Diabetologia

Gilbert, R. E.; Kelly, D. J.; Cox, A. J.; Wilkinson-Berka, J. L.; Rumble, J. R.; Osicka, T.; Panagiotopoulos, S.; Lee, V.; Hendrich, E. C.; Jerums, G.; Cooper, M. E.

doi: 10.1007/s001250051539pmid: 11126403

Aims/hypothesis. Angiotensin converting enzyme (ACE) inhibition has been recently suggested to have retinoprotective actions in diabetic patients but the mechanism of this effect is not known. In vitro, angiotensin II stimulates expression of vascular endothelial growth factor (VEGF), a permeability-inducing and endothelial cell specific angiogenic factor which has been implicated in the pathogenesis of diabetic retinopathy in humans and in experimental animals. We sought to determine the effects of ACE inhibition on retinal VEGF expression and permeability in experimental diabetic retinopathy.¶ Methods. Streptozotocin-induced diabetic rats and control animals were assigned at random to receive ACE inhibitor treatment or vehicle. At 24 weeks the retinal VEGF protein gene expression was assessed by northern blot analysis and in situ hybridisation. Retinal permeability to albumin was measured using a double isotope technique.¶ Results. Experimental diabetes was associated with cell specific two to fourfold increase in retinal VEGF protein gene expression ( p < 0.01) and a 2-fold increase in retinal vascular permeability to albumin ( p < 0.01). The localization of VEGF expression in the retina was not altered in animals with experimental diabetes. Angiotensin converting enzyme inhibitor treatment of diabetic rats reduced diabetes-associated changes in VEGF gene expression and vascular permeability.¶ Conclusion/interpretation. These findings implicate the renin-angiotensin system in the VEGF overexpression and hyperpermeability which accompany diabetic retinopathy and provide a potential mechanism for the beneficial effects of ACE inhibition in diabetic retinal disease. (Diabetologia (2000) 43: 1360–1367)

Andersen, N. Aa.; Larsen, C. M.; Mandrup-Poulsen, T.

doi: 10.1007/s001250051544pmid: 11126408

Aims/hypothesis. Interleukin-1 beta (IL-1β) in synergy with tumour necrosis factor alpha (TNFα) and interferon gamma (IFNγ) is cytotoxic to pancreatic beta cells. Mitogen-activated protein kinase (MAPK) activity that is induced by interleukin-1 beta has been suggested to signal nitric oxide-dependent as well as nitric oxide-independent beta-cell destructive pathways. The aim of this study was to investigate if TNFα and IFNγ signal through mitogen-activated protein kinases in isolated rat islets of Langerhans and if they potentiate mitogen-activated protein kinase activity induced by IL-1β.¶ Methods. Islets of Langerhans were isolated from 5- to 7-day-old Wistar rats and precultured for 7 days before stimulation with IL-1β, TNFα and/or IFNγ for 20 min followed by lysis. Kinase activity was measured with a whole cell lysate kinase assay and after immunoprecipitation of the kinase using immunocomplex kinase assay.¶ Results. Exposure to IL-1β or TNFα significantly increased mitogen-activated protein kinase activity, whereas IFN γ tended to decrease extracellular-signal-regulated kinase activity. Further, TNFα and IFNγ were found to synergistically increase mitogen-activated protein kinase activity induced by IL-1β.¶ Conclusion/interpretation. We hypothesise that the synergistic effect of IL-1β, TNFα and IFNγ in the functional inhibition and induction of cell death in pancreatic beta cells is signalled through a synergistic activation of mitogen-activated protein kinase activity (Diabetologia (2000) 43: 1389–1396).

Vay, D.; Vidali, M.; Allochis, G.; Cusaro, C.; Rolla, R.; Mottaran, E.; Bellomo, G.; Albano, E.

doi: 10.1007/s001250051543pmid: 11126407

Aims/hypothesis. N ɛ -(carboxymethyl)lysine (CML) is one of the end products of protein glycoxidation and its accumulation is associated with diabetes complications. Since CML-modified proteins are immunogenic, we have investigated the presence of anti-CML antibodies in diabetic patients.¶ Methods. Antibodies against CML-modified human serum albumin (HSA) were measured by direct enzyme-linked immunosorbent assay in the sera from 289 non-selected diabetic and in 120 healthy control subjects.¶ Results. Immunoglobulin-G reactivity towards CML-HSA was significantly higher in diabetic than in control sera. The presence of anti-CML IgG in diabetics, however, was not influenced by age, duration of disease or glycaemic control. Analysis of distribution frequency revealed that anti-CML IgG in both control and diabetic subjects were not normally distributed and that the distribution curves were similar in the two groups. Moreover, only 14 % of the diabetic subjects displayed antibody binding to CML-HSA above 95 centile in the control cohort. Competition experiments confirmed that the IgG detected in both control and diabetic groups were specific for CML epitopes and did not recognise glycated-HSA in which CML formation was inhibited.¶ Conclusion/interpretation. The presence of anti-CML IgG in diabetic sera is probably not related to the development of an immune response against protein glycoxidation products. (Diabetologia (2000) 43: 1385–1388)

Heitzer, T.; Krohn, K.; Albers, S.; Meinertz, T.

doi: 10.1007/s001250051551pmid: 11126415

Aims/hypothesis. Tetrahydrobiopterin is an essential cofactor of nitric oxide synthase, and its deficiency decreases nitric oxide bioactivity. Our aim was to find whether supplementation of tetrahydrobiopterin could improve endothelial dysfunction in diabetic patients.¶ Methods. Forearm blood flow responses to the endothelium-dependent vasodilator acetylcholine (0.75– 3.0 μg · 100 ml –1 · min –1 ) and to the endothelium-independent vasodilator sodium nitroprusside (0.1–1.0 μg · 100 ml –1 · min –1 ) before and during concomitant intra-arterial infusion of tetrahydrobiopterin (500 μg/min) were measured by venous occlusion plethysmography in 12 control subjects and 23 patients with Type II (non-insulin-dependent) diabetes mellitus.¶ Results. In control subjects, tetrahydrobiopterin had no effect on the dose-response curves to acetylcholine and sodium nitroprusside. In contrast, in diabetic patients, the attenuated endothelium-dependent vasodilation to acetylcholine was considerably improved by concomitant treatment with tetrahydrobiopterin, whereas the endothelium-independent vasodilation was not affected. This beneficial effect of tetrahydrobiopterin in diabetic patients could be completely blocked by N G -monomethyl- l -arginine.¶ Conclusion/interpretation. These findings suggest the possibility that endothelial dysfunction in Type II diabetes might be related to decreased availability of tetrahydrobiopterin. (Diabetologia (2000) 43: 1435–1438)

Rowley, K. G.; Iser, D. M.; Best, J. D.; O'Dea, K.; Leonard, D.; McDermott, R.

doi: 10.1007/s001250051545pmid: 11126409

Aims/hypothesis. To examine the prevalence and associations with the metabolic syndrome of albuminuria among Australian Aboriginal people.¶ Methods. Early-morning urine specimens were collected as part of community-based risk factor surveys assessing the prevalence of diabetes and cardiovascular disease in eight remote communities, with a sample size of 1,075 people. Microalbuminuria was defined as urinary albumin : creatinine ratio 3.4–33.9 mg/mmol, macroalbuminuria as albumin : creatinine ratio equal to or greater than 34 mg/mmol.¶ Results. There were high prevalences of microalbuminuria (men 22.2 %, women 26.9 %) and of macroalbuminuria (men 10.4 %, women 13.5 %). There were highly statistically significant linear associations of microalbuminuria and macroalbuminuria with increasing number of coexisting components of the metabolic syndrome (hypertension, glucose intolerance, dyslipidaemia, insulin resistance, abdominal obesity): among people with zero, one, two and three to five of these conditions, respectively, prevalence of microalbuminuria was 16 %, 20 %, 36 % and 32 % ( p < 0.001); prevalence of macroalbuminuria was 2 %, 6 %, 12 % and 32 % ( p < 0.001). There were independent associations of microalbuminuria with hypertension (odds ratio, 95 % confidence interval = 2.36, 1.63–3.42) and diabetes (2.10, 1.28–3.45): macroalbuminuria was independently associated with hypertension (6.39, 3.93–10.4), diabetes (3.49, 1.93–6.28) and abdominal obesity (4.56, 2.40–8.64) and had a weaker association with insulin resistance (1.99, 1.12–3.54). Dyslipidaemia and impaired glucose tolerance were neither independently associated with microalbuminuria or macroalbuminuria, nor was insulin resistance or abdominal obesity independently associated with microalbuminuria.¶ Conclusion/interpretation. There was a strong clustering of albuminuria with components of the metabolic syndrome. Diabetes, hypertension and abdominal obesity are major contributors to high rates of albuminuria among Australian Aboriginal people. (Diabetologia (2000) 43: 1397–1403)

Steinbrenner, H.; Lohmann, T.; Ostendorf, B.; Scherbaum, W. A.; Seissler, J.

doi: 10.1007/s001250051542pmid: 11126406

Aims/hypothesis. The majority of patients with Type I (insulin-dependent) diabetes mellitus has autoantibodies to insulin, glutamic acid decarboxylase and the tyrosine phosphatase-like protein IA-2. Some patients with Type I diabetes, in particular with adult onset diabetes, have, however, only cytoplasmic islet cell antibodies that could be directed to as yet unknown beta cell autoantigens. Recently, one potential antigen, ICA12, was identified as the high mobility group (HMG) box transcription factor SOX-13. Our aim was to evaluate the diagnostic sensitivity and specificity of autoantibodies to SOX-13 for autoimmune diabetes.¶ Methods. Full-length SOX-13 was cloned from human brain mRNA, expressed by vitro transcription/translation and used to detect autoantibodies by immunoprecipitation and radioligand assay in patients suffering from autoimmune diabetes or non-organ-specific autoimmune diseases.¶ Results. We found SOX-13 antibodies to be present in 11 of 125 (8.8 %) patients with newly diagnosed Type I diabetes and in 3 of 43 (7.0 %) patients with latent autoimmune diabetes in adults. There was no association with age, sex and a particular pattern of diabetes-specific autoantibodies. Similar frequencies of SOX-13 antibodies were found in 84 patients with rheumatic diseases (4.0–11.4 %) and 211 healthy control subjects (5.2 %).¶Conclusions/interpretation. Our data indicate that SOX-13 represents a minor target of autoantibodies in patients with autoimmune diabetes. Because SOX-13 antibodies were found not to be disease-specific, we assume they are not helpful in improving the diagnosis and prediction of Type I diabetes. (Diabetologia (2000) 43: 1381–1384)

Schrauwen, P.; Schaart, G.; Saris, W. H. M.; Slieker, L. J.; Glatz, J. F. C.; Vidal, H.; Blaak, E. E.

doi: 10.1007/s001250051547pmid: 11126411

Aims/hypothesis. The aim of this study was to examine the effect of weight loss on UCP2/UCP3 mRNA expression and UCP3 protein content in subjects with Type II (non-insulin-dependent) diabetes mellitus.¶ Methods. We studied seven Type II diabetic subjects who followed a 10-week very low calorie diet. Expression of skeletal muscle UCP2 and UCP3 mRNA was measured using RT-competitive PCR and UCP3 protein content by western blotting, before and after the diet. Total and plasma fatty acid oxidation was measured using infusion of 13 C labelled palmitate.¶ Results. Body weight decreased from 105.5 ± 8.2 kg to 91.6 ± 7.2 kg ( p < 0.001), after 10 weeks of diet intervention. Expression of UCP2 and UCP3 mRNA were significantly reduced after 10 weeks of diet ( p < 0.05) but UCP3 protein contents were not significantly altered. Notably, the change in UCP3L mRNA expression and UCP3 protein content after the very low calorie diet were negatively associated with changes in body weight ( r = – 0.97, p = 0.006 and r = – 0.83, p = 0.043, respectively) and BMI ( r = – 0.99, p = 0.0007 and r = – 0.9, p = 0.016, respectively). Furthermore, changes in UCP3L mRNA expression and UCP3 protein content induced by the diet were positively correlated with changes in cytosolic fatty acid-binding protein content ( r = 0.93, p = 0.023 and r = 0.84, p = 0.039, respectively). No correlation between diet-induced changes in UCP3 protein and resting energy expenditure or plasma non-esterified fatty acid concentrations were found.¶ Conclusion/interpretation. The negative correlation between the change in UCP3 protein content after weight loss and the change in BMI, suggests that the decrease in UCP3 during weight loss could prevent further weight loss. The finding that the change in UCP3 protein content correlates with the change in skeletal muscle fatty acid-binding protein content, suggests a role for UCPs in the handling of lipids as a fuel. (Diabetologia (2000) 43: 1408–1416)

Saeki, K.; Xie, J.; Notkins, A. L.

doi: 10.1007/s001250051550pmid: 11126414

Aims/hypothesis. IA-2 is a transmembrane protein with a tyrosine phosphatase (PTP)-like structure and a major autoantigen in Type I (insulin-dependent) diabetes mellitus. Because the nucleotide sequence of human and mouse IA-2 cDNA are closely related, it seemed likely that the genomic organization of the two molecules would be similar. To test this possibility the current experiments were initiated to characterize and compare the genomic structure of mouse and human IA-2 .¶ Methods. IA-2 cDNA was used to screen a 129SVJ mouse genomic library. We selected and mapped 7 overlapping clones. The subcloned inserts were used to determine intron-exon junctions by direct sequencing. Polymerase chain reaction and restriction mapping were used to estimate the size of the introns.¶ Results. The mouse IA-2 gene and the 5' upstream regulatory region were isolated and the intron-exon junctions determined. Mouse IA-2 encompasses approximately 20 kb and encodes 23 exons. Both the 3' and 5' ends were mapped by rapid amplification of cDNA ends (RACE) and a 2 kb 5'-upstream region was shown to have functional promoter activity.¶ Conclusion/interpretation. Comparison of the genomic structure of mouse and human IA-2 shows that they have the same number of exons and nearly identical intron-exon junctions. The region around the major transcription start site of mouse IA-2 is similar to human IA-2 and other transmembrane protein tyrosine phosphatases. It is concluded that human and mouse IA-2 are highly conserved and derived from a common ancestral gene. (Diabetologia (2000) 43: 1429–1434)

Soedamah-Muthu, S. S.; Colhoun, H. M.; Taskinen, M.-R.; Idzior-Walus, B.; Fuller, J. H.

doi: 10.1007/s001250051538pmid: 11126402

Aims/hypothesis. To examine whether the HDL-cholesterol:apoA-I + apoA-II ratio and the ɛ2 allele are related to albuminuria at baseline and whether they are risk factors for progression of albuminuria in a cohort study of patients with Type I (insulin-dependent) diabetes mellitus.¶ Methods. At baseline, the study cohort comprised 617 patients, aged 15–60 years, from seven European diabetic centres of the EURODIAB study. Albumin excretion rate, measured in a central laboratory, was categorised as normoalbuminuria at 20 μg/min or less, microalbuminuria between 20 and 200 μg/min or macroalbuminuria at 200 μg/min or over. Of the 250 patients who were normoalbuminuric at baseline and had follow-up albuminuria measurements, 34 patients were defined as early progressors.¶ Results. At baseline, the mean HDL-cholesterol:apoA-I + apoA-II ratio was lower in macroalbuminuric patients (0.79, 95 % CI:0.74–0.83) compared with normoalbuminuric (0.88, 95 % CI:0.87–0.90) patients ( p = 0.0002, adjusted for age and sex). At follow-up, 34 patients who progressed from normoalbuminuria to microalbuminuria or macroalbuminuria also had a slightly lower baseline ratio (0.85, 95 % CI:0.80–0.89) than those 216 who remained normoalbuminuric (0.89, 95 % CI:0.87–0.92) (adjusted p = 0.08). Neither of these relations were independent of LDL-cholesterol or fasting triglyceride. There was no association of the ɛ2 allele with albuminuria either at baseline (OR = 1.4, 95 % CI:0.7–2.8) or with progression of albuminuria (OR = 0.4, 95 % CI:0.1–3.5).¶ Conclusion/interpretation. There is an inverse relation of HDL-cholesterol:apoA-I + apoA-II ratio with albuminuria at baseline. This lower ratio in microalbuminuric or macroalbuminuric patients could contribute to the increased risk of cardiovascular disease associated with nephropathy. There is weak evidence that HDL-composition is a risk factor for progression of albuminuria and no association of the ɛ2 allele with diabetic nephropathy. (Diabetologia 2000 43: 1353–1359)

Meirhaeghe, A.; Amouyel, P.; Helbecque, N.; Cottel, D.; Otabe, S.; Froguel, P.; Vasseur, F.

doi: 10.1007/s001250051549pmid: 11126413

Aims/hypothesis. The UCP2 - UCP3 gene region has been previously associated with obesity and diabetes. In a large representative cohort of Northern France (MONICA project), we studied the effect of a recently reported C/T polymorphism located in the 5' sequences of the UCP3 gene on anthropometric measurements and lipid profile. We also examined the association of this polymorphism with obesity and Type II (non-insulin-dependent) diabetes mellitus.¶ Methods. The –55 C/T polymorphism of the UCP3 gene has been genotyped in 1155 subjects from the MONICA project. Association studies were done with diabetes, obesity and related phenotypes. Results were ascertained in a second cohort of well-characterized Type II diabetic and control subjects.¶ Results. The variant T allele was associated with a decreased risk of developing Type II diabetes. Frequencies of the T allele were 13.3 % compared with 22 %, p = 0.04, in the diabetic and control groups, respectively. This observation was confirmed in the second cohort of French Type II diabetic ( n = 171) and control ( n = 124) subjects: 17.8 % compared with 25 %, p = 0.03. Moreover, subjects bearing the TT genotype had higher plasma total cholesterol and LDL-cholesterol concentrations ( p = 0.0006 and p = 0.001, respectively) than subjects bearing wild or heterozygous genotypes.¶ Conclusion/interpretation. The UCP3 –55 C/T polymorphism was associated with a higher atherogenic profile and modified the risk for the development of Type II diabetes. (Diabetologia (2000) 43: 1424–1428)