Juliette C. Howe

Energy expenditure by indirect calorimetry in premenopausal women: variation within one menstrual cycle☆☆☆

Energy expenditure in relation to the menstrual cycle was determined by indirect calorimetry in premenopausal women. For each subject, three measurements were made within a single menstrual cycle. Energy expenditure measurements coincided with the subjects expected hormonal fluxes of estradiol and progesterone: menstrual phase-both hormones at basal levels; follicular phase-elevated estradiol; and luteal phase-elevated progesterone. In experiment I, resting energy expenditure of 14 women was determined for 1 hour using a canopy system for calorimetry; in experiment 2, 24-hour energy expenditures of 12 subjects were measured in a room-size calorimeter. Blood from fasted (12 hours) subjects was collected following measurements of energy expenditure and analyzed for serum estradiol-17B and progesterone by radioimmunoassay. In experiment 1, resting energy expenditure did not differ within one menstrual cycle; neither estradiol nor progesterone affected resting energy expenditure. In experiment 2, 24-hour energy expenditure was significantly lower (P < 0.013) during the follicular phase when compared with the menstrual (−3.8%) and luteal (−4.9%) phases. Lowered 24-hour energy expenditure during the follicular phase may in part be due to a decrease in spontaneous activity and exercise. Energy expenditure during sleep, an indicator of metabolic energy expenditure, was significantly greater (P < 0.0001) during the luteal phase than during the menstrual (+6.7%) and follicular (+5.4%) phases; this was a reflection of increased progesterone (P < 0.0001). Twenty-four hour energy expenditure (mean ± SEM) during the menstrual, follicular, and luteal phases was 8.86 ± 0.26, 8.52 ± 0.22, and 8.96 ± 0.21 MJ/d, respectively. Corresponding values for energy expenditure during sleep were 5.49 ± 0.09, 5.56 ± 0.10, and 5.86 ± 0.11 MJ/d. The menstrual cycle is a significant contributor to variation in energy expenditure through progesterone-mediated increases in metabolic rate. Variation in metabolic energy expenditure was detectable when the contributory components of 24-hour energy expenditure were measured.

Nutrient Database Improvement Project: The influence of USDA Quality and Yield Grade on the separable components and proximate composition of raw and cooked retail cuts from the beef chuck

This study was designed to provide updated information on the separable components, cooking yields, and proximate composition of retail cuts from the beef chuck. Additionally, the impact the United States Department of Agriculture (USDA) Quality and Yield Grade may have on such factors was investigated. Ultimately, these data will be used in the USDA - Nutrient Data Laboratorys (NDL) National Nutrient Database for Standard Reference (SR). To represent the current United States beef supply, seventy-two carcasses were selected from six regions of the country based on USDA Yield Grade, USDA Quality Grade, gender, and genetic type. Whole beef chuck primals from selected carcasses were shipped to three university laboratories for subsequent retail cut fabrication, raw and cooked cut dissection, and proximate analyses. The incorporation of these data into the SR will improve dietary education, product labeling, and other applications both domestically and abroad, thus emphasizing the importance of accurate and relevant beef nutrient data.

Comparison of resistive to aerobic exercise training on cardiovascular risk factors of sedentary, overweight premenopausal and postmenopausal women

Physical inactivity has been identified as a risk factor for cardiovascular disease similar to that of hypercholesterolemia. However, few studies compare the type of exercise to effects on plasma lipids, especially of postmenopausal women. Premenopausal and postmenopausal subjects participated in resistive (12 subjects) or aerobic (11 subjects) training program for 12 weeks. Triglyceride levels of the postmenopausal women and total and LDL cholesterol of both premenopausal and postmenopausal women were significantly lower after exercise compared to prestudy levels. No significant difference was found in the HDL cholesterol levels. Insulin and C-peptide area under the curve, but not glucose, significantly decreased with both types of exercise. The type of exercise was more important to postmenopausal than premenopausal women, and aerobic exercise had the greater affect (28% decrease) on the cardiovascular risk factor, cholesterol. Based on these results, health professionals can recommend walking as an effective exercise for older women.

Postprandial response of calcium metabolism in postmenopausal women to meals varying in protein level/source.

The postprandial response of calcium metabolism to single meals varying in protein source and level was determined in eight postmenopausal women, age 51 to 65 years. Following an overnight fast, subjects consumed a liquid meal containing either 15 g or 45 g of protein from beef (B), cottage cheese (C), or soy isolate (S; 45 g only); one meal provided 0 g protein (basal). Blood was collected before the meal and at 30, 60, 120, and 180 minutes post-meal. Urine was collected every 30 minutes post-meal. Urinary Ca excretion significantly increased following 45-g protein meals when compared with basal meals, but not when compared with 15 g protein meals. Although glomerular filtration rate (GFR) was unaffected by diet, percent renal tubular Ca reabsorption was significantly reduced following C45 or S45 meals. No consistent changes in serum levels of parathyroid hormone (PTH) and calcitonin (Ct) were observed in response to diet. Serum phosphorus levels were significantly reduced following high-protein meals when compared with no-protein meals. Insulin response varied with protein level and source (C45 greater than S45 greater than C15 greater than B45 greater than B15 greater than basal). Significant associations found between insulin and calcium metabolism indicate a possible role of insulin in the mechanism of protein-induced calciuria.

Effect of dietary protein level and kind of carbohydrate on growth and selected pathological and biochemical parameters in female BHE rats

Abstract Male BHE 1 rats were fed one of four levels of dietary protein (6%, 8%, 20%, or 45% casein) with either sucrose or cornstarch from weaning to 400 days of age. The effects of dietary carbohydrate and protein were independent of each other for all parameters measured. When the protein level was 8% or 45%, or when sucrose was the carbohydrate source, the young, rapidly growing rat responded differently than the mature rat to food consumption and this was reflected in body weight. Low protein diets generally resulted in small kidney weights, low total serum protein and prealbumin, as well as increased incidence and degree of kidney calcification. Nephrosis was a common pathological condition in the males at 400 days of age, regardless of the level of protein or type of carbohydrate fed. The extent of damage (hyalin score), however, was exacerbated when the diet contained 20% or 45% protein, or when sucrose was the carbohydrate source. By 175 days of age, changes in the percentage distribution of urinary proteins separated by electrophoresis suggested a possible means of predicting the onset of nephrosis.

Urinary catecholamine excretion in men and women: between- and within-subject variation

Twenty-two women and 12 men collected 24-hr urine samples under free-living conditions. The study was conducted to determine the variation in urinary catecholamine excretion between and within subjects, as well as the impact of alcohol consumption on this variation. Subjects were fed controlled diets (20% or 40% of energy from fat) for two 8-week periods; within each dietary group, subjects consumed a carrier beverage with ethanol (5% of daily energy intake) during one 8-week period. Urine samples were collected during week 5 of each period for 4 consecutive days and analyzed for epinephrine, norepinephrine, and dopamine by HPLC with electrochemical detection. There was no significant effect due to dietary fat on catecholamines excretion; therefore, all subjects were combined. Coefficients of variation were determined separately for men and women and for alcohol consumption within sex. Daily excretion of epinephrine and norepinephrine was significantly greater ( P < 0.01) in men than in women. Within- and between-subject variability presented large coefficients of variation for both men (28–48%) and women (22–47%). Although within-subject variation was similar for men and women, between-subject variation was consistently greater for women than for men regardless of alcohol consumption or abstention. Alcohol consumption did not significantly affect the levels of urinary catecholamine excretion within sex. However, both within- and between-subject variation decreased during alcohol consumption in all subjects.

Response of Two Strains of Rats to a High-Protein Diet Containing Sucrose or Cornstarch

Abstract Male BHE (carbohydrate-sensitive strain) and Wistar rats were fed from weaning to 400 days of age 45% casein diets containing sucrose or cornstarch. At this high protein intake type of carbohydrate had no effect on any of the parameters measured. Several significant differences, however, were observed between the two strains. Food utilization for weight gain was less efficient for young Wistar than for young BHE rats. BHE rats had a higher incidence and level of fat in the liver, and degree of nephrosis in the kidneys. Kidney calcium deposits were negligible in either strain. Urinary protein excretion was very low in young rats but increased with age. Urinary protein electrophoretic patterns changed with age; faster moving proteins were affected by age × strain interactions. At 400 days of age patterns were similar for both strains and probably related to the development of nephrosis. Total serum cholesterol and percentage prealbumin were higher, whereas serum albumin and very-low-density lipoproteins were lower in BHE than in Wistar rats. These differences probably were associated with kidney pathology as related to strain susceptibility.