APM/CD13 and FOS in the hypothalamus of monosodium glutamate obese and food deprived rats

Protein (western blotting) and gene (PCR) expressions, catalytic activity of puromycin-insensitive membrane-bound neutral aminopeptidase (APM/CD13) and in situ regional distribution of CD13 and FOS immunoreactivity (ir) were evaluated in the hypothalamus of monosodium glutamate obese (MSG) and/or food deprived (FD) rats in order to investigate their possible interplay with metabolic functions. Variations in protein and gene expressions of CD13 relative to controls coincided in the hypothalamus of MSG and MSG-FD (decreased 2- to 17-fold). Compared with controls, the reduction of hypothalamic CD13 content reflected a negative balance in its regional distribution in the supraoptic, paraventricular, periventricular and arcuate nuclei. CD13-ir increased in the supraoptic nucleus in MSG (2.5-fold) and decreased in the paraventricular nucleus (2-fold) together with FOS-ir (1.5-fold) in FD. In MSG-FD, FOS-ir decreased (7-fold) in the paraventricular nucleus, while CD13-ir decreased in the periventricular (5.6-fold) and the arcuate (3.7-fold) nuclei. It was noteworthy that all these changes of CD13 were not related to catalytic activity of APM. Data suggested that hypothalamic CD13 plays a role in the regulation of energy metabolism not by means of APM enzyme activity.

Research Highlights
► Fasting and MSG obesity alter cellular activity and CD13 gene and protein.
► Alterations occur in different hypothalamic regions.
► CD13 protein decreases with unaltered neutral aminopeptidase activity.
► Does CD13 play a role in energy metabolism as a cell surface receptor?.