Interaction between age and obesity on cardiomyocyte contractile function: role of leptin and stress signaling

PLoS One. 2010 Apr 9;5(4):e10085. doi: 10.1371/journal.pone.0010085.

Abstract

Objectives: This study was designed to evaluate the interaction between aging and obesity on cardiac contractile and intracellular Ca2+ properties.

Methods: Cardiomyocytes from young (4-mo) and aging (12- and 18-mo) male lean and the leptin deficient ob/ob obese mice were treated with leptin (0.5, 1.0 and 50 nM) for 4 hrs in vitro. High fat diet (45% calorie from fat) and the leptin receptor mutant db/db obesity models at young and older age were used for comparison. Cardiomyocyte contractile and intracellular Ca2+ properties were evaluated including peak shortening (PS), maximal velocity of shortening/relengthening (+/- dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR(90)), intracellular Ca2+ levels and decay. O2(-) levels were measured by dihydroethidium fluorescence.

Results: Our results revealed reduced survival in ob/ob mice. Aging and obesity reduced PS, +/- dL/dt, intracellular Ca2+ rise, prolonged TR(90) and intracellular Ca2+ decay, enhanced O2(-) production and p(47phox) expression without an additive effect of the two, with the exception of intracellular Ca2+ rise. Western blot analysis exhibited reduced Ob-R expression and STAT-3 phosphorylation in both young and aging ob/ob mice, which was restored by leptin. Aging and obesity reduced phosphorylation of Akt, eNOS and p38 while promoting pJNK and pIkappaB. Low levels of leptin reconciled contractile, intracellular Ca2+ and cell signaling defects as well as O2(-) production and p(47phox) upregulation in young but not aging ob/ob mice. High level of leptin (50 nM) compromised contractile and intracellular Ca2+ response as well as O2(-) production and stress signaling in all groups. High fat diet-induced and db/db obesity displayed somewhat comparable aging-induced mechanical but not leptin response.

Conclusions: Taken together, our data suggest that aging and obesity compromise cardiac contractile function possibly via phosphorylation of Akt, eNOS and stress signaling-associated O2(-) release.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / physiology*
  • Animals
  • Calcium Signaling / physiology
  • Cells, Cultured
  • Dietary Fats / administration & dosage
  • Dietary Fats / pharmacology
  • Leptin / deficiency
  • Leptin / physiology*
  • Male
  • Mice
  • Mice, Obese
  • Myocardial Contraction
  • Myocytes, Cardiac / cytology
  • Myocytes, Cardiac / physiology*
  • Nitric Oxide Synthase Type III / metabolism
  • Obesity / physiopathology*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Signal Transduction / physiology*
  • Stress, Physiological*
  • Superoxides / metabolism

Substances

  • Dietary Fats
  • Leptin
  • Superoxides
  • Nitric Oxide Synthase Type III
  • Proto-Oncogene Proteins c-akt