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Lynda A Wilmott, Megan Stiles, Timothy Lyons, Nawajes A Mandal; Analysis of Sphingolipid Composition of Human Vitreous from Control and Diabetic Individuals. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2522.
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Sphingolipids have a fundamental role in many cellular processes, and they have been implicated in insulin resistance and Diabetes Mellitus (DM) and its complications, including diabetic retinopathy (DM-DR). The majority of retinal sphingolipid research has been limited to rodent models, so little is known as to how bioactive sphingolipids influence human DM and DM-DR. In this study, our aim was to determine the sphingolipid composition of the human vitreous in Control, DM, and DM-DR samples.
We conducted an observational clinical study on post-mortem human vitreal samples from non-diabetic (controls; n=3; age: 73.7 ± 13.0 yrs, mean ± SD), Type II diabetic (n=4; age: 73.8 ± 3.6 yrs), and diabetic with retinopathy (n=5; age: 62.6 ± 9.4 yrs) to identify changes in retinal sphingolipid composition. Samples were subjected to sphingolipid extraction using previously established protocols, and individual sphingolipid species were confirmed and quantified using a triple quadrupole mass spectrometer. For quantitation, vitreal sphingolipid species were compared to a target lipid ion peak using an internal standard (C12 Ceramide) and normalized.
The total Ceramide (Cer) and sphingomyelin (SM) levels (pmol/mg protein) appeared to be increased in diabetic vitreous. Total Cer and certain individual Cer species (C22:0, C24:0, C24:1, C26:0, and C26:1) exhibited increases in diabetic vs. control vitreous significantly (DM vs. control; p<0.05). Cer species C22:0, C24:1, and C26:0 were increased in DM-DR vs. control (p<0.05). Interestingly, total Hexosyl-Ceramide (Hex-Cer) and certain species were higher in DM than DM-DR or control, including C18:0, C20:0, C22:0, and C26:0 (p<0.05). However, certain Hex-Cer species were significantly decreased in DM-DR vs DM: C24:1 and C26:1 (p=0.01 and p=0.05, respectively). Finally, the di-hydro Sphingosine-1-phospate (dh-S1P), showed greater levels in both DM and DM-DR samples vs controls (p<0.05), but there was no significant difference between DM and DM-DR.
Our results suggest that changes in sphingolipid composition are characteristic of the diabetic human vitreous. Further studies using animal models will be conducted to identify potential causes and consequences, and to investigate novel therapeutic targets.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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