O. V. Chistyakova

The Effect of Long-Term Intranasal Serotonin Treatment on Metabolic Parameters and Hormonal Signaling in Rats with High-Fat Diet/Low-Dose Streptozotocin-Induced Type 2 Diabetes.

In the last years the treatment of type 2 diabetes mellitus (DM2) was carried out using regulators of the brain signaling systems. In DM2 the level of the brain serotonin is reduced. So far, the effect of the increase of the brain serotonin level on DM2-induced metabolic and hormonal abnormalities has been studied scarcely. The present work was undertaken with the aim of filling this gap. DM2 was induced in male rats by 150-day high-fat diet and the treatment with low dose of streptozotocin (25 mg/kg) on the 70th day of experiment. From the 90th day, diabetic rats received for two months intranasal serotonin (IS) at a daily dose of 20 μg/rat. The IS treatment of diabetic rats decreased the body weight, and improved glucose tolerance, insulin-induced glucose utilization, and lipid metabolism. Besides, it restored hormonal regulation of adenylyl cyclase (AC) activity in the hypothalamus and normalized AC stimulation by β-adrenergic agonists in the myocardium. In nondiabetic rats the same treatment induced metabolic and hormonal alterations, some of which were similar to those in DM2 but expressed to a lesser extent. In conclusion, the elevation of the brain serotonin level may be regarded as an effective approach to treat DM2 and its complications.

Functional state of adenylyl cyclase signaling system in reproductive tissues of rats with experimental type-1 diabetes

Type-1 diabetes mellitus (DM) leads to numerous disturbances in the male and female reproductive systems. As was shown previously, one of the main causes of the development of complications in DM is a change in the sensitivity of the adenylyl cyclase signaling system (ACSS) to hormones. The aim of this work consisted in detection of disturbances in the hormone-regulated ACSS in reproductive system of rats with experimental type-1 DM (EDM1) caused by administration of streptozotocin. It has been shown that, in the testes of male rats with 5-day-long EDM1 the stimulating effects of human chorionic gonadotropin (HCG) and PACAP-38 on adenylyl cyclase (AC) and the GTP binding of G proteins are decreased considerably. In the uteri of female rats with EDM1 the effects of relaxin, PACAP-38, and biogenic amines are markedly decreased, whereas in ovaries only the effects of HCG are decreased. In all studied tissues of rats with EDM1 the attenuation of somatostatin inhibitory effects was observed, while in the uterus the inhibitory effects of serotonin and adrenalin were also decreased. Thus, in the reproductive tissues of rats with EDM1, the hormone regulatory effects on ACSS are decreased, especially the effect of HCG and the hormones, AC-inhibitors. We believe that the sensitivity of ACSS to hormones in EDM1 underlies the development of pathological changes in the reproductive system of diabetic rats under the conditions of hyperglycemia and insulin deficiency characteristic of type-1 DM.

Long-term intranasal insulin administration improves spatial memory in male rats with prolonged type 1 diabetes mellitus and in healthy rats

349 Type 1 diabetes mellitus (DM1) is a severe endo crine disease with a wide spectrum of complications in the CNS and peripheral organs leading to disability and premature death of patients. Though neurodegen erative diseases and related to them cognitive deficit are observed in many DM1 patients, physiological and biochemical processes of their development remain poorly studied [1, 2]. The approaches to prevention and treatment of diabetic encephalopathy are poorly developed; however, it is important for timely rehabil itation of DM1 patients and maintenance of their psy chosocial status.

Effect of intranasal insulin and serotonin on functional activity of the adenylyl cyclase system in myocardium, ovary, and uterus of rats with prolonged neonatal model of diabetes mellitus

The disturbances in hormonal signaling systems, adenylyl cyclase system (ACS) in particular, occur at the early stages of diabetes mellitus (DM) being one of the key causes of its complications. Since the correlation between the severity of DM and severity of disturbances in ACS is established, studying ACS activity can be used for monitoring DM and its complications and evaluating the effectiveness of their treatment. Recently, intranasal insulin (I-I) and the drugs increasing brain serotonin level, thus effectively restoring CNS functions, have begun to be used for the treatment of type 2 DM. However, the mechanisms of their action on peripheral tissues and organs at DM are not understood. The aim of this work was to study an influence of I-I and intranasal serotonin (I-S) on the functional activity of ACS in myocardium, ovary and uterus of rats with a neonatal model of type 2 DM. In the tissues of diabetic rats the changes in the regulation of adenylate cyclase (AC) by guanine nucleotides and hormones acting on enzyme in stimulatory and inhibitory manner were found, and these changes were characterized by receptor and tissue specificity. In diabetic rats I-I restored AC-stimulating effects of isoproterenol in the myocardium, that of guanine nucleotides and gonadotropin in the ovaries and relaxin in the uterus, as well as AC-inhibiting effects of somatostatin in all tissues and norepinephrine in the myocardium. Treatment with I-S led to a partial recovery of AC-inhibiting effect of norepinephrine in the diabetic myocardium, but did not affect the regulation of AC by other hormones. These data indicate that I-I normalizes the functional activity of ACS in the myocardium and in the tissues of reproductive system of female rats with neonatal DM, whereas the effect of I-S on ACS in the studied tissues is less pronounced. These results should be considered for the design and optimization of the strategy of I-I and I-S application for the treatment of DM and its complications.

Hormonal Sensitivity of Adenylyl Cyclase in the Myocardium, Brain and Testes of 18-month -old Non -Diabetic and Diabetic Rats

The alterations and abnormalities in hormone -sensitive adenylyl cyclase (AC) system occur at early stages of the type 2 diabetes mellitus (T2DM) and at later stages of the disease they are, according to our vi ew, one of the factors causing T2DM complications. To study the changes in AC system likely to be involved in the development of these complications one needs a very long model of T2DM. Purpose: The aim of this work was the study of AC system in the myocardium, brain and testes of three-, eight-and 18-month-old male rats with experimental T2DM compared with control animals of the same age.

Functional state of hypothalamic signaling systems in rats with type 2 diabetes mellitus treated with intranasal insulin

Intranasal insulin (II) administration is widely used in the last years to treat Alzheimer’s disease and other cognitive disorders. Meanwhile, it is almost not used to treat type 2 diabetes mellitus (DM2), mainly due to insufficiently studied molecular mechanisms of its effect on the hormonal and metabolic status of the organism. The effect of II on activity of the hypothalamic signaling systems playing a key role in central regulation of energy metabolism is also poorly studied. The aim of this work was to study the effect of 5-week II treatment of male rats with the neonatal model of DM2 (0.48 ME/rat) both on the metabolic parameters and functional activity of the hypothalamic signaling systems. II treatment of diabetic rats (DI group) was shown to normalize the blood glucose level and restore glucose tolerance and utilization. In the hypothalamus of the DI group, the regulatory effects of agonists of the type 4 melanocortin receptor (MC4R), type 2 dopamine receptor (D2-DAR) and serotonin 1B receptor (S1BR) on adenylyl cyclase (AC) activity, reduced under DM2, were found to be restored; moreover, the inhibitory effect of S1BR agonists became even stronger as compared to control. In the DI group, the restoration of AC hormonal regulation was associated with a considerable increase in expression of the genes encoding S1BR and MC4R. Besides, the attenuation of the AC-stimulating effect of D2-DAR agonists against the background of decreasing expression of the Drd1 gene was found to promote the enhancement of the negative effect of dopamine on AC activity. II treatment did not have a considerable effect on expression of the genes encoding the insulin receptor and insulin receptor substrate-2, which was slightly reduced in the hypothalamus of diabetic rats. Thus, II treatment of rats with the neonatal model of DM2 partially restores the hypothalamic AC signaling pathways regulated by melanocortin, serotonin and dopamine, demonstrating thereby one of the mechanisms of the positive influence of II on energy metabolism and insulin sensitivity in peripheral tissues.

The influence of bromocryptine treatment on activity of the adenylyl cyclase system in the brain of rats with type 2 diabetes mellitus induced by high-fat diet

186 Type 2 diabetes mellitus (DM2) is one of the most common diseases in the world, and the search for new approaches to its treatment is one of the most urgent problems of modern endocrinology. In recent years, it was established that disturbances in brain signaling systems, which are regulated by leptin, melanocortin, serotonin, and dopamine, lead to the development of insulin resistance, imbalance of energy metabolism, and lipotoxicity—processes characteristic of DM2 [1–4]. The restoration of the activity of these systems can normalize the insulin sensitivity and improve the glycemic control. For example, the treatment of DM2 patients with selective serotonin reuptake inhibitors, which increase the concentration of serotonin in the synaptic cleft, improves the glycometabolic paramee ters in these patients [5]. We have previously shown that a longgterm treatment of rats with a neonatal model of DM2 with intranasal serotonin increases the insulin sensitivity, improves the energy metabolism, and restores the activity of hormonal systems in the brain [6]. In recent years, it was established that the treatt ment of patients with Parkinsons disease and DM2 using bromocriptine (BC), a selective agonist of type 2 dopamine receptors (D 2 Rs), had a positive effect on the course of Parkinsons disease and corrected the metabolic disorders caused by DM2 [7]. For example, it was shown that the treatment with BC improved the glycometabolic parameters and reduced the risk of cardiovascular disease [8]. However, data on the use of BC for the treatment of DM2 apply only to the treatt ment of diabetic patients with Parkinsons disease and other neurodegenerative diseases, whereas the studies of the effect of BC on the development of DM2 with the use of experimental models of this disease are absent. These studies are required to elucidate the mechanisms of action and the targets of BC as well as for the development of optimal schemes of its applicaa tion in clinical practice for the treatment of DM2 and its complications. The aim of this work was to study the influence of longgterm BC treatment of male rats with DM2 caused by highhfat diet and treatment with lowwdose streptozotocin (STZ) on their glycometabolic paramm eters and functional activity of the hormoneesensitive adenylyl cyclase signaling system (ACSS) in the brain tissues. The selection of ACSS as a study object was due to the fact that the disturbances in this system are the key factors that cause the development of …

The functional activity of adenylyl cyclase signaling system in the brain, myocardium, and testes of rats with 8- and 18-month neonatal diabetes

43 The most common complications of a longgterm type 2 diabetes mellitus (DM) include the neurodee generative diseases and dysfunctions of the cardiovass cular and reproductive systems [1, 2]. However, in the case of type 1 diabetes, these complications occur rell atively rapidly as a result of the combined effect of acute insulin deficiency and severe hyperglycemia, whereas in type 2 diabetes, the main pathogenetic facc tor of which is the resistance of tissues to insulin, comm plications develop much more slowly and manifest themselves much later. To study the etiology and pathogenesis of complications of type 2 diabetes, proo longed animal models of this disease are required. We propose a longgterm (188monthhlong) model of neoo natal type 2 diabetes in male rats, which, in a number of characteristics, is similar to type 2 diabetes in humans. It is more adequate in comparison with the genetic models of this disease, because abnormalities that are not typical of normal animals develop in mutant animals with age [3]. To monitor the pathologg ical changes in the nervous, cardiovascular, and reproo ductive systems in type 2 diabetes, we studied the funcc tional state of adenylyl cyclase signaling system (ACSS) in the brain, myocardium, and testes of diaa betic animals. We have previously shown that disturr bances in the ACSS are one of the main causes of development of diabetes complications, and the severr ity of these disorders is positively correlated with the severity and duration of the disease [4–8]. The basal activity of adenylyl cyclase (AC) and its regulation by hormones in the tissues of rats with 188monthhlong neonatal DM was compared with those in agee matched healthy animals (control) as well as with 88monthhold diabetic and control rats. In the study we used the hormones that have both stimulatory (though G s proteins) and inhibitory (through G i proteins) effects on AC and are the key regulators of functions of the nervous, cardiovascular, and reproductive systems. We studied two groups of 188monthhold male Wistar rats with neonatal diabetes (n = 7; body weight, 377 ± 17 g; blood glucose, 6.0 ± 0.3 mM) and control (n = 7; body weight, 315 ± 14 g; blood glucose, 4.2 ± 0.2 mM) as well as two groups of 88monthhold male rats that were taken for comparison—with neonatal diabetes (n = 10; body weight, 312 ± 19 g; blood glucose, 6.7 ± 0.9 mM) and …

Biological activity in vitro and in vivo of peptides corresponding to the third intracellular loop of thyrotropin receptor

64 In recent years, one of the rapidly developing directions in molecular endocrinology and nanobioo technology is the peptide strategy, which has become widely used for studying the molecular mechanisms of transduction of hormonal signals into the cell and for designing highly selective and highly effective regg ulators of hormonal signaling systems [1, 2]. It is based on the search and development of peptides corr responding in structure to the functionally important parts of signaling proteins—receptors, heterotrimeric GGproteins, and enzymes that generate second mess sengers. The most promising direction in the peptide strategy is the synthesis and study of peptides derived from serpentineetype receptors, because at the level of these receptors not only the specific recognition of an external signal but also the choice of the pathway of its transduction into the cell takes place and, therefore, the intracellular targets of the hormone are deterr mined. We and other authors demonstrated that pepp tides corresponding to the cytoplasmic loops (CLs) of serpentineetype receptors selectively interact with G proteins, trigger signaling cascades in the absence of hormone, affect the transduction of the signal generr ated by them through a homologous receptor, thus functioning as regulators of intracellular signaling [3– 9]. One of the urgent problems of modern endocrinol ogy is the search for an effective regulator of the thyy roid gland and the entire hypothalamiccpituitaryythyy roid axis, which act at the stage of activation of the thyroiddstimulating hormone (TSH) receptor by the hormone. Disturbances that occur at this signal transs duction stage lead to a wide spectrum of thyroid gland diseases, including autoimmune thyroiditis and thyy roid cancer. The purpose of the study was to develop selective regulators of the TSHHsensitive signaling pathways on the basis of the peptides derived from the CCterminal region 612–627 of the third intracellular loop (CCICLL3) of the TSH receptor. We also studied the activity of the peptides in vitro by their effects on the basal and hormoneestimulated level of GTPPbindd ing of heterotrimeric G s and G q proteins, which are components of these cascades, and in vivo by the effect of intranasal administration of peptides on the level of thyroid hormones in the blood plasma of experimental animals. It should be noted that mutations in the CCICLL3 of the TSH receptor disturb its interaction with G s proteins and lead to loss of the ability of the mutant receptor to stimulate adenylate cyclase activity …

Intranasal administration of insulin eliminates the deficit of long-term spatial memory in rats with neonatal diabetes mellitus

216 Insulin has a regulatory effect on the metabolic and growth processes not only in peripheral tissues but also in the central nervous system (CNS). It had been shown that insulin controls the energy homeostasis in the brain tissue, affects the proliferation and differen tiation of neuronal cells, and is involved in the regula tion of learning and memory [1, 2]. Abnormalities in the insulin signaling system, resulting in type 2 diabe tes mellitus, which is characterized by insulin resis tance of tissues and moderate hyperglycemia, induce neurodegenerative processes in the CNS [3]. A reduced functional activity of the brain and cognitive deficits in patients with type 2 diabetes mellitus asso ciated with it is not only a medical but a social problem because its solution largely depends on the adaptation of patients in the community and their ability to work.