17 research outputs found
Inhibition or deletion of 11Β-HSD1 does not increase angiogenesis in ischemic retinopathy
No full text11-Hydroxysteroid dehydrogenase type I (11-HSD1) regenerates active glucocorticoids (cortisol in humans, corticosterone in rodents) from inert 11-keto metabolites [1]. Selective 11-HSD1 inhibitors have been shown to be safe and effective in the treatment of type 2 diabetes [2], lowering intracellular glucocorticoid concentrations in liver and adipose tissue (and thereby enhancing insulin sensitivity) [3]. They also improve a number of features of the metabolic syndrome, including liver fat content [4], are potentially atheroprotective [5] and improve cognition [6]. Although no longer under development for blood glucose lowering alone, 11-HSD1 inhibitors are being re-profiled for additional indications and may yet be prescribed in patients with type 2 diabetes.11-HSD1 is also expressed in smooth muscle cells throughout the vasculature [7]. By acting directly through glucocorticoid receptors in the blood vessel wall, glucocorticoids tonically inhibit angiogenesis [8]. Loss of 11-HSD1, and the resulting reduction of glucocorticoid action in blood vessels, is associated with enhanced angiogenesis in multiple sites and has been shown to be beneficial in the myocardium after coronary artery occlusion and in skin following wound incision [9]. Angiogenesis can also contribute to pathology, as seen in solid tumour development and ischemic retinopathies such as retinal vein occlusions and proliferative diabetic retinopathy (PDR). If 11-HSD1 inhibitors are to be used for chronic treatment in patients with type II diabetes, then there is a concern that they may accelerate the progression of inappropriate blood vessel growth in the retina and exacerbate progression to sight-threatening PDR.This study tests the hypothesis that pharmacological inhibition or deletion of 11-HSD1 promotes pathological retinal neovascularisation. Retinal vascular remodelling was induced using the oxygen induced retinopathy (OIR) model [10] in which exposure of neonatal mice to hyperoxia from postnatal days 7 to 12 causes obliteration and cessation of development of central retinal capillary beds so that, on return to normoxia, a potent pre-retinal neovascular response is induced. Expression and localisation of 11β-HSD1 in the retina was also investigated by immunohistochemistry.<br/
Effects of postnatal and maternal diet-induced obesity on physiology and vascular function
No full textIn recent years there has been an explosion in the rates of obesity, defined as a body mass
index greater than 30kg/ m2, and associated cardiovascular disease. Alterations in peripheral
glucocorticoid metabolism have been suggested to play a role in the development of obesity.
Obesity occurs in both sexes, but the risk of associated metabolic disturbance and vascular
dysfunction is greater in men. Although there is no accepted definition of obesity in rodents,
the term is used to describe animals with a significant increase in fat pad mass often
achieved by feeding a high fat diet. Although animal models of obesity have been useful in
delineating potential mechanisms linking obesity with its metabolic and vascular sequelae,
most studies have been in male animals and, thus, have not addressed sex differences.
Additionally, emerging evidence shows that obesity during pregnancy is associated with
increased cardio-metabolic and vascular disease in offspring, although the processes
underlying such ‘programming’ effects are unclear.
This thesis addresses the hypothesis that exposure to postnatal, or maternal obesity will alter
both metabolism and vascular function in mice.
Male and female mice maintained on a high fat and sugar diet from 5 weeks of age had
increased adipose tissue deposition in adulthood. However there were striking sex
differences in glucose homeostasis, mRNA levels and glucocorticoid metabolism, with males
being more severely affected. Treatment of male mice with 17β-estradiol ameliorated a
number of the effects of the high fat diet, including weight gain and altered glucose
homeostasis; additionally estradiol altered glucocorticoid metabolism in the adipose so that it
resembled that of females. Suprisingly, given the changes in metabolism, obesity in adult
mice produced only small changes in vascular function and did not alter vascular
remodelling following injury.
The effects of maternal obesity were studied using male offspring aged 3 and 6 months. The
offspring of obese mothers had similar body weight, adiposity, plasma lipid and plasma
hormone concentrations to controls. In contrast, exposure to obesity in utero was associated
with receptor specific changes in agonist-mediated contraction and decreased endothelium-dependent
relaxation in male offspring. Despite these changes in vascular function, no
alterations in blood pressure or vascular remodelling following injury were present.
These results demonstrate that the more profound changes in glucose-insulin homeostasis
associated with obesity in male humans can be recapitulated in rodent models and imply that
estradiol plays a role in protecting the metabolism of female mice, potentially by alteration
of glucocorticoid metabolism. Despite altered metabolism in postnatal obesity vascular
function remained normal suggesting metabolic and vascular dysfunction are not
intrinsically linked. Conversely, maternal obesity did not cause any overt changes in
offspring metabolism but caused vascular dysfunction implying these parameters can be
programmed independently
Role of glucocorticoids in development and growth of the cardiovascular system in the zebrafish
No full textINTRODUCTION:
Glucocorticoids (GCs) are synthesised endogenously in mammals by the
hypothalamic pituitary adrenal (HPA) axis in response to stress. These hormones can
elicit a number of physiological roles by binding to and activating specific receptors
(glucocorticoid or mineralocorticoid receptors- GR or MR). GCs are important in
tissue development and maturation and commonly used therapeutically.
Mammalian
animal studies have suggested that over-exposure to GCs, whether
pharmacologically or through induction of maternal stress, is associated with
increased cardiovascular disease risk in adult life. The underlying mechanisms
underpinning this early life programming are poorly understood, however GC
exposure during development may have direct and indirect effects on the structure
and function of developing tissues and organs which may predispose to disease in
later life. Current mammalian models of programming do not lend themselves well to
studying organ development during embryogenesis. The zebrafish provides an ideal
model to study this phenomenon due to the transparent nature of developing larvae
and the availability of transgenic lines expressing fluorescent markers.
METHODS:
GC pathways were comprehensively characterised during zebrafish embryo
development using qRT-PCR and steroid ELISAs. The physiological roles of GCs
were assessed during early zebrafish development (first 120 hours post fertilisation
(hpf)) assessing stress response, swim activity and global development following
various genetic and pharmacological manipulations of the GC system. The impact
that GC manipulation had on the cardiovascular system was also investigated.
Embryos which had been exposed to GC manipulation during early development
were then allowed to develop to adulthood in order to assess the long term impact.
The same parameters were investigated in the adult as in the embryo.
RESULTS:
The key components of the GC system are present and functional in the developing
embryo with de novo cortisol biosynthesis evident from 48hpf. A functioning
hypothalamic pituitary inter-renal (HPI) axis is demonstrable from 72hpf.
Manipulation of specific components of the GC pathway during early embryonic
development influences growth-rate, head-trunk angle, chorion hatch-rate and swim
behaviour. Manipulation of GCs during embryogenesis resulted in altered body
weight, length and girth in adulthood, with altered stress response and swim
behaviour also detected. Embryonic heart development was also affected with a
reduction in ventricle cardiomyocyte number, cardiac gene abundance (vhmc) and
cardiac function during embryogenesis resulting in structural abnormalities such as
fewer trabeculae and increased intra-ventricular space. Embryonic GC manipulation
also alters the formation and patterning of intersegmental blood vessels by 120hpf. In
adulthood this manifests as a reduced angiogenic capacity.
CONCLUSION:
The zebrafish embryo represents a valid and physiologically relevant model for GC
research. Manipulation of GCs during early development results in altered growth,
gene abundance and cardiovascular structure. These findings have significant
implications for on-going research addressing GC mediated programming and
suggest that the zebrafish is a highly suitable model for GC researc
Early-life glucocorticoids programme behaviour and metabolism in adulthood in zebrafish
No full textGlucocorticoids (GCs) in utero influence embryonic development with consequent programmed effects on adult physiology and pathophysiology and altered susceptibility to cardiovascular disease. However, in viviparous species, studies of these processes are compromised by secondary maternal influences. The zebrafish, being fertilised externally, avoids this problem and has been used here to investigate the effects of transient alterations in GC activity during early development. Embryonic fish were treated either with dexamethasone (a synthetic GC), an antisense GC receptor (GR) morpholino (GR Mo), or hypoxia for the first 120h post fertilisation (hpf); responses were measured during embryonic treatment or later, post treatment, in adults. All treatments reduced cortisol levels in embryonic fish to similar levels. However, morpholino- and hypoxia-treated embryos showed delayed physical development (slower hatching and straightening of head–trunk angle, shorter body length), less locomotor activity, reduced tactile responses and anxiogenic activity. In contrast, dexamethasone-treated embryos showed advanced development and thigmotaxis but no change in locomotor activity or tactile responses. Gene expression changes were consistent with increased (dexamethasone) and decreased (hypoxia, GR Mo) GC activity. In adults, stressed cortisol values were increased with dexamethasone and decreased by GR Mo and hypoxia pre-treatments. Other responses were similarly differentially affected. In three separate tests of behaviour, dexamethasone-programmed fish appeared ‘bolder’ than matched controls, whereas Mo and hypoxia pre-treated fish were unaffected or more reserved. Similarly, the dexamethasone group but not the Mo or hypoxia groups were heavier, longer and had a greater girth than controls. Hyperglycaemia and expression of GC responsive gene (pepck) were also increased in the dexamethasone group. We conclude that GC activity controls many aspects of early-life growth and development in the zebrafish and that, like other species, manipulating GC status pharmacologically, physiologically or genetically in early life leads to programmable metabolic and behavioural traits in adulthood
Comparison of mechanisms of angiostasis caused by the anti-inflammatory steroid 5α-tetrahydrocorticosterone versus conventional glucocorticoids
No full text5α-Tetrahydrocorticosterone (5αTHB) is an effective topical anti-inflammatory agent in mouse, with less propensity to cause skin thinning and impede new blood vessel growth compared with corticosterone. Its anti-inflammatory effects were not prevented by RU38486, a glucocorticoid receptor antagonist, suggesting alternative mechanisms. The hypothesis that 5αTHB directly inhibits angiogenesis to a lesser extent than hydrocortisone was tested, focussing on glucocorticoid receptor mediated actions. New vessel growth from aortae from C57BL/6 male mice was monitored in culture, in the presence of 5αTHB, hydrocortisone (mixed glucocorticoid/mineralocorticoid receptor agonist) or the selective glucocorticoid receptor agonist dexamethasone. Transcript profiles were studied, as was the role of the glucocorticoid receptor, using the antagonist, RU38486. Ex vivo, 5αTHB suppressed vessel growth from aortic rings, but was less potent than hydrocortisone (EC50 2512 nM 5αTHB, versus 762 nM hydrocortisone). In contrast to conventional glucocorticoids, 5αTHB did not alter expression of genes related to extracellular matrix integrity or inflammatory signalling, but caused a small increase in Per1 transcript, and decreased transcript abundance of Pecam1 gene. RU38486 did not antagonise the residual effects of 5αTHB to suppress vessel growth or regulate gene expression, but modified effects of dexamethasone. 5αTHB did not alter expression of glucocorticoid-regulated genes Fkbp51 and Hsd11b1, unlike hydrocortisone and dexamethasone. In conclusion, compared with hydrocortisone, 5αTHB exhibits limited suppression of angiogenesis, at least directly in blood vessels and probably independent of the glucocorticoid receptor. Discriminating the mechanisms employed by 5αTHB may provide the basis for the development of novel safer anti-inflammatory drugs for topical use.</p
Early-life perturbations in glucocorticoid activity impacts on the structure, function and molecular composition of the adult zebrafish
No full textBackground: Transient early-life perturbations in glucocorticoids (GC) are linked with cardiovascular disease risk in later life. Here the impact of early life manipulations of GC on adult heart structure, function and gene expression were assessed. Methods and results: Zebrafish embryos were incubated in dexamethasone (Dex) or injected with targetedglucocorticoid receptor (GR) morpholino knockdown (GR Mo) over the first 120 h post fertilisation (hpf); surviving embryos (>90%) were maintained until adulthood under normal conditions. Cardiac function, heart histology and cardiac genes were assessed in embryonic (120 hpf) and adult (120 days post fertilisation (dpf)) hearts. GR Mo embryos (120 hpf) had smaller hearts with fewer cardiomyocytes, less mature striation pattern, reduced cardiac function and reduced levels of vmhc and igf mRNA compared with controls. GR Mo adult hearts were smaller with diminished trabecular network pattern, reduced expression of vmhc and altered echocardiographic Doppler flow compared to controls. Dex embryos had larger hearts at 120 hpf (Dex 107.2 ± 3.1 vs. controls 90.2 ± 1.1 mm, p < 0.001) with a more mature trabecular network and larger cardiomyocytes (1.62 ± 0.13 cells/mm vs control 2.18 ± 0.13 cells/mm, p < 0.05) and enhanced cardiac performance compared to controls. Adult hearts were larger (1.02 ± 0.07 mg/mg vs controls 0.63 ± 0.06 mg/mg, p ¼ 0.0007), had increased vmhc and gr mRNA levels. Conclusion: Perturbations in GR activity during embryonic development results in short and long-term alterations in the heart
Why has the energy intensity fallen in China's industrial sector in the 1990s?: the relative importance of structural change and intensity change
No full textPublisher Correction: Discovery of rare variants associated with blood pressure regulation through meta-analysis of 1.3 million individuals (Nature Genetics, (2020), 52, 12, (1314-1332), 10.1038/s41588-020-00713-x)
No full textIn the version of this article originally published, the e-mail address of corresponding author Patricia B. Munroe was incorrect. The error has been corrected in the HTML and PDF versions of the article
Erratum to: Genetic analysis of over 1 million people identifies 535 new loci associated with blood pressure traits (Nature Genetics, (2018), 50, 10, (1412-1425), 10.1038/s41588-018-0205-x)
No full textIn the version of this article originally published, the name of author Martin H. de Borst was coded incorrectly in the XML. The error has now been corrected in the HTML version of the paper
Erratum to: Genetic analysis of over 1 million people identifies 535 new loci associated with blood pressure traits
No full textIn the version of this article originally published, the name of author Martin H. de Borst was coded incorrectly in the XML.
The error has now been corrected in the HTML version of the paper
