Specific plasma lipid classes and phospholipid fatty acids indicative of dairy food consumption associate with insulin sensitivity

Comparison of Adiposomal Lipids between Obese and Non-Obese Individuals

Our recent findings revealed that human adipose tissues (AT)-derived extracellular vesicles (adiposomes) vary in cargo among obese and lean individuals. The main objective of this study was to investigate the adiposomal lipid profiles and their correlation with cardiometabolic risk factors. AT samples were collected from obese subjects and lean controls and analyzed for their characteristics and lipid content. In addition, we measured the correlation between adiposomal lipid profiles and body composition, glucose and lipid metabolic profiles, brachial artery vasoreactivity, AT arteriolar flow-induced dilation, and circulating markers such as IL-6, C-reactive protein, and nitric oxide (NO). Compared to lean controls, adiposomes isolated from obese subjects were higher in number after normalization to AT volume. The two major lipid classes differentially expressed were lysophosphatidylcholine/phosphatidylcholine (LPC/PC) and ceramides (Cer). All lipids in the LPC/PC class were several-fold lower in adiposomes from obese subjects compared to lean controls, on top of which were PC 18:2, PC 18:1, and PC 36:3. Most ceramides were markedly upregulated in the obese group, especially Cer d37:0, Cer d18:0, and Cer d39:0. Regression analyses revealed associations between adiposomal lipid profiles and several cardiometabolic risk factors such as body mass index (BMI), fat percentage, insulin resistance, arteriolar and brachial artery vasoreactivity, NO bioavailability, and high-density lipoproteins (HDL-C). We conclude that the ability of adiposomes from obese subjects to disrupt cardiometabolic function could be partly attributed to the dysregulated lipid cargo.

The Association between the Plasma Phospholipid Profile and Insulin Resistance: A Population-Based Cross-Section Study from the China Adult Chronic Disease and Nutrition Surveillance

The dysfunction of phospholipid metabolism enzymes and the change in membrane phospholipid composition are associated with insulin resistance, indicating that phospholipids play an important role in the regulation of insulin sensitivity. The reflection of phospholipid changes in blood might provide clues for both mechanism understanding and intervention. Using a targeted phospholipidomic approach, 199 phospholipid molecular species were identified and quantified in the plasma of 1053 middle-aged participants from a national investigation. The associations of the phospholipid matrix, clusters, and molecular species with insulin resistance were investigated. A significant association was confirmed between the phospholipid matrix and the homeostatic-model assessment of insulin resistance (HOMA-IR) by a distance-based linear model. Furthermore, three clustered phospholipid modules and 32 phospholipid molecular species were associated with HOMA-IR with the strict control of demographic and lifestyle parameters, family history of diabetes, BMI, WC, and blood lipid parameters. The overall decline in lysophosphatidylcholines (LPCs), the decrease in saturated lysophosphatidylethanolamines (LPEs), the decrease in polyunsaturated/plasmenyl phosphatidylcholines (PCs), and the increase in polyunsaturated phatidylethanolamines (PEs) were the prominent characters of plasma phospholipid perturbation associated with insulin resistance. This suggested that PC- and PE-related metabolic pathways were widely involved in the process of insulin resistance, especially the disorder of LPC acylation to diacyl-PC.

Plasma Metabolites Related to the Consumption of Different Types of Dairy Products and Their Association with New-Onset Type 2 Diabetes: Analyses in the Fenland and EPIC-Norfolk Studies, United Kingdom

SCOPE

To identify metabolites associated with habitual dairy consumption and investigate their associations with type 2 diabetes (T2D) risk.

METHODS AND RESULTS

Metabolomics assays were conducted in the Fenland (n = 10,281) and EPIC-Norfolk (n = 1,440) studies. Using 82 metabolites assessed in both studies, we developed metabolite scores to classify self-reported consumption of milk, yogurt, cheese, butter, and total dairy (Fenland Study-discovery set; n = 6035). Internal and external validity of the scores was evaluated (Fenland-validation set, n = 4246; EPIC-Norfolk, n = 1440). The study assessed associations between each metabolite score and T2D incidence in EPIC-Norfolk (n = 641 cases; 16,350 person-years). The scores classified low and high consumers for all dairy types with internal validity, and milk, butter, and total dairy with external validity. The scores were further associated with lower incident T2D: hazard ratios (95% confidence interval) per standard deviation: milk 0.71 (0.65, 0.77); butter 0.62 (0.57, 0.68); total dairy 0.66 (0.60, 0.72). These associations persisted after adjustment for known dairy-fat biomarkers.

CONCLUSION

Metabolite scores identified habitual consumers of milk, butter, and total dairy products, and were associated with lower T2D risk. These findings hold promise for identifying objective indicators of the physiological response to dairy consumption.

Lysophospholipids Are Associated With Outcomes in Hospitalized Patients With Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) accounts for 70-90% of all TBI cases. Lipid metabolites have important roles in plasma membrane biogenesis, function, and cell signaling. As TBI can compromise plasma membrane integrity and alter brain cell function, we sought to identify circulating phospholipid alterations after mTBI, and determine if these changes were associated with clinical outcomes. Patients with mTBI (Glasgow Coma Score [GCS] ≥13 and loss of consciousness <30 min) were recruited. A total of 84 mTBI subjects were enrolled after admission to a level I trauma center, with the majority having evidence of traumatic intracranial hemorrhage on brain computed tomography (CT). Plasma samples were collected within 24 h of injury with 32 mTBI subjects returning at 3 months after injury for a second plasma sample to be collected. Thirty-five healthy volunteers were enrolled as controls and had a one-time blood draw. Lipid metabolomics was performed on plasma samples from each subject. Fold change of selected lipid metabolites was determined. Multivariable regression models were created to test associations between lipid metabolites and discharge and 6-month Glasgow Outcomes Scale-Extended (GOSE) outcomes (dichotomized between "good" [GOSE ≥7] and "bad" [GOSE ≤6] functional outcomes). Plasma levels of 31 lipid metabolites were significantly associated with discharge GOSE using univariate models; three of these metabolites were significantly increased, while 14 were significantly decreased in subjects with good outcomes compared with subjects with poor outcomes. In multivariable logistic regression models, higher circulating levels of the lysophospholipids (LPL) 1-linoleoyl-glycerophosphocholine (GPC) (18:2), 1-linoleoyl-GPE (18:2), and 1-linolenoyl-GPC (18:3) were associated with both good discharge GOSE (odds ratio [OR] 12.2 [95% CI 3.35, 58.3], p = 5.23 × 10-4; OR 9.43 [95% CI 2.87, 39.6], p = 7.26 × 10-4; and OR 5.26 [95% CI 1.99, 16.7], p = 2.04 × 10-3, respectively) and 6-month (OR 4.67 [95% CI 1.49, 17.7], p = 0.013; OR 2.93 [95% CI 1.11, 8.87], p = 0.039; and OR 2.57 [95% CI 1.08, 7.11], p = 0.046, respectively). Compared with healthy volunteers, circulating levels of these three LPLs were decreased early after injury and had normalized by 3 months after injury. Logistic regression models to predict functional outcomes were created by adding each of the described three LPLs to a baseline model that included age and sex. Including 1-linoleoyl-GPC (18:2) (8.20% improvement, p = 0.009), 1-linoleoyl-GPE (18:2) (8.85% improvement, p = 0.021), or 1-linolenoyl-GPC (18:3) (7.68% improvement, p = 0.012), significantly improved the area under the curve (AUC) for predicting discharge outcomes compared with the baseline model. Models including 1-linoleoyl-GPC (18:2) significantly improved AUC for predicting 6-month outcomes (9.35% improvement, p = 0.034). Models including principal components derived from 25 LPLs significantly improved AUC for prediction of 6-month outcomes (16.0% improvement, p = 0.020). Our results demonstrate that higher plasma levels of LPLs (1-linoleoyl-GPC, 1-linoleoyl-GPE, and 1-linolenoyl-GPC) after mTBI are associated with better functional outcomes at discharge and 6 months after injury. This class of phospholipids may represent a potential therapeutic target.

Interaction between plasma phospholipid odd-chain fatty acids and GAD65 autoantibodies on the incidence of adult-onset diabetes: the EPIC-InterAct case-cohort study

AIMS/HYPOTHESIS

Islet autoimmunity may progress to adult-onset diabetes. We investigated whether circulating odd-chain fatty acids (OCFA) 15:0 and 17:0, which are inversely associated with type 2 diabetes, interact with autoantibodies against GAD65 (GAD65Ab) on the incidence of adult-onset diabetes.

METHODS

We used the European EPIC-InterAct case-cohort study including 11,124 incident adult-onset diabetes cases and a subcohort of 14,866 randomly selected individuals. Adjusted Prentice-weighted Cox regression estimated HRs and 95% CIs of diabetes in relation to 1 SD lower plasma phospholipid 15:0 and/or 17:0 concentrations or their main contributor, dairy intake, among GAD65Ab-negative and -positive individuals. Interactions between tertiles of OCFA and GAD65Ab status were estimated by proportion attributable to interaction (AP).

RESULTS

Low concentrations of OCFA, particularly 17:0, were associated with a higher incidence of adult-onset diabetes in both GAD65Ab-negative (HR 1.55 [95% CI 1.48, 1.64]) and GAD65Ab-positive (HR 1.69 [95% CI 1.34, 2.13]) individuals. The combination of low 17:0 and high GAD65Ab positivity vs high 17:0 and GAD65Ab negativity conferred an HR of 7.51 (95% CI 4.83, 11.69), with evidence of additive interaction (AP 0.25 [95% CI 0.05, 0.45]). Low dairy intake was not associated with diabetes incidence in either GAD65Ab-negative (HR 0.98 [95% CI 0.94, 1.02]) or GAD65Ab-positive individuals (HR 0.97 [95% CI 0.79, 1.18]).

CONCLUSIONS/INTERPRETATION

Low plasma phospholipid 17:0 concentrations may promote the progression from GAD65Ab positivity to adult-onset diabetes.

Heptadecanoic Acid Is Not a Key Mediator in the Prevention of Diet-Induced Hepatic Steatosis and Insulin Resistance in Mice

Epidemiological studies found that the intake of dairy products is associated with an increased amount of circulating odd-chain fatty acids (OCFA, C15:0 and C17:0) in humans and further indicate that especially C17:0 is associated with a lower incidence of type 2 diabetes. However, causal relationships are not elucidated. To provide a mechanistic link, mice were fed high-fat (HF) diets supplemented with either milk fat or C17:0 for 20 weeks. Cultured primary mouse hepatocytes were used to distinguish differential effects mediated by C15:0 or C17:0. Despite an induction of OCFA after both dietary interventions, neither long-term milk fat intake nor C17:0 supplementation improved diet-induced hepatic lipid accumulation and insulin resistance in mice. HF feeding with milk fat actually deteriorates liver inflammation. Treatment of primary hepatocytes with C15:0 and C17:0 suppressed JAK2/STAT3 signaling, but only C15:0 enhanced insulin-stimulated phosphorylation of AKT. Overall, the data indicate that the intake of milk fat and C17:0 do not mediate health benefits, whereas C15:0 might be promising in further studies.

Development and validation of a simple and rapid HILIC-MS/MS method for the quantification of low-abundant lysoglycerophospholipids in human plasma

Lysoglycerophospholipids (Lyso-GPLs) are an essential class of signaling lipids with potential roles in human diseases, such as cancer, central nervous system diseases, and atherosclerosis. Current methods for the quantification of Lyso-GPLs involve complex sample pretreatment, long analysis times, and insufficient validation, which hinder the research of Lyso-GPLs in human studies, especially for Lyso-GPLs with low abundance in human plasma such as lysophosphatidic acid (LPA), lysophosphatidylinositol (LPI), lysophosphatidylglycerol (LPG), lysophosphatidylserine (LysoPS), lyso-platelet-activating factor (LysoPAF), and cyclic phosphatidic acid (cPA). Herein, we report the development and validation of a simple and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of Lyso-GPLs with low abundance in plasma. Protein precipitation using MeOH for Lyso-GPL extraction, quick separation (within 18 min) based on hydrophilic interaction liquid chromatography (HILIC), and sensitive MS detection under dynamic multiple reaction monitoring (dMRM) mode enabled efficient quantification of 22 Lyso-GPLs including 2 cPA, 4 LPG, 11 LPA, 2 LysoPS, and 3 LysoPAF in 50 μL of human plasma. The present method showed good linearity (goodness of fit, 0.99823-0.99995), sensitivity (lower limit of quantification, 0.03-14.06 ng/mL), accuracy (73-117%), precision (coefficient of variation ≤ 28%), carryover (≤ 17%), recovery (80-110%), and stability (83-123%). We applied the method in an epidemiological study and report concentrations of 18 Lyso-GPLs in 567 human plasma samples comparable to those of previous studies. Significant negative associations of LysoPAF C18, LysoPAF C18:1, and LysoPAF C16 with homeostatic model assessment for insulin resistance (HOMA-IR) level were observed; this indicates possible roles of LysoPAF in glucose homeostasis. The application of the present method will improve understanding of the roles of circulating low-abundant Lyso-GPLs in health and diseases.

Graduate Student Literature Review: A scoping review on the impact of consumption of dairy products on phosphatidylcholine and lysophosphatidylcholine in circulation and the liver in human studies and animal models

Dairy consumption is inversely related to the risk of developing type 2 diabetes in epidemiological research. One proposed hypothesis is that phospholipid (PL) species associated with dairy consumption mediate this relationship. This scoping review aimed to identify the existing literature in animal and human trials investigating the impact of dairy products, including milk, yogurt, and cheese as well as dairy-derived PL supplementation on PL and its species in the circulation, summarizing the characteristics of these studies and identifying research gaps. A systematic search was conducted across 3 databases (PubMed, Scopus, and Web of Science) in March 2021. Of 2,427 identified references, 15 studies (7 humans and 8 animal studies) met the eligibility criteria and were included in the final narrative synthesis. The evidence base was heterogeneous, involving a variety of clinical and preclinical studies, metabolically healthy or obese/diabetic participants or animal models, and displayed mixed findings. Circulating postprandial concentrations of total PL were elevated acutely but unchanged after longer intervention with dairy products. The PL concentration remained stable even after a high dosage of milk supplemented with dairy-derived PL, which may be related to increased fecal excretion; however, certain phosphatidylcholine (PC) or lysophosphatidylcholine species were increased in circulation by interventions. These include several PC species with 32 to 38 total carbons in addition to the dairy biomarkers C15:0 and C17:0. The results of this scoping review demonstrate a small body of literature indicating that dairy products can influence blood concentrations of PC and lysophosphatidylcholine species in both rodents and humans without alteration of total PL and PC. There is a lack of well-designed trials in humans and animals that explore the potential differences between individual dairy foods on PL species. In addition, trials to understand the bioactive properties of PC and lysophosphatidylcholine species on cardiometabolic risk are needed.

Dairy as a Source of Iodine and Protein in the UK: Implications for Human Health Across the Life Course, and Future Policy and Research

This narrative review summarizes key concepts in dairy nutrition for supporting human health throughout the life course. Milk and dairy products have been a staple component of our diet for thousands of years and provide a wide range of important nutrients that are otherwise difficult to obtain from dairy-free diets. In this review, we provide a broad perspective on the nutritional roles of iodine and dairy protein in supporting human health during pregnancy and early life, childhood and adolescence, mid- and later-life. New methodologies to identify biomarkers of dairy intake via high-throughput mass spectrometry are discussed, and new concepts such as the role of the food matrix in dairy nutrition are introduced. Finally, future policy and research related to the consumption of dairy and non-dairy alternatives for health are discussed with a view to improving nutritional status across the lifespan.

Milk Odd and Branched Chain Fatty Acids in Dairy Cows: A Review on Dietary Factors and Its Consequences on Human Health

This review highlights the importance of odd and branched chain fatty acids (OBCFAs) and dietary factors that may affect the content of milk OBCFAs in dairy cows. Historically, OBCFAs in cow milk had little significance due to their low concentrations compared to other milk fatty acids (FAs). The primary source of OBCFAs is ruminal bacteria. In general, FAs and OBCFAs profile in milk is mainly affected by dietary FAs and FAs metabolism in the rumen. Additionally, lipid mobilization in the body and FAs metabolism in mammary glands affect the milk OBCFAs profile. In cows, supplementation with fat rich in linoleic acid and α-linolenic acid decrease milk OBCFAs content, whereas supplementation with marine algae or fish oil increase milk OBCFAs content. Feeding more forage rather than concentrate increases the yield of some OBCFAs in milk. A high grass silage rate in the diet may increase milk total OBCFAs. In contrast to saturated FAs, OBCFAs have beneficial effects on cardiovascular diseases and type II diabetes. Furthermore, OBCFAs may have anti-cancer properties and prevent Alzheimer's disease and metabolic syndrome.

Mass recovery following caloric restriction reverses lipolysis and proteolysis, but not gluconeogenesis, in insulin resistant OLETF rats

Caloric restriction (CR) is one of the most important behavioral interventions to reduce excessive abdominal adiposity, which is a risk factor for the development of insulin resistance. Previous metabolomics studies have characterized substrate metabolism during healthy conditions; however, the effects of CR and subsequent mass recovery on shifts in substrate metabolism during insulin resistance (IR) have not been widely investigated. To assess the effects of acute CR and the subsequent mass recovery on shifts in substrate metabolism, a cohort of 15-week old Long Evans Tokushima Otsuka (LETO) and Otsuka Long Evans Tokushima Fatty (OLETF) rats were calorie restricted (CR: 50% × 10 days) with or without partial body mass recovery (PR; 73% x 7 days), along with their respective ad libitum controls. End-of-study plasma samples were analyzed for primary carbon metabolites by gas chromatography (GC) time-of-flight (TOF) mass spectrometry (MS) data acquisition. Data analysis included PCA, Pearson correlation vs previously reported variables (adipose and body masses, and insulin resistance index, IRI), and metabolomics maps (MetaMapp) generated for the most significant group comparisons. All treatments elicited a significant group differentiation in at least one principal component. CR improved TCA cycle in OLETF, and increased lipolysis and proteolysis. These changes were reversed after PR except for gluconeogenesis. Plasma lipid concentrations were inversely correlated to IRI in LETO, but not OLETF. These shifts in substrate metabolism suggest that the CR-induced decreases in adipose may not be sufficient to more permanently alter substrate metabolism to improve IR status during metabolic syndrome.

Lipid responses to environmental perfluoroalkyl substance exposure in a Taiwanese Child cohort

Although recent epidemiologic studies have focused on some of the health effects of perfluoroalkyl substance (PFASs) exposure in humans, the associations between PFASs exposure and the lipidome in children are still unclear. The purpose of this study was to assess lipid changes in children to understand possible molecular events of environmental PFASs exposure and suggest potential health effects. A total of 290 Taiwanese children (8-10 years old) were included in this study. Thirteen PFASs were analyzed in their serum by high-performance liquid chromatography-tandem mass spectrometry (LC-MS). MS-based lipidomic approaches were applied to examine lipid patterns in the serum of children exposed to different levels of PFASs. LC coupling with triple quadrupole MS technology was conducted to analyze phosphorylcholine-containing lipids. Multivariate analyses, such as partial least squares analysis along with univariate analyses, including multiple linear regression, were used to analyze associations between s exposure and unique lipid patterns. Our results showed that different lipid patterns were discovered in children exposed to different levels of specific PFASs, such as PFTrDA, PFOS, and PFDA. These changes in lipid levels may be involved in hepatic lipid metabolism, metabolic disorders, and PFASs-membrane interactions. This study showed that lipidomics is a powerful approach to identify critical PFASs that cause metabolite perturbation in the serum of children and suggest possible adverse health effects of these chemicals in children.

Changes in plasma phospholipids and sphingomyelins with aging in men and women: A comprehensive systematic review of longitudinal cohort studies

BACKGROUND

Aging affects the serum levels of various metabolites which may be involved in the pathogenesis of chronic diseases. The aim of this review article is to summarize the relationship between aging and alterations in the plasma phospholipids and sphingomyelins.

METHODS

PRISMA guidelines were employed during all steps. MEDLINE (PubMed), Scopus, Embase and Web of Sciences databases and Google Scholar were searched up to October 2020. Cohort studies investigating the relationship between aging and within-person changes in sphingomyelin (SM), phosphatidyl choline (PC), lyso PC (LPC) and phosphatidyl ethanolamine (PE) were included. Newcastle-Ottawa scale was used to assess the quality of included studies.

RESULTS

A total of 1425 studies were identified. After removing 610 duplicates and 723 irrelevant studies, full texts of 92 articles were evaluated. Of these 92, 6 studies (including data from 7 independent cohorts) met the inclusion criteria and are included in this review. All study populations were healthy and included both men and women. Results by sex were reported in 3 cohorts for PC, 5 cohorts for LPC, 3 cohorts for SM, and only 1 cohort for PE. In men, PC, SM, PE and LPC decreased with aging, although results for LPC were inconsistent. In women, LPC, SM, and PE increased age, whereas changes in PC were inconsistent.

CONCLUSION

Within-person serum levels of phospholipids and sphingomyelins, decrease during aging in men and increase in women. Notably, however, there were some inconsistencies across studies of LPC in men and of PC in women.

Invited review: Milk fat globule membrane-A possible panacea for neurodevelopment, infections, cardiometabolic diseases, and frailty

Milk is an evolutionary benefit for humans. For infants, it offers optimal nutrients for normal growth, neural development, and protection from harmful microbes. Humans are the only mammals who drink milk throughout their life. Lipids in colostrum originate mostly from milk fat globule membrane (MFGM) droplets extruded from the mammary gland. The MFGM gained much interest as a potential nutraceutical, due to their high phospholipid (PL), ganglioside (GD), and protein contents. In this review, we focused on health effects of MFGM ingredients and dairy food across the life span, especially on neurodevelopment, cardiometabolic health, and frailty in older adults. The MFGM supplements to infants and children reduced gastrointestinal and respiratory tract infections and improved neurodevelopment due to the higher content of protein, PL, and GD in MFGM. The MFGM formulas containing PL and GD improved brain myelination and fastened nerve conduction speed, resulting in improved behavioral developments. Administration of MFGM-rich ingredients improved insulin sensitivity and decreased inflammatory markers, LDL-cholesterol, and triglycerides by lowering intestinal absorption of cholesterol and increasing its fecal excretion. The MFGM supplements, together with exercise, improved ambulatory activities, leg muscle mass, and muscle fiber velocity in older adults. There are great variations in the composition of lipids and proteins in MFGM products, which make comparisons of the different studies impossible. In addition, investigations of the individual MFGM components are required to evaluate their specific effects and molecular mechanisms. Although we are currently only beginning to understand the possible health effects of MFGM products, the current MFGM supplementation trials as presented in this review have shown significant clinical health benefits across the human life span, which are worth further investigation.

Sex Differences in Insulin Sensitivity are Related to Muscle Tissue Acylcarnitine But Not Subcellular Lipid Distribution

OBJECTIVE

Sex differences in insulin sensitivity are present throughout the life-span, with men having a higher prevalence of insulin resistance and diabetes compared with women. Differences in lean mass, fat mass, and fat distribution-particularly ectopic fat-have all been postulated to contribute to the sexual dimorphism in diabetes risk. Emerging data suggest ectopic lipid composition and subcellular localization are most relevant; however, it is not known whether they explain sex differences in obesity-induced insulin resistance.

METHODS

To address this gap, this study evaluated insulin sensitivity and subcellular localization of intramuscular triacylglycerol, diacylglycerol, and sphingolipids as well as muscle acylcarnitines and serum lipidomics in people with obesity.

RESULTS

Insulin sensitivity was significantly lower in men (P < 0.05); however, no sex differences were found in localization of intramuscular triacylglycerol, diacylglycerol, or sphingolipids in skeletal muscle. In contrast, men had higher total muscle acylcarnitine (P < 0.05) and long-chain muscle acylcarnitine (P < 0.05), which were related to lower insulin sensitivity (r = -0.42, P < 0.05). Men also displayed higher serum ceramide (P = 0.05) and lysophosphatidylcholine (P < 0.01).

CONCLUSIONS

These data reveal novel sex-specific associations between lipid species involved in the coupling of mitochondrial fatty acid transport, β-oxidation, and tricarboxylic acid cycle flux that may provide therapeutic targets to improve insulin sensitivity.

Cow's Milk and Dairy Consumption: Is There Now Consensus for Cardiometabolic Health?

Cow's milk and dairy products derived from this complex food source have long been proposed as beneficial to human health, yet underlying clinical evidence of direct benefit continues to raise controversy. Limited evidence supports positive cardiometabolic effects of a number of dairy macro- and micronutrient components including whey protein and casein, unsaturated fats, milk fat globule membrane (MFGM) and polar phospholipids, vitamin D and calcium, in addition to non-bovine components including bacterial and yeast probiotics. More controversial remain lipid components trans fats, including trans vaccenic acid, trans palmitoleic acid, and conjugated cis trans linoleic acid (CLA), plus medium-chain and odd-chain dairy fats. New evidence is rapidly identifying multiple pathways by which these dairy nutrients may effect health. Processing, including fermentation and homogenization, may also have positive effects. Conversely, the high saturated fat content of dairy has long raised concern, aligned with international guidelines to minimize dietary intake of animal-origin saturated fatty acids (SFA) to achieve better cardiometabolic health. However, led in part by observational studies and meta-analyses showing dairy to have no or even an inverse association with cardiometabolic health, evidence from randomized controlled trials (RCTs) has been scrutinized over the last 5 years, and focus on low-fat dairy has been challenged. Recent evidence supports the hypothesis that adverse effects of SFAs on metabolic health may be ameliorated when these fats are consumed within a complex matrix such as milk, cheese or yogurt, and that dairy food categories may influence outcomes as much as total fat content. For example, yogurt and high-fat, high-SFA cheese have a negative association with risk of type 2 diabetes (T2D) in many, not all, published trials. However, large sample dairy RCTs of long duration with CVD or T2D incidence as primary endpoints are lacking. This is a clear research gap, with these clinical studies required if a causative link between dairy and improved cardiometabolic health is to be confirmed and in turn promoted through dietary guidelines. Current advisories from national guidance groups such as American Heart Association (AHA) and European Society of Cardiology (ESC) continue to promote consumption of low-fat dairy products, whilst liquid milk and yogurt remain part of nutrition guidelines from joint American Diabetes Association (ADA)/European Association for Study of Diabetes (EASD) reports, and as part of a "no-one-size-fits-all" answer to diet and T2D by the ADA in their most recent 2019 Consensus Report.

Identification of metabolites associated with prostate cancer risk: a nested case-control study with long follow-up in the Northern Sweden Health and Disease Study

BACKGROUND

Prostate cancer is the second most frequently diagnosed cancer in men. Metabolomics can potentially provide new insights into the aetiology of prostate cancer by identifying new metabolic risk factors. This study investigated the prospective association between plasma metabolite concentrations and prostate cancer risk, both overall and by stratifying for disease aggressiveness and baseline age.

METHODS

In a case-control study nested in the Northern Sweden Health and Disease Study, pre-diagnostic concentrations of 148 plasma metabolites were determined using targeted mass spectrometry- and nuclear magnetic resonance-based metabolomics in 777 prostate cancer cases (follow-up ≥ 5 years) and 777 matched controls. Associations between prostate cancer risk and metabolite concentrations were investigated using conditional logistic regression conditioned on matching factors (body mass index, age and sample storage time). Corrections for multiple testing were performed using false discovery rate (20%) and Bonferroni. Metabolomics analyses generated new hypotheses, which were investigated by leveraging food frequency questionnaires (FFQs) and oral glucose tolerance tests performed at baseline.

RESULTS

After correcting for multiple testing, two lysophosphatidylcholines (LPCs) were positively associated with risk of overall prostate cancer (all ages and in older subjects). The strongest association was for LPC C17:0 in older subjects (OR = 2.08; 95% CI 1.45-2.98; p < 0.0001, significant also after the Bonferroni correction). Observed associations with risk of overall prostate cancer in younger subjects were positive for glycine and inverse for pyruvate. For aggressive prostate cancer, there were positive associations with six glycerophospholipids (LPC C17:0, LPC C20:3, LPC C20:4, PC ae C38:3, PC ae C38:4 and PC ae C40:2), while there was an inverse association with acylcarnitine C18:2. Moreover, plasma LPC C17:0 concentrations positively correlated with estimated dietary intake of fatty acid C17:0 from the FFQs. The associations between glycerophospholipids and prostate cancer were stronger in case-controls with normal glucose tolerance.

CONCLUSIONS

Several glycerophospholipids were positively associated with risk of overall and aggressive prostate cancer. The strongest association was observed for LPC C17:0. The associations between glycerophospholipids and prostate cancer risk were stronger in case-controls with normal glucose tolerance, suggesting a link between the glucose metabolism status and risk of prostate cancer.

Perspective: The Potential Role of Circulating Lysophosphatidylcholine in Neuroprotection against Alzheimer Disease

Alzheimer disease (AD), the most common cause of dementia, is a progressive disorder involving cognitive impairment, loss of learning and memory, and neurodegeneration affecting wide areas of the cerebral cortex and hippocampus. AD is characterized by altered lipid metabolism in the brain. Lower concentrations of long-chain PUFAs have been described in the frontal cortex, entorhinal cortex, and hippocampus in the brain in AD. The brain can synthesize only a few fatty acids; thus, most fatty acids must enter the brain from the blood. Recent studies show that PUFAs such as DHA (22:6) are transported across the blood-brain barrier (BBB) in the form of lysophosphatidylcholine (LPC) via a specific LPC receptor at the BBB known as the sodium-dependent LPC symporter 1 (MFSD2A). Higher dietary PUFA intake is associated with decreased risk of cognitive decline and dementia in observational studies; however, PUFA supplementation, with fatty acids esterified in triacylglycerols did not prevent cognitive decline in clinical trials. Recent studies show that LPC is the preferred carrier of PUFAs across the BBB into the brain. An insufficient pool of circulating LPC containing long-chain fatty acids could potentially limit the supply of long-chain fatty acids to the brain, including PUFAs such as DHA, and play a role in the pathobiology of AD. Whether adults with low serum LPC concentrations are at greater risk of developing cognitive decline and AD remains a major gap in knowledge. Preventing and treating cognitive decline and the development of AD remain a major challenge. The LPC pathway is a promising area for future investigators to identify modifiable risk factors for AD.

Dairy Intake in 2 American Adult Cohorts Associates with Novel and Known Targeted and Nontargeted Circulating Metabolites

BACKGROUND

The role of dairy in health can be elucidated by investigating circulating metabolites associated with intake.

OBJECTIVES

We sought to identify metabolites associated with quantity and type of dairy intake in the Framingham Heart Study Offspring and Third Generation (Gen3) cohorts.

METHODS

Dairy intake (total dairy, milk, cheese, yogurt, and cream/butter) was analyzed in relation to targeted (Offspring, n = 2205, 55.1 ± 9.8 y, 52% female, 217 signals; Gen3, n = 866, 40.5 ± 8.8 y, 54.9% female, 79 signals) and nontargeted metabolites (Gen3, ∼7031 signals) in a 2-step analysis including orthogonal projections to latent structures with discriminant analysis (OPLS-DA) in discovery subsets to identify metabolites distinguishing between high and low intake; and linear regression in confirmation subsets to assess putative associations, subsequently tested in the total samples. Previously reported associations were also investigated.

RESULTS

OPLS-DA in the Offspring targeted discovery subset resulted in a variable importance in projection (VIP) >1 of 65, 60, 58, 66, and 60 metabolites for total dairy, milk, cream/butter, cheese, and yogurt, respectively, of which 5, 3, 1, 6, and 4 metabolites, respectively, remained after confirmation. In the Gen3 targeted discovery subset, OPLS-DA resulted in a VIP >1 of 17, 15, 13, 7, and 6 metabolites for total dairy, milk, cream/butter, cheese, and yogurt, respectively. In the Gen3 nontargeted discovery subset, OPLS-DA resulted in a VIP >2 of 203, 503, 78, 186, and 206 metabolites, respectively. Combining targeted and nontargeted results in Gen3, significant associations of 7 (6 unannotated), 2, 12 (11 unannotated), 0, and 61 (all unannotated) metabolites, respectively, remained. Candidate identities of unannotated signals included fatty acids and food flavorings. Results supported relations previously reported for C14:0 sphingomyelin, and marginal associations for deoxycholates.

CONCLUSIONS

Dairy in 2 American adult cohorts associated with numerous circulating metabolites. Reports about diet-metabolite relations and confirmation of previous findings might be limited by specificity of dietary intake and breadth of measured metabolites.

Supplementation of polar lipids-enriched milk fat globule membrane in high-fat diet-fed rats during pregnancy and lactation promotes brown/beige adipocyte development and prevents obesity in male offspring

Promoting brown adipose tissue (BAT) function or browning of white adipose tissue (WAT) provides a defense against obesity. The aim of the study was to investigate whether maternal polar lipids-enriched milk fat globule membrane (MFGM-PL) supplementation to high-fat diet (HFD) rats during pregnancy and lactation could promote brown/beige adipogenesis and protect against HFD-induced adiposity in offspring. Female SD rats were fed a HFD for 8 weeks to induce obesity and, then, fed a HFD during pregnancy and lactation with or without MFGM-PL. Male offspring were weaned at postnatal Day 21 and then fed a HFD for 9 weeks. MFGM-PL treatment to HFD dams decreased the body weight gain and WAT mass as well as lowered the serum levels of insulin and triglycerides in male offspring at weaning. MFGM-PL+HFD offspring showed promoted thermogenic function in BAT and inguinal WAT through the upregulation of UCP1 and other thermogenic genes. In adulthood, maternal MFGM-PL supplementation reduced adiposity and increased oxygen consumption, respiratory exchange ratio, and heat production in male offspring. The enhancement of energy expenditure was correlated with elevated BAT activity and inguinal WAT thermogenic program. In conclusion, maternal MFGM-PL treatment activated thermogenesis in offspring, which exerted long-term beneficial effects against HFD-induced obesity in later life.

Inclusion of Soluble Fiber in the Gestation Diet Changes the Gut Microbiota, Affects Plasma Propionate and Odd-Chain Fatty Acids Levels, and Improves Insulin Sensitivity in Sows

The transition from pregnancy to lactation is characterized by a progressive decrease in insulin sensitivity. Propionate increases with dietary fiber consumption and has been shown to improve insulin sensitivity. Recent studies suggest that plasma odd-chain fatty acids [OCFAs; pentadecanoic acid (C15:0) and heptadecanoic acid (C17:0)] that inversely correlated with insulin resistance are synthesized endogenously from gut-derived propionate. The present study investigated the effects of soluble fiber during gestation on gut microbiota, plasma non-esterified fatty acids and insulin sensitivity in sows. Sows were allocated to either control or 2.0% guar gum plus pregelatinized waxy maize starch (SF) dietary treatment during gestation. The SF addition changes the structure and composition of gut microbiota in sows. Genus Eubacterium increased by SF addition may promote intestinal propionate production. Moreover, the dietary SF increased circulating levels of plasma OCFAs, especially C17:0. The SF-fed sows had a higher insulin sensitivity and a lower systemic inflammation level during perinatal period. Furthermore, the plasma C15:0 and C17:0 was negatively correlated with the area under curve of plasma glucose after meal and plasma interleukin-6. In conclusion, dietary SF improves insulin sensitivity and alleviates systemic inflammation in perinatal sows, potentially related to its stimulating effect on propionate and OCFAs production.

Trans-palmitoleic acid (trans-9-C16:1, or trans-C16:1 n-7): Nutritional impacts, metabolism, origin, compositional data, analytical methods and chemical synthesis. A review

Since the early 2010s, dietary trans-palmitoleic acid (trans-9-hexadecenoic acid, trans-9-C16:1 in the Δ-nomenclature, trans-C16:1 n-7 in the Ω-nomenclature, TPA) has been epidemiologically associated with a lower risk of type 2 diabetes in humans. Thanks to these findings, TPA has become a nutrient of interest. However, there is a lot of unresolved crucial questions about this dietary fatty acid. Is TPA a natural trans fatty acid? What kind of foods ensures intakes in TPA? What about its metabolism? How does dietary TPA act to prevent type 2 diabetes? What are the biological mechanisms involved in this physiological effect? Clearly, it is high time to answer all these questions with the very first review specifically dedicated to this intriguing fatty acid. Aiming at getting an overview, we shall try to give an answer to all these questions, relying on appropriate and accurate scientific results. Briefly, this review underlines that TPA is indeed a natural trans fatty acid which is metabolically linked to other well-known natural trans fatty acids. Knowledge on physiological impacts of dietary TPA is limited so far to epidemiological data, awaiting for supplementation studies. In this multidisciplinary review, we also emphasize on methodological topics related to TPA, particularly when it comes to the quantification of TPA in foods and human plasma. As a conclusion, we highlight promising health benefits of dietary TPA; however, there is a strong lack in well-designed studies in both the nutritional and the analytical area.

Associations of dairy product consumption with mortality in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Italy cohort

BACKGROUND

The relation of dairy product consumption to health and mortality is controversial.

OBJECTIVES

We investigated associations of consumption of various dairy products with mortality in the Italian cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Italy study.

METHODS

Dairy product consumption was assessed by validated semiquantitative FFQs. Multivariable Cox models stratified by center, age, and sex and adjusted for confounders estimated associations of milk (total, full fat, and reduced fat), yogurt, cheese, butter, and dairy calcium consumption with mortality for cancer, cardiovascular disease, and all causes. Nonlinearity was tested by restricted cubic spline regression.

RESULTS

After a median follow-up of 14.9 y, 2468 deaths were identified in 45,009 participants: 59% from cancer and 19% from cardiovascular disease. No significant association of consumption of any dairy product with mortality was found in the fully adjusted models. A 25% reduction in risk of all-cause mortality was found for milk intake from 160 to 120 g/d (HR: 0.75; 95% CI: 0.61, 0.91) but not for the highest (>200 g/d) category of intake (HR: 0.95; 95% CI: 0.84, 1.08) compared with nonconsumption. Associations of full-fat and reduced-fat milk consumption with all-cause and cause-specific mortality were similar to those for milk as a whole.

CONCLUSIONS

In this Italian cohort characterized by low to average milk consumption, we found no evidence of a dose-response association between milk consumption and mortality and also no association of consumption of other dairy products investigated with mortality.

The Distribution of Fatty Acid Biomarkers of Dairy Intake across Serum Lipid Fractions: The Prospective Metabolism and Islet Cell Evaluation (PROMISE) Cohort

Circulating fatty acids (FA) derived largely from dairy consumption have most commonly been measured in total human serum or phospholipid (PL) fractions, and have been used as validated biomarkers of dairy intake in a growing number of epidemiological studies. Nevertheless, measurement and characterization of a wider spectrum of FA biomarkers of dairy across the four major serum lipid fractions is lacking. This study aimed to (1) quantify FA biomarkers of dairy in PL, triacylglycerol (TAG), cholesteryl ester (CE), and unesterified fatty acid (FFA) serum lipid fractions; and (2) identify potential demographic and metabolic factors that may modify the proportions of these FA across serum fractions. Baseline data from 444 adults in the PROMISE cohort were analyzed. FA biomarkers, 15:0, t16:1n-7, 18:2-c9,t11, and t18:1n-7 were quantified from serum. Dairy intake was estimated using the validated Canadian Diet History Questionnaire. Our results show that t18:1n-7 was the most abundant FA biomarker in all fractions except CE, where 18:2-c9,t11 was the most abundant. Positive correlations within fractions, and across FA in the PL, CE, and FFA fractions were found, however, TAG FA were negatively correlated with the other fractions. PL and CE FA were positively associated with dairy intake, and negatively associated with markers of dysmetabolism while, in contrast, these markers were predictors of higher TAG dairy FA. This study is the first to demonstrate distinct proportions of dairy FA in different serum lipid fractions. PL and CE FA marked dairy intake in this cohort, while TAG FA appeared to be markers of dysmetabolism.

Benefits of the Mediterranean diet: Epidemiological and molecular aspects

More than 50 years after the Seven Countries Study, a large number of epidemiological studies have explored the relationship between the Mediterranean diet (MD) and health, through observational, case-control, some longitudinal and a few experimental studies. The overall results show strong evidence suggesting a protective effect of the MD mainly on the risk of cardiovascular disease (CVD) and certain types of cancer. The beneficial effects have been attributed to the types of food consumed, total dietary pattern, components in the food, cooking techniques, eating behaviors and lifestyle behaviors, among others. The aim of this article is to review and summarize the knowledge derived from the literature focusing on the benefits of the MD on health, including those that have been extensively investigated (CVD, cancer) along with more recent issues such as mental health, immunity, quality of life, etc. The review begins with a brief description of the MD and its components. Then we present a review of studies evaluating metabolic biomarkers and genotypes in relation to the MD. Other sections are dedicated to observation and intervention studies for various pathologies. Finally, some insights into the relationship between the MD and sustainability are explored. In conclusion, the research undertaken on metabolomics approaches has identified potential markers for certain MD components and patterns, but more investigation is needed to obtain valid measures. Further evaluation of gene-MD interactions are also required to better understand the mechanisms by which the MD diet exerts its beneficial effects on health. Observation and intervention studies, particularly PREDIMED, have provided invaluable data on the benefits of the MD for a wide range of chronic diseases. However further research is needed to explore the effects of other lifestyle components associated with Mediterranean populations, its environmental impact, as well as the MD extrapolation to non-Mediterranean contexts.

Metabolomics reveals plausible interactive effects between dairy product consumption and metabolic syndrome in humans

BACKGROUND & AIMS

Metabolic syndrome (MetS) induces major disturbances in plasma metabolome, reflecting abnormalities of several metabolic pathways. Recent evidences have demonstrated that the consumption of dairy products may protect from MetS, but the mechanisms remains unknown. The present study aimed at identify how the consumption of different types of dairy products could modify the changes in plasma metabolome during MetS.

METHODS

In this observational study, we analyzed how the consumption of dairy products could modify the perturbations in the plasma metabolome induced by MetS in a sample of 298 participants (61 with MetS) from the French MONA LISA survey. Metabolomic profiling was analyzed with UPLC-MS/MS.

RESULTS

Subjects with MetS exhibited major changes in plasma metabolome. Significant differences in plasma levels of branched chain amino acids, gamma-glutamyl amino acids, and metabolites from arginine and proline metabolism were observed between healthy control and Mets subjects. Plasma levels of many lipid species were increased with MetS (mono- and diacylglycerols, eicosanoids, lysophospholipids and lysoplasmalogens), with corresponding decreases in short chain fatty acids and plasmalogens. The consumption of dairy products, notably with a low fat content (milk and fresh dairy products), altered metabolite profiles in plasma from MetS subjects. Specifically, increasing consumption of dairy products promoted accumulation of plasma C15:0 fatty acid and was inversely associated to some circulating lysophospholipids, sphingolipids, gamma-glutamyl amino acids, leukotriene B4 and lysoplasmalogens.

CONCLUSIONS

the consumption of low fat dairy products could mitigate some of the variations induced by MetS.

The effect of high compared with low dairy consumption on glucose metabolism, insulin sensitivity, and metabolic flexibility in overweight adults: a randomized crossover trial

BACKGROUND

Dairy products contain many nutritious components that may benefit metabolic health. There are indications that glucose metabolism and insulin sensitivity, which are generally disturbed in overweight and obese individuals, may improve by increased dairy intake. This may also affect one's metabolic flexibility.

OBJECTIVE

The aim of this study was to investigate the effects of high compared with low dairy intake on glucose metabolism, insulin sensitivity, and metabolic flexibility in overweight adults (aged 45-65 y).

METHODS

In this randomized intervention study, subjects consumed a high- and a low-dairy diet [HDD (5-6 dairy portions) and LDD (≤1 dairy portion), respectively] for 6 wk in a crossover design, with a washout period of 4 wk. Dairy portions were 200 g semi-skimmed yoghurt, 30 g reduced-fat (30+) cheese, and 250 mL semiskimmed milk and buttermilk. After 6 wk, a 75-g oral-glucose-tolerance test (13C-labeled) and a subsequent fasting challenge were performed. Metabolic flexibility was studied by determining the respiratory quotient (RQ) using indirect calorimetry. Fasting and postprandial plasma concentrations of glucose and insulin were analyzed. The dual isotope technique enabled calculation of glucose kinetics.

RESULTS

The study was completed by 45 overweight men and postmenopausal women [age 58.9 ± 4.3 y, BMI 27.9 ± 1.9 kg/m2 (mean ± SD)]. Fasting RQ and ΔRQ, reflecting metabolic flexibility, did not differ after both diets. Fasting glucose concentrations were similar, whereas fasting insulin concentrations were lower after the LDD (LDD: 8.1 ± 2.8 mU/L; HDD: 8.9 ± 3.3 mU/L; P = 0.024). This resulted in a higher HOMA-IR after the HDD (P = 0.027). Postprandial glucose and insulin responses as well as glucose kinetics were similar after both diets.

CONCLUSIONS

The amount of dairy intake during a 6-wk period had a neutral effect on metabolic flexibility or postprandial glucose metabolism in middle-aged overweight subjects. More trials are needed to study the effects of specific dairy types and to differentiate between metabolic subgroups. This trial was registered at trialregister.nl as NTR4899.

Alterations in the Plasma Levels of Specific Choline Phospholipids in Alzheimer's Disease Mimic Accelerated Aging

Alzheimer’s disease (AD) is the most common neurodegenerative disease and of continuously rising prevalence. The identification of easy-to-measure biomarkers capable to assist in the prediction and early diagnosis of AD is currently a main research goal. Lipid metabolites in peripheral blood of human patients have recently gained major attention in this respect. Here, we analyzed plasma of 174 participants (not demented at baseline; mean age: 75.70±0.44 years) of the Vienna Transdanube Aging (VITA) study, a longitudinal, population-based birth cohort study, at baseline and after 90 months or at diagnosis of probable AD. We determined the levels of specific choline phospholipids, some of which have been suggested as potential biomarkers for the prediction of AD. Our results show that during normal aging the levels of lysophosphatidylcholine, choline plasmalogen, and lyso-platelet activating factor increase significantly. Notably, we observed similar but more pronounced changes in the group that developed probable AD. Thus, our results imply that, in terms of choline-containing plasma phospholipids, the conversion to AD mimics an accelerated aging process. We conclude that age, even in the comparatively short time frame between 75 and 82.5 years, is a crucial factor in the quest for plasma lipid biomarkers for AD that must be carefully considered in future studies and trials.

Biomarker of food intake for assessing the consumption of dairy and egg products

Dairy and egg products constitute an important part of Western diets as they represent an excellent source of high-quality proteins, vitamins, minerals and fats. Dairy and egg products are highly diverse and their associations with a range of nutritional and health outcomes are therefore heterogeneous. Such associations are also often weak or debated due to the difficulty in establishing correct assessments of dietary intake. Therefore, in order to better characterize associations between the consumption of these foods and health outcomes, it is important to identify reliable biomarkers of their intake. Biomarkers of food intake (BFIs) provide an accurate measure of intake, which is independent of the memory and sincerity of the subjects as well as of their knowledge about the consumed foods. We have, therefore, conducted a systematic search of the scientific literature to evaluate the current status of potential BFIs for dairy products and BFIs for egg products commonly consumed in Europe. Strikingly, only a limited number of compounds have been reported as markers for the intake of these products and none of them have been sufficiently validated. A series of challenges hinders the identification and validation of BFI for dairy and egg products, in particular, the heterogeneous composition of these foods and the lack of specificity of the markers identified so far. Further studies are, therefore, necessary to validate these compounds and to discover new candidate BFIs. Untargeted metabolomic strategies may allow the identification of novel biomarkers, which, when taken separately or in combination, could be used to assess the intake of dairy and egg products.

Mediterranean diet and platelet-activating factor; a systematic review

Platelet-activating factor (PAF) is a glycerylether lipid and one of the most potent endogenous mediators of inflammation. Through its binding to a well-characterized receptor it initiates a plethora of cellular pro-inflammatory actions participating by this way to the pathology of most chronic diseases, including cardiovascular and renal diseases, CNS decline and cancer. Among the variety of prudent dietary patterns, Mediterranean Diet (MD) is the dietary pattern with the strongest evidence for its ability to prevent the same chronic diseases. In addition, micronutrients and extracts from several components and characteristic food of the MD can favorably modulate PAF's actions and metabolism either directly or indirectly. However, the role of this traditional diet on PAF metabolism and actions has rarely been studied before. This systematic review summarizes, presents and discusses the outcomes of epidemiologic and intervention studies in humans, investigating the relationships between PAF status and MD. Seventeen full-text articles trying to interlink the components of MD and PAF are found and presented. The results are inconsistent due to the variability of the measured indices and methodology followed. However, preliminary results indicate that the characteristic "healthy" components of the MD, especially, cereals, legumes, vegetables, fish and wine can favorably modulate the pro-inflammatory actions of PAF and regulate its metabolism. Larger, well-controlled studies are necessary to elucidate whether the attenuation of PAF actions can mediate the preventive properties of MD against chronic diseases.

Flaxseed Oil Alleviates Chronic HFD-Induced Insulin Resistance through Remodeling Lipid Homeostasis in Obese Adipose Tissue

Emerging evidence suggests that higher circulating long-chain n-3 polyunsaturated fatty acids (n-3PUFA) levels were intimately associated with lower prevalence of obesity and insulin resistance. However, the understanding of bioactivity and potential mechanism of α-linolenic acid-rich flaxseed oil (ALA-FO) against insulin resistance was still limited. This study evaluated the effect of FO on high-fat diet (HFD)-induced insulin resistance in C57BL/6J mice focused on adipose tissue lipolysis. Mice after HFD feeding for 16 weeks (60% fat-derived calories) exhibited systemic insulin resistance, which was greatly attenuated by medium dose of FO (M-FO), paralleling with differential accumulation of ALA and its n-3 derivatives across serum lipid fractions. Moreover, M-FO was sufficient to effectively block the metabolic activation of adipose tissue macrophages (ATMs), thereby improving adipose tissue insulin signaling. Importantly, suppression of hypoxia-inducible factors HIF-1α and HIF-2α were involved in FO-mediated modulation of adipose tissue lipolysis, accompanied by specific reconstitution of n-3PUFA within adipose tissue lipid fractions.

Use of Metabolomics in Improving Assessment of Dietary Intake

BACKGROUND

Nutritional metabolomics is rapidly evolving to integrate nutrition with complex metabolomics data to discover new biomarkers of nutritional exposure and status.

CONTENT

The purpose of this review is to provide a broad overview of the measurement techniques, study designs, and statistical approaches used in nutrition metabolomics, as well as to describe the current knowledge from epidemiologic studies identifying metabolite profiles associated with the intake of individual nutrients, foods, and dietary patterns.

SUMMARY

A wide range of technologies, databases, and computational tools are available to integrate nutritional metabolomics with dietary and phenotypic information. Biomarkers identified with the use of high-throughput metabolomics techniques include amino acids, acylcarnitines, carbohydrates, bile acids, purine and pyrimidine metabolites, and lipid classes. The most extensively studied food groups include fruits, vegetables, meat, fish, bread, whole grain cereals, nuts, wine, coffee, tea, cocoa, and chocolate. We identified 16 studies that evaluated metabolite signatures associated with dietary patterns. Dietary patterns examined included vegetarian and lactovegetarian diets, omnivorous diet, Western dietary patterns, prudent dietary patterns, Nordic diet, and Mediterranean diet. Although many metabolite biomarkers of individual foods and dietary patterns have been identified, those biomarkers may not be sensitive or specific to dietary intakes. Some biomarkers represent short-term intakes rather than long-term dietary habits. Nonetheless, nutritional metabolomics holds promise for the development of a robust and unbiased strategy for measuring diet. Still, this technology is intended to be complementary, rather than a replacement, to traditional well-validated dietary assessment methods such as food frequency questionnaires that can measure usual diet, the most relevant exposure in nutritional epidemiologic studies.

Changes in Lipids and Inflammatory Markers after Consuming Diets High in Red Meat or Dairy for Four Weeks

There is a body of evidence linking inflammation, altered lipid metabolism, and insulin resistance. Our previous research found that insulin sensitivity decreased after a four-week diet high in dairy compared to a control diet and to one high in red meat. Our aim was to determine whether a relationship exists between changes in insulin sensitivity and inflammatory biomarkers, or with lipid species. Fasting Tumor Necrosis Factor alpha (TNF-α), Tumor Necrosis Factor Receptor II (sTNF-RII), C-reactive protein (CRP), and lipids were measured at the end of each diet. TNF-α and the ratio TNF-α/sTNF-RII were not different between diets and TNF-α, sTNF-RII, or the ratio TNF-α/sTNF-RII showed no association with homeostasis model assessment-estimated insulin resistance (HOMA-IR). A number of phosphatidylethanolamine (PE) and phosphatidylinositol (PI) species differed between dairy and red meat and dairy and control diets, as did many phosphatidylcholine (PC) species and cholesteryl ester (CE) 14:0, CE15:0, lysophosphatidylcholine (LPC) 14:0, and LPC15:0. None had a significant relationship (p = 0.001 or better) with log homeostasis model assessment-estimated insulin resistance (HOMA-IR), although LPC14:0 had the strongest relationship (p = 0.004) and may be the main mediator of the effect of dairy on insulin sensitivity. LPC14:0 and the whole LPC class were correlated with CRP. The correlations between dietary change and the minor plasma phospholipids PI32:1 and PE32:1 are novel and may reflect significant changes in membrane composition. Inflammatory markers were not altered by changes in protein source while the correlation of LPC with CRP confirms a relationship between changes in lipid profile and inflammation.

Inflammatory Markers Are Positively Associated with Serum trans-Fatty Acids in an Adult American Population

BACKGROUND AND AIM

The relationship between serum trans-fatty acids (TFAs) and systemic inflammation markers is unclear. We investigated the association of serum TFAs with high sensitivity C-reactive protein (hs-CRP) and fibrinogen in adult Americans.

METHODS

The 1999 to 2000 National Health and Nutrition Examination Survey (NHANES) participants with measured data on hs-CRP and fibrinogen were included. TFAs were measured via capillary gas chromatography and mass spectrometry using negative chemical ionization. Analysis of covariance and multivariable-adjusted linear regression models were used to investigate the associations between these parameters, accounting for the survey design.

RESULTS

Of the 5446 eligible participants, 46.8% (n = 2550) were men. The mean age was 47.1 years overall: 47.8 years in men and 46.5 years in women (p = 0.085). After adjustment for age and sex, mean serum TFAs rose with the increasing quarters of hs-CRP and fibrinogen (both p < 0.001). In linear regression models adjusted for age, sex, race, education, marital status, body mass index, and smoking, serum TFAs were an independent predictor of plasma hs-CRP and fibrinogen levels.

CONCLUSION

A high level of TFAs appears to be a contributor to an unfavourable inflammatory profile. Because serum TFAs concentrations are affected by dietary TFA intake, these data suggest a possible contribution of TFAs intake modulation in the prevention of inflammation-related chronic diseases.

Breaking Up Prolonged Sitting Alters the Postprandial Plasma Lipidomic Profile of Adults With Type 2 Diabetes

Context

Postprandial dysmetabolism in type 2 diabetes (T2D) is exacerbated by prolonged sitting and may trigger inflammation and oxidative stress. It is unknown what impact countermeasures to prolonged sitting have on the postprandial lipidome.

Objective

In this study, we investigated the effects of regular interruptions to sitting, compared with prolonged sitting, on the postprandial plasma lipidome.

Design

Randomized crossover experimental trial.

Setting

Participants underwent three 7-hour conditions: uninterrupted sitting (SIT); light-intensity walking interruptions (LW); and simple resistance activity interruptions (SRA).

Participants and Samples

Baseline (fasting) and 7-hour (postprandial) plasma samples from 21 inactive overweight/obese adults with T2D were analyzed for 338 lipid species using mass spectrometry.

Main Outcome Measures

Using mixed model analysis (controlling for baseline outcome variable, gender, body mass index, and condition order), the percentage change in lipid species (baseline to 7 hours) was compared between conditions with Benjamini-Hochberg correction.

Results

Thirty-seven lipids were different between conditions (P < 0.05). Compared with SIT, postprandial elevations in diacylglycerols, triacylglycerols, and phosphatidylethanolamines were attenuated in LW and SRA. Plasmalogens and lysoalkylphosphatidylcholines were reduced in SIT, compared with attenuated reductions or elevations in LW and SRA. Phosphatidylserines were elevated with LW, compared with reductions in SIT and SRA.

Conclusion

Compared with SIT, LW and SRA were associated with reductions in lipids associated with inflammation; increased concentrations of lipids associated with antioxidant capacity; and differential changes in species associated with platelet activation. Acutely interrupting prolonged sitting time may impart beneficial effects on the postprandial plasma lipidome of adults with T2D. Evidence on longer-term intervention is needed.

Genetic correlation of the plasma lipidome with type 2 diabetes, prediabetes and insulin resistance in Mexican American families

Background

Differential plasma concentrations of circulating lipid species are associated with pathogenesis of type 2 diabetes (T2D). Whether the wide inter-individual variability in the plasma lipidome contributes to the genetic basis of T2D is unknown. Here, we investigated the potential overlap in the genetic basis of the plasma lipidome and T2D-related traits.

Results

We used plasma lipidomic data (1202 pedigreed individuals, 319 lipid species representing 23 lipid classes) from San Antonio Family Heart Study in Mexican Americans. Bivariate trait analyses were used to estimate the genetic and environmental correlation of all lipid species with three T2D-related traits: risk of T2D, presence of prediabetes and homeostatic model of assessment – insulin resistance. We found that 44 lipid species were significantly genetically correlated with one or more of the three T2D-related traits. Majority of these lipid species belonged to the diacylglycerol (DAG, 17 species) and triacylglycerol (TAG, 17 species) classes. Six lipid species (all belonging to the triacylglycerol class and containing palmitate at the first position) were significantly genetically correlated with all the T2D-related traits.

Conclusions

Our results imply that: a) not all plasma lipid species are genetically informative for T2D pathogenesis; b) the DAG and TAG lipid classes partially share genetic basis of T2D; and c) 1-palmitate containing TAGs may provide additional insights into the genetic basis of T2D.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-017-0515-5) contains supplementary material, which is available to authorized users.

Association between dairy intake, lipids and vascular structure and function in diabetes

AIM

To determine lipid species that change in response to a change in dairy consumption. In addition, to investigate whether dairy associated lipid species are correlated with changes in measures of vascular structure and function.

METHODS

A 12-mo randomised controlled trial was conducted to determine the effect of increased consumption of fruit, vegetables and dairy, compared to usual diet, on measures of vascular structure and function in adults with type 1 and type 2 diabetes (n = 108). This paper comprises post-hoc analyses investigating the relationship between dairy intake, serum lipid species and vascular health. Central and peripheral blood pressure, carotid femoral pulse wave velocity, augmentation index, serum lipid species and dietary intake were measured at baseline and 3-mo. Common carotid artery intima media thickness was measured at baseline and 12-mo.

RESULTS

Serum lipid species [lysophosphatidylcholine (LPC) 14:0, LPC 15:0, LPC 16:1, phosphatidylcholine (PC) 29:0 PC 30:0, PC 31:0 and cholesterol ester (CE) 14:0] were associated with the change in full fat dairy consumption (rho 0.19-0.25; P < 0.05). The 3-mo change in some lipids was positively associated with the 3-mo change in central systolic [LPC 14:0 (rho 0.30; P = 0.007), PC 30:0 (rho 0.28; P = 0.010)] and diastolic blood pressure [LPC 14:0 (rho 0.32; P = 0.004), LPC 15:0 (rho 0.23; P = 0.04), LPC 16:1 (rho 0.23; P = 0.035), PC 29:0 (rho 0.28; P = 0.01), PC 30:0 (rho 0.36; P = 0.001), PC 31:0 (rho 0.30; P = 0.007)] and 12-mo change in common carotid artery intimal medial thickness [CE 14:0 (rho 0.22; P = 0.02)]. Pulse wave velocity and augmentation index were unrelated to dairy and lipid species.

CONCLUSION

An increase in dairy associated lipids appears to be associated with an increase in blood pressure and common carotid intimal medial thickness.

Odd Chain Fatty Acids; New Insights of the Relationship Between the Gut Microbiota, Dietary Intake, Biosynthesis and Glucose Intolerance

Recent findings have shown an inverse association between circulating C15:0/C17:0 fatty acids with disease risk, therefore, their origin needs to be determined to understanding their role in these pathologies. Through combinations of both animal and human intervention studies, we comprehensively investigated all possible contributions of these fatty acids from the gut-microbiota, the diet, and novel endogenous biosynthesis. Investigations included an intestinal germ-free study and a C15:0/C17:0 diet dose response study. Endogenous production was assessed through: a stearic acid infusion, phytol supplementation, and a Hacl1^−/− mouse model. Two human dietary intervention studies were used to translate the results. Finally, a study comparing baseline C15:0/C17:0 with the prognosis of glucose intolerance. We found that circulating C15:0/C17:0 levels were not influenced by the gut-microbiota. The dose response study showed C15:0 had a linear response, however C17:0 was not directly correlated. The phytol supplementation only decreased C17:0. Stearic acid infusion only increased C17:0. Hacl1^−/− only decreased C17:0. The glucose intolerance study showed only C17:0 correlated with prognosis. To summarise, circulating C15:0 and C17:0 are independently derived; C15:0 correlates directly with dietary intake, while C17:0 is substantially biosynthesized, therefore, they are not homologous in the aetiology of metabolic disease. Our findings emphasize the importance of the biosynthesis of C17:0 and recognizing its link with metabolic disease.

Trans Fatty Acids Suppress TNF-α-Induced Inflammatory Gene Expression in Endothelial (HUVEC) and Hepatocellular Carcinoma (HepG2) Cells

Trans fatty acids (TFA) intake has been linked to cardiovascular diseases and liver diseases; yet the effect of TFA on inflammation remains controversial. Accordingly, the objective of this paper was to determine the in vitro effects of TFA on inflammatory gene expression. Human umbilical vein endothelial cells (HUVEC) and human hepatocellular carcinoma (HepG2) cells were treated for 24 h with either trans-vaccenic acid (tVA), trans-palmitoleic acid (tPA) or elaidic acid (EA) at concentrations of 5-150 µM, or with a mixture of tVA and tPA (150/50 µM). All TFA were highly incorporated into cell membranes, as determined by gas chromatography, representing 15-20% of total fatty acids in HUVEC and 3-8% in HepG2 cells. Incorporation of EA, a common industrial TFA, increased the ratio of the stearoyl-CoA desaturase (SCD-1), a key enzyme involved in fatty acid metabolism. Ruminant TFA, including tVA, tPA and the mixture of tVA and tPA, significantly reduced the TNF-α-induced gene expression of TNF, VCAM-1 and SOD2 in HUVEC, as well as TNF and IL-8 in HepG2 cells. EA also decreased inflammatory gene expression in HUVEC, but not in HepG2 cells. The inhibition of peroxisome proliferator-activated receptor (PPAR)-γ did not influence the effects of TFA on gene expression. Overall, physiological and supraphysiological concentrations of TFA, especially tVA and tPA, prevented inflammatory gene expression in vitro. This effect is independent of PPAR-γ activation and may be due to an alteration of fatty acid metabolism in cell membranes caused by the high incorporation of TFA.

Metabolomics, Nutrition, and Potential Biomarkers of Food Quality, Intake, and Health Status

Diet, dietary patterns, and other environmental factors such as exposure to toxins are playing an important role in the prevention/development of many diseases, like obesity, type 2 diabetes, and consequently on the health status of individuals. A major challenge nowadays is to identify novel biomarkers to detect as early as possible metabolic dysfunction and to predict evolution of health status in order to refine nutritional advices to specific population groups. Omics technologies such as genomics, transcriptomics, proteomics, and metabolomics coupled with statistical and bioinformatics tools have already shown great potential in this research field even if so far only few biomarkers have been validated. For the past two decades, important analytical techniques have been developed to detect as many metabolites as possible in human biofluids such as urine, blood, and saliva. In the field of food science and nutrition, many studies have been carried out for food authenticity, quality, and safety, as well as for food processing. Furthermore, metabolomic investigations have been carried out to discover new early biomarkers of metabolic dysfunction and predictive biomarkers of developing pathologies (obesity, metabolic syndrome, type-2 diabetes, etc.). Great emphasis is also placed in the development of methodologies to identify and validate biomarkers of nutrients exposure.

Markers of sympathetic nervous system activity associate with complex plasma lipids in metabolic syndrome subjects

BACKGROUND AND AIMS

Plasma sphingolipids including ceramides, and gangliosides are associated with insulin resistance (IR) through effects on insulin signalling and glucose metabolism. Our studies of subjects with metabolic syndrome (MetS) showed close relationships between IR and sympathetic nervous system (SNS) activity including arterial norepinephrine (NE). We have therefore investigated possible associations of IR and SNS activity with complex lipids that are involved in both insulin sensitivity and neurotransmission.

METHODS

We performed a cross-sectional assessment of 23 lipid classes/subclasses (total 339 lipid species) by tandem mass spectrometry in 94 overweight untreated subjects with IR (quantified by HOMA-IR, Matsuda index and plasma insulin).

RESULTS

Independently of IR parameters, several circulating complex lipids associated significantly with arterial NE and NEFA (non-esterified fatty acids) and marginally with heart rate (HR). After accounting for BMI, HOMA-IR, systolic BP, age, gender, and correction for multiple comparisons, these associations were significant (p < 0.05): NE with ceramide, phosphatidylcholine, alkyl- and alkenylphosphatidylcholine and free cholesterol; NEFA with mono- di- and trihexosylceramide, G_M3 ganglioside, sphingomyelin, phosphatidylcholine, alkyl- and alkenylphosphatidylcholine, phosphatidylinositol and free cholesterol; HR marginally (p = or <0.1>0.05) with ceramide, G_M3 ganglioside, sphingomyelin, lysophosphatidylcholine, phosphatidylinositol, lysophosphatidylinositol and free cholesterol. Multiple subspecies of these lipids significantly associated with NE and NEFA. None of the IR biomarkers associated significantly with lipid classes/subclasses after correction for multiple comparisons.

CONCLUSIONS

This is the first demonstration that arterial norepinephrine and NEFA, that reflect both SNS activity and IR, associate significantly with circulating complex lipids independently of IR, suggesting a role for such lipids in neural mechanisms operating in MetS.

Lipidomics: Techniques, Applications, and Outcomes Related to Biomedical Sciences

Lipidomics is a newly emerged discipline that studies cellular lipids on a large scale based on analytical chemistry principles and technological tools, particularly mass spectrometry. Recently, techniques have greatly advanced and novel applications of lipidomics in the biomedical sciences have emerged. This review provides a timely update on these aspects. After briefly introducing the lipidomics discipline, we compare mass spectrometry-based techniques for analysis of lipids and summarize very recent applications of lipidomics in health and disease. Finally, we discuss the status of the field, future directions, and advantages and limitations of the field.

Validation of a metabolite panel for early diagnosis of type 2 diabetes

BACKGROUND

Accurate, early diagnosis of type 2 diabetes (T2D) would enable more effective clinical management and a reduction in T2D complications. Therefore, we sought to identify plasma metabolite and protein biomarkers that, in combination with glucose, can better predict future T2D compared with glucose alone.

METHODS

In this case-control study, we used plasma samples from the Bavarian Red Cross Blood Transfusion Center study (61 T2D cases and 78 non-diabetic controls) for discovering T2D-associated metabolites, and plasma samples from the Personalized Medicine Research Project in Wisconsin (56 T2D cases and 445 non-diabetic controls) for validation. All samples were obtained before or at T2D diagnosis. We tested whether the T2D-associated metabolites could distinguish incident T2D cases from controls, as measured by the area under the receiver operating characteristic curve (AUC). Additionally, we tested six metabolic/pro-inflammatory proteins for their potential to augment the ability of the metabolites to distinguish cases from controls.

RESULTS

A panel of 10 metabolites discriminated better between T2D cases and controls than glucose alone (AUCs: 0.90 vs 0.87; p=2.08×10(-5)) in Bavarian samples, and associations between these metabolites and T2D were confirmed in Wisconsin samples. With use of either a Bayesian network classifier or ridge logistic regression, the metabolites, with or without the proteins, discriminated incident T2D cases from controls marginally better than glucose in the Wisconsin samples, although the difference in AUCs was not statistically significant. However, when the metabolites and proteins were added to two previously reported T2D prediction models, the AUCs were higher than those of each prediction model alone (AUCs: 0.92 vs 0.87; p=3.96×10(-2) and AUCs: 0.91 vs 0.71; p=1.03×10(-5), for each model, respectively).

CONCLUSIONS

Compared with glucose alone or with previously described T2D prediction models, a panel of plasma biomarkers showed promise for improved discrimination of incident T2D, but more investigation is needed to develop an early diagnostic marker.

Lipidomic risk score independently and cost-effectively predicts risk of future type 2 diabetes: results from diverse cohorts

Background

Detection of type 2 diabetes (T2D) is routinely based on the presence of dysglycemia. Although disturbed lipid metabolism is a hallmark of T2D, the potential of plasma lipidomics as a biomarker of future T2D is unknown. Our objective was to develop and validate a plasma lipidomic risk score (LRS) as a biomarker of future type 2 diabetes and to evaluate its cost-effectiveness for T2D screening.

Methods

Plasma LRS, based on significantly associated lipid species from an array of 319 lipid species, was developed in a cohort of initially T2D-free individuals from the San Antonio Family Heart Study (SAFHS). The LRS derived from SAFHS as well as its recalibrated version were validated in an independent cohort from Australia – the AusDiab cohort. The participants were T2D-free at baseline and followed for 9197 person-years in the SAFHS cohort (n = 771) and 5930 person-years in the AusDiab cohort (n = 644). Statistically and clinically improved T2D prediction was evaluated with established statistical parameters in both cohorts. Modeling studies were conducted to determine whether the use of LRS would be cost-effective for T2D screening. The main outcome measures included accuracy and incremental value of the LRS over routinely used clinical predictors of T2D risk; validation of these results in an independent cohort and cost-effectiveness of including LRS in screening/intervention programs for T2D.

Results

The LRS was based on plasma concentration of dihydroceramide 18:0, lysoalkylphosphatidylcholine 22:1 and triacyglycerol 16:0/18:0/18:1. The score predicted future T2D independently of prediabetes with an accuracy of 76 %. Even in the subset of initially euglycemic individuals, the LRS improved T2D prediction. In the AusDiab cohort, the LRS continued to predict T2D significantly and independently. When combined with risk-stratification methods currently used in clinical practice, the LRS significantly improved the model fit (p < 0.001), information content (p < 0.001), discrimination (p < 0.001) and reclassification (p < 0.001) in both cohorts. Modeling studies demonstrated that LRS-based risk-stratification combined with metformin supplementation for high-risk individuals was the most cost-effective strategy for T2D prevention.

Conclusions

Considering the novelty, incremental value and cost-effectiveness of LRS it should be used for risk-stratification of future T2D.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0234-3) contains supplementary material, which is available to authorized users.

Circulating Biomarkers of Dairy Fat and Risk of Incident Diabetes Mellitus Among Men and Women in the United States in Two Large Prospective Cohorts

BACKGROUND

In prospective studies, the relationship of self-reported consumption of dairy foods with risk of diabetes mellitus is inconsistent. Few studies have assessed dairy fat, using circulating biomarkers, and incident diabetes mellitus. We tested the hypothesis that circulating fatty acid biomarkers of dairy fat, 15:0, 17:0, and t-16:1n-7, are associated with lower incident diabetes mellitus.

METHODS AND RESULTS

Among 3333 adults aged 30 to 75 years and free of prevalent diabetes mellitus at baseline, total plasma and erythrocyte fatty acids were measured in blood collected in 1989 to 1990 (Nurses' Health Study) and 1993 to 1994 (Health Professionals Follow-Up Study). Incident diabetes mellitus through 2010 was confirmed by a validated supplementary questionnaire based on symptoms, diagnostic tests, and medications. Risk was assessed by using Cox proportional hazards, with cohort findings combined by meta-analysis. During mean±standard deviation follow-up of 15.2±5.6 years, 277 new cases of diabetes mellitus were diagnosed. In pooled multivariate analyses adjusting for demographics, metabolic risk factors, lifestyle, diet, and other circulating fatty acids, individuals with higher plasma 15:0 had a 44% lower risk of diabetes mellitus (quartiles 4 versus 1, hazard ratio, 0.56; 95% confidence interval, 0.37-0.86; P-trend=0.01); higher plasma 17:0, 43% lower risk (hazard ratio, 0.57; 95% confidence interval, 0.39-0.83; P-trend=0.01); and higher t-16:1n-7, 52% lower risk (hazard ratio, 0.48; 95% confidence interval, 0.33-0.70; P-trend <0.001). Findings were similar for erythrocyte 15:0, 17:0, and t-16:1n-7, although with broader confidence intervals that only achieved statistical significance for 17:0.

CONCLUSIONS

In 2 prospective cohorts, higher plasma dairy fatty acid concentrations were associated with lower incident diabetes mellitus. Results were similar for erythrocyte 17:0. Our findings highlight the need to better understand the potential health effects of dairy fat, and the dietary and metabolic determinants of these fatty acids.

Role of metabolic phenotyping in understanding obesity and related conditions in Gulf Co-operation Council countries

Obesity is a major health concern in the Middle East and the incidence is rising in all sections of the population. Efforts to control obesity through diet and lifestyle interventions, and by surgical means, have had limited effect, and the gene-environment interactions underpinning the development of obesity and related pathologies such as metabolic syndrome, cardiovascular disease and certain cancers are poorly defined. Lifestyle, genetics, inflammation and the interaction between the intestinal bacteria and host metabolism have all been implicated in creating an obesogenic environment. We summarize the role of metabolic and microbial phenotyping in understanding the aetiopathogenesis of obesity and in characterizing the metabolic responses to surgical and non-surgical interventions, and explore the potential for clinical translation of this approach.