The genetics of companion animals are affected by many factors, including diet, environment, and stress. By controlling these three aspects, we help care for our patients’ genes and extend their longevity.
There are two threats to well-being, as Dr. Deepak Chopra writes in Super Genes, a book he co-authored with Dr. Rudolph Tanzi. These threats are illness and aging, and they are constantly present. “Out of sight, without your knowing it, your present good health is being silently undermined,” Dr. Chopra writes.1 This is what we are forever up against as we try to “interrupt” the dying process in our animal patients. Every client wants their pet to live forever, or at least for as long as possible. No veterinarian has a magic pill to make this happen; if we did, we would be using it every day. I believe “our magic” lies in “caring” for the genes inside our patients. This genetic information holds answers to many of the questions we try to answer for our clients. What drives longevity in pets? And what can genetics tell us?
DOGS AS A MODEL FOR AGING
Much has been studied about aging and scientists are currently using the dog as a
model for aging in humans. Why the dog? Researchers have noted that dogs have been on the same evolutionary path as humans, and since they live with us, they share the same environments and stressors we do.2 Dogs also naturally develop age-related cognitive decline, with behavioral and histological characteristics that are very similar to those in humans. Researchers also know the genetic and biochemical pathways by which aging is controlled, and have identified nine common denominators. 3 These hallmarks are: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication.3 Half these hallmarks focus on DNA and genetic pathways.
GENETIC INSTABILITY AND AGING
Genetic injury or instability is one of the nine hallmarks of aging.3 I will focus only on genetic instability as this topic on its own is immense. The integrity and stability of DNA is continuously challenged by many exogenous and endogenous events. There are too many to detail, so for the purpose of this article we will focus on those we can control, including diet, the environment, and stress.
1. DIET
Diet is not as simple as recommending just any bag of food on the shelf. Pet diets have become very important; consumers are educating themselves on the best diets for themselves, and want that same level of nutritional quality for their pets. I surmise that some highly educated owners, thanks to access to peer-reviewed studies, have already done a great deal of research on their pets’ dietary needs.
There are so many options for pets as far as food is concerned. The discussion in this arena is broad and controversial among many veterinarians. From my experience seeing birds and exotics, in addition to dogs and cats, replicating a diet in the wild is most beneficial, and keeping it in moderation is key. Feeding one thing all the time is not ideal. When we do this, we create a microbiome that is lacking in diversity and susceptible to insult (stressors). I call these animals my “Sensitive Sallys”. They’re the pets that fall ill if they eat anything besides one certain food; this tells me their microbiome is not diverse and the genetic variation has not evolved to handle stressors.
Another factor of pet diets is food quality. Processed foods have preservatives, dyes, synthetic additives and chemicals that act as stressors on the genetic material in the microbiome. Also, thanks to chemical farming, much of our food is devoid of nutrients before it is even further processed to make pet food. Though a few studies have been done in this area, I believe it’s something that requires more independent research. Microbiome testing can be beneficial for understanding how a pet’s microbiome is currently working, and allows us to help regulate bacteria and general overall health. Some companies have done much work in this area to help our dogs’ and cats’ microbiomes build themselves with more variation and stability.
In my experience (based on 25 years of vetting pets), keeping animals lean is vital to longevity. Two key factors keep our pets lean — the food they eat and the activity they receive. Balancing these two factors keeps the animal lean — not average or a little heavy, but a little less than average, with a BSC of 3 or 4 out of 9). Research on longevity in nematodes, yeast, fruit flies, mice and rhesus monkeys shows that dietary restriction causes specific nutrient sensitive pathways to become more protective and conserve DNA.5 Though the following is a study of one, I had a Chocolate Labrador Retriever with severe heart disease live to be 17 years of age. He was very lean when diagnosed with heart disease and the owner was compliant with medications and veterinary visits. She focused on diet, exercise, medications for the heart, and lots of TLC. Typically, heart disease in dogs does not parallel longevity. Most pets (and humans) with heart disease are overweight. In this Labrador’s case, weight was eliminated as an underlying factor, and he flourished in his geriatric years.
2. ENVIRONMENT
A pet’s environment can be managed by providing appropriate shelter, exercise that replicates being “in the wild”, and paying attention to the effects of sun or lack thereof. Vitamin D levels have not been studied extensively in pets, except when it has been over-supplemented.6 Pet foods are fortified with vitamin D since many of animals do not go outside. Feeding commercially-prepared diets (when fed correctly) does provide the proper amount of vitamin D; however, with the plethora of diets available, owners home-cooking and supplementing on their own, vitamin D screening becomes, I believe, a crucial diagnostic. Human studies have shown that as people age, vitamin D levels decrease and supplementation is necessary. Vitamin D is necessary for gene expression and has a wide variety of functions in more than 160 pathways linked to cancer, autoimmune disorders, and cardiovascular disease.7 From reading the studies, this area may be useful in understanding how nutrients and nutrition affect a pet’s genomic expression.
Other environmental factors affecting gene expression include air quality, emotional stability within the home, and the time the owner has for the pet. Our pets are social creatures, and it is imperative we give them time so they are emotionally as well as nutritionally cared for. Human studies are not abundant, but researchers are starting to look very closely at DNA methylation and the maltreatment of children at a young age.8 This is a complex topic, but there are theories that biological genetic development may be influenced more than we think by psychological environmental factors.
3. STRESS
Stressors are abundant, and can be anything that causes an imbalance to homeostasis. Diet and environment are discussed above, but things like chronic pain, chronic inflammation, or chronic disease can affect pets at a cellular level. We often think of cancer when we consider chronic inflammation and disease. Genetics2 helps us understand cancer evolution a bit better. The problem with cancer is not that cell function is weakened by damage, but that it’s too vigorous.5 Most disease etiology is a combination of molecular (DNA) damage and hyperfunction5 Understanding hyperfunction is best explained by considering a young pet that we feed to help with growth and development. When the animal becomes an adult, we no longer need to support growth and development; but by overfeeding the pet (in the exam room I call it “over-loving”), we cause the genetic and cellular pathways to work at the same level they did during the growth and development phase of life. Hypertrophy and hyperplasia underlie many diseases, including cardiovascular, diabetes, cancer, inflammation, adipose and hyperglycemia.5 The progression of cancer is more a problem of too much than too little. Overworking our systems with too much could actually be the very problem causing our DNA to become damaged. Eliminating hyperfunction is protective.
Damage to cells from stressors, whether it be endogenous or exogenous, causes DNA to be injured and in need of repair. These repair mechanisms (there are many) are vital to keeping DNA in check.9 When repair mechanisms are no longer doing their job, they can cause accelerated aging and disease. Much research is being done on DNA repair, and the reasons why repair mechanisms sometimes work and sometimes don’t is still not fully understood.9 When they do not work, we feel like we are dead in the water. Disease happens, cancer happens, our pets age faster than we thought, and turning it around can seem an insurmountable task.
Focusing on prevention is much easier than trying to fix a broken genetic or cellular pathway after years of it being bombarded by the infinite array of DNA damaging agents. Working toward a chemical-free, preservative-free, organic, emotionally stable, and connected world, where we focus on the basics of care, clean and nutritious food, and optimal husbandry, is the best place to start. Preventative care, instead of reactionary care, is the key to longevity in our pets.
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