Reduced whole-body fat oxidation in women and in the elderly

The age-dependent regulation of pancreatic islet landscape is fueled by a HNF1a-immune signaling loop

Animal longevity is a function of global vital organ functionality and, consequently, a complex polygenic trait. Yet, monogenic regulators controlling overall or organ-specific ageing exist, owing their conservation to their function in growth and development. Here, by using pathway analysis combined with wet-biology methods on several dynamic timelines, we identified Hnf1a as a novel master regulator of the maturation and ageing in the adult pancreatic islet during the first year of life. Conditional transgenic mice bearing suboptimal levels of this transcription factor in the pancreatic islets displayed age-dependent changes, with a profile echoing precocious maturation. Additionally, the comparative pathway analysis revealed a link between Hnf1a age-dependent regulation and immune signaling, which was confirmed in the ageing timeline of an overly immunodeficient mouse model. Last, the global proteome analysis of human islets spanning three decades of life largely backed the age-specific regulation observed in mice. Collectively, our results suggest a novel role of Hnf1a as a monogenic regulator of the maturation and ageing process in the pancreatic islet via a direct or indirect regulatory loop with immune signaling.

Associations of minimally processed and ultra-processed food intakes with cardiovascular health in Korean adults: the Korea National Health and Nutrition Examination Survey (KNHANES VI), 2013-2015

BACKGROUND

Although recent studies have suggested the adverse effects of processed foods on cardiovascular disease, few studies have been conducted on the effects of food processing on cardiovascular health (CVH) in Koreans.

OBJECTIVE

This study aimed to investigate the associations of minimally processed foods (MPF) and ultra-processed foods (UPF) intakes with CVH.

METHODS

We used the data of 6945 adults (≥19) from the sixth Korea National Health and Nutrition Examination Survey. MPF and UPF intakes were based on the NOVA food classification. Using Life's simple 7 (LS7) proposed by the American Heart Association, the CVH indicator was estimated as the sum (0-12) of the scores of six components. Multiple linear and multinomial logistic regressions were used to estimate the associations between processed food intakes and CVH.

RESULTS

The mean (standard error) of MPF and UPF intake was 61.28 (0.28) and 20.27 (0.24) %kcal/day, respectively. After adjusting for sex, age, household income, educational attainment, family history of CVD, and stress, we found significant positive associations between MPF intake and CVH (p value < 0.001), while associations between UPF intake and CVH were significantly negative (p value < 0.001). Moreover, the magnitude of the observed association was more distinctive in females (p-interaction < 0.01) and with increasing age (p-interaction < 0.001).

CONCLUSIONS

A high intake of MPF is associated with improved CVH, while a high intake of UPF is associated with poorer CVH in Korean adults. Therefore, public health policies should be established to promote the choice of less processed foods to improve CVH among South Korean adults.

IMPACT STATEMENT

In modern society, processed foods have become ubiquitous and South Korea's consumption of processed foods is very high. This study had shown that the more processed a food is, the more negative impact it can have on cardiovascular health. Therefore, researching the effects of processed foods on the human body can increase understanding of population health and aid in the development of prevention and treatment strategies.

Telomere length as a marker of changes in body composition and fractures-an analysis of data from the NHANES 2001-2002

Purpose

There has been an association between changes in body composition, fracture incidence, and age in previous studies. Telomere length (TL) has been proposed as a biomarker of aging. However, the relationship between body composition, fractures, and TL has rarely been studied. Therefore, this study aimed to investigate the correlation between TL and body composition and fractures.Patients and methods: 20950 participants from the 2001-2002 National Health and Nutrition Examination Survey (NHANES) were included in the final analysis. In NHANES, body compositions were measured with DXA, and TL was determined with quantitative PCR. Correlation analysis of TL and body composition was conducted using multivariate weighted linear regression and logistic regression models.

Results

The results showed that TL positively correlated with bone mineral density (BMD) and bone mineral content (BMC) in most body parts. However, BMD and BMC were negatively connected with TL in the upper limbs and skull. Fat content was negatively associated with TL, while muscle content was positively linked to TL. In addition, TL's trend analysis results were consistent with the regression model when transformed from a continuous to a classified variable. An increase in TL was associated with a higher incidence of wrist fractures, while a decrease in spine fractures. The above correlation also has a certain degree of sex specificity.

Conclusion

Our study indicate that TL is associated with body composition as well as fractures, but further research is needed to confirm these contrasting associations in the skull, upper limbs, and wrists.

Energy metabolism and thermoregulation during sleep in young and old females

Core body temperature (CBT) shows a diurnal rhythm, and the nocturnal decrease in CBT is blunted in older people. The physiological mechanisms responsible for the blunted nocturnal decrease in CBT in older people remain to be revealed. The aim of this study was to compare heat production and heat dissipation in young and old subjects during sleep, as assessed by indirect calorimetry and the distal-proximal temperature gradient (DPG) of skin temperature. A complete dataset of 9 young (23.3 ± 1.1 years) and 8 old (72.1 ± 2.5 years) females was analyzed. CBT and energy metabolism were monitored during sleep using an ingestible temperature sensor in a metabolic chamber maintained at 25 °C. Skin temperature was measured at proximal and distal parts of the body. CBT, distal skin temperature, and DPG in older subjects were higher than in young subjects. Protein oxidation was similar between the two groups, but fat oxidation was lower and carbohydrate oxidation was higher in old subjects compared to young subjects. On the other hand, energy expenditure was similar between the two age groups. Thus, the elevated CBT in older subjects was not attributed to deteriorated heat dissipation or enhanced heat production, suggesting an alternative explanation such as deteriorated evaporative heat loss in old subjects.

A Narrative Review of Non-Pharmacological Strategies for Managing Sarcopenia in Older Adults with Cardiovascular and Metabolic Diseases

This narrative review examines the mechanisms underlying the development of cardiovascular disease (CVD) and metabolic diseases (MDs), along with their association with sarcopenia. Furthermore, non-pharmacological interventions to address sarcopenia in patients with these conditions are suggested. The significance of combined training in managing metabolic disease and secondary sarcopenia in type II diabetes mellitus is emphasized. Additionally, the potential benefits of resistance and aerobic training are explored. This review emphasises the role of nutrition in addressing sarcopenia in patients with CVD or MDs, focusing on strategies such as optimising protein intake, promoting plant-based protein sources, incorporating antioxidant-rich foods and omega-3 fatty acids and ensuring sufficient vitamin D levels. Moreover, the potential benefits of targeting gut microbiota through probiotics and prebiotic fibres in sarcopenic individuals are considered. Multidisciplinary approaches that integrate behavioural science are explored to enhance the uptake and sustainability of behaviour-based sarcopenia interventions. Future research should prioritise high-quality randomized controlled trials to refine exercise and nutritional interventions and investigate the incorporation of behavioural science into routine practices. Ultimately, a comprehensive and multifaceted approach is essential to improve health outcomes, well-being and quality of life in older adults with sarcopenia and coexisting cardiovascular and metabolic diseases.

Associations of resting and peak fat oxidation with sex hormone profile and blood glucose control in middle-aged women

BACKGROUND AND AIMS

Menopause may reduce fat oxidation. We investigated whether sex hormone profile explains resting fat oxidation (RFO) or peak fat oxidation (PFO) during incremental cycling in middle-aged women. Secondarily, we studied associations of RFO and PFO with glucose regulation.

METHOD AND RESULTS

We measured RFO and PFO of 42 women (age 52-58 years) with indirect calorimetry. Seven participants were pre- or perimenopausal, 26 were postmenopausal, and nine were postmenopausal hormone therapy users. Serum estradiol (E2), follicle-stimulating hormone, progesterone, and testosterone levels were quantified with immunoassays. Insulin sensitivity (Matsuda index) and glucose tolerance (area under the curve) were determined by glucose tolerance testing. Body composition was assessed with dual-energy X-ray absorptiometry; physical activity with self-report and accelerometry; and diet, with food diaries. Menopausal status or sex hormone levels were not associated with the fat oxidation outcomes. RFO determinants were fat mass (β = 0.44, P = 0.006) and preceding energy intake (β = -0.40, P = 0.019). Cardiorespiratory fitness (β = 0.59, P = 0.002), lean mass (β = 0.49, P = 0.002) and physical activity (self-reported β = 0.37, P = 0.020; accelerometer-measured β = 0.35, P = 0.024) explained PFO. RFO and PFO were not related to insulin sensitivity. Higher RFO was associated with poorer glucose tolerance (β = 0.52, P = 0.002).

CONCLUSION

Among studied middle-aged women, sex hormone profile did not explain RFO or PFO, and higher fat oxidation capacity did not indicate better glucose control.

System-level metabolic modeling facilitates unveiling metabolic signature in exceptional longevity

Although it is well known that metabolic control plays a crucial role in regulating the health span and life span of various organisms, little is known for the systems metabolic profile of centenarians, the paradigm of human healthy aging and longevity. Meanwhile, how to well characterize the system‐level metabolic states in an organism of interest remains to be a major challenge in systems metabolism research. To address this challenge and better understand the metabolic mechanisms of healthy aging, we developed a method of genome‐wide precision metabolic modeling (GPMM) which is able to quantitatively integrate transcriptome, proteome and kinetome data in predictive modeling of metabolic networks. Benchmarking analysis showed that GPMM successfully characterized metabolic reprogramming in the NCI‐60 cancer cell lines; it dramatically improved the performance of the modeling with an R² of 0.86 between the predicted and experimental measurements over the performance of existing methods. Using this approach, we examined the metabolic networks of a Chinese centenarian cohort and identified the elevated fatty acid oxidation (FAO) as the most significant metabolic feature in these long‐lived individuals. Evidence from serum metabolomics supports this observation. Given that FAO declines with normal aging and is impaired in many age‐related diseases, our study suggests that the elevated FAO has potential to be a novel signature of healthy aging of humans.

Attenuation of the Counter-Regulatory Glucose Response in CVLM C1 Neurons: A Possible Explanation for Anorexia of Aging

This study aimed to determine the effect of age on CVLM C1 neuron glucoregulatory proteins in the feeding pathway. Male Sprague Dawley rats aged 3 months and 24 months old were divided into two subgroups: the treatment group with 2-deoxy-d-glucose (2DG) and the control group. Rat brains were dissected to obtain the CVLM region of the brainstem. Western blot was used to determine protein expression of tyrosine hydroxylase (TH), phosphorylated TH at Serine40 (pSer40TH), AMP-activated protein kinase (AMPK), phosphorylated AMPK (phospho AMPK), and neuropeptide Y Y5 receptors (NPY5R) in CVLM samples. Immunofluorescence was used to determine TH-, AMPK-, and NPY5R-like immunoreactivities among other brain coronal sections. Results obtained denote a decrease in basal TH phosphorylation levels and AMPK proteins and an increase in TH proteins among aged CVLM neurons. Increases in the basal immunoreactivity of TH+, AMPK+, NPY5R+, TH+/AMPK+, and TH+/NPY5R+ were also observed among old rats. Young treatment-group rats saw a decrease in TH phosphorylation and AMPK proteins following 2DG administration, while an increase in AMPK phosphorylation and a decrease in TH proteins were found among the old-treatment-group rats. These findings suggest the participation of CVLM C1 neurons in counter-regulatory responses among young and old rats. Altering protein changes in aged CVLM C1 neurons may attenuate responses to glucoprivation, thus explaining the decline in food intake among the elderly.

Techniques for in vivo assessment of myopathies in broiler chicken breasts using a biopsy as a support tool

An experiment was conducted to validate non-invasive evaluation techniques as in vivo evaluation tools for the myopathies wooden breast and white striping that affect broilers, using biopsy as a support tool. It evaluated 30 Cobb 500® broiler chickens in a completely randomized design consisting of two sexes (males and females) and 15 replications per treatment. At 14, 21, 35, 42 and 49 days, the surface temperature of the birds' breasts was recorded using infrared thermography, analysis of fillet depth, and echogenicity by ultrasound imaging. All broiler chickens were sent for biopsy at 21, 35 and 42 days to collect a fragment of the pectoral muscle for descriptive morphological analyses of histological lesions and muscle fibre morphometry. Males had higher echogenicity values at 14, 21 and 42 days. There was no influence of bird sex on the occurrence of the wooden breast and white striping myopathies at 49 days of age in broilers selected and submitted to the biopsy protocol. There was a general trend of decreasing surface temperature for both sexes according to their age. Muscles with less area occupied with fibres had a lower surface temperature. It was concluded that ultrasonography with a 3.5 MHz transducer detects muscle changes after 28 days of age, which is consistent with the myopathic lesions studied. Infrared thermography is a potential method for detecting changes in breast temperature indicating myopathic lesions. A biopsy can be used as an auxiliary tool in the study of myopathies in broiler chicken breasts.RESEARCH HIGHLIGHTS Detection of changes in the breast muscle after 28 days of age with ultrasonography.Changes in the surface temperature range of pectoral muscle with infrared thermography.Use of biopsy as a tool for early diagnostic evaluation in broiler myopathies.

Free fatty acids, glicentin and glucose-dependent insulinotropic polypeptide as potential major determinants of fasting substrate oxidation

The selection of carbohydrates or fat to generate intracellular energy is thought to be crucial for long-term metabolic health. While most studies assess fuel selection after a metabolic challenge, the determinants of substrate oxidation in the fasted state remain largely unexplored. We therefore assessed the respiratory quotient by indirect calorimetry as a read-out for substrate oxidation following an overnight fast. This cross-sectional analysis consisted of 192 (92 women, 100 men) either lean or obese participants. Following an overnight fast, the respiratory quotient (RQ) was assessed, after which a 5-point 75-g oral glucose tolerance test was performed. Unlike glucose and insulin, fasting free fatty acids (FFA) correlated negatively with fasting RQ (p < 0.0001). Participants with high levels of the ketone body β-hydroxybutyric acid had significantly lower RQ values. Fasting levels of glucose-dependent insulinotropic polypeptide (GIP) and glicentin were positively associated with fasting RQ (all p ≤ 0.03), whereas GLP-1 showed no significant association. Neither BMI, nor total body fat, nor body fat distribution correlated with fasting RQ. No relationship between the RQ and diabetes or the metabolic syndrome could be observed. In the fasting state, FFA concentrations were strongly linked to the preferentially oxidized substrate. Our data did not indicate any relationship between fasting substrate oxidation and metabolic diseases, including obesity, diabetes, and the metabolic syndrome. Since glicentin and GIP are linked to fuel selection in the fasting state, novel therapeutic approaches that target these hormones may have the potential to modulate substrate oxidation.

The trophocytes and oenocytes of worker and queen honey bees (Apis mellifera) exhibit distinct age-associated transcriptome profiles

Despite the identical genomic context, trophocytes and oenocytes in worker bees exhibit aging-related phenotypes, in contrast to the longevity phenotypes in queen bees. To explore this phenomenon at the molecular level, we evaluated the age-associated transcriptomes of trophocytes and oenocytes in worker bees and queen bees using high-throughput RNA-sequencing technology (RNA-seq). The results showed that (i) while gene expression profiles were different between worker and queen bees, they remained similar between young and old counterparts; (ii) worker bees express a high proportion of low-abundance genes, whereas queen bee transcriptomes display a high proportion of moderate-expression genes; (iii) genes were upregulated to a greater extent in queen bees vs. worker bees; and (iv) distinct aging-related and longevity-related candidate genes were found in worker and queen bees. These results provide new insights into the cellular aging and longevity of trophocytes and oenocytes in honey bees. Identification of aging-associated biomarker genes also constitutes a basis for translational research of aging in higher organisms.

Sexual dimorphism in cardiometabolic health: the role of adipose tissue, muscle and liver

Obesity is associated with many adverse health effects, such as an increased cardiometabolic risk. Despite higher adiposity for a given BMI, premenopausal women are at lower risk of cardiometabolic disease than men of the same age. This cardiometabolic advantage in women seems to disappear after the menopause or when type 2 diabetes mellitus develops. Sexual dimorphism in substrate supply and utilization, deposition of excess lipids and mobilization of stored lipids in various key metabolic organs (such as adipose tissue, skeletal muscle and the liver) are associated with differences in tissue-specific insulin sensitivity and cardiometabolic risk profiles between men and women. Moreover, lifestyle-related factors and epigenetic and genetic mechanisms seem to affect metabolic complications and disease risk in a sex-specific manner. This Review provides insight into sexual dimorphism in adipose tissue distribution, adipose tissue, skeletal muscle and liver substrate metabolism and tissue-specific insulin sensitivity in humans, as well as the underlying mechanisms, and addresses the effect of these sex differences on cardiometabolic health. Additionally, this Review highlights the implications of sexual dimorphism in the pathophysiology of obesity-related cardiometabolic risk for the development of sex-specific prevention and treatment strategies.

Substrate oxidation in primary human skeletal muscle cells is influenced by donor age

Primary human myotubes represent an alternative system to intact skeletal muscle for the study of human diseases related to changes in muscle energy metabolism. This work aimed to study if fatty acid and glucose metabolism in human myotubes in vitro were related to muscle of origin, donor gender, age, or body mass index (BMI). Myotubes from a total of 82 donors were established from three different skeletal muscles, i.e., musculus vastus lateralis, musculus obliquus internus abdominis, and musculi interspinales, and cellular energy metabolism was evaluated. Multiple linear regression analyses showed that donor age had a significant effect on glucose and oleic acid oxidation after correcting for gender, BMI, and muscle of origin. Donor BMI was the only significant contributor to cellular oleic acid uptake, whereas cellular glucose uptake did not rely on any of the variables examined. Despite the effect of age on substrate oxidation, cellular mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) and peroxisome proliferator–activated receptor gamma coactivator 1 alpha (PPARGC1A) did not correlate with donor age. In conclusion, donor age significantly impacts substrate oxidation in cultured human myotubes, whereas donor BMI affects cellular oleic acid uptake.

Low capacity to oxidize fat and body weight

For a given positive energy balance, a low capacity to oxidize fat could contribute to weight gain (low fat oxidation hypothesis). This hypothesis is based on the arguments that for a given stable diet and food quotient (FQ), the respiratory quotient (RQ) is higher in obesity prone (OP) than in obesity resistant individuals (OR) and that a high RQ predicts higher future weight gain. A review of 42 studies shows that there is no convincing experimental support to these arguments and thus for the low fat oxidation hypothesis. A power analysis also shows that this hypothesis might be impossible to experimentally confirm because very large numbers of subjects would be needed to reject the null hypotheses that the 24-h RQ is not different in OP and OR or that future weight gain is not different in individuals with a low and high 24-h RQ at baseline. A re-examination of the significance of the 24-hour and fasting RQ also shows that the assumption underlying the low fat oxidation hypothesis that a high RQ reflects a low capacity to oxidize fat is not valid: For a stable diet, the 24-h RQ entirely depends on FQ and energy balance, and the fasting RQ mainly depends on the FQ and energy balance and on the size of glycogen stores.

Sex-specific effects of maternal and postweaning high-fat diet on skeletal muscle mitochondrial respiration

Exposure to maternal over-nutrition in utero is linked with developmental programming of obesity, metabolic syndrome and cardiovascular disease in offspring, which may be exacerbated by postnatal high-fat (HF) diet. Skeletal muscle mitochondrial function contributes to substrate metabolism and is impaired in metabolic disease. We examined muscle mitochondrial respiration in male and female mice exposed to maternal HF diet in utero, followed by postweaning HF diet until middle age. After in utero exposure to maternal control (Con) or HF diet (45% kcal fat; 39.4% lard, 5.5% soybean oil), offspring were weaned to Con or HF, creating four groups: Con/Con (male/female (m/f), n=8/8), Con/HF (m/f, n=7/4), HF/Con (m/f, n=9/6) and HF/HF (m/f, n=4/4). Oxidative phosphorylation (OXPHOS) and electron transfer system (ETS) capacity were measured in permeabilized gastrocnemius bundles. Maternal HF diet increased fasting glucose and lean body mass in males and body fat percentage in both sexes (P⩽0.05). Maximal adenosine diphosphate-stimulated respiration (complex I OXPHOS) was decreased by maternal HF diet in female offspring (-21%, P=0.053), but not in male (-0%, P>0.05). Sexually divergent responses were exacerbated in offspring weaned to HF diet. In females, OXPHOS capacity was lower (-28%, P=0.041) when weaned to high-fat (HF/HF) v. control diet (HF/Con). In males, OXPHOS (+33%, P=0.009) and ETS (+42%, P=0.016) capacity increased. Our data suggest that maternal lard-based HF diet, rich in saturated fat, affects offspring skeletal muscle respiration in a sex-dependent manner, and these differences are exacerbated by HF diet in adulthood.

Cardiovascular and skeletal muscle health with lifelong exercise

The purpose of this study was to examine the effects of aerobic lifelong exercise (LLE) on maximum oxygen consumption (V̇o_2max) and skeletal muscle metabolic fitness in trained women ( n = 7, 72 ± 2 yr) and men ( n = 21, 74 ± 1 yr) and compare them to old, healthy nonexercisers (OH; women: n = 10, 75 ± 1 yr; men: n = 10, 75 ± 1 yr) and young exercisers (YE; women: n = 10, 25 ± 1 yr; men: n = 10, 25 ± 1 yr). LLE men were further subdivided based on intensity of lifelong exercise and competitive status into performance (LLE-P, n = 14) and fitness (LLE-F, n = 7). On average, LLE exercised 5 day/wk for 7 h/wk over the past 52 ± 1 yr. Each subject performed a maximal cycle test to assess V̇o_2max and had a vastus lateralis muscle biopsy to examine capillarization and metabolic enzymes [citrate synthase, β-hydroxyacyl-CoA dehydrogenase (β-HAD), and glycogen phosphorylase]. V̇o_2max had a hierarchical pattern (YE > LLE > OH, P < 0.05) for women (44 ± 2 > 26 ± 2 > 18 ± 1 ml·kg^-1·min^-1) and men (53 ± 3 > 34 ± 1 > 22 ± 1 ml·kg^-1·min^-1) and was greater ( P < 0.05) in LLE-P (38 ± 1 ml·kg^-1·min^-1) than LLE-F (27 ± 2 ml·kg^-1·min^-1). LLE men regardless of intensity and women had similar capillarization and aerobic enzyme activity (citrate synthase and β-HAD) as YE, which were 20%-90% greater ( P < 0.05) than OH. In summary, these data show a substantial V̇o_2max benefit with LLE that tracked similarly between the sexes, with further enhancement in performance-trained men. For skeletal muscle, 50+ years of aerobic exercise fully preserved capillarization and aerobic enzymes, regardless of intensity. These data suggest that skeletal muscle metabolic fitness may be easier to maintain with lifelong aerobic exercise than more central aspects of the cardiovascular system. NEW & NOTEWORTHY Lifelong exercise (LLE) is a relatively new and evolving area of study with information especially limited in women and individuals with varying exercise intensity habits. These data show a substantial maximal oxygen consumption benefit with LLE that tracked similarly between the sexes. Our findings contribute to the very limited skeletal muscle biopsy data from LLE women (>70 yr), and similar to men, revealed a preserved metabolic phenotype comparable to young exercisers.

Cellular energy metabolism maintains young status in old queen honey bees (Apis mellifera)

Trophocytes and oenocytes of queen honey bees are used in studies of cellular longevity, but their cellular energy metabolism with age is poorly understood. In this study, the molecules involved in cellular energy metabolism were evaluated in the trophocytes and oenocytes of young and old queen bees. The findings indicated that there were no significant differences between young and old queen bees in β-oxidation, glycolysis, and protein synthesis. These results indicate that the cellular energy metabolism of trophocytes and oenocytes in old queen bees is similar to young queen bees and suggests that maintaining cellular energy metabolism in a young status may be associated with the longevity of queen bees. Fat and glycogen accumulation increased with age indicating that old queen bees are older than young queen bees.

Understanding Age-Related Changes in Skeletal Muscle Metabolism: Differences Between Females and Males

Skeletal muscle is the largest metabolic organ system in the human body. As such, metabolic dysfunction occurring in skeletal muscle impacts whole-body nutrient homeostasis. Macronutrient metabolism changes within the skeletal muscle with aging, and these changes are associated in part with age-related skeletal muscle remodeling. Moreover, age-related changes in skeletal muscle metabolism are affected differentially between males and females and are likely driven by changes in sex hormones. Intrinsic and extrinsic factors impact observed age-related changes and sex-related differences in skeletal muscle metabolism. Despite some support for sex-specific differences in skeletal muscle metabolism with aging, more research is necessary to identify underlying differences in mechanisms. Understanding sex-specific aging skeletal muscle will assist with the development of therapies to attenuate adverse metabolic and functional outcomes.

A Review of the Effect of Dietary Composition on Fasting Substrate Oxidation in Healthy and Overweight Subjects

AIM

The purpose of this review was to assess existing evidence on the effects of chronic dietary macronutrient composition on substrate oxidation during a fasted state in healthy and overweight subjects.

METHODS

A systematic review of studies was conducted across five databases. Studies were included if they were English language studies of human adults, ≥19 years, used indirect calorimetry (ventilated hood technique), specified dietary macronutrient composition, and measured substrate oxidation.

RESULTS

There was no evidence that variations of a typical, non-experimental diet influenced rate or ratio of substrate utilization, however there may be an upper and lower threshold for when macronutrient composition may directly alter preferences for fuel oxidation rates during a fasted state.

CONCLUSION

This review indicates that macronutrient composition of a wide range of typical, non-experimental dietary fat and carbohydrate intakes has no effect on fasting substrate oxidation. This suggests that strict control of dietary intake prior to fasting indirect calorimetry measurements may be an unnecessary burden for study participants. Further research into the effects of long-term changes in isocaloric macronutrient shift is required.

The effect of age and unilateral leg immobilization for 2 weeks on substrate utilization during moderate-intensity exercise in human skeletal muscle

KEY POINTS

This study aimed to provide molecular insight into the differential effects of age and physical inactivity on the regulation of substrate metabolism during moderate-intensity exercise. Using the arteriovenous balance technique, we studied the effect of immobilization of one leg for 2 weeks on leg substrate utilization in young and older men during two-legged dynamic knee-extensor moderate-intensity exercise, as well as changes in key proteins in muscle metabolism before and after exercise. Age and immobilization did not affect relative carbohydrate and fat utilization during exercise, but the older men had higher uptake of exogenous fatty acids, whereas the young men relied more on endogenous fatty acids during exercise. Using a combined whole-leg and molecular approach, we provide evidence that both age and physical inactivity result in intramuscular lipid accumulation, but this occurs only in part through the same mechanisms.

ABSTRACT

Age and inactivity have been associated with intramuscular triglyceride (IMTG) accumulation. Here, we attempt to disentangle these factors by studying the effect of 2 weeks of unilateral leg immobilization on substrate utilization across the legs during moderate-intensity exercise in young (n = 17; 23 ± 1 years old) and older men (n = 15; 68 ± 1 years old), while the contralateral leg served as the control. After immobilization, the participants performed two-legged isolated knee-extensor exercise at 20 ± 1 W (∼50% maximal work capacity) for 45 min with catheters inserted in the brachial artery and both femoral veins. Biopsy samples obtained from vastus lateralis muscles of both legs before and after exercise were used for analysis of substrates, protein content and enzyme activities. During exercise, leg substrate utilization (respiratory quotient) did not differ between groups or legs. Leg fatty acid uptake was greater in older than in young men, and although young men demonstrated net leg glycerol release during exercise, older men showed net glycerol uptake. At baseline, IMTG, muscle pyruvate dehydrogenase complex activity and the protein content of adipose triglyceride lipase, acetyl-CoA carboxylase 2 and AMP-activated protein kinase (AMPK)γ3 were higher in young than in older men. Furthermore, adipose triglyceride lipase, plasma membrane-associated fatty acid binding protein and AMPKγ3 subunit protein contents were lower and IMTG was higher in the immobilized than the contralateral leg in young and older men. Thus, immobilization and age did not affect substrate choice (respiratory quotient) during moderate exercise, but the whole-leg and molecular differences in fatty acid mobilization could explain the age- and immobilization-induced IMTG accumulation.

Age-related changes in basal substrate oxidation and visceral adiposity and their association with metabolic syndrome

PURPOSE

Ageing is directly associated with visceral fat (VAT) deposition and decline of metabolically active cellular mass, which may determine age-related shifts in substrate oxidation and increased cardiometabolic risk. We tested whether VAT and fasting respiratory quotient (RQ, an index of macronutrient oxidation) changed with age and if they were associated with increased risk of metabolic syndrome (MetSyn).

METHODS

A total of 2819 adult participants (age range: 18-81 years; men/women: 894/1925) were included; we collected history, anthropometric measures, biochemistry, smoking habits, and physical activity. The body mass index range was 18.5-60.2 kg/m(2). Gas exchanges (VO2 and VCO2) were measured by indirect calorimetry in fasting conditions, and RQ was calculated. Body composition was measured by bioelectrical impedance. Abdominal subcutaneous fat and VAT were measured by ultrasonography. MetSyn was diagnosed using harmonised international criteria. Multivariate linear and logistic regression models were utilised.

RESULTS

VAT increased with age in both men (r = 0.31, p < 0.001) and women (r = 0.37, p < 0.001). Basal RQ was not significantly associated with age (p = 0.49) and VAT (p = 0.20); in addition, basal RQ was not a significant predictor of MetSyn (OR 3.31, 0.57-19.08, p = 0.27). VAT was the primary predictor of MetSyn risk in a fully adjusted logistic model (OR 4.25, 3.01-5.99, p < 0.001).

CONCLUSIONS

Visceral adiposity remains one of the most important risk factors for cardiometabolic risk and is a significant predictor of MetSyn. Post-absorptive substrate oxidation does not appear to play a significant role in age-related changes in body composition and cardiometabolic risk, except for a correlation with triglyceride concentration.

The Sexual Dimorphism of Lipid Kinetics in Humans

In addition to the obvious differences in body shape, there are substantial differences in lipid metabolism between men and women. These differences include how dietary fatty acids are handled, the secretion and clearance of very low-density lipoprotein-triglycerides, the release rates of free fatty acids (FFA) from adipose tissue relative to energy needs, and the removal of FFA from the circulation, including the storage of FFA into adipose tissue via the direct uptake process. We will review what is known about these processes and how they may contribute to the sexual dimorphism of body fat distribution.

Strong influence of dietary intake and physical activity on body fatness in elderly Japanese men: age-associated loss of polygenic resistance against obesity

Genome-wide association studies identified single nucleotide polymorphisms (SNPs) associated with body mass index (BMI) in middle-aged populations; however, it is unclear whether these SNPs are associated with body fatness in elderly people. We examined the association between genetic risk score (GRS) from BMI-associated SNPs and body fatness in elderly Japanese men. We also examined the contribution of GRS, dietary macronutrient intake, and physical activity to body fatness by different age groups. GRS was calculated from 10 BMI-associated SNPs in 84 middle-aged (30-64 years) and 97 elderly (65-79 years) Japanese men; subjects were divided into low, middle, and high GRS groups. Dietary macronutrient intake was assessed using a questionnaire, and physical activity was evaluated using both a questionnaire and an accelerometer. The middle-aged individuals with a high GRS had greater BMI; waist circumference; and total abdominal fat, visceral fat, and subcutaneous fat areas than the middle-aged individuals with low GRS, whereas the indicators were not different between the GRS groups in elderly individuals. Multiple linear regression analysis showed that GRS was the strongest predictor of BMI, total abdominal fat, and visceral fat in the middle-aged group, whereas fat, alcohol, and protein intakes or vigorous-intensity physical activity were more strongly associated with these indicators than was GRS in the elderly group. These results suggest that GRS from BMI-associated SNPs is not predictive of body fatness in elderly Japanese men. The stronger contribution of dietary macronutrient intake and physical activity to body fatness may attenuate the genetic predisposition in elderly men.

Castration-induced changes in microRNA expression profiles in subcutaneous adipose tissue of male pigs

MicroRNAs (miRNAs) are class of molecular regulators found to participate in numerous biological processes, such as adipogenesis and obesity in mammals. To determine the roles of miRNAs involved in castration-induced body fatness, we investigated the different miRNA expression patterns in subcutaneous adipose tissue between intact and castrated male pigs. Our results showed that castration led to decrease serum testosterone but increase serum Leptin levels (P < 0.01). Moreover, castration also increased adipocyte size, body fat content and backfat thickness in male pigs (P < 0.01). Meanwhile, miRNA expression profiles in adipose tissue were changed by castration, and 18 miRNAs were considered as the differentially expressed candidates between intact and castrated male pigs. Furthermore, functional analysis indicated that the differential expressed miRNAs and their target genes are involved in the regulation of fatty acid metabolism. In brief, our present study provides a comprehensive view on how miRNAs works in subcutaneous adipose tissue with castration. These results suggested that miRNAs might play an important role in the castration-induced fat deposition in male pigs.

Gender differences in skeletal muscle substrate metabolism - molecular mechanisms and insulin sensitivity

It has become increasingly apparent that substrate metabolism is subject to gender-specific regulation, and the aim of this review is to outline the available evidence of molecular gender differences in glucose and lipid metabolism of skeletal muscle. Female sex has been suggested to have a favorable effect on glucose homeostasis, and the available evidence from hyperinsulinemic-euglycemic clamp studies is summarized to delineate whether there is a gender difference in whole-body insulin sensitivity and in particular insulin-stimulated glucose uptake of skeletal muscle. Whether an eventual higher insulin sensitivity of female skeletal muscle can be related to gender-specific regulation of molecular metabolism will be topic for discussion. Gender differences in muscle fiber type distribution and substrate availability to and in skeletal muscle are highly relevant for substrate metabolism in men and women. In particular, the molecular machinery for glucose and fatty acid oxidative and storage capacities in skeletal muscle and its implications for substrate utilization during metabolic situations of daily living are discussed, emphasizing their relevance for substrate choice in the fed and fasted state, and during periods of physical activity and recovery. Together, handling of carbohydrate and lipids and regulation of their utilization in skeletal muscle have implications for whole-body glucose homeostasis in men and women. 17-β estradiol is the most important female sex hormone, and the identification of estradiol receptors in skeletal muscle has opened for a role in regulation of substrate metabolism. Also, higher levels of circulating adipokines as adiponectin and leptin in women and their implications for muscle metabolism will be considered.

Impaired mitochondrial fatty acid oxidation and insulin resistance in aging: novel protective role of glutathione

Aging is associated with impaired fasted oxidation of nonesterified fatty acids (NEFA) suggesting a mitochondrial defect. Aging is also associated with deficiency of glutathione (GSH), an important mitochondrial antioxidant, and with insulin resistance. This study tested whether GSH deficiency in aging contributes to impaired mitochondrial NEFA oxidation and insulin resistance, and whether GSH restoration reverses these defects. Three studies were conducted: (i) in 82-week-old C57BL/6 mice, the effect of naturally occurring GSH deficiency and its restoration on mitochondrial (13) C1 -palmitate oxidation and glucose metabolism was compared with 22-week-old C57BL/6 mice; (ii) in 20-week C57BL/6 mice, the effect of GSH depletion on mitochondrial oxidation of (13) C1 -palmitate and glucose metabolism was studied; (iii) the effect of GSH deficiency and its restoration on fasted NEFA oxidation and insulin resistance was studied in GSH-deficient elderly humans, and compared with GSH-replete young humans. Chronic GSH deficiency in old mice and elderly humans was associated with decreased fasted mitochondrial NEFA oxidation and insulin resistance, and these defects were reversed with GSH restoration. Acute depletion of GSH in young mice resulted in lower mitochondrial NEFA oxidation, but did not alter glucose metabolism. These data suggest that GSH is a novel regulator of mitochondrial NEFA oxidation and insulin resistance in aging. Chronic GSH deficiency promotes impaired NEFA oxidation and insulin resistance, and GSH restoration reverses these defects. Supplementing diets of elderly humans with cysteine and glycine to correct GSH deficiency could provide significant metabolic benefits.

The use of honeybees reared in a thermostatic chamber for aging studies

Honeybees (Apis mellifera) are an attractive model system for studying aging. However, the aging level of worker honeybees from the field hive is in dispute. To eliminate the influence of task performance and confirm the relationship between chronological age and aging, we reared newly emerged workers in a thermostat at 34°C throughout their lives. A survivorship curve was obtained, indicating that workers can be reared away from the field hive, and the only difference between these workers is age. To confirm that these workers can be used for aging studies, we assayed age-related molecules in the trophocytes and fat cells of young and old workers. Old workers expressed more senescence-associated β-galactosidase, lipofuscin granules, lipid peroxidation, and protein oxidation than young workers. Furthermore, cellular energy metabolism molecules were also assayed. Old workers exhibited less ATP concentration, β-oxidation, and microtubule-associated protein light chain 3 (LC3) than young workers. These results demonstrate that honeybees reared in a thermostatic chamber can be used for aging studies and cellular energy metabolism in the trophocytes and fat cells of workers changes with advancing age.

DNA microarray analysis reveals differential gene expression in the soleus muscle between male and female rats exposed to a high fat diet

It is well recognized that diet-induced dysfunctions in skeletal muscle are closely related with many metabolic diseases, such as obesity and diabetes. In the present study, we identified global changes in gender-dependent gene expressions in the soleus muscle of lean and obese rats fed a high fat diet (HFD), using DNA microarray analysis. Prior to microarray analysis, the body weight gains were found to be higher in male HFD rats than the female HFD rats. To better understand the detailed phenotypic differences in response to HFD feeding, we identified differential gene expression in soleus muscle between the genders. To this end, we extracted and summarized the genes that were up- or down-regulated more than 1.5-fold between the genders in the microarray data. As expected, a greater number of genes encoding myofibrillar proteins and glycolytic proteins were expressed higher in males than females when exposed to HFD, reflecting greater muscular activity and higher capacity for utilizing glucose as an energy fuel. However, a series of genes involved in oxidative metabolism and cellular defenses were more up-regulated in females than males. These results allowed us to conclude that compared to males, females have greater fat clearing capacity in skeletal muscle through the activation of genes encoding enzymes for fat oxidation. In conclusion, our microarray data provide a better understanding of the molecular events underlying gender dimorphism in soleus muscle, and will provide valuable information in improving gender awareness in the health care system.

Aging-associated changes in physical performance and energy metabolism in the senescence-accelerated mouse

The aim of the study was to clarify the aging-associated changes in physical performance and energy metabolism in senescence-accelerated prone mouse (SAMP1). The endurance of aged SAMP1 was significantly lower by 28% than the age-matched senescence-resistant mouse (SAMR1). Oxygen consumption and fat oxidation in aged SAMP1 were lower by 19% and 22%, respectively. Peroxisome proliferator-activated receptor-γ coactivator-1β and medium-chain acyl coenzyme A dehydrogenase messenger RNA expression was significantly lower in aged SAMP1. Aged SAMP1 exhibited higher plasma glucose, insulin, leptin, and lower adiponectin concentrations. Aged SAMP1 also had higher malondialdehyde levels in plasma and tissues and lower peroxisome proliferator-activated receptor-γ messenger RNA and protein levels in adipose tissue. These results indicate that physical performance and energy expenditure decrease earlier with aging in SAMP1, accompanied by decreased fatty acid catabolism in muscle and liver and increased inflammation and oxidative stress in adipose tissue. SAMP1 could thus be a useful accelerated functional depression model for studying physical performance and energy metabolism.

Body composition changes with aging: the cause or the result of alterations in metabolic rate and macronutrient oxidation?

It has been well documented that as individuals age, body composition changes, even in the absence of changes in body weight. Studies have shown that fat mass increases and muscle mass decreases with age. However, it is unclear why such changes occur. Resting metabolic rate (RMR) and substrate oxidation rates have been examined with aging. It has been proposed that reductions in RMR and fat oxidation may lead to changes in body composition. Alternatively, changes in body composition with aging may lead to reductions in RMR. The purpose of this review is to provide an overview of the literature surrounding the impact of aging on RMR and substrate oxidation. Although long-term longitudinal studies are lacking, most cross-sectional studies or short-term longitudinal studies show a reduction in RMR with aging that cannot be explained by changes in body composition including loss in fat-free mass, where the latter includes atrophy or decreases in the mass of high metabolic rate organs. There is indirect evidence suggesting that the metabolic rate of individual organs is lower in older compared with younger individuals. With aging, we conclude that reductions in the mass of individual organs/tissues and in tissue-specific organ metabolic rate contribute to a reduction in RMR that in turn promotes changes in body composition favoring increased fat mass and reduced fat-free mass.

Effect of adipose tissue on the sexual dimorphism in metabolic flexibility

Metabolic flexibility is the ability to transition between fat oxidation (fasting state) and glucose oxidation (fed state). We hypothesized that adipose tissue inflammation and lipid metabolism contribute to sexual dimorphism in metabolic flexibility. Respiratory quotient (DeltaRQ, metabolic flexibility) and nonesterified fatty acids (NEFAs) before and during euglycemic-hyperinsulinemic clamp were measured in healthy young women (n = 22) and men (n = 56). Adiponectin levels were measured in plasma. Abdominal subcutaneous adipose tissue gene expression was measured by quantitative reverse transcriptase polymerase chain reaction. As compared with men, women had higher DeltaRQ (0.14 +/- 0.04 vs 0.09 +/- 0.04, P < .01). Fasting RQ and fat cell size were not different between sexes. As compared with men, women had lower insulin-suppressed NEFAs (P < .05); greater adiponectin levels; and higher expression of adipogenesis, fatty acid storage, and oxidation genes (PPARgamma2, PCK1, SCD1, and PPARalpha; P < .05). There were no sex differences in messenger RNA of macrophage markers or chemokines. Stepwise regression analysis revealed that the only adipose tissue characteristics that influenced metabolic flexibility in women were SCD1 and PCK1 messenger RNA (model R(2) = 0.49, P < .05); in men, these were serum adiponectin and insulin-suppressed NEFAs (model R(2) = 0.34, P < .05). Healthy young women are more metabolically flexible than men, driven by an increase in insulin-stimulated glucose oxidation rather than differences in fasting fat oxidation. Women have greater capacity for insulin suppression of NEFAs despite similar chemokine and macrophage content in adipose tissue. Combined, these results provide evidence for a role of adipose tissue characteristics in the sexual dimorphism of metabolic flexibility.

Oscillations in total body fat content through life: an evolutionary perspective

Adipose tissue is considered an efficient system in which to store energy. Throughout life, the total amount of body fat exhibits some oscillations. Typically, there are three specific periods in which there are notable increases in fat mass, specifically early in life, during pregnancy and lactation, and with ageing. The existence of the first two peaks in fat mass has been interpreted, from an evolutionary point of view, as a beneficial manoeuvre to protect against the scarcity of energy to the offspring of the species. Nevertheless, the role of increasing body fat with ageing is more dubious. However, recent evidence suggests that the gain in adiposity in senescence may also be interpreted in the same evolutionary context. The aim of this review is to focus on the age-related changes in fat depots. In addition, an evolutionary explanation to the observed changes has been emphasized.

Changes in 24-h substrate oxidation in older and younger men in response to exercise

The purpose of this study was to compare 24-h substrate oxidation in older (OM; 60-75 yr, n = 7) and younger (YM; 20-30 yr, n = 7) men studied on sedentary day (Con) and on a day with exercise (Ex; net energy expenditure = 300 kcal). Plasma glucose and free fatty acids were also measured at several time points during the 24-h measurement. Weight was not different in OM and YM (means +/- SD; 84.8 +/- 16.9 vs. 81.4 +/- 10.4 kg, respectively), although percent body fat was slightly higher in OM (25.9 +/- 3.5 vs. 21.9 +/- 9.7%; P = 0.17). Values of 24-h energy expenditure did not differ in OM and YM on the Con (means +/- SE; 2,449 +/- 162 vs. 2,484 +/- 104 kcal/day, respectively) or Ex (2,902 +/- 154 vs. 2,978 +/- 122 kcal/day) days. Under both conditions, 24-h respiratory quotient was significantly lower and fat oxidation significantly higher in OM. Glucose concentrations were not different at any time point, but plasma free fatty acid concentrations were higher in OM, particularly following meals. Thus, under these controlled conditions, 24-h fat oxidation was not reduced and was in fact greater in OM. We speculate that differences in the availability of circulating free fatty acids in the postprandial state contributed to the observed differences in 24-h fat oxidation in OM and YM.

Investigations of the effects of gender, diurnal variation, and age in human urinary metabolomic profiles

Metabolomics may have the capacity to revolutionize disease diagnosis through the identification of scores of metabolites that vary during environmental, pathogenic, or toxicological insult. NMR spectroscopy has become one of the main tools for measuring these changes since an NMR spectrum can accurately identify metabolites and their concentrations. The predominant approach in analyzing NMR data has been through the technique of spectral binning. However, identification of spectral areas in an NMR spectrum is insufficient for diagnostic evaluation, since it is unknown whether areas of interest are strictly caused by metabolic changes or are simply artifacts. In this paper, we explore differences in gender, diurnal variation, and age in a human population. We use the example of gender differences to compare traditional spectral binning techniques (NMR spectral areas) to novel targeted profiling techniques (metabolites and their concentrations). We show that targeted profiling produces robust models, generates accurate metabolite concentration data, and provides data that can be used to help understand metabolic differences in a healthy population. Metabolites relating to mitochondrial energy metabolism were found to differentiate gender and age. Dietary components and some metabolites related to circadian rhythms were found to differentiate time of day urine collection. The mechanisms by which these differences arise will be key to the discovery of new diagnostic tests and new understandings of the mechanism of disease.

Plasma triglycerides are not related to tissue lipids and insulin sensitivity in elderly following PPAR-alpha agonist treatment

Increases in plasma lipids, tissue triglycerides and decreases in mitochondrial function have been linked to insulin resistance and aging. In animals, peroxisome proliferator-activated receptor-alpha (PPAR-alpha) agonists decrease plasma lipids, intramyocellular fat (IMCL) and liver fat (LFAT) and improve mitochondrial beta-oxidative function and insulin sensitivity, but the effects in elderly were not known. Insulin sensitivity was assessed with a 2-h oral glucose tolerance test, magnetic resonance spectroscopy was used to asses IMCL, LFAT and plasma lipids were measured before and after 6, 11 and 61 days of PPAR-alpha agonist (fenofibrate) administration in 19 elderly (age 70+/-1 years) volunteers. Volunteers were stratified into healthy (N=7) and insulin resistant (N=12) groups. The baseline insulin sensitivity index (8.1+/-1.2 vs. 3.8+/-0.5, healthy vs. insulin resistant; P<0.001) was significantly higher in the healthy group. Fenofibrate treatment induced significant reductions in plasma triglycerides (P<0.001) and total cholesterol (P<0.001) in both groups. Nonetheless, neither fasted free fatty acids, glucose, insulin, nor insulin sensitivity improved in either group (day 1 vs. day 61, 8.1+/-1.2 vs. 8.1+/-0.9, healthy; and 3.8+/-0.5 vs. 4.2+/-0.05, insulin resistant). Furthermore, there was no change in IMCL or LFAT. These results indicate that whereas fenofibrate significantly lowers plasma lipids it neither affects insulin sensitivity nor intracellular lipids in elderly.

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

Changes in energy regulation occur during normal aging and contribute to the common phenomenon of weight and fat losses late in life. This review synthesizes data on aging-related changes in energy intake and energy expenditure and on the regulation of energy intake and expenditure. The ability of older adults to accurately regulate energy intake is impaired, with a number of possible explanations including delayed rate of absorption of macronutrients secondary to reductions in taste and smell acuity and numerous hormonal and metabolic mediators of energy regulation that change with aging. There are also changes in patterns of dietary intake and a reduction in the variety of foods consumed in old age that are thought to further reduce energy intake. Additionally, all components of energy expenditure decrease with aging, in particular energy expenditure for physical activity and basal metabolic rate, and the ability of energy expenditure to increase or decrease to attenuate energy imbalance during overeating or undereating also decreases. Combined, these changes result in an increased susceptibility to energy imbalance (both positive and negative) in old age that is associated with deteriorations in health. Practical interventions for prevention of weight and fat fluctuations in old age are anticipated here based on emerging knowledge of the role of such factors as dietary variety, taste, and palatability in late-life energy regulation.

Dietary Management for Older Subjects with Obesity

In recent years, obesity has been recognized as a form of malnutrition in older adults and a continuing risk factor for serious health problems. Weight reduction in older adults is not as reliable a recommendation as it is for younger adults; a decreased body mass index (BMI) seems to be associated with a higher incidence of stroke, and a normal or slightly elevated BMI has been linked to greater reserve capacity. Weight loss in older adults requires strategies that consider health status, functional ability, and rational targets. Strategies may include behavior modification, dietary alterations, exercise or physical activity, and reasonable goals that do not put the individual at nutritional risk. Studies that examine different approaches to weight reduction rarely include older subjects, so it is difficult to make judgments about various interventions (surgery, exercise, drugs, or diet) and their efficacy in this population. Fad diets may be lacking in essential nutrients and may prove to be risky for elderly people. Weight loss programs for older adults should focus on maintaining adequate intake of essential nutrients while reducing calories by controlling dietary fat intake.

Obesity in the elderly: who should we be treating, and why, and how?

PURPOSE OF REVIEW

To investigate emerging data on the relationship between obesity, increased morbidity and mortality, and decreased function in the elderly. To examine what is known about the effectiveness of interventions, and how treatment might be improved.

RECENT FINDINGS

Obesity is a common problem in the elderly, although its prevalence decreases in extreme old age. Decreased physical activity and decreased energy expenditure with ageing predispose to fat accumulation and fat redistribution. Reduction in muscle mass (sarcopenic obesity) is an important determinant of physical function and metabolic rate. Chronic inflammation and endocrine changes contribute to the changes in metabolism and body composition that accompany ageing, and are potential therapeutic targets. Body weight and body mass index are imperfect indicators of risk from obesity. The focus of treatment should be on reduction of intra-abdominal fat and preservation of muscle mass and strength. A number of recent studies have confirmed the effectiveness of exercise interventions in the elderly. Progressive resistance training, rather than endurance exercise, may be more effective in many cases. Reduced function and decreased quality of life accompany development of the complications of obesity such as diabetes and vascular disorders. There is considerable scope to impede the development of these complications in the elderly with lifestyle interventions.

SUMMARY

Sarcopenic obesity, with accumulation of intra-abdominal fat, is a major determinant of health status in the elderly. As in the younger population, prevention and treatment programmes have the potential to decrease the impact of diabetes, vascular disease, and other complications of obesity.

Is ribosomal capacity a potential metabolic marker of muscle development? Measurement by muscular biopsy

Metabolic markers of muscle metabolism could help geneticists and nutritionists predict the breast meat development of chickens. The aim of the current study was to test the ribosomal capacity (CS), a potential metabolic marker, and to evaluate a simple biopsy method on the pectoralis major muscle. Ribosomal capacity was measured in three commercial meat chicken genotypes differing in their growth rate. Fast-, medium-, and slow-growing male chickens were fed using three commercial dietary programs of increasing energy and protein concentration (nine treatments). Biopsy was performed at 4 wk of age on the p. major 12 chickens per treatment. Fast-, medium-, and slow-growing chickens were slaughtered at market weight, i.e., 6, 8, and 12 wk of age, respectively, and breast meat (right and left p. major + minor) was dissected. A significant reduction in BW at slaughter (-1 to -3%) and breast meat yield (-4%) occurred only in biopsied medium-growing chickens but not in the other two types. Slow-growing chickens had a significantly lower CS (8.75 microg/mg) than the two other chicken types (9.40 and 9.46 microg/mg for fast- and medium-growing chickens, respectively). No significant dietary effect or interaction of dietary treatment with genotype was measured. The CS was not significantly correlated to breast meat development. Under conditions of the present experiment, CS may not be a relevant marker of subsequent breast meat development at 4 wk of age. The biopsy technique can easily be applied to other markers.

Impaired substrate oxidation in healthy elderly men after eccentric exercise

The metabolic response to eccentric exercise in healthy older adults is unknown. Therefore, substrate metabolism was examined in the basal state and after sustained hyperglycemia (180 min, 10 mM) in eight healthy, sedentary older [66 +/- 2 yr; body mass index (BMI) of 25.5 +/- 1.2 kg/m] and nine younger (23 +/- 1 yr; BMI of 23.6 +/- 1.7 kg/m) men, under control conditions and 48 h after eccentric exercise. Indirect calorimetry was performed to evaluate carbohydrate and lipid oxidation (C(ox) and L(ox), respectively). Eccentric exercise caused muscle soreness and increased plasma creatine kinase in both groups of men (P < 0.02). Although a similar level of hyperglycemia was maintained in the two groups, glucose infusion rates were lower (P < 0.001) in the older men. Compared with basal levels, hyperglycemia stimulated an increase in C(ox) and a decrease in L(ox) during the control and exercise trials in the younger group (P < 0.03), but only during the control trial in the older subjects (P < 0.007). C(ox) was unchanged after eccentric exercise in the younger men [4.00 +/- 0.30 vs. 3.54 +/- 0.44 mg x kg fat-free mass (FFM)(-1) x min(-1); exercise vs. control] but was suppressed by 20% in the older group (3.37 +/- 0.37 vs. 4.21 +/- 0.23 mg x kg FFM(-1) x min(-1); P < 0.04). Moreover, L(ox) was reduced by 38% in the younger subjects (0.47 +/- 0.09 vs. 0.76 +/- 0.10 mg x kg FFM(-1) x min(-1); P< 0.03) but was augmented by 89% in the older group (0.68 +/- 0.11 vs. 0.36 +/- 0.08 mg x kg FFM(-1) x min(-1); P < 0.04). In addition, hyperglycemia-stimulated C(ox), L(ox), and respiratory exchange ratio responses to eccentric exercise were related to abdominal adiposity (r = -0.57, P < 0.04, r = 0.68, P < 0.02 and r = -0.60, P < 0.02, respectively). Despite normal glucose tolerance and the absence of obesity per se, older men experience a reduction in carbohydrate oxidation in response to hyperglycemia after eccentric exercise.

Gender differences in fat metabolism

Women generally have a higher percentage of body fat than men. Also, women store more fat in the gluteal-femoral region, whereas men store more fat in the visceral (abdominal) depot. This review focuses on differences in regional fatty acid storage, mobilization and oxidation that may contribute to gender-related differences in body fat distribution. There are pronounced regional differences in the regulation of regional fatty acid metabolism between men and women. Firstly, there is evidence that in vivo, catecholamine mediated leg free fatty acid release is lower in women than in men, whereas free fatty acid release from the upper body depots is comparable. These data correspond to in-vitro adipose tissue biopsy data, which indicate a more pronounced difference in catecholamine mediated lipolysis between upper body and lower body fat depots in women than in men. Secondly, free fatty acid release by the upper body subcutaneous fat depots is higher in men than in women, indicating a higher resistance to the antilipolytic effect of meal ingestion in the upper body fat depots in men. Thirdly, there are indications that basal fat oxidation (adjusted for fat free mass) is lower in females as compared to males, thereby contributing to a higher fat storage in women. Finally, postprandial fat storage may be higher in subcutaneous adipose tissue in women than in men, whereas storage in visceral adipose tissue has been hypothesized to be higher in men. All the above differences may play a role in the variation in net regional fat storage between men and women, but the number of in-vivo studies on gender-related differences in fatty acid metabolism is very limited and most findings require confirmation. Furthermore, there is abundant evidence that the proportion of energy derived from fat during exercise is higher in women than in men. With respect to total body fat, this finding seems counterintuitive, as percentage body fat is increased in women. Further studies are necessary to investigate the significance of differences in exercise-induced fat oxidation on 24-h fat balance.