Examining the Influence of Growth Hormone on the Extracellular Matrix of Adipose Tissue

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 649-677-Adipocyte Biology
Basic
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-662
Lara Householder*, Ellen Muriel Richardson Lubbers, Abigail Thaxton, Katie Troike, Edward Owen List, John Joseph Kopchick and Darlene E Berryman
Ohio University, Athens, OH
In obesity, white adipose tissue (WAT) is characterized by insulin resistance, inflammation, and accelerated remodeling. These dysfunctions ultimately contribute to obesity-associated diseases such as diabetes and cardiovascular disease. WAT fibrosis, an excess buildup of the extracellular matrix (ECM), has been observed in obese WAT and contributes to its characteristic dysfunctions and related diseases. Thus, it is an important new focus of obesity and adipose tissue research. Growth hormone (GH) has also been shown to increase collagen, the main component of the ECM, in tissues such as muscle and bone. However, little research has been conducted to assess its influence on ECM deposition in WAT.  Bovine GH transgenic (bGH) mice have high serum levels of GH, IGF-1 and insulin and are giant and lean with a shortened lifespan. Their contradictory phenotype – unhealthy leanness – allows us to investigate WAT fibrosis independent of adiposity as well as examining the chronic influence of GH. Previous research in our lab has shown that bGH mice have dramatically increased collagen, as assessed by picrosirus red staining, in the subcutaneous WAT depot. However, when the RNA levels of collagens I, III, IV, V, and VI were examined in 6-month-old male bGH and WT mice, no significant differences were found between the two genotypes or among depots. Therefore, we evaluated the chronic influence of GH on the expression of other types of collagens as well as ECM degradation enzymes and other ECM modification factors. In addition, the acute effect of GH and IGF-1 on ECM deposition was examined. Diet-induced obese mice were injected with GH or IGF-1 and then sacrificed after 2, 7, or 21 days of treatment. Expression of collagen VI in the subcutaneous and epididymal depots was assessed in all injected mouse groups as well as a high-fat fed control group through quantitative PCR analysis. Although increased expression of collagen VI was seen as a trend in both the GH and IGF-1 injected mice after 2 days of treatment, the effect of GH diminished over time and was similar to the control group at 7 days and 21 days. In contrast, the IGF-1 injected mice saw significantly increased collagen VI expression in the subcutaneous depot after 7 days of treatment. These results indicate that GH’s effect on collagen in WAT, seen in our histological data of bGH mice, may be mediated through IGF-1.

Nothing to Disclose: LH, EMRL, AT, KT, EOL, JJK, DEB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported in part by the State of Ohio’s Eminent Scholar Program that includes a gift from Milton and Lawrence Goll, by the AMVETS, by the Diabetes Institute at Ohio University, and by NIH grants DK083729, AG019899, AG031736.