Significant Increase In Phospholipids Research Articles

Human Cytomegalovirus pUL37x1 Is Important for Remodeling of Host Lipid Metabolism.

Human cytomegalovirus (HCMV) replication requires host metabolism. Infection alters the activity in multiple metabolic pathways, including increasing fatty acid elongation and lipid synthesis. The virus-host interactions regulating the metabolic changes associated with replication are essential for infection. While multiple host factors, including kinases and transcription factors, important for metabolic changes that occur following HCMV infection have been identified, little is known about the viral factors required to alter metabolism. In this study, we tested the hypothesis that pUL37x1 is important for the metabolic remodeling that is necessary for HCMV replication using a combination of metabolomics, lipidomics, and metabolic tracers to measure fatty acid elongation. We observed that fibroblast cells infected with wild-type (WT) HCMV had levels of metabolites similar to those in cells infected with a mutant virus lacking the UL37x1 gene, subUL37x1. However, we found that relative to WT-infected cells, subUL37x1-infected cells had reduced levels of two host proteins that were previously demonstrated to be important for lipid metabolism during HCMV infection: fatty acid elongase 7 (ELOVL7) and the endoplasmic reticulum (ER) stress-related kinase PERK. Moreover, we observed that HCMV infection results in an increase in phospholipids with very-long-chain fatty acid tails (PL-VLCFAs) that contain 26 or more carbons in one of their two tails. The levels of many PL-VLCFAs were lower in subUL37x1-infected cells than in WT-infected cells. Overall, we conclude that although pUL37x1 is not necessary for network-wide metabolic changes associated with HCMV infection, it is important for the remodeling of a subset of metabolic changes that occur during infection.IMPORTANCE Human cytomegalovirus (HCMV) is a common pathogen that asymptomatically infects most people and establishes a lifelong infection. However, HCMV can cause end-organ disease that results in death in the immunosuppressed and is a leading cause of birth defects. HCMV infection depends on host metabolism, including lipid metabolism. However, the viral mechanisms for remodeling of metabolism are poorly understood. In this study, we demonstrate that the viral UL37x1 protein (pUL37x1) is important for infection-associated increases in lipid metabolism, including fatty acid elongation to produce very-long-chain fatty acids (VLCFAs). Furthermore, we found that HCMV infection results in a significant increase in phospholipids, particularly those with VLCFA tails (PL-VLCFAs). We found that pUL37x1 was important for the high levels of fatty acid elongation and PL-VLCFA accumulation that occur in HCMV-infected cells. Our findings identify a viral protein that is important for changes in lipid metabolism that occur following HCMV infection.

Regulation of Galactolipid Biosynthesis by Overexpression of the Rice MGD Gene Contributes to Enhanced Aluminum Tolerance in Tobacco.

Membrane lipid alterations affect Al tolerance in plants, but little is known about the regulation of membrane lipid metabolism in response to Al stress. Transgenic tobacco (Nicotiana tabacum) overexpressing rice monogalactosyldiacylglycerol (MGDG) synthase (OsMGD) gene and wild-type tobacco plants were exposed to AlCl3, and the impact of Al toxicity on root growth, Al accumulation, plasma membrane integrity, lipid peroxidation and membrane lipid composition were investigated. Compared with the wild type, the transgenic plants exhibited rapid regrowth of roots after removal of Al and less damage to membrane integrity and lipid peroxidation under Al stress, meanwhile, the Al accumulation showed no difference between wild-type and transgenic plants. Lipid analysis showed that Al treatment dramatically decreased the content of MGDG and the ratio of MGDG to digalactosyldiacylglycerol (DGDG) in wild-type plants, while it was unchanged in transgenic plants. The stable of MGDG level and the ratio of MGDG/DGDG contribute to maintain the membrane stability and permeability. Moreover, Al caused a significant increase in phospholipids in wild-type plants, resulting in a high proportion of phospholipids and low proportion of galactolipids, but these proportions were unaffected in transgenic plants. The high proportion of phospholipids could contribute to a higher rate of Al3+ binding in the membrane and thereby leads to more membrane perturbation and damage. These results show that the regulation of galactolipid biosynthesis could play an important role in maintaining membrane structure and function under Al stress.

Microsomal triglyceride transfer protein: does insulin resistance play a role in the regulation of chylomicron assembly?

We have previously demonstrated that diabetes is associated with an increase in intestinal microsomal triglyceride transfer protein (MTP) mRNA in both the rat and rabbit models. The present study was designed to investigate the relationship between MTP expression and chylomicron assembly in an insulin resistant non-diabetic animal model. Ten insulin resistant Zucker obese fa/fa rats and ten lean fa/− rats were examined at 8–10 weeks of age. The lymph duct was cannulated and lymph collected for 4 h. Lymph chylomicrons were isolated by ultracentrifugation and their composition determined. RNA was extracted from intestinal mucosa and from the liver. MTP mRNA was measured using the RNase protection assay. Blood sugar in the fatty rats was significantly higher (6.3±1.2 vs. 5.4±0.4 P<0.05) and plasma insulin was almost six times that of the lean rats ( P<0.001). Plasma cholesterol and phospholipid but not triglyceride were significantly increased in the obese animals ( P<0.01). Obese animals secreted significantly more lymph chylomicron apo B48 (0.05±0.02 vs. 0.02±0.01mg/h P<0.005), triglyceride (9.7±5.3 vs. 3.8±1.9 mg/h P<0.005) and phospholipid (1.5±0.7 vs. 0.4±0.3 mg/h P<0.001). The only difference in the chylomicron particle composition between the two groups was a significant increase in phospholipid ( P<0.01). Intestinal MTP mRNA expression was significantly higher in the fatty compared to the lean rats (22.1±9.5 vs. 7.8±5.6 amol MTP mRNA/μg total RNA P<0.001) as was hepatic MTP mRNA expression (6.9±3.5 vs. 3.4±1.5 amol MTP mRNA/μg total RNA, P<0.01). Thus in this animal model of insulin resistance, increased MTP, which was associated with increased chylomicron particle number, may play a crucial role in the development of atherosclerosis.

Lipid profile in actinic keratosis and basal cell carcinoma.

The lipid content of the skin and its changes are important in the pathogenesis of many disorders affecting the skin, particularly actinic keratosis (AK) and basal cell carcinoma (BCC). Cholesterol, phospholipid, triglyceride, and total lipid levels were studied in paired lesional (AK and BCC) and nonlesional intact skin of 13 patients with AK and 12 patients with BCC. Serum concentrations of the same lipid fractions studied in the skin were investigated in AK and BCC patients and in 11 healthy, age-matched controls. Levels of all lipid fractions were increased in both AK and BCC skin. When AK and BCC skin were compared with each other, a significant increase in phospholipids (p < 0.02) and total lipids (p < 0.01) was found in BCC. Serum cholesterol (p < 0.001), phospholipid (p < 0.001), triglyceride (p < 0.05), and total lipid (p < 0.001) concentrations of AK patients were significantly higher than those of the control group. When BCC and controls were compared, a significant increase in phospholipids and total lipids (p < 0.001) was seen. Serum cholesterol in BCC patients was significantly lower (p < 0.001) and serum phospholipid levels were significantly higher (p < 0.05) than those in the AK group. An increase in the metabolically active serum phospholipid fraction is reflected in elevated neoplastic tissue phospholipid. This produces altered proportions between lipid fractions in tumorous areas and may result in changes in the intact nature of the cellular membrane, spread, and malignant proliferation.

Spontaneous Obesity and Increased Bile Saturation in the Ground Squirrel

Obesity is a well-known risk factor for developing cholesterol gallstones, but only indirect human studies are available. Presently available animal models of cholesterol gallstone disease do not become obese under normal conditions, while genetically obese or dietarily manipulated rats lack a gallbladder. The Richardson ground squirrel on a high-cholesterol diet develops impaired gallbladder contractility, excess cholesterol in its bile, and then cholesterol gallstones. To determine if ground squirrels would spontaneously become obese and serve as an appropriate model, animal weights were followed over several months while being maintained under a regulated laboralory environment. The five obese animals were twice the body weight of the live lean controls and also had a 20% rise in body fat. Plasma cholesterol levels were markedly increased and liver histology revealed mild microvesicular steatosis. Cholesterol saturation rose in the gallbladder bile of the obese group. This alteration was primarily due to a significant increase in phospholipid (33%) and cholesterol (86%) levels. Such a laboratory environment interrupts the natural annual rhythm of the ground squirrel and prevents hibernation. Animals continue to eat and develop severe obesity and abnormal gallbladder bile. These spontaneously obese animals provide an excellent means for examining altered hepatobiliary secretion and gallbladder motility relative to cholesterol gallstone disease.

Effect of dietary fat on lipids and enzyme activities of rat hepatic membranes

The effect of consumption of ω-3 fatty acids on membrane lipid composition and specific activities of some membrane-bound enzymes was investigated in rats fed a semisynthetic diet containing 14% by weight of either menhaden oil (MO), safflower oil (SO), or beef fat (BF). These diets also contained 2% corn oil to assure an adequate supply of essential fatty acids. The diets were fed to the experimental animals ab libitum for 2 or 7 weeks. The data obtained on lipid analysis indicated a significant increase in phospholipid: cholesterol ratio in membranes of animals fed the MO diet than those fed the SO diet, but was lower than that of animals fed the BF diet. These changes were due to the significantly higher phospholipid content in membranes of animals fed the MO diet when compared with the other diets, and to the significantly lower cholesterol content of animals fed the BF diet. These findings in lipid composition were observed after both 2 and 7 weeks of feeding the experimental diets. Significant effects from dietary MO were observed in the contents of two major phospholipids: phosphatidyl choline and phosphatidyl ethanolamine. No significant effect from the diet was observed in membrane phosphatidyl inositol content. There were significant differences in the fatty acid composition that were reflected on the unsaturation index (UI) of the membranes. Membranes of animals fed the MO diet had a 36% increase in membrane UI as compared with those fed either SO or BF. Hepatic alkaline phosphatase was 33% higher in membranes of animals fed the MO diet as compared to the other diets. No significant effect of MO feeding on hepatic (Na +, K +)-ATPase was observed. There was no significant difference between membrane glucose 6-phosphatase activity of animals fed MO and BF diets, which were, in turn, significantly higher than that of animals fed the SO diet. All the above enzyme activities were found to be uninfluenced by the length of the feeding period. The observed alterations in the lipid composition and specific activities of membrane-bound enzymes in addition to the increase in liver weight in animals fed the MO diet indicate significant effects on the liver and therefore warrant further studies on the effect of MO feeding on liver function.

Effect of histamine H2-receptor antagonist, ranitidine on renal brush border and basolateral membranes

The antiulcerogenic drug ranitidine, given orally to mice, brought about reductions of kidney-bound hydrolytic enzymes at three different dose levels, viz. 10 mg, 100 mg, and 1000 mg/kg body weight, and for three different time points (single administration for 2 h and 24 h, and daily administration for 15 days). The activities of Na+, K(+)-ATPase, Ca2(+)-ATPase, and Mg2(+)-ATPase (marker enzymes of basolateral membranes) were reduced, and these reductions were significant at higher doses and after a 24-h single treatment or 15 days' daily treatment. Maltase, alkaline phosphatase, and leucine aminopeptidase (marker enzymes of brush border membrane [BBM]) activities were significantly inhibited after ranitidine treatment. Kinetic analysis of BBM-associated enzymes indicated that ranitidine decreased the maximum of apparent initial enzyme velocity (Vmax) of maltase, alkaline phosphatase, and leucine aminopeptidase. The substrate affinity constant (Km) was decreased in the case of alkaline phosphatase and maltase, while it was not altered in the case of leucine aminopeptidase. In vitro addition of ranitidine to renal BBM also produced significant inhibition of these enzymes, the inhibition constants (Ki) for maltase, alkaline phosphatase, and leucine aminopeptidase being 7.5, 15.5, and 3.5 mM, respectively. Membrane-bound lipid estimation showed a significant increase in phospholipids, triglycerides, and free fatty acids. Cholesterol, however, was decreased in both renal basolateral and brush border membranes.

Postobstructive subcellular organelle and biliary lipid composition in the rat: A selective increase in biliary lecithin output is not reflected by changes in organelle composition

Rats infused intravenously with taurocholate shortly after relief of 48 h of biliary obstruction excrete in bile twice as much phospholipid in relation to cholesterol and bile acid as controls. In an effort to identify a subcellular compartment as the source of this biliary lipid, we examined several hepatic subcellular organelles for an increase in phospholipid to cholesterol ratio or an increase in biliary-type lecithins (16:0-18:2; 16:0-20:4) either absolute or relative to non-biliary-type lecithins (18:0-20:4; 18:0-22:6) as analyzed by high-performance liquid chromatography. Subcellular fractions studied were: three microsomal subfractions, Golgi heavy and intermediate fractions, and plasma membrane light (canaliculus-enriched) fraction. No organelle fraction from rats with biliary obstruction displayed either a significant increase in phospholipid to cholesterol ratio or a relative or absolute increase in biliary type lecithin. This suggests that biliary lipid changes are not attributable to measurable alterations in lipid composition of any anatomical compartment in the liver cells; changes are probably more related to changes in lipid turnover than to organelle total lipid pool sizes.

Effect of short-term and long-term treatment with a steroidal oral contraceptive on the intestinal absorption of nutrients in vitro in female rats.

The effect of steroidal oral contraceptive (SOC), comprising megestrol acetate (5 mg/kg body weight) plus ethinyl estradiol (0.05 mg/kg body weight), administered daily by stomach tube for 5, 15, 30 and 90 days, on the intestinal uptake of nutrients such as glucose, amino acids and calcium has been investigated in vitro in female rats. The administration of SOC for 5 days did not affect the uptake of nutrients, but treatment for 15, 30 and 90 days led to a progressive and significant increase in the uptake of glucose and amino acids. The calcium uptake was increased in the groups treated for 5 and 15 days, but decreased after 30 and 90 days of treatment. Kinetic studies done on glucose uptake indicated that the steroid contraceptive might be inducing the transport carrier protein of this nutrient, as elevation in Vmax was observed in the group treated for 30 days. There was no change in brush border membrane phospholipid and cholesterol contents after 30 and 90 days of treatment, but a significant increase in phospholipid after 5 and 15 days of treatment was observed. This study suggests that SOC treatment significantly altered the intestinal absorptive functions and the effect appears to be on the carrier-mediated transport of glucose.

Chemical and Biophysical Changes in the Plasma Membrane during Cold Acclimation of Mulberry Bark Cells (Morus bombycis Koidz. cv Goroji)

The lipid and protein composition of the plasma membrane isolated from mulberry (Morus bombycis Koidz.) bark cells was analyzed throughout the cold acclimation period under natural and controlled environment conditions. There was a significant increase in phospholipids and unsaturation of their fatty acids during cold acclimation. The ratio of sterols to phospholipids decreased with hardiness, primarily due to the large increase in phospholipids. The fluidity of the plasma membrane, as determined by fluorescent polarization technique, increased with hardiness. Electrophoresis of plasma membrane proteins including glycoproteins revealed change in banding pattern during the early fall to winter period. Some of the protein changes could be related to growth cessation and defoliation. However, minor changes in proteins also occurred during the most active period of hardening. Changes in glycoproteins were coincident both with changes in growth stages and with the development of cold hardiness.

Mechanism of Cholic Acid Protection in Lithocholate-Induced Intrahepatic Cholestasis in Rats

The mechanism(s) by which the coinfusion of primary bile acids with lithocholate protects against the development of intrahepatic cholestasis was assessed in the present study. Bile ducts of male Wistar rats were cannulated, and bile was collected for 2 hr. The rats were then divided into nine groups (six per group) and each was infused intravenously with one of the following: 7.5% albumin, lithocholic acid (LCA), taurolithocholic acid (T-LCA), cholic acid (CA), dehydrocholic acid (DHCA), CA + LCA, CA + T-LCA, DHCA + LCA, and DHCA + T-LCA at a rate of 0.2 μmol of each bile acid/100 g body wt/min for 60 min. At the end of the infusion the livers were examined by electron-microscopy, and the liver cell plasma membrane fraction rich in bile canalicular membranes was isolated. The morphologic lesion of lithocholate cholestasis was seen in LCA, T-LCA, DHCA + LCA, and DHCA + T-LCA groups. The liver cell plasma membrane fraction rich in bile canalicular membranes obtained from these groups contained high concentrations of cholesterol, but there were no changes in membrane phospholipids. Lithocholic acid was further incorporated in the membranes obtained from LCA and DHCA + LCA groups. In the other groups, the ultrastructure of the livers was normal, and membrane ultrastructure and composition was similar to that of the membranes obtained from control rats, except in the CA infusion where there was a significant increase in the membrane phospholipids. In LCA, T-LCA, DHCA + LCA, and DHCA + T-LCA, bile flow was significantly reduced (30-60 min) after infusion, however, in the other groups bile flow was increased as compared to control infusions. Lithocholate secretion was 0.40-1.32 nmol/g liver/min in LCA and T-LCA infusions alone or during their coinfusion with DHCA. The secretion of lithocholate was increased to 12.03-15.32 nmol/g liver/min in the CA + LCA, and CA + T-LCA, furthermore the LCA secreted was more than 95% in free form in the case of CA + LCA infusions. The increased secretion of lithocholate was associated with a five- to sevenfold increase in biliary cholesterol secretion as well as significant increase in phospholipids secretion. These data suggest that CA protects against lithocholate cholestasis by the formation of a LCA-CA complex that prevents its toxic effect on the bile canalicular membrane.

Effects of Testosterone, Progesterone and Testosterone plus Progesterone on Rat Testicular Lipids

The effects of testosterone, progesterone or testosterone plus progesterone on testicular lipids of pubertal rats are presented. The hormones were administered for 1 day as well as 7 days continuously to study both short and long term effects. Testosterone induced marked depletion of glycerides in short and long term treatments. It elicited a significant increase in phospholipids only in long term treatment. Progesterone brought about marked increase in esterified cholesterol with a congenital fall in free cholesterol. It had no significant effect on testicular glycerides and phospholipids Testosterone plus progesterone administration caused marked increase in phospholipids with a fall in glyceride levels even in short term treatment. There was a marked increase in esterified cholesterol with a concurrent fall in free cholesterol level. Thus, testosterone plus progesterone treatment brought out marked changes in phospholipids, glycerides and cholesterol fractions.These hormonal treatments did not have any significant effect on testicular weight in short as well as long term studies.

Abnormalities of erythrocyte membranes in biliary atresia: Ultrastructure and lipid composition

Biochemical and ultrastructural studies of red blood cell membranes from seven patients with congenital biliary atresia have been performed. Scanning electron microscopic observations revealed that more than half of these cells were of abnormal shapes, such as target, spur and cup-formed cells. By freeze-fracture electron microscopy, membrane particle-free smooth areas were noted in the fracture faces. In addition, the number of membrane-associated particles was 20% less than those in control subjects. The lipid analysis of red blood cells showed a significant increase in phospholipid and a marked increase in cholesterol content. The increase of phospholipid content was primarily caused by the increase of lecithin. The acyl chain analysis of erythrocyte lecithin demonstrated an increase in palmitic, palmitoleic and oleic acid, and a decrease in stearic and linoleic acid. These observations are similar to those of acquired biliary obstruction. The fluidity of erythrocyte membrane lipid, studied by a fluorescence technique using fluorescent probe l,6-diphenyl-1,3,5-hexatriene (DPH), was found to be less in an individual with congenital biliary atresia than in the control subject.