Protein quality as a complementary functional unit in life cycle assessment (LCA).

Goal and theoretical commentary: A number of recent life cycle assessment (LCA) studies have concluded that animal-sourced foods should be restricted-or even avoided-within the human diet due to their relatively high environmental impacts (particularly those from ruminants) compared with other protein-rich foods (mainly protein-rich plant foods). From a nutritional point of view, however, issues such as broad nutrient bioavailability, amino acid balances, digestibility and even non-protein nutrient density (e.g., micronutrients) need to be accounted for before making such recommendations to the global population. This is especially important given the contribution of animal sourced foods to nutrient adequacy in the global South and vulnerable populations of high-income countries (e.g., children, women of reproductive age and elderly). Often, however, LCAs simplify this reality by using 'protein' as a functional unit in their models and basing their analyses on generic nutritional requirements. Even if a 'nutritional functional unit' (nFU) is utilised, it is unlikely to consider the complexities of amino acid composition and subsequent protein accretion. The discussion herein focuses on nutritional LCA (nLCA), particularly on the usefulness of nFUs such as 'protein,' and whether protein quality should be considered when adopting the nutrient as an (n)FU. Further, a novel and informative case study is provided to demonstrate the strengths and weaknesses of protein-quality adjustment. Case study methods: To complement current discussions, we present an exploratory virtual experiment to determine how Digestible Indispensable Amino Acid Scores (DIAAS) might play a role in nLCA development by correcting for amino acid quality and digestibility. DIAAS is a scoring mechanism which considers the limiting indispensable amino acids (IAAs) within an IAA balance of a given food (or meal) and provides a percentage contribution relative to recommended daily intakes for IAA and subsequent protein anabolism; for clarity, we focus only on single food items (4 × animal-based products and 4 × plant-based products) in the current case exemplar. Further, we take beef as a sensitivity analysis example (which we particularly recommend when considering IAA complementarity at the meal-level) to elucidate how various cuts of the same intermediary product could affect the interpretation of nLCA results of the end-product(s). Recommendations: First, we provide a list of suggestions which are intended to (a) assist with deciding whether protein-quality correction is necessary for a specific research question and (b) acknowledge additional uncertainties by providing mitigating opportunities to avoid misinterpretation (or worse, dis-interpretation) of protein-focused nLCA studies. We conclude that as relevant (primary) data availability from supply chain 'gatekeepers' (e.g., international agri-food distributors and processors) becomes more prevalent, detailed consideration of IAA provision of contrasting protein sources needs to be acknowledged-ideally quantitatively with DIAAS being one example-in nLCA studies utilising protein as a nFU. We also contend that future nLCA studies should discuss the complementarity of amino acid balances at the meal-level, as a minimum, rather than the product level when assessing protein metabolic responses of consumers. Additionally, a broader set of nutrients should ideally be included when evaluating "protein-rich foods" which provide nutrients that extend beyond amino acids, which is of particular importance when exploring dietary-level nLCA.

Ameloblasts express type I collagen during amelogenesis.

Enamel and enameloid, the highly mineralized tooth-covering tissues in living vertebrates, are different in their matrix composition. Enamel, a unique product of ameloblasts, principally contains enamel matrix proteins (EMPs), while enameloid possesses collagen fibrils and probably receives contributions from both odontoblasts and ameloblasts. Here we focused on type I collagen (COL1A1) and amelogenin (AMEL) gene expression during enameloid and enamel formation throughout ontogeny in the caudate amphibian, Pleurodeles waltl. In this model, pre-metamorphic teeth possess enameloid and enamel, while post-metamorphic teeth possess enamel only. In first-generation teeth, qPCR and in situ hybridization (ISH) on sections revealed that ameloblasts weakly expressed AMEL during late-stage enameloid formation, while expression strongly increased during enamel deposition. Using ISH, we identified COL1A1 transcripts in ameloblasts and odontoblasts during enameloid formation. COL1A1 expression in ameloblasts gradually decreased and was no longer detected after metamorphosis. The transition from enameloid-rich to enamel-rich teeth could be related to a switch in ameloblast activity from COL1A1 to AMEL synthesis. P. waltl therefore appears to be an appropriate animal model for the study of the processes involved during enameloid-to-enamel transition, especially because similar events probably occurred in various lineages during vertebrate evolution.

Dental caries and enamelin haplotype.

In the literature, the enamelin gene ENAM has been repeatedly designated as a possible candidate for caries susceptibility. Here, we checked whether ENAM variants could increase caries susceptibility. To this aim, we sequenced coding exons and exon-intron boundaries of ENAM in 250 children with a severe caries phenotype and in 149 caries-free patients from 9 French hospital groups. In total, 23 single-nucleotide polymorphisms (SNPs) were found, but none appeared to be responsible for a direct change of ENAM function. Six SNPs had a high minor allele frequency (MAF) and 6 others were identified for the first time. Statistical and evolutionary analyses showed that none of these SNPs was associated with caries susceptibility or caries protection when studied separately and challenged with environmental factors. However, haplotype interaction analysis showed that the presence, in a same variant, of 2 exonic SNPs (rs7671281 and rs3796704; MAF 0.12 and 0.10, respectively), both changing an amino acid in the protein region encoded by exon 10 (p.I648T and p.R763Q, respectively), increased caries susceptibility 2.66-fold independent of the environmental risk factors. These findings support ENAM as a gene candidate for caries susceptibility in the studied population.

Common SNPs of AmelogeninX (AMELX) and dental caries susceptibility.

Genetic approaches have shown that several genes could modify caries susceptibility; AmelogeninX (AMELX) has been repeatedly designated. Here, we hypothesized that AMELX mutations resulting in discrete changes of enamel microstructure may be found in children with a severe caries phenotype. In parallel, possible AMELX mutations that could explain resistance to caries may be found in caries-free patients. In this study, coding exons of AMELX and exon-intron boundaries were sequenced in 399 individuals with extensive caries (250) or caries-free (149) individuals from nine French hospital groups. No mutation responsible for a direct change of amelogenin function was identified. Seven single-nucleotide polymorphisms (SNPs) were found, 3 presenting a high allele frequency, and 1 being detected for the first time. Three SNPs were located in coding regions, 2 of them being non-synonymous. Both evolutionary and statistical analyses showed that none of these SNPs was associated with caries susceptibility, suggesting that AMELX is not a gene candidate in our studied population.

[Child dental care: what's about parental presence?]. / Présence des parents au cours des soins dentaires.

The coping capacity of the children during dental care depends on different factors such as age, cognitive development, personal history and social background. A good knowledge and understanding of child developmental stages will help the dentist to treat them successfully. Parental presence during treatment has been largely discussed in pediatrics and pediatric dentistry. Dentists often let parents stay in the office during the first consultation but prefer them to be in the waiting room during treatment. Depending on the case, parental presence may be needed, essential, or advised against. Parental presence during child treatment must be analyzed, but the ultimate decision is the dentist's.

[First orthodontic consultation: children or teenagers?]. / Quand adresser un enfant chez l'orthodontiste ?

Orthodontic treatments aim at improving the positions of teeth, the form of dental arches and their reports relations. Determining the age to perform these treatments consists in defining the ideal moment to achieve them in the shortest time possible and with the best stability success. To know when to address the child or the teenager to the orthodontist, it is necessary for the pediatrician to observe the patient, his/her positions, orofacial functions (phonation, swallowing, aeration), his/her face and profile, oral cavity, particularly the way his/her teeth articulate in the three spatial directions. This orthodontic check-up allows the detection of abnormalities, for which two kinds of treatments exist. Firstly, early treatments which start in temporary dentition stage, in order to prevent or intercept abnormalities and, secondly, late treatments performed on permanent dentition, when well-developed bony and alveolar growths make it possible to correct these abnormalities.

Enameloid/enamel transition through successive tooth replacements in Pleurodeles waltl (Lissamphibia, Caudata).

Study of the evolutionary enameloid/enamel transition suffers from discontinuous data in the fossil record, although a developmental enameloid/enamel transition exists in living caudates, salamanders and newts. The timing and manner in which the enameloid/enamel transition is achieved during caudate ontogeny is of great interest, because the caudate situation could reflect events that have occurred during evolution. Using light and transmission electron microscopy, we have monitored the formation of the upper tooth region in six successive teeth of a tooth family (position I) in Pleurodeles waltl from late embryos to young adult. Enameloid has only been identified in embryonic tooth I(1) and in larval teeth I(2) and I(3). A thin layer of enamel is deposited later by ameloblasts on the enameloid surface of these teeth. From post-metamorphic juvenile onwards, teeth are covered with enamel only. The collagen-rich enameloid matrix is deposited by odontoblasts, which subsequently form dentin. Enameloid, like enamel, mineralizes and then matures but ameloblast participation in enameloid matrix deposition has not been established. From tooth I(1) to tooth I(3), the enameloid matrix becomes ever more dense and increasingly comes to resemble the dentin matrix, although it is still subjected to maturation. Our data suggest the absence of an enameloid/enamel transition and, instead, the occurrence of an enameloid/dentin transition, which seems to result from a progressive slowing down of odontoblast activity. As a consequence, the ameloblasts in post-metamorphic teeth appear to synthesize the enamel matrix earlier than in larval teeth.

The effect of time of introduction of a high-fructose, low-copper diet on copper deficiency in male rats.

The purpose of the present study was to compare the time of introduction of the high-fructose low-copper diet on the expression of copper (Cu) deficiency. Weanling male rats were randomly assigned to either a diet containing 62.7% fructose or starch, and 6.0 (F+Cu) or 0.6 (S-Cu) microgram Cu/g diet, respectively, for either 1, 2, or 3 wk before being transferred to a diet containing fructose and inadequate in copper (F-Cu). At week 10, body weight and relative heart size of rats initially consuming the F + Cu diet was inversely related to the week placed on the F-Cu diet, but not for those initially consuming S-Cu. Hematocrit, hepatic Cu concentration and RBC superoxide dismutase activity were significantly lower in rats initially consuming S-Cu when compared to those fed F + Cu. Mortality was greatest in rats switched to the F-Cu diet at weeks 1 and 2 when compared to those switched at week 3 regardless of the type of diet initially consumed. Plasma cholesterol, triacylglycerols, and blood urea nitrogen concentrations were not significantly altered by the type of diet initially consumed or by the time of introduction of the F-Cu diet. It was concluded that changing rats to a F-Cu diet at 1, 2, or 3 wk after weaning did not significantly improve some of the characteristic signs associated with Cu deficiency, but the later that the F-Cu diet was introduced after weaning the greater the chances for survival.

Minerals leached into drinking water from rubber stoppers.

Drinking water and its delivery system are potential sources of variation in animal research. Concern arose that rubber stoppers used to cork water bottles might be a source of some nutritionally required minerals which could leach into drinking water. Six types of stoppers, each having different compositions, were cleaned with stainless-steel sipper tubes inserted into them and attached to polypropylene bottles filled with either deionized water (pH 4.5) or acidified-deionized water (pH 2.5). After six days of contact, water levels of copper, magnesium, iron, manganese, zinc, chromium, and selenium were determined by atomic absorption spectroscopy. Additionally, three of the stopper types were analyzed for mineral content. Minerals were present in both stoppers and drinking water. Acidified-deionized water generally leached minerals from the stoppers than did deionized water. The black stopper which is commonly used in animal facilities contained and leached measurable levels of some minerals, but it still can be recommended for typical animal husbandry uses, although other types of stoppers would be more suitable for specific nutritional and toxicologic studies.

Copper deficiency in pregnancy: effect on maternal and fetal polyol metabolites.

The present study was undertaken to determine whether the mortality of the fetus and the neonate of copper-deficient rats consuming fructose during pregnancy is associated with an aberration in carbohydrate metabolism. A total of 84 Sprague-Dawley rats were fed a copper-deficient or a copper-adequate diet containing fructose or starch for 19 or 21 days after conception. The consumption of a fructose-based diet during pregnancy resulted in higher concentrations of maternal blood fructose, sorbitol, triglyceride, and uric acid when compared with a starch diet. The placenta contained more than 10-fold the concentration of glucose and more than double the concentrations of fructose, triglycerides, and sorbitol when fructose was the dietary carbohydrate compared with starch. The livers of fetuses belonging to the fructose dietary group exhibited high concentrations of glucose and sorbitol. In addition, fetal blood contained higher concentrations of glucose, fructose, sorbitol, and triglycerides than the corresponding values from the starch dietary group. The consumption of a copper-deficient diet containing fructose during pregnancy resulted in massive subcutaneous hemorrhages of the fetus. In contrast, this pathology was rare in other dietary groups. The combination of copper deficiency with fructose feeding resulted in more than double the concentration of sorbitol in fetal liver, and higher concentrations of insulin and dopamine of fetal blood compared with the consumption of a copper-deficient diet containing starch.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of various levels of fructose in a copper-deficient diet on Cu deficiency in male rats.

The present study was designed to examine the effects of various levels of fructose in a copper-deficient diet on some of the signs of Cu deficiency in the rat. Weanling male rats were randomly assigned to one of five diets which contained 0.6 micrograms Cu/g diet and 627 g carbohydrate/kg which was (g/kg): 627 fructose (diet 100); 470 fructose, 157 starch (diet 75); 313.5 fructose, 313.5 starch (diet 50); 157 fructose, 470 starch (diet 25); or 627 starch (diet 0). Rats ate their respective diets for either 2 or 5 weeks. There was a significant linear inverse response of body-weight (P less than 0.0001), packed cell volume (P less than 0.0001) and erythrocyte superoxide dismutase (EC 1.15.1.1) activity (P less than 0.008) to increasing levels of dietary fructose and a direct linear response of plasma cholesterol (P less than 0.05) and blood urea nitrogen concentrations (P less than 0.001) to increasing levels of dietary fructose. Liver, kidney and pancreatic Cu concentrations decreased in a dose-response manner as the level of dietary fructose increased. In general, if fructose was included in the diet the signs of Cu deficiency were exacerbated in a dose-response manner.

Effect of changing the type of dietary carbohydrate or copper level of copper-deficient, fructose-fed rats on tissue sorbitol concentrations.

This study was designed to examine the relationship between the fructose-copper interaction and tissue sorbitol concentrations. Weanling male rats were provided with a diet which contained 62.7% fructose and 0.6 microg copper/g (F-Cu) for 4 weeks. At this time, rats were changed to either a fructose diet which contained 6.0 microg copper/g or to a starch diet with or without copper for 2 weeks. When compared with the other dietary groups, it was found that rats fed the F-Cu diet grew poorly; had altered relative liver, pancreatic, heart, and kidney sizes; were anemic; and had higher tissue concentrations of pancreatic and heart glucose, liver, pancreatic, heart, and kidney fructose, and liver, pancreatic, and kidney sorbitol. When rats were changed from the F-Cu diet to one containing copper or to a starch diet with or without copper, weight gain, relative liver, pancreatic and heart sizes, and hematocrit improved significantly. In general, there was a reduction in pancreatic and heart glucose; liver, pancreatic, heart, and kidney fructose; and pancreatic and kidney sorbitol concentrations when rats were changed from the F-Cu diet to any of the other diets. We conclude that the fructose-copper interaction may have a common biochemical basis related to the metabolism of glucose, fructose, and sorbitol.

Blood risk factor metabolites associated with heart disease and myocardial fatty acids in copper-deficient male and female rats.

Intact and castrated males and intact and ovariectomized female rats were fed a copper-deficient diet in order to establish whether the protection provided in females against cardiovascular pathology and mortality is due to endogenous sex hormones, and different levels of blood lipids and/or myocardial fatty acids. Seventy-three male and female rats were assigned to a copper-deficient diet (0.6 micrograms of copper/g diet) containing 62% fructose for 8 weeks. Twelve of the male rats underwent castration and 12 of the females were ovariectomized. All animals exhibited high levels of plasma cholesterol, triglycerides, and uric acid, which were neither affected by the sex of the rat nor by the surgical treatment. The composition of fatty acids of the myocardium was similar in males and females. Except for those animals that were sacrificed by us, all other male rats died of heart pathology. In contrast, none of the female rats exhibited heart pathology and none died of the deficiency. It is suggested that heart pathology and mortality in copper deficiency are sex related and not due to high levels of plasma cholesterol, triglycerides, and uric acid or to differences in myocardial fatty acid composition.

Accumulation of sorbitol in copper deficiency: dependency on gender and type of dietary carbohydrate.

The present study was designed to examine tissue sorbitol levels in copper-deficient rats consuming dietary fructose as the only source of carbohydrate and to determine if any changes in tissue sorbitol levels are influenced by the sex of the rat. Tissue levels of glucose, sorbitol, fructose, and glyceraldehyde were measured along with the activities of aldose reductase and sorbitol dehydrogenase of male and female rats consuming copper-deficient or adequate diets containing either fructose or starch for 3 weeks. Regardless of copper status, sorbitol accumulated in the livers of males consuming fructose compared to females and to males eating starch. The greatest sorbitol accumulation in the kidney occurred in the copper-deficient male rat consuming the fructose diet. These results strongly suggest that the pathology and complications of copper deficiency in the male rat fed fructose may be due to the increased sorbitol contents of tissues.

Copper-carbohydrate interaction in maternal, fetal and neonate rat.

The present study was undertaken to determine whether the same type of interaction between dietary fructose and copper that affects young growing male rats also affects the fetus and the neonate. Female rats were fed copper-deficient (0.6 microgram Cu/g) or adequate (6.0 micrograms/g) diets containing 62% carbohydrate as fructose or starch either for 8 weeks prior to conception, and during mating, gestation and lactation, or just during gestation. Fetuses were killed at days 14, 18 or 21 of gestation and newborn pups were killed at days 0, 10, or 21 postpartum. Regardless of the duration of dietary copper deprivation, feeding the fructose diet deficient in copper during pregnancy resulted in either fetal resorption or mortality of all newborn pups during the first few hours postpartum. In contrast, copper-deficient rats fed the starch-containing diets delivered live pups. However, 40% of their pups died during the first 2 days postpartum and occurred only when dams had been fed the deficient diet for 12-13 weeks. When fed the deficient diet for a total of 3 weeks only, during pregnancy, all copper-deficient rats fed starch delivered live pups and no mortality occurred during the lactation period. Feeding the copper-adequate fructose diet during lactation resulted in a lower hepatic copper concentration of suckling pups compared with starch feeding. Female pups had higher levels of copper and iron than male pups. The data show that fetal resorption and mortality of the neonate pup was dependent on the type of dietary carbohydrate fed to copper-deficient animals during pregnancy.

Sexual differences in the expression of copper deficiency in rats.

The present investigation was undertaken to establish whether the severity of copper deficiency in rats fed diets containing fructose is affected by the presence and type of endogenous sex hormones. Intact and castrated male rats and intact and ovariectomized females were fed from weaning a copper-deficient diet (0.6 ppm) containing 62% fructose for 8 weeks. Regardless of castration, male rats were anemic, exhibited heart hypertrophy, and died of the deficiency. However, castration ameliorated the anemia and delayed the mortality. In contrast, none of the females died of the deficiency. It is suggested that in addition to the sex of the animal, levels of testosterone in the male may also play a role in the severity of copper deficiency.