Fed rats and fasted rats (17h of food deprivation) with intra-peritoneal administration of :
Interaction between olfaction and food intake: metabolic state drives changes in the astroglial deployment within the olfactory bulb glomeruli in rats
Fasting status of the rats
Virginie Daumas-Meyer, Gaëlle Champeil-Potokar, Catherine Papillon, Patrice Dahirel, Marielle Levillain, Patrice Congar, Isabelle Denis.
virginie.daumas-meyer@jouy.inra.fr
Glycemia
(n=6)
Glycemia (mg/dL)
Fed 17h 24h 48h
60 80 100 120 140 160
a
b b
b
Body weight loss
(n=12)
Difference of body weight on 48h (in %)
Fed 17h 24h 48h
-20 -10 0 10 20
a
b b
c
Leptinemia
(n=12)
[Leptinemia] ng/mL
Fed 17h 24h 48h
0 1 2 3
4 a
b
b,c
c
Olfactory food seeking
(n=6)
Time of sniffing (in %)
Fed 17h 24h 48h
0 10 20 30 40 50
a
b b b
Neurobiologie de l’Olfaction
Centre de Recherche de Jouy-en-Josas
Domaine de Vilvert • 78352 Jouy-en-Josas Cedex • FRANCE
Olfaction participates in the elaboration of the hedonic value of foods, food choice and the regulation of food intake. Reciprocally, the detection of food odors is influenced by metabolic state and thereby contributes to the initiation and termination of eating behavior. Fasting increases olfactory performances, notably by increasing neuronal activation in the olfactory bulb (OB) (Prud’homme et al, 2009), the first integration site of olfactory signals towards the central nervous system. Within the OB glomeruli, glutamatergic synapses between olfactory sensory neurons and mitral cells are regulated by periglomerular neurons and astrocytes.
Hypothesis
Conclusion Results
Astrocytes are now fully recognized as synaptic partners (Halassa & Haydon 2010) and are thought to generate some kind of “metaplasticity” in the brain (Min et al, 2012) as well as in the OB glomerular region (Roux et al, 2011).
The neuron-astrocyte cross-talk in the glomeruli, albeit poorly known, may be a central player in the metabolic regulation of the olfactory responses.
Models
Our results show that the deployment of astroglial processes within the OB glomeruli varies according to the metabolic status of the rats and is influenced by peptides involved in food intake regulation, such as PYY 3-36, and/or by changes in glycemia. This morphological plasticity may participate in the adaptation of olfactory sensitivity to food intake, by regulating the first step of odor signal integration in the CNS.
We are now seeking for the functional consequences of this astroglial plasticity on the olfactory signal and the underlying mechanisms.
Overnight (17h) food deprivation results in an increase in the astroglial deployment within glomeruli in all OB regions.
This increased deployment is also observed after 24h fasting in the medial and ventral OB regions but not after 48h fasting.
Fed rats 17h of food deprivation 24h of food deprivation 48h of food deprivation
Mitral cells
Olfactory sensory neurons
To test the hypothesis that glomerular astrocytes are involved in the metabolic sensing of the olfactory system, we have compared the expansion of the astroglial processes (Immunohistochemical – Quantification of the GFAP area) within the glomeruli in:
• fed or fasted rats
• Fed and fasted rats injected with differents anorexigenic and orexigenic peptides
GFAP/Hoechst labelling
Astroglial deployment within the OB glomeruli
Quantification of GFAP labelling area/glomerulus : 4 sections/OB region/rat (≈ 200 glomeruli/region/rat)
n= 7 rats/condition
OB Dorsal region
Medial region Ventral region
DORSAL
VENTRAL 640 µm 1840 µm 2620 µm
Context
Granule cell layer and internal plexiform layer
Mitral cell layer
External plexiform layer
Glomerular layer
Olfactory nerve layer
GLOMERULUS
Astrocytes
Objectives
17h fasting Fed
5 week old Wistar rats
Fasting
• ↗ Neuronal activation (OB) (Prud’homme et al, 2009)
• ↗ Olfactory sensitivity (Aimé P. et al, 2007)
Modification of the astroglial coverage within the olfactory
glomeruli
?
Fed rats and fasted rats (17h, 24h or 48h of food deprivation):
Anorexigenic peptide PYY 3-36
Orexigenic peptide Ghrelin
Anorexigenic peptide Leptin
Glucose Physiological
serum
FED RATS
Physiological serum
FASTED RATS
olfactory bulb level
% of GFAP labelling area/glomeruli area
Dorsal Middle Ventral
0 10 20 30 40 50 60 70 80 90 100
n= 6 or 8 rats/condition/region Permutation test (Software R)
* p0.05; **p0.01
**
** *
Fasted rats (17h)+i.p. Phy.S.
Fasted rats (17h)+i.p. Glucose
ASTROGLIAL DEPLOYMENT
olfactory bulb level
% of GFAP labelling area/glomeruli area
Dorsal Middle Ventral
0 10 20 30 40 50 60 70 80 90
100 n= 5 or 6 rats/condition/region
Permutation test (Software R)
* p0.05
Fed rats + i.p. Phy.S.
Fed rats + i.p. Ghrelin
ASTROGLIAL DEPLOYMENT
olfactory bulb level
% of GFAP labelling area/glomeruli area
Dorsal Middle Ventral
0 10 20 30 40 50 60 70 80 90
100 n= 6 rats/condition/region
Permutation test (Software R)
* p0.05; **p0.01
Fasting rats (17h)+i.p. S.Phy.
Fasting rats(17h)+i.p. PYY3-36
** * *
ASTROGLIAL DEPLOYMENT
olfactory bulb level
% of GFAP labelling area/glomeruli area
Dorsal Middle Ventral
0 10 20 30 40 50 60 70 80 90
100 n= 5 or 6 rats/condition/region
Permutation test (Software R)
* p0.05
Fed rats + i.p. Phy.S.
Fed rats + i.p. Leptin
ASTROGLIAL DEPLOYMENT
i.p. administration of GHRELIN (40µg/kg) in fed rats
i.p. administration of PYY 3-36 (100µg/kg) in fasted rats (17h)
i.p. administration of LEPTIN (25µg/kg) in fasted rats (17h)
i.p. administration of GLUCOSE (2g/kg) in fasted rats (17h)
FOOD INTAKE
% of Food intake (values relative to food intake of rats injected with physiological serum)
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
n=4 cages/condition
Permutation test (Software R)
* p0.05 p*0.05
FOOD INTAKE
% of Food intake (values relative to food intake of rats injected with physiological serum)
0 1000 2000 3000 4000 5000 6000 7000 8000
p<0.001***
100
n= 11 or 13 cages/condition Permutation test (Software R)
*** p0.001
FOOD INTAKE
% of Food intake (values relative to food intake of rats injected with physiological serum)
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
p***0.001
n=12 cages/condition
Permutation test (Software R)
* p0.05
GLYCEMIA
Glycemia (mg/dL)
60 80 100 120 140 160
FED rats FASTED rats (17h of food deprivation) GLYCEMIA Fed rats 1h after i.p. Phy.S.
GLYCEMIA Fasted rats 1h after i.p. Phy.S.
GLYCEMIA Fasted rats 1h after i.p. GLUCOSE
**
GFAP/Hoechst labelling
PYY 3-36 reverses the astroglial deployment induced by fasting
Ghrelin doesn’t mimic the effect of fasting on astroglial deployment
Glucose reverses the astroglial deployment induced by fasting
Leptin doesn’t mimic the effect of satiety on astroglial deployment
Perspectives
Fasted rats (17h) Fed rats
Neuronal activation (OB) PYY 3-36
Glycemia
% of GFAP labelling area/glomeruli area
Dorsal Medial Ventral
0 10 20 30 40 50 60 70 80 90 100
Fed
17h of food deprivation 24h of food deprivation 48h of food deprivation
n= 7 rats/condition/region
** p0.01, *p0.05
Permutation test (Software R)
** * **
Olfactory Bulb region
Astroglial deployement OB
Hoechst labelling
RAT HEMI HEAD