Unraveling the link: exploring the causal relationship between diabetes, multiple sclerosis, migraine, and Alzheimer's disease through Mendelian randomization

Introduction

Observational studies suggested that diabetes mellitus [type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM)], multiple sclerosis (MS), and migraine are associated with Alzheimer's disease (AD). However, the causal link has not been fully elucidated. Thus, we aim to assess the causal link between T1DM, T2DM, MS, and migraine with the risk of AD using a two-sample Mendelian randomization (MR) study.

Methods

Genetic instruments were identified for AD, T1DM, T2DM, MS, and migraine respectively from genome-wide association study. MR analysis was conducted mainly using the inverse-variance weighted (IVW) method.

Results

The result of IVW method demonstrated that T2DM is causally associated with risk of AD (OR: 1.237, 95% CI: 1.099-1.391, P: 0.0003). According to the IVW method, there is no causal association between TIDM, MS, migraine, and the risk of AD (all p value > 0.05). Here we show, there is a causal link between T2DM and the risk of AD.

Conclusion

These findings highlight the significance of active monitoring and prevention of AD in T2DM patients. Further studies are required to actively search for the risk factors of T2DM combined with AD, explore the markers that can predict T2DM combined with AD, and intervene and treat early.

Inside the diabetic brain: Insulin resistance and molecular mechanism associated with cognitive impairment and its possible therapeutic strategies

Type 2 diabetes mellitus (T2DM) the most prevalent metabolic disease that has evolved into a major public health issue. Concerning about its secondary complications, a growing body of evidence links T2DM to cognitive impairment and neurodegenerative disorders. The underlying pathology behind this secondary complication disease is yet to be fully known. Nonetheless, they are likely to be associated with poor insulin signaling as a result of insulin resistance. We have combed through a rising body of literature on insulin signaling in the normal and diabetic brains along with various factors like insulin resistance, hyperglycemia, obesity, oxidative stress, neuroinflammation and Aβ plaques which can act independently or synergistically to link T2DM with cognitive impairments. Finally, we explored several pharmacological and non-pharmacological methods in the hopes of accelerating the rational development of medications for cognitive impairment in T2DM by better understanding these shared pathways.

Long-Term Exposure of Alcohol Induced Behavioral Impairments and Oxidative Stress in the Brain Mitochondria and Synaptosomes of Adult Zebrafish

Alcoholism causes deleterious effects such as physiological and neuronal alterations leading to the cognitive and other behavioral impairments. Mitochondrial and synaptosomal deteriorations in the brain of alcoholic persons exhibited metabolic, biochemical changes and other related risk factors, which mainly affect the brain function. This study aimed to assess the effect of chronic alcohol-induced mitochondrial and synaptosomal oxidative damage along with behavioral impairment in adult zebrafish. Zebrafish of control group received the system water and normal diet ad libitum (group I); the other groups were treated with 0.20% alcohol (group II) and 0.40% alcohol (group III) directly in fish tank for 22 days. The result revealed significant increase in lipid peroxidation, protein carbonylation, superoxide dismutase, and glutathione, and significant decline in the activity of catalase and Na⁺/K⁺ ATPase compared to control. Furthermore, the alcohol-treated zebrafish also showed significant behavioral alterations. Collectively, this regulatory mechanism demonstrates the effect of long-term alcohol consumption in the zebrafish. Our results indicate that this recreational drug "alcohol" is harmful to brain mitochondria and synaptosomes, which are the main organelles, and play an important role in memory, learning, cognitive function, and ATP formation in the brain, which may represent a significant public health concern.

Neurocognitive impairment in type 2 diabetes mellitus

There is emerging evidence that cognitive impairment could be a diabetes mellitus-related complication. It has been suggested that diabetic people are at increased risk of cognitive decline, since the metabolic and vascular disturbances of the disease affect brain function. Additionally, prolonged exposure to olther potential detrimental factors leads to irreversible cognitive decrements over time due to the aging process. Neurocognitive impairment signifies decreased performance in cognitive domains such as verbal and nonverbal memory, both immediate and delayed memory, executive function, attention, visuospatial and psychomotor performance, information processing speed, semantic knowledge, and language abilities. The aim of the present article is to review the existing literature on the issue of the neurocognitive decline in type 2 diabetes. A literature search of databases was performed, using as keywords "diabetes" and "cognitive impairment," and the reference list of papers so identified were examined, with only English language papers being used. Understanding and preventing diabetes-associated cognitive deficits remains a key priority for future research. It is important to ascertain whether interventions to delay diabetes onset or better control of established disease could prevent some of its adverse effects on cognitive skills.

Review of the Effect of Natural Compounds and Extracts on Neurodegeneration in Animal Models of Diabetes Mellitus

Diabetes mellitus is a chronic metabolic disease with a high prevalence in the Western population. It is characterized by pancreas failure to produce insulin, which involves high blood glucose levels. The two main forms of diabetes are type 1 and type 2 diabetes, which correspond with >85% of the cases. Diabetes shows several associated alterations including vascular dysfunction, neuropathies as well as central complications. Brain alterations in diabetes are widely studied; however, the mechanisms implicated have not been completely elucidated. Diabetic brain shows a wide profile of micro and macrostructural changes, such as neurovascular deterioration or neuroinflammation leading to neurodegeneration and progressive cognition dysfunction. Natural compounds (single isolated compounds and/or natural extracts) have been widely assessed in metabolic disorders and many of them have also shown antioxidant, antiinflamatory and neuroprotective properties at central level. This work reviews natural compounds with brain neuroprotective activities, taking into account several therapeutic targets: Inflammation and oxidative stress, vascular damage, neuronal loss or cognitive impairment. Altogether, a wide range of natural extracts and compounds contribute to limit neurodegeneration and cognitive dysfunction under diabetic state. Therefore, they could broaden therapeutic alternatives to reduce or slow down complications associated with diabetes at central level.

Sweet Mitochondria: A Shortcut to Alzheimer's Disease

A growing body of evidence supports a clear association between Alzheimer's disease and diabetes and several mechanistic links have been revealed. This paper is mainly devoted to the discussion of the role of diabetes-associated mitochondrial defects in the pathogenesis of Alzheimer's disease. The research experience and views of the author on this subject will be highlighted.