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Cederblad, Gitten, Bylund, Ann-Christin, Holm, J. & Scherstén, T. Carnitine Concentration in Relation to Enzyme Activities and Substrate Utilization in Human Skeletal Muscles. Scand. J. clin. Lab. Invest. 36,547-552, 1976.The relationships between the carnitine concentration and enzyme activities representative of different metabolic pathways, glycogenolysis, glycolysis, β-oxidation of fatty acids, citric acid cycle, and respiratory chain were studied in skeletal muscle tissue from 18 volunteering subjects. In addition, the in vitro incorporation rates of glucose-carbon and palmitate-carbon into different metabolites, and the concentration of glycogen, triglycerides, and phospholipids were determined in the same tissue specimen. The carnitine concentration correlated positively and statistically significantly with the activities of 3-OH-acyl-CoA dehydrogenase and citrate synthase, with the incorporation rate of palmitate-carbon into CO2, and the incorporation rate of glucose-carbon into lactate in the muscle tissue. The results indicate a coupling between the concentration of carnitine and the capacity for long-chained fatty acid oxidation in human skeletal muscles.

Holm, J., Dahllöf, A.-G. & Scherstén, T. Metabolic Activity of Skeletal Muscle in Patients with Peripheral Arterial Insufficiency. Effect of Arterial Reconstructive Surgery. Scand. J. din. Lab. Invest. 35, 81-86, 1975.The metabolic capacity of leg muscles was determined in 12 patients with peripheral arterial insufficiency before and 6 months after vascular surgery. Succinic oxidase activity and the incorporation rates of glucose-carbon into glycogen, lipids, lactate, and CO2 were determined as a measure of metabolic capacity. Leg muscles from patients with intermittent claudication had high metabolic capacity, as shown previously. This capacity was reduced towards control values after successful revascularizations, while it remained unchanged if the surgery failed. In patients with gangrene the preoperative values of leg muscles' metabolic capacity were subnormal, and increased towards control values if surgery was successful. In 2 patients with limb gangrene the vascular surgery was only partially successful i.e. the gangrene threat was changed into intermittent claudication. In these 2 patients the metabolic capacity of leg muscles changed from sub- to supracontrol values. In 2 patients the vascular surgery failed, and the patients had no benefit from the operation. In these 2 patients the metabolic capacity of leg muscles remained unchanged. These results support the theory that changes in the amount of blood flow, i.e. the supply of oxygen and substrates to the leg, govern the level of metabolic capacity of the skeletal muscles. The results seem to justify the recommendation that reconstructive arterial surgery in patients with intermittent claudication ought to be followed by physical training to preserve the high metabolic capacity in the skeletal muscles.

Activity of α-1,4-glucosidase was studied in serum from healthy subjects and from patients with malignant tumor disease. The activity of α-1,4-glucosidase was found to have characteristics similar to those described for α-1,4-glucosidase activity in tissues from man and animals. In patients with malignant tumor disease, the activity of α-1,4-glucosidase in serum was significantly increased. It is suggested that the serum activity of α-1,4-glucosidase is probably derived from various organ sources. The specificity and significance of increased α-1,4-glucosidase activity in serum in malignant disease cannot be decided by the present investigation.

Activity of α-amylase and α-1,4-glucosidase was studied in subfractions of human liver homogenates obtained from operative biopsies in 22 patients operated on for uncomplicated gallstone disease. No activity of α-amylase was found in subfractions of homogenate. The activity of α-1,4-glucosidase was distributed in the same way as acid phosphatase and β-glucuronidase activity upon centrifugal fractionation of homogenate. The highest activity of α-1,4-glucosidase per unit of protein was found in the crude lysosomal fraction (L-fraction). The activity was easily solubilized from the L-fraction pellet. The lysosomal origin of the enzyme appears unambiguous considering its subcellular distribution and its acid hydrolytic properties.

Activity of α-amylase and α-1,4-glucosidase was determined in human liver tissue obtained from operative biopsies in patients operated on for uncomplicated gallstone disease or peptic ulcer. No or only traces of α-amylase activity were found. The absence of α-amylase activity in normal liver tissue indicates that the increased serum activity occasionally found in cases with liver or bile duct disease probably originates from other sites. High activity of α-1,4-glucosidase with an acid pH-optimum but no activity at neutral pH was found. The acid activity had characteristics similar to those reported for the corresponding activity in liver tissue from other species. It is concluded that human liver tissue probably does not contain α-amylase activity but yields high activity of an acid α-1,4-glucosidase of probable lysosomal origin.

A method for in vitro determination of glucose metabolism by human skeletal muscle tissue is presented. Muscle fibers were teased away from a biopsy specimen and incubated with glucose and [U-14C]glucose. The incorporation of label into glycogen, lipids, lactate, and CO2was determined. The incorporation rate of glucose in muscle tissue from two age groups of patients was determined. All the patients were in an ordinary state of physical fitness and had normal arterial circulation in their legs. The rate of incorporation was the same in the rectus, the lateral vastus, and the gastrocnemius muscle tissue. No age and sex differences were found. The calculated uptake of glucose per gram muscle tissue was of the same order of magnitude as reported from in vivo studies using the forearm technique.

Human liver slices were incubated with labelled glycerol and the incorporation of label into triglycerides and different phosphoglycerides was determined. Replacement of palmitic acid by linoleic acid in the incubation medium resulted in a decrease of the glycerol incorporation rate into phosphoglycerides. In response to addition of bile acids or choline to the incubation medium, a change in the distribution of incorporated glycerol among the different phosphoglyceride classes was observed. The incorporation rate into ethanol amine-phosphoglyceride was decreased and into choline phosphoglyceride increased. This finding indicates that bile acids exert a direct effect on the synthesis of phosphoglycerides in the liver.

Succinic oxidase was determined by a manometric method on a micro scale in human muscle obtained by percutaneous needle biopsy technique. Differences of activity along the muscle fibers in the vastus lateralis muscle region were found to be small while variation at different depths was higher. The activity was apparently not interfered with by surgical procedures. Human and rat femoral muscles contained higher succinic oxidase activity than abdominal muscle. The human heart showed extremely high activity. Succinic oxidase activity was higher in physically fit persons.

AbstractHuman liver slices were incubated with glycerol-1,3-14C or fructose-U-14C. 50 of the label was recovered as glucose and 10 was incorporated into CO2and into lipids, respectively. At high fatty acid concentration in the medium the incorporation into CO2and glucose was suppressed, into triglycerides increased, and into phospholipids unchanged. The incorporation of fructose was suppressed with glycerol in the medium. The mean synthesis rate for phospholipids was 0.14 ± 0.01 μmoles/g liver per hour and for triglycerides 0.34 ± 0.04 μmoles/g liver per hour.

The composition of phospholipids in hepatic bile, gall bladder bile, and plasma from 18 patients operated on for acute cholecystitis was compared to the corresponding composition in 11 patients operated on for uncomplicated gall stone disease or peptic ulcer.In acute cholecystitis the relative and absolute concentration of lysolecithin was found to be decreased in plasma and increased in hepatic bile. The absolute as well as the relative concentration of all the phosphatides in the gall bladder bile varied widely in cases with acute cholecystitis, which probably reflects a variation in the resorption of the content of the diseased gall bladder. In cases with colourless bile in the gall bladder all the phosphatides occurred in very low concentrations. However, the relative concentration of lysolecithin in the 'cholecystic' gall bladders was found to be significantly increased and in three cases the absolute concentration of this phosphatide was found to be very high. The increased concentration of lysolecithin in bile from cases with acute cholecystitis may be caused by extrahepatic hydrolysis of lecithin, and evidence in favour of this interpretation is given.Whether the increased concentration of lysolecithin in bile is primary or secondary to the acute cholecystitis cannot be answered by the present investigation.

Human liver slices, obtained from surgical biopsies in 38 patients, were incubated with labeled glycerol or fructose. Nine of the patients received 400 g fructose intravenously the day before operation. In the fructose-loaded patients the percental incorporation was significantly decreased into phospholipids, and significantly increased into triglycerides, and into the fatty acid moiety of glycerides. The incorporation rate of glycerol into phospholipids was significantly decreased and the incorporation rate of fructose into triglycerides was significantly increased in these patients.

Basal (latent) and maximal (induced by Triton X-100) activity of the enzymes acid phosphatase, aryl sulphatase, beta-glucuronidase, and cathepsin was determined in homogenate of human liver, obtained as biopsy from patients operated on for uncomplicated gallbladder disease and from patients operated on for obstructive jaundice caused by common bile-duct stones.Maximal activity of acid phosphatase and aryl sulphatase was significantly positively correlated to the age of the patient.The ratio between maximal and basal activity (an expression of the degree of retention of the enzymes to the lysosomes) of aryl sulphatase was significantly decreased with increasing age of the patient.In cholestatic liver the degree of retention of acid phosphatase and cathepsin activity to the lysosomes was significantly decreased.Cholic acid and bilirubin added in vitro to homogenate in concentrations assumed to be within physiological limits, caused a release of lysosomal enzymes.It is suggested that the retention of bile products in obstructive jaundice causes release of hydrolytic enzymes from liver lysosomes, and that this phenomenon could be responsible for the common occurrence of scattered cellular necrosis in the liver in cholestatic conditions.