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Biomedical subjects

L DiPietro

Publications and source records attributed to L DiPietro.

At least 19 recordsLinked to original sources
PubMed2002

Importance of plasma leptin in predicting future weight gain in obese children: a two-and-a-half-year longitudinal study.

OBJECTIVE: To determine whether relatively low leptin levels predict changes in adiposity in prepubertal and pubertal obese children. RESEARCH METHODS AND PROCEDURES: In a biracial cohort of 68 obese children (33 male and 35 female; 46 Caucasians and 22 African-Americans, age range 7-18 y), we measured at baseline fasting insulin and leptin levels, height and weight and calculated body mass index (kg/m(2)) and expressed body mass index as (BMI) Z-score. After a 2.5-y follow-up, anthropometric measurements were repeated and changes in weight gain were calculated as changes in BMI Z-score. RESULTS: At baseline obese preadolescent boys and girls had similar age and BMI Z-score, fasting insulin and leptin levels. After an average follow-up of 2.5 y, mean weight change calculated by changes in BMI Z-score from baseline was similar in both groups. In obese adolescent boys and girls at baseline, no significant gender differences were observed for BMI Z-score and insulin levels. In contrast, plasma leptin levels were significantly higher in obese girls compared with obese adolescent boys. At follow-up, there was no significant difference in change in BMI Z-score between obese boys and girls. Multiple linear regression analysis revealed that high basal leptin levels were positively associated with greater changes in BMI Z-score only in girls (r(2)=0.18, P<0.02), after adjusting for basal BMI Z-score, Tanner stage, years of follow-up and basal insulin. High basal leptin levels in girls explained 18% of the weight gain. CONCLUSION: High leptin levels are associated with excessive future weight gain only in girls.

Adolescent↗
PubMed2001

Physical activity in aging: changes in patterns and their relationship to health and function.

Sedentary behavior is an important risk factor for chronic disease morbidity and mortality in aging. However, there is a limited amount of information on the type and amount of activity needed to promote optimal health and function in older people. The purpose of this review is to describe the change in patterns of habitual physical activity in aging and the relationship of these changes to physical function and selected chronic diseases. We undertook a literature review of large population-based studies of physical activity in older people, and there is encouraging evidence that moderate levels of physical activity may provide protection from certain chronic diseases. Additionally, substantial health effects can be accrued independent of the fitness effects achieved through sustained vigorous activity. Thus, regular participation (i.e., 30 minutes/day on most days of the week) in activities of moderate intensity (such as walking, climbing stairs, biking, or yardwork/gardening), which increase accumulated daily energy expenditure and maintain muscular strength, but may not be of sufficient intensity for improving fitness, should be encouraged in older adults. Public policy should focus on ways of increasing volitional and lifestyle activity in older people, as well as on increasing the availability and accessibility of senior and community center programs for promoting physical activity throughout the life span.

Aged↗
PubMed2000

Role of exercise stress testing and safety monitoring for older persons starting an exercise program.

While the benefits of physical activity and exercise among older persons are becoming increasingly clear, the role of exercise stress testing and safety monitoring for older persons who want to start an exercise program is unclear. Current guidelines regarding exercise stress testing likely are not applicable to the majority of persons aged 75 years or older who are interested in restoring or enhancing their physical function through a program of physical activity and exercise. In addition to being expensive and of unproven benefit, the current policy of routine exercise stress testing potentially could deter many older persons from participating in an exercise program. Research is needed to investigate current physician practices, evaluate the risk of adverse cardiac events, determine the role of pharmacological stress testing, and measure and compare absolute and relative exercise intensities. To assist clinicians, we offer a set of recommendations regarding precautions that can be taken to minimize the risk of adverse cardiac events among previously sedentary older persons who do not have symptomatic cardiovascular disease and are interested in starting an exercise program. JAMA. 2000;284:342-349

Aged↗
PubMed2000

Do African Americans have lower energy expenditure than Caucasians?

OBJECTIVE: To review current studies that examine differences in energy expenditure between African Americans and Caucasians as possible modulators of attained differences in overweight status. DESIGN: Literature review of recent clinical and laboratory studies. METHODS: Studies chosen for review were those that examined directly resting metabolic rate (RMR), using indirect calorimetry, and total daily energy expenditure (TDEE) and physical activity energy expenditure (PAEE), using doubly labeled water. RESULTS: Ten of 15 studies reviewed reported a lower RMR in African Americans than in Caucasians. The differences in RMR between African Americans and Caucasians ranged from 81 to 274 kcal/day and could not be explained by differences in age, fat-free mass (FFM) or methodological concerns. Two of six studies of energy expenditure using doubly labeled water suggest that Black adults have a tendency for lower TDEE that can be accounted for primarily by a lower PAEE. CONCLUSIONS: If future studies indicate conclusively that African Americans do have lower RMR, TDEE and PAEE than Caucasians, then the disproportionally higher risk of obesity and associated metabolic disorders in Black adults may be preventable-especially in Black women. If these race differences are indeed a result of both physiological and behavioral factors, then interventions designed to reduce caloric intake and/or increase energy expenditure through lifestyle activity or structured exercise programs become especially important for African Americans and should be encouraged. International Journal of Obesity (2000)24, 4-13

Black People↗
PubMed2000

Respiratory fitness, free living physical activity, and cardiovascular disease risk in older individuals: a doubly labeled water study.

The objective of this study was to examine the importance of cardiorespiratory fitness vs. physical activity energy expenditure on selected cardiovascular disease risk factors in older individuals. One hundred and seventeen older individuals, 53 men (68 +/- 9 yr) and 63 women (67 +/- 7 yr), participated in the study. This cohort was divided into 4 groups: 1) high cardiorespiratory fitness and high physical activity, 2) high cardiorespiratory fitness and low physical activity, 3) low cardiorespiratory fitness and high physical activity, and 4) low cardiorespiratory fitness and low physical activity. Cardiorespiratory fitness (VO2max) was determined from a graded exercise test, physical activity energy expenditure was measured by doubly labeled water and indirect calorimetry, body composition was determined by dual energy x-ray absorptiometry, and dietary practices were determined by a 3-day recall. Cardiorespiratory fitness exerted greater effects on the cardiovascular disease risk profile than physical activity. That is, older individuals with higher levels of cardiorespiratory fitness, regardless of their physical activity levels, showed lower levels of fasting insulin (P < 0.01), triglycerides (P < 0.05), total cholesterol (P < 0.05), total to high density lipoprotein cholesterol ratio (P < 0.05), low density lipoprotein (P < 0.05), and lower waist circumference (P < 0.01). Moreover, individuals with a high cardiorespiratory fitness but low physical activity energy expenditure displayed a more favorable cardiovascular disease risk profile than individuals with low cardiorespiratory fitness and high physical activity energy expenditure. The results suggest that higher levels of cardiorespiratory fitness have greater cardioprotective effects than higher levels of free living physical activity in older individuals. Although these findings do not discount the health benefits of being physically active, it is possible that greater emphasis should be placed on aerobic exercise to increase cardiorespiratory fitness in the elderly.

Abdomen↗
PubMed1999

Intramyocellular lipid concentrations are correlated with insulin sensitivity in humans: a 1H NMR spectroscopy study.

Recent muscle biopsy studies have shown a relation between intramuscular lipid content and insulin resistance. The aim of this study was to test this relation in humans by using a novel proton nuclear magnetic resonance (1H NMR) spectroscopy technique, which enables non-invasive and rapid (approximately 45 min) determination of intramyocellular lipid (IMCL) content. Normal weight non-diabetic adults (n = 23, age 29+/-2 years. BMI = 24.1+/-0.5 kg/m2) were studied using cross-sectional analysis. Insulin sensitivity was assessed by a 2-h hyperinsulinaemic (approximately 450 pmol/l)-euglycaemic (approximately 5 mmol/l) clamp test. Intramyocellular lipid concentrations were determined by using localized 1H NMR spectroscopy of soleus muscle. Simple linear regression analysis showed an inverse correlation (r = -0.579, p = 0.0037) [corrected] between intramyocellular lipid content and M-value (100-120 min of clamp) as well as between fasting plasma non-esterified fatty acid concentration and M-value (r = -0.54, p = 0.0267). Intramyocellular lipid content was not related to BMI, age and fasting plasma concentrations of triglycerides, non-esterified fatty acids, glucose or insulin. These results show that intramyocellular lipid concentration, as assessed non invasively by localized 1H NMR spectroscopy, is a good indicator of whole body insulin sensitivity in non-diabetic, non-obese humans.

Adult↗
PubMed1999

Excess abdominal adiposity remains correlated with altered lipid concentrations in healthy older women.

OBJECTIVE: To determine associations between overall adiposity, absolute and relative abdominal adiposity, and lipid concentrations in healthy older women. DESIGN: Cross-sectional analysis of baseline data. SUBJECTS: Subjects were 21 healthy, untrained older women (71 +/- 1 y) entering a randomized, controlled aerobic training program. MEASUREMENTS: Overall adiposity was assessed by anthropometry and the body mass index (BMI=kg/m2). Absolute and relative abdominal adiposity was determined by computed tomography (CT) and circumference measures. Fasting serum lipid concentrations of total-, high density lipoprotein (HDL)-, and low density lipoprotein (LDL)-cholesterol (C) and triglycerides (TGs) were determined by standard enzymatic procedures. RESULTS: Compared to the measures of overall adiposity, we observed much stronger correlations between measures more specific to absolute or relative abdominal adiposity and lipid concentrations. Visceral fat area was the strongest correlate of HDL-C (r = -0.75; P < 0.001) and the total-/HDL-C ratio (r = 0.86; P < 0.001). The abdomen-to-hip circumference ratio (AHR) was strongly correlated with TGs (r = 0.54; P < 0.01), HDL-C (r= -0.69; P < 0.001), and the total-/HDL-C ratio (r = 0.75; P < 0.001). CONCLUSION: Excess abdominal adiposity remains an important correlate of lipid metabolism, even in healthy older women of normal weight. Thus, overall obesity is not a necessary condition for the correlation between excess abdominal fat and metabolic risk among postmenopausal women.

Abdomen↗
PubMed1999

Physical activity in the prevention of obesity: current evidence and research issues.

PURPOSE: The relation between habitual physical activity and the prevention of overweight and obesity in adults based on the evidence from the epidemiologic literature is described. METHODS: Literature was reviewed of current findings from large population-based studies of forward directionality in which physical activity was considered as a primary study factor. RESULTS: The longitudinal evidence suggests that habitual physical activity plays more of a role in attenuating age-related weight gain, rather than in promoting weight loss. Moreover, recent data suggest that increasing amounts of physical activity may be necessary to effectively maintain a constant body weight with increasing age. CONCLUSION: Over decades, small savings in excess weight gain accumulate into net savings that may be quite meaningful with regard to minimizing the risk associated with obesity-related disorders. The question remains as to how important maintaining a constant body weight through middle age and into older age is to healthy, already-active people of normal body weight.

Adult↗
PubMed1999

Physiological variability of fluid-regulation hormones in young women.

We tested the physiological reliability of plasma renin activity (PRA) and plasma concentrations of arginine vasopressin (P[AVP]), aldosterone (P[ALD]), and atrial natriuretic peptide (P[ANP]) in the early follicular phase and midluteal phases over the course of two menstrual cycles (n = 9 women, ages 25 +/- 1 yr). The reliability (Cronbach's alpha >/=0.80) of these hormones within a given phase of the cycle was tested 1) at rest, 2) after 2.5 h of dehydrating exercise, and 3) during a rehydration period. The mean hormone concentrations were similar within both the early follicular and midluteal phase tests; and the mean concentrations of P[ALD] and PRA for the three test conditions were significantly greater during the midluteal compared with the early follicular phase. Although Cronbach's alpha for resting and recovery P[ANP] were high (0.80 and 0.87, respectively), the resting and rehydration values for P[AVP], P[ALD], and PRA were variable between trials for the follicular (alpha from 0.49 to 0.55) and the luteal phase (alpha from 0.25 to 0. 66). Physiological reliability was better after dehydration for P[AVP] and PRA but remained low for P[ALD]. Although resting and recovery P[AVP], P[ALD], and PRA were not consistent within a given menstrual phase, the differences in the concentrations of these hormones between the different menstrual phases far exceeded the variability within the phases, indicating that the low within-phase reliability does not prevent the detection of menstrual phase-related differences in these hormonal variables.

Adult↗
PubMed1998

Improvements in cardiorespiratory fitness attenuate age-related weight gain in healthy men and women: the Aerobics Center Longitudinal Study.

OBJECTIVE: To determine the longitudinal relation of change in cardiopulmonary fitness to subsequent change in body weight in a cohort of healthy middle-aged adults. DESIGN: Prospective cohort study. SUBJECTS: Participants were 4599 men and 724 women (43 +/- 9 y) receiving at least three medical examinations between 1970 and 1994. Examinations included assessment of cardiorespiratory fitness by maximal exercise tests and measurement of body weight. MEASUREMENTS: Change in fitness was calculated as the difference in maximal treadmill time between the first and second examination (mean interval, 1.8 y). Weight change was calculated as the difference in body weight between the first and last examination (mean follow-up, 7.5 y). RESULTS: There was a small, yet statistically significant weight gain over the follow-up (0.61 +/- 5.29 kg for men and 1.51 +/- 4.67 kg for women; P << 0.001). Estimates from the multiple linear regression modeling show that each 1 min improvement in treadmill time, significantly attenuated weight gain in both men (b = -0.60; P << 0.001) and women (b = -0.60; P << 0.001), respectively. Moreover, each 1 min improvement in treadmill time, reduced the odds of a > or = 5 kg gain by 14% in men (odds ratios (OR)) = 0.86; 95% confidence interval (CI): 0.83-0.89) and by 9% in women (OR = 0.91; 95% CI:0.83-1.00) and the odds of a > or = 10 kg gain by 21% in both men (OR = 0.79;95% CI:0.75-0.84) and women (OR = 0.79;95% CI:0.67-0.93) CONCLUSIONS: Improvements in fitness, appear important in attenuating age-related weight gain in healthy middle-aged adults. Thus, an active life-style should be promoted early and maintained through adulthood to prevent substantial weight gain and obesity with age.

Adult↗
PubMed1998

Regulation of blood volume during training in post-menopausal women.

UNLABELLED: In younger people the increase in aerobic capacity following training is related, in part, to blood volume (BV) expansion and the consequent improvements in maximal cardiac output. This training-induced hypervolemia is associated with a decrease in cardiopulmonary baroreflex (CPBR) control of peripheral vascular tone. PURPOSE: To test the hypothesis that improvement in peak oxygen consumption (VO2peak) during training in older women is associated with specific central adaptations, such as BV expansion and a reduction in CPBR control of vascular tone. METHODS: Seventeen healthy older women were randomized into training (N = 9, 71 +/- 2 yr) and control (N = 8, 73 +/- 3 yr) groups. The training group exercised three to four times per wk for 30 min at 60% peak heart rate for 12 wk and then 40-50 min at 75% peak heart rate for 12 wk. The control group participated in yoga exercises over the same time period. We measured resting BV (Evans blue dye), VO2peak, and the forearm vascular resistance response to unloading low pressure mechanoreceptors during low levels of lower body negative pressure (through -20 mm Hg) before and after aerobic training. The slope of the increase in forearm vascular resistance (response) per unit decrease in central venous pressure (stimulus) was used to assess CPBR responsiveness. RESULTS: Aerobic training increased VO2peak 14.2% from 24.2 mL x kg(-1) x min(-1) to 27.7 mL x kg(-1) x min(-1) (P < 0.05), a smaller improvement than typically seen in younger subjects. Blood volume (59.9 +/- 1.9 and 60.9 +/- 1.9 mL x kg[-1]) and CPBR function (-3.98 +/- 0.92 and -3.46 +/- 0.94 units x mm(-1) Hg) were similar before and after training. CONCLUSIONS: These data indicate that the inability to induce adaptations in CPBR function may limit BV expansion during training in older women. In addition, the absence of these specific adaptations may contribute to the relatively poor improvements in VO2peak in older women during short (10-12 wk) periods of training.

Adaptation, Physiological↗
PubMed1998

Moderate-intensity aerobic training improves glucose tolerance in aging independent of abdominal adiposity.

OBJECTIVE: To test the hypothesis that training-related improvements in glucose and insulin responses to an oral glucose tolerance test (OGTT) are independent of changes in abdominal adiposity. DESIGN: Adiposity and responses to an OGTT were measured before and after a 4-month randomized, controlled aerobic training program. SETTING: An academic medical institution. PARTICIPANTS: Sixteen healthy older (73+/-1 year) men and women. INTERVENTION: Both the training (T) (n=9) and control (C) (n=7) groups exercised 4 times a week for 60-minute sessions. T exercised on mini-trampolines at 55 to 65% of HRmax (determined from a graded treadmill test) for 1 month and then at 75% for 3 months; C engaged in supervised stretching and yoga. MEASUREMENTS: At baseline and follow-up, we estimated abdominal fat (from computed tomography and anthropometry), plasma glucose, and serum insulin responses to the OGTT and fasting concentrations of free fatty acids (FFA). RESULTS: Aerobic training resulted in a 16% increase in VO2 peak and a 24% decrease in FFA in the T group (P < .05), but training had no effect on abdominal fat. In the T group, the glucose response curve shifted to the left, and the incremental area under the glucose curve decreased by 25% (P < .05). This improvement in glucose response occurred, however, only in those with impaired glucose tolerance at baseline and without any observed change in insulin response. No change in any variables occurred in the C group. CONCLUSIONS: Our data suggest that moderate-intensity aerobic training has a favorable effect on glucose tolerance in older people, independent of changes in abdominal adiposity.

Abdomen↗
PubMed1998

Estrogen influences osmotic secretion of AVP and body water balance in postmenopausal women.

To determine if estrogen upregulates osmotic secretion of arginine vasopressin (AVP) and alters body water balance, we infused hypertonic (3% NaCl) saline in 6 women (68 +/- 3 yr) after 14 days of 17 beta-estradiol (transdermal patch, approximately 0.1 mg/day, E2) and placebo (control) administration. Hypertonic saline was infused at 0.1 ml.kg-1.min-1 for 120 min, and after a 30-min equilibration period, the subjects drank water ad libitum for 180 min. E2 increased basal plasma estradiol concentration from < or = 12 to 80 +/- 12 pg/ml and plasma AVP concentration (P[AVP]) from 2.1 +/- 0.7 to 3.1 +/- 0.8 pg/ml (P < 0.05), but not plasma osmolality (Posm, 288 +/- 1 and 287 +/- 1, for control and E2, respectively). Hypertonic saline infusion increased Posm by 18 +/- 1 and 17 +/- 1 mosmol/kgH2O and P[AVP] by 5.2 +/- 0.5 and 4.9 +/- 0.4 pg/ml for control and E2 treatments, respectively. The P[AVP]-Posm relationship shifted upward after E2, with no change in sensitivity (slope, 0.36 +/- 0.02 and 0.33 +/- 0.03 pg.ml-1.mosmol-1 for control and E2, respectively). Water intake was similar between control and E2 (24 vs. 22 ml/kg), but by 180 min of drinking, urine output and free water clearance (CH2O) were reduced by 5.6 +/- 2.3 ml/kg and 2.6 +/- 2.0 ml/min, respectively (P < 0.05) after E2. Plasma aldosterone concentration was unaffected by E2, but fractional sodium excretion was reduced from 2.7 +/- 0.5 to 1.7 +/- 0.4% (P < 0.05) at 180 min of drinking. Our data suggest that E2 augments osmotic AVP secretion, thereby implicating elevated AVP as a contributor to water retention in high E2 states; however, an increase in renal sodium reabsorption was a major component of the enhanced fluid retention.

Aldosterone↗
PubMed1998

Physical activity patterns associated with cardiorespiratory fitness and reduced mortality: the Aerobics Center Longitudinal Study.

OBJECTIVES: This study examined cross sectionally the physical activity patterns associated with low, moderate, and high levels of cardiorespiratory fitness. METHODS: Physical activity was assessed by questionnaire in a clinic population of 13,444 men and 3972 women 20 to 87 years of age. Estimated energy expenditure (kcal.wk-1) and volume (min.wk-1) of reported activities were calculated among individuals at low, moderate, and high fitness levels (assessed by maximal exercise tests). RESULTS: Average leisure time energy expenditures of 525 to 1650 kcal.wk-1 for men and 420 to 1260 kcal.wk-1 for women were associated with moderate to high levels of fitness. These levels of energy expenditure can be achieved with a brisk walk of approximately 30 minutes on most days of the week. In fact, men in the moderate and high fitness categories walked between 130 and 138 min.wk-1, and women in these categories walked between 148 and 167 min.wk-1. CONCLUSIONS: Most individuals should be able to achieve these physical activity goals and thus attain a cardiorespiratory fitness level sufficient to result in substantial health benefits.

Adult↗
PubMed1997

Childhood sexual abuse and precursors of binge eating in an adolescent female population.

OBJECTIVE: We examined the cross-sectional association between childhood sexual abuse (CSA) and self-reported binge eating in an adolescent female population. METHODS: Study subjects were recruited from clinics specializing in the treatment of CSA, and control subjects were from high schools in the same cities. Height and weight were measured and subjects completed four questionnaires pertaining to binge eating, depression, locus of control, and self-esteem. RESULTS: Study subjects showed significantly higher depression, external locus of control, and binge eating, and significantly lower self-esteem and weight satisfaction scores than did control subjects. After adjusting for all covariables simultaneously, CSA was not an independent correlate of binge eating score. The strongest correlates of binge eating score in the multivariable analysis were depression, body mass index (BMI), and weight satisfaction. CONCLUSIONS: Psychological factors such as depression or weight satisfaction were more influential than is sexual abuse per se in the relationship between CSA and eating disorders.

Adolescent↗
PubMed1997

Mechanism of attenuated thirst in aging: role of central volume receptors.

To test the hypothesis that the inhibitory action of central blood volume expansion on thirst and renal fluid regulation is attenuated with aging, we monitored the drinking and renal responses of dehydrated older (70 +/- 2 yr, n = 6) and younger (24 +/- 1 yr, n = 6) subjects during 195 min of head-out water immersion (HOI), which shifts blood centrally and increases plasma volume (PV). Subjects dehydrated by exercising for 2 h at 36 degrees C in the evening and refraining from fluids overnight before HOI in 34 degrees C water or a seated control in water perfusion suit [time control (TC)] the next morning. Ad libitum water intake was allowed after 15 min of HOI. Dehydration decreased PV by 10.6 +/- 1 and 7.3 +/- 1.8% (P < 0.05) and increased plasma osmolality by 6 +/- 2 and 7 +/- 1 mosmol/kg H2O (P < 0.05) in older and younger subjects, respectively. Thirst ratings increased in both groups, but pre-HOI thirst perception on a line rating scale was lower in older (69 +/- 8 mm) than younger (94 +/- 6 mm, P < 0.05) subjects. Fifteen minutes of HOI restored PV by 7.8 +/- 1.0 and 5.7 +/- 1.0% in older and younger subjects, respectively, but suppressed thirst rating in younger subjects only (P < 0.05). Fluid intake was reduced in HOI compared with TC in younger (6.3 +/- 0.5 vs. 14.3 +/- 2.2 ml/kg, P < 0.05) but not in older (6.7 +/- 2.1 vs. 8.4 +/- 3.3 ml/kg) subjects. During HOI, older subjects had smaller suppression of plasma renin activity and aldosterone concentration but a greater increase in the plasma atrial natriuretic peptide concentration (P[ANP], P < 0.05). HOI increased fractional sodium excretion in both groups, but mean arterial pressure increased only in the older subjects (P < 0.05). We conclude that the inhibitory influence of central volume expansion on thirst and drinking behavior is diminished with aging. Furthermore, in contrast to younger people, HOI natriuresis is associated with exaggerated increases in P[ANP] and arterial blood pressure in older people, suggesting arterial baroreceptors may be involved in the fluid regulatory response to central blood volume expansion in older people.

Adult↗