| 1. |
- Garfinkel, A G, et al.
(author)
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Regulation of lipoprotein lipase. Induction by insulin
- 1976
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In: Biochimica et Biophysica Acta. - 0006-3002. ; 424:2, s. 264-273
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Journal article (peer-reviewed)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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| 2. |
- Nilsson-Ehle, Peter, et al.
(author)
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Intra- and extracellular forms of lipoprotein lipase in adipose tissue
- 1976
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In: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002. ; 431:1, s. 147-156
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Journal article (peer-reviewed)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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| 3. |
- Nilsson-Ehle, Peter, et al.
(author)
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Specific conditions for enhancement of lipoprotein lipase activity by platelets
- 1975
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In: Life Sciences. - : Elsevier BV. - 1879-0631 .- 0024-3205. ; 16:11, s. 1703-1709
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Journal article (peer-reviewed)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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