WHAT ARE CEREBROSIDES? STRUCTURE AND FUNCTIONS - BIOLOGY - 2024

The cerebrosides are a group of glycosphingolipids operating inside the human body and animal and cell membrane components muscle and nerve as well as the (central and peripheral) nervous system overall.

Within the sphingolipids, the cerebrosides are also formally called monoglycosylceramides. These molecular components are found in abundance in the myelin sheath of nerves, which is a multilayered coating made up of protein components that surround neuronal axons in the human nervous system.

β-D-Galactosylceramide, a galactocerebroside.

Cerebrosides are part of the large group of lipids that work within the nervous system. The group of sphingolipids have an important role as components of membranes, regulating their dynamics and forming part of their internal structures with their own functions.

Apart from the cerebrosides, other sphingolipids have been shown to be of great importance for the transmission of neuronal signals and recognition on the cell surface.

The cerebrosides were discovered along with the group of other sphingolipids by the German Johann LW Thudichum in 1884. By then it was not possible to find the function that they fulfilled specifically, but they began to have an idea about the structures that made up these molecular compounds.

In humans, the wear and tear of lipid components such as cerebrosides can cause dysfunctional diseases that can affect other organs of the body.

Diseases such as the bubonic plague or black plague have been attributed to symptoms caused by the deterioration and degradation of galactosylcerebrosides.

Structure of cerebrosides

The most important and fundamental element in the structure of cerebrosides is ceramide, a family of lipids made up of fatty acids and carbon variations that serve as the base molecule for the rest of the sphingolipids.

Because of this, the names of the different types of cerebrosides have ceramide present in the name, such as glucosylceramides (glucosylcerebrosides) or galactosylceramides (galactosylcerebrosides).

Cerebrosides are considered monosaccharides. A residual sugar is attached to the ceramide molecule that compose them through a glucoside bond.

Depending on whether the sugar unit is glucose or galactose, two types of cerebrosides can be generated: glucosylcerebrosides (glucose) and galactosylcerebrosides (galactose).

Of these two types, glucosylcerebrosides are those whose monosaccharide residue is glucose and are usually found and distributed in non-neuronal tissue.

Its excessive accumulation in a single place (cells or organs) begins the symptoms of Gaucher disease, which generates conditions such as fatigue, anemia and hypertrophy of organs such as the liver.

Galactosylcerebrosides have a composition similar to the previous ones, except for the presence of galactose as a residual monosaccharide instead of glucose.

These are usually distributed throughout all neuronal tissues (they represent 2% gray matter and up to 12% white matter) and serve as markers for the functioning of oligodendrocytes, cells responsible for the formation of myelin.

Glycosylcerebrosides and galactosylcebrosides can also be differentiated by the types of fatty acids that their molecules present: lignoceric (kerosene), cerebronic (brakein), nervonic (nervon), oxinervonic (oxinervon).

Cerebrosides can complement their functions in the company of other elements, especially in non-neuronal tissues.

An example of this is the presence of glycosylcerebrosides in skin lipids, which help to ensure the permeability of the skin against water.

Synthesis and properties of cerebrosides

The formation and synthesis of cerebrosides is carried out through a process of adhesion or direct transfer of sugar (glucose or galactose) from a nucleotide to the ceramide molecule.

The biosynthesis of glucosylcerebrosides or galactosylcerebrosides takes place in the endoplasmic reticulum (of a eukaryotic cell) and in the membranes of the Golgi apparatus.

Physically, cerebrosides have manifested their own thermal attributes and behaviors. They usually have a melting point much higher than the average temperature of the human body, presenting a liquid crystal structure.

Cerebrosides have the ability to form up to eight hydrogen bonds starting from the base elements of ceramide, such as sphingosine. This creation allows a higher level of compaction between the molecules, generating their own internal temperature levels.

Together with substances such as cholesterol, cerebrosides collaborate in the integration of proteins and enzymes.

The natural degradation of cerebrosides consists of a process of deconstruction or separation of their components. It takes place in the lysosome, responsible for separating the cerebroside into sugar, sphingosine and fatty acid.

Cerebrosides and diseases

As mentioned above, the wear of cerebrosides, as well as their excessive accumulation in a single place of the human and animal organic and cellular system, can generate conditions that at the time could end up wiping out a third of the continental population in Europe., for example.

Some of the diseases caused by defects in the functioning of the cerebrosides are considered hereditary.

In the case of Gaucher disease, one of its main causes is the absence of glucocerebrocidase, an enzyme that helps counteract the accumulation of fat.

This disease is not considered to have a cure, and in some cases, its early appearance (in newborns, for example) is almost always a fatal outcome.

Another of the most common diseases, a consequence of defects in galactosylcerebrosides, is Krabbe disease, which is defined as a dysfunctional failure of the lysosomal deposit, which generates an accumulation of galactosylcerebrosides that affect the myelin sheath, and therefore the white matter of the nervous system, causing an unbridled degenerative disorder.

Considered hereditary, you can be born with Krabbe disease and begin to manifest symptoms between the first three and six months of age. The most common are: stiff limbs, fevers, irritability, seizures and a slow development of motor and mental skills.

At a very different rate in young people and adults, Krabbe disease can also lead to more severe afflictions such as muscle weakness, deafness, optic atrophy, blindness and paralysis.

A cure has not been determined, although bone marrow transplantation is believed to aid treatment. Children at an early age have a low level of survival.

References

1. Medline Plus. (sf). Gaucher disease. Retrieved from Medline Plus: medlineplus.gov
2. O'Brien, JS, & Rouser, G. (1964). The fatty acid composition of brain sphingolipids: sphingomyelin, ceramide, cerebroside, and cerebroside sulfate. Journal of Lipid Research, 339-342.
3. O'Brien, JS, Fillerup, DL, & Mead, JF (1964). Brain lipids: I. Quantification and fatty acid composition of cerebroside sulfate in human cerebral gray and white matter. Journal of Lipid Research, 109-116.
4. Office of Communications and Public Liaison; National Institute of Neurological Disorders and Stroke; National Institutes of Health. (December 20, 2016). Lipid Storage Diseases Information Page. Obtained from the National Institute of Neurological Disorders and Stroke: ninds.nih.gov
5. Ramil, JS (nd). Lipids