2010 Volume 27 Pages 92-96
The elderly population in Japan is increasing, and one consequence of aging is a reduction in serum zinc levels. Zinc deficiency reduces the mRNA expression of Klotho, an anti-aging gene which, when disrupted in mice, accelerates the aging process. Although aging is one of the greatest risk factors for disease development later in life, adhering to a calorie-restricted (CR) diet can slow the aging rate and extend life span in many organisms. This study examined the effect of a CR diet on Klotho expression in the kidney of an animal model. Fourteen mature male SD rats were aged until they weighed ~500 g each and were then housed in individual cages and fed a special diet consisting of 65% carbohydrate, 20% protein, 10% fat, and 0.01% zinc, ad libitum. After 1 week, the animals were separated into a control group (n=7; mean body weight, 511.4 ± 13.7 g), in which each rat consumed 150 kcal/day, and a CR group (n=7; mean body weight, 529.3 ± 17.2 g), in which each rat consumed 60% of the control calorie intake. After 4 weeks, mean body weight in the CR group was reduced by 13% compared with that in the control group. Serum zinc levels were significantly lower in the CR group (109.7 ± 11.3 μg/dL) compared with the control (132.7 ± 4.9 μg/dL). Western blot analysis revealed significantly increased Klotho expression in the CR group (0.57 ± 0.05) compared with the control (0.28 ± 0.05). These results suggest that Klotho expression is induced by calorie restriction and is inversely related to serum zinc levels.
