Vitamin D Deficiency in Patients with Diabetes in French Guiana: Epidemiology and Relation with Microvascular and Macrovascular Complications.

Vitamin D (VD) insufficiency is common among patients with diabetes in French Guiana. The study aimed to evaluate the prevalence of VD deficiency in the different type of diabetes encountered and to analyze the relationship between VD deficiency and diabetes complications. METHODS: An observational study was conducted between May 2019 and May 2020 in French Guiana, based on data from the CODIAM study (Diabetes Cohort in French Amazonia), describing the characteristics of patients with diabetes mellitus. Among 600 patients enrolled with diabetes, 361 had an available VD assay. RESULTS: The mean 25(OH)VD (hydroxycalciferol) level was 27.9 ng/mL. The level of VD was inversely proportional to the HbA1c (glycated hemoglobin) level. Patients with angina pectoris had a greater proportion of deficiencies VD < 20 ng/mL than those without angina. By contrast, patients with retinopathy had higher vitamin D concentrations than those without retinopathy. There was no association between vitamin D and arteriopathy, stroke, nephropathy and polyneuropathy. VD deficiency was more frequent in women, and in patients with a high school education. CONCLUSION: The prevalence of VD deficiency was high in patients with diabetes in French Guiana, emphasizing the importance of VD supplementation.

Dietary glutamic acid and aspartic acid as biomarkers for predicting diabetic retinopathy.

The screening rate of diabetic retinopathy (DR) is low despite the importance of early diagnosis. We investigated the predictive value of dietary glutamic acid and aspartic acid for diagnosis of DR using the Korea National Diabetes Program cohort study. The 2067 patients with type 2 diabetes without DR were included. The baseline intakes of energy, glutamic acid and aspartic acid were assessed using a 3-day food records. The risk of DR incidence based on intake of glutamic acid and aspartic acid was analyzed. The DR group was older, and had higher HbA1c, longer DM duration, lower education level and income than non-DR group (all p < 0.05). The intake of total energy, glutamic acid and aspartic acid were lower in DR group than non-DR group (p = 0.010, p = 0.025 and p = 0.042, respectively). There was no difference in the risk of developing DR according to the intake of glutamic acid and ascorbic acid. But, aspartic acid intake had a negative correlation with PDR. Hence, the intake of glutamic acid and aspartic acid did not affect in DR incidence. However, lower aspartic acid intake affected the PDR incidence.

Terminalia catappa Fruit Extract Reverses Streptozotocin-Induced Diabetic Retinopathy in Rats.

OBJECTIVE AND BACKGROUND: Diabetic retinopathy is amongst the most common microvascular complications associated with diabetes. Controlling blood glucose level alone cannot manage diabetes associated complications. Thus, mechanisms that additionally prevent diabetes associated complications are the need of the hour, driving the researchers towards herbal therapies. Terminalia catappa is renowned for its anti-inflammatory, antioxidant, anti-hyperglycemic and anti-angiogenic activity. The current study explores the effect of Terminalia catappa fruit extract on streptozotocin-induced diabetic retinopathy in rats. METHODS: Streptozotocin-induced chronic diabetic rat model was utilized in the study. The hydroalcoholic fruit extract of T. catappa in 20mg/kg, 30mg/kg and 40mg/kg dose and standard anti-diabetic drug, glibenclamide (10mg/kg) was given orally. Retinopathy was evaluated by monitoring lenticular, fundus images and measuring arteriole and venule tortuosity index. Oxidative, angiogenic and inflammatory biomarkers were assessed at the 12th week in the retinal homogenate. Histopathological changes in the retina were also examined. Data was analyzed using one-way Repeated Measure ANOVA followed by the Mann-Whitney test. RESULTS: The hydro-alcoholic fruit extract of T. catappa significantly decreased blood glucose (p<0.001) in a dose-dependent manner in diabetic rats. Cataract lens was observed in all experimental groups and became clear (grade 0) with 40mg/kg and with 40mg/kg along with glibenclamide at the eighth and sixth week, respectively. The hydro-alcoholic fruit extract in all three doses significantly reduced (p<0.01) arteriole and venule tortuosity in diabetic rats. T. catappa in all three doses in diabetic rats showed a modulatory effect in oxidative, angiogenic and inflammatory biomarkers. CONCLUSION: T. catappa reverses diabetes-induced retinopathy by anti-hyperglycemic, anti-oxidant, anti-angiogenic and anti-inflammatory actions, and thus has a potential to be used in diabetes-induced retinopathy.

The effects of Bushen Yiqi Huoxue prescription and its disassembled prescriptions on a diabetic retinopathy model in Sprague Dawley rats.

BACKGROUND: Diabetic retinopathy (DR) is one of the most serious complications in the late stages of diabetes, with a complex mechanism. As a complication affecting local lesions, few studies have compared differences of cytokine expression in the serum and retina. Owing to the specific value of traditional Chinese medicine (TCM) to complex diseases, TCM research has recently boomed in the prevention and treatment of diabetes. Bushen Yiqi Huoxue (BYH) prescription is a Chinese herbal compound that has been independently developed by our research group and has been proved to have a positive effect on DR; however, its specific mechanism and compatibility rule remain to be further explored. OBJECTIVE: To construct a DR model of Sprague Dawley (SD) rats, simultaneously detect multiple factor expression in the serum and retina of rats, explore the effect of BYH prescription and its disassembled prescriptions on DR, and discuss the influence of various compatibility combinations. METHODS: BYH prescription was disassembled into two new compatibilities in the absence of Rehmanniae Radix (Yiqi Huoxue prescription, YH prescription) or Ginseng Radix et Rhizoma (Bushen Huoxue prescription, BH prescription). Male SD rats were induced using streptozotocin + high-fat and high-sugar diet to establish DR models and were divided into groups, then the intragastric administration and sampling. The body weight and fasting blood glucose of rats were continuously recorded during feeding; pathophysiological status observation of the retina by haematoxylin and eosin (HE) staining; advanced glycation end products (AGEs) and haemoglobin A1c (HbA1c) level detection in the rat serum by enzyme-linked immunosorbent assay; and the Luminex technique was used to detect the ICAM-1, IL-1ß, IL-6, TNF-α and vascular endothelial growth factor (VEGF) expression concentrations in the retinal tissue and serum. RESULTS: The results of blood glucose, body weight and HE staining proved that the model was successfully constructed, and the three combinations could reduce the retinal injury in DR rats. Serum AGEs and HbA1c levels of the model group increased compared with the control group (CG). Compared with the DR model group, only AGEs decreased in the BYH group, while the AGEs and HbA1c levels were significantly inhibited in the YH and BH groups, showing a significant correlation between the expression of AGEs and HbA1c in the serum of DR rats. In the serum of rats, IL-1ß, IL-6, TNF-α and VEGF concentrations in the DR model group increased, although no statistical difference was observed in the ICAM-1 data compared with the CG. Compared with the DR model group, the IL-1ß, IL-6 and TNF-α expression decreased in the BYH group. Moreover, the IL-6 and TNF-α expression decreased in the YH group and only the IL-6 expression decreased in the BH group. In the retina tissue, the model group had higher ICAM-1, IL-1ß, IL-6, TNF-α and VEGF levels than the CG. Compared with the DR model group, TNF-α in the BYH group rats decreased, and the ICAM-1, IL-6 and TNF-α concentrations decreased in the YH and BH groups. Furthermore, differences in the ICAM-1 and VEGF expression in the serum and retina existed. CONCLUSION: BYH compound and its disassembled prescriptions could improve the DR model rats induced with streptozotocin + high-fat and high-sugar diet, respectively, by inhibiting chronic blood glucose, AGEs, or inflammation response. The expression level and location of each factor are different, confirming that the effect of TCM prescriptions is not the simple addition of each single drug or its chemical components, but the rationality of its internal compatibility combination. Further, ICAM-1 and VEGF have exactly different expression levels, suggesting more attention to be paid by other researchers or doctors in future studies.

Association Between Vitamin D Status and Diabetic Complications in Patients With Type 2 Diabetes Mellitus: A Cross-Sectional Study in Hunan China.

Background: Vitamin D status has been linked to diabetes-related complications due to multiple extraskeletal effects. We aimed to investigate the association between vitamin D deficiency (VDD) and diabetic vascular complications, including diabetic retinopathy (DR), diabetic kidney disease (DKD), and diabetic foot ulcers (DFU). Methods: A total of 4,284 Chinese patients with type 2 diabetic mellitus (T2DM) were enrolled into the cross-sectional study. VDD was defined as serum 25-hydroxyvitamin D <50 nmol/L. Demographic data, physical measurements, laboratory measurements, comorbidities, and related medications were collected and analyzed by VDD status. Poisson regression with robust variance estimation and binary logistic regression were performed to explore the relationship between VDD and diabetic complications. Results: The prevalence of VDD, DR, DKD, DFU accounted to 71.7% (95% confidence intervals [CI]: 70.3-73.0%), 28.5% (95% CI: 27.2-29.9%), 28.2% (95% CI: 26.8-29.5%), and 5.7% (95% CI: 5.1-6.5%), respectively. The prevalence ratios (95% CI) for DR and DKD by VDD status, adjusted for demographics, physical measurements, laboratory measurements, related complications, and comorbidities, and medications, were 1.093 (0.983-1.215) and 1.041 (0.937-1.156), respectively. The odds ratio (95% CI) for DFU by VDD status was 1.656 (1.159-2.367) in the final adjusted model. Meanwhile, the prevalence of VDD was significantly higher in patients with DFU compared with patients without DFU. Conclusions: The present study firstly indicated that VDD was significantly associated with a higher prevalence of DFU among Chinese T2DM patients. The association between VDD status and DR or DKD was not significant when adjusting for all potential covariates. Vitamin D screening or supplementation may be beneficial to prevent DFU and improve the prognosis of T2DM patients.

Association between Serum Vitamin D and Diabetic Retinopathy in Portuguese Patients with Type 1 Diabetes.

INTRODUCTION: Recently, vitamin D has gained importance as a diabetes risk modifier. Our aim was to assess the association between serum vitamin D levels and the prevalence of diabetic retinopathy in patients with type 1 diabetes. MATERIAL AND METHODS: Retrospective review of a population of patients with type 1 diabetes followed in a Portuguese tertiary center. Patients were included if they had an ophthalmological evaluation and a serum 25-hydroxyvitamin D level determination within the same year. Logistic regression analysis was used to adjust for possible confounders. RESULTS: We included 182 patients (47% male), and 57% (n = 103) had signs of diabetic retinopathy. We found a significant association between lower circulating levels of 25-hydroxyvitamin D levels and a greater prevalence of diabetic retinopathy after adjusting for confounders (duration of diabetes, estimated glomerular filtration rate, age, sex, metabolic control, season, dyslipidemia and hypertension) (OR = 0.94; 95% CI 0.90 - 0.99, p = 0.023). Longer duration of diabetes and worse metabolic control also remained associated with diabetic retinopathy in the multivariate analysis (OR = 1.20; 95% CI 1.13 - 1.27, p < 0.001 and OR = 4.13; 95% CI 1.34 - 12.7, p = 0.013, respectively). CONCLUSION: Lower levels of vitamin D were associated with an increased prevalence of diabetic retinopathy in patients with type 1 diabetes, after adjusting for possible confounders. Future controlled studies may elucidate the molecular routes for this association as well as the role of supplementation in the prevention of diabetes microvascular complications.

Introdução: A vitamina D tem vindo a ganhar importância como um modificador do risco de diabetes. O objetivo deste estudo foi avaliar a associação entre os níveis séricos de vitamina D e a prevalência de retinopatia diabética em pacientes com diabetes tipo 1. Material e Métodos: Estudo retrospetivo de uma população de doentes com diabetes tipo 1, seguidos num centro hospitalar terciário português. Os pacientes foram incluídos se tivessem uma avaliação oftalmológica e um doseamento dos níveis de 25-hidroxivitamina D no mesmo ano. Os ajustes para eventuais variáveis confundidoras foi realizado recorrendo a uma análise de regressão logística. Resultados: Foram incluídos 182 doentes (47% sexo masculino), dos quais 57% (n = 103) demonstravam sinais de retinopatia diabética. Foi encontrada uma associação significativa entre níveis inferiores de 25-hidroxivitamina D circulante sérica e uma maior prevalência de retinopatia diabética, depois do ajuste para os confundidores incluídos (duração da diabetes, taxa de filtração glomerular estimada, idade, sexo, controlo metabólico, estação do ano, dislipidemia e hipertensão) (OR = 0,94; 95% IC 0,90 - 0,99, p = 0,023). Uma maior duração da diabetes, assim como um pior controlo metabólico, mantiveram também uma associação significativa com uma maior prevalência de retinopatia diabética na análise multivariada (OR = 1,20; 95% IC 1,13 - 1,27, p < 0,001; OR = 4,13; 95% IC 1,34 - 12,7, p = 0,013, respetivamente). Conclusão: Níveis inferiores de vitamina D séricos demonstraram-se associados a uma prevalência superior de retinopatia diabética em pacientes com diabetes tipo 1, após o ajuste para eventuais variáveis confundidoras. Futuramente, estudos experimentais poderão estabelecer as vias moleculares implicadas nesta associação, assim como um papel concreto da suplementação na prevenção das complicações microvasculares da diabetes.

Effect of vitamin B12 supplementation on retinal lesions in diabetic rats.

Purpose: Diabetic retinopathy (DR) is the most common complication of diabetes involving microvasculature and neuronal alterations in the retina. Previously, we reported that vitamin B12 deficiency could be an independent risk factor for DR in humans. However, the effect of vitamin B12 supplementation in experimental DR is unknown. Thus, in this study, we investigated the impact of dietary supplementation of vitamin B12 on retinal changes in diabetic rats. Methods: Diabetes was induced in 2-month-old Sprague-Dawley rats and maintained for 4 months. One group of diabetic rats were fed normal levels of vitamin B12, and one group double the quantity of vitamin B12 (50 µg/kg diet). Vitamin B12 and homocysteine levels in the plasma were analyzed with radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC), respectively. At the end of 4 months of experimentation, the eyeballs were collected. Retinal changes were analyzed with hematoxylin and eosin (H&E) staining, immunoblotting, and immunofluorescence methods. Results: Dietary supplementation of vitamin B12 had no effect on food intake, bodyweight, fasting blood glucose, and plasma homocysteine levels in the diabetic rats. However, vitamin B12 supplementation prevented loss of rhodopsin, and overexpression of VEGF, and completely prevented overexpression of HIF1α, GFAP, and endoplasmic reticulum (ER) stress markers (GRP78, ATF6α, XBP1, CHOP, and caspase 12) in the diabetic rat retina. Further, vitamin B12 ameliorated apoptosis in the retina as shown with terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) and prevented retinal thinning. Conclusions: Vitamin B12 supplementation of diabetic rats appeared to be beneficial by circumventing retinal hypoxia, VEGF overexpression, and ER stress-mediated cell death in the retina. The present study adds another potential therapeutic strategy of vitamin B12 in diabetes.

Traditional chinese medicine for diabetic retinopathy: A systematic review and meta-analysis.

BACKGROUND: Traditional Chinese medicine (TCM) has been used to treat diabetic complications including diabetic retinopathy for many years. OBJECTIVES: This review was performed to systematically assess the efficacy and safety of TCM for treating non- proliferative diabetic retinopathy (NPDR). METHODS: Retrieval from 7 electronic databases was conducted to determine eligible trials published until March 1, 2018. Randomized controlled trials of NPDR that comparing compound Chinese medicine containing the therapeutic method of activating blood and remove stasis versus controls were included for analysis. Primary outcomes were progression of retinopathy. Secondary outcomes included visual acuity, mean defect of visual field, micro-aneurysms, hemorrhage areas, exudates, capillary nonperfusion areas, hemorheological indicators, oscillatory potentials (Ops), glycated haemoglobin (HbA1c), and adverse events. Data extraction and quality assessment were performed. Results expressing as risk ratios (RRs) or mean differences (MD) were analyzed with a fixed- or random- effect model. I statistics were used to assess heterogeneity. RESULTS: A total of 33 trials and 3373 participants were included. Findings revealed that no included studies reported the progression of retinopathy. Compared with conventional medicine, TCM was significantly better at improving visual acuity (MD, -0.10; 95% confidence interval [CI] -0.16 to -0.05) and Ops (MD, -4.68, 95% CI -8.51 to -0.85), and reducing the mean defect of visual field (MD, -1.43; 95%CI, -2.17 to -0.68), micro-aneurysms (MD, -4.51; 95% CI, -6.23 to -2.79), hemorrhage areas (MD, -0.62; 95% CI, -1.06 to -0.19), plasma viscosity (MD, -0.10; 95% CI, -0.20 to 0.00), and HbA1c (MD, -0.22; 95% CI, -0.42 to -0.03). Compared with placebo, TCM was also associated with a decline in the number of microaneurysms (MD, -4.35; 95% CI, -6.25 to -2.45), exudates (MD, -0.17; 95% CI -0.31 to -0.03), capillary nonperfusion areas (MD, -0.18; 95% CI, -0.31 to -0.04), and HbA1c (MD, -0.88; 95% CI, -1.44 to -0.32). Compared with blank groups, TCM was superior at decreasing the mean defect of visual field (MD, -0.87; 95% CI -0.95 to -0.79) and the numbers of micro-aneurysms (MD, -3.35; 95% CI, -4.73 to -1.97). Adverse events were also assessed. CONCLUSION: Activating blood compound Chinese herbal medicine could help to improve visual acuity, micro-aneurysms and HbA1c. Further trials are needed to provide more reliable evidence.

Zinc supplementation does not influence serum levels of VEGF, BDNF, and NGF in diabetic retinopathy patients: a randomized controlled clinical trial.

Objectives: This study was aimed to evaluate the effects of zinc (Zn) supplementation on serum levels of vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and nerve growth factor (NGF) in patients with diabetic retinopathy (DR). Methods: In this randomized clinical trial, 50 patients with DR were allocated into the Zn (n = 25) and placebo (n = 25) groups to receive 30 mg Zn gluconate or maltose dextrin per day, respectively, for three months. Metabolic parameters and blood pressure were measured. Serum levels of Zn were assessed by atomic absorption spectrophotometry and serum levels of VEGF, BDNF and NGF by ELISA. Results: Forty-five patients completed the intervention. Levels of VEGF, BDNF and NGF were not affected by the Zn supplementation. Levels of VEGF correlated negatively with levels of Zn and positively with BDNF and NGF. There was also a positive correlation between BDNF and NGF. Serum levels of VEGF, BDNF and NGF were negatively correlated with serum levels of the diabetic parameters measured. Conclusions: Strong positive relationship between the growth factors and their inverse association with metabolic factors is possibly suggesting the contribution of these factors in the pathogenesis of DR through acting in a same biological pathway.

Oral supplementation with melatonin reduces oxidative damage and concentrations of inducible nitric oxide synthase, VEGF and matrix metalloproteinase 9 in the retina of rats with streptozotocin/nicotinamide induced pre-diabetes.

Hyperglycemia mediated oxidative stress and pro-angiogenic molecules such as vascular endothelial growth factor (VEGF) and matrix metalloproteinase 9 (MMP9) are considered important for diabetic retinopathy onset and progression. Melatonin is a pineal hormone that regulates circadian and seasonal rhythms and most likely is involved in regulating glucose metabolism. We aimed to evaluate the potential benefit of melatonin supplementation to the pre-diabetic retina by assessing melatonin effects on lipid peroxidation (thiobarbituric acid reactive substances, TBARS), protein oxidation (advanced oxidation protein products, AOPP) and concentrations of inducible nitric oxide synthase (iNOS), VEGF and MMP9 in the retina of rats with pre-diabetes. Pre-diabetes was induced by streptozotocin (45 mg/kg, i.p.) following nicotinamide injection (110 mg/kg, i.p.). Beside mild hyperglycemia, lower serum insulin, increased fructosamine and lower HDL cholesterol, the present study demonstrated decreased serum melatonin in pre-diabetic rats, as well as, increased concentration of retinal TBARS, AOPP, iNOS, VEGF, and MMP9. Oral supplementation with melatonin (85 µg/animal/day) caused melatonin and HDL cholesterol levels to rise in treated rats and reduced levels of fasting serum glucose and fructosamine. It also affected serum insulin and quantitative insulin sensitivity check index (QUICKI) in treated groups but had no significant effect on non-fasting glucose. Finally, supplementation with melatonin reduced concentrations of TBARS, AOPP, iNOS, VEGF, and MMP9 in significant level, thereby exerting an overall positive effect on oxidative stress and pro-angiogenic signaling in the pre-diabetic retina. Thus, oral melatonin might be considered in an early treatment or in the prevention of retinal changes associated with pre-diabetes.

Typhae pollen polysaccharides ameliorate diabetic retinal injury in a streptozotocin-induced diabetic rat model.

ETHNOPHARMACOLOGICAL RELEVANCE: According to ancient traditional Chinese medicine, Typhae Pollen (TP) is commonly used to treat fundus haemorrhage because it improves blood circulation. AIMS OF THE STUDY: This study evaluated the role of the main TP component, polysaccharides (TPP), on diabetic retinopathy (DR) and its possible mechanisms of inhibiting inflammation and improving blood circulation. MATERIALS AND METHODS: After successful establishment of a diabetic rat model, TPP was administered to diabetic rats for treatment, and the rats were sacrificed at 12 weeks. Retinal electrophysiology and ultrastructures were observed, and serum interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) levels were also measured. Changes in the retinal expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were examined by immunofluorescence. A mouse model of acute blood stasis was then established, and the effects of TPP on haemorheology were observed. The anti-inflammatory effect of TPP was analysed based on the changes in abdominal capillary permeability and the degree of auricle swelling in the mice. RESULTS: In streptozotocin (STZ)-induced DR rats, TPP (0.4 g/kg) treatment restored electrophysiology indexes and retinal ultrastructures, reduced serum IL-6 and TNF-α levels, decreased VEGF and bFGF expression in retinal tissues, and improved haemorheology indexes. Moreover, TPP reduced abdominal capillary permeability and relieved auricle swelling in a dose-dependent manner. CONCLUSIONS: TPP treatment ameliorated DR by inhibiting inflammation and improving blood circulation.

Neuroprotective effect of He-Ying-Qing-Re formula on retinal ganglion cell in diabetic retinopathy.

ETHNOPHARMACOLOGY RELEVANCE: He-Ying-Qing-Re Formula (HF) was empirically modified from Si-Miao-Yong-An Decoction (SD), which was recorded in the literature of Divine Doctor's Secret Transmission, and has been utilized for centuries to treat vasculopathy through clearing heat and accelerating bloodstream. HF has been used as an effective holistic treatment of diabetic retinopathy (DR) for decades and experimentally reported to ameliorate retinal condition in diabetic mice. AIM OF THE STUDY: Our study aims to investigate the effect of HF in preventing sustained hyperglycemia and hyperlipidemia-associated retinal ganglion cell (RGC) cell death and its possible mechanism. MATERIALS AND METHODS: Chromatographic fingerprint of HF was obtained upon the UPLC-based analytic system; Diabetic retinopathy was established in streptozotocin (STZ) injection-induced hyperglycemic mice; Alterations of retinal structure was assayed by H&E staining. Expression of PSD-95 and CHOP in retinae was assessed by immunofluorescence; RGC cell line (mRGC) was used for in vitro study. Cell death was analyzed by flow cytometry; Intracellular reactive oxygen species (ROS) was measured by 2',7'-dichlorofluorescin diacetate (DCFDA); Apoptosis-related proteins and signaling were monitored with immunoblotting and colorimetric assay. RESULTS: Chlorogenic acid, ferulic acid, and rutin were identified in HF. HF attenuates the loss of RGCs, thinning of inner retinal layers in diabetic mice. Furthermore, expressions of Brn3a and PSD-95 were restored while CHOP level was downregulated upon HF treatment. In vitro study, HF alleviates H2O2-induced apoptosis of mRGCs and loss of postsynaptic protein via scavenging ROS and suppressing ATF4/CHOP-mediated endoplasmic reticulum stress and mitochondria-related pro-apoptotic factors, probably as cleaved-caspase-3, and phospho-p38 mitogen-activated protein kinase (MARK). Meanwhile, both pro-survival protein levels like Bcl-2/Bcl-xL and postsynaptic protein of PSD-95 were upregulated upon HF treatment. CONCLUSION: HF administration was a valid therapeutic approach for DR treatment, oriented at the blockade of endoplasmic reticulum- and mitochondria-dependent oxidative stress-induced retinal neurodegeneration including RGC apoptosis.

Neuroprotective Effect of Hydroxytyrosol in Experimental Diabetic Retinopathy: Relationship with Cardiovascular Biomarkers.

The aim of the study was to test the neuroprotective effect of hydroxytyrosol (HT) on experimental diabetic retinopathy. Animals were divided in four groups: (1) control nondiabetic rats, (2) streptozotocin-diabetic rats (DR), (3) DR treated with 1 mg/kg/day p.o. HT, and (4) DR treated with 5 mg/kg/day p.o. HT. Treatment with HT was started 7 days before inducing diabetes and was maintained for 2 months. In the DR group, total area occupied by extracellular matrix was increased, area occupied by retinal cells was decreased; both returned to near-control values in DR rats treated with HT. The number of retinal ganglion cells in DR was significantly lower (44%) than in the control group, and this decrease was smaller after HT treatment (34% and 9.1%). Linear regression analysis showed that prostacyclin, platelet aggregation, peroxynitrites, and the dose of 5 mg/kg/day HT significantly influenced retinal ganglion cell count. In conclusion, HT exerted a neuroprotective effect on diabetic retinopathy, and this effect correlated significantly with changes in some cardiovascular biomarkers.

Jiangtang Xiaozhi Recipe () prevents diabetic retinopathy in streptozotocin-induced diabetic rats.

OBJECTIVE: To evaluate the prevention effect of diabetic retinopathy of Jiangtang Xiaozhi Recipe (, JXR) in streptozotocin (STZ)-induced diabetic rats. METHODS: Sprague-Dawley rats were randomly divided into normal control group and diabetic group. Rats in the diabetic group were induced by intraperitoneal administration of STZ (50 mg/kg), and subdivided into 5 groups. Rats in the diabetic control group were given saline; four treatment groups were given metformin (300 mg/kg), JXR (2, 4 and 8 g/kg) respectively for 8 weeks, while rats in the normal control group were injected with citrate buffer and given the same volume of vehicle. Body weight and food intake were measured every week. The hypoglycaemic effects were determined by testing fasting blood glucose (FBG) every other week, and hemoglobin A1c (HbA1c), insulin, and glucagon at the end of the treatment. The preventive effects of JXR on STZ-induced diabetic rats were determined by histopathological examination with hematoxylin and eosin staining, and periodic acid-schiff staining. The effects were further evaluated by serum superoxide dismutase (SOD) activity and malondialdehyde (MDA). RESULTS: High-dose JXR significantly reduced FBG and HbA1c level at the 8th week of administration (P<0.01, P<0.05). JXR significantly increased insulin level (P<0.05), and decreased glucagon level (P<0.05). JXR showed the antioxidant defense with increased SOD activity and decreased MDA contents in diabetic rats. Histopathological studies revealed that there were no basement membrane thickening and mild destruction in the treated groups. Morphometric measurements of retina microvascular showed that acellular capillary and capillary density decreased in treated rats while pericyte and endothelial cell increasing after the treatment. CONCLUSION: JXR have protective effect of diabetic retinopathy and its mechanism may be associated with the obvious hypoglycemic and antioxidant effect.

In vitro and in vivo inhibition of aldose reductase and advanced glycation end products by phloretin, epigallocatechin 3-gallate and [6]-gingerol.

Hyperglycemic stress activates polyol pathway and aldose reductase (AR) key enzyme responsible for generating secondary complications during diabetes. In this study the therapeutic potential of phloretin, epigallocatechin 3-gallate (EGCG) and [6]-gingerol were evaluated for anti-glycating and AR inhibitory activity in vitro and in vivo systems. Human retinal pigment epithelial (HRPE) cells were induced with high glucose supplemented with the phloretin, EGCG and [6]-gingerol. Aldose reductase activity, total advanced glycation end products (AGEs) and enzyme inhibitor kinetics were assessed. Male C57BL/6J mice were randomly assigned to one of the different treatments (bioactive compounds at 2 concentrations each) with either a low fat diet or high fat diet (HFD). After sixteen weeks, AGE accumulation and AR activity was determined in heart, eyes and kidney. High glucose induced toxicity decreased cell viability compared to the untreated cells and AR activity increased to 2-5 folds from 24 to 96h. Pre-treatment of cells with phloretin, EGCG and [6]-gingerol improved cell viability and inhibited AR activity. The enzyme inhibition kinetics followed a non-competitive mode of inhibition for phloretin and EGCG whereas [6]-gingerol indicated uncompetitive type of inhibition against AR. Data from the animal studies showed high plasma glucose levels in HFD group over time, compared to the low fat diet. HFD group developed cataract and AR activity increased to 4 folds compared to the group with low fat diet. Administration of EGCG, phloretin and [6]-gingerol significantly reduced blood sugar levels, AGEs accumulation, and AR activity. These findings could provide a basis to consider using the selected dietary components alone or in combination with other therapeutic approaches to prevent diabetes-related complications in humans.

Systemic confounders affecting serum measurements of omega-3 and -6 polyunsaturated fatty acids in patients with retinal disease.

BACKGROUND: Omega-3 polyunsaturated fatty acids (PUFAs) have a highly anti-angiogenic effect in animal models. However, the clinical relevance of omega-3PUFAs in human retinal pathologies remains unclear. The ARED 2 study found no effect of omega-3 PUFA supplementation on progression of age related macular degeneration (AMD). The aim of this study was to compare serum levels of omega-3- and omega-6 PUFAs between patients with diabetic retinopathy (DR), AMD and retinal vein occlusion (RVO), and to identify potential confounders of serum level measurements. METHODS: Venous blood samples were collected from 44 patients with DR, 25 with AMD, 12 with RVO and 27 controls. The lipid phase was extracted and analyzed using mass spectrometry. Retinal disease staging was done by indirect funduscopy and FAG where appropriate. Patient demographics and medical history including current medication and fasting state were acquired. Tukey contrasts for multiple comparisons of the mean and linear regression analysis were used for statistical analysis. RESULTS: Our data revealed no significant differences in omega-6 PUFA serum levels between patients with AMD, DR, RVO and controls (p > 0.858). Uncorrected omega-3 PUFA levels were significantly higher in patients with AMD compared to DR but not compared to controls (p = 0.004). However, after correcting for possible confounders such as body mass index (BMI), age, sex, fasting and use of statins, no statistically significant difference remained for serum omega-3 PUFA levels. Fasting was identified as an independent confounder of total omega-6 PUFAs, three individual omega-6 PUFAs and one omega-3 PUFA(p < 0.0427). Statin use was identified as an independent confounder of α-linolenic acid (an omega-3PUFA; p = 0.0210). CONCLUSION: In this pilot study with relatively low patient numbers, we report significant differences in serum levels of omega-3PUFAs among patients with different types of retinal diseases. However, these differences were not robust for disease specificity after correction for possible confounders in our cohort. Our results demonstrate that serum lipid profiles need to be interpreted with caution since they are significantly altered by variables like fasting and medication use independent from the underlying disease. Correcting for respective confounders is thus necessary to compare serum lipid profiles in clinical studies.

Lonicerae Japonicae Flos attenuates diabetic retinopathy by inhibiting retinal angiogenesis.

ETHNOPHARMACOLOGICAL RELEVANCE: Lonicerae Japonicae Flos (Jin-Yin-Hua) is a well-known traditional Chinese medicine used for clearing away heat and toxic material. AIM OF THE STUDY: This study aims to observe the attenuation of aqueous extract of Lonicerae Japonicae Flos (FL) against streptozotocin (STZ)-induced diabetic retinopathy (DR) and its engaged mechanism. MATERIALS AND METHODS: STZ-induced proliferative DR (PDR) for 5 month in C57BL/6 mice was used in this study. Retinal vessels were observed by immunofluorescence staining with cluster of differentiation 31 (CD31) and histopathological evaluation. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum vascular endothelial growth factor (VEGF) content. Cell proliferation was detected by 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyltetrazolium bromide (MTT) assay in choroid-retinal endothelial RF/6A cells. VEGF-induced tube formation in RF/6A cells was observed. The contents of chlorogenic acid (CGA), caffeic acid (CA), and luteolin in FL were detected by high-performance liquid chromatography (HPLC). RESULTS: Histopathological evaluation demonstrated that retinal vessels were increased in STZ-induced PDR mice, whereas FL decreased such increase. The results of CD31 staining also showed that FL decreased the increased number of retinal vessels in STZ-induced PDR mice. In addition, FL reduced the increased serum VEGF content in STZ-induced PDR mice. FL reduced VEGF-induced RF/6A cell proliferation in the concentration-dependent manner, but had no obvious effect on RF/6A cell viability without VEGF stimulation. VEGF-induced tube formation in RF/6A cells was inhibited by different concentrations of FL. CGA, CA and luteolin all inhibited VEGF-induced tube formation in RF/6A cells, and the lowest effective concentration of CGA and CA was both 0.625µM, but of luteolin was 5µM. Furthermore, the results of HPLC demonstrated that the amount of CGA was the highest in FL. CONCLUSIONS: FL ameliorates STZ-induced PDR by inhibiting retinal angiogenesis. Phenolic acid CGA is the main compound contributing to the inhibition of FL on retinal angiogenesis.

MicroRNA-126 contributes to Niaspan treatment induced vascular restoration after diabetic retinopathy.

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes and a major cause of blindness in the developing world. Early diabetic retinopathy is characterized by a loss of pericytes and vascular endothelial cells, a breakdown of the blood-retinal barrier, vascular dysfunction and vascular-neuroinflammation. However, optimal treatment options and related mechanisms are still unclear. MicroRNA-126 (miR-126) plays a potential role in the pathogenesis in DR, which may regulate VEGF, Ang-1 and VCAM-1 expressions. This study investigated the therapeutic effects and mechanisms of Niaspan treatment of DR in diabetes (DM) rats. DM rats exhibits significantly decreased miR-126 and tight junction Claudin-5/Occludin/ZO-1 genes expression, and increased Blood retinal-barrier (BRB) breakdown, retinal apoptosis and VEGF/VEGFR, as well as VCAM-1/CD45 expressions in the retina compared to normal control group. Niaspan treatment significantly improved clinical and histopathological outcomes; decreased the expressions of VEGF/VEGFR, VCAM-1/CD45, apoptosis and BRB breakdown, significantly increased tight junction proteins and Ang-1/Tie-2 expressions, as well as increased retinal miR-126 expression compared to non-treatment diabetic rats. These data are the first to show that Niaspan treatment ameliorates DR through its repair vascular and inhibits inflammatory effects, and also suggest that the miR-126 pathway may contribute to Niaspan treatment induced benefit effects.

A combination of the main constituents of Fufang Xueshuantong Capsules shows protective effects against streptozotocin-induced retinal lesions in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Fufang Xueshuantong Capsule, an herbal formula licensed for clinical use in China, which is composed of Panax notoginseng (Burkill) F.H. Chen, Salvia miltiorrhiza Bunge, Astragalus membranaceus (Fisch.) Bunge, and Scrophularia ningpoensis Hemsl, has proven effective for the treatment of diabetic retinopathy. However, its bioactive constituents are still ambiguous. In this study, the therapeutic effects of a combination of the main constituents of Fufang Xueshuantong Capsule (cFXT) were evaluated in streptozotocin (STZ)-induced retinal lesions to identify the bioactive constituents. METHODS: Sprague-Dawley rats, except for those in the control group (vehicle+vehicle), were administered a single injection of 60mg/kg STZ. One-week later, STZ-treated rats were randomly divided into three groups-one STZ group (STZ+vehicle) and two cFXT treatment groups (STZ+cFXT). The rats in the latter two groups received cFXT 44.8mg/kg or cFXT 22.4mg/kg by intragastric gavage once per day, for 24 consecutive weeks. The rats in the control and STZ groups received the vehicle in the same way. Body weights and fasting blood glucose levels were recorded every four weeks. After treatment, hemorheological tests were performed to record the erythrocyte aggregation indexes, blood viscosity, and plasma viscosity. The trypsin digestion method was used to observe pericyte and acellular capillary counts in the retina. Ultraviolet spectrophotometry was utilized to measure the activity of aldose reductase (AR) by measuring the nicotinamide adenine dinucleotide phosphate (NADPH) consumption at 340nm. An immunohistochemical assay was used to observe the expressions of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in the retina. The expression levels of intercellular adhesion molecule-1 (ICAM-1), endothelin-1 (RT-1),and occludin in the retina were tested by the western blot assay. RESULTS: cFXT is composed of 991.44mg/g saponins of Panax notoginseng, 1.62mg/g harpagoside, 0.70mg/g cryptotanshinone, 0.74mg/g tanshinone I, and 5.50mg/g astragaloside A. Although it showed no effects on the increased body weight and blood glucose levels induced by STZ in rats. However, it showed a tendency to attenuate the increase in erythrocyte aggregation, plasma viscosity, and acellular vessel and pericyte loss, paralleled with a reversal of the hyper-activation of AR, the hyper-expression of VEGF, ICAM-1, and ET-1, and the hypo-expression of PEDF and occludin in the retinas of STZ-treated rats. CONCLUSION: The saponins of Panax notoginseng, harpagoside, cryptotanshinone, tanshinone I, and astragaloside A are the main bioactive constituents of Fufang Xueshuantong Capsule and contribute to the attenuation of STZ-induced retinal lesions in rats. These constituents can be used as the base to optimize a new drug for the treatment of diabetic retinopathy, and can be selected for quality control of Fufang Xueshuantong Capsules.

Enhanced Oxidative Stress and Other Potential Biomarkers for Retinopathy in Type 2 Diabetics: Beneficial Effects of the Nutraceutic Supplements.

We have studied the global risk of retinopathy in a Mediterranean population of type 2 diabetes mellitus (T2DM) patients, according to clinical, biochemical, and lifestyle biomarkers. The effects of the oral supplementation containing antioxidants/omega 3 fatty acids (A/ω3) were also evaluated. Suitable participants were distributed into two main groups: (1) T2DMG (with retinopathy (+DR) or without retinopathy (-DR)) and (2) controls (CG). Participants were randomly assigned (+A/ω3) or not (-A/ω3) to the oral supplementation with a daily pill of Nutrof Omega (R) for 18 months. Data collected including demographics, anthropometrics, characteristics/lifestyle, ophthalmic examination (best corrected visual acuity, ocular fundus photographs, and retinal thickness as assessed by optical coherence tomography), and blood parameters (glucose, glycosylated hemoglobin, triglycerides, malondialdehyde, and total antioxidant capacity) were registered, integrated, and statistically processed by the SPSS 15.0 program. Finally, 208 participants (130 diabetics (68 +DR/62 -DR) and 78 controls) completed the follow-up. Blood analyses confirmed that the T2DMG+DR patients had significantly higher oxidative stress (p < 0.05), inflammatory (p < 0.05), and vascular (p < 0.001) risk markers than the T2DMG-DR and the CG. Furthermore, the A/ω3 oral supplementation positively changed the baseline parameters, presumptively by inducing metabolic activation and ameliorating the ocular health after 18 months of supplementation.