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Nutrigenomics for Companion Animals

 

© Copyright 2009 W. Jean Dodds

No portion of this article may be reproduced without permission of the copyright holder. Reprinted with permission from Copyright W. Jean Dodds.

Nutrigenomics is an emerging science that involves the study of molecular relationships between Nutrition and the response of Genes, in order to determine how even subtle genetic changes can affect human health and animal health. Nutrigenomics is linked to the concept that optimal nutrition can be designed based on an individual’s unique genetic makeup or genotype.

Nutrigenetics, a subcategory of nutrigenomics, is the retrospective analysis of genetic variations among individuals with regard to their clinical response to specific nutrients.

Background

To address the increasing incidence (epidemiology) and recognition of diet-related diseases in humans and animals, the role of diet and nutrition continues to be a major focus of study. Nutrition research is studying how dietary constituents can optimize and maintain cellular, tissue, organ and whole body homeostasis, in order to prevent disease. This necessitates an understanding of how nutrients act and interact at the molecular level [i.e. at the level of the gene, protein and metabolism]. Accordingly, nutrition research has shifted from epidemiology and physiology to molecular biology and genetics.

Nutrigenomics involves the characterization of gene products and the physiological function and interactions of these products. It also involves how nutrients impact on the production and action of specific gene products and how these proteins in turn affect the response to nutrients.

The development of nutrigenomics has been aided by powerful advances in geneticresearch. Genetic variability, the inter-individual differences in genetics, can affect metabolism as well as an individual’s phenotype. Genetic disorders of nutritional metabolism can cause pathophysiological effects that have been identified through examination of genetic polymorphisms. Simple examples would be the genes associated with obesity or diabetes in various species, and vitamin B12 –deficiency in Giant Schnauzers.

As there are thousands of potential gene polymorphisms which could cause only minor deviations in nutritional biochemistry, scientific efforts are fosused on those changes of clinical significance. The tools to study the physiological impact of these deviations include those that measure the transcriptome, such as DNA microarray, single nucleotide polymorphism arrays [SNPs] and genotyping. Tools that measure the proteome are less developed, and include gel electrophoresis, chromatography and mass spectrometry. Even less developed are methods for assessing the metabolome such as nuclear magnetic resonance imaging and mass spectrometry, in combination with gas and liquid chromatography

Rationale and Aims

Nutrients relay signals that tell a specific cell in the body about the diet. A sensory system in the cell interprets information from nutrients about the dietary environment. Once the nutrient interacts with this sensory system, it changes gene (genomics) and protein (proteomics) expression and metabolite production (metabolomics) accordingly. Thus, different diets elicit different patterns of gene and protein expression and metabolite production. Nutrigenomics describes the patterns of these effects, which are called molecular dietary signatures.

Part of the approach of nutrigenomics involves identifying markers of the early phase of diet -related diseases, so that nutritional intervention can return the patient to a healthy state. Another aim of nutrigenomics is being able to demonstrate the effect of biologically active food components on health, which should lead to the design of functional foods that will keep individuals according to their own specific needs.

Applying Nutrigenomics to Companion Animals.

Recently, veterinary and nutrition scientists have begun applying animal genomics to the field of nutrition. Nutritional genomics and proteomics will play a vital role in the future of pet foods. Functional genomics will emerge as important areas of study, now that genome maps for the dog and cat are available.

Compared with the dog, where the genome is smaller in overall size than that of humans and is split into many more chromosomes (~ 2.7 vs 3.3 billion nucleotides, and 39 vs 23 haploid chromosome number, respectively), the genome of the cat is more similar to that of humans (both have ~ 3.3 billion nucleotides, and 19 vs 23 haploid chromosome number, respectively).

Studying and monitoring the health of dogs and cats parallels that of humans. Close to 500 canine and 300 feline genetic diseases have been described to date. Molecular biological techniques have been used for several decades to identify the cause of single gene disorders in animals, which allows for prevention and treatment strategies. Currently, at least 30 canine disease genes have been cloned and characterized. This has lead to development of genetic mutation-based tests for diagnosis and carrier detection. Use of these tests permits elimination of carriers from the breeding population, which ultimately decreases or eliminates the incidence of disease.

However, while determination of the DNA sequences of single gene mutations is feasible today, identifying the genetic loci responsible for complex genetic diseases is a much more dificult task. Nevertheless, dogs and cats serve as excellent animal models for the nutritional diseases of other animal species and humans. Although a genetic component exists for these conditions, nutrition plays a major role in the development and/or treatment of many of them.

Changing lifestyles in urban populations has lead to a significant increase in obesity and diabetes mellitus in humans and companion animals. The negative health outcomes of obesity and diabetes observed in humans are also seen in dogs and cats. These are just two common examples of animal diseases having both a nutritional causal and therapeutic component.

Use of canine and feline genetic maps will enhance understanding of nutrient metabolic pathways for optimizing the nutritional and health status of individual animals. Certain dietary constituents such as vitamins A and D, zinc, and fatty acids can influence gene expression directly, whereas others such as dietary fiber can have an indirect effect through changes in hormonal signaling, mechanical stimuli, or metabolites produced from gut microflora.

So-called "functional" food ingredients and herbal supplements are now being incorporated into animal as well as human foods. The effects of these nutrients are being studied by gene expression profiling. Identifying and implementing genotype-nutrient interactions will require more complex adaptation and nutrient design. The nature of these interactions will have to be determined and taken into account when formulating diets for an individual’s given genotype.

Examples of nutrients currently added to pet foods include those intended to improve joint health such as glucosamine, chondroitin sulfate, and mussel); protect the body from free radical damage such as vitamin E, ß-carotene, and selenium; improve skin such as omega-3 fatty acids; and gut health such as oligosaccharides and probiotics.

Today, there are also pet foods designed for the animal’s life stages (e.g. puppy, adult and geriatric}, body type (e.g. toy, large and giant breeds), and life style (e.g. active, growth and performance). But, the claimed benefits provided by these “designer diets” may be well-suited for one dog and not for another . As genetic polymorphisms are identified that affect nutritional status and disease in combination with the biomarkers used for their detection, it should be possible to formulate diets not only for the prevention of structural abnormalities, but also for more complex diseases such as diabetes, cancer, aging, behavioural changes, and heart disease.

Summary

In summary, animal nutrition professionals need to be able to prescribe or recommend nutrients and diet formulations on the basis of more precise knowledge of how nutrients or food components interact at the level of the genome, where these constituents act by “up- or down-regulating” target genes. Diets for animals should be designed and tailored to the genome or genomic profile of individuals in order to optimize physiological homeostasis, disease prevention and treatment, and productive, athletic, obedience or reproductive performances.

The molecular dietary signature of an individual describes the pattern of the interaction between the nutritional environment and genome, also termed nutrigenomics. The basic concept is that chemical nutrients affect gene expressions in a specific mode by switching from health to a pathophysical condition or vice versa. The advancement of knowledge about human and animal genomes and the breadth of biotechnology offer the opportunity to individualize dietary intervention to prevent, mitigate or cure chronic diseases. The concept applies not only to companion animals and laboratory animals, but also to nutrient-genome interactions in farm animals.


References:

  • Swanson et al. J. Nutr. 133:3033-3040, 2003
  • Müller and Kersten. Nature Rev. Genetics, 4: 315 -322, 2003
  • Trayhurn Brit J Nutr. 89:1-2, 2003
  • Kaput et al. Pharmacogenomics. 8(4), 2007.

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