News & Views from the Editor-in-Chief - L. Bruce Gladden
There are many excellent articles in this month's issue, but I am choosing three to highlight. First, it is well-known that hospitalization results in a loss of muscle mass, perhaps particularly in geriatric patients. Karlsen and colleagues investigated the effect of muscle activation to counteract this muscle loss. Thirteen geriatric patients received daily bouts of electrical stimulation of the thigh muscles in one leg, while the other leg served as control. After 6.6 days, an ~2.5% decline in leg lean mass was prevented by electrical stimulation. Muscle biopsies (n = 9) provided novel insight at the cellular level and supported the notion of a positive effect of electrical stimulation, particularly affecting the expression of genes associated with muscle protein breakdown. These results highlight the importance and beneficial effects of including muscle activation for hospitalized geriatric patients.
My next choice deals with temperature regulation. The primary means to prevent heat loss during cold exposure is through vasoconstriction of cutaneous vessels. This reflex response is impaired in older adults, leading to reduced core temperature maintenance and increased risk of hypothermia. Lang et al. demonstrated that oral supplementation of L-tyrosine, the amino acid substrate for catecholamine biosynthesis, prior to whole-body cooling enhanced the reflex vasoconstriction response in aged skin, returning it to a similar magnitude as that observed in young skin. Consequently, oral L-tyrosine improved core temperature maintenance during cooling in older adults compared to placebo. These findings suggest that reduced substrate for catecholamine biosynthesis may explain the decline in thermoregulatory function that accompanies aging. Furthermore, L-tyrosine may be a supplement that improves core temperature maintenance during cold stress in older adults.
Finally, Beaulieu and coworkers examined the impact of 12 weeks of exercise training (500 kcal per day, 70% heart rate max, 5 days per week) in individuals with overweight/obesity on outcomes related to hedonic control over eating, such as binge eating and food reward. Changes in all outcomes were compared to those in a nonexercising control group. They found that exercise led to a reduction in wanting for high-fat relative to low-fat foods, with no change in liking. There was also an improvement in binge eating scores that was correlated to changes in body fat. These findings suggest that exercise has the potential to generate biological signals that cause adaptation to the dietary environment and restore control over eating in individuals with overweight/obesity.
L. Bruce Gladden
School of Kinesiology