Long-Lasting Exendin-4 Fusion Protein Improves Memory Deficits in High-Fat Diet/Streptozotocin-Induced Diabetic Mice

Interleukin-5: an indicator of mild cognitive impairment in patients with type 2 diabetes mellitus - a comprehensive investigation ranging from bioinformatics analysis to clinical research

PURPOSE

Neuroinflammation constitutes an underlying mechanism for cognitive impairment. Here, we endeavor to scrutinize the potential contribution of interleukin-5 (IL-5) towards mild cognitive impairment (MCI), and to assess its diagnostic value for MCI in patients with type 2 diabetes mellitus (T2DM).

METHODS

RNA-seq was used to explore the potential neuroinflammation factors in the hippocampus of diabetic mice with cognitive decline. Additionally, the promising risk factor was verified in animals. Finally, the association between IL-5 levels and cognitive function and its diagnostic value for MCI were assessed.

RESULTS

In animals, up-regulated IL-5 mRNA and protein levels were detected by RNA-seq and (or) verified experiments in the hippocampus of diabetic db/db mice with cognitive decline, compared to those of db/m mice without diabetes. In human, compared to diabetic patients without MCI, those with MCI demonstrate elevated levels of IL-5. It is natively associated with Montreal Cognitive Assessment (MoCA) scores, reflecting global cognitive function, and positively correlated with Trail Making Test A (TMTA) scores, reflecting information processing speed. Furthermore, an elevated level of IL-5 is identified as a risk factor for MCI, and a factor that influences TMTA scores. Finally, it is recommended that the cut-off value for IL-5 in the diagnosis of MCI is 22.98 pg/mL, with a sensitivity of 68.6% and specificity of 72.9%.

CONCLUSIONS

IL-5 is considered a risk factor for MCI in T2DM patients and is associated with their performance in information processing speed. Moreover, an elevated level of IL-5 is a plausible biomarker for MCI in T2DM patients.

Long-Lasting Exendin-4-Coated Gold Nanoparticles: Synthesis and In Vivo Evaluation of Hypoglycemic Activity

BACKGROUND

Gold nanoparticles (NPs) have drawn great attention in the area of biomedical research with their relatively safe and versatile properties. This study aimed to synthesize long-lasting exendin-4-coated gold NPs (EX-ABD-AFF-GoldNPs) and evaluate their anti-diabetic effects in vivo.

METHODS

In the present study, EX-ABD-AFF-GoldNPs were synthesized using a simple one-step aqueous reduction method. The physical characterization of the prepared particles verified the successful formation of the EX-ABD-AFF-GoldNPs through dynamic light scattering (DLS), transmission electron microscopy (TEM), ultraviolet-visible (UV-VIS) light spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The anti-hyperglycemic and anti-obesity effects were assessed in high-fat diet (HFD)-fed obese diabetic mice. Additionally, pharmacokinetics (PK) and biodistribution studies were performed to verify the long-lasting properties.

RESULTS

The EX-ABD-AFF-GoldNPs were conglomerates of smaller globular-shaped particles, and the average size was 110(±14) nm, based on the TEM images. Safety assessments using Min6, HepG2, and B16F10 cell lines demonstrated low cytotoxicity, with over 80% cell viability up to the highest tested concentration of 150 μg/mL (as EX-ABD-AFF). Notably, the animal studies showed that the EX-ABD-AFF-GoldNPs exhibited significant hypoglycemic activity, comparable to the EX-ABD-AFF, in the HFD-fed mice. A 4-week treatment with EX-ABD-AFF-GoldNPs produced similar reductions in blood glucose and body weight to the EX-ABD-AFF, without any apparent toxicity. Furthermore, the PK and biodistribution study results confirmed the long-lasting properties (plasma half-life: 43.6 h) of the particles.

CONCLUSIONS

Overall, this study demonstrated that the preparation of therapeutic protein-loaded gold NPs is feasible and, despite their much larger size compared with the protein, EX-ABD-AFF-GoldNPs can be successfully absorbed through the subcutaneous route and show nearly equivalent hypoglycemic activity to the EX-ABD-AFF protein. Finally, this study showed that long-lasting properties could be acquired by only coating EX-ABD-AFF onto gold NPs.

Experimental Type 2 diabetes and lipotoxicity-associated neuroinflammation involve mitochondrial DNA-mediated cGAS/STING axis: implication of Type-1 interferon response in cognitive impairment

Type-1 IFN (interferon)-associated innate immune response is increasingly getting attention in neurodegenerative and metabolic diseases like type 2 diabetes (T2DM). However, its significance in T2DM/lipotoxicity-induced neuroglia changes and cognitive impairment is missing. The present study aims to evaluate the involvement of cGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon gene), IRF3 (interferon regulatory factor-3), TBK (TANK binding kinase)-mediated Type-1 IFN response in the diabetic brain, and lipotoxicity (palmitate-bovine serum albumin conjugate/PA-BSA)-induced changes in cells (neuro2a and BV2). T2DM was induced in C57/BL6 mice by feeding on a high-fat diet (HFD, 60% Kcal) for 16 weeks and injecting a single dose of streptozotocin (100 mg/kg, i.p) in the 12th week. Plasma biochemical parameter analysis, neurobehavioral assessment, protein expression, and quantitative polymerase chain reaction study were carried out to decipher the hypothesis. T2DM-associated metabolic and lipotoxic stress led to mitochondrial impairment causing leakage of mtDNA to the cytoplasm further commencing cGAS activation and its downstream signaling. The diseased hippocampus and cortex showed decreased expression of synaptophysin (p < 0.01) and PSD-95 (p < 0.01, p < 0.05) with increased expression of cGAS (p < 0.001), p-STING (p < 0.001), p-STAT1 (signal transducer and activator of transcription) (p < 0.01), and IFN-β (p < 0.001) compared to normal control. The IFN-β/p-STAT1-mediated microglia activation was executed employing a conditioned media approach. C-176, a selective STING inhibitor, alleviated cGAS/p-STING/IFN-β expression and proinflammatory microglia/M1-associated markers (CD16 expression, CXCL10, TNF-α, IL-1β mRNA fold change) in the diabetic brain. The present study suggests Type-1IFN response may result in neuroglia dyshomeostasis affecting normal brain function. Alleviating STING signaling has the potential to protect T2DM-associated central ailment.

Drp1: Focus on Diseases Triggered by the Mitochondrial Pathway

Drp1 (Dynamin-Related Protein 1) is a cytoplasmic GTPase protein encoded by the DNM1L gene that influences mitochondrial dynamics by mediating mitochondrial fission processes. Drp1 has been demonstrated to play an important role in a variety of life activities such as cell survival, proliferation, migration, and death. Drp1 has been shown to play different physiological roles under different physiological conditions, such as normal and inflammation. Recently studies have revealed that Drp1 plays a critical role in the occurrence, development, and aggravation of a series of diseases, thereby it serves as a potential therapeutic target for them. In this paper, we review the structure and biological properties of Drp1, summarize the biological processes that occur in the inflammatory response to Drp1, discuss its role in various cancers triggered by the mitochondrial pathway and investigate effective methods for targeting Drp1 in cancer treatment. We also synthesized the phenomena of Drp1 involving in the triggering of other diseases. The results discussed herein contribute to our deeper understanding of mitochondrial kinetic pathway-induced diseases and their therapeutic applications. It is critical for advancing the understanding of the mechanisms of Drp1-induced mitochondrial diseases and preventive therapies.

High glucose impairs cognitive function through inducing mitochondrial calcium overload in Treg cells

High glucose has been proved to impair cognitive function in type 2 diabetes, but the underlying mechanisms remain elusive. Here, we found that high glucose increased transcription factors' SP1 O-GlcNAcylation in regulatory T (Treg) cells. Glycosylated SP1 further enhanced HDAC2 recruitment and histone deacetylation on Na+/Ca2+/Li+ exchanger (NCLX) promoter, which downregulated NCLX expression and led to mitochondrial calcium overload and oxidative damage, thereby promoting Treg cell dysfunction, M1 microglia polarization, and diabetes-associated cognitive impairment. Importantly, GLP-1 receptor agonist alleviated these deleterious effects via GLP-1-receptor-mediated upregulation of OGA and inhibition of SP1 O-GlcNAcylation in Treg cells. Our study highlighted a link between high-glucose-mediated SP1 O-GlcNAcylation and HDAC2/NCLX signaling in control of mitochondrial calcium concentrations in Treg cells. It also revealed a mechanism for linking Treg cell dysfunction and cognitive impairment in type 2 diabetes and provides an insight into the mechanism underlying the neuroprotective effects of GLP-1 receptor agonist.

Exendin-4: A potential therapeutic strategy for Alzheimer's disease and Parkinson's disease

Neurodegenerative disorders, which affect millions worldwide, are marked by a steady decline of neurons that are selectively susceptible. Due to the complex pathological processes underlying neurodegeneration, at present, there is no viable therapy available for neurodegenerative disorders. Consequently, the establishment of a novel therapeutic approach for such conditions is a clinical void that remains. The potential significance of various peptides as neuroprotective interventions for neurodegenerative disorders is gaining increasing attention. In the past few years, there has been growing scientific interest in glucagon-like peptide-1 receptor agonists due to their claimed neuroprotective effects. Exendin-4 is a glucagon-like peptide-1 receptor agonist that is known to possess anti-diabetic effects and does not degrade for hours, making it a superior candidate for such disorders. Moreover, exendin-4's neuroprotective effects have been reported in several preclinical studies. Exendin-4's diverse therapeutic targets suggest its potential therapeutic uses in neurodegenerative ailments like Alzheimer's disease and Parkinson's disease and have garnered an increasing amount of attention. Given the substantial body of evidence supporting the neuroprotective potential of exendin-4 in various research models, this article is dedicated to exploring the promising role of exendin-4 as a therapeutic agent for the treatment and management of Alzheimer's disease and Parkinson's disease. This review draws insights from the findings of numerous preclinical and clinical studies to highlight the collective neuroprotective advantages of exendin-4 and the potential mechanisms that underlie its neuroprotective effects.

Beneficial effects of empagliflozin and liraglutide on the cerebral microcirculation of diabetic rats

OBJECTIVES

This study aimed to evaluate the effects of the antidiabetics liraglutide, a GLP-1 analog, and empagliflozin, an SGLT-2 inhibitor, on the brain microcirculation of diabetic rats.

METHODS

Type 2 diabetes mellitus (DM) was experimentally induced in male Wistar rats by combining a high-fat diet and a low dose of streptozotocin (35 mg/kg). Liraglutide (100 μg/kg s.c.) and empagliflozin (10 mg/kg, oral) were administered for 5 weeks. Body weight was monitored periodically. Oral glucose tolerance, fasting glycemia, and blood triglycerides were evaluated after the treatments. Endothelial-leukocyte interactions in the brain microcirculation and structural capillary density were assessed.

RESULTS

DM rats presented metabolic and cerebrovascular alterations. Liraglutide treatment decreased body weight and blood triglycerides of DM rats. Empagliflozin treatment improved glucose tolerance but only the combination therapy significantly reduced fasting blood glucose. Both treatments and their combination reduced leukocyte adhesion into the endothelium of brain venules. However, empagliflozin was more effective in preventing DM-induced microvascular rarefaction.

CONCLUSION

These findings suggest that chronic treatment with SGLT2 inhibitors and GLP-1 receptor agonists may serve as potential therapeutic approaches to prevent microvascular complications associated with diabetes.

Physical activity in a swimming pool attenuates memory impairment by reducing glutamate and inflammatory cytokines and increasing BDNF in the brain of mice with type 2 diabetes

Type 2 diabetes is a risk factor for the development of cognitive impairment. Increasing evidence suggests that regular exercise is beneficial for the treatment of clinical symptoms in diabetic patients. The current study aimed to evaluate whether increasing physical activity through swimming training can reduce memory impairment in an animal model of type 2 diabetes. Diabetes and non-diabetes mice underwent swimming training for four weeks, and then working, spatial, and recognition memory were evaluated using three behavioral tests. Body weight, glucose, and insulin resistance were monitored. We also measured inflammatory cytokines (interleukin (IL)- 6, IL-1β, and tumor-necrosis-factor (TNF)-α), an anti-inflammatory cytokine (IL-10), and brain-derived-neurotrophic-factor (BDNF), and glutamate levels in the hippocampus or prefrontal cortex of mice. The findings showed that diabetes increased body weight, glucose, and insulin resistance, impaired working, spatial and recognition memory, increased levels of IL-6, IL-1β, TNF-α, and glutamate levels, and decreased BDNF in the hippocampus of diabetic mice. While higher physical activity was associated with reduced body weight, glucose, and insulin resistance, attenuated memory impairment, IL-6, IL-1β, TNF-α, and glutamate, and increased BDNF levels in the hippocampus and prefrontal cortex of diabetic mice. This study shows that swimming training can normalize body weight and glucose-insulin axis and reduce inflammation and glutamate in the hippocampus and enhance the neurotrophic system in both the hippocampus and prefrontal cortex of diabetic mice. This study also suggests that higher physical activity through swimming training can improve cognitive impairment in a mouse model of type 2 diabetes.

Taxifolin Suppresses Inflammatory Responses of High-Glucose-Stimulated Mouse Microglia by Attenuating the TXNIP-NLRP3 Axis

Type 2 diabetes mellitus is associated with an increased risk of dementia, potentially through multifactorial pathologies, including neuroinflammation. Therefore, there is a need to identify novel agents that can suppress neuroinflammation and prevent cognitive impairment in diabetes. In the present study, we demonstrated that a high-glucose (HG) environment elevates the intracellular reactive oxygen species (ROS) levels and triggers inflammatory responses in the mouse microglial cell line BV-2. We further found that thioredoxin-interacting protein (TXNIP), a ROS-responsive positive regulator of the nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, was also upregulated, followed by NLRP3 inflammasome activation and subsequent interleukin-1beta (IL-1β) production in these cells. Conversely, caspase-1 was not significantly activated, suggesting the involvement of noncanonical pathways in these inflammatory responses. Moreover, our results demonstrated that taxifolin, a natural flavonoid with antioxidant and radical scavenging activities, suppressed IL-1β production by reducing the intracellular ROS levels and inhibiting the activation of the TXNIP-NLRP3 axis. These findings suggest the novel anti-inflammatory effects of taxifolin on microglia in an HG environment, which could help develop novel strategies for suppressing neuroinflammation in diabetes.

Design and biological evaluation of Repaglinide loaded polymeric nanocarriers for diabetes linked neurodegenerative disorder: QbD-driven optimization, in situ, in vitro and in vivo investigation

Diabetes mellitus is a metabolic disorder characterized by inadequate insulin secretion and signaling dysfunction, leading to a vast spectrum of systemic complications. These complications trigger cascades of events that result in amyloid-beta plaque formation and lead to neurodegenerative disorders such as Alzheimer's. Repaglinide (REP) an insulinotropic agent, suppresses the down regulatory element antagonist modulator (DREAM) and enhances the ATF6 expression to provide neuroprotection following the DREAM/ATF6/apoptotic pathway. However, oral administration of REP for brain delivery becomes more complicated due to its physicochemical characteristics (high protein binding (>98%), low permeability, short half-life (∼1 h), low bioavailability). Therefore, to circumvent these problems, we develop a polymeric nanocarrier system (PNPs) by in-house synthesized di-block copolymer (PEG-PCL). PNPs were optimized using quality by design approach response surface methodology and characterized by particle size (112.53 ± 5.91 nm), PDI (0.157 ± 0.08), and zeta potential (-6.20 ± 0.82 mV). In vitro release study revealed that PNPs (∼70% in 48 h) followed the Korsmeyer-Peppas model with a Fickian diffusion release pattern, and in intestinal absorption assay PNPs showed increment of ∼1.3 folds compared of REP. Moreover, cellular studies confirmed that REP-loaded PNPs significantly enhance the cellular viability, uptake and reduce the peroxide-induced stress in neuroblastoma SHSY-5Y cells. Further, pharmacokinetic parameters of PNPs showed an increment in t_max (2.46-fold), and C_max (1.25-fold) associated with REP. In the brain biodistribution study, REP loaded PNPs was sustained for 24 h whereas free REP sustained only for12 h. In DM induced neurodegenerative murine model, a significantly (p < 0.01) enhanced pharmacodynamic was observed in PNP treated group by estimating biochemical and behavioral parameters. Hence, oral administration of REP-loaded PNPs promotes efficient brain uptake and improved efficacy of REP in the diseased model.

Necrostatin-1S mitigates type-2 diabetes-associated cognitive decrement and lipotoxicity-induced neuro-microglia changes through p-RIPK-RIPK3-p-MLKL axis

Type-2 diabetes mellitus (T2DM) is associated with neuroinflammation and cognitive decrement. Necroptosis programmed necrosis is emerging as the major contributing factor to central changes. It is best characterized by the upregulation of p-RIPK(Receptor Interacting Kinase), p-RIPK3, and the phosphorylated-MLKL (mixed-lineage kinase domain-like protein). The present study aims to evaluate the neuroprotective effect of Necrostatin (Nec-1S), a p-RIPK inhibitor, on cognitive changes in the experimental T2DM model in C57BL/6 mice and lipotoxicity-induced neuro-microglia changes in neuro2A and BV2 cells. Further, the study also explores whether Nec-1S would restore mitochondrial and autophago-lysosomal function.T2DM was developed in mice by feeding them a high-fat diet (HFD) for 16 weeks and injecting a single dose of streptozotocin (100 mg/kg, i.p) on the 12^th week. Nec-1S was administered for 3 weeks at (10 mg/kg, i.p) once every 3 days. Lipotoxicity was induced in neuro2A, and BV2 cells using 200 µM palmitate/bovine serum albumin conjugate. Nec-1S (50 µM), and GSK-872(10 µM) were further used to explore their relative effect. The neurobehavioral performance was assessed using mazes and task-assisted performance tests. To decipher the hypothesis plasma parameters, western blot, immunofluorescence, microscopy, and quantitative reverse transcription-PCR studies were carried out. The Nec-1S treatment restored cognitive performance and reduced the p-RIPK-p-RIPK3-p-MLKL mediated neuro-microglia changes in the brain and in cells as well, under lipotoxic stress. Nec-1S reduced tau, and amyloid oligomer load. Moreover, Nec-1S restored mitochondrial function and autophago-lysosome clearance. The findings highlight the central impact of metabolic syndrome and how Nes-1S, by acting as a multifaceted agent, improved central functioning.

Ganoderma lucidum Modulates Glucose, Lipid Peroxidation and Hepatic Metabolism in Streptozotocin-Induced Diabetic Pregnant Rats

The consumption of functional foods, such as mushrooms, apparently influences Gestational Diabetes Mellitus (GDM), and brings benefits to maternal-fetal health. Ganoderma lucidum contains a variety of bioactive compounds, such as polysaccharides, proteins and polyphenols that are able to control blood glucose and be used in anti-cancer therapy. We aimed to evaluate the effects of the consumption of Ganoderma lucidum (Gl) on maternal-fetal outcomes in streptozotocin-induced GDM (GDM-STZ). Pregnant rats were exposed to Gl (100 mg/kg/day) before and after the induction of GDM-STZ (single dose 40 mg/kg) on the eighth pregnancy day. Biochemical and oxidative stress parameters, reproductive performance and morphometry of fetuses were assessed. Gl reduced the glycemic response in the oral glucose tolerance test. Moreover, Gl decreased AST and ALT activities. GDM increased lipid peroxidation, which was reverted by Gl. Catalase and glutathione peroxidase activities were decreased in GDM and the administered Gl after the fetus implantation increased catalase activity. Measurements of the fetal head, thorax, craniocaudal and tail showed greater values in fetuses from rats exposed to Gl compared to GDM. Ganoderma lucidum has an encouraging nutritional and medicinal potential against GDM, since it modifies glucose metabolism, reduces lipid peroxidation, and has protective effects in fetuses born from GDM dams.

Liraglutide Is Protective against Brain Injury in Mice with Febrile Seizures by Inhibiting Inflammatory Factors

The febrile seizure (FS) is a common disease in emergency pediatrics, and about 30% of patients are children aged between 6 months and 5 years. Therefore, we aim to observe the protective impact of liraglutide (LIR) on brain injury in mice with FS and to explore its relevant mechanisms. Male SD mice were selected, and the FS model was established by heat bath method. The behavioral score was performed on mice with Racine grading, and nerve cells in apoptosis in the hippocampus were determined by TUNEL. The content of glutamate was determined by ELISA. mRNA levels and protein expression of GLP-1, GLP-1R, IL-1β, IL-6, TNF-α, and cleaved-caspase 3 were examined in mice by q-PCR and WB. Protein expression of γ-aminobutyric acid was influenced by WB as well. LIR prolonged the seizure latency and seizure duration in mice with FS. The GLP-1 and GLP-1R in the mouse hippocampus with FS expressed highly and also inhibited the number of nerve cells in apoptosis, decreased glutamate content, and increased γ-aminobutyric acid expression in the mouse hippocampus with FS. In addition, The IL-1β, IL-6, and TNF-α, in the mouse hippocampus with FS expressed to reduce with LIR. LIR is protective against brain injury in mice with FS and protects brain injury by inhibiting inflammatory factors in mice with FS. Our finding provides a reference for mitigating and delaying the development of FS as well as the prevention and treatment of brain injury caused by FS.

Effects of Glucagon-like peptide 1 (GLP-1) analogs in the hippocampus

The glucagon-like peptide-1 (GLP-1) is a pleiotropic hormone very well known for its incretin effect in the glucose-dependent stimulation of insulin secretion. However, GLP-1 is also produced in the brain, and it displays critical roles in neuroprotection by activating the GLP-1 receptor signaling pathways. GLP-1 enhances learning and memory in the hippocampus, promotes neurogenesis, decreases inflammation and apoptosis, modulates reward behavior, and reduces food intake. Its pharmacokinetics have been improved to enhance the peptide's half-life, enhancing exposure and time of action. The GLP-1 agonists are successfully in clinical use for the treatment of type-2 diabetes, obesity, and clinical evaluation for the treatment of neurodegenerative diseases.

Exendin-4 Pretreatment Attenuates Kainic Acid-Induced Hippocampal Neuronal Death

Exendin-4 (Ex-4) is a glucagon-like peptide-1 receptor (GLP-1R) agonist that protects against brain injury. However, little is known about the effect of Ex-4 on kainic acid (KA)-induced seizures and hippocampal cell death. Therefore, this study evaluated the neuroprotective effects of Ex-4 pretreatment in a mouse model of KA-induced seizures. Three days before KA treatment, mice were intraperitoneally injected with Ex-4. We found that Ex-4 pretreatment reversed KA-induced reduction of GLP-1R expression in the hippocampus and attenuated KA-induced seizure score, hippocampal neuronal death, and neuroinflammation. Ex-4 pretreatment also dramatically reduced hippocampal lipocalin-2 protein in KA-treated mice. Furthermore, immunohistochemical studies showed that Ex-4 pretreatment significantly alleviated blood–brain barrier leakage. Finally, Ex-4 pretreatment stimulated hippocampal expression of phosphorylated cyclic adenosine monophosphate (cAMP) response element-binding protein (p-CREB), a known target of GLP-1/GLP-1R signaling. These findings indicate that Ex-4 pretreatment may protect against KA-induced neuronal damage by regulating GLP-1R/CREB-mediated signaling pathways.

Ablation of dynamin-related protein 1 promotes diabetes-induced synaptic injury in the hippocampus

Dynamin-related protein 1 (Drp1)-mediated mitochondrial dysfunction is associated with synaptic injury in the diabetic brain. However, the dysfunctional mitochondria by Drp1 deletion in the diabetic brain are poorly understood. Here, we investigated the effects of neuron-specific Drp1 deletion on synaptic damage and mitophagy in the hippocampus of a high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice. HFD/STZ-induced diabetic mice exhibited metabolic disturbances and synaptic damages. Floxed Drp1 mice were crossed with Ca²⁺/calmodulin-dependent protein kinase IIα (CaMKIIα)-Cre mice, to generate neuron-specific Drp1 knockout (Drp1cKO) mice, which showed marked mitochondrial swelling and dendritic spine loss in hippocampal neurons. In particular, diabetic Drp1cKO mice exhibited an increase in dendritic spine loss and higher levels of oxidative stress and neuroinflammation compared with diabetic wild-type (WT) mice. Diabetic WT mice generally displayed increased Drp1-induced small mitochondrial morphology in hippocampal neurons, but large mitochondria were prominently observed in diabetic Drp1cKO mice. The levels of microtubule-associated protein 1 light-chain 3 and lysosomal-associated membrane protein 1 proteins were significantly increased in the hippocampus of diabetic Drp1cKO mice compared with diabetic WT mice. The inhibition of Drp1 adversely promotes synaptic injury and neurodegeneration in the diabetic brain. The findings suggest that the exploratory mechanisms behind Drp1-mediated mitochondrial dysfunction could provide a possible therapeutic target for diabetic brain complications.

Mitochondrial Dysfunction and Mitophagy Closely Cooperate in Neurological Deficits Associated with Alzheimer's Disease and Type 2 Diabetes

Alzheimer's disease (AD) and type 2 diabetes (T2D) are known to be correlated in terms of their epidemiology, histopathology, and molecular and biochemical characteristics. The prevalence of T2D leading to AD is approximately 50-70%. Moreover, AD is often considered type III diabetes because of the common risk factors. Uncontrolled T2D may affect the brain, leading to memory and learning deficits in patients. In addition, metabolic disorders and impaired oxidative phosphorylation in AD and T2D patients suggest that mitochondrial dysfunction is involved in both diseases. The dysregulation of pathways involved in maintaining mitochondrial dynamics, biogenesis and mitophagy are responsible for exacerbating the impact of hyperglycemia on the brain and neurodegeneration under T2D conditions. The first section of this review describes the recent views on mitochondrial dysfunction that connect these two disease conditions, as the pathways are observed to overlap. The second section of the review highlights the importance of different mitochondrial miRNAs (mitomiRs) involved in the regulation of mitochondrial dynamics and their association with the pathogenesis of T2D and AD. Therefore, targeting mitochondrial biogenesis and mitophagy pathways, along with the use of mitomiRs, could be a potent therapeutic strategy for T2D-related AD. The last section of the review highlights the known drugs targeting mitochondrial function for the treatment of both disease conditions.

Diagnostic value of miR-637 in patients with atherosclerosis and its predictive significance for the future cardiovascular events

Objectives

Atherosclerosis is a common vascular disease. MiR-637 has been demonstrated to be low-expressed in hypertensive patients, and atherosclerosis is closely related to hypertension. Therefore, this study speculated that miR-637 may play an important role in the development of atherosclerosis. In brief, this study examined the expression level of miR-637 in patients with atherosclerosis and further analyzed its clinical value in patients with atherosclerosis.

Methods

The expression level of miR-637 was detected in serum from 86 patients with atherosclerosis and 75 healthy controls by using quantitative reverse transcription-polymerase chain reaction. The receiver operating characteristic curve was used to assess the diagnostic value of miR-637 in atherosclerosis. Pearson’s correlation analysis was performed to evaluate the relationship between serum miR-637 and different clinical parameters. The prognostic value of miR-637 in atherosclerosis was analyzed by the Kaplan–Meier survival curve and multivariate cox regression analysis.

Results

Compared with healthy individuals, miR-637 was downregulated in the serum of atherosclerosis patients. The receiver operating characteristic curve suggested the high diagnostic value of miR-637 for atherosclerosis, with the AUC of 0.853, specificity of 77.9%, and sensitivity of 80.0%. The expression level of miR-637 was negatively correlated with CIMT (r = –0.8101, P <  0.0001) and CRP (r = –0.6154, P <  0.0001), respectively. Survival analysis indicated that miR-637 was also found to be an independent prognostic factor for atherosclerosis.

Conclusions

MiR-637 is a potential noninvasive diagnostic marker of atherosclerosis and has important predictive value for the occurrence of future cardiovascular events.

Liraglutide improved the cognitive function of diabetic mice via the receptor of advanced glycation end products down-regulation

Background and aims Advanced glycation end products (AGEs) and receptor of advanced glycation end products (RAGE), are associated with cognition decline. We aim to investigate the effect of liraglutide on cognitive function in diabetic mice.

Results Diabetic mice showed decreased cognitive function. Moreover, lower glucagon like peptide-1 (GLP-1) levels in plasma were detected in db/db mice. Additionally, up-regulated RAGE and down-regulated glucagon like peptide-1 (GLP-1R) levels were observed in db/db mice. However, decreased GLP-1R and increased RAGE were reversed by liraglutide. We also found decreased cellular activity in cells with AGEs. Moreover, AGEs up-regulated RAGE in PC12 and HT22 cells. However, liraglutide improved the cell activity damaged by AGEs. Although we did not discover the direct-interaction between RAGE and GLP-1R, elevated RAGE levels induced by AGEs were restored by liraglutide.

Conclusion We demonstrated that the cognitive function of diabetic mice was improved by liraglutide via the down-regulation of RAGE.

Methods db/db mice and db/m mice were used in this study. Liraglutide was used to remedy diabetic mice. Neurons and RAGE in hippocampus were shown by immunofluorescence. And then, PC12 cells or HT22 cells with AGEs were treated with liraglutide. GLP-1R and RAGE were measured by western blotting.

Drug Delivery Strategies for Enhancing the Therapeutic Efficacy of Toxin-Derived Anti-Diabetic Peptides

Toxin peptides derived from the skin secretions of amphibians possess unique hypoglycemic activities. Many of these peptides share cationic and amphipathic structural similarities and appear to possess cell-penetrating abilities. The mechanism of their insulinotropic action is yet not elucidated, but they have shown great potential in regulating the blood glucose levels in animal models. Therefore, they have emerged as potential drug candidates as therapeutics for type 2 diabetes. Despite their anti-diabetic activity, there remain pharmaceutical challenges to be addressed for their clinical applications. Here, we present an overview of recent studies related to the toxin-derived anti-diabetic peptides derived from the skin secretions of amphibians. In the latter part, we introduce the bottleneck challenges for their delivery in vivo and general drug delivery strategies that may be applicable to extend their blood circulation time. We focus our research on the strategies that have been successfully applied to improve the plasma half-life of exendin-4, a clinically available toxin-derived anti-diabetic peptide drug.