Pathophysiology and treatment of subclinical Cushing's disease and pituitary silent corticotroph adenomas [Review].

Pituitary adrenocorticotropic hormone (ACTH)-secreting tumor presents with a variety of clinical features. We outlined the features of ACTH release and characteristics of corticotroph adenoma cells. We especially focused on the corticotroph adenomas in patients with no clinical features of Cushing's disease. Subclinical Cushing's disease is defined by ACTH-induced mild hypercortisolism without typical features of Cushing's disease. Silent corticotroph adenomas (SCAs) are defined by normal cortisol secretion and ACTH-immunopositive staining without autonomous ACTH secretion. Clinicians who are not well-informed about the disease may sometimes confuse SCAs (because of their clinically silent nature) with "subclinical Cushing's disease". The recent criteria for diagnosing subclinical Cushing's disease in Japan are presented. Cortisol measurement was recently standardized in Japan, so plasma cortisol cutoff level should be reconsidered for the diagnosis. In patients with uncontrolled diabetes and hypertension despite appropriate treatment, subclinical Cushing's disease may be efficiently detected. Subclinical Cushing's disease may be associated with metabolic change. In subclinical Cushing's disease, mild hypercortisolism due to autonomous secretion of ACTH contributes to metabolic change and treatment of subclinical hypercortisolism can reverse this change.

Evaluation of the diagnostic criteria for Cushing's disease in Japan.

Adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome is caused by an ACTH-producing tumor, as is the case with Cushing's disease and ectopic ACTH syndrome (EAS). Diagnosis and differential diagnosis of Cushing's disease from EAS in ACTH-dependent Cushing's syndrome are thus challenging problems in clinical endocrinology. The diagnostic criteria for Cushing's disease in Japan, established by the working group of the Japan Ministry of Health, Labour and Welfare, were originally reported in 2003 and revised in 2007 and 2010. In addition, criteria for subclinical Cushing's disease were established in Japan in 2010. In this review, we evaluate the usefulness and accuracy of the most recent diagnostic criteria. Previous data suggest that as an initial test of Cushing's syndrome, 0.5 mg dexamethasone is more sensitive than 1 mg in the overnight dexamethasone suppression test (DST). Here, we recommend 0.5 mg plus a plasma cortisol cut-off level of 3 µg/dL as a suitable low-dose overnight DST for screening of all cases of ACTH-dependent Cushing's syndrome in Japan. Recently, standardization of cortisol measurements by the ID-LC/MS/MS method using seven assay kits with standard plasma material containing synthetic hydrocortisone-d4 was carried out in Japan. The resulting relative standard deviation was within 10%. The cut-off value remains valid even after standardization of plasma cortisol measurements. Although the recent diagnostic criteria achieve higher diagnostic specificity, care should be taken since data for Cushing's disease partially overlaps with some cases of EAS. Overall, therefore, this review suggests that the accuracy of each diagnostic test should be considered.

Signal transduction in the hypothalamic corticotropin-releasing factor system and its clinical implications.

Corticotropin-releasing factor (CRF) is a major regulatory peptide in the hypothalamic-pituitary-adrenal (HPA) axis under stress conditions. In response to stress, CRF is produced in the hypothalamic paraventricular nucleus. Forskolin- or pituitary adenylate cyclase-activating polypeptide-stimulated CRF gene transcription is mediated by the cyclic AMP (cAMP) response element on the CRF 5'-promoter region. Estrogens enhance activation of the CRF gene in stress, while inducible cAMP-early repressor suppresses the stress response via inhibition of the cAMP-dependent CRF gene. Glucocorticoid-dependent repression of cAMP-stimulated CRF promoter activity is mediated by both the negative glucocorticoid-response element and the serum-response element, while interleukin-6 (IL-6) stimulates the CRF gene. Suppressor of cytokine signaling-3, stimulated by IL-6 and cAMP, is involved in the negative regulation of CRF gene expression. Such complex mechanisms contribute to stress responses and homeostasis in the hypothalamus. Moreover, disruption of the HPA axis may cause a number of diseases related to stress. For example, CRF-induced p21-activated kinase 3 mRNA expression may be related to the proliferation of corticotrophs in Nelson's syndrome. A higher molecular weight form of immunoreactive ß-endorphin, putative proopiomelanocortin (POMC), is increased in CRF-knockout mice, suggesting the important role of CRF in the processing of POMC through changes in prohormone convertase type-1 expression levels.

Ghrelin stimulates corticotropin-releasing factor and vasopressin gene expression in rat hypothalamic 4B cells.

Corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) play a central role in regulating the stress response. In response to stress, CRF and AVP neurons in the hypothalamic paraventricular nucleus secrete the peptides to stimulate the release of adrenocorticotropic hormone from the anterior pituitary. Ghrelin, an endogenous ligand of the growth hormone-releasing peptide receptors (GHSR), has been shown to stimulate the release of CRF and AVP by rat hypothalamic explants. However, little is known about the ability of the ghrelin signaling pathways to activate the CRF and AVP genes in the hypothalamus. In the present study, we examined the direct effect of ghrelin on CRF and AVP gene expression in hypothalamic 4B cells, which show the characteristics of the hypothalamic parvocellular paraventricular nucleus neurons. Cells were transfected with CRF or AVP promoter to examine the activity of each promoter. Ghrelin stimulated the promoter activities and mRNA levels for both CRF and AVP. The involvement of a protein kinase pathway was examined using inhibitors. Protein kinase A and phospholipase C pathways were shown to be involved in ghrelin-induced increases in both CRF and AVP promoter activities. GHSR type 1a (GHSR1a) mRNA levels were also increased by ghrelin, and these ghrelin-induced levels were suppressed by a GHSR1a antagonist. Thus, ghrelin-dependent pathways are involved in the regulation of CRF and AVP gene expression in the hypothalamus: ghrelin, an orexigenic hormone, stimulates CRF, an anorexigenic/anxiogenic factor in the hypothalamus, resulting in hypothalamic-pituitary-adrenal axis activation to stimulate the release of glucocorticoids.

A case of hyponatremia after cervical spinal cord injury.

Hyponatremia is known as a complication of neurosurgical conditions or brain. The prevalence of hyponatremia in acute spinal cord injury has been known to be much higher than in the general medical or surgical patient population. We report here a case of hyponatremia, which occurred 10 days after cervical spinal cord injury. The data on sodium levels were improved under the tapered infusion volume and water intake restriction. Treatment for this case is the same as that for syndrome of inappropriate antidiuretic hormone, which have suggested that reduced extracellular volume is important to improve the hyponatremia after traumatic spinal cord injury. Uncontrolled hyponatremia may lead to lethargy, seizures, coma, cardiac arrhythmia and death. Therefore, the complication of hyponatremia should be paid attention after cervical spinal cord injury. A careful monitoring of sodium levels after the injury is required in the cases of cervical spinal cord injury.

The role of endogenous glucocorticoids in lymphocyte development in melanocortin receptor 2-deficient mice.

Glucocorticoids are extensively used in anti-inflammatory therapy and are thought to contribute to the steady-state regulation of hematopoiesis and lymphopoiesis. We have previously established MC2R(-/-) mice, a model of familial glucocorticoid deficiency, that show several similarities to patients with this disease, including undetectable levels of corticosterone, despite high levels of ACTH and unresponsiveness to ACTH. In this study, we analyzed the possible roles of endogenous glucocorticoids in hematopoiesis and lymphopoiesis in MC2R(-/-) and CRH(-/-) mice as models of chronic adrenal insufficiency. Our analysis of total peripheral blood cell counts revealed that the number of lymphocytes was increased and the number of erythrocytes was slightly, but significantly, decreased in MC2R(-/-) mice. Numbers of immature double negative (CD4(-) CD8(-)) thymocytes, transitional type 1 B cells in the spleen, and pre-B cells in the bone marrow, were significantly increased in MC2R(-/-) mice, suggesting that endogenous glucocorticoids contribute to steady-state regulation of lymphopoiesis. Oral glucocorticoid supplementation reversed peripheral blood cell counts and reduced numbers of T and B cells in the thymus and the spleen. T cells in the thymus and B cells in the spleen were also increased in CRH(-/-) mice, another animal model of chronic adrenal insufficiency. MC2R(-/-) mice were sensitive to age-related thymic involution, but they were resistant to fasting-associated thymic involution. Our data support the idea that endogenous glucocorticoids contribute to stress-induced as well as steady-state regulation of hematopoiesis and lymphopoiesis.

Involvement of nuclear factor-kB and Nurr-1 in cytokine-induced transcription of proopiomelanocortin gene in AtT20 corticotroph cells.

OBJECTIVE: The precise mechanism whereby proinflammatory cytokines activate the hypothalamo-pituitary-adrenal axis is still unclear. We examined whether transcription factors nuclear factor (NF)-kappaB and Nurr-1 are involved in the cytokine-induced proopiomelanocortin (POMC) gene expression. METHODS: The mouse corticotropinoma cell line AtT20 was treated with tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta (IL-1beta). Real-time PCR, luciferase assay and Western blotting were conducted to assess the gene expression, promoter activity and protein expression in various conditions. RESULTS: Intrinsic expression of NF-kappaB was confirmed by RT-PCR. An active component of NF-kappaB (p65) was upregulated in the nuclear fraction by both TNF-alpha and IL-1beta treatment in a dose- and time-related manner. These cytokines potently stimulated the promoter activity of NF-kappaB and Nurr-1. We also found rapid upregulation of the Nurr-1 gene and protein after treatment with these cytokines. Cotreatment of the cells with either of the cytokines and corticotropin-releasing hormone resulted in additive effects. Cytokine-induced Nurr-1 transcription and Nurr-1 transcription induced by overexpression of NF-kappaB were both blunted by mutagenesis within the NF-kappaB responsive element, which implies that Nurr-1 upregulation specifically requires NF-kappaB binding to its own DNA-binding site. Proinflammatory cytokines exert positive effects on POMC gene expression, which were inhibited by pretreatment with a specific NF-kappaB inhibitor. CONCLUSION: These results together imply that Nurr-1 expression is a connecting point between neuroendocrine and immune systems in mediating cytokine-induced POMC gene expression.

Cytokines induce NF-κB, Nurr1 and corticotropin-releasing factor gene transcription in hypothalamic 4B cells.

OBJECTIVE: In the hypothalamus, corticotropin-releasing factor (CRF) plays a central role in regulating stress responses. Cytokines are important mediators of the interaction between the neuroendocrine and immune systems, and are implicated in the regulation of CRF expression. Following inflammatory challenges, interleukin (IL)-1 or IL-6 stimulates the hypothalamic-pituitary-adrenal axis. CRF promoter contains multiple nuclear factor (NF)-kappaB and Nurr1 binding sites. In the present study, we determined the ability of the signaling pathways to activate the CRF gene in the hypothalamic paraventricular nucleus following inflammatory challenge. METHODS: Cytokine-induced changes in CRF gene expression were examined in the hypothalamic system. Luciferase assay and Western blotting were performed to assess transcriptional activity and the nuclear translocation of transcriptional factors. RESULTS: IL-1beta, IL-6 and tumor necrosis factor (TNF)-alpha stimulated the nuclear expression levels of NF-kappaB, NF-kappaB-dependent Nurr1 and c-Fos proteins. Direct stimulatory effects of TNF-alpha and IL-1beta, in addition to IL-6, were found on the transcriptional activity of the CRF gene in hypothalamic 4B cells. CONCLUSION: These cytokines are involved in the regulation of CRF gene activity in hypothalamic cells.

The frequency of type 2 diabetic patients who meet the endocrinological screening criteria of subclinical Cushing's disease.

Cushing's syndrome, including its mild form/state of adrenal-dependent subset (subclinical Cushing's syndrome; subCS), is known to enhance glucose intolerance, hypertension and obesity. Recently, subclinical Cushing's disease (subCD) has been identified, but its prevalence and the extent of consequent metabolic derangement are unclear. We screened 90 type 2 diabetic patients hospitalized in our department for subCD, according to the diagnostic guideline proposed by the working group of Japanese Ministry of Health, Welfare and Labor in 2006. Plasma ACTH and cortisol levels in the morning and at midnight were determined, and overnight 0.5 mg dexamethasone suppression test (DST) was performed. Those who showed poor cortisol suppression in DST underwent the desmopressin (DDAVP) test. Fifty-seven patients (63.3%) demonstrated abnormally high midnight cortisol levels (>or=2.5 microg/dL), while only nine of them failed to suppress plasma cortisol levels to <3 microg/dL after DST. Although none of the eight patients who underwent the DDAVP test demonstrated the anticipated paradoxical rise in plasma ACTH, these eight patients (8.9%) endocrinologically met the screening criteria of subCD. Since a considerable percentage of pituitary adenomas causing overt Cushing's disease are not identifiable in magnetic resonance imaging, many of those causing subCD may also be unidentifiable. Further follow-up studies including confirmatory testing and pituitary imaging are necessary.

Evaluation of plasma, salivary, and urinary cortisol levels for diagnosis of Cushing's syndrome.

As a screening test for Cushing's syndrome, the evaluation of late-night cortisol levels is indispensable. We evaluated the usefulness and accuracy of plasma, urinary, and salivary cortisol levels measured late at night for the diagnosis of Cushing's syndrome. High cortisol levels (> 5 microg/dL) during the night are indicative of Cushing's syndrome, although night plasma cortisol levels are not readily reproducible because of the stressful situation. There was no correlation between plasma and urinary cortisol levels late at night, and late-night urinary cortisol levels provided weak information for the diagnosis of Cushing's syndrome. By contrast, late-night plasma and salivary cortisol levels showed a positive correlation, and salivary cortisol sampling was found to be useful for the diagnosis of Cushing's syndrome, because more than 0.4 microg/dL of late-night salivary cortisol levels gave a sensitivity of 86% and a specificity of 100% in our hospital. This method is also useful for the diagnosis of early or mild stage Cushing's syndrome, so-called subclinical Cushing's syndrome. Inherent differences between assays make it difficult to define optimal diagnostic criteria. However, the relative levels of salivary cortisol ratio, which is presented as a relative level, compared with the mean levels of healthy subjects in each institute, is useful for the screening of Cushing's syndrome as the cut-off level of 1.5 shows both high sensitivity and specificity in subclinical and overt Cushing's syndrome. Late-night salivary cortisol measurement is therefore a primary method of choice in the screening of patients suspected of having Cushing's syndrome.

Regulation and role of p21-activated kinase 3 by corticotropin-releasing factor in mouse pituitary.

Corticotropin-releasing factor (CRF) is a major regulatory peptide in the hypothalamic-pituitary-adrenal (HPA) axis under stress conditions. In response to stress, CRF, produced in the hypothalamic paraventricular nucleus, releases adrenocorticotropic hormone (ACTH) from the anterior pituitary (AP). ACTH in turn stimulates the release of glucocorticoid from the adrenal glands. Glucocorticoid then inhibits hypothalamic production of CRF and pituitary production of ACTH. Mice lacking a functional gene for CRF (CRF KO) showed severe impairment of the HPA axis, indicating that CRF is required for its regulation. We applied oligonucleotide microarray analysis to the AP of CRF KO to identify gene expression induced by CRF. Twenty-four genes showed less than 60% expression in CRF KO compared with normal mice. Real-time PCR analysis revealed that p21-activated kinase 3 (Pak3), prohormone convertase type 1 (PC1), and CRF-binding protein (BP) mRNA expression levels were increased by CRF in AP cells. Both Pak3 and PC1 were also increased by dexamethasone in AP cells, while CRF-BP mRNA levels were reduced. Therefore, both Pak3 and PC1 mRNA levels would be regulated by both CRF and glucocorticoids. Pak3 knockdown inhibited CRF-induced cell viability in AtT-20 cells, suggesting the important role of Pak3 in the proliferation of corticotrophs.

Regulatory mechanisms underlying corticotropin-releasing factor gene expression in the hypothalamus.

The hypothalamic-pituitary-adrenal (HPA) axis is activated under various stressors. Corticotropin-releasing factor (CRF) plays a central role in controlling stress response, and regulating the HPA axis. CRF, produced in the hypothalamic paraventricular nucleus (PVN), stimulates adrenocorticotropic hormone (ACTH) production via CRF receptor type 1 (CRF(1) receptor) from the corticotrophs of the anterior pituitary (AP). Cyclic AMP (cAMP)-protein kinase A (PKA) pathway takes a main role in stimulating CRF gene transcription. Forskolin and pituitary adenylate cyclase-activating polypeptide (PACAP) stimulate adenylate cyclase, intracellular cAMP production, and then CRF and arginine vasopressin (AVP) gene expression in hypothalamic 4B cells. Interleukin (IL)-6, produced in the PVN, both directly and indirectly stimulates CRF and AVP gene expression. Estradiol may enhance the activation of CRF gene expression in response to stress. The HPA axis is regulated by a negative feedback mechanism, because glucocorticoids inhibit both CRF production in the hypothalamic PVN and ACTH production in the pituitary. Hypothalamic parvocellular neurons in the PVN are known to express glucocorticoid receptors, and glucocorticoids are able to regulate CRF gene transcription and expression levels directly in the PVN. Glucocorticoids-dependent repression of cAMP-stimulated CRF promoter activity is mainly localized to promoter sequences between -278 and -233 bp. Both negative glucocorticoid regulatory element (nGRE) and serum response element (SRE) are involved in the repression of the CRF gene in the hypothalamic cells.

Evaluation of diagnostic tests for ACTH-dependent Cushing's syndrome.

We evaluated the usefulness and accuracy of diagnostic tests for adrenocorticotropic hormone (ACTH)- dependent Cushing's syndrome, based on our experience of 88 cases, including 73 cases with Cushing's disease, and 15 cases with ectopic ACTH syndrome (EAS). In our study, 0.5 mg of dexamethasone failed to suppress the morning cortisol secretion in 100% of cases with Cushing's disease and EAS. Plasma ACTH levels were significantly increased by desmopressin (DDAVP) in 86% of cases with Cushing's disease, especially in microadenomas (90%), while these levels were not affected in normal subjects. In EAS, 44% responded to DDAVP. Plasma ACTH levels were increased in response to the human corticotropin-releasing hormone (CRH) test in 100% of microadenomas and 73% of macroadenomas with Cushing's disease, but only in 27% of cases with EAS. A high dose (8 mg) of dexamethasone suppressed the morning cortisol secretion in 89% of microadenomas with Cushing's disease, and in 82% of all cases with Cushing's disease, while it did in only 20% of cases with EAS. Taken together, the 0.5 mg dexamethasone suppression test (DST) and DDAVP test are considerably useful for the screening of ACTH-dependent Cushing's syndrome. The CRH test and 8 mg DST would be effective for the diagnosis of Cushing's diseases, because our study shows a sensitivity of 81% in cases with Cushing's disease when these tests are considered together. These data were submitted to prepare the diagnostic criteria for Cushing's disease, suggested by the working group of the Ministry of Health, Labour, and Welfare of Japan.

Development and validation of a 0.5 mg dexamethasone suppression test as an initial screening test for the diagnosis of ACTH-dependent Cushing's syndrome.

For the diagnosis of Cushing' s syndrome (CS), the overnight 1 mg dexamethasone suppression test (DST) has been widely used as a standard low-dose DST. However, it is evident that 1 mg DST may not be sensitive enough to detect CS when the cortisol cut-off concentration is 5 microg/dL. Therefore, we developed and validated 0.5 mg DST as a new screening method for diagnosis of ACTH-dependent CS. To compare 0.5 mg DST with 1 mg DST, 110 patients with ACTH-dependent CS were enrolled, including 88 with Cushing' s disease (CD), 8 with subclinical CD and 14 with ectopic ACTH syndrome, as well as 134 control subjects. Subjects were given either 0.5 mg or 1 mg dexamethasone orally at 23:00 on different days, with blood samples collected the following morning between 8:00 and 9:00 to determine plasma cortisol concentration. The area under the receiver operator characteristics curve observing the 0.5 mg DST was higher than that of the 1 mg DST. The most sensitive and specific cut-off value of plasma cortisol concentration using 0.5 mg DST was found to be 3.05 microg/dL with 99.1% sensitivity and 98.4% specificity, identical to the 3 microg/dL cut-off currently used in the Japanese guideline for diagnosis of subclinical CD. In conclusion, 0.5 mg DST is a sensitive and specific screening test for diagnosis of ACTH-dependent CS. We recommend 0.5 mg DST with a cortisol cut-off concentration of 3 microg/dL to be used as the initial step in diagnosing ACTH-dependent CS.

Effects of estradiol on regulation of corticotropin-releasing factor gene and interleukin-6 production via estrogen receptor type beta in hypothalamic 4B cells.

Corticotropin-releasing factor (CRF) is produced in the hypothalamic paraventricular nucleus (PVN) in response to stress and stimulates the release of adrenocorticotropic hormone in the corticotrophs. Estrogens acting centrally are able to modulate the stress responses. In fact, direct estrogenic regulation of CRF gene expression has been demonstrated in various tissues. However, the mechanisms responsible for the actions of estrogens on CRF regulation in the PVN remain undetermined. We investigated whether estradiol (E2) contributes to the regulation of CRF gene and promoter activity in hypothalamic 4B cells. Furthermore, the involvement of E2 in the regulation of interleukin (IL)-6 and its role in hypothalamic 4B cells was explored. We demonstrated the dominant expression of estrogen receptor type beta (ERbeta) and found that a physiologically relevant dose of E2 and an ERbeta agonist stimulated CRF gene transcription in hypothalamic 4B cells. E2 stimulated IL-6 transcriptional activity via ERbeta, and subsequently the levels of IL-6 mRNA and protein. We also found that treatment with IL-6 significantly reduced cell viability. Thus, these data suggest the important effects of E2 on the regulation of CRF gene and IL-6 production via ERbeta in hypothalamic 4B cells.

Corticotropin-releasing factor (CRF) is involved in the acute anorexic effect of alpha-melanocyte-stimulating hormone: a study using CRF-deficient mice.

Alpha-melanocyte-stimulating hormone (alpha-MSH) and its receptors are critical and indispensable for maintaining appropriate feeding behavior and energy homeostasis in both mice and humans. Corticotropin-releasing factor (CRF) is a candidate for mediating the anorexic effect of alpha-MSH. In the present study, we examined whether CRF and its receptors are involved in the anorexic effect of alpha-MSH, using CRF-deficient (CRFKO) mice and a CRF receptor antagonist. Intracerebroventricular administration of NDP-MSH, a synthetic alpha-MSH analogue, suppressed food intake in wild-type (WT) mice. This effect was abolished by pretreatment with a non-selective CRF receptor antagonist, astressin, suggesting that the effect of alpha-MSH-induced anorexia was mediated by a CRF receptor. In CRFKO mice, administration with NDP-MSH did not affect food intake at an early phase (0-4h). In addition, CRF mRNA levels in the hypothalamus were significantly increased in NDP-MSH-treated mice. Therefore, our findings, using CRFKO, strongly support evidence that CRF is involved in the acute anorexic effect of alpha-MSH. On the other hand, NDP-MSH administered to CRFKO mice led to suppressed food intake at the late phase (4-12h), similar to the effect in WT mice. Further, NDP-MSH similarly reduced food intake during the late phase in all types of mice, including WT, CRFKO, and CRFKO with corticosterone replacement. The results would suggest that alpha-MSH-induced suppression of food intake at late phase was independent of glucocorticoids and CRF.

HMG-CoA reductase inhibitor, simvastatin improves reverse cholesterol transport in type 2 diabetic patients with hyperlipidemia.

AIM: ApoA-I and HDL promote cellular cholesterol efflux in the early stages of the reverse cholesterol transport (RCT) pathway. A low plasma HDL-C level is characteristic of atherogenic dyslipidemia in patients with type 2 diabetes. We evaluated plasma lipid levels and the expression of factors related to RCT in type 2 diabetic patients, and the effects of an HMG-CoA reductase inhibitor, simvastatin, were studied. METHODS: Messenger RNA (mRNA) expression in circulating mononuclear cells was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), focusing on the following factors: liver X receptor alpha (LXR alpha), ATP-binding cassette A1 (ABCA1), scavenger receptor class B type 1 (SR-B1), apolipoprotein E (ApoE), apolipoprotein A-1 (ApoA-1), caveolin, and cholesterol ester transfer protein (CETP). Type 2 diabetic subjects (n=29) were divided into three subgroups: patients with normolipidemia (DM group, n=11), patients with untreated hyperlipidemia (DMHL group, n=10), and those with hyperlipidemia treated with simvastatin 5-10mg/day (DMST group, n=8). The control group (CNT group) included seven healthy volunteers. RESULTS: Simvastatin treatment significantly increased plasma levels of ApoA-I compared to the other three groups. Simvastatin treatment improved the expression of mRNA for LXRalpha, ABCA1, and ApoA-I compared with DMHL or control groups. CONCLUSION: Our data suggest that RCT may be reduced in type 2 diabetic patients with hyperlipidemia, and simvastatin may be able to improve reverse cholesterol transport for this population of diabetic patients.

Early changes in insulin receptor signaling and pain sensation in streptozotocin-induced diabetic neuropathy in rats.

UNLABELLED: The objective of the present study was to evaluate the time course of changes in peripheral nerve insulin receptor (IR) signaling and compare observed findings with behavioral responses to noxious mechanical and thermal stimuli in streptozotocin (STZ)-diabetic rats over 12 weeks of diabetes. Diabetic rats developed mechanical hyperalgesia, as indicated by decreased paw withdrawal thresholds to mechanical stimuli that were detectable after 2 weeks of diabetes; they also developed thermal hypoalgesia, as indicated by increased tail flick latencies to thermal stimuli that were detectable at 1 week of diabetes. Western blot analysis revealed decreased phosphorylated: total IR protein ratio that was detectable as early as 2 weeks of diabetes, whereas phosphorylated:total Akt protein ratio was decreased at 2 weeks and increased at 12 weeks of diabetes with unchanged PI-3K protein levels. To our knowledge, the present study is the first to demonstrate that impaired peripheral nerve IR signaling, as indicated by decreased phosphorylated:total IR protein ratio, coincides with early mechanical hyperalgesia and thermal hypoalgesia in STZ-diabetic rats. This finding may improve understanding of how altered pain sensation develops rapidly in this model. PERSPECTIVE: This study examined peripheral nerve IR signaling during the early course of altered nociception in STZ-diabetic rats. In diabetic rats, impaired peripheral nerve IR signaling is observed shortly after STZ injection, as is altered nociception. This finding suggests a possible role of impaired IR signaling in diabetic sensory neuropathy.

A case of multiple endocrine neoplasia type II accompanied by thyroid medullary carcinoma and pheochromocytomas expressing corticotropin-releasing factor and urocortins.

A 38-year-old woman with RET gene mutation presented with tumors in her thyroid and bilateral adrenal glands. I-metaiodobenzylguanidine scintigraphy revealed accumulation of the radioisotope in both adrenal glands. Both plasma adrenaline and noradrenaline levels were elevated. The circadian rhythms for plasma adrenocorticotropic hormone (ACTH) and cortisol levels were disturbed. Plasma ACTH and cortisol levels failed to be suppressed by an overnight dexamethasone test, suggesting autonomic secretion of ACTH and cortisol, although the patient had no typical Cushingoid features, hypertension, or impaired glucose tolerance. Pathological examination showed that these tumors were pheochromocytoma and thyroid medullary carcinoma, respectively, both of which highly expressed corticotropin-releasing factor, urocortin1, and urocortin3. Together with the endocrinological and pathological observations, the patient was diagnosed as multiple endocrine neoplasia type II with corticotropin-releasing factor- and urocortin-producing tumors that stimulated ACTH and glucocorticoid secretion.