Age- and diabetes-associated alterations in regional brain norepinephrine concentrations and adrenergic receptor populations in C57BL/KsJ mice

The Association between Hepatic Encephalopathy and Diabetic Encephalopathy: The Brain-Liver Axis

Hepatic encephalopathy (HE) is one of the main consequences of liver disease and is observed in severe liver failure and cirrhosis. Recent studies have provided significant evidence that HE shows several neurological symptoms including depressive mood, cognitive dysfunction, impaired circadian rhythm, and attention deficits as well as motor disturbance. Liver disease is also a risk factor for the development of diabetes mellitus. Diabetic encephalopathy (DE) is characterized by cognitive dysfunction and motor impairment. Recent research investigated the relationship between metabolic changes and the pathogenesis of neurological disease, indicating the importance between metabolic organs and the brain. Given that a diverse number of metabolites and changes in the brain contribute to neurologic dysfunction, HE and DE are emerging types of neurologic disease. Here, we review significant evidence of the association between HE and DE, and summarise the common risk factors. This review may provide promising therapeutic information and help to design a future metabolic organ-related study in relation to HE and DE.

Evaluation of the neuro-protective effect of Artemisia judaica extract in a murine diabetic model

Chronic hyperglycemia is associated with several negative outcomes including neuronal injury. Medicinal plants supplementation has been widely applied to treat or decrease diabetic complications. Here, the possible neuroprotective effect of Artemisia judaica extract (AjE. 300 mg kg^-1  day^-1 ) against neuronal deficits in diabetes model induced by high-fat diet (HFD) administration and streptozotocin (STZ, 30 mg/Kg) injection in rats was investigated. Diabetic rats showed a disturbance in the neuronal redox homeostasis as confirmed by the elevated lipoperoxidation and nitric oxide formation along with the decreased antioxidant molecules. In addition, a state of neuroinflammation and apoptosis were recorded in the brain tissue in diabetic rats. Furthermore, HFD/STZ provoked neurochemical alterations. However, AjE administration was found to abrogate significantly the neuronal impairments associated with diabetes. This neuroprotective effect comes from its strong antioxidant, anti-inflammatory, antiapoptotic, and neuromodulatory activity; suggesting that AjE may be applied to alleviate neurological impairments in diabetic patients. PRACTICAL APPLICATIONS: Diabetes mellitus (DM) is a metabolic disorder characterized by high blood glucose level comes from the dysregulation of insulin production and/or its action. The persisted hyperglycemia is correlated with the progression of several physical complications including renal, hepatic, vascular, retinal, and neuronal dysfunction. Artemisia is used in the nutritional and medicinal proposes due to the enriched bioactive molecules such as essential oil, flavonoids, phenolics, sesquiterpenoids, triterpenoids, and artemisinin. And we found that Artemisia judaica extract (AjE) administration was able to abrogate significantly the neuronal impairments associated with diabetes. This neuroprotective effect comes from its strong antioxidant, anti-inflammatory, anti-apoptotic and neuromodulatory activity; suggesting that AjE may be applied to alleviate neurological impairments in diabetic patients.

The functional state of hormone-sensitive adenylyl cyclase signaling system in diabetes mellitus

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

Contribution of single-minded 2 to hyperglycaemia-induced neurotoxicity

Diabetes mellitus is associated to central nervous system damage, which results in impairment of brain functions and cognitive deficits and decline in memory. However, the mechanisms mediating the actions of glucose on the neurons remained elusive. Single-minded 2 (Sim2), a basic helix-loop-helix (bHLH)-PAS transcriptional repressor, is thought to be involved in some symptoms of Down syndrome. We hypothesized that Sim2 mediated hyperglycaemia-induced neuronal injury and impairment of learning and memory. It was found that expression of Sim2 protein in cortical neurons was increased in streptozotocin-induced diabetes mellitus rat model. Drebrin, down-regulated by Sim2, was subsequently decreased as detected by confocal laser scanning microscopy and Western blot analysis. The expression pattern of Sim2 and Drebrin correspond to 50mmol/L glucose (hyperglycaemia) was also found in primary cultured neurons. Curcumin, one neuroprotective agent, inhibited hyperglycaemia-induced neurotoxicity. Moreover, curcumin alleviated Sim2 expression, and reversely raised Drebrin expression in neurons treated with hyperglycaemia. Finally, we found that silencing Sim2 expression decreased hyperglycaemia-induced neuronal injury. In conclusion, Sim2 may mediate neurotoxicity during hyperglycaemia and thereby play a critical role in the development of hyperglycaemia-induced cognitive deficits.

Hypercytolipidemia-induced nuclear lipoapoptosis: cytochemical analysis and integrated review of hypogonadal, diabetes-obesity syndrome-induced female reproductive axis disruption

Expression of the diabetes (db/db) mutation (i.e., leptin receptor defect) in C57BL/KsJ mice results in the functional suppression of the female pituitary-gonadal axis accompanied by premature utero-ovarian lipocytoatrophy. The current studies define the cytostructural, metabolic and endocrine disturbances associated with hypercytolipidemia and coincident nuclear lipoapoptosis following expression of the db/db-mutation. Adult, female C57BL/KsJ control (+/+ and +/? genotypes) and db/db mutant littermates were monitored for systemic alterations in blood glucose, insulin, luteinizing hormone (LH) and 17-B-estradiol (E2) concentrations associated with db/db-enhanced cytolipid depositions and TUNEL-labeled 3'-DNA fragmentation indexed nuclear lipoapoptosis. Obesity, hyperglycemia and hyperinsulinemia, in addition to depressed LH and E2 concentrations, characterized all db/db-mutants relative to control indices. Structural and cytochemical analysis of basophilic gonadotroph cells, ovarian follicular granulosa cells and uterine endometrial epithelial layers indicated that db/db mutants demonstrated prominent hypercytolipidemia relative to control cytoarchitecture profiles. Vasolipidemia and interstitial cytoadiposity were prominent in all db/db tissue compartments. In each affected cell type within the db/db pituitary-reproductive tract axis, hypercytolipidemia was localized with pronounced nuclear lipo-infiltration and 3'-DNA TUNEL-labeled fragmentation. These data indicate that coincident cytostructural, endocrine and metabolic disturbances associated with hypogonadal pituitary-reproductive tract hypercytolipidemia are functional manifestations of the expressed diabetes-obesity syndrome in db/db-mutants. The progressive vaso-, interstitial-, and cyto-lipidemic alterations in cytoarchitecture correlated with the coincident nuclear lipoapoptotic dissolution and pronounced organo-involution, alterations which contributed to the functional disruption of the pituitary-hypogonadal axis in C57BL/KsJ-db/db mice.

Curcumin modulates dopaminergic receptor, CREB and phospholipase C gene expression in the cerebral cortex and cerebellum of streptozotocin induced diabetic rats

Curcumin, an active principle component in rhizome of Curcuma longa, has proved its merit for diabetes through its anti-oxidative and anti-inflammatory properties. This study aims at evaluating the effect of curcumin in modulating the altered dopaminergic receptors, CREB and phospholipase C in the cerebral cortex and cerebellum of STZ induced diabetic rats. Radioreceptor binding assays and gene expression was done in the cerebral cortex and cerebellum of male Wistar rats using specific ligands and probes. Total dopaminergic receptor binding parameter, B_max showed an increase in cerebral cortex and decrease in the cerebellum of diabetic rats. Gene expression studies using real time PCR showed an increased expression of dopamine D1 and D2 receptor in the cerebral cortex of diabetic rats. In cerebellum dopamine D1 receptor was down regulated and D2 receptor showed an up regulation. Transcription factor CREB and phospholipase C showed a significant down regulation in cerebral cortex and cerebellum of diabetic rats. We report that curcumin supplementation reduces diabetes induced alteration of dopamine D1, D2 receptors, transcription factor CREB and phospholipase C to near control. Our results indicate that curcumin has a potential to regulate diabetes induced malfunctions of dopaminergic signalling, CREB and Phospholipase C expression in cerebral cortex and cerebellum and thereby improving the cognitive and emotional functions associated with these regions. Furthermore, in line with these studies an interaction between curcumin and dopaminergic receptors, CREB and phospholipase C is suggested, which attenuates the cortical and cerebellar dysfunction in diabetes. These results suggest that curcumin holds promise as an agent to prevent or treat CNS complications in diabetes.

Neuroprotective role of curcumin in the cerebellum of streptozotocin-induced diabetic rats

AIMS

Chronic hyperglycaemia in diabetes involves a direct neuronal damage caused by intracellular glucose which leads to altered neurotransmitter functions and reduced motor activity. The present study investigated the effect of curcumin in the functional regulation of muscarinic and alpha7 nicotinic acetylcholine receptors, insulin receptors, acetylcholine esterase and Glut3 in the cerebellum of streptozotocin (STZ)-induced diabetic rats.

MAIN METHODS

All studies were done in the cerebellum of male Wistar rats. Radioreceptor binding assays were done for total muscarinic, M(1) and M(3) receptors using specific ligands, and the gene expression was also studied using specific probes.

KEY FINDINGS

Our results showed an increased gene expression of acetylcholine esterase, Glut3, muscarinic M1, M3, alpha7 nicotinic acetylcholine and insulin receptors in the cerebellum of diabetic rats in comparison to control. Scatchard analysis of total muscarinic, M1 and M3 receptors showed an increased binding parameter, B(max) in diabetic rats compared to control. Curcumin and insulin inhibited diabetes-induced elevation in the gene expression of acetylcholine esterase, Glut3, insulin and cholinergic receptors in the cerebellum of diabetic rats.

SIGNIFICANCE

Our studies suggest that curcumin plays a vital role in regulating the activity of cholinergic and insulin receptors and mechanism of glucose transportation through Glut3, which results in normalizing the diabetes-mediated cerebellar disorders. Thus, curcumin has a significant role in a therapeutic application for the prevention or progression of diabetic complications in the cerebellum.

Muscarinic M(1), M(3) receptors function in the brainstem of streptozotocin induced diabetic rats: their role in insulin secretion from the pancreatic islets as a function of age

In the present study, we have investigated acetylcholine esterase (AChE) activity and muscarinic M(1), M(3) receptors kinetics in the brainstem of both young and old streptozotocin induced and insulin treated diabetic rats (D + I). Also, the functional role of acetylcholine and muscarinic receptors in insulin secretion from the pancreatic islets was studied in vitro. 90 week old control rats showed decreased V(max) (P < 0.001) for AChE compared to 7 week old control rats. V(max) was decreased (P < 0.001) in 7 week diabetic groups whereas 90 week old diabetic groups showed increased (P < 0.001) V(max) when compared to their respective controls. Binding studies using [(3)H]QNB and [(3)H]DAMP of 90 week old control showed significant increase in the B(max) (P < 0.001) and K(d) (P < 0.01) of muscarinic M(1) receptors whereas M(3) receptor number was decreased significantly (P < 0.001) with no change in affinity when compared to 7 week old control respectively. M(1) receptor number was decreased significantly (P < 0.001) whereas M(3) receptor number was increased significantly (P < 0.001) in both 7 week and 90 week old diabetic rat groups compared to their respective controls. The competition curve for [(3)H]QNB fitted for two sited model in 7 week old groups whereas fitted for one sited model in 90 week old groups. [(3)H]DAMP was fitted for two sited model in both 7 week and 90 week old groups. Insulin treatment significantly reversed (P < 0.001) the binding parameters to near control level. In vitro studies showed that acetylcholine through muscarinic M(1) and M(3) receptors stimulated insulin secretion from the pancreatic islets. Thus our studies suggest that both brainstem and pancreatic muscarinic M(1), M(3) receptors differentially regulate the cholinergic activity and insulin secretion which will have clinical significance in the management of diabetes and insulin treatment as a function of age.

Effects of experimentally induced diabetes mellitus on pharmacologically and electrically elicited myometrial contractility

1. Diabetes is one of the most frequent complications of gestation, affecting approximately 7% of pregnancies. However, little is known about its effects on electrically and pharmacologically stimulated myometrial contractility. The aim of the present study was to investigate the consequences of streptozotocin (STZ)-induced diabetes on: (i) electrical field stimulation (EFS)-evoked contraction of isolated uterine rings as a function of gestational age; and (ii) the uterotonic and tocolytic actions of α- and β-adrenoceptor stimulation, respectively. The effects of oxytocin in late pregnancy were also investigated. 2. During pregnancy, EFS-evoked contractions of isolated uterine rings from intact rats declined, whereas isolated uterine rings from diabetic rats exhibited continuously low sensitivity to EFS. 3. In non-pregnant rats, diabetes resulted in increased noradrenaline-mediated contractility and a decreased relaxation response to terbutaline. At the mRNA level, diabetes enhanced the expression of α1B-adrenoceptors in non-pregnant rats from 14.65 to 18.39 μg/mL (P < 0.05), whereas the expression of α1D-adrenoceptors decreased (from 42.87 to 35.67 μg/mL; P < 0.05). During pregnancy, the responses to these sympathomimetics did not differ between diabetic and intact rats. 4. In late pregnancy (on Days 15 and 21), oxytocin caused greater maximum contractility of uterine rings from diabetic rats without affecting the EC(50). In addition, on Day 15 of pregnancy, the expression of oxytocin receptors in the myometrium of diabetic rats was higher than that in intact rats. 5. The results of the present study indicate that experimental diabetes facilitates gestation-induced denervation and increases myometrial sensitivity to oxytocin in late pregnancy. If similar mechanisms operate in humans, this could contribute to a tendency to premature uterine contractions in diabetes-complicated pregnancies.

Influences of diabetes (db/db), obese (ob/ob) and dystrophic (dy/dy) genotype mutations on hind limb bone maturation: a morphometric, radiological and cytochemical indices analysis

The influences of single-gene missense mutations expressing diabetes (db/db), obese (ob/ob) or dystrophia (dy/dy) dysregulated metabolic syndromes on hind limb bone maturation and cytodevelopment in C57BL/KsJ mice were evaluated by radiological, macro- and cytomorphometric analysis of the resulting variances in os coxae, femur and tibia osteodevelopment indices relative to control parameters between 8 and 16 weeks of age. Associated with obesity and hyperglycaemic/hyperinsulinaemic states, both db/db and ob/ob mutants demonstrated significant suppression of hind limb maturation (length) and cytodensity indices relative to control growth parameters. By contrast, skeletal growth suppression induced by dy/dy mutation expression was associated with lean body mass and normoglycaemic/hypoinsulinaemic systemic endometabolic indices. In both db/db and ob/ob mutation syndromes, osteovascular, -interstitial and -cytolipidaemia were prominent cytochemical aberrations of the osteopaenic states relative to the dyslipidaemia/fibrodysplasia characteristic of dy/dy osteomaturation. Between 8 and 16 weeks of age, both ob/ob and db/db groups demonstrated extensive cortical interstitial (laminal) osteolipidaemia and suppressed cytodensities compared to control indices. These data demonstrate that the abnormal hyperglycaemic/hyperinsulinaemic endometabolic states associated with the expression of db/db and ob/ob genomutations promote extensive lipidaemia-induced osteopaenia, compromising hind limb osteomaturation and cytodensity indices, as compared to the hyperfibritic osteopaenia characteristic of dy/dy mutation syndromes. Recognized therapeutic modulation of the hypercytolipidaemic component of diabetes-obesity syndromes may prove to be effective towards amelioration of the deleterious influences of these expressed hyperglycaemic, dysregulated lipometabolic conditions on osteomaturation and cytodevelopment.

Hypercytolipidemia-induced cellular lipoapoptosis: Cytostructural and endometabolic basis of progressive organo-involution following expression of diabetes (db/db) and obese (ob/ob) mutation syndromes

Onset expression of Type 2 (NIDDM) diabetes and obesity metabolic syndromes (DOS) are characterized by premature, progressive cytoatrophy and organo-involution induced by dysregulated cellular gluco- and lipo-metabolic cascades. The consequential systemic, interstitial and intracellular hyperlipidemia disrupts normal cytointegrity and metabolic responsivity to the established hypercaloric pericellular environments. The sequential cytostructural, metabolic and endocrine disturbances associated with the development of progressive DOS-associated hypercytolipidemia compromises cellular metabolic response cascades and promotes cytochemical disturbances which culminate with nuclear lipoapoptosis and cytoatrophy. The dramatic alterations in interstitial glucose and lipid (free fatty acids/triglycerides) concentrations are recognized to influence interstitial and cytoplasmic microchemical environments, which markedly alter cellular nutrient diffusion and active trans-membrane flux rates. The progressive exacerbation of interstitial and cytoplasmic lipid imbibition has been demonstrated to be associated with DNA fragmentation by lipo-infiltration into the chromatin matrix, inducing structural disruption and physical dissolution, indexed as nuclear lipoapoptosis. Therapeutic reduction of the severity of hypercytolipidemia-induced structural and cytochemical compromise promotes the restoration of homeostatic metabolic support for normalized cytostructural indices and supportive cellular gluco- and lipo-metabolic cascades. The re-establishment of a homeostatic interstitial microenvironment moderates the severity of cytolipidemic compromise within affected cell types, reduces nuclear lipo-infiltration and DNA lipo-dissolution, resulting in the preservation of cytostructural integrity. Through the therapeutic restoration of extra- and intra-cellular microchemical environments in genetically dysregulated metabolic syndrome models, the coincident cytochemical, endocrine and metabolic disturbances associated with progressive hypercytolipidemia, resulting from the expressed systemic hypercaloric environmental and hepato-pancreatic endometabolic disturbances which characterize Type 2 (NIDDM) diabetes-obesity and metabolic (X) syndromes, may be ameliorated.

Enhanced β-adrenergic receptors in the brain and pancreas during pancreatic regeneration in weanling rats

Adrenergic stimulation has an important role in the pancreatic beta-cell proliferation and insulin secretion. In the present study, we have investigated how sympathetic system regulates the pancreatic regeneration by analyzing Epinephrine (EPI), Norepinephrine (NE) and beta-adrenergic receptor changes in the brain as well as in the pancreas. EPI and NE showed a significant decrease in the brain regions, pancreas and plasma at 72 hrs after partial pancreatectomy. We observed an increase in the circulating insulin levels at 72 hrs. Scatchard analysis using [(3)H] propranolol showed a significant increase in the number of both the low affinity and high affinity beta-adrenergic receptors in cerebral cortex and hypothalamus of partially pancreatectomised rats during peak DNA synthesis. The affinity of the receptors decreased significantly in the low and high affinity receptors of cerebral cortex and the high affinity hypothalamic receptors. In the brain stem, low affinity receptors were increased significantly during regeneration whereas there was no change in the high affinity receptors. The pancreatic beta-adrenergic receptors were also up regulated at 72 hrs after partial pancreatectomy. In vitro studies showed that beta-adrenergic receptors are positive regulators of islet cell proliferation and insulin secretion. Thus our results suggest that the beta-adrenergic receptors are functionally enhanced during pancreatic regeneration, which in turn increases pancreatic beta-cell proliferation and insulin secretion in weanling rats.

Influences of obese (ob/ob) and diabetes (db/db) genotype mutations on lumber vertebral radiological and morphometric indices: skeletal deformation associated with dysregulated systemic glucometabolism

Background

Both diabetes and obesity syndromes are recognized to promote lumbar vertebral instability, premature osteodegeneration, exacerbate progressive osteoporosis and increase the propensity towards vertebral degeneration, instability and deformation in humans.

Methods

The influences of single-gene missense mutations, expressing either diabetes (db/db) or obese (ob/ob) metabolic syndromes on vertebral maturation and development in C57BL/KsJ mice were evaluated by radiological and macro-morphometric analysis of the resulting variances in osteodevelopment indices relative to control parameters between 8 and 16 weeks of age (syndrome onset @ 4 weeks), and the influences of low-dose 17-B-estradiol therapy on vertebral growth expression evaluated.

Results

Associated with the indicative genotypic obesity and hyper-glycemic/-insulinemic states, both db/db and ob/ob mutants demonstrated a significant (P ≤ 0.05) elongation of total lumbar vertebrae column (VC) regional length, and individual lumbar vertebrae (LV1-5) lengths, relative to control VC and LV parameters. In contrast, LV1-5 width indices were suppressed in db/db and ob/ob mutants relative to control LV growth rates. Between 8 and 16 weeks of age, the suppressed LV1-5 width indices were sustained in both genotype mutant groups relative to control osteomaturation rates. The severity of LV1-5 width osteosuppression correlated with the severe systemic hyperglycemic and hypertriglyceridemic conditions sustained in ob/ob and db/db mutants. Low-dose 17-B-estradiol therapy (E2-HRx: 1.0 ug/ 0.1 ml oil s.c/3.5 days), initiated at 4 weeks of age (i.e., initial onset phase of db/db and ob/ob expressions) re-established control LV 1–5 width indices without influencing VC or LV lengths in db/db groups.

Conclusion

These data demonstrate that the abnormal systemic endometabolic states associated with the expression of db/db and ob/ob genomutation syndromes suppress LV 1–5 width osteomaturation rates, but enhanced development related VC and LV length expression, relative to control indices in a progressive manner similar to recognized human metabolic syndrome conditions. Therapeutic E2 modulation of the hyperglycemic component of diabetes-obesity syndrome protected the regional LV from the mutation-induced osteopenic width-growth suppression. These data suggest that these genotype mutation models may prove valuable for the evaluation of therapeutic methodologies suitable for the treatment of human diabetes- or obesity-influenced, LV degeneration-linked human conditions, which demonstrate amelioration from conventional replacement therapies following diagnosis of systemic syndrome-induced LV osteomaturation-associated deformations.

Structural, metabolic and endocrine analysis of the diabetes (db/db) hypogonadal syndrome: relationship to hypophyseal hypercytolipidemia

Expression of the diabetes (db/db) mutation in C57BL/KsJ mice results in functional suppression of the female pituitary-gonadal axis accompanied by premature utero-ovarian cytolipoatrophy. Cellular gluco- and lipo-metabolic disturbances promoted by the db/db systemic hyperglycemic-hyperinsulinemic state suppress pituitary gonadotropin release in response to gonadotropin-releasing hormone and gonadal steroid stimulation and results in a hypogonadal-infertility syndrome. Adult female C57BL/KsJ control (+/+ and +/? genotypes) and db/db littermates were monitored for associations in systemic and cellular alterations in luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadal steroid (binding) levels, and pituitary glucometabolic indices associated with db/db-enhanced lipid imbibition and cytostructural disruption. Obesity, hyperglycemia, and hyperinsulinemia characterized all db/db mutants relative to controls. Serum and pituitary progesterone and estradiol concentrations were suppressed in db/db mutants, in association with serum LH and FSH levels, but not with pituitary LH and FSH concentrations, which were comparable between groups. Pituitary insulin receptor binding and glucose utilization rates were suppressed in db/db groups relative to +/? indices. Structural and cytochemical analysis of anterior (AP), intermediate (IL), and neuro-(NP) hypophyseal lobes demonstrated prominent hypercytolipidemia in db/db mutants relative to controls. Prominent cytolipidemia was localized within well-granulated basophilic gonadotrophs and within IL and NP pituicytes. Vasolipidemia and interstitial cytoadiposity were prominent throughout all db/db pituitary lobes. Thus, disturbances associated with pituitary hypercytolipidemia are functional components of the expressed diabetes-associated hypogonadal syndrome in db/db mutants. Progressive alterations in hypophyseal cytoarchitecture are correlated with suppression of pituitary metabolic and endocrine indices, alterations that contribute to functional disruption of the pituitary-hypogonadal axis in C57BL/KsJ-db/db mice.

Estrogenic restoration of functional pancreatic islet cytoarchitecture in diabetes (db/db) mutant C57BL/KsJ mice: relationship to estradiol localization, systemic glycemia, and persistent hyperinsulinemia

The diabetes (db/db) genotype mutation induces a hyperglycemic-hyperinsulinemic endometabolic state in C57BL/KsJ mice, manifesting a type 2 NIDDM diabetes-obesity syndrome (DOS) in this hyperphagic, leptin receptor (lf) defective model. The severity of the DOS induced by the single gene, homozygous-recessive mutation may be therapeutically moderated by gonadal steroids and pre-steroidal metabolites. The current studies define the estradiol (E2)-modulated phenotypic, systemic, cytochemical, and cellular metabolic responses to db/db mutation expression as compared to littermate control (+/?) indices. The db/db mutation induced dramatic age- and DOS severity-related increases in body weights, blood glucose, and serum insulin concentrations relative to +/? indices between 4-week-old (i.e., initial onset stage of DOS phenotype) and 16-week-old (i.e., chronic stage of DOS) groups. Chronic, low-dose (0.1 microg/3.5 days) E2 treatment (E2-HRx) significantly reduced the obesity mass and blood glucose levels of db/db mutants relative to oil-HRx groups. Similarly, E2-HRx maintained pancreatic glucose utilization rates and pancreatic tissue weights in db/db mutants to near +/? indices. Concurrent amelioration of db/db-enhanced pancreatic lipogenesis and islet hypercytolipidemia occurred following E2-HRx. Pancreatic islet lipo-deposition was markedly reduced in db/db mutants following E2-HRx, and the restoration of islet size and cellular insulin concentrations correlated with beta-cell cytoplasmic regranulation of insulin secretory vesicles. In chronic E2-HRx db/db groups, autoradiographic localization of (3)H-E2 was demonstrated in the nuclear compartments of regranulated, nonhypertrophic islet cell populations, including insulin-containing beta-cells. In chronic E2-HRx db/db mutants, beta-cell insulin granulation was prominent in mildly hypertrophic pancreatic islets, with cytodistribution patterns and concentrations comparable to normal +/? indices. In contrast, E2-HRx maintained the systemic hyperinsulinemia characteristic of oil-HRx db/db mutants. The results of these studies indicate that the severity of the type 2 NIDDM endometabolic syndrome induced by the db/db genotypic mutation may be influenced by E2-HRx, including reduction of the islet hypercytolipidemia and hypertrophic atrophy which are indicators of impending pancreatic involution in this mutant model. The hypercytolipidemia-induced demise of beta-cell cytoarchitecture was reduced by E2-HRx, including the reestablishment of islet beta-cell cytogranulation. These data suggest that the severity of genomic db/db-mutation expression may be modified by E2-HRx, with the gonadal steroid probably acting as a nuclear-specific stimulatory transcriptional modulator of cellular glucometabolic cascades in the absence of leptin-directed homeostatic influences.

Cytochemical Analysis of Pancreatic Islet Hypercytolipidemia following Diabetes (db/db) and Obese (ob/ob) Mutation Expression: Influence of Genomic Background

Both diabetes (db/db) and obese (ob/ob) genotype mutations induce a hyperglycemic-hyperinsulinemic endometabolic state in C57BL mice, manifesting a type II NIDDM diabetes-obesity syndrome (DOS) in these leptin ligand/receptor-deficient models. The severity of the DOS induced by these single gene, homozygous-recessive mutations may be moderated by the background genome on which the mutation is expressed. The current studies define the phenotypic, systemic, cytochemical and cellular metabolic responses to db/db and ob/ob mutation expression when modified by /KsJ (severe DOS expression) or /6 (modified DOS expression) background strain influences as compared to littermate control (+/?) indices. Both db/db and ob/ob mutations induced dramatic increases in body weights, blood glucose and serum insulin concentrations relative to +/? indices when expressed on either the C57BL/KsJ (-/KsJ) or C57BL/6 (-/6) backgrounds. However, the -/KsJ background enhanced the severity of expression of these DOS indices relative to the -/6 strain. Similarly, the -/KsJ genome suppressed cellular glucose uptake rates, pancreatic tissue weights and insulin concentrations in both db/db and ob/ob mutants relative to /6 background strain influences or +/? indices. Concurrent enhancement of tissue and cellular lipogenic metabolism and islet cytolipid depositions were exaggerated when the mutations were expressed on the -/KsJ background relative to the -/6 genome. Pancreatic islet B-cell lipodeposition was markedly enhanced in ob/ob and db/db mutants expressed on either the -/KsJ or -/6 background. In both ob/ob and db/db models, B-cell insulin granulation was prominent in mildly hypertrophic pancreatic islets when the mutations were expressed on the -/6 background. In contrast, the severity of the DOS state expressed on the -/KsJ background resulted in pronounced B-cell atrophy, characterized by insulin degranulation, cellular hypertrophy and hypercytolipidemia associated with tissue involution, in both ob/ob and db/db mutants. Dramatic alterations in tissue norephinephrine (NE) and alpha-1-receptor populations in ob/ob and db/db mutants were exaggerated by the -/KsJ genome as compared to -/6 or control indices. The influences of the -/KsJ genome on the progressive expression of tissue NE counter-regulatory responses to enhanced cytolipidemic indices were inversely related, with cytochemical lipodeposition occurring under conditions of diminished adrenergic responses to the DOS indices. The results of these studies indicate that the severity of the type-II diabetes endometabolic syndrome induced by the ob/ob or db/db genotypic mutations is modified by the existing genome on which the mutations are expressed. These data suggest that the severity of genomic mutation expression may be modified depending on the capability of the background genome to counter-regulate the systemic, cellular or metabolic consequences of these mutations.

Cytolipotoxicity-induced involution of the female reproductive tract following expression of obese (ob/ob) and diabetes (db/db) genotype mutations: progressive, hyperlipidemic transformation into adipocytic tissues

Both diabetes (db/db) and obese (ob/ob) single gene mutations induce a progressive, hyperglycemic-hyperinsulinemic endometabolic environment which promotes hypercytolipidemic, utero-ovarian involution in C57BL/KsJ mice. The progressive expression of the induced diabetes-obesity syndrome (DOS) results in female reproductive sterility and eventual organoatrophy. In order to define the intra-cytoplasmic alterations induced by the progressive cytolipidemia on cellular vitality, utero-ovarian tissue samples were collected from both control (+/?) and littermate-matched ob/ob or db/db C57BL/KsJ mice at either 4 weeks (initial-onset DOS phase), 8 weeks (progressive, overt DOS phase), or 16 weeks (chronic-DOS phase) of age for cytolipid distribution analysis. All db/db and ob/ob mutant groups exhibited phenotypic obesity and systemic hyperglycemia-hyperinsulinemia relative to age-matched littermate +/? groups. In all db/db and ob/ob age groups, a progressive hypercytolipidemia was noted relative to +/? groups. When analyzed for lipid channeling, a progressive perinuclear mapping pattern of cytolipid distribution was noted. The primary locus of initial db/db and ob/ob cytolipid deposition was localized to the baso-polar regions in endometrial epithelia samples, or to the interstitium-thecal layer border of ovarian follicular compartments, during the initial-onset DOS phase. Progressively, intra-cytoplasmic lipid mobilization promoted a consistent perinuclear channeling of lipid vacuoles, ultimately isolating nuclear loci from the peripherally displaced cytoplasmic organelles within uterine epithelial layers. In db/db and ob/ob ovarian tissue samples, a progressive, gradient-related lipid infiltration of interstitial, thecal and, ultimately, granulosa cell layers promoted an enhanced rate of follicular-lipidemic atresia relative to +/? groups. In each tissue layer, the cytolipidemia promoted a dramatic perinuclear lipid-isolation barrier from intra-cytoplasmic organelle domains. With age-related exacerbation of the DOS syndrome, cytoplasmic nuclear-organelle displacement and lipoisolation resulted in cellular atresia, promoting the eventual utero-ovarian organoatrophy which characterized the chronic-DOS phase in db/db and ob/ob C57BL/KsJ mutants. These results indicate that the cytoinvolution associated with reproductive tract atrophy in these genetically mutant, diabetic-obese models is promoted by the disruption of the normal cytoarchitecture of utero-ovarian tissue layers induced by the progressive lipid sequestration, accumulation and ultimate isolation-induced disruption of intra-cellular organelle compartmentalization.

Hypercytolipidemia promotes diabetes (db/db) mutation-associated utero-ovarian involution: counter-regulatory influences of progesterone

Background: The diabetes (db/db) mutation induces a hyperglycemic-hyperinsulinemic endometabolic environment that promotes hypercytolipidemic, utero-ovarian involution in C57BL/KsJ mice, resulting in reproductive sterility and eventual organoatrophy. Objective: Evaluation of the effectiveness of progesterone therapy (P-HRx), initiated prior to the genetic expression of the overt diabetes-obesity syndrome (DOS), on moderating the severity of female reproductive tract involution promoted by db/db mutation expression was evaluated by analysis of cytoarchitectural, endocrine and tissue lipo-metabolic indices relative to oil (O)-vehicle-treated (HRx) control (+/?) and db/db groups. Experimental design: All HRx treatments were started at 4 weeks of age (pre-overt DOS stage) and continued through 16 weeks of age (chronic DOS expression) when tissue and cellular endometabolic parameters were evaluated. Results: The DOS induced a dramatic increase in phenotypic obesity, hyperglycemia and hyperinsulinemia in db/db groups, relative to +/?, throughout the experimental period. In contrast, utero-ovarian weights were dramatically reduced in db/db groups relative to +/? indices. Chronic P-HRx effectively reversed these DOS-induced trends in db/db groups, maintaining moderated body and tissue weights, as well as re-establishing normal insulin indices, under a persistent hyperglycemic condition. In addition, P-HRx moderated the dramatic hypercytolipidemic condition which promotes utero-ovarian involution in db/db mice as evidenced by the reduction in observed tissue cytolipidemia. The concurrent normalization of tissue lipase and enhancement of glucose utilization indices by db/db utero-ovarian compartments, under moderated insulin recognition parameters, indicated that P-HRx effectively suppressed the severity of both the structural and endometabolic consequences of the DOS in db/db groups, without restraining hyperglycemic conditions. Conclusion: These results indicate that the pathophysiological alterations induced by the db/db mutation may be modulated through low-dose steroidal therapy, the efficacy of which is suspected to occur by the augmentation of normal insulin-coupled, post-receptor directed glucose utilization via the stimulation of oxidative metabolic pathways capable of maintaining normal utero-ovarian structural continuity and metabolic homeostasis.

Hypophyseal lipoapoptosis: diabetes (db/db) mutation-associated cytolipidemia promotes pituitary cellular disruption and dysfunction

Expression of the diabetes (db/db) mutation in C57BL/KsJ mice suppresses the female pituitary-gonadal axis via progressive cytolipidemic disruption of hypophyseal gonadotropin release, culminating in premature involution of the reproductive tract and manifest infertility. The current studies define the systemic, endocrine, cytochemical and structural apoptotic changes that result from pituitary hypercytolipidemia induced by db/db mutation expression in this Type II diabetes-obesity syndrome (DOS) model. Adult female C57BL/KsJ control (+/? genotype) and db/db littermates were monitored for systemic and cellular alterations in LH-, FSH- and gonadal steroid-secretion, and coincident pituitary apoptosis, as indexed by TUNEL labeled 3' nuclear DNA-fragmentation, associated with cytolipid depositions. Obesity, hyperglycemia and hyperinsulinemia characterized all db/db-mutants relative to +/? groups. Serum progesterone (P) and estradiol (E2) concentrations were suppressed in db/db mutants coincident with decreased plasma LH and FSH concentrations relative to +/? values. Cytochemical analysis of anterior (AP) pituitary cell subtypes indicated that db/db mutants demonstrated prominent hypercytolipidemia relative to +/? pituitary cytoarchitecture. Cytolipidemic vacuoles were localized within protein vesiculated db/db hypophyseal basophilic and acidophilic cell populations. Hypophyseal cytoadiposity in db/db AP cells was co-localized with prominent cellular apoptotic TUNEL labeling of nuclear 3'-DNA fragments in cells demonstrating vesicular depopulation and cytolytic vacuolization. These data represent the first demonstration of co-localized hypercytolipidemic and cytoapoptotic disruptive events occurring concurrently in a hypopituitary-hypogonadal syndrome model following expression of the Type II (NIDDM) diabetes-obesity syndrome in db/db-mutants. The coincident and progressive vascular-, interstitial- and cyto-lipidemic alterations in hypophyseal cytoarchitecture correlated with the concurrent apoptotic disruption of pituitary endocrine cytoarchitecture and supressed gonadal steroid synthesis, influences which collectively contribute to the premature involution of the pituitary-gonadal axis in C57BL/KsJ- db/db mice.

Lipoatrophic diabetes-associated utero-ovarian dysfunction: influence of cellular lipid deposition on norepinephrine indices

OBJECTIVE

Elucidation of the intracellular lipoatrophic diabetic state and the concomitant alterations in norepinephrine (NE) parameters characterizing female reproductive failure.

METHODS

Quantitation of intrinsic NE levels in utero-ovarian and pancreatic tissue samples of C57BL/KsJ (+/?) control and (db/db) diabetic littermate mice was by high performance liquid chromatography (HPLC) and compared with the microspectrofluorometric histofluorescent (HF) localization of cellular and parenchymal NE.

RESULTS

Diabetes-associated elevations in HPLC-detectable tissue NE concentrations occurred in all pancreatic and reproductive tract tissue samples as compared to control-matched samples, whereas concurrent HF analysis revealed suppressed perivascular and parenchymal NE depositions in diabetic mice.

CONCLUSIONS

These data suggest that progressive hypertriglyceridemia/lipidemia may suppress the effectiveness of intrinsic elevations in tissue NE concentrations from effectively counterregulating the deleterious effects of the hyperglycemic, type-2 diabetic condition.

Aggression-associated changes in murine olfactory tubercle bioamines

The relationship between changes in regional brain bioamine levels and the expression of intraspecies aggressive behavior was evaluated in two murine models. In one study, normal male mice were maintained either in aggregate (i.e., normal, intraspecies social behavioral controls) or isolated (i.e., developed, non-social intraspecies aggressive 'fighter' behavior) housing environments, and the accompanying changes in both olfactory tubercle (OT) and hypothalamic (HYPOTH), norepinephrine (NE), dopamine (DA) and serotonin (5-HT) concentration indices quantitated by high-performance liquid chromatography (HPLC) for analysis of behavior-related alterations in localized bioamine deposition loci. Intact mice which had been housed in isolation cages and which exhibited aggressive, intraspecies reflexive-biting ('fighter') behavior when introduced to a novel (stimulus) animal, exhibited significant (P<0.05) elevations in NE levels, and depressed DA concentrations, in the OT regions relative to aggregated controls, indicating an intrinsic social influence on the maintenance of basal adrenergic indices at this neural locus. No changes in 5-HT levels were indicated between control and aggressive, isolated 'fighter' groups in either OT or HYPOTH loci. In addition, the NE and DA levels in the HYPOTH samples of both control and aggressive groups were found to be comparable. In the second study, utilizing an alternate type of aggression-induced murine model, changes in bioamine parameters were determined from samples obtained from aggregated, olfactory-bulbectomized (Obx) mice which are recognized to exhibit an overt, intraspecies, reflexive-biting behavior as compared to sham-operated (control) mice housed under identical conditions. In these studies, Obx-mice exhibited a significant increase in 5-HT levels in the OT relative to sham-operated controls, but similar NE and DA concentrations. In addition, all hypothalamic bioamine indices were found to be comparable between control and Obx groups. These data, collected for both isolation-developed, and experimentally-induced (i.e., OBX), intraspecies aggressive models, indicate that the distinctive types of aggressive behaviors displayed by these two murine models are accompanied by specific alterations in regional bioamine levels within the OT of these groups, relative to controls. These data suggest that the specific type of overt aggressive behavior demonstrated by these models may be causally related to the identified changes in bioamine concentrations in the forebrain regions of the CNS, in loci recognized to participate in environmental recognition and social processing activities.

Diabetes-induced, progressive endometrial involution characterization of periluminal epithelial lipoatrophy

The present studies detail the cytopathological alterations in uterine epithelial, basal lamina, and stromal endometrial subregions, and associated endocrine parameters that occur during the progressive exacerbation of the diabetes syndrome in this species of mouse. These alterations result in a cellular lipoatrophic condition that compromises uterine tissue integrity and promotes reproductive involution. Uterine tissue samples were obtained from litter-matched control (+/?) and diabetic (db/db) C57BL/KsJ mice at four designated stages of the progressive expression of the diabetes mutation. In db/db mice between the ages of 4 and 12 weeks, the uterine epithelial cellular architecture exhibited progressive deterioration, characterized by cytoplasmic lipid imbibition (accumulation), organelle disintegration, apical membrane ciliary regression, and peristromal lamina separation from basal membrane surfaces, as compared with control indexes. The cytoplasmic volume occupied by lipid inclusions dominated the epithelial cells in diabetic mice, presenting dense basal pole lipid vacuoles, with perinuclear-intracytoplasmic migration of the inclusions promoting an apical cytoplasmic lipid condensation of increasing volume 8-12 weeks after mutation expression. These cytoplasmic lipid accumulations occurred under altered metabolic and endocrine conditions characterized by hyperglycemic, hyperinsulinemic, hypertriglyceridemic, and enhanced noradrenergic indexes, which were exacerbated between 4- and 12-week stages. These structural changes were accompanied by enhanced adrenergic counterregulatory metabolic responses as well as elevated lipoprotein and triacylglycerol lipase activities. These data indicate that diabetes-associated uterine involution is characterized by a progressive cellular and peristromal lipoatrophy of epithelial cell cytology and metabolic parameters, promoting stromal separation and ultimate endometrial involution.

Modulation of Monoaminergic Neural Circuits

A plethora of data from experimental animals provide strong support for the concept that reduced dopaminergic neuronal activity and enhanced noradrenergic tone in specific hypothalamic nuclei are involved in the pathogenesis of the metabolic syndrome. The available information on these neurotransmitter systems in insulin-resistant humans with obesity is in keeping with the postulate that analogous mechanisms may underlie their adverse metabolic profile. Treatment with bromocriptine, which has dopaminergic (D2 receptor agonist) and sympatholytic (alpha2-adrenoceptor agonistic and an alpha1-adrenoceptor antagonistic) actions, can reverse the metabolic anomalies in a variety of obese mammalian species. Combined D1/D2 receptor activation appears to exert even more powerful effects on fuel metabolism in various animal models of the metabolic syndrome. The currently available data on the metabolic effects of bromocriptine in humans with obesity and type 2 diabetes mellitus point in the same direction. Bromocriptine favorably affects glucose metabolism and various other components of the metabolic syndrome simultaneously to ameliorate the risk of damage to eyes, neural tissue, kidneys and the cardiovascular system in patients with type 2 diabetes mellitus. Moreover, a substantial number of studies indicate that bromocriptine lowers blood pressure in animals and humans with hypertension via its sympatholytic capacities. However, the effects of bromocriptine alone are relatively modest, the metabolic mechanism of action in humans remains uncertain, and the long-term efficacy and safety profiles of this compound are unknown. It seems important to seek for ways to boost the action of bromocriptine, by combining dopaminergic D2 and D1 receptor activation, for example. Notably, there is no antidiabetic drug that acts through central (dopaminergic) mechanisms. This novel approach may, therefore, result in synergistic actions with other available agents to favorably impact the risk of tissue damage in patients with type 2 diabetes mellitus.

Increased responsiveness to the hyperglycemic, hyperglucagonemic and hyperinsulinemic effects of circulating norepinephrine in ob/ob mice

OBJECTIVE

Several studies have implicated increased sympathetic tone as a contributing factor to the hyperglycemia and hyperglucagonemia of ob/ob mice. However, the responsiveness of plasma glucose, insulin and glucagon to circulating norepinephrine (NE) in ob/ob vs normal lean mice has never been described. Therefore, the present study investigated the effect of a 15 min intravenous NE infusion (1 pmol/min/g) on plasma glucose, insulin and glucagon in anesthetized lean, ob/ob, ob/ob-concurrent yohimbine (alpha(2) antagonist) treated, and ob/ob-chronically sympatholytic dopamine agonist treated (for 14 days prior to infusion) mice. In an effort to gain insight into a possible relation between norepinephrine, hyperglucagonemia and hyperinsulinemia in ob/ob mice, this study also examined the isolated islet responses to NE and glucagon in lean, ob/ob and ob/ob-sympatholytic dopamine agonist treated mice.

RESULTS

Basal humoral values of glucose, insulin and glucagon were all elevated in ob/ob vs lean mice (by 63, 1900 and 63%, respectively, P<0.01). However, NE infusion further increased levels of glucose, insulin and glucagon in ob/ob (by 80, 90 and 60%, respectively, P<0.05) but not in lean mice (between group difference for all parameters P<0.05). Acute concurrent yohimbine treatment as well as chronic prior sympatholytic dopamine agonist treatment (bromocriptine plus SKF38393) simultaneously strongly aborgated or abolished all these humoral hypersensitivity responses to intravenous NE in ob/ob mice (P<0.05). Clamping the plasma glucose level in untreated ob/ob mice at a high level (30 mM) established by NE infusion did not significantly alter the plasma insulin level, suggesting that some other influence of NE was responsible for this insulin effect. Direct NE administration at 1 microM to islets from lean and ob/ob mice inhibited 15 mM glucose-stimulated insulin secretion in both groups, but at 0.1 microM it was inhibitory only in islets from ob/ob mice. However, glucagon (10 nM) increased 15 mM glucose-stimulated insulin secretion in ob/ob (by 170%, P<0.05) but not lean mice (between group difference P<0.05).

CONCLUSION

These findings suggest that hypersensitivity to circulating NE may potentiate hyperglycemia and hyperglucagonemia in ob/ob mice, and the subsequent hyperglucagonemia coupled with increased islet beta-cell insulin secretory responsiveness to glucagon in ob/ob mice may support hyperinsulinemia, thus explaining the increased plasma insulin level response to intravenous NE in these animals. These findings further support a role for increased peripheral noradrenergic activities in the development and maintenance of the hyperglycemic, hyperglucagonemic and hyperinsulinemic state, characteristic of type 2 diabetes.

Hypothalamic adrenergic receptor changes in the metabolic syndrome of genetically obese (ob/ob) mice

The genetically, seasonally, and diet-induced obese, glucose-intolerant states in rodents, including ob/ob mice, have each been associated with elevated hypothalamic levels of norepinephrine (NE). With the use of quantitative autoradiography on brain slices of 6-wk-old obese (ob/ob) and lean mice, the adrenergic receptor populations in several hypothalamic nuclei were examined. The binding of [(125)I]iodocyanopindolol to beta(1)- and beta(2)-adrenergic receptors in ob/ob mice was significantly increased in the paraventricular hypothalamic nucleus (PVN) by 30 and 38%, in the ventromedial hypothalamus (VMH) by 23 and 72%, and in the lateral hypothalamus (LH) by 10 and 15%, respectively, relative to lean controls. The binding of [(125)I]iodo-4-hydroxyphenyl-ethyl-aminomethyl-tetralone to alpha(1)-adrenergic receptors was also significantly increased in the PVN (26%), VMH (67%), and LH (21%) of ob/ob mice. In contrast, the binding of [(125)I]paraiodoclonidine to alpha(2)-adrenergic receptors in ob/ob mice was significantly decreased in the VMH (38%) and the dorsomedial hypothalamus (17%) relative to lean controls. This decrease was evident in the alpha(2A)- but not the alpha(2BC)-receptor subtype. Scatchard analysis confirmed this decreased density of alpha(2)-receptors in ob/ob mice. Together with earlier studies, these changes in hypothalamic adrenergic receptors support a role for increased hypothalamic NE activity in the development of the metabolic syndrome of ob/ob mice.

Hyperinsulinemia increases norepinephrine metabolism in the ventromedial hypothalamus of rats

Numerous studies have implicated increased ventromedial hypothalamic (VMH) norepinephrine (NE) activity as a contributing factor to the obese, hyperinsulinemic, glucose intolerant condition. However, factors contributing to the increased VMH NE activity remain unknown. This study therefore investigated in normal rats the effect of a hyperinsulinemic-euglycemic clamp on VMH monoamine turnover and utilization via simultaneous VMH microdialysis to establish a role for hyperinsulinemia in the stimulation of VMH NE activity. Within 20 min of initiation of the hyperinsulinemic-euglycemic clamp, VMH extracellular methoxyhydroxy phenylglycol (metabolite of NE) level increased by 54% and remained approximately at this level for the 100 min duration of the clamp relative to control values (p<0.05). Hyperinsulinemia did not affect VMH dopamine or serotonin metabolism. Subsequent establishment of a hyperinsulinemic-hypoglycemic camp did not alter the VMH monoamine metabolism profile relative to the hyperinsulinemic-euglycemic clamp. Infusion of saline (as control) in a separate group of rats over the entire clamp period induced no changes in any monoamine metabolic profile relative to baseline. Hyperinsulinemia can feedback to stimulate VMH NE activity and, as a result, may contribute to the initiation and/or perpetuation of the obese, hyperinsulinemic, glucose-intolerant state.

Chronic ventromedial hypothalamic infusion of norepinephrine and serotonin promotes insulin resistance and glucose intolerance

The ventromedial hypothalamus (VMH) is involved in the regulation of peripheral metabolism. We and others have shown that activities, or extracellular metabolites of norepinephrine (NE) and serotonin (5-HT) are elevated in the VMH of both genetically and seasonally insulin-resistant and glucose-intolerant animals. This study examined whether chronic increases in VMH NE and 5-HT concentration of normal animals might lead to insulin-resistant and glucose-intolerant conditions in hamsters. Euinsulinemic, glucose-tolerant hamsters were infused continuously for 5 weeks into the right VMH with either vehicle, NE (5 or 25 nmol/h), 5-HT (2.5 nmol/h), or NE (5 or 25 nmol/h) plus 5-HT (2.5 nmol/h) through osmotic minipumps. Compared to vehicle, NE (25 nmol/h) significantly increased the glucose total area under the curve (TAUC) by 32% during glucose tolerance tests (GTT) conducted after 5 weeks' infusion. 5-HT alone significantly increased the GTT insulin TAUC (131%) and basal plasma insulin level (116%) but not glucose TAUC. NE (5 nmol/h) plus 5-HT infusion significantly increased insulin TAUC (129%) and basal plasma insulin (120%), whereas NE (25 nmol/h) plus 5-HT infusion significantly increased both the GTT glucose and insulin TAUC (43 and 113%, respectively), as well as basal plasma insulin level (158%), relative to vehicle infusion. Our findings demonstrate for the first time the differential and, more importantly, interactive effects of increased VMH NE and 5-HT in producing hyperinsulinemia, insulin resistance and glucose intolerance.

Bromocriptine improves glycaemic control and serum lipid profile in obese Type 2 diabetic subjects: a new approach in the treatment of diabetes

Bromocriptine, a potent dopamine D(2) receptor agonist, has been shown to reduce insulin resistance, glucose intolerance and hyperlipidaemia in both numerous animal studies and in Phase II studies. Bromocriptine has been used worldwide for over 20 years to treat Parkinson's disease, macroprolactinoma and other disorders; it has been found to be generally safe. We therefore investigated the possible beneficial effects of Ergoset(R) (Ergo Science Corp.), a new quick release formulation of bromocriptine, on glycaemic control and serum lipid profile in obese Type 2 diabetic subjects in two large Phase III studies. A large, randomised, double-blind placebo-controlled study was conducted in which Ergoset was given once daily at 8 am. (4.8 mg maximum dose) for 24 weeks as adjunctive therapy to sulphonylurea (485 subjects) to obese Type 2 diabetics held on a weight- maintaining diet. Treatment efficacy parameters included change from baseline in glycated haemoglobin A(1c) (HbA(1c)), fasting and post-prandial serum glucose, insulin, triglyceride and free fatty acid levels. Baseline glycated haemoglobin, fasting glucose, insulin, triglyceride and free fatty acid levels did not differ between treatment groups. and on average were 9.4 +/- 0.05%, 222 +/- 2 mg/dl, 24 +/- 1 µU/ml, 248 +/- 11 mg/dl, and 850 +/- 32 µEq/l, respectively. A similarly designed study of Ergoset as monotherapy in Type 2 diabetics (154 subjects) with similar baseline clinical characteristics was conducted. Addition of Ergoset treatment to sulphonylurea reduced percent glycated HbA(1c) by 0.55 (P < 0.0001) (approximately 1.0 for responders, 65% of population), fasting and post-prandial glucose by 23 and 26 mg/dl (P < 0.0002), fasting and post-prandial triglycerides by 72 and 63 mg/dl (P < 0.005) and fasting and post-prandial free fatty acids by 150 and 165 µEq/l (P < 0.05), relative to placebo. Twelve percent of all Ergoset subjects, compared to 3% of placebo subjects, withdrew from the study due to adverse events. The most common events causing withdrawal were nausea, dizziness, asthenia, and rhinitis (representing 4.5, 3.3, 2.0, and 0.8% of the total Ergoset populations, respectively). The incidence of serious adverse events did not differ between Ergoset- (3.4%) and placebo- (4.3%) treated subjects. Ergoset as monotherapy also improved glycaemic control (0.56 HbA(1c) decrease relative to placebo after 24 weeks of treatment; P < 0.02). Once daily Ergoset treatment improves glycaemic control and serum lipid profile and is well-tolerated in obese Type 2 diabetics.

Alpha2 adrenergic and high affinity serotonergic receptor changes in the brain stem of streptozotocin-induced diabetic rats

The brain stems (BS) of streptozotocin (STZ)-diabetic rats were studied to see the changes in neurotransmitter content and their receptor regulation. The norepinephrine (NE) content determined in the diabetic brain stems did not show an increase, while epinephrine (EPI) content increased significantly compared with control. The NE to EPI turnover showed a significant increase. The alpha2 adrenergic receptor kinetics revealed that the receptor affinity was significantly reduced during diabetes. In insulin treated rats the NE content decreased while EPI content remained increased as in the diabetic state. Insulin treatment increased the Bmax for alpha2 adrenergic receptors significantly while the increase in Kd reversed to normal. Unlabelled clonidine inhibited [3H]NE binding in BS of control diabetic and insulin treated diabetic rats showed that alpha2 adrenergic receptors consisted of two populations of binding sites with Hill slopes significantly away from unity. In diabetic animals the ligand bound weaker to the low affinity site than in controls. Insulin treatment reversed this alteration to control levels. The displacement analysis using (-)-epinephrine against [3H]yohimbine in control and diabetic animals revealed two populations of receptor affinity states. In control animals, when GTP analogue added with epinephrine, the curve fitted for a single affinity model; but in the diabetic BS this effect was not observed. In both the diabetic and control BS the effects of monovalent cations on affinity alterations were intact. Our data thus show that alpha2 adrenergic receptors have a reduced affinity due to an altered post receptor affinity regulation The serotonin (5-HT) content in the brain stem increased. Its precursor (5-hydroxy) tryptophan (5-HTP) showed an increase and its breakdown metabolite (5-hydroxy) indoleacetic acid (5-HIAA) showed a significant decrease. This showed that in serotonergic nerves there is a disturbance in both synthetic and breakdown pathways which lead to an increased 5-HT. The high affinity serotonin receptor numbers remained unaltered with a decrease in the receptor affinity. The insulin treatment reversed these altered serotonergic receptor kinetic parameters to control level. Thus our study shows a decreased serotonergic receptor function. These changes in adrenergic and serotonergic receptor function were suggested to be important in insulin function during STZ diabetes.

Estrogenic stimulation of hypothalamic-limbic system metabolism in ageing diabetic C57BL/KsJ mice

The therapeutic influences of estrogen treatment on age- and diabetes-related declines in regional brain glucose utilization (RBGU) rates were evaluated in 8- to 20-week-old female C57BL/KsJ normal (+/?) and diabetic (db/db) mice. Following either oil vehicle (oil: 0.1 ml) or estradiol (E: 1 microgram/3.5 days) treatments starting at 3 weeks of age, RBGU rates were subsequently determined at 8, 12, 16 and 20 weeks of age. A gradual decline in the basal rate of brain glucose utilization was observed in all control (oil- and E-treated) groups between 8 and 20 weeks. Expression of the hyperglycemic-obese diabetes syndrome in db/db mice resulted in a significant reduction in RBGU rates between 8 and 20 weeks relative to control values. In estrogen-sensitive hypothalamic, septal and amygdaloid regions, E therapy modulated RBGU rates in db/db mice relative to oil-treated diabetics, but did not significantly alter utilization rates in +/? mice. In cortical samples, E therapy had no significant influence on glucose utilization rates in either control or diabetic groups. A noticeable pattern of maturation-associated decline in CNS glucose utilization rates in all brain regions resulted in comparable regional metabolic indices being exhibited by all groups at 20 weeks of age, with the exception of the diabetes-associated exacerbation of RBGU rates in the oil-treated db/db group. These data demonstrate that the normal development-related decline in regional brain carbohydrate metabolism is accelerated by the diabetes syndrome, and that E therapy can modulate the syndrome-associated suppression of glucose utilization in steroid-sensitive CNS loci. These data suggest that the depressive influences of the diabetes syndrome on brain carbohydrate utilization rates may be therapeutically modified in recognized CNS regions possessing steroid-sequestering, metabolically responsive neurons.

Intracerebroventricular administration of bromocriptine ameliorates the insulin-resistant/glucose-intolerant state in hamsters

Bromocriptine, a potent dopamine D2 receptor agonist, suppresses lipogenesis and improves glucose intolerance and insulin resistance. Recent evidence suggests that bromocriptine may produce these effects by altering central nervous system (CNS) regulation of metabolism. To determine whether or not the CNS plays a critical role in these bromocriptine-mediated effects on peripheral metabolism, we compared the metabolic responses to bromocriptine when administered peripherally versus centrally in naturally obese and glucose intolerant Syrian hamsters. Male hamsters (BW 194 +/- 5 g) were treated with bromocriptine or vehicle either intraperitoneally (i.p., 800 microgram/animal) or intracerebroventricularly (i.c.v., 1 microgram/animal) daily at 1 h after light onset for 14 days while held on 14-hour daily photoperiods. Glucose tolerance tests (GTTs, 3 g glucose/kg BW) were conducted after treatment. Compared to control animals, bromocriptine i.p. significantly reduced weight gain (11.7 vs. -2.4 g) and the areas under the glucose and insulin GTT curves by 29 and 48%, respectively. Similarly, compared with vehicle-treated controls, bromocriptine i.c.v. at 1 microgram/animal substantially reduced weight gain (8.7 vs. -6.3 g), the areas under the glucose and insulin GTT curves by 31 and 44% respectively, and the basal plasma insulin concentration by 41% (p < 0.05). Furthermore, both treatments significantly improved insulin-mediated suppression of hepatic glucose production during a hyperinsulinemic-euglycemic clamp. Thus, daily administration of bromocriptine at a very low dose i.c.v. replicates the metabolic effects of bromocriptine administered i.p. at a much higher dose. This finding demonstrates for the first time that the CNS is a critical target of bromocriptine's metabolic effects.

Behavioral and neurochemical alterations caused by diet restriction--the effect of tyrosine administration in mice

We have investigated the effect of tyrosine administration on the cognitive and neurochemical alterations caused by diet restriction (DR) in mice, as a possible model for some of the behavioral symptoms of patients with anorexia nervosa. Young female mice were fed to 100, 60, and 40% of the calculated daily nutritional requirements for a period of up to 18 days. Cognitive function was evaluated using a modified eight-arm maze with water as a reward. Animals fed to 60% of controls showed significantly improved maze performance while this was impaired in animals on DR to 40%. However, in these animals, injections of tyrosine (100 mg/kg/day) restored performance. Improved maze performance in the 60% DR and 40% DR + tyrosine animals was related to increased beta:alpha tone in the hippocampus- an area, together with the septum, responsible for spatial learning. This was associated with changes in alpha- and beta-receptor density (Bmax), without affecting affinity (Kd); and increased norepinephrine (NE) in the 40% DR + tyrosine group, and methoxyhydroxyphenylglycol (MHPG) in both groups. In the hypothalamus, the brain area responsible for energy metabolism, there was a progressive increase in alpha:beta tone with increasing DR associated with changes in Bmax. Tyrosine treatment reversed these alterations. Tyrosine improves some of the neurobiological disturbances of DR without causing an increase in body weight. Such a strategy might have important implications for the possible treatment of patients with anorexia nervosa.

Developmental and regional changes in brain norepinephrine levels in diabetic C57BL/KsJ mice: effects of estradiol and progesterone

Developmental and diabetes-associated changes in regional brain norepinephrine (NE) concentrations, and the influence of estradiol (E) and progesterone (P) on NE levels, were correlated with changes in blood glucose levels and body weight (obesity) in developing 4-16-week-old C57BL/KsJ (db/db) mice relative to corresponding age-matched control (+/?) parameters. Regional brain (i.e. amygdala, hypothalamus and medulla) NE levels were determined by high performance liquid chromatography. The (db/db) mice exhibited overt hyperglycemia and obesity relative to controls between 4 and 16 weeks of age. Hypothalamic NE levels in diabetics were chronically elevated as compared to those of age-matched controls by 8 weeks of age, and remained elevated through 16 weeks of age. Regional amygdaloid and medullary NE concentrations were comparable in (+/?) and (db/db) groups by 16 weeks. E-treatments normalized (db/db) hypothalamic NE concentrations to control levels between 8 and 16 weeks of age, but had no effect on amygdaloid or medullary values. In contrast, in 16 week old (db/db) mice, P-treatments elevated hypothalamic and medullary NE levels compared to controls and expected diabetic levels. These data demonstrate that a marked modification in regional brain NE concentrations occurs in association with the overt expression of the diabetes mutation during development in this species. Observed changes in adrenergic influences in specific CNS loci may be therapeutically modulated by ovarian steroid hormones, especially in the hypothalamic locus which is recognized to possess steroid-concentrating neurons. The observed normalization of regional brain NE concentrations by E-therapy may be causally related to the ovarian steroid-modulation of overt hyperglycemia and diabetes-associated neuronal degeneration in (db/db) mice.