Papers by Ali Keshavarzian
Journal of Pharmacology and Experimental Therapeutics, Jul 31, 2003
Oxidant damage and gut barrier disruption contribute to the pathogenesis of a variety of inflamma... more Oxidant damage and gut barrier disruption contribute to the pathogenesis of a variety of inflammatory gastrointestinal disorders, including inflammatory bowel disease (IBD). In our studies using a model of the gastrointestinal (GI) epithelial barrier, monolayers of intestinal (Caco-2) cells, we investigated damage to and protection of the monolayer barrier. We reported that activation of nuclear factor-B (NF-B) via degradation of its endogenous inhibitor I-B␣ is key to oxidant-induced disruption of barrier integrity and that growth factor (epidermal growth factor, EGF) protects against this injury by stabilizing the cytoskeletal filaments. Protein kinase C (PKC) activation seems to be required for monolayer maintenance, especially activation of the atypical isoform of PKC. In an attempt to investigate, at the molecular level, the fundamental events underlying EGF protection against oxidant disruption, we tested the intriguing hypothesis that EGF-induced activation of PKC-prevents oxidant-induced activation of NF-B and the consequences of NF-B activation, namely, cytoskeletal and barrier disruption. Monolayers of wild-type (WT) Caco-2 cells were incubated with oxidant (H 2 O 2) with or without EGF or modulators. In other studies, we used the first gastrointestinal cell clones created by stable transfection of varying levels (1-5 g) of cDNA to either overexpress PKC-or to inhibit its expression. Transfected cell clones were then pretreated with EGF or a PKC activator (diacylglycerol analog 1-oleoyl-2-acetyl-glycerol, OAG) before oxidant. We monitored the following endpoints: monolayer barrier integrity, stability of the microtubule cytoskeleton, subcellular distribution and activity of the PKC-isoform, intracellular levels and phosphorylation of the NF-B inhibitor I-B␣, and nuclear translocation and activity of NF-B subunits p65 and p50. Monolayers were also fractionated and processed to assess alterations in the structural protein of the microtubules, polymerized tubulin (S2), and monomeric tubulin (S1). Our data indicated that relative to WT monolayers exposed only to oxidant, pretreatment with EGF protected cell monolayers by 1) increasing native PKC
Frontiers in Neuroscience, Sep 1, 2015
Objective: An inflammation-driven model of PD has been proposed based on the endotoxin lipopolysa... more Objective: An inflammation-driven model of PD has been proposed based on the endotoxin lipopolysaccaride (LPS), a potential source of inflammation in the gastrointestinal system linked to neurotoxicity. Systemic exposure to bacterial endotoxin (LPS) can be determined by measuring plasma LPS binding protein (LBP). We aimed to evaluate whether lipopolysaccharide binding protein (LBP) can be used to distinguish PD subjects from control subjects and to assess whether LBP levels correlate with PD disease severity. Methods: We measured plasma LBP (ng/ml) using an ELISA kit in 94 PD subjects of various stages and 97 control subjects. Disease severity was assessed using the UPDRS and Hoehn and Yahr staging. The LBP level between the PD and control groups was compared using analysis of covariance. Spearman correlation was used to explore the relationship between LBP level and disease severity. Results: The mean LBP level in PD subjects (n = 94) was significantly different from control subjects (n = 95, p = 0.018). In PD subjects, we did not find a correlation between mean LBP level and disease severity. Conclusions: Our data suggests that LBP is one GI biomarker related to LPS induced neurotoxicity. However, there was significant variability in LBP levels within the PD and control groups, limiting its utility as a stand-alone biomarker. This study supports the role of LPS induced neurotoxicity in PD and further exploration of this pathway may be useful in developing sensitive and specific biomarkers for PD.
Alcoholism: Clinical and Experimental Research, Apr 1, 1996
Neutrophils lpolymorphonuclear neutrophils (PMNs)] play a pivotal role in host defense in man. Th... more Neutrophils lpolymorphonuclear neutrophils (PMNs)] play a pivotal role in host defense in man. These defenses may be compromised, however, in alcohol users and abusers. We therefore evaluated the effect of ethanol levels (12.5 to 500 mg/dl), on key functions of human PMNs-chemotaxis and production of reactive oxygen speciesand on changes in cytosolic-free calcium ([Ca2+],), a pivotal intracellular mechanism of PMN activation. Ethanol significantly inhibited chemotaxis as evaluated by formyl-methionyl-leucyl-phenylalanine (fMLP)-induced upregulation of surface adhesion molecules (CDllb). fMLP-induced PMN elongation was only inhibited by a very high ethanol concentration of 500 rng/dl. Production of reactive oxygen species by normal PMNs was assessed by either chemiluminescence (CL) for hypochlorous acid or ferricytochrome c reduction (FCR) for superoxide anions. For PMN stimulated by fMLP, ethanol inhibited CL but not FCR. For PMNs activated by phorbol myristate acetate, ethanol inhibited both CL and FCR. Ethanol did not alter baseline [Ca2+],, as assessed by videomicroscopy using the Ca2+sensing fluorescent dye Fura-2-AM, but did significantly potentiate the increase in peak [Ca2' ], levels that occurs in response to stimulation by fMLP. Calcium channel blockers attenuated ethanol's inhibition of CL. Thus, acute in vitro ethanol, at clinically relevant concentrations, can inhibit several critical aspects of PMN functions. But, in PMNs, unlike neural cells, these inhibitory effects do not seem to be mediated by decreases in Ca2+ influx or in [Ca2+Ij.
Proceedings of the National Academy of Sciences of the United States of America, Jun 14, 2021
Individuals who are minoritized as a result of race, sexual identity, gender, or socioeconomic st... more Individuals who are minoritized as a result of race, sexual identity, gender, or socioeconomic status experience a higher prevalence of many diseases. Understanding the biological processes that cause and maintain these socially-driven health inequities is essential for addressing them. The gut microbiome is strongly shaped by host environments and affects host metabolic, immune, and neuroendocrine functions. The gut microbiome is thus an important pathway by which differences in experiences caused by social, political, and economic forces could contribute to health inequities. Nevertheless, few studies have directly integrated the human gut microbiome into investigations of health inequities. Here we argue that accounting for host-gut microbe interactions will improve our understanding and management of health inequities, and that health policy must begin to consider human-microbiome interactions as important pathways linking social environments to population health.
European Journal of Neurology, Jan 18, 2023
BMC Microbiology, Jun 28, 2019
Background: Fecal samples are currently the most commonly studied proxy for gut microbiota. The g... more Background: Fecal samples are currently the most commonly studied proxy for gut microbiota. The gold standard of sample handling and storage for microbiota analysis is maintaining the cold chain during sample transfer and immediate storage at − 80°C. Gut microbiota studies in large-scale, population-based cohorts require a feasible sample collection protocol. We compared the effect of three different storage methods and mock shipment: immediate freezing at − 80°C, in 95% ethanol stored at room temperature (RT) for 48 h, and on blood collection card stored at RT for 48 h, on the measured composition of fecal microbiota of eight healthy, female volunteers by sequencing the V4 region of the 16S rRNA gene on an Illumina MiSeq. Results: Shared operational taxonomic units (OTUs) between different methods were 68 and 3% for OTUs > 0.01 and < 0.01% mean relative abundance within each group, respectively. α and β-diversity measures were not significantly impacted by different storage methods. With the exception of Actinobacteria, fecal microbiota profiles at the phylum level were not significantly affected by the storage method. Actinobacteria was significantly higher in samples collected on card compared to immediate freezing (1.6 ± 1.1% vs. 0.4 ± 0.2%, p = 0.005) mainly driven by expansion of Actinobacteria relative abundance in fecal samples stored on card in two individuals. There was no statistically significant difference at lower taxonomic levels tested. Conclusion: Consistent results of the microbiota composition and structure for different storage methods were observed. Fecal collection on card could be a suitable alternative to immediate freezing for fecal microbiota analysis using 16S rRNA gene amplicon sequencing.
The American Journal of Gastroenterology, Oct 1, 2014
Americans 2005. Subjects were randomized into 3 groups: 1) FOS intervention (receiving an active ... more Americans 2005. Subjects were randomized into 3 groups: 1) FOS intervention (receiving an active FOS supplement +placebo diet) (n=19); 2) placebo (receiving placebo supplement + placebo diet) (n=19); and 3) diet intervention (receiving placebo supplement + the" anti-IBD" diet) (n=16). Subjects rated their compliance with their assigned diet therapy in a daily diary, and kept a 7-day food log before each visit. An expert dietitian with over 20 years of experience with gastrointestinal disease saw each patient at every visit and assessed their compliance with interviews and review of food-logs. Interclass correlations (ICCs) were calculated to understand the agreement between patient-reported and dietitian-rating of compliance with diet. Results: Th e percentage of compliant patients with their respective diet therapy was 55.8 % and 69.8% based on patient-self-report and the dietitian-rated diet compliance, and did not diff er between groups for either rater (p=0.98 and 0.59, respectively). Th ere was high overall agreement between patientreported and dietitian-rated compliance (average ICC=0.645; p=0.0001). When divided by group, the average ICC remained high (0.786, 0.487, 0.542, for FOS, placebo and diet intervention groups, respectively), but reached statistical signifi cance only for the FOS and diet intervention groups, while there was a trend for the placebo group (p=0.001, 0.09, 0.026; for FOS, placebo and diet groups, respectively). When all patients receiving a placebo diet were examined, the average ICC was also high at 0.659 (p=0.001). Conclusion: Patient-reported and expert dietitian-rated compliance with dietary therapy are highly correlated, suggesting that either measurement could be used to track compliance in the context of a clinical trial of diet with motivated IBD patients.
British Journal of Nutrition, Dec 21, 2009
The American Journal of Gastroenterology, Aug 1, 2005
OBJECTIVES: Several studies suggest that stressful situations (stressors) worsen the course of in... more OBJECTIVES: Several studies suggest that stressful situations (stressors) worsen the course of inflammatory bowel disease (IBD), but the mechanism is not known. Based on several lines of evidence, we hypothesized that psychosocial stress activates the brain-gut axis (BGA) and mucosal mast cells (MC), and activated MC produce proinflammatory cytokines. To test this hypothesis, we determined whether stressor-induced activation of BGA is exaggerated in IBD patients. METHODS: Stress was induced in 15 IBD patients who were in remission (inactive IBD) and in seven controls by a widely used stressor, the cold pressor test (CPT), daily for five consecutive days. Induction of stress was confirmed objectively by measurement of stress hormones (serum cortisol and ACTH), and hemodynamic parameters and subjectively by questionnaire. Activation of the BGA by this stressor was assessed by evaluating colonic mucosal MC histology and degranulation, using electron microscopy (EM). The effects of the stressor on the intestinal mucosa were assessed by changes in inflammatory cell histology, epithelial mitochondria (EM), and oxidative tissue injury (assays for protein oxidation). RESULTS: In both study groups, the stressor resulted in (1) increased levels of stress hormones, (2) the expected changes in hemodynamic parameters, (3) activation and degranulation of MC, (4) mitochondrial damage to epithelial cells, and (5) mucosal protein oxidation. These changes were more marked in IBD patients. CONCLUSIONS: The heightened response to the stressors and the greater epithelial damage in IBD patients suggests that stress-induced activation of the BGA and of mucosal MC is important in the initiation and/or flare up of IBD.
International Journal of Clinical and Experimental Hypnosis, Aug 31, 2007
Hypnotically assisted treatments have been used to reduce stress, improve gastrointestinal motili... more Hypnotically assisted treatments have been used to reduce stress, improve gastrointestinal motility, strengthen immune function, and potentially reduce inflammation. Such treatments may also help reduce disease flares and improve quality of life in inflammatory bowel diseases (IBD). The authors report the results of a case series of 8 white female patients with inactive IBD. All participants initiated and completed treatment, supporting the general acceptability of hypnotically assisted treatment among IBD patients. There was a significant improvement in IBD-quality of life scores for the group posttreatment, t(7) = -3.38, p = .01, with a mean improvement in quality of life of 29 points with significant changes in all 4 subscales. No negative effects of treatment were found.
The American Journal of Gastroenterology, Sep 1, 2006
Gastroenterology, Oct 1, 1990
The aim was to compare upper gut transit and Roux limb motility in patients with (n=lO) and witho... more The aim was to compare upper gut transit and Roux limb motility in patients with (n=lO) and without (n=9) symptoms of food stasis after Roux-Y gastrectomy. Gastric emptying of solids (*Tc labelled eggs) taken per OS and Roux limb and small intestinal transit of a liquid marker ("'In DPTA) instilled into the Roux limb were measured, while Roux limb motility was assessed concurrently using a manometry catheter passed per OS. Identification of the Roux limb was accomplished using radioactive barium markers attached to the manometric catheter. Unoperated volunteers (n=lO) served as healthy controls. Roux limb transit was delayed in both operated groups compared to transit in the corresponding jejunal segment of unoperated controls. Reflux of "'In from the Roux limb into the stomach was found in four of ten symptomatic patients, but in none of the asymptomatic patients (P=O.O6). The rate of gastric emptying was highly variable in symptomatic Roux patients with < 95% gastreetomy (median TVs = 143 min; n=5), and did not differ from asymptomatic Roux patients with a similar gastreetomy (T% = 27 min; n=6) and controls (Fh= 116 min; n=lO). Computerized analysis of motility showed a decrease in overall pressure activity, an increase in simultaneous individual pressure waves, and less aboral migration of clustered waves postprandially in the Roux limb compared to the unoperated healthy jejunum. No differences in Roux limb motility were present, however, between symptomatic and asymptomatic patients. In conclusion, delayed transit and dysmotility in the Roux limb present after gastrectomy may produce. stasis of liquids and solids in the upper gut and jejunal-gastric reflux. However, symptoms cannot be predicted solely on the basis of Roux limb motility or transit. Support: USPHS NIH Grants DK07198, DK18278, and DK34988, and the Mayo Foundation.
The American Journal of Gastroenterology, Oct 1, 2009
Gastroenterology, May 1, 2023
Gastroenterology, May 1, 2023
Scientific Data, Jun 2, 2023
Next generation amplicon sequencing has created a plethora of data from human microbiomes. The ac... more Next generation amplicon sequencing has created a plethora of data from human microbiomes. The accessibility to this scientific data and its corresponding metadata is important for its reuse, to allow for new discoveries, verification of published results, and serving as path for reproducibility. Dietary fiber consumption has been associated with a variety of health benefits that are thought to be mediated by gut microbiota. To enable direct comparisons of the response of the gut microbiome to fiber, we obtained 16S rRNA sequencing data and its corresponding metadata from 11 fiber intervention studies for a total of 2,368 samples. We provide curated and pre-processed genetic data and common metadata for comparison across the different studies.
Current Neurology and Neuroscience Reports, May 28, 2022
Gastrointestinal (GI) symptoms are common in soldiers in combat or high-pressure operational situ... more Gastrointestinal (GI) symptoms are common in soldiers in combat or high-pressure operational situations and often lead to compromised performance. Underlying mechanisms are unclear, but neuroendocrine dysregulation, immune activation and increased intestinal permeability may be involved in stress-related GI dysfunction. To study the effects of prolonged, intense, mixed psychological and physical stress on intestinal permeability, systemic inflammatory and stress markers in soldiers during high-intensity combat-training. In 37 male army medical rapid response troops, GI symptoms, stress markers, segmental intestinal permeability using the 4-sugar test (sucrose, lactulose, mannitol and sucralose) and immune activation were assessed during the 4th week of an intense combat-training and a rest period. Combat-training elicited higher stress, anxiety and depression scores (all P &lt; 0.01) as well as greater incidence and severity of GI symptoms [irritable bowel syndrome symptom severity score (IBS-SSS), P &lt; 0.05] compared with rest. The IBS-SSS correlated with depression (r = 0.41, P &lt; 0.01) and stress (r = 0.40, P &lt; 0.01) ratings. Serum levels of cortisol, interleukin-6, and tumour necrosis factor-α, and segmental GI permeability increased during combat-training compared with rest (all P &lt; 0.05). The lactulose:mannitol ratio was higher in soldiers with GI symptoms (IBS-SSS ≥75) during combat-training than those without (IBS-SSS &lt;75) (P &lt; 0.05). Prolonged combat-training not only induces the expected increases in stress, anxiety and depression, but also GI symptoms, pro-inflammatory immune activation and increased intestinal permeability. Identification of subgroups of individuals at high-risk of GI compromise and of long-term deleterious effects of operational stress as well as the development of protective measures will be the focus of future studies.
Life Sciences, May 1, 1997
Calcn.un (Ca'+) entry from the extra-cellular space tnto the cytoplasm through voltagedependent C... more Calcn.un (Ca'+) entry from the extra-cellular space tnto the cytoplasm through voltagedependent Ca" channels, specifically dipyridamole (DHP) sensitive ones (L-type), control a variety of biological processes, including excitation-contraction coupling in vascular and GI muscle cells. It has also been proposed that these channels may control esophageal contractility. However, DHPsensitive Ca" channels in esophagus have not been well characterized biochemically. Thus, it is not known if these channels are similar in number or afEity to those in vascular or neural tissuesorgans for which clinical use of calcium channel blockers has been successful. Thus, the purpose of this study was to identify and characterize DHP-sensitive calcium channels in esophagus and compare them to vascular, neural, and other GI tissues. Methods-We carried out in vitro receptor binding assays on lower esophageal muscle homogenates, gastric and intestinal and colonic homogenates, and aortic muscle homogenates from ca; and on brain homogenates from rat. We used a radio-labeled dihydropyridine derivative [3H]nitrendipine, to label these sites and coadministration of unlabeled nimodipine to define specific binding. Results-As expected, ligand binding to L-type Ca2' channels in aortic vascular smooth muscle and brain was readily detectable: brain, Bmax=252 fmol/mg protein, Kd=0.88 nM; aorta, Bmax=326 fmol/mg protein, Kd=0.84 nM. For esophagus (Bmax=97; Kd=O.73) and for other GI tissues, using the same assay conditions, we detected a smaller signal, suggesting that L-type Ca*' channels are present in lower quantities. Conclusion-L-type Ca*' channel are present in esophagus and in other GI muscles, their affinity is similar, but their density is relatively sparse. These findings are consistent with the relatively limited success that has been experienced clinically in the use of calcium channel blockers for treatment of esophageal dysmotility.
Uploads
Papers by Ali Keshavarzian