1、POSSIBILITY OF THE USE OF LIPOSOMES FOR ORAL ADMINISTRATION OF INSULIN IN DIABETES MELLITUS Insulin is secreted by pancreatic cells of vertebrate peptide hormones, hypoglycemic have a unique effect, so far remains the drug of choice of insulin-dependent diabetes. Because it is easy to gastrointestin
2、al proteolytic enzymes degrade the oral invalid. Insulin injections are currently the most effective agents for the treatment of diabetes, usually after sc or im, its main drawback is slow to absorb the injection site, long-term injection will bring a lot of pain and inconvenience to the patient, an
3、d even inflammation, induration, allergies and other side effects. Research and easy to use, effective, safe and reliable insulin formulation is new domestic and international pharmaceutical industry issues of common concern. Liposomes are targeted drug carriers are targeted delivery system, the sam
4、e components with the cell membrane phospholipids, drugs are encapsulated within a phospholipid bilayer, can enhance the stability of drugs, a large number of suitable encapsulation easy to be damaged such polypeptide drug molecules, and its high compatibility biofilm, can promote the absorption of
5、drugs, the drug through the lipid bilayer slow controlled release, sustained release may play a role. Liposomes can be made into various particle sizes, by changing the composition of the phospholipid liposomes that may have different surface properties, and therefore suitable for various routes of
6、administration. Exists as a dimer of insulin molecule is a hydrophobic inner core consisting of a non-polar side chains, the entire outer surface of the polar side chain distribution, the structural characteristics of the hydrophilic surface, a hydrophobic core. Liposome bilayer membrane, and its st
7、ructure is characterized by a hydrophilic surface, the internal hydrophobic bilayer Insulin molecule having a hydrophilic surface groups, it is difficult within the liposome through a hydrophobic layer, the surface of the bilayer while the hydrophilic group to the surface of liposomes with a binding
8、 capacity, but the binding force weak,.Therefore, the combination of insulin and non-specific liposomes, the combination of weak adsorption, resulting in a process for preparing liposome encapsulated insulin passive entrapment efficiency and affected to some extent (generally reported in 30% between
9、 60%). However, because this non-specific binding in the liposomes, the liposomes will not alter the structure of insulin, and thus will not affect the efficacy of insulin. Insulin is encapsulated within the bilayer wrapped liposomes, phospholipids and can promote the absorption of insulin from prot
10、eolytic enzymes to preserve insulin destruction and degradation of the immune system, to some extent, improved bioavailability, to ensure the efficacy, and can make the drug through the role of phospholipid bilayer slow controlled release, can play a steady drop in blood sugar. In recent years, insu
11、lin liposomes due to its broad prospects attracted more and more attention. In insulin-dependent diabetes mellitus, treatment with subcutaneous injections of insulin in adequate doses not only does not prevent the development of diabetic complications in many cases, in particular, liver pathology, b
12、ut also promotes the appearance of lipodystrophies. Insulin injected in this way enters the general circulation earlier than the liver. On the contrary, under physiological conditions it immediately enters the liver through the portal vein from the pancreas, and 50-60% of the newly secreted insulin
13、is retained there . In view of this, the need for seeking a new means of introduction of the hormone lacking in the organism, closer to the physiological pathway, is understandable .It would be most convenient to introduce insulin per os, if it were protected from the action of the proteolytic enzym
14、es of the gastrointestinal tract. Repeated attempts have been made to introduce insulin into the organism without injections.Thus, for example, it has been suggested that a mixture of insulin with a vasodilating preparation be adsorbed under the tongue； however, the necessity of using large doses of
15、 the preparation over a prolonged period of time prevents the introduction of this method into clinical practice.A sugar-lowering effect of insulin administered to animals intraduodenally in a water-oil emulsion has also been suggested .Effectiveness of rectal introduction of insulin in the form of
16、an emulsion or suppositories has been reported in a number of studies A decrease in the blood sugar level has been detected after oral administration of insulin with synthetic polymers. A lowering of hyperglycemia has been detected in diabetes mellitus patients after inhalation of a stable suspensio
17、n of insulin in a propellant 7. In recent years attempts have been undertaken to introduce insulin per os in liposomes, prepared from phospholipids subjected to ultrasonic treatment.It has been shown that insulin enclosed within liposomes is protected from the action of proteolytic enzymes of the st
18、omach and is absorbed by the mucous membrane of thegastrointestinal tract, followed by delivery to the liver. The purpose of the present work was to investigate the effectiveness of insulin introduced per os in liposomes on the course of diabetes mellitis. The liposomes were produced by the Bangham
19、method ii from a mixture of phosphatidylcholine and cholesterol in an 8:2 mole ratio on the basis of I0 mg lipids per ml of suspension,followed by ultrasonic treatment. The method was described in detail in .Simple bovine insulin was used in a dose of about two units per rat, calculated so that abou
20、t 5% insulin was incorporated into the liposomes.In the experiment we used 128 noninbred white rats.Diabetes mellitus developed in the animals after intraperitoneal injection of alloxan hydrate,in a dose of 150 mg per kg of body weight.Insulin was administered in liposomes per os to 38 rats with sev
21、ere diabetes mellitis.Blood was collected for the investigation before the animals were fed.The concentration of immunoreactive insulin and the binding peptide (C-peptide) was determined in the blood serum (after sacrifice of the animals) by a radioimmune method. In rats with severe diabetes mellltu
22、s (see Table I), against a background of serious general condition (pronounced listlessness, thirst anorexia, dryness Of the mucosa and fur),substantial hyperglycemia and pronounced hypolnsullnemla were noted. The level of the C-peptide in the blood serum was significantly lower than in healthy anim
23、als. Without treatment such animals died within the first week after the administration of alloxan hydrate.After peroral administration :of insulin in llposomes, within only i h a tendency was noted for a decrease in the glucose content in the blood, intensified by the 4th hour after administration
24、of the preparation In certain animals signs of clinical hypoglycemia were even observed: excitation, agressiveness, a rapid drop in the blood sugar level, and convulsions in a number of cases. In healthy rats we did not detect such reactions. The conditions of the rats with hypoglycemia was improved
25、 after they were given a glucose solution. The hypoglycemic effect of simple insulin in liposomes was prolonged. After 24 h the blood sugar level was lower in 90%of the animals than before the administration of the preparation. The condition of most of the animals was significantly improved； they be
26、came more active .It should be noted that in rats with alloxan diabetes mellitus, against the background of admininstration of insulin in liposomes, high levels of insulin in the blood serum were detected,evidently as a result of the release of insulin from the llposomes. This is demonstrated,on the
27、 one hand, by the absence of an increase in insulinemia in rats of the control groups,and on the other hand, by detection of low levels of blood serum C-peptide, which is formed from proinsulin in equimolar amounts with insulin. The condition of the animals was improved against a background of admin
28、istration of insulin in liposomes, and the lifetime was increased(in each lot the animals treated with the liposomal form of insulin survived significantly better than the controls). The introduction of pure liposomes (without insulin) or a mixture of insulin with liposomes without enclosure of the
29、hormone inside did not give such a pronounced effect, although it did exhibit a small hypoglycemic action, which we are inclined to explain by an increase in the sensitivity of the peripheral tissues, in particular, the liver, to the action of circulating endogenous insulin, present in the organism
30、in small amounts, in connection with the incorporation of the liposomal phospholipids into the hepatocyte membrane,and possibly the removal of excess cholesterol from it and a consequent decrease in the viscosity of the membranes. Thus, the administration of insulin in liposome s to the experimental
31、 animals per os has a positive effect on them, which is expressed in an improvement of their condition, a lowering of the hyperglycemia, and a substantial increasein insulinemia, although the level of the C-peptide remains lowered. Evidently the results obtained associated with the release of insuli
32、n from the liposomes administered per os. The pronounced hypoglycemic action of the introduction of liposomal insulin once a day can be explained both by an increase in the sensitivity of the hepatocytes to insulin under the influence of the liposomes and by the direct passage of the bulk of the int
33、roduced insulin to the liver, in contrast to the conditions of its subcutaneous injection.In control animals that receive simple insulin subcutaneously in the same dose once a day, no improvement of the condition was noted after 24 h； the blood sugar level at this period was high although insulinemi
34、a increased.The administration of simple insulin per os also did not improve the condition of the animals. Thus, the introduction of insulin into liposomes provides a pronounced therapeutic and prolonged effect in animals with severe alloxan diabetes mellitus (a reduction of the listlessness, thirst
35、, lowering of the blood sugar level, significant rise in the level of insuinemia, and increase in lifetime). The positive effect detected after the administration of insulin in liposomes per os is associated with the penetration of this exogenous hormone into the organism, since an increase in the level of C-peptide in the blood is not noted against a background of the administration of the preparation .However, insulin liposomes factors are absorbed by the body, there are many, some of these factors has not been understood, the study needs to be further
