Haptoglobin gene polymorphism in type 2 diabetic patients with and without nephropathy: An Egyptian study

Relationship of haptoglobin phenotype and levels with sight-threatening diabetic retinopathy in type 2 diabetes: A Fenofibrate Intervention and Event Lowering in diabetes (FIELD) substudy

AIMS

Haptoglobin (HP) phenotype has been reported to modulate fenofibrate benefit on coronary artery disease in type 2 diabetes. It is unknown whether HP phenotype and levels modulate fenofibrate benefit on sight-threatening diabetic retinopathy (STDR).

METHODS

In plasma from 8,047 Australasian adults with type 2 diabetes in the FIELD trial, HP phenotype was determined, and HP levels were measured at baseline and after six-week fenofibrate run-in.

RESULTS

There were 307 new first on-trial STDR events over five years. Baseline HP levels and phenotype were not related to STDR risk. Fenofibrate benefit on STDR vs. placebo (-32 % overall), was greatest in participants with the lowest baseline HP level tertile (hazard ratio [95 % CI] 0.41 [0.26-0.65], vs. 0.82 [0.56-1.21] and 0.84 [0.56-1.27] for tertiles 2 and 3 respectively, P for heterogeneity = 0.019). During run-in, fenofibrate reduced HP levels by 20.7 %. However, fenofibrate benefit on STDR did not differ significantly by HP phenotype or change in HP levels during run-in after adjustment for confounding factors.

CONCLUSIONS

Regarding STDR, fenofibrate benefit is greatest in type 2 diabetes patients with the lowest baseline HP levels, which may reflect patients more susceptible to oxidative retinal injury. All HP phenotypes benefit from fenofibrate.

The association between interleukin family and diabetes mellitus and its complications: An overview of systematic reviews and meta-analyses

OBJECTIVE

To evaluate and summarize the association between interleukin (IL) concentrations and diabetes mellitus (DM) and its complications.

METHODS

Meta-analyses and eligible individual studies of observational studies investigating the associations between IL and DM and its complications were included. The random-effects model was used to estimate the summary effect, and the heterogeneity among studies was assessed using the Q-statistic and the I2 metric; The Egger's regression and the χ2 test were used to test for small study effects and excess significance bias.

RESULTS

This overview identified 34 meta-analyses that investigated the association between IL concentrations and DM and its complications. Meta-analyses of prospective studies indicated that elevated circulating IL-6 and IL-1β had predictive value for the incident of type 2 diabetes mellitus (T2DM), type 1 diabetes mellitus (T1DM) as well as gestational diabetes mellitus (GDM), and the overall Hazard Ratio (HR) of T2DM was 1.28 (95 % CI: 1.17, 1.40; P＜0.001) per 1 log pg/ml increment in IL-6 levels, however, there was no correlation between circulating IL-10 levels and DM. Meanwhile, the increased level of IL-6 was significantly associated several diabetic complications (Diabetic kidney disease[DKD], diabetic peripheral neuropathy[DPN], and cognitive impairment[CI]), and for the diabetic retinopathy (DR), the levels of IL-1β, IL-8 and IL-10 in the aqueous humor and vitreous humor, but not the blood were significantly correlated with it.

CONCLUSION

Multiple ILs, such as the IL-6 and IL-1β, are definitively linked to DM and its complications, and they may be new targets for the diagnosis and treatment, but stronger evidence needs to be confirmed by prospective studies with larger sample sizes and longer observation periods.

Genetic determinants of circulating haptoglobin concentration

Haptoglobin (Hp) is a major plasma acute-phase glycoprotein, which binds free haemoglobin to neutralize its toxicity. The HP gene exists as two copy number variants (CNV), Hp1 and HP2, which differ in two ways: serum Hp level and functional differences in Hp protein products. Both mechanisms may underlie the HP CNV's influence on susceptibility and/or outcome in several diseases. A single nucleotide polymorphism rs2000999 has also been associated with serum Hp level. In a meta-analysis of three studies from England, France and Japan, with a combined sample size of 1210 participants, we show that rs2000999's effect on circulating Hp level is independent from that of the HP CNV. The combined use of rs2000999 and the HP CNV can be an important genetic epidemiological tool to discriminate between the two potential mechanisms underlying differences between HP1 and HP2 alleles.

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.

Correlation of geographic distributions of haptoglobin alleles with prevalence of multiple sclerosis (MS) - a narrative literature review

We have proposed that the myelin damage observed in multiple sclerosis (MS) may be partly mediated through the long-term release and degradation of extracellular hemoglobin (Hb) and the products of its oxidative degradation [Cellular and Molecular Life Sciences, 71, 1789-1798, 2014]. The protein haptoglobin (Hpt) binds extracellular Hb as a first line of defense, and can serve as a vascular antioxidant. Humans have two different Hpt alleles: Hpt1 and Hpt2, giving either homozygous Hpt1-1 or Hpt2-2 phenotypes, or a heterozygous Hpt1-2 phenotype. We questioned whether those geographic regions with higher frequency of the Hpt2 allele (conversely, lower frequency of Hpt1 allele) would correlate with an increased incidence of MS, because different Hpt phenotypes will have variable anti-oxidative potentials in protecting myelin from damage inflicted by extracellular Hb and its degradation products. To test this hypothesis, we undertook a systematic analysis of the literature on reported geographic distributions of Hpt alleles to compare them with data reported in the World Health Organization Atlas of worldwide MS prevalence. We found the frequency of the Hpt1 allele to be low in European and North American countries with a high prevalence of MS, consistent with our hypothesis. However, this correlation was not observed in China and India, countries with the lowest Hpt1 frequencies, yet low reported prevalence of MS. Nevertheless, this work shows the need for continued refinement of geographic patterns of MS prevalence, including data on ethnic or racial origin, and for new clinical studies to probe the observed correlation and evaluate Hpt phenotype as a predictor of disease variability and progression, severity, and/or comorbidity with cardiovascular disorders.

Haptoglobin genotypes polymorphism as a risk factor for subclinical atherosclerosis in beta-thalassemia major children; a single center Egyptian study

Background/Objectives Haptoglobin (Hp) is an antioxidant protein. Its genotypic polymorphism had been proposed to influence vascular complications among diabetics, but no data are available about this association among thalassemia patients so far. We have investigated the assumption of an association between Hp genotypes and subclinical atherosclerosis among beta-thalassemia major (TM) children. Methods One hundred beta-TM children and 70 matched healthy controls were included. Serum ferritin level and fasting lipid profile were assayed. Haptoglobin genotyping was determined by amplification gel electrophoresis. Carotid intima media thickness (cIMT) was measured using high resolution ultrasound. Results The relative distribution of the three Hp genotypes among thalassemia group and the control group were 18 and 14.3% for Hp1-1; 38 and 37.1% for Hp2-1; and 44 and 48.6% for Hp2-2 respectively. There was no significant difference between patients and controls regarding Hp genotypes distribution. Hp2-2 genotype TM children had significantly higher cIMT compared to other genotypes (P < 0.0001). Elevated cIMT was significantly represented in Hp2-2 genotype patients (P < 0.0001) who had higher serum ferritin compared to their counterparts (P < 0.05). Hp2-2 patients were five times more likely to suffer from subclinical atherosclerosis than Hp1-1 and six times than Hp2-1 genotype patients (P = 0.008 and 0.001, respectively); a difference that persisted significant after adjustment for some risk factors compared to Hp2-1 patients (OR 3.96; P = 0.02). Conclusions Hp2-2 genotype is a significant predictor for premature atherosclerosis in TM children and confers them an increased risk for iron overload.

Serum proteomic analysis reveals high frequency of haptoglobin deficiency and elevated thyroxine level in heroin addicts

Heroin addiction is a chronic, complex disease, often accompanied by other concomitant disorders, which may encumber effective prevention and treatment. To explore the differences in expression profiles of serum proteins in control and heroin addicts, we used two-dimensional electrophoresis coupled to MALDI-TOF/TOF, and identified 4 proteins of interest. Following validation of the increase in serum transthyretin, we assessed serum levels of thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4), and observed a robust increase in T4 in heroin addicts compared to controls. In addition, we performed haptoglobin (Hp) phenotyping, and showed that the frequency of Hp0 (serum devoid of haptoglobin) was significantly higher in heroin addicts. Altogether, these findings indicated that: (1) thyroid hormone imbalance is present in heroin addicts; (2) anhaptoglobinemia (Hp0) might a risk factor or a deleterious effect of heroin abuse.

Haptoglobin2-2 phenotype is an additional risk factor of retinopathy in type 2 diabetes mellitus

AIMS

The aim of this study was to investigate the association between haptoglobin (Hp) phenotypes and risk of the development of diabetic retinopathy (DR) in patients of type 2 diabetes mellitus.

MATERIALS AND METHODS

This cross-sectional study included 45 normotensive type 2 diabetic patients (duration more than 5 years) admitted in the hospital divided into two groups (with and without DR) on the basis of fundus examination by direct ophthalmoscopy. Serum samples of all patients were subjected for Hp phenotyping by polyacrylamide gel electrophoresis.

RESULTS

DR was associated significantly in diabetic patients with Hp2-2 phenotype (79.31%) than diabetic patients with Hp2-1 phenotype (43.75%) and Hp2-2 had higher odds ratio (OR) for DR in univariate analysis (OR 4.929, [95% confidence interval [CI] (1.297-18.733)], P = 0.016) and multivariate analysis (OR 7.704 [95% CI (0.887-66.945)], P = 0.064). Furthermore, Hp2-2 was associated significantly with severe forms of DR.

CONCLUSION

Hp2-2 phenotype is associated with susceptibility to DR showing a graded risk relationship to the number of Hp2 alleles. Determination of Hp phenotype may be useful in the risk assessment and management of DR.

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.

Haptoglobin 2-2 genotype is associated with increased risk of type 2 diabetes mellitus in northern Chinese

The aim of this study was to investigate the association between haptoglobin (Hp) gene polymorphism and occurrence of type 2 diabetes mellitus (T2DM) in a northern Chinese population. We studied the association of the Hp gene polymorphism with T2DM in 584 unrelated T2DM patients and 690 control subjects with normal glucose tolerance among northern Chinese. The patients were diagnosed in accordance with the guidelines of the American Diabetes Association. The clinical characteristics of the study population were recorded, and the Hp genotype was determined. The frequencies of the genotypes in the group of T2DM patients and the controls were as follows: Hp2-2, 51.7% and 44.1%; Hp2-1, 39.7% and 45.1%; and Hp1-1, 8.6% and 10.9%, respectively. There was significant difference for the genotypic and allelic distribution between the two groups (p=0.021 and p=0.007, respectively). Even after readjusting for the confounding effects of age, gender, and body mass index, a significant effect of genotypes on T2DM was still found in the recessive model for the Hp2 allele tested (p=0.002). Those who had the Hp2-2 genotype had a significantly higher risk for T2DM than those with other genotypes (odds ratio=1.441, 95% confidence interval=1.143-1.817). The results showed that the Hp2-2 genotype is associated with increased risk of T2DM in the northern Chinese Han population.

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.

Plasma biomarkers of mouse aging

Normal aging is accompanied by a series of physiological changes such as gray hair, cataracts, reduced immunity, and increased susceptibility to disease. To identify novel biomarkers of normal aging, we analyzed plasma proteins of male mice longitudinally from 2 to 19 months of age. Plasma proteins were analyzed by two-dimensional gel electrophoresis and identified using mass spectrometry (MS), MS/MS and liquid chromatography MS/MS. We found that many plasma proteins exist as multiple isoforms with different masses and/or charges. Thirty-nine protein spots (corresponding to six distinct proteins) have been identified, 13 of which exhibited significant changes with age. For example, several proteins increased significantly during aging including one isoform of transthyretin, two isoforms of haptoglobin, and three isoforms of immunoglobulin kappa chain. Conversely, several proteins decreased significantly during aging including peroxiredoxin-2, serum amyloid protein A-1, and five isoforms of albumin. Identification of these proteins provides new biomarkers of normal aging in mice. If validated in humans, these biomarkers may facilitate therapeutic interventions to identify premature aging, delay aging, and/or improve healthspan of the elderly.

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.

Haptoglobin genotype- and diabetes-dependent differences in iron-mediated oxidative stress in vitro and in vivo

We have recently demonstrated in multiple independent population-based longitudinal and cross sectional analyses that the haptoglobin 2-2 genotype is associated with an increased risk for diabetic cardiovascular disease. The chief function of haptoglobin (Hp) is to bind to hemoglobin and thereby prevent hemoglobin-induced oxidative tissue damage. This antioxidant function of haptoglobin is mediated in part by the ability of haptoglobin to prevent the release of iron from hemoglobin on its binding. We hypothesized that there may be diabetes- and haptoglobin genotype-dependent differences in the amount of catalytically active redox active iron derived from hemoglobin. We tested this hypothesis using several complementary approaches both in vitro and in vivo. First, measuring redox active iron associated with haptoglobin-hemoglobin complexes in vitro, we demonstrate a marked increase in redox active iron associated with Hp 2-2-glycohemoglobin complexes. Second, we demonstrate increased oxidative stress in tissue culture cells exposed to haptoglobin 2-2-hemoglobin complexes as opposed to haptoglobin 1-1-hemoglobin complexes, which is inhibitable by desferrioxamine by either a chelation or reduction mechanism. Third, we demonstrate marked diabetes-dependent differences in the amount of redox active iron present in the plasma of mice genetically modified expressing the Hp 2 allele as compared with the Hp 1 allele. Taken together these data implicate redox active iron in the increased susceptibility of individuals with the Hp 2 allele to diabetic vascular disease.