Marmoset Metabolism, Nutrition, and Obesity

Impact of diet change on the gut microbiome of common marmosets (Callithrix jacchus)

Gastrointestinal diseases are the most frequently reported clinical problems in captive common marmosets (Callithrix jacchus), often affecting the health and welfare of the animal and ultimately their use as a research subject. The microbiome has been shown to be intimately connected to diet and gastrointestinal health. Here, we use shotgun metagenomics and untargeted metabolomics in fecal samples of common marmosets collected before, during, and after a dietary transition from a biscuit to a gel diet. The overall health of marmosets, measured as weight recovery and reproductive outcome, improved after the diet transition. Moreover, each marmoset pair had significant shifts in the microbiome and metabolome after the diet transition. In general, we saw a decrease in Escherichia coli and Prevotella species and an increase in Bifidobacterium species. Untargeted metabolic profiles indicated that polyamine levels, specifically cadaverine and putrescine, were high after diet transition, suggesting either an increase in excretion or a decrease in intestinal reabsorption at the intestinal level. In conclusion, our data suggest that Bifidobacterium species could potentially be useful as probiotic supplements to the laboratory marmoset diet. Future studies with a larger sample size will be beneficial to show that this is consistent with the diet change.

IMPORTANCE

Appropriate diet and health of the common marmoset in captivity are essential both for the welfare of the animal and to improve experimental outcomes. Our study shows that a gel diet compared to a biscuit diet improves the health of a marmoset colony, is linked to increases in Bifidobacterium species, and increases the removal of molecules associated with disease. The diet transition had an influence on the molecular changes at both the pair and time point group levels, but only at the pair level for the microbial changes. It appears to be more important which genes and functions present changed rather than specific microbes. Further studies are needed to identify specific components that should be considered when choosing an appropriate diet and additional supplementary foods, as well as to validate the benefits of providing probiotics. Probiotics containing Bifidobacterium species appear to be useful as probiotic supplements to the laboratory marmoset diet, but additional work is needed to validate these findings.

Weight as an indicator of enclosure suitability in Livingstone's fruit bats (Pteropus livingstonii)

Obesity is common in zoo animals, and both dietary management and the provision of adequate opportunities for exercise are needed to tackle it. We used 30 years of records from Jersey Zoo to compare the weight and forearm length of wild and captive-born Livingstone's fruit bats (Pteropus livingstonii), and to assess the impact on weight of enclosure space. The mean capture weight of wild-caught male Livingstone's bats was 657 g, significantly higher than that of females (544 g). In both wild and captive-born bats, males had significantly longer forearms than females, but there was no effect of birth location. Males weighed more in the mating season than at other times of year. Both sexes gained more weight during development if born in enclosures that restricted flight rather than a large aviary; this was particularly noticeable in females. After reaching maturity at 3 years, weights of bats born in restricted enclosures continued to increase, reached a peak of over 1000 g at 8-10 years, and then declined in both sexes. The weight of bats born in the aviary remained more stable after the age of three. Like wild bats, adult females born in the aviary weighed less than males. However, females born in restricted enclosures weighed more than males born in the same enclosures. Enclosure designs that maximize opportunities for flight can limit excessive weight gain in captive fruit bats and may therefore improve fitness and health, essential in planning for future reintroduction programs.

Comparing different strategies to reduce hepatocellular damage in obese common marmosets (Callithrix jacchus)

BACKGROUND

Obesity in common marmosets (Callithrix jacchus) can lead to various liver pathologies. In other species, reduced caloric intake and weight loss improve prognosis, and, often, hepatoprotectants are used to halt or reverse hepatocellular damage from fat deposition in the liver. There are no published therapies for reducing hepatocellular damage in obese marmosets.

METHODS

Fifteen obese marmosets were used to evaluate the ability of caloric restriction and pharmacologic therapy (S-adenosylmethionine + milk thistle extract, or SMT), alone and combined, to reduce elevated liver enzymes. Body weight and serum chemistries were measured every 4 weeks for 6 months.

RESULTS

Across treatment groups, there was a significant reduction in liver enzymes ALT and AST over time. SMT alone significantly reduced liver enzymes ALT and AST at 6 months from baseline.

CONCLUSIONS

Caloric restriction and SMT, alone and combined, are effective at reducing liver enzyme levels in obese marmosets.

Review of Environmental and Health Factors Impacting Captive Common Marmoset Welfare in the Biomedical Research Setting

As a small-bodied neotropical nonhuman primate species, common marmosets have unique requirements for adequate husbandry and veterinary care to ensure proper maintenance and to promote good animal welfare in a biomedical research setting. Environmental conditions, as well as medical and research-related manipulations, can impact marmoset welfare. Research focus areas, including basic neuroscience, transgenics, and aging, involve additional implications for marmoset welfare. This manuscript provides a comprehensive review of factors that should be considered and mitigated as needed by clinical and research staff working with marmosets in biomedical research facilities to optimize the welfare of captive marmosets.

The common marmoset as a model of neurodegeneration

Human life expectancy has increased over the past few centuries, and the incidence of dementia in the older population is also projected to continue to rise. Neurodegenerative diseases are complex multifactorial conditions for which no effective treatments are currently available. Animal models are necessary to understand the causes and progression of neurodegeneration. Nonhuman primates (NHPs) offer significant advantages for the study of neurodegenerative disease. Among them, the common marmoset, Callithrix jacchus, stands out due to its easy handling, complex brain architecture, and occurrence of spontaneous beta-amyloid (Aβ) and phosphorylated tau aggregates with aging. Furthermore, marmosets present physiological adaptations and metabolic alterations associated with the increased risk of dementia in humans. In this review, we discuss the current literature on the use of marmosets as a model of aging and neurodegeneration. We highlight aspects of marmoset physiology associated with aging, such as metabolic alterations, which may help understand their vulnerability to developing a neurodegenerative phenotype that goes beyond normal aging.

The Common Marmoset-Biomedical Research Animal Model Applications and Common Spontaneous Diseases

Marmosets are becoming more utilized in biomedical research due to multiple advantages including (1) a nonhuman primate of a smaller size with less cost for housing, (2) physiologic similarities to humans, (3) translatable hepatic metabolism, (4) higher numbers of litters per year, (5) genome is sequenced, molecular reagents are available, (6) immunologically similar to humans, (7) transgenic marmosets with germline transmission have been produced, and (8) are naturally occurring hematopoietic chimeras. With more use of marmosets, disease surveillance over a wide range of ages of marmosets has been performed. This has led to a better understanding of the disease management of spontaneous diseases that can occur in colonies. Knowledge of clinical signs and histologic lesions can assist in maximizing the colony's health, allowing for improved outcomes in translational studies within biomedical research. Here, we describe some basic husbandry, biology, common spontaneous diseases, and animal model applications for the common marmoset in biomedical research.

Current Topics in Research, Care, and Welfare of Common Marmosets

Although the common marmoset (Callithrix jacchus) has been maintained in captivity in biomedical research settings for decades, interest and use of the species as an animal model for a diverse array of purposes has increased in the 21st century. Unfortunately, the development of validated animal care standards such as nutrition, husbandry, and clinical care has not expanded with the same rapidity as the use of the species in research. The goal of this themed issue of the ILAR Journal is to review current literature relevant to topics that impact marmoset health, welfare, and use in research. As the population of captive marmosets increases worldwide, the editors urge scientists, veterinary clinicians, and colony managers to continue conducting and publishing robust studies to develop evidence-based standards related to marmoset care and use. The editors also encourage IACUCs and other institutional review bodies to seek training on topics relevant to marmoset welfare and develop related policies prior to acquiring animals as a novel species.