Astrocytes are important regulatory cells in the brain that support neuronal function. However, their role in hypoglycemia counterregulation is poorly understood. Moreover, astrocytic transcriptional responses to hypoglycemia and the mechanisms by which recurrent hypoglycemia (RH) suppresses counterregulation are not understood. Using human primary astrocytes (HPA) in vitro we tested whether recurrent low glucose (RLG), to model RH, would regulate differential gene expression (DGE). HPA cells were exposed to 3-hour bouts of 2.5 or 0.1 mM glucose over 4 days and mRNA expression was quantified using RNA-sequencing and DGE measured using DESeq2. Acute low glucose (LG) differentially expressed 31 genes including the downregulation of mitochondrial genes (mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 2, subunit 4 and subunit 4L; MT-ND2, MT-ND4 and MT-ND4L) and endoplasmic reticulum stress associated genes (X-box binding protein 1; XBP1, and heat shock protein family A; Hsp70, member 1A, and member 5; HSPA1A and HSPA5). However, neither antecedent RLG (aRLG) nor RLG treated cells have significantly altered gene expression compared to control. LG treatment decreased the expression of XBP1 and increased thioredoxin interacting protein (TXNIP) and exostosin Like glycosyltransferase 3 (EXTL3) which were also similarly altered by low glucose compared to aRLG.MT-ND2, MT-ND4 and MT-ND4L genes are associated with diabetes and neurodegeneration. Furthermore, LG-induced reduction of XBP1 may also increase fatty acid oxidation by disinhibiting inositol-requiring kinase 1α. This corroborates previous work indicating low glucose increases fatty acid utilisation in astrocytes and the hypothalamus. While the functional impact of differential gene expression needs assessing, this provides evidence that these genes may be important in astrocytic responses to hypoglycemia.
P.G. Weightman Potter: None. S.J. Washer: None. A. Jeffries: None. E.L. Dempster: None. C. Beall: None.
Novo Nordisk UK Research Foundation; Diabetes UK; Mary Kinross Charitable Trust