Influence of weight reduction on blood levels of C-reactive protein, tumor necrosis factor-α, interleukin-6, and oxylipins in obese subjects

Mutations on a conserved distal enhancer in the porcine C-reactive protein gene impair its expression in liver

C-reactive protein (CRP) is an evolutionary highly conserved protein. Like humans, CRP acts as a major acute phase protein in pigs. While CRP regulatory mechanisms have been extensively studied in humans, little is known about the molecular mechanisms that control pig CRP gene expression. The main goal of the present work was to study the regulatory mechanisms and identify functional genetic variants regulating CRP gene expression and CRP blood levels in pigs. The characterization of the porcine CRP proximal promoter region revealed a high level of conservation with both cow and human promoters, sharing binding sites for transcription factors required for CRP expression. Through genome-wide association studies and fine mapping, the most associated variants with both mRNA and protein CRP levels were localized in a genomic region 39.3 kb upstream of CRP. Further study of the region revealed a highly conserved putative enhancer that contains binding sites for several transcriptional regulators such as STAT3, NF-kB or C/EBP-β. Luciferase reporter assays showed the necessity of this enhancer-promoter interaction for the acute phase induction of CRP expression in liver, where differences in the enhancer sequences significantly modified CRP activity. The associated polymorphisms disrupted the putative binding sites for HNF4α and FOXA2 transcription factors. The high correlation between HNF4α and CRP expression levels suggest the participation of HNF4α in the regulatory mechanism of porcine CRP expression through the modification of its binding site in liver. Our findings determine, for the first time, the relevance of a distal regulatory element essential for the acute phase induction of porcine CRP in liver and identify functional polymorphisms that can be included in pig breeding programs to improve immunocompetence.

Bioactive oxylipins in type 2 diabetes mellitus patients with and without hypertriglyceridemia

Objective

Dyslipidemia, in particular elevated triglycerides (TGs) contribute to increased cardiovascular risk in type 2 diabetes mellitus (T2DM). In this pilot study we aimed to assess how increased TGs affect hepatic fat as well as polyunsaturated fatty acid (PUFA) metabolism and oxylipin formation in T2DM patients.

Methods

40 patients with T2DM were characterized analyzing routine lipid blood parameters, as well as medical history and clinical characteristics. Patients were divided into a hypertriglyceridemia (HTG) group (TG ≥ 1.7mmol/l) and a normal TG group with TGs within the reference range (TG < 1.7mmol/l). Profiles of PUFAs and their oxylipins in plasma were measured by gas chromatography and liquid chromatography/tandem mass spectrometry. Transient elastography (TE) was used to assess hepatic fat content measured as controlled attenuation parameter (CAP) (in dB/m) and the degree of liver fibrosis measured as stiffness (in kPa).

Results

Mean value of hepatic fat content measured as CAP as well as body mass index (BMI) were significantly higher in patients with high TGs as compared to those with normal TGs, and correlation analysis showed higher concentrations of TGs with increasing CAP and BMI scores in patients with T2DM. There were profound differences in plasma oxylipin levels between these two groups. Cytochrome P450 (CYP) and lipoxygenase (LOX) metabolites were generally more abundant in the HTG group, especially those derived from arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), γ-linolenic acid (γ-LA), and α-linolenic acid (α-LA), and a strong correlation between TG levels and plasma metabolites from different pathways was observed.

Conclusions

In adult patients with T2DM, elevated TGs were associated with increased liver fat and BMI. Furthermore, these patients also had significantly higher plasma levels of CYP- and LOX- oxylipins, which could be a novel indicator of increased inflammatory pathway activity, as well as a novel target to dampen this activity.

Oxylipin secretion by human CD3+ T lymphocytes in vitro is modified by the exogenous essential fatty acid ratio and life stage

Immune function changes across the life stages; for example, senior adults exhibit a tendency towards a weaker cell-mediated immune response and a stronger inflammatory response than younger adults. This might be partly mediated by changes in oxylipin synthesis across the life course. Oxylipins are oxidation products of polyunsaturated fatty acids (PUFAs) that modulate immune function and inflammation. A number of PUFAs are precursors to oxylipins, including the essential fatty acids (EFAs) linoleic acid (LA) and α-linolenic acid (ALA). LA and ALA are also substrates for synthesis of longer chain PUFAs. Studies with stable isotopes have shown that the relative amounts of LA and ALA can influence their partitioning by T lymphocytes between conversion to longer chain PUFAs and to oxylipins. It is not known whether the relative availability of EFA substrates influences the overall pattern of oxylipin secretion by human T cells or if this changes across the life stages. To address this, the oxylipin profile was determined in supernatants from resting and mitogen activated human CD3+ T cell cultures incubated in medium containing an EFA ratio of either 5:1 or 8:1 (LA : ALA). Furthermore, oxylipin profiles in supernatants of T cells from three life stages, namely fetal (derived from umbilical cord blood), adults and seniors, treated with the 5:1 EFA ratio were determined. The extracellular oxylipin profiles were affected more by the EFA ratio than mitogen stimulation such that n-3 PUFA-derived oxylipin concentrations were higher with the 5:1 EFA ratio than the 8:1 ratio, possibly due to PUFA precursor competition for lipoxygenases. 47 oxylipin species were measured in all cell culture supernatants. Extracellular oxylipin concentrations were generally higher for fetal T cells than for T cells from adult and senior donors, although the composition of oxylipins was similar across the life stages. The contribution of oxylipins towards an immunological phenotype might be due to the capacity of T cells to synthesize oxylipins rather than the nature of the oxylipins produced.

Photoperiod Conditions Modulate Serum Oxylipins Levels in Healthy and Obese Rats: Impact of Proanthocyanidins and Gut Microbiota

Seasonal rhythms are emerging as a key factor influencing gut microbiota and bioactive compounds functionality as well as several physiological processes such as inflammation. In this regard, their impact on the modulation of oxylipins (OXLs), which are important lipid mediators of inflammatory processes, has not been investigated yet. Hence, we aimed to investigate the effects of photoperiods on OXLs metabolites in healthy and obesogenic conditions. Moreover, we evaluated if the impact of proanthocyanidins and gut microbiota on OXLs metabolism is influenced by photoperiod in obesity. To this purpose, Fischer 344 rats were housed under different photoperiod conditions (L6: 6 h light, L12: 12 h light or L18:18 h light) and fed either a standard chow diet (STD) or a cafeteria diet (CAF) for 9 weeks. During the last 4 weeks, obese rats were daily administered with an antibiotic cocktail (ABX), an oral dose of a grape seed proanthocyanidin extract (GSPE), or with their combination. CAF feeding and ABX treatment affected OXLs in a photoperiod dependent-manner. GSPE significantly altered prostaglandin E2 (PGE2) levels, only under L6 and mitigated ABX-mediated effects only under L18. In conclusion, photoperiods affect OXLs levels influenced by gut microbiota. This is the first time that the effects of photoperiod on OXLs metabolites have been demonstrated.

Crosstalk between adenosine receptors and CYP450-derived oxylipins in the modulation of cardiovascular, including coronary reactive hyperemic response

Adenosine is a ubiquitous endogenous nucleoside or autacoid that affects the cardiovascular system through the activation of four G-protein coupled receptors: adenosine A₁ receptor (A₁AR), adenosine A_2A receptor (A_2AAR), adenosine A_2B receptor (A_2BAR), and adenosine A₃ receptor (A₃AR). With the rapid generation of this nucleoside from cellular metabolism and the widespread distribution of its four G-protein coupled receptors in almost all organs and tissues of the body, this autacoid induces multiple physiological as well as pathological effects, not only regulating the cardiovascular system but also the central nervous system, peripheral vascular system, and immune system. Mounting evidence shows the role of CYP450-enzymes in cardiovascular physiology and pathology, and the genetic polymorphisms in CYP450s can increase susceptibility to cardiovascular diseases (CVDs). One of the most important physiological roles of CYP450-epoxygenases (CYP450-2C & CYP2J2) is the metabolism of arachidonic acid (AA) and linoleic acid (LA) into epoxyeicosatrienoic acids (EETs) and epoxyoctadecaenoic acid (EpOMEs) which generally involve in vasodilation. Like an increase in coronary reactive hyperemia (CRH), an increase in anti-inflammation, and cardioprotective effects. Moreover, the genetic polymorphisms in CYP450-epoxygenases will change the beneficial cardiovascular effects of metabolites or oxylipins into detrimental effects. The soluble epoxide hydrolase (sEH) is another crucial enzyme ubiquitously expressed in all living organisms and almost all organs and tissues. However, in contrast to CYP450-epoxygenases, sEH converts EETs into dihydroxyeicosatrienoic acid (DHETs), EpOMEs into dihydroxyoctadecaenoic acid (DiHOMEs), and others and reverses the beneficial effects of epoxy-fatty acids leading to vasoconstriction, reducing CRH, increase in pro-inflammation, increase in pro-thrombotic and become less cardioprotective. Therefore, polymorphisms in the sEH gene (Ephx2) cause the enzyme to become overactive, making it more vulnerable to CVDs, including hypertension. Besides the sEH, ω-hydroxylases (CYP450-4A11 & CYP450-4F2) derived metabolites from AA, ω terminal-hydroxyeicosatetraenoic acids (19-, 20-HETE), lipoxygenase-derived mid-chain hydroxyeicosatetraenoic acids (5-, 11-, 12-, 15-HETEs), and the cyclooxygenase-derived prostanoids (prostaglandins: PGD₂, PGF_2α; thromboxane: Txs, oxylipins) are involved in vasoconstriction, hypertension, reduction in CRH, pro-inflammation and cardiac toxicity. Interestingly, the interactions of adenosine receptors (A_2AAR, A₁AR) with CYP450-epoxygenases, ω-hydroxylases, sEH, and their derived metabolites or oxygenated polyunsaturated fatty acids (PUFAs or oxylipins) is shown in the regulation of the cardiovascular functions. In addition, much evidence demonstrates polymorphisms in CYP450-epoxygenases, ω-hydroxylases, and sEH genes (Ephx2) and adenosine receptor genes (ADORA1 & ADORA2) in the human population with the susceptibility to CVDs, including hypertension. CVDs are the number one cause of death globally, coronary artery disease (CAD) was the leading cause of death in the US in 2019, and hypertension is one of the most potent causes of CVDs. This review summarizes the articles related to the crosstalk between adenosine receptors and CYP450-derived oxylipins in vascular, including the CRH response in regular salt-diet fed and high salt-diet fed mice with the correlation of heart perfusate/plasma oxylipins. By using A_2AAR^-/-, A₁AR^-/-, eNOS^-/-, sEH^-/- or Ephx2^-/-, vascular sEH-overexpressed (Tie2-sEH Tr), vascular CYP2J2-overexpressed (Tie2-CYP2J2 Tr), and wild-type (WT) mice. This review article also summarizes the role of pro-and anti-inflammatory oxylipins in cardiovascular function/dysfunction in mice and humans. Therefore, more studies are needed better to understand the crosstalk between the adenosine receptors and eicosanoids to develop diagnostic and therapeutic tools by using plasma oxylipins profiles in CVDs, including hypertensive cases in the future.

The association between eicosanoids and incident atrial fibrillation in the Framingham Heart Study

Chronic inflammation is a continuous low-grade activation of the systemic immune response. Whereas downstream inflammatory markers are associated with atrial fibrillation (AF), upstream inflammatory effectors including eicosanoids are less studied. To examine the association between eicosanoids and incident AF. We used a liquid chromatography-mass spectrometry for the non-targeted measurement of 161 eicosanoids and eicosanoid-related metabolites in the Framingham Heart Study. The association of each eicosanoid and incident AF was assessed using Cox proportional hazards models and adjusted for AF risk factors, including age, sex, height, weight, systolic/diastolic blood pressure, current smoking, antihypertensive medication, diabetes, history of myocardial infarction and heart failure. False discovery rate (FDR) was used to adjust for multiple testing. Eicosanoids with FDR < 0.05 were considered significant. In total, 2676 AF-free individuals (mean age 66 ± 9 years, 56% females) were followed for mean 10.8 ± 3.4 years; 351 participants developed incident AF. Six eicosanoids were associated with incident AF after adjusting for multiple testing (FDR < 0.05). A joint score was built from the top eicosanoids weighted by their effect sizes, which was associated with incident AF (HR = 2.72, CI = 1.71-4.31, P = 2.1 × 10^-5). In conclusion, six eicosanoids were associated with incident AF after adjusting for clinical risk factors for AF.

Substantial Fat Loss in Physique Competitors Is Characterized by Increased Levels of Bile Acids, Very-Long Chain Fatty Acids, and Oxylipins

Weight loss and increased physical activity may promote beneficial modulation of the metabolome, but limited evidence exists about how very low-level weight loss affects the metabolome in previously non-obese active individuals. Following a weight loss period (21.1 ± 3.1 weeks) leading to substantial fat mass loss of 52% (−7.9 ± 1.5 kg) and low body fat (12.7 ± 4.1%), the liquid chromatography-mass spectrometry-based metabolic signature of 24 previously young, healthy, and normal weight female physique athletes was investigated. We observed uniform increases (FDR < 0.05) in bile acids, very-long-chain free fatty acids (FFA), and oxylipins, together with reductions in unsaturated FFAs after weight loss. These widespread changes, especially in the bile acid profile, were most strongly explained (FDR < 0.05) by changes in android (visceral) fat mass. The reported changes did not persist, as all of them were reversed after the subsequent voluntary weight regain period (18.4 ± 2.9 weeks) and were unchanged in non-dieting controls (n = 16). Overall, we suggest that the reported changes in FFA, bile acid, and oxylipin profiles reflect metabolic adaptation to very low levels of fat mass after prolonged periods of intense exercise and low-energy availability. However, the effects of the aforementioned metabolome subclass alteration on metabolic homeostasis remain controversial, and more studies are warranted to unravel the complex physiology and potentially associated health implications. In the end, our study reinforced the view that transient weight loss seems to have little to no long-lasting molecular and physiological effects.

The effect of nutrition and exercise training on irisin and semaphorin-3E levels in obese patients

We aimed to firstly examine the effects of nutrition and exercise training on irisin, Sema-3E, biochemical and inflammatory parameters in obese patients. This study was conducted using 37 individuals were divided into three groups according to body mass index (BMI) as non-obese, 1nd degree and 2nd degree obese individuals. Nutrition and exercise training were applied to groups for eight weeks. Insulin resistance decreased in non-obese and 1st degree obese subjects. HsCRP values decreased only in the second degree obese individuals. Adiponectin values were significantly decreased in all three groups. There was a negative correlation between serum adiponectin and plasma irisin levels both before and after treatment. Sema-3E levels increased significantly in only the first degree obese individuals, whereas plexin-D1 values did not change significantly in any group. Our findings indicate that nutrition and exercise training we apply improved both anthropometric measurements and biochemical parameters in obese and non-obese individuals.

The addition of exercise to a weight loss diet on inflammatory markers: a systematic review and Meta-analysis of controlled clinical trials

This systematic review and meta-analysis of controlled clinical trials was performed to evaluate the effects of weight-loss diets plus exercise compared with weight-loss diets alone on inflammatory biomarkers in adults. PubMed, Scopus, EMBASE, Web of Science (ISI), and Google Scholar were searched up to April 2021. Overall effects were derived using a random effects model. The overall quality of evidence was assessed using Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Twenty-nine trials were included in this systematic review and meta-analysis. The meta-analysis showed no significant difference in serum high sensitivity C-reactive protein (hs-CRP) [weighted mean difference (WMD) = -0.004 mg/l, 95% CI: -0.140, 0.132, P = 0.954], interleukin-6 (IL-6) (WMD = -0.039 pg/ml, 95% CI: -0.233 to 0.156, P = 0.696), and tumor necrosis factor-α (TNF-α) (WMD = 0.405 ng/ml, 95% CI: -1.036 to 0.226, P = 0.209) after adding exercise to a weight-loss diet compared with a weight-loss diet alone. Subgroup analysis revealed that exercise plus a weight-loss diet significantly reduced TNF-α in studies greater than 16 weeks in duration (WMD = -0.742 ng/ml, 95% CI: -1.384 to -0.1, P = 0.024). This systematic review and meta-analysis indicate that exercise in addition to a weight-loss diet does not have a significant effect on further reducing inflammatory markers compared to a weight loss diet alone.

One-anastomosis gastric bypass modulates the serum levels of pro- and anti-inflammatory oxylipins, which may contribute to the resolution of inflammation

BACKGROUND/OBJECTIVES

Oxylipins are polyunsaturated fatty acid derivatives involved in the regulation of various processes, including chronic inflammation, insulin resistance and hepatic steatosis. They can be synthesized in various tissues, including adipose tissue. There is some evidence that obesity is associated with the deregulation of serum oxylipin levels. The aim of this study was to evaluate the effect of bariatric surgery (one-anastomosis gastric bypass) on the serum levels of selected oxylipins and their fatty acid precursors and to verify the hypothesis that their changes after surgery can contribute to the resolution of inflammation. Moreover, we compared the oxylipin levels (prostaglandin E2, 13-HODE, maresin 1 and resolvin E1), fatty acids and the expression of enzymes that synthesize oxylipins in adipose tissue of lean controls and subjects with severe obesity.

SUBJECTS/METHODS

The study included 50 patients with severe obesity that underwent bariatric surgery and 41 subjects in lean, control group. Fatty acid content was analyzed by GC-MS, oxylipin concentrations were measured with immunoenzymatic assay kits and real-time PCR analysis was used to assess mRNA levels in adipose tissue.

RESULTS

Our results show increased expression of some enzymes that synthesize oxylipins in adipose tissue and alterations in the levels of oxylipins in both adipose tissue and serum of subjects with obesity. After bariatric surgery, the levels of anti-inflammatory oxylipins increased, whereas pro-inflammatory oxylipins decreased.

CONCLUSIONS

In patients with obesity, the metabolism of oxylipins is deregulated in adipose tissue, and their concentrations in serum are altered. Bariatric surgery modulates the serum levels of pro- and anti-inflammatory oxylipins, which may contribute to the resolution of inflammation.

Association of Arachidonic Acid-derived Lipid Mediators with Subsequent Onset of Acute Myocardial Infarction in Patients with Coronary Artery Disease

Polyunsaturated fatty acids (PUFAs) have been suggested for cardiovascular health. This study was conducted to investigate the prognostic impacts of the PUFA metabolites, oxylipins, on clinical outcomes in coronary artery disease (CAD). A total of 2,239 patients with stable CAD were prospectively enrolled and followed up regularly. Among them, twenty-five consecutive patients with new onset of acute myocardial infarction (AMI) within 2-year follow-up were studied. Another 50 gender- and age-matched patients without clinical cardiovascular events for more than 2 years were studied for control. Baseline levels of specific arachidonic acid metabolites were significantly higher in patients with subsequent AMI than in the controls. In Kaplan-Meier analysis, the incidence of future AMI was more frequently seen in patients with higher baseline levels of 8-hydroxyeicosatetraenoic acid (HETE), 9-HETE, 11-HETE, 12-HETE, 15-HETE, 19-HETE, 20-HETE, 5,6-epoxyeicosatrienoic acid (EET), 8,9-EET, 11,12-EET, or 14-15-EET when compared to their counterparts (all the P < 0.01). Further, serum levels of these specific HETEs, except for 11,12-EET, were positively correlated to the levels of some inflammatory and cardiac biomarker such as tumor necrosis factor-α and N-terminal pro B-type natriuretic peptide. Accordingly, serum specific oxylipins levels are increased and associated with the consequent onset of AMI, suggesting their potential role for secondary prevention in clinically stable CAD.

Profiling of Endogenous and Gut Microbial Metabolites to Indicate Metabotype-Specific Dietary Responses: A Systematic Review

Upon dietary exposure, the endogenous metabolism responds to the diet-derived nutrients and bioactive compounds, such as phytochemicals. However, the responses vary remarkably due to the interplay with other dietary components, lifestyle exposures, and intrinsic factors, which lead to differences in endogenous regulatory metabolism. These physiological processes are evidenced as a signature profile composed of various metabolites constituting metabolic phenotypes, or metabotypes. The metabolic profiling of biological samples following dietary intake hence would provide information about diet-that is, as the intake biomarkers and the ongoing physiological reactions triggered by this intake-thereby enable evaluation of the metabolic basis required to distinguish the different metabotypes. The capacity of nontargeted metabolomics to also encompass the unprecedented metabolite species has enabled the profiling of multiple metabolites and the corresponding metabotypes with a single analysis, decoding the complex interplay between diet, other relevant factors, and health. In this systematic review, we screened 345 articles published in English in January 2007-July 2018, which applied the metabolomics approach to profile the changes of endogenous metabolites in the blood related to dietary interventions, either derived by metabolism of gut microbiota or the human host. We excluded all the compounds that were directly derived from diet, and also the dietary interventions focusing on supplementation with individual compounds. After the removal of less relevant studies and assessment of eligibility, 49 articles were included in this review. First, we mention the contribution of individual factors, either modifiable or nonmodifiable factors, in shaping metabolic profile. Then, how different aspects of the diet would affect the metabolic profiles are disentangled. Next, the classes of endogenous metabolites altered following included dietary interventions are listed. We also discuss the current challenges in the field, along with future research opportunities.

Actions of annatto-extracted tocotrienol supplementation on obese postmenopausal women: study protocol for a double-blinded, placebo-controlled, randomised trial

INTRODUCTION

Obesity is a major health concern in postmenopausal women, and chronic low-grade inflammation contributes to the development of obesity. Cellular studies and high-fat-diet-induced obese mouse model mimicking obesity show the antiobesity effect of annatto-extracted tocotrienols (TT) with antioxidant capability. We aim to assess the safety and efficacy of TT consumption for lipid-related parameters in obese postmenopausal women.

METHODS AND ANALYSIS

Eligible obese postmenopausal women will be randomly assigned to placebo group (430 mg olive oil) and TT group (DeltaGold Tocotrienol 70%) for 24 weeks. In the present study, the primary outcome is total/regional fat mass and visceral adipose tissue. The secondary outcomes include lipid profile in serum, mRNA expression of fatty acid synthase and carnitine palmitoyltransferase 1A in fat tissue, oxylipins and endocannabinoids in plasma and adipose tissue, abundance and composition of intestinal microbiome in faeces, high-sensitivity C-reactive protein (hs-CRP) in serum and leptin in serum. Every participant will be evaluated at 0 (prior to starting intervention) and 24 weeks of intervention, except for serum lipid profile and hs-CRP at 0, 12 and 24 weeks. 'Intent-to-treat' principle is employed for data analysis. Hierarchical linear modelling is used to estimate the effects of dietary TT supplementation while properly accounting for dependency of data and identified covariates. To our knowledge, this is the first randomised, placebo-controlled, double-blinded study to determine dietary TT supplementation on an obese population. If successful, this study will guide the future efficacy TT interventions and TT can be implemented as an alternative for obese population in antiobesity management.

ETHICS AND DISSEMINATION

This study has been approved by the Bioethics Committee of the Texas Tech University Health Sciences Center, Lubbock. An informed consent form will be signed by a participant before enrolling in the study. The results from this trial will be actively disseminated through academic conference presentation and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03705845.

5-Lipooxygenase Derivatives as Serum Biomarkers of a Successful Dietary Intervention in Patients with NonAlcoholic Fatty Liver Disease

Background: It was previously shown that a bodyweight reduction among patients with nonalcoholic fatty liver (NAFLD) was connected to the lower concentration of arachidonic and linoleic acid derivatives in their blood. We hypothesized that the concentration of these lipids was correlated with the extent of their body mass reduction and, thus, liver steatosis. Methods: We analyzed 68 individuals who completed the dietary intervention. Patients were divided into two groups depending on their body mass reduction (more or less than 7%). Before and after the dietary intervention, all patients had the following measurements recorded: body mass, waist circumference, stage of steatosis, fatty liver index, liver enzymes, lipid parameters, insulin and glucose. Concentrations of lipoxins A4 (LTX A4), hydroxyeicosatetraenoic fatty acids (5(S)-HETE, 12(S)-HETE and 16(S)-HETE), hydroxyoctadecaenoic acids (9(S)-HODE and 13(S)-HODE) and 5-oxo-eicosatetraenoic acid (5-oxo-ETE) were measured in serum samples collected before and after the dietetic intervention using high-performance liquid chromatography (HPLC). Results: Patients who reduced their body mass by more than 7% revealed a significant improvement in their steatosis stage, waist circumference, fatty liver index, triglycerides and cholesterol. Conclusion: A reduction in body mass by more than 7% but not by less than 7% revealed a significant improvement in steatosis stage; waist circumference; fatty liver index; and levels of triglycerides, cholesterol, 5-oxo-ETE and LTXA-4.

MS-based targeted metabolomics of eicosanoids and other oxylipins: Analytical and inter-individual variabilities

Oxylipins, including the well-known eicosanoids, are potent lipid mediators involved in numerous physiological and pathological processes. Therefore, their quantitative profiling has gained a lot of attention during the last years notably in the active field of health biomarker discovery. Oxylipins include hundreds of structurally and stereochemically distinct lipid species which today are most commonly analyzed by (ultra) high performance liquid chromatography-mass spectrometry based ((U)HPLC-MS) methods. To maximize the utility of oxylipin profiling in clinical research, it is crucial to understand and assess the factors contributing to the analytical and biological variability of oxylipin profiles in humans. In this review, these factors and their impacts are summarized and discussed, providing a framework for recommendations expected to enhance the interlaboratory comparability and biological interpretation of oxylipin profiling in clinical research.

Modern Methods of Sample Preparation for the Analysis of Oxylipins in Biological Samples

Oxylipins are potent lipid mediators derived from polyunsaturated fatty acids, which play important roles in various biological processes. Being important regulators and/or markers of a wide range of normal and pathological processes, oxylipins are becoming a popular subject of research; however, the low stability and often very low concentration of oxylipins in samples are a significant challenge for authors and continuous improvement is required in both the extraction and analysis techniques. In recent years, the study of oxylipins has been directly related to the development of new technological platforms based on mass spectrometry (LC–MS/MS and gas chromatography–mass spectrometry (GC–MS)/MS), as well as the improvement in methods for the extraction of oxylipins from biological samples. In this review, we systematize and compare information on sample preparation procedures, including solid-phase extraction, liquid–liquid extraction from different biological tissues.

Permissive underfeeding, cytokine profiles and outcomes in critically ill patients

Background

During critical illness in humans, the effects of caloric restriction on the inflammatory response are not well understood. The aim of this study is to examine the associations of caloric restriction, inflammatory response profiles and outcomes in critically ill patients.

Methods

This is a sub-study of the PermiT trial (Permissive Underfeeding or Standard Enteral Feeding in Critically Ill Adults Trial- ISRCTN68144998). Serum samples were collected on study days 1, 3, 5, 7 and 14 and analyzed for a panel of 29 cytokines. We used principal component analysis to convert possibly correlated variables (cytokine levels) into a limited number of linearly uncorrelated variables (principal components). We constructed repeated measures mixed linear models to assess whether permissive underfeeding compared to standard feeding was associated with difference cytokine levels over time.

Results

A total of 72 critically ill patients were enrolled in this study (permissive underfeeding n = 36 and standard feeding n = 36). Principal component analysis identified 6 components that were responsible for 78% of the total variance. When adjusted to principal components, permissive underfeeding was not associated with 90-day mortality (adjusted odds ratio 1.75, 95% confidence interval 0.44, 6.95, p = 0.43) or with incident renal replacement therapy. The cytokines did not differ with time between permissive underfeeding and standard feeding groups.

Conclusions

The association of permissive underfeeding compared to standard feeding with mortality was not influenced by the inflammatory profile. Permissive underfeeding compared to standard feeding was not associated with differences in the serum levels of cytokines in critically ill patients.

Obesity: outcome of standardized life-style change in a rehabilitation clinic. An observational study

Purpose: To explore differences in baseline characteristics following three weeks of semi-standardized in-patient care between patients with obesity without and with type 2 diabetes (T2D). Patients and methods: Patients without or with T2D were matched according to age, sex, and BMI. Food intake was restricted to 1,200-1,600 kcal/d to which a 400-600 kcal/d exercise load was added, and data were compared using Student's t-test, general linear models, and Spearman-rank correlations. Results: At baseline, patients with obesity and T2D displayed, besides elevated blood glucose and HbA_1c values, higher serum liver enzymes (p<0.001-0.05), triglycerides, and CRP (p<0.01) and a greater prevalence of treated hyperlipidemia (p<0.001) than those with plain obesity who showed only higher LDL and HDL cholesterol levels (+9.0% and +16.0%). In response to three-weeks of standardized life-style change, both groups improved their vital variables and risk scores (p<0.001). While improvement in cholesterol slightly favored patients with plain obesity, the need for anti-hyperlipidemics (+25%) rose in both groups, albeit that for anti-hypertensives (+50%) increased only in patients with obesity and add-on T2D. Conclusion: Moderate changes in lifestyle improve the clinical condition, including coronary heart disease and premature mortality risk scores (HARD-CHD and ABSI) in patients with obesity both in the absence and presence of T2D, with the latter seemingly increasing the risk of hepatic steatosis and systemic inflammation.

Effects of SGLT2 inhibitors on systemic and tissue low-grade inflammation: The potential contribution to diabetes complications and cardiovascular disease

Chronic low-grade inflammation is a recognized key feature associated with type 2 diabetes mellitus (T2DM) and its complications. In prospective randomized trials, sodium-glucose cotransporter type 2 (SGLT2) inhibitors have demonstrated benefits related to several cardiovascular and renal risk factors, including HbA_1c, blood pressure, body weight, renal hyperfiltration, and improvement of cardiorenal outcomes. SGLT2 inhibitors may improve adipose tissue function and induce decreases in serum leptin, TNF-α and IL-6 while increasing adiponectin. While data on high-sensitivity C-reactive protein and other inflammatory markers are relatively scarce in humans, in animals, a number of reports have shown reductions in cytokine and chemokine concentrations in parallel with protective effects against progression of atherosclerotic lesions. Experimental findings also suggest that part of the renoprotective effects of SGLT2 inhibition may be related to anti-inflammatory actions at the kidney level. Underlying mechanisms to explain this anti-inflammatory effect are multiple, but may involve weight loss, and reduction in adipose tissue inflammation, slight increase in ketone bodies and diminution of uric acid levels or attenuation of oxidative stress. However, further studies in diabetes patients with specific assessment of inflammatory markers are still necessary to determine the specific contribution of the anti-inflammatory action of SGLT2 inhibitors to the reduction of cardiovascular and renal complications and mortality observed with this class of antidiabetic drugs.

Role of oxylipins in cardiovascular diseases

Globally, cardiovascular diseases (CVDs) are the number one cause of mortality. Approximately 18 million people died from CVDs in 2015, representing more than 30% of all global deaths. New diagnostic tools and therapies are eagerly required to decrease the prevalence of CVDs related to mortality and/or risk factors leading to CVDs. Oxylipins are a group of metabolites, generated via oxygenation of polyunsaturated fatty acids that are involved in inflammation, immunity, and vascular functions, etc. Thus far, over 100 oxylipins have been identified, and have overlapping and interconnected roles. Important CVD pathologies such as hyperlipidemia, hypertension, thrombosis, hemostasis and diabetes have been linked to abnormal oxylipin signaling. Oxylipins represent a new era of risk markers and/or therapeutic targets in several diseases including CVDs. The role of many oxylipins in the progression or regression in CVD, however, is still not fully understood. An increased knowledge of the role of these oxygenated polyunsaturated fatty acids in cardiovascular dysfunctions or CVDs including hypertension could possibly lead to the development of biomarkers for the detection and their treatment in the future.

Impact of Diabetes Mellitus and Insulin on Nonalcoholic Fatty Liver Disease in the Morbidly Obese

INTRODUCTION AND AIM

The prevalence of obesity, type 2 diabetes mellitus and non-alcoholic fatty liver disease are increasing. Type 2 diabetes mellitus may aggravate non-alcoholic fatty liver disease, increasing the risk of developing cirrhosis and hepatocellular carcinoma. This study aims to determine the effect of type 2 diabetes mellitus and insulin therapy on non-alcoholic fatty liver disease in the patients with morbid obesity.

MATERIAL AND METHODS

Clinical, anthropometric and laboratory data were analyzed together with intraoperative liver biopsies from morbidly obese patients undergoing bariatric surgery.

RESULTS

219 patients with morbid obesity were evaluated. Systemic arterial hypertension (55.9% vs. 33.8%, p = 0.004) and dyslipidemia (67.1% vs. 39.0%, p &lt; 0.001) were more prevalent in patients with diabetes when compared to patients without diabetes. In multivariate analysis, type 2 diabetes mellitus was an independent risk factor for severe steatosis (RR = 2.04, p = 0.023) and severe fibrosis (RR = 4.57, p = 0.013). Insulin therapy was significantly associated with non-alcoholic steatohepatitis (RR = 1.89, p = 0.001) and fibrosis (RR = 1.75, p = 0.050) when all patients were analysed, but when only patients with diabetes were analysed, insulin therapy was not associated with non-alcoholic steatohepatitis or fibrosis.

CONCLUSION

Type 2 diabetes mellitus plays an important role in the progression of non-alcoholic fatty liver disease as an independent risk factor for severe fibrosis.

The possible factors affecting microglial activation in cases of obesity with cognitive dysfunction

Obesity has reached epidemic proportions in many countries around the world. Several studies have reported that obesity can lead to the development of cognitive decline. There is increasing evidence to demonstrate that microglia play a crucial role in cognitive decline in cases of obesity, Alzheimer's disease and also in the aging process. Although there have been several studies into microglia over the past decades, the mechanistic link between microglia and cognitive decline in obese models is still not fully understood. In this review, the current available evidence from both in vitro and in vivo investigations regarding the association between the alteration in microglial activity in different obese models with respect to cognition are included. The metabolite profiles from obesity, adiposity, dietary and hormone affected microglial activation and its function in the brain are comprehensively summarized. In addition, the possible roles of microglial activation in relation to cognitive dysfunction are also presented and discussed. To ensure a balanced perspective controversial reports regarding these issues are included and discussed.

Accumulating Data to Optimally Predict Obesity Treatment (ADOPT): Recommendations from the Biological Domain

BACKGROUND

The responses to behavioral, pharmacological, or surgical obesity treatments are highly individualized. The Accumulating Data to Optimally Predict obesity Treatment (ADOPT) project provides a framework for how obesity researchers, working collectively, can generate the evidence base needed to guide the development of tailored, and potentially more effective, strategies for obesity treatment.

OBJECTIVES

The objective of the ADOPT biological domain subgroup is to create a list of high-priority biological measures for weight-loss studies that will advance the understanding of individual variability in response to adult obesity treatments. This list includes measures of body composition, energy homeostasis (energy intake and output), brain structure and function, and biomarkers, as well as biobanking procedures, which could feasibly be included in most, if not all, studies of obesity treatment. The recommended high-priority measures are selected to balance needs for sensitivity, specificity, and/or comprehensiveness with feasibility to achieve a commonality of usage and increase the breadth and impact of obesity research.

SIGNIFICANCE

The accumulation of data on key biological factors, along with behavioral, psychosocial, and environmental factors, can generate a more precise description of the interplay and synergy among them and their impact on treatment responses, which can ultimately inform the design and delivery of effective, tailored obesity treatments.

Obesity-induced changes in lipid mediators persist after weight loss

BACKGROUND

Obesity induces significant changes in lipid mediators, however, the extent to which these changes persist after weight loss has not been investigated.

SUBJECTS/METHODS

We fed C57BL6 mice a high-fat diet to generate obesity and then switched the diet to a lower-fat diet to induce weight loss. We performed a comprehensive metabolic profiling of lipid mediators including oxylipins, endocannabinoids, sphingosines and ceramides in key metabolic tissues (including adipose, liver, muscle and hypothalamus) and plasma.

RESULTS

We found that changes induced by obesity were largely reversible in most metabolic tissues but the adipose tissue retained a persistent obese metabolic signature. Prostaglandin signaling was perturbed in the obese state and lasting increases in PGD2, and downstream metabolites 15-deoxy PGJ2 and delta-12-PGJ2 were observed after weight loss. Furthermore expression of the enzyme responsible for PGD2 synthesis (hematopoietic prostaglandin D synthase, HPGDS) was increased in obese adipose tissues and remained high after weight loss. We found that inhibition of HPGDS over the course of 5 days resulted in decreased food intake in mice. Increased HPGDS expression was also observed in human adipose tissues obtained from obese compared with lean individuals. We then measured circulating levels of PGD2 in obese patients before and after weight loss and found that while elevated relative to lean subjects, levels of this metabolite did not decrease after significant weight loss.

CONCLUSIONS

These results suggest that lasting changes in lipid mediators induced by obesity, still present after weight loss, may play a role in the biological drive to regain weight.

Effects of metformin treatment on serum levels of C-reactive protein and interleukin-6 in women with polycystic ovary syndrome: a meta-analysis: A PRISMA-compliant article

BACKGROUND

Metformin is effective for the treatment of polycystic ovary syndrome (PCOS), but conflicting results regarding its impact on serum levels of C-reactive protein (CRP) and interleukin-6 (IL-6) in women with PCOS have been reported. To provide high-quality evidence about the effect of treatment with metformin on CRP and IL-6 in PCOS, relevant studies that assessed the serum levels of CRP and IL-6 in women with PCOS receiving metformin treatment were reviewed and analyzed.

METHODS

A literature search was conducted in the Science Citation Index, PubMed, Embase, and Cochrane Library databases, and personal contact was made with the authors. Random-effects model was used to estimate the standardized mean differences (SMDs) with 95% confidence intervals (95% CIs). To ensure synthesis of the best available evidence, subgroup analysis, sensitivity analysis, meta-regression analysis, and publication bias were performed.

RESULTS

Of 216 studies identified, 20 were included in the meta-analysis (7 prospective, nonrandomized studies, and 13 randomized control trials). Data suggest that serum levels of CRP were decreased after metformin treatment in PCOS patients with an SMD (95% CI) of -0.86 [-1.24 to -0.48] and P = .000 (random-effects). However, significant heterogeneity was detected across studies (I = 84.6% and P = .000). Unfortunately, the sources of heterogeneity were not found by subgroup analysis and meta-regression analysis. Serum IL-6 concentrations were not significantly changed after metformin treatment in PCOS with an SMD (95% CI) of -0.48 [-1.26 to 0.31] and P > .05 (random-effects). Significant heterogeneity was also detected across studies (I = 90.9% and P = .000). The subgroup analysis suggested that treatment-related reductions in serum IL-6 levels were significantly correlated with BMI, whereas the sources of heterogeneity were not found. In addition, we noticed that metformin treatment could decrease BMI in the CRP and IL-6 related studies (SMD = -0.45, 95% CI: -0.68 to -0.23; SMD = -0.44, 95% CI: -0.73 to -0.16).

CONCLUSION

This meta-analysis showed a significant decrease of serum CRP levels, especially in obese women, but no significant changes in IL-6 levels after metformin treatment in women with PCOS. In general, the data support that early metformin therapy may ameliorate the state of chronic inflammation in women with PCOS. Considering the obvious heterogeneity reported in the literature, further well-designed investigations with larger samples are needed to ascertain the long-term effects of metformin on chronic inflammation in PCOS.

Dietary modulation of oxylipins in cardiovascular disease and aging

Oxylipins are a group of fatty acid metabolites generated via oxygenation of polyunsaturated fatty acids and are involved in processes such as inflammation, immunity, pain, vascular tone, and coagulation. As a result, oxylipins have been implicated in many conditions characterized by these processes, including cardiovascular disease and aging. The best characterized oxylipins in relation to cardiovascular disease are derived from the ω-6 fatty acid arachidonic acid. These oxylipins generally increase inflammation, hypertension, and platelet aggregation, although not universally. Similarly, oxylipins derived from the ω-6 fatty acid linoleic acid generally have more adverse than beneficial cardiovascular effects. Alternatively, most oxylipins derived from 20- and 22-carbon ω-3 fatty acids have anti-inflammatory, antiaggregatory, and vasodilatory effects that help explain the cardioprotective effects of these fatty acids. Much less is known regarding the oxylipins derived from the 18-carbon ω-3 fatty acid α-linolenic acid, but clinical trials with flaxseed supplementation have indicated that these oxylipins can have positive effects on blood pressure. Normal aging also is associated with changes in oxylipin levels in the brain, vasculature, and other tissues, indicating that oxylipin changes with aging may be involved in age-related changes in these tissues. A small number of trials in humans and animals with interventions that contain either 18-carbon or 20- and 22-carbon ω-3 fatty acids have indicated that dietary-induced changes in oxylipins may be beneficial in slowing the changes associated with normal aging. In summary, oxylipins are an important group of molecules amenable to dietary manipulation to target cardiovascular disease and age-related degeneration.NEW & NOTEWORTHY Oxylipins are an important group of fatty acid metabolites amenable to dietary manipulation. Because of the role they play in cardiovascular disease and in age-related degeneration, oxylipins are gaining recognition as viable targets for specific dietary interventions focused on manipulating oxylipin composition to control these biological processes.

Potential Impact of Nutrition on Immune System Recovery from Heavy Exertion: A Metabolomics Perspective

This review describes effective and ineffective immunonutrition support strategies for the athlete, with a focus on the benefits of carbohydrates and polyphenols as determined from metabolomics-based procedures. Athletes experience regular cycles of physiological stress accompanied by transient inflammation, oxidative stress, and immune perturbations, and there are increasing data indicating that these are sensitive to nutritional influences. The most effective nutritional countermeasures, especially when considered from a metabolomics perspective, include acute and chronic increases in dietary carbohydrate and polyphenols. Carbohydrate supplementation reduces post-exercise stress hormone levels, inflammation, and fatty acid mobilization and oxidation. Ingestion of fruits high in carbohydrates, polyphenols, and metabolites effectively supports performance, with added benefits including enhancement of oxidative and anti-viral capacity through fruit metabolites, and increased plasma levels of gut-derived phenolics. Metabolomics and lipidomics data indicate that intensive and prolonged exercise is associated with extensive lipid mobilization and oxidation, including many components of the linoleic acid conversion pathway and related oxidized derivatives called oxylipins. Many of the oxylipins are elevated with increased adiposity, and although low in resting athletes, rise to high levels during recovery. Future targeted lipidomics-based studies will help discover whether n-3-polyunsaturated fatty acid (n-3-PUFA) supplementation enhances inflammation resolution in athletes post-exercise.

Obesity is positively associated with arachidonic acid-derived 5- and 11-hydroxyeicosatetraenoic acid (HETE)

BACKGROUND

Oxylipids are oxygenated polyunsaturated fatty acid (PUFA) metabolites that are responsible for the onset and resolution of the inflammatory response. Enzymatic oxygenation through the lipoxygenase (LOX) or cytochrome P450 (CYP) pathways can form oxylipids that have either proinflammatory or proresolving functions depending on the type of PUFA substrate and degree of metabolism. The objective of this study was to determine how PUFA substrates and their corresponding oxylipids are associated with obesity.

METHODS

Plasma non-esterified FA and oxylipids were isolated from 123 Caucasian males using solid phase extraction and quantified using high performance liquid chromatography-tandem mass spectrometry. Statistical analyses included linear regressions and polytomous logistic regressions, and the responses were body mass index (BMI) and waist circumference (WC), and serum leptin, total adiponectin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and C-peptide. Models were adjusted for age and smoking, and p-values were corrected for false discovery per Benjamini-Hochberg and Bonferroni.

RESULTS

We report that BMI, WC, and several serum cytokines were highly associated arachidonic acid (ARA)-derived hydroxyeicosatetraenoic acids (HETEs), and vicinal diols (i.e., alcohols on adjacent carbon atoms) derived from several PUFAs. There was a significant linear relationship between BMI, WC, and serum leptin, and ARA-derived 5-, 11-, and 15-HETE. Specifically, BMI and WC were positively associated with proinflammatory 5- and 11-hydroxyeicosatetraenoic acid (HETE), even after normalization to ARA concentrations and false discovery p-value correction. Individuals with 5-HETE concentrations >5.01nmol/L or 11-HETE concentrations and >0.89nmol/L were over 5 times more likely to be obese compared to those with ≤1.86nmol/L and ≤0.39nmol/L, respectively. Vicinal diols from linoleic, eicosapentaenoic, and docosahexaenoic acid were inversely associated with obesity. Across all statistical tests, vicinal diols were inversely associated with obesity whether normalized to parent PUFA concentrations or normalized to precursor epoxides. Interestingly, the proinflammatory cytokines IL-6 and TNF-α were not associated with any oxylipids. Since 5-HETE is a 5LOX product, 11-HETE is marker of lipid peroxidation, and vicinal diols are formed through soluble epoxide hydrolase (sEH) metabolism of CYP epoxygenated PUFAs, therefore, these results indicate that obesity is likely associated with altered metabolism with distinct oxygenating pathways. Taken together, our results indicate that obesity is associated with specific oxylipids indicative of altered PUFA metabolism through several pathways (i.e., LOX, reactive oxygen species, and sEH and CYP epoxygenase), rather than attributed solely to altered dietary PUFA intake.

Effect of a long-term intensive lifestyle intervention on prevalence of cognitive impairment

OBJECTIVE

To assess whether an average of 10 years of lifestyle intervention designed to reduce weight and increase physical activity lowers the prevalence of cognitive impairment among adults at increased risk due to type 2 diabetes and obesity or overweight.

METHODS

Central adjudication of mild cognitive impairment and probable dementia was based on standardized cognitive test battery scores administered to 3,802 individuals who had been randomly assigned, with equal probability, to either the lifestyle intervention or the diabetes support and education control. When scores fell below a prespecified threshold, functional information was obtained through proxy interview.

RESULTS

Compared with control, the intensive lifestyle intervention induced and maintained marked differences in weight loss and self-reported physical activity throughout follow-up. At an average (range) of 11.4 (9.5-13.5) years after enrollment, when participants' mean age was 69.6 (54.9-87.2) years, the prevalence of mild cognitive impairment and probable dementia was 6.4% and 1.8%, respectively, in the intervention group, compared with 6.6% and 1.8%, respectively, in the control group (p = 0.93). The lack of an intervention effect on the prevalence of cognitive impairment was consistent among individuals grouped by cardiovascular disease history, diabetes duration, sex, and APOE ε4 allele status (all p ≥ 0.50). However, there was evidence (p = 0.03) that the intervention effect ranged from benefit to harm across participants ordered from lowest to highest baseline BMI.

CONCLUSIONS

Ten years of behavioral weight loss intervention did not result in an overall difference in the prevalence of cognitive impairment among overweight or obese adults with type 2 diabetes.

CLINICALTRIALSGOV IDENTIFIER

NCT00017953 (Action for Health in Diabetes).

LEVEL OF EVIDENCE

This study provides Class II evidence that for overweight adults with type 2 diabetes, a lifestyle intervention designed to reduce weight and increase physical activity does not lower the risk of cognitive impairment.

Modified lingguizhugan decoction incorporated with dietary restriction and exercise ameliorates hyperglycemia, hyperlipidemia and hypertension in a rat model of the metabolic syndrome

Background

Modified Lingguizhugan Decoction (MLD) came from famous Chinese medicine Linggui Zhugan Decoction. The MLD is used for the treatment of metabolic syndrome in the clinical setting. Our study focuses on the comprehensive treatment of MLD incorporated with dietary restriction and exercise in a rat model of the metabolic syndrome (MS).

Methods

Rats were divided into five groups: control group (Cont), high-fat diet group (HFD), high-fat diet incorporated with dietary restriction group (HFD-DR), exercise incorporated with dietary restriction group (HFD-DR-Ex) and MLD incorporated with dietary restriction and exercise group (HFD-DR-Ex-MLD). Treatments were conducted for 1 week after feeding high-fat diet for 12 weeks. The effects of treatments on high fat diet-induced obesity, hyperglycemia, hyperlipidemia, hypertension, hepatic injury and insulin resistance in rats of MS were examined. In addition, the tumor necrosis factor-α (TNF-α), leptin and protein kinase B (PKB) in rats serum and liver were also examined by enzyme-linked immunosorbent assay (ELISA).

Results

After a week’s intervention by dietary restriction, dietary restriction incorporated with exercise or MLD, compared with HFD rats, the relative weight of liver and fat, levels of triglyceride, total cholesterol, low-density lipoprotein, free fatty acid, aspartate aminotransferase, glutamic-pyruvic transaminase and alkaline phosphatase, insulin, were significantly decreased (p < 0.05 or 0.01). This treatment also inhibited abnormal increases of TNF-α, leptin and PKB in serum and liver.

Conclusion

MLD incorporated with dietary restriction and exercise treatment exhibit effects in alleviating high-fat diet-induced obesity, hyperglycemia, hyperlipidemia, hypertension, hepatic injury and insulin resistance, which are possibly due to the down-regulation of TNF-α, leptin and PKB.

Alterations of specific lipid groups in serum of obese humans: a review

Obesity is a major contributor to the dysfunction of liver, cardiac, pulmonary, endocrine and reproductive system, as well as a component of metabolic syndrome. Although development of obesity-related disorders is associated with lipid abnormalities, most previous studies dealing with the problem in question were limited to routinely determined parameters, such as serum concentrations of triacylglycerols, total cholesterol, low-density and high-density lipoprotein cholesterol. Many authors postulated to extend the scope of analysed lipid compounds and to study obesity-related alterations in other, previously non-examined groups of lipids. Comprehensive quantitative, structural and functional analysis of specific lipid groups may result in identification of new obesity-related alterations. The review summarizes available evidence of obesity-related alterations in various groups of lipids and their impact on health status of obese subjects. Further, the role of diet and endogenous lipid synthesis in the development of serum lipid alterations is discussed, along with potential application of various lipid compounds as risk markers for obesity-related comorbidities.

Obesity: systemic and pulmonary complications, biochemical abnormalities, and impairment of lung function

Obesity is currently one of the major epidemics of this millennium and affects individuals throughout the world. It causes multiple systemic complications, some of which result in severe impairment of organs and tissues. These complications involve mechanical changes caused by the accumulation of adipose tissue and the numerous cytokines produced by adipocytes. Obesity also significantly interferes with respiratory function by decreasing lung volume, particularly the expiratory reserve volume and functional residual capacity. Because of the ineffectiveness of the respiratory muscles, strength and resistance may be reduced. All these factors lead to inspiratory overload, which increases respiratory effort, oxygen consumption, and respiratory energy expenditure. It is noteworthy that patterns of body fat distribution significantly influence the function of the respiratory system, likely via the direct mechanical effect of fat accumulation in the chest and abdominal regions. Weight loss caused by various types of treatment, including low-calorie diet, intragastric balloon, and bariatric surgery, significantly improves lung function and metabolic syndrome and reduces body mass index. Despite advances in the knowledge of pulmonary and systemic complications associated with obesity, longitudinal randomized studies are needed to assess the impact of weight loss on metabolic syndrome and lung function.