Calorific restriction: can we extrapolate from animals to humans?

Myocardial dysfunction induced by food restriction is related to morphological damage in normotensive middle-aged rats

Previous works from our laboratory have revealed that food restriction (FR) promotes discrete myocardial dysfunction in young rats. We examined the effects of FR on cardiac function, in vivo and in vitro, and ultrastructural changes in the heart of middle-aged rats. Twelve-month-old Wistar-Kyoto rats were fed a control (C) or restricted diet (daily intake reduced to 50% of the control group) for 90 days. Cardiac performance was studied by echocardiogram and in isolated left ventricular (LV) papillary muscle by isometric contraction in basal condition, after calcium chloride (5.2 mM) and beta-adrenergic stimulation with isoproterenol (10(-6) M). FR did not change left ventricular function, but increased time to peak tension, and decreased maximum rate of papillary muscle tension development. Inotropic maneuvers promoted similar effects in both groups. Ultrastructural alterations were seen in most FR rat muscle fibers and included, absence and/or disorganization of myofilaments and Z line, hyper-contracted myofibrils, polymorphic and swollen mitochondria with disorganized cristae, and a great quantity of collagen fibrils. In conclusion, cardiac muscle sensitivity to isoproterenol and elevation of extracellular calcium concentration is preserved in middle-aged FR rats. The intrinsic muscle performance depression might be related to morphological damage.

Interaction du jeûne intermittent sur les effets cytotoxiques rénaux du nickel chez le rat pubère

This study has been undertaken with the aim of determining if intermittent fasting can be considered as a malnutrition that amplifies, according to numerous authors, the cytotoxic effects of environmental pollutants. We have used 200 male and female rats of 'Wistar' descent (BW approximately 180 g). These rats are distributed into two groups: some nourished daily (N) and others nourished one day over two (J) during a month. By the end of this month, each group is itself split into two subgroups, the first one receiving tap water as drinkable water (group NO and JO); the other one receiving the water enriched by the chloride of nickel at the rate of 100 mg NiCl2 per litre (groups NNi and JNi). Intermittent fasting goes on parallel to treatment during 2, 4, 10, 16, 30 and 60 days. For the exploration of the protein of stress (HSP) and of the metallothioneines (MT), the nickel is administered by injection at the rate of 4 mg NiCl2 per kg during 1 and 5 days. Our results show that the mineral seric and renal balance does not vary in conditions of intermittent fasting compared with conditions of normal nutrition. Our study show than that nickel induced a renal deficiency by decreasing the creatinemia and uraemia rate, which is confirmed by the histological study, and induced a decrease in the induction of the HSP73 and in the synthesis of the (MT). The association of nickel with intermittent fasting would inhibit these effects. In conclusion, intermittent fasting does not manifest itself as a malnutrition that amplifies the nickel's effects. Nevertheless, it seems that the calorific lack provoked by intermittent fasting is beneficial to the body by increasing its performances against the cytotoxic effects induced by nickel.

Synergistic action of olive oil supplementation and dietary restriction on serum lipids and cardiac antioxidant defences

Caloric intake is higher than recommended in many populations. Therefore, enhancing olive oil intake alone may not be the most effective way to prevent cardiovascular diseases. The purpose of the present study was to analyse the association of olive oil and dietary restriction on lipid profile and myocardial antioxidant defences. Male Wistar rats (180–200 g, n = 6) were divided into 4 groups: control ad libitum diet (C), 50% restricted diet (DR), fed ad libitum and supplemented with olive oil (3 mL/(kg·day)) (OO), and 50% restricted diet and supplemented with olive oil (DROO). After 30 days of treatments, OO, DR, and DROO groups had increased total cholesterol and high-density lipoprotein cholesterol concentrations. DR and DROO animals showed decreased low-density lipoprotein cholesterol. DROO had the lowest low-density lipoprotein cholesterol concentration. Total lipids and triacylglycerols were raised by dietary restriction and diminished by olive oil. OO rats had higher myocardial superoxide dismutase and lower catalase and glutathione peroxidase activities than C rats. DR and DROO showed enhanced cardiac superoxide dismutase, catalase, and glutathione peroxidase activities from the control. Olive oil supplementation alone improved the lipid profile but was more effective when coupled with dietary restriction. There was a synergistic beneficial action of dietary restriction and olive oil on serum lipids and myocardial antioxidant defences.Key words: dietary restriction, olive oil, lipid profile, cardiac tissue, antioxidant enzymes.

Dietary factors affecting uterine weights of immature CD-1 mice used in uterotrophic bioassays

A study was conducted to determine the effects of dietary factors in natural ingredient and purified diets on uterine weights of immature CD-1 mice used in uterotrophic bioassays. Factors evaluated included body weight gain, dietary phytoestrogen content, total metabolizable energy, and percent crude fiber. Fifteen to 147 mice per group, housed 5 per cage, were randomly assigned to each of the 20 test diets. The test diets were fed for 7 days to 15-day old immature female CD-1 mice and their body weight gain and uterine weights were determined. Analysis of covariance procedures were used to evaluate differences in uterine weights, after adjusting for body weight and time-related trends. Fisher's least significant difference test was used to compare adjusted uterine weights and weight gains among the test diets. Additionally, multiple linear regression procedures were used to identify those characteristics of the rodent diet that were most predictive of the adjusted uterine weights. Total metabolizable energy was significantly (P < 0.01) correlated with and was predictive of uterine weights. The following dietary variables were not significantly predictive of uterine weights: total daidzein and genistein content, percent protein, fat, N-FE (carbohydrates) or percent crude fiber. We concluded that: (1) total metabolizable energy (ME) in natural ingredient or purified diets has a significant (P < 0.01) effect on the uterine weights of immature mice used in 7-day uterotrophic bioassays; (2) a standardized, estrogen-free diet with a constant level of ME should be used for conducting uterotrophic assays when comparing results between different laboratories or when determining the estrogenic or anti-estrogenic activity of endocrine disruptor compounds; (3) the mouse uterotrophic assay remains a sensitive bioassay for assessing chemicals for estrogenic activity or for the detection of total estrogenic activity in rodent diets that may be contaminated with estrogenic compounds, and (4) chemical assays should be used to detect or measure low levels of the phytoestrogens in rodent diets.