Inherited metabolic disorders – a newborn’s lifelong condition
Daily stops at the bakery, fast food to go and chronic stress – there are countless factors that can harm our metabolism in the long term. We have all heard of the most commonly known metabolic disorder, diabetes. But while this type of imbalance occurs as a result of an unhealthy lifestyle, poor nutrition, and genetic factors, there is much more that can harm our metabolism and impact our lives.
Mutations in genes affecting the enzymes that orchestrate metabolic pathways have a severe impact on a person’s health. These kinds of mutations can be inherited – and predispose the entire life of a newborn.
This article will inform you about inherited metabolic disorders and how to treat the most common form: phenylketonuria, a protein disorder.
Our metabolism is our engine
When people talk about metabolism, it is mostly associated with weight gain or loss. However, our metabolism is much more complex and versatile than you think:
- It breaks down carbohydrates, proteins and fats for our daily energy supply,
- It processes chemicals and toxins that have entered our body and transports them outside,
- And certain metabolic pathways are used to build up new proteins or tissue from smaller molecules.
Our metabolism is responsible for several essential processes
To understand the way our metabolism works, let us try and visualize it as a clockwork. All the chemical reactions occurring in our body interact like the different wheels inside the clock. Now, imagine that one of the wheels is broken. Normally, our body would try to repair it or, if the right tools to do so are not available, compensate for it.
“All the chemical reactions occurring in our body interact like wheels inside a clock.”
Depending on how important the “wheel” was, imbalances will appear immediately or after a while. In the following, you will find several metabolic disorders that can occur:
- Acid-base imbalances: In case of this impairment, the body cannot keep the pH value of its plasma in its natural range between 7.35 to 7.45. Yet cells and proteins require this specific value to maintain their function. Changes in pH can lead to systemic failure.
- Mitochondrial diseases: Mitochondria are organelles that convert energy from our food to the energy driving most cellular functions. When mitochondria are impaired, it can lead to muscle weakness, poor growth, dementia and severe diseases affecting a multitude of organs.
- Lipid, iron, phosphorus or calcium metabolism disorders: Both lipid breakdown or synthesis can be impaired in case of a lipid metabolism disorder. If iron, phosphorus or calcium cannot be metabolized, a toxic overload of these elements is the result.
- Malabsorption: Food is digested in the gastrointestinal tract and nutrients are absorbed into the bloodstream. Impairment of this process leads to malnutrition and can result in severe weight loss, fluid retention, anemia, abnormal bleeding and muscle cramps.
- Inborn errors of metabolism: When parents are the carrier of a mutation causing a metabolic disorder, their children can inherit the defect.
Inborn errors of metabolism
As mentioned above, errors of metabolism can be inherited. A few possibilities of how faults in the programming of our DNA can manifest in the body are listed below:
- Phenylketonuria (PKU) leads to increased levels of phenylalanine in the blood, which can cause health problems and intellectual disabilities. PKU is considered the most common form of inborn errors of metabolism.
- Fructose intolerance means that patients cannot digest fructose, leading to severely low blood sugar (hypoglycemia).
- Maple sugar urine disease (MSDU) is characterized by the deficiency of certain enzymes required to digest branched-chain amino acids (BCAAs). When left untreated, accumulation of BCAAs a few hours after birth can lead to neurological dysfunctions and spasticity.
- Galactosemia describes a deficiency in the breakdown of galactose, which is a component of the lactose sugar that is commonly found in dairy products. If newborns with this condition do not receive special treatment, they will show impaired energy metabolism (lethargy), cannot gain weight and suffer from damages to their liver.
Inherited metabolic disorder – a rare disease?
According to Mendel’s law, there is a 25-percent chance to obtain mutated genes from both parents. Therefore, an inherited metabolic disorder can be considered a rare disease.
Genetic aberrations affecting enzymes and proteins related to metabolism can cause metabolic disorders. Fortunately, all of us have two copies of our set of genes. If one is damaged due to mutations and produces aberrant proteins, the sister gene is activated and compensates for the other. This guarantees that functional proteins are built. Our body is able to produce sufficient amounts of this gene and the disease will not be apparent.
However, in case of a recessive genetic transformation, a child inherits two defective gene copies. Because there is no healthy gene to compensate, the child will develop the specific genetic metabolic disorder linked to the defective genes.
Although inherited metabolic disorders are considered pediatric, meaning that it mostly will be diagnosed during childhood, effects can first occur at any age.
Symptoms can be acute or progressive
As you know, our metabolism is a complex network and will try to compensate any shortcomings to keep us alive. This can exhaust our body, which leads to symptoms like fatigue and concentration problems, but can also end in organ failure.
Furthermore, symptoms depend on the area that is affected: For instance, excess weight or kidney failure can result in a change of our pH value towards a more acidic range (acidosis). Patients with this condition experience prevalent sleepiness, confusion or headaches, whereas patients with fructose intolerance suffer from abdominal pain, gas or diarrhea.
Gout is an inflammatory arthritis that has become more common in recent decades. It is a disorder of purine metabolism, in which its downstream metabolite, uric acid, crystallizes and accumulates in joints and the surrounding tissue. The red, hot and swollen joints come along with a painful ache and appear in some adults with high consumption of purine-rich foods. Examples of foods that are high in purines include meat, poultry, fish, and others.
Metabolic disorders can cause sleepiness
When metabolic diseases are inherited, symptoms appear rapidly after birth. Their causes should be immediately diagnosed and treated to avoid developmental defects. Newer therapies for metabolic disorders include bone marrow transplantation or enzyme replacements to compensate for the malfunctioning gene. However, this is not a widespread treatment option yet.
Nevertheless, this does not mean there are no options to increase the health and quality of life of patients with metabolic conditions: An adapted approach to nutrition is key here.
“When metabolic diseases are inherited, symptoms appear rapidly after birth.”
Treatment of metabolic diseases is necessary
A metabolic disorder can be treated well with appropriate food management. We recommend visiting a specialized doctor or dietitian, who can design a nutrition plan. If metabolic diseases are diagnosed early, patients have an especially high chance to avoid chronic complications.
The same applies to inherited errors of metabolism. The right diet is essential to achieving an improved quality of life with few symptoms.
“The right diet is key for an improved quality of life with few symptoms.”
A closer look at phenylketonuria
Proteins in our food are digested and broken down to their building blocks called amino acids. Our body can digest proteins for energy production, a process called catabolism.
Furthermore, it can use the amino acid source to synthesize its own proteins into connective and supportive tissue, metabolic enzymes or transport proteins that carry nutrients from the blood to cells. This procedure allows our body to avoid unnecessary energy consumption for production.
Patients with phenylketonuria (PKU) show an accumulation of the amino acid phenylalanine in their body. PKU is caused due to a mutation in the PAH gene encoding for an enzyme called phenylalanine hydroxylase. This enzyme usually breaks phenylalanine down into tyrosine, a building block for neurotransmitters like dopamine. When this enzyme is missing, phenylalanine accumulates in the body, which has a toxic effect on the brain.
“Patients with phenylketonuria (PKU) show an accumulation of the amino acid phenylalanine in their body.”
How can PKU be prevented?
To limit the risk of inheritance, people who wish to have children can get tested for PAH mutations. If both potential parents are carriers, chances for the development of PKU in their future children are at 25 percent.
It is important that pregnant women with PKU maintain a low protein diet to avoid accumulation and transfer of phenylalanine to the fetus.
Symptoms of PKU vary from mild to severe
In the United States, newborns are routinely screened for PKU to ensure treatment directly after birth if needed. If phenylketonuria is not treated immediately, symptoms like cramps, tremors or growth defects will appear within a short time. After a few months, PKU can cause irreversible brain damage and behavioral problems.
How to deal with phenylketonuria
To avoid the effects caused by phenylketonuria, patients should limit their intake of food that is rich in protein, such as:
- Dairy products like eggs, cheese and milk,
- Nuts and seeds,
- Meat and fish,
PKU patients’ bodies are unable to tolerate sugar replacements like aspartame which contain phenylalanine. If you are diagnosed with PKU, make sure that any soft drinks you consume do not contain phenylalanine sources, as indicated on the label.
Infants diagnosed with PKU need to be fed with special milk. There are specific formulas that are limited in phenylalanine to avoid excessive accumulation of the substance, but provide just enough for normal growth. Phenylalanine-reduced milk is used exclusively for infants with phenylketonuria and should not be used as prophylaxis for healthy children.
In order to help patients with phenylketonuria, medications have been developed to lower phenylalanine levels. However, these drugs do not work for every PKU patient – and if they do, a PKU-friendly diet is key to ensure their effectiveness.
The dietary restrictions that go with metabolic disorders need to be maintained throughout patients’ entire lives in order to alleviate symptoms and avoid severe damage. This makes phenylketonuria patients feel excluded from social eating, since their food choice is very limited – and this can be especially hard for kids.
Even a quick-and-easy pasta, a favorite for many children, is problematic. We understand that it is very difficult to explain to your child why her sibling can eat spaghetti while she is not allowed to do so.
To avoid this kind of conflict, Flavis has developed low protein products including pasta, which can be consumed by PKU patients as well as their healthy family members.
“Dietary restrictions need to be maintained permanently to alleviate symptoms and avoid severe damage.”
The right food for children and adults with PKU
The main source of nutrients for patients diagnosed with PKU should be vegetables and fruits. But starting your day with fruits only and reaching your required daily caloric intake with little more than vegetables can be tough. Low protein versions of cereal and dairy products can help patients with PKU achieve a well-rounded diet that satisfies their nutritional and culinary needs – and does them good at the same time.
For a special treat, you can combine your favorite veggies with our low protein pizza base and have a pizza party with the whole family. Or you can start the day right with low protein white sliced bread covered with your kid’s most favorite jelly.
As an addition to a healthy lifestyle and to avoid nutrient deficiency, for example of vitamin B12, which is a consequence of the reduced consumption of meat and dairy products, we recommend that you supplement your daily vitamins according to your needs.
Vegetables and fruits are low in protein – a good source of nutrients for PKU patients
Your metabolism needs the right food
Malnutrition and diseases can severely affect our metabolism by inducing imbalances. In many cases, this can be corrected by the right choice of food. When errors are inborn, metabolic diseases like phenylketonuria require a lifelong restrictive diet that can feel like torture.
Instead of lamenting the limited food choice, you can replace your beloved “forbidden” food with metabolism-friendly substitutes. Your favorites are just waiting to be rediscovered by you.
For a better quality of life.
Cover picture by Rene Asmussen, additional pictures by VectorMine, Matheus Bertelli and Ella Olsson.