Abstract
Purpose :
The insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) is a pleiotropic member of the IGF family. We have previously reported that IGFBP-3 is present in human diabetic tears. Recently, we established a novel mito-protective role for IGFBP-3. The purpose of this study is to characterize the expression of IGFBP-3 in the cornea in a mouse model of Type 2 Diabetes Mellitus (T2DM) and associated changes in mitochondrial homeostasis
Methods :
Male TALLYHO/JngJ mice, a polygenic model of non-insulin dependent T2DM, were used in this study. SWR/J mice were used as control. Body mass and fasted serum glucose levels were measured at 8, 10 and 14 weeks of age. A fasted serum glucose level of greater 300 mg/dL was considered diabetic. Tear production was measured using the phenol red thread test. Corneal staining was assessed using fluorescein and a slit lamp biomicroscope equipped with a cobalt blue filter. At 14 weeks, whole corneas were removed and either snap frozen in liquid nitrogen or fixed in 1% paraformaldehyde. Frozen corneas were homogenized using TPER extraction buffer. Western blot was used to quantify expression levels of IGFBP-3 and mitophagy proteins PINK1, BNIP3, BNIP3L/NIX, and FUNDC1. Vinculin was used as a loading control. Expression and localization were further assessed by immunofluorescence in cryostat-sectioned corneas counterstained with DAPI. Tissue sections were imaged using laser scanning confocal microscopy. All animals were treated according to the ARVO statement for the use of animals in ophthalmic and vision research.
Results :
TALLYHO mice were hyperglycemic at all time points. SWR control mice remained normoglycemic. Body mass in TALLYHO mice was increased compared to controls. There was no difference in tear production at any time point tested. Corneal staining was increased in TALLYHO mice at 14 weeks. Expression of glycosylated and non-glycosylated isoforms of IGFBP-3 were decreased at 8, 10 and 14 weeks in TALLYHO mice.
Conclusions :
IGFBP-3 expression is decreased in the T2DM cornea. This reduction in expression is likely due to hyperinsulinemia in these mice. Further studies are needed to determine the effects of hyperinsulinemia on IGFBP-3.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.