Ling Charlotte, Svensson Louise, Odén Birgitta, Weijdegård Birgitta, Edén Barbro, Edén Staffan, Billig Håkan
Department of Physiology, Sahlgrenska University Hospital, Göteborg University, 405 30 Göteborg, Sweden.
J Clin Endocrinol Metab. 2003 Apr;88(4):1804-8. doi: 10.1210/jc.2002-021137.
During lactation serum levels of prolactin (PRL) are elevated, and the activity of lipoprotein lipase (LPL) is decreased in the adipose tissue and increased in the mammary gland. However, PRL has been suggested to affect the adipose tissue in an indirect fashion during lactation. In the present study, we demonstrated expression of four PRL receptor (PRLR) mRNA isoforms (L, I, S1(a), and S1(b)) in human sc abdominal adipose tissue and breast adipose tissue using RT-PCR/Southern blot analysis. In addition, L-PRLR [relative molecular mass (M(r)) 90,000] and I-PRLR (M(r) 50,000) protein expression was detected in human sc abdominal adipose tissue and breast adipose tissue using immunoblot analysis. Two additional protein bands with the molecular weight M(r) 40-35,000 were also detected. The direct effect of PRL on the regulation of LPL activity in human abdominal adipose tissue cultured in vitro was investigated. PRL (500 ng/ml) reduced the LPL activity in human adipose tissue to 31 +/- 7.7%, compared with control. GH (100 ng/ml) also reduced the LPL activity, to 45 +/- 8.6%, compared with control. In agreement with previous studies, cortisol increased the LPL activity and GH inhibited cortisol-induced LPL activity. Furthermore, we found that PRL also inhibited the cortisol-induced LPL activity. Taken together, these results demonstrate a direct effect of PRL, via functional PRLRs, in reducing the LPL activity in human adipose tissue, and these results suggest that LPL might also be regulated in this fashion during lactation.
在哺乳期，血清催乳素（PRL）水平升高，脂肪组织中脂蛋白脂肪酶（LPL）的活性降低，而乳腺中该酶的活性增加。然而，有研究表明PRL在哺乳期以间接方式影响脂肪组织。在本研究中，我们采用逆转录-聚合酶链反应/ Southern印迹分析，证实在人腹部皮下脂肪组织和乳腺脂肪组织中存在四种PRL受体（PRLR）mRNA亚型（L、I、S1(a)和S1(b)）的表达。此外，通过免疫印迹分析，在人腹部皮下脂肪组织和乳腺脂肪组织中检测到了L-PRLR [相对分子质量（M(r)）90,000]和I-PRLR（M(r) 50,000）蛋白表达。还检测到另外两条分子量为M(r) 40 - 35,000的蛋白条带。研究了PRL对体外培养的人腹部脂肪组织中LPL活性调节的直接作用。与对照组相比，PRL（500 ng/ml）将人脂肪组织中的LPL活性降低至31±7.7%。生长激素（GH，100 ng/ml）也使LPL活性降低，与对照组相比降至45±8.6%。与先前研究一致，皮质醇增加LPL活性，而GH抑制皮质醇诱导的LPL活性。此外，我们发现PRL也抑制皮质醇诱导的LPL活性。综上所述，这些结果表明PRL通过功能性PRLR对降低人脂肪组织中LPL活性具有直接作用，并且这些结果提示在哺乳期LPL可能也以这种方式受到调节。
