Serotonin (5-HT) affects expression of liver metabolic enzymes and mammary gland glucose transporters during the transition from pregnancy to lactation

• Published in: PloS one Vol. 8; no. 2; p. e57847
• Main Authors: Laporta, Jimena, Peters, Tonia L, Merriman, Kathryn E, Vezina, Chad M, Hernandez, Laura L
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 28.02.2013; Public Library of Science (PLoS)
• Subjects: 5-Hydroxytryptophan - pharmacology; Agriculture; AMP; AMP-activated protein kinase; AMP-Activated Protein Kinases - metabolism; Animal lactation; Animals; Biology; Biomarkers - metabolism; Blood Glucose - metabolism; Breasts; Dams; Diet; Endothelial cells; Energy balance; Energy metabolism; Energy Metabolism - drug effects; Energy Metabolism - genetics; Enzyme Activation - drug effects; Enzymes; Experiments; Feeding; Female; Gene expression; Gene Expression Regulation, Enzymologic - drug effects; Genomics; Gestation; Glands; Glucose; Glucose Transport Proteins, Facilitative - genetics; Glucose Transport Proteins, Facilitative - metabolism; Glycolysis; Growth and Development - drug effects; Homeostasis; Insulin; Insulin - blood; Lactation; Lactation - blood; Lactation - drug effects; Lactation - genetics; Lactation - metabolism; Liver; Liver - drug effects; Liver - enzymology; Liver - metabolism; Mammary gland; Mammary glands; Mammary Glands, Animal - drug effects; Mammary Glands, Animal - enzymology; Mammary Glands, Animal - metabolism; Metabolism; Metabolites; Milk; Milk - metabolism; Mothers; Phosphoproteins - metabolism; Pregnancy; Proteins; Rats; Rats, Sprague-Dawley; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; Serotonin; Serotonin - metabolism; Tryptophan; Tryptophan - pharmacology; United States > US; Wisconsin
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0057847

The aim of this experiment was to demonstrate the ability of feeding serotonin (5-HT; 5-hydroxytryptamine) precursors to increase 5-HT production during the transition from pregnancy to lactation and the effects this has on maternal energy metabolism in the liver and mammary gland. Pregnant rats (n = 45) were fed one of three diets: I) control (CON), II) CON supplemented with 0.2% 5-hydroxytryptophan (5-HTP) or III) CON supplemented with 1.35% L-tryptophan (L-TRP), beginning on d13 of pregnancy through d9 of lactation (d9). Serum (pre and post-partum), milk (daily), liver and mammary gland tissue (d9) were collected. Serum 5-HT was increased in the 5-HTP fed dams beginning on d20 of gestation and remained elevated through d9, while it was only increased on d9 in the L-TRP fed dams. 5-HT levels were increased in mammary gland and liver of both groups. Additionally, 5-HTP fed dams had serum and milk glucose levels similar to the CON, while L-TRP had decreased serum (d9) and milk glucose (all dates evaluated). Feeding 5-HTP resulted in increased mRNA expression of key gluconeogenic and glycolytic enzymes in liver and glucose transporters 1 and 8 (GLUT-1, -8) in the mammary gland. We demonstrated the location of GLUT-8 in the mammary gland both in the epithelial and vascular endothelial cells. Finally, phosphorylated 5' AMP-activated protein kinase (pAMPK), a known regulator of intracellular energy status, was elevated in mammary glands of 5-HTP fed dams. Our results suggest that increasing 5-HT production during the transition from pregnancy to lactation increases mRNA expression of enzymes involved in energy metabolism in the liver, and mRNA abundance and distribution of glucose transporters within the mammary gland. This suggests the possibility that 5-HT may be involved in regulating energy metabolism during the transition from pregnancy to lactation.