Activation of placental insulin and mTOR signaling in a mouse model of maternal obesity associated with fetal overgrowth.
Fetal overgrowth is common in obese women and is associated with perinatal complications and increased risk for the child to develop metabolic syndrome later in life. Placental nutrient transport capacity has been reported to be increased in obese women giving birth to large infants; however, the underlying mechanisms are not well established. Obesity in pregnancy is characterized by elevated maternal serum insulin and leptin, hormones that stimulate placental amino acid transporters in vitro. We hypothesized that maternal obesity activates placental insulin/IGF-I/mTOR and leptin signaling pathways. We tested this hypothesis in a mouse model of obesity in pregnancy that is associated with fetal overgrowth. C57BL/6J female mice were fed a control (C) or a high-fat/high-sugar (HF/HS) pelleted diet supplemented by ad libitum access to sucrose (20%) solution. Placentas were collected at embryonic day 18.5. Using Western blot analysis, placental mTOR activity was determined along with energy, inflammatory, leptin, and insulin signaling pathways (upstream modulators of mTOR). Phosphorylation of S6 ribosomal protein (S-235/236), 4E-BP1 (T-37/46), Insulin receptor substrate 1 (Y-608), Akt (T-308), and STAT-3 (Y-705) was increased in obese dams. In contrast, expression of placental caspase-1, IкBα, IL-1β, and phosphorylated-JNK(p46/54-T183/Y185) was unaltered. Fetal amino acid availability is a key determinant of fetal growth. We propose that activation of placental insulin/IGF-I/mTOR and leptin signaling pathways in obese mice stimulates placental amino acid transport and contributes to increased fetal growth.
Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado; and fredrick.joseph@ucdenver.edu.
Fredrick J
FJ
Rosario
Section of Neonatology, Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, Colorado.
Theresa L
TL
Powell
Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado; and.
Thomas
T
Jansson
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004195:Disease Models, Animal; D004734:Energy Metabolism; D004789:Enzyme Activation; D005260:Female; D048070:Fetal Nutrition Disorders / Q000201:enzymology / Q000209:etiology* / Q000503:physiopathology; D020567:Fetal Weight; D005865:Gestational Age; D018836:Inflammation Mediators / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D008810:Mice, Inbred C57BL; D009752:Nutritional Status; D009765:Obesity / Q000150:complications* / Q000201:enzymology / Q000503:physiopathology; D010766:Phosphorylation; D010920:Placenta / Q000201:enzymology*; D021041:Placental Circulation; D011247:Pregnancy; D039401:Prenatal Nutritional Physiological Phenomena; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
D018836:Inflammation Mediators; D007328:Insulin; D020738:Leptin; C519530:insulin-like growth factor-1, mouse; D007334:Insulin-Like Growth Factor I; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases
fetal growth; fetal programming; intracellular signaling proteins; maternal-fetal exchange; pregnancy