title: Association of aromatase (TTTAn) repeat polymorphism length and the relationship between obesity and decreased sperm concentration.
abstract: BACKGROUND
  Obesity in men is associated with low sperm count, however, this finding is inconsistent. Here, we describe length of the short tandem repeat aromatase (CYP19A1) polymorphism and its relationship to increased weight and sperm count.
  
  
  METHODS
  A cohort of 215 men was recruited from the community and BMI, hormone levels and sperm parameters were determined at enrollment. Men (196) were genotyped for length of the tetranucleotide TTTA repeats polymorphism (TTTA(n)), defined as short (S ≤ 7 repeats) or long (L > 7 repeats). Genotypes were categorized using allele combinations as 'low repeats' = S-S, or 'high repeats' = S-L/L-L. Weight and sperm parameters were examined in relation to size of TTTA(n) repeat.
  
  
  RESULTS
  Mean (±SD) age was 29.8 ± 8.6 years and mean BMI was 25.6 ± 4.6 kg/m(2). Men with high repeats had higher estradiol (E(2)) levels (98.0 ± 33.36 pmol/l) than men with low repeats (85.9 ± 26.61 pmol/l; P= 0.026). Lower FSH levels tended to be present in men with high repeats versus men with low repeats (P= 0.052). After stratification by genotype, a negative correlation between BMI and sperm count (Pearson's coefficient = 0.406) was seen only among men with high repeats (P= 0.019). Only men with high repeats exhibited increased E(2) with increased weight. A decrease in testosterone: E(2) ratio with increasing BMI was more pronounced in men with high versus low, repeats (R(2) = 0.436 versus 0.281).
  
  
  CONCLUSIONS
  Higher TTTA repeat numbers (>7 repeats) in the aromatase gene are associated with a negative relationship between obesity and sperm count. The effect of obesity on E(2) and sperm count appears to be absent in men with low (≤7) repeats.
authors.affiliation: Division of Reproductive Endocrinology and Infertility, University of Utah, Salt Lake City, UT, USA. ahmad.hammoud@hsc.utah.edu
authors.forename: Ahmad O
authors.initials: AO
authors.lastname: Hammoud
authors.forename: Jeanine
authors.initials: J
authors.lastname: Griffin
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Meikle
authors.forename: Mark
authors.initials: M
authors.lastname: Gibson
authors.forename: C Matthew
authors.initials: CM
authors.lastname: Peterson
authors.forename: Douglas T
authors.initials: DT
authors.lastname: Carrell
mesh_terms: D000328:Adult; D001141:Aromatase / Q000235:genetics*; D015992:Body Mass Index; D004958:Estradiol / Q000097:blood; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D009765:Obesity / Q000235:genetics*; D050177:Overweight / Q000235:genetics; D011110:Polymorphism, Genetic; D013076:Sperm Count; D013739:Testosterone / Q000097:blood
chemical_list: D013739:Testosterone; D004958:Estradiol; D001141:Aromatase