NR3C1/Glucocorticoid receptor activation promotes pancreatic β-cell autophagy overload in response to glucolipotoxicity

ABSTRACT

Diabetes is a complex and heterogeneous disorder characterized by chronic hyperglycemia. Its core cause is progressively impaired insulin secretion by pancreatic β-cell failures, usually upon a background of preexisting insulin resistance. Recent studies demonstrate that macroautophagy/autophagy is essential to maintain architecture and function of β-cells, whereas excessive autophagy is also involved in β-cell dysfunction and death. It has been poorly understood whether autophagy plays a protective or harmful role in β-cells, while we report here that it is dependent on NR3C1/glucocorticoid receptor activation. We proved that deleterious hyperactive autophagy happened only upon NR3C1 activation in β-cells under glucolipotoxic conditions, which eventually promoted diabetes. The transcriptome and the N6-methyladenosine (m⁶A) methylome revealed that NR3C1-enhancement upregulated the RNA demethylase FTO (fat mass and obesity associated) protein in β-cells, which caused diminished m⁶A modifications on mRNAs of four core Atg (autophagy related) genes (Atg12, Atg5, Atg16l2, Atg9a) and, hence, hyperactive autophagy and defective insulin output; by contrast, FTO inhibition, achieved by the specific FTO inhibitor Dac51, prevented NR3C1-instigated excessive autophagy activation. Importantly, Dac51 effectively alleviated impaired insulin secretion and glucose intolerance in hyperglycemic β-cell specific NR3C1 overexpression mice. Our results determine that the NR3C1-FTO-m⁶A modifications-Atg genes axis acts as a key mediator of balanced autophagic flux in pancreatic β-cells, which offers a novel therapeutic target for the treatment of diabetes.

Abbreviations: 3-MA: 3-methyladenine; AAV: adeno-associated virus; Ac: acetylation; Ad: adenovirus; AL: autolysosome; ATG: autophagy related; AUC: area under curve; Baf A1: bafilomycin A₁; βNR3C1 mice: pancreatic β-cell-specific NR3C1 overexpression mice; cFBS: charcoal-stripped FBS; Ctrl: control; ER: endoplasmic reticulum; FTO: fat mass and obesity associated; GC: glucocorticoid; GRE: glucocorticoid response element; GSIS: glucose-stimulated insulin secretion assay; HFD: high-fat diet; HG: high glucose; HsND: non-diabetic human; HsT2D: type 2 diabetic human; i.p.: intraperitoneal injected; KSIS: potassium-stimulated insulin secretion assay; m⁶A: N6-methyladenosine; MeRIP-seq: methylated RNA immunoprecipitation sequencing; NR3C1/GR: nuclear receptor subfamily 3, group C, member 1; NR3C1-Enhc.: NR3C1-enhancement; NC: negative control; Palm.: palmitate; RNA-seq: RNA sequencing; T2D: type 2 diabetes; TEM: transmission electron microscopy; UTR: untranslated region; WT: wild-type.

KEYWORDS:

• Autophagy
• diabetes
• FTO
• NR3C1
• m⁶A
• pancreatic β-cell

Acknowledgements

This work was supported by the National Natural Science Foundation of China (81830024 to X.H., 81970673 to F.C., 82000738 to T-J.W.) and the Natural Science Foundation of Jiangsu Province (BK20200670 to T-J.W.). This work was also supported by the Natural Science Research of Jiangsu Higher Education Institutions of China (20KJB310001 to T-J.W.). X.H. and F.C. are the guarantors of this work and, as such, had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Disclosure statement

The authors disclose no financial conflict of interest.

Data availability statement

All relevant datasets generated during and/or analyzed during the current study are available from the corresponding authors upon reasonable request. RNAseq data that support the findings of this study have been deposited in the NCBI’s Gene Expression Omnibus (GEO) under accession code GSE182267 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE182267). MeRIPseq data that support the findings of this study have been deposited in the GEO under accession code GSE182268 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE182268).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15548627.2023.2200625.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [81830024]; National Natural Science Foundation of China [81970673]; National Natural Science Foundation of China [82000738]; Natural Science Foundation of Jiangsu Province [BK20200670]; Natural Science Research of Jiangsu Higher Education Institutions of China [20KJB310001]