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)

Lipoprotein lipase activity was studied in mesenchymal cells isolated from rat hearts and cultured for up to 8 days. The enzyme activity increased markedly between day 3 and 5 while the subsequent increase was less pronounced. Addition of hydrocortisone to complete culture medium resulted in an increase in lipoprotein lipase activity at all stages of culture. Lipoprotein lipase activity did not increase after addition of insulin to the complete culture medium. In the presence of serum-poor medium between day 3 and 6, the increase in lipoprotein lipase activity was much lower than in the presence of complete culture medium. Addition of hydrocortisone and insulin to the serum-poor medium resulted in a significant rise in lipoprotein lipase activity while less consistent effects were obtained after addition of each hormone alone. Transfer of cells to serum-poor medium between day 6 and 7 of culture caused a fall in enzyme activity. Addition of hydrocortisone alone and with insulin restored enzyme activity to control values. No effect on lipoprotein lipase was seen with estradiol, growth hormone, or glucagon when added to serum-containing medium, or serum-poor medium. These results indicate that the lipoprotein lipase of heart is controlled by glucocorticoids and that this control might require the presence of insulin for optimal expression.
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PMID:Lipoprotein lipase of cultured mesenchymal rat heart cells. III. Effect of glucocorticoids and insulin on enzyme formation. 71 72

Destruction of the ventromedial hypothalamic nuclei (VMN) in the weanling rat without injury to the median eminence results in a series of somatic, endocrine, and metabolic changes that are characterized by normal food and water intake but decreased linear growth, normal body weight but increased carcass fat and reduced carcass protein, lean body mass, and water. The endocrine alterations comprise hyperinsulinemia in the face of normoglycemia, hypertriglyceridemia and hypercholesterolemia and reduced growth hormone levels. The metabolic changes include greater oxidation of glucose and incorporation into lipid and reduced palmitate oxidation but increased incorporation into lipid. Weanling rats with VMN lesions are normophagic in absolute terms, relative to body weight and per metabolic unit, but their nocturnal feeding and weight gain cycles are disrupted and their locomotor activity is reduced. The VMN are involved in the long-term control of feeding - as in the mature rat - as shown by intragastric preloading studies and dietary density manipulation, glucose preference tests and intraperitoneal injections with glucose. Hyperinsulinemia and hypertriglyceridemia are present four days after the VMN operation in the presence of subnormal food intake and plasma glucose levels. Manipulations of the fat content of the diet revealed that the hyperlipidemia is of both endogenous and exogenous origin and that lipoprotein lipase is increased; a 48-hour fast reduced the hyperlipidemia to control levels, however. This suggests that weanling VMN rat tissue may have an impaired ability to take up circulating lipid. An increased incorporation of glycerol into lipid may be due to induction of glycerokinase by hyperinsulinemia. Adipose tissue of weanling VMN rats showed glycerokinase by hyperinsulinemia. Adipose tissue of weanling VMN rats showed neither depressed lipolysis nor diminished lipolytic activity per milligram of tissue protein. Glucose oxidation and incorporation into adipose tissue is increased in several tissues in vitro and there is enhanced glucose disappearance from plasma and incorporation into tissue lipids in vivo. These changes develop within a short time after lesion production and persist at least partially up to six months: glucose utilization in liver increases already four hours after the operation whereas it takes 72 hours to commence in adipose tissue. Insulin resistance is not apparent either in vivo or in vitro. The decreased growth hormone levels are not critical to the metabolic changes, nor is the hyperinsulinemia totally necessary. The metabolic changes also appear on several different types of diet and persist with fasting. The latter does not reduce insulin sensitivity of VMN rat tissues, wheras it does so in normal rats. Mature rats developed the same metabolic changes even in the absence of hyperphagia. The metabolic alterations can be blocked by pharmacologic doses of glucocorticoids, but are enhanced by the administration of estrogen...
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PMID:Origin of endocrine-metabolic changes in the weanling rat ventromedial syndrome. 95 Jun 80

The lipid metabolic disorders in chronic renal insufficiency (CRI) are related to increased hepatic lipid synthesis, reduced triglyceride removal coupled with insulin insensitivity and impaired lipoprotein lipase activity. Growth hormone is lipolytic, and the effects of recombinant human growth hormone (rhGH) on the hypercholesterolemia of CRI are unsettled. To test this question, we gave rhGH for 14 days at a dosage of 3 units/day intraperitoneally to two-stage, 5/6 nephrectomized, male Sprague-Dawley rats (n = 18) compared to sex- and age-matched control (n = 27) and CRI (n = 40) rats. At the end of the study, CRI rats and those treated with rhGH had a similar degree of renal impairment, as assessed by serum concentrations (mean +/- SEM) of urea nitrogen (49 +/- 3 vs. 54 +/- 4 mg/dl), creatinine (0.9 +/- 0.0 vs. 1.0 +/- 0.1 mg/dl) and cumulative food intake (311 +/- 8 vs. 290 +/- 12 g). Serum urea nitrogen (16 +/- 4 mg/dl) and creatinine (0.4 +/- 0.1 mg/dl) concentrations as well as food intake (412 +/- 9 g) of control rats were significantly (p < 0.0001) different. Serum cholesterol concentration of CRI rats treated with rhGH (87 +/- 3 mg/dl) was not higher than those of CRI rats (81 +/- 2 mg/dl, p < 0.1338) but was significantly higher than in control rats (55 +/- 3 mg/dl, p < 0.0001). CRI rats treated with rhGH showed a similar serum albumin concentration and lower serum glucose than CRI rats (0.9 +/- 0.1 vs. 0.9 +/- 0.0 g/dl and 144 +/- 4 vs. 163 +/- 3 mg/dl, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hypercholesterolemia in rats with chronic renal insufficiency not aggravated by recombinant human growth hormone. 147 89

Pyrularia thionin is a 47 amino acid peptide isolated from the nuts of Pyrularia pubera. This peptide does not have intrinsic phospholipase A2 activity, but it increases the liberation of arachidonate from several tissues. Exposure of anterior pituitary cells to this toxin increases the liberation of arachidonate, increases the cellular levels of lysophospholipids, and decreases cellular phospholipids. Thus, phospholipase A2 is involved in the liberation of arachidonate stimulated by this peptide. Because this toxin also increases stearate liberation from the pituitary cells, either diacylglycerol lipase, phospholipase A1 or lysophospholipase may be directly or indirectly activated by this toxin. In addition to increasing fatty acid liberation, Pyrularia thionin increases the release of prolactin and growth hormone from anterior pituitary cells over the identical concentration ranges that this toxin liberates the fatty acids. Pyrularia thionin increased arachidonate liberation and prolactin release from perifused pituitary cells within 2 min, and following withdrawal of the toxin, arachidonate liberation and prolactin release returned to near basal levels within 6 min. Dopamine, a physiological inhibitor of prolactin release that closes calcium channels, decreased prolactin release stimulated by Pyrularia thionin. However, dopamine had no effect on the arachidonate liberation stimulated by this peptide. Similarly, D-600, an organic calcium channel blocker, decreased the prolactin and growth hormone release stimulated by the toxin without affecting the toxin-stimulated arachidonate liberation. Therefore, Pyrularia thionin increases arachidonate liberation through the rapid activation of phospholipase A2 by a mechanism that is not dependent on calcium uptake via D-600-inhibitable calcium channels. In contrast, the prolactin and growth hormone release stimulated by this toxin requires calcium uptake via D-600 inhibitable calcium channels.
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PMID:Pyrularia thionin increases arachidonate liberation and prolactin and growth hormone release from anterior pituitary cells. 148 65

It has been known for more than 30 years that growth hormone has a lipolytic properties and growth hormone excess (acromegaly) and growth hormone deficiency have been reported to be associated with abnormalities in serum lipoprotein concentrations. Due to the lipolytic effect of growth hormone, its administration in man has been reported to increase plasma nonesterified fatty acid (NEFA) concentrations. Ketone body production increases during acute growth hormone excess as a result of increased NEFA concentrations; similarly, the increase in serum triglycerides may be explained by an increase in substrate (NEFA) supply to the liver for VLDL production. The effect may be enhanced by a simultaneous decrease of serum lipoprotein lipase activity. The cholesterol-lowering effect of growth hormone administration has not been investigated in detail, specifically, the effect of growth hormone on LDL kinetics is unknown. Growth hormone-excess and growth hormone deficiency have been reported to be associated with increased risk for atherosclerosis; an association with serum lipoprotein changes is likely but evidence for a causal link is yet lacking.
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PMID:Growth hormone and lipids. 180 82

Among the candidate genes that have been reviewed herein, adipsin, calcitonin, cholecystokin, Gi alpha and Gs subunits of G proteins, insulin I and II, and lipoprotein lipase have all been mapped to specific chromosomes in mouse or rat or both. In none of these cases is the chromosomal location syntenic with murine obesity genes db (on chromosome 4), or ob (on chromosome 6). Thus, all of these genes that code for metabolic modulators that are altered in obese animals but not in lean animals can be ruled out as possible loci of the primary genetic defect, at least for the murine models of obesity. In the case of neuropeptide Y, growth hormone, glucose transporter GLUT-4, the insulin receptor, and glyceraldehyde-3-phosphate dehydrogenase, chromosomal mapping has not yet been reported. However, in each of these cases, the evidence available strongly argues against any one of these physiologic modulators as the likely site of the primary defect for any one of the obesity mutations. Rather, in all of these cases, regardless of whether or not the gene has been mapped, the evidence suggests that posttranscriptional and/or post-translational processes are involved in bringing about the specific alterations in level or activity of the protein product that is seen in the obese animal. Often hormonal regulation is invoked as a possible explanation for the changes observed in gene expression. The hormones most commonly identified as having a mediating effect on the particular metabolic pathways involved are insulin and/or the adrenal glucocorticoids. Since in each of the obese mutants, circulating amounts of these hormones are elevated, severely so in the case of insulin, it would not be surprising to find that they influence the levels and activities of many protein products involved in a variety of central nervous system and peripheral metabolic pathways. Glucocorticoids are known to exert direct effects on gene expression; however, with respect to adipsin gene expression, a direct effect has not been found. Furthermore, insulin itself has been considered as a candidate for the genetic lesion in these animals and has been ruled out by chromosomal localization. Thus, while it may certainly prove to be the case that both insulin and glucocorticoids affect these systems in some way, their effects appear to be indirect. The work by Platt and colleagues in transgenic mice provides the first evidence of signal transduction between an obese mutant allele and the promoter sequence for a gene that shows significantly altered expression in the obese animal.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Animal models of obesity: genetic aspects. 189 4

The differentiation of adipose precursor cells can be divided into early and late events. Growth arrest at the G1/S boundary triggers the activation of early genes, i.e., pOb24 and lipoprotein lipase; the expression of both genes is primarily regulated at a transcriptional level. The expression of late markers, which lead to terminal differentiation and accumulation of neutral lipids, takes place after a limited number of mitoses of early-marker-expressing cells. Only terminal differentiation requires the presence of growth hormone and triiodothyronine as obligatory hormones and insulin as a modulating hormone, and results in the formation of triacylglycerol-filled, non-dividing cells. It appears that terminal differentiation involves the cyclic AMP pathway, the diacylglycerol pathway, and a third pathway triggered by insulinlike growth factor-I and insulin. It is thus proposed that a combination of mitogenic-adipogenic signals is required to trigger terminal differentiation of preadipose cells.
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PMID:The adipocyte: relationships between proliferation and adipose cell differentiation. 217 64

Lipoprotein lipase (LPL) and pOb24 mRNAs are known to be early markers of adipose cell differentiation. Comparative studies of the expression of pOb24 and LPL genes during adipose conversion of Ob1771 preadipocyte cells and in mouse adipose tissue have shown the following: 1) the expression of both genes takes place at confluence; this event can also be triggered by growth arrest of exponentially growing cells at the G1/S stage of the cell cycle; 2) In contrast to glycerol-3-phosphate dehydrogenase mRNA, the emergence of pOb24 and lipoprotein lipase mRNAs requires neither growth hormone or tri-iodothyronine as obligatory hormones nor insulin as a modulating hormone; 3) in mouse adipose tissue, pOb24 mRNA is present at a high level in stromal-vascular cells and at a low level in mature adipocytes, and in contrast LPL mRNAs are preferentially expressed in mature adipocytes. Thus, these two genes do not appear to be regulated in a similar manner, as also shown by the differential inhibition of their expression by tumor necrosis factor (TNF) and transforming growth factor-beta (TGF-beta).
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PMID:Expression and regulation of pOb24 and lipoprotein lipase genes during adipose conversion. 219 67

The adipose conversion of cultured preadipose cells involves the activation of numerous genes and is controlled by various adipogenic and mitogenic factors. The differentiation program can be divided into early and late events. Early events are triggered by growth arrest at the G1/S boundary and characterized by the activation of a set of genes (pOb24, lipoprotein lipase, etc.). The expression of the terminal differentiation-related genes takes place after a limited growth resumption of early markers containing cells and requires the presence of permissive hormones (growth hormone and triiodothyronine). Insulin acts solely as a modulator in the expression of the terminal differentiation-related genes. In vivo studies suggest that the acquisition of new adipocytes might result from terminal differentiation of dormant, already committed (pOb24 positive) cells when exposed to appropriate mitogenic or adipogenic stimuli.
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PMID:[Gene expression regulation of adipocyte differentiation: cell cycle and hormones]. 220 47

Growth hormone regulates in a positive way the expression of the lipoprotein lipase gene at a transcriptional level in preadipocyte Ob1771 cells. Inhibition by serum components of this expression was investigated upon stimulation by growth hormone. Low-molecular weight, lipid-soluble components (a serum lipid extract, corticosteroids and oleic acid) and high-molecular weight, hydrophilic components (TGF-beta and those present in delipidated serum) were inhibitory. Inhibition of the expression of LPL mRNAs and that of LPL activity were parallel. It is concluded that the regulation of the expression of LPL gene occurs likely at a transcriptional level and that a balance between multiple effectors present in serum are active in an opposite manner.
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PMID:Inhibition by serum components of the expression of lipoprotein lipase gene upon stimulation by growth hormone. 230 31


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