Epidermal growth factor receptor internalization rate is regulated by negative charges near the SH2 binding site Tyr992

This study examines the effects of mutations at and in the vicinity of tyrosine 992 of the epidermal growth factor receptor (EGFr) on epidermal growth factor- (EGF-) stimulated internalization of the receptor. Two regions of the EGFr adjacent to this domain have been defined previously as internalization domains. The present work shows that the mutation of negatively charged amino acid residues near Tyr992 to their uncharged analogues increases the rate of EGF receptor internalization. In addition, the conversion of Tyr992, which is an EGFr ligand-induced autophosphorylation site, to phenylalanine also increases the rate of receptor internalization. However, the mutation of Tyr992 to a glutamate residue does not alter the receptor internalization rate. In addition, the truncation of the EGFr at glutamate 996 reduces the internalization rate by half. This result confirms previous reports that residues immediately C-terminal to Glu996 are necessary to allow the normal rate of ligand-induced receptor endocytosis. The data suggest that negative charge in the vicinity of Tyr992, and potentially the phosphorylation of the EGFr at Tyr992, reduces the rate of ligand-induced receptor endocytosis. This reduction in internalization rate increases the lifetime of the activated EGFr in the plasma membrane by about 70%, thus suggesting that phosphorylation of Tyr992 acts to increase the signaling capacity of the EGF receptor even as it directly acts as an SH2 binding site.

Impaired beta-cell functions induced by chronic exposure of cultured human pancreatic islets to high glucose

In type 2 diabetes, chronic hyperglycemia has been suggested to be detrimental to beta-cell function, causing reduced glucose-stimulated insulin secretion and disproportionately elevated proinsulin. In the present study, we investigated the effect on several beta-cell functions of prolonged in vitro exposure of human pancreatic islet cultures to high glucose concentrations. Islets exposed to high glucose levels (33 mmol/l) for 4 and 9 days showed dramatic decreases in glucose-induced insulin release and in islet insulin content, with increased proportion of proinsulin-like peptides relative to insulin. The depletion in insulin stores correlated with the reduction in insulin mRNA levels and human insulin promoter transcriptional activity. We also demonstrated that high glucose dramatically lowered the binding activity of pancreatic duodenal homeobox 1 (the glucose-sensitive transcription factor), whereas the transcription factor rat insulin promoter element 3b1 activator was less influenced and insulin enhancer factor 1 remained unaffected. Most of these beta-cell impairments were partially reversible when islets first incubated for 6 days in high glucose were transferred to normal glucose (5.5 mmol/l) concentrations for 3 days. We conclude that cultured human islets are sensitive to the deleterious effect of high glucose concentrations at multiple functional levels, and that such mechanisms may play an important role in the decreased insulin production and secretion of type 2 diabetic patients.

Stage-dependent effects of epidermal growth factor on Ca2+ efflux in mouse oocytes

Epidermal growth factor (EGF) has received much attention recently for its positive effects on mammalian oocyte maturation and embryo development and its potential importance in cytoplasmic maturation of oocytes. Calcium (Ca2+) homeostasis in germinal vesicle stage oocytes has also been suggested to play a role in cytoplasmic maturation. This study examined the effects of EGF on Ca2+ mobilization as measured by its efflux from mouse oocytes at three time periods throughout maturation (0-4 hr, 4-8 hr, and 12 hr). Immature cumulus oocyte complexes (COCs) removed from the ovary for less than 4 hr exhibit oscillations in Ca2+ efflux that initiated 5-30 min following EGF stimulation. This response was not observed in COCs matured for 4-8 hr or 12 hr or in unstimulated 0-4 hr COCs. Denuded oocytes and cumulus cells did not show the same response to EGF (8.2 nM and 16.4 nM). Immunohistochemistry for detection of the EGF receptor along with EGF internalization studies showed that receptors are present both on cumulus cells and the oocyte but EGF appears to be internalized mainly by the cumulus cells. These data demonstrate that EGF induces oscillations in Ca2+ efflux in COCs 0-4 hr old and this response is mediated by the cumulus cells.

Interaction between genetic and dietary factors determines beta-cell function in Psammomys obesus, an animal model of type 2 diabetes

The gerbil Psammomys obesus develops nutrition-dependent diabetes. We studied the interaction between diet and diabetic predisposition for beta-cell function. A 4-day high-energy (HE) diet induced a 3-, 4-, and 1.5-fold increase in serum glucose, insulin, and triglycerides, respectively, in diabetes-prone (DP) but not diabetes-resistant (DR) P. obesus. Hyperglycemia and concurrent 90% depletion of islet immunoreactive insulin stores were partially corrected by an 18-h fast. In vitro early insulin response to glucose was blunted in both DR and DP perifused islets. The HE diet augmented early and late insulin response in DR islets, whereas in DP islets, secretion progressively declined. Dose-response studies showed a species-related increase in islet glucose sensitivity, further augmented in DP P. obesus by a HE diet, concomitant with a decreased threshold for glucose and a 55% reduction in maximal response. These changes were associated with a fourfold increase in glucose phosphorylation capacity in DP islets. There were no differences in islet glucokinase (GK) and hexokinase (HK) Km; however, GK Vmax was 3.7- to 4.6-fold higher in DP islets, and HK Vmax was augmented 3.7-fold by the HE diet in DP islets. We conclude that the insulin-resistant P. obesus has an inherent deficiency in insulin release. In the genetically predisposed P. obesus (DP), augmented islet glucose phosphorylation ability and diet-induced reduction of the glucose threshold for secretion may lead to inadequate insulin secretion and depletion of insulin stores in the presence of caloric abundance. Thus, genetic predisposition and beta-cell maladaptation to nutritional load seem to determine together the progression to overt diabetes in this species. It is hypothesized that similar events may occur in obese type 2 diabetic patients.

Hyperglycemia-induced beta-cell apoptosis in pancreatic islets of Psammomys obesus during development of diabetes

The gerbil Psammomys obesus develops nutrition-dependent diabetes associated with moderate obesity. The disease is characterized by initial hyperinsulinemia, progressing to hypoinsulinemia associated with depleted pancreatic insulin stores. The contribution of changes in beta-cell turnover to insulin deficiency was investigated in vivo during transition to overt diabetes. Normo glycemic diabetes-prone P. obesus animals who were given a high-calorie diet developed hyperglycemia within 4 days, which was found to be associated with a progressive decline in pancreatic insulin content. This was accompanied by a transient increase in beta-cell proliferative activity and by a prolonged increase in the rate of beta-cell death, culminating in disruption of islet architecture. The hypothesis that "glucotoxicity" was responsible for these in vivo changes was investigated in vitro in primary islet cultures. Exposure of islets from diabetes-prone P. obesus to high glucose levels resulted in a dose-dependent increase in beta-cell DNA fragmentation. In contrast, high glucose levels did not induce DNA fragmentation in rat islets, whereas islets from a diabetes-resistant P. obesus line exhibited a reduced and delayed response. Aminoguanidine did not prevent glucose-induced beta-cell DNA fragmentation in vitro, suggesting that formation of nitric oxide and/or advanced glycation end products plays no major role. Elevated glucose concentrations stimulated beta-cell proliferation in both rat and P. obesus islets. However, unlike the marked long-lasting effect in rat islets, only a transient and reduced proliferative response was observed in P. obesus islets; furthermore, beta-cell proliferation was inhibited after prolonged exposure to elevated glucose levels. These results suggest that hyperglycemia-induced beta-cell death coupled with reduced proliferative capacity may contribute to the insulin deficiency and deterioration of glucose homeostasis in P. obesus. Similar adverse effects of hyperglycemia could play a role in the evolution of type 2 diabetes in genetically susceptible individuals.

Out-of-pocket health spending by poor and near-poor elderly Medicare beneficiaries

OBJECTIVE

To estimate out-of-pocket health care spending by lower-income Medicare beneficiaries, and to examine spending variations between those who receive Medicaid assistance and those who do not receive such aid. DATA SOURCES AND COLLECTION: 1993 Medicare Current Beneficiary Survey (MCBS) Cost and Use files, supplemented with data from the Bureau of the Census (Current Population Survey); the Congressional Budget Office; the Health Care Financing Administration, Office of the Actuary (National Health Accounts); and the Social Security Administration.

STUDY DESIGN

We analyzed out-of-pocket spending through a Medicare Benefits Simulation model, which projects out-of-pocket health care spending from the 1993 MCBS to 1997. Out-of-pocket health care spending is defined to include Medicare deductibles and coinsurance; premiums for private insurance, Medicare Part B, and Medicare HMOs; payments for non-covered goods and services; and balance billing by physicians. It excludes the costs of home care and nursing facility services, as well as indirect tax payments toward health care financing.

PRINCIPAL FINDINGS

Almost 60 percent of beneficiaries with incomes below the poverty level did not receive Medicaid assistance in 1997. We estimate that these beneficiaries spent, on average, about half their income out-of-pocket for health care, whether they were enrolled in a Medicare HMO or in the traditional fee-for-service program. The 75 percent of beneficiaries with incomes between 100 and 125 percent of the poverty level who were not enrolled in Medicaid spent an estimated 30 percent of their income out-of-pocket on health care if they were in the traditional program and about 23 percent of their income if they were enrolled in a Medicare HMO. Average out-of-pocket spending among fee-for-service beneficiaries varied depending on whether beneficiaries had Medigap policies, employer-provided supplemental insurance, or no supplemental coverage. Those without supplemental coverage spent more on health care goods and services, but spent less than the other groups on prescription drugs and dental care-services not covered by Medicare.

CONCLUSIONS

While Medicaid provides substantial protection for some lower-income Medicare beneficiaries, out-of-pocket health care spending continues to be a substantial burden for most of this population. Medicare reform discussions that focus on shifting more costs to beneficiaries should take into account the dramatic costs of health care already faced by this vulnerable population.

Prescription drug formularies in managed care: concerns for the elderly population

Prescription drug formularies are a key element in the rapidly growing trend of prescription drug benefit management. The use of formularies can increase the quality of prescribing and reduce the costs of prescription drug therapy. This is particularly important to older Americans, who represent about 13% of the population but consume roughly one third of the drugs prescribed in the United States. However, the question of whether the use of formularies affects patient access to pharmaceuticals has not been analyzed sufficiently. This paper identifies benefits and risks to older Americans from the use of prescription drug formularies by third-party payers, analyzes the evidence of those benefits and risks, and proposes areas for future research. An extensive review and synthesis of the literature were performed, focusing on three aspects of drug formulary design: (1) the extent to which health maintenance organizations and insurers consider consumer interests when using formularies; (2) the extent to which formulary design is affected by clinical and economic considerations; and (3) the impact of formularies on the quality of drug care received. Safeguards to guarantee that economic considerations of drug benefit managers do not restrict access to needed drugs are insufficient. Alternatively, no evidence to date shows that the use of formularies adversely affects patients' access to pharmaceutical care. More research is required to understand the process of drug formulary development and the extent to which different formulary recommendations impede on physicians' ability to provide high-quality care.

Time course of the initial [Ca2+]i response to extracellular ATP in smooth muscle depends on [Ca2+]e and ATP concentration

In response to extracellular application of 50 microM ATP, all individual porcine aortic smooth muscle cells respond with rapid rises from basal [Ca2+]i to peak [Ca2+]i within 5 s. The time from stimulus to the peak of the [Ca2+]i response increases with decreasing concentration of ATP. At ATP concentrations of 0.5 microM and below, the time to the [Ca2+]i peak varies more significantly from cell to cell than at higher concentrations, and each cell shows complicated initiation and decay kinetics. For any individual cell, the lag phase before a response decreases with increasing concentration of ATP. An increase in lag time with decreasing ATP concentration is also observed in the absence of extracellular Ca2+, but the lag phase is more pronounced, especially at concentrations of ATP below 0.5 microM. Whole-cell patch-clamp electrophysiology shows that in porcine aortic smooth muscle cells, ATP stimulates an inward current carried mainly by Cl- ion efflux with a time course similar to the [Ca2+]i changes and no detectable current from an ATP-gated cation channel. A simple signal cascade initiation kinetics model, starting with nucleotide receptor activation leading to IP3-mediated Ca2+ release from IP3-sensitive internal stores, fits the data and suggests that the kinetics of the Ca2+ response are dominated by upstream signal cascade components.

The influence of sequential annual vaccination and of DHEA administration on the efficacy of the immune response to influenza vaccine in the elderly

The present study examined the effect of repeated vaccination and of dehydroepiandrosterone (DHEA) treatment on the immune response to influenza vaccine in elderly subjects. Seventy-one elderly volunteers, aged 61-89 years, enrolled in a prospective randomized, double-blind study to receive either DHEA (50 mg qd p.o. for 4 consecutive days starting 2 days before immunization) or placebo. Antibody response against the three strains of vaccine was measured before and 28 days after vaccination, and compared between previously vaccinated and non-vaccinated subjects. DHEA treatment did not enhance established immunity. A significant decrease in attainment of protective antibody titer (titer of 1:40 or greater) against A/Texas in subjects with non-protective baseline antibody titer was recorded following DHEA treatment compared to placebo (52 vs. 84%, P < 0.05). Post-immunization titers against influenza A strains were significantly higher in those subjects who were never immunized before. Additionally, post-vaccination protective titers against the A/Johannesburg strain were more prevalent in those subjects who were never vaccinated before. The results were not the same for anti-B/Harbin antibodies-repeated vaccination caused a non-significant increase in HI titer in previously vaccinated subjects.

Amelioration of diabetes in nonobese diabetic mice with advanced disease by linomide-induced immunoregulation combined with Reg protein treatment

Oral linomide, (quinoline-3-carboxamide), has been shown to prevent autoimmune insulitis, islet destruction, and diabetes in NOD mice treated at an early stage of the disease, but confers only partial protection in animals with advanced disease. Reg protein, the gene product of a complementary DNA isolated from a regenerating rat islet library, has been previously shown to induce expansion of beta-cell mass in pancreatectomized rats. To determine the effect of treatment combining immunomodulation and Reg protein on advanced autoimmune diabetes, we treated female NOD mice with oral linomide and i.p. Reg protein injections. In 14-week-old animals with less severe disease (glucose tolerant), treatment with each agent alone resulted in amelioration of diabetes, as did treatment with Reg alone in 5-week-old prediabetic mice. In 14-week-old animals with more severe disease (glucose intolerant), only treatment with the combination of both agents, but not that with each separately, resulted in amelioration of diabetes. Our study suggests that treatment aimed at abrogation of autoimmunity combined with expansion of beta-cell mass constitutes a potential therapeutic approach for treatment of insulin-dependent diabetes mellitus.

Sporadic phaeochromocytomas are rarely associated with germline mutations in the von Hippel-Lindau and RET genes

OBJECTIVE

von Hippel-Lindau (VHL) disease and multiple endocrine neoplasia type 2 (MEN2) are autosomal dominant cancer syndromes. In both conditions, phaeochromocytoma is a prominent feature. It has recently been suggested that phaeochromocytoma can be the presenting and sole clinical manifestation of these multi-organ syndromes. The aim of this study was to ascertain the incidence of VHL and MEN2 among patients with sporadic phaeochromocytoma by mutational analysis.

PATIENTS

Twenty-seven unrelated patients with biochemically and/or anatomically proven sporadic phaeochromocytoma were evaluated.

DESIGN AND MEASUREMENTS

Constitutional DNA obtained from the patients was analysed by single stranded conformational analysis (SSCP) for mutations within the VHL gene coding sequence and by denaturing gradient gel electrophoresis (DGGE) for predominant mutations in exons 10, 11 and 16 of the RET proto-oncogene. The incidence of patients positive for either VHL or RET germline mutations was assessed.

RESULTS

Twenty-six of 27 patients had normal SSCP patterns in all three VHL gene exon segments and only one patient, with an atypical clinical presentation, had an aberrant pattern in exon 3 which upon DNA sequencing was shown to harbor a G to A transversion mutation at nucleotide 695. All patients had normal RET exon 10, 11 and 16 DGGE migration patterns.

CONCLUSION

Most, if not all, patients with typical unilateral sporadic phaeochromocytoma do not have von Hippel-Lindau disease or MEN2. Thus, clinical and/or molecular investigation for von Hippel-Lindau disease and MEN2 in this patient population does not appear to be indicated.

Dehydroepiandrosterone treatment is not beneficial to the immune response to influenza in elderly subjects

BACKGROUND

Dehydroepiandrosterone (DHEA) is a native steroid with an immunomodulating activity that was suggested to counter-regulate some phenomena of immunosenescence. Recently, it was shown to reverse the age-associated decline of immune response against influenza vaccine in aged mice. The present study was designed to evaluate the effect of DHEA on the immunization of elderly volunteers against influenza.

METHODS

Seventy-one elderly volunteers age 61-89 yr were enrolled in a prospective randomized, double-blind study to receive either DHEA (50 mg qd p.o. for four consecutive days starting two days before immunization) or placebo. Antibody response to the vaccine was measured before and 28 days after vaccination.

RESULTS

DHEA treatment significantly increased serum DHEA-sulfate (DHEA-S). No enhancement in established immunity was observed. A significant decrease in attainment of protective antibody titer (1:40 or higher) against the A/Texas strain in subjects with nonprotective baseline antibody titer was recorded following DHEA treatment compared with placebo (52% vs. 84%, P < 0.05). Baseline DHEA-S serum levels were inversely related to attainment of immunization in DHEA-treated subjects. Influenza-like morbidity during the winter was low in the study group with no difference between the DHEA and placebo groups.

CONCLUSIONS

Although highly effective in aged rodents, a short course of DHEA treatment did not improve the age-related declined response to immunization against influenza in human subjects. Higher baseline DHEA-S levels are not predictive of better immunization against influenza in the elderly.

Heterogeneity of epidermal growth factor binding kinetics on individual cells

Binding of fluorescein-conjugated epidermal growth factor (EGF) to individual A431 cells at 4 degrees C is measured by a quantitative fluorescence imaging technique. After background fluorescence and cell autofluorescence photobleaching corrections, the kinetic data are fit to simple models of one monovalent site and two independent monovalent sites, both of which include a first-order dye photobleaching process. Model simulations and the results from data analysis indicate that the one-monovalent-site model does not describe EGF binding kinetics at the single-cell level, whereas the two-site model is consistent with, but not proved by, the single-cell binding data. In addition, the kinetics of binding of fluorescein-EGF to different cells from the same coverslip often differ significantly from each other, indicating cell-to-cell variations in the binding properties of the EGF receptor.

Fluctuating hyper-hypocortisolaemia: a variant of Cushing's syndrome

We present a patient with severe Cushing's syndrome secondary to an invasive pituitary tumour. Cortisol secretion fluctuated between severe hypercortisolaemia associated with features of Cushing's syndrome to recurrent symptomatic hypocortisolaemia. Normal ACTH precursors to ACTH ratio during the various stages of cortisol secretion indicated that periodic decreased prohormone processing did not contribute to the unique presentation in the patient. Thus, the the extreme fluctuations of plasma cortisol levels are most probably due to unexplained erratic changes of ACTH secretion.

Characterization of the unusual insulin of Psammomys obesus, a rodent with nutrition-induced NIDDM-like syndrome

Psammomys obesus fed a high-calorie diet develops a NIDDM-like syndrome. The use of reverse-phase high-performance liquid chromatography (HPLC) to study Psammomys insulin biosynthesis and release revealed a very delayed elution time for the Psammomys insulin peak appearing near the position of human proinsulin. This unusual peak was initially thought to represent partially processed insulin on the basis of its molecular size and susceptibility to trimming by carboxypeptidase B (CpB). However, the findings of an active carboxypeptidase E (CpE) enzyme and the normal amidated forms of gastrin and cholecystokinin octapeptide (CCK-8) in Psammomys tissues were inconsistent with CpE-related aberrant processing of insulin. Moreover, amino acid sequencing of the delayed peak of Psammomys insulin revealed fully processed insulin with amino acid sequence as predicted by the cDNA. The unique presence of a B-30 phenylalanine residue, resulting in an increased hydrophobicity of the insulin molecule, probably underlies the marked delay in elution time on HPLC. The unusual structure of Psammomys insulin does not appear to contribute to the proinsulinemia observed in diabetic Psammomys since the HPLC-purified molecule did not inhibit PC1 and PC2 convertase activities in an in vitro assay.

High-resolution ultrasonography: highly sensitive, specific technique for preoperative localization of parathyroid adenoma in the absence of multinodular thyroid disease

The objective of this prospective study was to evaluate the role of preoperative ultrasonography (US) for parathyroid lesion localization in patients with primary hyperparathyroidism (PHPT) prior to initial surgery. Fifty-two consecutive patients with PHPT, diagnosed in our institution within a period of 2 years, were referred for preoperative US and subsequently for bilateral surgical neck exploration. The combination of a confirmatory pathologic report and normalization of blood calcium concentration for a period of at least 3 months was considered an operative success. In 50 patients (96.2%) a single parathyroid adenoma was excised, and in one patient (1.9%) hyperplasia of three glands was found at surgery. In the one surgical failure, no parathyroid pathology was identified in the neck; therefore the operative success in this series was 98%. The sensitivity of preoperative US was 83% with a specificity of 100%. In the absence of thyroid multinodular disease (MND), the sensitivity of preoperative US increased to 90%, whereas in patients with MND the sensitivity was only 64%. Our findings support the notion that patients with PHPT should be investigated with US before initial surgery. Bilateral surgical exploration is warranted in patients with MND. In the absence of such thyroid pathology, an US finding positive for adenoma should allow the surgeon to perform unilateral neck exploration only, with consequent reduction of operation time and postoperative complications.

From sand rats to diabetic patients: is non-insulin-dependent diabetes mellitus a disease of the beta cell?

It has been debated for the past two decades whether non-insulin-dependent diabetes mellitus (NIDDM) is caused by insulin deficiency or insulin resistance. In this review we summarise the data which unequivocally indicate that insulin response to glucose is grossly deficient in patients with impaired glucose tolerance and NIDDM. Furthermore, we review the findings for Psammomys obesus (the sand rat), an animal with spontaneous obesity, insulin resistance and diabetes which has been used as the prototype for "hyperinsulinaemic NIDDM". A large proportion of circulating insulin in this animal consists of proinsulin and its split products, apparently resulting from hyperglycaemia-driven overstimulation of the beta cell, with depletion of its insulin stores. In vitro studies demonstrate that this "glucose toxic" effect can be reproduced in Psammomys islets but not in those of normal rats. This would indicate that increased demand for insulin production leads to aberrations in proinsulin production and processing only in beta cells with inherent (genetic?) defects. We also point to clinical findings which cast doubt on the practical importance of insulin resistance for the glucose homeostasis of NIDDM patients. In these cases, moderate doses of insulin administered by insulin pumps can induce near-normoglycaemia in NIDDM.

The role of symmetry in fundamental physics

The role of symmetry in fundamental physics is reviewed.

Increased susceptibility of islets from diabetes-prone Psammomys obesus to the deleterious effects of chronic glucose exposure

Patients with noninsulin-dependent diabetes (NIDDM) show an increase in the relative plasma levels of proinsulin and proinsulin conversion intermediates, which is corrected by strict glycemic control. This observation suggests that hyperglycemia per se may be responsible for generating the aberrant plasma hormone profile. The question remains, however, whether a genetic predisposition to NIDDM underlies the failure of the insulin production machinery to meet a prolonged increase in secretory demand. In this study, islet monolayer cultures from the diabetes-prone Psammomys obesus and normal diabetes-resistant rats were exposed to RPMI 1640 medium containing either 11.1 or 33.3 mM glucose; insulin-related peptides were resolved by HPLC. Prolonged exposure (10 days) of rat islets to high glucose resulted in a reduced a secretory response to an acute glucose stimulus associated with a 37% reduction in the insulin content but no change in the proinsulin/insulin ratio. When subjected to a similar protocol, islets from prediabetic Psammomys lost the insulin response to glucose; beta-cell insulin content was reduced by about 70%, and the proportion of proinsulin-related peptides increased from 18% to 38%. In the in vivo situation, pancreatic extracts from nonfasted diabetic Psammomys contained 36% proinsulin-related peptides in contrast to 15% in pancreatic extracts from nondiabetic animals. Thus, prolonged in vitro exposure of prediabetic Psammomys islets to high levels of glucose could reproduce the modified beta-cell secretory profiles observed in vivo in the diabetic animal. These results support the hypothesis that hyperproinsulinemia in NIDDM is secondary to the inability of beta-cells to meet a sustained increase in insulin demand, whereas individuals with normal beta-cells may meet such demand with an adequate output of mature insulin.

Successful treatment of diabetes in NOD mice with advanced disease by islet isografts following immunoregulation with Linomide (quinoline-3-carboxamide)

We have recently documented that oral Linomide (quinoline-3-carboxamide) prevents autoimmune insulitis, islet destruction, and diabetes in NOD mice treated at an early stage (5 wk of age) of the disease. In this report, we show that treatment of female NOD mice with advanced disease (age 23-24 wk) by syngeneic islet transplantation and oral Linomide administration results in prevention of graft insulitis and diabetes in the Linomide group up to 40 wk (diabetes at 40 wk: isograft recipients with Linomide n = 0 of 6; isograft recipients alone n = 5 of 6; p < 0.0001). The extent of protection from glucose intolerance by the combination of transplantation with Linomide was superior to that of Linomide alone [blood glucose (mean +/- SD) 60 min post-i.p. injection of 1 g/kg body weight glucose: Linomide plus isograft 6.7 +/- 1 mmol/L; Linomide alone 18.7 +/- 6.3 mmol/L; p < 0.0001]. Thus, Linomide should be considered a potential immunoregulatory modality in patients undergoing pancreatic islet or whole organ transplantation.

Pre-clinical Cushing's syndrome: an unexpected frequent cause of poor glycaemic control in obese diabetic patients

OBJECTIVE

Autonomous cortisol secretion without clinical stigmata of Cushing's syndrome (CS) has been recently recognized and termed pre-clinical or sub-clinical CS. The common assumption is that CS is an extremely rare cause of uncontrolled diabetes; however, the prevalence of this entity has not been studied. We assessed the prevalence of pre-clinical CS among obese patients with uncontrolled diabetes.

PATIENTS AND DESIGN

(1) In a retrospective analysis, the medical records of 63 patients with endogenous CS were reviewed. (2) In a cross-sectional study, 90 obese patients (BMI > 25 kg/m2) followed in a University Hospital and the local Health Fund endocrine and diabetes clinics, with poorly controlled diabetes (glycosylated haemoglobin > 9%), underwent an overnight 1 mg dexamethasone suppression. In patients with non-suppressible cortisol levels (> 140 nmol/l), Liddle's 2 and 8 mg dexamethasone suppression tests and imaging studies were performed.

MEASUREMENTS

The prevalence of poorly controlled diabetes, the major presenting symptom of CS, was assessed in the retrospective analysis. The prevalence of "true' CS and the false positive rate in the overnight dexamethasone suppression test were calculated. The endocrine evaluation of the patients with pre-clinical CS and the effects of surgical cure on glycaemic control are described.

RESULTS

In the retrospective analysis, 11 (17.5%) had diabetes and 2 (3.2%) lacked the classic physical characteristics of the syndrome. In the cross-sectional study, 4 patients failed to suppress plasma cortisol (< 140 nmol/l). In one patient the diagnosis of CS was not confirmed by a standard Liddle's test and was therefore considered false positive. In the other 3, the diagnosis of CS was confirmed (prevalence of 3.3%, 95% confidence interval 1-9%). In all other patients the overnight cortisol suppression test was normal (cortisol level 47.3 +/- 2.5 nmol/l (mean +/- SEM)). After surgical treatment of CS, glycaemic control was markedly improved in all 5 patients (2 from retrospective and 3 from cross-sectional studies).

CONCLUSIONS

The prevalence of pre-clinical Cushing's syndrome in obese patients with poorly controlled diabetes appears to be considerably higher than previously believed. The overnight dexamethasone suppression test proved to be a simple, sensitive and highly specific screening test for Cushing's syndrome despite the presence of obesity and hyperglycaemia.