Mechanistic insights into the role of serum-glucocorticoid kinase 1 in diabetic nephropathy: A systematic review

Cholesterol promotes IFNG mRNA expression in CD4+ effector/memory cells by SGK1 activation

IFNγ-secreting T cells are central for the maintenance of immune surveillance within the central nervous system (CNS). It was previously reported in healthy donors that the T-cell environment in the CNS induces distinct signatures related to cytotoxic capacity, CNS trafficking, tissue adaptation, and lipid homeostasis. These findings suggested that the CNS milieu consisting predominantly of lipids mediated the metabolic conditions leading to IFNγ-secreting brain CD4 T cells. Here, we demonstrate that the supplementation of CD4+CD45RO+CXCR3+ cells with cholesterol modulates their function and increases IFNG expression. The heightened IFNG expression was mediated by the activation of the serum/glucocorticoid-regulated kinase (SGK1). Inhibition of SGK1 by a specific enzymatic inhibitor significantly reduces the expression of IFNG Our results confirm the crucial role of lipids in maintaining T-cell homeostasis and demonstrate a putative role of environmental factors to induce effector responses in CD4+ effector/memory cells. These findings offer potential avenues for further research targeting lipid pathways to modulate inflammatory conditions.

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.

Finerenone: Questions and Answers-The Four Fundamental Arguments on the New-Born Promising Non-Steroidal Mineralocorticoid Receptor Antagonist

Chronic kidney disease (CKD) is one of the most common complications of diabetes mellitus and an independent risk factor for cardiovascular disease. Despite guideline-directed therapy of CKD in patients with type 2 diabetes, the risk of renal failure and cardiovascular events still remains high, and diabetes remains the leading cause of end-stage kidney disease in affected patients. To date, current medications for CKD and type 2 diabetes mellitus have not reset residual risk in patients due to a high grade of inflammation and fibrosis contributing to kidney and heart disease. This question-and-answer-based review will discuss the pharmacological and clinical differences between finerenone and other mineralocorticoid receptor antagonists and then move on to the main evidence in the cardiovascular and renal fields, closing, finally, on the potential role of therapeutic combination with sodium-glucose cotransporter 2 inhibitors (SGLT2is).

SGK1, a Critical Regulator of Immune Modulation and Fibrosis and a Potential Therapeutic Target in Chronic Graft-Versus-Host Disease

Patients with severe chronic graft-versus-host disease (cGVHD) always experience debilitating tissue injury and have poorer quality of life and shorter survival time. The early stage of cGVHD is characterized by inflammation, which eventually leads to extensive tissue fibrosis in various organs, such as skin and lung, eventually inducing scleroderma-like changes and bronchiolitis obliterans syndrome. Here we review the functions of serum/glucocorticoid regulated kinase 1 (SGK1), a hub molecule in multiple signal transduction pathways and cell phosphorylation cascades, which has important roles in cell proliferation and ion channel regulation, and its relevance in cGVHD. SGK1 phosphorylates the ubiquitin ligase, NEDD4, and induces Th cells to differentiate into Th17 and Th2 phenotypes, hinders Treg development, and promotes inflammatory fibrosis. Phosphorylation of NEDD4 by SGK1 also leads to up-regulation of the transcription factor SMAD2/3, thereby amplifying the fibrosis-promoting effect of TGF-β. SGK1 also up-regulates the inflammatory transcription factor, nuclear factor-κB (NF-κB), which in turn stimulates the expression of multiple inflammatory mediators, including connective tissue growth factor. Overexpression of SGK1 has been observed in various fibrotic diseases, including pulmonary fibrosis, diabetic renal fibrosis, liver cirrhosis, hypertensive cardiac fibrosis, peritoneal fibrosis, and Crohn’s disease. In addition, SGK1 inhibitors can attenuate, or even reverse, the effect of fibrosis, and may be used to treat inflammatory conditions and/or fibrotic diseases, such as cGVHD, in the future.