Diabetes, Glycated Hemoglobin (HbA1c), and Neuroaxonal Damage in Parkinson's Disease (MARK-PD Study)

Nicotinamide Riboside Ameliorates Survival Time and Motor Dysfunction in an MPTP-Induced Parkinson's Disease Zebrafish Model through Effects on Glucose Metabolism and Endoplasmic Reticulum Stress

Nicotinamide riboside (NR) is a precursor and exogenous supplement of nicotinamide adenine dinucleotide (NAD+). NR has been shown to play a beneficial role in a variety of neurodegenerative diseases. A phase 1 clinical trial identified NR as a potential neuroprotective therapy for Parkinson's disease (PD). However, the mechanism of action of NR in PD has not been fully elucidated. Therefore, the present study aimed to investigate the potential effects of NR on a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in zebrafish and its underlying mechanisms. The results showed that NR improved motor dysfunction, survival time, dopamine neurons, and peripheral neurons, as well as the NAD+ levels in the MPTP-affected PD zebrafish model. In addition, transcriptome sequencing analysis revealed that, after NR treatment, differentially expressed genes were significantly enriched in the glucose metabolism and protein processing pathways in the endoplasmic reticulum (ER). Quantitative PCR (qPCR) revealed that the mRNA levels of the glycoheterotrophic enzyme (involved in glucose metabolism) were significantly decreased, and the glycolytic enzyme mRNA expression levels were significantly increased. The results of the non-targeted metabolomic analysis showed that NR treatment significantly increased the levels of metabolites such as nicotinic acid and nicotinamide, in addition to α-D-glucose from the gluconeogenesis and glycolysis metabolism pathways and some of the glucogenic amino acids, such as glutamine. Importantly, NR ameliorated MPTP-induced endoplasmic reticulum stress (ERS) in the PD zebrafish model through the Perk-Eif2α-Atf4-Chop pathway. These results highlight the neuroprotective effect of NR in the present PD zebrafish model through modulation of glucose metabolism and ER stress via the Perk-Eif2α-Atf4-Chop pathway and provide valuable mechanistic insights into the treatment of PD.

Frailty and Parkinson's disease: the role of diabetes mellitus

Parkinson's disease (PD) is a chronic neurodegenerative disease associated with a progressive loss of dopaminergic neurons, clinically characterized by motor and non-motor signs. Frailty is a clinical condition of increased vulnerability and negative health outcomes due to the loss of multiple physiological reserves. Chronic hyperglycemia and insulin resistance, which characterize diabetes mellitus (DM), have been reported to alter dopaminergic activity, increase the risk of PD, and influence the development of frailty. Even though diabetes may facilitate the development of frailty in patients with PD, this relationship is not established and a revision of the current knowledge is necessary. Furthermore, the synergy between DM, PD, and frailty may drive clinical complexity, worse outcomes, and under-representation of these populations in the research. In this review, we aimed to discuss the role of diabetes in the development of frailty among patients with PD. We summarized the clinical characteristics and outcomes of patients with concomitant DM, PD, and frailty. Finally, interventions to prevent frailty in this population are discussed.

Hyperglycemia affects axial signs in patients with Parkinson's disease through mechanisms of insulin resistance or non-insulin resistance

OBJECTIVE

To investigate the influence of hyperglycemia on motor symptoms, especially axial signs, and potential mechanisms related to insulin resistance (IR) in patients with Parkinson's disease (PWP).

METHODS

According to glycated hemoglobin (HbA1c) level, PWP were divided into the low-HbA1c and the high-HbA1c groups. Demographic information, glucose metabolism-related variables, Hoehn-Yahr stage, and motor function were compared between the two groups. Correlations between levels of HbA1c and the homeostatic model assessment (HOMA)-IR and motor function in PWP were further analyzed.

RESULTS

HbA1c level was significantly and positively correlated with the Movement Disorder Society Unified Parkinson's Disease Rating Scale Part III score, axial signs subscore, the Timed Get Up and Go test time, the center of pressure displacement of standing with eyes open and closed, and significantly and negatively correlated with the 10-m walk test comfortable gait speed. HOMA-IR level was significantly and negatively correlated with 10-m walk test comfortable gait speed, but not with others.

CONCLUSIONS

PWP with high HbA1c showed worse axial symptoms, including dysfunction of automatic walking, dynamic balance, and postural control than those with low HbA1c. In PWP, the effects of hyperglycemia on automatic walking speed may be associated with the IR-related mechanisms, and the effects on dynamic balance and postural control may be related to mechanisms other than IR.

Refining the clinical diagnosis of Parkinson's disease

Our ability to define, understand, and classify Parkinson's disease (PD) has undergone significant changes since the disorder was first described in 1817. Clinical features and neuropathologic signatures can now be supplemented by in-vivo interrogation of genetic and biological substrates of disease, offering great opportunity for further refining the diagnosis of PD. In this mini-review, we discuss the historical perspectives which shaped our thinking surrounding the definition and diagnosis of PD. We highlight the clinical, genetic, pathologic and biologic diversity which underpins the condition, and proceed to discuss how recent developments in our ability to define biologic and pathologic substrates of disease might impact PD definition, diagnosis, individualised prognostication, and personalised clinical care. We argue that Parkinson's 'disease', as currently diagnosed in the clinic, is actually a syndrome. It is the outward manifestation of any array of potential dysfunctional biologic processes, neuropathological changes, and disease aetiologies, which culminate in common outward clinical features which we term PD; each person has their own unique disease, which we can now define with increasing precision. This is an exciting time in PD research and clinical care. Our ability to refine the clinical diagnosis of PD, incorporating in-vivo assessments of disease biology, neuropathology, and neurogenetics may well herald the era of biologically-based, precision medicine approaches PD management. With this however comes a number of challenges, including how to integrate these technologies into clinical practice in a way which is acceptable to patients, promotes meaningful changes to care, and minimises health economic impact.

The comorbidity and co-medication profile of patients with progressive supranuclear palsy

BACKGROUND

Progressive supranuclear palsy (PSP) is usually diagnosed in elderly. Currently, little is known about comorbidities and the co-medication in these patients.

OBJECTIVES

To explore the pattern of comorbidities and co-medication in PSP patients according to the known different phenotypes and in comparison with patients without neurodegenerative disease.

METHODS

Cross-sectional data of PSP and patients without neurodegenerative diseases (non-ND) were collected from three German multicenter observational studies (DescribePSP, ProPSP and DANCER). The prevalence of comorbidities according to WHO ICD-10 classification and the prevalence of drugs administered according to WHO ATC system were analyzed. Potential drug-drug interactions were evaluated using AiDKlinik®.

RESULTS

In total, 335 PSP and 275 non-ND patients were included in this analysis. The prevalence of diseases of the circulatory and the nervous system was higher in PSP at first level of ICD-10. Dorsopathies, diabetes mellitus, other nutritional deficiencies and polyneuropathies were more frequent in PSP at second level of ICD-10. In particular, the summed prevalence of cardiovascular and cerebrovascular diseases was higher in PSP patients. More drugs were administered in the PSP group leading to a greater percentage of patients with polypharmacy. Accordingly, the prevalence of potential drug-drug interactions was higher in PSP patients, especially severe and moderate interactions.

CONCLUSIONS

PSP patients possess a characteristic profile of comorbidities, particularly diabetes and cardiovascular diseases. The eminent burden of comorbidities and resulting polypharmacy should be carefully considered when treating PSP patients.

Advanced glycation end products consumption and the decline of functional capacity in patients with Parkinson's disease: Cross-sectional study

INTRODUCTION

Advanced Glycation End-Products (AGEs) are a diverse group of highly reactive molecules that play a vital role in the development of neurodegenerative disorders, such as Parkinson's Disease (PD), leading to a decline in functional and cognitive capacity. The objective of this study was to assess the intake and quantification of AGEs in individuals with PD and to correlate them with their functional and cognitive abilities.

METHODS

This was a cross-sectional study involving 20 PD patients and 20 non-PD individuals as the Control group (C). The autofluorescence reader was used to evaluate skin AGEs, while food recall was used to quantify AGEs consumed for three different days. The Montreal Cognitive Assessment, Short Physical Performance Battery, and handgrip tests were used. PD patients demonstrated greater impairment in functional capacity compared to the control group.

RESULTS

Dominant Handgrip (p = 0.02) and motor performance, in the sit and stand test (p = 0.01) and Short Physical Performance Battery (SPPB) (p = 0.01) were inferior in PD patients than the control group. Although PD patients tended to consume less AGEs than the control group, AGE intake was negatively correlated with handgrip strength in individuals with PD (r = -0.59; p < 0.05).

CONCLUSION

PD patients had lower strength and functional capacity, suggesting that the effects of AGEs might be exacerbated during chronic diseases like Parkinson's.

Communal interaction of glycation and gut microbes in diabetes mellitus, Alzheimer's disease, and Parkinson's disease pathogenesis

Diabetes and its complications, Alzheimer's disease (AD), and Parkinson's disease (PD) are increasing gradually, reflecting a global threat vis-à-vis expressing the essentiality of a substantial paradigm shift in research and remedial actions. Protein glycation is influenced by several factors, like time, temperature, pH, metal ions, and the half-life of the protein. Surprisingly, most proteins associated with metabolic and neurodegenerative disorders are generally long-lived and hence susceptible to glycation. Remarkably, proteins linked with diabetes, AD, and PD share this characteristic. This modulates protein's structure, aggregation tendency, and toxicity, highlighting renovated attention. Gut microbes and microbial metabolites marked their importance in human health and diseases. Though many scientific shreds of evidence are proposed for possible change and dysbiosis in gut flora in these diseases, very little is known about the mechanisms. Screening and unfolding their functionality in metabolic and neurodegenerative disorders is essential in hunting the gut treasure. Therefore, it is imperative to evaluate the role of glycation as a common link in diabetes and neurodegenerative diseases, which helps to clarify if modulation of nonenzymatic glycation may act as a beneficial therapeutic strategy and gut microbes/metabolites may answer some of the crucial questions. This review briefly emphasizes the common functional attributes of glycation and gut microbes, the possible linkages, and discusses current treatment options and therapeutic challenges.

How should we be using biomarkers in trials of disease modification in Parkinson's disease?

The recent validation of the α-synuclein seed amplification assay as a biomarker with high sensitivity and specificity for the diagnosis of Parkinson's disease has formed the backbone for a proposed staging system for incorporation in Parkinson's disease clinical studies and trials. The routine use of this biomarker should greatly aid in the accuracy of diagnosis during recruitment of Parkinson's disease patients into trials (as distinct from patients with non-Parkinson's disease parkinsonism or non-Parkinson's disease tremors). There remain, however, further challenges in the pursuit of biomarkers for clinical trials of disease modifying agents in Parkinson's disease, namely: optimizing the distinction between different α-synucleinopathies; the selection of subgroups most likely to benefit from a candidate disease modifying agent; a sensitive means of confirming target engagement; and the early prediction of longer-term clinical benefit. For example, levels of CSF proteins such as the lysosomal enzyme β-glucocerebrosidase may assist in prognostication or allow enrichment of appropriate patients into disease modifying trials of agents with this enzyme as the target; the presence of coexisting Alzheimer's disease-like pathology (detectable through CSF levels of amyloid-β42 and tau) can predict subsequent cognitive decline; imaging techniques such as free-water or neuromelanin MRI may objectively track decline in Parkinson's disease even in its later stages. The exploitation of additional biomarkers to the α-synuclein seed amplification assay will, therefore, greatly add to our ability to plan trials and assess the disease modifying properties of interventions. The choice of which biomarker(s) to use in the context of disease modifying clinical trials will depend on the intervention, the stage (at risk, premotor, motor, complex) of the population recruited and the aims of the trial. The progress already made lends hope that panels of fluid biomarkers in tandem with structural or functional imaging may provide sensitive and objective methods of confirming that an intervention is modifying a key pathophysiological process of Parkinson's disease. However, correlation with clinical progression does not necessarily equate to causation, and the ongoing validation of quantitative biomarkers will depend on insightful clinical-genetic-pathophysiological comparisons incorporating longitudinal biomarker changes from those at genetic risk with evidence of onset of the pathophysiology and those at each stage of manifest clinical Parkinson's disease.

Glycated hemoglobin A1c, cerebral small vessel disease burden, and disease severity in Parkinson's disease

OBJECTIVE

Our study aimed to investigate the glucose levels in PD and controls. We also examine whether glucose control is associated with PD severity regardless of diabetic status, and test whether the correlation is mediated by cerebral small vessel disease (CSVD) burden.

METHODS

A total of 100 patients with idiopathic PD and 100 age- and sex-matched controls who underwent brain magnetic resonance imaging (MRI) were enrolled in this study. We collected the clinical data and blood parameters, including fasting blood glucose (FBG), glycated hemoglobin A1c (HbA1c), and blood lipid. Patients with PD were divided into early (n = 61) and advanced (n = 39) subgroups, based on Hoehn and Yahr (H&Y) stages. Differences between the PD and controls, PD with and without diabetes, and between two PD subgroups were compared. CSVD markers were assessed, including lacunes, white matter hyperintensities, enlarged perivascular spaces, and cerebral microbleeds. Multivariable logistic regressions were used to test the association between HbA1c and H&Y stages. Interaction between HbA1c and CSVD burden in relation to H&Y stages was also analyzed.

RESULTS

PD group exhibited higher HbA1c (p < 0.001), lower high-density lipoprotein cholesterol (p < 0.001) and triglyceride (p = 0.049) than controls. Advanced PD patients showed higher HbA1c than early PD group (p = 0.022). Increasing HbA1c (OR = 1.54, 95% CI 1.03-2.32, p = 0.036) along with longer disease duration (OR = 1.14, 95% CI 1.01-1.27, p = 0.028) and higher UPDRS III score (OR = 1.07, 95% CI 1.02-1.11, p = 0.002) increased the risk of belonging to the higher H&Y stage. However, interaction between HbA1c and CSVD burden in relation to H&Y stages was not significant.

INTERPRETATION

HbA1c is independently associated with H&Y stages in PD, and this correlation may not be mediated by CSVD burden.

Impact of diabetes and glycated hemoglobin level on the clinical manifestations of Parkinson's disease

BACKGROUND

The coexistence of diabetes mellitus (DM) has been suggested to accelerate the progression of Parkinson's disease (PD) and make the phenotype more severe. In this study, we investigated whether DM or glycated hemoglobin (HbA1c) levels affect the differences in motor and nonmotor symptoms.

METHODS

We conducted a cross-sectional study including 140 consecutive Japanese patients with PD for whom medical history and serum HbA1c records were available. The PD patients with a DM diagnosis were classified into the diabetes-complicated group (PD-DM) and the nondiabetes-complicated group (PD-no DM). Next, patients were classified based on a median HbA1c value of 5.7, and clinical parameters were compared. The correlations between HbA1c levels and other clinical variables were analyzed.

RESULTS

Of 140 patients, 23 patients (16%) had DM. Compared to PD-no DM patients, PD-DM patients showed lower MMSE scores. Compared to the lower HbA1c group, the higher HbA1c group showed a higher MDS-UPDRS part III score and a lower metaiodobenzylguanidine (MIBG) scintigraphy heart-to-mediastinum (H/M) ratio. HbA1c levels were positively correlated with age and the MDS-UPDRS part III score and negatively correlated with the MMSE score and H/M ratio on cardiac MIBG scintigraphy. Binary logistic regression analysis, which included age, sex, disease duration, and MMSE and MDS-UPDRS part III scores as independent variables, revealed that a lower MMSE score was an independent contributor to PD-DM and PD with high HbA1c levels.

CONCLUSIONS

DM complications and high HbA1c levels may affect cognitive function in patients with PD.

Relationship between acute glucose variability and cognitive decline in type 2 diabetes: A systematic review and meta-analysis

BACKGROUND

Cognitive decline is one of the most widespread chronic complications of diabetes, which occurs in more than half of the patients with type 2 diabetes (T2DM). Emerging evidences have suggested that glucose variability (GV) is associated with the pathogenesis of diabetic complications. However, the influence of acute GV on cognitive dysfunction in T2DM is still controversial. The aim of the study was to evaluate the association between acute GV and cognitive defect in T2DM, and provide a most recent and comprehensive summary of the evidences in this research field.

METHODS

PubMed, Cochrane library, EMBASE, Web of science, Sinomed, China National Knowledge Infrastructure (CNKI), and Wanfang were searched for articles that reported on the association between acute GV and cognitive impairment in T2DM.

RESULTS

9 eligible studies were included, with a total of 1263 patients with T2DM involved. Results showed that summary Fisher's z value was -0.23 [95%CI (-0.39, -0.06)], suggesting statistical significance (P = 0.006). Summary r value was -0.22 [95%CI (-0.37, -0.06)]. A lower cognitive performance was found in the subjects with greater glucose variation, which has statistical significance. Mean amplitude of glycemic excursions (MAGE) was associated with a higher risk of poor functional outcomes. Fisher's z value was -0.35 [95%CI (-0.43, -0.25)], indicating statistical significance (P = 0.011). Sensitivity analyses by omitting individual studies showed stability of the results.

CONCLUSIONS

Overall, higher acute GV is associated with an increased risk of cognitive impairment in patients with T2DM. Further studies should be required to determine whether targeted intervention of reducing acute GV could prevent cognitive decline.

Prediabetes is associated with a higher serum neurofilament light chain level in adolescents

Objective

Serum neurofilament light chain (sNfL) level, which is a biomarker indicative of neuroaxonal damage and cognitive impairment, has been reported in several neurological diseases. There has been a lack of studies on the association between sNfL levels and prediabetes in adolescents. This study investigated whether sNfL levels were higher in adolescents with prediabetes undergoing elective orthopedic surgery.

Methods

The sNfL level was measured in 149 adolescents aged from 12 to 18 years who underwent elective orthopedic surgery at the Hunan Children's Hospital (18 with and 131 without prediabetes). We evaluated the association between prediabetes and sNfL level after adjusting for age, sex, and triglycerides using a multivariable linear regression model.

Results

The prevalence of prediabetes in adolescents was 12.08%. Univariate logistic regression analysis showed that prediabetes was related to sNfL. In multivariate logistic regression analysis, the association between prediabetes with sNfL levels remained significant after adjustment for age, sex, and triglyceride. The relationship between the two was further visualized by a smoothed curve.

Conclusions

Prediabetes is associated with a higher sNfL. Further large-scale and prospective studies are needed to verify the clinical application of sNfL as a monitoring biomarker for adolescent prediabetes in adolescents and to evaluate the performance of sNfL in predicting the incidence of neuropathy and cognitive dysfunction in adolescents with prediabetes.

The heterogeneity of Parkinson's disease

The heterogeneity of Parkinson's disease (PD), i.e. the various clinical phenotypes, pathological findings, genetic predispositions and probably also the various implicated pathophysiological pathways pose a major challenge for future research projects and therapeutic trail design. We outline several pathophysiological concepts, pathways and mechanisms, including the presumed roles of α-synuclein misfolding and aggregation, Lewy bodies, oxidative stress, iron and melanin, deficient autophagy processes, insulin and incretin signaling, T-cell autoimmunity, the gut-brain axis and the evidence that microbial (viral) agents may induce molecular hallmarks of neurodegeneration. The hypothesis is discussed, whether PD might indeed be triggered by exogenous (infectious) agents in susceptible individuals upon entry via the olfactory bulb (brain first) or the gut (body-first), which would support the idea that disease mechanisms may change over time. The unresolved heterogeneity of PD may have contributed to the failure of past clinical trials, which attempted to slow the course of PD. We thus conclude that PD patients need personalized therapeutic approaches tailored to specific phenomenological and etiologic subtypes of disease.

Chaudhuri's Dashboard of Vitals in Parkinson's syndrome: an unmet need underpinned by real life clinical tests

We have recently published the notion of the "vitals" of Parkinson's, a conglomeration of signs and symptoms, largely nonmotor, that must not be missed and yet often not considered in neurological consultations, with considerable societal and personal detrimental consequences. This "dashboard," termed the Chaudhuri's vitals of Parkinson's, are summarized as 5 key vital symptoms or signs and comprise of (a) motor, (b) nonmotor, (c) visual, gut, and oral health, (d) bone health and falls, and finally (e) comorbidities, comedication, and dopamine agonist side effects, such as impulse control disorders. Additionally, not addressing the vitals also may reflect inadequate management strategies, leading to worsening quality of life and diminished wellness, a new concept for people with Parkinson's. In this paper, we discuss possible, simple to use, and clinically relevant tests that can be used to monitor the status of these vitals, so that these can be incorporated into clinical practice. We also use the term Parkinson's syndrome to describe Parkinson's disease, as the term "disease" is now abandoned in many countries, such as the U.K., reflecting the heterogeneity of Parkinson's, which is now considered by many as a syndrome.

Glucose Metabolism Impairment in Parkinson's Disease

Impairments in systematic and regional glucose metabolism exist in patients with Parkinson's disease (PD) at every stage of the disease course, and such impairments are associated with the incidence, progression, and special phenotypes of PD, which affect each physiological process of glucose metabolism including glucose uptake, glycolysis, tricarboxylic acid cycle, oxidative phosphorylation, and pentose phosphate shunt pathway. These impairments may be attributed to various mechanisms, such as insulin resistance, oxidative stress, abnormal glycated modification, blood-brain-barrier dysfunction, and hyperglycemia-induced damages. These mechanisms could subsequently cause excessive methylglyoxal and reactive oxygen species production, neuroinflammation, abnormal aggregation of protein, mitochondrial dysfunction, and decreased dopamine, and finally result in energy supply insufficiency, neurotransmitter dysregulation, aggregation and phosphorylation of α-synuclein, and dopaminergic neuron loss. This review discusses the glucose metabolism impairment in PD and its pathophysiological mechanisms, and briefly summarized the currently-available therapies targeting glucose metabolism impairment in PD, including glucagon-likepeptide-1 (GLP-1) receptor agonists and dual GLP-1/gastric inhibitory peptide receptor agonists, metformin, and thiazoledinediones.

Parkinson's Disease and Diabetes Mellitus: Synergistic Effects on Pathophysiology and GI Motility

PURPOSE OF REVIEW

Parkinson's disease and diabetes affect an increasing proportion of the aging global population. Both conditions extensively affect gastrointestinal (GI) motility with similar and differing clinical symptoms. Nonetheless, GI symptoms in Parkinson's disease and diabetes pose significant morbidity and impairment of quality of life. Their pathophysiology is poorly understood, and therefore, effective treatment options are lacking.

RECENT FINDINGS

Parkinson's disease patients have oropharyngeal dysphagia and constipation. They also have mild or absent upper GI symptoms associated with delayed gastric emptying, which is prevalent in 70% of patients. Delayed gastric emptying in Parkinson's disease leads to erratic medication absorption and fluctuating motor symptoms. Half of diabetics have upper GI symptoms, which correlate to gastric emptying and changes in brain activity of the insular cortex. The majority of diabetics also have constipation. Diabetics have an increased risk for developing Parkinson's disease and anti-diabetic medications are associated with risk reduction of developing Parkinson's disease. Hyperglycemia is associated with advanced glycated end products formation and acceleration of α-synuclein aggregation. GLP-1 receptor agonists have also demonstrated efficacy in improving motor symptoms and cognition in Parkinson's disease patients with diabetes. Parkinson's disease and diabetes are pan-enteric disorders with significant GI symptoms and impairment of gut motility. Both conditions have synergistic pathophysiologies that propagate neurodegenerative changes. Treatment options for GI symptoms in diabetic and Parkinson's disease patients are lacking. Anti-diabetic treatment improves motor symptoms in Parkinson's disease, however, its effect on GI symptoms is unclear.

Type 2 Diabetes and Parkinson's Disease: A Focused Review of Current Concepts

Highly reproducible epidemiological evidence shows that type 2 diabetes (T2D) increases the risk and rate of progression of Parkinson's disease (PD), and crucially, the repurposing of certain antidiabetic medications for the treatment of PD has shown early promise in clinical trials, suggesting that the effects of T2D on PD pathogenesis may be modifiable. The high prevalence of T2D means that a significant proportion of patients with PD may benefit from personalized antidiabetic treatment approaches that also confer neuroprotective benefits. Therefore, there is an immediate need to better understand the mechanistic relation between these conditions and the specific molecular pathways affected by T2D in the brain. Although there is considerable evidence that processes such as insulin signaling, mitochondrial function, autophagy, and inflammation are involved in the pathogenesis of both PD and T2D, the primary aim of this review is to highlight the evidence showing that T2D-associated dysregulation of these pathways occurs not only in the periphery but also in the brain and how this may facilitate neurodegeneration in PD. We also discuss the challenges involved in disentangling the complex relationship between T2D, insulin resistance, and PD, as well as important questions for further research. © 2022 International Parkinson and Movement Disorder Society.

In Vivo Investigation of Glucose Metabolism in Idiopathic and PRKN-Related Parkinson's Disease

BACKGROUND

Alterations in mitochondrial dysfunction have been implicated in the pathogenesis of Parkinson's disease (PD). Mitochondrial energy production is linked to glucose metabolism, and diabetes is associated with PD. However, studies investigating glucose metabolism in vivo in genetically stratified PD patients and controls have yet to be performed.

OBJECTIVES

The objectives of this study were to explore glucose production, gluconeogenesis, and the contribution of gluconeogenesis to glucose production in idiopathic and PRKN PD compared with healthy controls with state-of-the-art biochemical methods.

METHODS

We applied a dried-blood sampling/gas chromatography/mass spectrometry approach to monitor fluxes in the Cori cycle in vivo.

RESULTS

The contribution of gluconeogenesis to total glucose production is increased in idiopathic PD patients (n = 33), but not in biallelic PRKN mutation carriers (n = 5) compared with healthy controls (n = 13).

CONCLUSIONS

We provide first-time in vivo evidence for alterations in glucose metabolism in idiopathic PD, in keeping with the epidemiological evidence for an association between PD and diabetes. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Glucagon-like peptide-1 (GLP-1) receptor agonists and neuroinflammation: Implications for neurodegenerative disease treatment

Chronic, excessive neuroinflammation is a key feature of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, neuroinflammatory pathways have yet to be effectively targeted in clinical treatments for such diseases. Interestingly, increased inflammation and neurodegenerative disease risk have been associated with type 2 diabetes mellitus (T2DM) and insulin resistance (IR), suggesting that treatments that mitigate T2DM pathology may be successful in treating neuroinflammatory and neurodegenerative pathology as well. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that promotes healthy insulin signaling, regulates blood sugar levels, and suppresses appetite. Consequently, numerous GLP-1 receptor (GLP-1R) stimulating drugs have been developed and approved by the US Food and Drug Administration (FDA) and related global regulatory authorities for the treatment of T2DM. Furthermore, GLP-1R stimulating drugs have been associated with anti-inflammatory, neurotrophic, and neuroprotective properties in neurodegenerative disorder preclinical models, and hence hold promise for repurposing as a treatment for neurodegenerative diseases. In this review, we discuss incretin signaling, neuroinflammatory pathways, and the intersections between neuroinflammation, brain IR, and neurodegenerative diseases, with a focus on AD and PD. We additionally overview current FDA-approved incretin receptor stimulating drugs and agents in development, including unimolecular single, dual, and triple receptor agonists, and highlight those in clinical trials for neurodegenerative disease treatment. We propose that repurposing already-approved GLP-1R agonists for the treatment of neurodegenerative diseases may be a safe, efficacious, and cost-effective strategy for ameliorating AD and PD pathology by quelling neuroinflammation.

The 2022 Lady Estelle Wolfson lectureship on neurofilaments

Neurofilament proteins (Nf) have been validated and established as a reliable body fluid biomarker for neurodegenerative pathology. This review covers seven Nf isoforms, Nf light (NfL), two splicing variants of Nf medium (NfM), two splicing variants of Nf heavy (NfH), α -internexin (INA) and peripherin (PRPH). The genetic and epigenetic aspects of Nf are discussed as relevant for neurodegenerative diseases and oncology. The comprehensive list of mutations for all Nf isoforms covers Amyotrophic Lateral Sclerosis, Charcot-Marie Tooth disease, Spinal muscular atrophy, Parkinson Disease and Lewy Body Dementia. Next, emphasis is given to the expanding field of post-translational modifications (PTM) of the Nf amino acid residues. Protein structural aspects are reviewed alongside PTMs causing neurodegenerative pathology and human autoimmunity. Molecular visualisations of NF PTMs, assembly and stoichiometry make use of Alphafold2 modelling. The implications for Nf function on the cellular level and axonal transport are discussed. Neurofilament aggregate formation and proteolytic breakdown are reviewed as relevant for biomarker tests and disease. Likewise, Nf stoichiometry is reviewed with regard to in vitro experiments and as a compensatory mechanism in neurodegeneration. The review of Nf across a spectrum of 87 diseases from all parts of medicine is followed by a critical appraisal of 33 meta-analyses on Nf body fluid levels. The review concludes with considerations for clinical trial design and an outlook for future research.