Adenylyl Cyclase Signaling System Research Articles

Genes positively regulated by Mef2c in cortical neurons are enriched for common genetic variation associated with IQ and educational attainment.

The myocyte enhancer factor 2 C (MEF2C) gene encodes a transcription factor important for neurogenesis and synapse development and contains common variants associated with intelligence (IQ) and educational attainment (EA). Here, we took gene expression data from the mouse cortex of a Mef2c mouse model with a heterozygous DNA binding-deficient mutation of Mef2c (Mef2c-het) and combined these data with MEF2C ChIP-seq data from cortical neurons and single-cell data from the mouse brain. This enabled us to create a set of genes that were differentially regulated in Mef2c-het mice, represented direct target genes of MEF2C and had elevated in expression in cortical neurons. We found this gene-set to be enriched for genes containing common genetic variation associated with IQ and EA. Genes within this gene-set that were down-regulated, i.e. have reduced expression in Mef2c-het mice versus controls, were specifically significantly enriched for both EA and IQ associated genes. These down-regulated genes were enriched for functionality in the adenylyl cyclase signalling system, which is known to positively regulate synaptic transmission and has been linked to learning and memory. Within the adenylyl cyclase signalling system, three genes regulated by MEF2C, CRHR1, RGS6, and GABRG3, are associated at genome-wide significant levels with IQ and/or EA. Our results indicate that genetic variation in MEF2C and its direct target genes within cortical neurons contribute to variance in cognition within the general population, and the molecular mechanisms involved include the adenylyl cyclase signalling system's role in synaptic function.

Calcium as a Modulator of the Adenylyl Cyclase Activity of Potato Cells in Bacterial Pathogenesis.

This is the first study to detect the effect of calcium ions on the activity of transmembrane adenylyl cyclase (tmAC), the key enzyme of the adenylyl cyclase signaling system, under normal conditions and after a short-term exposure to exopolysaccharides (EPS) of the bacterial ring rot pathogen Clavibacter michiganensis ssp. sepedonicus (Cms). After the treatment of the roots of plants with the Cms EPS, the response to Ca2+ changed: the activity of the tmAC of plants of the resistant cultivar significantly increased, whereas in the cells of the susceptible cultivar it remained unchanged.

Molecular Mechanisms of the Relationship between Thyroid Dysfunctions and Diabetes Mellitus

Type 1 and type 2 diabetes mellitus (DM) are known to increase the incidence of thyroid gland (TG) dysfunctions. The review addresses the literature data and our experimental results on the molecular mechanisms that underlie thyroid disorders under DM. Most important of these mechanisms are the attenuation of thyrocyte adenylyl cyclase signaling system sensitivity to thyroid-stimulating hormone, the decrease in the number of thyroid hormone receptors in peripheral tissues, and the decline in activity as well as changes in the ratio of different deiodinase forms in these tissues. Decreased activity of D2 deiodinases, which convert thyroxine into the active form of triiodothyronine, is associated with the development of insulin resistance, while decreased activity of D3 deiodinases, which catalyze inactivation of triiodothyronine in pancreatic β cells, suppresses insulin secretion and leads to insulin deficiency. Thus, both the excess and the deficiency of thyroid hormones can entail diabetic pathology. Identification of thyroid disorders is of utmost importance for elaborating novel approaches to treat and prevent thyroid diseases associated with type 1 and type 2 DM.

Changes in Nociceptive Thresholds and Adenylyl Cyclase System Activity in Skeletal Muscles in Rats with Acute and Mild Type 1 Diabetes

Diabetic peripheral neuropathy (DPN) is one of the commonest complications of type 1 diabetes mellitus (DM1). The aims of the present work were to study the dynamics of the development of pain-type DPN and the functional status of the hormone-sensitive adenylyl cyclase signal system (ACSS) in the skeletal muscle of rats with models of acute and mild DM1 and to investigate the influences on these of insulin therapy using different routes of hormone administration – intranasal and peripheral. The nociceptive threshold in rats decreased in both models of DM1; the stimulatory effects of guanine nucleotides (GIDP) and adrenergic agonists (isoproterenol, BRL-37344) on adenylyl cyclase (AC) also decreased. The AC-stimulating effect of relaxin decreased in animals with acute DM1, while the change in mild DM1 was minor. Peripheral administration of insulin to rats with acute DM1 increased the nociceptive threshold and partially restored the AC effect of the β3 agonist BRL-37344. Intranasal administration of insulin to rats with mild DM1 also led to an increase in the nociceptive threshold and partially restored basal and BRL-37344-stimulated AC activity in the skeletal muscle of diabetic animals. Thus, skeletal muscle in rats with acute and mild DM1 showed impaired nociceptive sensitivity and ACSS function, which was partially restored by treatment of animals with insulin given peripherally (acute DM1) or intranasally (mild DM1).

Restoration of hypothalamic signaling systems as a cause of improved metabolic parameters in rats with neonatal diabetes model during treatment with bromocriptine mesylate

One approach to correction of diabetes mellitus 2 type (DM2) and its complications is the use of bromocriptine mesylate (BCM), a selective agonist of the dopamine receptor type 2 (DA2R). However, the effectiveness and mechanisms of the action of BCM in the treatment of severe forms of DM2 forms currently not understood. The purpose of this study was to investigate the influence of 4-week treatment of male rats with neonatal DM2 model using BCM (300 mg/kg daily) on their metabolic parameters and on the activity of the adenylyl cyclase signaling system (ACSS) in the hypothalamus. Exposure to BCM restored glucose tolerance and glucose utilization by exogenous insulin, normalized lipid metabolism, and lowered triglycerides and atherogenic cholesterol levels, which are elevated in DM2. In the hypothalamus of diabetic rats treated with BCM, the regulation of ACSS by agonists of melanocortin receptors type 4 (MC4R), DA2R, and serotonin 1B-subtype receptors and expression of the Mc4r gene encoding MC4R were restored. Furthermore, BCM treatment did not influence the insulin levels in the blood and its production by pancreatic β-cells. The data indicate that the use of BCM to correct severe forms of experimental DM2 holds promise and show that the therapeutic potential of this drug is based on its ability to restore signaling systems of the hypothalamus that are sensitive to monoamines and peptides of the melanocortin family, which are responsible for the control of energy metabolism and insulin sensitivity.

Changes in the hormonal status of cardiovascular and the thyroid systems in rats with 18-month type 2 diabetes mellitus

Among the most common complications of type 2 diabetes mellitus (DM2) are disorders of the cardiovascular and the thyroid systems. The functions of these systems may be weakened with increasing age. However, the mechanisms of these disorders, including the role of alterations in the adenylyl cyclase signaling system (ACSS), are not fully elucidated. Objective was to study thyroid status and ACSS activity of the myocardium and the thyroid gland (TG) of rats with 8- and 18-month DM2 (DM-8 and DM-18) as compared to control animals of the same age (C-8 and C-18). In the myocardium of rats with DM2 an imbalance of β-adrenergic regulation of ACSS was detected, and these disturbances were amplified with increasing age. In the myocardium of rats of the C-18 group the disturbances of ACSS hormonal regulation were also identified, but they were less pronounced. In diabetic rats, the levels of free thyroxine and total triiodothyronine decreased, the level of thyroid stimulating hormone (TSH) increased, and the stimulatory effect of TSH on the ACSS in TG was attenuated, which indicates the hypothyroid state in long-term DM2. In the C-18 group, these changes were absent. Thus, in the myocardium and TG of rats with 18-month DM2 the hormonal regulation of ACSS was violated, which may be one of the causes of cardiovascular pathology and hypothyroid states in long-term DM2.

In vitro and in vivo studies of functional activity of new low molecular weight agonists of the luteinizing hormone receptor

The use of luteinizing hormone (LH) and its structural and functional homolog human chorionic gonadotropin (hCG) leads to hyperstimulation of LH-dependent signalling pathways and to desensitization of LH receptors. Therefore, the development of low molecular weight agonists of the LH receptor without these disadvantages has been carried out in recent years. These agonists, unlike gonadotropins, are active when administered orally. The greatest prospects are associated with the development of the thienopyrimidine derivatives structurally similar to compound Org 43553. The purpose of this work was the synthesis of new thienopyrimidine derivatives TP03 and TP04, the study of the regulation of LH-sensitive adenylyl cyclase signalling system in rat testes, and the evaluation of the ability of TP03 and TP04 to stimulate testosterone synthesis in male rats at different routes of administration. In the concentration range 10–7–10–3 M, TP03 and TP04 induced an increase of the basal adenylyl cyclase (AC) activity in rat testicular membranes with the EC50 values of 390 and 759 nM, respectively. At a concentration of 10–4 M, AC-stimulating effects of TP03 and TP04 were 213 and 122%, respectively, which indicates a higher activity of TP03 under in vitro conditions. At the same time, the AC-stimulating effect of TP03 was approximately 2.5-fold weaker than that of hCG (10–8 M). Upon simultaneous administration of hCG and thienopyrimidine derivatives, their stimulating effects on the AC activity were additive due to the different localization of their binding sites in the LH receptor. Compound TP03 (25 mg/kg), when administered intraperitoneally to male rats, was more efficient than TP04: the maximal increase in the testosterone level (3 h after administration) was by 60% higher than that induced by TP04. TP03 increased the testosterone level after oral administration (50 mg/kg) as well, but the effect was weaker than in the case of the intraperitoneal injection. Orally administered TP04 exhibited a low activity. The results suggest that 5-amino-N-tert-butyl-2-(methylsulfonyl)-4-(3-(nicotinamide)phenyl) thieno[2,3-d]pyrimidine-6-carboxamide (TP03) can be used for the development of the drugs that stimulate steroidogenesis in Leydig cells.

The functional activity of hypothalamic signaling systems in rats with neonatal diabetes mellitus treated with metformin.

The effect of the two-month metformin treatment (200 mg/kg/day) of rats with the neonatal model of type 2 diabetes mellitus on the functional activity of hypothalamic signaling systems was studied. It was shown that metformin treatment restored the sensitivity of hypothalamic adenylyl cyclase signaling system to agonists of the type 4 melanocortin receptor and the type 2 dopamine receptor but did not influence significantly the functions of the insulin signaling system. These data suggest new targets and mechanisms of metformin action in the CNS, which may mediate its restoring effect on energy homeostasis impaired in diabetic pathology.

The effect of four-week levothyroxine treatment on hormonal regulation of adenylyl cyclase in the brain and peripheral tissues of obese rats

The decrease in the function of thyroid gland (TG), which is often observed in obesity and metabolic syndrome, results in the hypothyroid state and is one of the causes of metabolic and functional disorders. It is assumed that thyroid hormone treatment normalizing hormone levels in an organism is able to prevent these disorders. However, studies of the effect of this therapy on metabolic parameters in animals with experimental obesity are very scarce, and data concerning its influence on the activity of the adenylyl cyclase signaling system (ACSS) are absent. At the same time, it is known that disturbances in the hormonal regulation of ACSS play a key role in etiology and pathogenesis of diseases associated with metabolic disorders. This work was aimed at studying the effect of long-term levothyroxine treatment of obese male rats on their carbohydrate and lipid metabolism, thyroid status, and the activity of ACSS and its hormonal regulation in the brain, myocardium, epididymal fat, and TG. The rats with obesity caused by a three-month high-fat diet received levothyroxine for four weeks (orally, with a daily dose of 20 μg/kg) (group OB + LT), whereas the control animals and untreated obese rats received placebo instead of the hormone. As a result of the treatment, the levels of thyroid hormones increased, the body and adipose tissue weight decreased, the levels of triglycerides, total and atherogenic cholesterol decreased, and glucose utilization increased. In addition, the ACSS activity impaired in obesity was restored in the brain, myocardium, and epididymal fat tissue. In the brain, the levothyroxine treatment restored the stimulatory effects of serotonin and dopamine, as well as the inhibitory effects of the agonists of the subtype 1B 5-hydroxytryptamine receptor and type-2 dopamine receptor on the adenylyl cyclase (AC) activity. In the myocardium, the stimulatory effects of β1/β2-agonists and relaxin reduced in obesity were also restored. It should be noted, however, that the effects of β3-agonists augmented in obesity did not change in group OB + LT, resulting in the enhanced activating influence of β-agonists on AC and creating certain risks of the development of cardiovascular diseases. The increase in the lipolytic effect of β-agonists and the weakening of the antilipolytic effect of N6-cyclopentyladenosine, an agonist of type 1 adenosine receptor, was found in the epididymal fat, indicating the increased lipolysis in adipose tissue. The sensitivity of AC to the thyroid-stimulating hormone in TG decreased in group OB + LT with an excess of thyroid hormones. Thus, the treatment with levothyroxine not only improves the energy metabolism and prevents the deficiency of thyroid hormones in experimental obesity but also restores the hormonal regulation of ACSS, which can be one of the mechanisms of action of thyroid hormones on the brain and peripheral tissue functions in obesity and other metabolic disorders associated with the hypothyroid state.

The effect of prolonged metformin treatment on the activity of the adenylyl cyclase system and NO-synthase in the brain and myocardium of obese rats

The biguanide metformin, which is widely used for the treatment of type 2 diabetes, improves carbohydrate and lipid metabolism and has substantial cardioand neuroprotective effects. The positive effects of metformin on the activity of NO synthases catalyzing the synthesis of NO, a major vasodilator, and that of the hormone-sensitive adenylyl cyclase signaling system (ACSS) are believed to play an important role in the mediation of these effects. To prove this hypothesis, we initiated a study addressing the effect of prolonged metformin treatment of obese rats on metabolic parameters and the activity of ACSS and NO synthases in the myocardium and brain of the animals. Obesity was induced in Wistar rats by a high-fat diet, and the animals were subsequently treated with metformin for 2 months (the daily dose was 200 mg/kg). Metformin treatment induced a decrease in adipose tissue mass, total body mass, levels of insulin and glucose, and the insulin resistance index HOMA-IR, as well as improved glucose tolerance, and led to a decrease of the content of atherogenic forms of cholesterol. ACSS stimulation by agonists of β1/β2-adrenergic receptors (ARs) and enhancement of β3-AR signaling was detected in the myocardium of obese rats, while metformin treatment restored ACSS regulation by adrenergic agonists in the myocardium and normalized the balance between β-AR-signaling pathways. The stimulating effects of serotonin and agonists of type 4 melanocortin receptors on adenylyl cyclase, which are attenuated in obesity, were restored in the brain of rats treated with metformin. The treatment completely restored the total activity of NO synthases and the activity of endothelial NO synthase in the myocardium, which are reduced in obesity. Metformin treatment was also shown to induce hyperactivation of NO synthases in the brain and myocardium of healthy animals. It is proposed the effects of prolonged treatment of obese rats with metformin underlie the cardioand neuroprotective actions of this drug.

The effect of 2-month bromocriptine treatment on the activity of the adenylyl cyclase signaling system in the myocardium and testes of rats with type 2 diabetes

Cardiovascular diseases and dysfunctions of the reproductive system are common complications of type 2 diabetes (T2D), and, therefore, development of new approaches for the alleviation of these pathologies is highly important. Bromocriptine (BC), an agonist of type 2 dopamine receptors, recently became widely used for the treatment of type 2 diabetes; this drug both restores energy metabolism and prevents the development of cardiovascular disease. However, the targets of BC and mechanisms underlying its action are still poorly characterized. The aim of the present work was to investigate the effect of BC treatment on the functional activity of the adenylyl cyclase signaling system (ACSS) in the myocardium and testes of male rats suffering from type 2 diabetes induced by high-fat diet and administration of streptozotocin (25 mg/kg). Oral BC administration (0.6 mg/kg every other day for 60 days) started 90 days after the commencement of highfat diet. Body weight and triglyceride levels were elevated in diabetic rats. Glucose tolerance of the animals was impaired, and they developed insulin resistance. BC treatment enabled the recovery of glucose metabolism parameters and increased the sensitivity of tissues to insulin. Adenylyl cyclase (AC) stimulation by guanylyl imidodiphosphate (GppNHp), relaxin, and the β-adrenergic receptor (β-AR) agonists isoproterenol and norepinephrine in the myocardium of diabetic rats was impaired, while the stimulatory effects of the β3-agonists BRL-37344 and CL-316243 persisted. The inhibitory effect of somatostatin on forskolin-stimulated AC activity was attenuated, while the inhibitory effect of norepinephrine mediated by α2-AR was enhanced. BC treatment normalized adrenergic signaling in the myocardium and partially restored the effects of relaxin and somatostatin on AC. AC activity, both basal and stimulated by GppNHp, forskolin, human chorionic gonadotropin, and pituitary AC-activating polypeptide, decreased in the testis of diabetic rats, and the inhibitory effect of somatostatin was attenuated. BC treatment induced only slight changes in the testicular ACSS. Thus, prolonged BC treatment restored the functional activity of ACSS in the myocardium and testes of diabetic rats; this accounts for the therapeutic effect of BC on the impaired functioning of the cardiovascular and reproductive systems in T2D and should be taken into account upon the selection of treatment strategies for T2D and its complications.

The thyroid status of rats immunized with peptides derived from the extracellular regions of the types 3 and 4 melanocortin receptors and the 1B-subtype 5-hydroxytryptamine receptor

The activity of the hypothalamic-pituitary-thyroid (HPT) axis is controlled by the brain neurotransmitter systems, including the melanocortin signaling system. Pharmacological inhibition of type 4 melanocortin receptor (M4R) leads to disruption of the functioning of HPT axis and to reduction of the level of thyroid hormones. At the same time, the data on how prolonged inhibition of M4R affects this axis and on its role in regulation of M3R are absent. The relationship between the thyroid status and the activity of 1B-subtype 5-hydroxytryptamine receptor (5-HT1BR) is scarcely explored. The aim of this work to study the effects of chronic inhibition of M3R, M4R and 5-HT1BR induced by immunization of rats with BSA-conjugated peptide derived from the extracellular regions of these receptors on the thyroid status and the activity of thyroid stimulating hormone (TSH)-sensitive adenylyl cyclase signaling system (ACSS) in the thyroid glarid (TG) of the immunized animals. In rats immunized with the peptides K-[TSLHL WNRSSHGLHG11-25]-A of M4R, A[PTNPYCICTTAH269-280]-A of M3R and. [QAKAEE-EVSEC(Acm)-VVNTDH189-205]-A of 5-HT1BR levels of thyroid hormones such as fT4, tT4 and tT3 were significantly reduced. In rats immunized with M4R and M3R peptides, an increase of TSH was detected whereas in the animals immunized with 5-HT1BR peptide the level of TSH, on the contrary, was reduced. In the TG of rats immunized with M4R and M3R peptides, the stimulatory effects of hormones (TSH, PA-CAP-3 8) and GppNHp on adenylyl cyclase activity were attenuated, and the changes were most pronounced in the case M4R peptide immunization. After immunization with 5-HT1BR peptide the stimulatory effects of TSH, PACAP-38 and GppNHp were retained. Thus, the main cause of thyroid hormones deficit in rats immunized with M4R and M3R peptides was the decreased sensitivity of ACSS thyrocytes to TSH, whereas in rats iimunized with 5-HT1BR peptide the deficit of thyroid hormones was associated with decreased level of TSH. Our data on the negative impact of long-term immunization of rats with BSA-conjugated peptides derived from the extracellular regions of M4R, M3R.and 5-HT1BR on their thyroid status is a strong argument in favor of participation of these receptors and intracellular signaling pathways associated with them in the regulation of HPT axis.

Beta-adrenergic regulation of adenylyl cyclase signaling system in the myocardium and brain of rats with obesity and type 2 diabetes mellitus as affected by long-term intranasal insulin administration

The stimulatory effects of norepinephrine, isoproterenol and selective s3-adrenoceptor agonists BRL 37344 and CL 316.243 on the adenylyl cyclase signaling system (ACSS) in the brain and myocardium of young and mature rats with experimental obesity and type 2 diabetes mellitus (DM2) (disease induction at 2 and 4 months of age, respectively) and the influence of the long-term intranasal insulin (I-I) administration were studied. It was shown that the AC-stimulatory effects of s-agonist isoproterenol in animals with obesity and DM2 practically did not change. The respective effects of norepinephrine on the AC activity slackened in the brain of young and mature rats and myocardium of mature rats, while the I-I treatment led to their partial recovery. In the brain and myocardium of mature rats with obesity and DM2 an increase in the AC-stimulatory effects of s3- AR agonists was observed, while in young rats the similar influence of the same pathologies was missing. The I-I treatment resulted in an attenuation of the AC-stimulatory effects of s3-agonists to their control level. Since the disruption of the adrenergic agonist-sensitive ACSS is one of the causes of metabolic syndrome and DM2, the recovery of ACSS dysfunctions by the long-term I-I administration offers one of the ways of correcting these diseases and their complications in the nervous and cardiovascular systems.

Alterations in adenylyl cyclase sensitivity to hormones in the brain, myocardium, and testes of rats immunized with BSA-conjugated peptide 269–280 of type 3 melanocortin receptor

Binding of the type 3 melanocortin receptors (M3R) functionally coupled to Gs proteins with α-melanocyte-stimulating hormone (α-MSH) or M3R agonist γ-MSH results in the activation of adenylyl cyclase (AC) in the brain, which is responsible for the M3R-mediated regulation of physiological and biochemical processes in the central and peripheral nervous systems. A decrease in the M3R activity leads to energy metabolism disorders, metabolic syndrome, and functional disturbances of the nervous and cardiovascular systems. However, molecular mechanisms of these alterations and the role of the adenylyl cyclase signaling system (ACSS) are yet poorly understood. The aim of this work was to study the effects of a long-term (13 months, 8 injections) immunization of male rats with BSA-conjugated peptide A-[PTNPYCICTTAH269–280]-A (A-[269–280]-A), corresponding to the third extracellular loop of rat M3R, on the functional activity of ACSS and its regulation by neurotransmitters and hormones in rat brain, testes, and myocardium. At the end of the experiment, the body weight of animals decreased, the specific mass of adipose tissue increased, dyslipidemia was observed, and the sensitivity to insulin was reduced in spite of the increase in its secretion in response to a glycemic load. In the brain of immunized rats, the AC-stimulating effects of γ-MSH, noradrenaline, serotonin and PACAP-38 decreased, the stimulating effect of dopamine and AC-inhibiting effects of serotonin and 5-nonyloxytryptamine (an agonist of 5-hydroxytryptamine receptor (5-HTR) of the 1B/1D subtype) increased, while the effects of the M3R/M4R agonist α-MSH and the M4R agonist THIQ remained unchanged. In myocardial membranes, stimulation of AC by the agonists of β3-adrenergic receptors (β3-AR) was enhanced, while the AC-stimulating effects of β1- and β2-agonists were attenuated and the AC effect of relaxin weakened. In testicular membranes, the AC-stimulating effects of chorionic gonadotropin and PACAP-38 decreased, as well as the effect of GppNHp (non-hydrolysable GTP analog). These data indicate that the attenuation of the M3R signaling leads to considerable alterations in the ACSS sensitivity to the hormones playing a key role in the functioning of the nervous, cardiovascular and reproductive systems. The alterations in the ACSS sensitivity observed in brain, myocardium and testes are characterized by hormonal and receptor specificity. Identification of ACSS disorders is one of the approaches to studying etiology and pathogenesis of diseases associated with inhibition of M3R-melanocortin signaling system of the brain.

Attenuation of inhibitory influence of hormones on adenylyl cyclase systems in the myocardium and brain of obese and type 2 diabetic rats as affected by the intranasal insulin treatment

The functional state of adenylyl cyclase signaling system (ACSS) and its regulation by the hormones and the inhibitor of adenylyl cyclase (AC), somatostatine (SST), in the brain and myocardium and by 5-nonyloxytryptamine (5-NOT) in the brain of rats of different ages (2- and 7-month-old) with experimental obesity and combination of obesity and type 2 diabetes mellitus (DM2), as well as the effect of the long-term treatment with intranasally administered insulin (II) on ACSS were studied. It was shown that the basal AC activity in obese and DM2 rats increases in the myocardium and, to a lesser extent, in the brain and decreases under the II treatment. The AC stimulating effect of forskolin decreases in the myocardium, but not in the brain of obese and DM2 rats. The II treatment recovers the AC stimulating effect of forskolin in 7-month-old animals, but has little effect in 5-month-old rats. In obesity as well as under the II treatment, the basal AC activity and its stimulation by forskolin change insignificantly. The AC inhibitory effects of 5-NOT and, particularly, SST are strongly attenuated in the investigated pathology, supposedly due to a reduction in the functional activity of Gi-proteins. The treatment of obesity and its combination with DM2 recovers, completely or partially, the AC inhibitory effects of hormones, most of all in the brain. Since the ACSS dysfunctions are causal to metabolic syndrome and DM2, their elimination by the II treatment promises an effective approach to combat these pathologies and their CNS and cardiovascular complications.

Functional activity of thyroid gland in male rats with acute and mild streptozotocin diabetes

Type 1 diabetes mellitus (DM1) and dysfunction of the thyroid gland (TG) are the most common endocrine diseases, which are interrelated. However, the molecular mechanisms of thyroid dysfunction in DM1 and the role of adenylyl cyclase signaling system (ACSS) in this process remain poorly understood. Typically for studying etiology and pathogenesis of thyroid diseases in DM1 the models of acute DM1 induced by high doses of streptozotocin (STZ) are used. At the same time, a suitable model for this purpose is the model of mild DM1 initiated by moderate doses of STZ, which more closely resembles human DM1. The aim of this study was a comparative study of the functional state of the thyroid gland in rats with 30-day acute DM1 induced by injection of STZ at a dose of 65 mg/kg, and in rats with 30- and 210-day mild DM1 induced by three consecutive injections of STZ at medium doses (30–40 mg/kg). For this purpose in diabetic animals the levels of thyroid hormones and TSH and the functional activity of hormone-sensitive ACSS in membranes isolated from thyroid gland were studied. It was shown that in blood of rats with acute DM1 the levels of fT4, fT3, and tT3 were decreased by 45, 23 and 19%, respectively, while the level of TSH did not change significantly. In rats with the 30-day mild DM1 the concentration of fT4 was decreased by 32%, while the levels of tT4, tT3, and TSH were similar to that in control. In rats with prolonged mild DM1 after 150 and 210 days following the first treatment with STZ the levels of tT4, fT4, and tT3 were significantly reduced, but the concentration of TSH in rats with 210-day mild DM1 was increased by 119%. The results obtained in the study of thyroid status and TSH levels in rats with prolonged mild DM1 are in good agreement with the data obtained in the study of thyroid diseases in patients with DM1. It was found that the AC basal activity in the membranes isolated from the thyroid gland of diabetic rats did not change, except for the rats with the prolonged mild DM1 where this activity was increased by 21%. In all groups of diabetic rats the decrease of AC stimulating effects of GppNHp (10−5 M) and TSH (10−8 M) was found, and in the rats with prolonged mild DM1 the AC effect of PACAP-38 (10−6 M) was also reduced. The decrease of AC effect of TSH varied among different groups of the diabetic animals: in the rats with acute DM1 this effect was reduced by 46% and in the rats with 30- and 210-day mild DM1-by 18 and 34%. Thus, it was concluded that the key cause of the thyroid resistance to TSH under conditions of DM1 is a weakening of the signal transduction generated by TSH via the ACSS.

A change of hormonal regulation of adenylyl cyclase in epididymal adipose tissue of rats with experimental models of diabetes mellitus

One of the key causes of diabetes mellitus (DM) and its complications are hormonal disturbances in functioning of hormonal signaling systems, including the adenylyl cyclase signaling system (ACSS). The goal of this work was to study the functional state and hormonal sensitivity of ACSS in the epididymal adipose tissue of male rats in the 7-month model of mild type 1 DM (DM1), in the 18-month neonatal model of type 2 DM (DM2), and in the taken for comparison model of the 30-day acute DM1. It is shown for the first time that in adipocytes from the epididymal fat of rats with the studied DM models the basal AC activity and its stimulation by forskolin were decreased, which indicates a weakening of the catalytic function of the enzyme adenylyl cyclase (AC). Stimulation of AC by guanine nucleotides in DM changed to the lesser extent, which speaks in favor of preservation of functions of heterotrimeric G(s)-proteins in the epididymal fat. In rats with DM1 the sensitivity of AC of adipocytes to agonists of β-adrenergic receptors (β-AR), activators of lipolysis, remained practically unchanged, while in animals with DM2 the AC stimulating effects of β-AR-agonists were reduced or completely blocked, like in the case of β3-AR-agonist BRL-37344 and CL-316243. In adipocytes of rats with DM1 the AC inhibitory effect of N6-cyclopentyladenosine, agonist of type 1 adenosine receptors (Aden1R), an inhibitor of lipolysis, was attenuated, whe- reas in DM2 this effect was completely preserved. Thus, in the epididymal adipose tissue of rats with DM1 the antilipolytic AC cascades including Aden1R were decreased and the stimulation of AC by β-AR-agonists was preserved, whereas in rats with DM2 the β-AR-mediated AC cascades activating lipolysis were reduced, but Aden1R-mediated AC cascades inhibiting lipolysis did not change. The changes of hormonal regulation of ACSS in adipocytes from the epididymal fat lead to disturbances of the metabolic status of animal with DM1 and DM2 and should be considered in the diagnostics and treatment of DM and its complications.

The effect of long-term diabetes mellitus induced by treatment with streptozotocin in 6-week-old rats on functional activity of the adenylyl cyclase system

In type 1 diabetes mellitus (DM), changes occurring in the adenylyl cyclase signaling system (ACSS) are one of the key causes of complications of the disease. Since type 1 DM has been most often diagnosed in childhood and adolescence, the study of changes in ACSS in the early development of the disease is a genuine problem. For this, we developed a prolonged model of type 1 DM, which was induced by treatment of 6-week-old rats with moderate doses of streptozotocin (1.5M-DM), and studied the functional state of ACSS in the brain, myocardium, and testes of rats with this model of the disease 7 months after its start. The 1.5M-DM model was compared with the model that was induced by streptozotocin treatment of adult, 5-month-old animals (5M-DM). It was shown that, in 1.5M-DM, in the tissues of diabetic rats, the functional activity of ACSS sensitive to biogenic amines and polypeptide hormones was significantly changed. In rats with 1.5M-DM, the adenylate cyclase (AC) inhibitory effects of somatostatin (in all studied tissues), noradrenaline (in the myocardium and the brain), and agonists of type 1 serotonin receptor (in the brain) were weakened to the greatest degree. In the brain, the AC-stimulating effects of relaxin, isoproterenol, and agonists of Gs-protein-coupled serotonin receptors also decreased; in the myocardium, the corresponding effects of GppNHp, relaxin, and β-adrenergic agonists declined; and, in the testes, the AC effects of GppNHp and chorionic gonadotropin declined. When comparing the 1.5M-DM and 5M-DM models, the most pronounced differences between them were found in the effect of DM on hormonal regulation of ACSS in the brain, this being true both for AC-stimulating effects of dopamine and PACAP-38 and for AC-inhibiting effects of bromocriptine and somatostatin. These results indicate significant changes in hormonal regulation of the nervous, cardiovascular, and reproductive systems in rats with early induction of type 1 DM, in some cases more severe changes as compared with late model of 5M-DM. These changes may be the basis for development of diabetic cardiomyopathy, cognitive deficiency, and hypogonadotropic states, which are often detected in children and adolescents with type 1 DM.

Adenylyl cyclase signaling in the developing chick heart: the deranging effect of antiarrhythmic drugs.

The adenylyl cyclase (AC) signaling system plays a crucial role in the regulation of cardiac contractility. Here we analyzed the key components of myocardial AC signaling in the developing chick embryo and assessed the impact of selected β-blocking agents on this system. Application of metoprolol and carvedilol, two commonly used β-blockers, at embryonic day (ED) 8 significantly downregulated (by about 40%) expression levels of AC5, the dominant cardiac AC isoform, and the amount of Gsα protein at ED9. Activity of AC stimulated by forskolin was also significantly reduced under these conditions. Interestingly, when administered at ED4, these drugs did not produce such profound changes in the myocardial AC signaling system, except for markedly increased expression of Giα protein. These data indicate that β-blocking agents can strongly derange AC signaling during the first half of embryonic heart development.

The Functional State of Hormone-Sensitive Adenylyl Cyclase Signaling System in Diabetes Mellitus

Diabetes mellitus (DM) induces a large number of diseases of the nervous, cardiovascular, and some other systems of the organism. One of the main causes of the diseases is the changes in the functional activity of hormonal signaling systems which lead to the alterations and abnormalities of the cellular processes and contribute to triggering and developing many DM complications. The key role in the control of physiological and biochemical processes belongs to the adenylyl cyclase (AC) signaling system, sensitive to biogenic amines and polypeptide hormones. The review is devoted to the changes in the GPCR-G protein-AC system in the brain, heart, skeletal muscles, liver, and the adipose tissue in experimental and human DM of the types 1 and 2 and also to the role of the changes in AC signaling in the pathogenesis and etiology of DM and its complications. It is shown that the changes of the functional state of hormone-sensitive AC system are dependent to a large extent on the type and duration of DM and in experimental DM on the model of the disease. The degree of alterations and abnormalities of AC signaling pathways correlates very well with the severity of DM and its complications.