Cellular immunological changes in patients with LADA are a mixture of those seen in patients with type 1 and type 2 diabetes.

There is currently scarce knowledge of the immunological profile of patients with latent autoimmune diabetes mellitus in the adult (LADA) when compared with healthy controls (HC) and patients with classical type 1 diabetes (T1D) and type 2 diabetes (T2D). The objective of this study was to investigate the cellular immunological profile of LADA patients and compare to HC and patients with T1D and T2D. All patients and age-matched HC were recruited from Uppsala County. Peripheral blood mononuclear cells were isolated from freshly collected blood to determine the proportions of immune cells by flow cytometry. Plasma concentrations of the cytokine interleukin (IL)-35 were measured by enzyme-linked immunosorbent assay (ELISA). The proportion of CD11c+ CD123- antigen-presenting cells (APCs) was lower, while the proportions of CD11c+ CD123+ APCs and IL-35+ tolerogenic APCs were higher in LADA patients than in T1D patients. The proportion of CD3- CD56high CD16+ natural killer (NK) cells was higher in LADA patients than in both HC and T2D patients. The frequency of IL-35+ regulatory T cells and plasma IL-35 concentrations in LADA patients were similar to those in T1D and T2D patients, but lower than in HC. The proportion of regulatory B cells in LADA patients was higher than in healthy controls, T1D and T2D patients, and the frequency of IL-35+ regulatory B cells was higher than in T1D patients. LADA presents a mixed cellular immunological pattern with features overlapping with both T1D and T2D.

Coffee consumption, genetic susceptibility and risk of latent autoimmune diabetes in adults: A population-based case-control study.

AIM: Coffee consumption is inversely related to risk of type 2 diabetes (T2D). In contrast, an increased risk of latent autoimmune diabetes in adults (LADA) has been reported in heavy coffee consumers, primarily in a subgroup with stronger autoimmune characteristics. Our study aimed to investigate whether coffee consumption interacts with HLA genotypes in relation to risk of LADA. METHODS: This population-based study comprised incident cases of LADA (n=484) and T2D (n=1609), and also 885 healthy controls. Information on coffee consumption was collected by food frequency questionnaire. Odds ratios (ORs) with 95% CIs of diabetes were calculated and adjusted for age, gender, BMI, education level, smoking and alcohol intake. Potential interactions between coffee consumption and high-risk HLA genotypes were calculated by attributable proportion (AP) due to interaction. RESULTS: Coffee intake was positively associated with LADA in carriers of high-risk HLA genotypes (OR: 1.14 per cup/day, 95% CI: 1.02-1.28), whereas no association was observed in non-carriers (OR: 1.04, 95% CI: 0.93-1.17). Subjects with both heavy coffee consumption (≥4 cups/day) and high-risk HLA genotypes had an OR of 5.74 (95% CI: 3.34-9.88) with an estimated AP of 0.36 (95% CI: 0.01-0.71; P=0.04370). CONCLUSION: Our findings suggest that coffee consumption interacts with HLA to promote LADA.

Family history of type 1 and type 2 diabetes and risk of latent autoimmune diabetes in adults (LADA).

BACKGROUND: A family history of diabetes (FHD) is a strong predictor of diabetes risk, yet has rarely been investigated in latent autoimmune diabetes in adults (LADA). This study therefore investigated the risk of LADA and type 2 diabetes (T2D) in relation to FHD, taking into account the type of diabetes in relatives. METHODS: Data from a population-based study were used, including incident cases of LADA [glutamic acid decarboxylase antibody (GADA)-positive, n=378] and T2D (GADA-negative, n=1199), and their matched controls (n=1484). First-degree relatives with disease onset at age<40 years and taking insulin treatment were classified as type 1 diabetes (T1D) or, if otherwise, as T2D. Odds ratios (ORs) were adjusted for age, gender, BMI, education and smoking. Cases were genotyped for high- and low-risk HLA genotypes. RESULTS: Both FHD-T1D (OR: 5.8; 95% CI: 3.2-10.3) and FHD-T2D (OR: 1.9; 95% CI: 1.5-2.5) were associated with an increased risk of LADA, whereas the risk of T2D was associated with FHD-T2D (OR: 2.7; 95% CI: 2.2-3.3), but not FHD-T1D. In LADA patients, FHD-T1D vs FHD-T2D was associated with higher GADA but lower C-peptide levels, lower prevalence of low-risk HLA genotypes (5.0% vs 28.6%, respectively; P=0.038) and a tendency for higher prevalence of high-risk genotypes (90.0% vs 69.1%, respectively; P=0.0576). CONCLUSION: The risk of LADA is substantially increased with FHD-T1D but also, albeit significantly less so, with FHD-T2D. This supports the idea of LADA as a mix of both T1D and T2D, but suggests that the genes related to T1D have greater impact. LADA patients with FHD-T1D had more T1D-like features, emphasizing the heterogeneity of LADA.

Serious life events and the risk of latent autoimmune diabetes in adults (LADA) and Type 2 diabetes.

AIM: It has been suggested that experiencing serious life events may promote Type 1 diabetes in children. Studies in adults are lacking, as are studies on the interaction of life events with genetic factors. We aimed to investigate life events and the risk of latent autoimmune diabetes in adults (LADA) and Type 2 diabetes while taking into account HLA genotype. METHODS: Analysis was based on 425 incident cases of LADA, 1417 incident cases of Type 2 diabetes and 1702 population-based controls recruited in Sweden between 2010 and 2016. Self-reported information on life events including conflicts, divorce, illness/accidents, death and financial problems experienced during the 5 years preceding diagnosis/index year was used. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated by logistic regression and adjusted for age, sex, BMI, family history of diabetes, smoking, physical activity and education. RESULTS: Overall there was no association between experience of any life event and either LADA (OR 0.86, 95% CI 0.68-1.08) or Type 2 diabetes (OR 1.00, 95% CI 0.83-1.21). The results were similar for individual events as well as in separate analysis of men and women. Similar results were seen in more autoimmune LADA (glutamic acid decarboxylase antibodies > median) [OR (any life event) 0.88, 95% CI 0.64-1.21] and in LADA carriers of the high-risk HLADR4-DQ8 genotype (OR 0.89, 95% CI 0.61-1.29). CONCLUSIONS: Our findings indicate that experience of a serious life event, including the death of a family member, divorce or financial problems, is not associated with an increased risk of LADA, overall or in genetically susceptible individuals.

Use of Swedish smokeless tobacco (snus) and the risk of Type 2 diabetes and latent autoimmune diabetes of adulthood (LADA).

AIMS: It has been suggested that moist snuff (snus), a smokeless tobacco product that is high in nicotine and widespread in Scandinavia, increases the risk of Type 2 diabetes. Previous studies are however few, contradictory and, with regard to autoimmune diabetes, lacking. Our aim was to study the association between snus use and the risk of Type 2 diabetes and latent autoimmune diabetes of adulthood (LADA). METHOD: Analyses were based on incident cases (Type 2 diabetes, n = 724; LADA, n = 200) and population-based controls (n = 699) from a Swedish case-control study. Additional analyses were performed on cross-sectional data from the Norwegian HUNT study (n = 21 473) with 829 prevalent cases of Type 2 diabetes. Odds ratios (OR) were estimated adjusted for age, BMI family history of diabetes and smoking. Only men were included. RESULTS: No association between snus use and Type 2 diabetes or LADA was seen in the Swedish data. For Type 2 diabetes, the OR for > 10 box-years was 1.00 [95% confidence interval (CI), 0.47 to 2.11] and for LADA 1.01 (95% CI, 0.45 to 2.29). Similarly, in HUNT, the OR for Type 2 diabetes in ever-users was estimated at 0.91 (95% CI, 0.75 to 1.10) and in heavy users at 0.92 (95% CI, 0.46 to 1.83). CONCLUSION: The risk of Type 2 diabetes and LADA is unrelated to the use of snus, despite its high nicotine content. This opens the possibility of the increased risk of Type 2 diabetes seen in smokers may not be attributed to nicotine, but to other substances in tobacco smoke.

Rapid Restoration of Vascularity and Oxygenation in Mouse and Human Islets Transplanted to Omentum May Contribute to Their Superior Function Compared to Intraportally Transplanted Islets.

Transplantation of islets into the liver confers several site-specific challenges, including a delayed vascularization and prevailing hypoxia. The greater omentum has in several experimental studies been suggested as an alternative implantation site for clinical use, but there has been no direct functional comparison to the liver. In this experimental study in mice, we characterized the engraftment of mouse and human islets in the omentum and compared engraftment and functional outcome with those in the intraportal site. The vascularization and innervation of the islets transplanted into the omentum were restored within the first month by paralleled ingrowth of capillaries and nerves. The hypoxic conditions in the islets early posttransplantation were transient and restricted to the first days. Newly formed blood vessels were fully functional, and the blood perfusion and oxygenation of the islets became similar to that of endogenous islets. Furthermore, islet grafts in the omentum showed at 1 month posttransplantation functional superiority to intraportally transplanted grafts. We conclude that in contrast to the liver the omentum provides excellent engraftment conditions for transplanted islets. Future studies in humans will be of great interest to investigate the capability of this site to also harbor larger grafts without interfering with islet functionality.

Increased levels of irisin in people with long-standing Type 1 diabetes.

BACKGROUND: Irisin stimulates browning of white adipose tissue and improves metabolic control in mice. Betatrophin, another recently described hormone, improves metabolic control in mice by inducing ß-cell proliferation. In vitro, irisin stimulates the expression of betatrophin in rat adipocytes. There is a great interest in developing drugs that target or use these hormones for the treatment of obesity and diabetes. We have previously reported on increased levels of betatrophin in people with Type 1 diabetes, but the levels of irisin are currently unknown. AIM: To characterize the levels of irisin in Type 1 diabetes and investigate a potential correlation with betatrophin. METHODS: Irisin and betatrophin were measured by enzyme-linked immunosorbant assay (ELISA) in 45 individuals with Type 1 diabetes and in 25 healthy controls. RESULTS: Irisin levels were increased in people with Type 1 diabetes, and especially in women. Negative correlations between irisin levels and age at onset of Type 1 diabetes and plasma triacylglycerol levels were observed. Interestingly, in women with Type 1 diabetes a negative correlation between irisin and insulin doses was also observed. When computing correlations for all study participants, a positive correlation between irisin and total betatrophin was observed, but not between irisin and full-length betatrophin. CONCLUSION: We report on increased circulating levels of irisin in people with Type 1 diabetes, especially in women. For women with Type 1 diabetes, the levels of irisin correlated with lower insulin requirements. Further studies are clearly needed to determine the role of irisin in Type 1 diabetes.

Fatty fish consumption and risk of latent autoimmune diabetes in adults.

OBJECTIVE: It has been suggested that intake of fatty fish may protect against both type 1 and type 2 diabetes. Hypotheses rest on the high marine omega-3 fatty acid eicosapentaenoic acid+docosahexaenoic acid (EPA+DHA) and vitamin D contents, with possible beneficial effects on immune function and glucose metabolism. Our aim was to investigate, for the first time, fatty fish consumption in relation to the risk of latent autoimmune diabetes in adults (LADA). METHODS: Analyses were based on data from a Swedish case-control study with incident cases of LADA (n=89) and type 2 diabetes (n=462) and randomly selected diabetes-free controls (n=1007). Diabetes classification was based on the onset of age (⩾35), glutamic acid decarboxylase autoantibodies, and C-peptide. A validated food frequency questionnaire was used to derive information on previous intake of fish, polyunsaturated long-chain omega-3 fatty acids (n-3 PUFA) and supplementation of fish oil and vitamin D. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using logistic regression, adjusted for age, gender, body mass index (BMI), family history of diabetes, physical activity, smoking, education, and consumption of alcohol, fruit, vegetables and red meat. RESULTS: Weekly fatty fish consumption (⩾1 vs <1 serving per week), was associated with a reduced risk of LADA but not type 2 diabetes (OR 0.51, 95% CI 0.30-0.87, and 1.01, 95% CI 0.74-1.39, respectively). Similar associations were seen for estimated intake of n-3 PUFA (⩾0.3 g per day; LADA: OR 0.60, 95% CI 0.35-1.03, type 2 diabetes: OR 1.14, 95% CI 0.79-1.58) and fish oil supplementation (LADA: OR 0.47, 95% CI 0.19-1.12, type 2 diabetes: OR 1.58, 95% CI 1.08-2.31). CONCLUSIONS: Our findings suggest that fatty fish consumption may reduce the risk of LADA, possibly through effects of marine-originated omega-3 fatty acids.

Locally increased concentrations of inflammatory cytokines in an experimental intraabdominal adhesion model.

BACKGROUND: Peritoneal adhesions may cause bowel obstruction, infertility, and pain. This study investigated cytokines, proteins and growth factors thought to promote formation of adhesions in an experimental intraabdominal adhesion model. METHODS: Male Sprague-Dawley rats were subjected to laparotomy, cecal abrasion, and construction of a small bowel anastomosis and examined at various time points after surgery. Concentrations of cytokines and growth factors in plasma and peritoneal fluid were analyzed using electrochemoluminescence and quantitative sandwich enzyme immunoassay technique. RESULTS: Concentrations of interleukin-6 (IL-6), interleukin-1beta (IL-1ß), and tumor necrosis factor alpha (TNF-α) increased in peritoneal fluid from 6h after incision. Plasma concentrations of IL-6 increased at 6h, but plasma concentrations of IL-1ß and TNF-α remained low. Peritoneal fluid concentrations of platelet-derived growth factor-BB (PDGF-BB), transforming growth factor beta1 (TGF-ß1), vascular endothelial growth factor (VEGF), tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were below detection levels at all time points. CONCLUSION: Early elevations of IL-6, IL-1ß, and TNF-α concentrations in peritoneal fluid correlated to adhesion formation in this rodent model. Our model is relevant and reproducible, suitable for intervention, and indicates that antiadhesion strategies should be early, local and not systemic.

Coffee consumption and the risk of latent autoimmune diabetes in adults--results from a Swedish case-control study.

AIMS: Coffee consumption is associated with a reduced risk of Type 2 diabetes. Our aim was to investigate if coffee intake may also reduce the risk of latent autoimmune diabetes in adults, an autoimmune form of diabetes with features of Type 2 diabetes. METHODS: We used data from a population-based case-control study with incident cases of adult onset (≥ 35 years) diabetes, including 245 cases of latent autoimmune diabetes in adults (glutamic acid decarboxylase antibody positive), 759 cases of Type 2 diabetes (glutamic acid decarboxylase antibody negative), together with 990 control subjects without diabetes, randomly selected from the population. Using questionnaire information on coffee consumption, we estimated the odds ratio of latent autoimmune diabetes in adults and Type 2 diabetes adjusted for age, sex, BMI, smoking, physical activity, alcohol, education and family history of diabetes. RESULTS: Coffee intake was inversely associated with Type 2 diabetes (odds ratio 0.92, 95% CI 0.87-0.98 per cup/day). With regard to latent autoimmune diabetes in adults, the general trend was weak (odds ratio 1.04, 95% CI 0.96-1.13), but stratification by degree of autoimmunity (median glutamic acid decarboxylase antibody levels) suggested that coffee intake may be associated with an increased risk of high glutamic acid decarboxylase antibody latent autoimmune diabetes in adults (odds ratio 1.11, 95% CI 1.00-1.23 per cup/day). Furthermore, for every additional cup of coffee consumed per day, there was a 15.2% (P = 0.0268) increase in glutamic acid decarboxylase antibody levels. CONCLUSIONS: Our findings confirm that coffee consumption is associated with a reduced risk of Type 2 diabetes. Interestingly, the findings suggest that coffee may be associated with development of autoimmunity and possibly an increased risk of more Type 1-like latent autoimmune diabetes in adults.

Superior beta cell proliferation, function and gene expression in a subpopulation of rat islets identified by high blood perfusion.

AIMS/HYPOTHESIS: The blood perfusion of individual pancreatic islets is highly variable, with a subgroup of islets having high perfusion and blood vessels responsive to further blood flow increase induced by glucose. This study tested the hypothesis that there is heterogeneity between islets with regard to beta cell proliferation, function and gene expression based on differences in their blood perfusion. METHODS: Fluorescent microspheres were injected into the ascending aorta, and then microsphere-containing and non-microsphere-containing pancreatic islets were isolated for investigation. By this procedure, the 5% of islets with the greatest blood perfusion were identified for study. Islet endothelial cells were isolated separately to investigate the role of improved vascular support in the observed differences. RESULTS: The vascular network was found to be more dense and tortuous in microsphere-containing than other islets. The most highly blood-perfused islets also had a higher rate of beta cell proliferation, superior beta cell function and a markedly different gene expression from other islets. Cultured islets exposed to islet endothelial cell products had a similarly increased beta cell proliferation rate, yet significantly fewer changes in gene expression than observed in the most highly blood-perfused islets. CONCLUSIONS/INTERPRETATION: A novel heterogeneity between islets was observed, with superior beta cell proliferation, function and gene expression in a subpopulation of islets identified by high blood perfusion. In contrast with a previously described population of low-oxygenated, sleeping islets, which are recruited into functionality when needed, the presently described heterogeneity is shown to remain in vitro after islet isolation.

Endothelin-1 markedly decreases the blood perfusion of transplanted pancreatic islets in rats.

BACKGROUND: Transplantation of insulin-producing ß-cells is the only available curative treatment for type 1 diabetes. However, graft function declines within the first years after transplantation, which may reflect inadequate vascular engraftment. Endothelin-1 (ET-1) is a potent vasoconstrictor whose production is regulated by both hypoxia and inflammation. Moreover, the plasma concentration of ET-1 is elevated in patients with type 1 diabetes. The aim of this study was to investigate the gene expression and effects of ET-1 and its 2 receptor antagonists, BQ123 and BQ788, on blood flow in syngeneic rat islet transplants. METHODS: Pancreatic islets from Wistar Furth rats were isolated and transplanted syngeneically under the kidney capsule. Transplant and kidney cortex blood flow was measured using laser Doppler flowmetry after administration of ET-1 via topical application, or after administration of BQ123 and BQ788 intravenously. The grafts and isolated islets were analyzed for mRNA expression of ET-1, ET(A) receptor, ET(B) receptor, and endothelin-converting enzyme 1 using by reverse-transcription polymerase chain reaction. RESULTS: ET-1 markedly decreased transplant blood flow (77.5 ± 4.4% 1 minute after administration; n = 6), whereas neither BQ123 nor BQ788 had vascular effects. No differences in relative gene expression between the grafts and freshly isolated control islets were seen for ET-1 (0.65 ± 0.14 [n = 8] vs 0.79 ± 0.24 [n = 5]), ET(A) receptor (0.37 ± 0.14 [n = 8] vs 0.25 ± 0.04 [n =5]), ET(B) receptor (4.78 ± 1.43 [n = 8] vs 1.94 ± 0.32 [n = 5]), or endothelin converting enzyme 1 (7.25 ± 1.88 [n = 8] vs 11.83 ± 0.95 [n = 5]) when expressed as 2(-ΔCt). CONCLUSION: Exogenous ET-1 strongly affects the blood perfusion of transplanted islets, and endogenous levels can, if up-regulated, contribute to graft failure.

Endothelial cell signalling supports pancreatic beta cell function in the rat.

AIMS/HYPOTHESIS: The proximity of endothelial cells and beta cells in islets by necessity means that they are exposed to each other's products. Whereas islet endothelial cells require signals from beta cells to function properly, endothelin-1, thrombospondin-1 and laminins, among others, have been identified as endothelial-derived molecules, although their full effects on beta cells have not been explored. We tested the hypothesis that islet endothelial-derived products affect beta cell function. METHODS: Endothelial cells from rat islets were proliferated and purified. Endothelium-conditioned culture medium (ECCM) was obtained by maintaining the endothelial cells in culture medium. Islet function was evaluated following exposure of cultured islets to standard culture medium or ECCM. Changes in mRNA levels for key beta cell metabolic enzymes were also measured in islets after ECCM exposure. RESULTS: Glucose-stimulated insulin release and islet insulin content were markedly enhanced by exposure to ECCM. This was at least partly explained by improved mitochondrial function, as assessed by glucose oxidation and an upregulation of the mitochondrial gene for glycerol-3-phosphate dehydrogenase (mGpdh [also known as Gpd2]), combined with upregulation of the rate-limiting enzyme in the glycolysis, glucokinase, in the islets. The intracellular degradation of insulin was also decreased in the islets. Islet endothelial cells produced laminins, and the positive effects of islet endothelial cells were prevented by addition of a neutralising antibody to the beta1-chain of laminin. Addition of exogenous laminin stimulated islet function. CONCLUSIONS/INTERPRETATION: This study provides proof of principle that endothelial cells can affect the function of beta cells in their vicinity and that this is at least partially mediated by laminins.

New class of oxygen carriers improves islet isolation from long-term stored rat pancreata.

OBJECTIVE: Pancreas shipment is frequently associated with prolonged ischemia deteriorating islet graft function. The strategy to prevent ischemic damage utilizing perfluorodecalin (PFD) for human pancreas oxygenation does not seem to improve isolation outcome. The present study investigated the efficiency of perfluorohexyloctane (F6H8), a hyperoxygen carrier characterized by low specific density (1.33 g/cm3) and lipophilic qualities, to facilitate islet isolation from long-term stored rat pancreata. MATERIALS AND METHODS: Prior to islet isolation, pancreata were intraductally flushed in situ with Kyoto solution (KS) and stored for 24 hours in KS, oxygenated PFD, or F6H8. RESULTS: Islet isolation performed after 24-hour storage in KS failed completely. The intrapancreatic pO2 in PFD- and F6H8-incubated pancreata was almost the same. In correspondence, the ATP content and viability of isolated islets were similar as well. In contrast, islet yield and in vitro function were significantly reduced after storage in PFD compared with F6H8. CONCLUSION: This study suggested that islet isolation performed after long-term pancreas preservation can be significantly improved utilizing semifluorinated alkanes as oxygen carriers.

Hemodynamic effect of iopromide in pancreas-duodenum transplanted rats.

BACKGROUND: Radiological contrast media (CM) have been suggested to be able to impair pancreatic microcirculation, especially in acute pancreatitis. PURPOSE: To evaluate the effects of the low-osmolar CM iopromide on total pancreatic and especially islet blood perfusion after whole pancreas transplantation. MATERIAL AND METHODS: Rats receiving a pancreas-duodenum transplantation 2 days earlier, i.e., with graft pancreatitis, were injected with iopromide. Blood perfusion measurements were then made with a microsphere technique. RESULTS: The graft blood perfusion was decreased in control rats when compared to the endogenous pancreas. Administration of iopromide increased both total pancreatic and islet blood perfusion in the grafted pancreas, but not in the endogenous gland. No effects on blood perfusion to either the native or transplanted duodenum were seen after iopromide administration. CONCLUSION: Iopromide increases the blood perfusion of a whole pancreas transplant 2 days after implantation, i.e., when graft pancreatitis is present. The consequences of this CM-induced hyperperfusion for graft pancreatic function remain to be established.Key words: Intravascular contrast media; islet blood perfusion; graft pancreatitis;pancreas transplantation; pancreatic blood perfusion

Radiological contrast media and pancreatic blood perfusion in anesthetized rats.

BACKGROUND: Radiological contrast media (CM) have been suggested to be able to impair pancreatic microcirculation. PURPOSE: To evaluate the effects of an iso-osmolar (iodixanol, 290 mOsm/kg H2O) and a low-osmolar (iopromide, 660 mOsm/kg H2O) CM on total pancreatic and islet blood perfusion. MATERIAL AND METHODS: Thiobutabarbital-anesthetized rats were injected with iodine equivalent doses (600 mg I/kg body weight) of iodixanol or iopromide. Saline or low-osmolar mannitol (660 mOsm/kg H2O) solutions served as control substances. Blood perfusion measurements were then carried out with a microsphere technique. RESULTS: Iso-osmolar iodixanol had no effects on blood perfusion. Low-osmolar iopromide increased total pancreatic blood perfusion, whereas islet blood perfusion was unchanged. No differences were seen when mannitol solutions were given. CONCLUSION: Neither an iso-osmolar nor a low-osmolar CM affected pancreatic islet blood perfusion, whereas the low-osmolar CM increased total pancreatic blood perfusion. The absence of hemodynamic effect of low-osmolar mannitol suggests that the hyperosmolality per se of iopromide versus iodixanol does not induce the hemodynamic effect. The consequences of the effect of iopromide for pancreatic function remain to be established.

Diabetes-induced hyperfiltration in adenosine A(1)-receptor deficient mice lacking the tubuloglomerular feedback mechanism.

AIMS: Glomerular hyperfiltration is commonly found in diabetic patients early after the onset of disease. This is one of the first indications of the development of progressive diabetic nephropathy. It has been proposed that glomerular hyperfiltration is caused by decreased delivery of electrolytes to the macula densa due to the increased sodium and glucose reabsorption in the proximal tubule, which would increase the glomerular filtration rate (GFR) via the tubuloglomerular feedback (TGF) mechanism. In this study, we investigated the role of TGF in diabetes-induced glomerular hyperfiltration by inducing diabetes in adenosine A(1)-receptor knockout (A1AR(-/-)) mice known to lack a functional TGF mechanism. METHODS: Diabetes was induced by alloxan (75 mg kg(-1) bw) injected into the tail vein. The 24-hour urinary electrolyte excretion was measured in metabolic cages, the GFR determined by inulin clearance under isoflurane-anaesthesia, and histological changes evaluated. RESULTS: All alloxan-treated animals developed hyperglycaemia (> or =20 mm). Normoglycaemic animals had a similar GFR independent of genotype (A1AR(+/+) 9.3 +/- 0.5 vs. A1AR(-/-) 10.1 +/- 0.8 microL min(-1)g(-1) bw) and diabetes resulted in similar glomerular hyperfiltration in both groups (A1AR(+/+) 14.0 +/- 1.7, n = 9 vs. A1AR(-/-) 15.3 +/- 1.9 microL min(-1)g(-1) bw). Diabetic animals had a similar tendency to develop interstitial fibrosis, whereas the glomerular volume was similar in both genotypes, and unaltered by diabetes. CONCLUSIONS: This study shows that the A1AR(-/-) mice develop diabetes-induced glomerular hyperfiltration, demonstrating that the TGF mechanism is not the major cause of the development of hyperfiltration. Furthermore, the hyperfiltration in the present study was not related to alterations in the glomerular filtration area.

Improved vascular engraftment and function of autotransplanted pancreatic islets as a result of partial pancreatectomy in the mouse and rat.

AIMS/HYPOTHESIS: The few patients subjected to autotransplantation of pancreatic islets after pancreatectomy usually become normoglycaemic after using islets from the resected organ only, whereas allogeneic recipients usually require at least two grafts to retain normoglycaemia. Previous experimental studies have demonstrated that islets transplanted to non-pancreatectomised recipients acquire a markedly decreased blood vessel density, which leads to a hypoxic microenvironment. The aim of the present study was to test the hypothesis that autotransplanted islets have better vascular engraftment and function as a result of the pancreatic surgery involved. MATERIALS AND METHODS: In the present study, athymic mice and inbred rats were subjected to a 60% pancreatectomy and transplanted with human or rat islets, respectively, 4 days later. Control animals underwent sham surgery. Blood flow, oxygen tension, vascular density and endocrine volume in the islet grafts were measured 1 month after transplantation. Separate grafts were used for perfusion experiments and for assessment of beta cell proliferation and endocrine cellular apoptosis at different time periods after transplantation. RESULTS: Islet grafts in partially pancreatectomised recipients had an increased blood flow, oxygen tension, blood vessel density and endocrine mass 1 month post-transplantation compared with control animals. They also exhibited increased insulin release in perfusion experiments performed 1 month post-transplantation, and decreased cellular apoptosis early after transplantation. CONCLUSIONS/INTERPRETATION: The present study shows that the pancreatectomy procedure itself has beneficial effects on the engraftment of transplanted human and rat islets. Our results provide an additional explanation, besides diminished immunological responses, of the much better outcome of islet autotransplantations compared with allogeneic transplantations in the clinic.

Carbon monoxide and pancreatic islet blood flow in the rat: inhibition of haem oxygenase does not affect islet blood perfusion.

OBJECTIVE: To determine whether carbon monoxide, a known gaseous vasorelaxator, affects pancreatic islet blood flow in rats. MATERIAL AND METHODS: Sprague-Dawley rats were anaesthetized with thiobutabarbital and injected intravenously with the haem oxygenase inhibitor tin-protoporphyrin IX dichloride (SnPP; 4, 10 or 20 mg/kg body-weight). After 15 min, blood flow measurements were performed using a microsphere technique. RESULTS: There was a slight increase in mean arterial blood pressure with the highest dose of SnPP. No effects on total pancreatic, islet, duodenal, colonic, renal or adrenal blood flow were seen with any of the applied doses. CONCLUSIONS: The findings of this study suggest that the haem oxygenase-carbon monoxide system is likely to be of limited importance in the regulation of blood perfusion to the pancreas, the islets of Langerhans or any of the other studied organs.

Islets transplanted intraportally into the liver are stimulated to insulin and glucagon release exclusively through the hepatic artery.

Not much is known about the physiology of intraportally transplanted islets. One reason for this is that it is difficult to study such islets, since they are scattered throughout the liver. We employed a perfusion technique to characterize the functional properties of syngeneic intrahepatic 1-month-old islet grafts, and compared them to islets transplanted beneath the kidney capsule, as well as native islets. The cellular composition of the islet grafts was also examined. Glucose and arginine administered through the hepatic artery, but not through the portal vein, induced insulin release from the intraportally implanted islets. Moreover, arginine, only when administered through the hepatic artery, induced glucagon release from the same islets. The first phase of glucose-stimulated insulin release from both islets transplanted to the liver and kidney was delayed, and less prominent when compared to the pancreas. Intraportally transplanted islets contained fewer glucagon-positive cells than islets transplanted to the kidney and native islets. Our findings demonstrate that intraportally transplanted islets respond with insulin and glucagon to secretagogues, but only when stimulated through the hepatic artery. Whether intrahepatic islets may sense other substances than glucose or arginine occurring in high concentrations in the portal vein following intestinal uptake remains to be studied.