Glycogen metabolism in brain and neurons - astrocytes metabolic cooperation can be altered by pre- and neonatal lead (Pb) exposure.

Toxicology. 2017 Sep 12;390:146-158. doi: 10.1016/j.tox.2017.09.007. 

Baranowska-Bosiacka I1, Falkowska A2, Gutowska I3, Gąssowska M4, Kolasa-Wołosiuk A5, Tarnowski M6, Chibowska K2, Goschorska M2, Lubkowska A7, Chlubek D2.
Author information
Glycogen metabolism in brain and neurons - astrocytes metabolic cooperation can be altered by pre- and neonatal lead (Pb) exposure.
1 Department of Biochemistry and Medical Chemistry, Powstańców Wlkp. 72 St., 70-111 Szczecin, Pomeranian Medical University in Szczecin, Poland. Electronic address: Ten adres pocztowy jest chroniony przed spamowaniem. Aby go zobaczyć, konieczne jest włączenie w przeglądarce obsługi JavaScript..
2 Department of Biochemistry and Medical Chemistry, Powstańców Wlkp. 72 St., 70-111 Szczecin, Pomeranian Medical University in Szczecin, Poland.
3 Department of Biochemistry and Human Nutrition, Broniewskiego 24 St., 71-460 Szczecin, Pomeranian Medical University in Szczecin, Poland.
4 Department of Cellular Signalling, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawińskiego 5, 02-106 Warsaw, Poland.
5 Department of Histology and Embriology, Powstańców Wlkp. 72 St., 70-111 Szczecin, Pomeranian Medical University in Szczecin, Poland.
6 Department of Physiology, Powstańców Wlkp. 72 St., 70-111 Szczecin, Pomeranian Medical University in Szczecin, Poland.
7 Department of Functional Diagnostics and Physical Medicine, Pomeranian Medical University in Szczecin, Żołnierska 48 Str, 71-210 Szczecin, Poland.

ABSTRACT

Lead (Pb) is an environmental neurotoxin which particularly affects the developing brain but the molecular mechanism of its neurotoxicity still needs clarification. The aim of this paper was to examine whether pre- and neonatal exposure to Pb (concentration of Pb in rat offspring blood below the "threshold level") may affect the brain's energy metabolism in neurons and astrocytes via the amount of available glycogen. We investigated the glycogen concentration in the brain, as well as the expression of the key enzymes involved in glycogen metabolism in brain: glycogen synthase 1 (Gys1), glycogen phosphorylase (PYGM, an isoform active in astrocytes; and PYGB, an isoform active in neurons) and phosphorylase kinase β (PHKB). Moreover, the expression of connexin 43 (Cx43) was evaluated to analyze whether Pb poisoning during the early phase of life may affect the neuron-astrocytes' metabolic cooperation. This work shows for the first time that exposure to Pb in early life can impair brain energy metabolism by reducing the amount of glycogen and decreasing the rate of its metabolism. This reduction in brain glycogen level was accompanied by a decrease in Gys1 expression. We noted a reduction in the immunoreactivity and the gene expression of both PYGB and PYGM isoform, as well as an increase in the expression of PHKB in Pb-treated rats. Moreover, exposure to Pb induced decrease in connexin 43 immunoexpression in all the brain structures analyzed, both in astrocytes as well as in neurons. Our data suggests that exposure to Pb in the pre- and neonatal periods results in a decrease in the level of brain glycogen and a reduction in the rate of its metabolism, thereby reducing glucose availability, which as a further consequence may lead to the impairment of brain energy metabolism and the metabolic cooperation between neurons and astrocytes.

KEYWORDS:

Brain glycogen metabolism; Glycogen phosphorylase brain isoform (PYGB); Glycogen phosphorylase kinase (PHKB); Glycogen phosphorylase muscle isoform (PYGM); Glycogen synthase (Gys1); Lead (Pb) neurotoxicity

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