Improved physiological properties of gravity-enforced reassembled rat and human pancreatic pseudo-islets.

Previously we demonstrated the superiority of small islets vs large islets in terms of function and survival after transplantation, and we generated reaggregated rat islets (pseudo-islets) of standardized small dimensions by the hanging-drop culture method (HDCM). The aim of this study was to generate human pseudo-islets by HDCM and to evaluate and compare the physiological properties of rat and human pseudo-islets. Isolated rat and human islets were dissociated into single cells and incubated for 6-14 days by HDCM. Newly formed pseudo-islets were analysed for dimensions, morphology, glucose-stimulated insulin secretion (GSIS) and total insulin content. The morphology of reaggregated human islets was similar to that of native islets, while rat pseudo-islets had a reduced content of α and δ cells. GSIS of small rat and human pseudo-islets (250 cells) was increased up to 4.0-fold (p < 0.01) and 2.5-fold (p < 0.001), respectively, when compared to their native counterparts. Human pseudo-islets showed a more pronounced first-phase insulin secretion as compared to intact islets. GSIS was inversely correlated to islet size, and small islets (250 cells) contained up to six-fold more insulin/cell than large islets (1500 cells). Tissue loss with this new technology could be reduced to 49.2 ± 1.5% in rat islets, as compared to the starting amount. With HDCM, pseudo-islets of standardized size with similar cellular composition and improved biological function can be generated, which compensates for tissue loss during production. Transplantation of small pseudo-islets may represent an attractive strategy to improve graft survival and function, due to better oxygen and nutrient supply during the phase of revascularization. Copyright © 2014 John Wiley & Sons, Ltd.

Glucose control during a driving training in patients with type 1 and type 2 diabetes mellitus - a randomised, controlled trial.

AIM: To investigate the effect of prolonged acute mental stress by means of a driving training on glucose control in patients with type 1 and type 2 diabetes mellitus. METHODS: 39 patients with insulin-treated diabetes (18 type 1, 21 type 2 diabetes) were exposed to mental stress by means of a 2 h-driving training. The training session started 15 min after intake of a standard meal. Blood glucose, blood pressure, heart rate, salivary cortisol, and subjective stress perception were monitored in regular intervals and compared to a control day. RESULTS: On the stress testing day, blood pressure rose from 142/86±16/9 mmHg to 162/95±22/11 mmHg (p<0.001), heart rate from 72±11 bpm to 86±16 bpm (p<0.001) and subjective stress perception from 1.4±0.6 to 4.7±2.5 points (p<0.001). Salivary cortisol concentrations increased from a median of 5.1 nmol/l (Interquartile Range (IQR) 3.5-7.5 nmol/l) at baseline to 7.7 nmol/l (IQR 4.7-12.8 nmol/l, p<0.001), all these measurements remained stable on the control day. Glucose control showed no significant difference on the stress testing day compared to the control day (mean difference over time=0.22 mmol/l, 95%-CI -1.5 to +1.9 mmol/l, p=0.794). A multivariate linear regression and correlation analysis showed no association of demographic characteristics (diabetes type, age, body mass index (BMI), diabetes duration, HbA1c), objective or subjective stress parameters with the course of glucose concentrations during the driving training. CONCLUSIONS: Although a 2 h-driving training causes increased subjective and objective stress parameters, glucose control is maintained in patients with insulin-treated diabetes.

Smoking is associated with impaired long-term glucose metabolism in patients with type 1 diabetes mellitus.

BACKGROUND AND AIMS: Smoking is known to negatively influence glucose metabolism both in healthy subjects and in patients with diabetes. The aim of this study was to compare glycemic control in patients with type 1 diabetes mellitus who were smokers with those who did not smoke during a prospective long-term follow-up. METHODS AND RESULTS: In a single center, 763 patients with type 1 diabetes mellitus were included, 160 (21.0%) of them were smokers. Patients were treated with intensive insulin therapy according to existing guidelines. Glucose control was monitored quarterly, diabetes related complications and cardiovascular risk factors were assessed at least once a year. Glucose control in smokers was significantly worse than in non-smokers at baseline and during follow-up (mean HbA1c during 5047 patient-years of follow-up 7.9 ± 1.3% in smokers and 7.3 ± 1.1% in non-smokers, p < 0.001) despite a higher insulin dosage in smokers (0.71 ± 0.30 U/kg vs. 0.65 ± 0.31 U/kg in non-smokers, p = 0.046). HDL cholesterol was lower in smokers at baseline (1.53 ± 0.45 vs. 1.68 ± 0.51 in non-smokers, p = 0.048). Diabetes related complications tended to occur with a higher frequency in smokers, with a significant difference in macroalbuminuria (9.8% vs. 4.8% in non-smokers, p = 0.047). CONCLUSION: Smoking is associated with worse glucose control in patients with type 1 diabetes mellitus despite the same treatment strategies as in non-smokers. Hyperglycemia, therefore, may contribute to an earlier incidence of diabetes related complications in these patients, in addition to direct toxic effects of smoking.

Effect of psychological stress on glucose control in patients with Type 2 diabetes.

AIM: To investigate the effect of acute psychological stress on glucose concentrations in patients with Type 2 diabetes, in the fasting state as well as in the postprandial state. METHODS: Thirty patients (12 female) with Type 2 diabetes were included. Mean ± SD age was 60 ± 12 years, BMI 28.8 ± 4.2 kg/m(2), diabetes duration 8.9 ± 6.7 years and HbA(1c) 51 ± 9 mmol/mol (6.8 ± 0.8%). Using a non-randomized approach, all participants were exposed to moderate psychological stress by means of the Trier Social Stress Test: 10 participants in the fasting state and 20 participants 75 min after intake of a standard meal. Blood pressure, heart rate and salivary cortisol were monitored on the control day and the stress-test day. Glucose concentrations were assessed using a continuous glucose monitoring system. RESULTS: On the stress-test day, blood pressure rose from 117/73 ± 13/12 to 155/92 ± 22/14 mmHg, heart rate from 77 ± 11 to 91 ± 25 b min(-1) and salivary cortisol concentrations from 8.5 ± 3.7 to 26.4 ± 12.1 nmol/l (P < 0.001); these measurements remained unchanged on the control day. On the stress-test day, when the Trier Social Stress Test was applied 75 min after the intake of a standard meal, the glucose concentrations were significantly higher compared with the control day (mean difference 1.5 mmol/l, 95% CI 0.5-2.4, P = 0.003). In the fasting state, glucose concentrations slightly decreased during the control day but remained stable on the stress-test day (mean difference compared with the control day 0.7 mmol/l, 95% CI -0.7 to 2.0, P = 0.31). CONCLUSIONS: When stress is experienced in the postprandial period, acute psychological stress significantly increases glucose concentrations in patients with Type 2 diabetes.

ER stress in adipocytes inhibits insulin signaling, represses lipolysis, and alters the secretion of adipokines without inhibiting glucose transport.

The endoplasmic reticulum (ER) is the intra-cellular site, where secreted and membrane proteins are synthesized. ER stress and activation of the unfolded protein response (UPR) contribute to insulin resistance and the development of diabetes in obesity. It was shown previously in hepatocytes that the UPR activates c-jun N-terminal kinase (JNK), which phosphorylates insulin receptor substrate (IRS) proteins on serine residues thereby inhibiting insulin signal transduction. Here we describe how ER stress affects insulin signaling and the biological function of adipocytes. In addition to inhibition of IRS we found that ER stress downregulates the expression of the insulin receptor. Concomitantly, insulin-induced activation of Akt/PKB and of ERK1/2 was strongly inhibited. Ectopic expression of IRS1 or IRS2 strongly counteracted the inhibitory effect of ER stress on insulin signaling while pharmacological inhibition of JNK with SP600125 resulted only in a mild improvement. ER stress decreased the secretion of the adipokines adiponectin and leptin, but strongly increased secretion of IL-6. ER stress inhibited expression and insulin-induced phosphorylation of AS160, reduced lipolysis but did not inhibit glucose transport. Finally, supernatants collected from 3T3-L1 adipocytes undergoing ER stress improved or impaired proliferation when used to condition the culture medium of INS-1E beta-cells dependent on the degree of ER stress. It appears that ER stress in adipocytes might initially lead to changes resembling early prediabetic stages, which at least in part support the regulation of systemic energy homeostasis.

Interleukin-18 levels are associated with low-density lipoproteins size.

INTRODUCTION: Both low-density lipoproteins (LDL) size and serum interleukin (IL)-18 levels have been shown to be predictors of cardiovascular morbidity and mortality. However, it is still unknown whether IL-18 levels are independently associated with LDL size. METHODS: In this cross-sectional study including 53 premenopausal women (18-45 years), LDL size (by gradient gel electrophoresis), serum IL-18, high-sensitivity C-reactive protein (hs-CRP), serum lipids, insulin sensitivity (S(I), by frequently sampled intravenous glucose tolerance test) were measured. RESULTS: LDL size correlated with IL-18 (r = -0.38, P = 0.006), hs-CRP (r = -0.40, P = 0.003), S(I) (r = 0.36, P = 0.011), serum triglycerides (r = -0.32, P = 0.018) and high-density lipoproteins (HDL)-cholesterol (r = 0.40, P = 0.003). When these variables were entered into a regression model, serum IL-18 (beta = -0.26, P = 0.04), triglycerides (beta = -0.29, P = 0.02) and HDL-cholesterol (beta = 0.34, P = 0.01) levels were independently associated with LDL size, accounting for 42% of the variance (P < 0.001). Serum hs-CRP levels and S(I) were not significant independent predictors of LDL size in this model. CONCLUSIONS: This is the first report showing that elevated IL-18 levels are associated with reduced LDL size, independent of other inflammatory and metabolic risk factors. Future prospective studies are needed to evaluate the predictive role of IL-18 as an inflammatory marker of LDL size and the development of subclinical and/or clinical atherosclerosis.

Exenatide versus insulin glargine: a cost-effectiveness evaluation in patients with Type 2 diabetes in Switzerland.

OBJECTIVES: To investigate the long-term clinical and economic outcomes associated with exenatide versus insulin glargine as "add-on" treatments to oral therapy in individuals with Type 2 diabetes inadequately controlled with combination oral agents in the Swiss setting. METHODS: A computer simulation model of diabetes was used to project complications, life expectancy, quality-adjusted life expectancy and direct medical costs over a 35-year time horizon. Cohort characteristics and treatment effect data were derived from a 26-week randomized clinical trial comparing exenatide and insulin glargine. Modeled treatment effects included reductions in glycosylated hemoglobin (HbA1c) by -0.99% and -1.07% and in body mass index (BMI) by -0.80 and +0.55 kg/m2 with exenatide and insulin glargine respectively. Changes in systolic blood pressure and serum lipid levels were also captured. Simulations incorporated published quality of life utilities and Swiss costs from 2006. Extensive sensitivity analyses were conducted to assess the robustness of projected outcomes. Future clinical and economic outcomes were discounted at 2.5% per annum. RESULTS: In the base-case analysis exenatide was associated with comparable life expectancy (11,549 years versus 11,468 years) and an improvement in quality-adjusted life expectancy of 0.43 quality-adjusted life years (QALYs) versus insulin glargine over a 35-year time horizon. Exenatide was associated with a reduced cumulative incidence of most diabetes-related complications including an absolute reduction in myocardial infarction by 0.28%. Assuming an annual treatment cost of CHF 2,797.74 for exenatide, direct costs increased by CHF 8,378 per patient over the 35-year time horizon compared to insulin glargine. The resultant incremental cost-effectiveness ratio was CHF 19,450 per QALY gained for exenatide versus insulin glargine. CONCLUSIONS: Exenatide was associated with comparable life expectancy and an improvement in quality-adjusted life expectancy versus insulin glargine over a 35-year time horizon. Based on current standards exenatide would be a cost-effective treatment alternative to insulin glargine in Switzerland for Type 2 diabetes patients inadequately controlled on oral therapy.

Quantitative and qualitative effects of rosuvastatin on LDL-cholesterol: what is the clinical significance?

BACKGROUND: Statins have emerged as the global leader in pharmacologic therapy for dyslipidaemia, and rosuvastatin has demonstrated clinical efficacy as well as safety in several clinical trials and postmarketing analyses. AIM: The present article reviewed the effects of rosuvastatin on the quantity and the quality of low-density lipoproteins (LDL). METHODS: We searched for and reviewed all the available evidence in a systematic way. A literature search (by Medline and Scopus) was performed using the following headings: 'LDL-cholesterol', 'LDL size', 'LDL subclasses', 'small dense LDL', 'apolipoprotein B, apo B' and 'rosuvastatin' up to 11 November 2008. The authors also manually reviewed the references of selected articles for any pertinent material. RESULTS: Rosuvastatin reduces LDL-cholesterol levels to a greater extent than other statins and is able to modulate significantly LDL size and subclasses towards less atherogenic particles as well as the LDL particle number, as indirectly measured by the levels of apo B. DISCUSSION AND CONCLUSIONS: The recent Justification for the Use of statins in Primary prevention: an Intervention Trial Evaluating Rosuvastatin study provides more evidence about the effectiveness of rosuvastatin therapy in reducing cardiovascular risk, even among persons who would not currently be considered for pharmacotherapy. Further insights on cardiovascular outcomes will be available by the on-going trials included in the GALAXY program that includes subjects with type-2 diabetes, haemodialysis recipients, patients with congestive heart failure and specific ethnic groups, such as African American, Hispanic and South Asian populations.

Atherogenic forms of dyslipidaemia in women with polycystic ovary syndrome.

OBJECTIVE: Dyslipidaemia is very common in patients with polycystic ovary syndrome (PCOS) but, beyond plasma lipids, atherogenic lipoprotein (Lp) and apolipoprotein (apo) alterations are still ill defined. DESIGN: We measured concentrations of apoB, Lp(a) and small, dense low-density lipoprotein (LDL) in 42 patients with PCOS [age: 28 +/- 7 years, body mass index (BMI): 27 +/- 5 kg/m(2)] vs. 37 age- and BMI-matched healthy controls. METHODS: Elevated Lp(a) levels considered were those > 30 mg/dl while elevated apoB concentrations were those > 100 g/l. RESULTS: Polycystic ovary syndrome showed increased triglycerides levels (p = 0.0011) and lower high-density lipoprotein (HDL)-cholesterol concentrations (p = 0.0131) while total- and LDL cholesterol were similar. PCOS also showed smaller LDL size (p = 0.0005), higher levels of total small, dense LDL (p < 0.0001), higher concentrations of Lp(a), as considered as absolute values (p = 0.0143) and log-transformed (p = 0.0014), while no differences were found in apoB levels. Elevated Lp(a) concentrations were found in 24% of PCOS, while elevated apoB levels were relatively uncommon (14%). Spearman correlation analysis revealed that Lp(a) concentrations were weakly correlated only with HDL-cholesterol levels (r = -0.378, p = 0.0431). In addition, 36% of patients with PCOS with normal plasma lipid profile showed elevated levels of Lp(a), apoB or small, dense LDL. CONCLUSIONS: Atherogenic Lp abnormalities may be found in one-third of women with PCOS who have a normal lipid pattern. Future prospective studies are needed to test to which extent such atherogenic forms of dyslipidaemia may contribute to the increased cardiovascular risk in young women with PCOS.

Atherogenic lipoprotein phenotype and LDL size and subclasses in women with gestational diabetes.

AIMS: Women with gestational diabetes are more likely to develop Type 2 diabetes and cardiovascular disease after pregnancy; however, the exact nature of the lipid alterations present is not clear. In Mediterranean women with gestational diabetes, we measured low-density lipoprotein (LDL) size and all seven subclasses, as well as the 'atherogenic-lipoprotein phenotype'[ALP, e.g. concomitant presence of elevated triglycerides, reduced high-density lipoprotein (HDL)-cholesterol and increased small, dense LDL]. METHODS: In 27 women with gestational diabetes and 23 healthy pregnant women matched for age, weeks of gestation and body mass index, we measured plasma lipids and LDL size and subclasses by gradient gel electrophoresis between 24 and 28 weeks of gestation. RESULTS: Although no significant differences were found in the concentrations of any of the plasma lipids, compared with control subjects women with gestational diabetes had lower LDL size (P = 0.0007) due to reduced LDL-I (P = 0.0074) and increased LDL-IVA (P = 0.0146) and -IVB (P < 0.0001) subclasses. Correlation analysis revealed that fasting glucose, homeostasis model assessment and glycated haemoglobin were inversely correlated with LDL-I and positively with LDL-IVA and -IVB (all P < 0.05). ALP due to high HDL-cholesterol levels was not seen in either group, whereas elevated small, dense LDL were more common in women with gestational diabetes than control subjects (33% vs. 4%, P = 0.0107). CONCLUSIONS: Increased levels of small, dense LDL are common in Mediterranean women with gestational diabetes. Whether these findings affect the atherogenic process and clinical end-points in these women remains to be determined by future prospective studies.

The increase of fatty acid-binding protein aP2 in overweight and obese children: interactions with dietary fat and impact on measures of subclinical inflammation.

BACKGROUND: In adults, circulating aP2 may link obesity, inflammation and the metabolic syndrome, but there are few data in children. Experimental models support that dietary factors, particularly dietary fat, may be major determinants of phenotype. OBJECTIVE: The aim of this study was to investigate, in normal, overweight and obese children, the relationships among aP2, the metabolic syndrome, inflammation and diet. DESIGN: This was a cross-sectional study conducted in Northern Switzerland. SUBJECTS: Subjects for this study were 6- to 14-year-old, prepubertal and early pubertal, normal weight, overweight and obese children (n=124). MAIN OUTCOME MEASURES: Body mass index (BMI), body fat percent, waist-to-hip ratio, blood pressure, circulating aP2, fasting insulin, C-reactive protein (CRP), plasma lipids and dietary intakes of macro- and micronutrients were determined. RESULTS: Circulating aP2 markedly increased with increasing central and total adiposity, and predicted measures of insulin resistance. Independent of BMI standard deviation scores and puberty, aP2 correlated with intake of the antioxidant vitamins A, C and E as well as circulating concentrations of CRP, leptin and low-density lipoprotein cholesterol. Children with lower aP2 concentrations consuming high-fat diets did not show an increase in fasting insulin or CRP, whereas those with higher aP2 concentrations showed marked increases in these measures with high intakes of fat or saturated fat. CONCLUSIONS: Increased central and overall adiposity in children are associated with higher circulating aP2 concentrations. In children with high dietary intakes of total fat and saturated fat, but not those with low intakes, higher aP2 concentrations are associated with measures of insulin resistance and inflammation.

Has time come for new goals in human islet transplantation?

The enthusiasm regarding clinical islet transplantation has been dampened by the long-term results. Concerns about the associated risks of life-long immunosuppression and the striking imbalance between potential recipients and available donor pancreata warrant changes in some of the current goals. Islet transplantation will never be a cure of type 1 diabetes in the majority of patients with no secondary complications, but is a valid option for a limited number of patients with brittle diabetes waiting for an organ or after organ transplantation. Furthermore, insulin independence should not be the main goal of islet transplantation, but avoidance of severe hypoglycemia and good glycemic control, which can be achieved with a relatively small functional beta-cell mass. Therefore, initially one islet infusion is sufficient. Retransplantation at a later time point remains an option, if glucose control deteriorates. Efforts to improve islet transplantation should no longer focus on islet isolation and immunosuppression, but rather on the low posttransplant survival rate of islets caused by activation of the coagulation pathway and the limited oxygen delivery to the islets. Transplantation of smaller islets be it naturally small or size tailored reaggregated islets has the potential to facilitate these processes.

Simultaneous islet-kidney vs pancreas-kidney transplantation in type 1 diabetes mellitus: a 5 year single centre follow-up.

AIMS/HYPOTHESIS: The aim of this study was to compare the long-term outcomes--in terms of glucose control, renal function and procedure-related complications--of simultaneous islet-kidney (SIK) transplantation with those of simultaneous pancreas-kidney (SPK) transplantation in patients with type 1 diabetes mellitus. METHODS: HbA1c, need for insulin, GFR and complication rate were compared between 13 recipients of SIK and 25 recipients of SPK transplants at the same institution. The mean follow-up was 41 months. RESULTS: Two primary organ non-functions occurred in the SIK group. HbA1c did not differ at any time point during follow-up in the SIK group compared with the SPK group (mean during follow-up 6.3 vs 5.9%). Similarly, kidney function over time was not different between the two groups. A higher rate of insulin independence following SPK transplantation (after 1 year 96 vs 31% in the SIK group) was counterbalanced by a higher rate of serious adverse events (40% relaparotomies vs 0% in the SIK group). CONCLUSIONS/INTERPRETATION: The endogenous insulin production achieved by islet transplantation, combined with optimal insulin therapy, was sufficient for maintaining near-normal glucose levels. In terms of glucose control, islet transplantation provides results comparable to those achieved with pancreas transplantation. However, SPK results in a higher rate of insulin independence, albeit at the cost of more surgical complications. These results have led to a new paradigm in islet transplantation at our institution, where the primary goal is not insulin independence, but good glucose control and avoidance of severe hypoglycaemia.

Unsuspected osteomyelitis is frequent in persistent diabetic foot ulcer and better diagnosed by MRI than by 18F-FDG PET or 99mTc-MOAB.

AIM: Prevalence, optimal diagnostic approach and consequences of clinically unsuspected osteomyelitis in diabetic foot ulcers are unclear. Early diagnosis of this infection may be crucial to ensure correct management. METHODS: We conducted a prospective study in 20 diabetic patients with a chronic foot ulcer (>8 weeks) without antibiotic pretreatment and without clinical signs for osteomyelitis to assess the prevalence of clinically unsuspected osteomyelitis and to compare the value of magnetic resonance imaging (MRI), 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) and 99mTc-labelled monoclonal antigranulocyte antibody scintigraphy (99mTc-MOAB). Those with suggestive scans underwent bone biopsy for histology (n = 7). RESULTS: Osteomyelitis was confirmed by biopsy in seven of the 20 clinically unsuspected foot ulcers. Presence of osteomyelitis was not related to age, ulcer size, ulcer duration, duration of diabetes or HbA1c. C-reactive protein was slightly elevated in patients with osteomyelitis (35.1 +/- 16.0 mg L(-1) vs. 12.2 +/- 2.6 mg L(-1) in patients with and without osteomyelitis respectively; P = 0.07). MRI was positive in six of the seven patients with proven osteomyelitis, whereas 18F-FDG PET and 99mTc-MOAB were positive only in (the same) two patients. Of the seven patients with osteomyelitis, five had lower limb amputation and in one patient the ulcer was persisting after 24 months of follow-up. In contrast, of the 13 patients without detectable signs of osteomyelitis on imaging modalities only two had lower limb amputation and two persisting ulcers. CONCLUSIONS: Clinically unsuspected osteomyelitis is frequent in persisting foot ulcers and is a high risk factor for adverse outcome. MRI appears superior to 18F-FDG PET and 99mTc-MOAB in detecting foot ulcer-associated osteomyelitis and might be the preferred imaging modality in patients with nonhealing diabetic foot ulcers.

Assessment of basal insulin requirement using fasting tests in insulin-treated patients with type 2 diabetes mellitus.

AIMS: Characterizing the time course of the rise of blood glucose concentrations in the fasting state during the day and night in patients with type 2 diabetes. METHODS: 40 consecutive insulin-treated patients with type 2 diabetes underwent fasting tests on two different days with either no breakfast and lunch (fasting time of 20 hours) or no dinner (fasting time of 21 hours). Glucose-lowering medication was stopped prior to the test according to the half-life of the medication prescribed. At the start of the fasting tests, blood glucose concentrations were lowered to below 7 mmol/L using an insulin infusion. RESULTS: 26 men and 14 women were included in the study. Mean (+/-SD) age was 61+/-10 years, BMI 31+/-7 kg/m (2), and HbA1c 7.5+/-1%. Diabetes duration was 14+/-8 years and duration of insulin therapy had been prescribed for a mean of 6+/-6 years. During the daytime fast, plasma glucose concentrations rose by a mean of 0.8+/-1.6 mmol/L. During the nighttime fast, plasma glucose concentrations increased particularly after midnight, by 4.3+/-2.1 mmol/L, i.e. significantly more than during the daytime fast. CONCLUSIONS: Fasting blood glucose concentrations in the majority of insulin-treated patients with type 2 diabetes increase markedly after midnight. No similar increase is observed during the day. Thus, for most patients with type 2 diabetes, an intermediate- or long-acting insulin injected at bedtime with a peak action six to eight hours after injection should be appropriate.

Urinary excretion of an intravenous 26Mg dose as an indicator of marginal magnesium deficiency in adults.

BACKGROUND: Measurement of magnesium (Mg) status is problematic because tissue Mg deficiency can be present without low serum Mg concentrations. OBJECTIVE: To evaluate a modified version of the Mg retention test using stable isotopes for the assessment of Mg status in general, and the detection of marginal Mg deficiency in particular. DESIGN: A modified version of the Mg retention test using a small dose of (26)Mg was evaluated for assessment of Mg status in 22 healthy subjects. Muscle Mg concentration was used as reference for Mg status. A muscle biopsy was taken from the lateral portion of the quadriceps muscle from each subject. After 2 to 4 weeks, 11 mg of (26)Mg (as MgCl(2) in 14 ml water) were injected i.v. over a period of 10 min and all urine was collected for the following 24 h. Excretion of the isotopic label was expressed as percentage of the administered dose excreted in urine within 24 h. RESULTS: Mean +/- s.d. Mg concentration in muscle was 3.85 +/- 0.17 mmol/100 g fat-free dried solids. Mean +/- s.d. excretion of the injected dose within 24 h was 7.9 +/- 2.1%. No correlation was found between muscle Mg concentration and excretion of the isotopic label (r (2 ) = 0.061, P = 0.27). CONCLUSIONS: In this study, urinary excretion of an intravenous Mg tracer was not influenced by muscle Mg concentration and its usefulness for the detection of marginal Mg deficiency could therefore not be demonstrated. SPONSORSHIP: Swiss Foundation for Nutrition Research and Swiss Federal Institute of Technology, Zurich, Switzerland.

Nitric oxide contributes to cytokine-induced apoptosis in pancreatic beta cells via potentiation of JNK activity and inhibition of Akt.

AIMS/HYPOTHESIS: Pro-inflammatory cytokines cause beta cell secretory dysfunction and apoptosis--a process implicated in the pathogenesis of type 1 diabetes. Cytokines induce the expression of inducible nitric oxide (NO) synthase (iNOS) leading to NO production. NO contributes to cytokine-induced apoptosis, but the underlying mechanisms are unclear. The aim of this study was to investigate whether NO modulates signalling via mitogen-activated protein kinases (MAPKs) and Akt. MATERIALS AND METHODS: MAPK activities in INS-1 cells and isolated islets were determined by immunoblotting and in vitro kinase assay. Apoptosis was determined by ELISA measurement of histone-DNA complexes present in cytoplasm. RESULTS: Apoptosis in INS-1 cells induced by IL-1beta plus IFNgamma was dependent on NO production as demonstrated by the use of the NOS blocker NG-methyl-L-arginine. Accordingly, an NO donor (S-nitroso-N-acetyl-D, L-penicillamine, SNAP) dose-dependently caused apoptosis in INS-1 cells. SNAP activated c-Jun N-terminal kinase (JNK) and p38 MAPK, but suppressed the activity of extracellular signal-regulated kinase MAPK. In rat islets, NOS inhibition decreased JNK and p38 activities induced by a 6-h exposure to IL-1beta. Likewise, IL-1beta-induced JNK and p38 activities were lower in iNOS(-/-) mouse islets than in wild-type islets. In human islets, SNAP potentiated IL-1beta-induced JNK activation. The constitutive level of active, Ser473-phosphorylated Akt in INS-1 cells was suppressed by SNAP. IGF-I activated Akt and protected against SNAP-induced apoptosis. The anti-apoptotic effect of IGF-I was not associated with reduced JNK activation. CONCLUSIONS/INTERPRETATION: We suggest that NO contributes to cytokine-induced apoptosis via potentiation of JNK activity and suppression of Akt.

The metabolisable hexoses D-glucose and D-mannose enhance the expression of IRS-2 but not of IRS-1 in pancreatic beta-cells.

D-glucose regulates maintenance and function of pancreatic beta-cells. Several studies have shown that IRS-2, but not IRS-1, is necessary to maintain and sufficient to expand functional beta-cell mass. We therefore analyzed the expression of IRS-2 and IRS-1 in beta-cells after culture in the presence of various concentrations of D-glucose and other metabolisable or non-metabolisable hexoses. D-glucose increased Irs-2 transcription and IRS-2 accumulation in a dose-dependent manner (1.6 to 25 mmol/l), with a 3-fold increased plateau after 10 h. In contrast, the expression of IRS-1 remained unaffected. D-glucose also induced phosphorylation of IRS-2 while non-metabolisable hexoses did neither affect expression nor phosphorylation. D-glucose-mediated elevation and phosphorylation of IRS-2 were independent of autocrine insulin action although insulin itself could transiently and slightly enhance IRS-2 expression.

[Islet transplantation in type I diabetes mellitus]. / Inseltransplantation bei Typ I Diabetes mellitus.

Type 1 diabetes mellitus results from autoimmune destruction of the insulin-secreting cells in the pancreas. The dramatic breakthrough in 2000 with the "Edmonton protocol" for successful solitary islet transplantation has restored optimism for the application of islet transplantation as a treatment for type I diabetes. Due to the recent successes, islet transplantation has evolved from a theoretical concept to its current status as a therapeutic option for patients with type 1 diabetes. Islet transplantation has shown to normalize metabolic control in a way that has been virtually impossible to achieve with exogenous insulin. The less invasive procedure of islet transplantation as compared to whole pancreas transplantation in patients with type 1 diabetes mellitus would be expected to be safer and much less costly. However, this procedure also requires lifetime immunosuppression with drugs. The limited availability of donor organs and the necessity of transplantation of several pancreata in order to achieve insulin independence limit this procedure to a small minority of patients. Unlike the North American centers, the European centers concentrated their efforts on islet after kidney and simultaneous islet kidney transplantation. The two Swiss islet transplantation programs have been pioneers in applying the steroid-free "Edmonton protocol" to simultaneous islet-kidney and islet after kidney transplantation. The long term follow-up showed that islet function decreases over time. In order to maintain insulin independence repeated islet transplants would have to be given to the patients. Therefore, there has been a change in paradigm over time. The major goal of islet transplantation focuses now on achieving a good blood glucose control and avoidance of severe hypoglycaemic episodes rather than only insulin-independence. Thus, due to the limited supply of donor organs, more patients can benefit from islet transplantation. Small insulin doses of exogenous insulin prevent stress on the islet in particular after meals and might help to maintain the transplanted islet mass over time. Due to the severe limitations of immunosuppression solitary islet transplantation is limited to a very small number of patients with type 1 diabetes. The most common indication for islet transplantation in Switzerland is terminal kidney failure in patients with type I diabetes. A simultaneous islet-kidney or pancreas-kidney transplantation should be offered to these patients. The choice between islet or pancreas transplantation is a matter of age and diabetic complications because the perioperative risk is considerably higher in pancreas transplantation.

Overexpression of IRS2 in isolated pancreatic islets causes proliferation and protects human beta-cells from hyperglycemia-induced apoptosis.

Studies in vivo indicate that IRS2 plays an important role in maintaining functional beta-cell mass. To investigate if IRS2 autonomously affects beta-cells, we have studied proliferation, apoptosis, and beta-cell function in isolated rat and human islets after overexpression of IRS2 or IRS1. We found that beta-cell proliferation was significantly increased in rat islets overexpressing IRS2 while IRS1 was less effective. Moreover, proliferation of a beta-cell line, INS-1, was decreased after repression of Irs2 expression using RNA oligonucleotides. Overexpression of IRS2 in human islets significantly decreased apoptosis of beta-cells, induced by 33.3 mM D-glucose. However, IRS2 did not protect cultured rat islets against apoptosis in the presence of 0.5 mM palmitic acid. Overexpression of IRS2 in isolated rat islets significantly increased basal and D-glucose-stimulated insulin secretion as determined in perifusion experiments. Therefore, IRS2 is sufficient to induce proliferation in rat islets and to protect human beta-cells from D-glucose-induced apoptosis. In addition, IRS2 can improve beta-cell function. Our results indicate that IRS2 acts autonomously in beta-cells in maintenance and expansion of functional beta-cell mass in vivo.