The functional duality of SGK1 in the regulation of hyperglycemia

SGK1 promotes the lipid accumulation via regulating the transcriptional activity of FOXO1 in bovine

OBJECTIVES

Serum/glucocorticoid-inducible kinase 1 (SGK1) gene encodes a serine/threonine protein kinase that plays an essential role in cellular stress response and regulation of multiple metabolic processes. However, its role in bovine adipogenesis remains unknown. In this study, we aimed to clarify the role of SGK1 in bovine lipid accumulation and improvement of meat quality.

METHODS

Preadipocytes were induced to differentiation to detect the temporal expression pattern of SGK1. Heart, liver, lung, spleen, kidney, muscle and fat tissues were collected to detect its tissue expression profile. Recombinant adenovirus and the lentivirus were packaged for overexpression and knockdown. Oil Red O staining, quantitative real-time PCR, Western blot analysis, Yeast two-hybrid assay, luciferase assay and RNA-seq were performed to study the regulatory mechanism of SGK1.

RESULTS

SGK1 showed significantly higher expression in adipose and significantly induced expression in differentiated adipocytes. Furthermore, overexpression of SGK1 greatly promoted adipogenesis and inhibited proliferation, which could be shown by the remarkable increasement of lipid droplet, and the expression levels of adipogenic marker genes and cell cycle-related genes. Inversely, its knockdown inhibited adipogenesis and facilitated proliferation. Mechanistically, SGK1 regulates the phosphorylation and expression of two critical proteins of FoxO family, FOXO1/FOXO3. Importantly, SGK1 attenuates the transcriptional repression role of FOXO1 for PPARγ via phosphorylating the site S256, then promoting the bovine fat deposition.

CONCLUSIONS

SGK1 is a required epigenetic regulatory factor for bovine preadipocyte proliferation and differentiation, which contributes to a better understanding of fat deposition and meat quality improvement in cattle.

The effect of overexpression of CyPA on gene expression in human umbilical vein endothelial cells

The aim of this study is to screen the differentially expressed genes and genes with alternative splicing in PPIA overexpressing cells by transcriptome sequencing. Transcriptome sequencing was performed to identify differentially expressed genes and genes with altered alternative splicing in PPIA overexpressing cells and results were validated by real-time quantitative polymerase chain reaction. The biological function and pathways of those genes were further explored through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes analyses. A total of 157 significantly upregulated genes and 171 significantly downregulated genes were identified in PPIA overexpressing cells, and the splicing pattern of LHPP, APH1A, BRD1, and ORAI3 was found to be altered. GO analyses showed that the most enriched GO terms of the 157 upregulated genes included extracellular region, protein binding, and metal ion, and the most enriched GO terms of the 171 downregulated genes included binding neuron projection, protein binding, and endoplasmic reticulum unfolded protein response. Kyoto Encyclopedia of Genes and Genomes analyses showed that the 157 upregulated genes were mainly enriched in gastric acid secretion, Mitogen-activated protein kinase signaling pathway, etc, and the 171 downregulated genes were mainly enriched in transcriptional misregulation in cancer, Tumor necrosis factor signaling pathway, etc. The overexpression of PPIA in human umbilical vein endothelial cells causes changes in the expression of downstream genes and induces alternative splicing in multiple genes. PPIA alters the expression or the alternative splicing pattern of downstream genes, leading to pathogenesis of vascular endothelial injury by high glucose mediated through CyPA.

SGLT2 knockdown restores the Th17/Treg balance and suppresses diabetic nephropathy in db/db mice by regulating SGK1 via Na. Mol Cell Endocrinol 2024;584:112156. [PMID: 38278341 DOI: 10.1016/j.mce.2024.112156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The imbalance between T helper 17 (Th17) and regulatory T (Treg) cells is an important mechanism in the pathogenesis of diabetic nephropathy (DN). Serum/glucocorticoid regulated kinase 1 (SGK1) is a serine-threonine kinase critical for stabilizing the Th17 cell phenotype. Sodium-glucose cotransporter 2 (SGLT2) is a glucose transporter that serves as a treatment target for diabetes. Our study investigated the regulatory role of SGLT2 in the development of DN. The results revealed that SGLT2 knockdown suppressed high glucose-induced excessive secretion of sodium (Na+) and inflammatory cytokines in mouse renal tubular epithelial TCMK-1 cells. High Na+ content induced Th17 differentiation and upregulated SGK1, phosphorylated forkhead box protein O1 (p-FoxO1), and the interleukin 23 receptor (IL-23 R) in primary mouse CD4+ T cells. Co-culture of CD4+ T cells with the culture medium of TCMK-1 cells with insufficient SGLT2 expression significantly suppressed cell migration ability, reduced the production of pro-inflammatory cytokines, and inhibited Th17 differentiation possibly by downregulating SGK1, p-FoxO1, and IL-23 R. In addition, in vivo data demonstrated that SGLT2 knockdown markedly downregulated SGK1 in db/db mice. Insufficient SGLT2 or SGK1 expression also ameliorated the Th17/Treg imbalance, suppressed the development of DN, and regulated the expression of IL-23 R and p-FoxO1. In conclusion, this study showed that SGLT2 knockdown restored the Th17/Treg balance and suppressed DN possibly by regulating the SGK1/p-FoxO1/IL-23 R axis by altering Na+ content in the local environment. These findings highlight the potential use of SGLT2 and SGK1 for the management of DN.

The role of serum-glucocorticoid regulated kinase 1 in reproductive viability: implications from prenatal programming and senescence

OBJECTIVE

Organisms and cellular viability are of paramount importance to living creatures. Disruption of the balance between cell survival and apoptosis results in compromised viability and even carcinogenesis. One molecule involved in keeping this homeostasis is serum-glucocorticoid regulated kinase (SGK) 1. Emerging evidence points to a significant role of SGK1 in cell growth and survival, cell metabolism, reproduction, and life span, particularly in prenatal programming and reproductive senescence by the same token. Whether the hormone inducible SGK1 kinase is a major driver in the pathophysiological processes of prenatal programming and reproductive senescence?

METHOD

The PubMed/Medline, Web of Science, Embase/Ovid, and Elsevier Science Direct literature databases were searched for articles in English focusing on SGK1 published up to July 2023 RESULT: Emerging evidence is accumulating pointing to a pathophysiological role of the ubiquitously expressed SGK1 in the cellular and organismal viability. Under the regulation of specific hormones, extracellular stimuli, and various signals, SGK1 is involved in several biological processes relevant to viability, including cell proliferation and survival, cell migration and differentiation. In line, SGK1 contributes to the development of germ cells, embryos, and fetuses, whereas SGK1 inhibition leads to abnormal gametogenesis, embryo loss, and truncated reproductive lifespan.

CONCLUTION

SGK1 integrates a broad spectrum of effects to maintain the homeostasis of cell survival and apoptosis, conferring viability to multiple cell types as well as both simple and complex organisms, and thus ensuring appropriate prenatal development and reproductive lifespan.

Circular RNA COL1A2 Mediates High Glucose-Induced Oxidative Stress and Pyroptosis by Regulating MiR-424-5p/SGK1 in Diabetic Nephropathy

Diabetic nephropathy (DN) represents a major diabetes-related complication, which could undermine renal function. CircCOL1A2 has been previously reported to show abnormal expression during DN. However, its functional role in the progression of DN, as well as the potential molecular mechanisms, remains unclear. The present work examined the expression of circCOL1A2 in the plasma of DN patients, and employed high glucose (HG)-challenged HK-2 cells as the in vitro cell model of hyperglycemia (HG)-induced DN. CircCOL1A2 was silenced using siRNA in HK-2 cells to clarify the functional engagement of circCOL1A2 in HG-induced DN. We examined the roles of circCOL1A2 in regulating oxidative stress by measuring reactive oxygen species (ROS), lipid peroxidation, and superoxide dismutase (SOD) levels. Besides, the effects of circCOL1A2 silencing on pyroptosis were investigated by RT-qPCR, western blot (WB), and ELISA assays. StarBase (version 2.0) was used to identify the downstream effector of circCOL1A2, and their interactions were further verified through dual-luciferase reporter analysis, RNA pull-down assays, and RNA immunoprecipitation (RIP) assay. CircCOL1A2 was highly expressed in DN patients and HG-induced HK-2 cells. Knocking down circCOL1A2 alleviated oxidative stress and pyroptosis upon HG treatment. In addition, we demonstrated that circCOL1A2 knockdown could promote miR-424-5p expression while inhibiting Serum/Glucocorticoid Regulated Kinase 1 (SGK1) level. Furthermore, miR-424-5p inhibitor or SGK1 overexpression impaired the effects of circCOL1A2 knockdown on HG-induced oxidative stress and pyroptosis. Hence, our results demonstrated that the circCOL1A2 mediates HG-exposed pyroptosis and oxidative stress through modulating miR-424-5p/SGK1 axis in diabetic nephropathy, indicating that silencing circCOL1A2 is a potential intervention strategy for DN management.

Prognostic Value of SGK1 and Bcl-2 in Invasive Breast Cancer

It is crucial to understand molecular alterations in breast cancer and how they relate to clinicopathologic factors. We have previously shown that the glucocorticoid receptor (GCR) protein expression was reduced in invasive breast carcinoma compared to normal breast tissue. Glucocorticoids, signaling through the GCR, regulate several cellular processes via downstream targets such as serum/glucocorticoid-regulated kinase 1 (SGK1) and B-cell lymphoma 2 (Bcl-2). We measured the expression of SGK1 and Bcl-2, in respective breast cancer tissue arrays, from a multiracial cohort of breast cancer patients. Higher cytoplasmic SGK1 staining was stronger in breast cancer tissue compared to normal tissue, especially in hormone receptor-negative cases. Conversely, the expression of cytoplasmic Bcl-2 was reduced in breast cancer compared to normal tissue, especially in hormone receptor-negative cases. Bcl-2 staining was associated with the self-reported racial/ethnic category, an earlier clinical stage, a lower histological grade, and a higher survival rate. Bcl-2 expression was associated with longer survival in models adjusted for age and race (HR = 0.32, 95% CI: 0.15, 0.65), and Bcl-2 expression remained strongly positively associated with protection from breast cancer death, with additional adjustments for ER/PR status (HR = 0.41, 95% CI: 0.2, 0.85). SGK1 and Bcl-2 may play biological roles in breast cancer development and/or progression.

Vitamin C down-regulates the H3K9me3-dependent heterochromatin in buffalo fibroblasts via PI3K/PDK1/SGK1/KDM4A signal axis

The success of reprogramming is dependent on the reprogramming factors enriched in the cytoplasm of recipient oocytes and the potential of donor nucleus to be reprogrammed. Histone 3 lysine 9 trimethylation (H3K9me3) was identified as a major epigenetic barrier impeding complete reprogramming. Treating donor cell with vitamin C (Vc) can enhance the developmental potential of cloned embryos, but the underlying mechanisms still need to be elucidated. In this study, we found that 20μg/mL Vc could promote proliferation and inhibit apoptosis of BFFs, as well as down-regulate the H3K9me3-dependent heterochromatin and increase chromatin accessibility. Inhibited the expression of KDM4A resulted in increasing apoptosis rate and the H3K9me3-dependent heterochromatin, which can be restored by Vc. Moreover, Vc up-regulated the expression of KDM4A through PI3K/PDK1/SGK1 pathway. Inhibiting any factor in the signal axis of this PI3K pathway not only suppressed the activity of KDM4A but also substantially increased the level of H3K9me3 modification and the expression of the HP1α protein. Finally, Vc can rescue those negative effects induced by the blocking the PI3K/PDK1/SGK1 pathway. Collectively, Vc can down-regulate the H3K9me3-dependent heterochromatin in BFFs via PI3K/PDK1/SGK1/KDM4A signal axis, suggesting that Vc can turn the chromatin status of donor cells to be reprogrammed more easily.

microRNA-142-3p regulates osteogenic differentiation of human periodontal ligament stem cells via mediating SGK1

OBJECTIVE

Human periodontal ligament stem cells (hPDLSCs) refer to one kind of somatic stem cells that are capable of differentiating into multiple cell kinds and undergoing robust clonal self-renewal. This work was unearthed to elucidate the possible molecular mechanism of miR-142-3p in mediating osteogenic differentiation of hPDLSCs by targeting SGK1.

METHODS

The hPDLSCs were isolated, cultured, and identified. hPDLSCs were identified by immunofluorescence staining and multiple differentiation ability detection. Cell proliferation ability was assessed by CCK-8 assay. hPDLSCs were induced using osteogenic differentiation medium. ALP activity was detected by alkaline phosphatase (ALP) staining  and ALP activity assay, and mineralized nodule formation was determined by alizarin red staining. The expression levels of osteogenic differentiation marker proteins ALP, RUNX2, and OCN were measured by RT-qPCR. miR-142-3p candidate targets were obtained through bioinformatics analysis. The relationship between miR-142-3p and SKG1 was verified.

RESULTS

miR-142-3p in hPDLSCs after osteogenic induction was down-regulated. Elevated miR-142-3p restricted hPDLSCs proliferation, and diminished ALP activity and mineralized nodule formation, as well as the expression of ALP, RUNX2, and OCN, while miR-142-3p inhibition led to inverse results. miR-142-3p inhibited SKG1 expression. SKG1 overexpression promoted hPDLSC proliferation and osteogenic differentiation, and reversed the inhibitory function of miR-142-3p on hPDLSCs.

CONCLUSION

This study highlights that miR-142-3p represses osteogenic differentiation of hPDLSCs by reducing SGK1 expression.

Columbianetin alleviates lipopolysaccharides (LPS)-induced inflammation and apoptosis in chondrocyte through activation of autophagy by inhibiting serum and glucocorticoid-induced protein kinase 1 (SGK1) expression

Osteoarthritis (OA) is a degenerative disease of articular cartilage involving the entire joint tissue. Columbianetin (CBT) is a major active compound of radix angelicae pubescentis, which is used in the treatment of OA. This paper attempts to explore the role of CBT in OA. Lipopolysaccharides (LPS) was used to induce mouse chondrocytes ATDC5. The effect of CBT on cell viability in ATDC5 cells with or without LPS induction was determined by CCK-8 and LDH kits. The inflammatory response was evaluated using ELISA kits. Apoptosis in LPS-induced ATDC5 cells were examined by TUNEL staining. The expression of apoptosis and autophagy-related proteins was tested with Western blot. The relationship between CBT and serum and glucocorticoid-induced protein kinase 1 (SGK1) was examined by RT-qPCR, Western blot, and molecular docking. After SGK1 overexpression or addition of the autophagy inhibitor 3-methyladenine (3 MA), the above experiments were done again. Results revealed that CBT increased LPS-induced decrease in ATDC5 cell viability. CBT inhibited inflammation triggered by LPS, evidenced by reduced levels of TNF-α, IL-6 and IL-1β. Cell apoptosis was attenuated following CBT adding in ATDC5 cells exposed to LPS, accompanied by upregulated Bcl-2 expression and downregulated Bax and cleaved caspase 3 expression. In addition, CBT elevated Beclin1 and LC3II/LC3I expression but decreased p62 expression. Additionally, CBT inhibited SGK1 expression. However, SGK1 overexpression or 3 MA reversed the effects of CBT on LPS-induced loss of ATDC5 cell viability, inflammation, apoptosis and autophagy. Collectively, CBT could improve OA through the activation of chondrocyte autophagy by suppressing SGK1 expression.

Serum and Glucocorticoid-Inducible Kinase 1 (SGK1) in NSCLC Therapy

Non-small cell lung cancer (NSCLC) remains the most prevalent and one of the deadliest cancers worldwide. Despite recent success, there is still an urgent need for new therapeutic strategies. It is also becoming increasingly evident that combinatorial approaches are more effective than single modality treatments. This review proposes that the serum and glucocorticoid-inducible kinase 1 (SGK1) may represent an attractive target for therapy of NSCLC. Although ubiquitously expressed, SGK1 deletion in mice causes only mild defects of ion physiology. The frequent overexpression of SGK1 in tumors is likely stress-induced and provides a therapeutic window to spare normal tissues. SGK1 appears to promote oncogenic signaling aimed at preserving the survival and fitness of cancer cells. Most importantly, recent investigations have revealed the ability of SGK1 to skew immune-cell differentiation toward pro-tumorigenic phenotypes. Future studies are needed to fully evaluate the potential of SGK1 as a therapeutic target in combinatorial treatments of NSCLC. However, based on what is currently known, SGK1 inactivation can result in anti-oncogenic effects both on tumor cells and on the immune microenvironment. A first generation of small molecules to inactivate SGK1 has already been already produced.