title: Adaptive mechanisms to compensate for overnutrition-induced cardiovascular abnormalities.
abstract: In conditions of overnutrition, cardiac cells must cope with a multitude of extracellular signals generated by changes in nutrient load (glucose, amino acids, and lipids) and the hormonal milieu [increased insulin (INS), ANG II, and adverse cytokine/adipokine profile]. Herein, we review the diverse compensatory/adaptive mechanisms that counter the deleterious effects of excess nutrients and growth factors. We largely focus the discussion on evidence obtained from Zucker obese (ZO) and Zucker diabetic fatty (ZDF) rats, which are useful models to evaluate adaptive and maladaptive metabolic, structural, and functional cardiac remodeling. One adaptive mechanism present in the INS-resistant ZO, but absent in the diabetic ZDF heart, involves an interaction between the nutrient sensor kinase mammalian target of rapamycin complex 1 (mTORC1) and ANG II-type 2 receptor (AT2R). Recent evidence supports a cardioprotective role for the AT2R; for example, suppression of AT2R activation interferes with antihypertrophic/antifibrotic effects of AT1R blockade, and AT2R agonism improves cardiac structure and function. We propose a scenario, whereby mTORC1-signaling-mediated increase in AT2R expression in the INS-resistant ZO heart is a cardioprotective adaptation to overnutrition. In contrast to the ZO rat, heart tissues of ZDF rats do not show activation of mTORC1. We posit that such a lack of activation of the mTOR↔AT2R integrative pathway in cardiac tissue under conditions of obesity-induced diabetes may be a metabolic switch associated with INS deficiency and clinical diabetes.
authors.affiliation: University of Missouri School of Medicine, Department of Internal Medicine, Columbia, Missouri 65212, USA.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Pulakat
authors.forename: Vincent G
authors.initials: VG
authors.lastname: DeMarco
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Ardhanari
authors.forename: Anand
authors.initials: A
authors.lastname: Chockalingam
authors.forename: Rukhsana
authors.initials: R
authors.lastname: Gul
authors.forename: Adam
authors.initials: A
authors.lastname: Whaley-Connell
authors.forename: James R
authors.initials: JR
authors.lastname: Sowers
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D002318:Cardiovascular Diseases / Q000209:etiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D024821:Metabolic Syndrome / Q000503:physiopathology; D044343:Overnutrition / Q000150:complications / Q000503:physiopathology*; D051381:Rats; D011924:Rats, Zucker; D011945:Receptors, Angiotensin / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases / Q000502:physiology
chemical_list: D011945:Receptors, Angiotensin; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases