Glycosylphosphatidylinositol-specific Phospholipase Research Articles

The role of GPLD1 in chronic diseases.

Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is a specific enzyme for glycosylphosphatidylinositol (GPI) anchors, thereby exerting its biological functions by cleaving membrane-associated GPI molecules. GPLD1 is abundant in serum, with a concentration of approximately 5-10 µg/mL. Previous studies have demonstrated that GPLD1 plays a crucial role in the pathogenesis of numerous chronic diseases including disorders of lipid and glucose metabolism, cancer, and neurological disorders. In the present study, we reviewed the structure, functions, and localization of GPLD1 in chronic diseases, as well as exercise-mediated regulation of GPLD1, thus providing a theoretical support to develop GPLD1 as a new therapeutic target for chronic diseases.

Modulation of GPC-4 and GPLD1 serum levels by improving glycemic indices in type 2 diabetes: Resistance training and hawthorn extract intervention

AimsThis study was designed to investigate the effects of resistance training (RT) and hawthorn extract (Ha) on Glypican-4 (GPC-4) and Insulin-regulated glycosylphosphatidylinositol-specific phospholipase D (GPLD1) serum levels in T2DM and to examine the relationship of these variables with glycemic indexes. Method40 male Wistar rats were divided into five equal groups: Healthy Control (H-C), Diabetes Control (D-C), Diabetes Resistance training (D-RT), Diabetes Hawthorn (D-Ha), and Diabetes Resistance training Hawthorn (D-RT-Ha). T2DM was induced with a 4-week high-fat diet (HFD) and one dose of STZ intraperitoneal injection (35 mg/kg). 1-week after the injection, RT (with a range of 50%–100%1RM/3 day/week) and gavage of Ha extract (100 mg/kg/day) was performed for 12 weeks. ResultsThe glycemic indices improvement (reducing blood glucose and increasing serum insulin level) caused by RT and/or Ha increased GPC-4 and decreased GPLD1 in the T2DM rats, but these positive changes were more effective in the combination of RT + Ha. A strong correlation was also observed between GPC-4 and GPLD1 with blood glucose and insulin. ConclusionThe increase in serum GPC-4 levels was probably due to the direct effect of RT + Ha, and the improvement of glycemic indexes after RT and Ha. The double effect of RT + Ha can be a regulatory mechanism for GPC-4 and its related factors in controlling T2DM complications.

Transient early life growth hormone exposure permanently alters brain, muscle, liver, macrophage, and adipocyte statusin long-lived Ames dwarf mice.

The exceptional longevity of Ames dwarf (DF) mice can be abrogated by a brief course of growth hormone (GH) injections started at 2 weeks of age. This transient GH exposure also prevents the increase in cellular stress resistance and decline in hypothalamic inflammation characteristic of DF mice. Here, we show that transient early‐life GH treatment leads to permanent alteration of pertinent changes in adipocytes, fat‐associated macrophages, liver, muscle, and brain that are seen in DF mice. Ames DF mice, like Snell dwarf and GHRKO mice, show elevation of glycosylphosphatidylinositol specific phospholipase D1 in liver, neurogenesis in brain as indicated by BDNF and DCX proteins, muscle production of fibronectin type III domain‐containing protein 5 (a precursor of irisin), uncoupling protein 1 as an index of thermogenic capacity in brown and white fat, and increase in fat‐associated anti‐inflammatory macrophages. In each case, transient exposure to GH early in life reverts the DF mice to the levels of each protein seen in littermate control animals, in animals evaluated at 15–18 months of age. Thus, many of the traits seen in long‐lived mutant mice, pertinent to age‐related changes in inflammation, neurogenesis, and metabolic control, are permanently set by early‐life GH levels.

Fragment-Based Drug Discovery for Trypanosoma brucei Glycosylphosphatidylinositol-Specific Phospholipase C through Biochemical and WaterLOGSY-NMR Methods.

Glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) of Trypanosoma brucei, the causative protozoan parasite of African trypanosomiasis, is a membrane-bound enzyme essential for antigenic variation, because it catalyses the release of the membrane-bound form of variable surface glycoproteins. Here, we performed a fragment-based drug discovery of TbGPI-PLC inhibitors using a combination of enzymatic inhibition assay and water ligand observed via gradient spectroscopy (WaterLOGSY) NMR experiment. The TbGPI-PLC was cloned and overexpressed using an Escherichia coli expression system followed by purification using three-phase partitioning and gel filtration. Subsequently, the inhibitory activity of 873 fragment compounds against the recombinant TbGPI-PLC led to the identification of 66 primary hits. These primary hits were subjected to the WaterLOGSY NMR experiment where 10 fragment hits were confirmed to directly bind to the TbGPI-PLC. These included benzothiazole, chlorobenzene, imidazole, indole, pyrazol and quinolinone derivatives. Molecular docking simulation indicated that six of them share a common binding site, which corresponds to the catalytic pocket. The present study identified chemically diverse fragment hits that could directly bind and inhibit the TbGPI-PLC activity, which constructed a framework for fragment optimization or linking towards the design of novel drugs for African trypanosomiasis.

Label-free proteomics for discovering biomarker candidates of RAD140 administration to castrated horses.

Selective androgen receptor (AR) modulators (SARMs) are potent anabolic agents with a high potential of misuse in horseracing and equestrian sports. In this study, we applied label-free proteomics to discover plasma protein biomarkers in geldings (castrated horses) after administration with a popular SARM named RAD140. Tryptic peptides were prepared from plasma samples and analyzed by nano-flow ultrahigh-performance liquid chromatography-high-resolution tandem mass spectrometry (nano-UHPLC-HRMS/MS) using data-independent acquisition (DIA) method. Orthogonal projection on latent structure-discriminant analysis (OPLS-DA) has led to the development of a predictive model that could discriminate RAD140-administered samples from control samples and could also correctly classify 18 out of 19 in-training horses as control samples. The model comprises 75 proteins with variable importance in projection (VIP) score above 1. Gene Ontology (GO) enrichment analysis and literature review have identified upregulation of AR-regulated clusterin, and proteins associated with inflammation (haptoglobin, cluster of differentiation 14 [CD14], and inter-alpha-trypsin inhibitor heavy chain 4 [ITIH4]) and erythropoiesis (glycosylphosphatidylinositol-specific phospholipase D1 [GPLD1]) after RAD140 administration. Their changes were confirmed by selected reaction monitoring (SRM) experiments. Similar effects have been reported by the use of androgens and other SARMs. This is the first reported study that describes the use of a proteomic biomarker approach to detect horses that have been administered with RAD140 by applying label-free proteomic profiling of plasma samples. These results support the concept of a biomarker-driven approach to enhance the doping control of RAD140 and potentially other SARMs in the future.

Serum glypican4 and glycosylphosphatidylinositol-specific phospholipase D levels are associated with adipose tissue insulin resistance in obese subjects with different glucose metabolism status.

Glypican4 (GPC4) is a novel adipokine associated with obesity and insulin resistance. GPC4 was cleaved by the glycosylphosphatidylinositol-specific phospholipase D (GPLD1) in an anchored site of the glycosylphosphatidylinositol, and then was released into the extracellular environment. Herein, we investigated the changes of serum GPC4 and GPLD1 levels in obese subjects with different glucose metabolism status and their relationship with adipose tissue insulin resistance index (Adipo-IR) in Chinese north populations. A total of 221 obese subjects and 37 normal controls (NC) were recruited in this study. Obese subjects were divided into normal insulin (NI) group, hyperinsulinemia (HI) group, impaired glucose tolerance (IGT) group, and type 2 diabetes mellitus (DM) group. Serum GPC4, GPLD1, and adiponectin were determined by commercially available ELISA kits. Serum GPC4 levels in the HI, IGT, and DM groups were significantly higher than those in the NC and NI groups (2.27 ± 0.58ng/mL, 2.21 ± 0.60ng/mL, 2.49 ± 0.67ng/mL vs. 1.70 ± 0.33ng/mL, 1.93 ± 0.34ng/mL, P < 0.05). GPC4 was positively correlated with GPLD1, which was the most important influencing factor of GPC4. Adipo-IR was independently and positively associated with serum GPC4 and GPLD1. For GPC4, afteradjustmentforconfounders, the risk of adipose tissue insulin resistance in subjects with the highest tertile was 2.974-fold that of those with the lowest tertile (OR = 2.974, P = 0.013). For GPLD1, before adjustment for lipids, the increased probability still existed (Model 2, OR = 3.568, P = 0.003). GPC4 is an adipokine associated with adipose tissue insulin resistance, and its activitymay beregulatedby GPLD1. GPC4 may be a marker for adipose tissue insulin resistance in Chinese north obese populations.

Blood factors transfer beneficial effects of exercise on neurogenesis and cognition to the aged brain.

Reversing brain aging may be possible through systemic interventions such as exercise. We found that administration of circulating blood factors in plasma from exercised aged mice transferred the effects of exercise on adult neurogenesis and cognition to sedentary aged mice. Plasma concentrations of glycosylphosphatidylinositol (GPI)-specific phospholipase D1 (Gpld1), a GPI-degrading enzyme derived from liver, were found to increase after exercise and to correlate with improved cognitive function in aged mice, and concentrations of Gpld1 in blood were increased in active, healthy elderly humans. Increasing systemic concentrations of Gpld1 in aged mice ameliorated age-related regenerative and cognitive impairments by altering signaling cascades downstream of GPI-anchored substrate cleavage. We thus identify a liver-to-brain axis by which blood factors can transfer the benefits of exercise in old age.

Plasma transfers exercise benefit in mice

Aging Exercise has a broad range of beneficial healthful effects. Horowitz et al. tested whether the beneficial effects of exercise on neurogenesis in the brain and improved cognition in aged mice could be transferred in plasma (blood without its cellular components) from one mouse to another (see the Perspective by Ansere and Freeman). Indeed, aged mice that received plasma from young or old mice that had exercised showed beneficial effects in their brains without hitting the treadmill. The authors identified glycosylphosphatidylinositol-specific phospholipase D1 as a factor in plasma that might, in part, mediate this favorable effect. Science , this issue p. [167][1]; see also p. [144][2] [1]: /lookup/doi/10.1126/science.aaw2622 [2]: /lookup/doi/10.1126/science.abc8830

Endurance exercise training restores diabetes-induced alteration in circulating Glycosylphosphatidylinositol-specific phospholipase D levels in rats

BackgroundGlycosylphosphatidylinositol-specific phospholipase D (GPLD1) is responsible for cleaving membrane-associated glycosylphosphatidylinositol (GPI) molecules, which is affected by diabetes. We aimed to examine the effect of 14 weeks treadmill running on serum GPLD1 levels and its association with glycemic indexes and serum glypican-4 (GPC-4), a novel GPI-anchored adipokine, in streptozotocin-nicotinamide-induced diabetic rats.MethodsThirty-six male Wister rats were randomly divided into three groups of twelve animals each, involving sedentary control (SC), sedentary diabetic (SD), and trained diabetic (TD) groups. The diabetes was induced through intraperitoneal injection of 120 mg/kg nicotinamide 15 min prior to intraperitoneal injection of 65 mg/kg streptozotocin in SD and TD groups. The TD group was exercised on a treadmill for 60 min/days, 5 days/wk at 26 m/min, and zero grade for 14 weeks. Following the experiment period, blood samples were taken from all animals and analyzed for experimental indexes via sandwich ELISA.ResultsExercise training caused a significant decrease in the elevated blood glucose levels and a significant increase in the lowered blood insulin levels in TD rats (both p < 0.001). Glucose tolerance of TD rats significantly improved following experimental protocol, as indicated by OGTT (p < 0.001). Experimental diabetes significantly increased serum GPLD1 levels (p < 0.001), while exercise training significantly decreased its levels (p < 0.001). Serum GPLD1 levels correlated directly with glycemic indexes involving FBS, 2hOGTT, and AUC of glucose (r = 0.80, r = 0.79, r = 0.79, respectively, all p < 0.001) and inversely with serum insulin levels (r = − 0.83, p < 0.001). There were no significant differences in serum GPC-4 levels among groups, and no association with GPLD1 alteration.ConclusionsSedentary diabetic rats have higher circulating GPLD1 compared to controls, which can be reversed by exercise training and is associated with modifying in glycemic and insulin profile.

Upregulated phospholipase D activity toward glycosylphosphatidylinositol-anchored proteins in micelle-like serum complexes in metabolically deranged rats and humans.

Glycosylphosphatidylinositol-anchored proteins (GPI-AP) with the complete glycolipid anchor attached have previously been shown to be released from the outer plasma membrane leaflet of rat adipocytes in positive correlation to cell size and blood glucose/insulin levels of the donor rats. Furthermore, they are present in rat and human serum, however, at amounts that are lower in insulin-resistant/obese rats compared with normal ones. These findings prompted further evaluation of the potential of full-length GPI-AP for the prediction and stratification of metabolically deranged states. A comparison of the signatures of horizontal surface acoustic waves that were generated by full-length GPI-AP in the course of their specific capture by and subsequent dissociation from a chip-based sensor between those from rat serum and those reconstituted into lipidic structures strongly argues for expression of full-length GPI-AP in serum in micelle-like complexes in concert with phospholipids, lysophospholipids, and cholesterol. Both the reconstituted and the rat serum complexes were highly sensitive toward mechanical forces, such as vibration. Furthermore, full-length GPI-AP reconstituted into micelle-like complexes represented efficient substrates for cleavage by serum glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD). These findings raised the possibility that the upregulated release of full-length GPI-AP into micelle-like serum complexes from metabolically deranged cells is compensated by elevated GPI-PLD activity. In fact, serum GPI-PLD activity toward full-length GPI-AP in micelle-like complexes, but not in detergent micelles, was positively correlated to early states of insulin resistance and obesity in genetic and diet-induced rat models as well as to the body weight in humans. Moreover, the differences in the degradation of GPI-AP in micelle-like complexes were found to rely in part on the interaction of serum GPI-PLD with an activating serum factor. These data suggest that serum GPI-PLD activity measured with GPI-AP in micelle-like complexes is indicative of enhanced release of full-length GPI-AP from relevant tissues into the circulation as a consequence of early metabolic derangement in rats and humans.

On the possible participation of phosphatidylinositol-3-kinase in activation by insulin and epidermal growth factor phospholipase c, hydrolyzing glycosylphosphatidylinositol

The pleiotropic effect of insulin is based on signal transfer from insulin receptor to a series of intracellular effector systems, one of which is glycosyl phosphatidyl inositol (GPI) specific phospholipase C (PLC), hydrolyzing membranous inositol-containing glycophospholipids to produce diacylglycerol, a phospholipase C activator, and inositolphosphoglycane (IPG), a probable secondary messenger in transfer of insulin metabolic signal. For disclosing the mechanisms of GPI-PLC conjugation with insulin receptors and growth factors, we analyzed GPI hydrolysis in Rati cells and found that insulin and epidermal growth factors (EGF) activate GPI hydrolysis to IPG by 20 and 40%o, respectively (p&lt;0.001), while specific phosphatidylinositol- 3’-kinase (PIj kinase) inhibitor vortmannin cancels this insulin and EGF effect. These data permit us to hypothesize the participation of PIj kinase in signal transfer from insulin and EGF receptor GPI-PLC.

Serum protein profiles suggest a possible link between qi deficiency constitution and Pi-qi-deficiency syndrome of chronic superficial gastritis

Abstract Objective To identify potential serum protein candidates involved in linking the traditional Chinese medicine (TCM)-defined qi deficiency constitution (QDC) to Pi-qi-deficiency syndrome (PQDS) of chronic superficial gastritis (CSG). Methods Using participants with the TCM-defined balanced constitution as a control population, label-free quantitative proteomics was adopted to identify differentially expressed proteins (DEPs) in serum samples from two case populations: case population 1 (participants with QDC) and case population 2 (patients with PQDS of CSG). The DEPs discovered in both case populations were analyzed to identify common DEPs as potential candidates for proteins involved in the link between QDC and PQDS. Based on Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) and Gene Ontology (GO) enrichment analysis and analysis of protein–protein interaction networks, we evaluated the possible functions of these potential serum candidates. Results We discovered 24 and 28 proteins that were differentially expressed in case populations 1 and 2, respectively, compared with the control population. Hierarchical clustering analysis showed that the expression profile of DEPs of individuals from the same population clustered well, while those from different populations were segregated. Furthermore, GO analysis revealed the 10 DEPs that were common to both case populations to be mainly associated with negative regulation of cellular metabolic and immune system processes while KEGG analysis indicated these proteins to be associated with complement and coagulation cascades and peroxisome proliferator-activated receptor signaling. Notably, serum levels of C4b-binding protein beta chain, glycosylphosphatidylinositol-specific phospholipase D1 and MS-F1 light chain variable region proteins were notably higher in the two case populations compared with the control, particularly in the case of CSG with PQDS. Conclusion The results presented here provide new insights into the molecular mechanisms underlying development of PQDS of CSG from QDC, and suggest candidate serum biomarkers for future application in integrative medicine.

Protein markers and risk of type 2 diabetes and prediabetes: a targeted proteomics approach in the KORA F4/FF4 study

The objective of the present study was to identify proteins that contribute to pathophysiology and allow prediction of incident type 2 diabetes or incident prediabetes. We quantified 14 candidate proteins using targeted mass spectrometry in plasma samples of the prospective, population-based German KORA F4/FF4 study (6.5-year follow-up). 892 participants aged 42–81 years were selected using a case-cohort design, including 123 persons with incident type 2 diabetes and 255 persons with incident WHO-defined prediabetes. Prospective associations between protein levels and diabetes, prediabetes as well as continuous fasting and 2 h glucose, fasting insulin and insulin resistance were investigated using regression models adjusted for established risk factors. The best predictive panel of proteins on top of a non-invasive risk factor model or on top of HbA1c, age, and sex was selected. Mannan-binding lectin serine peptidase (MASP) levels were positively associated with both incident type 2 diabetes and prediabetes. Adiponectin was inversely associated with incident type 2 diabetes. MASP, adiponectin, apolipoprotein A-IV, apolipoprotein C-II, C-reactive protein, and glycosylphosphatidylinositol specific phospholipase D1 were associated with individual continuous outcomes. The combination of MASP, apolipoprotein E (apoE) and adiponectin improved diabetes prediction on top of both reference models, while prediabetes prediction was improved by MASP plus CRP on top of the HbA1c model. In conclusion, our mass spectrometric approach revealed a novel association of MASP with incident type 2 diabetes and incident prediabetes. In combination, MASP, adiponectin and apoE improved type 2 diabetes prediction beyond non-invasive risk factors or HbA1c, age and sex.

Impact of glycosylphosphatidylinositol-specific phospholipase D on hepatic diacylglycerol accumulation, steatosis, and insulin resistance in diet-induced obesity.

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is an enzyme that specifically cleaves GPI anchors. Previous human studies suggested the relationship of GPI-PLD to insulin resistance, type 1 and type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD). However, the biological roles of GPI-PLD have not been elucidated. Here, we hypothesized that GPI-PLD impacted on lipid and glucose metabolism, especially in the liver. GPI-PLD mRNA was most highly expressed in the liver, and the hepatic mRNA level and circulating concentration of GPI-PLD were significantly augmented in diabetic mice. To investigate in vivo functions of GPI-PLD, we generated GPI-PLD knockout (GP-KO) mice. Mice lacking GPI-PLD exhibited the amelioration of glucose intolerance and hepatic steatosis under high-fat and high-sucrose diet. Furthermore, diacylglycerol (DAG) content was significantly decreased, and PKCε activity was suppressed in the livers of GP-KO mice. In vitro knockdown and overexpression experiments of GPI-PLD using rat primary hepatocytes showed the GPI-PLD-dependent regulation of intracellular DAG content. Finally, serum GPI-PLD levels were strongly and independently associated with serum alanine transaminase (R = 0.37, P = 0.0006) and triglyceride (R = 0.34, P = 0.001) levels in male subjects with metabolic syndrome. In conclusion, upregulation of hepatic GPI-PLD in diabetic conditions leads to DAG accumulation in the liver by shedding GPI anchors intracellularly, which may play a causal role in impaired hepatic insulin signaling and the progression of NAFLD.

The response of serum Glypican-4 levels and its potential regulatory mechanism to endurance training and chamomile flowers' hydroethanolic extract in streptozotocin-nicotinamide-induced diabetic rats.

Glypican-4 (GPC-4) is a novel adipomyokine that enhances insulin signaling. Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is thought to release GPC-4 and is itself an insulin-regulated enzyme. Beneficial effects of exercise training and chamomile flowers extract (CFE) are shown through activation of PPARγ, which is a promising drug target in diabetes and associated with GPC-4 synthesis. This study investigated the effects of 14-week treadmill running and CFE on serum GPC-4, GPLD1, and insulin levels in streptozotocin-nicotinamide (STZ-NA)-induced diabetic rats. Thirty-two STZ-NA-induced diabetic male Wistar rats were randomly assigned to four groups: control (C), training (T), CFE treatment (CFE), and training plus CFE treatment (TCFE) groups. The training groups were exercised on treadmill 5days/week and the treating groups were fed with 200mg/kg/day CFE in drinking water for 14weeks. Finally, serum GPC-4, GPLD1, and insulin levels were analyzed via sandwich ELISA. Compared to the control group, serum insulin levels were significantly higher in the T, CFE, and TCFE groups (p < 0.05, p < 0.05, p < 0.01, respectively), while OGTT and serum GPLD1 levels were significantly lower in the T, CFE, and TCFE groups (all p < 0.001). Changes in serum GPC-4 levels were not significant. Serum GPLD1 levels were negatively correlated with insulin levels and HOMA-IS (both p < 0.001). This study suggests that endurance training and CFE may downregulate serum GPLD1 levels in STZ-NA-induced diabetic rats, which associate with the serum insulin profile. However, the results show that endurance training and CFE may not cause serum GPC-4 adaptation in STZ-NA-induced diabetic rats.

Purification, Characterization and Vaccine Potential of Trypanosoma brucei brucei Glycosyl Phosphatidyl Inositol Specific Phospholipase C

Aims: To investigate possible use of Glycosylphosphatidylinositol-specific phospholipase C (GPIPLC) as a target protein for the development of vaccine against Trypanosoma brucei brucei infection was investigated. Study Design: GPI-PLC from T. brucei brucei was purified, characterized and the protein was used as antigen in raising antibody against the parasite

GPI-PLD inhibits the growth of hepatoma cells by down-regulation of PI3K-Akt signaling pathway

To clarify the effect of glycosylphosphatidylinositol-specific phospholipase D (GPIPLD) on hepatoma cells HepG2 and the possible molecular mechanism. MTT, fluorescent staining and Western blot were applied to analyze the effect and molecular mechanism of GPI-PLD on hepatoma cells by transfected high expression GPI-PLD model. We inoculated HepG2 in nude mice models to further clarify the effect of GPI-PLD on hepatoma cells in vivo. Compared with the control groups, PI3K-Akt signaling pathway activity and proliferation of hepatoma cells were significantly inhibited in the GPI-PLD group. Nude mice models showed that the tumor growth and tumor weight [(1.87 ± 0.09) g] of the GPI-PLD group were significantly less than those of the blank control group [(2.20 ± 0.17) g] and the negative control group [(2.15 ± 0.09) g]. AST, ALT and AFP serum concentration in the GPI-PLD group were significantly lower than those of the control groups (P<0.05). GPI-PLD can inhibit the proliferation of hepatoma cells and growth in vivo, and promote the apoptosis of hepatoma cells by reducing the activity of PI3K-Akt signaling pathway.

Discovery of a Novel Circulating Biomarker in Patients with Abdominal Aortic Aneurysm: A Pilot Study Using a Proteomic Approach

Abdominal aortic aneurysm (AAA) is a common condition with high mortality when ruptured. Most clinicians agree that small AAAs are best managed by ultrasonographic surveillance. However, it has been stated in recent reviews that a serum/plasma biomarker that predicts AAA rupture risk would be a powerful tool in stratifying patients with small AAA. Identification of such circulating biomarkers has been to date unsuccessful. In this study, we used a proteomic approach to find new, potential plasma AAA biomarker candidates. Prefractionated plasma samples were analyzed by two-dimensional differential in-gel electrophoresis to identify differentially expressed proteins between four patients with small AAA and four controls without aneurysm. Protein spots that differed significantly between patients and controls were selected and identified by mass spectrometry. Three protein spots had significantly different expression between patients and controls. The most interesting finding was that patients with small AAA had increased levels of the enzyme glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) compared with the controls without aneurysm. In conclusion, by using a proteomic approach, this pilot-study provides evidence of GPI-PLD as a novel potential plasma biomarker for AAA.

Genetic variation of GPLD1 associates with serum GPI-PLD levels: A preliminary study

HDL is a heterogeneous mixture of lipoprotein particles varying in composition, size, and function. We and others have described a small (7.0nm), minor (0.1% of total apolipoprotein AI) particle containing apolipoprotein AI, AIV and glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) in humans the function of which is not entirely known. Circulating GPI-PLD levels are regulated by multiple factors including genetics. To determine if genetic variation in GPLD1 affects circulating GPI-PLD levels, we examined the relationship between 32 SNPS upstream, within, and downstream of GPLD1 and circulating GPI-PLD levels in Caucasians (n=77) and African-Americans (n=99). The genotype distribution among races differed at 13 SNPs. Nine SNPS were associated with circulating GPI-PLD levels in Caucasians but not African-Americans. These results suggest that genetic variation of GPLD1 appears to associate with circulating GPI-PLD levels. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945–2010).

Regulation of carcinoembryonic antigen release from colorectal cancer cells

Clinical and experimental evidence suggest that circulating carcinoembryonic antigen (CEA) released from tumor cells has an instrumental role in colorectal cancer-liver metastasis. However, the precise mechanism of the regulation of the CEA release from cancer cells is not known. We investigated if the rate of CEA and another GPI-anchored protein, alkaline phosphatase (AP) release is correlated with cellular glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) expression. We also evaluated the effects of phosphatidic acid (PA), a compound known to inhibit GPI-PLD activity, on the CEA and AP release from colon cancer cells. The expression of CEA, GPI-PLD, and AP in five colon carcinoma cells (LS180, Caco2, SW742, SW1116, and HT29/219) was verified by immunoblot and real-time RT-PCR analysis. The amounts of CEA and AP released into cell culture media were determined using ELISA and a colorimetric assay, respectively. We examined the effects of PA (20-100μM) on CEA and AP release from LS180 cells. All five cancer cell lines analyzed expressed GPI-PLD protein. While there was a positive relationship between AP release and the levels of GPI-PLD transcript expression, we found no direct correlation between CEA released from cancer cells and the GPI-PLD mRNA expression level. However, the rate of CEA release was positively associated with the level of CEA transcript expression. In comparison to controls, the release of GPI-anchored CEA and AP, but not CA19-9 was inhibited significantly by both crude and pure phosphatidic acid (by 56 and 54.5%, respectively). Using PA for inhibiting CEA release from cancer cells may have therapeutic application in preventing CRC-liver metastasis.