| First Author | Luque RM | Year | 2007 |
| Journal | Am J Physiol Endocrinol Metab | Volume | 292 |
| Issue | 3 | Pages | E891-9 |
| PubMed ID | 17122091 | Mgi Jnum | J:118904 |
| Mgi Id | MGI:3700623 | Doi | 10.1152/ajpendo.00258.2006 |
| Citation | Luque RM, et al. (2007) Effects of leptin replacement on hypothalamic-pituitary growth hormone axis function and circulating ghrelin levels in ob/ob mice. Am J Physiol Endocrinol Metab 292(3):E891-9 |
| abstractText | Leptin-deficient obese mice (ob/ob) have decreased circulating growth hormone (GH) and pituitary GH and ghrelin receptor (GHS-R) mRNA levels, whereas hypothalamic GH-releasing hormone (GHRH) and somatostatin (SST) expression do not differ from lean controls. Given the fact that GH is suppressed in diet-induced obesity (a state of hyperleptinemia), it remains to be determined whether the absence of leptin contributes to changes in the GH axis of ob/ob mice. Therefore, to study the impact of leptin replacement on the hypothalamic-pituitary GH axis of ob/ob mice, leptin was infused for 7 days (sc), resulting in circulating leptin levels that were similar to wild-type controls ( approximately 1 ng/ml). Leptin treatment reduced food intake, body weight, and circulating insulin while elevating circulating n-octanoyl ghrelin concentrations. Leptin treatment did not alter hypothalamic GHRH, SST, or GHS-R mRNA levels compared with vehicle-treated controls. However, leptin significantly increased pituitary GH and GHRH-R expression and tended to enhance circulating GH levels, but this latter effect did not reach statistical significance. In vitro, leptin (1 ng/ml, 24 h) did not affect pituitary GH, GHRH-R, or GHS-R mRNA but did enhance GH release. The in vivo effects of leptin on circulating hormone and pituitary mRNA levels were not replicated by pair feeding ob/ob mice to match the food intake of leptin-treated mice. However, leptin did prevent the fall in hypothalamic GHRH mRNA and circulating IGF-I levels observed in pair-fed mice. These results demonstrate that leptin replacement has positive effects on multiple levels of GH axis function in ob/ob mice. |
