Down-regulation of the cardiac sarcoplasmic reticulum ryanodine channel in severely food-restricted rats

We have shown that myocardial dysfunction induced by food restriction is related to calcium handling. Although cardiac function is depressed in food-restricted animals, there is limited information about the molecular mechanisms that lead to this abnormality. The present study evaluated the effects of food restriction on calcium cycling, focusing on sarcoplasmic Ca2+-ATPase (SERCA2), phospholamban (PLB), and ryanodine channel (RYR2) mRNA expressions in rat myocardium. Male Wistar-Kyoto rats, 60 days old, were submitted to ad libitum feeding (control rats) or 50% diet restriction for 90 days. The levels of left ventricle SERCA2, PLB, and RYR2 were measured using semi-quantitative RT-PCR. Body and ventricular weights were reduced in 50% food-restricted animals. RYR2 mRNA was significantly decreased in the left ventricle of the food-restricted group (control = 5.92 +/- 0.48 vs food-restricted group = 4.84 +/- 0.33, P < 0.01). The levels of SERCA2 and PLB mRNA were similar between groups (control = 8.38 +/- 0.44 vs food-restricted group = 7.96 +/- 0.45, and control = 1.52 +/- 0.06 vs food-restricted group = 1.53 +/- 0.10, respectively). Down-regulation of RYR2 mRNA expressions suggests that chronic food restriction promotes abnormalities in sarcoplasmic reticulum Ca2+ release.

Toxicity of dietary restriction of fat enriched diets on cardiac tissue

The present study examines the effects of caloric restriction in cardiac tissue evaluation markers of oxidative stress. High-fat dietary restrictions can have a long-term impact on cardiac health. Dietary restriction of control diet increased myocardial superoxide dismutase (SOD) and catalase activities. Dietary restriction of fatty acid-enriched diets increased myocardial lipoperoxide concentrations, while SOD activity was decreased in cardiac tissue of rats with dietary restriction of fatty acid-enriched diets. Dietary restriction of unsaturated fatty acid-enriched diet induced the highest lipoperoxide concentration and the lowest myocardial SOD activity. Dietary restriction of unsaturated fatty acid decreased myocardial glycogen, and increased the lactate dehydrogenase/citrate synthase ratio. Dietary restriction of fatty acid-enriched diets were more deleterious to cardiac tissue than normal ad lib.-fed diet. In conclusion, the effects of caloric restriction on myocardial oxidative stress is dependent on which nutrient is restricted. Dietary restriction of fatty acid-enriched diets is deleterious relative to ad lib.-fed chow diet. (C) 2002 Elsevier, Science Ltd. All rights reserved.

Beta-carotene supplementation attenuates cardiac remodeling induced by one-month tobacco-smoke exposure in rats

Objective: the objectives were to analyze the cardiac effects of exposure to tobacco smoke (ETS), for a period of 30 days, alone and in combination with beta-carotene supplementation (BC). Research methods and procedures: Rats were allocated into: Air (control, n = 13); Air + BC (n = 11); ETS (n = 11); and BC + ETS (n = 9). In Air + BC and BC + ETS, 500 mg of BC were added to the diet. After three months of randomization, cardiac structure and function were assessed by echocardiogram. After that, animals were euthanized and morphological data were analyzed post-morten. One-way and two-way ANOVA were used to assess the effects of ETS, BC and the interaction between ETS and BC on the variables. Results: ETS presented smaller cardiac output (0.087 +/- 0.001 vs. 0.105 +/- 0.004 l/min; p = 0.007), higher left ventricular diastolic diameter (19.6 +/- 0.5 vs. 18.0 +/- 0.5 mm/kg; p = 0.024), higher left ventricular (2.02 +/- 0.05 vs. 1.70 +/- 0.03 g/kg; p < 0.001) and atrium (0.24 +/- 0.01 vs. 0.19 +/- 0.01 g/kg; p = 0.003) weight, adjusted to body weight of animals, and higher values of hepatic lipid hydroperoxide (5.32 +/- 0.1 vs. 4.84 +/- 0.1 nmol/g tissue; p = 0.031) than Air. However, considering those variables, there were no differences between Air and BC + ETS (0.099 +/- 0.004 l/min; 19.0 +/- 0.5 mm/kg; 1.83 +/- 0.04 g/kg; 0.19 +/- 0.01 g/kg; 4.88 +/- 0.1 nmol/g tissue, respectively; p > 0.05). Ultrastructural alterations were found in ETS: disorganization or loss of myofilaments, plasmatic membrane infolding, sarcoplasm reticulum dilatation, polymorphic mitochondria with swelling and decreased cristae. In BC + ETS, most fibers showed normal morphological aspects. Conclusion: One-month tobacco-smoke exposure induces functional and morphological cardiac alterations and BC supplementation attenuates this ventricular remodeling process.

The influence of temporal food restriction on the performance of isolated cardiac muscle

In this study we assessed the mechanical function of isolated left ventricular papillary muscles from 60 day-old male Wistar-Kyoto rats (WKY) subjected to different periods of food restriction (FR). The food-restricted animals (R) were fed 50% of the amount of diet consumed by the ad Libitum-fed rats (C). The cardiac muscles were studied after 30, 60, and 90 days (R-30, R-60 and R-90) of FR. The effect of FR on myocardial collagen concentration was also evaluated. The parameters from the three control groups that were statistically identical were combined and the control pool group (CP) was formed. The left ventricular weight-to-body weight ratio was lower in the R-30 and higher in the R-60 and R-90 in relation to their control groups. Hydroxyproline concentration was higher only in R-90 compared to CP and R-30. Myocardial mechanical function was the same in the C groups. The comparisons between CP and FR groups showed that: the muscles of R-30 presented increased resting tension and maximum rate of tension decline, and decreased velocity of shortening; the muscles of R-60 and R-90 groups showed a prolongation of the time to peak tension (TPT) and the time to peak shortening (TPS); and R-30 had an increased time from peak tension to 50% relaxation (RT1/2). Increases in TPT, TPS, and RT1/2 in groups R-60 and R-90 were significant in relation to R-30. In conclusion, while FR for 30 days produces disparate effects on myocardial performance, FR for 60 and 90 days prolongs the contraction period. The change of relaxation time in R-90 might be related to the increased myocardial collagen content. (C) 2001 Elsevier B.V. All rights reserved.

Follow-up study of morphology and cardiac function in rats undergoing induction of supravalvular aortic stenosis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of protein-calorie restriction on mechanical function of hypertrophied cardiac muscle

OBJECTIVE: To assess the effect of food restriction (FR) on hypertrophied cardiac muscle in spontaneously hypertensive rats (SHR). METHODS: Isolated papillary muscle preparations of the left ventricle (LV) of 60-day-old SHR and of normotensive Wistar-Kyoto (WKY) rats were studied. The rats were fed either an unrestricted diet or FR diet (50% of the intake of the control diet) for 30 days. The mechanical function of the muscles was evaluated through monitoring isometric and isotonic contractions. RESULTS: FR caused: 1) reduction in the body weight and LV weight of SHR and WKY rats; 2) increase in the time to peak shortening and the time to peak developed tension (DT) in the hypertrophied myocardium of the SHR; 3) diverging changes in the mechanical function of the normal cardiac muscles of WKY rats with reduction in maximum velocity of isotonic shortening and of the time for DT to decrease 50% of its maximum value, and increase of the resting tension and of the rate of tension decline. CONCLUSION: Short-term FR causes prolongation of the contraction time of hypertrophied muscles and paradoxal changes in mechanical performance of normal cardiac fibers, with worsening of the shortening indices and of the resting tension, and improvement of the isometric relaxation.

Exercise Training and Caloric Restriction Prevent Reduction in Cardiac Ca2+-Handling Protein Profile in Obese Rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Combined exercise training in asymptomatic elderly with controlled hypertension: Effects on functional capacity and cardiac diastolic function

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Long-term high-fat diet-induced obesity decreases the cardiac leptin receptor without apparent lipotoxicity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)