Age-Dependent Effect of Cyclic Feeding Regimen on the Level of Serum Apolipoproteins in Young and Old Rats

Aims: the aim of this study was to investigate the influence of intermittent fasting (IF) on the content of blood serum apolipoproteins in young and old animals and to ascertain whether there exist adaptation mechanisms to this dietary regimen.

Study design: young (3-month) and old (20-month) rats were individually housed and randomly assigned to one of five groups (with 10 rats per group): (AL) - fed ad libitum; (IF1) - provided access to a limited amount of food (4g/100g and 2g/100g of food/body weight for young and old rats, respectively) every other day for 10 days; (R1) - refeeded ad libitum for 20 days after IF1; (IF2) - provided the same regimen as for IF1, but after successive IF1 and R1; (R2) - refeeded ad libitum for 10 days after IF2.

Methodology: plasma proteins were separated by one dimensional SDS-PAGE using a 7.5-15% gradient separating gel.

Results: IF1 with 30% weight loss resulted in ~28% and ~24% decrease and ~121% increase in serum apolipoprotein A-I (apoA-I), apolipoprotein B-100 (apoB-100), and apolipoprotein E (apoE) levels of young rats, respectively, and after R1 the level of these proteins was characterized by ~37%, ~66%, ~22% increase in comparison with control. IF1 and R1 in old animals were followed by ~53% increase in apoE content and ~13% decrease in the amount of apoB. IF2 was coupled with ~32% decrease in apoA-I level and ~133% increase in apoE concentration in young animals and ~39% and ~38% decrease in apoA-I and apoB-100 level in old animals, respectively. R2 produced ~48% and ~49% increase in apoA-I and apoE levels of young rats, respectively, and to ~31% increase in apoA-I content of old rats.

Conclusion: the main outcome reached is the identification of differences in the effects of the dietary regimen during reapplication on apoE and apoB-100 serum levels in old animals and on apoA-I level in the case of young animals.