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

High-fat diets (HFDs) are increasingly being studied in aquaculture because of their complex species-specific effects on fish physiology. While moderate fat levels can lower feed costs, supply essential fatty acids, and promote growth in some carnivorous and fast-growing species, excessive fat intake is linked to negative outcomes, such as impaired lipid metabolism, hepatic steatosis, immune suppression, and reduced growth. Although some studies have reported improved growth in zebrafish and other tolerant species, most finfish exhibited growth inhibition, metabolic dysfunction, and greater disease susceptibility under prolonged HFD exposure. Mechanistically, HFDs disrupt lipid homeostasis by downregulating lipolytic genes (e.g., cpt1a, pparα, and atgl) and upregulating lipogenic genes (e.g., srebp-1, fas, and acc), resulting in hepatic lipid accumulation. These shifts are associated with mitochondrial dysfunction, reduced fatty acid β-oxidation, oxidative stress, and activation of ER stress pathways such as ire1/xbp1. HFDs also stimulate inflammatory pathways through tlrs, nf-κb, and cytokines (il-6, tnf-α, and il-1β), contributing to immunometabolic imbalances. Additionally, HFDs negatively affect intestinal health by altering morphology, weakening barrier function, and disrupting microbiota composition, leading to poor nutrient absorption and increased infection risk. This review provides current evidence of HFD-induced changes in growth, immunity, lipid metabolism, mitochondrial function, and gut health in finfish. This emphasizes the importance of species-specific dietary fat optimization to improve feed efficiency, safeguard fish health, and ensure sustainable aquaculture practices.

During hibernation, golden-mantled ground squirrels (Spermophilus lateralis) breathe in distinct multi-breath episodes separated by prolonged periods of apnea. We hypothesized that vagal afferent feedback from pulmonary stretch receptors, and N-methyl-D-aspartate (NMDA) type glutamate receptor-mediated processes in the pons are instrumental in the production of this breathing pattern and analyzed the effects of disrupting vagal feedback, and blockade of NMDA type receptors by the non-competitive antagonist (+)-5-methyl-10,11-dihydro-5 H-dibenzo[a, d]-cyclohepten-5,10-imine maleate (MK-801), on breathing pattern and ventilatory responses to hypoxia and hypercapnia in ground squirrels during natural hibernation. The hibernating squirrels breathed episodically and exhibited a robust ventilatory response to hypercapnia but not hypoxia. The breathing episode (not the individual breath) was the major regulated variable in the breathing pattern. Vagal blockade did not alter breathing on a breath-by-breath basis but did decrease the breaths per episode decreasing overall ventilation and abolished the hypercapnic ventilatory response. MK-801 increased the number of breaths per episode and the frequency of breathing during episodes but did not alter overall ventilation nor the hypercapnic ventilatory response. Combined treatment with MK-801 and vagal blockade abolished episodic breathing but also initiated arousal from hibernation. The data suggest that in golden-mantled ground squirrels hibernating at 5°C body temperature, vagal feedback and NMDA receptor mediated processes still modulate breathing. Whether they are responsible for clustering breaths into episodes is suggested but remains equivocal.

This study investigates the scaling exponent (b) of standard metabolic rate (SMR) in western mosquitofish, focusing on both among- and within-individual levels while exploring the influences of growth and sex on within-individual b values. For group-reared fish, the intraspecific b value was determined by analyzing the relationship between SMR and body mass across individuals of varying sizes and ages. For individually-reared fish, the SMR of each fish was measured five times between 60 and 150 days of age, and both among- and within-individual b values were calculated. The among- and within-individual b values of the individually-reared fish across ages did not differ significantly from the intraspecific b value of the group-reared fish. The among-individual b values showed a nonsignificant V-shaped change with increasing age in the individually-reared fish, suggesting that the ontogenetic decrease of b value related to growth slowdown can be reversed post-maturation. Although there was no significant difference in within-individual b values between females and males, greater variability was observed among females. Furthermore, the relationship between within-individual b values and specific growth rate displayed sexual dimorphism, with females exhibiting a stronger positive correlation, suggesting higher energy demands associated with both somatic and gonadal development compared to males.

The pineal gland synchronizes the body's circadian rhythms by producing melatonin in response to changes in the light-dark cycle. Our study evaluated how prolonged exposure to constant lighting (LL) or darkness (DD) affects pineal physiology by monitoring the transcription of genes critical for rhythmic endocrine activity. To achieve this, rats were exposed to LL, DD, or LD (control) from P21 to P90. LL and DD impacted the rats' physiology, as evidenced by the shift from a bimodal voluntary activity pattern to a free-running one. Serum melatonin and the transcription of genes encoding key enzymes involved in melatonin synthesis and adrenergic receptors changed their characteristic diurnal pattern observed in the LD group. The transcription of clock genes important for pineal rhythmicity was disturbed under both LL and DD: LL attenuated or flattened the expression of core clock genes, while DD showed a weaker effect and shifted the peak of expression. In LL, altered expression of clock genes was associated with increased transcription of regulators of mitochondrial biogenesis, and markers of mitophagy and mitochondrial dynamics, resulting in elevated ATP production. Oppositely, in DD conditions, ATP decreased. Principal Component Analysis (PCA) revealed distinct clusters comprising clock and mitochondria-related genes, indicating a close association between the circadian clock and mitochondrial function. These findings suggest that long-term exposure to LL environment poses more significant challenges to the pineal gland than DD. This might be associated with the heightened blood corticosterone levels observed in LL conditions, indicating potential chronobiological stress.

Classical mammalian hibernators, such as the golden-mantled ground squirrel, exploit cold temperatures typical of torpor (~ 4 °C) as a robust cue for an imprecisely-coordinated depression of homeostatic processes such as protein synthesis and degradation. As a result, torpid metabolic rates may be 1/100th of active rates in ground squirrels. Tenrecs have profound thermal and metabolic plasticity; active tenrecs housed at low ambient temperatures may have body temperatures and resting metabolic rates similar to torpid tenrecs or more similar to that of the basal metabolic rate of comparably sized mammals. Importantly, tenrecs may be more or less active or torpid at both high and low body temperatures. Thus, temperature is likely an inappropriate cue for the regulation of homeostatic processes. Here, we demonstrate tenrecs have low but highly variable (~ tenfold) ubiquitylated protein concentrations, maintain robust ubiquitylation rates in the cold, have depressed proteolytic activities in the cold, and do not experience a marked depression of proteolysis in the torpid state. These data suggest an inability to regulate protein degradation when torpid or when body temperatures are reduced. We suggest that in ancestral-like mammals, a suitable approach was 'Life in the Slow Lane', wherein rates of processes like protein degradation (and presumably protein synthesis) were simply slow regardless of body temperature or torpor status. Low rates of processes are congruent with observed low metabolic rates and would help mitigate homeostatic mismatches incurred by a lack of coordination that might otherwise be deleterious.

To provide knowledge on growth performance and data that are helpful for resource assessment of Homatula variegata (Dabry de Thiersant, 1874) living in northern Guizhou, China, the current study focused on the length-weight relationship (LWR), the growth pattern, the condition factor (CF), as well as the relationship between muscle metabolomics and growth in H. variegata. A total of 135 H. variegata were collected during 19 months using our patented hookless fishing tackles. The lengths (from the snout tip to the base of the caudal fin) and weights were measured, and the LWR and CF was calculated. Furthermore, the muscle tissues from fin tissues of 8 fish in winter were used for the analyses of metabolomics. The lengths and weights of 135 individuals varied by seasons, and there were opposite changes of the parameter a and the parameter b among different seasons. The parameters of LWR indicated that the growth pattern of H. variegata was the negative allometric growth. Furthermore, the CF of H. variegata was consistent with the seasonal variations of the lengths. Our results displayed that H. variegata exhibited better growth during spring and winter in northern Guizhou. Moreover, the positive correlation between triglycerides (TG) metabolites and CF found in the metabolomics analysis of muscle tissue in winter revealed the potential importance of lipid-rich food for the well-being and growth performance of H. variegata. Taken together, our findings provided basic information on the growth patterns and the relationship between metabolic characteristics and CF of H. variegata.

Understanding how organisms respond to their environments is challenging, especially due to the complex processes related to metabolism, energetics, and reproduction. Glucocorticoids (GCs) are metabolic hormones that provide insight into internal process and may trigger a variety of behaviors. To understand how changes to the environment influence wildlife, we must ideally measure levels of GCs in wildlife populations that are relatively undisturbed by anthropogenic change or natural disaster. In free-ranging mammals, cortisol is a primary GC hormone and can be measured in fur. Bats are the only mammalian order to have evolved true flight and, in North America, most species of bats are in the family Vespertilionidae. By measuring cortisol levels during energetically expensive periods of an animal's life history, we can document 'baseline levels' related to different life stages, sexes, and ages. We collected fur from hoary (Lasiurus cinereus), silver-haired (Lasionycteris noctivagans), and little-brown Myotis (Myotis lucifugus) bats from southern Alberta and Saskatchewan. Herein we report their baseline levels of fur cortisol, noting interspecific differences between species. We found that bats known to migrate longer distances had higher levels compared to bats that migrate shorter distances, and then hibernate. Interestingly, we found no differences in levels between the reproductive stages for any species. Finally, both silver-haired and hoary bats show a strong difference in fur cortisol levels between adults and juveniles. We suggest that the elevated levels are likely associated with events for mothers during lactation which are then incorporated into the pups' fur while nursing.

Chronic stress is a major cause of affective pathogenesis, such as anxiety and depression. Experimental animal models, including rodents and zebrafish, are a valuable tool for translational neuroscience research focusing on stress-related brain disorders. Here, we examined the effects of 5- and 12-week chronic unpredictable stress (CUS5 and CUS12) on zebrafish behavior, whole-body cortisol and neuroinflammation-related biomarker gene expression, including markers of pro-inflammatory microglia (NOS2a, COX2, P75NTR) and astroglia (C3, GBP), and markers of anti-inflammatory microglia (ARG-1, CD206) and astroglia (S100a10, PTX). We also assessed stress-induced changes in brain monoamine levels and brain-blood-barrier permeability. Overall, CUS5 induced anxiety-like behavior, accompanied by elevated CNS pro-inflammatory marker gene expression, cortisol signaling and norepinephrine levels. In contrast, CUS12 induced depression-like behavior, accompanied by lowered cortisol levels, impaired serotonin turnover and activated anti-inflammatory biomarker gene expression, as well as upregulated histone deacetylase 4 gene (suggesting the involvement of epigenetic regulation). Collectively, this confirms the importance of stress duration as a key factor in the development of stress-related disorders in zebrafish models, and further implicates pro- and inti-inflammatory neuroglia in affective pathogenesis.

Mammalian birth and arousal from hibernation are both endogenously regulated transitional events, characterized by an increase in metabolic rate (MR) and onset of thermogenesis. Thyroid hormones (THs) are known to be key regulators of metabolic and thermogenic activity. To explore the similarities and differences in the role of THs during mammalian birth as opposed to arousal from hibernation, a comprehensive review is given of the levels and kinetics of serum thyrotropin-releasing hormone (TRH), thyroid stimulating hormone (TSH), thyroxine (T₄), triiodothyronine (T₃), and reverse triiodothyronine (rT₃) in hibernating mammals upon arousal and in mammalian neonates at birth. The results for arousal are more heterogeneous than those for birth, reflecting different hibernation patterns between species as well as varying sampling times and methods. Overall, serum TRH concentrations were found to be decreased, TSH unchanged, and T₄, T₃, and rT₃ mostly increased. In contrast, the data for mammalian birth show a marked increase in serum levels of TRH, TSH, T₄, and T₃, particularly in human neonates, with inconsistent results for rT₃. In conclusion, both during arousal from hibernation and mammalian birth, THs play a critical yet not exclusive role in metabolic transition. In hibernators, the metabolic effects of THs appear to be mediated by the conversion rates in target tissues rather than by their serum levels alone, suggesting a sustained readiness for arousal. This contrasts with mammalian newborns, who at the beginning of their autonomous life experience the first activation of their thyroid gland, resulting in a transitory "hyperthyroid" state.

This study investigated the impacts of Camel whey protein hydrolysate (CPH) supplementation on hepatocellular damage in Nile tilapia (Oreochromis niloticus) under hypoxic stress condition. Specifically, to elucidate the fundamental impacts of chronic hypoxia stress on the expression of key genes, cyp1a, hif-a, pk, cpt-1, pdk, and hsp70 in Oreochromis niloticus. Additionally, we aim to explore the involvement of the Nrf-2-Keap-1 expression as a potential mechanism through which chronic hypoxia stress may induce hepatic tissue damage. Also, other genes that catalyze the oxidative decarboxylation of pyruvate and glucose metabolism (pdk-1, cpt-1, pk, and ldh) reflect liver stress and vitality in hypoxic and normoxic conditions in Nile tilapia. Four groups of fish, each containing 40 fish (17.40 ± 0.50 g), were included for 4 weeks. The experimental diets embraced basal and 75 g CPH/kg enriched diets. Two fish groups persisted in normoxic conditions, while the others were restrained in hypoxic conditions (DO around 1.7 mg/L). The results revealed that a fortified diet with CPH significantly reversed the hypoxia-induced reduction in the antioxidants (CAT, GSH, and SOD), liver enzymes, and lipid profile changes. However, the hypoxic states caused the downregulation of cyp1a1 but up-regulated the expression of hif-a, and hsp-70 via nrf-2-keap-1 signaling pathways. Moreover, hypoxia stress-induced histopathological alterations in the fish liver tissue were substantially reversed by CPH dietary supplementation. These results concluded that CPH is a beneficial dietary supplement for mitigating the impacts of hypoxia stress on the liver.