A lot of studies have been conducted to examine the association of genetic polymorphism and athletic performance. A recent study found that genetic variants of uncoupling proteins-2 and -3 were associated with VO2max in different sports. A study in 323 Russian athletes and 467 nonathletic controls found that monocarboxylate transporter 1 gene A1470T polymorphism was associated with VO2max. A cohort of 67 Chinese men in Singapore suggested that the angiotensin-converting enzyme (ACE) DD genotype in young adult Chinese males was associated with higher levels of VO2max. The ACE I/D polymorphism altered the response of muscle energy supply lines to exercise. AKT1 G205T genotype influenced obesity-related metabolic phenotypes and their responses to aerobic exercise training in older Caucasians. The Genathlete cohort found preliminary evidence that the hypoxia-inducible factor-1alpha Pro582Ser polymorphism may be associated with elite endurance athletes in Caucasian men. A study in 1,423 Russian athletes and 1,132 controls suggested that the likelihood of becoming an elite endurance athlete depended on the carriage of a high number of endurance-related alleles. The A2962G polymorphism of the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) gene was associated with VO2max at baseline, as carriers of the G allele had higher levels of VO2max than the AA group endurance capacity in Chinese men. The HERITAGE Family Study found that peroxisome proliferator-activated receptor-delta (PPARdelta) polymorphisms were associated with physical performance and plasma lipids.
The APOE gene polymorphisms were associated with diseases of the respiratory system and cardiovascular disease. Small lung volumes were prospectively associated with an increased risk for poor cognitive function and dementia in non-carriers of the APOE E4. Studies in transgenic mice showed that alpha-tocopherol transport in the lung was affected by the APOE genotype. APOE E4 and cardiorespitatory fitness could interact to influence child adiposity in 8-year-old children from the Tasmanian Infant Health Survey. Although meta-analyses suggest that APOE E4 carriers may have a 40–50% increased coronary artery disease risk, the associations reported in individual studies are highly heterogeneous. In the Tunisian population the APOE E4 appears to be only indirectly involved in the severity of cardiovascular disease. Although the prevalence of the APOE E4 allele is generally low, there are areas with higher prevalence of the APOE E4 allele and a higher incidence of adult ischemic heart disease mortality in Spain. An autopsy study suggested that the risk of developing and dying from cardiovascular disease, including coronary heart disease and cerebrovascular disease, was influenced by the APOE polymorphism. The APOE E2 genotype might contribute to increased risk of cardiovascular complications in subjects with acromegaly. The APOE genotype predicted cardiovascular endpoints in dialysis patients with type 2 diabetes mellitus. A meta-analysis of 45 studies including 13,940 cases and 16,364 controls found that APOE gene polymorphisms were associated with essential hypertension.
How did the APOE gene polymorphisms affect VO2max after exercise training? The exact mechanism behind it is still unclear. There is animal evidence that Apo E can affect exercise performance. Controversy exists as to relationship of APOE polymorphism to the blood lipid response to exercise[34, 35]. It was unlikely to explain the present results. Apo E mRNA is expressed in skeletal muscle and appears to be most abundant at neuromuscular junctions. Therefore the effect of APOE genotype on exercise capacity may have been mediated by more direct effects on other tissues such as skeletal muscle.
There are some limitations to the present study that should be noted. First of all, the present study lacked a control group, since this is a self-control study. Second, the sample size of this study is relatively small, which may not have enough statistical power to explore the real association. Third, we cannot exclude the possibility that some other genetic factor associated with APOE variants is responsible for the differences in the VO2max response. Finally, these results should be interpreted with caution because the population was only from China, which reduces the possibility of confounding from ethnicity, so it does not permit extrapolation of the results to other ethnic groups.