Effect of cerebrocrast, a new long-acting compound on blood glucose and insulin levels in rats when administered before and after STZ-induced diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease that is characterized by selective destruction of insulin secreting pancreatic islets beta-cells. The formation of cytokines (IL-1beta, IL-6, TNF-alpha, etc.) leads to extensive morphological damage of beta-cells, DNA fragmentation, decrease of glucose oxidation, impaired glucose-insulin secretion and decreased insulin action and proinsulin biosynthesis. We examined the protective effect of a 1,4-dihydropyridine (DHP) derivative cerebrocrast (synthesized in the Latvian Institute of Organic Synthesis) on pancreatic beta-cells in rats possessing diabetes induced with the autoimmunogenic compound streptozotocin (STZ). Cerebrocrast administration at doses of 0.05 and 0.5 mg/kg body weight (p.o.) 1 h or 3 days prior to STZ as well as at 24 and 48 h after STZ administration partially prevented pancreatic beta-cells from the toxic effects of STZ, and delayed the development of hyperglycaemia. Administration of cerebrocrast starting 48 h after STZ-induced diabetes in rats for 3 consecutive days at doses of 0.05 and 0.5 mg/kg body weight (p.o.) significantly decreased blood glucose level, and the effect remained 10 days after the last administration. Moreover, in these rats, cerebrocrast evoked an increase of serum immunoreactive insulin (IRI) level during 7 diabetic days as compared to both the control normal rats and the STZ-induced diabetic control rats. The STZ-induced diabetic rats that received cerebrocrast had a significantly high serum IRI level from the 14th to 21st diabetic days in comparison with the STZ-induced diabetic control.The IRI level in serum as well as the glucose disposal rate were significantly increased after stimulation of pancreatic beta-cells with glucose in normal rats that received cerebrocrast, administered 60 min before glucose. Glucose disposal rate in STZ-induced diabetic rats as a result of cerebrocrast administration was also increased in comparison with STZ-diabetic control rats. Administration of cerebrocrast in combination with insulin intensified the effect of insulin. The hypoglycaemic effect of cerebrocrast primarily can be explained by its immunomodulative properties. Moreover, cerebrocrast can act through extrapancreatic mechanisms that favour the expression of glucose transporters, de novo insulin receptors formation in several cell membranes as well as glucose uptake.     

Effect of cerebrocrast on the lymphocyte blast transformation activity in normal and streptozotocin‐induced diabetic rats

Both IDDM and NIDDM are characterized by deviations in peripheral T and B lymphocyte count, T_helper:T_suppressor ratio, as well as by impaired T_suppressor function. These abnormalities may promote insulin antibody and other antibody production, contributing to overt diabetes mellitus development in early stage of the disease. In the present study we explored the effects of cerebrocrast (1,4‐dihydropyridine derivative) administration on Con A‐ and IL‐2‐stimulated tissue lymphocyte blast transformation activity and on the thymus and lymph node mass in normal and streptozotocin (STZ)‐induced diabetic rats. It was established that cerebrocrast, administered four times at the doses of 0·05 and 0·5 mg kg⁻¹, has long‐term (up to 14 days) effects on the immune system and protects against the toxic effect of STZ in STZ‐induced diabetic rats, preventing thymus and lymph node mass loss. We conclude that cerebrocrast administration leads to the increase in number and activity of T_helper and T_suppressor lymphocytes. Glycolysis and DNA synthesis in these cells is augmented under the influence of cerebrocrast administration. We propose that the increase in lymphocyte suppressive activity caused by cerebrocrast administration may prevent the development of IDDM and NIDDM in patients with pre‐diabetes, but in patients with early and overt diabetes mellitus the drug administration may prevent the overexpression of insulin antibodies and other antibodies. The effect of cerebrocrast on the de novo production of insulin and IL‐2 receptors may be beneficial for IDDM and NIDDM patients. Copyright © 1999 John Wiley & Sons, Ltd.     

Acute effect of antidiabetic 1,4-dihydropyridine compound cerebrocrast on cardiac function and glucose metabolism in the isolated, perfused normal rat heart

Diabetes mellitus (DM) is an important cardiovascular risk factor and is associated with abnormalities in endothelial and vascular smooth muscle cell function, evoked by chronic hyperglycemia and hyperlipidemia. Chronic insulin deficiency or resistance is marked by decreases in the intensity of glucose transport, glucose phosphorylation, and glucose oxidation, plus decreases in ATP levels in cardiac myocytes. It is important to search for new agents that promote glucose consumption in the heart and partially inhibit extensive fatty acid beta-oxidation observed in diabetic, ischemia. When the oxygen supply for myocardium is decreased, the heart accumulates potentially toxic intermediates of fatty acid beta-oxidation, that is, long-chain acylcarnitine and long-chain acyl-CoA metabolites. Exogenous glucose and heart glycogen become an important compensatory source of energy. Therefore we studied the effect of the antidiabetic 1,4-dihydropyridine compound cerebrocrast at concentrations from 10(-10) M to 10(-7) M on isolated rat hearts using the method of Langendorff, on physiological parameters and energy metabolism. Cerebrocrast at concentrations from 10(-10) M to 10(-7) M has a negative inotropic effect on the rat heart. It inhibits L-type Ca(2+)channels thereby diminishing the cellular Ca(2+) supply, reducing contractile activity, and oxygen consumption, that normally favors enhanced glucose uptake, metabolism, and production of high-energy phosphates (ATP content) in myocardium. Cerebrocrast decreases heart rate and left ventricular (LV) systolic pressure; at concentrations of 10(-10) M and 10(-9) M it evokes short-term vasodilatation of coronary arteries. Increase of ATP content in the myocytes induced by cerebrocrast has a ubiquitous role. It can preserve the integrity of the cell plasma membranes, maintain normal cellular function, and inhibit release of lactate dehydrogenase (LDH) from cells that is associated with diabetes and heart ischemia. Administration of cerebrocrast together with insulin shows that both compounds only slightly enhance glucose uptake in myocardium, but significantly normalize the rate of contraction and relaxation ( +/- dp/dt). The effect of insulin on coronary flow is more pronounced by administration of insulin together with cerebrocrast at a concentration of 10(-7) M. Cerebrocrast may promote a shift of glucose consumption from aerobic to anerobic conditions (through the negative inotropic properties), and may be very significant in prevention of cardiac ischemic episodes.     

Shorea roxburghii Leaf Extract Ameliorates Hyperglycemia Induced Abnormalities in High Fat/Fructose and Streptozotocin Induced Diabetic Rats

This study investigated the hypoglycemic effect of the methanol extract of Shorea roxburghii leaves (SRL) in high fat diet/high fructose solution (HFDHF) and streptozotocin (STZ) induced type 2 diabetes mellitus (T2DM) in rats as well as evaluating its ameliorative potentials in altered biochemical and hematological parameters in the treated rats. T2DM was induced in Sprague Dawley (SD) rats by feeding with HFDHF for 4 weeks and administering STZ (35 mg/kg, i. p.). Diabetic rats were given SRL extract at doses of 100 and 400 mg/kg for 30 days. The food and water intake were monitored on a daily basis, while the fasting blood glucose (FBG) levels and body weight were measured weekly. Biochemical and hematological parameters as well as histopathological studies of the pancreas were also evaluated. SRL significantly decreased FBG and improved the body weight, food and water intake of treated diabetic rats. Furthermore, biochemical and hematological parameters including liver and kidney function enzymes, lipid profiles, white blood and red blood cells parameters were markedly ameliorated by SRL. Histopathological analyses of the pancreas indicated reconstitution of β‐cells architecture in SRL treated rats. The results of this study suggest that SRL has antidiabetic potential and can be considered for the treatment of T2DM.     

Effect of new and known 1,4-dihydropyridine derivatives on blood glucose levels in normal and streptozotocin-induced diabetic rats

Analysis of the effect of several 1,4-DHP Ca(2+) channel antagonists on experimental and clinical diabetes shows that structurally similar Ca(2+) channel antagonists can exert opposite effects on Ca(2+) influx, glucose homeostasis and insulin secretion. The influence of the Ca(2+) channel antagonists on pancreatic beta cell functions is dependent on lipophilicity, interactions with the cell membrane lipid bilayer, with SNAREs protein complexes in cell and vesicle membranes, with intracellular receptors, bioavailability and time of elimination from several organs and the bloodstream. In the present work we studied the effect at several doses of new compounds synthesized in the Latvian Institute of Organic Synthesis on blood glucose levels in normal and STZ-induced diabetic rats. The compounds tested were: 1,4-DHP derivatives cerebrocrast (1), etaftoron (2), OSI-1190 (3), OSI-3802 (4), OSI-2954 (5) and known 1,4-DHP derivatives: niludipine (6), nimodipine (7) and nicardipine (8) which possess different lipophilicities. Analysis of the structure-function relationships of the effect of 1,4-DHP derivatives on glucose metabolism showed that cerebrocrast could evoke qualitative differences in activity. Insertion of an OCHF(2) group in position 2 of the 4-phenylsubstituent and propoxyethylgroup R in ester moieties in positions 3 and 5 of the DHP structure, as well as an increase in the number of carbon atoms in the ester moiety, significantly modified the properties of the compound. Thereby cerebrocrast acquired high lipophilicity and membranotropic properties. Cerebrocrast, in a single administration at low doses (0.05 and 0.5 mg x kg(-1), p.o.), significantly decreased the plasma level of glucose in normal rats and in STZ-induced diabetic rats returned plasma glucose to basal levels. This effect was characterized by a slow onset and a powerful long-lasting influence on glucose metabolism, especially in STZ-induced diabetic rats.     

Short‐Term Effects of Gastric Bypass Surgery on Circulating Ghrelin Levels

Objective: To prospectively evaluate the short‐term effects of Roux‐en‐Y gastric bypass (RYGBP) on ghrelin secretion and its relevance on food intake and body weight changes. Research Methods and Procedures: Ghrelin response to a standardized test meal was evaluated in eight obese patients (BMI, 43.5 to 59.1 kg/m²) before and 6 weeks after RYGBP. Ghrelin response was compared with that of an age‐matched group of six normal weight individuals (BMI, 19.6 to 24.9 kg/m²). Results: Fasting serum ghrelin levels were lower in obese subjects compared with controls (p < 0.05). Meal ingestion significantly suppressed ghrelin concentration in controls (p < 0.05) and obese subjects (p < 0.05), albeit to a lesser degree in the latter group (p < 0.05). Despite a 10.3 ± 1.5% weight loss, fasting serum ghrelin levels were paradoxically further decreased in obese subjects 6 weeks after RYGBP (p < 0.05). Moreover, at this time‐point, food intake did not elicit a significant ghrelin suppression. The changes in ghrelin secretion after RYGBP correlated with changes in insulin sensitivity (p < 0.05) and caloric intake (p < 0.05). Discussion: This study showed that the adaptive response of ghrelin to body weight loss was already impaired 6 weeks after RYGBP. Our study provides circumstantial evidence for the potential role of ghrelin in the negative energy balance in RYGBP‐operated patients.     

Liraglutide, a once-daily human glucagon-like peptide-1 analog, minimizes food intake in severely obese minipigs

Objectives: To evaluate the efficacy of liraglutide, a new, stable, once‐daily human analog of glucagon‐like peptide‐1, in a new animal model of obesity. Research Methods and Procedures: Liraglutide was administered subcutaneously once daily (7 μg/kg for 7 weeks) to six female obese Göttingen minipigs. Food intake and feeding patterns were monitored using a novel automated feeding system that allowed continuous recording of food intake. Results: Food intake was strongly suppressed. A steady‐state level of reduced food intake was achieved within 3 weeks and was maintained for the remaining 4 weeks of the treatment period. During the 4‐week steady‐state period with liraglutide treatment, daily food intake was 7.3 ± 0.3 megajoule (MJ) compared with 18.4 ± 0.6 MJ in the pre‐treatment period and 19.2 ± 0.5 MJ in the post‐treatment period (p < 0.001). The food intake in the treatment period was equivalent to the amount of food that would have been offered to normal‐weight pigs for maintenance. Body weight decreased 4.3 ± 1.2 kg (4% to 5%) during the 7 weeks of treatment and increased 7.0 ± 1.0 kg during the 7 weeks of post‐treatment (p < 0.01). Appetite suppression was quickly reversed within 4 days after termination of liraglutide administration. Discussion: Overall, liraglutide was well tolerated and had a profound and persistent anorectic effect that resulted in weight loss. These results, in conjunction with the previously established glucose‐lowering efficacy of liraglutide, suggest that the anorectic actions of liraglutide will be very important in clinical trials of both obese patients with type 2 diabetes and obese non‐diabetic patients.     

S 23521 Decreases Food Intake and Body Weight Gain in Diet‐Induced Obese Rats

Objective: To investigate the effect of S 23521, a new glucagon‐like peptide‐1‐(7‐36) amide analogue, on food intake and body weight gain in obese rats, as well as on gene expression of several proteins involved in energy homeostasis. Research Methods and Procedures: Lean and diet‐induced obese rats were treated with either S 23521 or vehicle. S 23521 was given either intraperitoneally (10 or 100 μg/kg) or subcutaneously (100 μg/kg) for 14 and 20 days, respectively. Because the low‐dose treatment did not affect food intake and body weight, the subcutaneous treatment at high dose was selected to test the effect on selected end‐points. Results: Treated obese rats significantly decreased their cumulative energy intake in relation to vehicle‐treated counterparts (3401 ± 65 vs. 3898 ± 72 kcal/kg per 20 days; p < 0.05). Moreover, their body weight gain was reduced by 110%, adiposity was reduced by 20%, and plasma triglyceride levels were reduced by 38%. The treatment also improved glucose tolerance and insulin sensitivity of obese rats. Regarding gene expression, no changes in uncoupling protein‐1, uncoupling protein‐3, leptin, resistin, and peroxisome proliferator‐activated receptor (PPAR)‐γ were observed. Discussion: S 23521 is an effective glucagon‐like peptide‐1‐(7‐36) amide analogue, which induced a decrease in energy intake, body weight, and adiposity in a rat model of diet‐induced obesity. In addition, the treatment also improved glucose tolerance and insulin sensitivity of obese rats. These results strongly support S 23521 as a putative molecule for the treatment of obesity.     

Leptin-Dependent Control of Glucose Balance and Locomotor Activity by POMC Neurons

Leptin plays a pivotal role in regulation of energy balance. Via unknown central pathways, leptin also affects peripheral glucose homeostasis and locomotor activity. We hypothesized that, specifically, pro-opiomelanocortin (POMC) neurons mediate those actions. To examine this possibility, we applied Cre-Lox technology to express leptin receptors (ObRb) exclusively in POMC neurons of the morbidly obese, profoundly diabetic, and severely hypoactive leptin receptor-deficient Lepr^db/db mice. Here, we show that expression of ObRb only in POMC neurons leads to a marked decrease in energy intake and a modest reduction in body weight in Lepr^db/db mice. Remarkably, blood glucose levels are entirely normalized. This normalization occurs independently of changes in food intake and body weight. In addition, physical activity is greatly increased despite profound obesity. Our results suggest that leptin signaling exclusively in POMC neurons is sufficient to stimulate locomotion and prevent diabetes in the severely hypoactive and hyperglycemic obese Lepr^db/db mice.     

Dietary linolenic acid and fasting glucose and insulin: the National Heart, Lung, and Blood Institute Family Heart Study

Objective: To assess whether dietary linolenic acid is associated with fasting insulin and glucose. Research Methods and Procedures: In a cross‐sectional design, we studied 3993 non‐diabetic participants of the National Heart, Lung, and Blood Institute Family Heart Study 25 to 93 years of age. Linolenic acid was assessed through a food frequency questionnaire, and laboratory data were obtained after at least a 12‐hour fast. We used generalized linear models to calculate adjusted means of insulin and glucose across quartiles of dietary linolenic acid. Results: From the lowest to the highest sex‐specific quartile of dietary linolenic acid, means ± standard error for logarithmic transformed fasting insulin were 4.06 ± 0.02 (reference), 4.09 ± 0.02, 4.13 ± 0.02, and 4.17 ± 0.02 pM, respectively (trend, p < 0.0001), after adjustment for age, sex, energy intake, waist‐to‐hip ratio, smoking, and high‐density lipoprotein‐cholesterol. When dietary linolenic acid was used as a continuous variable, the multivariable adjusted regression coefficient was 0.42 ± 0.08. There was no association between dietary linolenic acid and fasting glucose (trend p = 0.82). Discussion: Our data suggest that higher consumption of dietary linolenic acid is associated with higher plasma insulin, but not glucose levels, in non‐diabetic subjects. Additional studies are needed to assess whether higher intake of linolenic acid results in an increased insulin secretion and improved glucose use in vivo.     

Synthesis and evaluation of novel lipidated neuromedin U analogs with increased stability and effects on food intake

Neuromedin U (NMU) is a 25 amino acid peptide expressed and secreted in the brain and gastrointestinal tract. Data have shown that peripheral administration of human NMU decreases food intake and body weight and improves glucose tolerance in mice, suggesting that NMU receptors constitute a possible anti‐diabetic and anti‐obesity drug target. However, the clinical use of native NMU is hampered by a poor pharmacokinetic profile. In the current study, we report in vitro and in vivo data from a series of novel lipidated NMU analogs. In vitro plasma stability studies of native NMU were performed to investigate the proteolytic stability and cleavage sites using LC–MS. Native NMU was found to be rapidly cleaved at the C‐terminus between Arg²⁴ and Asn²⁵, followed by cleavage between Arg¹⁶ and Gly¹⁷. Lipidated NMU analogs were generated using solid‐phase peptide synthesis, and in vitro potency was investigated using a human embryonic kidney 293‐based inositol phosphate accumulation assay. All lipidated analogs had preserved in vitro activity on both NMU receptors with potency improving as the lipidation site was moved away from the receptor‐interacting C‐terminal octapeptide segment. In vivo efficacy was assessed in lean mice as reduction in food intake after acute subcutaneous administration of 1, 0.3, 0.1, and 0.03 µmol/kg. These lipidated NMU analogs prolonged the anorectic effect of NMU in a dose‐dependent manner. This was likely an effect of improved pharmacokinetic properties because of improved vitro plasma stability. Accordingly, the data demonstrate that lipidated NMU analogs may represent drug candidates for the treatment of obesity. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Effects of 1,4-dihydropyridine derivatives (cerebrocrast, gammapyrone, glutapyrone, and diethone) on mitochondrial bioenergetics and oxidative stress: a comparative study

The potential protective action of 1,4-dihydropyridine derivatives (cerebrocrast, gammapyrone, glutapyrone, and diethone) against oxidative stress was assessed on mitochondrial bioenergetics, inner membrane anion channel (IMAC), Ca2+-induced opening of the permeability transition pore (PTP), and oxidative damage induced by the oxidant pair adenosine diphosphate (ADP)/Fe2+ (lipid peroxidation) of mitochondria isolated from rat liver. By using succinate as the respiratory substrate, respiratory control ratio (RCR), ADP to oxygen ratio (ADP/O), state 3, state 4, and uncoupled respiration rates were not significantly affected by gammapyrone, glutapyrone, and diethone concentrations up to 100 microM. Cerebrocrast at concentrations higher than 25 microM depressed RCR, ADP/O, state 3, and uncoupled respiration rates, but increased three times state 4 respiration rate. The transmembrane potential (deltapsi) and the phosphate carrier rate were also decreased. At concentrations lower than 25 microM, cerebrocrast inhibited the mitochondrial IMAC and partially prevented Ca2+-induced opening of the mitochondrial PTP, whereas gammapyrone, glutapyrone, and diethone were without effect. Cerebrocrast, gammapyrone, and glutapyrone concentrations up to 100 microM did not affect ADP/Fe2+-induced lipid peroxidation of rat liver mitochondria, while very low diethone concentrations (up to 5 microM) inhibited it in a dose-dependent manner, as measured by oxygen consumption and thiobarbituric acid reactive substances formation. Diethone also prevented deltapsi dissipation due to lipid peroxidation initiated by ADP/Fe2+. It can be concluded that: none of the compounds interfere with mitochondrial bioenergetics at concentrations lower than 25 microM; cerebrocrast was the only compound that affected mitochondrial bioenergetics, but only for concentrations higher than 25 microM; at concentrations that did not affect mitochondrial bioenergetics (< or = 25 microM), only cerebrocrast inhibited the IMAC and partially prevented Ca2+-induced opening of the PTP; diethone was the only compound that expressed antioxidant activity at very low concentrations (< or = 5 microM). Cerebrocrast acting as an inhibitor of the IMAC and diethone acting as an antioxidant could provide effective protective roles in preventing mitochondria from oxidative damage, favoring their therapeutic interest in the treatment of several pathological situations known to be associated with cellular oxidative stress.     

The influence of long-term melatonin administration on basic physiological and metabolic variables of young Wistar:Han rats

The question of effects of long-term melatonin (MEL) administration have not yet been explained sufficiently, especially its metabolic consequences in young persons and animals. The aim of the present study was to analyze the effects of MEL given during prolonged time (for 3 months) and chronically (for 6 months) at the dose of 4 μg/mL of tap water, on the selected metabolic and hormonal parameters in young female and male Wistar:Han (WH) rats. The weights of selected organs, tissues, body weight gains and food and water intake were registered. Six weeks aged rats were adapted to standard housing conditions and light regimen L:D=12:12 h, fed standard laboratory diet and drank tap water (controls) or MEL solution ad libitum; finally they were sacrificed after overnight fasting. Prolonged MEL administration decreased serum glucose concentration and increased triacylglycerol and malondialdehyde concentration/content in the liver in females. In males MEL increased concentrations of serum phospholipids, corticosterone and liver malondialdehyde. MEL treatment reduced the body weight in both sexes and weight of epididymal fat in males, without any alterations of food and water intake. Chronic MEL administration reduced serum glucose concentration and increased concentration/content of glycogen, triacylglycerol and cholesterol in the liver and glycogen concentration/content in heart muscle in males. In females, the significant rise of serum corticosterone concentration and liver malondialdehyde content was recorded. MEL significantly increased liver weight and decreased thymus weight in males. MEL administration increased temporarily water intake in males, body and epididymal fat weights were similar to that in controls. Body weight of MEL drinking females was reduced in the 1^st half of experiment only; the food and water intake did not differ from control group. The response in WH rats on MEL was more prominent as in the Sprague-Dawley strain (our previous studies). Male rats were generally more affected, probably due to higher daily and total consumption of melatonin.     

Supplementation with a new trypsin inhibitor from peanut is associated with reduced fasting glucose,weight control,and increased plasma CCK secretion in an animal model

Ingestion of peanuts may have a beneficial effect on weight control, possibly due to the satietogenic action of trypsin inhibitors. The aim of this study was to isolate a new trypsin inhibitor in a typical Brazilian peanut sweet (paçoca) and evaluate its effect in biochemical parameters, weight gain and food intake in male Wistar rats. The trypsin inhibitor in peanut paçoca (AHTI) was isolated. Experimental diets were prepared with AIN-93G supplemented with AHTI. Animals had their weight and food intake monitored. Animals were anesthetized, euthanized, and their bloods collected by cardiac puncture for dosage of cholecystokinin (CCK) and other biochemical parameters. Supplementation with AHTI significantly decreased fasting glucose, body weight gain, and food intake. These effects may be attributed to increased satiety, once supplemented animals showed no evidence of impaired nutritional status and also because AHTI increased CCK production. Thus, our results indicate that AHTI, besides reducing fasting glucose, can reduce weight gain via food intake reduction.     

Effects of some 1,4‐dihydropyridine Ca antagonists on the blast transformation of rat spleen lymphocytes

Ca antagonists of different classes (verapamil, nifedipine, nicardipine, diltiazem) in a concentration of 10⁻⁵ m and higher are known to suppress Ca²⁺ transport into the lymphocyte cytosol, changing a normal response of lymphocytes to mitogens and antigens and so inhibiting their proliferation, as well as IL‐2‐induced cell proliferation, and their receptor expression on the surface of lymphocytes without cell cytotoxicity. In the present work we studied the effect of some 1,4‐dihydropyridines (DHP) such as nimodipine, nicardipine, nifedipine, niludipine, cerebrocrast, etaftoron, as well as metabolites of cerebrocrast: compounds 7 and 8, (four of the last were synthesized in the Latvian Institute of Organic Synthesis) on rat spleen isolated lymphocyte activation and proliferation in vitro following stimulation with the mitogens concanavalin A (Con A) and recombinant interleukin‐2 (IL‐2), insulin and insulin antibodies. Based on the experimental results we conclude that in low concentrations (10⁻⁷ to 10⁻⁹ M ) the tested 1,4‐DHP Ca antagonists stimulated the process of rat spleen lymphocyte proliferation and DNA synthesis, especially cerebrocrast. It is proposed that these Ca antagonists, as well as causing a concentration decrease of Ca²⁺, also activated phosphodiesterase, which in its turn, suppressed cAMP accumulation in the lymphocytes and eventually increased Ca²⁺ ion transport in the cells. Cerebrocrast among all the studied DHP Ca antagonists was the most potent in studies of activation of the lymphocytes in the presence of Con A, IL‐2 and insulin, which indicates the number of suppressor and helper lymphocytes and formation of insulin and interleukin receptors on their membrane surface. The increase in the lymphocyte suppressive activity produced by this compound effect can prevent diabetes mellitus types I and II at the stages of pre‐diabetes, early and distant diabetes, from hyperexpression of insulin and its receptor antibodies. Copyright © 1999 John Wiley & Sons, Ltd.     

Intracerebroventricular Glucocorticoid Infusion in Normal Rats: Induction of Parasympathetic‐Mediated Obesity and Insulin Resistance

Objective: The aims of the present study were to determine whether increased body weight resulting from intracerebroventricular (ICV) glucocorticoid (dexamethasone) infusion in normal rats is associated, as in obesity, with changes in glucose metabolism and to investigate whether the parasympathetic nervous system is involved in the glucocorticoid‐induced effects. Research Methods and Procedures: Male Sprague–Dawley rats were infused with ICV dexamethasone (2.5 μg/d) or its vehicle for 2 days during which food intake, body weight, and basal insulinemia were measured. Euglycemic–hyperinsulinemic clamps associated with the labeled 2‐deoxyglucose technique were then performed to determine the total rate of glucose disappearance and the tissue glucose use indices. Similar experiments were carried out in vagotomized rats. Results: Two days of ICV glucocorticoid infusion in normal rats resulted in increases in food intake, body weight, basal insulinemia, and produced decreases in the insulin‐stimulated total rate of glucose disappearance, as well as in glucose use indices of all muscle types studied. None of these alterations was observed when glucocorticoid infusion was carried out in vagotomized rats. Discussion: These data show that central glucocorticoid infusion favors anabolic processes, such as feeding behavior, body weight gain, and insulin output, while promoting muscle insulin resistance. These effects seem to be mediated by an activation of the parasympathetic nervous system, because they all disappear when tested in vagotomized rats.     

Effects of gastric bypass and gastric banding on glucose kinetics and gut hormone release

Background: Bariatric surgery markedly improves glucose homeostasis in patients with type 2 diabetes even before any significant weight loss is achieved. Procedures that involve bypassing the proximal small bowel, such as Roux‐en‐Y gastric bypass (RYGBP), are more efficient than gastric restriction procedures such as gastric banding (GB). Objective: To evaluate the effects of RYGBP and GB on postprandial glucose kinetics and gastro‐intestinal hormone secretion after an oral glucose load. Methods and Procedures: This study was a cross‐sectional comparison among non‐diabetic, weight‐stable women who had undergone RYGBP (n = 8) between 9 and 48 months earlier or GB (n = 6) from 25 to 85 months earlier, and weight‐ and age‐matched control subjects (n = 8). The women were studied over 4 h following ingestion of an oral glucose load. Total glucose and meal glucose kinetics were assessed using glucose tracers and plasma insulin, and gut hormone concentrations were simultaneously monitored. Results: Patients who had undergone RYGBP showed a a more rapid appearance of exogenous glucose in the systemic circulation and a shorter duration of postprandial hyperglycemia than patients who had undergone GB and C. The response in RYGBP patients was characterized by early and accentuated insulin response, enhanced postprandial levels of glucagon‐like peptide‐1 (GLP‐1) and polypeptide YY (PYY), and greater postprandial suppression of ghrelin. Discussion: These findings indicate that RYGBP is associated with alterations in glucose kinetics and glucoregulatory hormone secretion. These alterations are probably secondary to the anatomic rearrangement of the foregut, given the fact that they are not observed after GB. Increased PYY and GLP‐1 concentrations and enhanced ghrelin suppression are compatible with reduced food intake after RYGBP.     

Effects of Exendin‐4 Alone and With Peptide YY3–36 on Food Intake and Body Weight in Diet‐Induced Obese Rats

Significant weight loss following Roux‐en‐Y gastric bypass surgery (RYGB) in obese humans correlates with enhanced secretion of anorexigenic gut hormones glucagon‐like peptide‐1 (GLP‐1) and peptide YY_3–36 (PYY_3–36). Our aim here was to identify a dosing strategy for intraperitoneal (IP) infusion of GLP‐1 homologue exendin‐4 alone and with PYY_3–36 that produces a sustained reduction in daily food intake and body weight in diet‐induced obese (DIO) rats. We tested 12 exendin‐4 strategies over 10 weeks. Exendin‐4 infused during the first and last 3 h of the dark period at 15–20 pmol/h (0.15 nmol/kg/day) produced a sustained 24 ± 1% reduction in daily food intake for 17 days, and decreased body weight by 7%. In a separate group of DIO rats, none of seven dosing strategies combining exendin‐4 and PYY_3–36 produced a similar reduction in daily food intake for >10 days. The subsequent decline in efficacies of exendin‐4 alone and with PYY_3–36 on food intake and body weight in each experiment suggested possible receptor downregulation and tolerance to treatments. However, when treatments were discontinued for 1 day following losses in efficacies, daily food intake significantly increased. Together, these results demonstrate that (i) intermittent IP infusion of a low dose of exendin‐4 can produce a relatively prolonged reduction in daily food intake and body weight in DIO rats, (ii) co‐infusion of exendin‐4 and PYY_3–36 does not further prolong this response, and (iii) activation of an orexigenic mechanism gradually occurs to counteract the inhibitory effects of exendin‐4 alone and with PYY_3–36 on food intake and body weight.     

Viral mediated neuropeptide Y expression in the rat paraventricular nucleus results in obesity

Objective: Chronic central administration of neuropeptide Y (NPY) has dramatic effects on energy balance; however, the exact role of the hypothalamic paraventricular nucleus (PVN) in this is unknown. The aim of this study was to further unravel the contribution of NPY signaling in the PVN to energy balance. Research Methods and Procedures: Recombinant adeno‐associated viral particles containing NPY (rAAV‐NPY) were injected in the rat brain with coordinates targeted at the PVN. For three weeks, body weight, food intake, endocrine parameters, body temperature, and locomotor activity were measured. Furthermore, effects on insulin sensitivity and expression of NPY, agouti‐related protein (AgRP), and pro‐opiomelanocortin in the arcuate nucleus were studied. Results: Food intake was increased specifically in the light period, and dark phase body temperature and locomotor activity were reduced. This resulted in obesity characterized by increased fat mass; elevated plasma insulin, leptin, and adiponectin; decreased AgRP expression in the arcuate nucleus; and decreased insulin sensitivity; whereas plasma corticosterone was unaffected. Discussion: These data suggest that increased NPY expression targeted at the PVN is sufficient to induce obesity. Interestingly, plasma concentrations of leptin and insulin were elevated before a rise in food intake, which suggests that NPY in the PVN influences leptin and insulin secretion independently from food intake. This strengthens the role of the PVN in regulation of energy balance by NPY.     

Maternal zinc intake of Wistar rats has a protective effect in the alloxan-induced diabetic offspring

Zinc has a role in the synthesis, storage, and secretion of insulin, and has been suggested to be beneficial when used in the diabetic state. Effect of zinc intake in pregnant rats has been studied here on diabetized offspring. Pregnant rats were divided in two groups; the control group received normal food and water, and the experimental group received zinc sulfate during pregnancy and 3 weeks after offspring birth. Male offspring from the control (C) and experimental (E) groups were divided each in three groups: C1, fed with normal food and water; C2, diabetized with alloxan; C3, received zinc sulfate; E1, fed with normal food and water; E2, diabetized with alloxan; and E3, receiving zinc sulfate. After 30 days, the histological changes of pancreatic tissues were investigated by light microscopy. Body weight, blood glucose, serum insulin levels, food intake, water intake, and urine quantity were also compared between the groups. Water intake and urine quantity were decreased significantly (p?<?0.01and p?<?0.001) in E2 (experimental diabetic group) in comparison with C2 (control diabetic group), but there was no significant difference in the body weight in C2 in comparison with E2, while blood glucose was decreased significantly (p?<?0.001) and blood insulin level was increased significantly (p?<?0.01) in E2 in comparison with C2. Microscopic evaluation of pancreas showed that E2 were protected against alloxan-induced beta-cell degeneration. In conclusion, this work showed that maternal zinc intake may influence subsequent deleterious effects of diabetes on alloxan-diabetized offspring.