Publications by authors named "Karishma Sriram"

3 Publications

  • Page 1 of 1

The Dose-Response Relationship Between Physical Activity and Cardiometabolic Health in Adolescents.

Am J Prev Med 2021 01;60(1):95-103

Duke Clinical Research Institute, Durham, North Carolina; Duke Center for Childhood Obesity Research, Duke University School of Medicine, Durham, North Carolina; Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina; Duke Children's Health and Discovery Initiative, Duke University School of Medicine, Durham, North Carolina.

Introduction: This study examines the dose-response relationship between moderate-to-vigorous physical activity and cardiometabolic measures in adolescents.

Methods: Cross-sectional spline analyses were performed using 2003-2016 National Health and Nutrition Examination Survey data among adolescents (aged 12-19 years, N=9,195) on objectively measured (2003-2006) and self-reported (2007-2016) weekly mean minutes of moderate-to-vigorous physical activity and cardiometabolic measures (systolic and diastolic blood pressure, total cholesterol, high-density lipoprotein, BMI, and cardiorespiratory fitness). Inflection points were determined for nonlinear relationships.

Results: For objective moderate-to-vigorous physical activity, female adolescents had significant nonlinear associations with inflection points at 90 minutes/week for BMI percentile and systolic blood pressure. Male adolescents had inflection points at 150 weekly minutes of objective activity for BMI percentile and cardiorespiratory fitness. BMI percentile was about 7% lower for female and male adolescents at 150 weekly minutes of objectively measured moderate-to-vigorous physical activity than at 0 minutes. For self-reported moderate-to-vigorous physical activity, inflection points were at 375 minutes/week (diastolic blood pressure for female adolescents) and 500 minutes/week (systolic blood pressure for male adolescents).

Conclusions: Among several significant dose-response relationships between physical activity and cardiometabolic health in adolescents, consistent and often nonlinear relationships were identified for BMI, with inflection points at 90-150 minutes of objective moderate-to-vigorous physical activity. Notable differences in associations and linearity were identified by sex and physical activity measure (objective or self-reported). These results support calls for any increase in physical activity among adolescents and suggest that recommendations closer to the adult guidelines of 150 weekly minutes of physical activity may be health promoting and more attainable for youth than the current recommendation of 420 weekly minutes.
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http://dx.doi.org/10.1016/j.amepre.2020.06.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7769140PMC
January 2021

The Dose-Response Relationship Between Physical Activity and Cardiometabolic Health in Young Adults.

J Adolesc Health 2020 08 19;67(2):201-208. Epub 2020 Jun 19.

Duke Clinical Research Institute, Durham, North Carolina; Duke Center for Childhood Obesity Research, Duke University School of Medicine, Durham, North Carolina; Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina; Children's Health and Discovery Institute, Duke University School of Medicine, Durham, North Carolina. Electronic address:

Purpose: Guidelines recommend 150 minutes of weekly moderate-to-vigorous physical activity (MVPA) for all adults, although physical activity level correlation with cardiometabolic health is not well characterized for young adults. We determined the dose-response relationship of MVPA on measures of cardiometabolic health in young adults.

Methods: We examined young adults (aged 20-29 years; N = 5,395, 47.9% female) in the 2003-2016 National Health and Nutrition Examination Survey. Exposures were objective (accelerometer based) and self-reported weekly mean minutes of MVPA. Cardiometabolic outcome measures were body mass index (BMI), high-density lipoprotein (HDL), total cholesterol, systolic blood pressure, and diastolic blood pressure. The dose-response relationships were assessed with unadjusted spline analyses. Sex-stratified outcomes were modeled using multivariable linear regression with mean estimated change presented for 150-minute dose increases of MVPA.

Results: Among females, associations between objective activity and cardiometabolic measures were all linear. Compared with no activity, 150 minutes of objective activity was associated with a lower BMI (-1.37 kg/m) and total cholesterol (-4.89 mg/dL), whereas 150 minutes of self-reported activity was associated with a higher HDL (1 mg/dL) and lower diastolic blood pressure (-.42 mm Hg). Among males, an inflection point was identified in the dose-response curves for objective activity with BMI around 100 minutes. Compared with no activity, 150 self-reported minutes was associated with lower BMI (-.26 kg/m), higher HDL (.52 mg/dL), and lower total cholesterol (-1.35 mg/dL).

Conclusions: The dose-response relationships between physical activity and cardiometabolic markers in young adults were predominantly linear, supporting public health calls for any increase in physical activity in this population.
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http://dx.doi.org/10.1016/j.jadohealth.2020.04.021DOI Listing
August 2020

Human Neural Stem Cell Extracellular Vesicles Improve Tissue and Functional Recovery in the Murine Thromboembolic Stroke Model.

Transl Stroke Res 2018 10 28;9(5):530-539. Epub 2017 Dec 28.

ArunA Biomedical, Athens, GA, 30602, USA.

Over 700 drugs have failed in stroke clinical trials, an unprecedented rate thought to be attributed in part to limited and isolated testing often solely in "young" rodent models and focusing on a single secondary injury mechanism. Here, extracellular vesicles (EVs), nanometer-sized cell signaling particles, were tested in a mouse thromboembolic (TE) stroke model. Neural stem cell (NSC) and mesenchymal stem cell (MSC) EVs derived from the same pluripotent stem cell (PSC) line were evaluated for changes in infarct volume as well as sensorimotor function. NSC EVs improved cellular, tissue, and functional outcomes in middle-aged rodents, whereas MSC EVs were less effective. Acute differences in lesion volume following NSC EV treatment were corroborated by MRI in 18-month-old aged rodents. NSC EV treatment has a positive effect on motor function in the aged rodent as indicated by beam walk, instances of foot faults, and strength evaluated by hanging wire test. Increased time with a novel object also indicated that NSC EVs improved episodic memory formation in the rodent. The therapeutic effect of NSC EVs appears to be mediated by altering the systemic immune response. These data strongly support further preclinical development of a NSC EV-based stroke therapy and warrant their testing in combination with FDA-approved stroke therapies.
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http://dx.doi.org/10.1007/s12975-017-0599-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6132936PMC
October 2018