Effect of age, sex and gender on pain sensitivity: A narrative review

© 2017 Eltumi And Tashani. Introduction: An increasing body of literature on sex and gender differences in pain sensitivity has been accumulated in recent years. There is also evidence from epidemiological research that painful conditions are more prevalent in older people. The aim of this narrative review is to critically appraise the relevant literature investigating the presence of age and sex differences in clinical and experimental pain conditions. Methods: A scoping search of the literature identifying relevant peer reviewed articles was conducted on May 2016. Information and evidence from the key articles were narratively described and data was quantitatively synthesised to identify gaps of knowledge in the research literature concerning age and sex differences in pain responses. Results: This critical appraisal of the literature suggests that the results of the experimental and clinical studies regarding age and sex differences in pain contain some contradictions as far as age differences in pain are concerned. While data from the clinical studies are more consistent and seem to point towards the fact that chronic pain prevalence increases in the elderly findings from the experimental studies on the other hand were inconsistent, with pain threshold increasing with age in some studies and decreasing with age in others. Conclusion: There is a need for further research using the latest advanced quantitative sensory testing protocols to measure the function of small nerve fibres that are involved in nociception and pain sensitivity across the human life span. Implications: Findings from these studies should feed into and inform evidence emerging from other types of studies (e.g. brain imaging technique and psychometrics) suggesting that pain in the older humans may have unique characteristics that affect how old patients respond to intervention

Age-Related Variations in Jejunum and Distal Colon Contractile Response to Thyrotropin-Releasing Hormone in vitro

The effects of thyrotropin-releasing hormone (TRH) on the contractile activity of the proximal jejunum and distal colon of 3-, 7-, 14-, 21-, 28-, 50-day-old and adult male Sprague-Dawley rats were examined. Longitudinal segments were mounted in force displacement transducers and bathed in oxygenated, buffered Krebs’ solution. In the proximal jejunum TRH 10&lt;sup&gt;––6&lt;/sup&gt; &lt;i&gt;M&lt;/i&gt; produced a tetrodotoxin (TTX)-sensitive tension increase in 3- to 14-day-old rats and a TTX-resistant biphasic response in older rats. TRH 10&lt;sup&gt;––6&lt;/sup&gt;&lt;i&gt;M&lt;/i&gt; produced a transient tension in the distal colon of rats ≤ 21 days old. Incubation with TRH 10&lt;sup&gt;––6&lt;/sup&gt;&lt;i&gt;M&lt;/i&gt; for 30min increased responsiveness to acetylcholine 10&lt;sup&gt;––7&lt;/sup&gt;&lt;i&gt;M&lt;/i&gt; in approximately 50% of tissues studied. Direct and indirect effects of TRH are developmentally determined.</jats:p

Adrenalectomy and Pentagastrin Effects on Gastrointestinal Cholinergic Enzyme Activities

The present study examined the effects of pentagastrin and adrenalectomy on choline acetyltransferase (ChAT) and acetylcholine esterase (AChE), enzymes which synthesize and degrade acetylcholine in the rat gastrointestinal tract. Adrenalectomized and non-adrenalectomized rats, 14 and 21 days old, were treated with either pentagastrin (250 μg/kg i.p.) or saline for 7 days. Rats were sacrificed at 21 and 28 days of age. Adrenalectomy- and pentagastrin-treated 21-day-old rats had greater ChAT activities than those treated with pentagastrin alone, while AChE activities were higher in the pentagastrin-treated group. Adrenalectomy- and pentagastrin-treated 28-day-old rats had lower levels of activity as compared to pentagastrin-treated rats. The adrenal gland does appear to influence the response of cholinergic enzyme activities to pentagastrin.</jats:p

Stool and urine trefoil factor 3 levels: associations with symptoms, intestinal permeability, and microbial diversity in irritable bowel syndrome

Previously we showed that urine trefoil factor 3 (TFF3) levels were higher in females with irritable bowel syndrome (IBS) compared to non-IBS females. To assess if TFF3 is associated with symptoms and/or reflect alterations in gastrointestinal permeability and gut microbiota in an IBS population, we correlated stool and urine TFF3 levels with IBS symptoms, intestinal permeability, stool microbial diversity and relative abundance of predominant bacterial families and genera. We also tested the relationship of stool TFF3 to urine TFF3, and compared results based on hormone contraception use. Samples were obtained from 93 females meeting Rome III IBS criteria and completing 4-week symptom diaries. TFF3 levels were measured by ELISA. Permeability was assessed with the urine lactulose/mannitol (L/M) ratio. Stool microbiota was assessed using 16S rRNA. Stool TFF3, but not urine TFF3, was associated positively with diarrhoea and loose stool consistency. Higher stool TFF3 was also associated with lower L/M ratio and microbial diversity. Of the 20 most abundant bacterial families Mogibacteriaceae and Christensenellaceae were inversely related to stool TFF3, with only Christensenellaceae remaining significant after multiple comparison adjustment. There were no significant relationships between stool or urine TFF3 levels and other symptoms, nor between stool and urine levels. In premenopausal females, urine TFF3 levels were higher in those reporting hormone contraception. Collectively these results suggest that higher stool TFF3 levels are associated with IBS symptoms (loose/diarrhoeal stools), lower gut permeability, and altered stool bacteria composition (decreased diversity and decreased Christensenellaceae), which further suggests that TFF3 may be an important marker of host-bacteria interaction. </jats:p

Supplementary files for Beneficial Microbes: <b>Gut microbiome and symptoms in females with irritable bowel syndrome: a cross-sectional analysis</b>

Irritable bowel syndrome (IBS), a disorder of gut-brain interaction, is associated with abdominal pain and stool frequency/character alterations that are linked to changes in microbiome composition. We tested whether taxa differentially abundant between females with IBS vs healthy control females (HC) are associated with daily gastrointestinal and psychological symptom severity. Participants (age 18-50 year) completed a 3-day food record and collected a stool sample during the follicular phase. They also completed a 28-day diary rating symptom intensity; analysis focused on the three days after the stool sample collection. 16S rRNA gene sequencing was used for bacterial identification. Taxon abundance was compared between IBS and HC using zero-inflated quantile analysis (ZINQ). We found that females with IBS (n=67) had greater Bacteroides abundance (q=0.003) and lower odds of Bifidobacterium presence (q=0.036) compared to HC (n=46) after adjusting for age, race, body mass index, fibre intake, and hormonal contraception use. Intestimonas, Oscillibacter, and Phascolarctobacterium were more often present and Christensenellaceae R-7 group, Collinsella, Coprococcus 2, Moryella, Prevotella 9, Ruminococcaceae UCG-002, Ruminococcaceae UCG-005, and Ruminococcaceae UCG-014 were less commonly present in IBS compared to HC. Despite multiple taxon differences in IBS vs HC, we found no significant associations between taxon presence or abundance and average daily symptom severity within the IBS group. This may indicate the need to account for interactions between microbiome, dietary intake, metabolites, and host factors.</p