Signals derived from glucose metabolism are required for glucose regulation of pancreatic islet GLUT2 mRNA and protein.

Pancreatic islet GLUT2 mRNA is known to be regulated in vitro and in vivo by glucose. We have investigated several potential mechanisms mediating the response of islet GLUT2 to glucose. GLUT2 mRNA and protein were measured from isolated rat islets cultured for up to 24 h under selected conditions. Glucose at 11 mM stimulated GLUT2 mRNA 10-fold compared with 2 mM glucose, with no additional increase at 16.7 mM glucose, whereas maximal 4-fold induction of the protein was attained with 16 mM glucose. Time course studies showed a 2.5-fold induction of GLUT2 mRNA apparent after only 8 h of culture at 16.7 mM glucose. Glycolysis inhibitor mannoheptulose suppressed the stimulatory effect of 16.7 mM glucose on GLUT2 mRNA and protein. Metabolizable sugars mannose and glyceraldehyde enhanced transporter mRNA levels, in contrast with the lack of stimulation by nonmetabolizable 2-deoxy-D-glucose. Stimulation by different sugars and glycolysis inhibition led to analogous changes of proinsulin mRNA, suggesting that common signaling mechanisms are shared in glucose regulation of proinsulin and GLUT2 gene expression. Preexposure to mannoheptulose, however, failed to suppress glucose-stimulated insulin release. Tunicamycin, a glycoprotein synthesis inhibitor, did not block the effect of 16 mM glucose on GLUT2 mRNA levels. RNA and protein synthesis inhibitors actinomycin and cycloheximide abolished the enhancing effects of high glucose on GLUT2 mRNA. These findings indicate that glucose metabolism, but not glycoprotein synthesis or substrate interaction with the transporter protein, is instrumental in the stimulatory effects of glucose on beta-cell GLUT2 mRNA accumulation. In addition, ongoing RNA and protein synthesis are required for this effect.

Effects of thromboxane synthesis inhibitor triflusal on renal hemodynamics in microalbuminuric diabetic patients.

Triflusal (2-acetoxy-4-trifluormethylbenzoic acid) is a platelet-antiaggregant drug that selectively inhibits thromboxane synthesis with little effect on prostacyclin production. In this study, we evaluated the effect of 5-day administration of 900 mg/day triflusal on glomerular filtration rate (GFR), renal plasma flow (RPF), urinary albumin excretion (UAE), thromboxane B2 (TXB2), 6-ketoprostaglandin F1 alpha (PGF1 alpha), and PGE2 in nine normotensive insulin-dependent diabetic patients with UAE between 30 and 103 micrograms/min. Plasma TXB2 and plasma renin activity (PRA) were also determined. After administration of triflusal, we observed a reduction in microalbuminuria (59 +/- 25 vs. 33 +/- 22 micrograms/min, P less than 0.01), an increase in RPF (648 +/- 119 vs. 722 +/- 134 ml.min-1 x 1.73 m-2, P less than 0.01), and a reduction in filtration fraction (0.24 +/- 0.04 vs. 0.20 +/- 0.03, P less than 0.01). Triflusal produced a significant reduction in both plasma TXB2 (130 +/- 39 vs. 52 +/- 32 pg/ml, P less than 0.02) and urine TXB2 (523 +/- 249 vs. 312 +/- 11 pg/min, P less than 0.02), without changes in PRA and UAE of 6-keto-PGF1 alpha and PGE2. Metabolic control and arterial blood pressure did not change during the study. These results suggest that platelet-antiaggregant therapy can reduce microalbuminuria in diabetic patients. This effect could be mediated by a reduction in the transglomerular hydraulic pressure through a vasodilation of efferent arterioles secondary to renal thromboxane synthesis inhibition.

Reduced hepatic insulin extraction in obesity: relationship with plasma insulin levels.

To elucidate if there are alterations in insulin metabolic clearance in obesity under basal conditions, plasma insulin and C-peptide were measured in 22 obese patients and 8 normal subjects, and the plasma C-peptide to insulin molar ratio was used as an index of hepatic insulin extraction. In obese patients, the C-peptide to insulin molar ratio correlated indirectly with basal plasma insulin levels (r = 0.71; P less than 0.001), being low in the obese patients with higher insulin levels and within the normal range in obese patients in which insulin levels were similar to those of control subjects. It is suggested that hepatic insulin extraction is decreased in obesity, even under basal conditions, but this alteration is only manifested when plasma insulin levels are high.

Role of thyroid hormones on serum leptin levels.

Leptin is an adipose tissue hormone whose plasma levels reflect energy stores. Although pathological thyroid function is related to changes in energy expenditure and body composition, its possible influence on leptin levels remains to be determined. The objective of the study was to provide new data on the relationship between plasma leptin levels and thyroid function. Sixteen patients with primary autoimmune hypothyroidism, and seventeen patients with primary autoimmune hyperthyroidism were prospectively studied from the time of clinical diagnosis and then every 6-8 weeks until thyroid function was completely restored (plasma tri-iodothyronine, free thyroxine and TSH within normal ranges). Fasting immunoreactive plasma leptin levels and body composition (bioelectrical impedance) were assessed at every visit. Plasma leptin levels were correlated with percentage body fat, as previously described, both at the time of diagnosis (r=0.60, P<0.001) and after normalisation of thyroid function (r=0.63, P< 0.001). There was no correlation between serum leptin and thyroid hormone levels at any time during the study. Plasma leptin levels as well as percentage body fat (BF) did not change significantly from the beginning until the end of the study, either in the hypothyroid (leptin: 14.54+/-2.61 vs 16.92+/-2.61 ng/ml, BF: 25.25+/-2.47 vs 25.90+/-3.22%) or in the hyperthyroid (leptin: 10.69+/-1.81 vs 12.36+/-2.19 ng/ml, BF: 22.01+/-2.31 vs 25.39+/-1.13%) group of patients. In conclusion, these results suggest that thyroid function per se is not a major determinant of plasma leptin levels.

The role of IGF binding protein-3 as a parameter of activity in acromegalic patients.

OBJECTIVE: The production of insulin-like growth factor binding protein-3 (IGFBP-3), the main IGF-I binding protein, is regulated by GH, and its serum levels are increased in acromegaly. We investigated its potential value as a parameter of acromegaly activity or remission in comparison with IGF-I, taking GH suppression below 2 microg/l after glucose load as the normal standard. METHODS: Data from 40 acromegalic patients (12 males and 28 females, aged 28 to 79 years) were obtained retrospectively from stored samples. From these, 145 pairs of IGF-I/IGFBP-3 values were collected; in 67 of them, simultaneous measurement of GH after glucose loading allowed their classification as active or inactive acromegaly. Relationships between IGF-I, IGFBP-3 and GH after glucose load were assessed, as well as differences between IGF-I and IGFBP-3 levels in active and inactive acromegaly. RESULTS: Significant positive correlation between IGF-I and IGFBP-3 in 145 samples was observed (r=0.49, P<0. 0001). As for the 67 samples in which activity or remission could be defined in terms of GH after glucose load, 50 were active and 17 inactive. Both IGF-I and IGFBP-3 significantly correlated with minimum GH (r=0.53, P<0.0001 and r=0.41, P<0.001 respectively). For both parameters, significant differences of means between active and inactive cases were observed (623+/-296 vs 300+/-108 ng/ml, P<0.0001 for IGF-I, and 4.1+/-1.3 vs 3.2+/-0.9 microg/ml, P<0.006 for IGFBP-3). Yet, when comparing in individual cases their classification as active or inactive with the finding of normal or increased IGF-I and IGFBP-3, among active cases 16% appeared as normal according to IGF-I, and 50% appeared as normal in terms of IGFBP-3. Among inactive cases, 23.5% appeared as active according to IGF-I, while 17.5% appeared as active in terms of IGFBP-3. CONCLUSION: Even though IGFBP-3 reflects GH secretion, it offers no advantage over IGF-I in the assessment of acromegaly, and it may underestimate disease activity in acromegalic patients.

Presence of insulin autoantibodies at clinical diagnosis of diabetes mellitus type I predicts loss of beta cell function.

Recently the spontaneous development of insulin autoantibodies (IAA) has been detected in patients at diagnosis of Type I diabetes mellitus before the beginning of insulin treatment. The present study was undertaken to investigate if the presence of IAA at clinical onset of IDDM may act as a new marker of the beta cell function. The results obtained showed that IAA were present in 44% of newly diagnosed diabetic patients before therapy. Patients without IAA displayed a higher C-peptide secretion than those with IAA, at six months (12.11 +/- 5.08 versus 5.88 +/- 3.25 ng/ml/10 min.)(X +/- SD) and at twelve months (10.45 +/- 3.05 versus 4.90 +/- 5.25 ng/ml/10 min)(X +/- SD) of the follow up period. HbA1 levels, and insulin requirements were similar in both groups (IAA+ and IAA-). We conclude that the presence of insulin autoantibodies at clinical diagnosis, before initiating insulin treatment, may well predict the loss of the beta cell function.

Cryopreservation: in vitro results in rat pancreatic islets.

Cryopreservation is an effective method of islet storage and may facilitate clinical trials of islet transplantation. It was the aim of the present study to evaluate the in vitro viability of cryopreserved rat islets, including the response to nonglucose secretagogues and glucose oxidation. After pancreatic digestion via intraductal injection of collagenase, 75- to 200-micron Wistar rat islets were handpicked and cultured in RPMI 1640 (glucose 11.1 mmol/L) and randomized into two groups: control (cultured 20 to 24 hours at 37 degrees C) and cryopreserved (after 20 to 24 hours of culture at 37 degrees C, islets were cryopreserved according to Rajotte's protocol: freezing velocity, -0.25 degree C/min; thawing velocity, 200 degrees C/min). In the two groups, we evaluated recovery, insulin content per islet, staining viability (ethidium bromide/orange acridine; semiquantitative scoring, measuring the viable area of the islet from 0 = less viable to 3 = more viable), insulin secretion after glucose and nonglucose secretagogues, and oxidation of D-[U-14C]glucose. The results for the control group were always higher for the following: recovery (95.4% +/- 1.2% v 83.0% +/- 2.1%, P = .00), insulin content (2,203.9 +/- 335.2 v 1,443.3 +/- 171.8 microU/islet, P = .03), insulin secretion after 5.5 mmol/L glucose (61.3 +/- 8.0 v 28.3 +/- 3.4 microU/islet/90 min, p = .00), 16.7 mmol/L glucose (151.4 +/- 16.1 v 98.7 +/- 14.1 microU/islet/90 min, p = .03), 10 mmol/L L-leucine +10 mmol/L L-glutamine (125.6 +/- 27.9 v 56.8 +/- 6.4 microU/islet/90 min, P = .05), and 10 mmol/L L-arginine (202.5 +/- 27.5 v 128.8 +/- 14.2 microU/islet/90 min, P = .01), and glucose oxidation at 5.5 mmol/L (12.5 +/- 1.1 v 7.9 +/- 0.6 pmol/islet/120 min, P = .00) and at 16.7 mmol/L (26.1 +/- 2.6 v 14.3 +/- 1.6 pmol/islet/120 min, P = .00). No significant differences in staining viability were found between groups (2.35 and 2.48, respectively, P = .55). However, cryopreserved and control islets showed a significant increase in insulin secretion and glucose oxidation after increasing the glucose concentration from 5.5 to 16.7 mmol/L. We conclude that when glucose is increased, cryopreserved islets keep the capacity to increase insulin secretion, but cryopreservation produces a significant decrease in several islet viability characteristics. This decrease may be due to a decline of beta-cell number per islet and/or a decrease in the content of insulin per beta cell.

Analysis of the contribution of the HLA system to the inheritance in the Wolfram syndrome.

The Wolfram syndrome (WS) is an autosomal recessive disorder beginning in childhood that consists of four clinical features: diabetes insipidus, diabetes mellitus, optic atrophy and deafness. Its pathogenesis remains unknown, although the tendency to develop this syndrome has been related to some class II antigens of the HLA system. We report six new cases in four families. A review of published data from the genetic features of this syndrome is performed, establishing the high frequency of the HLA-DR2 antigen in the WS (44.4%) compared with a control group (21.9%; relative risk, 2.8) and to patients with Type 1 insulin-dependent diabetes mellitus (Type 1 diabetes) (6.77%; relative risk, 9.7). We also comment the high frequency of the HLA-DQw1 antigen (85.5%) in this syndrome, without statistical significance. A familial segregation study of the HLA haplotypes has been carried out without finding correlation between the autosomal recessive pattern attributed to the WS, and the major histocompatibility complex. In conclusion, whereas HLA may increase susceptibility to the WS, as shown by the existence of an HLA-DR2 association, the major genetic influence on the inheritance of the WS must be at another locus.

Effects of a short prednisone regime at clinical onset of type 1 diabetes.

The effect of corticosteroids on beta cell function and humoral immune response in type 1 diabetes was tested in a 2-month trial conducted on 32 newly diagnosed patients (age 22.8 +/- 1.4 years, mean +/- S.E.M.). Prednisone was administered at immunosuppressive dosage (1 mg.kg-1.day-1) during the initial 10 days and at a maintenance dosage (0.3 mg.kg-1.day-1) for 50 days. Patients (n = 32) were enrolled within 6 weeks after diagnosis and matched in pairs for age, sex, presence of islet cell antibodies (ICA) and glucagon stimulated C-peptide levels. Insulin discontinuation was not contemplated. All the patients who received prednisone became ICA during treatment but in some (4 out of 10) this effect was only transient. Insulin antibodies (IA) were significantly lower in the prednisone group at second and third month (P < 0.05). No patient experienced complete remission but in 10 prednisone and 4 control patients the insulin requirements were below 0.3 IU/kg (P < 0.05). With similar glycemia the fasting C-peptide levels were higher in the treated patients. The profile of the insulin requirements during the follow-up was different in the two groups and at 9 months the prednisone group needed less insulin than the control (P < 0.05). Interestingly, within the prednisone-treated group and after 6 months, the levels of stimulated C-peptide improved significantly among the ICA+ patients while they were steady or declined in ICA- (P < 0.01). The analysis of variance covariance confirmed a positive interaction between ICA and the administration of prednisone on the outcome of beta cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of hypoglycemic sulfonylureas on human red blood cell transglutaminase activity.

We have examined the effect of glipizide, a hypoglycemic sulfonylurea, upon transglutaminase activity in human red blood cells. In a first series of experiments the in vitro effect of the drug was assessed. The results obtained showed that glipizide inhibits transglutaminase activity in human red blood cells. In a second approach, glipizide was administered orally to six type 2 diabetic patients during 3 months, in order to evaluate the long-term effect upon transglutaminase activity. Again, glipizide induced a significant decrease in the enzyme activity in blood red cells (P less than 0.01). We suggest that treatment of type 2 diabetes mellitus with hypoglycemic sulfonylureas could improve insulin effects by inhibiting cellular transglutaminase activity.

Microalbuminuria development in short-term IDDM.

UNLABELLED: To assess risk factors associated with microalbuminuria development in short-term evolution insulin-dependent diabetes mellitus (IDDM) we undertake a cross-sectional study with retrospective examination of the 34 patients diagnosed with IDDM between 1982 and 1983 and followed up for at least 7 years in an outpatient endocrinology clinic. MAIN MEASURES: (1) At IDDM diagnosis: age, sex, parameters of metabolic control (fasting glycemia, HbA1), islet-cell antibodies, insulin autoantibodies, endogenous insulin secretion (EIS) and HLA type. (2) At 1 year evolution: EIS re-evaluation. (3) From IDDM diagnosis (every 3-4 month): body mass index, insulin schedule and dose, and parameters of metabolic control. (4) At 7-year evolution: 24-h urinary albumin excretion (UAE) and arterial blood pressure measurements on two consecutive outpatient controls. Microalbuminuria was defined as UAE above 30 micrograms/min on the two consecutive measurements. After 7-year follow-up, 8 (23.5%; 95% Cl: 9.3 to 37.7%) patients developed microalbuminuria. Their metabolic control was worse (7 years mean HbA1: 10.7 vs. 9.7%; P = 0.04) and 1 year EIS lower (1.9 vs. 7.6 ng/ml.10 min; P = 0.03) than in normoalbuminuric patients. They also had higher prevalence of 'high-normal' arterial blood pressure (P = 0.03) and diabetic retinopathy (P = 0.01) than normoalbuminuric patients did. Stepwise logistic regression analysis showed that diabetic retinopathy was the only independent and significant risk factor related to microalbuminuria development (P = 0.01). We conclude that in subjects with short-term evolution IDDM, microalbuminuria development was associated with glycemic control, EIS and arterial blood pressure levels, however the strongest association was found with diabetic retinopathy occurrence.

[Cushing's disease in a patient with primary empty sella turcica]. / Enfermedad de Cushing en una paciente con silla turca vacía primaria.

Primary empty sella is a neuroanatomical condition which is more common in middle aged obese multiparous females with long-standing hypertension. Usually there are no symptoms, but occasionally nonspecific headache may be present. Hormone studies are commonly normal in these patients, although several functional hypothalamic and pituitary abnormalities have been reported. We report a 64-year-old female with primary empty sella in whom Cushing's disease was diagnosed. The association of both disorders is exceptional.

[Evaluation of the treatment of Cushing's syndrome using ketoconazole]. / Evaluación del tratamiento del síndrome de Cushing con cetoconazol.

The effectiveness of ketoconazole for the therapy of Cushing's syndrome, both of adrenal and pituitary origin, was retrospectively evaluated. To this end, the clinical and hormonal results in 5 patients were assessed. There were 4 females and one male, with ages ranging between 17 and 64 years. Three of them, who had Cushing's disease, received sustained treatment with ketoconazole when other therapeutic measures had failed. The two remaining patients (one with Cushing's disease and the other with adrenal adenoma) were treated with this drug in the preoperative period to alleviate the deterioration in the clinical condition caused by hypercortisolism. The clinical evolution of the patients is described, as well as the plasma adrenocorticotropin (ACTH) and the free cortisol in 24 hour urine in the subsequent controls. In view of the study results, we feel that ketoconazole is an effective treatment for the long term control of Cushing's syndrome. In addition, it may be also useful as preoperative therapy in those patients severely deteriorated by the sustained hypercortisolism.

[Isolated ACTH deficiency]. / Déficit aislado de ACTH.

The isolated ACTH deficiency is a scarcely diagnosed disease of heterogeneous nature. Two patients with isolated deficiency of ACTH in whom the initial diagnosis was of primary suprarrenal failure are reported. In the first case this diagnosis was performed after hospital admission for deterioration of the level of consciousness and the development of an acute suprarrenal crisis in the course of nosocomial pneumonia. In the second case the clinical manifestations began as weakness, anorexia, weight loss and lymphocytosis with eosinophilia. In both patients an increase in the thyrotropic hormone was detected leading to suspicion of the existence of associated primary hypothyroidism. Finally, several studies were carried out (basal measurements of cortisol and ACTH, stimulation with continual perfusion of ACTH, insulinic hypoglycemia, global study of adenohypophysary function, ACTH CRF release factor test, computerized tomography of the pituitary region) in both patients leading to the definitive diagnosis of isolated ACTH deficiency of idiopathic cause of possible pituitary origin without the existence of other associated hormonal deficiencies.

[Diagnosis of Cushing's disease in pregnancy]. / Diagnóstico de la enfermedad de Cushing en la gestación.

The Cushing syndrome during pregnancy is very infrequent, being even more so that of hypophysary etiology despite corticotropic adenomas being more prevalent in fertile-aged women. Its diagnosis is difficult since it may be confused with the physiologic alterations of the cortisol and the ACTH which occur during pregnancy. The treatment is controversial. In the cases reported to date, pregnancy represented a worsening of the picture. The case of a patient diagnosed with Cushing disease during the first trimester of pregnancy is presented. The hypercorticism improved clinically and biochemically during the pregnancy with no maternofetal complications observed. The disease activity continued following delivery.

[Posttraumatic pituitary insufficiency. Value of pretreatment with LHRH in the differentiation between pituitary and hypothalamic deficits]. / Insuffisance hypophysaire post-traumatique. Intérêt du pré-traitement par la LHRH dans la différenciation des déficits hypophysaires et hypothalamiques.

A patient presented with post-traumatic hypopituitarism, where transient diabetes insipidus, high prolactin levels and prolonged and delayed TSH rise after TRH suggested a hypothalamic lesion. Although there was no gonadotropin response to LHRH as one could have expected, following repeated administration of LHRH, the LH response returned to normal, thus confirming a hypothalamic cause for his hypogonadism.