Lipocalin-2 counteracts metabolic dysregulation in obesity and diabetes.

Regulation of food intake is a recently identified endocrine function of bone that is mediated by Lipocalin-2 (LCN2). Osteoblast-secreted LCN2 suppresses appetite and decreases fat mass while improving glucose metabolism. We now show that serum LCN2 levels correlate with insulin levels and ß-cell function, indices of healthy glucose metabolism, in obese mice and obese, prediabetic women. However, LCN2 serum levels also correlate with body mass index and insulin resistance in the same individuals and are increased in obese mice. To dissect this apparent discrepancy, we modulated LCN2 levels in mice. Silencing Lcn2 expression worsens metabolic dysfunction in genetic and diet-induced obese mice. Conversely, increasing circulating LCN2 levels improves metabolic parameters and promotes ß-cell function in mouse models of ß-cell failure acting as a growth factor necessary for ß-cell adaptation to higher metabolic load. These results indicate that LCN2 up-regulation is a protective mechanism to counteract obesity-induced glucose intolerance by decreasing food intake and promoting adaptive ß-cell proliferation.

Aislamiento de componentes y efecto hipoglicemiante del extracto metanólico de albahaca (Ocium basilicum), en ratas C57bl/6 con hiperglicemia experimental / Isolation of components and hypoglycemic effect of methanolic basil extract (ocium basilicum) in C57bl/6 rats with experimental hyperglycemia

ResumenAntecedentes:la albahaca (Ocium basilicum) es una hierba perteneciente a la familia laminaceae, caracterizada por sus bondades medicinales. Se ha referido su uso en la terapéutica del cáncer, vitíiigo, hipercolesterolemia y la diabetes mellitus.Objetivo:evaluar el efecto hipoglicemiante del extracto metanólico de la albahaca, su aislamiento y purificación de sus principales compuestos.Métodos:las hojas y tallos fueron colectadas en el sector la Hechicera, estado Mérida, Venezuela.Las muestras se maceraron en 20L de metanol al 70% v/v, dosificándose a dosis crecientes entre 1,0 y 2,0 g/kg, usando como modelo experimental, ratas macho de la cepa C57BL/6, con hiperglicemia inducida con aloxano monohidratado. Se incluyó un control positivo usando como agente hipoglucemiante la sitagliptina (400μg/kg). El extracto se sometió a fraccionamiento mediante cromatografía de columna abierta, cuyas fracciones (175 ml cada una) se asociaron por similitud estructural y fueron dosificadas a la población en estudio. Se obtuvieron muestras sanguíneas seriadas de la vena de la base de la cola y se procesaron siguiendo el método de la glucosa oxidasa-peroxidasa.Resultados:se demostró una disminución de la concentración de glucosa sanguínea a la dosis de 2,0 g/kg (<120 mg/dL). Los análisis estructurales se realizaron mediante pruebas cromatográficas, espectroscópicas, espectrométricas y químicas. Del estudio se aislaron e identificaron los siguientes compuestos: nandecilato de metilo (C20O2H40); behenato de metilo (C23O2H46) hexacosanoato de metilo(C27O2H54), así como 18-metoxicarbonil-3,4-didehidroibogamina, el flavonoides 5,7,3´-trihydroxi-3,6,4´-trimetoxiflavona, los cuales son reportados por primera vez en los análisis fitoquímicos para O. basilicum.Conclusión:estos hallazgos sustentan el potencial uso de la albahaca como alternativa considerable en el tratamiento hipoglucemiante.

AbstractBackground:Basil (Ocium basilicum) is an herb belonging to the family laminaceae, characterized by its medicinal benefits. Its use has been referred for the treatment of cancer, vitiligo, hypercholesterolemia, and diabetes mellitus.Objective:to evaluate the hypoglycemic effect of the methanol extract of basil, isolation and purification of its main compounds.Methods:The leaves and stems were collected in the sector La Hechicera, Mérida, Venezuela State. Samples were macerated in 20L of methanol to 70% v/v, dosing to increaseddoses between 1.0 and2.0 g/kg, using as experimental model, male rats of the C57BL/6 strain with hyperglycemia induced with alloxan monohydrate. A positivecontrol was included using as a hypoglycemic agent sitagliptin (400μg/kg). The extract was submitted to fractionation by open column chromatography,, whose fractions (175 ml each) were partnered by structural similarity and were dosed to the population under study. Serial blood samples from the base of the tail vein were obtained and were processed using the method of the glucose oxidase-peroxidase.Results:they showed a decrease of the concentration of blood glucose at a dose of 2.0 g/kg (< 120 mg/dL). Structural analyses were conducted using chromatographic, spectroscopic, spectrometric and chemical tests. They were isolated from the study and the following compounds were identified: nandecilato of methyl (C20O2H40); methyl behenate (C23O2H46), methyl hexacosanoate (C27O2H54) as well as 18-methoxycarbonyl-3, 4-didehidroibogamina, 5,7,3´-trihydroxi-3,6,4´- trimetoxiflavona flavonoid, which are reported for the first time in the phytochemical analysis for O. basilicum.Conclusion:These findings support the potential use of Basil as a weed of traditional medicine in the hypoglycemic treatment.

Liver alpha-amylase gene expression as an early obesity biomarker.

BACKGROUND: Obesity is a major health problem worldwide, for which preventive and therapeutic means are still needed. Alpha-amylase is a digestive enzyme whose inhibition has been targeted as a potential anti-obesity strategy. However, alpha-amylase gene expression has not been particularly attended to, and in contrast with pancreatic and salivary amylases, fewer studies have focused on liver alpha-amylase. The present study aimed at investigating the expression of alpha-amylase gene in obese and normal mice at RNA and protein level as well as acarbose effect on this gene expression in hepatocyte cell culture. METHODS: Control and case groups were fed by normal mouse pellet and high-fat diet respectively, during 8 weeks. After this period, serum biochemical parameters including glucose, cholesterol, triglycerides, AST, ALT and alpha-amylase were assayed. Liver alpha-amylase gene was analyzed by real time PCR, and liver enzyme was assayed with Bernfeld and ELISA methods Hepatocyte cell culture derived from both group were also treated by acarbose and alpha-amylase activity and gene expression was analyzed by above mentioned methods. RESULTS: All biochemical factors showed an increase in obese mice, but the increase in ALT and AST were not statistically significant. Alpha-amylase levels were also increased in obese mice, both at RNA and protein level, while a decrease was seen in obese mice derived hepatocytes after acarbose treatment. CONCLUSIONS: Elevated liver alpha-amylase levels may be indicative of initial stages of obesity and the use of acarbose could be considered as a treatment of obesity which could be potentially effective at multiple levels.

Royal jelly improves hyperglycemia in obese/diabetic KK-Ay mice.

The study examined whether royal jelly (RJ) can prevent obesity and ameliorate hyperglycemia in type 2 diabetes. This study utilized obese/diabetic KK-Ay mice. RJ (10 mg/kg) was administered by oral gavage. Body weight, plasma glucose and insulin levels were measured. mRNA and protein levels were determined using quantitative reverse transcription polymerase chain reaction and western blotting, respectively. Four weeks of RJ administration improved hyperglycemia and partially suppressed body weight gain, although the latter effect did not reach statistical significance. In addition, RJ administration did not improve insulin resistance. RJ administration suppressed the mRNA expression of glucose-6-phosphatase (G6Pase), a key enzyme of gluconeogenesis, in the liver. Simultaneously, RJ administration induced adiponectin (AdipoQ) expression in abdominal fat, adiponectin receptor-1 (AdipoR1) expression in the liver and phosphorylated AMP-activated protein kinase (pAMPK) expression, which suppressed G6Pase levels in the livers of KK-Ay mice. pAMPK levels were also increased in skeletal muscle, but glucose transporter-4 (Glut4) translocation was not increased in the RJ supplementation group. The improvement in hyperglycemia due to long-term RJ administration may be because of the suppression of G6Pase expression through the upregulation of AdipoQ and AdipoR1 mRNA and pAMPK protein expressions.

MK-626, a dipeptidyl peptidase-4 inhibitor, does not improve the hyperglycemia or hyperinsulinemia of nonobese diabetic MKR mice.

Dipeptidyl peptidase-4 (DPP-4) inhibitors increase circulating levels of incretin hormones, which can enhance insulin secretion and ß cell function. The aim of this study was to evaluate the effectiveness of MK-626 (a novel DPP-4 inhibitor) to reduce the hyperglycemia and hyperinsulinemia of nonobese type 2 diabetic MKR mice. Twelve to 14-week-old hyperglycemic MKR mice were gavaged daily with MK-626 (3 mg/kg body weight) or vehicle (0.5% methyl cellulose (MC)) for 2 weeks. MK-626-treated mice displayed no change in body weight or adverse reactions, suggesting good tolerance of the drug. Fed blood glucose was significantly reduced over the 2-week experiment; however, it was also reduced in the MC group, suggesting an effect of gavage alone. Fed plasma insulin and glucagon levels and glucose tolerance of MK-626-treated mice were similar to those of MC mice. Therefore, treatment with MK-626 did not correct the prolonged hyperglycemia and impaired glucose tolerance of MKR mice.

Features of the metabolic syndrome in the Berlin Fat Mouse as a model for human obesity.

BACKGROUND: The Berlin Fat Mouse BFMI860 is a polygenic obesity mouse model which harbors a natural major gene defect resulting in early onset of obesity. To elucidate adult bodily responses in BFMI860 mice that develop juvenile obesity, we studied features of the metabolic syndrome at 20 weeks. METHODS: We examined fat deposition patterns, adipokines, lipid profiles in serum, glucose homeostasis, and insulin sensitivity in mice that were fed either a standard maintenance (SMD) or a high-fat diet (HFD). RESULTS: Like many obese humans, BFMI860 mice showed hyperleptinemia accompanied by hypoadiponectinemia already at SMD that was further unbalanced as a result of HFD. Furthermore, BFMI860 mice had high triglyceride concentrations. However, triglyceride clearance after an oral oil gavage was impaired on SMD but improved on HFD. The oral and intraperitoneal glucose as well as the insulin tolerance tests provided evidence for reduced insulin sensitivity under SMD and insulin resistance on HFD. BFMI860 mice can maintain normal glucose clearance over a wide range of feeding conditions according to an adaptation via increasing the insulin concentrations. CONCLUSIONS: BFMI860 mice show obesity, dyslipidemia, and insulin resistance as three major components of the metabolic syndrome. As these mice develop the described phenotype as a result of a major gene defect, they are a unique model for the investigation of genetic and pathophysiological mechanisms underlying the observed features of the metabolic syndrome and to search for potential strategies to revert the adverse effects under controlled conditions.

Whole blood aggregation and coagulation in db/db and ob/ob mouse models of type 2 diabetes.

Type 2 diabetes in humans is associated with a significant hypercoagulable state; however, the effects of this on stroke and cardiovascular disease are not completely understood. The genetic mutations in db/db and ob/ob mice produce metabolic abnormalities similar to type 2 diabetes, but little is known about their platelet or coagulation properties. The objective of this study was therefore to examine platelet function and coagulation in db/db and ob/ob mice to determine the degree of alteration induced by type 2 diabetes. Male db/db and ob/ob mice, 8-16 weeks old, and their respective genetic control mice were used for all experiments. To examine platelet function and coagulation, we measured ADP-induced whole blood aggregation at baseline and after inhibition with aspirin and fucoidan, whole blood coagulation by thromboelastography, and platelet CD61 expression by flow cytometry. Both db/db and ob/ob mice demonstrated significantly less ADP-induced whole blood aggregation compared with control mice (db/db mice, P < 0.001; ob/ob mice, P < 0.01). Aggregation was significantly inhibited with aspirin in all groups; however, fucoidan inhibited aggregation only in control mice. The db/db and ob/ob mice demonstrated significantly less maximal clot strength compared with control mice (P < 0.01), and ob/ob mice demonstrated premature clot fibrinolysis measured by thromboelastography. In conclusion, the db/db and ob/ob type 2 diabetes mouse models do not demonstrate a hypercoagulable state similar to humans with this disease. We caution their use for studying cardiovascular and cerebrovascular disease in the setting of type 2 diabetes.

Serum concentrations of resistin-like molecules beta and gamma are elevated in high-fat-fed and obese db/db mice, with increased production in the intestinal tract and bone marrow.

AIMS/HYPOTHESIS: Resistin and the resistin-like molecules (RELMs) comprise a novel class of cysteine-rich proteins. Among the RELMs, RELMbeta and RELMgamma are produced in non-adipocyte tissues, but the regulation of their expression and their physiological roles are largely unknown. We investigated in mice the tissue distribution and dimer formation of RELMbeta and RELMgamma and then examined whether their serum concentrations and tissue expression levels are related to insulin resistance. METHODS: Specific antibodies against RELMbeta and RELMgamma were generated. Dimer formation was examined using COS cells and the colon. RELMbeta and RELMgamma tissue localisation and expression levels were analysed by an RNase protection assay, immunoblotting and immunohistochemical study. Serum concentrations in high-fat-fed and db/db mice were also measured using the specific antibodies. RESULTS: The intestinal tract produces RELMbeta and RELMgamma, and colonic epithelial cells in particular express both RELMbeta and RELMgamma. In addition, RELMbeta and RELMgamma were shown to form a homodimer and a heterodimer with each other, in an overexpression system using cultured cells, and in mouse colon and serum. Serum RELMbeta and RELMgamma levels in high-fat-fed mice were markedly higher than those in mice fed normal chow. Serum RELMbeta and RELMgamma concentrations were also clearly higher in db/db mice than in lean littermates. Tissue expression levels revealed that elevated serum concentrations of RELMbeta and RELMgamma are attributable to increased production in the colon and bone marrow. CONCLUSIONS/INTERPRETATION: RELMbeta and RELMgamma form homo/heterodimers, which are secreted into the circulation. Serum concentrations of RELMbeta and RELMgamma may be a novel intestinal-tract-mediating regulator of insulin sensitivity, possibly involved in insulin resistance induced by obesity and a high-fat diet.

Hyperleptinemia of pregnancy associated with the appearance of a circulating form of the leptin receptor.

Leptin is a hormone produced in adipose cells that regulates energy expenditure, food intake, and adiposity. In mice, we observed that circulating leptin levels increase 20-40-fold during pregnancy. Pregnant ob/ob females had no detectable serum leptin, demonstrating that the heterozygous conceptus was not the source of the leptin. However, leptin RNA and protein levels in maternal adipose tissue were not elevated. The circulating leptin was in a high molecular weight complex, suggesting that the rise in leptin was due to expression of a binding protein. Indeed, quantitative assays of serum leptin binding capacity revealed a 40-fold increase, coincident with the rise in serum leptin. Leptin binding activity reached a capacity of 207 +/- 15 nmol/liter of serum at day 18 of gestation, and half-maximal binding was observed with approximately 3 nM leptin. The binding protein was purified and partially sequenced, revealing sequence identity to the extracellular domain of the leptin receptor. We found that the placenta produces large amounts of the OB-Re isoform of leptin receptor mRNA, which encodes a soluble binding protein. Thus, the extreme hyperleptinemia of late pregnancy is attributable to binding of the leptin by a secreted form of the leptin receptor made by the placenta.

Some physiological characteristics of (SLN X C3H/He)F1 obese mice.

(SLN x C3H/He)F1 mice of both sexes showed significantly heavier body weights than the parental strains associated with the higher food intake and an accumulation of adipose tissue in the subcutaneous and the abdominal regions. Furthermore, serum levels of free fatty acid and growth hormone of F1 mice were higher and lower, respectively, than those of the parental strains. The results indicate that the obesity of these F1 mice is ascribed to excess food intake and metabolic disorders and they are promising as an animal model for the study of several diseases related to obesity.

Plasma B-cell tropin (ACTH22-39) concentration in lean and obese (ob/ob) mice and lean and obese (fa/fa) Zucker rats.

A method has been developed for the measurement of plasma concentrations of Beta-cell tropin (BCT), which is a potent insulinotropic and lipogenic peptide secreted by the pituitary. The method was employed to compare plasma Beta-cell tropin concentrations between lean and genetically obese (ob/ob) mice and between lean and genetically obese (fa/fa) Zucker rats. The plasma concentration in lean mice was 0.17 +/- 0.02 (5)nmole/l (mean +/- SEM, n = 5), while that in obese (ob/ob) mice was significantly higher, being 2.88 +/- 1.13 (5)nmole/l. The plasma BCT concentration in Zucker rats was 0.14 +/- 0.02 (15)nmole/l, while that in obese Zucker (fa/fa) rats was significantly higher, being 1.69 +/- 0.72 (16)nmole/l. These results explain previously observed differences in the Beta-cell tropin-like biological activity in plasma from lean and obese animals, and support the hypothesis that the peptide has a role in the development of hyperinsulinaemia and obesity.

Serum lipoprotein and apolipoprotein profiles of the genetically obese ob/ob mouse.

The lipid transport system of 3-month-old male C57BL/6J obese (ob/ob) mice was investigated. Serum lipoproteins were separated by density gradient ultracentrifugation and characterized by their chemical and electrophoretic properties as well as their relative apolipoprotein contents, defined according to molecular weight and charge. Obese, ob/ob mice exhibited a marked hyperlipoproteinemia resulting from large increases in low-density lipoproteins (LDL, d 1.021-1.058 g/ml) and high-density lipoproteins (HDL, d 1.058-1.137 g/ml), particularly, the HDL2 subclass (d 1.058-1.109 g/ml). This increase in lipoproteins was entirely responsible for their hypercholesterolemia and hyperphospholipidemia. By contrast, these obese mice had a net decrease in very-low-density lipoproteins (VLDL, d less than 1.016 g/ml) and intermediate-density lipoproteins (IDL, d 1.016-1.021 g/ml), which accounted for their moderate hypotriglyceridemia. The chemical composition of heterogeneous light LDL (d 1.021-1.040 g/ml and dense LDL (d 1.040-1.058 g/ml) overlapped by HDL-like particles was highly modified. These modifications consisted of increases in the percentages of cholesteryl ester and phospholipid and decreases in that of triacylglycerol. There were also marked changes in the relative values of the apolipoproteins of VLDL, but principally, IDL and LDL. IDL and light LDL were poorer in apolipoproteins BH (Mr 340,000-320,000) and eventually in apolipoprotein BL (Mr 220,000-200,000) and enriched in apolipoproteins E (Mr 37,000-35,000) and C-A-II (Mr approximately equal to 12,000). A similar and very significant change occurred in VLDL for both the apolipoproteins BL and C-A-II. Dense LDL, mainly poorer in apolipoprotein BH and enriched in apolipoprotein A-I (Mr 28,000-27,000), closely resembled HDL2 in all the groups, and were enriched in apolipoproteins C-A-II in only the obese mice. We suggest that ob/ob mice are probably protected against atheromata because of the low VLDL and IDL levels, and the increase in HDL2.

Repeated electroconvulsive shock normalizes blood glucose levels in genetically obese mice (C57BL/6J ob/ob) but not in genetically diabetic mice (C57BL/KsJ db/db).

There are several conflicting reports on the effect of electroconvulsive shock (ECS) on diabetes in humans. The present study investigated the effect of repeated ECS on blood glucose levels in genetically obese mice, which are considered an animal model for non-insulin dependent (maturity onset) diabetes. These mice were compared with genetically diabetic mice which are thought to be an animal model for insulin-dependent (juvenile-type) diabetes. A marked decrease in blood glucose concentrations was observed in obese mice after the first ECS which lasted for 14 days after the last ECS. No effect was seen in genetically diabetic mice. The neural mechanisms by which ECS normalizes blood glucose in genetically obese mice are discussed.

Altered shape and size of red blood cells in obese hyperglycaemic mice.

Red blood cells (RBCs) from hyperglycaemic ob/ob-mice, normoglycaemic controls, and a healthy man were sucked into a narrow capillary, photographed and measured. Mouse RBCs had a smaller diameter than human ones. Although of normal diameter, the ob/ob-mouse RBCs exhibited increased area and volume, and more frequently than control RBCs had a minimum cylindrical diameter greater that 3 micron. Cross-sectional profiles with minimum bending resistance were computed for RBCs of mean area and volume. The diameters of these theoretical profiles agreed closely with those empirically observed, in both mice and man. The profile of ob/ob-mouse RBCs predicted a greater resistance to corpuscle bending than the control profile. It is concluded that changes in shape and size explain the decreased filtrability of diabetic ob/ob-mouse RBCs. The results also suggest that the actually occuring smooth biconcavity is in general the RBC shape with maximum flexibility.

Decreased deformability of erythrocytes in hyperglycaemic non-inbred ob/ob mice.

The deformability of erythrocytes from non-inbred ob/ob mice and lean controls was analyzed by filtration through Nuclepore polycarbonate under constant pressure. At the age of 1-2 months there was no difference in erythrocyte filtrability between the two types of mice, whereas from 3 months the ob/ob mouse erythrocytes exhibited a markedly decreased deformability. The filtrability of erythrocytes was sensitive to osmotic pressure (NaCl or glucose). However, the difference between normal and ob/ob mouse erythrocytes was not due to acute osmotic effects of the hyperglycaemia in the ob/ob mice. When filtration was performed in the same glucose concentration as that recorded in the blood of the erythrocyte-donor animal, the difference in filtrability between adult normal and ob/ob mice remained large and significant (p less than 0.01). Moreover, the most pronounced hyperglycaemia occurred in young ob/ob mice with normal erythrocyte filtrability. It is suggested that non-inbred ob/ob mice are a useful model for studying the damaging influence of diabetes on erythrocyte deformability.

The influence of plasma insulin concentrations on tissue insulin levels in rodents: a study of the diabetic Chinese hamster and the ob/ob mouse.

Immunoreactive insulin was measured in acid-ethanol extracts of kidney, brain, liver, and heart from genetically diabetic Chinese hamsters and their nondiabetic controls and from obese (ob/ob) mice and their thin littermates. Selected samples were filtered on Sephadex G-50 columns and the insulin concentration determined. There was a good correlation between the insulin level measured in the acid-ethanol extracts of tissues and the insulin level after gel filtration, suggesting that the concentration measured in the whole extract is representative of the true insulin content. The present data demonstrate that different extrapancreatic organs contain characteristic amounts of insulin that are often (sometimes several-fold) higher than the insulin level of plasma. The tissue insulin concentrations also exhibit a wide range of values, with occasional high values. The data also show a direct correlation between plasma and kidney insulins but no relationship between plasma and brain insulins and a mixed correlation among plasma and liver and heart insulins.

Differential changes in islet lysosomal enzyme activities in aging obese hyperglycemic mice.

The pattern of pancreatic islet lysosomal enzyme activities was investigated in adult obese mice (aged 5-7 months), old obese mice (aged 9-17 months) and aged-matched old "obese" mice suffering from excessive weight loss. A series of lean NMRI mice of comparable age was included as controls. It was observed that the islet activity of the glucose producing glycogenolytic hydrolase, acid amyloglucosidase, was excessively high in the adult obese mouse, being about 10 times higher than in the adult lean mouse. This high activity was reduced by about 65% in the islets of old obese mice and by about 80% in old mice suffering from weight loss. When glycogen and maltose were compared as substrates for the alpha-1,4-glucoside splitting activity, the ratio, glycogen splitting/maltose splitting activity in adult obese mice (1.68) showed amyloglucosidase predominance, whereas the ratio in old obese mice (0.67), and in old mice suffering from weight loss (0.79) revealed a significant change in this relation. The extremely elevated plasma insulin levels in the adult obese mice were reduced by about 65% in old obese mice and by about 95% in old mice with excessive weight loss and thus displaying the same pattern as islet amyloglucosidase activity. Further, in normoglycemic obese mice a highly significant correlation (r = 0.85; p less than 0.001) was found between islet acid amyloglucosidase activity and the actual insulin secretory rate as reflected by the plasma insulin concentrations. The activity of islet N-acetyl-beta-D-glucosaminidase showed an activity pattern opposite to that of acid amyloglucosidase.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal thyroid hormone binding to serum proteins in ob/ob and db/db genetically obese mice.

Sera from ob/ob and db/db genetically obese mice exhibited abnormal nonspecific (no antibody present) binding measurements in T4 and T3 RIAs employing dextran-charcoal separations. They also showed decreased charcoal uptake compared to sera of lean controls in a conventional charcoal T4 uptake binding test. After correction for the abnormal nonspecific binding and after extraction of serum, mean serum T4 concentrations were similar in control and ob/ob mice. Mean serum T3 concentrations differed significantly (85 ng/dl in controls and 178 ng/dl in ob/ob) when a correction for altered binding in the T3 assay was made, but not when extracted serum was assayed (109 ng/dl in lean and 124 ng/dl in ob/ob). Dialyzable fractions of T4 and T3 were significantly reduced in both ob/ob and db/db mice. Free T4 concentrations were 0.82 +/- 0.05 (+/- SE) ng/dl in control and 0.61 +/- 0.05 ng/dl in ob/ob sera (P less than 0.01). Polyacrylamide gel electrophoresis showed increased binding of tracer T4 and T3 in ob/ob and db/db sera to a postalbumin with mobility similar to that of human T4-binding globulin. In ob/ob sera, this appeared to result from an increased binding capacity of the postalbumin. After in vivo iv injection of tracer T4 and T3 to ob/ob and lean control mice, analysis of tissue and plasma radioactivity showed that, except for T4 in cerebral cortex, tissue to plasma T4 and T3 ratios were lower in cerebral cortex, cerebellum, and liver of ob/ob mice. In summary, these data show increased binding of T4 and T3 to a postalbumin in two strains of genetically obese mice and, in the ob/ob strain, complex relationships between tissue and serum concentrations of thyroid hormones.

Classically conditioned hyperglycemia in the obese mouse.

The obese (C57BL/6J ob/ob) mouse is a commonly used animal model of non-insulin-dependent diabetes mellitus. It has recently been demonstrated that this mouse is not consistently hyperglycemic, however, unless it is subjected to environmental stress. In the present study, hyperglycemia in obese mice was induced by classical conditioning. Obese diabetic mice and lean control animals were exposed to shaking stress. All animals developed hyperglycemia in response to shaking. To demonstrate classical conditioning, some obese and lean animals were exposed to a metronome prior to and during the shaking. Other animals were exposed to the metronome and shaking in a noncontingent fashion and one group of animals was exposed to the metronome without any exposure to shaking. All animals received seven exposures to one of the three above conditions over a 3-day period. On the 4th day all animals were exposed to the metronome alone, following which blood samples were drawn. Classical conditioning of stress hyperglycemia was demonstrated in obese, but not in lean, mice.

Anti-hyperglycaemic action of BRL 26830, a novel beta-adrenoceptor agonist, in mice and rats.

BRL 26830, (R*,R*)-(+/-)-methyl 4-[2-[(2-hydroxy-2-phenylethyl)amino] propyl] benzoate, is a new orally active anti-hyperglycaemic agent. In 24 hr-fasted rats and mice, BRL 26830 decreased the blood glucose concentration following the administration of a subcutaneous glucose load. It also improved oral and intravenous glucose tolerance in 24 hr-fasted rats and decreased the post-prandial blood glucose concentration following the consumption of the complete, milk-based, meal "Nutrament". BRL 26830 produced a dose-related increase in the plasma insulin concentration and since it was inactive in lowering blood glucose in streptozotocin-diabetic rats, it is likely that its acute action on glucose tolerance was through the stimulation of insulin secretion. In contrast to the sulphonylurea, glibenclamide, BRL 26830 had no effect on the blood glucose concentration in 5 hr-fasted rats and only produced a transient reduction in 24 hr-fasted rats. BRL 26830 did not improve glucose tolerance when given acutely to hyperinsulinaemic C57BL/6 ob/ob mice. However, chronic treatment of these mice with BRL 26830 for 14-43 days resulted in a significant improvement in glucose tolerance.