Insulin therapy in autoimmune diabetes: different aims

As autoimmune DM1 is a classic autoimmune disease, so we suppose to divide insulin therapy depending on the specific aim. A normoglycemic insulin therapy is a vicarious hormonotherapy, which principal aim is a compensation of physiological injury organs and tissues arisen owing to the loss of endogenic production of insulin, and so which main aim is prevention of diabetic complications. A basis insulin therapy that modifies the disease process includes: 1)Organoprotecting replacement hormonotherapy by insulin - the aim of the given version - the salvation of hormone-producing organ (b -cells) from proapoptotic action of the diabetic factors. 2)Prophylactic desensitizing insulin therapy consists in usage of insulin for holding an intensified insulin therapy with the purpose of reduction of b - cells into a rest state, that should inhibit their immunogenicity. The aim of the given therapy is the correction of autoimmune aggression, for reaching of the most complete immunological remission. 3)Tolerogenic insulotherapy is assembled of application of insulin and other islet antigens or its analogs within the framework of an induction of an immune tolerance. The aim of the given version of a basis insulin therapy is achievement regress of disease.

Thus, to our opinion, the conceptually new approach to an insulin therapy at DM1 is invoked to help to decide concrete practical problems of diabetology, first of all of the prognosis of manifestation and regression of the disease.

Abbreviations:

NOS - NO sinthase, NOD - nonobese diabetic mice, GH - growth hormone, IGFBP-3 - IGF binding protein -3, JDF - Juvenile Diabetes Foundation, ICA - islet cell antibodies, IAA - insulin autoantibodies, IA2-Ab - islet antigen 2 antibodies, CAMC - complement-dependent antibody mediated cytotoxicity , GAD-Ab- glutamic acid decarboxylase antibodies, HSP -heat shock proteins, ROS - reactive oxygen species, 1,25(OH)₂- д3 - 1,25-dihydroxyvitamin D3

The last achievements in the field of immunological diabetology allows to present the thesis about an insulin therapy at diabetes mellitus type 1 (DM1) as "the different aims - different names". Really, since 1986, when G.S. Eisenbarth has formulated conception about staging of DM1 (1) we have received a mass of facts confirming principled importance of such view on the etiopathogenesis of autoimmune diabetes mellitus (2).

1. GENETIC SUSCEPTIBILITY

2. TRIGGERING

3. AUTOIMMUNITY

4. LOSS OF INSULIN SECRETION

5. OVERT DIABETES

6. TERMINAL DIABETES

Moreover, in conformity with modern ideas the therapeutic intervention at the 3 and 4 stages are named as secondary prevention, i.e. the prophylaxis of overt, clinically manifested diabetes type 1. At the 5 and 6 stages the tertiary prevention, i.e. the prophylaxis of late diabetic complications is carried out. As things turned out in the last years such subdivision corresponds to different tactics of an insulin therapy. Such tactics at the 3 and 4 stages plays a role of secondary prevention, at the 5 and 6 stages executes a role of tertiary prevention, and at the 5 stage also plays an organoprotecting role in respect of b - cells.

Thus, since DM1 is a classic autoimmune disease, it is necessary to consider the insulin therapy at DM1 not only as glucose-lowering treatment for the correction of metabolic disorders, but also as the basis therapy, i.e. therapy that modifies the disease process and is directed on reaching of prolonged full-bodied remission. From the phenomenological point of view it is proposed to name such approach as "isohormonal" therapy, as the treatment is carried out by isohormone - insulin, instead of other designations of similar kinds of therapy, as for example, "suppressive" for diseases of a thyroid gland (3). Besides, different methods of isohormone administration, and accordingly, the different pathophysiological effects and mechanisms are not taken into consideration, and also that not only isohormone, but also its analogues containing isohormone epitopes are used. Thus, we suppose it is reasonable to consider an insulin therapy in the given context with the following items:

1. A normoglycemic insulin therapy

2. A basis insulin therapy.

   1. Organoprotecting replacement hormonotherapy by insulin.

   2. Prophylactic desensitizing insulin therapy.

   3. Tolerogenic insulotherapy.

From the point of view of a patient, a normoglycemic insulin therapy at the 5 and 6 stages of the disease is the act of salvation, i.e. liquidation of current signs of diabetes, and from the position of the doctor it is a measure of tertiary prophylaxis, i.e. prevention of a threatening acute and late diabetic complications development. The basic purpose of such therapy is the strictest metabolic monitoring indispensable for reaching of stable normal glycemia with the purpose of prevention of specific diabetic complications. The given principle was proved repeatedly, including prospective trials diabetes (4).

Thus, phenomenologically, a normoglycemic insulin therapy is a vicarious hormonotherapy, which principal aim is a compensation of physiological injury arisen owing to the loss of endogenic production of insulin.

Appropriate criteria for such therapy will be indexes of metabolic monitoring (compensation) of diabetes reflecting a degree of energy homeostat disorders immediately (a glycemia, lipidemia, including NEFA, insulinemia, somatotropinemia etc.) and indirectly, such as BMI and BP. The strictness of execution of such criteria will define probability of origin of manifestations of the disease, i.e. diabetic complications. As the example of such criteria are biomedical parameters offered by European IDDM Policy Group (1993; 1998).

Unlike a normoglycemic insulin therapy the basis insulin therapy is not " the act of salvation", but prevention and stabilization. Thus, if a normoglycemic insulin therapy is intended for maximal inhibition, as it possible, the progress of the disease, i.e. liquidate symptoms and remove manifestation complications, there should be also a purposeful therapy for reaching of a regression or a remission of the disease, as far as it possible. In such foreshortening it seems correct to speak about a basis insulin therapy, similar to a position, which one is applied in determination of a form of the treatment of other autoimmune nonendocrine diseases, which is used for the reaching of remission. Although, from the point of view of the thesis about secondary prevention such therapy of diabetes will be prophylactic.

Organoprotecting replacement hormonotherapy by insulin is variant of a basis insulin therapy. The point is that besides the necessity of holding of antihyperglycemic therapy for the removal of signs of diabetes, the existence of circulus vituosus is of significance. The understanding of circulus vituosus is very important. As it was told above, a leading factor in development of diabetic complications is the hyperglycemia owing to an absolute deficit of insulin or a deficit of its compensatory action. But hyperglycemia existing for a long time at a rather continuous exposition, as the damaging factor can lead as well to the full loss of a function of islets. It is a so-called phenomenon of glucose toxicity, which can be considered now as a concrete immunological phenomenon. It was found in vitro, that islets obtained from non-diabetic persons in conditions of high concentration of glucose express Fas-receptors. This expression, as well as subsequent death from apoptosis of b - cells is dose-dependent from a level of glucose in the environment. In usual terms Fas-receptors are not expressed on cells of normal pancreatic islands. The expression of Fas-receptors leads to the apoptosis owing to the collaboration with FasL molecules, which constitutionally present on surrounding b -cells. In these conditions the outcome to apoptosis takes place after a short period of a glucose-induced proliferation of b -cells. Thus, without participation of autoimmune mechanisms of diabetes per se can immunomediately promote own progress and exhaustion of a residual insulin secretion (5). At the same time the role played by a residual secretion of a C - peptide in the benign course of DM1 is clinically important (6). Therefore at the 5 stage it is necessary to speak about organoprotecting replacement hormonotherapy by insulin, as the purposeful vicarious insulin therapy with the goal not only to prevent complications of diabetes, but also to preserve a residual amount of b -cells.

Other side of a problem of insulin-producing organ preserving is the correction of b - cells apoptosis owing to other reasons, and a determination of a possible role in this process of an insulin therapy. The apoptosis of b - cells can be realized through different mechanisms (7). To all appearances the start of b -cells apoptosis through Fas-FasL (CD95) interaction has a key significance in a destruction of insular cells both for prodiabetic mice of a NOD line, and at human autoimmune diabetes (8). There are several reports containing information, that b -cells apoptosis in the animal model of autoimmune diabetes of NOD/Lt mice was verified before the appearance of lymphocytes (CD3 +) in islets. If apoptotic cells in islets were defined already on the 3-rd week of life, the insulitis phenomena were absent up to the 6-th week (9). In the given context it is essential, that the process of programmed death of b - cells can be accelerated also under the influence of another proЮpoptotic factors, linked with development of diabetes. So, in particular, at the increase of the insulin deficit the increase of ratio somatotropine / IGF-1 is observed, that also can promote the apoptosis of b -cells. It was shown in the test in vitro, that IGF-1 defended b -cell from cytokine- induced apoptosis (10). Also IGF-1 eliminated inhibition of an insulinic secretion and NнS induction in insular cells called by an IL-1 action.

As a whole, according to data known for today, problematics of an induction of programmed death of b -cells at DM1 is permissible to class as follows:

1. The spontaneous apoptosis - consist of decreasing of the expression of antiapoptotic genes (bcl-2?), etc.

2. Induced apoptosis - start of apoptosis process under the influence of cytokines, free radicals, etc, as consequence of immune attack against β-cells.

3. 3. Diabetic apoptosis- the apoptosis induction under the influence of the diabetic factors, i.e. hyperglycemia, oxidative stress, lipidemia, disturbances of a ratio somatotropine / IGF-1, etc.

According to the present classification an insulin therapy leveling 2 and 3 versions of apoptosis of b -cells shows organoprotecting function.

Thus, the aim of the given version of the therapy - the salvation of hormone-producing organ (b -cells) from proapoptotic action of the diabetic factors, i.e. regularly originating as far as progression of diabetes, such as glucose toxicity, lipotoxicity, disbalance of GH/IGF-1 system, etc.

The effectiveness criterions of such therapy will be indexes describing a mass of b -cells (level of a stimulated secretion of a C - peptide, amylin), level of the diabetic factors (NEFA, glycemia, etc.), and also indexes of insulinization of a liver (serum level of IGF-1 etc.). One of methods of the given therapy are the attempts of creation of hepatoselective analogues of insulin or the administration of insulin into a portal system by means of a catheterization of umbilicus vein or intraperitoneally. Thus, in the experiment, intraperitoneal administration of insulin with the help of the pump implanted to patients with DM1 without an effect on the glycemic profile practically normalized an initially depressive level of IGF-1 and IGFBP-3 in plasma (11).

Prophylactic desensitizing insulin therapy consists in usage of insulin for holding an intensified insulin therapy with the purpose of reduction of b - cells into a rest state ("rest therapy"), that should inhibit their immunogenicity. So, in vitro cells stimulated by glucose are more sensitive to immune attack, including cytokine action, than b -cells in the state of the functional rest (12). In experiences on animals rats treated by insulin had small b -cells, where autoantigens were not verified by monoclonal antibodies (13).

The aim of the given therapy at the 3 and 4, and also 5 stages of DM1 - the correction of autoimmune aggression, for reaching of the most complete immunological remission.

The criteria of such therapy should be indexes of functional activity of b -cells (level of a basal secretion of a C-peptide, proinsulin), and also immunological parameters of an autoaggression (р-cell-autoreactivity, titer and spectrum of diabetic autoantibodies, degree of an insulitis expressiveness, etc.).

The programme treatment with continuous intravenous infusions of insulin belongs to a number of such methods. Thus, the given approach was applied among patients with DM1 in a debut for the preserving of a residual secretion of a C-peptide. The patients were conducted intravenously 2 week courses of an insulin infusions in 12 months, that preserve a level of a C-peptide during period of observation (14). The group under the leadership of G.S. Eisenbarth in Joslin Diabetes Center has revealed a siblings group of high risk of diabetes development, including indexes of titers of ICA (> 80 units JDF), IAA and IVGTT at the age of 7-14 years. He realized the preventive program of treatment which includes small doses of subcutaneously administered insulin permanently and 5-day's courses of intravenous insulin infusions each 9 months. During all period of observation till 3.7 years each 1 of 5 treated patients were ill. At the same time, in the group where patients not received insulin all persons were ill (15).

In the randomized Яontrolled Schwabing Insulin Prophylaxis Pilot Trial after examination of 1 736 relatives of patients with DM1 there were selected 14 persons with a titer of ICA > 20 units JDF, reduced 1 phase of insulin secretion - less than 5 centiles and normal indexes of OGTT. The protocol of treatment consisted of 7-day courses of intravenous infusions of human insulin iterated in 6 months, and subcutaneous injections of insulin within 6 months after an infusion. During observation in experimental group 3 of 7 persons were ill, and in control group 6 of 7. The significant delay in a debut of diabetes (5 against 2 years) was noted in comparison with control group. It has to be mentioned, that there was no essential changes in the level of pro-diabetes antibodies (ICA, GAD-Ab, IA2-Ab), although during of an insulin therapy the significant increase of a level of antibodies to insulin was registered (16).

Tolerogenic insulotherapy is assembled of application of insulin and its peptides within the framework of an induction of an immune tolerance. The given method of mucous administration of an antigen with a consequent development of a tolerance to it, from the point of view of a evolutionary immunology, is explained by the second function of immunity (after protective) - acceptive, which consists of installation of symbiotic relationships of a macroorganism with a genetically xenogenic material for maintaining of constancy of the internal environment (17). The aim of the given version of a basis insulin therapy - the application of islet antigens, or their analogs at the 3-5 stages of DM1 for modification of the immune answer and liquidation of an autoaggression to b - cells. The criteria of such therapy should be immunological parameters of an autoaggression (р-cell autoreactivity, titer and spectrum of diabetic autoantibodies, degree of an insulitis expressiveness, etc.).

At the present time there is a restricted number of reports devoted to this theme. Thus, the DPT-1 trial of peroral insulin effectiveness in the group of intermediate risk of DM1 is not finished. The given research is going on, but preliminary stage results are pessimistic. Apparently, in particular, concerning peroral introduction there are doubts in expediency of an administered dose, which constitutes only a minor part of the dose value shown the efficiency on prodiabetic mice. There were also reports about apparent dose-dependent effect during the administration of peroral insulin as an antigen in experiments devoted to the suppression of diabetes transfer by generation of regulator р-lymphocytes of the irradiated mice of a NOD line (18).

The group IMDIAB under the leadership of P. Pozzilli has conducted appropriate double blind trial "IMDIAB VII" for the estimation of expediency of such approach in patients with a debut of DM1 (19). There were examined 46 patients who received insulin perorally (5 mg/day) and 36 patients who received placebo. The average age was 14 ? 8 years. All patients received an intensified insulin therapy. During the observations which have constituted 1 year the differences in the needs of insulin, secretion of a C - peptide and a level of a glycosylated haemoglobin. In the group received perorally insulin the tendency to the decrease on the 12 month of a heightened IAA titer after 3 months of treatment was registered. In patients younger than 15 years the IAA titer was reliably higher in all points than in elder ones. Probably, the patients need a dose adequate to their weigh. On the other hand, it is necessary to determine a possibility of an adjuvant administration which shown its efficiency on animals, for example IL-10 or 1,25(OH)₂- д3.

Another mucous way of administration - nasal is also perspective. In the experiment on the animal model of DM1 intranasal administration of a peptide 9-23 of B - chain of the insulin molecule, as well as nasal administration of an autoantigen of b -cells GAD65, prevented a development of diabetes for prodiabetic mice (20).

Remarks: methodical definitions

Conceptually another approach to an insulin therapy at autoimmune DM1 and modern understanding of etiopathogenic heterogeneity of DM1 requires, to our opinion, the formation of definite subtypes of disease, both for correct research works, and for practical use.

Working classification of autoimmune DM (type 1ю).

1. DM1vi - Virus - induced autoimmune DM1 - autoimmune version with the proved virus etiology.

2. DM1es - Essential autoimmune DM1 - version with autoimmune aggression to b -cells of the vague nature.

3. DM1ns - Nonspecific autoimmune DM1 - version of autoimmune diabetes as a part of an autoimmune syndrome-complex (autoimmune polyglandular syndrome types 1 and 2, "stiff-man" syndrome etc.).

4. DM1la - Latent autoimmune DM1 - version of the essential autoimmune DM1 with slowly progressing masquerading as type 2 diabetes (s. LADA).

5. DM1ch - Chemical autoimmune DM1 - version of autoimmune diabetes as consequence of affect chemical agents or drug (streptozotozin, IFN-α, hepatitis vaccine etc).

The given subdivision of DM1 has a preliminary character and, undoubtedly, requires further scientific findings on comparison of clinical, immunological, molecular-genetic and pathomorphological data, but, to our opinion, at the present time it is necessary for the regular work with a stream of the facts in the field of immunological diabetology.

From the point of view of a role, known for today, of diabetic autoantibodies in a pathogenesis of DM1, the subdivision of diabetic autoantibodies, known for us today, on the concrete subtypes is actual.

• Active, participating in the destruction of b - cells (CAMC);

• Passive, originating during autoimmune destruction (IAA, IA2-Ab etc.);

• Potentiating, such as GAD-Ab, which as it is supposed, initiate a tolerance to other "protective" antigens during vaccination;

• Autoantibodies to a protective system, including heat shock proteins (HSP) capable to increase a resistance of b - cells to damage by NO, streptozotocyn and ROS.

To the group of last antigens it is necessary to refer protein of the Reg family, gene of b -cells regeneration, to which the р-cell- reactivity was found (21). Thus, given antigens, on the one hand, being activated as a measure of defense, on the other hand, can accelerate autoimmune process by increasing of antigenic presentation of b -cells.

The given classification is invoked to help to regulate a large quantity of factological material obtained today by investigators, and to answer a number of questions, including about prognostic value of determination of concrete autoantibodies at definite stage of the disease or during holding a specific immunotherapy.

Undoubtedly, for the determination of immunological parameters of an autoaggression, the indexes of р-cell autoreactivity and the degree of insulitis expressiveness are the most perspective. Unfortunately, the data of different studies of р-cell autoreactivity are contradictory. The problem of certainty and standardization of methods of T-cell autoreactivity determination is discussed now.

The evaluation of insulitis

1. Direct methods - biopsy, scintigraphy of an insular tissue.

2. Indirect methods - determination of T-cell autoreactivity, titer and spectrum of autoantibodies.

It was reported about the application of labeled ⁹⁹рЯ IL-2 for a scintigraphy of a pancreas for the patients with the DM1 detected for the first time. Earlier the given method was applied for determination of infiltration of an organ by activated lymphocytes in immunomediated diseases, such as Graves disease and thyroiditis of Hashimoto. Patients were administered 2 mCi of ⁹⁹рЯ IL-2 and in one hour conducted a tomographic scintigraphy. The considerable accumulation of a radiolabel at the moment of verification of the DM1 diagnosis was determined in 35.4 % of patients. If in a debut of the study there were no differences in the metabolic status of positive and negative ⁹⁹рЯ IL-2 patients, after year of observation and the treatment by nicotinamidum positive ⁹⁹рЯ IL-2 patients have shown certain higher level of a secretion of a C - peptide and smaller needs in insulin (p=0.006). The accumulation of ⁹⁹рЯ IL-2 in a pancreas positively correlated with the age of the patients and was seen only in patients older than 10 years (22).

For the estimation of an expressiveness of inflammatory changes in a pancreas the usage of a combination of methods of tomographic tomography and scintigraphy in determination of accumulation of a radiolabeled human polyclonal immunoglobulin (^99mTc-HIG) is offered. The significant accumulation of a radiolabel was found for 8/15 patients with repeatedly diagnosed DM1. This given test has remained positive in patients a year after of primary examination (23).

Other investigators offer invasive methodics. Thus, the investigators of Osaka IDDM Study Group for several years use for patients with the DM1 diagnosed for the first time a method of a diagnostic punch biopsy of a pancreas under laparoscopic monitoring (24). This procedure, as the authors consider, is quite safe and high informative. The material for the study was obtained in 88,6 % cases. At the moment of a procedure the duration of diabetes of examined patients was ~3 months. The presence of insulitis was found in the form of р-cell infiltration, predominated mainly by the CD8+ cytotoxic lymphocytes, and hyperexpression on the insular cells of the I class HLA molecules in bioptatis of 17/29 patients with repeatedly diagnosed DM1. The authors underline, that given immunological signs certainly correlated with the presence in serum of diabetic autoantibodies GAD-Ab and IA-2Ab, but not with ICA titer (25).

Thus, to our opinion, the conceptually new approach to an insulin therapy at DM1 is invoked to unite efforts in understanding of a pathogenesis of autoimmune DM1 and to help to decide concrete practical problems of diabetology, first of all of the prognosis of manifestation and regression of the disease.

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