Clinical and metabolic characterization of obese subjects without non-alcoholic fatty liver: A targeted metabolomics approach

Unique metabolomics characteristics for distinguishing cirrhosis related to different liver diseases: A systematic review and meta-analysis

BACKGROUND AND AIM

Clinical evidence for early identification and diagnosis of liver cirrhosis (LC) caused by different types of liver disease is limited. We investigated this topic through a meta-analysis of quantitative metabolomics.

METHODS

Four databases were searched until October 31, 2022 for studies comparing metabolite levels between patients with different types of liver disease and control individuals. A random-effects model was applied for the meta-analysis.

RESULTS

This study included 55 studies with 8266 clinical participants, covering 348 metabolites. In LC related to drug-induced liver injury (DILI), hepatitis B virus (HBV) infection, and non-alcoholic fatty liver disease (NAFLD), the primary bile acid biosynthesis (taurocholic acid: SMD, 1.08[0.81, 1.35]; P < 0.00001; glycocholic acid: SMD, 1.35[1.07, 1.62]; P < 0.00001; taurochenodeoxycholic acid: SMD, 1.36[0.94, 1.78]; P < 0.00001; glycochenodeoxycholic acid: SMD, 1.49[0.93, 2.06]; P < 0.00001), proline and arginine (l-proline: SMD, 1.06[0.53, 1.58]; P < 0.0001; hydroxyproline: SMD, 0.81[0.30, 1.33]; P = 0.002), and fatty acid biosynthesis (palmitic acid: SMD, 0.44[0.21, 0.67]; P = 0.0002; oleic acid: SMD, 0.46[0.19, 0.73]; P = 0.0008; stearic acid: SMD, 0.37[0.07, 0.68]; P = 0.02) metabolic pathways were significantly altered.

CONCLUSION

We identified key biomarkers and metabolic characteristics for distinguishing and identifying LC related to different types of liver disease, providing a new perspective for early diagnosis, disease monitoring, and precise treatment.

Associations between muscle mass, strength, and performance and non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a rising global health issue. The influence of muscle in its pathophysiology has recently gained attention. Our aim was to investigate the association of low muscle mass, strength, and performance with the presence and severity of NAFLD.

METHODS

Patients with metabolic syndrome followed in an outpatient clinic, were consecutively included, between April 1st and December 31st, 2019. Abdominal ultrasound for the diagnosis of NAFLD, NAFLD fibrosis score (NFS) and Fibrosis-4 Index (FIB-4) for determination of significant fibrosis, dual-energy X-ray absorptiometry for calculation of skeletal muscle index (SMI = appendicular skeletal mass / weight x100) and sarcopenic index (SI = appendicular skeletal mass / Body Mass Index), and the Short Physical Performance Battery for muscle strength and performance assessment were performed. Sarcopenia was defined as low muscle strength and low SMI or SI.

RESULTS

A total of 157 patients were included, of which 68.8% had NAFLD, 66.2% low SMI, 50.3% low SI, 16.6% low performance and 11.5% low strength. In patients with NAFLD, prevalence of significant fibrosis by NFS was 15.7%. Low SMI was associated with presence of NAFLD when adjusted for age, sex, type 2 diabetes mellitus, hypertension, and dyslipidemia, but not for body mass index and waist circumference. Low SMI, low SI, and sarcopenia were associated with significant fibrosis in univariate analysis; the small number of events precluded a multivariable analysis.

CONCLUSIONS

Low SMI was associated with NAFLD independently of demographics and comorbidities but not of other parameters of body composition. This contrasts with most studies published on this matter.

Baseline Tyrosine Level Is Associated with Dynamic Changes in FAST Score in NAFLD Patients under Lifestyle Modification

Noninvasive risk stratification is a challenging issue in the management of patients with nonalcoholic fatty liver disease (NAFLD). This study aimed to identify multiomics-based predictors of NAFLD progression, as assessed by changes in serial FibroScan-aspartate aminotransferase (FAST) scores during lifestyle modification. A total of 266 patients with available metabolomics and genotyping data were included. The follow-up sub-cohort included patients with paired laboratory and transient elastography results (n = 160). The baseline median FAST score was 0.37. The PNPLA3 rs738409 genotype was significantly associated with a FAST score > 0.35. Circulating metabolomics significantly associated with a FAST score > 0.35 included SM C24:0 (odds ratio [OR] = 0.642; 95% confidence interval [CI], 0.463-0.891), PC ae C40:6 (OR = 0.477; 95% CI, 0.340-0.669), lysoPC a C18:2 (OR = 0.570; 95% CI, 0.417-0.779), and tyrosine (OR = 2.743; 95% CI, 1.875-4.014). A combination of these metabolites and PNPLA3 genotype yielded a c-index = 0.948 for predicting a FAST score > 0.35. In the follow-up sub-cohort (median follow-up = 23.7 months), 47/76 patients (61.8%) with a baseline FAST score > 0.35 had a follow-up FAST score ≤ 0.35. An improved FAST score at follow-up was significantly associated with age, serum alanine aminotransferase, and tyrosine. In conclusion, baseline risk stratification in NAFLD patients may be assisted using a multiomics-based model. Particularly, patients with increased tyrosine may benefit from an earlier switch to pharmacologic approaches.

Changes in Plasma Metabolomic Profile Following Bariatric Surgery, Lifestyle Intervention or Diet Restriction-Insights from Human and Rat Studies

Although bariatric surgery is known to change the metabolome, it is unclear if this is specific for the intervention or a consequence of the induced bodyweight loss. As the weight loss after Roux-en-Y Gastric Bypass (RYGB) can hardly be mimicked with an evenly effective diet in humans, translational research efforts might be helpful. A group of 188 plasma metabolites of 46 patients from the randomized controlled Würzburg Adipositas Study (WAS) and from RYGB-treated rats (n = 6) as well as body-weight-matched controls (n = 7) were measured using liquid chromatography tandem mass spectrometry. WAS participants were randomized into intensive lifestyle modification (LS, n = 24) or RYGB (OP, n = 22). In patients in the WAS cohort, only bariatric surgery achieved a sustained weight loss (BMI -34.3% (OP) vs. -1.2% (LS), p ≤ 0.01). An explicit shift in the metabolomic profile was found in 57 metabolites in the human cohort and in 62 metabolites in the rodent model. Significantly higher levels of sphingolipids and lecithins were detected in both surgical groups but not in the conservatively treated human and animal groups. RYGB leads to a characteristic metabolomic profile, which differs distinctly from that following non-surgical intervention. Analysis of the human and rat data revealed that RYGB induces specific changes in the metabolome independent of weight loss.

Multi-Omics Nutritional Approaches Targeting Metabolic-Associated Fatty Liver Disease

Currently, metabolic-associated fatty liver disease (MAFLD) is a leading global cause of chronic liver disease, and is expected to become one of the most common indications of liver transplantation. MAFLD is associated with obesity, involving multiple mechanisms such as alterations in lipid metabolism, insulin resistance, hyperinflammation, mitochondrial dysfunction, cell apoptosis, oxidative stress, and extracellular matrix formation. However, the onset and progression of MAFLD is variable among individuals, being influenced by intrinsic (personal) and external environmental factors. In this context, sequence structural variants across the human genome, epigenetic phenomena (i.e., DNA methylation, histone modifications, and long non-coding RNAs) affecting gene expression, gut microbiota dysbiosis, and metabolomics/lipidomic fingerprints may account for differences in MAFLD outcomes through interactions with nutritional features. This knowledge may contribute to gaining a deeper understanding of the molecular and physiological processes underlying MAFLD pathogenesis and phenotype heterogeneity, as well as facilitating the identification of biomarkers of disease progression and therapeutic targets for the implementation of tailored nutritional strategies. This comprehensive literature review highlights the potential of nutrigenetic, nutriepigenetic, nutrimetagenomic, nutritranscriptomics, and nutrimetabolomic approaches for the prevention and management of MAFLD in humans through the lens of precision nutrition.

The Emerging Role of Branched-Chain Amino Acids in Liver Diseases

Chronic liver diseases pose a substantial health burden worldwide, with approximately two million deaths each year. Branched-chain amino acids (BCAAs)-valine, leucine, and isoleucine-are a group of essential amino acids that are essential for human health. Despite the necessity of a dietary intake of BCAA, emerging data indicate the undeniable correlation between elevated circulating BCAA levels and chronic liver diseases, including non-alcoholic fatty liver diseases (NAFLD), cirrhosis, and hepatocellular carcinoma (HCC). Moreover, circulatory BCAAs were positively associated with a higher cholesterol level, liver fat content, and insulin resistance (IR). However, BCAA supplementation was found to provide positive outcomes in cirrhosis and HCC patients. This review will attempt to address the contradictory claims found in the literature, with a special focus on BCAAs' distribution, key signaling pathways, and the modulation of gut microbiota. This should provide a better understanding of BCAAs' possible contribution to liver health.

Comparison of the Lipidomic Signature of Fatty Liver in Children and Adults: A Cross-Sectional Study

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is an increasingly common condition in children characterised by insulin resistance and altered lipid metabolism. Affected patients are at increased risk of cardiovascular disease (CVD) and children with NAFLD are likely to be at risk of premature cardiac events. Evaluation of the plasma lipid profile of children with NAFLD offers the opportunity to investigate these perturbations and understand how closely they mimic the changes seen in adults with cardiometabolic disease.

METHODS

We performed untargeted liquid chromatography-mass spectrometry (LC-MS) plasma lipidomics on 287 children: 19 lean controls, 146 from an obese cohort, and 122 NAFLD cases who had undergone liver biopsy. Associations between lipid species and liver histology were assessed using regression adjusted for age and sex. Results were then replicated using data from 9500 adults with metabolic phenotyping.

RESULTS

More severe paediatric NAFLD was associated with lower levels of long chain, polyunsaturated phosphatidylcholines (pC) and triglycerides (TG). Similar trends in pC and TG chain length and saturation were seen in adults with hepatic steatosis; however, many of the specific lipids associated with NAFLD differed between children and adults. Five lipids replicated in adults (including PC(36:4)) have been directly linked to death and cardiometabolic disease, as well as indirectly via genetic variants.

CONCLUSION

These findings suggest that, whilst similar pathways of lipid metabolism are perturbed in paediatric NAFLD as in cardiometabolic disease in adults, the specific lipid signature in children is different.

Improvement in Mung Bean Peptide on High-Fat Diet-Induced Insulin Resistance Mice Using Untargeted Serum Metabolomics

This study aimed to elucidate the potential regulatory mechanism of mung bean peptides (MBPs) on glucolipid metabolism in insulin-resistant mice induced by high-fat diet (HFD) using untargeted serum metabolomics, enzyme linked immunosorbent assay (ELISA), intraperitoneal injection glucose tolerance test (IPGTT), insulin tolerance test (IPITT), and hematoxylin-eosin staining (H&amp;E). The regulatory effect of MBPs for alleviating insulin resistance was studied by measuring body weight, fasting blood glucose (FBG) and serum insulin levels, C-Peptide levels, inflammatory and antioxidant factors, and histopathological observation of C57BL/6 mice. The experimental results showed that dietary intervention with MBPs (245 mg/kg/d) for 5 weeks significantly relieved insulin resistance in HFD mice. The body weight, insulin resistance index, and the levels of FBG, C-Peptide, IL-6, TNF-α, and MDA in the serum of HFD mice significantly decreased (P &lt; 0.05). Conversely, SOD content and pancreatic β cell function index significantly increased (P &lt; 0.05), and the damaged pancreatic tissue was repaired. One biomarker associated with insulin resistance was glycine. In addition, there were four important differential metabolites: pyroglutamate, D-glutamine, aminoadipic acid, and nicotinamide, involved in 12 metabolic pathway changes. It was found that MBPs may regulate amino acid, glycerol phospholipid, fatty acid, alkaloid, and nicotinamide metabolism to regulate the metabolic profile of HFD mice in a beneficial direction.

Adiposity, metabolomic biomarkers, and risk of nonalcoholic fatty liver disease: a case-cohort study

BACKGROUND

Globally, the burden of obesity and associated nonalcoholic fatty liver disease (NAFLD) are rising, but little is known about the role that circulating metabolomic biomarkers play in mediating their association.

OBJECTIVES

We aimed to examine the observational and genetic associations of adiposity with metabolomic biomarkers and the observational associations of metabolomic biomarkers with incident NAFLD.

METHODS

A case-subcohort study within the prospective China Kadoorie Biobank included 176 NAFLD cases and 180 subcohort individuals and measured 1208 metabolites in stored baseline plasma using a Metabolon assay. In the subcohort the observational and genetic associations of BMI with biomarkers were assessed using linear regression, with adjustment for multiple testing. Cox regression was used to estimate adjusted HRs for NAFLD associated with biomarkers.

RESULTS

In observational analyses, BMI (kg/m2; mean: 23.9 in the subcohort) was associated with 199 metabolites at a 5% false discovery rate. The effects of genetically elevated BMI with specific metabolites were directionally consistent with the observational associations. Overall, 35 metabolites were associated with NAFLD risk, of which 15 were also associated with BMI, including glutamate (HR per 1-SD higher metabolite: 1.95; 95% CI: 1.48, 2.56), cysteine-glutathione disulfide (0.44; 0.31, 0.62), diaclyglycerol (C32:1) (1.71; 1.24, 2.35), behenoyl dihydrosphingomyelin (C40:0) (1.92; 1.42, 2.59), butyrylcarnitine (C4) (1.91; 1.38, 2.35), 2-hydroxybehenate (1.81; 1.34, 2.45), and 4-cholesten-3-one (1.79; 1.27, 2.54). The discriminatory performance of known risk factors was increased when 28 metabolites were also considered simultaneously in the model (weighted C-statistic: 0.84 to 0.90; P  < 0.001).

CONCLUSIONS

Among relatively lean Chinese adults, a range of metabolomic biomarkers are associated with NAFLD risk and these biomarkers may lie on the pathway between adiposity and NAFLD.

Contribution of Metabolomics to the Understanding of NAFLD and NASH Syndromes: A Systematic Review

Several differential panels of metabolites have been associated with the presence of metabolic syndrome and its related conditions, namely non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). This study aimed to perform a systematic review to summarize the most recent finding in terms of circulating biomarkers following NAFLD/NASH syndromes. Hence, the research was focused on NAFLD/NASH studies analysed by metabolomics approaches. Following Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, a systematic search was conducted on the PubMed database. The inclusion criteria were (i) publication date between 2010 and 2021, (ii) presence of the combination of terms: metabolomics and NAFLD/NASH, and (iii) published in a scholarly peer-reviewed journal. Studies were excluded from the review if they were (i) single-case studies, (ii) unpublished thesis and dissertation studies, and (iii) not published in a peer-reviewed journal. Following these procedures, 10 eligible studies among 93 were taken into consideration. The metabolisms of amino acids, fatty acid, and vitamins were significantly different in patients affected by NAFLD and NASH compared to healthy controls. These findings suggest that low weight metabolites are an important indicator for NAFLD/NASH syndrome and there is a strong overlap between NAFLD/NASH and the metabolic syndrome. These findings may lead to new perspectives in early diagnosis, identification of novel biomarkers, and providing novel targets for pharmacological interventions.

Oxidized low-density lipoprotein activates extracellular signal-regulated kinase signaling to downregulate sortilin expression in liver sinusoidal endothelial cells

BACKGROUND AND AIM

Both type 2 diabetes mellitus and non-alcoholic fatty liver disease are closely associated with elevated levels of low-density lipoprotein cholesterol and its oxidized form (ox-LDL). This study aimed to investigate the regulation of sortilin in liver tissue and its potential implications for lipid metabolism.

METHODS

Sixty male Wistar rats were randomly divided into four groups: control group (n = 15), ox-LDL group (n = 15), PD98059 group (n = 15), and ox-LDL + PD98059 group (n = 15). Liver sinusoidal endothelial cells were extracted from liver tissue of the control group and were identified using an anti-CD31 antibody. Lipid droplet accumulation was observed by Oil red O and hematoxylin-eosin staining. The protein expression levels were detected by immunohistochemical staining, real-time reverse transcription-polymerase chain reaction, and western blot. Histopathologic examinations were performed by Gomori methenamine silver staining.

RESULTS

The ox-LDL group exhibited increased lipid droplet accumulation. Further, ox-LDL activated the extracellular signal-regulated kinase (ERK)-mediated downregulation of sortilin expression, whereas blocking of ERK signaling by PD98059 increased sortilin protein expression. Consistently, hematoxylin-eosin staining showed that the structure of the hepatocytes was loose and disordered in arrangement, with lipid droplets present in the cytoplasm of the ox-LDL group. However, PD98059 significantly improved the integration of the scaffold structure. Gomori methenamine silver staining showed that the ox-LDL group had darker and more obvious fragmented silver nitrate deposits in the basement membrane and sinus space.

CONCLUSIONS

Sortilin can protect liver sinusoidal endothelial cells from injury and maintain integration of the liver scaffold structure in ox-LDL-induced lipid-injured liver.

Understanding the fundamentals of microbial remediation with emphasize on metabolomics

The post-genomic tool metabolomics is a great advancement in science and technology which acquires novel strategies and pathways to analyze various biological compounds. Metabolomics aids in retrieving the qualitative and quantitative data from the various biological system. The current review is focused on the application of metabolomics in bioremediation and helps to focus on the xenobiotic compounds which are discharged into the environment and have long term impact. The microbial based biodegradation can be effectively used along with the combination of metabolomic approach for a better understanding of the breakdown of certain recalcitrant. Additionally, this review also discusses the candidate gene approach which helps to comprehend the functional analysis of microbial genes in response to different contaminants. Therefore, this review intends to discuss the metabolomics in bioremediation by studying the complete set of metabolites involved during the process of degradation and their interaction with the environment.

Circulating microRNAs 34a, 122, and 192 are linked to obesity-associated inflammation and metabolic disease in pediatric patients

BACKGROUND

Obesity-associated chronic low-grade inflammation leads to dysregulation of central lipid and glucose metabolism pathways leading to metabolic disorders. MicroRNAs (miRNAs) are known to control regulators of metabolic homeostasis. We aimed to assess the relationship of circulating miRNAs with inflammatory modulators and metabolic disorders in pediatric obesity.

METHODS

From a pediatric cohort with severe obesity (n = 109), clinically thoroughly characterized including diverse routine blood parameters, oral glucose tolerance test, and liver MRI, a panel of 16 circulating miRNAs was quantified using qRT-PCR. Additionally, markers of inflammation TNFα, IL1 receptor antagonist, procalcitonin, CRP, and IL-6 were measured.

RESULTS

Markers of obesity-associated inflammation, TNFα, IL-1Ra, and procalcitonin, all significantly correlated with concentrations of miRNAs 122 and 192. Concentrations of these miRNAs negatively correlated with serum adiponectin and were among those strongly linked to parameters of dyslipidemia and liver function. Moreover, miRNA122 concentrations correlated with HOMA-IR. Several miRNA levels including miRNAs 34a, 93, 122, and 192 were statistically significantly differing between individuals with prediabetes, impaired glucose tolerance, metabolic syndrome, or nonalcoholic fatty liver disease compared to the respective controls. Additionally, miRNA 192 was significantly elevated in metabolically unhealthy obesity.

CONCLUSIONS

A miRNA pattern associated with obesity-associated inflammation and comorbidities may be used to distinguish metabolically healthy from unhealthy pediatric patients with obesity. Moreover, these changes in epigenetic regulation could potentially be involved in the etiology of obesity-linked metabolic disease in children and adolescents.

COVID-19 and non-alcoholic fatty liver disease: Two intersecting pandemics

BACKGROUND

Initial evidence from China suggests that most vulnerable subjects to COVID-19 infection suffer from pre-existing illness, including metabolic abnormalities. The pandemic characteristics and high-lethality rate of COVID-19 infection have raised concerns about interactions between virus pathobiology and components of the metabolic syndrome.

METHODS

We harmonized the information from the recent existing literature on COVID-19 acute pandemic and mechanisms of damage in non-alcoholic fatty liver disease (NAFLD), as an example of chronic (non-communicable) metabolic pandemic.

RESULTS

COVID-19-infected patients are more fragile with underlying metabolic illness, including hypertension, cardiovascular disease, type 2 diabetes, chronic lung diseases (e.g. asthma, chronic obstructive pulmonary disease and emphysema) and metabolic syndrome. During metabolic abnormalities, expansion of metabolically active fat ('overfat condition') parallels chronic inflammatory changes, development of insulin resistance and accumulation of fat in configuring NAFLD. The deleterious interplay of inflammatory pathways chronically active in NAFLD and acutely in COVID-19-infected patients, can explain liver damage in a subgroup of patients and might condition a worse outcome in metabolically compromised NAFLD patients. In a subgroup of patients with NAFLD, the underlying liver fibrosis might represent an additional and independent risk factor for severe COVID-19 illness, irrespective of metabolic comorbidities.

CONCLUSIONS

NAFLD can play a role in the outcome of COVID-19 illness due to frequent association with comorbidities. Initial evidences suggest that increased liver fibrosis in NAFLD might affect COVID-19 outcome. In addition, long-term monitoring of post-COVID-19 NAFLD patients is advisable, to document further deterioration of liver damage. Further studies are required in this field.

Oxidative Stress and Pro-Inflammatory Status in Patients with Non-Alcoholic Fatty Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive fat accumulation, especially triglycerides, in hepatocytes. If the pathology is not properly treated, it can progress to nonalcoholic steatohepatitis (NASH) and continue to fibrosis, cirrhosis or hepatocarcinoma.

OBJECTIVE

The aim of the current research was to identify the plasma biomarkers of liver damage, oxidative stress and inflammation that facilitate the early diagnosis of the disease and control its progression.

METHODS

Antioxidant and inflammatory biomarkers were measured in the plasma of patients diagnosed with NAFLD (n = 100 adults; 40-60 years old) living in the Balearic Islands, Spain. Patients were classified according to the intrahepatic fat content (IFC) measured by magnetic resonance imaging (MRI).

RESULTS

Circulating glucose, glycosylated haemoglobin, triglycerides, low-density lipoprotein-cholesterol, aspartate aminotransferase and alanine aminotransferase were higher in patients with an IFC ≥ 2 of NAFLD in comparison to patients with an IFC of 0 and 1. The plasma levels of catalase, irisin, interleukin-6, malondialdehyde, and cytokeratin 18 were higher in stage ≥2 subjects, whereas the resolvin D1 levels were lower. No differences were observed in xanthine oxidase, myeloperoxidase, protein carbonyl and fibroblast growth factor 21 depending on liver status.

CONCLUSION

The current available data show that the severity of NAFLD is associated with an increase in oxidative stress and proinflammatory status. It may be also useful as diagnostic purpose in clinical practice.

Hepatic consequences of COVID-19 infection. Lapping or biting?

The outbreak of coronavirus disease 2019 (COVID-19) starting last December in China placed emphasis on liver involvement during infection. This review discusses the underlying mechanisms linking COVID-19 to liver dysfunction, according to recent available information, while waiting further studies. The manifestations of liver damage are usually mild (moderately elevated serum aspartate aminotransferase activities), and generally asymptomatic. Few patients can still develop severe liver problems, and therapeutic options can be limited. Liver dysfunction may affect about one-third of the patients, with prevalence greater in men than women, and in elderly. Mechanisms of damage are complex and include direct cholangiocyte damage and other coexisting conditions such as the use of antiviral drugs, systemic inflammatory response, respiratory distress syndrome-induced hypoxia, sepsis, and multiple organ dysfunction. During new COVID-19 infections, liver injury may be observed. If liver involvement appears during COVID-19 infection, however, attention is required. This is particularly true if patients are older or have a pre-existing history of liver diseases. During COVID-19 infection, the onset of liver damage impairs the prognosis, and hospital stay is longer.

Comparison of the Serum Metabolic Fingerprint of Different Exercise Modes in Men with and without Metabolic Syndrome

Exercise plays a beneficial role in the treatment of metabolic syndrome (MetS). Metabolomics can provide new insights and facilitate the optimization of exercise prescription. This study aimed to investigate whether the response of the human serum metabolic fingerprint to exercise depends on exercise mode or the presence of MetS. Twenty-three sedentary men (nine with MetS and fourteen healthy) completed four trials: Resting, high-intensity interval exercise (HIIE), continuous moderate-intensity exercise (CME), and resistance exercise (RE). Blood samples were collected pre-exercise, immediately after exercise, and 1 h post-exercise for targeted metabolomic analysis in serum by liquid chromatography–mass spectrometry. Time exerted the strongest differentiating effect, followed by exercise mode. The largest changes from baseline were found in the immediate post-exercise samples. RE caused the strongest responses overall, followed by HIIE, while CME had minimal effect. Unlike previous results in urine, no valid model could separate the two groups in serum. Exercise exerted a beneficial effect on prominent serum biomarkers of metabolic risks, such as branched-chain amino acids, alanine, acetylcarnitine, choline, and betaine. These findings contribute to the ongoing research efforts to map the molecular responses to exercise and to optimize exercise guidelines for individuals at cardiometabolic risk.

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

INTRODUCTION

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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