Haptoglobin: a review of the major allele frequencies worldwide and their association with diseases

Simultaneous Genotyping of Three SNVs, rs5471, rs5472, and rs2000999 Involved in Serum Haptoglobin Levels by Fluorescent Probe-Based Melting Curve Analysis

Haptoglobin (Hp) is a hemoglobin-binding acute-phase serum protein. Several single nucleotide variations (SNVs) within the Hp gene (HP) or Hp-related protein gene (HPR), such as rs5471 (A > C) and rs5472 (A > G) in HP promoter region and rs2000999 (G > A) in intron 2 of HRP, are suggested to correlate with the serum Hp levels. To determine these three SNVs simultaneously, a genotyping assay based on duplex dual-labeled fluorescent probes was developed. The method was then validated by analyzing genomic DNA from 121 Ghanaian and two Japanese subjects who had been previously genotyped for rs5471, rs5472, and rs2000999. Both rs5471 and rs5472 could be determined as haplotypes with a single FAM-labeled fluorescent probe, and rs2000999 could be genotyped with a HEX-labeled fluorescent probe. The results obtained with the present method were consistent with the previous results except for those of three Ghanaian subjects. All three subjects appear to have multiple HPR copy number variants characteristic of African populations, which may have led to incorrect results during previous genotyping. This method allows us to genotype these three SNVs in a relatively large number of samples, especially in African populations where rs5471 is uniquely distributed.

Contribution of haptoglobin phenotypic variation to the presence of hyperhomocysteinemia in type 2 diabetics with and without angiopathy

BACKGROUND/AIM

The genetic polymorphism of haptoglobin (Hp) has been associated with several cardiovascular risk factors, but a possible relationship between Hp phenotypic variation and increased levels of homocysteine (Hcy) and cysteine (Cy) is still unknown. The objective of this study is to evaluate the relationship between the Hp polymorphism and hyperhomocysteinemia (HHcy) and hypercysteinemia (HCy) in type 2 diabetics (T2D) with and without angiopathy (AGP).

METHODS

A case-control study was carried out on 293 adults: Group I (GI) - 75 subjects with T2D and AGP; Group II (GII) - 75 subjects with T2D without AGP; Group III (GIII) - 143 controls. Plasma levels of Hcy, Cy and vitamin B6 were measured by high performance liquid chromatography (HPLC) and vitamins B9 and B12 determined by electrochemiluminescence (ECL). The Hp polymorphism was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and peroxidase staining. The results were analyzed in SPSS®, version 26.0 with a significance of 95%.

RESULTS

Mean Hcy concentrations were significantly lower in carriers of the Hp2-2 phenotype (6.14 µM; p = 0.046) compared to the other genotypes. The presence of Hp2-1 is associated with an approximately 3.3 times greater probability of occurrence of HHcy (p = 0.015) and 3.7 times greater probability occurrence of HCy (p = 0.021) in T2D with AGP.

CONCLUSION

The presence of the Hp2-1 phenotype is associated with the predisposition of HHcy and HCy in individuals with T2D and AGP, possibly through a positive heterosis mechanism. Carriers of the Hp2-2 phenotype appear to have a greater activation of the transsulfuration pathway in the Hcy cycle and consequent protection for its accumulation.

The relationship between repeated measurements of HbA1c and risk of coronary events among the common haptoglobin phenotype groups: the Action for Health in Diabetes (Look AHEAD) study

BACKGROUND

In the ACCORD study, participants with the haptoglobin (Hp) 2-2 phenotype and glycated hemoglobin (HbA1c) ≥ 8.0% had a higher risk of coronary artery disease (CAD) compared to those with HbA1c 7.0-7.9%. However, this association was not observed in participants without the Hp2-2 phenotype. The optimal glycemic target for CAD prevention for the Hp phenotypes remains uncertain and may vary based on demographic and clinical factors.

OBJECTIVE

To investigate how reaching clinically relevant HbA1c targets relates to the risk of CAD in different Hp phenotype groups among a diverse cohort of individuals with T2DM (the Look AHEAD study, HbA1c ≤ 11% at baseline).

METHODS

Cox regression models with time-varying covariables were used to quantify the association between time-varying achieved HbA1c (< 6.5%, 6.5-6.9%, and ≥ 8.0% compared to 7.0-7.9%), updated at years 1-4, 6, 8, and 10, and incident CAD in the Hp2-2 (n = 1,587) and non-Hp2-2 (n = 2,944) phenotypes separately. Further pre-specified subgroup analyses by age, sex, history of cardiovascular disease (CVD), race, and diabetes duration were performed in each Hp phenotype group separately.

RESULTS

Compared with HbA1c 7.0-7.9%, having HbA1c < 6.5% was associated with a 29% lower CAD risk among participants with the non-Hp2-2 phenotype (adjusted HR 0.71, 95% CI 0.55-0.90). In subgroup analyses, this association was present in participants with the non-Hp2-2 phenotype who were male (0.60, 0.44-0.83), who did not have a history of CVD (0.65, 0.47-0.90), who were aged ≥ 65 years (0.64, 0.44-0.94), who were White (0.68, 0.51-0.91), or who had diabetes duration > 10 years (0.58, 0.35-0.95). HbA1c ≥ 8.0% was associated with CAD risk only among participants with the Hp2-2 phenotype who had a history of CVD (1.79, 1.00-3.20). No associations were found between the other HbA1c targets and CAD risk when participants with the Hp2-2 phenotype were grouped together or divided into subgroups.

CONCLUSION

The differences in our results compared to our previous findings may be due to variations in the study populations and factors associated with weight loss, making it difficult to draw definitive conclusions. Our current findings should be considered in the context of hypothesis generation, and ideally, will encourage additional research in this field.

Involvement of haptoglobin in disease development

Haptoglobin (HP) is a liver glycoprotein that is actively synthesized during inflammatory and hemolytic processes. It also has pro-oxidant and proinflammatory properties, which are a function of its genotype. The genetic polymorphism of the chains leads to synthesis of three phenotypes/proteins, which are related to the number and type of chains and their molecular weight, namely HP1-1, HP1-2 and HP2-2. Patients with HP2-2 have more vascular complications, while those with HP1-1 have fewer. HP is involved in the worsening of diseases, such as HP2-2 in aggravation of vaso-occlusive crises in sickle cell disease, and worsening of the pathophysiology of other diseases. In contrast, HP1-1 confers better protection against diseases. All of this suggests that further studies should be conducted, including experimental and analytical studies focused on demonstrating the influence of different HP genotypes on individual clinical and hematological data. This would help in understanding the role played by this genetic polymorphism in the pathophysiology of diseases.

Unlocking the link between haptoglobin polymorphism and noninfectious human diseases: insights and implications

Haptoglobin (Hp) is a polymorphic protein that was initially described as a hemoglobin (Hb)-binding protein. The major functions of Hp are to scavenge Hb, prevent iron loss, and prevent heme-based oxidation. Hp regulates angiogenesis, nitric oxide homeostasis, immune responses, and prostaglandin synthesis. Genetic polymorphisms in the Hp gene give rise to different phenotypes, including Hp 1-1, Hp 2-1, and Hp 2-2. Extensive research has been conducted to investigate the association between Hp polymorphisms and several medical conditions including cardiovascular disease, inflammatory bowel disease, cancer, transplantation, and hemoglobinopathies. Generally, the Hp 2-2 phenotype is associated with increased disease risk and poor outcomes. Over the years, the Hp 2 allele has spread under genetic pressures. Individuals with the Hp 2-2 phenotype generally exhibit lower levels of CD163 expression in macrophages. The decreased expression of CD163 may be associated with the poor antioxidant capacity in the serum of subjects carrying the Hp 2-2 phenotype. However, the Hp 1-1 phenotype may confer protection in some cases. The Hp1 allele has strong antioxidant, anti-inflammatory, and immunomodulatory properties. It is important to note that the benefits of the Hp1 allele may vary depending on genetic and environmental factors as well as the specific disease or condition under consideration. Therefore, the Hp1 allele may not necessarily confer advantages in all situations, and its effects may be context-dependent. This review highlights the current understanding of the role of Hp polymorphisms in cardiovascular disease, inflammatory bowel disease, cancer, transplantation, hemoglobinopathies, and polyuria.

Haptoglobin phenotype and intensive glycemic control for coronary artery disease risk reduction in people with type two diabetes: The Veterans Affairs Diabetes Trial

Background

Intensive glycemic control reduced the risk of coronary artery disease (CAD) events among White ACCORD study participants with the haptoglobin (Hp)2-2 phenotype, and not among participants without the Hp2-2 phenotype. It is unknown whether these results persist in a population with more severe diabetes.

Methods

Haptoglobin phenotype was measured in 1746 (97 %) samples from the Veterans Affairs Diabetes Trial (VADT) randomized controlled trial. Multivariable-adjusted Cox regression models assessed the effect of intensive therapy on CAD risk among participants with and without the Hp2-2 phenotype separately and when stratified within pre-specified race/ethnicity-based subgroups. Time-varying (achieved) HbA1c data (<7.0 % or ≥8.0 % compared to 7.0-7.9, updated every 3 months) were also analyzed in relation to CAD risk within each phenotype.

Results

567 (32.5 %) participants had the Hp2-2 phenotype. Compared to standard therapy, intensive glycemic control was not associated with risk of CAD among participants with the non-Hp2-2 or the Hp2-2 phenotype or for any race/ethnicity-based group. Compared to HbA1c of 7.0-7.9 %, having HbA1c <7.0 % was not associated with CAD risk for either phenotype or among any race/ethnicity-based group. Having HbA1c ≥8.0 % was associated with an increased risk of CAD among Hispanic participants without the Hp2-2 phenotype (HR= 3.61, 95 % CI: 1.54-8.41, p-interaction=0.53).

Conclusion

The effect of intensive glycemic therapy on CAD events was not dependent on Hp phenotype in the VADT study of veterans with severe diabetes who may represent a population where Hp phenotype information would not be useful for personalizing diabetes management. However, further research is needed to determine if these results are conclusive.

Analysis of Genes Involved in Oxidative Stress and Iron Metabolism in Heart Failure: A Step Forward in Risk Stratification

INTRODUCTION

Heart failure (HF) is a clinical syndrome characterized by cardinal symptoms that may be accompanied by signs. It results from structural and/or functional abnormalities of the heart leading to elevated intracardiac pressures and/or inadequate cardiac output at rest and/or during exercise. The prevalence of iron deficiency and anemia justifies the current guidelines recommendation of screening. Genes HP, ACE, MTHFR, HFE, and CYBA are involved in oxidative mechanisms, iron metabolism, and hematologic homeostasis. This study investigates the contribution of variants Hp1/2 (HP), I/D (ACE), C677T (MTHFR), C282Y and H63D (HFE), and C242T (CYBA) to the development of HF, either independently or in epistasis.

METHODS

We used a database of 389 individuals, 143 HF patients, and 246 healthy controls. Genotypes were characterized through PAGE electrophoresis, PCR, PCR-RFLP, and multiplex-ARMS. Data analysis was performed with the SPSS® 26.0 software (IBM Corp., Armonk, NY).

RESULTS

We observed a significant association between the MTHFR gene and HF predisposition. The presence of allele T and genotype CT constituted risk, while genotype CC granted protection. Epistatic interactions revealed risk between genotype II of the ACE gene and genotypes CC (C282Y) or HH (H63D) of the HFE gene. Risk was also observed for interactions between genotype CC (CYBA)and genotypes 2-2 (HP), CT (MTHFR), or HH (HFE-H63D).

CONCLUSION

We concluded that genes HP, ACE, MTHFR, HFE, and CYBA contribute to the susceptibility for HF, individually or in epistasis. This study contributes to the clarification of the role that genes involved in oxidative mechanisms and iron metabolism play in the physiopathology of HF. It is, therefore, a step forward in risk stratification and personalized medicine.

Haptoglobin Phenotype and Intensive Glycemic Control for Coronary Artery Disease Risk Reduction in People With Type 2 Diabetes: The ADVANCE Study

OBJECTIVE

Intensive glycemic control reduced coronary artery disease (CAD) events among the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study participants with the haptoglobin (Hp)2-2 phenotype but not in participants without the Hp2-2 phenotype. It is unknown whether and how these results translate across different demographic/clinical characteristics and treatment strategies.

RESEARCH DESIGN AND METHODS

Haptoglobin phenotype was measured in available samples from the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation (ADVANCE) biomarker case-cohort study. Weighted multivariable-adjusted Cox regression models were used to evaluate the association between intensive glycemic control (HbA1c target of ≤6.5%) versus standard therapy (based on local guidelines) and major CAD events among participants with (n = 1,327) and without (n = 2,077) the Hp2-2 phenotype separately and within prespecified stratifications by sex, race, previous cardiovascular disease (CVD), diabetes duration, and HDL-cholesterol.

RESULTS

While the hazard ratios (HRs) were in the hypothesized differing directions, compared with standard therapy, intensive glycemic control was not significantly associated with risk of CAD events among participants without (1.04, 95% CI 0.82-1.32) or with (0.84, 0.63-1.14, Pinteraction = 0.27) the Hp2-2 phenotype overall. Intensive therapy was associated with lower CAD risk among participants with the Hp2-2 phenotype who had no previous CVD (0.47, 0.29-0.76, Pinteraction = 0.01).

CONCLUSIONS

Our findings suggest that intensive glycemic control contributes to the prevention of major CAD events among ADVANCE participants with the Hp2-2 phenotype and no previous CVD and are in alignment with our hypothesis that intensive glycemic control may be beneficial in a subset of people with the Hp2-2 phenotype.

Identification and Diagnosis of Complete Haptoglobin Gene Deletion, One of the Genes Responsible for Adverse Posttransfusion Reactions

Allergic reactions are the most frequent adverse events in blood transfusion, and anaphylactic shock, although less frequent, is systemic and serious. The cause of allergic reactions to blood transfusions are largely unknown, but deficiencies in serum proteins such as haptoglobin (Hp) can lead to anaphylactic shock. A complete deletion of the haptoglobin gene (HPdel) was first identified in families with anomalous inheritance and then verified as a genetic variant that can cause anaphylactic shock because homozygotes for HPdel have complete Hp deficiency. Thereby, they may produce antibodies against Hp from blood transfusions. HPdel is found in East and Southeast Asian populations, with a frequency of approximately 0.9% to 4%, but not in other populations. Diagnosis of Hp deficiency due to HPdel prior to transfusion is advisable because severe adverse reactions can be prevented by washing the red blood cells and/or platelets with saline or by administering plasma products obtained from an Hp-deficient donor pool. This review outlines the background of the identification of HPdel and several genetic and immunological methods developed for diagnosing Hp deficiency caused by HPdel.

Haptoglobin genotype is a risk factor for coronary artery disease in prediabetes: A case-control study

Objective

Coronary artery disease (CAD) prediction remains inconsistent with many unappreciated risk factors. Haptoglobin genotype determines the haptoglobin protein's effectiveness to bind free hemoglobin and prevent oxidative stress, a contributor to atherosclerosis. The haptoglobin 2-2 genotype increases the prevalence of cardiovascular disease (CVD) approximately five times compared to the 1-1 genotype in individuals with diabetes. The risk is unknown in prediabetes. The purpose of this study was to determine an association between haptoglobin genotype and CAD in prediabetes.

Methods

The researchers used case-control convenience sampling from two cardiovascular disease prevention clinics in Memphis, TN, and Spokane, WA, from January 1, 2016 to March 31, 2020. Participants were ages 35-70, had prediabetes, and free of chronic inflammatory or infectious diseases. Cases had a history of subclinical or clinical CAD, while controls did not have a history of CAD. Differences between cases and controls and among haptoglobin genotypes were analyzed using t-tests and ANOVA for continuous variables and chi-square or Fisher's exact tests for categorical variables. Associations among Hp genotypes and CAD were estimated using logistic regression.

Results

The sample (N = 178; 72 cases and 106 controls) was 96 % white and 64 % male. Cases had lower total cholesterol (p = 0.0001) and high-sensitivity C-reactive protein (p = 0.021). Except for CAD, haptoglobin genotype was independent of any demographic or clinical variable. Haptoglobin 2-2 genotype had 4.0 times higher odds of CAD than haptoglobin 1-1 (p = 0.01).

Conclusion

Haptoglobin 2-2 genotype had approximately four times higher odds of having CAD compared to the haptoglobin 1-1 genotype. Cases had more desirable clinical profiles, likely attributable to more aggressive treatment of traditional risk factors than controls. Haptoglobin genotype is a potentially important CAD risk factor in prediabetes (88 million Americans). Further studies are needed for interventions to reduce the oxidative stress associated with the Hp 2-2 genotype and glycosylated hemoglobin and for CAD reduction.

Intensive lifestyle intervention in type 2 diabetes and risk of incident coronary artery disease for the common haptoglobin phenotypes: the Look AHEAD study

BACKGROUND

Intensive glycemic control reduced coronary artery disease (CAD) events among the Action to Control Cardiovascular Disease Risk in Diabetes (ACCORD) participants with the haptoglobin (Hp) 2-2 phenotype only. It remains unknown whether Hp phenotype modifies the effect of an intensive lifestyle intervention (ILI) on CAD in type 2 diabetes.

METHODS

Haptoglobin phenotype was measured in 4542 samples from the Action for Health in Diabetes (Look AHEAD) study. Cox regression models assessed the effect of ILI (focused on weight loss from caloric restriction and physical activity) versus diabetes support and education (DSE) on CAD events in each phenotype group, and within pre-specified subgroups including race/ethnicity, sex, history of cardiovascular disease, diabetes medication use, and diabetes duration.

RESULTS

1590 (35%) participants had the Hp2-2 phenotype. The ILI did not lower glycated hemoglobin (%HbA1c) to < 6.5% in either phenotype, with a peak significant difference between treatment arms of 0.5% [non-Hp2-2] and 0.6% [Hp2-2]. The cumulative CAD incidence was 13.4% and 13.8% in the DSE arm and 12.2% and 13.6% in the ILI arm for non-Hp2-2 and Hp2-2 groups, respectively. Compared to DSE, the ILI was not associated with CAD among participants without (HR = 0.95, 95% CI 0.78-1.17) or with (0.89, 0.68-1.19) the Hp2-2 phenotype (p-interaction between Hp phenotype and ILI = 0.58). After Bonferroni correction, there were no significant results among any subgroups.

CONCLUSIONS

Hp phenotype did not modify the effect of the weight loss ILI on risk of CAD in Look AHEAD, potentially because it did not substantially impact glycemic control among participants with or without the Hp2-2 phenotype. Further research is needed to determine if these results are conclusive.

Human Nutrition Research in the Data Era: Results of 11 Reports on the Effects of a Multiple-Micronutrient-Intervention Study

Large datasets have been used in molecular and genetic research for decades, but only a few studies have included nutrition and lifestyle factors. Our team conducted an n-of-1 intervention with 12 vitamins and five minerals in 9- to 13-year-old Brazilian children and teens with poor healthy-eating indices. A unique feature of the experimental design was the inclusion of a replication arm. Twenty-six types of data were acquired including clinical measures, whole-genome mapping, whole-exome sequencing, and proteomic and a variety of metabolomic measurements over two years. A goal of this study was to use these diverse data sets to discover previously undetected physiological effects associated with a poor diet that include a more complete micronutrient composition. We summarize the key findings of 11 reports from this study that (i) found that LDL and total cholesterol and fasting glucose decreased in the population after the intervention but with inter-individual variation; (ii) associated a polygenic risk score that predicted baseline vitamin B12 levels; (iii) identified metabotypes linking diet intake, genetic makeup, and metabolic physiology; (iv) found multiple biomarkers for nutrient and food groups; and (v) discovered metabolites and proteins that are associated with DNA damage. This summary also highlights the limitations and lessons in analyzing diverse omic data.

A novel reagent for the screening of haptoglobin-deficient blood donors

BACKGROUND AND OBJECTIVES

In Japan, the prevalence of haptoglobin deficiency is approximately 1 in 4000. Haptoglobin-deficient individuals may produce anti-haptoglobin from allo-immunization, leading to serious transfusion reactions. Therefore, implementation of a consistent supply of haptoglobin-deficient fresh frozen plasma is crucial. We developed a novel reagent to facilitate large-scale identification of haptoglobin-deficient individuals as potential donors of plasma products.

MATERIALS AND METHODS

We established mouse monoclonal anti-haptoglobin-producing cell lines (three clones) using the hybridoma method by immunizing mice with the haptoglobin protein. Purified antibodies were conjugated with carboxylate-modified polystyrene latex beads and used for haptoglobin measurements by the latex agglutination method using an automatic analyser (LABOSPECT008). Samples with low protein concentrations were re-examined by enzyme-linked immunosorbent assay to confirm the results. Additionally, the haptoglobin gene was amplified by polymerase chain reaction to confirm the haptoglobin deletion allele (Hpdel ).

RESULTS

From February to October 2022, 7476 blood donor samples were screened. Two haptoglobin-deficient and 21 low-haptoglobin-expressing individuals were identified. Two haptoglobin-deficient donors were found homozygous for Hpdel , and 19 (90%) of the 21 low-haptoglobin-expressing individuals were heterozygous for Hpdel , which includes the first reported case of heterozygous Hpdel /HpJohnson .

CONCLUSION

We developed a new reagent for the detection of haptoglobin deficiency, which is automatable and inexpensive and appears useful for large-scale screening of blood donors.

Myeloid cell iron uptake pathways and paramagnetic rim formation in multiple sclerosis

In multiple sclerosis (MS), sustained inflammatory activity can be visualized by iron-sensitive magnetic resonance imaging (MRI) at the edges of chronic lesions. These paramagnetic rim lesions (PRLs) are associated with clinical worsening, although the cell type-specific and molecular pathways of iron uptake and metabolism are not well known. We studied two postmortem cohorts: an exploratory formalin-fixed paraffin-embedded (FFPE) tissue cohort of 18 controls and 24 MS cases and a confirmatory snap-frozen cohort of 6 controls and 14 MS cases. Besides myelin and non-heme iron imaging, the haptoglobin-hemoglobin scavenger receptor CD163, the iron-metabolizing markers HMOX1 and HAMP as well as immune-related markers P2RY12, CD68, C1QA and IL10 were visualized in myeloid cell (MC) subtypes at RNA and protein levels across different MS lesion areas. In addition, we studied PRLs in vivo in a cohort of 98 people with MS (pwMS) via iron-sensitive 3 T MRI and haptoglobin genotyping by PCR. CSF samples were available from 38 pwMS for soluble CD163 (sCD163) protein level measurements by ELISA. In postmortem tissues, we observed that iron uptake was linked to rim-associated C1QA-expressing MC subtypes, characterized by upregulation of CD163, HMOX1, HAMP and, conversely, downregulation of P2RY12. We found that pwMS with [Formula: see text] 4 PRLs had higher sCD163 levels in the CSF than pwMS with [Formula: see text] 3 PRLs with sCD163 correlating with the number of PRLs. The number of PRLs was associated with clinical worsening but not with age, sex or haptoglobin genotype of pwMS. However, pwMS with Hp2-1/Hp2-2 haplotypes had higher clinical disability scores than pwMS with Hp1-1. In summary, we observed upregulation of the CD163-HMOX1-HAMP axis in MC subtypes at chronic active lesion rims, suggesting haptoglobin-bound hemoglobin but not transferrin-bound iron as a critical source for MC-associated iron uptake in MS. The correlation of CSF-associated sCD163 with PRL counts in MS highlights the relevance of CD163-mediated iron uptake via haptoglobin-bound hemoglobin. Also, while Hp haplotypes had no noticeable influence on PRL counts, pwMS carriers of a Hp2 allele might have a higher risk to experience clinical worsening.

The Relationship Between Time-Varying Achieved HbA1c and Risk of Coronary Events Depends on Haptoglobin Phenotype Among White and Black ACCORD Participants

OBJECTIVE

Intensive glycemic therapy reduced coronary artery disease (CAD) events among White participants in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study with the haptoglobin (Hp)2-2 phenotype, while participants without the Hp2-2 phenotype had no CAD benefit. The association between achieved glycated hemoglobin (HbA1c) and CAD for each Hp phenotype remains unknown.

RESEARCH DESIGN AND METHODS

Achieved HbA1c was similar in each phenotype throughout the study. Prospectively collected HbA1c data (categorized as <6.0%, 6.0-6.5%, 6.6-6.9%, or ≥8.0% compared with 7.0-7.9%) from the ACCORD study, updated every 4 months over a median of 4.7 years, were analyzed in relation to CAD in the Hp2-2 (n = 3,322) and non-Hp2-2 (n = 5,949) phenotypes separately overall, and within White (63%, 37% Hp2-2) and Black (19%, 26% Hp2-2) participants using Cox proportional hazards regression with time-varying covariables.

RESULTS

Compared with HbA1c of 7.0-7.9%, having HbA1c ≥8.0% was associated with CAD risk among White (adjusted HR [aHR] 1.43, 95% CI 1.03-1.98) and Black (2.86, 1.09-7.51) participants with the Hp2-2 phenotype, but not when all Hp2-2 participants were combined overall (1.30, 0.99-1.70), and not among participants without the Hp2-2 phenotype. HbA1c <7.0% was not associated with a lower risk of CAD for any Hp phenotype.

CONCLUSIONS

Achieving HbA1c >8.0% compared with 7.0-7.9% was consistently associated with incident CAD risk among White and Black ACCORD participants with the Hp2-2 phenotype, while no association was observed among participants without the Hp2-2 phenotype. We found no evidence that HbA1c concentration <7.0% prevents CAD in either Hp phenotype group.

Interaction between haptoglobin genotype and glycemic variability on diabetic macroangiopathy: a population-based cross-sectional study

PURPOSE

Haptoglobin (Hp) is a hemoglobin-binding protein that functions as an antioxidant in human plasma. It is reported that glycemic variability (GV) plays a key role in diabetes-related complications associated with impaired glucose metabolism and oxidative stress. Here we aim to investigate whether the effect of GV on diabetic macroangiopathy depends on Hp genotype in type 2 diabetes.

METHODS

A number of 860 Chinese patients with type 2 diabetes was genotyped and assigned to two Hp subgroups (Hp 2-2 and Hp 1 carriers). Glycemic variability (GV) was assessed by using a retrospective continuous glucose monitoring system for three consecutive days, and it was measured using the glucose coefficient of variation (%CV), which is calculated as the ratio of glucose standard deviation to glucose mean. Clinical features, history of cardiac surgery, and vascular imaging tests were utilized to diagnose macroangiopathy. We evaluated the interaction between Hp genotypes and %CV on diabetic macroangiopathy. Furthermore, serum concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG) was measured using an enzyme-linked immunosorbent assay as a biomarker of oxidative stress.

RESULTS

Serum 8-OHdG levels were positively correlated with %CV in Hp 1 carriers (r = 0.117; p = 0.021). Patients in the highest %CV tertile were associated with a higher prevalence of diabetic macroangiopathy than those in the lowest %CV tertile in Hp 1 carriers (OR = 2.461 [95% CI, 1.183-5.121], p = 0.016), but not in those with Hp 2-2 genotype (OR = 0.540 [95% CI, 0.245-1.191], p = 0.127). A significant interactive effect of Hp genotypes and %CV on diabetic macroangiopathy was found (p interaction = 0.008).

CONCLUSION

Hp genotype modifies the effect of GV on diabetic macroangiopathy among Chinese patients with type 2 diabetes.

Relationship Between Time-Varying Achieved High-Density Lipoprotein Cholesterol and Risk of Coronary Events Depends on Haptoglobin Phenotype Within the ACCORD Lipid Study

Background The Hp (haptoglobin)2-2 phenotype (~40% of people) is associated with dysfunctional high-density lipoprotein (HDL) that is heavily oxidized in hyperglycemia, which may explain why raising HDL-cholesterol (HDL-C) does not reliably prevent coronary artery disease (CAD) in diabetes. Methods and Results In this observational study using longitudinal data from the ACCORD (Action to Control Cardiovascular Risk in Diabetes) lipid trial, time-varying (achieved) HDL-C updated at 4, 8, and 12 months, and annually thereafter over a mean of 4.7 years, was analyzed in relation to risk of CAD and secondary outcomes using Cox proportional hazards regression with time-varying covariables among participants with (n=1781) and without (n=3191) the Hp2-2 phenotype. HDL-C did not differ between the phenotypes throughout the study. Having low HDL-C (<40 mg/dL for male participants and <50 mg/dL for female participants) was associated with a greater risk of CAD compared with non-low HDL-C among participants with the non-Hp2-2 phenotype (hazard ratio [HR], 1.48 [95% CI, 1.18-1.87]) but not among the Hp2-2 phenotype (HR, 0.97 [95% CI, 0.70-1.35]; P interaction=0.03). Similarly, an inverse relationship was observed between HDL-C quintiles and CAD risk among participants without the Hp2-2 phenotype, whereas no significant inverse relationship was observed among participants with the Hp2-2 phenotype (P interaction=0.38). Among the Hp2-2 phenotype group, having low HDL-C was associated with higher risk of CVD mortality (HR, 2.09 [95% CI, 1.05-4.13]), and compared with the lowest HDL-C quintile, higher quintiles were associated with lower risk of CVD mortality and congestive heart failure. Conclusions Hp phenotype modified the association between HDL-C and risk of CAD in the ACCORD lipid study, suggesting that HDL dysfunction in the Hp2-2 phenotype may hinder CAD-protective properties of HDL-C.

Role of haptoglobin 2-2 genotype on disease progression and mortality among South Indian chronic kidney disease patients

BACKGROUND

Haptoglobin (HP), a plasma glycoprotein, binds to free hemoglobin and prevents the loss of iron and kidney damage. The variations of HP gene affect its enzyme activity, resulting in varied antioxidant, angiogenic and anti-inflammatory properties. HP 2-2 genotype showed 3.84 fold increased risk for the development of CKD in Taiwan population. With this background, the present work focused to conduct a prospective case-control study in South Indian population to evaluate whether the HP variants are associated to nondialysis (ND) (CKD stages 1-4) and ESRD (CKD stage 5) conditions.

METHODS AND RESULTS

Totally 392 CKD patients (nondialysis, ND; n = 170, end-stage renal disease, ESRD; n = 222) and 202 healthy individuals were enrolled. The blood samples collected from the patients were used to determine biochemical parameters and HP genotyping. Gene frequency and biochemical parameters were statistically analyzed for disease association. Results showed that HP 2-2 genotypes were significantly associated with ND and ESRD disease development compared to controls. Higher HP2-2 genotype frequency showed an increased hazard ratio for overall disease progression among ND patients (hazard ratio = 3.86; 95% CI 1.88 to 7.93; P = 0.0002). Survival analysis also showed that non-HP2-2 patients have a statistically significantly decreased risk for mortality compared to patients with the HP2-2 genotype (ESRD patients hazard ratio = 4.05; P = 0.04).

CONCLUSION

The present study confirms that HP2-2 polymorphism is statistically associated with the risk of CKD incidence, progression, and mortality among South Indians. Concluding our results, the HP2-2 genotype could be an independent predictor of all-cause mortality and disease progression in patients with CKD.

Intensified glycemic control by HbA1c for patients with coronary heart disease and Type 2 diabetes: a review of findings and conclusions

The occurrence and development of coronary heart disease (CHD) are closely linked to fluctuations in blood glucose levels. While the efficacy of intensified treatment guided by HbA1c levels remains uncertain for individuals with diabetes and CHD, this review summarizes the findings and conclusions regarding HbA1c in the context of CHD. Our review showed a curvilinear correlation between regulated level of HbA1c and therapeutic effectiveness of intensified glycemic control among patients with type 2 diabetes and coronary heart disease. It is necessary to optimize the dynamic monitoring indicators of HbA1c, combine genetic profiles, haptoglobin phenotypes for example and select more suitable hypoglycemic drugs to establish more appropriate glucose-controlling guideline for patients with CHD at different stage of diabetes.

Engineering Therapeutics to Detoxify Hemoglobin, Heme, and Iron

Hemolysis (i.e., red blood cell lysis) can increase circulatory levels of cell-free hemoglobin (Hb) and its degradation by-products, namely heme (h) and iron (Fe). Under homeostasis, minor increases in these three hemolytic by-products (Hb/h/Fe) are rapidly scavenged and cleared by natural plasma proteins. Under certain pathophysiological conditions, scavenging systems become overwhelmed, leading to the accumulation of Hb/h/Fe in the circulation. Unfortunately, these species cause various side effects such as vasoconstriction, hypertension, and oxidative organ damage. Therefore, various therapeutics strategies are in development, ranging from supplementation with depleted plasma scavenger proteins to engineered biomimetic protein constructs capable of scavenging multiple hemolytic species. In this review, we briefly describe hemolysis and the characteristics of the major plasma-derived protein scavengers of Hb/h/Fe. Finally, we present novel engineering approaches designed to address the toxicity of these hemolytic by-products.

Haptoglobin Gene Expression and Anthracycline-Related Cardiomyopathy in Childhood Cancer Survivors: A COG-ALTE03N1 Report

Background

Anthracycline-related cardiomyopathy is a leading cause of premature death in childhood cancer survivors. The high interindividual variability in risk suggests the need to understand the underlying pathogenesis.

Objectives

The authors interrogated differentially expressed genes (DEGs) to identify genetic variants serving regulatory functions or genetic variants not easily identified when using genomewide array platforms. Using leads from DEGs, candidate copy number variants (CNVs) and single-nucleotide variants (SNVs) were genotyped.

Methods

Messenger RNA sequencing was performed on total RNA from peripheral blood of 40 survivors with cardiomyopathy (cases) and 64 matched survivors without cardiomyopathy (control subjects). Conditional logistic regression analysis adjusting for sex, age at cancer diagnosis, anthracycline dose, and chest radiation was used to assess the associations between gene expression and cardiomyopathy and between CNVs and SNVs and cardiomyopathy.

Results

Haptoglobin (HP) was identified as the top DEG. Participants with higher HP gene expression had 6-fold greater odds of developing cardiomyopathy (OR: 6.4; 95% CI: 1.4-28.6). The HP2-specific allele among the HP genotypes (HP1-1, HP1-2, and HP2-2) had higher transcript levels, as did the G allele among SNVs previously reported to be associated with HP gene expression (rs35283911 and rs2000999). The HP1-2 and HP2-2 genotypes combined with the G/G genotype for rs35283911 and/or rs2000999 placed the survivors at 4-fold greater risk (OR: 3.9; 95% CI: 1.0-14.5) for developing cardiomyopathy.

Conclusions

These findings provide evidence of a novel association between HP2 allele and cardiomyopathy. HP binds to free hemoglobin to form an HP-hemoglobin complex, thereby preventing oxidative damage from free heme iron, thus providing biological plausibility to the mechanistic basis of the present observation.

Nitric Oxide in Cardiac Surgery: A Review Article

Perioperative organ injury remains a medical, social and economic problem in cardiac surgery. Patients with postoperative organ dysfunction have increases in morbidity, length of stay, long-term mortality, treatment costs and rehabilitation time. Currently, there are no pharmaceutical technologies or non-pharmacological interventions that can mitigate the continuum of multiple organ dysfunction and improve the outcomes of cardiac surgery. It is essential to identify agents that trigger or mediate an organ-protective phenotype during cardiac surgery. The authors highlight nitric oxide (NO) ability to act as an agent for perioperative protection of organs and tissues, especially in the heart-kidney axis. NO has been delivered in clinical practice at an acceptable cost, and the side effects of its use are known, predictable, reversible and relatively rare. This review presents basic data, physiological research and literature on the clinical application of NO in cardiac surgery. Results support the use of NO as a safe and promising approach in perioperative patient management. Further clinical research is required to define the role of NO as an adjunct therapy that can improve outcomes in cardiac surgery. Clinicians also have to identify cohorts of responders for perioperative NO therapy and the optimal modes for this technology.

Haptoglobin genotype and its relation to asymptomatic cerebral small-vessel disease in type 1 diabetes

AIM

Cerebral small-vessel disease (SVD) is prevalent in type 1 diabetes and has been associated with the haptoglobin variant allele Hp1. Contrarily, the Hp2-allele has been linked to cardiovascular disease and the role of haptoglobin-genotype in asymptomatic SVD is unknown. We, therefore, aimed to evaluate the alleles' association with SVD.

METHODS

This cross-sectional study included 179 neurologically asymptomatic adults with type 1 diabetes (women 53%, mean age 39 ± 7 years, diabetes duration 23 ± 10 years, HbA_1c 8.1 ± 3.2% [65 ± 12 mmol/mol]). Examinations included genotyping (genotypes Hp1-1, Hp2-1, Hp2-2) by polymerase chain reaction, clinical investigation, and magnetic resonance brain images assessed for SVD manifestations (white matter hyperintensities, cerebral microbleeds, and lacunar infarcts).

RESULTS

SVD prevalence was 34.6%. Haptoglobin genotype frequencies were 15.6% (Hp1-1), 43.6% (Hp1-2), and 40.8% (Hp2-2). Only diastolic blood pressure differed between the genotypes Hp1-1, Hp1-2, and Hp2-2 (81 [74-83], 75 [70-80], and 75 [72-81] mmHg, p = 0.019). Haptoglobin genotype frequencies by presence versus absence of SVD were 16.1%; 46.8%; 37.1% versus 15.4%; 41.9%; 42.7% (p = 0.758). Minor allele frequencies were 39.5% versus 36.3% (p = 0.553). Hp1 homozygotes and Hp2 carriers displayed equal proportions of SVD (35.7% vs 34.4%, p > 0.999) and SVD manifestations (white matter hyperintensities 14.3% vs 17.9%, p = 0.790; microbleeds 25.0% vs 21.9%, p = 0.904; lacunar infarcts 0% vs 3.6%, p > 0.999). Hp1-1 was not associated with SVD (OR 1.19, 95% CI 0.46-2.94, p = 0.712) when adjusting for age, blood pressure, and diabetic retinopathy.

CONCLUSIONS

Although the SVD prevalence was high, we detected no significant association between SVD and haptoglobin-genotype.

Genotype-specific reference interval of haptoglobin tests in a Chinese population on the BN II System

The distribution of Haptoglobin (HP) subtypes differs according to race and geography. It was also confirmed that the serum HP concentration was substantially affected by the HP subtypes. This study aimed to investigate the HP subtypes in northern Chinese and to establish reference intervals for the major HP subtypes using the BN II system. 1195 individuals were included in the study, grouped by haptoglobin subtype, and tested for concentrations by BN II System. Analysis of reference range was performed according to the EP28-A3c guideline. The need to establish reference ranges for subtype, gender, and age groupings was confirmed by the Z-test. The 2.5th and 97.5th percentiles were used as the upper and lower limits of the reference interval, respectively. In the population we investigated, the HP2-2 subtype had the highest proportion, accounting for 49.3%, followed by HP2-1 (38.0%), HP1-1 (7.2%). In addition, about 5.5% of individuals had HP^del-related subtypes. The concentrations of the major subtypes (HP1-1, HP2-1, HP2-2) were significantly different, and it was necessary to establish reference ranges by grouping according to the results of the Z-test. The reference intervals were as follows: HP1-1, 0.37-2.19 g/L; HP2-1, 0.38-2.12 g/L; HP2-2, 0.12-1.51 g/L. Significant differences in HP concentrations between genders and ages were found, however, it was not necessary to establish separate reference interval since the results of the Z-test was negative. We have established reference ranges of serum haptoglobin concentrations based on subtypes, which are necessary for the clinical application of haptoglobin.

Haptoglobin Genotype Does Not Confer a Risk of Stroke in Type 1 Diabetes

The exon copy number variant in the haptoglobin gene is associated with cardiovascular and kidney disease. For stroke, previous research is inconclusive. We aimed to study the relationship between the haptoglobin Hp1/2 genotype and stroke in individuals with type 1 diabetes from the Finnish Diabetic Nephropathy Study. We included two partially overlapping cohorts: one with haptoglobin genotypes determined using genotyping for 179 individuals with stroke and 517 matched control subjects, and the other using haptoglobin genotype imputation for a larger cohort of 500 individuals with stroke and 3,806 individuals without stroke. We observed no difference in the Hp1-1, Hp2-1, and Hp2-2 genotype frequencies between individuals with or without stroke, neither in the genotyping nor the imputation cohorts. Haptoglobin genotypes were also not associated with the ischemic or hemorrhagic stroke subtypes. In our imputed haptoglobin cohort, 61% of individuals with stroke died during follow-up. However, the risk of death was not related to the haptoglobin genotype. Diabetic kidney disease and cardiovascular events were common in the cohort, but the haptoglobin genotypes were not associated with stroke when stratified by these complications. To conclude, the Hp1/2 genotypes did not affect the risk of stroke or survival after stroke in our cohort with type 1 diabetes.

Duplex dual-labeled fluorescence probe-based melting curve and endpoint genotyping assays for genotyping of rs2000999 and haptoglobin gene deletion

Haptoglobin (Hp) is a hemoglobin-binding serum glycoprotein. Some variations in the Hp gene (HP) or Hp-related gene (HPR), including a single-nucleotide polymorphism in intron 2 of HRP, rs2000999, and a complete deletion of the HP gene (HP^{de l} ), one of the rare variants of HP, have been reported to correlate with the serum cholesterol concentration as well as the serum Hp concentration. In this study, we developed a duplex dual-labeled fluorescence probe-based method to simultaneously determine the rs2000999 G > A polymorphism by melting curve genotyping and the zygosity of HP^{de l} by endpoint genotyping. This method was then validated by using the genomic DNA from 94 Japanese subjects for whom genotypes of rs2000999 and HP^del zygosity had already been determined. The results obtained with this method were in perfect agreement with the previous ones. Thus, the present method enables us to estimate these two polymorphisms in relatively large-scale groups of subjects, especially in Asian populations where the HP^del is distributed.

Haptoglobin 1 allele predicts higher serum haptoglobin concentration and lower multiorgan failure risk in sickle cell disease

Haptoglobin (HP) is an acute-phase protein and the main scavenger of cell-free hemoglobin. When HP is depleted, as observed in hemolytic conditions such as sickle cell disease (SCD), cell-free hemoglobin can lead to acute organ damage. The impact of the HP 1-1, 2-1, and 2-2 isoforms on HP and cell-free hemoglobin concentrations and SCD-related complications is unclear. In a longitudinal cohort of patients with SCD, the HP 1 allele was associated with higher HP and lower cell-free hemoglobin concentrations at a routine clinic visit as well as during hospitalization for a vaso-occlusive episode or acute chest syndrome. With a median follow-up of 6.8 years, acute chest syndrome occurred in 42% (n = 163) and multiorgan failure in 14% (n = 53) of 391 patients with SCD with a minimum follow-up of 6 months. The HP 1 allele was independently associated with lower risk of developing multiorgan failure during acute chest syndrome (additive model hazard ratio, 0.5; P < .001). Future studies assessing the regulation of HP concentrations and ability to bind cell-free hemoglobin according to the HP genotype may help to identify patients with SCD at high risk for multiorgan failure and to guide interventions, such as rapid initiation of exchange transfusion or HP replacement therapy.

Prospective study of breakfast frequency and timing and the risk of incident type 2 diabetes in community-dwelling older adults: the Cardiovascular Health Study

BACKGROUND

No evidence-based recommendations regarding optimal breakfast frequency and timing and type 2 diabetes mellitus (T2DM) exist for older adults because of limited studies.

OBJECTIVES

We sought to prospectively assess relations between breakfast frequency and timing and T2DM risk among older adults and determine whether these depended on sex or cardiometabolic risk factors.

METHODS

Weekly breakfast frequency and usual daily breakfast time were assessed by questionnaire at baseline in 3747 older adults (aged ≥ 65 y) from the Cardiovascular Health Study (CHS) who were free of cancer and T2DM and followed for 17.6 y. Multivariable-adjusted hazard ratios (aHRs) with 95% CIs estimated from Cox proportional hazards models were used to quantify associations with T2DM.

RESULTS

Most CHS participants (median age: 74 y; IQR: 71-78 y) consumed breakfast daily (85.5%), and 73% had their first daily eating occasion between 07:00 and 09:00, both of which were associated with higher socioeconomic status, factors that are indicative of a healthier lifestyle, and lower levels of cardiometabolic risk indicators at baseline. During follow-up, 547 T2DM cases were documented. No strong evidence was observed linking breakfast frequency and risk of T2DM. Compared with participants whose breakfast timing (first eating occasion of the day) was 07:00-09:00, those who broke fast after 09:00 had an aHR for T2DM of 0.71 (95% CI: 0.51, 0.99). This association was present in participants with impaired fasting glucose at baseline (aHR: 0.61; 95% CI: 0.39, 0.95) but not in those without (aHR: 0.83; 95% CI: 0.50, 1.38). No associations between eating frequency or timing and T2DM were observed within other prespecified subgroups.

CONCLUSIONS

Eating breakfast daily was not associated with either higher or lower risk of T2DM in this cohort of older adults, whereas a later (after 09:00) daily first eating occasion time was associated with lower T2DM risk in participants with impaired fasting glucose at baseline.This trial was registered at clinicaltrials.gov as NCT00005133.

Haptoglobin Regulates Macrophage/Microglia-Induced Inflammation and Prevents Ischemic Brain Damage Via Binding to HMGB1

Background HMGB1 (high-mobility group box 1) is known to worsen the functional prognosis after cerebral ischemia. Hp (haptoglobin) binds and sequesters HMGB1. Furthermore, Hp-HMGB1 complexes are rapidly cleared by scavenger receptors on macrophages/microglia and modulate polarization of macrophages/microglia toward the M2 phenotype. Therefore, Hp may prevent aggravation by HMGB1 after cerebral ischemia and promote tissue repair by M2 macrophages/microglia. The aim of this study was to investigate the effects of Hp on ischemic brain damage induced by a high systemic HMGB1 level in mice subjected to 4 hours of middle cerebral artery occlusion (MCAO). Methods and Results One day after MCAO, Hp was administered intraperitoneally at a dose of 20 or 200 U/kg once daily for 7 days. Neurological scores, motor coordination, and plasma HMGB1 levels were measured 1, 3, and 7 days after MCAO. Expression of M1 and M2 macrophage/microglia markers, such as CD16/32 and CD206, were evaluated by immunostaining 7 days after MCAO. Treatment with Hp for 7 days improved the neurological score, motor coordination, and survival and prevented brain damage after MCAO. The systemic HMGB1 level increased 1 to 7 days after MCAO and was higher at 7 days than at day 1. Hp significantly decreased the systemic HMGB1 level and increased the M2 phenotype when compared with the M1 phenotype after MCAO. Conclusions Hp improved functional outcomes, including survival, motor function, and brain damage by binding to HMGB1 and modulating the polarization of macrophages/microglia. Hp may be an effective option in the treatment of cerebral ischemia.

Influence of Haptoglobin Polymorphism on Stroke in Sickle Cell Disease Patients

This review outlines the current clinical research investigating how the haptoglobin (Hp) genetic polymorphism and stroke occurrence are implicated in sickle cell disease (SCD) pathophysiology. Hp is a blood serum glycoprotein responsible for binding and removing toxic free hemoglobin from the vasculature. The role of Hp in patients with SCD is critical in combating blood toxicity, inflammation, oxidative stress, and even stroke. Ischemic stroke occurs when a blocked vessel decreases oxygen delivery in the blood to cerebral tissue and is commonly associated with SCD. Due to the malformed red blood cells of sickle hemoglobin S, blockage of blood flow is much more prevalent in patients with SCD. This review is the first to evaluate the role of the Hp polymorphism in the incidence of stroke in patients with SCD. Overall, the data compiled in this review suggest that further studies should be conducted to reveal and evaluate potential clinical advancements for gene therapy and Hp infusions.

Haptoglobin Phenotype Modifies the Effect of Fenofibrate on Risk of Coronary Event: ACCORD Lipid Trial

OBJECTIVE

The haptoglobin (Hp)2-2 phenotype (∼35-40% of people) is associated with increased oxidation and dysfunctional HDL in hyperglycemia and may explain why drugs designed to pharmacologically raise HDL cholesterol and lower triglycerides have not reliably prevented cardiovascular disease in diabetes. We aimed to determine whether the effect of adding fenofibrate versus placebo to simvastatin on the risk of coronary artery disease (CAD) events depends on Hp phenotype in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) lipid trial.

RESEARCH DESIGN AND METHODS

Cox proportional hazards regression models quantified the relationship between fenofibrate therapy and CAD events in the ACCORD lipid trial in participants with the Hp2-2 phenotype (n = 1,795) separately from those without (n = 3,201).

RESULTS

Fenofibrate therapy successfully lowered the risk of CAD events in participants without the Hp2-2 phenotype (multivariable adjusted hazard ratio 0.74 [95% CI 0.60-0.90] compared with no fenofibrate therapy) but not in participants with the Hp2-2 phenotype (1.16 [0.87-1.56]; P interaction = 0.009). Subgroup analyses revealed that this protective effect of fenofibrate against CAD events among the non-Hp2-2 phenotype group was pronounced in participants with severe dyslipidemia (P interaction = 0.01) and in males (P interaction = 0.02) with an increased CAD risk from fenofibrate treatment observed in females with the Hp2-2 phenotype (P interaction = 0.002).

CONCLUSIONS

The effect of fenofibrate added to simvastatin on risk of CAD events depends on Hp phenotype in the ACCORD lipid trial.

Haptoglobin as a Biomarker

Haptoglobin (Hp) is a glycoprotein that binds free hemoglobin (Hb) in plasma and plays a critical role in tissue protection and prevention of oxidative damage. Besides, it has some regulatory functions. Haptoglobin is an acute-phase protein, its concentration in plasma changes in pathology, and the test for its concentration is part of normal clinical practice. Haptoglobin is a conservative protein synthesized mainly in the liver and lungs and is the subject of research as a potential biomarker of many diseases, including various forms of malignant neoplasms. Haptoglobin has several unique biophysical characteristics. The human Нр gene is polymorphic, has three structural alleles that control the synthesis of three major phenotypes of haptoglobin: homozygous Нр1-1 and Нр2-2, and heterozygous Нр2-1, determined by a combination of allelic variants that are inherited. Numerous studies indicate that the phenotype of haptoglobin can be used to judge the individual predisposition of a person to various diseases. In addition, Hp undergoes various post-translational modifications (PTMs). These are structural transformations (removal of the signal peptide, cutting off the Pre-Hp precursor molecule into two subunits, α and β, limited proteolysis of α-chains, formation of disulfide bonds, multimerization), as well as chemical modifications of α-chains and glycosylation of the β-chain. Glycosylation of the β-chain of haptoglobin at four Asn sites is the most important variable PTM that regulates the structure and function of the glycoprotein. The study of modified oligosaccharides of the β-chain of Hp has become the main direction in the study of pathological processes, including malignant neoplasms. These characteristics indicate the possibility of the existence of Hp in the form of a multitude of proteoforms, probably performing different functions. This review is devoted to the description of the structural and functional diversity and the potential use of Hp as a biomarker of various pathologies.

Perioperative Serum Free Hemoglobin and Haptoglobin Levels in Valvular and Aortic Surgery With Cardiopulmonary Bypass: Their Associations With Postoperative Kidney Injury

OBJECTIVE

To observe the perioperative free hemoglobin and haptoglobin levels and to assess their associations with the risk of postoperative acute kidney injury (pAKI) in adult patients undergoing valvular and aortic surgery requiring cardiopulmonary bypass (CPB).

DESIGN

A single-center, prospective, observational study.

SETTING

Public teaching hospital.

PARTICIPANTS

The study comprised 74 adult patients without chronic renal failure who underwent cardiovascular surgery requiring CPB from 2014 to 2020.

MEASUREMENTS AND MAIN RESULTS

Perioperative free hemoglobin and haptoglobin levels during the study period were obtained from study participants. The primary outcome was pAKI defined by the Kidney Disease: Improving Global Outcomes criteria. Of the 74 patients in this study, pAKI occurred in 25 patients (33.8%). The free hemoglobin level began to increase after the initiation of CPB and reached a peak level at 30 minutes after weaning from CPB. It returned to the baseline level on postoperative day one. Haptoglobin levels were the highest after anesthesia induction and decreased continuously until postoperative day one. In the multivariate analysis, maximum free hemoglobin and minimum haptoglobin were associated independently with increased risk of pAKI (adjusted odds ratio 1.33 [95% confidence interval 1.12-1.58; p = 0.001] and 0.95 [95% confidence interval 0.91-1.00; p = 0.03], respectively). The free hemoglobin level began to have an independent association with pAKI at one hour after commencement of CPB, and the independent association disappeared at postoperative day one.

CONCLUSIONS

This study found that the perioperative increase of the free hemoglobin level and the decrease of the haptoglobin level had independent associations with the risk of pAKI.

[Haptoglobin as a biomarker]

Haptoglobin (Hp) is a blood plasma glycoprotein that binds free hemoglobin (Hb) and plays a critical role in tissue protection and the prevention of oxidative damage. In addition, it has a number of regulatory functions. Haptoglobin is an acute phase protein, its concentration in plasma changes in pathology, and the test for its concentration is part of normal clinical practice. Haptoglobin is a conservative protein synthesized mainly in the liver and lungs and is the subject of research as a potential biomarker of many diseases, including various forms of malignant neoplasms. Haptoglobin has several unique biophysical characteristics. Only in humans, the Hp gene is polymorphic, has three structural alleles that control the synthesis of three major phenotypes of Hp, homozygous Hp1-1 and Hp2-2, and heterozygous Hp2-1, determined by a combination of allelic variants that are inherited. Numerous studies indicate that the phenotype of haptoglobin can be used to judge the individual's predisposition to various diseases. In addition, Hp undergoes various post-translational modifications (PTMs). These are structural transformations (removal of the signal peptide, cutting of the Pre-Hp precursor molecule into two subunits, α and β, limited proteolysis of α-chains, formation of disulfide bonds, multimerization), as well as chemical modifications of α-chains and glycosylation of the β-chain. Glycosylation of the β-chain of haptoglobin at four Asn sites is the most important variable PTM that regulates the structure and function of the glycoprotein. The study of modified oligosaccharides of the Hp β-chain has become the main direction in the study of pathological processes, including malignant neoplasms. Many studies are focused on the identification of PTM and changes in the level of the α2-chain of this protein in pathology. These characteristics of Hp indicate the possibility of the existence of this protein as different proteoforms, probably with different functions. This review is devoted to the description of the structural and functional diversity of Hp and its potential use as a biomarker of various pathologies.

The Blood Gene Expression Signature for Kawasaki Disease in Children Identified with Advanced Feature Selection Methods

Kawasaki disease (KD) is an acute vasculitis, accompanied by coronary artery aneurysm, coronary artery dilatation, arrhythmia, and other serious cardiovascular diseases. So far, the etiology of KD is unclear; it is necessary to study the molecular mechanism and related factors of KD. In this study, we analyzed the expression profiles of 75 DB (identifying bacteria), 122 DV (identifying virus), 71 HC (healthy control), and 311 KD (Kawasaki disease) samples. 332 key genes related to KD and pathogen infections were identified using a combination of advanced feature selection methods: (1) Boruta, (2) Monte-Carlo Feature Selection (MCFS), and (3) Incremental Feature Selection (IFS). The number of signature genes was narrowed down step by step. Subsequently, their functions were revealed by KEGG and GO enrichment analyses. Our results provided clues of potential molecular mechanisms of KD and were helpful for KD detection and treatment.

Initial Evidence of Variation by Ethnicity in the Relationship between Vitamin C Status and Mental States in Young Adults

Higher fruit and vegetable intake has been associated with improved mood, greater vitality, and lower stress. Although the nutrients driving these benefits are not specifically identified, one potentially important micronutrient is vitamin C, an important co-factor for the production of peptide hormones, carnitine and neurotransmitters that are involved in regulation of physical energy and mood. The aim of our study was to investigate the cross-sectional relationship between blood plasma vitamin C status and mood, vitality and perceived stress. A sample of 419 university students (aged 18 to 35; 67.8% female) of various ethnicities (49.2% European, 16.2% East Asian, 8.1% Southeast/Other Asian, 9.1% Māori/Pasifika, 11.5% Other) provided a fasting blood sample to determine vitamin C status and completed psychological measures consisting of the Profile of Mood States Short Form (POMS-SF), the vitality subscale of the Rand 36-Item Short Form (SF-36), and the Perceived Stress Scale (PSS). Participants were screened for prescription medication, smoking history, vitamin C supplementation, fruit/juice and vegetable consumption, kiwifruit allergies, excessive alcohol consumption and serious health issues, and provided age, gender, ethnicity, and socioeconomic status information, which served as covariates. There were no significant associations between vitamin C status and the psychological measures for the sample overall. However, associations varied by ethnicity. Among Māori/Pasifika participants, higher vitamin C was associated with greater vitality and lower stress, whereas among Southeast Asian participants, higher vitamin C was associated with greater confusion on the POMS-SF subscale. These novel findings demonstrate potential ethnicity-linked differences in the relationship between vitamin C and mental states. Further research is required to determine whether genetic variation or cultural factors are driving these ethnicity differences.

Haptoglobin gene diversity and incidence of uncomplicated malaria among children in Iganga, Uganda

Background

Haptoglobin (Hp) is an acute phase protein that takes part in systemic regulation of haem during Plasmodium falciparum infections. Numerous genotypes of haptoglobin have been reported in malaria endemic populations. In this study, the relationship between haptoglobin genotypes and incidence of uncomplicated malaria in a cohort of children living in a malaria-endemic area of Uganda was determined.

Methods

This is an extension of a longitudinal study comprising of 423 children aged between six months and nine years, who were actively followed up for one year. Malaria episodes occurring in the cohort children were detected and the affected children treated with national policy drug regimen. Haptoglobin genotypes were determined by an allele-specific PCR method and their frequencies were calculated. A multivariate negative binomial regression model was used to estimate the impact of haptoglobin genotypes on incidence of uncomplicated malaria in the children’s cohort. In all statistical tests, a P–value of < 0.05 was considered as significant.

Results

The prevalence of the Hp 1–1, Hp 2–1 and Hp 2–2 genotypes in the children’s cohort was 41%, 36.2% and 22.9%, respectively. The overall frequency for the Hp 1 allele was 59%, while Hp 2 allele occurred at a frequency of 41%. After adjustment of incidence rates for age, insecticide treated bed net (ITN) use and malaria history, the incidence of uncomplicated malaria for children carrying the Hp 2–2 genotype and those with the Hp 2–1 genotype was statistically similar (P = 0.41). Also, no difference in the incidence of uncomplicated malaria was observed between children carrying the Hp 1–1 genotype and those having the Hp 2–1 genotype (P = 0.84) or between Hp 2–2 Vs Hp 1–1 genotypes (P = 0.50).

Conclusions

This study showed that the Hp 1–1 and Hp 2–1 genotypes each occur in nearly 4 in 10 children and the Hp 2–2 genotype occurs in 2 of every 10 children. No association with incidence of uncomplicated malaria was found. Additional studies of influence of haptoglobin genotypes on P. falciparum malaria severity are needed to understand the role of these genotypes in malarial protection.

Inconsistent effects of gluten on obesity: is there a role for the haptoglobin isoforms?

BACKGROUND AND AIMS

There is no clear evidence about the effects of gluten intake on obesity. It is known that gluten's effects on gut permeability are mediated by zonulin, a protein identified as pre-haptoglobin 2, a physiological regulator of the intestinal barrier. We investigated the obesogenic and inflammatory effects of gluten and its association with the haptoglobin genotype.

METHODS

This was a single blinded, crossover study, including 40 overweight or obesity women free of celiac disease. Participants adopted a gluten-free diet (GFD) for 8 weeks and consumed a gluten-free muffin (GF-M) or a gluten-containing muffin (GLU-M, 24 g gluten) for 4 weeks, switching muffin type during the subsequent 4 weeks. During a follow-up period of 4 weeks we evaluated the usual diet (UD). Food diaries were collected to estimate the macronutrient intake and dietary inflammatory index (DII®). Bodyweight and composition, resting energy expenditure (REE), and cytokines were assessed. Haptoglobin alleles (Hp1 and Hp2) were genotyped to characterize zonulin expression.

RESULTS

Energy and macronutrient intakes were similar during both periods, except for protein intake, which was higher during GLU-M. DII scores indicated a more inflammatory profile during the GF-M and GLU-M periods compared to UD. No differences were observed in body composition or REE between interventions when the Hp genotype was not considered. Nonetheless, those carrying the Hp2-2 genotype (overexpressing zonulin) presented lower REE and higher levels of IL6 and IL1beta only during gluten intake (GLU-M and UD) compared to age- and body mass index-matched Hp1-1 carrier. These results suggest an obesogenic and inflammatory action of gluten only in those overexpressing zonulin (Hp2-2).

CONCLUSION

These results highlight the importance of zonulin as the mediator of gluten obesogenic and inflammatory effects. Our data suggest that in the presence of gluten, zonulin release is associated with a reduction of REE and an increase of inflammatory markers that are not seen in zonulin low producers.

Haptoglobin Phenotype Modifies the Influence of Intensive Glycemic Control on Cardiovascular Outcomes

BACKGROUND

Whereas there exists a direct relationship between glycated hemoglobin and cardiovascular disease (CVD), clinical trials targeting glycated hemoglobin to near-normal levels using intensive therapy have failed to prevent CVD and have even increased mortality, making clinical decision making difficult. A common polymorphism at the haptoglobin (Hp) genetic locus is associated with CVD, especially coronary heart disease, in the setting of hyperglycemia.

OBJECTIVES

This study sought to determine whether the treatment difference of intensive versus standard glucose-lowering therapy on risk of CVD events in the ACCORD (Action to Control Cardiovascular Risk in Diabetes) study depended on Hp phenotype.

METHODS

Hp phenotype was measured within 5,806 non-Hispanic white ACCORD participants using a validated assay. Adjusted hazard ratios (aHR) with 95% confidence intervals (CI) estimated from stratified Cox regression models were used to quantify the association between intensive therapy and incident CVD for the 2 different Hp phenotype groups (Hp2-2, Hp1 carriers).

RESULTS

Compared with standard therapy, intensive therapy was associated with a lower risk of incident coronary heart disease among participants with the Hp2-2 phenotype (n = 2,133; aHR: 0.71; 95% CI: 0.55 to 0.91; p = 0.006), but not among the other 2 phenotypes (Hp1 allele carriers) (n = 3,673; aHR: 0.95; 95% CI: 0.79 to 1.13; p = 0.550). The same pattern was observed for CVD. Conversely, intensive therapy was associated with an increased risk of fatal CVD (aHR: 1.50; 95% CI: 1.00 to 2.25; p = 0.049) and total mortality (aHR: 1.40; 95% CI: 1.08 to 1.81; p = 0.011) among the Hp1 carriers, whereas this risk was not increased in the Hp2-2 phenotype (fatal CVD: aHR: 1.02; 95% CI: 0.59 to 1.77; p = 0.931; total mortality: aHR: 0.98; 95% CI: 0.68 to 1.41; p = 0.908).

CONCLUSIONS

Intensive glucose-lowering therapy was effective at preventing incident coronary heart disease and CVD events in ACCORD study participants with the Hp2-2 phenotype but not in Hp1 carriers, who had increased mortality risk from intensive therapy.

Haptoglobin polymorphisms in Latin American populations

Several genetic polymorphisms of the haptoglobin gene (HP) or haptoglobin-related gene (HPR) were reported to show a population-specific distribution and to be associated with not only serum haptoglobin (HP) but also cholesterol levels. For such association studies, it is important to know the distribution of polymorphisms or their haplotypes in the populations concerned. However, no comprehensive genetic studies have explored this in Latin Americans, and not every human variation or genotype is available in a database. In this study, we determined the genotypes of common HP (HP¹ and HP²), HP^del, rs5471, rs5472, and rs2000999 in several Latin American populations. Haplotypes of rs5472-common HP-rs2000999 polymorphisms were estimated. We did not encounter any HP^del, and the frequencies of rs5471 A, rs5472 A, HP¹, and rs2000999 G were higher than their counterpart alleles in studied populations. All of the alleles with higher frequency in the Latin Americans are associated with higher serum HP and lower cholesterol levels. Both A-1-G (probably HP^1S) and G-1-G (probably HP^1F) haplotypes were higher in Latin American populations than those in other geographic regions. In addition, the genetic influx from populations of other continents into Peruvians seems to be relatively lower than that into other Latin Americans.

Assessment of haptoglobin alleles in autism spectrum disorders

Gene-environment interactions, by means of abnormal macromolecular intestinal adsorption, is one of the possible causes of autism spectrum disorders (ASD) predominantly in patients with gastrointestinal disorders. Pre-haptoglobin-2 (zonulin), encoded by the Haptoglobin (HP) allele-2 gene, enhances the intestinal permeability by modulation of intercellular tight junctions. The two alleles of HP, HP1 and HP2, differ for 2 extra exons in HP2 that result in exon duplication undetectable by classic genome-wide association studies. To evaluate the role of HP2 in ASD pathogenesis and to set up a method to discriminate HP alleles, Italian subjects with ASD (n = 398) and healthy controls (n = 379) were genotyped by PCR analysis; subsequently, the PCR results were integrated with microarray genotypes (Illumina Human Omni 1S-8), obtained using a subset from the same subjects, and then we developed a computational method to predict HP alleles. On the contrary to our expectations, there was no association between HP2 and ASD (P > 0.05), and there was no significant allele association in subjects with ASD with or without gastrointestinal disorders (P > 0.05). With the aid of bioinformatics analysis, from a window frame of ~2 Mb containing 314 SNPs, we obtain imputation accuracy (r²) between 0.4 and 0.9 (median 0.7) and correct predictions were between 70% and 100% (median 90%). The conclusions endorse that enhanced intestinal permeability in subjects with ASD should not be imputed to HP2 but to other members of the zonulin family and/or to environmental factors.

Tight junction modulation at the blood-brain barrier: Current and future perspectives

The blood-brain barrier (BBB) is the one of the most robust physical barriers in the body, comprised of tight junction (TJ) proteins in brain microvascular endothelial cells. The need for drugs to treat central nervous systems diseases is ever increasing, however the presence of the BBB significantly hampers the uptake of drugs into the brain. To overcome or circumvent the barrier, many kinds of techniques are being developed. Modulating the paracellular route by disruption of the TJ complex has been proposed as a potential drug delivery system to treat brain diseases, however, it has several limitations and is still in a developmental stage. However, recent significant advance in medical equipment /tools such as targeted ultra-sound technologies may resolve these limitations. In this review, we introduce recent advances in site- or molecular size-selective BBB disruption/modulation technologies and we include details on pharmacological inhibitory molecules against intercellular TJ proteins to modulate the BBB.

Involvement of haptoglobin phenotypes and genotypes in non-muscle invasive bladder cancer: A possible prognostic marker for risk stratification

The association of haptoglobin (Hp) with various cancers has been reported and also it has been documented that the Hp phenotypes/genotypes have different functional ability. So, we examined phenotypes/genotypes of Hp in newly diagnosed, untreated non-muscle invasive bladder cancer (NMIBC) patients and investigated its prognostic value for risk stratification of the cancer. In eighty NMIBC patients and 80 healthy individuals the Hp genotypes and phenotypes were analyzed using polymerase chain reaction (PCR) and two-dimensional gel electrophoresis (2D-GE), respectively. Besides, the presence of the Hpα1, α2, and β chains in the sera was confirmed by Mass Spectrometry (MS). The frequencies of the 1-1 and 2-2 genotypes/phenotypes were respectively higher and lower in healthy subjects compared to the patients. Our results revealed that the 2-2 genotype/phenotype could increase the risk of NMIBC. There was a positive association between the 2-2 genotype/phenotype with the T category/grade of cancer (p<0.05). The present study implied a strong association between the Hp phenotypes and genotypes with NMIBC. It was found that the 2-2 genotype and phenotype could be a risk factor for NMIBC incidence, as well as, progression. This study introduced Hp genotyping as a possible cost-effective and precise method for prognosis of individuals at the risk of NMIBC.

Serum haptoglobin correlates positively with cholesterol and triglyceride concentrations in an obese Mongolian population

BACKGROUND

Recent studies revealed that several genetic polymorphisms of haptoglobin gene (HP) and the haptoglobin-related protein gene (HPR) associated not only with haptoglobin (HP) but total, non-HDL, and/or LDL cholesterol concentrations in various populations.

METHODS

Association between serum HP concentrations and polymorphisms of HP and the HPR gene, or anthropometric and metabolic factors were examined in Mongolian participants (n = 927) using linear regression analyses.

RESULTS

The association of HP and HPR polymorphisms with serum HP concentration but not serum lipids concentrations was observed. However, subgroup analysis revealed that the association of HP and HPR polymorphisms with serum HP concentration was weakened in subgroup of obese (BMI ≥ 30) subjects and positive correlations between serum HP and non-HDL cholesterol, HDL cholesterol or triglyceride concentrations were observed in the obese subjects as compared with in subgroups of normal weight (BMI < 25) and overweight (25 ≤ BMI < 30) subjects.

CONCLUSION

The degree of obesity strongly affects the relationships between serum HP concentrations and several genetic, anthropometric and metabolic factors. These results suggested that we need to take into account the degree of obesity when considering the HP polymorphisms as predictive markers for clinical states.

Metabo groups in response to micronutrient intervention: Pilot study

Micronutrients and their metabolites are cofactors in proteins involved in lipid metabolism. The present study was a subproject of the Harmonized Micronutrient Project (ClinTrials.gov # NCT01823744). Twenty participants were randomly selected from 136 children and adolescents that consumed a daily dose of 12 vitamins and 5 minerals supplementation for 6 weeks. The 20 individuals were divided into two pools of 10 individuals, according to their lipid profile at baseline (Pool 1 with lower triglycerides, LDL, and VLDL). The individuals were analyzed at baseline, after 6 weeks of daily supplementation, and after 6 weeks of a washout period in relation to anthropometric, body composition, food intake, lipid profile, micronutrient levels, and iTRAQ proteomic data. Genetic ancestry and its association with vitamin serum levels were also determined. After supplementation, LDL levels decreased while alpha-tocopherol and pantothenic acid levels increased in pool 2; lipid profiles in pool 1 did not change but had higher plasma levels of pantothenic acid, pyridoxal, and pyridoxic acid. In pool 2, expression of some proteins increased, and expression of other ones decreased after intervention, while in pool 1, the same proteins responded inversely or did not change their levels. Plasma alpha-tocopherol and Native American genetic ancestry explained a significant fraction of LDL plasma levels at baseline and in response to the intervention. After intervention, changes in expression of alpha-1 antitrypsin, haptoglobin, Ig alpha-1 chain C region, plasma protease C1 inhibitor, alpha-1-acid glycoprotein 1, fibrinogen alpha, beta, and gamma-chain in individuals in pool 2 may be associated with levels of LDL and vitamin E. Vitamin E and Native American genetic ancestry may also be implicated in changes of vitamin E and LDL levels. The results of this pilot study must be validated in future studies with larger sample size or in in vitro studies.

Haptoglobin Phenotypes Are Associated with the Postload Glucose and Insulin Levels in Pediatric Obesity

PURPOSE

Haptoglobin (Hp) is a protein involved in the acute-phase reaction of inflammation. Humans have three major phenotypes (Hp1-1, Hp1-2, and Hp2-2). Several studies have shown altered Hp regulation in adults with obesity and metabolic alterations. The Hp2-2 phenotype is associated with a high cardiovascular risk. Our aim was to investigate if Hp levels and the Hp2-2 phenotype are associated with glucose metabolism in pediatric obesity.

METHODS

We retrospectively studied 192 participants (92 males and 100 females), aged 4-18 years. Clinical and biochemical data were collected. The Hp phenotype (Hp1-1, Hp1-2, and Hp2-2) was identified through Western immunoblot.

RESULTS

Subjects carrying Hp1-1, Hp1-2, and Hp2-2 phenotypes were 13.6, 50.8, and 35.6%, respectively. Hp serum, fasting glucose, and insulin levels, as well as HOMA-IR, were similar among groups. Postload glucose and insulin levels (as insulin AUC) were progressively higher from the Hp1-1 to Hp2-2 phenotype.

CONCLUSION

To our knowledge, this is the first study on Hp phenotypes conducted in a pediatric population with obesity. We showed that the presence of Hp2 allele is associated with a worse response of glucose load in terms of both glucose and insulin levels. Thus, the Hp2-2 phenotype could predispose in pediatrics, at the same degree of obesity, to a worse glycemic and insulinemic compensation.

Haptoglobin-2 variant increases susceptibility to acute respiratory distress syndrome during sepsis

Acute respiratory distress syndrome (ARDS) is an inflammatory lung disorder that frequently complicates critical illness and commonly occurs in sepsis. Although numerous clinical and environmental risk factors exist, not all patients with risk factors develop ARDS, raising the possibility of genetic underpinnings for ARDS susceptibility. We have previously reported that circulating cell-free hemoglobin (CFH) is elevated during sepsis, and higher levels predict worse outcomes. Excess CFH is rapidly scavenged by haptoglobin (Hp). A common HP genetic variant, HP2, is unique to humans and is common in many populations worldwide. HP2 haptoglobin has reduced ability to inhibit CFH-mediated inflammation and oxidative stress compared with the alternative HP1. We hypothesized that HP2 increases ARDS susceptibility during sepsis when plasma CFH levels are elevated. In a murine model of sepsis with elevated CFH, transgenic mice homozygous for Hp2 had increased lung inflammation, pulmonary vascular permeability, lung apoptosis, and mortality compared with wild-type mice. We then tested the clinical relevance of our findings in 496 septic critically ill adults, finding that HP2 increased ARDS susceptibility after controlling for clinical risk factors and plasma CFH. These observations identify HP2 as a potentially novel genetic ARDS risk factor during sepsis and may have important implications in the study and treatment of ARDS.