Molecular regulation of the hypothalamo-pituitary-adrenal axis in streptozotocin-induced diabetes: effects of insulin treatment

The Role of the Adrenal-Gut-Brain Axis on Comorbid Depressive Disorder Development in Diabetes

Diabetic patients are more affected by depression than non-diabetics, and this is related to greater treatment resistance and associated with poorer outcomes. This increase in the prevalence of depression in diabetics is also related to hyperglycemia and hypercortisolism. In diabetics, the hyperactivity of the HPA axis occurs in parallel to gut dysbiosis, weakness of the intestinal permeability barrier, and high bacterial-product translocation into the bloodstream. Diabetes also induces an increase in the permeability of the blood-brain barrier (BBB) and Toll-like receptor 4 (TLR4) expression in the hippocampus. Furthermore, lipopolysaccharide (LPS)-induced depression behaviors and neuroinflammation are exacerbated in diabetic mice. In this context, we propose here that hypercortisolism, in association with gut dysbiosis, leads to an exacerbation of hippocampal neuroinflammation, glutamatergic transmission, and neuronal apoptosis, leading to the development and aggravation of depression and to resistance to treatment of this mood disorder in diabetic patients.

Ameliorative effect of Stevia rebaudiana Bertoni on sperm parameters, in vitro fertilization, and early embryo development in a streptozotocin-induced mouse model of diabetes

Diabetes mellitus (DM) is a common metabolic disease characterized by high blood sugar levels. It is well known that men with diabetes frequently experience reproductive disorders and sexual dysfunction. In fact, sperm quality has a significant effect on fertilization success and embryo development. The current study aimed to investigate the effect of Stevia rebaudiana hydroalcoholic extract on serum testosterone levels, sperm parameters, in vitro fertilization (IVF) success, and in vitro embryonic developmental potential to reach the blastocyst stage in a streptozotocin (STZ)-induced mouse model of diabetes. In this research, 30 male mice were distributed randomly into control, diabetic (streptozotocin 150 mg/kg) and diabetic + Stevia (400 mg/kg) groups. The results revealed a decrease in body and testis weight and elevated blood fasting blood sugar (FBS) levels in the diabetic group, compared with the control. However, Stevia treatment significantly increased body and testis weight, while serum FBS levels were decreased compared with the diabetic group. In addition, Stevia significantly increased blood testosterone levels compared with the diabetic group. Moreover, sperm parameters were improved considerably by Stevia treatment compared with the diabetic group. Furthermore, Stevia administration significantly promoted IVF success rate and in vitro development of fertilized oocytes compared with the diabetic group. In summary, our data indicated that Stevia enhanced sperm parameters, IVF success, and in vitro embryonic developmental competency in diabetic mice, probably because of its antioxidant effects. Therefore, Stevia could ameliorate sperm parameters that, in turn, increase fertilization outcomes in experimental-induced diabetes.

Protective effects of quercetin on uterine receptivity markers and blastocyst implantation rate in diabetic pregnant mice

OBJECTIVE

Diabetic women have different reproductive problems. In pregnant diabetic women, high rates of perinatal mortality, spontaneous abortion and congenital anomalies are observed. We hypothesized that quercetin, as an antidiabetic and phytoestrogen, might have protective effects on the embryo implantation in pregnant diabetic mice. We investigated the ameliorative effects of quercetin on the levels of serum estrogen and progesterone, rate of blastocyst implantation, and uterine receptivity markers in diabetic mice.

MATERIALS AND METHODS

Diabetic and healthy female mice were treated with quercetin (30 mg/kg/day) four weeks before pregnancy. Plasma sex-steroid levels were determined on day 4 of pregnancy. Also, uteri were harvested for investigation of protein and mRNA expression changes. In another set of our study, implantation rate was determined on day 5 of pregnancy.

RESULTS

Our results indicated that quercetin was significantly reduced blood glucose levels in diabetic mice. The number of implantation sites as well as serum estradiol level was reduced in diabetic mice, and then treatment with quercetin significantly increased both. On the other hand, insulin like growth factor1, integrin αvβ3, and cyclooxygenase2 mRNA expression in the uterus of diabetic mice were significantly reduced, and quercetin treatment augmented the expression level of these genes. Besides, the level of inactive β-catenin protein level in the uterus of diabetic mice was higher than normal group; treatment with quercetin reduced the level of inactive β-catenin protein as compared to diabetic mice.

CONCLUSION

We conclude that administration of quercetin before pregnancy can probably alleviate reproductive problems in diabetic women likely via its estrogenic and antihyperglycemic effects.

Hypothalamic insulin signalling as a nexus regulating mood and metabolism

Insulin has long been known as a metabolic hormone critical in the treatment of diabetes for its peripheral effects on blood glucose. However, in the last 50 years, insulin has entered the realm of neuroendocrinology and many studies have described its function on insulin receptors in the brain in relation to both metabolic and mood disorders. Indeed, rodent models of impaired insulin signalling show signs of dysregulated energy and glucose homeostasis, as well as anxiety-like and depressive behaviours. Importantly, many metabolic diseases such as obesity and diabetes increase the risk of developing mood disorders; however, the brain mechanisms underlying the connection between metabolism and mood remain unresolved. We present the current literature on the importance of the insulin receptor with respect to regulating glucose and energy homeostasis and mood-related behaviours. Specifically, we hypothesise that the insulin receptor in the hypothalamus, classically known as the homeostatic centre of the brain, plays a causal role in linking metabolic and behavioural effects of insulin signalling. In this review, we discuss insulin signalling in the hypothalamus as a critical point of neural integration controlling metabolism and mood.

Insulin and glucose responses to hypoxia in male and female neonatal rats: Effects of the androgen receptor antagonist flutamide

Hypoxia is common with preterm birth and may lead to long-term effects on adult pancreatic endocrine function and insulin sensitivity. This phenomenon may be sexually dimorphic due to the hypoxia-induced augmentation of the neonatal androgen surge in male newborns. We evaluated this phenomenon by pretreating neonatal rats on postnatal days (PD) 1, 6, 13, or 20 with flutamide (a nonsteroidal androgen receptor antagonist) at a standard or a high dose (10 or 50 mg/kg) compared to vehicle control. One day later, neonatal rats were exposed to either acute normoxic or hypoxic separation (fasting) for 90 min, and blood was sampled for the measurement of insulin and glucose and the calculation of HOMA-IR as an index of insulin resistance. During normoxic and hypoxic separation (fasting), flutamide increased insulin secretion in PD2, PD7, and PD14 pups, high dose flutamide attenuated insulin secretion, and high dose flutamide attenuated the increase in HOMA-IR due to hypoxia. Our studies suggest a unique role of the androgen receptor in the control of neonatal pancreatic function, possibly by blocking a direct effect of neonatal testosterone or in response to indirect regulatory effects of androgens on insulin sensitivity.

Activation of mineralocorticoid receptors facilitate the acquisition of fear memory extinction and impair the generalization of fear memory in diabetic animals

RATIONALE

Studies point out a higher prevalence of posttraumatic stress disorder (PTSD) in individuals with diabetes mellitus. It is known that glucocorticoid (GR) and mineralocorticoid (MR) receptors are implicated in fear memory processes and PTSD. However, there is no preclinical studies addressing the involvement of these receptors on abnormal fear memories related to diabetic condition.

OBJECTIVES

By inducing a contextual conditioned fear memory, we generate a suitable condition to investigate the extinction and the generalization of the fear memory in streptozotocin-induced diabetic (DBT) rats alongside the expression of the cytosolic and nuclear GR and MR in the hippocampus (HIP) and prefrontal cortex (PFC). Moreover, we investigated the involvement of the MR or GR on the acquisition of fear memory extinction and on the generalization of this fear memory. When appropriate, anxiety-related behavior was evaluated.

METHODS

Male Wistar rats received one injection of steptozotocin (i.p.) to induce diabetes. After 4 weeks, the animals (DBTs and non-DBTs) were subjected to a conditioned contextual fear protocol.

RESULTS

The expression of MR and GR in the HIP and PFC was similar among all the groups. The single injection of MR agonist was able to facilitate the acquisition of the impaired fear memory extinction in DBTs animals together with the impairment of its generalization. However, the GR antagonism impaired only the generalization of this fear memory which was blocked by the previous injection of the MR antagonist. All treatments were able to exert anxiolytic-like effects.

CONCLUSIONS

The results indicate that MR activation in DBT animals disrupts the overconsolidation of aversive memory, without discarding the involvement of emotional behavior in these processes.

Keap1/Nrf2/HO-1 signaling pathway contributes to p-chlorodiphenyl diselenide antidepressant-like action in diabetic mice

RATIONALE

The association between depression and diabetes has been recognized for many years, but the nature of this relationship remains uncertain.

OBJECTIVES

This study investigated the antidepressant-like effect of (p-ClPhSe)₂ on mice made diabetic by streptozotocin (STZ) and the contribution of cerebral cortical Keap1/Nrf2/HO-1 signaling pathway for this effect.

METHODS

Male adult Swiss mice received streptozotocin (STZ, 200 mg/kg, i.p.) to induce diabetes (glycemia ≥ 200 mg/dl) or citrate buffer (5 ml/kg, control group). The mice were treated with (p-ClPhSe)₂ at the dose of 5 mg/kg, i.g., for 7 days. Mice performed behavior tests, tail suspension (TST), and forced swimming tests (FST), to evaluate depressive-like phenotype.

RESULTS

Diabetic mice showed an increase in immobility time in the TST and FST when compared to the control group. The protein contents of Keap1/Nrf2/HO-1 pathway were decreased in the cerebral cortex of diabetic mice. Diabetic mice had an increase in the relative adrenal weight and a decrease in the protein content of glucocorticoid receptor. The levels of TBARS and RS and SOD activity were found altered in the cerebral cortex of diabetic mice. The number of FJC-positive cells was increased in the cerebral cortex of diabetic mice. Treatment with (p-ClPhSe)₂ was effective against depressive-like phenotype, oxidative stress, and FJC-positive cells of diabetic mice. (p-ClPhSe)₂ did not reverse the parameters of HPA axis evaluated in this study. (p-ClPhSe)₂ modulated the cerebral cortical Keap1/Nrf2/HO-1 pathway in diabetic mice.

CONCLUSIONS

This study demonstrates the contribution of cerebral cortical Keap1/Nrf2/HO-1 pathway in the (p-ClPhSe)₂ antidepressant-like action in diabetic mice.

Molecular effects of Moringa leaf extract on insulin resistance and reproductive function in hyperinsulinemic male rats

BACKGROUND

Many studies have reported that insulin resistance impairs the antioxidant defense system and causes male infertility. Moringa oleifera is a medicinal plant that has been employed for the medicament of many disorders. It controls the levels of glucose and manages male sexual disorders. However, its extracts can reverse insulin resistance-linked metabolic alterations remains unknown. Therefore, the current study investigated the potential of the aqueous leaves extract from Moringa oleifera to reverse insulin resistance and testicular disorders in rats.

METHODS

Rats were fed either a chow (as a control group) or a high fructose diet (HFD, to persuade a state of insulin resistance), in addition to a group of rats fed HFD and treated with Moringa (300 mg/kg) for 4 weeks.

RESULTS

Moringa reversed hepatic insulin insensitivity and this was linked to up-regulation of genes involved in insulin receptors and glucose uptake in the liver. These results were associated with amended the insulin level in serum and standardization of insulin sensitivity. In addition, it improved the serum testosterone level and the gene expression of the testicular steridogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD).

CONCLUSION

Taken together, our findings demonstrate that Moringa reversed HFD diet-induced insulin resistance and improved the testicular function.

Evaluation of testis hormonal and histopathological alterations in type I and type II diabetic rats

BACKGROUND

Diabetes is a devastating metabolic disease that causes long-term damage to various organs. An important leading complication of diabetes is a degenerative effect on the reproductive system including infertility and gonadal dysfunction. This study aimed to evaluate the effects of experimental type I and II diabetes on the levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone.

METHODS

Male Wistar rats were randomly divided into four separate groups: (1) type I diabetes (T1DM), (2) type II diabetes (T2DM), (3) cetrorelix acetate-treated nondiabetic control group, and (4) normal untreated group (n = 6). T1DM was experimentally induced by a single injection of alloxan (135 mg/kg) while T2DM was induced by feeding the animals with drinking water enriched with fructose (10%). Cetrorelix acetate (100 mg/kg, intraperitoneal for 1 week) treatment group was used as a positive control. All rats were killed and blood and testes were collected after 8 weeks of the study. The effects of induced diabetes on the levels of blood glucose and insulin were assessed. The levels of sex hormones and insulin were determined by radioimmunoassay. Histological staining was used to check abnormal patterns of testicular morphology, the diameter of seminiferous tubules, testicular diameter, and germinal layer thickness.

RESULTS

A significant reduction in the testosterone, FSH, and LH levels were observed in T1DM, T2DM, and also in cetrorelix acetate-treated groups. Analysis of testicular histology sections revealed significantly reduced thickness of cell layer in T1DM and cetrorelix acetate-treated groups compared with the T2DM group. In T2DM, the cell numbers, the thickness of cell layer, the diameter of seminiferous tubules, and weight of testicles were slightly increased. In contrast, total tubules of empty seminiferous increased significantly in T1D and cetrorelix treated groups compared with the control group.

CONCLUSION

Overall, diabetes can induce hypothalamus-pituitary-gonad axis dysfunction, affects hormonal secretion, and causes histological damage to testes, collectively leading to deleterious effects on male fertility.

Hyperactivation of the hypothalamo-pituitary-adrenocortical axis in streptozotocin-diabetic gerbils (Gerbillus gerbillus)

This study was designed to investigate the HPA-axis impairment in the streptozotocin (STZ)-diabetic gerbils (Gerbillus gerbillus). Twenty-six male gerbils (body weight ~27 g) were divided into 3 groups: vehicle control (n = 10), 2 days of diabetes (n = 09) and 30 days of diabetes (n = 07). The latter 2 groups received an intraperitoneal injection of STZ (150 mg/kg of body weight). At 2 and 30 days of diabetes, streptozotocin-diabetic gerbils underwent a retro-orbital puncture for assessment of biochemical and hormonal parameters. Subsequently the animals were decapitated and the adrenal glands were removed, weighed and processed for light microscopy and stereology. Nondiabetic control gerbils that had been injected with citrate buffer were examined as a comparison. At 2 days of diabetes, STZ gerbils exhibited symptoms that are characteristic of human diabetes type 1. The adrenal gland showed significant increase in weight, associated with a larger cortex layer, hypertrophy of the fasciculate cells and a significant decrease in the nucleocytoplasmic index. These changes were associated with higher plasma ACTH and cortisol concentrations compared to nondiabetic controls. At 30 days postdiabetes, ACTH levels remained elevated, whereas cortisol levels decreased compared to the early stage of diabetes. Histological analysis revealed the existence of a band of connective tissue (collagen) that separates the cortical and medullary zones and is not present in humans or laboratory rodents, which represents a striking change seen throughout the disease. STZ-induced diabetes mellitus in Gerbillus gerbillus resulted in hyperactivation of the HPA axis in the early stages of diabetes mellitus which did not persist into the final stages of the disease, suggesting a possible reduction in adrenocortical sensitivity over time.

Adiponectin Mediates Running-Restored Hippocampal Neurogenesis in Streptozotocin-Induced Type 1 Diabetes in Mice

Streptozotocin (STZ)-induced diabetes impairs learning and memory performance and reduces adult hippocampal neurogenesis. Physical exercise brings beneficial effects. We have previously shown that adiponectin, an adipocyte-secreted hormone critically involved in the pathology of diabetes, is a key mediator for exercise-enhanced adult hippocampal neurogenesis. Here, we tested whether adiponectin is required for exercise to restore adult hippocampal neurogenesis in an animal model of diabetes. The findings showed that a single injection of 195 mg/kg STZ-induced diabetes significantly increased serum levels of corticosterone and reduced hippocampal adiponectin levels in adult mice. STZ injection also significantly reduced the number of Ki67 and doublecortin (DCX) positive cells and the ratio of co-labeling of DCX and bromodeoxyuridine (BrdU) in the hippocampal dentate region, indicating a decrease in adult hippocampal neurogenesis. Two-week voluntary wheel running significantly restored hippocampal neurogenesis in the diabetic wild-type mice, but not adiponectin knockout mice, indicating that adiponectin is critical for physical exercise to restore hippocampal adult neurogenesis in mice with diabetes. The results suggest that increasing adiponectin levels could be a therapeutic approach to restore hippocampal neurogenesis impairment in individuals with diabetes.

Protective effects of Lycium barbarum polysaccharide on male sexual dysfunction and fertility impairments by activating hypothalamic pituitary gonadal axis in streptozotocin-induced type-1 diabetic male mice

Diabetes-associated male sexual dysfunction and fertility impairments are both common clinical complications with limited therapeutic options; hence it seriously affects the quality of life of the patients, in particular, the patients of reproductive age. Lycium barbarum polysaccharide (LBP) has long being believed to maintain and to promote reproductive functions in the traditional medical practice in China. The current study was to investigate if LBP may contribute to recovery of male sexual dysfunction and fertility impairments in diabetic individuals. The effects of LBP on sexual behaviors and histological changes of testis were studied in the type-1 diabetes male mice induced by intra-peritoneal (i.p.) injection of streptozotocin (STZ). After oral administration of LBP (10, 20 or 40 mg/kg), sildenafil citrate (SC, 5 mg/kg) or saline for 62 consecutive days, the typical abnormal changes in the sperm parameters, in relative weight of reproductive organs and in morphology of testis were observed in diabetic mice. LBP treatment of the diabetic mice considerably reversed those changes and Johnsen's testicular score, serum testosterone (T), follicular stimulating hormone (FSH) and luteinizing hormone (LH) level were also increased to different degrees. Moreover, our data have also shown that a marked improvement in sexual behavior and fertility level after administration of LBP (40 mg/kg) compared to the diabetic group. These results suggested that LBP can exert functional recovery of male sexual dysfunction and fertility damages induced by diabetes in male mice, which is likely to be mediated through regulating the hypothalamus- pituitary-gonadal axis endocrine activity.

Hair corticosterone measurement in mouse models of type 1 and type 2 diabetes mellitus

In diabetes, glucocorticoid secretion increases secondary to hyperglycemia and is associated with an extensive list of disease complications. Levels of cortisol in humans, or corticosterone in rodents, are usually measured as transitory biomarkers of stress in blood or saliva. Glucocorticoid concentrations accumulate in human or animal hair over weeks and could more accurately measure the cumulative stress burden of diseases like chronic diabetes. In this study, corticosterone levels were measured in hair in verified rodent models of diabetes mellitus. To induce type 1 diabetes, C57BL/6J mice were injected with streptozotocin and blood and hair samples were collected 28days following induction. Leptin receptor deficient (db/db) mice were used as a spontaneous model of type 2 diabetes and blood and hair samples were collected at 8weeks of age, after the development of hyperglycemia and obesity. Corticosterone levels from serum, new growth hair and total growth hair were analyzed using an enzyme immunoassay. Corticosterone levels in new growth hair and serum were significantly elevated in both models of diabetes compared to controls. In contrast, corticosterone levels in old hair growth did not differ significantly between diabetic and non-diabetic animals. Thus, hair removal and sampling of new hair growth was a more sensitive procedure for detecting changes in hair corticosterone levels induced by periods of hyperglycemia lasting for 4weeks in mice. These results validate the use of hair to measure long-term changes in corticosterone induced by diabetes in rodent models. Further studies are now needed to validate the utility of hair cortisol as a tool for measuring the stress burden of individuals with diabetes and for following the effects of long-term medical treatments.

Activation of PPAR-γ reduces HPA axis activity in diabetic rats by up-regulating PI3K expression

Increased hypothalamus-pituitary-adrenal axis (HPA) activity in diabetes is strongly associated with several morbidities noted in patients with the disease. We previously demonstrated that hyperactivity of HPA axis under diabetic conditions is associated with up-regulation of adrenocorticotrophic hormone (ACTH) receptors (MC2R) in adrenal and down-regulation of glucocorticoid receptors (GR and MR) in pituitary. This study investigates the role of peroxisome proliferator-activated receptor (PPAR)-γ in HPA axis hyperactivity in diabetic rats. Diabetes was induced by intravenous injection of alloxan into fasted rats. The PPAR-γ agonist rosiglitazone and/or PI3K inhibitor wortmannin were administered daily for 18 consecutive days, starting 3days after diabetes induction. Plasma ACTH and corticosterone were evaluated by radioimmunoassay, while intensities of MC2R, proopiomelanocortin (POMC), GR, MR, PI3K p110α and PPAR-γ were assessed using immunohistochemistry. Rosiglitazone treatment inhibited adrenal hypertrophy and hypercorticoidism observed in diabetic rats. Rosiglitazone also significantly reversed the diabetes-induced increase in the MC2R expression in adrenal cortex. We noted that rosiglitazone reduced the number of corticotroph cells and inhibited both anterior pituitary POMC expression and plasma ACTH levels. Furthermore, rosiglitazone treatment was unable to restore the reduced expression of GR and MR in the anterior pituitary of diabetic rats. Rosiglitazone increased the number of PPAR-γ⁺ cells and expression of PI3K p110α in both anterior pituitary and adrenal cortex of diabetic rats. In addition, wortmannin blocked the ability of rosiglitazone to restore corticotroph cell numbers, adrenal hypertrophy and plasma corticosterone levels in diabetic rats. In conclusion, our findings revealed that rosiglitazone down-regulates HPA axis hyperactivity in diabetic rats via a mechanism dependent on PI3K activation in pituitary and adrenal glands.

An adverse immune-endocrine profile in patients with tuberculosis and type 2 diabetes

Diabetes is a risk factor for the development of pulmonary tuberculosis (TB) and both diseases present endocrine alterations likely to play a role in certain immuno-endocrine-metabolic associated disorders. Patients with TB, or with TB and type 2 diabetes (TB + T2DM) and healthy controls (HCo) were assessed for plasma levels of cortisol, dehydroepiandrosterone (DHEA), estradiol, testosterone, growth hormone (GH), prolactin, insulin-like growth factor-1 (IGF-1), cytokines (IL-6, IL-10, IFN-γ) and the specific lymphoproliferative capacity of peripheral blood mononuclear cells. All patients had higher levels of cortisol with a reduction in DHEA, thus resulting in an increased cortisol/DHEA ratio (Cort/DHEA). Increased prolactin and particularly GH levels were found in both groups of TB patients. This was not paralleled by increased concentrations of IGF, which remained within the levels of HCo. Estradiol levels were significantly augmented in patients TB, and significantly more in TB + T2DM, whereas testosterone levels were decreased in both groups of patients. IFN- γ and IL-6 concentrations were significantly increased in all TB, even further in TB + T2DM; while IL-10 was equally increased in both groups of TB patients. The in vitro specific proliferative capacity was decreased in both groups of patients as compared to that of HCo. The adverse immune-endocrine profile of TB seems to be slightly more pronounced in patients who also have T2DM.

Diabetes and brain health: implications for practice

BACKGROUND

It is widely accepted that people with mental illness have increased risk of cardiometabolic complications such as obesity and type 2 diabetes mellitus. What is less well known is that individuals with diabetes have an increased risk of brain health complications including depression, cognitive impairment and dementia. These conditions can adversely influence disease self-management and further increase risk of other diabetes complications. Aim The aim of this paper is to highlight the increased risk of brain health complications in populations with diabetes in order to promote awareness of such complications among healthcare professionals and encourage timely intervention.

METHODS

An overview of the prevalence and potential mechanisms linking depression and cognitive impairment with diabetes as well as implications for detection, management and brain health protection, based on a narrative review of the literature.

CONCLUSIONS

Early detection and effective management of depression and cognitive impairment among individuals with diabetes has the potential to minimise adverse health outcomes. In order to promote screening healthcare professionals caring for individuals with diabetes in all settings must be aware of the increased risk of brain health complications in this vulnerable population.

Diabetes distress in adult type 1 diabetes mellitus men and women with disease onset in childhood and in adulthood

THE AIM

To determine whether or not diabetes distress varies by age of type 1 diabetes mellitus (T1DM) onset and/or gender.

SUBJECTS AND METHODS

A total of 700 adult T1DM patients were randomly selected from the Lithuanian Diabetes Registry; 214 of them (30.6%) agreed to participate and were recruited for the study. Diabetes distress (emotional burden, physician-related distress, regimen-related distress, interpersonal distress) was compared in 105 (42 men and 63 women) patients with T1DM diagnosed during 0-18years of life, and in 109 (61 men and 48 women) with T1DM diagnosed in adulthood, using Diabetes Distress Scale (DDS).

RESULTS

Adult childhood-onset T1DM women have higher regimen-related distress (36.3±21.3 vs 26.6±16.2, p=0.016) than adulthood-onset women. Adult childhood-onset T1DM women experience higher diabetes distress (higher emotional burden (27.0±22.0 vs 15.6±16.4, p=0.006), physician-related distress (34.4±33.9 vs 20.7±29.4, p=0.024), total diabetes distress (41.2±13.6 vs 34.8±10.9, p=0.011)) than childhood-onset men. Adulthood-onset T1DM women experience higher physician-related distress (39.2±37.6 vs 23.4±32.5, p=0.013), but lower regimen-related distress (26.6±16.2 vs 35.8±21.6, p=0.014) than adulthood-onset men. In conclusion our findings reinforce the interdependence of psychological and biomedical factors in influencing health outcomes and support the need to provide psychological assessment and support to patients with T1DM.

Antidepressant-like effect of simvastatin in diabetic rats

Diabetes mellitus is accompanied by hormonal and neurochemical changes that can be associated with anxiety and depression. I investigated the antidepressant effect of simvastatin (SMV) on diabetic rats. Rats were divided into control (CTR) and streptozotocin-induced diabetic (STZ) groups and were orally administered 0, 5, or 10 mg/kg of SMV daily for 14 days, then exposed to the forced swimming test (FST). Our results showed that diabetic rats had higher immobility duration than the CTR rats, and SMV decreased this depressive-like behavior in the diabetic rats. However, clomipramine lowered the immobility time in the CTR and STZ rats. STZ decreased serotonin concentration in the hippocampus, which was reversed by SMV and clomipramine. The dopamine concentration in the hippocampus decreased in the STZ groups compared with the CTR groups. However, SMV and clomipramine had no significant effect on the dopamine levels in either the CTR or STZ groups. Corticosterone levels were increased in the untreated STZ group; SMV and clomipramine significantly decreased corticosterone levels in the STZ groups, but had no effect on the CTR groups. In conclusion, SMV exerts an antidepressant-like effect on diabetic rats that are submitted to the FST. The antidepressant-like effect of SMV in the FST appears to be mediated, at least in part, by the biochemical changes to the blood levels of corticosterone and of serotonin concentration in the hippocampus.

Corticotropic axis drive of overnight cortisol secretion is suppressed in adolescents and young adults with type 1 diabetes mellitus

CONTEXT

Type 1 diabetes mellitus (T1DM) is a pro-inflammatory stress state, which, with its attendant hyperglycemia, likely disrupts hypothalamo-pituitary-adrenal (HPA) control, further dysregulating glucose homeostasis.

OBJECTIVE

To test the hypothesis that endogenous adrenocorticotropic hormone (ACTH)-cortisol dose-responsive drive, estimated analytically, is significantly accentuated in adolescents and young adults with T1DM compared with healthy individuals.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

This was a pilot study of 11 volunteers with T1DM and 10 controls, ages 16-30 yr, at a medical center. Subjects underwent overnight frequent blood sampling (every 10 min for ACTH and cortisol and every 60 min for blood glucose) from 10 pm to 8 am. T1DM volunteers maintained their home insulin regimen.

MAIN OUTCOMES

Deconvolution analysis and dose-response estimates were the key outcomes.

RESULTS

Mean free cortisol, but not ACTH, concentrations were lower in the T1DM group compared with controls (p = 0.012). Non-invasive ACTH-cortisol dose-response estimates revealed that T1DM patients had reduced ACTH efficacy (maximal cortisol secretion, p = 0.009), reduced ACTH potency as quantified by greater EC50 (ACTH concentration driving half-maximal cortisol secretion, p = 0.04), and increased ACTH sensitivity (more positive ACTH-cortisol slope, p = 0.03). Post-hoc gender comparisons indicated that these differences were limited to females. Linear regression in women showed a strong correlation of both ACTH efficacy and EC50 with C-peptide levels (both p < 0.01).

CONCLUSION

Compared with healthy individuals, T1DM patients manifest decreased overnight adrenal responsiveness to endogenous ACTH leading to lower free cortisol concentrations. These findings suggest impaired stress-related adaptations of the HPA axis in T1DM.

Cardiovascular risk factors and frontotemporal dementia: a case-control study

Cardiovascular risk factors (CRF) were widely described as related to dementia. There are very few studies regarding this association in FTD. The objective of the study was to compare the frequency of CRF in our population with FTD and controls. 100 consecutive subjects with FTD diagnosis according to Lund-Manchester clinical criteria and 200 controls matched by age and sex were included between January 2003 to February 2007 at the Cognitive and Behavior Unit of Hospital Italiano de Buenos Aires. Clinical evaluation, laboratory tests, brain images (CT/MRI), neuropsychological and neuropsychiatric assessment were performed. Multiple regression analysis was performed to analyze the association in CRF between FTD patients vs. controls. The mean age in FTD was 69.7 ± 0.9 vs. 70.1 ± 0.8 in controls (p 0.12). No difference in gender was observed between cases and controls. No differences were identified between patients and controls regarding hypertension (HTA) (65% vs. 67,3% p 0.44); dyslipidemia (57% vs. 54.7% p 0.74); obesity (39% vs. 27.6% p 0.14) and hypothyroidism (26% vs. 17.1% p 0.1). A significant difference was observed for Diabetes Mellitus (39% vs. 22.6% p 0.001). In our population, Diabetes Mellitus was associated as an independent risk factor for FTD. To our knowledge this is the first report in which CRF were evaluated prospectively in FTD patients. More studies are needed to confirm this finding in larger populations.

Programming of the hypothalamic-pituitary-adrenal axis by neonatal intermittent hypoxia: effects on adult male ACTH and corticosterone responses are stress specific

Intermittent hypoxia (IH) is an animal model of apnea-induced hypoxia, a common stressor in the premature neonate. Neonatal stressors may have long-term programming effects in the adult. We hypothesized that neonatal exposure to IH leads to significant changes in basal and stress-induced hypothalamic-pituitary-adrenal (HPA) axis function in the adult male rat. Rat pups were exposed to normoxia (control) or 6 approximately 30-second cycles of IH (5% or 10% inspired O₂) daily on postnatal days 2-6. At approximately 100 days of age, we assessed the diurnal rhythm of plasma corticosterone and stress-induced plasma ACTH and corticosterone responses, as well as mRNA expression of pertinent genes within the HPA axis. Basal diurnal rhythm of plasma corticosterone concentrations in the adult rat were not affected by prior exposure to neonatal IH. Adults exposed to 10% IH as neonates exhibited an augmented peak ACTH response and a prolonged corticosterone response to restraint stress; however, HPA axis responses to insulin-induced hypoglycemia were not augmented in adults exposed to neonatal IH. Pituitary Pomc, Crhr1, Nr3c1, Nr3c2, Avpr1b, and Hif1a mRNA expression was decreased in adults exposed to neonatal 10% IH. Expression of pertinent hypothalamic and adrenal mRNAs was not affected by neonatal IH. We conclude that exposure to neonatal 10% IH programs the adult HPA axis to hyperrespond to acute stimuli in a stressor-specific manner.

Ameliorating effect and potential mechanism of Rehmannia glutinosa oligosaccharides on the impaired glucose metabolism in chronic stress rats fed with high-fat diet

The aim of this study was to determine whether the Rehmannia glutinosa oligosaccharides (ROS) ameliorate the impaired glucose metabolism and the potential mechanism in chronic stress rats fed with high-fat diet. The rats were fed by a high-fat diet and simultaneously stimulated by chronic stress over 5 weeks. Body weight, fasting plasma glucose, intraperitoneal glucose tolerance test (IPGTT), plasma lipids, gluconeogenesis test (GGT), glycogen content, and corticosterone, insulin and leptin levels were measured. The results showed that ROS administration (100, 200 mg/kg, i.g.) for 5 weeks exerted the effects of increasing the organ weights of thymus and spleen, lowering the fasting plasma glucose level, improving impaired glucose tolerance, increasing the contents of liver and muscle glycogen, decreasing the gluconeogenesis ability, plasma-free fatty acid's level, as well as plasma triglyceride and total cholesterol levels in chronic stress and high-fat fed rats, especially in the group of 200mg/kg; while the plasma corticosterone level was decreased, and plasma leptin level was increased. These results suggest that ROS exert an ameliorating effect of impaired glucose metabolism in chronic stress rats fed with high-fat diet, and the potential mechanism may be mediated through rebuilding the glucose homeostasis in the neuroendocrine immuno-modulation (NIM) network through multilinks and multitargets.

Sequential alterations of glucocorticoid receptors in the hippocampus of STZ-treated type 1 diabetic rats

Type 1 diabetes is a common metabolic disorder accompanied by increased blood glucose levels along with glucocorticoid and cognitive deficits. The disease is also thought to be associated with environmental changes in brain and constantly induces oxidative stress in patients. Therefore, glucocorticoid-mediated negative feedback mechanisms involving the glucocorticoid receptor (GR) binding site are very important to understand the development of this disease. Many researchers have used streptozotocin (STZ)-treated diabetic animals to study changes in GR expression in the brain. However, few scientists have evaluated the hyperglycemic period following STZ exposure. In the present study, we found GR expression in the hippocampus varied based on the period after STZ administration for up to 4 weeks. We performed immunohistochemistry and Western blotting to validate the sequential alterations of GR expression in the hippocampus of STZ-treated type 1 diabetic rats. GR protein expression increased significantly until week 3 but decreased at week 4 following STZ administration. GR expression after 70 mg/kg STZ administration was highest at 3 weeks post-treatment and decreased thereafter. Although STZ-induced increase in GR expression in diabetic animals has been described, our data indicate that researchers should consider the sequential GR expression changes during the hyperglycemic period following STZ exposure.

Effects of prolonged exendin-4 administration on hypothalamic-pituitary-adrenal axis activity and water balance

Exendin-4 (Ex-4) is a natural agonist of the glucagon-like peptide-1 (GLP-1) receptor, currently being used as a treatment for type 2 diabetes mellitus due to its insulinotropic properties. Previous studies have revealed that acute administration of both GLP-1 and, in particular, Ex-4 potently stimulates hypothalamic-pituitary-adrenal (HPA) axis activity. In this work, the effects of prolonged Ex-4 exposure on HPA function were explored. To this end, Sprague-Dawley rats were subjected to a daily regimen of two Ex-4 injections (5 μg/kg sc) for a minimum of 7 days. We found that subchronic Ex-4 administration produced a number of effects that resemble chronic stress situations, including hyperactivation of the HPA axis during the trough hours, disruption of glucocorticoid circadian secretion, hypertrophy of the adrenal gland, decreased adrenal gland sensitivity, impaired pituitary-adrenal stress responses, and reductions in both food intake and body weight. In addition, a threefold increase in diuresis was observed followed by a 1.5-fold increase in water intake; these latter effects were abolished by adrenalectomy. Together, these findings indicate that Ex-4 induces a profound dysregulation of HPA axis activity that may also affect renal function.

Chronic treatment with the glucocorticoid receptor antagonist RU486 inhibits diabetes-induced enhancement of experimental periodontitis

BACKGROUND AND OBJECTIVE

Chronic hypothalamic-pituitary-adrenal (HPA) axis hyperactivity and excessive glucocorticoid hormone release have been associated with diabetes, altered immune responses and increased susceptibility to periodontitis. In the present study we tested the impact of streptozotocin (STZ)-induced diabetes on ligature-induced periodontitis and the effect of subsequent treatment with the glucocorticoid receptor (GR) antagonist, RU486.

MATERIAL AND METHODS

A single dose of STZ [45 mg/kg, intraperitoneally (i.p.)] or vehicle was given 10 d before induction of ligature-induced periodontitis and implantation subcutaneously of a drug pellet containing the GR antagonist, RU486, or a placebo pellet. Periodontitis was assessed when the ligatures had been in place for 21 d. Two hours before decapitation all rats received gram-negative bacterial lipopolysaccharide (LPS) (150 μg/kg, i.p.) to induce a robust immune and stress response.

RESULTS

Compared with control rats, STZ-treated rats developed significantly more periodontal bone loss, and RU486 treatment of STZ -treated rats significantly inhibited this effect. STZ-treated rats also showed significantly higher levels of the HPA axis-derived hormone, corticosterone, as well as of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-α), but lower levels of the anti-inflammatory cytokines interleukin-10 (IL-10) and transforming growth factor-1beta (TGF-1β) after LPS stimulation. GR blockade had no statistically significant effects on these measurements in diabetic rats, but tended to enhance the levels of TNF-α and TGF-1β, and reduce the levels of IL-10 and blood glucose.

CONCLUSION

In diabetic subjects, excessive GR activation as a result of chronic high levels of glucocorticoid hormones may alter immune-system responses in a manner that may increase the susceptibility to periodontitis.

Comparative study on the effects of type 1 and type 2 diabetes on structural changes and hormonal output of the adrenal cortex in male Wistar rats

INTRODUCTION

Diabetes is one of the most common endocrine disorders characterized by hyperglycemia due to defects in insulin secretion, insulin function, or both. Causing dysfunction in the body general metabolism, diabetes-induced chronic hyperglycemia leads to alterations in those endocrine glands involved in regulating the body metabolism. In this line, the present study has been conducted to investigate the effects of type 1 and type 2 diabetes on the structural changes and hormonal output of the adrenal cortex in male Wistar rat.

METHODS

Eighteen male Wistar rats were divided into three groups including control, experimental type 1 diabetes (subcutaneous injection of 135 mg/kg alloxan) and experimental type 2 diabetes (8 weeks treatment with drinking water containing 10% fructose). Two months after the induction of both types of diabetes, the level of blood biochemical factors (glucose, insulin, cortisol, triglycerides, cholesterol, LDL, and HDL) were measured. Structural changes of the adrenal cortex were then evaluated, using stereological techniques.

RESULTS

Serum biochemical analysis showed significant difference in the levels of glucose, triglycerides, insulin and cortisol in experimental groups, compared to the control. The results of structural alterations were also indicative of increase in adrenal cortex volume in both types of diabetes.

CONCLUSION

Probably through increasing HPA axis activity, type1 diabetes-induced hyperglycemia leads to adrenal hypertrophy and increase the hormonal output of adrenal gland.

Systemic and local ACTH produced during inflammatory states promotes osteochondrogenic mesenchymal cell differentiation contributing to the pathologic progression of calcified atherosclerosis

There are many well-known roles for the proopiomelanocortin (POMC) derived peptides and their receptors, the melanocortin receptors (MC-R). The focus here is on the evolving role of the melanocortin system in inflammation. Chronic inflammatory states such as those occurring in diabetes and obesity are associated with both a hyperactive hypothalamic-pituitary-adrenal (HPA) axis as well as increased incidence of atherosclerosis. An inflammation-induced hyperactive HPA axis along with increased leukocyte infiltration can lead to significant exposure to melanocortin peptides, particularly ACTH, in an inflamed vasculature. Mesenchymal progenitor cells are present throughout the vasculature, express receptors for the melanocortin peptides, and respond to ACTH with increased osteochondrogenic differentiation. Coupled to the increased exposure to ACTH during HPA hyperactivity is increased glucocorticoid (GC) exposure. GCs also promote chondrogenic differentiation of mesenchymal progenitors and increase their expression of MC-R as well as their expression of POMC and its cleavage products. It is hypothesized that during inflammatory states systemically produced ACTH and glucocorticoid as well as ACTH produced locally by macrophage and other immune cells, can influence and potentiate mesenchymal progenitor cell differentiation along the osteochondrogenic lineages. In turn the increase in osteochondrogenic matrix contributes to the pathophysiological progression of the calcified atherosclerotic plaque. The roles of the melanocortin system in inflammation and its resolution have just begun to be explored. Investigations into the ACTH-induced matrix changes among mesenchymal cell populations are warranted. ACTH signaling through the MC-R represents a new therapeutic target for the prevention and treatment of calcified atherosclerosis.

Type 1 diabetes mellitus and major depressive disorder: evidence for a biological link

AIMS/HYPOTHESIS

A growing body of research suggests that the prevalence of major depressive disorder (MDD) in children and youth with type 1 diabetes mellitus is significantly higher than that of youth without type 1 diabetes and is associated with increased illness severity. The objective of this article is to review the current literature on the pathophysiology of these two common diseases with respect to potential areas of overlapping biological dysfunction.

METHODS

A search of English language articles published between 1966 and 2010 was conducted and augmented with manual review of reference lists from the identified publications.

RESULTS

The evidence suggests plausible mechanisms whereby a biological relationship between type 1 diabetes and MDD may exist. These include the effects of circulating cytokines associated with autoimmune diabetes, the direct impact of insulin deficiency on neurogenesis/neurotransmitter metabolism, the effects of the chronic hyperglycaemic state, occurrence of iatrogenic hypoglycaemia and the impact of basal hyperactivity of the hypothalamic-pituitary-adrenal axis.

CONCLUSIONS/INTERPRETATION

Shared biological vulnerabilities may be implicated in the comorbidity of type 1 diabetes and MDD. Further research is warranted to determine the magnitude of associations and confirm their observation in clinical populations.

Odyssey between Scylla and Charybdis through storms of carbohydrate metabolism and diabetes: a career retrospective

This research perspective allows me to summarize some of my work completed over 50 years, and it is organized in seven sections. 1) The treatment of diabetes concentrates on the liver and/or the periphery. We quantified hormonal and metabolic interactions involved in physiology and the pathogenesis of diabetes by developing tracer methods to separate the effects of diabetes on both. We collaborated in the first tracer clinical studies on insulin resistance, hypertriglyceridemia, and the Cori cycle. 2) Diabetes reflects insulin deficiency and glucagon abundance. Extrapancreatic glucagon changed the prevailing dogma and permitted precise exploration of the roles of insulin and glucagon in physiology and diabetes. 3) We established the critical role of glucagon-insulin interaction and the control of glucose metabolism during moderate exercise and of catecholamines during strenuous exercise. Deficiencies of the release and effects of these hormones were quantified in diabetes. We also revealed how acute and chronic hyperglycemia affects the expression of GLUT2 gene and protein in diabetes. 4) We outlined molecular and physiological mechanisms whereby exercise training and repetitive neurogenic stress can prevent diabetes in ZDF rats. 5) We and others established that the indirect effect of insulin plays an important role in the regulation of glucose production in dogs. We confirmed this effect in humans and demonstrated that in type 2 diabetes it is mainly the indirect effect. 6) We indicated that the muscle and the liver protected against glucose changes. 7) We described molecular mechanisms responsible for increased HPA axis in diabetes and for the diminished responses of HPA axis, catecholamines, and glucagon to hypoglycemia. We proposed a new approach to decrease the threat of hypoglycemia.

Mineralocorticoid receptor activation restores medial perforant path LTP in diabetic rats

In the hippocampus, glucocorticoids bind to two types of receptors: the mineralocorticoid receptor, which binds corticosterone with high affinity and is tonically occupied; and the glucocorticoid receptor, which is occupied during stress and at certain phases in the circadian cycle. Diabetes mellitus increases levels of glucocorticoids in both humans and animal models. To explore the contributions of hippocampal corticosteroid receptors to the diabetes-induced suppression of neuroplasticity, we manipulated these receptors in hippocampal slices from streptozocin-diabetic rats, a model of Type 1 diabetes mellitus. STZ-diabetes reduced long-term potentiation (LTP) at medial perforant path synapses in the dentate gyrus, and induced a bias in favor of long-term depression following intermediate stimulation frequencies. Bath application of the mineralocorticoid receptor agonist aldosterone restored LTP in slices from diabetic animals. These results suggest additional mechanisms for diabetes-induced functional alterations and support a restorative role for dentate gyrus mineralocorticoid receptors.

Regular exercise prevents the development of hyperglucocorticoidemia via adaptations in the brain and adrenal glands in male Zucker diabetic fatty rats

We determined the effects of voluntary wheel running on the hypothalamic-pituitary-adrenal (HPA) axis, and the peripheral determinants of glucocorticoids action, in male Zucker diabetic fatty (ZDF) rats. Six-week-old euglycemic ZDF rats were divided into Basal, Sedentary, and Exercise groups (n = 8-9 per group). Basal animals were immediately killed, whereas Sedentary and Exercising rats were monitored for 10 wk. Basal (i.e., approximately 0900 AM in the resting state) glucocorticoid levels increased 2.3-fold by week 3 in Sedentary rats where they remained elevated for the duration of the study. After an initial elevation in basal glucocorticoid levels at week 1, Exercise rats maintained low glucocorticoid levels from week 3 through week 10. Hyperglycemia was evident in Sedentary animals by week 7, whereas Exercising animals maintained euglycemia throughout. At the time of death, the Sedentary group had approximately 40% lower glucocorticoid receptor (GR) content in the hippocampus, compared with the Basal and Exercise groups (P < 0.05), suggesting that the former group had impaired negative feedback regulation of the HPA axis. Both Sedentary and Exercise groups had elevated ACTH compared with Basal rats, indicating that central drive of the axis was similar between groups. However, Sedentary, but not Exercise, animals had elevated adrenal ACTH receptor and steroidogenic acute regulatory protein content compared with the Basal animals, suggesting that regular exercise protects against elevations in glucocorticoids by a downregulation of adrenal sensitivity to ACTH. GR and 11beta-hydroxysteroid dehydrogenase type 1 content in skeletal muscle and liver were similar between groups, however, GR content in adipose tissue was elevated in the Sedentary groups compared with the Basal and Exercise (P < 0.05) groups. Thus, the gradual elevations in glucocorticoid levels associated with the development of insulin resistance in male ZDF rats can be prevented with regular exercise, likely because of adaptations that occur primarily in the adrenal glands.

Shaping the stress response: interplay of palatable food choices, glucocorticoids, insulin and abdominal obesity

Activity of the hypothalamo-pituitary-adrenal (HPA) axis is regulated by a negative feedback loop that dampens central drive of the axis via the actions of the secreted glucocorticoids. Conversely, under conditions of chronic stress, glucocorticoids delivered centrally increase hypothalamic paraventricular nucleus (PVN) corticotrophin-releasing factor (CRF) expression and the response to restraint. However, HPA axis activity and PVN CRF mRNA expression under chronic stress conditions are often reduced, implying other indirect peripheral or extra-hypothalamic glucocorticoid actions. Glucocorticoids chronically increase palatable food intake, which increases abdominal fat depots and circulating insulin levels, both of which negatively correlate with PVN CRF mRNA expression and may in turn dampen the response to stress. Such an effect is dependent on food choices, rather than total calories ingested. Considering stress is omnipresent in the workplace, palatable food ingestion may represent a means to combat the feeling of stress which is ultimately maladaptive when unresolved.

Insulin and the constituent branches of the hepatic vagus interact to modulate hypothalamic and limbic neuropeptide mRNA expression differentially

Insulin and signalling through the vagus nerve act in concert to regulate metabolic homeostasis and ingestive behaviour. Our previous studies using streptozotocin (STZ)-diabetic rats have shown that hepatic branch vagotomy (HV), gastroduodenal branch vagotomy (GV) and capsaicin treatment of the common hepatic branch that selectively destroys afferent fibres (CapV), all promote lard, but not total, caloric intake to levels similar to those achieved with insulin treatment. Because hypothalamic and limbic mRNA expression of neuropeptides linked to energy balance is altered by STZ-diabetes and HV, we examined the role(s) of insulin and the common hepatic and gastroduodenal branches of the vagus nerve and hepatic afferent fibres in the regulation of these neuropeptides in rats with high, steady-state corticosterone levels. STZ-diabetic rats were prepared with osmotic minipumps containing either saline or insulin and were compared with nondiabetic counterparts: half of each group received a vagal manipulation, the other half were sham operated. Five days after surgery, rats were offered the choice of lard and chow to consume for another 5 days, when brains were collected and processed for in situ hybridisation. Paraventricular nucleus corticotrophin-releasing factor (CRF) mRNA was elevated by STZ treatment, an effect prevented by either insulin treatment or GV. By contrast, CRF mRNA expression in the central nucleus of the amygdala and bed nuclei of the stria terminalis was unaffected by STZ treatment, but HV and CapV manipulations elevated expression in the nondiabetic, but not STZ-diabetic groups. Arcuate nucleus neuropeptide Y, but not pro-opiomelanocortin, mRNA expression was elevated by STZ treatment and all vagal manipulations; however, exogenous insulin treatment failed to prevent this, in keeping with their previously documented elevated caloric intake. These results strongly suggest that the gastroduodenal branch and hepatic branch proper, which merge to form the common hepatic branch, differentially interact with prevailing insulin levels to regulate hypothalamic and limbic neuropeptide mRNA expression.

Glucocorticoid receptor changes associate with age in the paraventricular nucleus of type II diabetic rat model

Diabetes is a metabolic disorder that is associated with the dysregulation of a number of systems within the body. In the present study, we investigated glucocorticoid receptor (GR) immunoreactivity and its protein levels in the paraventricular nuclei of 4-, 12-, 20- and 30-week-old Zucker diabetic fatty (fa/fa, ZDF) and in Zucker lean control (fa/+ or +/+, ZLC) rats, because the progressive induction of diabetes is detectable in this model after 7 weeks of age and chronic diabetic conditions are maintained after 12 weeks of age. GR immunoreactivity was detected in parvocellular paraventricular nuclei and this and GR protein levels were exponentially increased according to the ages. In particular, GR immunoreactivities and protein levels were markedly more increased in 30-week-old ZDF rats than in age-matched ZLC group and in younger ZDF group. The present study suggests that GR immunoreactivity and its protein level is associated with a degenerative phenotype in the hypothalamus of from 12-weeks old in the ZDF rat type II diabetes model.

The effect of long-term insulin treatment with and without antecedent hypoglycemia on neuropeptide and corticosteroid receptor expression in the brains of diabetic rats

We previously demonstrated that while diabetic animals receiving long-term insulin treatment exhibited some impairment in their corticosterone response to hypoglycemia, the stress response to hypoglycemia was completely absent when these animals were subjected to recurrent hypoglycemia. In the current study, we examined potential mechanisms that may contribute to defects in the adrenocortical response to hypoglycemia in long-term insulin-treated diabetic animals exposed to antecedent hypoglycemia. Whereas insulin-treated diabetic animals exhibited a significant rise in corticotrophin-releasing hormone (CRH) mRNA levels during hypoglycemia, exposure to antecedent hypoglycemia completely abolished this response. Moreover, expression of hippocampal mineralocorticoid receptors (MR) mRNA, which normally act to suppress hypothalamo-pituitary-adrenal activity, decreased in the normal control and insulin-treated diabetic groups in response to hypoglycemia, whereas MR mRNA levels remained at baseline in animals subjected to antecedent hypoglycemia. Interestingly, hippocampal glucocorticoid receptor (GR) mRNA levels decreased in all three treatment groups following the hypoglycemic clamp. While GR mRNA levels in the paraventricular nucleus were lower in normal controls following hypoglycemia, this trend just failed to reach statistical significance in the two diabetic groups. These data suggest that (1) recurrent hypoglycemia, much like uncontrolled diabetes, has a pronounced effect on hippocampal mineralocorticoid receptor mRNA expression that may prevent it, and presumably also the stress axis, from responding properly to a subsequent bout of hypoglycemia, and (2) while long-term insulin treatment was sufficient to restore some of these responses in diabetic animals, tighter glycemic control may be necessary to see full restoration of the stress response.

Adrenal hypersensitivity precedes chronic hypercorticism in streptozotocin-induced diabetes mice

Previous studies have demonstrated that type 1 diabetes is characterized by hypercorticism and lack of periodicity in adrenal hormone secretion. In the present study, we tested the hypothesis that hypercorticism is initiated by an enhanced release of ACTH leading subsequently to adrenocortical growth and increased output of adrenocortical hormones. To test this hypothesis, we used the streptozotocin (STZ)-induced diabetes mouse model and measured hypothalamic-pituitary-adrenal axis activity at different time points. The results showed that the expected rise in blood glucose levels induced by STZ treatment preceded the surge in corticosterone secretion, which took place 1 d after diabetes onset. Surprisingly, circulating ACTH levels were not increased and even below control levels until 1 d after diabetes onset and remained low until d 11 during hypercorticism. In response to ACTH (but not vasopressin), cultures of adrenal gland cells from 11-d diabetic mice secreted higher amounts of corticosterone than control cells. Real-time quantitative PCR revealed increased expression of melanocortin 2 and melanocortin 5 receptors in the adrenal glands at 2 and 11 d of STZ-induced diabetes. AVP mRNA expression in the paraventricular nucleus of the hypothalamus was increased, whereas hippocampal MR mRNA was decreased in 11-d diabetic animals. GR and CRH mRNAs remained unchanged in hippocampus and paraventricular nucleus of diabetic mice at all time points studied. These results suggest that sensitization of the adrenal glands to ACTH rather than an increase in circulating ACTH level is the primary event leading to hypercorticism in the STZ-induced diabetes mouse model.

Adaptation to mild, intermittent stress delays development of hyperglycemia in the Zucker diabetic Fatty rat independent of food intake: role of habituation of the hypothalamic-pituitary-adrenal axis

Hypothalamic-pituitary-adrenal (HPA) axis hyperactivity occurs in type 2 diabetes, and stress is assumed to play a causal role. However, intermittent restraint stress, a model mimicking some mild stressors, delays development of hyperglycemia in Zucker diabetic fatty (ZDF) rats. We examine whether such stress delays hyperglycemia independent of stress-induced reductions in hyperphagia and is due to adaptations in gene expression of HPA-related peptides and receptors that ameliorate corticosteronemia and thus hyperglycemia. ZDF rats were intermittently restraint stressed (1 h/d, 5 d/wk) for 13 wk and compared with obese control, pair fed, and lean ZDF rats. After 13 wk, basal hormones were repeatedly measured over 24 h, and HPA-related gene expression was assessed by in situ hybridization. Although restraint initially induced hyperglycemia, this response habituated over time, and intermittent restraint delayed hyperglycemia. This delay was partly related to 5-15% decreased hyperphagia, which was not accompanied by decreased arcuate nucleus NPY or increased POMC mRNA expression, although expression was altered by obesity. Obese rats demonstrated basal hypercorticosteronemia and greater corticosterone responses to food/water removal. Basal hypercorticosteronemia was further exacerbated after 13 wk of pair feeding during the nadir. Importantly, intermittent restraint further delayed hyperglycemia independent of food intake, because glycemia was 30-40% lower than after 13 wk of pair feeding. This may be mediated by increased hippocampal MR mRNA, reduced anterior pituitary POMC mRNA levels, and lower adrenal sensitivity to ACTH, thus preventing basal and stress-induced hypercorticosteronemia. In contrast, 24-h catecholamines were unaltered. Thus, rather than playing a causal role, intermittent stress delayed deteriorations in glycemia and ameliorated HPA hyperactivity in the ZDF rat.

Effects of a high-glucose environment on the pituitary growth hormone-releasing hormone receptor: type 1 diabetes compared with in vitro glucotoxicity

The present study investigated the effects of diabetes and high glucose on GHRH receptor (GHRH-R) mRNA and protein levels in the pituitary of diabetic rats 2, 21, and 60 days post-streptozotocin (post-STZ) administration. Two days post-STZ, the 2.5-kb GHRH-R mRNA transcript was increased. Twenty-one days post-STZ, both the 2.5- and 4-kb transcripts and a 72-kDa (125)I-GHRH-GHRH-R complex were elevated. Sixty days post-STZ, the 4-kb transcript remained increased and the 45-kDa (125)I-GHRH-GHRH-R complex (functional receptor) was decreased. Hypothalamic GHRH mRNA and serum total IGF-I levels were reduced at all three time points. To better understand the role of high glucose on GHRH-R regulation, time-course effects of 33 compared with 6 mM d-glucose (DG) were examined in cultured anterior pituitary cells from 2-mo-old healthy rats. Membrane lipoperoxidation was present in 33 mM DG, and GHRH-R mRNA levels were diminished after 24 h, Fluo-GHRH internalization was marginal after 16-24 h, and GHRH-induced cAMP levels were decreased after 24 and 48 h. Altogether, these results indicate that the increase of the 2.5-kb GHRH-R mRNA transcript in vivo could be a consequence of a decrease of hypothalamic GHRH mRNA levels in STZ rats. Since it does not affect primarily functional GHRH-R levels, the initial diminution of circulating IGF-I levels could result from a decreased GHRH-R stimulation by GHRH. Thus, the effect of glucotoxicity would be related to a decrease of functional GHRH-R protein, as observed in rats 60 days post-STZ and in cultured pituitary cells from healthy rats exposed to a high-glucose environment.

Gene expression of mineralocorticoid and glucocorticoid receptors in the limbic system is related to type-2 like diabetes in leptin-resistant rats

Diabetes is often accompanied by a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis which is regulated centrally via glucocorticoid (GR) and mineralocorticoid receptors (MR). Here, we compared the expression of both receptor subtypes in the brain of Zucker fatty and Zucker diabetic fatty (ZDF) rats together with their respective control rats. Both strains are primarily leptin resistant due to a mutated leptin receptor; ZDF rats, however, develop type-2 like diabetes. Using quantitative real-time PCR (qPCR) we found increased hypothalamic corticotrophin releasing hormone (CRH) levels in rats with the genetic ZDF background independently from leptin resistance. This was accompanied by elevated plasma corticosterone levels and by a higher reactivity of the HPA axis in response to CRH. Rats with the genetic ZDF background showed increased mRNA levels of GR in the amygdala and hypothalamus and increased mRNA levels of MR in the hippocampus and hypothalamus compared to rats with the Zucker fatty background. In leptin resistant ZDF rats but not in Zucker fatty rats, the mRNA levels of MR were selectively increased in the amygdala compared to nondiabetic control rats. No differences in the GR mRNA levels were found between leptin resistant Zucker fatty rats and lean control rats. Thus, an increased drive of the HPA axis in rats with ZDF background is associated with a differential expression of GR and MR in the limbic system. This dysregulation of the HPA axis may eventually lead, in combination with leptin resistance, to the development of diabetes in ZDF rats.

Downregulation of prolactin-releasing peptide gene expression in the hypothalamus and brainstem of diabetic rats

We investigated the prolactin-releasing peptide (PrRP) mRNA levels in the hypothalamus and brainstem of streptozotocin (STZ)-induced diabetic rats and fa/fa Zucker diabetic rats, using in situ hybridization histochemistry. PrRP mRNA levels in the hypothalamus and brainstem of STZ-induced diabetic rats were significantly reduced in comparison with those of control rats. PrRP mRNA levels in the diabetic rats were reversed by both insulin and leptin. PrRP mRNA levels in the fa/fa diabetic rats were significantly reduced in comparison with those of Fa/? rats. PrRP mRNA levels in the fa/fa diabetic rats were significantly increased by insulin-treatment, but did not reach control levels in the Fa/? rats. We also investigated the effect of restraint stress on PrRP mRNA levels in STZ-induced diabetic rats. The PrRP mRNA levels in the control and the STZ-induced diabetic rats increased significantly after restraint stress. The diabetic condition and insulin-treatment may affect the regulation of PrRP gene expression via leptin and other factors, such as plasma glucose level. The diabetic condition may not impair the role of PrRP as a stress mediator.

Streptozotocin induces G2 arrest in skeletal muscle myoblasts and impairs muscle growth in vivo

Streptozotocin (STZ) is used extensively to induce pancreatic beta-cell death and ultimately diabetes mellitus in animal models. However, the direct effects of STZ on muscle are largely unknown. To delineate the effects of STZ from the effects of hypoinsulinemia/hyperglycemia, we injected young rats with 1) saline (control), 2) STZ (120 mg/kg) or 3) STZ and insulin (STZ-INS; to maintain euglycemia). STZ rats demonstrated significantly elevated blood glucose throughout the 48-h protocol, while control and STZ-INS rats were euglycemic. Body mass increased in control (13 +/- 4 g), decreased by 19 +/- 2 g in STZ and remained unchanged in STZ-INS rats (-0.3 +/- 2 g). Cross-sectional areas of gastrocnemius muscle fibers were smaller in STZ vs. control (1,480 +/- 149 vs. 1,870 +/- 40 microm(2), respectively; P < 0.05) and insulin treatment did not rescue this defect (STZ-INS: 1,476 +/- 143 microm(2)). Western blot analysis revealed a detectable increase in ubiquitinated proteins in the STZ skeletal muscles compared with control and STZ-INS. To further define the effects of STZ on skeletal muscle, independent of hyperglycemia, myoblasts were exposed to varying doses of STZ (0.25-3.0 mg/ml) in vitro. Both acute and chronic exposures of STZ significantly impaired proliferative capacity in a dose-dependent manner. Within STZ-treated myoblasts, increased reactive oxygen species was associated with significant G(2)/M phase cell-cycle arrest. Taken together, our findings show that the effects of STZ are not beta-cell specific and reveal that STZ should not be used for studies examining diabetic myopathy.

Hypothalamic paraventricular nucleus, but not vasopressin, participates in chronic hyperactivity of the HPA axis in diabetic rats

Diabetes mellitus (DM), as chronic stress activates the hypothalamo-pituitary-adrenocortical axis. We examined whether arginine vasopressin (AVP) and the hypothalamic paraventricular nucleus (PVN) participate in DM-induced chronic stress symptoms. AVP-deficient Brattleboro or PVN-lesioned Wistar rats were used with heterozygous or sham-operated controls. The rats were studied 2 wk after a single injection of streptozotocin. The appearance of DM (enhanced water consumption and blood glucose elevation) and the chronic stress-like somatic changes (body weight decrease, thymus involution, adrenal gland hypertrophy) were not influenced by the lack of AVP. By contrast, PVN lesion significantly attenuated DM-induced thymus involution and adrenal gland hypertrophy as well as the increase in water consumption. The corticotropin-releasing hormone mRNA in PVN was diminished by DM and elevated by the lack of AVP without interaction. DM elevated the proopiomelanocortin (POMC) mRNA in the anterior lobe of the pituitary. The lack of AVP had no effect, whereas lesioning the PVN significantly diminished the elevation. The elevated basal corticosterone plasma levels detectable in DM were influenced neither by the lack of AVP nor by lesioning the PVN. Thus the lack of AVP had no influence on DM-induced chronic stress symptoms, but lesioning the PVN attenuated part of them. However, the lack of elevation in POMC mRNA after PVN lesion, together with the maintained corticosterone elevation, suggests that direct adrenal gland activation occurs in untreated DM.

Changes in basal hypothalamo-pituitary-adrenal activity during exercise training are centrally mediated

The effects of exercise training on hypothalamo-pituitary-adrenal (HPA) function are unclear. We investigated whether pituitary-adrenal adaptation during exercise training is mediated by changes in neuropeptide and corticosteroid receptor gene expression in the brain and pituitary. Sprague-Dawley rats were subject to either daily swimming (DS) or sham exercise (SE) for 45 min/day, 5 days/week, for 2 (2W), 4 (4W), or 6 wk (6W) ( n = 7–10/group). Corticosterone (Cort) and catecholamine responses during swimming were robust at 6W compared with 2W and 4W, indicating that HPA response to exercise during training is not attenuated when absolute intensity is progressively increased. In DS, basal (morning) plasma ACTH and Cort levels increased from 2W to 4W but plateaued at 6W, whereas in SE, they increased from 4W to 6W, with 6W values higher than in DS. In DS, there was a transient decrease in glucocorticoid receptor (GR) mRNA in the paraventricular nucleus (PVN) and pituitary and a transient increase in corticotrophin-releasing hormone (CRH) mRNA. In contrast, hippocampal mineralocorticoid receptor mRNA and PVN GR mRNA decreased from 4W to 6W in SE, with 6W values lower than in DS. These findings suggest that exercise training prevents an elevation in basal pituitary-adrenal activity potentially via transient alterations in the gene transcription of PVN and pituitary GR as well as CRH to suppress central drive to the HPA axis. In contrast, the increase in basal pituitary-adrenal activity with repeated sham exercise appears to be associated with decreases in hippocampal MR and PVN GR mRNA expression.

Hyperglycemia does not increase basal hypothalamo-pituitary-adrenal activity in diabetes but it does impair the HPA response to insulin-induced hypoglycemia

Recently, we established that hypothalamo-pituitary-adrenal (HPA) and counterregulatory responses to insulin-induced hypoglycemia were impaired in uncontrolled streptozotocin (STZ)-diabetic (65 mg/kg) rats and insulin treatment restored most of these responses. In the current study, we used phloridzin to determine whether the restoration of blood glucose alone was sufficient to normalize HPA function in diabetes. Normal, diabetic, insulin-treated, and phloridzin-treated diabetic rats were either killed after 8 days or subjected to a hypoglycemic (40 mg/dl) glucose clamp. Basal: Elevated basal ACTH and corticosterone in STZ rats were normalized with insulin but not phloridzin. Increases in hypothalamic corticotrophin-releasing hormone (CRH) and inhibitory hippocampal mineralocorticoid receptor (MR) mRNA with STZ diabetes were not restored with either insulin or phloridzin treatments. Hypoglycemia: In response to hypoglycemia, rises in plasma ACTH and corticosterone were significantly lower in diabetic rats compared with controls. Insulin and phloridzin restored both ACTH and corticosterone responses in diabetic animals. Hypothalamic CRH mRNA and pituitary pro-opiomelanocortin mRNA expression increased following 2 h of hypoglycemia in normal, insulin-treated, and phloridzin-treated diabetic rats but not in untreated diabetic rats. Arginine vasopressin mRNA was unaltered by hypoglycemia in all groups. Interestingly, hypoglycemia decreased hippocampal MR mRNA in control, insulin-, and phloridzin-treated diabetic rats but not uncontrolled diabetic rats, whereas glucocorticoid receptor mRNA was not altered by hypoglycemia. In conclusion, despite elevated basal HPA activity, HPA responses to hypoglycemia were markedly reduced in uncontrolled diabetes. We speculate that defects in the CRH response may be related to a defective MR response. It is intriguing that phloridzin did not restore basal HPA activity but it restored the HPA response to hypoglycemia, suggesting that defects in basal HPA function in diabetes are due to insulin deficiency, but impaired responsiveness to hypoglycemia appears to stem from chronic hyperglycemia.

Hepatic vagotomy alters limbic and hypothalamic neuropeptide responses to insulin-dependent diabetes and voluntary lard ingestion

Hypothalamic anorexigenic [corticotropin-releasing factor (CRF) and proopiomelanocortin] peptides decrease and the orexigen, neuropeptide Y, increases with diabetic hyperphagia. However, when diabetic rats are allowed to eat lard (saturated fat) as well as chow, both caloric intake and hypothalamic peptides normalize. These neuropeptide responses to lard require an intact hepatic vagus [la Fleur et al. (2003) Diabetes, 52, 2321-2330]. Here, we delineate temporal interactions after lard consumption +/- hepatic vagotomy (HV) between feeding and brain neuropeptide expression in insulin-dependent diabetic rats. CRF-mRNA was reduced in the paraventricular nuclei (PVN) by 6 h after presentation of lard, before caloric intake increased in HV-diabetic rats, and did not increase at 30 or 36 h, as it did in shamHV-diabetic rats eating lard. CRF-mRNA was increased in the bed nuclei of the stria terminalis of HV-diabetic rats compared with shamHV-diabetic rats only when caloric intake was high at 30 or 36 h. At 36 h, shamHV-diabetic rats eating chow had increased CRF-mRNA in the central amygdala but diabetic rats eating lard had decreased CRF-mRNA, whereas HV-diabetic rats eating chow or lard had normal CRF-mRNA in the central amygdala. We conclude that eating lard restores peptide expression to normal in the hypothalamus of diabetic rats, and because decreased CRF-mRNA in the PVN precedes the increase in caloric intake in HV-diabetic rats eating lard, that the loss of a hepatic vagal signal to PVN may be responsible for increased intake; moreover, CRF-mRNA in limbic structures is also sensitive to both HV and lard ingestion in diabetic rats.

Effects of diabetes and recurrent hypoglycemia on the regulation of the sympathoadrenal system and hypothalamo-pituitary-adrenal axis

Epinephrine, norepinephrine, and corticosterone responses to hypoglycemia are impaired in diabetic rats. Recurrent hypoglycemia further diminishes epinephrine responses. This study examined the sympathoadrenal system and hypothalamo-pituitary-adrenal axis for molecular adaptations underlying these defects. Groups were normal (N) and diabetic (D) rats and diabetic rats exposed to 4 days of 2 episodes/day of hyperinsulinemic hypoglycemia (D-hypo) or hyperinsulinemic hyperglycemia (D-hyper). D-hypo and D-hyper rats differentiated effects of hypoglycemia and hyperinsulinemia. Adrenal tyrosine hydroxylase (TH) mRNA was reduced (P < 0.05 vs. N) 25% in all diabetic groups. Remarkably, mRNA for phenylethanolamine N-methyltransferase (PNMT), which converts norepinephrine to epinephrine, was reduced (P < 0.05 vs. all) 40% only in D-hypo rats. Paradoxically, dopamine beta-hydroxylase mRNA was elevated (P < 0.05 vs. D, D-hyper) in D-hypo rats. Hippocampal mineralocorticoid receptor (MR) mRNA was increased (P < 0.05 vs. N) in all diabetic groups. Hippocampal glucocorticoid receptor (GR), hypothalamic paraventricular nucleus (PVN) GR and corticotropin-releasing hormone (CRH), and pituitary GR and proopiomelanocortin (POMC) mRNA levels did not differ. We conclude that blunted corticosterone responses to hypoglycemia in diabetic rats are not due to altered basal expression of GR, CRH, and POMC in the hippocampus, PVN, and pituitary. The corticosterone defect also does not appear to be due to increased hippocampal MR, since we have reported normalized corticosterone responses in D-hypo and D-hyper rats. Furthermore, impaired epinephrine counterregulation in diabetes is associated with reduced adrenal TH mRNA, whereas the additional epinephrine defect after recurrent hypoglycemia is associated with decreases in both TH and PNMT mRNA.