Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology最新文献

Across many taxa, the complexes of the electron transport system associate with each other within the inner mitochondrial membrane to form supercomplexes (SCs). These SCs are thought to confer some selective advantage, such as increasing cellular respiratory capacity or decreasing the production of damaging reactive oxygen species (ROS). In this study, we investigate the relationship between supercomplex abundance and performance of liver mitochondria isolated from rats that do not hibernate and hibernating ground squirrels in which metabolism fluctuates substantially. We quantified the abundance of SCs (respirasomes (SCs containing CI, CIII, and CIV) or SCs containing CIII and CIV) and examined the relationship with state 3 (OXPHOS) and state 4 (LEAK) respiration rate, as well as net ROS production. We found that, in rats, state 3 and 4 respiration rate correlated negatively with respirasome abundance, but positively with CIII/CIV SC abundance. Despite the greater range of respiration rates in different hibernation stages, these relationships were similar in ground squirrels. This is, to our knowledge, the first report of differential effects of supercomplex types on mitochondrial respiration and ROS production.

Fetal metabolic programming produced by unfavorable prenatal nutritional conditions leads to the development of a disorder called "thrifty phenotype", which is associated with pathologies such as diabetes and obesity in adulthood. However, from an ecophysiological approach, few studies have addressed the development of thrifty phenotypes in terms of energy. This might represent an adaptive advantage against caloric deficiency conditions extending into adulthood. The objective of this study is to investigate the potential adaptive value of the thrifty phenotype expression through prenatal programming in a rodent model experiencing varying dietary conditions in different temporal contexts. To fill this gap, adult males of Mus musculus (BALB/C) from two maternal pregnancy groups were analyzed: control (ad libitum feeding) and caloric restriction from day 10 of gestation (70% restriction). Adult offspring of these groups were split further for two experiments: acute food deprivation and chronic caloric restriction at 60%. The acute food deprivation was performed for 24, 48 or 72 h while the caloric restriction regime was sustained for 20 days. For each experiment, morphological variables, such as body and organ mass, and gene expression related to lipid and carbohydrate metabolism from the liver and brain, were evaluated. In chronic caloric restriction, behavioral tests (open-field test and home-cage behavior) were performed. Our results indicate that under acute deprivation, the liver mass and triglyceride content remained unchanged in individuals subjected to prenatal restriction, in contrast to the reduction experienced by the control group. The latter is associated with the expression of the key genes involved in energy homeostasis (Pepck, Pparα/Pparγ), indicating a differential use of nutritional resources. In addition, thrifty animals, subjected to chronic caloric restriction, showed a severe reduction in locomotor and gluconeogenic activity, which is consistent with the regulatory role of Sirt1 and its downstream targets Mao and Pepck. Our results reveal that prenatal caloric restriction translates into a sparing metabolism in response to acute and chronic lack of food in adulthood.

Early life is a challenging phase because of the high rates of morphophysiological development and growth. Changes in ambient temperature, which directly affect energy metabolism and digestive functions in ectotherms, may be of great impact during this phase. We addressed this issue in red-footed tortoise (Chelonoidis carbonaria) hatchlings kept in captivity. To this end, we investigated the effect of temperature (28 °C and 18 °C) on mass-specific gross energy intake (GEI_m), daily body mass gain (MG), daily intake of gross energy (GEI), digestible energy (DEI), resting metabolic rate (RMR), and specific dynamic action (SDA) components during different seasons in the first 13 months after hatching. Greater GEI_m and MG were observed in spring (381.7 ± 84.9 J.g^-0.86.day^-1 and 0.9 ± 0.4 g.day^-1) and summer (356.9 ± 58.9 J.g^-0.86.day^-1 and 1.0 ± 0.4 g.day^-1). The highest and lowest RMRs at 28 °C were observed in spring (36.4 ± 5.1 kJ.kg^-1.day^-1) and winter (22.4 ± 6.2 kJ.kg^-1.day^-1), respectively. Regardless season, hatchlings showed greater GEI and DEI, O₂ consumption, CO₂ production, RMR, maximum metabolic rate after feeding (FMR_MAX), and heat increment (FMR_MAX- RMR) at 28 °C compared to 18 °C. In addition, the significant body mass influence showed allometric exponents of 0.62 at 28 °C and 0.92 at 18 °C for RMR. Our results indicate an important effect of environmental temperature on energy requirements and utilization in C. carbonaria hatchlings, which is seasonally influenced even in this early phase of life.

Melatonin is a multifunctional bioactive molecule present in almost all organisms and has been gradually used in the aquaculture industry in recent years. Energy metabolism is an essential process for individuals to maintain their life activities; however, the process through which melatonin regulates energy metabolism in aquatic animals remains unclear. The present study aimed to conduct a comprehensive analysis of the regulatory mechanism of melatonin for energy metabolism in Cherax destructor by combining metabolomics analysis with the detection of the key substance content, enzymatic activity, and gene expression levels in the energy metabolism process after culturing with dietary melatonin supplementation for 8 weeks. Our results showed that dietary melatonin increased the content of glycogen, triglycerides, and free fatty acids; decreased lactate levels; and promoted the enzymatic activity of pyruvate kinase (PK), malate dehydrogenase (MDH), and acetyl-CoA carboxylase. The results of gene expression analysis showed that dietary melatonin also increased the expression levels of hexokinase, PK, MDH, lactate dehydrogenase, lipase, and fatty acid synthase genes. The results of metabolomics analysis showed that differentially expressed metabolites were significantly enriched in lysine degradation and glycerophospholipid metabolism. In conclusion, our study demonstrates that dietary melatonin increased oxidative phosphorylation, improved glucose utilization, and promoted storage of glycogen and lipids in C. destructor. These lipids are used not only for energy storage but also to maintain the structure and function of cell membranes. Our results further add to the understanding of the mechanisms of energy regulation by melatonin in crustaceans.

The wild boar (Sus scrofa) originates from warm islands but now inhabits large areas of the world, with Antarctica as the only continent not inhabited by this species. One might be tempted to think that its wide distribution results from increasing environmental temperatures. However, any effect of temperature is only indirect: Abundant availability of critical food resources can fully compensate the negative effects of cold winters on population growth. Here, we asked if temperature as a habitat factor is unimportant compared with other habitat indices, simply because wild boars are excellent thermoregulators. We found that the thermoneutral zone in summer was approximately 6-24 °C. In winter, the thermoneutral zone was lowered to 0-7 °C. The estimated increase in the heart rate and energy expenditure in the cold was less than 30% per 10 °C temperature decline. This relatively small increase of energy expenditure during cold exposure places the wild boar in the realm of arctic animals, such as the polar bear, whereas tropical mammals raise their energy expenditure several fold. The response of wild boars to high T_a was weak across all seasons. In the heat, wild boars avoid close contact to conspecifics and particularly use wallowing in mud or other wet substrates to cool and prevent hyperthermia. Wild boars also rely on daily cycles, especially of rhythms in subcutaneous temperature that enables them to cheaply build large core-shell gradients, which serve to lower heat loss. We argue it is predominantly this ability which allowed wild boars to inhabit most climatically diverse areas in the world.

Hibernation confers resistance to ischemia-reperfusion injury in tissue, but the underlying mechanisms remain unclear. Suppression of mitochondrial respiration during torpor may contribute to this tolerance. To explore this concept, we subjected isolated liver mitochondria from torpid, interbout euthermic (IBE) and summer 13-lined ground squirrels (Ictidomys tridecemlineatus) to 5 min of anoxia, followed by reoxygenation (A/R). We also included rat liver mitochondria as a non-hibernating comparison group. Maximum respiration rates of mitochondria from torpid ground squirrels were not affected by A/R, but in IBE and summer, these rates decreased by 50% following A/R and in rats they decreased by 80%. Comparing net ROS production rates among groups, revealed seasonal differences; mitochondria from IBE and torpor produced 75% less ROS than summer ground squirrels and rats. Measurements of oxidative damage to these mitochondria, both freshly isolated, as well as pre- and post-A/R, demonstrated elevated damage to protein, but not lipids, in all groups. Hibernation likely generates oxidative stress, as freshly isolated mitochondria had greater protein damage in torpor and IBE than in summer and rats. When comparing markers of damage pre- and post-A/R, we found that when RET was active, rat macromolecules were more damaged than when RET is inhibited, but in TLGS markers of damage were similar. This result suggests that suppression of RET during hibernation, both in torpor and IBE, lessens oxidative stress produced during arousal. Taken together our study suggests that ischemia-reperfusion tolerance at the mitochondrial level is associated with metabolically suppressed oxidative phosphorylation during hibernation.

The present study aims to understand the feeding-related age-bound changes in gut histoarchitecture and its response to gut melatonin (GM) titer regulating major digestive enzymes in carp, Catla catla. Therefore, gut samples were collected from different growth stages of carp, viz. (i) fingerling (FL), body weight (BW) ≥ 3 g to ≤ 20 g; (ii) advanced fingerling (AFL), BW > 20 g to ≤ 40 g; (iii) early juvenile (EJv), BW > 40 g to ≤ 70 g; (iv) juvenile (Jv), BW > 70 g to ≤ 200 g; (v) late juvenile (LJv), BW > 200 g to ≤ 300 g; (vi) preadult (PA), BW > 300 g to ≤ 500 g; (vii) subadult (SA), BW > 500 g to ≤ 1.00 kg; and (viii) adult (AD), BW > 1 kg to ≤ 2.5 kg. Data analysis revealed that the highest titer of GM was noted in FL, moderate in AFL, Jv, and PA, lower in EJv, SA, and AD, and lowest in LJv. Results depicted a negative correlation between the development of the gut and its melatonin content. Moreover, GM was positively associated with feeding intensity and gastro-somatic index (GaSI) and negatively related to ovarian onset and development. Following correlation and principal component analysis, several pieces of evidence were recorded on the role of gut melatonin in regulating digestive physiology. Finally, it indicates that gut melatonin has a progressively influential role in improving digestion, particularly protein and microbial digestion, with the development of an adult gut from the fingerling stage.

The Orthoptera are a diverse insect order well known for their locomotive capabilities. To jump, the bush-cricket uses a muscle actuated (MA) system in which leg extension is actuated by contraction of the femoral muscles of the hind legs. In comparison, the locust uses a latch mediated spring actuated (LaMSA) system, in which leg extension is actuated by the recoil of spring-like structure in the femur. The aim of this study was to describe the jumping kinematics of Mecopoda elongata (Tettigoniidae) and compare this to existing data in Schistocerca gregaria (Acrididae), to determine differences in control of rotation during take-off between similarly sized MA and LaMSA jumpers. 269 jumps from 67 individuals of M. elongata with masses from 0.014 g to 3.01 g were recorded with a high-speed camera setup. In M. elongata, linear velocity increased with mass^0.18 and the angular velocity (pitch) decreased with mass^-0.13. In S. gregaria, linear velocity is constant and angular velocity decreases with mass^-0.24. Despite these differences in velocity scaling, the ratio of translational kinetic energy to rotational kinetic energy was similar for both species. On average, the energy distribution of M. elongata was distributed 98.8% to translational kinetic energy and 1.2% to rotational kinetic energy, whilst in S. gregaria it is 98.7% and 1.3%, respectively. This energy distribution was independent of size for both species. Despite having two different jump actuation mechanisms, the ratio of translational and rotational kinetic energy formed during take-off is fixed across these distantly related orthopterans.

Hibernation is a highly seasonal physiological adaptation that allows brown bears (Ursus arctos) to survive extended periods of low food availability. Similarly, daily or circadian rhythms conserve energy by coordinating body processes to optimally match the environmental light/dark cycle. Brown bears express circadian rhythms in vivo and their cells do in vitro throughout the year, suggesting that these rhythms may play important roles during periods of negative energy balance. Here, we use time-series analysis of RNA sequencing data and timed measurements of ATP production in adipose-derived fibroblasts from active and hibernation seasons under two temperature conditions to confirm that rhythmicity was present. Culture temperature matching that of hibernation body temperature (34 °C) resulted in a delay of daily peak ATP production in comparison with active season body temperatures (37 °C). The timing of peaks of mitochondrial gene transcription was altered as were the amplitudes of transcripts coding for enzymes of the electron transport chain. Additionally, we observed changes in mean expression and timing of key metabolic genes such as SIRT1 and AMPK which are linked to the circadian system and energy balance. The amplitudes of several circadian gene transcripts were also reduced. These results reveal a link between energy conservation and a functioning circadian system in hibernation.

Increasing water temperature because of climate change decreases the oxygen concentration while increasing the oxygen requirement of species in aquatic environments. Temperature is one of the most important environmental factors affecting the physiological functions of organisms, especially poikilothermic animals, such as shrimp at all levels. In intensive shrimp culture, it is of great importance to know the tolerable temperature range of cultured species and their metabolism since this affects the physiological condition. In this study, critical temperatures (CTM: CT_min and CT_max) of Pacific white shrimp, Litopenaeus vannamei, post-larvae (PL), were determined at different acclimation temperatures of 15, 20, 25, and 30 °C. Lower and upper incipient lethal temperatures (ILT: LILT and UILT) were also calculated for the PL. The thermal windows of the PL were developed using the CTM and ILT values. The standard metabolic rate (SMR) of the PL was determined based on the oxygen consumption rate (OCR) at the different acclimation temperatures mentioned above. The acclimation temperature had a subsequent effect on the thermal tolerance and SMR of the PL (P < 0.01). The PLs of Pacific white shrimp have high thermal tolerance and can survive at extreme temperatures (CT_min and CT_max: 8.2-43.8 °C) with their large dynamic and static thermal window areas of 1128 and 931 °C², respectively. The optimal temperature range for Pacific white shrimp PLs is the 25-30 °C range, where a decrease in SMR is determined with increasing temperature. The result of this study reveals that a range of 25-30 °C is optimal for effective PL culture of Pacific white shrimp.