Exploring the Potential of Antidiabetic Agents as Therapeutic Approaches for Alzheimer's and Parkinson's Diseases: A Comprehensive Review

Effects of cholecalciferol supplementation on depressive symptoms, C-peptide, serotonin, and neurotrophin-3 in type 2 diabetes mellitus: A double-blind, randomized, placebo-controlled trial

The coexistence of depression and type 2 diabetes mellitus (T2DM) can significantly worsen disease prognosis and lower quality of life. Emerging evidence suggests that vitamin D deficiency contributes to the progression of T2DM and is closely associated with the development of depression. The aim of this study was to investigate the effects of cholecalciferol on depression in patients with T2DM, exploring its mechanisms by analyzing its impact on C-peptide, serotonin, and neurotrophin-3 levels. A double-blind, randomized, placebo-controlled clinical trial was conducted at Cipto Mangunkusumo General Hospital, Jakarta, Indonesia, from April 2021 to September 2022. Patients with T2DM and depressive symptoms were randomly assigned to two groups: received 4000 IU of cholecalciferol daily and received a placebo for 12 weeks. Depression was assessed using the Beck Depression Inventory-II (BDI-II) before and 12 weeks after the intervention. The levels of C-peptide, serotonin, and neurotrophin-3 were measured at the end of the fourth week of intervention using the enzyme-linked immunosorbent assay (ELISA) method. Between-group comparisons were made using independent Student t- tests and Mann-Whitney U tests. Paired Student t-tests or Wilcoxon tests were applied for within-group comparisons between pre- and post-intervention. A total of 70 T2DM patients with depression were included in this study, comprising 38 patients in the cholecalciferol group and 32 in the placebo group. C-peptide levels increased significantly in the cholecalciferol group compared to the placebo group (p = 0.006). No significant differences were observed in serotonin and NT-3 levels between the cholecalciferol group compared to the placebo group. The cholecalciferol group had a significantly greater reduction in BDI-II scores compared to the placebo group (p < 0.001). This trial highlights that taking cholecalciferol might help ease mild to moderate depression symptoms in patients with T2DM by enhancing c-peptide levels, though its effects on serotonin and neurotrophin-3 are still unclear.

Advanced Glycation End Products-Induced Alzheimer's Disease and Its Novel Therapeutic Approaches: A Comprehensive Review

Advanced glycation end products (AGEs) accumulate in the brain, leading to neurodegenerative conditions such as Alzheimer's disease (AD). The pathophysiology of AD is influenced by receptors for AGEs and toll-like receptor 4 (TLR4). Protein glycation results in irreversible AGEs through a complicated series of reactions involving the formation of Schiff's base, the Amadori reaction, followed by the Maillard reaction, which causes abnormal brain glucose metabolism, oxidative stress, malfunctioning mitochondria, plaque deposition, and neuronal death. Amyloid plaque and other stimuli activate macrophages, which are crucial immune cells in AD development, triggering the production of inflammatory molecules and contributing to the disease's pathogenesis. The risk of AD is doubled by risk factors for atherosclerosis, dementia, advanced age, and type 2 diabetic mellitus (DM). As individuals age, the prevalence of neurological illnesses such as AD increases due to a decrease in glyoxalase levels and an increase in AGE accumulation. Insulin's role in proteostasis influences hallmarks of AD-like tau phosphorylation and amyloid β peptide clearance, affecting lipid metabolism, inflammation, vasoreactivity, and vascular function. The high-mobility group box 1 (HMGB1) protein, a key initiator and activator of a neuroinflammatory response, has been linked to the development of neurodegenerative diseases such as AD. The TLR4 inhibitor was found to improve memory and learning impairment and decrease Aβ build-up. Therapeutic research into anti-glycation agents, receptor for advanced glycation end products (RAGE) inhibitors, and AGE breakers offers hope for intervention strategies. Dietary and lifestyle modifications can also slow AD progression. Newer therapeutic approaches targeting AGE-related pathways are needed.

The GLP-1 receptor agonist exenatide improves recovery from spinal cord injury by inducing macrophage polarization toward the M2 phenotype

Although a wide variety of mechanisms take part in the secondary injury phase of spinal cord injury (SCI), inflammation is the most important factor implicated in the sequelae after SCI. Being central to the inflammation reaction, macrophages and their polarization are a topic that has garnered wide interest in the studies of SCI secondary injury. The glucagon-like peptide 1 (GLP-1) receptor agonist exenatide has been shown to enhance the endoplasmic reticulum stress response and improve motor function recovery after spinal cord injury (SCI). Since exenatide has also been reported to induce the production of M2 cells in models of cerebral infarction and neurodegenerative diseases, this study was conducted to examine the effects of exenatide administration on the inflammation process that ensues after spinal cord injury. In a rat contusion model of spinal cord injury, the exenatide group received a subcutaneous injection of 10 μg exenatide immediately after injury while those in the control group received 1 mL of phosphate-buffered saline. Quantitative RT-PCR and immunohistochemical staining were used to evaluate the effects of exenatide administration on the macrophages infiltrating the injured spinal cord, especially with regard to macrophage M1 and M2 profiles. The changes in hind limb motor function were assessed based on Basso, Beattie, Bresnahan locomotor rating scale (BBB scale) scores. The improvement in BBB scale scores was significantly higher in the exenatide group from day 7 after injury and onwards. Quantitative RT-PCR revealed an increase in the expression of M2 markers and anti-inflammatory interleukins in the exenatide group that was accompanied by a decrease in the expression of M1 markers and inflammatory cytokines. Immunohistochemical staining showed no significant difference in M1 macrophage numbers between the two groups, but a significantly higher number of M2 macrophages was observed in the exenatide group on day 3 after injury. Our findings suggest that exenatide administration promoted the number of M2-phenotype macrophages after SCI, which may have led to the observed improvement in hind limb motor function in a rat model of SCI.