Metabolic Chamber Research Articles

Evaluation of jacketed telemetry in rats for cardiorespiratory phenotyping at exercise

The challenge of cardiorespiratory function through physical exercise is highly relevant to reveal pathological phenotypes, both in humans and animals, but available monitoring tools (implanted telemetry, metabolic chamber) remain challenging to use in the context of exercise. Recently, jacketed telemetry systems for small laboratory animals have been developed, allowing non-invasive physiological monitoring in various conditions. The aim of this work was to evaluate the feasibility, using this new technology, to monitor cardiorespiratory function during treadmill exercise in rats. The effects of a moderate-intensity treadmill exercise protocol were monitored using a non-invasive telemetric jacket on a group of untrained male wistar rats (N = 9, 9–10 weeks). This incremental protocol consisted in increase the speed level of 5 cm/sec every 2 minutes (Speed: from 10 to 35 cm/sec max). Heart rate (HR), respiratory rate (RespR) and activity level (AL) were monitored with a small electronic Bluetooth device (15 g) and analyzed during a control state (Baseline), the last 30 seconds of each speed level and at post-exercise recovery. The animals were equipped with the device and placed back in their home cage. After 25 minutes of stabilization, HR was 392 ± 36 bpm, RespR was 173 ± 53 brpm, and AL was 15 ± 12 mg. All animals successfully ran on the treadmill with the jacket to the maximum speed of 35 cm/sec. Exercise induced a significant physiological increase in HR (+26%, 104 ± 21 bpm, P < 0.01) and RespR (+73%, 126 ± 22 brpm, P < 0.01). In conclusion, this novel telemetry jacket can be used to monitor cardiorespiratory parameters adaptation during a standard forced exercise protocol. Jacketed telemetry provides a completely non-invasive way to study the phenotypes of animals avoiding any additional risk on fragile pathological models and meeting the regulatory 3Rs requirements. As illustrated phenotype characterization can be enriched with a monitoring of the animal in various situations (treadmill, home cage, but also metabolic or hypoxia cage, etc.…).

Fibroblast growth factor-21 is required for weight loss induced by the glucagon-like peptide-1 receptor agonist liraglutide in male mice fed high carbohydrate diets

ObjectiveGlucagon-like peptide-1 receptor (GLP-1R) agonists (GLP-1RA) and fibroblast growth factor-21 (FGF21) confer similar metabolic benefits. GLP-1RA induce FGF21, leading us to investigate mechanisms engaged by the GLP-1RA liraglutide to increase FGF21 levels and the metabolic relevance of liraglutide-induced FGF21. MethodsCirculating FGF21 levels were measured in fasted male C57BL/6J, neuronal GLP-1R knockout, β-cell GLP-1R knockout, and liver peroxisome proliferator-activated receptor alpha knockout mice treated acutely with liraglutide. To test the metabolic relevance of liver FGF21 in response to liraglutide, chow-fed control and liver Fgf21 knockout (LivFgf21−/−) mice were treated with vehicle or liraglutide in metabolic chambers. Body weight and composition, food intake, and energy expenditure were measured. Since FGF21 reduces carbohydrate intake, we measured body weight in mice fed matched diets with low- (LC) or high-carbohydrate (HC) content and in mice fed a high-fat, high-sugar (HFHS) diet. This was done in control and LivFgf21−/− mice and in mice lacking neuronal β-klotho (Klb) expression to disrupt brain FGF21 signaling. ResultsLiraglutide increases FGF21 levels independently of decreased food intake via neuronal GLP-1R activation. Lack of liver Fgf21 expression confers resistance to liraglutide-induced weight loss due to attenuated reduction of food intake in chow-fed mice. Liraglutide-induced weight loss was impaired in LivFgf21−/− mice when fed HC and HFHS diets but not when fed a LC diet. Loss of neuronal Klb also attenuated liraglutide-induced weight loss in mice fed HC or HFHS diets. ConclusionsOur findings support a novel role for a GLP-1R-FGF21 axis in regulating body weight in a dietary carbohydrate-dependent manner.

Effects of demand-feeding and dietary protein level on nitrogen metabolism and symbiont dinitrogen gas production of common carp (Cyprinus carpio, L.).

Ammonia accumulation is a major challenge in intensive aquaculture, where fish are fed protein-rich diets in large rations, resulting in increased ammonia production when amino acids are metabolized as energy source. Ammonia is primarily excreted via the gills, which have been found to harbor nitrogen-cycle bacteria that convert ammonia into dinitrogen gas (N2) and therefore present a potential in situ detoxifying mechanism. Here, we determined the impact of feeding strategies (demand-feeding and batch-feeding) with two dietary protein levels on growth, nitrogen excretion, and nitrogen metabolism in common carp (Cyprinus carpio, L.) in a 3-week feeding experiment. Demand-fed fish exhibited significantly higher growth rates, though with lower feed efficiency. When corrected for feed intake, nitrogen excretion was not impacted by feeding strategy or dietary protein, but demand-fed fish had significantly more nitrogen unaccounted for in the nitrogen balance and less retained nitrogen. N2 production of individual fish was measured in all experimental groups, and production rates were in the same order of magnitude as the amount of nitrogen unaccounted for, thus potentially explaining the missing nitrogen in the balance. N2 production by carp was also observed when groups of fish were kept in metabolic chambers. Demand feeding furthermore caused a significant increase in hepatic glutamate dehydrogenase activities, indicating elevated ammonia production. However, branchial ammonia transporter expression levels in these animals were stable or decreased. Together, our results suggest that feeding strategy impacts fish growth and nitrogen metabolism, and that conversion of ammonia to N2 by nitrogen cycle bacteria in the gills may explain the unaccounted nitrogen in the balance.

"suMus," a novel digital system for arm movement metrics and muscle energy expenditure.

Objective: In the field of non-treatable muscular dystrophies, promising new gene and cell therapies are being developed and are entering clinical trials. Objective assessment of therapeutic effects on motor function is mandatory for economical and ethical reasons. Main shortcomings of existing measurements are discontinuous data collection in artificial settings as well as a major focus on walking, neglecting the importance of hand and arm movements for patients' independence. We aimed to create a digital tool to measure muscle function with an emphasis on upper limb motility. Methods: suMus provides a custom-made App running on smartwatches. Movement data are sent to the backend of a suMus web-based platform, from which they can be extracted as CSV data. Fifty patients with neuromuscular diseases assessed the pool of suMus activities in a first orientation phase. suMus performance was hence validated in four upper extremity exercises based on the feedback of the orientation phase. We monitored the arm metrics in a cohort of healthy volunteers using the suMus application, while completing each exercise at low frequency in a metabolic chamber. Collected movement data encompassed average acceleration, rotation rate as well as activity counts. Spearman rank tests correlated movement data with energy expenditure from the metabolic chamber. Results: Our novel application "suMus," sum of muscle activity, collects muscle movement data plus Patient-Related-Outcome-Measures, sends real-time feedback to patients and caregivers and provides, while ensuring data protection, a long-term follow-up of disease course. The application was well received from the patients during the orientation phase. In our pilot study, energy expenditure did not differ between overnight fasted and non-fasted participants. Acceleration ranged from 1.7 ± 0.7 to 3.2 ± 0.5m/sec2 with rotation rates between 0.9 ± 0.5 and 2.0 ± 3.4rad/sec. Acceleration and rotation rate as well as derived activity counts correlated with energy expenditure values measured in the metabolic chamber for one exercise (r = 0.58, p < 0.03). Conclusion: In the analysis of slow frequency movements of upper extremities, the integration of the suMus application with smartwatch sensors characterized motion parameters, thus supporting a use in clinical trial outcome measures. Alternative methodologies need to complement indirect calorimetry in validating accelerometer-derived energy expenditure data.

AAV Vector Mediated Delivery of NG2 Function Neutralizing Antibody and Neurotrophin NT-3 Improves Synaptic Transmission, Locomotion, and Urinary Tract Function after Spinal Cord Contusion Injury in Adult Rats.

NG2 is a structurally unique transmembrane chondroitin sulfate proteoglycan (CSPG). Its role in damaged spinal cord is dual. NG2 is considered one of key inhibitory factors restricting axonal growth following spinal injury. Additionally, we have recently detected its novel function as a blocker of axonal conduction. Some studies, however, indicate the importance of NG2 presence in the formation of synaptic contacts. We hypothesized that the optimal treatment would be neutralization of inhibitory functions of NG2 without its physical removal. Acute intraspinal injections of anti-NG2 monoclonal antibodies reportedly prevented an acute block of axonal conduction by exogenous NG2. For prolonged delivery of NG2 function neutralizing antibody, we have developed a novel gene therapy: adeno-associated vector (AAV) construct expressing recombinant single-chain variable fragment anti-NG2 antibody (AAV-NG2Ab). We examined effects of AAV-NG2Ab alone or in combination with neurotrophin NT-3 in adult female rats with thoracic T10 contusion injuries. A battery of behavioral tests was used to evaluate locomotor function. In vivo single-cell electrophysiology was used to evaluate synaptic transmission. Lower urinary tract function was assessed during the survival period using metabolic chambers. Terminal cystometry, with acquisition of external urethral sphincter activity and bladder pressure, was used to evaluate bladder function. Both the AAV-NG2Ab and AAV-NG2Ab combined with AAV-NT3 treatment groups demonstrated significant improvements in transmission, locomotion, and bladder function compared with the control (AAV-GFP) group. These functional improvements associated with improved remyelination and plasticity of 5-HT fibers. The best results were observed in the group that received combinational AAV-NG2Ab+AAV-NT3 treatment.SIGNIFICANCE STATEMENT We recently demonstrated beneficial, but transient, effects of neutralization of the NG2 proteoglycan using monoclonal antibodies delivered intrathecally via osmotic mini-pumps after spinal cord injury. Currently, we have developed a novel gene therapy tool for prolonged and clinically relevant delivery of a recombinant single-chain variable fragment anti-NG2 antibody: AAV-rh10 serotype expressing scFv-NG2 (AAV-NG2Ab). Here, we examined effects of AAV-NG2Ab combined with transgene delivery of Neurotrophin-3 (AAV-NT3) in adult rats with thoracic contusion injuries. The AAV-NG2Ab and AAV-NG2Ab+AAV-NT3 treatment groups demonstrated significant improvements of locomotor function and lower urinary tract function. Beneficial effects of this novel gene therapy on locomotion and bladder function associated with improved transmission to motoneurons and plasticity of axons in damaged spinal cord.

Superior cardiometabolic and cellular adaptive responses to multiple versus single daily sessions of high-intensity interval training in Wistar rats

This study aimed to compare in rats the cardiometabolic and cellular adaptative responses to 8 weeks of high-intensity interval training (HIIT) performed in a single (1xHIIT) or three shorter daily sessions (3xHIIT). Male Wistar rats were assigned to untrained (n = 10), 1xHIIT (n = 10), and 3xHIIT (n = 10) groups. Both HIIT groups performed 15 min of a treadmill run five times per week for 8 weeks. The 1xHIIT performed single daily sessions of 15 min, and the 3xHIIT performed three daily sessions of 5 min with an interval of 4 h between sessions. Resting VO2 and VO2max were measured using a metabolic chamber; blood pressure and heart rate were measured by plethysmography; body composition was estimated by DEXA; Glucose and insulin tolerance tests were performed; after euthanasia, hearts, gastrocnemius, and visceral fat were harvested for analysis of cardiac function, histology, and morphology. Mitochondrial densities of the gastrocnemius and left ventricle muscles were determined by electron microscopy. 3xHIIT induced similar positive adaptative responses to 1xHIIT on resting VO2 and VO2max, cardiac function, and mitochondria density. 3xHIIT was superior to 1xHIIT in reducing visceral fat weight and adipocyte size and improving insulin tolerance. Multiple short daily bouts of HIIT may be superior to single HIIT daily sessions in improving cardiometabolic and cellular adaptations in rats.

Middle-Aged Lpaatδ-Deficient Mice Have Altered Metabolic Measures.

Lysophosphatidic acid acyltransferases/acylglycerophosphate acyltransferases (LPAATs/AGPATs) are a group of homologous enzymes that catalyze the formation of phosphatidic acid (PA) from lysophosphatidic acid. We have previously reported that LPAATδ/AGPAT4 localizes to mitochondria, suggesting a potential role in energy metabolism. However, in prior studies of young Lpaatδ-deficient mice (age 9-12 weeks old), we found no differences in body weights, food intakes, activity levels, respiratory gas exchange, or energy expenditure compared to their wildtype (Wt) littermates. To test whether Lpaatδ-/- mice may develop differences in metabolic measures with advancing age, we recorded body weights and food intakes, and used metabolic chambers to assess ambulatory and locomotor activity levels, oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER), and total energy expenditure (heat). Fourteen-month-old Lpaatδ-/- mice had significantly lower mean body weights compared to Wt littermate controls (44.6 ± 1.08 g vs. 53.5 ± 0.42 g, respectively), but no significant differences in food intake or activity levels. This phenotypic difference was accompanied by significantly elevated 24 h daily, and 12 h light and dark photoperiod average VO2 (~20% higher) and VCO2 (~30% higher) measures, as well as higher RER and total energy expenditure (heat) values compared to Wt control littermates. Thus, an age-related metabolic phenotype is evident in Lpaatδ-/- mice. Future studies should examine the role of the lipid-modifying enzyme LPAATδ across the lifespan for greater insight into its role in normal and pathophysiology.

Maintenance Energy Requirement of Broilers and the Impact of Ambient Temperatures

Eight broiler weight groups, housed in metabolic chambers, were exposed to 3-5 ambient temperatures (AT) such that AT exposure fell below, near and above the projected thermoneutral (TN) zone. Birds were fed 0, 5, and 10% of body weight (W), or allowed to consume food ad libitum, to vary energy consumption. Energy needs for body weight homeostasis, efficiency of metabolizable energy (ME) use for maintenance and the exponent needed to convert live body weight to metabolic weight was estimated. Energy (Kcal W-1 d-1) and oxygen (l W-1 d-1) needs for body weight homeostasis declined curvilinearly as body weight increased from 0.042 kg to 2.44 kg. Such needs were impacted by AT. The efficiency of ME use to support maintenance energy need varied in a cubic fashion with bird mass. The estimated zone of thermoneutrality, at body weight homeostasis, was inversely related to W (kg), expressed as: TN (&amp;ordm;C) = 31.896 &amp;ndash; 0.4625∙W (R2 = 0.99). Under metabolic basal rate (MBR) conditions, the TN zone was curvilinearly related to weight as: TNMBR = 32.6466 &amp;minus; (94.4603∙W) &amp;minus; (0.7660∙W2) (R2 = 0.99). The exponent, to linearize live body weight with heat production (HP) of birds fed to W homeostasis, was determined to be 0.758 with all birds strictly housed at TN. Further, the exponent to linearize HP of birds under MBR (fasted) conditions was estimated to be 0.679. Equations relating chick energy and oxygen consumption need with body weight and AT, metabolizable energy for gain homeostasis (MEmg), metabolizable energy for retained energy homeostasis (MEmr), metabolizable energy for protein homeostasis (MEmp), and metabolizable energy for fat homeostasis (MEmf) are presented.

Abstracts from the NIH Office of Research on Women's Health 2022 Annual BIRCWH Meeting:Building Interdisciplinary Research Careers in Women's Health November 2, 2022

Abstracts from the NIH Office of Research on Women's Health 2022 Annual BIRCWH Meeting:Building Interdisciplinary Research Careers in Women's Health November 2, 2022

Suppression of estrogen receptor beta classical genomic activity enhances systemic and adipose-specific response to chronic beta-3 adrenergic receptor (β3AR) stimulation.

White adipose tissue (WAT) dysfunction independently predicts cardiometabolic disease, yet there is a lack of effective adipocyte-targeting therapeutics. B3AR agonists enhance adipocyte mitochondrial function and hold potential in this regard. Based on enhanced sensitivity to B3AR-mediated browning in estrogen receptor (ER)alpha-null mice, we hypothesized that ERβ may enhance the WAT response to the B3AR ligand, CL316,243 (CL). Methods: Male and female wild-type (WT) and ERβ DNA binding domain knock-out (ERβDBDKO) mice fed high-fat diet (HFD) to induce obesity were administered CL (1 mg/kg) daily for 2 weeks. Systemic physiological assessments of body composition (EchoMRI), bioenergetics (metabolic chambers), adipocyte mitochondrial respiration (oroboros) and glucose tolerance were performed, alongside perigonadal (PGAT), subcutaneous (SQAT) and brown adipose tissue (BAT) protein expression assessment (Western blot). Mechanisms were tested in vitro using primary adipocytes isolated from WT mice, and from Esr2-floxed mice in which ERβ was knocked down. Statistical analyses were performed using 2 × 2 analysis of variance (ANOVA) for main effects of genotype (G) and treatment (T), as well as GxT interactions; t-tests were used to determine differences between in vitro treatment conditions (SPSS V24). Results: There were no genotype differences in HFD-induced obesity or systemic rescue effects of CL, yet ERβDBDKO females were more sensitive to CL-induced increases in energy expenditure and WAT UCP1 induction (GxT, p < 0.05), which coincided with greater WAT B3AR protein content among the KO (G, p < 0.05). Among males, who were more insulin resistant to begin with (no genotype differences before treatment), tended to be more sensitive to CL-mediated reduction in insulin resistance. With sexes combined, basal WAT mitochondrial respiration trended toward being lower in the ERβDBDKO mice, but this was completely rescued by CL (p < 0.05). Confirming prior work, CL increased adipose tissue ERβ protein (T, p < 0.05, all), an effect that was enhanced in WAT and BAT the female KO (GxT, p < 0.01). In vitro experiments indicated that an inhibitor of ERβ genomic function (PHTPP) synergized with CL to further increase UCP1 mRNA (p = 0.043), whereas full ERβ protein was required for UCP1 expression (p = 0.042). Conclusion: Full ERβ activity appears requisite and stimulatory for UCP1 expression via a mechanism involving non-classical ERβ signaling. This novel discovery about the role of ERβ in adipocyte metabolism may have important clinical applications.

Estimation of nitrifying and heterotrophic bacterial activity in biofilm formed on RAS biofilter carriers by respirometry

Biofilm, the aggregates of microbial layers that are attached on the surface of biofilter carriers, plays a central role in the removal and conversion of nutrients in recirculating aquaculture systems (RAS). The bacterial activity in biofilm involves autotrophic and heterotrophic processes. These biological processes are crucial for the water quality in RAS but are difficult to monitor. In this study, we demonstrate a new method based on intermittent respirometry to selectively estimate bacterial activity in biofilm following a spike in substrate concentration. The method was tested with three different biofilter carriers (extruded polypropylene, injection molded polypropylene and polymeric foam) from moving bed biofilm reactors in a common freshwater RAS. Oxygen consumption rates of biofilm-associated bacteria were measured in closed metabolic chambers under standard conditions. The protocol included sequential flushes of either pure tap water, or tap water spiked with nitrite, ammonium or acetate. The results showed consistent carrier-specific metabolic activities of endogenous respiration, nitrite-oxidizing bacteria (NOB), ammonia-oxidizing bacteria (AOB) and heterotrophic bacteria (HB) in biofilm. The highest activities normalized to volumetric oxygen consumption rates, were found in polymeric foam with values of 677 ± 125, 764 ± 156 and 166 ± 36 g O2·m−3·d−1 for NOB, AOB and HB, respectively. The biofilter performance evaluation based on respirometric data showed satisfactory accordance with the values from substrate degradation batch kinetic tests for all three tested carriers, confirming the feasibility and robustness of the method as a means to assessing biofilter performance. Our study provides an on-site tool in biofilter performance tests and leads to a better understanding of dynamic and relationship between biofiltration and water quality.

Step-count outcomes of 13 different activity trackers: Results from laboratory and free-living experiments

BackgroundMany activity trackers have been developed, but steps can still be inconsistent from one monitor to another. Research questionWhat are the differences and associations between the steps of 13 selected consumer-based and research-grade wearable devices during 1 standardized day in a metabolic chamber and 15-day free-living trials? MethodsIn total, 19 healthy adults between 21 and 50 years-old participated in this study. Participants were equipped with 12 accelerometer-based active trackers and one pedometer (Yamasa) in order to monitor the number of steps per day. The devices were worn on the waist (ActiGraph, Omron, Actimarker, Lifedorder, Withings, and Yamasa) or non-dominant wrist (Fitbit, Garmin, Misfit, EPSON, and Jawbone), or placed in a pocket (Omron CaloriScan, and TANITA). Participants performed structured activities over a 24 h period in a chamber (Standardized day), and steps were monitored in the same participants in free-living trials for 15 successive days using the same monitors (free-living days). ResultsWhen the 13 monitors were ranked by their steps, waist-worn ActiGraph was located at the center (7th) of the monitors both in the Standardized (12,252 ± 598 steps/day, mean ± SD) and free-living days (9295 ± 4027 steps/day). The correlation between the accelerometer-based devices was very high (r = 0.87–0.99). However, the steps of Yamasa was significantly lower in both trials than ActiGraph. The wrist-worn accelerometers had significantly higher steps than other devices both trials (P < 0.05). The differences between ActiGraph and Actimarker or Lifecorder was less than 100 steps/day in the Standardized day, and the differences between ActiGraph and Active Style Pro was less than 100 steps/day in the free-living days. Regression equation was also performed for inter-device compatibility. SignificanceStep obtained from the wrist-worn, waist-worn, and pocket-type activity trackers were significantly different from each other but still highly correlated in free-living conditions.

Peculiarities of suction, extraction and assignment of calcium in experimental chronic hepatitis in rats

The aim. Study the degree of absorption, assimilation, and excretion of calcium in rats with chronic toxic hepatitis.&#x0D; Materials and methods. The studies were carried out on 1 month old Wistar rats. Toxic hepatitis in the experimental group was reproduced by intraperitoneal injection of hydrazine sulfate at a dose of 50 mg / kg twice a week. Studies of the absorption of substances in rats were carried out under thiopental anesthesia according to the Tyri method after 3 months of pathology modelling. In the intestinal contents, the amount of unabsorbed calcium and amino acids was determined. To determine the amount of assimilated and excreted calcium metabolic chambers were used for daily collection of urine, faeces and food residues, in which the calcium content was determined (average for three days per animal). After removing the rats from the experiment, the level of calcium in the blood serum was determined, in the bone tissue – the degree of its resorption by the activity of acid phosphatase and the content of calcium.&#x0D; Results and discussion. Toxic hepatitis reduced calcium absorption by 34.5 % in the small intestine of rats and did not have a significant effect on amino acids, the inhibition of absorption of which in hepatitis was only 5.5 %. The excretion of calcium in the urine of rats with toxic hepatitis was reduced by 1.8 times, and with faeces, on the contrary, increased by 1.5 times. As a result, calcium absorption in rats with hepatitis decreased by 24.2 %. Decreased absorption of calcium, and its increased excretion in the faeces, led to a decrease in the level of this element in the blood of animals with hepatitis by 14.7 %. Our studies found bone destruction in rats with hepatitis: an increase in bone acid phosphatase activity by 65.3 % and a decrease in calcium levels by 15.5 %.&#x0D; Conclusion. The triggering mechanism for the development of hepatic osteodystrophy is the inhibition of calcium absorption in the small intestine of rats with hepatitis, consequently - a decrease in its absorption and level in the blood, which ultimately leads to the activation of bone resorption. The established patterns will form the basis of the pathogenetic scheme for the prevention of hepatic osteodystrophy

Effects of Time-Restricted Feeding on Energy Balance: A Cross-Over Trial in Healthy Subjects.

Time-restricted feeding (TRF) has been recently reported as an effective dietary intervention for losing body weight, implying a negative energy balance, without restricting nutrient intake. However, the detailed energy balance alteration caused by TRF remains unclear. This study was a randomized controlled clinical trial using a within-subject cross-over design. Twelve healthy, normal-weighted volunteers (age: 24 ± 2.3 years; BMI: 21.9 ± 1.71 kg/m2; 7 females) were studied under a rigorous control for calorie intakes, physical activities as well as sleep-wake cycle to evaluate the energy balance systematically. Each participant consumed an isocaloric diet within either a 5.5-hour TRF or 11-hour control schedule. All energy intake and excretion were traced and collected and accessed by bomb calorimetry. Energy expenditure and substrates oxidation were monitored in a metabolic chamber. TRF compared with control schedule is associated with a 22.7% increase in fecal energy loss (Δ = 32.25 ± 9.33 Kcal, p = 0.005) and a trend in increasing 14.5% urine energy loss (Δ = 6.67 ± 3.14 Kcal, p = 0.058) without change energy expenditure. In total, a negative energy balance (Δ = -45.95 ± 19.00 Kcal, p = 0.034), which was equal to -2.6% of total energy intake, has been observed during TRF interventions. In the meantime, glycemic profiles, heart rate, respiration rate as well as metabolic flexibility were also improved during TRF intervention. Taken together, our findings unravel the mystery of how TRF regulates energy balance, supporting the use of TRF as an alternative dietary strategy for weight loss.

Abstract P208: The Impact Of Circadian Misalignment On Energy Metabolism And Substrate Oxidation In Adults With Adequate Sleep

Background: Circadian misalignment (CM), the mismatch between timing of behaviors and internal body clock, increases cardiometabolic risk, but the mechanisms are not fully understood. Population studies in night shift workers and intervention studies attempting to replicate CM have often been confounded by differences in energy intake, sleep duration and timing, and eating window duration. We aimed to investigate the effects of CM, induced by delaying mealtimes relative to wake time, independent of sleep timing and duration as well as duration of eating window, on energy expenditure (EE) and substrate oxidation. We hypothesized that CM would reduce EE and increase respiratory quotient (RQ) relative to meals closer to wake time (circadian alignment [CA]). Methods: We used a 2-phase, randomized, crossover study. Men and women (age 20-49 y) were studied under controlled feeding conditions (CA and CM). Each phase included a 10-h eating window at 0900-1900 h (CA) or 1300-2300 h (CM) with fixed mealtimes. Bedtimes were set at 2400-0800 h. Minute-by-minute EE, RQ, and substrate oxidation were obtained over 23 h in a metabolic chamber on d 3-4 and 14-15. Post-meal EE, RQ, and substrate oxidation were calculated as the average of 2-h, 1-h, and 30 min data collections following breakfast, dinner, and snack, respectively. Data were analyzed using a linear mixed effects model including condition, day, and day-by-condition interaction as main predictor variables, and phase as an adjusting covariate. As an exploratory aim, sex-by-condition interaction was also included in the model. Results: Three men and 4 women completed both study phases (age 37.6±8.8 y, BMI 30.8±3.2 kg/m 2 ). EE did not differ between CM and CA. Post-meal RQ for breakfast (p=0.06), dinner (p&lt;0.001), and snack (p&lt;0.001) were higher in CM vs CA. Glucose oxidation after dinner (p&lt;0.001) and snack (p&lt;0.01) were higher in CM vs CA. There were sex-by-condition interactions on EE and glucose oxidation after breakfast (both p=0.06) and dinner (p&lt;0.05), and on EE after snack (p&lt;0.01). In general, CA resulted in greater rise in EE and lesser reduction in glucose oxidation following meals in men compared to women. Conclusion: Delaying mealtimes by 4 h, independent of sleep duration, timing, or diet composition, shifts nutrient metabolism towards greater carbohydrate and lower fat oxidation. Sex may influence the effect of CM on energy metabolism and should be considered in investigations of cardiometabolic risk associated with shift work and late-night eating.

The influence of bright and dim light on substrate metabolism, energy expenditure and thermoregulation in insulin-resistant individuals depends on time of day

Aims/hypothesisIn our modern society, artificial light is available around the clock and most people expose themselves to electrical light and light-emissive screens during the dark period of the natural light/dark cycle. Such suboptimal lighting conditions have been associated with adverse metabolic effects, and redesigning indoor lighting conditions to mimic the natural light/dark cycle more closely holds promise to improve metabolic health. Our objective was to compare metabolic responses to lighting conditions that resemble the natural light/dark cycle in contrast to suboptimal lighting in individuals at risk of developing metabolic diseases.MethodsTherefore, we here performed a non-blinded, randomised, controlled, crossover trial in which overweight insulin-resistant volunteers (n = 14) were exposed to two 40 h laboratory sessions with different 24 h lighting protocols while staying in a metabolic chamber under real-life conditions. In the Bright day–Dim evening condition, volunteers were exposed to electric bright light (~1250 lx) during the daytime (08:00–18:00 h) and to dim light (~5 lx) during the evening (18:00–23:00 h). Vice versa, in the Dim day–Bright evening condition, volunteers were exposed to dim light during the daytime and bright light during the evening. Randomisation and allocation to light conditions were carried out by sequential numbering. During both lighting protocols, we performed 24 h indirect calorimetry, and continuous core body and skin temperature measurements, and took frequent blood samples. The primary outcome was plasma glucose focusing on the pre- and postprandial periods of the intervention.ResultsSpending the day in bright light resulted in a greater increase in postprandial triacylglycerol levels following breakfast, but lower glucose levels preceding the dinner meal at 18:00 h, compared with dim light (5.0 ± 0.2 vs 5.2 ± 0.2 mmol/l, n = 13, p=0.02). Dim day–Bright evening reduced the increase in postprandial glucose after dinner compared with Bright day–Dim evening (incremental AUC: 307 ± 55 vs 394 ± 66 mmol/l × min, n = 13, p=0.009). After the Bright day–Dim evening condition the sleeping metabolic rate was identical compared with the baseline night, whereas it dropped after Dim day–Bright evening. Melatonin secretion in the evening was strongly suppressed for Dim day–Bright evening but not for Bright day–Dim evening. Distal skin temperature for Bright day–Dim evening was lower at 18:00 h (28.8 ± 0.3°C vs 29.9 ± 0.4°C, n = 13, p=0.039) and higher at 23:00 h compared with Dim day–Bright evening (30.1 ± 0.3°C vs 28.8 ± 0.3°C, n = 13, p=0.006). Fasting and postprandial plasma insulin levels and the respiratory exchange ratio were not different between the two lighting protocols at any time.Conclusions/interpretationTogether, these findings suggest that the indoor light environment modulates postprandial substrate handling, energy expenditure and thermoregulation of insulin-resistant volunteers in a time-of-day-dependent manner.Trial registrationClinicalTrials.gov NCT03829982.FundingWe acknowledge the financial support from the Netherlands Cardiovascular Research Initiative: an initiative with support from the Dutch Heart Foundation (CVON2014–02 ENERGISE).Graphical abstract

Anatabine, Nornicotine, and Anabasine Reduce Weight Gain and Body Fat through Decreases in Food Intake and Increases in Physical Activity.

Obesity is a leading cause of preventable death in the United States. Currently approved pharmacotherapies for the treatment of obesity are associated with rebound weight gain, negative side effects, and the potential for abuse. There is a need for new treatments with fewer side effects. Minor tobacco alkaloids (MTAs) are potential candidates for novel obesity pharmacotherapies. These alkaloids are structurally related to nicotine, which can help reduce body weight, but without the same addictive potential. The purpose of the current study was to examine the effects of three MTAs (nornicotine, anatabine, and anabasine) and nicotine on weight gain, body composition, chow intake, and physical activity. We hypothesized that the MTAs and nicotine would reduce weight gain through reductions in chow intake and increases in physical activity. To test this, male Sprague Dawley rats were housed in metabolic phenotyping chambers. Following acclimation to these chambers and to (subcutaneous (sc)) injections of saline, animals received daily injections (sc) of nornicotine, anabasine, anatabine, or nicotine for one week. Compared to saline-injected animals that gained body weight and body fat during the treatment phase, injections of nornicotine and anatabine prevented additional weight gain, alongside reductions in body fat. Rats receiving anabasine and nicotine gained body weight at a slower rate relative to rats receiving saline injections, and body fat remained unchanged. All compounds reduced the intake of chow pellets. Nornicotine and nicotine produced consistent increases in physical activity 6 h post-injection, whereas anabasine’s and anatabine’s effects on physical activity were more transient. These results show that short-term, daily administration of nornicotine, anabasine, and anatabine has positive effects on weight loss, through reductions in body fat and food intake and increases in physical activity. Together, these findings suggest that MTAs are worthy of further investigations as anti-obesity pharmacotherapies.

Chronic bladder catheterization, but not the metabolic chambers, is suitable for collection of precise data on murine diuresis

Chronic bladder catheterization, but not the metabolic chambers, is suitable for collection of precise data on murine diuresis

Metabolic rate and substrate oxidation of young males with obesity at the different sleep stages

ObjectiveInsufficient and poor-quality sleep among young adults is closely related to obesity and may impact metabolic processes. The mobilization and use of endogenous substrates during sleep, especially fat oxidation, is essential for energy metabolism. This study investigated whether there are differences in sleep structure, metabolic rate, substrate oxidation, and the respiratory quotient (RQ) between young males with normal weight and obesity according to sleep stages and overnight sleep. MethodsFifteen young males with normal weight and fifteen with obesity posited electrodes of polysomnography (PSG) and slept in the metabolic chamber for estimation of sleep structure, sleep metabolic rate (SMR), carbohydrate oxidation (CHOO), fat oxidation (FATO), and RQ. Fat-free mass (FFM) was measured by bioelectrical impedance analysis. ResultsThe sleep period time (p = 0.038) and total sleep time (p = 0.032) were significantly shorter in the obesity group than in the normal-weight group. The obesity group also had a longer sleep latency (p = 0.034) and more sleep-turning events (p = 0.018). CHOO/FFM and the RQ were higher in the obesity group while FATO/FFM was significantly higher in the normal-weight group. FATO/FFM was also higher in the normal-weight group in each sleep stage whereas the RQ was higher in the obesity group (p < 0.05). ConclusionsYoung males with obesity showed lower fat oxidation and more dominant carbohydrate-derived fuel oxidation than normal-weight during sleep and experienced shorter sleep periods and total sleep time.

Effects of nocturnal light exposure on circadian rhythm and energy metabolism in healthy adults: A randomized crossover trial

ABSTRACT Exposure to continuous light at night, including night-shift work or a nocturnal lifestyle, is emerging as a novel deleterious factor for weight gain and obesity. Here, we examined whether a single bout of bright light (BL) exposure at night affects energy metabolism via changes in circadian rhythm and nocturnal melatonin production. Ten healthy young men were randomized to a two-way crossover experimental design protocol: control (< 50 lux) and BL (approximately 10000 lux) conditions, with at least seven days of interval. The participants were exposed to each condition for 3 h (21:00–24:00) before sleep (0 lux, 00:00–07:00) in a room-type metabolic chamber. On each experimental night (21:00–07:00), energy expenditure, respiratory quotient (RQ), and substrate oxidation were measured to determine the energy metabolism. BL exposure prior to bedtime altered biological rhythms, disrupted the nocturnal decline in body temperature, and suppressed the melatonin level before sleeping, resulting in an increase in sleep latency. Indirect calorimetry data revealed that BL exposure significantly decreased the fat oxidation and increased the RQ, an indicator of the carbohydrate-to-fat oxidation ratio, throughout the whole period (light exposure and sleep). We revealed that acute BL exposure prior to bedtime exacerbated circadian rhythms and substrate oxidations, suggesting that chronic BL exposure at night may lead to obesity risk due to disturbances in circadian rhythms and macronutrient metabolism.