Insulin Restores an Altered Corneal Epithelium Circadian Rhythm in Mice with Streptozotocin-induced Type 1 Diabetes

Topical insulin in neurotrophic keratopathy after diabetic vitrectomy

To assess the efficacy and safety of topical insulin (TI) for treating neurotrophic keratopathy (NK) within one-month post-diabetic vitrectomy (DV) compared to conventional non-invasive measures, we conducted this retrospective case-control study including all eyes that developed acute NK (stages 2 and 3) following DV between October 2020 and June 2023. The control group included NK cases managed with preservative-free lubricant eye drops and prophylactic topical antibiotics. In contrast, the study group included NK cases treated with TI [1 unit per drop] four times daily, in addition to the previously mentioned treatment. The primary outcome measure was time to epithelial healing. Secondary outcome measures included any adverse effect of TI or the need for amniotic membrane transplantation (AMT). During the study period, 19 patients with a mean age of 49.3 ± 8.6 years received TI versus 18 controls with a mean age of 52.5 ± 10.7 years. Corneal epithelial healing was significantly faster in the TI-treated group compared to controls, with a mean difference of 12.16 days (95% CI 6.1-18.3, P = 0.001). Survival analysis indicated that the insulin-treated group had 0% and 20% of NK stages 2 and 3, respectively, that failed to achieve corneal epithelial healing, compared to 20% and 66.7% for the control group (P < 0.001). In the control group, two eyes required AMT due to progressive thinning. Additionally, three patients in the control group, progressing to stage 3 NK, were switched to TI, achieving healing after a mean of 14 days. No adverse effects were reported in the TI-treated group. Our study suggests that TI can effectively and safely promote the healing of NK after DV.

Topical insulin, a novel corneal epithelial regeneration agent in dry eye disease

OBJECTIVE

To evaluate the efficacy of insulin eye drops for dry eye disease in reducing corneal staining and improving symptoms.

METHODS

In this retrospective case series, patients with dry eye disease treated with off-label use of insulin eye drops were collected. The main inclusion criterion was diagnosis of dry eye disease with epithelial damage and acceptance of the off-label use of topical insulin. Age, sex, type of dry eye disease, time since diagnosis, previous ocular surgeries, concomitant treatment, best corrected visual acuity, symptoms, conjunctival hyperemia and corneal staining were recorded. Data from the 1 and 3-month visit were included.

RESULTS

16 patients (32 eyes) were treated with insulin (14 females and 2 males; mean age 61.3 ± 16.8 years). 12 patients (71%) were also on autologous serum and 10 patients (63%) on cyclosporine. Symptoms were 3.4 ± 1.3 (range 2-5) when scaled from 0 to 5. Mean hyperemia was 1.0 ± 0.9 (range 0-3) and corneal staining was 2.5 ± 1.3 (range 0-5). After 3 months, 5 patients (31%) referred to be much better, 6 (38%) better, 3 (19%) slightly better and 2 patients (13%) were subjectively similar, mean symptoms being 2.3 ± 1.0 (range 1-4; p = 0.001). Hyperemia was 0.3 ± 0.4 (range 0-1) and corneal staining was 1.1 ± 1.0 (range 0-3; both p < 0.001). Topical insulin was well tolerated with no adverse events.

CONCLUSIONS

The excellent results presented in these case series illustrate topical insulin as a promising treatment in dry eye disease with refractory epithelial damage.

The Role of Insulin-like Growth Factor (IGF) System in the Corneal Epithelium Homeostasis-From Limbal Epithelial Stem Cells to Therapeutic Applications

The corneal epithelium, comprising three layers of cells, represents the outermost portion of the eye and functions as a vital protective barrier while concurrently serving as a critical refractive structure. Maintaining its homeostasis involves a complex regenerative process facilitated by the functions of the lacrimal gland, tear film, and corneal nerves. Crucially, limbal epithelial stem cells located in the limbus (transitional zone between the cornea and the conjunctiva) are instrumental for the corneal epithelium integrity by replenishing and renewing cells. Re-epithelialization failure results in persistent defects, often associated with various ocular conditions including diabetic keratopathy. The insulin-like growth factor (IGF) system is a sophisticated network of insulin and other proteins essential for numerous physiological processes. This review examines its role in maintaining the corneal epithelium homeostasis, with a special focus on the interplay with corneal limbal stem cells and the potential therapeutic applications of the system components.

Diurnal changes and topographical distribution of ocular surface epithelial dendritic cells in humans, and repeatability of density and morphology assessment

PURPOSE

Dendritic cells (DC) play a crucial role in ocular surface defence. DC can be visualised in vivo by confocal microscopy but have not yet been fully characterised in humans. This study investigated the diurnal variation, topographical distribution and repeatability of DC density and morphology measurements.

METHODS

In vivo confocal microscopy (IVCM) was conducted on 20 healthy participants (mean age 32.7 ± 6.4 years, 50% female) at baseline and repeated after 30 minutes, 2, 6 and 24 h. Images were captured at the corneal centre, inferior whorl, corneal periphery, limbus and bulbar conjunctiva. DC were counted manually, and their morphology was assessed for cell body size, presence of dendrites, and presence of long and thick dendrites. Mixed-model analysis, non-parametric analyses, Bland and Altman plots, coefficient of repeatability (CoR) and kappa were used.

RESULTS

There were no significant changes in DC density (p ≥ 0.74) or morphology (p > 0.07) at any location over the 24-h period. The highest DC density was observed at the corneal limbus followed by the peripheral cornea (p < 0.001), with the lowest density at the corneal centre, inferior whorl and bulbar conjunctiva. Most DC at the corneal periphery, limbus and bulbar conjunctiva had larger cell bodies compared with the corneal centre (p ≤ 0.01), and the presence of long dendrites was observed mostly at non-central locations. Day-to-day CoR for DC density ranged from ±28.1 cells/mm² at the corneal centre to ±56.4 cells/mm² at the limbus. Day-to-day agreement of DC morphology determined by kappa ranged from 0.5 to 0.95 for cell body size, 0.60 to 0.95 for presence of dendrites, and 0.55 to 0.80 for the presence of long dendrites at various locations.

CONCLUSIONS

No diurnal changes are apparent in corneal or conjunctival DC. Substantial topographical differences exist in DC density and morphology. IVCM provides good repeatability of DC density and acceptable agreement of DC morphology.

Optic Fiber Microsensor Reveals Specific Spatiotemporal Oxygen Uptake Profiles at the Mammalian Ocular Surface

Oxygen (O₂) uptake by cells and tissues is a critical indicator of metabolic demand, changes in microenvironment, and pathophysiology. O₂ uptake from the atmosphere accounts for virtually all the O₂ consumption in the avascular cornea; however, a detailed spatiotemporal profile of corneal O₂ uptake (COU) remains undetermined. Here, we used a non-invasive self-referencing optical fiber O₂ sensor-the scanning micro-optrode technique (SMOT)-to report the O₂ partial pressure and flux variations at the ocular surface of rodents and non-human primates. In vivo spatial mapping in mice revealed a distinct COU, characterized by a centripetal gradient with a significantly higher O₂ influx at the limbus and conjunctiva regions than at the center of the cornea. This regional COU profile was reproduced ex vivo in freshly enucleated eyes. The centripetal gradient was conserved across the following species analyzed: mice, rats, and rhesus monkeys. In vivo temporal mapping in mice showed a significant increase in the O₂ flux in the limbus in the evening compared to other times. Altogether, the data unveiled a conserved centripetal COU profile, which may be associated with the limbal epithelial stem cells residing at the intersection of the limbus and conjunctiva. These physiological observations will serve as a useful baseline for comparative studies with contact lens wear, ocular disease, diabetes, etc. Moreover, the sensor may be applied to understand the responses of the cornea and other tissues to various insults, drugs, or changes in the environment.

Activation of Conjunctiva-Associated Lymphoid Tissue in Diabetic Patients

PURPOSE

To evaluate changes in conjunctiva-associated lymphoid tissues (CALTs) in patients with type 2 diabetic mellitus (T2DM).

METHODS

Thirty-two patients with T2DM and 32 healthy volunteers underwent comprehensive examinations. In vivo confocal microscopy and Image J were used to observe and evaluate the patients' CALT-related parameters. Conjunctival impression cytology (CIC) samples of the tarsal conjunctiva were collected from the patients, and CD4+ and CD8+ cells were evaluated by immunofluorescence staining.

RESULTS

The diabetes group showed higher diffuse lymphocyte density(p < .001), follicular density(p < .001) and parafollicular lymphocyte density(p < .001). The percentages of CD4+ cells (p < .001) and CD8+ cells (p < .001) in the diabetes group were higher than those in the control group. CALT-related parameters of the diabetic patients with diabetic retinopathy showed higher degrees of activation than those of the diabetic patients without diabetic retinopathy.

CONCLUSIONS

CALT activation is observed in patients with T2DM, and the activation is more obvious in patients with diabetic retinopathy.

TRIAL REGISTRATION NUMBER

Retrospectively registered, ChiCTR2100046030.

Circadian rhythm and disease: Relationship, new insights, and future perspectives

The circadian system is responsible for internal functions and regulation of the organism according to environmental cues (zeitgebers). Circadian rhythm dysregulation or chronodisruption has been associated with several diseases, from mental to autoimmune diseases, and with life quality change. Following this, some therapies have been developed to correct circadian misalignments, such as light therapy and chronobiotics. In this manuscript, we describe the circadian-related diseases so far investigated, and studies reporting relevant data on this topic, evidencing this relationship, are included. Despite the actual limitations in published work, there is clear evidence of the correlation between circadian rhythm dysregulation and disease origin/development, and, in this way, clock-related therapies emerge as great progress in the clinical field. Future improvements in such interventions can lead to the development of successful chronotherapy strategies, deeply contributing to enhanced therapeutic outcomes.

Diabetic Corneal Neuropathy: Pathogenic Mechanisms and Therapeutic Strategies

Diabetes mellitus (DM) is a major global public health problem that can cause complications such as diabetic retinopathy, diabetic neuropathy, and diabetic nephropathy. Besides the reporting of reduction in corneal nerve density and decrease in corneal sensitivity in diabetic patients, there may be a subsequent result in delayed corneal wound healing and increased corneal infections. Despite being a potential cause of blindness, these corneal nerve changes have not gained enough attention. It has been proposed that corneal nerve changes may be an indicator for diabetic neuropathy, which can provide a window for early diagnosis and treatment. In this review, the authors aimed to give an overview of the relationship between corneal nerves and diabetic neuropathy as well as the underlying pathophysiological mechanisms of corneal nerve fiber changes caused by DM for improved prediction and prevention of diabetic neuropathy. In addition, the authors summarized current and novel therapeutic methods for delayed corneal wound healing, nerve protection and regeneration in the diabetic cornea.

Short-Term High Fructose Intake Impairs Diurnal Oscillations in the Murine Cornea

Purpose

Endogenous and exogenous stressors, including nutritional challenges, may alter circadian rhythms in the cornea. This study aimed to determine the effects of high fructose intake (HFI) on circadian homeostasis in murine cornea.

Methods

Corneas of male C57BL/6J mice subjected to 10 days of HFI (15% fructose in drinking water) were collected at 3-hour intervals over a 24-hour circadian cycle. Total extracted RNA was subjected to high-throughput RNA sequencing. Rhythmic transcriptional data were analyzed to determine the phase, rhythmicity, unique signature, metabolic pathways, and cell signaling pathways of transcripts with temporally coordinated expression. Corneas of HFI mice were collected for whole-mounted techniques after immunofluorescent staining to quantify mitotic cell number in the epithelium and trafficking of neutrophils and γδ-T cells to the limbal region over a circadian cycle.

Results

HFI significantly reprogrammed the circadian transcriptomic profiles of the normal cornea and reorganized unique temporal and clustering enrichment pathways, but did not affect core-clock machinery. HFI altered the distribution pattern and number of corneal epithelial mitotic cells and enhanced recruitment of neutrophils and γδ-T cell immune cells to the limbus across a circadian cycle. Cell cycle, immune function, metabolic processes, and neuronal-related transcription and associated pathways were altered in the corneas of HFI mice.

Conclusions

HFI significantly reprograms diurnal oscillations in the cornea based on temporal and spatial distributions of epithelial mitosis, immune cell trafficking, and cell signaling pathways. Our findings reveal novel molecular targets for treating pathologic alterations in the cornea after HFI.

Circadian clock genes as promising therapeutic targets for autoimmune diseases

Circadian rhythm is a natural, endogenous process whose physiological functions are controlled by a set of clock genes. Disturbance of the clock genes have detrimental effects on both innate and adaptive immunity, which significantly enhance pro-inflammatory responses and susceptibility to autoimmune diseases via strictly controlling the individual cellular components of the immune system that initiate and perpetuate the inflammation pathways. Autoimmune diseases, especially rheumatoid arthritis (RA), often exhibit substantial circadian oscillations, and circadian rhythm is involved in the onset and progression of autoimmune diseases. Mounting evidence indicate that the synthetic ligands of circadian clock genes have the property of reducing the susceptibility and clinical severity of subjects. This review supplies an overview of the roles of circadian clock genes in the pathology of autoimmune diseases, including BMAL1, CLOCK, PER, CRY, REV-ERBα, and ROR. Furthermore, summarized some circadian clock genes as candidate genes for autoimmune diseases and current advancement on therapy of autoimmune diseases with synthetic ligands of circadian clock genes. The existing body of knowledge demonstrates that circadian clock genes are inextricably linked to autoimmune diseases. Future research should pay attention to improve the quality of life of patients with autoimmune diseases and reduce the effects of drug preparation on the normal circadian rhythms.

The Protective Role of Bmal1-Regulated Autophagy Mediated by HDAC3/SIRT1 Pathway in Myocardial Ischemia/Reperfusion Injury of Diabetic Rats

PURPOSE

Histone deacetylase 3 (HDAC3) and silent information regulator 1 (SIRT1) are histone deacetylases that regulate important metabolic pathways and play important roles in diabetes and myocardial ischemia/reperfusion (IR) injury. In this study, we explored the protective mechanism of Bmal1-regulated autophagy mediated by the HDAC3/SIRT1 pathway in myocardial IR injury of diabetic rats.

METHODS AND RESULTS

Type 1 diabetes was established by administering an intraperitoneal injection of streptozotocin. After 8 weeks, the left anterior descending coronary artery was ligated for 30 min and reperfused for 120 min to establish a myocardial IR injury model in diabetic rats. H9c2 cardiomyocytes were exposed to high glucose concentration (30 mM) and hypoxia/reoxygenation (H/R) stimulation in vitro. The myocardial infarct size and levels of serum cTn-I, CK-MB, and LDH in diabetic rats subjected to myocardial IR injury were significantly higher. Upregulated HDAC3 and downregulated SIRT1 expression were observed in diabetic and IR hearts, along with a lower Bmal1 level. Autophagy was rapidly increased in the hearts of diabetic or non-diabetic rats in the IR group compared with the sham group, but significantly attenuated in the hearts of diabetic rats compared with the hearts of non-diabetic rats after IR insult. Consistent with decreased autophagy, we observed increased HDAC3 expression and decreased SIRT1 and Bmal1 levels in the myocardial tissue of diabetic rats after IR. Inhibition of HDAC3 by the inhibitor RGFP966 and activation of SIRT1 by the agonist SRT1720 could significantly attenuate myocardial IR injury in diabetic rats by restoring Bmal1-regulated autophagy.

CONCLUSION

Based on these findings, the disordered HDAC3/SIRT1 circuit (upregulated HDAC3 and downregulated SIRT1 levels) plays an important role in aggravating myocardial IR injury in diabetic rats by downregulating Bmal1-mediated autophagy. Treatments targeting HDAC3/SIRT1 to activate the autophagy may represent a novel strategy to alleviate myocardial IR injury in diabetes.

Light cycle phase advance as a model for jet lag reprograms the circadian rhythms of murine extraorbital lacrimal glands

PURPOSE

Jet lag causes a disruption in physiological rhythms in humans. This study aims to explore the extent to which jet lag affects the circadian rhythmicity in the lacrimal glands.

METHODS

C57BL/6J mice were subjected to a 12-h light/12-h dark (LD) cycle and an 8-h advanced LD schedule as a model for jet lag. On day 5 after the LD advance, the extraorbital lacrimal glands (ELGs) were collected at 3-h intervals during a 24-h cycle. Total mRNA was extracted from normal and advanced LD-treated ELGs and assayed using high-throughput RNA sequencing. The rhythmic transcripts were identified, analyzed, and visualized by bioinformatics techniques. Finally, (i) animal behavior; (ii) the mass, cell size, and secretion response of ELGs; and (iii) circadian migration of immune cells to ELGs were also assayed.

RESULTS

Jet lag treatment drastically altered the phase and composition of the rhythmic transcripts compared to that of normal ELGs. The key biological processes, signaling pathways, and protein-protein association networks were also dramatically altered in a spatiotemporal pattern. Furthermore, the circadian migration of neutrophils, T cells, B cells, and macrophages to the ELGs increased and shifted later by 6-h. Finally, the circadian rhythms of the ELGs with respect to mass, cell size, and secretion response were also impaired in jet lag-treated animals.

CONCLUSIONS

Jet lag impairs the circadian rhythm of the transcriptomic profile, structure, and secretion function of the lacrimal glands. This information provides novel insight into the negative effects of jet lag on ELGs.

Time-restricted feeding normalizes hyperinsulinemia to inhibit breast cancer in obese postmenopausal mouse models

Accumulating evidence indicates that obesity with its associated metabolic dysregulation, including hyperinsulinemia and aberrant circadian rhythms, increases the risk for a variety of cancers including postmenopausal breast cancer. Caloric restriction can ameliorate the harmful metabolic effects of obesity and inhibit cancer progression but is difficult to implement and maintain outside of the clinic. In this study, we aim to test a time-restricted feeding (TRF) approach on mouse models of obesity-driven postmenopausal breast cancer. We show that TRF abrogates the obesity-enhanced mammary tumor growth in two orthotopic models in the absence of calorie restriction or weight loss. TRF also reduces breast cancer metastasis to the lung. Furthermore, TRF delays tumor initiation in a transgenic model of mammary tumorigenesis prior to the onset of obesity. Notably, TRF increases whole-body insulin sensitivity, reduces hyperinsulinemia, restores diurnal gene expression rhythms in the tumor, and attenuates tumor growth and insulin signaling. Importantly, inhibition of insulin secretion with diazoxide mimics TRF whereas artificial elevation of insulin through insulin pumps implantation reverses the effect of TRF, suggesting that TRF acts through modulating hyperinsulinemia. Our data suggest that TRF is likely to be effective in breast cancer prevention and therapy.

Type 1 diabetes mellitus impairs diurnal oscillations in murine extraorbital lacrimal glands

PURPOSE

People with diabetes are at high risk of lacrimal gland dysfunction, but the underlying mechanism is not well understood. In this study, we determined how type 1 diabetes mellitus (T1DM) influences circadian homeostasis of the murine extraorbital lacrimal glands (ELGs).

METHODS

A T1DM animal model was established by systemic streptozotocin injection in C57BL/6J mice. After 5 weeks, ELGs were collected at 3-h intervals over a 24-h circadian cycle. Total extracted RNA was subjected to high-throughput RNA sequencing, and rhythmic transcriptional data were evaluated using the Jonckheere-Terpstra-Kendall algorithm, Kyoto Encyclopedia of Genes and Genomes pathway analysis, Phase Set Enrichment Analysis, and time series cluster analysis to determine the phase, rhythmicity, and unique signature of the transcripts over temporally coordinated expression. Additionally, mass, cell size, histology, and tear secretion of the ELGs were evaluated.

RESULTS

T1DM globally altered the composition of the ELG transcriptome. Specifically, T1DM significantly reprogrammed the circadian transcriptomic profiles of normal ELGs and reorganized core clock machinery. Unique temporal and clustering enrichment pathways were also rewired by T1DM. Finally, normal daily rhythms of mass, cell size, and tear secretion of mouse ELGs were significantly impaired by streptozotocin-induced diabetes.

CONCLUSIONS

T1DM significantly reprograms the diurnal oscillations of the lacrimal glands and impairs their structure and tear secretion. This information may reveal potential targets for improving lacrimal gland dysfunction in patients with diabetes.

The IGF/Insulin-IGFBP Axis in Corneal Development, Wound Healing, and Disease

The insulin-like growth factor (IGF) family plays key roles in growth and development. In the cornea, IGF family members have been implicated in proliferation, differentiation, and migration, critical events that maintain a smooth refracting surface that is essential for vision. The IGF family is composed of multiple ligands, receptors, and ligand binding proteins. Expression of IGF type 1 receptor (IGF-1R), IGF type 2 receptor (IGF-2R), and insulin receptor (INSR) in the cornea has been well characterized, including the presence of the IGF-1R and INSR hybrid (Hybrid-R) in the corneal epithelium. Recent data also indicates that each of these receptors display unique intracellular localization. Thus, in addition to canonical ligand binding at the plasma membrane and the initiation of downstream signaling cascades, IGF-1R, INSR, and Hybrid-R also function to regulate mitochondrial stability and nuclear gene expression. IGF-1 and IGF-2, two of three principal ligands, are polypeptide growth factors that function in all cellular layers of the cornea. Unlike IGF-1 and IGF-2, the hormone insulin plays a unique role in the cornea, different from many other tissues in the body. In the corneal epithelium, insulin is not required for glucose uptake, due to constitutive activation of the glucose transporter, GLUT1. However, insulin is needed for the regulation of metabolism, circadian rhythm, autophagy, proliferation, and migration after wounding. There is conflicting evidence regarding expression of the six IGF-binding proteins (IGFBPs), which function primarily to sequester IGF ligands. Within the cornea, IGFBP-2 and IGFBP-3 have identified roles in tissue homeostasis. While IGFBP-3 regulates growth control and intracellular receptor localization in the corneal epithelium, both IGFBP-2 and IGFBP-3 function in corneal fibroblast differentiation and myofibroblast proliferation, key events in stromal wound healing. IGFBP-2 has also been linked to cellular overgrowth in pterygium. There is a clear role for IGF family members in regulating tissue homeostasis in the cornea. This review summarizes what is known regarding the function of IGF and related proteins in corneal development, during wound healing, and in the pathophysiology of disease. Finally, we highlight key areas of research that are in need of future study.

Transcriptional Profiling of Daily Patterns of mRNA Expression in the C57BL/6J Mouse Cornea

Purpose: The purpose of this study was to determine how the transcriptome of the murine cornea adapts to diurnal changes in physiology. Methods: C57BL/6J mice were maintained under a 12-h light/12-h dark (LD) cycle for two weeks. Corneas were collected from euthanized mice at Zeitgeber time (ZT) 0, 3, 6, 9, 12, 15, 18, and 21. Total RNA was extracted and subjected to RNA sequencing (RNA-Seq). A JTK_CYCLE algoithm and other software tools were used to analyze the transcriptional data to determine the periodicity, rhythmicity, and amplitude of the transcripts. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the enrichment of cycling transcripts. Results: Approximately 24% of the total transcripts from the murine corneal genome were rhythmically expressed over an LD cycle. GO analysis showed that these cycling genes are primarily involved in cellular and metabolic processes. A KEGG pathway analysis identified 6 branches and 44 pathways that encode the gene outputs necessary for basic cellular functions and processes. More importantly, most of the rhythmic genes between the day and night are enriched in their own unique pathways in addition to some common pathways. Furthermore, most of the rhythmic gene expression was concentrated in the 12-h and 24-h periods. A comparative analysis of GO and KEGG showed large differences in metabolic processes, but not cellular processes. Finally, the murine cornea also rhythmically expressed 11 canonical components of circadian clock genes over an LD cycle at the transcriptional level. Conclusions: One fourth of the corneal transcriptome follows a rhythmic expression pattern involved in basic molecular and cellular mechanisms. This implies that the time of day contributes significantly to the overall temporal organization of the corneal transcriptome.

Ocular Clocks: Adapting Mechanisms for Eye Functions and Health

Vision is a highly rhythmic function adapted to the extensive changes in light intensity occurring over the 24-hour day. This adaptation relies on rhythms in cellular and molecular processes, which are orchestrated by a network of circadian clocks located within the retina and in the eye, synchronized to the day/night cycle and which, together, fine-tune detection and processing of light information over the 24-hour period and ensure retinal homeostasis. Systematic or high throughput studies revealed a series of genes rhythmically expressed in the retina, pointing at specific functions or pathways under circadian control. Conversely, knockout studies demonstrated that the circadian clock regulates retinal processing of light information. In addition, recent data revealed that it also plays a role in development as well as in aging of the retina. Regarding synchronization by the light/dark cycle, the retina displays the unique property of bringing together light sensitivity, clock machinery, and a wide range of rhythmic outputs. Melatonin and dopamine play a particular role in this system, being both outputs and inputs for clocks. The retinal cellular complexity suggests that mechanisms of regulation by light are diverse and intricate. In the context of the whole eye, the retina looks like a major determinant of phase resetting for other tissues such as the retinal pigmented epithelium or cornea. Understanding the pathways linking the cell-specific molecular machineries to their cognate outputs will be one of the major challenges for the future.

Acute tobacco smoke exposure exacerbates the inflammatory response to corneal wounds in mice via the sympathetic nervous system

Exposure to tobacco smoke is a major public health concern that can also affect ophthalmic health. Based on previous work demonstrating the important role of the sympathetic nervous system (SNS) in corneal wound repair, we postulated that acute tobacco smoke exposure (ATSE) may act through the SNS in the impairment of corneal wound repair. Here we find that ATSE rapidly increases the markers of inflammatory response in normal corneal limbi. After an abrasion injury, ATSE exaggerates inflammation, impairs wound repair, and enhances the expression of nuclear factor-κB (NF-κB) and inflammatory molecules such as interleukin-6 (IL-6) and IL-17. We find that chemical SNS sympathectomy, local adrenergic receptor antagonism, NF-κB1 inactivation, and IL-6/IL-17A neutralization can all independently attenuate ATSE-induced excessive inflammatory responses and alleviate their impairment of the healing process. These findings highlight that the SNS may represent a major molecular sensor and mediator of ATSE-induced inflammation.

Effect of Diabetes Mellitus Type 1 Diagnosis on the Corneal Cell Densities and Nerve Fibers

Relation of diabetes mellitus (DM) to the various stages of corneal nerve fiber damage is well accepted. A possible association between changes in the cornea of diabetic patients and diabetic retinopathy (DR), DM duration, and age at the time of DM diagnosis were evaluated. The study included 60 patients with DM type 1 (DM1) and 20 healthy control subjects. The density of basal epithelial cells, keratocytes and endothelial cells, and the status of the subbasal nerve fibers were evaluated using in vivo corneal confocal microscopy. Basal epithelial cell density increased with age (p=0.026), while stromal and endothelial cell density decreased with age (p=0.003, p=0.0005, p<0.0001). After the DM1 diagnosis was established, this association with age weaken. We showed nerve fiber damage in DM1 patients (p˂0.0001). The damage correlated with the degree of DR. DM1 patients with higher age at DM1 diagnosis had a higher nerve fiber density (p=0.0021). These results indicated that age at DM1 diagnosis potentially has an important effect on final nerve fiber and corneal cell density.

Insulin mediates de novo nuclear accumulation of the IGF-1/insulin Hybrid Receptor in corneal epithelial cells

Insulin and insulin-like growth factor-1 (IGF-1) are present in human tears and likely play an important role in mediating ocular surface homeostasis. We previously characterized the IGF-1/insulin hybrid receptor (Hybrid–R) in corneal epithelial cells and found that it was activated by IGF-1 and not insulin; and reported the novel finding that it localized to the corneal epithelial cell nucleus. Since the corneal epithelium is an insulin insensitive tissue and does not require insulin for glucose uptake, this study investigated the function of insulin in corneal epithelial cells. We show that stress induced by growth factor deprivation triggers transcriptional upregulation and de novo nuclear accumulation of Hybrid-R through the homodimeric insulin receptor (INSR). This occurs independent of PI3K/Akt signaling. Nuclear accumulation of Hybrid-R was associated with partial cell cycle arrest and a corresponding reduction in mitochondrial respiration. Treatment with insulin, and not IGF-1, attenuated IGF-1R and INSR transcription and restored cell cycle and metabolic homeostasis. Together, these findings support that insulin mediates receptor homeostasis in corneal epithelial cells, favoring an IGF-1 mediated pathway. This may have important implications in diabetic corneal disease and wound healing.

Development and validation of an ultra-performance liquid chromatography-tandem mass spectrometry method for quantification of SR1001, an inverse agonist of retinoid-related orphan receptors, and its application to pharmacokinetic studies in streptozotocin-induced diabetic mice

Retinoic acid receptor-related orphan receptors (RORs) play critical roles in the onset and progression of type I diabetes, an autoimmune disease characterized by the destruction of pancreatic β-cells. SR1001, an ROR inverse agonist, has been proven to be an effective diabetes treatment in the non-obese diabetic (NOD) mouse model. However, optimization of this treatment is challenging because knowledge of SR1001 pharmacokinetic (PK) behaviors in type I diabetic animals is limited. The aim of our study was to develop and validate a specific and sensitive ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method to measure the concentrations of SR1001 in plasma and biological samples. Using the developed UPLC-MS/MS method, SR1001 linearity ranges in biological matrices were determined to be 5-1000ng/mL, with correlation coefficients of >0.99. The limit of detection (LOD) and limit of quantification (LOQ) values of SR1001 were 1 and 5ng/mL, respectively. And the intra-day and inter-day variances were less than 10%, and accuracy was within 90%-110%. The extraction recoveries of SR1001 were ≥80%, and no significant matrix effect was observed. Using the validated UPLC-MS/MS method, levels of SR1001 in plasma and six major organs (heart, liver, spleen, lung, kidney, and brain) were determined in streptozotocin (STZ) -induced diabetic mice. The PK parameters of SR1001 were also calculated. The SR1001 drug concentration-time curves for organs and plasma showed similar trends, and the elimination half-lives of SR1001 in diabetic mice were about 12h. SR1001 was highly bound to plasma protein, resulting in a much higher maximum concentration (C_max=144394ng/mL) and area under the concentration-time curve (AUC_0-t=2728258ng/mL*h), but a low tissue/plasma partition coefficient (K_p) value of <0.3.

Diabetic complications in the cornea

Diabetic corneal alterations, such as delayed epithelial wound healing, edema, recurrent erosions, neuropathy/loss of sensitivity, and tear film changes are frequent but underdiagnosed complications of both type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus. The disease affects corneal epithelium, corneal nerves, tear film, and to a lesser extent, endothelium, and also conjunctiva. These abnormalities may appear or become exacerbated following trauma, as well as various surgeries including retinal, cataract or refractive. The focus of the review is on mechanisms of diabetic corneal abnormalities, available animal, tissue and organ culture models, and emerging treatments. Changes of basement membrane structure and wound healing rates, the role of various proteinases, advanced glycation end products (AGEs), abnormal growth and motility factors (including opioid, epidermal, and hepatocyte growth factors) are analyzed. Experimental therapeutics under development, including topical naltrexone, insulin, inhibitors of aldose reductase, and AGEs, as well as emerging gene and cell therapies are discussed in detail.