Biomedical subjects

Kumar B Rajan

Publications and source records attributed to Kumar B Rajan.

8 recordsLinked to original sources

PubMed2006

Moderate-intensity exercise reduces the incidence of colds among postmenopausal women.

PURPOSE: Our aim was to assess the effect of a moderate-intensity, year-long exercise program on the risk of colds and other upper respiratory tract infections in postmenopausal women. SUBJECTS: A total of 115 overweight and obese, sedentary, postmenopausal women in the Seattle area participated. METHODS: Participants were randomly assigned to the moderate-intensity exercise group or the control group. The intervention consisted of 45 minutes of moderate-intensity exercise 5 days per week for 12 months. Control participants attended once-weekly, 45-minute stretching sessions. Questionnaires asking about upper respiratory tract infections in the previous 3 months were administered quarterly during the course of the year-long trial. Poisson regression was used to estimate the effect of exercise on colds and other upper respiratory tract infections. RESULTS: Over 12 months, the risk of colds decreased in exercisers relative to stretchers (P = .02): In the final 3 months of the study, the risk of colds in stretchers was more than threefold that of exercisers (P = .03). Risk of upper respiratory tract infections overall did not differ (P = .16), yet may have been biased by differential proportions of influenza vaccinations in the intervention and control groups. CONCLUSIONS: This study suggests that 1 year of moderate-intensity exercise training can reduce the incidence of colds among postmenopausal women. These findings are of public health relevance and add a new facet to the growing literature on the health benefits of moderate exercise.

Aged↗

PubMed2005

Effects of exercise on metabolic risk variables in overweight postmenopausal women: a randomized clinical trial.

OBJECTIVE: This study examined the effects of exercise on metabolic risk variables insulin, leptin, glucose, and triglycerides in overweight/obese postmenopausal women. RESEARCH METHODS AND PROCEDURES: Sedentary women (n = 173) who were overweight or obese (BMI > or = 25 kg/m(2) or > or =24 kg/m(2) with > or =33% body fat), 50 to 75 years of age, were randomized to 12 months of exercise (> or =45 minutes of moderate-intensity aerobic activity 5 d/wk) or to a stretching control group. Body composition (DXA) and visceral adiposity (computed tomography) were measured at baseline and 12 months. Insulin, glucose, triglycerides, and leptin were measured at baseline and 3 and 12 months. Insulin resistance was evaluated by the homeostasis model assessment formula. Differences from baseline to follow-up were calculated and compared across groups. RESULTS: Exercisers had a 4% decrease and controls had a 12% increase in insulin concentrations from baseline to 12 months (p = 0.0002). Over the same 12-month period, leptin concentrations decreased by 7% among exercisers compared with remaining constant among controls (p = 0.03). Homeostasis model assessment scores decreased by 2% among exercisers and increased 14% among controls from baseline to 12 months (p = 0.0005). The exercise effect on insulin was modified by changes in total fat mass (trend, p = 0.03), such that the exercise intervention abolished increases in insulin concentrations associated with gains in total fat mass. DISCUSSION: Regular moderate-intensity exercise can be used to improve metabolic risk variables such as insulin and leptin in overweight/obese postmenopausal women. These results are promising for health care providers providing advice to postmenopausal women for lifestyle changes to reduce risk of insulin resistance, coronary heart disease, and diabetes.

Adipose Tissue↗

PubMed2004

Human plasma ghrelin levels increase during a one-year exercise program.

Weight loss resulting from decreased caloric intake raises levels of the orexigenic hormone, ghrelin. Because ingested nutrients suppress ghrelin, increased ghrelin levels in hypophagic weight loss may result from decreased inhibitory input by ingested food, rather than from lost weight. We assessed whether ghrelin levels increase in response to exercise-induced weight loss without decreased caloric intake. We randomized 173 sedentary, overweight, postmenopausal women to an aerobic exercise intervention or stretching control group. At baseline, 3 months, and 12 months, we measured body weight and composition, food intake, cardiopulmonary fitness (maximal oxygen consumption), leptin, insulin, and ghrelin. Complete data were available for 168 women (97%) at 12 months. Exercisers lost 1.4 +/- 0.4 kg (P < 0.05 compared with baseline; P = 0.01 compared with stretchers) and manifested a significant, progressive increase in ghrelin levels, whereas neither measure changed among stretchers. Ghrelin increased 18% in exercisers who lost more than 3 kg (P < 0.001). There was no change in caloric intake in either group and no effect on ghrelin of exercise per se independent of its impact on body weight. In summary, ghrelin levels increase with weight loss achieved without reduced food intake, consistent with a role for ghrelin in the adaptive response constraining weight loss and, thus, in long-term body weight regulation.

Body Mass Index↗

PubMed2004

UDP-glucuronosyltransferase and sulfotransferase polymorphisms, sex hormone concentrations, and tumor receptor status in breast cancer patients.

INTRODUCTION: UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes are involved in removing sex hormones from circulation. Polymorphic variation in five UGT and SULT genes - UGT1A1 ((TA)6/(TA)7), UGT2B4 (Asp458Glu), UGT2B7 (His268Tyr), UGT2B15 (Asp85Tyr), and SULT1A1 (Arg213His)--may be associated with circulating sex hormone concentrations, or the risk of an estrogen receptor-negative (ER-) or progesterone receptor-negative (PR-) tumor. METHODS: Logistic regression analysis was used to estimate the odds ratios of an ER- or PR- tumor associated with polymorphisms in the genes listed above for 163 breast cancer patients from a population-based cohort study of women in western Washington. Adjusted geometric mean estradiol, estrone, and testosterone concentrations were calculated within each UGT and SULT genotype for a subpopulation of postmenopausal breast cancer patients not on hormone therapy 2-3 years after diagnosis (n = 89). RESULTS: The variant allele of UGT1A1 was associated with reduced risk of an ER- tumor (P for trend = 0.03), and variants of UGT2B15 and SULT1A1 were associated with non-statistically significant risk reductions. There was some indication that plasma estradiol and testosterone concentrations varied by UGT2B15 and SULT1A1 genotypes; women with the UGT2B15 Asp/Tyr and Tyr/Tyr genotypes had higher concentrations of estradiol than women with the Asp/Asp genotype (P = 0.004). Compared with women with the SULT1A1 Arg/Arg and Arg/His genotypes, women with the His/His genotype had elevated concentrations of testosterone (P = 0.003). CONCLUSIONS: The risk of ER- breast cancer tumors may vary by UGT or SULT genotype. Further, plasma estradiol and testosterone concentrations in breast cancer patients may differ depending on some UGT and SULT genotypes.

Adult↗

PubMed2004

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

Elevated circulating estrogens and a sedentary lifestyle increase risk for breast cancer. The effect of exercise on circulating estrogens in sedentary postmenopausal women is unknown. The objective of this study was to examine the effects of a 12-month moderate-intensity exercise intervention on serum estrogens. We randomly assigned 173 sedentary, overweight (body mass index > 24.0 kg/m(2), body fat > 33%), postmenopausal women, ages 50-75 years, not using hormone therapy, living in the Seattle, Washington, area for the next year, and willing to be randomly assigned to an exercise intervention or stretching control group. The exercise intervention included facility and home-based exercise (45 min, 5 days/week moderate intensity sports/recreational exercise). A total of 170 (98.3%) women completed the study with exercisers averaging 171 min/week of exercise. After 3 months, exercisers experienced declines in estrone, estradiol, and free estradiol of 3.8, 7.7, and 8.2%, respectively, versus no change or increased concentrations in controls (P = 0.03, 0.07, and 0.02, respectively). At 12 months, the direction of effect remained the same, although the differences were no longer statistically significant. The effect was limited to women who lost body fat: women whose percentage of body fat [by dual energy x-ray absortiometry (DEXA)] decreased by >/==" BORDER="0">2% had statistically significant (comparing exercisers versus controls) decreases at 12 months of 11.9, 13.7, and 16.7% for serum estrone, estradiol, and free estradiol, respectively. We concluded that a 12-month moderate-intensity exercise intervention in postmenopausal women resulted in significant decreases in serum estrogens. The association between increased physical activity and reduced risk for postmenopausal breast cancer may be partly explained by effects on serum estrogens.

Aged↗

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↗

PubMed2003

Adiposity and sex hormones in postmenopausal breast cancer survivors.

PURPOSE: Overweight and obese women with breast cancer have poorer survival compared with thinner women. One possible reason is that breast cancer survivors with higher degrees of adiposity have higher concentrations of tumor-promoting hormones. This study examined the association between adiposity and concentrations of estrogens, androgens, and sex hormone-binding globulin (SHBG) in a population-based sample of postmenopausal women with breast cancer. METHODS: We studied the associations between body mass index (BMI), body fat mass, and percent body fat, measured by dual-energy x-ray absorptiometry scan, waist circumference, and waist-to-hip circumference ratio, with concentrations of estrone, estradiol, testosterone, SHBG, dehydroepiandrosterone sulfate, free estradiol, and free testosterone in 505 postmenopausal women in western Washington and New Mexico with incident stage 0 to IIIA breast cancer. Blood and adiposity measurements were performed between 4 and 12 months after diagnosis. RESULTS: Obese women (BMI > or = 30) had 35% higher concentrations of estrone and 130% higher concentrations of estradiol compared with lighter-weight women (BMI < 22.0; P =.005 and.002, respectively). Similar associations were observed for body fat mass, percent body fat, and waist circumference. Testosterone concentrations also increased with increasing levels of adiposity (P =.0001). Concentrations of free estradiol and free testosterone were two to three times greater in overweight and obese women compared with lighter-weight women (P =.0001). CONCLUSION: These data provide information about potential hormonal explanations for the association between adiposity and breast cancer prognosis. These sex hormones may be useful biomarkers for weight loss intervention studies in women with breast cancer.

Absorptiometry, Photon↗

PubMed2003

Nine-year prospective association between older siblings' smoking and children's daily smoking.

PURPOSE: To explore the hypothesis that older siblings' smoking, after controlling for parents' smoking, influences children's smoking. METHODS: Study participants were 2981 students in the control cohort of a school-based smoking prevention randomized trial for whom parents' smoking and older siblings' smoking data were collected at 3rd grade and daily smoking data was assessed 9 years later through a self-report questionnaire at the 12th grade. Data were analyzed using conditional logistic regression and likelihood ratio tests. RESULTS: For families in which no parent smoked, the 12th grade prevalence of daily smoking was 31% when at least one older sibling smoked compared to 18% when no older sibling smoked. For families in which at least one parent smoked, the 12th grade prevalence of daily smoking was 41% when at least one older sibling smoked compared to 29% when no older sibling smoked. There was a substantial increase in the odds (OR = 1.60, p =.004) of children's daily smoking at 12th grade when their older siblings smoked, even after adjusting for parents' smoking. CONCLUSIONS: Older siblings' smoking is associated with increased risk of children's smoking after adjusting for parents smoking. Furthermore, there was no evidence to suggest that the influence of older siblings' smoking was different in families where no parent smoked compared to those where at least one parent smoked. Also, there was no evidence that the influence of older siblings' smoking was different in boys vs. girls.

Adolescent↗