Neonatal animal testing paradigms and their suitability for testing infant formula

A 21-day safety evaluation of biotechnologically produced 3-fucosyllactose (3-FL) in neonatal farm piglets to support use in infant formulas

3-Fucosyllactose (3-FL) is one of the most abundant fucosylated oligosaccharides in human breast milk and is an approved infant formula ingredient world-wide. 3-FL functions as a prebiotic to promote early microbial colonization of the gut, increase pathogen resistance and modulate immune responses. To investigate safety and potential gut microbiota effects, 3-FL was fed for 21-days to farm piglets beginning on Postnatal Day (PND) 2. Fructooligosaccharide (FOS), an approved infant formula ingredient, was used as a reference control. Standard toxicological endpoints were evaluated, and the gut microbiota were assessed. Neither 3-FL (245.77 and 489.72 mg/kg/day for males and 246.57 and 494.18 mg/kg/day for females) nor FOS (489.44 and 496.33 mg/kg/day males and females, respectively) produced any adverse differences in growth, food intake or efficiency, clinical observations, or clinical or anatomic pathology changes. Differences in the gut microbiota after 3-FL consumption (versus control and FOS groups) included the absence of Bifidobacterium species from the piglets, enrichment of Prevotellamassilia timonensis, Blautia species, Mediterranea massiliensis, Lachnospiraceae incertae sedis, and Eubacterium coprostanoligens and lower relative abundance of Allisonella histaminiformans and Roseburia inulinivorans. This study further supports the safe use of 3-FL produced using biotechnology as a nutritional ingredient in foods.

Trends in ingredients added to infant formula: FDA's experiences in the GRAS notification program

While human milk is considered the optimal source of nutrition for infants for the first six and twelve months of age, with continued benefit of breastfeeding with complementary foods, a safe alternative, nutritionally adequate to support infant growth and development, is necessary. In the United States, the Food and Drug Administration (FDA) establishes the requirements necessary to demonstrate the safety of infant formula within the framework of the Federal Food, Drug, and Cosmetic Act. FDA's Center for Food Safety and Applied Nutrition/Office of Food Additive Safety evaluates the safety and lawfulness of individual ingredients used in infant formula, whereas the Office of Nutrition and Food Labeling oversees the safety of infant formula. Most infant formula ingredients are either from sources with history of safe consumption by infants or are like components in human milk. Information demonstrating the regulatory status of all ingredients is required in submissions for new infant formulas, and ingredient manufacturers often use the Generally Recognized as Safe (GRAS) Notification program to establish ingredient regulatory status. We provide an overview of ingredients used in infant formula evaluated through the GRAS Notification program to highlight trends and discuss the data and information used to reach these GRAS conclusions.

Rodent models of metabolic disorders: considerations for use in studies of neonatal programming

Epidemiologically, metabolic disorders have garnered much attention, perhaps due to the predominance of obesity. The early postnatal life represents a critical period for programming multifactorial metabolic disorders of adult life. Though altricial rodents are prime subjects for investigating neonatal programming, there is still no sufficiently generalised literature on their usage and methodology. This review focuses on establishing five approach-based models of neonatal rodents adopted for studying metabolic phenotypes. Here, some modelled interventions that currently exist to avoid or prevent metabolic disorders are also highlighted. We also bring forth recommendations, guidelines and considerations to aid research on neonatal programming. It is hoped that this provides a background to researchers focused on the aetiology, mechanisms, prevention and treatment of metabolic disorders.

Evaluation of the Safety of a Plant-Based Infant Formula Containing Almonds and Buckwheat in a Neonatal Piglet Model

A randomized neonatal piglet trial was conducted to evaluate the safety and the effects of a plant-based formula containing almonds and buckwheat as the main ingredients on growth and plasma parameters. From postnatal day (PND) 2 to 21, the piglets were fed a dairy-based milk formula (Similac Advance) or a plant-based formula (Else Nutrition) and all piglets were euthanized at day 21. No diarrhea was observed after PND 8 and all the piglets completed the trial. Body growth, kcal intake, the complete plasma count parameters and hematological parameters were within the reference range in both groups. Organ growth and development was similar between the two groups. Plasma glucose was higher in the dairy-based-fed piglets relative to the plant-based at 2 weeks of age. Liver function biomarkers levels were greater in the plasma of the plant-based compared to the dairy-based fed group. In addition, calcium levels were higher in the plant-based fed piglets at 1 week of age. Thus, the plant-based formula tested in this study was well tolerated by the piglets and supported similar growth compared to dairy-based milk formula. Therefore, the results support the safety of the tested plant-based infant formula during the neonatal period in comparison to the dairy-based formula fed group.

Toxicological evaluation of Microbacterium foliorum SYG27B-MF

Microbacterium foliorum is a naturally occurring bacteria in cruciferous vegetables and ripened cheese. The safety of M. foliorum SYG27B-MF has been assessed in both acute and subchronic studies and a battery of mutagenicity and clastogenicity tests. In a single dose acute study, the LD₅₀ of M. foliorum SYG27B-MF was greater than 3 g/kg bw or 5.1 × 10¹⁶ colony forming unit (CFU)/kg bw, the highest dose tested. In a 90-day subchronic toxicity study in 80 Sprague-Dawley rats, no animals died and there were no treatment-related abnormalities at doses of 0, 500, 1000, or 2000 mg/kg bw. In a 90-day repeated toxicity test, the no-observed-adverse-effect level (NOAEL) M. foliorum SYG27B-MF was 2000 mg/kg/day or 3.4 × 10¹⁶ CFU/kg bw/day, the highest level tested. A mutagenicity study using reverse bacterial mutation tests and a genotoxicity study employing cultured hamster ovarian fibroblasts (CHO-K1) cell showed that M. foliorum SYG27B-MF was not mutagenic or clastogenic in the presence or absence metabolic activation. In an in vivo mouse micronucleus assay, M. foliorum SYG27B-MF did not induce did not induce micronuclei formation in the bone marrow cells of mice, indicating that it is non-clastogenic. The results from these studies support the safety of M. foliorum SYG27B-MF for use as a production organism for human food ingredients.

Maternal obesity aggravates the abnormality of porcine placenta by increasing N6-methyladenosine

BACKGROUND

The growing prevalence of overweight or obese pregnancies shows an increasing risk for aberrant fetal growth and postnatal complications. Maternal obesity is associated with low birth weight (LBW) of piglets. However, the development of LBW from maternal obesity is not well understood.

OBJECTIVE

This study attempts to investigate the novel RNA modification N6-methyladenosine (m⁶A) in the placenta tissues by using sows with high backfat thickness as a model for obese pregnancy.

SUBJECTS/METHODS

Forty four placentas from eight sows (backfat thickness ≥21 mm) were divided into four groups by piglet weight, with group1 being LBW group (<1.0 kg), group2 (1.0-1.4 kg), group3 (1.4-1.6 kg), and group4 (>1.6 kg) as the comparative groups of normal birth weight. QPCR was used to measure the mRNA levels of the genes and western blot was used to test the content of proteins. At the same time, LC-MS/MS method was built to test the content of m⁶A modification in the placental RNA, and finally MeRIP-QPCR technology was employed to check the specific m⁶A modification in the key genes.

RESULTS

Compared with the comparative groups, the expression levels of PPARγ, VEGFA, ABHD5, and GPR120 in both mRNA and protein decreased noticeably in the LBW group. It was also observed that the density of the H&E stained vessels became attenuated in LBW group. Importantly, for the first time, the increased m⁶A levels were found in LBW placentas. Lower protein level of FTO (the key demethylase of m⁶A) was observed in LBW placentas, whereas no difference was found among the four groups in the expression levels of METTL3, the main methyltransferase of m⁶A. By using MeRIP-QPCR technology, the m⁶A modification in PPARγ, VEGFA, ABHD5, and GPR120, as well as FTO, was considerably enhanced in the placentas from LBW group.

CONCLUSION

We infer that in maternity obesity, the higher m⁶A modification displayed in the genes related to placental development, lipid metabolism and angiogenesis may result in the down regulation of these genes, which could be associated with m⁶A demethylase FTO.

Toxicological evaluation of 6'-sialyllactose (6'-SL) sodium salt

We performed a series of toxicity studies on the safety of 6'-sialyllactose (6'-SL) sodium salt as a food ingredient. 6'-SL sodium salt, up to a maximum dose of 5000 μg/plate, did not increase the number of revertant colonies in five strains of Salmonella typhimurium in the presence or absence of S9 metabolic activation. A chromosomal aberration assay (using Chinese hamster lung cells) found no clastogenic effects at any concentration of 6'-SL sodium salt in the presence or absence of S9 metabolic activation. An in vivo bone marrow micronucleus test in Kunming mice showed no clastogenic activities with 6'-SL sodium salt doses up to 2000 mg/kg body weight (bw). In an acute toxicity study, the mean lethal dose of 6'-SL sodium salt was greater than 20 g/kg bw in rats. In a 13-week subchronic toxicity investigation, no effects were found at doses up to 5.0 g/kg bw of 6'-SL sodium salt in food consumption, body weight, clinical signs, blood biochemistry and hematology, urinalysis, or ophthalmic and histological macroscopic examination of organs. The no-observed-adverse-effect level (NOAEL) was 5.0 g/kg bw/day in rats.

Toxicological evaluation of 3'-sialyllactose sodium salt

The safety of 3'-sialyllactose (3'-SL) sodium salt was evaluated by testing for gene mutations, in vivo and in vitro clastogenic activity, and animal toxicity in beagle dogs and rats. The results of all mutagenicity and genotoxicity tests were negative, indicating that 3'-SL does not have any mutagenic or clastogenic potential. The mean lethal dose (LD₅₀) of 3'-SL sodium salt was well above 20 g/kg body weight (bw) in rats. A dose escalation acute toxicity study in Beagle dogs also indicated no treatment-related abnormalities. Subsequent 28-day and 90-day toxicity studies in Sprague- Dawley (SD) rats involved dietary exposure to 500, 1,000, and 2000 mg/kg bw of 3'-SL sodium salt and a water (vehicle) control. There were no treatment-related abnormalities on clinical observations, body weight, food consumption, behavior, hematology, clinical chemistry, organ weights, relative organ weights, urinalysis parameters, or necropsy and histopathological findings. The No Observed Adverse Effect Level (NOAEL) of 3'-SL sodium salt was determined to be higher than 2000 mg/kg bw/day in an oral subchronic toxicity study in rats, indicating that the substance is an ordinary carbohydrate with the lowest toxicity rating. Results confirm that 3'-SL sodium salt has a toxicity profile similar to other non-digestible carbohydrates and naturally occurring human milk oligosaccharides (HMOs) and support its safety for human consumption in foods.

Pig models on intestinal development and therapeutics

The gastrointestinal tract plays a vital role in nutrient supply, digestion, and absorption, and has a crucial impact on the entire organism. Much attention is being paid to utilize animal models to study the pathogenesis of gastrointestinal diseases in response to intestinal development and health. The piglet has a body size similar to that of the human and is an omnivorous animal with comparable anatomy, nutritional requirements, and digestive and associated inflammatory processes, and displays similarities to the human intestinal microbial ecosystem, which make piglets more appropriate as an animal model for human than other non-primate animals. Therefore, the objective of this review is to summarize key attributes of the piglet model with which to study human intestinal development and intestinal health through probing into the etiology of several gastrointestinal diseases, thus providing a theoretical and hopefully practical, basis for further studies on mammalian nutrition, health, and disease, and therapeutics. Given the comparable nutritional requirements and strikingly similar brain developmental patterns between young piglets and humans, the piglet has been used as an important translational model for studying neurodevelopmental outcomes influenced by pediatric nutrition. Because of similarities in anatomy and physiology between pigs and mankind, more emphasises are put on how to use the piglet model for human organ transplantation research.

An integrated approach to the safety assessment of food additives in early life

During the development of international standards by the Codex Alimentarius Commission, infant foods and their constituent ingredients are subject to rigorous risk analysis and are strictly regulated by many authorities. Various jurisdictions have approved only a limited number of additives specifically with regard to infant foods to fulfill specific technical requirements of quality. As part of the approval process, a rigorous safety assessment is essential to confirm that the use of additives does not pose any health risk for the consumer. An acceptable daily intake (ADI) may be derived from the toxicological databases. However, the ADI may not be applicable to infants because of the possible developmental sensitivities and potentially high exposure scenarios, leading to possible lower margins of safety than would often be determined for adult populations. There is interest in defining better food safety assessment approaches for pre-weaned infants aged less than 12–16 weeks. To confirm safe use in infants, we reviewed the suitability of the existing safety databases of six additives with historical uses in infant nutrition products. To determine further toxicity testing strategies, it is necessary to understand whether the chemical used in the additives is identical to endogenous physiological metabolites and/or whether immature organs of infants are targets of toxicity. Combined with an in-depth review of the existing relevant toxicological and nutritional studies, this integrated approach will facilitate decision-making. We propose a decision tree as a tool within this approach to help guide appropriate data requirements and identify data gaps. In cases of reasonable uncertainty, studies of targeted juvenile should be considered to investigate the safe use levels in food products.

The biomedical piglet: establishing reference intervals for haematology and clinical chemistry parameters of two age groups with and without iron supplementation

Background

The similarities between swine and humans in physiological and genomic patterns, and the great correlation in size and anatomy, make pigs extremely useful in preclinical studies. New-born piglets can represent a model for congenital and genetic diseases in new-born children. It is known that piglets may have significant differences in clinicopathological results compared to adult pigs. Therefore, adult laboratory reference intervals cannot be applied to piglets. The aim of this study was to compare haematological and chemical variables in piglets of two ages and determinate age-related reference intervals for commercial hybrid young pigs.

Blood samples were collected under general anaesthesia from 130 animals divided into five- (P5) and 30- (P30) day-old piglets. Only P30 animals were treated with parenteral iron after birth. Samples were analysed using automated haematology (ADVIA 2120) and chemistry analysers, and age-related reference intervals were calculated.

Results

Significant higher values of RBC, Hb and HCT were observed in P30 animals when compared to P5, with an opposite trend for MCV. These results were associated with a reduction of the RBC regeneration process and the thrombopoietic response. The TSAT and TIBC were significantly higher in P30 compared to P5; however, piglets remained iron deficient compared to adult reference intervals reported previously.

Conclusions

In conclusion, this paper emphasises the high variability occurring in clinicopathological variables between new-born and 30-day-old pigs, and between piglets and adult pigs. This study provides valuable reference data for piglets at precise ages and could be used in the future as historical control improving the Reduction in animal experiments, as suggested by the 3Rs principle.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0946-2) contains supplementary material, which is available to authorized users.

Handling stress may confound murine gut microbiota studies

BACKGROUND

Accumulating evidence indicates interactions between human milk composition, particularly sugars (human milk oligosaccharides or HMO), the gut microbiota of human infants, and behavioral effects. Some HMO secreted in human milk are unable to be endogenously digested by the human infant but are able to be metabolized by certain species of gut microbiota, including Bifidobacterium longum subsp. infantis (B. infantis), a species sensitive to host stress (Bailey & Coe, 2004). Exposure to gut bacteria like B. infantisduring critical neurodevelopment windows in early life appears to have behavioral consequences; however, environmental, physical, and social stress during this period can also have behavioral and microbial consequences. While rodent models are a useful method for determining causal relationships between HMO, gut microbiota, and behavior, murine studies of gut microbiota usually employ oral gavage, a technique stressful to the mouse. Our aim was to develop a less-invasive technique for HMO administration to remove the potential confound of gavage stress. Under the hypothesis that stress affects gut microbiota, particularly B. infantis, we predicted the pups receiving a prebiotic solution in a less-invasive manner would have the highest amount of Bifidobacteria in their gut.

METHODS

This study was designed to test two methods, active and passive, of solution administration to mice and the effects on their gut microbiome. Neonatal C57BL/6J mice housed in a specific-pathogen free facility received increasing doses of fructooligosaccharide (FOS) solution or deionized, distilled water. Gastrointestinal (GI) tracts were collected from five dams, six sires, and 41 pups over four time points. Seven fecal pellets from unhandled pups and two pellets from unhandled dams were also collected. Qualitative real-time polymerase chain reaction (qRT-PCR) was used to quantify and compare the amount of Bifidobacterium, Bacteroides, Bacteroidetes, and Firmicutes.

RESULTS

Our results demonstrate a significant difference between the amount of Firmicutes in pups receiving water passively and those receiving FOS actively (p-value = 0.009). Additionally, we found significant differences between the fecal microbiota from handled and non-handled mouse pups.

DISCUSSION

From our results, we conclude even handling pups for experimental purposes, without gavage, may induce enough stress to alter the murine gut microbiota profile. We suggest further studies to examine potential stress effects on gut microbiota caused by experimental techniques. Stress from experimental techniques may need to be accounted for in future gut microbiota studies.

Safety evaluation of α-galacto-oligosaccharides for use in infant formulas investigated in neonatal piglets

Galacto-oligosaccharide (GOS), comprising galactoses with a glucose or sucrose, is a family of nondigestible oligosaccharides. The present study evaluates the safety of an α-GOS product (P-GOS® P) in a neonatal piglet model for 3 weeks. Three days after birth, neonatal piglets were divided into control and treated groups and provided with swine milk replacers in the absence and presence of 8 mg/mL—of the α-GOS product, respectively. An increase in the weight of the large intestines in treated males was noted, which is a common finding in studies of animals fed nondigestible oligosaccharides. There were no α-GOS product-related adverse effects in the piglets in terms of clinical signs, body weights, feed consumption, clinical chemistry, hematology, organ weights, or histopathology. The study demonstrated that formula supplemented with 8 mg/mL of P-GOS P is safe and well tolerated in neonatal piglets and supports the safe use of P-GOS P in infant formulas.

The development and validation of methods for evaluating the immune system in preweaning piglets

The preweaning piglet has been found to be a valuable research model for testing ingredients used in infant formula. As part of the safety assessment, the neonates' immune system is an important component that has to be evaluated. In this study three concurrent strategies were developed to assess immune system status. The methods included (1) immunophenotying to assess circulating innate immune cell populations, (2) monitoring of circulating cytokines, particularly in response to a positive control agent, and (3) monitoring of localized gastrointestinal tissue cytokines using immunohistochemistry (IHC), particularly in response to a positive control agent. All assays were validated using white papers and regulatory guidance within a GLP environment. To validate the assays precision, accuracy and sample stability were evaluated as needed using a fit for purpose approach. In addition animals were treated with proinflammtory substances to detect a positive versus negative signal. In conclusion, these three methods were confirmed to be robust assays to evaluate the immune system and GIT-specific immune responses of preweaning piglets.

A 3-week pre-clinical study of 2′-fucosyllactose in farm piglets

One of the most abundant oligosaccharides found in human milk is 2′-fucosyllactose, a trisaccharide composed of fucose and lactose, and multiple studies have demonstrated a health benefit to this compound. Recent advances have allowed for the large-scale production of oligosaccharides via fermentation, including 2′-fucosyllactose. A neonatal piglet model was used to evaluate the tolerability of 2′-fucosyllactose, produced through this process, in order to demonstrate the suitability of this compound for human infants under 12 weeks of age. Crossbred farm piglets, at lactation day 2, were assigned to one of four treatment groups receiving a liquid diet containing 0, 200, 500 or 2000 mg/L of 2′-fucosyllactose. The calculated consumption of 2′-fucosyllactose corresponded to dose levels of 29.37, 72.22 and 291.74 mg/kg/day, respectively, in males and 29.30, 74.31, and 298.99 mg/kg/day, respectively in females. Piglets were administered diet for 3 weeks; and there were no test article-related effects on growth and development (clinical observations, body weight and food consumption), clinical pathology parameters (hematology, clinical chemistry, coagulation and urinalysis), or any histopathologic changes. Therefore, dietary exposure to 2′-fucosyllactose at concentrations up to 2000 mg/L was well tolerated by neonatal farm piglets and did not result in adverse health effects or impact piglet growth.

A 3-week dietary safety study of octenyl succinic anhydride (OSA)-modified starch in neonatal farm piglets

Octenyl succinic anhydride (OSA)-modified starch functions as both an emulsifier and emulsion stabilizer in foods, and is intended for use in infant formula, follow-on formula, and formulae for special medical purposes. These formulae predominantly include extensively hydrolyzed protein or free amino acids, rather than intact protein, which otherwise would provide emulsifying functionality. The study objectives were to evaluate (1) the safety of OSA-modified starch after three weeks of administration to neonatal farm piglets, beginning 2 days after birth and (2) the impact of OSA-modified starch on piglet growth. OSA-modified starch was added to formula at concentrations of 2, 4, and 20 g/L. The vehicle control, low-dose, and mid-dose diets were supplemented with Amioca™ Powder to balance the nutritional profiles of all formulations. There were no test article-related effects of any diet containing OSA-modified starch on piglet growth and development (clinical observations, body weight, feed consumption), or clinical pathology parameters (hematology, clinical chemistry, coagulation, urinalysis). In addition, there were no adverse effects at terminal necropsy (macro- and microscopic pathology evaluations). Therefore, dietary exposure to OSA-modified starch at concentrations up to 20 g/L was well tolerated by neonatal farm piglets and did not result in adverse health effects or impact piglet growth.

The suckling piglet as an agrimedical model for the study of pediatric nutrition and metabolism

The neonatal pig ranks among the most prominent research models for the study of pediatric nutrition and metabolism. Its precocial development at birth affords ready adaptation to artificial rearing systems, and research using this model spans a wide array of nutrients. Sophisticated in vitro and in vivo methodologies supporting both invasive, reduction-science research as well as whole-animal preclinical investigations have been developed. Potential applications may dually benefit both agricultural and medical sciences (e.g., "agrimedical research"). The broad scope of this review is to outline the fundamental elements of the piglet model and to highlight key aspects of relevance to various macronutrients, including lipids, carbohydrates, proteins/amino acids, and calcium/phosphorus. The review examines similarities between piglets and infants and also piglet idiosyncrasies, concluding that, overall, the piglet represents an adaptable and robust model for pediatric nutrition and metabolism research.