Melamine, powdered milk, and nephrolithiasis in Chinese infants

Non-targeted detection of food adulteration using an ensemble machine-learning model

Recurrent incidents of economically motivated adulteration have long-lasting and devastating effects on public health, economy, and society. With the current food authentication methods being target-oriented, the lack of an effective methodology to detect unencountered adulterants can lead to the next melamine-like outbreak. In this study, an ensemble machine-learning model that can help detect unprecedented adulteration without looking for specific substances, that is, in a non-targeted approach, is proposed. Using raw milk as an example, the proposed model achieved an accuracy and F1 score of 0.9924 and 0. 0.9913, respectively, when the same type of adulterants was presented in the training data. Cross-validation with spiked contaminants not routinely tested in the food industry and blinded from the training data provided an F1 score of 0.8657. This is the first study that demonstrates the feasibility of non-targeted detection with no a priori knowledge of the presence of certain adulterants using data from standard industrial testing as input. By uncovering discriminative profiling patterns, the ensemble machine-learning model can monitor and flag suspicious samples; this technique can potentially be extended to other food commodities and thus become an important contributor to public food safety.

Prenatal cyanuric acid exposure depresses hippocampal synaptic plasticity and induces spatial learning and memory deficits

The infant and fetus may be exposed to cyanuric acid (CA) via several different routes into the diet or milk product as well as deliberate contamination. Previous findings indicated chronic CA treatment caused neurotransmission and synaptic impairment in the early developing hippocampus. This study was designed to characterize the effects of different doses (10 mg/kg, 20 mg/kg and 40 mg/kg) of CA exposure on the developing fetus. Pregnant rats were intraperitoneally exposed to CA during the entire period of gestation and male offspring were selected for water maze task, neural recording and N-methyl-d-aspartate (NMDA) receptor detection around the eighth postnatal week. We found that CA exposure impaired the learning and memory function in a dose-dependent manner. The paired-pulse ratio (PPR) and GluN2A-dependent long-term potentiation (LTP) at the Schaffer collateral-CA1 pathway were affected in CA-exposed rats. Remarkably, hippocampal levels of NMDA-GluN2A, but not NMDA-GluN2B, were significantly decreased. Meanwhile, the spine density of hippocampal CA1 neurons was not altered by the CA exposure. Our findings are consistent with the hypothesis that CA treatment during the prenatal period produces deficits in spatial cognition by disrupting hippocampal synaptic function.

Urolithiasis in children and exposure to melamine: A review of the epidemiological literature

Melamine (ME) is a high production volume compound, mainly used for the synthesis of ME-formaldehyde resins. There is an extensive toxicological and epidemiological database on this compound, but the epidemiology has so far not been reviewed. An extensive literature search in PubMed was conducted and relevant ME epidemiology studies were identified and assessed. The epidemiology data nearly entirely consisted of studies on the health effects due to the food tampering catastrophe in China discovered in 2008 where ME was intentionally added to powdered milk products. Most of these studies were aimed at assessing the extent of the catastrophe and the clinical follow-up of affected children. A reliable dose–response relationship could not be derived from the epidemiology studies. However, they do contain several strong data points that can assist in ranging the No Observed Adverse Effect Level (NOAEL) for humans, for children in particular.

Protean and intangible manifestation of renal stones in children

In the last decade, renal stones are being diagnosed more frequently in children across the globe. Children with renal stone often present with non-specific and subtle symptoms. Diagnosis of urolithiasis in children therefore requires a high index of suspicion especially for those living in endemic regions and with a positive family history. Additionally, management requires judicious use of radiological imaging by treating physicians.

Analysis of trace amounts of adulterants found in powders/supplements utilizing Raman spectroscopy coupled to direct analyte-probed nanoextraction-nanospray ionization-mass spectrometry

In the United States, all food products have to be regulated to inform the consumers of the ingredients contained within. Some ingredients are not included on the label and yet are still found in the products. Presented is a Raman imaging technique for rapid, nondestructive, and spatially relevant localization of adulterants in powders. Raman spectroscopy followed by direct analyte-probed nanoextraction coupled to nanospray ionization-mass spectrometry allows rapid determination of the presence of each adulterant, leading to positive identifications such as melamine. The location and identification of these trace particles can then be extracted using a nanomanipulator. The nanomanipulation technique uses a solvent filled capillary tip which can be positioned on the particle of interest. Direct mass spectrometric analysis via nanospray of the particulate of interest eliminates time consuming chromatographic techniques prior to mass spectrometry analysis. This coupled technique combines rapid Raman spectroscopy techniques with direct mass spectrometry to confirm the presence of an adulterant. This technique was applied to an FDA supplied test sample, in which sibutramine, phenolphthalein, and melamine were confirmed to be present.

Krüppel-like factor 5 associates with melamine-cyanurate crystal-induced nephritis in rats

BACKGROUND

Melamine and cyanuric acid (M/CA), when orally administered together to rats, can induce crystal formation within renal tubules and cause acute kidney injury.

METHODS

To investigate the pathomechanism of crystal-induced nephritis, melamine and/or cyanuric acid were administered to 3-week-old (young) and 8-week-old (adult) rats, respectively.

RESULTS

Crystal formation, blood urea nitrogen elevation, tubular cell injury and macrophage infiltration were noted in rats fed with M/CA, but not in rats fed with vehicle, melamine or CA alone. These parameters were significantly higher in young rats than those in adult rats fed with M/CA 200 mg/kg body weight (BW) for 3 days. Krüppel-like factor 5 (KLF5) was expressed on distal tubule cells, especially when crystals deposited within the lumens. Both mRNA and protein levels were higher in young rats than those in adult rats fed with M/CA (200 mg/kg BW). KLF5 expression has been shown to modulate renal tissue cytokine production, and we found that proinflammatory cytokines like monocyte chemoattractant protein-1 and interlukin-6 were increased in kidney tissues of young rats fed with M/CA for 3 days. In contrast, interlukin-10, an anti-inflammatory cytokine, was upregulated in kidneys of adult rats fed with M/CA for 3 days.

CONCLUSIONS

Crystals are prone to deposition in distal tubules of young rats fed with M/CA. M/CA Crystal-related nephritis might be induced by the KLF5 expression, which modulated macrophage recruitment and proinflammatory cytokine production, subsequently leading to renal tubular injury and interstitial inflammation.

Clinical observation of childhood urinary stones induced by melamine-tainted infant formula in Anhui province, China

INTRODUCTION

The current report detailed an investigation of melamine-linked urinary stones in children exposed to contaminated formula.

MATERIAL AND METHODS

A total of 1062 children fed with melamine-contaminated infant formula were screened for urinary stones. Sixty healthy children without melamine exposure were recruited as a control group. Ultrasonography of the urinary tract system was performed. Urinalysis, renal function, liver status, and serum electrolytes were determined.

RESULTS

We encountered 49 affected children from the 1062 screened ones, at a rate of 4.6% per ultrasound performed. Thirty-two were male, and 17 were female. The affected children ranged in age from 1 month to 96 months, with a mean of 25 months. Duration of exposure was from 1.3 months to 84 months, with a mean of 19.5 months. The melamine contents in serum were between 12 mg/kg and 2563 mg/kg, with mean concentration of 1295.3 mg/kg. Most affected children were asymptomatic with no urinary findings. Patients with urinary stones exhibited lower urine pH and serum HCO3 (-) than those in the healthy children, whereas for serum uric acid, alanine aminotransferase, aspartate aminotransferase, and anion gap the opposite trends were observed. The stone diameter ranged from 2 mm to 18 mm with a median of 6.5 mm. Multiple stones were noted in all patients. After 1 week of conservative management, stone diameters of 38 cases (77.6%) were significantly decreased. Among them, urinary stones were discharged completely in 21 affected children (42.9%).

CONCLUSIONS

The short-term outcome of melamine-linked urinary stones is satisfactory.

Inhibition of heme peroxidases by melamine

In 2008 melamine-contaminated infant formula and dairy products in China led to over 50,000 hospitalizations of children due to renal injuries. In North America during 2007 and in Asia during 2004, melamine-contaminated pet food products resulted in numerous pet deaths due to renal failure. Animal studies have confirmed the potent renal toxicity of melamine combined with cyanuric acid. We showed previously that the solubility of melamine cyanurate is low at physiologic pH and ionic strength, provoking us to speculate how toxic levels of these compounds could be transported through the circulation without crystallizing until passing into the renal filtrate. We hypothesized that melamine might be sequestered by heme proteins, which could interfere with heme enzyme activity. Four heme peroxidase enzymes were selected for study: horseradish peroxidase (HRP), lactoperoxidase (LPO), and cyclooxygenase-1 and -2 (COX-1 and -2). Melamine exhibited noncompetitive inhibition of HRP (K_i  9.5 ± 0.7 mM), and LPO showed a mixed model of inhibition (K_i  14.5 ± 4.7 mM). The inhibition of HRP and LPO was confirmed using a chemiluminescent peroxidase assay. Melamine also exhibited COX-1 inhibition, but inhibition of COX-2 was not detected. Thus, our results demonstrate that melamine inhibits the activity of three heme peroxidases.

Nutritional chemoprevention of urinary tract tumors (UTT) induced by lithogenic agents: risk for UTT in children exposed to melamine-contaminated milk formulas

Urinary tract tumors are tenth in frequency, and many environmental carcinogens are excreted by urine. Interplay between chronic inflammatory urolithiasis and urothelial carcinogenesis is not well understood. Experimental evidences show that dietary melamine induce these events even at low concentrations. This is important because thousands of children were exposed to melamine through intentionally contaminated milk formula worldwide. We propose that an increased risk for urinary tumors in adult life may occur and screenings for early urinary signs may be necessary. Therefore, urothelial biology, melamine carcinogenic potential, and related epidemiology are discussed, recommending a preventive dietary polyunsaturated fatty acid-based supplementation, since they modulate such interplay in rodents.

Food safety and security: what were favourite topics for research in the last decade?

The world is faced with the challenge to feed an estimated 9 billion population of the Earth by 2050. To address the scientific evidence for the safety of food, I searched the Web of Science bibliographical and citation database for most cited articles from this research area. The topics with greatest impact on the research community, judged by their annual rate of citations during the last decade, were food-borne pathogens and toxins, with emerging genetic studies and new methods of visualising toxins on surfaces. Epidemiological and survey studies demonstrated that there was systematic effort to document, rapidly detect and control epidemic spread of disease and that these measures decreased the threat to food safety in developed countries, but that there is still much room for improvement. Research relevant for developing countries included the potential molecular targets to alleviate accumulation of arsenic in rice. As in other areas of research and life, human factor seems to be the most important one for the safety of food. The five keys to safer food of the WHO - keep clean, separate raw and cooked, cook thoroughly, keep food at safe temperatures, use safe water and raw materials - are thus still very relevant for the developed as much as the developing world.

Assessment of melamine contamination in crop, soil and water in China and risks of melamine accumulation in animal tissues and products

The scandal of melamine-adulterated infant formula in China in September 2008 demanded the need to assess the extent of melamine contamination in the environment and food products and possible risks of consuming melamine-contaminated diets. In this work, our extensive work tested water, soil and crop samples from 21 provinces in China. Soils nearby and waste waters from melamine-manufacturing factories were examined, and the highest melamine concentrations in waste water and soil samples were 226.766 and 41.136 mg/kg, respectively. Six of 94 irrigation water samples had melamine at a concentration of 21-198 microg/L. Only 1 sample collected from 124 farmlands farther than 150 km from melamine factories was detected for melamine at a content of 176 microg/L. Only 3 out of 557 crop samples contaminated more than 1mg/kg melamine, with the highest level of 2.05 mg/kg in a wheat sample. When basal diets contained 2mg/kg melamine were fed to various animals, deposition of melamine in animal tissues and products was all lower than 122 microg/kg. The melamine deposition was much higher (e.g., 4483 microg/kg in the kidney of chicken) when diets contained 100 mg/kg melamine but was found to be completely depleted after 96 h for all animals after switching to the basal diets. Our work may be valuable to regulate melamine production and monitor the safety of food and animal products.

Identification of melamine/cyanuric acid-containing nephrolithiasis by infrared spectroscopy

Melamine-contaminated milk formula caused infant nephrolithiasis in some areas of China. Its combination with cyanuric acid causes crystallization in renal tubules. Following this renal damage and even renal failure that require long-term hemodialysis has been reported. Therefore, correct and timely diagnosis of these complex diseases is critical. Melamine containing stone is a combination of equal molar ratios of common stone compositions that has been reported from previous animal studies. We have previously identified the compositions of urinary tract stones with infrared (IR) spectroscopy. We hypothesized that the absorbance of wavelength of IR can identify melamine/cyanuric acid in the presence of mixing human stone compositions. In this study, we made an artificial stone composition and examine under IR absorbance by mixing equal molar ratios of melamine/cyanuric acid with different types of human urinary stones, and established a reference of IR analysis for the identification of melamine/cyanuric acid-containing human urinary tract stones. Knowledge of the precise stone composition allowed institution of appropriate prophylactic dietary and medical therapy and this may help in the prevention of urinary stone recurrence. The results are promising that melamine and cyanuric acid can be identified clearly in a low percentile (approximately 1%) of stone mixture pellet. Therefore, IR seems to be an ideal tool for the identification of melamine/cyanuric acid-containing stones.

The risk of melamine-induced nephrolithiasis in young children starts at a lower intake level than recommended by the WHO

We investigated 683 children with nephrolithiasis and 6,498 children without nephrolithiasis aged <3 years. Nephrolithiasis was diagnosed by renal ultrasonography in hospitals in Beijing in September/October 2008. In addition, data was collected on current and past formula feeding and on other possible risk factors for nephrolithiasis. Daily intake of melamine per kilogram of body weight was calculated for each individual. In general, the adjusted odds ratios between melamine dose and nephrolithiasis increased with an increasing daily level of melamine intake per kilogram of body weight. The risk of nephrolithiasis also increased with the increasing duration of exposure. Preterm infants, urinary malformation, and parents with a history of urinary stones were independent risk factors. In children exposed to melamine levels <0.2 mg/kg per day, the adjusted odds ratio expressing the risk for nephrolithiasis was still 1.7 times higher than in those without melamine exposure. These findings suggest that the risk of melamine-induced nephrolithiasis in young children starts at a lower intake level than the levels recommended by the World Health Organization.

LC-MS/MS method for the determination of melamine in rat plasma: toxicokinetic study in Sprague-Dawley rats

Most recently, melamine has raised international concern for its catastrophic health effects stemming from tainted infant formula. So far there is limited information concerning the pharmacokinetics of melamine in mammals. The present report concerns the development and validation of a sensitive HPLC-ESI-MS/MS method for the pharmacokinetic study of melamine in rat. The method employed a simple liquid-liquid extraction process for plasma sample cleanup, and the extraction recoveries of melamine from plasma were consistent at different concentrations. There was a linear relationship between chromatographic area and concentration over the range of 10-5000 ng/mL for melamine in plasma (R = 0.995). In this work, for the first time, melamine was administered intravenously and orally to Sprague-Dawley rats and the pharmacokinetic characteristics of this contaminant were investigated. The mean values of major pharmacokinetic parameters of oral availability, the mean steady-state distribution volume (V(ss)), clearance, and plasma elimination half-life (T(1/2)) of melamine in Sprague-Dawley rats were 72.9 +/- 13.2%, 102.5 +/- 12.5 mL/kg, 20.1 +/- 3.8 mL/h/kg, and 4.9 +/- 0.5 h, respectively. The rats pharmacokinetic study results suggested that melamine was predominantly restricted to blood or extracellular fluid and is not extensively distributed to most organ tissues. Meanwhile, melamine should be primarily eliminated by renal filtration for rats and does not undergo significant metabolism. These data should be useful to regulatory for risk assessment.