Insulin replacement restores the vesicular secretory apparatus in the diabetic rat lacrimal gland

Abstract

Purpose: In the lacrimal gland (LG) acinar cells, signaling regulates the release of secretory vesicles through specific Rab and SNARE exocytotic proteins. In diabetes mellitus (DM), the LGs are dysfunctional. The aim of this work was to determine if secretory apparatus changes were associated with any effects on the secretory vesicles (SV) in diabetic rats as well as the expression levels of constituent Rab and members of the SNARE family, and if insulin supplementation reversed those changes. Methods: DM was induced in male Wistar rats with an intravenous dose of streptozotocin (60 mg/kg). One of the two diabetic groups was then treated every other day with insulin (1 IU). A third control group was injected with vehicle. After 10 weeks, Western blotting and RT-PCR were used to compared the Rab and SNARE secretory factor levels in the LGs. Transmission electron microscopy evaluated acinar cell SV density and integrity. Results: In the diabetes mellitus group, there were fewer and enlarged SV. The Rab 27b, Rab 3d, and syntaxin-1 protein expression declined in the rats with diabetes mellitus. Insulin treatment restored the SV density and the Rab 27b and syntaxin expression to their control protein levels, whereas the Vamp 2 mRNA expression increased above the control levels. Conclusions: Diabetes mellitus LG changes were associated with the declines in protein expression levels that were involved in supporting exocytosis and vesicular formation. They were partially reversed by insulin replacement therapy. These findings may help to improve therapeutic management of dry eye in diabetes mellitus.Keywords: Diabetes mellitus/chemically induced; Lacrimal apparatus; Exocytosis; secretory vesicles; R-SNARE proteins; Animals; Rats RESUMO Objetivo: Células acinares da glândula lacrimal (GL) sinalizam a regulação da liberação através de vesículas secretórias específicas Rab proteínas exocitóticas SNARE. No diabetes mellitus (DM), as glândulas lacrimais são disfuncionais. O objetivo deste trabalho foi determinar se em ratos diabéticos, alterações dos aparatos secretórios estão associados a efeitos sobre vesículas secretoras (VS) e sobre os níveis de expressão do constituinte Rab, bem como membros da família SNARE, e se a suplementação de insulina reverte as alterações. Métodos: DM foi induzido em ratos Wistar machos com uma dose intravenosa de estreptozotocina (60 mg/kg). Um dos dois grupos diabéticos foi então tratado a cada dois dias com insulina (1 UI). Um terceiro grupo controle foi injetado com o veículo. Após 10 semanas, western blot e RT-PCR comparou níveis de fatores secretórios de

Dry Eye Syndrome in Patients with Diabetes Mellitus: Prevalence, Etiology, and Clinical Characteristics

“…Insulin is critical for proliferation of the acinar lacrimal gland (LG) and cornea epithelial cells. Insulin partially reversed the decreased protein expression induced by LG dysfunction; this process is involved in supporting exocytosis and vesicular formation through insulin replacement therapy [ 26 ]. It has been demonstrated that hyperglycemia induces histological alterations in the lacrimal gland, suggesting the role of diabetes-induced oxidative stress in DES [ 27 ].…”

Proteomic analysis of tears and serum for dry eye disease using ovariectomized cynomolgus monkey

“…Insulin receptors were found in lacrimal and ocular surface tissue [29]. At the same time, animal studies have shown that insulin loss causes lacrimal gland shrinkage, corneal innervation, and decreased tear volume [30,31]. In human, insulin resistance was observed with oral estrogen and progesterone replacement therapy in menopause women [32].…”

Oxidative Stress in the Protection and Injury of the Lacrimal Gland and the Ocular Surface: are There Perspectives for Therapeutics?

“…Although studies identified the suppression of antioxidant activities as triggers of DE, the action of genetic knockout enzymes may produce other nontracked effects associated with it. Moreover, all other models, including DM, hormone deficiency, and aging, present several competing factors, such as impaired neural transmission and metabolism, hypotrophism, and osmotic imbalance ( Rocha et al, 2003 ; Alves et al, 2005a ; Alves et al, 2005b ; Kojima et al, 2012 ; Uchino et al, 2012 ; Dias et al, 2015 ). Therefore, it is unlikely that OS induced by a deficiency in antioxidant enzymes in the LFU is the only cause of DE in major conditions such as aging, DM, and hormone deficiency.…”