FORKHEAD BOX PROTEIN O1 (FOXO-1) CONTENT IS ABNORMAL UPON INSULIN STIMULATION IN CYSTIC FIBROSIS (CF) SUGGESTING INSULIN RESISTANCE, IS RELATED TO THE CFTR ABNORMALITY, AND INCREASES WITH IGF-I TREATMENT

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 842-862-Insulin Signaling & Action
Basic/Translational
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-853
Maria Elisabeth Street*1, Arianna Smerieri2, Luisa Montanini3, Luigi Maiuri4 and Sergio Bernasconi1
1University Hospital of Parma, Parma, Italy, 2University hospital of Parma, 3University Hospital of Parma, 4European Institute for research in cystic fibrosis, San Raffaele Scientific Institute, Milan, Italy
Cystic Fibrosis Related Diabetes (CFRD) is to date the most frequent complication in Cystic Fibrosis (CF). A possible role of insulin-resistance is debated. We investigated for the first time insulin signal transduction.

We used CFBE41o- cells as they have the most common CFTR gene mutation in the caucasian population (F508del) in the homozygous state, and in their normal counterparts (16HBE14o- cells). This mutation is associated also with a higher risk of developing CFRD. We further investigated and confirmed our in vitro findings in young adult female CF mice, homozygous for the F508del mutation (129/FVB out-bred background), and in their wild-type littermates.

Total and phosphorylated contents of insulin receptor [Y1162/Y1163], IRS1 [Y941 and S307], p85-PI3K, and AKT [pS473] were similar in the two cell types, whereas total and p-FOXO-1 [S256] contents were reduced in both baseline conditions, and after insulin stimulation at 2,5 and 5 ng/mL, in the CF cells. In addition, these cells showed increased total and activated ERK1/2 [T202-Y204/T182-Y187], and reduced b-2 arrestin contents. The use of a CFTR inhibitor (inh 172) in the wild-type cells determined changes in FOXO-1 as in the CF cells. In the CF mouse model, reduced FOXO-1 contents were confirmed in muscle (vastus lateralis) while no difference was seen in the liver and in white adipose tissue. Both cells and mice were treated with IGF-I (50 ng/mL and 4µg/hg/day, respectively) which significantly increased the p/t-FOXO-1 ratio in the CF cells and in CF mouse muscle.

In conclusion, we provided evidence of insulin insensitivity on a molecular basis in CF. The data in CF cells showed reduced total FOXO-1 content in baseline conditions, corresponding to the fasting state, and in the presence of insulin, compatible with reduced gluconeogenesis and increased adipogenesis. These findings were related with CFTR loss of function. Changes were confirmed in the muscle, in the in vivo model. Finally, IGF-I treatment was effective in increasing FOXO-1 contents, suggesting it could be considered as potential treatment in CF patients. To address studies specifically on insulin sensitivity and signal transduction usually hepatocytes, adipocyte and myocyte cell models are used, however, these are unavailable for CF, thus, airway epithelial cells seemed to be an appropriate screening model to address for the first time a molecular study of insulin signal transduction in this disease.

 

Nothing to Disclose: MES, AS, LM, LM, SB

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

Sources of Research Support: Grant support was given by research funds from the Dept of Pediatrics, University of Parma, Italy, and from the Italian Association for Cystic Fibrosis, Emilia-Romagna Region, Italy.