Gastric myoelectrical activity and gut hormone secretion in myotonic dystrophy

Disturbance of the human gut microbiota in patients with Myotonic Dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a rare autosomal dominant genetic disorder. Although DM1 is primarily characterized by progressive muscular weakness, it exhibits many multisystemic manifestations, such as cognitive deficits, cardiac conduction abnormalities, and cataracts, as well as endocrine and reproductive issues. Additionally, the gastrointestinal (GI) tract is frequently affected, encompassing the entire digestive tract. However, the underlying causes of these GI symptoms remain uncertain, whether it is biomechanical problems of the intestine, involvement of bacterial communities, or both. The primary objective of this study is to investigate the structural changes in the gut microbiome of DM1 patients. To achieve this purpose, 35 patients with DM1 were recruited from the DM-Scope registry of the neuromuscular clinic in the Saguenay-Lac-St-Jean region of the province of Québec, Canada. Stool samples from these 35 patients, including 15 paired samples with family members living with them as controls, were collected. Subsequently, these samples were sequenced by 16S MiSeq and were analyzed with DADA2 to generate taxonomic signatures. Our analysis revealed that the DM1 status correlated with changes in gut bacterial community. Notably, there were differences in the relative abundance of Bacteroidota, Euryarchaeota, Fusobacteriota, and Cyanobacteria Phyla compared to healthy controls. However, no significant shift in gut microbiome community structure was observed between DM1 phenotypes. These findings provide valuable insights into how the gut bacterial community, in conjunction with biomechanical factors, could potentially influence the gastrointestinal tract of DM1 patients.

Principles and clinical methods of body surface gastric mapping: Technical review

BACKGROUND AND PURPOSE

Chronic gastric symptoms are common, however differentiating specific contributing mechanisms in individual patients remains challenging. Abnormal gastric motility is present in a significant subgroup, but reliable methods for assessing gastric motor function in clinical practice are lacking. Body surface gastric mapping (BSGM) is a new diagnostic aid, employs multi-electrode arrays to measure and map gastric myoelectrical activity non-invasively in high resolution. Clinical adoption of BSGM is currently expanding following studies demonstrating the ability to achieve specific patient subgrouping, and subsequent regulatory clearances. An international working group was formed in order to standardize clinical BSGM methods, encompassing a technical group developing BSGM methods and a clinical advisory group. The working group performed a technical literature review and synthesis focusing on the rationale, principles, methods, and clinical applications of BSGM, with secondary review by the clinical group. The principles and validation of BSGM were evaluated, including key advances achieved over legacy electrogastrography (EGG). Methods for BSGM were reviewed, including device design considerations, patient preparation, test conduct, and data processing steps. Recent advances in BSGM test metrics and reference intervals are discussed, including four novel metrics, being the 'principal gastric frequency', BMI-adjusted amplitude, Gastric Alimetry Rhythm Index™, and fed: fasted amplitude ratio. An additional essential element of BSGM has been the introduction of validated digital tools for standardized symptom profiling, performed simultaneously during testing. Specific phenotypes identifiable by BSGM and the associated symptom profiles were codified with reference to pathophysiology. Finally, knowledge gaps and priority areas for future BSGM research were also identified by the working group.

Congenital and childhood myotonic dystrophy: Current aspects of disease and future directions

Myotonic dystrophy type 1 (DM1) is multisystem disease arising from mutant CTG expansion in the non-translating region of the dystrophia myotonica protein kinase gene. While DM1 is the most common adult muscular dystrophy, with a worldwide prevalence of one in eight thousand, age of onset varies from before birth to adulthood. There is a broad spectrum of clinical severity, ranging from mild to severe, which correlates with number of DNA repeats. Importantly, the early clinical manifestations and management in congenital and childhood DM1 differ from classic adult DM1. In neonates and children, DM1 predominantly affects muscle strength, cognition, respiratory, central nervous and gastrointestinal systems. Sleep disorders are often under recognised yet a significant morbidity. No effective disease modifying treatment is currently available and neonates and children with DM1 may experience severe physical and intellectual disability, which may be life limiting in the most severe forms. Management is currently supportive, incorporating regular surveillance and treatment of manifestations. Novel therapies, which target the gene and the pathogenic mechanism of abnormal splicing are emerging. Genetic counselling is critical in this autosomal dominant genetic disease with variable penetrance and potential maternal anticipation, as is assisting with family planning and undertaking cascade testing to instigate health surveillance in affected family members. This review incorporates discussion of the clinical manifestations and management of congenital and childhood DM1, with a particular focus on hypersomnolence and sleep disorders. In addition, the molecular genetics, mechanisms of disease pathogenesis and development of novel treatment strategies in DM1 will be summarised.

Harnessing the beneficial properties of adipogenic microbes for improving human health

Obesity is associated with numerous metabolic comorbidities. Weight loss is an effective measure for alleviating many of these metabolic abnormalities. However, considering the limited success of most medical weight-management approaches in producing a sustained weight loss, approaches that improve obesity-related metabolic abnormalities independent of weight loss would be extremely attractive and of practical benefit. Metabolically healthy obesity supports the notion that a better metabolic profile is possible despite obesity. Moreover, adequate expansion of adipose tissue appears to confer protection from obesity-induced metabolic comorbidities. To this end, the 10th Stock conference examined new approaches to improve metabolic comorbidities independent of weight loss. In particular, human adenovirus 36 (Ad36) and specific gut microbes were examined for their potential to influence lipid and glucose homeostasis in animals and humans. While these microbes possess some undesirable properties, research has identified attributes of adenovirus Ad36 and gut microbes that may be selectively harnessed to improve metabolic profile without the obligatory weight loss. Furthermore, identifying the host signalling pathways that these microbes recruit to improve the metabolic profile may offer new templates and targets, which may facilitate the development of novel treatment strategies for obesity-related metabolic conditions.

Is there a difference in gastric emptying between myotonic dystrophy type 1 patients with and without gastrointestinal symptoms?

Gastrointestinal symptoms are frequent complaints in patients with myotonic dystrophy type 1 (MyD1) and may be associated with reduced gastrointestinal motility caused by smooth muscle dysfunction. Although previous studies have found delayed gastric emptying (GE) in MyD1 patients, the relationship between GE and symptoms has been unclear. We investigated GE in 23 MyD1 patients and 20 healthy volunteers using the 13C-acetate breath test. The MyD1 patients were divided into two groups: those with gastrointestinal symptoms (n = 9) and those without gastrointestinal symptoms (n = 14). The GE function was estimated using the 13C-acetate breath test as half-emptying time (HET) and peak time of the 13C-%-dose-excess curve (T max). GE (HET and T max) was more significantly delayed in patients with MyD1 than in the controls. The GE in MyD1 patients with gastrointestinal symptoms was significantly delayed compared to those without gastrointestinal symptoms. The GE in MyD1 patients with gastrointestinal symptoms was more significantly delayed than in the controls. The GE was significantly delayed in MyD1 patients with gastrointestinal symptoms for >5 years as compared to those with the disease for <5 years, while GE of MyD1 patients without gastrointestinal symptoms did not correlate with the duration of the disease. The GE in MyD1 patients did not correlate with the muscular disability rating scale. These findings suggest that impairment of GE evolves over time and that the progression of delayed GE and skeletal muscle impairment are independent. Smooth muscle impairment may be affected at an earlier stage in MyD1.

Bacterial overgrowth syndrome in myotonic muscular dystrophy is potentially treatable

Over one third of patients with myotonic muscular dystrophy type 1 (DM1) have gastrointestinal complaints. The cause is multifactorial, and treatment options are limited. Twenty DM1 patients with gastrointestinal symptoms were screened over a 2-year period using glucose breath hydrogen testing (GBHT) to evaluate the prevalence of small intestinal bacterial overgrowth (SIBO). Sixty-five percent of patients had a positive GBHT, and diarrhea was the most common presenting symptom. Ciprofloxacin was the most common antibiotic used for treatment, and 70% of patients reported a good response to the initial course of treatment. Although the causes of gastrointestinal symptoms in patients with DM1 are multifactorial, small intestinal bacterial overgrowth is an important diagnostic consideration that is easily diagnosed using glucose breath hydrogen testing and often shows a good response to treatment with common antibiotics.

Myotonic dystrophy types 1 and 2

Myotonic dystrophies (dystrophia myotonica, or DM) are inherited disorders characterized by myotonia and progressive muscle degeneration, which are variably associated with a multisystemic phenotype. To date, two types of myotonic dystrophy, type 1 (DM1) and type 2 (DM2), are known to exist; both are autosomal dominant disorders caused by expansion of an untranslated short tandem repeat DNA sequence (CTG)(n) and (CCTG)(n), respectively. These expanded repeats in DM1 and DM2 show different patterns of repeat-size instability. Phenotypes of DM1 and DM2 are similar but there are some important differences, most conspicuously in the severity of the disease (including the presence or absence of the congenital form), muscles primarily affected (distal versus proximal), involved muscle fiber types (type 1 versus type 2 fibers), and some associated multisystemic phenotypes. The pathogenic mechanism of DM1 and DM2 is thought to be mediated by the mutant RNA transcripts containing expanded CUG and CCUG repeats. Strong evidence supports the hypothesis that sequestration of muscle-blind like (MBNL) proteins by these expanded repeats leads to misregulated splicing of many gene transcripts in corroboration with the raised level of CUG-binding protein 1. However, additional mechanisms, such as changes in the chromatin structure involving CTCN-binding site and gene expression dysregulations, are emerging. Although treatment of DM1 and DM2 is currently limited to supportive therapies, new therapeutic approaches based on pathogenic mechanisms may become feasible in the near future.

Electrogastrography: Poor correlation with antro-duodenal manometry and doubtful clinical usefulness in adults

AIM: To investigate if there is a correlation between electrical activity measured by electrogastrography (EGG) and contractile activity of the stomach as measured by antroduodenal manometry (ADM). We also studied whether the underlying motility disorder could be predicted from EGG parameters.

METHODS: We compared 21 parameters measured from EGG with 8 parameters measured from ADM. The ability of EGG to identify the underlying diagnosis was tested by comparing EGG parameters for each diagnosis group against other patients. The study comprised recordings from 148 patients and 125 females. Their median age was 45 (range 17-76) years.

RESULTS: We found few and weak correlations between EGG and ADM. Specifically the correlation between parameters reflecting the response to meal was poor (r = -0.07, P = 0.39). The discriminatory power of EGG for underlying motility disorder was also low. Patients with slow transit constipation (STC) showed a lower postprandial power in normogastric (3.7 ± 0.5 vs 4.0 ± 0.5) and tachygastric (3.5 ± 0.4 vs 3.7 ± 0.4) regions, a lower percentage of time with normogastria [87.2 (56.5-100)% vs 95.7 (0-100)%], and a higher percentage of time with tachygastria [9.3 (0-33)% vs 3.5 (0-100)%] and bradygastria [1.8 (0-20)% vs 0 (0-17.1)%]. Patients with irritable bowel syndrome had a higher percentage of time with normogastria [96.5 (62.5-100)% vs 93.3 (0-100)%] and a less unstable dominant frequency as measured by the instability coefficient [15 (3-77) vs 24 (2-72)].

CONCLUSION: EGG and ADM seem to measure different aspects of gastric motor activity but cannot show a spatial correlation. The diagnostic value of EGG is poor, but EGG may have some value for the identification of patients with STC.

Gastric electrical activity and cardiovascular risk factors in relation to autonomic nervous function, hormonal responses, and health-related lifestyles in young men

BACKGROUND

Electrogastrography (EGG) is the noninvasive recording of gastric myoelectrical activity. The purpose of the present study was to assess associations of EGG with risk factors for cardiovascular disease (CVD), autonomic nervous function, hormonal responses, and health-related lifestyles.

METHODS

EGG was measured in 435 Japanese men, aged 24-39 years, who worked at the same company. In addition to anthropometric measurements and blood examinations, power spectral analysis of heart rate variability in low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.40 Hz) bands was conducted. LF/HF and HF were used as the indicators of sympathetic and parasympathetic nervous activity, respectively. Serum cortisol and catecholamine levels were measured as well.

RESULTS

In univariate analyses, the EGG frequency was associated positively with the serum high-density lipoprotein (HDL) and cholesterol level (both-P < 0.0001) and negatively with age, body mass index (BMI), serum triglyceride level, fasting blood sugar, and diastolic blood pressure (all P < 0.05). The EGG frequency tended to increase with increases in the HF band (P = 0.10) and was not significantly associated with the LF/HF ratio (P = 0.45). Neither hormonal responses nor health-related lifestyle factors such as smoking and alcohol were significant (all P > 0.05). A multivariate analysis indicated that both the HDL cholesterol level and BMI were independent predictors of EGG frequency (both P < 0.05), after adjusting for the significant effects of age, HF, and other CVD factors.

CONCLUSIONS

Slowed EGG frequency appeared to be linked with various CVD risk factors, including obesity and low HDL cholesterol levels, in young men.

Gastrointestinal manifestations in myotonic muscular dystrophy

Myotonic dystrophy (MD) is characterized by myotonic phenomena and progressive muscular weakness. Involvement of the gastrointestinal tract is frequent and may occur at any level. The clinical manifestations have previously been attributed to motility disorders caused by smooth muscle damage, but histologic evidence of alterations has been scarce and conflicting. A neural factor has also been hypothesized. In the upper digestive tract, dysphagia, heartburn, regurgitation and dyspepsia are the most common complaints, while in the lower tract, abdominal pain, bloating and changes in bowel habits are often reported. Digestive symptoms may be the first sign of dystrophic disease and may precede the musculo-skeletal features. The impairment of gastrointestinal function may be sometimes so gradual that the patients adapt to it with little awareness of symptoms. In such cases routine endoscopic and ultrasonographic evaluations are not sufficient and targeted techniques (electrogastrography, manometry, electromyography, functional ultrasonography, scintigraphy, etc.) are needed. There is a low correlation between the degree of skeletal muscle involvement and the presence and severity of gastrointestinal disturbances whereas a positive correlation with the duration of the skeletal muscle disease has been reported. The drugs recommended for treating the gastrointestinal complaints such as prokinetic, anti-dyspeptic drugs and laxatives, are mainly aimed at correcting the motility disorders. Gastrointestinal involvement in MD remains a complex and intriguing condition since many important problems are still unsolved. Further studies concentrating on genetic aspects, early diagnostic techniques and the development of new therapeutic strategies are needed to improve our management of the gastrointestinal manifestations of MD.

Electrogastrography: basic knowledge, recording, processing and its clinical applications

The slow wave (SW) of the gastrointestinal (GI) tract mainly functions to trigger the onset of spike to elicit smooth muscle contraction, which provides the essential power of motility. Smooth muscle myogenic control activity or SW is believed to originate in the interstitial cells of Cajal (ICC). The electrical coupling promotes interaction between muscle cells, and ICC additionally contribute to SW rhythmicity. Stomach SW originates in the proximal body showing the continuous rhythmic change in the membrane potential and propagates normally to the distal antrum with a regular rhythm of approximately 3 c.p.m. A technique using electrodes positioned on the abdominal skin to pick up stomach rhythmic SW refers to electrogastrography (EGG). The stomach SW amplitude is very weak, while many visceral organs also produce rhythmic electricities, for example heartbeat, respiration, other organs of the GI tract and even body movements. Thus noise other than SW should be filtered out during the recording, while motion artifacts are visually examined and deleted. Finally, the best signal among all recordings is selected to compute EGG parameters based on spectral analysis. The latter is done not only to tranform frequency domain to time domain but also to provide information of time variability in frequency. Obtained EGG parameters include dominant frequency/power, % normal rhythm, % bradygastria, % tachygastria, instability coefficient and power ratio. Clinical experience in EGG has been markedly accumulated since its rapid evolution. In contrast, lack of standardized methodology in terms of electrode positions, recording periods, test meals, analytic software and normal reference values makes the significance of EGG recording controversial. Unlike imaging or manometrical studies, stomach motility disorders are not diagnosed based only on abnormal EGG parameters. Limitations of EGG recording, processing, computation, acceptable normal parameters, technique and reading should be known to conduct subjective assessments when EGG is used to resolve stomach dysfunction. Understanding basic SW physiology, recording methodology and indications may open EGG as a new domain to approach the stomach motor dysfunction.

Delayed gastric emptying in patients with diffuse versus limited systemic sclerosis, unrelated to gastrointestinal symptoms and myoelectric gastric activity

OBJECTIVE

To study the gastric function in patients with diffuse and limited systemic sclerosis (SSc) in relation to the degree of upper gastrointestinal symptoms.

METHODS

Scintigraphic gastric emptying and recording of the myoelectric signals of the stomach were examined in 15 patients with diffuse SSc (dSSc), 13 patients with limited SSc (lSSc) and 15 healthy controls. The frequency of upper gastrointestinal symptoms was determined using a questionnaire.

RESULTS

Patients with dSSc had slower gastric emptying (scintigraphic gastric half-emptying time median (Md) 103 min, range 75-447 min) than control subjects (Md 70 min, range 38-94) and patients with lSSc (Md 76 min, range 43-460). Electrogastrographic recordings did not differ between dSSc, lSSc or controls. Symptoms tended to be more abundant in dSSc patients than in lSSc patients, however, patients with a high frequency of symptoms did not differ from patients with low frequency of symptoms in gastric function, as measured with scintigraphic gastric emptying or electrogastrography (EGG). Neither EGG nor a thorough review of upper gastrointestinal symptoms could predict delayed gastric emptying.

CONCLUSION

The higher prevalence of delayed gastric emptying in patients with dSSc in this study indicates a more severe involvement of the gastrointestinal tract in dSSc than in lSSc, and stresses the importance of differentiating between the subtypes of SSc patients. Since EGG dysrythmia did not correlate with gastric emptying we concluded that factors other than defective myoelectric signals might contribute to a disturbed gastric function.

Gastric emptying in myotonic dystrophy

BACKGROUND

Gastrointestinal symptoms are common and important for the quality of life in patients with myotonic dystrophy (MD). Gastric emptying was studied in patients with MD who suffered from symptoms suggesting slow gastric emptying and the effect of prokinetic treatment was evaluated.

METHODS

Gastric emptying was studied in 10 patients with MD who were suffering from nausea, early satiety, bloating, regurgitation, vomiting, or abdominal pain using a (99)Tc-labelled test meal, and was compared with gastric emptying in a group of healthy controls. The patients were subsequently treated with erythromycin and their gastrointestinal symptoms were recorded and the gastric emptying test was repeated.

RESULTS

Patients with MD had a significantly longer gastric lag phase (46.1 +/- 4.3 vs. 31.9 +/- 4.0 min, P = 0.03), a slower emptying phase (7.1 +/- 0.9 vs. 10.2 +/- 0.9 kJ min(-1), P = 0.02) and a longer half-emptying time, T50 (141.7 +/- 10.5 vs. 98.6 +/- 8.7 min, P = 0.01) than a matched control group. Erythromycin did not stimulate the gastric emptying rate. The effect on gastrointestinal symptoms was modest, except for a reduction of diarrhoea.

CONCLUSIONS

Patients with MD suffering from nausea, vomiting and early satiety, displayed a slow gastric emptying. Treatment with erythromycin had only moderate effect on gastric emptying or gastric symptoms, but reduced diarrhoea in a majority of the patients.