Age-related changes in total and regional fat distribution

Changes in human bone marrow fat content associated with changes in hematopoietic stem cell numbers and cytokine levels with aging

Hematological deficiencies increase with aging, including anemias, reduced responses to hematopoietic stress and myelodysplasias. This investigation tested the hypothesis that increased bone marrow (BM) fat content in humans with age was associated with decreased numbers of side population (SP) hematopoietic stem cells, and this decrease correlated with changes in cytokine levels. BM was obtained from the femoral head and trochanteric region of the femur removed at surgery for total hip replacement (N = 100 subjects). In addition, BM from cadavers (N = 36), with no evidence of hip disease, was evaluated for fat content. Whole trabecular marrow samples were ground in a sterile mortar and pestle, and cellularity and lipid content determined. Marrow cells were stained with Hoechst dye and SP profiles were acquired. Plasma levels of insulin-like growth factor (IGF)-1, stromal-derived factor (SDF)-1 and interleukin (IL)-6 were measured using ELISA. Fat content in the BM of human subjects and cadavers increased with age. The numbers of SP stem cells in BM as well as plasma IGF-1 and SDF-1 levels decreased in correlation with increased BM fat. IL-6 had no relationship to changes in marrow fat. These data suggest that increased BM fat may be associated with a decreased number of SP stem cells and IGF-1 and SDF-1 levels with aging. These data further raise a more general question as to the role of adipose cells in the regulation of tissue stem cells.

Mechanisms and implications of age-related changes in the liver: nonalcoholic Fatty liver disease in the elderly

Nonalcoholic fatty liver disease (NAFLD) is hepatic steatosis associated with metabolic abnormalities such as overweight/central obesity, insulin resistance, type 2 diabetes (T2D), and dyslipidemia. NAFLD is becoming the most common liver disease in contemporary society, with the highest prevalence in those over 60 years. NAFLD pathology ranges from simple steatosis to a necroinflammatory fibrosing disorder called steatohepatitis (SH), the latter associated with high risk of developing cirrhosis, often occuring in the seventh to ninth decades of life. While the main health implications of NAFLD are increased risk of developing T2D, cardiovascular diseases, and common cancers, there is substantantially increased standardized mortality, and deaths from decompensated cirrhosis and hepatocellular carcinoma (HCC). Little is known about the interactive effects of ageing and NAFLD, with most studies focusing on the younger population. This paper summarises the epidemiology, pathogenesis, and clinical course of NAFLD, with particular attention to persons over age 60 years. An approach to the management of NASH and its complications in the elderly, will also be presented here.

Changes in waist circumference and the incidence of diabetes in middle-aged men and women

BACKGROUND

Waist circumference (WC) is positively associated with diabetes, but the association with changes in WC (DWC) is less clear. We investigated the association between DWC and the subsequent risk of diabetes in middle-aged men and women, and evaluated the influence from concurrent changes in body mass index (DBMI).

METHODOLOGY/PRINCIPAL FINDINGS

Data on 15,577 men and 20,066 women from the Danish Diet, Cancer and Health study were analyzed. Anthropometry was assessed in 1993-97 and 1999-02. Information on diabetes was obtained from The Danish National Diabetes Register. Hazard ratios (HR) were calculated from Cox' proportional hazard models with individuals considered at risk from 1999-02 until December 31 2006. During 5.4 years of follow-up, 1,027 and 876 new cases of diabetes occurred among men and women, respectively. WC was positively associated with diabetes in both sexes also with adjustment for covariates and BMI. DWC was positively associated with diabetes in women, but not in men (HR per 5 cm change = 1.09 (1.04:1.15) in women, and 1.00 (0.94, 1.07) in men with adjustment for covariates, baseline WC, BMI and DBMI). Associations with DWC were not notably different in sub-groups stratified according to baseline WC or DBMI, or when individuals with diseases or diabetes occurring within the first years of follow-up were excluded.

CONCLUSIONS/SIGNIFICANCE

While this study confirmed that WC is positively associated with the risk of diabetes in middle-aged men and women, it surprisingly showed that changes in WC were not associated with the subsequent risk of diabetes in men, and only weakly positively associated with the risk of diabetes in women. Accordingly, these findings suggest that a reduction in WC may be a weak or insufficient or target for prevention of diabetes in middle-aged men and women.

Relationship between prostate-specific antigen bounce body fat distribution and body mass index in permanent seed brachytherapy for prostate cancer

PURPOSE

To analyze the influence of body mass index (BMI) and adipose tissue distribution on prostate-specific antigen (PSA) bounce after iodine-125 prostate brachytherapy.

METHODS AND MATERIALS

We studied 20 patients who had PSA bounce (≥0.50ng/mL) after exclusive prostate brachytherapy. These patients were compared with 48 patients without a bounce (<0.50ng/mL). All patients in the comparison group had a followup of ≥24 months and a last PSA ≤0.5ng/mL. Within these 48 patients, there was a group matched for age (n=20). Univariate and multivariate logistic models were estimated to assess the association between age, baseline PSA, prostate volume, D(90), visceral fat (VF) volume, and BMI on PSA-bouncing status.

RESULTS

When comparing the patients with a bounce to those without, only BMI showed a significantly different distribution (mean, 25.18 vs. 27.47kg/m(2); p=0.0342). On a multivariate analysis, BMI had an odds ratio of 0.85 (95% confidence interval, 0.71-0.99, p=0.049), indicating that an increase of 1kg/m(2) in BMI is associated with a 15% reduction in the odds of having a bounce. In the univariate analysis with the matching patients, BMI was a significant predictor of a bounce (p=0.0147). In the multivariate conditional logistic model, BMI showed a trend toward an influence on a bounce (p=0.0615). All other factors, including VF, did not have any influence on a PSA bounce.

CONCLUSIONS

Patients with a lower BMI are more likely to experience a PSA bounce ≥0.50ng/mL. VF did not have an influence on a PSA bounce.

Invited commentary: Discrimination--an emerging target for reducing risk of cardiovascular disease?

A growing body of research suggests that perceived discrimination, in multiple societies, is a neglected but important predictor of increased risk of disease for a broad range of health status indicators. Several prior studies propose that discrimination is adversely related to increased cardiovascular disease risk. The studies by Hunte (Am J Epidemiol. 2011;173(11):1223-1231) and Lewis et al. (Am J Epidemiol. 2011;173(11):1232-1239) find that self-reported discrimination is associated with increased risk of adiposity for men and women. These studies highlight the potentially important role of discrimination as a risk factor for excess fat but also raise important research questions regarding the role of fat in cardiovascular disease and racial differences in these processes. More generally, they also provide an important reminder to epidemiologists and medical professionals that discrimination and other aspects of racism persist in contemporary society and that increased efforts are needed to document the extent to which they may have pathogenic consequences and to identify the most promising initiatives to reduce any observed negative effects. Equally important, these studies remind us that, although social stressors are difficult to measure accurately and comprehensively, understanding how multiple stressors combine over the life course to affect the risk of morbidity and mortality remains an important priority for concerted research attention.

Caloric restriction attenuates the age-associated increase of adipose-derived stem cells but further reduces their proliferative capacity

White adipose tissue is a promising source of mesenchymal stem cells. Currently, little is known about the effect of age and caloric restriction (CR) on adipose-derived stem cells (ASC). This is important for three reasons: firstly, age and CR cause extensive remodeling of WAT; it is currently unknown how this remodeling affects the resident stem cell population. Secondly, stem cell senescence has been theorized as one of the causes of aging and could reduce the utility of a stem cell as a reagent. Thirdly, the mechanism by which CR extends lifespan is currently not known, one theory postulates that CR maintains the resident stem cell population in youthful "fit" state. For the purpose of this study, we define ASC as lineage negative (lin(-))/CD34(+(low))/CD31(-). We show that aging increases the abundance of ASC and the expression of Cdkn2a 9.8-fold and Isl1 60.6-fold. This would suggest that aging causes an accumulation of non-replicative ASC. CR reduced the percentage of ASC in the lin(-) SVF while also reducing colony forming ability. Therefore, CR appears to have anti-proliferative effects on ASC that may be advantageous from the perspective of cancer, but our data raises the possibility that it may be disadvantageous for regenerative medicine applications.

The role of bone marrow and visceral fat on bone metabolism

The protective effect of total fat mass on bone mineral density (BMD) has been challenged with studies showing no or negative association after adjusting for weight. Subsequently, more studies have evaluated the relationship of regional adiposity with BMD, and findings were inconsistent for central obesity. Advancements in imaging techniques enable us to directly and noninvasively study the role of adiposity on skeletal health. Visceral adiposity measured by computed tomography (CT) has consistently been shown to have negative effects on bone. Availability of magnetic resonance spectroscopy (MRS) also allows us to noninvasively quantify bone marrow fat (BMF), which has been known to be associated with osteoporosis from histomorphometric studies. Using MRS along with dual energy x-ray absorptiometry, studies have reported a detrimental role of BMF on BMD. With the increase in aging and obesity of the population, it is important to continue this effort in identifying the contribution of adipose tissues to bone quality and fracture.

Body mass index and long-term mortality in an elderly Mediterranean population

OBJECTIVES

To describe the relationship of body mass index and mortality in older adults, examining the influence of sex and cardiovascular morbidity.

METHODS

Sixteen-year cohort of a population sample of 1,008 people aged 65 and over. BMI mortality hazard ratios are estimated controlling for age, sex, education, physical activity, smoking, chronic conditions, and ADL (activities of daily living) disability.

RESULTS

At baseline the median BMI is 26.8 (Interquartile range: 24.2-29.7 Kg/m(2)). Findings show that during 16 years there were 672 deaths. The U-shaped curve of the mortality hazard by BMI is wide. The minimum mortality occur at BMI = 30.5 Kg/m(2). Findings show that men had lower mortality risk with increasing BMI and that cardiovascular disease was associated with high mortality in the low-BMI category.

DISCUSSION

Underweight is a risk factor for mortality among elderly people, whereas overweight and mild obesity are associated with the lowest mortality particularly among men and those with cardiovascular morbidity.

Physiological consequences of defects in ERCC1-XPF DNA repair endonuclease

ERCC1-XPF is a structure-specific endonuclease required for nucleotide excision repair, interstrand crosslink repair, and the repair of some double-strand breaks. Mutations in ERCC1 or XPF cause xeroderma pigmentosum, XFE progeroid syndrome or cerebro-oculo-facio-skeletal syndrome, characterized by increased risk of cancer, accelerated aging and severe developmental abnormalities, respectively. This review provides a comprehensive overview of the health impact of ERCC1-XPF deficiency, based on these rare diseases and mouse models of them. This offers an understanding of the tremendous health impact of DNA damage derived from environmental and endogenous sources.

The relation of high fat diet, metabolic disturbances and brain oxidative dysfunction: modulation by hydroxy citric acid

AIMS

This study aimed to examine the effect of high fat diet (HFD) to modulate brain dysfunction, and understand the linkages between obesity, metabolic disturbances and the brain oxidative stress (BOS) dysfunction and modulation with hydroxyl citric acid of G. Cambogia.

METHODS

Rats were divided into 3 groups; 1st control, maintained on standard normal rat chow diet, 2nd HFD, maintained on high fat diet along 12 week and 3rd HFD+G, administered G. Cambogia for 4 weeks and each group include 8 rats. Blood, brain and abdominal fat were collected for biochemical measurements.

RESULTS

HFD group showed significant increase in energy intake, final BW and BW gain. Also significant increase in weight of abdominal fat in HFD group. HFD induce metabolic disturbance through increasing the lipid profile (LDL, TG, TC), γGT and α-amylase activity, uric acid level and hyperglycemia, while decreasing creatine kinase (CK) activity.These changes associated with lowering in brain nitric oxide (NO) level and rising in serum butyrylcholinesterase (BChE), brain catalase activity and MDA levels as oxidative stress markers. These alterations improved by G. Cambogia that decrease BOS and increased NO level.

CONCLUSIONS

Rats fed HFD showed, metabolic disturbances produce hyperglycemia, hypertriglyceridemia, hypercholesterolemia and increased LDL associated with increased BOS. Involvement of BuChE, NO and oxidative stress associated with metabolic disturbances in the pathophysiological progression in brain, suggesting association between obesity, metabolic disorders and brain alteration while, using G. Cambogia, ameliorate the damaging effects of the HFD via lowering feed intake and BOS.

Wrist circumference is a clinical marker of insulin resistance in overweight and obese children and adolescents

BACKGROUND

Excess fat is one of the main determinants of insulin resistance, representing the metabolic basis for developing future cardiovascular disease. The aim of the current study was to find an easy-to-detect clinical marker of insulin resistance which can be used to identify young subjects at increased risk of cardiovascular disease.

METHODS AND RESULTS

Four-hundred and seventy-seven overweight/obese children and adolescents (mean age 10.31±2.80 years) were consecutively enrolled. Standard deviation score body mass index, fasting biochemical parameters, and homeostasis model assessment of insulin resistance were evaluated. Statistical differences were investigated using multiple linear regression analysis. Manual measure of wrist circumference was evaluated in all children and adolescents. Fifty-one subjects, randomly selected, underwent nuclear magnetic resonance imaging of the wrist to evaluate transversal wrist area at the Lister tubercle level. A statistically significant association was found between manual measure of wrist circumference and insulin levels or homeostasis model assessment of insulin resistance (β=0.34 and 0.35, respectively; P<10(-5) for both comparisons). These associations were more significant than those between SD score body mass index and insulin levels or homeostasis model assessment of insulin resistance (β=0.12 and 0.10, respectively; P≤0.02 for both comparisons). Nuclear magnetic resonance imaging acquisition clarified that the association between wrist circumference and insulin levels or homeostasis model assessment of insulin resistance reflected the association with bone tissue-related areas (P≤0.01 for both) but not with the adipose tissue ones (P>0.05), explaining 20% and 17% of the variances of the 2 parameters.

CONCLUSIONS

Our findings suggest a close relationship among wrist circumference, its bone component, and insulin resistance in overweight/obese children and adolescents, opening new perspectives in the prediction of cardiovascular disease.

White adipose tissue development in zebrafish is regulated by both developmental time and fish size

Adipocytes are heterogeneous. Whether their differences are attributed to anatomical location or to different developmental origins is unknown. We investigated whether development of different white adipose tissue (WAT) depots in zebrafish occurs simultaneously or whether adipogenesis is influenced by the metabolic demands of growing fish. Like mammals, zebrafish adipocyte morphology is distinctive and adipocytes express cell-specific markers. All adults contain WAT in pancreatic, subcutaneous, visceral, esophageal, mandibular, cranial, and tail-fin depots. Unlike most zebrafish organs that form during embryogenesis, WAT was not found in embryos or young larvae. Instead, WAT was first identified in the pancreas on 12 days postfertilization (dpf), and then in visceral, subcutaneous, and cranial stores in older fish. All 30 dpf fish exceeding 10.6 mm standard length contained the adult repertoire of WAT depots. Pancreatic, esophageal, and subcutaneous WAT appearance correlated with size, not age, as found for other features appearing during postembryonic zebrafish development.

The relationship of waist circumference and BMI to visceral, subcutaneous, and total body fat: sex and race differences

The purpose of this study was to examine sex and race differences in the relationship between anthropometric measurements and adiposity in white and African-American (AA) adults. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) areas were measured with computed tomography (CT). Fat mass (FM) was measured with dual-energy-X-ray absorptiometry (DXA). Correlation coefficients were used to assess the relationship of waist circumference (WC) and BMI to VAT, SAT, and FM within sex-by-race groups. General linear models were used to compare relationships between WC or BMI, and adiposity across sex and race, within age groups (18-39 and 40-64 years). The sample included 1,667 adults (men: 489 white; 120 AA; women: 666 white, 392 AA). WC and BMI correlations were highest for FM and SAT compared to VAT. Women had higher FM levels than men regardless of WC, but the sex difference in FM was attenuated in younger AA adults with a high BMI. For a given level of WC or BMI, women had higher levels of SAT than men; however, significant interactions indicated that the relationship was not consistent across all levels of BMI and WC. Sex and race differences in VAT varied significantly with WC and BMI. In general, white adults had higher levels of VAT than AA adults at higher levels of BMI and WC. Sex differences, and in some instances race differences, in the relationships between anthropometry and fat-specific depots demonstrate that these characteristics need to be considered when predicting adiposity from WC or BMI.

The pilot study of DXA assessment in chinese HIV-infected men with clinical lipodystrophy

The aim of this study was to evaluate human immunodeficiency virus (HIV)-infected patient's body composition changes by dual-energy X-ray absorptiometry (DXA) and to analyze factors associated with lipodystrophy (LD). Total-body composition was measured by DXA in HIV-infected men and healthy men. HIV-infected men were divided into LD patients and non-LD patients according to whether they were complicated with LD. Healthy men were selected as controls. Fat mass (FM) of HIV-infected patients correlated negatively with the duration of HIV infection and with the duration of highly active antiretroviral therapy regimen (r(s)=-0.448 and -0.563; p=0.032 and 0.000, respectively). Multiple linear regression results showed that FM had positive correlation with weight and bone mineral content (BMC) and had negative correlation with lean mass (LM). Total body and regional FMs were found to be significantly different among LD patients, non-LD patients, and controls-the lowest in LD patients and the highest in controls (p<0.05). Total body, trunk, and leg BMCs of LD patients were lower than those of controls (p<0.05). Lumbar bone mineral density of LD patients was lower than that of non-LD patients and controls (p=0.04 and 0.007). LM of LD patients was higher than that of non-LD patients, and trunk LM had statistical difference between the 2 groups (p=0.003). Applying DXA to assess HIV-infected patient's body composition changes could provide objective information for physicians to prevent LD and osteoporosis.

Comparative endocrinology of aging and longevity regulation

Hormones regulate growth, development, metabolism, and other complex processes in multicellular animals. For many years it has been suggested that hormones may also influence the rate of the aging process. Aging is a multifactorial process that causes biological systems to break down and cease to function in adult organisms as time passes, eventually leading to death. The exact underlying causes of the aging process remain a topic for debate, and clues that may shed light on these causes are eagerly sought after. In the last two decades, gene mutations that result in delayed aging and extended longevity have been discovered, and many of the affected genes have been components of endocrine signaling pathways. In this review we summarize the current knowledge on the roles of endocrine signaling in the regulation of aging and longevity in various animals. We begin by discussing the notion that conserved systems, including endocrine signaling pathways, "regulate" the aging process. Findings from the major model organisms: worms, flies, and rodents, are then outlined. Unique lessons from studies of non-traditional models: bees, salmon, and naked mole rats, are also discussed. Finally, we summarize the endocrinology of aging in humans, including changes in hormone levels with age, and the involvement of hormones in aging-related diseases. The most well studied and widely conserved endocrine pathway that affects aging is the insulin/insulin-like growth factor system. Mutations in genes of this pathway increase the lifespan of worms, flies, and mice. Population genetic evidence also suggests this pathway's involvement in human aging. Other hormones including steroids have been linked to aging only in a subset of the models studied. Because of the value of comparative studies, it is suggested that the aging field could benefit from adoption of additional model organisms.

Significant associations of age, menopausal status and lifestyle factors with visceral adiposity in African-American and European-American women

BACKGROUND

Elevated visceral adiposity is strongly predictive of cardiometabolic disease, but, due to the high cost of biomedical imaging, assessment of factors contributing to normal variation in visceral (VAT) and subcutaneous (SAT) adipose tissue partitioning in large cohorts of healthy individuals are few, particularly in ethnic and racial minority populations.

OBJECTIVE

To describe age, menopausal status, smoking and physical activity differences in VAT and abdominal subcutaneous adipose tissue (ASAT) mass in African-American (AA) and European-American (EA) women.

METHODS

Magnetic resonance imaging measures of VAT and ASAT mass and VAT% (VAT/VAT+ASAT, %) were obtained from a cross-sectional sample of 617 EA and 111 AA non-diabetic women aged 18-80 years. Multivariate linear regression was used to test independent effects of the covariates.

RESULTS

VAT and VAT% were higher in EA than AA women (p < 0.01). Differences in VAT, ASAT and VAT% across age groups began in early adulthood in both ethnic groups, but the association of age with VAT% was stronger in EA women (p for interaction = 0.03). Current smokers had higher VAT and VAT% (p < 0.01) and lower TBF than non-smokers. Frequent participation in sports activities was associated with ∼30% lower VAT in older (>55 years) as well as younger ( < 40 years) women (p < 0.0001).

CONCLUSION

Greater allocation of abdominal adipose tissue into the visceral compartment occurs in EA than AA women and in older than younger women. Avoidance of cigarette smoking and frequent participation in sports activities may partially counteract this deleterious phenomenon of ageing.

Aging, resistance training, and diabetes prevention

With the aging of the baby-boom generation and increases in life expectancy, the American population is growing older. Aging is associated with adverse changes in glucose tolerance and increased risk of diabetes; the increasing prevalence of diabetes among older adults suggests a clear need for effective diabetes prevention approaches for this population. The purpose of paper is to review what is known about changes in glucose tolerance with advancing age and the potential utility of resistance training (RT) as an intervention to prevent diabetes among middle-aged and older adults. Age-related factors contributing to glucose intolerance, which may be improved with RT, include improvements in insulin signaling defects, reductions in tumor necrosis factor-α, increases in adiponectin and insulin-like growth factor-1 concentrations, and reductions in total and abdominal visceral fat. Current RT recommendations and future areas for investigation are presented.

Body fat distribution and inflammation among obese older adults with and without metabolic syndrome

The protective mechanisms by which some obese individuals escape the detrimental metabolic consequences of obesity are not understood. This study examined differences in body fat distribution and adipocytokines in obese older persons with and without metabolic syndrome. Additionally, we examined whether adipocytokines mediate the association between body fat distribution and metabolic syndrome. Data were from 729 obese men and women (BMI ≥ 30 kg/m(2)), aged 70-79 participating in the Health, Aging and Body Composition (Health ABC) study. Thirty-one percent of these obese men and women did not have metabolic syndrome. Obese persons with metabolic syndrome had significantly more abdominal visceral fat (men: P = 0.04; women: P < 0.01) and less thigh subcutaneous fat (men: P = 0.09; women: P < 0.01) than those without metabolic syndrome. Additionally, those with metabolic syndrome had significantly higher levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and plasminogen activator inhibitor-1 (PAI-1) than individuals without metabolic syndrome. Per standard deviation higher in visceral fat, the likelihood of metabolic syndrome significantly increased in women (odds ratio (OR): 2.16, 95% confidence interval (CI): 1.59-2.94). In contrast, the likelihood of metabolic syndrome decreased in both men (OR: 0.56, 95% CI: 0.39-0.80) and women (OR: 0.49, 95% CI: 0.34-0.69) with each standard deviation higher in thigh subcutaneous fat. These associations were partly mediated by adipocytokines; the association between thigh subcutaneous fat and metabolic syndrome was no longer significant in men. In summary, metabolically healthy obese older persons had a more favorable fat distribution, characterized by lower visceral fat and greater thigh subcutaneous fat and a more favorable inflammatory profile compared to their metabolically unhealthy obese counterparts.

Obesity-mediated inflammatory microenvironment stimulates osteoclastogenesis and bone loss in mice

Clinical evidence indicates that fat is inversely proportional to bone mass in elderly obese women. However, it remains unclear whether obesity accelerates bone loss. In this report we present evidence that increased visceral fat leads to inflammation and subsequent bone loss in 12-month-old C57BL/6J mice that were fed 10% corn oil (CO)-based diet and a control lab chow (LC) for 6 months. As expected from our previous work, CO-fed mice demonstrated increased visceral fat and enhanced total body fat mass compared to LC. The adipocyte-specific PPARγ and bone marrow (BM) adiposity were increased in CO-fed mice. In correlation with those modifications, inflammatory cytokines (IL-1β, IL-6, TNF-α) were significantly elevated in CO-fed mice compared to LC-fed mice. This inflammatory BM microenvironment resulted in increased superoxide production in osteoclasts and undifferentiated BM cells. In CO-fed mice, the increased number of osteoclasts per trabecular bone length and the increased osteoclastogenesis assessed ex-vivo suggest that CO diet induces bone resorption. Additionally, the up-regulation of osteoclast-specific cathepsin k and RANKL expression and down-regulation of osteoblast-specific RUNX2/Cbfa1 supports this bone resorption in CO-fed mice. Also, CO-fed mice exhibited lower trabecular bone volume in the distal femoral metaphysis and had reduced OPG expression. Collectively, our results suggest that increased bone resorption in mice fed a CO-enriched diet is possibly due to increased inflammation mediated by the accumulation of adipocytes in the BM microenvironment. This inflammation may consequently increase osteoclastogenesis, while reducing osteoblast development in CO-fed mice.

Adipose tissue and volumetric bone mineral density of older Afro-Caribbean men

Although low body weight is a risk factor for osteoporosis-related fractures, conflicting data exist for the association between adiposity and bone mineral density (BMD). Studies examining these relationships have measured body fat and BMD with dual-energy X-ray absorptiometry (DXA), which cannot distinguish subcutaneous adipose tissue area (SAT) from total adiposity or trabecular from cortical bone. To investigate the relationship between adiposity and BMD further, we analyzed body composition and adipose tissue distribution by quantitative computed tomography (QCT) in 1829 Afro-Caribbean men aged 40 years and older from a population-based sample. Cortical volumetric BMD, muscle cross-sectional area, total adipose tissue area (TAT), and percentage SAT were measured at the proximal tibia. Trabecular volumetric BMD was measured at the distal tibia. We used analysis of covariance to test for associations between quartile of the adipose tissue measures and BMD, adjusting for anthropometric, health, and lifestyle factors. Higher TAT was associated with lower cortical BMD in both unadjusted and adjusted models (p < .001). Men with a higher percentage SAT had greater cortical BMD (p < .001). Similar associations were seen between percent SAT and trabecular BMD at the distal tibia. These results indicate that total adiposity is a potentially important correlate of bone mass in older men and that different fat depots may have opposing associations with bone mass. Additional research is needed to better understand the mechanisms underlying the relationship between body fat distribution and bone mass.

Fat tissue, aging, and cellular senescence

Fat tissue, frequently the largest organ in humans, is at the nexus of mechanisms involved in longevity and age-related metabolic dysfunction. Fat distribution and function change dramatically throughout life. Obesity is associated with accelerated onset of diseases common in old age, while fat ablation and certain mutations affecting fat increase life span. Fat cells turn over throughout the life span. Fat cell progenitors, preadipocytes, are abundant, closely related to macrophages, and dysdifferentiate in old age, switching into a pro-inflammatory, tissue-remodeling, senescent-like state. Other mesenchymal progenitors also can acquire a pro-inflammatory, adipocyte-like phenotype with aging. We propose a hypothetical model in which cellular stress and preadipocyte overutilization with aging induce cellular senescence, leading to impaired adipogenesis, failure to sequester lipotoxic fatty acids, inflammatory cytokine and chemokine generation, and innate and adaptive immune response activation. These pro-inflammatory processes may amplify each other and have systemic consequences. This model is consistent with recent concepts about cellular senescence as a stress-responsive, adaptive phenotype that develops through multiple stages, including major metabolic and secretory readjustments, which can spread from cell to cell and can occur at any point during life. Senescence could be an alternative cell fate that develops in response to injury or metabolic dysfunction and might occur in nondividing as well as dividing cells. Consistent with this, a senescent-like state can develop in preadipocytes and fat cells from young obese individuals. Senescent, pro-inflammatory cells in fat could have profound clinical consequences because of the large size of the fat organ and its central metabolic role.

Epigenetic changes play critical role in age-associated dysfunctions of the liver

CCAAT/Enhancer Binding Proteins family proteins are important regulators of liver functions. Here, we show the critical role of C/EBPα-mediated chromatin remodeling in the age-associated dysfunctions of the liver and in the maintenance of physiological homeostasis. Because ph-S193 isoform of C/EBPα is increased in livers of old mice, we have generated C/EBPα-S193D knockin mice, which mimic the ph-S193 isoform of C/EBPα. Analyses of these mice showed that the S193D mutation causes chromatin remodeling leading to histological appearance of 'foci-like' nodules, which are also observed in livers of old mice. These 'foci-like' structures contain K9 trimethylated histone H3, a marker of heterochromatin. The increase of heterochromatin regions in S193D mice correlates with the elevation of S193D-C/EBPα-HDAC1 complexes and with dys-regulation of gene expression including epigenetic silencing of cyclin D1 and D2 promoters and the inhibition of liver proliferation. The elimination of C/EBPα-HDAC1 complexes in S193D mice by inhibition of HDAC1 corrects chromatin structure and normalizes expression of cyclin D1 and D2. We found that epigenetic dys-regulation is also associated with the elevation of C/EBPβ and with the increase of C/EBPα/β heterodimers in S193D mice. The C/EBPα/β heterodimers activate transcription of Glut4 and increase the levels of Glut4. As the result, S193D livers have accelerated uptake of glucose and accumulation of glycogen in the liver. Thus, this study demonstrates that the phosphorylation of C/EBPα at S193 leads to the appearance of heterochromatin regions, which correlates with the development of age-related dysfunctions of the liver.

De novo generation of white adipocytes from the myeloid lineage via mesenchymal intermediates is age, adipose depot, and gender specific

It is generally assumed that white adipocytes arise from resident adipose tissue mesenchymal progenitor cells. We challenge this paradigm by defining a hematopoietic origin for both the de novo development of a subset of white adipocytes in adults and a previously uncharacterized adipose tissue resident mesenchymal progenitor population. Lineage and cytogenetic analysis revealed that bone marrow progenitor (BMP)-derived adipocytes and adipocyte progenitors arise from hematopoietic cells via the myeloid lineage in the absence of cell fusion. Global gene expression analysis indicated that the BMP-derived fat cells are bona fide adipocytes but differ from conventional white or brown adipocytes in decreased expression of genes involved in mitochondrial biogenesis and lipid oxidation, and increased inflammatory gene expression. The BMP-derived adipocytes accumulate with age, occur in higher numbers in visceral than in subcutaneous fat, and in female versus male mice. BMP-derived adipocytes may, therefore, account in part for adipose depot heterogeneity and detrimental changes in adipose metabolism and inflammation with aging and adiposity.

PAC1 gene knockout reveals an essential role of chaperone-mediated 20S proteasome biogenesis and latent 20S proteasomes in cellular homeostasis

The 26S proteasome, a central enzyme for ubiquitin-dependent proteolysis, is a highly complex structure comprising 33 distinct subunits. Recent studies have revealed multiple dedicated chaperones involved in proteasome assembly both in yeast and in mammals. However, none of these chaperones is essential for yeast viability. PAC1 is a mammalian proteasome assembly chaperone that plays a role in the initial assembly of the 20S proteasome, the catalytic core of the 26S proteasome, but does not cause a complete loss of the 20S proteasome when knocked down. Thus, both chaperone-dependent and -independent assembly pathways exist in cells, but the contribution of the chaperone-dependent pathway remains unclear. To elucidate its biological significance in mammals, we generated PAC1 conditional knockout mice. PAC1-null mice exhibited early embryonic lethality, demonstrating that PAC1 is essential for mammalian development, especially for explosive cell proliferation. In quiescent adult hepatocytes, PAC1 is responsible for producing the majority of the 20S proteasome. PAC1-deficient hepatocytes contained normal amounts of the 26S proteasome, but they completely lost the free latent 20S proteasome. They also accumulated ubiquitinated proteins and exhibited premature senescence. Our results demonstrate the importance of the PAC1-dependent assembly pathway and of the latent 20S proteasomes for maintaining cellular integrity.

Waist circumference but not body mass index predicts long-term mortality in elderly subjects with chronic heart failure

OBJECTIVES

To examine whether waist circumference (WC) and body-mass index (BMI) can predict long-term mortality in elderly subjects with and without chronic heart failure (CHF).

DESIGN

Longitudinal evaluation with a 12-year follow-up.

SETTING

Campania, a region of southern Italy.

PARTICIPANTS

One thousand three hundred thirty-two subjects aged 65 and older selected from the electoral rolls of Campania.

MEASUREMENTS

The relationship between WC or BMI and mortality during a 12-year follow-up in 125 subjects with and 1,143 subjects without CHF.

RESULTS

Mortality increased as WC increased in elderly subjects without CHF (from 47.8% to 56.7%, P=.01), and the increase was even greater in patients with CHF (from 58.1% to 82.0%, P=.01). In contrast, mortality decreased as BMI increased in elderly subjects without CHF (from 53.8% to 46.1%, P0=.046) but not in those with CHF. According to Cox regression analysis, BMI protected against long-term mortality in the absence but not in the presence of CHF. In the absence of CHF, WC was associated with a 2% increased risk of long-term mortality for each 1-cm greater WC (Hazard Ratio (HR)=1.02, 95% confidence interval (CI)=1.01-1.03; P<.001), versus 5% increased in the presence of CHF (HR=1.06, 95% CI=1.02-1.10; P<.001).

CONCLUSION

WC, but not BMI, is predictive of long-term mortality in elderly individuals with CHF and to a lesser extent in those without CHF.

High fat diet increases hippocampal oxidative stress and cognitive impairment in aged mice: implications for decreased Nrf2 signaling

Long term consumption of a high fat diet (HFD) contributes to increased morbidity and mortality. Yet the specific effects of HFD consumption on brain aging are poorly understood. In the present study 20-month old male C57Bl/6 mice were fed either 'western diet' (41% fat), very high fat lard diet (60% fat), or corresponding control diets for 16 weeks and then assessed for changes in metabolism and brain homeostasis. Although both HFDs increased adiposity and fasting blood glucose, only the high fat lard diet increased age-related oxidative damage (protein carbonyls) and impaired retention in the behavioral test. This selective increase in oxidative damage and cognitive decline was also associated with a decline in NF-E2-related factor 2 (Nrf2) levels and Nrf2 activity, suggesting a potential role for decreased antioxidant response. Taken together, these data suggest that while adiposity and insulin resistance following HFD consumption are linked to increased morbidity, the relationship between these factors and brain homeostasis during aging is not a linear relationship. More specifically, these data implicate impaired Nrf2 signaling and increased cerebral oxidative stress as mechanisms underlying HFD-induced declines in cognitive performance in the aged brain.

Intersection between metabolic dysfunction, high fat diet consumption, and brain aging

Deleterious neurochemical, structural, and behavioral alterations are a seemingly unavoidable aspect of brain aging. However, the basis for these alterations, as well as the basis for the tremendous variability in regards to the degree to which these aspects are altered in aging individuals, remains to be elucidated. An increasing number of individuals regularly consume a diet high in fat, with high-fat diet consumption known to be sufficient to promote metabolic dysfunction, although the links between high-fat diet consumption and aging are only now beginning to be elucidated. In this review we discuss the potential role for age-related metabolic disturbances serving as an important basis for deleterious perturbations in the aging brain. These data not only have important implications for understanding the basis of brain aging, but also may be important to the development of therapeutic interventions which promote successful brain aging.

Changes of muscular load with aging in the motion of pulling up disposable diapers

To elucidate how aging affects the muscular load required for pulling up pants-style disposable diapers, and why some elderly people cannot pull up the rear of their disposable diapers well, we evaluated the electromyogram (EMG) of 8 young subjects (21.5+/-1.5 years) and 7 elderly subjects (71.6+/-6.1 years). EMG was measured for four muscles--biceps brachii, deltoid, brachioradialis, and flexor carpi ulnaris. We evaluated the muscular load during a series of motions for pulling a disposable diaper up at the front and the rear of the body using an EMG-Video Synchronous Split Method. The analysis revealed that the front and the rear integral EMG of elderly subjects were both significantly larger than those of young subjects for all four muscles. For the deltoid and flexor carpi ulnaris muscles, the maximum amplitude of EMG when pulling up the rear of the disposable diapers was significantly larger in the elderly subjects than the young ones. These results suggest that the muscular load involved in pulling up the rear of disposable diapers may increase due to changes in body habitus caused by aging. Since muscular strength decreases with age, it seems likely that the elderly individuals will eventually be unable to pull up the rear of their diapers.

Epidemiology of myosteatosis

PURPOSE OF REVIEW

To summarize the epidemiology of myosteatosis and its association with diabetes.

RECENT FINDINGS

The role of myosteatosis (fat infiltration in skeletal muscle) in diabetes has received considerable attention. There is reasonably consistent evidence that myosteatosis contributes to glucose and insulin abnormalities and diabetes, possibly even independent of overall obesity. Novel hypotheses that link myosteatosis with insulin resistance and type 2 diabetes have also recently been proposed. These hypotheses suggest that impaired secretion of adipokines, modulation of nutritive blood flow to skeletal muscle, or both may be of importance for the development of myosteatosis. Recent longitudinal data also suggest that myosteatosis increases with aging, regardless of changes in body weight.

SUMMARY

Further studies are needed to identify the specific physiological mechanisms that influence myosteatosis, and the mechanisms that link this fat depot with insulin resistance. Longitudinal studies are also needed to evaluate the remodeling of skeletal muscle fat with aging, across a wider age spectrum, and across different populations, especially those at high risk of developing diabetes. There is also a need to evaluate whether myosteatosis influences the incidence of type 2 diabetes independent of overall adiposity. A better understanding of the factors that regulate myosteatosis may lead to the development of novel therapies that influence a more metabolically 'healthy' skeletal muscle.

Diet and age interactions with regards to cholesterol regulation and brain pathogenesis

Cholesterol is an essential molecule for brain homeostasis; yet, hypercholesterolemia and its numerous complications are believed to play a role in promoting multiple aspects of brain pathogenesis. An ever increasing number of individuals in modern Western Society are regularly consuming diets high in fat which promote the development of hypercholesterolemia. Additionally, modern societies are becoming increasingly aged, causing a collision between increased hypercholesterolemia and increased aging, which will likely lead to the development of increased pathological conditions due to hypercholesterolemia, thereby promoting deleterious neurochemical and behavioral changes in the brain. Lastly, while beneficial in controlling cholesterol levels, the long-term use of statins itself may potentially promote adverse effects on brain homeostasis, although specifics on this remain largely unknown. This review will focus on linking the current understanding of diet-induced hypercholesterolemia (as well as statin use) to the development of oxidative stress, neurochemical alterations, and cognitive disturbances in the aging brain.

Age-related molecular genetic changes of murine bone marrow mesenchymal stem cells

Background

Mesenchymal stem cells (MSC) are pluripotent cells, present in the bone marrow and other tissues that can differentiate into cells of all germ layers and may be involved in tissue maintenance and repair in adult organisms. Because of their plasticity and accessibility these cells are also prime candidates for regenerative medicine. The contribution of stem cell aging to organismal aging is under debate and one theory is that reparative processes deteriorate as a consequence of stem cell aging and/or decrease in number. Age has been linked with changes in osteogenic and adipogenic potential of MSCs.

Results

Here we report on changes in global gene expression of cultured MSCs isolated from the bone marrow of mice at ages 2, 8, and 26-months. Microarray analyses revealed significant changes in the expression of more than 8000 genes with stage-specific changes of multiple differentiation, cell cycle and growth factor genes. Key markers of adipogenesis including lipoprotein lipase, FABP4, and Itm2a displayed age-dependent declines. Expression of the master cell cycle regulators p53 and p21 and growth factors HGF and VEGF also declined significantly at 26 months. These changes were evident despite multiple cell divisions in vitro after bone marrow isolation.

Conclusions

The results suggest that MSCs are subject to molecular genetic changes during aging that are conserved during passage in culture. These changes may affect the physiological functions and the potential of autologous MSCs for stem cell therapy.

Obesity in the elderly: is faulty metabolism to blame?

The fastest growing segment of the US population, and that of other developed countries, is the oldest-old (aged >85 years). Many children born after the year 2000 in countries with the longest lived residents may live to see their 100th birthday. The combination of reduced mortality along with reduced fertility in developed countries is producing 'population aging', and the comorbidities associated with aging are becoming important public health issues. Age-associated obesity is one such important public health issue. Aging is associated with significant changes in body composition, including loss of skeletal muscle mass and increased visceral fat accumulation. The loss of muscle mass is accompanied by a disproportionate decline in muscle strength (up to three-times greater than the loss of mass), indicative of reduced muscle 'quality' or muscle dysfunctionality. Aging is characterized by markedly reduced physical activity and a drop in resting metabolic rate that is disproportionate to the loss of muscle mass, with a shift towards preferentially oxidizing carbohydrate at the expense of fat. A combination of these factors may act to increase muscular lipid infiltration and decrease insulin sensitivity; however, the cause and effect relationship remains undetermined. Changes in cellular energy (i.e., ATP) requirement owing to decreased ion channel activity, decreased protein synthesis or increased mitochondrial energy efficiency may underlie the decreased resting metabolic rate. Increasing energy demand through physical activity may alleviate some of the adverse metabolic changes that are associated with aging.

Arterial destiffening with weight loss in overweight and obese middle-aged and older adults

We tested the hypothesis that weight loss via a hypocaloric diet would reduce arterial stiffness in overweight and obese middle-aged and older adults. Thirty-six individuals were randomly assigned to a weight loss (n=25; age: 61.2+/-0.8 years; body mass index: 30.0+/-0.6 kg/m(2)) or a control (n=11; age: 66.1+/-1.9 years; body mass index: 31.8+/-1.4 kg/m(2)) group. Arterial stiffness was measured via carotid artery ultrasonography combined with applanation tonometry and carotid-femoral pulse wave velocity via applanation tonometry at baseline and after the 12-week intervention. Body weight, body fat, abdominal adiposity, blood pressure, beta-stiffness index, and carotid-femoral pulse wave velocity were similar in the 2 groups at baseline (all P>0.05). Body weight (-7.1+/-0.7 versus -0.7+/-1.1 kg), body fat, and abdominal adiposity decreased in the weight loss group but not in the control group (all P<0.05). Brachial systolic and diastolic blood pressures declined (P<0.05) only in the weight loss group. Central systolic and pulse pressures did not change significantly in either group. beta-Stiffness index (-1.24+/-0.22 versus 0.52+/-0.37 U) and carotid-femoral pulse wave velocity (-187+/-29 versus 15+/-42 cm/s) decreased in the weight loss group but not in the control group (all P<0.05). The reductions in carotid-femoral pulse wave velocity were correlated with reductions in total body and abdominal adiposity (r=0.357-0.602; all P<0.05). However, neither total body nor abdominal adiposity independently predicted reductions in arterial stiffness indices. In summary, our findings indicate that weight loss reduces arterial stiffness in overweight/obese middle-aged and older adults, and the magnitudes of these improvements are related to the loss of total and abdominal adiposity.

Two-year body composition analyses of long-lived GHR null mice

Growth hormone receptor gene-disrupted (GHR-/-) mice exhibit increased life span and adipose tissue mass. Although this obese phenotype has been reported extensively for young adult male GHR-/- mice, data for females and for other ages in either gender are lacking. Thus, the purpose of this study was to evaluate body composition longitudinally in both male and female GHR-/- mice. Results show that GHR-/- mice have a greater percent fat mass with no significant difference in absolute fat mass throughout life. Lean mass shows an opposite trend with percent lean mass not significantly different between genotypes but absolute mass reduced in GHR-/- mice. Differences in body composition are more pronounced in male than in female mice, and both genders of GHR-/- mice show specific enlargement of the subcutaneous adipose depot. Along with previously published data, these results suggest a consistent and intriguing protective effect of excess fat mass in the subcutaneous region.