Age-related Changes In Body Composition Research Articles

Body Adiposity in Late Life and Risk of Dementia or Cognitive Impairment in a Longitudinal Community-Based Study

The association between body adiposity at older ages and the development of cognitive impairment is unclear. The association of body mass index (BMI) and waist circumference in late life with incidence of cognitive impairment was prospectively examined in a cohort study of 1,351 Latinos, aged 60-101 and residents of the Sacramento, CA, area at study baseline. The status of dementia and "cognitive impairment but not demented" (CIND) was determined at baseline and at each of five follow-up examinations by a multistage assessment protocol. Incident cases of dementia and CIND were combined (dementia/CIND) for more than 8 years of follow-up. BMI was categorized as less than 25.0, 25.0-29.9 (overweight), and 30 kg/m(2) or greater (obese). Waist circumference was categorized into sex-specific tertiles. Dementia/CIND was diagnosed in 110 (8.2%) participants. Compared with the lowest BMI category, overweight participants had a 48% decreased rate of dementia/CIND (adjusted hazard ratio [HR] = 0.52, 95% confidence interval [CI]: 0.30-0.91) and obese participants had a 61% decreased rate of dementia/CIND (HR = 0.39, 95% CI: 0.20-0.78). Rates of dementia/CIND for the middle and high tertile of waist circumference, compared with the low tertile, were 80% and 90% higher, respectively (adjusted HR = 1.8, 95% CI: 1.1-3.1, and adjusted HR = 1.9, 95% CI: 0.91-3.8). Abdominal fat in late life appears to confer an increased risk for dementia/CIND, whereas overall obesity appears to be protective. This may reflect age-related changes in body composition and the association of visceral fat with metabolic dysregulation.

Modulation of GH/IGF-1 axis: Potential strategies to counteract sarcopenia in older adults

Aging is associated with progressive decline of skeletal muscle mass and function. This condition, termed sarcopenia, is associated with several adverse outcomes, including loss of autonomy and mortality. Due to the high prevalence of sarcopenia, a deeper understanding of its pathophysiology and possible remedies represents a high public health priority. Evidence suggests the existence of a relationship between declining growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels and age-related changes in body composition and physical function. Therefore, the age-dependent decline of GH and IGF-1 serum levels may promote frailty by contributing to the loss of muscle mass and strength. Preclinical studies showed that infusion of angiotensin II produced a marked reduction in body weight, accompanied by decreased serum and muscle levels of IGF-1. Conversely, overexpression of muscle-specific isoform of IGF-1 mitigates angiotensin II-induced muscle loss. Moreover, IGF-1 serum levels have been shown to increase following angiotensin converting enzyme inhibitors (ACEIs) treatment. Here we will review the most recent evidence regarding age-related changes of the GH/IGF-1 axis and its modulation by several interventions, including ACEIs which might represent a potential novel strategy to delay the onset and impede the progression of sarcopenia.

Longitudinal Body Composition Changes in Old Men and Women: Interrelationships With Worsening Disability

Few studies have evaluated prospectively age-related body composition changes and their relationships with worsening disability in the elderly population. Ninety-seven women and 62 men aged 71.4+/-2.2 and 71.6+/-2.2 years, respectively, at baseline underwent dual-energy x-ray absorptiometry determinations at baseline and at 2- and 5.5-year follow-up intervals to measure total body and leg fat (FM) and total, appendicular, and leg fat-free mass (FFM). Height, weight, body mass index (BMI), and waist circumference (as well as reported disabilities using a four-level scale) were evaluated at baseline and at 2- and 5.5-year follow-up. In both sexes, total FM did not change significantly, while total, appendicular, and leg FFM significantly decreased over the study follow-up. In men and women losing weight, BMI, total and leg FM, and total, appendicular, and leg FFM significantly decreased. In weight-stable men and women, appendicular and leg FFM significantly decreased and BMI, waist circumference, and total FM significantly increased. Men lost significantly more total, appendicular, and leg FFM than did women, irrespective of whether they maintained or lost weight. Over the follow-up period, 43.3% of women and 43.5% of men declined in one or more levels of reported disability. We evaluated the effect of age, baseline BMI, FM, FFM, number of diseases, baseline 6-minute walking test, categories of weight change, total, appendicular, or leg FFM changes, total FM and waist changes on the probability of a decline in one or more levels of reported disability score over the follow-up period, taking into account sex. Patients losing appendicular and leg FFM were 2.15 and 2.53 times, respectively, more likely to report increased disability than were patients without FFM loss. Reduction in appendicular or leg FFM was the main predictor of decline in one or more levels of reported disability in older men and women, and accounted for about a 2-fold increase in risk.

Pathways involved in the transition from hypertension to hypertrophy to heart failure. Treatment strategies

The renin-angiotensin-aldosterone system (RAAS) is critical in regulating systemic blood pressure, water and electrolyte balance, and pituitary gland hormones. These physiologies appear to be primarily mediated by the angiotensin II/AT(1) receptor subtype system. Overstimulation of this system can predispose cardiovascular disease (CVD) characterized by excessive vasoconstriction, fibrosis, and cardiac remodeling. If untreated, the patient typically displays a continuum of pathophysiologic conditions progressing from atherosclerosis to left ventricle hypertrophy (LVH), coronary thrombosis, myocardial infarcts, with heart failure as an endpoint. Intervention with antihypertensive therapy is necessary to inhibit this progression. RAAS blocking drugs appear to be the most effective approach. Diastolic heart failure patients benefit from treatment with angiotensin converting enzyme (ACE) inhibitors and angiotensin AT(1) receptor blockers (ARBs). Elderly CVD patients evidence age-related changes in body composition that alter the distribution and half-life of medications, thus presenting special challenges to treatment. The presence of comorbidities such as diabetes, renal dysfunction, liver insufficiency further complicates any therapeutic strategy. In addition, noncompliance because of cognitive impairment, depression, confusion due to the complexity of dose regimens, and lack of an appropriate social support system can disrupt positive outcome. The present review discusses the roles of an overactive RAAS and sympathetic nervous system as primary contributors to CVD. In addition, treatment strategies are discussed, focusing on middle aged and elderly hypertensive and heart failure patients.

Adipogenesis is inhibited by brief, daily exposure to high-frequency, extremely low-magnitude mechanical signals.

Obesity, a global pandemic that debilitates millions of people and burdens society with tens of billions of dollars in health care costs, is deterred by exercise. Although it is presumed that the more strenuous a physical challenge the more effective it will be in the suppression of adiposity, here it is shown that 15 weeks of brief, daily exposure to high-frequency mechanical signals, induced at a magnitude well below that which would arise during walking, inhibited adipogenesis by 27% in C57BL/6J mice. The mechanical signal also reduced key risk factors in the onset of type II diabetes, nonesterified free fatty acid and triglyceride content in the liver, by 43% and 39%, respectively. Over 9 weeks, these same signals suppressed fat production by 22% in the C3H.B6-6T congenic mouse strain that exhibits accelerated age-related changes in body composition. In an effort to understand the means by which fat production was inhibited, irradiated mice receiving bone marrow transplants from heterozygous GFP+ mice revealed that 6 weeks of these low-magnitude mechanical signals reduced the commitment of mesenchymal stem cell differentiation into adipocytes by 19%, indicating that formation of adipose tissue in these models was deterred by a marked reduction in stem cell adipogenesis. Translated to the human, this may represent the basis for the nonpharmacologic prevention of obesity and its sequelae, achieved through developmental, rather than metabolic, pathways.

Age-Related Changes in Trabecular Architecture Differ in Female and Male C57BL/6J Mice

We used microCT and histomorphometry to assess age-related changes in bone architecture in male and female C57BL/6J mice. Deterioration in vertebral and femoral trabecular microarchitecture begins early, continues throughout life, is more pronounced at the femoral metaphysis than in the vertebrae, and is greater in females than males. Despite widespread use of mice in the study of musculoskeletal disease, the age-related changes in murine bone structure and the relationship to whole body BMD changes are not well characterized. Thus, we assessed age-related changes in body composition, whole body BMD, and trabecular and cortical microarchitecture at axial and appendicular sites in mice. Peripheral DXA was used to assess body composition and whole body BMD in vivo, and microCT and histomorphometry were used to measure trabecular and cortical architecture in excised femora, tibia, and vertebrae in male and female C57BL/6J mice at eight time-points between 1 and 20 mo of age (n = 6-9/group). Body weight and total body BMD increased with age in male and female, with a marked increase in body fat between 6 and 12 mo of age. In contrast, trabecular bone volume (BV/TV) was greatest at 6-8 wk of age and declined steadily thereafter, particularly in the metaphyseal region of long bones. Age-related declines in BV/TV were greater in female than male. Trabecular bone loss was characterized by a rapid decrease in trabecular number between 2 and 6 mo of age, and a more gradual decline thereafter, whereas trabecular thickness increased slowly over life. Cortical thickness increased markedly from 1 to 3 mo of age and was maintained or slightly decreased thereafter. In C57BL/6J mice, despite increasing body weight and total body BMD, age-related declines in vertebral and distal femoral trabecular bone volume occur early and continue throughout life and are more pronounced in females than males. Awareness of these age-related changed in bone morphology are critical for interpreting the skeletal response to pharmacologic interventions or genetic manipulation in mice.

The Epidemiology of Adiposity and Dementia

Adipose tissue is the largest endocrine gland in the body, yet only recently has its role in neurodegenerative disease been considered. Prospective population level evidence has emerged to show that both obesity and overweight, is associated with an increased risk of all cause dementia, Alzheimer's disease (AD), and underlying neurodegenerative changes. Weight loss in late life however is associated with dementia, and those categorized as underweight are also at a greater risk of dementia. Given the current epidemic of obesity, and the expected age-related increase in dementia incidence, even a small association between these two diseases has far reaching public health implications. However, due to the effects of both AD-associated weight loss and age-related changes in body composition, there are methodological challenges in appropriately evaluating obesity as a risk factor for developing dementia. There is a need to take a 'life course approach' and to consider the role of risk factors prior to the onset of old age. Our work has shown that both obesity and overweight, as measured by body mass index and skinfold thickness, in middle-age are strongly associated with an increased risk of all cause dementia, Alzheimer disease & Vascular dementia, independent of the development of diabetes and cardiovascular-related morbidities. There is also value in assessing regional body shape distributions of adiposity, particular the role of abdominal obesity. Mechanistic pathways such as adipocyte secreted proteins and hormones, and inflammatory cytokines could explain the association between obesity and increased risk of dementia.

Effects of birth cohort and age on body composition in a sample of community-based elderly

The effect of the recent obesity epidemic on body composition remains unknown. Furthermore, age-related changes in body composition are still unclear. The objective was to simultaneously examine the effects of birth cohort and age on body composition. A total of 1786 well-functioning, community-based whites and blacks (52% women and 35% blacks) aged 70-79 y from the Health, Aging, and Body Composition Study underwent dual-energy X-ray absorptiometry annually from 1997 to 2003. At baseline, mean +/- SD percentage body fat, fat mass, and lean mass (bone-free) were 28 +/- 5%, 24 +/- 7 kg, and 56 +/- 7 kg, respectively, for men and 39 +/- 6%, 28 +/- 9 kg, and 40 +/- 6 kg for women. Mixed models were used to assess the effects of cohort and age-related changes on body composition. Later cohorts in men had a greater percentage body fat (0.32% per birth year, P < 0.0001) than did earlier cohorts. This cohort effect was due to a greater increase in fat mass than in lean mass (0.45 kg and 0.17 kg/birth year, respectively). With increasing age, percentage body fat in men initially increased and then leveled off. This age-related change was due to an accelerated decrease in lean mass and an initial increase and a later decrease in fat mass. Similar but less extreme effects of cohort and age were observed in women. The combination of effects of both birth cohort and age leads to bigger body size and less lean mass in the elderly.

DHEA in Elderly Women and DHEA or Testosterone in Elderly Men

One common approach to preventing or delaying age-related disorders is to supplement falling hormone levels. Animal studies give some evidence that dehydroepiandrosterone (DHEA) lessens age-related changes in body composition and has beneficial effects on diabetes and cardiovascular disease, but rodents—unlike humans—have very low DHEA levels. Whether or not to give supplemental testosterone to elderly men also is unsettled. This randomized 2-year placebo-controlled, double-blind study enrolled 87 men aged 60 years and older having low levels of sulfated DHEA and bioavailable testosterone, and 57 elderly women with low levels of sulfated DHEA. The men received 75 mg of DHEA daily in tablet form, 5 mg of testosterone daily via transdermal patch, or an appropriate placebo for 2 years. The women received either a 50-mg DHEA tablet daily or a placebo tablet. There were no major group differences at baseline. DHEA recipients had significant increases in levels of sulfated DHEA and estradiol, and treated women had increased total testosterone levels. Both bioavailable and total testosterone increased significantly in testosterone-treated men compared with placebo recipients. DHEA did not significantly alter gonadotropin levels in men or women, but lower levels were found in testosterone-treated men. Neither treatment significantly altered fasting plasma glucose levels or insulin sensitivity. Both men and women given DHEA had significant reductions in levels of high-density lipoprotein cholesterol. In men and women combined, those given DHEA had a slight but significant rise in fat-free mass and a reduction in proportion of body fat. Fat-free mass also increased in men given testosterone. Measures of muscle strength remained unchanged. Small increases in bone mineral density were noted at some but not all sites with both active treatments. Neither treatment significantly altered quality of life as reflected by scores on the Physical Component and Mental Component scales of the Health Status Questionnaire. Neither treatment altered prostate volume, liver function, or levels of electrolytes or hemoglobin. In this study, neither DHEA nor low-dose testosterone had physiologically meaningful beneficial effects on body composition, physical performance, or quality of life in elderly men or women. The investigators strongly recommend that these treatments not be used as anti-aging measures.

Obesity and Dementia: Lifecourse Evidence and Mechanisms

Recent work has indicated that obesity increases the risk of developing all-cause dementia, Alzheimer’s disease and neurodegenerative processes in the brain. Given the current epidemic of obesity and the expected age-related increase in dementia incidence, even a modest association between these two conditions has far reaching public health implications. However, due to the effects of both Alzheimer’s disease-associated weight loss and age-related changes in body composition, there are methodological challenges in assessing obesity as a risk factor for developing dementia. There is a need to take a ‘life-course approach’ and to consider the role of risk factors prior to old age. In addition, there is value in assessing regional body shape distributions of adiposity. Several mechanistic pathways such as comobid disease, leptin, adiponectin and inflammatory cytokines could explain the association between obesity and increased risk of dementia.

Reference values for the 6-min walk test in healthy subjects 20–50 years old

In 102 healthy Caucasians, 20-50 years old, we investigated the effect of anthropometrics on the 6-min walk test (6MWT), in order to provide reference values for walk distance (6MWD), oxygen saturation (SpO2), pulse rate (PR), respiratory rate (RR), breathlessness perception (VAS) and for the walking distance and body weight product (DW). The mean 6MWD and DW values were 593 +/- 57 and 638+/-44 m (P < 0.01) and 35,030 +/- 5306 and 48,882 +/- 6555 kg m (P < 0.01), respectively for women and for men. While walking, SpO2 remained unaltered and subjects reached 67 +/- 10% of their maximal predicted heart rate and a RR mean value of 19 +/- 4 bpm. VAS ratings were significantly higher in females as compared to males (24 +/- 15 vs. 18 +/- 5 mm, P < 0.05), however, when corrected for PR change while walking, they were not different. The equation by stepwise multiple regression analysis included height, age and gender for the 6MWD and accounted for 42% of the total variance. This study confirms the relevant effect of anthropometrics on walking capacity and suggests that when rating dyspnea, the change in heart rate during walking should be considered.

Postmenopausal hormone therapy and body composition—a substudy of the estrogen plus progestin trial of the Women’s Health Initiative

It has been suggested that hormone therapy may help counter undesirable changes in body composition in older women. This study was designed to test whether estrogen plus progestin (E+P) therapy favorably affects age-related changes in body composition in postmenopausal women. The substudy was composed of 835 women from the estrogen plus progestin trial of the Women's Health Initiative who were randomly assigned to receive either E+P therapy (n = 437) or placebo (n = 398). The women had a mean age of 63.1 y and, on average, were 13.8 y past menopause. More than 17% of the participants were from an ethnic minority. No significant differences in baseline body composition (measured with dual-energy X-ray absorptiometry) by intervention assignment were observed. After 3 y of intervention, the women who received active E+P therapy lost less lean soft tissue mass (-0.04 kg) than did the women who received placebo (-0.44 kg; P = 0.001). Additionally, the women in the E+P group had less upper-body fat distribution than did the women in the placebo group (change in ratio of trunk to leg fat mass: -0.025 for the E+P group and 0.004 for the placebo group; P = 0.003). A sensitivity analysis, which was conducted on the women who took > or = 80% of the study medication during the intervention period, corroborated the findings from the intent-to-treat analysis. A 3-y E+P intervention significantly reduced both the loss of lean soft tissue mass and the ratio of trunk to leg fat mass in postmenopausal women. However, the effect sizes were small, and whether these changes in body composition lead to significant health benefits remains to be confirmed.

Sarcopenia, obesity, and inflammation—results from the Trial of Angiotensin Converting Enzyme Inhibition and Novel Cardiovascular Risk Factors study

Age-related body-composition changes are associated with health-related outcomes in elders. This relation may be explained by inflammation and hemostatic abnormalities. Our objectives were to evaluate the relation between body-composition measures [body mass index (BMI), total fat mass, and appendicular lean mass (aLM)] and C-reactive protein (CRP), interleukin 6 (IL-6), and plasminogen activator inhibitor 1 (PAI-1) and to explore the effect of obesity and sarcopenia on CRP, IL-6, and PAI-1 concentrations. The data are from the Trial of Angiotensin Converting Enzyme Inhibition and Novel Cardiovascular Risk Factors (TRAIN) study baseline visit (n = 286; mean age = 66.0 y). Total fat mass and aLM were assessed with a dual-energy X-ray absorptiometry scan. Linear regressions were performed between body-composition measures and CRP, IL-6, or PAI-1 concentrations. The effect of sarcopenia and obesity (defined as the percentage of fat mass) on CRP, IL-6, and PAI-1 concentrations was evaluated with the use of analyses of covariance. CRP and IL-6 were positively associated with both BMI [beta = 0.027 (P = 0.03) and beta = 0.048 (P < 0.001), respectively] and total fat mass [beta = 0.049 (P < 0.001) and beta = 0.055 (P < 0.001), respectively] and were inversely associated with fat-adjusted aLM [beta = -0.629 (P = 0.002) and beta = -0.467 (P = 0.02), respectively]. PAI-1 was positively associated with both BMI (beta = 0.038, P = 0.005) and total fat mass (beta = 0.032, P = 0.007). No significant interaction was found between either obesity or sarcopenia and CRP, IL-6, and PAI-1 concentrations. Obesity remained significantly associated with high CRP and IL-6 concentrations after adjustments for sarcopenia. CRP and IL-6 are positively associated with total fat mass and negatively associated with aLM. Obesity-associated inflammation may play an important role in the age-related process that leads to sarcopenia. The relation of inflammation with sarcopenia was not independent of any of the considered obesity indexes.

Age-related changes in body composition among Turkana males of Kenya

To determine if age-related changes in body composition among males from an energetically limited population are similar to those of Western populations, we collected anthropometric data from Turkana pastoral nomads of northern Kenya. Measures included height, weight, and triceps, suprailiac, and subscapular skinfolds. Subjects were 132 nomadic and 90 settled Turkana males, with estimated ages 20+. Skinfold measures were used to calculate both fat-free mass (FFM) and percent body fat. Results were analyzed by 10-year age groups, using general linear models. Subpopulations did not differ in FFM, but percent body fat was significantly higher among settled males. Age-related changes in FFM were curvilinear, peaking in the 30 s for nomads and 40s for settled males, with a significant decline in men over 60 years of age. Nomadic males show declines in percent body fat from the 20 s onward, while percent body fat among settled males increased across age groups. These results indicate that age-related patterns of FFM in Turkana men are similar to those found in Western populations, but that age-related patterns of adiposity can differ. As such, they suggest that age-related patterns of fat-free mass in men may vary little across populations, while age-related patterns of adiposity are more closely related to environmental conditions.

Drug development and use in the elderly: search for the right dose and dosing regimen

Across the globe over the last few decades, there has been a remarkable increase in the proportion of the population which is elderly, and this trend is set to continue. Data from 10 countries that accounted for about 55% of the world population of 6079 million in the year 2000 provide an overview of this significant shift in demography. Table 1 summarizes the projections for the next 25 years. Hitherto, increases in life expectancy have been most obvious in the affluent countries; however, improvements in public health and disease control are also leading to increases in life expectancy in the less affluent countries. As a result of relatively larger increases in life expectancy at birth, significant shifts in demography are also expected in countries that are at present economically less affluent. The number of elderly people in the world is therefore expected to continue to increase for some considerable time. Interestingly, the most dramatic increases in the proportion of the population who are elderly are anticipated in countries where total populations are projected to decrease (such as Japan, Germany and Italy). Table 1 Age-related demography in 2000 and projected changes in 10 major countries The 2001 population census of the UK revealed that since the census of 1951, the proportion of elderly population above 65 years and 85 years has increased from 16% and 0.4% respectively to 21% and 1.9%, respectively. These changes in demography will have significant effects on the economics generally as well as on the provisions for healthcare. Cardiovascular and neurological diseases and cancers are the most prevalent in the elderly. These three groups of diseases account for about 54% of the total burden of disease in Europe in terms of disability adjusted life years. Of the total gross Hospital and Community Health Services expenditure of £31.9 billion in the year 2001–2002 in the UK, 13% was expended on people aged 65–74 years, 16% on those aged 75–84 years and 10% for people aged 85 years or more. Furthermore, about 55% of the community prescriptions during 2001 in the UK were dispensed for the elderly. Cardiovascular and psychoactive drugs accounted for more than 40% of these prescriptions. In view of many age-related changes in the pharmacokinetics and pharmacodynamics of a drug, the safe and effective prescribing of medicines in the elderly will continue to present a major challenge. This review provides an overview of the issues relevant to development and clinical use of drugs in the elderly population, with particular reference to determining the right dosage and dose regimen and the regulatory requirements that facilitate this process. It also examines whether, as a result of advancing age per se, the dosing regimens in the elderly and the frail elderly might be different from those in the non-elderly.

Testosterone, aging, and body composition in men from Harare, Zimbabwe

To examine age-related changes in body composition and testosterone (T) among men in an urban sub-Saharan African population, measures of body composition and salivary T were obtained from 109 males ages 20-78 in Harare, Zimbabwe. Measures included height, weight, suprailiac and triceps skinfold, and percent body fat by bioelectric impedance (BIA). Saliva samples were assayed for T using radioimmunoassay. Average BMI of the overall sample (23.16 (SD = 18.12) kg/m(2) was close to Western populations, while salivary T levels (AM = 196 +/- 96 pmol/l; pm = 172 +/- 98 pmol/l) were much lower. Both morning (beta = -0.535; P < 0.001) and afternoon salivary T declined with age (beta = -0.385; P < 0.001). Multiple regression models indicate that pm salivary T (beta = 0.24; P = 0.025), was a predictor of fat-free mass, but neither am nor pm salivary T was related to fat mass or other measures of body composition. In addition, height was significantly related to pm salivary T levels in men under the age of 60. Multivariate regression indicates that pm salivary T is a predictor of fat-free mass when controlled for height and adiposity. These findings suggest that T is related to both lean mass and overall body size among men from a non-Western nonsubsistence population. As such they are consistent with the hypothesis that bioavailable T plays a role in energetic allocation among human males.

Sarcopenia and increased adipose tissue infiltration of muscle in elderly African American women

Aging is associated with metabolic, physiologic, and functional impairments, in part through age-related changes in body composition. During the later adult years, skeletal muscle mass decreases and body fat becomes centralized. The goal of the study was to investigate body composition over time ( +/- SD: 2.04 +/- 0.6 y) in healthy, ambulatory, elderly African American women. The hypothesis that a reduction in total-body skeletal muscle (SM) and increases in visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and intermuscular adipose tissue (IMAT) are ongoing in healthy, weight-stable elderly was tested. The study was a longitudinal evaluation of 26 women (age at baseline: 75.5 +/- 5.1 y) with a body mass index (in kg/m(2)) of 27.0 +/- 4.0. Body composition was measured by using whole-body magnetic resonance imaging for the quantification of SM, total adipose tissue (TAT), VAT, SAT, and IMAT. SM (P < 0.001) and bone (P < 0.05) masses decreased, and regional analyses showed a decrease in dual-energy X-ray absorptiometry-derived leg SM (P < 0.05). VAT (P = 0.011) and IMAT (P < 0.001) increased. No changes occurred in TAT (P = 0.45), SAT (P = 0.96), physical function, or food intake. These data show an age-related remodeling of body composition with reductions in SM and corresponding increases in VAT and IMAT. Changes in the previously unstudied depot of IMAT may be involved in the deterioration of metabolic values frequently observed during aging.

Growth hormone-mediated alteration of fuel metabolism in the aged rat as determined from transcript profiles.

Age-related changes in body composition and serum lipids resemble symptoms of adult-onset growth hormone (GH) deficiency. GH treatment has been shown to normalize these changes in both GH-deficient adult patients and elderly subjects. The aim of this study was to identify GH-responsive genes that might mediate positive effects of GH treatment on fuel metabolism and body composition. cDNA microarrays were used to analyze age- and GH-induced changes in gene expression patterns in male rats. Tissues analyzed were liver, adipose tissue, and skeletal muscle from animals on or off GH treatment. A value of 1.5 was chosen to denote differences (increased or decreased expression) in the level of mRNA expression. In the liver, 7.3% of the expressed genes were affected by age and 6.5% by GH. Similar values for the other tissues were 8.3% and 5.3% (fat), and 7.9% and 9.6% (muscle), respectively. Among the differentially expressed genes, we identified several that encode proteins involved in fuel metabolism. Old rats were shown to have induced expression of genes involved in hepatic glucose oxidation and lipid synthesis, whereas these pathways were reduced in adipose tissue. GH treatment induced the expression of genes for lipid oxidation in liver and for glucose oxidation in skeletal muscle. In adipose tissue, GH reduced the expression of genes involved in lipogenesis even further. Changes in transcript levels were reflected in serum in terms of altered lipid profiles. Serum levels of triglycerides, high-density lipoprotein (HDL) cholesterol, and total cholesterol were higher in the old animals than in the young and normalized by GH treatment.

Salivary testosterone and body composition among Ariaal males

To determine if testosterone is negatively related to acute and/or chronic nutritional status among men in a subsistence society, saliva samples and anthropometric measures were compared among nomadic and settled Ariaal pastoralists of northern Kenya. Fifty-six nomadic men and 62 settled men facing drought conditions, estimated ages 22-96 years, were sampled. Measures included height, weight, four skinfolds, and %body fat by bioelectric impedance (BIA). Saliva samples were assayed for testosterone using radioimmunoassay. Overall, both body mass index (BMI) (avg. = 17.8 +/- 6.0 kg/m(2)) and salivary testosterone (T) levels (avg. am value = 176.8 +/- 74.8 pmol/l) were low compared to values from Western populations. Comparison of the two subpopulations revealed no significant difference in height, weight, BMI, or lean body mass. However, nomadic males exhibited significantly smaller skinfolds. Evening, but not morning, salivary T values differed between the subpopulations. Age-related changes in body composition included a significant decline in BMI with age, related to loss of body fat, but with little change in lean body mass. Age-related declines in BMI and %body fat were more pronounced among the nomadic males. am salivary T values declined with age; again, the decline was significantly greater among nomadic males. pm salivary T levels showed no significant decline with age. When controlled for residence and age, salivary T was positively related to %body fat and WHR ratio, but not lean body mass. These results provide evidence that salivary T is related to acute nutritional status among males in an energetically stressed subsistence population, in accordance with life history theories of somatic allocation.

Myosin heavy chain profiles and body composition are different in old versus young Standardbred mares

There are limited data on age-related changes in body composition or skeletal muscle in the horse. Therefore, the purpose of this study was to investigate any differences in muscle myosin heavy chain (MHC) and body composition associated with aging. Twenty-three young (4-8 years) and eight old (20+ years) unfit Standardbred mares were evaluated. Rump fat thickness was measured using B-mode ultrasound and per cent body fat (% fat) was calculated. Needle muscle biopsies were obtained from right gluteus medius muscle. MHC composition was determined via sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Three MHC isoforms were subsequently identified as type I, type IIA, and type IIX and quantified using a scanning and densometric system. There were no significant differences (p>0.05) between old and young mares in fat (%) (19.0+/-6.4 vs 20.5+/-5.4), fat mass (kg) (102.3+/-39.9 vs 106.9+/-37.1), or body weight (kg) (529.4+/-34.9 vs 512.7+/-57.7). However, the old mares had significantly (p<0.05) greater lean body mass than the young mares (427.1+/-24.5 vs 405.7+/-37.9). Aged mares had significantly (p<0.05) less type I (7.8+/-2.9% vs 12.1+/-4.4%) and IIA (27.8+/-7.1% vs 36.1+/-9.5%) fibres than the young group but more type IIX (64.6+/-4.7% vs 51.8+/-11.1%). The MHC data are consistent with the age-related changes seen in other species.