Combination therapy with semaglutide and rosiglitazone as a synergistic treatment for diabetic retinopathy in rodent animals

Neuroprotective effects of semaglutide and metformin against rotenone-induced neurobehavioral changes in male diabetic rats

Pre-existing diabetes raises the likelihood of Parkinson's disease (PD), according to epidemiological and animal research. Our study aimed to investigating the likely neuroprotective effect of metformin (Met) and/or semaglutide (Sem) in model of PD in male diabetic rats and the possible underlying mechanism. Type 2 diabetes (T2DM) was induced by giving high-fat diet (HFD) for 3 weeks followed by a single streptozotocin (STZ) injection (40 mg/kg, i.p., once dose) followed by injection of 9 doses of rotenone every 48 ± 2 h for induction of PD. Met and/or Sema were administered to DM+PD via gastric gavage once daily for 4 weeks. In comparison with the DM+PD group, Met and/or Sem significantly lowered blood glucose levels, HOMA-IR, HbA1C, cholesterol, triglycerides, and LDL with significantly increased insulin and HDL levels. In addition, there was enhanced brain antioxidant status with lower oxidative-inflammatory stress biomarkers associated with improved rat cognitive, locomotor, and olfactory functions. A significant downregulation of caspase 3 and GFAP with concomitant upregulation of NRF2 protein expressions were observed in treated groups. Overall, co-treatment with Met and Sem elicited more efficacy than that of the individual regimen. When combined, the results of this study have demonstrated for the first time that Met and Sem work in concert to create neuroprotection in PD model of male diabetic rats compared to when taken separately. The study's findings indicate that Met and/or Sem have a restorative effect on T2DM and PD-induced changes in neurobehavioral and biochemical/molecular indices ascribed to the improvement of endogenous antioxidant systems, decreased lipid peroxidation, suppression of oxidative/inflammatory stress, and-most importantly-regulation of Nrf2 and caspase 3.

IL-6 Exacerbates Oxidative Damage of RPE Cells by Indirectly Destabilizing the mRNA of DNA Repair Genes

Chronic inflammation has been associated with the progression of age-related macular degeneration (AMD) and diabetic retinopathy (DR), and the levels of various inflammatory factors are significantly increased in intraocular fluids of patients with AMD and DR. Therefore, elucidating the roles of inflammatory factors in the oxidative damage of RPE cells will help uncover the pathogenesis of AMD and DR. We have previously demonstrated that E2F1 plays an important role in the antioxidant capacity of RPE cells. Here, our transcriptome analysis shows that E2F1 affected the expressions of DNA repair genes in RPE cells. In addition, we found that E2F1 transactivated the splicing factor SRSF1. SRSF1 knockdown promoted DNA oxidative damage and apoptosis and decreased the mRNA stability of DNA repair genes XRCC2, POLK and LIG4 in RPE cells. Moreover, we found that SRSF1 could bind to the RNA stabilizing factor MATR3, and knockdown of the latter affected the mRNA stability of these DNA repair genes. Notably, interleukin-6 (IL-6), an inflammatory factor upregulated in intraocular fluids of patients with AMD and DR, decreased SRSF1 expression by inducing acetylation of E2F1 at the K125 position. Consistently, SRSF1 overexpression relieved IL-6-induced DNA oxidative damage and apoptosis in RPE cells. In vivo experiment results also confirmed that IL-6 could aggravate retinal oxidative damage. In conclusion, high levels of IL-6 in the eyes of patients with AMD and DR destabilize the mRNAs of DNA repair genes by disrupting the expression of SRSF1, leading to abnormal repair of DNA oxidative damage in RPE cells.

RAGE plays key role in diabetic retinopathy: a review

RAGE is a multiligand receptor for the immunoglobulin superfamily of cell surface molecules and is expressed in Müller cells, vascular endothelial cells, nerve cells and RPE cells of the retina. Diabetic retinopathy (DR) is a multifactorial disease associated with retinal inflammation and vascular abnormalities and is the leading cause of vision loss or impairment in older or working-age adults worldwide. Therapies aimed at reducing the inflammatory response and unnecessary angiogenesis can help slow the progression of DR, which in turn can save patients' vision. To maximize the efficacy and minimize the side effects, treatments that target key players in the pathophysiological process of DR need to be developed. The interaction between RAGE and its ligands is involved in a variety of cytopathological alterations in the retina, including secretion of inflammatory factors, regulation of angiogenesis, oxidative stress, structural and functional changes, and neurodegeneration. In this review, we will summarize the pathologic pathways mediated by RAGE and its ligand interactions and discuss its role in the progression of diabetic retinopathy to explore potential therapeutic targets that are effective and safe for DR.

Identification of Potential Molecular Targets and Active Ingredients of Mingmu Dihuang Pill for the Treatment of Diabetic Retinopathy Based on Network Pharmacology

Objective. Mingmu Dihuang Pill (MMDHP) is a traditional Chinese formula that has shown remarkable improvements of dry eyes, tearing, and blurry vision; however, the mechanisms underlying MMDHP treatment for diabetic retinopathy have not been fully understood. This study is aimed at identifying the molecular targets and active ingredients of MMDHP for the treatment of diabetic retinopathy based on network pharmacology. Methods. All active ingredients of MMDHP were retrieved from TCMSP and BATMAN-TCM databases, and the targets of active ingredients of MMDHP were predicted on the SwissTargetPrediction website. Diabetic retinopathy-related target sets were retrieved from GeneCards and OMIM databases, and the intersecting targets between targets of active ingredients of MMDHP and potential therapeutic targets of diabetic retinopathy were collected to generate the traditional Chinese medicine-ingredient-target-diabetic retinopathy network and to create the protein-protein interaction network. In addition, GO terms and KEGG pathway enrichment analyses were performed to identify the potential pathways, and molecular docking was employed to verify the binding of active ingredients of MMDHP to key targets of diabetic retinopathy. Results. Network pharmacology predicted 183 active ingredients and 904 targets from MMDHP, and 203 targets were intersected with the therapeutic targets of diabetic retinopathy. The top 10 hub targets included PIK3RA, TP53, SRC, JUN, HRAS, AKT1, VEGFA, EGFR, ESR1, and PI3KCA. GO terms and KEGG pathway enrichment analyses identified AGE-RAGE, PI3K-AKT, and Rap1 signaling pathways as major pathways involved in MMDHP treatment for diabetic retinopathy. Molecular docking confirmed a good binding affinity of active ingredients of MMDHP, including luteolin, acacetin, naringenin, and alisol B, with AKT1, SRC, and VEGFA as the three key targets of diabetic retinopathy. Conclusion. MMDHP may be effective for the treatment of diabetic retinopathy through active ingredients luteolin, acacetin, naringenin, and alisol B via AKT1, SRC, and VEGFA in AGE-RAGE, PI3K-AKT, and Rap1 signaling pathways.

The role of the mTOR pathway in diabetic retinopathy

The retina, the part of the eye, translates the light signal into an electric current that can be sent to the brain as visual information. To achieve this, the retina requires fine-tuned vascularization for its energy supply. Diabetic retinopathy (DR) causes alterations in the eye vascularization that reduce the oxygen supply with consequent retinal neurodegeneration. During DR, the mammalian target of rapamycin (mTOR) pathway seems to coordinate retinal neurodegeneration with multiple anabolic and catabolic processes, such as autophagy, oxidative stress, cell death, and the release of pro-inflammatory cytokines, which are closely related to chronic hyperglycemia. This review outlines the normal anatomy of the retina and how hyperglycemia can be involved in the neurodegeneration underlying this disease through over activation or inhibition of the mTOR pathway.

Semaglutide May Alleviate Hepatic Steatosis in T2DM Combined with NFALD Mice via miR-5120/ABHD6

Objective

Although the pathogenesis of non-alcoholic fatty liver disease (NAFLD) has been extensively studied, the role of its underlying pathogenesis remains unclear, and there is currently no approved therapeutic strategy for NAFLD. The purpose of this study was to observe the beneficial effects of Semaglutide on NAFLD in vivo and in vitro, as well as its potential molecular mechanisms.

Methods

Semaglutide was used to treat type 2 diabetes mellitus (T2DM) combined with NAFLD mice for 12 weeks. Hepatic function and structure were evaluated by liver function, blood lipids, liver lipids, H&E staining, oil red staining and Sirius staining. The expression of α/β hydrolase domain-6 (ABHD6) was measured by qPCR and Western blotting in vivo and in vitro. Then, dual-luciferase reporter assay was performed to verify the regulation of the upstream miR-5120 on ABHD6.

Results

Our data revealed that Semaglutide administration significantly improved liver function and hepatic steatosis in T2DM combined with NAFLD mice. Furthermore, compared with controls, up-regulation of ABHD6 and down-regulation of miR-5120 were found in the liver of T2DM+NAFLD mice and HG+FFA-stimulated Hepa 1-6 hepatocytes. Interestingly, after Semaglutide intervention, ABHD6 expression was significantly decreased in the liver of T2DM+NAFLD mice and in HG+FFA-stimulated Hepa 1-6 hepatocytes, while miR-5120 expression was increased. We also found that miR-5120 could regulate the expression of ABHD6 in hepatocytes, while Semaglutide could modulate the expression of ABHD6 through miR-5120. In addition, GLP-1R was widely expressed in mouse liver tissues and Hepa 1-6 cells. Semaglutide could regulate miR-5120/ABHD6 expression through GLP-1R.

Conclusion

Our data revealed the underlying mechanism by which Semaglutide improves hepatic steatosis in T2DM+NAFLD, and might shed new light on the pathological role of miR-5120/ABHD6 in the pathogenesis of T2DM+NAFLD.

mTOR Signalling Pathway: A Potential Therapeutic Target for Ocular Neurodegenerative Diseases

Recent advances in the research of the mammalian target of the rapamycin (mTOR) signalling pathway demonstrated that mTOR is a robust therapeutic target for ocular degenerative diseases, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma. Although the exact mechanisms of individual ocular degenerative diseases are unclear, they share several common pathological processes, increased and prolonged oxidative stress in particular, which leads to functional and morphological impairment in photoreceptors, retinal ganglion cells (RGCs), or retinal pigment epithelium (RPE). mTOR not only modulates oxidative stress but is also affected by reactive oxygen species (ROS) activation. It is essential to understand the complicated relationship between the mTOR pathway and oxidative stress before its application in the treatment of retinal degeneration. Indeed, the substantial role of mTOR-mediated autophagy in the pathogenies of ocular degenerative diseases should be noted. In reviewing the latest studies, this article summarised the application of rapamycin, an mTOR signalling pathway inhibitor, in different retinal disease models, providing insight into the mechanism of rapamycin in the treatment of retinal neurodegeneration under oxidative stress. Besides basic research, this review also summarised and updated the results of the latest clinical trials of rapamycin in ocular neurodegenerative diseases. In combining the current basic and clinical research results, we provided a more complete picture of mTOR as a potential therapeutic target for ocular neurodegenerative diseases.