MCU-knockdown attenuates high glucose-induced inflammation through regulating MAPKs/NF-κB pathways and ROS production in HepG2 cells

Human salivary histatin 1 regulating IP3R1/GRP75/VDAC1 mediated mitochondrial-associated endoplasmic reticulum membranes (MAMs) inhibits cell senescence for diabetic wound repair

RATIONALE

Difficulty in skin wound healing is a concern for diabetic patients across the world. Impaired mitochondrial dysfunction and aging-related vascular dysfunction in human umbilical vein endothelial cells (HUVECs) caused by oxidative stress are major impediments to diabetic wound healing. However, research on skin repair at the mechanistic level by improving mitochondrial function and inhibiting oxidative stress-induced HUVEC senescence remains lacking.

METHODS AND RESULTS

Human saliva effectively inhibits the natural aging of HUVECs through immunodepletion experiments. Histatin 1 (Hst1), a short peptide comprising 38 amino acids, is the primary component of human saliva that prevents HUVEC aging. Based on in vitro findings, Hst1 decreased staining for senescence-associated β-galactosidase activity and expression of mediators of senescence signaling, including p53, p21, and p16. Mechanistically, HUVEC senescence is associated with Hst1-modulated nuclear factor Nrf2 signaling as Hst1 induces ERK-mediated Nrf2 nuclear translocation through NADPH oxidase-dependent ROS regulation, reinforced Nrf2 antioxidant response, and suppressed oxidative stress. RNA sequencing identified that the mitochondrial-related gene set was enriched in the Hst1 group. Coimmunoprecipitation indicated that Hst1 delayed hydrogen peroxide-induced HUVEC senescence by inhibiting mitochondria-associated endoplasmic reticulum (ER) membrane formation mediated by inositol 1,4,5-trisphosphate receptor 1-glucose-regulated protein 75-voltage-dependent anion channel 1 (VDAC1) complex interactions. Furthermore, in aging HUVECs, Hst1 treatment or VDAC1 silencing with small interfering RNA hindered calcium (Ca2+) transfer from the ER to the mitochondria, thereby ameliorating mitochondrial Ca2+ overload and restoring mitochondrial function. In an in vivo mouse model of diabetes mellitus skin defects, Hst1 facilitated wound healing by stimulating the new blood vessel formation and impeding the expression of senescent biomarkers.

CONCLUSIONS

This study proposes a theoretical solution that Hst1 can restore mitochondrial function by inhibiting oxidative stress or cellular senescence, thereby promoting angiogenesis and diabetic wound repair.

Liver knockout of MCU leads to greater dysregulation of lipid metabolism in MAFLD

Metabolic-associated fatty liver disease (MAFLD) is a common chronic condition that poses a significant threat to human health. Mitochondrial dysfunction, particularly involving the mitochondrial Ca2+ uniporter (MCU), plays a key role in its pathogenesis. This study aimed to investigate the impact of the MCU gene on hepatic lipid metabolism in mice fed a high-fat diet. Using MCU knockout and wild-type mice, subjected to either a high-fat or normal diet for 14 weeks, we observed notable Steatosis and liver weight gain in MCU-deficient mice. Liver function markers, serum triglycerides, very low-density lipoprotein (VLDL) levels, and ApoB protein expression were all significantly elevated. Mechanistic studies revealed that MCU deletion led to mitochondrial dysfunction, increased oxidative stress. These findings highlight the critical role of the MCU gene in maintaining hepatic lipid balance and suggest its potential as a therapeutic target for managing nonalcoholic fatty liver disease.

Knockdown of hepatic mitochondrial calcium uniporter mitigates MASH and fibrosis in mice

BACKGROUND

Mitochondrial calcium uniporter (MCU) plays pleiotropic roles in cellular physiology and pathology that contributes to a variety of diseases, but the role and potential mechanism of MCU in the pathogenesis of metabolic dysfunction-associated steatohepatitis (MASH) remain poorly understood.

METHODS AND RESULTS

Here, hepatic knockdown of MCU in C57BL/6J mice was achieved by tail vein injection of AAV8-mediated the CRISPR/Cas9. Mice were fed a Choline-deficient, L-amino acid-defined high-fat diet (CDAHFD) for 8 weeks to induce MASH and fibrosis. We find that expression of MCU enhanced in MASH livers of humans and mice. MCU knockdown robustly limits lipid droplet accumulation, steatosis, inflammation, and hepatocyte apoptotic death during MASH development both in vivo in mice and in vitro in cellular models. MCU-deficient mice strikingly mitigate MASH-related fibrosis. Moreover, the protective effects of MCU knockdown against MASH progression are accompanied by a reduced level of mitochondrial calcium, limiting hepatic oxidative stress, and attenuating mitochondrial dysfunction. Mechanically, RNA sequencing analysis and protein immunoblotting indicate that knockdown MCU inhibited the Hippo/YAP pathway activation and restored the AMP-activated protein kinase (AMPK) activity during MASH development both in vitro and in vivo.

CONCLUSIONS

MCU is up-regulated in MASH livers in humans and mice; and hepatic MCU knockdown protects against diet-induced MASH and fibrosis in mice. Thus, targeting MCU may represent a novel therapeutic strategy for MASH and fibrosis.

Investigating the Effects and Mechanisms of Cyclomorusin on Osteoclasts in a High Glucose Environment

Diabetes mellitus is an endocrine disease characterized by prolonged hyperglycemia. Prolonged high blood sugar levels interfere with the differentiation and maturation process of OBs and OCs, leading to the onset of osteoporosis. However, OCs differentiation and maturation is a complex regulatory process. In this study, we used a co-culture system of RAW264.7 and MC3T3-E1 cells under HG concentration to explore the effect of CYM on OCs in a HG environment. The effects of CYM on the formation and function of OCs were observed using TRAP-positive cell counts and bone resorption pits. Then, mRNA and protein expression levels of OCs-related genes were detected by real-time qPCR and western blotting. The results showed that CYM had an inhibitory effect on OCs differentiation and bone resorption, reduced mRNAs expression of OCs-associated genes, and downregulated RANKL/RANK/TRAF6 pathway that mediates OCs differentiation. CYM could be a promising natural compound against diabetic osteoporosis.

Platelet mitochondria: the mighty few

PURPOSE OF REVIEW

Platelet mitochondrial dysfunction is both caused by, as well as a source of oxidative stress. Oxidative stress is a key hallmark of metabolic disorders such as dyslipidemia and diabetes, which are known to have higher risks for thrombotic complications.

RECENT FINDINGS

Increasing evidence supports a critical role for platelet mitochondria beyond energy production and apoptosis. Mitochondria are key regulators of reactive oxygen species and procoagulant platelets, which both contribute to pathological thrombosis. Studies targeting platelet mitochondrial pathways have reported promising results suggesting antithrombotic effects with limited impact on hemostasis in animal models.

SUMMARY

Targeting platelet mitochondria holds promise for the reduction of thrombotic complications in patients with metabolic disorders. Future studies should aim at validating these preclinical findings and translate them to the clinic.

Implications of MCU complex in metabolic diseases

Metabolic diseases are considered the primary culprit for physical and mental health of individuals. Although the diagnosis of these diseases is relatively easy, more effective and convenient potent drugs are still being explored. Ca2+ across the inner mitochondrial membrane is a vital intracellular messenger that regulates energy metabolism and cellular Ca2+ homeostasis and is involved in cell death. Mitochondria rely on a selective mitochondrial Ca2+ unidirectional transport complex (MCU complex) in their inner membrane for Ca2+ uptake. We found that the channel contains several subunits and undergoes dramatic transformations in various pathological processes, especially in metabolic diseases. In this way, we believe that the MCU complex becomes a target with significant potential for these diseases. However, there is no review linking the two factors, thus hindering the possibility of new drug production. Here, we highlight the connection between MCU complex-related Ca2+ transport and the pathophysiology of metabolic diseases, adding understanding and insight at the molecular level to provide new insights for targeting MCU to reverse metabolism-related diseases.

Ru360 Alleviates Postoperative Cognitive Dysfunction in Aged Mice by Inhibiting MCU-Mediated Mitochondrial Dysfunction

Purpose

Ru360, a selective inhibitor of mitochondrial calcium uptake, maintains mitochondrial calcium homeostasis. To evaluate whether mitochondrial calcium uniporter (MCU)-mediated mitochondrial function is associated with the pathological process of Postoperative cognitive dysfunction (POCD), elucidate its relationship with neuroinflammation, and observe whether the relevant pathological process can be improved with Ru360.

Methods

Aged mice underwent experimental open abdominal surgery after anesthesia. Open field tests, Novel object recognition tests and Y Maze Tests were used to conduct behavioral experiments. The reactive oxygen species (ROS) content, the levels of inflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), intra-mitochondrial calcium, mitochondrial membrane potential (MMP) and the activity of antioxidant superoxide dismutase (SOD) in the hippocampus of mice were detected using kits. The expression of proteins was detected using Western blot.

Results

After treatment with Ru360, MCU-mediated mitochondrial dysfunction was inhibited, neuroinflammation was reduced, and the learning ability of the mice was improved after surgery.

Conclusion

Our study demonstrated that mitochondrial function plays a crucial role in the pathology of POCD, and using Ru360 to improve mitochondrial function may be a new and necessary direction for the treatment of POCD.

Combinational administration of mesenchymal stem cell-derived exosomes and metformin reduces inflammatory responses in an in vitro model of insulin resistance in HepG2 cells

Diabetes is a highly common metabolic disorder in advanced societies. One of the causes of diabetes is insulin resistance, which is associated with a loss of sensitivity to insulin-sensitive cells. Insulin resistance develops in the body of a person prone to diabetes many years before diabetes development. Insulin resistance is associated with complications such as hyperglycemia, hyperlipidemia, and compensatory hyperinsulinemia and causes liver inflammation, which, if left untreated, can lead to cirrhosis, fibrosis, and even liver cancer. Metformin is the first line of treatment for patients with diabetes, which lowers blood sugar and increases insulin sensitivity by inhibiting gluconeogenesis in liver cells. The use of metformin has side effects, including a metallic taste in the mouth, vomiting, nausea, diarrhea, and upset stomach. For this reason, other treatments, along with metformin, are being developed. Considering the anti-inflammatory role of mesenchymal stem cells (MSCs) derived exosomes, their use seems to help improve liver tissue function and prevent damage caused by inflammation. This study investigated the anti-inflammatory effect of Wharton's jelly MSCs derived exosomes in combination with metformin in the HepG2 cells insulin resistance model induced by high glucose. This study showed that MSCs derived exosomes as an anti-inflammatory agent in combination with metformin could increase the therapeutic efficacy of metformin without needing to change metformin doses by decreasing inflammatory cytokines production, including IL-1, IL-6, and TNF-α and apoptosis in HepG2 cells.

Ameliorative Effect of Posidonia oceanica on High Glucose-Related Stress in Human Hepatoma HepG2 Cells

Metabolic disorders characterized by elevated blood glucose levels are a recognized risk factor for hepatocellular carcinoma (HCC). Lipid dysregulation is critically involved in the HCC progression, regulating energy storage, metabolism, and cell signaling. There is a clear link between de novo lipogenesis in the liver and activation of the NF-κB pathway, which is involved in cancer metastasis via regulation of metalloproteinases MMP-2/9. As conventional therapies for HCC reach their limits, new effective and safe drugs need to be found for the prevention and/or adjuvant therapy of HCC. The marine plant Posidonia oceanica (L.) Delile is endemic to the Mediterranean and has traditionally been used to treat diabetes and other health disorders. The phenol-rich leaf extract of Posidonia oceanica (POE) is known to have cell-safe bioactivities. Here, high glucose (HG) conditions were used to study lipid accumulation and fatty acid synthase (FASN) expression in human HepG2 hepatoma cells using Oil Red O and Western blot assays. Under HG conditions, the activation status of MAPKs/NF-κB axis and MMP-2/9 activity were determined by Western blot and gelatin zymography assays. The potential ameliorative role of POE against HG-related stress in HepG2 cells was then investigated. POE reduced lipid accumulation and FASN expression with an impact on de novo lipogenesis. Moreover, POE inhibited the MAPKs/NF-κB axis and, consequently, MMP-2/9 activity. Overall, these results suggest that P. oceanica may be a potential weapon in the HCC additional treatment.

Integrated network pharmacology and experimental validation to explore the mechanisms underlying naringenin treatment of chronic wounds

Naringenin is a citrus flavonoid with various biological functions and a potential therapeutic agent for skin diseases, such as UV radiation and atopic dermatitis. The present study investigates the therapeutic effect and pharmacological mechanism of naringenin on chronic wounds. Using network pharmacology, we identified 163 potential targets and 12 key targets of naringenin. Oxidative stress was confirmed to be the main biological process modulated by naringenin. The transcription factor p65 (RELA), alpha serine/threonine-protein kinase (AKT1), mitogen-activated protein kinase 1 (MAPK1) and mitogen-activated protein kinase 3 (MAPK3) were identified as common targets of multiple pathways involved in treating chronic wounds. Molecular docking verified that these four targets stably bound naringenin. Naringenin promoted wound healing in mice in vivo by inhibiting wound inflammation. Furthermore, in vitro experiments showed that a low naringenin concentration did not significantly affect normal skin cell viability and cell apoptosis; a high naringenin concentration was cytotoxic and reduced cell survival by promoting apoptosis. Meanwhile, comprehensive network pharmacology, molecular docking and in vivo and in vitro experiments revealed that naringenin could treat chronic wounds by alleviating oxidative stress and reducing the inflammatory response. The underlying mechanism of naringenin in chronic wound therapy involved modulating the RELA, AKT1 and MAPK1/3 signalling pathways to inhibit ROS production and inflammatory cytokine expression.

A diarylheptanoid compound from Alpinia officinarum Hance ameliorates high glucose-induced insulin resistance by regulating PI3K/AKT-Nrf2-GSK3β signaling pathways in HepG2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Alpinia officinarum Hance, a perennial natural medicine-food herb, has been traditionally used to treat colds, stomachache, and diabetes for thousands of years. 1,7-Diphenyl-4E-en-3-heptanone (DPH5), a diarylheptanoid isolated from the rhizome of A. officinarum has been reported to be safe and to have antioxidant and hypoglycemic effects, suggesting its potential in the treatment of insulin resistance (IR).

AIM OF THE STUDY

Aim of to investigate the protective effect of DPH5 on IR and elucidate its underlying mechanism of action.

MATERIALS AND METHODS

HepG2 cells were used as the research objects. Glucose uptake and reactive oxygen species (ROS) levels in high glucose-induced insulin-resistant HepG2 cells were assessed using flow cytometry. Glucose consumption and the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were analyzed using the corresponding assay kits. The expression of mRNA and proteins related to insulin signaling, glucose metabolism, and antioxidant factor, including insulin receptor substrate-1 (IRS1), phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), translocation of glucose transporter-4, glycogen synthase kinase-3β (GSK3β), glucokinase (GCK), pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), nuclear factor-erythroid 2 related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NADPH quinoneoxidoreductase (NQO1), and glutathione peroxidase (GSH-Px) was determined using real-time quantitative polymerase chain reaction and western blotting. Furthermore, molecular docking was performed to determine the spatial mechanism of DPH5 on the key targets PI3K, AKT, Nrf2, and GSK3β.

RESULTS

DPH5 could improve IR that manifested as increased glucose uptake and glucose consumption in insulin-resistant HepG2 cells. Moreover, DPH5 could enhance antioxidant capacity by activating Nrf2/HO-1 elements, including increasing Nrf2, HO-1, SOD, NQO1, and GSH-Px expression and reducing MDA, ROS, and JNK levels, thereby improving oxidative stress and ultimately alleviating IR. Additionally, DPH5 could promote the expression of IRS1, PI3K, AKT, GSK3β, GCK, and PK, and downregulate the expression of PEPCK and G6pase, thereby accelerating glucose utilization and enhancing insulin sensitivity. The mechanism underlying the effect of DPH5 in alleviating IR was related to the PI3K/AKT- and Nrf2/HO-1-mediated regulation of the GSK3β signaling pathway, and the results were further confirmed using the specific inhibitors LY294002 and ML385. Results from molecular docking indicated that there were different regulatory sites and interacting forces between DPH5 and PI3K, AKT, Nrf2, and GSK3β; however, the binding force was relatively strong.

CONCLUSIONS

DPH5 improved oxidative stress and glucose metabolism via modulating the PI3K/AKT-Nrf2-GSK3β pathway, thereby ameliorating IR. Overall, our findings suggest the potential of DPH5 as a natural medicine to treat type-2 diabetes mellitus.

High glucose induces apoptosis, glycogen accumulation and suppresses protein synthesis in muscle cells of olive flounder Paralichthys olivaceus

The effect and the mechanism of high glucose on fish muscle cells are not fully understood. In the present study, muscle cells of olive flounder (Paralichthys olivaceus) were treated with high glucose (33 mM) in vitro. Cells were incubated in three kinds of medium containing 5 mM glucose, 5 mM glucose and 28 mM mannitol (as an isotonic contrast) or 33 mM glucose named the Control group, the Mannitol group and the high glucose (HG) group, respectively. Results showed that high glucose increased the ADP:ATP ratio and the reactive oxygen species (ROS) level, decreased mitochondrial membrane potential (MMP), induced the release of cytochrome C (CytC) and cell apoptosis. High glucose also led to cell glycogen accumulation by increasing the glucose uptake ability and affecting the mRNA expressions of glycogen synthase and glycogen phosphorylase. Meanwhile, it activated AMP-activated protein kinase (AMPK), inhibited the activity of mammalian target of rapamycin (mTOR) signalling pathway and the expressions of myogenic regulatory factors (MRF). The expressions of myostatin-1 (mstn-1) and E3 ubiquitin ligases including muscle RING-finger protein 1 (murf-1) and muscle atrophy F-box protein (mafbx) were also increased by the high glucose treatment. No difference was found between the Mannitol group and the Control group. These results demonstrate that high glucose has the effects of inducing apoptosis, increasing glycogen accumulation and inhibiting protein synthesis on muscle cells of olive flounder. The mitochondria-mediated apoptotic signalling pathway, AMPK and mTOR pathways participated in these biological effects.

Metformin reduces lipid accumulation in HepG2 cells via downregulation of miR-33b

INTRODUCTION

Here, we aimed to investigate whether the beneficial effects of metformin on lipid accumulation is mediated through regulation of miR-33b.

METHODS

The expression of the genes and miRNAs and protein levels were evaluated using real-time PCR and western blot, respectively. To investigate the potential role of miR-33b in lipid accumulation, the mimic of the miR-33b was transfected into HepG2 cells.

RESULTS

We found that metformin reduces high glucose-induced lipid accumulation in HepG2 cells through inhibiting of SREBP1c and FAS and increasing the expression of CPT1 and CROT. Overexpression of miR-33b significantly prevented the decreasing effect of metformin on lipid content and intra and extra triglyceride levels. Importantly, miR-33b mimic inhibited the increasing effects of metformin on the expression of CPT1 and CROT.

CONCLUSION

These findings suggest that metformin attenuates high glucose-induced lipid accumulation in HepG2 cell by downregulating the expression of miR-33b.

Insight of the role of mitochondrial calcium homeostasis in hepatic insulin resistance

Due to the rapid rise in the prevalence of chronic metabolic disease, more and more clinicians and basic medical researchers focus their eyesight on insulin resistance (IR), an early and central event of metabolic diseases. The occurrence and development of IR are primarily caused by excessive energy intake and reduced energy consumption. Liver is the central organ that controls glucose homeostasis, playing a considerable role in systemic IR. Decreased capacity of oxidative metabolism and mitochondrial dysfunction are being blamed as the direct reason for the development of IR. Mitochondrial Ca²⁺ plays a fundamental role in maintaining proper mitochondrial function and redox stability. The maintaining of mitochondrial Ca²⁺ homeostasis requires the cooperation of ion channels in the inner and outer membrane of mitochondria, such as mitochondrial calcium uniporter complex (MCUC) and voltage-dependent anion channels (VDACs). In addition, the crosstalk between the endoplasmic reticulum (ER), lysosome and plasma membrane with mitochondria is also significant for mitochondrial calcium homeostasis, which is responsible for an efficient network of cellular Ca²⁺ signaling. Here, we review the recent progression in the research about the regulation factors for mitochondrial Ca²⁺ and how the dysregulation of mitochondrial Ca²⁺ homeostasis is involved in the pathogenesis of hepatic IR, providing a new perspective for further exploring the role of ion in the onset and development of IR.

Nobiletin mitigates hepatocytes death, liver inflammation, and fibrosis in a murine model of NASH through modulating hepatic oxidative stress and mitochondrial dysfunction

This study aimed to investigate the therapeutic effects of nobiletin (NOB) on nonalcoholic steatohepatitis (NASH) and liver fibrosis in mice and to elucidate its underlying molecular mechanisms. BALB/c mice were fed a normal chow diet or a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) for 8 wks and treated with NOB (50 mg/kg) or vehicle by daily intraperitoneally injection for the last 4 wks. In vitro, we used palmitate (PA) stimulated AML12 cells as the model of hepatocyte lipotoxicity to dissect the effect and molecular mechanisms of NOB' action. Our results exhibited that NOB dramatically reduced hepatic steatosis, lipid accumulation and hepatocyte apoptosis, and inhibited the infiltration of F4/80⁺ macrophages into the NASH livers. Furthermore, NOB limited liver fibrosis and hepatic stellate cells activation in NASH mice. In parallel, NOB alleviated hepatocytes apoptosis and lipid accumulation in PA-treated AML12 cells. Most importantly, these histological ameliorations in NASH and fibrosis in NOB-treated NASH mice were associated with improvement hepatic oxidative stress, lipid peroxidation product, mitochondrial respiratory chain complexes I and restored ATP production. Similarly, NOB attenuated PA-induced reactive oxygen species (ROS) generation and mitochondrial disfunction in cultured AML12 cells. Additionally, NOB diminished the expression of mitochondrial Ca²⁺ uniporter (MCU) both in NASH livers and in PA-treated AML12. Taken together, our results indicate that NOB mitigated NASH development and fibrosis through modulating hepatic oxidative stress and attenuating mitochondrial dysfunction. Therefore, NOB might be a novel and promising agent for treatment of NASH and liver fibrosis.

Mitochondria-ER contacts and glucose: the powerhouse of Alzheimer's disease?

A mechanism involving endoplasmic reticulum-mitochondria contacts noted in diabetes mellitus may explain the neurodegeneration and amyloidogenesis observed in these patients. Urolithin A, a metabolite found in the gut microbiome, is proposed as a therapeutic strategy for the treatment of the diabetes-related dementia.

Altered mitochondrial calcium handling and cell death by necroptosis: An emerging paradigm

The classical necroptosis signaling is mediated by death receptors (DRs) that work in synergy with traditional caspase inhibitory signals. Currently, potential therapeutic molecules are in various phases of clinical trials for a spectrum of pathological conditions associated with necroptosis. However, a non-classical model of necroptosis has also emerged over the last decade with a relatively unexplored molecular mechanism. Although in vitro studies and preclinical models have shown its close association with mitochondrial dysfunction (mito-dysfunction), contradictory reports have emerged which complicate its definitiveness. Though impaired mitochondrial calcium ([Ca²⁺]_m) handling is established in necrotic cell death, how this interplay regulates necroptosis is yet to be elucidated. Taking these questions into consideration, we have discussed various molecular aspects of necroptosis with the emerging role of mito-dysfunction. Based on the central role of altered [Ca²⁺]_m handling in mito-dysfunction mediated necroptosis, we have provided a comprehensive molecular insight into this emerging paradigm. Potential reasons for the contradictory findings regarding the role of mito-dysfunction in necroptosis in general and mitochondrial-dependent necroptosis in specific are discussed. We also provide insights into the current understanding of how [Ca²⁺]_m can be a critical determinant in deciding the cell fate under certain pathological conditions, while under others it may be dispensable. Lastly, we have highlighted the key molecular targets which have a direct implication for therapeutic intervention in conditions that are associated with impaired [Ca²⁺]_m handling and cell death by necroptosis.

Combination of metformin and chlorogenic acid attenuates hepatic steatosis and inflammation in high-fat diet fed mice

Non-alcoholic fatty liver disease (NAFLD) has become an important health problem in the world. Natural products, with anti-inflammatory properties, are potential candidates for alleviating NAFLD. Metformin (MET) and chlorogenic acid (CGA) have been reported to be effective in the improvement of NAFLD. Here, we aimed to evaluate the efficacy of MET and CGA combination in ameliorating NAFLD in high-fat diet (HFD) fed mice. Fifty C57BL/6 male mice were divided into two groups, one fed a standard chow diet (n = 10) and the other was fed an HFD (n = 40) for 10 weeks. Animals in the HFD group were then randomly divided into a four groups (HFD, HFD + MET (0.25%), HFD + CGA (0.02%) and HFD + MET + CGA (0.25 + 0.02%). MET and CGA combination decreases fasting blood glucose and improves glucose intolerance. Decreased hepatic triglyceride level was associated with lower expression levels of fatty acid synthase and sterol regulatory element-binding protein-1c in MET+CGA treated mice. MET and CGA combination treatment resulted in the polarization of macrophages to the M2 phenotype, reduction of the expression of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), and decreasing protein level of NF-kB p65. It was found that the lowering effect of combined MET and CGA on the expression of gluconeogenic genes was accompanied by increasing phosphorylation of glycogen synthase kinase 3β. Treatment of HFD mice with the combination of MET and CGA was found to be more effective at alleviating inflammation and lipid accumulation by increasing phosphorylation of AMP-activated protein kinase. In conclusion, these findings suggest that the MET + CGA combination might exert therapeutic effects against NAFLD.

Urolithin A suppresses high glucose-induced neuronal amyloidogenesis by modulating TGM2-dependent ER-mitochondria contacts and calcium homeostasis

Hyperglycemia in diabetes mellitus (DM) patients is a causative factor for amyloidogenesis and induces neuropathological changes, such as impaired neuronal integrity, neurodegeneration, and cognitive impairment. Regulation of mitochondrial calcium influx from the endoplasmic reticulum (ER) is considered a promising strategy for the prevention of mitochondrial ROS (mtROS) accumulation that occurs in the Alzheimer's disease (AD)-associated pathogenesis in DM patients. Among the metabolites of ellagitannins that are produced in the gut microbiome, urolithin A has received an increasing amount of attention as a novel candidate with anti-oxidative and neuroprotective effects in AD. Here, we investigated the effect of urolithin A on high glucose-induced amyloidogenesis caused by mitochondrial calcium dysregulation and mtROS accumulation resulting in neuronal degeneration. We also identified the mechanism related to mitochondria-associated ER membrane (MAM) formation. We found that urolithin A-lowered mitochondrial calcium influx significantly alleviated high glucose-induced mtROS accumulation and expression of amyloid beta (Aβ)-producing enzymes, such as amyloid precursor protein (APP) and β-secretase-1 (BACE1), as well as Aβ production. Urolithin A injections in a streptozotocin (STZ)-induced diabetic mouse model alleviated APP and BACE1 expressions, Tau phosphorylation, Aβ deposition, and cognitive impairment. In addition, high glucose stimulated MAM formation and transglutaminase type 2 (TGM2) expression. We first discovered that urolithin A significantly reduced high glucose-induced TGM2 expression. In addition, disruption of the AIP-AhR complex was involved in urolithin A-mediated suppression of high glucose-induced TGM2 expression. Markedly, TGM2 silencing inhibited inositol 1, 4, 5-trisphosphate receptor type 1 (IP3R1)-voltage-dependent anion-selective channel protein 1 (VDAC1) interactions and prevented high glucose-induced mitochondrial calcium influx and mtROS accumulation. We also found that urolithin A or TGM2 silencing prevented Aβ-induced mitochondrial calcium influx, mtROS accumulation, Tau phosphorylation, and cell death in neuronal cells. In conclusion, we suggest that urolithin A is a promising candidate for the development of therapies to prevent DM-associated AD pathogenesis by reducing TGM2-dependent MAM formation and maintaining mitochondrial calcium and ROS homeostasis.

Effect of photobiomodulation on CCC-ESF reactive oxygen species steady-state in high glucose mediums

Delayed wound healing is one of the most challenging complications of diabetes mellitus (DM) in clinical medicine, and it is related to the excessive generation of reactive oxygen species (ROS). Photobiomodulation (PBM) can promote wound healing in many ways, so it can be used as a method for the treatment of delayed healing of DM wounds. In this study, we investigated the effect of PBM on ROS homeostasis in human embryonic skin fibroblast cells (CCC-ESFs) cultured in high glucose concentrations. The CCC-ESFs were cultured in vitro and divided into two groups, including the control group and the 635 nm laser irradiation group. After 2 days of high glucose treatment, the experimental group was irradiated with different doses of laser for 3 days. First, we measured the cellular proliferation, and the results showed that laser irradiation could promote cellular proliferation. Then, we measured the generation of ROS, the activities of total superoxide dismutase (SOD), and total antioxidant capacity (TAC) of the cells; the results showed that high glucose destroyed cells by inducing high concentration of ROS, the balance of oxidation, and antioxidation cause oxidative stress damage to cells. PBM can increase the antioxidant capacity of cells, reducing the high concentration of ROS induced by high glucose. Finally, we measured the levels of mitochondrial membrane potential (∆ψ_m) and the secretion of nuclear factor kappa-B (NF-κB), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β); the results showed that PBM can reduce apoptosis and regulate the inflammatory state. We conclude that PBM can maintain the ROS homeostasis, increase the TAC of cells, and trigger the cellular proliferation, and the response of CCC-ESFs to PBM was dose-dependent.

Knockout of the Mitochondrial Calcium Uniporter Strongly Suppresses Stimulus-Metabolism Coupling in Pancreatic Acinar Cells but Does Not Reduce Severity of Experimental Acute Pancreatitis

Acute pancreatitis is a frequent disease that lacks specific drug treatment. Unravelling the molecular mechanisms of acute pancreatitis is essential for the development of new therapeutics. Several inducers of acute pancreatitis trigger sustained Ca²⁺ increases in the cytosol and mitochondria of pancreatic acinar cells. The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca²⁺ uptake that regulates bioenergetics and plays an important role in cell survival, damage and death. Aberrant Ca²⁺ signaling and mitochondrial damage in pancreatic acinar cells have been implicated in the initiation of acute pancreatitis. The primary aim of this study was to assess the involvement of the MCU in experimental acute pancreatitis. We found that pancreatic acinar cells from MCU^-/- mice display dramatically reduced mitochondrial Ca²⁺ uptake. This is consistent with the drastic changes of stimulus-metabolism coupling, manifested by the reduction of mitochondrial NADH/FAD⁺ responses to cholecystokinin and in the decrease of cholecystokinin-stimulated oxygen consumption. However, in three experimental models of acute pancreatitis (induced by caerulein, taurolithocholic acid 3-sulfate or palmitoleic acid plus ethanol), MCU knockout failed to reduce the biochemical and histological changes characterizing the severity of local and systemic damage. A possible explanation of this surprising finding is the redundancy of damaging mechanisms activated by the inducers of acute pancreatitis.

Mitochondrial Ca2+ Uptake Relieves Palmitate-Induced Cytosolic Ca2+ Overload in MIN6 Cells

Saturated fatty acids contribute to β-cell dysfunction in the onset of type 2 diabetes mellitus. Cellular responses to lipotoxicity include oxidative stress, endoplasmic reticulum (ER) stress, and blockage of autophagy. Palmitate induces ER Ca2+ depletion followed by notable store-operated Ca2+ entry. Subsequent elevation of cytosolic Ca2+ can activate undesirable signaling pathways culminating in cell death. Mitochondrial Ca2+ uniporter (MCU) is the major route for Ca2+ uptake into the matrix and couples metabolism with insulin secretion. However, it has been unclear whether mitochondrial Ca2+ uptake plays a protective role or contributes to lipotoxicity. Here, we observed palmitate upregulated MCU protein expression in a mouse clonal β-cell, MIN6, under normal glucose, but not high glucose medium. Palmitate elevated baseline cytosolic Ca2+ concentration ([Ca2+]i) and reduced depolarization-triggered Ca2+ influx likely due to the inactivation of voltage-gated Ca2+ channels (VGCCs). Targeted reduction of MCU expression using RNA interference abolished mitochondrial superoxide production but exacerbated palmitate-induced [Ca2+]i overload. Consequently, MCU knockdown aggravated blockage of autophagic degradation. In contrast, co-treatment with verapamil, a VGCC inhibitor, prevented palmitate-induced basal [Ca2+]i elevation and defective [Ca2+]i transients. Extracellular Ca2+ chelation as well as VGCC inhibitors effectively rescued autophagy defects and cytotoxicity. These observations suggest enhanced mitochondrial Ca2+ uptake via MCU upregulation is a mechanism by which pancreatic β-cells are able to alleviate cytosolic Ca2+ overload and its detrimental consequences.

Inhibiting miR-27a and miR-142-5p attenuate nonalcoholic fatty liver disease by regulating Nrf2 signaling pathway

The gene Nrf2 (nuclear factor-erythroid 2-related factor 2) is the most important regulator of the cellular antioxidant system and its dysregulation has a role in the etiology of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to investigate the association between Nrf2 targeted miRNAs (miR-27a, miR-142-5p, miR-153, and miR-128) with lipid accumulation in vitro and in vivo models of NAFLD. We used two in vivo and in vitro models of NAFLD. The expression of the genes and miRNAs was assessed by real-time PCR and the protein level was evaluated using western blot. To investigate the potential role of miRNAs in NAFLD, the inhibitors or mimics of the miR-27a and miR-142-5p were transfected into HepG2 cells. The mRNA and protein levels of Nrf2 were significantly decreased in the liver of high fat diet-fed mice as well as in HepG2 cells treated with high glucose (HG). Reduced expression of Nrf2 was associated with increased expression levels of miR-27a and miR-142-5p in both models of NAFLD. HG-induced triglyceride accumulation was attenuated by inhibition of miR-27a or miR-142-5p in HepG2 cells. Overexpression of miR-27a or miR-142-5p suppressed the expression of Nrf2 and its downstream antioxidant genes and increased production of reactive oxygen species, whereas inhibition of miR-27a or miR-142-5p reversed these effects. In conclusion, the data of this study may suggest that miR-27a and miR-142-5p are increased in NAFLD, where they suppress Nrf2 expression and contribute to the accumulation of lipids in the hepatocytes.

The protective effect of silk fibroin on high glucose induced insulin resistance in HepG2 cells

The therapeutic use of silk-derived materials such as fibroin in biomedicine is well-established in Southeast Asian countries. Studies indicated that silk fibroin (SF) peptide enhances insulin sensitivity and glucose metabolism phenomena associated with type 2 diabetes mellitus (T2DM) suggesting this peptide may be beneficial to treat this disease. However, the mechanisms underlying protective effect of SF in insulin-mediated hepatic metabolic dysfunction remains unclear. The aim of this study was to investigate the influence of SF on insulin resistant HepG2 cells which were used a model of T2DM. Treatment of cells with 30 mmol/L of glucose and 10^-6 mol/L insulin for 48 h significantly reduced glucose consumptions and intracellular glycogen levels but increased triglyceride (TG) levels. SF or metformin alone elevated glucose consumptions and glycogen accumulation accompanied by lower TG content. Greater effects in these metabolic parameters were found when SF and metformin were combined. Treatment of insulin resistant cells with SF or metformin alone decreased levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor (TNF-α) and interleukin-6 (IL-6); whereas antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activity, as well as total antioxidant capacity (T-AOC) ability increased. The combination of SF and metformin produced greater changes in these parameters compared to metformin alone. Data indicated that the protective effect of SF or metformin in insulin resistant HepG2 cells involves inhibition of oxidant processes and that the combination of agents may prove more effective therapeutically.

The modulatory effects of luteolin on cyclic AMP/Ciliary neurotrophic factor signaling pathway in experimentally induced autoimmune encephalomyelitis

Multiple sclerosis (MS) is considered to be an autoimmune disorder of the central nervous system (CNS) manifested by chronic inflammation. Although its etiology is not completely understood, inflammation and apoptosis are known to be major players involved in its pathogenesis. Luteolin, the naturally occurring flavonoid, is known by strong antioxidant and anti-inflammatory properties, yet research studies about its therapeutic role in MS are still lacking. The study aimed to provide insight into effects of luteolin in experimental autoimmune encephalomyelitis (EAE) by monitoring inflammatory, apoptotic, and antioxidant biochemical parameters in addition to histological examination findings. The study included 45 adult female Wistar rats allocated to three equal groups: (a) group I: control group, (b) group II: EAE group, EAE was induced by single intradermal injection of 0.2 mL inoculum comprising 20-μg recombinant rat myelin oligodendrocyte glycoprotein (MOG), and (c) group III: luteolin-treated EAE group, luteolin was given in a dose of 10 mg/kg/day, i.p. All groups were subjected to assessment of brain ciliary neurotropic factor (CNTF) mRNA gene expression and measurement of cleaved caspase 3, nuclear factor kappa B (NF-κB), cyclic AMP (cAMP), and macrophage inflammatory protein 1 alpha (MIP-1α) by the ELISA technique, total antioxidant capacity (TAC) level is assessed spectrophotometrically. Compared with the EAE group, luteolin-treated EAE group showed upregulation of CNTF expression and significant increase in cAMP and TAC levels, while it showed significant decrease in cleaved caspase 3, NF-κB, and MIP-1α levels. Based on our data herein, luteolin may provide a promising preclinical therapeutic line in MS being anti-inflammatory, antiapoptotic, and neurotrophic agent. © 2019 IUBMB Life, 71(9):1401-1408, 2019.

Mitochondrial calcium: Transport and modulation of cellular processes in homeostasis and cancer (Review)

In addition to their role in providing cellular energy, mitochondria fulfill a key function in cellular calcium management. The present review provides an integrative view of cellular and mitochondrial calcium homeostasis, and discusses how calcium regulates mitochondrial dynamics and functionality, thus affecting various cellular processes. Calcium crosstalk exists in the domain created between the endoplasmic reticulum and mitochondria, which is known as the mitochondria‑associated membrane (MAM), and controls cellular homeostasis. Calcium signaling participates in numerous biochemical and cellular processes, where calcium concentration, temporality and durability are part of a regulated, finely tuned interplay in non‑transformed cells. In addition, cancer cells modify their MAMs, which consequently affects calcium homeostasis to support mesenchymal transformation, migration, invasiveness, metastasis and autophagy. Alterations in calcium homeostasis may also support resistance to apoptosis, which is a serious problem facing current chemotherapeutic treatments. Notably, mitochondrial dynamics are also affected by mitochondrial calcium concentration to promote cancer survival responses. Dysregulated levels of mitochondrial calcium, alongside other signals, promote mitoflash generation in tumor cells, and an increased frequency of mitoflashes may induce epithelial‑to‑mesenchymal transition. Therefore, cancer cells remodel their calcium balance through numerous mechanisms that support their survival and growth.