Urinary Lipidomics: evidence for multiple sources and sexual dimorphism in healthy individuals.

Urinary lipidomics may add new valuable biomarkers to the diagnostic armamentarium for early detection of metabolic and kidney diseases. Sources and composition of urinary lipids in healthy individuals, however, have not been investigated in detail. Shotgun lipidomics was used to quantify lipidomic profiles in native urine samples from 16 individuals (eight men, eight women) collected in five fractions over 24 h. All probands were comprehensively characterized by urinary and clinical indices. The mean total urinary lipid concentration per sample was 0.84 µM in men and 1.03 µM in women. We observed significant intra- and interindividual variations of lipid concentrations over time, but failed to detect a clear circadian pattern. Based on quantity and subclass composition it seems very unlikely that plasma serves as major source for the urinary lipidome. Considering lipid metabolites occurring in at least 20% of all samples 38 lipid species from 7 lipid classes were identified. Four phosphatidylserine and one phosphatidylethanolamine ether species (PE-O 36:5) were detectable in almost all urine samples. Sexual dimorphism has been found mainly for phosphatidylcholines and phosphatidylethanolamines. In men and in women urinary lipid species were highly correlated with urinary creatinine and albumin excretion, reflecting glomerular filtration and tubular transport processes. In women, however, lipid species deriving from urinary cells and cellular constituents of the lower genitourinary tract considerably contributed to the urinary lipidome. In conclusion, our study revealed the potential of urinary lipidomics but also the complexity of methodological challenges which have to be overcome for its implementation as a routine diagnostic tool for renal, urological and metabolic diseases.

A latent genetic subtype of major depression identified by whole-exome genotyping data in a Mexican-American cohort.

Identifying data-driven subtypes of major depressive disorder (MDD) is an important topic of psychiatric research. Currently, MDD subtypes are based on clinically defined depression symptom patterns. Although a few data-driven attempts have been made to identify more homogenous subgroups within MDD, other studies have not focused on using human genetic data for MDD subtyping. Here we used a computational strategy to identify MDD subtypes based on single-nucleotide polymorphism genotyping data from MDD cases and controls using Hamming distance and cluster analysis. We examined a cohort of Mexican-American participants from Los Angeles, including MDD patients (n=203) and healthy controls (n=196). The results in cluster trees indicate that a significant latent subtype exists in the Mexican-American MDD group. The individuals in this hidden subtype have increased common genetic substrates related to major depression and they also have more anxiety and less middle insomnia, depersonalization and derealisation, and paranoid symptoms. Advances in this line of research to validate this strategy in other patient groups of different ethnicities will have the potential to eventually be translated to clinical practice, with the tantalising possibility that in the future it may be possible to refine MDD diagnosis based on genetic data.

The PHF21B gene is associated with major depression and modulates the stress response.

Major depressive disorder (MDD) affects around 350 million people worldwide; however, the underlying genetic basis remains largely unknown. In this study, we took into account that MDD is a gene-environment disorder, in which stress is a critical component, and used whole-genome screening of functional variants to investigate the 'missing heritability' in MDD. Genome-wide association studies (GWAS) using single- and multi-locus linear mixed-effect models were performed in a Los Angeles Mexican-American cohort (196 controls, 203 MDD) and in a replication European-ancestry cohort (499 controls, 473 MDD). Our analyses took into consideration the stress levels in the control populations. The Mexican-American controls, comprised primarily of recent immigrants, had high levels of stress due to acculturation issues and the European-ancestry controls with high stress levels were given higher weights in our analysis. We identified 44 common and rare functional variants associated with mild to moderate MDD in the Mexican-American cohort (genome-wide false discovery rate, FDR, <0.05), and their pathway analysis revealed that the three top overrepresented Gene Ontology (GO) processes were innate immune response, glutamate receptor signaling and detection of chemical stimulus in smell sensory perception. Rare variant analysis replicated the association of the PHF21B gene in the ethnically unrelated European-ancestry cohort. The TRPM2 gene, previously implicated in mood disorders, may also be considered replicated by our analyses. Whole-genome sequencing analyses of a subset of the cohorts revealed that European-ancestry individuals have a significantly reduced (50%) number of single nucleotide variants compared with Mexican-American individuals, and for this reason the role of rare variants may vary across populations. PHF21b variants contribute significantly to differences in the levels of expression of this gene in several brain areas, including the hippocampus. Furthermore, using an animal model of stress, we found that Phf21b hippocampal gene expression is significantly decreased in animals resilient to chronic restraint stress when compared with non-chronically stressed animals. Together, our results reveal that including stress level data enables the identification of novel rare functional variants associated with MDD.

Inflammasome signaling affects anxiety- and depressive-like behavior and gut microbiome composition.

The inflammasome is hypothesized to be a key mediator of the response to physiological and psychological stressors, and its dysregulation may be implicated in major depressive disorder. Inflammasome activation causes the maturation of caspase-1 and activation of interleukin (IL)-1ß and IL-18, two proinflammatory cytokines involved in neuroimmunomodulation, neuroinflammation and neurodegeneration. In this study, C57BL/6 mice with genetic deficiency or pharmacological inhibition of caspase-1 were screened for anxiety- and depressive-like behaviors, and locomotion at baseline and after chronic stress. We found that genetic deficiency of caspase-1 decreased depressive- and anxiety-like behaviors, and conversely increased locomotor activity and skills. Caspase-1 deficiency also prevented the exacerbation of depressive-like behaviors following chronic stress. Furthermore, pharmacological caspase-1 antagonism with minocycline ameliorated stress-induced depressive-like behavior in wild-type mice. Interestingly, chronic stress or pharmacological inhibition of caspase-1 per se altered the fecal microbiome in a very similar manner. When stressed mice were treated with minocycline, the observed gut microbiota changes included increase in relative abundance of Akkermansia spp. and Blautia spp., which are compatible with beneficial effects of attenuated inflammation and rebalance of gut microbiota, respectively, and the increment in Lachnospiracea abundance was consistent with microbiota changes of caspase-1 deficiency. Our results suggest that the protective effect of caspase-1 inhibition involves the modulation of the relationship between stress and gut microbiota composition, and establishes the basis for a gut microbiota-inflammasome-brain axis, whereby the gut microbiota via inflammasome signaling modulate pathways that will alter brain function, and affect depressive- and anxiety-like behaviors. Our data also suggest that further elucidation of the gut microbiota-inflammasome-brain axis may offer novel therapeutic targets for psychiatric disorders.

From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways.

The human body hosts an enormous abundance and diversity of microbes, which perform a range of essential and beneficial functions. Our appreciation of the importance of these microbial communities to many aspects of human physiology has grown dramatically in recent years. We know, for example, that animals raised in a germ-free environment exhibit substantially altered immune and metabolic function, while the disruption of commensal microbiota in humans is associated with the development of a growing number of diseases. Evidence is now emerging that, through interactions with the gut-brain axis, the bidirectional communication system between the central nervous system and the gastrointestinal tract, the gut microbiome can also influence neural development, cognition and behaviour, with recent evidence that changes in behaviour alter gut microbiota composition, while modifications of the microbiome can induce depressive-like behaviours. Although an association between enteropathy and certain psychiatric conditions has long been recognized, it now appears that gut microbes represent direct mediators of psychopathology. Here, we examine roles of gut microbiome in shaping brain development and neurological function, and the mechanisms by which it can contribute to mental illness. Further, we discuss how the insight provided by this new and exciting field of research can inform care and provide a basis for the design of novel, microbiota-targeted, therapies.

Is increased antidepressant exposure a contributory factor to the obesity pandemic?

Major depressive disorder (MDD) and obesity are both common heterogeneous disorders with complex aetiology, with a major impact on public health. Antidepressant prescribing has risen nearly 400% since 1988, according to data from the Centers for Disease Control and Prevention (CDC). In parallel, adult obesity rates have doubled since 1980, from 15 to 30 percent, while childhood obesity rates have more than tripled. Rising obesity rates have significant health consequences, contributing to increased rates of more than thirty serious diseases. Despite the concomitant rise of antidepressant use and of the obesity rates in Western societies, the association between the two, as well as the mechanisms underlying antidepressant-induced weight gain, remain under explored. In this review, we highlight the complex relationship between antidepressant use, MDD and weight gain. Clinical findings have suggested that obesity may increase the risk of developing MDD, and vice versa. Hypothalamic-pituitary-adrenal (HPA) axis activation occurs in the state of stress; concurrently, the HPA axis is also dysregulated in obesity and metabolic syndrome, making it the most well-understood shared common pathophysiological pathway with MDD. Numerous studies have investigated the effects of different classes of antidepressants on body weight. Previous clinical studies suggest that the tricyclics amitriptyline, nortriptyline and imipramine, and the serotonin norepinephrine reuptake inhibitor mirtazapine are associated with weight gain. Despite the fact that selective serotonin reuptake inhibitor (SSRI) use has been associated with weight loss during acute treatment, a number of studies have shown that SSRIs may be associated with long-term risk of weight gain; however, because of high variability and multiple confounds in clinical studies, the long-term effect of SSRI treatment and SSRI exposure on body weight remains unclear. A recently developed animal paradigm shows that the combination of stress and antidepressants followed by long-term high-fat diet results, long after discontinuation of antidepressant treatment, in markedly increased weight, in excess of what is caused by high-fat diet alone. On the basis of existing epidemiological, clinical and preclinical data, we have generated the testable hypothesis that escalating use of antidepressants, resulting in high rates of antidepressant exposure, might be a contributory factor to the obesity epidemic.

The effects of stress on brain and adrenal stem cells.

The brain and adrenal are critical control centers that maintain body homeostasis under basal and stress conditions, and orchestrate the body's response to stress. It is noteworthy that patients with stress-related disorders exhibit increased vulnerability to mental illness, even years after the stress experience, which is able to generate long-term changes in the brain's architecture and function. High levels of glucocorticoids produced by the adrenal cortex of the stressed subject reduce neurogenesis, which contributes to the development of depression. In support of the brain-adrenal connection in stress, many (but not all) depressed patients have alterations in the components of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis, with enlarged adrenal cortex and increased glucocorticoid levels. Other psychiatric disorders, such as post-traumatic stress disorder, bipolar disorder and depression, are also associated with abnormalities in hippocampal volume and hippocampal function. In addition, hippocampal lesions impair the regulation of the LHPA axis in stress response. Our knowledge of the functional connection between stress, brain function and adrenal has been further expanded by two recent, independent papers that elucidate the effects of stress on brain and adrenal stem cells, showing similarities in the way that the progenitor populations of these organs behave under stress, and shedding more light into the potential cellular and molecular mechanisms involved in the adaptation of tissues to stress.

Chronic administration of anticonvulsants but not antidepressants impairs bone strength: clinical implications.

Major depression and bipolar disorder are associated with decreased bone mineral density (BMD). Antidepressants such as imipramine (IMIP) and specific serotonin reuptake inhibitors (SSRIs) have been implicated in reduced BMD and/or fracture in older depressed patients. Moreover, anticonvulsants such as valproate (VAL) and carbamazepine (CBZ) are also known to increase fracture rates. Although BMD is a predictor of susceptibility to fracture, bone strength is a more sensitive predictor. We measured mechanical and geometrical properties of bone in 68 male Sprague Dawley rats on IMIP, fluoxetine (FLX), VAL, CBZ, CBZ vehicle and saline (SAL), given intraperitoneally daily for 8 weeks. Distinct regions were tested to failure by four-point bending, whereas load displacement was used to determine stiffness. The left femurs were scanned in a MicroCT system to calculate mid-diaphyseal moments of inertia. None of these parameters were affected by antidepressants. However, VAL resulted in a significant decrease in stiffness and a reduction in yield, and CBZ induced a decrease in stiffness. Only CBZ induced alterations in mechanical properties that were accompanied by significant geometrical changes. These data reveal that chronic antidepressant treatment does not reduce bone strength, in contrast to chronic anticonvulsant treatment. Thus, decreased BMD and increased fracture rates in older patients on antidepressants are more likely to represent factors intrinsic to depression that weaken bone rather than antidepressants per se. Patients with affective illness on anticonvulsants may be at particularly high risk for fracture, especially as they grow older, as bone strength falls progressively with age.

Plasma leptin concentrations are highly correlated to emotional states throughout the day.

Previous work has shown that leptin appears to regulate the plasma levels of hormones such as adrenocorticotropic hormone (ACTH) and cortisol in humans and that it has antidepressant effects in animals. It is unknown whether fluctuations in circulating leptin levels are correlated to changes in human emotions. This study was conducted to determine whether minute-to-minute fluctuations in the plasma concentrations of human leptin were associated with psychological variables. Leptin was sampled every 7 min throughout the day in 10 healthy subjects (five men and five women) studied in a clinical research center, and visual analog scales were applied every hour. We found highly significant correlations between fluctuations in plasma leptin concentrations and three psychological variables: sadness, carbohydrate craving and social withdrawal. We showed that during the course of the day increases in leptin levels are associated with decreased search for starchy foods, decreased feelings of sadness and increased social withdrawal. Our findings support the hypothesis that during the course of the day as leptin levels increase individuals subjectively feel happier (less sad) and have less inclination to interact socially. Conversely, when leptin levels decrease, we show increases in sadness and social cooperation, which might facilitate the search for food. We suggest that increased human leptin levels may promote positive feelings and that decreased leptin levels might modulate inner states that motivate and facilitate the search for nutrients.

Neutrophil gelatinase-associated lipocalin in dogs with naturally occurring renal diseases.

BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) is released from renal tubular cells after injury and serves in humans as a real-time indicator of active kidney damage, including acute kidney injury (AKI) and chronic kidney disease (CKD). However, NGAL concentrations in dogs with naturally occurring AKI or CKD rarely have been explored in detail. HYPOTHESIS/OBJECTIVES: The goal of this study was to evaluate whether NGAL can serve as a useful biomarker in dogs with naturally occurring renal disease. ANIMALS: Client-owned dogs with renal disease (57) and control dogs without any disease (12) were examined. METHODS: Serum NGAL (sNGAL) and urine NGAL (uNGAL) concentrations were measured in each animal by a newly developed ELISA system. Demographic, hematologic, and serum biochemical data were recorded. Survival attributable to AKI and CKD was evaluated at 30 days and 90 days, respectively. RESULTS: Serum and urine NGAL concentrations in azotemic dogs were significantly higher than in nonazotemic dogs and were highly correlated with serum creatinine concentration (P < .05). Among CKD dogs, death was associated with significantly higher sNGAL and uNGAL concentrations compared with survivors. Receiver-operating characteristic curve (ROC) analysis showed that sNGAL was better than serum creatinine concentration when predicting clinical outcomes for CKD dogs (P < .05). The best cutoff point for sNGAL was 50.6 ng/mL, which gave a sensitivity and a specificity of 76.9 and 100%, respectively. Furthermore, dogs that had higher concentrations of sNGAL survived for a significantly shorter time. CONCLUSION: sNGAL is a useful prognostic marker when evaluating dogs with CKD.

Lipidomic profiling before and after Roux-en-Y gastric bypass in obese patients with diabetes.

Bariatric surgery is a well-established approach to improve metabolic disease in morbidly obese patients with high cardiovascular risk. The post-operative normalization of lipid metabolism has a central role in the prevention of future cardiovascular events. The aim of the present study therefore was to characterize changes of plasma lipidomic patterns, consisting of 229 lipid species of 13 lipid classes, 3 months after Roux-en-Y gastric bypass (RYGB) in morbidly obese patients with and without diabetes. RYGB resulted in a 15-32% decrease of body mass index, which was associated with a significant reduction of total cholesterol (TC, -28.3%; P=0.02), LDL-cholesterol (LDL-C, -26.8%; P=0.03) and triglycerides (TGs, -63.0%; P=0.05) measured by routine clinical chemistry. HDL-cholesterol remained unchanged. The effect of RYGB on the plasma lipidomic profile was characterized by significant decreases of 87 lipid species from triacylglycerides (TAGs), cholesterol esters (CholEs), lysophosphatidylcholines (LPCs), phosphatidylcholines (PCs), phosphatidylethanolamine ethers (PEOs), phosphatidylinositols (PIs) and ceramides (Cers). The total of plasma lipid components exhibited a substantial decline of 32.6% and 66 lipid species showed a decrease by over 50%. A direct correlation with HbA1C values could be demonstrated for 24 individual lipid species (10 TAG, three CholE, two LPC, one lysophosphatidylcholine ethers (LPCO) (LPC ether), one PC, two phosphatidylcholine ethers (PCO) and five Cer). Notably, two lipid species (TAG 58:5 and PEO 40:5) were inversely correlated with HbA1C. LPCO, as single whole lipid class, was directly related to HbA1C. These data indicate that RYGB-induced modulation of lipidomic profiles provides important information about post-operative metabolic adaptations and might substantially contribute to improvements of glycemic control. These striking changes in the human plasma lipidome may explain acute, weight independent and long-term effects of RYGB on the cardiovascular system, mental status and immune regulation.

Metagenomic sequencing of the human gut microbiome before and after bariatric surgery in obese patients with type 2 diabetes: correlation with inflammatory and metabolic parameters.

Roux-en-Y gastric bypass (RYGB) has become a prominent therapeutic option for long-term treatment of morbid obesity and type 2 diabetes mellitus (T2D). Cross talk and pathogenetic consequences of RYGB-induced profound effects on metabolism and gut microbiome are poorly understood. The aim of the present study therefore was to characterize intra-individual changes of gut microbial composition before and 3 months after RYGB by metagenomic sequencing in morbidly obese patients (body mass index (BMI)>40 kg m(-)(2)) with T2D. Subsequently, metagenomic data were correlated with clinical indices. Based on gene relative abundance profile, 1061 species, 729 genera, 44 phyla and 5127 KO (KEGG Orthology) were identified. Despite high diversity, bacteria could mostly be assigned to seven bacterial divisions. The overall metagenomic RYGB-induced shift was characterized by a reduction of Firmicutes and Bacteroidetes and an increase of Proteobacteria. Twenty-two microbial species and 11 genera were significantly altered by RYGB. Using principal component analysis, highly correlated species were assembled into two common components. Component 1 consisted of species that were mainly associated with BMI and C-reactive protein. This component was characterized by increased numbers of Proteobacterium Enterobacter cancerogenus and decreased Firmicutes Faecalibacterium prausnitzii and Coprococcus comes. Functional analysis of carbohydrate metabolism by KO revealed significant effects in 13 KOs assigned to phosphotransferase system. Spearmen's Rank correlation indicated an association of 10 species with plasma total- or low-density lipoprotein cholesterol, and 5 species with triglycerides. F. prausnitzii was directly correlated to fasting blood glucose. This is the first clinical demonstration of a profound and specific intra-individual modification of gut microbial composition by full metagenomic sequencing. A clear correlation exists of microbiome composition and gene function with an improvement in metabolic and inflammatory parameters. This will allow to develop new diagnostic and therapeutic strategies based on metagenomic sequencing of the human gut microbiome.

Prediction of susceptibility to major depression by a model of interactions of multiple functional genetic variants and environmental factors.

Major depressive disorder (MDD) is the most common psychiatric disorder and the second overall cause of disability. Even though a significant amount of the variance in the MDD phenotype is explained by inheritance, specific genetic variants conferring susceptibility to MDD explain only a minimal proportion of MDD causality. Moreover, genome-wide association studies have only identified two small-sized effect loci that reach genome-wide significance. In this study, a group of Mexican-American patients with MDD and controls recruited for a pharmacogenetic study were genotyped for nonsynonymous single-nucleotide polymorphisms (nsSNPs) and used to explore the interactions of multiple functional genetic variants with risk-classification tree analysis. The risk-classification tree analysis model and linkage disequilibrium blocks were used to replicate exploratory findings in the database of genotypes and phenotypes (dbGaP) for major depression, and pathway analysis was performed to explore potential biological mechanisms using the branching events. In exploratory analyses, we found that risk-classification tree analysis, using 15 nsSNPs that had a nominal association with MDD diagnosis, identified multiple increased-MDD genotype clusters and significant additive interactions in combinations of genotype variants that were significantly associated with MDD. The results in the dbGaP for major depression disclosed a multidimensional dependent phenotype constituted of MDD plus significant modifiers (smoking, marriage status, age, alcohol abuse/dependence and gender), which then was used for the association tree analysis. The reconstructed tree analysis for the dbGaP data showed robust reliability and replicated most of the genes involved in the branching process found in our exploratory analyses. Pathway analysis using all six major events of branching (PSMD9, HSD3B1, BDNF, GHRHR, PDE6C and PDLIM5) was significant for positive regulation of cellular and biological processes that are relevant to growth and organ development. Our findings not only provide important insights into the biological pathways underlying innate susceptibility to MDD but also offer a predictive framework based on interactions of multiple functional genetic variants and environmental factors. These findings identify novel targets for therapeutics and for translation into preventive, clinical and personalized health care.