The following are the supplementary data related to

The following are the supplementary data related to this article.
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Introduction Since the introduction of platinum-based chemotherapy, metastatic testicular cancer has become a curable disease and most testicular cancer patients have an excellent prognosis. However, long-term toxicity can undermine life after treatment of testicular cancer [1], [2]. Cardiovascular disease, e.g. myocardial infarction, is more prevalent in testicular cancer survivors in comparison with age-matched controls [3], [4]. Several studies have shown that testicular cancer survivors are prone to develop cardiovascular risk factors, often clustered in the metabolic syndrome, following orchidectomy and platinum-based chemotherapy [5], [6], [7], [8]. The metabolic syndrome comprises central obesity, dyslipidemia, hypertension and insulin resistance. Due to its pre-diabetic and pro-atherogenic characteristics, the metabolic syndrome forms a seedbed for cardiovascular disease. Studies in the general population have shown that low levels of testosterone are associated with metabolic syndrome [9], [10]. The relationship is probably bi-directional. On one hand, an increase in adipose tissue enhances aromatization of testosterone, thereby contributing to hypogonadism. On the other hand, testosterone and its more potent metabolite dihydrotestosterone have several regulatory functions in adipose tissue and lower levels of androgens may lead to adverse metabolic changes, such as central obesity and insulin resistance [11], [12]. Testosterone is also a vasoactive hormone, as well as a regulating factor in hbv and lipid metabolism [13], [14], [15]. Subclinical hypogonadism appears to be a prominent risk factor for the metabolic syndrome in testicular cancer survivors [16]. A substantial proportion of testicular cancer survivors have a deteriorated gonadal function after chemotherapy that may persist for >10 years [17], [18]. It is difficult to predict which cancer survivors would benefit from testosterone supplementation. In a recent study by Finkelstein et al. in which 198 healthy men received different amounts of testosterone, the authors concluded that the amount of testosterone required for maintaining lean mass, fat mass, strength, and sexual function varied widely in men and argued that more personalized approaches for treating hypogonadism are needed [19]. Genetic variations that result in functional changes in androgenic enzymes may explain why some patients are more at risk for hormonal or metabolic changes and may help identify patients that are more likely to benefit from interventions, like testosterone supplementation therapy. In a recent study by Aschim et al., it was shown that polymorphisms in genes involved in androgen metabolism may partially explain inter-individual differences in gonadal toxicity in testicular cancer survivors [20]. Functional single-nucleotide polymorphisms (SNPs) in steroid 5-α-reductase type II (SRD5A2) result in variations in enzymatic activity of 5-α-reductase type II, affecting the conversion of testosterone into dihydrotestosterone [21]. We investigated whether SNPs rs523349 (V89L) and rs9282858 (A49T) in SRD5A2 are associated with cardiometabolic status in testicular cancer survivors.
Patients and methods
Results
Discussion We found an association between SNP rs523349 in the gene SRD5A2 and the prevalence of the metabolic syndrome in testicular cancer survivors. Our findings suggest a role of impaired androgen metabolism in the etiology of the metabolic syndrome in testicular cancer patients after orchidectomy and cisplatin-based chemotherapy. The metabolic syndrome was present in 25% of the total testicular cancer survivor population studied, as reported earlier [7]. Patients with testosterone levels <15 nmol/l (22% the cohort) had an odds ratio of 4.1 (95% CI 1.8–9.3) for developing or having the metabolic syndrome after chemotherapy. The current study suggests that genetic variations related to the androgen metabolism are involved in the development of an adverse cardiometabolic profile after treatment for testicular cancer. The group of patients with both a low testosterone (<15 nmol/l) and the variant genotype for SNP rs523349 showed a high prevalence (66.7%) of the metabolic syndrome.