Insulin resistance and cardiovascular disease.

Insulin resistance (IR) and cardiovascular disease (CVD) represent two universal public health hazards, especially in today's Western societies. A causal-effect relationship has been established that links IR with CVD. The mediating mechanisms are perplexing, under ongoing, rigorous investigation and remain to be fully elucidated. IR is a condition encompassing hyperglycemia and compensatory hyperinsulinemia. It occurs when insulin is not capable of exerting its maximum effects on target tissues, including skeletal muscles, liver and adipose tissue. This alteration of insulin signaling pathways results in the development of cardiometabolic disorders, including obesity, dyslipidemia, low-grade inflammation, endothelial dysfunction and hypertension, all of which are predisposing factors for atherosclerosis and CVD. The management of IR can be achieved through dietary modifications, the inclusion of regular exercise routines in everyday life, pharmacological agents and other interventions tailored to each individual patient's needs. It is important to underline though that, although various antidiabetic drugs that may improve IR are available, no medications are as yet specifically approved for the treatment of IR. This narrative review will focus on the current scientific and clinical evidence pertaining to IR, the mechanisms connecting IR with CVD, as well as plausible strategies for a holistic, personalized approach for IR management.

The Triglyceride/High-Density Lipoprotein Cholesterol (TG/HDL-C) Ratio as a Risk Marker for Metabolic Syndrome and Cardiovascular Disease.

Atherosclerosis is an immunoinflammatory pathological procedure in which lipid plaques are formed in the vessel walls, partially or completely occluding the lumen, and is accountable for atherosclerotic cardiovascular disease (ASCVD). ACSVD consists of three components: coronary artery disease (CAD), peripheral vascular disease (PAD) and cerebrovascular disease (CCVD). A disturbed lipid metabolism and the subsequent dyslipidemia significantly contribute to the formation of plaques, with low-density lipoprotein cholesterol (LDL-C) being the main responsible factor. Nonetheless, even when LDL-C is well regulated, mainly with statin therapy, a residual risk for CVD still occurs, and it is attributable to the disturbances of other lipid components, namely triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C). Increased plasma TG and decreased HDL-C levels have been associated with metabolic syndrome (MetS) and CVD, and their ratio, TG/HDL-C, has been proposed as a novel biomarker for predicting the risk of both clinical entities. Under these terms, this review will present and discuss the current scientific and clinical data linking the TG/HDL-C ratio with the presence of MetS and CVD, including CAD, PAD and CCVD, in an effort to prove the value of the TG/HDL-C ratio as a valuable predictor for each aspect of CVD.

Expanding the Molecular Disturbances of Lipoproteins in Cardiometabolic Diseases: Lessons from Lipidomics.

The increasing global burden of cardiometabolic diseases highlights the urgent clinical need for better personalized prediction and intervention strategies. Early diagnosis and prevention could greatly reduce the enormous socio-economic burden posed by these states. Plasma lipids including total cholesterol, triglycerides, HDL-C, and LDL-C have been at the center stage of the prediction and prevention strategies for cardiovascular disease; however, the bulk of cardiovascular disease events cannot be explained sufficiently by these lipid parameters. The shift from traditional serum lipid measurements that are poorly descriptive of the total serum lipidomic profile to comprehensive lipid profiling is an urgent need, since a wealth of metabolic information is currently underutilized in the clinical setting. The tremendous advances in the field of lipidomics in the last two decades has facilitated the research efforts to unravel the lipid dysregulation in cardiometabolic diseases, enabling the understanding of the underlying pathophysiological mechanisms and identification of predictive biomarkers beyond traditional lipids. This review presents an overview of the application of lipidomics in the study of serum lipoproteins in cardiometabolic diseases. Integrating the emerging multiomics with lipidomics holds great potential in moving toward this goal.

Effect of Clinical and Laboratory Parameters on HDL Particle Composition.

The functional status of High-Density Lipoprotein (HDLs) is not dependent on the cholesterol content but is closely related to structural and compositional characteristics. We reported the analysis of HDL lipidome in the healthy population and the influence of serum lipids, age, gender and menopausal status on its composition. Our sample comprised 90 healthy subjects aged between 30 and 77 years. HDL lipidome was investigated by Nuclear Magnetic Resonance (NMR) spectroscopy. Among serum lipids, triglycerides, apoAI, apoB and the ratio HDL-C/apoAI had a significant influence on HDL lipid composition. Aging was associated with significant aberrations, including an increase in triglyceride content, lysophosphatidylcholine, free cholesterol, and a decrease in esterified cholesterol, phospholipids, and sphingomyelin that may contribute to increased cardiovascular risk. Aging was also associated with an atherogenic fatty acid pattern. Changes occurring in the HDL lipidome between the two genders were more pronounced in the decade from 30 to 39 years of age and over 60 years. The postmenopausal group displayed significant pro-atherogenic changes in HDLs compared to the premenopausal group. The influence of serum lipids and intrinsic factors on HDL lipidome could improve our understanding of the remodeling capacity of HDLs directly related to its functionality and antiatherogenic properties, and also in appropriate clinical research study protocol design. These data demonstrate that NMR analysis can easily follow the subtle alterations of lipoprotein composition due to serum lipid parameters.

A Study of the Metabolic Pathways Affected by Gestational Diabetes Mellitus: Comparison with Type 2 Diabetes.

BACKGROUND: Gestational diabetes mellitus (GDM) remains incompletely understood and increases the risk of developing Diabetes mellitus type 2 (DM2). Metabolomics provides insights etiology and pathogenesis of disease and discovery biomarkers for accurate detection. Nuclear magnetic resonance (NMR) spectroscopy is a key platform defining metabolic signatures in intact serum/plasma. In the present study, we used NMR-based analysis of macromolecules free-serum to accurately characterize the altered metabolic pathways of GDM and assessing their similarities to DM2. Our findings could contribute to the understanding of the pathophysiology of GDM and help in the identification of metabolomic markers of the disease. METHODS: Sixty-two women with GDM matched with seventy-seven women without GDM (control group). 1H NMR serum spectra were acquired on an 11.7 T Bruker Avance DRX NMR spectrometer. RESULTS: We identified 55 metabolites in both groups, 25 of which were significantly altered in the GDM group. GDM group showed elevated levels of ketone bodies, 2-hydroxybutyrate and of some metabolic intermediates of branched-chain amino acids (BCAAs) and significantly lower levels of metabolites of one-carbon metabolism, energy production, purine metabolism, certain amino acids, 3-methyl-2-oxovalerate, ornithine, 2-aminobutyrate, taurine and trimethylamine N-oxide. CONCLUSION: Metabolic pathways affected in GDM were beta-oxidation, ketone bodies metabolism, one-carbon metabolism, arginine and ornithine metabolism likewise in DM2, whereas BCAAs catabolism and aromatic amino acids metabolism were affected, but otherwise than in DM2.

Omics Analysis of Chemoresistant Triple Negative Breast Cancer Cells Reveals Novel Metabolic Vulnerabilities.

The emergence of drug resistance in cancer poses the greatest hurdle for successful therapeutic results and is associated with most cancer deaths. In triple negative breast cancer (TNBC), due to the lack of specific therapeutic targets, systemic chemotherapy is at the forefront of treatments, but it only benefits a fraction of patients because of the development of resistance. Cancer cells may possess an innate resistance to chemotherapeutic agents or develop new mechanisms of acquired resistance after long-term drug exposure. Such mechanisms involve an interplay between genetic, epigenetic and metabolic alterations that enable cancer cells to evade therapy. In this work, we generated and characterized a chemoresistant TNBC cell line to be used for the investigation of mechanisms that drive resistance to paclitaxel. Transcriptomic analysis highlighted the important role of metabolic-associated pathways in the resistant cells, prompting us to employ 1H-NMR to explore the metabolome and lipidome of these cells. We identified and described herein numerous metabolites and lipids that were significantly altered in the resistant cells. Integrated analysis of our omics data revealed MSMO1, an intermediate enzyme of cholesterol biosynthesis, as a novel mediator of chemoresistance in TNBC. Overall, our data provide a critical insight into the metabolic adaptations that accompany acquired resistance in TNBC and pinpoint potential new targets.

Progressive, Qualitative, and Quantitative Alterations in HDL Lipidome from Healthy Subjects to Patients with Prediabetes and Type 2 Diabetes.

Prediabetes is a clinically silent, insulin-resistant state with increased risk for the development of type 2 diabetes (T2D) and cardiovascular disease (CVD). Since glucose homeostasis and lipid metabolism are highly intersected and interrelated, an in-depth characterization of qualitative and quantitative abnormalities in lipoproteins could unravel the metabolic pathways underlying the progression of prediabetes to T2D and also the proneness of these patients to developing premature atherosclerosis. We investigated the HDL lipidome in 40 patients with prediabetes and compared it to that of 40 normoglycemic individuals and 40 patients with established T2D using Nuclear Magnetic Resonance (NMR) spectroscopy. Patients with prediabetes presented significant qualitative and quantitative alterations, potentially atherogenic, in HDL lipidome compared to normoglycemic characterized by higher percentages of free cholesterol and triglycerides, whereas phospholipids were lower. Glycerophospholipids and ether glycerolipids were significantly lower in prediabetic compared to normoglycemic individuals, whereas sphingolipids were significantly higher. In prediabetes, lipids were esterified with saturated rather than unsaturated fatty acids. These changes are qualitatively similar, but quantitatively milder, than those found in patients with T2D. We conclude that the detailed characterization of the HDL lipid profile bears a potential to identify patients with subtle (but still proatherogenic) abnormalities who are at high risk for development of T2D and CVD.

Environmental Factors Modifying HDL Functionality.

BACKGROUND: Currently, it has been recognized that High-Density Lipoprotein (HDL) functionality plays a much more essential role in protection from atherosclerosis than circulating HDLcholesterol (HDL-C) levels per se. Cholesterol efflux capacity (CEC) from macrophages to HDL has been shown to be a key metric of HDL functionality. Thus, quantitative assessment of CEC may be an important tool for the evaluation of HDL functionality, as improvement of HDL function may lead to a reduction of the risk for Cardiovascular disease (CVD). INTRODUCTION: Although the cardioprotective action of HDLs is exerted mainly through their involvement in the reverse cholesterol transport (RCT) pathway, HDLs have also important anti-inflammatory, antioxidant, antiaggregatory and anticoagulant properties that contribute to their favorable cardiovascular effects. Certain genetic, pathophysiologic, disease states and environmental conditions may influence the cardioprotective effects of HDL either by inducing modifications in lipidome and/or protein composition, or in the enzymes responsible for HDL metabolism. On the other hand, certain healthy habits or pharmacologic interventions may actually favorably affect HDL functionality. METHODS: The present review discusses the effects of environmental factors, including obesity, smoking, alcohol consumption, dietary habits, various pharmacologic interventions, as well as aerobic exercise, on HDL functionality. RESULTS: Experimental and clinical studies or pharmacological interventions support the impact of these environmental factors in the modification of HDL functionality, although the involved mechanisms are not fully understood. CONCLUSION: Further research should be conducted to identify the underlying mechanisms of these environmental factors and to identify new pharmacologic interventions capable of enhancing CEC, improving HDL functionality and potentially improving cardiovascular risk.

Altered RBC membrane lipidome: A possible etiopathogenic link for the microvascular impairment in Type 2 diabetes.

AIMS: Disturbances in red blood cells' (RBCs) membrane structure, that result in altered rheological properties, have been implicated in the pathogenesis of microvascular complications of diabetes mellitus(T2DM). However, the compositional alterations in RBCs membranes of T2DM patients have not been characterized in detail. METHODS: NMR-based lipidomic approach used for the global investigation of the lipidome of RBCs membrane in 20 newly diagnosed T2DM patients. Twenty healthy individuals served as controls. RESULTS: In the lipidomic analysis, the discrimination power among the two groups was of high significance. T2DM patients characterized by an increased content of cholesterol, total sphingolipids, sphingomyelin and glycolipids, and decreased total phospholipids, mainly due to phosphatidylethanolamine, total ether glycerolipids and plasmalogen-phospholipids, and higher cholesterol-to-phospholipids molecular ratio compared to controls. In T2DM, lipids were esterified with saturated rather than unsaturated fatty acids, an atherogenic pattern that may be involved in the impairment of membrane fluidity and rigidity. CONCLUSIONS: NMR-based lipidomic analysis of RBCs can provide insights into molecular lipid features of membrane microenvironment that influence their vital function and rheological behavior in microvascular network in T2DM.Early identification of these disturbances, even before the onset of diabetes, could critically help to the development of novel preventative and curative therapies for reducing the risk of microvascular dysfunction.

Early Signs of Atherogenic Features in the HDL Lipidomes of Normolipidemic Patients Newly Diagnosed with Type 2 Diabetes.

Cardiovascular disease (CVD) is the major cause of death in patients with type-2 diabetes mellitus (T2DM), although the factors that accelerate atherosclerosis in these patients are poorly understood. The identification of the altered quantity and quality of lipoproteins, closely related to atherogenesis, is limited in routine to a pattern of high triglycerides and low HDL-cholesterol (HDL-C) and in research as dysfunctional HDLs. We used the emerging NMR-based lipidomic technology to investigate compositional features of the HDLs of healthy individuals with normal coronary arteries, drug-naïve; recently diagnosed T2DM patients with normal coronary arteries; and patients with recent acute coronary syndrome. Patients with T2DM and normal serum lipid profiles even at diagnosis presented significant lipid alterations in HDL, characterized by higher triglycerides, lysophosphatidylcholine and saturated fatty acids; and lower cholesterol, phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, plasmalogens and polyunsaturated fatty acids, an atherogenic pattern that may be involved in the pathogenesis of atherosclerosis. These changes are qualitatively similar to those found, more profoundly, in normolipidemic patients with established Coronary Heart Disease (CHD). We also conclude that NMR-based lipidomics offer a novel holistic exploratory approach for identifying and quantifying lipid species in biological matrixes in physiological processes and disease states or in disease biomarker discovery.

Lipidomics in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disorder in Western countries, comprises steatosis to nonalcoholic steatohepatitis (NASH), with the latter having the potential to progress to cirrhosis. The transition from isolated steatosis to NASH is still poorly understood, but lipidomics approach revealed that the hepatic lipidome is extensively altered in the setting of steatosis and steatohepatitis and these alterations correlate with disease progression. Recent data suggest that both quantity and quality of the accumulated lipids are involved in pathogenesis of NAFLD. Changes in glycerophospholipid, sphingolipid, and fatty acid composition have been described in both liver biopsies and plasma of patients with NAFLD, implicating that specific lipid species are involved in oxidative stress, inflammation, and cell death. In this article, we summarize the findings of main human lipidomics studies in NAFLD and delineate the currently available information on the pathogenetic role of each lipid class in lipotoxicity and disease progression.

Lipidome of plasma lipoproteins and liver is zinc- modulated in High fat diet treated mice.

Zinc (Zn) and Zn-transcription Factors regulate the metabolic pathways of lipids and glucose, consequently nutritional zinc deficiency or excess, activates stress pathways and deranges the hepatic metabolism of lipids. High fat diet (HFD) also leads to lipids' profile disorders as well as to intracellular free radicals (FR) accumulation and finally to metabolic stress-syndrome. Study of nutritional Zn effects on the lipidome of plasma lipoproteins and liver, in HFD-mice, was the aim of the present research. Three Zn enriched HF-Diets as follows, 3 mg/kg feed (Zn deficient diet), 30 mg/kg feed (Zn sufficient diet), 300mgZn /kg feed (Zn excess diet) (Mucedola s.r.l Italy-55% cal) were applied respectively to three groups of male wild type (wt) mice (Hybrid F1/F1),C57Bl/6xCBA, one month old, for 10 weeks. Accordingly, mice body weight rate and 1H-NMR spectrum analysis of liver extracts and plasma HDL and non-HDL lipoproteins were evaluated at the end of the experimental period. It is concluded that Zn sufficient diet (30 mg/Kg Feed) creates a highly protective lipidomic profile on plasma and liver lipoproteins of HFD-mice, related to significantly increased antiatherogenic indicators in lipids' composition, compared to mice in nutritional Zn deficiency or excess.

NMR-Based Lipid Profiling of High Density Lipoprotein Particles in Healthy Subjects with Low, Normal, and Elevated HDL-Cholesterol.

Recent studies suggest that the cholesterol content of HDL (high density lipoproteins) may provide limited information on their antiatherogenic properties and that the composition and particles' structure provide more information on their functionality. We used NMR-based (nuclear magnetic resonance-based) lipidomics to study the relationships of serum HDL-C (HDL-cholesterol) levels with the lipid composition of HDL particles in three groups of subjects selected on the basis of their HDL-C levels. Subjects with low and high HDL-C levels exhibited differences in HDL lipidome compared to those with normal HDL-C levels. In pattern recognition analysis, the discrimination power among all groups was of high significance. The low HDL-C group presented enrichment of the core in triglycerides and depletion in cholesterol esters, whereas the high HDL-C group showed a decrease in triglycerides content. Additionally, as HDL-C increases, all lipid classes are esterified with higher percentage of unsaturated than saturated fatty acids. In addition to the aforementioned differences, the surface layer is enriched in sphingomyelin and free cholesterol in the high HDL-C level group. NMR-based lipidomic analysis of HDL can be particularly useful since it provides insights into molecular features and helps in the characterization of the atheroprotective function of HDL lipoproteins and in the identification of novel biomarkers of cardiovascular risk.

NMR-based lipidomic analysis of blood lipoproteins differentiates the progression of coronary heart disease.

Abnormal lipid composition and metabolism of plasma lipoproteins play a crucial role in the pathogenesis of coronary heart disease (CHD). A (1)H NMR-based lipidomic approach was used to investigate the correlation of coronary artery stenosis with the atherogenic (non-HDL) and atheroprotective (HDL) lipid profiles in 99 patients with CHD of various stages of disease and compared with 60 patients with normal coronary arteries (NCA), all documented in coronary angiography. The pattern recognition models created from lipid profiles predicted the presence of CHD with a sensitivity of 87% and a specificity of 88% in the HDL model and with 90% and 89% in the non-HDL model, respectively. Patients with mild, moderate, and severe coronary artery stenosis were progressively differentiated from those with NCA in the non-HDL model with a statistically significant separation of severe stage from both mild and moderate. In the HDL model, the progressive differentiation of the disease stages was statistically significant only between patients with mild and severe coronary artery stenosis. The lipid constituents of lipoproteins that mainly characterized the initial stages and then the progression of the disease were the high levels of saturated fatty acids in lipids in both HDL and non-HDL particles, the low levels of HDL-phosphatidylcholine, HDL-sphingomyelin, and omega-3 fatty acids and linoleic acid in lipids in non-HDL particles. The conventional lipid marker, total cholesterol, found in low levels in HDL and in high levels in non-HDL, also contributed to the onset of the disease but with a much lower coefficient of significance. (1)H NMR-based lipidomic analysis of atherogenic and atheroprotective lipoproteins could contribute to the early evaluation of the onset of coronary artery disease and possibly to the establishment of an appropriate therapeutic option.

Effects of rosuvastatin combined with olmesartan, irbesartan, or telmisartan on indices of glucose metabolism in Greek adults with impaired fasting glucose, hypertension, and mixed hyperlipidemia: a 24-week, randomized, open-label, prospective study.

BACKGROUND: Statin therapy has been reported to be associated with new-onset diabetes. Angiotensin II-receptor blockers (ARBs) are effective antihypertensive drugs that have been reported to activate peroxisome proliferator-activated receptor gamma (PPARgamma) to differing extents, with favorable effects on glucose metabolism and the incidence of new-onset diabetes. Among the ARBs, telmisartan is a partial activator of PPARgamma, irbesartan is a weak partial activator, and olmesartan has no effect on PPARgamma activation. OBJECTIVE: The goal of this study was to evaluate the effects on glucose homeostasis of combining rosuvastatin with ARBs of varying PPARgamma-activating potency in Greek adults with impaired fasting glucose, mixed dyslipidemia, and stage 1 hypertension. METHODS: This was a 24-week, randomized, open-label study. Inclusion criteria were impaired fasting plasma glucose (FPG) (100-125 mg/dL [5.6-6.9 mmol/L]), mixed dyslipidemia (LDL-C >160 mg/dL [4.14 mmol/L] and triglycerides >150 mg/dL [1.69 mmol/L]), and stage 1 hypertension (systolic blood pressure 140-159 mm Hg and/or diastolic blood pressure 90-99 mm Hg). After 12 weeks of dietary intervention, patients were randomly allocated to receive rosuvastatin 10 mg/d plus telmisartan 80 mg/d (RT group), irbesartan 300 mg/d (RI group), or olmesartan 20 mg/d (RO group) for 24 weeks. The primary end point was change in the following indices of glucose metabolism after 6 months of treatment: FPG, homeostasis model assessment of insulin resistance (HOMA-IR), HOMA of beta-cell function (HOMA-B), and glycosylated hemoglobin (HbA(1c)). Secondary end points included changes in anthropometric variables, blood pressure, serum lipids, and high-sensitivity C-reactive protein (hs-CRP). Tolerability was monitored throughout the study. RESULTS: After the 12-week dietary intervention, 151 white patients (78 female, 73 male) met the inclusion criteria and were randomized to receive RT (n = 52), RI (n = 48), or RO (n = 51). The mean (SD) age of the 3 groups was 60 (10), 60 (10), and 58 (12) years, respectively; their mean weight was 79 (11), 81 (12), and 78 (11) kg. At 6 months, the RT group had a 29% decrease in HOMA-IR (from a median [range] of 2.6 [0.6-6.6] to 1.8 [0.5-5.1]), the RI group had a 16% increase (from 2.5 [0.5-6.2] to 2.9 [0.5-8.1]), and the RO group had a 14% increase (from 2.4 [0.5-7.9] to 2.7 [0.5-5.2]) (all, P < 0.05 vs baseline). The improvement in the RT group was statistically significant compared with the RI group (P < 0.01) and the RO group (P < 0.05). The changes from baseline in FPG and HbA(1c) were not significant in any group. Fasting serum insulin decreased by 21% in the RT group (from 10.4 [2.4-28.1] to 8.2 [2.4-18.8] microU/mL), whereas it increased by 12% in the RI group (from 9.1 [2.0-26.5] to 10.2 [2.0-25.2] microU/mL) and by 8% in the RO group (from 10.1 [2.0-29.6] to 10.9 [2.0-19.1] microU/mL) (all, P < 0.05 vs baseline). Again, there was a significant difference between the RT group and the RI group (P < 0.01) and RO group (P < 0.05). Levels of hs-CRP decreased by 44% in the RT group (from 2.2 [0.3-7.9] to 1.2 [0.4-7.0] mg/L), by 12% in the RI group (from 2.2 [0.3-12.3] to 1.9 [0.2-11.4] mg/L), and by 22% in the RO group (from 2.1 [0.7-4.0] to 1.7 [0.7-6.2] mg/L). The difference was statistically significant for the RT group compared with baseline and with the RI and RO groups (all comparisons, P < 0.05). Blood pressure was significantly reduced from baseline in all 3 groups, with no significant differences between groups. No serious adverse events were reported during the study, nor were there any clinically significant elevations in aminotransferases or creatine kinase. CONCLUSION: In this small, randomized, open-label study, the RT combination had favorable effects on HOMA-IR, fasting serum insulin, and hs-CRP compared with the RI and RO combinations in Greek adults with impaired fasting glucose, mixed hyperlipidemia, and stage 1 hypertension.

Evaluation of established coronary heart disease on the basis of HDL and non-HDL NMR lipid profiling.

A (1)H NMR-based lipid profiling approach was used to investigate the prediction of coronary heart disease (CHD) and examine the confounding effect of factors such as gender, triglycerides, HDL-cholesterol and age levels on the prediction of disease. The HDL and non-HDL lipid profiles in 47 patients with triple vessel disease (TVD) and 41 patients with normal coronary arteries (NCA) both documented angiographically were generated. The presence of CHD was predicted with a sensitivity and specificity of 52% and 75% for HDL model and 78% and 80% for non-HDL, respectively. The lipid constituents of HDL lipoproteins which contributed to the separation between the two groups were the saturated fatty acids, cholesterol, total omega-3 fatty acids, degree of unsaturation, diallylic protons from polyunsaturated fatty acids, linoleic acid and, to a lesser extent, the number of fatty acids, triglycerides, unsaturated fatty acids and phosphatidylcholine. Respectively, for non-HDL, lipoproteins were the saturated fatty acids, number of fatty acids, cholesterol, unsaturated fatty acids and phosphatidylcholine. Gender, triglycerides, HDL-cholesterol and age influenced the lipid constituents of HDL and non-HDL lipoproteins that contributed to the separation between subgroups and confounded the predictive power of the models. NMR-based lipid profiling analysis could contribute to the identification of noninvasive markers for the presence and the development of the disease.

Evaluation of the proximal tubular function in individuals with primary renal hypouricemia: an NMR-based metabonomic study.

Primary renal hypouricemia (PRH) refers to a rare condition of increased renal urate clearance, caused by an isolated inborn error of membrane transport of urate in the renal proximal tubule. Several cases of exercise-induced acute renal failure and urolithiasis have been reported. This is the first study that assessed tubular function in PRH using NMR-based metabonomic urine analysis. The study groups consisted of 36 unrelated asymptomatic subjects with PRH, defined as serum uric acid levels (sUA) <2.5 mg/dL and fractional excretion of uric acid (FEUA) >10%, after exclusion of diseases and drugs that may affect urate homeostasis, and 39 sex and age-matched healthy individuals with normal sUA levels (>4.0 mmol/L) and FEUA<10%. Individuals with primary hypouricemia presented similar biochemical profiles to the controls without significant differences with regard to FE of electrolytes and renal threshold for phosphate excretion. Individuals with primary hypouricemia were differentiated from healthy individuals in the orthogonal signal correction/partial least-squares-discriminant analysis models of the NMR data with a statistically significant separation. The components that contributed to this separation were the lower levels of hippurate, creatinine, and trimethylaminoxide, and the higher levels of phenylalanine, alanine, glycine, glutamate, acetate, and of an unidentified metabolite (3.3 ppm) observed in hypouricemic subjects compared with controls. Primary hypouricemia, though considered an isolated renal tubular defect, is often associated with a more generalized proximal tubular disorder that mimics a partial Fanconi syndrome.