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Gibbs is abstract winner for CCHA Oral Presentation Competition

September 22, 2015

“Ambient Temperature Energetic Challenge Improves Healthspan in Male C57BL/6 Mice,” an abstract by Katie Gibbs, PhD, postdoctoral scholar in the Nutrition Obesity Research Center (NORC) and Department of Nutrition Sciences, has been selected as a winner to compete in the Comprehensive Center for Healthy Aging (CCHA) Oral Presentation Competition. Dr. Gibbs will present the research at the CCHA Annual Symposium, to be held on October 23, 2015, at the Edge of Chaos.

The study was designed to address the theory that a perceived energy shortage in an environment triggers physiological changes in an organism that slow the effects of aging. Dr. Gibbs and her colleagues hypothesize that mice that perceive and experience an energy limitation will live longer and healthier lives.

To simulate the energetic conditions of caloric restriction, a state of energetic insecurity was induced in 160 male mice of the common inbred laboratory strain C57BL/6 by not allowing for increased energy intake to compensate for the energy expended maintaining body temperature in a cool ambient temperature setting. At age 12 weeks, the mice were randomized to individual housing at 22 degrees Celsius (71.6 degrees Fahrenheit) or 27 degrees Celsius (80.6 degrees Fahrenheit). Mice at 27 degrees Celsius (near thermoneutrality) were allowed to eat freely, while mice at 22 degrees Celsius were fed the amount of food the mice at 27 degrees Celsius consumed, approximately 30 percent less than desired by the cooler mice. The researchers measured body weight weekly and body composition monthly; in addition, they evaluated functional measures of healthspan every 12 weeks, using motor-health assessments starting at age 68 weeks and grip strength tests starting at age 74 weeks. Total locomotion (the distance traveled in 40 x 40 x 20 cm arena during a 4-minute trial) was assessed at age 75 weeks (young adult) and again at 100 weeks (middle age).

By week 114, survival was 72 percent for mice at 22 degrees Celsius and 32 percent for mice at 27 degrees Celsius. Dr. Gibbs noted, “Median lifespan for mice at 27°C was 805 days. At the start of healthspan assessments, mice at 27°C had higher body, fat, and lean mass than mice at 22°C (p<0.0001). Mice at 27°C attained maximum body weight by age 70 weeks (41.2 ± 0.6 g, mean ± SE) and began a steady decline in body weight by age 72 weeks, primarily due to fat mass loss. Mice at 22°C reached a maximum body weight by age 78 weeks (27.1 ± 0.2 g, mean ± SE) but maintained ca. 26 g body weight through week 114 of the study. Total motor-health assessment scores noted greater deficiencies for mice at 27°C than mice at 22°C at age 68 (p=0.0058) and age 76 (p=0.0004), but were similar at age 88 weeks (p=0.1185). Mice at 27°C had lower maximum grip strength at 74 (p<0.0001) and 87 (p<0.0001), but not at 98 weeks (p=0.1655). Total locomotion was similar for mice in both treatments at age 75 (p=0.1051) and age 100 weeks (p=0.3541); however, total locomotion declined with age across treatments (p<0.001).”

Conclusions indicate that “[c]onsidering median lifespan, mice at 22°C are longer lived than mice at 27°C despite consuming the same amount of energy. While this longevity study is ongoing, healthspan metrics suggest age-related declines in skeletal muscle strength and motor function may be attenuated for mice at 22°C who face a greater energetic demand, relative to those at 27°C.”

Co-authors of the study are Maria S. Johnson, PhD, research associate; Daniel L. Smith, Jr., PhD, assistant professor; and Tim R. Nagy, PhD, professor, in the Department of Nutrition Sciences, as well as David B. Allison, PhD, distinguished professor and director of the NORC.