Health-related behaviours in a remote Indigenous population with Type 2 diabetes: a Central Australian primary care survey in the Telehealth Eye and Associated Medical Services Network [TEAMSnet] project.

AIM: There is a wealth of data concerning the health behaviours of Indigenous Australians, but the health behaviours of Indigenous Australians with diabetes are not systematically documented. At the clinical level, understanding a person's health behaviours can help identify and address barriers to diabetes care and promote good clinical outcomes. METHODS: We used a novel survey tool to systematically collect health behaviour data on Smoking, Nutrition, Alcohol consumption, Physical activity and Emotional well-being (SNAPE) from Indigenous Australians with Type 2 diabetes in a remote primary care setting in Alice Springs. RESULTS: At least one of the five surveys in the SNAPE tool was completed by 210 participants: 30% male, mean age 52.6 years (range 22.9 - 87.4). Fifty per cent of men and 23% of women were current smokers (P < 0.001). None of the participants reported an adequate intake of vegetables. Only 9.6% reported an adequate fruit intake. Some 49% of men and 32% of women consumed alcohol in the past year (P = 0.022), and 46% of drinkers were considered high-risk or likely-dependent drinkers. On average, participants walked 10 min or more at a time 6.0 days a week and spent 4.8 h sitting on a weekday. Mean adapted Patient Health Questionnaire 9 score was 4.61, with 34% of participants having mild depressive symptoms and 11% having moderate-severe depressive symptoms. CONCLUSIONS: Our SNAPE survey tool results present a high-risk, disadvantaged Indigenous population with Type 2 diabetes. More resources will be needed to sustainably implement interventions with the goal of improving health behaviours and subsequent long-term health.

Evolving telehealth reimbursement in Australia.

Video-based consultation is the only telehealth service reimbursed by the Medicare Benefits Schedule in Australia, but the uptake of telehealth is still low and inconsistent. There is a clear need for the development of appropriate medical evidence to support implementation of telehealth services. With the ubiquitous use of mobile phones, mobile health becomes important in facilitating health services and impacting clinical outcomes anywhere.

Amelioration of vascular dysfunctions in diabetic rats by an oral PKC beta inhibitor.

The vascular complications of diabetes mellitus have been correlated with enhanced activation of protein kinase C (PKC). LY333531, a specific inhibitor of the beta isoform of PKC, was synthesized and was shown to be a competitive reversible inhibitor of PKC beta 1 and beta 2, with a half-maximal inhibitory constant of approximately 5 nM; this value was one-fiftieth of that for other PKC isoenzymes and one-thousandth of that for non-PKC kinases. When administered orally, LY333531 ameliorated the glomerular filtration rate, albumin excretion rate, and retinal circulation in diabetic rats in a dose-responsive manner, in parallel with its inhibition of PKC activities.

Vasodilation of rat retinal microvessels induced by monobutyrin. Dysregulation in diabetes.

1-Butyryl-glycerol (monobutyrin) is a simple lipid product of adipocytes with angiogenic activity. Recent studies have shown that the biosynthesis of this compound is tightly linked to lipolysis, a process associated with changes in blood flow. We now present data indicating that monobutyrin is an effective vasodilator of rodent blood vessels using a fluorescent retinal angiogram assay. The vasodilatory activity of monobutyrin is potent (ED50 = 3.3 x 10(-7) M), dose dependent, and stereospecific. Because diabetes represents a catabolic, lipolytic state with numerous vascular complications, we examined the action and regulation of monobutyrin in insulin-deficient diabetic rats. Serum levels of monobutyrin in streptozotocin-induced diabetic rats were greatly elevated compared to normal animals. At the same time, the retinal vessels of the diabetic animals develop a resistance to the vasodilatory activity of monobutyrin. These results demonstrate a role for monobutyrin in the control of vascular tone and suggest a possible involvement in the pathology of diabetes.

Retinal expression, regulation, and functional bioactivity of prostacyclin-stimulating factor.

Prostacyclin-stimulating factor (PSF) acts on vascular endothelial cells to stimulate the synthesis of the vasodilatory molecule prostacyclin (PGI2). We have examined the expression, regulation, and hemodynamic bioactivity of PSF both in whole retina and in cultured cells derived from this tissue. PSF was expressed in all retinal cell types examined in vitro, but immunohistochemical analysis revealed PSF mainly associated with retinal vessels. PSF expression was constitutive in retinal pericytes (RPCs) but could be modulated in bovine retinal capillary endothelial cells (RECs) by cell confluency, hypoxia, serum starvation, high glucose concentrations, or inversely by soluble factors present in early vs. late retinopathy, such as TGF-beta, VEGF, or bFGF. In addition, RPC-conditioned media dramatically increased REC PGI2 production, a response inhibited by blocking PSF with a specific antisense oligodeoxynucleotide (ODN). In vivo, PGI2 increased retinal blood flow (RBF) in control and diabetic animals. Furthermore, the early drop in RBF during the initial weeks after inducing diabetes in rats, as well as the later increase in RBF, both correlated with levels of retinal PSF. RBF also responded to treatment with RPC-conditioned media, and this effect could be partially blocked using the antisense PSF ODN. We conclude that PSF expressed by ocular cells can induce PGI2, retinal vascular dilation, and increased retinal blood flow, and that alterations in retinal PSF expression may explain the biphasic changes in RBF observed in diabetes.

Normalization of diacylglycerol-protein kinase C activation by vitamin E in aorta of diabetic rats and cultured rat smooth muscle cells exposed to elevated glucose levels.

Hyperglycemia and diabetes have been shown to increase diacylglycerol (DAG) level and activate protein kinase C (PKC) activity in the vascular tissues, possibly altering vascular function. We have characterized the effects of D-alpha-tocopherol (vitamin E) on PKC activities and DAG levels in rat aortic smooth muscle cells (ASMCs) cultured with elevated glucose levels as well as in the vascular tissues obtained from control and diabetic rats. In ASMCs, the specific PKC activity from the membraneous fraction and total DAG level were increased by 31 +/- 4% (P < 0.05) and 50 +/- 7% (P < 0.05), respectively, when the glucose levels were changed from 5.5 to 22 mmol/l. The addition of D-alpha-tocopherol and another lipophilic antioxidant, probucol, prevented the glucose-stimulated increases in DAG level and PKC activity. By immunoblotting studies, D-alpha-tocopherol treatment was able to reduce the enhancement of PKC beta II isoform in the membraneous fraction isolated from ASMCs. Comparing streptozotocin-induced diabetic rats with their nondiabetic controls, both membraneous-specific PKC activities and total cellular DAG levels were increased in aorta by 162% (P < 0.05) and 60% (P < 0.05), respectively. Intraperitoneal injection of D-alpha-tocopherol (40 mg/kg) every other day prevented the increases in membraneous-specific PKC activities and total DAG levels in parallel with a significant increase of D-alpha-tocopherol contents in the aorta and plasma. These findings have demonstrated that D-alpha-tocopherol can prevent the activation of PKC activities in the vascular cells and tissues induced by hyperglycemia by lowering DAG levels, possibly via its antioxidant effect.

Reversibility of retinal flow abnormalities is disease-duration dependent in diabetic rats.

Decreased retinal blood flow has been measured in streptozotocin (STZ)-induced diabetes of 1 week's duration, and primary insulin intervention was effective in maintaining normal retinal blood flow in diabetic rats. Retinal blood-flow abnormalities precede clinical diabetic retinopathy in both diabetic animals and patients. An important characteristic of diabetic retinopathy is the difficulty of reversibility once it has been established. Because altered retinal hemodynamics is a possible marker of early diabetic retinopathy, we investigated in this study whether retinal blood-flow changes in rats can be normalized by secondary insulin intervention following short and chronic periods of untreated STZ-induced diabetes. Subcutaneous insulin pumps were placed into diabetic rats for 1 week after 1 week of diabetes (2-week group) and after 3 weeks of diabetes (4-week group). Retinal circulatory parameters were determined using image analysis of video fluorescein angiogram recordings. For the 2-week group, retinal blood flow was significantly (P < 0.05) reduced in the untreated diabetic rats compared with nondiabetic and insulin-treated diabetic rats (80.6+/-29.2, 131.9+/-50.1, and 151.3+/-54.0 pixels2/s respectively). Retinal blood flow was also significantly (P < 0.05) reduced in the 4-week untreated diabetic rats compared with nondiabetic rats (95.7+/-22.2 vs. 125.7+/-29.5 pixels2/s). In contrast to the shorter-duration group, insulin treatment for 1 week after 3 weeks of diabetes did not totally normalize retinal blood flow (117.5+/-32.4 pixels2/s). These results suggest that vascular abnormalities could become more resistant to normalization following short-term (1 week) insulin treatment after longer periods of untreated diabetes.

Vascular endothelial growth factor-induced retinal permeability is mediated by protein kinase C in vivo and suppressed by an orally effective beta-isoform-selective inhibitor.

Increased vascular permeability and excessive neovascularization are the hallmarks of endothelial dysfunction, which can lead to diabetic macular edema and proliferative diabetic retinopathy in the eye. Vascular endothelial growth factor (VEGF) is an important mediator of ocular neovascularization and a known vasopermeability factor in nonocular tissues. In these studies, we demonstrate that intravitreal injection of VEGF rapidly activates protein kinase C (PKC) in the retina at concentrations observed clinically, inducing membrane translocation of PKC isoforms alpha, betaII, and delta and >threefold increases in retinal vasopermeability in vivo. The effect of VEGF on retinal vascular permeability appears to be mediated predominantly by the beta-isoform of PKC with >95% inhibition of VEGF-induced permeability by intravitreal or oral administration of a PKC beta-isoform-selective inhibitor that did not inhibit histamine-mediated effects. These studies represent the first direct demonstration that VEGF can increase intraocular vascular permeability through activation of PKC in vivo and suggest that oral pharmacological therapies involving PKC beta-isoform-selective inhibitors may prove efficacious for the treatment of VEGF-associated ocular disorders such as diabetic retinopathy.

von Willebrand factor and retinal circulation in early-stage retinopathy of type 1 diabetes.

OBJECTIVE: Although retinopathy is a common microvascular complication of type 1 diabetes, the mechanism for this complication is still unknown. Changes in retinal circulation have been noted before the development of overt retinal pathology. Because von Willebrand factor (vWF) is a marker for endothelial dysfunction and mediates platelet adhesion, we determined if there was an association between vWF and retinal circulation in the early stages of diabetic retinopathy. RESEARCH DESIGN AND METHODS: Twenty subjects (aged 32.4 +/- 7.8 years) with type 1 diabetes and minimal or no retinopathy were studied. The mean duration of diabetes was 4.7 +/- 2.6 years. Data were collected at baseline and after 4 months of 1,800 IU vitamin E therapy or placebo. Retinal circulation was evaluated by video fluorescein angiography. Plasma vWF antigen levels were measured by enzyme-linked immunosorbent assay and fibrinogen by the Clauss method. RESULTS: Retinal blood flow was negatively correlated with vWF levels (r = -0.44, P = 0.008), whereas retinal circulation time was positively correlated with vWF levels (r = 0.33, P = 0.048). Fibrinogen levels were not significantly associated with either retinal index. However, fibrinogen levels were positively associated with HbA1c levels (r = 0.34, P = 0.01), indicating an association between poor glycemic control and higher fibrinogen levels. CONCLUSIONS: Increased vWF was associated with a prolonged retinal circulation time and reduced retinal blood flow in early-stage retinopathy of type 1 diabetes. Reduced blood flow associated with increased vWF levels may promote stasis in the retinal circulation and lead to local hypoxemia. These changes might contribute to the microvascular complications of diabetes. Whether the vWF levels predict retinal complications deserves further investigation.

High-dose vitamin E supplementation normalizes retinal blood flow and creatinine clearance in patients with type 1 diabetes.

OBJECTIVE: To determine the effectiveness of vitamin E treatment in normalizing retinal blood flow and renal function in patients with <10 years of type 1 diabetes. RESEARCH DESIGN AND METHODS: An 8-month randomized double-masked placebo-controlled crossover trial evaluated 36 type 1 diabetic and 9 nondiabetic subjects. Subjects were randomly assigned to either 1,800 IU vitamin E/day or placebo for 4 months and followed, after treatment crossover, for a further 4 months. Retinal blood flow was measured using video fluorescein angiography, and renal function was assessed using normalized creatinine clearance from timed urine collections. RESULTS: After vitamin E treatment, serum levels of vitamin E were significantly elevated (P<0.01) in both type 1 diabetic and control patients. Hemoglobin A1c was not affected by vitamin E treatment. Diabetic patient baseline retinal blood flow (29.1+/-7.5 pixel2/s) was significantly (P = 0.030) decreased compared with that of nondiabetic subjects (35.2+/-7.2 pixel2/s). After vitamin E treatment, diabetic patient retinal blood flow (34.5+/-7.8 pixel2/s) was significantly increased (P<0.001) and was comparable with that of nondiabetic subjects. Additionally, vitamin E treatment significantly (P = 0.039) normalized elevated baseline creatinine clearance in diabetic patients. CONCLUSIONS: Oral vitamin E treatment appears to be effective in normalizing retinal hemodynamic abnormalities and improving renal function in type 1 diabetic patients of short disease duration without inducing a significant change in glycemic control. This suggests that vitamin E supplementation may provide an additional benefit in reducing the risks for developing diabetic retinopathy or nephropathy.

Diabetic eye disease.

Diabetic retinopathy accounts for most visual loss in the United States among working-age individuals. With appropriate detection, evaluation, and treatment, the risk for severe visual loss from this condition is dramatically reduced. This article details the natural history, pathophysiology, complications, grading, evaluation, and treatment for patients with diabetic retinopathy and discusses potential novel treatment modalities currently under investigation.

The in vivo effect of endothelins on retinal circulation in nondiabetic and diabetic rats.

PURPOSE: The endothelins are potent vasoactive peptides. This study was performed to characterize the in vivo effects of the endothelin peptides on the retinal circulation in nondiabetic and diabetic rats. METHODS: The video fluorescein angiography methodology was used to quantitate retinal hemodynamic responses to endothelin-1 (ET-1) and endothelin-3 (ET-3) in rats. A total of 99 rats were used for these experiments. Video fluorescein angiography recordings were performed before and at different times after intravitreal injection of different concentrations of ET-1 and ET-3 in nondiabetic and diabetic rats. Vascular diameters and retinal circulation times were determined using computer-assisted image analysis of the recorded angiograms. RESULTS: The maximal response to ET-1 was observed at 15 minutes after intravitreal injection and was maintained for as long as 30 minutes after injection. Subsequent data measured at 15 minutes after intravitreal injection showed significant prolongation of retinal circulation times and retinal artery constriction. For example, at a concentration of 10(-7) M, the retinal circulation time increased by 270% +/- 121% of the baseline value. In contrast, 10(-7) M ET-3 injection showed a 52% +/- 29.5% increase in circulation time compared to baseline. In diabetic animals, 10(-7) M ET-1 injection showed a blunted response (only 26% +/- 8% of baseline) compared to the same ET-1 injected concentration in nondiabetic rats. CONCLUSIONS: The rat retinal circulation shows a pronounced retinal response to ET-1 intravitreal injection. The response to ET-3 is significantly less than it is to ET-1, and in diabetic animals there was also a significant blunting of the retinal response to ET-1. The blunted response to ET-3 is consistent with the lower affinity of retinal vessel ET-1 receptors to ET-3. The blunted ET-1 response in diabetic rats is consistent with previously reported results, demonstrating resistance to ET-1 action in retinal pericytes exposed to high glucose.

Endothelin-3 regulation of retinal hemodynamics in nondiabetic and diabetic rats.

PURPOSE: To investigate the mechanisms of action of endothelin (ET)-3 on the regulation of retinal hemodynamics in diabetic and nondiabetic rats. METHODS: Retinal blood flow changes were measured using video fluorescein angiography. Measurements were made before and after intravitreal injections of different ET-3 concentrations in nondiabetic rats and rats with streptozotocin (STZ)-induced diabetes. The effect of ET-3 on retinal blood flow was also investigated in nondiabetic rats after pretreatment with N:(G)-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (NOS) inhibitor; BQ-788, an ET receptor B (ETB) antagonist; and BQ-123, an ET receptor A (ETA) antagonist. Control animals were injected intravitreally with vehicle alone. RESULTS: In nondiabetic rats, ET-3 induced a dose-dependent rapid increase in retinal blood flow 2 minutes after intravitreal injection (maximal at 10(-)(8) M, P < 0. 01) followed 15 and 30 minutes after ET-3 injection by dose-dependent decreases in retinal blood flow (maximal effect at 10(-)(6) M, P < 0.05). The ET-3-stimulated retinal blood flow increase was inhibited by 10(-)(4) M BQ-788 (P < 0.01) and 10(-)(3) M L-NMMA (P < 0.05). The ET-3-stimulated decrease in retinal blood flow at later times (15 minutes) was inhibited (P < 0.03) by 10(-4) M BQ-123. In diabetic rats, baseline retinal blood flows were decreased compared with nondiabetic rats (P < 0.01), showed dose-dependent increases 2 minutes after ET-3 injection (P < 0.03), and at later times remained significantly increased (P < 0.05) in contrast to flows in nondiabetic rats. CONCLUSIONS: The ET-3-induced initial rapid retinal blood flow increase in nondiabetic rats is mediated by the ET-3/ETB and NOS action. The subsequent retinal blood flow decrease is mediated by ET-3/ETA action. Diabetic rats showed comparable ET-3-induced retinal blood flow increases indicating normal ET-3/ETB action. However, at later times, retinal blood flow remained increased, suggesting an abnormal ET-3/ETA action.

Normalization of retinal blood flow in diabetic rats with primary intervention using insulin pumps.

PURPOSE: Prior results have demonstrated a significant reduction in retinal blood flow in streptozotocin (STZ)-induced diabetic rats. These studies were extended to investigate whether retinal blood flow changes, in the diabetic rat model, could be prevented with strict glycemic control using insulin pumps. Retinal blood flow changes also were measured during hyperoxia and after intravitreal histamine infusion to validate the methodology. METHODS: Retinal blood flow changes were measured using video-based fluorescein angiography and computer-assisted image analysis. A total of 48 male Sprague-Dawley and 9 Brown Norway rats were used in these experiments. Retinal blood flow after primary insulin intervention was evaluated in diabetic rats implanted with mini-osmotic insulin pumps within 24 hours of STZ-induced diabetes. Diabetic rats, not treated with insulin, were used for comparison. RESULTS: Hyperoxia caused a significant (P = 0.001) reduction (54%) in retinal blood flow, whereas intravitreal infusion of 10(-3) M histamine caused a significant (P = 0.009) increase (108%) in retinal blood flow. Retinal blood flow in the primary insulin intervention group, after 1 week of diabetes, was not statistically different from retinal blood flow of nondiabetic controls as measured at baseline from the animals used in the hyperoxia and histamine infusion experiments. In contrast there was a significant (P = 0.0001) retinal blood flow reduction in the untreated diabetic group. CONCLUSIONS: The results showed that the local effect of histamine and hyperoxia on the retina produced the expected responses in retinal blood flow, further confirming the validity of the methodology. Primary insulin intervention demonstrated that strict glycemic control initiated immediately after induction of diabetes was sufficient to maintain normal retinal blood flow in STZ-induced diabetic rats.

Endothelin-1 action via endothelin receptors is a primary mechanism modulating retinal circulatory response to hyperoxia.

PURPOSE: To determine the role of endothelin (ET)-ETA receptor mediation and endogenous production of endothelin-1 (ET-1) in the retinal response to hyperoxia. METHODS: Brown-Norway rats (n = 30) were injected intravitreally with an ETA receptor-selective antagonist, BQ-123, and an inhibitor of ET-converting enzyme (ECE), phosphoramidon, and were exposed to a 100% oxygen breathing mixture. Control rats underwent intravitreal injection of vehicle alone (2.5% Emulphor in phosphate-buffered saline). The retinal hemodynamic responses were analyzed using video-based fluorescein angiography (VFA) methodology. Baseline measurements were made with the animals breathing room air, and this was followed by intravitreal injections of the above agents. Subsequent VFA measurements were made after 5, 10, and 15 minutes of breathing 100% oxygen. RESULTS: The 10 rats injected with vehicle alone demonstrated the expected retinal response to hyperoxia, with significant (P < 0.001) vessel constriction (18% +/- 5%), an increase in retinal mean circulation time (0.84 +/- 0.13 seconds in room air and 1.59 +/- 0.27 seconds in 100% oxygen), and a decrease in blood flow (110.7 +/- 19.2 pixel2/second in room air and 41.9 +/- 9.0 pixel2/second in 100% oxygen), compared to values measured during room air breathing. The hyperoxic response in rats (n = 9) injected with 10(-4) M BQ-123 was significantly (P < 0.001) blunted compared to the group injected with vehicle alone. In contrast, intravitreal injection of saralasin, a specific angiotensin II receptor antagonist, had no significant effect on the retinal response to hyperoxia (n = 5). Intravitreal phosphoramidon (10(-3) M, n = 6) injection also resulted in a significantly (P < 0.001) blunted circulatory response to hyperoxia compared to rats injected with vehicle alone. This blunted response after ECE inhibition was comparable to that measured after ETA receptor antagonism with BQ-123 injection. CONCLUSIONS: These results demonstrate that the enhancement of ET-1 action, possibly caused by the activation of ECE, plays a primary role in regulating the retinal hemodynamic response to hyperoxia.

Automated morphometric analysis of corneal endothelial cells.

This paper describes a feasibility study for computer image analysis of corneal endothelial specular micrographs. The analysis involved image enhancement, boundary detection of individual cells, and subsequent calculation of cell area, cell area distribution, cell perimeter, cell orientation, and cell diameter. Cell areas produced by automated analysis agreed well with manually measured cell areas from the same photomicrographs. The computer methods required little human guidance or correction, produced accurate results, and could be made to run fairly quickly with modest computing resources.

Regulation of retinal hemodynamics in diabetic rats by increased expression and action of endothelin-1.

PURPOSE: To investigate the role of endogenous endothelin-1 (ET-1) expression and its interaction with the ETA receptor in the physiologic regulation of vascular tone as well as in the development of abnormal retinal hemodynamics in diabetes. METHODS: Retinal blood flow, using digitized video fluorescein angiography recordings, was quantitated after intravitreous injections of ET-1; BQ-123, an ETA receptor antagonist; and phosporamindon, an endothelin converting enzyme inhibitor in the eyes of diabetic and nondiabetic rats. A total of 154 rats were used for these experiments. Message levels of preproendothelin-1 (preproET-1) were measured from the retina of diabetic and nondiabetic rats using competitive polymerase chain reaction (PCR) techniques. RESULTS: Retinal blood flow was reduced (33%, P < 0.001) in diabetic rats compared to nondiabetic rats. BQ-123, an ETA receptor antagonist, but not saralasin, an angiotensin receptor antagonist, increased retinal blood flow in a dose-dependent manner in diabetic (EC50 of 8 x 10(-7) M) and in nondiabetic rats (EC50 of 8 x 10(-8) M). Besides being resistant to BQ-123, the maximal response in diabetic animals occurred 20 minutes later than in nondiabetic animals. Decreasing ET-1 levels by inhibiting endothelin-converting enzyme with phosphoramidon normalized retinal blood flow in diabetic rats. In nondiabetic rats, the intravitreous injection of exogenous ET-1 (10(-8) M) resulted in retinal blood flow decreases comparable to those measured in diabetic animals, and the subsequent injection of 10(-4) M BQ-123 produced retinal blood flow changes comparable to those measured in BQ-123 injected diabetic rats. Comparison of preproET-1 messenger RNA expression in the retina, brain and lung of control and diabetic rats using quantitative PCR and Northern blot analysis showed 2.0- and 1.7-fold increases in the retina and the brain, respectively, without changes in the lung. CONCLUSIONS: These data suggest that ET-1 is involved in the regulation of retinal blood flow in normal physiologic outcome, and an increase in the endogenous expression of ET-1 contributes to the reduction of retinal blood flow reported in the early stages of diabetes mellitus.

Integrin-mediated neutrophil adhesion and retinal leukostasis in diabetes.

PURPOSE: A critical early event in the pathogenesis of diabetic retinopathy is leukocyte adhesion to the diabetic retinal vasculature. The process is mediated, in part, by intercellular adhesion molecule-1 (ICAM-1) and results in blood-retinal barrier breakdown and capillary nonperfusion. This study evaluated the expression and function of the corresponding ICAM-1-binding leukocyte beta2-integrins in experimental diabetes. METHODS: Diabetes was induced in Long Evans rats with streptozotocin. The expression of the surface integrin subunits CD11a, CD11b, and CD18 on rat neutrophils isolated from peripheral blood was quantitated with flow cytometry. In vitro neutrophil adhesion was studied using quantitative endothelial cell-neutrophil adhesion assays. The adhesive role of the integrin subunits CD11a, CD11b, and CD18 was tested using specific neutralizing monoclonal antibodies. CD18 bioactivity was blocked in vivo with anti-CD18 F(ab')2 fragments, and the effect on retinal leukocyte adhesion was quantitated with acridine orange leukocyte fluorography. RESULTS: Neutrophil CD11a, CD11b, and CD18 surface integrin levels were 62% (n = 5, P = 0.006), 54% (n = 5, P = 0.045), and 38% (n = 5, P = 0.009) greater in diabetic versus nondiabetic animals, respectively. Seventy-five percent more neutrophils from diabetic versus nondiabetic animals adhered to rat endothelial cell monolayers (n = 6, P = 0.02). Pretreatment of leukocytes with either anti-CD11b or anti-CD18 antibodies lowered the proportion of adherent diabetic neutrophils by 41% (n = 6, P = 0.01 for each treatment), whereas anti-CD11a antibodies had no significant effect (n = 6, P = 0.5). In vivo, systemic administration of anti-CD18 F(ab')2 fragments decreased diabetic retinal leukostasis by 62% (n = 5, P = 0.001). CONCLUSIONS: Neutrophils from diabetic animals exhibit higher levels of surface integrin expression and integrin-mediated adhesion. In vivo, CD18 blockade significantly decreases leukostasis in the diabetic retinal microvasculature. Integrin adhesion molecules may serve as therapeutic targets for the treatment and/or prevention of early diabetic retinopathy.

Specific retinal diacylglycerol and protein kinase C beta isoform modulation mimics abnormal retinal hemodynamics in diabetic rats.

PURPOSE: Elevation of diacylglycerol (DAG) and protein kinase C (PKC) levels in diabetic vascular tissue is associated with abnormalities of retinal and renal hemodynamics. The object of this study was to determine whether direct elevation of retinal DAG levels, in the absence of diabetes or hyperglycemia, can mimic the hemodynamic abnormalities normally observed in diabetic rats. Retinal DAG levels were elevated using an inhibitor of DAG kinase that converts DAG to phosphatidic acid. The effectiveness of a specific PKC-beta isoform inhibitor introduced directly into the retinas of diabetic rats in reversing diabetes-related abnormal retinal hemodynamics was also investigated. METHODS: For retinal blood flow studies, diacylglycerol kinase (DGK) inhibitor R59949, at various concentrations, was injected into the vitreous of nondiabetic Sprague-Dawley rats (n = 33), and a PKC-beta isoform-selective inhibitor LY333531 was injected into the vitreous of rats with streptozotocin (STZ)-induced diabetes of 2 weeks' duration (n = 21). Retinal hemodynamic changes were quantitated using video-based fluorescein angiography. Total DAG levels were assayed from five nondiabetic rat retinas after DGK inhibition and retinal PKC activities were assayed from six diabetic rat retinas after PKC-beta inhibition. RESULTS: DGK inhibitor R59949 injected into the vitreous dose dependently increased the mean circulation time (MCT) and decreased retinal blood flow (EC50 = 10(-8) M). After 30 minutes, 10(-5) M R59949 induced a 1.7-fold increase in total retinal DAG levels, compared with the levels in vehicle-injected eyes, an increase in MCT from 0.87 +/- 0.05 seconds to 1.44 +/- 0.12 seconds (P < 0.01) and a decrease in retinal blood flow from 105.3 +/- 6.5 pixel2/second to 64.1 +/- 5 pixel2/second (P < 0.01). The effect of R59949 was sustained for 60 minutes after injection. These retinal hemodynamic parameters after DGK inhibition were comparable to those measured at baseline in rats with STZ-induced diabetes of 2 weeks' duration (MCT = 1.38 +/- 0.20 seconds; retinal blood flow = 68 +/- 11.2 pixel2/second). Intravitreal injection of the PKC-beta inhibitor (LY333531) at 10(-5) M in diabetic rats decreased by a factor of 1.6 the diabetes-related increased PKC activation, decreased the prolonged MCT (0.98 +/- 0.13 seconds; P < 0.01) and increased retinal blood flow (93.4 +/- 14.2 pixel2/second; P < 0.01). The measured retinal circulatory parameters after PKC inhibition in the retina were comparable to those measured at baseline in the nondiabetic rats. CONCLUSIONS: These results provide direct evidence that DAG elevation and subsequent PKC-beta isoform activation are the primary biochemical sequelae responsible for the development of the abnormal retinal hemodynamics observed in diabetic rats.

Vitreous fluorophotometric evaluation of diabetics.

Vitreous fluorophotometry measurements taken from diabetic patients with different degrees of retinopathy and from normal volunteers were used to evaluate the integrity of the blood-ocular barrier. The contributions of lens and retinal fluorescence to the measured vitreous fluorescence were investigated. Lens autofluorescence was significantly higher for diabetics than for age-matched normals, and in age-matched diabetics the lens autofluorescence increased significantly with the progression of diabetic retinopathy. Natural ocular fluorescence was corrected for by subtracting baseline values from all vitreous measurements. Analysis of the baseline-corrected vitreous fluorescence values showed that both degree of retinopathy and age significantly affected the measured fluorescence. In age-matched groups, vitreous fluorescence values were greater in diabetics than in normals, and these values increased with the progression of retinopathy. Our results suggest that clinical vitreous fluorophotometry may be useful in evaluating the activity and predicting the progression of diabetic retinopathy.