Search PubMed⌕ Search

Biomedical subjects

John D Potter

Publications and source records attributed to John D Potter.

At least 91 records · Page 5Linked to original sources
PubMed2004

Sex-specific differences in colon cancer associated with p53 mutations.

INTRODUCTION: Sex-specific differences in observed incidence rates, tumor subsite, and diet and lifestyle associations with colon cancer have been observed. We evaluate sex-specific associations with p53 mutations in colon cancer to add to understanding of these differences. Data from a large population-based incident case-control study of colon cancer were used to evaluate age and gender associations with p53 mutations. To obtain a better understanding of gender-specific associations, we evaluated the role of estrogen as a mediator of risk. For these analyses, women were classified as estrogen positive or negative, based on menopausal status and use of hormone replacement therapy (HRT). RESULTS: There was a significant interaction between age and sex and risk of an acquired p53 mutation compared with p53 Wt. Among men, there was an increase in p53 mutations with age, whereas among women the opposite was observed. Associations with parity, oral contraceptive use, and total ovulatory months were not associated with p53 mutations. However, recent use of HRT reduced risk of all tumors, as did being estrogen positive. Women who were estrogen positive (either premenopausal or recent users of HRT) were at a significantly increased risk of an acquired p53 mutation if they consumed a diet with a high sugar index (odds ratio = 2.94; 95% confidence interval = 1.47-5.89); similar increases in risk of p53 mutations were not observed for men or women who were estrogen negative. CONCLUSIONS: Although sex-specific associations were detected for acquired p53 mutations, they do not indicate a unique role of estrogens in the mutation of p53. These data are consistent with a role for estrogen in altering susceptibility to diet and lifestyle factors possibly via an insulin-related mechanism.

Age Factors↗
PubMed2004

Signatures of environmental exposures using peripheral leukocyte gene expression: tobacco smoke.

Functional biological markers of environmental exposures are important in epidemiological studies of disease risk. Such markers not only provide a measure of the exposure, they also reflect the degree of physiological and biochemical response to the exposure. In an observational study, using DNA microarrays, we show that it is possible to distinguish between 85 individuals exposed and unexposed to tobacco smoke on the basis of mRNA expression in peripheral leukocytes. Furthermore, we show that active exposure to tobacco smoke is associated with a biologically relevant mRNA expression signature. These findings suggest that expression patterns can be used to identify a complex environmental exposure in humans.

Adult↗
PubMed2004

Soy isoflavones do not modulate prostate-specific antigen concentrations in older men in a randomized controlled trial.

Mortality rates for prostate cancer are low in Asia but high in the West. One explanation is the high level of soy consumption in Asia. Soy isoflavones reduce prostate tumor growth in many, but not all, animal models. Elevated levels of serum prostate-specific antigen (PSA) are a marker of prostate tumor growth. Our objective was to determine whether 12-month soy isoflavone supplementation would alter serum PSA concentrations in healthy, older men. The parent study was a double-blinded, parallel-arm, randomized trial in which participants were assigned to consume either a soy protein drink providing 83 mg/day isoflavones (+ISO) or a similar drink with isoflavones removed (-ISO). Participants in the parent study were 85% men. Of the 128 men enrolled in the trial, 112 completed. These men were later contacted for consent to allow their stored sera to be analyzed for PSA and 81 men consented. We measured PSA in serum collected at 0 and 12 months using a commercial radioimmunometric assay. Serum PSA concentrations increased in both groups over the 12-month intervention, but the changes were similar: Geometric mean PSA concentration increased 0.5% more in the +ISO group than in the -ISO group (P = 0.94; 95% confidence interval = -17.3 to 22.2). The proportion of participants having a serum PSA velocity greater than 1 ng/ml/year was similar in the +ISO and -ISO groups (17.6% versus 12.8%; P = 0.54). We found no evidence that a 12-month 83 mg/day isoflavone treatment alters serum PSA concentration or velocity in seemingly healthy men aged 50-80 years.

Aged↗
PubMed2004

No evidence of an association of JC virus and colon neoplasia.

JC virus (JCV) is an ubiquitous human polyomavirus that frequently resides in the kidneys of healthy individuals and is excreted in the urine of a large proportion of the adult population. Polyomaviruses are associated with disease largely in immunocompromised individuals (progressive multifocal leukoencephalopathy). Colorectal cancers can show chromosome instability and it was hypothesized that JCV may account for some of this instability. We screened urine from 45 healthy donors and 233 colorectal cancer/normal tissue pairs for the presence of JCV sequences using a Taqman assay. This assay could detect 1 virus genome in 10 human genomes. In the urine samples, we found an infection rate of approximately 70%. The JCV isolates in these samples could be categorized into four JCV types (2B, 4, 7, and 8), none of which had a rearranged regulatory region. Among the colon tissues, one normal tissue (<0.5%) and none of the matched tumors tested positive for JCV. There is no evidence in these data to indicate that JCV is the cause of genetic instability in colorectal cancer.

Adult↗
PubMed2004

Effects of a moderate intensity exercise intervention on estrogen metabolism in postmenopausal women.

Physical activity has been associated with reduced breast cancer risk, potentially via hormonal pathways, and high urinary excretion of 2-hydroxyestrone (2-OH E(1)) relative to 16alpha-hydroxyestrone (16alpha-OH E(1)) also has been associated with reduced breast cancer risk. Studies suggest that body composition and exercise can influence estrogen metabolism. We determined the effects of a 12-month moderate intensity aerobic exercise intervention on urinary 2-OH E(1), 16alpha-OH E(1), and their ratio in overweight and obese, previously sedentary, postmenopausal women, ages 50-75 years. Women were randomized to a 12-month exercise intervention (n = 87) or stretching control group (n = 86); 170 completed the study. Urinary 2- and 16alpha-OH E(1) were measured in spot urines collected at baseline, 3, and 12 months. Body composition was measured at baseline and 12 months. Differences between exercisers and controls for excretion of estrogen metabolites were determined using general estimating equations. Further analyses assessed change in estrogen metabolites and their ratio by subgroups of change in body composition. Overall, there were no significant effects of the exercise intervention on 2-OH E(1), 16alpha-OH E(1), or their ratio (P > 0.05). There appeared to be an effect of change in intra-abdominal fat and adherence to the exercise intervention on change in the estrogen metabolites or their ratio. However, this did not reflect a potentially desirable change in estrogen metabolites associated with the exercise intervention. Thus, this 12-month moderate intensity exercise intervention did not significantly alter urinary excretion of 2-OH E(1), 16alpha-OH E(1), or their ratio in this population of women.

Aged↗
PubMed2004

Polymorphisms in PTGS1 (=COX-1) and risk of colorectal polyps.

Two isoforms of prostaglandin H synthase (PTGS = COX) are key enzymes in prostaglandin synthesis and primary targets for aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs). Use of aspirin or other NSAIDs is associated with a lower risk and reduced recurrence of colorectal adenomas, established precursors of adenocarcinoma. This study investigated risk of colorectal adenomatous and hyperplastic polyps associated with several polymorphisms in the coding region of PTGS1. Within the Minnesota polyp case-control study, patients with colorectal adenomatous (n = 521) or hyperplastic (n = 194) polyps and n = 621 polyp-free controls were genotyped for four PTGS1 polymorphisms (R8W, L15-L16del, P17L, L237M); these had been predicted to affect protein function based on sequence-homology software. Age- and sex-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were computed. Whereas there was no appreciable difference in adenoma or hyperplastic polyp risk associated with R8W, P17L, and L237M, an increased risk was observed for individuals heterozygous for the L15-L16del polymorphism (OR = 3.6, 95% CI 1.2-11.2). The variant L15-L16del allele appeared to be associated with a stronger increase in adenoma risk among nonusers of aspirin/other NSAIDs. The reduced risk observed with aspirin/other NSAID use was limited to those wild type for P17L [PP users: OR = 0.6 (0.5-0.8) versus PP nonusers: 1.0 (referent) (P interaction = 0.03)]. To our knowledge, this study represents the first investigation of polymorphisms in PTGS1 and risk of colorectal polyps. The L15-L16del variant allele may result in an increased risk of colorectal adenomas, whereas P17L may be relevant to the pharmacogenetics of aspirin. These preliminary findings require confirmation in larger studies of colorectal neoplasia.

Adenomatous Polyps↗
PubMed2004

Effect of exercise on serum androgens in postmenopausal women: a 12-month randomized clinical trial.

Postmenopausal women with elevated circulating androgen concentrations have an increased risk of developing breast cancer, yet interventions to reduce androgen levels have not been identified. We examined the effects of a 12-month moderate intensity exercise intervention on serum androgens. The study was a randomized clinical trial in 173 sedentary, overweight (body mass index > or = 24.0 kg/m(2), body fat > 33%), postmenopausal women, ages 50 to 75 years, not using hormone therapy and living in the Seattle, WA area. The exercise intervention included facility-based and home-based exercise (45 minutes, 5 days per week of moderate intensity sports/recreational exercise). A total of 170 (98.3%) women completed the study, with exercisers averaging 171 minutes per week of exercise. Women in the exercise and control groups experienced similar, nonsignificant declines in most androgens. Among women who lost >2% body fat, testosterone and free testosterone concentrations fell by 10.1% and 12.2% between baseline and 12 months in exercisers compared with a decrease of 1.6% and 8.0% in controls (P = 0.02 and 0.03 compared with exercisers, respectively). Concentrations of testosterone and free testosterone among exercisers who lost between 0.5% and 2% body fat declined by 4.7% and 10.4%. In controls who lost this amount of body fat, concentrations of testosterone and free testosterone declined by only 2.8% and 4.3% (P = 0.03 and 0.01 compared with exercisers, respectively). In summary, given similar levels of body fat loss, women randomized to a 12-month exercise intervention had greater declines in testosterone and free testosterone compared with controls. The association between exercise and breast cancer risk may be partly explained by the effects of exercise on these hormones.

Adipose Tissue↗
PubMed2004

Adherence to the AICR cancer prevention recommendations and subsequent morbidity and mortality in the Iowa Women's Health Study cohort.

In 1997, the American Institute for Cancer Research (AICR) published 14 recommendations related to diet for individuals to reduce cancer incidence on a global basis; smoking was also discouraged. We operationalized these into nine recommendations that are particularly relevant to western populations in a cohort of 29,564 women ages 55 to 69 years at baseline in 1986 who had no history of cancer or heart disease. The cohort was followed through 1998 for cancer incidence (n = 4,379), cancer mortality (n = 1,434), cardiovascular disease (CVD) mortality (n = 1,124), and total mortality (n = 3,398). The median number (range) of recommendations followed was 4 (0-8), and 33% of the cohort had ever smoked. Women who followed no or one recommendation compared with six to nine recommendations were at an increased risk of cancer incidence [relative risk (RR) 1.35, 95% confidence interval (CI) 1.15-1.58] and cancer mortality (RR 1.43, 95% CI 1.11-1.85), but there was no association with CVD mortality (RR 1.06, 95% CI 0.78-1.43). We calculated the population attributable risk (PAR) to estimate the proportion of cancer incidence, cancer mortality, and CVD mortality that theoretically would have been avoidable if the entire cohort had never smoked, had followed six to nine recommendations, or had done both. The PARs for smoking were 11% (95% CI 10-13) for cancer incidence, 21% (95% CI 17-24) for cancer mortality, and 20% (95% CI 16-23) for CVD mortality. The PARs for not following six to nine recommendations were 22% (95% CI 12-30) for cancer incidence, 11% (95% CI -5 to 24) for cancer mortality, and 4% (95% CI -20 to 19) for CVD mortality. When smoking and the operationalized AICR recommendations were combined together, the PARs were 31% (95% CI 19-37) for cancer incidence, 30% (95% CI 15-40) for cancer mortality, and 22% (95% CI 4-36) for CVD mortality. These data suggest that the adherence to the AICR recommendations, independently and in conjunction with not smoking, is likely to have a substantial public health impact on reducing cancer incidence and, to a lesser degree, cancer mortality at the population level.

Aged↗
PubMed2004

Insulin, macronutrient intake, and physical activity: are potential indicators of insulin resistance associated with mortality from breast cancer?

High levels of insulin have been associated with increased risk of breast cancer, and poorer survival after diagnosis. Data and sera were collected from 603 breast cancer patients, including information on diet and physical activity, medical history, family history, demographic, and reproductive risk factors. These data were analyzed to test the hypothesis that excess insulin and related factors are directly related to mortality after a diagnosis of breast cancer. The cohort was recruited from breast cancer patients treated at the British Columbia Cancer Agency between July 1991 and December 1992. Questionnaire and medical record data were collected at enrollment and outcomes were ascertained by linkage to the BC Cancer Registry after 10 years of follow-up. The primary outcome of interest was breast cancer-specific mortality (n = 112). Lifestyle data were analyzed using Cox proportional hazards regression models to relate risk factors to outcomes, controlling for potential confounders, such as age and stage at diagnosis. Data for biological variables were analyzed as a nested case-control study due to limited serum volumes, with at least one survivor from the same cohort as a control for each breast cancer death, matched on stage and length of follow-up. High levels of insulin were associated with poorer survival for postmenopausal women [odds ratio, 1.9; 95% confidence interval (CI), 0.7-6.6, comparing highest to lowest tertile, P trend = 0.10], while high dietary fat intake was associated with poorer survival for premenopausal women (relative risk, 4.8; 95% CI, 1.3-18.1, comparing highest to lowest quartile). Higher dietary protein intake was associated with better survival for all women (relative risk, 0.4; 95% CI, 0.2-0.8, comparing highest to lowest quartile).

Adult↗
PubMed2004

Raw versus cooked vegetables and cancer risk.

This review of the medical literature from 1994 to 2003 summarizes the relationship between raw and cooked vegetables and cancer risk and examines whether they may affect cancer risk differently. Twenty-eight studies examined the relationship between raw and cooked vegetables and risk for various cancers. Twenty-one studies assessed raw, but not cooked, vegetables and cancer risk. The majority of these assessed risk of oral, pharyngeal, laryngeal, esophageal, lung, gastric, and colorectal cancers. Most showed that vegetables, raw or cooked, were inversely related to these cancers. However, more consistent results were found for oral, pharyngeal, laryngeal, esophageal, and gastric cancers. Nine of the 11 studies of raw and cooked vegetables showed statistically significant inverse relationships of these cancers with raw vegetables, but only 4 with cooked vegetables. The few studies of breast, lung, and colorectal cancers also suggested an inverse relationship with both raw and cooked vegetables, but these results were less consistent. In the two studies of prostate cancer, there was no association with either raw or cooked vegetables. One of two bladder cancer studies found an inverse relationship with cooked, but not raw, vegetables. Possible mechanisms by which cooking affects the relationship between vegetables and cancer risk include changes in availability of some nutrients, destruction of digestive enzymes, and alteration of the structure and digestibility of food. Both raw and cooked vegetable consumption are inversely related to epithelial cancers, particularly those of the upper gastrointestinal tract, and possibly breast cancer; however, these relationships may be stronger for raw vegetables than cooked vegetables.

Case-Control Studies↗
PubMed2003

Waist-to-hip ratio and breast cancer mortality.

High insulin levels have been associated with increased risk of breast cancer and poorer survival after a breast cancer diagnosis. Waist-to-hip ratio (WHR) is a marker for insulin resistance and hyperinsulinemia. In this study, the authors tested the hypothesis that elevated WHR is directly related to breast cancer mortality. For identification of modifiable factors affecting survival, data were collected on 603 patients with incident breast cancer who visited the Vancouver Cancer Centre of the British Columbia Cancer Agency (Vancouver, British Columbia, Canada) in 1991-1992, including body measurements and information on demographic, medical, reproductive, and dietary factors. These patients were followed for up to 10 years. Cox proportional hazards regression models were used to relate the variables to breast cancer mortality (n = 112). After adjustment for age, body mass index, family history, estrogen receptor (ER) status, tumor stage at diagnosis, and systemic treatment (chemotherapy or tamoxifen), WHR was directly related to breast cancer mortality in postmenopausal women (for highest quartile vs. lowest, relative risk = 3.3, 95% confidence interval: 1.1, 10.4) but not in premenopausal women (relative risk = 1.2, 95% confidence interval: 0.4, 3.4). Stratification according to ER status showed that the increased mortality was restricted to ER-positive postmenopausal women. Elevated WHR was confirmed as a predictor of breast cancer mortality, with menopausal status and ER status at diagnosis found to be important modifiers of that relation.

Adult↗
PubMed2003

Associations of total energy and macronutrients with colon cancer risk in African Americans and Whites: results from the North Carolina colon cancer study.

The higher incidence of colon cancer in African Americans compared with other US racial/ethnic groups is largely unexplained. This report describes associations of total energy and macronutrients with colon cancer risk in African Americans and Whites from a case-control study in North Carolina between 1996 and 2000. Incident cases of histologically confirmed colon cancer, aged 40-80 years (n = 613), and matched controls (n = 996) were interviewed in person to elicit information on potential colon cancer risk factors. A validated food frequency questionnaire adapted to include regional foods was used to assess diet over the year prior to diagnosis or interview date. Cases generally reported higher mean daily intakes of total energy and macronutrients and lower dietary fiber consumption than did controls. Total energy intake was positively associated with colon cancer risk in both racial groups and, although there were some differences by race, high intakes of individual energy sources were also generally associated with two- to threefold increases in risk in models not controlled for total energy. However, these associations largely disappeared when total energy was taken into account. A high level of dietary fiber was associated with a statistically significant 50-60% risk reduction in African Americans and a nonsignificant 30% decreased risk in Whites. Alcohol intake was not statistically significantly associated with colon cancer in either racial group. Total energy intake was consistently associated with colon cancer risk, but associations with individual macronutrients varied somewhat by race and by adjustment for energy intake. These findings may provide an explanation for some of the racial differences in colon cancer incidence.

Adenocarcinoma↗
PubMed2003

Effects of a yearlong moderate-intensity exercise and a stretching intervention on sleep quality in postmenopausal women.

STUDY OBJECTIVES: To examine the effects of a moderate-intensity exercise or stretching intervention and changes in fitness, body mass index, or time spent outdoors on self-reported sleep quality and to examine the relationship between the amount and timing of exercise and sleep quality. DESIGN: A randomized intervention trial. SETTING: A cancer research center in Seattle, Washington. PARTICIPANTS: Postmenopausal, overweight or obese, sedentary women not taking hormone replacement therapy, aged 50 to 75 years, and recruited from the Seattle metropolitan area. INTERVENTIONS: A yearlong moderate-intensity exercise (n=87) and a low-intensity stretching (n=86) program. MEASUREMENTS AND RESULTS: Among morning exercisers, those who exercised at least 225 minutes per week had less trouble falling asleep (odds ratio [OR]: 0.3, P < or = .05) compared with those who exercised less than 180 minutes per week. However, among evening exercisers, those who exercised at least 225 minutes per week had more trouble falling asleep (OR: 3.3, P < or = .05) compared to those who exercised less than 180 minutes per week. Stretchers were less likely to use sleep medication (OR = 0.4, P < or = .05) and have trouble falling asleep (OR: 0.7, P < or = .10) during the intervention period compared with baseline. A greater than 10% versus a 1% or less increase in maximum O2 consumption over the year was associated with longer sleep duration (P < or = .05), less frequently falling asleep during quiet activities (P < or = .05), and less use of sleep medication (P < or = .05). Reductions in body mass index and increases in time spent outdoors had inconsistent effects on sleep quality. CONCLUSIONS: Both stretching and exercise interventions may improve sleep quality in sedentary, overweight, postmenopausal women. Increased fitness was associated with improvements in sleep. However, the effect of moderate-intensity exercise may depend on the amount of exercise and time of day it is performed.

Aged↗
PubMed2003

Reliability and validity of self-report of vitamin and mineral supplement use in the vitamins and lifestyle study.

In the United States, dietary supplements contribute a large proportion of micronutrient intakes. Therefore, it is important to collect accurate information on supplement use for studies of micronutrients and disease risk. This report describes the test-retest reliability and validity of a detailed, self-administered mailed questionnaire on vitamin and mineral supplement use. Participants (n = 220) completed the questionnaire at baseline and 3 months later. During an in-person interview, participants provided spot urine and blood samples, and interviewers transcribed nutrient information from their supplement bottle labels. The questionnaire had very good test-retest reliability for mean supplement intake over the past 10 years, with intraclass correlations ranging from 0.69 for beta-carotene to 0.87 for vitamin E. Pearson's correlation coefficients comparing current supplemental intakes from the questionnaire and interviews/label transcriptions were high, ranging from 0.58 for beta-carotene to 0.82 for chromium; however, for some nutrients, median intakes from the questionnaire were slightly lower than from the interviews. Beta-carotene, vitamin C, and vitamin E (alpha-tocopherol) showed clear linear trends of increasing blood concentrations with higher self-reported supplemental intakes (Pearson's correlation coefficients adjusted for potential confounding factors and diet = 0.31, 0.29, and 0.69, respectively; all p < 0.0001). Creatinine-adjusted spot urinary calcium values were not associated with supplemental calcium intakes (Pearson's r = -0.07). This self-administered questionnaire demonstrated high reproducibility and validity for collecting detailed information on supplement use.

Aged↗
PubMed2003

Long-term efficacy of sigmoidoscopy in the reduction of colorectal cancer incidence.

Screening sigmoidoscopy is associated with a reduction in both the incidence and mortality of colorectal cancer. Although current guidelines recommend sigmoidoscopy screening every 5 years, the duration of risk reduction is not known. We conducted a population-based case-control study to examine the association between sigmoidoscopy screening and colorectal cancer incidence. We collected information on screening history and risk factors from case patients with distal (n = 1026) and proximal (n = 642) colorectal cancer and from 1294 control subjects from October 1998 through February 2002. Screening sigmoidoscopy was associated with a statistically significant reduction in the incidence of distal colorectal cancer (odds ratio [OR] = 0.24, 95% confidence interval [CI] = 0.17 to 0.33). These reductions were sustained for up to 16 years with little attenuation. We also observed strong inverse associations between cancer incidence and sigmoidoscopy in analyses that included subjects with symptom-related tests. Current recommendations regarding the frequency of sigmoidoscopy screening may be unnecessarily aggressive.

Adult↗