Topical administration of DPP-IV inhibitors prevents retinal neurodegeneration in experimental diabetes.

AIMS/HYPOTHESIS: The main aims of the present study were: (1) to assess the expression and content of dipeptidyl peptidase IV (DPP-IV) in human and db/db mouse retinas, and in human vitreous fluid; and (2) to determine whether the topical administration of the DPP-IV inhibitors (DPP-IVi) would prevent retinal neurodegeneration and vascular leakage in db/db mice by reducing endogenous glucagon-like peptide 1 (GLP-1) degradation. METHODS: To assess the expression and content of DPP-IV, human samples of vitreous fluid and retinas were obtained from participants with type 2 diabetes (n = 8) and age-matched non-diabetic individuals (n = 8), as well as from db/db (n = 72) and db/+ (n = 28) mice. The interventional study, which included 72 db/db mice, consisted of the topical administration (eye drops) of saxagliptin, sitagliptin or vehicle for 14 days. DPP-IV mRNA levels were assessed by RT-PCR, and protein content was measured by ELISA or western blotting. GLP-1 was assessed by immunofluorescence, and its downstream effector exchange protein activated by cAMP-1 (EPAC-1) was used as a measure of GLP-1 receptor activation. Retinal analyses were performed in vivo by electroretinography and ex vivo by RT-PCR (Epac-1, Iba-1 [also known as Aif1]), western blotting (EPAC-1, glial fibrillar acidic protein [GFAP], glutamate-aspartate transporter [GLAST]) and immunofluorescence measurements (GLP-1, GFAP, ionised calcium binding adaptor molecule 1 [IBA-1], TUNEL, GLAST, albumin and collagen IV). Glutamate was quantified by HPLC. In addition, vascular leakage was examined by the Evans Blue method. RESULTS: DPP-IV was present in human vitreous fluid but in a range 100-fold less than in plasma. Both mRNA levels and protein content were much lower in the retina than in the liver or bowel, but were significantly higher in retinal pigment epithelium (RPE) from diabetic donors in comparison to non-diabetic donors (p < 0.05). Topical treatment with DPP-IVi prevented glial activation, apoptosis and vascular leakage induced by diabetes in db/db mice (p < 0.05). Moreover, it also significantly prevented diabetes-induced functional abnormalities in the electroretinogram. A significant increase of both GLP-1 and EPAC-1 was found after treatment with DPP-IVi (p < 0.05). Furthermore, GLAST downregulation induced by diabetes was prevented, resulting in a significant reduction of extracellular glutamate concentrations. All these effects were observed without any changes in blood glucose levels. CONCLUSIONS/INTERPRETATION: The topical administration of DPP-IVi is effective in preventing neurodegeneration and vascular leakage in the diabetic retina. These effects can be attributed to an enhancement of GLP-1, but other mechanisms unrelated to the prevention of GLP-1 degradation cannot be ruled out.

Out-of-Hospital Tissue Donation: Multidisciplinary Donor Circuit in a Forensic Institute.

OBJECTIVE: We aimed to implement an out-of-hospital system of generating donors that increases donation and answers the growing demand for tissue for therapeutic purposes. MATERIAL: The Catalan Health Service issued the 4/2015 instruction promoting the integration of the donation network through collaboration with the Donor Center of Catalonia (DCC). The creation of DCC facilitated the signing of an agreement between The Blood and Tissue Bank, the Department of Justice of the Generalitat de Catalunya, the Emergency Medical System, and the Hospital Clínic Barcelona for the procurement of tissues in the Institute of Legal Medicine and Forensic Sciences of Catalonia (IMLCFC), where the autopsies of all judicial deaths in the province of Barcelona are performed. METHODS: The Emergency Medical System informed the DCC of those instances that ended with the code "deceased." DCC assessed the possible donor on arrival at the IMLCFC, checked the medical history through the shared clinical record, and obtained family consent by telephone interview. If consent was obtained, then judicial authorization was sought. RESULTS: In 2016, 152 donors of corneas were obtained (9.7% of the annual amount in Catalonia), 149 in 2017 (9.4% of the annual amount), and 133 donations in 2018. At the end of 2017, we started multitissue retrieval and obtained in 2018 a total of 76 donors. CONCLUSIONS: Out-of-hospital tissue donation in a forensic institute is possible. In less than 3 years, IMLCFC has become the third largest eye tissue contributor among the Catalan tissue donation network and the first contributor in musculoskeletal tissues in 2018.