Diabetic retinopathy

Retinal proteome alterations in a mouse model of type 2 diabetes

AIMS/HYPOTHESIS

Diabetic retinopathy is a major complication of type 2 diabetes and the leading cause of blindness in adults of working age. Neuronal defects are known to occur early in disease, but the source of this dysfunction is unknown. The aim of this study was to examine differences in the retinal membrane proteome among non-diabetic mice and mouse models of diabetes either with or without metformin treatment.

METHODS

Alterations in the retinal membrane proteome of 10-week-old diabetic db/db mice, diabetic db/db mice orally treated with the anti-hyperglycaemic metformin, and congenic wild-type littermates were examined using label-free mass spectrometry. Pathway enrichment analysis was completed with Genomatix and Ingenuity. Alterations in Slc17a7 mRNA and vesicular glutamate transporter 1 (VGLUT1) protein expression were evaluated using real-time quantitative PCR and IMMUNOFLUORESCENCE.

RESULTS

A total of 98 proteins were significantly differentially abundant between db/db and wild-type animals. Pathway enrichment analysis indicated decreases in levels of proteins related to synaptic transmission and cell signalling. Metformin treatment produced 63 differentially abundant proteins compared with untreated db/db mice, of which only 43 proteins were found to occur in both datasets, suggesting that treatment only partially normalises the alterations induced by diabetes. VGLUT1, which is responsible for loading glutamate into synaptic vesicles, was found to be differentially abundant in db/db mice and was not normalised by metformin. The decrease in Slc17a7/VGLUT1 was confirmed by transcriptomic and immunocytochemical analysis.

CONCLUSIONS/INTERPRETATION

These findings expand the knowledge of the protein changes in diabetic retinopathy and suggest that membrane-associated signalling proteins are susceptible to changes that are partially ameliorated by treatment

Neural constraints on visual acuity in proliferative diabetic retinopathy

PURPOSE

Visual acuity (VA) in normally sighted individuals is highly correlated with equivalent intrinsic blur, a measure of the amount of blur within the visual system that is generated by optical and neural sources. This study assessed the extent to which VA, equivalent intrinsic blur, optical blur, and neural blur are abnormal in subjects with proliferative diabetic retinopathy (PDR) and characterized the relationships among these parameters.

METHODS

Best-corrected VA of 10 subjects with PDR (ages 25 to 68) and 10 normally sighted individuals (ages 46 to 63) was measured for tumbling E optotypes. The Es were either unblurred or blurred through convolution with Gaussian functions of different widths. Values of equivalent intrinsic blur (σ(int)) and unblurred VA (MAR0) were derived using a standard model. Optical blur (σ(opt)), a measure of blur generated by higher-order aberrations, was quantified using Shack-Hartmann aberrometry. An index of neural blur (η) was defined as 1--σ(opt)/σ(int), which represents the remaining blur once the contributions of σ(opt) to σ(int) have been accounted for.

RESULTS

Log MAR0 and log σ(int) were correlated significantly (r = 0.98, p < 0.05) for the PDR subjects and the values of these parameters ranged from normal to more than a factor of 2 above the upper limit of normal. In comparison, log MAR measured for the most blurred E was elevated by a relatively small amount for all PDR subjects and was not correlated significantly with log σ(int) (r = 0.40, p = 0.25). MAR0, σ(int), and η differed significantly between the PDR subjects and the controls (all p < 0.05) but σ(opt) did not (p = 0.50).

CONCLUSIONS

Subjects with PDR and VA loss had higher than normal equivalent intrinsic blur that resulted primarily from neural blur elevations, suggesting that neural blur is an important factor that limits VA in these patients.

Streptozotocin induced diabetic retinopathy in rat and the expression of vascular endothelial growth factor and its receptor

AIM

To establish the rat model of streptozotocin (STZ)-induced diabetic retinopathy (DR), which is the most common cause of visual loss and blindness in patients with diabetes, and observe the gene expression of vascular endothelial growth factor (VEGF) and its receptors during the development of DR.

METHODS

A rat model of diabetes was established by intraperitoneal injection of STZ. The diabetic rats were housed for 2, 3 and 4 months after the development of diabetes. Retinal histopathological observation was performed. The retinal vessels were observed by immunofluorescence staining by CD31. The mRNA expression of VEGF, VEGF receptor 1 and 2 (VEGFR1/2) in rat retina was detected by reverse transcription-polymerase chain reaction (RT-PCR) analysis.

RESULTS

Retinal histopathological observation showed the morphological changes of inner nuclear layer (INL) and outer nuclear layer (ONL) at any time-point, and also demonstrated the increased new vessels at both 3, 4 months after the development of diabetes. The CD31 staining results showed that the number of vessels was increased in the retinas of diabetic rats at both 3 and 4 months after the development of diabetes. As compared to the normal rats, the mRNA expression of VEGF was increased in retinas of diabetic rats at 3 months after the development of diabetes, while VEGFR1 and VEGFR2 mRNA expression was increased at 2, 3 and 4 months after the development of diabetes.

CONCLUSION

Taken together, our results demonstrated that DR was occurred at 3 months after the development of diabetes, and the mRNA expression of VEGF, VEGFR1 and VEGFR2 were increased in the process of DR. The present study further evidenced the involvement of VEGF and its receptors in the process of DR.

Comparison of logistic regression and neural network classifiers in the detection of hard exudates in retinal images

Diabetic Retinopathy (DR) is a common cause of visual impairment in industrialized countries. Automatic recognition of DR lesions in retinal images can contribute to the diagnosis and screening of this disease. The aim of this study is to automatically detect one of these lesions: hard exudates (EXs). Based on their properties, we extracted a set of features from image regions and selected the subset that best discriminated between EXs and the retinal background using logistic regression (LR). The LR model obtained, a multilayer perceptron (MLP) classifier and a radial basis function (RBF) classifier were subsequently used to obtain the final segmentation of EXs. Our database contained 130 images with variable color, brightness, and quality. Fifty of them were used to obtain the training examples. The remaining 80 images were used to test the performance of the method. The highest statistics were achieved for MLP or RBF. Using a lesion based criterion, our results reached a mean sensitivity of 95.9% (MLP) and a mean positive predictive value of 85.7% (RBF). With an image-based criterion, we achieved a 100% mean sensitivity, 87.5% mean specificity and 93.8% mean accuracy (MLP and RBF).

Is there a link between neutrophil-lymphocyte ratio and microvascular complications in geriatric diabetic patients?

BACKGROUND

Chronic inflammation plays an important role on development and progression of Type 2 diabetes (T2DM) through immunologic inflammatory mechanisms. Neutrophil to lymphocyte ratio (NLR) is a new, simple and cheap marker of subclinical inflammation. NLR has recently been used as a systemic inflammation marker in chronic diseases as well as a predictor of prognosis in cardiovascular diseases and malignancies.

AIM

The objective of the present study was to investigate the relationship between NLR and microvascular complications of diabetes mellitus (DM) in elderly population.

SUBJECTS AND METHODS

Two hundred and forty-two patients with DM (145 diabetic patients with complications, 97 diabetic patients without complications) and 218 control subjects were enrolled in this study. NLR and microvascular complications because of DM were evaluated and compared with other inflammatory markers.

RESULTS

NLR was higher in the diabetic group (2.21±1.14) than in the controls (2.18±0.76). Furthermore, there was a statistically significant difference between NLR levels in diabetic patients with and without complications (2.46±1.26 vs 2.04±0.51, respectively; p<0.001). The results of themultiple logistic regression analysis depicted that NLR is also an independent predictor for microvascular complications (odds ratio 2.217; 95%confidence interval 1.086-4.526, p=0.029). Receiver operating curve analysis suggested that the optimum NLR cutoff point for microvascular complication was 2.89 with 96.72% specificity, 94.4% positive predictive value.

CONCLUSION

Increased NLR levels may be associated with microvascular complications of DM in the elderly population.

Role of ceramide in diabetes mellitus: evidence and mechanisms

Diabetes mellitus is a metabolic disease with multiple complications that causes serious diseases over the years. The condition leads to severe economic consequences and is reaching pandemic level globally. Much research is being carried out to address this disease and its underlying molecular mechanism. This review focuses on the diverse role and mechanism of ceramide, a prime sphingolipid signaling molecule, in the pathogenesis of type 1 and type 2 diabetes and its complications. Studies using cultured cells, animal models, and human subjects demonstrate that ceramide is a key player in the induction of β-cell apoptosis, insulin resistance, and reduction of insulin gene expression. Ceramide induces β-cell apoptosis by multiple mechanisms namely; activation of extrinsic apoptotic pathway, increasing cytochrome c release, free radical generation, induction of endoplasmic reticulum stress and inhibition of Akt. Ceramide also modulates many of the insulin signaling intermediates such as insulin receptor substrate, Akt, Glut-4, and it causes insulin resistance. Ceramide reduces the synthesis of insulin hormone by attenuation of insulin gene expression. Better understanding of this area will increase our understanding of the contribution of ceramide to the pathogenesis of diabetes, and further help in identifying potential therapeutic targets for the management of diabetes mellitus and its complications.

Neuroprotective effects of cilostazol on retinal ganglion cell damage in diabetic rats

Neurodegeneration is an important component of diabetic retinopathy, with increasing evidence that retinal ganglion cell (RGC) death occurs early in diabetes. We investigated the effects of cilostazol, which has been widely used to manage diabetic complications, on retinal ganglion cell death in the diabetic retina. Four-week-old Otsuka Long-Evans Tokushima fatty (OLETF) rats and Long-Evans Tokushima Otsuka (LETO) rats as matched nondiabetic controls were treated with daily oral cilostazol at 30 mg/kg or 0.9% saline solution. In OLETF rats at the age of 40 weeks, glial fibrillary acidic protein (GFAP) immunofluorescence staining was upregulated in vertical sections, and showed a more ramified pattern in whole-mount retinas compared with that in LETO rats. Vascular endothelial growth factor (VEGF) expression was limited to the ganglion cell layer in LETO rats, but extended into the outer plexiform layer in OLETF rats. Immunofluorescence staining and Western blotting demonstrated that cilostazol treatment reduced GFAP and VEGF expression in the retinas of OLETF rats. Terminal deoxynucleotidyl transferase-mediated terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine nick-end labeling (TUNEL) staining revealed an increase in the RGC layer in OLETF compared with LETO rats (P < 0.05), and cilostazol treatment reduced the number of TUNEL-positive cells in OLETF rats (P < 0.05). Relieving retinal ischemia by systemic cilostazol treatment had a noticeable protective effect on RGCs in diabetic rats. Cilostazol treatment may be useful for the management of diabetic retinal vascular dysfunction and neuronal degeneration.

Association of hyperglycemia mediated increased advanced glycation and erythrocyte antioxidant enzyme activity in different stages of diabetic retinopathy

AIM

This study aimed to evaluate whether hyperglycemia mediated increased formation of advanced glycation end products (AGEs) was associated with erythrocyte antioxidant enzyme activity in subjects with different stages of diabetic retinopathy (DR).

METHODS

Serum level of AGEs was determined by enzyme linked immunosorbent assay. Erythrocyte superoxide dismutase (SOD), glutathione reductase (GR) and catalase activity were estimated by enzymatic reaction based spectrophotometric assay in patients with type 2 diabetes with proliferative diabetic retinopathy (PDR), non-proliferative diabetic retinopathy (NPDR) and no retinopathy (DNR) and also in healthy non-diabetic controls (HC).

RESULT

Erythrocyte SOD and GR activity was significantly lower among NPDR (p=0.024, 0.0017, respectively) and PDR (p=0.0003, 0.0001, respectively) subjects compared with DNR individuals. A significant inverse correlation was observed between serum AGEs and erythrocyte SOD or GR activity in DNR (p=0.0019; r=-0.3033, p=0.0021; r=-0.3015, respectively), NPDR (p=0.0001; r=-0.4602, p=0.0003; r=-0.4161, respectively), and PDR (p<0.0001; r=-0.6753, p<0.0001; r=-0.5854, respectively) individuals.

CONCLUSION

Poor glycemia may be the key factor enhancing AGE formation, which may be associated with lower erythrocyte SOD and GR activity along with increased catalase activity in DR.

Phytochemicals in ocular health: Therapeutic potential and delivery challenges

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are the leading causes of blindness in adults. The impact of these conditions on the quality of life is increasing in significance with a rise in life expectancy. The role of hyperglycemia, oxidative stress and inflammatory responses in the development and/or progression of DR and AMD, and several other sight threatening ocular diseases, is well established. In proliferative retinopathy, signals sent by the retina for nourishment, triggers the growth of fragile and abnormal blood vessels. Changes in ocular pressure may lead to rupture of these blood vessels causing severe vision problems. Recent in vitro and preclinical studies demonstrate that certain phytochemicals possessing potent antioxidant and anti-inflammatory activity and ocular blood flow enhancing properties may be very useful in the treatment of, or as a prophylactic measure for, DR and AMD. Apart from these properties they have also been investigated for their anti-bacterial, hormonal, enzyme stimulation, and anti-angiogenic activities. The attractive aspect of these potential therapeutic candidates is that they can act on multiple pathways identified in the etiology of DR, AMD, cataract and other ocular diseases. However, results from clinical trials have been somewhat ambiguous, raising questions about the concentrations of these bioflavonoids achieved in the neural retina following oral administration. Unfortunately, as of date, an efficient noninvasive means to deliver therapeutic agents/candidates to the back-of-the eye is still not available. This review examines some of these promising natural agents and discusses the challenges encountered in delivering them to the posterior segment ocular tissues through the oral route.

Diabetic retinopathy in predicting diabetic nephropathy in patients with type 2 diabetes and renal disease: a meta-analysis

AIMS/HYPOTHESIS

The aim of this meta-analysis is to determine the predictive value of diabetic retinopathy in differentiating diabetic nephropathy from non-diabetic renal diseases in patients with type 2 diabetes and renal disease.

METHODS

Medline and Embase databases were searched from inception to February 2012. Renal biopsy studies of participants with type 2 diabetes were included if they contained data with measurements of diabetic retinopathy. Pooled sensitivity, specificity, positive predictive value, negative predictive value and other diagnostic indices were evaluated using a random-effects model.

RESULTS

The meta-analysis investigated 26 papers with 2012 patients. The pooled sensitivity and specificity of diabetic retinopathy to predict diabetic nephropathy were 0.65 (95% CI 0.62, 0.68) and 0.75 (95% CI 0.73, 0.78), respectively. The pooled positive and negative predictive value of diabetic retinopathy to predict diabetic nephropathy were 0.72 (95% CI 0.68, 0.75) and 0.69 (95% CI 0.67, 0.72), respectively. The area under the summary receiver operating characteristic curve was 0.75, and the diagnostic odds ratio was 5.67 (95% CI 3.45, 9.34). For proliferative diabetic retinopathy, the pooled sensitivity was 0.25 (95% CI 0.16, 0.35), while the specificity was 0.98 (95% CI 0.92, 1.00). There was heterogeneity among studies (p < 0.001), and no publishing bias was identified.

CONCLUSIONS/INTERPRETATION

Diabetic retinopathy is useful in diagnosing or screening for diabetic nephropathy in patients with type 2 diabetes and renal disease. Proliferative diabetic retinopathy may be a highly specific indicator for diabetic nephropathy.

The diabetic ocular environment facilitates the development of endogenous bacterial endophthalmitis

PURPOSE

We tested the hypothesis that changes in the diabetic ocular environment facilitate the development of endogenous bacterial endophthalmitis (EBE).

METHODS

C57BL/6J mice were rendered diabetic with streptozotocin (STZ) for 1, 3, or 5 months' duration. Diabetic and age-matched nondiabetic mice were tail vein-injected with 10(8) CFU of Klebsiella pneumoniae, a common cause of EBE in diabetics. After either 2 or 4 days postinfection, the EBE incidence was assessed by electroretinography, histology, bacterial counts, and myeloperoxidase ELISAs. Blood-retinal barrier (BRB) permeability in uninfected diabetic mice also was determined.

RESULTS

No cases of EBE were observed among the 1-month diabetic group. Extending the time from diabetes induction to 3 months resulted in a 23.8% EBE incidence after 2 days, and a 22% incidence after 4 days. The incidence of EBE increased to 27% in the 5-month diabetic group. Infected eyes had an average 8.01 × 10(2) and 6.19 × 10(4) CFU/eye for the 3- and 5-month diabetic groups, respectively. There was no significant difference in BRB permeability between control and 1-month uninfected diabetic mice. However, 3- and 5-month diabetic mice had significantly greater BRB permeability than control mice. These results suggested that increasing the time from STZ diabetes induction to 3 and 5 months resulted in an ocular environment more conducive to the development of EBE.

CONCLUSIONS

These results demonstrated a correlation between an increase in BRB permeability and an increase in EBE incidence, supporting the hypothesis that diabetic ocular changes contribute to the development of EBE.

Role of inflammation in the pathogenesis of diabetic retinopathy

Diabetic retinopathy (DR) remains a major cause of worldwide preventable blindness. The microvasculature of the retina responds to hyperglycemia through a number of biochemical changes, including activation of protein kinase C, increased advanced glycation end products formation, polyol pathway, and oxidative stress, and activation of the renin angiotensin system (RAS). There is an accumulating body of evidence that inflammation plays a prominent role in the pathogenesis of DR.

Therapeutic interventions against inflammatory and angiogenic mediators in proliferative diabetic retinopathy

The global prevalence of diabetes is estimated to be 336 million people, with diabetic complications contributing to significant worldwide morbidity and mortality. Diabetic retinopathy results from cumulative microvascular damage to the retina and inflammation is recognized as a critical driver of this disease process. This paper outlines the pathophysiology leading to proliferative diabetic retinopathy and highlights many of the inflammatory, angiogenic, and cytokine mediators implicated in the development and progression of this disease. We focus a detailed discussion on the current targeted therapeutic interventions used to treat diabetic retinopathy.

Activating transcription factor 4 mediates hyperglycaemia-induced endothelial inflammation and retinal vascular leakage through activation of STAT3 in a mouse model of type 1 diabetes

AIMS/HYPOTHESIS

There is convincing evidence that endoplasmic reticulum (ER) stress is implicated in the pathogenesis of diabetes and its complications; however, the mechanisms are not fully understood. This study aimed to dissect the role and signalling pathways of activating transcription factor 4 (ATF4) in ER-stress-associated endothelial inflammation and diabetic retinopathy.

METHODS

ER stress and ATF4 activity were manipulated by complementary pharmacological and genetic approaches in cultured retinal endothelial (TR-iBRB) cells. Diabetes was induced by streptozotocin in heterozygous Atf4 knockout and wild-type mice. ER stress markers, inflammatory cytokines and adhesion molecules, activation of the signal transducer and activator of transcription 3 (STAT3) pathway, and retinal vascular permeability were measured.

RESULTS

High-glucose treatment resulted in rapid induction of ER stress, activation of ATF4, and increased production of inflammatory factors in TR-iBRB cells. Suppressing ER stress or inhibiting ATF4 activity markedly attenuated high-glucose-induced production of intercellular adhesion molecule 1, TNF-α and vascular endothelial growth factor. Conversely, enhancing ER stress or overexpressing Atf4 was sufficient to induce endothelial inflammation, which was, at least in part, through activation of the STAT3 pathway. Furthermore, knockdown of the Stat3 gene or inhibiting STAT3 activity restored ER homeostasis in cells exposed to high glucose and prevented ATF4 activation, suggesting that STAT3 is required for high-glucose-induced ER stress. Finally, we showed that downregulation of Atf4 significantly ameliorated retinal inflammation, STAT3 activation and vascular leakage in a mouse model of type 1 diabetes.

CONCLUSIONS/INTERPRETATION

Taken together, our data reveal a pivotal role of ER stress and the ATF4/STAT3 pathway in retinal endothelial inflammation in diabetic retinopathy.

Elevated serum levels of AGEs, sRAGE, and pentosidine in Tunisian patients with severity of diabetic retinopathy

OBJECTIVES

The advanced glycation end products (AGEs)-receptor for AGE (RAGE) axis activity are implicated in diabetic vascular complications. We measured serum AGE, sRAGE and pentosidine levels in Tunisian patients with diabetic retinopathy (DR) and examined whether these biomarkers are related to the severity of DR.

DESIGN AND METHODS

We included 30 healthy control subjects and 100 diabetic patients were divided into 2 subgroups: 40 patients with nonproliferative diabetic retinopathy (NPDR), and 60 patients with proliferative diabetic retinopathy (PRD). AGEs, sRAGE and pentosidine were measured in serum by ELISA.

RESULTS

Serum levels of AGEs, sRAGE and pentosidine were significantly increased in patients with diabetes mellitus compared to nondiabetic controls (P<.01, P<.001, P<.001 respectively). In diabetic patients, serum AGEs, sRAGE and pentosidine levels were significantly higher in patients who had PDR than in those with NPDR (P=.001, P=.01, P=.005 respectively). Furthermore, in stepwise multivariate regression analysis, the levels of pentosidine and duration of diabetes were independently associated with severity of DR.

CONCLUSION

Serum AGEs, sRAGE, and pentosidine levels are related with the presence of DR. Duration of diabetes and pentosidine were independently correlated with the severity of DR.

Modulation of diabetic retinopathy pathophysiology by natural medicines through PPAR-γ-related pharmacology

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and remains a major cause of preventable blindness among adults at working age. DR involves an abnormal pathology of major retinal cells, including retinal pigment epithelium, microaneurysms, inter-retinal oedema, haemorrhage, exudates (hard exudates) and intraocular neovascularization. The biochemical mechanisms associated with hyperglycaemic-induced DR are through multifactorial processes. Peroxisome proliferator-activated receptor-γ (PPAR-γ) plays an important role in the pathogenesis of DR by inhibiting diabetes-induced retinal leukostasis and leakage. Despite DR causing eventual blindness, only a few visual or ophthalmic symptoms are observed until visual loss develops. Therefore, early medical interventions and prevention are the current management strategies. Laser photocoagulation therapy is the most common treatment. However, this therapy may cause retinal damage and scarring. Herbal and traditional natural medicines may provide an alternative to prevent or delay the progression of DR. This review provides an analysis of the therapeutic potential of herbal and traditional natural medicines or their active components for the slowdown of progression of DR and their possible mechanism through the PPAR-γ pathway.

Genetic and environmental factors associated with type 2 diabetes and diabetic vascular complications

Faced with a global epidemic of type 2 diabetes (T2D), it is critical that researchers improve our understanding of the pathogenesis of T2D and related vascular complications. These findings may ultimately lead to novel treatment options for disease prevention or delaying progression. Two major paradigms jointly underlie the development of T2D and related coronary artery disease, diabetic nephropathy, and diabetic retinopathy. These paradigms include the genetic risk variants and behavioral/environmental factors. This article systematically reviews the literature supporting genetic determinants in the pathogenesis of T2D and diabetic vasculopathy, and the functional implications of these gene variants on the regulation of beta-cell function and glucose homeostasis. We update the discovery of diabetes and diabetic vasculopathy risk variants, and describe the genetic technologies that have uncovered them. Also, genomic linkage between obesity and T2D is discussed. There is a complementary role for behavioral and environmental factors modulating the genetic susceptibility and diabetes risk. Epidemiological and clinical data demonstrating the effects of behavioral and novel environmental exposures on disease expression are reviewed. Finally, a succinct overview of recent landmark clinical trials addressing glycemic control and its impact on rates of vascular complications is presented. It is expected that novel strategies to exploit the gene- and exposure-related underpinnings of T2D will soon result.

Retinal blood flow abnormalities following six months of hyperglycemia in the Ins2(Akita) mouse

The aim of this study was to characterize the microvascular flow abnormalities and oxygenation changes that are present following six months of hyperglycemia in the diabetic Ins2(Akita) mouse. Previous studies have shown decreased retinal blood flow in the first several weeks of hyperglycemia in rodents, similar to the decreases seen in the early stages of human diabetes. However, whether this alteration in the mouse retina continues beyond the initial weeks of diabetes has yet to be determined, as are the potential consequences of the decreased flow on retinal oxygenation. In this study, male Ins2(Akita) and age-matched C57BL/6 (non-diabetic) mice were maintained for a period of six months, at which time intravital microscopy was used to measure retinal blood vessel diameters, blood cell velocity, vascular wall shear rates, blood flow rates, and transient capillary occlusions. In addition, the presence of hypoxia was assessed using the oxygen-sensitive probe pimonidazole. The diabetic retinal microvasculature displayed decreases in red blood cell velocity (30%, p<0.001), shear rate (25%, p<0.01), and flow rate (40%, p<0.001). Moreover, transient capillary stoppages in flow were observed in the diabetic mice, but rarely in the non-diabetic mice. However, no alterations were observed in retinal hypoxia as determined by a pimonidazole assay, suggesting the possibility that the decreases seen in retinal blood flow may be dictated by a decrease in retinal oxygen utilization.

Early local functional changes in the human diabetic retina: a global flash multifocal electroretinogram study

PURPOSE

To investigate early functional changes of local retinal defects in type II diabetic patients using the global flash multifocal electroretinogram (MOFO mfERG).

METHODS

Thirty-eight diabetic patients and 14 age-matched controls were recruited. Nine of the diabetics were free from diabetic retinopathy (DR), while the remainder had mild to moderate non-proliferative diabetic retinopathy. The MOFO mfERG was performed at high (98 %) and low (46 %) contrast levels. MfERG responses were grouped into 35 regions for comparison with DR classification at those locations. Z-scores of the regional mfERG responses were compared across different types of DR defects.

RESULTS

The mfERG waveform consisted of the direct component (DC) and the induced component (IC). Local reduction in DC and IC amplitudes were found in diabetic patients with and without DR. With increasing severity of retinopathy, there was a further deterioration in amplitude of both components. Under MOFO mfERG paradigm, amplitude was a useful screening parameter.

CONCLUSION

The MOFO mfERG can help in detecting early functional anomalies before the appearance of visible signs, and may assist in monitoring further functional deterioration in diabetic patients.

Endoplasmic reticulum stress and inflammation: mechanisms and implications in diabetic retinopathy

The endoplasmic reticulum (ER) is the primary cellular compartment where proteins are synthesized and modified before they can be transported to their destination. Dysfunction of the ER impairs protein homeostasis and leads to the accumulation of misfolded/unfolded proteins in the ER, or ER stress. While it has long been recognized that ER stress is a major cause of conformational disorders, such as Alzheimer's disease, Huntington's disease, certain types of cancer, and type 2 diabetes, recent evidence suggests that ER stress is also implicated in many chronic inflammatory diseases. These diseases include irritable bowel syndrome, atherosclerosis, diabetic complications, and many others. Diabetic retinopathy is a common microvascular complication of diabetes, characterized by chronic inflammation, progressive damage to retinal vascular and neuronal cells, vascular leakage, and abnormal blood vessel growth (neovascularization). In this review, we discuss the role and mechanisms of ER stress in retinal inflammation and vascular damage in diabetic retinopathy.

Association between retinoid-X receptor-gamma genetic polymorphisms and diabetic retinopathy

Retinoid-X receptor (RXR) is one of the members of the nuclear hormone receptor superfamily. It forms heterodimers with many nuclear receptors, such as the peroxisome proliferative-activated receptor, which has been proposed to be involved in diabetic complications, including retinopathy. A recent study revealed that RXR-alpha has antioxidant properties and is associated with diabetic retinopathy. We found that the RXR-gamma gene is involved in the pathogenesis of diabetic nephropathy. We also hypothesized that the RXR-gamma gene has a role in the development of diabetic retinopathy. We examined 213 diabetic patients, who were divided into retinopathy or no retinopathy groups. Nine selected single nucleotide polymorphisms (SNPs) in the RXR-gamma gene were evaluated. The diabetic retinopathy group had longer diabetes duration, higher body mass indexes, and higher systolic blood pressure, as well as higher concentrations of fasting plasma glucose, blood urine nitrogen, and creatine. One SNP--rs3818569 of the RXR-gamma gene was found to be associated with increased risk for diabetic retinopathy in both allele and genotype frequencies (P = 0.0023 and 0.0057, respectively). Analysis with multivariate logistic regression revealed that the dominant RXR-gamma GG genotype is a risk factors for the development of diabetic retinopathy (odds ratio = 2.388; 95% confidence interval = 1.17-4.875). We conclude that the RXR-gamma rs3818569 SNP is associated with diabetic retinopathy development in the Taiwanese population.

Retinal arteriolar caliber and urine albumin excretion: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Changes in retinal microvascular caliber, which occur prior to onset of retinopathy, may indicate presence of kidney damage.

METHODS

This study examined the association between retinal arteriolar [central retinal artery equivalent (CRAE)] and venular caliber [central retinal venule equivalent (CRVE)] and presence of albuminuria (micro- or macroalbuminuria) among participants of the Multi-Ethnic Study of Atherosclerosis (MESA), a cohort of adults aged 45-84 years without baseline clinical cardiovascular disease. During the second MESA exam, digital fundus photography was completed in 5897 participants who provided spot urine specimens. Albuminuria was defined by spot urine albumin/creatinine ratios ≥ 30 mg/g. Multivariable adjusted odds of albuminuria by quintiles of CRAE and CRVE were determined using logistic regression. Analyses were repeated after stratifying by presence of type 2 diabetes.

RESULTS

Albuminuria was noted in 11.5% (n = 675) and included 584 subjects with microalbuminuria and 91 with macroalbuminuria. A significant U-shaped pattern was seen with higher prevalence of albuminuria across quintile extremes in CRAE (15.7, 8.8 and 10.6% in CRAE Quintiles 1, 3 and 5, respectively; P <0.0001). After adjustment for covariates, both narrower CRAE [odds ratios (OR) 1.55; 95% confidence interval (CI) 1.17-2.04, Quintile 1 versus 3) and wider CRAE (OR 1.44; 95% CI 1.07-1.93, Quintile 5 versus 3) were significantly associated with albuminuria. Associations appeared substantially stronger in adults with than without type 2 diabetes but the interaction term for diabetes and CRAE on presence of albuminuria did not meet statistical significance (P = 0.3). No association was noted between CRVE quintiles and albuminuria.

CONCLUSIONS

Albuminuria is associated with narrower and wider arteriolar caliber. Future studies should determine whether variation in arteriolar caliber predicts incident albuminuria and whether associations are mediated by hypertension and diabetes. Such information could further clarify early microvascular processes in the pathogenesis of kidney disease.

The influence of type 2 diabetes mellitus on the expression of inflammatory mediators and tissue inhibitor of metalloproteinases-2 in human chronic periodontitis

PURPOSE

The purpose of this study was to compare and quantify the expression of C-reactive protein (CRP), matrix metalloproteinase (MMP)-14, and tissue inhibitor of metalloproteinases (TIMP)-2 in gingival tissues of patients with chronic periodontitis accompanied with inflammatory reaction related to alveolar bone resorption with or without type 2 diabetes mellitus (DM).

METHODS

Twelve patients with type 2 DM and chronic periodontitis (group 3), twelve patients with chronic periodontitis (group 2), and twelve healthy individuals (group 1) were included in the study. Gingival tissue biopsies were collected from each patient and from healthy individuals at the time of periodontal surgery (including surgical crown lengthening) or tooth extraction. The concentrations of cytokines were determined by a western blot analysis.

RESULTS

The expression levels of CRP and MMP-14 increased in group 2 and 3, and they were highest in group 3. The expressions of TIMP-2 also increased in group 2 and 3.

CONCLUSIONS

This study demonstrated that the expression levels of CRP, MMP-14, and TIMP-2 might be inflammatory markers in periodontal inflamed tissue. It can be assumed that CRP, MMP-14, and TIMP-2 may be partly involved in the progression of periodontal inflammation associated to type 2 DM.

New approach to modulate retinal cellular toxic effects of high glucose using marine epa and dha

Background

Protective effects of omega-3 fatty acids against cellular damages of high glucose were studied on retinal pigmented epithelial (RPE) cells.

Methods

Retinal epithelial cells were incubated with omega-3 marine oils rich in EPA and DHA and then with high glucose (25 mM) for 48 hours. Cellular responses were compared to normal glucose (5 mM): intracellular redox status, reactive oxygen species (ROS), mitochondrial succinate deshydrogenase activity, inflammatory cytokines release and caveolin-1 expression were evaluated using microplate cytometry, ELISA and flow cytometry techniques. Fatty acids incorporation in retinal cell membranes was analysed using chromatography.

Results

Preincubation of the cells with fish oil decreased ROS overproduction, mitochondrial alterations and TNFα release. These protective effects could be attributed to an increase in caveolin-1 expression induced by marine oil.

Conclusion

Marine formulations rich in omega-3 fatty acids represent a promising therapeutic approach for diabetic retinopathy.

Role of advanced glycation end product receptors in the pathogenesis of diabetic retinopathy

PROBLEM

Advanced glycation end products (AGEs) and the interaction with their receptors (RAGE) play an important role in the pathogenesis of diabetic retinopathy (DR). Our study investigated whether serum soluble (s) RAGE (sRAGE) could serve as a prognostic tool for identifying the susceptibility to DR. Moreover, we examined the association between soluble forms of vascular cell adhesion molecules (sVCAM-1), nitric oxide (NO) and sRAGE levels in serum and the severity of DR.

METHODS

Circulating levels of sRAGE, sVCAM-1, and NO were examined in 37 type 2 diabetic patient and 20 age-matched healthy nondiabetic subjects using ELISA. The diabetic subjects were categorized as patients without retinopathy, patients with nonproliferative DR (NPDR), and patients with proliferative DR (PDR).

RESULTS

Serum sRAGE levels were significantly lower in patients with NPDR and PDR than in healthy controls and in those without retinopathy (1331.13 ± 126.13, 934.87 ± 66.27 vs. 1712.69 ± 167.3, 1833.1 ± 153.06 pg/ml, respectively, P<.05). Serum sVCAM-1 and NO were significantly higher in diabetic patients (1310.215 ± 54.712 vs. 616.55 ± 12.9 ng/ml and 96.432 ± 0.864 vs. 28.78 ± 5.88 μmol/l, respectively, P<.05) and were positively associated with the severity of DR.

CONCLUSIONS

The results indicate that sRAGE is an endogenous protection factor against the occurrence of accelerated DR.

Diabetic retinopathy and its risk factors in a population-based study

AIM

To assess the prevalence of diabetic retinopathy and its risk factors among people with diabetes using a population-based survey and discuss strategies that can be used to both prevent and manage diabetes-related complications in a primary care setting.

METHODS

The prevalence of self-reported doctor-diagnosed diabetic retinopathy and its risk factors were estimated using data from the Arkansas Behavioral Risk Factor Survey, 2003-2007. Five years of survey data were combined and weighted to the population to assess the risk factors that predict the prevalence of diabetic retinopathy. The study involved 2477 people who reported that they have been diagnosed with diabetes.

RESULTS

Twenty-two percent of survey respondents with diabetes had been diagnosed with diabetic retinopathy. Using a multivariate adjusted model, blacks (odds ratio [OR] = 1.76, 95% confidence interval [CI], 1.26, 2.45), those with some high school education (OR = 2.78, 95% CI, 1.80, 4.28), people with diabetes for more than 10 years (OR = 2.14, 95% CI 1.61, 2.85), people on insulin treatment (OR = 2.35, 95% CI 1.78, 3.08), those who had taken a course to manage their diabetes (OR = 1.54, 95% CI 1.20, 1.99), and those with chronic foot ulcers (OR = 2.24, 95% CI 1.62, 3.09) were more likely to have been diagnosed with diabetic retinopathy.

CONCLUSIONS

The prevalence of diabetic retinopathy and its risk factors are evident. Novel approaches to increase the screening and treatment of these frequent complications are key to optimize diabetes care.

Automated detection of red lesions from digital colour fundus photographs

Earliest signs of diabetic retinopathy, the major cause of vision loss, are damage to the blood vessels and the formation of lesions in the retina. Early detection of diabetic retinopathy is essential for the prevention of blindness. In this paper we present a computer-aided system to automatically identify red lesions from retinal fundus photographs. After pre-processing, a morphological technique was used to segment red lesion candidates from the background and other retinal structures. Then a rule-based classifier was used to discriminate actual red lesions from artifacts. A novel method for blood vessel detection is also proposed to refine the detection of red lesions. For a standarised test set of 219 images, the proposed method can detect red lesions with a sensitivity of 89.7% and a specificity of 98.6% (at lesion level). The performance of the proposed method shows considerable promise for detection of red lesions as well as other types of lesions.

A new supervised method for blood vessel segmentation in retinal images by using gray-level and moment invariants-based features

This paper presents a new supervised method for blood vessel detection in digital retinal images. This method uses a neural network (NN) scheme for pixel classification and computes a 7-D vector composed of gray-level and moment invariants-based features for pixel representation. The method was evaluated on the publicly available DRIVE and STARE databases, widely used for this purpose, since they contain retinal images where the vascular structure has been precisely marked by experts. Method performance on both sets of test images is better than other existing solutions in literature. The method proves especially accurate for vessel detection in STARE images. Its application to this database (even when the NN was trained on the DRIVE database) outperforms all analyzed segmentation approaches. Its effectiveness and robustness with different image conditions, together with its simplicity and fast implementation, make this blood vessel segmentation proposal suitable for retinal image computer analyses such as automated screening for early diabetic retinopathy detection.

Assessment of four neural network based classifiers to automatically detect red lesions in retinal images

Diabetic retinopathy (DR) is an important cause of visual impairment in industrialised countries. Automatic detection of DR early markers can contribute to the diagnosis and screening of the disease. The aim of this study was to automatically detect one of such early signs: red lesions (RLs), like haemorrhages and microaneurysms. To achieve this goal, we extracted a set of colour and shape features from image regions and performed feature selection using logistic regression. Four neural network (NN) based classifiers were subsequently used to obtain the final segmentation of RLs: multilayer perceptron (MLP), radial basis function (RBF), support vector machine (SVM) and a combination of these three NNs using a majority voting (MV) schema. Our database was composed of 115 images. It was divided into a training set of 50 images (with RLs) and a test set of 65 images (40 with RLs and 25 without RLs). Attending to performance and complexity criteria, the best results were obtained for RBF. Using a lesion-based criterion, a mean sensitivity of 86.01% and a mean positive predictive value of 51.99% were obtained. With an image-based criterion, a mean sensitivity of 100%, mean specificity of 56.00% and mean accuracy of 83.08% were achieved.

Algorithms for the automated detection of diabetic retinopathy using digital fundus images: a review

Diabetes is a chronic end organ disease that occurs when the pancreas does not secrete enough insulin or the body is unable to process it properly. Over time, diabetes affects the circulatory system, including that of the retina. Diabetic retinopathy is a medical condition where the retina is damaged because fluid leaks from blood vessels into the retina. Ophthalmologists recognize diabetic retinopathy based on features, such as blood vessel area, exudes, hemorrhages, microaneurysms and texture. In this paper we review algorithms used for the extraction of these features from digital fundus images. Furthermore, we discuss systems that use these features to classify individual fundus images. The classifications efficiency of different DR systems is discussed. Most of the reported systems are highly optimized with respect to the analyzed fundus images, therefore a generalization of individual results is difficult. However, this review shows that the classification results improved has improved recently, and it is getting closer to the classification capabilities of human ophthalmologists.

Automated detection of diabetic retinopathy: barriers to translation into clinical practice

Automated identification of diabetic retinopathy (DR), the primary cause of blindness and visual loss for those aged 18-65 years, from color images of the retina has enormous potential to increase the quality, cost-effectiveness and accessibility of preventative care for people with diabetes. Through advanced image analysis techniques, retinal images are analyzed for abnormalities that define and correlate with the severity of DR. Translating automated DR detection into clinical practice will require surmounting scientific and nonscientific barriers. Scientific concerns, such as DR detection limits compared with human experts, can be studied and measured. Ethical, legal and political issues can be addressed, but are difficult or impossible to measure. The primary objective of this review is to survey the methods, potential benefits and limitations of automated detection in order to better manage translation into clinical practice, based on extensive experience with the systems we have developed.

Retinal imaging and image analysis

Many important eye diseases as well as systemic diseases manifest themselves in the retina. While a number of other anatomical structures contribute to the process of vision, this review focuses on retinal imaging and image analysis. Following a brief overview of the most prevalent causes of blindness in the industrialized world that includes age-related macular degeneration, diabetic retinopathy, and glaucoma, the review is devoted to retinal imaging and image analysis methods and their clinical implications. Methods for 2-D fundus imaging and techniques for 3-D optical coherence tomography (OCT) imaging are reviewed. Special attention is given to quantitative techniques for analysis of fundus photographs with a focus on clinically relevant assessment of retinal vasculature, identification of retinal lesions, assessment of optic nerve head (ONH) shape, building retinal atlases, and to automated methods for population screening for retinal diseases. A separate section is devoted to 3-D analysis of OCT images, describing methods for segmentation and analysis of retinal layers, retinal vasculature, and 2-D/3-D detection of symptomatic exudate-associated derangements, as well as to OCT-based analysis of ONH morphology and shape. Throughout the paper, aspects of image acquisition, image analysis, and clinical relevance are treated together considering their mutually interlinked relationships.

A comparison of injection force and dosage scale size between NovoPen 3 and NovoPen 4

BACKGROUND

Easy-to-use insulin devices are an important tool in the treatment of diabetes. In this study, injection force requirements and dosage scale displays were evaluated for NovoPen 3 and NovoPen 4 (both from Novo Nordisk A/S, Copenhagen, Denmark).

METHODS

To simulate 5 years of expected lifetime usage, 5,475 injections were performed automatically. Before and after lifetime testing, the force required to expel 60 U of insulin from NovoPen 3 and NovoPen 4 with 30-gauge or 31-gauge needles was measured. To compare dosage scale displays, digital images of multiple settings were made, and the total inked areas of digits were converted to mm(2).

RESULTS

At baseline, the mean +/- SD injection force of NovoPen 4 was 9.14 +/- 0.87 N and 16.55 +/- 1.17 N, which was significantly lower (P < 0.001) than for NovoPen 3, at 18.36 +/- 1.06 N and 29.81 +/- 1.26 N, with the 30-gauge and 31-gauge needle, respectively. After simulated lifetime testing, mean +/- SD injection force was 10.93 +/- 0.77 N and 17.77 +/- 1.14 N for NovoPen 4, which was significantly lower than the injection force of 18.54 +/- 0.94 N and 31.69 +/- 1.98 N for NovoPen 3 (P < 0.001). The mean dosage scale digit size was 1.63 mm(2) for NovoPen 3 and 7.82 mm(2) for NovoPen 4, with a mean difference of 6.19 mm(2). The display for NovoPen 4 was 4.74 times larger (P < 0.001).

CONCLUSIONS

The mean injection force required to operate NovoPen 4 was reduced up to 50% compared with NovoPen 3 (P < 0.001), and the mean dosage display for NovoPen 4 was over four times larger than for NovoPen 3 (P < 0.001). Based on these findings, patients with diabetes who have manual or visual impairment should find it easier to dose insulin with NovoPen 4.

Comparison of the retinal microvasculature in European and African-Caribbean people with diabetes

Diabetes aggravates the impact of elevated BP (blood pressure) on the microcirculation, and people of African ancestry with diabetes are more susceptible to microvascular damage than Europeans. In the present study, we investigated possible differences in the retinal microcirculation in people of European and African-Caribbean ethnicity with diabetes that might account for this. A total of 51 subjects with Type 2 diabetes (age 40–65 years; 25 male; 29 African-Caribbean) were studied. Clinic and 24 h ambulatory BP, and fasting glucose, insulin and lipids were measured. Digital retinal images were analysed using custom-written semi-automatic software to determine: LDR (length/diameter ratio) and AVR (arteriolar/venular diameter ratio), branching angles, vessel tortuosity and NT (number of terminal vessel branches). Arterioles were narrower in European people with diabetes than in African-Caribbean people with diabetes [mean (S.D.) arteriolar diameter, 76 (7) compared with 82 (11) μm respectively (P=0.03); arteriolar LDR, 28.1 (8.5) compared with 23.7 (7.0) respectively (P=0.046); and AVR, 0.66 (0.21) compared with 0.90 (0.36) respectively (P=0.028)]. Ethnic differences in arteriolar LDR, arteriolar diameter and AVR were not explained by differences in BP, but were attenuated by adjustment for the duration of diabetes. There was no significant relationship between BP and arteriolar narrowing in the group as a whole, although the relationship between arteriolar LDR and systolic BP was stronger in Europeans than African-Caribbeans [β=0.08 (0.07) compared with β=0.03 (0.06); P=0.03]. In conclusion, in the presence of diabetes, a relationship between BP and retinal arteriolar diameter was not evident and implies impaired small artery remodelling in the presence of diabetes. African-Caribbean people with diabetes have wider retinal arterioles and this could contribute to enhanced microvascular damage in this ethnic group.

Screening for diabetic retinopathy using computer vision and physiological markers

BACKGROUND

Hyperglycemia and diabetes result in vascular complications, most notably diabetic retinopathy (DR). The prevalence of DR is growing and is a leading cause of blindness and/or visual impairment in developed countries. Current methods of detecting, screening, and monitoring DR are based on subjective human evaluation, which is also slow and time-consuming. As a result, initiation and progress monitoring of DR is clinically hard.

METHODS

Computer vision methods are developed to isolate and detect two of the most common DR dysfunctions-dot hemorrhages (DH) and exudates. The algorithms use specific color channels and segmentation methods to separate these DR manifestations from physiological features in digital fundus images. The algorithms are tested on the first 100 images from a published database. The diagnostic outcome and the resulting positive and negative prediction values (PPV and NPV) are reported. The first 50 images are marked with specialist determined ground truth for each individual exudate and/or DH, which are also compared to algorithm identification.

RESULTS

Exudate identification had 96.7% sensitivity and 94.9% specificity for diagnosis (PPV = 97%, NPV = 95%). Dot hemorrhage identification had 98.7% sensitivity and 100% specificity (PPV = 100%, NPV = 96%). Greater than 95% of ground truth identified exudates, and DHs were found by the algorithm in the marked first 50 images, with less than 0.5% false positives.

CONCLUSIONS

A direct computer vision approach enabled high-quality identification of exudates and DHs in an independent data set of fundus images. The methods are readily generalizable to other clinical manifestations of DR. The results justify a blinded clinical trial of the system to prove its capability to detect, diagnose, and, over the long term, monitor the state of DR in individuals with diabetes.

Systemic administration of HMG-CoA reductase inhibitor protects the blood-retinal barrier and ameliorates retinal inflammation in type 2 diabetes

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) are frequently used lipid-lowering drugs in type 2 diabetes. Recent emerging evidence suggests that statins protect cardiovascular function via lipid-independent mechanisms. However, the potential role of statins in diabetic retinopathy in type 2 diabetes is largely unclear. In the present study we have investigated the effect of lovastatin on blood-retinal barrier and inflammatory status in the retina of db/db mice and in cultured retinal cells. Male C57BL/KsJ db/db mice were randomly chosen to receive gastric gavage of lovastatin (10mg/kg/day) or vehicle control for 6 weeks. Retinal vascular permeability, the tight junction and inflammation were determined. The results showed that db/db mice at the age of 19 weeks exhibited significantly increased retinal vascular leakage and decreased tight junction protein level in the retina. Moreover, the expression of pro-inflammatory factors, e.g. ICAM-1 and TNF-alpha, was drastically up-regulated in diabetic retina. Lovastatin treatment normalized all of these changes. In cultured bovine retinal capillary endothelial cells (RCECs) and human ARPE-19 cells, lovastatin attenuated the decrease of tight junction protein (occludin) and adherens junction protein (VE-cadherin) expression-induced by TNF-alpha, a major pro-inflammatory cytokine in diabetic retinopathy. Lovastatin also attenuated TNF-alpha expression in RCEC. Towards the mechanism, we showed that lovastatin ameliorated ICAM-1 expression-induced by hypoxia and TNF-alpha in both RCECs and ARPE-19 cells, in part through inhibition of NF-kappaB activation. Taken together, these findings indicate that lovastatin protects blood-retinal barrier in diabetic retinopathy, which is likely via its anti-inflammatory effects.

[Diabetic retinopathy risk factors]

Diabetic retinopathy (DR) occurs in about 95% of patients with type 1 diabetes mellitus (DM) and in 60% of type 2 DM patients and it is the main cause of legal blindness in adult people. The aim of this manuscript was to review the main risk factors for DR. The major environmental risk factors are hyperglycemia, high blood pressure levels, and long-term duration of DM. However, not all patients will not develop DR, suggesting the presence of a genetic predisposition to DR, especially for severe forms of DR. Special strategies has been used to evaluate the genetic role in DR. Family studies shown that there is a familial aggregation of DR. Candidates genes have been studied (RAGE; VEGF; PPAR-delta; ICAM-1; ECA; ENPP 1; eNOS) and positive or negative associations with DR were demonstrated. Some chromosomes were also associated to DR in selected populations. Finally, genetic expression studies reinforce the association of candidate genes, or participation of others genes, with the presence of DR. DR is a common complication of DM and, along with non-genetic or environmental risk factors, the identification of genes related to DR could result in more specific and efficient DR treatment.

Diabetes mellitus and apoptosis: inflammatory cells

Since the early observation that similarities between thyroiditis and insulitis existed, the important role played by inflammation in the development of diabetes has been appreciated. More recently, experiments have shown that inflammation also plays a prominent role in the development of target organ damage arising as complications, with both elements of the innate and the adaptive immune system being involved, and that cytokines contributing to local tissue damage may arise from both infiltrating and resident cells. This review will discuss the experimental evidence that shows that inflammatory cell-mediated apoptosis contributes to target organ damage, from beta cell destruction to both micro- and macro-vascular disease complications, and also how alterations in leukocyte turnover affects immune function.

A comparative cost analysis of digital fundus imaging and direct fundus examination for assessment of diabetic retinopathy

The objective of this study was to compare the cost between two procedures for fundus examination in patients with diabetes. In our setting, two alternatives for fundus examination are available for patients with diabetes. In the first alternative, a digital image is taken with a nonmydriatic fundus camera when the patient is at the endocrinology consultation, and the image is then examined by an ophthalmologist. In the second alternative, a direct fundus examination is made by an ophthalmologist. We calculated the costs of both procedures from both Public Healthcare System (PHS) and patient perspectives using the official scales to compute personnel, consumables, capital cost of equipment, travel expenses, and time loss of the patient caused by attending the consultation. The first alternative (digital fundus image) required 2.69, 0.03, and 1.62 Euros per patient for personnel, consumables, and capital cost of the equipment, respectively. A direct fundus examination was needed in 31% of patients that had an additional cost of 0.97 Euros per patient for the PHS plus 14.97 Euros per patient because of travel cost and loss of income. The second alternative (direct fundus examination) required 2.69, 0.11, and 0.33 Euros per patient for personnel, consumables, and capital cost, respectively. All patients in this second alternative had to attend a consultation that implied travel and loss of income costs. Attending a consultation represented a cost of 48.29 Euros per patient. From the PHS perspective, direct fundus examination is less costly than using digital fundus images. The higher cost of the digital fundus option is a consequence of the higher capital costs required by the equipment needed to obtain the digital image. However, from a global perspective, the digital image alternative is more convenient because the travel cost and loss of income of the patient are lower.