Sphingomyelin is involved in multisite musculoskeletal pain: evidence from metabolomic analysis in 2 independent cohorts

Fibromyalgia patients have altered lipid concentrations associated with disease symptom severity and anti-satellite glial cell IgG antibodies

Autoimmunity and immunoglobulin G (IgG) autoantibodies may contribute to pain in a subset of fibromyalgia (FM) patients. Previously, IgG from FM patients was found to induce pain-like behavior in mice and bind to satellite glial cells (anti-SGC IgG). The anti-SGC IgG levels were also associated with more severe symptomatology. Lipid metabolism in FM subjects is altered with lysophosphatidylcholines (LPCs) acting as pain mediators. The relationship between autoantibodies, lipid metabolism, and FM symptomatology remains unclear. Serum lipidomics with liquid chromatography mass spectrometry, anti-SGC IgG levels, and clinical measures were examined in 35 female FM subjects and 33 age- and body mass index-balanced healthy controls (HC). Fibromyalgia subjects with higher anti-SGC IgG levels experienced more intense pain than those with lower levels. Sixty-three lipids were significantly altered between FM subjects and HC or between FM subjects with severe (FM severe) and mild symptoms (FM mild). Compared to HC, FM subjects had lower concentrations of lipid species belonging to the classes LPC (n = 10), lysophosphatidylethanolamine (n = 7), phosphatidylcholine (n = 4), and triglyceride (n = 5), but higher concentrations of diglyceride (n = 3). Additionally, FM severe had higher LPC 19:0, 22:0, and 24:1 and lower sphingomyelin (n = 9) concentrations compared to FM mild. Positive associations were seen for LPC 22:0 and 24:1 with pain intensity and anti-SGC IgG levels in FM subjects. Taken together, these results suggest an association between altered lipid metabolism and autoimmune mechanisms in FM.

Serum phospholipids and sphingolipids are linked to early-stage osteoarthritis by lipidomic profiling

BACKGROUND

Osteoarthritis (OA) is associated with abnormal lipid metabolism, wherein elevated levels of phospholipids (PLs) and sphingolipids (SLs) in human and canine synovial fluid (SF) have been observed. The aim of this lipidomic study was to evaluate how closely blood lipid levels reflect changes in SF, building on previous findings.

METHODS

Lipids were extracted from knee SF and serum of 44 joint-healthy donors and 58 early (eOA) or late OA (lOA) patients. By electrospray ionization tandem mass spectrometry (ESI-MS/MS), we quantified the extracted lipids and conducted comprehensive statistical analyses.

RESULTS

Human SF and serum had similar PL and SL compositions. Quantifying 91 lipid species from 6 major classes revealed OA-related changes in serum, with the lowest levels in healthy controls and elevated levels already in the eOA cohort. Generally, serum PL and SL levels were 3-12 times higher than in SF. Specific PL species were elevated in both SF and serum of eOA and lOA patients compared to healthy controls, while nearly 10% of the PL species measured were higher exclusively in the serum of OA patients.

CONCLUSIONS

The significant lipidomic alterations that were detected at an average Outerbridge score of less than 2 suggest that certain serum PLs may serve as indicators for monitoring the early stages of OA even before radiologic detection is possible. With 10% of PL species elevated only in OA serum, our data implicate the existence of a systemic response that parallels the local lipid metabolic response to OA.

Preliminary investigations of plasma lipidome and selenium levels in adults with treated hypothyroidism and in healthy individuals without selenium deficiency

The present preliminary study aimed to provide a targeted lipidomic analysis of Hashimoto (HT) and non-HT patients with well-controlled hypothyroidism as well as in healthy adults, and is the first to demonstrate the association of several components of the human lipidome with hypothyroidism in relation to the total plasma selenium content. All the patients and age-, sex-, and BMI-matched healthy controls met the very strict qualification criteria. Se levels were analyzed by ICP-MS, and lipidome studies were conducted using TQ-LC/MS. The 40 acylcarnitines, 90 glycerophospholipids, and 15 sphingomyelins were identified and quantified. PCaaC26:0 and PCaaC40:1 were negatively correlated with Se concentrations. Other lipids that were negatively correlated with Se concentrations but did not present significant differences between the three groups in the Kruskal-Wallis ANOVA test were PCaaC32:0, PCaeC30:0, PCaeC36:5, SMC18:0, and SM C18:1. In the multiple linear regression analyses, Se levels showed negative relationship, whereas different phosphatidylcholines: PCaaC24:0, PCaaC26:0, PCaeC30:1, PCaeC34:0, PCaeC36:4, PCaeC42:0 were positively associated with the presence of (H). Different lipidome components were identified in healthy and hypothyroid patients regardless of the cause of that condition. Studies on larger populations are needed to determine cause-and-effect relations and the potential mechanisms underlying these associations.

Dysregulation of sphingolipid metabolism in pain

Pain is a clinical condition that is currently of great concern and is often caused by tissue or nerve damage or occurs as a concomitant symptom of a variety of diseases such as cancer. Severe pain seriously affects the functional status of the body. However, existing pain management programs are not fully satisfactory. Therefore, there is a need to delve deeper into the pathological mechanisms underlying pain generation and to find new targets for drug therapy. Sphingolipids (SLs), as a major component of the bilayer structure of eukaryotic cell membranes, also have powerful signal transduction functions. Sphingolipids are abundant, and their intracellular metabolism constitutes a huge network. Sphingolipids and their various metabolites play significant roles in cell proliferation, differentiation, apoptosis, etc., and have powerful biological activities. The molecules related to sphingolipid metabolism, mainly the core molecule ceramide and the downstream metabolism molecule sphingosine-1-phosphate (S1P), are involved in the specific mechanisms of neurological disorders as well as the onset and progression of various types of pain, and are closely related to a variety of pain-related diseases. Therefore, sphingolipid metabolism can be the focus of research on pain regulation and provide new drug targets and ideas for pain.

Restricting Branched-Chain Amino Acids within a High-Fat Diet Prevents Obesity

Obesity is a global pandemic, but there is yet no effective measure to control it. Recent metabolomics studies have identified a signature of altered amino acid profiles to be associated with obesity, but it is unclear whether these findings have actionable clinical potential. The aims of this study were to reveal the metabolic alterations of obesity and to explore potential strategies to mitigate obesity. We performed targeted metabolomic profiling of the plasma/serum samples collected from six independent cohorts and conducted an individual data meta-analysis of metabolomics for body mass index (BMI) and obesity. Based on the findings, we hypothesized that restriction of branched-chain amino acids (BCAAs), phenylalanine, or tryptophan may prevent obesity and tested our hypothesis in a dietary restriction trial with eight groups of 4-week-old male C57BL/6J mice (n = 5/group) on eight different types of diets, respectively, for 16 weeks. A total of 3397 individuals were included in the meta-analysis. The mean BMI was 30.7 ± 6.1 kg/m2, and 49% of participants were obese. Fifty-eight metabolites were associated with BMI and obesity (all p ≤ 2.58 × 10-4), linked to alterations of the BCAA, phenylalanine, tryptophan, and phospholipid metabolic pathways. The restriction of BCAAs within a high-fat diet (HFD) maintained the mice's weight, fat and lean volume, subcutaneous and visceral adipose tissue weight, and serum glucose and insulin at levels similar to those in the standard chow group, and prevented obesity, adipocyte hypertrophy, adipose inflammation, and insulin resistance induced by HFD. Our data suggest that four metabolic pathways, BCAA, phenylalanine, tryptophan, and phospholipid metabolic pathways, are altered in obesity and restriction of BCAAs within a HFD can prevent the development of obesity and insulin resistance in mice, providing a promising strategy to potentially mitigate diet-induced obesity.

Lipidomic Profiling Identifies Serum Lipids Associated with Persistent Multisite Musculoskeletal Pain

Lipid mediators have been suggested to have a role in pain sensitivity and response; however, longitudinal data on lipid metabolites and persistent multisite musculoskeletal pain (MSMP) are lacking. This study was to identify lipid metabolic markers for persistent MSMP. Lipidomic profiling of 807 lipid species was performed on serum samples of 536 participants from a cohort study. MSMP was measured by a questionnaire and defined as painful sites ≥4. Persistent MSMP was defined as having MSMP at every visit. Logistic regression was used with adjustment for potential confounders. The Benjamini–Hochberg method was used to control for multiple testing. A total of 530 samples with 807 lipid metabolites passed quality control. Mean age at baseline was 61.54 ± 6.57 years and 50% were females. In total, 112 (21%) of the participants had persistent MSMP. Persistent MSMP was significantly associated with lower levels of monohexosylceramide (HexCer)(d18:1/22:0 and d18:1/24:0), acylcarnitine (AC)(26:0) and lysophosphatidylcholine (LPC)(18:1 [sn1], 18:2 [sn1], 18:2 [sn2], and 15-MHDA[sn1] [104_sn1]) after controlling for multiple testing. After adjustment for age, sex, body mass index, comorbidities, and physical activity, HexCer(d18:1/22:0 and d18:1/24:0) and LPC(15-MHDA [sn1] [104_sn1]) were significantly associated with persistent MSMP [Odds Ratio (OR) ranging from 0.25–0.36]. Two lipid classes—HexCer and LPC—were negatively associated with persistent MSMP after adjustment for covariates (OR = 0.22 and 0.27, respectively). This study identified three novel lipid signatures of persistent MSMP, suggesting that lipid metabolism is involved in the pathogenesis of persistent pain.