Structural-functional characteristics of the adenylyl cyclase signaling system regulated by biogenic amines and peptide hormones in muscles of the earthworm Lumbricus terrestris

It has been shown for the first time that biogenic amines (catecholamines and tryptophane derivatives) stimulate dose-dependently activity of adenylyl cyclase (AC) and GTP-binding of G-proteins in muscle of the skin-muscle sac of the earthworm Lumbricus terrestris. By efficiency of their stimulating action on the AC activity, biogenic amines can be arranged in the following sequence: octopamine > tyramine > tryptamine ≈ serotonin > dopamine > isoproterenol ≈ adrenalin. The sequence of efficiency of their action on GTP-binding is somewhat different: serotonin > tryptamine > octopamine > dopamine ≈ tyramine > adrenaline > isoproterenol. Sensitivity of AC and G-proteins in the worm muscle to biogenic amines is similar with that in smooth muscle of the mollusc Anodonta cygnea (invertebrates), but differs markedly by this parameter from the rat myocardium (vertebrates). It has also been revealed that AC in the worm muscle is regulated by peptide hormones, relaxin and somatostatin, whose action is comparable with that in the mollusc muscle, but much weaker that the action of these hormones on the rat myocardium AC activity. Use of Cterminal peptides of α-subunits of G-proteins of the stimulatory (385–394 Gαs) and inhibitory (346–355 Gαi2) types that disrupt selectively the hormonal signal transduction realized via Gsand Giproteins, respectively, allowed establishing that the AC-stimulating effects of relaxin, octopamine, tyramine, and dopamine in the worm muscle are realized via the receptors coupled functionally with Gs-protein; the AC-inhibiting effect of somatostatin is realized via the receptor coupled with Gi-protein, whereas serotonin and tryptamine activate both types of G-proteins.     

Disturbance of transduction of adenylyl cyclase-inhibiting hormonal signaling in the myocardium and brain of rats with experimental type 2 diabetes

Presently, our work, as well as that of other authors, has produced convincing evidence in favor of the idea that disturbances in hormonal signaling systems are one of the main causes of the development of pathological alterations and complications in diabetes. However, the molecular mechanisms underlying these disturbances remain practically unstudied, particularly in insulin-independent type 2 diabetes. Using a neonatal streptozotocin model of type 2 diabetes, whose duration was either 80 or 180 days, we studied changes in the functional activity of components of the hormone-regulated adenylyl cyclase (AC) signaling system in the myocardium and brain striatum of diabetic rats as compared with control animals. In diabetes, the G_i-realized process of transduction of the hormonal signal inhibiting AC activity has been shown to be markedly impaired. This is manifested as a decrease of the inhibitory effect of hormones on AC activity and an attenuation of their stimulation of the G-protein’s GTP-binding activity. In the case of noradrenaline (myocardium), the inhibitory pathway of the AC system regulation is completely suppressed, while the stimulatory pathway is preserved. An increase in the duration of diabetes development from 80 to 180 days leads to some decrease in the transduction of hormonal signals realized via G_i-proteins. The stimulatory effects of biogenic amines and relaxin on AC activity and GTP binding in the myocardium and brain of diabetic rats change relatively little, both in the 80-and in the 180-day diabetes. Thus, in the experimental type 2 diabetes, disturbances in G_i-protein coupled signal cascades are primarily observed, through which hormones realize their inhibition of AC activity.     

Reversal of defective G-proteins and adenylyl cyclase/cAMP signal transduction in diabetic rats by vanadyl sulphate therapy

Vanadium salts exhibit a wide variety of insulinomimetic effects. In the present studies, we have examined the modulation of G-protein levels and adenylyl cyclase activity in the liver of streptozotocin-induced chronic diabetic rats (STZD) by vanadyl sulfate treatment and compared it with that of insulin. The basal enzyme activity, as well as the stimulatory effects of guanine nucleotides, glucagon, N-Ethylcarboxamideadenosine (NECA), isoproterenol, forskolin and sodium fluoride (NaF) on adenylyl cyclase were significantly increased in STZ-D rat liver as compared to control. In addition, the levels of stimulatory (Gs) as well as inhibitory (Gi_-2 and Gi_-3) as determined by immunoblotting techniques were also significantly higher in the STZ-D rat liver, however, the inhibitory effects of oxotremorine and low concentration of GTPS on adenylyl cyclase were not different in the two groups. Vanadyl sulfate and insulin treatments restored the augmented basal enzyme activity, the stimulations exerted by stimulatory inputs on adenylyl cyclase and the G-protein levels to various degrees, however, vanadyl sulfate was more effective than insulin. In addition, unlike vanadyl sulfate, insulin was unable to improve the stimulation exerted by glucagon and isoproterenol on adenylyl cyclase activity in STZD rats. These results suggest that vanadyl sulfate mimics the effects of insulin to restore the defective levels of G-proteins and adenylyl cyclase activity. From these results it may be suggested that one of the mechanisms by which vanadyl sulfate improves the glucose homeostasis in STZ-D rats may be through its ability to modulate the levels of G-proteins and adenylyl cyclase signal transduction system.Abbreviations NECA N-ethylcarboxamideadenosine - Iso Isoproterenol - Glu Glucagon - FSK forskolin - GTPS guanosine 5-[-thio]triphosphate - Gs stimulatory guanine nucleotide regulatory protein - Gi inhibitory guanine nucleotide regulatory protein - STZ streptozotocin This work was supported by grants from Medical Research Council and Canadian Diabetes Association.     

Involvement of the adenylyl cyclase signaling system in the action of insulin and mollusk insulin-like peptide

Involvement of the adenylyl cyclase signaling system in the mechanism of action of the mammalian insulin and epidermal growth factor as well as of insulin-like peptide isolated from the bivalve mollusk Anodonta cygnea has been studied. It was shown for the first time that insulin and insulin-like peptide exert in vitro the GTP-dependent stimulating action on the adenylyl cyclase activity. Epidermal growth factor has an analogous effect. Effectiveness of the peptides decreased in the order insulin-like peptide > epidermal growth factor > insulin in the foot smooth muscles of A. cygnea and insulin > epidermal growth factor > insulin-like peptide in the skeletal muscles of rat.     

Streptozotocin model of diabetes mellitus in the mollusc <Emphasis Type="Italic">Anodonta cygnea</Emphasis>: functional state of the adenylyl cyclase mechanisms of action of insulin superfamily peptides and their effect on carbohydrate metabolism enzymes

In terms of development of evolutionary biomedicine using invertebrate animals as models for study of molecular grounds of various human diseases, for the first time the streptozotocin (ST) model of insulin-dependent diabetes in the mollusc Anodonta cygnea has been developed. This model is based on the following authors’ data: (1) redetection of insulin-related peptides (IRP) in mollusc tissues: (2) discovery of the adenylyl cyclase signal mechanism (ACSM) of action of insulin and other peptides of the insulin superfamily in tissues of mammals, human, and mollusc A. cygnea; (3) concept of molecular defects in hormonal signal systems as causes of endocrine diseases. Studies on the ST model have revealed in mollusc smooth muscle on the background of hyperglycemia at the 2nd, 4th, and 8th day after the ST administration a decrease of the ACSM response to activating action of insulin, IGF-1, and relaxin. These functional disturbances were the most pronounced at the 2nd day of development and rather less marked at the 4th and 8th day. Analysis of data on effect of hormonal and non-hormonal (NaF, GIDP, and forskolin) ACSM activators has shown that the causes of impair of signal-transducing function of this mechanism are (1) a hyperglycemia-induced increase of the basal AC activity and as a consequence—a decrease of the enzyme catalytic potentials in response to hormone; (2) a decrease of functions of G_s-protein and of its coupling with AC. Besides, administration of ST produced in the mollusc muscle an attenuation of regulation by insulin of carbohydrate metabolism enzyme (glucose-6-phosphate dehydrogenase, glycogensynthase). The pattern of disturbances in the studied parameters in the mollusc is very similar to that revealed by the authors in rat and human muscle tissues in type 1 diabetes.     

Histopathological changes in rat pancreas and skeletal muscle associated with high fat diet induced insulin resistance

The effects of a high fat diet on the development of diabetes mellitus, insulin resistance and secretion have been widely investigated. We investigated the effects of a high fat diet on the pancreas and skeletal muscle of normal rats to explore diet-induced insulin resistance mechanisms. Forty-four male Wistar rats were divided into six groups: a control group fed standard chow, a group fed a 45% fat diet and a group fed a 60% fat diet for 3 weeks to measure acute effects; an additional three groups were fed the same diet regimens for 8 weeks to measure chronic effects. The morphological effects of the two high fat diets were examined by light microscopy. Insulin in pancreatic islets was detected using immunohistochemistry. The homeostasis model assessment of insulin resistance index and insulin staining intensity in islets increased significantly with acute administration of high fat diets, whereas staining intensity decreased with chronic administration of the 45% fat diet. Islet areas increased significantly with chronic administration. High fat diet administration led to islet degeneration, interlobular adipocyte accumulation and vacuolization in the pancreatic tissue, as well as degeneration and lipid droplet accumulation in the skeletal muscle tissue. Vacuolization in the pancreas and lipid droplets in skeletal muscle tissue increased significantly with chronic high fat diet administration. We suggest that the glucolipotoxic effects of high fat diet administration depend on the ratio of saturated to unsaturated fatty acid content in the diet and to the total fat content of the diet.     

Alterations in 5-HT(1A) receptors and adenylyl cyclase response by trazodone in regions of rat brain

The in vivo effect of trazodone on the density of [(3)H]5-HT binding sites and 5-HT(1A) receptors and adenylyl cyclase (AC) response was studied in regions of rat brain. The chronic administration of trazodone (10 mg/Kg body wt, 40 days) resulted in a significant downregulation of [(3)H]5-HT binding sites and 5-HT(1A) receptors in cortex and hippocampus. Trazodone significantly (p < 0.0001) decreased the density of [(3)H]5-HT binding sites in cortex (42.6 +/- 3.6 fmol/mg protein, 65%) and hippocampus (12.6 +/- 1.6 fmol/mg protein, 87%) when compared to control values of 121.9 +/- 5.4 and 99.3 +/- 7.5 fmol/mg protein in these regions, respectively. Similarly there was a significant (p < 0.0001) decrease in the density of 5-HT(1A) receptors in both cortex (7.2 +/- 0.5 fmol/mg protein, 70%) and hippocampus (6.3 +/- 1.2 fmol/mg protein, 79%) when compared to control values of 24.2 +/- 2.1 and 30.6 +/- 3.7 fmol/mg protein, in these regions respectively. However, the affinity of [(3)H]5-HT to 5-HT binding sites (1.83 +/- 0.26 nM, p < 0.0001) and [(3)H]8-OH-DPAT to 5-HT(1A) receptors (0.60 +/- 0.06 nM, p < 0.05) was significantly decreased only in cortex when compared to the control K(d) values of 0.88 +/- 0.04 nM and 0.47 +/- 0.02 nM in these regions, respectively.The basal AC activity did not alter in treated rats, where as, the inhibition of forskolin-stimulated AC activity by 5-HT (10 microM) was significantly (p < 0.0001) decreased both in cortex (43%) and hippocampus (40%) when compared to control levels. In conclusion, chronic treatment with trazodone results in downregulation of 5-HT(1A) receptors in cortex and hippocampus along with concomitant increased AC response, suggesting the involvement of 5-HT(1A) receptor-mediated AC response in the mechanism of action of trazodone.     

Amylin evokes protein p20 phosphorylation and insulin resistance in rat skeletal muscle extensor digitorum longus

In the present study, we investigate effect of amylin on the insulin sensitivity of rat skeletal muscle extensor digitorum longus (EDL) using in vitro intact muscle incubation in combination with metabolic radioactive labeling. The molecular basis of the amylin action was further examined using proteomic analysis. In particular, proteins of interest were characterized using an integrated microcharacterization procedure that involved in-gel trypsin digestion, organic solvent extraction, high performance liquid chromatography separation, microsequencing and microsequence analysis. We found that amylin significantly decreased the insulin-stimulated glucose incorporation into glycogen (p < 0.01) and produced a protein spot of approximately 20 ku in size. This amylin responsive protein (hereby designated as amylin responsive protein 1, APR1) was identified to be protein p20. Moreover, ARP1 spots on gels were found to consistently produce a corresponding radioactive spot on X-ray films in ³²Pi but not in ³⁵S-methionine labeling experiments. In conclusion, our results showed that in vitro amylin concomitantly evoked the production of ARP1 and caused insulin resistance in EDL muscle. It is suggested that protein p20 may be involved in amylin signal transduction and the appearance of ARP1 may be a step in a molecular pathway leading to the development of insulin resistance. ARP1 might therefore be a useful molecular marker for amylin action, insulin resistance and Type 2 diabetes.     

Study of structural-functional arrangement of the adenylyl cyclase signaling mechanism of action of insulin-like growth factor 1 revealed in muscle tissue of representatives of vertebrates and invertebrates

Based on the earlier discovered by the authors adenylyl cyclase signaling mechanisms (ACSM) of action of insulin and relaxin, a study was performed of the existence of a similar action mechanism of another representative of the insulin superfamily-the insulin—like growth factor 1 (IGF-1) in the muscle tissue of vertebrates (rat) and invertebrates (mollusc). For the first time there was detected participation of ACSM in the IGF-1 action, including the six-component signaling cascade: receptor tyrosine kinase → Gi-protein (βγ-dimer) → phosphatidylinositol-3-kinase (PI-3K) → protein kinase Cζ (PKCζ) → Gs-protein → adenylyl cyclase. By structural-functional organization at postreceptor stages, it coincides completely with that of insulin and relaxin, which we revealed in rat skeletal muscle. In smooth muscle of the mollusc Anodonta cygnea this ACSM of action of IGF-1 has only one difference-the protein kinase C included in this mechanism is represented not by the PKCζ isoform, but by another isoform close to PKCε of the vertebrate brain. Earlier we revealed the same differences in muscles of this mollusc in the ACSM of action of insulin and relaxin.     

Beta-cell dysfunctions and insulin resistance in subjects with increased risk for type 2 diabetes mellitus

The aim of this study was to test if a beta-cell defect is associated to deterioration of glucose tolerance early during the natural history of the type 2 diabetes mellitus . In 41 overweight women, with macrosomic infants in their antecedent deliveries, measures of insulin response and insulin sensitivity were derived from a short (45 min) iv glucose test. The early (EIR) and the late (LIR) phase insulin responses and the insulin sensitivity index (Si) were calculated. According the response to 75 g oral glucose test the subjects were divided into two groups: Imparired glucose tolerance (IGT;n = 12), and normal glucose tolerance (NGT; n = 29). EIR was reduced in IGT group (14.9 ± 3.6 vs 37.0 ± 4.0; p< 0.002). Glucose tolerance during oral glucose tolerance test (OGTT), correlated inversly to EIR (r=-0.45; n=41; p< 0.01). A strong correlation of EIR to LIR (r=0.88; n = 41; p< 0.001) but no correlation between glucose tolerance and Si was found.     

Autophagic adaptations in diabetic cardiomyopathy differ between type 1 and type 2 diabetes

Little is known about the association between autophagy and diabetic cardiomyopathy. Also unknown are possible distinguishing features of cardiac autophagy in type 1 and type 2 diabetes. In hearts from streptozotocin-induced type 1 diabetic mice, diastolic function was impaired, though autophagic activity was significantly increased, as evidenced by increases in microtubule-associated protein 1 light chain 3/LC3 and LC3-II/-I ratios, SQSTM1/p62 (sequestosome 1) and CTSD (cathepsin D), and by the abundance of autophagic vacuoles and lysosomes detected electron-microscopically. AMP-activated protein kinase (AMPK) was activated and ATP content was reduced in type 1 diabetic hearts. Treatment with chloroquine, an autophagy inhibitor, worsened cardiac performance in type 1 diabetes. In addition, hearts from db/db type 2 diabetic model mice exhibited poorer diastolic function than control hearts from db/+ mice. However, levels of LC3-II, SQSTM1 and phosphorylated MTOR (mechanistic target of rapamycin) were increased, but CTSD was decreased and very few lysosomes were detected ultrastructurally, despite the abundance of autophagic vacuoles. AMPK activity was suppressed and ATP content was reduced in type 2 diabetic hearts. These findings suggest the autophagic process is suppressed at the final digestion step in type 2 diabetic hearts. Resveratrol, an autophagy enhancer, mitigated diastolic dysfunction, while chloroquine had the opposite effects in type 2 diabetic hearts. Autophagy in the heart is enhanced in type 1 diabetes, but is suppressed in type 2 diabetes. This difference provides important insight into the pathophysiology of diabetic cardiomyopathy, which is essential for the development of new treatment strategies.     

DNA methylation of loci within ABCG1 and PHOSPHO1 in blood DNA is associated with future type 2 diabetes risk

Identification of subjects with a high risk of developing type 2 diabetes (T2D) is fundamental for prevention of the disease. Consequently, it is essential to search for new biomarkers that can improve the prediction of T2D. The aim of this study was to examine whether 5 DNA methylation loci in blood DNA (ABCG1, PHOSPHO1, SOCS3, SREBF1, and TXNIP), recently reported to be associated with T2D, might predict future T2D in subjects from the Botnia prospective study. We also tested if these CpG sites exhibit altered DNA methylation in human pancreatic islets, liver, adipose tissue, and skeletal muscle from diabetic vs. non-diabetic subjects. DNA methylation at the ABCG1 locus cg06500161 in blood DNA was associated with an increased risk for future T2D (OR = 1.09, 95% CI = 1.02–1.16, P-value = 0.007, Q-value = 0.018), while DNA methylation at the PHOSPHO1 locus cg02650017 in blood DNA was associated with a decreased risk for future T2D (OR = 0.85, 95% CI = 0.75–0.95, P-value = 0.006, Q-value = 0.018) after adjustment for age, gender, fasting glucose, and family relation. Furthermore, the level of DNA methylation at the ABCG1 locus cg06500161 in blood DNA correlated positively with BMI, HbA1c, fasting insulin, and triglyceride levels, and was increased in adipose tissue and blood from the diabetic twin among monozygotic twin pairs discordant for T2D. DNA methylation at the PHOSPHO1 locus cg02650017 in blood correlated positively with HDL levels, and was decreased in skeletal muscle from diabetic vs. non-diabetic monozygotic twins. DNA methylation of cg18181703 (SOCS3), cg11024682 (SREBF1), and cg19693031 (TXNIP) was not associated with future T2D risk in subjects from the Botnia prospective study.     

Circadian rhythm of intracellular protein synthesis signaling in rat cardiac and skeletal muscles

Intracellular signaling exhibits circadian variation in the suprachiasmatic nucleus and liver. However, it is unclear whether circadian regulation also extends to intracellular signaling pathways in the cardiac and skeletal muscles. Here, we examined circadian variation in the intracellular mammalian target of rapamycin (mTOR)/70 kDa ribosomal protein S6 kinase 1 (p70S6K) and extracellular signal-regulated kinase (ERK) pathways, which regulate protein synthesis in rat cardiac and skeletal muscles. Seven-week-old male Wistar rats were assigned to six groups: Zeitgeber time (ZT) 2, ZT6, ZT10, ZT14, ZT18, and ZT22 (ZT0, lights on; ZT12, lights off). The cardiac, plantaris, and soleus muscles were removed after a 12-h fasting period, and signal transducers involved in protein synthesis (mTOR, p70S6K, and ERK) were analyzed by western blotting. Circadian rhythms of signal transducers were observed in both cardiac (mTOR, p70S6K, and ERK) and plantaris (p70S6K and ERK) muscles (p<0.05), but not in the soleus muscle. In the cardiac muscle, the phosphorylation rate of mTOR was significantly higher at ZT6 (peak) than at ZT18 (bottom), and the phosphorylation rate of p70S6K was significantly higher at ZT2 (peak) than at ZT18 (bottom). In contrast, in the plantaris muscle, the phosphorylation rate of ERK was significantly lower at ZT2 (bottom) than at ZT18 (peak). Our data suggested that protein synthesis via mTOR/p70S6K and ERK signaling molecules exhibits circadian variation in rat cardiac and fast-type plantaris muscles.     

锌转运蛋白8与1型和2型糖尿病的研究进展

ZnT8(zinc transporter,member8)是锌离子转运蛋白,主要定位于胰岛β细胞,能将胞浆锌离子转运至胰岛素储存/分泌性囊泡内,其转运功能降低会影响胰岛素合成、储存和分泌,能增加2型糖尿病(T2DM)的发病风险。ZnT8蛋白也可作为抗原引起β细胞自身免疫损伤,诱发1型糖尿病(T1DM)。ZnT8基因多态性是引起其锌离子转运功能和免疫原性变化的重要因素,与糖尿病的发生、发展密切相关。该文综述了ZnT8与T1DM和T2DM的研究进展,提示ZnT8可作为糖尿病防治的新药物靶点。     

Proteomic study of skeletal muscle in obesity and type 2 diabetes: progress and potential

ABSTRACT

Introduction: Skeletal muscle is the major site of insulin-stimulated glucose uptake and imparts the beneficial effects of exercise, and hence is an important site of insulin resistance in obesity and type 2 diabetes (T2D). Despite extensive molecular biology-oriented research the molecular mechanisms underlying insulin resistance in skeletal muscle remain to be established.

Areas covered: The proteomic capabilities have greatly improved over the last decades. This review summarizes the technical challenges in skeletal muscle proteomics studies as well as the results of quantitative proteomic studies of skeletal muscle in relation to obesity, T2D, and exercise.

Expert commentary: Current available proteomic studies contribute to the view that insulin resistance in obesity and T2D is associated with increased glycolysis and reduced mitochondrial oxidative metabolism in skeletal muscle, and that the latter can be improved by exercise. Future proteomics studies should be designed to markedly intensify the identification of abnormalities in metabolic and signaling pathways in skeletal muscle of insulin-resistant individuals to increase the understanding of the pathogenesis of T2D, but more importantly to identify multiple novel targets of treatment of which at least some can be safely targeted by novel drugs to treat and prevent T2D and reduce risk of cardiovascular disease.     

In vivo effects of insulin and bis(maltolato)oxovanadium (IV) on PKB activity in the skeletal muscle and liver of diabetic rats

In this study, the in vivo effects of insulin and chronic treatment with bis(maltolato)oxovanadium (IV) (BMOV) on protein kinase B (PKB) activity were examined in the liver and skeletal muscle from two animal models of diabetes, the STZdiabetic Wistar rat and the fatty Zucker rat. Animals were treated with BMOV in the drinking water (0.75–1 mg/ml) for 3 (or 8) weeks and sacrificed with or without insulin injection. Insulin (5 U/kg, i.v.) increased PKB activity more than 10fold and PKB activity more than 3fold in both animal models. Despite the development of insulin resistance, insulininduced activation of PKB was not impaired in the STZdiabetic rats up to 9 weeks of diabetes, excluding a role for PKB in the development of insulin resistance in type 1 diabetes. Insulin-induced PKB activity was markedly reduced in the skeletal muscle of fatty Zucker rats as compared to lean littermates (fatty: 7fold vs. lean: 14fold). In contrast, a significant increase in insulinstimulated PKBa activity was observed in the liver of fatty Zucker rats (fatty: 15.7fold vs. lean: 7.6fold). Chronic treatment with BMOV normalized plasma glucose levels in STZdiabetic rats and decreased plasma insulin levels in fatty Zucker rats but did not have any effect on basal or insulininduced PKB and PKB activities. In conclusion (i) in STZdiabetic rats PKB activity was normal up to 9 weeks of diabetes; (ii) in fatty Zucker rats insulininduced activation of PKB (but not PKB) was markedly altered in both tissues; (iii) changes in PKB activity were tissue specific; (iv) the glucoregulatory effects of BMOV were independent of PKB activity.     

Involvement of betagamma subunits of G(q/11) in muscarinic M(1) receptor potentiation of corticotropin-releasing hormone-stimulated adenylyl cyclase activity in rat frontal cortex

In the present study, we investigated the involvement of betagamma subunits of G(q/11) in the muscarinic M(1) receptor-induced potentiation of corticotropin-releasing hormone (CRH)-stimulated adenylyl cyclase activity in membranes of rat frontal cortex. Tissue exposure to either one of two betagamma scavengers, the QEHA fragment type II adenylyl cyclase and the GDP-bound form of the alpha subunit of transducin, inhibited the muscarinic M(1) facilitatory effect. Moreover, like acetylcholine (ACh), exogenously added betagamma subunits of transducin potentiated the CRH-stimulated adenylyl cyclase activity, and this effect was not additive with that elicited by ACh. Western blot analysis indicated the expression in frontal cortex of both type II and type IV adenylyl cyclases, two isoforms stimulated by betagamma subunits in synergism with activated G(s). The M(1) receptor-induced enhancement of the adenylyl cyclase response to CRH was counteracted by the G(q/11) antagonist GpAnt-2A but not by GpAnt-2, a preferential G(i/o) antagonist. In addition, the muscarinic facilitatory effect was inhibited by membrane preincubation with antiserum directed against the C terminus of the alpha subunit of G(q/11), whereas the same treatment with antiserum against either G(i1/2) or G(o) was without effect. These data indicate that in membranes of rat frontal cortex, activation of muscarinic M(1) receptors potentiates CRH-stimulated adenylyl cyclase activity through betagamma subunits of G(q/11).     

Effects of zinc supplementation in patients with type 1 diabetes

The purpose of this study was to identify the effect of oral zinc supplementation in patients with type 1 diabetes (T1DM) on metabolic control and zinc blood concentrations. The sample consisted of 20 patients with T1DM and a control group (n=17). Metabolic control was evaluated by glycemia at fast, 24 h glycosuria, and HbA1c. Zinc concentrations were measured in plasma and erythrocytes. After the first collection of biological material, oral zinc supplementation was initiated and continued for 4 mo in T1MD patients (T1). Daily dosages were established based on Dietary Recommended Intakes (DRIs), considering zinc intake based on data from other studies previously performed with this population. All analyses were repeated after supplementation (T2). Metabolic control was unsatisfactory, with an HbA1c increase at T2. There was no difference in zinc concentrations in plasma and erythrocytes between patients with T1DM and control. Zinc concentrations in plasma were within the normal range in T1MD before and after supplementation and the control. Zinc concentrations in erythrocyte presented lower than normal values for all groups. A zinc increase in erythrocyte after supplementation was observed in T1DM patients, although without statistical significance. More studies are needed to confirm oral zinc supplementation as nutritional management in diabetes.