High stability of blood parameters during mouse lifespan: sex-specific effects of every-other-day fasting.

Every-other-day fasting (EODF) is one type of caloric restriction that is proposed to have significant health benefits, including slowing aging-related processes. The present study evaluated multiple parameters of blood homeostasis comparing mice of different ages and mice on different diet regimes: ad libitum (AL) versus EODF. Hematological and classical biochemical parameters of blood were measured in young (6-month), middle-aged (12-month) and old (18-month) C57BL/6J mice of both sexes subjected either to EODF, or AL feeding. Middle-aged AL males showed a decrease in erythrocyte and total leucocyte counts and an increase in plasma alkaline phosphatase activity, whereas old animals showed a decrease in relative levels of lymphocytes and an increase in relative levels of neutrophils, a decrease in plasma lactate and an increase in total cholesterol levels, compared to young mice. AL-fed females demonstrated higher stability of blood parameters during aging than males did. The EODF regimen did not significantly affect hematological parameters in females but prevented a decline in total leukocyte count with age in males. In both sexes, EODF partially prevented age-associated changes in levels of plasma lactate and cholesterol and activity of alkaline phosphatase. Thus, during normal aging, mice showed a sex-dependent maintenance of blood homeostasis which was not significantly affected by EODF.

Feeding to satiation induces mild oxidative/carbonyl stress in the brain of young mice.

Intermittent fasting as a dietary intervention can prevent overweight and obesity in adult organisms. Nevertheless, information regarding consequences of intermittent fasting for redox status and reactive metabolite-mediated processes that are crucial for the normal functioning of organisms is limited. Since the information on effects of intermittent fasting on parameters of oxidative/carbonyl stress in the brains of young mice was absent, the present study addressed these questions using an every-other-day fasting (EODF) protocol. The levels of carbonyl proteins were ~28 %, 22 % and 18 % lower in the cerebral cortex of EODF males and females and middle parts of the brain of EODF males, respectively, as compared to their ad libitum fed counterparts. Lipid peroxides and α-dicarbonyl compounds were lower only in the cortex and medulla part of EODF male brain. The EODF regimen resulted in higher total non-specific antioxidant capacity in different parts of male brain and a tendency to be higher this parameter in females. At the same time, EODF regimen had no effect on the activities of the defensive antioxidant enzymes, namely superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase, glyoxylase 1 and glucose-6-phosphate dehydrogenase in the cortex of both sexes, but even decreased activities of these enzymes in medulla and middle part of the brain. In general, the results suggest that in the brain of young mice ad libitum feeding induces mild oxidative/carbonyl stress which may be partially alleviated by the EODF regimen. The effect of EODF regimen is more pronounced in the medulla part than in the cortex.

Middle aged turn point in parameters of oxidative stress and glucose catabolism in mouse cerebellum during lifespan: minor effects of every-other-day fasting.

The cerebellum is considered to develop aging markers more slowly than other parts of the brain. Intensification of free radical processes and compromised bioenergetics, critical hallmarks of normal brain aging, may be slowed down by caloric restriction. This study aimed to evaluate the intensity of oxidative stress and the enzymatic potential to utilize glucose via glycolysis or the pentose phosphate pathway (PPP) in the cerebellum of mice under ad libitum versus every-other-day fasting (EODF) feeding regimens. Levels of lipid peroxides, activities of antioxidant and key glycolytic and PPP enzymes were measured in young (6-month), middle-aged (12-month) and old (18-month) C57BL/6J mice. The cerebellum showed the most dramatic increase in lipid peroxide levels, antioxidant capacity and PPP key enzyme activities and the sharpest decline in the activities of key glycolytic enzymes under transition from young to middle age but these changes slowed when transiting from middle to old age. A decrease in the activity of the key glycolytic enzyme phosphofructokinase was accompanied by a concomitant increase in the activities of hexokinase and glucose-6-phosphate dehydrogenase (G6PDH), which may suggest that during normal cerebellar aging glucose metabolism shifts from glycolysis to the pentose phosphate pathway. The data indicate that intensification of free radical processes in the cerebellum occurred by middle age and that activation of the PPP together with increased antioxidant capacity can help to resist these changes into old age. However, the EODF regime did not significantly modulate or alleviate any of the metabolic processes studied in this analysis of the aging cerebellum.

Middle age as a turning point in mouse cerebral cortex energy and redox metabolism: Modulation by every-other-day fasting.

Normal brain aging is accompanied by intensification of free radical processes and compromised bioenergetics. Caloric restriction is expected to counteract these changes but the underlying protective mechanisms remain poorly understood. The present work aimed to investigate the intensity of oxidative stress and energy metabolism in the cerebral cortex comparing mice of different ages as well as comparing mice given one of two regimens of food availability: ad libitum versus every-other-day fasting (EODF). Levels of oxidative stress markers, ketone bodies, glycolytic intermediates, mitochondrial respiration, and activities of antioxidant and glycolytic enzymes were assessed in cortex from 6-, 12- and 18-month old C57BL/6J mice. The greatest increase in oxidative stress markers and the sharpest decline in key glycolytic enzyme activities was observed in mice upon the transition from young (6 months) to middle (12 months) age, with smaller changes occurring upon transition to old-age (18 months). Brain mitochondrial respiration showed no significant changes with age. A decrease in the activities of key glycolytic enzymes was accompanied by an increase in the activity of glucose-6-phosphate dehydrogenase suggesting that during normal brain aging glucose metabolism is altered to lower glycolytic activity and increase dependence on the pentose-phosphate pathway. Interestingly, levels of ketone bodies and antioxidant capacity showed a greater decrease in the brain cortex of females as compared with males. The EODF regimen further suppressed glycolytic enzyme activities in the cortex of old mice, and partially enhanced oxygen consumption and respiratory control in the cortex of middle aged and old males. Thus, in the mammalian cortex the major aging-induced metabolic changes are already seen in middle age and are slightly alleviated by an intermittent fasting mode of feeding.

Corrigendum: Every-Other-Day Feeding Decreases Glycolytic and Mitochondrial Energy-Producing Potentials in the Brain and Liver of Young Mice.

[This corrects the article DOI: 10.3389/fphys.2019.01432.].

Every-Other-Day Feeding Decreases Glycolytic and Mitochondrial Energy-Producing Potentials in the Brain and Liver of Young Mice.

Intermittent fasting is used to reduce body mass in obese adult humans and animals. However, information on the impact of one type of intermittent fasting (IF) called every-other-day feeding (EODF) on young animals is scarce. In this study, 1-month-old mice of both sexes were subjected to a 4-week regimen of EODF using age-matched counterparts fed ad libitum as controls. At the end of EODF exposure, experimental male and female mice weighed 14 and 13% less than the control counterparts. The EODF regimen resulted in lower liver levels of glycogen, glucose, and lactate, but did not affect lactate level in mouse cerebral cortex of both sexes. Activities of key glycolytic enzymes (hexokinase, phosphofructokinase, and pyruvate kinase) in liver of experimental mice were lower than those in controls. In the cerebral cortex, only hexokinase and pyruvate kinase activities were lower than in controls, but phosphofructokinase activity was not affected in IF females and was higher in IF males as compared with ad libitum fed males. Mitochondria isolated from liver of IF mice had lower respiratory control ratios, but those from the cortex had the same values as control animals. The concentration of ß-hydroxybutyrate and the activity of ß-hydroxybutyrate dehydrogenase were lower in the IF mouse liver, but not changed or enhanced in the IF cerebral cortex. Thus, animal responses to IF do not depend significantly on sex and are directed to decrease energy metabolism to save resources, and the effects are more pronounced in the liver than in the brain.