GLP-1 contributes to increases in PGC-1α expression by downregulating miR-23a to reduce apoptosis

Emerging role and the signaling pathways of uncoupling protein 2 in kidney diseases

OBJECTIVES

Uncoupling protein 2 (UCP2) was involved in the pathogenesis and development of kidney diseases. Many signaling pathways and factors regulate the expression of UCP2. We aimed to investigate the precise role of UCP2 and its signaling pathways in kidney diseases.

METHODS

We summarized the available evidence to yield a more detailed conclusion of the signal transduction pathways of UCP2 and its role in the development and progression of kidney diseases.

RESULTS

UCP2 could interact with 14.3.3 family proteins, mitochondrial phospholipase iPLA2γ, NMDAR, glucokinase, PPARγ2. There existed a signaling pathway between UCP2 and NMDAR, PPARγ. UCP2 can inhibit the ROS production, inflammatory response, and apoptosis, which may protect against renal injury, particularly AKI. Meanwhile UCP2 can decrease ATP production and inhibit the secretion of insulin, which may alleviate chronic renal damages, such as diabetic nephropathy and kidney fibrosis.

CONCLUSIONS

Homeostasis of UCP2 is helpful for kidney health. UCP2 may play different roles in different kinds of renal injury.

The Cardiovascular Benefits of Glucagon-Like Peptide-1 Receptor Agonists as Novel Diabetes Drugs Are Mediated via the Suppression of miR-203a-3p and miR-429 Expression

Coronary artery disease (CAD) is associated with a high fatality rate and a heavy global health care burden. Glucagon-like peptide-1 (GLP-1) exerts positive cardiovascular effects, although the molecular mechanisms are unclear. Therefore, this study aimed to verify whether the cardioprotective effects of GLP-1 are mediated through the regulation of micro-RNA (miRNA) expression. Follow-up assessments were conducted for 116 patients with type 2 diabetes mellitus (T2DM) alone (controls) and 123 patients with both T2DM and CAD. After matching, each group comprised 63 patients, and age, body mass index, and serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), triglycerides (TG), and hemoglobin A1C (HbA1c) were compared. Subsequently, the expression profiles of four circulating miRNAs (miR-203a-3p, miR-429, miR-205-5p, and miR-203b-5p) were assessed via quantitative reverse transcription real-time polymerase chain reaction in the 63 patients with diabetes and CAD between 6 months (baseline) and 12 months after the initiation of GLP-1 receptor (GLP-1R) therapy. As expected, the metabolic factors were significantly improved after 6 months of treatment with GLP-1R compared with pre-treatment values, and the expression levels of two of the miRNAs (miR-203a-3p and miR-429) decreased from baseline levels in those with diabetes and CAD. The results suggest that the cardiovascular benefits induced by GLP-1R are mediated via suppressed expression of two miRNAs: miR-203a-3p and miR-429.

Glucagon-Like Peptide-1: New Regulator in Lipid Metabolism

Glucagon-like peptide-1 (GLP-1) is a 30-amino acid peptide hormone that is mainly expressed in the intestine and hypothalamus. In recent years, basic and clinical studies have shown that GLP-1 is closely related to lipid metabolism, and it can participate in lipid metabolism by inhibiting fat synthesis, promoting fat differentiation, enhancing cholesterol metabolism, and promoting adipose browning. GLP-1 plays a key role in the occurrence and development of metabolic diseases such as obesity, nonalcoholic fatty liver disease, and atherosclerosis by regulating lipid metabolism. It is expected to become a new target for the treatment of metabolic disorders. The effects of GLP-1 and dual agonists on lipid metabolism also provide a more complete treatment plan for metabolic diseases. This article reviews the recent research progress of GLP-1 in lipid metabolism.

Lower risks of cirrhosis and hepatocellular carcinoma with GLP-1RAs in type 2 diabetes: A nationwide cohort study using target trial emulation framework

BACKGROUND

To assess the association of cirrhosis and hepatocellular carcinoma (HCC) with the use of glucagon-like peptide-1 receptor agonists (GLP-1RAs) versus long-acting insulins (LAIs), which are the two commonly prescribed injectable glucose-lowering agents (GLAs) for patients with type 2 diabetes (T2D) after the failure of multiple oral GLAs.

METHODS

We emulated a target trial using the nationwide data of a Taiwanese cohort with T2D. Incident new users of GLP-1RAs and LAIs during 2013-2018 were identified, and propensity score (PS) matching was applied to ensure between-group comparability in baseline patient characteristics. The primary outcome was the composite liver disease including cirrhosis or HCC. Each patient was followed until the occurrence of a study outcome, death, or the end of 2019, whichever came first. Subdistribution hazard models were employed to assess the treatment-outcome association. Sensitivity (e.g., stabilized inverse probability of treatment weighting analysis, time-dependent analysis), E-value, and negative control outcome analyses were performed to examine the robustness of study findings.

RESULTS

We included 7171 PS-matched pairs of GLP-1RA and LAI users with no significant between-group differences at baseline. Compared with LAIs, the use of GLP-1RAs was associated with significantly reduced risks of composite liver disease (subdistribution hazard ratio [95% confidence interval]: 0.56 [0.42-0.76]), cirrhosis (0.59 [0.43-0.81]), and HCC (0.47 [0.24-0.93]). Results were consistent across sensitivity analyses and among patients with different baseline characteristics.

CONCLUSION

Among T2D patients who require injectable GLAs, the use of GLP-1RAs versus LAIs was associated with lower risks of cirrhosis and HCC.

GLP-1(7-36) protected against oxidative damage and neuronal apoptosis in the hippocampal CA region after traumatic brain injury by regulating ERK5/CREB

BACKGROUND

Glucagon-like peptide-1 (GLP-1) (7-36) amide, an endogenous active form of GLP-1, has been shown to modulate oxidative stress and neuronal cell survival in various neurological diseases.

OBJECTIVE

This study investigated the potential effects of GLP-1(7-36) on oxidative stress and apoptosis in neuronal cells following traumatic brain injury (TBI) and explored the underlying mechanisms.

METHODS

Traumatic brain injury (TBI) models were established in male SD rats for in vivo experiments. The extent of cerebral oedema was assessed using wet-to-dry weight ratios following GLP-1(7-36) intervention. Neurological dysfunction and cognitive impairment were evaluated through behavioural experiments. Histopathological changes in the brain were observed using haematoxylin and eosin staining. Oxidative stress levels in hippocampal tissues were measured. TUNEL staining and Western blotting were employed to examine cell apoptosis. In vitro experiments evaluated the extent of oxidative stress and neural apoptosis following ERK5 phosphorylation activation. Immunofluorescence colocalization of p-ERK5 and NeuN was analysed using immunofluorescence cytochemistry.

RESULTS

Rats with TBI exhibited neurological deterioration, increased oxidative stress, and enhanced apoptosis, which were ameliorated by GLP-1(7-36) treatment. Notably, GLP-1(7-36) induced ERK5 phosphorylation in TBI rats. However, upon ERK5 inhibition, oxidative stress and neuronal apoptosis levels were elevated, even in the presence of GLP-1(7-36).

CONCLUSION

In summary, this study suggested that GLP-1(7-36) suppressed oxidative damage and neuronal apoptosis after TBI by activating ERK5/CREB.

The regulatory effects of second-generation antipsychotics on lipid metabolism: Potential mechanisms mediated by the gut microbiota and therapeutic implications

Second-generation antipsychotics (SGAs) are the mainstay of treatment for schizophrenia and other neuropsychiatric diseases but cause a high risk of disruption to lipid metabolism, which is an intractable therapeutic challenge worldwide. Although the exact mechanisms underlying this lipid disturbance are complex, an increasing body of evidence has suggested the involvement of the gut microbiota in SGA-induced lipid dysregulation since SGA treatment may alter the abundance and composition of the intestinal microflora. The subsequent effects involve the generation of different categories of signaling molecules by gut microbes such as endogenous cannabinoids, cholesterol, short-chain fatty acids (SCFAs), bile acids (BAs), and gut hormones that regulate lipid metabolism. On the one hand, these signaling molecules can directly activate the vagus nerve or be transported into the brain to influence appetite via the gut-brain axis. On the other hand, these molecules can also regulate related lipid metabolism via peripheral signaling pathways. Interestingly, therapeutic strategies directly targeting the gut microbiota and related metabolites seem to have promising efficacy in the treatment of SGA-induced lipid disturbances. Thus, this review provides a comprehensive understanding of how SGAs can induce disturbances in lipid metabolism by altering the gut microbiota.

LncRNA Hnf4αos exacerbates liver ischemia/reperfusion injury in mice via Hnf4αos/Hnf4α duplex-mediated PGC1α suppression

LncRNAs are involved in the pathophysiologic processes of multiple diseases, but little is known about their functions in hepatic ischemia/reperfusion injury (HIRI). As a novel lncRNA, the pathogenetic significance of hepatic nuclear factor 4 alpha, opposite strand (Hnf4αos) in hepatic I/R injury remains unclear. Here, differentially expressed Hnf4αos and Hnf4α antisense RNA 1 (Hnf4α-as1) were identified in liver tissues from mouse ischemia/reperfusion models and patients who underwent liver resection surgery. Hnf4αos deficiency in Hnf4αos-KO mice led to improved liver function, alleviated the inflammatory response and reduced cell death. Mechanistically, we found a regulatory role of Hnf4αos-KO in ROS metabolism through PGC1α upregulation. Hnf4αos also promoted the stability of Hnf4α mRNA through an RNA/RNA duplex, leading to the transcriptional activation of miR-23a and miR-23a depletion was required for PGC1α function in hepatoprotective effects on HIRI. Together, our findings reveal that Hnf4αos elevation in HIRI leads to severe liver damage via Hnf4αos/Hnf4α/miR-23a axis-mediated PGC1α inhibition.

The miR-23-27-24 cluster: an emerging target in NAFLD pathogenesis

The incidence of non-alcoholic fatty liver disease (NAFLD) is increasing globally, being the most widespread form of chronic liver disease in the west. NAFLD includes a variety of disease states, the mildest being non-alcoholic fatty liver that gradually progresses to non-alcoholic steatohepatitis, fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Small non-coding single-stranded microRNAs (miRNAs) regulate gene expression at the miRNA or translational level. Numerous miRNAs have been shown to promote NAFLD pathogenesis and progression through increasing lipid accumulation, oxidative stress, mitochondrial damage, and inflammation. The miR-23-27-24 clusters, composed of miR-23a-27a-24-2 and miR-23b-27b-24-1, have been implicated in various biological processes as well as many diseases. Herein, we review the current knowledge on miR-27, miR-24, and miR-23 in NAFLD pathogenesis and discuss their potential significance in NAFLD diagnosis and therapy.

Mitochondria homeostasis: Biology and involvement in hepatic steatosis to NASH

Mitochondrial biology and behavior are central to the physiology of liver. Multiple mitochondrial quality control mechanisms remodel mitochondrial homeostasis under physiological and pathological conditions. Mitochondrial dysfunction and damage induced by overnutrition lead to oxidative stress, inflammation, liver cell death, and collagen production, which advance hepatic steatosis to nonalcoholic steatohepatitis (NASH). Accumulating evidence suggests that specific interventions that target mitochondrial homeostasis, including energy metabolism, antioxidant effects, and mitochondrial quality control, have emerged as promising strategies for NASH treatment. However, clinical translation of these findings is challenging due to the complex and unclear mechanisms of mitochondrial homeostasis in the pathophysiology of NASH.

Semaglutide early intervention attenuated testicular dysfunction by targeting the GLP-1-PPAR-α-Kisspeptin-Steroidogenesis signaling pathway in a testicular ischemia-reperfusion rat model

Testicular torsion is a serious emergency and a well-known cause of male infertility. It represents 10 %-15 % of scrotal diseases in children. Kisspeptin (KISS1) is a hormone secreted from the hypothalamic nuclei and testis, but its role in testis is not fully understood. Semaglutide is a novel antidiabetic glucagon-like peptide 1 (GLP-1) analog. Hence, we designed the current study to elucidate the possible ameliorative effect of semaglutide on ischemia/reperfusion-induced testicular dysfunction in rats and highlight the role of the testicular GLP-1/PCG-1α-PPAR-α-KISS1 signaling pathway. We randomly divided 50 male Sprague Dawley into five equal groups (10 rats each): SHAM, exendin 9-39 -treated (EX), testicular torsion/detorsion (T/D), testicular torsion/detorsion and semaglutide-treated (SEM + T/D), and testicular torsion/detorsion, exendin, and semaglutide-treated (EX + SEM + T/D). We quantified serum follicle-stimulating hormone, luteinizing hormone, total testosterone, testicular oxidative stress markers, testicular gene expression of GLP-1/KISS1 pathway-related genes (KISS1, KISS1R, GLP-1, GLP-1R, PGC-1α, PPAR-α), steroidogenesis pathway-related genes (STAR, CYP11A1, CYP17A1, HSD17B3, CYP19A1), HO-1, Nrf-2, and testicular protein expression of HIF-1α, TNF-α, NF-κβ, Caspase-3, FAS, proliferating cell nuclear antigen, and KISS1 through testicular histopathology and immunohistochemistry assays. Testicular torsion/detorsion markedly elevated proapoptotic, proinflammatory, and oxidative stress marker levels, noticeably downregulating the expression of GLP-1/KISS1 and steroidogenesis pathway-related proteins. Semaglutide administration significantly ameliorated all these deleterious effects. Nevertheless, injecting exendin, a GLP1-R antagonist, before semaglutide abolished all the documented improvements. We concluded that semaglutide ameliorated ischemia/reperfusion-induced testicular dysfunction by modulating the GLP-1/PGC-1α-PPAR-α/KISS1/steroidogenesis signaling pathway, improving testicular oxidative state, and suppressing testicular inflammation and apoptosis.

The Effect of PGC-1alpha-SIRT3 Pathway Activation on Pseudomonas aeruginosa Infection

The innate immune response to P. aeruginosa pulmonary infections relies on a network of pattern recognition receptors, including intracellular inflammasome complexes, which can recognize both pathogen- and host-derived signals and subsequently promote downstream inflammatory signaling. Current evidence suggests that the inflammasome does not contribute to bacterial clearance and, in fact, that dysregulated inflammasome activation is harmful in acute and chronic P. aeruginosa lung infection. Given the role of mitochondrial damage signals in recruiting inflammasome signaling, we investigated whether mitochondrial-targeted therapies could attenuate inflammasome signaling in response to P. aeruginosa and decrease pathogenicity of infection. In particular, we investigated the small molecule, ZLN005, which transcriptionally activates peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis, antioxidant defense, and cellular respiration. We demonstrate that P. aeruginosa infection promotes the expression of inflammasome components and attenuates several components of mitochondrial repair pathways in vitro in lung epithelial cells and in vivo in an acute pneumonia model. ZLN005 activates PGC-1α and its downstream effector, Sirtuin 3 (SIRT3), a mitochondrial-localized deacetylase important for cellular metabolic processes and for reactive oxygen species homeostasis. ZLN005 also attenuates inflammasome signaling induced by P. aeruginosa in bronchial epithelial cells and this action is dependent on ZLN005 activation of SIRT3. ZLN005 treatment reduces epithelial-barrier dysfunction caused by P. aeruginosa and decreases pathogenicity in an in vivo pneumonia model. Therapies that activate the PGC-1α—SIRT3 axis may provide a complementary approach in the treatment of P. aeruginosa infection.

Endocrine regulation of cancer stem cell compartments in breast tumors

Cancer cells within breast tumors exist within a hierarchy in which only a small and rare subset of cells is able to regenerate growths with the heterogeneity of the original tumor. These highly malignant cancer cells, which behave like stem cells for new cancers and are called "cancer stem cells" or CSCs, have also been shown to possess increased resistance to therapeutics, and represent the root cause underlying therapy failures, persistence of residual disease, and relapse. As >90% of cancer deaths are due to refractory tumors, identification of critical molecular drivers of the CSC-state would reveal vulnerabilities that can be leveraged in designing therapeutics that eradicate advanced disease and improve patient survival outcomes. An expanding and complex body of work has now described the exquisite susceptibility of CSC pools to the regulatory influences of local and systemic hormones. Indeed, breast CSCs express a plethora of hormonal receptors, which funnel hormonal influences over every aspect of breast neoplasia - be it tumor onset, growth, survival, invasion, metastasis, or therapy resistance - via directly impacting CSC behavior. This article is intended to shed light on this active area of investigation by attempting to provide a systematic and comprehensive overview of the available evidence directly linking hormones to breast CSC biology.

Liraglutide Increases Serum Levels of MicroRNA-27b, -130a and -210 in Patients with Type 2 Diabetes Mellitus: A Novel Epigenetic Effect

Liraglutide has shown favourable effects on several cardiometabolic risk factors, beyond glucose control. MicroRNAs (miRNAs) regulate gene expression, resulting in post-transcriptional modifications of cell response and function. Specific miRNAs, including miRNA-27b, miRNA-130a, and miRNA-210, play a role in cardiometabolic disease. We aimed to determine the effect of liraglutide on the serum levels of miRNA-27b, miRNA-130a and miRNA-210. Twenty-five subjects with type-2 diabetes mellitus (T2DM), naïve to incretin-based therapy, were treated with liraglutide (1.2 mg/day as an add-on to metformin) for 4 months. miRNAs were quantified using real-time polymerase chain reaction. After liraglutide treatment, we found significant reductions in fasting glucose (from 9.8 ± 5.3 to 6.7 ± 1.6 mmol/L, p = 0.0042), glycosylated haemoglobin (HbA1c) (from 8.1 ± 0.8 to 6.6 ± 1.0%, p = 0.0008), total cholesterol (from 5.0 ± 1.0 to 4.0 ± 0.7 mmol/L, p = 0.0011), triglycerides (from 1.9 ± 1.0 to 1.5 ± 0.8 mmol/L, p = 0.0104) and low-density lipoprotein cholesterol (from 2.9 ± 1.2 to 2.2 ± 0.6 mmol/L, p = 0.0125), while the serum levels of miRNA-27b, miRNA-130a and miRNA-210a were significantly increased (median (interquartile range, IQR) changes: 1.73 (7.12) (p = 0.0401), 1.91 (3.64) (p = 0.0401) and 2.09 (11.0) (p = 0.0486), respectively). Since the changes in miRNAs were independent of changes in all the metabolic parameters investigated, liraglutide seems to exert a direct epigenetic effect in T2DM patients, regulating microRNAs involved in the maintenance of endothelial cell homeostasis. These changes might be implicated in liraglutide’s benefits and may represent useful targets for cardiometabolic management.

Linagliptin, the dipeptidyl peptidase-4 enzyme inhibitor, lessens CHOP and GRP78 biomarkers levels in cisplatin-induced neurobehavioral deficits: A possible restorative gateway

Cisplatin (CP) is a cornerstone chemotherapeutic agent, however, its neurotoxicity is a chief cause of its limited usage. Linagliptin, which is a dipeptidyl peptidase-4 enzyme inhibitor, has exhibited considerable neuroprotective potential. We aimed to evaluate the linagliptin modulatory effects on endoplasmic reticulum (ER) stress, redox status, and apoptosis in CP-induced neurotoxicity. Thirty mice were allocated equally into the control group, Group II: CP group, and Group III: linagliptin treated CP group. All groups were subjected to the measurement of hippocampal messenger RNA gene expression of glucose-regulated protein-78 and C/EBP homologous protein (CHOP). Peroxisome proliferator-activated receptor γ coactivator 1α and cleaved caspase-3 levels were assessed by the enzyme-linked immunosorbent assay technique while malondialdehyde, reduced glutathione levels and superoxide dismutase activity were detected spectrophotometrically. Linagliptin ameliorated ER stress and enhanced antioxidant status with cognitive function improvement. Linagliptin may be considered a promising neuroprotective agent owing to its ability to reduce ER/oxidative stress.

Glucagon-Like Peptide-1 Receptor Agonist Prevented the Progression of Hepatocellular Carcinoma in a Mouse Model of Nonalcoholic Steatohepatitis

Glucagon-like peptide-1 (GLP-1) receptor agonists are used to treat diabetes, but their effects on nonalcoholic steatohepatitis (NASH) and the development of hepatocellular carcinoma (HCC) remain unclear. In this study, mice with streptozotocin- and high-fat diet-induced diabetes and NASH were subcutaneously treated with liraglutide or saline (control) for 14 weeks. Glycemic control, hepatocarcinogenesis, and liver histology were compared between the groups. Fasting blood glucose levels were significantly lower in the liraglutide group than in the control group (210.0 ± 17.3 mg/dL vs. 601.8 ± 123.6 mg/dL), and fasting insulin levels were significantly increased by liraglutide (0.18 ± 0.06 ng/mL vs. 0.09 ± 0.03 ng/mL). Liraglutide completely suppressed hepatocarcinogenesis, whereas HCC was observed in all control mice (average tumor count, 5.5 ± 3.87; average tumor size, 8.1 ± 5.0 mm). Liraglutide significantly ameliorated steatosis, inflammation, and hepatocyte ballooning of non-tumorous lesions in the liver compared with the control findings, and insulin-positive β-cells were observed in the pancreas in liraglutide-treated mice but not in control mice. In conclusion, liraglutide ameliorated NASH and suppressed hepatocarcinogenesis in diabetic mice. GLP-1 receptor agonists can be used to improve the hepatic outcome of diabetes.

Incretins and microRNAs: Interactions and physiological relevance

MicroRNAs (miRNA) are one class of the small regulatory RNAs that can impact the expression of numerous genes including incretin hormones and their G protein-coupled receptors. Incretin peptides, including GLP-1, GLP-2, and GIP, are released from the gastrointestinal tract and have an crucial role in the glucose hemostasis and pancreatic beta-cell function. These hormones and their analogs with a longer half-life, glucagon like peptide-1 receptor agonists (GLP1RA), modify the expression of miRNAs. Dipeptidyl peptidase IV (DPP-4) is an enzyme that degrades the incretin hormones and is inactivated by DPP-4 inhibitors, which are a class of compounds used in the management of type 2 diabetes. DPP-4 inhibitors may also increase or reduce the expression of miRNAs. In this review, we describe the possible interactions between miRNAs and incretin hormones and the relevance of such interactions to physiological processes and diseases.

Requirement of the transcription factor YB-1 for maintaining the stemness of cancer stem cells and reverting differentiated cancer cells into cancer stem cells

BACKGROUND

Cancer stem cells always express high levels of stemness-associated transcription factors to maintain their features. However, the regulatory mechanism of the stemness of cancer stem cells mediated by transcription factors has not been extensively explored.

METHODS

The YB-1 gene in cancer stem cells was knocked out by the CRISPR/Cas9 system. The YB-1 knockout cancer stem cells were transfected with a vector expressing YB-1 to rescue YB-1, and then the cell proliferation, cell cycle, apoptosis, and stemness, as well as tumorigenesis in nude mice, were assessed to examine the effect of YB-1 in cancer stem cells. The target genes of YB-1 were confirmed by CHIP-seq. The totipotency or pluripotency of differentiated cancer stem cells were detected by tumorsphere formation assay and quantitative real-time PCR.

RESULTS

The deletion of YB-1 gene inhibited the proliferation of breast cancer stem cells and melanoma stem cells, leading to cell cycle arrest and apoptosis, and induced irreversible differentiation of cancer stem cells. The tumorigenicity ability of YB-1-deleted cancer stem cells was significantly reduced in vitro and in vivo. The results of ChIP-seq showed that YB-1 maintained the stemness of cancer stem cells by promoting the expressions of stemness-associated genes (FZD-1, p21, GLP-1, GINS1, and Notch2). Furthermore, simultaneous expressions of YB-1 and the other four (SOX2, POU3F2, OCT-4, and OLIG1) or five (SOX2, SALL2, OCT-4, POU3F2, and Bmi-1) transcription factors in YB-1 knockout cancer stem cells restored the stemness of YB-1 knockout cancer stem cells.

CONCLUSIONS

Our study indicated that YB-1 was required for maintaining the stemness of cancer stem cells and reverting the differentiated tumor cells into cancer stem cells.

MiR-1197-3p regulates testosterone secretion in goat Leydig cells via targeting PPARGC1A

As a fundamental regulator of mitochondrial function, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) acts as a powerful coactivator of many transcriptional factors that relate to steroidogenesis, while the regulatory mechanism remains unclear. In the present study, testosterone secretion of goat Leydig cells (LCs) mediated by miR-1197-3p via PPARGC1A was investigated. We found PPARGC1A protein was diversely localized in testis, and the expression of PPARGC1A in testis of 9-month-old goat was significantly higher than that in 3-month-old goat. In addition, suppression of PPARGC1A significantly decreased the testosterone secretion in goat LCs, as well as reduced the expressions of key steroidogenesis related genes [steroidogenic acute regulatory protein (StAR), cytochrome P450 family 11 subfamily A member 1 (CYP11A1), and 3 beta-hydroxysteroid dehydrogenase (3BHSD)], and overexpression of PPARGC1A showed the opposite effects. Moreover, we observed suppression of miR-1197-3p increased the synthesis of testosterone and promoted the expressions of PPARGC1A, StAR, CYP11A1, and 3BHSD by directly targeting PPARGC1A in the LCs. Furthermore, overexpression of PPARGC1A could alleviate miR-1197-3p induced aberrant steroidogenesis related gene expressions and testosterone synthesis. Taken together, miR-1197-3p could act as an essential regulator of LC testosterone secretion in goat testis by targeting PPARGC1A. These results provide a novel view of the regulatory mechanisms involved in male sexual maturation and help us to understand the molecular role of PPARGC1A in testosterone synthesis.

Suppression of miR-1197-3p attenuates H2O2-induced apoptosis of goat luteinized granulosa cells via targeting PPARGC1A

Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PPARGC1A) acts as a powerful coactivator of many transcriptional factors that relate to granulosa cell (GC) apoptosis. In this study, the miRNAs mediating goat follicular atresia and luteinized granulosa cell (LGC) apoptosis induced by hydrogen peroxide (H₂O₂) via PPARGC1A were investigated. Our results showed that miR-1197-3p targeted PPARGC1A was predicted by bioinformatics algorithm and verified by luciferase reporter assay. In addition, miR-1197-3p promoted goat LGC apoptosis via PPARGC1A through mitochondrial-dependent apoptosis pathway, and these effects could be restored by PPARGC1A overexpression. Moreover, H₂O₂-induced LGC apoptosis significantly upregulated miR-1197-3p expression and downregulated PPARGC1A level. Pretreatment of miR-1197-3p inhibitor alleviated LGC apoptosis induced by 400 μM H₂O₂ for 12 h, and preserved the mitochondrial membrane potential by increasing PPARGC1A expression. In conclusion, miR-1197-3p might act as an essential regulator of goat LGC apoptosis potentially via the mitochondrial-dependent apoptosis pathway by targeting PPARGC1A.

Glucagon-Like Peptide-1 Receptor Agonist Protects Dorsal Root Ganglion Neurons against Oxidative Insult

OBJECTIVE

Diabetic polyneuropathy (DPN) is one of the most prevalent diabetic complications. We previously demonstrated that exendin-4 (Ex4), a glucagon-like peptide-1 receptor agonist (GLP-1RA), has beneficial effects in animal models of DPN. We hypothesized that GLP-1 signaling would protect neurons of the peripheral nervous system from oxidative insult in DPN. Here, the therapeutic potential of GLP-1RAs on DPN was investigated in depth using the cellular oxidative insult model applied to the dorsal root ganglion (DRG) neuronal cell line.

RESEARCH DESIGN AND METHODS

Immortalized DRG neuronal 50B11 cells were cultured with and without hydrogen peroxide in the presence or absence of Ex4 or GLP-1(7-37). Cytotoxicity and viability were determined using a lactate dehydrogenase assay and MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt), respectively. Antioxidant enzyme activity was evaluated using a superoxide dismutase assay. Alteration of neuronal characteristics of 50B11 cells induced by GLP-1RAs was evaluated with immunocytochemistry utilizing antibodies for transient receptor potential vanilloid subfamily member 1, substance P, and calcitonin gene-related peptide. Cell proliferation and apoptosis were also examined by ethynyl deoxyuridine incorporation assay and APOPercentage dye, respectively. The neurite projection ratio induced by treatment with GLP-1RAs was counted. Intracellular activation of adenylate cyclase/cyclic adenosine monophosphate (cAMP) signaling was also quantified after treatment with GLP-1RAs.

RESULTS

Neither Ex4 nor GLP-1(7-37) demonstrated cytotoxicity in the cells. An MTS assay revealed that GLP-1RAs amended impaired cell viability induced by oxidative insult in 50B11 cells. GLP-1RAs activated superoxide dismutase. GLP-1RAs induced no alteration of the distribution pattern in neuronal markers. Ex4 rescued the cells from oxidative insult-induced apoptosis. GLP-1RAs suppressed proliferation and promoted neurite projections. No GLP-1RAs induced an accumulation of cAMP.

CONCLUSIONS

Our findings indicate that GLP-1RAs have neuroprotective potential which is achieved by their direct actions on DRG neurons. Beneficial effects of GLP-1RAs on DPN could be related to these direct actions on DRG neurons.

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.

Differential Effects of a Glucagon-Like Peptide 1 Receptor Agonist in Non-Alcoholic Fatty Liver Disease and in Response to Hepatectomy

Non-alcoholic fatty liver disease (NAFLD) is associated with post-operative liver failure (PLF) and impaired liver regeneration. We investigated the effects of a glucagon-like peptide-1 (GLP-1) receptor agonist on NAFLD, PLF and liver regeneration in mice fed chow diet or methionine/choline-deficient diet (MCD) or high fat diet (HFD). Fc-GLP-1 decreased transaminases, reduced intrahepatic triglycerides (TG) and improved MCD-induced liver dysfuction. Macrophage/Kupffer cell-related markers were also reduced although Fc-GLP-1 increased expression of genes related to natural killer (NK), cytotoxic T lymphocytes and hepatic stellate cell (HSC) activation. After partial hepatectomy (PH), survival rates increased in mice receiving Fc-GLP-1 on chow or MCD diet. However, the benefit of Fc-GLP-1 on NASH-like features was attenuated 2 weeks post-PH and liver mass restoration was not improved. At this time-period, markers of NK cells and cytotoxic T lymphocytes were further elevated in Fc-GLP-1 treated mice. Increased HSC related gene expression in livers was observed together with decreased retinyl ester content and increased retinal and retinoic acid, reflecting HSC activation. Similar effects were found in mice fed HFD receiving Fc-GLP-1. Our results shed light on the differential effects of a long-acting GLP-1R agonist in improving NAFLD and PLF, but not enhancing liver regeneration in mice.

Glucagon-like peptide-1 receptor antagonism impairs basal exercise capacity and vascular adaptation to aerobic exercise training in rats

Cardiorespiratory fitness (CRF) inversely predicts cardiovascular (CV) mortality and CRF is impaired in people with type 2 diabetes (T2D). Aerobic exercise training (ET) improves CRF and is associated with decreased risk of premature death in healthy and diseased populations. Understanding the mechanisms contributing to ET adaptation may identify targets for reducing CV mortality of relevance to people with T2D. The antihyperglycemic hormone glucagon-like peptide-1 (GLP-1) influences many of the same pathways as exercise and may contribute to CV adaptation to ET. We hypothesized that GLP-1 is necessary for adaptation to ET. Twelve-week-old male Wistar rats were randomized (n = 8-12/group) to receive PBS or GLP-1 receptor antagonist (exendin 9-39 (Ex(9-39)) via osmotic pump for 4 weeks ± ET. CRF was greater with ET (P < 0.01). Ex(9-39) treatment blunted CRF in both sedentary and ET rats (P < 0.001). Ex(9-39) attenuated acetylcholine-mediated vasodilation, while this response was maintained with Ex(9-39)+ET (P = 0.04). Aortic stiffness was greater with Ex(9-39) (P = 0.057) and was made worse when Ex(9-39) was combined with ET (P = 0.004). Ex vivo aortic vasoconstriction with potassium and phenylephrine was lower with Ex(9-39) (P < 0.0001). Carotid strain improved with PBS + ET but did not change in the Ex(9-39) rats with ET (P < 0.0001). Left ventricular mitochondrial respiration was elevated with Ex(9-39) (P < 0.02). GLP-1 receptor antagonism impairs CRF with and without ET, attenuates the vascular adaptation to ET, and elevates cardiac mitochondrial respiration. These data suggest that GLP-1 is integral to the adaptive vascular response to ET.

The expression of microRNA-23a regulates acute myocardial infarction in patients and in vitro through targeting PTEN

Cardiovascular disease is responsible for one of the highest rates of fatality worldwide. The present study investigated the presence and influence of microRNA (miRNA)-23a in the regulation of acute myocardial infarction (AMI). A total of 6 patients with AMI and 6 normal volunteers without myocardial disease were included, and blood samples were taken to analyze the expression of miRNA‑23a by reverse transcription‑quantitative polymerase chain reaction. miRNA‑23a expression in patients with AMI was downregulated compared with the normal group. In H9C2 cells treated with H2O2, upregulation of miRNA‑23a expression increased the superoxide dismutase, glutathione and catalase activity levels, and suppressed the malonaldehyde activity level, as determined by ELISA. Western blot analysis and a caspase‑3 substrate assay demonstrated that upregulation of miRNA‑23a expression suppressed the Bcl‑2‑associated X (Bax)/Bcl‑2 protein expression ratio, caspase‑3 activity level and tumor suppressor p53 (p53) protein expression in H2O2‑induced H9C2 cells. Furthermore, downregulation of phosphatase and tensin homolog (PTEN), by the PTEN inhibitor bpV(HOpic), increased miRNA‑23a expression and suppressed the Bax/Bcl‑2 protein expression ratio, caspase‑3 activity level and p53 protein expression in H2O2‑induced H9C2 cells. Therefore, the results of the present study indicate that the expression of miRNA‑23a may regulate AMI through targeting PTEN in patients and in vitro, and PTEN/miRNA‑23a may therefore be potential targets for the clinical treatment of AMI.

Glucagon-like peptide-1 effects lipotoxic oxidative stress by regulating the expression of microRNAs

Aim to confirm whether the treatment of GLP-1 can modulated body weight, lipid metabolism, insulin content, pancreas oxidative stress, improved T-AOC, MDA levels related to FFA-Induced oxidative stress in C57BL/6 mice and INS-1 cells. In this study, GLP-1 makes the expression of AMPK, PPARα, CPT1A and SIRT1 increased, and the expression of SREBP1c, miR-33 and miR-370 decreased. Interestingly, the effects of GLP-1 were less dose dependent as GLP-1 regulated the FFA, which related to gene expression at much lower doses (3 μg/kg, 10 mM, mice and INS-1 respectively) and effects were relatively maintained at higher dose (30 μg/kg, 100 mM, mice and INS-1 respectively) as well. Subsequently, the analysis showed that inhibited expression of miR-33 and miR-370 upregulated the expression of CPT1A and SIRT1, reversely mimics. These results demonstrated for the first time that GLP-1 improve lipotoxic oxidative stress of pancreas by regulate expression of microRNAs.

Perspectives in GLP-1 Research: New Targets, New Receptors

The incretin hormone glucagon-like peptide-1 (GLP-1) binds to and activates its G-protein-coupled-receptor GLP-1R to reduce glycaemia through the stimulation of insulin and suppression of pancreatic glucagon secretion. Recently, GLP-1 effects unrelated to glucose homeostasis have been discovered in myocardium, bone, adipose tissue, and other target organs, which appear to be mainly mediated by GLP-1R-independent pathways. Here, we summarize knowledge on GLP-1R agonists (GLP-1RAs) as they relate to the improvement of glucose control, and focus on the most recently described effects, discussing the preclinical evidence of the involvement of alternative receptors and signalling mechanisms. It is now evident that the universe of GLP-1RAs is expanding further from the initial incretin effect, opening new unforeseen avenues for research and clinical applications.

Obesity alters molecular and functional cardiac responses to ischemia/reperfusion and glucagon-like peptide-1 receptor agonism

This study tested the hypothesis that obesity alters the cardiac response to ischemia/reperfusion and/or glucagon like peptide-1 (GLP-1) receptor activation, and that these differences are associated with alterations in the obese cardiac proteome and microRNA (miRNA) transcriptome. Ossabaw swine were fed normal chow or obesogenic diet for 6 months. Cardiac function was assessed at baseline, during a 30-minutes coronary occlusion, and during 2 hours of reperfusion in anesthetized swine treated with saline or exendin-4 for 24 hours. Cardiac biopsies were obtained from normal and ischemia/reperfusion territories. Fat-fed animals were heavier, and exhibited hyperinsulinemia, hyperglycemia, and hypertriglyceridemia. Plasma troponin-I concentration (index of myocardial injury) was increased following ischemia/reperfusion and decreased by exendin-4 treatment in both groups. Ischemia/reperfusion produced reductions in systolic pressure and stroke volume in lean swine. These indices were higher in obese hearts at baseline and relatively maintained throughout ischemia/reperfusion. Exendin-4 administration increased systolic pressure in lean swine but did not affect the blood pressure in obese swine. End-diastolic volume was reduced by exendin-4 following ischemia/reperfusion in obese swine. These divergent physiologic responses were associated with obesity-related differences in proteins related to myocardial structure/function (e.g. titin) and calcium handling (e.g. SERCA2a, histidine-rich Ca(2+) binding protein). Alterations in expression of cardiac miRs in obese hearts included miR-15, miR-27, miR-130, miR-181, and let-7. Taken together, these observations validate this discovery approach and reveal novel associations that suggest previously undiscovered mechanisms contributing to the effects of obesity on the heart and contributing to the actions of GLP-1 following ischemia/reperfusion.