Antioxidant Drug Tempol Promotes Functional Metabolic Changes in the Gut Microbiota

Evaluation of the effects of Tempol on oxidative stress and angiotensin-II induced hypertension in mice exposed to nicotine from electronic and tobacco cigarettes

Electronic cigarette (E-Cig) is commonly used as an alternative to tobacco cigarette (T-Cig), as it lacks many of the toxicants present in T-Cigs. However, the toxicological mechanisms underlying E-Cig-induced hypertension are not yet well understood. The goal of this research was to explore the effects of Tempol in reducing hypertension caused by T-Cig and E-Cig exposure by mitigating oxidative stress and regulating angiotensin-II production in mouse models subjected to T-Cig and E-Cig smoke. Male C57BL/6 J mice were assigned to eight distinct groups: Air, Air + Tempol, T-Cig, T-Cig + Tempol, NIC-free E-Cig, NIC-free E-Cig + Tempol, E-Cig, and E-Cig + Tempol. Mice exposed to smoking for 12 min per hour, 6 cycles/day, 7 days/week for 4 weeks. Blood pressure was monitored, and Angiotensin-II and cGMP levels were measured using ELISA. Oxidative stress markers (GPx, GSTA1, SOD, MDA, nitrite) were assessed by RT-PCR and biochemical assays. The collected data showed a weight loss with high blood pressure and vasoconstriction in the T-Cig and E-Cig groups. Results showed an induction of angiotensin-II, GPx, GSTA1, SOD, and MDA. In contrast, cGMP and nitrite levels were reduced in the T-Cig and E-Cig groups. Tempol treatment regulated oxidative stress markers, angiotensin-II and cGMP levels, leading to a significant reduction in blood pressure. The results indicate that Tempol is essential in reducing oxidative stress and the effects of angiotensin-II caused by T-Cig and E-Cig exposure, thereby contributing to the regulation of systemic hemodynamic function.

Aged gut microbiota promotes arrhythmia susceptibility via oxidative stress

Arrhythmias and sudden cardiac death (SCD) impose a significant burden. Their prevalence rises with age and is linked to gut dysbiosis. Our study aimed to determine whether aged gut microbiota affects arrhythmogenesis. Here, we demonstrated that arrhythmia susceptibility in aged mice could be transmitted to young mice using fecal microbiota transplantation (FMT). Mechanistically, increased intestinal reactive oxygen species (ROS) in aged mice reduced ion channel protein expression and promoted arrhythmias. Gut microbiota depletion by an antibiotic cocktail reduced ROS and arrhythmia in aged mice. Interestingly, oxidative stress in heart induced by hydrogen peroxide (H2O2) increased arrhythmia. Moreover, aged gut microbiota could induce oxidative stress in young mice colon by gut microbiota metabolites transplantation. Vitexin could reduce aging and arrhythmia through OLA1-Nrf2 signaling pathway. Overall, our study demonstrated that the gut microbiota of aged mice reduced cardiac ion channel protein expression through systemic oxidative stress, thereby increased the risk of arrhythmias.

Rebalancing NOX2/Nrf2 to limit inflammation and oxidative stress across gut-brain axis in migraine

Migraine is one of the most common neurological illnesses, and it is characterized by complicated neurobiology. It was confirmed the influence of inflammation and oxidative stress in migraines and also in distal organs such as the intestine. Indeed, the constant bidirectional communication between the Central Nervous System (CNS) and the gastrointestinal (GI) tract, known as the gut-brain axis, has become an attractive target involved in different human disorders. Herein, we explored the role of NADPH oxidase 2 (NOX2) in nitroglycerin (NTG)-induced migraine in mice models to discover the mechanism by which, during migraine attack, oxidative stress is sustained within trigeminal neurons and GI. Considering the inverse relationship between NOX2 and Nrf2, Nrf2 upregulation seems to be a promising approach to decrease NOX2 expression and consequently limit oxidative stress and inflammation spread in neurological and non-neurological diseases. With this aim, we exploited tempol's Nrf2-inducer ability to better understand the involvement of Nrf2/NOX2 axis in migraine and associated GI comorbidities. Behavioral tests confirmed that tempol, in a dose-dependent manner, moderated clinical signs of migraine and abdominal pain. Moreover, we demonstrated that the decrease in migraine-related symptomatology was strongly linked to the modulation of Nrf2/NOX2 signaling pathway in the brain and colon. In the brain, the rebalancing of Nrf2/NOX2 prevented neuronal loss, decreased glia reactivity while inhibiting NF-κB and NLRP3 inflammasome activation. In the colon, Nrf2 upregulation and consequent NOX2 decrease reduced the histological damage, mast cells infiltration as well as tumor necrosis factor (TNF)-α and interleukin (IL)-1β release. Furthermore, the attenuation of inflammation and oxidative stress led to the restoration of the intestinal barrier through TJs replacement. Taken as a whole, data suggested that the regulation of Nrf2/NOX2 balance is a successful way to reduce neurological and related intestinal impairments during migraine and could be of relevance for migraine-like attacks in humans.

Saikosaponin a ameliorates diet-induced fatty liver via regulating intestinal microbiota and bile acid profile in laying hens

Fatty liver hemorrhagic syndrome is a widespread metabolic disease in laying hens that decreases egg production and even causes death in severe cases. Many traditional Chinese medicine ingredients, such as saikosaponin a (SSa), have been shown to alleviate fatty liver, but the underlying mechanisms remain unclear. In this study, we aimed to explore the alleviation of dietary SSa on excessive hepatic lipid deposition and the interactions between intestinal microbiota and bile acid (BA) in laying hens. Fifty-four 35-wk-old laying hens were randomly allocated into 3 treatment groups with 6 replicates (3 birds per replicate) and fed with a basal diet (CON), high-energy and low-protein diet (HELP), and HELP diet with 30 mg/kg SSa (HELP + SSa). SSa reversed diet-induced egg production rate decrease (P < 0.05). SSa could potently ameliorate HELP-induced accumulation of hepatic cholesterol and liver injury via the increase (P < 0.05) of mRNA expression of BA synthesis gene, such as cholesterol 7 alpha-hydroxylase 1. SSa treatment alleviated gut dysbiosis, especially reducing (P < 0.05) the relative abundance of bile salt hydrolase (BSH)-producing bacteria such as Lactobacillus, Bifidobacterium, and Turicibacter. Ileal BA metabolomic analysis revealed that SSa increased (P < 0.05) the content of tauro-conjugated BAs, mainly taurochenodeoxycholic acid and tauro-α-muricholic acid. The mRNA expression of farnesoid X receptor (FXR) and fibroblast growth factor 19 were decreased (P < 0.05) in intestine, which was associated with increased gene expression of enzymes in the BA synthesis that reduced the levels of cholesterol. Moreover, SSa treatment inhibited intestinal BA reabsorption via decreasing (P < 0.05) the mRNA expression of apical sodium-dependent bile acid transporter. Our findings indicated that SSa reduced liver cholesterol accumulation and alleviated fatty liver in laying hens through microbiota-BA-intestinal FXR crosstalk.

Bile acid metabolism and signaling, the microbiota, and metabolic disease

The diversity, composition, and function of the bacterial community inhabiting the human gastrointestinal tract contributes to host health through its role in producing energy or signaling molecules that regulate metabolic and immunologic functions. Bile acids are potent metabolic and immune signaling molecules synthesized from cholesterol in the liver and then transported to the intestine where they can undergo metabolism by gut bacteria. The combination of host- and microbiota-derived enzymatic activities contribute to the composition of the bile acid pool and thus there can be great diversity in bile acid composition that depends in part on the differences in the gut bacteria species. Bile acids can profoundly impact host metabolic and immunological functions by activating different bile acid receptors to regulate signaling pathways that control a broad range of complex symbiotic metabolic networks, including glucose, lipid, steroid and xenobiotic metabolism, and modulation of energy homeostasis. Disruption of bile acid signaling due to perturbation of the gut microbiota or dysregulation of the gut microbiota-host interaction is associated with the pathogenesis and progression of metabolic disorders. The metabolic and immunological roles of bile acids in human health have led to novel therapeutic approaches to manipulate the bile acid pool size, composition, and function by targeting one or multiple components of the microbiota-bile acid-bile acid receptor axis.

The antioxidant tempol transforms gut microbiome to resist obesity in female C3H mice fed a high fat diet

The nitroxide, Tempol, prevents obesity related changes in mice fed a high fat diet (HFD). The purpose of this study was to gain insight into the mechanisms that result in such changes by Tempol in female C3H mice. Microarray methodology, Western blotting, bile acid analyses, and gut microbiome sequencing were used to identify multiple genes, proteins, bile acids, and bacteria that are regulated by Tempol in female C3H mice on HFD. The effects of antibiotics in combination with Tempol on the gut microflora were also studied. Adipose tissue, from Tempol treated mice, was analyzed using targeted gene microarrays revealing up-regulation of fatty acid metabolism genes (Acadm and Acadl > 4-fold, and Acsm3 and Acsm5 > 10-fold). Gene microarray studies of liver tissue from mice switched from HFD to Tempol HFD showed down-regulation of fatty acid synthesis genes and up-regulation of fatty acid oxidation genes. Analyses of proteins involved in obesity revealed that the expression of aldehyde dehydrogenase 1A1 (ALDH1A1) and fasting induced adipose factor/angiopoietin-like protein 4 (FIAF/ANGPTL4) was altered by Tempol HFD. Bile acid studies revealed increases in cholic acid (CA) and deoxycholic acid (DCA) in both the liver and serum of Tempol treated mice. Tempol HFD effect on the gut microbiome composition showed an increase in the population of Akkermansia muciniphila, a bacterial species known to be associated with a lean, anti-inflammatory phenotype. Antibiotic treatment significantly reduced the total level of bacterial numbers, however, Tempol was still effective in reducing the HFD weight gain. Even after antibiotic treatment Tempol still positively influenced several bacterial species such as as Akkermansia muciniphila and Bilophila wadsworthia. The positive effects of Tempol moderating weight gain in female mice fed a HFD involves changes to the gut microbiome, bile acids composition, and finally to changes in genes and proteins involved in fatty acid metabolism and storage.

The East Asian gut microbiome is distinct from colocalized White subjects and connected to metabolic health

East Asians (EAs) experience worse metabolic health outcomes compared to other ethnic groups at lower body mass indices; however, the potential role of the gut microbiota in contributing to these health disparities remains unknown. We conducted a multi-omic study of 46 lean and obese East Asian and White participants living in the San Francisco Bay Area, revealing marked differences between ethnic groups in bacterial richness and community structure. White individuals were enriched for the mucin-degrading Akkermansia muciniphila. East Asian subjects had increased levels of multiple bacterial phyla, fermentative pathways detected by metagenomics, and the short-chain fatty acid end-products acetate, propionate, and isobutyrate. Differences in the gut microbiota between the East Asian and White subjects could not be explained by dietary intake, were more pronounced in lean individuals, and were associated with current geographical location. Microbiome transplantations into germ-free mice demonstrated stable diet- and host genotype-independent differences between the gut microbiotas of East Asian and White individuals that differentially impact host body composition. Taken together, our findings add to the growing body of literature describing microbiome variations between ethnicities and provide a starting point for defining the mechanisms through which the microbiome may shape disparate health outcomes in East Asians.

The community of microbes living in the human gut varies based on where a person lives, in part because of differences in diets but also due to factors still incompletely understood. In turn, this ‘microbiome’ may have wide-ranging effects on health and diseases such as obesity and diabetes.

Many scientists want to understand how differences in the microbiome emerge between people, and whether this may explain why certain diseases are more common in specific populations. Self-identified race or ethnicity can be a useful tool in that effort, as it can serve as a proxy for cultural habits (such as diets) or genetic information.

In the United States, self-identified East Asian Americans often have worse ‘metabolic health’ (e.g. levels of sugar or certain fat molecules in the blood) at a lower weight than those identifying as White. Ang, Alba, Upadhyay et al. investigated whether this health disparity was linked to variation in the gut microbiome. Samples were collected from 46 lean and obese individuals living in the San Francisco Bay Area who identified as White or East Asian.

The analyses showed that while the gut microbiome of White participants changed in association with obesity, the microbiomes of East Asian participants were distinct from their White counterparts even at normal weight, with features mirroring what was seen in White individuals in the context of obesity. Although these differences were connected to people’s current address, they were not attributable to dietary differences.

Ang, Alba, Upadhyay et al. then transplanted the microbiome of the participants into genetically identical mice with microbe-free guts. The differences between the gut microbiomes of White and East Asian participants persisted in recipient animals. When fed the same diet, the mice also gained different amounts of weight depending on the ethnic identity of the microbial donor.

These results show that self-identified ethnicity may be an important variable to consider in microbiome studies, alongside other factors such as geography. Ultimately, this research may help to design better, more personalized treatments for an array of conditions.

Exposure to cigarette smoke precipitates simple hepatosteatosis to NASH in high-fat diet fed mice by inducing oxidative stress

Consumption of diet rich in fat and cigarette smoking (CS) are independent risk factors of non-alcoholic steatohepatitis (NASH), and they often occur together in some populations. The present study investigated the mechanisms of high-fat diet (HFD) and CS, individually and in combination, on the pathogenesis of NASH in mice. C57BL/6 male mice were subjected to either a low-fat chow (CH) or HFD with or without mainstream CS-exposure (4 cigarettes/day, 5 days/ week for 14 weeks). HFD alone caused hepatosteatosis (2.5-fold increase in TG content) and a significant increase in 3-nitrotyrisine (by ∼40-fold) but without an indication of liver injury, inflammation or fibrosis. CS alone in CH-fed mice increased in Tnfα expression and macrophage infiltration by 2-fold and relatively less increase in 3-nitrotyrosine (18-fold). Combination of HFD and CS precipitated hepatosteatosis to NASH reflected by exacerbated makers of liver inflammation and fibrosis which were associated with much severe liver oxidative stress (90-fold increase in 3-nitrotyrisine along with 6-fold increase in carbonylated proteins and 56% increase in lipid oxidations). Further studies were performed to administer the antioxidant tempol to CS exposed HFD mice and the results showed that the inhibition of liver oxidative stress prevented inflammatory and fibrotic changes in liver despite persisting hepatosteatosis. Our findings suggest that oxidative stress is a key mechanism underlying CS-promoted progression of simple hepatosteatosis to NASH. Targeting hepatic oxidative stress may be a viable strategy in halting the progression of metabolic associated fatty liver disease.

Propionate and Alzheimer's Disease

Propionate, a short-chain fatty acid, serves important roles in the human body. However, our review of the current literature suggests that under certain conditions, excess levels of propionate may play a role in Alzheimer's disease (AD). The cause of the excessive levels of propionate may be related to the Bacteroidetes phylum, which are the primary producers of propionate in the human gut. Studies have shown that the relative abundance of the Bacteroidetes phylum is significantly increased in older adults. Other studies have shown that levels of the Bacteroidetes phylum are increased in persons with AD. Studies on the diet, medication use, and propionate metabolism offer additional potential causes. There are many different mechanisms by which excess levels of propionate may lead to AD, such as hyperammonemia. These mechanisms offer potential points for intervention.

The Gut Microbiome and Xenobiotics: Identifying Knowledge Gaps

There is an increasing awareness that the gut microbiome plays a critical role in human health and disease, but mechanistic insights are often lacking. In June 2018, the Health and Environmental Sciences Institute (HESI) held a workshop, "The Gut Microbiome: Markers of Human Health, Drug Efficacy and Xenobiotic Toxicity" (https://hesiglobal.org/event/the-gut-microbiome-workshop) to identify data gaps in determining how gut microbiome alterations may affect human health. Speakers and stakeholders from academia, government, and industry addressed multiple topics including the current science on the gut microbiome, endogenous and exogenous metabolites, biomarkers, and model systems. The workshop presentations and breakout group discussions formed the basis for identifying data gaps and research needs. Two critical issues that emerged were defining the microbial composition and function related to health and developing standards for models, methods and analysis in order to increase the ability to compare and replicate studies. A series of key recommendations were formulated to focus efforts to further understand host-microbiome interactions and the consequences of exposure to xenobiotics as well as identifying biomarkers of microbiome-associated disease and toxicity.

Phenotypic effects of dietary stress in combination with a respiratory chain bypass in mice

The alternative oxidase (AOX) from Ciona intestinalis was previously shown to be expressible in mice and to cause no physiological disturbance under unstressed conditions. Because AOX is known to become activated under some metabolic stress conditions, resulting in altered energy balance, we studied its effects in mice subjected to dietary stress. Wild‐type mice (Mus musculus, strain C57BL/6JOlaHsd) fed a high‐fat or ketogenic (high‐fat, low‐carbohydrate) diet show weight gain with increased fat mass, as well as loss of performance, compared with chow‐fed animals. Unexpectedly, AOX‐expressing mice fed on these metabolically stressful, fat‐rich diets showed almost indistinguishable patterns of weight gain and altered body composition as control animals. Cardiac performance was impaired to a similar extent by ketogenic diet in AOX mice as in nontransgenic littermates. AOX and control animals fed on ketogenic diet both showed wide variance in weight gain. Analysis of the gut microbiome in stool revealed a strong correlation with diet, rather than with genotype. The microbiome of the most and least obese outliers reared on the ketogenic diet showed no consistent trends compared with animals of normal body weight. We conclude that AOX expression in mice does not modify physiological responses to extreme diets.

Nutrient Sensing in CD11c Cells Alters the Gut Microbiota to Regulate Food Intake and Body Mass

Microbial dysbiosis and inflammation are implicated in diet-induced obesity and insulin resistance. However, it is not known whether crosstalk between immunity and microbiota also regulates metabolic homeostasis in healthy animals. Here, we report that genetic deletion of tuberous sclerosis 1 (Tsc1) in CD11c+ myeloid cells (Tsc1f/fCD11cCre mice) reduced food intake and body mass in the absence of metabolic disease. Co-housing and fecal transplant experiments revealed a dominant role for the healthy gut microbiota in regulation of body weight. 16S rRNA sequencing, selective culture, and reconstitution experiments further confirmed that selective deficiency of Lactobacillus johnsonii Q1-7 contributed to decreased food intake and body mass in Tsc1f/fCD11cCre mice. Mechanistically, activation of mTORC1 signaling in CD11c cells regulated production of L. johnsonii Q1-7-specific IgA, allowing for its stable colonization in the gut. Together, our findings reveal an unexpected transkingdom immune-microbiota feedback loop for homeostatic regulation of food intake and body mass in mammals.

Chemical Nanomotors at the Gram Scale Form a Dense Active Optorheological Medium

The rheological properties of a colloidal suspension are a function of the concentration of the colloids and their interactions. While suspensions of passive colloids are well studied and have been shown to form crystals, gels, and glasses, examples of energy-consuming "active" colloidal suspensions are still largely unexplored. Active suspensions of biological matter, such as motile bacteria or dense mixtures of active actin-motor-protein mixtures have, respectively, reveals superfluid-like and gel-like states. Attractive inanimate systems for active matter are chemically self-propelled particles. It has so far been challenging to use these swimming particles at high enough densities to affect the bulk material properties of the suspension. Here, it is shown that light-triggered asymmetric titanium dioxide that self-propel, can be obtained in large quantities, and self-organize to make a gram-scale active medium. The suspension shows an activity-dependent tenfold reversible change in its bulk viscosity.

Multiplatform Physiologic and Metabolic Phenotyping Reveals Microbial Toxicity

The gut microbiota is susceptible to modulation by environmental stimuli and therefore can serve as a biological sensor. Recent evidence suggests that xenobiotics can disrupt the interaction between the microbiota and host. Here, we describe an approach that combines in vitro microbial incubation (isolated cecal contents from mice), flow cytometry, and mass spectrometry- and 1H nuclear magnetic resonance (NMR)-based metabolomics to evaluate xenobiotic-induced microbial toxicity. Tempol, a stabilized free radical scavenger known to remodel the microbial community structure and function in vivo, was studied to assess its direct effect on the gut microbiota. The microbiota was isolated from mouse cecum and was exposed to tempol for 4 h under strict anaerobic conditions. The flow cytometry data suggested that short-term tempol exposure to the microbiota is associated with disrupted membrane physiology as well as compromised metabolic activity. Mass spectrometry and NMR metabolomics revealed that tempol exposure significantly disrupted microbial metabolic activity, specifically indicated by changes in short-chain fatty acids, branched-chain amino acids, amino acids, nucleotides, glucose, and oligosaccharides. In addition, a mouse study with tempol (5 days gavage) showed similar microbial physiologic and metabolic changes, indicating that the in vitro approach reflected in vivo conditions. Our results, through evaluation of microbial viability, physiology, and metabolism and a comparison of in vitro and in vivo exposures with tempol, suggest that physiologic and metabolic phenotyping can provide unique insight into gut microbiota toxicity. IMPORTANCE The gut microbiota is modulated physiologically, compositionally, and metabolically by xenobiotics, potentially causing metabolic consequences to the host. We recently reported that tempol, a stabilized free radical nitroxide, can exert beneficial effects on the host through modulation of the microbiome community structure and function. Here, we investigated a multiplatform phenotyping approach that combines high-throughput global metabolomics with flow cytometry to evaluate the direct effect of tempol on the microbiota. This approach may be useful in deciphering how other xenobiotics directly influence the microbiota.

Structural and Functional Analysis of the Gut Microbiome for Toxicologists

Characterizing the reciprocal interactions between toxicants, the gut microbiota, and the host, holds great promise for improving our mechanistic understanding of toxic endpoints. Advances in culture-independent sequencing analysis (e.g., 16S rRNA gene amplicon sequencing) combined with quantitative metabolite profiling (i.e., metabolomics) have provided new ways of studying the gut microbiome and have begun to illuminate how toxicants influence the structure and function of the gut microbiome. Developing a standardized protocol is important for establishing robust, reproducible, and importantly, comparative data. This protocol can be used as a foundation for examining the gut microbiome via sequencing-based analysis and metabolomics. Two main units follow: (1) analysis of the gut microbiome via sequencing-based approaches; and (2) functional analysis of the gut microbiome via metabolomics. © 2018 by John Wiley & Sons, Inc.

Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders

The vagus nerve represents the main component of the parasympathetic nervous system, which oversees a vast array of crucial bodily functions, including control of mood, immune response, digestion, and heart rate. It establishes one of the connections between the brain and the gastrointestinal tract and sends information about the state of the inner organs to the brain via afferent fibers. In this review article, we discuss various functions of the vagus nerve which make it an attractive target in treating psychiatric and gastrointestinal disorders. There is preliminary evidence that vagus nerve stimulation is a promising add-on treatment for treatment-refractory depression, posttraumatic stress disorder, and inflammatory bowel disease. Treatments that target the vagus nerve increase the vagal tone and inhibit cytokine production. Both are important mechanism of resiliency. The stimulation of vagal afferent fibers in the gut influences monoaminergic brain systems in the brain stem that play crucial roles in major psychiatric conditions, such as mood and anxiety disorders. In line, there is preliminary evidence for gut bacteria to have beneficial effect on mood and anxiety, partly by affecting the activity of the vagus nerve. Since, the vagal tone is correlated with capacity to regulate stress responses and can be influenced by breathing, its increase through meditation and yoga likely contribute to resilience and the mitigation of mood and anxiety symptoms.

Orthogonal Comparison of GC-MS and 1H NMR Spectroscopy for Short Chain Fatty Acid Quantitation

Short chain fatty acids (SCFAs) are important regulators of host physiology and metabolism and may contribute to obesity and associated metabolic diseases. Interest in SCFAs has increased in part due to the recognized importance of how production of SCFAs by the microbiota may signal to the host. Therefore, reliable, reproducible, and affordable methods for SCFA profiling are required for accurate identification and quantitation. In the current study, four different methods for SCFA (acetic acid, propionic acid, and butyric acid) extraction and quantitation were compared using two independent platforms including gas chromatography coupled with mass spectrometry (GC-MS) and 1H nuclear magnetic resonance (NMR) spectroscopy. Sensitivity, recovery, repeatability, matrix effect, and validation using mouse fecal samples were determined across all methods. The GC-MS propyl esterification method exhibited superior sensitivity for acetic acid and butyric acid measurement (LOD < 0.01 μg mL-1, LOQ < 0.1 μg mL-1) and recovery accuracy (99.4%-108.3% recovery rate for 100 μg mL-1 SCFA mixed standard spike in and 97.8%-101.8% recovery rate for 250 μg mL-1 SCFAs mixed standard spike in). NMR methods by either quantitation relative to an internal standard or quantitation using a calibration curve yielded better repeatability and minimal matrix effects compared to GC-MS methods. All methods generated good calibration curve linearity (R2 > 0.99) and comparable measurement of fecal SCFA concentration. Lastly, these methods were used to quantitate fecal SCFAs obtained from conventionally raised (CONV-R) and germ free (GF) mice. Results from global metabolomic analysis of feces generated by 1H NMR and bomb calorimetry were used to further validate these approaches.

Omics Approaches To Probe Microbiota and Drug Metabolism Interactions

The drug metabolism field has long recognized the beneficial and sometimes deleterious influence of microbiota in the absorption, distribution, metabolism, and excretion of drugs. Early pioneering work with the sulfanilamide precursor prontosil pointed toward the necessity not only to better understand the metabolic capabilities of the microbiota but also, importantly, to identify the specific microbiota involved in the generation and metabolism of drugs. However, technological limitations important for cataloging the microbiota community as well as for understanding and/or predicting their metabolic capabilities hindered progress. Current advances including mass spectrometry-based metabolite profiling as well as culture-independent sequence-based identification and functional analysis of microbiota have begun to shed light on microbial metabolism. In this review, case studies will be presented to highlight key aspects (e.g., microbiota identification, metabolic function and prediction, metabolite identification, and profiling) that have helped to clarify how the microbiota might impact or be impacted by drug metabolism. Lastly, a perspective of the future of this field is presented that takes into account what important knowledge is lacking and how to tackle these problems.

Oxidized LDL at the crossroads of immunity in non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is viewed as the hepatic manifestation of the metabolic syndrome and is a condition hallmarked by lipid accumulation in the liver (steatosis) along with inflammation (hepatitis). Currently, the etiology and mechanisms leading to obesity-induced hepatic inflammation are not clear and, as a consequence, strategies to diagnose or treat NASH in an accurate manner do not exist. In the current review, we put forward the concept of oxidized lipids as a significant risk factor for NASH. We will focus on the contribution of the different types of oxidized lipids as part of the oxidized low-density lipoprotein (oxLDL) to the hepatic inflammatory response. Furthermore, we will elaborate on the underlying mechanisms linking oxLDL to inflammatory responses in the liver and on how these cascades can be used as therapeutic targets to combat NASH. This article is part of a Special Issue entitled: Lipid modification and lipid peroxidation products in innate immunity and inflammation edited by Christoph J. Binder.