron2 X 10(-2) +/- 0.5, P less than 0.001), and there was a smaller proportional number of type II fibres in patients (35 per cent vs. 65 per cent, P less than 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 mumol min-1 g-1, P less than 0.01) and both type II fibre size (40.6 +/- 18.5 to 47.4 micron2 +/- 20.3 X 10(-2), P less than 0.05) and number (42 per cent +/- 6 to 56 per cent +/- 5, P less than 0.05) also rose. Intravenous nutrition may therefore increase maximum glycolytic rate and improve muscle function in undernourished surgical patients.