Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To study the regulation of adipose tissue lipoprotein lipase (LPL) in human adipocytes, omental adipose tissue was obtained from healthy subjects and digested in collagenase. The isolated adipocytes thus obtained were suspended in Medium 199 and cultured at 37 degrees C. Cell viability was demonstrated in adipocytes cultured for up to 72 h by constancy of cell number, cell size, trypan-blue exclusion, and specific 125I-insulin binding. In addition, chloroquine induced an increase in cell-associated 125I-insulin at 24, 48, and 72 h after preparation. Thus, isolated adipocytes retained their ability to bind, internalize, and degrade insulin. LPL was measured as activity secreted into the culture medium (CM), released from cells by heparin (HR), and extracted from cell digests. A broad range of heparin concentrations produced a prompt release of LPL from a rapidly replenishable pool of cellular activity. When cells were cultured in medium containing 10% fetal bovine serum, there was a marked stimulation of CM and HR. The secretory response to serum (CM) correlated strongly with HR 24 h after preparation (rs = 0.731, P less than 0.001). In addition, HR was found to correlate logarithmically and inversely with body mass index (r = -0.731, P less than 0.001). Insulin, at 400 ng/ml only, increased HR by 36 +/- 10%, an effect simulated by lower concentrations of insulin-like growth factor-1 (IGF1). Thus, LPL is produced and regulated in isolated human adipocytes. The degree of adiposity and serum are important regulators of HR activity, whereas insulin is stimulatory only at a pharmacologic concentration. This effect of insulin may be mediated through the IGF1 receptor. Isolated human adipocytes represent a novel and useful system for the study of LPL and lipid metabolism as well as for other aspects of adipocyte biology.
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PMID:Regulation of lipoprotein lipase in primary cultures of isolated human adipocytes. 388 Jul 72

Eighteen male marathon runners (mean marathon performance: 2 h 36 min, SD = 7.0 min; VO2 max = 64.1 +/- 15.1 ml/kg . min-1) were submitted to a needle biopsy in the suprailiac region and to various measurements of body fatness: percent body fat (% fat), seven skinfold thicknesses, and mean fat cell diameter. Basal and insulin-stimulated glucose conversion into triglycerides were measured in collagenase-isolated fat cells, while heparin-releasable lipoprotein lipase activity (LPLa) was determined in intact adipose tissue. All body fatness indicators were significantly smaller in marathon runners in comparison to a sedentary control group (P less than 0.001). Fat cell basal and insulin-stimulated glucose conversion into triglycerides as well as LPLa were significantly higher for the runners group (P less than 0.01), differences being particularly important when comparisons were performed between subjects paired for mean fat cell diameter. Pearson interclass correlations between body fatness and fat cell glucose incorporation into triglycerides were low and positive for the sedentary group (0.04 less than or equal to r less than or equal to 0.41), while they were negative for the marathon runners groups (-0.28 less than or equal to r less than or equal to -0.40) with the exception of % fat. Moreover, correlations between LPLa and indicators of body fatness were positive in the sedentary group (0.47 less than or equal to r less than or equal to 0.79), while they were negative in the marathon runners group (-0.03 less than or equal to r less than or equal to -0.63).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Adipose tissue lipid accumulation pathways in marathon runners. 405 90

Free fat cells and stromal-vascular cells were prepared from rat adipose tissue by incubation with collagenase. NH(4)OH-NH(4)Cl extracts of acetone-ether powders prepared from fat cells contained lipoprotein lipase activity but extracts of stromal-vascular cells did not. Intact fat cells released lipoprotein lipase activity into incubation medium, but intact stromal-vascular cells did not. The lipoprotein lipase activity of the medium was increased when fat cells were incubated with heparin, and this was accompanied by a corresponding decrease in the activity of subsequently prepared fat cell extracts. Heparin did not release lipoprotein lipase activity from stromal-vascular cells. The lipoprotein lipase activity of NH(4)OH-NH(4)Cl extracts of fat cell acetone powders is increased by the presence of heparin during the assay. This increase is not due to preservation of enzyme activity, but to increased binding of lipoprotein lipase to chylomicrons. Protamine sulfate and sodium chloride have little effect on the binding of lipoprotein lipase to chylomicrons, but they inhibit enzyme activity after binding to substrate has occurred. These inhibitors do, however, inhibit the stimulatory effect of heparin on enzyme-substrate binding.
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PMID:The mechanism of heparin stimulation of rat adipocyte lipoprotein lipase. 430 30

Sucrose gradient centrifugation has been used to examine the triglyceride lipases present in extracts of rat epididymal adipose tissue. The aqueous infranatant recovered between the pellet and fat cake of tissue homogenates which had been centrifuged at 40,000 g was shown to contain two types of triglyceride lipase activity. One of these appears in the 15s region and has been identified as the active form of the "hormone-sensitive lipase" believed to be responsible for initiating the hydrolysis of tissue triglyceride stores in response to lipolytic stimuli. The activity of this enzyme was selectively increased in extracts prepared from tissue exposed to epinephrine and decreased in extracts of insulin-treated tissue. The increased lipolytic activity of extracts of tissue from fasted or fasted-refed rats was also found largely in this region. When the tissue was incubated with orthophosphate-(32)P, radioactivity was incorporated into a protein migrating at 15s. A second peak of triglyceride lipase activity appeared in the 6s region coincident with the location of the monoglyceride and diglyceride lipase activities. The amount of 6s triglyceride lipase activity did not correlate with changes in the lipolytic activity of the tissue from which the extracts were prepared, and its physiological function remains to be elucidated. The lipoprotein lipase and the short-chain triglyceride lipase ("tributyrinase") each moved more slowly in the gradient than the 6s triglyceride lipase. Both the 6s and 15s enzymes were shown to be present in washed adipocytes isolated from the tissue by collagenase digestion.
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PMID:Studies on the hormone-sensitive lipase of adipose tissue. 432 8

1. The metabolism of VLD lipoproteins (very-low-density lipoproteins) was studied in intact isolated beating-heart cells and isolated perfused rat heart from starved animals by using [14C]triacylglycerol fatty acid-labelled VLD lipoprotein prepared from rats previously injected with [1-14C]palmitate. 2. 14C-labelled VLD lipoprotein was metabolized by the isolated perfused heart, but was only minimally metabolized by the heart cells unless an exogenous source of lipoprotein lipase was added. 3. Measurements of lipoprotein lipase at pH 7.4 with the natural substrate 14C-labelled VLD lipoprotein indicated that during collagenase perfusion of the heart the enzyme was released into the perfusate, the activity released being proportional to the concentration of collagenase used. Lipoprotein lipase activity in homogenates of hearts that had been perfused with collagenase showed a corresponding loss of activity. 4. At high perfusate concentrations of collagenase, inactivation of the released lipoprotein lipase occurred. 5. Lipoprotein lipase activity was largely undetectable in the homogenate of the isolated heart cells. 6. It is concluded that the lipoprotein lipase responsible for the hydrolysis of VLD lipoprotein triacylglycerol is predominantly located externally to the heart muscle cells and that its release can be facilitated by perfusion of the heart with bacterial collagenase.
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PMID:Differences in the metabolism of very-low-density lipoproteins by isolated beating-heart cells and the isolated perfused rat heart. Evidence for collagenase-released extracellular lipoprotein lipase. 624 85

Lipogenesis from glucose and lipoprotein lipase activity were investigated in humans. The reliability of measurements was quantified and correlations with fat cell weight were assessed. Twenty-four subjects (7 women, 17 men) were studied twice within a 2-week period, along with 17 additional male subjects who were studied once and used only in the correlation analyses. All subjects were not regularly involved in an exercise-training program and were between 18 and 30 years of age. Following an overnight fast, adipose tissue specimens were obtained by suprailiac biopsy and fat cells were collagenase isolated. Mean fat cell weight was obtained from 400 to 500 cell diameter determinations per subject. Basal and insulin-stimulated fat cell lipogenesis from glucose were determined using D-[U-14C]glucose and were reported in nanomoles of glucose per hour per 10(6) cells. Adipose tissue heparin-releasable lipoprotein lipase activity was also determined and expressed in micromoles of free fatty acids per hour per gram of tissue and per 10(6) cells. Fat cell weight, basal and insulin-stimulated lipogenesis and lipoprotein lipase activity per gram showed high reliability of measurement, interclass and intraclass coefficients being 0.83 and over. Lipoprotein lipase activity per 10(6) cells showed a somewhat lower degree of reliability, interclass and intraclass coefficients being, respectively, 0.69 and 0.81. On the other hand, fat cell weight was positively correlated with lipoprotein lipase activity (r = 0.80), while no significant correlation was observed between basal lipogenesis and fat cell weight. Moreover, basal lipogenesis presented no significant correlation with lipoprotein lipase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lipogenesis and lipoprotein lipase in human adipose tissue: reproducibility of measurements and relationships with fat cell size. 639 48

Endothelial cells from rat epididymal fat pad capillaries were isolated from rats immediately after weaning. The cells were obtained after an initial brief incubation with collagenase under conditions of minimal breakage of cells. Adipocytes were removed by flotation and endothelial cells were then obtained as cell aggregates by fractional filtration procedures whereby intact tissue as well as free cells were removed. These aggregates were then dispersed and cultured in supplemented medium 199 whereby a monolayer of cells with a growth pattern, numerous pinocytotic vesicles, and intercellular junctions typical of endothelial cells were obtained. Minor contaminations of precursor cells to adipocytes were absent after one subculture. Here greater than 95% of the cells showed the presence of Factor VIII. Further subcultures produced nonhomogenous cells and decreasing rates of replication. The endothelial cells showed a very low rate of triglyceride synthesis and release, and collected no visible lipid upon prolonged cultures in the presence of an abundance of triglyceride substrate. They bound lipoprotein lipase from rat adipocytes, whereby the lipase was stabilized. This binding was released by heparin, and the cells did not synthesize the enzyme.
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PMID:Isolation and characterization of endothelial cells from the epididymal fat pad of the rat. 683 87

The expression of lipoprotein lipase (LPL) mRNA and the LPL activity were studied in macrophages (CD14 positive) from human atherosclerotic tissue. Macrophages were isolated after collagenase digestion by immunomagnetic isolation. About 90% of the cells were foam cells with oil red O positive lipid droplets. To analyze the mRNA expression, PCR with specific primers for LPL was used. Arterial macrophages were analyzed directly after isolation and the data showed low expression of LPL mRNA when compared with monocyte-derived macrophages. To induce the expression of LPL mRNA in macrophages, PMA was used. When incubating arterial macrophages with PMA for 24 h we could not detect any increase in LPL mRNA levels. Similarly, the cells secreted very small amounts of LPL even after PMA stimulation. In conclusion, these studies show a very low expression of LPL mRNA in the CD14-positive macrophage-derived foam cells isolated from human atherosclerotic tissue. These data suggest that the CD14-positive cells are a subpopulation of foam cells that express low levels of lipoprotein lipase, and the lipid content could be a major factor for downregulation of LPL. However, the cells were isolated from advanced atherosclerotic lesions, and these findings may not reflect the situation in early fatty streaks.
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PMID:Expression of lipoprotein lipase mRNA and secretion in macrophages isolated from human atherosclerotic aorta. 840 28

Fat and liver are the major sites for the deposition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) given in vivo to rats. Although a great deal of information is available on the effects of TCDD in liver, very little is known of the effects in fat. The epididymal fat pads were removed and the stromal-vascular cells, released by collagenase digestion, were put into primary culture, 2, 4, 6 and 8 days after intubating 175 micrograms/kg TCDD into male Sprague-Dawley rats. Following 7 days in culture, the cells were examined morphologically, and assayed for an early (lipoprotein lipase, LPL) and late marker of fat cell differentiation (glycerol-3-phosphate dehydrogenase, GPDH). With rats sacrificed 6 or 8 days after TCCD intubation, the harvested cells from pair-fed rats contained significantly more fat and had a significantly higher level of GPDH enzyme activity, indicating more differentiation. The mRNA for LPL and GPDH genes was also higher for cells from pair-fed rats. In addition, for the rats that were sacrificed 4-8 days after TCDD intubation, despite similar food intake, the pair-fed control rats gained more total body weight than the treated rats. Although there was a body weight difference, there was no significant different between the weights of the epididymal fat pads. This is the first report to demonstrate that TCDD inhibits the differentiation of fat cells.
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PMID:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) inhibition of fat cell differentiation. 859 78

Explant cultures of adult human trabecular bone fragments give rise to osteoblastic cells, that are known to express osteoblast-related genes and mineralize extracellular matrix. These osteoblastic cells have also been shown to undergo adipogenesis in vitro and chondrogenesis in vivo. Here we report the in vitro developmental potential of adult human osteoblastic cells (hOB) derived from explant cultures of collagenase-pretreated trabecular bone fragments. In addition to osteogenic and adipogenic differentiation, these cells are capable of chondrogenic differentiation in vitro in a manner similar to adult human bone marrow-derived mesenchymal progenitor cells. High-density pellet cultures of hOB maintained in chemically defined serum-free medium, supplemented with transforming growth factor-beta1, were composed of morphologically distinct, chondrocyte-like cells expressing mRNA transcripts of collagen types II, IX and X, and aggrecan. The cells within the high-density pellet cultures were surrounded by a sulfated proteoglycan-rich extracellular matrix that immunostained for collagen type II and proteoglycan link protein. Osteogenic differentiation of hOB was verified by an increased number of alkaline phosphatase-positive cells, that expressed osteoblast-related transcripts such as alkaline phosphatase, collagen type I, osteopontin and osteocalcin, and formed mineralized matrix in monolayer cultures treated with ascorbate, beta-glycerophosphate, and bone morphogenetic protein-2. Adipogenic differentiation of hOB was determined by the appearance of intracellular lipid droplets, and expression of adipocyte-specific genes, such as lipoprotein lipase and peroxisome proliferator-activated receptor gamma2, in monolayer cultures treated with dexamethasone, indomethacin, insulin and 3-isobutyl-1-methylxanthine. Taken together, these results show that cells derived from collagenase-treated adult human trabecular bone fragments have the potential to differentiate into multiple mesenchymal lineages in vitro, indicating their developmental plasticity and suggesting their mesenchymal progenitor nature.
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PMID:Multilineage mesenchymal differentiation potential of human trabecular bone-derived cells. 1238 74


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