Abnormal ghrelin secretion contributes to gastrointestinal symptoms in multiple system atrophy patients

Understanding the potential causes of gastrointestinal dysfunctions in multiple system atrophy

Multiple system atrophy (MSA) is a rare, progressive neurodegenerative disorder characterised by autonomic, pyramidal, parkinsonian and/or cerebellar dysfunction. Autonomic symptoms of MSA include deficits associated with the gastrointestinal (GI) system, such as difficulty swallowing, abdominal pain and bloating, nausea, delayed gastric emptying, and constipation. To date, studies assessing GI dysfunctions in MSA have primarily focused on alterations of the gut microbiome, however growing evidence indicates other structural components of the GI tract, such as the enteric nervous system, the intestinal barrier, GI hormones, and the GI-driven immune response may contribute to MSA-related GI symptoms. Here, we provide an in-depth exploration of the physiological, structural, and immunological changes theorised to underpin GI dysfunction in MSA patients and highlight areas for future research in order to identify more suitable pharmaceutical treatments for GI symptoms in patients with MSA.

Gastrointestinal dysfunction in the synucleinopathies

Interest in gastrointestinal dysfunction in Parkinson's disease has blossomed over the past 30 years and has generated a wealth of investigation into this non-motor aspect of the disorder, research that has encompassed its pathophysiology, its clinical features, and its impact on quality of life. The question of gastrointestinal dysfunction in the other synucleinopathies has not received nearly as much attention, but information and knowledge are growing. In this review, the current knowledge, controversies, and gaps in our understanding of the pathophysiology of gastrointestinal dysfunction in Parkinson's disease and the other synucleinopathies will be addressed, and extended focus will be directed toward the clinical problems involving saliva management, swallowing, gastric emptying, small intestinal function, and bowel function that are so problematic in these disorders.

Characterization of low active ghrelin ratio in patients with advanced pancreatic cancer

PURPOSE

Acyl ghrelin is an orexigenic peptide. Active ghrelin ratio, the ratio of acyl ghrelin to total ghrelin, has an important role in physiological functions and gastrointestinal symptoms. However, low active ghrelin ratio-related characteristics, gastrointestinal symptoms, and chemotherapy-induced gastrointestinal toxicity in patients with advanced pancreatic cancer have not been previously evaluated. The goal of this study was to identify low active ghrelin ratio-related factors in treatment-naïve advanced pancreatic cancer patients.

METHODS

Patients with treatment-naïve advanced pancreatic cancer were eligible for inclusion in this study. Active ghrelin ratio and clinical parameters of patients were prospectively recorded. Factors correlated with low active ghrelin ratio and survival were analyzed.

RESULTS

In total, 92 patients were analyzed. Low active ghrelin ratio-related factors were advanced age (P < 0.01), severe appetite loss (P < 0.01), and decreased cholinesterase (P < 0.01). The adverse events of grade 2 or higher anorexia tended to increase in patients with low active ghrelin ratio. However, no differences were found in survival and body composition between low and high active ghrelin ratio groups.

CONCLUSIONS

Low active ghrelin ratio was related to lack of appetite and low cholinesterase and tended to be related to anorexia grade 2 or higher in patients with treatment-naïve advanced pancreatic cancer.

The Potential Role of Gut-Derived Inflammation in Multiple System Atrophy

BACKGROUND

Recent evidence suggests that Parkinson's disease (PD) is associated with intestinal microbiota dysbiosis, abnormal intestinal permeability, and intestinal inflammation.

OBJECTIVE

Our study aimed to determine if these gut abnormalities are present in another synucleinopathy, multiple system atrophy (MSA).

METHODS

In six MSA and 11 healthy control subjects, we performed immunohistochemistry studies of colonic sigmoid mucosa to evaluate the intestinal barrier marker Zonula Occludens-1 and the endotoxin-related inflammation marker Toll-like-receptor-4 expression. We also assessed colonic sigmoid mucosal and fecal microbiota compositions using high-throughput 16S ribosomal RNA gene amplicon sequencing.

RESULTS

MSA subjects showed disrupted tight junction protein Zonula Occludens-1 structure in sigmoid mucosa tissue suggesting intestinal barrier dysfunction. The lipopolysaccharide specific inflammatory receptor Toll-like-receptor-4 was significantly higher in the colonic sigmoid mucosa in MSA relative to healthy controls. Microbiota analysis suggested high relative abundance of gram-negative, putative "pro-inflammatory" bacteria in various family and genus level taxa, from the phylum Bacteroidetes and Proteobacteria, in MSA feces and mucosa. At the taxonomic level of genus, putative "anti-inflammatory" butyrate-producing bacteria were less abundant in MSA feces. Predictive functional analysis indicated that the relative abundance of a number of genes involved in metabolism were lower in MSA feces, whereas the relative abundance of genes involved in lipopolysaccharide biosynthesis were higher in both MSA feces and mucosa compared to healthy controls.

CONCLUSIONS

This proof-of-concept study provides preliminary evidence that like PD, MSA subjects display evidence of disrupted intestinal barrier integrity, increased marker of endotoxin-related intestinal inflammation, and pro-inflammatory colonic microbiota.

[Clinical picture and diagnostic criteria of multiple system atrophy]

In 2013, European MSA Study Group demonstrated the prospective natural history of MSA. This study was greatly useful for better patients' management and future development of disease-modifying therapy. Although the diagnosis of early symptomatic stage is also an important factor for successful outcome of disease-modifying therapy, current diagnostic criteria for MSA, which has focused on the combination of motor and autonomic manifestations cannot diagnose MSA patients showing isolated autonomic failure in the early course of illness. We presented four premotor MSA patients who had sudden death prior to fulfilling the diagnostic criteria. 4 cases had very mild OPC and SN pathology, but significant autonomic system involvement including the intermediolateral nucleus, Onuf's nucleus, and medullary autonomic nucleus. Contrary, Petrovic et al reported four pathologically proven MSA patients with disease duration of 15 years or more. All patients presented isolated parkinsonism for a long time and mean duration from onset to dysautonomia was 9 years. Novel diagnostic biomarkers, which have a potential for evaluation of the component of glial cytoplasmic inclusion such as alpha-synuclein radiotracer and serum and CSF alpha-synuclein levels may be a key way to support the diagnosis of patients at the stage of "mono system atrophy".

Gastrointestinal hormones and gut motility

PURPOSE OF REVIEW

To summarize the recent findings.

RECENT FINDINGS

Studies of changes in the plasma levels confirm the earlier concepts, but offer little proof of causal effect. It is increasingly realized that peptides produced in the gut have a paracrine role or an indirect effect via the gut-brain axis. Interest in prokinetic peptide agonists remains high despite the failure of two candidate drugs, but relamorelin and camicinal offer new hope.

SUMMARY

We review the original studies published since January 2013 on peptides produced in the gut and with an effect on gastrointestinal motility.