Incidence of childhood diabetes mellitus in Yorkshire, northern England, is associated with nitrate in drinking water: an ecological analysis

Summary The relationship between the incidence of childhood-onset insulin-dependent diabetes mellitus and levels of nitrate in drinking water in the former Yorkshire Regional Health Authority was investigated by means of an ecological analysis. A population-based register contributed 1797 0–16-year-olds diagnosed with diabetes between 1978 and 1994. Nitrate data were based on 9330 samples of drinking water tested between 1990 and 1995 in 148 water supply zones, for which 1991 census small area statistics were taken on population density, ethnicity and socio-economic status. Diabetes incidence was positively associated with raised mean nitrate levels with a standardised incidence ratio of 115 in zones with greater than 14.85 mg · l^–1 (χ² = 26.81, 1 df, p < 0.001). Significant negative trends were found between standardised incidence ratios and proportion of non-whites in the population (χ² = 33.57, 1 df, p < 0.001), childhood population density (χ² = 30.81, 1 df, p < 0.001) and the Townsend deprivation score (χ² = 33.89, 1 df, p < 0.001). Poisson regression modelling, adjusting for the other factors, showed a significant increase in relative incidence rate ratio from a baseline of 1 at nitrate levels below 3.22 mg · l^–1 to 1.27 (95 % confidence interval 1.09,1.48) for mean nitrate levels above 14.85 mg · l^–1. An association between higher nitrate levels in domestic drinking water and incidence of childhood diabetes has been demonstrated. This was not explained by the ethnic composition of the population, population density or socioeconomic status. Nitrate in drinking water may be a precursor of chemicals which are toxic to the pancreas. [Diabetologia (1997) 40: 550–556] Received: 24 October 1996 and in revised form: 20 December 1996     

AUGMENTED ENDOGENOUS NITRIC OXIDE PRODUCTION IN PARTIAL PORTAL VEIN-LIGATED RATS

1. Endothelium-derived nitric oxide (NO) is a potent vasodilator. Because the body oxidizes it to nitrate ions, NO₃-, measurement of the serum concentration and the urinary excretion of NO₃- may be an index for endogenous NO. We investigated the role of NO on hyperdynamic circulation in cirrhotic and partial portal vein-ligated rats by measuring NO₃. 2. Liver cirrhosis was induced by administration of thioacetamide. Systemic and splanchnic haemodynamics and splenic-systemic shunting were determined by tracer microspheres. The concentration of NO₃- was measured by using high-performance liquid chromatography with an anion-column. 3. We found that systemic and splanchnic hyperdynamic circulation existed to almost the same extent in cirrhotic and in portal vein-ligated rats as compared to the controls and sham-operated rats, respectively. Splenic-systemic shunting was markedly greater in portal vein-ligated rats than in cirrhotic rats. 4. Serum NO₃- levels and urinary excretion of NO₃- in cirrhotic rats tended to increase as compared to the controls. On the other hand, the levels in portal vein-ligated rats were significantly increased as compared to those of the sham-operated rats, and were significantly and negatively correlated to the splanchnic arterial resistance and total vascular resistance. The amount of urinary excretion of NO₃- significantly correlated to splenic-systemic shunting (r = 0.61, P<0.05) only in portal vein-ligated rats. 5. We suggest that these high levels of NO₃- in portal vein-ligated rats relate to the extensive formation of porto-collateral vasculature or acute changes in systemic and splanchnic haemodynamics due to portal vein-ligation.     

Use of gene chip technology for the characterisation of the regulation of renal transport processes and of nephrotoxicity in rats

Gene expression profiling using microarrays (rat-specific array RG-U34A, Affymetrix, U.S.A.) was employed for the investigation of: (1) hormonal regulation of renal function and (2) nephrotoxicity. For this purpose about 8,800 genes were analysed in kidney and, additionally, in liver tissue.

Ad 1.) Kidney functions develop during postnatal life. Thus, in vivo transport and accumulation of p-aminohippurate (PAH) was investigated on renal cortical slices (RCS) from 10- and 55-day-old rats. The animals were treated with dexamethasone (DEXA; 60 μg/100 g b.wt./day) for 3 days, which caused a significant reduction in the accumulation of PAH in 10-day-old rats (42 ± 5% whereas it was only slightly reduced in 55-day-old rats (70 ± 8%). To further clarify the regulation of renal function by DEXA, results were compared with those obtained previously after in vitro stimulation with DEXA. RCS were incubated for 24 hours in DEXA-containing medium (10⁻⁹ M). Under these conditions DEXA significantly increased the PAH uptake capacity in RCS obtained from 10- and 55-day-old rats up to 126 and 136%, respectively. Thus a stimulation of tubular transport capacity is possible in vitro. The effect of DEXA treatment on the gene expression of the kidney (in vivo) was moderate. Focussing especially on transporters, ion channels, ATPases, glucuronyltransferases, glutathione-S-transferase and cytochrome P450, the expression of only few genes were significantly changed (3 to 50-fold up- or down-regulation). Moreover, distinct age differences were found after in vivo administration of DEXA. The investigation of in vitro effects of DEXA is currently been performed.

Ad 2.) The kidney is threatened by nephrotoxins because of its ability to accumulate them. We used a single administration of uranyl nitrate (UN; 0.5 mg/100 g b.wt.) as a model for chronic renal failure (CRF). Clearance experiments were performed 10 weeks after UN administration (maximal symptoms of CRF) in adult female rats. As expected, UN induced interstitial cicatrices with reduced GFR and diminished PAH transport capacity. Despite the impressive morphological and functional changes in the kidney after exposure to UN, the gene expression profiles in the kidneys were only minimally affected: we found significantly changed expression levels for only 20 genes (5 genes were up-regulated [e.g. transgelin], 15 down-regulated [among these the Na-K-Cl-symporter, insulin-like growth factor, kallikrein, and ornithine decarboxylase). The lack of agreement between gene expression data and the nephrotoxic effects of UN can probably be explained by the long time interval between dosing and the assessment of the effect. The results confirm that primary genomic responses are likely to be strongest transiently after exposure and then decrease in intensity.     

选择性破坏胰岛A细胞的大鼠空肠肌间神经丛胆碱能末梢VAChT的定量研究

目的　探讨胰岛A细胞与肠胆碱能神经的关系。方法　采用免疫组化SP方法检测硝酸钴选择性破坏胰岛A细胞的大鼠空肠肌间神经丛胆碱能末梢VAChT阳性反应物的变化 (注钴后 1,2 ,3,4,6 ,10d) ,并进行显微图象定量分析。结果　注钴后 2d开始 ,VAChT阳性反应物显著减少 (P <0 0 5 ) ;尤以 3,4d后最为显著 (P <0 0 1) ,10天后恢复。结论　胰岛A细胞可能参与肠胆碱能神经的功能调节     

Type 2 nitric oxide synthase and protein nitration in chronic lung infection

Inflammation in the lung can lead to increased expression of inducible nitric oxide synthase (iNOS) and enhanced NO production. It has been postulated that the resultant highly reactive NO metabolites may have an important role in host defence, although they might also contribute to tissue damage. However, in a number of inflammatory lung diseases, including bronchiectasis, iNOS expression is increased but no elevation of airway NO can be detected. A potential explanation for this finding is that NO is rapidly scavenged by reaction with superoxide radicals, forming peroxynitrite, which is preferentially metabolized via nitration and nitrosation reactions. To test this hypothesis, anaesthetized, specific pathogen-free rats were inoculated with Pseudomonas aeruginosa incorporated into agar beads (chronically infected group) or sterile agar beads (control group). Ten to 15 days later, the lungs were isolated and fixed. Pseudomonas organisms were isolated from the lungs of the chronically infected group. These lungs showed extensive inflammatory cell infiltration and tissue damage, which were not observed in control lungs. Expression of iNOS was increased in the chronically infected group when compared with the control group. However, the mean number of cells staining for nitrotyrosine in the chronically infected group was not significantly different from that in the controls, nor was there an excess of nitrotyrosine, nitrate, nitrite or nitrosothiol concentrations in the infected lungs. Thus, no evidence was found of increased NO metabolites in chronically infected lungs, including products of the peroxynitrite pathway. These findings suggest that chronic infection does not cause increased iNOS activity in the lung, despite increased expression of iNOS.     

Acceptability and Feasibility of a 13-Week Pilot Randomised Controlled Trial Testing the Effects of Incremental Doses of Beetroot Juice in Overweight and Obese Older Adults

Nitrate-rich food can increase nitric oxide production and improve vascular and brain functions. This study examines the feasibility of a randomised controlled trial (RCT) testing the effects of prolonged consumption of different doses of dietary nitrate (NO₃⁻) in the form of beetroot juice (BJ) in overweight and obese older participants. A single-blind, four-arm parallel pilot RCT was conducted in 62 overweight and obese (30.4 ± 4 kg/m²) older participants (mean ± standard deviation (SD), 66 ± 4 years). Participants were randomized to: (1) high-NO₃⁻ (HN: 2 × 70 mL BJ/day) (2) medium-NO₃⁻ (MN: 70 mL BJ/day), (3) low-NO₃⁻ (LN: 70 mL BJ on alternate days) or (4) Placebo (PL: 70 mL of NO₃⁻-depleted BJ on alternate days), for 13 weeks. Compliance was checked by a daily log of consumed BJ, NO₃⁻ intake, and by measuring NO₃⁻ and NO₂⁻ concentrations in plasma, saliva, and urine samples. Fifty participants completed the study. Self-reported compliance to the interventions was >90%. There were significant positive linear relationships between NO₃⁻ dose and the increase in plasma and urinary NO₃⁻ concentration (R² = 0.71, p < 0.001 and R² = 0.46 p < 0.001, respectively), but relationships between NO₃⁻ dose and changes in salivary NO₃⁻ and NO₂⁻ were non-linear (R² = 0.35, p = 0.002 and R² = 0.23, p = 0.007, respectively). The results confirm the feasibility of prolonged BJ supplementation in older overweight and obese adults.     

急性低压缺氧暴露后血脑屏障通透性的变化及其意义

目的：观察在急性低压缺氧条件下,大鼠血脑屏障通秀性的变化特点,为阐明低压缺氧作用下脑功能障碍的可能机理及临床上特殊病例治疗方案的确定提供生理学依据。方法：选择在雄性SD大鼠12只,随机分为对照组、5000m急性低压缺氧暴露组。实验组动物于低压舱内,以20m/s的速率上升,至5000m,停留5hm,而后以20m/s的速率下降至地面;出舱后立即经心脏灌注硝酸镧固定液,开颅取脑,制成切片,置透射电镜下观察。结果：急性低压缺氧暴露5h后即刻,即可见镧颗粒通过大鼠脑皮质的毛细血管内皮细胞膜,沉积于毛细血管内皮细胞浆内、细胞核膜上以及血管周围,弥漫性地分布于脑间质细胞间隙,并附着于神经细胞膜上,而对照组大鼠,镧颗粒仅滞留于大脑皮层的毛细血管腔内。结论：5000m以上低压缺氧连续暴露5h,可引起大鼠血脑屏障通透性增加。这可能在低压缺氧导致脑水肿的发生以及脑功能障碍的过程中起重要作用,对确定临床上特殊病例的治疗也有一定参考价值。     

Nerve-induced release of nitric oxide in the rabbit gastrointestinal tract as measured by in vivo microdialysis

1. Nitric oxide (NO) has been suggested as a gastrointestinal neurotransmitter, mediating the gastric receptive relaxation and the relaxation in the peristaltic reflex. The aim of the present study was to measure nerve-induced NO formation in vivo in the gastrointestinal tract.
2. Formation of the nitric oxide oxidation products nitrite and nitrate during vagal nerve stimulation were measured in the anaesthetized rabbit. Microdialysis probes were inserted into the wall of the stomach and proximal colon, and nitrite and nitrate in dialysate measured by capillary electrophoresis.
3. During bilateral vagal nerve stimulation there was an increase in nitrite and nitrate formation at the level of the stomach and in nitrite formation at the level of the colon. This increase was inhibited by intravenous administration of the NO synthase inhibitor N^ω-nitro-L-arginine methyl ester (L-NAME 30 mg kg⁻¹). Furthermore, L-NAME significantly increased nerve-induced gastric and colonic contractions, as well as spontaneous colonic contractions.
4. In summary, we present a new methodological procedure for quantification of small changes in nitric oxide formation in vivo. This study provides evidence that nitric oxide is released in the stomach and colonic wall during vagal nerve activity, at concentrations able to cause inhibition of smooth muscle contractions in vivo.

     

Application of Pharmacodynamic Modeling for Designing Time-Variant Dosing Regimens to Overcome Nitroglycerin Tolerance in Experimental Heart Failure

Purpose. Prolonged continuous administration of nitroglycerin (NTG) leads to hemodynamic tolerance. We used a previously developed pharmacokinetic-pharmacodynamic (PK/PD) model of NTG tolerance in experimental heart failure to test whether dosage regimens, designed from this model, may allow avoidance of tolerance development upon continuous NTG inftision. Methods. Simulation experiments (using ADAPT II) were performed to evolve a time-variant infusion regimen that would theoretically provide sustained hemodynamic effect (30% reduction in left ventricular end-diastolic pressure, LVEDP) throughout 10 hours of drug dosing. A computer controlled infusion pump was utilized to deliver this time-variant input. Infusion experiments were then conducted in CHF rats to challenge the predictability of the applied PK/PD model. Results. Simulations showed that exponentially increasing input functions provided more sustained LVEDP effects when compared to linear or hyperbolic input functions delivering the same total NTG dose. A computer-selected infusion regimen of 6.56e^{0.00156×minutes} g/min was anticipated to provide the desired hemodynamic profile in our animal model. Experiments conducted in rats with congestive heart failure (n = 4) confirmed the prediction of sustained hemodynamic effect without tolerance (28 ± 4% reduction in LVEDP at 10 hrs). Conclusions. These findings support the utility of our PK/PD model of NTG tolerance in predicting NTG action, and serve as an example of therapeutic optimization through PK/PD considerations.