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How Dopamine Affects Parkinson’s Disease

Dopaminergic Input And Organizational Features Of The Dorsal And Lateral Striatum

What causes the loss of dopamine neurons in Parkinson’s disease?

As reviewed above, it is generally accepted that dysfunction in PD stems from the degeneration of SNc neurons , which leads to motor dysfunction and the loss of VTA neurons , which leads to behavioral dysregulation, including demotivation, anhedonia, and depression within PD . While both pathways have been studied extensively across an array of conditions and pathologies, the modulatory mechanisms of the nigrostriatal pathway neurons have been fairly well described while the varied mechanisms and roles of VTA efferents continue to be elucidated. Within the nigrostriatal pathway, GABAergic medium spiny neurons of the dorsal/lateral striatum receive excitatory glutamatergic signals that can be modulated via dopaminergic inputs originating from the SNc. MSNs are moderately sized cells with large, multi-structured dendritic arbors that constitute a staggering 95% of all postsynaptic nigrostriatal neurons . Local circuit interneurons of the dorsal striatum are also actively involved in regulating MSN activity and can be subdivided into cholinergic interneurons and aspiny GABAergic interneurons known as low-threshold, fast-spiking neurons . Striatal cholinergic and MSNs express several neurotransmitter receptors including the ?-aminobutyric acid , glutamate, DA, adenosine, serotonin, opioids, and substance P receptors .

Causes Of Parkinsons Disease

At present, we do not know the cause of Parkinsons disease. In most people there is no family history of Parkinsons Researchers worldwide are investigating possible causes, including:;

  • environmental triggers, pesticides, toxins, chemicals
  • genetic factors
  • combinations of environment and genetic factors;
  • head trauma.

Medications For People With Parkinsons Disease

Symptoms of Parkinsons disease result from the progressive degeneration of nerve cells in the brain and other organs such as the gut, which produce a neurotransmitter called dopamine. This causes a deficiency in the availability of dopamine, which is necessary for smooth and controlled movements.;Medication therapy focuses on maximising the availability of dopamine in the brain. Medication regimes are individually tailored to your specific need. Parkinsons medications fit into one of the following broad categories:;

  • levodopa dopamine replacement therapy
  • dopamine agonists mimic the action of dopamine
  • COMT inhibitors used along with levodopa. This medication blocks an enzyme known as COMT to prevent levodopa breaking down in the intestine, allowing more of it to reach the brain
  • anticholinergics block the effect of another brain chemical to rebalance its levels with dopamine
  • amantadine has anticholinergic properties and improves dopamine transmission
  • MAO type B inhibitors prevent the metabolism of dopamine within the brain.

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Pathophysiology Of Parkinsons Disease

Although we are learning more each day about the pathophysiology of Parkinsons disease, it is still considered largely idiopathic . It likely involves the interaction of host susceptibility and environmental factors. A small percentage of cases are genetically linked and genetic factors are being intensely studied.

Physiologically, the symptoms associated with Parkinsons disease are the result of the loss of a number of neurotransmitters, most notably dopamine. Symptoms worsen over time as more and more of the cells affected by the disease are lost. The course of the disease is highly variable, with some patients exhibiting very few symptoms as they age and others whose symptoms progress rapidly.

Parkinsons is increasingly seen as a complex neurodegenerative disease with a sequence of progression. There is strong evidence that it first affects the dorsal motor nucleus of the vagus nerve and the olfactory bulbs and nucleus, then the locus coeruleus, and eventually the substantia nigra. Cortical areas of the brain are affected at a later stage. Damage to these various neuronal systems account for the multi-faceted pathophysiologic changes that cause impairments not just to the motor system but also to the cognitive and neuropsychological systems .

Parkinsons Disease: Why Dopamine Replacement Therapy Has A Paradoxical Effect On Cognition

Illustration of Parkinsons disease. It affects dopamine ...
Date:
University of Montreal
Summary:
Dopamine replacement therapy, which is used to manage motor symptoms associated with Parkinsons disease, can, at times, adversely affect cognition. Now researchers have identified the reasons why.

Dopamine replacement therapy, which is used to manage motor symptoms associated with Parkinsons disease, can, at times, adversely affect cognition. Dr. Oury Monchi, Ph. D. in neuronal modeling and Head of the Neurophysiological and Neuroimaging Research theme at the Centre de recherche de lInstitut universitaire de gériatrie de Montréal , which is affiliated with the Université de Montréal, and Dr. Penny A. MacDonald, Neurologist and postdoctoral fellow in Dr. Monchis laboratory, have identified the reasons why within the framework of a clinical study recently published in Brain: A Journal of Neurology.

Until now, the effect of dopamine replacement therapy on cognition in individuals with Parkinsons disease was controversial. The purpose of this study however, was to further investigate. This led to a series of laboratory tests and neuroimaging studies that allowed researchers to clearly define the distinct cognitive functions performed by the dorsal and ventral striatum, thereby shedding some light on the issue.

Summary of the Research

Parkinsons disease

The authors are grateful for the support provided by the IUGM Foundation and the Canadian Institutes of Health Research.

Story Source:

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Treating Parkinsons Disease With Levodopa

The discovery of levodopa helped revolutionize the treatment of Parkinsons disease. At its most basic level, levodopa is the precursor to dopamineits what dopamine is made of.

When a person takes levodopa, the drug easily crosses the blood-brain barrier and builds up inside the brain. Once levels are high enough, levodopa is converted to dopamine, and Parkinsons symptoms lessen or go away entirely. For many people, using levodopa is one of the most effective ways to manage symptoms of Parkinsons disease.

Common Pathogenic Mechanisms Of Systemic And Brain Insulin Resistance

As epidemiological evidence for a link between PD and T2DM accumulates, parallel experimental evidence indicates potential overlap in disease mechanisms and pathways. Systemic insulin resistance has long been an established key feature of T2DM. Recently, studies have found that insulin resistance is present in the brain in neurodegenerative diseases such as Alzheimers disease and other dementias , and PD . Both systemic and local insulin resistance may drive pathology in the brain. Systemic insulin resistance may do so through hyperglycaemia and its consequences , microvascular disease, chronic inflammation, and dysfunction of the blood brain barrier, which may be compounded by associated comorbidities such as hypertension, dyslipidaemia and renal impairment . Local brain insulin resistance may act via protein deposition and aggregation, and failure of clearance mechanisms, independent of systemic insulin resistance .

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Translational Implication Of The Catecholaldehyde Hypothesis

On this ground, another strategy might be the scavenging of reactive aldehydes by an excess of amino-molecules, which would compete with protein lysines. As an example, metformin is a biguanidine molecule and an FDA-approved drug for the treatment of Type 2 Diabetes Mellitus . Interestingly, T2DM has been recognized as a risk factor for PD . Treatments with metformin were showed to have not only antidiabetic but also neuroprotective action . From a molecular point of view, metformin acts on different pathways i.e. controlling mitochondrial physiology, activating the autophagic pathway and modulating neuroinflammation. It has been also demonstrated to reduce the elevation of phosphorylated Syn by activating mTOR-dependent phosphatase 2A .

Nevertheless, a more comprehensive understanding of the DA catabolic pathway and its functionality in PD patients would allow to design more targeted and effective therapeutic strategies.

Can Parkinsons Disease Be Prevented

Understanding Parkinson’s Disease

Unfortunately, no. Parkinsons disease is long-term disease that worsens over time. Although there is no way to prevent or cure the disease , medications may significantly relieve your symptoms. In some patients especially those with later-stage disease, surgery to improve symptoms may be an option.

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Dopaminergic Treatments And Their Side Effects

The overall goal of Parkinsons disease treatment is to alleviate the symptoms as much as possible with as few side effects as possible. No medication is perfect, but treatment should improve quality of life, and the benefits should outweigh the risks. Dyskinesia usually occurs when taking levodopa, but it can also occur with dopamine agonists, MAOIs, and COMT inhibitors.

Earlier Research On The Link Between Type 2 Diabetes And Parkinsons Disease

Some previous research has linked certain medications for type 2 diabetes to a lower risk of the development or progression of Parkinsons disease.

A found Parkinsons disease symptoms improved in participants who took exenatide, a diabetes drug in a family of medicines known as GLP1 agonists, and worsened when subjects took a placebo. Another , found that individuals with type 2 diabetes who took GLP1 agonists or another type of diabetes drugs known as DPP4 inhibitors had a lower risk of developing Parkinsons disease.

Slightly elevated blood sugar or variations in blood sugar may contribute to the risk of Parkinsons disease even in people without diabetes, according to a .

Age is the biggest risk factor for Parkinsons disease, though, and genetics also account for up to 20 percent of the risk, Foltynie says.

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Strategies For The Treatment Of Parkinsons Disease: Beyond Dopamine

  • 1Laboratorio de Neurobiología, Facultad de Ciencias de la Salud, Universidad San Sebastián, Concepción, Chile
  • 2Department of Biological Sciences, University of Limerick, Limerick, Ireland
  • 3Health Research Institute, University of Limerick, Limerick, Ireland
  • 4Department of Psychology and Neuroscience, Center for Neuroscience, University of Colorado, Boulder, CO, United States
  • 5Research & Development Service, Bay Pines VA Healthcare System, Bay Pines, FL, United States

Parkinsons disease is the second-leading cause of dementia and is characterized by a progressive loss of dopaminergic neurons in the substantia nigra alongside the presence of intraneuronal ?-synuclein-positive inclusions. Therapies to date have been directed to the restoration of the dopaminergic system, and the prevention of dopaminergic neuronal cell death in the midbrain. This review discusses the physiological mechanisms involved in PD as well as new and prospective therapies for the disease. The current data suggest that prevention or early treatment of PD may be the most effective therapeutic strategy. New advances in the understanding of the underlying mechanisms of PD predict the development of more personalized and integral therapies in the years to come. Thus, the development of more reliable biomarkers at asymptomatic stages of the disease, and the use of genetic profiling of patients will surely permit a more effective treatment of PD.

What Should I Do If Im Managing Type 2 Diabetes And Concerned About My Parkinsons Risk

Structure of Parkinson

The takeaway of the new analysis for people currently managing or caring for a person with diabetes is unclear. This specific research, for example, doesnt illustrate how someone with diabetes may help lower their risk of Parkinsons disease, says Dr. Cereda.

Unfortunately, although there is some evidence that diabetes is a risk factor for developing Parkinsons disease, there is no evidence that optimal diabetes control reduces the risk of Parkinsons disease, says Cereda.

Yet managing blood sugar is still essential for people with type 2 diabetes, because failing to do this increases the risk of a wide range of health problems including heart disease, stroke, and kidney failure, Cereda says. The study results suggest that we might one day add Parkinsons disease to the long list of conditions that can be prevented at least in part by good diabetes management, Cereda adds.

Noyce agrees, emphasizing the importance of blood sugar management regardless of potential Parkinsons risk. There are many other negative health outcomes that are associated with type 2 diabetes, such as heart disease, stroke, nerve and kidney damage, and visual loss, Noyce says. These are all more common than Parkinsons, and the risk of these things can be reduced with treatment of diabetes, modification of diet, exercise and self-care.

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Support For People With Parkinsons Disease

Early access to a multidisciplinary support team is important. These teams may include doctors, physiotherapists, occupational therapists, speech therapists, dietitians, social workers and specialist nurses.;Members of the team assess the person with Parkinsons disease and identify potential difficulties and possible solutions.There are a limited number of multidisciplinary teams in Victoria that specialise in Parkinsons disease management. But generalist teams are becoming more aware of how to help people with Parkinsons disease.;;

Links Between Insulin Resistance Metabolic Syndrome And Parkinsons Disease

Insulin resistance and metabolic syndrome are very common in the United States, but are also noted to have increased incidence in patients with Parkinsons disease . Insulin resistance may precede the development of diabetes by many years, but with treatment, diabetes can be avoided.

Growing evidence now shows an association of insulin resistance and metabolic syndrome with worse symptoms and progression of Parkinsons disease . Lima et al. have shown diabetes incidence in PD is associated with faster progression of both motor and cognitive symptoms.

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What Are The Different Stages Of Parkinsons Disease

Each person with Parkinsons disease experiences symptoms in in their own unique way. Not everyone experiences all symptoms of Parkinsons disease. You may not experience symptoms in the same order as others. Some people may have mild symptoms; others may have intense symptoms. How quickly symptoms worsen also varies from individual to individual and is difficult to impossible to predict at the outset.

In general, the disease progresses from early stage to mid-stage to mid-late-stage to advanced stage. This is what typically occurs during each of these stages:

Early stage

Early symptoms of Parkinsons disease are usually mild and typically occur slowly and do not interfere with daily activities. Sometimes early symptoms are not easy to detect or you may think early symptoms are simply normal signs of aging. You may have fatigue or a general sense of uneasiness. You may feel a slight tremor or have difficulty standing.

Often, a family member or friend notices some of the subtle signs before you do. They may notice things like body stiffness or lack of normal movement slow or small handwriting, lack of expression in your face, or difficulty getting out of a chair.

Mid stage

Mid-late stage

Standing and walking are becoming more difficult and may require assistance with a walker. You may need full time help to continue to live at home.

Advanced stage

The Association Between Type 2 Diabetes Mellitus And Parkinsons Disease

Dopamine receptor agonists for Parkinson Disease (PD)

Article type: Review Article

Affiliations: Barts and The London School of Medicine, Queen Mary University of London, London, UK | Reta Lila Weston Institute of Neurological Studies, UCL Queen Square Institute of Neurology, London, UK | Department of Clinical and Movement Neurosciences, University College London Institute of Neurology, London, UK | Preventive Neurology Unit, Wolfson Institute of Preventive Medicine, Queen Mary University of London, London, UK

Correspondence: Correspondence to: Alastair J. Noyce, MRCP, PhD, Preventive Neurology Unit, Wolfson Institute of Preventive Medicine, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK. Tel.: +44 207 882 5841; E-mail: .

Keywords: Parkinsons disease, type 2 diabetes mellitus, epidemiology, therapeutics, mechanisms

DOI: 10.3233/JPD-191900

Journal: Journal of Parkinsons Disease, vol. 10, no. 3, pp. 775-789, 2020

Abstract

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Study Examines Connection Between Diabetes Medication And Parkinsons Disease

It was first suggested in the 1960s that people with type-2 diabetes are at increased risk for developing Parkinsons disease and when they do develop PD, its progression is faster and often more severe. This may be due, in part, to an apparent relationship in the brain between dopamine, insulin resistance, and glucose control. Insulin is not only made in the pancreas, its also present in the brain where it has been shown to impact dopamine levels.

Parkinsons is generally believed by scientists to be caused by the loss of dopamine-producing neurons. Parkinsons symptoms, such as slowness, rigidity, and tremor, typically develop after approximately 40-80% of these dopamine-producing neurons die.

Why does this matter? Currently, more than 30 million people in the United States have type-2 diabetes, and that number is growing. The lifetime is also on the rise. In light of these trends, it would be valuable to know whether any specific type-2 diabetes medications might be associated with an increased or decreased risk for developing PD.

1) Thiazolidinediones , like pioglitazone or rosiglitazone , which specifically target insulin resistance

2) Drugs, like albiglutide or dulaglutide , that mimick glucagon-like peptide-1 a hormone that promotes insulin secretion, and

3) Dipeptidyl peptidase 4 inhibitors, which increase GLP-1 levels, and lead to insulin secretion and lowering of blood sugar levels

Results

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What Is The Goal Of Dopaminergic Treatments For Parkinsons

People with Parkinsons disease have low levels of dopamine in their brains. Dopaminergic treatments are used to increase dopamine levels or mimic the chemical to improve symptoms. These drugs are mainly used to address motor problems, such as tremors or difficulty walking. Over time, dopamine treatments can become less effective, and higher doses may be required.

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Dopamine Agonists For Parkinsons Disease Therapeutic Effects And Side Effects

Dopamine agonists are a class of drugs that are used to treat Parkinsons disease symptoms. Generally, they are prescribed for patients under 60 years of age or for those whose symptoms are not well-controlled by a drug called levodopa, which is used as first-line therapy for Parkinsons disease. In some patients, dopamine agonists are used alone. In others, they are used in a combination with levodopa.

Incidence Of Parkinsons Disease

Dopamine level in parkinson

Its estimated that approximately four people per 1,000 in Australia have Parkinsons disease, with the incidence increasing to one in 100 over the age of 60. In Australia, there are approximately 80,000 people living with Parkinsons disease, with one in five of these people being diagnosed before the age of 50. In Victoria, more than 2,225 people are newly diagnosed with Parkinsons every year.

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