Blood and aqueous humor phoenixin, endocan and spexin in patients with diabetes mellitus and cataract with and without diabetic retinopathy

Recent Progression of Pathogenesis and Treatment for Diabetic Cataracts

Background: Cataracts are still the main cause of blindness worldwide. The incidence of cataracts in the diabetic population is 3-5 times higher than in healthy people. With the increasing incidence of diabetes and the development of aging, as well as the higher risk of surgical and postoperative complications of diabetic patients undergoing surgery, it is still necessary to study the occurrence and development mechanism of diabetic cataracts as well as potential therapeutic targets and therapeutic drugs.Methods: A retrospective review of the literature from PubMed (2017-2024).Results: We summarized the the current literature on the molecular mechanism and prevention and treatment of diabetic cataracts.Conclusions: The aqueous humor metabolism changes, oxidative stress, reactive oxygen species generation increase, the conversion of polyol pathway, as well as non-coding RNA expression changes play important roles in diabetic cataract and these processes is closely linked with each other. Inhibitors or drugs target to these processes, such as aldose reductase inhibitors, antioxidants, natural flavonoid compounds, as well as nanotechnology-based therapeutic product, have shown promising prospects in the prevention and treatment of diabetic cataract.

A systematic scoping review of the multifaceted role of phoenixin in metabolism: insights from in vitro and in vivo studies

Phoenixin (PNX) is an emerging neuropeptide that plays a significant role in regulating metabolism and reproduction. This comprehensive review examines findings from human, in vivo, and in vitro studies to elucidate the functions of PNX in metabolic processes. PNX has been identified as a key player in essential metabolic pathways, including energy homeostasis, glucose, lipid and electrolyte metabolism, and mitochondrial dynamics. It modulates food and fluid intake, influences glucose and lipid profiles, and affects mitochondrial biogenesis and function. PNX is abundantly expressed in the hypothalamus, where it plays a crucial role in regulating reproductive hormone secretion and maintaining energy balance. Furthermore, PNX is also expressed in peripheral tissues such as the heart, spleen, and pancreas, indicating its involvement in the regulation of metabolism across central and peripheral systems. PNX is a therapeutic peptide that operates through the G protein-coupled receptor 173 (GPR173) at the molecular level. It activates signaling pathways such as cAMP-protein kinase A (PKA) and Epac-ERK, which are crucial for metabolic regulation. Research suggests that PNX may be effective in managing metabolic disorders like obesity and type 2 diabetes, as well as reproductive health issues like infertility. Since metabolic processes are closely linked to reproduction, further understanding of PNX's role in these areas is necessary to develop effective management/treatments. This review aims to highlight PNX's involvement in metabolism and identify gaps in current knowledge regarding its impact on human health. Understanding the mechanisms of PNX's action is crucial for the development of novel therapeutic strategies for the treatment of metabolic disorders and reproductive health issues, which are significant public health concerns globally.

Serum Spexin Level Is Negatively Associated With Peripheral Neuropathy and Sensory Pain in Type 2 Diabetes

Background: Spexin is a novel peptide hormone and has shown antinociceptive effects in experimental mice. This study is aimed at evaluating the association of serum spexin level with diabetic peripheral neuropathy (DPN) and related pain in a Chinese population. Methods: We enrolled 167 type 2 diabetes mellitus (T2DM) including 56 patients without DPN (non-DPN), 67 painless DPN, and 44 painful DPN. Serum spexin was measured using ELISA. Logistic regression models were performed to analyze the independent effects of spexin on prevalence of DPN and painful DPN. In streptozotocin (STZ)-induced diabetic mice, mechanical pain threshold was measured using electronic von Frey aesthesiometer. Human peripheral blood mononuclear cells (PBMCs) were isolated and further stimulated with lipopolysaccharide without or with spexin. The gene expression was assayed by qPCR. Results: Compared with non-DPN, serum spexin level decreased in painless DPN and further decreased in painful DPN. The odds of DPN was associated with low spexin level in T2DM, which was similar by age, sex, BMI, and diabetes duration, but attenuated in smokers. The odds of having pain was associated with decreased spexin level in DPN, which was similar by age, sex, smoking status, and diabetes duration, but attenuated in normal weight. Furthermore, we observed that mechanical pain threshold increased in spexin-treated diabetic mice. We also found that lipopolysaccharide treatment increased the mRNA level of TNF-α, IL-6, and MCP-1 in human PBMCs, while spexin treatment prevented this increase. Conclusions: These results suggested that spexin might serve as a protective factor for diabetes against neuropathology and pain-related pathogenesis.

Exploring the Potential Link between Acute Central Serous Chorioretinopathy and Trimethylamine N-Oxide, Phoenixin, Spexin, and Alarin Molecules

PURPOSE

Acute central serous chorioretinopathy (ACSCR) is a condition characterized by decreased visual acuity, macular thickening, and edema under the retinal layer. Although the underlying mechanisms of the disease are not fully understood, oxidative stress is considered to be a critical risk factor. The aim of this study was to shed light on the pathophysiology of ACSCR by investigating the levels of circulating trimethylamine N-oxide (TMAO), phoenixin (PNX), alarin (ALA), and spexin (SPX) molecules in ACSCR patients.

METHODS

The study included 30 ACSCR patients and 30 healthy individuals as controls. ACSCR was diagnosed using optical coherence tomography (OCT) imaging. Five mL blood samples were collected from all participants following overnight fasting. The levels of TMAO, PNX, ALA, and SPX in the blood samples were measured using the ELISA method.

RESULTS

Visual acuity was found to be significantly reduced in ACSCR patients compared to the control group (<0.05), while macular thickness was increased (<0.05). Furthermore, TMAO, PNX, and ALA levels were significantly higher in ACSCR patients (<0.05), while SPX levels were significantly lower compared to the control group (<0.05). In ACSCR patients, there was a positive correlation between macular thickness and TMAO, PNX, and ALA; there was, however, a negative correlation with SPX. Additionally, visual acuity was negatively correlated with TMAO, PNX, and ALA, while SPX levels decreased as visual acuity decreased.

CONCLUSIONS

These results demonstrate a correlation between the TMAO, PNX, ALA, and SPX levels of ACSCR patients and their visual acuity and macular thickness. Given the role of these molecules in ACSCR's pathophysiology, they hold promise as potential diagnostic, therapeutic, and follow-up markers in the future.

Endocan in prediabetes, diabetes, and diabetes-related complications: a systematic review and meta-analysis

BACKGROUND

Diabetes is one of the chronic conditions with a high burden all around the world. Macrovascular and microvascular involvement are among the common mechanisms by which diabetes can impact patients' lives. Endocan as an inflammatory endothelial biomarker has been shown to increase in several communicable and non-communicable diseases. Herein, we aim to investigate the role of endocan as a biomarker in diabetes as a systematic review and meta-analysis.

METHODS

International databases, including PubMed, Web of Science, Scopus, and Embase were searched for relevant studies assessing blood endocan in diabetic patients. Estimation of the standardized mean difference (SMD) and 95% confidence interval (CI) for comparison of circulating endocan levels between diabetic patients and non-diabetic controls were conducted through random-effect meta-analysis.

RESULTS

Totally, 24 studies were included, assessing 3354 cases with a mean age of 57.4 ± 8.4 years. Meta-analysis indicated that serum endocan levels were significantly higher in diabetic patients in comparison with healthy controls (SMD 1.00, 95% CI 0.81 to 1.19, p-value < 0.01). Moreover, in the analysis of studies with only type-2 diabetes, the same result showing higher endocan was obtained (SMD 1.01, 95% CI 0.78 to 1.24, p-value < 0.01). Higher endocan levels were also reported in chronic diabetes complications such as diabetic retinopathy, diabetic kidney disease, and peripheral neuropathy.

CONCLUSION

Based on our study's findings, endocan levels are increased in diabetes, however, further studies are needed for assessing this association. In addition, higher endocan levels were detected in chronic complications of diabetes. This can help researchers and clinicians in recognizing disease endothelial dysfunction and potential complications.

The Role of Endocan in Cardiometabolic Disorders

Discovered two decades ago, endocan still represents an intriguing biomarker related to inflammation. Endocan is a soluble dermatan sulphate proteoglycan secreted by endothelial cells. Its expression is observed in tissues related to the enhanced proliferation, especially hepatocytes, lungs, kidneys, etc. Endocan has been investigated in many cardiometabolic disorders that are tightly connected with inflammation, such as type 2 diabetes mellitus, hypertension, atherosclerotic cardiovascular disease, kidney disease, obesity, polycystic ovary syndrome, metabolic syndrome, non-alcoholic fatty liver disease, etc. In this narrative, comprehensive review of the currently available literature, special attention will be paid to the role of endocan in the broad spectrum of cardiometabolic disorders. Since endocan has emerged as a novel endothelial dysfunction marker, the discovery of potential therapeutic strategies for patients with certain cardiometabolic risk factors would be of great importance to delay or even prevent the onset and progression of related complications, mainly cardiovascular.

Galanin receptor 3 - A new pharmacological target in retina degeneration

The neuropeptide galanin receptor 3 (GALR3) is a class A G protein-coupled receptor (GPCR) broadly expressed in the nervous system, including the retina. GALR3 is involved in the modulation of immune and inflammatory responses. Tight control of these processes is critical for maintaining homeostasis in the retina and is required to sustain vision. Here, we investigated the role of GALR3 in retina pathologies triggered by bright light and P23H mutation in the rhodopsin (RHO) gene, associated with the activation of oxidative stress and inflammatory responses. We used a multiphase approach involving pharmacological inhibition of GALR3 with its antagonist SNAP-37889 and genetic depletion of GALR3 to modulate the GALR3 signaling. Our in vitro experiments in the retinal pigment epithelium-derived cells (ARPE19) susceptible to all-trans-retinal toxicity indicated that GALR3 could be involved in the cellular stress response to this phototoxic product. Indeed, blocking the GALR3 signaling in Abca4-/-/Rdh8-/- and wild-type Balb/cJ mice, sensitive to bright light-induced retina damage, protected retina health in these mice exposed to light. The retina morphology and function were substantially improved, and stress response processes were reduced in these mouse models compared to the controls. Furthermore, in P23H Rho knock-in mice, a model of retinitis pigmentosa (RP), both pharmacological inhibition and genetic ablation of GALR3 prolonged the survival of photoreceptors. These results indicate that GALR3 signaling contributes to acute light-induced and chronic RP-linked retinopathies. Together, this work provides the pharmacological knowledge base to evaluate GALR3 as a potential target for developing novel therapies to combat retinal degeneration.

Regulation and physiological functions of phoenixin

Phoenixin is a newly discovered neuropeptide generated from small integral membrane protein 20. Phoenixin is a ligand for the G protein-coupled receptor 173 (GPR173) and has been detected in central and peripheral tissues of human, rats, mice, bovine, and zebrafish. It was initially involved in regulating reproductive function by stimulating the luteinizing hormone release from pituitary cells by increasing the level of gonadotropin-releasing hormone. Recently, many functions of phoenixin have been generalized, including regulation of food intake, memory, Alzheimer’s disease, anxiety, inflammation, neuronal and microglial activity, energy metabolism and body fluid balance, cardiovascular function, and endocrine activity. In addition, the interaction between phoenixin and nesfatin-1 have been revealed. The present article summarized the latest research progress on physiological function of phoenixin, suggesting that it is a potential target for novel drug development and clinical application.

Super-conserved receptors expressed in the brain: biology and medicinal chemistry efforts

The super-conserved receptors expressed in the brain (SREB) constitute a family of orphan G protein-coupled receptors that include GPR27 (SREB1), GPR85 (SREB2) and GPR173 (SREB3). Their sequences are highly conserved in vertebrates, and they are almost exclusively expressed in the central nervous system. This family of receptors has attracted much attention due to their putative physiological functions and their potential as novel drug targets. The SREB family has been postulated to play important roles in a wide range of different diseases, including pancreatic β-cell insulin secretion and regulation, schizophrenia, autism and atherosclerosis. This review intends to provide a comprehensive overview of the SREB family and its recent advances in biology and medicinal chemistry.