Astaxanthin attenuates the apoptosis of retinal ganglion cells in db/db mice by inhibition of oxidative stress

Clinical management of eye diseases: carotenoids and their nanoformulations as choice of therapeutics

Eye diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR), impose a substantial health cost on a worldwide scale. Carotenoids have emerged as intriguing candidates for pharmacological treatment of various disorders. Their therapeutic effectiveness, however, is hindered by poor solubility and vulnerability to degradation. Nanocarriers, such as nanoparticles, liposomes, and micelles, provide a transformational way to overcome these limits. This review explores the pharmacological potential of carotenoids, namely lutein, zeaxanthin, and astaxanthin, to treat several ocular disorders. The main emphasis is on their anti-inflammatory and antioxidant actions, which help to counteract inflammation and oxidative stress, crucial factors in the development of AMD and DR. The review evaluates the significant benefits of nano-formulated carotenoids, such as improved bioavailability, higher cellular absorption, precise administration to particular ocular tissues, and greater biostability, which make them superior to conventional carotenoids. Some clinical studies on the beneficial properties of carotenoids in eye diseases are discussed. Furthermore, safety and regulatory concerns are also taken into account. Ultimately, carotenoids, especially when created in their nano form, have significant potential for safeguarding eyesight and enhancing the overall well-being of several individuals afflicted with vision-endangering eye diseases.

Effect of High-Sucrose Diet on the Occurrence and Progression of Diabetic Retinopathy and Dietary Modification Strategies

As the most serious of the many worse new pathological changes caused by diabetes, there are many risk factors for the occurrence and development of diabetic retinopathy (DR). They mainly include hyperglycemia, hypertension, hyperlipidemia and so on. Among them, hyperglycemia is the most critical cause, and plays a vital role in the pathological changes of DR. High-sucrose diets (HSDs) lead to elevated blood glucose levels in vivo, which, through oxidative stress, inflammation, the production of advanced glycation end products (AGEs) and vascular endothelial growth factor (VEGF), cause plenty of pathological damages to the retina and ultimately bring about loss of vision. The existing therapies for DR primarily target the terminal stage of the disease, when irreversible visual impairment has appeared. Therefore, early prevention is particularly critical. The early prevention of DR-related vision loss requires adjustments to dietary habits, mainly by reducing sugar intake. This article primarily discusses the risk factors, pathophysiological processes and molecular mechanisms associated with the development of DR caused by HSDs. It aims to raise awareness of the crucial role of diet in the occurrence and progression of DR, promote timely changes in dietary habits, prevent vision loss and improve the quality of life. The aim is to make people aware of the importance of diet in the occurrence and progression of DR. According to the dietary modification strategies that we give, patients can change their poor eating habits in a timely manner to avoid theoretically avoidable retinopathy and obtain an excellent prognosis.

Astaxanthin targets IL-6 and alleviates the LPS-induced adverse inflammatory response of macrophages

Numerous natural compounds are recognized for their anti-inflammatory properties attributed to antioxidant effects and the modulation of key inflammatory factors. Among them, astaxanthin (AST), a potent carotenoid antioxidant, remains relatively underexplored regarding its anti-inflammatory mechanisms and specific molecular targets. In this study, human monocytic leukemia cell-derived macrophages (THP-1) were selected as experimental cells, and lipopolysaccharides (LPS) served as inflammatory stimuli. Upon LPS treatment, the oxidative stress was significantly increased, accompanied by remarkable cellular damage. Moreover, LPSs escalated the expression of inflammation-related molecules. Our results demonstrate that AST intervention could effectively alleviate LPS-induced oxidative stress, facilitate cellular repair, and significantly attenuate inflammation. Further exploration of the anti-inflammatory mechanism revealed AST could substantially inhibit NF-κB translocation and activation, and mitigate inflammatory factor production by hindering NF-κB through the antioxidant mechanism. We further confirmed that AST exhibited protective effects against cell damage and reduced the injury from inflammatory cytokines by activating p53 and inhibiting STAT3. In addition, utilizing network pharmacology and in silico calculations based on molecular docking, molecular dynamics simulation, we identified interleukin-6 (IL-6) as a prominent core target of AST anti-inflammation, which was further validated by the RNA interference experiment. This IL-6 binding capacity actually enabled AST to curb the positive feedback loop of inflammatory factors, averting the onset of possible inflammatory storms. Therefore, this study offers a new possibility for the application and development of astaxanthin as a popular dietary supplement of anti-inflammatory or immunomodulatory function.

The Interplay between Neurotransmitters and Calcium Dynamics in Retinal Synapses during Development, Health, and Disease

The intricate functionality of the vertebrate retina relies on the interplay between neurotransmitter activity and calcium (Ca2+) dynamics, offering important insights into developmental processes, physiological functioning, and disease progression. Neurotransmitters orchestrate cellular processes to shape the behavior of the retina under diverse circumstances. Despite research to elucidate the roles of individual neurotransmitters in the visual system, there remains a gap in our understanding of the holistic integration of their interplay with Ca2+ dynamics in the broader context of neuronal development, health, and disease. To address this gap, the present review explores the mechanisms used by the neurotransmitters glutamate, gamma-aminobutyric acid (GABA), glycine, dopamine, and acetylcholine (ACh) and their interplay with Ca2+ dynamics. This conceptual outline is intended to inform and guide future research, underpinning novel therapeutic avenues for retinal-associated disorders.

The modulating effects of astaxanthin on apoptosis in women with polycystic ovarian syndrome: A randomized clinical trial

Objective

Astaxanthin (ASX) is a lipid-soluble keto-carotenoid with several biological effects. These effects may benefit polycystic ovarian syndrome (PCOS) patients. Imbalanced apoptosis/anti-apoptosis signaling has been considered the major pathogenesis of PCOS. In a randomized clinical trial, we tested the impact of ASX on the apoptotic pathway in PCOS granulosa cells (GCs). The present study hypothesizes that ASX may improve apoptosis in PCOS patients.

Materials and Methods

This trial recruited patients with confirmed PCOS. A total of 58 patients were randomly assigned to take ASX (12 mg) or placebo for 8 weeks. Aspirated follicular fluid (FF) and blood samples were taken from both groups to measure BAX and BCL2 protein expression. Following FF aspiration, GCs from both groups were obtained; Real-Time PCR and Western blotting were used to evaluate the apoptotic pathway's gene and protein expression levels in GCs.BAXBCL2.

Results

In GCs analysis, ASX reduced DR5 gene and protein expression after 8 weeks compared to placebo(p<0.05). Also, Caspase8 (p>0.05) and BAX (p<0.05) gene expression declined, although the difference was not statistically significant for Caspase8. Besides,ASX treatment contributed to an elevated BCL2 gene expression in GCs(p<0.05). In FF and serum analysis, a statistically significant increase was found in BCL2 concentration in the ASX group (p<0.05). Moreover, a reduction in BAX level was confirmed in both FF and serum of the ASX group; however, this change was not significant in the serum (p>0.05).

Conclusion

It seems that ASX consumption among women with PCOS improved serum and FF levels of apoptotic factors and modulated genes and protein expression of the apoptosis pathway in GCs. Nevertheless, further investigations are needed to reveal the potential role of this compound in PCOS treatment.

Synergism of mechanisms underlying early-stage changes in retina function in male hyperglycemic db/db mice in the absence and presence of chemically-induced dyslipidemia

The study was designed to quantify retina function in a spontaneous mutation mouse model of diabetes, in which sustained dyslipidemia was induced chemically. The goal of the study was to identify if dyslipidemia in the presence of hyperglycemia resulted in either a synergistic, or a merely additive, exacerbation of retinal and visual dysfunctions in diabetes. Two cohorts of mice, male C57BL/6 and C57BL/KsJ-db/db mice were divided into two groups each. One group of each strain received the triblock copolymer, poloxamer 407 (P-407), administered by intraperitoneal injection ("WT P-407" and "db/db P-407" groups) with saline as a control in the remaining two groups ("WT" and "db/db" groups). Blood glucose, total cholesterol (TC) and total triglyceride (TG) levels were quantified using enzyme-based colorimetric assays. Retina function was measured using electroretinography (ERG) and visual acuity was determined by behaviorally assessing parameters of the optomotor reflex. TC and TG levels were normal in both saline controls (WT) and db/db mice but were significantly elevated in the WT P-407 group (p < 0.01 for TC; p < 0.001 for TG), while levels of the same lipids were further elevated in the db/db P-407 group when compared to the WT P-407 group levels (p < 0.001 for both TC and TG). Behavioral assessment of the optomotor reflex indicated reduced visual acuity for the db/db P-407 group when compared to either the WT P-407 or the db/db groups (p < 0.001, p < 0.0001). ERG measurements of scotopic retina function showed a significant decline in the scotopic b-wave amplitude of the WT P-407 animals (p < 0.01) and a further reduction for the db/db P-407 group when compared to controls (p < 0.0001). Very significant, strong correlations between scotopic b-wave amplitude and implicit time to TC (r =  - 0.8376, p =  < 0.0001 and r = 0.7069, p = 0.0022, respectively) and TG levels (r =  - 0.8554, p =  < 0.0001 and r = 0.7150, p = 0.0019, respectively) were found. Dyslipidemia in the presence of hyperglycemia synergistically exacerbated the severity of retinal dysfunction in diabetes. P-407 administration significantly elevated plasma TC and TG levels in male wild-type (WT) and diabetic mice (db/db), but the resulting hyperlipidemia was more significantly pronounced in the diabetic mice. While elevated plasma lipid and blood glucose levels were individually correlated with a decline in retinal function, the combination of both exacerbated retinal dysfunction. This model of combined hyperglycemia and dyslipidemia can be used to dissect individual contributions of features of the metabolic syndrome to the pathogenesis of retinal dysfunction in diabetes.

Protective effect of astaxanthin nanoemulsion on mammalian inner ear hair cells

Background

Aminoglycoside antibiotics are used for treating certain acute infections. However, these drugs cause ototoxicity by inducing inner ear hair cell death.

Aims/Objectives

We investigated the protective effect of a nanoemulsion of the carotenoid astaxanthin on mammalian inner ear hair cells against neomycin-induced ototoxicity.

Material and Methods

Dose-response relationship, quantification of hair cell loss, and reactive oxygen species production were assayed in response to neomycin with and without astaxanthin in cultured utricles of CBA/N mice. In addition, auditory brain response (ABR) and hair cell loss after exposure to the nanoformulation and loud noise were examined in vivo in guinea pigs.

Results

Astaxanthin suppressed neomycin-induced reduction of hair cells by reducing the production of hydroxy radicals. Furthermore, hair cell loss in the second rotation of the cochlea was significantly lower in the astaxanthin group than in the noise-only group.

Conclusions and Significance

The blood-labyrinth barrier limits the successful delivery of drugs for inner ear complications. However, in the nanoemulsion form, astaxanthin can penetrate the round window (fenestra ovale) membrane, enabling topical administration. Thus, astaxanthin nanoemulsion could be useful in treating ototoxicity in individuals with inner ear complications.

Astaxanthin inhibits oxidative stress and apoptosis in diabetic retinopathy

BACKGROUND

The pathophysiology of diabetic retinopathy (DR) is thought to be influenced by oxidative stress. Astaxanthin (ASX) is a natural product with antioxidant effect, but it is not clear whether its mechanism of inhibiting the development of DR is related to anti-oxidation.

METHODS

Rats were intraperitoneally injected with streptozotocin (60 mg/kg) to create DR rat models followed by ASX (20 mg/kg) for 45 days. Retinal tissue was examined by Hematoxylin and Eosin staining. By using Enzyme-linked immunosorbent assay (ELISA), 2,7-Dichlorodrhydrofluorescein diace (DCFH-DA) probes, immunohistochemistry and western blot, it was feasible to evaluate the contents of inflammation-related factors (tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6 and macrophage inhibitory cytokine-1 (MIC-1)), oxidative stress-related indicators (glutathione (GSH), malonic dialdehyde (MDA), glutathione peroxidase (GPx), reactive oxygen species (ROS) and Total antioxidant capacity (T-AOC)), antioxidant enzymes (hemoxgenase-1(HO-1) and Quinone Oxidoreductase 1 (NQO1)), and apoptosis-related proteins (Bcl-2, Bcl2 Associated X Protein (BAX), and cleaved-caspase-3). Additionally, antioxidant proteins downstream of the nuclear factor E2 related factors (Nrf-2) pathway, expression levels of Nrf2/ Kelch-like ECH-associated protein 1(Keap 1) pathway-associated proteins, and nuclear and cytoplasmic levels of Nrf2 were assessed using immunohistochemistry, western blot, or quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

ASX alleviated retinal tissue damage by increasing overall retina thickness and ganglion cell layer (GCL) cell numbers and exerted the anti-inflammatory, anti-oxidative stress, and anti-apoptosis effects in DR rats. Additionally, ASX could inhibit the expression of Keap1, promote the transport of Nrf2 from cytoplasm to nucleus and facilitate the expressions of HO-1, NQO1, γ-glutamylcysteine synthetase, (γ-GCS) and GPx.

CONCLUSION

ASX exerted antioxidant effects through Nrf2/keap1 pathway, thereby alleviating apoptosis, inflammation, and oxidative stress in retinal tissues of DR rats.

Melatonin Alleviates Retinal Ischemia-Reperfusion Injury by Inhibiting p53-Mediated Ferroptosis

Retinal ischemia-reperfusion (RIR) injury caused by high intraocular pressure (IOP) is an important risk factor contributing to retinal ganglion cell (RGC) death, eventually causing blindness. A key progressive pathological process in the development of RIR is the death of RGCs. However, the detailed mechanisms underlying RGC death caused by RIR have not yet been clearly elucidated, and effective treatments are lacking. Ferroptosis is a recently defined form of programmed cell death that is closely related to organ injury. Melatonin (MT) is a promising neuroprotective agent, but its effects on RIR injury remain unclear. In this study, murine models of acute ocular hypertension and oxygen and glucose deprivation/reoxygenation (OGD/R) model were adopted to simulate retinal ischemia. MT alleviated retinal damage and RGC death in RIR mice, significantly attenuating RIR-induced ferroptosis. Furthermore, MT reduced the expression of p53, a master regulator of ferroptosis pathways, and the upregulation of p53 promoted ferroptosis and largely abolished the neuroprotective effects of MT. Mechanistically, the overexpression (OE) of p53 suppressed the expression of the solute carrier family 7 member 11 (Slc7a11), which was accompanied by increased 12-lipoxygenase (Alox12) expression, triggering retinal ferroptosis. Moreover, MT-ameliorated apoptosis, neuroinflammation and microglial activation were observed. In summary, MT conferred neuroprotection against RIR injury by inhibiting p53-mediated ferroptosis. These findings indicate that MT is a retina-specific ferroptosis inhibitor and a promising therapeutic agent for retinal neuroprotection.

Corneal endothelial cells and acoustic cavitation in phacoemulsification

Postoperative complications of phacoemulsification, such as corneal edema caused by human corneal endothelial cell (CEC) injury, are still a matter of concern. Although several factors are known to cause CEC damage, the influence of ultrasound on the formation of free radicals during surgery should be considered. Ultrasound in aqueous humor induces cavitation and promotes the formation of hydroxyl radicals or reactive oxygen species (ROS). ROS-induced apoptosis and autophagy in phacoemulsification have been suggested to significantly promote CEC injury. CEC cannot regenerate after injury, and measures must be taken to prevent the loss of CEC after phacoemulsification or other CEC injuries. Antioxidants can reduce the oxidative stress injury of CEC during phacoemulsification. Evidence from rabbit eye studies shows that ascorbic acid infusion during operation or local application of ascorbic acid during phacoemulsification has a protective effect by scavenging free radicals or reducing oxidative stress. Both in experiments and clinical practice, hydrogen dissolved in the irrigating solution can also prevent CEC damage during phacoemulsification surgery. Astaxanthin (AST) can inhibit oxidative damage, thereby protecting different cells from most pathological conditions, such as myocardial cells, luteinized granulosa cells of the ovary, umbilical vascular endothelial cells, and human retina pigment epithelium cell line (ARPE-19). However, existing research has not focused on the application of AST to prevent oxidative stress during phacoemulsification, and the related mechanisms need to be studied. The Rho related helical coil kinase inhibitor Y-27632 can inhibit CEC apoptosis after phacoemulsification. Rigorous experiments are required to confirm whether its effect is realized through improving the ROS clearance ability of CEC.

Astaxanthin as a King of Ketocarotenoids: Structure, Synthesis, Accumulation, Bioavailability and Antioxidant Properties

Astaxanthin (3,3-dihydroxy-β, β-carotene-4,4-dione) is a ketocarotenoid synthesized by Haematococcus pluvialis/lacustris, Chromochloris zofingiensis, Chlorococcum, Bracteacoccus aggregatus, Coelastrella rubescence, Phaffia rhodozyma, some bacteria (Paracoccus carotinifaciens), yeasts, and lobsters, among others However, it is majorly synthesized by Haematococcus lacustris alone (about 4%). The richness of natural astaxanthin over synthetic astaxanthin has drawn the attention of industrialists to cultivate and extract it via two stage cultivation process. However, the cultivation in photobioreactors is expensive, and converting it in soluble form so that it can be easily assimilated by our digestive system requires downstream processing techniques which are not cost-effective. This has made the cost of astaxanthin expensive, prompting pharmaceutical and nutraceutical companies to switch over to synthetic astaxanthin. This review discusses the chemical character of astaxanthin, more inexpensive cultivating techniques, and its bioavailability. Additionally, the antioxidant character of this microalgal product against many diseases is discussed, which can make this natural compound an excellent drug to minimize inflammation and its consequences.

Evaluation of the Role of Soybean Lecithin, Egg Yolk Lecithin, and Krill Oil in Promoting Ovarian Development in the Female Redclaw Crayfish Cherax quadricarinatus

The optimal supplementation of lipid nutrients in the diet showed crucial physiological functions in gonadal development and maturation in adult female aquatic animals. Four isonitrogenous and isolipidic diets with no extra lecithin supplementation (control), 2% soybean lecithin (SL), egg yolk lecithin (EL), or krill oil (KO) supplementation were formulated for Cherax quadricarinatus (72.32 ± 3.58 g). Ovary development and physiological characteristics of crayfish were evaluated after a 10-week feeding trial. The results indicated that SL, EL, or KO supplementation all significantly increased the gonadosomatic index, especially in the KO group. Crayfish fed the diet with SL showed the highest hepatosomatic index compared with those fed the other experimental diets. KO was more efficient than SL and EL in promoting triacylglycerol and cholesterol deposition in the ovary and hepatopancreas but also showed the lowest concentration of low-density lipoprotein cholesterol in the serum. KO significantly increased yolk granule deposition and accelerated oocyte maturation than other experimental groups. Furthermore, dietary phospholipids significantly enhanced the gonad-stimulating hormone concentration in the ovary and reduced the secretion of gonad-inhibiting hormones in the eyestalk. KO supplementation also significantly improved organic antioxidant capacity. From the ovarian lipidomics results, phosphatidylcholine and phosphatidylethanolamine are two main glycerophospholipids that respond to different dietary phospholipids. Polyunsaturated fatty acids (especially C18:2n-6, C18:3n-3, C20:4n-6, C20:5n-3, and C22:6n-3) were pivotal participants during ovarian development of crayfish regardless of lipid type. Combined with the ovarian transcriptome, the best positive function of KO was due to activated steroid hormone biosynthesis, sphingolipid signaling, retinol metabolism, lipolysis, starch and sucrose metabolism, vitamin digestion and absorption, and pancreatic secretion. As a consequence, dietary supplementation with SL, EL, or KO all improved the ovarian development quality of C. quadricarinatus, especially KO, which was the optimum choice for promoting ovary development in adult female C. quadricarinatus.

The protective effects of flavonoids and carotenoids against diabetic complications-A review of in vivo evidence

Diabetes mellitus is a chronic metabolic disorder caused either by inadequate insulin secretion, impaired insulin function, or both. Uncontrolled diabetes is characterized by hyperglycemia which over time leads to fatal damage to both macro-and microvascular systems, causing complications such as cardiovascular diseases, retinopathy and nephropathy. Diabetes management is conventionally delivered through modifications of diet and lifestyle and pharmacological treatment, using antidiabetic drugs, and ultimately insulin injections. However, the side effects and financial cost of medications often reduce patient compliance to treatment, negatively affecting their health outcomes. Natural phytochemicals from edible plants such as fruits and vegetables (F&V) and medicinal herbs have drawn a growing interest as potential therapeutic agents for treating diabetes and preventing the onset and progression of diabetic complications. Flavonoids, the most abundant polyphenols in the human diet, have shown antidiabetic effects in numerous in vitro and preclinical studies. The underlying mechanisms have been linked to their antioxidant, anti-inflammatory and immunomodulatory activities. Carotenoids, another major group of dietary phytochemicals, have also shown antidiabetic potential in recent in vitro and in vivo experimental models, possibly through a mechanism of action similar to that of flavonoids. However, scientific evidence on the efficacy of these phytochemicals in treating diabetes or preventing the onset and progression of its complications in clinical settings is scarce, which delays the translation of animal study evidence to human applications and also limits the knowledge on their modes of actions in diabetes management. This review is aimed to highlight the potential roles of flavonoids and carotenoids in preventing or ameliorating diabetes-related complications based on in vivo study evidence, i.e., an array of preclinical animal studies and human intervention trials. The current general consensus of the underlying mechanisms of action exerted by both groups of phytochemicals is that their anti-inflammatory action is key. However, other potential mechanisms of action are considered. In total, 50 in vivo studies were selected for a review after a comprehensive database search via PubMed and ScienceDirect from January 2002 to August 2022. The key words used for analysis are type-2 diabetes (T2DM), diabetic complications, flavonoids, carotenoids, antioxidant, anti-inflammatory, mechanisms of prevention and amelioration, animal studies and human interventions.

Biological and neurological activities of astaxanthin (Review)

Astaxanthin is a lipid‑soluble carotenoid produced by various microorganisms and marine animals, including bacteria, yeast, fungi, microalgae, shrimps and lobsters. Astaxanthin has antioxidant, anti‑inflammatory and anti‑apoptotic properties. These characteristics suggest that astaxanthin has health benefits and protects against various diseases. Owing to its ability to cross the blood‑brain barrier, astaxanthin has received attention for its protective effects against neurological disorders, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, cerebral ischemia/reperfusion, subarachnoid hemorrhage, traumatic brain injury, spinal cord injury, cognitive impairment and neuropathic pain. Previous studies on the neurological effects of astaxanthin are mostly based on animal models and cellular experiments. Thus, the biological effects of astaxanthin on humans and its underlying mechanisms are still not fully understood. The present review summarizes the neuroprotective effects of astaxanthin, explores its mechanisms of action and draws attention to its potential clinical implications as a therapeutic agent.

Dietary astaxanthin-rich extract ameliorates atherosclerosis/retinopathy and restructures gut microbiome in apolipoprotein E-deficient mice fed on a high-fat diet

Scope: Atherosclerosis (AS) is the leading cause of ischemic disease. However, the anti-AS effects of astaxanthin and its potential mechanisms remain unclear. This study is aimed to investigate the function of astaxanthin-rich extract (ASTE) on AS and gut microbiota as well as the difference from atorvastatin (ATO) in apolipoprotein E-deficient (ApoE^-/-) mice. Methods and results: Wild type (WT) and ApoE^-/- mice were divided into seven groups: the low-fat diet (LFD) and high-fat diet (HFD) groups (in both types) as well as three ApoE^-/- groups based on HFD added with two doses of ASTE and one dose of ATO, respectively. After 30 weeks of intervention, results showed that ASTE significantly inhibited body weight increase, lipids accumulation in serum/liver, and AS-lesions in the aorta. Furthermore, fundus fluorescein angiography and retinal CD31 immunohistochemical staining showed that ASTE could alleviate the occurrence of AS-retinopathy. H&E staining showed that ASTE could protect the colon's mucosal epithelium from damage. The gas chromatographic and gene expression analyses showed that ASTE promoted the excretion of fecal acidic and neutral sterols from cholesterol by increasing LXRα, CYP7A1, and ABCG5/8 and decreasing FXR, NPC1L1, ACAT2, and MTTP expressions. Remarkably, the ASTE administration maintained the gut barrier by enhancing gene expression of JAM-A, Occludin, and mucin2 in the colon and reshaped gut microbiota with the feature of blooming Akkermansia. Conclusion: Our results suggested that ASTE could prevent AS in both macrovascular and/or microvascular as well as used as novel prebiotics by supporting the bile acid excretion and growth of Akkermansia.

Unconventional avenues to decelerated diabetic retinopathy

Diabetic retinopathy (DR) is an important microvascular complication of diabetes mellitus (DM), causing significant visual impairment worldwide. Current gold standards for retarding the progress of DR include blood sugar control and regular fundus screening. Despite these measures, the incidence and prevalence of DR and vision-threatening DR remain high. Given its slowly progressive course and long latent period, opportunities to contain or slow DR before it threatens vision must be explored. This narrative review assesses the recently described unconventional strategies to retard DR progression. These include gut-ocular flow, gene therapy, mitochondrial dysfunction-oxidative stress, stem cell therapeutics, neurodegeneration, anti-inflammatory treatments, lifestyle modification, and usage of phytochemicals. These therapies impact DR directly, while some of them also influence DM control. Most of these strategies are currently in the preclinical stage, and clinical evidence remains low. Nevertheless, our review suggests that these approaches have the potential for human use to prevent the progression of DR.

Health benefits of astaxanthin against age-related diseases of multiple organs: A comprehensive review

Age-related diseases are associated with increased morbidity in the past few decades and the cost associated with the treatment of these age-related diseases exerts a substantial impact on social and health care expenditure. Anti-aging strategies aim to mitigate, delay and reverse aging-associated diseases, thereby improving quality of life and reducing the burden of age-related pathologies. The natural dietary antioxidant supplementation offers substantial pharmacological and therapeutic effects against various disease conditions. Astaxanthin is one such natural carotenoid with superior antioxidant activity than other carotenoids, as well as well as vitamins C and E, and additionally, it is known to exhibit a plethora of pharmacological effects. The present review summarizes the protective molecular mechanisms of actions of astaxanthin on age-related diseases of multiple organs such as Neurodegenerative diseases [Alzheimer's disease (AD), Parkinson's disease (PD), Stroke, Multiple Sclerosis (MS), Amyotrophic lateral sclerosis (ALS), and Status Epilepticus (SE)], Bone Related Diseases [Osteoarthritis (OA) and Osteoporosis], Cancers [Colon cancer, Prostate cancer, Breast cancer, and Lung Cancer], Cardiovascular disorders [Hypertension, Atherosclerosis and Myocardial infarction (MI)], Diabetes associated complications [Diabetic nephropathy (DN), Diabetic neuropathy, and Diabetic retinopathy (DR)], Eye disorders [Age related macular degeneration (AMD), Dry eye disease (DED), Cataract and Uveitis], Gastric Disorders [Gastritis, Colitis, and Functional dyspepsia], Kidney Disorders [Nephrolithiasis, Renal fibrosis, Renal Ischemia reperfusion (RIR), Acute kidney injury (AKI), and hyperuricemia], Liver Diseases [Nonalcoholic fatty liver disease (NAFLD), Alcoholic Liver Disease (AFLD), Liver fibrosis, and Hepatic Ischemia-Reperfusion (IR) Injury], Pulmonary Disorders [Pulmonary Fibrosis, Acute Lung injury (ALI), and Chronic obstructive pulmonary disease (COPD)], Muscle disorders (skeletal muscle atrophy), Skin diseases [Atopic dermatitis (ATD), Skin Photoaging, and Wound healing]. We have also briefly discussed astaxanthin's protective effects on reproductive health.

Recent Advances and the Mechanism of Astaxanthin in Ophthalmological Diseases

Astaxanthin (AST) is a naturally occurring carotenoid that has strong antioxidant, anti-inflammatory, and antiapoptosis effects and is used for the prevention of cancer. There is growing evidence that AST has multiple protective effects against various eye diseases. This article reviews the function and the potential mechanism of AST in dry eye syndrome, keratitis, cataract, diabetic retinopathy, age-related macular degeneration, high intraocular pressure, and other ocular diseases. It provides a theoretical basis for the clinical application of AST as a potential nutraceutical.

Astaxanthin Enhances Gingival Wound Healing following High Glucose-Induced Oxidative Stress

Fibroblasts of the gingiva play a key role in oral wound healing in diabetes. In this study, effects of astaxanthin (ASTX), a xanthophyll carotenoid, were tested on gingival fibroblasts in a wound healing assay in vitro. The aim of this study was to determine whether ASTX can recover delayed wound healing or not when oxidative stress is elevated by high glucose exposure. For this purpose, human gingival fibroblasts were incubated with or without ASTX following exposure to systemic doses of low glucose (LG) and high glucose (HG) in culture media (5- and 25-, 50 mM D-glucose in DMEM Ham's F12) following 24 hours of incubation. Levels of ROS (Reactive oxygen species) were determined for each experimental group by confocal microscopy. Cell proliferation and viability were assessed by an automated cell counter with trypan blue assay. Wound healing assay was designed in 60 mm petri dishes. Cells were exposed to 5-, 25-, and 50 mM glucose for 24 hours, and a straight line free of cells was created upon full confluency. 100 μM ASTX was added to the recovery group, simultaneously. Cells were monitored with JuLI^Ⓡ-Br Cell History Recorder. ROS levels were significantly increased with increasing glucose levels, while cell proliferation and viability demonstrated a negative correlation with increasing oxidative stress. ROS levels significantly decreased in the 100 μM ASTX-treated group compared to the gingival fibroblasts treated with 50 mM HG medium-only, as well as growth rate and viability. Wound healing was delayed in a dose-dependent manner following high glucose exposure, while ASTX treatment recovered wounded area by 1.16-fold in the 50 mM HG group. Our results demonstrated that ASTX enhances gingival wound healing through its antioxidative properties following high glucose induced oxidative stress. Therefore, ASTX can be suggested as a promising candidate to maintain oral health in chronic wounds of the oral tissues related to diabetes.

Neuroprotective Effects of Nicotinamide (Vitamin B3) on Neurodegeneration in Diabetic Rat Retinas

The loss of inner retinal neurons is an initial event in diabetic retinopathy. In diabetic retinas, oxidative stress is increased, which could lead to increased oxidative DNA damage. Nicotinamide is a precursor to nicotinamide adenine dinucleotide, which contributes to the DNA damage response. We investigated whether nicotinamide plays a neuroprotective role in diabetic retinal neurodegeneration in terms of DNA repair. Male Sprague Dawley rats with streptozotocin-induced diabetes were orally administered nicotinamide (500 mg/kg/day) for 4 or 12 weeks. Oxidative stress exhibited by dihydroethidium was upregulated at 4 and 12 weeks after onset of diabetes, and nicotinamide treatment reduced oxidative stress at 4 weeks after induction of diabetes. Oxidative DNA damage measured by 8-hydroxy-2′-deoxyguanosine (8-OHdG) increased at 4 and 12 weeks after induction of diabetes and decreased following nicotinamide treatment. The elevated expression of glial fibrillary acidic protein (GFAP) induced by diabetes was attenuated by nicotinamide treatment. In Western blot analysis, the increased expression of cleaved PARP-1 in diabetes was attenuated by nicotinamide treatment at 12 weeks after induction of diabetes. The diabetes-induced apoptosis of inner retinal cells detected by the TUNEL assay was reduced by nicotinamide treatment. In conclusion, nicotinamide attenuated retinal neurodegeneration in diabetes, probably by reducing oxidative DNA damage and supporting DNA repair.

Comparative Efficiency of Lutein and Astaxanthin in the Protection of Human Corneal Epithelial Cells In Vitro from Blue-Violet Light Photo-Oxidative Damage

The aim of this study was to compare in vitro the protective and antioxidant properties of lutein and astaxanthin on human primary corneal epithelial cells (HCE-F). To this purpose, HCE-F cells were irradiated with a blue-violet light lamp (415–420 nm) at different energies (20 to 80 J/cm2). Lutein and astaxanthin (50 to 250 μM) were added to HCE-F right before blue-violet light irradiation at 50 J/cm2. Viability was evaluated by the CKK-8 assay while the production of reactive oxygen species (ROS) by the H2DCF-DA assay. Results have shown that the viability of HCE-F cells decreased at light energies from 20 J/cm2 to 80 J/cm2, while ROS production increased at 50 and 80 J/cm2. The presence of lutein or astaxanthin protected the cells from phototoxicity, with lutein slightly more efficient than astaxanthin also on the blunting of ROS, prevention of apoptotic cell death and modulation of the Nrf-2 pathway. The association of lutein and astaxanthin did not give a significant advantage over the use of lutein alone. Taken together, these results suggest that the association of lutein and astaxanthin might be useful to protect cells of the ocular surface from short (lutein) and longer (astaxanthin) wavelengths, as these are the most damaging radiations hitting the eye from many different LED screens and solar light.

[The effect of astaxanthin on the adaptation of the oral mucosa to a removable denture]

THE AIM

Of this study was the evaluation of the effect of the antioxidant gel on the oral mucosa and reduction of the time of adaptation to a removable denture in patients with partial adentia.

MATERIAL AND METHODS

The study comprised 105 patients aged 30-65 years divided into three groups: the main group of 45 patients, the comparison group of 35 patients, the control group of 25 patients. The main group was given a prophylactic gel with natural astaxanthin after the delivery of a removable prosthesis. The patients of the control group and the comparison group do not received an antioxidant gel. Patients of all three groups underwent a study of the hygienic state of the oral mucosa and oral fluid to assess the state of oral microbiocenosis. The main group and the comparison group underwent visual examination and photoplanimetric control after the placement of a removable denture.

RESULTS

A positive preventive and anti-inflammatory effect of astaxanthin gel was found in patients who received an immediate and a partial removable dentures. The use of the gel for 7 days helps to reduce the values of hygiene indices, concentrations of bacterial plasmalogen and endotoxin in the oral fluid in the short-term perspective.

CONCLUSION

Preventive dental gel with astaxanthin decreases the time of adaptation to removable dentures by 1.7-2 times and reduces the risk of prosthetic stomatitis due to its wound-healing, anti-inflammatory and antimicrobial actions.

Self-Assembling Antioxidants for Ischemia-Reperfusion Injuries

Significance: Ischemia-reperfusion (IR) injury is a major component of severe damage in vascular occlusion during stroke, myocardial infarction, surgery, and organ transplantation, and is exacerbated by the excessive generation of reactive oxygen species (ROS), which occurs particularly during reperfusion. With the aging of the population, IR injury is becoming a serious problem in various organs, such as the kidney, brain, and heart, as well as in the mesenteric capillaries. Recent Advances: To prevent reperfusion injuries, natural and synthetic low-molecular-weight (LMW) antioxidants have been well studied. Critical Issues: However, these LMW antioxidants have various problems, including adverse effects due to excessive cellular uptake and their rapid clearance by the kidney, and cannot fully exert their potent antioxidant capacity in vivo. Future Directions: To overcome these problems, we designed and developed redox polymers with antioxidants covalently conjugated with them. These polymers self-assemble into nanoparticles in aqueous media, referred to as redox nanoparticles (RNPs). RNPs suppress their uptake into normal cells, accumulate at inflammation sites, and effectively scavenge ROS in damaged tissues. We had developed two types of RNPs: RNP^N, which disintegrates in response to acidic pH; and RNP^O, which does not collapse, regardless of the environmental pH. Utilizing the pH-sensitive and -insensitive characteristics of RNP^N and RNP^O, respectively, RNPs were found to exhibit remarkable therapeutic effects on various oxidative stress disorders, including IR injuries. Thus, RNPs are promising nanomedicines for use as next-generation antioxidants. This review summarizes the therapeutic impacts of RNPs in the treatment of kidney, cerebral, myocardial, and intestinal IR injuries. Antioxid. Redox Signal. 36, 70-80.

The role of inflammation and neurodegeneration in diabetic macular edema

The pathogenesis of diabetic macular edema (DME) is complex. Persistently high blood glucose activates multiple cellular pathways and induces inflammation, oxidation stress, and vascular dysfunction. Retinal ganglion cells, macroglial and microglial cells, endothelial cells, pericytes, and retinal pigment epithelium cells are involved. Neurodegeneration, characterized by dysfunction or apoptotic loss of retinal neurons, occurs early and independently from the vascular alterations. Despite the increasing knowledge on the pathways involved in DME, only limited therapeutic strategies are available. Besides antiangiogenic drugs and intravitreal corticosteroids, alternative therapeutic options tackling inflammation, oxidative stress, and neurodegeneration have been considered, but none of them has been currently approved.

Antitumor Effects of Astaxanthin on Esophageal Squamous Cell Carcinoma by up-Regulation of PPARγ

Esophageal squamous cell carcinoma is a malignant tumor that is difficult to find and has a poor prognosis. The aim of this study is to explore the chemoprevention effect of Astaxanthin (AST) and reveal the possible mechanism of AST on the development of esophageal cancer based on PPARγ. We found that a stable and strong binding between PPARγ molecules and AST molecules using Autodock 4.0 software. AST significantly inhibited the viability of EC109 cells in a dose and time dependent manners (all P < 0.05), and up-regulated the protein expression level of PPARγ from the concentration of 6.25 µM (P < 0.05). Animal experiment showed that AST significantly decreased the incidences of NMBzA-induced esophageal carcinogenesis at 50 mg/kg AST in F344 rats (P < 0.05). AST inhibited the oxidative stress by improving the levels of superoxide dismutase (SOD), total antioxidant capacity (TAOC) and suppressing malondialdehyde (MDA) in serum, and increasing the protein of PPARγ, Bax/Bcl-2, Caspase-3 in esophagus tissue, especially in the 50 mg/kg of AST intervention group (all P < 0.05). In conclusion, our data suggested that protective effect of AST on esophageal cancer by inhibiting oxidative stress, up-regulating PPARγ, and activating the apoptotic pathway, which could provide a basis for clinical application of AST.

The Role of Astaxanthin on Chronic Diseases

Natural astaxanthin exists widely in algae, fungi, shrimp and crab, and, as a strong antioxidant, has potential effects on cardiovascular diseases, cancer, liver diseases and other physical health diseases. The treatment of many diseases involves the body’s signal transduction to regulate the body’s antioxidant defense system and inflammation. Astaxanthin is usually used as a dietary supplement, which plays an antioxidant and anti-inflammatory role in the organism. This article reviews the structure, source of astaxanthin and how it plays an anti-inflammatory and anti-oxidant role in organisms, especially in treating diabetes.

The Effect of Astaxanthin and Metformin on Oxidative Stress in Granulosa Cells of BALB C Mouse Model of Polycystic Ovary Syndrome

Reactive oxygen species (ROS), involved in the pathogenesis of the polycystic ovary syndrome (PCOS), play a key role in the onset of apoptosis in follicles and granulosa cells (GCs). We aimed to investigate the antioxidant effects of AST and metformin separately and in combination on GCs using a PCOS mouse model. Forty-eight prepubertal female BALB C mice aged 25-30 days and weighing 12-14 g were studied. The PCOS model was created by subcutaneous injection of the dehydroepiandrosterone (DHEA) hormone in 8 mice of BALB C for 20 consecutive days. Apoptosis and the amount of ROS were evaluated in GCs of the ovaries via flow cytometry. The activity of AKT protein was measured by western blot, and the viability of GCs was investigated using spectrophotometry. Ovarian tissue sections were prepared, stained with H&E, and the morphology of the sections was examined. Statistical analysis was performed by SPSS v22.0 software using one-way ANOVA. We found that AST administration leads to a significant reduction in oxidative stress (P<0.01) and consequently a significant decrease in the rate of apoptosis (P<0.01). While the expression of AKT in the AST group revealed a significant increase (P<0.05), it decreased in the metformin group. However, it was still significantly higher than the control and PCOS groups. Ovulation was confirmed in both metformin and AST groups. Further studies are warranted to prove the efficacy of AST and to introduce it as a complementary therapeutic agent in PCOS.

Therapeutic Potential of Astaxanthin in Diabetic Kidney Disease

Astaxanthin is a carotenoid that has potent protective effects on diabetic kidney disease (DKD) in diabetic mice models. DNA microarray study clearly demonstrated the involvement of mitochondrial oxidative phosphorylation pathway in the renal glomerular cells of diabetic mice and also showed that the expression of upregulated genes associated with this pathway was decreased by the treatment with astaxanthin. Proteomic analysis confirmed that the increases of 4-hydroxy-2-nonenal (HNE)- and N^ε-(hexanonyl)lysine (HEL)-modified proteins were inhibited by the treatment with astaxanthin. These results demonstrated that astaxanthin exerts a protective effect against hyperglycemia-induced DKD by attenuating mitochondrial oxidative stress and subsequent cellular dysfunction.

Astaxanthin mediated regulation of VEGF through HIF1α and XBP1 signaling pathway: An insight from ARPE-19 cell and streptozotocin mediated diabetic rat model

Breakdown of outer blood-retina barrier (BRB) has been associated with the pathogenesis of diabetic retinopathy (DR) and diabetic macular edema (DME). Vascular endothelial growth factor (VEGF) might play a detrimental role in the pathogenesis of DME, a major clinical manifestation of DR. In the present study, we investigated the inhibitory mechanism of astaxanthin on VEGF and its upstream signaling pathways under in vitro and in vivo conditions. Astaxanthin has been observed to downregulate VEGF expression under hyperglycemic (HG) and CoCl₂ induced hypoxic conditions in ARPE-19 cells. There were compelling pieces of evidence for the involvement of transcription factors like HIF1α and XBP1 in the upregulation of VEGF under HG and hypoxic conditions. Thus, we investigated the role of astaxanthin in the expression and nuclear translocation of HIF1α and XBP1. The activation and translocation of HIF1α and XBP1 induced by HG or CoCl₂ conditions were hindered by astaxanthin. Additionally, treatment with HIF1α siRNA and IRE1 inhibitor STF-083010 also inhibited the expression of VEGF induced by HG and CoCl₂ conditions. These results indicated that the anti-VEGF property of astaxanthin might be associated with the downregulation of HIF1α and XBP1. Furthermore, astaxanthin mitigated the enhanced migration of retinal pigment epithelial (RPE) cells under DR conditions. As well, astaxanthin protected disorganization of zona occludin-1 (ZO-1) tight junction protein in RPE and reduced HG or hypoxic induced permeability of RPE cells. In streptozotocin-induced diabetic rat model, astaxanthin reduced the expression of HIF1α, XBP1, and VEGF as well as protected the abnormalities in the retinal layers induced by diabetes condition. Thus, astaxanthin may be used as a potential nutraceutical to prevent or treat retinal dysfunction in diabetic patients.

Natural antioxidants in diabetes treatment and management: prospects of astaxanthin

Diabetes remains a major health emergency in our entire world, affecting hundreds of millions of people worldwide. In conjunction with its much-dreaded complications (e.g., nephropathy, neuropathy, retinopathy, cardiovascular diseases, etc.) it substantially reduces the quality of life, increases mortality as well as economic burden among patients. Over the years, oxidative stress and inflammation have been highlighted as key players in the development and progression of diabetes and its associated complications. Much research has been devoted, as such, to the role of antioxidants in diabetes. Astaxanthin is a powerful antioxidant found mostly in marine organisms. Over the past years, several studies have demonstrated that astaxanthin could be useful in the treatment and management of diabetes. It has been shown to protect β-cells, neurons as well as several organs including the eyes, kidney, liver, etc. against oxidative injuries experienced during diabetes. Furthermore, it improves glucose and lipid metabolism along with cardiovascular health. Its beneficial effects are exerted through multiple actions on cellular functions. Considering these and the fact that foods and natural products with biological and pharmacological activities are of much interest in the 21st-century food and drug industry, astaxanthin has a bright prospect in the management of diabetes and its complications.

Grape seed proanthocyanidins protect retinal ganglion cells by inhibiting oxidative stress and mitochondrial alteration

Grape seed proanthocyanidins (GSP) are known as condensed tannins and have been used as an anti-oxidant in various neurodegenerative diseases. In our study, GSP was used as a daily dietary supplement and the neuroprotective effects were evaluated on the retinal ganglion cells (RGCs) in the retinal tissues in glaucomatous DBA/2D (D2) mice. D2 mice and age-matched non-glaucomatous DBA/2J-Gpnmb⁺ (D2-Gpnmb⁺) mice were fed with GSP or a control diet for up to 6 months. The intraocular pressure (IOP), RGC survival, glial fibrillary acidic protein (GFAP), the levels of apoptotic proteins, and the expression of oxidative stress markers in retinal tissues were determined. In our study, the neuroprotective effects of GSP on retinal tissues were confirmed, as evidenced by (a) GSP inhibited the IOP elevation in D2 mice; (b) GSP enhanced RGC survival and mediated the apoptotic protein expression; (c) GSP suppressed GFAP expression; and (d) the oxidative stress and the levels of mitochondrial reactive oxygen species were regulated by GSP. Our findings indicate that GSP has promising potential to preserve retinal tissue functions via regulating oxidative stress and mitochondrial functions.

The cells involved in the pathological process of diabetic retinopathy

Diabetic retinopathy(DR) is an expanding global health problem, the exact mechanism of which has not yet been clarified clearly, new insights into retinal physiology indicate that diabetes-induced retinal dysfunction may be viewed as an impairment of the retinal neurovascular unit, including retinal ganglion cells, glial cells, endothelial cells, pericytes, and retinal pigment epithelium. Different retinal cells have unique structure and functions, while the interactions among which are less known. Cells are the basic unit of organism structure and function, their impairment could lead to abnormal physiological functions and even organ disorder. Considering the body is multi-dimension and the complexity of DR, one point or a single type of cell can't be used to illustrate the mechanism of occurrence and development of DR. In this review, we provided a systematic and comprehensive elaboration of the cells that are involved in the process of DR. We underlined the importance of considering the neurovascular unit, not just retinal vascular and neural cells, in understanding the pathophysiology of DR. Our studies provided a better understanding of the pathological process in DR and provide a theoretical basis for further research.

Cytoprotective Effect of Astaxanthin in a Model of Normal Intraocular Pressure Glaucoma

Glaucoma is characterized by axonal degeneration of retinal ganglion cells (RGCs) and apoptotic death of their cell bodies. Lowering intraocular pressure is currently the only way to treat glaucoma, but it is often insufficient to inhibit the progression of the disease. Glaucoma is a multifactorial disease, and the involvement of oxidative stress has recently received much attention. In the present study, we investigated the cytoprotective effect of astaxanthin (AST) on RGC degeneration using a normal-tension glaucoma (NTG) mouse model, which lacks the glutamate/aspartate transporter (Glast) and demonstrates spontaneous RGC and optic nerve degeneration without elevated intraocular pressure. Three-week-old Glast^± mice were given intraperitoneal injections of AST at 10, 30, or 60 mg/kg/day or vehicle alone, and littermate control mice were given vehicle alone for 14 days, respectively. Five weeks after birth, the number of RGCs was counted in paraffin sections of retinal tissues stained with hematoxylin and eosin. We also used a retrograde labeling technique to quantify the number of RGCs. Additionally, the phosphorylated (p) IκB/total IκB ratio and the 4-hydroxynonenal (HNE) were measured in retinal tissues. The number of RGCs in Glast^± mice was significantly decreased compared with that in control mice. RGC loss was suppressed by the administration of AST at 60 mg/kg/day, compared with vehicle alone. Following AST administration, the concentration of 4-HNE in the retina was also suppressed, but the pIκB/IκB ratio did not change. Our study revealed that the antioxidative stress effects of AST inhibit RGC degeneration in the retina and may be useful in the treatment of NTG.

Astaxanthin Protects Retinal Photoreceptor Cells against High Glucose-Induced Oxidative Stress by Induction of Antioxidant Enzymes via the PI3K/Akt/Nrf2 Pathway

Diabetic retinopathy (DR) is a major microvascular complication that can lead to severe visual impairment in patients with diabetes. The elevated oxidative stress and increased reactive oxygen species (ROS) production induced by hyperglycemia have been reported to play an important role in the complex pathogenesis of DR. Astaxanthin (AST), a natural carotenoid derivative, has been recently recognized as a strong free radical scavenger and might, therefore, be beneficial in different diseases, including DR. In this study, we evaluated the potential role of AST as an antioxidative and antiapoptotic agent in protecting retinal cells and also investigated the involvement of the PI3K/Akt/Nrf2 pathway in AST-mediated effects. We treated high glucose-cultured mouse photoreceptor cells (661W) with different concentrations of AST and analyzed ROS production and cell apoptosis in the different regimens. Moreover, we also analyzed the expression of PI3K, Akt, Nrf2, and Phase II enzymes after AST treatment. Our results showed that AST dose-dependently reduced ROS production and attenuated 661W cell apoptosis in a high glucose environment. Importantly, its protective effect was abolished by treatment with PI3K or Nrf2 inhibitors, indicating the involvement of the PI3K/Akt/Nrf2 pathway. These results suggest AST as a nutritional supplement that could benefit patients with DR.

Impact of Astaxanthin on Diabetes Pathogenesis and Chronic Complications

Oxidative stress (OS) plays a pivotal role in diabetes mellitus (DM) onset, progression, and chronic complications. Hyperglycemia-induced reactive oxygen species (ROS) have been shown to reduce insulin secretion from pancreatic β-cells, to impair insulin sensitivity and signaling in insulin-responsive tissues, and to alter endothelial cells function in both type 1 and type 2 DM. As a powerful antioxidant without side effects, astaxanthin (ASX), a xanthophyll carotenoid, has been suggested to contribute to the prevention and treatment of DM-associated pathologies. ASX reduces inflammation, OS, and apoptosis by regulating different OS pathways though the exact mechanism remains elusive. Based on several studies conducted on type 1 and type 2 DM animal models, orally or parenterally administrated ASX improves insulin resistance and insulin secretion; reduces hyperglycemia; and exerts protective effects against retinopathy, nephropathy, and neuropathy. However, more experimental support is needed to define conditions for its use. Moreover, its efficacy in diabetic patients is poorly explored. In the present review, we aimed to identify the up-to-date biological effects and underlying mechanisms of ASX on the ROS-induced DM-associated metabolic disorders and subsequent complications. The development of an in-depth research to better understand the biological mechanisms involved and to identify the most effective ASX dosage and route of administration is deemed necessary.

Genome-Protecting Compounds as Potential Geroprotectors

Throughout life, organisms are exposed to various exogenous and endogenous factors that cause DNA damages and somatic mutations provoking genomic instability. At a young age, compensatory mechanisms of genome protection are activated to prevent phenotypic and functional changes. However, the increasing stress and age-related deterioration in the functioning of these mechanisms result in damage accumulation, overcoming the functional threshold. This leads to aging and the development of age-related diseases. There are several ways to counteract these changes: 1) prevention of DNA damage through stimulation of antioxidant and detoxification systems, as well as transition metal chelation; 2) regulation of DNA methylation, chromatin structure, non-coding RNA activity and prevention of nuclear architecture alterations; 3) improving DNA damage response and repair; 4) selective removal of damaged non-functional and senescent cells. In the article, we have reviewed data about the effects of various trace elements, vitamins, polyphenols, terpenes, and other phytochemicals, as well as a number of synthetic pharmacological substances in these ways. Most of the compounds demonstrate the geroprotective potential and increase the lifespan in model organisms. However, their genome-protecting effects are non-selective and often are conditioned by hormesis. Consequently, the development of selective drugs targeting genome protection is an advanced direction.

Effects of Astaxanthin on Inflammation and Insulin Resistance in a Mouse Model of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a condition in which a hormone made by the placenta prevents the body from using insulin effectively. It is important to find an effective treatment. A mouse model of GDM was used to testify the effects of astaxanthin on glucose tolerance and insulin sensitivity. Production of inflammatory cytokines, reactive oxygen species (ROS), and glucose transporter type 4 (GLUT4) translocation and insulin-related signaling were measured in the presence of astaxanthin both in vivo and in vitro. It was found that astaxanthin improved insulin sensitivity, glucose tolerance, and litter size of offspring and reduced birth weight of offspring and inflammation in GDM mouse. Moreover, astaxanthin increased GLUT4 translocating to membrane without altering its secretion/expression and glucose uptake and consumption in C2C12 skeletal muscle cells. Furthermore, ROS generation and insulin-related signaling inhibited by tumor necrosis factor α was restored by astaxanthin. It is concluded that astaxanthin has the potential to attenuate GDM symptoms by regulating inflammation and insulin resistance in skeletal muscle of pregnant mice. Our findings suggest that astaxanthin could be a promising and effective molecule to treat GDM.

Clinical Applications of Astaxanthin in the Treatment of Ocular Diseases: Emerging Insights

Astaxanthin is a naturally occurring red carotenoid pigment belonging to the family of xanthophylls, and is typically found in marine environments, especially in microalgae and seafood such as salmonids, shrimps and lobsters. Due to its unique molecular structure, astaxanthin features some important biologic properties, mostly represented by strong antioxidant, anti-inflammatory and antiapoptotic activities. A growing body of evidence suggests that astaxanthin is efficacious in the prevention and treatment of several ocular diseases, ranging from the anterior to the posterior pole of the eye. Therefore, the present review aimed at providing a comprehensive evaluation of current clinical applications of astaxanthin in the management of ocular diseases. The efficacy of this carotenoid in the setting of retinal diseases, ocular surface disorders, uveitis, cataract and asthenopia is reported in numerous animal and human studies, which highlight its ability of modulating several metabolic pathways, subsequently restoring the cellular homeostatic balance. To maximize its multitarget therapeutic effects, further long-term clinical trials are warranted in order to define appropriate dosage, route of administration and exact composition of the final product.

Optimized nonionic emulsifier for the efficient delivery of astaxanthin nanodispersions to retina: in vivo and ex vivo evaluations

Astaxanthin (AST) is a naturally occurring carotenoid with potent anti-oxidative and anti-inflammatory potency against chronic diseases. In this study, we suspended AST in different nonionic emulsifiers to produce nanodispersions. The basic physicochemical properties of the produced AST nanodispersions were verified to select the optimized nonionic emulsifier. Among the tested emulsifiers, Polysorbate 20 produced the AST nanoemulsions with smaller particle diameters, narrower size distributions, and higher AST contents among these emulsifiers. The N-methyl-N-nitrosourea (MNU) administered mouse is a chemically induced retinal degeneration (RD) model with rapid progress rate. AST suspended in Polysorbate 20 was demonstrated to ameliorate the dramatic consequences of MNU on retina architectures and function in several different tests encompassing from electrophysiology to histology and molecular tests. Furthermore, the multi-electrodes array (MEA) was used to detect the firing activities of retinal ganglion cells within the inner retinal circuits. We found that AST nanodispersions could restrain the spontaneous firing response, enhance the light induced firing response, and preserve the basic configurations of visual signal pathway in degenerative retinas. The MEA assay provided an appropriate example to evaluate the potency of pharmacological compounds on retinal plasticity. In summary, emulsifier type affects the basic physicochemical characteristic of AST nanodispersions. Polysorbate 20 acts as an optimized nonionic emulsifier for the efficient delivery of AST nanodispersions to retina. AST nanodispersions can alleviate the photoreceptor loss and rectify the abnormities in visual signal transmission.

Mechanisms behind Retinal Ganglion Cell Loss in Diabetes and Therapeutic Approach

Diabetes produces several changes in the body triggered by high glycemia. Some of these changes include altered metabolism, structural changes in blood vessels and chronic inflammation. The eye and particularly the retinal ganglion cells (RGCs) are not spared, and the changes eventually lead to cell loss and visual function impairment. Understanding the mechanisms resulting in RGC damage and loss from diabetic retinopathy is essential to find an effective treatment. This review focuses mainly on the signaling pathways and molecules involved in RGC loss and the potential therapeutic approaches for the prevention of this cell death. Throughout the manuscript it became evident that multiple factors of different kind are responsible for RGC damage. This shows that new therapeutic agents targeting several factors at the same time are needed. Alpha-1 antitrypsin as an anti-inflammatory agent may become a suitable option for the treatment of RGC loss because of its beneficial interaction with several signaling pathways involved in RGC injury and inflammation. In conclusion, alpha-1 antitrypsin may become a potential therapeutic agent for the treatment of RGC loss and processes behind diabetic retinopathy.

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).

Effect of astaxanthin on metabolic cataract in rats with type 1 diabetes mellitus

OBJECTIVE

The purpose of this study was to investigate the effect of astaxanthin on metabolic cataract in rats with type 1 diabetes and its antioxidant capacity to lens.

METHODS

Rats were randomly divided into four groups (n = 8): control group, diabetes mellitus (DM) group, low-dose astaxanthin (DM + AL) and low-dose astaxanthin (DM + AH) group. A rat model of type I diabetes mellitus was established by intraperitoneal injection of 60 mg/kg streptozotocin (STZ). After successful modeling, rats in the administration group were given different doses of astaxanthin (AST) for 12 weeks. The lens opacity of rats was observed by slit-lamp camera system. The double antibody sandwich method was used to detect the levels of advanced glycation end product (AGE), lipid peroxide/malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) in the lens. Hematoxylin-eosin (HE) staining was used to examine the morphologic changes in the lens.

RESULTS

The severity of cataract in the lens was obviously increased after induced by STZ, whereas it was significantly decreased after treatment with AST (p < .05, respectively). In addition, in the AST groups, the levels of AGE and MDA in the lens tissue were notably decreased when compared with those in the DM group (p < .05, respectively). However, the levels of GSH, SOD, and CAT were increased in the AST group in comparison with those in the DM group (p < .05, respectively).

CONCLUSIONS

Astaxanthin may play an antioxidant role in the lens. Additionally, it exerts a protective function in the lens by delaying the development and progression of metabolic cataract and inhibiting the oxidative stress of lens in diabetic rats.

Activation of ALDH2 attenuates high glucose induced rat cardiomyocyte fibrosis and necroptosis

Necroptosis is one of a regulated programmed death mode, fibrosis is closely related with cell death. It has been reported that inhibition of necroptosis can play the protective role in cardiac ischemia and reperfusion injury, stroke and other diseases, but the mechanisms of aldehyde dehydrogenases 2 (ALDH2) against high glucose induced neonatal rat ventricular primary cardiomyocytes fibrosis and necroptosis had not been elucidated clearly. This study was to observe the effect of ALDH2 on high glucose (HG) induced myocardial fibrosis and necroptosis in primary rat cardiomyocytes model. In contrast to normal glucose group, in HG group, with the decreases of ALDH2 activity, mRNA and protein levels, the cardiomyocytes viability was decreased, reactive oxygen species (ROS), the inflammation factors - tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) levels, collagen I (col I) and col III mRNA expressions and tissue inhibitors of matrix metalloproteinase 4 (TIMP4) protein expression were increased, while matrix metalloproteinase 14 (MMP14) protein level, the ratio of MMP14/TIMP4 were decreased, and the necroptosis key factors - the receptor interacting protein 1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL) at mRNA and protein expressions were increased, the inflammasome core proteins - NLRP3 and ASC protein expressions were also increased, the apoptosis rate and necrosis rate were also increased. When the cardiomyocytes were treated with Alda-1 (the ALDH2 agonist) in HG intervention, the cell viability, ALDH2 activity, mRNA and protein levels, MMP14 protein level, the ratio of MMP14/TIMP4 were higher, ROS and TNF-α, IL-6, IL-1β levels, RIP1, RIP3, MLKL, NLRP3 and ASC expressions, col I and col III, TIMP4 expressions, the apoptosis rate and necrosis rate were lower than in HG group. Daidzin, the antagonist of ALDH2 abolished the role of Alda-1. In summary, ALDH2 maybe is a key regulator in high glucose induced cardiomyocytes injury. Activation of ALDH2 prevented the happening of fibrosis, apoptosis and necroptosis in high glucose induced primary cardiomyocytes injury model, the protective effects were related to the inhibiting of oxidative stress and inflammation, changing of MMP14 and TIMP4, then inhibiting the happening of fibrosis, apoptosis and necroptosis. These findings advance our understanding of the intensive mechanisms of ALDH2's cardioprotection, and provide the targeted basis for clinical diabetes treatment.

Astaxanthin Ameliorates Ischemic-Hypoxic-Induced Neurotrophin Receptor p75 Upregulation in the Endothelial Cells of Neonatal Mouse Brains

Ischemic stroke is a leading cause of human death in present times. Two phases of pathological impact occur during an ischemic stroke, namely, ischemia and reperfusion. Both periods include individual characteristic effects on cell injury and apoptosis. Moreover, these conditions can cause severe cell defects and harm the blood-brain barrier (BBB). Also, the BBB components are the major targets in ischemia-reperfusion injury. The BBB owes its enhanced protective roles to capillary endothelial cells, which maintain BBB permeability. One of the nerve growth factor (NGF) receptors initiating cell signaling, once activated, is the p75 neurotrophin receptor (p75NTR). This receptor is involved in both the survival and apoptosis of neurons. Although many studies have attempted to explain the role of p75NTR in neurons, the mechanisms in endothelial cells remain unclear. Endothelial cells are the first cells to encounter p75NTR stimuli. In this study, we found the upregulated p75NTR expression and reductive expression of tight junction proteins after in vivo and in vitro ischemia-reperfusion injury. Moreover, astaxanthin (AXT), an antioxidant drug, was utilized and was found to reduce p75NTR expression and the number of apoptotic cells. This study verified that p75NTR plays a prominent role in endothelial cell death and provides a novel downstream target for AXT.

Biomass and Astaxanthin Productivities of Haematococcus pluvialis in an Angled Twin-Layer Porous Substrate Photobioreactor: Effect of Inoculum Density and Storage Time

The microalga Haematococcus pluvialis is mainly cultivated in suspended systems for astaxanthin production. Immobilized cultivation on a Twin-Layer porous substrate photobioreactor (TL-PSBR) has recently shown promise as an alternative approach. In Vietnam, a TL-PSBR was constructed as a low-angle (15 °) horizontal system to study the cultivation of H. pluvialis for astaxanthin production. In this study, the biomass and astaxanthin productivities and astaxanthin content in the dry biomass were determined using different initial biomass (inoculum) densities (from 2.5 to 10 g dry weight m^-2), different storage times of the initial biomass at 4 °C (24, 72, 120 and 168 h) and different light intensities (300-1000 µmol photons m^-2 s^-1). The optimal initial biomass density at light intensities between 400-600 µmol photons^-2 s^-1 was 5-7.5 g m^-2. Algae stored for 24 h after harvest from suspension for immobilization on the TL-PSBR yielded the highest biomass and astaxanthin productivities, 8.7 g m^-2 d^-1 and 170 mg m^-2 d^-1, respectively; longer storage periods decreased productivity. Biomass and astaxanthin productivities were largely independent of light intensity between 300-1000 µmol photons m^-2 s^-1 but the efficiency of light use per mole photons was highest between 300-500 µmol photons m^-2 s^-1. The astaxanthin content in the dry biomass varied between 2-3% (w/w). Efficient supply of CO₂ to the culture medium remains a task for future improvements of angled TL-PSBRs.

Oxidative Stress as the Main Target in Diabetic Retinopathy Pathophysiology

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus (DM) causing vision impairment even at young ages. There are numerous mechanisms involved in its development such as inflammation and cellular degeneration leading to endothelial and neural damage. These mechanisms are interlinked thus worsening the diabetic retinopathy outcome. In this review, we propose oxidative stress as the focus point of this complication onset.