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Abstract Introduction The endothelial glycocalyx regulates vascular permeability, inflammation, and coagulation, and acts as a mechanosensor. The loss of glycocalyx can cause endothelial injury and contribute to several microvascular complications and, therefore, may promote diabetic retinopathy. Studies have shown a partial loss of retinal glycocalyx in diabetes, but with few molecular details of the changes in glycosaminoglycan (GAG) composition. Therefore, the purpose of our study was to investigate the effect of hyperglycemia on GAGs of the retinal endothelial glycocalyx. Methods GAGs were isolated from rat retinal microvascular endothelial cells (RRMECs), media, and retinas, followed by liquid chromatography-mass spectrometry assays. Quantitative real-time polymerase chain reaction was used to study mRNA transcripts of the enzymes involved in GAG biosynthesis. Results and Conclusions Hyperglycemia significantly increased the shedding of heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA). There were no changes to the levels of HS in RRMEC monolayers grown in high-glucose media, but the levels of CS and HA decreased dramatically. Similarly, while HA decreased in the retinas of diabetic rats, the total GAG and CS levels increased. Hyperglycemia in RRMECs caused a significant increase in the mRNA levels of the enzymes involved in GAG biosynthesis (including EXTL-1,2,3, EXT-1,2, ChSY-1,3, and HAS-2,3), with these increases potentially being compensatory responses to overall glycocalyx loss. Both RRMECs and retinas of diabetic rats exhibited glucose-induced alterations in the disaccharide compositions and sulfation of HS and CS, with the changes in sulfation including N,6-O-sulfation on HS and 4-O-sulfation on CS.
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This content will become publicly available on February 1, 2027
Gender-Associated Differences in the Regulation of Potassium Channels in Astrocytes of Type 2 Diabetic Mice
Hyperglycemia is linked to a higher risk of diabetes, epilepsy, and seizures, which contribute to increased mortality. Previous research has shown that hyperglycemia impairs the function of the polyamine-dependent Kir4.1 channels in cultured astrocytes, and a similar effect was observed in male astrocytes from diabetic (db/db) mice. However, whether there are sex differences in this effect remains unclear. This study aims to compare Kir4.1 channel function in 10–12 week old brains of female db/db mice with that in males and non-diabetic heterozygous (db/+). We performed mRNA analyses, Western blotting (WB), glucose level measurements, and patch-clamp recordings from hippocampal astrocytes in brain slices to assess Kir4.1 channel activity in db/db and db/+ mice of both sexes. Our results showed increased glucose levels in diabetic db/db mice, especially in males, along with (1) reduced synthesis of Kir4.1 channel protein, (2) reduced membrane potential, (3) decreased Kir currents, and (4) compromised potassium uptake. Female diabetic astrocytes exhibited significantly lower barium-blocked Kir4.1 currents compared to diabetic males. Additionally, barium-insensitive currents (leakage currents) were upregulated in db/db mice, likely as a compensatory response to hyperglycemia. In conclusion, diabetes impairs astrocyte function by downregulating Kir4.1 channels, with a more pronounced effect in male diabetic mice. This impairment may increase seizure risk by affecting the ability of astrocytes to maintain extracellular ion balance.
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- Award ID(s):
- 2122203
- PAR ID:
- 10674144
- Publisher / Repository:
- Cells
- Date Published:
- Journal Name:
- Cells
- Volume:
- 15
- Issue:
- 4
- ISSN:
- 2073-4409
- Page Range / eLocation ID:
- 330
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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