Filipowska Joanna, Cisneros Zelda, Varghese Sneha S, Leon-Rivera Nancy, Wang Peng, Kang Randy, Lu Geming, Yuan Yate-Ching, Shih Hung-Ping, Bhattacharya Supriyo, Dhawan Sangeeta, Garcia-Ocaña Adolfo, Kondegowda Nagesha Guthalu, Vasavada Rupangi C
Arthur Riggs Diabetes and Metabolism Research Institute, City of Hope, Duarte, CA 91010, USA; Department of Translational Research and Cellular Therapeutics, City of Hope, Duarte, CA 91010, USA.
Diabetes, Obesity and Metabolism Institute, and Division of Endocrinology, Diabetes and Bone Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
Mol Metab. 2025 Feb;92:102097. doi: 10.1016/j.molmet.2025.102097. Epub 2025 Jan 7.
Loss of functional β-cell mass is a major cause of diabetes. Thus, identifying regulators of β-cell health is crucial for treating this disease. The Leucine-rich repeat-containing G-protein-coupled receptor (GPCR) 4 (LGR4) is expressed in β-cells and is the fourth most abundant GPCR in human islets. Although LGR4 has regenerative, anti-inflammatory, and anti-apoptotic effects in other tissues, its functional significance in β-cells remains unknown. We have previously identified Receptor Activator of Nuclear Factor Kappa B (NFκB) (RANK) as a negative regulator of β-cell health. In this study, we assessed the regulation of Lgr4 in islets, and the role of LGR4 and LGR4/RANK stoichiometry in β-cell health under basal and stress-induced conditions, in vitro and in vivo.
We evaluated Lgr4 expression in mouse and human islets in response to acute (proinflammatory cytokines), or chronic (high fat fed mice, db/db mice, and aging) stress. To determine the role of LGR4 we employed in vitro Lgr4 loss and gain of function in primary rodent and human β-cells and examined its mechanism of action in the rodent INS1 cell line. Using Lgr4 and Lgr4/Rank × Ins1-Cre mice we generated conditional knockout (cko) mice to test the role of LGR4 and its interaction with RANK in vivo under basal and stress-induced conditions.
Lgr4 expression in rodent and human islets was reduced by multiple stressors. In vitro, Lgr4 knockdown decreased proliferation and survival in rodent β-cells, while overexpression protected against cytokine-induced cell death in rodent and human β-cells. Mechanistically, LGR4 protects β-cells by suppressing RANK- Tumor necrosis factor receptor associated factor 6 (TRAF6) interaction and subsequent activation of NFκB. Lgr4cko mice exhibit normal glucose homeostasis but increased β-cell death in both sexes and decreased β-cell proliferation and maturation only in females. Male Lgr4cko mice under stress displayed reduced β-cell proliferation and a further increase in β-cell death. The impaired β-cell phenotype in Lgr4cko mice was rescued in Lgr4/Rank double ko (dko) mice. Upon aging, both male and female Lgr4cko mice displayed impaired β-cell homeostasis, however, only female mice became glucose intolerant with decreased plasma insulin.
These data demonstrate a novel role for LGR4 as a positive regulator of β-cell health under basal and stress-induced conditions, through suppressing the negative effects of RANK.
功能性β细胞量的丧失是糖尿病的主要病因。因此，确定β细胞健康的调节因子对于治疗该疾病至关重要。富含亮氨酸重复序列的G蛋白偶联受体（GPCR）4（LGR4）在β细胞中表达，是人类胰岛中第四丰富的GPCR。尽管LGR4在其他组织中具有再生、抗炎和抗凋亡作用，但其在β细胞中的功能意义仍不清楚。我们之前已确定核因子κB受体激活剂（NFκB）（RANK）是β细胞健康的负调节因子。在本研究中，我们评估了胰岛中Lgr4的调节，以及LGR4和LGR4/RANK化学计量在基础和应激诱导条件下、体外和体内β细胞健康中的作用。
我们评估了小鼠和人类胰岛中Lgr4在急性（促炎细胞因子）或慢性（高脂喂养小鼠、db/db小鼠和衰老）应激反应中的表达。为了确定LGR4的作用，我们在原代啮齿动物和人类β细胞中采用了体外Lgr4功能丧失和功能获得，并在啮齿动物INS1细胞系中研究了其作用机制。使用Lgr4和Lgr4/Rank×Ins1-Cre小鼠，我们生成了条件性敲除（cko）小鼠，以测试LGR4及其与RANK在基础和应激诱导条件下在体内的作用以及它们之间的相互作用。
多种应激源可降低啮齿动物和人类胰岛中Lgr4的表达。在体外，Lgr4敲低可降低啮齿动物β细胞的增殖和存活率，而过表达可保护啮齿动物和人类β细胞免受细胞因子诱导的细胞死亡。从机制上讲，LGR4通过抑制RANK-肿瘤坏死因子受体相关因子6（TRAF6）相互作用及随后的NFκB激活来保护β细胞。Lgr4cko小鼠表现出正常的葡萄糖稳态，但两性的β细胞死亡均增加，且仅雌性的β细胞增殖和成熟减少。应激状态下的雄性Lgr4cko小鼠β细胞增殖减少，β细胞死亡进一步增加。Lgr4/Rank双敲除（dko）小鼠挽救了Lgr4cko小鼠中受损的β细胞表型。衰老时，雄性和雌性Lgr4cko小鼠均表现出β细胞内环境稳定受损，然而，只有雌性小鼠出现葡萄糖不耐受且血浆胰岛素降低。
这些数据表明，在基础和应激诱导条件下，LGR4通过抑制RANK的负面影响，作为β细胞健康的正调节因子发挥新的作用。
