Provocation of kainic acid receptor mRNA changes in the rat paraventricular nucleus by insulin-induced hypoglycaemia

Hypoglycaemia induced by insulin injection is a powerful stimulus to the hypothalamic-pituitary-adrenal (HPA) axis and drives the secretion of corticotropin-releasing hormone and vasopressin from the neurones in the paraventricular nucleus (PVN), as well as the downstream hormones, adrenocorticotropic hormone and corticosterone. In some brain regions, hypoglycaemia also provokes increases in extracellular fluid concentrations of glutamate. Regulation of glutamatergic mechanisms could be involved in the control of the HPA axis during hypoglycaemic stress and one potential site of regulation might be at the receptors for glutamate, which are expressed in the PVN. Insulin (2.0 IU/kg, i.p.) or saline was administered to adult male Sprague-Dawley rats and the animals were sacrificed 30 min, 180 min and 24 h after injection. The amount of several kainic acid-preferring glutamate receptor mRNAs (i.e. KA2, GluR5 and GluR6) were assessed in the PVN by in situ hybridisation histochemistry. Injection of insulin induced a rapid fall in plasma glucose concentrations, which was mirrored by an increase in plasma corticosterone concentrations. KA2 and GluR5 mRNAs are highly expressed within the rat PVN, and responded to hypoglycaemia with robust increases in expression that endured beyond the period of hypoglycaemia itself. However, GluR6 mRNA is expressed in the areas adjacent to the PVN and hypoglycaemic stress failed to alter expression of this mRNA. These experiments suggest that kainic acid-preferring glutamate receptors are responsive to changes in plasma glucose concentrations and may participate in the activation of the PVN neurones during hypoglycaemic stress.

Polymorphism in IGF-2 as a Surrogate Marker for Predisposition towards Tobacco Chewing-Mediated Oral Cancer

Insulin and insulin-like growth factors (IGFs) are major determinants of proliferation and apoptosis, thereby playing a significant role in carcinogenesis. Epidemiological evidence associates high levels of INS and IGFs with an increased risk of cancer. Polymorphism of the genes involved in insulin-signaling pathways has been associated with a variable risk for neoplasms in different ethnic and environmental backgrounds. In this study, using PCR-RFLP-based assays, we investigated the distribution of genetic polymorphism in INS and IGF-2 genes in tobacco chewing-mediated oral cancer patients (n = 60) and healthy controls (n = 45) of Indian ethnic origin. The genotyping was performed for +1127 INS-Pst1 in INS and +3580 IGF-2-Msp1 in IGF-2. The frequencies of the IGF-2 genotypes AG, GG and AA found in oral cancer patients were 0.68, 0.2 and 0.12, respectively, whereas in noncancer controls these frequencies were 0.27, 0.71 and 0.02. Frequencies of each allele, i.e. CT, TT and CC of INS gene, were found to be nearly equal in the tumor (0.22, 0.75 and 0.03) as well as the normal (0.27, 0.67 and 0.06) population. A significant difference was observed in genotypic frequencies of IGF-2 and INS in the Indian ethnic population as compared to the Caucasian, African and Hispanic populations. Polymorphism at +1127 INS-Pst1 locus of INS gene does not show an implication in oral cancer, whereas the genotype AG or AA at +3580 IGF-2-Msp1 locus of IGF-2 is associated with progression and increased risk of oral cancer. From our study we can conclude that single nucleotide polymorphisms in the IGF-2 gene can be used as a marker for prediction of the risk of oral carcinogenesis.

Promoting glycemic control through diabetes self-management: evaluating a patient activation intervention

This study compared an activation intervention to passive education in a randomized attention-control trial of 232 patients with type 2 diabetes. The activation intervention was based on Expanding Patient Involvement in Care (EPIC) trials, and was compared to time-matched passive education viewing of ADA video-tapes. Patient demographics and clinical characteristics of their diabetes were assessed with questionnaires, active involvement was assessed via ratings of taped interactions between patients and providers, and serum samples were analyzed for HbA1c. Patients in the activation condition were rated as more actively involved in discussions of diabetes self-management, and rated active involvement was predictive of improvement in glycemic control. No effect of the activation intervention was found on HbA1c. Thus, the activation intervention increased the active involvement of patients with type 2 diabetes in visits with practitioners, and active involvement led to improved glycemic control. However, the activation intervention did not improve glycemic control directly.

Effect of estrogen on hypoglycemia induced neurological impairment in ovariectomized rats

The risk of hypoglycemia and the resulting functional derangement of the brain are one of the major complications with stringently controlled diabetes mellitus. Ovarian steroid hormones, particularly estradiol, play a modulatory role in the ability of the female brain to utilize glucose. In the present study, the effects of estrogen on hypoglycemia-induced neurological impairment were done in ovariectomized rats. Animals received either vehicle or estradiol benzoate treatment. Hypoglycemia (Blood glucose levels <50 mg/dl) was induced in all the rats by insulin (2 U/kg, IP). Neurological functions were assessed using an 18 point scale at different time intervals of hypoglycemia. Estradiol benzoate (100 microg/kg IP) significantly (p<0.05) deteriorated the neurological functions in ovariectomized rats during hypoglycemia. The present study thus reveals that estradiol benzoate is responsible for further aggravation of neurological impairment induced by insulin hypoglycemia in female rats.

The desmopressin test as a predictive factor of outcome after pituitary surgery for Cushing's disease

OBJECTIVE

Taking advantage of the over-expression of V3 receptors in adenomatous corticotroph cells, we evaluated the response to the vasopressin agonist desmopressin in 22 patients operated on for Cushing's disease, with a mean follow-up of 4.5 years.

SUBJECTS AND METHODS

Twenty-two patients (17 women) operated on for Cushing's disease with a follow-up >2 years (median, 48; range, 24-141 months) underwent one desmopressin test (10 microg i.v. bolus) 3-6 months postoperatively. Twelve were in remission (R group), five had immediate failure (IF) after surgery and five had late recurrence (LR).

RESULTS

Both ACTH and cortisol peaks after desmopressin were significantly lower in the R group than in the LR group (P=0.003 and P=0.013 respectively). The receiver operator characteristic curve method defined an ACTH peak threshold > or =22 pg/ml or ACTH rise > or =35%; cortisol peak > or =350 nmol/l or cortisol rise > or =14%. None of twelve patients in remission had ACTH or cortisol peaks above these thresholds vs three of five patients from the LR group and five of five in the IF group.

DISCUSSION

On the basis of ACTH or cortisol peaks respectively, the desmopressin test was predictive of a later recurrence with a positive predictive value of 100% or 80% respectively, and a negative predictive value of 92%. Sensitivity and specificity were 80% and 100% respectively based on ACTH peak, and 80% and 92% respectively based on cortisol peak.

CONCLUSION

In this first long-term study, a marked response of ACTH or cortisol to desmopressin was predictive of a later recurrence with good specificity and sensitivity.

Comparison of equivalence and determination of diagnostic utility of min-mod and clamp methods for insulin resistance in diabetes free subjects: a meta-analysis

The gold standard for quantifying insulin sensitivity (IS) is the hyperinsulinemic-euglycemic clamp (Clamp) with a cut-off point of 5x10-2 (dL/min)/(microU/mL) or less to indicate insulin resistance. Bergman's minimal model (Min-Mod) is also being used to estimate IS, but there are doubts as to its equivalence with Clamp. The objective of the present study is to determine if Clamp and the tolbutamide and insulin techniques of Min-Mod are equivalent. Meta-analysis based on a bibliographic search from 1970 until the present was made for the MeSH terms: insulin resistance, hyperglycemic-clamp, euglycemic-clamp, Min-Mod, minimal model approach. Concordance was determined with both simple and intraclass correlation and Bland and Altman's concordance limits using R. Three of the 109 articles found were included. The concordance limits indicate that Clamp and Min-Mod are not equivalent, which could result in diagnostic errors if the accepted cut-off point is used for both methods. Given this lack of equivalence, a ROC analysis was performed and new diagnostic cut-off points of 2.4 and 4.6x0-2 (dL/min)/(microU/mL) for insulin and tolbutamide techniques of Min-Mod, respectively, are proposed, with adequate sensitivity, specificity, and predictive value. These values should be prospectively validated.

Obesity-prone rats have preexisting defects in their counterregulatory response to insulin-induced hypoglycemia

Rats that develop diet-induced obesity (DIO) on a 31% fat [high-energy (HE)] diet have defective sensing and responding to altered glucose levels compared with diet-resistant (DR) rats. Thus we postulated that they would also have defective counterregulatory responses (CRR) to insulin-induced hypoglycemia (IIH). Chow-fed selectively bred DIO and DR rats underwent three sequential 60-min bouts of IIH separated by 48 h. Glucose levels fell comparably, but DIO rats had 22–29% lower plasma epinephrine (Epi) levels during the first two bouts than DR rats. By the third trial, despite comparable Epi levels, DIO rats had lower 30-min glucose levels and rebounded less than DR rats 85 min after intravenous glucose. Although DIO rats gained more carcass and fat weight after 4 wk on an HE diet than DR rats, they were unaffected by prior IIH. Compared with controls, DR rats with prior IIH and HE diet had higher arcuate nucleus neuropeptide Y (50%) and proopiomelanocortin (POMC; 37%) mRNA and an inverse correlation ( r = 0.85; P = 0.004) between POMC expression and body weight gain on the HE diet. These data suggest that DIO rats have a preexisting defect in their CRR to IIH but that IIH does not affect the expression of their hypothalamic neuropeptides or weight gain as it does in DR rats.

Insulin-induced hypoglycemia suppresses plasma parathyroid hormone levels in patients with adrenal insufficiency

Hypoglycemia has been reported to cause suppression of parathyroid hormone (PTH) levels in serum in normal subjects. It is possible that increasing cortisol levels in response to hypoglycemia was responsible. To examine this possibility the acute PTH response to insulin administration and resulting hypoglycemia was examined in patients with adrenal insufficiency. The possible acute impact of insulin-induced hypoglycemia on bone formation and bone resorption in the absence of an endogenous cortisol response was also examined. A prospective open study was undertaken to examine the acute effects of insulin and resulting hypoglycemia on PTH levels, on bone formation as indicated by serum levels of aminoterminal propeptide of type 1 procollagen (PINP), and on bone resorption as indicated by serum levels of beta carboxy terminal telopeptide of type 1 collagen (beta-CTx). Seven patients with adrenal insufficiency participated. These patients were studied on 3 occasions under different conditions: (1) when insulin was administered to induce hypoglycemia while the patients received their routine glucocorticoid replacement; (2) when the patients received their routine glucocorticoid replacement, but were not rendered hypoglycemic; and (3) when they did not receive glucocorticoid replacement and were not rendered hypoglycemic, ie, untreated. This facilitated isolation of the PTH response to insulin and hypoglycemia from the effects of the normal increase in endogenous cortisol levels in response to hypoglycemia. Blood samples were taken at baseline and after 3 hours while the subjects continued fasting for measurement of plasma glucose, serum ionized calcium (Cai), magnesium, phosphate, PINP, PTH, and beta-CTx. Insulin 0.075 IU/kg body weight was given intravenously after the first blood sample. The usual morning glucocorticoid replacement dose was given 20 minutes after the baseline blood sample was obtained. After the administration of insulin, plasma glucose decreased from 4.8 +/- 0.5 to 2.7 +/- 0.5 mmol/L, mean +/- SD (P < .0001). PTH was not influenced by time or glucocorticoid treatment, but decreased in response to insulin-induced hypoglycemia (P < .05). Serum levels of PINP and beta-CTx decreased when untreated between 9 AM and 12 PM (P < .05), but were not independently influenced by insulin-induced hypoglycemia or glucocorticoid treatment. Serum levels of Cai increased and serum phosphate levels decreased in response to insulin-induced hypoglycemia, while serum phosphate levels were also independently influenced by time decreasing between 9 AM and 12 PM (P < .05). There was no effect of time, insulin-induced hypoglycemia, or glucocorticoid treatment on serum levels of magnesium. Possible mechanisms involved in the acute decrease in serum PTH observed include a direct effect of insulin or hypoglycemia or an indirect effect, eg, increased sympathomimetic activity on PTH secretion or on calcium or phosphate intercompartmental shifts.

Adiponectin concentrations in sera from patients with type 2 diabetes are negatively associated with sympathovagal balance as evaluated by power spectral analysis of heart rate variation

OBJECTIVE

To investigate whether cardiac autonomic activity, particularly sympathovagal balance as estimated by power spectral analysis (PSA) of heart rate variation (HRV), is associated with serum adiponectin concentrations in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We studied 105 patients with type 2 diabetes (51 women and 54 men). Serum adiponectin concentrations were measured by sandwich enzyme-linked immunosorbent assay. HRV was determined automatically every 5 min over 24 h using Holter electrocardiographic recording. PSA of R-R intervals was performed using fast Fourier transformation. Low-frequency (both sympathetic and parasympathetic activities), high- frequency (pure parasympathetic activity), and the ratio of low-frequency-to-high-frequency power (LF-to-HF ratio), an index of sympathovagal balance, were used as indexes of cardiac autonomic activity.

RESULTS

We found no significant correlation between serum adiponectin and low-frequency or high-frequency power in patients with diabetes. Serum adiponectin concentration correlated negatively with the 24-h LF-to-HF ratio (r = -0.343, P = 0.0009) and creatinine clearance (r = -0.411, P < 0.0001). Serum adiponectin concentrations were significantly higher in patients with overt albuminuria than in those with normoalbuminuria or microalbuminuria. In multivariate analysis controlling for sex, BMI, glycemic control, lipid profile, and renal function, serum adiponectin concentration showed an independent negative association with 24-h LF-to-HF ratio (beta = -0.332, P = 0.020). Furthermore, sex, HDL cholesterol, and renal function retained significant influence on the serum adiponectin concentration in patients with diabetes.

CONCLUSIONS

Sympathovagal balance favoring relative sympathetic activation was associated with low serum concentrations of adiponectin in patients with type 2 diabetes.

Population and individual minimal modeling of the frequently sampled insulin-modified intravenous glucose tolerance test

Population approaches are more robust estimators of insulin sensitivity (SI) and glucose effectiveness (SG) with the minimal model of glucose kinetics during an intravenous glucose tolerance test (IVGTT). We assessed the performance of 3 population methods, iterative two-stage (ITS), Bayesian hierarchical Markov chain Monte Carlo (MCMC), and NONMEM first-order conditional estimation (FOCE) with interaction (NM), and made a comparison with the standard two-stage method (STS) employing the weighted nonlinear regression analysis. To evaluate accuracy of individual and population estimates, 40 simulated insulin-modified frequently sampled IVGTTs (IM-FSIVGTT) were derived from real IM-FSIVGTTs (0.3 g glucose per kg body weight with 0.02 U/kg insulin at 20 minutes; 30 samples over 180 minutes) performed in 40 healthy Caucasian subjects (male/female, 22/18; age, 46 +/- 9 years; body mass index [BMI], 26.7 +/- 5.7 kg. m(-2); mean +/- SD). The population methods assumed a log-normal population distribution of parameters. All methods gave a similar but overestimated population SG by 9% to 13%. Population SI was underestimated to a different degree by the methods (STS 6%, ITS 10%, MCMC 13%, and NM 7%). The between-subject variability of SG was overestimated by STS and underestimated by the population methods (true 33%, STS 40%, ITS 19%, MCMC 24%, NM 24%; coefficient of variation). For SI, this quantity was well estimated by all methods (true 79%, STS 80%, ITS 82%, MCMC 83%, NM 82%). The results for individual estimates indicate that STS performs better than the population methods when estimating SI (STS 12%, ITS 16%, MCMC 16%, NM 16%; 1 outlying subject excluded; root mean squared error expressed as percent of mean) but worse for SG (STS 28%, ITS 21%, MCMC 20%, NM 19%). We conclude that the robust performance of population approaches, preventing parameter estimation failures associated with the nonlinear regression analysis, is not required with IM-FSIVGTT in subjects with normal glucose tolerance. The standard two-stage technique is the preferred method under such circumstances.

The G972R variant of the insulin receptor substrate-1 (IRS-1) gene is associated with insulin resistance in "uncomplicated" obese subjects evaluated by hyperinsulinemic-euglycemic clamp

Several association studies have indicated the insulin receptor substrate-1 (IRS-1) gene G972R variant as a genetic risk factor for insulin resistance, particularly in presence of obesity. A few studies have also suggested a possible effect of the G972R variant on insulin secretion. The aim of this study was to evaluate the role of the IRS-1 gene G972R variant in 61 subjects with "uncomplicated" obesity [i.e. without diabetes, hypertension, dyslipidemia, coronary artery disease (CAD)], studied by hyperinsulinemic-euglycemic clamp. The presence of the G972R variant, detected in real-time with LightCycler hybridisation probes, was related to the indexes of insulin sensitivity. Furthermore, the possible role of this variant on insulin secretion was studied by means of insulin release indexes derived from oral tolerance test (OGTT). Twenty-four point five percent (24.5%) (no.=15) of the obese subjects proved to be carriers of the G972R variant. M index (p<0.05), non-oxidative glucose (p<0.01), insulin clearance (p<0.03) and insulin sensitivity index (ISI) (p<0.005) were all significantly reduced in G972R carriers compared to non-carriers, indicating a significant reduction in insulin sensitivity in carriers of the variant. A logistic regression analysis confirmed the independent association between the G972R variant and reduced insulin sensitivity (p<0.03). The interaction between obesity and the G972R variant was also independently associated with a reduced insulin sensitivity (p<0.005), suggesting that obesity and G972R variant were more than additive in predicting insulin resistance. The analysis of insulin release indexes did not show any significant differences. Our results demonstrate the association of the G972R variant of the IRS-1 gene with reduced insulin sensitivity in obese subjects, and indicate a possible interaction between the IRS-1 variant and obesity in worsening of insulin sensitivity.

Improvement of glucose homeostasis in obese diabetic db/db mice given Plasmodium yoelii glycosylphosphatidylinositols

We have previously reported that infection with Plasmodium yoelii, Plasmodium chabaudi, or injection of extracts from malaria-parasitized red blood cells induces hypoglycemia in normal mice and normalizes the hyperglycemia in streptozotocin (STZ)-diabetic mice. P yoelii glycosylphosphatidylinositols (GPIs) were extracted in chloroform:methanol:water (CMW) (10:10:3), purified by high-performance thin layer chromatography (HPTLC) and tested for their insulin-mimetic activities. The effects of P yoelii GPIs on blood glucose were investigated in insulin-resistant C57BL/ks-db/db diabetic mice. A single intravenous injection of GPIs (9 and 30 nmol/mouse) induced a significant dose-related decrease in blood glucose (P < .001), but insignificantly increased plasma insulin concentrations. A single oral dose of 2.7 micromol GPIs per db/db mouse significantly lowered blood glucose (P < .01). P yoelii GPIs in vitro (0.062 to 1 micromol/L) significantly stimulated lipogenesis in rat adipocytes in a dose-dependent manner both in the presence and absence of 10(-8) mol/L insulin (P < .01). P yoelii GPIs stimulated pyruvate dehydrogenase phosphatase (PDH-Pase) and inhibited both cyclic adenosine monophosphate (cAMP)-dependent protein kinase A and glucose-6-phosphatase (G6Pase). P yoelii GPIs had no effect on the activity of the gluconeogenic enzymes fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase (PEPCK). This is the first report of the hypoglycemic effect of P yoelii GPIs in murine models of type 2 diabetes. In conclusion, P yoelii GPIs demonstrated acute antidiabetic effects in db/db mice and in vitro. We suggest that P yoelii GPIs, when fully characterized, may provide structural information for the synthesis of new drugs for the management of diabetes.

Effect of scoparia dulcis (Sweet Broomweed) plant extract on plasma antioxidants in streptozotocin-induced experimental diabetes in male albino Wistar rats

Clinical research has confirmed the efficacy of several plants in the modulation of oxidative stress associated with diabetes mellitus. Scoparia dulcis plant extract is tried for prevention and treatment of diabetes mellitus induced experimentally by streptozotocin injection. A single dose of streptozotocin (45 mg/kg body weight) produced decrease in insulin, hyperglycemia, increased lipid peroxidation (Thiobarbituric reactive substances and lipid hydroperoxides) and decreased antioxidant levels (vitamin C, vitamin E, reduced glutathione, ceruloplasmin). Oral administration of an aqueous extract of Scoparia dulcis plant (200 mg/kg body weight) for 6 weeks to diabetic rats significantly increased the plasma insulin and plasma antioxidants and significantly decreased lipid peroxidation. The effect of Scoparia dulcis plant extract at 200 mg/kg body weight was better than that of glibenclamide, a reference drug.

The influence of 17beta-oestradiol on corticotrophin-releasing hormone induced suppression of luteinising hormone pulses and the role of CRH in hypoglycaemic stress-induced suppression of pulsatile LH secretion in the female rat

Corticotrophin-releasing hormone (CRH) released during stress has been implicated in the disruption of the reproductive neuroendocrine axis, and 17beta-oestradiol (E2) has been shown to enhance stress-induced suppression of pulsatile gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH) release. The aims of the present study were to examine the role of CRH in hypoglycaemic stress-induced suppression of LH pulses, and to investigate the influence of E2 on the inhibitory effect of CRH on pulsatile LH secretion in the female rat. Suppression of LH pulses by insulin-induced hypoglycaemic (IIH) stress was completely prevented by intracerebroventricular (icv) administration of a CRH antagonist. Central administration of CRH (5 microg) resulted in an interruption of LH pulses in E2 treated animals, but had little or no effect in the absence of this gonadal steroid. These results provide evidence of a pivotal role for CRH in mediating the suppressive effect of IIH stress on pulsatile LH secretion in the female rat, and highlight a sensitising role for E2 in CRH-induced suppression of LH pulses.

Glucoreceptors Located Inside the Blood-Brain Barrier Mediate Hypoglycemia-Induced LH Inhibition in Man

OBJECTIVE

To establish the role of hyperinsulinemia and hypoglycemia during the insulin tolerance test (ITT) in the regulation of luteinizing hormone (LH) secretion and the location with respect to the blood-brain barrier (BBB) of the glucosensitive areas controlling LH release.

METHODS

The LH-secretory pattern during an ITT (0.15 IU/kg body weight) was evaluated in 8 normal men during infusion with normal saline (control test), glucose or fructose.

RESULTS

lnsulin-induced hypoglycemia produced a significant decrement in serum LH levels in the control test, but not when the concomitant infusion of glucose prevented hypoglycemia. Fructose infusion did not change LH decrease during ITT.

CONCLUSIONS

These data exclude a direct role of hyperinsulinemia in the mechanism underlying the inhibition of LH secretion during ITT. Furthermore, since glucose but not fructose crosses the BBB, the LH decrease during ITT appears to be generated by hypoglycemia at the level of glucosensitive areas located inside the BBB.

[Transgenic mice overexpressing PACAP in pancreatic beta-cells: acute and chronic effects on insulin and glucose homeostasis]

PACAP belongs to the vasoactive intestinal polypeptide (VIP)/secretin/glucagon superfamily, which also includes glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). PACAP shares an insulinotropic property with the latter two peptides; for instance, it stimulates insulin secretion from islets in a glucose-dependent manner at femtomolar concentrations. However, the pathophysiological significance of PACAP in diabetes remains largely unknown, for several reasons, including a lack of low-molecular weight PACAP ligands and a lack of suitable animal models. As an approach to understanding PACAP's pancreatic function in vivo, we have recently generated transgenic mice overexpressing PACAP in islet beta cells under the control of human insulin promoter (Tg mice). As a consequence, it has been demonstrated that in addition to stimulating insulin secretion, PACAP has long-term effects on pancreatic endocrine cells, including proliferation of beta cells during streptozotocin-induced diabetes development as well as aging. These observations provide additional information to support the possibility that drugs associated with PACAP-signaling pathways might be of therapeutic value for the treatment of diabetes. In this review, we briefly summarize these previous studies using Tg mice and also focus on the physiological and pathophysiological roles mediated by PACAP during diabetes development.

Low- and standard-dose corticotropin and insulin hypoglycemia testing in the assessment of hypothalamic-pituitary-adrenal function after pituitary surgery

The optimal means of assessing the integrity of the hypothalamic-pituitary-adrenal (HPA) axis after pituitary surgery remains controversial. We compared low-dose (1 micro g iv) and standard-dose (250 micro g im) corticotropin tests performed 1 and 4-6 wk after pituitary surgery with an insulin hypoglycemia test performed at 4-6 wk. Forty-one patients (21 male and 20 female; median age, 52 yr; range, 23-73 yr) who had undergone pituitary surgery were studied (Cushing's disease excluded). Twenty-two of the 41 patients had normal cortisol responses to all tests both at 1 and 4-6 wk after surgery. Eight patients had subnormal cortisol responses to all tests. Of the 11 patients with discrepant results, seven had subnormal responses only after the low-dose corticotropin test; the remaining four patients had borderline responses to one or more tests. At 4-6 wk after surgery, subjects with a 30-min serum cortisol after standard-dose corticotropin of less than 350 nmol/liter (12.7 micro g/dl) consistently had a subnormal response to hypoglycemia, and those with a serum cortisol greater than 650 nmol/liter (23.6 micro g/dl) had a normal response to hypoglycemia. Definitive testing of the HPA axis using the standard-dose corticotropin test can be carried out provided it is performed at least 4 wk after pituitary surgery. A 30-min cortisol level greater than 650 nmol/liter (23.6 micro g/dl) indicates adequacy of the HPA axis, and a level of less than 350 nmol/liter (12.7 micro g/dl) indicates ACTH deficiency. No further testing is then required. An intermediate level of 350-650 nmol/liter (12.7-23.6 micro g/dl) warrants further assessment using the insulin hypoglycemia test.

Inactivation of the DMH selectively inhibits the ACTH and corticosterone responses to hypoglycemia

We have previously reported that repeated bouts of insulin-induced hypoglycemia (IIH) in the rat result in blunted activation of the paraventricular, arcuate, and dorsomedial hypothalamic (DMH) nuclei. Because DMH activation has been implicated in the sympathoadrenal and hypothalamic-pituitary-adrenal (HPA) responses to stressors, we hypothesized that its blunted activation may play a role in the impaired counterregulatory response that is also observed with repeated bouts of IIH. In the present study, we evaluated the role of normal DMH activation in the counterregulatory response to a single bout of IIH. Local infusion of lidocaine (n = 8) to inactivate the DMH during a 2-h bout of IIH resulted in a significant overall decrease of the ACTH response and a delay of onset of the corticosterone response compared with vehicle-infused controls (n = 9). We observed suppression of the ACTH response at time (t) = 90 and 120 min (50 +/- 12 and 63 +/- 6%, respectively, of control levels) and early suppression of the corticosterone response at t = 30 min (59 +/- 13% of the control level). The epinephrine, norepinephrine, and glucagon responses were not altered by DMH inactivation. Our finding suggests that DMH inactivation may play a specific role in decreasing the HPA axis response after repeated bouts of IIH.

The hormonal phenotype of Nonclassic 3 beta-hydroxysteroid dehydrogenase (HSD3B) deficiency in hyperandrogenic females is associated with insulin-resistant polycystic ovary syndrome and is not a variant of inherited HSD3B2 deficiency

To test our hypothesis that the hormonal phenotype of mild 3beta-hydroxysteroid dehydrogenase (HSD3B) deficiency in hyperandrogenic females (HF) is related to insulin-resistant polycystic ovary syndrome (PCOS), we compared insulin sensitivity and gonadotropin secretion in HF with compromised ( downward arrow ) adrenal HSD3B phenotype despite normal HSD3B2 genes (n = 6) to those in HF with classic PCOS (n = 9) of similar ages (14-36 yr). The same was examined in premature pubarche (PP) girls with (n = 4) and without the descending HSD3B phenotype (n = 5). The descending HSD3B phenotype was defined by ACTH-stimulated Delta(5)-precursor steroid levels and Delta(5)-precursors to Delta(4)-product steroid ratios higher than those in normal females (n = 30 for adult, n = 12 for pubertal). Classic PCOS HF had elevated testosterone levels and normal ACTH-stimulated hormonal profiles. The insulin sensitivity index determined by the frequently sampled iv glucose-tolbutamide test (FSIVGTT) in all HF with descending HSD3B phenotype and in all HF with classic PCOS, regardless of body mass index (BMI), was lower than in all eight normal BMI and five high BMI normal females. Integrated incremental insulin determined by FSIVGTT, the area under the curve for insulin, and fasting and 2 h glucose load insulin levels determined by an oral glucose tolerance test in both HF groups were higher (P < 0.01-0.0001) than those in normal females with normal or high BMI. LHRH-stimulated LH levels and LH/FSH ratios in both HF groups were higher (P < 0.01) than those in normal females. No statistical differences were found in the insulin sensitivity and gonadotropin parameter between the two PP girl groups. The insulin sensitivity index in each half of PP girls with the descending HSD3B phenotype was lower than or similar to that in control PP girls with a similar weight length index. The fasting glucose to insulin ratio in three of four PP girls with the descending HSD3B phenotype was lower than that in control PP girls, but one of four with the descending HSD3B phenotype had a higher fasting glucose to insulin ratio than the control PP girls. The findings of insulin sensitivity and gonadotropin data in both HF with the descending HSD3B phenotype and classic PCOS indicate significant insulin resistance and LH hypersecretion in both. These suggest that the descending HSD3B phenotype in HF is associated with a variant of insulin-resistant PCOS. The variable insulin sensitivity parameter in the small number of PP girls with the descending HSD3B phenotype warrants a further large scale study to examine this phenotype association with childhood insulin resistance.

Acute insulin responses to calcium and tolbutamide do not differentiate focal from diffuse congenital hyperinsulinism

Congenital hyperinsulinism (CHI) is related to two main histological pancreas anomalies: focal adenomatous hyperplasia and diffuse beta-cell hypersecretion. Pharmacological tests to measure acute insulin responses (AIR) to peripheral i.v. injections of glucose, calcium, and tolbutamide have been reported as potential means to distinguish between these histological forms. In patients with defects in ATP-sensitive potassium channels, tolbutamide will fail to induce insulin release in affected portions of the pancreas, whereas calcium gluconate will enhance insulin release through spontaneously active voltage-gated Ca(2+) channels. Consequently, in focal CHI patients, calcium should promote AIRs from the lesion, whereas tolbutamide should act to promote insulin secretion from the healthy region of the pancreas (outside the focal hyperplasia). We therefore studied AIRs to calcium and tolbutamide stimulation tests in 16 children with focal (n = 9) or diffuse (n = 7) CHI before pancreatic surgery. We found hypervariable AIRs to glucose and calcium stimulation in both focal and diffuse CHI patients. AIRs to tolbutamide stimulation were found modest in focal CHI patients, which might account for beta-cell quiescence in the healthy portion of the pancreas of these patients. We conclude that AIRs to calcium and tolbutamide stimulation tests are not sufficient to differentiate the focal from the diffuse CHI patients.

[Biological activities of Salacia chinensis originating in Thailand: the quality evaluation guided by alpha-glucosidase inhibitory activity]

In the course of our characterization studies on anti-obese and antidiabetogenic principles in medicinal foodstuffs, we found that the methanolic extract from the stems of Salacia chinensis (Hippocerateaceae) showed potent anti-hyperglycemic effects in oral sucrose or maltose-loaded rats, inhibitory effects on intestinal alpha-glucosidase, rat lens aldose reductase, formation of Amadori compounds and advanced glycation end-products, nitric oxide production from lipopolysaccharide-activated mouse peritoneal macrophage, and radical scavenging activities. Those in vivo and in vitro biological activities were compared with those of S. oblonga and S. reticulata. In addition, we isolated the principal alpha-glucosidase inhibitor, salacinol, from the stems of S. chinensis and examined alpha-glucosidase inhibitory activities of eleven samples of S. chinensis collected in Thailand.

Strain- and sex-related differences of carbonyl reductase activities in kidney microsomes and cytosol of rats

This study was designed to elucidate strain- and sex-related differences of carbonyl reductase activity in rat kidney by using the oral antidiabetic drug acetohexamide as substrate. The frequency distribution of carbonyl reductase activities in kidney microsomes of male Fischer 344 (Fischer), Sprague-Dawley, Wistar and Wistar-Imamichi (Wistar-IM) rats exhibited a marked strain-related difference. Furthermore, the enzyme activities in kidney microsomes of Fischer, Sprague-Dawley and Wistar rats were male-specific, resulting insignificant sex-related differences in these strains. There was no sex-related difference of carbonyl reductase activity in kidney microsomes of the Wistar-IM strain, which lacked its activity in both sexes. On the other hand, although carbonyl reductase activities were fully detectable in kidney cytosols from all the strains of male and female rats, no strain- or sex-related difference was observed among the cytosolic enzyme activities. These results provide new information for understanding the influence of internal factors on the renal metabolism of ketone-containing xenobiotics.