What are the lipase? Lipases are hydrolytic enzymes that mediate the breakdown (hydrolysis) of dietary lipids.
THE triglycerides they are thus broken down by the lipases into fatty acids is glycerol; some of the intermediate metabolites of this process are i diglycerides (or diacylglycerol) and i monoglycerides (or monoacylglycerol).
What are lipids?
Lipids are fundamental molecules for our body, as they perform various physiological functions and constitute more than 10% of our body weight.
The functions of lipids I'm:
- function energy: they satisfy the energy needs of our body (their calorific value is 9 Kcal / g and is therefore double that of carbohydrates and proteins).
- function thermal: the subcutaneous adipose tissue - that is the subcutaneous "fat", allows to isolate the underlying organs from the external environment and therefore protect them from the cold.
- function mechanics: in this case it acts as a kind of cushion, which protects the underlying organs from mechanical impacts.
- function structural: some lipids are used to build biological membranes and some hormones (e.g. steroid hormones derive from cholesterol, which is a lipid).
There digestion of the lipids introduced with the diet occurs in the intestine and, more specifically, in the duodenum and jejunum, thanks to the combined action of: enzymes produced by the pancreas - which make up the pancreatic juice and the bile - which guarantees the emulsion of the lipids (ie the formation of a stable suspension in the aqueous phase, since the lipids are naturally hydrophobic).
It is good to remember that the mechanism of fat digestion, like the rest of the digestion process, is subjected to hormonal regulation, in this case mediated above all by the cholecystokinin, which stimulates biliary secretion and pancreatic secretion.
Others enzymes involved in the process of hydrolytic digestion of lipids are: la cholesterol esterase and the phospholipase A2.
Others digestive enzymes products at the pancreatic level are: amylase, trypsin, chymotrypsin is carboxypeptidase (involved in the degradation of carbohydrates and proteins respectively).
Types of lipases
What is lipase and how many different types of lipases are there? They are present in our organism different lipase:
- salivary lipase
- gastric lipase
- pancreatic lipase
- intra-adipocyte lipase
- vascular endothelial lipase or lipoprotein lipase
- hepatic lipase
The differences among the various forms of lipase consist of different location and different headquarters of production.
There hepatic lipase it is an enzyme synthesized in the liver and is mainly involved in the hydrolysis of residual triglycerides in chylomicromes (forms "remnants" in fact) and IDL, lipoproteins not of great biological significance but which represent a phase of transformation of VLDL into LDL.
It was found that an increase of lipase hepatic is obtained following the administration of intravenous heparin, since the latter mediates the detachment of the same from the endothelium, leading to an increase in its activity in the circulation.
There endothelial lipase it is found, similarly to hepatic lipase, in the endothelium and acts by hydrolyzing the triglycerides transported by the VLDLs.
Since their role in lipid metabolism is clear, their malfunction is involved in dyslipidemias - that is, alterations in lipid metabolism that may involve triglycerides alone (hypo-hypertriglyceridemias), cholesterol (hypo-hypercholesterolemias) or both forms (mixed dyslipidemias).
What are IDL, Chylomicrons and VLDL?
These abbreviations indicate the lipoproteins, or macromolecular complexes formed by proteins and lipids, classified according to their density.
- Chylomicrons: carry mainly exogenous triglycerides.
- VLDL: very low density lipoprotein (very low density lipoprotein).
- IDL: intermidiate density lipoprotein (intermediate density lipoprotein).
- LDL: low density lipoprotein (low density lipoprotein - also known as bad cholesterol).
- HDL: high density lipoprotein (high density lipoprotein - also known as good cholesterol).
There pancreatic lipase specifically hydrolyzes the ester bond between fatty acids and primary alcohols, transforming triglycerides into monoglycerides.
Lipase is produced in the form of a pro-enzyme (pro-lipase), a still inactive substance that is activated by another enzyme, the colipase. The action of colipase, in addition to activating the pro-lipase, is to facilitate hydrolysis, favoring the link between lipase and triglyceride.
Normal values of lipase
The value of lipase can be studied in the blood. The sample must be taken on an empty stomach, preferably in the morning
THE normal values of lipase are: 0-55 U / L.
This digestive enzyme vand is its main use in the diagnosis and monitoring of acute pancreatitis, chronic or, more generally, of diseases that involve pancreatic compromise
Hyperlipasemia - high lipases
The finding of high pancreatic lipase is associated with a fortunately reduced number of conditions. Let's see the main causes of elevated lipases.
Causes of high lipases
- Acute pancreatitis
- Obstructions of the pancreatic duct (e.g. stones, primary neoplasms or neoplasms of adjacent organs that I compress ab extrinsic)
- Pancreatic cancer (involving an increase in lipases approximately 20% of cases)
High Lipase Symptoms
When is the lipase dosage prescribed? The hypothesis of hyperlipasaemia in the presence of a symptomatology clinic characterized by:
- bar pain
- loss of appetite
Lipase is amylase are tests currently used for the diagnosis of pancreatitis. Even today, however, even if there is several evidence in favor of the "superiority" of the evaluation of lipase as a marker of pancreatitis, his study continues to be associated with the study of amylasemia.
Amylase is an enzyme also produced from pancreas, involved in the digestion of carbohydrates. In addition to pancreatic amylase, there is salivary amylase (which represents about 60% of the total).
The study of amylase, despite being widely used, is not a very specific test for pancreatic diagnostics, as various conditions can induce its increase (eg inflammation of the salivary glands or macroamylasemia).
Therefore, if the object of our interest is the diagnosis of pancreatitis, we can directly execute the evaluation of blood lipase, without having to resort to an evaluation of the same at the urinary level, since, to date, a condition that can be associated with macrolipasemia, which can therefore cause its blood increase in the absence of a pathological picture. Unlike the condition of hyperamylasemia, which in order to exclude a cause associated with macroamylasemia, requires the evaluation of amylasuria (amylase in the urine).
Although there are different forms of lipase, is the evaluation of lipaseemia a specific test for the pancreas?
Yes, the study of blood lipases turns out to be quite specific and diagnostic with regard to pancreatitis and / or pancreatic insults, since the levels of the other forms of lipase are significantly lower than that of pancreatic lipase.
There lipase, therefore, it is an excellent laboratory parameter for the evaluation of pancreatic functionality.
The values of lipase they increase 4-8 hours after clinical manifestation, reaching a peak around 24 hours and a gradual decrease after 2 weeks.
The sensitivity of this test is 86-100% and the specificity 50-99%, with a distinct advantage over amylasemia.
The sensitivity and specificity of a test allow to evaluate thereliability of the test and, therefore, its ability to identify the pathology, reducing false negatives and / or false positives.
False negative= the patient has the disease, but the laboratory data gave a negative result.
False positive= the laboratory data is altered, suggesting the presence of disease, but the patient is not actually affected by the pathological picture.
The ranges of "normality" of lipase they can undergo physiological variations related to age, sex, ethnicity, lifestyle etc therefore they are to be considered as reference values, there which evaluation cannot in any way disregard clinical evaluation.
High lipase and acute pancreatitis
There pancreatitis it is an inflammation of the pancreas that is associated with a characteristic symptomatology: presence of bar pain, which is pain in the upper abdominal area, which can extend to the back.
Concomitant symptoms may include: nausea, temperature, loss of appetite is weight loss.
Other laboratory parameters also help us in the evaluation of pancreatitis:
- in the early stages we will have a increased blood sugar, resulting from alterations in the pancreatic parenchyma and the release into the circulation of glucagon - hyperglycemic hormone produced by pancreatic alpha cells.
- in the subsequent stages, as the destruction of the pancreatic parenchyma continues, we will observe an involvement of pancreatic beta cells, responsible for the production of insulin - hypoglycemic hormone, which, following its release, will lead to a decreased blood sugar.
- blood count and indexes of inflammation: laboratory investigation that can guide us in the evaluation of an inflammatory picture through an increase in leukocytes (a condition known as leukocytosis) and an increase in the CRP.
- hypocalcemia: blood calcium is reduced, with values below 8 mg / dL.
The assessment of calcium also has a prognostic role, as a reduction of the same is associated with a worse prognosis.
High lipase and chronic pancreatitis
In addition to acute pancreatitis, there is also chronic inflammation of the pancreas. It is associated with an impaired digestion of lipids and is characterized by steatorrhea - that is the presence of lipids in the stool, and is typically found in the alcoholic. During chronic pancreatitis the values of lipase and amliasis can be normal or modestly altered: in the latter case we speak of pancreatic cleavage.
In the course of chronic pancreatitis, phases of exacerbation in which the dosage of:
- trypsin in some cases
Hypolipasemia - low lipases
Causes of low lipase
Although hypolipasemia is a rare condition, the lipase can shrink in the late phase of chronic pancreatitis, following total (or almost) damage to the pancreatic cells, which will no longer be able to produce enzymes.
Other pathologies that have a secondary influence on pancreatic exocrine activity (eg Cystic Fibrosis and Diabetes) may lead to the finding of low lipase.
Symptoms of hypolipasemia
Some symptoms that can be associated with a reduction in serum lipase are:
- steatorrhea (undigested fatty substances> 6 g per day).
- weight loss (weight loss)
- Chronic abdominal pain
Following a reduction of lipases, an altered digestion of lipids occurs which therefore will remain undigested, leading to their increase in the faeces.
Among the most frequent causes of steatorrhea, in addition to pancreatic insufficiency, the chronic inflammatory pathologies affecting the intestinal mucosa, which involve impaired absorption, should be remembered.