Lifelong constipation in Parkinson's disease and other clinically defined alpha-synucleinopathies: A population-based study in Southeast Minnesota

Alpha Synuclein Toxicity and Non-Motor Parkinson's

Parkinson's disease (PD) is a common multisystem neurodegenerative disorder affecting 1% of the population over the age of 60 years. The main neuropathological features of PD are the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the presence of alpha synuclein (αSyn)-rich Lewy bodies both manifesting with classical motor signs. αSyn has emerged as a key protein in PD pathology as it can spread through synaptic networks to reach several anatomical regions of the body contributing to the appearance of non-motor symptoms (NMS) considered prevalent among individuals prior to PD diagnosis and persisting throughout the patient's life. NMS mainly includes loss of taste and smell, constipation, psychiatric disorders, dementia, impaired rapid eye movement (REM) sleep, urogenital dysfunction, and cardiovascular impairment. This review summarizes the more recent findings on the impact of αSyn deposits on several prodromal NMS and emphasizes the importance of early detection of αSyn toxic species in biofluids and peripheral biopsies as prospective biomarkers in PD.

Predicting Depression in Parkinson's Disease Using Commonly Available PD Questionnaires

Background: Depression is common in patients with Parkinson's disease (PD) and significantly impacts both the patients and their caregivers. The associations between depression and the responses from commonly used questionnaires for PD patients were assessed. New patients presenting to the Movement Disorder Center completed a number of questionnaires, including assessments of the motor and non-motor symptoms of PD, including depression. Methods: The PD patients were grouped according to severity of depression: none, mild, and moderate-severe, based on the Geriatric Depression Scale (GDS) scores. The mean scores of the Unified PD Rating Scale (UPDRS), Montreal Cognitive Assessment (MoCA), Epworth Sleepiness Scale (ESS), Non-motor Symptoms Scale (NMSS), PD Quality of life (PDQ-39), Hoehn and Yahr score (H&Y), levodopa equivalent daily dose (LEDD), and number of antidepressants used were collected. There were 1214 PD patients included. Results: Increasing depression scores were associated with worsening motor symptoms (according to the UPDRS and H&Y), non-motor symptoms (according to the NMSS), cognition (according to the MoCA), sleepiness (according to the ESS), and quality of life (according to the PDQ-39) (all p-values of p < 0.001). Only half of the patients with mild or moderate-severe depression were taking antidepressants, and the LEDD increased with depression severity. The risk of depression increased by 16% and 5% for every 1-point increase in the NMSS and PDQ-39 scores, respectively. Conclusions: Depression is often unrecognized and undertreated and should be assessed regularly in PD patients, especially in those who demonstrate changes in motor or non-motor symptoms.

Caenorhabditis elegans RAC1/ced-10 mutants as a new animal model to study very early stages of Parkinson's disease

Patients with Parkinson's disease (PD) display non-motor symptoms arising prior to the appearance of motor signs and before a clear diagnosis. Motor and non-motor symptoms correlate with progressive deposition of the protein alpha-synuclein (Asyn) both within and outside of the central nervous system, and its accumulation parallels neurodegeneration. The genome of Caenorhabditis elegans does not encode a homolog of Asyn, thus rendering this nematode an invaluable system with which to investigate PD-related mechanisms in the absence of interference from endogenous Asyn aggregation. CED-10 is the nematode homolog of human RAC1, a small GTPase needed to maintain the function and survival of dopaminergic neurons against human Asyn-induced toxicity in C. elegans. Here, we introduce C. elegans RAC1/ced-10 mutants as a predictive tool to investigate early PD symptoms before neurodegeneration occurs. Deep phenotyping of these animals reveals that, early in development, they displayed altered defecation cycles, GABAergic abnormalities and an increased oxidation index. Moreover, they exhibited altered lipid metabolism evidenced by the accumulation of lipid droplets. Lipidomic fingerprinting indicates that phosphatidylcholine and sphingomyelin, but not phosphatidylethanolamine or phosphatidylserine, were elevated in RAC1/ced-10 mutant nematodes. These collective characteristics reflect the non-motor dysfunction, GABAergic neurotransmission defects, upregulation of stress response mechanisms, and metabolic changes associated with early-onset PD. Thus, we put forward an easy-to-manipulate preclinical animal model to deepen our understanding of early-stage PD and accelerate the translational path for therapeutic target discovery.

Constipation in Parkinson's Disease

Constipation is one of the most common gastrointestinal features of Parkinson's disease (PD), occurring in over 50% of all PD patients during the course of their disease. Furthermore, constipation is now recognized as an important, prodromal symptom and may predate the onset of the classical motor symptoms by decades. Thereafter, the prevalence and severity of constipation in PD tend to parallel the course of both motor and nonmotor phenomena such as cognitive decline and depression. Difficult defecation (obstructed defecation, dyssynergia) is the primary pathophysiology underlying constipation and likely reflects involvement by the PD process of one or more of the many skeletal muscle groups that are involved in effecting defecation. Management of constipation in PD may be complicated by several patient factors including dysphagia, cognitive impairment, depression, and weak sphincter tone. While the armamentarium available to those who treat constipation, in general, has expanded considerably in recent years, the evidence supporting any therapy in the management of this symptom in PD has remained slim.

Association of laxatives use with incident dementia and modifying effect of genetic susceptibility: a population-based cohort study with propensity score matching

BACKGROUND

Constipation was associated with incidence of dementia and cognitive decline. Laxatives are the mainstay of constipation management and are commonly used among older populations for both treatment and prevention of constipation. However, the association between use of laxatives and incident dementia, and whether laxatives use may modify the effect of genetic predisposition on dementia remains unclear.

METHODS

We applied 1:3 propensity score matching to balance the baseline characteristics of the laxative users versus non-users and to reduce potential confounders using multi-variates adjusted Cox hazards regression models. We categorized genetic risk into three groups (low, middle, and high) through a genetic risk score of common genetic variants. Information on laxatives use was assessed at baseline and categories into four varieties, including bulk forming laxatives, softeners and emollients, osmotic laxatives, and stimulant laxatives.

RESULTS

Of 486,994 participants, there were 14,422 laxatives users in UK Biobank. After propensity score matching, participants with use of laxatives (n = 14,422) and matched non-laxative (n = 43,266) exposed individuals were enrolled. Over follow-up to 15 years, there were 1377 participants developed dementia (539 for Alzheimer's disease, and 343 for vascular dementia). The use of laxatives had greater risk of dementia (HR, 1.72; 95% CI:1.54-1.92), Alzheimer's disease (HR, 1.36; 95% CI: 1.13-1.63), and vascular dementia (HR, 1.53; 95% CI: 1.23-1.92). Compared to non-laxative exposed participants, those with use of softeners and emollients drugs, stimulant laxatives, and osmotic laxatives were associated with 96% (HR, 1.96; 95 CI: 1.23-3.12; P = 0.005), 80% (HR, 1.80; 95% CI: 1.37-2.37; P < 0.001), and 107% (HR, 2.07; 95% CI: 1.47-2.92; P < 0.001) higher risk of developed incident dementia, respectively. In joint effect analysis, compared to participants with low/middle genetic susceptibility and non-laxatives use, the HR (95% CIs) of dementia was 4.10 (3.49-4.81) for those with high genetic susceptibility plus use of laxatives. There was an additive interaction between laxatives use and genetic susceptibility on dementia (RERI: 0.736, 95% CI: 0.127 to 1.246; AP: 0.180, 95% CI: 0.047 to 0.312).

CONCLUSIONS

Use of laxatives was associated with higher risk of dementia and modify the effect of genetic susceptibility on dementia. Our findings suggested that attention should be paid to the relationship between laxatives use and dementia, especially in people at high genetic susceptibility.