Parathyroid hormone-related protein induces cachectic syndromes without directly modulating the expression of hypothalamic feeding-regulating peptides.
OBJECTIVE
Parathyroid hormone-related protein (PTHrP) is a causative factor of humoral hypercalcemia of malignancy (HHM) and concurrent anorexia and wasting. Because changes in the expression of hypothalamic feeding-regulating peptides can directly affect appetites and thereby can cause anorexia and wasting, we addressed whether the cachectic syndromes induced by PTHrP rely on the action of hypothalamic feeding-regulating peptides.


METHODS
Rats were inoculated with a LC-6 human cancer xenograft that secreted PTHrP, and the mRNA levels of the hypothalamic feeding-regulating peptide genes and serum leptin levels were examined before and after the development of HHM by in situ hybridization histochemistry and ELISA, respectively. Some rats were given the anti-PTHrP antibody.


CONCLUSIONS
The mRNA levels for the orexigenic peptides, such as the agouti-related protein and the neuropeptide Y in the arcuate nucleus (Arc), were significantly increased after the development of HHM, whereas the mRNA levels for the anorexigenic peptides, such as the proopiomelanocortin in the Arc, the cocaine and amphetamine-regulated transcript in the Arc, and the corticotropin-releasing factor in the paraventricular nucleus, were significantly decreased after the development of HHM. Plasma leptin levels were also reduced in cachectic rats, and the administration of anti-PTHrP antibody to the cachectic rats not only improved the cachectic symptoms but also restored the mRNA levels of these orexigenic and anorexigenic peptides, except for orexin. Thus, PTHrP induces HHM and concurrent cachectic syndromes by mechanisms other than directly modulating the leptin or hypothalamic feeding-regulated peptides.
Hashimoto
Hirofumi
H
Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Azuma
Yumiko
Y
Kawasaki
Makoto
M
Fujihara
Hiroaki
H
Onuma
Etsuro
E
Yamada-Okabe
Hisafumi
H
Takuwa
Yoh
Y
Ogata
Etsuro
E
Ueta
Yoichi
Y
D000818:Animals; D002100:Cachexia / Q000209:etiology*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D017403:In Situ Hybridization; D020738:Leptin / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009478:Neuropeptide Y / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism / Q000502:physiology*; D010455:Peptides / Q000737:chemistry*; D051381:Rats; D011923:Rats, Nude
D020738:Leptin; D009478:Neuropeptide Y; D044162:Parathyroid Hormone-Related Protein; D010455:Peptides