Cachexia is a major complication of chronic diseases such as heart failure, kidney failure and cancer. In these conditions the renin-angiotensin system (RAS) is often activated. We have shown that Angiotensin II (Ang II) induces skeletal muscle wasting, while Insulin-like growth factor 1 (IGF-1) prevents it. Ang II disrupts insulin and IGF-1 signaling, induces mitochondrial dysfunction, depletes muscle ATP, and inhibits 5'-Adenosine Monophosphate Activated Protein Kinase (AMPK) signaling, preventing the normal response to energy depletion. Activation of AMPK with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) restores energy balance and prevents Ang II wasting, indicating that AMPK plays a critical role in Ang II effects on skeletal muscle. Ang II also reduces the regenerative capacity of skeletal muscle following injury by depleting the muscle stem cell (MuSC) compartment, likely via AT1a receptor (AT1aR) mediated inhibition of Notch signaling. Muscle specific overexpression of IGF-1 activates AMPK, increases MuSC, and prevents Ang II-induced wasting, implicating AMPK and MuSC as key points of convergence for the opposing effects of Ang II and IGF- 1 in muscle. The long-term objectives of this project are to understand how Ang II alters skeletal muscle biology and how IGF-1 exerts its protective effects against Ang II-induced wasting;we will achieve these goals through three specific aims:
Specific Aim 1. To demonstrate that impairment of energy balance and AMPK signaling mediate ANG II-induced skeletal muscle atrophy and to determine the mechanisms involved. We will use Ang II infusion with skeletal muscle specific AT1aR-/- mice, AMPK kinase dead (AMPK- KD) mice, Akt-/- mice, and constructs overexpressing constitutively active AMPK or Akt to examine whether the negative effects of Ang II on energy balance are mediated by alterations in AMPK and/or Akt signaling, and to ascertain the mechanisms of AICAR mediated rescue. We will also study human skeletal muscle tissue samples.
Specific Aim 2 : To demonstrate that Ang II induced insulin/IGF-1 resistance and dysregulation of glucose and protein metabolism are prevented by IGF-1 activation of AMPK. We will utilize AMPK-KD mice, MLC-IGF-1 mice (muscle specific IGF-1 transgenics), muscle specific IGF-1R-/- mice to assess effects of Ang II on insulin/IGF-1 signaling, to examine if rescue effects of IGF-1 are AMPK-dependent and study the effects of AICAR.
Specific Aim 3 : To demonstrate that Ang II and IGF-1 regulate muscle stem cells and, via this mechanism, alter muscle regeneration. We will use human tissue samples, MLC-IGF-1 mice, AT1aR-/- mice, Myf5LacZ/+ mice and the cardiotoxin-injury model to examine mechanisms whereby Ang II inhibits and IGF-1 stimulates muscle regeneration. Our results will provide key insights into mechanisms whereby Ang II impairs skeletal muscle metabolism, depletes MuSC and inhibits regeneration;as well as insights into novel effects of IGF-1 on skeletal muscle. These findings will allow development of innovative therapies to treat cachexia in chronic conditions in which the RAS is activated.
Skeletal muscle wasting (cachexia) is a major public health issue contributing to the morbidity and mortality of a variety of disease states, including congestive heart failure, chronic renal failure, chronic obstructive pulmonary disease, diabetes mellitus, and cancer. This proposal will focus on elucidating the mechanisms of wasting caused by angiotensin II and the mechanisms of rescue by insulin-like growth factor 1, and should provide new avenues for targeted and specific therapeutic interventions.
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|Hou, Xuwei; Snarski, Patricia; Higashi, Yusuke et al. (2017) Nuclear complex of glyceraldehyde-3-phosphate dehydrogenase and DNA repair enzyme apurinic/apyrimidinic endonuclease I protect smooth muscle cells against oxidant-induced cell death. FASEB J 31:3179-3192|
|Yoshida, Tadashi; Delafontaine, Patrice (2016) An Intronic Enhancer Element Regulates Angiotensin II Type 2 Receptor Expression during Satellite Cell Differentiation, and Its Activity Is Suppressed in Congestive Heart Failure. J Biol Chem 291:25578-25590|
|Higashi, Yusuke; Sukhanov, Sergiy; Shai, Shaw-Yung et al. (2016) Insulin-Like Growth Factor-1 Receptor Deficiency in Macrophages Accelerates Atherosclerosis and Induces an Unstable Plaque Phenotype in Apolipoprotein E-Deficient Mice. Circulation 133:2263-78|
|Sakamuri, Siva S V P; Valente, Anthony J; Siddesha, Jalahalli M et al. (2016) TRAF3IP2 mediates aldosterone/salt-induced cardiac hypertrophy and fibrosis. Mol Cell Endocrinol 429:84-92|
|Somanna, Naveen K; Valente, Anthony J; Krenz, Maike et al. (2016) The Nox1/4 Dual Inhibitor GKT137831 or Nox4 Knockdown Inhibits Angiotensin-II-Induced Adult Mouse Cardiac Fibroblast Proliferation and Migration. AT1 Physically Associates With Nox4. J Cell Physiol 231:1130-41|
|Delafontaine, Patrice; Yoshida, Tadashi (2016) THE RENIN-ANGIOTENSIN SYSTEM AND THE BIOLOGY OF SKELETAL MUSCLE: MECHANISMS OF MUSCLE WASTING IN CHRONIC DISEASE STATES. Trans Am Clin Climatol Assoc 127:245-258|
|Sakamuri, Siva Sankara Vara Prasad; Higashi, Yusuke; Sukhanov, Sergiy et al. (2016) TRAF3IP2 mediates atherosclerotic plaque development and vulnerability in ApoE(-/-) mice. Atherosclerosis 252:153-160|
|Sukhanov, Sergiy; Snarski, Patricia; Vaughn, Charlotte et al. (2015) Insulin-like growth factor I reduces lipid oxidation and foam cell formation via downregulation of 12/15-lipoxygenase. Atherosclerosis 238:313-20|
|Yoshida, Tadashi; Delafontaine, Patrice (2015) Mechanisms of Cachexia in Chronic Disease States. Am J Med Sci 350:250-6|
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