Frontiers in Pharmacology (Nov 2024)

Dipeptide alanine-glutamine ameliorates retinal neurodegeneration in an STZ-induced rat model

  • Yuhan Zhang,
  • Mingyan Wei,
  • Xin Wang,
  • Yuan Xu,
  • Rongrong Zong,
  • Xiang Lin,
  • Shiying Li,
  • Wensheng Chen,
  • Wensheng Chen,
  • Zuguo Liu,
  • Zuguo Liu,
  • Qian Chen,
  • Qian Chen

DOI
https://doi.org/10.3389/fphar.2024.1490443
Journal volume & issue
Vol. 15

Abstract

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IntroductionDiabetic retinopathy (DR) is a common complication of diabetes. Retinal neuronal degeneration is an early event in DR, indicated by the declined electroretinogram (ERG). Dipeptide alanine-glutamine (Ala-Gln) is widely used as a nutritional supplement in the clinic and has anti-inflammatory effects on the gastrointestinal system. Studies also reported that glutamine has beneficial effects on diabetes. This study aimed to investigate the possible therapeutic effects of Ala-Gln in diabetic retinal neurodegeneration and to delineate its mechanism of action.MethodsThe Streptozotocin (STZ)-induced rat model was used as a DR model. ERG was used to measure the neuronal function of the retina. Western blot analysis was performed to test the expression of proteins. Immunofluorescence staining was used for the detection and localization of proteins.ResultsIn diabetic rats, the amplitudes of ERG were declined, while Ala-Gln restored the declined ERG. Retinal levels of inflammatory factors were significantly decreased in Ala-Gln-treated diabetic rats. Ala-Gln mitigated the declined levels of glutamine synthetase and ameliorated the upregulated levels of glial fibrillary acidic protein (GFAP) in diabetic retinas. Moreover, Ala-Gln upregulated the glycolytic enzymes pyruvate kinase isozymes 2 (PKM2), lactate dehydrogenase A (LDHA) and LDHB and stimulated the mTOR signaling pathway in diabetic retinas. The mitochondrial function was improved after the treatment of Ala-Gln in diabetic retinas.DiscussionAla-Gln ameliorates retinal neurodegeneration by reducing inflammation and enhancing glucose metabolism and mitochondrial function in DR. Therefore, manipulation of metabolism by Ala-Gln may be a novel therapeutic avenue for retinal neurodegeneration in DR.

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