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1.
Effect of acylation stimulating protein on the triacylglycerol synthetic pathway of human adipose tissue 总被引:3,自引:0,他引:3
Zivart Yasruel Katherine Cianflone Allan D. Sniderman Mark Rosenbloom Mark Walsh Miguel A. Rodriguez 《Lipids》1991,26(7):495-499
Acylation stimulating protein (ASP) is a 14 kDa plasma protein which causesin vitro triacylglycerol synthesis in human adipocytes and fibroblasts to increase substantially. ASP was found to stimulate human
adipose tissue microsomal glycerophosphate acyltransferase and diacylglycerol acyltransferase activities by 23% and 90%, respectively.
However, phosphatidate phosphohydrolase activity showed no increase in activity, nor did microsomal acyl-CoA synthetase activity.
Moreover, ASP did not decrease the apparent Km of diacylglycerol acyltransferase (DGAT), but rather increased its apparent Vmax suggesting direct interaction of ASP with DGAT. 相似文献
2.
Diacylglycerol acyltransferase from rat adipose tissue is shown to be inactivated by 30 to 40% upon incubation with adenosine
5′-triphosphate (ATP) and Mg2+. The activity responsible for this inactivation is associated with the cytosolic fraction, specific for ATP, prevented when
ATP is substituted by β,γ-methylene-ATP, and partially blocked by 1 mM ethylenediaminetetraacetate or 40 mM NaF, but not by
inhibitors of adenosine 3′,5′-cyclic-monophosphate (cAMP)-dependent protein kinase and/or protein kinase C (PKC). The cytosolic
activity cannot be mimicked by (cAMP)-protein kinase nor by PKC. Inactivated diacylglycerol acyltransferase from ATP/cytosol-treated
microsomes can be reactivated by incubation with partially purified protein phosphate from rat liver, and can be inactivated
again by further addition of ATP in the presence of cytosol. The results suggest the existence in adipose tissue of a protein
kinase other than cAMP-protein kinase or PKC, which may be involved in the regulation of triacylglycerol synthesis. 相似文献
3.
Phosphatidic acid (PtdOH) and lysophosphatidic acid (lysoPtdOH) have been shown to enhance T-lymphocyte function. However,
the FA preference and influence of acyl-CoA binding proteins on lysoPtdOH and PtdOH biosynthesis are not known. Therefore,
we determined glycerol-3-phosphate acyltransferase (GPAT) and lysophosphatidic acid acyltransferase (LAT) activity in rat
T-lymphocyte and liver membrane preparations in the presence of palmitoyl-CoA and oleoyl-CoA with or without BSA. We found
two different properties of GPAT and LAT in whole T-lymphocyte membrane preparations relative to liver. First, T-lymphocyte
basal GPAT and LAT activities were similar, whereas in liver membranes LAT activity was 10-fold higher than GPAT. Second,
T-lymphocyte LAT, but not GPAT, activity was inducible (fivefold) by the addition of albumin in the presence of palmitoyl-CoA
but not oleoyl-CoA. In contrast, albumin stimulated GPAT, but not LAT, activity in liver membranes in the presence of palmitoyl-CoA.
These results show, for the first time, that T-lymphocyte LAT activity can be increased by the presence of an acyl-CoA binding
protein, which may indicate a new important control mechanism for regulating intracellular lysoPtdOH and PtdOH levels in T-lymphocytes. 相似文献
4.
Factors enhancing diacylglycerol acyltransferase activity in microsomes from cell-suspension cultures of oilseed rape 总被引:1,自引:1,他引:0
Several factors, including an unidentified endogenous component, were found to stimulate microsomal diacylglycerol acyltransferase
(DGAT, EC 2.3.1.20) from a microspore-derived cell-suspension culture of oilseed rape (Brassica napus L. cv. Jet Neuf). At a concentration of 25mM, MgSO4 and MgCl2 stimulated microsomal DGAT 25- and 10-fold, respectively. AIP and CoA at concentrations of 2 and 1 mM stimulated the enzyme
2.4- and 12-fold, respectively, although the effects were lessened in the presence of higher Mg2+ concentrations. Although microsomal DGAT activity was increased only slightly by the addition of exogenous sn-1,2-diacylglycerol to the reaction mixture, it was increased substantially by the addition of exogenous phosphatidate. sn-Glycerol-3-phosphate and other phospholipids tested did not have this stimulatory effect. DGAT activity did not decrease
when microsomes were incubated with ATP in the presence of the cytosolic fraction. This fraction, however, contained a small
organic compound(s) that stimulated microsomal DGAT activity. 相似文献
5.
The effects of hyper- and hypothyroidism on enzyme activities involved in phospholipid metabolism in the rat liver were studied.
Hyperthyroidism significantly decreases activities of both microsomal acyl-CoA:glycero-3-phosphate acyltransferase (GPAT)
(34%, p<0.01) and microsomal acyl-CoA:1-acylglycero-3-phosphocholine acyltransferase (GPCAT) (28–33%, p<0.01). This may contribute
to the decreased proportions of certain unsaturated fatty acids found in microsomal phosphoglycerides in hyperthyroidism.
Mitochondrial GPAT, phospholipase A2 and cytosol lysophospholipase are unaffected by hyperthyroidism. In contrast, hypothyroidism stimulates mitochondrial GPAT
(38%, p<0.01) and microsomal GPCAT (14–19%) activities but decreases both mitochondrial phospholipase A2 (36%, p<0.01) and cytosol lysophospholipase (56%, p<0.01) activities. The increased GPCAT activity may contribute to the
increased proportions of certain unsaturated fatty acids found in microsomal phosphoglycerides in hypothyroidism. Triiodothyronine
(T3) treatment of the hypothyroid rat (25 μg/100 g body weight/day for four days) corrected phospholipase A2 and lysophospholipase activities to the level of the control rat, but failed to correct the increased mitochondrial GPAT
activity and not only corrected but lowered GPCAT activity to the level of the hyperthyroid rat. 相似文献
6.
We have studied the effect of streptozotocin (SZ)-induced diabetes on fatty acyltransferase and phospholipase enzyme activities
involved in the synthesis and degradation of rat liver phosphoglycerides. Neither mitochondrial nor microsomal acyl-CoA: glycerol
3-phosphate acyltransferase (GPAT) activity was altered, although insulin treatment stimulated mitochondrial GPAT activity.
However, microsomal acyl-CoA: 1-acylglycerol 3-phosphate acyltransferase (1-acyl-GPAT) activity increased (24–33 per cent,
p<0.01) in the diabetic animals using 3 different acyl-CoA donors: palmitoyl-CoA, oleoyl-CoA and linoleoyl-CoA. SZ-induced
diabetes also increased acyl-CoA:1-acylglycerol 3-phosphorylcholine acyltransferase (GPCAT) activity (38–45 per cent, p<0.01)
with 3 different acyl-CoA donors: oleoyl-CoA, linoleoyl-CoA and arachidonoyl-CoA. 1-acyl-GPAT and GPCAT activity returned
to normal with insulin treatment. In contrast to the increased activity of the microsomal fatty acyltransferases 1-acyl-GPAT
and GPCAT, SZ-induced diabetes decreased mitochondrial phospholipase A2 activity and lysophospholipase activity (49–70 per cent, p<0.01). Insulin treatment of the diabetic rats corrected the decreased
lysophospholipase and stimulated phospholipase A2 activity 35 per cent higher than controls. Since microsomal 1-acyl-GPAT and GPCAT are known to have higher activity toward
unsaturated fatty acyl-CoA donors, the increased GPCAT activity coupled with the decreased lysophospholipase activity and
the increased 1-acyl-GPAT activity in diabetes would tend to increase the formation of newly synthesized phospholipids containing
unsaturated fatty acids. This mechanism plus the decreased fatty acid desaturase (4) may be the factors which alter the fatty
acid composition of phosphoglycerides in diabetic rat liver microsomes. 相似文献
7.
M. Pellon-Maison C. F. Garcia E. R. Cattaneo R. A. Coleman M. R. Gonzalez-Baro 《Lipids》2009,44(4):337-344
Mammals express four isoforms of glycerol-3-phosphate acyltransferase (GPAT). The mitochondrial isoform GPAT1 may have been
the acyltransferase that appeared first in evolution. The hepatopancreas of the crustacean Macrobrachium borellii has a high capacity for triacylglycerol (TAG) biosynthesis and storage. In order to understand the mechanism of glycerolipid
biosynthesis in M. borellii, we investigated its hepatopancreas GPAT activity. In hepatopancreas mitochondria, we identified a GPAT activity with characteristics
similar to those of mammalian GPAT1. The activity was resistant to inactivation by SH-reactive N-ethylmaleimide, it was activated by polymyxin-B, and its preferred substrate was palmitoyl-CoA. The reaction products were
similar to those of mammalian GPAT1. A 70-kDa protein band immunoreacted with an anti-rat liver GPAT1 antibody. Surprisingly,
we did not detect high GPAT specific activity in hepatopancreas microsomes. GPAT activity in microsomes was consistent with
mitochondrial contamination, and its properties were similar to those of the mitochondrial activity. In microsomes, TAG synthesis
was not dependent on the presence of glycerol-3 phosphate as a substrate, and the addition of monoacylglycerol as a substrate
increased TAG synthesis 2-fold. We conclude that in M. borellii the de novo triacylglycerol biosynthetic pathway can be completed in the mitochondria. In contrast, TAG synthesis in the
ER may function via the monoacylglycerol pathway. 相似文献
8.
Diacylglycerol acyltransferase (DGAT) catalyzes the final step in the acyl-CoA-dependent biosynthesis of triacylglycerol (TAG), a high-energy compound composed of three fatty acids esterified to a glycerol backbone. In vitro DGAT assays, which are usually conducted with radiolabeled substrate using microsomal fractions, have been useful in identifying compounds and genetic modifications that affect DGAT activity. Here, we describe a high-temperature gas chromatography (GC)/mass spectrometry (MS)-based method for monitoring molecular species of TAG produced by the catalytic action of microsomal DGAT. This method circumvents the need for radiolabeled or modified substrates, and only requires a simple lipid extraction prior to GC. The utility of the method is demonstrated using a recombinant type-1 Brassica napus DGAT produced in a strain of Saccharomyces cerevisae that is deficient in TAG synthesis. The GC/MS-based assay of DGAT activity was strongly correlated with the typical in vitro assay of the enzyme using [1-14C] acyl-CoA as an acyl donor. In addition to determining DGAT activity, the method is also useful for determining substrate specificity and selectivity properties of the enzyme. 相似文献
9.
Cécile Mazière Jean-Claude Mazière Liliana Mora Martine Auclair Jacques Polonovski 《Lipids》1986,21(8):525-528
Incorporation of various exogenous saturated or unsaturated [14C]labeled fatty acids (palmitic, stearic, oleic, linoleic and arachidonic) into triacylglycerols by hamster fibroblasts was
markedly enhanced (two-to fourfold) in the presence of theophylline or dibutyryl cyclic adenosinemonophosphate (dbcAMP). This
effect was observed for short-term (1–6 hr) as well as long-term (15–24 hr) preincubation with dbcAMP. In the presence of
sodium fluoride, a phosphoprotein phosphatase inhibitor, measurement of diacylglycerol acyltransferase (DGAT) activity in
cells pretreated with dbcAMP pointed out a marked increase (3X) in specific activity. The results suggest that DGAT activity
in fibroblasts could be activated by a cAMP-dependent phosphorylation process. 相似文献
10.
Tomasz Furmanek Kamil Demski Walentyna Banaś Richard Haslam Jonathan Napier Sten Stymne Antoni Banaś 《Lipids》2014,49(4):327-333
The triacylglycerol of Crambe abyssinica seeds consist of 95 % very long chain (>18 carbon) fatty acids (86 % erucic acid; 22:1?13) in the sn‐1 and sn‐3 positions. This would suggest that C. abyssinica triacylglycerols are not formed by the action of the phospholipid:diacylglycerol acyltransferase (PDAT), but are rather the results of acyl‐CoA:diacylglycerol acyltransferase (DGAT) activity. However, measurements of PDAT and DGAT activities in microsomal membranes showed that C. abyssinica has significant PDAT activity, corresponding to about 10 % of the DGAT activity during periods of rapid seed oil accumulation. The specific activity of DGAT for erucoyl‐CoA had doubled at 19 days after flowering compared to earlier developmental stages, and was, at that stage, the preferred acyl donor, whereas the activities for 16:0‐CoA and 18:1‐CoA remained constant. This indicates that an expression of an isoform of DGAT with high specificity for erucoyl‐CoA is induced at the onset of rapid erucic acid and oil accumulation in the C. abyssinica seeds. Analysis of the composition of the acyl‐CoA pool during different stages of seed development showed that the percentage of erucoyl groups in acyl‐CoA was much higher than in complex lipids at all stages of seed development except in the desiccation phase. These results are in accordance with published results showing that the rate limiting step in erucic acid accumulation in C. abyssinica oil is the utilization of erucoyl‐CoA by the acyltransferases in the glycerol‐3‐phosphate pathway. 相似文献
11.
Ayman Al-Shurbaji Carin Larsson-Backström Lars Berglund Gösta Eggertsen Ingemar Bjökhem 《Lipids》1991,26(5):385-389
The effect of long-chain n−3 fatty acids on hepatic key enzymes of cholesterol metabolism and triglyceride biosynthesis was
investigated in two rat models. In the first model, rats were intravenously infused for two weeks with a fat emulsion containing
20% of triglycerides in which either n−6 or n−3 fatty acids predominated. The treatment with n−3 fatty acids led to a reduction
primarily of serum cholesterol (45%), but also of serum triglycerides (18%). HMG-CoA reductase activity and cholesterol 7α-hydroxylase
activity were reduced by 45% and 36%, respectively. There were no significant effects on diacylglycerol acyltransferase (DGAT)
or phosphatidate phosphohydrolase (PAP) activities. In the second model, rats were fed a diet enriched with sucrose, coconut
oil and either sunflower oil (n−6 fatty acids) or fish oil (long-chain n−3 fatty acid ethyl esters). The treatment with n−3
fatty acids decreased serum triglycerides (41%) and, to a lesser extent, serum cholesterol (17%). Neither glycerol 3-phosphate
acyltransferase (GPAT) or DGAT were affected by n−3 fatty acids. In contrast, PAP activity was reduced by 26%. HMG-CoA reductase
was not significantly affected, whereas cholesterol 7α-hydroxylase activity was reduced by 36%. The results indicate that
part of the TG-lowering effect of long-chain n−3 fatty acids may be mediated by inhibition of the soluble phosphatidate phosphohydrolase.
The effect on serum cholesterol may be partly due to inhibition of HMG-CoA reductase. 相似文献
12.
13.
In view of previous reports that the activity of the Mg++-dependent phosphatidic acid phosphatase in adipose tissues of rat and mouse is elevated in obesity, we attempted to assay
this activity in biopsies of human omental adipose tissue obtained from normal-weight and morbidly obese subjects in connection
with operations.
The major portion of the phosphatidic acid phosphatase activity was found in the cytosol, and the small amount found in the
microsomal fraction was too low for accurate measurement. It was not possible to assay the activity in the crude cytosol.
After precipitation with ammonium sulfate, however, the enzyme activity was linear with both the incubation time and the concentration
of enzyme. It was not possible to obtain substrate saturation of the enzyme under the conditions employed.
When assayed in the presence of a high concentration of substrate (0.6 mmol/l) the activity obtained in normalweight pateints,
7.8±2.4 nmol/mg protein/min (n=10), was not significantly different from that in morbidly obese patients, 5.6±0.8 nmol/mg
protein/min (n=10). There was no relation between the size of adipose cells and phosphatidic acid phosphatase activity. Furthermore,
there was no apparent relation between phosphatidic acid phosphatase activity in omental adipose tissue and that in the liver
The findings suggest that the increased biosynthesis of triglycerides in human obesity is not associated with an increased
capacity of the soluble phosphatidic acid phosphatase in adipose tissue. 相似文献
14.
15.
Diacylglycerol acyltransferase (DGAT) catalyzes the final step of triacylglycerol (TAG) synthesis, and is considered as a
potential target to control hypertriglyceridemia or other metabolic disorders. In this study, we found that the extract of
rose petals suppressed TAG synthesis in cultured cells, and that the extract showed DGAT inhibitory action in a dose-dependent
manner. Fractionation of the rose extract revealed that the DGAT inhibitory substances in the extract were ellagitannins;
among them rugosin B, and D, and eusupinin A inhibited DGAT activity by 96, 82, and 84% respectively, at 10 μM. These substances
did not inhibit the activities of other hepatic microsomal enzymes, glucose-6-phosphatase and HMG-CoA reductase, or pancreatic
lipase, suggesting that ellagitannins inhibit DGAT preferentially. In an oral fat load test using mice, postprandial plasma
TAG increase was suppressed by rose extract; TAG levels 2 h after the fat load were significantly lower in mice administered
a fat emulsion containing rose extract than in control mice (446.3 ± 33.1 vs 345.3 ± 25.0 mg/dL, control vs rose extract group;
P < 0.05). These results suggest that rose ellagitannins or rose extract could be beneficial in controlling lipid metabolism
and used to improve metabolic disorders. 相似文献
16.
Therapeutic Strategies for Metabolic Diseases: Small‐Molecule Diacylglycerol Acyltransferase (DGAT) Inhibitors
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Ravi Naik Minkyoung Kim Prof. Yongseok Choi Dr. Hyun Sun Lee Prof. Kyeong Lee 《ChemMedChem》2014,9(11):2410-2424
Metabolic diseases such as atherogenic dyslipidemia, hepatic steatosis, obesity, and type II diabetes are emerging as major global health problems. Acyl‐CoA:diacylglycerol acyltransferase (DGAT) is responsible for catalyzing the final reaction in the glycerol phosphate pathway of triglycerol synthesis. It has two isoforms, DGAT‐1 and DGAT‐2, which are widely expressed and present in white adipose tissue. DGAT‐1 is most highly expressed in the small intestine, whereas DGAT‐2 is primarily expressed in the liver. Therefore, the selective inhibition of DGAT‐1 has become an attractive target with growing potential for the treatment of obesity and type II diabetes. Furthermore, DGAT‐2 has been suggested as a new target for the treatment of DGAT‐2‐related liver diseases including hepatic steatosis, hepatic injury, and fibrosis. In view the discovery of drugs that target DGAT, herein we attempt to provide insight into the scope and further reasons for optimization of DGAT inhibitors. 相似文献
17.
The inhibitory effects of 1,3-diacylglycerol (DAG) on diet-induced lipid accumulation in liver and abdominal adipose tissue
of rats were investigated in the present study. Male Sprague-Dawley rats were given free access to diets containing 7 wt%
TAG (low TAG), 20 wt% TAG (high TAG), or 20 wt% DAG (high DAG), respectively, for 8 wk. The body weight of rats in the 20%
high-TAG group increased significantly, and the weights of their abdominal adipose tissue and liver also showed a significant
increase compared with rats in the low-TAG group. However, the high-DAG diet resulted in both a significant reduction in body
weight gain (with a decrease of 70.5%) and an increase in the ratio of abdominal fat to body weight (by 127%) compared with
the high-TAG diet. As well, the liver TAG and serum TAG levels of the high-DAG group were significantly lower than those of
the high-IAG group. These effects were associated with up-regulation of acyl-CoA carnitine acyltransferase (ACAT) and down-regulation
of acyl-CoA DAG acyltransferase (DGAT) in the liver. However, no significant difference was observed in the activities of
alanine aminotransferase and aspartate aminotransferase among the groups (P>0.05). The present results indicate that dietary DAG reduced fat accumulation in viscera and body, and these effects may
be involved with up-regulation of ACAT and down-regulation of DGAT in the liver. 相似文献
18.
Incubation of Caco-2 cells, a human intestinal cell line, with 25-hydroxycholesterol (25-HOC) markedly enhanced cellular cholesteryl
ester formation determined by incorporation of [14C]oleic acid into intracellular cholesteryl [14C]oleate. The stimulation by 25-HOC of cholesteryl ester formation was suppressed by staurosporine, a kinase inhibitor, but
not by cycloheximide or actinomycin D. The specific activity of microsomal acyl-coenzyme A:cholesterol acyltransferase (ACAT)
increased two-fold in cells treated with 10 μM 25-HOC for 5 h. ACAT activity decreased when microsomes were incubated without
sodium fluoride, a phosphatase inhibitor, but the decrease in ACAT activity in cells stimulated with 25-HOC was more pronounced.
The results suggest that protein phosphorylation may be involved in the stimulation of cholesteryl ester formation by 25-HOC
in Caco-2 cells. 相似文献
19.
In an attempt to clarify the mechanism of lipid accumulation inMortierella ramanniana var.angulispora, diacylglycerol acyltransferase (DGAT) in the membrane fraction from this fungus was characterized. The enzyme had an optimum
pH of 7.0–7.5, and enzyme activity was blocked by SH-reagents. Metal ions were not essential for maintaining DGAT activity.n-Octyl-β-d-glucoside, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and Tween 80 were found to preserve activity, while
Triton X-100 and sucrose monolaurate inhibited it. As the inhibition of DGAT activity by Triton X-100 was overcome by the
addition of diacylglycerol (DG), the dependency of DGAT activity on exogenous DG was determined in the presence of 0.1% Triton
X-100. DGAT activity in the membrane fraction was traced in fungi cultured for different time periods or in media at different
carbon to nitrogen (C/N) ratios. Although the increase in total lipid content with culture time was accompanied by an increase
in DGAT activity, total lipid changes related to changes in C/N ratio did not correlate with DGAT activity. Factors other
than DGAT activity in the membrane fraction would appear to be involved in the regulation of total lipid content in this fungus. 相似文献
20.
Many plants deposit TAG in seeds and fruits as the major form of storage lipid. TAG production is of tremendous socioeconomic
value in food, nutraceutical, and industrial applications, and thus numerous conventional and molecular genetic strategies
have been explored in attempts to increase TAG content and modify the FA composition of plant seed oils. Much research has
focused on the acyl-CoA-dependent reaction catalyzed by diacylglycerol acyltransferase (DGAT), which is an integral endoplasmic
reticulum protein and has also been shown to be present in oil bodies and plastids. DGAT enzymes exhibit diverse biochemical
properties among different plant species, many of which are summarized here. In addition to catalyzing a critical step in
TAG biosynthesis, there is evidence that DGAT has roles in lipid metabolism associated with germination and leaf senescence.
TAG can also be formed in plants via two different acyl-CoA-independent pathways, catalyzed by phospholipid: diacylglycerol
acyltransferase and diacylglycerol transacylase. The current understanding of the terminal step in TAG formation in plants
and the development of molecular genetic approaches aimed at altering TAG yield and FA composition of TAG are discussed. 相似文献