Wnt Signaling in Atherosclerosis: Mechanisms to Therapeutic Implications

Atherosclerosis is a vascular disease in which inflammation plays a pivotal role. Receptor-mediated signaling pathways regulate vascular inflammation and the pathophysiology of atherosclerosis. Emerging evidence has revealed the role of the Wnt pathway in atherosclerosis progression. The Wnt pathway influences almost all stages of atherosclerosis progression, including endothelial dysfunction, monocyte infiltration, smooth muscle cell proliferation and migration, and plaque formation. Targeting the Wnt pathway to treat atherosclerosis represents a promising therapeutic approach that remains understudied. Blocking Wnt signaling utilizing small molecule inhibitors, recombinant proteins, and/or neutralizing antibodies ameliorates atherosclerosis in preclinical models. The Wnt pathway can be potentially manipulated through targeting Wnt ligands, receptors, co-receptors, and downstream signaling molecules. However, there are challenges associated with developing a real world therapeutic compound that targets the Wnt pathway. This review focuses on the role of Wnt signaling in atherosclerosis development, and the rationale for targeting this pathway for the treatment of atherosclerosis.

Loss of endothelial glucocorticoid receptor accelerates organ fibrosis in db/db mice

Endothelial cells play a key role in maintaining homeostasis and are deranged in many disease processes, including fibrotic conditions. Absence of the endothelial glucocorticoid receptor (GR) has been shown to accelerate diabetic kidney fibrosis in part through upregulation of Wnt signaling. The db/db mouse model is a model of spontaneous type 2 diabetes that has been noted to develop fibrosis in multiple organs over time, including the kidneys. This study aimed to determine the effect of loss of endothelial GR on organ fibrosis in the db/db model. db/db mice lacking endothelial GR showed more severe fibrosis in multiple organs compared with endothelial GR-replete db/db mice. Organ fibrosis could be substantially improved either through administration of a Wnt inhibitor or metformin. IL-6 is a key cytokine driving the fibrosis phenotype and is mechanistically linked to Wnt signaling. The db/db model is an important tool to study the mechanisms of fibrosis and its phenotype in the absence of endothelial GR highlights the synergistic effects of Wnt signaling and inflammation in the pathogenesis or organ fibrosis.NEW & NOTEWORTHY The major finding of this work is that endothelial glucocorticoid receptor-mediated upregulation of Wnt signaling and concurrent hyperinflammation work synergistically to exacerbate organ fibrosis in a genetic mouse model of diabetes. This study adds to our understanding of diabetic renal fibrosis and has important implications for the use of metformin in this condition.

Loss of endothelial glucocorticoid receptor accelerates organ fibrosis in db/db mice

Endothelial cells play a key role in maintaining homeostasis and are deranged in many disease processes, including fibrotic conditions. Absence of the endothelial glucocorticoid receptor (GR) has been shown to accelerate diabetic kidney fibrosis in part through up regulation of Wnt signaling. The db/db mouse model is a model of spontaneous type 2 diabetes that has been noted to develop fibrosis in multiple organs over time, including the kidneys. This study aimed to determine the effect of loss of endothelial GR on organ fibrosis in the db/db model. Db/Db mice lacking endothelial GR showed more severe fibrosis in multiple organs compared to endothelial GR-replete db/db mice. Organ fibrosis could be substantially improved either through administration of a Wnt inhibitor or metformin. IL-6 is a key cytokine driving the fibrosis phenotype and is mechanistically linked to Wnt signaling. The db/db model is an important tool to study mechanisms of fibrosis and its phenotype in the absence of endothelial GR highlights the synergistic effects of Wnt signaling and inflammation in the pathogenesis or organ fibrosis.

Coronavirus Disease (COVID)-19 and Diabetic Kidney Disease

The present review describes COVID-19 severity in diabetes and diabetic kidney disease. We discuss the crucial effect of COVID-19-associated cytokine storm and linked injuries and associated severe mesenchymal activation in tubular epithelial cells, endothelial cells, and macrophages that influence neighboring cell homeostasis, resulting in severe proteinuria and organ fibrosis in diabetes. Altered microRNA expression disrupts cellular homeostasis and the renin-angiotensin-system, targets reno-protective signaling proteins, such as angiotensin-converting enzyme 2 (ACE2) and MAS1 receptor (MAS), and facilitates viral entry and replication in kidney cells. COVID-19-associated endotheliopathy that interacts with other cell types, such as neutrophils, platelets, and macrophages, is one factor that accelerates prethrombotic reactions and thrombus formation, resulting in organ failures in diabetes. Apart from targeting vital signaling through ACE2 and MAS, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are also associated with higher profibrotic dipeptidyl transferase-4 (DPP-4)-mediated mechanisms and suppression of AMP-activated protein kinase (AMPK) activation in kidney cells. Lowered DPP-4 levels and restoration of AMPK levels are organ-protective, suggesting a pathogenic role of DPP-4 and a protective role of AMPK in diabetic COVID-19 patients. In addition to standard care provided to COVID-19 patients, we urgently need novel drug therapies that support the stability and function of both organs and cell types in diabetes.

Interactions among Long Non-Coding RNAs and microRNAs Influence Disease Phenotype in Diabetes and Diabetic Kidney Disease

Large-scale RNA sequencing and genome-wide profiling data revealed the identification of a heterogeneous group of noncoding RNAs, known as long noncoding RNAs (lncRNAs). These lncRNAs play central roles in health and disease processes in diabetes and cancer. The critical association between aberrant expression of lncRNAs in diabetes and diabetic kidney disease have been reported. LncRNAs regulate diverse targets and can function as sponges for regulatory microRNAs, which influence disease phenotype in the kidneys. Importantly, lncRNAs and microRNAs may regulate bidirectional or crosstalk mechanisms, which need to be further investigated. These studies offer the novel possibility that lncRNAs may be used as potential therapeutic targets for diabetes and diabetic kidney diseases. Here, we discuss the functions and mechanisms of actions of lncRNAs, and their crosstalk interactions with microRNAs, which provide insight and promise as therapeutic targets, emphasizing their role in the pathogenesis of diabetes and diabetic kidney disease.

Endothelial SIRT3 regulates myofibroblast metabolic shifts in diabetic kidneys

Defects in endothelial cells cause deterioration in kidney function and structure. Here, we found that endothelial SIRT3 regulates metabolic reprogramming and fibrogenesis in the kidneys of diabetic mice. By analyzing, gain of function of the SIRT3 gene by overexpression in a fibrotic mouse strain conferred disease resistance against diabetic kidney fibrosis, whereas its loss of function in endothelial cells exacerbated the levels of diabetic kidney fibrosis. Regulation of endothelial cell SIRT3 on fibrogenic processes was due to tight control over the defective central metabolism and linked activation of endothelial-to-mesenchymal transition (EndMT). SIRT3 deficiency in endothelial cells stimulated the TGFβ/Smad3-dependent mesenchymal transformations in renal tubular epithelial cells. These data demonstrate that SIRT3 regulates defective metabolism and EndMT-mediated activation of the fibrogenic pathways in the diabetic kidneys. Together, our findings show that endothelial SIRT3 is a fundamental regulator of defective metabolism regulating health and disease processes in the kidney.

Loss of endothelial glucocorticoid receptor promotes angiogenesis via upregulation of Wnt/β-catenin pathway

Objective

The glucocorticoid receptor (GR) is a member of the nuclear receptor family that controls key biological processes in the cardiovascular system and has recently been shown to modulate Wnt signaling in endothelial cells. Wnt/β-catenin signaling has been demonstrated to be crucial in the process of angiogenesis. In the current study, we studied whether GR could regulate angiogenesis via the Wnt/β-catenin pathway.

Approach and Resultsa

Key components of the Wnt/β-catenin pathway were evaluated using quantitative PCR and Western blot in the presence or absence of GR. Enhanced angiogenesis was found in GR deficiency in vitro and confirmed with cell viability assays, proliferation assays and tube formation assays. Consistent with these in vitro findings, endothelial cell-specific GR loss GR in vivo promoted angiogenesis in both a hind limb ischemia model and sponge implantation assay. Results were further verified in a novel mouse model lacking endothelial LRP5/6, a key receptor in canonical Wnt signaling, and showed substantially suppressed angiogenesis using these same in vitro and in vivo assays. To further investigate the mechanism of GR regulation of Wnt signaling, autophagy flux was investigated in endothelial cells by visualizing auto phagolysosomes as well as by assessing P62 degradation and LC3B conversion. Results indicated that potentiated autophagy flux participated in GR-Wnt regulation.

Conclusions

Lack of endothelial GR triggers autophagy flux, leads to activation of Wnt/β-catenin signaling and promotes angiogenesis. There may also be a synergistic interaction between autophagy and Wnt/β-catenin signaling.

Supplementary Information

The online version of this article (10.1007/s10456-021-09773-x) contains supplementary material, which is available to authorized users.

Loss of Mitochondrial Control Impacts Renal Health

Disruption of mitochondrial biosynthesis or dynamics, or loss of control over mitochondrial regulation leads to a significant alteration in fuel preference and metabolic shifts that potentially affect the health of kidney cells. Mitochondria regulate metabolic networks which affect multiple cellular processes. Indeed, mitochondria have established themselves as therapeutic targets in several diseases. The importance of mitochondria in regulating the pathogenesis of several diseases has been recognized, however, there is limited understanding of mitochondrial biology in the kidney. This review provides an overview of mitochondrial dysfunction in kidney diseases. We describe the importance of mitochondria and mitochondrial sirtuins in the regulation of renal metabolic shifts in diverse cells types, and review this loss of control leads to increased cell-to-cell transdifferentiation processes and myofibroblast-metabolic shifts, which affect the pathophysiology of several kidney diseases. In addition, we examine mitochondrial-targeted therapeutic agents that offer potential leads in combating kidney diseases.

Metabolic reprogramming by N-acetyl-seryl-aspartyl-lysyl-proline protects against diabetic kidney disease

BACKGROUND AND PURPOSE

ACE inhibitors (ACEIs) and AT₁ receptor antagonists (ARBs) are first-line drugs that are believed to reduce the progression of end-stage renal disease in diabetic patients. Differences in the effects of ACEIs and ARBs are not well studied and the mechanisms responsible are not well understood.

EXPERIMENTAL APPROACH

Male diabetic CD-1 mice were treated with ACEI, ARB, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), ACEI + AcSDKP, ARB + AcSDKP, glycolysis inhibitors or non-treatment. Moreover, prolyl oligopeptidase inhibitor (POPi)-injected male diabetic C57Bl6 mice were treated with ACEI, AcSDKP and ARB or non-treatment. Western blot and immunofluorescent staining were used to examine key enzymes and regulators of central metabolism.

KEY RESULTS

The antifibrotic action of ACEI imidapril is due to an AcSDKP-mediated antifibrotic mechanism, which reprograms the central metabolism including restoring SIRT3 protein and mitochondrial fatty acid oxidation and suppression of abnormal glucose metabolism in the diabetic kidney. Moreover, the POPi S17092 significantly blocked the AcSDKP synthesis, accelerated kidney fibrosis and disrupted the central metabolism. ACEI partly restored the kidney fibrosis and elevated the AcSDKP level, whereas the ARB (TA-606) did not show such effects in the POPi-injected mice. ACE inhibition and AcSDKP suppressed defective metabolism-linked mesenchymal transformations and reduced collagen-I and fibronectin accumulation in the diabetic kidneys.

CONCLUSION AND IMPLICATIONS

The study envisages that AcSDKP is the endogenous antifibrotic mediator that controls the metabolic switch between glucose and fatty acid metabolism and that suppression of AcSDKP leads to disruption of kidney cell metabolism and activates mesenchymal transformations leading to severe fibrosis in the diabetic kidney.

Cancer Biology and Prevention in Diabetes

The available evidence suggests a complex relationship between diabetes and cancer. Epidemiological data suggest a positive correlation, however, in certain types of cancer, a more complex picture emerges, such as in some site-specific cancers being specific to type I diabetes but not to type II diabetes. Reports share common and differential mechanisms which affect the relationship between diabetes and cancer. We discuss the use of antidiabetic drugs in a wide range of cancer therapy and cancer therapeutics in the development of hyperglycemia, especially antineoplastic drugs which often induce hyperglycemia by targeting insulin/IGF-1 signaling. Similarly, dipeptidyl peptidase 4 (DPP-4), a well-known target in type II diabetes mellitus, has differential effects on cancer types. Past studies suggest a protective role of DPP-4 inhibitors, but recent studies show that DPP-4 inhibition induces cancer metastasis. Moreover, molecular pathological mechanisms of cancer in diabetes are currently largely unclear. The cancer-causing mechanisms in diabetes have been shown to be complex, including excessive ROS-formation, destruction of essential biomolecules, chronic inflammation, and impaired healing phenomena, collectively leading to carcinogenesis in diabetic conditions. Diabetes-associated epithelial-to-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndMT) contribute to cancer-associated fibroblast (CAF) formation in tumors, allowing the epithelium and endothelium to enable tumor cell extravasation. In this review, we discuss the risk of cancer associated with anti-diabetic therapies, including DPP-4 inhibitors and SGLT2 inhibitors, and the role of catechol-o-methyltransferase (COMT), AMPK, and cell-specific glucocorticoid receptors in cancer biology. We explore possible mechanistic links between diabetes and cancer biology and discuss new therapeutic approaches.

Characterization of Circular RNA and microRNA Profiles in Septic Myocardial Depression: a Lipopolysaccharide-Induced Rat Septic Shock Model

Septic shock with heart dysfunction is common in intensive care units. However, the mechanism underlying myocardial depression is still unclear. Whether circular RNA (circRNA) or microRNA (miRNA) profiles differ between patients with and without myocardial depression is unknown. We generated a hypodynamic septic shock model induced by lipopolysaccharide (LPS) in adolescent rats. A total of 12 rats were utilized and heart tissue from each was collected. RNA sequencing was performed on left ventricular tissue. We focused on features of circRNAs and miRNAs, predicting their function by bioinformatic analysis and constructing circRNA-associated and miRNA-associated regulatory networks in heart tissue. We detected 851 circRNAs in heart samples, and 11 showed differential expression. A total of 639 annotated miRNAs and 91 novel miRNAs were explored including 78 showing differential expression between the two groups. We then constructed the most comprehensive circRNA-associated and miRNA-associated networks to explore their regulatory relationship in septic heart tissue, and demonstrated that different networks could potentially participate in and regulate the pathological process of sepsis. Furthermore, gene ontology term enrichment indicated miRNAs, and miRNA-mRNA networks could be associated with regulation and metabolic process, or influence cellular functions. The construction of regulator networks could improve the understanding of the basic molecular mechanisms underlying myocardial depression. It will be important for future investigations to ascertain the biological mechanisms present during the development of sepsis-induced myocardial depression to influence approaches to treatment.

Inhibition of Angiotensin-Converting Enzyme Ameliorates Renal Fibrosis by Mitigating DPP-4 Level and Restoring Antifibrotic MicroRNAs

Two class of drugs 1) angiotensin-converting enzyme inhibitors (ACEis) and 2) angiotensin II receptor blockers (ARBs) are well-known conventional drugs that can retard the progression of chronic nephropathies to end-stage renal disease. However, there is a lack of comparative studies on the effects of ACEi versus ARB on renal fibrosis. Here, we observed that ACEi ameliorated renal fibrosis by mitigating DPP-4 and TGFβ signaling, whereas, ARB did not show. Moreover, the combination of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), one of the substrates of ACE, with ACEi slightly enhanced the inhibitory effects of ACEi on DPP-4 and associated-TGFβ signaling. Further, the comprehensive miRome analysis in kidneys of ACEi+AcSDKP (combination) treatment revealed the emergence of miR-29s and miR-let-7s as key antifibrotic players. Treatment of cultured cells with ACEi alone or in combination with AcSDKP prevented the downregulated expression of miR-29s and miR-let-7s induced by TGFβ stimulation. Interestingly, ACEi also restored miR-29 and miR-let-7 family cross-talk in endothelial cells, an effect that is shared by AcSDKP suggesting that AcSDKP may be partially involved in the anti-mesenchymal action of ACEi. The results of the present study promise to advance our understanding of how ACEi regulates antifibrotic microRNAs crosstalk and DPP-4 associated-fibrogenic processes which is a critical event in the development of diabetic kidney disease.

Endothelial cell-glucocorticoid receptor interactions and regulation of Wnt signaling

Vascular inflammation is present in many cardiovascular diseases, and exogenous glucocorticoids have traditionally been used as a therapy to suppress inflammation. However, recent data have shown that endogenous glucocorticoids, acting through the endothelial glucocorticoid receptor, act as negative regulators of inflammation. Here, we performed ChIP for the glucocorticoid receptor, followed by next-generation sequencing in mouse endothelial cells to investigate how the endothelial glucocorticoid receptor regulates vascular inflammation. We identified a role of the Wnt signaling pathway in this setting and show that loss of the endothelial glucocorticoid receptor results in upregulation of Wnt signaling both in vitro and in vivo using our validated mouse model. Furthermore, we demonstrate glucocorticoid receptor regulation of a key gene in the Wnt pathway, Frzb, via a glucocorticoid response element gleaned from our genomic data. These results suggest a role for endothelial Wnt signaling modulation in states of vascular inflammation.

The Effect of Glucocorticoids on Angiogenesis in the Treatment of Solid Tumors

Glucocorticoids are steroid hormones produced by the adrenal cortex in a circadian manner and they participate in many physiological and pathological processes. Synthetic glucocorticoids have been universally applied to treat inflammatory diseases and immune disorders. Due to their angiostatic property, glucocorticoids are often added to regimens for cancer treatment. In the current review, we summarize how glucocorticoids influence angiogenesis in common solid tumors based on literature from the last ten years. Usage of glucocorticoids can be a double-edged sword in the treatment of some malignancies. There are still unanswered questions about the role of glucocorticoids in the treatment regimens of some common cancers. Therefore, we suggest prudent and restricted administration of glucocorticoids to treat solid tumors.

The Glucocorticoid Receptor in Cardiovascular Health and Disease

The glucocorticoid receptor is a member of the nuclear receptor family that controls many distinct gene networks, governing various aspects of development, metabolism, inflammation, and the stress response, as well as other key biological processes in the cardiovascular system. Recently, research in both animal models and humans has begun to unravel the profound complexity of glucocorticoid signaling and convincingly demonstrates that the glucocorticoid receptor has direct effects on the heart and vessels in vivo and in vitro. This research has contributed directly to improving therapeutic strategies in human disease. The glucocorticoid receptor is activated either by the endogenous steroid hormone cortisol or by exogenous glucocorticoids and acts within the cardiovascular system via both genomic and non-genomic pathways. Polymorphisms of the glucocorticoid receptor are also reported to influence the progress and prognosis of cardiovascular disease. In this review, we provide an update on glucocorticoid signaling and highlight the critical role of this signaling in both physiological and pathological conditions of the cardiovascular system. With increasing in-depth understanding of glucocorticoid signaling, the future is promising for the development of targeted glucocorticoid treatments and improved clinical outcomes.

microRNA Crosstalk Influences Epithelial-to-Mesenchymal, Endothelial-to-Mesenchymal, and Macrophage-to-Mesenchymal Transitions in the Kidney

microRNAs (miRNAs) are small, non-coding nucleotides that regulate diverse biological processes. Altered microRNA biosynthesis or regulation contributes to pathological processes including kidney fibrosis. Kidney fibrosis is characterized by deposition of excess extracellular matrix (ECM), which is caused by infiltration of immune cells, inflammatory cells, altered chemokines, and cytokines as well as activation and accumulation of fibroblasts in the kidney. These activated fibroblasts can arise from epithelial cells via epithelial-to-mesenchymal transition (EMT), from bone marrow-derived M2 phenotype macrophages via macrophage-to-mesenchymal transition (MMT), from endothelial cells via endothelial-to-mesenchymal transition (EndMT), from resident fibroblasts, and from bone marrow-derived monocytes and play a crucial role in fibrotic events. Disrupted microRNA biosynthesis and aberrant regulation contribute to the activation of mesenchymal programs in the kidney. miR-29 regulates the interaction between dipeptidyl peptidase-4 (DPP-4) and integrin β1 and the associated active transforming growth factor β (TGFβ) and pro-EndMT signaling; however, miR-let-7 targets transforming growth factor β receptors (TGFβRs) to inhibit TGFβ signaling. N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is an endogenous anti-fibrotic peptide, which is associated with fibroblast growth factor receptor 1 (FGFR1) phosphorylation and subsequently responsible for the production of miR-let-7. miR-29 and miR-let-7 family clusters participate in crosstalk mechanisms, which are crucial for endothelial cell homeostasis. The physiological level of AcSDKP is vital for the activation of anti-fibrotic mechanisms including restoration of anti-fibrotic microRNA crosstalk and suppression of profibrotic signaling by mitigating DPP-4-associated mesenchymal activation in the epithelial cells, endothelial cells, and M2 phenotype macrophages. The present review highlights recent advancements in the understanding of both the role of microRNAs in the development of kidney disease and their potential as novel therapeutic targets for fibrotic disease states.

Characterization of Long Noncoding RNA and mRNA Profiles in Sepsis-Induced Myocardial Depression

Septic shock with heart dysfunction is very common in intensive care units. However, whether long noncoding RNA (lncRNA) and mRNA profiles differ between patients with and without myocardial depression is unknown. We generated rat models of hypodynamic septic shock induced by lipopolysaccharide. A total of 12 rat models was constructed and heart tissue from each was collected. Whole genomic RNA sequencing was performed on left ventricular tissue; 6,508 novel lncRNAs and 432 annotated lncRNAs were identified in heart samples, and 74 lncRNAs were expressed differently in the sepsis and control groups. Gene ontology term enrichment indicated apoptosis and its related pathways showed obvious enrichment, which suggested cell apoptosis could play a critical role in the process of myocardial depression. Furthermore, we focused on one lncRNA from the Pvt1 gene. By silencing this lncRNA, we demonstrated knockdown of Pvt1 expression could induce cell apoptosis in lipopolysaccharide-induced heart cells, through increasing the expression of c-Myc, Bid, Bax, and caspase-3 and decreasing the expression of Myd88 and Bcl-2, thereby proving its functional role in myocardial depression. These results demonstrate that lncRNAs both participate in and mediate the pathological process of myocardial depression. Our study improves the understanding of the basic molecular mechanisms underlying myocardial depression.

Role of the glucocorticoid receptor in glomerular disease

Glucocorticoids are potent anti-inflammatory agents that are commonly used in the treatment of various glomerular diseases. Data from in vitro and in vivo studies, in both animals and humans, convincingly demonstrate that glucocorticoids have many beneficial direct effects on glomeruli, including podocytes, suggesting that, in theory, systemic administration is not necessary to achieve therapeutic benefit. Indeed, it is increasingly recognized that systemic steroids often have an unfavorable risk-to-benefit ratio. As we move into an age of personalized medicine, strategies to develop targeted steroid delivery systems and individualized risk assessment algorithms are desirable in clinicians' efforts to "first, do no harm."

SIRT3 deficiency leads to induction of abnormal glycolysis in diabetic kidney with fibrosis

The regulation of aberrant glucose metabolism in diabetes associated-kidney fibrosis is not well known. In this study we found the suppression of SIRT3 protein level in diabetic kidney, displays responsibility in fibrogenic programming associated with aberrant glycolysis and such abnormal glycolysis is the therapeutic target in diabetes associated-kidney fibrosis. When analyzing different strains of streptozotocin-induced diabetic mice model (fibrotic model: CD-1, less fibrotic model: C57Bl6), we found SIRT3 suppression was associated with kidney fibrosis in fibrotic CD-1; further SIRT3 suppression by systemic administration of SIRT3 siRNA in the diabetic mice, showed profound fibrogenic phenotype in the kidney. Such suppression in SIRT3 was associated with the induction of transforming growth factor-β (TGF-β)/smad signaling, higher level of HIF1α accumulation and PKM2 dimer formation; these alterations subsequently led to abnormal glycolysis and linked abnormal mesenchymal transformations in vivo and in vitro. Inhibition of such aberrant glycolysis suppressed fibrogenic programming and restored SIRT3 level as well. Such aberrant glycolysis was confirmed in the KK/Ta-Ins2Akita mouse, the mouse model of progressive diabetic kidney disease. These data demonstrate that SIRT3 deficiency promotes abnormal glycolysis which is responsible for the fibrogenic pathway in diabetic kidney. Restoration of SIRT3 could be an alternative strategy in combating diabetes associated-kidney fibrosis via inhibition of aberrant glycolysis.

Lighter and heavier initial loads yield similar gains in strength when employing a progressive wave loading scheme

Progressive wave loading strategies are common within strength and conditioning practice. The purpose of this study was to contribute to the understanding of this strategy by evaluating the effectiveness of 2 wave loading bench press training programmes that differed only in the initial load that was used to start the first wave. Thirty-four resistance-trained men were divided into 2 groups and performed 2 training sessions each week for 20 weeks. One session consisted of 6 sets of 2 repetitions, while the other consisted of 5 sets of 5 repetitions. The load used was incremented by 2.5% of one repetition maximum (1RM) each week until the subject could no longer complete the programmed repetitions. At this point, the load was decreased, and then started to ascend again. The initial loads for the 2 sessions were 87.5% and 80% 1RM respectively for the heavier group, and for the lighter group were 82.5% and 75% 1RM. The subjects experienced a significant improvement in their bench press performance (higher load group: pre test = 106.5 kg ± 14.6, post test = 112.2 kg ± 12.4, p ≤ 0.05; lower load group: pre test = 105.7 kg ± 14.1, post test = 114.3 kg ± 11.0, p ≤ 0.05), but there was no difference in the magnitude of the improvment between the two groups. These results tend to support the common practical recommendation to start with a lighter load when employing a progressive wave loading strategy, as such a strategy yields similar improvements in performance with a lower level of exertion in training.

Endothelial glucocorticoid receptor suppresses atherogenesis--brief report

OBJECTIVE

The purpose of this study was to determine the role of the endothelial glucocorticoid receptor in the pathogenesis of atherosclerosis.

APPROACH AND RESULTS

Control mice and mice lacking the endothelial glucocorticoid receptor were bred onto an Apoe knockout background and subjected to high-fat diet feeding for 12 weeks. Assessment of body weight and total cholesterol and triglycerides before and after the diet revealed no differences between the 2 groups of mice. However, mice lacking the endothelial glucocorticoid receptor developed more severe atherosclerotic lesions in the aorta, brachiocephalic artery, and aortic sinus, as well as a heightened inflammatory milieu as evidenced by increased macrophage recruitment in the lesions.

CONCLUSIONS

These data suggest that the endothelial glucocorticoid receptor is important for tonic inhibition of inflammation and limitation of atherosclerosis progression in this model.

Loss of the endothelial glucocorticoid receptor prevents the therapeutic protection afforded by dexamethasone after LPS

Glucocorticoids are normally regarded as anti-inflammatory therapy for a wide variety of conditions and have been used with some success in treating sepsis and sepsis-like syndromes. We previously demonstrated that mice lacking the glucocorticoid receptor in the endothelium (GR EC KO mice) are extremely sensitive to low-dose LPS and demonstrate prolonged activation and up regulation of NF-κB. In this study we pre-treated these GR EC KO mice with dexamethasone and assessed their response to an identical dose of LPS. Surprisingly, the GR EC KO mice fared even worse than when given LPS alone demonstrating increased mortality, increased levels of the inflammatory cytokines TNF-α and IL-6 and increased nitric oxide release after the dexamethasone pre-treatment. As expected, control animals pre-treated with dexamethasone showed improvement in all parameters assayed. Mechanistically we demonstrate that GR EC KO mice show increased iNOS production and NF-κB activation despite treatment with dexamethasone.

The glucocorticoid receptor in the distal nephron is not necessary for the development or maintenance of dexamethasone-induced hypertension

Glucocorticoids are used as a treatment for a variety of conditions and hypertension is a well-recognized side effect of their use. The mechanism of glucocorticoid-induced hypertension is incompletely understood and has traditionally been attributed to promiscuous activation of the mineralocorticoid receptor by cortisol. Multiple lines of evidence, however, point to the glucocorticoid receptor as an important mediator as well. We have developed a mouse model of glucocorticoid-induced hypertension, which is dependent on the glucocorticoid receptor. To determine the site(s) of glucocorticoid receptor action relevant to the development of hypertension, we studied glucocorticoid-induced hypertension in a mouse with a tissue-specific knockout of the glucocorticoid receptor in the distal nephron. Although knockout mice had similar body weight, nephron number and renal histology compared to littermate controls, their baseline blood pressure was mildly elevated. Nevertheless, distal nephron glucocorticoid receptor knockout mice and controls had a similar hypertensive response to dexamethasone. Urinary excretion of electrolytes, both before and after administration of glucocorticoid was also indistinguishable between the two groups. We conclude that the glucocorticoid receptor in the distal nephron is not necessary for the development or maintenance of dexamethasone-induced hypertension in our model.

A modified version of the Bayley Scales of Infant Development-II for cognitive matching of infants with and without Down syndrome

BACKGROUND

Many measures of infants' early cognitive development, including the BSID-II (The Bayley Scales of Infant Development), mix together test items that assess a number of different developmental domains including language, attention, motor functioning and social abilities, and some items contribute to the assessment of more than one domain. Consequently, the scales may lead to under- or over-estimates of cognitive abilities in some clinical samples and may not be the best measure to use for matching purposes.

METHOD

To address this issue we created a modified form of the BSID-II (the BSID-M) to provide a 'purer' assessment of the general cognitive capacities in infants with Down syndrome (DS) from 6 to 18 months of age. We excluded a number of items that implicated language, motor, attentional and social functioning from the original measure. This modified form was administered to 17 infants with Down syndrome when 6, 12 and 18 months old and to 41 typically developing infants at 4, 7 and 10 months old.

RESULTS

The results suggested that the modified form continued to provide a meaningful and stable measure of cognitive functioning and revealed that DS infants may score marginally higher in terms of general cognitive abilities when using this modified form than they might when using the standard BSID-II scales.

CONCLUSIONS

This modified form may be useful for researchers who need a 'purer' measure with which to match infants with DS and other infants with intellectual disabilities on cognitive functioning.

A critical role for vascular smooth muscle in acute glucocorticoid-induced hypertension

Although glucocorticoid (GC)-induced hypertension has commonly been attributed to promiscuous activation of the mineralocorticoid receptor by cortisol, thereby promoting excess reabsorption of sodium and water, numerous lines of evidence indicate that this is not the only or perhaps even the primary mechanism. GC induce a number of effects on vascular smooth muscle (VSM) in vitro that may be pertinent to hypertension, but their contribution in vivo is unknown. To address this question, a mouse model with a tissue-specific knockout (KO) of the GC receptor in the VSM was created and characterized. Similar to control mice, KO mice exhibited normal baseline BP and, interestingly, showed normal circadian variation in BP. When dexamethasone was administered, however, the acute hypertensive response was markedly attenuated in KO mice, and there was a trend toward a decreased chronic hypertensive response. These data suggest that the GC receptor in VSM plays a critical role in the acute hypertensive response to GC in vivo.

Testing specificity and guidance hypotheses by manipulating relative frequency of KR scheduling in motor skill acquisition

This investigation tested predictions of specificity and guidance hypotheses by manipulating relative frequency of knowledge of results scheduling using a shuffleboard task. Participants were assigned to either a 100%-KR, three 50%-KR conditions (Constant, Fade, Reverse), or 00%-KR condition. Based on predictions of the specificity hypothesis, it was expected the 00%-KR condition would perform the best on a no-KR retention test. It was also expected the 100%-KR condition would perform poorly on a no-KR retention test based on predictions of the guidance hypothesis. Analysis for 55 men's and 55 women's retention did not support predictions of the specificity hypothesis and provided partial support for the guidance hypothesis.

Athletic training education programs: to rank or not to rank?

OBJECTIVE

To discuss the literature regarding educational program ranking and to provide insights concerning undergraduate and graduate athletic training education ranking systems.

BACKGROUND

The demand for accountability and the need to evaluate the quality of educational programs have led to program ranking in many academic disciplines. As athletic training becomes more recognized within the medical community, determining a program's quality will become increasingly important.

DESCRIPTION

We describe program rankings used in other disciplines for determining quality and providing measures of accountability. We discuss the strengths and weaknesses of both subjective and objective ranking systems, as well as the arguments for using program rankings in athletic training. Future directions for program ranking and potential research questions are suggested.

APPLICATIONS

Ranking systems on the basis of levels of perceived quality and academic productivity of programs that prepare future professionals will help potential undergraduate and graduate students make informed decisions when selecting an educational program.

Effect of different quantities of variable practice on acquisition, retention, and transfer of an applied motor skill

This investigation examined the effect of manipulating different quantities of variable practice in the acquisition phase on the retention and transfer performance of a dart throw. Participants in the Specific condition practiced a total of 75 acquisition trials from a distance of 2.39 m. Participants in the Specific + Variable condition practiced a total of 75 acquisition trials with 25 trials from distances of 1.47 m, 2.39 m, and 3.30 m. Participants in the Specific + Varplus condition practiced a total of 75 acquisition trials with 15 trials from distances of 1.47 m, 1.93 m, 2.39 m, 2.84 m, and 3.30 m. Results of the one-way analysis of variance on the 24-hr. retention test from 2.39 m yielded no significant differences among practice conditions for mean radial error. A one-way analysis of variance on the 24-hr. transfer test from 3.76 m indicated that the Specific + Variable and Specific + Varplus conditions performed with significantly smaller mean radial error than the Specific condition. The results are discussed in regard to recent research and applicability to instructional settings.

Investigation of the contextual interference effect in the manipulation of the motor parameter of over-all force

This investigation examined the contextual interference effect when manipulating over-all force in a golf-putting task. Undergraduate women (N = 30) were randomly assigned to a Random, Blocked-Random, or Blocked practice condition and practiced golf putting from distances of 2.43 m, 3.95 m, and 5.47 m during acquisition. Subjects in the Random condition practiced trials in a quasirandom sequence and those in the Blocked-Random condition practiced trials initially in a blocked sequence with the remainder of the trials practiced in a quasirandom sequence. In the Blocked condition subjects practiced trials in a blocked sequence. A 24-hr. transfer test consisted of 30 trials with 10 trials each from 1.67 m, 3.19 m, and 6.23 m. Transfer scores supported the Magill and Hall (1990) hypothesis that, when task variations involve learning parameters of a generalized motor program, the benefit of random practice over blocked practice would not be found.

Using bandwidth knowledge of results to alter relative frequencies during motor skill acquisition

This investigation examined the predictions of the guidance and specificity hypotheses by manipulating different distributions of relative frequency of knowledge of results (KR) using bandwidth (BW) conditions. Subjects (N = 120) were randomly assigned to either a BW0%, BW10%, Shrinking-BW, or Expanding-BW condition. After 100 acquisition trials were completed, a double transfer design was employed in which the subjects were divided in half and randomly assigned to a no-KR or KR retention condition. Retention tests of 10 min and 48 hr were completed under a no-KR or KR retention condition. Results of the 48-hr retention test under the no-KR retention condition suggested that receiving high relative frequencies of KR at the end of the acquisition phase was as detrimental to motor skill learning as receiving high relative frequencies of KR throughout acquisition. The results are discussed with respect to the guidance and specificity hypotheses.