Altered oxylipin levels in human vitreous indicate imbalance in pro-/anti-inflammatory homeostasis in proliferative diabetic retinopathy

Metabolomic biomarkers in vitreous humor: unveiling the molecular landscape of diabetic retinopathy progression

BACKGROUND

Diabetic retinopathy (DR) is a progressive retinal disease that leads to vision loss if not detected early. Metabolomic analysis of vitreous humor offers a promising approach to identifying biomarkers associated with disease onset and progression. This pilot study investigates the metabolomic profiles of vitreous humor from patients at different stages of DR, aiming to uncover potential biomarkers for early detection and monitoring of disease progression.

METHODS

Vitreous samples were collected during therapeutic pars plana vitrectomy of 23 patients without diabetes (CTRL), with diabetes and without retinopathy (DIA), non-proliferative DR (NPDR) and proliferative DR (PDR). Metabolomics was performed using high-performance liquid chromatography coupled with high-resolution mass spectrometry.

RESULTS

Principal component analysis revealed distinct metabolic signatures differentiating the patient groups. Lysine, proline, and arginine levels progressively increased from DIA to NPDR and PDR stages, highlighting their association with disease progression. Methionine and threonine showed notable increases in PDR compared to all other groups, while carnitine, a key metabolite in lipid metabolism, exhibited stage-specific increases, peaking in PDR. The detection of systemic and topical drugs, including metformin and tropicamide, in the vitreous further emphasizes altered ocular permeability in DR.

CONCLUSION

Our findings suggest that metabolomic profiling could provide valuable insights into the underlying pathogenesis of DR and serve as a foundation for personalized therapeutic strategies.

Shenzhuo formulation ameliorates diabetic nephropathy by regulating cytochrome P450-mediated arachidonic acid metabolism

BACKGROUND

Diabetic nephropathy (DN) is a major complication of diabetes, marked by progressive renal damage and an inflammatory response. Although research has investigated the pathological mechanisms underlying DN, effective treatment options remain limited.

AIM

To evaluate the therapeutic impact of Shenzhuo formulation (SZF) on a DN mouse model and to examine its potential molecular mechanisms using transcriptomic and metabolomic approaches.

METHODS

We established a DN mouse model through a high-fat diet combined with streptozotocin (STZ) injection, followed by SZF treatment. We analyzed SZF’s effects on gene expression and metabolite profiles in renal tissues of DN mice using transcriptomics and metabolomics techniques. Additionally, based on transcriptomic and non-targeted metabolomic findings, we further assessed SZF’s influence on the expression of factors related to the cytochrome P450 (CYP450)-mediated arachidonic acid (AA) metabolism pathway, as well as its effects on inflammation and oxidative stress.

RESULTS

SZF intervention significantly decreased hyperglycemia and mitigated renal function impairment in DN mice. Pathological analysis revealed that SZF treatment improved renal tissue damage, reduced fibrosis, and diminished glycogen deposition. Transcriptomic analysis indicated that SZF influenced mRNA expression of CYP450-related genes, including Cyp2j13, Cyp2b9, Pla2 g2e/Cyp4a12a, Cyp4a32, Cyp2e1, and Cyp4a14. Non-targeted metabolomic results demonstrated that SZF altered the levels of metabolites associated with the AA metabolic pathway, including 5,6-EET, 14,15-EET, phosphatidylcholine, and 20-HETE. Further experiments showed that SZF upregulated the expression of CYP4A and CYP2E proteins in renal tissue, as well as CYP2J and CYP2B proteins. Additionally, SZF significantly reduced the expression of inflammatory factors in renal tissue, enhanced antioxidant enzyme activity, and alleviated oxidative stress.

CONCLUSION

SZF exerts anti-inflammatory and antioxidant effects by regulating CYP450-mediated AA metabolism, leading to improved renal function and improved pathological state in DN mice.

Spatial characterization of RPE structure and lipids in the PEX1-p.Gly844Asp mouse model for Zellweger spectrum disorder

Zellweger Spectrum Disorder (ZSD) is caused by defects in PEX genes, whose proteins are required for peroxisome assembly and function. Peroxisome dysfunction in ZSD causes multisystem effects, with progressive retinal degeneration (RD) among the most frequent clinical findings. However, much remains unknown about how peroxisome deficiency causes RD. To study RD pathophysiology in ZSD, we used the PEX1-p.Gly844Asp (G844D) mouse model, which represents the common human PEX1-p.Gly843Asp (G843D) variant. We previously reported diminished retinal function, diminished functional vision, and neural retina structural defects in this model. Here, we investigate the retinal pigment epithelium (RPE) phenotype, examining morphological, inflammatory, and lipid changes at 1, 3, and 6 months of age. We report that RPE cells exhibit evident degeneration by 3 months that worsens with time, starts in the dorsal pole, and is accompanied by subretinal inflammatory cell infiltration. We match these events with imaging mass spectrometry for regional analysis of lipids in the RPE. We identified 47 lipid alterations preceding structural changes, 9 of which localize to the dorsal pole. 29 of these persist to 3 months, with remodeling of the dorsal pole lipid signature. 13 new alterations occur concurrent with histological changes. Abnormalities in peroxisome-dependent lipids detected by LC/MS/MS are exacerbated over time. This study represents the first characterization of RPE in a ZSD model, and the first in situ lipid analysis in peroxisome-deficient tissue. Our findings uncover potential lipid drivers of RD progression in ZSD, and identify candidate biomarkers for retinopathy progression and response to therapy.

Prostanoid signaling in retinal cells elicits inflammatory responses relevant to early-stage diabetic retinopathy

Inflammation is a critical driver of the early stages of diabetic retinopathy (DR) and offers an opportunity for therapeutic intervention before irreversible damage and vision loss associated with later stages of DR ensue. Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown mixed efficacy in slowing early DR progression, notably including severe adverse side effects likely due to their nonselective inhibition of all downstream signaling intermediates. In this study, we investigated the role of prostanoids, the downstream signaling lipids whose production is inhibited by NSAIDs, in promoting inflammation relevant to early-stage DR in two human retinal cell types: Müller glia and retinal microvascular endothelial cells. When cultured in multiple conditions modeling distinct aspects of systemic diabetes, Müller glia significantly increased production of prostaglandin E2 (PGE2), whereas retinal endothelial cells significantly increased production of prostaglandin F2α (PGF2α). Müller glia stimulated with PGE2 or PGF2α increased proinflammatory cytokine levels dose-dependently. These effects were blocked by selective antagonists to the EP2 receptor of PGE2 or the FP receptor of PGF2α, respectively. In contrast, only PGF2α stimulated adhesion molecule expression in retinal endothelial cells and leukocyte adhesion to cultured endothelial monolayers, effects that were fully prevented by FP receptor antagonist treatment. Together these results identify PGE2-EP2 and PGF2α-FP signaling as novel, selective targets for future studies and therapeutic development to mitigate or prevent retinal inflammation characteristic of early-stage DR.

Molecular-Genetic Biomarkers of Diabetic Macular Edema

Background: Diabetic macular edema (DME) is a leading cause of vision impairment and blindness among diabetic patients, requiring effective diagnostic and monitoring strategies. This systematic review aims to synthesize current knowledge on molecular biomarkers associated with DME, focusing on their potential to improve diagnostic accuracy and disease management. Methods: A comprehensive search was conducted in PubMed, Embase, Medline, and the Cochrane Central Register of Controlled Trials, covering literature from 2004 to 2023. Out of 1074 articles initially identified, 48 relevant articles were included in this systematic review. Results: We found that molecules involved in several cellular processes, such as neuroinflammation, oxidative stress, vascular dysfunction, apoptosis, and cell-to-cell communication, exhibit differential expression profiles in various biological fluids when comparing diabetic individuals with or without macular edema. Conclusions: The study of these molecules could lead to the proper identification of specific biomarkers that may improve the diagnosis, prognosis, and therapeutic management of DME patients.

Diet supplementation with hemp (Cannabis sativa L.) inflorescences: effects on quanti-qualitative milk yield and fatty acid profile on grazing dairy goats

Hemp (Cannabis sativa L.) is an annual plant belonging to the family of Cannabaceae with several varieties characterized by different fatty acid profile, content in flavonoids, polyphenols, and cannabinoid compounds. Hemp is mostly used in livestock nutrition as oil or as protein cake, but not as inflorescences. The aim of this study was to evaluate the effect of dietary hemp inflorescences on milk yield and composition in grazing dairy goats. Twenty Camosciata delle Alpi goats at their 3rd parity and with a mean body weight of 45.2 ± 2.0 kg, immediately after kidding, were equally allocated into two groups (G: Grazing and GH: grazing and hemp). For three months, all goats were fed on a permanent pasture and received 700/head/day of concentrate; diet of group GH was supplemented with 20 g/head/day of hemp inflorescences. Goats' body weight did not change during the trial. Individual milk yield was daily recorded and samples collected every 20 days for chemical composition and fatty acid profile analysis. No significant differences were found for milk yield and chemical composition. Caproic (C6:0) (1.80 vs. 1.74%; p < 0.01) and lauric acids (C12:0) were significantly higher in milk of group GH (4.83 vs. 4.32%; p < 0.01) as well as linoleic (C18:2) (2.04 vs. 1.93%; p < 0.05), adrenic acid (C22:4) (0.046 vs. 0.031%, p < 0.05), omega-6/omega-3 ratio (3.17 vs. 2.93, p < 0.05) and total conjugated linoleic acids (CLAs) (0.435 vs. 0.417%; p < 0.01). The results of this study suggest that the supplementation of grazing goats' diet with hemp inflorescences may enhance the milk nutritional characteristics by increasing its content of CLAs and other beneficial fatty acids.

Prostanoid signaling in retinal vascular diseases

The vasculature of the retina is exposed to systemic and local factors that have the capacity to induce several retinal vascular diseases, each of which may lead to vision loss. Prostaglandin signaling has arisen as a potential therapeutic target for several of these diseases due to the diverse manners in which these lipid mediators may affect retinal blood vessel function. Previous reports and clinical practices have investigated cyclooxygenase (COX) inhibition by nonsteroidal anti-inflammatory drugs (NSAIDs) to address retinal diseases with varying degrees of success; however, targeting individual prostanoids or their distinct receptors affords more signaling specificity and poses strong potential for therapeutic development. This review offers a comprehensive view of prostanoid signaling involved in five key retinal vascular diseases: retinopathy of prematurity, diabetic retinopathy, age-related macular degeneration, retinal occlusive diseases, and uveitis. Mechanistic and clinical studies of these lipid mediators provide an outlook for therapeutic development with the potential to reduce vision loss in each of these conditions.

Untargeted and temporal analysis of retinal lipidome in bacterial endophthalmitis

Bacterial endophthalmitis is a blinding infectious disease typically acquired during ocular surgery. We previously reported significant alterations in retinal metabolism during Staphylococcus (S) aureus endophthalmitis. However, the changes in retinal lipid composition during endophthalmitis are unknown. Here, using a mouse model of S. aureus endophthalmitis and an untargeted lipidomic approach, we comprehensively analyzed temporal alterations in total lipids and oxylipin in retina. Our data showed a time-dependent increase in the levels of lipid classes, sphingolipids, glycerolipids, sterols, and non-esterified fatty acids, whereas levels of phospholipids decreased. Among lipid subclasses, phosphatidylcholine decreased over time. The oxylipin analysis revealed increased prostaglandin-E2, hydroxyeicosatetraenoic acids, docosahexaenoic acid, eicosapentaenoic acid, and α-linolenic acid. In-vitro studies using mouse bone marrow-derived macrophages showed increased lipid droplets and lipid-peroxide formation in response to S. aureus infection. Collectively, these findings suggest that S. aureus-infection alters the retinal lipid profile, which may contribute to the pathogenesis of bacterial endophthalmitis.

Integration of Vitreous Lipidomics and Metabolomics for Comprehensive Understanding of the Pathogenesis of Proliferative Diabetic Retinopathy

As a vision-threatening complication of diabetes mellitus (DM), proliferative diabetic retinopathy (PDR) is associated with sustained metabolic disorders. Herein, we collected the vitreous cavity fluid of 49 patients with PDR and 23 control subjects without DM for metabolomics and lipidomics analyses. Multivariate statistical methods were performed to explore relationships between samples. For each group of metabolites, gene set variation analysis scores were generated, and we constructed a lipid network by using weighted gene co-expression network analysis. The association between lipid co-expression modules and metabolite set scores was investigated using the two-way orthogonal partial least squares (O2PLS) model. A total of 390 lipids and 314 metabolites were identified. Multivariate statistical analysis revealed significant vitreous metabolic and lipid differences between PDR and controls. Pathway analysis showed that 8 metabolic processes might be associated with the development of PDR, and 14 lipid species were found to be altered in PDR patients. Combining metabolomics and lipidomics, we identified fatty acid desaturase 2 (FADS2) as an important potential contributor to the pathogenesis of PDR. Collectively, this study integrates vitreous metabolomics and lipidomics to comprehensively unravel metabolic dysregulation and identifies genetic variants associated with altered lipid species in the mechanistic pathways for PDR.

Factors affecting variability in free oxylipins in mammalian tissues

PURPOSE OF THE REVIEW

Along with the growing interest in oxylipins is an increasing awareness of multiple sources of variability in oxylipin data. This review summarizes recent findings that highlight the experimental and biological sources of variation in free oxylipins.

RECENT FINDINGS

Experimental factors that affect oxylipin variability include different methods of euthanasia, postmortem changes, cell culture reagents, tissue processing conditions and timing, storage losses, freeze-thaw cycles, sample preparation techniques, ion suppression, matrix effects, use and availability of oxylipin standards, and postanalysis procedures. Biological factors include dietary lipids, fasting, supplemental selenium, vitamin A deficiency, dietary antioxidants and the microbiome. Overt, but also more subtle differences in health affect oxylipin levels, including during resolution of inflammation and long-term recovery from disease. Sex, genetic variation, exposure to air pollution and chemicals found in food packaging and household and personal care products, as well as many pharmaceuticals used to treat health conditions also affect oxylipin levels.

SUMMARY

Experimental sources of oxylipin variability can be minimized with proper analytical procedures and protocol standardization. Fully characterizing study parameters will help delineate biological factors of variability, which are rich sources of information that can be used to probe oxylipin mechanisms of action and to investigate their roles in health.

New insight of metabolomics in ocular diseases in the context of 3P medicine

Metabolomics refers to the high-through untargeted or targeted screening of metabolites in biofluids, cells, and tissues. Metabolome reflects the functional states of cells and organs of an individual, influenced by genes, RNA, proteins, and environment. Metabolomic analyses help to understand the interaction between metabolism and phenotype and reveal biomarkers for diseases. Advanced ocular diseases can lead to vision loss and blindness, reducing patients' quality of life and aggravating socio-economic burden. Contextually, the transition from reactive medicine to the predictive, preventive, and personalized (PPPM / 3P) medicine is needed. Clinicians and researchers dedicate a lot of efforts to explore effective ways for disease prevention, biomarkers for disease prediction, and personalized treatments, by taking advantages of metabolomics. In this way, metabolomics has great clinical utility in the primary and secondary care. In this review, we summarized much progress achieved by applying metabolomics to ocular diseases and pointed out potential biomarkers and metabolic pathways involved to promote 3P medicine approach in healthcare.

Metabolomics in Diabetic Retinopathy: From Potential Biomarkers to Molecular Basis of Oxidative Stress

Diabetic retinopathy (DR), the leading cause of blindness in working-age adults, is one of the most common complications of diabetes mellitus (DM) featured by metabolic disorders. With the global prevalence of diabetes, the incidence of DR is expected to increase. Prompt detection and the targeting of anti-oxidative stress intervention could effectively reduce visual impairment caused by DR. However, the diagnosis and treatment of DR is often delayed due to the absence of obvious signs of retina imaging. Research progress supports that metabolomics is a powerful tool to discover potential diagnostic biomarkers and therapeutic targets for the causes of oxidative stress through profiling metabolites in diseases, which provides great opportunities for DR with metabolic heterogeneity. Thus, this review summarizes the latest advances in metabolomics in DR, as well as potential diagnostic biomarkers, and predicts molecular targets through the integration of genome-wide association studies (GWAS) with metabolomics. Metabolomics provides potential biomarkers, molecular targets and therapeutic strategies for controlling the progress of DR, especially the interventions at early stages and precise treatments based on individual patient variations.

A Review of Oxylipins in Alzheimer's Disease and Related Dementias (ADRD): Potential Therapeutic Targets for the Modulation of Vascular Tone and Inflammation

There is now a convincing body of evidence from observational studies that the majority of modifiable Alzheimer's disease and related dementia (ADRD) risk factors are vascular in nature. In addition, the co-existence of cerebrovascular disease with AD is more common than AD alone, and conditions resulting in brain ischemia likely promote detrimental effects of AD pathology. Oxylipins are a class of bioactive lipid mediators derived from the oxidation of long-chain polyunsaturated fatty acids (PUFAs) which act as modulators of both vascular tone and inflammation. In vascular cognitive impairment (VCI), there is emerging evidence that oxylipins may have both protective and detrimental effects on brain structure, cognitive performance, and disease progression. In this review, we focus on oxylipin relationships with vascular and inflammatory risk factors in human studies and animal models pertinent to ADRD. In addition, we discuss future research directions with the potential to impact the trajectory of ADRD risk and disease progression.

Molecules related to diabetic retinopathy in the vitreous and involved pathways

Diabetic retinopathy (DR) is one of the most common complications of diabetes and major cause of blindness among people over 50 years old. Current studies showed that the vascular endothelial growth factor (VEGF) played a central role in the pathogenesis of DR, and application of anti-VEGF has been widely acknowledged in treatment of DR targeting retinal neovascularization. However, anti-VEGF therapy has several limitations such as drug resistance. It is essential to develop new drugs for future clinical practice. The vitreous takes up 80% of the whole globe volume and is in direct contact with the retina, making it possible to explore the pathogenesis of DR by studying related factors in the vitreous. This article reviewed recent studies on DR-related factors in the vitreous, elaborating the VEGF upstream hypoxia-inducible factor (HIF) pathway and downstream pathways phosphatidylinositol diphosphate (PIP2), phosphoinositide-3-kinase (PI3K), and mitogen-activated protein kinase (MAPK) pathways. Moreover, factors other than VEGF contributing to the pathogenesis of DR in the vitreous were also summarized, which included factors in four major systems, kallikrein-kinin system such as bradykinin, plasma kallikrein, and coagulation factor XII, oxidative stress system such as lipid peroxide, and superoxide dismutase, inflammation-related factors such as interleukin-1β/6/13/37, and interferon-γ, matrix metalloproteinase (MMP) system such as MMP-9/14. Additionally, we also introduced other DR-related factors such as adiponectin, certain specific amino acids, non-coding RNA and renin (pro) receptor in separate studies.