Natural Ingredient Diet Research Articles

Effects of dietary phytosterols or phytosterol esters supplementation on growth performance, biochemical blood indices and intestinal flora of C57BL/6 mice.

This study was conducted to evaluate the effects of phytosterols (PS) and phytosterol esters (PSE) on C57BL/6 mice. Three groups of 34 six-week-old C57BL/6 mice of specific pathogen free (SPF) grade, with an average initial body weight (IBW) of 17.7g, were fed for 24 days either natural-ingredient diets without supplements or diets supplemented with 89 mg/kg PS or diets supplemented with 400 mg/kg PSE. Growth performance, blood biochemistry, liver and colon morphology as well as intestinal flora status were evaluated. Both PS and PSE exhibited growth promotion and feed digestibility in mice. In blood biochemistry, the addition of both PS and PSE to the diet resulted in a significant decrease in Total Cholesterol (TC) and Triglyceride (TG) levels and an increase in Superoxide Dismutase (SOD) activity. No significant changes in liver and intestinal morphology were observed. Both increased the level of Akkermansia in the intestinal tract of mice. There was no significant difference between the effects of PS and PSE. It was concluded that dietary PS and PSE supplementation could improve growth performance, immune performance and gut microbiome structure in mice, providing insights into its application as a potential feed additive in animals production.

Diet induced changes in microbiota composition affect the development of small intestinal T cells over generations

Abstract The relationship of microbiota and host is a dynamic and bidirectional process. The microbiota has a strong influence in the development of the host’s immune system, yet the host shapes the composition of the microbiota as well, through the immune response, and importantly, through diet. In the current study we evaluated how modification in the carbohydrate and fiber content of a diet impacts the intestinal immune response. Mice were weaned into a standard natural ingredient diet (Reg) or a purified non-fermentable fiber only diet (NFF) and the immune cell composition was analyzed after four weeks. Animals in the NFF diet had strong changes in their microbiota composition and defects in the development of small intestinal intraepithelial T cells including the lack of CD4+CD8aa+ T cells and TCRab+CD8ab+ T cells. The effect of NFF consumption both in microbiota composition as well as IEL T cell development, was reversible if animals were fed a Reg diet. However, if animals were born from parents fed an NFF diet and kept on NFF diet until weaning, the effect on IEL T cells was non reversible and the offspring of these mice did not develop IEL T cells even if fed a reg diet. Fecal matter transplant from mice fed a Reg diet, together with a Reg diet was able to induce the development of IEL T cells, suggesting the defect observed in the offspring of mice fed a NFF diet is the result of the loss of microbes required for the development of IEL T cells. This study shows how changes in the diet can result in the loss of specific microbiota species over generations that are important for the correct development of the intestinal immune system. Supported by grant from NIH RO1 DK129950-01

Growth Performance, Biochemical Blood Indices, and Large Intestine Physiology of Rats Fed Diets with Alfalfa Protein-Xanthophyll Concentrate.

Simple SummaryAlfalfa protein-xantophyll concentrate is a rich source of nutrients and bioactive compounds. It provides protein, lutein, vitamins, minerals, phytoestrogens, and other plant metabolites. Thus, it may affect animal health in many ways; however, its impact is not fully recognized. Therefore, the aim of the study was to determine the effect of dietary supplementation with 1.5% and 3% concentrate on growth performance, blood biochemical profile, and large intestine physiology of rats as a model animals. The results showed that feeding a diet supplemented with alfalfa concentrate could reduce thickness of the protective mucus layer in the colon of rats but did not affect animal growth and microbial activity in the caecum.The effect of dietary levels of alfalfa protein-xanthophyll concentrate (PXC) was determined in growing rats. Three groups of eight four-week-old male Wistar rats, with an average initial body weight of 61 g, were fed for 28 days either natural-ingredient diets without PXC or supplemented with 1.5% or 3% PXC. Growth performance, blood biochemistry, caecal fermentation, morphology of the large intestine, and mucin gene expression were evaluated. PXC did not affect growth performance but tended to decrease relative liver weight. Among biochemical blood parameters, only bilirubin decreased and uric acid increased in response to 1.5% and 3% PXC, respectively. Caecal fermentation was not affected, with the exception of isovaleric acid concentration, which tended to be higher in rats fed the diet containing 3% PXC. Colonic crypts tended to be deeper in rats fed the 3% PXC diet and the thickness of the colonic mucus layer was reduced by both PXC levels. In conclusion, PXC did not affect growth performance or caecal fermentation but decreased thickness of the protective mucus layer in the colon.

Dietary Matrix Alters Fecal Lipids and Lipoprotein Profiles in Healthy C57Bl/6 Mice

Plant proteins are oft thought to confer health benefits over animal proteins. In a prior study, lipoprotein profiles improved and body weight gain reduced in mice fed milk protein rather than soy protein fed in a purified diet (PD) matrix. Non‐nutrient components such as fiber can alter macro‐ and micro‐nutrient utilization; this study tested the effect of dietary matrix on lipoprotein profiles, fecal lipids and bile acids. Weanling C57Bl/6 mice (n=15/diet) were fed either PD containing isolated soy protein (ISP) or dried whole milk powder (DWMP) as the protein source, or natural ingredient diets (NID) containing soybean meal (SPC), or dried whole milk powder (DMC) as protein sources in a 14 wk feeding trial. Diets provided 50%EN CHO, 20% PRO, 30% FAT. ISP & DWMP provided 14% neutral detergent fiber primarily from cellulose, while SPC & DMC contained 11.4% and 8.4% NDF, respectively, from wheat mids, corn, corn gluten meal and soybean meal (SPC only). Terminal measures: bodyweight, lipoprotein density distribution (https://doi.org/10.1177/1040638718793677), and fecal fatty acids (FA), sterols, primary (PBA) and secondary (SBA) bile acids by IS‐controlled GC/MS. Values are means with differences tested by one‐way ANOVA and Tukey's HSD. Energy intake was similar among groupsaveraging 12 kcal/day. Diet Weight, g Fatty acids mg/mg feces Fecal content / 48 hours Body, final Feces, 48h Sterols, mg (%phyto‐) Bile acids, ug Primary Secondary ISP 35.0a 1.14a 17.6b 2.66c(52.6%) 378b 426a DWMP 31.9ab 1.22a 14.8b 1.87d(31.7%) 510ab 370ab SPC 28.8b 0.88b 39.7a 4.82a(68.6%) 398b 295bc DMC 29.7b 0.66c 31.1a 3.69b(60.1%) 551a 263c Mice fed ISP & DWMP were heavier than SPC & DMC fed mice (p<0.001). ISP‐fed mice were heaviest (p<0.0002 vs. SPC & DMC). SPC & DMC excreted 46.0 ug fecal FA/mg feces, 3‐fold greater than the 13.5 ug fecal FA/mg feces excreted by ISP&DWMP (p<0.000). Total fecal FA excretion in 48h was ≤ 1 kcal; unable to account for differences in body weight. Total fecal sterol excretion was 1.9‐fold greater in NID vs PD, p<0.0001. Phytosterols comprised a greater fraction of fecal sterols in NID that in PD; soy diets (ISP & SPC) excreted 2.5 and 1.5‐fold more than dairy protein comparators. Zoosterols were increased 17% in NID fed mice (1.49 mg avg) compared to PD mice (1.27 mg avg) and unaffected by phytosterols. Bile acid excretion in DWMP was 9% greater than ISP, and DMC was 17% greater than SPC. Secondary bile acids avg 22.4% lower in mice fed milk‐based diets compared to soy. When expressed as % of total, PBAs were highest in NIDs (61.0 vs 50.7%, p<0.0002), whereas SBAs were lower compared to purified diets (38.3 vs 48.4%, p<0.0002). Compared to all other diets, mice fed ISP had a 30% increase in small, dense LDL (d=1.05 – 1.063 g/mL) (p<0.000). Carbohydrate refinement has a greater effect fecal lipids than protein source. Milk protein‐containing diets resulted in improved lipoprotein profiles in PD and NID diets.Support or Funding InformationSupported in part by Texas A&M AgriLife Research project 8738 (to R.L.W.)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Dose and Diet - Sources of Arsenic Intake in Mouse in Utero Exposure Scenarios.

In humans, early life exposure to inorganic arsenic is associated with adverse health effects. Inorganic arsenic in utero or in early postnatal life also produces adverse health effects in offspring of pregnant mice that consumed drinking water containing low part per billion levels of inorganic arsenic. Because aggregate exposure of pregnant mice to inorganic arsenic from both drinking water and food has not been fully evaluated in experimental studies, quantifying arsenic exposure of the developing mouse is problematic. Here, we determined levels of total arsenic and arsenic species in natural ingredient rodent diets that are composed of many plant and animal-derived foodstuffs and in a purified ingredient rodent diet that is composed of a more restricted mixture of foodstuffs. In natural ingredient diets, total arsenic levels ranged from ∼60 to ∼400 parts per billion, and in the purified ingredient diet, total arsenic level was 13 parts per billion. Inorganic arsenic was the predominant arsenic species in trifluoroacetic acid extracts of each diet. Various exposure scenarios were evaluated using information on inorganic arsenic levels in diet and drinking water and on daily food and water consumption of pregnant mice. In a scenario in which pregnant mice consumed drinking water with 10 parts per billion of inorganic arsenic and a natural ingredient diet containing 89 parts per billion of inorganic arsenic, drinking water contributed only ∼20% of inorganic arsenic intake. Quantitation of arsenic species in diets used in studies in which drinking water is the nominal source of arsenic exposure provides more accurate dosimetry and improves understanding of dose-response relations. Use of purified ingredient diets will minimize the discrepancy between the target dosage level and the actual dosage level attained in utero exposure studies designed to evaluate effects of low level exposure to inorganic arsenic.

Comparison of endpoints relevant to toxicity assessments in 3 generations of CD-1 mice fed irradiated natural and purified ingredient diets with varying soy protein and isoflavone contents

Diet is an important variable in toxicology. There are mixed reports on the impact of soy components on energy utilization, fat deposition, and reproductive parameters. Three generations of CD-1 mice were fed irradiated natural ingredient diets with varying levels of soy (NIH-41, 5K96, or 5008/5001), purified irradiated AIN-93 diet, or the AIN-93 formulation modified with ethanol-washed soy protein concentrate (SPC) or SPC with isoflavones (SPC-IF). NIH-41 was the control for pairwise comparisons. Minimal differences were observed among natural ingredient diet groups. F0 males fed AIN-93, SPC, and SPC-IF diets had elevated glucose levels and lower insulin levels compared with the NIH-41 group. In both sexes of the F1 and F2 generations, the SPC and SPC-IF groups had lower body weight gains than the NIH-41 controls and the AIN-93 group had an increased percent body fat at postnatal day 21. AIN-93 F1 pups had higher baseline glucose than NIH-41 controls, but diet did not significantly affect breeding performance or responses to glucose or uterotrophic challenges. Reduced testes weight and sperm in the AIN-93 group may be related to low thiamine levels. Our observations underline the importance of careful selection, manufacturing procedures, and nutritional characterization of diets used in toxicological studies.

Diet Composition Affects Surgery-Associated Weight Loss in Rats with a Compromised Alimentary Tract

Esophageal adenocarcinoma (EAC) is the fastest growing cancer in terms of incidence and has a high mortality rate. The animal model to study EAC uses esophagoduodenal anastomosis (EDA) to induce mixed-reflux (bile/acid) causing esophagitis, Barrett's esophagus, and EAC sequence within 6 mo. However, the lack of fully functional stomach in these rats leads to the development of malnutrition. We have assessed the ability of a chemically pure, purified ingredient diet (AIN-93M) to reduce surgery-associated malnutrition in rats that have undergone the EDA-surgery. Animals were either sham- (SH) or EDA-operated and fed either a grain-based rodent diet (RD) (SH-RD, n=3; EDA-RD, n=10) or a purified diet (PD) (SH-PD, n=4; EDA-PD, n=11). The animals were weighed periodically for assessment of weight gain and euthanized at the end of 24 wk to measure esophageal tumor incidence. Animals that underwent sham surgery continued to gain weight throughout the study period and no tumors were detected. The EDA-operated animals had significantly lower weight gain compared with sham animals. There was no significant difference in weight gain among EDA animals fed two different types of diets until 9 wk after the surgery. After 9 wk, EDA-RD continued to lose weight significantly, whereas the weight loss leveled in EDA-PD (P<0.001). At termination, neither tissue histopathology nor tumor incidence was significantly different between the groups. These results show that compared with a natural ingredient diet, a purified ingredient diet can reduce surgery-associated weight loss in rats with a compromised alimentary tract. This reduction in malnutrition has the potential to reduce the confounding effects of weight loss on future animal studies reported.

Dietary Modulation of p-Nonylphenol–Induced Polycystic Kidneys in Male Sprague-Dawley Rats

We had previously found that p-nonylphenol (NP) at 1000-2000 ppm in a soy- and alfalfa-free diet induced severe polycystic kidney disease (PKD) in both male and female pups exposed from gestation day 7 through postnatal day (PND) 50 and hypothesized that differences in dietary components contributed to the severity of lesions relative to those reported in other studies using similar doses of NP. The present study investigated the dietary modulation of NP-induced PKD using the same exposure regimen with 2000 ppm NP in four different diets: the natural ingredient soy- and alfalfa-free diet that had been used in the earlier study, Purina 5K96; two defined diets AIN-93G, designated AIN-CAS, and a modified AIN-93G with soy protein isolate replacing casein as the protein source (AIN-SPI); and the commonly used natural ingredient diet Purina 5001 (P5001). Serum isoflavone levels were negligible in animals fed the soy-free AIN-CAS and 5K96 diets and were 2- to 18-fold higher in animals fed P5001 than in those fed AIN-SPI. Consumption of P5001 was significantly greater than consumption of the other diets, and those animals fed P5001 were generally significantly heavier than animals receiving the other diets. NP significantly reduced body weight gain in male pups regardless of the diet fed. There was no evidence of NP-induced kidney toxicity in male pups at PND 2, 14, or 21 or in the dams. In PND 50 male pups, serum blood urea nitrogen was significantly elevated by NP in all diet groups. Urine volume and urinary N-acetyl beta-glucuronidase were significantly increased by NP in the soy-free 5K96 and AIN-CAS diet groups. Relative kidney weights were increased by NP in all diet groups except P5001, with the greatest increase in AIN-CAS and 5K96 diet groups. Microscopic evaluation of kidneys from the PND 50 males showed that NP induced PKD in all diet groups but with marked variation in the severity depending on the diet. PKD was severe in 100% of the NP-treated animals in the AIN-CAS and 5K96 groups, moderate in 88% of the AIN-SPI diet group, and mild in only 40% of the P5001 diet group. Thus, diet can significantly modulate the development of PKD induced by dietary NP in rats. Soy components, as well as other complex dietary factors, may account for the level of protection afforded by the P5001 diet.

Post-weaning diet affects genomic imprinting at the insulin-like growth factor 2 (Igf2) locus

IGF2 loss of imprinting (LOI) is fairly prevalent and implicated in the pathogenesis of human cancer and developmental disease; however, the causes of this phenomenon are largely unknown. We determined whether the post-weaning diet of mice affects allelic expression and CpG methylation of Igf2. C57BL/6JxCast/EiJ F1 hybrid mice were weaned onto (1) a standard natural ingredient control diet, (2) a synthetic control diet or (3) a synthetic methyl-donor-deficient diet lacking folic acid, vitamin B(12), methionine and choline. Maternal Igf2 expression in kidney was negligible at birth, but increased to approximately 10% of total expression after 60 days on the natural control diet. By 60 days post-weaning, both synthetic diets caused significant LOI of Igf2 relative to animals weaned onto the natural control diet. Total Igf2 expression was significantly reduced in these groups, however, indicating that the increase in relative maternal Igf2 expression was caused by specific down-regulation of the paternal allele. The LOI induced by the synthetic-deficient diet persisted during a subsequent 100-day 'recuperation' period on natural ingredient diet. There were no group differences in overall or allele-specific CpG methylation in the H19 differentially methylated region (DMR), Igf2 DMR0 or Igf2 DMR1. At 30 and 60 days post-weaning, however, the paternal allele of Igf2 DMR2 was hypermethylated in the kidneys of mice on the control synthetic diet. These results indicate that post-weaning diet can permanently affect expression of Igf2, suggesting that childhood diet could contribute to IGF2 LOI in humans.

Nutrient intake and growth characteristics of male Sprague-Dawley rats fed AIN-93M purified diet or NIH-31 natural-ingredient diet in a chronic two-year study.

Daily nutrient intake and growth of male Sprague-Dawley (SD) rats fed compositionally different diets were monitored over 114 weeks to determine whether rats fed ad libitum (AL) or diet restricted (DR) followed normal growth parameters. A second objective was to evaluate the usefulness of the American Institutes of Nutrition's AIN-93M (maintenance formulation) diet for aging and DR studies. Rats were fed NIH-31 cereal-based diet AL, or a vitamin-fortified modification of the NIH-31 diet at 10, 25, or 40% DR. Other SD rats were fed AIN-93M diet AL or 31% DR; daily nutrient intake and growth response were reported. At all intervals up to 36 weeks of age, rats fed AL the NIH-31 diet consumed significantly (p<0.001) more than rats fed AL the AIN-93M diet, and required more diet per unit of gain than AIN-93M AL rats. However, body weight (BW) gain in rats AL-fed the AIN-93M diet demonstrated that energy components were more efficiently metabolized than in those fed the NIH-31 diet. Whereas diet restriction decreased BW, the rate of maturation, i.e., the rate of reaching a mature BW, increased as intake level decreased. Growth response showed all growth curves were normal, but intake level effects on mature BW and maturation rate differed significantly (p<0.001). Curves for rats AL- and DR-fed the AIN-93M diets were similar to those of rats AL- and DR-fed NIH-31 diet formulations, suggesting that diets adequately met growth requirements and supported normal growth parameters of male SD rats when fed AL or DR. A modification in the AIN-93M energy components to reduce total calories and an evaluation of other nutrient profiles could improve its usefulness as a maintenance and aging diet.

Toxicity and carcinogenicity of acidogenic or alkalogenic diets in rats; effects of feeding NH4Cl, KHCO3 or KCl

The effects of diet-induced acid-base disturbances were examined in 4-week, 13-week and 18-month toxicity studies, and in a 30-month carcinogenicity study. Rats were fed a natural ingredient diet (controls), supplemented with 2% or 4% KHCO3 (base-forming diets), or with 1% or 2.1% NH4Cl (acid-forming diets). Additional controls were fed 3% KCl (neutral diet providing K+ and Cl− in amounts equimolar to those in the 4% KHCO3 diet and the 2.1% NH4Cl diet, respectively). NH4Cl induced the expected metabolic acidosis, as shown by decreased base excess in blood, decreased urinary pH and increased urinary net acid excretion. KHCO3 induced the opposite effects. KCl did not affect the acid-base balance. Clinical condition and death rate were not affected. The feeding of high levels of each salt resulted in growth retardation and increased water intake and urinary volume. Plasma potassium and urinary potassium excretion were increased with KHCO3 and KCl. Plasma chloride was increased with NH4Cl, but not with KCl. Urinary calcium and phosphate excretion were increased with NH4Cl, but there were no indications that bone minerals were involved (weight, calcium content and fat free solid of the femur were not affected). Standard haematological and clinical chemistry parameters were not affected. Kidney weights were increased with 2.1% NH4Cl. Hypertrophy of the adrenal zona glomerulosa occurred with KHCO3, KCl and NH4Cl, due to chronic stimulation of the adrenal cortex by either K+ or by NH4Cl-induced acidosis. An early onset (from week 13) of oncocytic tubules was noted in the kidneys of rats fed KHCO3 and, after 30 months, the incidence of this lesion was much higher than the background incidence in ageing controls. No progression to oncocytomas was noted. KCl showed only slight effects on the early onset of oncocytic tubules (from 18 months). In contrast, the severity of nephrosis and the incidence of oncocytic tubules were decreased with 2.1% NH4Cl, suggesting a protective effect of acidosis. The feeding of KHCO3 resulted in hyperplasia, papillomas and carcinomas of the urinary bladder. With KCl only a slight increase in proliferative urothelial lesions was noted. Apart from these (pre-)neoplastic lesions in the urinary bladder there were no treatment-related differences in tumour response among the groups. We concluded that most of the observed changes represent physiological adaptations to the feeding of acid- or base-forming salts. Remarkable effects noted with KHCO3, and to a far lesser extent with KCl, consisted of renal oncocytic tubules and (pre-)neoplastic lesions of the urinary bladder epithelium. NH4Cl-induced chronic metabolic acidosis was not associated with dissolution of alkaline bone salts in rats. Finally, a protective effect of chronic acidosis on tumour development was not found.

Diet and the duration of testosterone-dependent prostate cancer in Lobund–Wistar rats

Hormone-related cancers in the prostate, breast, endometrium, ovary and testicle account for 30% of malignancies in humans. We have developed a unique model of spontaneous prostate cancer (PC) in Lobund–Wistar [L–W] rats that shares many of its characteristics with the natural history of PC in man, including (a) inherent predisposition, high production of testosterone and aging risk factors, (b) endogenous tumorigenic mechanisms, and (c) early stage testosterone-dependent and late stage testosterone-independent tumors. About 30% of L–W rats on diet L-485 develop spontaneous palpable cancer in the anterior prostate-seminal vesicle (P-SV) complex in average of 20.5 months. At age 12 months early stage spontaneous PC was prevented or reversed by testosterone-deprivation through change of diet from L-485 to soy protein isolate/isoflavone (SPII) diet, thereby preventing the late lethal clinical disease: about 75% of rats at risk of developing testosterone-independent P-SV tumors were free of detectable cancer and about 25% had developed testosterone-independent cancer at age 12 months. The duration of the dependent stage exceeded age 12 months in 75% of the rats at risk. Dietary soymeal, found in most natural ingredient diets, may promote PC tumorigenesis, but only in L–W rats.

Effects of dietary transition metals on oxidative DNA lesions in neonatal rats

Bulky endogenous oxidative lesions (type II I-compounds) reflect DNA damage associated with oxidative stress. As shown by 32 P -postlabeling, their levels are enhanced by pro-oxidant genotoxins and also shortly after normal birth in several rat tissues as a function of time and the maternal diet. In order to elucidate which dietary components contribute to postnatal DNA damage, we have focused, herein, on the possible role of transition metals (iron, copper, and nickel). Pregnant Fischer 344 (F344) rats were fed AIN-93G purified diet containing different amounts of iron, copper, and nickel, or Purina-5001 natural-ingredient diet (which contains relatively high concentrations of these metals). Type II I-compounds were estimated by nuclease P1-enhanced 32 P -postlabeling in liver and lung DNA of fetuses and at 24 h and day 9 post-partum. Increased postnatal oxidative damage was detected in liver but not lung DNA of neonates exposed to higher amounts of dietary transition metals. There were significant positive linear correlations between maternal transition metal intake and neonatal, but not fetal and maternal type II I-compound levels. The results show that transition metals in the maternal diet affect perinatal oxidative DNA damage, presumably via a Fenton-type reaction. They also provide evidence for optimal levels in the maternal diet of transition metals, which on one hand, are essential for life, but on the other, can cause potentially deleterious DNA alterations in the offspring.

Boron Supplementation of a Semipurified Diet for Weanling Pigs Improves Feed Efficiency and Bone Strength Characteristics and Alters Plasma Lipid Metabolites

Two experiments were conducted to determine effects of dietary boron (B) on performance, plasma minerals and metabolites, and bone characteristics in young pigs. In Experiment 1, 48 pigs (24 males, 24 females; 21 d old) were allotted to pens, which were randomly assigned to one of the following dietary treatments: 1) control (natural ingredient diet; 6.7 mg B/kg diet), 2) control + 5 mg B/kg diet and 3) control + 15 mg B/kg diet. Boron was supplemented as sodium borate. In Experiment 2, 48 pigs (24 males, 24 females; 21 d old) were assigned to the same treatments described in Experiment 1; however, the basal diet was a semipurified diet (0.98 mg B/kg diet). Diets were fed for 40 d; on d 40, blood samples were obtained for determination of plasma mineral and metabolite concentrations. Femurs were harvested from 8 pigs per treatment on d 40 for determination of mechanical properties, ash and lipid percentage. In Experiment 1, B did not affect performance, plasma minerals or metabolites or bone properties. In Experiment 2, B supplementation improved (P: < 0.05) the gain:feed ratio and increased plasma cholesterol and triglyceride concentrations. There was a treatment x sex interaction (P: < 0.05) in Experiment 2 for bone lipid to be lower and bending moment to be higher, with the response occurring in male pigs. Other dependent variables in Experiment 2 were not affected by treatment. In conclusion, B supplementation of a low B diet elicited responses of physiologic importance to pigs. However, B supplementation of a natural ingredient diet did not elicit a response.

Prevention of spontaneous prostate-related cancer in Lobund-Wistar rats by a soy protein isolate/isoflavone diet.

Epidemiological surveys recorded that men in the Orient (Japan and China) consuming diets high in soy food were at low risk of developing clinical prostate cancer, compared to a relatively high risk among men in the West who consumed diets low in soy food. Soybeans contain phytoestrogens (isoflavones) with many recorded anticancer mechanisms. The Lobund-Wistar (L-W) rat is a unique model system: approximately 30% develop metastasizing adenocarcinomas spontaneously in the anterior prostate-seminal vesicle complex (P-SV), from which the tumors expand into the dorsolateral lobes. L-W rats are inherently predisposed, possibly by unusually high levels of circulating testosterone (T), to develop P-SV tumors which are T-dependent in the early stages and T-independent in advanced stages of tumorigenesis. L-W rats were fed two diets from age 2-24 months: 1) natural ingredient diet L-485 (Harlan TekLad Diets, Madison, WI) containing soy meal, or 2) a modified starch-casein diet in which soy protein isolate/isoflavones (SPII) replaced casein as a source of protein. At age 24 months, 3 of 99 (3%) rats on diet SPII and 30 of 100 (30%) rats on diet L-485 developed spontaneous P-SV cancers. Rats on the SPII diet manifested a significant reduction of circulating T, approaching physiological levels. Failure of the rats on diet L-485 to prevent P-SV cancer development suggests that soy meal contained a factor(s) that blocked the antiandrogenic action of the phytoestrogen. The spontaneous development of P-SV cancers was significantly prevented in L-W rats consuming the SPII diet from age 2-24 months, possibly through an agonist effect of the soy-derived phytoestrogens.

Acute Elevation by Short-Term Dietary Restriction or Food Deprivation of Type I I-Compound Levels in Rat Liver DNA

Type I I-compounds are bulky endogenous DNA modifications detectable by 32P postlabeling that exhibit age, species, tissue, genotype, gender, and diet dependence. Their formation appears unrelated to oxidative stress. In fact, several lines of indirect evidence suggest that many type I I-compounds may represent normal functional DNA modifications. For example, long-term dietary restriction (DR), which retards the development of age-related diseases including cancer and extends median and maximum life spans, unexpectedly elicits significant increases rather than decreases in the levels of many I-compounds in different rodent tissues. Positive linear correlations have been observed between such levels and median life spans of the animals. In the present work we have investigated 1) whether elevation of I-compound levels does not depend on chronic DR, i.e., occurs after a short period of DR or fasting, and 2) whether I-compound levels return to control values after the animals are returned to unrestricted feeding after food deprivation. Female Fischer 344 rats (approx 140 g each) were randomized into three groups. Group 1 was fed a natural ingredient (Purina 5001) diet ad libitum (AL) throughout the study, Group 2 was switched to 60% of the AL amount (40% DR) at 0 hour, and Group 3 was given no food for up to 72 hours and then returned to AL feeding until the end of the experiment. Liver DNA of individual rats (n = 4) was isolated for I-compound analysis at 24, 72, and 240 hours. Restricted and food-deprived rats showed elevated levels of hepatic I-compounds, with fasting eliciting the highest levels. These effects were seen as early as the 24-hour time point. Refeeding after 72 hours of food deprivation restored the levels to control values, measured at 240 hours. Our observations are discussed in relation to carcinogenesis and tumor promotion. The almost instantaneous changes of endogenous DNA modifications showed their exquisite sensitivity to nutritional factors and provided strong new evidence for precise regulation of their formation and removal.

The Role of Environmental Antigens in the Spontaneous Development of Autoimmunity in MRL-lprMice

AbstractIt has been proposed that the “normal” stimulation of the immune system that occurs from interactions with environmental stimuli, whether infectious or dietary, is necessary for the initiation and/or continuation of autoimmunity. We tested this hypothesis by deriving a group of MRL-lpr mice into a germfree (GF) environment. At 5 mo of age, no differences between GF and conventional MRL-lpr mice were noted in lymphoproliferation, flow cytometric analysis of lymph node cells (LN), or histologic analysis of the kidneys. Autoantibody levels were comparably elevated in both groups. A second experiment tested the role of residual environmental stimuli by contrasting GF mice fed either a low m.w., ultrafiltered Ag-free (GF-AF) diet or an autoclaved natural ingredient diet (GF-NI). At 4 mo of age, both groups showed extensive lymphoproliferation and aberrant T cell formation, although the GF-AF mice had ∼50% smaller LNs compared with sex-matched GF-NI controls. Autoantibody formation was present in both groups. Histologic analysis of the kidneys revealed that GF-AF mice had much lower levels of nephritis, while immunofluorescence analysis demonstrated no difference in Ig deposits but did reveal a paucity of C3 deposition in the kidneys of GF-AF mice.These data do not support a role for infectious agents in the induction of lymphoproliferation and B cell autoimmunity in MRL-lpr mice. Furthermore, they suggest that autoantibodies do not originate from B cells that were initially committed to exogenous Ags. They do suggest a possible contributory role for dietary exposure in the extent of lymphoproliferation and development of nephritis in this strain.

The Effects of Diet, Overfeeding and Moderate Dietary Restriction on Sprague-Dawley Rat Survival, Disease and Toxicology

Overfeeding by ad libitum (AL) food consumption is the most significant, uncontrolled variable affecting the outcome of the current rodent bioassay. The correlation of food consumption, the resultant adult body weight and the 2-y survival in Sprague-Dawley rats is highly significant. Feeding natural ingredient diets that varied in protein, fiber and metabolizable energy content did not improve low 2-y survival if Sprague-Dawley rats were allowed AL food consumption. Moderate dietary restriction (DR) of all diets tested significantly improved survival and delayed the onset of spontaneous degenerative disease (i.e., nephropathy and cardiomyopathy) and diet-related tumors. By 2 y, moderate DR resulted in an incidence of spontaneous tumors similar to that seen with AL consumption; however, the tumors were more likely to be incidental and did not result in early mortality. There was a decreased age-adjusted incidence in pituitary and mammary gland tumors, but tumor volume and growth time were similar in the AL and DR groups, indicating a similar tumor progression with a delay in tumor onset. Moderate DR did not significantly alter drug-metabolizing enzyme activities or the toxicologic response to five pharmaceuticals tested at maximum tolerated doses (MTD). However, moderate DR did require higher doses of compounds to be given before classical MTD were produced with four pharmaceutical drug candidates. Toxicokinetic studies of two of these compounds demonstrated steady-state systemic exposures that were equal or higher in moderate DR-fed rats. These and other data indicate that moderate DR is the most appropriate method of dietary control for rodent bioassays used to assess human safety of candidate pharmaceuticals.

Dietary Nucleotides: Effects on Cell Proliferation Following Partial Hepatectomy in Rats Fed NIH-31, AIN-76A, or Folate/Methyl-Deficient Diets

The requirement of a number of tissues for dietary nucleotides could explain some of the differences observed in animals fed natural ingredient diets vs. those fed purified diets lacking a source of dietary nucleotides. Lack of dietary nucleotides is exacerbated in animals fed folate- or methyl-deficient semipurified diets, in which both salvage and folate-dependent de novo synthetic pathways are diminished. We examined hepatocyte proliferation following partial hepatectomy in weanling male Fischer-344 rats fed natural ingredient NIH-31 diet, nucleotide-free purified AIN-76A diet or a basal diet similar to AIN-76A but deficient in the methyl donors folate, choline and methionine. Additional groups were fed AIN-76A or folate/methyl-deficient diets supplemented with 0.25% yeast RNA. Compared with NIH-31, AIN-76A increased dUMP/dTTP ratios, reduced the mitotic index (MI) and increased the ratio of proliferating cell index (PCI) to mitotic cells, an indication that hepatocytes were delayed in S-phase. Addition of yeast RNA to AIN-76A reversed (by approximately 50%) the effects of AIN-76A on dUMP/dTTP and cell proliferation. A folate/methyl-deficient diet also produced an increased dUMP/dTTP ratio and markedly reduced the MI, increasing the PCI/MI, which suggested even further delay of cells in S-phase. Addition of yeast RNA to the folate/methyl-deficient diet was effective in significantly reversing the effects of folate/methyl deficiency.

Growth and reproductive performance of the Asian catfish Clarias macrocephalus (Gunther) fed artificial diets

Four natural ingredient diets similar in nutrient composition (crude protein = 42–44%; P/E ratio = 115–120 mg/kcal) but different in protein sources, were formulated and fed to hatchery-reared catfish to measure the relative performance of the catfish fed alternative broodstock diets. The control feed was a combination of fish-by-catch and commercial fish pellets. In trial I, growth of the catfish was slow over a 36-week period, but some fish became gravid. Diets 1, 2, and 3 and the control feed were tested in trial II. Growth of fish did not differ significantly (P > 0.05) and female fish in all treatments became gravid. For fish induced to spawn from April to August (1994), hatching rate showed significant differences among treatments (P < 0.05). Relative fecundity, fertilization and hatching rates, and production of 3-day-old larvae were significantly different among fish induced to spawn in November (1994) when another incubation setup was used. Among the diets, diets 2 and 3 best enhanced reproductive performance of the catfish.