Factors affecting longitudinal trajectories of plasma sphingomyelins: the Baltimore Longitudinal Study of Aging

Metabolomics biomarkers of frailty: a longitudinal study of aging female and male mice

Frailty is an age-related geriatric syndrome, for which the mechanisms remain largely unknown. We performed a longitudinal study of aging female (n = 40) and male (n = 47) C57BL/6NIA mice, measured frailty index and derived metabolomics data from plasma samples. We identify differentially abundant metabolites related to aging, determine frailty related metabolites via a machine learning approach, and generate a union set of frailty features, both in the whole cohort and in sex-stratified subgroups. Using the features, we perform an association study and build a metabolomics-based frailty clock. We find that frailty related metabolites are enriched for amino acid metabolism and metabolism of cofactors and vitamins, include ergothioneine, tryptophan, and alpha-ketoglutarate, and present sex dimorphism. We identify B vitamin metabolism related flavin adenine dinucleotide and pyridoxate as female-specific frailty biomarkers, and lipid metabolism related sphingomyelins, glycerophosphoethanolamine and glycerophosphocholine as male-specific frailty biomarkers. These associations are confirmed in a validation cohort, with ergothioneine and perfluorooctanesulfonate identified as robust frailty biomarkers. In summary, our results identify sex-specific metabolite biomarkers of frailty in aging, and shed light on potential mechanisms involved in frailty.

Exploring age and gender disparities in cardiometabolic phenotypes and lipidomic signatures among Chinese adults: a nationwide cohort study

Understanding sex disparities in modifiable risk factors across the lifespan is essential for crafting individualized intervention strategies. We aim to investigate age-related sex disparity in cardiometabolic phenotypes in a large nationwide Chinese cohort. A total of 254,670 adults aged 40 years or older were selected from a population-based cohort in China. Substantial sex disparities in the prevalence of metabolic diseases were observed across different age strata, particularly for dyslipidemia and its components. Generalized additive models were employed to characterize phenotype features, elucidating how gender differences evolve with advancing age. Half of the 16 phenotypes consistently exhibited no sex differences, while four (high-density lipoprotein [HDL] cholesterol, apolipoprotein A1, diastolic blood pressure, and fasting insulin) displayed significant sex differences across all age groups. Triglycerides, apolipoprotein B, non-HDL cholesterol, and total cholesterol demonstrated significant age-dependent sex disparities. Notably, premenopausal females exhibited significant age-related differences in lipid levels around the age of 40-50 years, contrasting with the relatively stable associations observed in males and postmenopausal females. Menopause played an important but not sole role in age-related sex differences in blood lipids. Sleep duration also had an age- and sex-dependent impact on lipids. Lipidomic analysis and K-means clustering further revealed that 58.6% of the 263 measured lipids varied with sex and age, with sphingomyelins, cholesteryl esters, and triacylglycerols being the most profoundly influenced lipid species by the combined effects of age, sex, and their interaction. These findings underscore the importance of age consideration when addressing gender disparities in metabolic diseases and advocate for personalized, age-specific prevention and management.

Circulating sphingolipids in relation to cognitive decline and incident dementia: The Cardiovascular Health Study

INTRODUCTION

Whether circulating levels of sphingolipids are prospectively associated with cognitive decline and dementia risk is uncertain.

METHODS

We measured 14 sphingolipid species in plasma samples from 4488 participants (mean age 76.2 years; 40% male; and 25% apolipoprotein E (APOE) ε4 allele carriers). Cognitive decline was assessed annually across 6 years using modified Mini-Mental State Examination (3MSE) and Digital Symbol Substitution Test (DSST). Additionally, a subset of 3050 participants were followed for clinically adjudicated dementia.

RESULTS

Higher plasma levels of sphingomyelin-d18:1/16:0 (SM-16) were associated with a faster cognitive decline measured with 3MSE, in contrast, higher levels of sphingomyelin-d18:1/22:0 (SM-22) were associated with slower decline in cognition measured with DSST. In Cox regression, higher levels of SM-16 (hazard ration [HR] = 1.24 [95% confidence interval [CI]: 1.08-1.44]) and ceramide-d18:1/16:0 (Cer-16) (HR = 1.26 [95% CI: 1.10-1.45]) were associated with higher risk of incident dementia.

DISCUSSION

Several sphingolipid species appear to be involved in cognitive decline and dementia risk.

Highlights

Plasma levels of sphingolipids were associated with cognitive decline and dementia risk.Ceramides and sphingomyelins with palmitic acid were associated with faster annual cognitive decline and increased risk of dementia.The direction of association depended on the covalently bound saturated fatty acid chain length in analysis of cognitive decline.

Plasma Sphingomyelins and Carnitine Esters of Infants Consuming Whole Goat or Cow Milk-Based Infant Formulas or Human Milk

BACKGROUND

Infant formulas are typically manufactured using skimmed milk, whey proteins, and vegetable oils, which excludes milk fat globule membranes (MFGM). MFGM contains polar lipids, including sphingomyelin (SM).

OBJECTIVE

The objective of this study was comparison of infant plasma SM and acylcarnitine species between infants who are breastfed or receiving infant formulas with different fat sources.

METHODS

In this explorative study, we focused on SM and acylcarnitine species concentrations measured in plasma samples from the TIGGA study (ACTRN12608000047392), where infants were randomly assigned to receive either a cow milk-based infant formula (CIF) with vegetable oils only or a goat milk-based infant formula (GIF) with a goat milk fat (including MFGM) and vegetable oil mixture to the age ≥4 mo. Breastfed infants were followed as a reference group. Using tandem mass spectrometry, SM species in the study formulas and SM and acylcarnitine species in plasma samples collected at the age of 4 mo were analyzed.

RESULTS

Total SM concentrations (∼42 μmol/L) and patterns of SM species were similar in both formulas. The total plasma SM concentrations were not different between the formula groups but were 15 % (CIF) and 21% (GIF) lower in the formula groups than in the breastfed group. Between the formula groups, differences in SM species were statistically significant but small. Total carnitine and major (acyl) carnitine species were not different between the groups.

CONCLUSIONS

The higher total SM concentration in breastfed than in formula-fed infants might be related to a higher SM content in human milk, differences in cholesterol metabolism, dietary fatty acid intake, or other factors not yet identified. SM and acylcarnitine species composition in plasma is not closely related to the formula fatty acid composition. This trial was registered at Australian New Zealand Clinical Trials Registry as ACTRN12608000047392.

Circulating sphingolipids and subclinical brain pathology: the cardiovascular health study

Background

Sphingolipids are implicated in neurodegeneration and neuroinflammation. We assessed the potential role of circulating ceramides and sphingomyelins in subclinical brain pathology by investigating their association with brain magnetic resonance imaging (MRI) measures and circulating biomarkers of brain injury, neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in the Cardiovascular Health Study (CHS), a large and intensively phenotyped cohort of older adults.

Methods

Brain MRI was offered twice to CHS participants with a mean of 5 years between scans, and results were available from both time points in 2,116 participants (mean age 76 years; 40% male; and 25% APOE ε4 allele carriers). We measured 8 ceramide and sphingomyelin species in plasma samples and examined the associations with several MRI, including worsening grades of white matter hyperintensities and ventricular size, number of brain infarcts, and measures of brain atrophy in a subset with quantitative measures. We also investigated the sphingolipid associations with serum NfL and GFAP.

Results

In the fully adjusted model, higher plasma levels of ceramides and sphingomyelins with a long (16-carbon) saturated fatty acid were associated with higher blood levels of NfL [β = 0.05, false-discovery rate corrected P (PFDR) = 0.004 and β = 0.06, PFDR = < 0.001, respectively]. In contrast, sphingomyelins with very long (20- and 22-carbon) saturated fatty acids tended to have an inverse association with levels of circulating NfL. In secondary analyses, we found an interaction between ceramide d18:1/20:0 and sex (P for interaction = <0.001), such that ceramide d18:1/20:0 associated with higher odds for infarcts in women [OR = 1.26 (95%CI: 1.07, 1.49), PFDR = 0.03]. We did not observe any associations with GFAP blood levels, white matter grade, ventricular grade, mean bilateral hippocampal volume, or total brain volume.

Conclusion

Overall, our comprehensive investigation supports the evidence that ceramides and sphingomyelins are associated with increased aging brain pathology and that the direction of association depends on the fatty acid attached to the sphingosine backbone.

Effect of biological sex on human circulating lipidome: An overview of the literature

Cardiovascular diseases (CVD) are the leading cause of death worldwide for both men and women, but their prevalence and burden show marked sex differences. The existing knowledge gaps in research, prevention, and treatment for women emphasize the need for understanding the biological mechanisms contributing to the sex differences in CVD. Sex differences in the plasma lipids that are well-known risk factors and predictors of CVD events have been recognized and are believed to contribute to the known disparities in CVD manifestations in men and women. However, the current understanding of sex differences in lipids has mainly come from the studies on routinely measured standard lipids- low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total triglycerides, and total cholesterol, which have been the mainstay of the lipid profiling. Sex differences in individual lipid species, collectively called the lipidome, have until recently been less explored due to the technological challenges and analytic costs. With the technological advancements in the last decade and growing interest in understanding mechanisms of sexual dimorphism in metabolic disorders, many investigators utilized metabolomics and lipidomics based platforms to examine the effect of biological sex on detailed lipidomic profiles and individual lipid species. This review presents an overview of the research on sex differences in the concentrations of circulating lipid species, focusing on findings from the metabolome- and lipidome-wide studies. We also discuss the potential contribution of genetic factors including sex chromosomes and sex-specific physiological factors such as menopause and sex hormones to the sex differences in lipidomic profiles.

Prospective Association Between Plasma Concentrations of Fatty Acids and Other Lipids, and Multimorbidity in Older Adults

Biological mechanisms that lead to multimorbidity are mostly unknown, and metabolomic profiles are promising to explain different pathways in the aging process. The aim of this study was to assess the prospective association between plasma fatty acids and other lipids, and multimorbidity in older adults. Data were obtained from the Spanish Seniors-ENRICA 2 cohort, comprising noninstitutionalized adults ≥65 years old. Blood samples were obtained at baseline and after a 2-year follow-up period for a total of 1 488 subjects. Morbidity was also collected at baseline and end of the follow-up from electronic health records. Multimorbidity was defined as a quantitative score, after weighting morbidities (from a list of 60 mutually exclusive chronic conditions) by their regression coefficients on physical functioning. Generalized estimating equation models were employed to assess the longitudinal association between fatty acids and other lipids, and multimorbidity, and stratified analyses by diet quality, measured with the Alternative Healthy Eating Index-2010, were also conducted. Among study participants, higher concentrations of omega-6 fatty acids [coef. per 1-SD increase (95% CI) = -0.76 (-1.23, -0.30)], phosphoglycerides [-1.26 (-1.77, -0.74)], total cholines [-1.48 (-1.99, -0.96)], phosphatidylcholines [-1.23 (-1.74, -0.71)], and sphingomyelins [-1.65 (-2.12, -1.18)], were associated with lower multimorbidity scores. The strongest associations were observed for those with a higher diet quality. Higher plasma concentrations of omega-6 fatty acids, phosphoglycerides, total cholines, phosphatidylcholines, and sphingomyelins were prospectively associated with lower multimorbidity in older adults, although diet quality could modulate the associations found. These lipids may serve as risk markers for multimorbidity.

Expression of Ceramide-Metabolizing Enzymes in the Heart Adipose Tissue of Cardiovascular Disease Patients

Here, we examined the expression of ceramide metabolism enzymes in the subcutaneous adipose tissue (SAT), epicardial adipose tissue (EAT) and perivascular adipose tissue (PVAT) of 30 patients with coronary artery disease (CAD) and 30 patients with valvular heart disease (VHD) by means of quantitative polymerase chain reaction and fluorescent Western blotting. The EAT of patients with CAD showed higher expression of the genes responsible for ceramide biosynthesis (SPTLC1, SPTLC2, CERS1, 5, 6, DEGS1, and SMPD1) and utilization (ASAH1, SGMS1). PVAT was characterized by higher mRNA levels of CERS3, CERS4, DEGS1, SMPD1, and ceramide utilization enzyme (SGMS2). In patients with VHD, there was a high CERS4, DEGS1, and SGMS2 expression in the EAT and CERS3 and CERS4 expression in the PVAT. Among patients with CAD, the expression of SPTLC1 in SAT and EAT, SPTLC2 in EAT, CERS2 in all studied AT, CERS4 and CERS5 in EAT, DEGS1 in SAT and EAT, ASAH1 in all studied AT, and SGMS1 in EAT was higher than in those with VHD. Protein levels of ceramide-metabolizing enzymes were consistent with gene expression trends. The obtained results indicate an activation of ceramide synthesis de novo and from sphingomyelin in cardiovascular disease, mainly in EAT, that contributes to the accumulation of ceramides in this location.

Human Metabolome Reference Database in a Biracial Cohort across the Adult Lifespan

As one of the OMICS in systems biology, metabolomics defines the metabolome and simultaneously quantifies numerous metabolites that are final or intermediate products and effectors of upstream biological processes. Metabolomics provides accurate information that helps determine the physiological steady state and biochemical changes during the aging process. To date, reference values of metabolites across the adult lifespan, especially among ethnicity groups, are lacking. The "normal" reference values according to age, sex, and race allow the characterization of whether an individual or a group deviates metabolically from normal aging, encompass a fundamental element in any study aimed at understanding mechanisms at the interface between aging and diseases. In this study, we established a metabolomics reference database from 20-100 years of age from a biracial sample of community-dwelling healthy men and women and examined metabolite associations with age, sex, and race. Reference values from well-selected healthy individuals can contribute to clinical decision-making processes of metabolic or related diseases.

The lipidomes of C. elegans with mutations in asm-3/acid sphingomyelinase and hyl-2/ceramide synthase show distinct lipid profiles during aging

Lipid metabolism affects cell and physiological functions that mediate animal healthspan and lifespan. Lipidomics approaches in model organisms have allowed us to better understand changes in lipid composition related to age and lifespan. Here, using the model C. elegans, we examine the lipidomes of mutants lacking enzymes critical for sphingolipid metabolism; specifically, we examine acid sphingomyelinase (asm-3), which breaks down sphingomyelin to ceramide, and ceramide synthase (hyl-2), which synthesizes ceramide from sphingosine. Worm asm-3 and hyl-2 mutants have been previously found to be long- and short-lived, respectively. We analyzed longitudinal lipid changes in wild type animals compared to mutants at 1-, 5-, and 10-days of age. We detected over 700 different lipids in several lipid classes. Results indicate that wildtype animals exhibit increased triacylglycerols (TAG) at 10-days compared to 1-day, and decreased lysophoshatidylcholines (LPC). We find that 10-day hyl-2 mutants have elevated total polyunsaturated fatty acids (PUFA) and increased LPCs compared to 10-day wildtype animals. These changes mirror another short-lived model, the daf-16/FOXO transcription factor that is downstream of the insulin-like signaling pathway. In addition, we find that hyl-2 mutants have poor oxidative stress response, supporting a model where mutants with elevated PUFAs may accumulate more oxidative damage. On the other hand, 10-day asm-3 mutants have fewer TAGs. Intriguingly, asm-3 mutants have a similar lipid composition as the long-lived, caloric restriction model eat-2/mAChR mutant. Together, these analyses highlight the utility of lipidomic analyses to characterize metabolic changes during aging in C. elegans.

Lipidome- and Genome-Wide Study to Understand Sex Differences in Circulatory Lipids

Background Despite well-recognized differences in the atherosclerotic cardiovascular disease risk between men and women, sex differences in risk factors and sex-specific mechanisms in the pathophysiology of atherosclerotic cardiovascular disease remain poorly understood. Lipid metabolism plays a central role in the development of atherosclerotic cardiovascular disease. Understanding sex differences in lipids and their genetic determinants could provide mechanistic insights into sex differences in atherosclerotic cardiovascular disease and aid in precise risk assessment. Herein, we examined sex differences in plasma lipidome and heterogeneity in genetic influences on lipidome in men and women through sex-stratified genome-wide association analyses. Methods and Results We used data consisting of 179 lipid species measured by shotgun lipidomics in 7266 individuals from the Finnish GeneRISK cohort and sought for replication using independent data from 2045 participants. Significant sex differences in the levels of 141 lipid species were observed (P<7.0×10-4). Interestingly, 121 lipid species showed significant age-sex interactions, with opposite age-related changes in 39 lipid species. In general, most of the cholesteryl esters, ceramides, lysophospholipids, and glycerides were higher in 45- to 50-year-old men compared with women of same age, but the sex differences narrowed down or reversed with age. We did not observe any major differences in genetic effect in the sex-stratified genome-wide association analyses, which suggests that common genetic variants do not have a major role in sex differences in lipidome. Conclusions Our study provides a comprehensive view of sex differences in circulatory lipids pointing to potential sex differences in lipid metabolism and highlights the need for sex- and age-specific prevention strategies.

High-Fat Diet and Short-Term Unpredictable Stress Increase Long-Chain Ceramides Without Enhancing Behavioral Despair

Clinical and preclinical studies suggest that increases in long-chain ceramides in blood may contribute to the development of depressive-like behavior. However, which factors contribute to these increases and whether the increases are sufficient to induce depressive-like behaviors is unclear. To begin to address this issue, we examined the effects of high fat diet (HFD) and short-term unpredictable (STU) stress on long-chain ceramides in the serum of male and female rats. We found that brief exposure to HFD or unpredictable stress was sufficient to induce selective increases in the serum concentrations of long-chain ceramides, associated with depression in people. Furthermore, combined exposure to HFD and unpredictable stress caused a synergistic increase in C16:0, C16:1, and C18:0 ceramides in both sexes and C18:1 and C24:1 in males. However, the increased peripheral long-chain ceramides were not associated with increases in depressive-like behaviors suggesting that increases in serum long-chain ceramides may not be associated with the development of depressive-like behaviors in rodents.

Ceramides as Mediators of Oxidative Stress and Inflammation in Cardiometabolic Disease

Ceramides, composed of a sphingosine and a fatty acid, are bioactive lipid molecules involved in many key cellular pathways (e.g., apoptosis, oxidative stress and inflammation). There is much evidence on the relationship between ceramide species and cardiometabolic disease, especially in relationship with the onset and development of diabetes and acute and chronic coronary artery disease. This review reports available evidence on ceramide structure and generation, and discusses their role in cardiometabolic disease, as well as current translational chances and difficulties for ceramide application in the cardiometabolic clinical settings.

Ceramides and Cardiovascular Risk Factors, Inflammatory Parameters and Left Ventricular Function in AMI Patients

Background: Ceramides, biologically active lipids correlated to oxidative stress and inflammation, have been associated with adverse outcomes in acute myocardial infarction (AMI). The purpose of this study was to assess the association between ceramides/ratios included in the CERT1 score and increased cardiovascular (CV) risk, inflammatory and left ventricular function parameters in AMI. Methods: high performance liquid chromatography-tandem mass spectrometry was used to identify Cer(d18:1/16:0), Cer(d18:1/18:0), and Cer(d18:1/24:1) levels and their ratios to Cer(d18:1/24:0), in 123 AMI patients (FTGM coronary unit, Massa, Italy). Results: Cer(d18:1/16:0): higher in female patients (<0.05), in patients with dyslipidemia (<0.05), and it directly and significantly correlated with aging, brain natriuretic peptide-BNP, erythrocyte sedimentation rate-ESR and fibrinogen. Cer(d18:1/18:0): higher in females (<0.01) and patients with dyslipidemia (<0.01), and increased according to the number of CV risk factors (considering hypertension, dyslipidemia and diabetes). Moreover, it significantly correlated with BNP, troponin at admission, ESR, C reactive protein-CRP, and fibrinogen. Cer(d18:1/24:1): significantly correlated with aging, BNP, fibrinogen and neutrophils. Cer(d18:1/16:0)/Cer(d18:1/24:0): higher in female patients (<0.05), and in patients with higher wall motion score index-WMSI (>1.7; ≤0.05), and in those with multivessel disease (<0.05). Moreover, it significantly correlated with aging, BNP, CRP, ESR, neutrophil-to-lymphocyte ratio-NRL, and fibrinogen. Cer(d18:1/18:0)/Cer(d18:1/24:0): higher in female patients (<0.001), and increased according to age. Moreover, it was higher in patients with lower left ventricular ejection fraction (<35%, ≤0.01), higher WMSI (>1.7, <0.05), and in those with multivessel disease (0.13 ± 0.06 vs. 0.10 ± 0.05 µM, <0.05), and correlates with BNP, ESR, CRP, fibrinogen and neutrophils, platelets, NLR, and troponin at admission. Multiple regression analysis showed that Cer(d18:1/16:0)/Cer(d18:1/24:0) and Cer(d18:1/18:0)/Cer(d18:1/24:0) remained as independent determinants for WMSI after multivariate adjustment (Std coeff 0.17, T-value 1.9, ≤0.05; 0.21, 2.6, <0.05, respectively). Conclusion: Distinct ceramide species are associated with CV risk, inflammation and disease severity in AMI. Thus, a detailed analysis of ceramides may help to better understand CV pathobiology and suggest these new biomarkers as possible risk predictors and pharmacological targets in AMI patients.

The accelerated aging phenotype: The role of race and social determinants of health on aging

The pursuit to discover the fundamental biology and mechanisms of aging within the context of the physical and social environment is critical to designing interventions to prevent and treat its complex phenotypes. Aging research is critically linked to understanding health disparities because these inequities shape minority aging, which may proceed on a different trajectory than the overall population. Health disparities are characteristically seen in commonly occurring age-associated diseases such as cardiovascular and cerebrovascular disease as well as diabetes mellitus and cancer. The early appearance and increased severity of age-associated disease among African American and low socioeconomic status (SES) individuals suggests that the factors contributing to the emergence of health disparities may also induce a phenotype of 'premature aging' or 'accelerated aging' or 'weathering'. In marginalized and low SES populations with high rates of early onset age-associated disease the interaction of biologic, psychosocial, socioeconomic and environmental factors may result in a phenotype of accelerated aging biologically similar to premature aging syndromes with increased susceptibility to oxidative stress, premature accumulation of oxidative DNA damage, defects in DNA repair and higher levels of biomarkers of oxidative stress and inflammation. Health disparities, therefore, may be the end product of this complex interaction in populations at high risk. This review will examine the factors that drive both health disparities and the accelerated aging phenotype that ultimately contributes to premature mortality.

Association between serum sphingolipids and necroinflammation of liver tissue pathology in chronic hepatitis B

Background & Aims: Accurately identifying liver necroinflammation was essential for the timely implementation of antiviral therapy in chronic hepatitis B(CHB) patients. The sphingolipids were involved in various chronic inflammatory processes. This study aimed to evaluate the association between serum sphingolipids and liver necroinflammation in CHB patients. Methods: The study prospectively enrolled patients with a diagnosis of chronic hepatitis B who were subsequently treated with nucleos(t)ide analogs (NAs). Liver biopsy was performed at baseline and 5-year follow-up, and serum sphingolipid levels were measured by ultra-high-performance liquid chromatography tandem mass spectrometry. Results: A total of 70 CHB patients were enrolled with baseline liver necroinflammation of 27(38.6%) G1, 23(32.9%) G2, and 20(28.6%) G ≥ 3, respectively. A total of 126 liver biopsies were performed on the study population over a 5-year period, of which 80 (63.5%) G<2 and 46 (36.5%) G≥2. Serum ALT, ALP, SM d16:0/16:1, SM d16:0/17:1, SM d18:0/17:0 and Cer d18:2/22:0 showed significant differences between two groups (P<0.01). Multivariate analysis showed that serum ALT (OR 1.006, 95% CI: 1.000-1.011), SM d16:0/16:1 (OR 1.552, 95% CI: 1.150-2.093), Cer d18:2/22:0 (OR 0.003, 95% CI: 0.000-0.173) were associated with G ≥ 2. In the subgroup of patients with normal serum ALT, serum Cer d18:2/22:0 was lower in patients with G ≥ 2 than that with G < 2. After 5 years, alleviated inflammation was accompanied by decreased serum SM d16:0/16:1 and increased serum Cer d18:2/22:0 in patients with baseline G ≥ 2. Conclusions: Lower serum Cer d18:2/22:0 could reflect hepatic necroinflammation (G ≥ 2) in CHB patients including those with normal serum ALT, and its elevation predicts the inflammation improvement after NAs treatment.

Long-lived humans have a unique plasma sphingolipidome

A species-specific lipidome profile is an inherent feature linked to longevity in the animal kingdom. However, there is a lack of lipidomic studies on human longevity. Here, we use mass spectrometry-based lipidomics to detect and quantify 151 sphingolipid molecular species and use these to define a phenotype of healthy humans with exceptional life span. Our results demonstrate that this profile specifically comprises a higher content of complex glycosphingolipids (hexosylceramides and gangliosides), and lower levels of ceramide species from the de novo pathway, sphingomyelin and sulfatide; while for ceramide-derived signaling compounds, their content remains unchanged. Our findings suggest that structural glycosphingolipids may be more relevant to achieve the centenarian condition than signaling sphingolipids.

Application of lipidomics strategy to explore aging-related biomarkers and potential anti-aging mechanisms of ginseng

Aging often leads to an increase risk of age-related diseases, and the development of anti-aging drugs have become the trend and focus of the current scientific research. In this experiment, serum samples from healthy people of different ages were analyzed based on clinical lipidomics, and a total of 10 potential biomarkers in middle-aged and youth group, 20 biomarkers in the youth and the elderly group were obtained. Furthermore, dhSph and dhCer involved above may affect the aging process through sphingolipid metabolic pathway. As the first and rate-limiting step of catalyzing de novo sphingolipid pathway, SPT may play a key role in human anti-aging, which is revealed by lipidomics liposome tracer analysis. The potential active components in ginseng on SPT was further verified by molecular docking virtual screening and atomic force microscope. Four ingredients of ginseng may reduce the levels of metabolites dhSph and dhCer by inhibiting the activity of SPT, and play an anti-aging effect by affecting the sphingolipid metabolism pathway.A clinical trials registration number: ChiCTR1900026836.

Lipidomic changes of LDL after consumption of Camelina sativa oil, fatty fish and lean fish in subjects with impaired glucose metabolism-A randomized controlled trial

BACKGROUND

There is little knowledge on the effects of alpha-linolenic acid (ALA) and n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) on the LDL lipidome and aggregation of LDL particles.

OBJECTIVE

We examined if consumption of Camelina sativa oil (CSO) as a source of ALA, fatty fish (FF) as a source of n-3 LCPUFA and lean fish (LF) as a source of fish protein affect the lipidome of LDL as compared to a control diet.

METHODS

Participants with impaired glucose tolerance (39 women and 40 men) were randomized to 4 study groups (CSO providing 10 g/d ALA, FF and LF [both 4 fish meals/wk] and control limiting their fish and ALA intake) in a 12-week, parallel trial. Diets were instructed and dietary fats were provided to the participants. The lipidome of LDL particles isolated from samples collected at baseline and after intervention was analyzed with electrospray ionization-tandem mass spectrometry.

RESULTS

In the CSO group, the relative concentrations of saturated and monounsaturated cholesteryl ester species in LDL decreased and the species with ALA increased. In the FF group, LDL phosphatidylcholine (PC) species containing n-3 LCPUFA increased. There was a significant positive correlation between the change in total sphingomyelin and change in LDL aggregation, while total PC and triunsaturated PC species were inversely associated with LDL aggregation when all the study participants were included in the analysis.

CONCLUSION

Dietary intake of CSO and FF modifies the LDL lipidome to contain more polyunsaturated and less saturated lipid species. The LDL surface lipids are associated with LDL aggregation.

Changes in plasma phospholipids and sphingomyelins with aging in men and women: A comprehensive systematic review of longitudinal cohort studies

BACKGROUND

Aging affects the serum levels of various metabolites which may be involved in the pathogenesis of chronic diseases. The aim of this review article is to summarize the relationship between aging and alterations in the plasma phospholipids and sphingomyelins.

METHODS

PRISMA guidelines were employed during all steps. MEDLINE (PubMed), Scopus, Embase and Web of Sciences databases and Google Scholar were searched up to October 2020. Cohort studies investigating the relationship between aging and within-person changes in sphingomyelin (SM), phosphatidyl choline (PC), lyso PC (LPC) and phosphatidyl ethanolamine (PE) were included. Newcastle-Ottawa scale was used to assess the quality of included studies.

RESULTS

A total of 1425 studies were identified. After removing 610 duplicates and 723 irrelevant studies, full texts of 92 articles were evaluated. Of these 92, 6 studies (including data from 7 independent cohorts) met the inclusion criteria and are included in this review. All study populations were healthy and included both men and women. Results by sex were reported in 3 cohorts for PC, 5 cohorts for LPC, 3 cohorts for SM, and only 1 cohort for PE. In men, PC, SM, PE and LPC decreased with aging, although results for LPC were inconsistent. In women, LPC, SM, and PE increased age, whereas changes in PC were inconsistent.

CONCLUSION

Within-person serum levels of phospholipids and sphingomyelins, decrease during aging in men and increase in women. Notably, however, there were some inconsistencies across studies of LPC in men and of PC in women.

Plasma Ceramides and Risk of Impaired Lower-Extremity Function in Older Adults: A Nested Case-Control Study

BACKGROUND

Higher levels of ceramides have been linked to several chronic diseases; also there is emerging cross-sectional evidence that ceramides are associated with lower physical functioning. This research assessed for the first time the prospective relationship between ceramide species and impaired lower-extremity function (ILEF) in older adults.

METHODS

Case-control study with 43 cases of ILEF and 86 age- and sex-matched controls, which was nested in the Seniors-ENRICA cohort of community-dwelling older adults. Incident ILEF from 2015 to 2017 was ascertained with the Short Physical Performance Battery. In 2015, 27 ceramide species were measured in plasma by liquid chromatography-tandem mass spectrometry. Conditional logistic regression models were used to assess the longitudinal relationship between ceramides concentration and incidence of ILEF.

RESULTS

After adjusting for education level, body mass index, alcohol and total energy intake, physical activity, and presence of chronic conditions, some ceramide species were related to 2-year incidence of ILEF. Specifically, the odds ratios of ILEF per 1-SD increase in ceramide concentration were: 1.66 [95% CI = (1.03, 2.68)] for ceramide C14:0, 1.61 (1.00, 2.59) for ceramide C16:0, and 1.64 (1.03, 2.60) for ceramide C16:1 (n-7). In the case of ceramides C16:0 and C16:1 (n-7), a stronger relationship was found in those with a higher body mass index; systolic blood pressure could also mediate the relationship between ceramide C16:1 (n-7) and ILEF (p for interaction = .03).

CONCLUSIONS

Higher plasma levels of ceramides C14:0, C16:0, and C16:1 (n-7) are associated with higher risk of ILEF, and might serve as risk markers for functional decline in older adults.

Metabolomic differences between critically Ill women and men

Metabolism differs in women and men at homeostasis. Critically ill patients have profound dysregulation of homeostasis and metabolism. It is not clear if the metabolic response to critical illness differs in women compared to men. Such sex-specific differences in illness response would have consequences for personalized medicine. Our aim was to determine the sex-specific metabolomic response to early critical illness. We performed a post-hoc metabolomics study of the VITdAL-ICU trial where subjects received high dose vitamin D3 or placebo. Using mixed-effects modeling, we studied sex-specific changes in metabolites over time adjusted for age, Simplified Acute Physiology Score II, admission diagnosis, day 0 25-hydroxyvitamin D level, and 25-hydroxyvitamin D response to intervention. In women, multiple members of the sphingomyelin and lysophospholipid metabolite classes had significantly positive Bonferroni corrected associations over time compared to men. Further, multiple representatives of the acylcarnitine, androgenic steroid, bile acid, nucleotide and amino acid metabolite classes had significantly negative Bonferroni corrected associations over time compared to men. Gaussian graphical model analyses revealed sex-specific functional modules. Our findings show that robust and coordinated sex-specific metabolite differences exist early in critical illness.

Sphingolipids and physical function in the Atherosclerosis Risk in Communities (ARIC) study

Long-chain sphingomyelins (SMs) may play an important role in the stability of myelin sheath underlying physical function. The objective of this study was to examine the cross-sectional and longitudinal associations of long-chain SMs [SM (41:1), SM (41:2), SM (43:1)] and ceramides [Cer (41:1) and Cer (43:1)] with physical function in the Atherosclerosis Risk in Communities (ARIC) study. Plasma concentrations of SM (41:1), SM (41:2), SM (43:1), Cer (41:1) and Cer (43:1) were measured in 389 ARIC participants in 2011-13. Physical function was assessed by grip strength, Short Physical Performance Battery (SPPB), 4-m walking speed at both 2011-13 and 2016-17, and the modified Rosow-Breslau questionnaire in 2016-2017. Multivariable linear and logistic regression analyses were performed, controlling for demographic and clinical confounders. In cross-sectional analyses, plasma concentrations of SM 41:1 were positively associated with SPPB score (β-coefficients [95% confidence internal]: 0.33 [0.02, 0.63] per 1 standard deviation [SD] increase in log-transformed concentration, p value 0.04), 4-m walking speed (0.042 m/s [0.01, 0.07], p value 0.003), and negatively with self-reported disability (odds ratio = 0.73 [0.65, 0.82], p value < 0.0001). Plasma concentrations of the five metabolites examined were not significantly associated with longitudinal changes in physical function or incidence of poor mobility. In older adults, plasma concentrations of long-chain SM 41:1 were cross-sectionally positively associated with physical function.

Plasma Sphingomyelins in Late-Onset Alzheimer's Disease

BACKGROUND

Altered plasma levels of sphingolipids, including sphingomyelins (SM), have been found in mouse models of Alzheimer's disease (AD) and in AD patient plasma samples.

OBJECTIVE

This study assesses fourteen plasma SM species in a late-onset AD (LOAD) patient cohort (n = 138).

METHODS

Specimens from control, preclinical, and symptomatic subjects were analyzed using targeted mass-spectrometry-based metabolomic methods.

RESULTS

Total plasma SM levels were not significantly affected by age or cognitive status. However, one metabolite that has been elevated in manifest AD in several recent studies, SM OHC14:1, was reduced significantly in pre-clinical AD and MCI relative to normal controls.

CONCLUSION

We recommend additional comprehensive plasma lipidomics in experimental and clinical biospecimens related to LOAD that might advance the utility of plasma sphingomyelin levels in molecular phenotyping and interpretations of pathobiological mechanisms.

Serum ceramide levels are altered in multiple sclerosis

BACKGROUND

Sphingolipids are myelin components and inflammatory signaling intermediates. Sphingolipid metabolism may be altered in people with multiple sclerosis (PwMS), but existing studies are limited by small sample sizes.

OBJECTIVES

To compare the levels of serum ceramides between PwMS and healthy controls (HCs) and to determine whether ceramide levels correlate with disability status, as well as optical coherence tomography (OCT)-derived rates of retinal layer atrophy.

METHODS

We performed targeted lipidomics analyses for 45 ceramides in PwMS (n = 251) and HCs (n = 68). For a subset of PwMS, baseline and 5-year Expanded Disability Status Scale (EDSS) assessments (n = 185), or baseline and serial spectral-domain OCT (n = 180) were assessed.

RESULTS

Several ceramides, including hexosylceramides, lactosylceramides, and dihydroceramides, were altered in PwMS compared with HCs. Higher levels of Cer16:0 were associated with higher odds of EDSS worsening at 5 years in univariable (odds ratio (OR) = 3.84, 95% confidence interval (CI) = 1.41-10.43) and multivariable analyses accounting for age, sex, and race (OR = 2.97, 95% CI = 1.03-8.59). Each 1 ng/mL higher concentration of Hex-Cer22:0 and DH-HexCer22:0 was associated with accelerated rates (μm/year) of ganglion cell + inner plexiform layer (-0.138 ± 0.053, p = 0.01; -0.158 ± 0.053, p = 0.003, respectively) and peripapillary retinal nerve fiber layer thinning (-0.305 ± 0.107, p = 0.004; -0.358 ± 0.106, p = 0.001, respectively).

CONCLUSION

Ceramide levels are altered in PwMS and may be associated with retinal neurodegeneration and physical disability.

Astrocytes deliver CK1 to neurons via extracellular vesicles in response to inflammation promoting the translation and amyloidogenic processing of APP

Chronic inflammation is thought to contribute to the early pathogenesis of Alzheimer's disease (AD). However, the precise mechanism by which inflammatory cytokines promote the formation and deposition of Aβ remains unclear. Available data suggest that applications of inflammatory cytokines onto isolated neurons do not promote the formation of Aβ, suggesting an indirect mechanism of action. Based on evidence astrocyte derived extracellular vesicles (astrocyte derived EVs) regulate neuronal functions, and data that inflammatory cytokines can modify the molecular cargo of astrocyte derived EVs, we sought to determine if IL-1β promotes the formation of Aβ indirectly through actions of astrocyte derived EVs on neurons. The production of Aβ was increased when neurons were exposed to astrocyte derived EVs shed in response to IL-1β (astrocyte derived EV-IL-1β). The mechanism for this effect involved an enrichment of Casein kinase 1 (CK1) in astrocyte derived EV-IL-1β. This astrocyte derived CK1 was delivered to neurons where it formed a complex with neuronal APC and GSK3 to inhibit the β-catenin degradation. Stabilized β-catenin translocated to the nucleus and bound to Hnrnpc gene at promoter regions. An increased cellular concentration of hnRNP C promoted the translation of APP by outcompeting the translational repressor fragile X mental retardation protein (FMRP) bound to APP mRNA. An increased amount of APP protein became co-localized with BACE1 in enlarged membrane microdomains concurrent with increased production of Aβ. These findings identify a mechanism whereby inflammation promotes the formation of Aβ through the actions of astrocyte derived EV-IL-1β on neurons.

Resolving Modifications on Sphingoid Base and N-Acyl Chain of Sphingomyelin Lipids in Complex Lipid Extracts

Sphingomyelins (SMs) are an essential class of lipids widely existing in different organisms. The sphingoid base and N-acyl chain are two building blocks which can undergo different types of modifications during lipogenesis, including desaturation, hydroxylation, and methyl branching. Current lipidomic analysis methods cannot provide detailed information on these structural motifs. Herein, we developed a tandem mass spectrometric method by harnessing radical-directed dissociation (RDD) from collision-induced dissociation (CID) of the bicarbonate anion adduct of SM ([M + HCO₃]^-). A major RDD channel produced a high-abundance fragment carrying the intact N-acyl chain, termed as "N-acyl fragment", allowing the assignment of the sphingoid base/N-acyl composition and relative quantitation of compositional isomers of SM at high sensitivity. RDD also produced intrachain fragments in lower abundances, which helped localization of methyl branching and hydroxylation in SM. The acetone Paternò-Büchi (PB) reaction was found to be capable of derivatizing the Δ4 carbon-carbon double bond (C═C) in sphingosine (SPH) base and producing C═C diagnostic ions upon CID, albeit at much lower efficiencies than those of the isolated C═C in alkyl chains. A liquid chromatography-mass spectrometry workflow was developed by incorporating MS² CID of SM via [M + HCO₃]^- and PB-MS² CID. The capability of profiling SM with detailed structural information was demonstrated by analyzing complex lipid extracts from porcine brain and Caenorhabditis elegans. These results provided visualization of the sphingoid base/N-acyl compositional isomers of SM lipids and revealed large structural diversity from each sample. These included identification of the sphingadiene base [d18:1(Δ4,14)], C═C location isomers in N-acyls, C-2 hydroxylation of N-acyls, and iso-methyl branched SPH base.

Upregulation of Serum Sphingosine (d18:1)-1-P Potentially Contributes to Distinguish HCC Including AFP-Negative HCC From Cirrhosis

Background

Serum sphingolipids are widely involved in the development of hepatocellular carcinoma (HCC). We investigated the serum sphingolipid profile in patients with HCC or cirrhosis and explored the potential diagnostic efficiency of serum sphingolipid metabolites which may be helpful in differentiating HCC including α-fetoprotein (AFP)-negative HCC from cirrhosis.

Methods

Seventy-two HCC patients (including 24 AFP-negative HCC) and 104 cirrhotic patients were consecutively enrolled in this study. High-performance liquid chromatography–tandem mass spectrometry was used to detect a panel of 57 serum sphingolipid metabolites.

Results

Twenty-four sphingolipid metabolites showed significant differences between HCC and cirrhotic patients (all P < 0.05). Sphingosine (d18:1)-1-P was found to have the potential to differentiate HCC from cirrhosis by orthogonal partial least squares discriminant analysis (OPLS-DA). There was no significant difference in the efficacy of Sphingosine (d18:1)-1-P and AFP to distinguish HCC from cirrhosis, and the area under the receiver operating curve (AUC) were 0.85 and 0.83 (P > 0.05), respectively. When the cut-off value of Sphingosine (d18:1)-1-P was set at 56.29 pmol/0.1 ml, the sensitivity and specificity were 79.20% and 78.70%, respectively. Notably, the upregulation of Sphingosine (d18:1)-1-P could also distinguish AFP-negative HCC from cirrhosis with an AUC of 0.79. The sensitivity and specificity were 62.50% and 77.90% at a cut-off value of 56.29 pmol/0.1 ml. Spearman rank correlation analysis revealed that serum Sphingosine (d18:1)-1-P was not correlated with AFP in patients with cirrhosis, AFP-positive HCC, and AFP-negative HCC. Moreover, the difference in the diagnostic efficiency of serum Sphingosine (d18:1)-1-P was not statistically significant between tumor size (≤2 cm vs. >2 cm, P = 0.476). Also, there was no difference among patients with different TNM stages and BCLC stages.

Conclusion

The upregulation of serum Sphingosine (d18:1)-1-P exhibits good diagnostic performance for HCC. Particularly, Sphingosine (d18:1)-1-P could also serve as a biomarker for the diagnosis of AFP-negative HCC. These findings may contribute to the non-invasive diagnosis of HCC including AFP-negative HCC.

Inhibition of neutral sphingomyelinase 2 promotes remyelination

Myelination requires a highly organized synthesis of multiple lipid species that regulate myelin curvature and compaction. For reasons that are not understood, central nervous system remyelinated axons often have thin myelin sheaths with a disorganized structure susceptible to secondary demyelination. We found that expression of the sphingomyelin hydrolase neutral sphingomyelinase 2 (nSMase2) during the differentiation of oligodendrocyte progenitor cells (OPCs) to myelinating oligodendrocytes changes their response to inflammatory cytokines. OPCs do not express nSMase2 and exhibit a protective/regenerative response to tumor necrosis factor-α and interleukin-1β. Oligodendrocytes express nSMase2 and exhibit a stress response to cytokine challenge that includes an overproduction of ceramide, a sphingolipid that forms negative curvatures in membranes. Pharmacological inhibition or genetic deletion of nSMase2 in myelinating oligodendrocytes normalized the ceramide content of remyelinated fibers and increased thickness and compaction. These results suggest that inhibition of nSMase2 could improve the quality of myelin and stabilize structure.

The Lipidome Fingerprint of Longevity

Lipids were determinants in the appearance and evolution of life. Recent studies disclose the existence of a link between lipids and animal longevity. Findings from both comparative studies and genetics and nutritional interventions in invertebrates, vertebrates, and exceptionally long-lived animal species—humans included—demonstrate that both the cell membrane fatty acid profile and lipidome are a species-specific optimized evolutionary adaptation and traits associated with longevity. All these emerging observations point to lipids as a key target to study the molecular mechanisms underlying differences in longevity and suggest the existence of a lipidome profile of long life.

Longitudinal plasma metabolomics of aging and sex

Understanding how metabolites are longitudinally influenced by age and sex could facilitate the identification of metabolomic profiles and trajectories that indicate disease risk. We investigated the metabolomics of age and sex using longitudinal plasma samples from the Wisconsin Registry for Alzheimer’s Prevention (WRAP), a cohort of participants who were dementia free at enrollment. Metabolomic profiles were quantified for 2,344 fasting plasma samples among 1,212 participants, each with up to three study visits. Of 1,097 metabolites tested, 623 (56.8%) were associated with age and 695 (63.4%) with sex after correcting for multiple testing. Approximately twice as many metabolites were associated with age in stratified analyses of women versus men, and 68 metabolite trajectories significantly differed by sex, most notably including sphingolipids, which tended to increase in women and decrease in men with age. Using genome-wide genotyping, we also report the heritabilities of metabolites investigated, which ranged dramatically (0.2–99.2%); however, the median heritability of 36.2% suggests that many metabolites are highly influenced by a complex combination of genomic and environmental influences. These findings offer a more profound description of the aging process and may inform many new hypotheses regarding the role metabolites play in healthy and accelerated aging.

Lipid-based biomarkers for CVD, COPD, and aging - A translational perspective

For many diseases, there is an unmet need for new or better biomarkers for improved disease risk assessment and monitoring, as available markers lack sufficient specificity. Lipids are drawing major interest as potential candidates for filling these gaps. This has recently been demonstrated by the identification of selective ceramides for prediction of cardiovascular mortality, enabling improved risk assessment of cardiovascular disease compared with conventional clinical markers. In this review, we discuss current lipid biomarker findings and the possible connection between cardiovascular disease, chronic obstructive pulmonary disease, and aging. Moreover, we discuss how to overcome the current roadblocks facing lipid biomarker research. We stress the need for improved quantification, standardization of methodologies, and establishment of initial reference values to allow for an efficient transfer path of research findings into the clinical landscape, and, ultimately, to put newly identified biomarkers into practical use.

Lipidomics reveals carnitine palmitoyltransferase 1C protects cancer cells from lipotoxicity and senescence

Lipotoxicity, caused by intracellular lipid accumulation, accelerates the degenerative process of cellular senescence, which has implications in cancer development and therapy. Previously, carnitine palmitoyltransferase 1C (CPT1C), a mitochondrial enzyme that catalyzes carnitinylation of fatty acids, was found to be a critical regulator of cancer cell senescence. However, whether loss of CPT1C could induce senescence as a result of lipotoxicity remains unknown. An LC/MS-based lipidomic analysis of PANC-1, MDA-MB-231, HCT-116 and A549 cancer cells was conducted after siRNA depletion of CPT1C. Cellular lipotoxicity was further confirmed by lipotoxicity assays. Significant changes were found in the lipidome of CPT1C-depleted cells, including major alterations in fatty acid, diacylglycerol, triacylglycerol, oxidative lipids, cardiolipin, phosphatidylglycerol, phosphatidylcholine/phosphatidylethanolamine ratio and sphingomyelin. This was coincident with changes in expressions of mRNAs involved in lipogenesis. Histological and biochemical analyses revealed higher lipid accumulation and increased malondialdehyde and reactive oxygen species, signatures of lipid peroxidation and oxidative stress. Reduction of ATP synthesis, loss of mitochondrial transmembrane potential and down-regulation of expression of mitochondriogenesis gene mRNAs indicated mitochondrial dysfunction induced by lipotoxicity, which could further result in cellular senescence. Taken together, this study demonstrated CPT1C plays a critical role in the regulation of cancer cell lipotoxicity and cell senescence, suggesting that inhibition of CPT1C may serve as a new therapeutic strategy through induction of tumor lipotoxicity and senescence.

Association Between Sphingolipids and Cardiopulmonary Fitness in Coronary Artery Disease Patients Undertaking Cardiac Rehabilitation

The long-term benefits conferred by cardiac rehabilitation (CR) in those with coronary artery disease (CAD) are strongly linked with an improvement in cardiopulmonary fitness. This study aimed to determine the association between peripheral sphingolipids and cardiopulmonary fitness in CAD subjects undertaking CR. Patients with CAD (n = 100, mean age = 64 ± 6 years, 85% male, mean years of education = 17 ± 3 years) underwent 6 months of CR with blood collected at baseline, 3 and 6 months. Cardiopulmonary fitness was assessed by measuring peak oxygen uptake (VO2peak) at all time points. High performance liquid chromatography coupled electrospray ionization tandem mass spectrometry was used to quantify plasma sphingolipid concentrations. Cross-sectional and longitudinal associations between sphingolipids and VO2peak were assessed using linear regressions and mixed models, respectively. Higher concentrations of sphingomyelin C18:1 (β = -0.26, p = .01), ceramides C16:0 (β = -0.24, p = .02), C18:0 (β = -0.29, p = .002), C20:0 (β = -0.24, p = .02) and C24:1 (β = -0.24, p = .01) and monohexylceramide C18:0 (β = -0.23, p = .02) were associated with poorer VO2peak at baseline. An improvement in VO2peak was associated with a decrease in sphingomyelin C18:1 (b = -10.09, p = .006), ceramides C16:0 (b = -9.25, p = .0003), C18:0 (b = -5.44, p = .0003) and C24:1 (b = -2.46, p = .006) and monohexylceramide C18:0 (b = -5.37, p = .005). Specific long chain sphingolipids may be useful markers of fitness and response to exercise in CAD.

Blood Metabolite Signature of Metabolic Syndrome Implicates Alterations in Amino Acid Metabolism: Findings from the Baltimore Longitudinal Study of Aging (BLSA) and the Tsuruoka Metabolomics Cohort Study (TMCS)

Rapid lifestyle and dietary changes have contributed to a rise in the global prevalence of metabolic syndrome (MetS), which presents a potential healthcare crisis, owing to its association with an increased burden of multiple cardiovascular and neurological diseases. Prior work has identified the role that genetic, lifestyle, and environmental factors can play in the prevalence of MetS. Metabolomics is an important tool to study alterations in biochemical pathways intrinsic to the pathophysiology of MetS. We undertook a metabolomic study of MetS in serum samples from two ethnically distinct, well-characterized cohorts-the Baltimore Longitudinal Study of Aging (BLSA) from the U.S. and the Tsuruoka Metabolomics Cohort Study (TMCS) from Japan. We used multivariate logistic regression to identify metabolites that were associated with MetS in both cohorts. Among the top 25 most significant (lowest p-value) metabolite associations with MetS in each cohort, we identified 18 metabolites that were shared between TMCS and BLSA, the majority of which were classified as amino acids. These associations implicate multiple biochemical pathways in MetS, including branched-chain amino acid metabolism, glutathione production, aromatic amino acid metabolism, gluconeogenesis, and the tricarboxylic acid cycle. Our results suggest that fundamental alterations in amino acid metabolism may be central features of MetS.

Lipidomic profiles, lipid trajectories and clinical biomarkers in female elite endurance athletes

We assessed whether blood lipid metabolites and their changes associate with various cardiometabolic, endocrine, bone- and energy-related comorbidities of Relative Energy Deficiency in Sport (RED-S) in female elite endurance athletes. Thirty-eight Scandinavian female elite athletes underwent a day-long exercise test. Five blood samples were obtained during the day - at fasting state and before and after two standardized exercise tests. Clinical biomarkers were assessed at fasting state, while untargeted lipidomics was undertaken using all blood samples. Linear and logistic regression was used to assess associations between lipidomic features and clinical biomarkers. Overrepresentations of findings with P < 0.05 from these association tests were assessed using Fisher's exact tests. Self-organizing maps and a trajectory clustering algorithm were utilized to identify informative clusters in the population. Twenty associations P_FDR < 0.05 were detected between lipidomic features and clinical biomarkers. Notably, cortisol demonstrated an overrepresentation of associations with P < 0.05 compared to other traits (P_Fisher = 1.9×10^-14). Mean lipid trajectories were created for 201 named features for the cohort and subsequently by stratifying participants by their energy availability and menstrual dysfunction status. This exploratory analysis of lipid trajectories indicates that participants with menstrual dysfunction might have decreased adaptive response to exercise interventions.

Increased monohexosylceramide levels in the serum of established rheumatoid arthritis patients

Objectives

To identify serum sphingolipids that could act as candidate biomarkers in RA.

Methods

We performed lipidomic analyses in the serum of 82 participants: 19 established RA patients, 18 untreated early RA patients, 13 untreated early arthritis patients not fulfilling the classification criteria for RA, 12 established SpA patients and 20 controls. We compared the lipid levels from the different patient groups with the control group through multiple-regression analyses controlling for age at diagnosis, gender and medication (cDMARDs and corticoids).

Results

Established RA patients had significantly increased levels of sphingosine, monohexosylceramide and ceramide compared with controls, when controlling for age and gender. Monohexosylceramide levels remained significantly increased when additionally controlling for medication. On the contrary, SpA patients had significantly decreased levels of ceramide, in both analyses.

Conclusion

We observed a detectable increase in the levels of certain sphingolipids in the serum of established RA patients when compared with controls, in line with previous observations in the synovial fluid. Such findings provide further evidence that sphingolipids may play a key role in the pathophysiology of RA.

Plasma Sphingolipids are Associated With Gait Parameters in the Mayo Clinic Study of Aging

Background

Disrupted gait has been associated with an increased risk of frailty, disability, and death, but the causal molecular pathways are not well understood. Sphingolipids, including ceramides, are associated with multiple age-related diseases. Ceramides promote atrophy, necrosis, and proteolysis in cellular and animal models, and ceramide C16:0 levels are negatively correlated with muscle mass in men. However, there is a paucity of evidence examining sphingolipids and physical function.

Methods

We examined the cross-sectional association between plasma ceramides, sphingosine-1-phosphate (S1P), and ceramide/S1P ratios and gait, a robust measure of physical function, in 340 clinically normal participants aged 70 years and older enrolled in the Mayo Clinic Study of Aging. GAITRite® instrumentation was used to measure gait speed, cadence, step width, double support time, and intra-individual stride time variability. Based on previous studies, we hypothesized that higher plasma levels of ceramide C16:0 would be associated with worse gait.

Results

Multivariable adjusted linear regression models revealed that higher levels of ceramide C16:0 were associated with slower gait speed, decreased cadence, and increased double support time.

Conclusions

These results suggest an association between plasma ceramide C16:0 and physical function. Longitudinal studies are needed to determine whether elevated ceramide C16:0 can be utilized as a prognostic marker for functional decline.

Comparison of Single Phase and Biphasic Extraction Protocols for Lipidomic Studies Using Human Plasma

Lipidomic profiling of plasma is an emerging field, given the importance of lipids in major cellular pathways, and is dependent on efficient lipid extraction protocols. Recent attention has turned to plasma lipidomics as a means to identify potential diagnostic and prognostic biomarkers related to dementia, neuropsychiatric health and disease. Although several solvent-based lipid extraction protocols have been developed and are currently in use, novel and more efficient methods could greatly simplify lipid analysis in plasma and warrant investigation. Human plasma from normolipidemic adult volunteers was collected to evaluate three different solvent extraction protocols, including the classical Folch method, the methanol/tert-butyl methyl ether (MTBE) (Matyash) method, and a recent single-phase methanol/1-butanol (Alshehry) method. Extracted lipids were analyzed using liquid chromatography mass spectrometry (LC-MS) in positive and negative ion mode. Overall, more than 500 different lipids were identified in positive and negative ion mode combined. Our data show that the single phase Alshehry method was as effective as the Folch and Matyash methods in extracting most lipid classes and was more effective in extraction of polar lipids. Normalized peak areas of the Alshehry method were highly and positively correlated with both the Folch and Matyash methods (r 2 = 0.99 and 0.97, respectively). Within- and between- subject correlations were r = 0.99 and 0.96, respectively. Median intra-assay coefficient of variation (CV%) in positive mode was 14.1, 15.1, and 21.8 for the Alshehry, Folch and Matyash methods, respectively. Median Alshehry inter-assay CV (collected over 5 separate days) was 14.4%. In conclusion, the novel Alshehry method was at least as good as, if not better than the established biphasic extraction methods in detecting a wide range of lipid classes, using as little as 10 μL of plasma, and was highly reproducible, safer and more environmentally-friendly as it doesn't require chloroform.

Ceramide Accumulation Is Associated with Declining Verbal Memory in Coronary Artery Disease Patients: An Observational Study

Background:

Biomarkers in cognitively vulnerable populations, like those with coronary artery disease (CAD), may inform earlier intervention in vascular neurodegeneration. Circulating ceramide C18:0 (CerC18:0) is associated with changes in verbal memory in early neurodegeneration and CAD progression.

Objective:

To investigate whether plasma CerC18:0 accumulation is associated with longitudinal declines in verbal memory performance in CAD.

Methods:

In addition to total CerC18:0, we assessed its relative abundance to its precursors as ratios: CerC18:0 to monohexosylceramide C18:0 (MHxCer18:0), CerC18:0 to sphingomyelin C18:0 (SM18:0), and CerC18:0 to sphingosine-1-phosphate (S1P). Verbal memory was assessed using the California Verbal Learning Test 2^nd Ed. Using mixed models in 60 CAD participants, we evaluated associations between baseline CerC18:0 ratios and changes in verbal memory performance, adjusting for age, body mass index, and education. Given that cognitive decline is more rapid following onset of deficits, these associations were compared between those with possible mild vascular neurocognitive disorder (MVND).

Results:

Increased baseline CerC18:0 concentrations correlated with worse verbal memory performance over time (b[SE] = – 0.91[0.30], p = 0.003). Increased baseline CerC18:0/SM18:0 (b[SE] = – 1.11[`], p = 0.03) were associated with worse verbal memory performance over time. These associations were not mediated by whether or not patients had possible MVND at baseline.

Conclusion:

These findings support aberrant CerC18:0 metabolism as an early neurobiological change in vascular neurodegeneration. Future studies should measure enzymes responsible for conversion of sphingolipid precursors into CerC18:0 to assess enzymatic activity.

The Cross-Talk Between Sphingolipids and Insulin-Like Growth Factor Signaling: Significance for Aging and Neurodegeneration

Bioactive sphingolipids: sphingosine, sphingosine-1-phosphate (S1P), ceramide, and ceramide-1-phosphate (C1P) are increasingly implicated in cell survival, proliferation, differentiation, and in multiple aspects of stress response in the nervous system. The opposite roles of closely related sphingolipid species in cell survival/death signaling is reflected in the concept of tightly controlled sphingolipid rheostat. Aging has a complex influence on sphingolipid metabolism, disturbing signaling pathways and the properties of lipid membranes. A metabolic signature of stress resistance-associated sphingolipids correlates with longevity in humans. Moreover, accumulating evidence suggests extensive links between sphingolipid signaling and the insulin-like growth factor I (IGF-I)-Akt-mTOR pathway (IIS), which is involved in the modulation of aging process and longevity. IIS integrates a wide array of metabolic signals, cross-talks with p53, nuclear factor κB (NF-κB), or reactive oxygen species (ROS) and influences gene expression to shape the cellular metabolic profile and stress resistance. The multiple connections between sphingolipids and IIS signaling suggest possible engagement of these compounds in the aging process itself, which creates a vulnerable background for the majority of neurodegenerative disorders.

Plasma Metabolites Associated with Brain MRI Measures of Neurodegeneration in Older Adults in the Atherosclerosis Risk in Communities⁻Neurocognitive Study (ARIC-NCS)

Background: Plasma metabolites are associated with cognitive and physical function in the elderly. Because cerebral small vessel disease (SVD) and neurodegeneration are common causes of cognitive and physical function decline, the primary objective of this study was to investigate the associations of six plasma metabolites (two plasma phosphatidylcholines [PCs]: PC aa C36:5 and PC aa 36:6 and four sphingomyelins [SMs]: SM C26:0, SM [OH] C22:1, SM [OH] C22:2, SM [OH] C24:1) with magnetic resonance imaging (MRI) features of cerebral SVD and neurodegeneration in older adults. Methods: This study included 238 older adults in the Atherosclerosis Risk in Communities study at the fifth exam. Multiple linear regression was used to assess the association of each metabolite (log-transformed) in separate models with MRI measures except lacunar infarcts, for which binary logistic regression was used. Results: Higher concentrations of plasma PC aa C36:5 had adverse associations with MRI features of cerebral SVD (odds ratio of 1.69 [95% confidence interval: 1.01, 2.83] with lacunar infarct, and beta of 0.16 log [cm3] [0.02, 0.30] with log [White Matter Hyperintensities (WMH) volume]) while higher concentrations of 3 plasma SM (OH)s were associated with higher total brain volume (beta of 12.0 cm3 [5.5, 18.6], 11.8 cm3 [5.0, 18.6], and 7.3 cm3 [1.2, 13.5] for SM [OH] C22:1, SM [OH] C22:2, and SM [OH] C24:1, respectively). Conclusions: This study identified associations between certain plasma metabolites and brain MRI measures of SVD and neurodegeneration in older adults, particularly higher SM (OH) concentrations with higher total brain volume.

Effect of Sex on Biomarker Response in a Mouse Model of the Hematopoietic Acute Radiation Syndrome

Sex is an important confounding variable in biomarker development that must be incorporated into biomarker discovery and validation. Additionally, understanding of sex as a biological variable is essential for effective translation of biomarkers in animal models to human populations. Toward these ends, we conducted high-throughput targeted metabolomics using liquid chromatography tandem mass spectrometry and multiplexed immunoassay analyses using a Luminex-based system in both male and female mice in a model of total-body irradiation at a radiation dose consistent with the hematopoietic acute radiation syndrome. Metabolomic and immunoassay analyses identified metabolites and cytokines that were significantly different in plasma from naive and irradiated C57BL/6 mice consisting of equal numbers of female and male mice at 3 d after 8.0 or 8.72 Gy, an approximate LD60-70/30 dose of total-body irradiation. An additional number of metabolites and cytokines had sex-specific responses after radiation. Analyses of sham-irradiated mice illustrate the presence of stress-related changes in several cytokines due simply to undergoing the irradiation procedure, absent actual radiation exposure. Basal differences in metabolite levels between female and male were also identified as well as time-dependent changes in cytokines up to 9 d postexposure. These studies provide data toward defining the influence of sex on plasma-based biomarker candidates in a well-defined mouse model of acute radiation syndrome.

Plasma lipidome variation during the second half of the human lifespan is associated with age and sex but minimally with BMI

Recent advances in mass spectrometry-based techniques have inspired research into lipidomics, a subfield of ‘–omics’, which aims to identify and quantify large numbers of lipids in biological extracts. Although lipidomics is becoming increasingly popular as a screening tool for understanding disease mechanisms, it is largely unknown how the lipidome naturally varies by age and sex in healthy individuals. We aimed to identify cross-sectional associations of the human lipidome with ‘physiological’ ageing, using plasma from 100 subjects with an apolipoprotein E (APOE) E3/E3 genotype, and aged between 56 to 100 years. Untargeted analysis was performed by liquid chromatography coupled-mass spectrometry (LC-MS/MS) and data processing using LipidSearch software. Regression analyses confirmed a strong negative association of age with the levels of various lipid, which was stronger in males than females. Sex-related differences include higher LDL-C, HDL-C, total cholesterol, particular sphingomyelins (SM), and docosahexaenoic acid (DHA)-containing phospholipid levels in females. Surprisingly, we found a minimal relationship between lipid levels and body mass index (BMI). In conclusion, our results suggest substantial age and sex-related variation in the plasma lipidome of healthy individuals during the second half of the human lifespan. In particular, globally low levels of blood lipids in the ‘oldest old’ subjects over 95 years could signify a unique lipidome associated with extreme longevity.

The Role of Ceramide and Sphingosine-1-Phosphate in Alzheimer's Disease and Other Neurodegenerative Disorders

Bioactive sphingolipids-ceramide, sphingosine, and their respective 1-phosphates (C1P and S1P)-are signaling molecules serving as intracellular second messengers. Moreover, S1P acts through G protein-coupled receptors in the plasma membrane. Accumulating evidence points to sphingolipids' engagement in brain aging and in neurodegenerative disorders such as Alzheimer's, Parkinson's, and Huntington's diseases and amyotrophic lateral sclerosis. Metabolic alterations observed in the course of neurodegeneration favor ceramide-dependent pro-apoptotic signaling, while the levels of the neuroprotective S1P are reduced. These trends are observed early in the diseases' development, suggesting causal relationship. Mechanistic evidence has shown links between altered ceramide/S1P rheostat and the production, secretion, and aggregation of amyloid β/α-synuclein as well as signaling pathways of critical importance for the pathomechanism of protein conformation diseases. Sphingolipids influence multiple aspects of Akt/protein kinase B signaling, a pathway that regulates metabolism, stress response, and Bcl-2 family proteins. The cross-talk between sphingolipids and transcription factors including NF-κB, FOXOs, and AP-1 may be also important for immune regulation and cell survival/death. Sphingolipids regulate exosomes and other secretion mechanisms that can contribute to either the spread of neurotoxic proteins between brain cells, or their clearance. Recent discoveries also suggest the importance of intracellular and exosomal pools of small regulatory RNAs in the creation of disturbed signaling environment in the diseased brain. The identified interactions of bioactive sphingolipids urge for their evaluation as potential therapeutic targets. Moreover, the early disturbances in sphingolipid metabolism may deliver easily accessible biomarkers of neurodegenerative disorders.

Comprehensive and Reproducible Untargeted Lipidomic Workflow Using LC-QTOF Validated for Human Plasma Analysis

The goal of this work was to develop a label-free, comprehensive, and reproducible high-resolution liquid chromatography-mass spectrometry (LC-MS)-based untargeted lipidomic workflow using a single instrument, which could be applied to biomarker discovery in both basic and clinical studies. For this, we have (i) optimized lipid extraction and elution to enhance coverage of polar and nonpolar lipids as well as resolution of their isomers, (ii) ensured MS signal reproducibility and linearity, and (iii) developed a bioinformatic pipeline to correct remaining biases. Workflow validation is reported for 48 replicates of a single human plasma sample: 1124 reproducible LC-MS signals were extracted (median signal intensity RSD = 10%), 50% of which are redundant due to adducts, dimers, in-source fragmentation, contaminations, or positive and negative ion duplicates. From the resulting 578 unique compounds, 428 lipids were identified by MS/MS, including acyl chain composition, of which 394 had RSD < 30% inside their linear intensity range, thereby enabling robust semiquantitation. MS signal intensity spanned 4 orders of magnitude, covering 16 lipid subclasses. Finally, the power of our workflow is illustrated by a proof-of-concept study in which 100 samples from healthy human subjects were analyzed and the data set was investigated using three different statistical testing strategies in order to compare their capacity in identifying the impact of sex and age on circulating lipids.

Copper-dependent amino oxidase 3 governs selection of metabolic fuels in adipocytes

Copper (Cu) has emerged as an important modifier of body lipid metabolism. However, how Cu contributes to the physiology of fat cells remains largely unknown. We found that adipocytes require Cu to establish a balance between main metabolic fuels. Differentiating adipocytes increase their Cu uptake along with the ATP7A-dependent transport of Cu into the secretory pathway to activate a highly up-regulated amino-oxidase copper-containing 3 (AOC3)/semicarbazide-sensitive amine oxidase (SSAO); in vivo, the activity of SSAO depends on the organism's Cu status. Activated SSAO oppositely regulates uptake of glucose and long-chain fatty acids and remodels the cellular proteome to coordinate changes in fuel availability and related downstream processes, such as glycolysis, de novo lipogenesis, and sphingomyelin/ceramide synthesis. The loss of SSAO-dependent regulation due to Cu deficiency, limited Cu transport to the secretory pathway, or SSAO inactivation shifts metabolism towards lipid-dependent pathways and results in adipocyte hypertrophy and fat accumulation. The results establish a role for Cu homeostasis in adipocyte metabolism and identify SSAO as a regulator of energy utilization processes in adipocytes.