Sensory nerves affect the recruitment and differentiation of rat periovarian brown adipocytes during cold acclimation.
Rat periovarian adipose tissue contains a low number of uncoupling protein-expressing brown adipocytes scattered into lobules of white fat. Their increase following cold acclimation is matched by a major increase in noradrenergic and neuropeptide Y-, substance P- and calcitonin gene-related peptide-containing nerves. To ascertain whether periovarian fat is provided with sensory nerves, and whether any relationship exists between such nerves (in particular the calcitonin gene-related peptide-containing fibers found in cold-acclimated rats in close association with brown adipocytes) and brown fat recruitment, the effects of capsaicin desensitization on neuropeptide-containing nerves and brown adipocyte density were studied in the periovarian tissue of rats kept at 20 degrees C and on a group acclimated to 4 degrees C for 14 days. In both groups, systemic capsaicin administration considerably reduced the expression of substance P and calcitonin gene-related peptide in vascular-nerve bundles and parenchyma. In cold-acclimated rats, the increase in brown adipocyte density was significantly checked by capsaicin administration (21.11 versus 7.96 brown adipocytes/mm2, P<0.05). Finally, ultrastructural investigation showed the occurrence of brown adipocyte precursors filled with aggregates of glycogen and poorly differentiated multilocular adipocytes in capsaicin-treated cold-acclimated rats. These data suggest that periovarian adipose tissue is indeed provided with sensory neuropeptide-containing nerves and that they play a role in the recruitment and differentiation of brown adipocytes.
Institute of Normal Human Morphology, School of Medicine, University of Ancona, Ancona, Italy.
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A
Giordano
M
M
Morroni
F
F
Carle
R
R
Gesuita
G F
GF
Marchesi
S
S
Cinti
D000064:Acclimatization / Q000502:physiology*; D017667:Adipocytes / Q000166:cytology* / Q000502:physiology*; D002001:Adipose Tissue, Brown / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis / Q000096:biosynthesis / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D002452:Cell Count / Q000187:drug effects; D002454:Cell Differentiation / Q000502:physiology; D003080:Cold Temperature; D005260:Female; D008854:Microscopy, Electron; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000032:analysis; D010053:Ovary / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000032:analysis / Q000096:biosynthesis / Q000502:physiology; D013696:Temperature
D009479:Neuropeptides; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin