Efecto hipoglicemiante de la NeuroEPO en ratas con y sin diabetes mellitus / Hypoglycemic effect of NeuroEPO in diabetic and non-diabetic rats

RESUMEN Introducción: La NeuroEPO es una variante no-hematopoyética de la eritropoyetina recombinante humana, que pudiera tener efecto hipoglicemiante. Objetivo: Evaluar la influencia de la NeuroEPO sobre la glicemia de ratas con diabetes mellitus y ratas no-diabéticas. Material y Métodos: Se realizaron experimentos en ratas Wistar con diabetes inducida por estreptozotocina, con y sin tratamiento con insulina, y en ratas no-diabéticas con una sobrecarga de glucosa. En cada experimento, un grupo recibió una inyección subcutánea de NeuroEPO (0,5 mg/kg) y otro el vehículo, y se determinó la glicemia durante 120 minutos. Se realizaron comparaciones mediante análisis de varianza de una y dos vías, seguidas por la prueba de Bonferroni. Las diferencias se consideraron significativas con valores de p < 0,05. Resultados: En las ratas diabéticas sin tratamiento con insulina, los niveles de glicemia del grupo con NeuroEPO disminuyeron de forma significativa. En las ratas no-diabéticas que recibieron NeuroEPO y una sobrecarga de glucosa, la glicemia fue similar al grupo control. En las ratas diabéticas que recibieron NeuroEPO e insulina la reducción de la glicemia fue mayor que en el grupo que solo recibió insulina. Conclusiones: La NeuroEPO tiene un efecto hipoglicemiante en ratas diabéticas, por un mecanismo insulinotrópico que muestra sinergismo con la insulina en el tratamiento de la hiperglicemia. Sin embargo, la NeuroEPO no influye en la tolerancia a la glucosa de ratas no-diabéticas, al menos de forma inmediata. Es necesario profundizar en los mecanismos mediante los cuales la NeuroEPO puede reducir la hiperglicemia, y la influencia de esta sustancia en condiciones de normoglicemia.

ABSTRACT Introduction: NeuroEPO is a non-hematopoietic variant of human recombinant erythropoietin, which may have a hypoglycemic effect. Objectives: To evaluate the influence of NeuroEPO on glycemia in diabetic and non-diabetic rats. Material and Methods: The experiments were conducted in Wistar rats with streptozotocin-induced diabetes with and without insulin treatment, and in non-diabetic rats with glucose overload. In each experiment, one group received a subcutaneous injection of NeuroEPO (0.5 mg/kg) and the other group received a vehicle. Glycemia was determined in 120 min. Comparisons were made using one-and two-way analysis of variance, followed by the Bonferroni test. The differences were considered significant with p values < 0,05. Results: In diabetic rats without insulin treatment, glycemic levels decreased significantly in the group that received NeuroEPO. In nondiabetic rats that received NeuroEPO and a glucose overload, glycemia was similar to that in the control group. In diabetic rats that received NeuroEPO and insulin, the glycemia reduction was greater than in the group that only received insulin. Conclusions: NeuroEPO has a hypoglycemic effect in diabetic rats due to an insulinotropic mechanism that shows synergism with insulin in the treatment of hyperglycemia. However, NeuroEPO does not influence the glucose tolerance in non-diabetic rats, at least immediately. It is necessary to delve into the mechanisms by which NeuroEPO can reduce hyperglycemia and the influence of this substance under conditions of normoglycemia.

Is biochemical hypoglycemia necessary during an insulin tolerance test?

ABSTRACT Objective The insulin tolerance test (ITT) has been accepted as the gold standard test for assessing the integrity of the growth hormone (GH) - insulin-like growth factor (IGF-1) axis and the hypothalamic-pituitary-adrenal (HPA) axis. The goal of the test is to achieve clinical and biochemical hypoglycemia at a blood glucose level ≤ 40 mg/dL to effectively and correctly assess the HPA and GH-IGF-1 axes. In this study, the GH and cortisol responses of patients who achieved and failed to achieve biochemical hypoglycemia during an ITT were compared. Subjects and methods One hundred thirty-five patients with pituitary disorders were included in the study. Samples for blood glucose levels were obtained after clear symptoms of clinical hypoglycemia developed. The patients were enrolled in the hypoglycemic and nonhypoglycemic groups according to whether their plasma glucose level ≤ 40 mg/dL or > 40 mg/dL during an ITT, and the groups were compared in terms of their GH and cortisol responses. Results The mean age, body mass index and waist circumference of the two patient groups were found to be similar. The mean blood glucose level was significantly lower in the hypoglycemic group than in the nonhypoglycemic group (19.3 and 52.0 mg/dL, respectively). When the two groups were compared in terms of peak cortisol and GH responses, no statistically significant differences were found. Conclusion The data presented suggest that clinically symptomatic hypoglycemia is as effective as biochemically confirmed hypoglycemia during an ITT. Arch Endocrinol Metab. 2020;64(1):82-8

Evaluación de parámetros clínicos y de laboratorio relacionados con el diagnóstico de insulino resistencia / Evaluation of clinical and laboratory parameters related to the diagnosis of insulin resistance

The evaluation of insulin resistance (IR) in clinical practice is based on the determination of fasting insulin (I0) and insulin level after 2 hours in an oral glucose tolerance test (OGT). However, there are not adequate cutoff points to discriminate IR patients. Objectives: to evaluate the reliability of insulin levels in the diagnosis of IR using the intravenous insulin tolerance test (IVITT) as the gold standard. Patients and Method: The OGT and IVITT of patients who participated as cases or controls in research protocols were analyzed. We excluded those cases with fasting glycemia over126 mg/dl. Results: 128 cases, 111 F, 17 M; Age: 40.3 +/- 14.8 years; BMI: 33 +/- 8 kg/m2; Waist circumference, M: 100.3 +/- 9.4 cm, F: 96 +/- 15 cm. According to IVITT (KITT), 103 (80.5 percent) were IR (KITT < 4.5 percent) and 25 (19.5 percent) were non IR (KITT > 4.5 percent). Fasting (G0) and 120 minutes after glucose challenge glycemia (G120), I0 and I120, HOMA and area under the glycemia and insulin curve, were significantly higher in the IR, as the same as, hypertension and acanthosis nigricans features (p < 0.05). According to G120, 45 cases (35.2 percent) had glucose intolerance, 9 (7 percent) diabetes and 74 (57.8 percent) were normals. In addition to G0, only IVITT was significantly different among the 3 groups (p = 0.025), identifying most insulin resistant subjects. The sensitivity and specificity for a cutoff point of I120 at 60 µIU/mL, were 30 percent and 88 percent, respectively. Conclusion: Baseline and 120 minutes post glucose charge insulin levels and HOMA, do not discriminate insulin resistant subjects, especially when there is fasting or post-stimulus hyperglycemia. Therefore, they are not recommended for individual diagnosis or therapeutic decisions

Validation of HOMA-IR in a model of insulin-resistance induced by a high-fat diet in Wistar rats

ABSTRACT Objective The present study aimed to validate homeostasis model assessment of insulin resistance (HOMA-IR) in relation to the insulin tolerance test (ITT) in a model of insulin-resistance in Wistar rats induced by a 19-week high-fat diet. Materials and methods A total of 30 male Wistar rats weighing 200-300 g were allocated into a high-fat diet group (HFD) (55% fat-enriched chow, ad lib, n = 15) and a standard-diet group (CD) standard chow, ad lib, n = 15), for 19 weeks. ITT was determined at baseline and in the 19th week. HOMA-IR was determined between the 18-19th week in three different days and the mean was considered for analysis. Area under the curve (AUC-ITT) of the blood glucose excursion along 120 minutes after intra-peritoneal insulin injection was determined and correlated with the corresponding fasting values for HOMA-IR. Results AUC-ITT and HOMA-IR were significantly greater after 19th week in HFD compared to CD (p < 0.001 for both). AUC-OGTT was also higher in HFD rats (p = 0.003). HOMA-IR was strongly correlated (Pearson’s) with AUC-ITT r = 0.637; p < 0.0001. ROC curves of HOMA-IR and AUC-ITT showed similar sensitivity and specificity. Conclusion HOMA-IR is a valid measure to determine insulin-resistance in Wistar rats. Arch Endocrinol Metab. 2016;60(2):138-42.

Beneficial effects of Ginkgo biloba extract on insulin signaling cascade, dyslipidemia, and body adiposity of diet-induced obese rats

Ginkgo biloba extract (GbE) has been indicated as an efficient medicine for the treatment of diabetes mellitus type 2. It remains unclear if its effects are due to an improvement of the insulin signaling cascade, especially in obese subjects. The aim of the present study was to evaluate the effect of GbE on insulin tolerance, food intake, body adiposity, lipid profile, fasting insulin, and muscle levels of insulin receptor substrate 1 (IRS-1), protein tyrosine phosphatase 1B (PTP-1B), and protein kinase B (Akt), as well as Akt phosphorylation, in diet-induced obese rats. Rats were fed with a high-fat diet (HFD) or a normal fat diet (NFD) for 8 weeks. After that, the HFD group was divided into two groups: rats gavaged with a saline vehicle (HFD+V), and rats gavaged with 500 mg/kg of GbE diluted in the saline vehicle (HFD+Gb). NFD rats were gavaged with the saline vehicle only. At the end of the treatment, the rats were anesthetized, insulin was injected into the portal vein, and after 90s, the gastrocnemius muscle was removed. The quantification of IRS-1, Akt, and Akt phosphorylation was performed using Western blotting. Serum levels of fasting insulin and glucose, triacylglycerols and total cholesterol, and LDL and HDL fractions were measured. An insulin tolerance test was also performed. Ingestion of a hyperlipidic diet promoted loss of insulin sensitivity and also resulted in a significant increase in body adiposity, plasma triacylglycerol, and glucose levels. In addition, GbE treatment significantly reduced food intake and body adiposity while it protected against hyperglycemia and dyslipidemia in diet-induced obesity rats. It also enhanced insulin sensitivity in comparison to HFD+V rats, while it restored insulin-induced Akt phosphorylation, increased IRS-1, and reduced PTP-1B levels in gastrocnemius muscle. The present findings suggest that G. biloba might be efficient in preventing and treating obesity-induced insulin signaling impairment.

Effects of Pollen Typhae Total Flavone on Inflammatory Factors and Insulin Sensitivity in Type 2 Diabetic Rats / 广州中医药大学学报

Objective To investigate the effects of Pollen Typhae total flavone ( PTF) , an extract from Pollen Typhae which has the actions of activating blood and removing stasis, on inflammatory factors and insulin sensitivity in type 2 diabetic rats. Methods SD rats were used as the experimental animal. Type 2 diabetic rats induced by high fat diet plus low dose of streptozotocin were randomly divided into model group, PTF group (in the dosage of 200 mg·kg-1·d-1) , and rosiglitazone group (in the dosage of 4 mg·kg-1·d-1) . Additionally, normal control group was set up. After treatment for 4 weeks, plasma interleukin 6 ( IL-6) and tumor necrosis factor alpha ( TNF-α) levels were detected, the insulin tolerance test ( ITT) was performed, and the protein expression of suppressor of cytokine signaling-3 ( SOCS-3) in skeletal muscle was determined. Results After treatment for 4 weeks, the plasma levels of IL-6 and TNF-α, the homeostasis model of insulin resistance ( HOMA-IR) , and expression level of SOCS-3 in skeletal muscle in the model groups were significantly increased ( P﹤0.05) as compared with those in the normal control group, and insulin tolerance was also impaired in the model group ( P﹤0.05) . Compared with the model group, IL-6 level and HOMA-IR were markedly decreased in the PTF group ( P﹤0.05) , and the impaired insulin tolerance was obviously improved (P﹤0.05) . The level of SOCS-3 in the skeletal muscle of PTF group was also much lower than that of the model group and rosiglitazone group (P﹤0.05) . Conclusion PTF has effects on decreasing the levels of plasma IL-6 and SOCS-3 in the skeletal muscle and on improving insulin sensitivity in type 2 diabetic rats.

Influencing factors of growth hormone in response to insulin tolerance test in 50 healthy adults / 中华内分泌代谢杂志

The peak level of growth hormone (GH) stimulated by insulin tolerance test (ITT) is thegold standard for diagnosis of growth hormone deficiency in adults.This study was aimed to explore the factors influencing GH response to ITT in 50 healthy adults.The results showed that the nadir or decreased amplitude of blood glucose was not related to GH peak level.In multivariable analysis,the GH level stimulated by ITT was negatively associated with body mass index(P＜0.01),but there was no any association with age,gender,and waist circumference.

Significance of insulin tolerance test in the diagnosis of adult growth hormone deficiency / 中华内分泌代谢杂志

Objective To assess the significance of insulin tolerance test(ITT) in clinical diagnosis of adult growth hormone deficiency(GHD).Methods Eighty-two patients with an established diagnosis of adult GHD [53males,29 females,mean age (30.9 ± 12.3) years (18-65 years)] were reviewed retrospectively for evaluating the GH response to ITT in the General Hospital of the People' s Liberation Army.Control data for peak GH after ITT were obtained in 15 healthy subjects [9 males,6 females,mean age (26.7 ± 5.6) years (22-41 years)].Receiver operating characteristic (ROC) curve analysis and the area under the curve (AUC) were used to evaluate the diagnostic cut-off point of peak GH and GH increment response to ITT.Results (1) Mean peak GH response to ITT was significantly higher in 15 controls compared with 82 patients (the median 14 μg/L vs 0.62 μg/L,P =0.001).The cut-off point of the peak GH(chemiluminescent immunoassay,CLIA) response to ITT in adult GHD was 4.935 μg/L (AUC 0.993).(2) Mean GH increment was significantly higher in 15 controls compared with 82 patients (the median 13.17 μg/L vs 0.19 ug/L,P＜0.001).The cut-off point of the GH increment was 4.088 μg/L(AUC 0.937),with a 91.5％ sensitivity and 100％ specificity.(3) The peak GH showed even higher diagnostic value than the GH increment after ITT.(4)The above mentioned cut-off points (peak GH less than 4.935 μg/L and 5 μg/L) had a coincidence with a 95.1％ sensitivity and 100％ specificity,respectively.Conclusion The current guidelines for the diagnosis of adult GHD based on the optimal cut-off point of the peak GH(CLIA) response to ITT less than 5 μg/L turned to be of reliable diagnostic value in our country.

Basal serum cortisol as a predictor for adrenal reserve in children with adrenal insufficiency

Background: Secondary adrenocortical insufficiency occurs in children who have been suffering from pathological conditions in the hypothalamo-pituitary region such as infection, irradiation, and after tumor removal. The basal serum cortisol level as a predictor of secondary adrenocortical insufficiency has been studied mostly in adult and rarely in children. The aim of this study is to evaluate the basal morning cortisol level as a predictor of secondary adrenocortical insufficiency. Material and method: Forty-nine children, aged 2-15 years, were recruited for this study. Forty-six had tumors in the suprasellar region, two had suprasellar arachnoid cysts, and one had a history of high dose cranial irradiation. In addition, 52 idiopathic short children with proven normal hypothalamo-pituitary function were a control group. Serum basal morning cortisol level (7.30-9.00 am) was measured, and then the insulin tolerance test (ITT) was performed as a gold standard in all children. Results: A basal morning cortisol level of less than 4 μg/dL suggested the diagnosis of secondary adrenocortical insufficiency with specificity of 100% and positive predictive value (PPV) of 100%. In addition, basal cortisol level of more than 18 μg/dL could exclude the secondary adrenocorticol insufficiency with specificity of 100% and PPV of 100%. The more additional pituitary hormone deficiency was, the less was serum basal cortisol level, which represented the potential severity of pituitary gland insult. Conclusion: Measurement of morning basal cortisol level finding less than 4 and more than18 μg/dL can predict the outcome of hypothalamo-pituitary reserve function with 100% PPV in order to avoid a complicated and risky ITT in children with pathology around suprasellar region.

Factors for persistent growth hormone deficiency in young adults with childhood onset growth hormone deficiency / 소아과

PURPOSE: Growth hormone (GH) replacement after retesting is necessary because impairment of body composition and cardiovascular health has been more severe in adult patients with persistent GH deficiency (GHD) from childhood to adulthood. This study aimed to investigate the factors for persistent GHD and define a highly probable group of persistent GHD in young adults with childhood-onset GHD. METHODS: GHD was reassessed by insulin tolerance test (ITT) in 55 adult patients (39 males, 16 females) with childhood-onset GHD. Twelve patients presented with idiopathic GHD and 43 patients presented with organic GHD caused by tumors involving the hypothalamus-pituitary (H-P) region (n=33), other brain tumors (n=3), meningitis (n=3), leukemia (n=2) and others (n=2). RESULTS: Forty-nine (89.1%) of 55 patients had persistent GHD. IGF-I was positively correlated with log of peak GH (r=0.57, P<0.001). There was no difference in the proportion of persistent GHD between idiopathic and organic GHD. The percentage of patients with persistent GHD was 40%, 80%, and 95.6% for patients with zero, one, two or more additional pituitary hormone deficiencies (PHDs), respectively (P=0.002). The probability of persistent GHD was higher in patients with diseases involving the H-P region (P=0.003). GHD persisted in 15 of 18 patients treated with cranial irradiation. CONCLUSION: We suggest that the probability of persistent GHD in adulthood was high in patients with 2 or more additional PHDs, and diseases involving the H-P region.

Short Insulin Tolerance Test Can Determine the Effects of Thiazolidinediones Treatment in Type 2 Diabetes

PURPOSE: The short insulin tolerance test is a simple and reliable method of estimating insulin sensitivity. This study was designed to compare the insulin sensitizing effects of thiazolidinediones (TZDs) on the degree of insulin resistance, determined by a short insulin tolerance test (Kitt) in type 2 diabetic patients. PATIENTS AND METHODS: Eighty-three subjects (mean age = 57.87 +/- 10.78) with type 2 diabetes mellitus were enrolled and received daily one dose of rosiglitazone (4mg) or pioglitazone (15mg). The mean follow-up duration was 25.39 +/- 9.66 months. We assessed insulin sensitivity using HOMA-IR and the short insulin tolerance test before and after TZDs treatment. RESULTS: When we compared patients' characteristics before and after TZDs treatment, the mean fasting glucose level was significantly decreased (183.27 +/- 55.04 to 137.35 +/- 36.42mg/dL, p or = 2.5%/min; 3.50 +/- 0.75%/min to 2.75 +/- 1.12%/min, p = 0.002). CONCLUSION: The glucose lowering effects of TZDs by improving insulin resistance could be determined by using Kitt. However, Kitt may be a beneficial tool to determine TZDs' effects only when patients' Kitt values are less than 2.5%/min.

Comparison of Provocative Tests for the Diagnosis of Adult Growth Hormone Deficiency in Normal Adults

OBJECTIVE: To compare the Madopar(R) (Levodopa Benserazide) test with Insulin Tolerance Test (ITT) as a provocation test for growth hormone (GH). METHOD: One hundred eighty-seven subjects who had not organic disease such as hypothalamic-pituitary disease were studied. Seventy-one subjects underwent an ITT by injection of 0.1 U/kg of regular insulin and blood samples for GH assay were taken at 0, 30, 60 and 120 minutes. One hundred sixteen subjects underwent a Madopar(R) test by administration of Madopar(R) and blood samples for GH assay were taken at 0, 60, 120 and 180 minutes. RESULTS: The GH mean peak response in ITT was significantly higher than that of the Madopar(R) test. Below 50 years, 18 of ITT and 24 of Madopar(R) test showd a GH peak response of less than 5 ng/ml. Above 50 years, 14 of ITT and 53 of Madopar(R) test showd a GH peak response of less than 5 ng/ml. CONCLUSION: The results suggested that the GH response to the Madopar(R) test was much less than that of the ITT. The Madopar(R) test was limited in diagnosis of the adult GH deficiency in normal adults.