Serum bilirubin concentration is associated with eGFR and urinary albumin excretion in patients with type 1 diabetes mellitus

The Evaluation of the Genetic Variation Types of the Uridine Diphosphate Glucuronosyl Transferase 1A1 Gene by Next-Generation Sequencing and Their Effects on Bilirubin Levels in Obese Children

Background and Objectives: Obesity is a major nutritional problem with an increasing prevalence among children and adolescents. The uridine-diphosphate-glucuronosyl-transferase1A1 (UGT1A1) gene encodes the UDP-glucuronosyl transferase enzyme, converting the toxic form of bilirubin to a soluble, nontoxic form. There are yet to be studies on the evaluation of the UGT1A1 variant types detected by next-generation sequencing (NGS) and their effects on bilirubin levels in nonsyndromic obese children. Methods: Forty-five children with body mass index (BMI) >95 percentile (p) constituted the obesity group and fourteen healthy children with BMI <85p constituted the control group. Anthropometric, clinical features, and biochemical parameters were evaluated. Furthermore, the UGT1A1 gene was sequenced by NGS. Results: The obese patients had lower total, direct, and indirect bilirubin levels (p = 0.422, 0.026, and 0.568, respectively). In addition, obese patients had more genetic variations in the UGT1A1 gene compared with the control group (62.2% and 50%, respectively). We found that children with variations had higher total direct and indirect bilirubin levels compared with those without variation (p = 0.016, 0.028, and 0.015, respectively). Children diagnosed with obesity in the first two years of their life had fewer genetic variations and lower total bilirubin levels (p = 0.000 and 0.013, respectively). Conclusions: It is assumed that bilirubin can be protective against many chronic diseases. Although bilirubin levels are found to be lower in obese children compared with the control group, some variations in the UGT1A1 gene may be supported by raising bilirubin. We suggest that high bilirubin levels caused by those UGT1A1 variations may be protective against obesity and its many negative effects.

Low Levels of Metrnl are Linked to the Deterioration of Diabetic Kidney Disease

Objective

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. Metrnl is a secreted protein that plays an important role in kidney disease. The aim of this study was to investigate DKD-related factors and the correlation between serum Metrnl levels and the severity of DKD.

Methods

Ninety-six type 2 diabetes mellitus (T2DM) patients and 45 DKD patients were included in the study. A range of parameters were measured simultaneously, including waist-to-hip ratio (WHR), body mass index (BMI), urinary albumin/creatinine ratio (UACR), monocyte-lymphocyte ratio (MLR), albumin/globulin (A/G), liver and kidney function, blood lipid profile, islet function, and others. Subsequently, the related factors and predictive significance of DKD were identified. The correlation between the relevant factors of DKD and serum Metrnl levels with DKD was evaluated.

Results

The duration of the disease (OR: 1.12, 95% CI: 1.01-1.24, P=0.031), hypertension (OR: 4.86, 95% CI: 1.16-20.49, P=0.031), fasting blood glucose (OR: 1.23, 95% CI: 1.03-1.48, P=0.025), WHR (OR: 2.53, 95% CI: 1.03-6.22, P=0.044), and MLR (OR: 1.91, 95% CI: 1.18-3.08, P=0.008) are independent risk factors for DKD (P < 0.05). Conversely, A/G (OR: 0.13, 95% CI: 0.02-0.76, P=0.024) and Metrnl (OR: 0.99, 95% CI: 0.98-1.00, P=0.001) have been identified as protective factors against DKD. Furthermore, the level of Metrnl was negatively correlated with the severity of DKD (rs=-0.447, P<0.001). The area under receiver operating characteristic (ROC) curves for the diagnostic accuracy of Metrnl for DKD is 0.765 (95% CI: 0.686-0.844).

Conclusion

The duration of the disease, hypertension, fasting blood glucose, WHR, and MLR are major risk factors for DKD. Metrnl and A/G are protective factors for DKD. Serum Metrnl concentrations are inversely correlated with DKD severity.

Association between serum total bilirubin and diabetic kidney disease in US diabetic patients

Background

Bilirubin has been widely reported to be a protective factor against diabetic kidney disease (DKD) in Asian populations. However, few large-sample analyses have been conducted in American populations. This study aimed to investigate the association between serum total bilirubin (STB) level and DKD in a US diabetic cohort.

Methods

This cross-sectional study enrolled participants from the National Health and Nutrition Examination Survey (NHANES) 2003-2018. Univariate and multivariate logistic regression analyses were performed to assess the association between STB level and DKD. Three models were conducted to control the potential confounding factors. Subgroup analysis was carried out for further validation.

Results

Among the 5,355 participants, the median age [interquartile range (IQR)] was 62 [52-71] years; 2,836 (52.96%) were male, and 1,576 (29.43%) were diagnosed with DKD. In the entire cohort, no significant association between STB level and DKD was observed in any logistic regression models (p > 0.05). Subgroup analysis revealed that, in U.S. diabetic males, STB levels > 11.98 µmol/L were associated with a nearly 30% lower risk of DKD than STB levels ≤ 8.55 µmol/L. Additionally, a moderate STB level (8.56-11.98 μmol/L) was found associated with a nearly 25% lower risk of DKD in U.S. diabetic patients over 65 years old.

Conclusion

The association of STB level with DKD may depict differences across diverse populations, among which the impact of race, sex, and age requires thorough consideration and relevant inferences should be interpreted cautiously.

Association between bilirubin and chronic kidney disease in hypertensive patients: The China hypertension registry study

Limited data exists on the association between Direct bilirubin (DBIL) and Indirect bilirubin (IBIL) with the risk of chronic kidney disease (CKD) among patients with hypertension. This study aimed to assess the relationship between DBIL and IBIL with the risk of CKD in a cohort of Chinese adults diagnosed with hypertension. This study included 14 182 Chinese patients with hypertension between the ages of 27 and 96. CKD, the outcome variable, was defined by an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 . The study employed multivariate linear and multivariate logistic regression analysis to evaluate the correlation between DBIL and IBIL with the risk of CKD. The prevalence of CKD in the study population was 9.77%. Multivariate logistic regression analysis showed that the increase in DBIL (OR: 0.66; 95% CI: 0.61, 0.71) and IBIL (OR: 0.75; 95% CI: 0.71, 0.81) were independently and negatively correlated with CKD. Further analyses using a restricted cubic spline (smooth-fitting curve) confirmed the linearly negative association between DBIL and IBIL with the risk of CKD. The subgroup analysis showed that the correlation between IBIL and CKD was stronger among men and populations <65 years of age (p for interaction <.05). DBIL and IBIL were independently and negatively associated with CKD. Furthermore, the correlation between DBIL and IBIL with CKD in the hypertensive population is more significant in those under 65 years of age. These findings may inform future strategies for the management of CKD.

Bilirubin levels and kidney function decline: An analysis of clinical trial and real world data

Objective

To evaluate if previously found associations between low serum bilirubin concentration and kidney function decline is independent of hemoglobin and other key confounders.

Research design and methods

Clinical trial data from the SAVOR-TIMI 53 trial as well as the UK primary care electronic healthcare records, Clinical Practice Research Datalink (CPRD), were used to construct three cohorts of patients at risk of chronic kidney disease (CKD). The randomized clinical trial (RCT) cohort from the subset of SAVOR-TIMI 53 trial consisted of 10,555 type-2 diabetic patients with increased risk of cardiovascular disease. The two observational data cohorts from CPRD consisted of 71,104 newly diagnosed type-2 diabetes (CPRD-DM2) and 82,065 newly diagnosed hypertensive (CPRD-HT) patients without diabetes. Cohorts were stratified according to baseline circulating total bilirubin levels to determine association on the primary end point of a 30% reduction from baseline in estimated glomerular filtration rate (eGFR) and the secondary end point of albuminuria.

Results

The confounder adjusted hazard ratios of the subpopulation with lower than median bilirubin levels compared to above median bilirubin levels for the primary end point were 1.18 (1.02–1.37), 1.12 (1.05–1.19) and 1.09 (1.01–1.17), for the secondary end point were 1.26 (1.06–1.52), 1.11 (1.01–1.21) and 1.18 (1.01–1.39) for SAVOR-TIMI 53, CPRD-DM2, CPRD-HT, respectively.

Conclusion

Our findings are consistent across all cohorts and endpoints: lower serum bilirubin levels are associated with a greater kidney function decline independent of hemoglobin and other key confounders. This suggests that increased monitoring of kidney health in patients with lower bilirubin levels may be considered, especially for diabetic patients.

Patients with Gilbert syndrome and type 2 diabetes have lower prevalence of microvascular complications

Objective

Accumulating clinical evidence indicates an inverse relationship between oxidative stress and unconjugated hyperbilirubinemia. This study aimed to compare the prevalence of diabetes microvascular complications in patients with Gilbert syndrome and type 2 diabetes mellitus (T2D).

Methods

A total of 1200 electronic records with T2D were reviewed. From them, 50 patients with Gilbert syndrome (cases [indirect bilirubin ≥1.2 mg/dl without evidence of hemolysis or liver disease]) and 50 controls (T2D without hyperbilirubinemia) were included. Linear and logistic regression models were performed to evaluate the independent association between indirect hyperbilirubinemia with microvascular complications related with T2D.

Results

Both case and control group had the same proportion of gender (female = 20 [40 %]) and diabetes duration (14.0 ± 6.5 years) and similar mean of age (60 ± 9.6 and 60 ± 9.2 years, respectively, p = 0.91). The median of unconjugated bilirubin of case and control group was 1.4 (1.2–1.6) vs. 0.4 (0.2–0.6) mg/dl (p < 0.001), respectively. Patients with elevated unconjugated bilirubin had less urine albumin-creatinine ratio compared with control group (8.5 [4.3–23] vs. 80 [8–408] mg/g, p < 0.001), and lower rate of diabetes microvascular complications and metabolic syndrome. After adjustment for BMI, age, HbA1c, blood pressure, triglycerides, and the metabolic syndrome, the lineal regression analysis showed that unconjugated bilirubin protects against microalbuminuria in T2D patients (β = −414.11, 95 % CI [-747.9, −80.3], p = 0.006. Also, unconjugated hyperbilirubinemia was independently associated with a better glomerular filtration rate (GFR) (β = 9.87, 95 % CI [1.5, 18.3], P = 0.02).

Conclusions

Patients with Gilbert syndrome and T2D had a lower prevalence of diabetes microvascular complications.

Association between serum bilirubin levels and progression of albuminuria in Taiwanese with type 2 diabetes mellitus

BACKGROUND

To investigate the association between serum bilirubin (BIL) levels and the progression of albuminuria in type 2 diabetic Taiwanese.

METHODS

Longitudinal data from January 2001 to June 2015 were retrospectively reviewed from Chang Gung Memorial Hospital in Taiwan. A total of 2877 type 2 diabetic patients with normal total BIL levels were divided into 4 groups according to BIL, with the highest BIL in the fourth group. The urinary albumin/creatinine ratio (UACR) trend and progression, as well as other laboratory measurements, were evaluated among the four groups. The cumulative incidence and Cox proportional hazard model analysis were performed to examine the relationship between BIL and the risk of albuminuria progression (AUPr).

RESULTS

The mean duration of follow-up was 1.5 years (±1.37 years). The mean patient age, glycosylated hemoglobin level, and duration of diabetes were 62.52 years, 7.9%, and 3.94 years, respectively. A significant correlation was observed between BIL and both the UACR at baseline (P < 0.001) and the cumulative incidence of AUPr (log-rank test, P = 0.031). Hazard ratio (HR) analysis revealed that patients in the fourth BIL quartile had the lowest HR risk of AUPr among the four groups (adjusted HR = 0.70; 95% Confidence Interval = 0.56-0.89, P < 0.05).

CONCLUSIONS

Higher serum BIL levels are associated with a lower risk of AUPr in type 2 diabetes patients in Taiwan.

Association between serum total bilirubin levels and the risk of type 2 diabetes mellitus

AIM

To confirm whether serum bilirubin is an independent risk factor of type 2 diabetes mellitus (T2DM) onset in patients with impaired fasting glycemia (IFG) and impaired glucose tolerance (IGT).

METHODS

This was a prospective cohort study carried out at the Diabetic Identification Center of Tianjin Metabolic Diseases Hospital. Serum total bilirubin (TBIL) was measured at baseline and the patients were grouped according to baseline bilirubin quartiles. The outcome was the confirmation of T2DM by oral glucose tolerance test (OGTT) during the 3-year follow-up. Logistic regression was used to determine the risk factors for T2DM development and whether bilirubin levels are independently associated with T2DM development.

RESULTS

Finally, 523 patients were analyzed. After 3 years, 310 participants were diagnosed with diabetes based on OGTT. Baseline quartiles of total bilirubin were inversely associated with diabetes risk, even after multivariable adjustment. The adjusted ORs for diabetes were 1.0 (reference), 0.83 (95% CI 0.74-0.96), 0.78 (95% CI 0.68-0.90), 0.74 (95% CI 0.64-0.87) for the 1st, 2nd, 3rd, and 4th quartiles of baseline serum total bilirubin, respectively (P < 0.001).

CONCLUSION

In patients with IFG or IGT, low levels of serum total bilirubin were associated with a significantly increased risk of T2DM.

THE ASSOCIATION OF SERUM BILIRUBIN ON KIDNEY CLINICOPATHOLOGIC FEATURES AND RENAL OUTCOME IN PATIENTS WITH DIABETIC NEPHROPATHY: A BIOPSY-BASED STUDY

Objective: To explore the relationship between serum bilirubin concentration and clinicopathologic features and renal outcome in biopsy-diagnosed diabetic nephropathy (DN) in patients with type 2 diabetes mellitus. Methods: In this retrospective study, 118 patients with DN were enrolled. Participants were divided into two groups according to their median baseline serum bilirubin concentration: Group 1 (serum bilirubin ≤7.5 μmol /L); Group 2 (serum bilirubin >7.5 μmol /L). Basic clinical parameters were measured at the time of renal biopsy, and the relationships between serum bilirubin and the clinicopathologic features and renal outcome were analyzed. Results: Patients in Group 1 often had inferior renal function. Compared with Group 2, the glomerular classification and interstitial inflammation were more severe in subjects of Group 1, while arteriolar hyalinosis and interstitial fibrosis and tubular atrophy (IFTA) were comparable between the groups. Serum bilirubin was negatively correlated with the severity of the glomerular classification, interstitial inflammation, and IFTA. In the prognostic analysis, higher serum bilirubin level was associated with a lower risk of progression to end-stage renal disease, which was independent of the effects of age, gender, duration of diabetes, anemia, serum glucose, and hypertension but not of estimated glomerular filtration rate (hazard ratio, 0.406; 95% confidence interval, 0.074 to 2.225; P = .299). Conclusion: Our study showed a negative correlation between serum bilirubin level and renal pathologic lesions in patients with DN; serum bilirubin showed an inverse association with DN progression, but this was not independent. Abbreviations: CI = confidence interval; CKD = chronic kidney disease; DM = diabetes mellitus; DN = diabetic nephropathy; DR = diabetic retinopathy; eGFR = estimated glomerular filtration rate; ESRD = end-stage renal disease; HbA1c = glycated hemoglobin; HO-1 = heme oxygenase 1; HR = hazard ratio; IFTA = interstitial fibrosis and tubular atrophy; log-BIL = log-transformed baseline serum bilirubin; T2DM = type 2 diabetes mellitus.

Lower serum total bilirubin concentration is associated with higher prevalence of gestational diabetes mellitus in Japanese pregnant women

We aimed to clarify the pathophysiological significance of total bilirubin (TB) in gestational diabetes mellitus (GDM). This was a cross-sectional study that included 616 pregnant Japanese women (368 normal glucose tolerance [NGT] and 248 GDM). Serum TB concentration, homeostasis model assessment of insulin resistance (HOMA-IR), and other clinical parameters were compared in NGT and GDM women. TB concentration was also compared according to the number of abnormal OGTT values. Logistic regression analysis was used to evaluate the association between TB and GDM prevalence. A multiple linear regression model was used to evaluate the association between TB and HOMA-IR. TB concentrations were significantly lower in GDM women than in NGT women. This result did not change after adjustments for TB sampling timing were made. Out of 248 GDM women, the prevalences of 1- and 2/3- abnormal OGTT values (1- and 2/3-AV) GDM were 72.2% (n = 179) and 27.8% (n = 69), respectively. In the multiple comparisons, TB concentrations were significantly lower in women with 2/3-AV GDM than in women with NGT and 1-AV GDM. Multiple logistic regression analysis showed that TB was a significantly associated factor for 2/3-AV, but not for total GDM. HOMA-IR was significantly higher in GDM women than in NGT women. The univariate, but not multivariate, analysis showed that TB was a significantly associated factor for HOMA-IR. Our findings suggest that hypobilirubinemia may be involved in the pathogenesis of GDM.

Association between Thyroid Hormone Levels and Diabetic Kidney Disease in Euthyroid Patients with Type 2 Diabetes

The association between normal thyroid function and diabetic kidney disease (DKD) has gained increasing attention. The present study evaluated the relationship between normal thyroid hormone levels and DKD in type 2 diabetes mellitus (T2DM) patients. A total of 862 type 2 diabetes patients were enrolled in this cross-sectional study in Xi^’an, Shaanxi Province, China. The subjects were evaluated for anthropometric measurements, thyroid function and DKD. Of 862 patients, 246 (28.5%) suffered from DKD, and the prevalence of DKD did not differ between men and women. The prevalence of DKD showed a significantly decreasing trend across the quartiles based on free triiodothyronine (FT3) levels (41.1%, 30.6%, 23.8%, and 18.9%, P < 0.001). In comparison with all participants categorized in the first FT3 quartile group (FT3-Q1) (<4.380), the adjusted odds ratio of DKD in the second FT3 quartile group (FT3-Q2), the third FT3 quartile group (FT3-Q3), and the fourth FT3 quartile group (FT3-Q4) were 0.655(95%CI: 0.406–1.057), 0.493(95%CI: 0.299–0.813), 0.406(0.237–0.697) (P < 0.05). Also, similar results were observed in men. Conversely, none of the FT3 groups was associated with DKD in women. The present study showed that FT3 within normal range was negatively correlated with DKD in T2DM patients.

Inverse Relationship Between Serum Bilirubin Levels and Diabetic Foot in Chinese Patients with Type 2 Diabetes Mellitus

BACKGROUND Several studies demonstrated that bilirubin, a potent endogenous antioxidant, is a strong protective factor for many diabetic complications such as nephropathy, retinopathy, neuropathy, and vasculopathy. The purpose of this study was to assess the association between serum bilirubin levels and diabetic foot (DF) in Chinese patients with type 2 diabetes mellitus (T2DM). MATERIAL AND METHODS The present cross-sectional study of bilirubin levels in relation to DF was conducted in 1,269 T2DM patients with (n=578) and without (n=691) DF. Blood test results were obtained on hospital admission, including total bilirubin (T-BIL), direct bilirubin (D-BIL), and indirect bilirubin (I-BIL). Data on Wagner classification and amputation procedure in patients with DF were collected by reviewing electronic medical records. Univariate or multivariate analysis were performed to explore the association between bilirubin and DF. RESULTS Serum I-BIL levels were shown to play a protective role regarding the presence and severity of DF (OR=0.75, p=0.029 and OR=0.90, p=0.021, respectively). In addition, in a comparison of the lowest and highest tertiles of serum bilirubin concentration, the highest tertile of serum T-BIL (OR=0.51, p=0.011) and I-BIL (OR=0.28, p<0.001) was significantly related with a lower Wagner grade of DF. Patients with DF in the highest tertiles of T-BIL carried a significantly lower risk of amputation events than those in the lowest tertiles (OR=0.47, p=0.025). CONCLUSIONS The present study provided evidence that decreased serum bilirubin levels were independently associated with the presence and severity of DF and amputation events in patients with DF.

Elevated bilirubin levels and risk of developing chronic kidney disease: a dose-response meta-analysis and systematic review of cohort studies

AIMS

Previous studies have indicated the link of bilirubin levels and risk of developing chronic kidney disease (CKD); however, the findings were inconsistent.

METHODS

We searched for cohort studies examining bilirubin as an exposure and CKD as an outcome in the Medline, EMBASE, and Web of Science databases from inception through November 31, 2016. A generalized least-squares approach was applied to assess the dose-response relationship between them by pooling rate ratios with 95% confidence intervals. Subgroup analyses, sensitivity analysis, meta-regression, and publication bias were also conducted.

RESULTS

Seven cohort studies with 1316 cases and 21,076 participants were identified for inclusion in the meta-analysis. The combined RR for the highest versus lowest bilirubin level was 0.36 (95% CI 0.19-0.68; P _{heterogeneity} = 0.001; Power = 0.72; n = 6). In the linear dose-response analysis, each 1-μmol/L increase in bilirubin was associated with a 5% reduced risk of CKD (RR = 0.95; 95% CI 0.92-0.97; P for trend test = 0.113; P _{heterogeneity} = 0.001; Power = 0.99; n = 7). The subgroup analyses and sensitivity analyses showed consistent results, and publication bias may exist.

CONCLUSION

This meta-analysis suggests that elevated bilirubin level may be associated with decreased risk of developing CKD.

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.

Relationship between serum bilirubin concentrations and diabetic nephropathy in Shanghai Han's patients with type 1 diabetes mellitus

Background

Recent studies highlight a negative association between total bilirubin concentrations and albuminuria in patients with type 2 diabetes mellitus. Our study evaluated the relationship between bilirubin concentrations and the prevalence of diabetic nephropathy (DN) in Chinese patients with type 1 diabetes mellitus (T1DM).

Methods

A total of 258 patients with T1DM were recruited and bilirubin concentrations were compared between patients with or without diabetic nephropathy. Multiple stepwise regression analysis was used to examine the relationship between bilirubin concentrations and 24 h urinary microalbumin. Binary logistic regression analysis was performed to assess independent risk factors for diabetic nephropathy. Participants were divided into four groups according to the quartile of total bilirubin concentrations (Q1, 0.20–0.60; Q2, 0.60–0.80; Q3, 0.80–1.00; Q4, 1.00–1.90 mg/dL) and the chi-square test was used to compare the prevalence of DN in patients with T1DM.

Results

The median bilirubin level was 0.56 (interquartile: 0.43–0.68 mg/dL) in the DN group, significantly lower than in the non-DN group (0.70 [interquartile: 0.58–0.89 mg/dL], P < 0.001). Spearman’s correlational analysis showed bilirubin concentrations were inversely correlated with 24 h urinary microalbumin (r = -0.13, P < 0.05) and multiple stepwise regression analysis showed bilirubin concentrations were independently associated with 24 h urinary microalbumin. In logistic regression analysis, bilirubin concentrations were significantly inversely associated with nephropathy. In addition, in stratified analysis, from the first to the fourth quartile group, increased bilirubin concentrations were associated with decreased prevalence of DN from 21.90% to 2.00%.

Conclusion

High bilirubin concentrations are independently and negatively associated with albuminuria and the prevalence of DN in patients with T1DM.

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.

Antioxidant status of serum bilirubin and uric acid in patients with polymyositis and dermatomyositis

OBJECTIVE

Oxidative stress and variations in antioxidant status are implicated in the pathogenesis of inflammatory and autoimmune diseases. Polymyositis and dermatomyositis (PM/DM) are autoimmune diseases with inflammatory cells infiltrating into skeletal muscles, and the antioxidant status is still controversial. The aim of our study was to investigate the correlation between PM/DM and the antioxidant status of serum bilirubin (Tbil, Dbil and Ibil) and uric acid (UA).

MATERIALS AND METHODS

We measured serum concentrations of bilirubin (Tbil, Dbil and Ibil) and uric acid in 384 individuals, including 110 PM/DM patients and 274 healthy controls.

RESULTS

We found that PM/DM patients had significantly lower serum concentrations of bilirubin (Tbil and Ibil) and uric acid than healthy controls, whether male or female. Also, after separately adjusting the covariances of age and gender, Tbil, Dbil, Ibil and UA were all relevant factors for PM/DM. Moreover, there were no significant differences in serum antioxidant molecule levels between PM and DM subgroups.

CONCLUSION

Our study demonstrated the low serum levels of bilirubin and uric acid in patients with PM/DM. This suggested low antioxidant status in PM/DM patients with excessive oxidative stress.

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.