Diabetes Mellitus is Associated with a Higher Relative Risk for Parkinson’s Disease in Women than in Men

Diabetes: a tipping point in neurodegenerative diseases

Diabetes is associated with an increased risk and progression of Alzheimer's (AD) and Parkinson's (PD) diseases. Conversely, diabetes may confer neuroprotection against amyotrophic lateral sclerosis (ALS). It has been posited that perturbations in glucose and insulin regulation, cholesterol metabolism, and mitochondrial bioenergetics defects may underlie the molecular underpinnings of diabetes effects on the brain. Nevertheless, the precise molecular mechanisms remain elusive. Here, we discuss the evidence from molecular, epidemiological, and clinical studies investigating the impact of diabetes on neurodegeneration and highlight shared dysregulated pathways between these complex comorbidities. We also discuss promising antidiabetic drugs, molecular diagnostics currently in clinical trials, and outstanding questions and challenges for future pursuit.

Association between diabetes mellitus, prediabetes and risk, disease progression of Parkinson's disease: A systematic review and meta-analysis

Background

Previous studies reported inconsistent results regarding association between diabetes mellitus (DM), prediabetes and risk, disease progression of Parkinson's disease (PD). The meta-analysis was made to investigate association between DM, prediabetes and risk, disease progression of PD.

Methods

Literatures investigating association between DM, prediabetes and risk, disease progression of PD were searched in these databases: PubMed and Web of Science. Included literatures were published before October 2022. STATA 12.0 software was used to compute odds ratios (ORs)/relative risks (RRs) or standard mean differences (SMDs).

Results

DM was associated with a higher risk of PD, compared to non-diabetic participants with a random effects model (OR/RR = 1.23, 95% CI 1.12-1.35, I 2 = 90.4%, p < 0.001). PD with DM (PD-DM) was associated with a faster motor progression compared to PD without DM (PD-noDM) with a fixed effects model (RR = 1.85, 95% CI 1.47-2.34, I 2 = 47.3%, p = 0.091). However, meta-analysis for comparison in change rate of United Rating Scale (UPDRS) III scores from baseline to follow-up time between PD-DM and PD-noDM reported no difference in motor progression between PD-DM and PD-noDM with a random effects model (SMD = 2.58, 95% CI = -3.11 to 8.27, I 2 = 99.9%, p < 0.001). PD-DM was associated with a faster cognitive decline compared to PD-noDM with a fixed effects model (OR/RR = 1.92, 95% CI 1.45-2.55, I 2 = 50.3%, p = 0.110).

Conclusions

In conclusion, DM was associated with a higher risk and faster disease decline of PD. More large-scale cohort studies should be adopted to evaluate the association between DM, prediabetes and PD.

PKM2-mediated neuronal hyperglycolysis enhances the risk of Parkinson's disease in diabetic rats

Epidemiological and animal studies indicate that pre-existing diabetes increases the risk of Parkinson's disease (PD). However, the mechanisms underlying this association remain unclear. In the present study, we found that high glucose (HG) levels in the cerebrospinal fluid (CSF) of diabetic rats might enhance the effect of a subthreshold dose of the neurotoxin 6-hydroxydopamine (6-OHDA) on the development of motor disorders, and the damage to the nigrostriatal dopaminergic neuronal pathway. In vitro, HG promoted the 6-OHDA-induced apoptosis in PC12 cells differentiated to neurons with nerve growth factor (NGF) (NGF-PC12). Metabolomics showed that HG promoted hyperglycolysis in neurons and impaired tricarboxylic acid cycle (TCA cycle) activity, which was closely related to abnormal mitochondrial fusion, thus resulting in mitochondrial loss. Interestingly, HG-induced upregulation of pyruvate kinase M2 (PKM2) combined with 6-OHDA exposure not only mediated glycolysis but also promoted abnormal mitochondrial fusion by upregulating the expression of MFN2 in NGF-PC12 cells. In addition, we found that PKM2 knockdown rescued the abnormal mitochondrial fusion and cell apoptosis induced by HG+6-OHDA. Furthermore, we found that shikonin (SK), an inhibitor of PKM2, restored the mitochondrial number, promoted TCA cycle activity, reversed hyperglycolysis, enhanced the tolerance of cultured neurons to 6-OHDA, and reduced the risk of PD in diabetic rats. Overall, our results indicate that diabetes promotes hyperglycolysis and abnormal mitochondrial fusion in neurons through the upregulation of PKM2, leading to an increase in the vulnerability of dopaminergic neurons to 6-OHDA. Thus, the inhibition of PKM2 and restoration of mitochondrial metabolic homeostasis/pathways may prevent the occurrence and development of diabetic PD.

The Interrelated Multifactorial Actions of Cortisol and Klotho: Potential Implications in the Pathogenesis of Parkinson's Disease

The pathogenesis of Parkinson's disease (PD) is complex, multilayered, and not fully understood, resulting in a lack of effective disease-modifying treatments for this prevalent neurodegenerative condition. Symptoms of PD are heterogenous, including motor impairment as well as non-motor symptoms such as depression, cognitive impairment, and circadian disruption. Aging and stress are important risk factors for PD, leading us to explore pathways that may either accelerate or protect against cellular aging and the detrimental effects of stress. Cortisol is a much-studied hormone that can disrupt mitochondrial function and increase oxidative stress and neuroinflammation, which are recognized as key underlying disease mechanisms in PD. The more recently discovered klotho protein, considered a general aging-suppressor, has a similarly wide range of actions but in the opposite direction to cortisol: promoting mitochondrial function while reducing oxidative stress and inflammation. Both hormones also converge on pathways of vitamin D metabolism and insulin resistance, also implicated to play a role in PD. Interestingly, aging, stress and PD associate with an increase in cortisol and decrease in klotho, while physical exercise and certain genetic variations lead to a decrease in cortisol response and increased klotho. Here, we review the interrelated opposite actions of cortisol and klotho in the pathogenesis of PD. Together they impact powerful and divergent mechanisms that may go on to influence PD-related symptoms. Better understanding of these hormones in PD would facilitate the design of effective interventions that can simultaneously impact the multiple systems involved in the pathogenesis of PD.

Diabetes mellitus is associated with a higher relative risk for venous thromboembolism in females than in males

AIMS

The risk for developing venous thromboembolism (VTE) is about equal in both sexes. Research suggests diabetes mellitus (DM) is a risk factor for pulmonary embolism and deep vein thrombosis, both forms of VTE. We aimed at investigating the sex-specific impact of DM on VTE risk.

MATERIALS AND METHODS

Medical claims data were analyzed in a retrospective, population-level cohort study in Austria between 1997 and 2014. 180,034 patients with DM were extracted and compared to 540,102 sex and age-matched controls without DM in terms of VTE risk and whether specific DM medications might modulate VTE risk.

RESULTS

The risk to develop VTE was 1.4 times higher amongst patients with DM than controls (95% CI 1.36-1.43, p < 0.001). The association of DM with newly diagnosed VTE was significantly greater in females (OR = 1.52, 95% CI 1.46-1.58, p < 0.001) resulting in a relative risk increase of 1.17 (95% CI 1.11-1.23) across all age groups with a peak of 1.65 (95% CI 1.43-1.89) between 50 and 59 years. Dipeptidyl peptidase 4 inhibitors were associated with a higher risk for VTE amongst female DM patients (OR = 2.3, 95% CI 1.3-4.3, p = 0.0096).

CONCLUSION

Amongst DM patients, females appear to be associated with a higher relative risk increase in VTE than males, especially during perimenopause.

Parkinson's Disease and Sugar Intake-Reasons for and Consequences of a Still Unclear Craving

Lately, studies have shown that patients with Parkinson’s disease (PD) report a strong craving for sweets and consume significantly more fast-acting carbohydrates than healthy controls. Consuming food with a high-sugar content is assumed to lead to an increase in insulin concentration, which could positively influence dopamine concentration in the brain and unconsciously be used by patients as kind of “self-medication” to compensate for a lack of dopamine in PD. On the other hand, high-sugar intake could also lead to insulin resistance and diabetes, which is discussed as a causative factor for progressive neurodegeneration in PD. In this critical appraisal, we discuss the role of sugar intake and insulin on dopamine metabolism in patients with PD and how this could influence the potential neurodegeneration mediated by insulin resistance.

Parkinson's disease and diabetes mellitus: common mechanisms and treatment repurposing

In the last decade, attention has become greater to the relationship between neurodegeneration and abnormal insulin signaling in the central nervous system, as insulin in the brain is implicated in neuronal survival, plasticity, oxidative stress and neuroinflammation. Diabetes mellitus and Parkinson’s disease are both aging-associated diseases that are turning into epidemics worldwide. Diabetes mellitus and insulin resistance not only increase the possibility of developing Parkinson’s disease but can also determine the prognosis and progression of Parkinsonian symptoms. Today, there are no available curative or disease modifying treatments for Parkinson’s disease, but the role of insulin and antidiabetic medications in neurodegeneration opens a door to treatment repurposing to fight against Parkinson’s disease, both in diabetic and nondiabetic Parkinsonian patients. Furthermore, it is essential to comprehend how a frequent and treatable disease such as diabetes can influence the progression of neurodegeneration in a challenging disease such as Parkinson’s disease. Here, we review the present evidence on the connection between Parkinson’s disease and diabetes and the consequential implications of the existing antidiabetic molecules in the severity and development of Parkinsonism, with a particular focus on glucagon-like peptide-1 receptor agonists.

Association of serum cholesterol with Parkinson's disease in a cohort of statin-free individuals

INTRODUCTION

The role of serum cholesterol in the pathogenesis of Parkinson's disease (PD) remains unclear. The objective of this study was to assess the association between serum cholesterol and PD in a cohort of statin-free newly diagnosed PD patients.

METHODS

This retrospective study used fasting lipid profiles obtained from 672 consecutive statin-free newly diagnosed PD individuals and 540 controls. These PD individuals were identified from three medical institutions during 2017-2021, and the controls were identified from three physical examination centers during the same time period. Logistic regressions were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), with adjustment of age, sex, and tobacco use history.

RESULTS

Among 672 PD individuals, 112 were excluded in accordance with the current criteria, leaving 560 PD patients. The multivariate binary logistic regression analysis showed that LDL-C was the only variable contributing to the occurrence of PD (OR 1.39, 95% CI: 1.07-2.31, p < .001) after adjusting for age, sex, and tobacco use history; this association persisted following further adjustment for TC and HDL-C. In the subgroup analysis of the adjusted results of LDL-C after correcting for TC and HDL-C, lower LDL-C was associated with a higher risk of PD.

CONCLUSION

Among selected populations of statin-free newly diagnosed PD individuals, low LDL-C might be associated with the occurrence of PD.

The Effect of Cardiovascular Comorbidities on Women Compared to Men: Longitudinal Retrospective Analysis

Background

Although men are more prone to developing cardiovascular disease (CVD) than women, risk factors for CVD, such as nicotine abuse and diabetes mellitus, have been shown to be more detrimental in women than in men.

Objective

We developed a method to systematically investigate population-wide electronic health records for all possible associations between risk factors for CVD and other diagnoses. The developed structured approach allows an exploratory and comprehensive screening of all possible comorbidities of CVD, which are more connected to CVD in either men or women.

Methods

Based on a population-wide medical claims dataset comprising 44 million records of inpatient stays in Austria from 2003 to 2014, we determined comorbidities of acute myocardial infarction (AMI; International Classification of Diseases, Tenth Revision [ICD-10] code I21) and chronic ischemic heart disease (CHD; ICD-10 code I25) with a significantly different prevalence in men and women. We introduced a measure of sex difference as a measure of differences in logarithmic odds ratios (ORs) between male and female patients in units of pooled standard errors.

Results

Except for lipid metabolism disorders (OR for females [ORf]=6.68, 95% confidence interval [CI]=6.57-6.79, OR for males [ORm]=8.31, 95% CI=8.21-8.41), all identified comorbidities were more likely to be associated with AMI and CHD in females than in males: nicotine dependence (ORf=6.16, 95% CI=5.96-6.36, ORm=4.43, 95% CI=4.35-4.5), diabetes mellitus (ORf=3.52, 95% CI=3.45-3.59, ORm=3.13, 95% CI=3.07-3.19), obesity (ORf=3.64, 95% CI=3.56-3.72, ORm=3.33, 95% CI=3.27-3.39), renal disorders (ORf=4.27, 95% CI=4.11-4.44, ORm=3.74, 95% CI=3.67-3.81), asthma (ORf=2.09, 95% CI=1.96-2.23, ORm=1.59, 95% CI=1.5-1.68), and COPD (ORf=2.09, 95% CI 1.96-2.23, ORm=1.59, 95% CI 1.5-1.68). Similar results could be observed for AMI.

Conclusions

Although AMI and CHD are more prevalent in men, women appear to be more affected by certain comorbidities of AMI and CHD in their risk for developing CVD.

Prediabetes, type 2 diabetes mellitus and risk of Parkinson's disease: A population-based cohort study

BACKGROUND

Association of type 2 diabetes mellitus (T2D) with subsequent Parkinson's disease (PD) has supported the link between glucose metabolism and PD. We assessed the risk of PD not only in T2D but also in prediabetes.

METHODS

We conducted a retrospective cohort study of the population attended in primary care centres of the Catalan Health Institute in Catalonia between 2006 and 2018. The data were obtained from the Information System for Research in Primary Care (SIDIAP). We created a cohort of T2D and prediabetes patients (HbA1c ≥ 5.7-6.4% without antidiabetic drugs or previous T2D diagnosis) and compared to a reference cohort. The outcome was PD diagnosis and we excluded PD before or during the first year of follow-up. We used multivariate Cox regression models to calculate hazard ratios (HR) and 95% confidence intervals (95%CI). We excluded subjects with atypical and secondary parkinsonisms.

RESULTS

The exposed cohorts comprised of 281.153 patients with T2D and 266.379 with prediabetes and a reference cohort of 2.556.928 subjects. T2D and prediabetes were associated with higher risk of PD (HRadjusted 1.19, 95%CI 1.13-1.25, and 1.07, 1.00-1.14; respectively). In analyses stratified by sex, prediabetes was only associated with PD risk in women (1.12, 1.03-1.22 vs. 1.01, 0.99-1.10 in men). When analysis was stratified by age, T2D and prediabetes were associated with a greater PD risk both in women (2.36, 1.96-2.84 and 2.10, 1.70-2.59 respectively) and men (1.74, 1.52-2.00 and 1.90, 1.57-2.30 respectively) below 65 years-old.

CONCLUSIONS

We report for the first time that prediabetes increases the odds of subsequent PD and replicate the association with established T2D. Both associations predominate in women and young individuals.