Zinc and diabetic retinopathy

Zinc and Diabetes: A Connection between Micronutrient and Metabolism

Diabetes mellitus is a global health problem and a major contributor to mortality and morbidity. The management of this condition typically involves using oral antidiabetic medication, insulin, and appropriate dietary modifications, with a focus on macronutrient intake. However, several human studies have indicated that a deficiency in micronutrients, such as zinc, can be associated with insulin resistance as well as greater glucose intolerance. Zinc serves as a chemical messenger, acts as a cofactor to increase enzyme activity, and is involved in insulin formation, release, and storage. These diverse functions make zinc an important trace element for the regulation of blood glucose levels. Adequate zinc levels have also been shown to reduce the risk of developing diabetic complications. This review article explains the role of zinc in glucose metabolism and the effects of its inadequacy on the development, progression, and complications of diabetes mellitus. Furthermore, it describes the impact of zinc supplementation on preventing diabetes mellitus. The available information suggests that zinc has beneficial effects on the management of diabetic patients. Although additional large-scale randomized clinical trials are needed to establish zinc's clinical utility further, efforts should be made to increase awareness of its potential benefits on human health and disease.

Biochemical Changes in Anterior Chamber of the Eye in Diabetic Patients-A Review

This article aims to provide a comprehensive review of the biochemical changes observed in the anterior chamber of the eye in diabetic patients. The increased levels of inflammatory markers, alterations in antioxidant defense mechanisms, and elevated levels of advanced glycation end products (AGEs) in the aqueous humor (AH) are explored. Additionally, the impact of these biochemical changes on diabetic retinopathy progression, increased intraocular pressure, and cataract formation is discussed. Furthermore, the diagnostic and therapeutic implications of these findings are presented. This study explores potential biomarkers for detecting diabetic eye disease at an early stage and monitoring its progression. An investigation of the targeting of inflammatory and angiogenic pathways as a potential treatment approach and the role of antioxidant agents in managing these biochemical changes is performed.

Detection of insulin oligomeric forms by a novel surface plasmon resonance-diffusion coefficient based approach

Insulin is commonly used to treat diabetes and undergoes aggregation at the site of repeated injections in diabetic patients. Moreover, aggregation is also observed during its industrial production and transport and should be avoided to preserve its bioavailability to correctly adjust glucose levels in diabetic patients. However, monitoring the effect of various parameters (pH, protein concentration, metal ions, etc.) on the insulin aggregation and oligomerization state is very challenging. In this work, we have applied a novel Surface Plasmon Resonance (SPR)-based experimental approach to insulin solutions at various experimental conditions, monitoring how its diffusion coefficient is affected by pH and the presence of metal ions (copper and zinc) with unprecedented sensitivity, precision, and reproducibility. The reported SPR method, hereby applied to a protein for the first time, besides giving insight into the insulin oligomerization and aggregation phenomena, proved to be very robust for determining the diffusion coefficient of any biomolecule. A theoretical background is given together with the software description, specially designed to fit the experimental data. This new way of applying SPR represents an innovation in the bio-sensing field and expanding the potentiality of commonly used SPR instruments well over the canonical investigation of biomolecular interactions.

Key Nutrients for Optimal Blood Glucose Control and Mental Health in Individuals with Diabetes: A Review of the Evidence

Diabetes is associated with an increased risk of mental disorders, including depression, anxiety, and cognitive decline. Mental disorders can also contribute to the development of diabetes through various mechanisms including increased stress, poor self-care behaviors, and adverse effects on glucose metabolism. Consequently, individuals suffering from either of these conditions frequently experience comorbidity with the other. Nutrition plays an important role in both diabetes and mental health disorders including depression and anxiety. Deficiencies in specific nutrients such as omega-3 fatty acids, vitamin D, B vitamins, zinc, chromium, magnesium, and selenium have been implicated in the pathogenesis of both diabetes and mental disorders. While the impact of nutrition on the progression and control of diabetes and mental disorders is broadly acknowledged, there is a notable knowledge gap concerning the implications of distinct nutrients in preventing and mitigating symptoms of both conditions when they coexist. The aim of this study was to examine the role of nutrition in improving glucose homeostasis and promoting mental well-being among individuals with diabetes. Further, we evaluated the preventive or delaying effects of key nutrients on the simultaneous manifestation of these conditions when one of them is present. Our findings indicated that the use of personalized dietary interventions and targeted nutrient supplementation can improve metabolic and mental health outcomes in patients with type 2 diabetes.

Pharmacotherapy and Nutritional Supplements for Neovascular Eye Diseases

In this review, we aim to provide an overview of the recent findings about the treatment of neovascular retinal diseases. The use of conventional drugs and nutraceuticals endowed with antioxidant and anti-inflammatory properties that may support conventional therapies will be considered, with the final aim of achieving risk reduction (prevention) and outcome improvement (cooperation between treatments) of such sight-threatening proliferative retinopathies. For this purpose, we consider a medicinal product one that contains well-defined compound(s) with proven pharmacological and therapeutic effects, usually given for the treatment of full-blown diseases. Rarely are prescription drugs given for preventive purposes. A dietary supplement refers to a compound (often an extract or a mixture) used in the prevention or co-adjuvant treatment of a given pathology. However, it must be kept in mind that drug-supplement interactions may exist and might affect the efficacy of certain drug treatments. Moreover, the distinction between medicinal products and dietary supplements is not always straightforward. For instance, melatonin is formulated as a medicinal product for the treatment of sleep and behavioral problems; at low doses (usually below 1 mg), it is considered a nutraceutical, while at higher doses, it is sold as a psychotropic drug. Despite their lower status with respect to drugs, increasing evidence supports the notion of the beneficial effects of dietary supplements on proliferative retinopathies, a major cause of vision loss in the elderly. Therefore, we believe that, on a patient-by-patient basis, the administration of nutraceuticals, either alone or in association, could benefit many patients, delaying the progression of their disease and likely improving the efficacy of pharmaceutical drugs.

Effect of Trace Metal Ions on the Conformational Stability of the Visual Photoreceptor Rhodopsin

Trace metals are essential elements that play key roles in a number of biochemical processes governing human visual physiology in health and disease. Several trace metals, such as zinc, have been shown to play important roles in the visual phototransduction process. In spite of this, there has been little research conducted on the direct effect of trace metal elements on the visual photoreceptor rhodopsin. In the current study, we have determined the effect of several metal ions, such as iron, copper, chromium, manganese, and nickel, on the conformational stability of rhodopsin. To this aim, we analyzed, by means of UV-visible and fluorescence spectroscopic methods, the effects of these trace elements on the thermal stability of dark rhodopsin, the stability of its active Metarhodopsin II conformation, and its chromophore regeneration. Our results show that copper prevented rhodopsin regeneration and slowed down the retinal release process after illumination. In turn, Fe³⁺, but not Fe²⁺, increased the thermal stability of the dark inactive conformation of rhodopsin, whereas copper ions markedly decreased it. These findings stress the important role of trace metals in retinal physiology at the photoreceptor level and may be useful for the development of novel therapeutic strategies to treat retinal disease.

A Mediterranean Diet May Be Protective in the Development of Diabetic Retinopathy

The Mediterranean diet is recognized as one of the healthiest available dietary patterns. This perception results from its beneficial effects on the cardiovascular system and, also, on hypertension, diabetes, and cancer compared with other diets. Its impact on the course of diabetes is assessed in the available scientific literature; however, little information is available about its impact on diabetic retinopathy. The MD is characterized mainly by the consumption of fish, seafood, foods of plant origin, and fresh fruit and vegetables. It is also recommended to consume legumes, which are a source of folic acid, magnesium, iron, and dietary fiber. High consumption of nuts and unrefined grains is also recommended in the MD. Marine fish provide polyunsaturated acids from the omega-3 group. Olive oil plays a very important role, especially olive oil obtained from mechanical pressing. Additionally, olive oil contains vitamins E, K, and polyphenols. Polyphenols, which are present in a diverse range of vegetables, fruits, and seeds, have the ability to decrease oxidative stress, inflammation, and insulin resistance. Resveratrol is naturally found in grape skins and seeds, as well as in peanuts and berries, and is a constituent of red wine. Resveratrol can inhibit increased vascular leakage and loss of pericytes and regulate the level of VEGF protein in the retina, thus inhibiting the development of DR. Consumption of fruits, vegetables, fish, and olive oil may be correlated with a lower risk of diabetic retinopathy. This paper presents the definition of the Mediterranean diet and its influence on the course of diabetes and diabetic retinopathy.

Metallothioneins, a Part of the Retinal Endogenous Protective System in Various Ocular Diseases

Metallothioneins are the metal-rich proteins that play important roles in metal homeostasis and detoxification. Moreover, these proteins protect cells against oxidative stress, inhibit proapoptotic mechanisms and enhance cell differentiation and survival. Furthermore, MTs, mainly MT-1/2 and MT-3, play a vital role in protecting the neuronal retinal cells in the eye. Expression disorders of these proteins may be responsible for the development of various age-related eye diseases, including glaucoma, age-related macular degeneration, diabetic retinopathy and retinitis pigmentosa. In this review, we focused on the literature reports suggesting that these proteins may be a key component of the endogenous protection system of the retinal neurons, and, when the expression of MTs is disrupted, this system becomes inefficient. Moreover, we described the location of different MT isoforms in ocular tissues. Then we discussed the changes in MT subtypes' expression in the context of the common eye diseases. Finally, we highlighted the possibility of the use of MTs as biomarkers for cancer diagnosis.

Association of glutathione S-transferase M1 and T1 polymorphisms on the susceptibility of diabetic retinopathy in the Bangladeshi population

Objectives

This study investigated the role of glutathione-S-transferase gene (GSTM1 and GSTT1) polymorphisms in the predisposition of type 2 diabetes mellitus (T2DM) with or without diabetic retinopathy (DR).

Methods

The case-control study included 188 subjects: 50 T2DM with DR, 63 T2DM without DR, and 75 healthy individuals' presenting no clinical signs or evidence of diabetes mellitus. Zinc and magnesium levels were measured using a flame atomic absorption spectrophotometer, and the lipid profile was evaluated using standard methods. The gene polymorphism of GSTs was performed by the multiplex-PCR method.

Results

Compared to the control, DR and T2DM had considerably greater total cholesterol, LDL-C, and decreased HDL-C levels. Magnesium levels were significantly lower in DR and T2DM than in control. Total cholesterol, LDL, TG, and magnesium levels didn't differ significantly between DR and T2DM groups. In DR, the GSTT1-null genotype was more prevalent than in T2DM subjects and controls (26.0%, 12.7%, and 10.7%, respectively). GSTT1-null genotype was considerably more common in DR than in controls and associated with 2.94-folds enhancing the chance of developing DR (OR = 2.94; 95% CI = 1.12-7.75; p = 0.02). However, the recurrence of GSTM1-null genotype was not clearly distinguishable among these three populations (28.0%, 38.1% and 29.3%, respectively) and not particularly prone to the risk of DR compared to T2DM subjects and controls (OR = 0.63; 95% CI = 0.28-1.41; p = 0.26; OR = 0.94; 95% CI = 0.42-2.07; p = 0.87, respectively).

Conclusions

Taken together, these findings suggest the potential role of GSTT1 deletion mutation as a risk factor for the vulnerability of DR among T2DM patients in the Bangladeshi population.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

The impact of zinc on the molecular signaling pathways in the diabetes disease

Since there's been an upsurge in people with diabetes or pre-diabetes conditions, many studies have been conducted to evaluate approaches for reducing the complications of diabetes. One of the most common therapeutic elements suggested for this purpose is zinc (Zn). Zn has long been shown to positively improve complications of both type 1 and type 2 diabetes. This review aims to provide comprehensive information about the influence of Zn on the various signaling pathways in multiple tissues with diabetic conditions, with great attention to the treatment period and effective dose of Zn.

The Effect of Diet and Lifestyle on the Course of Diabetic Retinopathy-A Review of the Literature

Diabetes is a major social problem. As shown by epidemiological studies, the world incidence of diabetes is increasing and so is the number of people suffering from its complications. Therefore, it is important to determine possible preventive tools. In the prevention of diabetic retinopathy, it is essential to control glycemia, lipid profile and blood pressure. This can be done not only by pharmacological treatment, but first of all by promoting a healthy lifestyle, changing dietary habits and increasing physical activity. In our work, we present a review of the literature to show that physical exercise and an adequate diet can significantly reduce the risk of diabetes and diabetic retinopathy.

Preventive Efficacy of an Antioxidant Compound on Blood Retinal Barrier Breakdown and Visual Dysfunction in Streptozotocin-Induced Diabetic Rats

In diabetic retinopathy (DR), high blood glucose drives chronic oxidative stress and inflammation that trigger alterations of the neurovascular balance finally resulting in vascular abnormalities and retinal cell death, which converge towards altered electroretinogram (ERG). In the last years, a growing body of preclinical evidence has suggested that nutrients with anti-inflammatory/antioxidant properties can be able to hamper DR progression since its very early stages. In the present study, we used a streptozotocin-induced rat model of DR, which mimics most aspects of the early stages of human DR, to test the preventive efficacy of a novel compound containing cyanidin-3-glucoside (C3G), verbascoside and zinc as nutrients with antioxidant and anti-inflammatory properties. Western blot, immunofluorescence and electroretinographic analyses demonstrated a dose-dependent inhibition of oxidative stress- and inflammation-related mechanisms, with a significant counterpart in preventing molecular mechanisms leading to DR-associated vasculopathy and its related retinal damage. Preventive efficacy of the compound on dysfunctional a- and b-waves was also demonstrated by electroretinography. The present demonstration that natural compounds, possibly as a consequence of vascular rescue following ameliorated oxidative stress and inflammation, may prevent the apoptotic cascade leading to ERG dysfunction, adds further relevance to the potential application of antioxidants as a preventive therapy to counteract DR progression.

Effects of oxidative stress-induced increases in Zn2+ concentrations in human gingival epithelial cells

BACKGROUND AND OBJECTIVE

Previous studies have reported that oxidative stress increases intracellular Zn²⁺ concentrations and induces cytotoxicity. However, no studies have investigated whether oxidative stress induces such changes in periodontal tissue cells. In the present study, we investigated the effect of oxidative stress on intracellular Zn²⁺ concentration in periodontium constituent cells and its potential relationship with periodontal disease.

METHODS

We analyzed changes in intracellular Zn²⁺ concentrations in human gingival epithelial (epi4) cells treated with hydrogen peroxide (H₂ O₂ ). The fluorescent probes FluoZin-3 AM and CellTracker Green CMFDA were used to detect intracellular Zn²⁺ and thiol groups, respectively. Western blot analyses, luciferase reporter assays, and real-time polymerase chain reaction (PCR) analyses were performed to examine the effect of intracellular Zn²⁺ on epi4 cells.

RESULTS

H₂ O₂ treatment increased intracellular concentrations of Zn²⁺ in epi4 cells by facilitating the movement of Zn²⁺ from cellular nonprotein thiols to the cytoplasm and promoting cell membrane permeability to Zn²⁺ . Furthermore, H₂ O₂ -induced increases in intracellular Zn²⁺ activated the p38 cAMP response element-binding protein/mitogen-activated protein kinase (p38 CREB/MAPK) cascade, upregulated nuclear factor kappa B (NF-κB) DNA binding, and increased the expression of inflammatory cytokines and matrix metallopeptidase-9 (MMP-9).

CONCLUSION

Increases in intracellular Zn²⁺ induced by oxidative stress activate signaling pathways involved in inflammation, potentially contributing to the progression of periodontal disease.

A dark decrement for enhanced dynamic sensitivity of retinal photoreceptors

The skate retina provides a native all-rod retina suited for investigating a single type of photoreceptor regarding its properties and signaling to second order cells. Using the aspartate-induced isolated A-wave of the skate eyecup electroretinogram (ERG), it has been shown that adaptation in rods remains Weber-Fechner-like over a 6-log unit increase in background light intensity. Zinc, which can block calcium channels, has been found in the rod synaptic terminal and the synaptic cleft. Histidine is a zinc chelator. Voltage signals from neurons post-synaptic to rods indicate that histidine increases the dark release of glutamate and increases the horizontal cell light response. In histidine, the A-wave response to various light intensities in the dark-adapted retina increased more than fifty percent, corresponding to the effect on horizontal cells. In the presence of background light, although histidine-treated rod light responses remained Weber-Fechner-like, their increment threshold was raised significantly. This indicates that endogenous zinc feedback serves to increase rod sensitivity in a light-adapted retina, despite a corresponding reduction of threshold sensitivity in the dark. We propose that the increase in A-wave amplitude is a result of the increased conductance at the synaptic terminal and that the A-wave can be used to monitor changes in rod transmitter release. Furthermore, endogenous zinc may also provide the benefit of reducing metabolic stress and the risk of glutamate toxicity in the dark.

The role of labile Zn2+ and Zn2+-transporters in the pathophysiology of mitochondria dysfunction in cardiomyocytes

An important energy supplier of cardiomyocytes is mitochondria, similar to other mammalian cells. Studies have demonstrated that any defect in the normal processes controlled by mitochondria can lead to abnormal ROS production, thereby high oxidative stress as well as lack of ATP. Taken into consideration, the relationship between mitochondrial dysfunction and overproduction of ROS as well as the relation between increased ROS and high-level release of intracellular labile Zn²⁺, those bring into consideration the importance of the events related with those stimuli in cardiomyocytes responsible from cellular Zn²⁺-homeostasis and responsible Zn²⁺-transporters associated with the Zn²⁺-homeostasis and Zn²⁺-signaling. Zn²⁺-signaling, controlled by cellular Zn²⁺-homeostatic mechanisms, is regulated with intracellular labile Zn²⁺ levels, which are controlled, especially, with the two Zn²⁺-transporter families; ZIPs and ZnTs. Our experimental studies in mammalian cardiomyocytes and human heart tissue showed that Zn²⁺-transporters localizes to mitochondria besides sarco(endo)plasmic reticulum and Golgi under physiological condition. The protein levels as well as functions of those transporters can re-distribute under pathological conditions, therefore, they can interplay among organelles in cardiomyocytes to adjust a proper intracellular labile Zn²⁺ level. In the present review, we aimed to summarize the already known Zn²⁺-transporters localize to mitochondria and function to stabilize not only the cellular Zn²⁺ level but also cellular oxidative stress status. In conclusion, one can propose that a detailed understanding of cellular Zn²⁺-homeostasis and Zn²⁺-signaling through mitochondria may emphasize the importance of new mitochondria-targeting agents for prevention and/or therapy of cardiovascular dysfunction in humans.

Oxidative stress and diabetic retinopathy: Molecular mechanisms, pathogenetic role and therapeutic implications

Oxidative stress, a cytopathic outcome of excessive generation of ROS and the repression of antioxidant defense system for ROS elimination, is involved in the pathogenesis of multiple diseases, including diabetes and its complications. Retinopathy, a microvascular complication of diabetes, is the primary cause of acquired blindness in diabetic patients. Oxidative stress has been verified as one critical contributor to the pathogenesis of diabetic retinopathy. Oxidative stress can both contribute to and result from the metabolic abnormalities induced by hyperglycemia, mainly including the increased flux of the polyol pathway and hexosamine pathway, the hyper-activation of protein kinase C (PKC) isoforms, and the accumulation of advanced glycation end products (AGEs). Moreover, the repression of the antioxidant defense system by hyperglycemia-mediated epigenetic modification also leads to the imbalance between the scavenging and production of ROS. Excessive accumulation of ROS induces mitochondrial damage, cellular apoptosis, inflammation, lipid peroxidation, and structural and functional alterations in retina. Therefore, it is important to understand and elucidate the oxidative stress-related mechanisms underlying the progress of diabetic retinopathy. In addition, the abnormalities correlated with oxidative stress provide multiple potential therapeutic targets to develop safe and effective treatments for diabetic retinopathy. Here, we also summarized the main antioxidant therapeutic strategies to control this disease.

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Oxidative stress can both contribute to and result from hyperglycemia-induced metabolic abnormalities in retina.

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Genes important in regulation of ROS are epigenetically modified, increasing ROS accumulation in retina.

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Oxidative stress is closely associated with the pathological changes in the progress of diabetic retinopathy.

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Antioxidants ameliorate retinopathy through targeting multiple steps of oxidative stress.

Effect of A Multinutrient Complex on Retinal Microcirculation in Diabetic Patients Investigated Using an Adaptive Optics Retinal Camera

CONTEXT

Alimentary supplements may have beneficial effects on retinal microvasculature in diabetic patients.

OBJECTIVE AND DESIGN

State-of-the-art imaging techniques were used to assess retinal microcirculation in diabetic patients in an observational study before and after 3 months treatment with a multinutrient complex including resveratrol, vitamins D3, C, E, essential fatty acids, trace elements (zinc and copper) and macular pigments (lutein and zeaxanthin)-Resvega.

SUBJECTS AND METHODS

Fifteen subjects were included in this study. Adaptive optics ophthalmoscopy was used to measure the parameters of temporal retinal arterioles. Optical coherence tomography angiography was employed to assess foveal avascular zone and vessel densities of the superficial capillary plexus, deep capillary plexus and choricapillary plexus.

RESULTS

After 3 months of treatment, there was a statistically significant median decrease in wall-to-lumen ratio (p=0.0001). The same tendencies were noticed for wall thickness values (p=0.008) and wall cross sectional area values (p=0.001). On the other side, no significant changes were noticed concerning the OCTA parameters.

CONCLUSIONS

Resvega seems to have a beneficial effect on the retinal arterioles in diabetic patients.

Impact of groundwater samples and leachates from Gbagede dumpsite, Amoyo, Kwara State, Nigeria, on testes and prostate of male Wistar rats: A biochemical and histological study

This study evaluated the impact of groundwater samples and leachate from Gbagede dumpsite in Amoyo, Kwara State, on the testicular and prostatic function indices of male rats. The groundwater sample 1 (GW1), groundwater sample 2 (GW2), 2.5%, 5.0%, 7.5% and 10.0% leachate progressively reduced (p < .05) feed intake, groundwater and leachate intake, body weight, weights of testes and prostate, and testes-body weight ratio. The groundwater and leachates significantly (p < .05) reduced the sperm count, motility, normal morphology and testicular volume; activities of semen acid phosphatase (ACP) and α-glucosidase, testicular alkaline phosphatase, ACP, ᵧ-GT, lactate dehydrogenase, glutathione reductase, catalase and superoxide dismutase; testicular total protein, glycogen, total cholesterol, sialic acid, testosterone, reduced glutathione, total antioxidant capacity, zinc, iron and copper; serum LH and FSH; prostatic calcium and phosphate. Treatments increased testicular malondialdehyde, prostate-specific antigen and ACP whilst prostatic pH remained significantly unaltered. Only the leachates reduced prostate-body weight ratio. The treatments induced distortions of seminiferous tubules, destroyed spermatogonic cells and degenerated prostatic acinus. The study concluded that metals in the groundwater and leachate samples have adversely impacted on the testes and prostates of the male rats via endocrine disruption and oxidative stress, with attendant implications on reproductive capacity.

Nutritional and medical food therapies for diabetic retinopathy

Diabetic retinopathy (DR) is a form of microangiopathy. Reducing oxidative stress in the mitochondria and cell membranes decreases ischemic injury and end-organ damage to the retina. New approaches are needed, which reduce the risk and improve the outcomes of DR while complementing current therapeutic approaches. Homocysteine (Hcy) elevation and oxidative stress are potential therapeutic targets in DR. Common genetic polymorphisms such as those of methylenetetrahydrofolate reductase (MTHFR), increase Hcy and DR risk and severity. Patients with DR have high incidences of deficiencies of crucial vitamins, minerals, and related compounds, which also lead to elevation of Hcy and oxidative stress. Addressing the effects of the MTHFR polymorphism and addressing comorbid deficiencies and insufficiencies reduce the impact and severity of the disease. This approach provides safe and simple strategies that support conventional care and improve outcomes. Suboptimal vitamin co-factor availability also impairs the release of neurotrophic and neuroprotective growth factors. Collectively, this accounts for variability in presentation and response of DR to conventional therapy. Fortunately, there are straightforward recommendations for addressing these issues and supporting traditional treatment plans. We have reviewed the literature for nutritional interventions that support conventional therapies to reduce disease risk and severity. Optimal combinations of vitamins B1, B2, B6, L-methylfolate, methylcobalamin (B12), C, D, natural vitamin E complex, lutein, zeaxanthin, alpha-lipoic acid, and n-acetylcysteine are identified for protecting the retina and choroid. Certain medical foods have been successfully used as therapy for retinopathy. Recommendations based on this review and our clinical experience are developed for clinicians to use to support conventional therapy for DR. DR from both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) have similar retinal findings and responses to nutritional therapies.

Adjuvant Therapies in Diabetic Retinopathy as an Early Approach to Delay Its Progression: The Importance of Oxidative Stress and Inflammation

Diabetes mellitus (DM) is a progressive disease induced by a sustained state of chronic hyperglycemia that can lead to several complications targeting highly metabolic cells. Diabetic retinopathy (DR) is a multifactorial microvascular complication of DM, with high prevalence, which can ultimately lead to visual impairment. The genesis of DR involves a complex variety of pathways such as oxidative stress, inflammation, apoptosis, neurodegeneration, angiogenesis, lipid peroxidation, and endoplasmic reticulum (ER) stress, each possessing potential therapeutic biomarkers. A specific treatment has yet to be developed for early stages of DR since no management is given other than glycemic control until the proliferative stage develops, offering a poor visual prognosis to the patient. In this narrative review article, we evaluate different dietary regimens, such as the Mediterranean diet, Dietary Pattern to Stop Hypertension (DASH) and their functional foods, and low-calorie diets (LCDs). Nutraceuticals have also been assessed in DR on account of their antioxidant, anti-inflammatory, and antiangiogenic properties, which may have an important impact on the physiopathology of DR. These nutraceuticals have shown to lower reactive oxygen species (ROS), important inflammatory factors, cytokines, and endothelial damage biomarkers either as monotherapies or combined therapies or concomitantly with established diabetes management or nonconventional adjuvant drugs like topical nonsteroidal anti-inflammatory drugs (NSAIDs).

Diabetic macular oedema: under-represented in the genetic analysis of diabetic retinopathy

Diabetic retinopathy, a complication of both type 1 and type 2 diabetes, is a complex disease and is one of the leading causes of blindness in adults worldwide. It can be divided into distinct subclasses, one of which is diabetic macular oedema. Diabetic macular oedema can occur at any time in diabetic retinopathy and is the most common cause of vision loss in patients with type 2 diabetes. The purpose of this review is to summarize the large number of genetic association studies that have been performed in cohorts of patients with type 2 diabetes and published in English-language journals up to February 2017. Many of these studies have produced positive associations with gene polymorphisms and diabetic retinopathy. However, this review highlights that within this large body of work, studies specifically addressing a genetic association with diabetic macular oedema, although present, are vastly under-represented. We also highlight that many of the studies have small patient numbers and that meta-analyses often inappropriately combine patient data sets. We conclude that there will continue to be conflicting results and no meaningful findings will be achieved if the historical approach of combining all diabetic retinopathy disease states within patient cohorts continues in future studies. This review also identifies several genes that would be interesting to analyse in large, well-defined cohorts of patients with diabetic macular oedema in future candidate gene association studies.

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.

Nutrition for diabetic retinopathy: plummeting the inevitable threat of diabetic vision loss

Diabetic retinopathy (DR) is among the leading causes of preventable blindness. Hyperglycemia, hypertension, hyperlipidemia and anemia majorly predispose its pathogenesis. The current treatment modalities of DR include laser photocoagulation therapy, intravitreal corticosteroids, intravitreal anti-vascular endothelial growth factor (VEGF) agents and vitreo-retinal surgery which are costly, highly invasive, unproven for prolonged use and opted in advanced stages of DR. By then retina already encounters a vast damage. Nutrients by their natural physiological, biochemical and molecular action can preserve retinal structure and functions by interfering with the various pathological steps prompting DR incidence, thereby altering the risk of developing this ocular morbidity. Nutrients can also play a central role in DR patients resistant towards the conventional medical treatments. However due to the byzantine interplay existing between nutrients and DR, the worth of nutrition in curbing this vision-threatening ocular morbidity remains silent. This review highlights how nutrients can halt DR development. A nutritional therapy, if adopted in the initial stages, can provide superior-efficacy over the current treatment modalities and can be a complementary, inexpensive, readily available, anodyne option to the clinically unmet requirement for preventing DR. Assessment of nutritional status is presently considered relevant in various clinical conditions except DR. Body Mass Index (BMI) conferred inconclusive results in DR subjects. Subjective Global Assessment (SGA) of nutritional status has recently furnished relevant association with DR status. By integrating nutritional strategies, the risk of developing DR can be reduced substantially. This review summarizes the subsisting knowledge on nutrition, potentially beneficial for preventing DR and sustaining good vision among diabetic subjects.

Relationship Between Serum Zinc Level and Microvascular Complications in Patients with Type 2 Diabetes

Background:

Previous studies suggested that zinc level was related to a certain diabetic microvascular complication. However, the relationship between zinc level and all the microvascular complications in type 2 diabetic patients remains unknown. The purpose of this study was to analyze the relationship between zinc level and each diabetic microvascular complication and identify the features related to low serum zinc level.

Methods:

We included the hospitalized patients with type 2 diabetes (T2D) at our department from May 30, 2013 to March 31, 2014. We initially compared the serum zinc levels between patients with specific microvascular complications and those without. We then analyzed the association between zinc level and each microvascular complication. Furthermore, we identified the unique features of patients with high and low serum zinc levels and analyzed the risk factors related to low zinc level.

Results:

The 412 patients included 271 with microvascular complications and 141 without any microvascular complications. Serum zinc level was significantly lower in patients with diabetic retinopathy (P < 0.001), diabetic nephropathy (DN, P < 0.001), or diabetic peripheral neuropathy (P = 0.002) compared with patients without that specific complication. Lower zinc level was an independent risk factor for DN (odds ratio = 0.869, 95% confidence interval = 0.765–0.987, P < 0.05). The subjects with lower serum zinc level had manifested a longer duration of diabetes, higher level of hemoglobin A1c, higher prevalence of hypertension and microvascular complications, and lower fasting and 2-h C-peptide levels.

Conclusions:

Lower serum zinc level in T2D patients was related to higher prevalence of diabetic microvascular complications, and represented as an independent risk factor for DN. Patients with lower zinc level were more likely to have a longer duration of diabetes, poorer glucose control, and worse β-cell function.

Association of trace elements with lipid profiles and glycaemic control in patients with type 1 diabetes mellitus in northern Sardinia, Italy: An observational study

Sardinia is an Italian region with a high incidence of type 1 diabetes mellitus. This study aimed to determine the associations of trace elements with lipid profiles and glycaemic control in patients with T1DM. A total of 192 patients with T1DM who attended the Unit of Diabetology and Metabolic Diseases in Sassari, Italy, were enrolled. Trace elements zinc, copper, selenium, chromium, and iron were measured in whole blood by sector field inductively coupled plasma mass spectrometry. The correlations between metabolic variables and the levels of trace elements were determined. Zinc was positively correlated with total cholesterol (P=0.023), low-density lipoprotein (P=0.0015), and triglycerides (P=0.027). Iron as significantly correlated with TC (P=0.0189), LDL (P=0.0121), and high-density lipoprotein (HDL) (P=0.0466). In males, Cr was positively correlated with HDL (P=0.0079) and Se, in females was correlated with TG (P=0.0113). The mean fasting plasma glucose was166.2mgdL(-1). Chromium was correlated with fasting plasma glucose (P=0.0149), particularly in males (P=0.0038). Overall, 63.5% of the patients had moderate HbA1c (7-9%). Copper was significantly correlated with HbA1c% in males (P=0.0155). In conclusion, the results of this study indicate that trace elements show different associations with lipid levels and glycaemic control in T1DM. Zinc, Fe, and Se were associated with lipid levels whereas Cu and Cr were associated with HbA1c%.

Comparing the Levels of Trace Elements in Patients With Diabetic Nephropathy and Healthy Individuals

Background:

Diabetic nephropathy is the most common cause of end stage renal disease (ESRD) in developed countries. Several trace elements were reported to be changed in diabetic nephropathy.

Objectives:

The aim of this study was to investigate changes in serum levels of zinc, copper and chromium and their association with the incidence of ESRD in patients with diabetes.

Patients and Methods:

This study was performed on 70 patients with type 2 diabetic nephropathy (macro and micro-albuminuria) and 70 healthy individuals. Samples were collected to survey metals by atomic absorption spectrophotometer. Data was analyzed by SPSS18 using descriptive and inferential analysis methods.

Results:

Mean ± SD levels of Zn, Cu and Cr were significantly decreased in blood samples of patients compared to healthy subjects (P < 0.01). Also the mean concentrations of Cu, Zn and Cr in drinking water of Sari were lower than the accepted limit. Only in one case, Cu was higher than the accepted limit, which was the possibility of contamination by water supply pipes.

Conclusions:

Cu, Zn and Cr play a specific role in the pathophysiology of diabetic nephropathy. Meanwhile in these patients, low serum levels of Cu, Zn and Cr were not associated with factors such as drinking water. Possible causes should be sought in other factors like urine, intervention factors in absorption and utilization and individual conditions.

Seaweeds as potential therapeutic interventions for the metabolic syndrome

Seaweeds are a characteristic part of the traditional diet in countries such as Japan and Korea; these countries also have a lower prevalence of metabolic syndrome than countries such as the USA and Australia. This suggests that seaweeds may contain compounds that reduce the characteristic signs of obesity, diabetes, hypertension, fatty liver and inflammation in the metabolic syndrome. Potentially bioactive compounds from seaweeds include polysaccharides, peptides, pigments, minerals and omega-3 fatty acids. This review emphasises current research on these compounds in isolated cells, animal models and patients. Key problems for future research include chemical characterisation of the bioactive principles, defining pharmacological responses in all aspects of the metabolic syndrome, determining if a therapeutic dose has been administered, and defining oral bioavailability of the active ingredients.