Haptoglobin polymorphism and diabetic nephropathy in Brazilian diabetic patients

Serum haptoglobin levels are associated with renal function decline in type 2 diabetes mellitus patients in a Chinese Han population

AIMS

We investigated whether serum haptoglobin (Hp) levels play a role in the development and progression of diabetic kidney disease (DKD) in type 2 diabetes mellitus (T2DM) patients in a Chinese Han population, which has not been previously investigated.

METHODS

We recruited 233 participants who had suffered from T2DM for more than 10 years, including 118 subjects with DKD (case) and 115 subjects without DKD (control). Serum Hp levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Serum Hp levels were significantly higher (P = 0.0258) in case group (2.74 (1.77, 3.48) g/L) than control (2.29 (0.98, 3.48) g/L). The serum Hp level was significantly positively associated with both logarithmically transformed (log-transformed) serum creatinine (r = 0.1663, P = 0.011) and albuminuria levels (r = 0.1793, P = 0.0062) and was negatively associated with the log-transformed estimated glomerular filtration rate (r = -0.1482, P = 0.0237). Multiple linear regression analysis revealed that serum Hp levels were significantly correlated with serum creatinine levels (P = 0.0088) after adjusting for confounding risk factors.

CONCLUSIONS

Our findings suggest that serum Hp levels may be used as a potential biomarker for the early diagnosis and monitoring of DKD in T2DM patients.

The protean role of haptoglobin and haptoglobin genotypes on vascular complications in diabetes mellitus

Introduction and background Haptoglobin (Hp) is considered to be an antioxidant and protective against cardiovascular complications. Polymorphisms in the Hp gene interact with diabetes mellitus to affect the risk of vascular complications. Methods We review the updated literature about the protean role of Hp and Hp genotypes spanning genomics, molecular, translational and clinical studies. We searched Pubmed, SCOPUS and Google Scholar for all articles using the keywords: haptoglobin and/or haptoglobin polymorphism and diabetes. We review the diverse Hp genotypes, phenotypes and the impact on diabetes complications, including lessons from animal models and in vitro models. We describe the clinical studies on the associations of Hp genotypes with vascular complications in type 1 and type 2 diabetes comprehensively. We review the studies looking at vitamin E supplementation in a personalized manner in Hp2-2 diabetes individuals. Results and conclusion Hp genotypes have evolved as a result of deletions in the traditional Hp genes. The Hp genotypes have been associated with microvascular and macrovascular complications in type 1 diabetes mellitus but the association in type 2 diabetes is more consistent with cardiovascular complications. A preferential benefit of vitamin E and other antioxidants in the Hp2-2 genotype for cardiovascular complications in type 2 diabetes has been seen presumably secondary to interaction with high-density lipoprotein function. Hence, the Hp genotype can be used to personalize antioxidant therapeutics in diabetes patients. These results need to be corroborated in large, global, pragmatic, prospective, cardiovascular outcome trials in type 2 diabetes patients.

Genetic markers for urine haptoglobin is associated with decline in renal function in type 2 diabetes in East Asians

Urine haptoglobin (uHP) level prospectively predicts diabetic kidney disease (DKD) progression. Here, we aim to identify genetic determinants of uHP level and evaluate association with renal function in East Asians (EA) with type 2 diabetes (T2D). Genome-wide association study (GWAS) among 805 [236 Chinese (discovery) and 569 (57 Malay and 512 Chinese) (validation)] found that rs75444904/kgp16506790 variant was robustly associated with uHP level (MetaP = 1.21 × 10^-60). rs75444904 correlates well with plasma HP protein levels and multimerization in EA but was not in perfect LD (r² = 0.911 in Chinese, r² = 0.536 in Malay) and is monomorphic in Europeans (1000 G data). Conditional probability analysis indicated weakening of effects but residual significant associations between rs75444904 and uHP when adjusted on HP structural variant (MetaP = 8.22 × 10^-7). The rs75444904 variant was associated with DKD progression (OR = 1.77, P = 0.014) independent of traditional risk factors. In an additional validation-cohort of EA (410 end-stage renal disease (ESRD) cases and 1308 controls), rs75444904 was associated with ESRD (OR = 1.22, P = 0.036). Furthermore, increased risk of DKD progression (OR = 2.09, P = 0.007) with elevated uHP level through Mendelian randomisation analysis provide support for potential causal role of uHP in DKD progression in EA. However, further replication of our findings in larger study populations is warranted.

THE SERUM PROTEIN FRACTIONS IN THYMOQUINONE TREATED RATS

Background:

TQ has been used as treatment and preventive agent for many diseases over the years. The goal of this study was to investigate the effects of TQ supplement on fractions of serum proteins.

Materials and methods:

Fourteen male Wistar-Albino rats (200-250 g weight) were used as material for two groups; (control (C) and thymoquinone (TQ) respectively. Each group contained seven rats. The control group had only corn oil, while the TQ group was dissolved in corn oil. 30 mg/kg/day were given by oral gavage for four weeks. The serum protein fractions were identified using cellulose acetate technique.

Results:

The total protein level and albumin, α-1, α-2 fractions and A/G ratio have showed no difference between groups (p>0.05). β-globulin fractions of TQ group were higher than control’s (p<0.05). In addition, it was observed that the γ-globulin levels of TQ group were lower than that of the control group’s (p<0.05).

Conclusion:

From the results, it was observed that the changes of these fractions may have originated from elevation or decline synthesis, or activities of containing proteins.

The Association of Haptoglobin Gene Variants and Retinopathy in Type 2 Diabetic Patients: A Meta-Analysis

AIMS/INTRODUCTION

To collectively evaluate the association between haptoglobin (Hp) gene variants and diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM).

METHODS

A comprehensive literature review was performed for eligible studies. After inclusion and exclusion selection as well as quality assessment, those studies meeting quality standards were included. In this study, diabetic patients with retinopathy were selected as the case group and those ones without DR were treated as the control group. The recessive model, allele model, additive model, heterozygote model, and homozygote model were utilized to investigate the association of three Hp gene variants and DR. Subgroup analysis on different severity of DR including nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) was also conducted.

RESULTS

Six trials from different regions were finally included. A total of 1145 subjects containing 564 T2DM patients with retinopathy were included. The recessive model, allele model, additive model, and homozygote model results showed that Hp gene variants were not associated with DR, NPDR, and PDR. However, the heterozygote model indicated the association of Hp gene variants with DR.

CONCLUSIONS

No association was found between the Hp gene variants and PDR and NPDR. More studies are required to verify these findings.

Inflammatory markers and haptoglobin polymorphism in Saudi with non-insulin-dependent diabetes mellitus

Objectives:

Haptoglobin (Hp) polymorphism associated with clinical evolution of several inflammatory diseases and considered as a predictive factor for development of diabetes complications. We designed the present study to investigate the frequency distribution of Hp phenotypes among Saudi with non-insulin-dependent diabetes mellitus compared to healthy nondiabetic subjects. Moreover, we explored the possibility of relationship between serum levels of inflammatory markers (namely, high-sensitive C-reactive proteins “hs-CRP”, interleukin (IL)-6, and Hp) and Hp phenotypes.

Methods:

In the present case-control study, we enrolled 60 type 2 diabetic patients as the study group and 60 healthy subjects as the control group. We assayed serum levels of Hp and hs-CRP by immunoturbidimetric method; while IL-6 was measured by ELISA. Native polyacrylamide gel electrophoresis was used for determination of Hp phenotypes.

Results:

In type 2 diabetics, serum concentrations of IL-6, hs-CRP, and Hp were significantly elevated and correlated to body mass index. Moreover, there was a significant correlation between plasma glucose level and Hp (r = 0.577, p = 0.000), IL-6 (r = 0.448, p = 0.000), and hs-CRP (r = 0.380, p = 0.001). In addition, data demonstrated a positive correlation between HbA1c and Hp (r = 0.521, p = 0.000), IL-6 (r = 0.420, p = 0.001), and hs-CRP (r = 0.353, p = 0.008). Hp 2-1 phenotype predominated among subjects in both study and control groups. No significant association between Hp phenotypes with any of the investigated inflammatory markers was documented.

Conclusion:

Inflammation may represent the link between type 2 diabetes and obesity. Hp 2-1 was the predominant phenotype among Saudi type 2 diabetics as well as healthy subjects. In addition to Hp; other possible genetic polymorphisms like CRP may have its effect on diabetes through different mechanisms.

Proximal tubule haptoglobin gene activation is an integral component of the acute kidney injury "stress response"

Haptoglobin (Hp) synthesis occurs almost exclusively in liver, and it is rapidly upregulated in response to stress. Because many of the pathways that initiate hepatic Hp synthesis are also operative during acute kidney injury (AKI), we tested whether AKI activates the renal cortical Hp gene. CD-1 mice were subjected to six diverse AKI models: ischemia-reperfusion, glycerol injection, cisplatin nephrotoxicity, myoglobinuria, endotoxemia, and bilateral ureteral obstruction. Renal cortical Hp gene induction was determined either 4-72 h or 1-3 wk later by measuring Hp mRNA and protein levels. Relative renal vs. hepatic Hp gene induction during endotoxemia was also assessed. Each form of AKI induced striking and sustained Hp mRNA increases, leading to ∼10- to 100-fold renal Hp protein elevations (ELISA; Western blot). Immunohistochemistry, and isolated proximal tubule assessments, indicated that the proximal tubule was the dominant (if not only) site of the renal Hp increases. Corresponding urinary and plasma Hp elevations were surrogate markers of this response. Endotoxemia evoked 25-fold greater Hp mRNA increases in kidney vs. liver, indicating marked renal Hp gene reactivity. Clinical relevance of these findings was suggested by observations that urine samples from 16 patients with established AKI had statistically higher (∼12×) urinary Hp levels than urine samples from either normal subjects or from 15 patients with chronic kidney disease. These AKI-associated urinary Hp increases mirrored those seen for urinary neutrophil gelatinase-associated lipoprotein, a well accepted AKI biomarker gene. In summary, these studies provide the first evidence that AKI evokes rapid, marked, and sustained induction of the proximal tubule Hp gene. Hp's known antioxidant, as well as its protean pro- and anti-inflammatory, actions imply potentially diverse effects on the evolution of acute tubular injury.

Does haptoglobin genotype affect early onset of diabetic retinopathy in patients with type 2 diabetes?

PURPOSE

There are 2 common alleles for Hp (Hp-1 and Hp-2) and 3 common Hp genotypes: Hp1-1, Hp2-1, and Hp2-2. The haptoglobin genotype may play a dual role in morbidities of diabetes: Hp1-1, protective and Hp2-2, provocative. This study investigated the possible association of haptoglobin genotypes with onset of retinopathy in Type 2 diabetes (DM2).

METHODS

The sample included 98 consecutive adults with DM2 under routine outpatient follow-up from 2007 to 2009 who met the criteria for either no retinopathy at ≥10 years after diagnosis (Group 1) or proliferative retinopathy at ≤10 years after diagnosis (Group 2). Blood samples were collected for haptoglobin genotyping by polymerase chain reaction. Findings were compared between and within groups.

RESULTS

Eighty-four patients had no retinopathy and 14 had early proliferative retinopathy. The distributions of the Hp genotypes were as follows: no-retinopathy group: 28.6% Hp1-1, 35.7% Hp2-1, and 35.7% Hp2-2 and proliferative retinopathy group: 22.6% Hp1-1, 27.4% Hp2-1, and 50% Hp2-2 (NS). On statistical analysis (limited to the larger no-retinopathy group), a predominance of Hp1-1 was noted in older patients; Hp2-2 was associated with an increased rate of stroke.

CONCLUSION

The Hp genotype apparently plays no role in the development or worsening of proliferative retinopathy in DM2. Hp1-1 may be involved in delaying the onset of diabetes. Hp2-2 may pose a microvascular risk.

Haptoglobin polymorphism as a risk factor for chronic kidney disease: a case-control study

AIMS

Taiwan has the highest incidence and prevalence of end-stage renal disease worldwide. Haptoglobin (Hp) has a role in renal protection, and there are known differences in the function of different Hp alleles. We aim to study the association between Hp genotype and chronic kidney disease (CKD) in Taiwan.

METHODS

We performed one hospital-based, age-matched case-control study of 213 patients with CKD and 213 controls to evaluate the association between Hp polymorphism and CKD. Three major Hp genotypes were determined using polymerase chain reaction and electrophoresis. An unconditional logistic regression model was used to identify the associated risk factors for the development of CKD.

RESULTS

The frequency of Hp2-2 genotype and Hp(2) allele was significantly higher in the CKD group than in controls (p = 0.032 and 0.024, respectively). After adjustment for covariates, the Hp2-2 genotype (vs. Hp1-1; OR 3.841) remained significantly associated with the development of CKD, together with diabetes (OR 3.131), hypertension (OR 1.748) and dyslipidemia (OR 1.646).

CONCLUSION

This present study shows that Hp2-2 genotype is an independent risk factor for CKD. Determination of the Hp genotype may be of potential value to the prediction of genetic risk for CKD.