Association of bilirubin and malondialdehyde levels with retinopathy in type 2 diabetes mellitus

Altered trace elements, antioxidant vitamin C, and malondialdehyde levels are associated with the pathophysiology and development of pre-hepatic jaundice: A case-control study

Objectives

Pre-hepatic jaundice results from an imbalance between bilirubin production and clearance, often linked to hemoglobinopathies. Antioxidant vitamin C, malondialdehyde, and trace elements play roles in jaundice, yet their specific associations remain unclear. The objective is to assess and compare these biomarkers in pre-hepatic jaundice patients and healthy controls, aiming to identify potential diagnostic markers and understand distinctive characteristics related to the disease's pathogenesis.

Methods

This case-control study enrolled 50 pre-hepatic jaundice patients and 50 healthy controls, utilizing advanced techniques for biomarker quantification. We completed blood sample collection from study participants between 1 September 2023 and 31 December 2023. This study investigates the correlation between various biomarkers and pre-hepatic jaundice using serum samples with a focus on antioxidant vitamin C, malondialdehyde, and trace elements.

Results

This study demonstrates elevated concentrations of malondialdehyde in patients with pre-hepatic jaundice, suggesting alterations in bilirubin metabolism and increased oxidative stress. We found that the serum levels of malondialdehyde were significantly higher in pre-hepatic jaundice patients compared to healthy controls. Our observations revealed a notable decrease in the average serum vitamin C levels in patients with pre-hepatic jaundice compared to healthy controls. The patients had lower serum Zn levels and higher serum Cu and Mn levels compared to the healthy controls. The correlation study demonstrates robust positive correlations among these biomarkers in pre-hepatic jaundice. As the levels of vitamin C rise, the levels of the other criteria often fall, and vice versa. There is an inverse relationship between higher levels of vitamin C and lower levels of malondialdehyde. The current investigation identifies possible changes in antioxidant vitamins, malondialdehyde levels, and trace elements, which provide significant insights for targeted interventions.

Conclusions

The present research highlights the integrated significance of vitamin C, malondialdehyde, and trace elements in the progression of the disease.

High-normal serum bilirubin is a useful indicator to assess the risk of diabetic retinopathy in type 2 diabetes: A real-world study

BACKGROUND

To investigate the association of serum bilirubin within normal range, especially unconjugated bilirubin (UCB), with diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM).

METHODS

In this cross-sectional, real-world study, 7617 T2DM patients were stratified into quartiles based on serum UCB levels. DR was determined by digital fundus photography and further classified into non-proliferative diabetic retinopathy (NPDR) and PDR. The associations of serum bilirubin levels and UCB quartiles with DR were investigated by logistic regression analysis.

RESULTS

After controlling for age, sex, and diabetes duration, the DR prevalence was significantly decreased across the serum UCB quartiles (40.4 %, 33.4 %, 29.7 %, 26.6 % for each quartile, respectively, p < 0.001 for trend). The subjects with DR had lower serum total bilirubin (TB) and UCB, rather than conjugated bilirubin (CB), compared with those without DR (p = 0.003 for TB, p < 0.001 for UCB, and p = 0.528 for CB, respectively), while all three types of serum bilirubin in the subjects with PDR were obviously lower than those with NPDR (p = 0.006 for TB, and p < 0.001 for UCB and CB, respectively). After adjustment for confounding factors, logistic regression demonstrated negative associations of serum TB and UCB levels, rather than CB, with the presence of DR (OR: 0.844, 95%CI: 0.774-0.920, p < 0.001 for TB; OR: 0.828, 95%CI: 0.763-0.899, p < 0.001 for UCB; and OR: 0.984, 95%CI: 0.900-1.074, p = 0.713 for CB, respectively). Additionally, a fully-adjusted analysis revealed a negative correlation between UCB quartiles and DR (p < 0.001).

CONCLUSION

High-normal serum TB and UCB were closely associated with the decreased odds of DR, while all types of serum bilirubin were negatively correlated with the severity of DR in T2DM patients. Serum bilirubin may be used as a potential indicator to assess the risk and severity of DR in T2DM.

Malondialdehyde levels in diabetic retinopathy patients: a systematic review and meta-analysis

BACKGROUND

It remains unclear whether circulating malondialdehyde (MDA) levels change in people with diabetic retinopathy (DR). This systematic review compared circulating MDA levels in diabetic people with and without DR.

METHODS

PubMed, Medline (Ovid), Embase (Ovid), and Web of Science were searched for case-control studies conducted before May 2022 in English that compared circulating MDA levels in people with and without DR. The following MeSH search terms were used: ("malondialdehyde" or "thiobarbituric acid reactive substances [TBARS]" or "lipid peroxidation" or "oxidative stress") and "diabetic retinopathy." Newcastle-Ottawa Quality Assessment Scale was used to evaluate the quality of the included studies. Random-effects pairwise meta-analysis pooled the effect size with standardized mean difference (SMD) and 95% confidence intervals (CIs).

RESULTS

This meta-analysis included 29 case-control studies with 1680 people with DR and 1799 people with diabetes but not DR. Compared to people without DR, the circulating MDA levels were higher in those with DR (SMD, 0.897; 95% CI, 0.631 to 1.162; P  < 0.001). The study did not identify credible subgroup effects or publication bias and the sensitivity analysis confirmed the robustness of the study.

CONCLUSIONS

Circulating MDA levels are higher in people with DR compared to those without. Future comparative studies that use more specific methods are required to draw firm conclusions.

REGISTRATION

PROSPERO; https://www.crd.york.ac.uk/PROSPERO/ ; No. CRD42022352640.

Evaluation of some oxidative markers in diabetes and diabetic retinopathy

Aims

Diabetes mellitus and diabetic retinopathy (DR) are major public health concerns globally. Oxidative stress plays a central role in the pathogenesis of diabetes and DR. The aim of this study was to investigate the association of malondialdehyde, uric acid and bilirubin with diabetes and diabetic retinopathy development.

Methods

This study was conducted on 110 diabetics (with and without retinopathy). Beside 40 healthy individuals as a control group. The level of three markers (malondialdehyde, uric acid and bilirubin) was estimated in the studied groups. Receiver operating characteristic analysis and a logistic regression model was performed.

Results

The present study revealed significantly higher uric acid and malondialdehyde levels, while bilirubin showed significantly lower levels in diabetics compared to control and similarly in diabetic retinopathy compared to those without DR. Furthermore, combination of the three markers increased the accuracy and effect size for differentiation between diabetes with and without DR. In addition, higher levels of uric acid and malondialdehyde were associated with risk of diabetes and DR development.

Conclusion

This study concluded that higher levels of uric acid and malondialdehyde were associated with increase in the risk of diabetes and DR development, while bilirubin wasn't associated with decreasing the risk of diabetes or DR. However, the combination of malondialdehyde, uric acid and bilirubin may be a valuable addition to the current options for the prognosis of DR. In addition, malondialdehyde may be independent predictor of diabetes and DR as well as uric acid may be used as independent biomarker to predict the risk of DR.

Pharmacological actions and therapeutic potentials of bilirubin in islet transplantation for the treatment of diabetes

Islet transplantation is the experimental strategy to treat type 1 diabetes by transplanting isolated islets from a donor pancreas into the recipient. While significant progress has been made in the islet transplantation field, islet loss before and after transplantation is still the major obstacle that currently precludes its widespread application. Islet must survive from possible cellular damages during the isolation procedure, storage time, islet injection process and post-transplantation immune rejection, only then the survived islets could produce insulin, actively regulating the blood glucose level. Therefore, islet protection needs to be addressed, especially regarding oxidative stress and immune response induced islet cell damages in diabetic patients. Many clinical data have shown that mildly elevated bilirubin levels in the body negatively correlate to the occurrence of an array of diseases that are related to increased oxidative stress, especially diabetes, and its complications. Recent studies confirmed that bilirubin helps receivers to suppress immune reaction and enable prolonged tolerance to islet transplantation. In this paper, we will review the pharmacological mechanism of bilirubin to modulate oxidative cellular damage and chronic inflammatory reaction in both diabetes and islet transplantation process. Also, we will present the clinical evidence of a strong correlation in bilirubin and diabetes. More importantly, we will summarize undergoing therapeutic applications of bilirubin in islet transplantation and discuss formulation approaches designed to overcome bilirubin delivery issues for future use.

Elevated Serum Total Bilirubin Concentrations Are Negatively Associated with Diabetic Retinopathy among the Chinese Northeastern Population

OBJECTIVE

To evaluate the association between serum total bilirubin concentration (STBC) and diabetic retinopathy (DR) among the Chinese northeastern population.

METHODS

A cross-sectional study was conducted in Liaoning between January 2015 and May 2017.

RESULTS

A total of 742 subjects (419 men and 323 women) with type 2 diabetes mellitus (DM) who visited an ophthalmic clinic were included in this study. The mean age of the subjects was 59.55 ± 10.63 years, and 43.5% of the subjects were women. The mean of DM duration was 11.01 ± 7.35 years. STBC were negatively correlated with DM duration, urea nitrogen, serum creatinine, uric acid, and urine microalbumin. After adjusting for confounding factors, as a continuous variable, STBC was inversely associated with the risk of DR in total subjects (OR: 0.95, 95% CI: 0.93-0.99). When STBC was used as a tertiary variable, compared with the first tertile, the OR in the third tertile was 0.37 (95% CI: 0.22-0.64) in total subjects.

CONCLUSION

Our results demonstrate that a significant negative association was found between STBC and DR. STBC might be an early clinical marker for predicting the occurrence of DR.

Serum bilirubin levels are negatively associated with diabetic retinopathy in patients with type 1 diabetes and normal renal function

INTRODUCTION

Previous studies suggested that total serum bilirubin levels are negatively associated with diabetic retinopathy (DR) and nephropathy in patients with diabetes mellitus. The objective of this study was to explore the relationship between serum total bilirubin levels and prevalence of DR in patients with type 1 diabetes (T1DM) and normal renal function.

METHODS

Study included 163 T1DM with normal renal function (urinary albumin excretion rate <30 mg/24 h, estimated glomerular filtration rate (eGFR) >60 ml min^-11.73 m^-2). Photo-documented retinopathy status was made according to the EURODIAB protocol.

RESULTS

Patients with DR were older (49 vs 42 years, p = 0.001), had higher systolic blood pressure (130 vs 120 mmHg, p = 0.001), triglycerides (0.89 vs 0.77 mmol/L, p = 0.01), and lower serum total bilirubin (12 vs 15 U/L, p = 0.02) and eGFR (100 vs 106 ml min^-11.73 m^-2, p = 0.03). In multivariate logistic regression analysis, only total serum bilirubin was significantly associated with risk of DR in our subjects (OR 0.88, CI 0.81-0.96, p = 0.006).

CONCLUSION

These data suggest that serum total bilirubin levels are independently negatively associated with DR in T1DM with normal renal function. Prospective studies are needed to confirm whether lower serum total bilirubin has predictive value for the development of DR in T1DM with normal renal function.

Supplementation with Phycocyanobilin, Citrulline, Taurine, and Supranutritional Doses of Folic Acid and Biotin-Potential for Preventing or Slowing the Progression of Diabetic Complications

Oxidative stress, the resulting uncoupling of endothelial nitric oxide synthase (eNOS), and loss of nitric oxide (NO) bioactivity, are key mediators of the vascular and microvascular complications of diabetes. Much of this oxidative stress arises from up-regulated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Phycocyanobilin (PhyCB), the light-harvesting chromophore in edible cyanobacteria such as spirulina, is a biliverdin derivative that shares the ability of free bilirubin to inhibit certain isoforms of NADPH oxidase. Epidemiological studies reveal that diabetics with relatively elevated serum bilirubin are less likely to develop coronary disease or microvascular complications; this may reflect the ability of bilirubin to ward off these complications via inhibition of NADPH oxidase. Oral PhyCB may likewise have potential in this regard, and has been shown to protect diabetic mice from glomerulosclerosis. With respect to oxidant-mediated uncoupling of eNOS, high-dose folate can help to reverse this by modulating the oxidation status of the eNOS cofactor tetrahydrobiopterin (BH4). Oxidation of BH4 yields dihydrobiopterin (BH2), which competes with BH4 for binding to eNOS and promotes its uncoupling. The reduced intracellular metabolites of folate have versatile oxidant-scavenging activity that can prevent oxidation of BH4; concurrently, these metabolites promote induction of dihydrofolate reductase, which functions to reconvert BH2 to BH4, and hence alleviate the uncoupling of eNOS. The arginine metabolite asymmetric dimethylarginine (ADMA), typically elevated in diabetics, also uncouples eNOS by competitively inhibiting binding of arginine to eNOS; this effect is exacerbated by the increased expression of arginase that accompanies diabetes. These effects can be countered via supplementation with citrulline, which efficiently enhances tissue levels of arginine. With respect to the loss of NO bioactivity that contributes to diabetic complications, high dose biotin has the potential to "pinch hit" for diminished NO by direct activation of soluble guanylate cyclase (sGC). High-dose biotin also may aid glycemic control via modulatory effects on enzyme induction in hepatocytes and pancreatic beta cells. Taurine, which suppresses diabetic complications in rodents, has the potential to reverse the inactivating impact of oxidative stress on sGC by boosting synthesis of hydrogen sulfide. Hence, it is proposed that concurrent administration of PhyCB, citrulline, taurine, and supranutritional doses of folate and biotin may have considerable potential for prevention and control of diabetic complications. Such a regimen could also be complemented with antioxidants such as lipoic acid, N-acetylcysteine, and melatonin-that boost cellular expression of antioxidant enzymes and glutathione-as well as astaxanthin, zinc, and glycine. The development of appropriate functional foods might make it feasible for patients to use complex nutraceutical regimens of the sort suggested here.

Inverse Association between Serum Bilirubin Levels and Retinopathy in Patients with Type 2 Diabetes Mellitus

INTRODUCTION

Oxidative stress plays a central role in the pathogenesis of Diabetic Retinopathy (DR) and serum bilirubin has been shown to have antioxidant properties.

AIM

To investigate the association between serum bilirubin concentration and DR in patients with Type 2 Diabetes Mellitus (DM).

MATERIALS AND METHODS

This was a hospital based, cross- sectional study where in 86 patients with Type 2 DM and 30 controls were recruited. The study was conducted at a tertiary care centre in Southern India between January 2014 and December 2014. The presence and the severity of DR were determined by fundus examination and grading of colour fundus photographs using the international clinical disease severity scale for DR. Serum total, direct and indirect bilirubin levels were determined in all subjects and the association between bilirubin levels and severity of DR was studied.

RESULTS

Among the 86 diabetics, 24 had no retinopathy and 62 had DR of varying grades. The mean total bilirubin level among diabetic subjects (0.52±0.17) and controls (0.51±0.19) were found to be similar. The mean total as well as direct bilirubin levels were found to be lower in patients with retinopathy as compared to no retinopathy group (p<0.001). The severity of DR was inversely proportional to the serum bilirubin levels (p=0.010). Serum total bilirubin was found to have a negative association with glycosylated haemoglobin and served as an independent determinant of DR even after adjusting for risk factors known to be associated with DR (p=0.001).

CONCLUSION

Low serum bilirubin levels are significantly associated with increased risk of DR independent of classic risk factors. Serum bilirubin can serve as a useful biomarker in identifying patients at risk for developing proliferative DR.

Effect of bilirubin concentration on the risk of diabetic complications: A meta-analysis of epidemiologic studies

Diabetes can affect many parts of the body and is associated with serious complications. Oxidative stress is a major contributor in the pathogenesis of diabetic complications and bilirubin has been shown to have antioxidant effects. The number of studies on the effect of bilirubin on the risk of diabetic complications has increased, but the results are inconsistent. Thus, we performed a meta-analysis to determine the relationship between bilirubin concentration and the risk of diabetic complications, and to investigate if there was a dose-response relationship. We carried out an extensive search in multiple databases. A fixed or random-effects model was used to calculate the pooled estimates. We conducted a dose-response meta-analysis to analyze the association between these estimates. A total of 132,240 subjects from 27 included studies were analyzed in our meta-analysis. A negative nonlinear association between bilirubin concentration and the risk of diabetic complications was identified (OR: 0.77, 95% CI: 0.73-0.81), with a nonlinear association. We also found that there was a negative association between bilirubin concentration and the risk of diabetic nephropathy, diabetic retinopathy and diabetic neuropathy. The results of our meta-analysis indicate that bilirubin may play a protective role in the occurrence of diabetic complications.

The Negative Relationship between Bilirubin Level and Diabetic Retinopathy: A Meta-Analysis

Objectives

Findings on the relationship between total bilirubin level (TBL) and diabetic retinopathy (DR) are inconsistent. Thus, we carried out a meta-analysis to investigate the relationship between TBL and the risk of DR.

Methods

Relevant studies were selected from six databases up to 31 May 2016 using a search strategy. The relevant data were extracted from the included studies according to the inclusion and exclusion criteria, and the mean value with standard errors or odds ratio (OR) with 95% confidence intervals (CIs) were calculated. We compared TBL in patients with DR with that in patients with diabetes but without retinopathy (NDR), and analyzed the dose-response relationship between TBL and the risk of DR.

Results

Twenty-four studies were selected in this meta-analysis. Twenty studies were included to calculate the pooled SMD, and the results showed that TBL in the DR group was lower than that in the NDR group (SMD: –0.52, 95% CI: –0.67, –0.38). Nine studies were included to calculate the pooled ORs, and the results showed that there was a significant negative relationship between TBL and the risk of DR (OR: 0.19, 95% CI: 0.14, 0.25). Six studies were included to investigate the dose-response relationship between TBL and the risk of DR, and we found a nonlinear relationship between TBL and the risk of DR. The results of our meta-analysis were found to be reliable using subgroup and sensitivity analyses.

Conclusions

The results of our meta-analysis indicate that higher TBL may be protective against DR in subjects with diabetes, and TBL could be used as a biomarker to predict the risk of DR.

Does bilirubin protect against developing diabetes mellitus?

After 25 years of evaluating bilirubin as a possible protective agent in neonatal and cardiovascular disease, interest has moved on to a exploring a possible protective role in diabetes mellitus (DM). This review finds conflicting prospective data for a protective relationship though there are retrospective, case-controlled data, that can only show association, which is not causality. Only prospective studies can show causality. Also, it would appear that the underlying biochemical assumptions do not readily translate from the animal to the human setting. Given that many factors impact on circulating bilirubin levels, it is not surprising that a clear-cut answer is not available; the jury is still out. Any relationship between DM and bilirubin might relate to intermediates in bilirubin metabolism, including relationships involving the genes for the enzymes participating in those steps. Nevertheless, the pursuit of bilirubin in disease causation is opening new avenues for research and if it is established that serum bilirubin can predict risks, much will have been achieved. The answer may have to come from molecular genetic analyses.