Open AccessThe Influence of Human Growth Hormone (GH) and Thyroxine (T 4 ) on the Differentiation of Adipose Tissue in the Fetus
Author(s) -
Hausman Gary J.,
Wright J. Thom,
Latimer Amanda,
Watson Rosetta,
Martin Roy J.
Publication year - 1993
Publication title -
obesity research
Language(s) - English
Resource type - Journals
eISSN - 1550-8528
pISSN - 1071-7323
DOI - 10.1002/j.1550-8528.1993.tb00012.x
Subject(s) - medicine , endocrinology , adipose tissue , fetus , thyroid , hormone , lipoprotein lipase , biology , pregnancy , genetics
Late term fetuses from genetically obese dams have slightly larger fat cells, greater adipose tissue lipoprotein lipase (LPL) activities, elevated levels of thyroid hormones, and depressed growth hormone (GH) levels when compared to fetuses from lean dams. We have investigated the influence of thyroid hormone and GH status per se on these and other adipose tissue traits by chronically treating hypophysectomized (hypox) fetuses (day 70) between day 90 and 105 of gestation with either thyroxine (T4) or human GH. Treatment with T4 decreased body weights ( P <.05), increased serum T 4 levels ( P <.05), and enhanced skin and hair development ( P <.05). Quantitative analysis of sections of perirenal and subcutaneous adipose tissue indicated that T 4 increased LPL activity ( P <.05), slightly increased fat cell size, and more than doubled ( P <.05) lipid accretion. A hypox induced deficit in fat cell cluster number in the outer layer of subcutaneous tissue was normalized by T 4 ( P <.05). Conversely, human GH (hGH) treatment had no influence on body weight, increased serum hGH levels, decreased fat cell size ( P <.05) and LPL activity ( P <.05) but had no influence on lipid accretion. Quantitative analysis of adipose tissue sections provided direct and indirect evidence of a “critical” or “sensitive” period between 90 and 105 days, since fetal hypox at day 70 severely impeded preadipocyte recruitmentheplication during this period. Furthermore, T 4 but not GH effectively normalized this hypox‐induced deficiency in preadipocyte development. Therefore, T 4 may have a major role in preadipocyte recruitmentheplication during late fetal life.