P.J. Talmud

Human gene for physical performance

A specific genetic factor that strongly influences human physical performance has not so far been reported, but here we show that a polymorphism in the gene encoding angiotensin-converting enzyme does just that. An ‘insertion’ allele of the gene is associated with elite endurance performance among high-altitude mountaineers. Also, after physical training, repetitive weight-lifting is improved eleven-fold in individuals homozygous for the ‘insertion’ allele compared with those homozygous for the ‘deletion’ allele.

Triglyceride-mediated pathways and coronary disease: Collaborative analysis of 101 studies

Summary Background Whether triglyceride-mediated pathways are causally relevant to coronary heart disease is uncertain. We studied a genetic variant that regulates triglyceride concentration to help judge likelihood of causality. Methods We assessed the −1131T>C (rs662799) promoter polymorphism of the apolipoprotein A5 (APOA5) gene in relation to triglyceride concentration, several other risk factors, and risk of coronary heart disease. We compared disease risk for genetically-raised triglyceride concentration (20 842 patients with coronary heart disease, 35 206 controls) with that recorded for equivalent differences in circulating triglyceride concentration in prospective studies (302 430 participants with no history of cardiovascular disease; 12 785 incident cases of coronary heart disease during 2·79 million person-years at risk). We analysed −1131T>C in 1795 people without a history of cardiovascular disease who had information about lipoprotein concentration and diameter obtained by nuclear magnetic resonance spectroscopy. Findings The minor allele frequency of −1131T>C was 8% (95% CI 7–9). −1131T>C was not significantly associated with several non-lipid risk factors or LDL cholesterol, and it was modestly associated with lower HDL cholesterol (mean difference per C allele 3·5% [95% CI 2·6–4·6]; 0·053 mmol/L [0·039–0·068]), lower apolipoprotein AI (1·3% [0·3–2·3]; 0·023 g/L [0·005–0·041]), and higher apolipoprotein B (3·2% [1·3–5·1]; 0·027 g/L [0·011–0·043]). By contrast, for every C allele inherited, mean triglyceride concentration was 16·0% (95% CI 12·9–18·7), or 0·25 mmol/L (0·20–0·29), higher (p=4·4×10−24). The odds ratio for coronary heart disease was 1·18 (95% CI 1·11–1·26; p=2·6×10−7) per C allele, which was concordant with the hazard ratio of 1·10 (95% CI 1·08–1·12) per 16% higher triglyceride concentration recorded in prospective studies. −1131T>C was significantly associated with higher VLDL particle concentration (mean difference per C allele 12·2 nmol/L [95% CI 7·7–16·7]; p=9·3×10−8) and smaller HDL particle size (0·14 nm [0·08–0·20]; p=7·0×10−5), factors that could mediate the effects of triglyceride. Interpretation These data are consistent with a causal association between triglyceride-mediated pathways and coronary heart disease. Funding British Heart Foundation, UK Medical Research Council, Novartis.

Apo B versus cholesterol in estimating cardiovascular risk and in guiding therapy: report of the thirty-person/ten-country panel.

There is abundant evidence that the risk of atherosclerotic vascular disease is directly related to plasma cholesterol levels. Accordingly, all of the national and transnational screening and therapeutic guidelines are based on total or LDL cholesterol. This presumes that cholesterol is the most important lipoprotein‐related proatherogenic risk variable. On the contrary, risk appears to be more directly related to the number of circulating atherogenic particles that contact and enter the arterial wall than to the measured concentration of cholesterol in these lipoprotein fractions. Each of the atherogenic lipoprotein particles contains a single molecule of apolipoprotein (apo) B and therefore the concentration of apo B provides a direct measure of the number of circulating atherogenic lipoproteins. Evidence from fundamental, epidemiological and clinical trial studies indicates that apo B is superior to any of the cholesterol indices to recognize those at increased risk of vascular disease and to judge the adequacy of lipid‐lowering therapy. On the basis of this evidence, we believe that apo B should be included in all guidelines as an indicator of cardiovascular risk. In addition, the present target adopted by the Canadian guideline groups of an apo B <90 mg dL−1 in high‐risk patients should be reassessed in the light of the new clinical trial results and a new ultra‐low target of <80 mg dL−1 be considered. The evidence also indicates that the apo B/apo A‐I ratio is superior to any of the conventional cholesterol ratios in patients without symptomatic vascular disease or diabetes to evaluate the lipoprotein‐related risk of vascular disease.

Association of Angiotensin-Converting Enzyme Gene I/D Polymorphism With Change in Left Ventricular Mass in Response to Physical Training

BACKGROUND The absence (deletion allele [D]) of a 287-base pair marker in the ACE gene is associated with higher ACE levels than its presence (insertion allele [I]). If renin-angiotensin systems regulate left ventricular (LV) growth, then individuals of DD genotype might show a greater hypertrophic response than those of II genotype. We tested this hypothesis by studying exercise-induced LV hypertrophy. METHODS AND RESULTS Echocardiographically determined LV dimensions and mass (n=140), electrocardiographically determined LV mass and frequency of LV hypertrophy (LVH) (n=121), and plasma brain natriuretic peptide (BNP) levels (n=49) were compared at the start and end of a 10-week physical training period in male Caucasian military recruits. Septal and posterior wall thicknesses increased with training, and LV mass increased by 18% (all P<.0001). Response magnitude was strongly associated with ACE genotype: mean LV mass altered by +2.0, +38.5, and +42.3 g in II, ID and DD, respectively (P<.0001). The prevalence of electrocardiographically defined LVH rose significantly only among those of DD genotype (from 6 of 24 before training to 11 of 24 after training, P<.01). Plasma brain natriuretic peptide levels rose by 56.0 and 11.5 pg/mL for DD and II, respectively (P<.001). CONCLUSIONS Exercise-induced LV growth in young males is strongly associated with the ACE I/D polymorphism.

Triglyceride-mediated pathways and coronary disease: collaborative analysis of 101 studies.

Summary Background Whether triglyceride-mediated pathways are causally relevant to coronary heart disease is uncertain. We studied a genetic variant that regulates triglyceride concentration to help judge likelihood of causality. Methods We assessed the −1131T>C (rs662799) promoter polymorphism of the apolipoprotein A5 (APOA5) gene in relation to triglyceride concentration, several other risk factors, and risk of coronary heart disease. We compared disease risk for genetically-raised triglyceride concentration (20 842 patients with coronary heart disease, 35 206 controls) with that recorded for equivalent differences in circulating triglyceride concentration in prospective studies (302 430 participants with no history of cardiovascular disease; 12 785 incident cases of coronary heart disease during 2·79 million person-years at risk). We analysed −1131T>C in 1795 people without a history of cardiovascular disease who had information about lipoprotein concentration and diameter obtained by nuclear magnetic resonance spectroscopy. Findings The minor allele frequency of −1131T>C was 8% (95% CI 7–9). −1131T>C was not significantly associated with several non-lipid risk factors or LDL cholesterol, and it was modestly associated with lower HDL cholesterol (mean difference per C allele 3·5% [95% CI 2·6–4·6]; 0·053 mmol/L [0·039–0·068]), lower apolipoprotein AI (1·3% [0·3–2·3]; 0·023 g/L [0·005–0·041]), and higher apolipoprotein B (3·2% [1·3–5·1]; 0·027 g/L [0·011–0·043]). By contrast, for every C allele inherited, mean triglyceride concentration was 16·0% (95% CI 12·9–18·7), or 0·25 mmol/L (0·20–0·29), higher (p=4·4×10−24). The odds ratio for coronary heart disease was 1·18 (95% CI 1·11–1·26; p=2·6×10−7) per C allele, which was concordant with the hazard ratio of 1·10 (95% CI 1·08–1·12) per 16% higher triglyceride concentration recorded in prospective studies. −1131T>C was significantly associated with higher VLDL particle concentration (mean difference per C allele 12·2 nmol/L [95% CI 7·7–16·7]; p=9·3×10−8) and smaller HDL particle size (0·14 nm [0·08–0·20]; p=7·0×10−5), factors that could mediate the effects of triglyceride. Interpretation These data are consistent with a causal association between triglyceride-mediated pathways and coronary heart disease. Funding British Heart Foundation, UK Medical Research Council, Novartis.

Angiotensin-converting-enzyme gene insertion/deletion polymorphism and response to physical training.

BACKGROUND The function of local renin-angiotensin systems in skeletal muscle and adipose tissue remains largely unknown. A polymorphism of the human angiotensin converting enzyme (ACE) gene has been identified in which the insertion (I) rather than deletion (D) allele is associated with lower ACE activity in body tissues and increased response to some aspects of physical training. We studied the association between the ACE gene insertion or deletion polymorphism and changes in body composition related to an intensive exercise programme, to investigate the metabolic effects of local human renin-angiotensin systems. METHODS We used three independent methods (bioimpedance, multiple skinfold-thickness assessment of whole-body composition, magnetic resonance imaging of the mid-thigh) to study changes in body composition in young male army recruits over 10 weeks of intensive physical training. FINDINGS Participants with the II genotype had a greater anabolic response than those with one or more D alleles for fat mass (0.55 vs -0.20 kg, p=0.04 by bioimpedance) and non-fat mass (1.31 vs -0.15 kg, p=0.01 by bioimpedance). Changes in body morphology with training measured by the other methods were also dependent on genotype. INTERPRETATION II genotype, as a marker of low ACE activity in body tissues, may conserve a positive energy balance during rigorous training, which suggests enhanced metabolic efficiency. This finding may explain some of the survival and functional benefits of therapy with ACE inhibitors.

Variation in the PPARα gene is associated with altered function in vitro and plasma lipid concentrations in Type II diabetic subjects

Aims/hypothesis. Peroxisome proliferator activated receptor alpha (PPARα) regulates genes involved in lipid metabolism, haemostasis and inflammation, in response to fatty acids and fibrates, making it a candidate gene for risk of dyslipidaemia, atherosclerosis and coronary artery disease. Plasma non-esterified fatty acids are increased in subjects with Type II (non-insulin-dependent) diabetes mellitus, suggesting that PPARα could link Type II diabetes and dyslipidaemia, and affect response to fibrates. This has been investigated in association studies in healthy and diabetic subjects and in vitro studies. Methods. The human PPARα gene was isolated and screened for variation by single strand conformation polymorphism analysis. Genotypes were determined for 129 Type II diabetic subjects and 2508 healthy men. The association with plasma lipid concentrations was examined. The function of the V162 variant was examined in co-transfection assays. Results. We identified two polymorphisms, one in intron 3 and a missense mutation, leucine 162 to valine, in the DNA binding domain. In Type II diabetic patients, V162 allele carriers had higher total cholesterol, HDL cholesterol and apoAI whereas intron 3 rare allele carriers had higher apoAI concentrations. By contrast, no effect was observed in healthy rare allele carriers. In vitro, the V162 variant showed greater transactivation of a reporter gene construct. Conclusion/interpretation. Naturally occurring variation alters PPARα function, influencing plasma lipid concentrations in Type II diabetic patients but not healthy people. This demonstrates that PPARα is a link between diabetes and dyslipidaemia, and so could influence the risk of coronary artery disease, the greatest cause of morbidity and mortality in Type II diabetes. [Diabetologia (2000) 43: 673–680]

The Insertion Allele of the ACE Gene I/D Polymorphism A Candidate Gene for Insulin Resistance?

BACKGROUND The insertion/deletion (ID) polymorphism of the angiotensin-converting enzyme (ACE) gene has been associated with increased coronary heart disease (CHD), although the mechanism of this association is not apparent. We tested the hypothesis that the deletion allele of the ACE gene is associated with insulin resistance. METHODS AND RESULTS We related ACE genotype to components of the insulin-resistance syndrome in 103 non-insulin-dependent diabetic (NIDDM) and 533 nondiabetic white subjects. NIDDM subjects with the DD genotype had significantly lower levels of specific insulin (DD 38.6, ID 57.1, and II 87.4 pmol.L-1 by ANOVA, P = .011). Non-insulin-treated subjects with the DD genotype had increased insulin sensitivity by HOMA % (DD 56.4%, II 29.4%, P = .027) and lower levels of des 31,32 proinsulin (DD 3.3, II 7.6 pmol.L-1, P = .012) compared with II subjects. There were no differences in prevalence of CHD or levels of blood pressure, serum lipids, or plasminogen activator inhibitor-1 (PAI-1) activity between the three ACE genotypes. In nondiabetic subjects there were no differences in insulin sensitivity, levels of insulin-like molecules, blood pressure, PAI-1, serum lipids, or CHD prevalence between the three ACE genotypes. CONCLUSIONS We conclude that increased cardiovascular risk of the DD genotype is not mediated through insulin resistance or abnormalities in fibrinolysis. Conversely, we report an increased sensitivity in NIDDM subjects with the ACE DD genotype.

Family History is a Coronary Heart Disease Risk Factor in the Second Northwick Park Heart Study

We have estimated the risk of coronary heart disease (CHD) from family history of CHD (FHCHD) in 2827 healthy European middle‐aged men, and explored the extent to which this can be explained by classical and genetic risk factors. Men with FHCHD (obtained by questionnaire) had a hazard ratio of CHD of 1.73 (95% confidence interval: 1.30, 2.31) compared to those without FHCHD; after adjusting for classical risk factors this did not change substantially. Those with FHCHD had 2.3% lower Factor VIIc (p = 0.03) and 1.14% higher systolic and 1.21% higher diastolic blood pressure (p = 0.04 and p = 0.02), with evidence of interaction between blood pressure and FHCHD status on risk (p = 0.01). The risk for those with a positive family history who were also current smokers was 3.01 compared to non‐smokers without FHCHD, which is greater than the risk posed by smoking or FHCHD alone (1.96 and 2.05 respectively compared to non‐smokers without FHCHD), but not significantly different from a multiplicative model (p‐value for interaction 0.33). Allele frequencies for 13 candidate gene variants were not significantly different between those with and without FHCHD. In those with FHCHD, current smokers who carried the APOE4 allele (e4+) had a hazard ratio of 5.66 compared to non‐smokers who had no FHCHD and were not APOE4+, with a significant interaction between smoking and APOE4 in those with FHCHD p = 0.001. These data demonstrate the complex interaction between genetic and environmental factors in determining CHD risk, and suggest that the causes of the familial clustering of CHD remain largely unexplained.

The Significant Increase in Cardiovascular Disease Risk in APOEɛ4 Carriers is Evident Only in Men Who Smoke: Potential Relationship Between Reduced Antioxidant Status and ApoE4

Data from 1668 men (316 cardiovascular disease events) from the Framingham Offspring Study was reanalysed, specifically examining APOE:smoking interactions. Overall hazard ratio (HR) for smoking was 1.95 (1.52, 2.50) compared to non‐smokers. Using ɛ3/3 as a referent group, in non‐smokers HRs for ɛ2 carriers (ɛ2+; 1.04 (0.61, 1.76) and ɛ4 carriers (ɛ4+; 1.04 (0.70, 1.54) showed no major risk increase. In smokers, HRs were 1.96 (1.26, 2.78) in ɛ3ɛ3 men, 3.46 (2.14, 5.60; p = 0.09 for interaction) in ɛ2+ and 3.81 (2.49, 5.84; p = 0.01 for interaction), with a significant interaction between daily cigarette consumption and APOE genotype on risk (p = 0.03). The potential mechanism for this APOEɛ4:smoking interaction was examined in a second study of 728 Caucasian patients with diabetes, where markers of reactive oxygen species were available. APOE genotype was not associated with plasma OX‐LDL or total antioxidant status (TAOS) in non‐smokers. However, in smokers ɛ4+ had 26.7% higher plasma OX‐LDL than other genotypes (APOE:smoking interaction p = 0.04), while ɛ2+ had 28.4% higher plasma TAOS than ɛ3ɛ3 and ɛ4+ combined (APOE:smoking interaction p = 0.026). Although direct extrapolation needs to be considered with caution, these results identify that the cardiovascular disease risk‐raising effect of ɛ4+ is confined to smokers, and a feasible mechanism is presented by the reduced antioxidant capacity/increased OX‐LDL of apoE4.