Light-responsive adipose-hypothalamus axis controls metabolic regulation.

Light is fundamental for biological life, with most mammals possessing light-sensing photoreceptors in various organs. Opsin3 is highly expressed in adipose tissue which has extensive communication with other organs, particularly with the brain through the sympathetic nervous system (SNS). Our study reveals a new light-triggered crosstalk between adipose tissue and the hypothalamus. Direct blue-light exposure to subcutaneous white fat improves high-fat diet-induced metabolic abnormalities in an Opsin3-dependent manner. Metabolomic analysis shows that blue light increases circulating levels of histidine, which activates histaminergic neurons in the hypothalamus and stimulates brown adipose tissue (BAT) via SNS. Blocking central actions of histidine and denervating peripheral BAT blunts the effects of blue light. Human white adipocytes respond to direct blue light stimulation in a cell-autonomous manner, highlighting the translational relevance of this pathway. Together, these data demonstrate a light-responsive metabolic circuit involving adipose-hypothalamus communication, offering a potential strategy to alleviate obesity-induced metabolic abnormalities.

Identification and validation of N-acetylputrescine in combination with non-canonical clinical features as a Parkinson's disease biomarker panel.

Parkinson's disease is a progressive neurodegenerative disorder in which loss of dopaminergic neurons in the substantia nigra results in a clinically heterogeneous group with variable motor and non-motor symptoms with a degree of misdiagnosis. Only 3-25% of sporadic Parkinson's patients present with genetic abnormalities that could represent a risk factor, thus environmental, metabolic, and other unknown causes contribute to the pathogenesis of Parkinson's disease, which highlights the critical need for biomarkers. In the present study, we prospectively collected and analyzed plasma samples from 194 Parkinson's disease patients and 197 age-matched non-diseased controls. N-acetyl putrescine (NAP) in combination with sense of smell (B-SIT), depression/anxiety (HADS), and acting out dreams (RBD1Q) clinical measurements demonstrated combined diagnostic utility. NAP was increased by 28% in Parkinsons disease patients and exhibited an AUC of 0.72 as well as an OR of 4.79. The clinical and NAP panel demonstrated an area under the curve, AUC = 0.9 and an OR of 20.4. The assessed diagnostic panel demonstrates combinatorial utility in diagnosing Parkinson's disease, allowing for an integrated interpretation of disease pathophysiology and highlighting the use of multi-tiered panels in neurological disease diagnosis.

Chronic exercise improves hepatic acylcarnitine handling.

Exercise mediates tissue metabolic function through direct and indirect adaptations to acylcarnitine (AC) metabolism, but the exact mechanisms are unclear. We found that circulating medium-chain acylcarnitines (AC) (C12-C16) are lower in active/endurance trained human subjects compared to sedentary controls, and this is correlated with elevated cardiorespiratory fitness and reduced adiposity. In mice, exercise reduced serum AC and increased liver AC, and this was accompanied by a marked increase in expression of genes involved in hepatic AC metabolism and mitochondrial ß-oxidation. Primary hepatocytes from high-fat fed, exercise trained mice had increased basal respiration compared to hepatocytes from high-fat fed sedentary mice, which may be attributed to increased Ca2+ cycling and lipid uptake into mitochondria. The addition of specific medium- and long-chain AC to sedentary hepatocytes increased mitochondrial respiration, mirroring the exercise phenotype. These data indicate that AC redistribution is an exercise-induced mechanism to improve hepatic function and metabolism.

Exercise and ageing impact the kynurenine/tryptophan pathway and acylcarnitine metabolite pools in skeletal muscle of older adults.

Exercise-induced perturbation of skeletal muscle metabolites is a probable mediator of long-term health benefits in older adults. Although specific metabolites have been identified to be impacted by age, physical activity and exercise, the depth of coverage of the muscle metabolome is still limited. Here, we investigated resting and exercise-induced metabolite distribution in muscle from well-phenotyped older adults who were active or sedentary, and a group of active young adults. Percutaneous biopsies of the vastus lateralis were obtained before, immediately after and 3 h following a bout of endurance cycling. Metabolite profile in muscle biopsies was determined by tandem mass spectrometry. Mitochondrial energetics in permeabilized fibre bundles was assessed by high resolution respirometry and fibre type proportion was assessed by immunohistology. We found that metabolites of the kynurenine/tryptophan pathway were impacted by age and activity. Specifically, kynurenine was elevated in muscle from older adults, whereas downstream metabolites of kynurenine (kynurenic acid and NAD+ ) were elevated in muscle from active adults and associated with cardiorespiratory fitness and muscle oxidative capacity. Acylcarnitines, a potential marker of impaired metabolic health, were elevated in muscle from physically active participants. Surprisingly, despite baseline group difference, acute exercise-induced alterations in whole-body substrate utilization, as well as muscle acylcarnitines and ketone bodies, were remarkably similar between groups. Our data identified novel muscle metabolite signatures that associate with the healthy ageing phenotype provoked by physical activity and reveal that the metabolic responsiveness of muscle to acute endurance exercise is retained [NB]:AUTHOR: Please ensure that the appropriate material has been provide for Table S2, as well as for Figures S1 to S7, as also cited in the text with age regardless of activity levels. KEY POINTS: Kynurenine/tryptophan pathway metabolites were impacted by age and physical activity in human muscle, with kynurenine elevated in older muscle, whereas downstream products kynurenic acid and NAD+ were elevated in exercise-trained muscle regardless of age. Acylcarnitines, a marker of impaired metabolic health when heightened in circulation, were elevated in exercise-trained muscle of young and older adults, suggesting that muscle act as a metabolic sink to reduce the circulating acylcarnitines observed with unhealthy ageing. Despite the phenotypic differences, the exercise-induced response of various muscle metabolite pools, including acylcarnitine and ketone bodies, was similar amongst the groups, suggesting that older adults can achieve the metabolic benefits of exercise seen in young counterparts.

Dynamics of the gut microbiome, IgA response, and plasma metabolome in the development of pediatric celiac disease.

BACKGROUND: Celiac disease (CD) is an autoimmune disorder triggered by gluten consumption. Almost all CD patients possess human leukocyte antigen (HLA) DQ2/DQ8 haplotypes; however, only a small subset of individuals carrying these alleles develop CD, indicating the role of environmental factors in CD pathogenesis. The main objective of this study was to determine the contributory role of gut microbiota and microbial metabolites in CD onset. To this end, we obtained fecal samples from a prospective cohort study (ABIS) at ages 2.5 and 5 years. Samples were collected from children who developed CD after the final sample collection (CD progressors) and healthy children matched by age, HLA genotype, breastfeeding duration, and gluten-exposure time (n=15-16). We first used 16S sequencing and immunoglobulin-A sequencing (IgA-seq) using fecal samples obtained from the same children (i) 16 controls and 15 CD progressors at age 2.5 and (ii) 13 controls and 9 CD progressors at age 5. We completed the cytokine profiling, and plasma metabolomics using plasma samples obtained at age 5 (n=7-9). We also determined the effects of one microbiota-derived metabolite, taurodeoxycholic acid (TDCA), on the small intestines and immune cell composition in vivo. RESULTS: CD progressors have a distinct gut microbiota composition, an increased IgA response, and unique IgA targets compared to healthy subjects. Notably, 26 plasma metabolites, five cytokines, and one chemokine were significantly altered in CD progressors at age 5. Among 26 metabolites, we identified a 2-fold increase in TDCA. TDCA treatment alone caused villous atrophy, increased CD4+ T cells, Natural Killer cells, and two important immunoregulatory proteins, Qa-1 and NKG2D expression on T cells while decreasing T-regulatory cells in intraepithelial lymphocytes (IELs) in C57BL/6J mice. CONCLUSIONS: Pediatric CD progressors have a distinct gut microbiota composition, plasma metabolome, and cytokine profile before diagnosis. Furthermore, CD progressors have more IgA-coated bacteria and unique targets of IgA in their gut microbiota. TDCA feeding alone stimulates an inflammatory immune response in the small intestines of C57BJ/6 mice and causes villous atrophy, the hallmark of CD. Thus, a microbiota-derived metabolite, TDCA, enriched in CD progressors' plasma, has the potential to drive inflammation in the small intestines and enhance CD pathogenesis. Video Abstract.

Serum metabolomic analysis of men on a low-carbohydrate diet for biochemically recurrent prostate cancer reveals the potential role of ketogenesis to slow tumor growth: a secondary analysis of the CAPS2 diet trial.

BACKGROUND: Systemic treatments for prostate cancer (PC) have significant side effects. Thus, newer alternatives with fewer side effects are urgently needed. Animal and human studies suggest the therapeutic potential of low carbohydrate diet (LCD) for PC. To test this possibility, Carbohydrate and Prostate Study 2 (CAPS2) trial was conducted in PC patients with biochemical recurrence (BCR) after local treatment to determine the effect of a 6-month LCD intervention vs. usual care control on PC growth as measured by PSA doubling time (PSADT). We previously reported the LCD intervention led to significant weight loss, higher HDL, and lower triglycerides and HbA1c with a suggested longer PSADT. However, the metabolic basis of these effects are unknown. METHODS: To identify the potential metabolic basis of effects of LCD on PSADT, serum metabolomic analysis was performed using baseline, month 3, and month 6 banked sera to identify the metabolites significantly altered by LCD and that correlated with varying PSADT. RESULTS: LCD increased the serum levels of ketone bodies, glycine and hydroxyisocaproic acid. Reciprocally, LCD reduced the serum levels of alanine, cytidine, asymmetric dimethylarginine (ADMA) and 2-oxobutanoate. As high ADMA level is shown to inhibit nitric oxide (NO) signaling and contribute to various cardiovascular diseases, the ADMA repression under LCD may contribute to the LCD-associated health benefit. Regression analysis of the PSADT revealed a correlation between longer PSADT with higher level of 2-hydroxybutyric acids, ketone bodies, citrate and malate. Longer PSADT was also associated with LCD reduced nicotinamide, fructose-1, 6-biphosphate (FBP) and 2-oxobutanoate. CONCLUSION: These results suggest a potential association of ketogenesis and TCA metabolites with slower PC growth and conversely glycolysis with faster PC growth. The link of high ketone bodies with longer PSADT supports future studies of ketogenic diets to slow PC growth.

Multiplexed LC-MS/MS analysis of methylsuccinic acid, ethylmalonic acid, and glutaric acid in plasma and urine.

Low molecular-mass aliphatic carboxylic acids are critically important for intermediate metabolism and may serve as important biomarkers for metabolic homeostasis. Here in, we focused on multiplexed method development of aliphatic carboxylic analytes, including methylsuccinic acid (MSA), ethylmalonic acid (EMA), and glutaric acid (GA). Also assessed was their utility in a population's health as well as metabolic disease screening in both plasma and urine matrices. MSA, EMA, and GA are constitutional isomers of dicarboxylic acid with high polarity and poor ionization efficiency, resulting in such challenges as poor signal intensity and retention, particularly in reversed-phase liquid chromatography with electrospray mass spectrometry (RP-LC-ESI-MS/MS). Derivatization using n-butanol was performed in the sample preparation to enhance the signal intensity accompanied with a positive charge from ionization in complicated biomatrices as well as to improve the separation of these isomers with optimal retention. Fit-for-purpose method validation results demonstrated quantitative ranges for MSA/EMA/GA from 5/10/20 ng/mL to 400 ng/mL in plasma analysis, and 100/200/100 ng/mL to 5000/10000/5000 ng/mL in urine analysis. This validated method demonstrates future utility when exploring population health analysis and biomarker development in metabolic diseases.

Impact of hemolysis on multi-OMIC pancreatic biomarker discovery to derisk biomarker development in precision medicine studies.

Cancer biomarker discovery is critically dependent on the integrity of biofluid and tissue samples acquired from study participants. Multi-omic profiling of candidate protein, lipid, and metabolite biomarkers is confounded by timing and fasting status of sample collection, participant demographics and treatment exposures of the study population. Contamination by hemoglobin, whether caused by hemolysis during sample preparation or underlying red cell fragility, contributes 0-10 g/L of extraneous protein to plasma, serum, and Buffy coat samples and may interfere with biomarker detection and validation. We analyzed 617 plasma, 701 serum, and 657 buffy coat samples from a 7-year longitudinal multi-omic biomarker discovery program evaluating 400+ participants with or at risk for pancreatic cancer, known as Project Survival. Hemolysis was undetectable in 93.1% of plasma and 95.0% of serum samples, whereas only 37.1% of buffy coat samples were free of contamination by hemoglobin. Regression analysis of multi-omic data demonstrated a statistically significant correlation between hemoglobin concentration and the resulting pattern of analyte detection and concentration. Although hemolysis had the greatest impact on identification and quantitation of the proteome, distinct differentials in metabolomics and lipidomics were also observed and correlated with severity. We conclude that quality control is vital to accurate detection of informative molecular differentials using OMIC technologies and that caution must be exercised to minimize the impact of hemolysis as a factor driving false discovery in large cancer biomarker studies.

Bacterial neurotoxic metabolites in multiple sclerosis cerebrospinal fluid and plasma.

The identification of intestinal dysbiosis in patients with neurological and psychiatric disorders has highlighted the importance of gut-brain communication, and yet the question regarding the identity of the components responsible for this cross-talk remains open. We previously reported that relapsing remitting multiple sclerosis patients treated with dimethyl fumarate have a prominent depletion of the gut microbiota, thereby suggesting that studying the composition of plasma and CSF samples from these patients may help to identify microbially derived metabolites. We used a functional xenogeneic assay consisting of cultured rat neurons exposed to CSF samples collected from multiple sclerosis patients before and after dimethyl fumarate treatment to assess neurotoxicity and then conducted a metabolomic analysis of plasma and CSF samples to identify metabolites with differential abundance. A weighted correlation network analysis allowed us to identify groups of metabolites, present in plasma and CSF samples, whose abundance correlated with the neurotoxic potential of the CSF. This analysis identified the presence of phenol and indole group metabolites of bacterial origin (e.g. p-cresol sulphate, indoxyl sulphate and N-phenylacetylglutamine) as potentially neurotoxic and decreased by treatment. Chronic exposure of cultured neurons to these metabolites impaired their firing rate and induced axonal damage, independent from mitochondrial dysfunction and oxidative stress, thereby identifying a novel pathway of neurotoxicity. Clinical, radiological and cognitive test metrics were also collected in treated patients at follow-up visits. Improved MRI metrics, disability and cognition were only detected in dimethyl fumarate-treated relapsing remitting multiple sclerosis patients. The levels of the identified metabolites of bacterial origin (p-cresol sulphate, indoxyl sulphate and N-phenylacetylglutamine) were inversely correlated to MRI measurements of cortical volume and directly correlated to the levels of neurofilament light chain, an established biomarker of neurodegeneration. Our data suggest that phenol and indole derivatives from the catabolism of tryptophan and phenylalanine are microbially derived metabolites, which may mediate gut-brain communication and induce neurotoxicity in multiple sclerosis.

The influence of low-carbohydrate diets on the metabolic response to androgen-deprivation therapy in prostate cancer.

BACKGROUND: Prostate cancer (PC) is the second most lethal cancer for men. For metastatic PC, standard first-line treatment is androgen deprivation therapy (ADT). While effective, ADT has many metabolic side effects. Previously, we found in serum metabolome analysis that ADT reduced androsterone sulfate, 3-hydroxybutyric acid, acyl-carnitines but increased serum glucose. Since ADT reduced ketogenesis, we speculate that low-carbohydrate diets (LCD) may reverse many ADT-induced metabolic abnormalities in animals and humans. METHODS: In a multicenter trial of patients with PC initiating ADT randomized to no diet change (control) or LCD, we previously showed that LCD intervention led to significant weight loss, reduced fat mass, improved insulin resistance, and lipid profiles. To determine whether and how LCD affects ADT-induced metabolic changes, we analyzed serum metabolites after 3-, and 6-months of ADT on LCD versus control. RESULTS: We found androsterone sulfate was most consistently reduced by ADT and was slightly further reduced in the LCD arm. Contrastingly, LCD intervention increased 3-hydroxybutyric acid and various acyl-carnitines, counteracting their reduction during ADT. LCD also reversed the ADT-reduced lactic acid, alanine, and S-adenosyl methionine (SAM), elevating glycolysis metabolites and alanine. While the degree of androsterone reduction by ADT was strongly correlated with glucose and indole-3-carboxaldehyde, LCD disrupted such correlations. CONCLUSIONS: Together, LCD intervention significantly reversed many ADT-induced metabolic changes while slightly enhancing androgen reduction. Future research is needed to confirm these findings and determine whether LCD can mitigate ADT-linked comorbidities and possibly delaying disease progression by further lowering androgens.

Diagnostic Utility of Serum and Urinary Metabolite Analysis in Patients with Interstitial Cystitis/Painful Bladder Syndrome.

OBJECTIVE: To identify the potential biomarkers of interstitial cystitis/painful bladder syndrome (IC), a chronic syndrome of bladder-centric pain with unknown etiology that has an adverse impact on quality of life, we analyzed the urine and serum metabolomes of a cohort of IC patients and non-disease controls (NC). METHODS: Home collection of serum and urine samples was obtained from 19 IC and 20 NC females in the Veterans Affairs (VA) Health Care System. IC was diagnosed independently by thorough review of medical records using established criteria. Biostatistics and bioinformatics analyses, including univariate analysis, unsupervised clustering, random forest analysis, and metabolite set enrichment analysis (MSEA), were then utilized to identify potential IC biomarkers. RESULTS: Metabolomics profiling revealed distinct expression patterns between NC and IC. Random forest analysis of urine samples suggested discriminators specific to IC; these include phenylalanine, purine, 5-oxoproline, and 5-hydroxyindoleacetic acid. When these urinary metabolomics-based analytes were combined into a single model, the AUC was 0.92, suggesting strong potential clinical value as a diagnostic signature. Serum-based metabolomics did not provide potential IC discriminators. CONCLUSION: Analysis of serum and urine revealed that women with IC have distinct metabolomes, highlighting key metabolic pathways that may provide insight into the pathophysiology of IC. The findings from this pilot study suggest that integrated analyses of urinary metabolites, purine, phenylalanine, 5-oxoproline, and 5-HIAA, can lead to promising IC biomarkers for pathophysiology of IC. Validation of these results using a larger dataset is currently underway.

Paracardial fat remodeling affects systemic metabolism through alcohol dehydrogenase 1.

The relationship between adiposity and metabolic health is well established. However, very little is known about the fat depot, known as paracardial fat (pCF), located superior to and surrounding the heart. Here, we show that pCF remodels with aging and a high-fat diet and that the size and function of this depot are controlled by alcohol dehydrogenase 1 (ADH1), an enzyme that oxidizes retinol into retinaldehyde. Elderly individuals and individuals with obesity have low ADH1 expression in pCF, and in mice, genetic ablation of Adh1 is sufficient to drive pCF accumulation, dysfunction, and global impairments in metabolic flexibility. Metabolomics analysis revealed that pCF controlled the levels of circulating metabolites affecting fatty acid biosynthesis. Also, surgical removal of the pCF depot was sufficient to rescue the impairments in cardiometabolic flexibility and fitness observed in Adh1-deficient mice. Furthermore, treatment with retinaldehyde prevented pCF remodeling in these animals. Mechanistically, we found that the ADH1/retinaldehyde pathway works by driving PGC-1α nuclear translocation and promoting mitochondrial fusion and biogenesis in the pCF depot. Together, these data demonstrate that pCF is a critical regulator of cardiometabolic fitness and that retinaldehyde and its generating enzyme ADH1 act as critical regulators of adipocyte remodeling in the pCF depot.

Brown Fat-Activating Lipokine 12,13-diHOME in Human Milk Is Associated With Infant Adiposity.

CONTEXT: Little is known about the specific breastmilk components responsible for protective effects on infant obesity. Whether 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), an oxidized linoleic acid metabolite and activator of brown fat metabolism, is present in human milk, or linked to infant adiposity, is unknown. OBJECTIVE: To examine associations between concentrations of 12,13-diHOME in human milk and infant adiposity. DESIGN: Prospective cohort study from 2015 to 2019, following participants from birth to 6 months of age. SETTING: Academic medical centers. PARTICIPANTS: Volunteer sample of 58 exclusively breastfeeding mother-infant pairs; exclusion criteria included smoking, gestational diabetes, and health conditions with the potential to influence maternal or infant weight gain. MAIN OUTCOME MEASURES: Infant anthropometric measures including weight, length, body mass index (BMI), and body composition at birth and at 1, 3, and 6 months postpartum. RESULTS: We report for the first time that 12,13-diHOME is present in human milk. Higher milk 12,13-diHOME level was associated with increased weight-for-length Z-score at birth (ß = 0.5742, P = 0.0008), lower infant fat mass at 1 month (P = 0.021), and reduced gain in BMI Z-score from 0 to 6 months (ß = -0.3997, P = 0.025). We observed similar associations between infant adiposity and milk abundance of related oxidized linoleic acid metabolites 12,13-Epoxy-9(Z)-octadecenoic acid (12,13-epOME) and 9,10-Dihydroxy-12-octadecenoic acid (9,10-diHOME), and metabolites linked to thermogenesis including succinate and lyso-phosphatidylglycerol 18:0. Milk abundance of 12,13-diHOME was not associated with maternal BMI, but was positively associated with maternal height, milk glucose concentration, and was significantly increased after a bout of moderate exercise. CONCLUSIONS: We report novel associations between milk abundance of 12,13-diHOME and adiposity during infancy.

Author Correction: Divergence in the metabolome between natural aging and Alzheimer's disease.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Chronic stress and antidepressant treatment alter purine metabolism and beta oxidation within mouse brain and serum.

Major depressive disorder (MDD) is a complex condition with unclear pathophysiology. Molecular disruptions within limbic brain regions and the periphery contribute to depression symptomatology and a more complete understanding the diversity of molecular changes that occur in these tissues may guide the development of more efficacious antidepressant treatments. Here, we utilized a mouse chronic social stress model for the study of MDD and performed metabolomic, lipidomic, and proteomic profiling on serum plus several brain regions (ventral hippocampus, nucleus accumbens, and medial prefrontal cortex) of susceptible, resilient, and unstressed control mice. To identify how commonly used tricyclic antidepressants impact the molecular composition in these tissues, we treated stress-exposed mice with imipramine and repeated our multi-OMIC analyses. Proteomic analysis identified three serum proteins reduced in susceptible animals; lipidomic analysis detected differences in lipid species between resilient and susceptible animals in serum and brain; and metabolomic analysis revealed dysfunction of purine metabolism, beta oxidation, and antioxidants, which were differentially associated with stress susceptibility vs resilience by brain region. Antidepressant treatment ameliorated stress-induced behavioral abnormalities and affected key metabolites within outlined networks, most dramatically in the ventral hippocampus. This work presents a resource for chronic social stress-induced, tissue-specific changes in proteins, lipids, and metabolites and illuminates how molecular dysfunctions contribute to individual differences in stress sensitivity.

CRISPR-engineered human brown-like adipocytes prevent diet-induced obesity and ameliorate metabolic syndrome in mice.

Brown and brown-like beige/brite adipocytes dissipate energy and have been proposed as therapeutic targets to combat metabolic disorders. However, the therapeutic effects of cell-based therapy in humans remain unclear. Here, we created human brown-like (HUMBLE) cells by engineering human white preadipocytes using CRISPR-Cas9-SAM-gRNA to activate endogenous uncoupling protein 1 expression. Obese mice that received HUMBLE cell transplants showed a sustained improvement in glucose tolerance and insulin sensitivity, as well as increased energy expenditure. Mechanistically, increased arginine/nitric oxide (NO) metabolism in HUMBLE adipocytes promoted the production of NO that was carried by S-nitrosothiols and nitrite in red blood cells to activate endogenous brown fat and improved glucose homeostasis in recipient animals. Together, these data demonstrate the utility of using CRISPR-Cas9 technology to engineer human white adipocytes to display brown fat-like phenotypes and may open up cell-based therapeutic opportunities to combat obesity and diabetes.

Divergence in the metabolome between natural aging and Alzheimer's disease.

Alzheimer's disease (AD) is a progressive and debilitating neurodegenerative disorder and one of the leading causes of death in the United States. Although amyloid plaques and fibrillary tangles are hallmarks of AD, research suggests that pathology associated with AD often begins 20 or more years before symptoms appear. Therefore, it is essential to identify early-stage biomarkers in those at risk for AD and age-related cognitive decline (ARCD) in order to develop preventative treatments. Here, we used an untargeted metabolomics analysis to define system-level alterations following cognitive decline in aged and APP/PS1 (AD) mice. At 6, 12, and 24 months of age, both control (Ctrl) and AD mice were tested in a 3-shock contextual fear conditioning (CFC) paradigm to assess memory decline. AD mice exhibited memory deficits across age and these memory deficits were also seen in naturally aged mice. Prefrontal cortex (PFC), hippocampus (HPC), and spleen were then collected and analyzed for metabolomic alterations. A number of significant pathways were altered between Ctrl and AD mice and naturally aged mice. By identifying systems-level alterations following ARCD and AD, these data could provide insights into disease mechanisms and advance the development of biomarker panels.

Integrated metabolomics reveals altered lipid metabolism in adipose tissue in a model of extreme longevity.

Adipose tissue plays an essential role in metabolic health. Ames dwarf mice are exceptionally long-lived and display metabolically beneficial phenotypes in their adipose tissue, providing an ideal model for studying the intersection between adipose tissue and longevity. To this end, we assessed the metabolome and lipidome of adipose tissue in Ames dwarf mice. We observed distinct lipid profiles in brown versus white adipose tissue of Ames dwarf mice that are consistent with increased thermogenesis and insulin sensitivity, such as increased cardiolipin and decreased ceramide concentrations. Moreover, we identified 5-hydroxyeicosapentaenoic acid (5-HEPE), an ω-3 fatty acid metabolite, to be increased in Ames dwarf brown adipose tissue (BAT), as well as in circulation. Importantly, 5-HEPE is increased in other models of BAT activation and is negatively correlated with body weight, insulin resistance, and circulating triglyceride concentrations in humans. Together, these data represent a novel lipid signature of adipose tissue in a mouse model of extreme longevity.

Current Status of Metabolomic Biomarker Discovery: Impact of Study Design and Demographic Characteristics.

Widespread application of omic technologies is evolving our understanding of population health and holds promise in providing precise guidance for selection of therapeutic interventions based on patient biology. The opportunity to use hundreds of analytes for diagnostic assessment of human health compared to the current use of 10-20 analytes will provide greater accuracy in deconstructing the complexity of human biology in disease states. Conventional biochemical measurements like cholesterol, creatinine, and urea nitrogen are currently used to assess health status; however, metabolomics captures a comprehensive set of analytes characterizing the human phenotype and its complex metabolic processes in real-time. Unlike conventional clinical analytes, metabolomic profiles are dramatically influenced by demographic and environmental factors that affect the range of normal values and increase the risk of false biomarker discovery. This review addresses the challenges and opportunities created by the evolving field of clinical metabolomics and highlights features of study design and bioinformatics necessary to maximize the utility of metabolomics data across demographic groups.

Older adults with sarcopenia have distinct skeletal muscle phosphodiester, phosphocreatine, and phospholipid profiles.

The loss of skeletal muscle mass and function with age (sarcopenia) is a critical healthcare challenge for older adults. 31-phosphorus magnetic resonance spectroscopy (31 P-MRS) is a powerful tool used to evaluate phosphorus metabolite levels in muscle. Here, we sought to determine which phosphorus metabolites were linked with reduced muscle mass and function in older adults. This investigation was conducted across two separate studies. Resting phosphorus metabolites in skeletal muscle were examined by 31 P-MRS. In the first study, fifty-five older adults with obesity were enrolled and we found that resting phosphocreatine (PCr) was positively associated with muscle volume and knee extensor peak power, while a phosphodiester peak (PDE2) was negatively related to these variables. In the second study, we examined well-phenotyped older adults that were classified as nonsarcopenic or sarcopenic based on sex-specific criteria described by the European Working Group on Sarcopenia in Older People. PCr content was lower in muscle from older adults with sarcopenia compared to controls, while PDE2 was elevated. Percutaneous biopsy specimens of the vastus lateralis were obtained for metabolomic and lipidomic analyses. Lower PCr was related to higher muscle creatine. PDE2 was associated with glycerol-phosphoethanolamine levels, a putative marker of phospholipid membrane damage. Lipidomic analyses revealed that the major phospholipids, (phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol) were elevated in sarcopenic muscle and were inversely related to muscle volume and peak power. These data suggest phosphorus metabolites and phospholipids are associated with the loss of skeletal muscle mass and function in older adults.