A lipidomics analysis of the relationship between dietary fatty acid composition and insulin sensitivity in young adults

Full-fat versus non-fat yogurt consumption improves glucose homeostasis and metabolic hormone regulation in individuals with prediabetes: A randomized-controlled trial

Dietary guidance recommends consuming low- or non-fat dairy foods for metabolic health, yet observational research indicates full-fat yogurt intake may not detrimentally affect type 2 diabetes risk. Randomized-controlled trials are needed to further explore this relationship. Our aim was to evaluate the effect of substituting full-fat (3.25%) yogurt for non-fat yogurt on type 2 diabetes risk in individuals with prediabetes. We hypothesized beneficial effects on measures of glucose homeostasis, insulin sensitivity, and metabolic hormone response following short-term consumption of 3 full-fat yogurt servings daily. Thirteen individuals completed the 8-week randomized, double-masked crossover controlled-feeding trial comprised 2, 3-week experimental diet periods in which participants consumed 3 daily servings of full-fat or non-fat yogurt; a 1-week control preceded each diet period. Following each diet period, changes in whole-body glucose handling and metabolic hormone concentrations were measured using mixed meal and oral glucose tolerance tests. Our primary outcome measure was the blood glucose concentration at the 120-minute time point during the oral glucose tolerance test. Though differences in the primary outcome measure were not observed, the full-fat yogurt diet resulted in lower concentrations of blood fructosamine, a marker of average blood glucose concentrations over 2 to 3 weeks. Further, fasting glucagon-like peptide-1 and post-prandial glucose-dependent insulinotropic polypeptide concentrations were greater following the full-fat yogurt diet. Our preliminary results indicate that short-term consumption of full-fat relative to non-fat yogurt beneficially affected aspects of glucose homeostasis and metabolic hormone regulation in individuals with prediabetes, warranting further randomized-controlled research. This trial is registered at clinicaltrials.gov (NCT03577119).

Determinants of increased muscle insulin sensitivity of exercise-trained versus sedentary normal weight and overweight individuals

The athlete's paradox states that intramyocellular triglyceride accumulation associates with insulin resistance in sedentary but not in endurance-trained humans. Underlying mechanisms and the role of muscle lipid distribution and composition on glucose metabolism remain unclear. We compared highly trained athletes (ATHL) with sedentary normal weight (LEAN) and overweight-to-obese (OVWE) male and female individuals. This observational study found that ATHL show higher insulin sensitivity, muscle mitochondrial content, and capacity, but lower activation of novel protein kinase C (nPKC) isoforms, despite higher diacylglycerol concentrations. Notably, sedentary but insulin sensitive OVWE feature lower plasma membrane-to-mitochondria sn-1,2-diacylglycerol ratios. In ATHL, calpain-2, which cleaves nPKC, negatively associates with PKCε activation and positively with insulin sensitivity along with higher GLUT4 and hexokinase II content. These findings contribute to explaining the athletes' paradox by demonstrating lower nPKC activation, increased calpain, and mitochondrial partitioning of bioactive diacylglycerols, the latter further identifying an obesity subtype with increased insulin sensitivity (NCT03314714).

Role of dietary and nutritional interventions in ceramide-associated diseases

Ceramides are important intermediates in sphingolipid metabolism and serve as signaling molecules with independent biological significance. Elevated cellular and circulating ceramide levels are consistently associated with pathological conditions including cardiometabolic diseases, neurological diseases, autoimmune diseases, and cancers. Although pharmacological inhibition of ceramide formation often protects against these diseases in animal models, pharmacological modulation of ceramides in humans remains impractical. Dietary interventions including the Mediterranean diet, lacto-ovo-vegetarian diet, calorie-restricted diet, restriction of dairy product consumption, and dietary supplementation with polyunsaturated fatty acids, dietary fibers, and polyphenols, all have beneficial effects on modulating ceramide levels. Mechanistic insights into these interventions are discussed. This article reviews the relationships between ceramides and disease pathogenesis, with a focus on dietary intervention as a viable strategy for lowering the concentration of circulating ceramides.

Non-canonical pathways associated to Amyloid beta and tau protein dyshomeostasis in Alzheimer's disease: A narrative review

Alzheimer's Disease (AD) is the most common form of dementia among elderly people. This disease imposes a significant burden on the healthcare system, society, and economy due to the increasing global aging population. Current trials with drugs or bioactive compounds aimed at reducing cerebral Amyloid beta (Aβ) plaques and tau protein neurofibrillary tangles, which are the two main hallmarks of this devastating neurodegenerative disease, have not provided significant results in terms of their neuropathological outcomes nor met the expected clinical end-points. Ageing, genetic and environmental risk factors, along with different clinical symptoms suggest that AD is a complex and heterogeneous disorder with multiple interconnected pathological pathways rather than a single disease entity. In the present review, we highlight and discuss various non-canonical, Aβ-independent mechanisms, like gliosis, unhealthy dietary intake, lipid and sugar signaling, and cerebrovascular damage that contribute to the onset and development of AD. We emphasize that challenging the traditional "amyloid cascade hypothesis" may improve our understanding of this age-related complex syndrome and help fight the progressive cognitive decline in AD.

Plasma C24:0 ceramide impairs adipose tissue remodeling and promotes liver steatosis and glucose imbalance in offspring of rats

Fetal programming by exposure to high-energy diets increases the susceptibility to type 2 diabetes mellitus (T2DM2) in the offspring. Glucose imbalance during fetal programming might be associated to still unknown selective lipid species and their characterization might be beneficial for T2DM diagnosis and treatment. We aim to characterize the effect of the lipid specie, C24:0 ceramide, on glucose imbalance and metabolic impairment in cellular and murine models. A lipidomic analysis identified accumulation of C24:0 ceramide in plasma of offspring rats exposed to high-energy diets during fetal programing, as well as in obese-T2DM subjects. In vitro experiments in 3T3L-1, hMSC and HUH7 cells and in in vivo models of Wistar rats and C57BL/6 mice demonstrated that C24:0 ceramide disrupted glucose balance, and differentiation and lipid accumulation in adipocytes, whereas promoted liver steatosis. Mechanistically, C24:0 ceramide impaired mitochondrial fatty acid oxidation in adipocytes and hepatic cells, tentatively by favoring reactive oxygen species accumulation and calcium overload in the mitochondria; and also, activates endoplasmic reticulum (ER) stress in hepatocytes. We propose that C24:0 ceramide accumulation in the offspring followed a prenatal diet exposure, impair lipid allocation into adipocytes and enhances liver steatosis associated to mitochondrial dysfunction and ER stress, leading to glucose imbalance.

Emerging Roles for Sphingolipids in Cardiometabolic Disease: A Rational Therapeutic Target?

Cardiovascular disease is a leading cause of morbidity and mortality. New research elucidates increasingly complex relationships between cardiac and metabolic health, giving rise to new possible therapeutic targets. Sphingolipids are a heterogeneous class of bioactive lipids with critical roles in normal human physiology. They have also been shown to play both protective and deleterious roles in the pathogenesis of cardiovascular disease. Ceramides are implicated in dysregulating insulin signalling, vascular endothelial function, inflammation, oxidative stress, and lipoprotein aggregation, thereby promoting atherosclerosis and vascular disease. Ceramides also advance myocardial disease by enhancing pathological cardiac remodelling and cardiomyocyte death. Glucosylceramides similarly contribute to insulin resistance and vascular inflammation, thus playing a role in atherogenesis and cardiometabolic dysfunction. Sphingosing-1-phosphate, on the other hand, may ameliorate some of the pathological functions of ceramide by protecting endothelial barrier integrity and promoting cell survival. Sphingosine-1-phosphate is, however, implicated in the development of cardiac fibrosis. This review will explore the roles of sphingolipids in vascular, cardiac, and metabolic pathologies and will evaluate the therapeutic potential in targeting sphingolipids with the aim of prevention and reversal of cardiovascular disease in order to improve long-term cardiovascular outcomes.

Ceramides as Emerging Players in Cardiovascular Disease: Focus on Their Pathogenetic Effects and Regulation by Diet

Impaired lipid metabolism is a pivotal driver of cardiovascular disease (CVD). In this regard, the accumulation of ceramides within the circulation as well as in metabolically active tissues and atherosclerotic plaques is a direct consequence of derailed lipid metabolism. Ceramides may be at the nexus between impaired lipid metabolism and CVD. Indeed, although on one hand ceramides have been implicated in the pathogenesis of CVD, on the other specific ceramide subspecies have also been proposed as predictors of major adverse cardiovascular events. This review will provide an updated overview of the role of ceramides in the pathogenesis of CVD, as well as their pathogenetic mechanisms of action. Furthermore, the manuscript will cover the importance of ceramides as biomarkers to predict cardiovascular events and the role of diet, both in terms of nutrients and dietary patterns, in modulating ceramide metabolism and homeostasis.

Ceramides are fuel gauges on the drive to cardiometabolic disease

Ceramides are signals of fatty acid excess that accumulate when a cell's energetic needs have been met and its nutrient storage has reached capacity. As these sphingolipids accrue, they alter the metabolism and survival of cells throughout the body including in the heart, liver, blood vessels, skeletal muscle, brain, and kidney. These ceramide actions elicit the tissue dysfunction that underlies cardiometabolic diseases such as diabetes, coronary artery disease, metabolic-associated steatohepatitis, and heart failure. Here, we review the biosynthesis and degradation pathways that maintain ceramide levels in normal physiology and discuss how the loss of ceramide homeostasis drives cardiometabolic pathologies. We highlight signaling nodes that sense small changes in ceramides and in turn reprogram cellular metabolism and stimulate apoptosis. Finally, we evaluate the emerging therapeutic utility of these unique lipids as biomarkers that forecast disease risk and as targets of ceramide-lowering interventions that ameliorate disease.

ER stress inhibition enhances formation of triacylglcerols and protects endothelial cells from lipotoxicity

Elevated concentrations of palmitate in serum of obese individuals can impair endothelial function, contributing to development of cardiovascular disease. Although several molecular mechanisms of palmitate-induced endothelial dysfunction have been proposed, there is no consensus on what signaling event is the initial trigger of detrimental palmitate effects. Here we report that inhibitors of ER stress or ceramid synthesis can rescue palmitate-induced autophagy impairment in macro- and microvascular endothelial cells. Furthermore, palmitate-induced cholesterol synthesis was reverted using these inhibitors. Similar to cell culture data, autophagy markers were increased in serum of obese individuals. Subsequent lipidomic analysis revealed that palmitate changed the composition of membrane phospholipids in endothelial cells and that these effects were not reverted upon application of above-mentioned inhibitors. However, ER stress inhibition in palmitate-treated cells enhanced the synthesis of trilglycerides and restored ceramide levels to control condition. Our results suggest that palmitate induces ER-stress presumably by shift in membrane architecture, leading to impaired synthesis of triglycerides and enhanced production of ceramides and cholesterol, which altogether enhances lipotoxicity of palmitate in endothelial cells.

Optimization of Extraction and Refining Parameters of Oil from Dotted Gizzard Shad (Konosirus punctatus)

To address the challenges associated with resource inefficiency, low extraction rates, environmental concerns, and high energy consumption in traditional fish oil production from dotted gizzard shad (Konosirus punctatus), a novel approach is needed. This study aimed to develop and evaluate two innovative methods for fish oil extraction and refinement, focusing on their effects on fish oil quality, fatty acid profile, and volatile compound composition throughout the respective processes. The findings of the study revealed that the ethanol-assisted enzymatic extraction method surpassed the conventional enzymatic approach in extraction efficiency, achieving an optimal extraction rate of 74.94% ± 0.45% under optimized process conditions. Moreover, the ethanol-NaOH one-step degumming and deacidification method proved effective in simultaneously removing phospholipids and free fatty acids. Under optimal conditions, a notable reduction in phospholipid content in dotted gizzard shad oil, from 6.80 ± 0.01 mg/g to 1.18 ± 0.01 mg/g, and a substantial decrease in acid value, from 3.31 mg/g to 0.31 mg/g, were observed. In summary, the study analyzed the physicochemical properties, fatty acid composition, and volatile components of fish oil before and after refinement. The refining process was found to preserve the fatty acid composition while efficiently eliminating hydroperoxides and reducing unpleasant odors in the crude oil.

Comparative oil extraction from mutt (Myliobatis goodei) liver by enzymatic hydrolysis: free versus immobilized biocatalyst

BACKGROUND

The development and fine-tuning of biotechnological processes for fish oil extraction constitute a very important focus to contribute to the development of a food industry based on fish consumption. This work lies in a comparative analysis of the oil extraction yield of Myliobatis goodei livers using free and immobilized enzymes.

RESULTS

An immobilized biocatalyst was designed from the cell-free extract of a Bacillus sp. Mcn4. A complete factorial design was used to study the components of the bacterial culture medium and select the condition with the highest titers of extracellular enzymatic activities. Wheat bran had a significant effect on the culture medium composition for enzymatic production. The immobilized biocatalyst was designed by covalent binding of the proteins present in the cocktail retaining a percentage of different types of enzymatic activities (Mult.Enz@MgFe2 O4 ). Among the biocatalyst used, Alcalase® 2.4 L and Purazyme® AS 60 L (free commercial proteases) showed extraction yields of 87.39% and 84.25%, respectively, while Mult.Enz@MgFe2 O4 achieved a better one of 89.97%. The oils obtained did not show significant differences in their physical-chemical properties while regarding the fatty acid content, the oil extracted with Purazyme® AS 60 L showed a comparatively lower proportion of polyunsaturated fatty acids.

CONCLUSIONS

Our results suggest that the use of by-products of M. goodei is a valid alternative and encourages the use of immobilized multienzyme biocatalysts for the treatment of complex substrates in the fishing industry. © 2023 Society of Chemical Industry.

Dietary palmitic acid to oleic acid ratio modulates energy metabolism and biological rhythms in young healthy Japanese males

The present study investigated the potential role of the composition of dietary fatty acids in the regulation of biological rhythms, such as the sleep architecture, core body temperature and leukocyte clock gene expression, in subjects fed meals rich in palmitic acid (PA) or oleic acid (OA). Eleven males participated in two sessions of indirect calorimetry in a whole-room metabolic chamber. In each session, subjects consumed three meals rich in PA (44·3 % of total fat as PA and 42·3 % as OA) or OA (11·7 % of total fat as PA and 59·3 % as OA) in the metabolic chamber. The ratio of PA to OA in plasma was significantly lower and fat oxidation was significantly higher during 24 h of indirect calorimetry in the session with meals rich in OA than in that with meals rich in PA. The duration of slow wave sleep (SWS) was shorter, the latency of SWS was longer and the nadir of core body temperature after bedtime was later in the session with meals rich in PA than in that with meals rich in OA. The peak in CRY1 gene expression was earlier and its amplitude was higher in the session with meals rich in PA than in that with meals rich in OA. In healthy young males, meals rich in PA decreased fat oxidation and disrupted biological rhythms, particularly the sleep architecture and core body temperature during sleep, more than meals rich in OA.

Alzheimer's Disease in Diabetic Patients: A Lipidomic Prospect

Diabetes Mellitus (DM) and Alzheimer's disease (AD) have been two of the most common chronic diseases affecting people worldwide. Type 2 DM (T2DM) is a metabolic disease depicted by insulin resistance, dyslipidemia, and chronic hyperglycemia while AD is a neurodegenerative disease marked by Amyloid β (Aβ) accumulation, neurofibrillary tangles aggregation, and tau phosphorylation. Various clinical, epidemiological, and lipidomics studies have linked those diseases claiming shared pathological pathways raising the assumption that diabetic patients are at an increased risk of developing AD later in their lives. Insulin resistance is the tipping point beyond where advanced glycation end (AGE) products and free radicals are produced leading to oxidative stress and lipid peroxidation. Additionally, different types of lipids are playing a crucial role in the development and the relationship between those diseases. Lipidomics, an analysis of lipid structure, formation, and interactions, evidently exhibits these lipid changes and their direct and indirect effect on Aβ synthesis, insulin resistance, oxidative stress, and neuroinflammation. In this review, we have discussed the pathophysiology of T2DM and AD, the interconnecting pathological pathways they share, and the lipidomics where different lipids such as cholesterol, phospholipids, sphingolipids, and sulfolipids contribute to the underlying features of both diseases. Understanding their role can be beneficial for diagnostic purposes or introducing new drugs to counter AD.

Impact of saturated compared with unsaturated dietary fat on insulin sensitivity, pancreatic β-cell function and glucose tolerance: a systematic review and meta-analysis of randomized, controlled trials

BACKGROUND

The impact of the dietary fat type on type 2 diabetes (T2D) remains unclear.

OBJECTIVES

We aimed to evaluate the effects of replacing dietary saturated fatty acids (SFA) with mono- or poly-unsaturated fatty acids (MUFA and PUFA, respectively) on insulin sensitivity, pancreatic β-cell function, and glucose tolerance, as surrogate endpoints for T2D.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials that replaced ≥5% of total energy intake provided by SFA with MUFA or PUFA and reported indexes of insulin sensitivity, β-cell function, and/or glucose tolerance. We searched MEDLINE, Scopus, and the Cochrane Library (CENTRAL) up to 9 January, 2023. Eligible interventions had to be isocaloric, with no significant difference in other macronutrients. Data were synthesized using random-effects model meta-analysis.

RESULTS

Of 6355 records identified, 10 parallel and 20 crossover trials with 1586 participants were included. The mean age of the participants was 42 years, 47% were male, mean body mass index (BMI; in kg/m2) was 26.8, median baseline fasting glucose was 5.13 mmol/L, and the median duration of interventions was 5 weeks. Replacing SFA with MUFA or PUFA had no significant effects on insulin sensitivity [standardized mean difference (SMD) SFA compared with MUFA: 0.01, 95% confidence interval (CI): -0.06 to 0.09, I2 = 0% and SMD SFA compared with PUFA: 0, 95% CI: -0.15 to 0.14, I2 = 0%]. Replacing SFA with MUFA did not significantly impact the β-cell function, evaluated by the disposition index (mean difference: -12, 95% CI: -158 to 133, I2=0%). Evidence on glucose tolerance (SFA compared with MUFA or PUFA) and on β-cell function when SFA were replaced with PUFA was scant.

CONCLUSIONS

Short-term substitution of saturated with unsaturated fat does not significantly affect insulin sensitivity nor β-cell function (the latter in the SFA compared with MUFA comparison). Future studies are needed to elucidate longer term effects of dietary fat saturation on glucose homeostasis. This trial was registered at PROSPERO as CRD42020178382.

Clinical Blood Metabogram: Application to Overweight and Obese Patients

Recently, the concept of a mass spectrometric blood metabogram was introduced, which allows the analysis of the blood metabolome in terms of the time, cost, and reproducibility of clinical laboratory tests. It was demonstrated that the components of the metabogram are related groups of the blood metabolites associated with humoral regulation; the metabolism of lipids, carbohydrates, and amines; lipid intake into the organism; and liver function, thereby providing clinically relevant information. The purpose of this work was to evaluate the relevance of using the metabogram in a disease. To do this, the metabogram was used to analyze patients with various degrees of metabolic alterations associated with obesity. The study involved 20 healthy individuals, 20 overweight individuals, and 60 individuals with class 1, 2, or 3 obesity. The results showed that the metabogram revealed obesity-associated metabolic alterations, including changes in the blood levels of steroids, amino acids, fatty acids, and phospholipids, which are consistent with the available scientific data to date. Therefore, the metabogram allows testing of metabolically unhealthy overweight or obese patients, providing both a general overview of their metabolic alterations and detailing their individual characteristics. It was concluded that the metabogram is an accurate and clinically applicable test for assessing an individual's metabolic status in disease.

Pyruvate-supported flux through medium-chain ketothiolase promotes mitochondrial lipid tolerance in cardiac and skeletal muscles

Even-chain acylcarnitine (AC) metabolites, most of which are generated as byproducts of incomplete fatty acid oxidation (FAO), are viewed as biomarkers of mitochondrial lipid stress attributable to one or more metabolic bottlenecks in the β-oxidation pathway. The origins and functional implications of FAO bottlenecks remain poorly understood. Here, we combined a sophisticated mitochondrial phenotyping platform with state-of-the-art molecular profiling tools and multiple two-state mouse models of respiratory function to uncover a mechanism that connects AC accumulation to lipid intolerance, metabolic inflexibility, and respiratory inefficiency in skeletal muscle mitochondria. These studies also identified a short-chain carbon circuit at the C4 node of FAO wherein reverse flux of glucose-derived acetyl CoA through medium-chain ketothiolase enhances lipid tolerance and redox stability in heart mitochondria by regenerating free CoA and NAD⁺. The findings help to explain why diminished FAO capacity, AC accumulation, and metabolic inflexibility are tightly linked to poor health outcomes.

Deleterious liver-adipose crosstalk in obesity: Hydroethanolic extract of Lampaya medicinalis Phil. (Verbenaceae) counteracts fatty acid-induced fibrotic marker expression in human hepatocytes

Elevated circulating fatty acids in obesity may induce hepatic steatosis, leading to liver inflammation, fibrosis and nonalcoholic fatty liver disease (NAFLD). On the other hand, impaired communication between hepatocytes and adipose tissue (AT) in obesity influences adipose lipolysis and fibrosis, negatively affecting metabolic function. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in Chilean folk medicine to treat inflammatory diseases. Hydroethanolic extract of lampaya (HEL) contains flavonoids that may explain its anti-inflammatory effect, but it is unknown whether HEL modulates fibrogenic processes in hepatocytes. We studied lipolysis and expression of fibrosis markers after exposure of visceral AT explants from subjects with obesity to HepG2-secreted factors. In addition, we evaluated the effect of HEL on palmitic acid (PA, C16:0) and oleic acid (OA; C18:1)-induced fibrotic marker expression in HepG2 hepatocytes. Results: Exposure to HepG2-secreted factors increased visceral AT lipolysis and expression of CTGF and collagen I. Exposure to OA/PA elevated collagen I, CTGF, fibronectin, α-smooth muscle actin, MMP-2 and MMP-9 expression in HepG2 cells, and these effects were prevented by HEL co-treatment. Conclusion: HEL effect counteracting OA/PA-induced fibrotic marker expression in HepG2 hepatocytes may represent a preventive approach against hepatic fibrosis and deleterious liver-adipose crosstalk in obesity.

Alteration of brain function and systemic inflammatory tone in older adults by decreasing the dietary palmitic acid intake

Prior studies in younger adults showed that reducing the normally high intake of the saturated fatty acid, palmitic acid (PA), in the North American diet by replacing it with the monounsaturated fatty acid, oleic acid (OA), decreased blood concentrations and secretion by peripheral blood mononuclear cells (PBMCs) of interleukin (IL)-1β and IL-6 and changed brain activation in regions of the working memory network. We examined the effects of these fatty acid manipulations in the diet of older adults. Ten subjects, aged 65-75 years, participated in a randomized, cross-over trial comparing 1-week high PA versus low PA/high OA diets. We evaluated functional magnetic resonance imaging (fMRI) using an N-back test of working memory and a resting state scan, cytokine secretion by lipopolysaccharide (LPS)-stimulated PBMCs, and plasma cytokine concentrations. During the low PA compared to the high PA diet, we observed increased activation for the 2-back minus 0-back conditions in the right dorsolateral prefrontal cortex (Broadman Area (BA) 9; p < 0.005), but the effect of diet on working memory performance was not significant (p = 0.09). We observed increased connectivity between anterior regions of the salience network during the low PA/high OA diet (p < 0.001). The concentrations of IL-1β (p = 0.026), IL-8 (p = 0.013), and IL-6 (p = 0.009) in conditioned media from LPS-stimulated PBMCs were lower during the low PA/high OA diet. This study suggests that lowering the dietary intake of PA down-regulated pro-inflammatory cytokine secretion and altered working memory, task-based activation and resting state functional connectivity in older adults.

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.

Differences in the Distribution of Ceramides and Sphingosine among Lipoprotein and Lipoprotein-Depleted Fractions in Patients with Type 2 Diabetes Mellitus

AIM

In addition to the quantity and quality, the carriers, such as lipoproteins and albumin, can affect the physiological properties and clinical significance of lipids. This study aimed to elucidate the modulation of the levels of ceramides and sphingosine, which are considered as proatherosclerotic lipids, in lipoproteins and lipoprotein-depleted fractions in subjects with type 2 diabetes.

METHODS

We separated the serum samples collected from healthy subjects (n=22) and subjects with type 2 diabetes (n=39) into Triglyceride (TG)-rich lipoproteins (TRL), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and lipoprotein-depleted fractions via ultracentrifugation. Then, we measured the levels of six species of ceramides, sphingosine, and dihydrosphingosine via LC-MS/MS and statistically analyzed them to identify the sphingolipids in each fraction, which are associated with diabetes as well as cardiovascular and renal complications.

RESULTS

In subjects with diabetes, the levels of sphingosine and dihydrosphingosine in the TRL, LDL, and lipoprotein-depleted fractions were higher, whereas those in the HDL were lower. In addition, the ceramide levels in HDL were lower, whereas those in lipoprotein-depleted fractions were higher. Furthermore, The levels of ceramides in lipoproteins, especially LDL, were negatively associated with the presence of cardiovascular diseases and stage 4 diabetic nephropathy.

CONCLUSIONS

The contents of ceramides and sphingosine in lipoproteins and lipoprotein-depleted fractions were differently modulated in diabetes and associated with cardiovascular diseases and diabetic nephropathy. The carrier might be an important factor for the biological properties and clinical significance of these sphingolipids.

Isolated and combined impact of dietary olive oil and exercise on markers of health and energy metabolism in female mice

An olive oil (OO) rich diet or high-intensity interval training (HIIT) independently improve markers of health and energy metabolism, but it is unknown if combining OO and HIIT synergize to improve these markers. This study characterized the isolated and combined impact of OO and HIIT on markers of health and energy metabolism in various tissues in C57BL/6J female mice. Nine-week-old mice were divided into four groups for a 12-week diet and/or exercise intervention including: (1) Control Diet without HIIT (CD), (2) Control Diet with HIIT (CD+HIIT), (3) OO diet (10% kcal from olive oil) without HIIT, and (4) OO diet with HIIT (OO+HIIT). Neither dietary OO or HIIT altered body weight, glucose tolerance, or serum lipids. HIIT, regardless of diet, increased aerobic capacity and HDL cholesterol levels. In liver and heart tissue, OO resulted in similar adaptations as HIIT including increased mitochondrial content and fatty acid oxidation but combining OO with HIIT did not augment these effects. In skeletal muscle, HIIT increased mitochondrial content in type II fibers similarly between diets. An RNA sequencing analysis on type I fibers revealed OO reduced muscle regeneration and lipid metabolism gene abundance, whereas HIIT increased the abundance of these genes, independent of diet. HIIT training, independent of diet, induced subcutaneous white adipose tissue (sWAT) hypertrophy, whereas OO induced gonadal white adipose tissue (gWAT) hypertrophy, an effect that was augmented with HIIT. These data highlight the pleiotropic effects of OO and HIIT, although their combination does not synergize to further improve most markers of health and energy metabolism.

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.

Crocodile Oil Disrupts Mitochondrial Homeostasis and Exacerbates Diabetic Kidney Injury in Spontaneously Diabetic Torii Rats

Diabetic nephropathy is currently the leading cause of end-stage renal disease (ESRD) in type 2 diabetes. Studies have suggested that supplementation with some fatty acids might reduce the risk and delay the progression to ESRD in patient with chronic kidney disease. Crocodile oil (CO) contains a variety of fatty acids, especially omega-3, -6 and -9, that have been reported to be beneficial to human health. This study examined the impact of long-term CO supplementation on the development of diabetic nephropathy in spontaneously diabetic Torii (SDT) rats. After diabetic verification, SDT rats were assigned to receive vehicle or CO at 500 and 1000 mg/kg BW, respectively, by oral gavage. Age-matched nondiabetic Sprague–Dawley rats were given vehicle or high-dose CO. After 28 weeks of intervention, CO failed to improve hyperglycemia and pancreatic histopathological changes in SDT rats. Unexpectedly, CO dose-dependently exacerbated the impairment of kidney and mitochondrial functions caused by diabetes. CO also disturbed the expressions of proteins involved in mitochondrial biogenesis, dynamics, and mitophagy. However, no significant alterations were observed in nondiabetic rats receiving high-dose CO. The findings reveal that CO has deleterious effects that aggravate diabetic kidney injury via disrupting mitochondrial homeostasis, possibly due to its improper omega-6: omega-3 ratio.

Ceramide metabolism mediates the impaired glucose homeostasis following short-term black carbon exposure: A targeted lipidomic analysis

BACKGROUND

Ambient particulate matter (PM), especially its carbonaceous composition black carbon (BC) increases cardiometabolic risks, yet the underlying mechanisms are incompletely understood. Ceramides (Cer; a class of sphingolipids) are biological intermediates in glucose metabolism.

OBJECTIVES

To explore whether Cer metabolism mediates impaired glucose homeostasis following short-term PM exposure.

METHODS

In a panel study in Beijing, China, 112 participants were followed-up between 2016 and 2017. Targeted lipidomic analyses quantified 26 sphingolipids in 387 plasma samples. Ambient BC and PM with aerodynamic diameter ≤ 2.5 μm (PM_2.5) were continuously monitored in a station. We examined the associations of sphingolipid levels with average BC and PM_2.5 concentrations 1-14 days before clinical visits using linear mixed-effects models, and explored the mediation effects of sphingolipids on PM-associated fasting blood glucose (FBG) difference using mediation analyses.

RESULTS

Increased levels of FBG and multiple sphingolipids in Cer metabolic pathways were associated with BC exposure in 1-14-day time window, but not with PM_2.5 exposure. For each 10 μg/m³ increase in the average BC concentration 1-14 days before the clinical visits, species in the Cer C24:1 pathway (Cer, dihydroceramide, hexosylceramide, lactosylceramide, and sphingomyelin C24:1) increased in levels ranging from 11.8% (95% confidence interval [CI]: -6.2-33.2) to 48.7% (95% CI: 8.8-103.4), as did the Cer C16:0, C18:0, and C20:0 metabolic pathway species, ranging from 3.2% (95% CI: -5.6-12.9) to 32.4% (95% CI: 7.0-63.8), respectively. The Cer C24:1 metabolic pathway species mediated 6.5-25.5% of the FBG increase associated with BC exposure in 9-day time window. The Cer C16:0, C18:0, and C20:0 metabolic pathway species mediated 5.4-26.2% of the BC-associated FBG difference.

CONCLUSIONS

In conclusion, Cer metabolism may mediate impaired glucose homeostasis following short-term BC exposure. The current findings are preliminary, which need to be corroborated by further studies.

NAXE deficiency: A neurometabolic disorder of NAD(P)HX repair amenable for metabolic correction

The NAD(P)HX repair system is a metabolite damage repair mechanism responsible for restoration of NADH and NADPH after their inactivation by hydration. Deficiency in either of its two enzymes, NAD(P)HX dehydratase (NAXD) or NAD(P)HX epimerase (NAXE), causes a fatal neurometabolic disorder characterized by decompensations precipitated by inflammatory stress. Clinical findings include rapidly progressive muscle weakness, ataxia, ophthalmoplegia, and motor and cognitive regression, while neuroimaging abnormalities are subtle or nonspecific, making a clinical diagnosis challenging. During stress, nonenzymatic conversion of NAD(P)H to NAD(P)HX increases, and in the absence of repair, NAD(P)H is depleted, and NAD(P)HX accumulates, leading to decompensation; however, the contribution of each to the metabolic derangement is not established. Herein, we summarize the clinical knowledge of NAXE deficiency from 30 cases and lessons learned about disease pathogenesis from cell cultures and model organisms and describe a metabolomics signature obtained by untargeted metabolomics analysis in one case at the time of crisis and after initiation of treatment. Overall, biochemical findings support a model of acute depletion of NAD⁺, signs of mitochondrial dysfunction, and altered lipidomics. These findings are further substantiated by untargeted metabolomics six months post-crisis showing that niacin supplementation reverses primary metabolomic abnormalities concurrent with improved clinical status.

Lipidomics Reveals That Rice or Flour as a Single Source of Carbohydrates Cause Adverse Health Effects in Rats

The type of diet is very important for the maintenance of health and nutrition. How the sole source of carbohydrates from rice- or flour-based diet affect blood sugar has not been elucidated for a long time. In order to explore the effects of these diets, sixty SD rats were randomly divided into three groups: control group (C group, AIN-93, standard diet), rice diet group (R group), and flour diet group (F group). All the rats were fed for 7 weeks in total by the assigned diets for 4 weeks (stage 1, S1) and all by the AIN-93 diet for 3 weeks (stage 2, S2). The body weights of all the rats were monitored and serum samples were taken for testing blood glucose, biochemical indicators and untargeted lipidome. It was found that both rice and flour-based diets caused weight gain, but the flour diet had a significant increase in blood sugar and low-density lipoprotein (LDL), while a significant decrease in albumin (ALB) and triglycerides (TG). Twenty-three and 148 lipids were changed by lipidomics in the rice diet group and flour diet group, respectively, and two lipids showed the same changes in the two groups, all belonging to TGs, namely TG (16:0/16:0/16:1) and TG (16:0/16:1/18:2), which showed that a single diet source had a significant effect on the health of rats. Fortunately, we can recover this effect through the subsequent standard diet, allowing the rats to return to normal blood sugar, weight and biochemical indicators. A model can predict the diet types through the logistic regression method. Finally, we proposed that a single diet increased blood sugar and weight through a decrease in TGs, and blood sugar and weight returned to normal after a standard diet. Taken together, the short-term negative effects caused by a single diet can be recovered by a standard diet and further proves the importance of diet types.

The Use and Effectiveness of Selected Alternative Markers for Insulin Sensitivity and Secretion Compared with Gold Standard Markers in Dietary Intervention Studies in Individuals without Diabetes: Results of a Systematic Review

Background: The gold-standard techniques for measuring insulin sensitivity and secretion are well established. However, they may be perceived as invasive and expensive for use in dietary intervention studies. Thus, surrogate markers have been proposed as alternative markers for insulin sensitivity and secretion. This systematic review aimed to identify markers of insulin sensitivity and secretion in response to dietary intervention and assess their suitability as surrogates for the gold-standard methodology. Methods: Three databases, PubMed, Scopus, and Cochrane were searched, intervention studies and randomised controlled trials reporting data on dietary intake, a gold standard of analysis of insulin sensitivity (either euglycaemic-hyperinsulinaemic clamp or intravenous glucose tolerance test and secretion (acute insulin response to glucose), as well as surrogate markers for insulin sensitivity (either fasting insulin, area under the curve oral glucose tolerance tests and HOMA-IR) and insulin secretion (disposition index), were selected. Results: We identified thirty-five studies that were eligible for inclusion. We found insufficient evidence to predict insulin sensitivity and secretion with surrogate markers when compared to gold standards in nutritional intervention studies. Conclusions: Future research is needed to investigate if surrogate measures of insulin sensitivity and secretion can be repeatable and reproducible in the same way as gold standards.

Novel Lipidomic Signature Associated With Metabolic Risk in Women With and Without Polycystic Ovary Syndrome

CONTEXT

Dyslipidemia is a feature of polycystic ovary syndrome (PCOS) and may augment metabolic dysfunction in this population.

OBJECTIVE

Using comprehensive lipidomic profiling and gold-standard metabolic measures, we examined whether distinct lipid biomarkers were associated with metabolic risk in women with and without PCOS.

METHODS

Using preexisting data and biobanked samples from 76 women (n = 42 with PCOS), we profiled > 700 lipid species by mass spectrometry. Lipids were compared between women with and without PCOS and correlated with direct measures of adiposity (dual x-ray absorptiometry and computed tomography) and insulin sensitivity (hyperinsulinemic-euglycemic clamp), as well as fasting insulin, HbA1c, and hormonal parameters (luteinizing and follicle-stimulating hormones; total and free testosterone; sex hormone-binding globulin [SHBG]; and free androgen index [FAI]). Multivariable linear regression was used with correction for multiple testing.

RESULTS

Despite finding no differences by PCOS status, lysophosphatidylinositol (LPI) species esterified with an 18:0 fatty acid were the strongest lipid species associated with all the metabolic risk factors measured in women with and without PCOS. Across the cohort, higher concentrations of LPI(18:0) and lower concentrations of lipids containing docosahexaenoic acid (DHA, 22:6) n-3 polyunsaturated fatty acids were associated with higher adiposity, insulin resistance, fasting insulin, HbA1c and FAI, and lower SHBG.

CONCLUSION

Our data indicate that a distinct lipidomic signature comprising high LPI(18:0) and low DHA-containing lipids are associated with key metabolic risk factors that cluster in PCOS, independent of PCOS status. Prospective studies are needed to corroborate these findings in larger cohorts of women with varying PCOS phenotypes.

Therapeutic Properties and Use of Extra Virgin Olive Oil in Clinical Nutrition: A Narrative Review and Literature Update

Extra virgin olive oil (EVOO) is a cornerstone of the Mediterranean diet (MedD). In this narrative review, we synthesize and illustrate the various characteristics and clinical applications of EVOO and its components—such as oleic acid, hydroxytyrosol, and oleuropein—in the field of clinical nutrition and dietetics. The evidence is split into diet therapy, oleic acid-based enteral nutrition formulations and oral supplementation formulations, oleic acid-based parenteral nutrition, and nutraceutical supplementation of minor components of EVOO. EVOO has diverse beneficial health properties, and current evidence supports the use of whole EVOO in diet therapy and the supplementation of its minor components to improve cardiovascular health, lipoprotein metabolism, and diabetes mellitus in clinical nutrition. Nevertheless, more intervention studies in humans are needed to chisel specific recommendations for its therapeutic use through different formulations in other specific diseases and clinical populations.

Altered Plasma Fatty Acid Abundance Is Associated with Cachexia in Treatment-Naïve Pancreatic Cancer

Cachexia occurs in up to 80% of pancreatic ductal adenocarcinoma (PDAC) patients and is characterized by unintentional weight loss and tissue wasting. To understand the metabolic changes that occur in PDAC-associated cachexia, we compared the abundance of plasma fatty acids (FAs), measured by gas chromatography, of subjects with treatment-naïve metastatic PDAC with or without cachexia, defined as a loss of > 2% weight and evidence of sarcopenia (n = 43). The abundance of saturated, monounsaturated, and polyunsaturated FAs was not different between subjects with cachexia and those without. Oleic acid was significantly higher in subjects with cachexia (p = 0.0007) and diabetes (p = 0.015). Lauric (r = 0.592, p = 0.0096) and eicosapentaenoic (r = 0.564, p = 0.015) acids were positively correlated with age in cachexia patients. Subjects with diabetes (p = 0.021) or both diabetes and cachexia (p = 0.092) had low palmitic:oleic acid ratios. Linoleic acid was lower in subjects with diabetes (p = 0.018) and correlated with hemoglobin (r = 0.519, p = 0.033) and albumin (r = 0.577, p = 0.015) in subjects with cachexia. Oleic or linoleic acid may be useful treatment targets or biomarkers of cachexia in patients with metastatic PDAC, particularly those with diabetes.

Dietary palmitate and oleate differently modulate insulin sensitivity in human skeletal muscle

AIMS/HYPOTHESIS

Energy-dense nutrition generally induces insulin resistance, but dietary composition may differently affect glucose metabolism. This study investigated initial effects of monounsaturated vs saturated lipid meals on basal and insulin-stimulated myocellular glucose metabolism and insulin signalling.

METHODS

In a randomised crossover study, 16 lean metabolically healthy volunteers received single meals containing safflower oil (SAF), palm oil (PAL) or vehicle (VCL). Whole-body glucose metabolism was assessed from glucose disposal (R_d) before and during hyperinsulinaemic-euglycaemic clamps with D-[6,6-²H₂]glucose. In serial skeletal muscle biopsies, subcellular lipid metabolites and insulin signalling were measured before and after meals.

RESULTS

SAF and PAL raised plasma oleate, but only PAL significantly increased plasma palmitate concentrations. SAF and PAL increased myocellular diacylglycerol and activated protein kinase C (PKC) isoform θ (p < 0.05) but only PAL activated PKCɛ. Moreover, PAL led to increased myocellular ceramides along with stimulated PKCζ translocation (p < 0.05 vs SAF). During clamp, SAF and PAL both decreased insulin-stimulated R_d (p < 0.05 vs VCL), but non-oxidative glucose disposal was lower after PAL compared with SAF (p < 0.05). Muscle serine¹¹⁰¹-phosphorylation of IRS-1 was increased upon SAF and PAL consumption (p < 0.05), whereas PAL decreased serine⁴⁷³-phosphorylation of Akt more than SAF (p < 0.05).

CONCLUSIONS/INTERPRETATION

Lipid-induced myocellular insulin resistance is likely more pronounced with palmitate than with oleate and is associated with PKC isoforms activation and inhibitory insulin signalling.

TRIAL REGISTRATION

ClinicalTrials.gov .NCT01736202.

FUNDING

German Federal Ministry of Health, Ministry of Culture and Science of the State North Rhine-Westphalia, German Federal Ministry of Education and Research, European Regional Development Fund, German Research Foundation, German Center for Diabetes Research.

An extra virgin olive oil-enriched chocolate spread positively modulates insulin-resistance markers compared with a palm oil-enriched one in healthy young adults: A double-blind, cross-over, randomised controlled trial

AIMS

To investigate if extra virgin olive oil (EVOO) or palm oil enriched chocolate spreads consumption leads to different results in terms of plasma ceramides concentration, glucose and lipid metabolism, inflammatory markers and appetite regulation in young healthy subjects.

METHODS

In a 2-week, double-blind, cross-over, randomised controlled trial, 20 healthy, normal-weight subjects with a mean age of 24.2 years (SD: 1.2), consumed chocolate spread snacks (73% of energy [%E] from fat, 20% from carbohydrates and 7% from proteins), providing 570 Kcal/day added to an isocaloric diet. The chocolate spreads were identical, except for the type of fat: EVOO oil, rich in monounsaturated fatty acids (MUFAs), or palm oil, rich in Saturated Fatty Acids (SFAs).

RESULTS

EVOO-enriched chocolate spread consumption led to better circulating sphingolipids and glucose profile, with reduced plasma ceramide C16:0, ceramide C16:0/ceramide C22:0-ceramide C24:0 ratio and sphingomyelin C18:0 (P = 0.030, P= 0.032 and P = 0.042, respectively) compared to the palm oil-enriched chocolate spread diet. HOMA-IR and plasma insulin were lower, while the Quicki and the McAuley Index were higher after the EVOO diet compared to the palm oil diet (P = 0.046, P = 0.045, P = 0.018 and P = 0.039 respectively). Subjects maintained a stable weight throughout the study. No major significant changes in total cholesterol, triglycerides, HDL, inflammatory markers, and appetite-regulating hormones/visual analogue scale were observed between the groups.

CONCLUSIONS

Partially replacing SFAs with MUFAs in a chocolate-based snack as part of a short-term isocaloric diet in healthy individuals may limit SFAs detrimental effects on insulin sensitivity and decrease circulating harmful sphingolipids in young adults.

Adverse Effects of Refeeding on the Plasma Lipidome in Young Individuals With Anorexia Nervosa?

OBJECTIVE

Refeeding is the cornerstone of anorexia nervosa (AN) treatment, but little is known regarding the optimal pace and dietary composition or possible adverse effects of current clinical practices. Plasma lipids may be a moderating factor underlying unfavorable refeeding effects in AN, such as an abnormal central body fat distribution. The objective of this study was to analyze the plasma lipidome in the acutely underweight state of AN before and after refeeding.

METHOD

Using high-throughput quantitative mass spectrometry-based shotgun lipidomics, we measured 13 lipid classes and 204 lipid species or subspecies in the plasma of young female patients with acute AN, before (n = 39) and after (n = 23) short-term weight restoration during an intensive inpatient refeeding program (median body mass index [BMI] increase = 26.4%), in comparison to those in healthy control participants (n = 37).

RESULTS

Before inpatient treatment, patients with AN exhibited increased concentrations of cholesterol and several other lipid classes. After refeeding, multiple lipid classes including cholesterol and ceramides, as well as certain ceramide species previously associated with obesity or overfeeding, showed increased concentrations, and a pattern of shorter and more saturated triacylgycerides emerged. A machine learning model trained to predict BMI based on the lipidomic profiles revealed a sizable overprediction in patients with AN after weight restoration.

CONCLUSION

The results point toward a profound lipid dysregulation with similarities to obesity and other features of the metabolic syndrome after short-term weight restoration. Thus, this study provides evidence for possible short-term adverse effects of current refeeding practices on the metabolic state and should inspire more research on nutritional interventions in AN.

Unwrapping the mechanisms of ceramide and fatty acid-initiated signals leading to immune-inflammatory responses in obesity

Obesity is considered a global epidemic developed in part as a consequence of the overconsumption of high fat diets. One of the main negative outcomes of obesity is the development of low-grade chronic systemic inflammation, induced by dysregulated immune responses, which can lead to multiple obesity-related diseases. Ceramides are a group of bioactive lipids known to be elevated in obesity and obesity-associated conditions, including cardiovascular disease and type II diabetes. Ceramides may be key players in promoting an obesity-induced inflammatory environment due to their ability to activate key pathways such as Toll-like receptor 4 (TLR4) and NLR pyrin domain containing receptor 3 (Nlrp3), while studies have shown that inhibition of ceramide synthesis gives rise to an anti-inflammatory environment. N-3 polyunsaturated fatty acids (n-3 PUFA) have been of interest due to their anti-inflammatory actions and shown to have beneficial effects in obesity-related diseases. This review will highlight the impact of ceramides in promoting an obesity-induced inflammatory microenvironment and discuss how n-3 PUFA could potentially counteract these responses and have a regulatory effect promoting immune homeostasis.

Circulating ceramides as biomarkers of cardiovascular disease: Evidence from phenotypic and genomic studies

There is a need for new biomarkers of atherosclerotic cardiovascular disease (ACVD), the main cause of death globally. Ceramides, a class of potent bioactive lipid mediators, have signalling roles in apoptosis, cellular stress and inflammation. Recent studies have highlighted circulating ceramides as novel biomarkers of coronary artery disease, type-2 diabetes and insulin resistance. Ceramides are highly regulated by enzymatic reactions throughout the body in terms of their activity and metabolism, including production, degradation and transport. The genetic studies that have been completed to date on the main ceramide species found in circulation are described, highlighting the importance of DNA variants in genes involved in ceramide biosynthesis as key influencers of heritable, circulating ceramide levels. We also review studies of disease associations with ceramides and discuss mechanistic insights deriving from recent genomic studies. The signalling activities of ceramides in vascular inflammation and apoptosis, associations between circulating ceramides and coronary artery disease risk, type-2 diabetes and insulin resistance, and the potential importance of ceramides with regard to ACVD risk factors, such as blood pressure, lipoproteins and lifestyle factors, are also discussed.

Lysophospholipid acylation modulates plasma membrane lipid organization and insulin sensitivity in skeletal muscle

Aberrant lipid metabolism promotes the development of skeletal muscle insulin resistance, but the exact identity of lipid-mediated mechanisms relevant to human obesity remains unclear. A comprehensive lipidomic analysis of primary myocytes from individuals who were insulin-sensitive and lean (LN) or insulin-resistant with obesity (OB) revealed several species of lysophospholipids (lyso-PLs) that were differentially abundant. These changes coincided with greater expression of lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme involved in phospholipid transacylation (Lands cycle). Strikingly, mice with skeletal muscle-specific knockout of LPCAT3 (LPCAT3-MKO) exhibited greater muscle lysophosphatidylcholine/phosphatidylcholine, concomitant with improved skeletal muscle insulin sensitivity. Conversely, skeletal muscle-specific overexpression of LPCAT3 (LPCAT3-MKI) promoted glucose intolerance. The absence of LPCAT3 reduced phospholipid packing of cellular membranes and increased plasma membrane lipid clustering, suggesting that LPCAT3 affects insulin receptor phosphorylation by modulating plasma membrane lipid organization. In conclusion, obesity accelerates the skeletal muscle Lands cycle, whose consequence might induce the disruption of plasma membrane organization that suppresses muscle insulin action.

Plasma lipidomic profiles after a low and high glycemic load dietary pattern in a randomized controlled crossover feeding study

BACKGROUND

Dietary patterns low in glycemic load are associated with reduced risk of cardiometabolic diseases. Improvements in serum lipid concentrations may play a role in these observed associations.

OBJECTIVE

We investigated how dietary patterns differing in glycemic load affect clinical lipid panel measures and plasma lipidomics profiles.

METHODS

In a crossover, controlled feeding study, 80 healthy participants (n = 40 men, n = 40 women), 18-45 y were randomized to receive low-glycemic load (LGL) or high glycemic load (HGL) diets for 28 days each with at least a 28-day washout period between controlled diets. Fasting plasma samples were collected at baseline and end of each diet period. Lipids on a clinical panel including total-, VLDL-, LDL-, and HDL-cholesterol and triglycerides were measured using an auto-analyzer. Lipidomics analysis using mass-spectrometry provided the concentrations of 863 species. Linear mixed models and lipid ontology enrichment analysis were implemented.

RESULTS

Lipids from the clinical panel were not significantly different between diets. Univariate analysis showed that 67 species on the lipidomics panel, predominantly in the triacylglycerol class, were higher after the LGL diet compared to the HGL (FDR < 0.05). Three species with FA 17:0 were lower after LGL diet with enrichment analysis (FDR < 0.05).

CONCLUSION

In the context of controlled eucaloric diets with similar macronutrient distribution, these results suggest that there are relative shifts in lipid species, but the overall pool does not change. Further studies are needed to better understand in which compartment the different lipid species are transported in blood, and how these shifts are related to health outcomes. This trial was registered at clinicaltrials.gov as NCT00622661.

An unbiased lipidomics approach identifies key lipid molecules as potential therapeutic targets of Dohongsamul-tang against non-alcoholic fatty liver diseases in a mouse model of obesity

ETHNOPHARMACOLOGICAL RELEVANCE

Dohongsamul-tang (DST) is a traditional herbal formula used to promote the blood circulation and inhibit inflammation, and also widely has been used in the treatment of patients with chronic liver diseases in Korea and China.

AIM OF THE STUDY

This study aimed to investigate the effect of DST on regulation of lipid metabolism of chronic liver diseases in mouse model of non-alcoholic fatty liver diseases (NAFLD).

MATERIALS AND METHODS

In this study, we evaluated the effect of DST on high-fat and high-cholesterol diet (HFHC, 40% fat and 1% cholesterol)-induced NAFLD, and applied unbiased lipidomics using ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UPLC/Q-TOF MS) coupled with multivariate analysis.

RESULTS

DST improved hepatic morphology and reduced levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). In addition, DST inhibited hepatic lipid accumulation through the downregulation of C/EBPα, PPARγ, and pAMPK. To further elucidate the effect of DST on hepatic lipid metabolism, we applied UPLC/Q-TOF MS-based lipidomics. The score plots of partial least squares-discriminant analysis (PLS-DA) showed that DST changed the lipid metabolic pattern of high-fat and high-cholesterol diet (HFHC) mice. Twenty-two lipid metabolites were selected as biomarkers regulated by DST and pathway analysis revealed that sphingolipid metabolism and glycerophospholipid metabolism were associated with the effect of DST on NAFLD. Among the 22 selected biomarkers, 14 were phospholipids, and DST significantly reversed the increased expression of lysophospholipase 3 (LYPLA3) and neuropathy target esterase (NTE), which are key enzymes in glycerophospholipid metabolism. Given that alterations in sphingolipids and phospholipids can have effects on apoptosis and insulin resistance (IR), we subsequently investigated changes in the expression of apoptosis-related proteins, including Bcl-2-associated X protein (Bax) and B-cell lymphoma 2 (Bcl2), and IR-related markers after DST treatment. We accordingly found that the ratio of Bax to Bcl-2 expression, a maker of apoptosis, was also elevated in HFHC mice and reduced by DST treatment. In addition, DST enhanced hepatic insulin signaling by upregulating the expression of insulin receptor substrate 1 (IRS-1) and phospho-protein kinase B (pAKT), and oral glucose tolerance test (OGTT) analysis indicated that this herbal preparation also ameliorated systemic IR.

CONCLUSIONS

This study suggested that DST might have an effect on NAFLD by regulating the metabolism of lipids such as phospholipids and sphingolipids and demonstrated that lipidomic profiling is useful to investigate the therapeutic effects of herbal decoctions from traditional Korean and Chinese medicine.

Consequences of Lipid Remodeling of Adipocyte Membranes Being Functionally Distinct from Lipid Storage in Obesity

Obesity is a complex disorder where the genome interacts with diet and environmental factors to ultimately influence body mass, composition, and shape. Numerous studies have investigated how bulk lipid metabolism of adipose tissue changes with obesity and, in particular, how the composition of triglycerides (TGs) changes with increased adipocyte expansion. However, reflecting the analytical challenge posed by examining non-TG lipids in extracts dominated by TGs, the glycerophospholipid composition of cell membranes has been seldom investigated. Phospholipids (PLs) contribute to a variety of cellular processes including maintaining organelle functionality, providing an optimized environment for membrane-associated proteins, and acting as pools for metabolites (e.g. choline for one-carbon metabolism and for methylation of DNA). We have conducted a comprehensive lipidomic study of white adipose tissue in mice which become obese either through genetic modification (ob/ob), diet (high fat diet), or a combination of the two, using both solid phase extraction and ion mobility to increase coverage of the lipidome. Composition changes in seven classes of lipids (free fatty acids, diglycerides, TGs, phosphatidylcholines, lyso-phosphatidylcholines, phosphatidylethanolamines, and phosphatidylserines) correlated with perturbations in one-carbon metabolism and transcriptional changes in adipose tissue. We demonstrate that changes in TGs that dominate the overall lipid composition of white adipose tissue are distinct from diet-induced alterations of PLs, the predominant components of the cell membranes. PLs correlate better with transcriptional and one-carbon metabolism changes within the cell, suggesting that the compositional changes that occur in cell membranes during adipocyte expansion have far-reaching functional consequences. Data are available at MetaboLights under the submission number: MTBLS1775.

Adipocyte Ceramides-The Nexus of Inflammation and Metabolic Disease

Adipose depots are heterogeneous tissues that store and sense fuel levels. Through the secretion of lipids, cytokines, and protein hormones (adipokines), they communicate with other organ systems, informing them of the organism's nutritional status. The adipose tissues include diverse types of adipocytes (white, beige, and brown) distinguished by the number/size of lipid droplets, mitochondrial density, and thermogenic capacity. Moreover, they include a spectrum of immune cells that modulate metabolic activity and tissue remodeling. The unique characteristics and interplay of these cells control the production of ceramides, a class of nutrient signals derived from fat and protein metabolism that modulate adipocyte function to regulate glucose and lipid metabolism. The excessive accumulation of ceramides contributes to the adipose tissue inflammation and dysfunction that underlies cardiometabolic disease. Herein we review findings on this important class of lipid species and discuss their role at the convergence point that links overnutrition/inflammation to key features of the metabolic syndrome.

Dietary substitution of SFA with MUFA within high-fat diets attenuates hyperinsulinaemia and pancreatic islet dysfunction

Preliminary evidence has suggested that high-fat diets (HFD) enriched with SFA, but not MUFA, promote hyperinsulinaemia and pancreatic hypertrophy with insulin resistance. The objective of this study was to determine whether the substitution of dietary MUFA within a HFD could attenuate the progression of pancreatic islet dysfunction seen with prolonged SFA-HFD. For 32 weeks, C57BL/6J mice were fed either: (1) low-fat diet, (2) SFA-HFD or (3) SFA-HFD for 16 weeks, then switched to MUFA-HFD for 16 weeks (SFA-to-MUFA-HFD). Fasting insulin was assessed throughout the study; islets were isolated following the intervention. Substituting SFA with MUFA-HFD prevented the progression of hyperinsulinaemia observed in SFA-HFD mice (P < 0·001). Glucose-stimulated insulin secretion from isolated islets was reduced by SFA-HFD, yet not fully affected by SFA-to-MUFA-HFD. Markers of β-cell identity (Ins2, Nkx6.1, Ngn3, Rfx6, Pdx1 and Pax6) were reduced, and islet inflammation was increased (IL-1β, 3·0-fold, P = 0·007; CD68, 2·9-fold, P = 0·001; Il-6, 1·1-fold, P = 0·437) in SFA-HFD - effects not seen with SFA-to-MUFA-HFD. Switching to MUFA-HFD can partly attenuate the progression of SFA-HFD-induced hyperinsulinaemia, pancreatic inflammation and impairments in β-cell function. While further work is required from a mechanistic perspective, dietary fat may mediate its effect in an IL-1β-AMP-activated protein kinase α1-dependent fashion. Future work should assess the potential translation of the modulation of metabolic inflammation in man.

Mass spectrometry-based lipidomics in food science and nutritional health: A comprehensive review

With the advance in science and technology as well as the improvement of living standards, the function of food is no longer just to meet the needs of survival. Food science and its associated nutritional health issues have been increasingly debated. Lipids, as complex metabolites, play a key role both in food and human health. Taking advantages of mass spectrometry (MS) by combining its high sensitivity and accuracy with extensive selective determination of all lipid classes, MS-based lipidomics has been employed to resolve the conundrum of addressing both qualitative and quantitative aspects of high-abundance and low-abundance lipids in complex food matrices. In this review, we systematically summarize current applications of MS-based lipidomics in food field. First, common MS-based lipidomics procedures are described. Second, the applications of MS-based lipidomics in food science, including lipid composition characterization, adulteration, traceability, and other issues, are discussed. Third, the application of MS-based lipidomics for nutritional health covering the influence of food on health and disease is introduced. Finally, future research trends and challenges are proposed. MS-based lipidomics plays an important role in the field of food science, promoting continuous development of food science and integration of food knowledge with other disciplines. New methods of MS-based lipidomics have been developed to improve accuracy and sensitivity of lipid analysis in food samples. These developments offer the possibility to fully characterize lipids in food samples, identify novel functional lipids, and better understand the role of food in promoting healt.

Lipidomic analysis reveals therapeutic effects of Yijin-Tang on high-fat/high-cholesterol diet-induced obese mice

BACKGROUND

In Traditional Korean and Chinese medicine, the herbal remedy Yijin (Erchen)-Tang (YJT) is widely used to treat obesity-related disorders, and its therapeutic potential has been demonstrated in numerous studies. However, the systemic effect of YJT on obesity status and change of lipid metabolism by YJT still remains unknown.

PURPOSE

This study aimed to investigate the therapeutic mechanism of the YJT on obesity by using lipidomics.

METHODS

To evaluate the effects of treatment with YJT on obesity, C57BL/6 J mice were fed a high-fat and high-cholesterol (HFHC, 40% fat and 1% cholesterol) diet for 8 weeks and treated them with YJT for an additional 6 weeks. We then performed untargeted lipidomic analysis using ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry mass spectroscopy coupled with multivariate statistical analysis.

RESULTS

YJT ameliorated obesity induced systemic inflammation and improved insulin resistance. Additionally, YJT protected against HFHC-diet-induced hepatic inflammation. To explore specific changes in lipid metabolism associated with the therapeutic effects of YJT, we performed untargeted lipid profiling of the plasma. Partial least squares-discriminant analysis (PLS-DA) score plots showed that YJT altered the lipid metabolic pattern of HFHC mice. In particular, ceramides and triglycerides with saturated fatty acids and monounsaturated fatty acids were significantly changed by YJT, which were significantly associated with insulin resistance, the AGE-RAGE signaling pathway in diabetic complications and adipocytokine signaling pathway in pathway enrichment analysis. Thus, we analyzed the changes in adipocytes and adipokine caused by YJT, and confirmed that YJT alleviated adipocytes inflammation and macrophage infiltration, and reversed HFHC-induced alterations in leptin and adiponectin levels in adipose tissue and plasma.

CONCLUSION

These data suggest that YJT ameliorates obesity-induced systemic inflammation and insulin resistance by regulating lipid metabolism, and demonstrated that lipidomic profiling is a useful method to investigate the therapeutic effects of herbal decoctions in traditional Korean and Chinese medicine.

Gastrointestinal Disorders and Metabolic Syndrome: Dysbiosis as a Key Link and Common Bioactive Dietary Components Useful for their Treatment

Gastrointestinal (GI) diseases, which include gastrointestinal reflux disease, gastric ulceration, inflammatory bowel disease, and other functional GI disorders, have become prevalent in a large part of the world population. Metabolic syndrome (MS) is cluster of disorders including obesity, hyperglycemia, hyperlipidemia, and hypertension, and is associated with high rate of morbidity and mortality. Gut dysbiosis is one of the contributing factors to the pathogenesis of both GI disorder and MS, and restoration of normal flora can provide a potential protective approach in both these conditions. Bioactive dietary components are known to play a significant role in the maintenance of health and wellness, as they have the potential to modify risk factors for a large number of serious disorders. Different classes of functional dietary components, such as dietary fibers, probiotics, prebiotics, polyunsaturated fatty acids, polyphenols, and spices, possess positive impacts on human health and can be useful as alternative treatments for GI disorders and metabolic dysregulation, as they can modify the risk factors associated with these pathologies. Their regular intake in sufficient amounts also aids in the restoration of normal intestinal flora, resulting in positive regulation of insulin signaling, metabolic pathways and immune responses, and reduction of low-grade chronic inflammation. This review is designed to focus on the health benefits of bioactive dietary components, with the aim of preventing the development or halting the progression of GI disorders and MS through an improvement of the most important risk factors including gut dysbiosis.

Pharmacokinetics of omega-3 fatty acids in patients with severe sepsis compared with healthy volunteers: A prospective cohort study

BACKGROUND

Pharmacokinetics (PK) of pharmaceuticals and pharmaconutrients are poorly understood in critically ill patients, and dosing is often based on healthy subject data. This might be particularly problematic with enteral medications due to metabolic abnormalities and impaired gastrointestinal tract absorption common in critically ill patients. Utilizing enteral fish oil, this study was undertaken to better understand and define PK of enteral omega-3 fatty acids (eicospentaenoic acid [EPA] and docosahexaenoic acid [DHA]) in critically ill patients with severe sepsis.

MATERIALS AND METHODS

Healthy volunteers (n = 15) and mechanically ventilated (MV) adults with severe sepsis (n = 10) were recruited and received 9.75 g EPA and 6.75 g DHA daily in two divided enteral doses of fish oil for 7 days. Volunteers continued their normal diet without other sources of fish oil, and sepsis patients received standard enteral feeding. Blood was collected at frequent intervals during the 14-day study period. Peripheral blood mononuclear cells (PMBCs) and neutrophils were isolated and analyzed for membrane fatty acid (FA) content. Mixed linear models and t-tests were used to analyze changes in FA levels over time and FA levels at individual time points, respectively. PK parameters were obtained based on single compartment models of EPA and DHA kinetics.

RESULTS

Healthy volunteers were 41.1 ± 10.3 years; 67% were women. In patients with severe sepsis (55.6 ± 13.4 years, 50% women), acute physiologic and chronic health evaluation (APACHE) II score was 27.2 ± 8.8 at ICU admission and median MV duration was 10.5 days. Serum EPA and DHA were significantly lower in sepsis vs. healthy subjects over time. PBMC EPA concentrations were generally not different between groups over time, while PBMC DHA was higher in sepsis patients. Neutrophil EPA and DHA concentrations were similar between groups. The half-life of EPA in serum and neutrophils was significantly shorter in sepsis patients, whereas other half-life parameters did not vary significantly between healthy volunteers and sepsis patients.

CONCLUSIONS

While incorporation of n-3 FAs into PBMC and neutrophil membranes was relatively similar between healthy volunteers and sepsis patients receiving identical high doses of fish oil for one week, serum EPA and DHA were significantly lower in sepsis patients. These findings imply that serum concentrations and EPA and DHA may not be the dominant driver of leukocyte membrane incorporation of EPA and DHA. Furthermore, lower serum EPA and DHA concentrations suggest that either these n-3 FAs were being metabolized rapidly in sepsis patients or that absorption of enteral medications and pharmaconutrients, including fish oil, may be impaired in sepsis patients. If enteral absorption is impaired, doses of enteral medications administered to critically ill patients may be suboptimal.

No Influence of Overweight/Obesity on Exercise Lipid Oxidation: A Systematic Review

Compared to lean counterparts, overweight/obese individuals rely less on lipid during fasting. This deficiency has been implicated in the association between overweight/obesity and blunted insulin signaling via elevated intramuscular triglycerides. However, the capacity for overweight/obese individuals to use lipid during exercise is unclear. This review was conducted to formulate a consensus regarding the influence of overweight/obesity on exercise lipid use. PubMed, ProQuest, ISI Web of Science, and Cochrane Library databases were searched. Articles were included if they presented original research on the influence of overweight/obesity on exercise fuel use in generally healthy sedentary adults. Articles were excluded if they assessed older adults, individuals with chronic disease, and/or exercise limitations or physically-active individuals. The search identified 1205 articles with 729 considered for inclusion after duplicate removal. Once titles, abstracts, and/or manuscripts were assessed, 24 articles were included. The preponderance of evidence from these articles indicates that overweight/obese individuals rely on lipid to a similar extent during exercise. However, conflicting findings were found in eight articles due to the outcome measure cited, participant characteristics other than overweight/obesity and characteristics of the exercise bout(s). We also identified factors other than body fatness which can influence exercise lipid oxidation that should be controlled in future research.

Dietary Fish Oil Concentrates Associated Health Benefits: A Recent Development of Cardiovascular Risk Reduction

Fish oil is an abundant source of omega-3 (n-3 or ω-3) polyunsaturated fatty acids (PUFAs) and contains Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA). PUFAs are very effective in preventing/ inhibiting cardiovascular incidents, particularly in individuals with high cardiovascular risk/accidents. In this review, composition, extraction of fish oil and its favorable/beneficial effects in Cardiovascular Diseases (CVDs) and molecular mechanism for its treatment/reduction have been discussed. Moreover, the application of fish oil for preventive/protective and remedial/curative properties in nutritive and health benefits has been summarized. All these aspects further search the opportunities/hope and scope with its expected opening and anticipations/ possibilities to provide additional therapeutic substitutes for the reduction of CVDs and registration of new drugs.

Are we close to defining a metabolomic signature of human obesity? A systematic review of metabolomics studies

INTRODUCTION

Obesity is a disorder characterized by a disproportionate increase in body weight in relation to height, mainly due to the accumulation of fat, and is considered a pandemic of the present century by many international health institutions. It is associated with several non-communicable chronic diseases, namely, metabolic syndrome, type 2 diabetes mellitus (T2DM), cardiovascular diseases (CVD), and cancer. Metabolomics is a useful tool to evaluate changes in metabolites due to being overweight and obesity at the body fluid and cellular levels and to ascertain metabolic changes in metabolically unhealthy overweight and obese individuals (MUHO) compared to metabolically healthy individuals (MHO).

OBJECTIVES

We aimed to conduct a systematic review (SR) of human studies focused on identifying metabolomic signatures in obese individuals and obesity-related metabolic alterations, such as inflammation or oxidative stress.

METHODS

We reviewed the literature to identify studies investigating the metabolomics profile of human obesity and that were published up to May 7th, 2019 in SCOPUS and PubMed through an SR. The quality of reporting was evaluated using an adapted of QUADOMICS.

RESULTS

Thirty-three articles were included and classified according to four types of approaches. (i) studying the metabolic signature of obesity, (ii) studying the differential responses of obese and non-obese subjects to dietary challenges (iii) studies that used metabolomics to predict weight loss and aimed to assess the effects of weight loss interventions on the metabolomics profiles of overweight or obese human subjects (iv) articles that studied the effects of specific dietary patterns or dietary compounds on obesity-related metabolic alterations in humans.

CONCLUSION

The present SR provides state-of-the-art information about the use of metabolomics as an approach to understanding the dynamics of metabolic processes involved in human obesity and emphasizes metabolic signatures related to obesity phenotypes.

Associations of Adiposity and Diet Quality with Serum Ceramides in Middle-Aged Adults with Cardiovascular Risk Factors

Rates of adverse cardiovascular events have increased among middle-aged adults. Elevated ceramides have been proposed as a risk factor for cardiovascular events. Diet quality and weight status are inversely associated with several traditional risk factors; however, the relationship to ceramides is less clear. This study aimed to determine associations of adiposity and diet quality with circulating ceramides in middle-aged adults (n = 96). Diet quality was estimated using the Healthy Eating Index 2015 (HEI-2015). Serum ceramide concentrations were determined by liquid chromatography-mass spectrometry. A ceramide risk score was determined based on ceramides C16:0, C18:0, and C24:1 and their ratios to C24:0. Participants who were classified as at 'moderate risk' compared to 'lower-risk' based on a ceramide risk score had significantly higher body mass index (BMI) values, as well as higher rates of elevated fibrinogen levels, metabolic syndrome, and former smoking status. BMI was positively associated with the ceramide C18:0 (R2 = 0.31, p < 0.0001), the ratio between C18:0/C24:0 ceramides (R2 = 0.30, p < 0.0001), and the ceramide risk score (R2 = 0.11, p < 0.009). Total HEI-2015 scores (R2 = 0.42, p = 0.02), higher intakes of vegetables (R2 = 0.44, p = 0.02) and whole grains (R2 = 0.43, p = 0.03), and lower intakes of saturated fats (R2 = 0.43, p = 0.04) and added sugar (R2 = 0.44, p = 0.01) were associated with lower C22:0 values. These findings suggest that circulating ceramides are more strongly related to adiposity than overall diet quality. Studies are needed to determine if improvements in weight status result in lower ceramides and ceramide risk scores.