Exposure to mitochondrial genotoxins and dopaminergic neurodegeneration in Caenorhabditis elegans.

Neurodegeneration has been correlated with mitochondrial DNA (mtDNA) damage and exposure to environmental toxins, but causation is unclear. We investigated the ability of several known environmental genotoxins and neurotoxins to cause mtDNA damage, mtDNA depletion, and neurodegeneration in Caenorhabditis elegans. We found that paraquat, cadmium chloride and aflatoxin B1 caused more mitochondrial than nuclear DNA damage, and paraquat and aflatoxin B1 also caused dopaminergic neurodegeneration. 6-hydroxydopamine (6-OHDA) caused similar levels of mitochondrial and nuclear DNA damage. To further test whether the neurodegeneration could be attributed to the observed mtDNA damage, C. elegans were exposed to repeated low-dose ultraviolet C radiation (UVC) that resulted in persistent mtDNA damage; this exposure also resulted in dopaminergic neurodegeneration. Damage to GABAergic neurons and pharyngeal muscle cells was not detected. We also found that fasting at the first larval stage was protective in dopaminergic neurons against 6-OHDA-induced neurodegeneration. Finally, we found that dopaminergic neurons in C. elegans are capable of regeneration after laser surgery. Our findings are consistent with a causal role for mitochondrial DNA damage in neurodegeneration, but also support non mtDNA-mediated mechanisms.

Association of prostate-specific antigen doubling time and cancer in men undergoing repeat prostate biopsy.

OBJECTIVES: To analyze the association between prostate-specific antigen doubling time with prostate cancer risk and grade among men with prostate-specific antigen levels ≥4.0 ng/mL undergoing repeat prostate biopsy. METHODS: A total of 286 patients with prostate-specific antigen ≥4 ng/mL and available prostate-specific antigen doubling time data, who underwent repeat prostate biopsy from 1996-2009, were included in this analysis. Prostate-specific antigen doubling time was divided into three groups: >9 years, 3-9 years and <3 years. Multivariate analyses of prostate-specific antigen doubling time with cancer risk and grade (≤3 + 4 vs ≥4 + 3) were carried out using logistic regression adjusting for prebiopsy prostate-specific antigen, race, age, digital rectal examination, year of biopsy and number of prior negative biopsies. RESULTS: The median prostate-specific antigen doubling time before biopsy was 4.5 years (interquartile range = 2.5-10). Shorter prostate-specific antigen doubling time was associated with higher prostate-specific antigen (P < 0.001), but it was unrelated to age, digital rectal examination or race. Shorter prostate-specific antigen doubling time as a continuous variable was associated with greater prostate cancer risk in both uni- (hazard ratio = 0.99, 95% confidence interval = 0.98-0.99, P = 0.001) and multivariate analysis (hazard ratio = 0.99, 95% confidence interval = 0.98-0.99, P = 0.004). The prevalence of cancer among prostate-specific antigen doubling time groups (>9, 3-9, <3 years) was 17%, 37% and 40%, respectively. Shorter prostate-specific antigen doubling time groups were associated with higher cancer risk (P = 0.001). Stratified by grade, short prostate-specific antigen doubling time as a continuous variable significantly predicted both low- (P = 0.010) and high-grade disease (P = 0.049). The inclusion of prostate-specific antigen doubling time groups in a multivariate model to predict biopsy positivity increased its accuracy from 0.69 to 0.74. CONCLUSION: Prostate-specific antigen doubling time seems to provide further cancer risk assessment in men undergoing repeat biopsy for prostate-specific antigen ≥4.0 ng/mL. If validated in future studies, the present findings support the use of prostate-specific antigen doubling time in the risk stratification of this patient population.

Dietary calcium and risk for prostate cancer: a case-control study among US veterans.

OBJECTIVE: The objective of this study was to examine the association between calcium intake and prostate cancer risk. We hypothesized that calcium intake would be positively associated with lower risk for prostate cancer. METHODS: We used data from a case-control study conducted among veterans between 2007 and 2010 at the Durham Veterans Affairs Medical Center. The study consisted of 108 biopsy-positive prostate cancer cases, 161 biopsy-negative controls, and 237 healthy controls. We also determined whether these associations differed for blacks and whites or for low-grade (Gleason score <7) and high-grade prostate cancer (Gleason score ≥7). We administered the Harvard food frequency questionnaire to assess diet and estimate calcium intake. We used logistic regression models to obtain odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Intake of calcium from food was inversely related to risk for prostate cancer among all races in a comparison of cases and biopsy-negative controls (P = .05) and cases and healthy controls (P = .02). Total calcium was associated with lower prostate cancer risk among black men but not among white men in analyses of healthy controls. The highest tertile of calcium from food was associated with lower risk for high-grade prostate cancer in a comparison of high-grade cases and biopsy-negative controls (OR, 0.37; 95% CI, 0.15-0.90) and high-grade cases and healthy controls (OR, 0.38; 95% CI, 0.17-0.86). CONCLUSION: Calcium from food is associated with lower risk for prostate cancer, particularly among black men, and lower risk for high-grade prostate cancer among all men.

The association of diabetes mellitus and high-grade prostate cancer in a multiethnic biopsy series.

OBJECTIVE: To analyze the association of diabetes mellitus (DM) with risk of prostate cancer and cancer grade among men undergoing prostate biopsy and to analyze how obesity and race modify these associations. MATERIALS AND METHODS: Retrospective analysis of 998 men from the Durham VA undergoing first prostate biopsy between 2001 and 2009 with complete data available. History of DM was determined by chart review. Patients' characteristics at biopsy were analyzed with chi-square and ranksum. Multivariable analyses of DM and risk of cancer and cancer grade were done using logistic regression adjusting for PSA, body mass index, race, age, year, and digital rectal exam. RESULTS: At biopsy, 284 (28%) men had DM. DM was associated with African American (AAM; p = 0.010) and higher BMI (p < 0.001). DM was not associated with prostate cancer risk on either bivariate (p = 0.600) or multivariate analysis (p = 0.485). Similar results were found after stratification by race and obesity. In multivariable analysis, DM was associated with greater risk of high-grade disease (RR = 2.13, p = 0.024). The association was stronger among obese men (RR = 3.84, p = 0.020) and null in non-obese subjects (RR = 1.39, p = 0.460). After further stratification by race, DM was associated with high-grade disease only in obese Caucasian men (CM; RR = 5.81, p = 0.025) but not in obese AAM. DM was not associated with risk of low-grade disease in all men together or after stratification by obesity or race. CONCLUSION: History of DM was associated with greater risk of high-grade disease. The association was strongest among obese CM suggesting the effect of DM on high-grade prostate cancer is modified by race and obesity.

A high ratio of dietary n-6/n-3 polyunsaturated fatty acids is associated with increased risk of prostate cancer.

Experimental studies suggest omega-3 (n-3) polyunsaturated fatty acids (PUFA) suppress and n-6 PUFA promote prostate tumor carcinogenesis. Epidemiologic evidence remains inconclusive. The objectives of this study were to examine the association between n-3 and n-6 PUFA and prostate cancer risk and determine if these associations differ by race or disease aggressiveness. We hypothesize that high intakes of n-3 and n-6 PUFA will be associated with lower and higher prostate cancer risk, respectively. A case-control study comprising 79 prostate cancer cases and 187 controls was conducted at the Durham VA Medical Center. Diet was assessed using a food frequency questionnaire. Logistic regression analyses were used to obtain odds ratios (ORs) and 95% confidence intervals (95% CI) for the associations between n-3 and n-6 PUFA intakes, the dietary ratio of n-6/n-3 fatty acids, and prostate cancer risk. Our results showed no significant associations between specific n-3 or n-6 PUFA intakes and prostate cancer risk. The highest dietary ratio of n-6/n-3 was significantly associated with elevated risk of high-grade (OR, 3.55; 95% CI, 1.18-10.69; P(trend) = 0.03), but not low-grade prostate cancer (OR, 0.95; 95% CI, 0.43-2.17). In race-specific analyses, an increasing dietary ratio of n-6/n-3 fatty acids correlated with higher prostate cancer risk among white men (P(trend) = 0.05), but not black men. In conclusion, our findings suggest that a high dietary ratio of n-6/n-3 fatty acids may increase the risk of overall prostate cancer among white men and possibly increase the risk of high-grade prostate cancer among all men.