Recent Advances in Hepatic Metabolic Regulation by the Nuclear Factor Rev-erbɑ

Rev-erbɑ (NR1D1) is a nuclear receptor superfamily member that plays a vital role in mammalian molecular clocks and metabolism. Rev-erbɑ can regulate the metabolism of drugs and the body's glucose metabolism, lipid metabolism, and adipogenesis. It is even one of the important regulatory factors regulating the occurrence of metabolic diseases (e.g., diabetes, fatty liver). Metabolic enzymes mediate most drug metabolic reactions in the body. Rev-erbɑ has been recognized to regulate drug metabolic enzymes (such as Cyp2b10 and Ugt1a9). Therefore, this paper mainly reviewed that Rev-erbɑ regulates I and II metabolic enzymes in the liver to affect drug pharmacokinetics. The expression of these drug metabolic enzymes (up-regulated or down-regulated) is related to drug exposure and effects/ toxicity. In addition, our discussion extends to Rev-erbɑ regulating some transporters (such as P-gp, Mrp2, and Bcrp), as they also play an essential role in drug metabolism. Finally, we briefly describe the role and mechanism of nuclear receptor Rev-erbɑ in lipid and glucose homeostasis, obesity, and metabolic disorders syndrome. In conclusion, this paper aims to understand better the role and mechanism of Rev-erbɑ in regulating drug metabolism, lipid, glucose homeostasis, obesity, and metabolic disorders syndrome, which explores how to target Rev-erbɑ to guide the design and development of new drugs and provide scientific reference for the molecular mechanism of new drug development, rational drug use, and drug interaction.

The combination of nuclear receptor NR1D1 and ULK1 promotes mitophagy in adipocytes to ameliorate obesity

Obesity is a severe disease worldwide. Mitochondrial autophagy (mitophagy) may be related to metabolic abnormalities in obese individuals, but the mechanism is still unclear. We aimed to investigate whether nuclear receptors NR1D1 and ULK1 influence obesity by affecting mitophagy. In vitro model was established by inducing 3T3-L1 cells differentiation. MTT was detected cell viability. ELISA was tested triglyceride (TG). Oil red O staining was performed to detect lipid droplets. Flow cytometry was measured mtROS. ChIP and Dual-luciferase reporter assay were verified NR1D1 bind to ULK1. LC3 level was detected by IF. After differentiation medium treatment, cell viability was decreased, TG content and lipid droplets were increased Moreover, NR1D1 expression was reduced in Model group. NR1D1 overexpression was increased cell viability, reduced TG content and lipid droplets. Subsequently, NR1D1 inhibited TOM20 and mtROS, whereas, Parkin and PINK1 were accelerated. NR1D1 overexpression facilitated LC3 expression, whereas ULK1 knockdown was reversed the effect of NR1D1 overexpression. Liensinine also reversed the effect of NR1D1 overexpression, that is, cell viability was reduced, mtROS, TG content and lipid droplets were increased. The combination of nuclear receptor NR1D1 and ULK1 promoted mitophagy in adipocytes to alleviate obesity, which provided new target and strategy for obesity treatment.Abbreviations: Mitochondrial autophagy (mitophagy), triglyceride (TG), Uncoordinated-51 like autophagy activating kinase 1 (ULK1), Nuclear receptor subfamily 1 group D member 1 (NR1D1), American Type Culture Collection (ATCC), fetal bovine serum (FBS), 3-isobutyl-1-methylxanthine (IBMX), dexamethasone (DEX), short hairpin RNA ULK1 (sh-ULK1), wild-type (WT), mutant (MUT), Enzyme-linked immunosorbent assay (ELISA), mitochondrial reactive oxygen species (mtROS), Chromatin immunoprecipitation (ChIP), Quantitative real-time PCR (qRT-PCR), Immunofluorescence (IF), standard deviation (SD).

Effects of Maternal Obesity On Placental Phenotype

The incidence of obesity is rising rapidly worldwide with the consequence that more women are entering pregnancy overweight or obese. This leads to an increased incidence of clinical complications during pregnancy and of poor obstetric outcomes. The offspring of obese pregnancies are often macrosomic at birth although there is also a subset of the progeny that are growth-restricted at term. Maternal obesity during pregnancy is also associated with cardiovascular, metabolic and endocrine dysfunction in the offspring later in life. As the interface between the mother and fetus, the placenta has a central role in programming intrauterine development and is known to adapt its phenotype in response to environmental conditions such as maternal undernutrition and hypoxia. However, less is known about placental function in the abnormal metabolic and endocrine environment associated with maternal obesity during pregnancy. This review discusses the placental consequences of maternal obesity induced either naturally or experimentally by increasing maternal nutritional intake and/or changing the dietary composition. It takes a comparative, multi-species approach and focusses on placental size, morphology, nutrient transport, metabolism and endocrine function during the later stages of obese pregnancy. It also examines the interventions that have been made during pregnancy in an attempt to alleviate the more adverse impacts of maternal obesity on placental phenotype. The review highlights the potential role of adaptations in placental phenotype as a contributory factor to the pregnancy complications and changes in fetal growth and development that are associated with maternal obesity.

The trophoblast clock controls transport across placenta in mice

In mammals, 24-h rhythms of physiology and behavior are organized by a body-wide network of clock genes and proteins. Despite the well-known function of the adult circadian system, the roles of maternal, fetal and placental clocks during pregnancy are poorly defined. In the mature mouse placenta, the labyrinth zone (LZ) is of fetal origin and key for selective nutrient and waste exchange. Recently, clock gene expression has been detected in LZ and other fetal tissues; however, there is no evidence of a placental function controlled by the LZ clock. Here, we demonstrate that specifically the trophoblast layer of the LZ harbors an already functional clock by late gestation, able to regulate in a circadian manner the expression and activity of the xenobiotic efflux pump, ATP-binding cassette sub-family B member 1 (ABCB1), likely gating the fetal exposure to drugs from the maternal circulation to certain times of the day. As more than 300 endogenous and exogenous compounds are substrates of ABCB1, our results might have implications in choosing the maternal treatment time when aiming either maximal/minimal drug availability to the fetus/mother.

Hormonal fine-tuning of clock in decidual region of mouse placenta by dopamine, melatonin, insulin, leptin and ghrelin

INTRODUCTION

The maternal part of the rodent placenta harbors a circadian clock which robustly responds to glucocorticoids, however, its sensitivity to other hormones has not been elucidated. In this study, we tested five selected hormones (dopamine, melatonin, insulin, leptin and ghrelin) for their effectiveness to affect the clock in decidual region of mouse placenta in vitro.

METHODS

We administered the hormones or corresponding vehicles at various time points over 24 h to organotypic placental explants of mPer2^Luc mice containing the decidua basalis (DB) region and monitored their effects on amplitude, period, median expression level (mesor) and phase of PER2-driven bioluminescence rhythms.

RESULTS

Dopamine significantly increased the amplitude, robustly dampened the mesor, and during a narrow time interval (corresponding to daytime) induced phase delays of the rhythms. In contrast, melatonin had no effect on amplitude, but induced phase advances of the rhythms at the opposite time window than dopamine (corresponding to nighttime). Leptin and ghrelin, but not insulin, slightly increased amplitudes and moderately modulated phase delays of the clock, suggesting that the DB clock, in contrast to other peripheral clocks, is rather resilient to abrupt changes in levels of feeding- and metabolism-related hormones.

DISCUSSION

The results demonstrate for the first time that dopamine and melatonin exhibit delicate yet specific effects on parameters of the DB clock and may thus potentially contribute to fine-tuning of its phase under in vivo conditions. It also implies that dysregulation of their levels, which accompany various pathologies, may account for malfunction of the clock in DB.

The Rhythmicity of Clock Genes is Disrupted in the Choroid Plexus of the APP/PS1 Mouse Model of Alzheimer's Disease

BACKGROUND

The choroid plexus (CP), which constitutes the blood-cerebrospinal fluid barrier, was recently identified as an important component of the circadian clock system.

OBJECTIVE

The fact that circadian rhythm disruption is closely associated to Alzheimer's disease (AD) led us to investigate whether AD pathology can contribute to disturbances of the circadian clock in the CP.

METHODS

For this purpose, we evaluated the expression of core-clock genes at different time points, in 6- and 12-month-old female and male APP/PS1 mouse models of AD. In addition, we also assessed the effect of melatonin pre-treatment in vitro before amyloid-β stimulus in the daily pattern of brain and muscle Arnt-like protein 1 (Bmal1) expression.

RESULTS

Our results showed a dysregulation of circadian rhythmicity of Bmal1 expression in female and male APP/PS1 transgenic 12-month-old mice and of Period 2 (Per2) expression in male mice. In addition, a significant circadian pattern of Bmal1 was measured the intermittent melatonin pre-treatment group, showing that melatonin can reset the CP circadian clock.

CONCLUSION

These results demonstrated a connection between AD and the disruption of circadian rhythm in the CP, representing an attractive target for disease prevention and/or treatment.

Maternal vitamin D deficiency during rat gestation elicits a milder phenotype compared to the mouse model: Implications for the placental glucocorticoid barrier

Maternal vitamin D deficiency disturbs fetal development and programmes neurodevelopmental complications in offspring, possibly through increased fetal glucocorticoid exposure. We aimed to determine whether prenatal exposure to excess glucocorticoids underlies our rat model of early-life vitamin D deficiency, leading to altered adult behaviours. Vitamin D deficiency reduced the expression of the glucocorticoid-inactivating enzyme Hsd11b2 in the female placenta, but did not alter maternal glucocorticoid levels, feto-placental weights, or placental expression of other glucocorticoid-related genes at mid-gestation. This differs to the phenotype previously observed in vitamin D deficient mice, and highlights important modelling considerations.

Obesity Disrupts Rhythmic Clock Gene Expression in Maternal Adipose Tissue during Rat Pregnancy

Obesity during pregnancy causes numerous maternal and fetal health complications, but the underlying mechanisms remain unclear. Adipose tissue dysfunction in obesity has previously been linked to disruption of the intrinsic adipose clock gene network that is crucial for normal metabolic function. This adipose clock also undergoes major change as part of the maternal metabolic adaptation to pregnancy, but whether this is affected by maternal obesity is unknown. Consequently, in this study we tested the hypothesis that obesity disturbs rhythmic gene expression in maternal adipose tissue across pregnancy. A rat model of maternal obesity was established by cafeteria (CAF) feeding, and adipose expression of clock genes and associated nuclear receptors ( Ppars and Pgc1α) was measured across days 15-16 and 21-22 of gestation (term = 23 days). CAF feeding suppressed the mesor and/or amplitude of adipose tissue clock genes (most notably Bmal1, Per2, and Rev-erbα) relative to chow-fed controls (CON) across both days of gestation. On day 15, the CAF diet also induced adipose Pparα, Pparδ, and Pgc1α rhythmicity but repressed that of Pparγ, while expression of Pparα, Pparδ, and Pgc1α was reduced at select time points. CAF mothers were hyperleptinemic at both stages of gestation, and at day 21 this effect was time-of-day dependent. Fetal plasma leptin exhibited clear rhythmicity, albeit with low amplitude, but interestingly these levels were unaffected by CAF feeding. Our data show that maternal obesity disrupts rhythmic expression of clock and metabolic genes in maternal adipose tissue and leads to maternal but not fetal hyperleptinemia.

Diet-induced obesity reduces core body temperature across the estrous cycle and pregnancy in the rat

Obesity during pregnancy causes adverse maternal and fetal health outcomes and programs offspring for adult-onset diseases, including cardiovascular disease. Obesity also disrupts core body temperature (T_c) regulation in nonpregnant rodents; however, it is unknown whether obesity alters normal maternal T_c adaptations to pregnancy. Since T_c is influenced by the circadian system, and both obesity and pregnancy alter circadian biology, it was hypothesized that obesity disrupts the normal rhythmic patterns of T_c before and during gestation. Obesity was induced by cafeteria (CAF) feeding in female Wistar rats for 8 weeks prior to and during gestation, whereas control (CON) animals had free access to chow. Intraperitoneal temperature loggers measured daily T_c profiles throughout the study, while maternal body composition and leptin levels were assessed near term. Daily temperature profiles were examined for rhythmic features (mesor, amplitude and acrophase) by cosine regression analysis. CAF animals exhibited increased fat mass (93%) and associated hyperleptinemia (3.2-fold increase) compared to CON animals. CAF consumption reduced the average T_c (by up to 0.29°C) across the estrous cycle and most of pregnancy; however, T_c for CAF and CON animals converged toward the end of gestation. Obesity reduced the amplitude of T_c rhythms at estrus and proestrus and on day 8 of pregnancy, but increased the amplitude at day 20 of pregnancy. Photoperiod analysis revealed that obesity reduced T_c exclusively in the light period during pre-pregnancy but only during the dark period in late gestation. In conclusion, obesity alters rhythmic T_c profiles and reduces the magnitude of the T_c decline late in rat gestation, which may have implications for maternal health and fetal development.