Animal model: metabolic and thermic responses to diet and environment (4 degrees C) in obesity during aging in the LA/Ntul//-cp rat.

Abstract

The results of this study indicate that aging is associated with progressive declines in the normal dietary and metabolic responses to diet and environment in this animal model. The normal thermic and hormonal responses to diet and environment are thought to contribute to the fine regulation of energy balance by modulation of the efficiency of energy utilization or storage [25]. In the obese phenotype, the declines in the above variables may be further complicated by the presence of long-standing insulin resistance, and by perturbations in the normal metabolism and action of thyroid hormones, particularly T3. These may further contribute, individually or in combination with other factors, to an enhancement of energy storage and thereby contribute to maintaining the obese state. Moreover, the effects of progressive increases in obesity further exacerbate the decline in the economy of energy utilization and storage. Thus the impact of these physiologic changes of aging and obesity may impart significant alterations on the efficiency of energy metabolism, which in turn may contribute to some of the pathophysiologic changes associated with longevity, and could influence nutritional indices in affected individuals. As nations become progressively more industrialized, the incidence of overweight conditions--including obesity, NIDDM, and related metabolic disorders--has been shown to become increased and, along with those changes, the metabolic and pathophysiologic sequelae related to those disorders become more common [6-8]. A greater understanding of mechanisms of impaired energy metabolism and energy balance in aging may provide new insight into the nutritional factors that may contribute to obesity in aging, their modulation, and the emergence of a longer, healthier lifestyle.