Diabetic retinopathy at the time of diagnosis of NIDDM in south Indian subjects

Functional and structural changes in the neuroretina are accompanied by mitochondrial dysfunction in a type 2 diabetic mouse model

BACKGROUND

Diabetic retinopathy (DR), one of the leading causes of blindness and vision impairment, is suggested to exhibit functional and structural changes in retinal neurons as the earliest manifestation, which could be used to predict the progression of related angiopathy. While neural function and survival rely on proper mitochondrial function, and a growing body of literature has supported the role of mitochondrial dysfunction in the development of DR, how diabetes affects mitochondrial function in retinal tissue remains elusive. This study primarily aimed to investigate mitochondrial functional changes in a diabetic rodent model. We also characterized the early DR phenotype, in particular, neurodegeneration.

METHODS

C57BLKsJ-db/db (db/db) mice (a type 2 diabetic mouse model) were used with their normoglycemic heterozygous littermates (db/+) serving as controls. Longitudinal changes in retinal function and morphology were assessed with electroretinography (ERG) and optical coherence tomography (OCT), respectively, at 9, 13, 17, and 25 weeks of age. At 25 weeks, the retinas were harvested for immunohistochemistry and ex vivo mitochondrial bioenergetics.

RESULTS

Decreased ERG responses were observed in db/db mice as early as 13 weeks of age. OCT revealed that db/db mice had significantly thinner retinas than the controls. Immunohistochemistry showed that the retinas of the db/db mice at 25 weeks were thinner at the outer and inner nuclear layers, with lower photoreceptor and cone cell densities compared with the db/+ mice. The number of rod-bipolar cell dendritic boutons and axon terminals was significantly reduced in db/db mice relative to the db/+ mice, suggesting that diabetes may lead to compromised synaptic connectivity. More importantly, the retinas of db/db mice had weaker mitochondrial functions than the controls.

CONCLUSIONS

Our longitudinal data suggest that diabetes-induced functional deterioration and morphological changes were accompanied by reduced mitochondrial function in the retina of db/db mice. These findings suggest that mitochondrial dysfunction may be a contributing factor triggering the development of DR. While the underlying mechanistic cause remains elusive, the db/db mice could be a useful animal model for testing potential treatment regimens targeting neurodegeneration in DR.

Prevalence of microvascular and macrovascular complications of diabetes in newly diagnosed type 2 diabetes in low-and-middle-income countries: A systematic review and meta-analysis

There is an excessive burden of diabetes complications in low-resource settings. We conducted a systematic review to determine the nature and frequency of diabetes complications in newly diagnosed with type 2 diabetes. A systematic search was performed using Medline, CINAHL and Global Health online databases from inception to July 2020. Articles reporting prevalence of microvascular or macrovascular complications within six months of type 2 diabetes diagnosis and published in English or French from low- and middle-income countries (LMICs) were eligible for analysis. Data were extracted using a standardized data extraction tool. Descriptive statistics were used to describe the prevalence of micro and macrovascular complications in newly diagnosed type 2 diabetes. Assessment of heterogeneity was conducted using the inconsistency index (I2) and Cochran-Q chi2 statistical tests. Publication bias was assessed by the Funnel plot and Egger test. A total of 3 292 records underwent title or abstract screening and 95 articles underwent full text review. Thirty-three studies describing 13 283 participants (aged 20 years and older) met the inclusion criteria. The eligible studies were from Asia (n = 24), Africa (n = 4), Oceania (n = 2), South America (n = 2) and the Caribbean (n = 1). For microvascular complications, the median prevalence (interquartile range) of retinopathy, nephropathy and neuropathy were 12% (6%-15%), 15% (7%-35%) and 16% (10%25%) respectively. For macrovascular complications, the median prevalence (interquartile range) was 10% (7%-17%) for ischaemic heart disease, 6% (1%-20%) for peripheral arterial disease and 2% (1%-4%) for stroke. There was evidence of substantial heterogeneity between studies for all outcomes (I2 > 90%. We found a high prevalence of complications in newly diagnosed type 2 diabetes in LMICs. Findings suggest that many people live with diabetes and are only diagnosed when they present with complications in LMICs. Research is needed to guide timely and effective identification of people living with diabetes in these settings.

The prevalence of retinopathy among type 2 diabetic patients in Iran: A systematic review and meta-analysis

Diabetic retinopathy is one of the most major causes of blindness and disability in diabetic patients and imposes very high cost on Health Care System. Studies conducted in the country showed different and inconsistent prevalence of the disease. The study aims to determine the overall prevalence of retinopathy in patients with type 2 diabetes in Iran through a systematic review and meta-analysis. The present study was conducted via meta-analysis method during March, 2000 to October, 2018. The articles related to the subject under study were obtained from Magiran, SID, Medline (PubMed), Science Direct, Scopus and Google Scholar databases. I2 index was used to examine the heterogeneity of articles studied; and the data was analyzed by Comprehensive Meta-Analysis Software. Through the study of 34 articles and 17,079 individuals with age range of 5-83, the overall prevalence of retinopathy for type 2 diabetic patients in Iran and on the basis of meta-analysis, was obtained that was 37.8% (32.84-43%, 95% confidence interval); the highest prevalence of retinopathy for type 2 diabetic patients was in Tehran province with 78% (68.8-85.1%, 95% confidence interval) in 2006 and the lowest prevalence of retinopathy for type 2 diabetic patients was in Isfahan province with 9% (7.1-11.4, 95% confidence interval) in 2006; furthermore, the prevalence of retinopathy for type 2 diabetic patients in Iran increases with increased sample size that it was statistically significant (P < 0.05). Regarding the high prevalence of retinopathy for type 2 diabetic patients in the country, it is essential that health policy makers take effective measures to reduce the disease incidence in diabetic patients.

Effect of race and ethnicity on vildagliptin efficacy: A pooled analysis of phase II and III studies

AIMS

To determine the impact of race and ethnicity on the efficacy, body weight and hypoglycaemia incidence with vildagliptin treatment in patients with type 2 diabetes mellitus using patient-level data from the vildagliptin clinical trial programme.

METHODS

Data from 22 randomized, placebo-controlled global and local (Japan, China) registration studies of vildagliptin (50 mg once-daily or twice-daily) of ≥12-week duration were analysed by race (Caucasian [n = 2764] and Asian [n = 2232]) and by ethnicity (Japanese, Chinese, and Indian). The placebo-subtracted differences in the change in glycated haemoglobin (HbA1c) and body weight from baseline to week 12 or week 24 were evaluated by race or ethnicity using repeated measure analysis of unstructured covariance. Hypoglycaemia incidences were summarized using descriptive statistics.

RESULTS

The HbA1c reduction from baseline with vildagliptin was similar across the racial/ethnic subgroups (-0.83% ± 0.02% to -1.01% ± 0.05%). Placebo-corrected HbA1c reduction was similar between Caucasian (-0.68% ± 0.03%) and Asian (-0.80% ± 0.03%) patients ( P value for interaction = .56); analysis by race and ethnicity showed better efficacy ( P < .02) in Japanese patients. Japanese patients were drug-naïve and treated with a single oral anti-diabetes drug only; they showed no response to placebo. Weight neutrality of vildagliptin was demonstrated in all groups (0.47 ± 0.11 kg to -0.29 ± 0.08 kg). Hypoglycaemic events (≥1) were infrequent in all ethnic subgroups.

CONCLUSIONS

The glycaemic efficacy of vildagliptin was similar in Caucasian and Asian patients. The slightly better efficacy observed in Japanese patients was driven by the absence of placebo effect and might be explained by their earlier stage of diabetes compared to other subgroups.

Estimating the delay between onset and diagnosis of type 2 diabetes from the time course of retinopathy prevalence

OBJECTIVE

By correlating known diabetes duration with the prevalence of retinopathy, more than 10 years have been estimated to lapse between the onset and diagnosis of type 2 diabetes. Such calculations, however, assumed a linear model, included stages of retinopathy not specific to diabetes, and allowed 5 years for retinopathy to occur after the onset of diabetes. We calculated the duration of undiagnosed type 2 diabetes in outpatients screened for retinopathy in a hospital-based diabetes clinic after correcting these assumptions.

RESEARCH DESIGN AND METHODS

Diabetic patients (n = 12,074; 35,545 fundus examinations) were stratified into younger onset (YO; age at onset <30 years) or older onset (OO; age at onset ≥30 years), insulin treated (IT) or not IT (NIT), and with mild/more severe diabetic retinopathy (AnyDR) or moderate/more severe diabetic retinopathy (ModDR). The best-fitting equation correlating known duration among the OO-NIT group with the prevalence of ModDR was used to extrapolate time from appearance of retinopathy to diagnosis of type 2 diabetes. Time for retinopathy to develop after diabetes was calculated from the equation correlating the duration among the YO-IT group with appearance of ModDR.

RESULTS

There were 1,719 patients in the OO-NIT group with AnyDR and 685 with ModDR and 756 in the YO-IT group with AnyDR and 385 with ModDR. A linear model showed ModDR appeared 2.66 years before diagnosis among those in the OO-NIT group. A quadratic model suggested that ModDR appeared 3.29 years after diagnosis among those in the YO-IT group. The resulting estimate was 6.05 years (2.66 + 3.29) between the onset and diagnosis of diabetes, compared with 13.36 years using standard criteria.

CONCLUSIONS

Using best-fitting models and stratifying by glucose-lowering treatment and severity of retinopathy substantially lowers the estimated duration of undiagnosed type 2 diabetes.

Changes in detection of retinopathy in type 2 diabetes in the first 4 years of a population-based diabetic eye screening program: retrospective cohort study

OBJECTIVE

Annual diabetic eye screening has been implemented in England since 2008. This study aimed to estimate changes in the detection of retinopathy in the first 4 years of the program.

RESEARCH DESIGN AND METHODS

Participants included 32,340 patients with type 2 diabetes resident in three London boroughs with one or more screening records between 2008 and 2011. Data for 87,570 digital images from 2008 to 2011 were analyzed. Frequency of sight-threatening diabetic retinopathy (STDR) was estimated by year of screen for first screens and for subsequent screens according to retinopathy status at first screen.

RESULTS

Among 16,621 first-ever screens, the frequency of STDR was 7.1% in 2008, declining to 6.4% in 2011 (P = 0.087). The proportion with a duration of diabetes of <1 year at first screen increased from 18.7% in 2008 to 48.6% in 2011. Second or later screens were received by 26,308 participants. In participants with mild nonproliferative retinopathy at first screen, the proportion with STDR at second or later screen declined from 21.6% in 2008 to 8.4% in 2011 (annual change -2.2% [95% CI -3.3 to -1.0], P < 0.001). In participants with no retinopathy at first screen, STDR declined from 9.2% in 2008 to 3.2% in 2011 (annual change -1.8% [-2.0 to -1.7], P < 0.001). Declining trends were similar in sociodemographic subgroups.

CONCLUSIONS

After the inception of population-based diabetic eye screening, patients at lower risk of STDR contribute an increasing proportion to the eligible population, and the proportion detected with STDR at second or subsequent screening rounds declines rapidly.

Early diagnosis and prevention of diabetes in developing countries

Type 2 diabetes has an insidious onset with a long latent period of dysglycaemia. By the time the diagnosis of diabetes is made, diabetes-related tissue damage occurs in nearly half of the patients. Even after diagnosis, the glycaemic control is suboptimal in more than 50%, leading to the vascular complications. Evidences suggest that early detection of diabetes by appropriate screening methods, especially in subjects with high risk for diabetes will help to prevent or delay the vascular complications and thus reduce the clinical, social and economic burden of the disease. There are also evidences to show that intervention at the prediabetic stage is superior to diagnosis of diabetes.

Epidemiology of diabetic retinopathy and macular oedema: a systematic review

AIMS

To systematically review the literature on the prevalence and incidence of diabetic retinopathy (DR) and macular oedema (MO).

METHODS

A search of the bibliographic databases (Medline, Embase, CINAHL) was conducted up to October 2001. Selected relevant studies were scrutinized and included in the review.

RESULTS

A total of 359 studies were included. The studies were reported in nearly 100 different journals and in over 50 countries. The majority of the studies were US-based, with large studies such as the Wisconsin Epidemiologic Study of Diabetic Retinopathy dominating the literature. The studies were quite dated and highly heterogeneous in nature in terms of patient selection with variable inclusion criteria (age range, gender, diabetes duration and type, ethnicity, comorbidity, and DR status, assessment, and classification).

CONCLUSIONS

There are inconsistencies between epidemiological studies, and differences in study methods may contribute to conflicting reports of prevalence and incidence of DR and MO in diabetic populations. As new therapies for DR and its associated complications emerge, the need to capture and monitor new epidemiological data becomes increasingly important to be able to assess the impact and effectiveness of these therapies. Robust, longitudinal capture of patient data is, therefore, essential to evaluate the impact of current practice on the epidemiology of diabetic eye complications.

Diabetic retinopathy in Oman: a hospital based study

The magnitude of diabetic retinopathy, its determinants, and coverage of laser treatment for diabetic retinopathy among registered people with diabetes in Oman are presented. 2249 randomly selected subjects representing 5564 registered diabetics were examined. WHO recommended definitions of diabetes, retinopathy, and other related conditions were used. Physicians reported the profile of the diabetes while ophthalmologists reported ocular profile and the eye care provided to them. The prevalence of diabetic retinopathy was 14.39% (95% CI 13.46 to 15.31). Men had significantly higher rate of retinopathy than women. The retinopathy rate was higher in age groups 50-59 years and 60-69 years. The rates of background retinopathy, proliferative retinopathy, and diabetic maculopathy were 8.65%, 2.66%, and 5.12%, respectively. The rate was higher among subjects with longer duration of diabetes than those with a shorter duration. Those with an HbA(1c) level more than 9% had significantly higher rates of diabetic retinopathy than those with an HbA(1c) level less than 9%. The retinopathy rate was higher in cases with hypertension, nephropathy, and neuropathy. Of those with diabetic retinopathy who were advised to have treatment at the time of registration, only 20% were treated with laser therapy.

Diabetic retinopathy among self reported diabetics in southern India: a population based assessment

AIMS

To estimate the prevalence of diabetic retinopathy among self reported diabetics in a population of southern India.

METHODS

A cross sectional sample of subjects aged 50 years and older was selected using a cluster sampling technique from Palakkad district of Kerala state. Eligible subjects were identified through a door to door survey. Ocular examinations including visual acuity and anterior and posterior segment examinations were performed at preselected sites within clusters. History of diabetes was elicited, and height, weight, and blood pressure were measured for all subjects.

RESULTS

Among the 5212 examined people (92% response rate), 68 (26.2%) of 260 people with self reported history of diabetes had diabetic retinopathy. The age-sex adjusted prevalence of diabetes among people aged 50 years and older was 5.1% (95% CI 3.9, 6.3, deff 4.33) and of diabetic retinopathy among the diabetics was 26.8% (95% CI: 19.2, 34.4, deff 1.99). Non-proliferative diabetic retinopathy (94.1%) was the most common form of retinopathy seen. Two eyes were blind (presenting vision <6/60) as a result of retinopathy.

CONCLUSION

Preventive strategies have to be evolved to ensure that blindness due to diabetic retinopathy does not become a public health problem in India. Further studies are required to understand the risk factors for retinopathy and vision loss in this population.

Prevalence of retinopathy at diagnosis among type 2 diabetic patients attending a diabetic centre in South India

AIM

To assess the prevalence of retinopathy in newly diagnosed south Indian type 2 diabetic patients attending a diabetic centre.

METHODS

448 consecutive newly diagnosed type 2 diabetic patients were recruited. Four field retinal colour photography was performed and graded using a modified form of the Early Treatment Diabetic Retinopathy Study grading system.

RESULTS

Of the 438 patients with assessable photographs, 32 (7.3%, 95% confidence interval 5.0 to 10. 2) had retinopathy. None of the variables tested showed a significant association with retinopathy on univariate or multivariate logistic regression analysis.

CONCLUSION

The overall prevalence of retinopathy at diagnosis among clinic based south Indian patients with type 2 diabetes appears to be lower than that reported among Europeans.

Prevalence of retinopathy in non insulin dependent diabetes mellitus at a diabetes centre in southern India

A cohort of 6792 NIDDM patients attending a diabetes centre at Madras in South India was screened using a combination of retinal photography and clinical examination by retinal specialists. A total of 2319 patients (34.1%) had evidence of retinopathy. This included 2090 patients (30.8%) with non-proliferative diabetic retinopathy including 435 patients (6.4%) with maculopathy and 229 patients (3.4%) with proliferative diabetic retinopathy. Multiple logistic regression analyses showed that duration of diabetes, glycosylated haemoglobin, type of treatment (insulin treatment versus non-insulin treatment), systolic and diastolic blood pressures and serum creatinine, showed a positive association with retinopathy while body mass index (BMI) showed an inverse association. The prevalence rates of retinopathy in Southern Indians are comparable to those seen in Europeans. However in view of the high prevalence of diabetes in the Indian sub-continent, diabetic retinopathy could become a formidable challenge in the future.