Optimization of a GC-MS Injection-Port Derivatization Methodology to Enhance Metabolomics Analysis Throughput in Biological Samples.

Advances in metabolomics analysis and data treatment increase the knowledge of complex biological systems. One of the most used methodologies is gas chromatography-mass spectrometry (GC-MS) due to its robustness, high separation efficiency, and reliable peak identification through curated databases. However, methodologies are not standardized, and the derivatization steps in GC-MS can introduce experimental errors and take considerable time, exposing the samples to degradation. Here, we propose the injection-port derivatization (IPD) methodology to increase the throughput in plasma metabolomics analysis by GC-MS. The IPD method was evaluated and optimized for different families of metabolites (organic acids, amino acids, fatty acids, sugars, sugar phosphates, etc.) in terms of residence time, injection-port temperature, and sample/derivatization reagent ratio. Finally, the method's usefulness was validated in a study consisting of a cohort of obese patients with or without nonalcoholic steatohepatitis. Our results show a fast, reproducible, precise, and reliable method for the analysis of biological samples by GC-MS. Raw data are publicly available at MetaboLights with Study Identifier MTBLS5151.

The Proteome of Extracellular Vesicles Produced by the Human Gut Bacteria Bacteroides thetaiotaomicron In Vivo Is Influenced by Environmental and Host-Derived Factors.

Bacterial extracellular vesicles (BEVs) released from both Gram-negative and Gram-positive bacteria provide an effective means of communication and trafficking of cell signaling molecules. In the gastrointestinal tract (GIT) BEVs produced by members of the intestinal microbiota can impact host health by mediating microbe-host cell interactions. A major unresolved question, however, is what factors influence the composition of BEV proteins and whether the host influences protein packaging into BEVs and secretion into the GIT. To address this, we have analyzed the proteome of BEVs produced by the major human gut symbiont Bacteroides thetaiotaomicron both in vitro and in vivo in the murine GIT in order to identify proteins specifically enriched in BEVs produced in vivo. We identified 113 proteins enriched in BEVs produced in vivo, the majority (62/113) of which accumulated in BEVs in the absence of any changes in their expression by the parental cells. Among these selectively enriched proteins, we identified dipeptidyl peptidases and an asparaginase and confirmed their increased activity in BEVs produced in vivo. We also showed that intact BEVs are capable of degrading bile acids via a bile salt hydrolase. Collectively these findings provide additional evidence for the dynamic interplay of host-microbe interactions in the GIT and the existence of an active mechanism to drive and enrich a selected group of proteins for secretion into BEVs in the GIT. IMPORTANCE The gastrointestinal tract (GIT) harbors a complex community of microbes termed the microbiota that plays a role in maintaining the host's health and wellbeing. How this comes about and the nature of microbe-host cell interactions in the GIT is still unclear. Recently, nanosized vesicles naturally produced by bacterial constituents of the microbiota have been shown to influence responses of different host cells although the molecular basis and identity of vesicle-born bacterial proteins that mediate these interactions is unclear. We show here that bacterial extracellular vesicles (BEVs) produced by the human symbiont Bacteroides thetaiotaomicron in the GIT are enriched in a set of proteins and enzymes, including dipeptidyl peptidases, an asparaginase and a bile salt hydrolase that can influence host cell biosynthetic pathways. Our results provide new insights into the molecular basis of microbiota-host interactions that are central to maintaining GIT homeostasis and health.

In vitro fermentability of a broad range of natural ingredients by fecal microbiota from lean and obese individuals: potential health benefits.

The prevalence of obesity and related complications is continuously increasing while the gut microbiota might have a significant role to address this challenge. In this context, the food industry generates large amounts of residues that could be likely revalorised as functional ingredients. Hence, we evaluated the fermentability of food skins, husks, shells, trimming residues, mosses and mushrooms, which were subjected to in vitro fermentation with faecal microbiota from lean and obese adults. We demonstrated for the first time that pumpkin skin is highly fermented by human faecal microbiota showing pH-lowering effects and promoting gas and SCFA production. Furthermore, brewers' spent grain generated an inulin-like SCFA profile after microbial fermentation, whereas Irish moss, plum skin, quinoa husk and mushrooms, including Armillaria mellea and Boletus edulis, showed high fermentation rates. Remarkably, although propionate production was significantly higher in obese individuals, the fermentability of the ingredients was similar between lean and obese conditions.

Multi-omics approach to elucidate the gut microbiota activity: Metaproteomics and metagenomics connection.

Over the last few years, the application of high-throughput meta-omics methods has provided great progress in improving the knowledge of the gut ecosystem and linking its biodiversity to host health conditions, offering complementary support to classical microbiology. Gut microbiota plays a crucial role in relevant diseases such as obesity or cardiovascular disease (CVD), and its regulation is closely influenced by several factors, such as dietary composition. In fact, polyphenol-rich diets are the most palatable treatment to prevent hypertension associated with CVD, although the polyphenol-microbiota interactions have not been completely elucidated. For this reason, the aim of this study was to evaluate microbiota effect in obese rats supplemented by hesperidin, after being fed with cafeteria or standard diet, using a multi meta-omics approaches combining strategy of metagenomics and metaproteomics analysis. We reported that cafeteria diet induces obesity, resulting in changes in the microbiota composition, which are related to functional alterations at proteome level. In addition, hesperidin supplementation alters microbiota diversity and also proteins involved in important metabolic pathways. Overall, going deeper into strategies to integrate omics sciences is necessary to understand the complex relationships between the host, gut microbiota, and diet.

Immunohistochemical analysis of paraoxonases and chemokines in arteries of patients with peripheral artery disease.

Oxidative damage to lipids and lipoproteins is implicated in the development of atherosclerotic vascular diseases, including peripheral artery disease (PAD). The paraoxonases (PON) are a group of antioxidant enzymes, termed PON1, PON2, and PON3 that protect lipoproteins and cells from peroxidation and, as such, may be involved in protection against the atherosclerosis process. PON1 inhibits the production of chemokine (C-C motif) ligand 2 (CCL2) in endothelial cells incubated with oxidized lipoproteins. PON1 and CCL2 are ubiquitously distributed in tissues, and this suggests a joint localization and combined systemic effect. The aim of the present study has been to analyze the quantitative immunohistochemical localization of PON1, PON3, CCL2 and CCL2 receptors in a series of patients with severe PAD. Portions of femoral and/or popliteal arteries from 66 patients with PAD were obtained during surgical procedures for infra-inguinal limb revascularization. We used eight normal arteries from donors as controls. PON1 and PON3, CCL2 and the chemokine-binding protein 2, and Duffy antigen/chemokine receptor, were increased in PAD patients. There were no significant changes in C-C chemokine receptor type 2. Our findings suggest that paraoxonases and chemokines play an important role in the development and progression of atherosclerosis in peripheral artery disease.

Autophagy is an inflammation-related defensive mechanism against disease.

The inflammatory response is an energy-intensive process. Consequently, metabolism is closely associated with immune function. The autophagy machinery plays a role in metabolism by providing energy but may also be used to attack invading pathogens (xenophagy). The autophagy machinery may function to protect against not only the threats of infection but also the threats of the host's own response acting on the central immunological tolerance and the negative regulation of innate and inflammatory signaling. The balance between too little and too much autophagy is critical for the survival of immune cells because autophagy is linked to type 2-cell death programmed necrosis and apoptosis. Changes in inflammatory cells are driven by extracellular signals; however, the mechanisms by which cytokines mediate autophagy regulation and govern immune cell function remain unknown. Certain cytokines increase autophagy, whereas others inhibit autophagy. The relationship between autophagy and inflammation is also important in the pathogenesis of metabolic, non-communicable diseases. Inflammation per se is not the cause of obesity-associated diseases, but it is secondary to both the positive energy balance and the specific cellular responses. In metabolic tissues, the suppression of autophagy increases inflammation with the overexpression of cytokines, resulting in an activation of autophagy. The physiological role of these apparently contradictory findings remains uncertain but exemplifies future challenges in the therapeutic modulation of autophagy in the management of disease.

A single-blinded, randomized, parallel intervention to evaluate genetics and omics-based personalized nutrition in general population via an e-commerce tool: The PREVENTOMICS e-commerce study.

BACKGROUND: Personalized nutrition (PN) has been proposed as a strategy to increase the effectiveness of dietary recommendations and ultimately improve health status. OBJECTIVES: We aimed to assess whether including omics-based PN in an e-commerce tool improves dietary behavior and metabolic profile in general population. METHODS: A 21-wk parallel, single-blinded, randomized intervention involved 193 adults assigned to a control group following Mediterranean diet recommendations (n = 57, completers = 36), PN (n = 70, completers = 45), or personalized plan (PP, n = 68, completers = 53) integrating a behavioral change program with PN recommendations. The intervention used metabolomics, proteomics, and genetic data to assist participants in creating personalized shopping lists in a simulated e-commerce retailer portal. The primary outcome was the Mediterranean diet adherence screener (MEDAS) score; secondary outcomes included biometric and metabolic markers and dietary habits. RESULTS: Volunteers were categorized with a scoring system based on biomarkers of lipid, carbohydrate metabolism, inflammation, oxidative stress, and microbiota, and dietary recommendations delivered accordingly in the PN and PP groups. The intervention significantly increased MEDAS scores in all volunteers (control-3 points; 95% confidence interval [CI]: 2.2, 3.8; PN-2.7 points; 95% CI: 2.0, 3.3; and PP-2.8 points; 95% CI: 2.1, 3.4; q < 0.001). No significant differences were observed in dietary habits or health parameters between PN and control groups after adjustment for multiple comparisons. Nevertheless, personalized recommendations significantly (false discovery rate < 0.05) and selectively enhanced the scores calculated with biomarkers of carbohydrate metabolism (ß: -0.37; 95% CI: -0.56, -0.18), oxidative stress (ß: -0.37; 95% CI: -0.60, -0.15), microbiota (ß: -0.38; 95% CI: -0.63, -0.15), and inflammation (ß: -0.78; 95% CI: -1.24, -0.31) compared with control diet. CONCLUSIONS: Integration of personalized strategies within an e-commerce-like tool did not enhance adherence to Mediterranean diet or improved health markers compared with general recommendations. The metabotyping approach showed promising results and more research is guaranteed to further promote its application in PN. This trial was registered at clinicaltrials.gov as NCT04641559 (https://clinicaltrials.gov/study/NCT04641559?cond=NCT04641559&rank=1).

Physiological, metabolic and microbial responses to obesogenic cafeteria diet in rats: The impact of strain and sex.

Cafeteria (CAF) diet is known to accurately mimic the human Western diet in modern societies, thereby inducing severe obesity accompanied by drastic alterations on the gut microbiome in animal models. Notably, the dietary impact in the gut microbiota composition might be influenced by genetic factors, thus distinctively predisposing the host to pathological states such as obesity. Therefore, we hypothesized that the influence of strain and sex on CAF-induced microbial dysbiosis leads to distinct obese-like metabolic and phenotypic profiles. To address our hypothesis, two distinct cohorts of male Wistar and Fischer 344 rats, as well as male and female Fischer 344 animals, were chronically fed with a standard (STD) or a CAF diet for 10 weeks. The serum fasting levels of glucose, triglycerides and total cholesterol, as well as the gut microbiota composition, were determined. CAF diet triggered hypertriglyceridemia and hypercholesterolemia in Fischer rats, while Wistar animals developed a marked obese phenotype and severe gut microbiome dysbiosis. Furthermore, CAF diet-induced changes on gut microbiota were related to more profound alterations in body composition of female than male rats. We revealed that distinct rat strains and genders chronically consuming a free-choice CAF diet develop distinct and robust microbiota perturbations. Overall, we showed that genetic background might have a key role in diet-induced obesity, thus distinguishing the suitability of different animal models for future nutritional studies focused on gut microbiota dysbiosis induced by a CAF dietary model.

Transient Viral Rebound in Children with Perinatally Acquired HIV-1 Induces a Unique Soluble Immunometabolic Signature Associated with Decreased CD4/CD8 Ratio.

BACKGROUND: To determine by multi-omic analysis changes in metabolites, lipids, and proteins as a consequence of transient viral rebound (tVR) in children with perinatally acquired HIV-1 (PHIV). METHODS: Plasma samples from children with PHIV and with tVR (first episode of transient RNA-HIV viral load >20 copies/ml followed by suppression) on the time-point immediately before (pre-tVR) and after (post-tVR) the tVR were assessed. Multi-omic analyses were performed using nLC-Orbitrap, GC-qTOF-MS, and LC-qTOF-MS. RESULTS: Comparing pre- and post-tVR time-points, HIV-1 children with tVR (n = 5) showed a trend to a decrease in ratio CD4/CD8 (p = 0.08) but no significant differences were observed in plasma metabolites, lipids, or proteins. Post-tVR condition was compared with a reference group of children with PHIV with persistent viral control (n = 9), paired by sex, age, and time under antiretroviral treatment. A total of 10 proteins, 8 metabolites, and 2 lipids showed significant differences (p < 0.05): serotransferrin, clusterin, kininogen-1, succinic acid, threonine, 2-hydroxyisovaleric acid, methionine, 2-hydroxyglutaric, triacylglyceride 50:0 (TG50:0), and diacylglyceride 34:1 (DG34:1) were upregulated while alpha-2-macroglobulin, apolipoprotein A-II, carboxylic ester hydrolase, apolipoprotein D, coagulation factor IX, peptidase inhibitor 16, SAA2-SAA4 readthrough, oleic acid, palmitoleic acid, and D-sucrose downregulated on post-tVR time-point compared to the reference group. Ratio CD4/CD8 correlated with apolipoprotein A-II, DG34:1, and methionine (p = 0.004; ρ = 0.71, p = 0.016; ρ = -0.63; and p = 0.032; ρ = -0.57, respectively). Nadir CD4+ correlated inversely with kininogen-1 (p = 0.022; ρ = -0.60) and positively with D-sucrose (p = 0.001; ρ = 0.77). CONCLUSIONS: tVR followed by suppression implies changes in soluble proteins, lipids, and metabolites that correlate with immunological parameters, mainly ratio CD4/CD8, that decreased after tVR. These distinct soluble biomarkers could be considered potential biomarkers of immune progression.

Analysis of oxylipins to differentiate between organic and conventional UHT milks.

Nowadays, there is a strong interest in analytical approaches for assessing organic farming practices. Here, we propose that oxylipins, a group of oxidised metabolites derived from various polyunsaturated fatty acids, could be promising biomarkers for organic milk assessment because their biosynthesis is modulated by both precursor fatty acid availability and physiological or pathological status. Thus, we determined 31 fatty acids, 53 triacylglycerols and 37 oxylipins in one hundred commercial UHT milks by chromatographic methods coupled to mass spectrometry. Of these, 52 milks were conventional (34 whole milk, 11 semi-skimmed milk and 7 skimmed milk) and 48 were organic (31 whole milk, 11 semi-skimmed milk and 6 skimmed milk). Several oxylipins (8-HEPE, 5-HEPE, 11-HEPE, 9-HEPE, 18-HEPE, 9-HOTrE, 13-HOTrE, 12,13-DiHODE and 15,16-DiHODE) could distinguish between organic and conventional milks. Within these oxylipins, arachidonic and linoleic acid derived do not correlate with their fatty acid precursors; therefore these oxylipins could be promising as not only diet-dependent biomarkers for organic milk assessment.

Metabolomics Elucidates Dose-Dependent Molecular Beneficial Effects of Hesperidin Supplementation in Rats Fed an Obesogenic Diet.

Metabolic syndrome (MetS) is a global epidemic concern. Polyphenols are proposed as good candidates for its prevention, although their mechanisms are not fully understood. The gut microbiota seems to play a key role in polyphenol beneficial effects. Here, we assessed the effects of the citrus polyphenol hesperidin combining an untargeted metabolomics approach, which has an inherent potential to elucidate the host-microbiome interplay, with extensive anthropometric and biochemical characterizations and integrating metabolomics results with our previous 16S rRNA bacterial sequencing data. The rats were fed either a standard or an obesogenic cafeteria diet (CAF) for 17 weeks. After nine weeks, rats were supplemented with vehicle; low- (H1), or high- (H2) hesperidin doses. CAF animals developed MetS features. Hesperidin supplementation in CAF rats decreased the total cholesterol, LDL-C, and free fatty acids. The highest hesperidin dose also ameliorated blood pressure, insulin sensitivity, and decreased markers of arterial stiffness and inflammation. Metabolomics revealed an improvement of the lipidomic profile, decreases in circulating amino acids, and lower excretions of inflammation- and oxidative stress-related metabolites. Bacteroidaceae increases in the CAF-H2 group paralleled higher excretions of microbial-derived metabolites. Overall, our results provide detailed insights into the molecular effects of hesperidin on MetS and suggest that it is a promising prebiotic for the treatment of MetS and related conditions.

Proteomic Analysis of Heart and Kidney Tissues in Healthy and Metabolic Syndrome Rats after Hesperidin Supplementation.

SCOPE: Proteomics has provided new strategies to elucidate the mechanistic action of hesperidin, a flavonoid present in citrus fruits. Thus, the aim of the present study is to determine the effects of hesperidin supplementation (HS) on the proteomic profiles of heart and kidney tissue samples from healthy and metabolic syndrome (MS) rats. METHODS AND RESULTS: 24 Sprague Dawley rats are randomized into four groups: healthy rats fed with a standard diet without HS, healthy rats administered with HS (100 mg kg-1 day-1 ), MS rats without HS, and MS rats administered with HS (100 mg kg-1 day-1 ) for eight weeks. Heart and kidney samples are obtained, and proteomic analysis is performed by mass spectrometry. Multivariate, univariate, and ingenuity pathways analyses are performed. Comparative and semiquantitative proteomic analyses of heart and kidney tissues reveal differential protein expression between MS rats with and without HS. The top diseases and functions implicated are related to the cardiovascular system, free radical scavenging, lipid metabolism, glucose metabolism, and renal and urological diseases. CONCLUSION: This study is the first to demonstrate the protective capacity of hesperidin to change to the proteomic profiles in relation to different cardiovascular risk biomarkers in the heart and kidney tissues of MS rats.

Impact of different hypercaloric diets on obesity features in rats: a metagenomics and metabolomics integrative approach.

Diet is considered a key influencing agent affecting the gut microbiome. Dysbiosis of microbial communities contributes to the development of metabolic diseases such as obesity. We aimed to characterize the physiological, microbial and metabolic changes induced by different obesogenic diets to understand the diet-specific modulation of the host-microbiota co-metabolism in rodents. For this purpose, Wistar rats were fed standard, cafeteria (CAF), low-fat (LF), high-fat (HF) and high-fat high-sucrose (HFS) diets for 10 weeks. The CAF diet strongly induced an obese phenotype accompanied by dyslipidemia, hyperleptinemia, insulin resistance and hepatic steatosis, whereas both HF and HFS diets promoted overweight. Concerning the microbiome, CAF feeding induced a rise of the Bacteroidetes-to-Firmicutes ratio, while few microbial genera were altered in the HF or HFS group. Changes in microbial activity according to dietary treatment were also reflected in the disruption of short-chain fatty acid production and bile acid metabolism, which were mainly associated with fiber intake. Urinary metabolomics revealed a significant increase in metabolites related to oxidative stress and metabolic inflammation together with an altered excretion of host-microbiota co-metabolites only in the CAF group. Moreover, several associations between metabolic patterns, physiological status and specific microbial communities were described, helping to elucidate the crucial role of the microbiota in host homeostasis. Overall, our study suggests that different hypercaloric dietary models distinctively influence gut microbiota composition and reveals robust and similar clustering patterns concerning both cecal microbiome and urinary metabolome profiles.

Effects from diet-induced gut microbiota dysbiosis and obesity can be ameliorated by fecal microbiota transplantation: A multiomics approach.

Obesity and its comorbidities are currently considered an epidemic, and the involved pathophysiology is well studied. Hypercaloric diets are tightly related to the obesity etiology and also cause alterations in gut microbiota functionality. Diet and antibiotics are known to play crucial roles in changes in the microbiota ecosystem and the disruption of its balance; therefore, the manipulation of gut microbiota may represent an accurate strategy to understand its relationship with obesity caused by diet. Fecal microbiota transplantation, during which fecal microbiota from a healthy donor is transplanted to an obese subject, has aroused interest as an effective approach for the treatment of obesity. To determine its success, a multiomics approach was used that combined metagenomics and metaproteomics to study microbiota composition and function. To do this, a study was performed in rats that evaluated the effect of a hypercaloric diet on the gut microbiota, and this was combined with antibiotic treatment to deplete the microbiota before fecal microbiota transplantation to verify its effects on gut microbiota-host homeostasis. Our results showed that a high-fat diet induces changes in microbiota biodiversity and alters its function in the host. Moreover, we found that antibiotics depleted the microbiota enough to reduce its bacterial content. Finally, we assessed the use of fecal microbiota transplantation as a complementary obesity therapy, and we found that it reversed the effects of antibiotics and reestablished the microbiota balance, which restored normal functioning and alleviated microbiota disruption. This new approach could be implemented to support the dietary and healthy habits recommended as a first option to maintain the homeostasis of the microbiota.

Comparison of metaproteomics workflows for deciphering the functions of gut microbiota in an animal model of obesity.

Metaproteomics has emerged as a new, revolutionary approach to study gut microbiota functionality, but the lack of consistent studies in this field due to the great complexity of samples has prompted to search new strategies to achieve better metaproteome characterization. Some steps in sample preparation and data analysis procedures are critical for obtaining accurate results, therefore protein extraction buffers, digestion procedures and fractionation steps were tested here. Initially, two lysis buffers were used to improve protein extraction, two common digestion protocols were compared, and fractionation processes were employed at both the peptide and protein levels. The combination of these procedures resulted in five different methodologies; SDS buffer, in-gel digestion and fractionation at the peptide level provided the best results. Finally, the metaproteomics workflow was tested in a real case study with obese rats, in which a metagenomics study was previously performed. Important differences in protein levels were observed between groups that were potentially related to the taxonomical family, indicating that functional processes are modulated by the microbiota. Therefore, in addition to the necessity of combining different metaomics approaches, an optimized metaproteomics workflow such as the presented in this study is required to obtain a better understanding of the microbiota function. SIGNIFICANCE: Gut microbiota has emerged as an important factor with affects the health balance in host. To study its function new methodologies are necessary and the most appropriate one seems to be metaproteomics. The lack of studies in this field requires a deeply research in the most accurate workflow to better comprehend such complex samples. In this paper, five different methodologies have been compared, mainly in the most critical steps in classical proteomics and the methodology chosen was validated in a real case study in obese animals.

Liver fat deposition and mitochondrial dysfunction in morbid obesity: An approach combining metabolomics with liver imaging and histology.

AIM: To explore the usefulness of magnetic resonance imaging (MRI) and spectroscopy (MRS) for assessment of non-alcoholic fat liver disease (NAFLD) as compared with liver histological and metabolomics findings. METHODS: Patients undergoing bariatric surgery following procedures involved in laparoscopic sleeve gastrectomy were recruited as a model of obesity-induced NAFLD in an observational, prospective, single-site, cross-sectional study with a pre-set duration of 1 year. Relevant data were obtained prospectively and surrogates for inflammation, oxidative stress and lipid and glucose metabolism were obtained through standard laboratory measurements. To provide reliable data from MRI and MRS, novel procedures were designed to limit sampling variability and other sources of error using a 1.5T Signa HDx scanner and protocols acquired from the 3D or 2D Fat SAT FIESTA prescription manager. We used our previously described (1)H NMR-based metabolomics assays. Data were obtained immediately before surgery and after a 12-mo period including histology of the liver and measurement of metabolites. Values from (1)H NMR spectra obtained after surgery were omitted due to technical limitations. RESULTS: MRI data showed excellent correlation with the concentration of liver triglycerides, other hepatic lipid components and the histological assessment, which excluded the presence of non-alcoholic steatohepatitis (NASH). MRI was sufficient to follow up NAFLD in obese patients undergoing bariatric surgery and data suggest usefulness in other clinical situations. The information provided by MRS replicated that obtained by MRI using the -CH3 peak (0.9 ppm), the -CH2- peak (1.3 ppm, mostly triglyceride) and the -CH=CH- peak (2.2 ppm). No patient depicted NASH. After surgery all patients significantly decreased their body weight and steatosis was virtually absent even in patients with previous severe disease. Improvement was also observed in the serum concentrations of selected variables. The most relevant findings using metabolomics indicate increased levels of triglyceride and monounsaturated fatty acids in severe steatosis but those results were accompanied by a significant depletion of diglycerides, polyunsaturated fatty acids, glucose-6-phosphate and the ATP/AMP ratio. Combined data indicated the coordinated action on mitochondrial fat oxidation and glucose transport activity and may support the consideration of NAFLD as a likely mitochondrial disease. This concept may help to explain the dissociation between excess lipid storage in adipose tissue and NAFLD and may direct the search for plasma biomarkers and novel therapeutic strategies. A limitation of our study is that data were obtained in a relatively low number of patients. CONCLUSION: MRI is sufficient to stage NAFLD in obese patients and to assess the improvement after bariatric surgery. Other data were superfluous for this purpose.