Liraglutide activates autophagy via GLP-1R to improve functional recovery after spinal cord injury

Therapeutic effects of exendin-4 on spinal cord injury via restoring autophagy function and decreasing necroptosis in neuron

AIMS

Necroptosis is one of programmed death that may aggravate spinal cord injury (SCI). We aimed to investigate the effect and mechanism of exendin-4 (EX-4) on the recovery of motor function and necroptosis after SCI.

METHODS

The SD rats with left hemisection in the T10 spinal cord as SCI model were used. The behavior tests were measured within 4 weeks. The effects of EX-4 on necroptosis-associated proteins and autophagy flux were explored. In addition, the SHSY5Y cell model was introduced to explore the direct effect of EX-4 on neurons. The effect of lysosome was explored using mTOR activator and AO staining.

RESULTS

EX-4 could improve motor function and limb strength, promote the recovery of autophagy flux, and accelerate the degradation of necroptosis-related protein at 3 d after injury in rats. EX-4 reduced lysosome membrane permeability, promoted the recovery of lysosome function and autophagy flux, and accelerated the degradation of necroptosis-related proteins by inhibiting the phosphorylation level of mTOR in the SHSY5Y cell model.

CONCLUSION

Our results demonstrated that EX-4 may improve motor function after SCI via inhibiting mTOR phosphorylation level and accelerating the degradation of necroptosis-related proteins in neurons. Our findings may provide new therapeutic targets for clinical treatment after SCI.

Comprehensive Evaluation of a Levonorgestrel Intrauterine Device (LNG-IUD), Metformin, and Liraglutide for Fertility Preservation in Endometrial Cancer: Protocol for a Randomized Clinical Trial

Endometrial cancer is a leading gynecological malignancy, with obesity being a significant risk factor due to increased estrogen production in body fat. Current treatments often involve hysterectomy, which precludes fertility, thus highlighting the need for fertility-preserving options. This study aims to evaluate the combined efficacy of a levonorgestrel intrauterine device (LNG-IUD), metformin, and liraglutide for treating women with endometrial hyperplasia or early stage endometrial cancer while preserving fertility. The study will enroll 264 women aged 18-45 with a BMI > 30 who desire uterine preservation. Participants will be randomized into three groups: LNG-IUD alone, LNG-IUD plus metformin, and LNG-IUD plus metformin and liraglutide. Primary outcomes will include complete pathological remission, while secondary outcomes will assess histological changes, glucose, insulin levels, and weight changes over a 12-month period. This study protocol hypothesizes that LNG-IUD combined with metformin and liraglutide may potentially lead to higher regression rates of endometrial hyperplasia (EH) and early stage endometrial cancer (EC) compared to LNG-IUD alone. Furthermore, the protocol anticipates that these combination therapies will demonstrate good tolerability with minimal adverse effects, suggesting the potential benefit of integrating metabolic interventions with LNG-IUD to enhance treatment efficacy while preserving fertility in women with EH and EC.

Topography of the GLP-1/GLP-1 receptor system in the spinal cord of male mice

Glucagon-like peptide-1 receptor (GLP-1R) agonists are now commonly used to treat type 2 diabetes and obesity. GLP-1R signaling in the spinal cord has been suggested to account for the mild tachycardia caused by GLP-1R agonists, and may also be involved in the therapeutic effects of these drugs. However, the neuroanatomy of the GLP-1/GLP-1R system in the spinal cord is still poorly understood. Here we applied in situ hybridization and immunohistochemistry to characterize this system, and its relation to cholinergic neurons. GLP-1R transcript and protein were expressed in neuronal cell bodies across the gray matter, in matching distribution patterns. GLP-1R-immunolabeling was also robust in dendrites and axons, especially in laminae II-III in the dorsal horn. Cerebrospinal fluid-contacting neurons expressed GLP-1R protein at exceedingly high levels. Only small subpopulations of cholinergic neurons expressed GLP-1R, including a subset of sympathetic preganglionic neurons at the rostral tip of the intermediolateral nucleus. GLP-1 axons innervated all regions where GLP-1R neurons were distributed, except laminae II-III. Scattered preproglucagon (Gcg) mRNA-expressing neurons were identified in the cervical and lumbar enlargements. The results will facilitate further studies on how GLP-1 regulates the sympathetic system and other autonomic and somatic functions via the spinal cord.

Dietary salt promotes cognition impairment through GLP-1R/mTOR/p70S6K signaling pathway

Dietary salt has been associated with cognitive impairment in mice, possibly related to damaged synapses and tau hyperphosphorylation. However, the mechanism underlying how dietary salt causes cognitive dysfunction remains unclear. In our study, either a high-salt (8%) or normal diet (0.5%) was used to feed C57BL/6 mice for three months, and N2a cells were cultured in normal medium, NaCl medium (80 mM), or NaCl (80 mM) + Liraglutide (200 nM) medium for 48 h. Cognitive function in mice was assessed using the Morris water maze and shuttle box test, while anxiety was evaluated by the open field test (OPT). Western blotting (WB), immunofluorescence, and immunohistochemistry were utilized to assess the level of Glucagon-like Peptide-1 receptor (GLP-1R) and mTOR/p70S6K pathway. Electron microscope and western blotting were used to evaluate synapse function and tau phosphorylation. Our findings revealed that a high salt diet (HSD) reduced the level of synaptophysin (SYP) and postsynaptic density 95 (PSD95), resulting in significant synaptic damage. Additionally, hyperphosphorylation of tau at different sites was detected. The C57BL/6 mice showed significant impairment in learning and memory function compared to the control group, but HSD did not cause anxiety in the mice. In addition, the level of GLP-1R and autophagy flux decreased in the HSD group, while the level of mTOR/p70S6K was upregulated. Furthermore, liraglutide reversed the autophagy inhibition of N2a treated with NaCl. In summary, our study demonstrates that dietary salt inhibits the GLP-1R/mTOR/p70S6K pathway to inhibit autophagy and induces synaptic dysfunction and tau hyperphosphorylation, eventually impairing cognitive dysfunction.

G protein-coupled receptor-mediated autophagy in health and disease

G protein-coupled receptors (GPCRs) constitute the largest and most diverse superfamily of mammalian transmembrane proteins. These receptors are involved in a wide range of physiological functions and are targets for more than a third of available drugs in the market. Autophagy is a cellular process involved in degrading damaged proteins and organelles and in recycling cellular components. Deficiencies in autophagy are involved in a variety of pathological conditions. Both GPCRs and autophagy are essential in preserving homeostasis and cell survival. There is emerging evidence suggesting that GPCRs are direct regulators of autophagy. Additionally, autophagic machinery is involved in the regulation of GPCR signalling. The interplay between GPCR and autophagic signalling mechanisms significantly impacts on health and disease; however, there is still an incomplete understanding of the underlying mechanisms and therapeutic implications in different tissues and disease contexts. This review aims to discuss the interactions between GPCR and autophagy signalling. Studies on muscarinic receptors, beta-adrenoceptors, taste receptors, purinergic receptors and adhesion GPCRs are summarized, in relation to autophagy.

The Effect of Liraglutide on Axon Regeneration and Functional Recovery after Peripheral Nerve Lesion

Peripheral nerve injuries inflict severe consequences, necessitating innovative therapeutic strategies. This study investigates the potential of liraglutide, a glucagon-like peptide-1 receptor agonist, in mitigating the consequences of peripheral nerve injury. The existing treatment methods for such injuries underscore the importance of ongoing translational research efforts. Thirty adult Wistar rats underwent sciatic nerve dissection and repair surgery. The nerves were surgically transected using micro scissors at a precise location located 1.5 cm proximal to the trifurcation site. The study included a control group and two experimental groups, one treated with saline (placebo group) and the other with liraglutide (experimental group) for 12 weeks. Motor function, electromyography (EMG), and biochemical and histopathological analyses were performed after 12 weeks of treatment. Electrophysiological assessments revealed that liraglutide improved the compound muscle action potential (CMAP) amplitude and motor function compared to the saline-treated group. Histological and immunohistochemical analyses demonstrated increased NGF expression, total axon number, and diameter and reduced fibrosis in the liraglutide group. Biochemical analyses illustrated liraglutide's antioxidative properties, evidenced by reduced malondialdehyde (MDA) levels. Galectin-3 levels were suppressed and GDF-11 levels were modulated by liraglutide, indicating anti-inflammatory and anti-apoptotic effects. Liraglutide is a promising therapeutic intervention for peripheral nerve injuries, promoting functional recovery and histopathological improvement. Its multifaceted positive impact, beyond glycemic control, suggests constructive effects on the acute and chronic inflammatory processes associated with peripheral neuropathy. These findings warrant further research to elucidate molecular mechanisms and facilitate clinical translation. The study contributes valuable insights to the growing understanding of GLP-1 receptor agonists' neuroprotective properties in the context of peripheral nerve injuries.

Gut microbiota changes in animal models of spinal cord injury: a preclinical systematic review and meta-analysis

BACKGROUND

An increasing number of studies show that the intestinal flora is closely related to spinal cord injury. Many researchers are exploring the changes in the richness, diversity, and evenness of intestinal flora in spinal cord injury animal models to identify the characteristic bacteria.

METHODS

A comprehensive literature search was conducted using three databases: PubMed, Embase, and Web of Science. A meta-analysis was performed using R 4.3.1 to evaluate the comparison of microbiota diversity, richness, and evenness and the relative abundance of intestinal microbiota in animals with spinal cord injury and blank controls.

RESULTS

Fifteen studies were included in the meta-analysis, of which 12 involved gut microbiota distribution indicators and 11 included intestinal microflora relative abundance indicators. Meta-analysis of high-dimensional indicators describing the distribution of the gut microbiota identified a substantial decline in the evenness and richness of the intestinal flora. In addition, the Actinobacteria phylum and Erysipelotrichales and Clostridiales orders were significantly different between the spinal cord injury and sham groups; therefore, they may be the characteristic bacteria in spinal cord injury models.

CONCLUSION

Our meta-analysis suggested that the gut microbiota in the spinal cord injury animal model group was altered compared with that in the control group, with varying degrees of changes in richness and evenness and potentially pathogenic characteristic flora. More rigorous methodological studies are needed because of the high heterogeneity and limited sample size. Further research is needed to clinically apply intestinal microbiota and potentially guide fecal microbiota transplantation therapy.

Liraglutide modulates adhesion molecules and enhances cell properties in three-dimensional cultures of olfactory ensheathing cells

Cell transplantation using olfactory ensheathing cells (OECs) is a promising approach for nerve repair but there are numerous limitations with their delivery method. Three-dimensional (3D) cell culture systems potentially offer a powerful approach for cell production and delivery options. To further optimise the use of OECs, strategies to promote cell viability and maintain cell behaviours in 3D cultures become important. We previously demonstrated an anti-diabetic drug, liraglutide, could modulate OEC migration and re-model extracellular matrix in two-dimensional (2D) cultures. In the present study, we further investigated its beneficial effects in our 3D culture system using primary OECs. OECs treated with liraglutide at 100 nM showed improved cell viability and had modulated expression of N-cadherin and β1-integrin (two important cell adhesion molecules). When formed into 3D spheroids, the pre-treated OECs generated spheroids with an increased volume and a decreased cell density compared to control spheroids. OECs that subsequently migrated out of the liraglutide pre-treated spheroids had higher capacity for migration with increased duration and length, which was attributed to a reduction in the pauses during the migration. Moreover, OECs that migrated out from liraglutide spheroids had a more bipolar morphology consistent with higher migratory capacity. In summary, liraglutide improved the viability of OECs, modulated cell adhesion molecules, and resulted in stable 3D cell constructs which conferred enhanced migratory capacity on the OECs. Overall, liraglutide may potentially improve the therapeutic use of OECs for neural repair by enhancing the generation of stable 3D constructs and increasing the migratory behaviour of OECs.

GLP-1 receptor agonists as promising disease-modifying agents in WFS1 spectrum disorder

WFS1 spectrum disorder (WFS1-SD) is a rare monogenic neurodegenerative disorder whose cardinal symptoms are childhood-onset diabetes mellitus, optic atrophy, deafness, diabetes insipidus, and neurological signs ranging from mild to severe. The prognosis is poor as most patients die prematurely with severe neurological disabilities such as bulbar dysfunction and organic brain syndrome. Mutation of the WFS1 gene is recognized as the prime mover of the disease and responsible for a dysregulated ER stress signaling, which leads to neuron and pancreatic β-cell death. There is no currently cure and no treatment that definitively arrests the progression of the disease. GLP-1 receptor agonists appear to be an efficient way to reduce elevated ER stress in vitro and in vivo, and increasing findings suggest they could be effective in delaying the progression of WFS1-SD. Here, we summarize the characteristics of GLP-1 receptor agonists and preclinical and clinical data obtained by testing them in WFS1-SD as a feasible strategy for managing this disease.

MiR-27a-3p Targets GLP1R to Regulate Differentiation, Autophagy, and Release of Inflammatory Factors in Pre-Osteoblasts via the AMPK Signaling Pathway

Objective: Osteoporosis is caused by the dysregulation of bone homeostasis which is synergistically mediated by osteoclasts and osteoblasts. MiR-27a-3p is a key inhibitor of bone formation. Hence, unearthing the downstream target gene of miR-27a-3p is of great significance to understand the molecular mechanism of osteoporosis. Methods: Bioinformatics analysis was utilized to find the downstream target gene of miR-27a-3p, and dual-luciferase reporter assay was conducted to validate the interplay of miR-27a-3p and GLP1R. Besides, qRT-PCR, Western blot, and enzyme-linked immunosorbent assay (ELISA) were employed to verify the impact of miR-27a-3p on GLP1R expression and the differentiation, autophagy, and inflammatory response of MC3T3-E1 pre-osteoblasts. Results: Dual-luciferase assay validated that miR-27a-3p directly targeted GLP1R. Additionally, posttreatment of MC3T3-E1 cells with miR-27a-3p mimics resulted in a remarkable decrease in expression levels of GLP1R, cell differentiation marker gene, autophagy marker gene, and AMPK. These results indicated that miR-27a-3p targeted GLP1R to inhibit AMPK signal activation and pre-osteoblast differentiation and autophagy, while promoting the release of inflammatory factors. Conclusion: The miR-27a-3p/GLP1R regulatory axis in pre-osteoblasts contributes to understanding the molecular mechanism of osteoporosis.

Autophagy induced by Schwann cell-derived exosomes promotes recovery after spinal cord injury in rats

Spinal cord injury (SCI) is catastrophic to humans and society. However, there is currently no effective treatment for SCI. Autophagy is known to serve critical roles in both the physiological and pathological processes of the body, but its facilitatory and/or deleterious effects in SCI are yet to be completely elucidated. This study aimed to use primary Schwann cell-derived exosomes (SCDEs) to treat rats after SCI. In the present study, SCDEs were purified and their efficacy in ameliorating the components of SCI was examined. Using both in vivo and in vitro experiments, it was demonstrated that SCDEs increased autophagy and decreased apoptosis after SCI, which promoted axonal protection and the recovery of motor function. Furthermore, it was discovered that an increased number of SCDEs resulted in a decreased expression level of EGFR, which subsequently inhibited the Akt/mTOR signaling pathway, which upregulated the level of autophagy to ultimately induce microtubule acetylation and polymerization. Collectively, the present study identified that SCDEs could induce axonal protection after SCI by increasing autophagy and decreasing apoptosis, and it was suggested that this may involve the EGFR/Akt/mTOR signaling pathway.

Teneligliptin Exerts Antinociceptive Effects in Rat Model of Partial Sciatic Nerve Transection Induced Neuropathic Pain

Neuropathic pain (NP), is a chronic pain resulting from nerve injury, with limited treatment options. Teneligliptin (TEN) is a dipeptidyl peptidase-4 inhibitor (DPP-4i) approved to treat type 2 diabetes. DPP-4is prevent the degradation of the incretin hormone glucagon-like peptide 1 (GLP-1) and prolong its circulation. Apart from glycemic control, GLP-1 is known to have antinociceptive and anti-inflammatory effects. Herein, we investigated the antinociceptive properties of TEN on acute pain, and partial sciatic nerve transection (PSNT)-induced NP in Wistar rats. Seven days post PSNT, allodynia and hyperalgesia were confirmed as NP, and intrathecal (i.t) catheters were implanted and connected to an osmotic pump for the vehicle (1 μL/h) or TEN (5 μg/1 μL/h) or TEN (5 μg) + GLP-1R antagonist Exendin-3 (9–39) amide (EXE) 0.1 μg/1 μL/h infusion. The tail-flick response, mechanical allodynia, and thermal hyperalgesia were measured for 7 more days. On day 14, the dorsal horn was harvested and used for Western blotting and immunofluorescence assays. The results showed that TEN had mild antinociceptive effects against acute pain but remarkable analgesic effects against NP. Furthermore, co-infusion of GLP-1R antagonist EXE with TEN partially reversed allodynia but not tail-flick latency. Immunofluorescence examination of the spinal cord revealed that TEN decreased the immunoreactivity of glial fibrillary acidic protein (GFAP). Taken together, our findings suggest that TEN is efficient in attenuation of PSNT-induced NP. Hence, the pleiotropic effects of TEN open a new avenue for NP management.

Liraglutide modulates olfactory ensheathing cell migration with activation of ERK and alteration of the extracellular matrix

Transplantation of olfactory ensheathing cells (OECs) is a promising approach for repairing the injured nervous system that has been extensively trialed for nervous system repair. However, the method still needs improvement and optimization. One avenue of improving outcomes is to stimulate OEC migration into the injury site. Liraglutide is a glucagon-like peptide-1 receptor agonist used for management of diabetes and obesity. It has been shown to be neuroprotective and to promote cell migration, but whether it can stimulate glial cells remains unknown. In the current study, we investigated the effects of liraglutide on OEC migration and explored the involved mechanisms. We showed that liraglutide at low concentration (100 nM) overall promoted OEC migration over time. Liraglutide modulated the migratory behavior of OECs by reducing time in arrest, and promoted random rather than straight migration. Liraglutide also induced a morphological change of primary OECs towards a bipolar shape consistent with improved migration. We found that liraglutide activated extracellular signal-regulated kinase (ERK), which has key roles in cell migration; the timing of ERK activation correlated with stimulation of migration. Furthermore, liraglutide also modulated the extracellular matrix by upregulating laminin-1 and down-regulating collagen IV. In summary, we found that liraglutide can stimulate OEC migration and re-model the extracellular matrix to better promote cell migration, and possibly also to become more conducive for axonal regeneration. Thus, liraglutide may improve OEC transplantation outcomes.

Sitagliptin improves functional recovery via GLP-1R-induced anti-apoptosis and facilitation of axonal regeneration after spinal cord injury

Axon growth and neuronal apoptosis are considered to be crucial therapeutic targets against spinal cord injury (SCI). Growing evidences have reported stimulation of glucagon‐like peptide‐1 (GLP‐1)/GLP‐1 receptor (GLP‐1R) signalling axis provides neuroprotection in experimental models of neurodegeneration disease. Endogenous GLP‐1 is rapidly degraded by dipeptidyl peptidase‐IV (DPP4), resulting in blocking of GLP‐1/GLP1R signalling process. Sitagliptin, a highly selective inhibitor of DPP4, has approved to have beneficial effects on diseases in which neurons damaged. However, the roles and the underlying mechanisms of sitagliptin in SCI repairing remain unclear. In this study, we used a rat model of SCI and PC12 cells/primary cortical neurons to explore the mechanism of sitagliptin underlying SCI recovery. We discovered the expression of GLP‐1R decreased in the SCI model. Administration of sitagliptin significantly increased GLP‐1R protein level, alleviated neuronal apoptosis, enhanced axon regeneration and improved functional recovery following SCI. Nevertheless, treatment with exendin9‐39, a GLP‐1R inhibitor, remarkably reversed the protective effect of sitagliptin. Additionally, we detected the AMPK/PGC‐1α signalling pathway was activated by sitagliptin stimulating GLP‐1R. Taken together, sitagliptin may be a potential agent for axon regrowth and locomotor functional repair via GLP‐1R‐induced AMPK/ PGC‐1α signalling pathway after SCI.

Therapeutic effect of regulating autophagy in spinal cord injury: a network meta-analysis of direct and indirect comparisons

OBJECTIVE

An increasing number of studies indicate that autophagy plays an important role in the pathogenesis of spinal cord injury, and that regulating autophagy can enhance recovery from spinal cord injury. However, the effect of regulating autophagy and whether autophagy is detrimental or beneficial after spinal cord injury remain unclear. Therefore, in this study we evaluated the effects of autophagy regulation on spinal cord injury in rats by direct and indirect comparison, in an effort to provide a basis for further research.

DATA SOURCE

Relevant literature published from inception to February 1, 2018 were included by searching Wanfang, CNKI, Web of Science, MEDLINE (OvidSP), PubMed and Google Scholar in English and Chinese. The keywords included "autophagy", "spinal cord injury", and "rat".

DATA SELECTION

The literature included in vivo experimental studies on autophagy regulation in the treatment of spinal cord injury (including intervention pre- and post-spinal cord injury). Meta-analyses were conducted at different time points to compare the therapeutic effects of promoting or inhibiting autophagy, and subgroup analyses were also conducted.

OUTCOME MEASURE

Basso, Beattie, and Bresnahan scores.

RESULTS

Of the 622 studies, 33 studies of median quality were included in the analyses. Basso, Beattie, and Bresnahan scores were higher at 1 day (MD = 1.80, 95% CI: 0.81-2.79, P = 0.0004), 3 days (MD = 0.92, 95% CI: 0.72-1.13, P < 0.00001), 1 week (MD = 2.39, 95% CI: 1.85-2.92, P < 0.00001), 2 weeks (MD = 3.26, 95% CI: 2.40-4.13, P < 0.00001), 3 weeks (MD = 3.13, 95% CI: 2.51-3.75, P < 0.00001) and 4 weeks (MD = 3.18, 95% CI: 2.43-3.92, P < 0.00001) after spinal cord injury with upregulation of autophagy compared with the control group (drug solvent control, such as saline group). Basso, Beattie, and Bresnahan scores were higher at 1 day (MD = 6.48, 95% CI: 5.83-7.13, P < 0.00001), 2 weeks (MD = 2.43, 95% CI: 0.79-4.07, P = 0.004), 3 weeks (MD = 2.96, 95% CI: 0.09-5.84, P = 0.04) and 4 weeks (MD = 4.41, 95% CI: 1.08-7.75, P = 0.01) after spinal cord injury with downregulation of autophagy compared with the control group. Indirect comparison of upregulation and downregulation of autophagy showed no differences in Basso, Beattie, and Bresnahan scores at 1 day (MD = -4.68, 95% CI: -5.840 to -3.496, P = 0.94644), 3 days (MD = -0.28, 95% CI: -2.231-1.671, P = 0.99448), 1 week (MD = 1.83, 95% CI: 0.0076-3.584, P = 0.94588), 2 weeks (MD = 0.81, 95% CI: -0.850-2.470, P = 0.93055), 3 weeks (MD = 0.17, 95% CI: -2.771-3.111, P = 0.99546) or 4 weeks (MD = -1.23, 95% CI: -4.647-2.187, P = 0.98264) compared with the control group.

CONCLUSION

Regulation of autophagy improves neurological function, whether it is upregulated or downregulated. There was no difference between upregulation and downregulation of autophagy in the treatment of spinal cord injury. The variability in results among the studies may be associated with differences in research methods, the lack of clearly defined autophagy characteristics after spinal cord injury, and the limited autophagy monitoring techniques. Thus, methods should be standardized, and the dynamic regulation of autophagy should be examined in future studies.

Treatment With Liraglutide Exerts Neuroprotection After Hypoxic-Ischemic Brain Injury in Neonatal Rats via the PI3K/AKT/GSK3β Pathway

Neonatal hypoxic–ischemic (HI) brain injury is a detrimental disease, which results in high mortality and long-term neurological deficits. Nevertheless, the treatment options for this disease are limited. Thus, the aim of the present study was to assess the role of liraglutide in neonatal HI brain injury in rats and investigate the associated mechanisms. The results showed that treatment with liraglutide significantly reduced infarct volume and ameliorated cerebral edema, decreased inflammatory response, promoted the recovery of tissue structure, and improved prognosis following HI brain injury. Moreover, treatment with liraglutide inhibited apoptosis and promoted neuronal survival both in the rat model and following oxygen-glucose deprivation (OGD) insult. LY294002, an inhibitor of phosphoinositide 3-kinase (PI3K), partially reversed these therapeutic effects, suggesting that the PI3K/protein kinase B (Akt) pathway was involved. In conclusion, our data revealed that treatment with liraglutide exerts neuroprotection after neonatal HI brain injury via the PI3K/Akt/glycogen synthase kinase-3β (GSK3β) pathway and may be a promising therapy for this disease.

Grape seed procyanidins suppress the apoptosis and senescence of chondrocytes and ameliorates osteoarthritis via the DPP4-Sirt1 pathway

Osteoarthritis (OA) is a complicated pathological condition affecting thousands of people around world, many with substantial unmet medical care needs and without any effective therapies.

Activation of Nrf2/HO-1 signal with Myricetin for attenuating ECM degradation in human chondrocytes and ameliorating the murine osteoarthritis

BACKGROUND

Osteoarthritis (OA), one of the prevailing joint degenerative disorders, contributes to the disability around the world. However, no effective therapeutic was introduced currently. Myricetin was reported to possess the function of anti-inflammatory, anti-diabetic and anti-cancer. Thus, we investigate the protection role of myricetin in OA progression and the potential molecular mechanism in present study.

METHODS

Quantitative realtime PCR and western blotting were performed to evaluate the expression of MMP-13, Aggrecan, iNOS, and COX-2 at both gene and protein levels. An enzyme-linked immunosorbent assay was used to evaluate the levels of inflammatory factors (PGE2, TNF-α, and IL-6). The PI3K/AKT, Nrf2/HO-1 and nuclear factor kappa B (NF-κB) signaling pathways were analyzed by western blotting, and immunofluorescence was used to assess the expression of Nrf2, Collagen II and MMP13. The in vitro effect of myricetin was evaluated by intragastric administration into a mouse osteoarthritis model induced by destabilization of the medial meniscus.

RESULTS

Myricetin not only inhibited the generation of inflammatory mediators and cytokines such as nitric oxide (NO), prostaglandin E2 (PGE2), TNF-α and IL-6, but also suppressed the production of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in human chondrocytes under IL-1β stimulation. Moreover, Metalloproteinase 13 (MMP13) and thrombospondin motifs 5 (ADAMTS5), which resulted in the degradation of cartilage, were also suppressed in chondrocytes with the treatment of myricetin. To explore the potential mechanism, we found out that myricetin suppressed NF-κB signaling pathway through Nrf2/HO-1 axis in human chondrocytes. Besides, myricetin regulated the Nrf2 signaling pathway through PI3K/Akt pathway. In addition, in vivo study demonstrated that myricetin could ameliorated the progression of OA in mice DMM model through PI3K/Akt mediated Nrf2 signaling pathway.

CONCLUSION

Taken together, our data first demonstrated that myricetin possesses the therapeutic potential on OA through PI3K/Akt mediated Nrf2/HO-1 signaling pathway.

GLP-1's role in neuroprotection: a systematic review

Glucagon-like peptide 1 (GLP-1) is a target for treatment of diabetes; however, its function in the brain is not well studied. In this systematic review, we aimed to analyze the neuroprotective role of GLP-1 and its defined mechanisms. Methods: We searched 'Web of Science' and 'Pubmed' to identify relevant studies using GLP-1 as the keyword. Two hundred and eighty-nine clinical and preclinical studies have been included. Data have been presented by grouping neurodegenerative, neurovascular and specific cell culture models. Results: Recent literature shows that GLP-1 and its agonists, DPP-4 inhibitors and combined GLP-1/GIP molecules are effective in partially or fully reversing the effects of neurotoxic compounds, neurovascular complications of diabetes, neuropathological changes related with Alzheimer's disease, Parkinson's disease or vascular occlusion. Possible mechanisms that provide neuroprotection are enhancing the viability of the neurons and restoring neurite outgrowth by increased neurotrophic factors, increasing subventricular zone progenitor cells, decreasing apoptosis, decreasing the level of pro-inflammatory factors, and strengthening blood-brain barrier. Conclusion: Based on the preclinical studies, GLP-1 modifying agents are promising targets for neuroprotection. On the other hand, the number of clinical studies that investigate GLP-1 as a treatment is low and further clinical trials are needed for a benchside to bedside translation of recent findings.

Incremental effect of liraglutide on traditional insulin injections in rats with type 2 diabetes mellitus by maintaining glycolipid metabolism and cardiovascular function

Type 2 diabetes mellitus (T2DM) is characterized by chronic hyperglycemia, damaged insulin secretion and insulin resistance with high morbidity and mortality. Liraglutide (liragl) and insulin are effective hypoglycemic agents used in T2DM treatment. The potential effect of liragl in combination with insulin on T2DM remains unclear. The aim of the current study was to explore effects of liragl combined with insulin on glycolipid metabolism and cardiovascular function in rats with diabetes. A diabetes model was established in Sprague Dawley rats exposed to a high calorie and high sugar diet in conjunction with intraperitoneal injections of streptozotocin. Results indicated that liragl or insulin used alone decreased glucose and elevated insulin and c-peptide levels. However, their combination revealed greater effects. A significant increase in high-density lipoprotein cholesterol levels along with a decrease in total cholesterol, triglycerides and low-density lipoprotein cholesterol were observed in liragl- and insulin-treated rats compared with STZ-induced diabetes rats. Furthermore, co-administration of liragl and insulin significantly decreased sterol regulatory element-binding protein 1 levels and increased adenosine 5'-monophosphate kinase-α1 and carnitine palmitoyltransferase 1 expression. Combining liragl with insulin reduced myocardial hypertrophy level and gaps between cardiomyocytes compared with liragl or insulin treatment alone. Caspase-3 expression was significantly decreased by combination treatment of liragl and insulin. Oxidative damage was significantly decreased by co-administration of liragl and insulin through enhancing superoxide dismutase expression and reducing malondialdehyde. Furthermore, combination of liragl and insulin significantly reduced myocardial enzyme expression, including myoglobin, creatine kinase-muscle/brain and cardiac troponin I. In summary, the current study demonstrated synergistic effects of liragl and insulin injections on a T2DM rat model by maintaining glycolipid metabolism and cardiovascular function.

Pleiotropic Effects of GLP-1 and Analogs on Cell Signaling, Metabolism, and Function

The incretin hormone Glucagon-Like Peptide-1 (GLP-1) is best known for its "incretin effect" in restoring glucose homeostasis in diabetics, however, it is now apparent that it has a broader range of physiological effects in the body. Both in vitro and in vivo studies have demonstrated that GLP-1 mimetics alleviate endoplasmic reticulum stress, regulate autophagy, promote metabolic reprogramming, stimulate anti-inflammatory signaling, alter gene expression, and influence neuroprotective pathways. A substantial body of evidence has accumulated with respect to how GLP-1 and its analogs act to restore and maintain normal cellular functions. These findings have prompted several clinical trials which have reported GLP-1 analogs improve cardiac function, restore lung function and reduce mortality in patients with obstructive lung disease, influence blood pressure and lipid storage, and even prevent synaptic loss and neurodegeneration. Mechanistically, GLP-1 elicits its effects via acute elevation in cAMP levels, and subsequent protein kinase(s) activation, pathways well-defined in pancreatic β-cells which stimulate insulin secretion in conjunction with elevated Ca2+ and ATP. More recently, new studies have shed light on additional downstream pathways stimulated by chronic GLP-1 exposure, findings which have direct relevance to our understanding of the potential therapeutic effects of longer lasting analogs recently developed for clinical use. In this review, we provide a comprehensive description of the diverse roles for GLP-1 across multiple tissues, describe downstream pathways stimulated by acute and chronic exposure, and discuss novel pleiotropic applications of GLP-1 mimetics in the treatment of human disease.

Metformin Plus Caloric Restriction Show Anti-epileptic Effects Mediated by mTOR Pathway Inhibition

Caloric restriction (CR) has anti-epileptic effects in different animal models, at least partially due to inhibition of the mechanistic or mammalian target of rapamycin (mTOR) signaling pathway. Adenosine monophosphate-activated protein kinase (AMPK) inhibits mTOR cascade function if energy levels are low. Since hyper-activation of mTOR participates in epilepsy, its inhibition results in beneficial anti-convulsive effects. A way to attain this is to activate AMPK with metformin. The effects of metformin, alone or combined with CR, on the electrical kindling epilepsy model and the mTOR cascade in the hippocampus and the neocortex were studied. Combined metformin plus CR beneficially affected many kindling aspects, especially those relating to generalized convulsive seizures. Therefore, metformin plus CR could decrease measures of epileptic activity in patients with generalized convulsive seizures. Patients that are obese, overweight or that have metabolic syndrome in addition to having an epileptic disease are an ideal population for clinical trials to test the effectiveness of metformin plus CR.

Nanoparticle-Based Systems for Delivery of Protein Therapeutics to the Spinal Cord

Recent studies have demonstrated that delivery of protein therapeutics to the spinal cord may promote functional axon regeneration, providing a pathway for recovery of certain motor skills. The timeframe for delivery of protein therapeutics, however, must be modulated to prevent bulk release of the therapeutics and minimize the frequency of implantations. This perspective examines both affinity-based and nanoparticle-based strategies for delivery of neurotrophic factors (NFs) to the spinal cord in an effective, safe, and tunable manner.

Combined Transcriptomics, Proteomics and Bioinformatics Identify Drug Targets in Spinal Cord Injury

Spinal cord injury (SCI) causes irreversible tissue damage and severe loss of neurological function. Currently, there are no approved treatments and very few therapeutic targets are under investigation. Here, we combined 4 high-throughput transcriptomics and proteomics datasets, 7 days and 8 weeks following clinically-relevant rat SCI to identify proteins with persistent differential expression post-injury. Out of thousands of differentially regulated entities our combined analysis identified 40 significantly upregulated versus 48 significantly downregulated molecules, which were persistently altered at the mRNA and protein level, 7 days and 8 weeks post-SCI. Bioinformatics analysis was then utilized to identify currently available drugs with activity against the filtered molecules and to isolate proteins with known or unknown function in SCI. Our findings revealed multiple overlooked therapeutic candidates with important bioactivity and established druggability but with unknown expression and function in SCI including the upregulated purine nucleoside phosphorylase (PNP), cathepsins A, H, Z (CTSA, CTSH, CTSZ) and proteasome protease PSMB10, as well as the downregulated ATP citrate lyase (ACLY), malic enzyme (ME1) and sodium-potassium ATPase (ATP1A3), amongst others. This work reveals previously unappreciated therapeutic candidates for SCI and available drugs, thus providing a valuable resource for further studies and potential repurposing of existing therapeutics for SCI.

Beneficial Effects of Resveratrol-Mediated Inhibition of the mTOR Pathway in Spinal Cord Injury

Spinal cord injury (SCI) causes a high rate of morbidity and disability. The clinical features of SCI are divided into acute, subacute, and chronic phases according to its pathophysiological events. The mammalian target of rapamycin (mTOR) signaling pathway plays an important role in cell death and inflammation in the acute phase and neuroregeneration in the subacute/chronic phases at different times. Resveratrol has the potential of regulating cell growth, proliferation, metabolism, and angiogenesis through the mTOR signaling pathway. Herein, we explicate the role of resveratrol in the repair of SCI through the inhibition of the mTOR signaling pathway. The inhibition of the mTOR pathway by resveratrol has the potential of serving as a neuronal restorative mechanism following SCI.