The influence of acute exercise on bone biomarkers: protocol for a systematic review with meta-analysis.

BACKGROUND: Bone is a plastic tissue that is responsive to its physical environment. As a result, exercise interventions represent a potential means to influence the bone. However, little is currently known about how various exercise and participant characteristics interact to influence bone metabolism. Acute, controlled, interventions provide an in vivo model through which the acute bone response to exercise can be investigated, typically by monitoring circulating bone biomarkers. Currently, substantial heterogeneity in factors such as study design, quality, exercise, and participant characteristics render it difficult to synthesize and evaluate the available evidence. Using a systematic review and meta-analytic approach, the aim of this investigation is to quantify the effect of an acute exercise bout on circulating bone biomarkers as well as examine the potential factors that may moderate this response, e.g., variation in participant, exercise, and sampling characteristics. METHODS: This protocol was designed in accordance with the PRISMA-P guidelines. Seven databases (MEDLINE, Embase, Sport Discus, Cochrane CENTRAL, PEDro, LILACS, and Ibec) will be systematically searched and supplemented by a secondary screening of the reference lists of all included articles. The PICOS (Population, Intervention, Comparator, Outcomes and Study Design) approach was used to guide the determination of the eligibility criteria. Participants of any age, sex, training, or health status will be considered for inclusion. We will select studies that have measured the bone biomarker response before and after an acute exercise session. All biomarkers considered to represent the bone metabolism will be considered for inclusion, and sensitivity analyses will be conducted using reference biomarkers for the measurement of bone resorption and formation (namely ß-CTX-1 and P1NP). Multi-level, meta-regression models within a Bayesian framework will be used to explore the main effect of acute exercise on bone biomarkers as well as potential moderating factors. The risk of bias for each individual study will be evaluated using a modified version of the Downs and Black checklist while certainty in resultant outcomes will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. DISCUSSION: A better understanding of the bone metabolic response to an acute bout of exercise has the potential to advance our understanding of the mechanisms through which this stimulus impacts bone metabolism, including factors that may moderate this response. Additionally, we will identify current gaps in the evidence base and provide recommendations to inform future research. SYSTEMATIC REVIEW REGISTRATION: This protocol was prospectively registered in the Open Science Framework Registry ( https://osf.io/6f8dz ).

Effects of montmorency tart cherry (L. Prunus Cerasus) consumption on nitric oxide biomarkers and exercise performance.

The purpose of this study was to investigate the effects of Montmorency tart cherry juice (MC) on nitric oxide (NO) biomarkers, vascular function, and exercise performance. In a randomized, double-blind, placebo (PLA)-controlled, crossover study, 10 trained cyclists (mean ± SD; V˙O2peak 59.0 ± 7.0 mL/kg/min) acutely ingested 30 mL of either MC or PLA following dietary restrictions of polyphenol-rich compounds and completed 6-minutes moderate- and severe-intensity cycling bouts 1.5 hour post-ingestion on 2 occasions for each experimental condition. The severe-intensity cycling test was continued to exhaustion on 1 occasion and immediately followed by a 60-seconds all-out sprint on the other occasion. Blood pressure, pulse wave measures, tissue oxygenation index, and plasma nitrite concentration were assessed pre- and 1.5 hour post-ingestion. Time to exhaustion was not different between conditions (P > .05), but peak power over the first 20 seconds (363 ± 42 vs 330 ± 26 W) and total work completed during the 60-seconds all-out sprint (21 ± 3 vs 19 ± 3 kJ) were 10% higher in the MC trial compared to the PLA trial (P < .05). Systolic blood pressure was 5 ± 2 mm Hg lower 1.5 hour post-MC supplementation compared to PLA supplementation (P < .05). There were no differences in pulse wave measures, plasma nitrite concentration, or tissue oxygenation between the MC and PLA trials (P > .05). These results suggest that acute supplementation with MC can lower blood pressure and improve some aspects of exercise performance, specifically end-sprint performance, in trained cyclists.

Montmorency Tart cherries (Prunus cerasus L.) modulate vascular function acutely, in the absence of improvement in cognitive performance.

Cerebral blood volume and metabolism of oxygen decline as part of human ageing, and this has been previously shown to be related to cognitive decline. There is some evidence to suggest that polyphenol-rich foods can play an important role in delaying the onset or halting the progression of age-related health disorders such as CVD and Alzheimer's disease and to improve cognitive function. In the present study, an acute, placebo-controlled, double-blinded, cross-over, randomised Latin-square design study with a washout period of at least 14 d was conducted on twenty-seven, middle-aged (defined as 45-60 years) volunteers. Participants received either a 60 ml dose of Montmorency tart cherry concentrate (MC), which contained 68·0 (sd 0·26) mg cyanidin-3-glucoside/l, 160·75 (sd 0·55) mean gallic acid equivalent/l and 0·59 (sd 0·02) mean Trolox equivalent/l, respectively, or a placebo. Cerebrovascular responses, cognitive performance and blood pressure were assessed at baseline and 1, 2, 3 and 5 h following consumption. There were significant differences in concentrations of total Hb and oxygenated Hb during the task period 1 h after MC consumption (P≤0·05). Furthermore, MC consumption significantly lowered systolic blood pressure (P≤0·05) over a period of 3 h, with peak reductions of 6±2 mmHg at 1 h after MC consumption relative to the placebo. Cognitive function and mood were not affected. These results show that a single dose of MC concentrate can modulate certain variables of vascular function; however, this does not translate to improvements in cognition or mood.

Contribution of the ICE family to neurodegeneration.

The ICE family of cysteine proteases mediates necrotic or apoptotic events in the nervous system as well as in other tissues. This suggests that inhibitors may be of therapeutic value in acute and, perhaps, chronic neurodegenerative disease. In addition, some members of this family may respond to intercellular signals controlling proliferation or differentiation. This possibility should be kept in mind as therapeutics are pursued.

Inhibition of the interleukin-1 beta converting enzyme family rescues neurons from apoptotic death.

The interleukin-1 beta converting enzyme (ICE) family of cysteine proteases has been implicated in apoptosis. This study tested the effects of a novel pan-ICE family inhibitor, bocaspartyl(OMe)-fluoromethylketone (boc-Asp-CH2F), against low potassium-induced apoptosis of cultured rat cerebellar granule neurons (CGN). A single application of this cell-permeant compound (20 microM) inhibited apoptotic cell death up to 48 h. Classical apoptotic changes were monitored by fluorescence microscopy, DNA fragmentation and scanning electron microscopy (SEM). A control peptidic fluoromethylketone (boc-Thr-CH2F), and inhibitors to calpain (Ac-Leu-Leu-norleucinal), cathepsin B (Z-Phe-Ala-CH2F), and CPP32-like proteases (Z-DEVD-CH2F), failed to prevent apoptotic death. An 35S-methionine incorporation assay verified that, unlike cycloheximide, boc-Asp-CH2F did not inhibit protein synthesis, hence excluding this as a rescuing mechanism. Although ICE was not detected by northern blot analysis, both CPP32 and Nedd2 expression were found to increase during apoptosis. Kinetic assays with cell extracts from boc-Asp-CH2F-treated neurons measured reduced rates of cleavage for DEVD-pNA and LEVD-pNA. At present, ICE-like proteases remain viable candidates for mediating neuronal death.

IL-1 beta converting enzyme (ICE) is not required for apoptosis induced by lymphokine deprivation in an IL-2-dependent T cell line.

Clonal T cells undergo programmed cell death (PCD) or apoptosis when cultured without the appropriate cytokines. The cysteine protease, IL-1 beta converting enzyme (ICE), is implicated in apoptosis based on its structural similarity to the PCD gene, ced-3, in Caenorhabditis elegans and the induction of PCD in fibroblasts transfected with recombinant ICE. We show that the murine IL-2-dependent CTLL T cell line expresses ICE but not IL-1 beta. Interestingly, ICE mRNA and protein levels increase during apoptosis. Yet inhibition of ICE enzymatic activity (> 90%) with either of two cell-permeable ICE inhibitors does not abrogate or delay apoptosis following IL-2 deprivation, as measured by DNA fragmentation and viability. Our results suggest that ICE is not required for apoptosis in lymphokine-deprived T cells.

Cloning, tissue expression and regulation of rat interleukin 1 beta converting enzyme.

Using oligomer primers based on the cDNA sequence of human interleukin 1 beta converting enzyme (ICE), we have employed the RT-PCR method and rat spleen RNA to clone and sequence rat ICE. We report here that the predicted amino acid sequence of rat ICE proenzyme consists of 402 amino acids (p45) and shares 61% and 90% identity, respectively, with human and mouse ICE amino acid sequences. The active site cysteine (Cys284) and 3 or 3 potential processing sites are conserved suggesting that their the rat ICE heterodimer consists of a p22 (Ser104-Asp296) and a p10 (Gly315-His402) subunit or a cryptic processing site creates a smaller heterodimer. Northern blot analysis has revealed a approximately 2.2 kb and a more abundant approximately 1.45 kb ICE transcript both widely expressed in the rat with the highest expression in spleen and intestine and lowest in brain. IL-1 beta mRNA was similarly distributed. Injection of the immunostimulant, lipopolysaccharide (0.2 mg/kg, i.p.), increased rICE mRNA content between 2- to 3-fold in the rat brain with smaller increases measured in testis and spleen. The structural conservation of this enzyme suggests that rat models of inflammation will be useful for evaluating the therapeutic potential of ICE inhibitors in humans.

Expression of growth hormone receptor, insulin-like growth factor 1 (IGF-1) and IGF-1 receptor mRNA and proteins in human skin.

A cDNA corresponding to the membrane receptor for growth hormone (GH) was amplified by polymerase chain reaction (PCR) directly from human skin. The cDNA was cloned and found to have complete sequence homology to the extracellular domain of human liver GH receptor (GH-R). Northern analysis, using the cloned GH-R as probe, revealed relatively higher levels of GH-R transcripts in cultured human dermal fibroblasts compared to cultured keratinocytes or keratome biopsies. Semi-quantitative PCR analysis indicated that the level of GH-R mRNA in cultured melanocytes was similar to that in fibroblasts. The receptor protein encoded by GH-R mRNA in fibroblasts was shown by affinity cross-linking to have an apparent M(r) of 115-120 kDa, similar to that of 3T3-F442A fibroblasts used as a control. mRNA transcripts for the major mediator of GH actions, insulin-like growth factor 1 (IGF-1), were detected by PCR in fibroblasts, melanocytes, and keratome biopsies, but not in keratinocytes. In contrast, IGF-1 receptor mRNA were abundant in cultured keratinocytes and skin biopsies, as determined by Northern analysis. IGF-1 but not GH (5-50 ng/ml) promoted clonal proliferation of cultured keratinocytes. In contrast, GH (10 ng/ml) after 5 d markedly increased fibroblast cell numbers (70%, p less than 0.009) over 0.2% serum control. These data indicate that human skin cells possess the molecular elements necessary to respond to GH and raise the possibility that GH may influence skin growth in vivo.

Cellular localization of mRNA for cellular retinoic acid-binding protein II and nuclear retinoic acid receptor-gamma 1 in retinoic acid-treated human skin.

We have previously shown that cellular retinoic acid-binding protein II (CRABP-II), but not cellular retinoic acid-binding protein I (CRABP-I), mRNA expression is markedly induced in human skin by topical retinoic acid. In the present study, we have investigated the pattern of expression of CRABP-II transcripts in 4-d RA-treated human skin by non-radioactive in situ hybridization (n = 5) and Northern analysis (n = 4). RA induced accumulation of CRABP-II transcripts throughout the epidermis, dermal fibroblasts, and endothelial cells as determined by in situ hybridization. In skin treated with vehicle, a faint hybridization signal was observed only in basal layers of the epidermis consistent with low-level expression of CRABP-II mRNA. RA-mediated accumulation of CRABP-II transcripts in skin was also confirmed by Northern analysis. Neither RA nor vehicle induced significant changes in nuclear RA receptor-gamma 1 or keratin 5 gene expression in skin as determined by in situ or Northern hybridization. These results indicate that RA-induced CRABP-II mRNA accumulation is primarily localized to spinous and granular layers in epidermis, and in superficial dermis.