Metformin Protects Against Diabetes-Induced Cognitive Dysfunction by Inhibiting Mitochondrial Fission Protein DRP1

Mitochondrial proteins as therapeutic targets in diabetic ketoacidosis: evidence from Mendelian randomization analysis

Introduction

Diabetic ketoacidosis (DKA) is a severe and potentially fatal acute complication in diabetic patients, commonly occurring in type 1 diabetes (T1D) but also seen in type 2 diabetes (T2D). The pathogenesis of DKA involves complex physiological processes that are not fully understood, especially the role of mitochondria. Mitochondria, known as the powerhouse of cells, plays a crucial role in oxidative phosphorylation and ATP production, which is vital in various metabolic diseases, including diabetes. However, the exact causal relationship between mitochondrial dysfunction and DKA remains unclear.

Methods

This study employed Mendelian randomization (MR) analysis and protein-protein interaction (PPI) networks to systematically explore the causal relationships between mitochondrial DNA copy number (mtDNA-CN) and specific mitochondrial proteins with DKA. We used bidirectional MR analysis and genome-wide association study (GWAS) data from openGWAS database to investigate the causal effects of mtDNA-CN and 64 mitochondrial-related proteins on DKA and its subtypes (T1DKA, T2DKA, unspecified-DKA).

Results

The study revealed that increased mtDNA-CN significantly reduces the risk of DKA, whereas the effect of DKA on mtDNA-CN was not significant. Mitochondrial-related proteins such as MRPL32, MRPL33, COX5B, DNAJC19, and NDUFB8 showed a negative causal relationship with DKA, indicating their potential protective roles. Conversely, ATP5F1B and COX4I2 have a positive causal relationship with DKA, indicating that excessive ATP production in diabetic patients may be detrimental to health and increase the risk of severe complications such as DKA.

Discussion

The results emphasize the necessity of protecting mitochondrial function in order to reduce the risk of DKA. The study offers novel perspectives on the molecular pathways involved in DKA, emphasizing the critical functions of mt-DNA and distinct proteins. These evidences not only enhance our comprehension of the implications of mitochondrial dysfunction in diabetes-related complications but also identify potential therapeutic targets for individualized treatment approaches, thereby making a substantial contribution to clinical care and public health initiatives.

Cellular Components of the Blood-Brain Barrier and Their Involvement in Aging-Associated Cognitive Impairment

Human life expectancy has been significantly extended, which poses major challenges to our healthcare and social systems. Aging-associated cognitive impairment is attributed to endothelial dysfunction in the cardiovascular system and neurological dysfunction in the central nervous system. The central nervous system is considered an immune-privileged tissue due to the exquisite protection provided by the blood-brain barrier. The present review provides an overview of the structure and function of blood-brain barrier, extending the cell components of blood-brain barrier from endothelial cells and pericytes to astrocytes, perivascular macrophages and oligodendrocyte progenitor cells. In particular, the pathological changes in the blood-brain barrier in aging, with special focus on the underlying mechanisms and molecular changes, are presented. Furthermore, the potential preventive/therapeutic strategies against aging-associated blood-brain barrier disruption are discussed.

Cai's herbal tea enhances mitochondrial autophagy of type 1 diabetic mellitus β cells through the AMPK/mTOR pathway and alleviates inflammatory response

BACKGROUND

This study investigates the therapeutic mechanisms of Cai's Herbal Tea in Type 1 Diabetes Mellitus (T1DM) mice, focusing on its effects on mitochondrial change and autophagy via the AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) pathway.

METHODS

The composition of Cai's Herbal Tea was analyzed by Ultra-High Performance Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry (UHPLC-Q/TOF-MS). C57BL/6 mice and Min6 pancreatic beta cells were divided into control, diabetic mellitus (DM)/high glucose (HG), and treatment groups (low, medium, and high doses of Cai's Tea, and Metformin). Key physiological parameters, pancreatic islet health, Min6 cell morphology, viability, and insulin (INS) secretion were assessed. Small Interfering RNA-AMPK (si-AMPK) was utilized to confirm the pathway involvement.

RESULTS

Cai's Herbal Tea improved body weight, pancreatic islet pathological injury, and INS secretion whereas reduced total triglycerides, fasting blood sugar, and Interferon gamma (INF-γ) in T1DM mice, particularly at higher doses. In Min6 cells, Cai's Tea mitigated HG-induced damage and proinflammatory response, enhancing cell viability and INS secretion. Notably, it reduced swelling and improved cristae structure in treated groups of mitochondria and promoted autophagy via the AMPK-mTOR pathway, evidenced by increased LC3II/LC3I and P-AMPK/AMPK ratios, and decreased P-mTOR/mTOR and P62 expressions in pancreatic islet β-cells. Furthermore, these effects were converted by si-AMPK interference.

CONCLUSION

Cai's Herbal Tea exhibits significant therapeutic efficacy in T1DM mice by improving mitochondrial health and inducing autophagy through the AMPK-mTOR pathway in pancreatic islet β-cells. These findings highlight its potential as a therapeutic approach for T1DM management.

Synergistic Effect of Flavonoids and Metformin on Protection of the Methylglyoxal-Induced Damage in PC-12 Neuroblastoma Cells: Structure-Activity Relationship and Potential Target

Methylglyoxal-induced ROS elevation is the primary cause of neuronal damage. Metformin is a traditional hypoglycemic drug that has been reported to be beneficial to the nervous system. In this study, flavonoids were found to enhance the protective effect of metformin when added at a molar concentration of 0.5%. The structure-activity relationship (SAR) analysis indicated that ortho- substitution in the B ring, and the absence of double bonds between the 2 and 3 position combined with the gallate substitution with R configuration at the 3 position in the C ring played crucial roles in the synergistic effects, which could be beneficial for designing a combination of the compounds. Additionally, the mechanism study revealed that a typical flavonoid, EGCG, enhanced ROS scavenging and anti-apoptotic ability via the BCL2/Bax/Cyto C/Caspase-3 pathway, and synergistically inhibited the expression of GSK-3β, BACE-1, and APP in PC-12 cells when used in combination with metformin. The dose of metformin used in the combination was only 1/4 of the conventional dose when used alone. These results suggested that ROS-mediated apoptosis and the pathways related to amyloid plaques (Aβ) formation can be the targets for the synergistic neuroprotective effects of flavonoids and metformin.

Imeglimin Exhibits Novel Anti-Inflammatory Effects on High-Glucose-Stimulated Mouse Microglia through ULK1-Mediated Suppression of the TXNIP-NLRP3 Axis

Type 2 diabetes mellitus (T2DM) is an epidemiological risk factor for dementia and has been implicated in multifactorial pathologies, including neuroinflammation. In the present study, we aimed to elucidate the potential anti-inflammatory effects of imeglimin, a novel antidiabetic agent, on high-glucose (HG)-stimulated microglia. Mouse microglial BV2 cells were stimulated with HG in the presence or absence of imeglimin. We examined the effects of imeglimin on the levels of proinflammatory cytokines, intracellular reactive oxygen species (ROS), mitochondrial integrity, and components related to the inflammasome or autophagy pathways in these cells. Our results showed that imeglimin suppressed the HG-induced production of interleukin-1beta (IL-1β) by reducing the intracellular ROS levels, ameliorating mitochondrial dysfunction, and inhibiting the activation of the thioredoxin-interacting protein (TXNIP)-NOD-like receptor family pyrin domain containing 3 (NLRP3) axis. Moreover, the inhibitory effects of imeglimin on the TXNIP-NLRP3 axis depended on the imeglimin-induced activation of ULK1, which also exhibited novel anti-inflammatory effects without autophagy induction. These findings suggest that imeglimin exerted novel suppressive effects on HG-stimulated microglia through the ULK1-TXNIP-NLRP3 axis, and may, thereby, contribute to the development of innovative strategies to prevent T2DM-associated cognitive impairment.

Banxia Xiexin Decoction Prevents HT22 Cells from High Glucose-induced Neurotoxicity via JNK/SIRT1/Foxo3a Signaling Pathway

BACKGROUND

Type 2 diabetes-associated cognitive dysfunction (DCD) is a chronic complication of diabetes that has gained international attention. The medicinal compound Banxia Xiexin Decoction (BXXXD) from traditional Chinese medicine (TCM) has shown potential in improving insulin resistance, regulating endoplasmic reticulum stress (ERS), and inhibiting cell apoptosis through various pathways. However, the specific mechanism of action and medical value of BXXXD remain unclear.

METHODS

We utilized TCMSP databases to screen the chemical constituents of BXXXD and identified DCD disease targets through relevant databases. By using Stitch and String databases, we imported the data into Cytoscape 3.8.0 software to construct a protein-protein interaction (PPI) network and subsequently identified core targets through network topology analysis. The core targets were subjected to Gene Ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The results were further validated through in vitro experiments.

RESULTS

Network pharmacology analysis revealed the screening of 1490 DCD-related targets and 190 agents present in BXXXD. The topological analysis and enrichment analysis conducted using Cytoscape software identified 34 core targets. Additionally, GO and KEGG pathway analyses yielded 104 biological targets and 97 pathways, respectively. BXXXD exhibited its potential in treating DCD by controlling synaptic plasticity and conduction, suppressing apoptosis, reducing inflammation, and acting as an antioxidant. In a high glucose (HG) environment, the expression of JNK, Foxo3a, SIRT1, ATG7, Lamp2, and LC3 was downregulated. BXXXD intervention on HT22 cells potentially involved inhibiting excessive oxidative stress, promoting neuronal autophagy, and increasing the expression levels of JNK, SIRT1, Foxo3a, ATG7, Lamp2, and LC3. Furthermore, the neuroprotective effect of BXXXD was partially blocked by SP600125, while quercetin enhanced the favorable role of BXXXD in the HG environment.

CONCLUSION

BXXXD exerts its effects on DCD through multiple components, targets, levels, and pathways. It modulates the JNK/SIRT1/Foxo3a signaling pathway to mitigate autophagy inhibition and apoptotic damage in HT22 cells induced by HG. These findings provide valuable perspectives and concepts for future clinical trials and fundamental research.

Involvement of mitochondrial dynamics and mitophagy in diabetic endothelial dysfunction and cardiac microvascular injury

Endothelial cells (ECs), found in the innermost layer of blood vessels, are crucial for maintaining the structure and function of coronary microcirculation. Dysregulated coronary microcirculation poses a fundamental challenge in diabetes-related myocardial microvascular injury, impacting myocardial blood perfusion, thrombogenesis, and inflammation. Extensive research aims to understand the mechanistic connection and functional relationship between cardiac EC dysfunction and the development, diagnosis, and treatment of diabetes-related myocardial microvascular injury. Despite the low mitochondrial content in ECs, mitochondria act as sensors of environmental and cellular stress, influencing EC viability, structure, and function. Mitochondrial dynamics and mitophagy play a vital role in orchestrating mitochondrial responses to various stressors by regulating morphology, localization, and degradation. Impaired mitochondrial dynamics or reduced mitophagy is associated with EC dysfunction, serving as a potential molecular basis and promising therapeutic target for diabetes-related myocardial microvascular injury. This review introduces newly recognized mechanisms of damaged coronary microvasculature in diabetes-related microvascular injury and provides updated insights into the molecular aspects of mitochondrial dynamics and mitophagy. Additionally, novel targeted therapeutic approaches against diabetes-related microvascular injury or endothelial dysfunction, focusing on mitochondrial fission and mitophagy in endothelial cells, are summarized.

Therapeutic Potential of P110 Peptide: New Insights into Treatment of Alzheimer's Disease

Mitochondrial degeneration in various neurodegenerative diseases, specifically in Alzheimer's disease, involves excessive mitochondrial fission and reduced fusion, leading to cell damage. P110 is a seven-amino acid peptide that restores mitochondrial dynamics by acting as an inhibitor of mitochondrial fission. However, the role of P110 as a neuroprotective agent in AD remains unclear. Therefore, we performed cell culture studies to evaluate the neuroprotective effect of P110 on amyloid-β accumulation and mitochondrial functioning. Human SH-SY5Y neuronal cells were incubated with 1 µM and 10 µM of P110, and Real-Time PCR and Western blot analysis were done to quantify the expression of genes pertaining to AD and neuronal health. Exposure of SH-SY5Y cells to P110 significantly increased APP mRNA levels at 1 µM, while BACE1 mRNA levels were increased at both 1 µM and 10 µM. However, protein levels of both APP and BACE1 were significantly reduced at 10 µM of P110. Further, P110 treatment significantly increased ADAM10 and Klotho protein levels at 10 µM. In addition, P110 exposure significantly increased active mitochondria and reduced ROS in live SH-SY5Y cells at both 1 µM and 10 µM concentrations. Taken together, our results indicate that P110 might be useful in attenuating amyloid-β generation and improving neuronal health by maintaining mitochondrial function in neurons.

Glycolytic enzyme PFKFB3 regulates sphingosine 1-phosphate receptor 1 in proangiogenic glomerular endothelial cells under diabetic condition

Glomerular angiogenesis is a characteristic feature of diabetic nephropathy (DN). Enhanced glycolysis plays a crucial role in angiogenesis. The present study was designed to investigate the role of glycolysis in glomerular endothelial cells (GECs) in a mouse model of DN. Mouse renal cortex and isolated glomerular cells were collected for single-cell and RNA sequencing. Cultured GECs were exposed to high glucose in the presence (proangiogenic) and absence of a vascular sprouting regimen. MicroRNA-590-3p was delivered by lipofectamine in vivo and in vitro. In the present study, a subgroup of GECs with proangiogenic features was identified in diabetic kidneys by using sequencing analyses. In cultured proangiogenic GECs, high glucose increased glycolysis and phosphofructokinase/fructose bisphosphatase 3 (PFKFB3) protein expression, which were inhibited by overexpressing miRNA-590-3p. Mimics of miRNA-590-3p also increased receptor for sphingosine 1-phosphate (S1pR1) expression, an angiogenesis regulator, in proangiogenic GECs challenged with high glucose. Inhibition of PFKFB3 by pharmacological and genetic approaches upregulated S1pR1 protein in vitro. Mimics of miRNA-590-3p significantly reduced migration and angiogenic potential in proangiogenic GECs challenged with high glucose. Ten-week-old type 2 diabetic mice had elevated urinary albumin levels, reduced renal cortex miRNA-590-3p expression, and disarrangement of glomerular endothelial cell fenestration. Overexpressing miRNA-590-3p via perirenal adipose tissue injection restored endothelial cell fenestration and reduced urinary albumin levels in diabetic mice. Therefore, the present study identifies a subgroup of GECs with proangiogenic features in mice with DN. Local administration of miRNA-590-3p mimics reduces glycolytic rate and upregulates S1pR1 protein expression in proangiogenic GECs. The protective effects of miRNA-590-3p provide therapeutic potential in DN treatment.NEW & NOTEWORTHY Proangiogenetic glomerular endothelial cells (GECs) are activated in diabetic nephropathy. High glucose upregulates glycolytic enzyme phosphofructokinase/fructose bisphosphatase 3 (PFKFB3) in proangiogenetic cells. PFKFB3 protects the glomerular filtration barrier by targeting endothelial S1pR1. MiRNA-590-3p restores endothelial cell function and mitigates diabetic nephropathy.

Mitochondrial dynamics-related genes DRP1 and OPA1 contributes to early diagnosis of cognitive impairment in diabetes

BACKGROUND AND AIM

DRP1 and OPA1 play important roles in mitochondrial fusion and fission. However, the role of DRP1 and OPA1 amplification in mitochondrial cognitive impairment has not been reported. This study aimed to investigate the relationship between DRP1 and OPA1 and the risk of cognitive impairment.

METHODS

In this study, 45 elderly patients with diabetes admitted to the Lianyungang Second People's Hospital from September 2020 to January 2021 were included. The patients were divided into normal group, mild cognitive impairment group and dementia group by using MMSE score, and the clinical characteristics of the three groups were compared. The amplification multiples of the two genes' DNA were calculated by ΔΔCT and defined as 2- K. Spearman rank correlation was used to analyze the correlation between the DNA amplification multiples of patients' DRP1 and OPA1 and AD8 and MoCA scores. The sensitivity and specificity of DNA amplification multiples of DRP1 and OPA1 to predict clinical outcomes of diabetic cognitive impairment were evaluated using Receiver operator characteristic (ROC) curves. Multiple logistic regression was used to evaluate the relationship between DNA amplification factor of DRP1 and OPA1 and cognitive function.

RESULTS

DRP1(2- K) and OPA1(2- K) significantly increased and decreased in dementia and MCI groups compared with the normal group (P ≤ 0.001). The DNA amplification factor of DRP1 was positively correlated with AD8 score and negatively correlated with MoCA score (P < 0.001). The DNA amplification factor of OPA1 was positively correlated with the MoCA score (P = 0.0002). Analysis of ROCs showed that the DNA amplification factor of OPA1 had a higher predictive value for dementia (P < 0.0001), and that it had a higher predictive value when used in combination with DRP1. Multiple logistic regression results showed that increased DNA amplification in DRP1 was associated with increased risk of dementia (OR 1.149;95%CI,1.035-1.275), and increased DNA amplification in OPA1 was associated with decreased risk of MCI (OR 0.004;95%CI,0.000-0.251) and dementia (OR 0.000;95%CI,0.000-0.134).

CONCLUSION

DNA amplification multiples of DRP1 and OPA1 are associated with the risk of dementia in elderly patients and may serve as potential biomarkers.

The Role of PGC-1α-Mediated Mitochondrial Biogenesis in Neurons

Neurons are highly dependent on mitochondrial ATP production and Ca²⁺ buffering. Neurons have unique compartmentalized anatomy and energy requirements, and each compartment requires continuously renewed mitochondria to maintain neuronal survival and activity. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key factor in the regulation of mitochondrial biogenesis. It is widely accepted that mitochondria are synthesized in the cell body and transported via axons to the distal end. However, axonal mitochondrial biogenesis is necessary to maintain axonal bioenergy supply and mitochondrial density due to limitations in mitochondrial axonal transport rate and mitochondrial protein lifespan. In addition, impaired mitochondrial biogenesis leading to inadequate energy supply and neuronal damage has been observed in neurological disorders. In this review, we focus on the sites where mitochondrial biogenesis occurs in neurons and the mechanisms by which it maintains axonal mitochondrial density. Finally, we summarize several neurological disorders in which mitochondrial biogenesis is affected.

Mulberry-Derived 1-Deoxynojirimycin Prevents Type 2 Diabetes Mellitus Progression via Modulation of Retinol-Binding Protein 4 and Haptoglobin

Pre-diabetic or early-stage type 2 diabetes patients may develop an adverse diabetic progression, leading to several complications and increasing hospitalization rates. Mulberry leaves, which contain 1-deoxynojirimycin (DNJ), have been used as a complementary medicine for diabetes prevention and treatment. Our recent study demonstrated that mulberry leaf powder with 12 mg of DNJ improves postprandial hyperglycemia, fasting plasma glucose, and glycated hemoglobin. However, the detailed mechanisms are still unknown. This study investigates the effect of long-term (12-week) supplementation of mulberry leaves in obese people with prediabetes and patients with early-stage type 2 diabetes. Participants’ blood was collected before and after supplementation. The protein profile of the plasma was examined by proteomics. In addition, the mitochondrial function was evaluated by energetic and homeostatic markers using immunoelectron microscopy. The proteomics results showed that, from a total of 1291 proteins, 32 proteins were related to diabetes pathogenesis. Retinol-binding protein 4 and haptoglobin protein were downregulated, which are associated with insulin resistance and inflammation, respectively. For mitochondrial function, the haloacid dehalogenase-like hydrolase domain-containing protein 3 (HDHD-3) and dynamin-related protein 1 (Drp-1) displayed a significant increment in the after treatment group. In summary, administration of mulberry leaf powder extract in prediabetes and the early stage of diabetes can alleviate insulin resistance and inflammation and promote mitochondrial function in terms of energy production and fission.