Plasma ceramides predict all-cause and cause-specific mortality in individuals with type 2 diabetes.

CONTEXT: The CERT1 (Cardiovascular Event Risk Test) score derived from plasma ceramides has been applied clinically for cardiovascular risk assessment. OBJECTIVE: To study whether plasma ceramides predict risk of mortality in patients with type 2 diabetes. DESIGN, SETTING AND PARTICIPANTS: A prospective study which included 1903 outpatients with type 2 diabetes in a regional hospital and a primary care facility in Singapore. EXPOSURE AND OUTCOME: Plasma ceramides (d18:1/16:0, d18:1/18:0, d18:1/24:0, d18:1/24:1) were measured by mass spectrometry and CERT1 score was calculated accordingly. Main outcomes were all-cause and cause-specific mortality. RESULTS: 252 death events were identified during median of 9.3 years of follow-up. Compared to those with low score (≤ 2), participants with a high CERT1 score (≥ 7) had 1.86 (95% CI 1.30-3.65) fold increased risk for all-cause death after adjustment for cardio-renal risk factors including eGFR and albuminuria. As continuous variable, one- unit increment in CERT1 was associated with 8% increased risk for all-cause death (adjusted HR 1.08 [1.04-1.13]). Adding CERT1 onto RECODe (Risk Equations for Complications Of type 2 Diabetes) mortality risk engine significantly improved prediction of 10- year risk of all-cause death (AUC 0.810 to 0.823, delta 0.013 [0.005-0.022]). The association between CERT1 and non-cardiovascular death remained significant (adjusted HR 2.12 [1.32-3.42]), whereas its association with cardiovascular death became non-significant after adjustment for kidney measurements (adjusted HR 1.41 [0.78-2.56]). CONCLUSION: CERT1 score predicts mortality risk independent of clinical cardio-renal risk factors. Further studies are warranted to elucidate the mechanistic linkage between ceramide and mortality, especially non-cardiovascular mortality.

Association of plasma ceramide with decline in kidney function in patients with type 2 diabetes.

Circulating ceramide levels are dysregulated in kidney disease. However, their associations with rapid decline in kidney function (RDKF) and end-stage kidney disease (ESKD) in patients with type 2 diabetes (T2D) are unknown. In this prospective study of 1746 T2D participants, we examined the association of plasma ceramide Cer16:0, Cer18:0, Cer24:0, and Cer24:1 with RDKF, defined as an estimated glomerular filtration rate (eGFR) decline of 5 ml/min/1.73 m2 per year or greater, and ESKD defined as eGFR <15/min/1.73 m2 for at least 3 months, on dialysis or renal death at follow-up. During a median follow-up period of 7.7 years, 197 patients experienced RDKF. Ceramide Cer24:0 (odds ratio [OR] = 0.71, 95% CI 0.56-0.90) and ratios Cer16:0/Cer24:0 (OR = 3.54 [1.70-7.35]), Cer18:0/Cer24:0 (OR = 1.89 [1.10-3.25]), and Cer24:1/Cer24:0 (OR = 4.01 [1.93-8.31]) significantly associated with RDKF in multivariable analysis; 124 patients developed ESKD. The ratios Cer16:0/Cer24:0 (hazard ratio [HR] = 3.10 [1.44-6.64]) and Cer24:1/Cer24:0 (HR = 4.66 [1.93-11.24]) significantly associated with a higher risk of ESKD. The Cer24:1/Cer24:0 ratio improved risk discrimination for ESKD beyond traditional risk factors by small but statistically significant margin (Harrell C-index difference: 0.01; P = 0.022). A high ceramide risk score also associated with RDKF (OR = 2.28 [1.26-4.13]) compared to lower risk score. In conclusion, specific ceramide levels and their ratios are associated with RDKF and conferred an increased risk of ESKD, independently of traditional risk factors, including baseline renal functions in patients with T2D.

Lipidome atlas of the adult human brain.

Lipids are the most abundant but poorly explored components of the human brain. Here, we present a lipidome map of the human brain comprising 75 regions, including 52 neocortical ones. The lipidome composition varies greatly among the brain regions, affecting 93% of the 419 analyzed lipids. These differences reflect the brain's structural characteristics, such as myelin content (345 lipids) and cell type composition (353 lipids), but also functional traits: functional connectivity (76 lipids) and information processing hierarchy (60 lipids). Combining lipid composition and mRNA expression data further enhances functional connectivity association. Biochemically, lipids linked with structural and functional brain features display distinct lipid class distribution, unsaturation extent, and prevalence of omega-3 and omega-6 fatty acid residues. We verified our conclusions by parallel analysis of three adult macaque brains, targeted analysis of 216 lipids, mass spectrometry imaging, and lipidome assessment of sorted murine neurons.

Association of acylcarnitines with maternal cardiometabolic risk factors is defined by chain length: the S-PRESTO study.

CONTEXT: Due to the essential role of carnitine as an intermediary in amino acid, carbohydrate and lipid metabolism, a detailed characterization of circulating and urinary carnitine concentrations will aid in elucidating the molecular basis of impaired maternal metabolic flexibility and facilitating timely intervention for expectant mothers. OBJECTIVE: To investigate the association of maternal plasma and urinary free carnitine and acylcarnitines with cardiometabolic risk factors. METHODS: LC-MS/MS-based quantification of free carnitine and acylcarnitines (C2-C18) was performed on 765 plasma and 702 urine samples collected at preconception, 26-28 weeks' pregnancy, and three months postpartum in the Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO) cohort study. RESULTS: Plasma concentrations of free carnitine and acylcarnitines decreased coupled with increased renal clearance in pregnancy compared to preconception and postpartum. Renal clearance of carnitine increased with an increase in pre-pregnancy body mass index (ppBMI) and gestational weight gain. Plasma short-chain acylcarnitines were positively associated with ppBMI, irrespective of the physiological state, while medium- and long-chain acylcarnitines were negatively associated with ppBMI at preconception and postpartum but showed a positive association in pregnancy. Similarly, plasma short-chain acylcarnitines were positively associated with HOMA-IR whereas medium- and long-chain acylcarnitines were negatively associated with HOMA-IR at preconception and in pregnancy. Mothers who developed gestational diabetes mellitus during pregnancy had ∼10% higher plasma propionylcarnitine concentration and ∼18% higher urine tiglylcarnitine concentration compared to mothers with normal glucose metabolism at preconception. CONCLUSIONS: This study provides the metabolic and physiological basis of maternal carnitine homeostasis, which can be used in assessment of maternal cardiometabolic health at preconception to improve pregnancy outcomes.

Lack of SPNS1 results in accumulation of lysolipids and lysosomal storage disease in mouse models.

Accumulation of sphingolipids, especially sphingosines, in the lysosomes is a key driver of several lysosomal storage diseases. The transport mechanism for sphingolipids from the lysosome remains unclear. Here, we identified SPNS1, which shares the highest homology to SPNS2, a sphingosine-1-phosphate (S1P) transporter, functions as a transporter for lysolipids from the lysosome. We generated Spns1-KO cells and mice and employed lipidomic and metabolomic approaches to reveal SPNS1 ligand identity. Global KO of Spns1 caused embryonic lethality between E12.5 and E13.5 and an accumulation of sphingosine, lysophosphatidylcholines (LPC), and lysophosphatidylethanolamines (LPE) in the fetal livers. Similarly, metabolomic analysis of livers from postnatal Spns1-KO mice presented an accumulation of sphingosines and lysoglycerophospholipids including LPC and LPE. Subsequently, biochemical assays showed that SPNS1 is required for LPC and sphingosine release from lysosomes. The accumulation of these lysolipids in the lysosomes of Spns1-KO mice affected liver functions and altered the PI3K/AKT signaling pathway. Furthermore, we identified 3 human siblings with a homozygous variant in the SPNS1 gene. These patients suffer from developmental delay, neurological impairment, intellectual disability, and cerebellar hypoplasia. These results reveal a critical role of SPNS1 as a promiscuous lysolipid transporter in the lysosomes and link its physiological functions with lysosomal storage diseases.

Effects of wolfberry (Lycium barbarum) consumption on the human plasma lipidome and its association with cardiovascular disease risk factors: a randomized controlled trial of middle-aged and older adults.

Background: Long-term wolfberry intake as part of a healthy dietary pattern was recognized to have beneficial vascular outcomes. Characterization of the plasma lipidome may further provide comprehensive insights into pathways underlying these cardiovascular protective effects. Objective: We analyzed the plasma lipidome of subjects who adhered to a healthy dietary pattern either with or without wolfberry and investigated the associations between the plasma lipidomic profile and cardiovascular health-related indicators. Methods: In this 16-week, parallel design, randomized controlled trial, middle-aged and older adults (n = 41) were provided dietary counseling and assigned to either consume or not consume 15 g of wolfberry daily. At baseline and post-intervention, plasma lipidomics was assayed, and its relationships with classical CVD risk factors, vascular health, oxidant burden, carotenoids status, body composition, and anthropometry were examined. Results: From the plasma lipidome, 427 lipid species from 26 sub-classes were quantified. In the wolfberry and control groups, significant changes were prominent for 27 and 42 lipid species, respectively (P < 0.05 with > 0.2-fold change). Fold changes for seven lipid species were also markedly different between the two groups. Examining the relationships between the plasma lipidome and CVD-related risk factors, total cholesterol revealed a marked positive correlation with 13 ceramide species, while HDL-cholesterol which was notably increased with wolfberry consumption showed a positive correlation with 10 phosphatidylcholine species. Oxidant burden, as represented by plasma 8-isoprostanes, was also inversely associated with lipidomic triglycerides and ether-triglycerides (41 species) and directly associated with hexosylceramides (eight species) and sphingomyelins (six species). There were no differential associations with CVD risk detected between groups. Conclusion: Characteristic alterations to the plasma lipidome were observed with healthy dietary pattern adherence and wolfberry consumption. An examination of these fluctuations suggests potential biochemical mechanisms that may mediate the antioxidant and cardiovascular protective effects of healthy dietary pattern adherence and wolfberry intake. This study was registered at clinicaltrials.gov as NCT0353584.

MFSD7c functions as a transporter of choline at the blood-brain barrier.

Mutations in the orphan transporter MFSD7c (also known as Flvcr2), are linked to Fowler syndrome. Here, we used Mfsd7c knockout (Mfsd7c-/-) mice and cell-based assays to reveal that MFSD7c is a choline transporter at the blood-brain barrier (BBB). We performed comprehensive metabolomics analysis and detected differential changes of metabolites in the brains and livers of Mfsd7c-/-embryos. Particularly, we found that choline-related metabolites were altered in the brains but not in the livers of Mfsd7c-/- embryos. Thus, we hypothesized that MFSD7c regulates the level of choline in the brain. Indeed, expression of human MFSD7c in cells significantly increased choline uptake. Interestingly, we showed that choline uptake by MFSD7c is greatly increased by choline-metabolizing enzymes, leading us to demonstrate that MFSD7c is a facilitative transporter of choline. Furthermore, single-cell patch clamp analysis showed that the import of choline by MFSD7c is electrogenic. Choline transport function of MFSD7c was shown to be conserved in vertebrates, but not in yeasts. We demonstrated that human MFSD7c is a functional ortholog of HNM1, the yeast choline importer. We also showed that several missense mutations identified in patients exhibiting Fowler syndrome had abolished or reduced choline transport activity. Mice lacking Mfsd7c in endothelial cells of the central nervous system suppressed the import of exogenous choline from blood but unexpectedly had increased choline levels in the brain. Stable-isotope tracing study revealed that MFSD7c was required for exporting choline derived from lysophosphatidylcholine in the brain. Collectively, our work identifies MFSD7c as a choline exporter at the BBB and provides a foundation for future work to reveal the disease mechanisms of Fowler syndrome.

Umbilical Cord Plasma Lysophospholipids and Triacylglycerols Associated with Birthweight Percentiles.

Dysregulated transplacental lipid transfer and fetal-placental lipid metabolism affect birthweight, as does maternal hyperglycemia. As the mechanisms are unclear, we aimed to identify the lipids in umbilical cord plasma that were most associated with birthweight. Seventy-five Chinese women with singleton pregnancies recruited into the GUSTO mother-offspring cohort were selected from across the glycemic range based on a mid-gestation 75 g oral glucose tolerance test, excluding pre-existing diabetes. Cord plasma samples collected at term delivery were analyzed using targeted liquid-chromatography tandem mass-spectrometry to determine the concentrations of 404 lipid species across 17 lipid classes. The birthweights were standardized for sex and gestational age by local references, and regression analyses were adjusted for the maternal age, BMI, parity, mode of delivery, insulin treatment, and fasting/2 h glucose, with a false discovery-corrected p < 0.05 considered significant. Ten lysophosphatidylcholines (LPCs) and two lysophosphatidylethanolamines were positively associated with the birthweight percentiles, while twenty-four triacylglycerols were negatively associated with the birthweight percentiles. The topmost associated lipid was LPC 20:2 [21.28 (95%CI 12.70, 29.87) percentile increase in the standardized birthweight with each SD-unit increase in log10-transformed concentration]. Within these same regression models, maternal glycemia did not significantly associate with the birthweight percentiles. Specific fetal circulating lysophospholipids and triacylglycerols associate with birthweight independently of maternal glycemia, but a causal relationship remains to be established.

Lipidomics profiling reveals distinct patterns of plasma sphingolipid alterations in Alzheimer's disease and vascular dementia.

BACKGROUND: Alzheimer's disease (AD) and vascular dementia (VaD) are two of the commonest causes of dementia in the elderly. Of the myriad biomolecules implicated in dementia pathogenesis, sphingolipids have attracted relatively scant research attention despite their known involvement in multiple pathophysiological processes. The potential utility of peripheral sphingolipids as biomarkers in dementia cohorts with high concomitance of cerebrovascular diseases is also unclear. METHODS: Using a lipidomics platform, we performed a case-control study of plasma sphingolipids in a prospectively assessed cohort of 526 participants (non-cognitively impaired, NCI = 93, cognitively impaired = 217, AD = 166, VaD = 50) using a lipidomics platform. RESULTS: Distinct patterns of sphingolipid alterations were found in AD and VaD, namely an upregulation of d18:1 species in AD compared to downregulation of d16:1 species in VaD. In particular, GM3 d18:1/16:0 and GM3 d18:1/24:1 showed the strongest positive associations with AD. Furthermore, evaluation of sphingolipids panels showed specific combinations with higher sensitivity and specificity for classification of AD (Cer d16:1/24:0. Cer d18:1/16:0, GM3 d16:1/22:0, GM3 d18:1/16:0, SM d16:1/22:0, HexCer d18:1/18:0) and VAD (Cer d16:1/24:0, Cer d18:1/16:0, Hex2Cer d16:1/16:0, HexCer d18:1/18:0, SM d16:1/16:0, SM d16:1/20:0, SM d18:2/22:0) compared to NCI. CONCLUSIONS: AD and VaD are associated with distinct changes of plasma sphingolipids, warranting further studies into underlying pathophysiological mechanisms and assessments of their potential utility as dementia biomarkers and therapeutic targets.

Q-RAI data-independent acquisition for lipidomic quantitative profiling.

Untargeted lipidomics has been increasingly adopted for hypothesis generation in a biological context or discovery of disease biomarkers. Most of the current liquid chromatography mass spectrometry (LC-MS) based untargeted methodologies utilize a data dependent acquisition (DDA) approach in pooled samples for identification and MS-only acquisition for semi-quantification in individual samples. In this study, we present for the first time an untargeted lipidomic workflow that makes use of the newly implemented Quadrupole Resolved All-Ions (Q-RAI) acquisition function on the Agilent 6546 quadrupole time-of-flight (Q-TOF) mass spectrometer to acquire MS2 spectra in data independent acquisition (DIA) mode. This is followed by data processing and analysis on MetaboKit, a software enabling DDA-based spectral library construction and extraction of MS1 and MS2 peak areas, for reproducible identification and quantification of lipids in DIA analysis. This workflow was tested on lipid extracts from human plasma and showed quantification at MS1 and MS2 levels comparable to multiple reaction monitoring (MRM) targeted analysis of the same samples. Analysis of serum from Ceramide Synthase 2 (CerS2) null mice using the Q-RAI DIA workflow identified 88 lipid species significantly different between CerS2 null and wild type mice, including well-characterized changes previously associated with this phenotype. Our results show the Q-RAI DIA as a reliable option to perform simultaneous identification and reproducible relative quantification of lipids in exploratory biological studies.

Myo-inositol alters the effects of glucose, leptin and insulin on placental palmitic acid and oleic acid metabolism.

Well-regulated placental palmitic acid (PA) and oleic acid (OA) metabolism is vital for optimal placental function and fetal development, but dysregulation occurs with gestational diabetes (GDM). We hypothesized that such dysregulation might arise from increased maternofetal glucose, leptin or insulin concentrations present in GDM, and that dysregulated PA and OA lipid metabolism could be moderated by myo-inositol, a natural polyol and potential GDM intervention. Placental explants from 21 women were incubated with stable isotope-labelled 13 C-PA or 13 C-OA for 48 h. Explants were treated with glucose (5, 10 mm) or leptin (13 nm) or insulin (150 nm) in combination with myo-inositol (0.3, 30, 60 µm). Forty-seven 13 C-PA lipids and 37 13 C-OA lipids were measured by liquid chromatography-mass spectrometry (LCMS). Compared with controls (5 mm glucose), glucose (10 mm) increased 19 13 C-OA lipids and nine 13 C-PA lipids, but decreased 13 C-OA phosphatidylethanolamine 38:5 and 13 C-PA phosphatidylethanolamine 36:4. The effects of leptin and insulin were less prominent than glucose, with leptin increasing 13 C-OA acylcarnitine 18:1, and insulin increasing four 13 C-PA triacylglycerides. Most glucose, leptin and insulin-induced alterations in lipids were attenuated by co-incubation with myo-inositol (30 or 60 µm), with attenuation also occurring in all subgroups stratified by GDM status and fetal sex. However, glucose-induced increases in acylcarnitine were not attenuated by myo-inositol and were even exaggerated in some instances. Myo-inositol therefore appears to generally act as a moderator, suppressing the perturbation of lipid metabolic processes by glucose, leptin and insulin in placenta in vitro. Whether myo-inositol protects the fetus and pregnancy from unfavourable outcomes requires further research. KEY POINTS: Incubation of placental explants with additional glucose, or to a lesser extent insulin or leptin, alters the placental production of 13 C-lipids from 13 C-palmitic acid (PA) and 13 C-oleic acid (OA) in vitro compared with untreated controls from the same placenta. Co-incubation with myo-inositol attenuated most alterations induced by glucose, insulin or leptin in 13 C-lipids, but did not affect alterations in 13 C-acylcarnitines. Alterations induced by glucose and leptin in 13 C-PA triacylglycerides and 13 C-PA phospholipids were influenced by fetal sex and gestational diabetes status, but were all still attenuated by myo-inositol co-incubation. Insulin differently affected 13 C-PA triacylglycerides and 13 C-PA phospholipids depending on fetal sex, with alterations also attenuated by myo-inositol co-incubation.

Mfsd2a-mediated lysolipid transport is important for renal recovery after acute kidney injury.

Acute kidney injury (AKI) is a global public health concern with high mortality and morbidity. In ischemic-reperfusion injury (IRI), a main cause of AKI, the brush border membrane of S3 proximal tubules (PT) is lost to the tubular lumen. How injured tubules reconstitute lost membrane lipids during renal recovery is not known. Here, we identified Mfsd2a, a sodium-dependent lysophosphatidylcholine (LPC) transporter, to be expressed specifically in the basolateral membrane of S3 PT. Using an in vivo activity probe for Mfsd2a, transport activity was found to be specific to the S3 PT. Mice with haploinsufficiency of Mfsd2a exhibited delayed recovery of renal function after acute IRI, with depressed urine osmolality and elevated levels of histological markers of damage, fibrosis, and inflammation, findings corroborated by transcriptomic analysis. Lipidomics revealed a deficiency in docosahexaenoic acid (DHA) containing phospholipids in Mfsd2a haploinsufficiency. Treatment of Mfsd2a haploinsufficient mice with LPC-DHA improved renal function and reduced markers of injury, fibrosis, and inflammation. Additionally, LPC-DHA treatment restored S3 brush border membrane architecture and normalized DHA-containing phospholipid content. These findings indicate that Mfsd2a-mediated transport of LPC-DHA is limiting for renal recovery after AKI and suggest that LPC-DHA could be a promising dietary supplement for improving recovery following AKI.

Blood-derived lysophospholipid sustains hepatic phospholipids and fat storage necessary for hepatoprotection in overnutrition.

The liver has a high demand for phosphatidylcholine (PC), particularly in overnutrition, where reduced phospholipid levels have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). Whether other pathways exist in addition to de novo PC synthesis that contribute to hepatic PC pools remains unknown. Here, we identified the lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (Mfsd2a) as critical for maintaining hepatic phospholipid pools. Hepatic Mfsd2a expression was induced in patients having NAFLD and in mice in response to dietary fat via glucocorticoid receptor action. Mfsd2a liver-specific deficiency in mice (L2aKO) led to a robust nonalcoholic steatohepatitis-like (NASH-like) phenotype within just 2 weeks of dietary fat challenge associated with reduced hepatic phospholipids containing linoleic acid. Reducing dietary choline intake in L2aKO mice exacerbated liver pathology and deficiency of liver phospholipids containing polyunsaturated fatty acids (PUFAs). Treating hepatocytes with LPCs containing oleate and linoleate, two abundant blood-derived LPCs, specifically induced lipid droplet biogenesis and contributed to phospholipid pools, while LPC containing the omega-3 fatty acid docosahexaenoic acid (DHA) promoted lipid droplet formation and suppressed lipogenesis. This study revealed that PUFA-containing LPCs drive hepatic lipid droplet formation, suppress lipogenesis, and sustain hepatic phospholipid pools - processes that are critical for protecting the liver from excess dietary fat.

Decreased DHA-containing phospholipids in the neocortex of dementia with Lewy bodies are associated with soluble Aß42 , phosphorylated α-synuclein, and synaptopathology.

Docosahexaenoic acid (DHA) is an essential omega-3 polyunsaturated fatty acid implicated in cognitive functions by promoting synaptic protein expression. While alterations of specific DHA-containing phospholipids have been described in the neocortex of patients with Alzheimer's disease (AD), the status of these lipids in dementia with Lewy bodies (DLB), known to manifest aggregated α-synuclein-containing Lewy bodies together with variable amyloid pathology, is unclear. In this study, post-mortem samples from the parietal cortex of 25 DLB patients and 17 age-matched controls were processed for phospholipidomics analyses using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) platform. After controlling for false discovery rate, six out of the 46 identified putative DHA-phospholipid species were significantly decreased in DLB, with only one showing increase. Altered putative DHA-phospholipid species were subsequently validated with further LC-MS/MS measurements. Of the DHA-containing phospholipid (DCP) species showing decreases, five negatively correlated with soluble beta-amyloid (Aß42) levels, whilst three also correlated with phosphorylated α-synuclein (all p < 0.05). Furthermore, five of these phospholipid species correlated with deficits of presynaptic Rab3A, postsynaptic neurogranin, or both (all p < 0.05). Finally, we found altered immunoreactivities of brain lysolipid DHA transporter, MFSD2A, and the fatty acid binding protein FABP5 in DLB parietal cortex. In summary, we report alterations of specific DCP species in DLB, as well as their associations with markers of neuropathological burden and synaptopathology. These results support the potential role of DHA perturbations in DLB as well as therapeutic targets.

Restoration of PITPNA in Type 2 diabetic human islets reverses pancreatic beta-cell dysfunction.

Defects in insulin processing and granule maturation are linked to pancreatic beta-cell failure during type 2 diabetes (T2D). Phosphatidylinositol transfer protein alpha (PITPNA) stimulates activity of phosphatidylinositol (PtdIns) 4-OH kinase to produce sufficient PtdIns-4-phosphate (PtdIns-4-P) in the trans-Golgi network to promote insulin granule maturation. PITPNA in beta-cells of T2D human subjects is markedly reduced suggesting its depletion accompanies beta-cell dysfunction. Conditional deletion of Pitpna in the beta-cells of Ins-Cre, Pitpnaflox/flox mice leads to hyperglycemia resulting from decreasing glucose-stimulated insulin secretion (GSIS) and reducing pancreatic beta-cell mass. Furthermore, PITPNA silencing in human islets confirms its role in PtdIns-4-P synthesis and leads to impaired insulin granule maturation and docking, GSIS, and proinsulin processing with evidence of ER stress. Restoration of PITPNA in islets of T2D human subjects reverses these beta-cell defects and identify PITPNA as a critical target linked to beta-cell failure in T2D.

Increasing maternal age associates with lower placental CPT1B mRNA expression and acylcarnitines, particularly in overweight women.

Older pregnant women have increased risks of complications including gestational diabetes and stillbirth. Carnitine palmitoyl transferase (CPT) expression declines with age in several tissues and is linked with poorer metabolic health. Mitochondrial CPTs catalyze acylcarnitine synthesis, which facilitates fatty acid oxidization as fuel. We hypothesized that the placenta, containing maternally-inherited mitochondria, shows an age-related CPT decline that lowers placental acylcarnitine synthesis, increasing vulnerability to pregnancy complications. We assessed CPT1A, CPT1B, CPT1C and CPT2 mRNA expression by qPCR in 77 placentas and quantified 10 medium and long-chain acylcarnitines by LC-MS/MS in a subset of 50 placentas. Older maternal age associated with lower expression of placental CPT1B, but not CPT1A, CPT1C or CPT2. CPT1B expression positively associated with eight acylcarnitines and CPT1C with three acylcarnitines, CPT1A negatively associated with nine acylcarnitines, while CPT2 did not associate with any acylcarnitine. Older maternal age associated with reductions in five acylcarnitines, only in those with BMI≥ 25 kg/m2, and not after adjusting for CPT1B expression. Our findings suggest that CPT1B is the main transferase for placental long-chain acylcarnitine synthesis, and age-related CPT1B decline may underlie decreased placental metabolic flexibility, potentially contributing to pregnancy complications in older women, particularly if they are overweight.

An integrated signature of extracellular matrix proteins and a diastolic function imaging parameter predicts post-MI long-term outcomes.

Background: Patients suffering from acute myocardial infarction (AMI) are at risk of secondary outcomes including major adverse cardiovascular events (MACE) and heart failure (HF). Comprehensive molecular phenotyping and cardiac imaging during the post-discharge time window may provide cues for risk stratification for the outcomes. Materials and methods: In a prospective AMI cohort in New Zealand (N = 464), we measured plasma proteins and lipids 30 days after hospital discharge and inferred a unified partial correlation network with echocardiographic variables and established clinical biomarkers (creatinine, c-reactive protein, cardiac troponin I and natriuretic peptides). Using a network-based data integration approach (iOmicsPASS+), we identified predictive signatures of long-term secondary outcomes based on plasma protein, lipid, imaging markers and clinical biomarkers and assessed the prognostic potential in an independent cohort from Singapore (N = 190). Results: The post-discharge levels of plasma proteins and lipids showed strong correlations within each molecular type, reflecting concerted homeostatic regulation after primary MI events. However, the two molecular types were largely independent with distinct correlation structures with established prognostic imaging parameters and clinical biomarkers. To deal with massively correlated predictive features, we used iOmicsPASS + to identify subnetwork signatures of 211 and 189 data features (nodes) predictive of MACE and HF events, respectively (160 overlapping). The predictive features were primarily imaging parameters, including left ventricular and atrial parameters, tissue Doppler parameters, and proteins involved in extracellular matrix (ECM) organization, cell differentiation, chemotaxis, and inflammation. The network signatures contained plasma protein pairs with area-under-the-curve (AUC) values up to 0.74 for HF prediction in the validation cohort, but the pair of NT-proBNP and fibulin-3 (EFEMP1) was the best predictor (AUC = 0.80). This suggests that there were a handful of plasma proteins with mechanistic and functional roles in predisposing patients to the secondary outcomes, although they may be weaker prognostic markers than natriuretic peptides individually. Among those, the diastolic function parameter (E/e' - an indicator of left ventricular filling pressure) and two ECM proteins, EFEMP1 and follistatin-like 3 (FSTL3) showed comparable performance to NT-proBNP and outperformed left ventricular measures as benchmark prognostic factors for post-MI HF. Conclusion: Post-discharge levels of E/e', EFEMP1 and FSTL3 are promising complementary markers of secondary adverse outcomes in AMI patients.

Deficiency in the omega-3 lysolipid transporter Mfsd2a leads to aberrant oligodendrocyte lineage development and hypomyelination.

Patients with autosomal recessive microcephaly 15 caused by deficiency in the sodium-dependent lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain-containing 2a (Mfsd2a) present with both microcephaly and hypomyelination, suggesting an important role for LPC uptake by oligodendrocytes in the process of myelination. Here we demonstrate that Mfsd2a is specifically expressed in oligodendrocyte precursor cells (OPCs) and is critical for oligodendrocyte development. Single-cell sequencing of the oligodendrocyte lineage revealed that OPCs from OPC-specific Mfsd2a-KO mice (2aOKO mice) underwent precocious differentiation into immature oligodendrocytes and impaired maturation into myelinating oligodendrocytes, correlating with postnatal brain hypomyelination. 2aOKO mice did not exhibit microcephaly, a finding consistent with the notion that microcephaly is the consequence of an absence of LPC uptake at the blood-brain barrier rather than a deficiency in OPCs. Lipidomic analysis showed that OPCs and iOLs from 2aOKO mice had significantly decreased levels of phospholipids containing omega-3 fatty acids, with a corresponding increase in unsaturated fatty acids, the latter being products of de novo synthesis governed by Srebp-1. RNA-Seq indicated activation of the Srebp-1 pathway and defective expression of regulators of oligodendrocyte development. Taken together, these findings indicate that the transport of LPCs by Mfsd2a in OPCs is important for maintaining OPC state to regulate postnatal brain myelination.

Mfsd2a utilizes a flippase mechanism to mediate omega-3 fatty acid lysolipid transport.

Major Facilitator Superfamily Domain containing 2a (Mfsd2a) is a sodium-dependent lysophosphatidylcholine (LPC) transporter expressed at the blood-brain barrier that constitutes the main pathway by which the brain obtains omega-3 fatty acids, such as docosahexanoic acid. Mfsd2a deficiency in humans results in severe microcephaly, underscoring the importance of LPC transport by Mfsd2a for brain development. Biochemical studies and recent cryo-electron microscopy (cryo-EM) structures of Mfsd2a bound to LPC suggest that Mfsd2a transports LPC via an alternating access mechanism between outward-facing and inward-facing conformational states in which the LPC inverts during transport between the outer and inner leaflet of a membrane. However, direct biochemical evidence of flippase activity by Mfsd2a has not been demonstrated and it is not understood how Mfsd2a could invert LPC between the outer and inner leaflet of the membrane in a sodium-dependent manner. Here, we established a unique in vitro assay using recombinant Mfsd2a reconstituted in liposomes that exploits the ability of Mfsd2a to transport lysophosphatidylserine (LPS) coupled with a small molecule LPS binding fluorophore that allowed for monitoring of directional flipping of the LPS headgroup from the outer to the inner liposome membrane. Using this assay, we demonstrate that Mfsd2a flips LPS from the outer to the inner leaflet of a membrane bilayer in a sodium-dependent manner. Furthermore, using cryo-EM structures as guides together with mutagenesis and a cell-based transport assay, we identify amino acid residues important for Mfsd2a activity that likely constitute substrate interaction domains. These studies provide direct biochemical evidence that Mfsd2a functions as a lysolipid flippase.