Abstract
BackgroundIntracellular calcium is a biochemical messenger that regulates part of the metabolic adaptations in the daily fed-fast cycle. The aim of this study was to characterize the 24-h variations of the liver ryanodine and IP3 receptors (RyR and IP3R) as well as of the endoplasmic-reticulum and plasma-membrane Ca2+-ATPases (SERCA and PMCA) in daytime restricted feeding protocol.MethodsA biochemical and immunohistochemical approach was implemented in this study: specific ligand-binding for RyR and IP3R, enzymatic activity (SERCA and PMCA), and protein levels and zonational hepatic-distribution were determined by immunoblot and immunohistochemistry respectively under conditions of fasting, feeding, and temporal food-restriction.ResultsBinding assays and immunoblots for IP3R1 and 2 showed a peak at the light/dark transition in the ad-libitum (AL) group, whereas in the restricted-feeding (RF) group the peak shifted towards the food-access time. In the case of RyR binding experiments, both AL and RF groups showed a modest elevation during the dark period, with the RF rats exhibiting increased binding in response to feeding. The AL group showed 24-h rhythmicity in SERCA level; in contrast, RF group showed a pronounced amplitude elevation and a peak phase-shift during the light-period in SERCA level and activity. The activity of PMCA was constant along day in both groups; PMCA1 levels showed a 24-h rhythmicity in the RF rats (with a peak in the light period), meanwhile PMCA4 protein levels showed rhythmicity in both groups. The fasted condition promoted an increase in IP3R binding and protein level; re-feeding increased the amount of RyR; neither the activity nor expression of SERCA and PMCA protein was affected by fasting–re-feeding conditions. Histochemical experiments showed that the distribution of the Ca2+-handling proteins, between periportal and pericentral zones of the liver, varied with the time of day and the feeding protocol.ConclusionsOur findings show that RF influences mainly the phase and amplitude of hepatic IP3R and SERCA rhythms as well as discrete zonational distribution for RyR, IP3Rs, SERCA, and PMCA within the liver acinus, suggesting that intracellular calcium dynamics could be part of the rheostatic adaptation of the liver due to diurnal meal entrainment/food entrained oscillator expression.
Highlights
Intracellular calcium is a biochemical messenger that regulates part of the metabolic adaptations in the daily fed-fast cycle
When animals are under a restricted feeding schedule over a period of several weeks, they display a behavior known as food anticipatory activity (FAA), an arousal behavior that precedes the availability of food
Materials Antibodies against PER1, IP3R1(sc-6093) and IP3R2, SERCA2, PMCA1 and PMCA4, and Actin as well as alkaline phosphatase (AP)-conjugated rabbit anti-goat and goat anti-mouse secondary antibodies were obtained from Santa Cruz Biotechnology (Santa Cruz, CA, USA), and the Ryanodine Receptor was from Millipore (MA, USA). [3H]-IP3 and [3H]-ryanodine were purchased from New England Nuclear (NEN, MA, USA). (1,4,5)-Inositol trisphosphate and ryanodine were from Calbiochem (CA, USA)
Summary
Intracellular calcium is a biochemical messenger that regulates part of the metabolic adaptations in the daily fed-fast cycle. Given that in nature the food sometimes is scarce, organisms have developed strategies to optimize the finding of food, the processing of nutrients, and the assimilation of biomolecules precisely when mealtime result a predictable event. Part of these adaptations is a timing system that underlies the events involved in the circadian rhythmicity. When animals are under a restricted feeding schedule over a period of several weeks, they display a behavior known as food anticipatory activity (FAA), an arousal behavior that precedes the availability of food This FAA behavior is associated with the FEO [4]
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