Repeatability of exercise-induced changes in mRNA expression and technical considerations for qPCR analysis in human skeletal muscle

NEW FINDINGS

What is the central question of this study? Are individual changes in exercise-induced mRNA expression repeatable (i.e. representative of the true response to exercise rather than random error)? What is the main finding and its importance? Exercise-induced changes in mRNA expression are not repeatable even under identical experimental conditions, thereby challenging the use of mRNA expression as a biomarker of adaptive potential and/or individual responsiveness to exercise.

ABSTRACT

It remains unknown if (1) the observed change in mRNA expression reflects an individual's true response to exercise or random (technical and/or biological) error, and (2) the individual responsiveness to exercise is protocol-specific. We examined the repeatability of skeletal muscle PGC-1α, PDK4, NRF-1, VEGF-A, HSP72 and p53 mRNA expression following two identical endurance exercise (END) bouts (END-1, END-2; 30 min of cycling at 65% of peak work rate (WR_peak ), n = 11) and inter-individual variability in PGC-1α and PDK4 mRNA expression following END and sprint interval training (SIT; 8 × 20 s cycling intervals at ∼170% WR_peak , n = 10) in active young males. The repeatability of key gene analysis steps (RNA extraction, reverse transcription, qPCR) and within-sample fibre-type distribution (n = 8) was also determined to examine potential sources of technical error in our analyses. Despite highly repeatable exercise bout characteristics (work rate, heart rate, blood lactate; ICC > 0.71; CV < 10%; r > 0.85, P < 0.01), gene analysis steps (ICC > 0.73; CV < 24%; r > 0.75, P < 0.01), and similar group-level changes in mRNA expression, individual changes in PGC-1α, PDK4, VEGF-A and p53 mRNA expression were not repeatable (ICC < 0.22; CV > 20%; r < 0.21). Fibre-type distribution in two portions of the same muscle biopsy was highly variable and not significantly related (ICC = 0.39; CV = 26%; r = 0.37, P = 0.37). Since individual changes in mRNA expression following identical exercise bouts were not repeatable, inferences regarding individual responsiveness to END or SIT were not made. Substantial random error exists in changes in mRNA expression following acute exercise, thereby challenging the use of mRNA expression for analysing individual responsiveness to exercise.

Pregnancy Outcomes Following In Utero Exposure to Lamotrigine: A Systematic Review and Meta-Analysis

INTRODUCTION

Lamotrigine is used in pregnancy to control epilepsy and mood disorders. The reproductive safety of this widely used drug remains undefined and may represent a significant public health concern.

OBJECTIVE

We aimed to perform a systematic review and meta-analysis of existing knowledge related to malformation rates and maternal-neonatal outcomes after in utero exposure to monotherapy with lamotrigine.

METHODS

Relevant studies were identified through systematic searches conducted in MEDLINE (Ovid), Embase (Ovid), CENTRAL (Ovid), and Web of Science (Thomson Reuters) from database inception to July 2016; no language or date restrictions were applied. All publications of clinically relevant outcomes of pregnancies following in utero exposure to lamotrigine were included in this systematic review and meta-analysis.

RESULTS

A total of 21 studies describing immediate pregnancy outcomes and rates of congenital malformations fulfilled the inclusion criteria. Compared with disease-matched controls (n = 1412, total number of patients) and healthy controls (n = 774,571, total number of patients), in utero exposure to lamotrigine monotherapy was found to be associated with significantly decreased rates of inborn defects (odds ratio [OR] 1.15; 95% confidence interval [CI] 0.62-2.16 and OR 1.25; 95% CI 0.89-1.74, respectively). Rates of miscarriages, stillbirths, preterm deliveries, and small for gestational age (SGA) neonates were not found to have been increased after in-utero exposure to LTG compared to the general population. Similarly, in utero exposure to lamotrigine monotherapy was not found to be associated with increased rates of inborn defects compared with in utero exposure to carbamazepine, and lamotrigine was found to be statistically significantly less teratogenic than valproic acid (n = 12,958 and 10,748; OR 0.84; 95% CI 0.68-1.03 and OR 0.32; 95% CI 0.26-0.39, respectively).

CONCLUSION

No association was found between prenatal lamotrigine monotherapy and increased rates of birth defects and other explored variables related to adverse pregnancy outcomes.

Preserving central blood volume: changes in body fluid compartments during hemodialysis

The understanding of fluid changes during hemodialysis (HD is essential for reducing complications as well as efficacy of the procedure. Bioimpedance spectroscopy provides a non invasive method of measuring total body water (TBW), the distribution of intra (ICF) and extracellular (ECF) fluids, and their changes during HD. Segmental bioimpedance may be used to measure the same fluid shifts but from different body segments; the technique has previously been shown to com pare well with whole body measures. It is possible that fluid shifts occur differently in different body compartments during HD. Based on previous hemodynamic studies we postulated that during HD ultrafiltration (UF) the body attempts to preserve its central blood volume (cardiopulmonary circula tion plus great vessels), and thus fluid shifts would be greater from the periphery than from central compartments. To test this hypothesis, segmental bioimpedance (Xitron Technolo gies, San Diego, CA) was performed on 11 subjects undergoing HD where ECF and ICF values were obtained from the legs, arms and trunk before and after a period of UF. Blood volume change (ABV%) was also followed using an on-line optical hematocrit (Hct) sensor (Crit-Line monitor, In-Line Diagnostics, UT) where deltaBV% = deltaBV% = (1 - Hct1/Hct0) x 100 (Hct0 = baseline Hct; Hct1 = postultrafiltration Hct) The UF of 2.0 L +/- 0.79 L (M +/- SD) over 75 minutes was associated with a deltaBV% of -9.43% +/- 3.6% (M +/- SD), a significant (Student's paired t-test) reduction in total body (TB) ECF (p < 0.02), a weak correlation in reduction in TBW (p = 0.09) but not in TB ICF. The ECF reductions from the trunk, legs, and arms were all significant (minimum p < 0.02); no ICF changes from these compartments were significant. The amount of ECF reduction was greater from the legs (0.7 L +/- 0.6 L) than the arms (0.12 L +/- 0.08 L) and trunk (0.2 L +/- 0.2 L) (all M +/- SD). Multiple regression analysis showed that TB ECF changes correlated strongly with leg (r = 0.94, p < 0.001) and arm (r = 0.72, p = 0.002) ECF changes but not with trunk changes. deltaBV% correlated weakly with leg (r = 0.45, p = 0.08) and arm (r = 0.42, p = 0.10) ECF changes but not with the trunk. As the deltaBV% represents the net volume change between UF and plasma water refilling, thiss indicates that plasma water is being removed more from the peripheral compartments than from the trunk. These data suggest that plasma refilling during HD to preserve central blood volume is more dynamic from the leg ECF than from elsewhere and may, in turn, explain the frequent occurrence of leg cramps during and after hemodialysis.

Primary uroepithelial cultures. A model system to analyze umbrella cell barrier function

Despite almost 25 years of effort, the development of a highly differentiated and functionally equivalent cell culture model of uroepithelial cells has eluded investigators. We have developed a primary cell culture model of rabbit uroepithelium that consists of an underlying cell layer that interacts with a collagen substratum, an intermediate cell layer, and an upper cell layer of large (25-100 micrometer) superficial cells. When examined at the ultrastructural level, the superficial cells formed junctional complexes and had an asymmetric unit membrane, a hallmark of terminal differentiation in bladder umbrella cells. These cultured "umbrella" cells expressed uroplakins and a 27-kDa uroepithelial specific antigen that assembled into detergent-resistant asymmetric unit membrane particles. The cultures had low diffusive permeabilities for water (2.8 x 10(-4) cm/s) and urea (3.0 x 10(-7) cm/s) and high transepithelial resistance (>8000 Omega cm2) was achieved when 1 mM CaCl2 was included in the culture medium. The cell cultures expressed an amiloride-sensitive sodium transport pathway and increases in apical membrane capacitance were observed when the cultures were osmotically stretched. The described primary rabbit cell culture model mimics many of the characteristics of uroepithelium found in vivo and should serve as a useful tool to explore normal uroepithelial function as well as dysfunction as a result of disease.

Effect of nonsteroidal anti-inflammatory drugs on the action of misoprostol in a regimen for early abortion

Nonsteroidal anti-inflammatory drugs are frequently avoided by some investigators in protocols for medical abortion because of a concern over potential inhibition of prostaglandin action on uterine contractions. To evaluate the effects of nonsteroidal anti-inflammatory drugs on uterine cramping and resultant pregnancy expulsion, analgesic use by 449 participants with gestational age of < or = 56 days in three previously reported medical abortion trials involving methotrexate and misoprostol was reviewed. Subjects from each of the three trials were included in this analysis only if they received 50 mg/m2 methotrexate intramuscularly followed 3 or 7 days later by 800 micrograms misoprostol vaginally. Misoprostol administration was repeated if the abortion did not occur after the first misoprostol dose. A total of 416 subjects met the study criteria. For the women who took a nonsteroidal anti-inflammatory drug after the first dose of misoprostol, 132/246 (53.7%) aborted within 24 h. For those that did not take a nonsteroidal anti-inflammatory drug, 83/170 (48.8%, p = 0.38) aborted within 24 h. Similarly, 27/56 (48.2%) of the women who took a nonsteroidal anti-inflammatory drug aborted within 24 h of the second dose of misoprostol. However, only 32/145 (22.1%, p = 0.002) of the women who did not take a nonsteroidal anti-inflammatory drug aborted. Use of a nonsteroidal anti-inflammatory drug does not interfere with the action of misoprostol to induce uterine contractions and pregnancy expulsion in women receiving methotrexate and misoprostol for early abortion.

An antibody reactive with domain 4 of the platelet-derived growth factor beta receptor allows BB binding while inhibiting proliferation by impairing receptor dimerization

A panel of murine monoclonal antibodies was generated against the extracellular domain of the human platelet-derived growth factor (PDGF) beta receptor (PDGFRbeta). These antibodies were assayed for both the ability to inhibit binding of PDGF BB to PDGFRbeta+ cells as well as the capacity to inhibit PDGF BB-mediated mitogenesis. As expected, all antibodies that could prevent PDGF BB binding also inhibited mitogenesis. However one antibody (M4TS.11), with no detectable ability to inhibit PDGF BB binding, was a potent inhibitor of proliferation induced by PDGF BB. Further characterization indicated that M4TS.11 impaired PDGFRbeta dimerization, revealing the mechanism by which it prevented PDGF BB-mediated mitogenesis. Using domain deletion mutants of the extracellular portion of PDGFRbeta, the determinant recognized by this antibody was localized to the fourth extracellular domain of PDGFRbeta, indicating that this domain, which is not involved in ligand binding, actively participates in receptor dimerization and signal transduction. The M4TS.11 antibody could also inhibit PDGF BB-mediated proliferation of responsive cells from both the baboon and the rabbit, indicating the determinant recognized by the antibody is not limited to humans and making it possible to use this antibody to evaluate the therapeutic benefit of interfering with PDGF in animal models of human disease.