Association between Related Purine Metabolites and Diabetic Retinopathy in Type 2 Diabetic Patients

Association between uric acid and referable diabetic retinopathy in patients with type 2 diabetes

Plasmatic uric acid (UA) has been inconsistently associated with diabetic retinopathy (DR). Specific sight-threatening stages of DR have not been studied for their association with UA. Cross-sectional, comparative study. Between 2014 and 2018 we recruited 210 Mexican individuals > 18 years-old with type 2 diabetes (T2D). Clinical, ophthalmological and biochemical assessment was performed with standardized funduscopic examination. Certified readers classified DR stages. The association between DR and UA was assessed by multiple logistic regression analysis, calculating odds ratios (OR) and 95% CI, after adjustment for covariates. Two hundred and ten patients were included, 41 (19.5%) had referable DR. Subjects with referable (severe or worse) DR had longer diabetes duration, 22 (15-28) vs 15 (8-20) years (P < 0.01); higher levels of UA, 6.5 (5.8-8.1) vs 5.4 (4.5-6.6) mg/dL (P < 0.01); higher systolic blood pressure, 130 (120-140) vs 120 (110-130) mmHg (P < 0.01); higher diastolic blood pressure, 78.4 ± 9.7 vs 75.4 ± 9.2 mmHg (P = 0.03); and lower glomerular filtration rate , 54.1 (41.5-69.6) vs 87.3 (66.8-108.3) mL/min/1.73m2 (P < 0.01) compared with those without referable DR. With multiple logistic regression, after adjustment, per each unit of change (mg/dL) in UA the probability of having referable DR increased 45% (OR = 1.45, 95% CI 1.12-1.87, P < 0.01). When UA was evaluated as dichotomous variable, those with levels ≥ 7.8 mg/dL had almost two times (OR = 2.81, 95% CI 1.00-7.9., P = 0.049) the probability of having referable DR compared with those with levels < 7.8 mg/dL. UA may contribute to the microvascular damage in retinal vessels and therefore hyperuricemia could be a therapeutic target to prevent DR progression.

Causal relationships between blood metabolites and diabetic retinopathy: a two-sample Mendelian randomization study

Background

Diabetic retinopathy (DR) is a microvascular complication of diabetes, severely affecting patients' vision and even leading to blindness. The development of DR is influenced by metabolic disturbance and genetic factors, including gene polymorphisms. The research aimed to uncover the causal relationships between blood metabolites and DR.

Methods

The two-sample mendelian randomization (MR) analysis was employed to estimate the causality of blood metabolites on DR. The genetic variables for exposure were obtained from the genome-wide association study (GWAS) dataset of 486 blood metabolites, while the genetic predictors for outcomes including all-stage DR (All DR), non-proliferative DR (NPDR) and proliferative DR (PDR) were derived from the FinnGen database. The primary analysis employed inverse variance weighted (IVW) method, and supplementary analyses were performed using MR-Egger, weighted median (WM), simple mode and weighted mode methods. Additionally, MR-Egger intercept test, Cochran's Q test, and leave-one-out analysis were also conducted to guarantee the accuracy and robustness of the results. Subsequently, we replicated the MR analysis using three additional datasets from the FinnGen database and conducted a meta-analysis to determine blood metabolites associated with DR. Finally, reverse MR analysis and metabolic pathway analysis were performed.

Results

The study identified 13 blood metabolites associated with All DR, 9 blood metabolites associated with NPDR and 12 blood metabolites associated with PDR. In summary, a total of 21 blood metabolites were identified as having potential causal relationships with DR. Additionally, we identified 4 metabolic pathways that are related to DR.

Conclusion

The research revealed a number of blood metabolites and metabolic pathways that are causally associated with DR, which holds significant importance for screening and prevention of DR. However, it is noteworthy that these causal relationships should be validated in larger cohorts and experiments.

Uric acid and diabetes mellitus: an update

The relationship between diabetes mellitus (DM) and high serum uric acid is complex and controversial. Many epidemiological studies have reported a positive association, whereas others have reported an inverse association or none. In the pathogenesis of DM it is the intracellular urate that is more important than the extracellular and dissociation between the two is possible. Evidence suggests that high serum uric acid induces insulin resistance and beta cell failure in animal models. Reduction of intracellular uric acid can be achieved by dietary measures such as reducing fructose and salt intake, and uric acid-lowering drugs. We suggest that in the Western diet, these elements play a crucial role in pathogenesis of DM. To determine the precise and exact interrelationship between intracellular and extracellular uric acid, well-designed studies are required. Besides this, clinical trials are needed to determine whether intracellular and extracellular urate reduction will provide benefit in prevention and treatment of DM and complications associated with it.

Untargeted Multiomics Approach Coupling Lipidomics and Metabolomics Profiling Reveals New Insights in Diabetic Retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus (DM) which is the main cause of vision loss in the working-age population. Currently known risk factors such as age, disease duration, and hemoglobin A1c lack sufficient efficiency to distinguish patients with early stages of DR. A total of 194 plasma samples were collected from patients with type 2 DM and DR (moderate to proliferative (PDR) or control (no or mild DR) matched for age, gender, diabetes duration, HbA1c, and hypertension. Untargeted lipidomic and metabolomic approaches were performed. Partial-least square methods were used to analyze the datasets. Levels of 69 metabolites and 85 lipid species were found to be significantly different in the plasma of DR patients versus controls. Metabolite set enrichment analysis indicated that pathways such as metabolism of branched-chain amino acids (methylglutaryl carnitine p = 0.004), the kynurenine pathway (tryptophan p < 0.001), and microbiota metabolism (p-Cresol sulfate p = 0.004) were among the most enriched deregulated pathways in the DR group. Moreover, Glucose-6-phosphate (p = 0.001) and N-methyl-glutamate (p < 0.001) were upregulated in DR. Subgroup analyses identified a specific signature associated with PDR, macular oedema, and DR associated with chronic kidney disease. Phosphatidylcholines (PCs) were dysregulated, with an increase of alkyl-PCs (PC O-42:5 p < 0.001) in DR, while non-ether PCs (PC 14:0-16:1, p < 0.001; PC 18:2-14:0, p < 0.001) were decreased in the DR group. Through an unbiased multiomics approach, we identified metabolites and lipid species that interestingly discriminate patients with or without DR. These features could be a research basis to identify new potential plasma biomarkers to promote 3P medicine.

Influence of Serum Uric Acid on Macular Choroidal Thickness and Ganglion Cell Inner Plexiform Layer Thickness

Purpose

The purpose of this study was to determine the influence of serum uric acid (UA) on macular choroidal and ganglion cell inner plexiform layer (GC-IPL) thickness.

Methods

This cross-sectional study enrolled adult individuals in communities in Guangzhou, China. All participants underwent a comprehensive ophthalmologic examination. They were divided into four groups according to UA quartiles. The choroidal and GC-IPL thickness was measured by swept-source optical coherence tomography (SS-OCT).

Results

A total of 719 subjects (1389 eyes) were included in the study. The average UA was 348.50 ± 86.16 mmol/L. The average choroidal and GC-IPL thickness decreased with UA quartiles (P < 0.001). Multivariate linear regression analyses showed that UA was negatively associated with average choroidal (β = -0.073, 95% confidence interval [CI] = -0.117 to -0.028, P = 0.001) and GC-IPL thickness (β = -0.006, 95% CI = -0.009 to -0.002, P = 0.001). After adjusting for confounding factors, the average choroidal thickness was decreased in quartile 4 as compared with quartile 1 by -14.737 µm (95% CI = -24.460 to -5.015, P = 0.003). The average GC-IPL thickness was decreased in quartile 4 versus quartile 1 by -1.028 (95% CI = -1.873 to -0.290, P = 0.007).

Conclusions

Higher UA levels were independently associated with macular choroid and GC-IPL thinning. These contribute to a better understanding of ocular pathological mechanisms.

Translational Relevance

The associated UA with choroidal and GC-IPL thickness helps to understand the ocular pathological and retinal neurodegenerative mechanism.

Integrated Metabolomics and Transcriptomics Reveal Metabolic Patterns in Retina of STZ-Induced Diabetic Retinopathy Mouse Model

Diabetic retinopathy (DR), as the leading cause of vision loss in the working-age population, exhibits unique metabolite profiles in human plasma and vitreous. However, those in retina are not fully understood. Here, we utilized liquid and gas chromatography-tandem mass spectrometry technology to explore metabolite characteristics of streptozotocin (STZ)-induced diabetic mice retina. A total of 145 metabolites differed significantly in diabetic retinas compared with controls. These metabolites are mainly enriched in the Warburg effect, and valine, leucine and isoleucine degradation pathways. To further identify underlying regulators, RNA sequencing was performed to integrate metabolic enzyme alterations with metabolomics in STZ-induced diabetic retina. Retinol metabolism and tryptophan metabolism are the shared pathways enriched by metabolome and transcriptome. Additionally, transcriptomic analysis identified 71 differentially expressed enzyme-related genes including Hk2, Slc7a5, Aldh1a3 and Tph integrated with altered metabolic pathways. In addition, single nucleotide polymorphisms within 6 out of 71 genes are associated with increased diabetes risk. This study lays the foundation for mechanism research and the therapeutic target development of DR.

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.

Integrated multi-omics reveals the activated retinal microglia with intracellular metabolic reprogramming contributes to inflammation in STZ-induced early diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment and blindness among working-age people. Inflammation is recognized as a critical driver of the DR process. However, the main retina-specific cell type producing pro-inflammatory cytokines and its mechanism underlying DR are still unclear. Here, we used single-cell sequencing to identify microglia with metabolic pathway alterations that were the main source of IL-1β in STZ-induced DR mice. To profile the full extent of local metabolic shifts in activated microglia and to reveal the metabolic microenvironment contributing to immune mechanisms, we performed integrated metabolomics, lipidomics, and RNA profiling analyses in microglia cell line samples representative of the DR microenvironment. The results showed that activated microglia with IL-1β increase exhibited a metabolic bias favoring glycolysis, purine metabolism, and triacylglycerol synthesis, but less Tricarboxylic acid (TCA). In addition, some of these especially glycolysis was necessary to facilitate their pro-inflammation. These findings suggest that activated microglia with intracellular metabolic reprogramming in retina may contribute to pro-inflammation in the early DR.

Precise Detection of Cataracts with Specific High-Risk Factors by Layered Binary Co-Ionizers Assisted Aqueous Humor Metabolic Analysis

Diabetes and high myopia as well-known high-risk factors can aggravate cataracts, yet clinical coping strategy remains a bottleneck. Metabolic analysis tends to be powerful for precisely detection and mechanism exploration since most of diseases including cataracts are accompanied by metabolic disorder. Herein, a layered binary co-ionizers assisted aqueous humor metabolic analysis tool is proposed for potentially etiological typing and detection of cataracts, including age-related cataracts (ARC), cataracts with diabetes mellitus (CDM), and cataracts with high myopia (CHM). Startlingly, taking advantage of the optimal machine learning algorithm and all metabolic fingerprints, 100% of accuracy, precision, and recall rates are achieved for arbitrary comparison between groups. Moreover, 11, 9, and 7 key metabolites with explicit identities are confirmed as markers of discriminating CDM from ARC, CHM from ARC, and CDM from CHM, and the corresponding area under the curve values of validation cohorts are 0.985, 1.000, and 1.000. Finally, the critical impact of diabetes/high myopia on cataracts is revealed by excavating the change levels and metabolic pathways of key metabolites. This work updates the insights of prevention and treatment about cataracts at metabolic level and throws out huge surprises and progresses metabolic diagnosis toward a reality.

Uric Acid and Diabetic Retinopathy: A Systematic Review and Meta-Analysis

Background

The relationship between uric acid (UA) and diabetic retinopathy (DR) remains ambiguous, and the results of current studies on the UA levels in patients with DR are conflicting. A meta-analysis was performed to provide a better understanding of the relationship between UA levels and DR.

Methods

PubMed, Web of Science, Embase, and the Cochrane Library databases were searched until December 11, 2021 to identify eligible studies, that compared the UA levels of the case group (patients with DR) and control group (controls with diabetes and healthy participants). The weighted mean difference (WMD) with a 95% confidence interval (CI) was used to evaluate the difference in UA levels between the case and control groups.

Results

Twenty-one studies involving 4,340 patients with DR and 8,595 controls (8,029 controls with diabetes and 566 healthy participants) were included in this meta-analysis. We found that patients with DR had significantly higher UA levels than those in the controls with diabetes (WMD = 36.28; 95% CI: 15.68, 56.89; P < 0.001) and healthy participants (WMD = 70.80; 95% CI: 19.85, 121.75; P = 0.006). There was an obvious heterogeneity among the 21 studies (I² = 97%, P < 0.001). Subgroup analyses of different phases of DR showed that UA levels were significantly increased in participants with proliferative diabetic retinopathy (PDR) (WMD = 46.57; 95% CI: 28.51, 64.63; P < 0.001) than in controls with diabetes; however, the difference is not statistically significant when comparing UA levels in patients with non-proliferative diabetic retinopathy (NPDR) and controls with diabetes (WMD = 22.50; 95% CI: −6.07, 51.08; P = 0.120). In addition, UA levels were higher in participants with a body mass index (BMI) ≥25.0 kg/m² and over 15 years of diabetes. Univariate meta-regression analysis revealed that BMI (P = 0.007, Adj R² = 40.12%) and fasting blood glucose (FBG) (P = 0.040, Adj R² = 29.72%) contributed to between-study heterogeneity.

Conclusions

In conclusion, our study provides evidence that UA levels are higher in patients with DR than those in the controls, but this difference is not statistically significant in the early phases. UA might be a potential biomarker for identifying disease severity in patients with DR, rather than predicting the onset of DR among patients with diabetes. However, more prospective and high-quality clinical evidence is required to confirm these present findings.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=297708.

Metabolic and Metabo-Clinical Signatures of Type 2 Diabetes, Obesity, Retinopathy, and Dyslipidemia

Macro- and microvascular complications of type 2 diabetes (T2D), obesity, and dyslipidemia share common metabolic pathways. In this study, using a total of 1,300 metabolites from 996 Qatari adults (57% with T2D) and 1,159 metabolites from an independent cohort of 2,618 individuals from the Qatar BioBank (11% with T2D), we identified 373 metabolites associated with T2D, obesity, retinopathy, dyslipidemia, and lipoprotein levels, 161 of which were novel. Novel metabolites included phospholipids, sphingolipids, lysolipids, fatty acids, dipeptides, and metabolites of the urea cycle and xanthine, steroid, and glutathione metabolism. The identified metabolites enrich pathways of oxidative stress, lipotoxicity, glucotoxicity, and proteolysis. Second, we identified 15 patterns we defined as "metabo-clinical signatures." These are clusters of patients with T2D who group together based on metabolite levels and reveal the same clustering in two or more clinical variables (obesity, LDL, HDL, triglycerides, and retinopathy). These signatures revealed metabolic pathways associated with different clinical patterns and identified patients with extreme (very high/low) clinical variables associated with extreme metabolite levels in specific pathways. Among our novel findings are the role of N-acetylmethionine in retinopathy in conjunction with dyslipidemia and the possible roles of N-acetylvaline and pyroglutamine in association with high cholesterol levels and kidney function.

Purine metabolites can indicate diabetes progression

AIM

To find the association between purine metabolites and diabetic complications in rats.

MATERIALS AND METHODS

Alloxan was administered to induce diabetes in rats. After 30 days, the levels of uric acid, inosine, xanthine, hypoxanthine and AMP were assessed in both plasma and liver tissues using HPLC technique.

RESULTS

A significant increase in xanthine, hypoxanthine, AMP levels (p < .001 and t-value 2.78) and inosine in plasma and liver tissues (p < .05 and t-value 2.11) with a concomitant increase in uric acid levels (p < .001 and t-value 2.80) was observed in diabetic group.

CONCLUSION

Purine metabolites like uric acid and other intermediate products of purine metabolism are increased in diabetes. These results can be used in addition or separately in evaluating the progression of diabetes.

Metabolomics Based on 1H-NMR Reveal the Regulatory Mechanisms of Dietary Methionine Restriction on Splenic Metabolic Dysfunction in Obese Mice

Methionine restriction (MR) has been reported to have many beneficial health effects, including stress resistance enhancement and lifespan extension. However, the effects of MR on the splenic metabolic dysfunction induced by obesity in mice remain unknown. This study aimed to investigate the scientific problem and clarify its possible mechanisms. C57BL/6J mice in the control group were fed a control diet (0.86% methionine, 4.2% fat) for 34 weeks, and others were fed a high-fat diet (0.86% methionine, 24% fat) for 10 weeks to establish diet-induced obese (DIO) mouse models. Then, the obtained DIO mice were randomly divided into two groups: the DIO group (DIO diet), the DIO + MR group (0.17% methionine, 24% fat) for 24 weeks. Our results indicated that MR decreased spleen weight, and spleen and plasma lipid profiles, promoted lipid catabolism and fatty acid oxidation, glycolysis and tricarboxylic acid cycle metabolism, and improved mitochondrial function and ATP generation in the spleen. Moreover, MR normalized the splenic redox state and inflammation-related metabolite levels, and increased plasma levels of immunoglobulins. Furthermore, MR increased percent lean mass and splenic crude protein levels, activated the autophagy pathway and elevated nucleotide synthesis to maintain protein synthesis in the spleen. These findings indicate that MR can ameliorate metabolic dysfunction by reducing lipid accumulation, oxidative stress, and inflammation in the spleen, and the mechanism may be the activation of autophagy pathway.

Choroidal thickness in children with type 1 diabetes depending on the pubertal status and metabolic parameters analyzed by optical coherence tomography

To assess choroidal thickness (CT) in children with type 1diabetes (T1D) regarding their pubertal status and seek for factors influencing this parameter, using optical coherence tomography.

MATERIAL AND METHODS

333 eyes out of 167 children with T1D without symptoms of diabetic retinopathy (mean age 12.81 ± 3.63 years, diabetes duration 4.59 ± 3.71 years) were enrolled. CT in all quadrants was evaluated. The studied population was divided into three groups: prepubertal, pubertal and postpubertal. The multivariate regression model was carried out using all metabolic parameter and then it was built using only the significant ones.

RESULTS

Significant differences in CT between males and females, except nasal and superior quadrants were observed. We revealed significant differences in CT between the three independent groups (Chi-square 18.6, p < 0.0001). In the statistically significant multiple regression model (R = 0.9, R² = 0.82, p < 0.0000), the serum level of free thyroxine, triiodothyronine, total hemoglobin, uric acid, low- and high-density cholesterol, daily insulin dose per kilogram, weight and level of vitamin D were significant.

CONCLUSION

In our studied group CT increases during puberty. Metabolic parameters such as cholesterol, uric acid, thyroid hormones, and hemoglobin concentration even within the normal range, significantly influence the CT, and these factors likely affect other blood vessels in the body.

Impact of Plasma Xanthine Oxidoreductase Activity on the Mechanisms of Distal Symmetric Polyneuropathy Development in Patients with Type 2 Diabetes

To unravel associations between plasma xanthine oxidoreductase (XOR) and diabetic vascular complications, especially distal symmetric polyneuropathy (DSP), we investigated plasma XOR activities using a novel assay. Patients with type 2 diabetes mellitus (T2DM) with available nerve conduction study (NCS) data were analyzed. None were currently taking XOR inhibitors. XOR activity of fasting blood samples was assayed using a stable isotope-labeled substrate and LC-TQMS. JMP Clinical version 5.0. was used for analysis. We analyzed 54 patients. Mean age was 64.7 years, mean body mass index was 26.0 kg/m², and mean glycated hemoglobin was 9.4%. The logarithmically transformed plasma XOR activity (ln-XOR) correlated positively with hypoxanthine, xanthine, visceral fatty area, and liver dysfunction but negatively with HDL cholesterol. ln-XOR correlated negatively with diabetes duration and maximum intima-media thickness. Stepwise multiple regression analysis revealed ln-XOR to be among selected explanatory factors for various NCS parameters. Receiver operating characteristic curves showed the discriminatory power of ln-XOR. Principal component analysis revealed a negative relationship of ln-XOR with F-waves as well as positive relationships of ln-XOR with hepatic steatosis and obesity-related disorders. Taken together, our results show plasma XOR activity to be among potential disease status predictors in T2DM patients. Plasma XOR activity measurements might reliably detect pre-symptomatic DSP.

Antidiabetic Effect of Noodles Containing Fermented Lettuce Extracts

The aim of the current study was to examine the antidiabetic effect of noodle containing fermented lettuce extract (FLE) on diabetic mice as a pre-clinical study. The γ-aminobutyric acid (GABA) content, antioxidant capacity, and total polyphenol content of the FLE noodles were analyzed and compared with those of standard noodles. In addition, oral glucose and sucrose tolerance, and fasting blood glucose tests were performed using a high-fat diet/streptozotocin-mediated diabetic mouse model. Serum metabolite profiling of mice feed standard or FLE noodles was performed using gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) to understand the mechanism changes induced by the FLE noodles. The GABA content, total polyphenols, and antioxidant activity were high in FLE noodles compared with those in the standard noodles. In vivo experiments also showed that mice fed FLE noodles had lower blood glucose levels and insulin resistance than those fed standard noodles. Moreover, glycolysis, purine metabolism, and amino acid metabolism were altered by FLE as determined by GC-TOF-MS-based metabolomics. These results demonstrate that FLE noodles possess significant antidiabetic activity, suggesting the applicability of fermented lettuce extract as a potential food additive for diabetic food products.

Gender-Specific Risk Factors for the Development of Retinal Changes in Children with Type 1 Diabetes

The aim of the study was to determine gender-specific risk factor sets which could influence optical coherence tomography (OCT) results in children with type 1 diabetes (T1D).

MATERIAL AND METHODS

175 children with T1D without symptoms of diabetic retinopathy were enrolled, but 330 eyes were used for the final analysis (168 children, mean age 12.81 ± 3.63 years, diabetes duration 4.59 ± 3.71 years). The multivariate regression models for retinal thickness (foveal FT, and parafoveal PFT) and vascular densities (superficial and deep) were carried out separately for both genders using all metabolic and demographic parameters.

RESULTS

In the statistically significant multiple regression models for all analyzed OCT parameters for both genders, pH at the onset of diabetes were in existence, as well as for retinal thickness current HbA1c. Duration of continuous insulin infusion (CSII) was an important factor in all parameters, except PFT. For the girls, the most significant factors were daily insulin dose, uric acid, and triglycerides, but for the boys, it was serum creatinine, systolic pressure, and free thyroxine level.

CONCLUSIONS

We detected significant risk factors set for development of OCT parameters changes, and they were not identical for both genders. Current metabolic control, diabetic ketoacidosis at the disease onset, serum creatinine and longer use of CSII are the most important factors for retinal thickness and vessel densities in both genders in children with type 1 diabetes. For the girls, elements of metabolic syndrome (uric acid and triglycerides) and parameters of insulin amount were more pronounced.

Purinergic Signaling During Hyperglycemia in Vascular Smooth Muscle Cells

The activation of purinergic receptors by nucleotides and/or nucleosides plays an important role in the control of vascular function, including modulation of vascular smooth muscle excitability, and vascular reactivity. Accordingly, purinergic receptor actions, acting as either ion channels (P2X) or G protein-coupled receptors (GCPRs) (P1, P2Y), target diverse downstream effectors, and substrates to regulate vascular smooth muscle function and vascular reactivity. Both vasorelaxant and vasoconstrictive effects have been shown to be mediated by different purinergic receptors in a vascular bed- and species-specific manner. Purinergic signaling has been shown to play a key role in altering vascular smooth muscle excitability and vascular reactivity following acute and short-term elevations in extracellular glucose (e.g., hyperglycemia). Moreover, there is evidence that vascular smooth muscle excitability and vascular reactivity is severely impaired during diabetes and that this is mediated, at least in part, by activation of purinergic receptors. Thus, purinergic receptors present themselves as important candidates mediating vascular reactivity in hyperglycemia, with potentially important clinical and therapeutic potential. In this review, we provide a narrative summarizing our current understanding of the expression, function, and signaling of purinergic receptors specifically in vascular smooth muscle cells and discuss their role in vascular complications following hyperglycemia and diabetes.

Dietary Supplementation of Vine Tea Ameliorates Glucose and Lipid Metabolic Disorder via Akt Signaling Pathway in Diabetic Rats

A traditional Chinese tea with many pharmacological effects, vine tea (VT) is considered a potential dietary supplement to improve type 2 diabetes (T2D). To investigate the effect and mechanism of VT on glucose and lipid metabolic disorders in T2D rats, Wistar rats fed a normal diet served as the normal control, while rats fed a high-fat diet combined with low-dose streptozotocin (STZ)-induced T2D were divided into three groups: The model group (MOD); the positive control group (MET, metformin at 200 mg/kg/d); and the VT-treated group (VT500, allowed to freely drink 500 mg/L VT). After four weeks of intervention, biochemical metrics indicated that VT significantly ameliorated hyperglycemia, hyperlipidemia and hyperinsulinemia in T2D rats. Metabolomics research indicated that VT regulated the levels of metabolites closely related to glucose and lipid metabolism and promoted glycogen synthesis. Furthermore, VT had a significant influence on the expression of key genes involved in the Akt signaling pathway, inhibited gluconeogenesis through the Akt/Foxo1/Pck2 signaling pathway, and reduced fatty acid synthesis via the SREBP1c/Fasn signaling pathways. In conclusion, VT has great potential as a dietary supplement to ameliorate glucose and lipid metabolic disorders via the Akt signaling pathway in T2D rats.

microRNA Profiling in Glaucoma Eyes With Varying Degrees of Optic Neuropathy by Using Next-Generation Sequencing

Purpose

To explore the microRNA (miRNA) profile and its putative role in glaucomatous optic neuropathy by using next-generation sequencing.

Methods

Aqueous humor (AH) samples were collected from 19 primary open-angle glaucoma (POAG) eyes and 17 cataract eyes before surgery. Next-generation sequencing was performed for RNA samples extracted from 18 AH samples, and the bioinformatics approach was applied for samples with adequate clean data output. The other 18 samples were used for quantitative PCR validation of sequencing results.

Results

In total, 12 (six POAG and six cataract controls) samples with sufficient clean data output after sequencing were used for further data analysis. Four hundred sixty-six and 480 mature miRNAs were detected in the POAG and cataract control groups, respectively. Among them, 164 miRNAs were detected in all POAG samples, and 96 miRNAs were detected in all cataract control samples. Furthermore, 88 miRNAs were identified as differently expressed between POAG and cataract control eyes. In addition, 16 miRNAs were differently expressed between POAG eyes with severe visual field damage and eyes with moderate visual field damage. This differential expression was predicted to regulate thiamine metabolism, purine metabolism, and transcriptional misregulation. Relative expression patterns of hsa-miR-184, hsa-miR-486-5p, and hsa-miR-93-5p were confirmed by quantitative PCR.

Conclusions

This study comprehensively demonstrated the miRNA expression profile in the AH of POAG eyes, especially the differential expression of miRNA in eyes with varying degrees of visual field damage, which, together with the underlying miRNA-related pathways, indicate new targets for the pathogenesis and progression of POAG.

Correlations between related-purine derivatives and renal disorders in patients with psoriasis vulgaris

Recent data suggest that severe psoriasis is an independent risk factor for chronic renal disease. In the present study, we investigated the role of related-purine derivatives as predictors of renal dysfunctions in patients with psoriasis. A prospective study was conducted on a group of 45 patients with psoriasis vulgaris and 45 control cases, monitored over a 5-year period. Alterations of renal function, albumin/creatinine ratio (ACR, mg/g) and UA/creatinine ratio (UACR, mg/mg) were determined in spontaneous urine samples. The status of related-purine derivatives was evaluated by quantification of uric acid (UA, mg/dl), adenosine deaminase (ADA, UI/mg protein), xanthine oxidase (XO, UI/mg protein) and 8-hydroxy-deoxy-guanosine levels (8-OHdG, ng/ml) in serum samples. Compared to the controls, in patients with psoriasis there was an increase in related-purine derivatives levels, which was demonstrated by the elevated serum levels of UA (5.1±0.4 vs. 5.4±1.0, P=0.066), ADA (0.14±0.08 vs. 0.29±0.12, P=0.052), XO (0.22±0.11 vs. 0.42±0.21, P=0.011) and 8-OHdG (3.1±0.05 vs. 8.3±4.7, P=0.002). The serum levels of related-purine derivatives were associated with the severity of psoriasis. In addition, there was a link between the serum levels of related-purine derivatives and markers of renal impairment. There were positive correlations between 8-OHdG and ACR (r=0.452, P=0.028) and between ADA, XO, UA, 8-OHdG and UACR (r=0.297 and P=0.032, r=0.301 and P=0.002, r=0.431 and P=0.027, r=0.508 and P=0.002) and negative correlations between UA, 8-OHdG and the estimated glomerular filtration rate (r=-0.301 and P=0.036, r=-0.384 and P=0.002). Thus, severe psoriasis is a risk factor for the development of renal disease.

Metabolomics Analysis of Human Vitreous in Diabetic Retinopathy and Rhegmatogenous Retinal Detachment

The vitreous humor is a highly aqueous eye fluid interfacing with the retina and lens and providing shape. Its molecular composition provides a readout for the eye's physiological status. Changes in cellular metabolism underlie vitreoretinal pathologies, but despite routine surgical collection of vitreous, only limited reports of metabolism in the vitreous of human patients have been described. Vitreous samples from patients with rhegmatogenous retinal detachment ( n = 25) and proliferative diabetic retinopathy ( n = 9) were profiled along with control human vitreous samples ( n = 8) by untargeted mass-spectrometry-based metabolomics. Profound changes were observed in diabetic retinopathy vitreous, including altered glucose metabolism and activation of the pentose phosphate pathway, which provides reducing equivalents to counter oxidative stress. In addition, purine metabolism was altered in diabetic retinopathy, with decreased xanthine and elevated levels of related purines (inosine, hypoxanthine, urate, allantoate) generated in oxidant-producing reactions. In contrast, the vitreous metabolite profiles of retinal detachment patients were similar to controls. In total, our results suggest a rewiring of vitreous metabolism in diabetic retinopathy that underlies disease features such as oxidative stress and furthermore illustrates how the vitreous metabolic profile may be impacted by disease.

Recent advances in the applications of metabolomics in eye research

Metabolomics, the identification and quantitation of metabolites in a system, have been applied to identify new biomarkers or elucidate disease mechanism. In this review, we discussed the application of metabolomics in several ocular diseases and recent developments in metabolomics regarding tear fluids analysis, data acquisition and processing.

Correlation of retinal nerve fibre layer and macular thickness with serum uric acid among type 2 diabetes mellitus

Background

Uric acid is a final breakdown product of purine catabolism in humans. It’s a potent antioxidant and can also act as a pro-oxidant that induces oxidative stress on the vascular endothelial cells, thus mediating progression of diabetic related diseases. Various epidemiological and experimental evidence suggest that uric acid has a role in the etiology of type 2 diabetes mellitus. We conducted a cross-sectional study to evaluate the correlation of retinal nerve fibre layer (RNFL) and macular thickness with serum uric acid in type 2 diabetic patients.

Methods

A cross-sectional study was conducted in the Eye Clinic, Hospital Universiti Sains Malaysia, Kelantan between the period of August 2013 till July 2015 involving type 2 diabetes mellitus patients with no diabetic retinopathy and with non-proliferative diabetic retinopathy (NPDR). An evaluation for RNFL and macular thickness was measured using Spectralis Heidelberg optical coherence tomography. Six ml of venous blood was taken for the measurement of serum uric acid and glycosylated haemoglobin (HbA1_C).

Results

A total of 180 diabetic patients were recruited (90 patients with no diabetic retinopathy and 90 patients with NPDR) into the study. The mean level of serum uric acid for both the groups was within normal range and there was no significance difference between the two groups. Based on gender, both male and female gender showed significantly higher level of mean serum uric acid in no diabetic retinopathy group (p = 0.004 respectively). The mean serum uric acid was significantly higher in patient with HbA1_C < 6.5% (p < 0.031). Patients with NPDR have thicker RNFL and macular thickness compared to patients with no diabetic retinopathy. However, only the RNFL thickness of the temporal quadrant and the macular thickness of the superior outer, inferior outer and temporal outer subfields were statistically significant (p = 0.038, p = 0.004, 0.033 and <0.001 respectively). There was poor correlation between RNFL and macular thickness with serum uric acid in both the groups.

Conclusion

Serum uric acid showed a poor correlation with RNFL and macular thickness among type 2 diabetic patients.

Can allopurinol improve retinopathy in diabetic rats? Oxidative stress or uric acid; which one is the culprit?

Allopurinol, an inhibitor of xanthine oxidase, reduces both plasma uric acid and oxidative stress and shows useful effects on some complications of diabetes. However, it is not defined which of the above mentioned properties are involved. Moreover, to the best of our knowledge no study has been done on the effects of allopurinol on diabetic retinopathy. In the present study, the effect of allopurinol on experimental diabetic retinopathy and its possible mechanism has been investigated. Thirty two rats were divided into four groups of eight rats each; (1) normal, (2) diabetic control, (3) diabetic + allopurinol (50 mg/kg.day), (4) diabetic + benzbromarone (10 mg/kg.day). Drugs were administered daily and orally from the day after diabetes induction for eight weeks. Thereafter retinal function and structure were evaluated by electroretinography and microscopic studies. Uric acid and oxidative stress biomarkers were measured biochemically. Diabetes significantly increased plasma uric acid and oxidative stress markers and reduced body weight and amplitude of electroretinogram (ERG) b-wave and oscillatory potentials. Treatment of diabetic rats with allopurinol caused a significant increase in the amplitude of ERG b-wave (87%) and decrease in blood sugar (20%), uric acid (49%), and 8-iso-prostaglandin F2a (56%), but had no effect on the number of retinal ganglionic cells and oscillatory potentials. Benzbromarone showed no significant effects on the considered parameters except the reduction of uric acid. Allopurinol improved the b-wave amplitude of diabetic rats. It seems that this beneficial effect is due to the reduction of oxidative stress rather than its effect on plasma uric acid.

Subpathway-GMir: identifying miRNA-mediated metabolic subpathways by integrating condition-specific genes, microRNAs, and pathway topologies

MicroRNAs (miRNAs) regulate disease-relevant metabolic pathways. However, most current pathway identification methods fail to consider miRNAs in addition to genes when analyzing pathways. We developed a powerful method called Subpathway-GMir to construct miRNA-regulated metabolic pathways and to identify miRNA-mediated subpathways by considering condition-specific genes, miRNAs, and pathway topologies. We used Subpathway-GMir to analyze two liver hepatocellular carcinomas (LIHC), one stomach adenocarcinoma (STAD), and one type 2 diabetes (T2D) data sets. Results indicate that Subpathway-GMir is more effective in identifying phenotype-associated metabolic pathways than other methods and our results are reproducible and robust. Subpathway-GMir provides a flexible platform for identifying abnormal metabolic subpathways mediated by miRNAs, and may help to clarify the roles that miRNAs play in a variety of diseases. The Subpathway-GMir method has been implemented as a freely available R package.

Gut microbiota from metabolic disease-resistant, macrophage-specific RIP140 knockdown mice improves metabolic phenotype and gastrointestinal integrity

While fecal microbiota transplantation (FMT) presents an attractive therapeutic strategy, it remains unclear how to choose the microbiota repertoire that most effectively transfers benefit to recipients. We identified a beneficial taxonomic repertoire in a transgenic mouse model (RIP140mϕKD) which resists the development of high fat diet (HFD)-induced metabolic diseases due to enhanced anti-inflammation engineered by lowering receptor interacting protein (RIP140) expression in macrophage. We confirmed using FMT from HFD-fed RIP140mϕKD to wild type (WT) mice that recipient mice acquired the microbiota repertoire of donor mice. Importantly, FMT from RIP140mϕKD to WT not only effectively transferred the beneficial taxonomic repertoire to WT recipients, but also enabled recipient animals acquiring the anti-inflammatory status of RIP140mϕKD donor animals and avoid HFD-induced insulin resistance, which is associated with significantly improved intestinal integrity. We conclude that FMT can transfer not only microbiota but also the donors' intestinal innate immune status and improved intestinal integrity.

Association between uric acid, cancer incidence and mortality in patients with type 2 diabetes: Shanghai diabetes registry study

BACKGROUND

An elevated serum uric acid level has often been observed with type 2 diabetes or cancer progression. This study aimed to investigate the association between the serum uric acid, cancer incidence, and mortality in Chinese patients with type 2 diabetes.

METHODS

A total of 8274 patients with type 2 diabetes from the Shanghai Diabetes Registry (SDR) participated. The follow-up rate was 85.4%. All subjects were divided into four groups according to the serum uric acid concentration: group 1 (1.0 mg/dL ≤ SUA < 3.0 mg/dL), group 2 (3.0 mg/dL ≤ SUA <5.0 mg/dL), group 3 (5.0 mg/dL ≤ SUA < 7.0 mg/dL), and group 4 (SUA ≥ 7.0 mg/dL). The primary outcome was the first diagnosis of any cancer. The secondary outcome was all-cause mortality. A Cox proportional hazards model was used to estimate the relative risks of cancer and death.

RESULTS

One hundred thirty-seven men and 115 women had cancer by the end of the study. In women, group 1 had the lowest incidence rate of cancer at 30.3 cases per 10 000 person-years, followed by group 2 (48.2). The cancer incidence rates in groups 3 (80.4) and 4 (100.8) were significantly higher than in group 2 (p < 0.05). No significant differences were observed in the incidence of cancer in men (p = 0.76). The risks of overall mortality and death from cancer were not significantly different among the different serum uric acid groups in either sex (Pmale = 0.480, Pfemale = 0.075).

CONCLUSION

In Chinese female diabetic patients, the incidence of cancer increased with serum uric acid levels.

Hyperuricaemia in patients with type 2 diabetes in a tertiary healthcare centre in sub-Saharan Africa: prevalence and determinants

Hyperuricaemia in type 2 diabetes mellitus (T2DM) has been less well investigated in sub-Saharan Africans. Our study of 438 patients found that alcohol intake, body mass index ≥25 kg/m², hydrochlorothiazide use, statin use, diabetic retinopathy and glomerular filtration rate <60 mL/min/1.73m² were independently positively associated with hyperuricaemia; whereas smoking reduced this risk. Hyperuricaemia is strongly associated with some modifiable factors, diabetic complications and certain drugs. Our results suggest that further studies should evaluate the potential cost-benefit of screening for hyperuricaemia in type 2 diabetes.

The Adenosinergic System in Diabetic Retinopathy

The neurodegenerative and inflammatory environment that is prevalent in the diabetic eye is a key player in the development and progression of diabetic retinopathy. The adenosinergic system is widely regarded as a significant modulator of neurotransmission and the inflammatory response, through the actions of the four types of adenosine receptors (A1R, A2AR, A2BR, and A3R), and thus could be revealed as a potential player in the events unfolding in the early stages of diabetic retinopathy. Herein, we review the studies that explore the impact of diabetic conditions on the retinal adenosinergic system, as well as the role of the said system in ameliorating or exacerbating those conditions. The experimental results described suggest that this system is heavily affected by diabetic conditions and that the modulation of its components could reveal potential therapeutic targets for the treatment of diabetic retinopathy, particularly in the early stages of the disease.

Decreased urine uric acid excretion is associated with diabetic retinopathy but not with lower limb atherosclerosis in hospitalized patients with type 2 diabetes

OBJECTIVE

To explore the associations between urine uric acid excretion (UUAE) and diabetic retinopathy (DR)/lower limb atherosclerotic lesions in hospitalized Chinese patients with type 2 diabetes.

METHODS

This cross-sectional study was conducted in 2529 hospitalized Chinese patients with type 2 diabetes. UUAE was determined enzymatically using a single 24-h urine collection. The subjects were stratified into quartile based on UUAE levels. DR was determined by digital fundus photography. Lower limb atherosclerotic lesions were assessed by Doppler ultrasound. Both DR and lower limb atherosclerosis were compared among the UUAE quartile groups, respectively.

RESULTS

There was a significant decrease in the prevalence of DR in patients across the UUAE quartiles after adjustment for sex, age and diabetic duration (35.0%, 30.7%, 26.1%, and 21.5%, respectively, p = 0.000001 for trend). A fully adjusted multiple logistic regression analyses revealed that UUAE quartiles were markedly inversely associated with the presence of DR (p = 0.030). The prevalence of lower limb plaque (73.9% vs. 62.6%, p = 0.000044) and stenosis (16.3% vs. 9.7%, p = 0.000015) was markedly higher in the diabetics with DR than in those without DR. However, there was no statistical association between the UUAE and lower limb atherosclerotic lesions in type 2 diabetes.

CONCLUSIONS

Decreased UUAE was an independent risk factor for DR but not for lower limb atherosclerosis in hospitalized Chinese patients with type 2 diabetes. In selected populations, such as those with type 2 diabetes, the role of uric acid in atherosclerosis may be result from other concomitantly atherosclerotic risk factors, such as DR.

The MCP-1 Gene A-2518G Polymorphism Confers an Increased Risk of Vascular Complications in Type 2 Diabetes Mellitus Patients

OBJECTIVE

We aimed to evaluate the correlation of the monocyte chemoattractant protein 1 (MCP-1) A-2518G polymorphism with type 2 diabetes mellitus (T2DM) and vascular complications in T2DM, to aid in understanding its role in pathogenesis.

METHODS

A total of 150 T2DM patients and 50 healthy controls (group A) were enrolled. The T2DM patients were divided into three groups based on the absence of complications (group B) presence of microvascular disease (group C) or macrovascular disease (group D). DNA of all enrolled subjects was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for the MCP-1 A-2518G polymorphism. Serum MCP-1 levels were measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Participants in group D had increased serum MCP-1 levels relative to group B, group C, and group A (all p<0.01). Compared with group A, the frequencies of the MCP-1 A-2518G G/G genotype and G allele were significantly higher in group C and group D (all p<0.05). In contrast to group B, group C had higher frequencies of the G/G genotype and G allele, while group D had higher G allele frequencies (all p<0.05). Logistic regression analysis showed that lower body-mass index (BMI) and free cholesterol (FC), as well as higher high-density lipoprotein cholesterol (HDL-C) levels may be the protective factors for T2DM, while higher levels of triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and G/G genotype frequency were independent risk factors for T2DM.

CONCLUSIONS

Our data indicates a correlation between the MCP-1 A-2518G polymorphism with macrovascular complications in T2DM patients; lower BMI and FC, as well as higher HDL-C levels may be the protective factors for T2DM, while higher levels of TG, LDL-C, and G/G genotype frequency were independent risk factors for T2DM.

A novel image recuperation approach for diagnosing and ranking retinopathy disease level using diabetic fundus image

Retinal fundus images are widely used in diagnosing and providing treatment for several eye diseases. Prior works using retinal fundus images detected the presence of exudation with the aid of publicly available dataset using extensive segmentation process. Though it was proved to be computationally efficient, it failed to create a diabetic retinopathy feature selection system for transparently diagnosing the disease state. Also the diagnosis of diseases did not employ machine learning methods to categorize candidate fundus images into true positive and true negative ratio. Several candidate fundus images did not include more detailed feature selection technique for diabetic retinopathy. To apply machine learning methods and classify the candidate fundus images on the basis of sliding window a method called, Diabetic Fundus Image Recuperation (DFIR) is designed in this paper. The initial phase of DFIR method select the feature of optic cup in digital retinal fundus images based on Sliding Window Approach. With this, the disease state for diabetic retinopathy is assessed. The feature selection in DFIR method uses collection of sliding windows to obtain the features based on the histogram value. The histogram based feature selection with the aid of Group Sparsity Non-overlapping function provides more detailed information of features. Using Support Vector Model in the second phase, the DFIR method based on Spiral Basis Function effectively ranks the diabetic retinopathy diseases. The ranking of disease level for each candidate set provides a much promising result for developing practically automated diabetic retinopathy diagnosis system. Experimental work on digital fundus images using the DFIR method performs research on the factors such as sensitivity, specificity rate, ranking efficiency and feature selection time.

Diagnosing and ranking retinopathy disease level using diabetic fundus image recuperation approach

Retinal fundus images are widely used in diagnosing different types of eye diseases. The existing methods such as Feature Based Macular Edema Detection (FMED) and Optimally Adjusted Morphological Operator (OAMO) effectively detected the presence of exudation in fundus images and identified the true positive ratio of exudates detection, respectively. These mechanically detected exudates did not include more detailed feature selection technique to the system for detection of diabetic retinopathy. To categorize the exudates, Diabetic Fundus Image Recuperation (DFIR) method based on sliding window approach is developed in this work to select the features of optic cup in digital retinal fundus images. The DFIR feature selection uses collection of sliding windows with varying range to obtain the features based on the histogram value using Group Sparsity Nonoverlapping Function. Using support vector model in the second phase, the DFIR method based on Spiral Basis Function effectively ranks the diabetic retinopathy disease level. The ranking of disease level on each candidate set provides a much promising result for developing practically automated and assisted diabetic retinopathy diagnosis system. Experimental work on digital fundus images using the DFIR method performs research on the factors such as sensitivity, ranking efficiency, and feature selection time.

Monoamine oxidases are novel sources of cardiovascular oxidative stress in experimental diabetes

Diabetes mellitus (DM) is widely recognized as the most severe metabolic disease associated with increased cardiovascular morbidity and mortality. The generation of reactive oxygen species (ROS) is a major event causally linked to the development of cardiovascular complications throughout the evolution of DM. Recently, monoamine oxidases (MAOs) at the outer mitochondrial membrane, with 2 isoforms, MAO-A and MAO-B, have emerged as novel sources of constant hydrogen peroxide (H2O2) production in the cardiovascular system via the oxidative deamination of biogenic amines and neurotransmitters. Whether MAOs are mediators of endothelial dysfunction in DM is unknown, and so we studied this in a streptozotocin-induced rat model of diabetes. MAO expression (mRNA and protein) was increased in both arterial samples and hearts isolated from the diabetic animals. Also, H2O2 production (ferrous oxidation - xylenol orange assay) in aortic samples was significantly increased, together with an impairment of endothelium-dependent relaxation (organ-bath studies). MAO inhibitors (clorgyline and selegiline) attenuated ROS production by 50% and partially normalized the endothelium-dependent relaxation in diseased vessels. In conclusion, MAOs, in particular the MAO-B isoform, are induced in aortas and hearts in the streptozotocin-induced diabetic rat model and contribute, via the generation of H2O2, to the endothelial dysfunction associated with experimental diabetes.

Linking uric acid metabolism to diabetic complications

Hyperuricemia have been thought to be caused by the ingestion of large amounts of purines, and prevention or treatment of hyperuricemia has intended to prevent gout. Xanthine dehydrogenase/xanthine oxidase (XDH/XO) is rate-limiting enzyme of uric acid generation, and allopurinol was developed as a uric acid (UA) generation inhibitor in the 1950s and has been routinely used for gout prevention since then. Serum UA levels are an important risk factor of disease progression for various diseases, including those related to lifestyle. Recently, other UA generation inhibitors such as febuxostat and topiroxostat were launched. The emergence of these novel medications has promoted new research in the field. Lifestyle-related diseases, such as metabolic syndrome or type 2 diabetes mellitus, often have a common pathological foundation. As such, hyperuricemia is often present among these patients. Many in vitro and animal studies have implicated inflammation and oxidative stress in UA metabolism and vascular injury because XDH/XO act as one of the major source of reactive oxygen species Many studies on UA levels and associated diseases implicate involvement of UA generation in disease onset and/or progression. Interventional studies for UA generation, not UA excretion revealed XDH/XO can be the therapeutic target for vascular injury and renal dysfunction. In this review, the relationship between UA metabolism and diabetic complications is highlighted.