One class of poststroke restorative therapy focuses on promoting axon outgrowth by blocking myelin-based inhibitory proteins such as myelin-associated glycoprotein. The purpose of the current study ...was to extend preclinical and clinical findings of GSK249320, a humanized monoclonal antibody to myelin-associated glycoprotein with disabled Fc region, to explore effects on motor outcomes poststroke.
In this phase IIb double-blind, randomized, placebo-controlled study, patients at 30 centers with ischemic stroke 24 to 72 hours prior and gait deficits were randomized to 2 IV infusions of GSK249320 or placebo. Primary outcome measure was change in gait velocity from baseline to day 90.
A total of 134 subjects were randomized between May 2013 and July 2014. The 2 groups were overall well matched at baseline. The study was stopped at the prespecified interim analysis because the treatment difference met the predefined futility criteria cutoff; change in gait velocity to day 90 was 0.55±0.46 (mean±SD) in the GSK249320 group and 0.56±0.50 for placebo. Secondary end points including upper extremity function were concordant. The 2 IV infusions of GSK249320 were well tolerated. No neutralizing antibodies to GSK249320 were detected.
GSK249320, within 72 hours of stroke, demonstrated no improvement on gait velocity compared with placebo. Possible reasons include challenges translating findings into humans and no direct evidence that the therapy reached the biological target. The antibody was well tolerated and showed low immunogenicity, findings potentially useful to future studies aiming to use a monoclonal antibody to modify activity in specific biological pathways to improve recovery from stroke.
URL: http://www.clinicaltrials.gov. Unique identifier: NCT01808261.
Abstract Investigations of intermanual transfer of learning have demonstrated that individuals can transfer acquired motor skills from one hand to the other. The purpose of the current study was to ...use fMRI to investigate the potential overlap of neural regions engaged during learning and at transfer of learning from the dominant arm to the non-dominant arm during sensorimotor adaptation. Participants performed a visuomotor adaptation joystick task where they adapted manual aiming movements to a 30° rotation of the visual feedback display. They performed eleven blocks (24 trials/block) of right-hand adaptation before performing the task with their left hand (transfer). Participants showed a selective transfer of learning effect: prior right-hand practice led to reduced endpoint errors but not trajectory errors for the left hand. This is consistent with work showing that the right arm is specialized for trajectory control while the left is specialized for endpoint control Sainburg, R.L., 2005. Handedness, Differential specializations for control of trajectory and position. Exerc Sport Sci Rev 33, 206–213.. Early adaptation processes were associated with activation in frontal and parietal regions, including bilateral dorsal premotor cortex. At transfer, activation was seen in the temporal cortex as well as the right medial frontal gyrus and the middle occipital gyrus. These regions have been observed in other studies during the late phases of sensorimotor adaptation. Integrating these data with the existing literature, we suggest that the left dorsal premotor cortex contributes to trajectory control, while the left visual and temporal cortices contribute to endpoint control.
Serum leptin levels are upregulated in proportion to body fat and also increase over the short term in response to meals or insulin. To understand the mechanisms involved, we assessed leptin ...synthesis and secretion in samples of adipose tissue from subjects with a wide range of BMI. Tissue leptin content and relative rates of leptin biosynthesis, as determined by metabolic labeling, were highly correlated with each other and with BMI and fat cell size. To understand mechanisms regulating leptin synthesis in obesity, we used biosynthetic labeling to directly assess the effects of insulin and glucocorticoids (dexamethasone) on leptin synthesis and secretion in human adipose tissue. Chronic treatment (1-2 days in organ culture) with insulin increased relative rates of leptin biosynthesis without affecting leptin mRNA levels. In contrast, dexamethasone increased leptin mRNA and biosynthesis in parallel. Acute treatment with insulin or dexamethasone (added during 1-h preincubation and 45-min pulse labeling) did not affect relative rates of leptin biosynthesis, but pulse-chase studies showed that addition of insulin nearly doubled the release of 35Sleptin after a 1-h chase. We conclude that the higher leptin stores in adipose tissue of obese humans are maintained by chronic effects of insulin and glucocorticoids acting at pre- and posttranslational levels and that the ability of insulin to increase the release of preformed leptin may contribute to short-term variations in circulating leptin levels.
Regulation of Leptin Production in Humans Fried, Susan K.; Ricci, Matthew R.; Russell, Colleen D. ...
The Journal of nutrition,
12/2000, Letnik:
130, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Serum levels of the adipocyte hormone leptin are increased in proportion to body fat stores as a result of increased production in enlarged fat cells from obese subjects. In vitro studies indicate ...that insulin and glucocorticoids work directly on adipose tissue to upregulate in a synergistic manner leptin mRNA levels and rates of leptin secretion in human adipose tissue over the long term. Thus, the increased leptin expression observed in obesity could result from the chronic hyperinsulinemia and increased cortisol turnover. Superimposed upon the long-term regulation, nutritional status can influence serum leptin over the short term, independent of adiposity. Fasting leads to a gradual decline in serum leptin that is probably attributable to the decline in insulin and the ability of catecholamines to decrease leptin expression, as observed in both in vivo and in vitro studies. In addition, increases in serum leptin occur ∼4–7 h after meals. Increasing evidence indicates that insulin, in concert with permissive effects of cortisol, can increase serum leptin over this time frame and likely contributes to meal-induced increases in serum leptin. Further research is required to elucidate the cellular and molecular mechanisms underlying short- and long-term nutritional and hormonal regulation of leptin production and secretion.
GHRP-2 is a synthetic agonist of ghrelin, the newly-discovered gut peptide which binds to the growth hormone (GH) secretagogue receptor. Ghrelin has two major effects, stimulating both GH secretion ...and appetite/meal initiation. GHRP-2 has been extensively studied for its utility as a growth hormone secretagogue (GHS). Animal studies have shown its effect on food intake. However, whether GHRP-2 can also stimulate appetite in humans when administered acutely is not known. We subcutaneously infused 7 lean, healthy males with GHRP-2 (1 μg/kg/h) or saline for 270 minutes and then measured their intake of an ad libitum, buffet-style meal. Similar to what has been reported for ghrelin administration, our subjects ate 35.9 ± 10.9% more when infused with GHRP-2 vs. saline, with every subject increasing their intake even when calculated per kg body weight (136.0 ± 13.0 kJ/kg 32.5 ± 3.1 kcal/kg vs. 101.3 ± 10.5 kJ/kg 24.2 ± 2.5 kcal/kg, p = 0.008). The macronutrient composition of consumed food was not different between conditions. As expected, serum GH levels rose significantly during GHRP-2 infusion (AUC 5550 ± 1090 μg/L/240 min vs. 412 ± 161 μg/L/240 min, p = 0.003). These data are the first to demonstrate that GHRP-2, like ghrelin, increases food intake, suggesting that GHRP-2 is a valuable tool for investigating ghrelin effects on eating behavior in humans.
In vivo and in vitro studies indicate that beta-adrenergic receptor agonists decrease leptin release from fat cells in as little as 30 min. Our objective was to determine whether alterations in ...leptin biosynthesis or secretion were involved in the short-term adrenergic regulation of leptin in human and rat adipose tissue. Isoproterenol (Iso) decreased leptin release from incubated adipose tissue of both nonobese and obese subjects to similar extent (-28 vs. -21% after 3 h). Inhibition of protein synthesis with cycloheximide did not block the effect of Iso on leptin release from human adipose tissue, suggesting that the Iso effect is independent of leptin synthesis. Iso also tended to increase tissue leptin content at the end of the 3-h incubation, as expected from the observed inhibition of release. Consistent with a posttranslational mechanism, Iso treatment did not affect leptin mRNA levels or relative rate of leptin biosynthesis as directly assessed by 35Smethionine incorporation into immunoprecipitable leptin. In contrast to these results in human adipose tissues, Iso did not decrease basal leptin release from rat adipose tissue. However, Iso did decrease insulin-stimulated leptin release by inhibiting the ability of insulin to increase leptin biosynthesis without detectably affecting leptin mRNA levels. Thus, in both human and rat, adrenergic regulation of posttranscriptional events (secretion in humans, translation in rats) may contribute to the rapid decline in circulating leptin that occurs when the sympathetic nervous system is activated, such as during fasting and cold exposure. Furthermore, the rat does not provide an ideal model to study mechanisms of cellular leptin regulation in humans.
Mineralogical transformations of 2-line ferrihydrite were studied under oxic and Fe3+-reducing conditions to establish the role, if any, of 6-line ferrihydrite ("well" organized ferrihydrite) in the ...reaction pathway and as a final product. In oxic experiments, concentrated suspensions (0.42 mol/L Fe3+ in 0.1 mol/L NaClO4) of freshly synthesized 2-line ferrihydrite, with and without 3% Ni2+, were aged at an initial pH = 7.2 (unbuffered and unadjusted) and 25°C for more than three years. X-ray diffraction, transmission electron microscopy, and Mossbauer spectroscopy measurements were performed on the solids after different aging periods. The primary mineralogical products observed were 6-line ferrihydrite and goethite, with minor hematite. Aggregation and crystallization of the 2-line ferrihydrite liberated protons and depressed suspension pH, but coprecipitated Ni2+ retarded this process. The joint, interrelated effects of Ni and pH influenced both the extent of conversion of 2-line ferrihydrite and the identity of the major transformation products. Six-line ferrihydrite dominated in the Ni ferrihydrite suspension, whereas goethite dominated in the absence of Ni. Aggregation-induced crystallization of 2-line ferrihydrite particles seemed responsible for 6-line ferrihydrite formation. Mineralogical changes to Ni ferrihydrite under anaerobic conditions were investigated at circumneutral pH using the Fe3+-reducing bacterium Shewanella putrefaciens. Residual 6-line ferrihydrite dominated bioreduced samples that also contained goethite and magnetite. The conversion of 2-line ferrihydrite to 6-line ferrihydrite was considerably more rapid under anaerobic conditions. The sorption of biogenic Fe2+ apparently induced intra-aggregate transformation of 2-line ferrihydrite to 6-line ferrihydrite. Collectively, abiotic and biotic studies indicated that 6-line ferrihydrite can be a transformation product of 2-line ferrihydrite, especially when 2-line ferrihydrite is undergoing transformation to more stable hematite or magnetite.
Context: Administration of glucocorticoids increases serum leptin levels in lean and obese individuals. A morning meal produces an increase in insulin, a cortisol peak, and an increase in leptin; ...these changes do not occur during fasting.
Objective: The objective of this study was to investigate whether inhibiting endogenous cortisol secretion with metyrapone decreases 24-h serum leptin levels and to determine whether a meal-related midmorning surge in cortisol is a prerequisite for the meal-entrained nocturnal rise in leptin.
Design: This was a randomized, cross-over study.
Setting: The study was performed at the General Clinical Research Center.
Participants: Lean males were studied.
Intervention: In study 1, seven lean men were studied for 24 h while their endogenous cortisol secretions were manipulated as follows: 1) CONTROL; 2) cortisol suppression by metyrapone (MET); and 3) MET and oral hydrocortisone (at 0900 h) (MET + CORT). Subjects were all fed a eucaloric diet (two meals at 1100 and 1700 h). In study 2, six men were studied without pharmacological intervention for 24 h on two occasions: once under a complete fast (FAST) and once in a feeding condition (one meal at 1100 h; FED).
Main Outcome Measure: The main outcome measure was serum leptin.
Results: MET significantly suppressed serum cortisol at 0800 h, midmorning, and over the 24-h period. As a result of cortisol suppression, 24-h serum leptin levels were decreased vs. control values despite similar insulin responses to meals. Administering a single dose of hydrocortisone to MET subjects potently stimulated serum leptin compared with the effect of MET alone.
Conclusions: Our data demonstrate that endogenous cortisol secretion is necessary for the maintenance of serum leptin levels over 24 h in lean, normally fed males.
Background: The use of mobile technologies for data capture and transmission has the potential to streamline clinical trials, but researchers lack methods for collecting, processing, and interpreting ...data from these tools. Objectives: To assess the performance of a technical platform for collecting and transmitting data from six mobile technologies in the clinic and at home, to apply methods for comparing them to clinical standard devices, and to measure their usability, including how willing subjects were to use them on a regular basis. Methods: In part 1 of the study, conducted over 3 weeks in the clinic, we tested two device pairs (mobile vs. clinical standard blood pressure monitor and mobile vs. clinical standard spirometer) on 25 healthy volunteers. In part 2 of the study, conducted over 3 days both in the clinic and at home, we tested the same two device pairs as in part 1, plus four additional pairs (mobile vs. clinical standard pulse oximeter, glucose meter, weight scale, and activity monitor), on 22 healthy volunteers. Results: Data collection reliability was 98.1% in part 1 of the study and 95.8% in part 2 (the percentages exclude the wearable activity monitor, which collects data continuously). In part 1, 20 of 1,049 overall expected measurements were missing (1.9%), and in part 2, 45 of 1,083 were missing (4.2%). The most common reason for missing data was a single malfunctioning spirometer (13 of 20 total missed readings) in part 1, and that the subject did not take the measurement (22 of 45 total missed readings) in part 2. Also in part 2, a higher proportion of at-home measurements than in-clinic readings were missing (12.6 vs. 2.7%). The data from this experimental study were unable to establish repeatability or agreement for every mobile technology; only the pulse oximeter demonstrated repeatability, and only the weight scale demonstrated agreement with the clinical standard device. Most mobile technologies received high “willingness to use” ratings from the patients on the questionnaires. Conclusions: This study demonstrated that the wireless data transmission and processing platform was dependable. It also identified three critical areas of study for advancing the use of mobile technologies in clinical research: (1) if a mobile technology captures more than one type of endpoint (such as blood pressure and pulse), repeatability and agreement may need to be established for each endpoint to be included in a clinical trial; (2) researchers need to develop criteria for excluding invalid device readings (to be identified by algorithms in real time) for the population studied using ranges based on accumulated subject data and established norms; and (3) careful examination of a mobile technology’s performance (reliability, repeatability, and agreement with accepted reference devices) during pilot testing is essential, even for medical devices approved by regulators.
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