Increase in omega-6 and decrease in omega-3 polyunsaturated fatty acid oxidation elevates the risk of exudative AMD development in adults with Chinese diet

An overview of retinal light damage models for preclinical studies on age-related macular degeneration: identifying molecular hallmarks and therapeutic targets

Age-related macular degeneration (AMD) is a complex, multifactorial disease leading to progressive and irreversible retinal degeneration, whose pathogenesis has not been fully elucidated yet. Due to the complexity and to the multiple features of the disease, many efforts have been made to develop animal models which faithfully reproduce the overall AMD hallmarks or that are able to mimic the different AMD stages. In this context, light damage (LD) rodent models of AMD represent a suitable and reliable approach to mimic the different AMD forms (dry, wet and geographic atrophy) while maintaining the time-dependent progression of the disease. In this review, we comprehensively reported how the LD paradigms reproduce the main features of human AMD. We discuss the capability of these models to broaden the knowledge in AMD research, with a focus on the mechanisms and the molecular hallmarks underlying the pathogenesis of the disease. We also critically revise the remaining challenges and future directions for the use of LD models.

Understanding the Impact of Polyunsaturated Fatty Acids on Age-Related Macular Degeneration: A Review

Age-related Macular Degeneration (AMD) is a multifactorial ocular pathology that destroys the photoreceptors of the macula. Two forms are distinguished, dry and wet AMD, with different pathophysiological mechanisms. Although treatments were shown to be effective in wet AMD, they remain a heavy burden for patients and caregivers, resulting in a lack of patient compliance. For dry AMD, no real effective treatment is available in Europe. It is, therefore, essential to look for new approaches. Recently, the use of long-chain and very long-chain polyunsaturated fatty acids was identified as an interesting new therapeutic alternative. Indeed, the levels of these fatty acids, core components of photoreceptors, are significantly decreased in AMD patients. To better understand this pathology and to evaluate the efficacy of various molecules, in vitro and in vivo models reproducing the mechanisms of both types of AMD were developed. This article reviews the anatomy and the physiological aging of the retina and summarizes the clinical aspects, pathophysiological mechanisms of AMD and potential treatment strategies. In vitro and in vivo models of AMD are also presented. Finally, this manuscript focuses on the application of omega-3 fatty acids for the prevention and treatment of both types of AMD.

Metabolomic Profiling of Long-Chain Polyunsaturated Fatty Acid Oxidation in Adults with Retinal Vein Occlusion: A Case-Control Study

BACKGROUND

Long-chain polyunsaturated fatty acids (LCPUFAs) and their metabolites are closely related to neovascular eye diseases. However, the clinical significance of their oxylipins in retinal vein occlusion (RVO) remains inconclusive.

OBJECTIVES

This case-control study aimed to explore metabolomic profiles of LCPUFA oxidation in RVO and to identify potential indicators for diagnosis and pathologic progression.

METHODS

The plasma concentrations of ω-3 (n-3) and ω-6 (n-6) LCPUFA and their oxylipins in 44 adults with RVO and 36 normal controls were analyzed using ultraperformance liquid chromatography tandem mass spectrometry. Univariate analysis combined with principal component and orthogonal projections to latent structure discriminant analysis was used to screen differential metabolites. Aortic ring and choroidal explant sprouting assays were used to investigate the effects of 5-oxo-eicosatetraenoic acids (ETE) on angiogenesis ex vivo. Tubule formation and wound healing assays were performed to verify its effects on human retinal microvascular endothelial cell functions.

RESULTS

Higher ω-6 and lower ω-3 LCPUFA plasma concentrations were measured in the adults with RVO compared with control (odds ratio [OR]: 2.34; 95% confidence interval [CI]: 1.42, 3.86; P < 0.001; OR: 0.28; 95% CI: 0.15, 0.51; P < 0.001). Metabolomic analysis revealed 20 LCPUFA and their oxylipins dysregulated in RVO, including increased arachidonic acid (ω-6, OR: 1.85; 95% CI: 1.18, 2.90; P < 0.001) and its lipoxygenase product 5-oxo-ETE (OR: 11.76; 95% CI: 3.73, 37.11; P < 0.001), as well as decreased docosahexaenoic acid (ω-3, OR: 0.13; 95% CI: 0.05, 0.33; P < 0.001). Interestingly, 5-oxo-ETE was downregulated in ischemic compared with nonischemic central RVO. Exogenous 5-oxo-ETE attenuated aortic ring and choroidal explant sprouting and inhibited tubule formation and migration of human retinal microvascular endothelial cells in a dose-dependent manner, possibly via suppressing the vascular endothelial growth factor signaling pathway.

CONCLUSIONS

The plasma concentrations of ω-6 and ω-3 LCPUFA and their oxylipins were associated with RVO. The ω-6 LCPUFA-derived metabolite 5-oxo-ETE was a potential marker of RVO development and progression.

The inhibitory mechanism of 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx) formation by ultraviolet-gallic acid (UV-GA) during the oil-frying process of squid

The inhibitory effect of ultraviolet-gallic acid (UV-GA) on carbonyl valence and intermediates and precursors of 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx) was investigated to futher clarify the inhibitory mechanism for safety control the quality of oil-fried squid. Ultraviolet C-treated gallic acid (UVC-GA) and ultraviolet B-treated gallic acid (UVB-GA) were produced by ultraviolet 225 nm of band C and 300 nm of band B, respectively. The MeIQx contents in oil-fried squid were significantly higher, and UVC-GA and UVB-GA could significantly inhibit the MeIQx formation and the formation rates of carbonyl valence and precursors (threonine (Thr), creatinine, and glucose). The UVB-GA inhibited formaldehyde formation, while UVC-GA significantly reduced the formaldehyde, acetaldehyde, and 2,5-dimethyl pyrazine contents. In conculsion, UV-GA reduced carbonyl produced from the lipid oxidation to further weaken the catalysis of carbonyl, rendering the MeIQx precursor degrading into the intermediates during Strecker degradation. Thus, the MeIQx formation was inhibited.

Oxidative Stress and Antioxidants in Age-Related Macular Degeneration

Oxidative stress plays a crucial role in aging-related eye diseases, including age-related macular degeneration (AMD), cataracts, and glaucoma. With age, antioxidant reparative capacity decreases, and excess levels of reactive oxygen species produce oxidative damage in many ocular cell types underling age-related pathologies. In AMD, loss of central vision in the elderly is caused primarily by retinal pigment epithelium (RPE) dysfunction and degeneration and/or choroidal neovascularization that trigger malfunction and loss of photo-sensing photoreceptor cells. Along with various genetic and environmental factors that contribute to AMD, aging and age-related oxidative damage have critical involvement in AMD pathogenesis. To this end, dietary intake of antioxidants is a proven way to scavenge free radicals and to prevent or slow AMD progression. This review focuses on AMD and highlights the pathogenic role of oxidative stress in AMD from both clinical and experimental studies. The beneficial roles of antioxidants and dietary micronutrients in AMD are also summarized.

Omega-6: Its Pharmacology, Effect on the Broiler Production, and Health

Lipids and oils are the primary sources of monounsaturated and polyunsaturated fatty acids (MUFA and PUFA), which are necessary for human and animal health. Omega-3 and omega-6 are essential nutrients for broilers. Omega-6 members, such as linolenic acid, are essential for broilers and must be obtained through feed. Vegetable oils are the primary source of omega-6 added to broiler feeds. Unsaturated fatty acids are better digested and absorbed than saturated fatty acids and generate more energy at a lower cost, boosting productivity. Feeding supplements with omega-6 can increase the fatty acid content in meat and increase weight, carcass, viscera, and FCR. The quality of meat taste and antioxidant content was also improved after giving omega-6 and influencing mineral metabolism. Broiler reproductive performance is also enhanced by reducing late embryonic mortality, hence enhancing fertility, hatchability, sperm quality, and sperm quantity. Meanwhile, for broiler health, omega-6 can lower cholesterol levels, triglycerides, very low-density lipoprotein, and low-density lipoprotein. It also supports support for T-helper cell (TH)-2-like IgG titers, increasing prostaglandins, eicosanoids, and antioxidants. In addition, it also supports anti-inflammation. Other researchers have extensively researched and reviewed studies on the effects of omega-6 on poultry. Meanwhile, in this review, we provide new findings to complement previous studies. However, further studies regarding the effects of omega-6 on other poultry are needed to determine the performance of omega-6 more broadly.

Potential mechanisms of macular degeneration protection by fatty fish consumption

Age-related macular degeneration (AMD) is a progressive retinal disease that is a leading cause of visual impairment and severe vision loss. The number of people affected by AMD is increasing and constitutes a huge worldwide health problem. The beneficial effects of fish consumption on AMD have been revealed over the past decades, and in this review, we summarizes the beneficial effects of fatty fish on AMD and its mechanism of action. Fatty fish affects the development of AMD by inhibiting neovascularization, interacting with retinal pigment epithelial (RPE) cells, displacing Omega-6, and inducing cellular responses. It is recommended that people at high risk or with moderate or more severe AMD should consider eating more fatty fish in addition to maintaining a healthy lifestyle of weight control and smoking cessation and the need to promote new models of personalized AMD prevention and treatment.

Long-Chain Polyunsaturated Fatty Acids and Their Metabolites Regulate Inflammation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a blinding eye disease, whose incidence strongly increases with ages. The etiology of AMD is complex, including aging, abnormal lipid metabolism, chronic inflammation and oxidative stress. Long-chain polyunsaturated fatty acids (LCPUFA) are essential for ocular structures and functions. This review summarizes the regulatory effects of LCPUFA on inflammation in AMD. LCPUFA are related to aging, autophagy and chronic inflammation. They are metabolized to pro- and anti-inflammatory metabolites by various enzymes. These metabolites stimulate inflammation in response to oxidative stress, causing innate and acquired immune responses. This review also discusses the possible clinical applications, which provided novel targets for the prevention and treatment of AMD and other age-related diseases.

Isoprostanoid Plasma Levels Are Relevant to Cerebral Adrenoleukodystrophy Disease

Cerebral adrenoleukodystrophy (ALD) is a rare neuroinflammatory disorder characterized by progressive demyelination. Mutations within the ABCD1 gene result in very long-chain fatty acid (VLCFA) accumulation within the peroxisome, particularly in the brain. While this VLCFA accumulation is known to be the driving cause of the disease, oxidative stress can be a contributing factor. For patients with early cerebral disease, allogeneic hematopoietic stem cell transplantation (HSCT) is the standard of care, and this can be supported by antioxidants. To evaluate the involvement of fatty acid oxidation in the disease, F2-isoprostanes (F2-IsoPs), F2-dihomo-isoprostanes (F2-dihomo-IsoPs) and F4-neuroprostanes (F4-NeuroPs)-which are oxygenated metabolites of arachidonic (ARA), adrenic (AdA) and docosahexaenoic (DHA) acids, respectively-in plasma samples from ALD subjects (n = 20)-with various phenotypes of the disease-were measured. Three ALD groups were classified according to patients with: (1) confirmed diagnosis of ALD but without cerebral disease; (2) cerebral disease in early period post-HSCT (<100 days post-HSCT) and on intravenous N-acetyl-L-cysteine (NAC) treatment; (3) cerebral disease in late period post-HSCT (beyond 100 days post-HSCT) and off NAC therapy. In our observation, when compared to healthy subjects (n = 29), in ALD (i), F2-IsoPs levels were significantly (p < 0.01) increased in all patients, with the single exception of the early ALD and on NAC subjects; (ii) significant elevated (p < 0.0001) amounts of F2-dihomo-IsoPs were detected, with the exception of patients with a lack of cerebral disease; (iii), a significant increase (p < 0.003) in F4-NeuroP plasma levels was detected in all ALD patients. Moreover, F2-IsoPs plasma levels were significantly higher (p = 0.038) in early ALD in comparison to late ALD stage, and F4-NeuroPs were significantly lower (p = 0.012) in ALD subjects with a lack of cerebral disease in comparison to the late disease stage. Remarkably, plasma amounts of all investigated isoprostanoids were shown to discriminate ALD patients vs. healthy subjects. Altogether, isoprostanoids are relevant to the phenotype of X-ALD and may be helpful in predicting the presence of cerebral disease and establishing the risk of progression.

Moving forward with isoprostanes, neuroprostanes and phytoprostanes: where are we now?

Polyunsaturated fatty acids (PUFAs) are essential components in eukaryotic cell membrane. They take part in the regulation of cell signalling pathways and act as precursors in inflammatory metabolism. Beside these, PUFAs auto-oxidize through free radical initiated mechanism and release key products that have various physiological functions. These products surfaced in the early nineties and were classified as prostaglandin isomers or isoprostanes, neuroprostanes and phytoprostanes. Although these molecules are considered robust biomarkers of oxidative damage in diseases, they also contain biological activities in humans. Conceptual progress in the last 3 years has added more understanding about the importance of these molecules in different fields. In this chapter, a brief overview of the past 30 years and the recent scope of these molecules, including their biological activities, biosynthetic pathways and analytical approaches are discussed.

Analysis of Lipid Peroxidation by UPLC-MS/MS and Retinoprotective Effects of the Natural Polyphenol Pterostilbene

The loss of redox homeostasis induced by hyperglycemia is an early sign and key factor in the development of diabetic retinopathy. Due to the high level of long-chain polyunsaturated fatty acids, diabetic retina is highly susceptible to lipid peroxidation, source of pathophysiological alterations in diabetic retinopathy. Previous studies have shown that pterostilbene, a natural antioxidant polyphenol, is an effective therapy against diabetic retinopathy development, although its protective effects on lipid peroxidation are not well known. Plasma, urine and retinas from diabetic rabbits, control and diabetic rabbits treated daily with pterostilbene were analyzed. Lipid peroxidation was evaluated through the determination of derivatives from arachidonic, adrenic and docosahexaenoic acids by ultra-performance liquid chromatography coupled with tandem mass spectrometry. Diabetes increased lipid peroxidation in retina, plasma and urine samples and pterostilbene treatment restored control values, showing its ability to prevent early and main alterations in the development of diabetic retinopathy. Through our study, we are able to propose the use of a derivative of adrenic acid, 17(RS)-10-epi-SC-Δ¹⁵-11-dihomo-IsoF, for the first time, as a suitable biomarker of diabetic retinopathy in plasmas or urine.

Investigation of enhanced oxidation stability of microencapsulated enzymatically produced tuna oil concentrates using complex coacervation

Tuna oil was selectively hydrolysed using Thermomyces lanuginosus lipase for 6 h to prepare omega-3 acylglycerol concentrate with the DHA content significantly increased from 24.9% in tuna oil to 36.3% in the acylglycerol concentrate. The acylglycerol concentrate was subsequently encapsulated into the "multi-core" microcapsules using gelatin-sodium hexametaphosphate complex coacervates as the shell material. Rancimat, Oxipres and thermogravimetric analyses all showed that the microencapsulated acylglycerol concentrate had unexpectedly improved oxidation stability, compared to those produced using tuna oil, even though the concentrated oils themselves were significantly less stable than tuna oil. The incorporation of enzymatic tuna oil acylglycerol concentrate also significantly improved the oxidation stability of microencapsulated standard refined unconcentrated tuna oil. A wide range of characteristics including lipid and fatty acid composition, oil-in-water (O/W) emulsion properties, morphology, nanomechanical strength and physicochemical stability of acylglycerol, acylglycerol oil-in-water (O/W) emulsion and final microcapsules were investigated throughout the preparation. The result suggests that high levels of monoacylglycerol (about 35%) and diacylglycerol (about 8.5%) were produced in the acylglycerol. The acylglycerol O/W emulsion exhibited significantly smaller droplet size, lower zeta-potential and higher surface hydrophobicity, which contributed to the formation of the microcapsule with a significantly smoother surface and more compact structure, finally leading to improved oxidative stability compared to those prepared from native tuna oil.

Lactobacillus rhamnosus GG and Oat Beta-Glucan Regulated Fatty Acid Profiles along the Gut-Liver-Brain Axis of Mice Fed with High Fat Diet and Demonstrated Antioxidant and Anti-Inflammatory Potentials

SCOPE

This study takes a novel approach to investigate the anti-inflammatory and antioxidant effects of prebiotic oat beta-glucan (OAT) and the probiotic Lactobacillus rhamnosus GG (LGG) against high-fat diets (HFD) by examining the fatty acid profiles in the gut-liver-brain axis.

METHOD AND RESULTS

HFD-fed C57BL/6N mice are supplemented with OAT and/or LGG for 17 weeks. Thereafter, mass spectrometry-based targeted lipidomics is employed to quantify short-chain fatty acids (SCFA), polyunsaturated fatty acids (PUFA), and oxidized PUFA products in the tissues. Acetate levels are suppressed by HFD in all tissues but reversed in the brain and liver by supplementation with LGG, OAT, or LGG + OAT, and in cecum content by LGG. The n-6/n-3 polyunsaturated fatty acid (PUFA) ratio is elevated by HFD in all tissues but is lowered by LGG and OAT in the cecum and the brain, and by LGG + OAT in the brain, suggesting the anti-inflammatory property of LGG and OAT. LGG and OAT synergistically, but not individually attenuate the increase in non-enzymatic oxidized products, indicating their synbiotic antioxidant property.

CONCLUSION

The regulation of the fatty acid profiles by LGG and OAT, although incomplete, but demonstrates their anti-inflammatory and antioxidant potentials in the gut-liver-brain axis against HFD.

Measurement of Enzymatic and Nonenzymatic Polyunsaturated Fatty Acid Oxidation Products in Plasma and Urine of Macular Degeneration Using LC-QTOF-MS/MS

Oxidized polyunsaturated fatty acids (PUFA) are associated to pathogenesis of diseases including cardiovascular and neurodegeneration. The novel products are not only biomarkers but also lipid mediators in gene regulation and signaling pathways. Herein, simultaneous quantitation of 28 products derived from nonenzymatic and enzymatic oxidation of PUFA i.e. 5-, 15-F_2t -isoprostanes, 7-, 17-F_2t -dihomo-isoprostanes, 7-, 17-F_2t -dihomo-isofurans, 5-, 8-, 18-F_3t -isoprostanes, 4-, 10-, 13-, 14-, 20-F_4t -neuroprostanes, 5-, 8-, 9-, 11-,12-, 15-, 20-HETE, 4-, 7-, 11-, 14-, 17-HDHA, RvE1, and NPD1 using LC-(ESI)-QTOF-MS/MS was developed. These products were measurable in a single sample and the analytical time was relative short (~15 min). Furthermore, we showed that the use of internal standards is a requisite to normalize matrix effects and preparation loss for the quantitation. Validation assays indicated the method to be robust for plasma and mid-stream urine sample analysis in particular from those of age-related macular degeneration subjects, where the accuracy of quantitation displayed good repeatability.