A large cross-sectional study of Asian men suggests that visceral adipose tissue is positively associated with prostate volume.
The Korean researchers noted in their paper, online in the Journal of Urology, that a longitudinal study is required to confirm the findings.
Dr Jin-ho Park of Seoul National University College of Medicine and colleagues say body mass index (BMI) is negatively associated with prostate specific antigen (PSA), possibly because of dilution via increased plasma volume.
There is some indication, however, that BMI in obesity is positively associated with prostate volume, which in turn is positively associated with PSA, although the obesity components have not been identified.
Obesity affects PSA
It's confusing, the authors acknowledge. "If obesity negatively affects PSA via hemodilution without positively influencing it, it would be difficult to explain the contradictory effect of obesity on PSA (negative effect) and PV (positive effect), especially since PV has a positive effect on PSA," they write.
To investigate, the team used transrectal ultrasound to estimate prostate volume in 6,389 men aged 30 to 79 years. Visceral and subcutaneous adipose tissue was measured by CT.
BMI, waist circumference and subcutaneous adipose tissue were inversely associated with PSA. Waist circumference and visceral and subcutaneous adipose tissue were positively associated with PSA mass.
BMI, waist circumference and subcutaneous adipose tissue negatively affected the PSA mass ratio - but the same was not true of visceral adipose tissue. When the researchers adjusted for visceral adipose tissue, BMI was not associated with prostate volume. But when they adjusted for BMI, the association between visceral adipose tissue and prostate volume remained.
BMI lower in Asian men
The researchers conclude, "Visceral adiposity is the main determining factor of the prostate volume increase and prostate specific antigen production."
"Controlling central obesity," they suggest, "may prevent prostate enlargement and its related discomforts."
Moreover, they advise, men "with central obesity and prostate enlargement are at greater risk for false-positive prostate cancer screening results due to the high basal PSA."
The results can't be generalised to all races, however. As the authors point out, "BMI tends to be lower in Asian men than in Western men and serum PSA is lower in Korean men than in white or black American men."
Obese prostate patients likely to die
Dr Lionel L. Banez, co-author of an accompanying editorial, agrees that findings in other races will need conformation.
Dr Banez of Duke University Medical Centre, Durham, North Carolina also told Reuters Health by email, "Understanding the complex relationship between obesity and prostate biology will be key to uncovering the reason why obese prostate cancer patients are more likely to die from their disease compared to their non-obese counterparts. If these findings are validated, the underlying mechanism by which visceral adiposity impacts prostate health truly deserves investigation."
Dr Park did not respond to requests for comments.
(David Douglas, Reuters Health, April 2012)