Genes that prolong life: relationships of growth hormone and growth to aging and life span

Modeling of age-related neurological disease: utility of zebrafish

Many age-related neurological diseases still lack effective treatments, making their understanding a critical and urgent issue in the globally aging society. To overcome this challenge, an animal model that accurately mimics these diseases is essential. To date, many mouse models have been developed to induce age-related neurological diseases through genetic manipulation or drug administration. These models help in understanding disease mechanisms and finding potential therapeutic targets. However, some age-related neurological diseases cannot be fully replicated in human pathology due to the different aspects between humans and mice. Although zebrafish has recently come into focus as a promising model for studying aging, there are few genetic zebrafish models of the age-related neurological disease. This review compares the aging phenotypes of humans, mice, and zebrafish, and provides an overview of age-related neurological diseases that can be mimicked in mouse models and those that cannot. We presented the possibility that reproducing human cerebral small vessel diseases during aging might be difficult in mice, and zebrafish has potential to be another animal model of such diseases due to their similarity of aging phenotype to humans.

Does diet influence aging? Evidence from animal studies

Nutrition profoundly influences the risk for many age-related diseases. Whether nutrition influences human aging biology directly is less clear. Studies in different animal species indicate that reducing food intake ("caloric restriction" [CR]) can increase lifespan and delay the onset of diseases and the biological hallmarks of aging. Obesity has been described as "accelerated aging" and therefore the lifespan and health benefits generated by CR in both aging and obesity may occur via similar mechanisms. Beyond calorie intake, studies based on nutritional geometry have shown that protein intake and the interaction between dietary protein and carbohydrates influence age-related health and lifespan. Studies where animals are calorically restricted by providing free access to diluted diets have had less impact on lifespan than those studies where animals are given a reduced aliquot of food each day and are fasting between meals. This has drawn attention to the role of fasting in health and aging, and exploration of the health effects of various fasting regimes. Although definitive human clinical trials of nutrition and aging would need to be unfeasibly long and unrealistically controlled, there is good evidence from animal experiments that some nutritional interventions based on CR, manipulating dietary macronutrients, and fasting can influence aging biology and lifespan.

Distinguishing between driver and passenger mechanisms of aging

Understanding why we age is a long-standing question, and many mechanistic theories of aging have been proposed. Owing to limitations in studying the aging process, including a lack of adequate quantitative measurements, its mechanistic basis remains a subject of debate. Here, I explore theories of aging from the perspective of causal relationships. Many aging-related changes have been observed and touted as drivers of aging, including molecular changes in the genome, telomeres, mitochondria, epigenome and proteins and cellular changes affecting stem cells, the immune system and senescent cell buildup. Determining which changes are drivers and not passengers of aging remains a challenge, however, and I discuss how animal models and human genetic studies have been used empirically to infer causality. Overall, our understanding of the drivers of human aging is still inadequate; yet with a global aging population, elucidating the causes of aging has the potential to revolutionize biomedical research.

Female scent accelerates growth of juvenile male mice

Exposing female house mice (Mus musculus) to male urinary scent accelerates their sexual development (Vandenbergh effect). Here, we tested whether exposing juvenile male mice to females' urine similarly influences male growth and size of their sexual organs. We exposed three-week old male house mice to female urine or water (control) for ca. three months. We found that female-exposed males grew significantly faster and gained more body mass than controls, despite all males being reared on a controlled diet, but we detected no differences in males' muscle mass or sexual organs. In contrast, exposing juvenile males to male urine had no effect their growth. We tested whether the males' accelerated growth imposed functional trade-offs on males' immune resistance to an experimental infection. We challenged the same male subjects with an avirulent bacterial pathogen (Salmonella enterica), but found no evidence that faster growth impacted their bacterial clearance, body mass or survival during infection compared to controls. Our results provide the first evidence to our knowledge that juvenile male mice accelerate their growth when exposed to the urine of adult females, though we found no evidence that increased growth had negative trade-offs on immune resistance to infectious disease.

Improved impedance to maladaptation and enhanced VCAM-1 upregulation with resistance-type training in the long-lived Snell dwarf (Pit1dw/dw) mouse

Snell dwarf mice with the Pit1^dw/dw mutation are deficient in growth hormone, prolactin, and thyroid stimulating hormone and exhibit >40% lifespan extension. This longevity is accompanied by compromised muscular performance. However, research regarding young (3-month-old) Snell dwarf mice demonstrate exceptional responsivity to resistance-type training especially in terms of a shifted fiber type distribution and increased protein levels of vascular cell adhesion molecule-1 (VCAM-1), a possible mediator of such remodeling. In the present study, we investigated whether this responsiveness persists at 12 months of age. Unlike 12-month-old control mice, age-matched Snell dwarf mice remained resistant to training-induced maladaptive decreases in performance and muscle mass. This was accompanied by retainment of the remodeling capacity in muscles of Snell dwarf mice to increase VCAM-1 protein levels and a shift in myosin heavy chain (MHC) isoform distribution with training. Even decreasing training frequency for control mice, an alteration which protected muscles from maladaptation at 12 months of age, did not result in the overt remodeling observed for Snell dwarf mice. The results demonstrate a distinct remodeling response to resistance-type exercise operative in the context of the Pit1^dw/dw mutation of long-lived Snell dwarf mice.

Mice with gene alterations in the GH and IGF family

Much of our understanding of GH's action stems from animal models and the generation and characterization of genetically altered or modified mice. Manipulation of genes in the GH/IGF1 family in animals started in 1982 when the first GH transgenic mice were produced. Since then, multiple laboratories have altered mouse DNA to globally disrupt Gh, Ghr, and other genes upstream or downstream of GH or its receptor. The ability to stay current with the various genetically manipulated mouse lines within the realm of GH/IGF1 research has been daunting. As such, this review attempts to consolidate and summarize the literature related to the initial characterization of many of the known gene-manipulated mice relating to the actions of GH, PRL and IGF1. We have organized the mouse lines by modifications made to constituents of the GH/IGF1 family either upstream or downstream of GHR or to the GHR itself. Available data on the effect of altered gene expression on growth, GH/IGF1 levels, body composition, reproduction, diabetes, metabolism, cancer, and aging are summarized. For the ease of finding this information, key words are highlighted in bold throughout the main text for each mouse line and this information is summarized in Tables 1, 2, 3 and 4. Most importantly, the collective data derived from and reported for these mice have enhanced our understanding of GH action.

Evolution of natural lifespan variation and molecular strategies of extended lifespan in yeast

To understand the genetic basis and selective forces acting on longevity, it is useful to examine lifespan variation among closely related species, or ecologically diverse isolates of the same species, within a controlled environment. In particular, this approach may lead to understanding mechanisms underlying natural variation in lifespan. Here, we analyzed 76 ecologically diverse wild yeast isolates and discovered a wide diversity of replicative lifespan (RLS). Phylogenetic analyses pointed to genes and environmental factors that strongly interact to modulate the observed aging patterns. We then identified genetic networks causally associated with natural variation in RLS across wild yeast isolates, as well as genes, metabolites, and pathways, many of which have never been associated with yeast lifespan in laboratory settings. In addition, a combined analysis of lifespan-associated metabolic and transcriptomic changes revealed unique adaptations to interconnected amino acid biosynthesis, glutamate metabolism, and mitochondrial function in long-lived strains. Overall, our multiomic and lifespan analyses across diverse isolates of the same species shows how gene-environment interactions shape cellular processes involved in phenotypic variation such as lifespan.

Determinants and long-term costs of early reproduction in males of a long-lived polygynous mammal

In long-lived polygynous species, male reproductive success is often monopolized by a few mature dominant individuals. Young males are generally too small to be dominant and may employ alternative tactics; however, little is known about the determinants of reproductive success for young males. Understanding the causes and consequences of variability in early reproductive success may be crucial to assess the strength of sexual selection and possible long-term trade-offs among life-history traits. Selective pressures driven by fluctuating environmental conditions may depend on age class. We evaluated the determinants of reproduction in male bighorn sheep (Ovis canadensis) aged 2-4 years using 30 years of individual-level data. These young males cannot defend estrous ewes and use alternative mating tactics. We also investigated how the age of first detected reproduction was correlated to lifetime reproductive success and longevity. We found that reproductive success of males aged 3 years was positively correlated to body mass, to the proportion of males aged 2-4 years in the competitor pool, and to the number of females available per adult male. These results suggest that reproductive success depends on both competitive ability and population age-sex structure. None of these variables, however, had significant effects on the reproductive success of males aged 2 or 4 years. Known reproduction before the age of five increased lifetime reproductive success but decreased longevity, suggesting a long-term survival cost of early reproduction. Our analyses reveal that both individual-level phenotypic and population-level demographic variables influence reproductive success by young males and provide a rare assessment of fitness trade-offs in wild polygynous males.

Fate of Hematopoiesis During Aging. What Do We Really Know, and What are its Implications?

There is an ongoing shift in demographics such that older persons will outnumber young persons in the coming years, and with it age-associated tissue attrition and increased diseases and disorders. There has been increased information on the association of the aging process with dysregulation of hematopoietic stem (HSC) and progenitor (HPC) cells, and hematopoiesis. This review provides an extensive up-to date summary on the literature of aged hematopoiesis and HSCs placed in context of potential artifacts of the collection and processing procedure, that may not be totally representative of the status of HSCs in their in vivo bone marrow microenvironment, and what the implications of this are for understanding aged hematopoiesis. This review covers a number of interactive areas, many of which have not been adequately explored. There are still many unknowns and mechanistic insights to be elucidated to better understand effects of aging on the hematopoietic system, efforts that will take multidisciplinary approaches, and that could lead to means to ameliorate at least some of the dysregulation of HSCs and HPCs associated with the aging process. Graphical Abstract.

Relationship between the FRAX index and physical and cognitive functioning in older people

OBJECTIVE

To assess the relationship between the FRAX index and the Barthel index/MiniMental State Examination in older people.

PATIENTS AND METHODS

Observational descriptive study. Demographic data, comorbidity, dependency and cognitive state, and risk of osteoporotic fracture were collected.

RESULTS

A total of 375 patients were included (60% female) Patients with a low-risk FRAX for hip fractures had a higher Mini-mental (25, 95% CI = 24-27 vs. 22, 95% = 21 to 23, p = .0001), a higher Barthel index (88, 95% CI = 84-93 vs 72, 69 to 76, p = .0001) without differences in the Charlson index. Bivariate analysis showed an inverse association between FRAX and scales but logistic regression showed only female sex (OR 4.4, 95% CI = 2.6-7.6) and the non-dependent Barthel index (OR = 0.104, 95% CI = 0.014-0.792) remained significant and. Barthel index/Mini-mental constructed a significant model capable of predicting a risk of hip fracture of >3% measured by the FRAX index, with an area under the curve of 0.76 (95% CI = 0.7-0.81).

CONCLUSIONS

The FRAX index is related to other markers of geriatric assessment and the association between these variables can predict a risk of hip fracture of >3% measured by the FRAX index. Key messages Geriatric assessment indexes may be as important as the FRAX index, which is based on clinical risk factors, in predicting the fracture risk in older patient.

Differences in growth rates and pre-hibernation body mass gain between early and late-born juvenile garden dormice

Juvenile hibernators have to allocate energy to both growth and fattening, to survive winter, and to avoid possible disadvantages during their first reproductive season. Being born late in the active season may have important effects on growth and fattening. This study aimed at determining potential differences in rates and maximal level of growth, and in pre-hibernation body fat mass between early and late-born juvenile garden dormice (Eliomys quercinus), and kept in outdoor enclosures with ad libitum food and water. We first assessed mean pup mass in early and late-born litters (n = 31) from birth to their early weaning phase, at which time body composition was determined. Then, growth and body mass of early and late-born individuals (six males and six females, for each group) were measured weekly until hibernation onset (n = 24). We also assessed fat content in a group of juveniles during pre-hibernation fattening (n = 16) and after their first winter hibernation (n = 18). During the pre-weaning phase, young from early and late litters mainly grew structurally and gained mass at similar rates. After weaning, late-born juveniles grew and gained mass twice as fast as early born individuals. Body mass was positively associated with fat content during pre-hibernation fattening. Late-born females reached similar structural sizes, but had lower pre-hibernation fat reserves than early born females. Conversely, late-born males showed lower maximal size and pre-hibernation body fat content, compared with early born males. Thus, individuals born late in the season cannot fully compensate the lack of available time before the winter onset.

Intrinsic versus Extrinsic Aging: A Histopathological, Morphometric and Immunohistochemical Study of Estrogen Receptor β and Androgen Receptor

Skin is a target organ of sex steroids which play important roles in skin health and disease. The aim of this study is to investigate the expression of estrogen receptor β (ERβ) and androgen receptor (AR) in human skin from different age groups for a better understanding of the hormonal regulation of skin aging. Using standard immunohistochemical techniques, biopsies of sun-unprotected and sun-protected skin were taken from 60 normal subjects. Sun-protected skin showed significantly higher immunoreactivity for ERβ and AR compared to sun-unprotected skin of all age groups. Significantly higher ERβ H score and percent of expression were associated with the 20-35 years age group compared to the groups that were 35-50 years and >50 years old (p < 0.02, p = 0.03, respectively) in sun-unprotected and sun-protected skin (p < 0.001, p = 0.01, respectively). AR H score showed a negative correlation with age (p = 0.04) with no significant difference in immunoreactivity in different age groups, either in sun-unprotected or sun-protected skin. There was also a significant correlation between ERβ H score and epidermal thickness in sun-unprotected (p = 0.04) and sun-protected skin (p = 0.04) in studied subjects regardless of age. The same relationships did not reach significance with AR expression. However, a significant positive correlation was detected between H scores and percent of expression of ERβ and AR in sun-unprotected (p = 0.01, p = 0.02, respectively) and sun-protected skin (p = 0.005, p = 0.02, respectively) regardless of age. In conclusion, both ERβ and AR decline gradually with intrinsic and extrinsic aging. This decline is more obvious with extrinsic aging. Further large-scaled studies are recommended to expand, validate and translate current findings to clinically significant, diagnostic and therapeutic applications. Molecular studies to investigate the probable ligand-independent action of both receptors are warranted. In addition, their gene expression patterns and associated signaling and metabolic pathways can also be tackled to provide a basis for further interventions in pathological processes that involve their dysregulation.

Original Research: Metabolic alterations from early life thyroxine replacement therapy in male Ames dwarf mice are transient

Ames dwarf mice are exceptionally long-lived due to a Prop1 loss of function mutation resulting in deficiency of growth hormone, thyroid-stimulating hormone and prolactin. Deficiency in thyroid-stimulating hormone and growth hormone leads to greatly reduced levels of circulating thyroid hormones and insulin-like growth factor 1, as well as a reduction in insulin secretion. Early life growth hormone replacement therapy in Ames dwarf mice significantly shortens their longevity, while early life thyroxine (T4) replacement therapy does not. Possible mechanisms by which early life growth hormone replacement therapy shortens longevity include deleterious effects on glucose homeostasis and energy metabolism, which are long lasting. A mechanism explaining why early life T4 replacement therapy does not shorten longevity remains elusive. Here, we look for a possible explanation as to why early life T4 replacement therapy does not impact longevity of Ames dwarf mice. We found that early life T4 replacement therapy increased body weight and advanced the age of sexual maturation. We also find that early life T4 replacement therapy does not impact glucose tolerance or insulin sensitivity, and any deleterious effects on oxygen consumption, respiratory quotient and heat production are transient. Lastly, we find that early life T4 replacement therapy has long-lasting effects on bone mineral density and bone mineral content. We suggest that the transient effects on energy metabolism and lack of effects on glucose homeostasis are the reasons why there is no shortening of longevity after early life T4 replacement therapy in Ames dwarf mice.

The Long Intron 1 of Growth Hormone Gene from Reeves' Turtle (Chinemys reevesii) Correlates with Negatively Regulated GH Expression in Four Cell Lines

Turtles grow slowly and have a long lifespan. Ultrastructural studies of the pituitary gland in Reeves’ turtle (Chinemys reevesii) have revealed that the species possesses a higher nucleoplasmic ratio and fewer secretory granules in growth hormone (GH) cells than other animal species in summer and winter. C. reevesii GH gene was cloned and species-specific similarities and differences were investigated. The full GH gene sequence in C. reevesii contains 8517 base pairs (bp), comprising five exons and four introns. Intron 1 was found to be much longer in C. reevesii than in other species. The coding sequence (CDS) of the turtle’s GH gene, with and without the inclusion of intron 1, was transfected into four cell lines, including DF-1 chicken embryo fibroblasts, Chinese hamster ovary (CHO) cells, human embryonic kidney 293FT cells, and GH4C1 rat pituitary cells; the turtle growth hormone (tGH) gene mRNA and protein expression levels decreased significantly in the intron-containing CDS in these cell lines, compared with that of the corresponding intronless CDS. Thus, the long intron 1 of GH gene in Reeves’ turtle might correlate with downregulated gene expression.

Neuroendocrine Regulation of Growth Hormone Secretion

This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions. One important event was the application of deconvolution analysis to the pulsatile patterns of GH secretion in different mammalian species, including Man, according to gender, hormonal environment and ageing. Concerning this last phenomenon, a great body of evidence now supports the role of an attenuation of the GHRH/GH/Insulin-like growth factor-1 (IGF-1) axis in the control of mammalian aging.

Deconstructing the Growth Hormone Receptor(GHR): Physical and Metabolic Phenotypes of Tissue-Specific GHR Gene-Disrupted Mice

Growth hormone (GH)-induced signaling results in numerous effects in multiple tissues throughout the body. Elucidation of several of these effects has come from studies observing the various phenotypes of the GH receptor (GHR) gene-disrupted (GHR-/-) mouse. These mice are dwarf and obese with increased insulin sensitivity, are resistant to cancer and diabetes, and have an extended lifespan. While these mice have proven to be a valuable tool for understanding the pleiotropic effects of GH, we and others have generated novel tissue-specific GHR gene-disrupted mouse lines that are now helping to further dissect the actions of GH on specific cells/tissues. In this chapter, we summarize the various phenotypes observed in these mice.

Being cool: how body temperature influences ageing and longevity

Temperature is a basic and essential property of any physical system, including living systems. Even modest variations in temperature can have profound effects on organisms, and it has long been thought that as metabolism increases at higher temperatures so should rates of ageing. Here, we review the literature on how temperature affects longevity, ageing and life history traits. From poikilotherms to homeotherms, there is a clear trend for lower temperature being associated with longer lifespans both in wild populations and in laboratory conditions. Many life-extending manipulations in rodents, such as caloric restriction, also decrease core body temperature. Nonetheless, an inverse relationship between temperature and lifespan can be obscured or reversed, especially when the range of body temperatures is small as in homeotherms. An example is observed in humans: women appear to have a slightly higher body temperature and yet live longer than men. The mechanisms involved in the relationship between temperature and longevity also appear to be less direct than once thought with neuroendocrine processes possibly mediating complex physiological responses to temperature changes. Lastly, we discuss species differences in longevity in mammals and how this relates to body temperature and argue that the low temperature of the long-lived naked mole-rat possibly contributes to its exceptional longevity.

Ames hypopituitary dwarf mice demonstrate imbalanced myelopoiesis between bone marrow and spleen

Ames hypopituitary dwarf mice are deficient in growth hormone, thyroid-stimulating hormone, and prolactin. The phenotype of these mice demonstrates irregularities in the immune system with skewing of the normal cytokine milieu towards a more anti-inflammatory environment. However, the hematopoietic stem and progenitor cell composition of the bone marrow (BM) and spleen in Ames dwarf mice has not been well characterized. We found that there was a significant decrease in overall cell count when comparing the BM and spleen of 4-5 month old dwarf mice to their littermate controls. Upon adjusting counts to differences in body weight between the dwarf and control mice, the number of granulocyte-macrophage progenitors, confirmed by immunophenotyping and colony-formation assay was increased in the BM. In contrast, the numbers of all myeloid progenitor populations in the spleen were greatly reduced, as confirmed by colony-formation assays. This suggests that there is a shift of myelopoiesis from the spleen to the BM of Ames dwarf mice; however, this shift does not appear to involve erythropoiesis. The reasons for this unusual shift in spleen to marrow hematopoiesis in Ames dwarf mice are yet to be determined but may relate to the decreased hormone levels in these mice.

Off-label use of hormones as an antiaging strategy: a review

Given demographic evolution of the population in modern societies, one of the most important health care needs is successful aging with less frailty and dependency. During the last 20 years, a multitude of anti-aging practices have appeared worldwide, aiming at retarding or even stopping and reversing the effects of aging on the human body. One of the cornerstones of anti-aging is hormone replacement. At present, women live one third of their lives in a state of sex-hormone deficiency. Men are also subject to age-related testosterone decline, but andropause remains frequently under-diagnosed and under-treated. Due to the decline of hormone production from gonads in both sexes, the importance of dehydroepiandrosterone (DHEA) in steroid hormone production increases with age. However, DHEA levels also decrease with age. Also, growth hormone age-associated decrease may be so important that insulin growth factor-1 levels found in elderly individuals are sometimes as low as those encountered in adult patients with established deficiency. Skin aging as well as decreases in lean body mass, bone mineral density, sexual desire and erectile function, intellectual activity and mood have all been related to this decrease of hormone production with age. Great disparities exist between recommendations from scientific societies and actual use of hormone supplements in aging and elderly patients. In this article, we review actual data on the effects of age related hormone decline on the aging process and age-related diseases such as sarcopenia and falls, osteoporosis, cognitive decline, mood disorders, cardiovascular health and sexual activity. We also provide information on the efficiency and safety of hormone replacement protocols in aging patients. Finally, we argue on future perspectives of such protocols as part of everyday practice.

Elevated ATF4 function in fibroblasts and liver of slow-aging mutant mice

Work in yeast has shown that longevity extension induced by nutrient deprivation, altered ribosomal function, or diminished target of rapamycin action requires the activity of GCN4. We hypothesized that increased activity of ATF4, the mammalian equivalent of yeast GCN4, might be characteristic of mutations that extend mouse life span. Fibroblasts from the skin of two such mutants (Snell dwarf and PAPP-A knockout) were found to have higher levels of ATF4 protein and expression of several ATF4 target genes in responses to amino acid withdrawal, cadmium, hydrogen peroxide, and tunicamycin. ATF4 pathways were also elevated in liver of both kinds of long-lived mutant mice. Thus, a connection between ATF4 pathways and longevity may have deep evolutionary roots, and further studies of ATF4 mechanisms may provide insights into the links between cellular stress resistance, protein translation control, and aging.

Contribution of genetic polymorphisms on functional status at very old age: a gene-based analysis of 38 genes (311 SNPs) in the oxidative stress pathway

Preservation of functional ability is a well-recognized marker of longevity. At a molecular level, a major determinant of the physiological decline occurring with aging is the imbalance between production and accumulation of oxidative damage to macromolecules, together with a decreased efficiency of stress response to avoid or repair such damage. In this paper we investigated the association of 38 genes (311 SNPs) belonging to the pro-antioxidant pathways with physical and cognitive performances, by analyzing single SNP and gene-based associations with Hand Grip strength (HG), Activities of Daily Living (ADL), Walking Speed (WS), Mini Mental State Examination (MMSE) and Composite Cognitive Score (CCS) in a Cohort of 1089 Danish nonagenarians. Moreover, for each gene analyzed in the pro-antioxidant pathway, we tested the influence on longitudinal survival. In the whole sample, nominal associations were found for TXNRD1 variability with ADL and WS, NDUFS1 and UCP3 with HG and WS, GCLC and UCP2 with WS (p<0.05). Stronger associations although not holding the multiple comparison correction, were observed between MMSE and NDUFV1, MT1A and GSTP1 variability (p<0.009). Moreover, we found that association between genetic variability in the pro-antioxidant pathway and functional status at old age is influenced by sex. In particular, most significant associations were observed in nonagenarian females, between HG scores and GLRX and UCP3 variability, between ADL levels and TXNRD1, MMSE and MT1A genetic variability. In males, a borderline statistically significant association with ADL level was found for UQCRFS1 gene. Nominally significant associations in relation to survival were found in the female sample only with SOD2, NDUFS1, UCP3 and TXNRD1 variability, the latter two confirming previous observations reported in the same cohort. Overall, our work supports the evidence that genes belonging to the pro-anti-oxidant pathway are able to modulate physical and cognitive performance after the ninth decade of life, finally influencing extreme survival.

Aging is not programmed: genetic pseudo-program is a shadow of developmental growth

Aging is not and cannot be programmed. Instead, aging is a continuation of developmental growth, driven by genetic pathways such as mTOR. Ironically, this is often misunderstood as a sort of programmed aging. In contrast, aging is a purposeless quasi-program or, figuratively, a shadow of actual programs.

“The brightest flame casts the darkest shadow.” -George Martin

Metabolic phenotype modulation by caloric restriction in a lifelong dog study

Modeling aging and age-related pathologies presents a substantial analytical challenge given the complexity of gene-environment influences and interactions operating on an individual. A top-down systems approach is used to model the effects of lifelong caloric restriction, which is known to extend life span in several animal models. The metabolic phenotypes of caloric-restricted (CR; n = 24) and pair-housed control-fed (CF; n = 24) Labrador Retriever dogs were investigated by use of orthogonal projection to latent structures discriminant analysis (OPLS-DA) to model both generic and age-specific responses to caloric restriction from the ¹H NMR blood serum profiles of young and older dogs. Three aging metabolic phenotypes were resolved: (i) an aging metabolic phenotype independent of diet, characterized by high levels of glutamine, creatinine, methylamine, dimethylamine, trimethylamine N-oxide, and glycerophosphocholine and decreasing levels of glycine, aspartate, creatine and citrate indicative of metabolic changes associated largely with muscle mass; (ii) an aging metabolic phenotype specific to CR dogs that consisted of relatively lower levels of glucose, acetate, choline, and tyrosine and relatively higher serum levels of phosphocholine with increased age in the CR population; (iii) an aging metabolic phenotype specific to CF dogs including lower levels of liproprotein fatty acyl groups and allantoin and relatively higher levels of formate with increased age in the CF population. There was no diet metabotype that consistently differentiated the CF and CR dogs irrespective of age. Glucose consistently discriminated between feeding regimes in dogs (≥312 weeks), being relatively lower in the CR group. However, it was observed that creatine and amino acids (valine, leucine, isoleucine, lysine, and phenylalanine) were lower in the CR dogs (<312 weeks), suggestive of differences in energy source utilization. ¹H NMR spectroscopic analysis of longitudinal serum profiles enabled an unbiased evaluation of the metabolic markers modulated by a lifetime of caloric restriction and showed differences in the metabolic phenotype of aging due to caloric restriction, which contributes to longevity studies in caloric-restricted animals. Furthermore, OPLS-DA provided a framework such that significant metabolites relating to life extension could be differentiated and integrated with aging processes.

Do Ames dwarf and calorie-restricted mice share common effects on age-related pathology?

Since 1996, aging studies using several strains of long-lived mutant mice have been conducted. Among these studies, Ames dwarf mice have been extensively examined to seek clues regarding the role of the growth hormone/insulin-like growth factor-1 axis in the aging process. Interestingly, these projects demonstrate that Ames dwarf mice have physiological characteristics that are similar to those seen with calorie restriction, which has been the most effective experimental manipulation capable of extending lifespan in various species. However, this introduces the question of whether Ames dwarf and calorie-restricted (CR) mice have an extended lifespan through common or independent pathways. To answer this question, we compared the disease profiles of Ames dwarf mice to their normal siblings fed either ad libitum (AL) or a CR diet. Our findings show that the changes in age-related diseases between AL-fed Ames dwarf mice and CR wild-type siblings were similar but not identical. Moreover, the effects of CR on age-related pathology showed similarities and differences between Ames dwarf mice and their normal siblings, indicating that calorie restriction and Ames dwarf mice exhibit their anti-aging effects through both independent and common mechanisms.

MTOR-driven quasi-programmed aging as a disposable soma theory: blind watchmaker vs. intelligent designer

If life were created by intelligent design, we would indeed age from accumulation of molecular damage. Repair is costly and limited by energetic resources, and we would allocate resources rationally. But, albeit elegant, this design is fictional. Instead, nature blindly selects for short-term benefits of robust developmental growth. "Quasi-programmed" by the blind watchmaker, aging is a wasteful and aimless continuation of developmental growth, driven by nutrient-sensing, growth-promoting signaling pathways such as MTOR (mechanistic target of rapamycin). A continuous post-developmental activity of such gerogenic pathways leads to hyperfunctions (aging), loss of homeostasis, age-related diseases, non-random organ damage and death. This model is consistent with a view that (1) soma is disposable, (2) aging and menopause are not programmed and (3) accumulation of random molecular damage is not a cause of aging as we know it.

Young little mice express a premature cardiovascular aging phenotype

To investigate the effect of growth hormone and insulin-like growth factor 1 deficiency on the aging mouse arterial system, we compared the hemodynamics in young (4 months) and old (30 months) growth hormone-releasing hormone receptor null dwarf (Little) mice and their wild-type littermates. Young Little mice had significantly lower peak and mean aortic velocity and significantly higher aortic impedance than young wild-type mice. However, unlike the wild-type mice, there were no significant changes in arterial function with age in the Little mice. Aortic pulse wave velocity estimated using characteristic impedance increased with age in the wild-type mice, but it changed minimally in the Little mouse. We therefore conclude that arterial function in Little mice expresses a premature aging phenotype at young age and may neither enhance nor reduce their longevity.

Dietary protein source influence on body size and composition in growing zebrafish

The importance of nutritional components on growth and body composition outcomes has been demonstrated in multiple model organisms. Although zebrafish (Danio rerio) have an established role in research laboratories for its utility in understanding developmental biology and genetics, the influence of diet composition on basic growth outcomes is less well demonstrated. In the current study, four protein sources were tested in isolation using isonitrogenous diets or combined using a defined lab diet. Fish (n≈60/group) were group housed (n≤10 fish/1.8 L tank) and fed ad libitum three times daily for 12 weeks. Fish were assessed for effects on length, body weight, and body composition (lean and fat mass). Individuals fed wheat gluten protein were significantly shorter in length, with significantly lower body weight and lean mass in both male and female fish, although percent body fat was high compared with other diets. Casein-fed fish similarly had significantly reduced body length, body weight, and lean and fat mass in both male and female fish, with a low percent body fat compared with other diets (leanest). Fish protein hydrolysate-fed fish had significantly lower lean mass and a high percent body fat, whereas soy protein isolate diet performed similarly to a mixed-protein control diet for all measured outcomes. These results suggest that the protein source, with accompanying amino acid ratios or additional protein source differences, has a significant impact on growth and body composition outcomes in zebrafish when fed in a semipurified, defined diet background.

The size-life span trade-off decomposed: why large dogs die young

Large body size is one of the best predictors of long life span across species of mammals. In marked contrast, there is considerable evidence that, within species, larger individuals are actually shorter lived. This apparent cost of larger size is especially evident in the domestic dog, where artificial selection has led to breeds that vary in body size by almost two orders of magnitude and in average life expectancy by a factor of two. Survival costs of large size might be paid at different stages of the life cycle: a higher early mortality, an early onset of senescence, an elevated baseline mortality, or an increased rate of aging. After fitting different mortality hazard models to death data from 74 breeds of dogs, we describe the relationship between size and several mortality components. We did not find a clear correlation between body size and the onset of senescence. The baseline hazard is slightly higher in large dogs, but the driving force behind the trade-off between size and life span is apparently a strong positive relationship between size and aging rate. We conclude that large dogs die young mainly because they age quickly.

Mechanistic or mammalian target of rapamycin (mTOR) may determine robustness in young male mice at the cost of accelerated aging

Males, who are bigger and stronger than females, live shorter in most species from flies to mammals including humans. Cellular mass growth is driven in part by mTOR (Target of Rapamycin). When developmental growth is completed, then, instead of growth, mTOR drives aging, manifested by increased cellular functions, such as hyper-secretion by fibroblasts, thus altering homeostasis, leading to age-related diseases and death. We hypothesize that MTOR activity is elevated in male mice compared with females. Noteworthy, 6 months old males were 28 % heavier than females. Also levels of phosphorylated S6 (pS6) and phospho-AKT (p-AKT, Ser 473), markers of the mTOR activity, were higher in male organs tested. Levels of pS6 were highly variable among mice and correlated with body weight and p-AKT. With age, the difference between levels of pS6 between sexes tended to minimize, albeit males still had hyperactive mTOR. Unlike fasting, the intraperitoneal (i.p.) administration of rapamycin eliminated pS6 in all organs of all females measured by immunoblotting and immunohistochemistry without affecting p-AKT and blood insulin. Although i.p. rapamycin dramatically decreased levels of pS6 in males too, it was still detectable by immunoblotting upon longer exposure. Our study demonstrated that both tissue p-AKT and pS6 were higher in young male mice and were associated with increased body weight and insulin. These data can explain bigger body size and faster aging in males. Our data suggest higher efficacy of rapamycin compared to fasting. Higher sensitivity of females to rapamycin may explain more pronounced life extension by rapamycin observed in females compared to males in several studies.

Decreased thyroid follicle size in dwarf mice may suggest the role of growth hormone signaling in thyroid growth regulation

Background

Altered somatotrophic signaling is among the most important potential mechanisms of extended longevity. Ames dwarf (df/df) mice are homozygous for mutation at the Prop-1 gene, leading to a lack of growth hormone (GH), prolactin and thyroid stimulating hormone (TSH). Mice homozygous for targeted disruption of the growth hormone receptor/growth hormone binding protein gene are known as GH receptor knockout (GHRKO) mice or “Laron dwarf”. Both, df/df and GHRKO mice, are characterized by reduced body size, low plasma insulin and insulin-like growth factor-I (IGF-I), remarkably extended longevity, and severe (in df/df mice) or mild (in GHRKO mice) thyroid hypofunction. Recently, by crossing df/df and GHRKO mice, double-mutant Ames dwarf/GHRKO (df/KO) mice were created. Interestingly, these mice are smaller than Ames dwarfs or GHRKOs, and also have reduced insulin and IGF-I levels. The aim of the study was to investigate if and to what extent certain thyroid morphological parameters, such as inner follicular surface area, inner follicular perimeter, as well as the follicular epithelium thickness are changed in the examined dwarf mice.

Methods

This quantification was performed in thyroids collected from df/df, GHRKO and df/KO female mice, at approximately 5–6 months of age. We used a computerized plotting programme that combines a live microscopic image of the slide with an operator-generated overlay.

Results

Inner follicular surface area and inner follicular perimeter were decreased in all examined kinds of dwarf mice as compared to normal animals. Furthermore, decreases in these two parameters were more pronounced in df/df and df/KO than in GHRKO mice. Concerning the follicular epithelium thickness, only a tendency towards decrease of this parameter was found in all three kinds of dwarf mice.

Conclusions

Parameters characterizing thyroid follicle size are decreased in all three examined models of dwarf mice, which may explain decreased thyroid hormone levels in both basal mutants (Ames dwarfs and GHRKOs). df/df mutation seems to predominate over GHRKO genetic intervention concerning their effects on thyroid growth. Beside TSH, also GH signaling seems to constitute a crucial element in the regulation of thyroid growth and, possibly, function.

Hormonal therapy of intrinsic aging

Intrinsic skin aging represents the biological clock of the skin cells per se and reflects the reduction processes that are common in internal organs. The reduced secretion of the pituitary, adrenal glands, and the gonads contributes to characteristic aging-associated body and skin phenotypes as well as behavior patterns. Our knowledge of whether there is a direct or indirect connection between hormonal deficiency and skin aging still remains limited. In females, serum levels of 17β-estradiol, dehydroepiandrosterone, progesterone, growth hormone (GH), and its downstream hormone insulin-like growth factor I (IGF-I) are significantly decreased with increasing age. In males, serum levels of GH and IGF-I decrease significantly, whereas it can decrease in late age in a part of the population. Hormones have been shown to influence skin morphology and functions, skin permeability, wound healing, sebaceous lipogenesis, and the metabolism of skin cells. Prevention of skin aging by estrogen/progesterone replacement therapy is effective if administered early after menopause and influences intrinsically aged skin only. Vitamin D substitution and antioxidant treatment may also be beneficial. Replacement therapy with androgens, GH, IGF-I, progesterone, melatonin, cortisol, and thyroid hormones still remains controversial.

Aging biology and novel targets for drug discovery

Despite remarkable technological advances in genetics and drug screening, the discovery of new pharmacotherapies has slowed and new approaches to drug development are needed. Research into the biology of aging is generating many novel targets for drug development that may delay all age-related diseases and be used long term by the entire population. Drugs that successfully delay the aging process will clearly become "blockbusters." To date, the most promising leads have come from studies of the cellular pathways mediating the longevity effects of caloric restriction (CR), particularly target of rapamycin and the sirtuins. Similar research into pathways governing other hormetic responses that influence aging is likely to yield even more targets. As aging becomes a more attractive target for drug development, there will be increasing demand to develop biomarkers of aging as surrogate outcomes for the testing of the effects of new agents on the aging process.

Healthy aging: is smaller better? - a mini-review

A recent report of virtually complete protection from diabetes and cancer in a population of people with hereditary dwarfism revived interest in elucidating the relationships between growth, adult body size, age-related disease and longevity. In many species, smaller individuals outlive those that are larger and a similar relationship was shown in studies of various human populations. Adult body size is strongly dependent on the actions of growth hormone (GH) and the absence of GH or GH receptor in mice leads to a remarkable extension of longevity. Many mechanisms that may account for, or contribute to, this association have been identified. It is suggested that modest modifications of the diet at different ages may extend human healthspan and lifespan by reducing levels of hormones that stimulate growth.

[Comparison of three methods for measuring multiple morbidity according to the use of health resources in primary healthcare]

OBJECTIVE

To compare three methods of measuring multiple morbidity according to the use of health resources (cost of care) in primary healthcare (PHC).

DESIGN

Retrospective study using computerized medical records.

SETTING

Thirteen PHC teams in Catalonia (Spain).

PARTICIPANTS

Assigned patients requiring care in 2008.

MAIN MEASUREMENTS

The socio-demographic variables were co-morbidity and costs. Methods of comparison were: a) Combined Comorbidity Index (CCI): an index itself was developed from the scores of acute and chronic episodes, b) Charlson Index (ChI), and c) Adjusted Clinical Groups case-mix: resource use bands (RUB). The cost model was constructed by differentiating between fixed (operational) and variable costs.

STATISTICAL ANALYSIS

3 multiple lineal regression models were developed to assess the explanatory power of each measurement of co-morbidity which were compared from the determination coefficient (R(2)), p< .05.

RESULTS

The study included 227,235 patients. The mean unit of cost was €654.2. The CCI explained an R(2)=50.4%, the ChI an R(2)=29.2% and BUR an R(2)=39.7% of the variability of the cost. The behaviour of the ICC is acceptable, albeit with low scores (1 to 3 points), showing inconclusive results.

CONCLUSIONS

The CCI may be a simple method of predicting PHC costs in routine clinical practice. If confirmed, these results will allow improvements in the comparison of the case-mix.

The effects of aging and genotype on NMDA receptor expression in growth hormone receptor knockout (GHRKO) mice

Caloric restriction enhances N-methyl-D-aspartate (NMDA) receptor binding and upregulates messenger RNA expression of the GluN1 subunit during aging. Old growth hormone receptor knockout mice resemble old calorically restricted rodents in enhanced life span and brain function, as compared with aged controls. This study examined whether aged growth hormone receptor knockout mice also show enhanced expression of NMDA receptors. Six or 23- to 24-month-old male normal-sized control or dwarf growth hormone receptor knockout mice were assayed for NMDA-displaceable [(3)H]glutamate binding (autoradiography) and GluN1 subunit messenger RNA (in situ hybridization). There was slight sparing of NMDA receptor binding densities within aged medial prefrontal and motor cortices, similar to caloric restriction, but there were greater age-related declines in GluN1 messenger RNA in growth hormone receptor knockout versus control mice. These results suggest that some of the functional improvements in aged mice with altered growth hormone signaling may be due to enhancement of NMDA receptors, but not through the upregulation of messenger RNA for the GluN1 subunit.

Adaptive senectitude: the prolongevity effects of aging

In the past, it has been assumed that all the biological and medical changes that occur in old age are deleterious. It has therefore been concluded that treatment and prevention of such changes in old age should increase healthspan and delay death. However, accruing epidemiological and clinical trial evidence in older humans suggests that this is not the case. Some studies have shown that antioxidants and hormone supplements increase mortality, whereas high blood pressure, obesity, and metabolic syndrome are often associated with improved outcomes in very elderly people. Perhaps, some of these supposedly detrimental changes accompanying old age are in fact evolutionary adaptations to prolong life after reproduction in humans. Indeed, a form of reverse antagonistic pleiotropy or adaptive senectitude might be occurring. Some common biological and medical changes in old age might actually enhance longevity and represent novel targets for improving health in older people.

Cardiac aging in mice and humans: the role of mitochondrial oxidative stress

Age is a major risk factor for cardiovascular diseases, not only because it prolongs exposure to several other cardiovascular risks, but also owing to intrinsic cardiac aging, which reduces cardiac functional reserve, predisposes the heart to stress, and contributes to increased cardiovascular mortality in the elderly. Intrinsic cardiac aging in the murine model closely recapitulates age-related cardiac changes in humans, including left ventricular hypertrophy, fibrosis, and diastolic dysfunction. Cardiac aging in mice is accompanied by accumulation of mitochondrial protein oxidation, increased mitochondrial DNA mutations, increased mitochondrial biogenesis, as well as decreased cardiac SERCA2 protein. All of these age-related changes are significantly attenuated in mice overexpressing catalase targeted to mitochondria. These findings demonstrate the critical role of mitochondrial reactive oxygen species in cardiac aging and support the potential application of mitochondrial antioxidants to cardiac aging and age-related cardiovascular diseases.

The heat dissipation limit theory and evolution of life histories in endotherms--time to dispose of the disposable soma theory?

A major factor influencing life-history strategies of endotherms is body size. Larger endotherms live longer, develop more slowly, breed later and less frequently, and have fewer offspring per attempt at breeding. The classical evolutionary explanation for this pattern is that smaller animals experience greater extrinsic mortality, which favors early reproduction at high intensity. This leads to a short lifespan and early senescence by three suggested mechanisms. First, detrimental late-acting mutations cannot be removed because of the low force of selection upon older animals (mutation accumulation). Second, genes that promote early reproduction will be favored in small animals, even if they have later detrimental effects (antagonistic pleiotropy). Third, small animals may be forced to reduce their investment in longevity assurance mechanisms (LAMs) in favor of investment in reproduction (the disposable soma theory, DST). The DST hinges on three premises: that LAMs exist, that such LAMs are energetically expensive and that the supply of energy is limited. By contrast, the heat dissipation limit (HDL) theory provides a different conceptual perspective on the evolution of life histories in relation to body size. We suggest that rather than being limited, energy supplies in the environment are often unlimited, particularly when animals are breeding, and that animals are instead constrained by their maximum capacity to dissipate body heat, generated as a by-product of their metabolism. Because heat loss is fundamentally a surface-based phenomenon, the low surface-to-volume ratio of larger animals generates significant problems for dissipating the body heat associated with reproductive effort, which then limits their current reproductive investment. We suggest that this is the primary reason why fecundity declines as animal size increases. Because large animals are constrained by their capacity for heat dissipation, they have low reproductive rates. Consequently, only those large animals living in habitats with low extrinsic mortality could survive leading to the familiar patterns of life-history trade-offs and their links to extrinsic mortality rates. The HDL theory provides a novel mechanism underpinning the evolution of life history and ageing in endotherms, and makes a number of testable predictions that directly contrast with the predictions arising from the DST.

[Comorbidity in the elderly: utility and validity of assessment tools]

Comorbidity is common in the elderly and contributes to the complexity of this population subgroup. This problem is a risk factor for major adverse events such as functional decline, disability, dependency, poor quality-of-life, institutionalization, hospitalization and death, but is not the most important factor. Age and risk of functional decline rather than comorbidity (understood as a compilation of diseases) are the main characteristics defining the target population attended by geriatricians. Comorbidity indexes should not be interpreted independently in the elderly, but within a context of comprehensive geriatric assessment that includes age-related preclinical dysfunctions, frailty measures, and functional, mental and psychosocial issues. The clinical management of comorbidity in the elderly requires advanced knowledge of geriatrics because the treatment of one condition may worsen or lead to the development of others and because preclinical physiological dysfunctions modulate drug response. Recommending a specific comorbidity index is difficult and depends on multiple factors, due to their psychometric characteristics, applicability in the elderly and their construct. However, the Cumulative Illness Rating Scale, in the version adapted to the elderly, could be highly suitable. Other instruments, such as the Charlson index, the Index of CoExistent Disease and the Kaplan index are also valid and reproducible.

[Is there any scientific evidence supporting antiaging medicine?]

The objective of antiaging medicine is to interfere in the normal human biological aging process. Is there any scientific basis to justify classifying antiaging medicine as a medical specialty and not a branch of basic biological science? This review evaluated 110 papers, nine of which (8.2% of the total) reported studies involving human subjects. Only one of these studies was randomized and double-blinded (Jadad 2). In accordance with their classification of recommendations and level of evidence, these studies were considered CII. Three of the nine articles were published in journals with an impact factor over 1.110. Therefore, there does not appear to be any solid scientific and/or clinical evidence that would justify the application of antiaging medicine in current medical practice.

Ventral tegmental area leptin receptor neurons specifically project to and regulate cocaine- and amphetamine-regulated transcript neurons of the extended central amygdala

Leptin acts via its receptor (LepRb) to regulate neural circuits in concert with body energy stores. In addition to acting on a number of hypothalamic structures, leptin modulates the mesolimbic dopamine (DA) system. To determine the sites at which LepRb neurons might directly influence the mesolimbic DA system, we examined the distribution of LepRb neurons and their projections within mesolimbic brain regions. Although the ventral tegmental area (VTA) contains DA LepRb neurons, LepRb neurons are absent from the amygdala and striatum. Also, LepRb-EGFPf mice (which label projections from LepRb neurons throughout the brain) reveal that few LepRb neurons project to the nucleus accumbens (NAc). In contrast, the central amygdala (CeA) and its rostral extension receive copious projections from LepRb neurons. Indeed, LepRb-specific anterograde tracing demonstrates (and retrograde tracing confirms) that VTA LepRb neurons project to the extended CeA (extCeA) but not the NAc. Consistently, leptin promotes cAMP response element-binding protein phosphorylation in the extCeA, but not NAc, of leptin-deficient animals. Furthermore, transgenic mice expressing the trans-synaptic tracer wheat germ agglutinin in LepRb neurons reveal the innervation of CeA cocaine- and amphetamine-regulated transcript (CART) neurons by LepRb neurons, and leptin suppresses the increased CeA CART expression of leptin-deficient animals. Thus, LepRb VTA neurons represent a subclass of VTA DA neurons that specifically innervates and controls the extCeA; we hypothesize that these neurons primarily modulate CeA-directed behaviors.

Insights from comparative analyses of aging in birds and mammals

Many laboratory models used in aging research are inappropriate for understanding senescence in mammals, including humans, because of fundamental differences in life history, maintenance in artificial environments, and selection for early aging and high reproductive rate. Comparative studies of senescence in birds and mammals reveal a broad range in rates of aging among a variety of taxa with similar physiology and patterns of development. These comparisons suggest that senescence is a shared property of all vertebrates with determinate growth, that the rate of senescence has been modified by evolution in response to the potential life span allowed by extrinsic mortality factors, and that most variation among species in the rate of senescence is independent of commonly ascribed causes of aging, such as oxidative damage. Individuals of potentially long-lived species, particularly birds, appear to maintain high condition to near the end of life. Because most individuals in natural populations of such species die of aging-related causes, these populations likely harbor little genetic variation for mechanisms that could extend life further, or these mechanisms are very costly. This, and the apparent evolutionary conservatism in the rate of increase in mortality with age, suggests that variation in the rate of senescence reflects fundamental changes in organism structure, likely associated with the rate of development, rather than physiological or biochemical processes influenced by a few genes. Understanding these evolved differences between long-lived and short-lived organisms would seem to be an essential foundation for designing therapeutic interventions with respect to human aging and longevity.

Effects of growth hormone and thyroxine replacement therapy on insulin signaling in Ames dwarf mice

Ames dwarf (Prop1(df), df/df) mice lack growth hormone (GH), prolactin, and thyrotropin and live remarkably longer than their normal siblings. Significance of reduced activity of the somatotropic and thyroid axes during development and adulthood on longevity are unknown. Because enhanced insulin sensitivity and reduced insulin levels are among likely mechanisms responsible for increased longevity in these mutants, we compared the effects of GH and thyroxine (T4) replacement on various parameters related to insulin signaling in young and old male df/df mice. The results suggest that altered plasma adiponectin and insulin-like growth factor-1 (IGF-1) and hepatic IGF-1, insulin receptor (IR), IR substrate-1, peroxisome proliferator-activated receptor (PPAR) gamma, and PPARgamma coactivator-1 alpha may contribute to increased insulin sensitivity in Ames dwarfs. The stimulatory effect of GH and T4 treatment on plasma insulin and inhibitory effect on expression of hepatic glucose transporter-2 were greater in old than in young dwarfs. These results indicate that GH and T4 treatment has differential impact on insulin signaling during development and adulthood.

Hypothalamic and dietary control of temperature-mediated longevity

Temperature is an important modulator of longevity and aging in both poikilotherms and homeotherm animals. In homeotherms, temperature homeostasis is regulated primarily in the preoptic area (POA) of the hypothalamus. This region receives and integrates peripheral, central and environmental signals and maintains a nearly constant core body temperature (T(core)) by regulating the autonomic and hormonal control of heat production and heat dissipation. Temperature sensitive neurons found in the POA are considered key elements of the neuronal circuitry modulating these effects. Nutrient homeostasis is also a hypothalamically regulated modulator of aging as well as one of the signals that can influence T(core) in homeotherms. Investigating the mechanisms of the regulation of nutrient and temperature homeostasis in the hypothalamus is important to understanding how these two elements of energy homeostasis influence longevity and aging as well as how aging can affect hypothalamic homeostatic mechanisms.

[Barthel and Charlson indexes for the prognosis of mortality and institutionalization in hospitalized geriatric patients]

INTRODUCTION

To compare the validity of the Barthel (BI) and Charlson comorbidity index (CCI) as well as the age-adjusted CCI for the prognosis of mortality and institutionalization in hospitalized geriatric patients.

MATERIAL AND METHODS

A retrospective study was conducted to evaluate patients admitted to an acute care geriatric ward and mid-term care facility in 2006 (n=343). The independent variables were the admission BI (registered in the clinical history in all patients) and the CCI and the age-adjusted CCI, which were registered "a posteriori" using the available information. The outcome variable was mortality or institutionalization when the patient was discharged. The sensitivity and specificity values for each of the cut-off points selected from the scales analyzed were recorded and ROC curves were constructed for each of these points; the area under the curve (AUC) with a confidence interval (CI) of up to 95% was calculated.

RESULTS

The mean age was 82.3 years (58.6% women). The AUC was 0.736 (95% CI=0.68-0.79) for the BI, 0.61 (95% CI=0.55-0.67) for the CCI and 0.625 (95% CI=0.56-0.69) for the age-adjusted CCI. Statistically significant differences were found among the AUC of the BI compared with that of the other two indexes (p<0.01).

CONCLUSIONS

As predictors of mortality and institutionalization, the BI was superior to the CCI and the age-adjusted CCI. The BI could therefore be more useful than the other two indexes when considering an adequate use of healthcare services.