O-glycan structures in apo(a) subunit of human lipoprotein(a) suppresses the pro-angiogenic activity of galectin-1 on human umbilical vein endothelial cells.

Apolipoprotein(a) [apo(a)] is a highly polymorphic O-glycoprotein circulating in human plasma as lipoprotein(a) [Lp(a)]. The O-glycan structures of apo(a) subunit of Lp(a) serve as strong ligands of galectin-1, an O-glycan binding pro-angiogenic lectin abundantly expressed in placental vascular tissues. But the pathophysiological significance of apo(a)-galectin-1 binding is not yet been revealed. Carbohydrate-dependent binding of galectin-1 to another O-glycoprotein, neuropilin-1 (NRP-1) on endothelial cells activates vascular endothelial growth factor receptor 2 (VEGFR2) and mitogen-activated protein kinase (MAPK) signaling. Using apo(a), isolated from human plasma, we demonstrated the potential of the O-glycan structures of apo(a) in Lp(a) to inhibit angiogenic properties such as proliferation, migration, and tube-formation in human umbilical vein endothelial cells (HUVECs) as well as neovascularization in chick chorioallantoic membrane. Further, in vitro protein-protein interaction studies have confirmed apo(a) as a superior ligand to NRP-1 for galectin-1 binding. We also demonstrated that the protein levels of galectin-1, NRP-1, VEGFR2, and downstream proteins in MAPK signaling were reduced in HUVECs in the presence of apo(a) with intact O-glycan structures compared to that of de-O-glycosylated apo(a). In conclusion, our study shows that apo(a)-linked O-glycans prevent the binding of galectin-1 to NRP-1 leading to the inhibition of galectin-1/neuropilin-1/VEGFR2/MAPK-mediated angiogenic signaling pathway in endothelial cells. As higher plasma Lp(a) level in women is an independent risk factor for pre-eclamsia, a pregnancy-associated vascular complication, we propose that apo(a) O-glycans-mediated inhibition of the pro-angiogenic activity of galectin-1 may be one of the underlying molecular mechanism of pathogenesis of Lp(a) in pre-eclampsia.

Hyperhomocysteinemia-related serum metabolome alterations not normalized by short-term folic acid treatment.

INTRODUCTION: Hyperhomocysteinemia (HHCys) is an independent risk factor for various diseases such as cardiovascular diseases, Alzheimer's, and cancers. Folate deficiency is one of the significant reasons for HHCys. However, it is not known whether folate deficiency with HHCys is associated with any serum metabolites. OBJECTIVES: Our objective was to identify the metabolic alterations in people having folate deficiency with HHCys and check whether a short-term folic acid therapy could reverse those metabolic changes. METHODS: The study enrolled 34 participants aged between 18 and 40 years having folate deficiency (< 4.6 ng/mL) with HHCys (> 15 µmol/L) and 21 normal healthy individuals. A short-term intervention of oral folic acid (5 mg/day) was done in the HHCys group for 30 days. Untargeted metabolomics analysis of serum was performed in all study subjects before and after the folic acid treatment. Different univariate methods and the multivariable-adjusted linear regression models were employed to determine an association between homocysteine level and metabolite profile. RESULTS: Metabolomics analysis data showed that many metabolites involved in the biochemical pathways of lipid metabolisms such as polyunsaturated fatty acids, glycerolipids, and phospholipids were downregulated in the HHCys group. Short-term oral folic acid therapy significantly reduced their serum homocysteine level. However, the metabolic pathway alterations observed in folate-deficient HHCys-condition were unaltered even after the folic acid treatment. CONCLUSIONS: Our study revealed that people who have a folic acid deficiency with HHCys have an altered metabolite profile related to lipid metabolism, which cannot be reversed by short-term folic acid therapy.

Plasma leptin level mirrors metabolome alterations in young adults.

INTRODUCTION: Leptin is known to regulate pathways of energy metabolism, reproduction, and control appetite. Whether plasma leptin levels reflect changes in metabolites of these pathways is unknown. OBJECTIVES: We aimed to find whether there is an association between leptin levels and levels of metabolites of energy and hormone metabolism. METHODS: We performed an untargeted metabolomics analysis of plasma from 110 healthy adults (men: women = 1:1; aged 18-40 years), using liquid chromatography-tandem mass spectrometry. Blood samples were collected from all the study subjects in the fasting state. Clinical features and markers of obesity and Type 2 diabetes mellitus (T2DM) were assessed in all. The association between levels of metabolites and clinical and biochemical parameters was identified using the multivariable-adjusted linear regression model and PLS-DA analysis. RESULTS: The leptin level was found to have a significant association with a substantial number of metabolites in women and men. Leptin level was positively associated with glycocholic acid and arachidic acid, metabolites related to energy metabolisms, pregnanediol-3-glucuronide, a metabolite of progesterone metabolism, and quercetin 3'-sulfate, a diet-derived metabolite. Leptin level was negatively associated with ponasteroside A and barringtogenol C levels. Leptin level was positively correlated with adiponectin and negatively with total calorie intake and levels of triglyceride and very-low-density lipoprotein. Leptin levels were associated with lipid and sex hormone metabolism in women, while metabolites involved in amino acid metabolism were correlated to leptin in men. CONCLUSION: Our study indicates that leptin level reflects metabolome alterations and hence could be a useful marker to detect early changes in energy and hormone metabolisms.

Proteomics Analysis Reveals Diverse Molecular Characteristics between Endocardial and Aortic-Valvular Endothelium.

The variations in the protein profile of aortic-valvular (AVE) and endocardial endothelial (EE) cells are currently unknown. The current study's objective is to identify differentially expressed proteins and associated pathways in both the endothelial cells. We used endothelial cells isolated from the porcine (Sus scrofa) aortic valve and endocardium for the profiling of proteins. Label-free proteomics was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Our proteomics analysis revealed that 29 proteins were highly expressed, and 25 proteins were less expressed in the valve than the endocardial endothelium. The cell surface markers, such as CD63, ICAM1, PECAM1, PROCR, and TFRC, were highly expressed in EE. In contrast, CD44 was highly expressed in AVE. The pathway analysis showed that metabolic process-related proteins and extracellular matrix-related proteins were enriched in valves. Differential enrichment of signaling pathways was observed in the endocardium. The hemostasis function-related proteins were increased in both endothelial cells. The proteins and pathways enriched in aortic-valvular and endocardial endothelial cells revealed the distinct phenotype of these two closely related cells.

Metabolomics-Based Prospective Studies and Prediction of Type 2 Diabetes Mellitus Risks.

The preceding decade has witnessed an intense upsurge in the diabetic population across the world making type 2 diabetes mellitus (T2DM) more of an epidemic than a lifestyle disease. Metabolic disorders are often latent for a while before becoming clinically evident, thus reinforcing the pursuit of early biomarkers of metabolic alterations. A prospective study along with metabolic profiling is the most appropriate way to detect the early pathophysiological changes in metabolic diseases such as T2DM. The aim of this review was to summarize the different potential biomarkers of T2DM identified in prospective studies, which used tools of metabolomics. The review also demonstrates on how metabolomic profiling-based prospective studies can be used to address a concern like population-specific disease mechanism. We performed a literature search on metabolomics-based prospective studies on T2DM using the key words "metabolomics," "Type 2 diabetes," "diabetes mellitus", "metabolite profiling," "prospective study," "metabolism," and "biomarker." Additional articles that were obtained from the reference lists of the articles obtained using the above key words were also examined. Articles on dietary intake, type 1 diabetes mellitus, and gestational diabetes were excluded. The review revealed that many studies showed a direct association of branched-chain amino acids and an inverse association of glycine with T2DM. Majority of the prospective studies conducted were targeted metabolomics-based, with Caucasians as their study cohort. The whole disease risk in populations, including Asians, could therefore not be identified. This review proposes the utility of prospective studies in conjunction with metabolomics platform to unravel the altered metabolic pathways that contribute to the risk of T2DM.

Postprandial Metabolism is Impaired in Overweight Normoglycemic Young Adults without Family History of Diabetes.

While the risk factors for Type 2 diabetes (T2DM) are known, early predictive markers of transition from normal to a prediabetes state are unidentified. We studied the basal metabolism and metabolic response to a mixed-meal challenge in 110 healthy subjects in the age group of 18 to 40 years (Male:Female = 1:1); grouped into first degree relatives of patients with T2DM (n = 30), those with a body mass index >23 kg/m2 but <30 kg/m2 (n = 30), those with prediabetes (n = 20) and normal controls (n = 30). We performed an untargeted metabolomics analysis of plasma and related that with clinical and biochemical parameters, markers of inflammation, and insulin sensitivity. Similar to prediabetes subjects, overweight subjects had insulin resistance and significantly elevated levels of C-peptide, adiponectin and glucagon and lower level of ghrelin. Metabolites such as MG(22:2(13Z, 16Z)/0:0/0:0) and LysoPC (15:0) were reduced in overweight and prediabetes subjects. Insulin sensitivity was significantly lower in men. Fasting levels of uric acid, xanthine, and glycochenodeoxycholic-3-glucuronide were elevated in men. However, both lysophospholipids and antioxidant defense metabolites were higher in women. Impaired postprandial metabolism and insulin sensitivity in overweight normoglycemic young adults indicates a risk of developing hyperglycemia. Our results also indicate a higher risk of diabetes in young men.