Fructose-1,6-bisphosphate does not preserve ATP in hypoxic–ischemic neonatal cerebrocortical slices

Abstract

Fructose-1,6-bisphosphate (FBP), an endogenous intracellular metabolite in glycolysis, was found in many preclinical studies to be neuroprotective during hypoxia-ischemia (HI) when administered exogenously. We looked for HI neuroprotection from FBP in a neonatal rat brain slice model, using 14.1 Tesla 1 H / 31 P/ 13 C NMR spectroscopy of perchloric acid slice extracts to ask: 1) if FBP preserves high energy phosphates during HI; and 2) if exogenous [1-13 C]FBP enters cells and is glycolytically metabolized to [3-13 C]lactate. We also asked: 3) if substantial superoxide production occurs during and after HI, thinking such might be treatable by exogenous FBP's antioxidant effects. Superfused P7 rat cerebrocortical slices (350μm) were treated with 2 mM FBP before and during 30 min of HI, and then given four hours of recovery with an FBP-free oxygenated superfusate. Slices were removed before HI, at the end of HI, and at 1 and 4 hours after HI. FBP did not improve high energy phosphate levels or change 1 H metabolite profiles. Large increases in [3-13 C]lactate were seen with 13 C NMR, but the lactate fractional enrichment was always (1.1±0.5)%, implying that all of lactate's 13 C was natural abundance 13 C, that none was from metabolism of 13 C-FBP. FBP had no effect on the fluorescence of ethidium produced from superoxide oxidation of hydroethidine. Compared to control slices, ethidium fluorescence was 25% higher during HI and 50% higher at the end of recovery. Exogenous FBP did not provide protection or enter glycolysis. Its use as an antioxidant might be worth studying at higher FBP concentrations.

Fructose-1,6-bisphosphate attenuates induction of nitric oxide synthase in microglia stimulated with lipopolysaccharide

“…In contrast, several other reports showed FBP failed to preserve ATP in in vivo and in vitro models of hypoxia or ischemia (Hofer et al, 2009;Kelleher et al, 1995;Liu et al, 2008). It was speculated that the lack of its effect on energy metabolism was probably because it was prevented from entering cells in adequate quantities.…”

Outcome-Related Metabolomic Patterns from1H/31P NMR after Mild Hypothermia Treatments of Oxygen—Glucose Deprivation in a Neonatal Brain Slice Model of Asphyxia

“…The protocol was followed the methods published in an earlier study (Liu et al 2008). In brief, a parallel superfusion channel with an independent ACSF reservoir containing 5 μM HEt was established for this procedure.…”

Fructose-1,6-bisphosphate suppresses lipopolysaccharide-induced expression of ICAM-1 through modulation of toll-like receptor-4 signaling in brain endothelial cells

“…Cytoprotective action of FBP has been explained mainly by the hypothesis that it can act as a glycolytic intermediate capable of producing ATP and preserve ATP levels in stress situations [14,[17][18][19]. However, it has been a matter of dispute whether FBP can enter cells in adequate amounts to provide energy required for the maintenance of cell function upon exposure to insults [20,21]. In this context, alternative mechanisms other than augmentation of energy metabolism have been suggested for the neuroprotective action of FBP.…”

“…It was proposed that FBP exerts its protective role through the preservation of ATP levels by serving as a high energy substrate under pathologic conditions [14,[17][18][19]. However, this hypothesis has been challenged by recent reports [20,21]. Thus, it has been suggested that mechanisms other than augmentation of energy metabolism might be also important for the cytoprotective effects of FBP [21].…”