Study examines perfect storm interplay in Mexican-American children
SAN ANTONIO (Oct. 24, 2012) — Just as a mingling of air masses and currents can create the perfect storm, the interaction of genetics and environment can create a perfect storm of cardio-metabolic risk in children. A study of more than 670 Mexican-American children, conducted by the Texas Biomedical Research Institute and the School of Medicine at The University of Texas Health Science Center San Antonio, found strong interactions between low- and high-physical-activity environments and children’s underlying genetic makeup.
The team compared children’s sedentary behavior, physical fitness and genetic patterns with data from their study exams and lab results. What they found was troubling: from a tender age, sedentary lifestyle and low physical fitness increased children’s risk of obesity, metabolic syndrome and cardiovascular disease. But more troubling, such environments can be even more harmful to children who already have underlying genetic susceptibility to these conditions.
The children are participants in the San Antonio Family Assessment of Metabolic Risk Indicators in Youth (SAFARI). The SAFARI participants, ages 6-17, are the children and extended family members of adults enrolled in one of three community-based, genetic epidemiological studies: the San Antonio Family Heart Study, the San Antonio Family Diabetes/Gallbladder Study and the Veterans Administration Genetic Epidemiology Study.
“A lifestyle of regular physical activity serves as a protective environment, but a sedentary lifestyle of little or no physical activity is a high-risk environment,” said Rector Arya, Ph.D., lead author of the study. “Our study examined how each environment is modulating individuals’ genetic susceptibility to cardio-metabolic risk factors.”
Dr. Arya is a genetic epidemiologist in the Department of Pediatrics of the School of Medicine at the UT Health Science Center.
Effects on risk factors
Major interactions between genetics and environment were observed for waist circumference, fasting insulin level, high-density lipoprotein (HDL) cholesterol and other factors, Dr. Arya said at the Obesity Society’s Annual Scientific Meeting in San Antonio. Sedentary lifestyle was shown to interact with genetic factors to produce statistically significant effects on risk factors for obesity, type 2 diabetes and future cardiovascular complications.
Over the past 30 years, metabolic syndrome — a complex of risk factors including obesity, insulin resistance and hypertension — has grown alarmingly prevalent. Today it represents a public health crisis for children and adults alike, especially among minority populations such as Mexican Americans.
The major objective of the SAFARI study is to determine genetic and environmental influences and their interactive effects on susceptibility to metabolic syndrome and its risk factors. “Since our genes have not changed radically over the past 30 years, the explosion of metabolic syndrome risk factors in recent decades appears to be attributable to genetic and environmental interactive influences,” said SAFARI Principal Investigator Ravindranath Duggirala, Ph.D., of the Texas Biomedical Research Institute in San Antonio.
The team tested the physical fitness of each child using a five-minute step test. Heart rate was recorded before and after testing. The team also asked the youngsters about the amount of time they spent in sedentary activities, such as television viewing, both “yesterday” and “usually.” Finally, each child gave a blood sample to be analyzed for glucose, insulin, lipids and other risk markers. All clinical examinations were done under the supervision of Daniel E. Hale, M.D., chief of endocrinology in the Department of Pediatrics of the School of Medicine at the UT Health Science Center. Dr. Hale is medical director of the SAFARI study.
Statistical modeling of the step test results, blood samples and self-reported time spent in sedentary activities revealed these and other findings:
- Children’s cardio-metabolic risk decreased with increasing physical fitness, but increased with the amount of time spent in sedentary activities, such as television viewing.
- Significant gene interaction with physical fitness was detected for fat mass, HDL cholesterol (the “good cholesterol”) and insulin resistance, a condition in which the body is not able to use its own insulin properly.
- Significant gene interaction with sedentary lifestyle was detected for waist circumference, fasting insulin, HDL cholesterol, fat mass and other markers.
“Genes don’t change radically within one generation, but our behavior has,” said study co-author Sharon Fowler from the Division of Clinical Epidemiology in the School of Medicine. “This study’s results provide evidence that an inactive lifestyle may be particularly harmful to those kids who are already genetically susceptible to elevated cardio-metabolic risk.”
Acknowledgment of authors: Rector Arya¹, Vincent P. Diego², Sharon P. Fowler¹, Sobha Puppala², Vidya S. Farook², Geetha Chittoor², Jennifer Schneider², Roy G. Resendez², Kelly J. Hunt³, Benjamin S. Bradshaw⁴, Laura Almasy², Joanne E. Curran², Anthony G. Comuzzie², Donna M. Lehman¹, Christopher P. Jenkinson¹, Jane L. Lynch¹, Ralph A. DeFronzo¹, John Blangero², Daniel E. Hale¹, Ravindranath Duggirala² (¹ = UT Health Science Center San Antonio; ² = Texas Biomedical Research Institute; ³ = Medical University of South Carolina; ⁴= UT Houston School of Public Health)
The University of Texas Health Science Center at San Antonio, one of the country’s leading health sciences universities, ranks in the top 3 percent of all institutions worldwide receiving federal funding. Research and other sponsored program activity totaled $231 million in fiscal year 2011. The university’s schools of medicine, nursing, dentistry, health professions and graduate biomedical sciences have produced approximately 28,000 graduates. The $736 million operating budget supports eight campuses in San Antonio, Laredo, Harlingen and Edinburg. For more information on the many ways “We make lives better®,” visit www.uthscsa.edu.
The Texas Biomedical Research Institute, formerly the Southwest Foundation for Biomedical Research, is one of the world’s leading independent biomedical research institutions dedicated to advancing health worldwide through innovative biomedical research. Located on a 200-acre campus on the northwest side of San Antonio, Texas, the Institute partners with hundreds of researchers and institutions around the world, targeting advances in the fight against AIDS, hepatitis, malaria, parasitic infections and a host of other infectious diseases, as well as cardiovascular disease, diabetes, obesity, cancer, psychiatric disorders, and problems of pregnancy. For more information on Texas Biomed, go to www.TxBiomed.org.