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Advanced Neurology Gastrointestinal symptoms in PD

constipation before the onset of motor symptoms indicates PD and GI symptoms may have different mechanisms.
the vulnerability and susceptibility of the intestinal nerves. If PD does originate from the intestine, novel PD
Because of its susceptibility, GI dysfunction acts like a treatment methods may include improving the intestinal
sentry in PD rather than a pathogenic cause [111] . Recent flora, regulating intestinal function, and supplementing
research has found that there is a nigro-vagal monosynaptic corresponding SCFAs and branched chain fatty acids.
pathway controlling gastric tension and gastric motility However, there is currently insufficient evidence to prove
in the rat model of PD induced by 6-hydroxydopamine, that PD originates from the intestine.
which suggests that GI symptoms may be a manifestation If PD is an overall degenerative disease, neurons such as
of dopamine deficiency outside the CNS [112] .
SN dopaminergic neurons, locus coeruleus noradrenergic
The etiology of PD is often compared to prion disease neurons, and the dorsal vagus nucleus are more vulnerable
(Creutzfeldt-Jakob disease) because its pathology may arise because of their long axons, greater number of branches,
from the vagus nerve. Creutzfeldt-Jakob disease is divided higher energy consumption, and greater damage caused
into sporadic and familial Creutzfeldt-Jakob disease. The by free radicals. Thus, the treatment of PD and related
pathogens of sporadic and familial Creutzfeldt-Jakob GI symptoms should include methods to protect neurons
disease originate from the PNS and CNS, respectively. from damage.
Analogously, PD can be divided into two subtypes that
originate from the PNS or occur idiopathically in the 7. Conclusions
CNS [113] . Different subtypes of PD may show specific There is no doubt that GI dysfunction exists in PD and
phenotypes and prognoses. Patients with constipation seriously decreases quality of life. However, it remains
have more serious axial symptoms, indicating that the unclear whether GI dysfunction is part of the symptoms
progress of PD is relatively fast in these patients, especially of PD or an initial cause of PD. Although there are many
those who develop constipation before the onset of available treatments for GI symptoms, including compound
motor symptoms, suggesting that axial symptoms and drugs, natural herbs, physical stimulation, and a healthy
constipation are interactive factors in PD [114] . Similarly, diet, it is still difficult to treat PD-related GI symptoms,
patients with constipation are at greater risk of dementia [110] . especially in patients with advanced PD. Therefore, further
This suggests that patients with PD that originates from drug research and development is needed. In addition,
the intestine may have different characteristics regarding more in-depth clinical and basic research is warranted to
phenotype and even pathogenesis. uncover the causes of the intestinal symptoms of PD.
Patients with PD have GI symptoms, regardless of
whether PD originates in the gut or whether GI dysfunction Funding
is one of the manifestations of PD outside the CNS. This work was partially supported by grants from the
6. Challenges Jiangsu Provincial Key R&D Program (BE2018658),
Discipline Construction Program of the Second Affiliated
At present, there is no fundamental solution to the GI Hospital Soochow University (XKTJ-XK202001), Priority
symptoms of PD. The current treatment is mainly based Academic Program Development of Jiangsu Higher
on the physical function of the digestive tract itself, such Education Institutions (PAPD), and Seventh Batch of GuSu
as increasing the viscosity of food, increasing the osmotic District Health Talent Training Project (GSWS2020118).
pressure of the intestinal tract, and locally promoting GI
peristalsis. However, these treatments cannot radically Conflict of interest
alleviate the symptoms of PD, such as excessive salivation The authors report no conflicts of interest.
and constipation. Moreover, most effects of the current
treatments can only be maintained for a certain period. For Author contributions
example, the tension relief achieved through the injection Conceptualization: Chun-Feng Liu
of BoNT is generally maintained for 3 months, and the
regulation of intestinal flora by the ingestion of beneficial Writing – original draft: Xiao-Yu Cheng and Ya-Li Wang
microbes is sustained for several days. Writing – review and editing: Xiao-Yu Cheng and Ya-Li
The main reason for the poor management of PD-related Wang
GI symptoms is that the GI symptoms of PD and even the
mechanism of PD itself are not yet completely clear. The References
GI symptoms cannot be completely relieved by dopamine 1. Mukherjee A, Biswas A, Das SK, 2016, Gut dysfunction in
replacement, which suggests that the motor symptoms of Parkinson’s disease. World J Gastroenterol, 22(25): 5742–5752.

Volume 1 Issue 1 (2022) 10 https://doi.org/10.36922/an.v1i1.9