Plasma leptin concentrations, basal metabolic rates and respiratory quotients in young and older adults

The Impact of the Metabolic Syndrome and Its Components on Resting Energy Expenditure

We determined whether metabolic syndrome (MetS) and the increasing number of its components influenced the resting energy expenditure (REE). Data on adult men (n = 72, 40%) and women (n = 108, 60%) from European (n = 154, 86%) and Sub-Saharan African (n = 26, 14%) ancestry were used. Ninety-five (53%) participants had MetS (MetS+), while 85 (47%) were without MetS (MetS−). REE was determined through indirect calorimetry, body composition by DEXA, and clinical biochemistry by standard laboratory techniques. MetS+ had a significantly higher REE (mean ± se: MetS+: 5995 ± 87.3 vs. MetS−: 5760 ± 86.3 kJ/d, p = 0.025) when adjusted for age, gender, fat mass (FM), fat-free mass (FFM), ethnicity, season, 25OHD, insulin sensitivity, and time of data collection. Within each MetS status group, an increase in the number of components (C) resulted in a stepwise increase in REE. Relative to zero components, those with 1C had adjusted REE higher by +526 ± 248.1 kJ/d (p = 0.037), while 2C were higher than 1C by +298 ± 140.8 kJ/d (p = 0.037). Similarly, relative to 3C, those with 4C had REE higher by +242 ± 120.7 kJ/d (p = 0.049). The higher REE of 5C over 4C by 132 ± 174.5 kJ/d did not achieve statistical significance. MetS was associated with a significantly higher REE. This greater energetic cost varied directly with the numbers of its components but was most evident in those not diagnosed with the syndrome.

Higher Leptin and Adiponectin Concentrations Predict Poorer Performance-based Physical Functioning in Midlife Women: the Michigan Study of Women's Health Across the Nation

BACKGROUND

Excess fat mass is a greater contributor to functional limitations than is reduced lean mass or the presence of obesity-related conditions. The impact of fat mass on physical functioning may be due to adipokines, adipose-derived proteins that have pro- or anti-inflammatory properties.

METHODS

Serum samples from 1996 to 2003 that were assayed for leptin, adiponectin, and resistin were provided by 511 participants from the Michigan site of the Study of Women's Health Across the Nation. Physical functioning performance was assessed annually during study visits from 1996 to 2003.

RESULTS

Among this population of Black and White women (mean baseline age = 45.6 years, SD = 2.7 years), all of whom were premenopausal at baseline, higher baseline leptin concentrations predicted longer stair climb, sit-to-rise, and 2-pound lift times and shorter forward reach distance (all p < .01). This relationship persisted after adjustment for age, BMI, percent skeletal muscle mass, race/ethnicity, economic strain, bodily pain, diabetes, knee osteoarthritis, and C-reactive protein. Baseline total adiponectin concentrations did not predict any mobility measures but did predict quadriceps strength; a 1 µg/mL higher adiponectin concentration was associated with 0.64 Nm lower quadriceps strength (p = .02). Resistin was not associated with any of the physical functioning performance measures. Change in the adipokines was not associated with physical functioning.

CONCLUSION

In this population of middle-aged women, higher baseline leptin concentrations predicted poorer mobility-based functioning, whereas higher adiponectin concentrations predicted reduced quadriceps strength. These findings suggest that the relationship between the adipokines and physical functioning performance is independent of other known correlates of poor functioning.

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.

Best-fitting prediction equations for basal metabolic rate: informing obesity interventions in diverse populations

Basal metabolic rate (BMR) represents the largest component of total energy expenditure and is a major contributor to energy balance. Therefore, accurately estimating BMR is critical for developing rigorous obesity prevention and control strategies. Over the past several decades, numerous BMR formulas have been developed targeted to different population groups. A comprehensive literature search revealed 248 BMR estimation equations developed using diverse ranges of age, gender, race, fat-free mass, fat mass, height, waist-to-hip ratio, body mass index and weight. A subset of 47 studies included enough detail to allow for development of meta-regression equations. Utilizing these studies, meta-equations were developed targeted to 20 specific population groups. This review provides a comprehensive summary of available BMR equations and an estimate of their accuracy. An accompanying online BMR prediction tool (available at http://www.sdl.ise.vt.edu/tutorials.html) was developed to automatically estimate BMR based on the most appropriate equation after user-entry of individual age, race, gender and weight.

Distribution of plasma levels of adiponectin and leptin in an adult Caucasian population

OBJECTIVES

Little is known regarding the distribution and the determinants of leptin and adiponectin levels in the general population.

DESIGN

Cross-sectional study.

PATIENTS

Women (3004) and men (2552) aged 35-74 living in Lausanne, Switzerland.

MEASUREMENTS

Plasma levels of leptin and adiponectin (ELISA measurement).

RESULTS

Women had higher leptin and adiponectin levels than men. In both genders, leptin and adiponectin levels increased with age. After adjusting for fat mass, leptin levels were significantly and negatively associated with age in women: 18.1 +/- 0.3, 17.1 +/- 0.3, 16.7 +/- 0.3 and 15.5 +/- 0.4 ng/ml (adjusted mean +/- SE) for age groups [35-44], [45-54], [55-64] and [65-75], respectively, P < 0.001. A similar but nonsignificant trend was also found in men. Conversely, the age-related increase of adiponectin was unrelated to body fat in both genders. Post-menopausal women had higher leptin and adiponectin levels than premenopausal women, independently of hormone replacement therapy. Although body fat mass was associated with leptin and adiponectin, the associations were stronger with body mass index (BMI), waist and hip in both genders. Finally, after adjusting for age and anthropometry, no relationships were found between leptin or adiponectin levels with alcohol, caffeine consumption and physical activity, whereas smoking and diabetes decreased leptin and adiponectin levels in women only.

CONCLUSIONS

The age-related increase in leptin levels is attributable to changes in fat mass in women and probably also in men. Leptin and adiponectin levels are more related to BMI than to body fat mass. The effects of smoking and diabetes appear to be gender-specific.

Aging and induced senescence as factors in the pathogenesis of lung emphysema

Classically, the development of emphysema in chronic obstructive pulmonary disease is believed to involve inflammation induced by cigarette smoke and leukocyte activation, including oxidant-antioxidant and protease-antiprotease imbalances. While there is substantial evidence for this, additional aspects have been suggested by a number of clinical and experimental observations. Smokers exhibit signs of premature aging, particularly obvious in the skin. The link between aging and chronic disease is well-known, e.g., for the brain and musculoskeletal or cardiovascular system, as well as the clinical link between malnutrition and emphysema, and the experimental link to caloric restriction. Interestingly, this intervention also increases lifespan, in parallel with alterations in metabolism, oxidant burden and endocrine signaling. Of special interest is the observation that, even in the absence of an inflammatory environment, lung fibroblasts from patients with emphysema show persistent alterations, possibly based on epigenetic mechanisms. The importance of these mechanisms for cellular reprogramming and response patterns, individual risk profile and therapeutic options is becoming increasingly recognized. The same applies to cellular senescence. Recent findings from patients and experimental models open novel views into the arena of gene-environment interactions, including the role of systemic alterations, cellular stress, telomeres, CDK inhibitors such as p16, p21, pRb, PI3K, mTOR, FOXO transcription factors, histone modifications, and sirtuins. This article aims to outline this emerging picture and to stimulate the identification of challenging questions. Such insights also bear implications for the long-term course of the disease in relation to existing or future therapies and the exploration of potential lung regeneration.

The anorexia of aging in humans

Energy intake is reduced in older individuals, with several lines of evidence suggesting that both physiological impairment of food intake regulation and non-physiological mechanisms are important. Non-physiological causes of the anorexia of aging include social (e.g. poverty, isolation), psychological (e.g. depression, dementia), medical (e.g. edentulism, dysphagia), and pharmacological factors. Physiological factors include changes in taste and smell, diminished sensory-specific satiety, delayed gastric emptying, altered digestion-related hormone secretion and hormonal responsiveness, as well as food intake-related regulatory impairments for which specific mechanisms remain largely unknown. Studies in healthy elderly individuals have shown that men who consume diets over several weeks providing either too few or too many calories relative to dietary energy needs subsequently do not compensate for the resulting energy deficit or surplus when provided an ad libitum diet. Healthy elders have also been shown to be less hungry at meal initiation and to become more rapidly satiated during a standard meal compared to younger adults. Studies in animal models are required to investigate potential mechanisms underlying these observations, while human studies should focus on examining the potential consequences of this phenomenon and practical therapeutic strategies for the maintenance of appropriate energy intake with increasing age. In light of this need, we have recently demonstrated that low reported hunger assessed using a simple questionnaire predicts unintentional weight loss in a sample of healthy older women, and thus may provide a clinically useful tool for identifying older individuals at risk for undesirable weight change and therefore at high priority for intervention.

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.

The acute effects of olive oil v. cream on postprandial thermogenesis and substrate oxidation in postmenopausal women

The influence of the source of dietary fat on postprandial thermogenesis and substrate oxidation rates, was examined in twelve postmenopausal women aged 57-73 years, with BMI 21.9-38.3 kg/m(2). A single blind, randomised, paired comparison of two high-fat, isoenergetic, mixed test meals was conducted. The major source of fat was either cream (CREAM) or extra virgin olive oil (EVOO). RMR, diet-induced thermogenesis (DIT) and substrate oxidation rates over 5 h were measured by indirect calorimetry. There were no differences in body weight, RMR, fasting carbohydrate or fat oxidation rates between the two occasions. DIT (EVOO 97 (SD 46) v. CREAM 76 (SD 69) kJ/5 h and EVOO 5.2 (SD 2.5) v. CREAM 4.1 (SD 3.7)% energy) did not differ between the two test meals. The postprandial increase in carbohydrate oxidation rates, relative to their respective fasting values (DeltaCOX), was significantly lower following the EVOO meal (EVOO 10.6 (SD 8.3) v. CREAM 17.5 (SD 10) g/5 h; paired t test, P=0.023), while postprandial fat oxidation rates (DeltaFOX) were significantly higher (EVOO 0.0 (SD 4.4) v. CREAM -3.6 (sd 4.0) g/5 h; P=0.028). In the eight obese subjects, however, DIT was significantly higher following the EVOO meal (EVOO 5.1 (SD 2.0) v. CREAM 2.5 (sd 2.9) %; P=0.01). This was accompanied by a significantly lower DeltaCOX (EVOO 10.9 (SD 9.9) v. CREAM 17.3 (SD 10.5) g/5 h; P=0.03) and significantly higher DeltaFOX (EVOO 0.11 (SD 4.4) v. CREAM -4.1 (SD 4.5) g/5 h, P=0.034). The present study showed that olive oil significantly promoted postprandial fat oxidation and stimulated DIT in abdominally obese postmenopausal women.

Overweight, waist circumference, age, gender, and insulin resistance as risk factors for hyperleptinemia

OBJECTIVE

To evaluate the influence of overweight, waist circumference, age, gender, and insulin resistance as risk factors for hyperleptinemia.

RESEARCH METHODS AND PROCEDURES

A cross-sectional study was carried out in a population of 197 subjects: 59 men (21 aged < 60 years and 38 aged > or =60 years) and 138 women (37 aged < 60 years and 101 aged > or =60 years). The groups were stratified by overweight and normal weight. After a 12-hour fasting period, we measured serum leptin and insulin levels with radioimmunoassay methods. We also measured serum glucose and lipid profile. The data were analyzed by means of comparative tests. A variance-stabilizing transformation (natural logarithmic) was used to meet multiple linear regression, analysis of covariance, and logistic regression models.

RESULTS

The leptin serum levels were higher and statistically significant in young and older women than they were in men. We observed an interaction between gender and body mass index to explain the difference in leptin levels (p < 0.0001). Our study demonstrated an inverse relationship between leptin with age and high-density lipoprotein cholesterol. In logistic regression analysis, the overweight x gender interaction and waist circumference have a statistically significant influence as independent variables on hyperleptinemia (overweight x gender odds ratio = 6.81; 95% confidence interval, 1.10 to 46.86; p < 0.05 and waist circumference odds ratio = 4.34; 95% confidence interval, 1.47 to 12.83; p = 0.001).

DISCUSSION

Women who were overweight or had a higher waist circumference (women > or = 88 cm and men > or = 102 cm) have a significantly higher risk of having hyperleptinemia. The increase in age as an isolated variable is not a risk factor for hyperleptinemia.

Leptin and its role in lipid metabolism

Since the discovery of leptin in 1994, a considerable amount of research has focused on leptin as a central regulator of body weight. In the animal model, research has demonstrated leptin action through hypothalamic centres altering both satiety and energy expenditure. In contrast to animal studies, it is unlikely that leptin functioning in the human system exerts such a profound role in body weight regulation. Human studies suggest that leptin levels are strongly correlated with both percentage fat mass and body mass index, in accordance with the proposed 'lipostatic theory'. Current research suggests the existence of a unique inter-relationship between dietary fat, leptin expression and leptin action within the peripheral system. More specifically, it has been demonstrated that polyunsaturated fatty acid (PUFA) intake influences adipose tissue expression of leptin, and of several lipogenic enzymes and transcription factors. In addition, leptin stimulates triglyceride depletion in white adipose tissue without increasing free fatty acid release, thus favouring fatty acids versus glucose as a fuel source. Recent studies suggest that the reduction in adipose hypertrophy observed with n-3 PUFA-containing fish oil feeding might involve a leptin-specific process. A large amount of evidence supports direct functioning of leptin in peripheral lipid metabolism in vivo and in vitro. It is possible that PUFAs will maintain an efficient level of circulating leptin, thus preventing leptin insensitivity and weight gain. There has been much recent progress in clinical leptin research, from energy expenditure to leptin analogue efficacy; the purpose of the present review is to summarize our current understanding of leptin functioning.