| 1. |
- Belfrage, Per, et al.
(författare)
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Alterations of lipid metabolism in healthy volunteers during long-term ethanol intake
- 1977
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Ingår i: European Journal of Clinical Investigation. - : Wiley. - 0014-2972 .- 1365-2362. ; 7:2, s. 127-131
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Tidskriftsartikel (refereegranskat)abstract
- Nine young, healthy male volunteers were given ethanol (75 g/day) for 5 weeks. The ethanol was divided into five daily doses and taken so that blood ethanol levels never exceeded 0.04% (w/v). During the latter part of the ethanol intake period, there was a significant, transient increase of plasma triglyceride (TG) concentrations followed by reduction to normal levels. A three-fold increase of lipoprotein lipase activity (LLA) occurred in biopsy specimens of adipose tissue. An increase of alpha-lipoprotein concentrations, which correlated significantly with the decrease in plasma TG levels and the increase in adipose LLA, was also observed during the ethanol intake period. No changes were observed in plasma cholesterol and beta-lipoprotein levels. A transient, three-fold increase of TG concentrations occurred in liver biopsy specimens. Ultrastructural and cytochemical examinations of the biopsy specimens showed hyperplasia of the smooth endoplasmic reticulum, and increased canallicular activity of gamma-glutamyl transferase (gamma-GT) activity in most subjects towards the end of and after the ethanol intake period. Serum gamma-GT levels also increased significantly.
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| 2. |
- Garfinkel, A G, et al.
(författare)
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Regulation of lipoprotein lipase. Induction by insulin
- 1976
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Ingår i: Biochimica et Biophysica Acta. - 0006-3002. ; 424:2, s. 264-273
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Tidskriftsartikel (refereegranskat)abstract
- Lipoprotein lipase activity in intact epididymal adipose tissue of fasted rats increased rapidly after treatment with insulin in vivo. In contrast, lipoprotein lipase activity in adipocytes isolated from the contralateral fat pads remained essentially unchanged. When adipocytes were incubated for 30 min at ambient temperature in vitro, about 2 times more lipoprotein lipase activity was found in the medium of cells from insulin-treated rats than in medium from cells of control animals. Following insulin treatment, extracts of tissue acetone powders separated by gel chromatography showed increases in both enzyme activity fractions obtained (designated lipoprotein lipase a and b). However, no consistent differences were observed between fractions derived from adipocyte acetone powders of insulin-treated and control animals. All the observed effects of insulin on lipoprotein lipase activity were abolished by cycloheximide treatment in vivo. These data indicate that following insulin treatment, increased lipoprotein lipase activity in adipose tissue results from enhanced enzyme secretion by the fat cell and subsequent accumulation in the tissue, thus implicating the adipocyte secretory mechanism as a major site of regulation of lipoprotein lipase activity in adipose tissue.
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| 3. |
- Nilsson-Ehle, Peter, et al.
(författare)
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Effects of ethanol intake on lipoprotein lipase activity in adipose tissue of fasting subjects
- 1978
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Ingår i: Lipids. - 0024-4201. ; 13:6, s. 433-437
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Tidskriftsartikel (refereegranskat)abstract
- Ethanol (ca. 1 g/kg body weight) was given alone or together with glucose or lipid (mixed triglycerides) perorally to young, fasting subjects. The changes with time (0-6 hr) of lipoprotein lipase activity (LLA) in adipose tissue, plasma glycerol, triglyceride, insulin, blood glucose, and alcohol concentrations were followed. A maximal mean blood alcohol concentration of 0.09% (w/v) was obtained 1 hr after ingestion with no apparent intoxicating effects. Ethanol intake prevented the previously observed [Nilsson-Ehle, P., S. Carlstrom, and P. Belfrage, Scand, J. Clin. Lab. Invest. 35:373 (1975)] glucose-induced rapid elevation of adipose tissue LLA but had small effects on this enzymatic activity when given alone or together with lipid. Confirming results by others, ethanol intake decreased plasma glycerol concentration and increased plasma triglycerides, especially after intake of lipid. It is suggested that ethanol intake interferes with the normal carbohydrate-induced elevation of adipose tissue LLA after a mixed meal, thereby decreasing the removal capacity for circulating dietary lipid and causing enhanced and prolonged alimentary hyperlipemia.
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| 4. |
- Nilsson-Ehle, Peter, et al.
(författare)
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Intra- and extracellular forms of lipoprotein lipase in adipose tissue
- 1976
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002. ; 431:1, s. 147-156
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Tidskriftsartikel (refereegranskat)abstract
- The location of lipoprotein lipase activity in rat adipose tissue was studied using intact epididymal fat pads, isolated adipocytes, and lipoprotein lipase activity secreted from adipocytes as enzyme sources. The enzyme activities of these preparations were characterized by gel filtration. The method used for isolation of adipocytes had been modified to minimize activation of lipoprotein lipase during the procedures. Extracts of intact adipose tissue separated into two major lipoprotein lipase activity peaks, designated "a" and "b", the "a" fraction representing about 30 (fasted rats) to 50% (fed rats) of the total enzyme activity. An intermediate fraction (designated "i") was frequently observed. Extracts of isolated adipocytes from fed rats contained about 35% and those from fasted rats about 65% of the lipoprotein lipase activity present in intact tissue. The "b" fraction constituted 80--97% of the adipocyte lipoprotein lipase activity. In contrast, the enzyme activity secreted from the adipocytes contained only the "a" and "i" fractions. These data implicate the existance of one intracellular form of lipoprotein lipase (corresponding to the "b" fraction), different from extracellular forms of the enzyme (corresponding to fractions "a" and "i"). A transformation of the intracellular to the extracellular forms appears to occur in conjunction with secretion of enzyme from the fat cell.
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| 5. |
- Nilsson-Ehle, Peter, et al.
(författare)
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Specific conditions for enhancement of lipoprotein lipase activity by platelets
- 1975
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Ingår i: Life Sciences. - : Elsevier BV. - 1879-0631 .- 0024-3205. ; 16:11, s. 1703-1709
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Tidskriftsartikel (refereegranskat)abstract
- Homogenates of human blood platelets, but not of red blood cells, have been found to stimulate lipoprotein lipase activity only when assayed against an emulsified triglyceride substrate sonicated for a short period of time. The degree of stimulation was inversely related to the time of sonication of the substrate. Using chylomicrons as substrate no stimulation of lipoprotein lipase activity by platelet homogenate was seen.
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| 6. |
- Tornqvist, H, et al.
(författare)
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Enzymes catalyzing the hydrolysis of long-chain monoacyglycerols in rat adipose tissue
- 1978
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Ingår i: Biochimica et Biophysica Acta. - 0006-3002. ; 530:3, s. 474-486
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Tidskriftsartikel (refereegranskat)abstract
- Acetone-ether preparations of epididymal fat pads from fasted or fed rats contained two enzymes catalyzing the hydrolysis of long-chain monoacylglycerols. The enzymes were identified as monoacylglycerol lipase (Tornqvist, H. and Belfrage, P., (1976) J. Biol Chem. 251, 813--819) and lipoprotein lipase by their apparent pI values after electrofocusing in non-ionic detergent, selective inhibition properties, substrate specificity and positional specificity. It was estimated that monoacylglycerol lipase accounted for about 90% of the total monoacylglycerol-hydrolyzing activity in acetone-ether preparations from fasted and 70% from fed rats. Its enzyme activity did not change with the nutritional state in contrast to that of lipoprotein lipase. The latter enzyme hydrolyzed 2-monoacylglycerols at a much lower rate than the 1(3)-isomers. Monoacylglycerol lipase was located almost entirely in the adipocytes, thus most of the enzyme activity towards monoacylglycerols in the adipose tissue was found in this site. Fractionated sucrose homogenates of rat epididymal fat pads also contained a third enzyme with monoacylglycerol-hydrolyzing activity, identified as hormone-sensitive lipase by its pI, selective inhibition properties and substrate specificity. It was estimated that hormone-sensitive lipase accounted for less than 20% of the total activity against monoacylglycerols in these tissue preparations from fasted rats. Over-all quantitative estimations emphasized the dominant role of monoacylglycerol lipase over the other two enzymes in the hydrolysis of monoacylglycerols.
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