Sensory or sympathetic white adipose tissue denervation differentially affects depot growth and cellularity

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2005-04, Vol.288 (4), p.R1028-R1037
• Main Authors: Shi, Haifei, Song, C. Kay, Giordano, Antonio, Cinti, Saverio, Bartness, Timothy J
• Format: Article
• Language: English
• Subjects: Adipocytes - physiology; Adipocytes - ultrastructure; Adipose Tissue - cytology; Adipose Tissue - growth & development; Adipose Tissue - innervation; Animals; Body Composition - physiology; Body Weight - physiology; Capsaicin - pharmacology; Cell Size; Chromatography, High Pressure Liquid; Cricetinae; Denervation; Immunohistochemistry; Male; Neurons, Afferent - drug effects; Neurons, Afferent - physiology; Norepinephrine - metabolism; Phodopus; Receptors, Calcitonin Gene-Related Peptide - metabolism; Sympathetic Nervous System - drug effects; Sympathetic Nervous System - physiology; Tyrosine 3-Monooxygenase - metabolism
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00648.2004

1 Department of Biology, Neurobiology and Behavior Program, Center for Behavioral Neuroscience, Georgia State University, Atlanta, Georgia; and 2 Institute of Normal Human Morphology, University of Ancona, Ancona, Italy Submitted 21 September 2004 ; accepted in final form 15 November 2004 Functional and histological evidence for the sympathetic nervous system (SNS) innervation of white adipose tissue (WAT) exists for several species; however, its sensory innervation has only been shown in laboratory rats, and its function is unclear. We tested the effects of sensory and SNS innervation of Siberian hamster epididymal and inguinal WAT (EWAT and IWAT) by assessing calcitonin gene-related peptide (CGRP)- and tyrosine hydroxylase-immunoreactivity (ir), respectively. Next, we tested the role of the sensory innervation of WAT on growth and cellularity because WAT surgical denervation increases pad mass via selective increases in fat cell number, an effect ascribed to SNS denervation but that could be due to the accompanying surgical disruption of WAT sensory innervation. Sensory denervation was accomplished via multiple local microinjections of capsaicin into WAT, and its effects were compared with those of surgical denervation. Surgically denervated IWAT and EWAT showed significantly decreased tyrosine hydroxylase-ir and CGRP-ir, whereas capsaicin-treated WAT had only significantly decreased CGRP-ir. Surgically denervated pad masses were significantly increased; this was accompanied by increased total fat cell number in IWAT, with no change in fat cell size. EWAT only showed a significant increase in the number of small- to medium-sized adipocytes (75–125 µm diameter). By contrast, sensory-denervated pad masses were unchanged, but IWAT showed significantly increased average fat cell size. Collectively, these data provide immunohistochemical evidence for sensory and SNS innervation of WAT in Siberian hamsters and differential control of WAT cellularity by these innervations, as well as the ability of locally applied capsaicin to selectively reduce WAT sensory innervation. surgical denervation; capsaicin; immunohistochemistry; tyrosine hydroxylase; calcitonin gene-related peptide Address for reprint requests and other correspondence: T. J. Bartness, Dept. of Biology, Georgia State Univ., 24 Peachtree Center Ave. NE, Atlanta, GA 30302-4010 (E-mail: bartness{at}gsu.edu )