Differential effects of leptin administration on the abundance of UCP2 and glucocorticoid action during neonatal development

Abstract

In the neonate, adipose tissue and the lung both undergo a rapid transition after birth, which results in dramatic changes in uncoupling protein abundance and glucocorticoid action. Leptin potentially mediates some of these adaptations and is known to promote the loss of uncoupling protein (UCP)1, but its effects on other mitochondrial proteins or glucocorticoid action are not known. We therefore determined the effects of acute and chronic administration of ovine recombinant leptin on brown adipose tissue (BAT) and/or lung in neonatal sheep. For the acute study, eight pairs of 1-day-old lambs received, sequentially, 10, 100, and 100 μg of leptin or vehicle before tissue sampling 4 h from the start of the study, whereas in the chronic study, nine pairs of 1-day-old lambs received 100 μg of leptin or vehicle daily for 6 days before tissue sampling on day 7. Acute leptin decreased the abundance of UCP2, glucocorticoid receptor, and 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1 mRNA and increased 11β-HSD type 2 mRNA abundance in BAT, a pattern that was reversed with chronic leptin administration, which also diminished lung UCP2 protein abundance. In BAT, UCP2 mRNA abundance was positively correlated to plasma leptin and nonesterified fatty acids and negatively correlated to mean colonic temperature in the leptin group at 7 days. In conclusion, leptin administration to the neonatal lambs causes differential effects on UCP2 abundance in BAT and lung. These effects may be important in the development of these tissues, thereby optimizing lung function and fat growth.

Different effects of maternal parity, cold exposure and nutrient restriction in late pregnancy on the abundance of mitochondrial proteins in the kidney, liver and lung of postnatal sheep

“…It is associated with a decrease in breathing frequency and a concomitant rise in the recruitment of laryngeal braking (Symonds et al 1993), the function of which is to extend expiratory time, thereby increasing the time for gaseous exchange within the lung and potentially increasing energy requirements (Symonds et al 1993). Differences in mitochondrial protein responses within the lungs over the period in which there are rapid changes in function are, therefore, not unexpected and are consistent with the very different endocrine regulation of UCP and VDAC during fetal and postnatal development (Gnanalingham et al 2005f).…”

“…The specificity of the procedure was confirmed by the absence of binding when adjacent sections were incubated with rabbit serum from an unimmunised rabbit in place of rabbit anti-ovine primary antibody. It was not able to perform the same analyses with respect to the location of UCP2 in the lung due to the lack of available antibodies (Gnanalingham et al 2005f).…”

“…Due to the very limited amount of this antibody available, it was only possible to determine UCP2 abundance in mitochondria prepared from lungs of 1-day old offspring. There are currently no other antibodies that are able to convincingly detect ovine UCP2 (Gnanalingham et al 2005f). Specificity of detection was confirmed using non-immune rabbit serum.…”

Nutritional manipulation between early to mid-gestation: effects on uncoupling protein-2, glucocorticoid sensitivity, IGF-I receptor and cell proliferation but not apoptosis in the ovine placenta

“…This contrasts with adipose tissue in which nutritional programming of all of these proteins is observed (Mostyn et al 2003) and emphasizes their tissue-specific regulation (Gnanalingham et al 2005b(Gnanalingham et al , 2006. Unfortunately, we were unable to confirm whether UCP2 protein was similarly affected because of the current unavailability of specific antibodies for ovine UCP2 (Gnanalingham et al 2005f). The functional consequence of an increase in placental UCP2 remains to be established.…”

“…The specificity of the procedure was confirmed by the absence of binding when adjacent sections were incubated with rabbit serum from an unimmunized rabbit in place of rabbit antiovine primary antibody. It was not possible to perform the same analyses with respect to the location of UCP2 due to the lack of appropriately validated antibodies (Gnanalingham et al 2005f). The same analyses were undertaken for the GR and IGF-IR, but in accord with our failure to detect protein at the correct molecular weight by Western blotting neither antibody showed specificity of binding to the placenta.…”