Shany Blum

Vitamin E supplementation reduces cardiovascular events in a subgroup of middle-aged individuals with both type 2 diabetes mellitus and the haptoglobin 2-2 genotype: a prospective double-blinded clinical trial.

Objective—Clinical trials of vitamin E have failed to demonstrate a decrease in cardiovascular events. However, these studies did not address possible benefit to subgroups with increased oxidative stress. Haptoglobin (Hp), a major antioxidant protein, is a determinant of cardiovascular events in patients with Type 2 diabetes mellitus (DM). The Hp gene is polymorphic with 2 common alleles, 1 and 2. The Hp 2 allelic protein product provides inferior antioxidant protection compared with the Hp 1 allelic product. We sought to test the hypothesis that vitamin E could reduce cardiovascular events in DM individuals with the Hp 2-2 genotype, a subgroup that comprises 2% to 3% of the general population. Methods and Results—1434 DM individuals ≥55 years of age with the Hp 2-2 genotype were randomized to vitamin E (400 U/d) or placebo. The primary composite outcome was myocardial infarction, stroke, and cardiovascular death. At the first evaluation of events, 18 months after initiating the study, the primary outcome was significantly reduced in individuals receiving vitamin E (2.2%) compared with placebo (4.7%; P=0.01) and led to early termination of the study. Conclusions—Vitamin E supplementation appears to reduce cardiovascular events in individuals with DM and the Hp 2-2 genotype (ClinicalTrials.gov NCT00220831).

Haptoglobin: Basic and Clinical Aspects

Haptoglobin is an abundant hemoglobin-binding protein present in the plasma. The function of haptoglobin is primarily to determine the fate of hemoglobin released from red blood cells after either intravascular or extravascular hemolysis. There are two common alleles at the Hp genetic locus denoted 1 and 2. There are functional differences between the Hp 1 and Hp 2 protein products in protecting against hemoglobin-driven oxidative stress that appear to have important clinical significance. In particular, individuals with the Hp 2-2 genotype and diabetes mellitus appear to be at significantly higher risk of microvascular and macrovascular complications. A pharmacogenomic strategy of administering high dose antioxidants specifically to Hp 2-2 DM individuals may be clinically effective.

Correction of HDL Dysfunction in Individuals With Diabetes and the Haptoglobin 2-2 Genotype

OBJECTIVE—Pharmacogenomics is a key component of personalized medicine. The Israel Cardiovascular Events Reduction with Vitamin E Study, a prospective placebo-controlled study, recently demonstrated that vitamin E could dramatically reduce CVD in individuals with diabetes and the haptoglobin (Hp) 2-2 genotype (40% of diabetic individuals). However, because of the large number of clinical trials that failed to demonstrate benefit from vitamin E coupled with the lack of a mechanistic explanation for why vitamin E should be beneficial only in diabetic individuals with the Hp 2-2 genotype, enthusiasm for this pharmacogenomic paradigm has been limited. In this study, we sought to provide such a mechanistic explanation based on the hypothesis that the Hp 2-2 genotype and diabetes interact to promote HDL oxidative modification and dysfunction. RESEARCH DESIGN AND METHODS—Hb and lipid peroxides were assessed in HDL isolated from diabetic individuals or mice with the Hp 1-1 or Hp 2-2 genotypes. HDL function was assessed based on its ability to promote cholesterol efflux from macrophages. A crossover placebo-controlled study in Hp 2-2 diabetic humans and in Hp 1-1 and Hp 2-2 diabetic mice assessed the ability of vitamin E to favorably modify these structural and functional parameters. RESULTS—Hb and lipid peroxides associated with HDL were increased and HDL function was impaired in Hp 2-2 diabetic individuals and mice. Vitamin E decreased oxidative modification of HDL and improved HDL function in Hp 2-2 diabetes but had no effect in Hp 1-1 diabetes. CONCLUSIONS—Vitamin E significantly improves the quality of HDL in Hp 2-2 diabetic individuals.

Vitamin E reduces cardiovascular disease in individuals with diabetes mellitus and the haptoglobin 2-2 genotype

AIMS Individuals with both diabetes mellitus (DM) and the Haptoglobin (Hp) 2-2 genotype are at increased risk of cardiovascular disease. As the antioxidant function of the Hp 2-2 protein is impaired, we sought to test the pharmacogenomic hypothesis that antioxidant vitamin E supplementation would provide cardiovascular protection to Hp 2-2 DM individuals. MATERIALS & METHODS We determined the Hp genotype on DM participants from two trials (HOPE and ICARE) and assessed the effect of vitamin E by Hp genotype on their common prespecified outcome, the composite of stroke, myocardial infarction and cardiovascular death. Data was analyzed with a fixed-effect model. These results were input into a simulation model, the Evidence Based Medicine Integrator, in order to estimate their long-term implications in a real-world population from Kaiser Permanente (CA, USA). RESULTS Meta-analysis of the two trials demonstrated a significant overall reduction in the composite end point in Hp 2-2 DM individuals with vitamin E (odds ratio: 0.58; 95% CI: 0.40-0.86; p = 0.006). There was a statistically significant interaction between the Hp genotype and vitamin E on the composite end point. In these trials, Hp typing of 69 DM individuals and treating those with the Hp 2-2 with vitamin E prevented one myocardial infarct, stroke or cardiovascular death. Lifelong administration of vitamin E to Hp 2-2 DM individuals in the Kaiser population would increase their life expectancy by 3 years. CONCLUSION A pharmacogenomic strategy of screening DM individuals for the Hp genotype and treating those with Hp 2-2 with vitamin E appears to be highly clinically effective.

Haptoglobin Genotype Is a Regulator of Reverse Cholesterol Transport in Diabetes In Vitro and In Vivo

Two common alleles exist at the haptoglobin (Hp) locus, and the Hp2 allele is associated with an increased incidence of cardiovascular disease, specifically in diabetes mellitus (DM). Oxidative stress is increased in Hp2 mice and humans with DM. Oxidative modification of the apolipoprotein A-I inhibits reverse cholesterol transport. We sought to test the hypothesis that reverse cholesterol transport is impaired in Hp2 DM mice and humans. In vitro, using serum from non-DM and DM individuals, we measured cholesterol efflux from 3H-cholesterol–labeled macrophages. In vivo, we injected 3H-cholesterol–loaded macrophages intraperitoneally into non-DM and DM mice with the Hp1-1 or Hp2-2 genotype and monitored 3H-tracer levels in plasma, liver, and feces. In vitro, in DM individuals only, we observed significantly decreased cholesterol efflux from macrophages incubated with serum from Hp2-1 or Hp2-2 as compared with Hp1-1 individuals (P<0.01). The interaction between Hp type and DM was recapitulated using purified Hp and glycated Hb. In vivo, DM mice loaded with 3H-cholesterol–labeled macrophages had a 40% reduction in 3H-cholesterol in plasma, liver, and feces as compared with non-DM mice (P<0.01). The reduction in reverse cholesterol transport associated with DM was significantly greater in Hp2-2 mice as compared with Hp1-1 mice (54% versus 25% in plasma; 52% versus 27% in liver; 57% versus 32% in feces; P<0.03). reverse cholesterol transport is decreased in Hp2-2 DM. This may explain in part the increased atherosclerotic burden found in Hp2-2 DM individuals.

Effect of a Mediterranean Meal on Postprandial Carotenoids, Paraoxonase Activity and C-Reactive Protein Levels

Background and Aim: Atherosclerosis involves oxidative and inflammatory mediators regulated by fat and antioxidants. Therefore, we studied the postprandial evolution of plasma lipids, carotenoids, C-reactive protein (CRP), and human serum paraoxanase activity (PON1) following two different fatty meals. Subjects and Methods: Eight healthy males consumed a 45% fat 1,000 Kcal Mediterranean-like (Med) meal (monounsaturated 61% of fat) compared to a Western-like (Wes) (saturated 57% of fat) meal. Blood was collected at baseline (time 0) 2, 4 and 7 h postprandial. Plasma lipids, glucose, insulin, total carotenoids, CRP, and PON1 were analyzed. Results: There was a marginal increase in cholesterol and glucose after both meals. Triglycerides increased modestly (to less than 200 mg/dl) and insulin increased (more in the Wes-like meal) but still within normal range, indicating a low glycemic index for both meals. Only the Med-like meal resulted in a significant increase in both PON1 activity (16%, p < 0.02) and carotenoids (74%, p < 0.02) with a 2-hour postprandial decrease in CRP (6%, p < 0.02). Conclusion: A postprandial monounsaturated fatty acid rich meal increases both plasma carotenoids and PON1 with a decrease in CRP levels, thus providing a novel potential explanation to the protective properties of a Mediterranean diet against atherogenesis.

Vitamin E therapy results in a reduction in HDL function in individuals with diabetes and the haptoglobin 2-1 genotype

OBJECTIVE Vitamin E provides cardiovascular protection to individuals with diabetes and the haptoglobin 2-2 genotype but appears to increase cardiovascular risk in individuals with diabetes and the haptoglobin 2-1 genotype. We have previously demonstrated that the haptoglobin protein is associated with HDL and that HDL function and its oxidative modification are haptoglobin genotype dependent. We set out to test the hypothesis that the pharmacogenetic interaction between the haptoglobin genotype on cardiovascular risk might be secondary to a parallel interaction between the haptoglobin genotype and vitamin E on HDL function. RESEARCH DESIGN AND METHODS Fifty-nine individuals with diabetes and the haptoglobin 2-1 or 2-2 genotypes were studied in a double-blind placebo controlled crossover design. Participants were treated with either vitamin E (400IU) or placebo for 3 months and crossed over for an equivalent duration. Serum was collected at baseline and after the completion of each treatment. HDL functionality as well as HDL associated markers of oxidation and inflammation were measured after each interval in HDL purified from the cohort. RESULTS Compared to placebo, vitamin E significantly increased HDL function in haptoglobin 2-2 but significantly decreased HDL function in haptoglobin 2-1. This pharmacogenetic interaction was paralleled by similar non-significant trends in HDL associated lipid peroxides, glutathione peroxidase, and inflammatory cargo. CONCLUSION There exists a pharmacogenetic interaction between the haptoglobin genotype and vitamin E on HDL function (clinicaltrials.gov NCT01113671).

Dual Therapy With Statins and Antioxidants Is Superior to Statins Alone in Decreasing the Risk of Cardiovascular Disease in a Subgroup of Middle-Aged Individuals With Both Diabetes Mellitus and the Haptoglobin 2-2 Genotype

Diabetes Mellitus (DM) is associated with a state of increased oxidative stress.1 Paradoxically, however, antioxidants have not been found to provide CVD benefit to DM individuals in several prospective clinical trials.2–11 However, the inability to demonstrate benefit may have been attributable to inadequate patient selection as antioxidants may only benefit those with particularly high levels of oxidative stress.12 A polymorphism in the Haptoglobin (Hp) gene, an antioxidant protein, appears to permit identification of individuals with high oxidative stress and who may benefit from antioxidant therapy.13 There exists 2 classes of alleles at the Hp genetic locus, 1 and 2, and the antioxidant capacity of the Hp 2 protein is inferior to the Hp 1 protein.14–18 Robust clinical data has shown that individuals homozygous for the Hp 2 allele (Hp 2-2 genotype), 40% of DM individuals, have an up to 500% increased risk of CVD.19–22 A vast amount of basic science, animal, and epidemiological data has provided the logic for targeting vitamin E administration specifically to DM individuals with the Hp 2-2 genotype.13 Most importantly we have recently reported in the ICARE study (Israel CArdiovascular events Reduction with vitamin E [ClinicalTrials.gov# NCT00220831]) a prospective randomized placebo controlled trial of vitamin E therapy in DM individuals with the Hp 2-2 genotype, that vitamin E therapy results in a 50% reduction in CVD events.22 …

The cardioprotective efficacy of TVP1022 in a rat model of ischaemia/reperfusion

Because myocardial infarction is a major cause of morbidity and mortality worldwide, protecting the heart from the ischaemia and reperfusion (I/R) damage is the focus of intense research. Based on our in vitro findings showing that TVP1022 (the S‐enantiomer of rasagiline, an anti‐Parkinsonian drug) possesses cardioprotective effects, in the present study we investigated the hypothesis that TVP1022 can attenuate myocardial damage in an I/R model in rats.

Pharmacogenomics in prevention of diabetic cardiovascular disease: utilization of the haptoglobin genotype in determining benefit from vitamin E.

Numerous large clinical trials have been carried out over the past several years testing the ability of the antioxidant vitamin E to prevent diabetic cardiovascular disease. Meta-analysis of these studies has demonstrated that vitamin E does not provide any cardiovascular protection and may be associated with an increase in mortality. However, these studies did not address possible benefit to subgroups with increased oxidative stress. In this review we provide supporting clinical evidence and a mechanistic basis for utilizing a genetic marker, the haptoglobin genotype, in determining whether vitamin E therapy may or may not be beneficial for a given patient with diabetes.