Exploring the link between Parkinson's disease and type 2 diabetes mellitus in Drosophila

Evaluation of type 1 diabetes mellitus as a risk factor of Parkinson's disease in a Drosophila model

Diabetes mellitus (DM) is a chronic metabolic disease characterized by high blood glucose levels, resulting from insulin dysregulation. Parkinson's disease (PD) is the most common neurodegenerative motor disorder caused by the selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. DM and PD are both age-associated diseases that are turning into epidemics worldwide. Previous studies have indicated that type 2 DM might be a risk factor of developing PD. However, scarce information about the link between type 1 DM (T1DM) and PD does exist. In this work, we have generated a Drosophila model of T1DM based on insulin deficiency to evaluate if T1DM could be a risk factor to trigger PD onset. As expected, model flies exhibited T1DM-related phenotypes such as insulin deficiency, increased content of carbohydrates and glycogen, and reduced activity of insulin signaling. Interestingly, our results also demonstrated that T1DM model flies presented locomotor defects as well as reduced levels of tyrosine hydroxylase (a marker of DA neurons) in brains, which are typical PD-related phenotypes. In addition, T1DM model flies showed elevated oxidative stress levels, which could be causative of DA neurodegeneration. Therefore, our results indicate that T1DM might be a risk factor of developing PD, and encourage further studies to shed light into the exact link between both diseases.

Plantamajoside Alleviates Substantia Nigra Damage in Parkinson's Disease Mice by Inhibiting HDAC2/MAPK Signaling and Reducing Microglia Polarization

Parkinson's disease (PD) is a common neurodegenerative disorder caused by dopaminergic neuron progressive degeneration. Inhibition of microglial activation may contribute to the treatment and prevention of PD. Plantamajoside (PMS) is a natural compound extracted from plantain seeds. It has a wide range of biological activities, including anti-inflammatory, antioxidative, as well as antitumor effects. However, its possible effects on PD are still unclear. In this study, lipopolysaccharide (LPS) was first injected into the right midbrain substantia nigra (SN) of male C57BL/6 mice to establish the PD mouse model. We found that PMS improved LPS-induced behavioral dysfunction in PD mice. PMS attenuated LPS-induced SN injury in PD mice. PMS could suppress LPS-induced microglial overactivation in PD mice. In addition, MS inhibited LPS-induced activation of the HDAC2/MAPK pathway in PD mice and BV-2 cells. It further revealed that PMS alleviated microglia polarization by inhibiting HDAC2. The limitation of this study was the lack of experiments for investigating the further molecular mechanism and in vivo animal validation, which needs to be further confirmed in the future. Collectively, our data suggested that PMS could serve as a promising drug for PD.

Type 2 diabetes mellitus augments Parkinson's disease risk or the other way around: Facts, challenges and future possibilities

About 10% of the adult population is living with type 2 diabetes mellitus (T2DM) and 1% of the population over 60 years of age is suffering from Parkinson's disease (PD). A school of thought firmly believes that T2DM, an age-related disease, augments PD risk. Such relationship is reflected from the severity of PD symptoms in drug naive subjects possessing T2DM. Onset of Parkinsonian feature in case controls possessing T2DM corroborates the role of hyperglycemia in PD. A few cohort, meta-analysis and animal studies have shown an increased PD risk owing to insulin resistance. High fat diet and role of insulin signaling in the regulation of sugar metabolism, oxidative stress, α-synuclein aggregation and accumulation, inflammatory response and mitochondrial function in PD models and sporadic PD further connect the two. Although little is reported about the implication of PD in hyperglycemia and T2DM, a few studies have also contradicted. Ameliorative effect of anti-diabetic drugs on Parkinsonian symptoms and vague outcome of anti-PD medications in T2DM patients also suggest a link. The article reviews the literature supporting augmented risk of one by the other, analysis of proof of the concept, facts, challenges, future possibilities and standpoint on the subject.