Willemijntje A. Hoogerwerf

The Impact of Rotating Shift Work on the Prevalence of Irritable Bowel Syndrome in Nurses

OBJECTIVES:Shift work has been associated with gastrointestinal symptoms such as abdominal pain, constipation, and diarrhea. These symptoms overlap with those reported by patients with functional bowel disorders. Because shift work will lead to misalignment between the endogenous circadian timing system and the external 24 h environment, we hypothesized that nurses participating in shift work will have a higher prevalence of functional bowel disorders when compared with nurses participating in day shifts.METHODS:Nurses engaged in patient care were invited to complete Rome III, irritable bowel syndrome–quality of life measure (IBS-QOL) and modified Sleep-50 questionnaires. Respondents were classified as working day, night, or rotating shifts. The prevalence of IBS, functional constipation, functional diarrhea, and individual gastrointestinal symptoms was determined.RESULTS:Data were available for 399 nurses (214 day shift, 110 night shift, and 75 rotating shift workers). Rotating shift nurses had a significantly higher prevalence of IBS compared to day shift nurses (48% vs. 31%, P<0.01). Multivariable logistic regression correcting for age, gender, and sleep quality proved this association robust. IBS-QOL scores among groups were similar. Prevalence of functional constipation and functional diarrhea was similar between groups. Rotating shift nurses had a significantly higher prevalence of abdominal pain compared to day shift (81% vs. 54%, P<0.0001) and night shift workers (61%, P=0.003).CONCLUSIONS:Participation in shift work, especially rotating shift work, is associated with the development of IBS and abdominal pain that is independent of sleep quality. Circadian rhythm disturbances may have a function in the pathogenesis of IBS and abdominal pain.

Transcriptional Profiling of mRNA Expression in the Mouse Distal Colon

BACKGROUND & AIMS Intestinal epithelial cells and the myenteric plexus of the mouse gastrointestinal tract contain a circadian clock-based intrinsic time-keeping system. Because disruption of the biological clock has been associated with increased susceptibility to colon cancer and gastrointestinal symptoms, we aimed to identify rhythmically expressed genes in the mouse distal colon. METHODS Microarray analysis was used to identify genes that were rhythmically expressed over a 24-hour light/dark cycle. The transcripts were then classified according to expression pattern, function, and association with physiologic and pathophysiologic processes of the colon. RESULTS A circadian gene expression pattern was detected in approximately 3.7% of distal colonic genes. A large percentage of these genes were involved in cell signaling, differentiation, and proliferation and cell death. Of all the rhythmically expressed genes in the mouse colon, approximately 7% (64/906) have been associated with colorectal cancer formation (eg, B-cell leukemia/lymphoma-2 [Bcl2]) and 1.8% (18/906) with various colonic functions such as motility and secretion (eg, vasoactive intestinal polypeptide, cystic fibrosis transmembrane conductance regulator). CONCLUSIONS A subset of genes in the murine colon follows a rhythmic expression pattern. These findings may have significant implications for colonic physiology and pathophysiology.

Role of biological rhythms in gastrointestinal health and disease.

The molecular basis for biological rhythms is formed by clock genes. Clock genes are functional in the liver, within gastrointestinal epithelial cells and neurons of the enteric nervous system. These observations suggest a possible role for clock genes in various circadian functions of the liver and the gastrointestinal tract through the modulation of organ specific clock-controlled genes. Consequently, disruptions in circadian rhythmicity may lead to adverse health consequences. This review will focus on the current understanding of the role of circadian rhythms in the pathogenesis of gastrointestinal- and hepatic disease such as obesity, non-alcoholic fatty liver disease, alcoholic fatty liver disease and alterations in colonic motility.

Role of clock genes in gastrointestinal motility

Biological rhythms coordinate the timing of our internal bodily functions. Colonic motility follows a rhythm as well: most people will have a bowel movement in the morning and rarely during the night. Recent work provides a potential mechanism for this observation: the mouse colon possesses a functional circadian clock as well as a subset of rhythmically expressed genes that may directly impact on colonic motility. Furthermore, measures of colonic motility such as the colonic tissue contractile response to acetylcholine, stool output, and intracolonic pressure changes vary as a function of the time of day, but these variations are attenuated in mice with disrupted clock function. These laboratory findings are supported by clinical observations. Gastrointestinal symptoms such as diarrhea or constipation are prevalent among shift workers and time-zone travelers, both of which are conditions associated with disruptions in biological rhythms. This review will discuss new insights into the role of clock genes in colonic motility and their potential clinical relevance.

Rhythmic changes in colonic motility are regulated by period genes

Human bowel movements usually occur during the day and seldom during the night, suggesting a role for a biological clock in the regulation of colonic motility. Research has unveiled molecular and physiological mechanisms for biological clock function in the brain; less is known about peripheral rhythmicity. This study aimed to determine whether clock genes such as period 1 (per1) and period2 (per2) modulate rhythmic changes in colonic motility. Organ bath studies, intracolonic pressure measurements, and stool studies were used to examine measures of colonic motility in wild-type and per1per2 double-knockout mice. To further examine the mechanism underlying rhythmic changes in circular muscle contractility, additional studies were completed in neuronal nitric oxide synthase (nNOS) knockout mice. Intracolonic pressure changes and stool output in vivo, and colonic circular muscle contractility ex vivo, are rhythmic with greatest activity at the start of night in nocturnal wild-type mice. In contrast, rhythmicity in these measures was absent in per1per2 double-knockout mice. Rhythmicity was also abolished in colonic circular muscle contractility of wild-type mice in the presence of N(omega)-nitro-L-arginine methyl ester and in nNOS knockout mice. These findings suggest that rhythms in colonic motility are regulated by both clock genes and a nNOS-mediated inhibitory process and suggest a connection between these two mechanisms.

The role of mast cells in the pathogenesis of pain in chronic pancreatitis

BackgroundThe biological basis of pain in chronic pancreatitis is poorly understood. Mast cells have been implicated in the pathogenesis of pain in other conditions. We hypothesized that mast cells play a role in the pain of chronic pancreatitis.We examined the association of pain with mast cells in autopsy specimens of patients with painful chronic pancreatitis. We explored our hypothesis further using an experimental model of trinitrobenzene sulfonic acid (TNBS) -induced chronic pancreatitis in both wild type (WT) and mast cell deficient mice (MCDM).MethodsArchival tissues with histological diagnoses of chronic pancreatitis were identified and clinical records reviewed for presence or absence of reported pain in humans. Mast cells were counted.The presence of pain was assessed using von Frey Filaments (VFF) to measure abdominal withdrawal responses in both WT and MCDM mice with and without chronic pancreatitis.ResultsHumans with painful chronic pancreatitis demonstrated a 3.5-fold increase in pancreatic mast cells as compared with those with painless chronic pancreatitis.WT mice with chronic pancreatitis were significantly more sensitive as assessed by VFF pain testing of the abdomen when compared with MCDM.ConclusionHumans with painful chronic pancreatitis have an increased number of pancreatic mast cells as compared with those with painless chronic pancreatitis. MCDM are less sensitive to mechanical stimulation of the abdomen after induction of chronic pancreatitis as compared with WT. Mast cells may play an important role in the pathogenesis of pain in chronic pancreatitis.

Expression of clock proteins in developing tooth

Morphological and functional changes during ameloblast and odontoblast differentiation suggest that enamel and dentin formation is under circadian control. Circadian rhythms are endogenous self-sustained oscillations with periods of 24h that control diverse physiological and metabolic processes. Mammalian clock genes play a key role in synchronizing circadian functions in many organs. However, close to nothing is known on clock genes expression during tooth development. In this work, we investigated the expression of four clock genes during tooth development. Our results showed that circadian clock genes Bmal1, clock, per1, and per2 mRNAs were detected in teeth by RT-PCR. Immunohistochemistry showed that clock protein expression was first detected in teeth at the bell stage (E17), being expressed in EOE and dental papilla cells. At post-natal day four (PN4), all four clock proteins continued to be expressed in teeth but with different intensities, being strongly expressed within the nucleus of ameloblasts and odontoblasts and down-regulated in dental pulp cells. Interestingly, at PN21 incisor, expression of clock proteins was down-regulated in odontoblasts of the crown-analogue side but expression was persisting in root-analogue side odontoblasts. In contrast, both crown and root odontoblasts were strongly stained for all four clock proteins in first molars at PN21. Within the periodontal ligament (PDL) space, epithelial rests of Malassez (ERM) showed the strongest expression among other PDL cells. Our data suggests that clock genes might be involved in the regulation of ameloblast and odontoblast functions, such as enamel and dentin protein secretion and matrix mineralization.

Molecular cloning of the rat proteinase-activated receptor 4 (PAR4)

BackgroundThe proteinase-activated receptor 4 (PAR4) is a G-protein-coupled receptor activated by proteases such as thrombin and trypsin. Although activation of PAR4 has been shown to modulate rat gastrointestinal motility, the rat PAR4 sequence was unknown until now. This study aimed to identify the rat PAR4 cDNA.ResultsThe cDNA coding for the rat PAR4 homologue was cloned from the duodenum. Northern blots demonstrated a 3.0 kb transcript in the duodenum. Protein homology with mouse and human counterparts was 90% and 75% respectively. PAR4 is expressed predominantly in the esophagus, stomach, duodenum and the spleen. When expressed in COS cells, PAR4 is activated by trypsin (1 nM), thrombin (50 nM), mouse PAR4 specific peptide (500 μM) and a putative rat PAR4 specific activating peptide (100 μM), as measured by intracellular Ca2+-changes.ConclusionsWe have identified and characterized cDNA encoding the rat PAR4 homologue. PAR4 is expressed predominantly in the upper gastrointestinal tract. It is activated by trypsin, thrombin and its newly identified rat PAR4 specific activating peptide.

Achalasia: Treatment options revisited

The aim of all current forms of treatment of achalasia is to enable the patient to eat without disabling symptoms such as dysphagia, regurgitation, coughing or choking. Historically, this has been accomplished by mechanical disruption of the lower esophageal sphincter fibres, either by means of pneumatic dilation (PD) or by open surgical myotomy. The addition of laparoscopic myotomy and botulinum toxin (BTX) injection to the therapeutic armamentarium has triggered a recent series of reviews to determine the optimal therapeutic approach. Both PD and BTX have excellent short term (less than three months) efficacy in the majority of patients. New data have been published that suggest that PD and BTX (with repeat injections) can potentially obtain long term efficacy. PD is still considered the first-line treatment by most physicians; its main disadvantage is risk of perforation. BTX injection is evolving as an excellent, safe option for patients who are considered high risk for more invasive procedures. Laparoscopic myotomy with combined antireflux surgery is an increasingly attractive option in younger patients with achalasia, but long term follow-up studies are required to establish its efficacy and the potential for reflux-related sequelae.

Stress, geomagnetic disturbance, infradian and circadian sampling for circulating corticosterone and models of human depression?

While certain circadian hormonal changes are prominent, their predictable assessment requires a standardization of conditions of sampling. The 24-hour rhythm in circulating corticosterone of rodents, known since the 1950s, was studied as a presumed proxy for stress on 108 rats divided into 9 groups of 6 male and 9 groups of 6 female animals sampled every 4 hours for 24 hours. In a first stress study, the “no-rhythm” (zero-amplitude) assumption failed to be rejected at the 5% probability level in the two control groups and in 16 out of the 18 groups considered. A circadian rhythm could be detected with statistical significance, however, in three separate follow-up studies in the same laboratory, each on 168 rats kept on two antiphasic lighting regimens, with 4-hourly sampling for 7 or 14 days. In the first stress study, pooling of certain groups helped the detection and assessment of the circadian corticosterone rhythm. Without extrapolating to hormones other than corticosterone, which may shift more slowly or adjust differently and in response to different synchronizers, the three follow-up studies yielded uncertainty measures (95% confidence intervals) for the point estimate of its circadian period, of possible use in any future study as a reference standard.The happenstance of a magnetic disturbance at the start of two follow-up studies was associated with the detection of a circasemiseptan component, raising the question whether a geomagnetic disturbance could be considered as a “load”. Far beyond the limitations of sample size, the methodological requirements for standardization in the experimental laboratory concerning designs of studies are considered in the context of models of depression. Lessons from nature’s unforeseen geomagnetic contribution and from human studies are noted, all to support the advocacy, in the study of loads, of sampling schedules covering more than 24 hours.