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.

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.

Molecular modeling of ARF6 dysregulation caused by mutations in IQSEC2

IQSEC2 gene mutations are associated with epilepsy, autism, and intellectual disability. The primary function IQSEC2, mediated via its Sec 7 domain, is to act as a guanine nucleotide exchange factor for ARF6. We sought to develop a molecular model, which may explain the aberrant Sec 7 activity on ARF6 of different human IQSEC2 mutations. We integrated experimental data of IQSEC2 mutants with protein structure prediction by the RaptorX server combined with molecular modeling and molecular dynamics simulations. Normally, apocalmodulin (apoCM) binds to IQSEC2 resulting in its N-terminal fragment inhibiting access of its Sec 7 domain to ARF6. An increase in Ca2+ concentration destabilizes the interaction of IQSEC2 with apoCM and removes steric hindrance of Sec 7 binding with ARF6. Mutations at amino acid residue 350 of IQSEC2 result in loss of steric hindrance of Sec 7 binding with ARF6 leading to constitutive activation of ARF6 by Sec 7. On the other hand, a mutation at amino acid residue 359 of IQSEC2 results in constitutive hindrance of Sec 7 binding to ARF6 leading to the loss of the ability of IQSEC2 to activate ARF6. These studies provide a model for dysregulation of IQSEC2 Sec 7 activity by mutant IQSEC2 proteins.Communicated by Ramaswamy H. Sarma.

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.

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.

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.

Housing of A350V IQSEC2 pups at 37 °C ambient temperature prevents seizures and permits the development of social vocalizations in adulthood

OBJECTIVES

Mutations in the human IQSEC2 gene are associated with drug-resistant epilepsy and severe behavioral dysfunction. We have focused on understanding one human IQSEC2 missense mutation (A350V) for which we have created a corresponding A350V IQSEC2 mouse model by CRISPR which demonstrates seizures when the mice are 15-20 days old and impaired social vocalizations in adulthood. We observed that a child with the A350V mutation stops having seizures when experiencing a fever of greater than 38 °C. In this study, we first sought to determine if we could recapitulate this phenomenon in A350V 15-20 day old mice using a previously established protocol to raise body temperature to 39 °C achieved by housing the mice at 37 °C. We then sought to determine if mice in whom seizure activity had been prevented as pups would develop social vocalization activity in adulthood.

METHODS

15-20 day old A350V male mice were housed either at 37 °C or 22 °C. Ultrasonic vocalizations of these mice were assessed at 8-10 weeks in response to a female stimulus.

RESULTS

Housing of 15-20 day old A350V mice at 37 °C resulted in a reduction in lethal seizures to 2% (1/41) compared to 45% (48/108) in mice housed at 22 °C, p = 0.0001. Adult A350V mice who had been housed at 37 °C as pups displayed a significant improvement in the production of social vocalizations.

CONCLUSION

Raising the body temperature by raising the ambient temperature might provide a means to reduce seizures associated with the A350V IQSEC2 mutation and thereby allow for an improved neurodevelopmental trajectory.

Reduction in seizure burden in a child with a A350V IQSEC2 mutation using heat therapy with a Jacuzzi

A child with a A350V IQSEC2 missense mutation resulting in drug-resistant epilepsy stops having seizures when he has a fever. We demonstrate that raising the body temperature of the child using a commercial Jacuzzi dramatically reduces his seizures and appears to improve his social behavioral interactions.

Pharmacological modulation of AMPA receptors rescues specific impairments in social behavior associated with the A350V Iqsec2 mutation

In this study we tested the hypothesis that pharmacological modulation of glutamatergic neurotransmission could rescue behavioral deficits exhibited by mice carrying a specific mutation in the Iqsec2 gene. The IQSEC2 protein plays a key role in glutamatergic synapses and mutations in the IQSEC2 gene are a frequent cause of neurodevelopmental disorders. We have recently reported on the molecular pathophysiology of one such mutation A350V and demonstrated that this mutation downregulates AMPA type glutamatergic receptors (AMPAR) in A350V mice. Here we sought to identify behavioral deficits in A350V mice and hypothesized that we could rescue these deficits by PF-4778574, a positive AMPAR modulator. Using a battery of social behavioral tasks, we found that A350V Iqsec2 mice exhibit specific deficits in sex preference and emotional state preference behaviors as well as in vocalizations when encountering a female mouse. The social discrimination deficits, but not the impaired vocalization, were rescued with a single dose of PF-4778574. We conclude that social behavior deficits associated with the A350V Iqsec2 mutation may be rescued by enhancing AMPAR mediated synaptic transmission.

Structural and functional brain-wide alterations in A350V Iqsec2 mutant mice displaying autistic-like behavior

IQSEC2 is an X-linked gene that is associated with autism spectrum disorder (ASD), intellectual disability, and epilepsy. IQSEC2 is a postsynaptic density protein, localized on excitatory synapses as part of the NMDA receptor complex and is suggested to play a role in AMPA receptor trafficking and mediation of long-term depression. Here, we present brain-wide structural volumetric and functional connectivity characterization in a novel mouse model with a missense mutation in the IQ domain of IQSEC2 (A350V). Using high-resolution structural and functional MRI, we show that animals with the A350V mutation display increased whole-brain volume which was further found to be specific to the cerebral cortex and hippocampus. Moreover, using a data-driven approach we identify putative alterations in structure-function relations of the frontal, auditory, and visual networks in A350V mice. Examination of these alterations revealed an increase in functional connectivity between the anterior cingulate cortex and the dorsomedial striatum. We also show that corticostriatal functional connectivity is correlated with individual variability in social behavior only in A350V mice, as assessed using the three-chamber social preference test. Our results at the systems-level bridge the impact of previously reported changes in AMPA receptor trafficking to network-level disruption and impaired social behavior. Further, the A350V mouse model recapitulates similarly reported brain-wide changes in other ASD mouse models, with substantially different cellular-level pathologies that nonetheless result in similar brain-wide alterations, suggesting that novel therapeutic approaches in ASD that result in systems-level rescue will be relevant to IQSEC2 mutations.

The Role of Haptoglobin Polymorphism in Cardiovascular Disease in the Setting of Diabetes

Atherosclerotic cardiovascular disease (CVD) is the major cause of morbidity and mortality in individuals with diabetes mellitus (DM). Preclinical models have suggested that excessive oxidative stress and hyperglycemia are directly responsible for this pathological association. However, numerous clinical trials involving the administration of high doses of the antioxidant vitamin E or attempts at strict glycemic control have failed to show a significant reduction of CVD in DM patients. We describe here a possible explanation for the failure of these trials, that being their lack of proper patient selection. The haptoglobin (Hp) genotype is a major determinant of the risk of CVD in the setting of DM. Treatment of individuals with the high-risk Hp genotype with antioxidants or aggressive glycemic control has shown benefit in several small studies. These studies suggest a precision medicine-based approach to preventing diabetes complications. This approach would have a profound effect on the costs of diabetes care and could dramatically reduce morbidity from diabetes.

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.

IQSEC2-Associated Intellectual Disability and Autism

Mutations in IQSEC2 cause intellectual disability (ID), which is often accompanied by seizures and autism. A number of studies have shown that IQSEC2 is an abundant protein in excitatory synapses and plays an important role in neuronal development as well as synaptic plasticity. Here, we review neuronal IQSEC2 signaling with emphasis on those aspects likely to be involved in autism. IQSEC2 is normally bound to N-methyl-D-aspartate (NMDA)-type glutamate receptors via post synaptic density protein 95 (PSD-95). Activation of NMDA receptors results in calcium ion influx and binding to calmodulin present on the IQSEC2 IQ domain. Calcium/calmodulin induces a conformational change in IQSEC2 leading to activation of the SEC7 catalytic domain. GTP is exchanged for GDP on ADP ribosylation factor 6 (ARF6). Activated ARF6 promotes downregulation of surface α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors through a c-jun N terminal kinase (JNK)-mediated pathway. NMDA receptors, AMPA receptors, and PSD-95 are all known to be adversely affected in autism. An IQSEC2 transgenic mouse carrying a constitutively active mutation (A350V) shows autistic features and reduced levels of surface AMPA receptor subunit GluA2. Sec7 activity and AMPA receptor recycling are presented as two targets, which may respond to drug treatment in IQSEC2-associated ID and autism.

Haptoglobin Phenotype Is Associated With High-Density Lipoprotein–Bound Hemoglobin Content and Coronary Endothelial Dysfunction in Patients With Mild Nonobstructive Coronary Artery Disease

Objective—

Coronary endothelial dysfunction (ED) is an early stage of atherosclerosis and is associated with impaired high-density lipoprotein (HDL) function. A functional polymorphism at the haptoglobin (Hp) gene locus (rs72294371) has been associated with marked differences in HDL structure and function. We sought to determine whether Hp phenotype was associated with coronary ED and whether the amount of hemoglobin (Hb) tethered to HDL via Hp was Hp-type dependent and associated with ED.

Approach and Results—

Microvascular and epicardial coronary endothelial function was assessed in 338 individuals with nonobstructive coronary artery disease. Microvascular ED was defined as <50% change in coronary blood flow and epicardial ED as ≥20% decrease in coronary artery diameter after intracoronary acetylcholine infusion. The amount of Hb bound to HDL was measured by ELISA after HDL purification from plasma samples using immune-affinity chromatography. One hundred and seventy of the individuals in this study (50.3%) were diagnosed with microvascular ED, 143 (42.3%) with epicardial ED, and 67 (19.7%) had diabetes mellitus (DM). Hp phenotype was significantly associated with microvascular ( P =0.01) and epicardial ED ( P =0.04) among DM individuals. There was a significant and inverse correlation between the amount of HDL-bound Hb and change in coronary blood flow (r=−0.40; P <0.0001) and in coronary artery diameter (r=−0.44; P <0.0001) in response to acetylcholine infusion. Hb content of HDL was significantly increased in individuals with Hp 2-2 and DM. In a logistic regression model, Hp 2-2 phenotype was associated with microvascular ED (odds ratio, 1.9; P =0.03) and the amount of HDL-bound Hb was an independent predictor of both microvascular (odds ratio, 4.6 for each 1-SD increase; P <0.0001) and epicardial (odds ratio, 2.2; P <0.0001) ED.

Conclusions—

Hp phenotype is significantly associated with coronary ED in DM individuals. This association is likely related to increased Hb tethering to HDL via Hp 2-2 in DM.

An IQSEC2 Mutation Associated With Intellectual Disability and Autism Results in Decreased Surface AMPA Receptors

We have recently described an A350V mutation in IQSEC2 associated with intellectual disability, autism and epilepsy. We sought to understand the molecular pathophysiology of this mutation with the goal of developing targets for drug intervention. We demonstrate here that the A350V mutation results in interference with the binding of apocalmodulin to the IQ domain of IQSEC2. We further demonstrate that this mutation results in constitutive activation of the guanine nucleotide exchange factor (GEF) activity of IQSEC2 resulting in increased production of the active form of Arf6. In a CRISPR generated mouse model of the A350V IQSEC2 mutation, we demonstrate that the surface expression of GluA2 AMPA receptors in mouse hippocampal tissue was significantly reduced in A350V IQSEC2 mutant mice compared to wild type IQSEC2 mice and that there is a significant reduction in basal synaptic transmission in the hippocampus of A350V IQSEC2 mice compared to wild type IQSEC2 mice. Finally, the A350V IQSEC2 mice demonstrated increased activity, abnormal social behavior and learning as compared to wild type IQSEC2 mice. These findings suggest a model of how the A350V mutation in IQSEC2 may mediate disease with implications for targets for drug therapy. These studies provide a paradigm for a personalized approach to precision therapy for a disease that heretofore has no therapy.

Association of the Haptoglobin Gene Polymorphism With Cognitive Function and Decline in Elderly African American Adults With Type 2 Diabetes: Findings From the Action to Control Cardiovascular Risk in Diabetes-Memory in Diabetes (ACCORD-MIND) Study

IMPORTANCE

African American individuals have higher dementia risk than individuals of white race/ethnicity. They also have higher rates of type 2 diabetes, which may contribute to this elevated risk. This study examined the association of the following 2 classes of alleles at the haptoglobin (Hp) locus that are associated with poor cognition, cardiovascular disease, and mortality: Hp 1-1 (associated with poor cognition and cerebrovascular disease) and Hp 2-1 and Hp 2-2 (associated with greater risk of myocardial infarction and mortality). An additional polymorphism in the promoter region of the Hp 2 allele, restricted to individuals of African descent, yields a fourth genotype, Hp 2-1m. African American adults have a higher prevalence of Hp 1-1 (approximately 30%) compared with individuals of white race/ethnicity (approximately 14%), but the potential role of the Hp genotype in cognition among elderly African American individuals with type 2 diabetes is unknown.

OBJECTIVE

To assess the association of the Hp genotypes with cognitive function and decline in elderly African American adults with type 2 diabetes.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used publicly available data and specimens from the Action to Control Cardiovascular Risk in Diabetes-Memory in Diabetes (ACCORD-MIND) study to investigate the association of the Hp genotypes with cognitive function and decline in 466 elderly African American participants with type 2 diabetes. The hypothesis was that the Hp 1-1 genotype compared with the other genotypes would be associated with more cognitive impairment and faster cognitive decline in elderly African American adults with type 2 diabetes. The initial ACCORD trial was performed from October 28, 1999, to September 15, 2014. This was a multicenter clinical study performed in an academic setting.

EXPOSURES

The Hp genotypes were determined from serum samples by polyacrylamide gel electrophoresis and by enzyme-linked immunosorbent assay.

MAIN OUTCOMES AND MEASURES

The Mini-Mental State Examination (MMSE) was used to measure cognitive function and change after 40 months. The MMSE score ranges from 0 to 30 points; higher scores represent better cognition. Associations were examined with analysis of covariance and linear regression, adjusting for age, sex, education, baseline glycated hemoglobin level, systolic blood pressure, diastolic blood pressure, cholesterol level, creatinine level, and treatment arm (intensive vs standard). The cognitive change model adjusted also for the baseline MMSE score.

RESULTS

Among 466 African American study participants (mean [SD] age, 62.3 [5.7] years), 64.8% were women, and the genotype prevalences were 29.4% (n = 137) for Hp 1-1, 36.1% (n = 168) for Hp 2-1, 10.9% (n = 51) for Hp 2-1m, and 23.6% (n = 110) for Hp 2-2. The groups differed in their baseline MMSE scores (P = .006): Hp 1-1 had the lowest MMSE score (mean [SE], 25.68 [0.23]), and Hp 2-1m had the highest MMSE score (mean [SE], 27.15 [0.36]). Using the least squares method, the 40-month decline was significant for Hp 1-1 (mean [SE], -0.41 [0.19]; P = .04) and for Hp 2-2 (mean [SE], -0.68 [0.21]; P = .001). However, the overall comparison across the 4 groups did not reach statistical significance for the fully adjusted model. The interaction of age with the Hp 1-1 genotype on MMSE score decline estimate per year change was significant (mean [SE], -0.87 [0.37]; P = .005), whereas it was not significant for Hp 2-1 (mean [SE], 0.06 [0.37]; P = .85), Hp 2-1m (mean [SE], -0.06 [0.51]; P = .89), and Hp 2-2 (mean [SE], -0.44 [0.41]; P = .29), indicating that cognitive decline in Hp 1-1 carriers was accentuated in older ages, whereas it was not significant for the other Hp genotypes.

CONCLUSIONS AND RELEVANCE

In this study, the Hp 1-1 genotype, which is 2-fold (approximately 30%) more prevalent among African American individuals than among individuals of white race/ethnicity, was associated with poorer cognitive function and greater cognitive decline than the other Hp genotypes. The Hp gene polymorphism may explain the elevated dementia risk in African American adults. The neuropathological substrates and mechanisms for these associations merit further investigation.

Meta-analysis of the association of the haptoglobin genotype with cardiovascular outcomes and the pharmacogenomic interactions with vitamin E supplementation

Objectives

The objectives of the study were to compile and summarize the data from all of the clinical trials designed to examine the association between haptoglobin (Hp) genotype and incidence of cardiovascular (CV) events in patients with diabetes mellitus (DM) and to assess the impact of vitamin E treatment on CV outcomes according to the Hp genotype.

Background

The Hp genotype could serve as a predictive biomarker to DM patients who may benefit from vitamin E therapy.

Methods

The electronic databases MEDLINE, PubMed, EMBASE and the Cochrane Library for Central Register of Clinical Trials were searched systematically using the following MESH terms: "haptoglobin genotype", "diabetes mellitus" and "cardiovascular events".

Results

Overall, 13 studies fit the inclusion criteria for this analysis, yielding a large study population that included 6,161 patients without Hp 2-2 and 4,684 patients with Hp 2-2. The analysis of these studies showed that the incidence of CV events in DM patients with the Hp 2-2 genotype was significantly increased as compared to non-Hp 2-2 patients in all three subgroups of case-control (OR: 2.2, 95% CI: 1.3-3.6; P=0.003), cohort (OR: 1.3, 95% CI: 1.2-1.5; P=0.001) and randomized controlled trials (OR: 1.6, 1.2-2.2; P=0.005). Among patients with the Hp 2-2 genotype, administration of vitamin E was associated with lower rates of CV events (OR: 0.66, 95% CI: 0.45-0.95; P=0.025). Further investigation into the association between Hp 2-2 and myocardial infarction, stroke, mortality and end-stage renal disease was also performed.

Conclusion

The Hp genotype is a risk factor for CV events in patients with DM, and administration of vitamin E appears to offer a low cost and accessible means of reducing CV events and mortality in this population.

Haptoglobin Genotype Is a Determinant of Hemoglobin Adducts and Vitamin E Content in HDL

Haptoglobin (Hp) is an abundant hemoglobin- (Hb-) binding serum protein and a constituent of the HDL proteome. In man, there exists a common polymorphism at the Hp locus with two common alleles defined by the presence (Hp 2 allele) or absence (Hp 1 allele) of a 1.7 kb in-frame partial duplication of exons 3 and 4 of the Hp gene. Numerous studies have demonstrated that the Hp 2-2 genotype is associated with a 3-5-fold increase in vascular disease among individuals with diabetes mellitus (DM). Increased Hp-Hb complex has been shown to be associated with the HDL of Hp 2-2 DM individuals. Hb-associated HDL has been proposed to result in the oxidation of HDL and the consumption of antioxidants in HDL, such as vitamin E, rendering the HDL further susceptible to oxidation. In this study, we set out to identify proteins which become cross-linked to Hb in HDL and to measure vitamin E in HDL as a function of the Hp genotype. We report on the identification of a novel 72 kd Hb reactive species which is cross-linked to HDL and demonstrate that vitamin E in HDL is decreased in Hp 2-2 DM individuals.

The Iron-Klotho-VDR Axis Is a Major Determinant of Proximal Convoluted Tubule Injury in Haptoglobin 2-2 Genotype Diabetic Nephropathy Patients and Mice

The haptoglobin (Hp) genotype (1-1 and 2-2) is a major determinant of nephropathy progression in diabetes mellitus patients. Hp 2-2 diabetic mice have impaired Hb clearance and increased iron deposits and oxidative stress in the proximal tubules (PCT), leading to increased renal injury. However, the precise mechanism of the PCT injury in diabetic nephropathy (DN) remains elusive. In the kidney, 1,25(OH)₂D3 suppresses the inflammatory response to renal tubular injury and requires normal renal expression of the α-klotho protein. In this study, we set out to test the hypothesis that the increased renal iron deposits in the PCT of Hp 2-2 DN affect the α-klotho-vitamin D receptor (VDR) axis and thereby exacerbates the PCT injury generated by the iron deposits. Immunohistochemical analysis of human and mouse kidney biopsies along with western blot analysis showed that the increased iron deposits in the PCT of the Hp 2-2 genotype were accompanied with significantly decreased α-klotho and VDR renal expression but significantly increased 1-α-hydroxylase renal expression. In conclusion, the iron-klotho-VDR axis is a major player in the mechanism contributing to iron-mediated PCT injury in diabetic Hp 2-2 mice and patients. Targeting this axis may open the way for new ideas regarding the pathogenesis and treatment of DN.

Evaluation of a course to prepare international students for the United States Medical Licensing Examination step 2 clinical skills exam

PURPOSE

United States (US) and Canadian citizens attending medical school abroad often desire to return to the US for residency, and therefore must pass US licensing exams. We describe a 2-day United States Medical Licensing Examination (USMLE) step 2 clinical skills (CS) preparation course for students in the Technion American Medical School program (Haifa, Israel) between 2012 and 2016.

METHODS

Students completed pre- and post-course questionnaires. The paired t-test was used to measure students' perceptions of knowledge, preparation, confidence, and competence in CS pre- and post-course. To test for differences by gender or country of birth, analysis of variance was used. We compared USMLE step 2 CS pass rates between the 5 years prior to the course and the 5 years during which the course was offered.

RESULTS

Ninety students took the course between 2012 and 2016. Course evaluations began in 2013. Seventy-three students agreed to participate in the evaluation, and 64 completed the pre- and post-course surveys. Of the 64 students, 58% were US-born and 53% were male. Students reported statistically significant improvements in confidence and competence in all areas. No differences were found by gender or country of origin. The average pass rate for the 5 years prior to the course was 82%, and the average pass rate for the 5 years of the course was 89%.

CONCLUSION

A CS course delivered at an international medical school may help to close the gap between the pass rates of US and international medical graduates on a high-stakes licensing exam. More experience is needed to determine if this model is replicable.

Anti-oxidative treatment with vitamin E improves peripheral vascular function in patients with diabetes mellitus and Haptoglobin 2-2 genotype: A double-blinded cross-over study

Vascular dysfunction in both conduit arteries and small vessels is a major contributor to the development of cardiovascular disease (CVD) in diabetes mellitus (DM). In diabetes there is a process of systemic chronic inflammation accompanied by high oxidative stress causing a subsequent decrease in vascular reactivity and negatively affect the metabolic processes responsible for functioning of the microvasculature. Vitamin E is classified as an antioxidant due to its ability to scavenge lipid radicals and terminate oxidative chain reactions. We conducted a double-blinded cross-over study with vitamin E versus placebo in individuals with type 2DM and the Hp2-2 genotype and assessed different aspects of peripheral vascular function in these patients. Twenty patients completed the study with 10 individuals in each study cohort. We were able to show significant improvement of indirect indices of vascular function following 8weeks of treatment with vitamin E. This improvement was consistent for weeks even after stopping the vitamin E treatment. We concluded that a pharmacogenomic rationale utilizing the Hp genotype might potentially provide cardiovascular benefit with vitamin E.

Developmental progression of intellectual disability, autism, and epilepsy in a child with an IQSEC2 gene mutation

The neurodevelopmental progression of a school‐aged child with a spontaneous IQSEC2 mutation has demonstrated apparent regression of milestones and language. Seizures associated with the disorder have been refractory to medical treatment. Late treatment of autism in this child has led to improved social skills.

Interaction Between the Haptoglobin Genotype and Vitamin E on Cardiovascular Disease in Diabetes

PURPOSE OF REVIEW

Despite compelling evidence regarding the importance of oxidant stress in the development of vascular complications and observational studies suggesting that vitamin E may be protective from these complications, multiple clinical trials have failed to show benefit from vitamin E supplementation in the prevention of vascular complications in diabetes. One possible explanation for this failure of vitamin E may have been inappropriate patient selection. This review seeks to provide the clinical evidence and mechanistic basis for why a subset of individuals defined by their haptoglobin (Hp) genotype may derive cardiovascular protection by vitamin E supplementation.

RECENT FINDINGS

Clinical trial data from the HOPE, ICARE, and WHS studies is presented showing a pharmacogenomic interaction between the Hp genotype and vitamin E on the development of CVD. Specifically, in individuals with diabetes and the Hp2-2 genotype, vitamin E has been shown to be associated with an approximately 35% reduction in CVD. Cardioprotection by vitamin E in individuals with the Hp2-2 genotype appears to be mediated in part by an improvement in HDL functionality as demonstrated in three independent trials in both type 1 diabetes and type 2 diabetes. Vitamin E may provide benefit in reducing CVD in Hp2-2 individuals with diabetes. However, in order for this pharmacogenomic algorithm to be accepted as a standard of care and used clinically, an additional large prospective study will need to be performed.

Haptoglobin 2-2 genotype and the risk of coronary artery disease in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications study (DCCT/EDIC)

AIMS/HYPOTHESIS

Haptoglobin(Hp) 2-2 genotype has been shown to increase coronary artery disease (CAD) risk in numerous type 2 diabetes studies but in only one type 1 diabetes cohort. We assessed the association of Hp2-2 with incident CAD over 26years of follow-up in 1303 Caucasian participants of the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study.

METHODS

DCCT randomized volunteers with type 1 diabetes to intensive versus conventional therapy within two cohorts: 'primary prevention' with 1-5years diabetes duration and 'secondary intervention' with 1-15years diabetes duration and early retinopathy, with or without albuminuria, but no advanced complications. CAD was defined as myocardial infarction (MI) or death judged to be from CAD, silent MI, angina, coronary revascularization, or congestive heart failure due to CAD.

RESULTS

In the entire DCCTcohort, Hp2-2 was not significantly associated with incident CAD or MI. However, in pre-specified exploratory subgroup analyses, an increased MI risk was suggested in the secondary cohort for those with Hp2-2.

CONCLUSIONS/INTERPRETATION

The analysis does not statistically confirm an overall association between Hp 2-2 and incident CAD, however, some suggestions of associations were observed in secondary analyses.

Haptoglobin phenotype as a predictive factor of mortality in diabetic haemodialysis patients

Introduction: The mortality rate in diabetic dialysis patients (DDPs) is over 15% per year, with the cause of death most often attributed to cardiovascular disease (CVD) or bacterial infection (sepsis). Identification of genetic markers predictive of early mortality would be useful in the evaluation of therapies for the reduction of mortality rate in this population. Haptoglobin (Hp) is a polymorphic protein which appears to confer differential susceptibility to bacterial infection and CVD. We therefore proposed that Hp phenotype can predict mortality in DDPs.

Methods: We tested this hypothesis prospectively in a longitudinal study of 392 dialysis patients from eight medical centres in Israel. Hp was determined by polyacrylamide gel electrophoresis. Patients were followed for all-cause mortality over a 3-year period.

Results: We found that Hp phenotype was a significant predictor of mortality in DDPs stratified by age. In diabetic individuals over 60 years of age there was a decrease in mortality associated with the Hp 1-1 phenotype ( P = 0.03). However, in younger DDPs the Hp 2-2 phenotype was associated with a decreased mortality rate ( P = 0.003).

Conclusion: Hp phenotype may be useful in the risk stratification algorithm and management of DDPs.

Haptoglobin 2-2 Genotype Is Associated With Cerebral Salt Wasting Syndrome in Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Haptoglobin (Hp) genotype has been shown to be a predictor of clinical outcomes in subarachnoid hemorrhage. Cerebral salt wasting (CSW) has been suggested to precede the development of symptomatic vasospasm.

OBJECTIVE

To determine if Hp genotype was associated with CSW and subsequent vasospasm after aneurysmal subarachnoid hemorrhage.

METHODS

Hp genotypic determination was done for patients admitted with a diagnosis of subarachnoid hemorrhage. Outcome measures included CSW, delayed cerebral infarction, and Glasgow Outcome Score of 4 to 5 at 30 days. Criteria for CSW included hyponatremia <135 mEq/L, and urine output >4 L in 12 hours with urine sodium >40 mEq/L.

RESULTS

A total of 133 patients were included in the study. The 3 Hp subgroups did not differ in terms of baseline characteristics. CSW occurred in 1 patient (3.4%) with Hp 1-1, 8 (14.0%) patients with Hp 2-1, and 15 (31.9%) patients with Hp 2-2 (P = .004). In the multivariate regression model, Hp 2-2 was associated with CSW (odds ratio [OR]: 4.94; CI: 1.78-17.43; P = .01), but Hp 2-1 was not (OR: 2.92; CI: 0.56-4.95; P = .15) compared with Hp 1-1. There were no associations between Hp genotypes and functional outcome or delayed cerebral infarction. CSW was associated with delayed cerebral infarction (OR: 7.46; 95% CI: 2.54-21.9; P < .001).

CONCLUSION

Hp 2-2 genotype was an independent predictor of CSW after subarachnoid hemorrhage. Because CSW is strongly associated with delayed cerebral infarction, the use of Hp genotype testing requires more investigation, and larger prospective confirmation is warranted. Additionally, a more objective definition of CSW needs to be delineated.

Effect of vitamin E supplementation on HDL function by haptoglobin genotype in type 1 diabetes: results from the HapE randomized crossover pilot trial

AIMS

Haptoglobin (Hp) genotype 2-2 increases cardiovascular diabetes complications. In type 2 diabetes, α-tocopherol was shown to lower cardiovascular risk in Hp 2-2, potentially through HDL function improvements. Similar type 1 diabetes data are lacking. We conducted a randomized crossover pilot of α-tocopherol supplementation on HDL function [i.e., cholesterol efflux (CE) and HDL-associated lipid peroxides (LP)] and lipoprotein subfractions in type 1 diabetes.

METHODS

Hp genotype was assessed in members of two Allegheny County, PA, type 1 diabetes registries and the CACTI cohort; 30 were randomly selected within Hp genotype, and 28 Hp 1-1, 31 Hp 2-1 and 30 Hp 2-2 were allocated to daily α-tocopherol or placebo for 8 weeks with a 4-week washout.

RESULTS

Baseline CE decreased with the number of Hp 2 alleles (p-trend = 0.003). There were no differences in LP or lipoprotein subfractions. In intention-to-treat analysis stratified by Hp, α-tocopherol increased CE in Hp 2-2 (β = 0.79, p = 0.03) and LP in Hp 1 allele carriers (β Hp 1-1 = 0.18, p = 0.05; β Hp 2-1 = 0.21, p = 0.07); reduced HDL particle size (β = -0.07, p = 0.03) in Hp 1-1 carriers; increased LDL particle concentration in Hp 1-1; and decreased it in Hp 2-2 carriers. However, no significant interactions were observed by Hp.

CONCLUSIONS

In this type 1 diabetes study, HDL function worsened with the number of Hp 2 alleles. α-Tocopherol improved HDL function in Hp 2-2 carriers and appeared to adversely affect lipid peroxides and lipoprotein subfractions among Hp 1 allele carriers. As no significant interactions were observed, findings require replication in larger studies.

The Risk of Coronary Heart Disease Associated With Glycosylated Hemoglobin of 6.5% or Greater Is Pronounced in the Haptoglobin 2-2 Genotype

BACKGROUND

Research targeting glycosylated hemoglobin A1c (HbA1c) to <6.5% to prevent coronary heart disease (CHD) events has conflicting results. We previously observed the haptoglobin (Hp) Hp2-2 genotype is associated with a ∼10-fold increased CHD risk among individuals with HbA1c ≥6.5%, and thus might be useful in identifying those at high risk of CHD who would benefit from maintaining HbA1c <6.5%.

OBJECTIVES

This study sought to model whether HbA1c ≥ 6.5% in the Hp2-2 genotype is associated with CHD in a prospective case-control study nested within the Health Professionals Follow-Up Study (HPFS).

METHODS

HbA1c concentration and Hp genotype were determined for 695 incident cases of CHD from 1994 to 2010 and matched control participants. Logistic regression models calculated relative risk (RR) and 95% CI, for the first and second halves of follow-up, adjusting for confounding variables. A dataset from the Nurses' Health Study served as a replication cohort.

RESULTS

The prevalence of the Hp2-2 genotype in HPFS was 39%. Compared with HbA1c <6.5%, the RR of CHD for HbA1c ≥6.5% for the Hp2-2 genotype over full follow-up was 3.07 (95% CI: 1.37 to 6.86) to 3.88 (95% CI: 1.31 to 11.52) during the first half of follow-up and 2.16 (95% CI: 0.61 to 7.61) in the second half. The corresponding RRs for the Hp1-1 + Hp2-1 genotypes were: full follow-up, 2.19 (95% CI: 1.14 to 4.24); first half, 1.60 (95% CI: 0.73 to 3.53); and second half, 4.72 (95% CI: 1.26 to 17.65).

CONCLUSIONS

In 2 independent cohorts, the risk of CHD associated with HbA1c ≥6.5% is pronounced in the Hp2-2 genotype, particularly in early cases. The Hp2-2 genotype may identify individuals at greatest CHD risk from hyperglycemia.

Abstract 42: Haptoglobin 2-2 Phenotype Is associated with Cerebral Salt Wasting Syndrome in Aneurysmal Subarachnoid Hemorrhage

INTRODUCTION: The Haptoglobin (Hp) phenotype has been shown to be a predictor of clinical outcomes in cerebrovascular disorders. We sought to determine if the Hp phenotype was predictive of cerebral salt wasting (CSW) following aneurysmal subarachnoid hemorrhage (SAH).

METHODS: Patients admitted with a diagnosis of SAH were divided into three groups based on their genetically determined Hp phenotype: 1-1, 2-1, and 2-2. Outcome measures included CSW, delayed cerebral infarction (DCI) and favorable outcome -Glasgow Outcome score (GOS) of 4-5 at 30 days. CSW was diagnosed by a clinician, and met the following criteria: hyponatremia 4 liters in 12 hours with urine sodium > 40 mEq/L. Pearson’s Chi Square and Wilcoxon-Mann-Whitney tests were used for categorical and continuous variables respectively. Logistic regression was used to assess association between Hp phenotype and SAH outcomes.

RESULTS: A total of 133 patients were included in the study. The distribution of Hp phenotype was- Hp 1-1: 29 (21.8%), Hp 2-1: 57 (42.9%), Hp 2-2: 47 (35.3%). The three Hp subgroups did not differ in terms of demographic variables, comorbidities or SAH characteristics. CSW occurred in 1 patient (3.4%) with Hp 1-1, 8 (14.0%) with Hp 2-1 and 15 (31.9%) with Hp 2-2 (p=0.004). In the multivariate analysis adjusted for age, sex, race, Hunt-Hess score and hydrocephalus, Hp 2-2 was associated with CSW (OR: 4.94 CI: 1.78-17.43, p=0.013) but Hp 2-1 was not (OR: 2.92, CI: 0.56-4.95, p=0.150). There were no associations between Hp phenotypes and favorable outcomes or DCI. CSW correlated strongly with development of DCI (OR: 7.16, OR: 2.48-20.62, p<0.001).

CONCLUSIONS: Hp 2-2 phenotype was an independent predictor of cerebral salt wasting following SAH. There were no associations between Hp phenotype and DCI or good functional outcome.

Pharmacogenomic interaction between the Haptoglobin genotype and vitamin E on atherosclerotic plaque progression and stability

OBJECTIVE

Homozygosity for a 1.7 kb intragenic duplication of the Haptoglobin (Hp) gene (Hp 2-2 genotype), present in 36% of the population, has been associated with a 2-3 fold increased incidence of atherothrombosis in individuals with Diabetes (DM) in 10 longitudinal studies compared to DM individuals not homozygous for this duplication (Hp 1-1/2-1). The increased CVD risk associated with the Hp 2-2 genotype has been shown to be prevented with vitamin E supplementation in man. We sought to determine if there was an interaction between the Hp genotype and vitamin E on atherosclerotic plaque growth and stability in a transgenic model of the Hp polymorphism.

METHODS AND RESULTS

Brachiocephalic artery atherosclerotic plaque volume was serially assessed by high resolution ultrasound in 28 Hp 1-1 and 26 Hp 2-2 mice in a C57Bl/6 ApoE(-/-) background. Hp 2-2 mice had more rapid plaque growth and an increased incidence of plaque hemorrhage and rupture. Vitamin E significantly reduced plaque growth in Hp 2-2 but not in Hp 1-1 mice with a significant pharmacogenomic interaction between the Hp genotype and vitamin E on plaque growth.

CONCLUSIONS

These results may help explain why vitamin E supplementation in man can prevent CVD in Hp 2-2 DM but not in non Hp 2-2 DM individuals.

Interaction between the Haptoglobin 2 Phenotype and Diabetes Mellitus on Systolic Pulmonary Arterial Pressure and Nitric Oxide Bioavailability in Hemodialysis Patients

Elevated systolic pulmonary artery pressure (s-PAP, ≥35 mmHg) serves as an independent predictor of mortality in hemodialysis (HD) and diabetic (DM) patients. A polymorphism in the antioxidant Haptoglobin (Hp) gene has been shown to regulate the bioavailability of nitric oxide (NO), a major mediator of pulmonary vascular tone. We therefore set out to test the hypothesis that the Hp polymorphism may be a determinant of developing elevated s-PAP specifically in the DM state due to a decreased bioavailability of NO. To test our hypothesis we Hp typed and performed transthoracic echocardiography on a series of HD patients and stratified them into elevated and normal s-PAP groups and then evaluated whether there was a significant association between the Hp type, elevated s-PAP, and decreased NO bioavailability as defined by low plasma nitrite. We found a statistically significant interaction between the Hp type and DM on the prevalence of elevated s-PAP and lower mean nitrite levels with the combination of elevated s-PAP and low nitrite levels being significantly more prevalent in Hp 2-2 DM individuals. We conclude that the Hp 2 type is associated with elevated s-PAP levels and low plasma nitrite levels in HD patients specifically in the DM state.

Presence of haptoglobin-2 allele is associated with worse functional outcomes after spontaneous intracerebral hemorrhage

OBJECTIVE

To determine if the haptoglobin (Hp) phenotype, which has been shown to be a predictor of clinical outcomes in cerebrovascular disorders, particularly subarachnoid hemorrhage, was predictive of functional outcomes after spontaneous intracerebral hemorrhage (ICH).

METHODS

Patients admitted with a diagnosis of ICH were prospectively included and divided into 3 groups based on their genetically determined Hp phenotype: 1-1, 2-1, and 2-2. Outcome measures included mortality and 30-day modified Rankin Scale scores. Demographics and outcomes were compared for each phenotype using multivariate linear regression analysis.

RESULTS

The study included 94 patients. The distribution of Hp phenotype was Hp 1-1, 12 (13%); Hp 2-1, 46 (49%); and Hp 2-2, 36 (38%). The 3 Hp subgroups did not differ in terms of demographic variables, comorbidities, or ICH characteristics. There was a nonsignificant trend toward increased mortality in Hp 2-1 and Hp 2-2 compared with Hp 1-1, with mortality of 8% in Hp 1-1, 17% in Hp 2-1, and 25% in Hp 2-2 (P = 0.408). In the regression model adjusted for confounders, Hp 2-1 (odds ratio = 0.05, 95% confidence interval = 0.01-0.47, P < 0.001) and Hp 2-2 phenotypes (odds ratio = 0.14, 95% confidence interval = 0.02-0.86, P = 0.045) had significantly lower odds of modified Rankin Scale scores 0-2 compared with Hp 1-1.

CONCLUSIONS

After ICH, individuals with the Hp-2 allele (2-1 and 2-2) had worse functional outcomes than individuals with the Hp-1 allele (Hp 1-1). There was a nonsignificant association between Hp phenotype and mortality. Larger prospective studies with better surrogates of ICH outcomes are warranted.

Haptoglobin genotype-dependent differences in macrophage lysosomal oxidative injury

The major function of the Haptoglobin (Hp) protein is to control trafficking of extracorpuscular hemoglobin (Hb) thru the macrophage CD163 receptor with degradation of the Hb in the lysosome. There is a common copy number polymorphism in the Hp gene (Hp 2 allele) that has been associated with a severalfold increased incidence of atherothrombosis in multiple longitudinal studies. Increased plaque oxidation and apoptotic markers have been observed in Hp 2-2 atherosclerotic plaques, but the mechanism responsible for this finding has not been determined. We proposed that the increased oxidative injury in Hp 2-2 plaques is due to an impaired processing of Hp 2-2-Hb complexes within macrophage lysosomes, thereby resulting in redox active iron accumulation, lysosomal membrane oxidative injury, and macrophage apoptosis. We sought to test this hypothesis in vitro using purified Hp-Hb complex and cells genetically manipulated to express CD163. CD163-mediated endocytosis and lysosomal degradation of Hp-Hb were decreased for Hp 2-2-Hb complexes. Confocal microscopy using lysotropic pH indicator dyes demonstrated that uptake of Hp 2-2-Hb complexes disrupted the lysosomal pH gradient. Cellular fractionation studies of lysosomes isolated from macrophages incubated with Hp 2-2-Hb complexes demonstrated increased lysosomal membrane oxidation and a loss of lysosomal membrane integrity leading to lysosomal enzyme leakage into the cytoplasm. Additionally, markers of apoptosis, DNA fragmentation, and active caspase 3 were increased in macrophages that had endocytosed Hp 2-2-Hb complexes. These data provide novel mechanistic insights into how the Hp genotype regulates lysosomal oxidative stress within macrophages after receptor-mediated endocytosis of Hb.

An enzyme linked immunosorbent assay (ELISA) for the determination of the human haptoglobin phenotype

BACKGROUND

Haptoglobin (Hp) is an abundant serum protein which binds extracorpuscular hemoglobin (Hb). Two alleles exist in humans for the Hp gene, denoted 1 and 2. Diabetic individuals with the Hp 2-2 genotype are at increased risk of developing vascular complications including heart attack, stroke, and kidney disease. Recent evidence shows that treatment with vitamin E can reduce the risk of diabetic vascular complications by as much as 50% in Hp 2-2 individuals. We sought to develop a rapid and accurate test for Hp phenotype (which is 100% concordant with the three major Hp genotypes) to facilitate widespread diagnostic testing as well as prospective clinical trials.

METHODS

A monoclonal antibody raised against human Hp was shown to distinguish between the three Hp phenotypes in an enzyme linked immunosorbent assay (ELISA). Hp phenotypes obtained in over 8000 patient samples using this ELISA method were compared with those obtained by polyacrylamide gel electrophoresis or the TaqMan PCR method.

RESULTS

Our analysis showed that the sensitivity and specificity of the ELISA test for Hp 2-2 phenotype is 99.0% and 98.1%, respectively. The positive predictive value and the negative predictive value for Hp 2-2 phenotype is 97.5% and 99.3%, respectively. Similar results were obtained for Hp 2-1 and Hp 1-1 phenotypes. In addition, the ELISA was determined to be more sensitive and specific than the TaqMan method.

CONCLUSIONS

The Hp ELISA represents a user-friendly, rapid and highly accurate diagnostic tool for determining Hp phenotypes. This test will greatly facilitate the typing of thousands of samples in ongoing clinical studies.

Vitamin E and diabetic nephropathy in mice model and humans

Diabetes mellitus (DM) is associated with increased oxidative stress due to elevated glucose levels in the plasma. Glucose promotes glycosylation of both plasma and cellular proteins with increased risk for vascular events. Diabetic patients suffer from a higher incidence of cardiovascular complications such as diabetic nephropathy. Haptoglobin (Hp) is an antioxidant plasma protein which binds free hemoglobin, thus preventing heme-iron mediated oxidation. Two alleles exist at the Hp gene locus (1 and 2) encoding three possible Hp genotypes that differ in their antioxidant ability, and may respond differently to vitamin E treatment. Several clinical studies to have shown that Hp 1-1 genotype is a superior antioxidant to the Hp 2-2 genotype and Hp 2-2 genotype is associated with a higher incidence of cardiovascular disease. Vitamin E was found to have beneficial effect in patient and mice with Hp 2-2 genotype. In this review we have summarized the results of our studies in patients with diabetic nephropathy treated with vitamin E and in diabetic mice with different haptoglobin genotypes.

Haptoglobin genotype and the rate of renal function decline in the diabetes control and complications trial/epidemiology of diabetes interventions and complications study

Many patients with type 1 diabetes develop renal disease despite moderately good metabolic control, suggesting other risk factors may play a role. Recent evidence suggests that the haptoglobin (HP) 2-2 genotype, which codes for a protein with reduced antioxidant activity, may predict renal function decline in type 1 diabetes. We examined this hypothesis in 1,303 Caucasian participants in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study. HP genotype was determined by polyacrylamide gel electrophoresis. Glomerular filtration rate was estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and albumin excretion based on timed urine samples. Participants were followed up for a mean of 22 years. HP genotype was significantly associated with the development of sustained estimated glomerular filtration rate (GFR) <60 mL/min/1.73 m(2) and with end-stage renal disease (ESRD), with HP 2-2 having greater risk than HP 2-1 and 1-1. No association was seen with albuminuria. Although there was no treatment group interaction, the associations were only significant in the conventional treatment group, where events rates were much higher. We conclude that the HP genotype is significantly associated with the development of reduced GFR and ESRD in the DCCT/EDIC study.

Patient selection and vitamin E treatment in diabetes mellitus

In diabetes, there is an increase in oxidative stress due to elevated glucose levels in the plasma. High glucose promotes glycosylation, of both plasma and cellular proteins, which particularly affects the endothelial-cell lining of the blood vessel wall and interferes with its normal function. Thus, diabetes mellitus patients suffer from a higher incidence of cardiovascular complications such as atherosclerosis as compared with the nondiabetic population. Haptoglobin (Hp) is a plasma protein that binds free hemoglobin and prevents heme-iron mediated oxidation. There are three different types of Hp, which differ in their antioxidant ability. Several clinical studies have shown that the Hp 2-2 genotype is associated with higher incidence of cardiovascular diseases among diabetics. Vitamin E, a low-cost, easy-to-use antioxidant, was found to decrease the risk of developing cardiovascular diseases in Hp 2-2 diabetic patients. This review summarizes several studies that show the importance of vitamin E supplementation in a specific subgroup of patients, diabetic individuals carrying the Hp 2-2 genotype.

Is the Hp 2-2 diabetic mouse model a good model to study diabetic nephropathy?

Diabetic nephropathy (DN) is the leading cause of end stage renal disease and dialysis worldwide. Despite aggressive treatment, the number of patients on hemodialysis due to type 1 and type 2 diabetes mellitus is increasing annually. The lack of reliable animal models that mimic human disease has delayed the identification of specific factors that cause or predict DN. Different investigators around the world are testing different murine models. Validation criteria for early and advanced DN, phenotypic methods, background strain have recently been developed. Establishment of an authentic mouse model of DN will undoubtedly facilitate the understanding of the underlying genetic mechanisms that contribute to the development of DN and to study new treatments. Here we describe the characteristics of our new mouse model with type 1 diabetes mellitus and different haptoglobin genotypes that can mimic human DN.

Vitamin E in the prevention of cardiovascular disease: the importance of proper patient selection

Vitamin E is a naturally occurring fat-soluble antioxidant which has been proposed as a treatment for both primary and secondary protection against cardiovascular (CV) events. Promising data from observational epidemiological studies associating higher vitamin E dietary intake with lower risk of CV events have not been validated in randomized controlled clinical trials assessing the effect of vitamin E on CV outcomes. While the pendulum of medical opinion has swung to suggest that high dose vitamin E supplements have no place in the treatment and prevention of CV disease, new data is emerging that allows identification of a specific target population for this treatment, namely patients with diabetes mellitus and the haptoglobin genotype 2-2. This review details the scientific basis and clinical evidence related to the effect of vitamin E on CV outcomes, and the importance of proper patient selection in gaining therapeutic benefit from this intervention.

Haptoglobin genotype is a consistent marker of coronary heart disease risk among individuals with elevated glycosylated hemoglobin

OBJECTIVES

This study sought to investigate into the biologically plausible interaction between the common haptoglobin (Hp) polymorphism rs#72294371 and glycosylated hemoglobin (HbA(1c)) on risk of coronary heart disease (CHD).

BACKGROUND

Studies of the association between the Hp polymorphism and CHD report inconsistent results. Individuals with the Hp2-2 genotype produce Hp proteins with an impaired ability to prevent oxidative injury caused by elevated HbA(1c).

METHODS

HbA(1c) concentration and Hp genotype were determined for 407 CHD cases matched 1:1 to controls (from the NHS [Nurses' Health Study]) and in a replication cohort of 2,070 individuals who served as the nontreatment group in the ICARE (Prevention of Cardiovascular Complications in Diabetic Patients With Vitamin E Treatment) study, with 29 CHD events during follow-up. Multivariate models were adjusted for lifestyle and CHD risk factors as appropriate. A pooled analysis was conducted of NHS, ICARE, and the 1 previously published analysis (a cardiovascular disease case-control sample from the Strong Heart Study).

RESULTS

In the NHS, Hp2-2 genotype (39% frequency) was strongly related to CHD risk only among individuals with elevated HbA(1c) (≥ 6.5%), an association that was similar in the ICARE trial and the Strong Heart Study. In a pooled analysis, participants with both the Hp2-2 genotype and elevated HbA(1c) had a relative risk of 7.90 (95% confidence interval: 4.43 to 14.10) for CHD compared with participants with both an Hp1 allele and HbA(1c) <6.5% (p for interaction = 0.004), whereas the Hp2-2 genotype with HbA(1c) <6.5% was not associated with risk (relative risk: 1.34 [95% confidence interval: 0.73 to 2.46]).

CONCLUSIONS

Hp genotype was a significant predictor of CHD among individuals with elevated HbA(1c).

Haptoglobin genotype and cardiovascular outcomes in diabetes mellitus - natural history of the disease and the effect of vitamin E treatment. Meta-analysis of the medical literature

BACKGROUND

Diabetes mellitus carries a high risk for vascular events. Diabetics with different haptoglobin (Hp) types may carry different risk profiles, and may respond differently to vitamin E treatment. We aim to summarize the evidence about cardiovascular risk in diabetic patients, according to their Hp type, and the effect of vitamin E treatment on these sub-groups.

METHODS

We searched MEDLINE and on-going trials' databases until February 2011; gray literature; reference lists of identified articles; and experts. Two investigators screened and selected studies that prospectively followed cardiovascular outcomes in diabetic patients with different Hp types (natural history analysis), and randomized controlled trials reporting the effect of vitamin E on cardiovascular outcomes in diabetics, in which Hp typing was performed (interventional analysis).

RESULTS

Five and three studies, comprising 1829 and 2110 patients, were eligible for the natural history and the interventional analyses, respectively. The percentage of diabetic patients experiencing non-fatal MI, stroke, or cardiovascular death was significantly higher in the Hp 2-2 population (odds ratio (OR) 2.03 (95% confidence interval (CI) 1.46 to 2.81)). In patients with Hp 2-2 genotype, the OR for a combined endpoint was 0.66 in favor of the vitamin E treated group (95% CI 0.48 to 0.9). This effect was not shown in other Hp types.

CONCLUSION

Hp type 2-2 carries a high risk of cardiovascular events in diabetic patients. A pharmacogenomic approach towards treatment of diabetic patients with vitamin E may be warranted.

Poor lysosomal membrane integrity in proximal tubule cells of haptoglobin 2-2 genotype mice with diabetes mellitus

The haptoglobin (Hp) genotype is a major determinant of progression of nephropathy in individuals with diabetes mellitus (DM). The major function of the Hp protein is to bind and modulate the fate of extracorpuscular hemoglobin and its iron cargo. We have previously demonstrated an interaction between the Hp genotype and the DM on the accumulation of iron in renal proximal tubule cells. The primary objective of this study was to determine the intracellular localization of this iron in the proximal tubule cell and to assess its potential toxicity. Transmission electron microscopy demonstrated a marked accumulation of electron-dense deposits in the lysosomes of proximal tubules cells in Hp 2-2 DM mice. Energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to perform elemental analysis of these deposits and demonstrated that these deposits were iron rich. These deposits were associated with lysosomal membrane lipid peroxidation and loss of lysosomal membrane integrity. Vitamin E administration to Hp 2-2 DM mice resulted in a significant decrease in both intralysosomal iron-induced oxidation and lysosomal destabilization. Iron-induced renal tubular injury may play a major role in the development of diabetic nephropathy and may be a target for slowing the progression of renal disease.

HDL dysfunction in diabetes: causes and possible treatments

HDL is known to be inversely correlated with cardiovascular disease due to its diverse antiatherogenic functions. These functions include cholesterol efflux and reverse cholesterol transport, antioxidative and anti-inflammatory activities. However, HDL has been shown to undergo a loss of function in several pathophysiological states, as in the acute phase response, obesity and chronic inflammatory diseases. Some of these diseases were also shown to be associated with increased risk for cardiovascular disease. One such disease that is associated with HDL dysfunction and accelerated atherosclerosis is diabetes mellitus, a disease in which the HDL particle undergoes diverse structural modifications that result in significant changes in its function. This review will summarize the changes that occur in HDL in diabetes mellitus and how these changes lead to HDL dysfunction. Possible treatments for HDL dysfunction are also briefly described.