Progeria

Generality

Progeria is a rare genetic disorder that causes rapid aging.

The disease starts from early childhood, during which the patient begins to show unequivocal physical signs. Death occurs during adolescence, almost always due to cardiocirculatory disorders.
Unfortunately, there is no cure for progeria and the prognosis is poor.However, therapeutic countermeasures can be put into practice, capable of extending the life of patients by a few years. In the near future, great steps forward are expected from research, which sees progeria as a model of study to understand human aging.

DNA, RNA and proteins

To understand the causes of progeria, a brief review of what DNA, RNA and proteins are and what is meant by gene expression is a good idea.

  • DNA contains genetic information, ie genes
  • RNA is the transcription of genetic information into a "simpler" language to translate into proteins
  • Proteins are the "working" form of DNA genes.

The mechanism that leads DNA to be translated into proteins is called gene expression.
For the gene expression system to function properly, the DNA must be undamaged and the translation into proteins must be faithful and error-free.

So is progeria

Progeria (from the Greek, πρό Œ = early, early; and γῆρας = old age) is a genetic disease of childhood, which causes premature aging. It is also known as Hutchinson-Gilford syndrome.
Affected children begin to show the first signs already during the first year of life. In a short time, the symptoms gradually become more severe, leading to the death of patients during adolescence. Although rarely, some individuals manage to reach the age of 20.
Progeria does not alter the mental faculties of young patients, who, from this point of view, are exactly like their peers.

EPIDEMIOLOGY

Progeria is a very rare disease: it affects one child for every 8 million new births. It seems that the confirmed cases are currently about a hundred. However, it is suspected that around the world there are another 100-150 undiagnosed patients.
Most affected children die around the age of 13 from cardiovascular disease; cardiovascular disorders, which are, by far, the main causes of death.

WHY "STUDY PROGERIA?

Progeria, as mentioned, has a very low incidence. However, it draws the attention of several researchers, as it could serve as a model for studying how normal human aging works. In this regard, we are looking for common mechanisms and treatments with satisfactory results.

Causes

Background: A genetic disease, such as progeria, is caused by the mutation of one of the many genes that make up DNA. When a gene is mutated, it produces an abnormal protein instead of the normal healthy one. If the affected protein is viable, the effects of this mutation endanger the life of the organism involved.


The researchers found that the gene responsible for progeria is the so-called LMNA. The LMNA gene is located on chromosome 1 and produces a protein called lamina A.

Figure: Comparison between the cell nuclei of a healthy cell (top) and a cell without lamina A (bottom). From http://it.wikipedia.org/wiki/Progeria

WHAT IS LAMINA A? WHAT FUNCTIONS DOES IT PERFORM?

Lamin A protein provides essential structural support to the cell nucleus. Without it, the core takes on a different, misshapen appearance. A deformed nucleus, lacking the support offered by lamina A, affects many vital functions of the cell, such as mitosis.

LAMINA A AND PROGERIA

In patients with progeria, lamina A has a small difference compared to lamina A in a healthy person. The difference concerns only one amino acid: this small detail is enough to determine dramatic circumstances.
Below is an in-depth information sheet, dedicated to readers who want to know what exactly happens to sheet A.


In-depth information sheet

In progeria, mutated lamina A has, compared to healthy lamina A, a different amino acid at position 1824. Instead of a cytosine, c "is a thymine. This small difference is enough to change the maturation of the protein itself. Indeed, lamina A, before acting on the core, must undergo small structural adjustments, fundamental to make it functional.
One such adjustment is the binding of the protein to a molecule, called farnesyl. In the case of healthy lamina A, the binding is temporary and farnesyl is removed; in the case of mutated lamina A, farnesyl remains bound to the protein.

Lamina A and farnesyl, if they stay together, form an abnormal protein, called progerin precisely, since it determines progeria.

WHEN DOES THE MUTATION HAPPEN? IS PROGERIA TRANSMITTED BY PARENTS?

Since it is a genetic disease, it is questionable whether progeria is also a hereditary disease. Well, a 2003 study appeared on Nature, testified that progeria arises due to a spontaneous mutation, which affects a gamete (egg or sperm cell), or an embryo in the early stages. Therefore, the parents are healthy, not carriers. This event is called, in genetics, mutation de novo.
On the other hand, it could not be otherwise: most patients die in adolescence, even before they can have children.

Symptoms, signs and complications

For further information: Progeria Symptoms


The first symptoms of progeria appear just after birth, within the first twelve months of life. They consist of:

  • Slowed growth
  • Scleroderma

In a few years, the symptomatological picture is completed with the appearance of the following pathological manifestations:

  • Small and narrow face
  • Head large and disproportionate to the face
  • Beaked nose
  • Prominent eyes
  • Loss of hair, eyelashes and eyebrows (total alopecia areata)
  • Thin lips
  • Small, lowered jaw (micrognathy)
  • Obvious veins
  • High pitched tone of voice
  • Abnormal and delayed teething
  • Decrease in muscle tone and body fat
  • Joint stiffness
  • Hip dislocation
  • Insulin resistance
  • Arrhythmias

COMPLICATIONS

Patients with progeria inevitably face various complications. In fact, cardiovascular problems, atherosclerosis, renal insufficiency, vision loss and progressive musculoskeletal degeneration arise. Those affected are frail and cannot perform the same motor activities as their peers.
The main cause of death, which occurs during adolescence, is linked, above all, to heart and vascular disorders (more than 90% of deaths).
Contrary to what one might think, premature aging does not determine a particular predisposition to tumors or neurodegenerative diseases, typical of old age.


The most common heart and vascular disorders, with a fatal outcome, are: Heart attack
Congestive heart failure
Stroke
Coronary insufficiency

DEPRESSION

As mentioned at the beginning, the patient with progeria does not manifest mental retardation: he, from the point of view of brain development, is like his peers. The patient is lucid and, therefore, even more aware of the physical differences between him. and children of the same age. This makes it even more difficult to accept the situation and the inevitable fate that the affected individual will encounter. From this, depression and a feeling of strong moral despondency arise.

Diagnosis

Diagnosis of progeria is based on the doctor's observation of the characteristic signs of the disease. Over all:

  • Growth slowed
  • Total alopecia areata
  • The hardening of the skin on the extremities of the body (scleroderma)

For unambiguous confirmation, the doctor may subject the patient to a genetic test, which evaluates the presence or absence of mutations in the LMNA gene.

Therapy

Unfortunately, there is no specific treatment for progeria. However, researchers are working hard to develop a drug, known as a "farnesyltransferase inhibitor" (FTI), which appears to be providing appreciable results (see the chapter dedicated to the research).
Pending further developments, the only therapeutic measures, feasible today, are aimed at:

  • Reduce the severity of symptoms and complications
  • Extend the life of patients by a few years

Cardiovascular disorders deserve the greatest attention from the attending physician. These must be monitored daily.
Physiotherapy, a careful diet and the moral support of a psychotherapist are also very important.

TREATMENT OF CARDIOVASCULAR DISORDERS

For some patients, it may be vital to undergo coronary artery bypass surgery and angioplasty. In this way, the blood circulation of the heart is favored and the possibility of a myocardial infarction is avoided, albeit temporarily.

It is also advisable to take low doses of aspirin, statins and anticoagulants.


Medicines for cardiovascular disorders Scope Aspirin Prevents heart attacks and strokes Statin Keeps cholesterol levels low Anticoagulants Avoid the formation of blood clots

PROMOTE GROWTH

To promote the growth of young patients, a therapy based on growth hormone is sometimes used. The effects are not always satisfactory.

PHYSIOTHERAPY, PHYSICAL ACTIVITIES AND ORTHOPEDIC MEASURES

Physical activity and physiotherapy are essential to cope with the progressive joint stiffness and the decrease in muscle tone, which causes, for example, hip dislocation.
In addition, the constant loss of body fat results in a painful sensation in the feet, especially if the patient has been walking for a long time. In these situations, it is very useful to equip the patient with special shoes, with an "internal padding that absorbs the impacts with the ground.

DIET

Patients with progeria suffer from scleroderma. Therefore, they benefit from constant hydration. It is recommended to drink frequently, especially during the warmer seasons.
Furthermore, it has been observed that muscle and growth deficits are attenuated with a constant and higher than normal caloric intake. In this regard, patients are advised to divide the three canonical daily meals into several snacks, so as to avoid a potential fasting situation.

PSYCHOTHERAPY

It is used to treat depression, which, very often, grips the progeria patient.
The psychotherapist also advises the family and the patient to turn to support groups, created specifically to help those suffering from incurable diseases and their families. In these locations, as far as possible, efforts are made to alleviate the discomfort, due to an inevitable fate, and to teach the closest relatives how to best relate to the suffering individual.

Prognosis

The prognosis of progeria can never be positive, as there is no cure and treatments provide little effect. Some people benefit more than others, extending their life by a few years. However, death almost always occurs before the age of 20.
Therefore, the affection of family members and a welcoming and informed school environment are of fundamental importance.

Research (February 2014)

The hope of a cure for progeria is represented by an anti-tumor drug, a farnesyltransferase inhibitor. It is also known as Lonafarnib.
Researchers are carrying out considerable research in this regard and it seems that it favors the detachment of the farnesyl group from lamina A (see the in-depth information sheet). In animal models, the experimentation has given positive results: the detachment of the farnesyl group from lamina A has occurred and the cell nucleus has resumed its normal shape; the mice were also better off. In May 2007, phase II of the human trial of Lonafarnib began and developments are awaited.
Furthermore, comforting results come from some studies on two drugs, already on the market for other purposes: Pravastatin and Zoledronate. The first serves to lower cholesterol, the second is taken against hypercalcemia. Administered in combination with Lonafarnib, it seems to be able to prevent, more effectively, the link between the farnesyl group and lamina A. Could this be the solution to progeria?


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