The modern view on the role of glyprolines by metabolic syndrome

The analysis of the literature data and own experimental studies on the effect of glyproline peptides on fat, carbohydrate metabolism, and hemostasis system when modeling metabolic syndrome in animals (rats) was carried out. Violations of fat and carbohydrate metabolism are characterized by hypercoagulation, increased glucose levels, dyslipidemia, and decreased rheological properties of blood. In this condition, the arginine‐ and lysine‐containing glyprolines (PGP, PRP, RPGP, KKRRPGP, RKKRPGP, and KRRKPGP) at multiple (7 days) intranasal introduction had a complex effect on the hemostatic parameters, increasing antiplatelet, anticoagulant, and fibrinolytic activity of blood plasma. All the studied drugs also showed normoglycemic and normolipidemic effects and led to a slowdown or decrease in body weight growth. The analysis of the presented material allows us to speak about the prospects of using hit compounds as protective therapeutic agents. In the case of violations of fat and carbohydrate metabolism, regulatory glyprolines protect the body by displaying antithrombotic, hypolipidemic, and hypoglycemic properties.


| Lipid metabolism
One of the main problems of modern society has become the obesity epidemic, primarily because of its clinical and social сonsequences. 2 The cause of overweight is an increase in body weight as a result of an increase in adipose tissue. 25 MS is a complex of clinical, hormonal, and metabolic disorders that play an important role in accelerating cardiovascular (CVD) and atherosclerotic diseases. 5 The main symptoms of MS can be three or more of the following disorders: abdominal obesity (the main feature), increased triglyceride levels, decreased high-density lipoprotein cholesterol (HDL-C), increased LDL-C, hypertension, hyperglycemia, insulin resistance, and impaired glucose tolerance. 26 The excessive consumption of animal fats containing saturated fatty acids leads to structural changes in cell membrane phospholipids and impaired expression of genes that control the development of insulin resistance. 4 Hypertriglyceridemia, often obtained in patients with the abdominal type of obesity, is accompanied by excessive deposition of lipids in the muscles, which also leads to insulin resistance. 5 Despite the fact that all components of MS are risk factors for CVD, individual signs of the syndrome within MS can only be considered if there is insulin resistance. 2 Currently, it can be considered established that a key role in the development and progression of MS is played by obesity of the abdominal-visceral type, especially when it is combined with T2DM. 27 Therefore, the first step in treating MS should be to reduce the weight of abdominal visceral fat through diet therapy and increased physical activity.
Changes in lipid metabolism can occur as a result of violations of fat absorption in the intestine, the transition of fat from the blood to the tissue, fat deposition, and interdaily fat metabolism. Normal absorption of fat provides its emulsification, splitting into glycerol and fatty acids, and the formation of compounds with bile acids. Lack of lipase, which occurs in diseases of the pancreas, as well as a deficiency of bile acids are accompanied by a violation of fat absorption. Lipase, which is localized in the vascular endothelium and enters the blood under the influence of heparin, also cleaves chylomicrons, and the resulting nonesterified fatty acids are transported to organs and tissues.
Fats entering the tissues are oxidized or deposited. 26

| The system of hemostasis
Many metabolic changes that are closely related to the development of MS have an impact on blood clotting and vascular-endothelial function, increasing the risk of both atherothrombotic cardiovascular events and venous thromboembolism. 25 The pathogenesis of atherothrombosis in MS is multifactorial, requiring a close relationship between the main components of MS, including not only insulin resistance, changes in the glycemic and lipid pattern, but also a violation of hemodynamics and the early appearance of endothelial dysfunction. 28,29 Hemostatic changes (i.e., coagulation balance, fibrinolysis, and platelet function), aimed at thrombogenicity of circulating blood, play an important role both in the progression of arterial wall damage and in acute vascular disorders.
Mechanisms that link abdominal obesity with prothrombotic changes in MS may be due to inflammation, oxidative stress, and dyslipidemia. 30 On the other hand, the MS comorbidities like procoagulant and hypofibrinolytic state is explained by the appearance of dysfunctions in the endocrine activity of adipose tissue, coagulological tendency, and chronic inflammation caused by the ability of adipocytes to produce and/or release cytokines and adipokines that affect blood clotting and fibrinolysis, platelet function, and pro-inflammatory state of the body. 31 The pathophysiology of MS-associated traits is complex. The effect of MS on platelet and plasma hemostasis of blood is the result of an inflammatory condition, dyslipidemia, and the accumulation of fat in the liver that accompany this pathology. 4,28 Among hemostatic disorders, there is a significant increase in plasma levels of the type 1 plasminogen activator inhibitor (PAI-1), which is a known anomaly associated with oxidative stress and an inflammatory condition. 25 Endothelial dysfunction is also the main sign of MS development. 29 In addition, adipokines are now considered to have a direct modulating effect on vascular and circulating cells. 32 Elevated platelet levels and their activating ability are well known as determining parameters for the physiological and pharmacological prediction of thrombotic events. 4 In preabdominal syndrome, a high level of basalactivated platelet mass, due to hyperlipidemia and damage livers, was detected. In this case, the activating ability of platelets was low, but increased with hyperglycemia and hyperlipidemia, which proved that high-calorie nutrition disrupted platelet function. 33 It is also known that patients with MS and T2DM have a high risk of microcirculatory complications and microangiopathies. 28 An increase in thrombogenic risk associated with platelet hyperaggregation, hypercoagulability, and hypofibrinolysis. Factors leading to platelet activation in MS and T2D include insulin resistance, MYASOEDOV ET AL. | 2825 hyperglycemia, nonenzymatic glycosylation, oxidative stress, and inflammation. 27 In the regulation of platelet adhesion and aggregation processes, NO plays a significant role, which is synthesized in both endothelial cells, smooth muscle cells, macrophages, and platelets. 34 Modification of platelet NO-synthase (NOS) activity in MS patients may play a central role in the manifestation of platelet hyperactivation. Metabolic changes accompanying T2DM can lead to abnormal NOS expression and activity in platelets. 4 A decrease in the number and sensitivity of insulin receptors on platelets in T2DM causes platelet hyperactivity. Antiplatelet effects of insulin are mediated by a NO-induced increase in cGMP levels and increased regulation of cAMP and cGMP-dependent pathways. The ability of platelets to synthesize humoral factors that stimulate thrombogenesis, inflammation, T2DM, cardiovascular complications, development of dyslipidemia, and insulin resistance was established. 35 When considering the relationship between MS and hemostasis, much attention is paid to endothelial function, platelet activity, blood clotting, fibrinolysis, and hemorheological markers. 28 Endothelium-dependent vasodilation is impaired in MS, which is mainly mediated by reduced expression of vasodilators (i.e., nitric oxide and prostacyclin) with concomitant increases in vasoconstrictors (i.e., endothelin-1, angiotensin II, and thromboxane A2). 29 Crossinteraction between the activated endothelium and platelets leads to a prothrombotic vicious cycle. Increased coagulation along with impaired fibrinolysis is also present in MS. This is reflected in the high level of fibrinogen and PAI-1. Endothelial dysfunction associated with high concentrations of von Willebrand factor and tissue factor in the blood also contributes to this pathology. The viscosity of the whole blood and plasma increases with MS. Intervention in the lifestyle of patients with MS, namely weight loss and improving the composition of the diet, can improve the prothrombotic state in MS. 36 Metabolic and genetic factors induce excessive expression of PAI-1 in the blood, and this contributes to a decrease in fibrinolysis, which leads to atherothrombosis. Patients with T2DM and MS have elevated levels of PAI-1 before clinical manifestations of atherothrombotic disease. 37

| The insulin system
Obesity has been shown to increase the risk of developing hypertension, T2DM, and also leads to vascular complications such as stroke or heart attack. 35 Adipose tissue, which is excessive in obesity, is the source of many hormone-active compounds (adipokines) that affect the body's homeostasis. The most famous among them are tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL6), leptin, adiponectin, resistin, omentin, visfatin, and ghrelin.
In addition, adipokines can reduce tissue sensitivity to insulin and cause inflammatory processes, endothelial dysfunction, and atherosclerotic changes. 38 Currently, much attention is paid to the definition of adipokines as modern markers of insulin resistance. It is assumed that changes in adipokine concentrations may be observed at least a few years earlier than the first symptoms of improper glucose metabolism. 39 Some researchers believe that the endocrine activity of adipose tissue, as well as the immunological status laid down genetically, play an important role in the pathogenesis of T2DM. 40 Diabetes is a complex endocrinological disease associated with metabolic disorders. MS can lead to insulin resistance through several pathways: an imbalance in the concentration of hormones (e.g., increased leptin, reduced adiponectin, and increased glucagon), increased concentrations of cytokines (TNF-alpha, IL6) and other proinflammatory factors, and possibly retinol-binding protein. 41 It is especially important that in obesity, increased release of nonesterified fatty acids from intra-abdominal adipose tissue increases the concentration of intracellular diacylglycerol and fatty acyl-CoA, which reduce the signal post-receptor of insulin. 25 Often during this period there are simultaneous changes in the function of β-cells, namely, there is compensatory hyperinsulinemia with abnormal secretory dynamics. As MS develops, the function of pancreatic β cells decreases, which cannot secrete enough insulin to overcome insulin resistance, and impaired glucose tolerance progresses to T2DM. Decreased function of pancreatic β cells may be associated with chronic hyperglycemia or glucotoxicity, chronic exposure to nonesterified fatty acids followed by lipotoxicity, oxidative stress, and inflammation. 42 Glucose homeostasis is controlled by islet cells using two main glucoregulatory hormones, namely insulin and glucagon, secreted by the βand α-cells of the pancreas, respectively. However, when carbohydrate metabolism is impaired, their secretion changes: insufficient insulin production is noted along with dysregulated glucagon secretion. 43 To date, oral medications approved for the treatment of hyperglycemia in T2DM are a group of biguanides, glinides, and preparations of the second generation of sulfonylureas, glitazones, PPAR-γ agonists, α-glucosidase inhibitors, SGLT2 inhibitors, GLP-1 analogs, and dipeptidyl peptidase-4 inhibitors. 44 There is a choice of medications that facilitate the course of the disease, but it is not yet possible to prevent the progression of hyperglycemia. 45 Potentially new drug compounds are needed that can reduce blood glucose levels, maintain the number of pancreatic β cells with minimal risk of hypoglycemia, and a long period of effectiveness.

| The nervous system
Patients with MS are characterized by a relationship between melatonin hypersecretion, indicators of hyperactivity of the sympathetic nervous system, and vascular endothelial dysfunction. 46 These correlations are age-specific.
Regulation of fat metabolism in the body is carried out by the nervous and endocrine systems. On the one hand, this process of self-regulation, due to the relationship between the level of blood glucose and nonesterified fatty acids (NEFA): when excess glucose is part of NEFA is deposited in the fat depots, a deficiency of glucose reverses the process. On the other hand, fat metabolism is also regulated in a neurohumoral way. 47 With prolonged emotional stress, irritation of the sympathetic nerves, fat is mobilized from the fat depots and weight loss occurs, and irritation of the parasympathetic nerves is accompanied by fat deposition. Insulin inhibits the release of fat from the depot, promotes the conversion of carbohydrates into fats, and the accumulation of glycogen in the liver.
Violation of this complex system of neurohumoral regulation is the basis of excess fat deposition in adipose tissue, which leads to obesity.
Lipids in the nervous system are represented by cholesterol and phospholipids as components of cell membranes and guarantee the physiological and psychological functions of the body. Violation of lipid homeostasis can lead to various pathological conditions. 48 Changes in cholesterol metabolism in the central nervous system lead to diseases, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and others. In the peripheral nervous system, changes in lipid metabolism are associated with the development of peripheral neuropathy, which can be caused by metabolic disorders, injuries, therapeutic, and autoimmune diseases. Transcription factors, such as liver x-receptors (LXR), regulate the metabolism of cholesterol and fatty acids in the nervous system. In the past few years, several studies have been conducted on the biology of LXR in the nervous system.
In recent years, among the factors contributing to the development of neurodegenerative diseases, MS has come out on top, having reached epidemic proportions. In the survival of neurons in MS, the importance of the sirtuin family is shown, which opens up opportunities for new pharmacological targets. It has been demonstrated that a high-fat diet used for the development of MS does not exacerbate the neurodegeneration caused by quinolinic acid, but it does worsen the sirtuin pathway that promotes fat metabolism. 49 Other researchers indicate that many neurodegenerative diseases are associated with metabolic dysfunction, which is manifested by changes in lipid metabolism, since neurons have a heterogeneous lipid composition necessary for the development and functioning of the nervous system. The relationship between neurodegeneration and changes in the metabolism of phospholipids and sphingolipids, mitochondrial morphology, and membrane remodeling was established. 50 To understand the pathogenesis of neurodegenerative disorders, the body's cellular response to danger, which is an evolutionarily preserved metabolic response, is of great importance. It protects the cell from chemical, physical, or biological influences that exceed its ability to homeostasis. The first wave of signals is the release of metabolic substances such as ATP and ADP, oxygen and reactive oxygen species, and is supported by purinergic receptors. After this, anti-inflammatory and regenerative pathways are activated, and then the cellular response stops. If the cellular response is not eliminated, the body's metabolism is disrupted, many systems and organs work, behavior changes, and chronic diseases occur. In MS, the memory of past stressful contacts is stored in the form of altered content of mitochondria and cellular macromolecules, which leads to an increase in functional reserve capabilities. The cellular response and purinergic response to life threats are directly controlled by the centers of the brain stem. Chemosensory integration of the entire body's metabolism also occurs in the brain stem and is a prerequisite for its normal development. 51 The effects of the ethyl acetate fraction from Aruncus dioicus var. kamtschaticus (EFAD) for the treatment of neurodegenerative processes and cognitive disorders caused by a high-fat diet induced by obesity are also known.
EFAD has been shown to inhibit lipid accumulation, reduce individual body weight, and prevent impaired glucose tolerance and insulin resistance. 52

| CHAPTER 2: PROTECTIVE (CORRECTIVE) ROLE OF GLYPROLINES BY MS
In this chapter, we present mainly our data on the effect of various glyproline peptides on the parameters of hemostasis, lipid metabolism, and body defenses with antithrombotic, hypolipidemic, and hypoglycemic properties in disorders of fat and carbohydrate metabolism during the MS.
The synthesis of the following peptides (Table 1) was performed using classical peptide chemistry in solution.
Both derivatives of L-amino acids and amino acids with free functional groups were used. The evaporation of solutions was carried out on a vacuum evaporator at 40°C. The identity of the obtained compounds was checked using thin-layer chromatography (TLC) on plates with Silufol silica gel. The substances were detected in ultraviolet light (UV light), using ninhydrin, Barton, Pauli, and Reindel-Hoppe reagents, and o-tolidine in a chlorine medium. All the solvents used in the synthesis of peptides were appropriately purified.
The synthesis of peptides performed using the method of mixed anhydrides, the carbodiimide method with the addition of 1-hydroxybenzotriazole (HOBT), and the method of activated esters. Both sequential build-up of the peptide chain and block build-up were used.
The homogeneity of the synthesized peptides was checked using high-performance liquid chromatography (HPLC) on a Milichrom-A02 chromatograph.
All the synthesized peptides were characterized using mass spectrometry on the LCQ Advantage Thermoelectron device, MAX.
Using the method of HPLC, chromatographic systems for purification of the synthesized peptides have been developed. The purity of all the synthesized peptides is shown in Table 1.   After 20 h (at the 50th day) and again 7 days (at the 57th day) after discontinuation of treatment blood samples were obtained from each animal for biochemical analyses.
The content of rats for 6 weeks on a HCD led to the development of MS, as evidenced by established hypercoagulation and a decrease in fibrinolysis: in the blood of animals, coagulation according to activated partial thromboplastin time (APTT) data significantly increased by 12%, FXIIIa activity (an increase of 17%), summary fibrinolytic activity decreased by 100%, fibrindepolymerization activity (FDPA) by 145% and fermentative fibrinolytic activity by 256%, at increased more than two times compared to the corresponding normal values. It is known that the development of MS in rats also increases the concentration of cholesterol, triglycerides, and glucose control animals contained in the HCD significantly increased the concentration of total cholesterol (TC; by 18%-20%), TG (by 75%), and LDL-C (by 45%) and reduced the concentration of HDL-C (by 17%) compared to normal healthy rats. 53 The data obtained indicated the development of MS in the body of rats that were subsequently treated with peptides.

| Changes in the hemostatic system
Fibrindepolymerization or nonenzymatic fibrinolytic activity of animal blood plasma characterizes its ability to prevent the processes of beginning fibrin or thrombosis.  Table 2).
In earlier studies, the antifibrin-stabilizing effect of short proline-containing peptides (PG, PGP) was established under in vitro conditions that inhibited the activity of factor XIIIа (FXIIIа) in blood plasma. 6 In this study, the effects of three lysine-containing peptides KKRRPGP, RKKRPGP, and KRRKPGP in vivo were also determined by their antifibrin-stabilizing effect. Thus, 20 h after sevenfold administration of peptides in the blood plasma of rats, the activity of FXIIIа decreased by 33%, 41%, and 55%, respectively. After 7 days (i.e., 168 h) after the discontinuation of the peptide administration, the antifibrin-stabilizing activity was maintained in the rat blood during the continued feeding of rats in accordance with the HCD, although to a lesser extent than 20 h after the last administration of the peptides.
So, 20 h after the end of the introduction of peptides, the greatest anticoagulating effect in the blood was observed when using PRP and RPGP, as well as RKKRPGP and KRRKPGP.
Seven days after the discontinuation of the use of peptides against the background of continuing HCD, the preservation of increased anticoagulant-fibrinolytic and antiplatelet activity of the blood was noted.

| Changes in the lipid profile
A study on the effect of PGP, PRP and RPGP peptides on lipid profile parameters in animals with MS showed that after sevenfold intranasal use of PGP and PRP at a dose of 50 mcg/kg, there was a slight decrease in the concentration of LDL-C In the blood of animals, which was 92% and 83% compared to the control group (rats with MS without treatment; Figure 2A). Treatment of rats with MS peptide RPGP resulted in a more pronounced decrease in the concentration of LDL-C (69% relative to control). As seen in Figure 2B, there was a significant decrease in the concentration of triglycerides: the level of TG was 51% (PGP), 60% (PRP), and 52% (RPGP) relative to the control values (p < .01).
Seven days after discontinuation of treatment with PGP and PRP peptides, the level of LDL-C continued to drop, since this indicator was 65% relative to the control in both cases, and the TG concentration remained the same. The effect on the lipid profile of the RPGP peptide decreased slightly a week after discontinuation of treatment, since there were no significant differences from the control of LDL-C levels. The level of TG in these conditions increased, but was significantly lower than the control values and was 71% compared to MS without treatment.
Sevenfold intranasal administration of peptides KKRRPGP, RKKRPGP, and KRRKPGP at a dose of 100 mcg/kg resulted in changes in the lipid profile. Thus, the use of RKKRPGP and KRRKPGP peptides caused a significant reduction in LDL-C to 79% and 83% relative to MS in untreated rats. An even greater decrease in this indicator was due to treatment with the KKRRPGP peptide (48% compared to the control). Also, treatment with these peptides had a significant drop (two to three times) in the level of TG in the blood of animals: KKRRPGP-up to 41%, RKKRPGP-up to 52%, and KRRKPGP-up to 28% relative to control.
A week after the discontinuation of the KKRRPGP and KRRKPGP peptides, the concentration of LDL-C in the blood of animals remained at the same level (42% and 83% relative to control, respectively), and after treatment, F I G U R E 2 The effect of peptides on lipid profile parameters of rats with metabolic syndrome (MS). Showed the level of LDL-C (A) and triglycerides (B) in rat (with MS) blood plasma after 20 h and 7 days after sevenfold intranasal treatment with peptides (a dose of 50 mcg/kg). *p < .05, **p < .01, the accuracy of the differences relative to the corresponding samples of the "MS Control" group, taken as 100%

| Changes in blood glucose levels
Given that the MS is accompanied by hyperglycemia, determining the concentration of glucose in the blood of animals with this pathology after the introduction of the studied peptides is of particular interest. The changes in the above parameter after the introduction of various glyprolines were studied. Thus, the administration of PGP and PRP tripeptides, as well as PGP peptide at a dose of 50 mcg/kg, only slightly reduced the glucose concentration. Peptides containing the amino acid lysine (at a dose of 100 mcg/kg) had a hypoglycemic effect. The maximum effect was found after the intranasal administration of KKRRPGP (4.96 ± 0.5 mmol/L; Figure 3). This may be due to the presence of lysine, which facilitates fibrinolytic processes in the bloodstream and promotes normal blood supply to tissues. 23 Seven days after the discontinuation of peptides, the glucose concentration increased only in the group of animals with MS, who were previously been administered with a peptide KKRRPGP intranasally. For all other peptides, a significant decrease in glucose concentration was observed on average by 39%, relative to the values in control animals.

| Changes in body weight
Weighing animals before the introduction of peptides (day 43 of the experiment), 20 h after their last introduction (day 50), and 7 days after treatment (day 57) showed that the use of studied glyprolines against the background of HCD led to a slowdown in body weight gain in all experimental groups (Figure 4).
Studies have shown that after the introduction of PGP, PRP, and RPGP ( Figure 4A), the increase in body weight in animals of these groups (weight gain) was 7.0 ± 1.7, 11.3 ± 0.8, and 4.3 ± 0.6 g, which was 56%, 28%, and 72% less than in rats with MS without treatment (control, 15.7 ± 0.8 g). After 1 week of discontinuation of treatment in rats of the experimental groups, the slowdown in body weight growth remained, since the total weight gain (from the 43rd to the 57th day of the experiment) was 62% (PGP), 72% (PRP), and 48% (RPGP), although it did not reach the values of the Normal group.
As one can see in Figure 4B, the use of peptides KKRRPGP, RKKRPGP, and KRRKPGP against MS led to either a slowdown in body weight growth (RKKRPGP) or a decrease in this indicator (KKRRPGP and KRRKPGP). The weight gain on the 50th day of the experiment after treatment with RKKRPGP was +6.8 ± 1.9 g (38% less than in the control), and after treatment with KKRRPGP and KRRKPGP, the rats lost weight by 9% and 34% (gain −1.0 ± 1.5 and −3.7 ± 1.1 g, respectively) relative to the values of body weight in the control (gain +11.0 ± 2.2 g).
F I G U R E 3 The effect of peptides on blood glucose concentration in MS rats. Showed the blood glucose level after 20 h and 7 days after sevenfold intranasal administration of different peptides to rats with MS. *p < .05, **p < .01, the accuracy of the differences relative to the corresponding samples of the "Control MS" group, taken as 100%. MS, metabolic syndrome After 1 week of discontinuation of treatment with these peptides, the weight loss of the experimental group of animals continued and reached values corresponding to healthy animals of the Normal group. The decrease in t-PA under the influence of the peptides may also be due to their interaction with platelet glycoprotein receptors, followed by inhibition of platelet binding to fibrinogen. 59 It is known that RGD-, RGDS-, RPD-amino acid sequences with the additional inclusion of proline exhibit a high antiplatelet effect due to the interruption of the final stage of fibrinogen binding to the GP IIb/IIIa of activated platelets. 60 This fact is noteworthy because peptides with this sequence of amino acids can be used for future designs of bifunctional antithrombotic agents. 61 So, based on our results and available literature data, we can assume that the antiplatelet effects of proline peptides we studied, expressed in the suppression of ADP-dependent platelet aggregation, are due either to their interaction with fibrinogen or inhibition of platelet receptors. It is known that both thrombin inhibitors and platelet activation inhibitors, which play a key role in the formation of a blood clot, are used to suppress pathological thrombosis. Natural RGD-containing peptides had not only an antiplatelet effect, but also a significant anticoagulant effect. 54 The peptides we studied had a similar effect. Their anticoagulant activity is probably related to the inhibition of blood clotting factors (Xa and prothrombin complex factors), as evidenced by the increase in APTT activity that we have established.
To explain the mechanism fibrin-depolymerization effect of the above peptides is possible as a direct effect of peptides, because they have both FDPA and indirect effect. Peptides inhibit the conversion of fibrinogen to fibrin mainly at the "self-assembly" stage of fibrin, as described in Byshevsky et al. 62 The mechanism of antifibrinstabilizing action of arginine-and lysine-containing peptides is probably their ability to inhibit thrombin involved in the activation of FXIIIa. 59 Previously, it was shown that the regulatory peptide PGP in intranasal multiple administration to animals with hypercholesterolemia, along with fibrin-depolymerization and anticoagulant activity in the bloodstream, has a normocholesterolemic effect. 13 In the present review described the combined effect of arginine-and lysinecontaining glyprolines as the process of blood clotting and lipid and carbohydrate metabolism in the body.
The studied glyprolines affected lipid and carbohydrate metabolism, reducing LDL-C and triglycerides in the blood, as well as the level of blood glucose, which is due to their structural features and due to the additional action of individual amino acids included in their composition. 63 In addition, the effects may be related to the property of glyproline peptides like heparin to reduce the atherogenic properties of blood through activation of blood lipoprotein lipase. 64 The results obtained indicate the potential of the studied compounds to influence homeostatic processes, change the metabolism and functions of cells, participate in the regulation of metabolism, and maintain metabolic balance. These results provide new factual material that characterizes the features of structural and functional interaction that underlie the ability of the studied regulatory peptides to influence the body's homeostasis. It is becoming increasingly obvious that low-molecular-weight peptide compounds play a significant role in regulating the body's metabolic processes.

| CONCLUSION
Based on the presented literature data and experimental studies, it can be concluded that glyproline lysine-and arginine-containing peptides have a unique combined effect on the parameters of fat and carbohydrate metabolism and indicators of the hemostatic system, showing antithrombotic, hypocholesterolemic, and hypoglycemic properties in the blood plasma.
The results obtained indicate the potential of arginine-and lysine-containing peptides to influence the homeostatic processes, to change the metabolism of organs and tissues, and to participate in the regulation of metabolism, as well as to maintain the metabolic and hemostatic balance of the body.
Under the conditions of modeling MS in rats, the studied peptides had a complex effect on the hemostatic system parameters, increasing the antiplatelet, anticoagulant, fibrindepolymerization, and antifibrin-stabilizing properties of blood plasma. When violations of fat metabolism, accompanied by increased blood clotting and a decrease in its rheological properties, arginine-and lysine-containing peptides have a combined effect not only on primary and plasma hemostasis, but also on the function of the vascular endothelium, expressing a tissue activator of plasminogen in the bloodstream. As for the lipid-lowering effect of peptides, after treatment with peptides PGP, PRP, RPGP, KKRRPGP, RKKRPGP, and KRRKPGP, the parameters of lipid metabolism (LDL-C and TG) in different degrees approached the values corresponding to the lipid profile of healthy animals. All the studied peptides led to a slowdown in body weight growth, and KKRRPGP and KRRKPGP even led to a decrease in this indicator.
According to our data changes in the peptide, molecule may lead to altering of these peptides effect. 6,[13][14][15] Modification of the amino acid sequence in molecules of KRRKPGP, KKRRPGP, and RKKRPGP leads to significant changes in the peptide properties. We assume that this largely depends on the location of arginine and lysine in the peptide molecules, since there is evidence that confirms the importance of the participation of arginine-and lysinecontaining polypeptides in blood clotting processes.
The results indicate the prospects of using regulatory with antithrombotic, hypolipidemic, and hypoglycemic properties to protect the body in cases of violations of fat and carbohydrate metabolism. Because the presence of a regulatory continuum of glyproline peptides, the body creates a continuity of processes of regulation and implementation of response physiological reactions.

ACKNOWLEDGMENTS
This study was supported by the Russian Foundation for Basic Research, RFBR (Grant no. 18-04-00260) and the Russian Foundation for Basic Research, COMFI (Grant/Award no. 17-00-00104).