The justification for providing dietary guidance for the nutritional intake of boron

Because a biochemical function has not been defined for boron (B), its nutritional essentiality has not been firmly established. Nonetheless, dietary guidance should be formulated for B, because it has demonstrated beneficial, if not essential, effects in both animals and humans. Intakes of B commonly found with diets abundant in fruits, vegetables, legumes, pulses, and nuts have effects construed to be beneficial in macromineral, energy, nitrogen, and reactive oxygen metabolism, in addition to enhancing the response to estrogen therapy and improving psychomotor skills and cognitive processes of attention and memory. Perhaps the best-documented beneficial effect of B is on calcium (Ca) metabolism or utilization, and thus, bone calcification and maintenance. The paradigm emerging for the provision of dietary guidance that includes consideration of the total health effects of a nutrient, not just the prevention of a deficiency disease, has resulted in dietary guidance for chromium (Cr) and fluoride; both of these elements have beneficial effects in humans, but neither has a defined biochemical function. Knowledge of B nutritional effects in humans equals or is superior to that of Cr and fluoride; thus, establishing a dietary reference intake for B is justified. An analysis of both human and animal data suggests that an acceptable safe range of population mean intakes of B for adults could well be 1–13 mg/d. Recent findings indicate that a significant number of people do not consistently consume more than 1 mg B/d; this suggests that B could be a practical nutritional or clinical concern.     

Dietary boron intakes of selected populations in the United States

Knowledge of daily boron (B) intakes will assist researchers in establishing B requirements and elucidating the metabolic role of B in humans. B concentrations in commonly consumed foods were utilized to approximate the B intake of selected US populations. Triplicate food samples were digested at low temperatures with 16M HNO₃ and 30% H₂O₂, and analyzed by inductively coupled plasma spectroscopy (ICP). Milk and dairy products, juices, and beverages were the largest contributors to dietary B. Total B content of average daily diets ranged from 548 μg for toddlers (2 yr old) to 883 μg for mature males (60–65 yr old), excluding tap water contributions. Toddlers consumed 3.7 times more B than mature males when adjusted for body weight (body wt) and consumed the diet with the highest boron density (1.8 μg/kJ or 0.43 μg/kcal). Adolescent females consumed a diet with the lowest B density (1.12 μg/kJ or 0.26 μg/kcal). Food B concentrations applied to diet records (1020 μg/d) and ICP analysis of the corresponding food composites (1170 μg/d) were comparable (p < 0.05). Current estimations of B in US diets are consistent with reports in the literature stating that normal adult daily B intakes are approx 1 mg. Presented at the symposium “Second International Symposium on the Health Effects of Boron and Its Compounds” held in Irvine, CA, on October 23, 1997. This symposium was presented by the University of California, Irvine. The publication of the symposium was supported by U.S. Borax Inc. Guest editors for this symposium were B. Dwight Culver (University of California, Irvine, CA) and James R. Coughlin (Coughlin and Associates, Newport Coast, CA). US Department of Agriculture, Agricultural Research Service, Northern Plains Area is an equal opportunity/affirmative action employer, and all agency services are available without discrimination.     

Fallback foraging as a way of life: Using dietary toughness to compare the fallback signal among capuchins and implications for interpreting morphological variation

The genus Cebus is one of the best extant models for examining the role of fallback foods in primate evolution. Cebus includes the tufted capuchins, which exhibit skeletal features for the exploitation of hard and tough foods. Paradoxically, these seemingly “specialized” taxa belong to the most ubiquitous group of closely related primates in South America, thriving in a range of different habitats. This appears to be a consequence of their ability to exploit obdurate fallback foods. Here we compare the toughness of foods exploited by two tufted capuchin species at two ecologically distinct sites; C. apella in a tropical rainforest, and C. libidinosus in a cerrado forest. We include dietary data for one untufted species (C. olivaceus) to assess the degree of difference between the tufted species. These data, along with information on skeletal morphology, are used to address whether or not a fallback foraging species exhibits a given suite of morphological and behavioral attributes, regardless of habitat. Both tufted species ingest and masticate a number of exceedingly tough plant tissues that appear to be used as fallback resources, however, C. libidinosus has the toughest diet both in terms of median and maximal values. Morphologically, C. libidinosus is intermediate in absolute symphyseal and mandibular measurements, and in measures of postcranial robusticity, but exhibits a higher intermembral index than C. apella. We propose that this incongruence between dietary toughness and skeletal morphology is the consequence of C. libidinosus' use of tools while on the ground for the exploitation of fallback foods. Am J Phys Anthropol 140:687–699, 2009. © 2009 Wiley-Liss, Inc.     

Effects of low dietary protein on the metabolites and microbial communities in the caecal digesta of piglets

Thirty-six healthy piglets (weighing 10 ± 1 kg; three animals per pen) were randomly allocated to two treatments: (i) a low protein diet (14% crude protein [CP]) supplemented with lysine, methionine, threonine and tryptophan (Group LP) and (ii) a normal protein diet (20% CP, Group NP), resulting in six replicate pens per treatment. One piglet from each pen was slaughtered at days 10, 25 and 45 of the experiment. For the whole experimental period of 45 d, Group LP had lower feed intake and daily gain and a higher feed-to-gain ratio compared with Group NP. At day 10, no effects on measured caecum metabolites were observed, but at days 25 and 45 in Group LP the concentration of ammonia-N, cadaverine, branched chain fatty acids and acetate were reduced. This was also true for the concentration of short chain fatty acids at day 45. The results of denaturing gradient gel electrophoresis showed that microbial diversity in Group LP was less abundant at day 25, but there was no difference at days 10 and 45. An unweighted pair group mean average analysis showed that the similarities were lower between Groups LP and NP at day 10 and higher at days 25 and 45. Quantitation results indicated that the numbers of Firmicutes and Clostridium cluster IV were lower in Group LP than in Group NP at day 25, but there were no differences at days 10 and 45. In conclusion, the low protein diet markedly reduced the metabolites of protein and carbohydrate fermentation and altered microbial communities in the caecal digesta of piglets.     

Effect of sex,dietary glycerol or dietary fat during late fattening,on fatty acid composition and positional distribution of fatty acids within the triglyceride in pigs

The effect of sex, source of saturated fat (lard v. palm oil) and glycerol inclusion in the fattening diet on composition and fatty acid positional distribution in the triglyceride molecule was studied in pigs from 78 to 110 kg BW. Average daily gain and carcass characteristics, including ham and loin weight, were not affected by dietary treatment but sex affected backfat depth (P<0.01). A significant interaction between sex and glycerol inclusion was observed; dietary glycerol increased lean content in gilts but not in barrows (P<0.05 for the interaction). Individual and total saturated fatty acid (SFA) concentrations were greater in barrows than in gilts. In contrast, the concentration of total polyunsaturated fatty acids (PUFA) and of C18:2n-6, C18:3n-3, C20:3n-9 and C20:4n-6 in the intramuscular fat (IMF) was higher (P<0.05) in gilts than in barrows. Sex did not affect total monounsaturated fatty acids (MUFA) concentration in the IMF. The proportion of SFA in the subcutaneous fat (SF) was higher in barrows than in gilts (P<0.001). Within the individual SFA, sex affected only the concentrations of C14:0 and C16:0 (P<0.001). Dietary fat did not affect total SFA or PUFA concentrations of the IMF but the subcutaneous total MUFA concentration tended to be higher (P=0.079) in pigs fed lard than in pigs fed palm oil. Dietary glycerol increased total MUFA and C18:1n-9 concentration in the IMF and increased total MUFA and decreased C18:2n-6, C18:3n-3 and total PUFA concentrations in the SF. The data indicate that altering the fatty acid composition of the triglyceride molecule at the 2-position, by dietary intervention during the fattening phase, is very limited.     

Evolutionary dynamics of ecological niche in three Rhinogobio fishes from the upper Yangtze River inferred from morphological traits

In the past decades, it has been debated whether ecological niche should be conserved among closely related species (phylogenetic niche conservatism, PNC) or largely divergent (traditional ecological niche theory and ecological speciation) and whether niche specialist and generalist might remain in equilibrium or niche generalist could not appear. In this study, we employed morphological traits to describe ecological niche and test whether different niche dimensions exhibit disparate evolutionary patterns. We conducted our analysis on three Rhinogobio fish species (R. typus, R. cylindricus, and R. ventralis) from the upper Yangtze River, China. Among the 32 measured morphological traits except body length, PCA extracted the first four principal components with their loading scores >1.000. To find the PNC among species, Mantel tests were conducted with the Euclidean distances calculated from the four principal components (representing different niche dimensions) against the pairwise distances calculated from mitochondrial cytochrome b sequence variations. The results showed that the second and the third niche dimension, both related to swimming ability and behavior, exhibited phylogenetic conservatism. Further comparison on niche breadth among these three species revealed that the fourth dimension of R. typus showed the greatest width, indicating that this dimension exhibited niche generalism. In conclusion, our results suggested that different niche dimensions could show different evolutionary dynamic patterns: they may exhibit PNC or not, and some dimensions may evolve generalism.     

Green tea epigallocatechin gallate binds to and inhibits respiratory complexes in swelling but not normal rat hepatic mitochondria

Epigallocatechin gallate (EGCG), the major flavonoid in green tea, is consumed via tea products and dietary supplements, and has been tested in clinical trials. However, EGCG can cause hepatotoxicity in humans and animals by unknown mechanisms. Here EGCG effects on rat liver mitochondria were examined. EGCG showed negligible effects on oxidative phosphorylation at 7.5–100 μM in normal mitochondria. However, respiratory chain complexes (RCCs) were profoundly inhibited by EGCG in mitochondria undergoing Ca²⁺ overload-induced mitochondrial permeability transition (MPT). As RCCs are located in mitochondrial inner membranes (IM) and matrix, it was reasoned that EGCG could not readily pass through IM to affect RCCs in normal mitochondria but may do so when IM integrity is compromised. This speculation was substantiated in three ways. (1) Purified EGCG-bound proteins were barely detectable in normal mitochondria and contained no RCCs as determined by Western blotting, but swelling mitochondria contained about 1.5-fold more EGCG-bound proteins which included four RCC subunits together with cyclophilin D that locates in mitochondrial matrix. (2) Swelling mitochondria consumed more EGCG than normal ones. (3) The MPT blocker cyclosporine A diminished the above-mentioned difference. Among four subunits of RCC II, only SDHA and SDHB which locate in mitochondrial matrix, but not SDHC or SDHD which insert into the IM, were found to be EGCG targets. Interestingly, EGCG promoted Ca²⁺ overload-induced MPT only when moderate MPT already commenced. This study identified hepatic RCCs as targets for EGCG in swelling but not normal mitochondria, suggesting EGCG may trigger hepatotoxicity by worsening pre-existing mitochondria abnormalities.     

Effects of acute or chronic exposure to dietary organic anions on secretion of methotrexate and salicylate by Malpighian tubules of Drosophila melanogaster larvae

The effects of dietary exposure to organic anions on the physiology of isolated Malpighian tubules and on tubule gene expression were examined using larvae of Drosophila melanogaster. Acute (24 h) or chronic (7 d) exposure to type I organic anions (fluorescein or salicylate) was associated with increased fluid secretion rates and increased fluxes of both salicylate and the type II organic anion methotrexate. By contrast, chronic exposure to dietary methotrexate was associated with increased fluid secretion rate and increased flux of methotrexate, but not salicylate. Exposure to methotrexate in the diet resulted in increases in the expression of a multidrug efflux transporter gene (MET; CG30344) in the Malpighian tubules. There were also increases in expression of genes for either a Drosophila multidrug resistance–associated protein (dMRP; CG6214) or an organic anion transporting polypeptide (OATP; CG3380), depending on the concentration of methotrexate in the diet. Exposure to salicylate in the diet was associated with an increase in expression of dMRP and with decreases of MET and OATP. Exposure to dietary salicylate or methotrexate was also associated with different patterns of expression of heat shock protein genes. The results suggest that exposure to specific type I or type II organic anions has multiple effects and results not only in increased organic anion transport but also in increased rates of inorganic ion transport, which drives osmotically‐obliged fluid secretion. Increased fluid secretion may enhance secretion of organic anions by eliminating diffusive backflux from the tubule lumen to the hemolymph. © 2010 Wiley Periodicals, Inc.     

The effect of high dietary zinc on trypsin activity in carp (Cyprinus carpio)

Carp fed pellets containing a range of zinc concentrations showed a significant increase in trypsin activity in the intestine with increasing zinc in the diet.     

Monounsaturated fatty acyl-coenzyme A is predictive of atherosclerosis in human apoB-100 transgenic, LDLr-/- mice

ACAT2, the enzyme responsible for the formation of cholesteryl esters incorporated into apolipoprotein B-containing lipoproteins by the small intestine and liver, forms predominantly cholesteryl oleate from acyl-CoA and free cholesterol. The accumulation of cholesteryl oleate in plasma lipoproteins has been found to be predictive of atherosclerosis. Accordingly, a method was developed in which fatty acyl-CoA subspecies could be extracted from mouse liver and quantified. Analyses were performed on liver tissue from mice fed one of four diets enriched with one particular type of dietary fatty acid: saturated, monounsaturated, n-3 polyunsaturated, or n-6 polyunsaturated. We found that the hepatic fatty acyl-CoA pools reflected the fatty acid composition of the diet fed. The highest percentage of fatty acyl-CoAs across all diet groups was in monoacyl-CoAs, and values were 36% and 46% for the n-3 and n-6 polyunsaturated diet groups and 55% and 62% in the saturated and monounsaturated diet groups, respectively. The percentage of hepatic acyl-CoA as oleoyl-CoA was also highly correlated to liver cholesteryl ester, plasma cholesterol, LDL molecular weight, and atherosclerosis extent. These data suggest that replacing monounsaturated with polyunsaturated fat can benefit coronary heart disease by reducing the availability of oleoyl-CoA in the substrate pool of hepatic ACAT2, thereby reducing cholesteryl oleate secretion and accumulation in plasma lipoproteins.