Post-Heparin Lipolytic and Monoglyceridase Activities in Fasted Man

Abstract

Animal studies reveal diminished adipose tissue "clearing factor" lipase after starvation (1, 2 ) ; however, no measurements of heparin-releasable lipases have been made in fasted humans. Since plasma post-heparin lipolytic activity is used clinically to assess defects in the removal of triglycerides ( 3 ) , it seemed essential to recognize the physiologic factors that affect such activity. Accordingly, we measured plasma post-heparin activity against a soy bean oil emulsion and micellar monoolein in individuals fasted for 10 days, and then after refeeding. Prolonged fasting in man causes a significant decrease in postheparin lipolytic and monoglyceridase activity. Plasma triglyceride fell in the face of these declines in post-heparin lipolytic activi ty.Methods and Materials. Six euthyroid, obese volunteers were fasted on a metabolic ward after a t least 3 days of an equilibration diet consisting of 40% mixed carbohydrate, 20% protein, and 40% fat (60% unsaturated, 40% saturated; approximately 700 mg cholesterol). Patients were studied before fast, and on days 3, 7, and 10 of total caloric restriction during which daily intake consisted of 50 mEq NaCl, 87 mEq KCl, and 2008 ml of water. Patients were restudied between 8 and 9 a.m. after 1 day of refeeding with 1500 calories. Nonobese euthyroid controls ( N = 15) recruited among hospital personnel and convalescing patients were studied after an overnight fast. All subjects were free of renal, hepatic, or lipid disorders, and none was pregnant or taking oral contraceptives. The nature of the studies was fully explained and signed consent obtained.On the morning of study, subjects were given 0.1 mg/kg of sodium heparin (Lipo-Hepin, Riker) intravenously and four venous plasma samples were obtained at 2-min intervals between 6 and 12 min after injection. Samples were centrifuged at 4O, the postheparin plasma pooled and stored at -20'. Post-heparin lipolytic activity (PHLA) was determined by a modified Frederickson method ( 3 ) using a soy bean oil emulsion (Intralipid, Vitrum, Stockholm) as described previously (4). Post-heparin monoglyceridase activity (PHMA) was determined using a mono-olein micelle solution. Glyceryl monooleate, 90% ( Calbiochem2) was sonicated (Sonifier Cell Disrupter, model W140D, U1trasonics, Inc.) in a solution of 4% taurodeoxycholic acid (sodium salt, Sigma) in KRP buffer at ph 7.4 to give a final concentration of 3 % . Post-heparin plasma (0.4 ml) was incubated with 0.6 ml of the substrate at 37" for 90 min. Free fatty acids were measured by the method of Dole ( 5 ) . Pre-heparin plasma triglycerides were measured as described previously (4).Partial thromboplastin times (6) were performed on pre-and 10-min post-heparin (0.1 mg/kg) samples after 9 days of starvation to rule out heparin antagonism in the evaluation of post-heparin lipases. Statistical analyses were made on the Mathatron 4280 computer.Results. I n 15 nonobese volunteers, the mean t SEM PHLA was 6.4 t 0.4 p&I FFA/ml/hr and PHMA was 8.4 t 0.4 pM 2 Thin-layer chromatography (methan...

Plasma Post-Heparin Lipolytic Activity in Patients with Malabsorption: Effect of Intravenous Fat Administration

“…This was not an unexpected finding in view of previous reports of reduced activities in patients with malabsorption (Slack et al, 1962) and in obese subjects during a total fast (Persson, Hood & Angervall, 1970;Arons, Schreibman & Arky, 1971). Although the average age of malabsorbers in the present study was higher than that of the controls the reduction in their post-heparin lipolytic activities was greater than could be explained on this basis alone (Baker, 1957;Brodows & Campbell, 1972).…”

A Spectrophotometric Method for the Determination of Monoglyceride Hydrolase

“…The activity of monoglyceride hydrolase can be determined either by the fatty acids or by the glycerol liberated over a certain time from a monoglyceride substrate (1,2,(5)(6)(7)(8). In the following paper a new method is introduced.…”