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Biology, Volume 8, Issue 1 (March 2019)

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Open AccessReview Cold and Exercise: Therapeutic Tools to Activate Brown Adipose Tissue and Combat Obesity
Received: 28 December 2018 / Revised: 1 February 2019 / Accepted: 4 February 2019 / Published: 12 February 2019
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Abstract
The rise in obesity over the last several decades has reached pandemic proportions. Brown adipose tissue (BAT) is a thermogenic organ that is involved in energy expenditure and represents an attractive target to combat both obesity and type 2 diabetes. Cold exposure and [...] Read more.
The rise in obesity over the last several decades has reached pandemic proportions. Brown adipose tissue (BAT) is a thermogenic organ that is involved in energy expenditure and represents an attractive target to combat both obesity and type 2 diabetes. Cold exposure and exercise training are two stimuli that have been investigated with respect to BAT activation, metabolism, and the contribution of BAT to metabolic health. These two stimuli are of great interest because they have both disparate and converging effects on BAT activation and metabolism. Cold exposure is an effective mechanism to stimulate BAT activity and increase glucose and lipid uptake through mitochondrial uncoupling, resulting in metabolic benefits including elevated energy expenditure and increased insulin sensitivity. Exercise is a therapeutic tool that has marked benefits on systemic metabolism and affects several tissues, including BAT. Compared to cold exposure, studies focused on BAT metabolism and exercise display conflicting results; the majority of studies in rodents and humans demonstrate a reduction in BAT activity and reduced glucose and lipid uptake and storage. In addition to investigations of energy uptake and utilization, recent studies have focused on the effects of cold exposure and exercise on the structural lipids in BAT and secreted factors released from BAT, termed batokines. Cold exposure and exercise induce opposite responses in terms of structural lipids, but an important overlap exists between the effects of cold and exercise on batokines. In this review, we will discuss the similarities and differences of cold exposure and exercise in relation to their effects on BAT activity and metabolism and its relevance for the prevention of obesity and the development of type 2 diabetes. Full article
(This article belongs to the Special Issue New Players in Adipocyte Biology)
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Open AccessReview The Importance of Peripheral Nerves in Adipose Tissue for the Regulation of Energy Balance
Received: 11 January 2019 / Revised: 5 February 2019 / Accepted: 6 February 2019 / Published: 12 February 2019
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Abstract
Brown and white adipose tissues are essential for maintenance of proper energy balance and metabolic health. In order to function efficiently, these tissues require both endocrine and neural communication with the brain. Brown adipose tissue (BAT), as well as the inducible brown adipocytes [...] Read more.
Brown and white adipose tissues are essential for maintenance of proper energy balance and metabolic health. In order to function efficiently, these tissues require both endocrine and neural communication with the brain. Brown adipose tissue (BAT), as well as the inducible brown adipocytes that appear in white adipose tissue (WAT) after simulation, are thermogenic and energy expending. This uncoupling protein 1 (UCP1)-mediated process requires input from sympathetic nerves releasing norepinephrine. In addition to sympathetic noradrenergic signaling, adipose tissue contains sensory nerves that may be important for relaying fuel status to the brain. Chemical and surgical denervation studies of both WAT and BAT have clearly demonstrated the role of peripheral nerves in browning, thermogenesis, lipolysis, and adipogenesis. However, much is still unknown about which subtypes of nerves are present in BAT versus WAT, what nerve products are released from adipose nerves and how they act to mediate metabolic homeostasis, as well as which cell types in adipose are receiving synaptic input. Recent advances in whole-depot imaging and quantification of adipose nerve fibers, as well as other new research findings, have reinvigorated this field of research. This review summarizes the history of research into adipose innervation and brain–adipose communication, and also covers landmark and recent research on this topic to outline what we currently know and do not know about adipose tissue nerve supply and communication with the brain. Full article
(This article belongs to the Special Issue New Players in Adipocyte Biology)
Open AccessReview Immunometabolic Links between Estrogen, Adipose Tissue and Female Reproductive Metabolism
Received: 7 January 2019 / Revised: 26 January 2019 / Accepted: 3 February 2019 / Published: 7 February 2019
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Abstract
The current knowledge of sex-dependent differences in adipose tissue biology remains in its infancy and is motivated in part by the desire to understand why menopause is linked to an increased risk of metabolic disease. However, the development and characterization of targeted genetically-modified [...] Read more.
The current knowledge of sex-dependent differences in adipose tissue biology remains in its infancy and is motivated in part by the desire to understand why menopause is linked to an increased risk of metabolic disease. However, the development and characterization of targeted genetically-modified rodent models are shedding new light on the physiological actions of sex hormones in healthy reproductive metabolism. In this review we consider the need for differentially regulating metabolic flexibility, energy balance, and immunity in a sex-dependent manner. We discuss the recent advances in our understanding of physiological roles of systemic estrogen in regulating sex-dependent adipose tissue distribution, form and function; and in sex-dependent healthy immune function. We also review the decline in protective properties of estrogen signaling in pathophysiological settings such as obesity-related metaflammation and metabolic disease. It is clear that the many physiological actions of estrogen on energy balance, immunity, and immunometabolism together with its dynamic regulation in females make it an excellent candidate for regulating metabolic flexibility in the context of reproductive metabolism. Full article
(This article belongs to the Special Issue New Players in Adipocyte Biology)
Open AccessEditorial Acknowledgement to Reviewers of Biology in 2018
Published: 24 January 2019
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Abstract
Rigorous peer-review is the corner-stone of high-quality academic publishing [...] Full article
Open AccessReview Role of Rhodopsins as Circadian Photoreceptors in the Drosophila melanogaster
Received: 3 October 2018 / Revised: 14 December 2018 / Accepted: 4 January 2019 / Published: 10 January 2019
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Abstract
Light profoundly affects the circadian clock and the activity levels of animals. Along with the systematic changes in intensity and spectral composition, over the 24-h day, light shows considerable irregular fluctuations (noise). Using light as the Zeitgeber for the circadian clock is, therefore, [...] Read more.
Light profoundly affects the circadian clock and the activity levels of animals. Along with the systematic changes in intensity and spectral composition, over the 24-h day, light shows considerable irregular fluctuations (noise). Using light as the Zeitgeber for the circadian clock is, therefore, a complex task and this might explain why animals utilize multiple photoreceptors to entrain their circadian clock. The fruit fly Drosophila melanogaster possesses light-sensitive Cryptochrome and seven Rhodopsins that all contribute to light detection. We review the role of Rhodopsins in circadian entrainment, and of direct light-effects on the activity, with a special emphasis on the newly discovered Rhodopsin 7 (Rh7). We present evidence that Rhodopsin 6 in receptor cells 8 of the compound eyes, as well as in the extra retinal Hofbauer-Buchner eyelets, plays a major role in entraining the fly’s circadian clock with an appropriate phase-to-light–dark cycles. We discuss recent contradictory findings regarding Rhodopsin 7 and report original data that support its role in the compound eyes and in the brain. While Rhodopsin 7 in the brain appears to have a minor role in entrainment, in the compound eyes it seems crucial for fine-tuning light sensitivity to prevent overshooting responses to bright light. Full article
(This article belongs to the Special Issue Biological Clocks)
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Open AccessDiscussion Lipid Production in Nannochloropsis gaditana during Nitrogen Starvation
Received: 10 December 2018 / Accepted: 3 January 2019 / Published: 8 January 2019
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Abstract
The microalga Nannochloropsis gaditana is a natural producer of triacylglycerol (TAG) and the omega-3 fatty acid eicosapentaenoic acid (EPA). TAG accumulation is induced by nitrogen starvation. The biomass-specific photon supply rate used had an effect on EPA and TAG accumulation during nitrogen starvation [...] Read more.
The microalga Nannochloropsis gaditana is a natural producer of triacylglycerol (TAG) and the omega-3 fatty acid eicosapentaenoic acid (EPA). TAG accumulation is induced by nitrogen starvation. The biomass-specific photon supply rate used had an effect on EPA and TAG accumulation during nitrogen starvation as well as on the localization of EPA accumulation. Clear differences in TAG yield on light were found for different biomass-specific photon supply rates and light regimes during nitrogen starvation. De novo EPA synthesis or the translocation of EPA between lipid fractions might be limiting for EPA accumulation in TAG. Further studies are needed to fully understand EPA accumulation in TAG during nitrogen starvation. To elucidate the function of EPA in TAG nitrogen recovery, experiments are suggested. The overexpression of genes involved in de novo EPA synthesis and translocation is proposed to elucidate the exact metabolic routes involved in these processes during nitrogen starvation. This work addresses future opportunities to increase EPA accumulation. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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Open AccessArticle Formyl-methionyl-leucyl-phenylalanine Induces Apoptosis in Murine Neurons: Evidence for NO-Dependent Caspase-9 Activation
Received: 28 November 2018 / Revised: 21 December 2018 / Accepted: 28 December 2018 / Published: 4 January 2019
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Abstract
Formyl-methionyl-leucyl-phenylalanine (fMLP) may be present in the brain in the course of some infectious diseases of the central nervous system (CNS), although little is known about its role. This investigation was performed to study the effect of fMLP on neuron apoptosis. Our results [...] Read more.
Formyl-methionyl-leucyl-phenylalanine (fMLP) may be present in the brain in the course of some infectious diseases of the central nervous system (CNS), although little is known about its role. This investigation was performed to study the effect of fMLP on neuron apoptosis. Our results showed that fMLP treatment of primary cultures of neurons was able to induce morphological features of apoptosis in cell cultures, as well as activation of the intrinsic apoptotic pathway, through the upregulation of caspase-9 and caspase-3. This effect contextually occurred to the pro-apoptotic protein Bax activation and cytochrome c release. The in vitro fMLP treatment was also able to induce, in a dose-dependent manner, the increase of inducible nitric oxide synthase (iNOS) expression accompanied by an up-regulation of nitric oxide (NO) release. When neuron cultures were pre-treated with 1400 W, a selective iNOS inhibitor, all of the apoptotic features were significantly reversed. Overall, these results demonstrated that fMLP treatment of neurons leads to intrinsic apoptosis activation, through iNOS expression regulation, suggesting a role for fMLP in CNS neurodegenerative processes. Full article
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Open AccessReview Cyclin C: The Story of a Non-Cycling Cyclin
Received: 15 November 2018 / Revised: 21 December 2018 / Accepted: 28 December 2018 / Published: 4 January 2019
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Abstract
The class I cyclin family is a well-studied group of structurally conserved proteins that interact with their associated cyclin-dependent kinases (Cdks) to regulate different stages of cell cycle progression depending on their oscillating expression levels. However, the role of class II cyclins, which [...] Read more.
The class I cyclin family is a well-studied group of structurally conserved proteins that interact with their associated cyclin-dependent kinases (Cdks) to regulate different stages of cell cycle progression depending on their oscillating expression levels. However, the role of class II cyclins, which primarily act as transcription factors and whose expression remains constant throughout the cell cycle, is less well understood. As a classic example of a transcriptional cyclin, cyclin C forms a regulatory sub-complex with its partner kinase Cdk8 and two accessory subunits Med12 and Med13 called the Cdk8-dependent kinase module (CKM). The CKM reversibly associates with the multi-subunit transcriptional coactivator complex, the Mediator, to modulate RNA polymerase II-dependent transcription. Apart from its transcriptional regulatory function, recent research has revealed a novel signaling role for cyclin C at the mitochondria. Upon oxidative stress, cyclin C leaves the nucleus and directly activates the guanosine 5’-triphosphatase (GTPase) Drp1, or Dnm1 in yeast, to induce mitochondrial fragmentation. Importantly, cyclin C-induced mitochondrial fission was found to increase sensitivity of both mammalian and yeast cells to apoptosis. Here, we review and discuss the biology of cyclin C, focusing mainly on its transcriptional and non-transcriptional roles in tumor promotion or suppression. Full article
(This article belongs to the Special Issue Top 35 of Biology Travel Awards 2018)
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Open AccessArticle ISSR Analysis of Genetic Diversity and Structure of Plum Varieties Cultivated in Southern China
Received: 17 October 2018 / Revised: 10 December 2018 / Accepted: 11 December 2018 / Published: 21 December 2018
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Abstract
Plums (Prunus spp.) are important deciduous fruit crops in the world. China is a major producer of P. salicina Lindl., but the genetic relationship of Chinese plums in key production regions remain unclear. In this study, 14 University of British Columbia (UBC) [...] Read more.
Plums (Prunus spp.) are important deciduous fruit crops in the world. China is a major producer of P. salicina Lindl., but the genetic relationship of Chinese plums in key production regions remain unclear. In this study, 14 University of British Columbia (UBC) inter simple sequence repeats (ISSR) primers were used to analyze 33 plum varieties cultivated in Fujian Province to determine their genetic diversity and population structure. A total of 146 bands were generated, of which 130 were polymorphic. Mean percentage of polymorphic bands was 89.04%, Shannon’s information index value was 0.38, and the Nei’s genetic index value was 0.24. Using unrooted trees (Neighbor-Joining method), 33 varieties were classified into four groups. Split graph separated them into two major groups, each with two subgroups. The two phylogenetic trees indicate that environmental or natural selection pressure is an important factor influencing their genetic relationship. Analysis of population structure revealed that they have frequent genetic exchanges among closed subpopulations; thus, genetic variation mainly occurs within the population. Additionally, based on the phylogenetic analysis and unique morphological characteristics of fruits, we propose that the Chinese landrace Nai could contribute significantly to development of the famous variety Wickson. Full article
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Open AccessReview Guide snoRNAs: Drivers or Passengers in Human Disease?
Received: 25 October 2018 / Revised: 16 December 2018 / Accepted: 18 December 2018 / Published: 20 December 2018
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Abstract
In every domain of life, RNA-protein interactions play a significant role in co- and post-transcriptional modifications and mRNA translation. RNA performs diverse roles inside the cell, and therefore any aberrancy in their function can cause various diseases. During maturation from its primary transcript, [...] Read more.
In every domain of life, RNA-protein interactions play a significant role in co- and post-transcriptional modifications and mRNA translation. RNA performs diverse roles inside the cell, and therefore any aberrancy in their function can cause various diseases. During maturation from its primary transcript, RNA undergoes several functionally important post-transcriptional modifications including pseudouridylation and ribose 2′-O-methylation. These modifications play a critical role in the stability of the RNA. In the last few decades, small nucleolar RNAs (snoRNAs) were revealed to be one of the main components to guide these modifications. Due to their active links to the nucleoside modification, deregulation in the snoRNA expressions can cause multiple disorders in humans. Additionally, host genes carrying snoRNA-encoding sequences in their introns also show differential expression in disease. Although few reports support a causal link between snoRNA expression and disease manifestation, this emerging field will have an impact on the way we think about biomarkers or identify novel targets for therapy. This review focuses on the intriguing aspect of snoRNAs that function as a guide in post-transcriptional RNA modification, and regulation of their host genes in human disease. Full article
(This article belongs to the Special Issue Top 35 of Biology Travel Awards 2018)
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