[Molecular mechanisms of action and physiological effects of the proinsulin C-peptide (a systematic review)]

The C-peptide is a fragment of proinsulin, the cleavage of which forms active insulin. In recent years, new information has appeared on the physiological effects of the C-peptide, indicating its positive effect on many organs and tissues, including the kidneys, nervous system, heart, vascular endothelium and blood microcirculation. Studies on experimental models of diabetes mellitus in animals, as well as clinical trials in patients with diabetes, have shown that the C-peptide has an important regulatory effect on the early stages of functional and structural disorders caused by this disease. The C-peptide exhibits its effects through binding to a specific receptor on the cell membrane and activation of downstream signaling pathways. Intracellular signaling involves G-proteins and Ca2+-dependent pathways, resulting in activation and increased expression of endothelial nitric oxide synthase, Na+/K+-ATPase and important transcription factors involved in apoptosis, anti-inflammatory and other intracellular defense mechanisms. This review gives an idea of the C-peptide as a bioactive endogenous peptide that has its own biological activity and therapeutic potential.

[Diagnostics value and regulatory functions of roinsulin.]

Proinsulin is one of the indicators reflecting the functional activity of the pancreas. In insulin-independent diabetes mellitus the ratio proinsulin / insulin is increased. The review examined the causes of hyperproinsulinemia and the diagnostic value of proinsulin in patients with diabetes mellitus type 1 and 2. The role of proinsulin in the regulation of metabolic pathways and the preservation of the functional activity of cells under physiological conditions, during aging and during pathological processes is discussed. Studies in these areas justify the inclusion of proinsulin in the superfamily of signaling factors. The neuroprotective activity of proinsulin and its potential as a therapeutic tool for neurodegenerative diseases and retinal dystrophy are considered.

[Antidiabetic role of high density lipoproteins]

Disturbance in lipid metabolism can be both a cause and a consequence of the development of diabetes mellitus (DM). One of the most informative indicator of lipid metabolism is the ratio of atherogenic and antiatherogenic fractions of lipoproteins and their protein components. The review summarizes literature data and own results indicating the important role of high-density lipoprotein (HDL) and their main protein component, apolipoprotein A-I (apoA-I), in the pathogenesis of type 2 DM. On the one hand, HDL are involved in the regulation of insulin secretion by b-cells and insulin-independent absorption of glucose. On the other hand, insulin resistance and hyperglycemia lead to a decrease in HDL levels and cause modification of their protein component. In addition, HDL, possessing anti-inflammatory and mitogenic properties, provide anti-diabetic protection through systemic mechanisms. Thus, maintaining a high concentration of HDL and apoA-I in blood plasma and preventing their modification are important issues in the context of prevention and treatment of diabetes.

[The study of activity of matrix metalloproteinases abd reactants of inflammation in patients with endocarditis.]

The purpose of study is to establish and compare concentration of acute-phase indices, total activity of matrix metalloproteinases-2, -7 (MMP-2, MMP-7) of blood serum in patients with vegetations on heart valvular apparatus of infectious and noninfectious nature; to apply a correlation analysis between these indices; to evaluate advantages of technique of detection of total activity of MMP-2 and MMP-7 in patients with endocarditis of various etiology. The sampling consisted of 175 examined patients separated on two groups. The first group included 81 patients with noninfectious endocarditis; the second group included 94 patients with infectious endocarditis. The activity of MMP-2 and MMP-7 was detected using fluorescent substrate, specific to MMP-2 and MMP-7. The significant increasing of activity of MMP-2 and MMP-7 in blood serum of patients with vegetation syndrome as compared with activity of enzymes in blood of healthy individuals (control group). In the group with noninfectious endocarditis activity of MMP-2 and MMP-7 made up to 84,10 ± 12,37; in the group with infectious endocarditis - 227,30 ± 44,70; in the control group - 4,16 ± 2,28 mkmol/MCA/l per hour (р < 0,05). No reliable difference between endocarditis of various nature was established. The correlation was observed between activity of matrix metalloproteinases and reactants of acute phase of inflammation.

[Apolipoprotein A-I stimulates secretion of insulin and matrix metalloproteinases by islets of Langerhans]

The development of type 2 diabetes mellitus (DM2) is accompanied by disturbances in lipid metabolism. These include the increase in serum levels of atherogenic fractions of very low-density (VLDL) and low-density lipoproteins (LDL), total cholesterol, triglycerides and apo B. In contrast, the level of antiatherogenic high density lipoproteins (HDL) and the content of apolipoprotein A-I (apoA-I) decreased. To study the effect of the observed metabolic changes on insulin secretion in vitro, we used the islets of Langerhans isolated from the rat pancreas. It has been found that incubation of the islets in the presence of serum of the obese patients and patients with decompensated DM2 leads to a decrease in insulin secretion by 2.4 and 5.0 times, respectively. On the contrary, the addition of HDL to the incubation medium increased the insulin secretion by 3.4 times. A similar effect was observed in the presence of apoA-I, the main protein component of HDL. In the presence of apoA-I, the extracellular activity of matrix metalloproteinases (MMPs) demonstrated a 10-fold increase. The addition of LDL and VLDL to the islets did not change the secretion of insulin and activity of MMP. Our results testify to the important role of HDL and apoA-I in regulation of the insulin secretion by b-cells and the activity of MMPs in the islets of Langerhans.

[Proinsulin as a diagnostic biochemical marker of decompensated diabetes mellitus type II.]

The proinsulin is one of indices reflecting functional activity of pancreas. Under insulin-independent diabetes ration proinsulin/insulin increases. The study was carried out to evaluate content of proinsulin and other biochemical indices of blood serum depending on stage of compensation of diabetes mellitus type II. The content of proinsulin in blood serum was detected using "sandwich"-technique enzyme-linked immunosorbent assay (BioVender, Czechia). The concentration of proinsulin in blood serum of control group comprised 2,56 ± 0,23 nmol/l. No gender and age differences were established concerning content of proinsulin in blood serum of patients. The concentration of proinsulin was twice higher than control level in group of patients. Two main groups were singled out: one with high content (concentration thrice exceeded average value in control group) and another with low content of proinsulin (within standard value). The patients with stages of compensated and sub-compensated diabetes (n=35) retained low concentration of proinsulin. At the stage of decompensation of diabetes (n=40) concentration of proinsulin was thrice higher than standard value. This group was characterized by increasing of concentration of glucose, fructosamine and decreasing of concentration of C-peptide. At the stage of decompensation concentrations of triglycerides, total cholesterol and atherogenicity index increased reliably. The concentration of proinsulin at the stage of decompensation positively correlated with level of glucose and concentration of triglycerides. Therefore, measurement of concentration of proinsulin can be used as an important diagnostic criterion permitting to judge about degree of decompensation of diabetes and development of its complications.

Content of circulating extracellular DNA, plasma activities of matrix metalloproteinases, and ultrastructure of the myocardium in hypothyroid rats with hypercholesterolemia

Free circulating extracellular DNA, plasma activities of matrix metalloproteinases in hypothyroid rats, and ultrastructural changes in the myocardium were studied under conditions of experimental hypercholesterolemia. For suppression of thyroid function, the animals received antithyroid drug mercazolyl under conditions of cholesterol diet. Hypercholesterolemia in hypothyroid rats (thyroxine concentration 2-fold below the normal) was paralleled by a pronounced increase of the concentration of free circulating extracellular DNA and total matrix metalloproteinases 2 and 7 activity. These changes were associated with lytic and destructive changes in cardiomyocytes and blood capillary endotheliocytes. Changes in the cardiomyocyte and endotheliocyte ultrastructure were more pronounced in hypothyroid rats.

Activity of matrix metalloproteinases during antimycobacterial therapy in mice with simulated tuberculous inflammation

Matrix metalloproteinases are shown to be involved in the pathogenesis of tuberculosis inflammation. In the early stages of BCG-granuloma formation in mouse liver and lungs, the serum levels of matrix metalloproteinases 2 and 7 increased by 4.5 times and remained unchanged while the pathology developed. Antimycobacterial therapy with isoniazid reduced enzyme activity almost to the level of intact control. The decrease in activity of matrix metalloproteinases 2 and 7 that play the most prominent role in the development of destructive forms of tuberculosis is of great therapeutic importance.

Cystein proteinase inhibitor stefin A as an indicator of efficiency of tumor treatment in mice

The concentration of stefin A (cystatin A in mice) was measured in animals with experimental tumors (LS lymphosarcoma, HA-1-hepatoma, and Lewis lung carcinoma) during effective antitumor therapy. In mice with these tumors serum concentrations of stefin A increased, while the concentration of cystatin C (extracellular cystein proteinase inhibitor) decreased. The concentration of stefin A in tumor tissue in Lewis lung carcinoma was higher than in LS lymphosarcoma and HA-1-hepatoma ascitic cells, which can be explained by the degree of their malignancy. The content of stefin A in tumor tissue was similar to that in the liver and spleen of tumor-bearing animals, while its concentration in the liver and spleen of tumor-bearing animals was lower than in intact mice. The level of stefin A is an important marker of malignancy and an indicator of the efficiency of antitumor therapy.

Effect of polysaccharides and human plasma lipoproteins on the secretion of cystatin C by peritoneal macrophages from normal and tumor bearing mice

Intact peritoneal macrophages in vitro secreted the cysteine proteinase inhibitor cystatin C. Polysaccharides stimulated cystatin C secretion: lipopolysaccharide < carboxymethylated beta-D-glucan < sulfoethylated beta-D-glucan. Human plasma low-density- (LDL) and high-density lipoproteins (HDL) are still more potent inducers of cystatin C secretion by macrophages. Peritoneal macrophages from mice with experimental HA-1 hepatoma compared to those from intact mice secreted more cystatin C with maximum polysaccharide-stimulated secretion after 30 min of incubation. LDL and HDL induced cystatin C secretion by tumor macrophages also.

Cystatin C and cysteine proteinases during the development and therapy of Lewis lung adenocarcinoma in mice

We measured plasma cystatin C concentration and activity of cathepsins B and L in tumor tissue as possible markers for the efficiency of antitumor therapy and prognostic criteria for Lewis lung adenocarcinoma in mice. Plasma cystatin C concentration markedly decreased in mice with tumors. During successive therapy the increase in plasma cystatin C concentration correlated with the degree of inhibition of tumor growth. Activities of cathepsins B and L in the liver increased in animals with tumors. In mice receiving successive antitumor therapy activities of cathepsins B and L increased in tumor tissue, but decreased in the liver (compared to untreated animals).

Activity and concentration of cathepsin B as prognostic criteria for the development of mouse LS lymphosarcoma and Lewis lung adenocarcinoma

We measured activity and content of cathepsin B in tumor tissues, liver, and spleen in mice with Lewis adenocarcinoma and LS-lymphosarcoma. Cathepsin B activity in Lewis adenocarcinoma cells was lower than in LS-lymphosarcoma cells, which was probably related to differences in their metastatic properties. Antitumor therapy increased activity and content of cathepsin B in tumor tissues. Changes in the content and activity of cathepsin B in tumor tissues can serve as a prognostic criterion for tumor regression during therapy. Cathepsin B is probably involved in apoptosis of tumor cells during chemotherapy of lymphosarcoma-LS with cyclophosphamide.

Cysteine proteinase inhibitor level in tumor and normal tissues in control and cured mice

Cystatin C is the best known extracellular endogenous cysteine proteinase inhibitor and has been studied as a possible index of tumor growth and as a marker of the effectiveness of antitumor therapy. The aim of this study was to evaluate cystatin C concentrations in murine tumor tissues (compared with other organs not directly involved with tumor development, such as the liver and spleen) during treatment with several antitumor drugs (Ukrain and/or cyclophosphane). Cystatin C concentrations in murine tissues and biological fluids was determined by enzyme-linked immunosorbent (ELISA) assay. The cystatin C ELISA test is a sandwich immunoassay, which uses immobilized rabbit antihuman cystatin C Pab and mouse antihuman cystatin C Mab-HRP (monoclonal antibodies, conjugated with horseradish peroxidase). We observed decreased serum cystatin C concentrations compared with controls in all nontreated tumor models: HA-1 hepatoma (solid and ascitic forms), lung adenocarcinoma (solid and ascitic forms) and LS lymphosarcoma. In the ascitic fluid of mice with HA-1 hepatoma the cystatin C concentration was much lower than in the serum of the same mice (about 20-fold lower). In the HA-1 model of hepatoma cells cystatin C concentration decreased about 2-3-fold compared with the control (intact liver) and Ukrain significantly increased the cystatin C concentration. Cyclophosphane treatment of LS lymphosarcoma significantly increased the cystatin C concentration in serum. Cyclophosphane treatment (50 mg/kg, single injection) increased cystatin C by up to 8-fold more in tumor issue. Ukrain treatment of LS lymphosarcoma was also followed by increased levels of cystatin C in tumor tissue (4-fold); cyclophosphane plus Ukrain had a similar positive effect. In the group with LS lymphosarcoma Ukrain or cyclophosphane plus Ukrain treatment induced a significant increase in cystatin C concentration in liver. Liver cystatin C concentration decreased in the HA-1 hepatoma group and treatment with Ukrain or carboxymethylated beta-1, 3-glucan (CMG) increased this index in both groups. Spleen cystatin C concentrations decreased about 5-fold in LS lymphosarcoma compared with controls and combined treatment with cyclophosphane plus Ukrain restored the index to the normal value. We can conclude that both murine tumors studied were characterized by low cystatin C concentrations in tumor tissues and decreased cystatin C concentrations (to a lesser degree) were also observed in liver and spleen as a result of the "toxic" effect of tumor bearing. Effective treatment in all cases (especially with Ukrain or a combination of cyclophosphane plus Ukrain) induced a significant increase in cystatin C. Obviously, the decrease in cystatin C concentration predominantly in tumor tissue was connected with tumor development and restoration of cystatin C level may be used as a marker of efficacy of antitumor therapy.

Cystatin C in LS lymphosarcoma and HA-1 hepatoma treated with Ukrain and cyclophosphamide and involvement of apoptosis

The concentration of cystatin C, a cysteine proteinase inhibitor, was measured during the treatment of murine LS lymphosarcoma with cyclophosphamide and HA-1 murine hepatoma with the antitumor drug Ukrain. It was shown that concentrations of cystatin C were very low in both the tumor tissues studied (HA-1 hepatoma cells and LS lymphosarcoma); increased cystatin C concentrations were found only in Ukrain-treated murine hepatoma, suggesting the mechanism of antitumor effect of this drug. Cyclophosphamide treatment in LS lymphosarcoma did not influence the concentration of cystatin C in tumor cells. At the same time, a marked increase in cathepsin B and cathepsin L activity in LS lymphosarcoma was found, indicating the involvement of apoptosis in the mechanism of antitumor action of cyclophosphamide. While the DNA from untreated LS lymphosarcoma was very homogenous and its molecular weight was high, the DNA from tumors of treated mice broke down, giving rise to the ladder figure characteristically produced by cells dying from apoptosis. Evidence was obtained that cyclophosphamide-induced tumor regression was effected by apoptosis.

Macrophage Stimulator beta-(1-->3)-D-carboxymethylglucan improves the efficiency of chemotherapy of Lewis lung carcinoma

We studied the effect of macrophage stimulator water-soluble beta-(1-->3)-D-carboxymethylglucan on the efficiency of cyclophosphamide chemotherapy in Lewis lung carcinoma. Cyclophosphamide inhibited the growth of primary tumor nodes by 57%. The preparation possessed pronounced antimetastatic activity: metastases were found in 40.9% animals. Combination therapy with cyclophosphamide and (1-->3)-beta;-D-glucan inhibited the growth of intramuscular tumors by 75-89% and reduced the incidence of metastases into the lungs by 92-94%. The therapeutic effect was most pronounced after simultaneous administration of these preparations: tumor growth was suppressed by 89.3% and metastases were found in only 7.5% animals (vs. 100% in the control). The potentiating effect of beta-(1-->3)-D-carboxymethylglucan is related to accumulation of cysteine proteinase inhibitors in the tumor tissue and plasma, but not to changes in blood cell composition.

Role of cystatin C and cysteine proteinases in the development of mouse LS-lymphosarcoma

The growth of LS-lymphosarcoma in CBA mice was accompanied by a decrease in the content of the major extracellular inhibitor cystatin C in the tumor, plasma and, to a lesser extent, in tissues not involved in tumor process (liver and spleen). Cyclophosphamide in a dose of 50 mg/kg prolonged the life-span of animals and decreased tumor size by 80%. Cathepsin B and L activities in the tumor tissue increased by 3 and 7 times, respectively. Cystatin C content in the tumor tissue, spleen, and plasma also increased. Cystatin C assay in tumor tissue and plasma helps to predict the rate of tumor growth and to evaluate the efficiency of antitumor therapy.

Acute phase proteins as biological markers of addictive disorders in teenagers and children

Acute phase proteins (APP), including C-reactive protein (CRP), alpha-1-proteinase inhibitor (PI) activity and albumin level were studied in serum of 183 teenagers and children with drug addictive disorders (DAD) (mainly home-made opiate dependence and glue-sniffing), hospitalised at Municipal Drug Addictive Centre, Novosibirsk (1996-1999). Serum CRP concentration increased several times during early withdrawal period in the teenager group with opiate dependence. In most cases of DAD decreased level of albumin (negative APP reactant) as well as decreased activity of PI was revealed. After treatment (about 21 days after onset of hospitalisation) the level of albumin still remained decreased. These indexes were suggested as a possible surrogate biological marker of DAD, and immune-stimulators were recommended during DAD treatment to restore the decreased level of protective APP of these patients.

Distribution of tocopherol and apolipoprotein A-I immunoreactivity in rat liver chromatin

[125I]Labelled lipoproteins (HDL, LDL, and VLDL) are actively taken up by the rat liver. The uptake rate in nonparenchymal liver cells was significantly higher than that in hepatocytes. Analysis of the distribution of the labelled lipoproteins in liver subcellular structures showed the presence of these compounds in the nuclei. The presence of apoA-I, apoB and apoE immunoreactivity in liver cell nuclei was demonstrated by immunochemical methods (ELISA and dot immunoassay). The nuclear matrix and transcriptionally active chromatin displayed the highest apoA-I levels, which considerably exceeded those in the total and transcriptionally inactive chromatins. A similar distribution pattern was observed for alpha-tocopherol. It is concluded that blood serum lipoproteins, primarily HDL, may transport tocopherol and other lipids into cell nuclei.