Forty male weanling albino rats were divided into 4 groups and fed 20% casein diets of high fat (40% ) or low fat (5% ) content with adequate or exces sive quantities of niacin. The niacin content of both the high and low fat diets was increased by supplementing the diets with 0.1% of niacin. Two control groups, one fed high fat and the other low fat, containing adequate (0.5 mg/100 g) quantities of niacin, were fed the diet simultaneously. Blood samples were collected for pyridine nucleotide determinations on the twenty-first and the forty-second day of the experi ment. The animals were killed after 44 days and the livers analyzed for pyridine nucleotide concentration, fatty acid oxidase activity, and proximate composition. Re sults from this study indicate that excess niacin enters metabolic pathways to produce at least 2 unrelated effects, increased concentrations of pyridine nucleotides in blood and liver and increased levels of fat in the liver. The first effect occurs regardless of the level of fat in the diet, but the second occurs only in conjunction with a high level of dietary fat. The possibility that an increased consumption of niacin and fat increases the animals' requirement for choline is discussed.
Group A rotavirus is the leading cause of diarrhea among children aged 3-36 mo worldwide. Introducing fermented milk products into the infant diet has been proposed for the prevention or treatment of rotavirus diarrhea. The preventive effect of milk fermented by the Lactobacillus casei strain DN-114 001 was studied in a model of germfree suckling rats supplemented daily from d 2 of life and infected with SA11 rotavirus at d 5 (RF group). One group was supplemented with nonfermented milk (RM) and two uninfected groups (CM and CF) received either nonfermented or fermented milk. Frequency and severity of diarrhea were observed. Rats were killed at various times from 0 to 120 h postinfection (p.i.). Bacteria were measured in the intestine, and rotavirus antigens were detected by ELISA in fecal samples and in different parts of the intestine. Histologic observations were made, including vacuolation, morphology of intestinal villi and number of mucin cells. RM rats had diarrhea for 6 d; compared with the CM group, they had alterations of the intestinal mucosa characterized by cellular vacuolation 48 and 72 h p.i. and a lower number of sulfated mucin cells 72 and 96 h p.i. (P: < 0.05). Early supplementation with fermented milk significantly decreased the clinical signs of diarrhea from 24 to 144 h p.i. (P: < 0.05) and prevented rotavirus infection in all sections of the intestine. Histologic lesions of the small intestine were greatly reduced (P: < 0.05) and the number of mucin cells remained unchanged. The data are discussed with respect to the possibility of reducing rotavirus diarrhea in young children by consumption of fermented milk.
The effects of storage condition on the shelf life of the AIN-76 diet were investigated. Samples of the diet were stored at -70 degrees, 4 degrees, 20 degrees, and 23-30 degrees under atmospheric air and at 4 degrees and 20 degrees under argon. Levels of vitamin A, thiamine, rancidity, bacteria and mold were monitored during 168 days of storage. A 41.3% loss of vitamin A occurred in samples stored at 23-30 degrees. A marked decline in thiamine was observed in all samples stored at 20 degrees or above. Loss of thiamine was significantly greater in samples stored at 20 degrees than in those stored at 4 degrees, and greater in samples stored under air than those stored under argon. Rancidity reached a level previously shown to be associated with a disagreeable odor and taste (peroxide value greater than 140) with in 30, 50 and 90 days when the diet was stored at 23-30 degrees or 20 degrees under air and 20 degrees under argon, respectively. Peroxide values remained well below 140 in samples stored at 4 degrees or colder. None of the nutritional parameters tested reached unacceptable levels in any of the samples stored at 4 degrees or colder during the 168 days. These results indicate that to achieve maximum shelf life, the AIN-76 diet should be stored at 4 degrees or colder. Although less effective than low temperature, an argon atmosphere extended the shelf life and was additive with lower temperatures.
Measurement of micronutrient status in the presence of inflammation is difficult for several reasons. Changes in levels of acute phase proteins are associated with increased plasma levels of some indicators of micronutrient status, such as ferritin, and decrease of others, such as retinol. Alterations in the plasma levels of acute phase proteins can occur from hemodilution, sequestration and increased or decreased rates of synthesis and breakdown. How much these relate to functional deficiency is not known. Assays that are less perturbed by inflammation, such as the transferrin receptor assay, and adjustment of plasma micronutrient levels according to different cutoff levels for acute phase proteins are helpful but they do not enable precise assessment of micronutrient status among individuals who are infected. Improving assessment of micronutrient status is important if micronutrient interventions are to be targeted to those with the greatest need.
Dietary sphingomyelin (SM) inhibits early stages of colon cancer (appearance of aberrant crypt foci, ACF) and decreases the proportion of adenocarcinomas vs. adenomas in 1,2-dimethylhydrazine (DMH)-treated CF1 mice. To elucidate the structural specificity of this inhibition, the effects of the other major sphingolipids in milk (glycosphingolipids) were determined. Glucosylceramide (GluCer), lactosylceramide (LacCer) and ganglioside G(D3) were fed individually to DMH-treated (six doses of 30 mg/kg body weight) female CF1 mice at 0.025 or 0.1 g/100 g of the diet for 4 wk. All reduced the number of ACF by > 40% (P < 0.001), which is comparable to the reduction by SM in earlier studies. Immunohistochemical analysis of the colons revealed that sphingolipid feeding also reduced proliferation, with the most profound effect (up to 80%; P < 0.001) in the upper half of the crypts. Since the bioactive backbones of the glycosphingolipids (i.e., ceramide and other metabolites) are the likely mediators of these effects, the susceptibility of these complex sphingolipids to digestion in the colon was examined by incubating 500 microgram of each sphingolipid with colonic segments from mice and analysis of substrate disappearance and product formation by tandem mass spectrometry. All of the sphingolipids (including SM) disappeared over time with a substantial portion appearing as ceramide. Partially hydrolyzed intermediates (such as GluCer from LacCer or G(D3)) were not detected, which suggests that the cleavage involves colonic (or microflora) endoglycosidases. In summary, consumption of dairy SM and glycosphingolipids suppresses colonic cell proliferation and ACF formation in DMH-treated mice; hence, many categories of sphingolipids affect these key events in colon carcinogenesis.
We investigated whether increased levels of dietary calcium and vitamin D could inhibit colon carcinogenesis in rats injected with a single dose of 1,2-dimethylhydrazine. Rats were given a single subcutaneous injection (200 mg/kg body wt) 2 wk before they were fed purified diets containing 20% fat for 32 wk. Diets contained one of three levels of calcium (5, 10 or 15 g/kg diet) as calcium gluconate and one of three levels of vitamin D (0.025, 0.05 or 0.1 mg/kg diet) as cholecalciferol in a 3 x 3 factorial design. Rats receiving the highest level of vitamin D had greater plasma concentrations of 25-hydroxy-vitamin D. Autoradiographic examination of [3H]thymidine-treated rats demonstrated that a higher dietary level of calcium as well as higher levels of vitamin D significantly affected cellular kinetic indices. The total tumor incidence and tumor incidence in the distal colon was 45% lower in rats fed the highest level of both calcium and vitamin D compared with the other eight groups, although this decrease was not statistically significant (P = 0.12). The possible importance of these observations is discussed.
Dietary supplementation with milk sphingolipids inhibits colon tumorigenesis in CF1 mice treated with a colon carcinogen [1,2-dimethylhydrazine (DMH)] and in multiple intestinal neoplasia (Min) mice, which develop intestinal tumors spontaneously. Plant sphingolipids differ structurally from those of mammals [soy glucosylceramide (GlcCer) consists predominantly of a 4,8-sphingadiene backbone and alpha-hydroxy-palmitic acid], which might affect their bioactivity. Soy GlcCer was added to the AIN-76A diet (which contains <0.005% sphingolipid) to investigate whether it would also suppress tumorigenesis in these mouse models. Soy GlcCer reduced colonic cell proliferation in the upper half of the crypts in mice treated with DMH by 50 and 56% (P < 0.05) at 0.025 and 0.1% of the diet (wt/wt), respectively, and reduced the number of aberrant colonic crypt foci (an early marker of colon carcinogenesis) by 38 and 52% (P < 0.05). Min mice fed diets containing 0.025 and 0.1% (wt/wt) soy GlcCer developed 22 and 37% fewer adenomas (P < 0.05), respectively. The effects of dietary sphingolipids on gene expression in the intestinal mucosal cells of Min mice were analyzed using Affymetrix GeneChip microarrays. Soy GlcCer affected the expression of 96 genes by > or = 2-fold in a dose-dependent manner, increasing 32 and decreasing 64. Decreases in the mRNA expression of two transcription factors associated with cancer, hypoxia-induced factor 1 alpha (HIF1 alpha) and transcription factor 4 (TCF4), were confirmed by quantitative RT-PCR. In conclusion, soy GlcCer suppressed colon tumorigenesis in two mouse models; hence, plant sphingolipids warrant further investigation as inhibitors of colon cancer. Because soy contains relatively high amounts of GlcCer, sphingolipids may partially account for the anticancer benefits attributed to soy-based foods.
This study was conducted to examine the effect of consumption of buckwheat protein product (BWP) on 1,2-dimethylhydrazine (DMH)-induced colon tumor in rats. Male growing Sprague-Dawley rats were fed diets containing either casein or BWP (net protein level, 200 g/kg; n = 20/group) for 124 d. The rats were gavaged weekly with DMH (20 mg/kg body) for the first 8 wk. Food intake and growth were unaffected by dietary manipulation. Dietary BWP caused a 47% reduction in the incidence of colonic adenocarcinoma (P < 0.05), but did not affect the incidence of colonic adenomas. BWP intake tended to reduce the number of colon adenocarcinomas (P = 0.16). Consumption of BWP significantly reduced cell proliferation and expression of c-myc and c-fos proteins in colonic epithelium. The results suggest that dietary BWP has a protective effect against DMH-induced colon carcinogenesis in rats by reducing cell proliferation.
Glycine plays several roles in human metabolism, e.g. as a 1-carbon donor, in purine synthesis, and as a component of glutathione. Glycine is decarboxylated via the glycine cleavage system (GCS) that yields concurrent generation of a 1-carbon unit as 5,10-methylenetetrahydrofolate (methyleneTHF). Serine hydroxymethyltransferase (SHMT) catalyzes the interconversion of glycine and serine, another 1-carbon donor. The quantitative role of glycine in human 1-carbon metabolism has received little attention. The aim of this protocol was to quantify whole body glycine flux, glycine to serine flux, and rate of glycine cleavage in humans. A primed, constant infusion with 9.26 micromol x kg(-1) x h(-1) [1,2-(13)C2]glycine and 1.87 micromol x kg(-1) x h(-1) [(2)H3]leucine was used to quantify the kinetic behavior of glycine in young, healthy volunteers (n = 5) in a fed state. The isotopic enrichment of infused tracers and metabolic products in plasma, as well as breath (13)CO2 enrichment, were determined for use in kinetic analysis. Serine synthesis by direct conversion from glycine via SHMT occurred at 193 +/- 28 micromol x kg(-1) x h(-1) (mean +/- SEM), which comprised 41% of the 463 +/- 55 micromol x kg(-1) x h(-1) total glycine flux. Nearly one-half (46%) of the glycine-to-serine conversion occurred using GCS-derived methyleneTHF 1-carbon units. Based on breath (13)CO2 measurement, glycine decarboxylation (190 +/- 41 micromol x kg(-1) x h(-1)) accounted for 39 +/- 6% of whole body glycine flux. This study is the first to our knowledge to quantify human glycine cleavage and glycine-to-serine SHMT kinetics. GCS is responsible for a substantial proportion of whole body glycine flux and constitutes a major route for the generation of 1-carbon units.
The effects of two carcinogens benzo[a]pyrene (BP) and symmetrical 1,2-dimethylhydrazine dihydrochloride (DMH), on plasma amino acid concentrations and on excretion of lipids and nitrogenous metabolites were studied in 7- to 8-wk-old male and female B6C3F1 mice. BP and DMH were fed at concentrations of 0.3125 and 0.0225 g/kg, respectively, in purified diets containing 10 or 40% soybean protein. Nutritional balances were measured over a 7-d period after 7 d of acclimatization. Females excreted less urea and more NH3 than males. Urinary urea-nitrogen, NH3, allantoin, uric acid and total urinary nitrogen were consistently higher in mice fed 40% protein than in those fed 10% protein. The increases in total and NH3 nitrogen paralleled the increase in nitrogen intake. Nitrogen of urea rose more, while that of allantoin and uric acid rose less, than nitrogen intake. Fecal lipid excretion, as a percentage of intake, was consistently higher in mice fed the 40% protein diets than in mice fed 10% protein. Plasma glycine and branched-chain amino acids were higher, but citrulline was lower, when the 40% protein diet was fed. Body weight gain was higher when the 10% protein diet was fed with BP than without it, but BP made no apparent difference in weight gain when the 40% protein diet was fed. BP interacted with dietary protein to influence the excretion of nitrogenous metabolites. In addition, BP feeding produced numerous BP X sex and BP X protein interactions for plasma amino acid concentrations. Compared to controls, feed intake and weight gain were, respectively, 8 and 61% lower in DMH-fed animals during wk 1, but no differences in intake or weight gain were found during wk 2. In contrast to BP, DMH had no significant effects on urinary or fecal nitrogen metabolites, except that urinary uric acid (relative to nitrogen intake) was 9% higher in DMH-fed mice than in controls. DMH-fed mice had 43% higher serum glutamate and 6% lower glutamine than controls.
Recent evidence introduces the possibility that lutein and zeaxanthin may protect against the development of the two common eye diseases of aging, cataract and macular degeneration. This potential and the lack of other effective means to slow the progression of macular degeneration have fueled high public interest in the health benefits of lutein and zeaxanthin and the proliferation of supplements containing them on pharmacy shelves. An understanding of the biologic consequences of limiting or supplementing with these carotenoids is only beginning to emerge. Some epidemiologic evidence supports a role in eye disease and, to a lesser extent, cancer and cardiovascular disease. However, the overall body of evidence is insufficient to conclude that increasing levels of lutein and zeaxanthin, specifically, will confer an important health benefit. Future advances in scientific research are required to gain a better understanding of the biologic mechanisms of their possible role in preventing disease. Additional research is also required to understand the effect of their consumption, independent of other nutrients in fruits and vegetables, on human health. The newly advanced ability to measure levels of lutein and zeaxanthin in the retina in vivo creates a unique opportunity to contribute some of this needed evidence.
Sphingolipids are in all eukaryotic cells and modulate cell growth, differentiation, and transformation; however, little is known about the physiological effects of their consumption. Mice were fed diets supplemented with milk sphingomyelin to determine effects on colon carcinogenesis. Cancer was initiated in CF1 mice by 1,2-dimethylhydrazine. Mice were then fed AIN76A diets supplemented with 0.025 to 0.1 g sphingomyelin/100 g for 28 wk until the supply of sphingomyelin was depleted and then fed unsupplemented diet for 24 wk. Sphingomyelin did not affect weight gain. Mice fed sphingomyelin had a 20% incidence of colon tumors compared with 47% in controls (P = 0.08 for all sphingomyelin-fed mice vs. controls). Tumors were adenomas or adenocarcinomas and located in the distal third of the colon. In shorter-term studies, colonic epithelial cell proliferation was significantly greater than controls in mice fed 0.025 g sphingomyelin/100 g diet, but not in those fed higher amounts of sphingomyelin. The number of aberrant crypts was significantly lower in 1,2-dimethylhydrazine-treated mice fed 0.05 g sphingomyelin/100 g diet than in controls. These results demonstrate that consumption of sphingomyelin affects the behavior of colonic cells. Because sphingolipids are present in food, the reduction in 1,2-dimethylhydrazine-induced premalignant lesions and the incidence of colon tumors in CF1 mice implies that these compounds may be another important class of nutritional modulators of carcinogenesis.
The purpose of this study was to determine if high levels of dietary calcium could inhibit the induction of colon tumors in rats injected with a single dose of 1,2-dimethylhydrazine (DMH). Rats were given a single subcutaneous injection of DMH (200 mg/kg body weight) 2 wk before they were fed purified diets containing 5% fat and four different levels of calcium (as calcium gluconate). After 8 mo, the following incidences of colon tumors (total) were seen: 0.2% Ca, 56%; 0.5% Ca [National Academy of Sciences/National Research Council (NAS/NRC) recommended level], 75%; 1.0% Ca, 61%; 2.0% Ca, 41%. Thus, rats fed calcium at levels above or below the NAS/NRC recommendation had lower tumor incidences. The total tumor incidence and the incidence of adenocarcinomas (with or without invasion) were not significantly affected by calcium, but the incidences of benign adenomatous polyps and of distal colon tumors were significantly affected. Autoradiographic examination of [3H]thymidine-treated rats revealed that the level of calcium did not significantly alter the cell kinetic indices in the distal colon. In the proximal colon, however, the 0.2% Ca group had a significantly larger proliferative zone, with significantly more labeled cells present at the bottom of the colon crypt. Mineral analysis of tibias and serum samples revealed that rats fed higher levels of calcium had lower bone Fe and serum Mg contents, but no significant trends were seen for Ca, P, Zn or Cu. Therefore, increasing or decreasing the calcium content above or below the NAS/NRC recommendation (supplemented to low fat diets) during the promotional phase of colon carcinogenesis altered the tumor incidence, but the effect was confined to the distal colon and to benign adenomatous polyps.
Since propanediol is glucogenic and is extensively used in therapy of bovine ketosis, its metabolic fate was investigated. DL-1,2-propanediol-2-¹⁴C with 400 g of carrier propanediol was administered intraruminally to a lactating cow. During the next 24 hours, the percentage of the dose recovered was 43.7 in CO2, 12.4 in milk, 3.5 to 7 in urine, and less than 0.1 in feces. The propanediol was predominantly absorbed from the rumen without alteration, although some conversion to propionic acid in the rumen was detected. The maximal level of propanediol in milk was 0.04 mg/ml. Distribution of ¹⁴C among the carbons of lactose and glutamic acid indicated conversion of propanediol to glucose via carboxylation of pyruvate to oxalacetate. These results demonstrate that propanediol is glucogenic in the classical sense of that term; namely, that it is metabolized via intermediates, probably pyruvate and oxalacetate, which can lead to net synthesis of glucose. The small concentrations of propanediol in peripheral blood and the approximately 2-hour delay in attaining maximal specific activity in CO2 after attaining maximal specific activity of blood glucose indicated that glucogenesis was primarily hepatic with oxidation primarily occurring in other tissues.
The Grains for Health Foundation's Whole Grains Summit, held May 19-22, 2012 in Minneapolis, was the first meeting of its kind to convene >300 scientists, educators, food technologists, grain breeders, food manufacturers, marketers, health professionals, and regulators from around the world. Its goals were to identify potential avenues for collaborative efforts and formulate new approaches to whole-grains research and health communications that support global public health and business. This paper summarizes some of the challenges and opportunities that researchers and nutrition educators face in expanding the knowledge base on whole grains and health and in translating and disseminating that knowledge to consumers. The consensus of the summit was that effective, long-term, public-private partnerships are needed to reach across the globe and galvanize the whole-grains community to collaborate effectively in translating whole-grains science into strategies that increase the availability and affordability of more healthful, grain-based food products. A prerequisite of that is the need to build trust among diverse multidisciplinary professionals involved in the growing, producing, marketing, and regulating of whole-grain products and between the grain and public health communities.
Iron deficiency anemia in early life is related to altered behavioral and neural development. Studies in human infants suggest that this is an irreversible effect that may be related to changes in chemistry of neurotransmitters, organization and morphology of neuronal networks, and neurobiology of myelination. The acquisition of iron by the brain is an age-related and brain-region-dependent process with tightly controlled rates of movement of iron across the blood-brain barrier. Dopamine receptors and transporters are altered as are behaviors related to this neurotransmitter. The growing body of evidence suggests that brain iron deficiency in early life has multiple consequences in neurochemistry and neurobiology.
The effects of varying colon bile acid concentrations on rat colon epithelial cell proliferation were studied. Bile acid concentrations were altered by intrarectally injecting either deoxycholic or lithocholic acid for 4 weeks or by increasing the dietary fat or fiber (wheat bran, agar, or carrageenan) intake for 4 weeks. 1,2-Dimethylhydrazine (DMH) was s.c. injected into half of the rats 1 week before treatments began. Colon epithelial cell proliferation was measured by [3H]thymidine autoradiography of colon crypts. Rats injected with DMH had more DNA-synthesizing cells per crypt. Neither bile acid injection nor any of the diets altered the number of DNA-synthesizing cells per crypt. DMH injections, deoxycholic and lithocholic acid intrarectal injections, and dietary agar and wheat bran all increased the total number of cells per crypt. High fat diets and dietary carrageenan did not affect cell number. All diets containing fiber lowered total fecal bile acid concentrations, but increasing the fat content of the diet did not affect them. These results indicate that the bile acid injections and dietary agar and wheat bran induce a slight hyperplasia in the colon.
Garlic has been reported to have chemopreventive effects against a variety of cancers. However, different garlic preparations contain different constituents. We investigated the chemopreventive effect of aged garlic extract (AGE), an odorless product from prolonged extraction of fresh garlic, on colon carcinogenesis and cell proliferation in 1,2-dimethylhydrazine (DMH)-induced colon neoplastic rats. Rats were given weekly subcutaneous injections of DMH (20 mg/kg) for 20 wk, and fed either a basal diet or one containing 4% AGE. Serum from AGE-treated rats contained detectable S-allylcysteine. The AGE diet significantly reduced the number of colon tumors and aberrant crypt foci compared to the basal diet. Cell proliferation of normal-appearing colonic mucosa was assessed by MIB-5 immunohistochemistry. AGE treatment significantly decreased the mean MIB-5-labeling index. These findings suggest AGE has a chemopreventive effect on colon carcinogenesis through suppression of cell proliferation.
C57BL/6J (B/6J) mice are genetically predisposed to become overweight and develop hyperglycemia if raised on a high fat diet. The purpose of the present study was to explore the effect of dietary supplementation of L-glutamine (Gln), an inhibitor of fatty acid oxidation, on the development of hyperglycemia and excessive weight gain. Groups of 10 age- and weight-matched male B/6J mice were raised on one of four diets: 1) a low fat, low sucrose (LL), studied separately, 2) a high fat, low sucrose (HL) diet alone, 3) high fat, low sucrose supplemented with L-glutamine (HL+Gln) and 4) high fat, low sucrose supplemented with L-alanine (HL+Ala). Energy intake, body weight, plasma glucose and insulin concentrations were monitored over time. We found no difference in energy intake per unit body weight between any groups after the first 2 wk of feeding. However, the mean +/- SEM for body weight (27.1 +/- 0.6 g) of the LL group measured at 16 wk was lower (P < 0.05) than that of the HL group at 37.9 +/- 1.9 g. Also, after 5.5 mo, the mean +/- SEM for plasma glucose and insulin concentrations in the LL group of mice were 6.9 +/- 0.4 mmol/l and 146 +/- 30 pmol/l, which were lower (P < 0.05) than those in the HL group at 10.1 +/- 0.9 mmol/l and 438 +/- 84 pmol/l, respectively. Although both amino acids caused a 10% reduction (P < 0.05) in body weight compared with HL feeding at wk 16, only Gln supplementation resulted in persistent reductions in both plasma glucose and insulin concentrations over 5.5 mo. In another experiment, when Gln was added to the high fat (HL) diet of heavy hyperglycemic animals for 2 mo, body weight gain, hyperglycemia and hyperinsulinemia were attenuated. In conclusion, supplementing glutamine to a high fat diet reduces body weight and attenuated hyperglycemia and hyperinsulinemia in B/6J mice.
1,25-Dihydroxyvitamin D3 [1,25-(OH)2-D3] is known to be an immunosuppressive hormone. This review primarily deals with in vitro and in vivo effects of 1,25-(OH)2-D3 and analogue, 1,25-dihydroxy-16ene-vitamin D3 [1,25-(OH)2-16ene-D3], on T helper subsets type 1 (Th1) or type 2 (Th2) that have distinctive functional characteristics in humans. Th1 secrete interferon (IFN-gamma), interleukin (IL-2) and induce B cells to produce immunoglobulin IgG2a while Th2 secrete IL-4, IL-10 and induce the production of IgG1 and IgE by B cells. The sterol inhibits the secretion of IL-12, a cytokine produced by monocytes and B cells, which leads to the activation and differentiation of Th1. In addition, 1,25-(OH)2-D3 directly inhibits IFN-gamma secretion by Th1 clones while it has little effect on IL-4 secretion by Th2 clones. The analogue, 1,25-(OH)2-16ene-D3, is 100-fold more potent than 1,25-(OH)2-D3 in inhibiting IFN-gamma secretion but also has little effect on IL-4 secretion. In mice, when given in vivo, the sterol prevents the induction of spontaneous and induced autoimmune diseases and inhibits Th1 induce IgG2a responses. These actions of the vitamin D3 compounds suggest that it may have potential therapeutic applications in Th1-mediated clinical situations such as autoimmunity and transplantation.
These studies were conducted to determine if supplementation of a corn-soybean meal diet with 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] would increase the utilization of natural phytate phosphorus by broiler chickens. Two experiments were conducted to evaluate the effect of dietary 1,25-(OH)2D3 in the presence and absence of supplemental phytase and at several dietary levels of inorganic phosphorus supplementation. The criteria measured in these studies were weight gain, gain:feed ratio, bone ash, rickets due to phosphorus deficiency, plasma calcium and phosphorus and retention of calcium, phosphorus and phytate phosphorus. In the first experiment, the types and amounts of fecal inositol phosphates were determined by HPLC, and the total fecal phytate was determined by the classic FeCl3 precipitation technique. In the first experiment, the addition of 1,25-(OH)2D3 to the diet in the presence of dietary phytase resulted in greater 9-d weight and bone ash and lower incidence of rickets; the retention of total fecal phytate and phytate phosphorus was greater than in controls. The second experiment was a complete 2 x 2 x 2 factorial design [phosphorus levels x phytase x 1,25-(OH)2D3]. The addition of 1,25-(OH)2D3 alone to the diet resulted in greater 9-d weight and bone ash, lower incidence of rickets, and greater retention of total calcium and phosphorus and phytate phosphorus. The highest retention of phytate phosphorus (79.4%) was obtained when both phytase and 1,25-(OH)2D3 were present in the diet. The possible mode of action and importance of these results in many areas of nutrition and environmental science are discussed.
The influence of triiodothyronine (T3) on the induction of intestinal calcium and inorganic phosphate (Pi) transport by 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) was studied in 48 h cultures of embryonic chick jejunum. While T3 alone had no effect on calcium uptake by gut segments cultured on d 20 of embryonic development, the thyroid hormone amplified the effect of 1,25-(OH)2D3 on calcium transport and effectively shifted the dose-response curve to lower 1,25-(OH)2D3 concentrations. T3 had a dual effect on Pi uptake by cultured jejunum: It induced transport activity even in the absence of the steroid hormone, and, in addition, synergistically raised 1,25-(OH)2D3-related Pi uptake. In d 17 embryonic small intestine, which does not respond to 1,25-(OH)2D3 by a significant increase in Pi transport, T3 permitted the induction of Pi transport by the sterol. In general, the thyroid hormone enhanced the responsiveness of cultured embryonic intestine toward 1,25-(OH)2D3 by two orders of magnitude, resulting in facilitated induction of calcium and Pi transport by the sterol and, in particular, modulated the stage-specific expression of 1,25-(OH)2D3 action on intestinal Pi transport.
1,25-Dihydroxycholecalciferol, the apparent active form of vitamin D3 (cholecalciferol) which mediates calcium translocation in bone and intestine, has been tested for its nutritional efficacy in preventing rickets. Chicks were fed a vitamin D-deficient diet and received oral supplements of 1,25-dihydroxycholecalciferol, 25-hydroxycholecalciferol or cholecalciferol for 3 weeks. Growth, plasma calcium concentration, calcium absorption and percentage bone ash were determined; sections of tibia were examined microscopically for evidence of rickets, 1,25-Dihydroxycholecalciferol displayed an effectiveness similar to 25-hydroxycholecalciferol, with both metabolities being between 1.5 and 2.2 times as active as cholecalciferol with respect to stimulation of weight gain and maintenance of plasma calcium levels. The antirachitic potency of 1,25-dihydroxycholecalciferol in chicks is estimated to be 1.3 times that of cholecalciferol. Thus, 1,25-dihydroxycholecalciferol was found to be more potent than the parent sterol in terms of supporting normal calcium and bone metabolism, and the metabolite alleviated all signs of rickets. These data substantiate the conclusion that 1,25-dihydroxycholecalciferol is the hormonal form of vitamin D and indicate that other metabolites of the vitamin are not required for the regulation of calcium metabolism and prevention of bone disease.
The purpose of this study was to determine the effect of food restriction on age-related changes in serum 1,25-dihydroxyvitamin D and PTH, two important regulators of Ca metabolism. Starting at 6 wk, male F344 rats were fed a purified diet either ad libitum (non-restricted) or 60% of ad libitum (restricted). Rats from each group were killed at 5, 13, 22 and 28 mo of age. Dietary restriction increased the median lifespan from 24 to 31 mo. It delayed the rapid decrease in serum 1,25-dihydroxyvitamin D from 1.5-5.0 mo in the non-restricted group to 5-13 mo in the restricted group. It also completely suppressed the marked rise in serum PTH which occurred at 22 and 28 mo in the non-restricted group. Dietary restriction had these effects even though both groups of animals consumed the same amount of Ca per gram body weight. Diet had no effect on serum Ca and P, except at 28 mo. These effects of dietary restriction on serum 1,25-dihydroxyvitamin D and PTH may result in altered Ca metabolism in dietary restricted F344 rats.
Dietary 25-hydroxycholecalciferol (25-hydroxycholecalciferol (25-OH-D3) and 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] showed vitamin D activity in rainbow trout. However, inclusion of dietary cholecalciferol (vitamin D3 or D3), ergocalciferol (vitamin D2 or D2), 25-OH-D3 or 1,25-(OH)2D3 did not result in the presence of detectable levels of vitamin D or 25-OH-D in the blood plasma of the fish. Fish fed the diet devoid of vitamin D over an extended period of time showed symptoms of a droopy-tail or "lordosis-like" syndrome that appeared to be related to muscle weakness since x-ray examination indicated no abnormality in vertebral development. The requirement for vitamin D as cholecalciferol was in excess of 1600 IU/kg diet and may be as high as, or higher than 2400 IU/kg diet.
Male Lewis rats (n = 27) were fed a nonpurified diet containing 0.9% calcium, 0.7% phosphorus, and 0.005% zinc until 8 wk of age. At this time rats were assigned randomly to one of two groups. Both groups were fed a low calcium, low zinc, purified diet (0.2% calcium, 0.4% phosphorus, less than 0.00007% zinc), but one group was fed 1.78 mg Zn/(animal.d). The zinc-replete animals were individually matched by weight to the zinc-depleted animals and pari-fed. Balances and plasma concentrations of zinc, calcium, and phosphorus and parathyroid hormone, 25 hydroxycholecalciferol [25(OH)D] and 1,25-dihydroxycholecalciferol [1,25(OH)2D] were determined at the start of calcium depletion and 2 wk later. Calcium and 25(OH)D levels were lower in both groups after calcium depletion. Dietary zinc had no significant effect on calcium or 25(OH)D levels. Phosphorus concentrations were lower after calcium depletion, but phosphorus concentration was higher in the zinc-depleted compared with the zinc-replete group at the end of the experiment. 1,25(OH)2D increased in both groups, but was higher in the zinc-replete than the zinc-depleted group at the end of the experiment. Calcium and phosphorus balances were greater in the zinc-depleted group at the end of the experiment. We conclude zinc depletion diminishes the response of 1,25(OH)2D to calcium depletion in rats. The mechanism is unknown, but may involve nonhormonally mediated changes in gastrointestinal absorption of calcium and phosphorus or an affect of zinc on extraintestinal processes.
The relative potencies of 1,25-dihydroxycholecalciferol, 24-F-1,25-dihydroxycholecalciferol, and 24,24-F2-1,25-dihydroxycholecalciferol at three doses (25, 100 or 400 micrograms) were assessed in nonlactating Jersey cows. The 24,24-F2-1,25-dihydroxycholecalciferol induced a significantly greater hypercalcemia and hyperphosphatemia than did 1,25-dihydroxycholecalciferol. The 24-F-1,25-dihydroxycholecalciferol was intermediate in its hypercalcemic and hyperphosphatemic potency. Urinary hydroxyproline excretion rate and plasma hydroxyproline concentration were not significantly increased by treatment with any of the compounds. This indicates that these compounds did not stimulate bone resorption in nonlactating, nongravid cows. Renal function was significantly impaired in cows that received a 400-micrograms dose of any compound. There was a severe reduction in glomerular filtration rate (up to 42%) and urine specific gravity. Renal function was most severely affected in cows treated with 24,24-F2-dihydroxycholecalciferol and was evident even at the 100-micrograms dosage level.
1,25-dihydroxycholecalciferol [1,25(OH)(2)D(3)] is important in the regulation of cell growth, differentiation, and apoptosis. Previous results from our laboratory demonstrate that 1,25(OH)(2)D(3) inhibits vitamin E succinate (VES) mediated apoptosis in untransformed C3H10T1/2 mouse fibroblast cells. The current work investigated cell survival signaling pathways that may be activated by 1,25(OH)(2)D(3), leading to protection from apoptosis. Results showed that nuclear factor kappaB (NFkappaB) transcriptional activity was significantly increased 1.8-fold over vehicle controls by 1,25(OH)(2)D(3) after 4 h of treatment. Protein kinase B/AKT, a downstream effector of phosphoinositide 3-kinase (PI3K), was activated 4-fold and 8-fold at 2 and 4 h, respectively, after treatment with 1,25(OH)(2)D(3). Pretreatment with two PI3K inhibitors, LY294002 and wortmannin, abolished the activation of NFkappaB by 1,25(OH)(2)D(3), suggesting that this pathway is essential for NFkappaB transcriptional activation. Additionally, the use of a p-21 activated kinase (PAK1) inhibitory construct (PAK(R299)) demonstrated that PAK1 was also required for NFkappaB transcriptional activation by 1,25(OH)(2)D(3). Inhibition of NFkappaB activity with transfection of the NFkappaB inhibitory construct (IkappaB(Ala32)) abolished the protective effect of 1,25(OH)(2)D(3) on VES-mediated apoptosis. In summary, NFkappaB transcriptional activation was essential to 1,25(OH)(2)D(3) protection from VES-mediated apoptosis and 1,25(OH)(2)D(3) regulated NFkappaB activity through PI3K and PAK pathways.
Vitamin D is a conditionally required nutrient traditionally thought to influence physiology as the metabolite 1,25-dihydroxyvitamin D [1,25(OH)(2) D] by binding to the vitamin D receptor (VDR) and stimulating the transcription of genes through direct VDR-DNA interactions. However, over the past 15 y research has demonstrated that 1,25(OH)(2) D, as well as other steroid hormones, can rapidly stimulate ion fluxes and activate protein kinases by transcription-independent mechanisms. This review summarizes recent research on the rapid actions of 1,25(OH)(2) D and identifies questions that remain to be answered in this area.
Anecdotal data suggest that the amount of vitamin D available in the environment either from sunshine exposure or diet may be an important factor affecting the development of inflammatory bowel disease (IBD) in humans. We tested the vitamin D hypothesis in an experimental animal model of IBD. Interleukin (IL)-10 knockout (KO) mice, which spontaneously develop symptoms resembling human IBD, were made vitamin D deficient, vitamin D sufficient or supplemented with active vitamin D (1,25-dihydroxycholecalciferol). Vitamin D-deficient IL-10 KO mice rapidly developed diarrhea and a wasting disease, which induced mortality. In contrast, vitamin D-sufficient IL-10 KO mice did not develop diarrhea, waste or die. Supplementation with 50 IU of cholecalciferol (5.0 microgram/d) or 1, 25-dihydroxycholecalciferol (0.005 microgram/d) significantly (P < 0. 05) ameliorated symptoms of IBD in IL-10 KO mice. 1, 25-Dihydroxycholecalciferol treatment (0.2 microgram/d) for as little as 2 wk blocked the progression and ameliorated (P < 0.05) symptoms in IL-10 KO mice with already established IBD.
A possible role of vitamin D in the growth and development of rats was investigated. Impaired development was observed in normocalcemic, vitamin D-deficient male and female rats, as revealed by low intestinal calcium transport, low renal vitamin D receptor levels and poor bone mineralization. Analogs of 1,25-dihydroxycholecalciferol, possessing reduced calcium-mobilizing activity in intestine and bone but retaining differentiation activity in cultured cells, were unable to support normal development of normocalcemic, vitamin D-deficient male rats. These results suggest that either the calcium-mobilizing activity alone or both the calcium-mobilizing activity and differentiating activity of vitamin D are required for normal development or that the analogs are inactive in vivo. We also demonstrated sex-related differences in intestinal calcium transport, renal vitamin D receptor regulation and bone mineralization that were independent of vitamin D status.
We examined how cholecalciferol (vitamin D) nutrition affected serum 25-hydroxycholecalciferol (25(OH)D) and 1, 25-dihydroxycholecalciferol (1,25(OH)(2)D). Rats were fed conventional diet (vitamin D, 4.5 IU/g, or 7 nmol/d) or the same diet plus 18 nmol/d of extra vitamin D for 3 wk. The extra vitamin D resulted in greater serum 25(OH)D (51 +/- 3, vs. control of 21 +/- 2 nmol/L), and kidney mRNA for vitamin D receptor [VDR mRNA] (P = 0. 026) and lower serum 1,25(OH)(2)D (72 +/- 16 vs. control of 161 +/- 10 pmol/L, P = 0.001), and parathyroid hormone (PTH) (89 +/- 4 vs. control of 160 +/- 15 ng/L, P = 0.001). Kidney VDR mRNA relative to GAPDH mRNA correlated inversely with serum 1,25(OH)(2)D (r = -0.714, P = 0.006). There were no differences in serum calcium, phosphate, alkaline phosphatase, or weight gain. Experiment 2 compared groups supplemented with 0.2, 2 or 20 nmol/d of vitamin D orally, or 20 nmol/d dermally to see how vitamin D nutrition influenced the response of 1,25(OH)(2)D to changes in diet calcium. Vitamin D did not affect urinary calcium or pyridinoline excretion, serum calcium, phosphate, vitamin D binding protein or alkaline phosphatase. In groups given 20 nmol/d of vitamin D, renal mitochondrial 25(OH)D-1alpha-hydroxylase was lower (P < 0.01) and 25(OH)D-24-hydroxylase was higher (P < 0.05). Higher 25(OH)D concentration was related to proportionally lower 1,25(OH)(2)D at every calcium intake, indicating greater tissue sensitivity to 1, 25(OH)(2)D. We conclude suppression of 1,25(OH)(2)D and PTH, and higher renal VDR mRNA and 24-hydroxylase did not involve higher free 1,25(OH)(2)D concentration or a first pass effect at the gut. Thus, 25(OH)D or a metabolite other than 1,25(OH)(2)D is a physiological, transcriptionally and biochemically active, noncalcemic vitamin D metabolite.
An antagonistic interaction between retinol and calciferol has been established. However, the mechanism by which this antagonism occurs is unclear. One possibility is that retinol affects the metabolism of calciferol. To investigate this hypothesis, retinol- and calciferol-depleted rats were given various amounts of ergocalciferol, cholecalciferol, 1alpha,25-dihydroxycholecalciferol [1,25(OH)2D3], or 24,24-difluoro-1alpha,25-dihydroxycholecalciferol [24-F2-1,25(OH)2D3] in combination with various amounts of retinyl acetate or all-trans retinoic acid (ATRA) in a series of studies. Rats administered 1720 or 3440 microg retinyl acetate once every 3 d for 33 d in combination with 25.8 ng ergocalciferol or 25 ng cholecalciferol every 3 d had lower serum calcium and greater serum phosphorus concentrations than rats fed 0 or 11.4 mug retinyl acetate every 3 d. In addition, rats fed 400 microg ATRA/d in combination with 25.8 ng ergocalciferol every 3 d, 25 ng cholecalciferol every 3 d, 2-5 ng 1,25(OH)2D3/d, or 0.5-1 ng 24-F2-1,25(OH)2D3/d had significantly lower serum calcium and higher serum phosphorus concentrations than rats not given ATRA in the diet. Therefore, both retinyl acetate and ATRA are able to antagonize the action of ergocalciferol and cholecalciferol in vivo. Additionally, ATRA antagonizes the in vivo action of 1,25(OH)2D3 and an analog, 24-F2-1,25(OH)2D3, that cannot be 24-hydroxylated. Together, these results suggest that retinol does not antagonize the action of calciferol by altering the metabolism of calciferol or 1,25(OH)2D3, but does so by another mechanism.
Extracts of the calcinogenic plants Solanum malocoxylon and Cestrum diurnum stimulate phosphate absorption by the jejunum of vitamin D-deficient chicks, as determined by everted gut sac technique. Their action on cellular pathways of transepithelial phosphate transport is indistinguishable thereby from that of cholecalciferol. Increased net absorption from the lumen was due to enhanced uptake of phosphate from the luminal side, while leakage of tissue phosphate in the opposite direction was apparently unaffected. Steep serosa/mucosa concentration gradients were observed as consequence of enhanced levels of transepithelial phosphate flux in the mucosa-to-serosa direction. With respect to their stimulatory action on phosphate absorption, the calcinogenic plant factors retained their biological activity when phosphate transport was depressed by a high strontium diet. Their action in overcoming the strontium inhibition of phosphate absorption, calcium-binding protein synthesis, and alkaline phosphatase activity, was comparable to the effect of 1,25-dihydroxycholecalciferol. On the basis of these biological responses, the action of the plant factors from Solanum malacoxylon and Cestrum diurnum provides further evidence for their close resemblance to the hormonally active sterol.
Dihydroxycholecalciferol, the metabolite of vitamin D be lieved to be the metabolically active form in the stimulation of intestinal calcium absorption and in the mobilization of calcium from bone, is much less effective administered orally and chronically than either choleealciferoi or 25-hydroxy- cholecalciferol in the calcification of bone and in the elevation of serum calcium concentration of rats. However, when it is administered either intravenously or intraperitoneally, it is at least as effective and possibly more effective than 25- hydroxycholecalciferol in the elevation of plasma calcium and phosphorus and in the calcification of bone. These results are consistent with the concept that 1,25-dihydroxycholecalciferol represents the hormonal form of vitamin D respon sible for the maintenance of serum calcium at the expense of either bone or diet. J. Nutr. 102: 1569-1578, 1972.
Keratinocytes produce vitamin D, metabolize it to its most biologically active form, 1,25(OH)2D, and respond to the 1,25(OH)2D they produce with a decrease in proliferation and an increase in differentiation. 1,25(OH)2D production by keratinocytes is tightly controlled and changes as the cells differentiate, increasing during the early stages of differentiation and then decreasing again as terminal differentiation ensues. The 1,25(OH)2D produced endogenously or supplied exogenously acts in concert with calcium and products of phosphoinositide metabolism to stimulate the transition from a proliferating basal cell to a terminally differentiated corneocyte. The mechanisms involved include changes in gene transcription and messenger RNA stability. These antiproliferative, prodifferentiating actions of 1,25(OH)2D3 have led to its successful use in psoriasis, a hyperproliferative skin disease, and may lead to its use as a chemopreventive agent in malignancy.
Recent research suggests that 1,25-dihydroxyvitamin D [1,25(OH)(2)D], a steroid hormone that regulates calcium homeostasis, may also play a role in the development and progression of cancer, multiple sclerosis, cardiovascular, and other diseases. Decreased serum 1,25(OH)(2)D concentrations are often observed in overweight and obese patients. However, little is known about the factors that may influence 1,25(OH)(2)D renal synthesis, because it is generally accepted that serum 1,25(OH)(2)D concentration is strictly regulated by parathyroid hormone and serum concentrations of calcium and phosphorus. In this study, the associations among serum 1,25(OH)(2)D, serum 25-hydroxyvitamin D [25(OH)D], and body composition were analyzed in 1779 patients with excess body weight registered in a Metabolic and Medical Lifestyle Management Clinic in Oslo, Norway. According to our results, serum 25(OH)D, adiposity, age, season of blood sampling, and gender directly influence serum 1,25(OH)(2)D (r = 0.33; P < 0.001), with serum 25(OH)D being the strongest predictor for serum 1,25(OH)(2)D. The 1,25(OH)(2)D concentrations were 25.4 pmol/L (95% Cl: 19.3-31.5; P < 0.001) lower in the lowest 25(OH)D quartile to compared with highest quartile. A seasonal variation was observed for both vitamin D metabolites. Thus, our results suggest that in patients with excess body weight, serum 1,25(OH)(2)D concentrations were associated with 25(OH)D and varied during the year. Therefore, it may also be valuable to measure both serum 25(OH)D and 1,25(OH)(2)D for the evaluation of vitamin D status in overweight and obese persons.
1,25-Dihydroxycholecalciferol [1,25-(OH)2D3] has been shown to inhibit the progression of experimental autoimmune encephalomyelitis (EAE). Here we tested the possibility that 1, 25-dihydroxycholecalciferol might be therapeutic for another autoimmune disease, arthritis. Two different animal models of arthritis were tested, namely, murine Lyme arthritis and collagen-induced arthritis. Infection of mice with Borrelia burgdorferi (the causative agent of human Lyme arthritis) produced acute arthritic lesions including footpad and ankle swelling. Supplementation with 1,25-dihydroxycholecalciferol of an adequate diet fed to mice infected with B. burgdorferi minimized or prevented these symptoms. Mice immunized with type II collagen also developed arthritis. The symptoms of this disease were also prevented by dietary supplementation with 1,25-dihydroxycholecalciferol. 1, 25-Dihydroxycholecalciferol given to mice with early symptoms of collagen-induced arthritis prevented the progression to severe arthritis compared with untreated controls. These results suggest that 1,25-dihydroxycholecalciferol and/or its analogs may be a valuable treatment approach to this disease.
A number of model systems now exist for studying the nonnuclear actions of the seco-steroid hormone 1,25(OH)2D3. The perfused duodenal loop of vitamin D-replete chicks has provided the best correlation between nonnuclear actions and a physiological end point, namely enhanced calcium transport. Recent progress has been made in identifying and purifying an integral protein of the basal lateral membrane that may be a receptor for 1,25(OH)2D3. Studies with analogues (particularly 1,25(OH)2-7-dehydrocholesterol and 1,25(OH)2-lumisterol3) have provided definite correlations between binding to the solubilized membrane receptor and the ability to initiate transcaltachia (the rapid hormonal stimulation of calcium transport).
Metabolic balance studies were undertaken to determine whether sodium bicarbonate (NaHCO3) supplements (4.5 mmol/day) altered 7-day cumulative calcium (Ca) phosphorus (P) balances in growing rats consuming either a basal diet providing 0.6% Ca and 0.3% P, or this diet plus 1,25-dihydroxycholecalciferol [40 ng 1,25(OH)2D3/day]. Feeding bicarbonate lowered urinary Ca but raised fecal Ca so that Ca balance became less positive. However, 1,25(OH)2D3 increased net absorption of Ca and P to the same degree when given to control rats and rats consuming bicarbonate. Nevertheless, bicarbonate-fed rats had lower net Ca absorption than controls, even when treated with high doses of 1,25(OH)2D3. Changes in net Ca absorption induced by bicarbonate may occur at a point in the gut distal to the duodenum since duodenal 45Ca absorption was decreased by bicarbonate feeding. The present results show that bicarbonate consumption depressed net Ca absorption in the rat. The effect appears to be independent of changes in 1,25(OH)2D3 metabolism because it is manifest in animals receiving high doses of 1,25(OH)2D3, which stimulate alimentary Ca absorption maximally, and because bicarbonate-fed rats are able to respond normally to exogenous 1,25(OH)2D3 by increasing their net absorption of Ca and P. In view of this demonstration that NaHCO3 supplements elevate fecal Ca loss in the rat, it is suggested that studies should be undertaken to determine whether bicarbonate exerts similar adverse effects on Ca balance in humans.
Recent studies have identified a heterodimer of the vitamin D receptor (VDR) and the retinoid X receptor (RXR) as the active complex for mediating positive transcriptional effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the active hormonal form of vitamin D. The VDR-RXR heterodimer has been shown to bind to direct repeat vitamin D-responsive elements (VDREs) upstream of positively controlled genes in the target tissues for vitamin D, including bone (osteocalcin, osteopontin, and beta 3 integrin), kidney (24-hydroxylase) and intestine (calbindin). Residues that participate in heterodimer formation have been identified in the C-terminal hormone-binding domain by analysis of VDR mutants. The role of the 1,25(OH)2D3 ligand in transcriptional activation by the VDR-RXR heterodimer is not entirely clear, but studies of two natural VDR mutants suggest that the binding of both hormone and RXR are required to induce a receptor conformation that is competent to activate transcription. A final level of complexity is added by recent observations that VDR is modified by phosphorylation. Thus, the VDR-mediated action of 1,25(OH)2D3 is now known to involve multiple factors that may provide a conceptual basis for future understanding of the tissue-specific genomic effects of 1,25(OH)2D3.
To determine the relevance of circulating 1,25-dihydroxycholecalciferol [1,25(OH)2D3] to the pathogenesis of hypocalcemia during magnesium deficiency, growing chicks were pair fed control or Mg-deficient diets with or without 1,25(OH)2D3 supplementation. Within 14 d, chicks fed the Mg-deficient diet without 1,25(OH)2D3 supplementation exhibited hypomagnesemia and hypocalcemia compared to control chicks. 1,25-Dihydroxycholecalciferol supplementation in Mg-deficient chicks elevated plasma 1,25(OH)2D3 twofold and increased plasma calcium to control levels. Supplementation with 1,25(OH)2D3 did not increase plasma Mg concentration in Mg-deficient chicks, indicating that exogenous 1,25(OH)2D3 prevented hypocalcemia in the absence of greater Mg availability. Magnesium-deficient chicks supplemented with 1,25(OH)2D3 had more intestinal calbindin D-28K relative to Mg-deficient nonsupplemented chicks, suggesting that increased absorption of dietary Ca may have contributed to the greater plasma Ca concentration in 1,25(OH)2D3 supplemented Mg-deficient chicks. Although clinical hypomagnesemia has been associated with vitamin D resistance, our data indicate that primary Mg deficiency did not impair target tissue responsiveness to 1,25(OH)2D3, at least at the level of the intestine. Supplementation with 1,25(OH)2D3 did not increase bone Mg concentration and did not alter the characteristic skeletal morphology. It also did not increase bone Ca concentration in Mg-deficient chicks. The data suggest that skeletal alterations during Mg deficiency result from hypomagnesemia per se, rather than hypocalcemia or insufficient 1,25(OH)2D3.
The combined effects of dietary calcium level and lead level on several indices of vitamin D endocrine function were examined in young, growing chicks. Day-old animals fed a nutritionally adequate diet for 2 wk were fed diets either adequate (1.2%) or low (0.1%) in calcium, and containing 0, 0.2 or 0.8% lead for an additional 1 or 2 wk. In the calcium-adequate group, lead ingestion significantly elevated intestinal calbindin-D28k protein and mRNA levels as well as plasma 1,25-dihydroxyvitamin D concentration compared with the control animals fed a lead-free diet. The effect was apparent after 1 wk of treatment and continued through wk 2. In the calcium-deficient group, the early (1 wk) increases in plasma 1,25-dihydroxyvitamin D and calbindin-D28k protein and mRNA were significantly reversed by lead ingestion over the 2-wk trial period in a dose-dependent fashion. In these circumstances, vitamin D endocrine function is severely compromised. Therefore, lead ingestion may result in either enhanced or diminished circulating 1,25-dihydroxyvitamin D concentrations and ensuing intestinal responses, depending of dietary calcium level and the duration of lead intake. These results provide possible explanations for several apparently conflicting sets of observations regarding lead-calcium interactions.
Four experiments were conducted to determine the effect of dietary cholecalciferol (vitamin D3), 25-hydroxycholecalciferol (25-OHD3) and 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) on the changes in growth, feed efficiency and bone ash, and the incidence, severity and number of #3 scores of tibial dyschondroplasia caused by the addition of disulfiram to the diet. The basal diet used was low in calcium and high in phosphorus and chlorine and known to promote a high incidence of tibial dyschondroplasia in broiler chickens. The chickens in all experiments received enough ultraviolet radiation from fluorescent lights in the pens to nearly satisfy their need for vitamin D. The addition of disulfiram to the diet caused an increase in most of the measurements indicating development of tibial dyschondroplasia in all of the experiments, and caused a decrease in bone ash in two of the experiments and a decrease in growth and gain:feed in one experiment. The addition of D3 to a diet containing no D3 caused higher bone ash and lower incidence of tibial dyschondroplasia in the absence or presence of disulfiram. The effects of the addition of 25-OHD3 to diets containing approximately five times the requirement of D3 in the absence and presence of disulfiram caused variable results. The addition of 1,25-(OH)2D3 to the D3-supplemented diet in the absence or presence of disulfiram caused dramatic increases in bone ash and a decrease in most of the criteria used to measure development of tibial dyschondroplasia. There was no indication of interaction of the effects of D3, 25-OHD3 and 1,25-(OH)2D3 with the action of disulfiram.
The active form of vitamin D (1,25-dihydroxycholecalciferol) is a potent immune system regulator. Treating mice with 1, 25-dihydroxycholecalciferol and feeding them diets high in calcium can completely suppress the induction of experimental autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE). Experiments described here were carried out on mice in which development of EAE was induced. Mice were fed diets containing various amounts of calcium and 1,25-dihydroxychole-calciferol. Variables measured were as follows: 1) incidence and severity of EAE; 2) serum calcium concentrations; 3) body weight; 4) total number of cells in the lymph nodes; and 5) interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) mRNA levels. When calcium was removed from the diet, the incidence of EAE was reduced 20% in both males and females. Further, the lower the dietary level of calcium, the higher was the dose of 1,25-dihydroxycholecalciferol required to prevent the symptoms. Thus, 1, 25-dihydroxycholecalciferol was found most effective in mice fed a diet adequate or high in calcium. 1,25-Dihydroxycholecalciferol treatment of mice fed high dietary calcium resulted in a decreased number of lymphocytes in the lymph nodes and increased IL-4 and TGF-beta1 mRNA levels. When calcium was omitted from the diet, 1, 25-dihydroxycholecalciferol supplementation increased TGF-beta1 mRNA. Increased IL-4 mRNA and decreased lymphocytes in the lymph nodes in response to 1,25-dihydroxycholecalciferol occurred only when dietary calcium was adequate or high. Our results suggest that dietary calcium and 1,25-dihydroxycholecalciferol are both involved in the prevention of symptomatic EAE.
1,3-Butanediol-1,3-dioctanoate (BDDO), a synthetic source of energy, has been shown to be equal to corn oil when fed to chicks recovering from moderate and severe Newcastle disease virus infections. Body weight increments of chicks fed diets containing 10% BDDO were equal to or greater than those of chicks fed 10% corn oil, both with restricted feeding regimens. Kilocalories of metabolizable energy required to produce 100 g of body weight increment over a basal group was used as a means of quantitating energy demand. BDDO was comparable to corn oil as an energy source with no adverse effects. Liver/body weight ratios were greater in the BDDO-fed chicks. Circadian rhythmicity of liver size and liver glycogen content was demonstrated. Chicks fed BDDO had total liver glycogen content threefold that of the corn oil controls, which was attributed to stimulation of insulin secretion. Catch-up growth in the chick following the growth depression of disease appears to be as well facilitated by a synthetic source as by a natural one.
The activities of malic and phosphoenolpyruvate carboxykinase (PEPcK) enzymes of 105,000 X u (1 hour) supernatants of liver and epididymal fat from rats fed 1,3-butanediol (BD) were examined. In animals fed a BD diet the liver PEPcK activity was increased. Malic enzyme activity in both liver and adipose tissue was the same with and without BD. Mitochondrial synthesis of precursors for glu- coneogenesis from pyruvate and bicarbonate by liver pyruvate carboxylase was slightly increased in animals fed BD. All other metabolites remained unchanged. The concen trations of metabolites in liver and kidney were measured in animals fed a BD diet. There was an increase in 3-carbon phosphorylated intermediates in kidney but not liver. In both liver and kidney the lÃ¡clate levels were lower in animals fed BD. The decrease in blood glucose levels in rats fed BD diets is attributed to the block of glu- coneogenesis in kidney at the conversion of 3-phosphoglycerate to glyceraldehyde-3- phosphate. It is also suggested from malic enzyme activity that BD does not interfere with lipogenesis in liver and adipose tissues.
The influence of feeding the polyhydric alcohol 1,3-butanediol (BD), on tissue lipids of normal and cold-exposed rats was investigated. The addition of 20% BD to a 30% fat diet lowered adipose tissue lipids with a concomitant elevation of liver lipids at either normal or cold environments. Feeding a 30% fat diet to rats for 2 weeks and then exposing them to moderate cold of 5Â°,or severe cold â€"10Â° without food for 72 hours produced decreases in the total lipid content of epididymal adipose tissue, liver, and muscle. Rats fed a similar diet, without cold exposure but also starved for 72 hours, showed no decrease in the total quantity of adipose tissue lipids.