Effect of H<Subscript>2</Subscript>S on the circadian rhythm of mouse hepatocytes

Background  

Dysregulation of circadian rhythms can contribute to diseases of lipid metabolism. NAD-dependent deacetylase sirtuin-1(SIRT1) is an important hub which links lipid metabolism with circadian clock by its deacetylation activity depends on intracellular NAD⁺/NADH content ratio. Hydrogen sulfide (H₂S) is an endogenous reductant which can affect the intracellular redox state. Therefore, we hypothesized that exogenous H₂S can affect the expression of circadian clock genes mediated by sirt1 thereby affecting body's lipid metabolism. And also because the liver is a typical peripheral circadian clock oscillator that is intimately linked to lipid metabolism. Thus the effect of H₂S were observed on 24-hour dynamic expression of 4 central circadian clock genes and sirt1gene in primary cultured hepatocytes.     

Telomeres shorten with age in rat cerebellum and cortex in vivo

Normal somatic cells have a finite replicative capacity. With each cell division, telomeres, the ends of linear chromosomes, progressively shorten until they reach a critical length, at which point the cells enter replicative senescence. Some cells maintain their telomeres by the action of the telomerase enzyme. Glia, particularly microglia, are the only adult cell type in the central nervous system (CNS) that exhibit a significant mitotic potential, and are thus susceptible to telomere shortening. Previous research in our laboratory has found that telomeres shorten in rat microglia with increasing time in vitro. Our current hypothesis is that telomeres shorten in rat brain in vivo with increasing age. Tissue samples of cerebellum and cortex were obtained from Sprague-Dawley rats of various ages. Genomic DNA and total protein was isolated from each sample for telomere length measurement via Southern blot analysis (up to 5 months) and telomerase activity measurement via TRAP analysis (up to 6 months), respectively. Telomere shortening occurs in vivo in both rat cerebellum and cortex from day 21 to approximately 5 months of age. Cortex samples possessed shorter telomeres than did cerebellum samples. The longest telomeres undergo the most dramatic shortening, while the shortest telomeres exhibit only slight attrition. Telomerase activity slowly increases from day 21 to approximately 6 months of age, with the cerebellum exhibiting higher activity than cortex in all instances. These results indicate that telomere shortening occurs in rat brain in vivo with increasing age, and that the low levels of telomerase activity present may be preferentially recruited to maintain the shortest telomeres while allowing the longer ones to shorten more rapidly. Since microglia are thought to be the only mature cells of the postnatal CNS undergoing appreciable cell division, we propose that the telomere shortening occurring in the adult rat brain with age can be largely attributed to microglial cell division. Our findings provide an impetus to further investigate the pattern of telomere length and telomerase activity that emerges with further aging in the rat brain.     

长期睡眠剥夺下调AMPK/SIRT1/PGC-1α通路引起小鼠脂代谢紊乱

目的探讨长期睡眠剥夺对小鼠肝组织腺苷酸激活蛋白激酶(adenosine 5’-monophosphateactivated protein kinase,AMPK)/沉默信息调节因子1(silent information regulation1,SIRT1)/过氧化物酶体增殖物激活受体γ共激活因子-1α(peroxisome proliferator-activated receptorγcoactivator 1α,PGC-1α)系统的影响。方法2月龄C57BL/6J小鼠16只随机分为睡眠剥夺组和正常对照组,睡眠剥夺组利用睡眠剥夺仪每天剥夺睡眠20 h,每周剥夺6 d,连续10周。正常对照组在相同实验条件下自由睡眠10周。每周测量一次体重,10周后进行小鼠体成分测定,并采集血液、肝脏和脂肪组织样本,检测血清褪黑素水平、肝组织AMPKα、SIRT1、PGC-1α及胆固醇调节元件结合蛋白1C(sterol regulatory element-binding protein 1C,SREBP-1C)蛋白表达水平,以及脂肪组织中脂肪合成关键酶脂肪酸合成酶(fatty acid synthase,FAS)、乙酰辅酶A羧化酶1(acetyl CoA carbosylase 1,ACC1)表达水平。结果建模结束后,睡眠剥夺组小鼠体重显著高于对照组(F=10.955,P=0.006),且从第6周末开始,睡眠剥夺组小鼠体重明显高于对照组(F=8.535,P=0.012),并且睡眠剥夺组小鼠体脂量[(14.58±1.70)%]高于对照组[(11.24±1.64)%](t=4.007,P=0.001),血清褪黑素浓度[(2.33±0.53)ng/ml]低于对照组[(2.87±0.23)ng/ml](t=2.643,P=0.019),AMPK通路中的AMPKα(t=7.134,P<0.001)、SIRT1(t=7.531,P<0.001)、PGC-1α(t=11.537,P<0.001)表达水平降低,AMPK/SIRT1/PGC-1α通路下调。而SREBP-1C表达水平升高,差异有统计学意义(t=-4.496,P=0.001)。同时睡眠剥夺小鼠脂肪组织中FAS(t=-4.375,P=0.001)、ACC1表达水平均升高(t=-4.072,P=0.001)。结论长期睡眠剥夺可致褪黑素受体介导的AMPK/SIRT1/PGC-1α通路抑制,并且脂肪合成相关基因表达增强,引起能量代谢特别是脂代谢稳态失调和体脂增加。     

Physiological and pathophysiological role of the circadian clock system

It has been well known for ages that in living organisms the rhythmicity of biological processes is linked to the ~ 24-hour light-dark cycle. However, the exact function of the circadian clock system has been explored only in the past decades. It came to light that the photosensitive primary "master clock" is situated in the suprachiasmatic photosensitive nuclei of the special hypothalamic region, and that it is working according to ~24-hour changes of light and darkness. The master clock sends its messages to the peripheral "slave clocks". In many organs, like pancreatic β-cells, the slave clocks have autonomic functions as well. Two essential components of the clock system are proteins encoded by the CLOCK and BMAL1 genes. CLOCK genes are in interaction with endonuclear receptors such as peroxisoma-proliferator activated receptors and Rev-erb-α, as well as with the hypothalamic-pituitary-adrenal axis, regulating the adaptation to stressors, energy supply, metabolic processes and cardiovascular system. Melatonin, the product of corpus pineale has a significant role in the functions of the clock system. The detailed discovery of the clock system has changed our previous knowledge about the development of many diseases. The most explored fields are hypertension, cardiovascular diseases, metabolic processes, mental disorders, cancers, sleep apnoe and joint disorders. CLOCK genes influence ageing as well. The recognition of the periodicity of biological processes makes the optimal dosing of certain drugs feasible. The more detailed discovery of the interaction of the clock system might further improve treatment and prevention of many disorders.     

Postnatal ontogenesis of clock genes in mouse suprachiasmatic nucleus and heart

Background  

The master clock within the hypothalamic suprachiasmatic nucleus (SCN) synchronizing clocks in peripheral tissues is entrained by the environmental condition, such as the light-dark (LD) cycle. The mechanisms of circadian clockwork are similar in both SCN and peripheral tissues. The aim of the present work was to observe the profiles of clock genes expression in mouse central and peripheral tissues within postnatal day 5 (P5). The daily expression of four clock genes mRNA (Bmal1, Per2, Cry1 and Rev-erb alpha) in mouse SCN and heart was measured at P1, P3 and P5 by real-time PCR.     

Assessment of telomere length during post-natal period in offspring produced by a bull and its fibroblast derived clone

ObjectiveTo investigate the telomere length in bovine offspring produced by a cloned and control bull, and the telomerase activity in embryos produced with the same technology.MethodsFive daughters of a control and five daughters of a bull cloned using a fibroblast of the control were produced by IVF using sperm of the two bulls. Blood samples of the offspring were collected at 2, 6, and 12 months of age and the relative telomere length (RTL) was assessed by flow cytometry. At same time the body growth, hematological profile, and clinical biochemistry of the same progeny was extensively surveyed, and results have been reported in a previous work. Thereafter, the telomerase activity was assessed using a real time PCR quantitative assay in groups of embryos produced with the same technology.ResultsThe offspring of the clone exhibited a modest, but significant (P<0.05), shortening of the telomeres (21.36%, 20.56% and 20.56%) compared to that of the control (23.78%, 23.53% and 22.43%) as mean values determined at 2, 6 and 12 months, respectively. Shortening of telomeres in respect to the age was not significant. No statistical difference was reported between telomerase activity assessed in 144 cloned (3.4⁻⁰³ ± 2.4⁻⁰³ amoles/μL) and 80 control (2.1⁻⁰³ ± 1.8⁻⁰³ amoles/μL) embryos.ConclusionsThe results have revealed a moderate shortening of telomeres in the offspring of the clone with respect to control. However, this study did not evidence differences in the two progenies that suggest welfare problems during the first year of life.     

Polyporus and Bupleuri radix effectively alter peripheral circadian clock phase acutely in male mice

In mammals, daily physiological events are precisely regulated by an internal circadian clock system. An important function of this system is to readjust the phase of the clock daily. In Japan, traditional herb medicines, so-called crude drugs (Shoyaku), are widely used for many diseases, and some are reported to affect circadian clock impairment, suggesting that some of them might have an ability to modify clock gene expression rhythms. Therefore, from selected 40 crude drugs, finding candidates that control the circadian clock phases was the first purpose of this study. As there are several crude drugs used for liver- and/or kidney-related diseases, the second aim of the present study was to find some crude drugs affecting liver/kidney circadian clock in vivo. To assess phase changes in the daily circadian rhythm, bioluminescence from the core clock gene product Period 2 was continuously monitored in mouse embryonic fibroblasts in vitro and in some peripheral tissues (kidney, liver, and submandibular gland) of PERIOD2::LUCIFERASE knock-in mice in vivo. In our screening, Polyporus and Bupleuri radix were found to be good candidates to effectively manipulate the peripheral circadian clock phase acutely, with stimulation time-of-day dependency in vitro as well as in vivo. Interestingly, Polyporus and Bupleuri radix are traditional herb medicines use for treating edema and promoting diuresis, and for chronic hepatitis, respectively. These crude drugs may be therefore good modulators of the circadian peripheral clocks including liver and kidney, and circadian clock genes become new molecular targets for these crude drugs.     

Central and peripheral regulation of feeding and nutrition by the mammalian circadian clock: implications for nutrition during manned space flight

Circadian clocks have evolved to predict and coordinate physiologic processes with the rhythmic environment on Earth. Space studies in non-human primates and humans have suggested that this clock persists in its rhythmicity in space but that its function is altered significantly in long-term space flight. Under normal circumstances, the clock is synchronized by the light-dark cycle via the retinohypothalamic tract and the suprachiasmatic nucleus. It is also entrained by restricted feeding regimes via a suprachiasmatic nucleus-independent circadian oscillator. The site of this suboscillator (or oscillators) is not known, but new evidence has suggested that peripheral tissues in the liver and viscera may express circadian clock function when forced to do so by restricted feeding schedules or other homeostatic disruptions. New research on the role of the circadian clock in the control of feeding on Earth and in space is warranted.     

PGC-1α与卵巢功能及相关研究进展

过氧化物酶体增殖物激活受体γ共激活因子1α(peroxisome proliferator-activated receptor gamma coactivator 1 alpha,PGC-1α)属于人体内一种重要的核转录辅助激活因子,是线粒体生成的关键调节因子,通过与核受体及转录因子的相互作用参与线粒体的生物合成、适...     

Inula Viscosa Extracts Induces Telomere Shortening and Apoptosis in Cancer Cells and Overcome Drug Resistance

Telomerase is activated in human papillomavirus (HPV) positive cervical cancer and targeting telomeres offers a novel anticancer therapeutic strategy. In this study, the telomere targeting properties, the cytotoxic as well as the pro-apoptotic effects of hexane (IV-HE) and dichloromethane (IV-DF) fractions from Inula viscosa L. extracts were investigated on human cervical HeLa and SiHa cancer cells. Our data demonstrate that IV-HE and IV-DF extracts were able to inhibit cell growth in HeLa and SiHa cells in a dose-dependent manner and studied resistant cell lines exhibited a resistance factor less than 2 when treated with the extracts. IV-HE and IV-DF extracts were able to inhibit telomerase activity and to induce telomere shortening as shown by telomeric repeat amplification protocol and TTAGGG telomere length assay, respectively. The sensitivity of fibroblasts to the extracts was increased when telomerase was expressed. Finally, IV-HE and IV-DF were able to induce apoptosis as evidenced by an increase in annexin-V labeling and caspase-3 activity. This study provides the first evidence that the IV-HE and IV-DF extracts from Inula viscosa L. target telomeres induce apoptosis and overcome drug resistance in tumor cells. Future studies will focus on the identification of the molecules involved in the anticancer activity.     

Evidence for clock genes circadian rhythms in human full-term placenta

Abstract

Biological rhythms are driven by endogenous biological clocks; in mammals, the master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. This master pacemaker can synchronize other peripheral oscillators in several tissues such as some involved in endocrine or reproductive functions. The presence of an endogenous placental clock has received little attention. In fact, there are no studies in human full-term placentas. To test the existence of an endogenous pacemaker in this tissue we have studied the expression of circadian locomoter output cycles kaput (Clock), brain and muscle arnt-like (Bmal)1, period (Per)2, and cryptochrome (Cry)1 mRNAs at 00, 04, 08, 12, 16, and 20 hours by qPCR. The four clock genes studied are expressed in full-term human placenta. The results obtained allow us to suggest that a peripheral oscillator exists in human placenta. Data were analyzed using Fourier series where only the Clock and Bmal1 expression shows a circadian rhythm.     

Korean mistletoe (Viscum album coloratum) extract improves endurance capacity in mice by stimulating mitochondrial activity

The beneficial effects of exercise on overall health make it desirable to identify the orally active agents that enhance the effects of exercise in an effort to cure metabolic diseases. Natural compounds such as resveratrol (RSV) are known to increase endurance by potentiating mitochondrial function. Korean mistletoe (Viscum album coloratum) extract (KME) has characteristics similar to those of RSV. In the present study, we determined whether KME could increase mitochondrial activity and exert an anti-fatigue effect. We found that KME treatment significantly increased the mitochondrial oxygen consumption rate (OCR) in L6 cells and increased the expression of peroxisome proliferator-activated receptor γ coactivator (PGC)-1α and silent mating type information regulation 2 homolog 1 (SIRT1), two major regulators of mitochondria function, in C2C12 cells. In the treadmill test, KME-treated mice could run 2.5-times longer than chow-fed control mice. Additionally, plasma lactate levels of exhausted mice were significantly lower in the KME-treated group. In addition, the swimming time to exhaustion of mice treated with KME was prolonged by as much as 212% in the forced-swim test. Liver and kidney histology was similar between the KME-treated and phosphate-buffered saline-treated animals, indicating that KME was nontoxic. Taken together, our data show that KME induces mitochondrial activity, possibly by activating PGC-1α and SIRT1, and improves the endurance of mice, strongly suggesting that KME has great potential as a novel mitochondria-activating agent.     

Chronobiology and Obesity: Interactions between Circadian Rhythms and Energy Regulation

Recent advances in the understanding of the molecular, genetic, neural, and physiologic basis for the generation and organization of circadian clocks in mammals have revealed profound bidirectional interactions between the circadian clock system and pathways critical for the regulation of metabolism and energy balance. The discovery that mice harboring a mutation in the core circadian gene circadian locomotor output cycles kaput (Clock) develop obesity and evidence of the metabolic syndrome represented a seminal moment for the field, clearly establishing a link between circadian rhythms, energy balance, and metabolism at the genetic level. Subsequent studies have characterized in great detail the depth and magnitude of the circadian clock’s crucial role in regulating body weight and other metabolic processes. Dietary nutrients have been shown to influence circadian rhythms at both molecular and behavioral levels; and many nuclear hormone receptors, which bind nutrients as well as other circulating ligands, have been observed to exhibit robust circadian rhythms of expression in peripheral metabolic tissues. Furthermore, the daily timing of food intake has itself been shown to affect body weight regulation in mammals, likely through, at least in part, regulation of the temporal expression patterns of metabolic genes. Taken together, these and other related findings have transformed our understanding of the important role of time, on a 24-h scale, in the complex physiologic processes of energy balance and coordinated regulation of metabolism. This research has implications for human metabolic disease and may provide unique and novel insights into the development of new therapeutic strategies to control and combat the epidemic of obesity.     

Sirtuin1功能及调控研究进展

Sirtuin1(SIRT1)是依赖于烟酰胺腺嘌呤二核苷酸辅酶(nicotinamide adenine dinucleotide,NAD+)的去乙酰化酶(Sirtuins,SIRTs)家族7个成员中最大的一个,是近年来研究最为广泛的长寿因子。SIRT1除了对组蛋白赖氨酸残基去乙酰化修饰调节表观遗传外,SIRT1还可以调节细胞其他关键蛋白活性,控制细胞增殖、分化和细胞凋亡等生理功能。最近研究发现,SIRT1调控细胞功能除了与其酶活性水平有关,也可能与其在细胞中的定位有关。SIRT1在细胞核质之间穿梭和SIRT1活性水平及其相对应的生理功能仍需深入研究.     

High-fat diet inhibits PGC-1α suppressive effect on NFκB signaling in hepatocytes

Purpose

The peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) regulates the expression of genes implicated in fatty acid oxidation and oxidative phosphorylation. Its role in liver steatosis is well established, since mice with liver-specific deletion of PGC-1α exhibit lipid accumulation and high-fat diet reduces hepatic PGC-1α expression in mice. In this study, we investigated the role of PGC-1α in the inflammatory changes observed in steatohepatitis induced by high-fat diet.

Methods

C57black/6 mice were fed a high-fat diet containing 30% fat for 10 weeks. After euthanasia, liver morphology was examined by HE staining and inflammation was determined by IL-6, TNF-α, and IL-1β quantification. Liver gene expression of PGC-1 isoforms was evaluated by real-time PCR and p65 NFκB nuclear translocation by Western blotting. HepG2 cells were treated with linoleic acid overload for 72 h to create an in vitro model of steatohepatitis. RNA interference (RNAi) was used to evaluate the involvement of PGC-1α on inflammatory mediators’ production by hepatocytes.

Results

The high-fat diet led to a state of nonalcoholic steatohepatitis, associated with increased deposits of intra-abdominal fat, hyperglycemia and hyperlipidemia. Mice liver also exhibited increased proinflammatory cytokines’ levels, decreased PGC-1α expression, and marked increase in p65 NFκB nuclear translocation. Linoleic acid treated cells also presented increased expression of proinflammatory cytokines and decreased PGC-1α expression. The knockdown of PGC-1α content caused an increase in IL-6 expression and release via enhanced IκBα phosphorylation and subsequent increase of p65 NFκB nuclear translocation.

Conclusion

High-fat diet induces liver inflammation by inhibiting PGC-1α expression and its suppressive effect in NFκB pathway.