Seasonal oscillation of liver-derived hibernation protein complex in the central nervous system of non-hibernating mammals

c-fos induction in the choroid plexus, tanycytes and pars tuberalis is an early indicator of spontaneous arousal from torpor in a deep hibernator

Hibernation is an extreme state of seasonal energy conservation, reducing metabolic rate to as little as 1% of the active state. During the hibernation season, many species of hibernating mammals cycle repeatedly between the active (aroused) and hibernating (torpid) states (T-A cycling), using brown adipose tissue (BAT) to drive cyclical rewarming. The regulatory mechanisms controlling this process remain undefined but are presumed to involve thermoregulatory centres in the hypothalamus. Here, we used the golden hamster (Mesocricetus auratus), and high-resolution monitoring of BAT, core body temperature and ventilation rate, to sample at precisely defined phases of the T-A cycle. Using c-fos as a marker of cellular activity, we show that although the dorsomedial hypothalamus is active during torpor entry, neither it nor the pre-optic area shows any significant changes during the earliest stages of spontaneous arousal. Contrastingly, in three non-neuronal sites previously linked to control of metabolic physiology over seasonal and daily time scales - the choroid plexus, pars tuberalis and third ventricle tanycytes - peak c-fos expression is seen at arousal initiation. We suggest that through their sensitivity to factors in the blood or cerebrospinal fluid, these sites may mediate metabolic feedback-based initiation of the spontaneous arousal process.

Proteomic analysis of pikeperch seminal plasma provides novel insight into the testicular development of domesticated fish stocks

Control of the reproduction of domesticated stocks is considered a prerequisite for aquaculture development of pikeperch. However, knowledge about the physiology of the captive pikeperch male reproductive system and the biology of semen is very limited, especially regarding protein characteristics. The aims of our study were to characterize pikeperch sperm quantity and quality parameters and to analyze changes in the proteome of the same males spawned for the first and second times. Moreover, attempts were made to generate the first proteomic library of seminal plasma proteins. Semen collected during the first spawning season was characterized by lower sperm concentration and volume than for the second season. Using mass spectrometry-based label-free quantitative proteomics, we identified 850 proteins in the seminal plasma of pikeperch from both spawning seasons, and 65 seminal proteins were found to be differentially abundant between the first and second spawning seasons. The majority of differentially abundant proteins were involved in stress and immune responses, developmental processes, cofactor metabolic processes, proteolysis, cellular oxidant detoxification and organization of the extracellular matrix (ECM). In addition, several proteins unique to pikeperch seminal plasma were identified, including antifreeze proteins, hibernation-specific plasma proteins, lectins and vitellogenin. In summary, our results indicate that males that spawned for the first time were characterized by incompletely mature gonads and the expression of proteins associated with the early phase of spermatogenesis and ECM organization. On the other hand, males that spawned for the second time exhibited advanced gonadal maturation and expression of proteins related to the late stage of spermatogenesis and sperm maturation, including regulation of reactive oxygen species generation, bicarbonate production, sperm elongation and separation. The identification of a large number of seminal plasma proteins provides a valuable resource for understanding the functions of seminal plasma and the molecular mechanisms involved in testicular development and maturation in domesticated fish, which is a prerequisite for better control of reproduction in captivity.

Epigenetic regulation of hibernation-associated HP-20 and HP-27 gene transcription in chipmunk liver

The chipmunk hibernation-related proteins (HPs) HP-20 and HP-27 are components of a 140-kDa complex that dramatically decreases in the blood during hibernation. The HP-20 and HP-27 genes are expressed specifically in the liver and are downregulated in hibernating chipmunks. Hibernation-associated physiological changes are assumed to be under genetic control. Therefore, to elucidate the molecular mechanisms of hibernation, here we examined the mechanisms behind the altered HP-20 and HP-27 gene expression in nonhibernating versus hibernating chipmunks. Chromatin immunoprecipitation (ChIP) analyses revealed that histone H3 on the HP-20 and HP-27 gene promoters was highly acetylated at lysine (K) 9 and K14 and highly trimethylated at K4 in the liver of nonhibernating chipmunks, while these active histone modifications were nearly absent in hibernating chipmunks. Furthermore, histone acetyltransferases and a histone methyltransferase were associated with the HP-20 and HP-27 gene promoters primarily in nonhibernating chipmunks. Consistent with a previous finding that HNF-1 and USF can activate HP-20 and HP-27 gene transcription by binding to the proximal promoter region, ChIP-quantitative PCR (qPCR) analyses revealed that significantly less HNF-1 and USF were bound to these gene promoters in hibernating than in nonhibernating chipmunks. These findings collectively indicated that the hibernation-associated HP-20 and HP-27 gene expression is epigenetically regulated at the transcriptional level by the binding of HNF-1 and USF to their proximal promoters, and that histone modification has a key role in hibernation-associated transcriptional regulation.

HNF-4 participates in the hibernation-associated transcriptional regulation of the chipmunk hibernation-related protein gene

The chipmunk hibernation-related protein 25 (HP-25) is involved in the circannual control of hibernation in the brain. The liver-specific expression of the HP-25 gene is repressed in hibernating chipmunks under the control of endogenous circannual rhythms. However, the molecular mechanisms that differentially regulate the HP-25 gene during the nonhibernation and hibernation seasons are unknown. Here, we show that the hibernation-associated HP-25 expression is regulated epigenetically. Chromatin immunoprecipitation analyses revealed that significantly less hepatocyte nuclear receptor HNF-4 bound to the HP-25 gene promoter in the liver of hibernating chipmunks compared to nonhibernating chipmunks. Concurrently in the hibernating chipmunks, coactivators were dissociated from the promoter, and active transcription histone marks on the HP-25 gene promoter were lost. On the other hand, small heterodimer partner (SHP) expression was upregulated in the liver of hibernating chipmunks. Overexpressing SHP in primary hepatocytes prepared from nonhibernating chipmunks caused HNF-4 to dissociate from the HP-25 gene promoter, and reduced the HP-25 mRNA level. These results suggest that hibernation-related HP-25 expression is epigenetically regulated by the binding of HNF-4 to the HP-25 promoter, and that this binding might be modulated by SHP in hibernating chipmunks.

Disrupted seasonal biology impacts health, food security and ecosystems

The rhythm of life on earth is shaped by seasonal changes in the environment. Plants and animals show profound annual cycles in physiology, health, morphology, behaviour and demography in response to environmental cues. Seasonal biology impacts ecosystems and agriculture, with consequences for humans and biodiversity. Human populations show robust annual rhythms in health and well-being, and the birth month can have lasting effects that persist throughout life. This review emphasizes the need for a better understanding of seasonal biology against the backdrop of its rapidly progressing disruption through climate change, human lifestyles and other anthropogenic impact. Climate change is modifying annual rhythms to which numerous organisms have adapted, with potential consequences for industries relating to health, ecosystems and food security. Disconcertingly, human lifestyles under artificial conditions of eternal summer provide the most extreme example for disconnect from natural seasons, making humans vulnerable to increased morbidity and mortality. In this review, we introduce scenarios of seasonal disruption, highlight key aspects of seasonal biology and summarize from biomedical, anthropological, veterinary, agricultural and environmental perspectives the recent evidence for seasonal desynchronization between environmental factors and internal rhythms. Because annual rhythms are pervasive across biological systems, they provide a common framework for trans-disciplinary research.

Growth promotion in pigs by oxytetracycline coincides with down regulation of serum inflammatory parameters and of hibernation-associated protein HP-27

The growth promoting effect of supplementing animal feed with antibiotics like tetracycline has traditionally been attributed to their antibiotic character. However, more evidence has been accumulated on their direct anti-inflammatory effect during the last two decades. Here we used a pig model to explore the systemic molecular effect of feed supplementation with sub therapeutic levels of oxytetracycline (OTC) by analysis of serum proteome changes. Results showed that OTC promoted growth, coinciding with a significant down regulation of different serum proteins related to inflammation, oxidation and lipid metabolism, confirming the anti-inflammatory mechanism of OTC. Interestingly, apart from the classic acute phase reactants also down regulation was seen of a hibernation associated plasma protein (HP-27), which is to our knowledge the first description in pigs. Although the exact function in non-hibernators is unclear, down regulation of HP-27 could be consistent with increased appetite, which is possibly linked to the anti-inflammatory action of OTC. Given that pigs are good models for human medicine due to their genetic and physiologic resemblance, the present results might also be used for rational intervention in human diseases in which inflammation plays an important role such as obesity, type 2 diabetes and cardiovascular diseases.

Metabolic Flexibility: Hibernation, Torpor, and Estivation

Many environmental conditions can constrain the ability of animals to obtain sufficient food energy, or transform that food energy into useful chemical forms. To survive extended periods under such conditions animals must suppress metabolic rate to conserve energy, water, or oxygen. Amongst small endotherms, this metabolic suppression is accompanied by and, in some cases, facilitated by a decrease in core body temperature-hibernation or daily torpor-though significant metabolic suppression can be achieved even with only modest cooling. Within some ectotherms, winter metabolic suppression exceeds the passive effects of cooling. During dry seasons, estivating ectotherms can reduce metabolism without changes in body temperature, conserving energy reserves, and reducing gas exchange and its inevitable loss of water vapor. This overview explores the similarities and differences of metabolic suppression among these states within adult animals (excluding developmental diapause), and integrates levels of organization from the whole animal to the genome, where possible. Several similarities among these states are highlighted, including patterns and regulation of metabolic balance, fuel use, and mitochondrial metabolism. Differences among models are also apparent, particularly in whether the metabolic suppression is intrinsic to the tissue or depends on the whole-animal response. While in these hypometabolic states, tissues from many animals are tolerant of hypoxia/anoxia, ischemia/reperfusion, and disuse. These natural models may, therefore, serve as valuable and instructive models for biomedical research.