Plasma Ceramides containing Saturated Fatty Acids are Associated with Risk of Type 2 Diabetes

Cohort-based strategies as an in-house tool to evaluate and improve phenotyping robustness of LC-MS/MS lipidomics platforms

In recent years, instrumental improvements have enabled the spread of mass spectrometry-based lipidomics platforms in biomedical research. In mass spectrometry, the reliability of generated data varies for each compound, contingent on, among other factors, the availability of labeled internal standards. It is challenging to evaluate the data for lipids without specific labeled internal standards, especially when dozens to hundreds of lipids are measured simultaneously. Thus, evaluation of the performance of these platforms at the individual lipid level in interlaboratory studies is generally not feasible in a time-effective manner. Herein, using a focused subset of sphingolipids, we present an in-house validation methodology for individual lipid reliability assessment, tailored to the statistical analysis to be applied. Moreover, this approach enables the evaluation of various methodological aspects, including discerning coelutions sharing identical selected reaction monitoring transitions, pinpointing optimal labeled internal standards and their concentrations, and evaluating different extraction techniques. While the full validation according to analytical guidelines for all lipids included in a lipidomics method is currently not possible, this process shows areas to focus on for subsequent method development iterations as well as the robustness of data generated across diverse methodologies.

Withdrawn: Combinatorial lipidomics and proteomics underscore erythrocyte lipid membrane aberrations in the development of adverse cardio-cerebrovascular complications in maintenance hemodialysis patients

This article has been withdrawn: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). The authors reached out to the Publisher to alert the Publisher to incorrect text published in the article. After investigating the situation, the journal came to the conclusion that the wrong version of the file was sent by the authors to the production team during the proof stage and the misplaced text was not noticed by the authors when they approved the final version. After consulting with the Editor-in-Chief of the journal, the decision was made to withdraw the current version of the article.

Severity Ranking of Missense and Frameshift Genetic Variants in SCD1 by In Silico and In Vitro Functional Analysis

BACKGROUND

A considerable proportion of the symptoms associated with excessive dietary intake can be attributed to systemic imbalances in lipid metabolism. The prominent toxicity of saturated fatty acids has been repeatedly demonstrated and sheds light on the protective role of stearoyl-CoA desaturase-1 (SCD1), the key enzyme for fatty acid desaturation. SCD1 protein expression is regulated at the levels of transcription, translation, and degradation. However, the modulating effect of the variability of the human genome must also be taken into account. Therefore, we aimed to ascertain whether natural missense or frameshift mutations in SCD1 (p.H125P, p.M224L, p.A333T, p.R253AfsTer7) could influence the expression, degradation, or function of the enzyme.

METHODS

In silico and in vitro experiments were conducted to comprehensively evaluate the consequences associated with each genetic variation, with the objective of using the results to propose a risk or severity ranking of SCD1 variants.

RESULTS

As anticipated, the p.R253AfsTer7 variant was identified as the most deleterious in structural, functional, and quantitative terms. The p.H125P variant also reduced the desaturation capacity of the enzyme in accordance with the predicted structural alterations and augmented degradation resulting from folding complications. This was aggravated by increased mRNA instability and accompanied by mild endoplasmic reticulum stress induction. The p.A333T protein exhibited an intermediate phenotype, whereas p.M224L showed no deleterious effects and even increased the amount of SCD1.

CONCLUSIONS

In conclusion, the large-scale identification of genetic variations needs to be supplemented with comprehensive functional characterization of these variations to facilitate adequate personalized prevention and treatment of lipid metabolism-related conditions.

Moderate-intensity Combined Training Induces Lipidomic Changes in Individuals With Obesity and Type 2 Diabetes

CONTEXT

Alterations in the lipid metabolism are linked to metabolic disorders such as insulin resistance (IR), obesity and type 2 diabetes (T2D). Regular exercise, particularly combined training (CT), is a well-known nonpharmacological treatment that combines aerobic (AT) and resistance (RT) training benefits. However, it is unclear whether moderate-intensity exercise without dietary intervention induces changes in lipid metabolism to promote a "healthy lipidome."

OBJECTIVE

The study aimed to investigate the effect of 16 weeks of CT on plasma and white adipose tissue in both sexes, middle-aged individuals with normal weight, obesity (OB), and T2D using an ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) untargeted lipidomics approach.

METHODS

Body composition, maximum oxygen consumption (VO2max), strength, and biochemical markers were evaluated before and after the control/training period and correlated with lipid changes. CT consisted of 8 to 10 RT exercises, followed by 35 minutes of AT (45%-70% VO2max), 3 times a week for 16 weeks.

RESULTS

The CT significantly reduced the levels of saturated and monounsaturated fatty acid side-chains (SFA/MUFA) in sphingolipids, glycerolipids (GL) and glycerophospholipids (GP) as well as reducing fat mass, circumferences and IR. Increased levels of polyunsaturated fatty acids in GPs and GLs were also observed, along with increased fat-free mass, VO2 max, and strength (all P < .05) after training.

CONCLUSION

Our study revealed that 16 weeks of moderate-intensity CT remodeled the lipid metabolism in OB, and T2D individuals, even without dietary intervention, establishing a link between exercise-modulated lipid markers and mechanisms that reduce IR and obesity-related comorbidities.

Associations of plasma sphingolipids with measures of insulin sensitivity, β-cell function, and incident diabetes in Japanese Americans

BACKGROUND AND AIMS

To prospectively investigate associations of plasma sphingolipids with insulin sensitivity, β-cell function, and incident diabetes in the Japanese American Community Diabetes Study.

METHODS AND RESULTS

Baseline plasma samples from adults without diabetes (n = 349; mean age 56.7 years, 51 % men) were assayed for circulating ceramide and sphingomyelin species. Adjusted regression models examined cross-sectional and longitudinal associations with insulin sensitivity (HOMA2-%S), β-cell function (oral disposition index: DIo) and with incident diabetes over 5 years follow-up. Concentrations of four species (Ceramide C16:0, C18:0, C20:0, and C22:0) were inversely associated with HOMA2-%S at baseline (all P values < 0.05, Q values < 0.05) and change in HOMA2-%S over 5 years (all P values < 0.05, Q values < 0.05). No sphingolipids were associated with baseline or change in DIo. Of the four species associated with HOMA2-%S, only Ceramide C18:0 was significantly and positively associated with incident diabetes (RR/1SD 1.44, 95 % CI 1.10-1.80, P = 0.006, Q = 0.024). The association of plasma Ceramide C18:0 with the risk of diabetes was partially mediated by change in HOMA2-%S between baseline and 5 years (mediation proportion: 61.5 %, 95 % CI 21.1%-212.5 %).

CONCLUSION

Plasma Ceramide C18:0 was associated with higher risk of incident diabetes which was partially mediated through a decrease in insulin sensitivity between baseline and five years. Circulating Ceramide C18:0 could be a potential biomarker for identifying those at risk of developing diabetes.

Plasma Sphingolipid Profile of Healthy Black and White Adults Differs Based on Their Parental History of Type 2 Diabetes

CONTEXT

Ceramides and sphingolipids have been linked to type 2 diabetes (T2D). The Ceramides and Sphingolipids as Predictors of Incident Dysglycemia (CASPID) study is designed to determine the association of plasma sphingolipids with the pathophysiology of human T2D.

OBJECTIVE

A comparison of plasma sphingolipids profiles in Black and White adults with (FH+) and without (FH-) family history of T2D.

DESIGN

We recruited 100 Black and White FH- (54 Black, 46 White) and 140 FH+ (75 Black, 65 White) adults. Fasting plasma levels of 58 sphingolipid species, including 18 each from 3 major classes (ceramides, monohexosylceramides, and sphingomyelins, all with 18:1 sphingoid base) and 4 long-chain sphingoid base-containing species, were measured by liquid chromatography/mass spectrometry.

RESULTS

Sphingomyelin was the most abundant sphingolipid in plasma (89% in FH-), and was significantly elevated in FH+ subjects (93%). Ceramides and monohexosylceramides comprised 5% and 6% of total sphingolipids in the plasma of FH- subjects, and were reduced significantly in FH+ subjects (3% and 4%, respectively). In FH+ subjects, most ceramide and monohexosylceramide species were decreased but sphingomyelin species were increased. The level of C18:1 species of all 3 classes was elevated in FH+ subjects.

CONCLUSION

Elevated levels of sphingomyelin, the major sphingolipids of plasma, and oleic acid-containing sphingolipids in healthy FH+ subjects compared with healthy FH- subjects may reflect heritable elements linking sphingolipids and the development of T2D.

Association of Serum Very-Long-Chain Saturated Fatty Acids With Changes in Insulin Sensitivity and β-Cell Function: The Prospective Metabolism and Islet Cell Evaluation (PROMISE) Cohort

A unique group of circulating very-long-chain saturated fatty acids (VLCSFAs), including arachidic acid (20:0), behenic acid (22:0), and lignoceric acid (24:0), have been associated with a lower risk of type 2 diabetes, although associations with early metabolic risk phenotypes preceding type 2 diabetes have received limited study. We aimed to examine the associations of VLCSFAs with longitudinal changes in insulin sensitivity and β-cell function in a cohort at risk for type 2 diabetes. VLCSFAs in the four main serum pools (phospholipid, triacylglycerol, cholesteryl ester, and nonesterified fatty acid) were extracted from fasting baseline samples (n = 467). Generalized estimating equations were used to determine the associations between VLCSFAs and changes over 9 years in validated indices of insulin sensitivity (HOMA2-%S [insulin sensitivity as percentage of normal population and ISI) and β-cell function (insulinogenic index [IGI], IGI divided by HOMA-insulin resistance [IGI/IR], and insulin secretion sensitivity index 2 [ISSI-2]). Associations of VLCSFAs with outcomes were strongest in the triacylglycerol lipid pool: 20:0 was positively associated with both insulin sensitivity and β-cell function (5.01% increase in HOMA2-%S and 4.01-6.28% increase in IGI/IR and ISSI-2 per SD increase in 20:0); 22:0 was positively associated with insulin sensitivity, with a 6.55% increase in HOMA2-%S and a 5.80% increase in ISI per SD increase in 22:0. Lastly, 24:0 was positively associated with insulin sensitivity and β-cell function (7.94-8.45% increase in HOMA2-%S and ISI, and a 4.61-6.93% increase in IGI/IR and ISSI-2 per SD increase in 24:0). Fewer significant associations were observed in the cholesteryl ester and nonesterified pools. Overall, our results indicate positive longitudinal associations of VLCSFAs with insulin sensitivity and β-cell function, especially within the triacylglycerol pool.

ARTICLE HIGHLIGHTS

Circulating Sphingolipids in Insulin Resistance, Diabetes and Associated Complications

Sphingolipids play an important role in the development of diabetes, both type 1 and type 2 diabetes, as well as in the development of both micro- and macro-vascular complications. Several reviews have been published concerning the role of sphingolipids in diabetes but most of the emphasis has been on the possible mechanisms by which sphingolipids, mainly ceramides, contribute to the development of diabetes. Research on circulating levels of the different classes of sphingolipids in serum and in lipoproteins and their importance as biomarkers to predict not only the development of diabetes but also of its complications has only recently emerged and it is still in its infancy. This review summarizes the previously published literature concerning sphingolipid-mediated mechanisms involved in the development of diabetes and its complications, focusing on how circulating plasma sphingolipid levels and the relative content carried by the different lipoproteins may impact their role as possible biomarkers both in the development of diabetes and mainly in the development of diabetic complications. Further studies in this field may open new therapeutic avenues to prevent or arrest/reduce both the development of diabetes and progression of its complications.

The lipidomic correlates of epigenetic aging across the adult lifespan: A population-based study

Lipid signaling is involved in longevity regulation, but which specific lipid molecular species affect human biological aging remains largely unknown. We investigated the relation between complex lipids and DNA methylation-based metrics of biological aging among 4181 participants (mean age 55.1 years (range 30.0-95.0)) from the Rhineland Study, an ongoing population-based cohort study in Bonn, Germany. The absolute concentration of 14 lipid classes, covering 964 molecular species and 267 fatty acid composites, was measured by Metabolon Complex Lipid Panel. DNA methylation-based metrics of biological aging (AgeAccelPheno and AgeAccelGrim) were calculated based on published algorithms. Epigenome-wide association analyses (EWAS) of biological aging-associated lipids and pathway analysis were performed to gain biological insights into the mechanisms underlying the effects of lipidomics on biological aging. We found that higher levels of molecular species belonging to neutral lipids, phosphatidylethanolamines, phosphatidylinositols, and dihydroceramides were associated with faster biological aging, whereas higher levels of lysophosphatidylcholine, hexosylceramide, and lactosylceramide species were associated with slower biological aging. Ceramide, phosphatidylcholine, and lysophosphatidylethanolamine species with odd-numbered fatty acid tail lengths were associated with slower biological aging, whereas those with even-numbered chain lengths were associated with faster biological aging. EWAS combined with functional pathway analysis revealed several complex lipids associated with biological aging as important regulators of known longevity and aging-related pathways.

Circulating Sphingolipids and Glucose Homeostasis: An Update

Sphingolipids are a family of lipid molecules produced through different pathways in mammals. Sphingolipids are structural components of membranes, but in response to obesity, they are implicated in the regulation of various cellular processes, including inflammation, apoptosis, cell proliferation, autophagy, and insulin resistance which favors dysregulation of glucose metabolism. Of all sphingolipids, two species, ceramides and sphingosine-1-phosphate (S1P), are also found abundantly secreted into the bloodstream and associated with lipoproteins or extracellular vesicles. Plasma concentrations of these sphingolipids can be altered upon metabolic disorders and could serve as predictive biomarkers of these diseases. Recent important advances suggest that circulating sphingolipids not only serve as biomarkers but could also serve as mediators in the dysregulation of glucose homeostasis. In this review, advances of molecular mechanisms involved in the regulation of ceramides and S1P association to lipoproteins or extracellular vesicles and how they could alter glucose metabolism are discussed.

Interleukin-18 Is a Potential Biomarker Linking Dietary Fatty Acid Quality and Insulin Resistance: Results from a Cross-Sectional Study in Northern Italy

Dietary lipids are pivotal in modulating metabolic inflammation. Among the inflammatory mediators characterizing metabolic inflammation, interleukin 18 (IL-18) has been consistently associated with obesity and insulin resistance. This study aims to evaluate whether the quality of lipid intake impacts upon IL-18 plasma levels and the implications on insulin resistance computed by the homeostatic model assessment for insulin resistance (HOMA-IR). Using a cross-sectional design, this study confirmed that IL-18 correlated positively with insulin resistance and individuals with a HOMA-IR ≥ 2.5 displayed higher circulating IL-18 levels compared with their insulin-sensitive counterparts. In terms of the effect of the quality of dietary lipids on IL-18 circulating levels, the ratio between monounsaturated, omega-3, polyunsaturated and saturated fatty acids as well as the intake of eicosapentaenoic and docosahexaenoic acids correlated negatively with IL-18. Despite this, IL-18 circulating levels, but not dietary fatty acid quality, predicted insulin resistance. Nevertheless, the ratio between omega 3 and saturated fatty acids was a predictor of IL-18 plasma levels. Thus, the downregulation of IL-18 may underpin, at least partially, the beneficial metabolic effects of substituting omega 3 for saturated fatty acids with this cytokine potentially representing a biomarker linking dietary lipids and metabolic outcomes.

The roles of dietary lipids and lipidomics in gut-brain axis in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM), one of the main types of Noncommunicable diseases (NCDs), is a systemic inflammatory disease characterized by dysfunctional pancreatic β-cells and/or peripheral insulin resistance, resulting in impaired glucose and lipid metabolism. Genetic, metabolic, multiple lifestyle, and sociodemographic factors are known as related to high T2DM risk. Dietary lipids and lipid metabolism are significant metabolic modulators in T2DM and T2DM-related complications. Besides, accumulated evidence suggests that altered gut microbiota which plays an important role in the metabolic health of the host contributes significantly to T2DM involving impaired or improved glucose and lipid metabolism. At this point, dietary lipids may affect host physiology and health via interaction with the gut microbiota. Besides, increasing evidence in the literature suggests that lipidomics as novel parameters detected with holistic analytical techniques have important roles in the pathogenesis and progression of T2DM, through various mechanisms of action including gut-brain axis modulation. A better understanding of the roles of some nutrients and lipidomics in T2DM through gut microbiota interactions will help develop new strategies for the prevention and treatment of T2DM. However, this issue has not yet been entirely discussed in the literature. The present review provides up-to-date knowledge on the roles of dietary lipids and lipidomics in gut-brain axis in T2DM and some nutritional strategies in T2DM considering lipids- lipidomics and gut microbiota interactions are given.

Nutrients, Physical Activity, and Mitochondrial Dysfunction in the Setting of Metabolic Syndrome

Metabolic syndrome (MetS) is a cluster of metabolic risk factors for diabetes, coronary heart disease, non-alcoholic fatty liver disease, and some tumors. It includes insulin resistance, visceral adiposity, hypertension, and dyslipidemia. MetS is primarily linked to lipotoxicity, with ectopic fat deposition from fat storage exhaustion, more than obesity per se. Excessive intake of long-chain saturated fatty acid and sugar closely relates to lipotoxicity and MetS through several pathways, including toll-like receptor 4 activation, peroxisome proliferator-activated receptor-gamma regulation (PPARγ), sphingolipids remodeling, and protein kinase C activation. These mechanisms prompt mitochondrial dysfunction, which plays a key role in disrupting the metabolism of fatty acids and proteins and in developing insulin resistance. By contrast, the intake of monounsaturated, polyunsaturated, and medium-chain saturated (low-dose) fatty acids, as well as plant-based proteins and whey protein, favors an improvement in sphingolipid composition and metabolic profile. Along with dietary modification, regular exercises including aerobic, resistance, or combined training can target sphingolipid metabolism and improve mitochondrial function and MetS components. This review aimed to summarize the main dietary and biochemical aspects related to the physiopathology of MetS and its implications for mitochondrial machinery while discussing the potential role of diet and exercise in counteracting this complex clustering of metabolic dysfunctions.

The Impact of Phytochemicals in Obesity-Related Metabolic Diseases: Focus on Ceramide Metabolism

The prevalence of obesity and related metabolic diseases has increased dramatically worldwide. As obesity progresses, various lipid species accumulate in ectopic tissues. Amongst them, ceramides-a deleterious sphingolipid species-accumulate and cause lipotoxicity and metabolic disturbances. Dysregulated ceramide metabolism appears to be a key feature in the pathogenesis of obesity-related metabolic diseases. Notably, dietary modification might have an impact on modulating ceramide metabolism. Phytochemicals are plant-derived compounds with various physiological properties, which have been shown to protect against obesity-related metabolic diseases. In this review, we aim to examine the impact of a myriad of phytochemicals and their dietary sources in altering ceramide deposition and ceramide-related metabolism from in vitro, in vivo, and human clinical/epidemiological studies. This review discusses how numerous phytochemicals are able to alleviate ceramide-induced metabolic defects and reduce the risk of obesity-related metabolic diseases via diverse mechanisms.

Circulating ceramides and sphingomyelins and the risk of incident cardiovascular disease among people with diabetes: the strong heart study

BACKGROUND

Plasma ceramides and sphingomyelins have been independently linked to diabetes risk, glucose and insulin levels, and the risk of several cardiovascular (CVD) outcomes. However, whether individual ceramide and sphingomyelin species contribute to CVD risk among people with type 2 diabetes is uncertain. Our goal was to evaluate associations of 4 ceramide and 4 sphingomyelin species with incident CVD in a longitudinal population-based study among American Indians with diabetes.

METHODS

This analysis included participants with prevalent type 2 diabetes from two cohorts: a prospective cohort of 597 participants in the Strong Heart Family Study (116 incident CVD cases; mean age: 49 years; average length of follow-up: 14 years), and a nested case-control sample of 267 participants in the Strong Heart Study (78 cases of CVD and 189 controls; mean age: 61 years; average time until incident CVD in cases: 3.8 years). The average onset of diabetes was 7 years prior to sphingolipid measurement. Sphingolipid species were measured using liquid chromatography and mass spectrometry. Cox regression and logistic regression were used to assess associations of sphingolipid species with incident CVD; results were combined across cohorts using inverse-variance weighted meta-analysis.

RESULTS

There were 194 cases of incident CVD in the two cohorts. In meta-analysis of the 2 cohort results, higher plasma levels of Cer-16 (ceramide with acylated palmitic acid) were associated with higher CVD risk (HR per two-fold higher Cer-16: 1.85; 95% CI 1.05-3.25), and higher plasma levels of sphingomyelin species with a very long chain saturated fatty acid were associated with lower CVD risk (HR per two-fold higher SM-22: 0.48; 95% CI 0.26-0.87), although none of the associations met our pre-specified threshold for statistical significance of p = 0.006.

CONCLUSIONS

While replication of the findings from the SHS in other populations is warranted, our findings add to a growing body of research suggesting that ceramides, in particular Cer-16, not only are associated with higher diabetes risk, but may also be associated with higher CVD risk after diabetes onset. We also find support for the hypothesis that sphingomyelins with a very long chain saturated fatty acid are associated with lower CVD risk among adults with type 2 diabetes.

Ceramide Acyl Chain Length and Its Relevance to Intracellular Lipid Regulation

Ceramides are a class of sphingolipids which are implicated in skin disorders, obesity, and other metabolic diseases. As a class with pleiotropic effects, recent efforts have centred on discerning specific ceramide species and their effects on atopic dermatitis, obesity, type 2 diabetes, and cardiovascular diseases. This delineation has allowed the identification of disease biomarkers, with long acyl chain ceramides such as C16- and C18-ceramides linked to metabolic dysfunction and cardiac function decline, while ultra-long acyl chain ceramides (>25 carbon acyl chain) were reported to be essential for maintaining a functional skin barrier. Given the intricate link between free fatty acids with ceramides, especially the de novo synthetic pathway, intracellular lipid droplet formation is increasingly viewed as an important mechanism for preventing accumulation of toxic ceramide species. Here, we review recent reports of various ceramide species involved in skin abnormalities and metabolic diseases, and we propose that promotion of lipid droplet biogenesis can be seen as a potential protective mechanism against deleterious ceramides.

The Lard Works in Mysterious Ways: Ceramides in Nutrition-Linked Chronic Disease

Diet influences onset, progression, and severity of several chronic diseases, including heart failure, diabetes, steatohepatitis, and a subset of cancers. The prevalence and clinical burden of these obesity-linked diseases has risen over the past two decades. These metabolic disorders are driven by ectopic lipid deposition in tissues not suited for fat storage, leading to lipotoxic disruption of cell function and survival. Sphingolipids such as ceramides are among the most deleterious and bioactive metabolites that accrue, as they participate in selective insulin resistance, dyslipidemia, oxidative stress and apoptosis. This review discusses our current understanding of biochemical pathways controlling ceramide synthesis, production and action; influences of diet on ceramide levels; application of circulating ceramides as clinical biomarkers of metabolic disease; and molecular mechanisms linking ceramides to altered metabolism and survival of cells. Development of nutritional or pharmacological strategies to lower ceramides could have therapeutic value in a wide range of prevalent diseases.

Following Roux-en-Y gastric bypass surgery, serum ceramides demarcate patients that will fail to achieve normoglycemia and diabetes remission

BACKGROUND

Obesity is a prevalent health threat and risk factor for type 2 diabetes. In this study, we evaluate the relationship between ceramides, which inhibit insulin secretion and sensitivity, and markers of glucose homeostasis and diabetes remission or recursion in patients who have undergone a Roux-en-Y gastric bypass (RYGB).

METHODS

The Utah Obesity Study is a prospective cohort study, with targeted ceramide and dihydroceramide measurements performed on banked serum samples. The Utah Obesity Study consists of 1,156 participants in three groups: a RYGB surgery group, a non-surgery group denied insurance coverage, and severely obese population controls. Clinical examinations and ceramide assessments were performed at baseline and 2 and 12 years after RYGB surgery.

FINDINGS

Surgery patients (84% female, 42.2 ± 10.6 years of age at baseline) displayed lower levels of several serum dihydroceramides and ceramides at 2 and 12 years after RYGB. By contrast, neither the control group (77% female, 48.7± 6.4 years of age at baseline) nor the non-surgery group (95% female, 43.0± 11.4 years of age at baseline) experienced significant decreases in any species. Using a linear mixed effect model, we found that multiple dihydroceramides and ceramides positively associated with the glycemic control measures HOMA-IR and HbA1c. In surgery group participants with prevalent diabetes, ceramides inversely predict diabetes remission, independent of changes in weight.

CONCLUSIONS

Ceramide decreases may explain the insulin sensitization and diabetes resolution observed in most RYGB surgery patients.

FUNDING

Funded by the National Institutes of health (NIH), The Juvenile Diabetes Research Foundation, and the American Heart Association.

Lipidomics in diabetes

PURPOSE OF REVIEW

Multiple studies have shown a strong association between lipids and diabetes. These are usually described through the effects of cholesterol content of lipid particles and in particular low-density lipoprotein. However, lipoprotein particles contain other components, such as phospholipids and more complex lipid species, such as ceramides and sphingolipids. Ceramides, such as sphingolipids are also produced intracellularly and have signalling actions in regulating cell metabolism including effects on inflammation, and potentially have a mechanistic role in the development of insulin resistance.

RECENT FINDINGS

Recently, techniques have been developed to analyse detailed molecular profiles of lipid particles - lipidomics. Proteomics has confirmed the different proteins associated with different particles but far less is known about the relationship of individual lipid species with diabetes and cardiovascular risk. A number of studies have now shown that the plasma lipidome, and in particular, ceramides and sphingolipids may predict the development of diabetes.

SUMMARY

Lipidomics had identified ceramides and sphingolipids as potential mediators of cellular dysfunction in diabetes. Further work is required to ascertain whether they have clinical utility.

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.

Very long-chain saturated fatty acids and diabetes and cardiovascular disease

PURPOSE OF REVIEW

In contrast to other saturated fatty acids, very long-chain saturated fatty acids (VLSFAs) have received limited attention The purpose of this review is to summarize the associations of VLSFAs, including arachidic acid, behenic acid, and lignoceric acid, with cardiovascular disease outcomes and type 2 diabetes; to discuss the findings implications; and to call for future studies of the VLSFAs.

RECENT FINDINGS

Increased levels of circulating VLSFAs have been found associated with lower risks of incident heart failure, atrial fibrillation, coronary heart disease, mortality, sudden cardiac arrest, type 2 diabetes, and with better aging. The VLSFA associations are paralleled by associations of plasma ceramide and sphingomyelin species carrying a VLSFA with lower risks of heart failure, atrial fibrillation, and mortality, suggesting VLSFAs affect the biological activity of ceramides and sphingomyelins thereby impacting health. For diabetes, there is no such parallel and the associations of VLSFAs with diabetes may be confounded or mediated by triglyceride and circulating palmitic acid, possible biomarkers of de novo lipogenesis.

SUMMARY

In many ways, the epidemiology has preceded our knowledge of VLSFAs biology. We hope this review will spur interest from the research community in further studying these potentially beneficial fatty acids.

Association between the metabolic profile of serum fatty acids and diabetic nephropathy: a study conducted in northeastern China

BACKGROUND AND PURPOSE

With the progressive increase in the prevalence of type 2 diabetes mellitus (T2DM), diabetic nephropathy (DN) - one of the most common chronic microvascular complications - has evolved into a significant cause of death worldwide among end-stage renal disease patients. Academic researchers have for decades focused on the development of DN and recently found that free fatty acids (FFAs) constituted an independent risk factor for vascular complications in T2DM patients. It is therefore critical to determine whether the metabolic profile of FFAs is related to DN.

METHODS

This study comprised 611 research subjects in Dalian, a city in northeast China: 52 DN patients, 115 T2DM patients, and 444 healthy controls. We determined 15 forms of serum FFAs, including arachidonic acid (AA, C20:4), docosahexaenoic acid (DHA, C22:6), erucic acid (C22:1), nervonic acid (NA, C24:1), estimated total omega-3s, total omega-6s, the omega-3/omega-6 ratio, and total FFA content by liquid chromatography-mass spectrometry (LC-MS).

RESULTS

The levels of NA (mean = 45.27, range = 0.84-76.57) and DHA (mean = 324.58, range = 205.38-450.03) in DN patients were slightly lower than those in T2DM patients or healthy controls. The serum omega-3 polyunsaturated fatty acid (PUFA) DHA (C22:6) was significantly negatively correlated with microalbuminuria (MAU), the albumin/creatinine ratio (ACR), body mass index (BMI), fasting plasma glucose (FPG), and glycosylated hemoglobin (HbA1c). The serum monounsaturated fatty acid (MUFA) NA (C24:1) was significantly negatively correlated with BMI, FPG, and HbA1c. After adjustment of variables, multiple logistic regression analysis revealed significant odds ratios (ORs) [with confidence intervals (CIs)] for DHA (0.991, 0.985-0.997; p = 0.002) and NA (0.978, 0.958-0.999; p = 0.037).

CONCLUSION

In this study, we ascertained that the contents of NA and DHA in patients with DN were relatively low, and that DHA was negatively correlated with MAU and the ACR. However, large-scale, population-based studies focusing on the role of NA and DHA in the pathogenesis of DN are still required in the future.