Temporal and compositional dietary restrictions modulate age-related changes in serum lipids.

Life-lon restriction of food, which markedly increases the length of life of rats, also delays the occurrence of age-related physiological deteriorations including the age-related changes in serum lipids. The aim of this study was to explore the effects of 1) food restriction limited to early life, 2) food restriction initiated in adult life and 3) restriction of protein without restriction of calories on the age-related changes in serum lipids. Food restriction started at 6 months of age was as effective as food restriction started at 6 weeks of age in modulating the age-related changes in serum lipids, whereas food restriction from 6 weeks to 6 months of age and restriction of protein but not calories were much less effective. Changes in the rate of very low density lipoprotein-triglyceride removal from the blood were not responsible for the age-related increase in triglyceride concentration or for the modulation of this increase by the dietary regimens. Age-related changes in serum or plasma levels of glucose, ketone bodies, insulin and glucagon were also measured and the modulating effects of the dietary regimens studied; possible relationships between the concentrations of these substances and the concentrations of the serum lipids are discussed.