Inflammation and Metabolism of Influenza-Stimulated Peripheral Blood Mononuclear Cells From Adults With Obesity Following Bariatric Surgery

BACKGROUND

Obesity dysregulates immunity to influenza infection. Therefore, there is a critical need to investigate how obesity impairs immunity and to establish therapeutic approaches that mitigate the impact of increased adiposity. One mechanism by which obesity may alter immune responses is through changes in cellular metabolism.

METHODS

We studied inflammation and cellular metabolism of peripheral blood mononuclear cells (PBMCs) isolated from individuals with obesity relative to lean controls. We also investigated if impairments to PBMC metabolism were reversible upon short-term weight loss following bariatric surgery.

RESULTS

Obesity was associated with systemic inflammation and poor inflammation resolution. Unstimulated PBMCs from participants with obesity had lower oxidative metabolism and adenosine triphosphate (ATP) production compared to PBMCs from lean controls. PBMC secretome analyses showed that ex vivo stimulation with A/Cal/7/2009 H1N1 influenza led to a notable increase in IL-6 with obesity. Short-term weight loss via bariatric surgery improved biomarkers of systemic metabolism but did not improve markers of inflammation resolution, PBMC metabolism, or the PBMC secretome.

CONCLUSIONS

These results show that obesity drives a signature of impaired PBMC metabolism, which may be due to persistent inflammation. PBMC metabolism was not reversed after short-term weight loss despite improvements in measures of systemic metabolism.

Enriched Marine Oil Supplement Increases Specific Plasma Specialized Pro-Resolving Mediators in Adults with Obesity

BACKGROUND

Specialized pro-resolving mediators (SPMs), synthesized from PUFAs, resolve inflammation and return damaged tissue to homeostasis. Thus, increasing metabolites of the SPM biosynthetic pathway may have potential health benefits for select clinical populations, such as subjects with obesity who display dysregulation of SPM metabolism. However, the concentrations of SPMs and their metabolic intermediates in humans with obesity remains unclear.

OBJECTIVES

The primary objective of this study was to determine if a marine oil supplement increased specific metabolites of the SPM biosynthetic pathway in adults with obesity. The second objective was to determine if the supplement changed the relative abundance of key immune cell populations. Finally, given the critical role of antibodies in inflammation, we determined if ex vivo CD19 + B-cell antibody production was modified by marine oil intervention.

METHODS

Twenty-three subjects [median age: 56 y; BMI (in kg/m2): 33.1] consumed 2 g/d of a marine oil supplement for 28-30 d. The supplement was particularly enriched with 18-hydroxyeicosapentaenoic (HEPE), 14-hydroxydocosahexaenoic acid (14-HDHA), and 17-HDHA. Blood was collected pre- and postsupplementation for plasma mass spectrometry oxylipin and fatty acid analyses, flow cytometry, and B-cell isolation. Paired t-tests and Wilcoxon tests were used for statistical analyses.

RESULTS

Relative to preintervention, the supplement increased 6 different HEPEs and HDHAs accompanied by changes in plasma PUFAs. Resolvin E1 and docosapentaenoic acid-derived maresin 1 concentrations were increased 3.5- and 4.7-fold upon intervention, respectively. The supplement did not increase the concentration of D-series resolvins and had no effect on the abundance of immune cells. Ex vivo B-cell IgG but not IgM concentrations were lowered postsupplementation.

CONCLUSIONS

A marine oil supplement increased select SPMs and their metabolic intermediates in adults with obesity. Additional studies are needed to determine if increased concentrations of specific SPMs control the resolution of inflammation in humans with obesity. This trial was registered at clinicaltrials.gov as NCT04701138.

Modeling human heterogeneity of obesity with diversity outbred mice reveals a fat mass-dependent therapeutic window for resolvin E1

Resolvin E1 (RvE1), a specialized pro-resolving mediator (SPM), improves glucose homeostasis in inbred mouse models of obesity. However, an impediment toward translation is that obesity is a highly heterogenous disease in which individuals will respond very differently to interventions such as RvE1. Thus, there is a need to study SPMs in the context of modeling the heterogeneity of obesity that is observed in humans. We investigated how RvE1 controls the concentration of key circulating metabolic biomarkers using diversity outbred (DO) mice, which mimic human heterogeneity. We first demonstrate that weights of DO mice can be classified into distinct distributions of fat mass (i.e., modeling differing classes of obesity) in response to a high-fat diet and in the human population when examining body composition. Next, we show RvE1 administration based on body weight for four consecutive days after giving mice a high-fat diet led to approximately half of the mice responding positively for serum total gastric inhibitory polypeptide (GIP), glucagon, insulin, glucose, leptin, and resistin. Interestingly, RvE1 improved hyperleptinemia most effectively in the lowest class of fat mass despite adjusting the dose of RvE1 with increasing adiposity. Furthermore, leptin levels after RvE1 treatment were the lowest in those mice that were also RvE1 positive responders for insulin and resistin. Collectively, these results suggest a therapeutic fat mass-dependent window for RvE1, which should be considered in future clinical trials. Moreover, the data underscore the importance of studying SPMs with heterogenous mice as a step toward precision SPM administration in humans.

Resolvin E1-ChemR23 Axis Regulates the Hepatic Metabolic and Inflammatory Transcriptional Landscape in Obesity at the Whole Genome and Exon Level

Resolvin E1 (RvE1) is an immunoresolvent that is synthesized from eicosapentaenoic acid and can bind the receptor ERV1/ChemR23. We previously showed activation of the RvE1-ChemR23 axis improves hyperglycemia and hyperinsulinemia of obese mice; however, it remains unclear how RvE1 controls glucose homeostasis. Here we investigated hepatic metabolic and inflammatory transcriptional targets of the RvE1-ChemR23 axis using lean and obese wild type (WT) and ChemR23 knockout (KO) mice. We conducted an in-depth transcriptional study by preforming whole gene-level and exon-level analyses, which provide insight into alternative splicing variants and miRNA regulation. Compared to controls, WT and KO obese mice in the absence of RvE1 displayed similar gene-level profiles, which entailed dysregulated pathways related to glucose homeostasis. Notably, obese WT mice relative to lean controls showed a robust decrease in pathways related to the biosynthesis of unsaturated fatty acids. At the exon-level, obese ChemR23 KOs compared to obese WT mice displayed changes in pathways related to hepatic lipid transport, cholesterol metabolism, and immunological functions such as complement cascades and platelet activation. Importantly, upon RvE1 administration to WT obese mice, we discovered upregulated genes in pathways relating to insulin sensitivity and downregulated genes related to regulators of TGF-β signaling. This transcriptional profile was generally not recapitulated with obese ChemR23 KO mice administered RvE1. Collectively, gene and exon-level analyses suggest RvE1 controls the hepatic transcriptional profile related to glucose homeostasis, insulin sensitivity, and inflammation in a manner that is largely dependent on ChemR23. These studies will drive future mechanistic experiments on the RvE1-ChemR23 axis.

Metabolic and functional impairment of CD8+ T cells from the lungs of influenza-infected obese mice

Obesity is an independent risk factor for morbidity and mortality in response to influenza infection. However, the underlying mechanisms by which obesity impairs immunity are unclear. Herein, we investigated the effects of diet-induced obesity on pulmonary CD8+ T cell metabolism, cytokine production, and transcriptome as a potential mechanism of impairment during influenza virus infection in mice. Male C57BL/6J lean and obese mice were infected with sub-lethal mouse-adapted A/PR/8/34 influenza virus, generating a pulmonary anti-viral and inflammatory response. Extracellular metabolic flux analyses revealed pulmonary CD8+ T cells from obese mice, compared with lean controls, had suppressed oxidative and glycolytic metabolism at day 10 post-infection. Flow cytometry showed the impairment in pulmonary CD8+ T cell metabolism with obesity was independent of changes in glucose or fatty acid uptake, but concomitant with decreased CD8+ GrB+ IFNγ+ populations. Notably, the percent of pulmonary effector CD8+ GrB+ IFNγ+ T cells at day 10 post-infection correlated positively with total CD8+ basal extracellular acidification rate and basal oxygen consumption rate. Finally, next-generation RNA sequencing revealed complex and unique transcriptional regulation of sorted effector pulmonary CD8+ CD44+ T cells from obese mice compared to lean mice following influenza infection. Collectively, the data suggest diet-induced obesity increases influenza virus pathogenesis, in part, through CD8+ T cell-mediated metabolic reprogramming and impaired effector CD8+ T cell function.

Polyunsaturated fatty acids, specialized pro-resolving mediators, and targeting inflammation resolution in the age of precision nutrition

Chronic inflammation contributes toward the pathogenesis of numerous diseases including, but not limited to, obesity, autoimmunity, cardiovascular diseases, and cancers. The discovery of specialized pro-resolving mediators (SPMs), which are critical for resolving inflammation, has commenced investigation into targeting pathways of inflammation resolution to improve physiological outcomes. SPMs are predominately synthesized from the n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Therefore, one viable strategy to promote inflammation resolution would be to increase dietary intake of EPA/DHA, which are deficient in select populations. However, there are inconsistencies between the use of EPA/DHA as dietary or pharmacological supplements and improved inflammatory status. Herein, we review the literature on the relationship between the high n-6/n-3 PUFA ratio, downstream SPM biosynthesis, and inflammatory endpoints. We highlight key studies that have investigated how dietary intake of EPA/DHA increase tissue SPMs and their effects on inflammation. We also discuss the biochemical pathways by which EPA/DHA drive SPM biosynthesis and underscore mechanistic gaps in knowledge about these pathways which include a neglect for host genetics/ethnic differences in SPM metabolism, sexual dimorphism in SPM levels, and potential competition from select dietary n-6 PUFAs for enzymes of SPM synthesis. Altogether, establishing how dietary PUFAs control SPM biosynthesis in a genetic- and sex-dependent manner will drive new precision nutrition studies with EPA/DHA to prevent chronic inflammation in select populations.

Resolvin E1 derived from eicosapentaenoic acid prevents hyperinsulinemia and hyperglycemia in a host genetic manner

Eicosapentaenoic acid (EPA) has garnered attention after the success of the REDUCE‐IT trial, which contradicted previous conclusions on EPA for cardiovascular disease risk. Here we first investigated EPA's preventative role on hyperglycemia and hyperinsulinemia. EPA ethyl esters prevented obesity‐induced glucose intolerance, hyperinsulinemia, and hyperglycemia in C57BL/6J mice. Supporting NHANES analyses showed that fasting glucose levels of obese adults were inversely related to EPA intake. We next investigated how EPA improved murine hyperinsulinemia and hyperglycemia. EPA overturned the obesity‐driven decrement in the concentration of 18‐hydroxyeicosapentaenoic acid (18‐HEPE) in white adipose tissue and liver. Treatment of obese inbred mice with RvE1, the downstream immunoresolvant metabolite of 18‐HEPE, but not 18‐HEPE itself, reversed hyperinsulinemia and hyperglycemia through the G‐protein coupled receptor ERV1/ChemR23. To translate the findings, we determined if the effects of RvE1 were dependent on host genetics. RvE1's effects on hyperinsulinemia and hyperglycemia were divergent in diversity outbred mice that model human genetic variation. Secondary SNP analyses further confirmed extensive genetic variation in human RvE1/EPA‐metabolizing genes. Collectively, the data suggest EPA prevents hyperinsulinemia and hyperglycemia, in part, through RvE1's activation of ERV1/ChemR23 in a host genetic manner. The studies underscore the need for personalized administration of RvE1 based on genetic/metabolic enzyme profiles.

Exon level machine learning analyses elucidate novel candidate miRNA targets in an avian model of fetal alcohol spectrum disorder

Gestational alcohol exposure causes fetal alcohol spectrum disorder (FASD) and is a prominent cause of neurodevelopmental disability. Whole transcriptome sequencing (RNA-Seq) offer insights into mechanisms underlying FASD, but gene-level analysis provides limited information regarding complex transcriptional processes such as alternative splicing and non-coding RNAs. Moreover, traditional analytical approaches that use multiple hypothesis testing with a false discovery rate adjustment prioritize genes based on an adjusted p-value, which is not always biologically relevant. We address these limitations with a novel approach and implemented an unsupervised machine learning model, which we applied to an exon-level analysis to reduce data complexity to the most likely functionally relevant exons, without loss of novel information. This was performed on an RNA-Seq paired-end dataset derived from alcohol-exposed neural fold-stage chick crania, wherein alcohol causes facial deficits recapitulating those of FASD. A principal component analysis along with k-means clustering was utilized to extract exons that deviated from baseline expression. This identified 6857 differentially expressed exons representing 1251 geneIDs; 391 of these genes were identified in a prior gene-level analysis of this dataset. It also identified exons encoding 23 microRNAs (miRNAs) having significantly differential expression profiles in response to alcohol. We developed an RDAVID pipeline to identify KEGG pathways represented by these exons, and separately identified predicted KEGG pathways targeted by these miRNAs. Several of these (ribosome biogenesis, oxidative phosphorylation) were identified in our prior gene-level analysis. Other pathways are crucial to facial morphogenesis and represent both novel (focal adhesion, FoxO signaling, insulin signaling) and known (Wnt signaling) alcohol targets. Importantly, there was substantial overlap between the exomes themselves and the predicted miRNA targets, suggesting these miRNAs contribute to the gene-level expression changes. Our novel application of unsupervised machine learning in conjunction with statistical analyses facilitated the discovery of signaling pathways and miRNAs that inform mechanisms underlying FASD.