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Bednarska, Olga
Publications (3 of 3) Show all publications
Bednarska, O. (2019). Peripheral and Central Mechanisms in Irritable Bowel Syndrome: in search of links. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Peripheral and Central Mechanisms in Irritable Bowel Syndrome: in search of links
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Irritable bowel syndrome (IBS) is a chronic visceral pain disorder with female predominance, characterized by recurrent abdominal pain and disturbed bowel habits in the absence of an identifiable organic cause. This prevalent and debilitating disease, which accounts for a substantial economic and individual burden, lacks exact diagnostic tools and effective treatment, since its pathophysiology remains uncertain. The bidirectional and multilayered brain-gut axis is a well-established disease model, however, the interactions between central and peripheral mechanisms along the brain-gut axis remain incompletely understood. One of the welldescribed triggering factors, yet accounting for only a fraction of IBS prevalence, is bacterial gastroenteritis that affects mucosal barrier function. Altered gut microbiota composition as well as disturbed intestinal mucosal barrier function and its neuroimmune regulation have been reported in IBS, however, the impact of live bacteria, neither commensal nor pathogenic, on intestinal barrier has not been studied yet. Furthermore, abnormal central processing of visceral sensations and psychological factors such as maladaptive coping have previously been suggested as centrally-mediated pathophysiological mechanisms of importance in IBS. Brain imaging studies have demonstrated an imbalance in descending pain modulatory networks and alterations in brain regions associated with interoceptive awareness and pain processing and modulation, particularly in anterior insula (aINS), although biochemical changes putatively underlying these central alterations remain poorly understood. Most importantly, however, possible associations between these documented changes on central and peripheral levels, which may as complex interactions contribute to disease onset and chronification of symptoms, are widely unknown.

This thesis aimed to investigate the peripheral and central mechanisms in women with IBS compared to female healthy controls (HC) and to explore possible mutual associations between these mechanisms.

In Paper I, we studied paracellular permeability and passage of live bacteria, both commensal and pathogenic through colonic biopsies mounted in Ussing chambers. We explored the regulation of the mucosal barrier function by mast cells and the neuropeptide vasoactive intestinal polypeptide (VIP) as well as a correlation between mucosal permeability and gastrointestinal and psychological symptoms. We observed increased paracellular permeability and the passage of commensal and pathogenic live bacteria in patients with IBS compared with HC, which was diminished by blocking the VIP receptors as well as after stabilizing mast cells in both groups. Moreover, higher paracellular permeability was associated with less somatic and psychological symptoms in patients.

In Paper II, we aimed to determine the association between colonic mucosa paracellular permeability and structural and resting state functional brain connectivity. We demonstrated different patterns of associations between mucosa permeability and functional and structural brain connectivity in IBS patients compared to HC. Specifically, lower paracellular permeability in IBS, similar to the levels detected in HC, was associated with more severe IBS symptoms and increased functional and structural connectivity between intrinsic brain resting state network and descending pain modulation brain regions. Our findings further suggested that this association between mucosa permeability and functional brain connectivity was mainly mediated by coping strategies.

In Paper III, we investigated putative alterations in excitatory and inhibitory neurotransmission of aINS, as the brain’s key node of the salience network crucially involved in cognitive control, in IBS patients relative to HC and addressed possible connections with both symptoms and psychological factors. We found decreased concentrations of the excitatory neurotransmitter Glx in bilateral aINS in IBS patients compared to HC, while inhibitory neurotransmitter GABA+ levels were comparable. Further, we demonstrated hemisphere-specific associations between abdominal pain, coping and aINS excitatory neurotransmitter concentration.

In conclusion, this thesis broadens the knowledge on peripheral and central mechanisms in IBS and presents novel findings that bring together the ends of brain-gut axis. Our results depict association between mucosal permeability, IBS symptoms and functional and structural connectivity engaging brain regions involved in emotion and pain modulation as well as underlying neurotransmitter alterations.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 95
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1678
National Category
Neurosciences Neurology Gastroenterology and Hepatology Surgery Clinical Science
urn:nbn:se:liu:diva-156669 (URN)10.3384/diss.diva-156669 (DOI)9789176850930 (ISBN)
Public defence
2019-06-05, Berzeliussalen, Campus US, Linköping, 09:00 (English)
Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-09-02Bibliographically approved
Bednarska, O., Icenhour, A., Tapper, S., Witt, S. T., Tisell, A., Lundberg, P., . . . Walter, S. (2019). Reduced excitatory neurotransmitter levels in anterior insulae are associated with abdominal pain in irritable bowel syndrome. Pain, 160(9), 2004-2012
Open this publication in new window or tab >>Reduced excitatory neurotransmitter levels in anterior insulae are associated with abdominal pain in irritable bowel syndrome
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2019 (English)In: Pain, ISSN 0304-3959, E-ISSN 1872-6623, Vol. 160, no 9, p. 2004-2012Article in journal (Refereed) Published
Abstract [en]

Irritable bowel syndrome (IBS) is a visceral pain condition with psychological comorbidity. Brain imaging studies in IBS demonstratealtered function in anterior insula (aINS), a key hub for integration of interoceptive, affective, and cognitive processes. However,alterations in aINS excitatory and inhibitory neurotransmission as putative biochemical underpinnings of these functional changesremain elusive. Using quantitative magnetic resonance spectroscopy, we compared women with IBS and healthy women (healthycontrols [HC]) with respect to aINS glutamate 1 glutamine (Glx) and g-aminobutyric acid (GABA1) concentrations and addressedpossible associations with symptoms. Thirty-nine women with IBS and 21 HC underwent quantitative magnetic resonancespectroscopy of bilateral aINS to assess Glx and GABA1 concentrations. Questionnaire data from all participants and prospectivesymptom-diary data from patients were obtained for regression analyses of neurotransmitter concentrations with IBS-related andpsychological parameters. Concentrations of Glx were lower in IBS compared with HC (left aINS P , 0.05, right aINS P , 0.001),whereas no group differences were detected for GABA1concentrations. Lower right-lateralized Glx concentrations in patients weresubstantially predicted by longer pain duration, while less frequent use of adaptive pain‐coping predicted lower Glx in left aINS. Ourfindings provide first evidence for reduced excitatory but unaltered inhibitory neurotransmitter levels in aINS in IBS. The results alsoindicate a functional lateralization of aINS with a stronger involvement of the right hemisphere in perception of abdominal pain and ofthe left aINS in cognitive pain regulation. Our findings suggest that glutaminergic deficiency may play a role in pain processing in IBS.

Place, publisher, year, edition, pages
Lippincott Williams & Wilkins, 2019
Irritable bowel syndrome, Functional magnetic resonance imaging, Quantitative magnetic resonance spectroscopy, Insula, Visceral pain, Coping
National Category
Radiology, Nuclear Medicine and Medical Imaging
urn:nbn:se:liu:diva-160012 (URN)10.1097/j.pain.0000000000001589 (DOI)31045748 (PubMedID)
Available from: 2019-09-02 Created: 2019-09-02 Last updated: 2019-09-09Bibliographically approved
Bednarska, O., Tapper, S., Lundberg, P., Tisell, A., Lowén, M. & Walter, S. (2014). Neurotransmittor Concentration in Pregenual ACC in Stool Consistency Patient Subgroups With IBS. In: : . Paper presented at United European Gastroenterology (UEG), Austria. , 2(Supplement 1)
Open this publication in new window or tab >>Neurotransmittor Concentration in Pregenual ACC in Stool Consistency Patient Subgroups With IBS
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2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]


The Anterior Cingulate Cortex (ACC) is a key region of the central autonomic brain network. Irritable Bowel Syndrome (IBS) is characterized abdominal pain and bowel habit disturbances. Autonomic dysregulation has been reported in IBS as well as altered ACC activation in pregenual ACC during visceral stimulation 1 2. Glutamate is the major excitatory and Gamma-aminobutyric acid (GABA) the major inhibitory neurotransmitter in the brain.

Aim & Methods

We aimed to measure neurotransmitter concentration in the pregenual ACC, in stool consistency subgroups with IBS by using quantitative neurotransmitter Magnetic Resonance Spectroscopy (qMRS)Seven patients with IBS-mixed (6 women) and five patients with IBS -diarrhea (4 women) according to Rome 3 were included. Mean age was 34.2 years (SD 5.3) with no significant difference between subgroups.  Patients completed symptom severity score (IBS-SSS). Quantitative MRS was measured in a 3T MRI scanner. A water-suppressed MEGA-PRESS sequence (TR 2.0 s, TE 68 ms) was used with the editing pulses placed at 1.90 ppm (‘ON-dynamics’) and at 7.46 ppm (‘OFF-dynamics’) with a voxel (3x3x3 cm3) placed in the pACC. Each MEGA-PRESS measurement resulted in a sequence of 40 OFF- and ON-dynamics, where each was computed by 8 phase cycles. Directly after each water-suppressed MEGA-PRESS measurement, a shorter 2-dynamic unsuppressed water MEGA-PRESS measurement was performed within the same voxel, which was used to obtain the concentrations in physically well-defined units of [mM]. The GABA concentrations were computed by averaging the difference spectra obtained by subtracting each OFF-dynamic from subsequent ON-dynamic and using LCModel (Version 6.3) for the final quantification. The Glutamate concentrations were obtained by only averaging the OFF-dynamics, which were not affected by the editing pulses. Additionally, all dynamics were phase and frequency corrected prior to the averaging. For group comparison unpaired T-tests were used.


Patients had moderate to severe symptoms with IBS-SSS of 367 (SD 79.7). There was no significant difference between IBS subgroups in terms of IBS-SSS. Mean pACC GABA concentration was 1.66 (SD 0.17) mM in IBS-M and 1.65 (SD 0.27) mM in IBS-D. There was no significant difference between groups (p=0.9). Mean pACC Glutamate concentration was 4.54 (0.35) mM in IBS-M and 5.13 (SD 0.64) mM in IBS-D. There was no significant difference between groups, although a trend with p=0.06 was observed.


Further qMRS data have to be collected in IBS patients as well as healthy controls to evaluate if IBS subgroups demonstrate alterations in pACC glutamate and GABA concentrations

National Category
Clinical Medicine
urn:nbn:se:liu:diva-114346 (URN)
United European Gastroenterology (UEG), Austria
Available from: 2015-02-19 Created: 2015-02-19 Last updated: 2017-01-19Bibliographically approved

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