Vitamin D Supplementation Enhances C18(dihydro)ceramide Levels in Type 2 Diabetes Patients

Comprehensive profiling of ceramides in human serum by liquid chromatography coupled to tandem mass spectrometry combining data independent/dependent acquisition modes

Ceramides are sphingolipids with a structural function in the cell membrane and are involved in cell differentiation, proliferation and apoptosis. Recently, these chemical species have been pointed out as potential biomarkers in different diseases, due to their abnormal levels in blood. In this research, we present an overall strategy combining data-independent and dependent acquisitions (DIA and DDA, respectively) for identification, confirmation, and quantitative determination of ceramides in human serum. By application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in DIA mode we identified 49 ceramides including d18:1, d18:0, d18:2, d16:1, d17:1 and t18:0 species. Complementary, quantitative determination of ceramides was based on a high-throughput and fully automated method consisting of solid-phase extraction on-line coupled to LC-MS/MS in DDA to improve analytical features avoiding the errors associated to sample processing. Quantitation limits were at pg mL-1 level, the intra-day and between-days variability were below 20 and 25 %, respectively; and the accuracy, expressed as bias, was always within ±25 %. The proposed method was tested with the CORDIOPREV cohort in order to obtain a qualitative and quantitative profiling of ceramides in human serum. This characterization allowed identifying d18:1 ceramides as the most concentrated with 70.8% of total concentration followed by d18:2 and d18:0 with 13.0 % and 8.8 %, respectively. Less concentrated ceramides, d16:1, d17:1 and t18:0, reported a 7.1 % of the total content. Combination of DIA and DDA LC-MS/MS analysis enabled to profile qualitative and quantitatively ceramides in human serum.

Interplay between Vitamin D and Sphingolipids in Cardiometabolic Diseases

Sphingolipids (SLs) are structural, bioactive molecules with several key cellular roles, whereas 1,25-dihydroxyvitamin D (1,25(OH)D), the active form of vitamin D, is considered the major regulator of calcium homeostasis, although it also exerts other extraskeletal effects. Many studies reported the physiological connection between vitamin D and SLs, highlighting not only the effects of vitamin D on SL metabolism and signaling but also the influence of SLs on vitamin D levels and function, thus strongly suggesting a crosstalk between these molecules. After a brief description of 1,25(OH)D and SL metabolism, this review aims to discuss the preclinical and clinical evidence on the crosstalk between SLs and 1,25(OH)D, with a special focus on cardiometabolic diseases.

The nutritional functions of dietary sphingomyelin and its applications in food

Sphingolipids are common structural components of cell membranes and are crucial for cell functions in physiological and pathophysiological conditions. Sphingomyelin and its metabolites, such as sphingoid bases, ceramide, ceramide-1-phosphate, and sphingosine-1-phosphate, play signaling roles in the regulation of human health. The diverse structures of sphingolipids elicit various functions in cellular membranes and signal transduction, which may affect cell growth, differentiation, apoptosis, and maintain biological activities. As nutrients, dietary sphingomyelin and its metabolites have wide applications in the food and pharmaceutical industry. In this review, we summarized the distribution, classifications, structures, digestion, absorption and metabolic pathways of sphingolipids, and discussed the nutritional functioning of sphingomyelin in chronic metabolic diseases. The possible implications of dietary sphingomyelin in the modern food preparations including dairy products and infant formula, skin improvement, delivery system and oil organogels are also evaluated. The production of endogenous sphingomyelin is linked to pathological changes in obesity, diabetes, and atherosclerosis. However, dietary supplementations of sphingomyelin and its metabolites have been shown to maintain cholesterol homeostasis and lipid metabolism, and to prevent or treat these diseases. This seemly paradoxical phenomenon shows that dietary sphingomyelin and its metabolites are candidates for food additives and functional food development for the prevention and treatment of chronic metabolic diseases in humans.

Metabolomic analysis reveals the influence of IC50 vitamin D3 on RAW264.7 cells based on 1 H NMR and UPLC-MS/MS

BACKGROUND

As a lipid-soluble vitamin necessary for normal human physiology, vitamin D is mostly used in fortified foods, medicines and adjuvant treatment of diseases. However, taken in high doses, vitamin D can be toxic.

METHODS

We treated RAW264.7 cells with a semi-inhibitory concentration (IC₅₀ ) of vitamin D₃ . The metabolic changes in the treated cells were analyzed by ¹ H nuclear magnetic resonance (NMR) and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

RESULTS

After treatment of RAW264.7 cells with an IC₅₀ dose of 55 μm vitamin D₃ , tunor necrosis factor-α levels decreased significantly and remarkable metabolic differences were also observed, with 12 types of metabolites were identified by ¹ H NMR and 87 identified by UPLC-MS/MS. Moreover, the metabolism of amino acids, sugars, lipids and other metabolic pathways were also affected.

CONCLUSION

Although vitamin D₃ is an indispensable nutrient in the body, excessive exposure has negative effects on cells and their metabolism. The present study will assist further analyses of the mechanism underlying vitamin D₃ toxicity. © 2022 Society of Chemical Industry.

Metabolomics Profiling of Vitamin D Status in Relation to Dyslipidemia

Vitamin D deficiency is a global disorder associated with several chronic illnesses including dyslipidemia and metabolic syndrome. The impact of this association with both dyslipidemia and vitamin D deficiency on metabolomics profile is not yet fully understood. This study analyses the metabolomics and lipidomic signatures in relation to vitamin D status and dyslipidemia. Metabolomics data were collected from Qatar Biobank database and categorized into four groups based on vitamin D and dyslipidemia status. Metabolomics multivariate analysis was performed using the orthogonal partial least square discriminate analysis (OPLS-DA) whilst linear models were used to assess the per-metabolite association with each of the four dyslipidemia/vitamin D combination groups. Our results indicate a high prevalence of vitamin D deficiency among the younger age group, while dyslipidemia was more prominent in the older group. A significant alteration of metabolomics profile was observed among the dyslipidemic and vitamin D deficient individuals in comparison with control groups. These modifications reflected changes in some key pathways including ceramides, diacylglycerols, hemosylceramides, lysophospholipids, phosphatidylcholines, phosphatidylethanol amines, and sphingomyelins. Vitamin D deficiency and dyslipidemia have a deep impact on sphingomyelins profile. The modifications were noted at the level of ceramides and are likely to propagate through downstream pathways.

Sex-Specific Catabolic Metabolism Alterations in the Critically Ill following High Dose Vitamin D

Pharmacological interventions are essential for the treatment and management of critical illness. Although women comprise a large proportion of the critically ill, sex-specific pharmacological properties are poorly described in critical care. The sex-specific effects of vitamin D₃ treatment in the critically ill are not known. Therefore, we performed a metabolomics cohort study with 1215 plasma samples from 428 patients from the VITdAL-ICU trial to study sex-specific differences in the metabolic response to critical illness following high-dose oral vitamin D₃ intervention. In women, despite the dose of vitamin D₃ being higher, pharmacokinetics demonstrated a lower extent of vitamin D₃ absorption compared to men. Metabolic response to high-dose oral vitamin D₃ is sex-specific. Sex-stratified individual metabolite associations with elevations in 25(OH)D following intervention showed female-specific positive associations in long-chain acylcarnitines and male-specific positive associations in free fatty acids. In subjects who responded to vitamin D₃ intervention, significant negative associations were observed in short-chain acylcarnitines and branched chain amino acid metabolites in women as compared to men. Acylcarnitines and branched chain amino acids are reflective of fatty acid B oxidation, and bioenergesis may represent notable metabolic signatures of the sex-specific response to vitamin D. Demonstrating sex-specific pharmacometabolomics differences following intervention is an important movement towards the understanding of personalized medicine.

Sphingolipids in foodstuff: Compositions, distribution, digestion, metabolism and health effects - A comprehensive review

Sphingolipids (SLs) are common in all eukaryotes, prokaryotes, and viruses, and played a vital role in human health. They are involved in physiological processes, including intracellular transport, cell division, and signal transduction. However, there are limited reviews on dietary effects on endogenous SLs metabolism and further on human health. Various dietary conditions, including the SLs-enriched diet, high-fat diet, and vitamins, can change the level of endogenous SLs metabolites and even affect human health. This review systematically summarizes the main known SLs in foods concerning their variety and contents, as well as their isolation and identification approaches. Moreover, the present review discusses the role of dietary (particularly SLs-enriched diet, high-fat diet, and vitamins) in endogenous SLs metabolism, highlighting how exogenous SLs are digested and absorbed. The role of SLs family in the pathogenesis of diseases, including cancers, neurological disorders, infectious and inflammatory diseases, and cardiovascular diseases, and in recently coronavirus disease-19 outbreak was also discussed. In the post-epidemic era, we believe that the concern for health and the need for plant-based products will increase. Therefore, a need for research on the absorption and metabolism pathway of SLs (especially plant-derived SLs) and their bioavailability is necessary. Moreover, the effects of storage treatment and processing on the content and composition of SLs in food are worth exploring. Further studies should also be conducted on the dose-response of SLs on human health to support the development of SLs supplements. More importantly, new approaches, such as, making SLs based hydrogels can effectively achieve sustained release and targeted therapies.

On the nature of ceramide-mitochondria interactions - Dissection using comprehensive mitochondrial phenotyping

Sphingolipids are a unique class of lipids owing to their non-glycerol-containing backbone, ceramide, that is constructed from a long-chain aliphatic amino alcohol, sphinganine, to which a fatty acid is attached via an amide bond. Ceramide plays a star role in the initiation of apoptosis by virtue of its interactions with mitochondria, a control point for a downstream array of signaling cascades culminating in apoptosis. Many pathways converge on mitochondria to elicit mitochondrial outer membrane permeabilization (MOMP), a step that corrupts bioenergetic service. Although much is known regarding ceramides interaction with mitochondria and the ensuing cell signal transduction cascades, how ceramide impacts the elements of mitochondrial bioenergetic function is poorly understood. The objective of this review is to introduce the reader to sphingolipid metabolism, present a snapshot of mitochondrial respiration, elaborate on ceramides convergence on mitochondria and the upstream players that collaborate to elicit MOMP, and introduce a mitochondrial phenotyping platform that can be of utility in dissecting the fine-points of ceramide impact on cellular bioenergetics.

Vitamin D3 Supplementation Increases Long-Chain Ceramide Levels in Overweight/Obese African Americans: A Post-Hoc Analysis of a Randomized Controlled Trial

Sphingolipid metabolism plays a critical role in cell growth regulation, lipid regulation, neurodevelopment, type 2 diabetes, and cancer. Animal experiments suggest that vitamin D may be involved in sphingolipid metabolism regulation. In this study, we tested the hypothesis that vitamin D supplementation would alter circulating long-chain ceramides and related metabolites involved in sphingolipid metabolism in humans. We carried out a post-hoc analysis of a previously conducted randomized, placebo-controlled clinical trial in 70 overweight/obese African-Americans, who were randomly assigned into four groups of 600, 2000, 4000 IU/day of vitamin D₃ supplements or placebo for 16 weeks. The metabolites were measured in 64 subjects (aged 26.0 ± 9.4 years, 17% male). Serum levels of N-stearoyl-sphingosine (d18:1/18:0) (C18Cer) and stearoyl sphingomyelin (d18:1/18:0) (C18SM) were significantly increased after vitamin D₃ supplementation (ps < 0.05) in a dose–response fashion. The effects of 600, 2000, and 4000 IU/day vitamin D₃ supplementation on C18Cer were 0.44 (p = 0.049), 0.52 (p = 0.016), and 0.58 (p = 0.008), respectively. The effects of three dosages on C18SM were 0.30 (p = 0.222), 0.61 (p = 0.009), and 0.68 (p = 0.004), respectively. This was accompanied by the significant correlations between serum 25-hydroxyvitamin D₃ [25(OH)D] concentration and those two metabolites (ps < 0.05). Vitamin D₃ supplementations increase serum levels of C18Cer and C18SM in a dose–response fashion among overweight/obese African Americans.

Druggable Sphingolipid Pathways: Experimental Models and Clinical Opportunities

Intensive research in the field of sphingolipids has revealed diverse roles in cell biological responses and human health and disease. This immense molecular family is primarily represented by the bioactive molecules ceramide, sphingosine, and sphingosine 1-phosphate (S1P). The flux of sphingolipid metabolism at both the subcellular and extracellular levels provides multiple opportunities for pharmacological intervention. The caveat is that perturbation of any single node of this highly regulated flux may have effects that propagate throughout the metabolic network in a dramatic and sometimes unexpected manner. Beginning with S1P, the receptors for which have thus far been the most clinically tractable pharmacological targets, this review will describe recent advances in therapeutic modulators targeting sphingolipids, their chaperones, transporters, and metabolic enzymes.

A Role for Neutral Sphingomyelinase in Wound Healing Induced by Keratinocyte Proliferation upon 1α, 25-Dihydroxyvitamin D3 Treatment

The skin has many functions, such as providing a barrier against injury and pathogens, protecting from ultraviolet light, and regulating body temperature. Mechanical causes and many different pathologies can lead to skin damage. Therefore, it is important for the skin to be always adaptable and renewable and for cells to undergo proliferation. Here, we demonstrate that 1α, 25-dihydroxyvitamin D₃ (VD3) stimulates keratinocyte proliferation, leading to wound closure in a simulation model of injury. Functionally, our results show that VD3 acts by stimulating cyclin D1, a cyclin that promotes the G1/S transition of the cell cycle. The study on the mechanism underlying cyclin D1 expression upon VD3 stimulation clearly demonstrates a key role of neutral sphingomyelinase. The enzyme, whose gene and protein expression is stimulated by VD3, is itself able to induce effects on cyclin D1 and wound healing similar to those obtained with VD3. These results could be very useful in the future to better understand wound mechanisms and improve therapeutic interventions.

Blood ceramides as novel markers for renal impairment in systemic lupus erythematosus

BACKGROUND

Lupus nephritis (LN) is the most common organ manifestation in systemic lupus erythematosus (SLE) and associated with a poor prognosis. Still, a noninvasive but reliable method to diagnose LN has not been established. Thus, we evaluated whether blood sphingolipids could serve as valid biomarkers for renal injury.

METHODS

In this cross-sectional study, 82 participants were divided into three groups: 36 healthy controls and 17 SLE patients without renal injury (both: estimated glomerular filtration rate (eGFR) ≥ 80 ml/min/1.73 m² and albumin/creatinine ≤ 30 mg/g) and 29  LN patients. LN patients were identified by renal biopsies and impaired renal function (eGFR < 80 ml/min/1.73 m² and albumin/creatinine ratio > 30 mg/g). Venous blood was collected from all participants and sphingolipid levels in plasma and serum were measured by LC-MS/MS.

RESULTS

Most interesting, concentrations of some specific ceramides, C16ceramide (Cer), C18Cer, C20Cer and C24:1Cer, were elevated in both, plasma and serum samples of patients suffering from biopsy-proven LN and impaired renal function, compared to healthy controls as well as SLE patients without renal injury. C24:1dhCer levels were elevated in plasma and serum samples from LN patients compared to SLE patients. Sphingosine levels were higher in plasma and serum of LN patients compared to healthy controls, but not compared to SLE patients. Sphinganine concentrations were significantly elevated in serum samples from LN patients compared to healthy controls and SLE. S1P and SA1P levels were higher in plasma samples of SLE and LN patients compared to healthy controls. Subsequent ROC analyses of plasma and serum data of the most altered ceramide species (C16Cer, C18Cer, C20Cer, C24:1Cer) between LN patients and SLE patients display a high diagnostic differentiation with significant AUCs especially for C24:1Cer serum levels. Further, C24:1Cer serum levels were not affected by glucocorticoid treatment and did not correlate with other renal markers, such as serum creatinine, eGFR and albumin/creatinine ratio.

CONCLUSION

Our data reveal that chain-length specific ceramides in blood, most likely C24:1Cer levels in serum, could act as potent biomarkers for renal impairment in patients suffering from SLE.

Vitamin D effects on sphingosine 1-phosphate signaling and metabolism in monocytes from type 2 diabetes patients and controls

Elevated sphingosine 1-phopshate (S1P) concentration was observed in type 2 diabetes mellitus (T2D). On the other side, 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) can influence the formation of sphingosine 1-phopshate (S1P) and the expression of S1P receptors, which are known to be involved in T2D. In order to evaluate mechanisms for the antiinflammatory potential of 1,25(OH)₂D₃, we investigated whether 1,25(OH)₂D₃ alters S1P signaling and metabolism in human CD14⁺ monocytes. Primary monocytes isolated from healthy controls (HC) and T2D patients were treated for 24 h with 10 nM 1,25(OH)₂D₃ in the absence or presence of 500 IU/ml interleukin-(IL)-1β. Thereafter, sphingosine kinase (SPHK)1, SPHK2 and S1P receptor 1-5 (S1P_1-5) mRNA expression levels were measured by TaqMan^™ analyses. Sphingolipid levels in cell supernatant were determined by high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS). 1,25(OH)₂D₃ treatment downregulated S1P₁ and S1P₂ mRNA expression compared to untreated monocytes of HC and T2D patients. In contrast, SPHK1, S1P₃ and S1P₄ mRNA expression levels were upregulated by 1,25(OH)₂D₃ treatment compared to the respective controls. Furthermore, reduced S1P₂ and increased S1P₃ and S1P₄ mRNA expression levels upon treatment with 1,25(OH)₂D₃ occurred in the presence of IL-1β. Additionally, S1P levels in cell supernatants were decreased in monocytes from HC and T2D patients by 1,25(OH)₂D₃ with or without IL-1β costimulation. The levels of sphingosine in cell supernatants were not influenced by 1,25(OH)₂D_3. Overall, our results demonstrate for the first time that 1,25(OH)₂D₃ treatment can influence S1P receptor and SPHK expression and S1P levels in primary monocytes of both HC and subjects with T2D. These findings justify further investigations into the sphingolipid metabolism and potential benefits of vitamin D treatment in diabetes.

The Onus of Sphingolipid Enzymes in Cancer Drug Resistance

Chemotherapy resistance, inherent or acquired, represents a serious barrier to the successful treatment of cancer. Although drug efflux, conducted by plasma membrane-resident proteins, detoxification enzymes, cell death inhibition, and DNA damage repair are ensemble players in this unwanted biology, a full understanding of the many in concert molecular mechanisms driving drug resistance is lacking. Recent discoveries in sphingolipid (SL) metabolism have provided significant insight into the role of these lipids in cancer growth; however, considerably less is known with respect to SLs and the drug-resistant phenotype. One exception here is enhanced ceramide glycosylation, a hallmark of multidrug resistance that is believed responsible, in part, for diminishing ceramides tumor-suppressor potential. This chapter will review various aspects of SL biology that relate to chemotherapy resistance and extend this topic to acknowledge the role of chemotherapy selection pressure in promoting dysregulated SL metabolism, a characteristic in cancer and an exploitable target for therapy.

Calcitriol concomitantly enhances insulin sensitivity and alters myocellular lipid partitioning in high fat-treated skeletal muscle cells

Vitamin D reduces myocellular insulin resistance, but the effects of vitamin D on intramyocellular lipid (IMCL) partitioning are unknown. The purpose of this study was to understand how calcitriol, the active vitamin D metabolite, affects insulin sensitivity and lipid partitioning in skeletal muscle cells. C2C12 myotubes were treated with calcitriol (100 nM) or vehicle control for 96 h. Insulin-stimulated Akt phosphorylation (Thr 308) was determined by western blot. Intramyocellular triacylglycerol (IMTG), diacylglycerol (DAG), and ceramide content were measured by LC/MS. IMTG partitioning and lipid droplet accumulation were assessed by oil red O. Expression of genes involved in lipid droplet packaging and lipolysis were measured by RT-PCR. Compared to vehicle-treated myotubes, calcitriol augmented insulin-stimulated pAkt. Calcitriol increased total ceramides and DAG in a subspecies-specific manner. Specifically, calcitriol preferentially increased ceramide 24:1 (1.78 fold) and di-18:0 DAG (46.89 fold). Calcitriol increased total IMTG area as assessed by oil red O, but decreased the proportion of lipid within myotubes. Calcitriol increased mRNA content of genes involved in lipid droplet packaging (perilipin 2; PLIN 2, 2.07 fold) and lipolysis (comparative gene identification-58; CGI-58 and adipose triglyceride lipase; ATGL, ~ 1.80 fold). Calcitriol alters myocellular lipid partitioning and lipid droplet packaging which may favor lipid turnover and partially explain improvements in insulin sensitivity.