BADERC-Barbara Kahn

Barbara Kahn, M.D.

Molecular Basis of Insulin and Leptin Action

Resistance to the stimulatory effect of insulin on glucose transport and metabolism is a major pathogenic factor in Type 2 diabetes and contributes to the morbidity of obesity. A major goal of my laboratory is to determine the cellular and molecular mechanisms for insulin resistance in diabetes and obesity. Leptin is a critical regulator of food intake and body weight. The other major goal of my laboratory is to understand the signaling pathways that mediate leptin’s effects. We employ complementary experimental approaches including in vivo physiology, transgenic and gene knock out technology, adenovirus-mediated gene delivery, and signal transduction. Four major project areas include:

1) Tissue specific knock out of the GLUT4 glucose transporter using Cre recombinase loxP technology. We made three different transgenic mouse lines in which we knocked out GLUT4 selectively in adipocytes, in skeletal muscle, or in cardiac muscle. Mice lacking GLUT4 in adipocytes or muscle become insulin resistant and glucose intolerant and a subset develop overt diabetes. Mice lacking GLUT4 in the heart have normal glucose homeostasis but they have cardiomegaly. Mechanistic studies in these mice are yielding important insights about insulin action and the cell biology of GLUT4 as well as the relative importance of muscle and adipose tissue in glucose homeostasis and in the development of obesity. DNA array and proteomic studies on tissues from these mice are yielding novel molecules that may alter insulin action in an endocrine manner.

2) Mechanisms by which leptin enhances insulin sensitivity. We are investigating cross-talk and convergence of insulin and leptin signaling pathways and determining which effects of leptin are exerted directly at the level of insulin target tissues and which are mediated through the central nervous system. These studies focus on the interplay of signaling through the Jak-Stat, PI3 kinase and AMP kinase pathways.

3) AMP-activated protein kinase (AMPK) – physiologic role in the hypothalamus. We are investigating the role of AMPK in the hypothalamus.

4) Role of tyrosine phosphatases in the pathogenesis of insulin resistance. We “knocked out” protein tyrosine phosphatase 1B (PTP1B) in mice in collaboration with Ben Neel in the Cancer Biology Program at BIDMC. PTP1B-/- mice are lean and have increased sensitivity to insulin and leptin. We are reconstituting PTP1B expression in individual peripheral tissues and in the brain either trangenically or with adenoviruses to determine which tissues are responsible for the phenotype.
Ideally, insights from these projects will elucidate the molecular mechanisms underlying insulin resistance and obesity and lead to new therapeutic approaches to prevent or ameliorate obesity and Type 2 diabetes.

References:

1. Klaman LD, Boss O, Peroni O, Kim JK, Zabolotny J, Kim Y-B, Sharpe AK, Stricker-Krongrad A, Shulman, GI, Neel BG, Kahn BB. Increased energy expenditure, decreased adiposity and tissue-specific insulin sensitivity in protein-tyrosine phosphatase 1B (PTP-1B)-deficient mice. Mol. Cell. Bio. 2000;20:5479-5489.

2. Zisman A, Peroni OD, Abel ED, Michael MD, Mauvais-Jarvis F, Lowell BB, Wojtaszewski JFP, Hirshman MF, Virkamaki A, Goodyear LJ, Kahn CR, Kahn BB. Targeted disruption of the glucose transporter 4 selectively in muscle causes insulin resistance and glucose intolerance. Nature Medicine. 2000;6:924-928.

3. Abel ED*, Peroni O*, Kim JK, Kim Y-B, Boss O, Hadro E, Minnemann T, Shulman GI, Kahn BB. Adipose-selective targeting of the GLUT4 gene impairs insulin action in muscle and liver. Nature. 2001;409:729-733. (* contributed equally)

4. Zabolotny JM, Kim Y-B, Peroni OD, Kim JK, Pani MA, Boss O, Klaman LD, Kamatkar S, Shulman GI, Kahn BB+, Neel BG+. Overexpression of the leukocyte antigen-related (LAR) protein tyrosine phosphatase in muscle causes insulin resistance. Proc. National Academy of Science. 2001;98:5187-5192. (+corresponding authors)

5. Minokoshi Y, Kim Y-B, Peroni OD, Fryer LGD, Muller C, Carling D, Kahn BB. Leptin stimulates fatty acid oxidation by activation of AMP-activated protein kinase. Nature 2002;415:339-343.

6. Zabolotny JM*, Bence-Hanulec KK*, Stricker-Krongrad A, Haj FG, Wang YP, Minokoshi Y, Kim Y-B, Elmquist JK, Tartaglia LA, Kahn BB*+, Neel BG*. PTP1B regulates leptin signal transduction in vivo. Developmental Cell 2002;2:489-495. (*contributed equally; + corresponding author).

7. Bluher M, Michael MD, Peroni OD, Ueki K, Carter N, Kahn BB, Kahn CR. Adipose tissue selective insulin receptor knockout protects against obesity and obesity-related glucose intolerance. Developmental Cell 2002;3:25-38.

8. Kim Y-B, Shulman GI, Kahn BB. Fatty acid infusion selectively impairs insulin action on Akt1 and PKCl/z but not on glycogen synthase kinase-3. J. Biol. Chem. 2002;277: 32915-32922.

9. Yamauchi T, Kamon J, Minokoshi Y, Ito Y, Waki H, Uchida S, Yamashita S, Noda M, Kita S, Ueki K, Eto K, Akanuma Y, Froguel P, Foufelle F, Ferre P, Carling D, Nagai R, Kimura S, Kahn BB and Kadowaki T. Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase. Nature Medicine 2002;8:1-8.

10. Bluher M, Kahn BB, Kahn CR. Extended longevity in mice lacking the insulin receptor in adipose tissue. Science 2003;299:572-574.

11. Minokoshi Y, Kahn CR, Kahn BB. Tissue-specific ablation of the GLUT4 glucose transporter or the insulin receptor challenges assumptions about insulin action and glucose homeostasis. J Biol Chem. 2003;278:33609-12.

12. Minokoshi Y, Alquier T, Furukawa N, Kim YB, Lee A, Xue B, Mu J, Foufelle F, Ferre P, Birnbaum MJ, Stuck BJ, Kahn BB. AMP-kinase regulates food intake by responding to hormonal and nutrient signals in the hypothalamus.Nature. 2004;428:569-74.

13. Zabolotny JM, Haj FG, Kim YB, Kim HJ, Shulman GI, Kim JK, Neel BG, Kahn BB. Transgenic overexpression of protein-tyrosine phosphatase 1B in muscle causes insulin resistance, but overexpression with leukocyte antigen-related phosphatase does not additively impair insulin action. J Biol Chem. 2004;279:24844-51.

14. Carvalho E, Schellhorn SE, Zabolotny JM, Martin S, Tozzo E, Peroni OD, Houseknecht KL, Mundt A, James DE, Kahn BB. GLUT4 overexpression or deficiency in adipocytes of transgenic mice alters the composition of GLUT4 vesicles and the subcellular localization of GLUT4 and insulin-responsive aminopeptidase. J Biol Chem. 2004;279:21598-605.






			Barbara Kahn, M.D. Molecular Basis of Insulin and Leptin Action Resistance to the stimulatory effect of insulin on glucose transport and metabolism is a major pathogenic factor in Type 2 diabetes and contributes to the morbidity of obesity. A major goal of my laboratory is to determine the cellular and molecular mechanisms for insulin resistance in diabetes and obesity. Leptin is a critical regulator of food intake and body weight. The other major goal of my laboratory is to understand the signaling pathways that mediate leptin’s effects. We employ complementary experimental approaches including in vivo physiology, transgenic and gene knock out technology, adenovirus-mediated gene delivery, and signal transduction. Four major project areas include: 1) Tissue specific knock out of the GLUT4 glucose transporter using Cre recombinase loxP technology. We made three different transgenic mouse lines in which we knocked out GLUT4 selectively in adipocytes, in skeletal muscle, or in cardiac muscle. Mice lacking GLUT4 in adipocytes or muscle become insulin resistant and glucose intolerant and a subset develop overt diabetes. Mice lacking GLUT4 in the heart have normal glucose homeostasis but they have cardiomegaly. Mechanistic studies in these mice are yielding important insights about insulin action and the cell biology of GLUT4 as well as the relative importance of muscle and adipose tissue in glucose homeostasis and in the development of obesity. DNA array and proteomic studies on tissues from these mice are yielding novel molecules that may alter insulin action in an endocrine manner. 2) Mechanisms by which leptin enhances insulin sensitivity. We are investigating cross-talk and convergence of insulin and leptin signaling pathways and determining which effects of leptin are exerted directly at the level of insulin target tissues and which are mediated through the central nervous system. These studies focus on the interplay of signaling through the Jak-Stat, PI3 kinase and AMP kinase pathways. 3) AMP-activated protein kinase (AMPK) – physiologic role in the hypothalamus. We are investigating the role of AMPK in the hypothalamus. 4) Role of tyrosine phosphatases in the pathogenesis of insulin resistance. We “knocked out” protein tyrosine phosphatase 1B (PTP1B) in mice in collaboration with Ben Neel in the Cancer Biology Program at BIDMC. PTP1B-/- mice are lean and have increased sensitivity to insulin and leptin. We are reconstituting PTP1B expression in individual peripheral tissues and in the brain either trangenically or with adenoviruses to determine which tissues are responsible for the phenotype. Ideally, insights from these projects will elucidate the molecular mechanisms underlying insulin resistance and obesity and lead to new therapeutic approaches to prevent or ameliorate obesity and Type 2 diabetes. References: 1. Klaman LD, Boss O, Peroni O, Kim JK, Zabolotny J, Kim Y-B, Sharpe AK, Stricker-Krongrad A, Shulman, GI, Neel BG, Kahn BB. Increased energy expenditure, decreased adiposity and tissue-specific insulin sensitivity in protein-tyrosine phosphatase 1B (PTP-1B)-deficient mice. Mol. Cell. Bio. 2000;20:5479-5489. 2. Zisman A, Peroni OD, Abel ED, Michael MD, Mauvais-Jarvis F, Lowell BB, Wojtaszewski JFP, Hirshman MF, Virkamaki A, Goodyear LJ, Kahn CR, Kahn BB. Targeted disruption of the glucose transporter 4 selectively in muscle causes insulin resistance and glucose intolerance. Nature Medicine. 2000;6:924-928. 3. Abel ED, Peroni O, Kim JK, Kim Y-B, Boss O, Hadro E, Minnemann T, Shulman GI, Kahn BB. Adipose-selective targeting of the GLUT4 gene impairs insulin action in muscle and liver. Nature. 2001;409:729-733. (* contributed equally) 4. Zabolotny JM, Kim Y-B, Peroni OD, Kim JK, Pani MA, Boss O, Klaman LD, Kamatkar S, Shulman GI, Kahn BB+, Neel BG+. Overexpression of the leukocyte antigen-related (LAR) protein tyrosine phosphatase in muscle causes insulin resistance. Proc. National Academy of Science. 2001;98:5187-5192. (+corresponding authors) 5. Minokoshi Y, Kim Y-B, Peroni OD, Fryer LGD, Muller C, Carling D, Kahn BB. Leptin stimulates fatty acid oxidation by activation of AMP-activated protein kinase. Nature 2002;415:339-343. 6. Zabolotny JM, Bence-Hanulec KK, Stricker-Krongrad A, Haj FG, Wang YP, Minokoshi Y, Kim Y-B, Elmquist JK, Tartaglia LA, Kahn BB+, Neel BG. PTP1B regulates leptin signal transduction in vivo. Developmental Cell 2002;2:489-495. (*contributed equally; + corresponding author). 7. Bluher M, Michael MD, Peroni OD, Ueki K, Carter N, Kahn BB, Kahn CR. Adipose tissue selective insulin receptor knockout protects against obesity and obesity-related glucose intolerance. Developmental Cell 2002;3:25-38. 8. Kim Y-B, Shulman GI, Kahn BB. Fatty acid infusion selectively impairs insulin action on Akt1 and PKCl/z but not on glycogen synthase kinase-3. J. Biol. Chem. 2002;277: 32915-32922. 9. Yamauchi T, Kamon J, Minokoshi Y, Ito Y, Waki H, Uchida S, Yamashita S, Noda M, Kita S, Ueki K, Eto K, Akanuma Y, Froguel P, Foufelle F, Ferre P, Carling D, Nagai R, Kimura S, Kahn BB and Kadowaki T. Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase. Nature Medicine 2002;8:1-8. 10. Bluher M, Kahn BB, Kahn CR. Extended longevity in mice lacking the insulin receptor in adipose tissue. Science 2003;299:572-574. 11. Minokoshi Y, Kahn CR, Kahn BB. Tissue-specific ablation of the GLUT4 glucose transporter or the insulin receptor challenges assumptions about insulin action and glucose homeostasis. J Biol Chem. 2003;278:33609-12. 12. Minokoshi Y, Alquier T, Furukawa N, Kim YB, Lee A, Xue B, Mu J, Foufelle F, Ferre P, Birnbaum MJ, Stuck BJ, Kahn BB. AMP-kinase regulates food intake by responding to hormonal and nutrient signals in the hypothalamus.Nature. 2004;428:569-74. 13. Zabolotny JM, Haj FG, Kim YB, Kim HJ, Shulman GI, Kim JK, Neel BG, Kahn BB. Transgenic overexpression of protein-tyrosine phosphatase 1B in muscle causes insulin resistance, but overexpression with leukocyte antigen-related phosphatase does not additively impair insulin action. J Biol Chem. 2004;279:24844-51. 14. Carvalho E, Schellhorn SE, Zabolotny JM, Martin S, Tozzo E, Peroni OD, Houseknecht KL, Mundt A, James DE, Kahn BB. GLUT4 overexpression or deficiency in adipocytes of transgenic mice alters the composition of GLUT4 vesicles and the subcellular localization of GLUT4 and insulin-responsive aminopeptidase. J Biol Chem. 2004;279:21598-605.