Short-Term Caloric Restriction Induces Accumulation of Myocardial Triglycerides and Decreases Left Ventricular Diastolic Function in Healthy Subjects

Abstract

Diabetes and obesity are associated with increased plasma nonesterified fatty acid (NEFA) levels, myocardial triglyceride accumulation, and myocardial dysfunction. Because a very low-calorie diet (VLCD) also increases plasma NEFA levels, we studied the effect of a VLCD on myocardial triglyceride content and cardiac function in healthy subjects. Fourteen healthy nonobese men underwent (1)H-magnetic resonance spectroscopy (MRS) to determine myocardial and hepatic triglyceride content, (31)P-MRS to assess myocardial high-energy phosphate (HEP) metabolism (phosphocreatine/ATP), and magnetic resonance imaging of myocardial function at baseline and after a 3-day VLCD. After the dietary intervention, plasma NEFA levels increased compared with those at baseline (from 0.5 +/- 0.1 to 1.1 +/- 0.1 mmol/l, P < 0.05). Concomitantly, myocardial triglyceride content increased by approximately 55% compared with that at baseline (from 0.38 +/- 0.05 to 0.59 +/- 0.06%, P < 0.05), whereas liver triglyceride content decreased by approximately 32% (from 2.2 +/- 0.5 to 1.5 +/- 0.4%, P < 0.05). The VLCD did not change myocardial phosphocreatine-to-ATP ratio (2.33 +/- 0.15 vs. 2.33 +/- 0.08, P > 0.05) or systolic function. Interestingly, deceleration of the early diastolic flow across the mitral valve decreased after the VLCD (from 3.37 +/- 0.20 to 2.91 +/- 0.16 ml/s(2) x 10(-3), P < 0.05). This decrease in diastolic function was significantly correlated with the increase in myocardial triglyceride content. Short-term VLCD induces accumulation of myocardial triglycerides. In addition, VLCD decreases left ventricular diastolic function, without alterations in myocardial HEP metabolism. This study documents diet-dependent physiological variations in myocardial triglyceride content and diastolic function in healthy subjects.