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

Grain versus AIN: Common rodent diets differentially affect health outcomes in adult C57BL/6j mice

Semi-synthetic and grain-based diets are common rodent diets for biomedical research. Both diet types are considered nutritionally adequate to support breeding, growth, and long life, yet there are fundamental differences between them that may affect metabolic processes. We have characterized the effects of diet type on breeding outcomes, metabolic phenotype, and microbiota profile in adult mice. Healthy 8-week-old female and male C57BL/6J mice were fed a semi-synthetic or a grain-based diet for 12 weeks and changes in body weight and body composition were monitored. Breeding outcomes were determined. Body fat accumulation of female mice was lower on the semi-synthetic diet than on the grain-based diet. Pregnancy rate and newborn pup survival appeared to be lower in mice exposed to semi-synthetic diet compared to grain-based diet. Both female and male mice showed a profound change in fecal microbiota alpha and beta diversity depending on diet type. Our study shows that type of rodent diet may affect breeding outcomes whilst influencing metabolism and health of female laboratory mice. These factors have the potential to influence other experimental outcomes and the results suggest that semi-synthetic and grain-based diets are not interchangeable in research using rodent models. Careful consideration and increased understanding of the consequences of diet choice would lead to improvements in experimental design and reproducibility of study results.

Comparison of the Nutritional Status of Swiss Albino Mice Fed on Either a Purified or Cereal-Based Diet for 15 weeks

Background

Laboratory animals are commonly fed on cereal-based diets (CBDs) whose nutrient composition is unknown and may confound the metabolic response to study interventions. Purified diets such as AIN-93M are therefore recommended, as their nutrient composition is known. However, few studies have evaluated their use as adequate control diets. The aim of this study was to compare the nutrition status of Swiss albino mice fed on either CBD or AIN-93M for 15 weeks.

Methods

Twenty Swiss albino mice aged 6-8 weeks and weighing 21.7 g ± 0.6 were fed on either CBD or AIN-93M diet for 15 weeks. Their nutritional status was evaluated using anthropometric and hematological indices, serum glucose, total protein, albumin, and total cholesterol to select an appropriate normal control diet.

Results

The CBD had low-calorie content (2.57 kcal/g) and protein (11 ± 3.8 g/100 g) compared to AIN-93M (3.8 kcal/g and 14 g/100 g, respectively). The BMI of male mice fed on CBD and AIN-93M diets was significantly higher (P=0.0139 and P=0.0325, respectively) compared to that of females fed on similar diets. Animals in the CBD group had lower hemoglobin (15.1-16.9 g/dl) compared to those in the AIN-93M group (18.1-20.8 g/dl). Serum albumin levels were higher in both male (P=0.001) and female (P=3 × 10^-6) mice fed on AIN-93M compared to those fed on CBD. Females in the AIN-93M group had higher cholesterol (P=0.026) than those in the CBD group.

Conclusion

The AIN-93 diet of caloric value 3.85 kcal/g (total protein 14 g, total fat 4 g of soy bean oil, fibre 5 g, and total carbohydrate 42 g per 100 g) can be safely used as a normal control diet in long-term research studies using Swiss albino mice.

Chow diet in mouse aging studies: nothing regular about it

Chow diet is used in the majority of rodent studies and, although assumed to be standardized for dietary source and nutritional contents, it varies widely across commercial formulations. Similarly, current approaches to study aging in rodents involve a single-diet formulation across the lifespan and overlook age-specific nutritional requirements, which may have long-term effects on aging processes. Together, these nutrition-based disparities represent major gaps in geroscience research, affecting the interpretation and reproducibility of the studies. This perspective aims to raise awareness on the importance of rodent diet formulation and proposes that geroscientists include detailed descriptions of all experimental diets and feeding protocols. Detailed reporting of diets will enhance rigor and reproducibility of aging rodent studies and lead to more translational outcomes in geroscience research.

Chemopreventive Effects of Silibinin on Colitis-Associated Tumorigenesis by Inhibiting IL-6/STAT3 Signaling Pathway

Inflammatory bowel disease (IBD), characterized by sustained inflammation, is a latent risk factor of colon tumorigenesis. Silibinin has been reported to be anti-inflammatory and antineoplastic, but its efficacy on colitis-associated cancer (CAC) has not been reported. Interlukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) is the key signaling pathway involved in CAC. We evaluated the chemopreventive effect of silibinin on a CAC mouse model and determined its impact on IL-6/STAT3 signaling. Intestinal tumor cells (IMCE and HCT-116 cell lines) were also treated by graded concentration of silibinin, and cellular viability was determined. Silibinin (750 mg/kg/day) was administered to an azoxymethane/dextran sulfate sodium (AOM/DSS) C57BL/6 mouse model for 10 weeks by gavage. Body weight, colon length, and the amount and diameter of colon tumors were documented, respectively. Specimens were subjected to H&E staining for colitis and tumor scoring, immunohistochemical staining and terminal deoxynucleotidyl transferase dUTP nick end labeling for proliferation assessment, and immunofluorescent staining for intestinal mucosa barrier assessment. Production of inflammatory cytokines was determined by real-time PCR. IL-6/STAT3 pathway activation was evaluated through immunohistochemical staining and western blot. In the current study, silibinin significantly inhibited the viability of intestinal tumor cells. The production of inflammatory cytokines and the phosphorylation of STAT3 were both inhibited in intestinal tumor cells. Meanwhile, silibinin decreased the amount and size of tumors in AOM/DSS mice. Colitis and tumor scores were decreased accompanying with inhibition of colonic tumor cell proliferation and promotion of cellular apoptosis. Additionally, silibinin could reduce the production of inflammatory cytokines and attenuate the impairment of colonic mucosal barrier. Furthermore, STAT3 phosphorylation was significantly suppressed by silibinin. In conclusion, silibinin could protect against colitis-associated tumorigenesis in mice via inhibiting IL-6/STAT3, which showed promising chemopreventive potential of CAC.

Modeling the Disease Progression from Healthy to Overt Diabetes in ZDSD Rats

Studying the critical transitional phase between healthy to overtly diabetic in type 2 diabetes mellitus (T2DM) is of interest, but acquiring such clinical data is impractical due to ethical concerns and would require a long study duration. A population model using Zucker diabetic Sprague-Dawley (ZDSD) rats was developed to describe this transition through altering insulin sensitivity (IS, %) as a result of accumulating excess body weight and β-cell function (BCF, %) to affect glucose-insulin homeostasis. Body weight, fasting plasma glucose (FPG), and fasting serum insulin (FSI) were collected biweekly over 24 weeks from ZDSD rats (n = 23) starting at age 7 weeks. A semi-mechanistic model previously developed with clinical data was adapted to rat data with BCF and IS estimated relative to humans. Non-linear mixed-effect model estimation was performed using NONMEM. Baseline IS and BCF were 41% compared to healthy humans. BCF was described with a non-linear rise which peaked at 14 weeks before gradually declining to a negligible level. A component for excess growth reflecting obesity was used to affect IS, and a glucose-dependent renal effect exerted a two- to sixfold increase on the elimination of glucose. A glucose-dependent weight loss effect towards the end of experiment was implemented. A semi-mechanistic model to describe the dynamics of glucose and insulin was successfully developed for a rat population, transitioning from healthy to advanced diabetes. It is also shown that weight loss can be modeled to mimic the glucotoxicity phenomenon seen in advanced hyperglycemia.

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.

Oil in a commercial standard diet needs its product specifications

As our survey found that some commercial standard diets for laboratory animals contained oil with chemical properties of highly deteriorated oil, their influence should be checked on animals especially of very young age. Three-week old weanling Wistar rats were fed a commercial standard diet (commercial standard diet group) or AIN93G (AIN93G group), defined diet, for 7 weeks. Then both groups were fed AIN93G for 12 weeks. As a result, all the rats grew normally without diarrhea, seborrhea, dermatitis, or excessive hair loss through the feeding period and there was no significant difference in body weight increase, feed ingestion amounts and organ weights. But fecal excretion was high at 10 weeks of age when the diet was switched from the commercial standard diet to AIN93G. Although serum aspartate aminotransferase (AST) and alanin aminotransferase (ALT) of the commercial standard diet group were not statistically higher than those of the AIN93G group, two rats out of 8 in the former group showed dark-red patches on the liver surface, and necrosis in histological analysis. In addition, slight fatty degeneration of all the liver, and swelling tubuler epithelium of kidneys were also found in the group. Serum levels of triacylglycerol (TG), glucose (GLC) and total cholesterol (T-CHO) were high, and free fatty acids (NEFA), low in the commercial standard diet group in good accordance with our previous result from the study on ingestion of deteriorated oil. In conclusion, product specifications of oil in commercial standard diets should be laid down to pursue a reliable animal experimentation.

Neoplastic pathology in male Sprague-Dawley rats fed AIN-93M diet ad libitum or at restricted intakes

The primary purpose of this study was to evaluate the effects of age and long-term dietary reduction on neoplastic diseases in rats fed the AIN-93M purified diet. Second, pathologic profiles are critical to comprehensive dietary evaluation. Male Sprague-Dawley rats assigned to 2 groups, ad libitum (AL) and dietary restricted (DR), were fed the AIN-93M (casein protein) diet free choice and reduced in amount by 31%, respectively. At 58 weeks of age, the predominant types of lesions in AL and DR rats were pituitary and skin tumors. At 114 weeks of age, the most common lesions were pituitary, adrenal gland, skin, mammary, brain, and pancreatic tumors and mononuclear cell leukemia. However, DR had no significant effect on these lesions. Primary findings demonstrate that DR significantly reduced the total number of tumors per rat and incidence of benign and primary tumors (all organs) but did not reduce the incidence of malignant tumors (all organs). Dietary restriction increased the percentage of unknown deaths. These results may explain why survival rates for AL and DR rats were not significantly different at 114 weeks (43.3 vs 57.5%, respectively). These findings differ from previous studies using NIH-31 cereal diet (Aging Clin Exp Res 2001;13:263; J Nutr 2002;132:101; Aging Clin Exp Res 2003;16(6):68; Aging Clin Exp Res 2004;16:448) where neoplastic lesions rather than nonneoplastic lesions were linked to a significant increase in survival rate among cohorts of DR-fed rats (J Nutr 2002;132:101). Factors such as diet composition and digestibility, although not independent of body weight, may have contributed to differences in rat mortality and may affect humans in a similar manner.

Nonneoplastic pathology in male Sprague-Dawley rats fed the American Institute of Nutrition-93M purified diet at ad libitum and dietary-restricted intakes

This study evaluates the effects of age and chronic dietary restriction (DR) on nonneoplastic diseases in rats that were fed the American Institute of Nutrition (AIN)-93M purified diet. Male Sprague-Dawley (SD) rats were divided into an ad libitum (AL) group and a DR group that was fed the AIN-93M diet with intake reduced by 31%. Nonneoplastic disease profiles were developed to clarify whether the AIN-93M diet fulfills long-term nutritional requirements of rats. Subsets of rats were killed at 58 and 114 weeks of age, and histopathology was performed. At 58 weeks of age, the 2 main types of nonneoplastic diseases in AL rats were liver vacuolization and cardiomyopathy. Dietary restriction reduced the severity and incidence of both lesions. At 114 weeks of age, the most common lesions in AL rats were cardiomyopathy, nephropathy, liver vacuolization, and degeneration with renal failure and genitourinary infections causing the greatest mortality. Dietary restriction reduced the incidence and severity of these lesions. Nonneoplastic diseases accounted for 28.9% and 0.0% of total mortalities in the AL and DR groups, respectively; however, there was a higher incidence of unknown deaths in the DR rats (52.6%) compared to AL rats (28.9%), which may have limited the success of DR to improve survival. Although the AIN-93M diet supported chronic rat growth, alterations in some dietary component concentrations may be required to lower body weight in chronic rodent and human studies. Factors such as diet composition and digestibility may alter nonneoplastic diseases and mortality in rats and humans in a similar fashion.

Exploiting the rodent model for studies on the pharmacology of lifespan extension

The rodent is a particularly valuable model with which to test therapeutic interventions for aging, as rodent physiology is close enough to human physiology to give the findings relevance for human aging, and it is small enough to allow for use of statistically robust sample sizes. There are many rodent models to choose from, with advantages and disadvantages to each. The choice of model system, as well as other experimental design decisions such as diet and housing, is extremely important for the success of lifespan studies. These issues are discussed in this review of the use of the rodent model. The National Institute on Aging (NIA) Interventions Testing Program, which has grappled with all of these issues, is described.

RhoA, Rho kinase, JAK2, and STAT3 may be the intracellular determinants of longevity implicated in the progeric influence of obesity: Insulin, IGF-1, and leptin may all conspire to promote stem cell exhaustion

The aging process in higher mammals is increasingly being shown to feature a potentially substantial contribution from the longitudinal deterioration of normative stem cell dynamics seen with the passage of time. The precise mechanistic sequence producing this phenomenon is not entirely understood, but recent evidence has strongly implicated intracellular downstream effectors of endocrinologic pathways thought to be engaged by the obese state, specifically the insulin, IGF-1, and leptin signaling pathways. Among the intracellular effectors of these signals, a uniquely potent influence on stem cell dynamics may be attributable to Rho/ROCK, JAK kinase activity and STAT3 activity. In particular, it has already been shown that specific tyrosine kinase activities, such as that seen with Rho kinase, are presently thought to be associated with adverse health outcomes in numerous clinical contexts. Furthermore, the Rho GTPase is thought to be contributing to end-stage renal disease. However, in addition to its contribution to organ system dysfunction, the Rho/ROCK pathway has recently been shown to be activated by insulin and IGF-1, providing a tantalizing connection to nutrition and aging science. The JAK-STAT pathway, in contrast, has long been associated with pro-inflammatory cytokines, but has recently been implicated in leptin signaling as well. Importantly, JAK-STAT signaling has, similarly to Rho/ROCK signaling, been implicated as capable of accelerating stem cell proliferation. The implications of these recent determinations, in light of the recent finding of telomere attrition in humans associated with obesity, are that the intracellular determinants of aging may already be known, and the known common influence of these signaling elements on longitudinal stem cell dynamics is a pronounced induction of proliferation, an elevation that has been linked to the pathologic evolution of longitudinal organ-level dysfunction and the organismal-level physiologic decline seen with the inexorable passage of time. Besides the obvious utility for the management for human age-related dysfunction that investigation of pharmacologic inhibitors of these proteins would provide, interventions such as caloric restriction and possibly intermittent fasting may beneficially influence stem cell proliferation dynamics and reduce intracellular correlates of mitogenic drive. Integrating the findings present in the present body of research may reveal endocrinological states that are compatible with longevity, and will also provide novel insight into the specific proteomic determinants of age-related physiologic decline, ushering in a new epoch of medicine that fosters the management of the "pre-etiopathology" of chronic disease and disability of aging, therefore mitigating the suffering widely thought to be inherent in the latter stages of life.

The effects of different levels of dietary restriction on neoplastic pathology in the male Sprague-Dawley rat

BACKGROUND AND AIMS

The primary purpose of this study was to evaluate the effects of varied levels of dietary restriction (DR) on neoplastic pathologies in rodents at 58 and 110 weeks of age.

METHODS

Male Sprague-Dawley (SD) rats were divided into four nutritional groups; an ad libitum (AL) control group, and three dietary restricted (DR) groups that were fed the NIH-31 diet reduced in amount by 10, 25, and 40%.

RESULTS

At 110 weeks of age, compared to AL rats, the incidence of benign tumors was significantly lower in all DR groups while primary tumors were significantly lower in the 10 and 40% DR groups; no malignant tumors were detected in the 10% DR group. Most defined mortalities were caused by neoplastic lesions. All levels of DR reduced the percentage of tumor-bearing animals, the incidence of skin tumors (combined), and the total number of tumors. Pituitary, skin, and pancreatic tumors were the most prolific lesions; pituitary and skin tumors were the most fatal. Compared to AL rats, the time to onset of skin and pancreatic tumors was longer in all of the DR groups.

CONCLUSION

In many cases, the incidences of neoplastic lesions were similar among the DR groups, clearly indicating that the DR effect is not linear and that even a very low level of DR (10%) can have a significant effect on many important neoplastic lesions and tumor burden. The main effect of DR was to decrease the incidence of some neoplastic lesions and to increase the time to onset and/or decrease the progression of tumors, thereby increasing the 110-week survival rate of DR rats.