PhD from Cornell University
Graduate fields: Animal Science, Nutrition
Area(s) of interest: Hormonal regulation of metabolism, growth and development. Study of the leptin and growth hormone - IGF systems at the molecular , cellular and organismal levels.
Teaching:
- ANSC 3920 Mechanisms of Growth and Development
- ANSC 6220 Seminars in Animal Metabolism
- American Association for the Advancement of Science
- American Society of Animal Science
- American Society for Nutritional Sciences
- Endocrine Society
Current Research:
The overall goal of my research program is to understand the regulation of metabolism, growth and development by hormones. We pursue this goal at the molecular, cellular and organismal level using mice, sheep or cattle. Our research activities can be categorized in three areas:
1) Hormonal coordination of metabolism in energy deficient ruminants Dairy cattle experience dramatic changes in metabolism during the period from pregnancy to lactation when they enter a period of severe nutritional insufficiency. The energy shortfall of early lactation is met by mobilization of endogenous reserves, and by shifting the pattern of nutrients used by non-mammary tissues. When these adaptations fail, cows develop metabolic and infectious disorders (ketosis, hepatic lipidosis, parturient paresis, retained placenta and metritis, and mastitis). The goal of this research program is to identify the roles of growth hormone (GH) and leptin in inducing beneficial adaptations in the early lactating dairy cows. Our research shows that these two hormones complement each other in early lactation, with leptin inducing adaptations in the central nervous system whereas GH does the same in peripheral tissues. We are now focusing on understanding which adaptations are induced in liver, adipose tissue and skeletal muscles by variation in central leptin signaling and peripheral GH signaling.
2) Regulation and function of vascular insulin-like growth factors (IGFs) IGFs are insulin-like proteins that are necessary for normal body growth and for the development of specific tissues (muscle, bone, mammary gland, etc). They are also involved in diseases such as cancer and diabetes and in the aging process. Two major pools of IGFs exist: IGFs can either be produced by the liver and secreted in plasma or synthesized locally within tissues. Prior to this research, the prevalent idea was that plasma IGFs represented a non-functional pool. To test this model, we developed a mouse knockout with a substantial reduction in plasma IGF-I (e.g., The acid labile subunit (ALS) knockout mouse). We have used this model alone or in combination with other transgenic models to show that plasma IGF-I is important in regulating bone growth and carbohydrate metabolism. We are now focusing on functional actions of circulating IGF-I in animals subjected to anabolic or catabolic conditions.
3) Effect of fetal under-nutrition on postnatal energy metabolism Epidemiological studies of human populations link fetal under-nutrition to juvenile obesity and higher incidence of chronic diseases during adult life (diabetes, cardiovascular diseases and cancer). Obesity stems from an imbalance between energy intake and expenditure, two processes controlled by hypothalamic regions of the brain. These observations have led to the hypothesis that fetal under-nutrition alters hypothalamic development such that obesity is favored after birth. We are currently using the sheep, an animal that is identical to humans in terms of hypothalamic development and also develops excessive appetite and lipid deposition after intrauterine undernutrition. Our current efforts are focused on the causal relation between intrauterine under-nutrition, impaired fetal hypothalamic development and postnatal obesity.
Recent papers and reviews providing an overview of our research:
Boisclair, Y.R.; and S. Thorn. 2007. Regulation and Role of Leptin: Ruminants. In Encyclopedia of Animal Science; Pond, W.G. and A.W. Bell, Eds.; Taylor & Francis Group.
Rhoads, R.P., J.W. Kim, M.E. VanAmburgh, R.A. Ehrhardt, S.J. Frank, and Y.R. Boisclair. 2007 Effect of nutrition on the growth hormone responsiveness of liver and adipose tissue in dairy cows. J. Endocrinol. 195:49-58.
Thorn, S.R., M.J. Meyer, M.E. VanAmburgh, and Y.R. Boisclair. 2007. Effect of estrogen on leptin and expression of leptin receptor transcripts in prepubertal dairy heifers. J. Dairy Sci. 90:3742-3750.
Boisclair, Y.R., S.R. Wesolowski, J.W. Kim, and R.A. Ehrhardt. 2006. Roles of growth hormone and leptin in the periparturient dairy cow. Proceedings of the Xth International Symposium on Ruminant Physiology (K. Sejrsen, T. Hvelplund and M.O. Nielsen, Eds). Wageningen Academic Publishers, Wageningen, The Netherlands. Pages 327-346.
Domene, H.M., S.V. Bengolea, H.G. Jasper, and Y.R. Boisclair. 2005. Acid-labile subunit deficiency: Phenotypic similarities and differences between human and mouse. J. Endocrinol. Invest. 28 (Suppl. 5):43-46.
Gu, F., N. Dube, J.W. Kim, A. Cheng, M.J. Ibarra-Sanchez, M.L. Tremblay, and Y.R. Boisclair. 2003. Protein tyrosine phosphatase-1B attenuates growth hormone-mediated JAK2-STAT signaling. Mol. Cell. Biol. .23:3753-3762.
Haluzik, M., S. Yakar, O. Gavrilova, J. Setser, Y.R. Boisclair, and D. LeRoith. 2003. Insulin resistance in the liver-specific IGF-1 gene deleted mouse is abrogated by deletion of the acid-labile subunit of the IGF-binding protein-3 complex: relative roles of growth hormone and IGF-I in insulin resistance. Diabetes. 52:2483-2489.