Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.34 (lipoprotein lipase)
 7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some hormonal factors, possibly involved in the proliferation and differentiation of adipose precursor cells in vivo, have been characterized in vitro using different preadipocyte cell lines established from rodent adipose tissue. The process of adipose conversion has also been studied using these cell lines; in this process, stem cells (adipoblasts) were committed at any cell division during the growth phase. At confluence, committed cells (preadipocytes) underwent a limited number of mitoses and differentiated into adipose cells, whereas the uncommitted cells remained as stem cells in the cell population. This stochastic model could be extended to the development of rat adipose tissue in vivo. The study of adipose conversion showed the early emergence of lipoprotein lipase (LPL) and monoglyceride lipase (MGL). LPL activity appeared in the cells before any triglyceride accumulation. In contrast, this accumulation seemed dependent upon the emergence of glycerol-3-phosphate dehydrogenase. In vitro experiments clearly established that LPL-containing (differentiating) cells underwent postconfluent mitoses. This limited proliferation was in agreement with previous data obtained in vivo and indicates that only triglyceride-containing (mature) cells could not divide.
 ...
PMID:[Lipoprotein lipase and adipocyte differentiation]. 388 22

The ob17 preadipocyte clonal line has been established from the adipocyte fraction of the epididymal fat pads of adult C57 BL/6J ob/ob mice. In vivo, injection of ouabain-resistant mutant cells (ob 17OR11 cell line) into athymic mice is followed by the formation of fat pads containing ouabain-resistant mature fat cells. In vitro, ob17 cells develop after confluence biochemical and morphological characteristics of adipocytes. The adipose conversion process is best represented by a stochastic model in which a pool of stem cells (adipoblasts) give rise to clusters of adipose cells and to additional stem cells that remain in the population. The role of the different factors involved in such conversion is discussed; (1) factors that enhance the number of susceptible cells (ACF or ACF-like compounds), (2) factors without which no adipose conversion takes place (triiodothyronine, growth hormone and other factors still to be characterized), (3) factors that enhance the expression of the differentiation program (insulin). The early emergence of lipoprotein lipase occurs normally in insulin-depleted medium. The separation of ob17 cells by isopycnic centrifugation shows that lipoprotein lipase is present at high levels in early differentiating cells which are still devoid of late markers, ie glycerol-3-phosphate dehydrogenase and triglycerides. These results are discussed with respect to the determination of cellularity during development of adipose tissue in vivo.
 ...
PMID:Adipose conversion of ob17 cells and hormone-related events. 390 48

The stroma vascular fraction of adipose tissue partly consists of adipose precursor cells which can convert into adipocytes in vitro. The aim of this study was to investigate the possible contribution of cells from the stroma vascular compartment to the initiation of obesity induced by overfeeding during the early neonatal weeks in rats. Overfeeding during the suckling period was obtained by reducing the litter size. The inguinal adipose tissue of overfed rats raised in litters of 4 pups each was overdeveloped compared to that of controls raised in litters of 8 pups each, and the difference between the two groups became significant as early as 10 days of age. At this age, adipose tissue enlargement was only due to adipocyte hypertrophy; afterwards, hyperplasia of the mature fat cells contributed to the overdevelopment of adipose tissue in 15-day old overfed rats. The cell number in the stroma vascular fraction increased in the overfed group as early as 10 days of age and thus preceded the onset of mature fat cell hyperplasia. The developmental pattern of lipoprotein lipase, glycerol-3-phosphate dehydrogenase, glycerol-acyl-transferase and acyl-CoA ligase activities in stromal cells did not depend on litter size, but specific enzyme activities wee increased in 10-day old overfed rats compared to the controls. These results indicate that early overfeeding induced cell proliferation in the stroma vascular compartment and also induced the enzyme activities involved in adipose conversion to increase in these cells. This strongly suggests that precursor cell differentiation was greater in overfed rats than in control rats.
 ...
PMID:[Role of adipocyte precursors in the initiation of nutritional obesity before weaning]. 399 88

A clonal cell line has been established from the epididymal fat pad of the C57 BL/6J +/? mouse. This line, designated HGFu, is aneuploid and exhibits both morphological and biochemical properties characteristic of mature adipocytes. Adipose conversion begins after confluence and is accompanied by (a) an early emergence of lipoprotein lipase, (b) an increase in the incorporation of [14C]acetate into lipids and in the activities of acid:CoA ligase and glycerol-3-phosphate dehydrogenase, (c) a 27- to 35-fold increase in the average triglyceride content per cell. In the presence of a beta-agonist (isoproterenol) a full lipolytic response (measured by fatty acid release) is observed with differentiated cells, whereas the responsiveness examined by cyclic AMP (cAMP) production is present both in undifferentiated and differentiated cells. Adipose conversion, estimated by activities of enzyme markers, is accelerated by the continuous presence in the culture medium of insulin and triiodothyronine both within their physiological range of concentrations, whereas insulin at supraphysiological concentrations shows a growth promoting activity. The concentrations of insulin and triiodothyronine required for half-maximal lipogenic effects are in agreement with the Kd values of their respective high affinity binding sites present in HGFu cells. The HGFu cell line seems to be a useful model for the study on a long term basis of the mechanisms of action both of insulin and triiodothyronine. Moreover it will make it possible to realize comparative studies between clonal lines established from the lean adult mouse (HGFu line) and from the genetically obese adult mouse (Ob17 line).
 ...
PMID:Establishment of a preadipocyte cell line from the epididymal fat pad of the lean C57 BL/6J mouse--long term effects of insulin and triiodothyronine on adipose conversion. 634 28

Using mature adipocytes and preadipocytes from genetically obese Zucker rats, we investigated the cells' ability to maintain abnormal fat storage capacity when withdrawn from their in vivo environment. Long-term adipocyte cultures from obese rats displayed an increase in both glucose consumption (GC) and enzyme activities, including fatty acid synthase (4-fold), glycerol-3-phosphate dehydrogenase (4.5-fold), lipoprotein lipase (LPL; 6-fold), and malic enzyme (2.5-fold). Fully differentiated obese predipocytes exhibited a twofold increase in these enzyme activities, together with higher glucose metabolism. In obese cells, LPL mRNA was increased in both adipocytes (6-fold) and differentiated preadipocytes (2-fold). Insulin mediated an increase in GC and lipogenic enzymes in both adipocytes and preadipocytes regardless of the genotype; this effect was more marked in obese cells. Examining cultured adipocytes from rats fed a high-fat diet, we showed that the nutritional effect upon GC and lipogenic enzymes was abolished after culture. These results demonstrated that fatty mutation may be intrinsically expressed in prolonged cultured mature adipocytes and in newly differentiated adipocytes.
 ...
PMID:Evidence for a sustained genetic effect on fat storage capacity in cultured adipose cells from Zucker rats. 794 24

Ageing results in decreased replicative potential of preadipocytes, as well as reduced capacities for the lipid accumulation and increases in lipogenic enzyme activities during differentiation of preadipocytes into fat cells. To determine whether decreased differentiation is associated with decreased levels of mRNA for differentiation-dependent genes and whether early as well as late components of the differentiation programme are affected by ageing, we measured beta-actin, alpha-tubulin, lipoprotein lipase, and glycerol-3-phosphate dehydrogenase mRNA levels in undifferentiated and differentiated epididymal preadipocytes from 3-, 17-, and 24-month-old Fischer 344 rats. During ageing, diminished differentiation-related changes occurred in mRNAs affected early (actin, tubulin), midway through (lipoprotein lipase), and late (glycerol-3-phosphate dehydrogenase) in the preadipocyte differentiation process. Hence, early as well as late phases of the differentiation programme were affected by ageing. The effects involved changes in gene transcription or mRNA processing. Our results were not consistent with the hypothesis that age-related decreases in replication are caused by an increased tendency for cell differentiation.
 ...
PMID:Ageing, differentiation, and gene expression in rat epididymal preadipocytes. 819 92

Prostaglandin F2 alpha (PGF2 alpha) is a potent adipose differentiation inhibitor for the adipogenic cell line 1246 and for adipocyte precursors in primary culture with an ED50 of 3 x 10(-8) M. In this paper, we examined the effect of several prostaglandins which have structural similarities with PGF2 alpha on the differentiation of 1246 cells and of adipocyte precursors in primary culture. The results show that only 9 alpha,11 beta-PGF2 alpha is as potent as PGF2 alpha to inhibit differentiation of adipocyte precursors in primary culture and of the adipogenic cell line 1246. In the presence of 9 alpha,11 beta-PGF2 alpha, the cells remained fibroblast-like, typical of undifferentiated adipocyte precursors. Triglyceride accumulation and increase of specific activity for glycerol-3-phosphate dehydrogenase were inhibited. In addition, mRNA expression of early markers of differentiation such as lipoprotein lipase (LPL) and fatty acid binding protein (FAB) was decreased. The isomer 9 beta,11 alpha-PGF2 alpha and other PGF2 alpha derivatives were inactive. These results provide new information on the biological activity of 9 alpha,11 beta-PGF2 alpha as an inhibitor of adipose differentiation and about the structural characteristics of prostaglandins required for maintenance of a high adipose differentiation inhibitory effect.
 ...
PMID:Inhibition of adipose differentiation by 9 alpha, 11 beta-prostaglandin F2 alpha. 829 81

Nontransformed 3T3 T mesenchymal/proadipocyte stem cells can be readily induced to differentiate, yet previous work has shown that 3T3 T cells that are spontaneously or virally transformed not only lose their normal growth control mechanisms but also lose the ability to differentiate. Loss of growth control can be due to autocrine mechanisms in some transformed cells, but the mechanisms involved in disrupting differentiation control are poorly understood. Our goal is to further define the growth and differentiation defects that arise in neoplastically transformed cells and the mechanisms underlying those defects. For example, exogenous transforming growth factor beta and tumor necrosis factor, both of which are secreted aberrantly by some tumor cells, are known inhibitors of different steps of the normal 3T3 T adipocyte differentiation process, suggesting a potential role as autocrine factors in disrupting differentiation of transformed 3T3 T cells. In the current study we transformed 3T3 T cells in vitro with chemical or UV irradiation treatment in order to determine if the acquisition of the transformed phenotype after these treatments is also associated with loss of differentiation control as it is with spontaneously or virally transformed cells. Four chemically and two UV-treated 3T3 T cell lines were isolated from type III foci and all have been found to be tumorigenic in syngeneic animals and to have lost the ability to differentiate. Relative to the parental cell line the differentiation abilities of the transformed clones ranged from 0 to less than 5%. In this regard, we also analyzed the normal and aberrant expression of three growth factors and differentiation inhibitors in transformed cells. Both transforming growth factor alpha and beta were found to be expressed in non-transformed 3T3 T cells as determined by Northern blot analyses. In addition, both were found to be down-regulated during differentiation of 3T3 T cells. Transformed/differentiation-defective 3T3 T cells expressed varied levels of transforming growth factor alpha and beta. Three of the new transformed clones expressed particularly high levels of transforming growth factor alpha. Very low levels of tumor necrosis factor expression were found in the normal cells and the transformed cells appeared to express tumor necrosis factor at similar levels. In contrast, none of the transformed cells expressed any of the differentiation-specific genes tested (lipoprotein lipase, glycerol-3-phosphate dehydrogenase, etc.). Even a transformed clone which could undergo growth arrest but not morphological differentiation expressed no differentiation-specific genes. Together, these data suggest that neoplastic transformation in general disrupts differentiation control.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Loss of differentiation control in transformed 3T3 T proadipocytes. 846 95

Acylation Stimulating Protein (ASP) is a human plasma protein that stimulates both triacylglycerol synthesis and glucose transport. ASP is identical to C3adesArg and is generated by the interaction of factor B, complement C3 and adipsin. We have demonstrated that mature fat cells express messages for factors B, complement C3 and adipsin; that human pre-adipocytes, when cultured under differentiating conditions to produce adipocytes, generate ASP in the culture medium; and that human adipocytes also become more responsive to ASP as they differentiate. The aim of this study, therefore, was to examine the temporal production of ASP during adipocyte differentiation in relation to other adipose specific factors involved in lipogenesis. The results demonstrate that (i) there was little ASP production by differentiating adipocytes over the first 7 days, with a marked increase in ASP thereafter (up to sixfold); (ii) this increase was paralleled by large increases in the message level of factor B and complement C3 and moderate increases in adipsin message; (iii) increases in lipoprotein lipase (LPL) message and glycerol-3-phosphate dehydrogenase (GPDH) activity (both key enzymes for substrate supply for triacylglycerol synthesis) occurred earlier than the increase in ASP; and (iv) in spite of the increase in LPL and GPDH, triacylglycerol synthetic capacity only markedly increases following the increase in ASP production in adipocytes. Although the present study cannot be interpreted as showing causality with respect to triacylglycerol synthesis, it does point to an important role for ASP in human adipose tissue physiology.
 ...
PMID:Differentiation-induced production of ASP in human adipocytes. 858 46

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.
 ...
PMID:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) inhibition of fat cell differentiation. 859 78


<< Previous 1 2 3 4 5 6 7 8 Next >>