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Rick van der Geest, Ronald J van der Sluis, Albert K Groen, Miranda Van Eck and Menno Hoekstra

Chronic glucocorticoid overexposure predisposes to the development of atherosclerotic cardiovascular disease in humans. Cholestatic liver disease is associated with increased plasma glucocorticoid levels. Here, we determined – in a preclinical setting – whether the chronic presence of cholestatic liver disease also induces a concomitant negative impact on atherosclerosis susceptibility. Hereto, regular chow diet-fed atherosclerosis-susceptible hypercholesterolemic apolipoprotein E (APOE)-knockout mice were treated with the bile duct toxicant alpha-naphthylisothiocyanate (ANIT) for 8 weeks. ANIT exposure induced the development of fibrotic cholestatic liver disease as evident from collagen deposits and compensatory bile duct hyperproliferation within the liver and the rise in plasma levels of bilirubin (+60%; P < 0.01) and bile acids (10-fold higher; P < 0.01). Adrenal weights (+22%; P < 0.01) and plasma corticosterone levels (+72%; P < 0.01) were increased in ANIT-treated mice. In contrast, atherosclerosis susceptibility was not increased in response to ANIT feeding, despite the concomitant increase in plasma free cholesterol (+30%; P < 0.01) and cholesteryl ester (+42%; P < 0.001) levels. The ANIT-induced hypercorticosteronemia coincided with marked immunosuppression as judged from the 50% reduction (P < 0.001) in circulating lymphocyte numbers. However, hepatic glucocorticoid signaling was not enhanced after ANIT treatment. It thus appears that the immunosuppressive effect of glucocorticoids is uncoupled from their metabolic effect under cholestatic disease conditions. In conclusion, we have shown that cholestatic liver disease-associated endogenous glucocorticoid overexposure does not increase atherosclerosis susceptibility in APOE-knockout mice. Our studies provide novel preclinical evidence for the observations that the hypercholesterolemia seen in cholestatic human subjects does not translate into a higher risk for atherosclerotic cardiovascular disease.

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Guillermo García-Eguren, Oriol Giró, María del Mar Romero, Mar Grasa and Felicia A Hanzu

Excessive and prolonged glucocorticoid (GC) exposure, resulting from either prescribed or endogenous hypercortisolism, is associated with a high cardiovascular and metabolic burden (Cushing’s syndrome). Although previous studies in humans and mice have reported heterogeneous data about the persistence of metabolic syndrome features after remission of hypercortisolism, there is still controversy as to whether this is due to the deleterious changes induced by GCs during active disease or the result of various other factors interfering in the recovery period. In order to study metabolic effects after remission, we used a reversible mouse model of corticosterone (CORT) (100 µg/mL) administration in drinking water for 5 weeks, followed by a 10-week recovery period. We compared CORT-induced effects at these time points with a high-fat diet-treated group (HFD 45%) and a vehicle group (VEH). Plasma CORT, 11β-HSD activity, food intake, glucose levels, interscapular brown adiposity, hepatic triglycerides and muscle mass were found altered during CORT treatment but normalized after recovery. Although hyperinsulinemia and insulin resistance were increased during CORT and HFD treatment, insulin homeostasis remained altered following the recovery period only in CORT-treated mice. Subcutaneous and visceral adipose tissues (SAT and VAT) were enlarged during HFD and CORT treatment as measured by MRI. However, increased muscle lipid content, adiposity and macrophage infiltration in VAT were only present in the CORT group following recovery. Taken together, CORT-induced insulin alterations were more potent than HFD-induced ones during the same period of treatment, and also more persistent long term. Moreover, we demonstrated that CORT treatment induces more long-lasting VAT enlargement than HFD.

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Yingxin Xian, Zonglan Chen, Hongrong Deng, Mengyin Cai, Hua Liang, Wen Xu, Jianping Weng and Fen Xu

Obesity-associated chronic inflammation in adipose tissue is partly attributed to hypoxia with insufficient microcirculation. Previous studies have shown that exenatide, a glucagon-like peptide 1 (GLP-1) receptor agonist, plays an anti-inflammatory role. Here, we investigate its effects on inflammation, hypoxia and microcirculation in white adipose tissue of diet-induced obese (DIO) mice. DIO mice were injected intraperitoneally with exenatide or normal saline for 4 weeks, while mice on chow diet were used as normal controls. The mRNA and protein levels of pro-inflammatory cytokines, hypoxia-induced genes and angiogenic factors were detected. Capillary density was measured by laser confocal microscopy and immunochemistry staining. After 4-week exenatide administration, the dramatically elevated pro-inflammatory cytokines in serum and adipose tissue and macrophage infiltration in adipose tissue of DIO mice were significantly reduced. Exenatide also ameliorated expressions of hypoxia-related genes in obese fat tissue. Protein levels of endothelial markers and pro-angiogenic factors including vascular endothelial growth factor and its receptor 2 were augmented in accordance with increased capillary density by exenatide in DIO mice. Our results indicate that inflammation and hypoxia in adipose tissue can be mitigated by GLP-1 receptor agonist potentially via improved angiogenesis and microcirculation in obesity.

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Isis Gabrielli Barbieri de Oliveira, Marcos Divino Ferreira Junior, Paulo Ricardo Lopes, Dhiogenes Balsanufo Taveira Campos, Marcos Luiz Ferreira-Neto, Eduardo Henrique Rosa Santos, Paulo Cezar de Freitas Mathias, Flávio Andrade Francisco, Bruna Del Vechio Koike, Carlos Henrique de Castro, André Henrique Freiria-Oliveira, Gustavo Rodrigues Pedrino, Rodrigo Mello Gomes and Daniel Alves Rosa

Disruptions in circadian rhythms have been associated with several diseases, including cardiovascular and metabolic disorders. Forced internal desynchronization induced by a period of T-cycles of 22 h (T22 protocol) reaches the lower limit of entrainment and dissociates the circadian rhythmicity of the locomotor activity into two components, driven by different outputs from the suprachiasmatic nucleus (SCN). The main goal of this study was to evaluate the cardiovascular and metabolic response in rats submitted to internal desynchronization by T22 protocol. Male Wistar rats were assigned to either a control group subjected to a usual T-cycles of 24 h (12 h–12 h) or an experimental group subjected to the T22 protocol involving a 22-h symmetric light–dark cycle (11 h–11 h). After 8 weeks, rats subjected to the T22 exhibited desynchrony in their locomotor activity. Although plasma glucose and insulin levels were similar in both groups, desynchronized rats demonstrated dyslipidemia, significant hypertrophy of the fasciculate zone of the adrenal gland, low IRB, IRS2, PI3K, AKT, SOD and CAT protein expression and an increased expression of phosphoenolpyruvate carboxykinase in the liver. Furthermore, though they maintained normal baseline heart rates and mean arterial pressure levels, they also presented reduced baroreflex sensitivity. The findings indicate that circadian timing desynchrony following the T22 protocol can induce cardiometabolic disruptions. Early hepatic metabolism dysfunction can trigger other disorders, though additional studies are needed to clarify the causes.

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Qiongge Zhang, Chaoqun Wang, Yehua Tang, Qiangqiang Zhu, Yongcheng Li, Haiyan Chen, Yi Bao, Song Xue, Liangliang Sun, Wei Tang, Xiangfang Chen, Yongquan Shi, Lefeng Qu, Bin Lu and Jiaoyang Zheng

Hyperglycemia plays a major role in the development of diabetic macrovascular complications, including atherosclerosis and restenosis, which are responsible for the most of disability and mortality in diabetic patients. Osteopontin (OPN) is an important factor involved in atherogenesis, and hyperglycemia enhances the transcriptional activity of FoxO1 which is closely association with insulin resistance and diabetes. Here, we showed that plasma OPN levels were significantly elevated in type 2 diabetic patients and positively correlated with glycated albumin (GA). The more atherosclerotic lesions were observed in the aorta of diabetic ApoE−/− mice analyzed by Sudan IV staining. High glucose increased both the mRNA and protein expression levels of OPN and inhibited the phosphorylation of FoxO1 in RAW 264.7 cells. Overexpression of WT or constitutively active mutant FoxO1 promoted the expression levels of OPN, while the dominant-negative mutant FoxO1 decreased slightly the expression of OPN. Conversely, knockdown of FoxO1 reduced the expression of OPN. Luciferase reporter assay revealed that high glucose and overexpression of FoxO1 enhanced the activities of the OPN promoter region nt −1918 ~ −713. Furthermore, the interactions between FoxO1 and the OPN promoter were confirmed by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation assay (ChIP). Our results suggest that high glucose upregulates OPN expression via FoxO1 activation, which would play a critical role in the development of diabetic atherogenesis.

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Sivaporn Sivasinprasasn, Siripong Palee, Kenneth Chattipakorn, Thidarat Jaiwongkum, Nattayaporn Apaijai, Wasana Pratchayasakul, Siriporn C Chattipakorn and Nipon Chattipakorn

Myocardial damage and mitochondrial dysfunction caused by cardiac ischemia-reperfusion (I/R) injury are intensified by endogenous estrogen deprivation. Although N-acetylcysteine (NAC) exerted cardioprotective effects, its benefits when used in combination with hormone therapy are unknown. We tested the hypothesis that a combination of NAC with low-dose estrogen improves cardiometabolic function and protects cardiac mitochondria against I/R injury, to a similar extent to regular-dose estrogen treatment, in estrogen-deprived rats. Female Wistar rats had a bilateral ovariectomy (OVX) or sham operation. Twelve weeks after the operation, OVX rats were treated with regular-dose estrogen (E; 50 µg/kg/day), low-dose estrogen (e; 25 µg/kg/day), NAC (N; 100 mg/kg/day) or combined low-dose estradiol with NAC (eN) for 4 weeks (n = 6/group). Metabolic parameters, echocardiography, heart rate variability and then cardiac I/R protocol involving 30-min coronary artery ligation, followed by 120-min reperfusion, were performed. OVX rats had increased body weight, visceral fat, fasting plasma glucose, HOMA-IR index, triglycerides, cholesterol and LDL levels (P < 0.05 vs sham). Only OVX-E and OVX-eN had a similarly improved HOMA-IR index. LVEF was increased in all treatment groups, but HRV was restored only by OVX-E and OVX-eN. After I/R, myocardial infarct size was decreased in both OVX-E and OVX-eN groups. OVX-E and OVX-eN rats similarly had a reduced mitochondrial ROS level and increased mitochondrial membrane potential in the ischemic myocardium. In conclusion, combined NAC with low-dose estrogen and regular-dose estrogen therapy similarly improve cardiometabolic function, prevent cardiac mitochondrial dysfunction and reduces the infarct size in estrogen-deprived rats with cardiac I/R injury.

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Alia H Sukkar, Aaron M Lett, Gary Frost and Edward S Chambers

Short-chain fatty acids (SCFAs) are metabolites produced from the fermentation of dietary fibre by the gut microbiota. High-fibre diets have been associated with lower weight gain and a number of reports have therefore investigated if these positive effects of a dietary fibre on body weight can be replicated through the direct administration of SCFAs. Many of these studies have reported that SCFAs can prevent or attenuate long-term body weight gain by increasing energy expenditure through increased lipid oxidation. The aim of the present review is to therefore evaluate the current evidence for an effect of SCFAs on whole-body energy expenditure and to assess the potential underlying mechanisms. The available data highlights that SCFAs can exert multiple effects at various organ and tissue sites that would cumulatively raise energy expenditure via a promotion of lipid oxidation. In conclusion, the present review proposes that dietary interventions and other therapies that augment gut-derived SCFAs and systemic availability may present an effective strategy to improve long-term energy balance and body weight management.

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Masaki Nakano, Mika Ikegame, Junko Igarashi-Migitaka, Yusuke Maruyama, Nobuo Suzuki and Atsuhiko Hattori

Many studies have investigated the actions of melatonin on osteoblasts and osteoclasts. However, the underlying mechanisms, especially regarding osteocyte function, remain largely unknown. Therefore, this study aimed to clarify the underlying mechanisms of melatonin action on bone tissue via osteocyte function. Chick calvariae were employed as a model. In ovo injection of melatonin (5, 50 and 500 µg) dose-dependently decreased the mRNA expression levels of cathepsin K and matrix metalloproteinase 9 (MMP9) in chick calvariae without affecting the expression levels of receptor activator of NF-κB ligand or osteoprotegerin. Surprisingly enough, the expression of calcitonin mRNA in chick calvariae was significantly raised. After 3 days of in vitro treatment of melatonin (10−7 and 10−5 M) on newly hatched chick calvariae, both calcitonin mRNA expression in calvariae and the concentration of calcitonin in cultured medium were augmented in a dose-dependent manner, coincident with the decreased mRNA expression levels of cathepsin K and MMP9. Immunohistochemical analyses revealed expression of melatonin receptors and calcitonin by osteocytes buried in bone matrix. Moreover, the mRNA expression levels of melatonin receptors, calcitonin and sclerostin (a marker of osteocyte), were strongly and positively correlated. In conclusion, we demonstrated the expression of melatonin receptors and calcitonin expression in osteocytes for the first time and suggest a new mechanism underlying the suppressive effect of melatonin on osteoclasts via upregulation of calcitonin secretion by osteocytes.

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Stephen G Hillier and Richard Lathe

The year 2019 marks the 80th anniversary of the 1939 Nobel Prize in Chemistry awarded to Leopold Ruzicka (1887–1976) for work on higher terpene molecular structures, including the first chemical synthesis of male sex hormones. Arguably his crowning achievement was the ‘biogenetic isoprene rule’, which helped to unravel the complexities of terpenoid biosynthesis. The rule declares terpenoids to be enzymatically cyclized products of substrate alkene chains containing a characteristic number of linear, head-to-tail condensed, C5 isoprene units. The number of repeat isoprene units dictates the type of terpene produced (i.e., 2, monoterpene; 3, sesquiterpene; 4, diterpene, etc.). In the case of triterpenes, six C5 isoprene units combine into C30 squalene, which is cyclized into one of the signature carbon skeletons from which myriad downstream triterpenoid structures are derived, including sterols and steroids. Ruzicka also had a keen interest in the origin of life, but the pivotal role of terpenoids has generally been overshadowed by nucleobases, amino acids, and sugars. To redress the balance, we provide a historical and evolutionary perspective. We address the potential abiotic generation of isoprene, the crucial role that polyprene terpenoids played in early membranes and cellular life, and emphasize that endocrinology from microbes to plants and vertebrates is firmly grounded on Ruzicka’s pivotal insights into the structure and function of terpenes. A harmonizing feature is that all known lifeforms (including bacteria) biosynthesize triterpenoid substances that are essential for cellular membrane formation and function, from which signaling molecules such as steroid hormones and cognate receptors are likely to have evolved.

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Jacqueline M Wallace

The competition for nutrients that arises when pregnancy coincides with continuing or incomplete growth in young adolescent girls increases the risk of preterm delivery and low birthweight with negative after-effects for mother and child extending beyond the perinatal period. Sheep paradigms involving nutritional management of weight and adiposity in young, biologically immature adolescents have allowed the consequences of differential maternal growth status to be explored. Although nutrient reserves at conception play a modest role, it is the dietary manipulation of the maternal growth trajectory thereafter which has the most negative impact on pregnancy outcome. Overnourishing adolescents to promote rapid maternal growth is particularly detrimental as placental growth, uteroplacental blood flows and fetal nutrient delivery are perturbed leading to a high incidence of fetal growth restriction and premature delivery of low birthweight lambs, whereas in undernourished adolescents further maternal growth is prevented, and depletion of the maternal body results in a small reduction in birthweight independent of placental size. Maternal and placental endocrine systems are differentially altered in both paradigms with downstream effects on fetal endocrine systems, organ development and body composition. Approaches to reverse these effects have been explored, predominantly targeting placental growth or function. After birth, growth-restricted offspring born to overnourished adolescents and fed to appetite have an altered metabolic phenotype which persists into adulthood, whereas offspring of undernourished adolescents are largely unaffected. This body of work using ovine paradigms has public health implications for nutritional advice offered to young adolescents before and during pregnancy, and their offspring thereafter.