Association of diabetic neuropathy with Na/K ATPase gene polymorphism

Summary Diabetes mellitus induces a decrease in Na/K ATpase activity in man and animals, and this decrease plays a role in the development of diabetic neuropathy. Na/K ATPase is encoded by various genes, of which the ATP1 A1 gene is expressed predominantly in peripheral nerves and in erythrocytes. To investigate whether a polymorphism in the Na/K ATPase genes could explain the predisposition of some patients with insulin-dependent diabetes mellitus (IDDM) to develop polyneuropathy, a restriction fragment length polymorphism (RFLP) of the ATP1 A1 gene was studied together with erythrocyte Na/K ATPase activity in 81 Caucasian patients with more than 10 years' duration of IDDM. Associations with diabetic neuropathy, retinopathy and nephropathy were sought. Digestion of the first intron of the ATP1 A1 gene by the Bgl II restriction enzyme revealed a dimorphic allelism. Frequency of the restricted allele was 0.18 in this selected series (however, it was 0.10 in representative samples of IDDM patients and of normal subjects in our area). Mean erythrocyte Na/K ATPase activity was lower in diabetic patients than in 42 control subjects (292 ± 10, vs 402 ± 13 nmol Pi · mg protein^{− 1}· h^{− 1}, p < 0.0001) and was not related to HbA_1c value or to diabetes duration. It was lower in the group of the 28 patients bearing the restricted allele (241 ± 10 vs 319 ± 11 nmol Pi · mg protein^{− 1}· h^{− 1}, p < 0.0001). Neuropathy was absent in 50 patients, mild in 15 and severe in 16. When classified accordingly the three groups of patients did not differ with respect to sex, age and duration of diabetes. The respective frequency of the restricted allele among the groups was 10, 73 and 81 %, (p < 0.0001) and mean erythrocyte Na/K ATPase activity was respectively: 322 ± 10.7 nmol Pi · mg protein^{− 1}· h^{− 1}, 268 ± 15 and 229 ± 17, (p < 0.001). A borderline association between renal status or retinal status and repartition of polymorphism and a borderline correlation between renal status and Na/K ATPase activity were found, but significance disappeared after checking for the presence or absence of neuropathy. IDDM patients bearing the ATP1 A1 variant detected by Bgl II RFLP are much more frequently affected by neuropathy (relative risk 6.5, with 95 % CI 3.3–13). Identification of this risk factor may help to prevent this complication. It is suggested that the restricted allele is in linkage disequilibrium with a genomic mutation allowing diabetes to induce a greater impairment of Na/K ATPase activity which could in turn favour the development of neuropathy. [Diabetologia (1997) 40: 506–511] Received: 26 August 1996 and in revised form: 28 January 1997     

Na/K ATP酶活性及其ATP1A1基因多态性与2型糖尿病周围神经病变的相关性

目的研究大连地区汉族人Na／KATP酶活性及ATP1A1基因多态性与2型糖尿病（T2DM）周围神经病变（DPN）的关系。方法用聚合酶链反应-限制性片段长度多态性方法对大连地区的106例T2DM患者和45例正常对照者（NC）的ATP1A1基因进行扩增，对其基因多态性进行研究，并用比色法测定其红细胞的Na／KATP酶活性。结果与NC组相比，T2DM组红细胞Na／KATP酶活性降低，在伴有DPN组，Na／KATP酶活性的降低更为明显。在T2DM患者中，有DPN组与无DPN组相比，基因型分布差异有统计学意义（P〈0．05）。T2DM患者携带有限制性等位基因A与非携带者Na／KATP酶活性的差异有统计学意义（P〈0．05）。结论Na／KATP酶活性的降低在DPN的发病中起重要作用，Na／KATP酶的基因ATP1A1多态性与T2DM患者发生DPN相关。T2DM携带有限制性等位基因A的患者DPN的发生率低于非携带者。     

Differential effects of proinsulin C-peptide fragments on Na +, K +-ATPase activity of renal tubule segments

Summary Proinsulin C-peptide has been shown to stimulate the activity of Na ⁺ K ⁺ ATPase of rat renal tubule segments. Thirty-six peptides and amino acids, corresponding to parts of the intact rat C-peptide and suitable controls were screened for capacity to stimulate Na ⁺, K ⁺-ATPase in an attempt to determine potential active sites in the C-peptide molecule. The carboxy-terminal tetra and penta peptides were found to elicit 92–103 % of the intact molecule's activity, and the remaining segment, des-(27–31) C-peptide, did not possess stimulatory activity. Peptides from the middle C-peptide segment, however, centering around a GGPEAG sequence, stimulated Na ⁺, K ⁺-ATPase activity (36–80 % of the intact molecule's effect) but this effect was not balanced by corresponding inactivity of other parts. Furthermore, it was paralleled by activity of a non-native dipeptide d-form. It is concluded that the latter effect and that of the middle segment may represent complex interactions other than the apparently specific effects of the C-terminal segment. [Diabetologia (1998) 41: 287–291] Received: 31 July 1997 and in revised form: 30 October 1997     

Functional Communication Between Cardiac ATPSensitive K+ Channel and Na/K ATPase

K_ATP Channel and Na/K ATPase. Introduction: Functional interaction between K_ATP channel and Na/K ATPase was studied in single guinea pig ventricular myocytes because both membrane molecules are known to he involved in ischemic episodes. Methods and Results: K_ATP channel currents were recorded at 36°C by using whole cell, cell attached, inside-out, and open cell-attached modes of patch clamp techniques on enzymatically isolated ventricular myocytes. In the whole cell mode, ouabain (1 μM) reversibly inhibited the K_ATP currents induced by metabolic stress (ATP-free pipette solution and 1 mM NaCN), but not those activated by cromakalim (100 μM), a K_ATP channel opener. In the cell-attached mode, ouabain concentration dependently inhibited K_ATP, channel opening induced by metabolic suppression (5.5 μM 2-deoxyglucose and 1 mM CN). Half-inhibition concentration for ouabain was 21.0 ± 5.5 nM and the Hill coefficient was 0.8 ± 0.1 (n = 26). However, ouabain did not have an effect on the channel activity induced by cromakalim (100 μM). In the inside-out mode, ouabain applied to the internal side of membrane did not affect the channel. In the open cell-attached mode made by preincubation with streptolysin-0 (0.08 U/mL), the K_ATP channels were not activated by the metabolic inhibitors but were by reducing extracellular ATP concentrations, because subsarcolenimal ATP concentration could he controlled through tiny membrane holes. The channels thus activated were not suppressed by ouabain. Conclusion: The inhibition of Na/K ATPase by ouahain appeared to block the K_ATP channels by accumulating subsarcolemmal ATP caused by a decrease of the transition from ATP to ADP. In the presence of ischemic episodes, the administration of digitalis compounds may affect the opening of K_ATP channels, which is primarily protective against the development of irreversible myocardial damage.     

Fasting plasma C-peptide,glucagon stimulated plasma C-peptide,and urinary C-peptide in relation to clinical type of diabetes

Summary Many patients with Type 2 (non-insulin-dependent) diabetes mellitus are treated with insulin in order to control hyperglycaemia. We studied fasting plasma C-peptide, glucagon stimulated plasma C-peptide, and 24 h urinary C-peptide in relation to clinical type of diabetes in 132 insulin treated diabetic subjects. Patients were classified clinically as Type 1 (insulin-dependent) diabetic subjects in the presence of at least two of the following criteria: 1) significant ketonuria, 2) insulin treatment started within one year after diagnosis, 3) age of diagnosis 40 years, and 4) weight below 110% of ideal weight of the same age and sex. Eighty patients were classified as Type 1 and 52 as Type 2 diabetic subjects. A second classification of patients into 6 C-peptide classes was then performed. Class I consisted of patients without islet B-cell function. Class II-VI had preserved islet B-cell function and were separated according to the 20%, 40%, 60% and 80% C-peptide percentiles. The two classifications of patients were compared by calculating the prevalence of clinical Type 1 and Type 2 diabetes in each of the C-peptide classes. This analysis showed that patients with a fasting plasma C-peptide value <0.20 nmol/l, a glucagon stimulated plasma C-peptide value <0.32 nmol/l, and a urinary C-peptide value <3.1 nmol/l, or <0.54 nmol/mmol creatinine/24 h, or <5.4 nmol/24 h mainly were Type 1 diabetic patients; while patients with C-peptide levels above these values mainly were Type 2. At these limits the percentage, predictive value of positive tests as indicators of Type 2 diabetes were as follows: fasting C-peptide 83%, stimulated C-peptide 86%, and urinary C-peptide expressed as nmol/l 76%, as nmol/mmol creatinine/24 h 79%, and as nmol/24 h 78%. Similarly, the percentage predictive value of negative tests as indicators of Type 1 diabetes were as follows: fasting C-peptide 86%, stimulated C-peptide 88%, and urinary C-peptide expressed as nmol/l 79%, as nmol· mmol creatinine·24 h 81%, and as nmol/24 h 80%. If patients without detectable C-peptide were excluded, the predictive value of negative tests were as follows: fasting C-peptide 81%, stimulated C-peptide 88%, urinary C-peptide expressed as nmol/l 61%, as nmol/mmol creatinine/24 h 69%, and as nmol/24 h 64%. In conclusion, post glucagon C-peptide gives a good distinction between Type 1 and Type 2 diabetes mellitus in insulin treated diabetes while 24 h urinary C-peptide gives a less sensitive distinction between the clinical types of diabetes.     

The N-terminal domain of the mineralocorticoid receptor modulates both mineralocorticoid receptor- and glucocorticoid receptor-mediated transactivation from Na/K ATPase beta1 target gene promoter

Mineralocorticoid and glucocorticoid hormones activate the expression of the Na/K ATPase β1 through direct binding of the mineralocorticoid receptor (MR) and glucocorticoid receptors (GR) to a mineralocorticoid-and glucocorticoid-responsive element in the β1 promoter region, but activation of the β1 promoter is inhibited by coexpression of both receptors. Here, using a series of mutated and chimeric receptors, we show that the N-terminal region of MR mediates an inhibitory effect on MR and GR activation from the β1 promoter, in CV-1 cells. Deletion of the N-terminal region of MR (1-603) enhanced MR activation four-fold. Activation by chimeric MR, in which the N-terminus of GR replaces the N-terminal region of MR, was threefold that of wild-type MR. In addition, whereas coexpression of wild-type MR and GR was inhibitory, coexpression of chimeric MR and wild-type GR was nearly equal to that of MR. By contrast, mutated GR lacking its N-terminal region (1–420) was less efficient than the wild type in activating this promoter. These results demonstrate that the N-terminal domains of MR and GR have opposite transactivation properties and that MR region 1–603 is indeed inhibitory for both MR- and GR-mediated regulation of the Na/K ATPase β1 gene promoter.     

非胰岛素依赖型糖尿病微量白蛋白尿患者红细胞膜ATPases活力的变化

测定非胰岛素依赖型糖尿病(NIDDM)微量白蛋白尿患者20例及NIDDM无微量白蛋白尿患者20例和正常人20例红细胞膜ATPases活力。结果NIDDM微量白蛋白尿患者Na~+-K+ATPase,Ca~(2+)+ATPase活力明显低于正常人(P分别<0.05及0.001),Mg~(2+)ATPase活力无明显改变(P>0.05).NIDDM无微量白蛋白尿患者Ca~(2+)ATPase活力也低于正常人(P<0.01),但不及微量白蛋白尿组明显;无白蛋白尿组Na~+-K~+ATPase活力虽有下降,但P>0.05,Mg~(2+)ATPese活力无明显变化(P>0.05).     

CC-chemokine receptor CCR5-del32 mutation as a modifying pathogenetic factor in type I diabetes

The purpose of this study was to determine the CCR5-del32 allele frequency in type I (insulin-dependent) and type II (noninsulin-dependent) diabetes patients, and to test whether and how this mutation is associated with both types of diabetes. Thirty-eight type I diabetes and 111 type II diabetes patients' genotyping was performed by polymerase chain reaction assaying, and amplified products were digested with restriction enzyme EcoRI. The results were analyzed using statistical methods. No statistical differences were found in CCR5-del32 allele frequencies in types I and II diabetes patients compared with the control group of native Estonians. However, an association exists between CCR5 gene polymorphism and the clinical course of type I diabetes. In the case of wild-type CCR5, the disease starts at an earlier age. In type II diabetes, there was a difference between genotypes in morbidity to concomitant diseases, being higher in the CCR5 wild-type genotype.     

Frequency of type I and II diabetes in newly diagnosed diabetic patients: Measuring C-Peptide level

AimsDiabetes mellitus is a metabolic disease that manifested as hyperglycemia due to the defect in secretion or function of insulin. This study aimed was to survey about frequency type I and II diabetes in newly diagnosed diabetic patients base on c-peptide and anti-glutamate acid decarboxylase (GAD) tests.Materials & methodsThis study was conducted as a prospective study on 70 diabetic patients aged 15–45 years old who referred to diabetes clinics in Ahvaz city during 2012–2014 and their diabetes was diagnosed for the first time, but their type of diabetes was not clinically definitive. Patients with anti-GAD positive and fasting C-peptide level of less than 0.65 were diagnosed as type I diabetes. Patients with anti-GAD negative fasting C-peptide level of greater than or equal to 0.65 were considered as type II diabetes.ResultsEighty two patients (49 males and 33 females) with a mean age of 21.64 ± 4.36 years (range 15–34) and a mean BMI of 22.05 ± 4.41 kg/m² (range 14–18) were studied. Twenty three patients (28.5%) had type I diabetes and 59 patients (71.95%) had type II diabetes. In patients with type I diabetes, the mean BMI was 24.86 ± 2.36 kg/m² and the number of patients with family history (56.22%) was higher. In type II diabetic patients, the number of women (62.71%) was higher than that of men.ConclusionAnti-GAD test can be used as a predictive test for early diagnosis of disease and screening of people with a diagnosis of diabetes based on the type of diabetes.     

血清抵抗素水平与肥胖及2型糖尿病的关系

目的　研究血清抵抗素水平与肥胖、2型糖尿病 (T2DM )和胰岛素抵抗 (IR)的关系。　方法　用酶免疫测定法检测 31例单纯肥胖、2 7例T2DM及 30名正常人空腹血清抵抗素水平。　结果　单纯肥胖组、T2DM组及正常对照组空腹抵抗素分别为 ( 4 1± 13)、( 4 3± 11)和 ( 5 3± 7) μg/L。单纯肥胖组和T2DM组血清抵抗素浓度均低于正常对照组 (P <0 0 1)。空腹血清抵抗素与体质指数(BMI)、胰岛素抵抗指数 (HOMA IR)分别呈负相关 (r =- 0 2 92及 - 0 319,P <0 0 1) ,与空腹胰岛素、腰围和体脂百分比 (BF % )也呈负相关 (r =- 0 2 5 9,- 0 2 31及 - 0 2 39,P <0 0 5 )。多元逐步回归分析显示 ,HOMA IR为影响抵抗素最为显著的因素 (R2 =0 0 86 )。　结论　肥胖及T2DM患者血清抵抗素水平偏低。血清抵抗素与BMI、体脂百分比、腰围、空腹胰岛素和HOMA IR呈负相关。抵抗素可能在人类IR的发病中起一定的作用     

An association between activity of the Na/K-pump and resistance of Schistosoma mansoni towards complement-mediated killing

The Na/K-pump or Na⁺/K⁺-ATPase (EC 3.6.1.37), couples the hydrolysis of ATP to the active transport of Na⁺ and K⁺ ions across the plasma membrane of virtually all animal cells. The relationship between activity of the Na⁺/K⁺-ATPase and the sensitivity of Schistosoma mansoni to immunological attack has been investigated. It has been observed that ouabain, the specific inhibitor of the pump, via a synergistic effect with specific antibody and complement, affects the average membrane potential causing depolarization and death of complement resistant parasites. Thus, apparently, there is association between the inhibition of the Na/K-pump and the lysis and death of the complement-resistant parasite.     

Proinsulin and C-peptide at onset and during 12 months cyclosporin treatment of Type 1 (insulin-dependent) diabetes mellitus

Summary An increased proinsulin to C-peptide molar ratio at the onset of Type 1 (insulin-dependent) diabetes mellitus has been suggested. We studied fasting proinsulin levels and proinsulin/C-peptide ratios in the newly diagnosed diabetic subjects participating in the Canadian/European placebo controlled cyclosporin study at entry, during the one year treatment period and six months of follow-up. Available entry data from 176 out of the 188 allocated patients were compared to 60 age and weight matched control subjects. Fasting proinsulin was significantly elevated in male patients compared to male control subjects (p<0.01), whereas the levels only tended to be elevated in female patients. The proinsulin/C-peptide ratio was three to fourfold elevated in the diabetic groups of both sexes, (p<0.001). Further, proinsulin and C-peptide were studied in 83 cyclosporin and 86 placebo-treated subjects during the trial and follow-up. An additional increase of proinsulin/C-peptide ratio was observed during the first three months of placebo treatment. It remained constantly high for nine months and then declined to entry level. This pattern was not seen in the cyclosporintreated group, where the ratio was unchanged during the 12 months trial and follow-up. The effect of cyclosporin on the induction of non-insulin requiring remission was unrelated to fasting and glucagon stimulated C-peptide levels at entry, whereas 64% of the cyclosporin-treated against 28% of the placebo-treated subjects (p<0.01) went into remission if the proinsulin/C-peptide ratio at entry was above 0.024. If the ratio was below 0.024 at entry, 42% and 33% went into non-insulin requiring remission, respectively (NS). We conclude that fasting proinsulin to C-peptide molar ratio is elevated at the onset of Type 1 diabetes mellitus. A further plateaushape elevation lasting nine months was seen during the remission period. Cyclosporin seems to inhibit or delay this development. The proinsulin/C-peptide ratio at diagnosis may show to be of value in the prediction of remission during cyclosporin treatment.Prepared by the authors for The Canadian/European Diabetes Study Group.     

Reduction of erythrocyte (Na+-K+)ATPase activity in Type 1 (insulin-dependent) diabetic subjects and its activation by homologous plasma

Summary The (Na⁺-K⁺)ATPase and (Mg²⁺)ATPase activities of erythrocyte membranes of Type 1 (insulin-dependent) diabetic patients were found to be significantly reduced compared to matched controls (p < 0.005). On the contrary, erythrocyte Na⁺ and K⁺ contents were similar in diabetic patients and in normal subjects. When erythrocyte membranes from diabetic patients were incubated with their own plasma, a significant increase was observed in sodium-potassium ATPase activity (p < 0.005), whereas (Mg²⁺)ATPase activity was not affected. The plasma stimulatory effect showed saturation kinetics. Maximum average stimulation was 96% (±21.3). A similar stimulation pattern, although more limited in extent (maximum 48.3 % ± 12.2), was found when erythrocyte membranes from normal subjects were incubated with diabetic plasma. Normal plasma exhibited a modest stimulatory effect on erythrocyte (Na⁺-K⁺ATPase activity. Similar stimulatory effects by diabetic plasma were observed on a (Na⁺-K⁺) ATPase preparation from beef heart. It is proposed that diabetic plasma contains a specific (Na⁺-K⁺)ATPase activator in a higher concentration than normal plasma. This may explain why a normal cellular electrolyte content was found in diabetic erythrocytes in spite of a reduced Na⁺-K⁺ pump activity. Purification experiments indicate that the plasma activator is a protein with a molecular weight greater than 50,000. Both the (Na⁺-K⁺)ATPase activity and the stimulatory effect of diabetic plasma were not influenced by the metabolic control, since they did not correlate significantly with fasting blood glucose and daily insulin dosage. Moreover, no correlation was found with duration of diabetes or age at diagnosis of diabetes. It is suggested that the enzyme defect of erythrocyte membrane and the stimulation of (Na⁺-K⁺)ATPase activity by homologous plasma are early biochemical alterations in the course of diabetes mellitus.     

Parameters associated with residual insulin secretion during the first year of disease in children and adolescents with Type 1 diabetes mellitus

Factors associated with residual insulin secretion and spontaneous remission in Type 1 diabetic patients are important in the evaluation of treatment aimed at modifying the natural history of Type 1 DM. We investigated the effect of parameters at onset on residual beta cell function in 215 Type 1 DM children and adolescents. Blood gas analysis, HLA, GAD and IA-2 antibodies before the start of insulin treatment were recorded for each patient. Residual C-peptide secretion was assessed by the glucagon test, and parameters of metabolic control (HbA_1c and insulin dose U kg⁻¹ day⁻¹) were examined at disease onset and after 3, 6, and 12 months. Residual C-peptide secretion throughout the first year of disease was significantly reduced in patients with disease onset before age 5. Multiple regression analysis showed that low pH at onset showed a significant and independent association with reduced C-peptide at 3 months (p = 0.02) and that the detection of GAD antibodies had a significant independent association with decreased C-peptide secretion at 6 months of follow-up (p = 0.02). Insulin requirement was higher in the youngest patients group and in patients with GAD antibodies. Spontaneous insulin remission (HbA_1c <6 % and insulin <0.3 U kg⁻¹ day⁻¹) occurred in 22/192 (11 %) patients at 3 months of follow-up, in 15/190 (8 %) patients at 6 months and in 8/169 (5 %) patient at 12 months. Remission was more prevalent in older patients (p = 0.01) and in patients without detectable GAD antibodies: (14/64 vs 8/128, p = 0.001). Sex, IA-2 antibodies and HLA DR were not independently associated with C-peptide secretion, insulin requirement or remission in the first year of Type 1 DM. This study confirms the association of young age, severe acidosis at disease onset, and GAD antibodies with decreased residual beta-cell function and spontaneous remission during the first year of insulin treatment. These factors should be considered in trials evaluating therapies to retain beta-cell function and induce remission at and after disease onset. © 1998 John Wiley & Sons, Ltd.     

Glycaemic variability and hypoglycaemia are associated with C-peptide levels in insulin-treated type 2 diabetes

AimThe aim of the study was to evaluate the association between C-peptide levels, glycaemic variability and hypoglycaemia in patients with insulin-treated type 2 diabetes (T2D).MethodsA total of 98 patients with T2D treated with basal-bolus insulin were enrolled in a cross-sectional study. Glycaemic variability and hypoglycaemia were assessed from continuous glucose monitoring (CGM) data recorded over 6 days: Glycemic variability was assessed by calculating the mean coefficient of variation (CV), while hypoglycemia was defined as sensor glucose levels ≤ 3.9 mmol/L or < 3.0 mmol/L. Fasting C-peptide and fasting glucose were measured on day 1.ResultsLow levels of fasting C-peptide correlated with higher CV (r = −0.53, P < 0.0001). In a multivariate regression model with HbA_1c, body mass index, diabetes duration and total daily insulin dose, only C-peptide was significantly associated with CV. Patients with ≥ 1 episode of hypoglycaemia had significantly lower median C-peptide levels than patients without hypoglycaemia (274 (136–620) pmol/L vs. 675 (445–1013) pmol/L, respectively; P = 0.0004). Also, 17 patients clinically diagnosed with T2D had detectable glutamic acid decarboxylase (GAD) antibodies (≥ 5 U/mL). These GAD-positive patients had significantly lower fasting C-peptide, higher CV and greater frequency of hypoglycaemia than GAD-negative patients.ConclusionIn patients with insulin-treated T2D, low levels of C-peptide are associated with greater glycaemic variability and higher risk of hypoglycaemia, suggesting that C-peptide levels should be taken into consideration when optimizing insulin treatment and assessing hypoglycaemia risk.     

2型糖尿病精氨酸刺激后胰岛素原的释放及其与血糖的关系

目的探讨2型糖尿病(T2DM)患者精氨酸刺激后胰岛素原(PI)释放的变化及其与血糖水平的关系。方法选择2001年11月至2003年8月上海交通大学附属第六人民医院的106例T2DM患者及35名正常糖耐量(NGT)健康对照者行精氨酸刺激试验,分析比较精氨酸刺激试验后PI及其增值(ΔPI)和PI/[真胰岛素(TI) PI]的变化。结果(1)T2DM组精氨酸刺激后各时间点PI、PI/(TI PI)值显著高于NGT组(P均<0.01),其PI在2min时达峰值,随后呈逐渐下降趋势。(2)不同空腹血糖(FPG)的T2DM患者各时间点PI、PI/(TI PI)分析显示FPG2组(7mmol/L≤FPG<9mmol/L)和FPG3组(FPG≥9mmol/L)明显高于FPG1组(FPG<7mmol/L,P均<0.05)。结论精氨酸刺激后PI“不成比例”增加是T2DM患者胰岛B细胞功能缺陷的重要表现之一,因此在比较T2DM与NGT人群胰岛B细胞功能时应测定TI以减少PI的干扰。     

The LEW.1AR1/Ztm-iddm rat: a new model of spontaneous insulin-dependent diabetes mellitus

Aims/hypothesis: We describe a new Type I (insulin-dependent) diabetes mellitus rat model (LEW.1AR1/Ztm-iddm) which arose through a spontaneous mutation in a congenic Lewis rat strain with a defined MHC haplotype (RT1.A ^a B/D ^u C ^u ). Methods: The development of diabetes was characterised using biochemical, immunological and morphological methods. Results: Diabetes appeared in the rats with an incidence of 20 % without major sex preference at 58 ± 2 days. The disease was characterised by hyperglycaemia, glycosuria, ketonuria and polyuria. In peripheral blood, the proportion of T lymphocytes was in the normal range expressing the RT6.1 differentiation antigen. Islets were heavily infiltrated with B and T lymphocytes, macrophages and NK cells with beta cells rapidly destroyed through apoptosis in areas of insulitis. Conclusion/interpretation: This Type I diabetic rat develops a spontaneous insulin-dependent autoimmune diabetes through beta cell apoptosis. It could prove to be a valuable new animal model for clarifying the mechanisms involved in the development of autoimmune diabetes. [Diabetologia (2001) 44: 1189–1196] Received: 6 December 2000 and in revised form: 28 May 2001     

C-peptide prevents and improves chronic Type I diabetic polyneuropathy in the BB/Wor rat

Aims/hypothesis. Insulin and C-peptide exert neuroprotective effects and are deficient in Type I (insulin-dependent) diabetes mellitus but not in Type II (non-insulin-dependent) diabetes mellitus. These studies were designed to test the preventive and interventional effects of C-peptide replacement on diabetic polyneuropathy in the Type I diabetic BB/Wor rat. Methods. Diabetic BB/Wor rats were replaced with rat C-peptide from onset of diabetes and between 5 and 8 months of diabetes. They were examined at 2 and 8 months and compared to non-C-peptide replaced BB/Wor rats, Type II diabetic (non-C-peptide deficient) BB/Z rats and non-diabetic control rats. Animals were monitored as to hyperglycaemia and nerve conduction velocity (NCV). Acute changes such as neural Na⁺/K⁺-ATPase and paranodal swelling were examined at 2 months, morphometric and teased fiber analyses were done at 8 months. Results. C-peptide replacement for 2 months in Type I diabetic rats prevented the acute NCV defect by 59 % (p < 0.005), the neural Na⁺/K⁺-ATPase defect by 55 % (p < 0.001) and acute paranodal swelling by 61 % (p < 0.001). Eight months of C-peptide replacement prevented the chronic nerve conduction defect by 71 % (p < 0.001) and totally prevented axoglial dysjunction (p < 0.001) and paranodal demyelination (p < 0.001). C-peptide treatment from 5 to 8 months showed a 13 % (p < 0.05) improvement in NCV, a 33 % (p < 0.05) improvement in axoglial dysjunction, normalization (p < 0.001) of paranodal demyelination, repair of axonal degeneration (p < 0.01), and a fourfold (p < 0.001) increase in nerve fibre regeneration. Conclusion/interpretation. C-peptide replacement of Type I BB/Wor-rats partially prevents acute and chronic metabolic, functional and structural changes that separate Type I diabetic polyneuropathy from its Type II counterpart suggesting that C-peptide deficiency plays a pathogenetic role in Type I diabetic polyneuropathy. [Diabetologia (2001) 44: 889–897]     

The impact of a family history of Type II (non-insulin-dependent) diabetes mellitus on the risk of diabetic nephropathy in patients with Type I (insulin-dependent) diabetes mellitus

Aims/hypothesis. There is substantial evidence for a role of genetic factors in the development of diabetic nephropathy. In Pima Indians, a link between susceptibility to diabetic nephropathy and Type II (non-insulin-dependent) diabetes mellitus has been proposed. In this study, our aim was to examine the association between a family history of Type II diabetes and diabetic nephropathy in patients with Type I (insulin-dependent) diabetes mellitus. Methods. In a cross-sectional case-control study, we assessed the prevalence of Type II diabetes in the parents of 137 Type I diabetic patients with diabetic nephropathy (albuminuria > 300 μg/min in two of three overnight urine collections) compared with the parents of 54 Type I diabetic patients without nephropathy (albuminuria < 20 μg/min). Results. Thirty-four (25 %) of the patients with nephropathy compared with five (9 %) of the patients without nephropathy had a parental history of Type II diabetes (p = 0.019). A parental history of Type II diabetes was associated with a three-fold risk [odds ratio 2.95 (95 % confidence interval: 1.03 to 8.40), p = 0.043] of diabetic nephropathy after adjustment for sex, glycaemic control and family history of hypertension. Furthermore, there was an excess of risk factors for development of Type II diabetes (higher fasting plasma glucose concentrations, higher prevalence of hypertension, higher waist-hip ratio and a tendency towards more glucose intolerance) among previously non-diabetic parents of patients with nephropathy. Conclusion/interpretation. Genetic or environmental factors or both related to familial Type II diabetes increase susceptibility to diabetic nephropathy in patients with Type I diabetes. [Diabetologia (1999) 42: 519–526] Received: 30 September 1998 and in final revised form: 28 December 1998     

Renal and splanchnic exchange of human biosynthetic C-peptide in Type 1 (insulin-dependent) diabetes mellitus

Summary Biosynthetic human C-peptide or NaCl (154 mmol·l^–1) was given intravenously to 13 Type 1 (insulin-dependent) diabetic patients to determine the renal and splanchnic exchange of C-peptide. Catheters were inserted percutaneously into an artery and a renal and hepatic vein. Infusions of C-peptide were given for 60 min at two dose levels (5 and 30 pmol·kg^–1·min^–1). Insulin was infused throughout the study (0.5 mU·kg^–1·min^–1) and plasma glucose was kept constant by a variable glucose infusion. The regional blood flows were measured by indicator dilution techniques. In 11 of the 13 patients basal C-peptide levels were not detectable. The arterial steady-state C-peptide concentration was 0.81±0.10 nmol·l^–1 and 2.33±0.30 nmol·l^–1 at the low and high rate infusions, respectively. Renal uptake was 124±18 pmol·min^–1 at the low infusion corresponding to 39% of the infused amount. At the higher dose C-peptide infusion renal uptake increased to 155±21 pmol·min^–1 (p<0.05). Urinary excretion of C-peptide was 7±2 pmol·min^–1 at the low dose infusion and increased to 34±6 pmol·min^–1 at the high dose infusion (p<0.01). The proportions of infused amount excreted were fairly constant and between 2% and 3%. No net exchange of C-peptide was found across the splanchnic vascular bed. The rate of glucose infusion had to be increased by 35% during the low dose C-peptide, but not during NaCl infusion in order to maintain a constant plasma glucose concentration. Arterial plasma concentrations of noradrenaline increased by 15–25% during both C-peptide and NaCl infusions. It is concluded that in patients with Type 1 diabetes (a) the kidney is the primary site of C-peptide removal, (b) renal metabolism rather than urinary excretion is the dominating process for C-peptide elimination (c) the excreted proportions of an infused amount of C-peptide were fairly constant between 2% and 3% and (d) no hepatic C-peptide catabolism could be detected.