Blood pressure, cardiorespiratory fitness and body mass : results from the Tromsø activity study

<em><strong>Aims:</strong></em> Modifiable lifestyle factors, as cardiorespiratory fitness (CRF) and body mass, may prevent hypertension.<br />However, it remains unclear whether blood pressure is associated with CRF, independently of body mass index (BMI). Thus, the purpose was to study the relationship between CRF, body composition and blood pressure among 40-44 year old men and women.<br /><em><strong>Methods</strong></em>: During 2007-2008, 12,900 men and women aged 30-85 years attended the sixth survey of the Tromsø study. Blood pressure (mm Hg), height (cm) and weight (kg) were measured and body mass index (BMI kg/m2) was estimated. In a sub-study, the Tromsø Activity Study, CRF [VO2max (ml/kg/min)] was objectively measured using a treadmill test among 313 healthy men and women aged 40-44 years.<br /><em><strong>Results</strong></em>: Among men and women participating in both studies, the mean BMI was 27.1 kg/m2 for men and 25.1 kg/m2 for women. Mean arterial blood pressure (MAP) was 92.4 mm Hg for men and 86.0 mm Hg for women. The proportion defined as pre-hypertensive/hypertensive (systolic/diastolic blood pressure &gt; 120/80) were 33% and 56% for women and men, respectively. The proportion of low, medium and high CRF for both sexes combined differed significantly (p &lt; 0.0001) by BMI level (&lt; 25 or ≥ 25 kg/m2). Increased fitness tended to reduce blood pressure among overweight and obese men (p trend = 0.03), whereas increased fitness tended to reduce blood pressure among normal weighted women (p trend = 0.01).<br /><em><strong>Conclusion:</strong></em> Among healthy 40-44 year old men and women in this study, BMI was positively associated and CRF was negatively associated with blood pressure. Moreover, our results suggest that BMI may be a more important factor than CRF in predicting systolic blood pressure in both sexes. However, cardiorespiratory<br />fitness and weight control may both be important targets for prevention of hypertensio

Glutathione S-Transferase M1 Genetic Polymorphism Is Associated With Salivary 17-βestradiol Levels: A Study Based On Hormonal Profiles From Entire Menstrual Cycles

Introduction: Studies suggest that enzymes involved in the estrogen metabolic pathway are susceptibility factors for breast cancer; however, there is limited direct evidence in relation to estradiol levels. The glutathione-S-transferase M1 enzyme (GSTM1) enzyme is involved in estrogen peroxidation, and a shortage seems to enhance estrogen exposure. A homozygous deletion of the GSTM1 gene leads to total absence of enzyme activity, and studies indicate that an association with breast cancer risk may be modified by body mass. So far, parallel studies on intermediate biomarkers (i.e. estradiol) are largely missing. Thus, in the present study, we assessed the association between a GSTM1 genetic polymorphism (null/rs1065411) and daily salivary levels of 17-βestradiol throughout one entire menstrual cycle and evaluated modification of genotype effects according to metabolic profile in 190 premenopausal women aged 25-35 years. Methods: The women participated in the Energy Balance and Breast Cancer Aspects study (EBBA-I, 2000-2002) in Tromsø, North Norway (inclusion criteria: healthy, non-pregnant, non-lactating, no current use of exogenous hormones). Salivary levels of 17-βestradiol were assessed by radioimmunoassay (The Reproductive Ecology Laboratory, Harvard University). Height and weight were measured. Genomic DNA was extracted from EDTAwhole blood. GSTM1 genotyping was done on the ABI PRISM® 3100 Genetic Analyzer (Fred Hutchinson Cancer Research Center). The GSTM1 assay distinguishes between the GSTM1*Aallele (G nucleotide, Lys at aminoacid 173), the GSTM1*B allele (C nucleotide, Asn at aminoacid 173), and the homozygous gene deletion. Regression models were used to study the relation between genetic (null genotype versus all other alleles combined) and metabolic susceptibility factors, and levels of 17-βestradiol. Results: Mean body mass index (BMI) was 24.4 kg/m2. The homozygous gene deletion of GSTM1 had a prevalence of 52%, and the frequency of the null genotype was similar in heavy women (BMI ≥26.3 kg/m2, upper quartile) as compared to other women (p = .18). The null genotype was associated with lower levels of 17-βestradiol by cycle day compared to other alleles (p = .04). However, the association was confined to women that were normal weight to slightly overweight (p for interaction = .01). In women with BMI < 26.3 kg/m2, the null genotype was associated with significantly lower levels of 17-βestradiol by cycle day compared to other alleles (p = .02) and an 18% reduction in overall average level of 17-β estradiol throughout the cycle (p = .02), while in heavy women no association with estradiol levels was observed. Conclusion: In our study, GSTM1 genotype was a significant determinant of circulating estradiol levels in premenopausal women without marked adiposity. Thus, interestingly our results strongly support that the effect of body mass on estradiol levels and subsequent breast cancer development may be modified by GSTM1 genotype.AnthropologyHuman Evolutionary Biolog

Adult Height, Insulin Levels and 17β-Estradiol in Young Women

Background: Adult height and insulin levels have independently been associated with breast cancer risk. However, little is known about whether these factors influence estradiol levels. Thus, we hypothesize that adult height in combination with insulin levels may influence premenopausal 17β-estradiol throughout the entire menstrual cycle of possible importance of breast cancer risk. Methods: Among 204 healthy women, aged 25-35 years who participated in the Norwegian EBBA I study, birth weight and age at menarche were assessed by questionnaire, personal health record and interview. 17β-estradiol concentrations were estimated by daily saliva samples throughout one entire menstrual cycle using radioimmunoassay (RIA). Measures of height (cm) were taken as well as waist circumference (cm), body mass index (BMI kg/m2) and total fat percentage (DEXA % fat). Fasting blood samples were drawn, and serum concentrations of insulin were determined. Results: The women reported a mean height of 166.5 cm, birth weight of 3389 g and age at menarche 13.1 years. Mean BMI was 24.4 kg/m2, mean waist circumference 79.5 cm and mean total fat percentage 34.1%. Women with an adult height of more than 170 cm and insulin levels higher than 90 pmol/L experienced on average an 37.2 % increase in 17β- estradiol during an entire menstrual cycle compared to those with the same height, and insulin levels below 90 pmol/L. Moreover, this was also observed throughout the entire menstrual cycle. Conclusion: Our findings support that premenopausal levels of 17β-estradiol vary in response to adult height and insulin levels, suggesting that women who become taller are put at risk for higher estradiol levels when their insulin levels rise of possible importance for breast cancer risk.Anthropolog

17β-Estradiol Levels During An Entire Menstrual Cycle In Response To Adult Stature and Insulin, Of Possible Importance For Breast Cancer Risk: The EBBA-I study.

Background: The normal breast cells develop into malignant cells as a result of a complex interplay between genetic, environmental, nutritional and hormonal factors. Attained adult stature and insulin levels, risk factors for breast cancer, may also vary in response to the same factors. Thus, we hypothesize that 17β-estradiol, a key factor in the carcinogenesis of the breast, may vary in response to adult height in combination with insulin levels of possible importance of breast cancer risk. Methods: Among 204 healthy women, aged 25-35 years who participated in the Norwegian EBBA-I study, 17β-estradiol concentrations were measured in daily saliva samples throughout one entire menstrual cycle using radioimmunoassay (RIA). Attained height (cm) was measured, and serum concentrations of insulin were determined in fasting blood samples. The associations between adult height, insulin and 17β-estradiol levels throughout a menstrual cycle were studied using multivariate linear regression analyses and linear mixed models for repeated measures. Adjustments for potential confounding factors were performed. Results: A 37.2 % increase in 17β-estradiol levels was observed during the entire menstrual cycle among women with an adult height ≥170 cm (upper tertile) and insulin levels ≥ 90 pmol/L (upper tertile) compared to women with the same attained adult height, and insulin levels < 90pmol/L. The association was even more pronounced when we looked into those women with attained adult height ≥170 cm (upper tertile) and serum insulin ≥ 101 pmol/L (upper quartile) (Fig. 1). Adjustments for potential confounding factors were performed. Conclusion: Our findings support that premenopausal levels of 17β-estradiol vary in response to adult height and insulin levels, suggesting that women who become taller are put at risk for higher estradiol levels throughout the entire menstrual cycle when their insulin levels rise, of possible importance for breast cancer risk.AnthropologyHuman Evolutionary Biolog

Duration of Lactation, Maternal Metabolic Profile, and Body Composition in the Norwegian EBBA I-Study

Objective There is conflicting evidence as to whether duration of lactation may decrease the risk of subsequent development of an unfavorable maternal metabolic profile including overweight and obesity. We hypothesized that duration of lactation is associated with a more favorable metabolic profile and healthier anthropometrical measurements. Methods 98 parous women from the Norwegian EBBA I-study (Energy Balance and Breast cancer Aspects-study), a cross-sectional study of healthy premenopausal women aged 25–35 years, historical lactation data were collected, anthropometrical measurements were taken, fasting blood samples (serum glucose, triglycerides, total cholesterol and HDL-cholesterol) were drawn and women were asked to fill in a pre-coded food diary. Results Mean time since last birth was 4.7 years, mean number of children was 1.9, mean total duration of lactation was 19 months and average length of lactation per child was 10.3 months. Women who on average lactated for less than 10 months per child had higher mean levels of fasting serum glucose (5.2 mmol/L vs. 5.0 mmol/L, p = 0.04), serum triglyceride (0.91 mmol/L vs. 0.66 mmol/L, p = 0.001) and serum cholesterol (4.78 mmol/L vs. 4.32 mmol/L, p = 0.004), and a higher waist-to-hip ratio (0.81 vs. 0.77, p = 0.001) than women who lactated for 10 months or more per child. The inverse association between average length of lactation per child and waist-to-hip ratio persisted after adjustment for potential confounders. Conclusions These results support the hypothesis that duration of lactation may be associated with a healthier metabolic profile and healthier anthropometrical measurements, especially lipid levels and waist-to-hip ratio even years after weanin

Physical Activity, Heart Rate, Metabolic Profile, and Estradiol in Premenopausal Women

Purpose: To study whether physical inactive women with a tendency to develop metabolic syndrome have high levels of 17[beta]-estradiol (E2) of importance for breast cancer risk. Methods: Two hundred and four healthy women of reproductive age were assessed for self-reported leisure-time physical activity (LPA), resting heart rate (HR), blood pressure (BP), anthropometry, and serum glucose, lipids, and insulin [Norwegian Energy Balance and Breast Cancer Aspect (EBBA) study]. E2 was measured in daily saliva samples throughout an entire menstrual cycle. A clustered metabolic risk score [z metabolic syndrome (zMS); total cholesterol-high-density lipoprotein-cholesterol (HDL-C) ratio, insulin resistance, total fat tissue, BP, and triglycerides] was defined. Linear regression and linear mixed models were used, and confounding factors were tested. Results: Physically active women had lower fat percentage (Ptrend = 0.003) and HRs (Ptrend = 0.003) than sedentary women. We estimated an increase in E2 of 1.27 pmol[middle dot]L-1 [95% confidence interval (CI), 0.06-2.47] for each 11.7 beats[middle dot]min-1 (1 SD) increase in HR, and this corresponds to the 7% change in mean concentration of E2 for the total group. Associations with E2 were also found for fat tissue, total cholesterol-HDL-C ratio, insulin resistance, and triglycerides. A dose-response relationship was observed among the three levels of LPA and HR and zMS (Ptrend = 0.03 for LPA; Ptrend = 0.004 for HR). Women in the highest tertile of the clustered metabolic risk score had average salivary E2profiles that were markedly higher, throughout the cycle, than those of the other groups, with a cycle peak-day difference in E2 of 22-28%. Conclusion: LPA and HR were associated with metabolic risk score, and this score was associated with daily level of E2, pointing to important biologic mechanisms operating between a sedentary lifestyle and an increased breast cancer risk.AnthropologyHuman Evolutionary Biolog

Blood pressure, cardiorespiratory fitness and body mass: Results from the Tromsø Activity Study

<em><strong>Aims:</strong></em> Modifiable lifestyle factors, as cardiorespiratory fitness (CRF) and body mass, may prevent hypertension.<br />However, it remains unclear whether blood pressure is associated with CRF, independently of body mass index (BMI). Thus, the purpose was to study the relationship between CRF, body composition and blood pressure among 40-44 year old men and women.<br /><em><strong>Methods</strong></em>: During 2007-2008, 12,900 men and women aged 30-85 years attended the sixth survey of the Tromsø study. Blood pressure (mm Hg), height (cm) and weight (kg) were measured and body mass index (BMI kg/m2) was estimated. In a sub-study, the Tromsø Activity Study, CRF [VO2max (ml/kg/min)] was objectively measured using a treadmill test among 313 healthy men and women aged 40-44 years.<br /><em><strong>Results</strong></em>: Among men and women participating in both studies, the mean BMI was 27.1 kg/m2 for men and 25.1 kg/m2 for women. Mean arterial blood pressure (MAP) was 92.4 mm Hg for men and 86.0 mm Hg for women. The proportion defined as pre-hypertensive/hypertensive (systolic/diastolic blood pressure &gt; 120/80) were 33% and 56% for women and men, respectively. The proportion of low, medium and high CRF for both sexes combined differed significantly (p &lt; 0.0001) by BMI level (&lt; 25 or ≥ 25 kg/m2). Increased fitness tended to reduce blood pressure among overweight and obese men (p trend = 0.03), whereas increased fitness tended to reduce blood pressure among normal weighted women (p trend = 0.01).<br /><em><strong>Conclusion:</strong></em> Among healthy 40-44 year old men and women in this study, BMI was positively associated and CRF was negatively associated with blood pressure. Moreover, our results suggest that BMI may be a more important factor than CRF in predicting systolic blood pressure in both sexes. However, cardiorespiratory<br />fitness and weight control may both be important targets for prevention of hypertensio

Duration of Lactation, Maternal Metabolic Profile, and Body Composition in the Norwegian EBBA I-Study

Objective There is conflicting evidence as to whether duration of lactation may decrease the risk of subsequent development of an unfavorable maternal metabolic profile including overweight and obesity. We hypothesized that duration of lactation is associated with a more favorable metabolic profile and healthier anthropometrical measurements. Methods 98 parous women from the Norwegian EBBA I-study (Energy Balance and Breast cancer Aspects-study), a cross-sectional study of healthy premenopausal women aged 25–35 years, historical lactation data were collected, anthropometrical measurements were taken, fasting blood samples (serum glucose, triglycerides, total cholesterol and HDL-cholesterol) were drawn and women were asked to fill in a pre-coded food diary. Results Mean time since last birth was 4.7 years, mean number of children was 1.9, mean total duration of lactation was 19 months and average length of lactation per child was 10.3 months. Women who on average lactated for less than 10 months per child had higher mean levels of fasting serum glucose (5.2 mmol/L vs. 5.0 mmol/L, p = 0.04), serum triglyceride (0.91 mmol/L vs. 0.66 mmol/L, p = 0.001) and serum cholesterol (4.78 mmol/L vs. 4.32 mmol/L, p = 0.004), and a higher waist-to-hip ratio (0.81 vs. 0.77, p = 0.001) than women who lactated for 10 months or more per child. The inverse association between average length of lactation per child and waist-to-hip ratio persisted after adjustment for potential confounders. Conclusions These results support the hypothesis that duration of lactation may be associated with a healthier metabolic profile and healthier anthropometrical measurements, especially lipid levels and waist-to-hip ratio even years after weanin