Influence of insulin treatment on the lacrimal gland and ocular surface of diabetic rats

Previous studies have observed changes in the lacrimal gland and ocular surface related to diabetes mellitus and related it to insulin resistance or insufficiency and oxidative damage. The aim of this study was to evaluate whether insulin treatment inhibits those changes. Diabetes was induced in male Wistar rats with a single intravenous injection of streptozotocin and a subgroup was treated with insulin. After 5 and 10 weeks, the three groups (n = 5-10/group/experimental procedure) were compared for biochemical, functional, and histological parameters. After 5 weeks, changes in morphology and increased numbers of lipofucsin-like inclusions were observed in lacrimal glands of diabetic but not insulin-treated rats. After 5 weeks, malonaldehyde and total peroxidase activity were significantly higher in diabetic rats, but similar to control in insulin-treated diabetic rats (P = 0.03, P = 0.02, respectively). Our data indicate that diabetes induces histological alterations in lacrimal gland and suggests that hyperglycemia-related oxidative stress may participate in diabetic dry eye syndrome. Prevention by insulin replacement suggests direct hormone action and/or benefit by early sub optimal metabolic control.

Two-Year Outcome of Partial Lacrimal Punctal Occlusion in the Management of Dry Eye Related to Sjogren Syndrome

Purpose: To analyze the influence of thermal partial punctal occlusion on the ocular surface of dry eye related to Sjogren syndrome. Material and Methods: Thirty-seven eyes of 19 patients (3 male and 16 female; 49.11 +/- 14.33 years old) with keratoconjunctivitis sicca were enrolled in this study. Superior and inferior partial occlusion were performed in both eyes under topical anesthesia using thermal cautery with a sterile tip to obtain lacrimal punctum smaller than 0.5 mm. Schirmer I, break-up-time, diameter of lacrimal puncta, corneal fluorescein, and rose Bengal staining scores were analyzed before and after 24 weeks and after 24 months of the procedure. All measurements were performed under controlled climate. Results: The average lacrimal punctum diameter before the procedure was 0.65 +/- 0.134 mm. All lacrimal puncta were successfully reduced to less than 0.5 mm after 4 weeks of the procedure. The average Schirmer I test values improved statistically after 24 weeks and maintained stable after 24 months. Average break-up-time, rose Bengal, and fluorescein staining score values improved statistically after 24 weeks and improved even more after 24 months. Average Schirmer I test, break-up-time, rose Bengal, and fluorescein staining scores showed significant improvement (p < 0.0001) after 24 months of partial thermal punctal occlusion. Conclusion: Our study showed that reducing the punctum diameter to 0.5 mm can improve vital staining scores, break-up-time, and Schirmer I test in dry eye related to Sjogren syndrome.

Aspirin prevents diabetic oxidative changes in rat lacrimal gland structure and function

The aim of this study is to evaluate whether aspirin reduces Diabetis Mellitus (DM) oxidative damage in the lacrimal gland (LG), and ocular surface (OS). Ten weeks after streptozotocin induced DM and aspirin treatment, LG and OS of rats were compared for tear secretion, hidtology, peroxidase activity, and expression of uncoupling proteins (UCPs). DM reduction of tear secretion was prevented by aspirin (P < 0.01). Alterations of LG morphology and increased numbers of lipofucsin-like inclusions were observed in diabetic but not in aspirin-treated diabetic rats. Peroxidase activity levels were higher and UCP-2 was reduced in DM LG but not in aspirin treated (P = 0.0025 and P < 0.05, respectively). The findings prevented by aspirin indicate a direct inhibitory effect on oxidative pathways in LG and their inflammatory consequences, preserving the LG structure and function against hyperglycemia and/or insulin deficiency damage.

The aging lacrimal gland: Changes in structure and function

The afferent nerves of the cornea and conjunctiva, efferent nerves of the lacrimal gland, and the lacrimal gland are a functional unit that works cooperatively to produce the aqueous component of tears. A decrease in the lacrimal gland secretory function can lead to dry eye disease. Because aging is a risk factor for dry eye disease, study of the changes in the function of the lacrimal gland functional unit with age is important for developing treatments to prevent dry eye disease. No one mechanism is known to induce the changes that occur with aging, although multiple different mechanisms have been associated with aging. These fall into two theoretical categories: programmed theories of aging (immunological, genetic, apoptotic, and neuroendocrine) and error theories of aging (protein alteration, somatic mutation, etc). Lacrimal glands undergo structural and functional alteration with increasing age. In mouse models of aging, it has been shown that neural stimulation of protein secretion is an early target of aging, accompanied by an increase in mast cells and lipofuscin accumulation. Hyperglycemia and increased lymphocytic infiltration can contribute to this loss of function at older ages. These findings suggest that an increase in oxidative stress may play a role in the loss of lacrimal gland function with age. For the afferent and efferent neural components of the lacrimal gland functional unit, immune or inflammatory mediated decrease in nerve function could contribute to loss of lacrimal gland secretion with age. More research in this area is critically needed.