Nutrition and Aging: Changes in the Regulation of Energy Metabolism With Aging

Analysis of the effect of the mitochondrial prohibitin complex, a context-dependent modulator of longevity, on the C. elegans metabolome

The mitochondrial prohibitin complex, composed of two proteins, PHB-1 and PHB-2, is a context-dependent modulator of longevity. Specifically, prohibitin deficiency shortens the lifespan of otherwise wild type worms, while it dramatically extends the lifespan under compromised metabolic conditions. This extremely intriguingly phenotype has been linked to alterations in mitochondrial function and in fat metabolism. However, the true function of the mitochondrial prohibitin complex remains elusive. Here, we used gas chromatography coupled to a flame ionization detector (GC/FID) and ¹H NMR spectroscopy to gain molecular insights into the effect of prohibitin depletion on the Caenorhabditis elegans metabolome. We analysed the effect of prohibitin deficiency in two different developmental stages and under two different conditions, which result in opposing longevity phenotypes, namely wild type worms and daf-2(e1370) insulin signalling deficient mutants. Prohibitin depletion was shown to alter the fatty acid (GC/FID) and ¹H NMR metabolic profiles of wild type animals both at the fourth larval stage of development (L4) and at the young adult (YA) stage, while being more pronounced at the later stage. Furthermore, wild type and the diapause mutant daf-2(e1370), either expressing or not prohibitin, were clearly distinguishable based on their metabolic profiles, revealing changes in fatty acid composition, as well as in carbohydrate and amino acid metabolism. Moreover, the metabolic data indicate that daf-2(e1370) mutants are more robust than the wild type animals to changes induced by prohibitin depletion. The impact of prohibitin depletion on the C. elegans metabolome will be discussed herein in the scope of its effect on longevity. This article is part of a Special Issue entitled: Mitochondrial Dysfunction in Aging. Guest Editor: Aleksandra Trifunovic

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Impact of the mitochondrial prohibitin (PHB) complex on the C. elegans metabolome

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Depletion of individual PHB subunits results in similar metabolic profiles.

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PHB affects fatty acid composition, amino acid and carbohydrate metabolism.

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daf-2 mutants are more robust than wild type worms to the effect of PHB depletion.

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Modulation of fermentation may contribute to the longevity of PHB-depleted worms.

Nutritional status and eating habits of the institutionalised elderly in Turkey: a follow-up study

BACKGROUND

As the elderly population increases in Turkey, so do the associated health and nutritional problems. The main purpose of the present study was to determine the nutritional status of elderly individuals who live in institutions.

METHODS

A total of 102 elderly volunteers was recruited from seven residential homes of the Ministry of Family and Social Policies in Ankara. In the consecutive years of 2007, 2008 and 2009, dietary intake was assessed using a 24-h food recall. Nutritional status was screened using a questionnaire from the Mini-Nutritional Assessment, basic characteristics were determined and anthropometric measurements were assessed.

RESULTS

The percentage of elderly participants who were malnourished or at risk for malnutrition increased by the completion of the follow-up (P < 0.05). It was found that energy, total protein, animal proteins, carbohydrates, niacin, vitamin C, vitamin E and zinc intake of men decreased significantly over the years studied (P < 0.05). A significant decrease occurred among women in animal protein, vitamin B1 , niacin and the percentage of energy from proteins (P < 0.05); however, an increase in energy from fat (P < 0.05) was determined. Within the years studied, the percentage of nutrients meeting the Turkish recommended daily allowances decreased from 2007 to 2009 both in men and women. During the years 2007 to 2009, the percentage of waist circumferences >102 cm for men was 46.4%, 45.6% and 48.1%, respectively, and the percentage of waist circumferences for women >88 cm was 75.6%, 75.6% and 81.8%, respectively.

CONCLUSIONS

During the follow-up, significant nutritional changes were determined. To prevent malnutrition, periodical screening of nutritional status should be a priority and a standard policy for elderly people, especially for those institutionalised.

Age-related changes in resting energy expenditure in normal weight, overweight and obese men and women

OBJECTIVES

Aging is associated with changes in resting energy expenditure (REE) and body composition. We investigated the association between age and changes in REE in men and women stratified by body mass index (BMI) categories (normal weight, overweight and obesity). We also examined whether the age-related decline in REE was explained by concomitant changes in body composition and lifestyle factors.

STUDY DESIGN

Cross-sectional.

MAIN OUTCOME MEASURES

3442 adult participants (age range: 18-81 y; men/women: 977/2465) were included. The BMI range was 18.5-60.2 kg/m(2). REE was measured by indirect calorimetry in fasting conditions and body composition by bioelectrical impedance. Regression models were used to evaluate age-related changes in REE in subjects stratified by sex and BMI. Models were adjusted for body composition (fat mass, fat free mass), smoking, disease count and physical activity.

RESULTS

In unadjusted models, the rate of decline in REE was highest in obese men (slope=-8.7±0.8 kcal/day/year) whereas the lowest rate of decline was observed in normal weight women (-2.9±0.3 kcal/day/year). Gender differences were observed for the age of onset of REE adaptive changes (i.e., not accounted by age related changes in body composition and lifestyle factors). In women, adaptive changes appeared to occur in middle-age (∼47 y) across all BMI groups whereas changes seemed to be delayed in obese men (∼54 y) compared to overweight (∼43 y) and normal weight (∼39 y) men.

CONCLUSIONS

Sex and BMI influenced the rate and degree of the age-related decline in REE. Critical age windows have been identified for the onset of putative mechanisms of energy adaptation. These findings require confirmation in prospective studies.

Energy density, energy intake, and body weight regulation in adults

The role of dietary energy density (ED) in the regulation of energy intake (EI) is controversial. Methodologically, there is also debate about whether beverages should be included in dietary ED calculations. To address these issues, studies examining the effects of ED on EI or body weight in nonelderly adults were reviewed. Different approaches to calculating dietary ED do not appear to alter the direction of reported relations between ED and body weight. Evidence that lowering dietary ED reduces EI in short-term studies is convincing, but there are currently insufficient data to determine long-term effectiveness for weight loss. The review also identified key barriers to progress in understanding the role of ED in energy regulation, in particular the absence of a standard definition of ED, and the lack of data from multiple long-term clinical trials examining the effectiveness of low-ED diet recommendations for preventing both primary weight gain and weight regain in nonobese individuals. Long-term clinical trials designed to examine the impact of dietary ED on energy regulation, and including multiple ED calculation methods within the same study, are still needed to determine the importance of ED in the regulation of EI and body weight.

Ghrelin receptor regulates appetite and satiety during aging in mice by regulating meal frequency and portion size but not total food intake

Aging is often associated with overweight and obesity. There exists a long-standing debate about whether meal pattern also contributes to the development of obesity. The orexigenic hormone ghrelin regulates appetite and satiety by activating its receptor, growth hormone secretagogue receptor (GHS-R). In mice, circulating ghrelin concentrations and brain GHS-R expression were shown to increase with aging. To assess whether GHS-R regulates feeding pattern during aging, we studied meal patterns for the following cohorts of male mice fed a normal unpurified diet: 1) 3-4 mo, young wild-type (WT) mice; 2) 3-4 mo, young Ghsr-null (Ghsr(-/-)) mice; 3) 12-14 mo, middle-aged WT (WT-M) mice; 4) 12-14 mo, middle-aged Ghsr(-/-) (Ghsr(-/-)-M) mice; 5) 24-26 mo, old WT (WT-O) mice; and 6) 24-26 mo, old Ghsr(-/-) (Ghsr(-/-)-O) mice. Although the total daily food intake of Ghsr(-/-) mice was similar to that of WT controls, Ghsr(-/-)-M and Ghsr(-/-)-O mice had 9% (P = 0.07) and 16% (P < 0.05) less body weight compared with WT-M and WT-O mice, respectively, primarily due to reduced fat mass (P < 0.05, WT-M vs. Ghsr(-/-)-M and WT-O vs. Ghsr(-/-)-O). Intriguingly, Ghsr(-/-)-M mice ate larger meals (on average, Ghsr(-/-)-M mice ate 0.117 g/meal and WT-M mice ate 0.080 g/meal; P < 0.01) and took a longer time to eat (Ghsr(-/-)-M, 196.0 s and WT-M, 128.9 s; P < 0.01), but ate less frequently (Ghsr(-/-)-M, 31.0 times/d and WT-M, 42.3 times/d; P < 0.05) than WT-M controls. In addition, we found that expression of hypothalamic orexigenic peptides, neuropeptide Y (NPY) and agouti-related peptide (AgRP), was relatively lower in aged WT mice (P = 0.09 for NPY and P = 0.06 for AgRP), but anorexic peptide pro-opiomelanocortin (POMC) expression remained unchanged between the WT age groups. Interestingly, old Ghsr(-/-) mice had greater hypothalamic NPY expression (102% higher; P < 0.05) and AgRP expression (P = 0.07) but significantly lower POMC expression (P < 0.05) when compared with age-matched WT-O controls. Thus, our results indicate that GHS-R plays an important role in the regulation of meal pattern and that GHS-R ablation may modulate feeding behavior through the regulation of hypothalamic neuropeptides. Our results collectively suggest that ghrelin receptor antagonism may have a beneficial effect on metabolism during aging.

Promoting longevity by maintaining metabolic and proliferative homeostasis

Aging is characterized by a widespread loss of homeostasis in biological systems. An important part of this decline is caused by age-related deregulation of regulatory processes that coordinate cellular responses to changing environmental conditions, maintaining cell and tissue function. Studies in genetically accessible model organisms have made significant progress in elucidating the function of such regulatory processes and the consequences of their deregulation for tissue function and longevity. Here, we review such studies, focusing on the characterization of processes that maintain metabolic and proliferative homeostasis in the fruitfly Drosophila melanogaster. The primary regulatory axis addressed in these studies is the interaction between signaling pathways that govern the response to oxidative stress, and signaling pathways that regulate cellular metabolism and growth. The interaction between these pathways has important consequences for animal physiology, and its deregulation in the aging organism is a major cause for increased mortality. Importantly, protocols to tune such interactions genetically to improve homeostasis and extend lifespan have been established by work in flies. This includes modulation of signaling pathway activity in specific tissues, including adipose tissue and insulin-producing tissues, as well as in specific cell types, such as stem cells of the fly intestine.

Northward range expansion requires synchronization of both overwintering behaviour and physiology with photoperiod in the invasive Colorado potato beetle (Leptinotarsa decemlineata)

Photoperiodic phenological adaptations are prevalent in many organisms living in seasonal environments. As both photoperiod and growth season length change with latitude, species undergoing latitudinal range expansion often need to synchronize their life cycle with a changing photoperiod and growth season length. Since adaptive synchronization often involves a large number of time-consuming genetic changes, behavioural plasticity might be a faster way to adjust to novel conditions. We compared behavioural and physiological traits in overwintering (diapause) preparation in three latitudinally different European Colorado potato beetle (Leptinotarsa decemlineata) populations reared under two photoperiods. Our aim was to study whether behavioural plasticity could play a role in rapid range expansion into seasonal environments. Our results show that while burrowing into the soil occurred in the southernmost studied population also under a non-diapause-inducing long photoperiod, the storage lipid content of these beetles was very low compared to the northern populations. However, similar behavioural plasticity was not found in the northern populations. Furthermore, the strongest suppression of energy metabolism was seen in pre-diapause beetles from the northernmost population. These results could indicate accelerated diapause preparation and possibly energetic adjustments due to temporal constraints imposed by a shorter, northern, growth season. Our results indicate that behavioural plasticity in burrowing may have facilitated initial range expansion of L. decemlineata in Europe. However, long-term persistence at high latitudes has required synchronization of burrowing behaviour with physiological traits. The results underline that eco-physiological life-history traits of insects, such as diapause, should be included in studies on range expansion.

Increased number of chews during a fixed-amount meal suppresses postprandial appetite and modulates glycemic response in older males

Aging is associated with a reduction in appetite. Older adults require a higher number of chews to form a bolus before swallowing. However, whether this ingestive behavior contributes to the reduced appetite in this population is unknown. Fifteen males aged 65 years or older participated in this randomized cross-over trial and attended two test sessions. After an overnight fast, they consumed a fixed-amount meal (2050 kJ) by chewing each portion of food 15 or 40 times before swallowing. Subjective appetite was measured using visual analogue scales at regular intervals for 3 h after completion of the meal. Blood samples were collected at the same time for measurement of glucose, insulin, and glucose-dependent insulinotropic peptide (GIP). Participants were provided an ad libitum meal 3 h later. Compared with 15 chews, chewing food 40 times before swallowing resulted in significantly lower postprandial hunger (P=0.003), preoccupation with food (P<0.001), and desire to eat (P<0.001). Plasma concentrations of glucose, insulin, and GIP were significantly higher at meal completion when 40 chews were made (all P<0.01), and became significantly lower during the late postprandial period (all P<0.05). Food intake at the subsequent ad libitum meal did not differ significantly between test sessions. Our findings suggested that increased number of chews reduced postprandial hunger and desire to eat, and modulated glucose metabolism in older males. The number of chews made during a fixed-amount meal may influence short-term appetite; how this ingestive behavior contributes to energy balance in the long term warrants further investigation.

Chronic starvation secondary to anorexia nervosa is associated with an adaptive suppression of resting energy expenditure

BACKGROUND

Chronic starvation is accompanied by a reduction in resting energy expenditure (REE). It is not clear whether this is due mainly to a reduction in body mass or also involves a significant reduction in the cellular metabolic rate of the fat-free mass (FFM).

OBJECTIVES

The main goal was to compare measured REE (REEm) with REE predicted by dual-energy X-ray absorptiometry modeling of organ-tissue mass (REEp) in malnourished patients with severe anorexia nervosa (AN) and in healthy lean control subjects. REE adjusted for FFM and fat mass was also compared between the groups.

DESIGN

This was a cross-sectional study of 30 patients with AN and 25 lean control subjects. REE was measured by indirect calorimetry. Body composition was modeled using dual-energy X-ray absorptiometry, and REE was predicted for each group based on organ-tissue mass.

RESULTS

REEm was significantly lower than REEp in subjects with AN (854 ± 41 vs 1080 ± 25 kcal/d, P < .001), but not in control subjects. In addition, REE adjusted for both FFM and fat mass was significantly lower in the subjects with AN (1031 ± 37 vs 1178 ± 32 kcal/d, P < .01). Finally, compared with the lean control subjects, both organ and skeletal muscle mass were approximately 20% smaller in subjects with AN.

CONCLUSIONS

Chronic starvation is accompanied by a significant reduction in the metabolic rate of the FFM. The organs and/or tissues accounting for this are unknown. In addition, this study suggests that protein is mobilized proportionately from organs and skeletal muscle during starvation. This too may be an adaptive response to chronic starvation.

Intestinal inflammation and stem cell homeostasis in aging Drosophila melanogaster

As a barrier epithelium, the intestinal epithelium has to coordinate physiological functions like digestion and nutrient resorption with the control of commensal bacteria and the prevention of pathogenic infections. It can therefore mount powerful innate immune and inflammatory responses, while, at the same time, maintaining tissue homeostasis through regenerative processes. How these different functions are coordinated remains unclear, and further insight is required to understand the age-related loss of homeostasis in this system, as well as the etiology of inflammatory and proliferative diseases of the gut. Recent work in Drosophila melanogaster has provided important new insight into the regulation of regenerative activity, innate immune homeostasis, commensal control, as well as age-related dysfunction in the intestine. Interestingly, many of the identified processes and mechanisms mirror similar homeostatic processes in the vertebrate intestine. This review summarized the current understanding of how innate immune responses, changes in commensal bacteria, and other challenges influence regenerative activity in the aging intestinal epithelium of flies and draws parallels to similar processes in mammals.

Improvement of metabolic parameters in healthy older adult men following a fasting calorie restriction intervention

OBJECTIVE

Calorie restriction and intermittent fasting are two dietary interventions that can improve aging. Religious fasting also suggested having similar benefit; however, such studies are still scarce. Thus, this study aimed to determine the effect of fasting calorie restriction (FCR) on metabolic parameters and DNA damage among healthy older adult men.

METHODS

A randomized controlled study was done on men, aged 50-70 years in Klang Valley, Malaysia. Subjects were divided into two groups; FCR (reduction of 300-500 kcal/d combined with 2 days/week of Muslim Sunnah Fasting) and control. Assessment was ascertained at three time point; baseline, weeks 6 and 12. Blood samples were analyzed for lipid profile, DNA damage and malondialdehyde (MDA).

RESULTS

The FCR group reduced their energy intake for approximately 18% upon completion of the study. A significant interaction effect was found in body weight, body mass index, fat percentage, fat mass, blood pressure, total cholesterol, low-density lipoprotein cholesterol and the ratio of total cholesterol/high-density lipoprotein cholesterol (p < 0.05). A significant improvement (p < 0.001) in total DNA rejoining cells and MDA (p < 0.05) was also observed in the FCR group.

CONCLUSION

FCR improved metabolic parameters and DNA damage in healthy older adult men. Therefore, there is a need to further examine the mechanism of FCR.

Appropriate physical activity and dietary intake achieve optimal metabolic control in older type 2 diabetes patients

Aims/Introduction

The aim of the present study was to investigate an appropriate level of physical activity and optimal dietary intake in older type 2 diabetes patients.

Materials and Methods

The cross‐sectional study enrolled 210 older type 2 diabetes patients. Participants were interviewed to obtain information on physical activity, 24‐h dietary recall and typical weekly dietary patterns. Anthropometric measurements, and biochemical analysis of blood and urine were determined.

Results

Moderate physical activity (either moderate leisure‐time physical activity or moderate physical activity level) and diet with protein intake of ≥0.8 g/kg/day were associated with lower glycated hemoglobin and triglyceride, higher high‐density lipoprotein, lower waist circumference, body mass index and body fat, as well as better serum magnesium and albumin levels in older diabetic patients. In contrast, inadequate protein intake was correlated with higher glycated hemoglobin, triglyceride, body fat percentage, waist circumference and body mass index. In addition, high physical activity with inadequate protein and magnesium intake might exacerbate magnesium deficiency, resulting in poor glycemic control in older diabetic patients. Furthermore, low physical activity and inadequate protein intake were linked with poor glycemic control, and lower high‐density lipoprotein, and higher triglyceride, body fat percentage, waist circumference and body mass index.

Conclusions

Moderate physical activity and adequate dietary protein intake (≥0.8 g/kg/day) might be the optimal recommendation for better metabolic control in older adults with type 2 diabetes.

Food for thought: understanding the multifaceted nature of orexins

Orexins are a pair of hypothalamic neuropeptides that were discovered in the late 1990s and named initially for their ability to promote feeding. Subsequent studies have revealed the importance of orexins to a variety of physiological functions, including brown fat thermogenesis, sleep/wake cycles, physical activity, and cognition. We aim to elucidate the various roles of orexins and discuss how these multiple functions are interlinked. We explain that although the unique dual roles of orexins in increasing feeding while concomitantly elevating energy expenditure appear counterproductive, they are necessary for physiological scenarios during which simultaneous stimulation of energy expenditure and feeding occur, namely diet-induced thermogenesis and arousal from hibernation. The position of orexins at the interface between sleep/wake cycles, energy homeostasis, and environmental factors has important implications in the treatment of obesity.

Obesity in the ageing man

As the population is ageing globally, both ageing and obesity are recognized as major public health challenges. The aim of this narrative review is to present and discuss the current evidence on the changes in body composition, energy balance and endocrine environment that occur in the ageing man. Obesity in the ageing man is related to changes in both body weight and composition due to alterations in energy intake and total energy expenditure. In addition, somatopenia (decreased GH secretion), late-onset hypogonadism (LOH), changes in thyroid and adrenal function, as well as changes in appetite-related peptides (leptin, ghrelin) and, most importantly, insulin action are related to obesity, abnormal energy balance, redistribution of the adipose tissue and sarcopenia (decreased muscle mass). A better understanding of the complex relationship of ageing-related endocrine changes and obesity could lead to more effective interventions for elderly men.

Anorexia of aging and gut hormones

We are expected to live longer than if we had been born 100 years ago however, the additional years are not necessarily spent in good health or free from disability. Body composition changes dramatically over the course of life. There is a gradual increase in body weight throughout adult life until the age of about 60-65 years. In contrast, body weight appears to decrease with age after the age of 65-75 years, even in those demonstrating a previous healthy body weight. This age related decrease in body weight, often called unintentional weight loss or involuntary weight loss can be a significant problem for the elderly. This has been shown to be related to decline in appetite and food intake is common amongst the elderly and is often referred to the anorexia of aging. Underlying mechanisms regulate energy homeostasis and appetite may change as people age. In this review, peripheral factors regulating appetite have been summarized in regards to their age-dependent changes and role in the etiology of anorexia of aging. Understanding the alterations in the mechanisms regulating appetite and food intake in conjunction with aging may help inform strategies that promote healthy aging and promote health and wellbeing in the elderly years, with the end goal to add life to the years and not just years to our lives.

Moderate to high levels of exercise are associated with higher resting energy expenditure in community-dwelling postmenopausal women

Postmenopausal women experience an age-related decline in resting energy expenditure (REE), which is a risk factor for energy imbalance and metabolic disease. Exercise, because of its association with greater lean tissue mass and other factors, has the potential to mediate REE decline, but the relation between exercise and REE in postmenopausal women is not well characterized. This study tests the hypothesis that exercise energy expenditure (EEE) is positively associated with REE and can counter the effects of age and menopause. It involves a cross-sectional sample of 31 healthy postmenopausal women (aged 49-72 years) with habitual exercise volumes at or above levels consistent with current clinical recommendations. Subjects kept exercise diaries for 4 weeks that quantified exercise activity and were measured for body composition, maximal oxygen uptake, and REE. Multiple regression analysis was used to test for associations between EEE, age, body composition, and REE. There was a significant positive relation between EEE and lean tissue mass (fat-free mass and fat-free mass index). The relation between REE and EEE remained significant even after controlling for lean tissue mass. These results support the hypothesis that exercise is positively associated with REE and can counter the negative effects of age and menopause. They also indicate a continuous relation between exercise and REE across ranges of exercise, from moderate to high. Exercise at levels that are at or above current clinical guidelines might, in part, ameliorate the risk for energy imbalance and metabolic disease because of its positive relation with REE.

Effects of age, gender and chronic obstructive pulmonary disease on taste acuity

PRIMARY OBJECTIVE

Multifactoral interactions of age, gender and medical conditions were investigated because of lack of definitive results in previous studies.

METHODS

Absolute detection and recognition were determined thresholds using a three-alternative forced-choice test by younger men (n=50) and women (n=48); and by older men (n=43) and women (n=46) for each of the four basic tastes (sweet, sour, bitter, salty). Data from 46 elderly men with chronic obstructive pulmonary disease (COPD) were included.

RESULTS

Age was consistently associated with elevated recognition thresholds for each of the four tastants for men only. Gender differences were seen for absolute sweet thresholds and for sour, bitter, and sweet recognition thresholds for older participants. Men with COPD had the highest levels for absolute and recognition thresholds for each tastant.

CONCLUSIONS

Gender plays a role in taste perception. COPD diminishes taste.

Misregulation of an adaptive metabolic response contributes to the age-related disruption of lipid homeostasis in Drosophila

Loss of metabolic homeostasis is a hallmark of aging and is commonly characterized by the deregulation of adaptive signaling interactions that coordinate energy metabolism with dietary changes. The mechanisms driving age-related changes in these adaptive responses remain unclear. Here, we characterize the deregulation of an adaptive metabolic response and the development of metabolic dysfunction in the aging intestine of Drosophila. We find that activation of the insulin-responsive transcription factor Foxo in intestinal enterocytes is required to inhibit the expression of evolutionarily conserved lipases as part of a metabolic response to dietary changes. This adaptive mechanism becomes chronically activated in the aging intestine, mediated by changes in Jun-N-terminal kinase (JNK) signaling. Age-related chronic JNK/Foxo activation in enterocytes is deleterious, leading to sustained repression of intestinal lipase expression and the disruption of lipid homeostasis. Changes in the regulation of Foxo-mediated adaptive responses thus contribute to the age-associated breakdown of metabolic homeostasis.

Many faces of mitochondrial uncoupling during age: damage or defense?

An increased mitochondrial proton leak occurs in aging, but the origin of such modification remains unclear. This study defined the cause of mitochondrial uncoupling in mitotic (liver) and postmitotic (heart) rat tissues during aging and its effects on energy homeostasis and free radical production. Proton leak in old heart mitochondria was dependent on uncoupling proteins' upregulation, whereas it was caused by alterations in the mitochondrial membrane composition in old liver. ATP homeostasis was impaired in both tissues from old animals and was associated to disrupted F0F1-ATPase activity. H2O2 production rate and 4-hydroxy-2-nonenalprotein adducts were higher in old liver mitochondria compared with young liver mitochondria, but they were similar in heart mitochondria from both groups. Moreover, key mitochondrial biogenesis regulators were upregulated in old liver but downregulated in old heart. In conclusion, uncoupling proteins mediate proton leak and avoid oxidative damage in heart, acting as a protective mechanism. This does not occur in liver, where ATP depletion and oxidative stress may stimulate mitochondrial biogenesis and eliminate damaged cells.

Adenosine nucleotide biosynthesis and AMPK regulate adult life span and mediate the longevity benefit of caloric restriction in flies

A common thread among conserved life span regulators lies within intertwined roles in metabolism and energy homeostasis. We show that heterozygous mutations of AMP biosynthetic enzymes extend Drosophila life span. The life span benefit of these mutations depends upon increased AMP:ATP and ADP:ATP ratios and adenosine monophosphate-activated protein kinase (AMPK). Transgenic expression of AMPK in adult fat body or adult muscle, key metabolic tissues, extended life span, while AMPK RNAi reduced life span. Supplementing adenine, a substrate for AMP biosynthesis, to the diet of long-lived AMP biosynthesis mutants reversed life span extension. Remarkably, this simple change in diet also blocked the prolongevity effects of dietary restriction. These data establish AMP biosynthesis, adenosine nucleotide ratios, and AMPK as determinants of adult life span; provide a mechanistic link between cellular anabolism and energy sensing pathways; and indicate that dietary adenine manipulations might alter metabolism to influence animal life span.

A long life in the fast lane: positive association between peak metabolic rate and lifespan in a butterfly

High peak metabolic rates may provide a performance advantage, but it may also entail a physiological cost. A long-held assumption is that high mass-specific energy expenditure is associated with short lifespan. To examine the relationship between energy expenditure and lifespan we asked two questions. First, do individuals have a consistent rate of metabolism throughout their life? Second, is metabolic rate correlated with lifespan? We analysed the repeatability of measurements of resting (RMR) and peak flight metabolic rate (MR(peak)) throughout the life of the Glanville fritillary butterfly (Melitaea cinxia). Measurements of MR(peak) showed significant repeatability. Senescence occurred only shortly before death. RMR showed a U-shaped relationship with age and very low repeatability. Intraspecific association between metabolic rates and lifespan was tested under three conditions: in the laboratory, under field conditions and in a laboratory experiment with repeated flight treatments. There was a significant correlation between MR(peak) and lifespan in all three experiments, but the correlation was positive, not negative. RMR was not correlated with lifespan. Both MR(peak) and lifespan may reflect physiological condition and therefore be positively correlated. Individuals with a large resource pool may be able to invest in mechanisms that slow down ageing. Individuals with high metabolic capacity may also possess adaptations against ageing. Molecular polymorphism in the gene phosphoglucose isomerase (Pgi) was significantly associated with both MR(peak) and lifespan, and may have coevolved with defence mechanisms against senescence. Generalisations such as 'live fast, die young' may be too simple to explain the complex processes affecting ageing and lifespan.

Adenosine monophosphate-activated protein kinase overactivation leads to accumulation of α-synuclein oligomers and decrease of neurites

Neuronal inclusions of α-synuclein (α-syn), termed Lewy bodies, are a hallmark of Parkinson disease (PD). Increased α-syn levels can occur in brains of aging human and neurotoxin-treated mice. Because previous studies have shown increased brain lactate levels in aging brains, in PD affected subjects when compared with age-matched controls, and in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP), we tested the effects of lactate exposure on α-syn in a cell-based study. We demonstrated that (1) lactate treatment led to α-syn accumulation and oligomerization in a time- and concentration-dependent manner; (2) such alterations were mediated via adenosine monophosphate-activated protein kinase (AMPK) and associated with increasing cytoplasmic phosphorylated AMPK levels; (3) AMPK activation facilitated α-syn accumulation and phosphorylation; (4) lactate treatment or overexpression of the active form of AMPK decreased α-syn turnover and neurite outgrowth; and (5) Lewy body-bearing neurons displayed abnormal cytoplasmic distribution of phosphorylated AMPK, which normally is located in nuclei. Together, our results suggest that chronic neuronal accumulation of α-syn induced by lactate-triggered AMPK activation in aging brains might be a novel mechanism underlying α-synucleinopathies in PD and related disorders.

Post-glucose load changes of plasma key metabolite and insulin concentrations during pregnancy and lactation in ewes with different susceptibility to pregnancy toxaemia

Insulin resistance during late gestation may act as a predisposing factor of ovine pregnancy toxaemia (OPT). To evaluate the insulin action on energy metabolism in ewes with different susceptibilities to OPT, intravenous glucose tolerance tests (1 mmol glucose/kg body weight) were performed in 5.6 ± 0.7 year old, slightly underfed German Blackheaded Mutton ewes [high-risk (HR) ewes] and 2.5 year old, overnourished Finnish Landrace ewes [low-risk (LR) ewes] during mid and late pregnancy, during early lactation and during the dry period. Plasma samples were analysed for glucose, insulin, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (β-HB). The glucose elimination rate and the glucose-stimulated first-phase insulin secretion were significantly (p < 0.05) lower in the HR, in relation to the LR group combining the data of all gestational stages. The basal rate of lipolysis was significantly increased in the HR ewes during late pregnancy, but the NEFA clearance after the glucose load was similar in both groups during all reproductive stages. Plasma β-HB concentrations decreased only in the LR ewes after the glucose load during late pregnancy. Results indicate an insulin resistance in the HR ewes regarding the glucose utilization and the ketone body formation during late pregnancy. The insulin resistance in the HR ewes may represent one predisposing factor responsible for the susceptibility to OPT. Further scientific work is necessary to elucidate whether this insulin resistance was due to breed, age or nutritional state.

Decreased insulin sensitivity and increased oxidative damage in wasting adipose tissue depots of wild-type mice

Unintentional weight loss (wasting) in the elderly is a major health concern as it leads to increased mortality. Several studies have focused on muscle loss, but little is known about the mechanisms giving rise to loss of fat mass at old ages. To investigate potential mechanisms, white adipose tissue (WAT) characteristics and proteomic profiles were compared between adult (10-12-month-old) and aged (22-24-month-old) wild-type mice. Four individual WAT depots were analyzed to account for possible depot-specific differences. Proteomic profiles of WAT depots, along with body weights and compositions, plasma levels of insulin, leptin and adiponectin, insulin tolerance, adipocyte sizes, and products of oxidative damage in each WAT depot were determined. We found that lean mass remained constant while fat mass and insulin tolerance were decreased in old age, as were adipocyte sizes in the WAT depots. Proteomic results showed increased levels of enolase, pyruvate dehydrogenase E1β, NAD(+)-dependent isocitrate dehydrogenase α, and ATP synthase subunit β, and decreased levels of carbonic anhydrase 3 in WAT of aged mice. These data suggest increased aerobic glucose oxidation in wasting WAT, consistent with decreased insulin signaling. Also, Cu/Zn superoxide dismutase and two chaperones were increased in aged WAT depots, indicating higher stress resistance. In agreement, lipid peroxidation (HNE-His adducts) increased in old age, although protein oxidation (carbonyl groups) showed no increase. In conclusion, features of wasting WAT were similar in the four depots, including decreased adipocyte sizes and alterations in protein expression profiles that indicated decreased insulin sensitivity and increased lipid peroxidation.

Metabolic syndrome in obese men and women with binge eating disorder: developmental trajectories of eating and weight-related behaviors

Metabolic syndrome (MetSyn), characterized by vascular symptoms, is strongly correlated with obesity, weight-related medical diseases, and mortality and has increased commensurately with secular increases in obesity in the United States. Little is known about the distribution of MetSyn in obese patients with binge eating disorder (BED) or its associations with different developmental trajectories of dieting, binge eating, and obesity problems. Furthermore, inconsistencies in the limited data necessitate elucidation. This study examined the frequency and correlates of MetSyn in a consecutive series of 148 treatment-seeking obese men and women with BED assessed with structured clinical interviews. Almost half of the participants met the criteria for MetSyn. Participants with MetSyn did not differ from those without MetSyn on demographic variables or disordered eating psychopathology. However, our findings suggest that MetSyn is associated with a distinct developmental trajectory, specifically a later age at BED onset and shorter BED duration. Although the findings from this study shed some light on MetSyn and its associations with developmental trajectories of eating and weight-related behaviors, notable inconsistencies characterize the limited literature. Prospective studies are needed to examine causal connections in the development of the MetSyn in relation to disordered eating in addition to excess weight.

Cultured senescent myoblasts derived from human vastus lateralis exhibit normal mitochondrial ATP synthesis capacities with correlating concomitant ROS production while whole cell ATP production is decreased

The free radical theory of aging says that increased oxidative stress and mitochondrial dysfunction are associated with old age. In the present study we have investigated the effects of cellular senescence on muscle energetic by comparing mitochondrial content and function in cultured muscle satellite cells at early and late passage numbers. We show that cultured muscle satellite cells undergoing senescence express a reduced mitochondrial mass, decreased whole cell ATP level, normal to increased mitochondrial ATP production under ATP utilization, increased mitochondrial membrane potential and increased superoxide/mitochondrial mass and hydrogen peroxide/mitochondrial mass ratios. Moreover, the increased ROS production correlates with the corresponding mitochondrial ATP production. Thus, myotubes differentiated from human myoblasts undergoing senescence have a reduced mitochondrial content, but the existent mitochondria express normal to increased functional capabilities. The present data suggest that the origin of aging lies outside the mitochondria and that a malfunction in the cell might be preceding and initiating the increase of mitochondrial ATP synthesis and concomitant ROS production in the single mitochondrion in response to decreased mitochondrial mass and reduced extra-mitochondrial energy supply. This then can lead to the increased damage of DNA, lipids and proteins of the mitochondria as postulated by the free radical theory of aging.

Further support to the uncoupling-to-survive theory: the genetic variation of human UCP genes is associated with longevity

In humans Uncoupling Proteins (UCPs) are a group of five mitochondrial inner membrane transporters with variable tissue expression, which seem to function as regulators of energy homeostasis and antioxidants. In particular, these proteins uncouple respiration from ATP production, allowing stored energy to be released as heat. Data from experimental models have previously suggested that UCPs may play an important role on aging rate and lifespan. We analyzed the genetic variability of human UCPs in cohorts of subjects ranging between 64 and 105 years of age (for a total of 598 subjects), to determine whether specific UCP variability affects human longevity. Indeed, we found that the genetic variability of UCP2, UCP3 and UCP4 do affect the individual's chances of surviving up to a very old age. This confirms the importance of energy storage, energy use and modulation of ROS production in the aging process. In addition, given the different localization of these UCPs (UCP2 is expressed in various tissues including brain, hearth and adipose tissue, while UCP3 is expressed in muscles and Brown Adipose Tissue and UCP4 is expressed in neuronal cells), our results may suggest that the uncoupling process plays an important role in modulating aging especially in muscular and nervous tissues, which are indeed very responsive to metabolic alterations and are very important in estimating health status and survival in the elderly.

A Simple Model Predicting Individual Weight Change in Humans

Excessive weight in adults is a national concern with over 2/3 of the US population deemed overweight. Because being overweight has been correlated to numerous diseases such as heart disease and type 2 diabetes, there is a need to understand mechanisms and predict outcomes of weight change and weight maintenance. A simple mathematical model that accurately predicts individual weight change offers opportunities to understand how individuals lose and gain weight and can be used to foster patient adherence to diets in clinical settings. For this purpose, we developed a one dimensional differential equation model of weight change based on the energy balance equation is paired to an algebraic relationship between fat free mass and fat mass derived from a large nationally representative sample of recently released data collected by the Centers for Disease Control. We validate the model's ability to predict individual participants' weight change by comparing model estimates of final weight data from two recent underfeeding studies and one overfeeding study. Mean absolute error and standard deviation between model predictions and observed measurements of final weights are less than 1.8 ± 1.3 kg for the underfeeding studies and 2.5 ± 1.6 kg for the overfeeding study. Comparison of the model predictions to other one dimensional models of weight change shows improvement in mean absolute error, standard deviation of mean absolute error, and group mean predictions. The maximum absolute individual error decreased by approximately 60% substantiating reliability in individual weight change predictions. The model provides a viable method for estimating individual weight change as a result of changes in intake and determining individual dietary adherence during weight change studies.

Two variants located in the upstream enhancer region of human UCP1 gene affect gene expression and are correlated with human longevity

The brown fat specific UnCoupling Protein 1 (UCP1) is involved in thermogenesis, a process by which energy is dissipated as heat in response to cold stress and excess of caloric intake. Thermogenesis has potential implications for body mass control and cellular fat metabolism. In fact, in humans, the variability of the UCP1 gene is associated with obesity, fat gain and metabolism. Since regulation of metabolism is one of the key-pathways in lifespan extension, we tested the possible effects of UCP1 variability on survival. Two polymorphisms (A-3826G and C-3740A), falling in the upstream promoter region of UCP1, were analyzed in a sample of 910 subjects from southern Italy (475 women and 435 men; age range 40-109). By analyzing haplotype specific survival functions we found that the A-C haplotype favors survival in the elderly. Consistently, transfection experiments showed that the luciferase activity of the construct containing the A-C haplotype was significantly higher than that containing the G-A haplotype. Interestingly, the different UCP1 haplotypes responded differently to hormonal stimuli. The results we present suggest a correlation between the activity of UCP1 and human survival, indicating once again the intricacy of mechanisms involved in energy production, storage and consumption as the key to understanding human aging and longevity.

Signaling proteins that influence energy intake may affect unintentional weight loss in elderly persons

After age 70 to 75 years, average body weight decreases both in ailing and healthy people because of a loss of appetite that results in reduced energy intake and the loss of body fat and lean muscle tissue. This so-called anorexia of aging predisposes elderly people to continued pathologic weight loss and malnutrition-major causes of morbidity and mortality. Health care professionals must understand the many factors involved in the anorexia of aging to help older adults prevent unintentional weight loss. Psychological, social, and cultural factors are important effectors; however, physiological factors are emphasized here because they are not thoroughly understood and they make it inherently difficult for most people to alter their body weight. Monoamines, steroid hormones (glucocorticoids and mineralocorticoids), endocannabinoids, and proteins all influence body weight. This review is an analysis of proteins from the brain, pancreas, adipose tissue, and gastrointestinal tract that are known to affect energy intake and energy balance, with an attempt to identify those factors that may change with aging. The articles included in this review were obtained by a PubMed database search using the keywords mouse OR rat OR human AND aged OR aging OR older OR elderly AND adult AND anorexia OR "unintentional weight loss," and each of the individual proteins discussed, as well as from the reference lists of those articles. The results reveal that some proteins may be important in the development of unintentional weight loss in elderly persons, whereas others may not have a significant role. However, many of the proteins that could conceivably have a role in unintentional weight loss have not yet been studied with that question in mind. Preventing unintentional weight loss in older adults is an important goal and further research on the role of proteins important for the maintenance of energy balance and the development of unintentional weight loss in elderly persons is warranted.

Effects of carbohydrates on satiety: differences between liquid and solid food

PURPOSE OF REVIEW

To examine the satiety effect of carbohydrates with a focus on the comparison of liquid and solid food and their implications for energy balance and weight management.

RECENT FINDINGS

A number of studies have examined the role of dietary fiber, whole grains, and glycemic index or glycemic load on satiety and subsequent energy intake, but results remain inconclusive. Intake of liquid carbohydrates, particularly sugar-sweetened beverages, has increased considerably across the globe in recent decades in both adolescents and adults. In general, liquid carbohydrates produce less satiety compared with solid carbohydrates. Some energy from liquids may be compensated for at subsequent meals but because the compensation is incomplete, it leads to an increase in total long-term energy intake. Recent studies also suggest some potential differential responses of satiety by characteristics of the patients (e.g., race, sex, and body weight status). These differences warrant further research.

SUMMARY

Satiety is a complex process influenced by a number of properties in food. The physical form (solid vs. liquid) of carbohydrates is an important component that may affect the satiety process and energy intake. Accumulating evidence suggests that liquid carbohydrates generally produce less satiety than solid forms.

Age and androgen-deprivation therapy on exercise outcomes in men with prostate cancer

PURPOSE

The purpose of this study is to examine the effects of age (≤ 65 years or >65 years) and androgen-deprivation therapy (ADT, presence or absence) as factors that may predict changes in body composition and fitness following a 24-week exercise program in prostate cancer patients.

METHODS

One hundred twenty-one men were randomly allocated to either: (1) aerobic exercise (AE), (2) resistance exercise (RE), or (3) usual care (UC). Body composition was assessed by DXA. Aerobic fitness was assessed through a maximal treadmill test. Muscular strength was assessed by leg extension and bench press using the eight-repetition maximum test. Responses were compared between younger (≤ 65 years) and older (> 65 years) patients with or without ADT.

RESULTS

There did not appear to be an interaction between age and ADT on body composition or fitness, nor were there any significant changes in body composition for participants ≤ 65 years. In participants aged >65 years, lean mass decreased in AE (p = 0.013) and UC (p = 0.006), but was preserved in RE. In participants receiving ADT, there was a decrease in lean mass in AE (p = 0.003) and UC (p < 0.001) but not in RE. The non-ADT group did not show any changes in body composition but did show improvements in muscular fitness following resistance training (p < 0.001).

CONCLUSION

Changes in body composition and physical fitness following a 24-week exercise program in men with prostate cancer are not influenced by age and/or ADT. Resistance training appears to attenuate the age-related decrease in lean mass and increase in body fat in older patients with prostate cancer and those receiving ADT.

Human myotubes from myoblast cultures undergoing senescence exhibit defects in glucose and lipid metabolism

Adult stem cells are known to have a finite replication potential. Muscle biopsy-derived human satellite cells (SCs) were grown at different passages and differentiated to human myotubes in culture to analyze the functional state of various carbohydrate and lipid metabolic pathways. As the proliferative potential of myoblasts decreased dramatically with passage number, a number of cellular functions were altered: the capacity of myoblasts to fuse and differentiate into myotubes was reduced, and metabolic processes in myotubes such as glucose uptake, glycogen synthesis, glucose oxidation and fatty acid β-oxidation became gradually impaired. Upon insulin stimulation, glucose uptake and glycogen synthesis increased but as the cellular proliferative capacity became gradually exhausted, the response dropped concomitantly. Palmitic acid incorporation into lipids in myotubes decreased with passage number and could be explained by reduced incorporation into diacyl- and triacylglycerols. The levels of long-chain acyl-CoA esters decreased with increased passage number. Late-passage, non-proliferating, myoblast cultures showed strong senescence-associated β-galactosidase activity indicating that the observed metabolic defects accompany the induction of a senescent state. The main function of SCs is regeneration and skeletal muscle-build up. Thus, the metabolic defects observed during aging of SC-derived myotubes could have a role in sarcopenia, the gradual age-related loss of muscle mass and strength.

Effects of food form on food intake and postprandial appetite sensations, glucose and endocrine responses, and energy expenditure in resistance trained v. sedentary older adults

Limited research has suggested that the food form of nutritional supplements (FFNS) and resistance training (RT) influence ingestive behaviour and energy balance in older adults. The effects of the FFNS and RT on acute appetitive, endocrine and metabolic responses are not adequately documented. The present study assessed the effects of the FFNS and RT on postprandial appetite sensations (hunger and fullness), endocrine responses (plasma insulin, cholecystokinin, ghrelin and glucagon-like peptide-1 (GLP-1)), metabolism (glucose, energy expenditure and RER) and food intake (satiation) in older adults. On separate days, eighteen sedentary (Sed) and sixteen RT healthy adults (age 62-84 years) consumed 12·5 % of their energy need as an isoenergetic- and macronutrient-matched solid or beverage. Postprandial responses were assessed over 4 h. No RT × FFNS interactions were observed for any parameter. Fasting cholecystokinin was higher in the RT v. Sed group (P < 0·05). RT did not influence fullness, but fullness was higher following the solid v. beverage intake (P < 0·01). Neither RT nor FFNS influenced hunger. Glucose and insulin were higher after the solid v. beverage intake (P < 0·01). Ghrelin, GLP-1 and energy expenditure were not different between the RT and FFNS groups. Postprandial cholecystokinin was higher in the RT v. Sed group (P < 0·01) and for solid v. beverage (P < 0·05). RER was lower for solid v. beverage (P < 0·001). Neither RT nor FFNS independently or interactively influenced food intake 2 h after post-nutritional supplements. In conclusion, RT had little influence on ingestive behaviour. The appetitive and endocrine responses suggested the solid-promoted satiety; however, the FFNS did not alter subsequent food intake.

An energy systems approach to Parkinson's disease

The cause of Parkinson's disease (PD) remains unknown despite it being the second most prevalent neurodegenerative condition. Indeed, there is a growing consensus that there is no single cause, and that PD is a multifactorial systemic condition, in which a number of factors may determine its etiopathogenesis. We describe a systems approach that addresses the multifactorial aspects of PD and overcomes constraints on conventional experimentation imposed by PD's causal complexity, its long temporal duration, and its uniqueness to human brains. Specifically, a mathematical model of brain energy metabolism is used as a core module to which other modules describing cellular processes thought to be associated with PD can be attached and studied in an integrative environment. Employing brain energy usage as the core of a systems approach also enables the potential role that compromised energy metabolism may have in the etiology of PD. Although developed for PD, it has not escaped our attention that the energy systems approach outlined here could also be applied to other neurodegenerative disorders-most notably Alzheimer's disease.

An evolutionary review of human telomere biology: the thrifty telomere hypothesis and notes on potential adaptive paternal effects

Telomeres, repetitive DNA sequences found at the ends of linear chromosomes, play a role in regulating cellular proliferation, and shorten with increasing age in proliferating human tissues. The rate of age-related shortening of telomeres is highest early in life and decreases with age. Shortened telomeres are thought to limit the proliferation of cells and are associated with increased morbidity and mortality. Although natural selection is widely assumed to operate against long telomeres because they entail increased cancer risk, the evidence for this is mixed. Instead, here it is proposed that telomere length is primarily limited by energetic constraints. Cell proliferation is energetically expensive, so shorter telomeres should lead to a thrifty phenotype. Shorter telomeres are proposed to restrain adaptive immunity as an energy saving mechanism. Such a limited immune system, however, might also result in chronic infections, inflammatory stress, premature aging, and death--a more "disposable soma." With an increased reproductive lifespan, the fitness costs of premature aging are higher and longer telomeres will be favored by selection. Telomeres exhibit a paternal effect whereby the offspring of older fathers have longer telomeres due to increased telomere lengths of sperm with age. This paternal effect is proposed to be an adaptive signal of the expected age of male reproduction in the environment offspring are born into. The offspring of lineages of older fathers will tend to have longer, and thereby less thrifty, telomeres, better preparing them for an environment with higher expected ages at reproduction.

Feed efficiency, food choice, and food reward behaviors in young and old Fischer rats

Increased susceptibility to energy imbalance and anorexia in old age are risk factors for malnutrition during aging, but the underlying mechanisms are not well understood. Here, we explored changes in taste-guided hedonic value ("liking") and motivation to obtain ("wanting") palatable foods as potential mediators of age-associated anorexia and weight loss in old Fischer-344 rats. "Liking" as measured by the number of positive hedonic orofacial responses to sucrose and corn oil was not different in old compared with young rats. Taste-guided, low effort "wanting" as measured by the number of licks per 10 seconds was also not different, although old rats exhibited a slight oromotor impairment as revealed by significantly increased interlick intervals. Medium effort "wanting" as measured by performance in the incentive runway was significantly decreased in old versus young rats. Although decreased net running speed was partially accountable, significantly increased duration of distractions suggested additional deficits in motivation and/or reinforcement learning. Together with early satiation on corn oil but not sucrose in aged rats, these changes are likely to have resulted in the significantly greater sucrose preference of old rats in 12-hour tests, and may ultimately lead to reduced energy intake and weight loss.

Associations between energy demands, physical activity, and body composition in adult humans between 18 and 96 y of age

BACKGROUND

Associations between body composition and the energy expended on basal metabolism and activity are complex and age dependent.

OBJECTIVE

The objective was to examine associations between body composition and daily (DEE), basal (BEE), and activity energy expenditure (AEE) throughout the adult life span.

DESIGN

A cross-sectional study was conducted in 529 adults aged 18-96 y. DEE was measured by using doubly labeled water, BEE by using respirometry, and body composition by isotope dilution. AEE was calculated as DEE - BEE, and physical activity level (PAL) was calculated as DEE/BEE.

RESULTS

Up to age 52 y, fat-free mass (FFM) and fat mass (FM) were positively associated with age in men, but no significant effect was observed in women. No effects of age on DEE and AEE were observed. The average DEE in men (14.1 MJ/d) was 27% greater than that in women (10.7 MJ/d). PAL averaged 1.84 in men and 1.75 in women. Above and including the age of 52 y, FFM, FM, DEE, BEE, and AEE were all negatively associated with greater age. The effect of age on AEE was greater than on BEE; consequently, PAL by the age of 95 y was only 1.36. PAL and AEE were both unrelated to FFM (both age adjusted).

CONCLUSIONS

PAL and AEE were not associated with age in subjects aged <52 y. AEE, BEE, and PAL were all negatively associated with age in subjects aged ≥52 y. An absence of a relation between age-adjusted PAL and FFM suggested that greater physical activity was not associated with higher FFM in the elderly.

Regulation of skeletal muscle transcriptome in elderly men after 6 weeks of endurance training at lactate threshold intensity

A compromised muscle function due to aging, sarcopenia and reduced level of physical activity can lead to metabolic complications and chronic diseases. Endurance exercise counters these diseases by inducing beneficial adaptations whose molecular mechanisms remain unclear. We have investigated the transcriptomic changes following mild-intensity endurance training in skeletal muscle of elderly men. Seven healthy subjects followed an exercise program of cycle ergometer training at lactate threshold (LT) level for 60 min/day, five times/week during six weeks. Physiological and transcriptomic changes were analyzed before and after training. LT training decreased percentage body fat and fasting levels of plasma glucose, while increasing high-density lipoprotein cholesterol and lecithin-cholesterol acyltransferase levels. Transcriptomic analysis revealed fast-to-slow fiber type transition, increased amount of mtDNA encoded transcripts and modulation of 12 transcripts notably related to extracellular matrix (ECM), oxidative phosphorylation (OXPHOS), as well as partially characterized and novel transcripts. The training simultaneously induced the expression of genes related to slow fiber type transition, OXPHOS and ECM, which might contribute to the improvement of glucose and lipid metabolisms and whole body aerobic capacity.