Increase In Basal Metabolic Rate Research Articles

Evaluation of body composition, resting metabolic rate and frequency of metabolic disorders in adolescents with Klinefelter syndrome

Kleinfelter syndrome (KS) is a common genetic disease characterized by hypergonadotropic hypogonadism. The high risk of developing of metabolic disorders in patients with KS is be explained by the presence of androgen deficiency, which leads to a decrease in the amount of lean soft mass and an increase of the adipose tissue content. The basal metabolic rate (BMR) is determined by the amount of lean soft mass, and its reduction can contribute to weight gain and the progression of metabolic disorders in KS. Body composition, assessment of basal metabolism and metabolic profile in adolescents with KS. The study included 28 adolescents with KS, comparable in age and stage of sexual maturation. All patients were divided into two groups depending on the presence of clinical laboratory signs of hypogonadism. Patients passed through the evaluation of metabolic profile, bioelectrical impedance analysis for the body composition and chamber-based indirect calorimetry for the evaluation of BMR. Normal indicants of body composition were determined in 20 (71.4%) adolescents, excess of adipose mass – in 6 (21.4%) patients, and deficit of adipose mass – in 7.2% of cases. Among 6 patients with excess of adipose mass, three were obese or overweight, while the rest had normal SDS body mass index (BMI). 64.3% of adolescents showed normal indicants of energy exchange at rest, 6 (21.4%) – a decrease of BMR, 4 (14.3%) - an increase of BMR. A comparative analysis of patient groups did not reveal statistically significant differences in BMR adjusted to a lean soft mass (OO/TM) (p=0.36). Insulin resistance was detected in 11 patients (39.3%), and the incidence of dyslipidemia was 3.6%. The groups did not significantly differ in terms of glycemia levels in the fasted state and lipid profile indicants. Most adolescents with KS have normal indicants of body composition and basal metabolism, as well as a low frequency of metabolic disorders, regardless of the level of total testosterone in blood. In some patients with normal SDS BMI, excess of adipose mass is detected. The lack of correlation between the level of testosterone and the intensity of BMR may indicate a slight effect of androgen deficiency on energy exchange at rest in adolescents with KS.

Increased PIP3 activity blocks nanoparticle mRNA delivery.

The biological pathways that affect drug delivery in vivo remain poorly understood. We hypothesized that altering cell metabolism with phosphatidylinositol (3,4,5)-triphosphate (PIP3), a bioactive lipid upstream of the metabolic pathway PI3K (phosphatidylinositol 3-kinase)/AKT/ mTOR (mammalian target of rapamycin) would transiently increase protein translated by nanoparticle-delivered messenger RNA (mRNA) since these pathways increase growth and proliferation. Instead, we found that PIP3 blocked delivery of clinically-relevant lipid nanoparticles (LNPs) across multiple cell types in vitro and in vivo. PIP3-driven reductions in LNP delivery were not caused by toxicity, cell uptake, or endosomal escape. Interestingly, RNA sequencing and metabolomics analyses suggested an increase in basal metabolic rate. Higher transcriptional activity and mitochondrial expansion led us to formulate two competing hypotheses that explain the reductions in LNP-mediated mRNA delivery. First, PIP3 induced consumption of limited cellular resources, "drowning out" exogenously-delivered mRNA. Second, PIP3 triggers a catabolic response that leads to protein degradation and decreased translation.

Low basal metabolic rate as a risk factor for development of insulin resistance and type 2 diabetes

IntroductionIdentification of physiological factors influencing susceptibility to insulin resistance and type 2 diabetes (T2D) remains an important challenge for biology and medicine. Numerous studies reported energy expenditures as one of...

MON-593 Single-Dose Effects of Anti-Obesity Drugs on Human Basal Metabolic Rate

Design and rationale: Obesity results from energy intake exceeding energy expenditure (EE) over a prolonged period. Many anti-obesity drugs are designed to decrease energy intake. However, their potential impact on EE is not well documented. We designed a placebo-controlled, double-blind, randomized cross-over study to determine the acute effects of several FDA-approved anti-obesity drugs on basal metabolic rate (BMR) under well-controlled conditions. Protocol and inclusion criteria: This ongoing study is limited to healthy males of all ethnicities aged 18–35 years with a BMI of 18.5 to 25.0 kg/m2. Following an overnight stay in the Metabolic Clinical Research Unit, fasting subjects were measured from 8:00am to 12:00pm in a whole-room indirect calorimeter, which was maintained at a thermoneutral temperature (26.7±0.9°C) to prevent non-shivering thermogenesis. The six treatments include placebo, caffeine as the positive control (300 mg), phentermine (37.5 mg), topiramate (200 mg), Qsymia (phentermine 15 mg / topiramate 92 mg), and naltrexone (100 mg), with a 1-week outpatient washout period after each treatment. Drug-naïve subjects received a single dose of each drug to minimize potential metabolic adaptations that may occur with weight-loss or chronic use. The prespecified primary outcome was a ≥5% increase in BMR vs. placebo for each drug. This difference can be detected for 16 subjects with 0.83 power at α=0.05 allowing for ≤25% dropout. Secondary outcomes include respiratory quotient (RQ), heart rate (HR), mean arterial pressure (MAP), and self-reported hunger. Preliminary data: To date, 7 subjects were recruited and 6 have completed the study (26.1±4.3 years, BMI 23.1±1.4 kg/m2, body fat percentage 18.4±4.1%). Interim analysis using paired t-tests shows, compared to placebo, caffeine trended towards increasing EE (1.17±0.07 vs. 1.27±0.12 kcal/min; p=0.07) and increased MAP by 5.5±4.2% (88±2 vs. 93±4; p<0.05), but did not change heart rate (59±10 vs. 61±13 bpm). Naltrexone increased EE by 5.9±4.3% (p<0.05). No treatments altered resting RQ compared to placebo (0.83±0.05). Phentermine increased resting HR, both alone (15.7±7.9%, p<0.01) and in Qsymia (9.2±3.6%, p<0.05), compared to placebo. Of the five drug-treatments, only Qsymia reduced self-reported hunger scores compared to placebo. Summary and future directions: Anti-obesity drugs may increase energy expenditure by upregulating sympathetic nervous system activity. Combined with appetite suppression, the impact on energy balance can lead to weight loss. We aim to complete our study to determine whether these drugs can acutely increase EE with minimal cardiovascular side-effects and compare our findings with long-term interventions.

The decoupled nature of basal metabolic rate and body temperature in endotherm evolution.

The origins of endothermy in birds and mammals are important events in vertebrate evolution. Endotherms can maintain their body temperature (Tb) over a wide range of ambient temperatures primarily using the heat that isgenerated continuously by their high basal metabolic rate (BMR)1. There is also an important positive feedback loop as Tb influences BMR1-3. Owing to this interplay between BMRs and Tb, many ecologists and evolutionary physiologists posit that the evolution of BMR and Tb must have been coupled during the radiation of endotherms3-5, changing with similar trends6-8. However, colder historical environments might have imposed strong selective pressures on BMR to compensate for increased rates of heat loss and to keep Tb constant9-12. Thus, adaptation to cold ambient temperatures through increases in BMR could have decoupled BMR from Tb and caused different evolutionary routes to the modern diversity in these traits. Here we show that BMR and Tb were decoupled in approximately 90% of mammalian phylogenetic branches and 36% of avian phylogenetic branches. Mammalian BMRs evolved with rapid bursts but without a long-term directional trend, whereas Tb evolved mostly at a constant rate and towards colder bodies from a warmer-bodied common ancestor. Avian BMRs evolved predominantly at a constant rate and without a long-term directional trend, whereas Tb evolved with much greater rate heterogeneity and with adaptive evolution towards colder bodies. Furthermore, rapid shifts that lead to both increases and decreases in BMRs were linked to abrupt changes towards colder ambient temperatures-although only in mammals. Our results suggest that natural selection effectively exploited the diversity in mammalian BMRs under diverse, often-adverse historical thermal environments.

Effects of Testosterone and Resistance Training on Anabolic and Inflammatory Biomarkers Following Spinal Cord Injury

Resistance training (RT) evokes skeletal muscle hypertrophy via increasing insulin growth factors-1 (IGF-1) after spinal cord injury (SCI). Muscle hypertrophy increases basal metabolic rate (BMR) following 16 weeks of RT; increase in BMR is also linked positively to adiponectin after SCI. The effects of combining testosterone replacement therapy (TRT) and RT on circulating growth factors, adiponectin and inflammatory biomarkers are still unclear. PURPOSE: To examine the effects of TRT+RT on IGF-1, insulin growth factors binding protein-3 (IGFBP-3), adiponectin and interlukin-6 (IL-6) compared to TRT only in men with SCI. METHODS: Twenty-two men with motor complete SCI were randomized into either 16 weeks of TRT+RT (n = 11) or TRT (n = 11). After overnight fast, IGF-1, IGFBP-3, adiponectin and IL-6 were measured. Evoked progressive RT using neuromuscular electrical stimulation (2 lbs. increments) was administered twice weekly. Daily TRT patches (2-6 mg/day) were applied on both shoulders at bedtime for 16 weeks. RESULTS: IGF-1 showed a decrease (P=0.008) in both TRT+RT (n=11; B2: 169.5±96.5 to PI: 101.5±28 ng/ml) and TRT only (n=11; B2: 136±74 to PI: 99±36 ng/ml) groups. IGFBP-3 increased significantly (P=0.0001) in both TRT+RT (n=11; B2: 1764±665 to PI: 2548.5±853 ng/ml) and TRT (n=11; B2: 1918.5±587 to PI: 2778±967 ng/ml). A significant interaction was noted between TRT+RT and TRT groups in the circulating adiponectin (P=0.024). IL-6 decreased (P=0.039) in TRT+RT (n=8; B2:5.5±5.6 to PI: 2.9±5.4 pg/ml) and TRT (n=10; B2:5.9±6.0 to PI: 3.9±4.4 pg/ml) groups. CONCLUSION: Greater adipose tissue in men with SCI may have resulted in aromatization of testosterone to estradiol that has been previously shown to decrease IGF-1 and increase IGFBP-3. Increased circulating testosterone following TRT+RT may be responsible for suppressing adiponectin but not in the TRT group. Finally, administering TRT with or without RT may elicit anti-inflammatory effects after SCI.

Functional Status of Maternal Thyroid Gland in Eclampsia

Marked changes in maternal thyroid activity occur in pregnancy. During pregnancy bodily hormonal changes and metabolic demands result in complex alteration in the bio-chemical parameters of thyroid activities. Besides these, thyroid enlargement, increased thyroid capability for iodine uptake and increase in basal metabolic rate are evidential though these findings are not usually associated with symptoms of hyperthyroidism in pregnancy. Serum concentration of thyroid hormone thyroxine and triiodothyronine in complicated pregnancy like eclamptic toxemia is another field of controversy. To evaluate the changes in thyroid function in normal pregnancy and eclamptic toxemia, a study was undertaken in Rajshahi Medical College Hospital. We collected serum specimens from non pregnant but married women, normal 3rd trimester pregnant women and patients with eclampsia at 3rd trimester of pregnancy and measured serum concentrations of total and free thyroxine (TT4 &amp; FT4) and total and free triiodothyronine (TT3 &amp; FT3 ) by using RIA. Among the study subjects, 10 women were married but non pregnant, 12 women were in their 3rd trimester of normal pregnancy and 32 patients of eclamptic toxemia with 3rd trimester of pregnancy. In normal pregnancy, FT4 and FT3 levels remained normal while TT4 and TT3 levels were elevated. In patients with toxemia of pregnancy, the mean serum TT3 concentration was significantly lower than that of normal pregnancy and the serum FT3 concentrations were below the normal pregnancy range. The mean serum TT4 and FT4 concentrations in patients with eclampsia were however, significantly higher than those in normal pregnant women.&#x0D; TAJ 2018; 31(1): 9-14

Low-Dose Testosterone and Evoked Resistance Exercise after Spinal Cord Injury on Cardio-Metabolic Risk Factors: An Open-Label Randomized Clinical Trial.

The purpose of the work is to investigate the effects of low-dose testosterone replacement therapy (TRT) and evoked resistance training (RT) on body composition and metabolic variables after spinal cord injury (SCI). Twenty-two individuals with chronic motor complete SCI (ages 18-50 years) were randomly assigned to either TRT+RT (n = 11) or TRT (n = 11) for 16 weeks following a 4 -week delayed entry period. TRT+RT men underwent twice weekly progressive RT using electrical stimulation with ankle weights. TRT was administered via testosterone patches (2-6 mg/day). Body composition was tested using anthropometrics, dual energy x-ray absorptiometry, and magnetic resonance imaging. After an overnight fast, basal metabolic rate (BMR), lipid panel, serum testosterone, adiponectin, inflammatory and anabolic biomarkers (insulin-like growth factor-1 and insulin-like growth factor-binding protein 3 [IGFBP-3]), glucose effectiveness (Sg), and insulin sensitivity (Si) were measured. Total body lean mass (LM; 2.7 kg, p < 0.0001), whole muscle (p < 0.0001), and whole muscle knee extensor cross-sectional areas (CSAs; p < 0.0001) increased in the TRT+RT group, with no changes in the TRT group. Visceral adiposity decreased (p = 0.049) in the TRT group, with a trend in the TRT+RT (p = 0.07) group. There was a trend (p = 0.050) of a 14-17% increase in BMR following TRT+RT. Sg showed a trend (p = 0.07) to improvement by 28.5-31.5% following both interventions. IGFBP-3 increased (p = 0.0001) while IL-6 decreased (p = 0.039) following both interventions, and TRT+RT suppressed adiponectin (p = 0.024). TRT+RT resulted in an increase in LM and whole thigh and knee extensor muscle CSAs, with an increase in BMR and suppressed adiponectin. Low-dose TRT may mediate modest effects on visceral adipose tissue, Sg, IGFBP-3, and IL-6, independent of changes in LM.

Impact of Eccentric or Concentric Training on Body Composition and Energy Expenditure.

To compare the effects of 8-wk eccentric (ECC) versus concentric (CON) training using downhill and uphill running in rats on whole body composition, bone mineral density (BMD), and energy expenditure. Animals were randomly assigned to one of the following groups: 1) control (CTRL), 2) +15% uphill-running slope (CON), 3) -15% downhill-running slope (ECC15), and 4) -30% downhill-running slope (ECC30). Those programs enabled to achieve conditions of isopower output for CON and ECC15 and of iso-oxygen uptake (V˙O2) for CON and ECC30. Trained rats ran 45 min at 15 m·min five times per week. Total body mass, fat body mass, and lean body mass (LBM) measured through EchoMRI™, and 24-h energy expenditure including basal metabolic rate (BMR) assessed using PhenoMaster/LabMaster™ cage system were obtained before and after training. At sacrifice, the right femur was collected for bone parameters analysis. Although total body mass increased in all groups over the 8-wk period, almost no change occurred for fat body mass in exercised groups (CON, -4.8 ± 6.18 g; ECC15, 0.6 ± 3.32 g; ECC30, 2.6 ± 6.01 g). The gain in LBM was mainly seen for ECC15 (88.9 ± 6.85 g) and ECC30 (101.6 ± 11.07 g). ECC was also seen to positively affect BMD. An increase in BMR from baseline was seen in exercise groups (CON, 13.9 ± 4.13 kJ·d; ECC15, 11.6 ± 5.10 kJ·d; ECC30, 18.3 ± 4.33 kJ·d) but not in CTRL one. This difference disappeared when BMR was normalized for LBM. Results indicate that for iso-V˙O2 training, the impact on LBM and BMD is enhanced with ECC as compared with CON, and that for isopower but lower V˙O2 ECC, an important stimulus for adaptation is still observed. This provides further insights for the use of ECC in populations with cardiorespiratory exercise limitations.

Examination the Effects of Aerobic and Resistance Exercise on Body Compositions of Sedentary Male Individuals

The present study was conducted to determine the effects of 8-week aerobic and resistance training on body composition values of sedentary male individuals. A total of 30 healthy sedentary male subjects volunteered to participate in the study and were divided into two groups randomly: aerobic training group (n = 15, age = 34.0 ± 5.22 years), and resistance training group (n = 15, age = 34.2 ± 6.12). Body heights of the participants were measured and their body compositions body weight (BW), body mass index (BMI), basal metabolic rate (BMR), body fat percentage (BFP), body fat mass (BFM), lean body mass (LBM) were measured with bioelectric impedance analysis (BIA) device, and then evaluated. Their resting heart rates were determined, and maximum heart rates were calculated with the Karvonen formula. The Brzycki Equation was used to predict one-repetition maximum strength. There were statistically significant decreases in BW, BMI, BFP and BFM values of the aerobic training group (p&lt;0.05). There was no significant difference between pre- and post-test values of BMR and LBM (p&gt;0.05). BW and BMI values of the resistance training group did not show a significant difference in pre-test and post-test (p&gt;0.05). Significant decreases were found in BFP and BFM values (p&lt;0.05). The increase in BMR and LBM values were found to be statistically significant (p&lt;0.05). There were significant differences between BW, BMI, BMR, BFM and LBM values in the comparison of pre- and post-test values of the aerobic and resistance training groups (p&lt;0.05). However, there was no statistically significant difference in BFP (p&gt;0.05). In conclusion, it was found out that regular aerobic and resistance training caused positive effects on body composition of sedentary male individuals.

Screening for basal metabolic rate and visceral fat among postmenopausal osteoporosis with type 2 diabetes mellitus

BackgroundIn people with type 2 diabetes mellitus, there is an increase in basal metabolic rate (BMR) which is associated with level of glycaemic control. Women with postmenopausal osteoporosis have decreased BMR. The aim of the present study is to find the BMR using Meffin-St Jeor predictive equation in women with type 2 diabetes mellitus (T2DM) who have attained menopause with osteoporosis. Materials & methods100 women who have attained menopause, who were diagnosed to have osteoporosis with type 2 diabetes mellitus were assessed for BMR using Meffin-St Jeor predictive equation. Detailed history of diabetes and menopause were obtained. Blood glucose value was measured using standard glucometers. Body composition for visceral fat (VF) was measured using bioelectrical impedance analysis. Level of physical activity of the participants was measured using global physical activity questionnaire (GPAQ). ResultsThe median BMR of the participants was 1.075 (714, 1483.25). Statistically significant correlation was found between BMR and GPAQ (rs = 0.731), BMR and VF (rs = 0.678). However BMR was not correlated with FBS (rs = 0.083) duration of diabetes (rs = −0.046). ConclusionThere is a decrease in BMR in women with T2DM with postmenopausal osteoporosis. BMR was significantly correlated with level of physical activity and visceral fat.

Does Basal Metabolism Set the Limit for Metabolic Downregulation during Torpor?

The evolution of endothermic thermoregulation is rooted in the processes involving high metabolism, which allows the maintenance of high and stable body temperatures (Tb). In turn, selection for high endothermic metabolism correlates with increased size of metabolically active organs and thus with high basal metabolic rate (BMR). Endothermic animals are characterized by an MR several times that of similar-sized ectotherms. However, many small mammals are temporally heterothermic and are able to temporally decrease Tb and MR by entering daily torpor or hibernation. Both BMR and minimum MR during torpor (TMRmin) likely result from oxidative respiration in mitochondria of the same tissues. It should be expected that these two MRs are positively correlated, suggesting that the evolution of endothermy and higher BMR set the limit for the ability to reduce MR while entering torpor. Using published data for 96 mammal species, we tested the hypothesis that, among heterothermic mammals, the processes leading to the evolution of higher BMR limit the ability to downregulate metabolism during torpor. We found that body mass (mb)-adjusted BMR was positively correlated with mb- and Tb-adjusted TMRmin, in a phylogenetically corrected analysis. Phylogenetic path modeling indicated that the mechanisms underlying the evolutionary increase of BMR in endotherms most likely constrain their ability to reduce MR during torpor. Given that heterothermy is considered an ancestral state in mammals, these results suggest an increase in BMR during the evolution of endothermy in homeothermic animals, which leads to the loss of their ability to enter torpor.

Critical Considerations in Anticancer Drug Development and Dosing Strategies: The Past, Present, and Future.

Critical Considerations in Anticancer Drug Development and Dosing Strategies: The Past, Present, and Future.

The performing animal: causes and consequences of body remodeling and metabolic adjustments in red knots facing contrasting thermal environments.

Using red knots (Calidris canutus) as a model, we determined how changes in mass and metabolic activity of organs relate to temperature-induced variation in metabolic performance. In cold-acclimated birds, we expected large muscles and heart as well as improved oxidative capacity and lipid transport, and we predicted that this would explain variation in maximal thermogenic capacity (Msum). We also expected larger digestive and excretory organs in these same birds and predicted that this would explain most of the variation in basal metabolic rate (BMR). Knots kept at 5°C were 20% heavier and maintained 1.5 times more body fat than individuals kept in thermoneutral conditions (25°C). The birds in the cold also had a BMR up to 32% higher and a Msum 16% higher than birds at 25°C. Organs were larger in the cold, with muscles and heart being 9-20% heavier and digestive and excretory organs being 21-36% larger than at thermoneutrality. Rather than the predicted digestive and excretory organs, the cold-induced increase in BMR correlated with changes in mass of the heart, pectoralis, and carcass. Msum varied positively with the mass of the pectoralis, supracoracoideus, and heart, highlighting the importance of muscles and cardiac function in cold endurance. Cold-acclimated knots also expressed upregulated capacity for lipid transport across mitochondrial membranes [carnitine palmitoyl transferase (CPT)] in their pectoralis and leg muscles, higher lipid catabolism capacity in their pectoralis muscles [β-hydroxyacyl CoA-dehydrogenase (HOAD)], and elevated oxidative capacity in their liver and kidney (citrate synthase). These adjustments may have contributed to BMR through changes in metabolic intensity. Positive relationships among Msum, CPT, and HOAD in the heart also suggest indirect constraints on thermogenic capacity through limited cardiac capacity.

Body composition, resting energy expenditure and inflammatory markers: impact in users of depot medroxyprogesterone acetate after 12 months follow-up.

The aim of this study was to evaluate for 12 months the changes of body weight using Depot Medroxyprogesterone Acetate (DMPA) and if these changes are related to inflammatory markers. Twenty women of childbearing age who chose the DMPA, without previous use of this method, BMI < 30 kg/m2, and 17 women using IUD TCu 380A, participated in the study. At the baseline and after one year, changes in weight gain, body composition by the bioimpedance electric method, resting energy expenditure (REE) by the indirect calorimetry method, inflammatory markers and HOMA-IR were assessed. After 12 months of evaluation, we could observe a significant increase in the DMPA group in weight (3,01 kg) and BMI, while the IUD group's only significant increase was observed in the BMI. Relative to REE there was an increase of basal metabolic rate (BMR) in both groups after one year. The sub-group DMPA that gained < 3 kg had increased significant weight, BMI and body surface (BS) with respiratory quotient (RQ) reduction, while the sub-group that gained ≥ 3 kg had a significant increase in weight, BMI, BS, fat-free mass, fat mass, BMR, Leptin, HOMA-IR and waist circumference, with RQ significantly reduced. Our study found significant changes in weight, body composition and metabolic profile of the population studied in the first 12 months of contraceptive use. These changes mainly increased body weight, leptin levels and HOMA-IR which can contribute to the development of some chronic complications, including obesity, insulin resistance and diabetes mellitus.

Global patterns of seasonal acclimatization in avian resting metabolic rates

The adjustment of resting metabolic rates represents an important component of avian seasonal acclimatization, with recent studies revealing substantial differences between summer and winter in birds from a wide range of latitudes. We compared seasonal variation in basal metabolic rate (BMR) and summit metabolism (M sum) between temperate and tropical/subtropical latitudes, and examined correlations with latitude and temperature. The direction and magnitude of seasonal adjustments in BMR are broadly related to temperature and latitude, but are significantly more variable among tropical and subtropical species compared to those inhabiting temperate zones. Winter adjustments in BMR among subtropical species, when expressed relative to summer values, range from decreases of approximately 35 % to increases of more than 60 %, whereas the majority of temperate-zone species show increases in BMR during winter. Relatively few seasonal M sum data exist for tropical/subtropical species, but those that are available involve responses ranging from winter decreases to increases of similar magnitude to those characteristic of many temperate-zone species. Recent studies also highlight the substantial variation in seasonal adjustments that may occur within species, and reiterate the need for further investigations of the relative roles of environmental variables such as temperature and food availability as determinants of seasonal metabolic variation.

Metabolic activity and energy expenditure in primates

Hibernation is not a physiologic function that is normally associated with primates, but can perhaps be considered an extreme of the spectrum of metabolic activity and energy expenditure. The perspective that energy expenditure is directly proportional to physical activity may apply across the zoologic record, but has been questioned for primates [1]. Pontzer [1] stated that primates use half the energy of other mammals. Among the factors affecting energy demands, body mass/size is the major overriding determinant of thereutral resting metabolic rate [1]. This holds across mammalian phylogeny, with notable exception of marsupials, edentates, and among primates, strepsirrhines [2,3]. Hypometabolism among Strepsirrhini is greatest for Eulemur fulvus and Lemur catta (69% reduction in basal metabolic rate), Nycticebus coucang (63%), Varecia varecia (70%), Propithecus verrauxi (87%) and least for Galago elegantulus (1.5%), with Lepilemur ruficaudatus, Loris tardigradus, Otolemur crossicaudatus and garnetti and Periodictus potto intermediately reduced at 45% [4]. This contrasts with Haplorhini which is a highly variable suborder. Most approximate anticipated (for their mass) metabolic rate, with the exception of hypometabolism in Aotus triviragautus, Cebuella and Tarsius syrichta. This contrasts with increased basal metabolism in Cercopithicus mitus, Erythrocebus and Macacca fasculatus and fuscata, Saguinus geoffroyi, Papio cynocephalus and Calithix geoffroyi. It is intriguing that the 20% increase in basal metabolic rate in Calithix geoffroyi contrasts with a 30% decrease in C. jacchus decreased 30%. Similarly, basal metabolic rate was as anticipated for weight in Macacca mulatta and Papio papio, in contrast to M. fasculatus, M. fuscata, and Papio cynocephalus.

How does flexibility in body composition relate to seasonal changes in metabolic performance in a small passerine wintering at northern latitude?

Abstract Small avian species wintering at northern latitudes typically show increases in basal metabolic rate (BMR) and maximal thermogenic capacity (Msum). Those are widely assumed to reflect changes in body composition, with enlargement of digestive and excretory organs resulting in elevated winter BMR and larger body muscles driving the increase in Msum. Using free-living black-capped chickadees (Poecile atricapillus) as our model species, we investigated seasonal changes in body composition and tested for relationships between mass variations of body organs and variability of both BMR and Msum. Our results confirmed the expected winter increase in mass of body muscles and cardiopulmonary organs (heart + lungs) and showed that 64% of the observed Msum variations throughout the year were explained by changes in these organs. In contrast, we found little support for an effect of the digestive organs (gizzard + intestines) on BMR seasonal changes. Instead, this variable was mainly influenced by variations in mass of body muscles and excretory organs (liver + kidney), explaining up to 35% of its variability.

Obesity-associated variants within FTO form long-range functional connections with IRX3

Genome-wide association studies (GWAS) have reproducibly associated variants within introns of FTO with increased risk for obesity and type-2 diabetes (T2D) 1–3. While the molecular mechanisms linking these noncoding variants with obesity are not immediately obvious, subsequent studies in mice demonstrated that FTO expression levels influence body mass and composition phenotypes 4–6. Yet, no direct connection between the obesity-associated variants and FTO expression or function has been made 7–9. Here, we show that the obesity-associated noncoding sequences within FTO are functionally connected, at megabase distances, with the homeobox gene IRX3. The obesity-associated FTO region directly interacts with the promoters of IRX3 as well as FTO in the human, mouse, and zebrafish genomes. Furthermore, long-range enhancers within this region recapitulate aspects of IRX3 expression, suggesting that the obesity-associated interval belongs to the regulatory landscape of IRX3. Supporting this, obesity-associated SNPs are associated with expression of IRX3, but not FTO, in human brains. Directly linking IRX3 expression with regulation of body mass and composition, Irx3-deficient mice exhibit a 25–30% reduction in body weight, primarily through the loss of fat mass and increase in basal metabolic rate with browning of white adipose tissue. Furthermore, hypothalamic expression of a dominant negative form of Irx3 reproduces the metabolic phenotypes of Irx3-deficient mice. Our data posit that IRX3 is a functional long-range target of obesity-associated variants within FTO, and represents a novel determinant of body mass and composition.

Intra-Seasonal Flexibility in Avian Metabolic Performance Highlights the Uncoupling of Basal Metabolic Rate and Thermogenic Capacity

Stochastic winter weather events are predicted to increase in occurrence and amplitude at northern latitudes and organisms are expected to cope through phenotypic flexibility. Small avian species wintering in these environments show acclimatization where basal metabolic rate (BMR) and maximal thermogenic capacity (MSUM) are typically elevated. However, little is known on intra-seasonal variation in metabolic performance and on how population trends truly reflect individual flexibility. Here we report intra-seasonal variation in metabolic parameters measured at the population and individual levels in black-capped chickadees ( Poecile atricapillus ). Results confirmed that population patterns indeed reflect flexibility at the individual level. They showed the expected increase in BMR (6%) and MSUM (34%) in winter relative to summer but also, and most importantly, that these parameters changed differently through time. BMR began its seasonal increase in November, while MSUM had already achieved more than 20% of its inter-seasonal increase by October, and declined to its starting level by March, while MSUM remained high. Although both parameters co-vary on a yearly scale, this mismatch in the timing of variation in winter BMR and MSUM likely reflects different constraints acting on different physiological components and therefore suggests a lack of functional link between these parameters.