Levels Of Dietary Restriction Research Articles

Daily caloric restriction limits tumor growth more effectively than caloric cycling regardless of dietary composition

Cancer incidence increases with age and is a leading cause of death. Caloric restriction (CR) confers benefits on health and survival and delays cancer. However, due to CR’s stringency, dietary alternatives offering the same cancer protection have become increasingly attractive. Short cycles of a plant-based diet designed to mimic fasting (FMD) are protective against tumorigenesis without the chronic restriction of calories. Yet, it is unclear whether the fasting time, level of dietary restriction, or nutrient composition is the primary driver behind cancer protection. Using a breast cancer model in mice, we compare the potency of daily CR to that of periodic caloric cycling on FMD or an isocaloric standard laboratory chow against primary tumor growth and metastatic burden. Here, we report that daily CR provides greater protection against tumor growth and metastasis to the lung, which may be in part due to the unique immune signature observed with daily CR.

Función y metabolismo de ácidos grasos en el tejido adiposo y hepático de rumiantes en producción: una revisión

El tejido adiposo (TA) y hepático influencian el metabolismo de ácidos grasos (AG), al ser en gran parte los responsables de regular su biosíntesis, degradación y almacenamiento en tejidos corporales, como también de su secreción en leche y carne de animales en producción. De esta forma, un mejor entendimiento de la funcionalidad del metabolismo de AG en estos tejidos y los factores que lo afectan, podría dar las bases para el diseño de estrategias productivas en rumiantes. Así, el objetivo de esta revisión es presentar un panorama general de la funcionalidad y metabolismo de los AG en el TA y hepático en rumiantes de producción. A partir de la revisión, se pudo establecer, que el tipo de lípidos mayoritarios en TA y hepático, lo forman los AG y triglicéridos. El TA es el principal sitio de almacenamientobenergético tanto en rumiantes como en no rumiantes. El TA se encuentra. metabólicamente asociado con el tejido hepático mediante un equilibrio que regula los procesos de β-oxidación, síntesis de novo y transporte de AG a nivel tisular. Finalmente, se pudo establecer que el metabolismo de AG en TA y hepático es afectado por diversos factores, tales como la nutrición, nivel de restricción dietaria, genética, estado fisiológico y medio ambiente, de los cuales, la nutrición tiene el mayor impacto.

The effect of different levels of dietary restriction on glucose homeostasis and metabolic memory

Over the past 50 years, dietary restriction (DR) has been shown to extend the life span of a wide variety of organisms. A hallmark feature of DR is improved glucose homeostasis resulting in increased glucose tolerance and insulin sensitivity of animals ranging from rodents to humans. In this study, we demonstrate the early effects of varying levels of DR on glucose tolerance. Within 10 days of 40% DR, glucose tolerance was significantly improved and by 120 days; 10 and 20% DR also showed enhanced glucose tolerance. All three levels of DR showed reduced adiposity, increased expression of genes involved in fat turnover, and a reduction in the expression for markers of inflammation. Studies have shown that mice fed a DR diet retained metabolic memory in terms of improved glucose tolerance even after DR is discontinued. We show that 40% DR not only has an early effect on glucose tolerance but also maintained it after DR was discontinued for 2 months. Therefore, improvement in glucose tolerance is brought about by all three levels of DR but the metabolic memory is not dose responsive.

Maintenance and growth requirements in male and female hair lambs

An experiment was conducted to evaluate the energy and protein requirements of intact male, castrated male and female Morada Nova lambs. The animals were distributed in a completely randomized 3×3 factorial design with three sexes (15 intact males, 16 castrated males and 16 females) and three levels of dietary restriction (ad libitum, 30% and 60% feed restriction) with an initial body weight (BW) of 14.50±0.89kg. Four animals per sex were slaughtered at the start of the trial as a baseline group. When the mean BW in the ad libitum treatment reached 28kg, at day 120 of the experiment, all lambs were slaughtered. For all sexes, the net energy requirement for maintenance was 73.0kcal/kg0.75 empty body weight (EBW)/d (P=0.17). The metabolizable energy efficiency for maintenance (km) was 0.58. The metabolizable energy efficiency utilization for gain (kg) was 0.36; 0.25 and 0.28 for intact males, castrated males and females, respectively. The net energy requirement for gain (NEg) differed (P<0.01) between sexes. The NEg was 0.191, 0.198 and 0.276Mcal/kg0.75 EBW/d for intact males, castrated males and females, respectively, with a BW of 20kg and a body weight gain (BWG) of 100g. The net and metabolizable protein requirements for maintenance obtained for lambs were 1.06g/kg0.75 BW/d (P=0.78) and 3.46g/kg0.75 BW/d (P=0.39), respectively. The net protein for gain (NPg) differed (P<0.01) between sexes. For animals weighing 20kg and with an average daily gain of 100g/d, NPg was 7.08, 7.11 and 6.78g/d for intact males, castrated males and females, respectively. The net energy and protein requirements for maintenance of Morada Nova lambs slaughtered between 15 and 28kg did not vary by sex. The net energy for gain increases and the net protein for gain decreased with the increase in body weight in hair lambs.

Effect of feed restriction with voluntary hay intake on the performance and quality of laying hen eggs - doi: 10.4025/actascianimsci.v34i2.12451

The objective was to evaluate the effect of a quantitative feed restriction on the voluntary intake of hay, the performance of laying hens, and on egg quality. A total of 150 Hisex Brown laying hens at 51-weeks old were distributed into five treatments and five replications of six hens each. The treatments consisted of control, with supply of 100 g of feed bird -1 day -1 without hay; and the others consisting of a feed restriction of 5, 10, 15 and 20% of the diet offered to the birds in the control treatment, along with an ad libitum supply of cunha hay (CH), leucaena leaf meal (LLM) and tifton hay (TH). A linear increase was found in the hay intake with increasing level of dietary restriction. However, egg production, egg weight, egg mass and feed conversion decreased linearly. Yolk color was affected by the treatments. Birds with 20% feed restriction presented the greatest yolk pigmentation. In conclusion, laying hens can be subjected to a 5% feed restriction with supply of hay ad libitum.

The growth hormone receptor gene‐disrupted mouse fails to respond to an intermittent fasting diet

The interaction of longevity-conferring genes with longevity-conferring diets is poorly understood. The growth hormone receptor gene-disrupted (GHR-KO) mouse is long lived; and this longevity is not responsive to 30% caloric restriction, in contrast to wild-type animals from the same strain. To determine whether this may have been limited to a particular level of dietary restriction, we subjected GHR-KO mice to a different dietary restriction regimen, an intermittent fasting diet. The intermittent fasting diet increased the survivorship and improved insulin sensitivity of normal males, but failed to affect either parameter in GHR-KO mice. From the results of two paradigms of dietary restriction, we postulate that GHR-KO mice would be resistant to any manner of dietary restriction; potentially due to their inability to further enhance insulin sensitivity. Insulin sensitivity may be a mechanism and/or a marker of the lifespan extending potential of an intervention.

Dietary Restriction Does Not Adversely Affect Bone Geometry and Mechanics in Rapidly Growing Male Wistar Rats

The present study assessed the effects of dietary restriction on tibial and vertebral mechanical and geometrical properties in 2-mo-old male Wistar rats. Two-month-old male Wistar rats were randomized to the ad libitum (n=8) or the 35% diet-restricted (DR) feeding group (n=9) for 5 mo. Tibiae and L6 vertebrae were dissected out for microcomputed tomography (microCT) scanning and subsequently fractured in biomechanical testing to determine geometrical and mechanical properties. The DR group had significantly lower mean tibial length, mass, area, and cross-sectional moment of inertia, as well as vertebral energy to maximal load. After adjustment for body mass, however, DR tibial mean maximal load and stiffness, and DR vertebral area, height, volume, and maximal load were significantly greater, relative to ad libitum means. No significant differences were found between the DR and ad libitum mineral ash fractions. Because the material properties of the tibiae between the two groups were not significantly different, presumably the material integrity of the bones was not adversely affected as a consequence of DR. The similar material characteristics were consistent with mineral ash fractions that were not different between the two groups. Vertebral maximal load and stiffness were not significant between the DR and ad libitum animals. Importantly, we show that a level of dietary restriction (35%) that is less severe than many studies (40%), and without micronutrient compensation does not adversely affect tibial and vertebral mechanical properties in young growing male rats when normalized for body mass.

The effects of different levels of dietary restriction on non-neoplastic diseases in male Sprague-Dawley rats.

The primary purpose of the present study was to investigate the effects of 10, 25, and 40% dietary restriction (DR) on non-neoplastic diseases in rodents at 58 and 110 weeks of age, and to determine whether low-level DR (10 and 25%) can increase the survival rate and decrease variability in chronic bioassay studies. Male Sprague-Dawley (SD) rats (NCTR colony) were divided into four nutritional groups, consisting of an ad libitum (AL) group with unlimited access to the NIH-31 diet, and three dietary restricted (DR) groups given the NIH-31 diet reduced in amount by 10, 25, and 40%. At 110 weeks of age, the incidence of cardiomyopathy was 95, 75, 45, and 15% for AL and 10, 25, and 40% DR rats, respectively; the incidence of nephropathy was 55, 20, 15, and 0% for AL and 10, 25, and 40% DR rats, respectively. The severity of chronic heart and kidney diseases was significantly reduced in all DR rat groups, with significant DR-dependent linear trends for these diseases. Moreover, DR prevented the progression of skin irritation to foot ulcers, and reduced the age-related degeneration in the adrenal, lacrimal, and thymus glands, and the liver. These results clearly indicate that even low DR levels were effective in preventing or slowing the progression of these non-neoplastic diseases.

Effect of caloric restriction on aflatoxin B 1-DNA adduct formation and associated factors in Fischer 344 rats: Preliminary findings

In this first report of an effect of caloric restriction on in vivo DNA binding by a chemical carcinogen in rats, hepatic nuclear binding by aflatoxin B 1 (AFB) (pmol/mg DNA) in ad libitum-fed (AL) animals was 2.1 times greater than in rats restricted to 60% of AL consumption for 6 weeks. Data indicating more rapid plasma clearance, increased urinary excretion of the toxin, and less microsome-mediated epoxidation of AFB by the restricted group suggest that decreased macromolecular binding may be attributable in part to metabolic alterations. Moreover, various levels of dietary restriction, initiated at different ages, significantly inhibited hepatic DNA synthesis, thus indicating that effects of cell proliferation could also be involved mechanistically. Finally, circulating levels of the lysosomal enzyme, β-glucuronicase (βG), were significantly reduced in the restricted rats, and the implications of this finding regarding potential relationships to aging and carcinogenesis are discussed.

Restricted feeding and reproductive performance of individually caged broiler breeder males.

Two experiments were conducted, one in the summer and another in the fall, involving 95 Hubbard broiler breeder males per experiment. Breeder males were randomly placed in individual cages at 26 (Trial 2) or 30 (Trial 1) weeks of age and provided with five levels of feed intake. The Hubbard White Mountain male Management Guide recommendation (154 g/bird/day) was designated as the control level (100%). Other levels were 115, 85, 70, and 55% of the control level. The effects of feed intake on body weight, semen volume, percent semen-packed cell volume, luteinizing hormone (LH), and testes weight were determined. Body weights were significantly decreased as feed intake was decreased. Dietary restriction levels of 115, 100, 85, and 70% had no significant effects on semen volume or semen-packed cell volume. Dietary restriction of 55% resulted in reduced semen volume, semen-packed cell volume (except in Trial 1), and testes weight. Dietary restriction had no significant effect on LH. A calculated metabolizable energy (ME) value of 346 kcal of ME/bird/day, which lies between the 85 and 70%-fed groups, should be adequate for normal body weight maintenance with the Hubbard broiler breeder male grown in individual cages.