Corrigendum: Adaptive yoga versus low-impact exercise for adults with chronic acquired brain injury: a pilot randomized control trial protocol

[This corrects the article DOI: 10.3389/fnhum.2023.1291094.].

Brain Structure and Function Predict Adherence to an Exercise Intervention in Older Adults

INTRODUCTION

Individual differences in brain structure and function in older adults are potential proxies of brain reserve or maintenance and may provide mechanistic predictions of adherence to exercise. We hypothesized that multimodal neuroimaging features would predict adherence to a 6-month randomized controlled trial of exercise in 131 older adults (age, 65.79 ± 4.65 yr, 63% female), alone and in combination with psychosocial, cognitive, and health measures.

METHODS

Regularized elastic net regression within a nested cross-validation framework was applied to predict adherence to the intervention in three separate models (brain structure and function only; psychosocial, health, and demographic data only; and a multimodal model).

RESULTS

Higher cortical thickness in somatosensory and inferior frontal regions and less surface area in primary visual and inferior frontal regions predicted adherence. Higher nodal functional connectivity (degree count) in default, frontoparietal, and attentional networks and less nodal strength in primary visual and temporoparietal networks predicted exercise adherence ( r = 0.24, P = 0.004). Survey and clinical measures of gait and walking self-efficacy, biological sex, and perceived stress also predicted adherence ( r = 0.17, P = 0.056); however, this prediction was not significant when tested against a null test statistic. A combined multimodal model achieved the highest predictive strength ( r = 0.28, P = 0.001).

CONCLUSIONS

Our results suggest that there is a substantial utility of using brain-based measures in future research into precision and individualized exercise interventions older adults.

Resting state functional connectivity provides mechanistic predictions of future changes in sedentary behavior

Sedentary behaviors are increasing at the cost of millions of dollars spent in health care and productivity losses due to physical inactivity-related deaths worldwide. Understanding the mechanistic predictors of sedentary behaviors will improve future intervention development and precision medicine approaches. It has been posited that humans have an innate attraction towards effort minimization and that inhibitory control is required to overcome this prepotent disposition. Consequently, we hypothesized that individual differences in the functional connectivity of brain regions implicated in inhibitory control and physical effort decision making at the beginning of an exercise intervention in older adults would predict the change in time spent sedentary over the course of that intervention. In 143 healthy, low-active older adults participating in a 6-month aerobic exercise intervention (with three conditions: walking, dance, stretching), we aimed to use baseline neuroimaging (resting state functional connectivity of two a priori defined seed regions), and baseline accelerometer measures of time spent sedentary to predict future pre-post changes in objectively measured time spent sedentary in daily life over the 6-month intervention. Our results demonstrated that functional connectivity between (1) the anterior cingulate cortex and the supplementary motor area and (2) the right anterior insula and the left temporoparietal/temporooccipital junction, predicted changes in time spent sedentary in the walking group. Functional connectivity of these brain regions did not predict changes in time spent sedentary in the dance nor stretch and tone conditions, but baseline time spent sedentary was predictive in these conditions. Our results add important knowledge toward understanding mechanistic associations underlying complex out-of-session sedentary behaviors within a walking intervention setting in older adults.

Diffusion tensor imaging of cerebral white matter integrity in cognitive aging

In this article we review recent research on diffusion tensor imaging (DTI) of white matter (WM) integrity and the implications for age-related differences in cognition. Neurobiological mechanisms defined from DTI analyses suggest that a primary dimension of age-related decline in WM is a decline in the structural integrity of myelin, particularly in brain regions that myelinate later developmentally. Research integrating behavioral measures with DTI indicates that WM integrity supports the communication among cortical networks, particularly those involving executive function, perceptual speed, and memory (i.e., fluid cognition). In the absence of significant disease, age shares a substantial portion of the variance associated with the relation between WM integrity and fluid cognition. Current data are consistent with one model in which age-related decline in WM integrity contributes to a decreased efficiency of communication among networks for fluid cognitive abilities. Neurocognitive disorders for which older adults are at risk, such as depression, further modulate the relation between WM and cognition, in ways that are not as yet entirely clear. Developments in DTI technology are providing a new insight into both the neurobiological mechanisms of aging WM and the potential contribution of DTI to understanding functional measures of brain activity. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Quantitative structure-activity relationships for gammadelta T cell activation by bisphosphonates

gammadelta T cells are the first line of defense against many infectious organisms and are also involved in tumor cell surveillance and killing. They are stimulated by a broad range of small, phosphorus-containing antigens (phosphoantigens) as well as by the bisphosphonates commonly used in bone resorption therapy, such as pamidronate and risedronate. Here, we report the activation of gammadelta T cells by a broad range of bisphosphonates and develop a pharmacophore model for gammadelta T cell activation, in addition to using a comparative molecular similarity index analysis (CoMSIA) approach to make quantitative relationships between gammadelta T cell activation by bisphosphonates and their three-dimensional structures. The CoMSIA analyses yielded R(2) values of approximately 0.8-0.9 and q(2) values of approximately 0.5-0.6 for a training set of 45 compounds. Using an external test set, the activities (IC(50) values) of 16 compounds were predicted within a factor of 4.5, on average. The CoMSIA fields consisted of approximately 40% hydrophobic, approximately 40% electrostatic, and approximately 20% steric interactions. Since bisphosphonates are known to be potent, nanomolar inhibitors of the mevalonate/isoprene pathway enzyme farnesyl pyrophosphate synthase (FPPS), we also compared the pharmacophores for gammadelta T cell activation with those for FPPS inhibition, using the Catalyst program. The pharmacophores for gammadelta T cell activation and FPPS inhibition both consisted of two negative ionizable groups, a positive charge feature and an endocyclic carbon feature, all having very similar spatial dispositions. In addition, the CoMSIA fields were quite similar to those found for FPPS inhibition by bisphosphonates. The activities of the bisphosphonates in gammadelta T cell activation were highly correlated with their activities in FPPS inhibition: R = 0.88, p = 0.002, versus a human recombinant FPPS (N = 9 compounds); R = 0.82, p < 0.0001, for an expressed Leishmania major FPPS (N = 45 compounds). The bisphosphonate gammadelta T cell activation pharmacophore differs considerably, however, from that reported previously for gammadelta T cell activation by phosphoantigens (Gossman, W.; Oldfield, E. J. Med. Chem. 2002, 45, 4868-4874), suggesting different primary targets for the two classes of compounds. The ability to quite accurately predict the activity of bisphosphonates as gammadelta T cell activators by using 3D QSAR techniques can be expected to help facilitate the design of additional bisphosphonates for potential use in immunotherapy.

3-D QSAR investigations of the inhibition of Leishmania major farnesyl pyrophosphate synthase by bisphosphonates

We report the activities of 62 bisphosphonates as inhibitors of the Leishmania major mevalonate/isoprene biosynthesis pathway enzyme, farnesyl pyrophosphate synthase. The compounds investigated exhibit activities (IC(50) values) ranging from approximately 100 nM to approximately 80 microM (corresponding to K(i) values as low as 10 nM). The most active compounds were found to be zoledronate (whose single-crystal X-ray structure is reported), pyridinyl-ethane-1-hydroxy-1,1-bisphosphonates or picolyl aminomethylene bisphosphonates. However, N-alicyclic aminomethylene bisphosphonates, such as incadronate (N-cycloheptyl aminomethylene bisphosphonate), as well as aliphatic aminomethylene bisphosphonates containing short (n = 4, 5) alkyl chains, were also active, with IC(50) values in the 200-1700 nM range (corresponding to K(i) values of approximately 20-170 nM). Bisphosphonates containing longer or multiple (N,N-) alkyl substitutions were inactive, as were aromatic species lacking an o- or m-nitrogen atom in the ring, or possessing multiple halogen substitutions or a p-amino group. To put these observations on a more quantitative structural basis, we used three-dimensional quantitative structure-activity relationship techniques: comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA), to investigate which structural features correlated with high activity. Training set results (N = 62 compounds) yielded good correlations with each technique (R(2) = 0.87 and 0.88, respectively), and were further validated by using a training/test set approach. Test set results (N = 24 compounds) indicated that IC(50) values could be predicted within factors of 2.9 and 2.7 for the CoMFA and CoMSIA methods, respectively. The CoMSIA fields indicated that a positive charge in the bisphosphonate side chain and a hydrophobic feature contributed significantly to activity. Overall, these results are of general interest since they represent the first detailed quantitative structure-activity relationship study of the inhibition of an expressed farnesyl pyrophosphate synthase enzyme by bisphosphonate inhibitors and that the activity of these inhibitors can be predicted within about a factor of 3 by using 3D-QSAR techniques.

Activity of bisphosphonates against Trypanosoma brucei rhodesiense

We report the results of a comparative molecular field analysis (CoMFA) investigation of the growth inhibition of the bloodstream form of Trypanosoma brucei rhodesiense trypomastigotes by bisphosphonates. A quantitative three-dimensional structure-activity relationship CoMFA model for a set of 26 bisphosphonates having a range of activity spanning approximately 3 orders of magnitude (minimum IC(50) = 220 nM; maximum IC(50) = 102 microM) yielded an R(2) value of 0.87 with a cross-validated R(2) value of 0.79. The predictive utility of this approach was tested for three sets of three compounds: the average pIC(50) error was 0.23. For the nitrogen-containing bisphosphonates, in general, the activity was aromatic- >> aliphatic-containing side chains. The activity of aromatic species lacking an alkyl ring substitution decreased from ortho to meta to para substitution; halogen substitutions also reduced activity. For the aliphatic bisphosphonates, the IC(50) values decreased nearly monotonically with increasing chain length (down to IC(50) = 2.0 microM for the n-C(11) alkyl side chain species). We also show, using a "rescue" experiment, that the molecular target of the nitrogen-containing bisphosphonate, risedronate, in T. b. rhodesiense is the enzyme farnesyl pyrophosphate synthase. In addition, we report the LD(50) values of bisphosphonates in a mammalian cell general toxicity screen and present a comparison between the therapeutic indices and the IC(50) values in the T. b. rhodesiense growth inhibition assay. Several bisphosphonates were found to have large therapeutic indices (> or =200:1) as well as low IC(50) values, suggesting their further investigation as antiparasitic agents against T. b. rhodesiense.