Effects of a copper-deficient diet on the biochemistry, neural morphology and behavior of aged mice

Abstract

Copper dyshomeostasis has been suggested as an aetiological risk factor for some neurodegenerative diseases, such as Alzheimer's disease. However, the precise mechanism at the base of this involvement is still obscure. In this work, we show the effects of a copper-deficient diet in aged CD1 mice and the influence of such a diet on: a) the concentration of various metal ions (aluminium, copper, iron, calcium, zinc) in the main organs and in different brain areas; b) the alteration of metallothioneins I-II and tyrosine hydroxylase immunopositivity in the brain; c) behavioural tests (open field, pole, predatory aggression, and habituation/dishabituation smell tests). Our data suggested that the copper-deficiency was able to produce a sort of "domino effect" which altered the concentration of the other tested metal ions in the main organs as well as in the brain, without, however, significantly affecting the animal behaviour.

Figure 1. Metal content in the brain.

(A) Schematic representation of the outline of the study. 15 month old CD1 mice were fed with a Cu-adequate (CuA) or Cu-deficient (CuD) diet for 12 weeks. Behavioural tests were performed the last 2 weeks of the treatment. Mice were then sacrificed and metal determination, IHC as well as biochemical investigations were performed. (B) Cu, (C) Fe, (D) Al, (E) Zn, and (F) Ca content (µg/g wet tissue) in the parietal, frontal, occipital cortex, and cerebellum. *p<0.05; **p<0.01; ***p<0.001.

Figure 2. Cu content.

Cu (µg/g wet tissue) in the lungs, kidneys, small intestine, large intestine, heart, liver, and muscle. ** p<0.01.

Figure 3. Fe content.

Fe (µg/g wet tissue) in the lungs, kidneys, small intestine, large intestine, heart, liver, and muscle. * p<0.05; ** p<0.01.

Figure 4. Zn content.

Zn (µg/g wet tissue) in the lungs, kidneys, small intestine, large intestine, heart, liver, and muscle. * p<0.05.

Figure 5. Ca content.

Ca (µg/g wet tissue) in the lungs, kidneys, small intestine, large intestine, heart, liver, muscle, and spleen. ** p<0.01.

Figure 6. Metallothionein (MT) content in the brain.

MT (µg/g wet tissue) in the parietal, frontal, occipital cortex, and cerebellum. *p<0.05; ***p<0.001.

Figure 7. Representation of Immunohistochemical results.

The images are relative to sagittal sections of the brain. Left column (A, C, E): CuD mice. Right column (B, D, F): control group. (A, B) MT I-II immunohistochemistry, cerebellum; scale bar = 200 µm; C, ventral tegmental area of the mesencephalon, scale bar = 50 µm; (D) locus cœruleus, scale bar = 50 µm; (E, F) TH-immunohistochemistry, (E) substantia nigra, scale bar = 50 µm.

Figure 8. Pole test.

Means+SEM are shown. Both groups can learn efficiently to climb down from the pole.