Activation of methionine synthase by insulin-like growth factor-1 and dopamine: a target for neurodevelopmental toxins and thimerosal

Methylation events play a critical role in the ability of growth factors to promote normal development. Neurodevelopmental toxins, such as ethanol and heavy metals, interrupt growth factor signaling, raising the possibility that they might exert adverse effects on methylation. We found that insulin-like growth factor-1 (IGF-1)- and dopamine-stimulated methionine synthase (MS) activity and folate-dependent methylation of phospholipids in SH-SY5Y human neuroblastoma cells, via a PI3-kinase- and MAP-kinase-dependent mechanism. The stimulation of this pathway increased DNA methylation, while its inhibition increased methylation-sensitive gene expression. Ethanol potently interfered with IGF-1 activation of MS and blocked its effect on DNA methylation, whereas it did not inhibit the effects of dopamine. Metal ions potently affected IGF-1 and dopamine-stimulated MS activity, as well as folate-dependent phospholipid methylation: Cu(2+) promoted enzyme activity and methylation, while Cu(+), Pb(2+), Hg(2+) and Al(3+) were inhibitory. The ethylmercury-containing preservative thimerosal inhibited both IGF-1- and dopamine-stimulated methylation with an IC(50) of 1 nM and eliminated MS activity. Our findings outline a novel growth factor signaling pathway that regulates MS activity and thereby modulates methylation reactions, including DNA methylation. The potent inhibition of this pathway by ethanol, lead, mercury, aluminum and thimerosal suggests that it may be an important target of neurodevelopmental toxins.

Iodine fortification is related to increased weight-for-age and birthweight in children in Asia

Severe iodine deficiency causes stunting and mental retardation in utero, but the relation between mild deficiency and child growth is not well known. The use of iodated salt in relation to anthropometric data was examined from recent survey data. After potential confounding factors had been controlled for, significant associations were seen in Bangladesh, India, Nepal, and Sri Lanka. The use of iodated salt was related to increased weight-for-age and mid-upper-arm circumference, most strongly in the second year of life, mainly affecting soft tissue (thinness). The relation with weight-for-age was greater among children of mothers with lower body mass index. The use of iodated salt was related to birthweight in Sri Lanka and in the Philippines, where iodized oil capsules given during pregnancy had a negative effect when used with high levels of iodine in salt. The associations generally were concentrated in large geographic areas, possibly because of interactions with other environmental factors (e.g., selenium and arsenic). The apparent growth response to iodine may reflect functional effects of mild deficiency, which is widespread, possibly including effects on brain development.

Morphology and morphometry of in vivo- and in vitro-produced bovine concepti from early pregnancy to term and association with high birth weights

This study was designed to characterize conceptus development based on pre- and postnatal measurements of in vivo- and in vitro-derived bovine pregnancies. In vivo-produced embryos were obtained after superovulation, whereas in vitro-produced embryos were derived from established procedures for bovine IVM, IVF and IVC. Blastocysts were transferred to recipients to obtain pregnancies of single (in vivo/singleton or in vitro/singleton groups) or twin fetuses (in vitro/twins group). Ultrasonographic examinations were performed weekly, from Day 30 of gestation through term. Videotaped images were digitized, and still-frames were used for the measurement of conceptus traits. Calves and fetal membranes (FM) were examined and measured upon delivery. In vitro-produced fetuses were smaller than in vivo controls (P < 0.05) during early pregnancy (Day 37 to Day 58), but in vitro/singletons presented significantly higher weights at birth than in vivo/control and in vitro/twin calves (P < 0.05). From late first trimester of pregnancy (Day 72 to Day 93), placentomes surrounding in vitro-derived singleton fetuses were longer and thinner than controls (P < 0.05). At term, the presence of giant cotyledons in the fetal membranes in the in vitro group was associated with a larger cotyledonary surface area in the fetal horn (P < 0.05). The biphasic growth pattern seen in in vitro-produced pregnancies was characterized by conceptus growth retardation during early pregnancy, followed by changes in the development of the placental tissue. Resulting high birth weights may be a consequence of aberrant placental development due to the disruption of the placental restraint on fetal growth toward the end of pregnancy.

Early failures in total knee arthroplasty

Total knee arthroplasty is a predictable operation. Unfortunately, there is a subset of patients who do not do well and require revision surgery within the first 5 years. The purpose of the current study was to analyze the mechanisms of failure in patients who had revision surgery within 5 years of their index arthroplasty. Between 1986 and 1999, 440 patients with total knee arthroplasties were referred for revision surgery. An analysis of patients in whom the arthroplasties failed within 5 years of the index arthroplasty and the reasons for early failure were documented. Of the 440 patients who had revision surgery, 279 (63%) had revision surgery within 5 years of their index arthroplasty: 105 of the 279 patients with early failures (38%) had revision surgery because of infection; 74 (27%) had revision surgery because of instability; 37 (13%) had revision surgery because of failure of ingrowth of a porous-coated implant; 22 (8%) had revision surgery because of patellofemoral problems; and 21 (7%) had revision surgery because of wear or osteolysis. Only eight of the 279 patients with early failures (3%) had revision surgery because of aseptic loosening of a cemented implant. The remaining 12 patients had revision surgery because of miscellaneous problems. Host factors may prevent infection from ever being eradicated totally. The two other major patterns of failure in this series were failure of cementless fixation and instability. If all of the arthroplasties in the patients in this early failure group would have been cemented routinely and balanced carefully, the total number of early revisions would have decreased by approximately 40%, and the overall failures would have been reduced by 25%.

Acetabular labral tears in the athlete

Pathologic involvement of the acetabular labrum is an increasingly recognized phenomenon. Athletes involved in sports that require repetitive twisting or who suffer trauma to the hip are at risk of injury to the acetabular labrum. Injury mechanisms that include hyperextension, hyperflexion, or extremes of abduction place the labrum at particular risk. Symptoms may be acute in onset or, more commonly, insidious onset with persistence or escalation of symptoms. The orthopaedic surgeon evaluating patients with sports-related hip injuries needs to remain cognizant of intraarticular injuries within the hip and, in particular, injuries to the acetabular labrum. Further investigation is needed to fully define the functional importance of the acetabular labrum. Arthroscopic management has been successful in evaluation and management of acetabular labral tears.

Folate status among patients with non-small cell lung cancer: a case-control study

BACKGROUND AND OBJECTIVES

This case control study explored the purported inverse relationship between folate status and lung cancer development.

METHODS

Folate status of 46 postoperative non-small cell lung cancer (NSCLC) patients was compared to that of 44 non-cancer patients. Cancer patients had completed treatment > 3 months prior and had no evidence of cancer. Ineligibility criteria for all patients included (1) > 2 alcoholic drinks/day (2) ongoing tobacco use, or (3) folate supplementation > 400 microg/day.

RESULTS

No differences were found between groups in serum and RBC folate after adjustment for age and use of folate-interfering medications: geometric means (GM) x /geometric standard error (GSE): 7.9 ng/ml x /1.1 vs. 7.8 ng/ml x /1.1, respectively (P = 0.91) for serum folate; 264 ng/ml x /1.1 vs. 263 ng/ml x /1.1, respectively (P = 0.97) for RBC folate. Age- and creatinine-adjusted homocysteine was no different between groups: GM x /GSE: 9.4 micromol/L x /1.0 vs. 8.6 micromol/L x /1.0, respectively (P = 0.17). No difference were seen in folate intake. Frequencies of the homozygous genotype for the MTHFR polymorphism, an enzyme important in folate metabolism and associated with a reduced risk of other cancers, were no different.

CONCLUSIONS

This case control study does not support the hypothesis that low folate is an independent risk factor for NSCLC.

Colonic mucosal concentrations of folate are accurately predicted by blood measurements of folate status among individuals ingesting physiologic quantities of folate

Folate status is inversely related to the risk of colorectal cancer. Whether conventional blood measurements of folate status accurately reflect folate concentrations in the colorectal mucosa has been a controversial topic. This is an important issue because accurate measures of folate status in the colorectal mucosa are important for ascertaining the risk of colorectal cancer in epidemiological studies and for determining the effects of folate supplementation in clinical trials. We examined whether conventional blood measurements of folate and a more sensitive, inverse indicator of systemic folate status, serum homocysteine, accurately reflect folate concentrations in human colonic mucosa obtained by endoscopic biopsy. Study subjects (n = 20) were participants in a randomized trial that investigated the effect of folate supplementation (5 mg daily for 1 year) on provisional molecular markers of colon cancer. Blood samples and biopsies of normal rectosigmoid mucosa were obtained at baseline, at 6 months, and at 1 year. Serum, RBC, and colonic mucosal folate and serum homocysteine concentrations were determined. Colonic mucosal folate concentrations correlated directly with serum folate concentrators at each time point (r = 0.572-0.845; P < 0.015) and with RBC folate concentrations at 6 months and 1 year (r = 0.747-0.771; P < 0.001). Colonic mucosal folate concentrations correlated inversely with serum homocysteine concentrations at each time point (r = -0.622-0.666; P < 0.008). Systemic measures of folate status did not correlate with colonic mucosal folate concentrations among individuals receiving supplemental folate. Our observations indicate that colonic mucosal concentrations of folate may be predicted accurately by blood measurements of folate status only among individuals not ingesting supraphysiological quantities of folate.

Effects of folate supplementation on two provisional molecular markers of colon cancer: a prospective, randomized trial

OBJECTIVES

Dietary folate intake is inversely associated with the risk of colorectal cancer. This study investigated the effect of folate supplementation on genomic DNA methylation and DNA strand breaks in exons 5-8 of the p53 gene of the colonic mucosa, two provisional biomarkers of colon cancer.

METHODS

Twenty subjects with adenomas were randomized to receive either folate (5 mg/day) or placebo for 1 yr after polypectomy. At baseline, 6 months and 1 yr, systemic and colonic measures of folate status were determined, as were the biomarkers mentioned earlier.

RESULTS

Folate supplementation increased serum, red blood cell and colonic mucosal folate concentrations (p < 0.02). Folate supplementation also increased the extent of genomic DNA methylation at 6 months and 1 yr (p = 0.001), whereas placebo administration was associated with an increase in the extent of genomic DNA methylation only at 1 yr. Similarly, folate supplementation decreased the extent of p53 strand breaks in exons 5-8 at 6 months and 1 yr (p < 0.02), whereas placebo administration was associated with a decrease in the extent of p53 strand breaks only at 1 yr.

CONCLUSIONS

Both of these provisional biomarkers of colon cancer underwent accelerated improvement at 6 months with folate supplementation. However, these markers also improved with placebo at 1 yr. Therefore, potential confounding factors that seem to modulate these biomarkers need to be identified and corrected in order for these markers to serve as suitable surrogate endpoints in folate chemoprevention trials.

Articulating versus static spacers in revision total knee arthroplasty for sepsis. The Ranawat Award

Antibiotic laden spacer blocks frequently are used to treat an infected total knee arthroplasty. Static spacer blocks make exposure at reimplantation difficult secondary to quadriceps shortening. Unexpected bone loss attributable to migration of the spacer block also has been reported. To avoid these problems, a temporary articulating molded implant made of antibiotic cement was used in a consecutive series. The authors sought to determine whether its use would affect the reinfection rate, improve functional results, or prevent bone loss compared with static spacers. Twenty-five patients were treated with static nonarticulating spacers. Since 1996, 30 patients have been treated with tobramycin-laden articulating spacers. The knee arthroplasties in three patients treated with a static spacer became reinfected (12%). The knee arthroplasty in one patient with an articulating spacer became reinfected (7%). Fifteen of the 25 patients with static spacers had unexpected bone loss between stages. No appreciable bone loss could be measured in the patients who received articulating spacers. The average Hospital for Special Surgery score was 83 points in the patients with static spacers and 84 points for the patients with articulating spacers. Range of motion at final followup averaged 98 degrees in the patients who received static spacers and 105 degrees in the patients who received articulating spacers. Articulating spacers seem to facilitate reimplantation of infected total knee arthroplasty without additional risk of infection. Unexpected bone loss is no longer a concern with this two-stage technique. Articulating spacers offered no functional advantage over static spacers in this study group.

Effects of dietary folate on intestinal tumorigenesis in the apcMin mouse

Dietary folate appears to be inversely related to colorectal cancer risk. This study investigated the effects of dietary intervention with folate or the development of intestinal polyps in Min (Apc +/-) mice. Weanling Mil mice were fed diets containing 0, 2 (basal requirement), 8, or 20 mg folate/kg diet. At 3 and 6 months of dietary intervention, 50% of the mice from each group were sacrificed, and the small intestine and colon were analyzed for polyps and aberrant crypt foci (ACF). Serum folate concentrations accurately reflected dietary folate levels (P < 0.001). At 3 months no significant difference in the average number of total small intestinal polyps was observed among the four groups. However, increasing dietary folate levels significantly reduced the number of ileal, but not duodenal or jejunal, polyps in a dose-dependent manner (P-trend = 0.001); folate supplementation at 20 mg/kg diet was associated with a 68-78% reduction in the number of ileal polyps compared with the other three diets (P < 0.007). The number of ileal polyps was inversely correlated with serum folate concentrations (P = 0.03). At 3 months, increasing dietary folate levels significantly decreased the number of colonic ACF in a dose-dependent manner (P = 0.05); the control and two folate supplemented diets significantly reduced the number of colonic ACF by 75 100% compared with the folate-deficient diet (P < 0.04). The number of colonic ACF was inversely correlated with serum folate concentration (P = 0.05). No significant difference in the number of colonic adenoma was observed among the four groups at 3 months. At 6 months, no significant differences in the average number of total small intestinal, duodenal, and jejunal polyps, colonic adenomas, and colonic ACF wer observed among the four groups. However, the folate-deficient diet had 62-76% lower number of ileal polyps compared with the control and two folate-supplemented diets (P < 0.003). Serum folate concentrations, but not dietary folate levels, were directly correlated with the number of ilea polyps (P = 0.006). These data suggest that dietary folate supplementation suppresses the development of ileal polyps and colonic ACF in this model However, at later time points, folate supplementation appears to have an opposite effect on ileal polyps. These data generally support the role of folate in intestinal tumorigenesis suggested in epidemiological studies and chemical carcinogen animal models. Notwithstanding the limitations associated with this model, these data suggest that the optimal timing and dose of folate intervention need to be determined for safe and effective folate chemoprevention.

Genomic DNA hypomethylation, a characteristic of most cancers, is present in peripheral leukocytes of individuals who are homozygous for the C677T polymorphism in the methylenetetrahydrofolate reductase gene

DNA methylation is an epigenetic feature of DNA that influences cellular development and function, and aberrations of DNA methylation are a candidate mechanism for the development of cancer. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate, the methyl donor for methionine synthesis and the precursor of S-adenosylmethionine. S-adenosylmethionine is the universal methyl donor for methylation reactions, including that of DNA methylation. In the present study, we investigated whether a common C677T mutation in the MTHFR gene, which results in reduced enzyme activity in vitro, affects genomic DNA methylation. We selected 9 subjects homozygous for the wild-type MTHFR and 10 subjects homozygous for the mutation (T/T). Genomic DNA methylation was determined by an established enzymatic assay that measures the capacity of DNA to accept methyl groups in vitro, which is inversely related to endogenous methylation. DNA from subjects with the T/T MTHFR genotype had a significantly higher methyl group acceptance capacity (12,615 +/- 1836 dpm/2 microg of DNA) compared with wild-type MTHFR (7843 +/- 1043 dpm/2 microg of DNA; P < 0.05), indicating DNA hypomethylation in the T/T genotype. Furthermore, DNA methylation was directly and significantly related to RBC folate concentrations in persons with the T/T genotype, but not in those with wild-type MTHFR. These data are consistent with prior observations, which suggest that the T/T genotype is associated with impaired MTHFR activity in vivo and that the cellular impact of this impairment is determined, in part, by folate status. The relationship of genomic DNA hypomethylation in persons with the T/T MTHFR genotype to the development of cancer remains to be defined.

Effects of dietary folate on DNA strand breaks within mutation-prone exons of the p53 gene in rat colon

BACKGROUND & AIMS

Diminished folate status has been observed to increase colorectal cancer risk. Folate plays an important role in DNA synthesis and repair. This study investigated the effects of dietary folate on DNA strand breaks in the p53 and Apc genes, and how these changes are related to steady-state levels of the corresponding transcripts.

METHODS

Three groups of rats were fed diets containing 0, 2 (basal requirement), or 8 mg folate/kg for 5 weeks. At each weekly time point, plasma and colonic mucosal folate concentrations were determined. Site-specific DNA strand breaks were assessed by semiquantitative PCR. Steady-state levels of messenger RNA were measured by semiquantitative RT-PCR.

RESULTS

Dietary folate deficiency produced progressive DNA strand breaks within exons 5-8 of the p53 gene in rat colon (P<0.02). Accumulation of strand breaks was not observed in other exons of the p53 gene, in the Apc and beta-actin genes, or at the genomic level. Folate supplementation at 4 times the basal requirement significantly increased p53 integrity compared with the basal and deficient diets (P<0.05). p53 integrity in exons 5-8 was significantly correlated with folate status (P<0.03). Dietary folate deprivation progressively decreased, whereas supplementation increased, steady-state levels of p53 transcript over 5 weeks (P<0.05). No such changes were observed for the Apc gene. Steady-state levels of p53 transcript were significantly correlated with folate status and p53 integrity in exons 5-8 (P<0.002).

CONCLUSIONS

These data provide a plausible mechanism by which folate deficiency promotes, and folate supplementation suppresses, colorectal carcinogenesis.

Effect of chronic alcohol consumption on total plasma homocysteine level in rats

BACKGROUND

Chronic alcoholism in humans is associated with the development of hyperhomocysteinemia, the mechanism of which remains unclear. Among the causes of hyperhomocysteinemia is depletion of folate, vitamin B12, or vitamin B6. Population-based studies indicate that folate is the strongest vitamin determinant of hyperhomocysteinemia and, in most settings, folate supplementation effectively lowers elevated homocysteine levels. However, it is not clear whether folate deficiency is the cause of alcohol-related hyperhomocysteinemia.

METHODS

In the present study, 10 male Sprague Dawley rats were fed ethanol-containing Lieber-DeCarli diets with 13 mg of folic acid per kilogram of diet. This represents a folate intake more than 20 times the basal requirement. Ethanol represented 36% of total energy, which yielded a concentration of 6.2% (vol/vol). The same number of rats were pair-fed with isocaloric control diets that contained an identical level of folate in which ethanol was entirely replaced by maltodextrin.

RESULTS

At the end of 4 weeks, alcohol-fed rats did not show any significant reduction in plasma or hepatic folate concentrations, plasma pyridoxal-5'-phosphate concentration, or plasma vitamin B12 concentration. On the other hand, alcohol-fed rats were significantly hyperhomocysteinemic (17.24 +/- 4.63 micromol/liter,p < 0.01) compared to the nonalcohol group (10.73 +/- 2.76 micromol/liter). Alcohol-fed rats also had a significantly lower hepatic S-adenosylmethionine and higher hepatic S-adenosylhomocysteine levels.

CONCLUSIONS

Chronic alcohol consumption produces hyperhomocysteinemia by a mechanism that is related to interference with one-carbon metabolism, and not through vitamin depletion.

Folate and carcinogenesis: an integrated scheme

Collectively, the evidence from epidemiologic, animal and human studies strongly suggests that folate status modulates the risk of developing cancers in selected tissues, the most notable of which is the colorectum. Folate depletion appears to enhance carcinogenesis whereas folate supplementation above what is presently considered to be the basal requirement appears to convey a protective effect. The means by which this modulation of cancer risk is mediated is not known with certainty, but there are several plausible mechanisms which have been described. Folate plays a major role in the formation of S-adenosylmethionine, the universal methyl donor, as well as in the formation of purine and thymidine synthesis for DNA and RNA. Therefore, most mechanistic studies performed to date have focused on alterations in DNA methylation, disruption of DNA integrity and disruption of DNA repair, all of which have been observed with folate depletion. These aberrations in DNA are believed to enhance carcinogenesis by altering the expression of critical tumor suppressor genes and proto-oncogenes. Recently, the role of a common polymorphism of the methylenetetrahydrofolate reductase gene has been highlighted as well. This review presents those mechanisms which are the most likely candidates to explain folate's effects and it proposes an integrated scheme to explain how these mechanisms might interact.

The effect of dietary folate on Apc and p53 mutations in the dimethylhydrazine rat model of colorectal cancer

Dietary inadequacy of folate enhances and folate supplementation suppresses colorectal carcinogenesis in the dimethylhydrazine rat model. Folate is an essential factor for DNA methylation and the de novo biosynthesis of nucleotides, aberrations of which play important roles in mutagenesis. This study investigated whether the mutational hot spots of the Apc and p53 genes for human colorectal cancer are mutated in dimethylhydrazine-induced colorectal neoplasms and whether dietary folate can modulate mutations in these regions. Rats were fed diets containing 0, 2 (basal requirement), 8 or 40 mg folate/kg diet. Five weeks after diet initiation, dimethylhydrazine was injected weekly for 15 weeks. Mutations were determined by direct sequencing in 11 low and seven high grade dysplasias and 13 invasive adenocarcinomas. A total of six Apc mutations were found in four dysplastic and carcinomatous lesions: two in two low grade dysplasias, two in one high grade dysplasia and two in one adenocarcinoma. All mutations were single base substitutions, four of which were A:T-->G:C transitions. Five of the six mutations were located upstream from the region corresponding to the human APC mutation cluster region. Dietary folate had no effect on the frequency and type of Apc mutations. No mutations were detected in exons 5-9 of the p53 gene in neoplastic lesions. These data suggest that in the dimethylhydrazine rat model of colorectal cancer, the Apc gene is mutated in early stages, albeit to a lesser degree than observed in human colorectal cancer, whereas the mutational hot spot of the p53 gene for human colorectal cancer is not commonly mutated. Although the low frequency of Apc mutations and the small number of neoplasms studied in this study might have precluded our ability to observe modulatory effects of folate, dietary folate appears to have no significant effect on Apc and p53 mutations.

Chronic alcohol consumption induces genomic but not p53-specific DNA hypomethylation in rat colon

Alcohol consumption has been implicated as an etiologic agent in colorectal carcinogenesis, but the mechanism by which alcohol enhances the development of colorectal cancer is not yet known. Recent reports indicate that alcohol consumption can diminish cellular S-adenosylmethionine levels, thus possibly altering normal patterns of DNA methylation, a phenomenon that is mediated by S-adenosylmethionine and whose abnormalities are observed in colonic neoplasia. This study investigated the effect of chronic alcohol consumption on genomic DNA methylation of rat colonic epithelium and methylation of the p53 tumor suppressor gene, abnormalities of which have been implicated in colonic carcinogenesis. Two groups of rats (n = 10/group) were pair-fed either an alcohol-containing or an isocaloric control Lieber-DeCarli diet for 4 wk. The extent of genomic DNA methylation was assessed by incubating the extracted DNA with [(3)H]S-adenosylmethionine and Sss1 methyltransferase. Gene-specific methylation was assessed by using semiquantitative polymerase chain reaction (PCR). Tritiated methyl uptake by colonic DNA (which is inversely correlated with genomic methylation) from alcohol-fed rats was 57% less than that in control DNA (P < 0.05). However, gene-specific DNA methylation, both in the p53 gene (exons 5-8) and in the beta-actin gene, a control gene, did not differ between the two groups. In conclusion, this study indicates that chronic alcohol consumption produces genomic DNA hypomethylation in the colonic mucosa. This may constitute a means by which carcinogenesis is enhanced, although further studies are required to establish causality.

Nutritional strategies in the prevention of colorectal cancer

A variety of dietary factors have been implicated as agents that can modulate the development of malignancies of the gastrointestinal tract, particularly colorectal cancer. The effects of fat, red meat, fruits, vegetables, and alcohol on colorectal carcinogenesis have been examined extensively and appear to play substantial roles. Although fiber may play a protective role, recent studies raise the question of whether the protection is conveyed by other components in fiber-laden foods. Folate, selenium, calcium, and omega-3 fatty acids have emerged as factors more recently but may be equally important agents in nutritional chemoprevention, whereas the role of antioxidant vitamins is less certain. Until more firm data are available, the dietary recommendations provided by the American Cancer Society and the National Cancer Institute are appropriate for use in counseling patients on this issue.

Protein-calorie malnutrition does not predict subtle vitamin K depletion in hospitalized patients

OBJECTIVE

Recent studies suggest that subtle vitamin K depletion has far-reaching consequences. As this entity is not associated with prothrombin time elevation, it is important to determine whether alternate methods can help identify it. We investigated subtle vitamin K depletion in a hospital setting and determined whether protein calorie malnutrition predicts its presence.

DESIGN, SETTING, SUBJECTS

Using a high-pressure liquid chromatography (HPLC) assay of plasma phylloquinone and a food frequency questionnaire for phylloquinone intake, we examined the phylloquinone status of 27 hospitalized patients with normal coagulation parameters, no liver disease, and no recent warfarin use. We assessed protein-calorie nutritional status with Reilly's criteria and anthropometrics.

RESULTS

51% of patients (95% CI = 31% to 70%) had evidence of subtle vitamin K depletion as defined by a subnormal plasma phylloquinone concentration. Patients whose phylloquinone intake was less than the Recommended Daily Allowance (RDA) over the preceding year had lower plasma phylloquinone concentrations when compared to other patients: median (range) 0.106 nmol/l (0.022-0.461) versus 0.301 nmol/l (0.067-3.928), respectively (P = 0.023). Plasma phylloquinone concentrations were no different, however, between well-nourished and malnourished patients: median (range) 0.245 nmol/l (0.022-0.522) versus 0.188 nmol/l (0.067-3.928), respectively (P=0.782).

CONCLUSIONS

Subtle vitamin K depletion is common among hospitalized patients and protein-calorie malnutrition does not predict its presence.

Colonic mucosal concentrations of folate correlate well with blood measurements of folate status in persons with colorectal polyps

BACKGROUND

Estimates of habitual dietary folate intake are known to be imprecisely correlated with systemic measures of folate status. Furthermore, measurements of blood folate concentrations may not accurately reflect the concentration of folate in tissues of interest. This issue is important for assessing folate status in the colorectal mucosa because low dietary intake or blood concentrations of folate are associated with an increased risk of colorectal neoplasia.

OBJECTIVE

We examined whether conventional measures of folate in blood and a more sensitive, inverse indicator of systemic folate status, serum homocysteine, accurately reflected folate concentrations in human colonic mucosa obtained by endoscopic biopsy.

DESIGN

In 30 persons with colorectal polyps, blood samples were taken and biopsies of normal rectosigmoid mucosa performed at the time of colonoscopic polypectomy. Serum, red blood cell, and colonic mucosal folate and serum homocysteine concentrations were measured.

RESULTS

Serum and red blood cell folate and serum homocysteine concentrations accurately reflected colonic mucosal folate concentrations; among these, serum homocysteine correlated best with mucosal concentrations. Folate concentrations in the normal rectosigmoid mucosa were significantly lower in persons with adenomatous polyps than in those with hyperplastic polyps (P=0.04). Conventional measures of systemic folate status were not significantly lower in those with adenomas, although serum homocysteine was mildly elevated (P=0.04).

CONCLUSIONS

Our data underscore the ability of systemic measures of folate status, particularly serum homocysteine, to reflect folate concentrations in the colonic mucosa. Nevertheless, future studies that examine the ability of folate to modulate colorectal carcinogenesis may benefit from direct measurement of folate in the colon.

A cross-sectional study of vitamin intake in postoperative non-small cell lung cancer patients

BACKGROUND AND OBJECTIVES

This cross-sectional study of postoperative non-small cell lung cancer (NSCLC) patients examined possible effects of vitamin intake and folate status on disease-free survival.

METHODS

Supplemental vitamin usage, dietary vitamin intake (Willett Food Frequency Questionnaire), red blood cell (RBC) folate, and serum folate concentrations were assessed in patients with a history of NSCLC. Exclusion criteria included factors that alter folate status or that are associated with altered nutritional habits: (1) evidence of cancer on history, physical, or chest radiograph; (2) tobacco, alcohol ingestion (>2 drinks/ day), or cancer treatment within 3 months; (3) use of folate antagonists; and (4) age <60 years.

RESULTS

36 subjects were evaluated. The median disease-free censored survival was 24 months (range 4-41). Nineteen of 36 patients (53%) reported vitamin supplementation. Vitamin users had a longer median censored survival compared with nonusers (41 months versus 11 months; P = 0.002). With adjustment for cancer stage, the association between RBC folate and censored survival (r = 0.35; P = 0.055) and between serum folate and censored survival (r = 0.32; P = 0.083) approached statistical significance.

CONCLUSIONS

NSCLC patients who took vitamin supplements were more likely to be long-term survivors in the patients studied; a similar trend toward long-term survival was seen among patients with higher circulating folate concentrations.

Folate depletion impairs DNA excision repair in the colon of the rat

BACKGROUND/AIMS

Diminished folate status appears to promote colonic carcinogenesis by, as of yet, undefined mechanisms. Impaired DNA repair plays a significant role in the evolution of many colon cancers. Since folate is essential for the de novo synthesis of nucleotides and since folate depletion has previously been associated with excessive DNA strand breaks, it was hypothesised that folate depletion may impair DNA repair. Studies were therefore performed to examine whether folate depletion affects the two major categories of DNA repair.

METHODS

Study 1: eight weanling male Sprague-Dawley rats were fed on diets containing either 0 or 8 mg folate/kg diet with 1% succinylsulphathiazole for four weeks. After viable colonocytes had been harvested, DNA excision repair was evaluated by a single cell gel electrophoresis assay. Study 2: eighteen animals were fed on similar diets for five weeks. Also in study 2, 18 additional rats were fed on the same defined diet without succinylsulphathiazole for 15 weeks. Weekly injections with the procarcinogen, 1,2-dimethylhydrazine (20 mg base/kg), were administered to the latter group of animals. Five microsatellite loci from different chromosomes were investigated for instability in hepatic and colonic DNA.

RESULTS

In study 1, a significantly retarded rate of DNA excision repair was observed in the folate deficient colonocytes compared with controls (p < 0.05). In study 2, there was no evidence of instability at the five microsatellite loci associated with either short or long term folate depletion.

CONCLUSIONS

Folate deficiency impairs DNA excision repair in rat colonic mucosa; a similar degree of deficiency, even when administered in conjunction with a colonic carcinogen, did not produce evidence of a widespread defect in mismatch repair.

Bioavailability of phylloquinone from an intravenous lipid emulsion

This randomized, controlled study evaluated the bioavailability of phylloquinone from an intravenous lipid emulsion. A mild vitamin K deficiency was induced in 12 healthy adult men and women by dietary restriction of phylloquinone (40 microg/d, days 1-11) and by administration of warfarin (1.0 mg/d, days 5-11). On day 11, subjects received a 500-mL intravenous solution of either lipid or saline, both of which contained 154 microg phylloquinone. Bioavailability was assessed by serial measurements of plasma phylloquinone, vitamin K1-2,3-epoxide. PIVKA-II (proteins induced by vitamin K absence or antagonists-II), and percentage undercarboxylated osteocalcin. As a result of vitamin K deficiency and minidose warfarin, vitamin K1-2,3-epoxide, PIVKA-II, and percentage undercarboxylated osteocalcin increased significantly between days 1 and 11 (P = 0.05, 0.016, and 0.001, respectively). With the infusions, plasma phylloquinone increased in both groups (P = 0.001). After the infusions vitamin K,-2,3-epoxide decreased in both groups (P = 0.002). Changes in plasma phylloquinone and vitamin K1-2,3-epoxide were no different in the two groups (mean areas under the curves +/- SEM: 116+/-13 nmol x h/L for the saline group and 102+/-20 nmol x h/L for the lipid group for phylloquinone; 38.6+/-7.5 nmol x h/L for the saline group and 31.3+/-9.0 nmol x h/L for the lipid group for vitamin K1-2,3-epoxide). PIVKA-II decreased significantly from baseline values (P = 0.005) in both groups after the infusions. Intravenous lipid reversed the effects of minidose warfarin and of dietary restriction of phylloquinone on hemostasis and vitamin K nutritional status. This reversal was no different from that seen with the infusion of phylloquinone in a saline solution.

A prospective survey for central line skin-site colonization by the pathogen Malassezia furfur among hospitalized adults receiving total parenteral nutrition

BACKGROUND

Over 50 case reports suggest that Malassezia furfur is an emerging systemic pathogen in neonates who receive IV lipid emulsions. Because isolation of this fungus requires special culture techniques, which are not routinely used, the authors of many case reports of M. furfur infections in adults question whether infections caused by this organism are being underdiagnosed in older patients.

METHODS

Catheter insertion site colonization rates in adults receiving total parenteral nutrition (TPN) were prospectively evaluated in 149 hospitalized patients with 928 cultures handled specifically for M. furfur detection. Positive control samples consisted of M. furfur cultures in neonates and in adults, who had not been enrolled in the study, and of a separate positive culture obtained from a skin site inoculated with M. furfur.

RESULTS

M. furfur was not cultured from any of the 928 study samples (95% confidence interval [CI] -0.4% to +0.4%).

CONCLUSIONS

These results suggest that M. furfur is less of a threat to hospitalized adults receiving TPN than has been otherwise postulated. These data do not support the inclusion of special cultures for M. furfur in routine skin-site surveillance programs among hospitalized adults receiving TPN.

Folate deficiency in rats induces DNA strand breaks and hypomethylation within the p53 tumor suppressor gene

Folate is essential for the de novo biosynthesis of purines and thymidylate, and is an important mediator in the transfer of methyl groups for DNA methylation. Folate deficiency, therefore, could contribute to abnormal DNA integrity and methylation patterns. We investigated the effect of isolated folate deficiency in rats on DNA methylation and DNA strand breaks both at the genomic level and within specific sequences of the p53 tumor suppressor gene. Our data indicate that folate deficiency induces DNA strand breaks and hypomethylation within the p53 gene. Such alterations either did not occur or were chronologically delayed when examined on a genome-wide basis, indicating some selectivity for the exons examined within the p53 gene. Folate insufficiency has been implicated in the development of several human and experimental cancers, and aberrations within these regions of the p53 gene that were examined in this study are thought to play an integral role in carcinogenesis. The aforementioned molecular alterations may therefore be a means by which dietary folate deficiency enhances carcinogenesis.

Dietary folate protects against the development of macroscopic colonic neoplasia in a dose responsive manner in rats

BACKGROUND AND AIMS

Diminished folate status is associated with enhanced colorectal carcinogenesis. This study investigated the potential chemopreventive role of dietary folate in the dimethylhydrazine colorectal cancer model.

SUBJECTS AND METHODS

Sprague-Dawley rats were fed diets containing either 0, 2 (daily dietary requirement), 8 or 40 mg folate/kg diet for 20 weeks. After five weeks of diet, rats were injected with dimethyl-hydrazine (44 mg/kg) weekly for 15 weeks. Fifteen weeks after the first injection of dimethylhydrazine, all rats were killed. Folate status was determined, and the entire colorectum from each rat was analysed for macroscopic and microscopic neoplasms.

RESULTS

Plasma and colonic folate concentrations correlated directly with dietary folate levels (p < 0.005). The incidence of microscopic neoplasms was similar among the four groups. However, the incidence and the average number of macroscopic tumours per rat decreased progressively with increasing dietary folate levels up to 8 mg/kg diet (p < 0.05). In the strongly procarcinogenic milieu used in this study, folate supplementation at 20 times the basal requirement was associated with rates of macroscopic tumour development that were intermediate, and not statistically distinct, from rates observed at either 0 or 8 mg/kg diet.

CONCLUSIONS

These data indicate that in this rat model, (a) increasing dietary folate up to four times the basal requirement leads to a progressive reduction in the evolution of macroscopic neoplasms from microscopic foci; and (b) folate supplementation beyond four times the requirement does not convey further benefit.

Folate: effects on carcinogenesis and the potential for cancer chemoprevention

A provocative array of observations from both laboratory and clinical investigations indicates that alterations in folate status modulate the process of neoplastic transformation in selected epithelial tissues. Diminished folate status appears to promote carcinogenesis. Considerably more speculative is the concept that supraphysiologic folate status may afford some protection against cancer. Although observations to this effect support such a relationship in the uterine cervix, lung, stomach, and esophagus, present evidence clearly is most compelling for the colorectum. This article reviews these observations, particularly as they apply to the colorectum, and outlines some of the possible mechanisms by which these effects may be exerted.

Exon-specific DNA hypomethylation of the p53 gene of rat colon induced by dimethylhydrazine. Modulation by dietary folate

Folate deficiency enhances colorectal carcinogenesis in dimethylhydrazine-treated rats. Folate is an important mediator of DNA methylation, an epigenetic modification of DNA that is known to be dysregulated in the early stages of colorectal cancer. This study investigated the effect of dimethylhydrazine on DNA methylation of the colonic p53 gene and the modulation of this effect by dietary folate. Sprague-Dawley rats were fed diets containing 0, 2, 8, or 40 mg of folate/kg of diet. Five weeks after diet initiation, dimethylhydrazine was injected weekly for fifteen weeks. Folate-depleted and folate-replete control animals did not receive dimethylhydrazine and were fed the 0- and 8-mg folate diets, respectively. The extent of p53 methylation was determined by a quantitative HpaII-polymerase chain reaction. In exons 6 and 7, significant p53 hypomethylation was observed in all dimethylhydrazine-treated rats relative to controls (P < 0.01), independent of dietary folate. In exon 8, significant p53 hypomethylation was observed only in the dimethylhydrazine-treated folate-depleted rats compared with controls (P = 0.038) and was effectively overcome by increasing levels of dietary folate (P = 0.008). In this model, dimethylhydrazine induces exon-specific p53 hypomethylation. In some exons, this occurs independent of dietary folate, and in others, increasing levels of dietary folate effectively override the induction of hypomethylation in a dose-responsive manner. This may be a mechanism by which increasing levels of dietary folate inhibit colorectal carcinogenesis.

Setting and evaluating the energy content of emergency rations

This paper examines the setting and evaluation of emergency rations for refugees and displaced people. After defining the purpose for which rations are designed, the variables affecting their quantification are discussed. The debate concerning the use of one as opposed to a range of energy levels for different populations is highlighted in a review of recent proposals for ration levels. It is demonstrated that up to a twofold range occurs if different combinations of the main parameters are used. This has important implications for the large-scale provision of food. The use of one figure for the setting and evaluation of rations for all populations is inappropriate; figures should be set according to specific context and need. To achieve this, a practical two-stage approach is proposed. Stage 1, probably a desk exercise, uses pre-calculated 'look-up' tables which provide energy values for each country. These figures are for immediate use as 'rule-of-thumb' estimates, based on clearly defined parameters. The second stage involves refining the values using improved information on local conditions collected by field assessment.

Nutrition chemoprevention of gastrointestinal cancers: a critical review

Various strategies utilizing specific dietary factors have been investigated for their ability to modulate the development of several cancers of the gastrointestinal tract. The effects of fat, red meat, fiber, fruits and vegetables, and alcohol on colorectal carcinogenesis have been reasonably well defined. Folate, selenium, and omega-3 fatty acids are rapidly emerging as important agents in nutrition chemoprevention, while the role of antioxidant vitamins and calcium is less certain. Although recent intervention studies from China have suggested a protective role of certain vitamins and minerals for esophageal and gastric cancers, further data from prospective randomized intervention studies are needed. Until more firm data are available, the dietary recommendations provided by the American Cancer Society and the National Cancer Institute are appropriate guidelines.

DNA hypomethylation in inflammatory arthritis: reversal with methotrexate

This study investigated whether methotrexate, by interrupting the methyl transfer function of folate, can induce genomic DNA hypomethylation in patients with inflammatory arthritis. Consecutive subjects with inflammatory arthritis (rheumatoid or psoriatic), who were taking methotrexate (n = 7) or other medications (n = 6), and control subjects, either healthy or with osteoarthritis and taking nonsteroidal anti-inflammatory agents only (n = 9) were recruited. The methylation status of genomic DNA from peripheral blood mononuclear cells was determined. Plasma levels of folate, B12, and pyridoxal-5'-phosphate (PLP), all of which are involved in biologic methylation, were also examined. The extent of genomic DNA methylation was lowest in subjects with inflammatory arthritis who were not taking methotrexate, highest in subjects with inflammatory arthritis who were taking methotrexate, and intermediate in control subjects (p < 0.05). Plasma levels of folate and B12 were similar among the three groups. The mean plasma PLP level in subjects with inflammatory arthritis was 33% lower than that in control subjects (p = 0.04). No significant correlation between genomic DNA methylation and folate, B12, and PLP levels was observed. These data do not support the hypothesis that methotrexate induces genomic DNA hypomethylation. However, these data indicate that inflammatory arthritis is associated with genomic DNA hypomethylation that is reversed with methotrexate. Future studies using a larger number of subjects are warranted to confirm these findings.

Folate synthesized by bacteria in the human upper small intestine is assimilated by the host

BACKGROUND & AIMS

Some intestinal flora are known to synthesize folate. The aim of this study was to determine whether folate synthesized by small intestinal flora is assimilated by the human host.

METHODS

Subjects with atrophic gastritis and healthy volunteers were studied before and after omeprazole administration. A double-lumen perfusion tube was placed in the duodenum. 3H-labeled P-aminobenzoic acid, a precursor substrate for bacterial folate synthesis, was perfused. Downstream intestinal aspirates and a 48-hour urine collection were obtained.

RESULTS

Atrophic gastritis and omeprazole administration were associated with increases in duodenal pH and in small intestinal flora. Bacterially synthesized folates were isolated from the intestinal aspirates. Tritiated 5-methyltetrahydrofolate, a major metabolite of folate, was isolated from the urine of omeprazole-treated subjects in greater quantities than from drug-free subjects (P<0.01); the quantity of tritiated 5-methyltetrahydrofolate in the urine of the subjects with atrophic gastritis was similarly elevated.

CONCLUSIONS

(1) Mild bacterial overgrowth caused by atrophic gastritis and administration of omeprazole are associated with de novo folate synthesis in the lumen of the small intestine; (2) the human host absorbs and uses some of these folates; and (3) the contribution to folate nutriture from this source remains unclear.

Total joint replacement and golf

Definitive characterization of the effects of golf on a total joint replacement remains elusive. However, from our study of active golfers and solicitation of the opinions of orthopedists who specialize in joint replacements, and from a careful review of the literature regarding exercise and total joint replacement, it appears possible for patients to remain active golfers with no significant increase in either symptoms or rates of revision of implants following total hip, knee, or shoulder replacement.

Moderate folate deficiency does not cause global hypomethylation of hepatic and colonic DNA or c-myc-specific hypomethylation of colonic DNA in rats

Global and gene-specific DNA hypomethylation is considered to be an important early epigenetic event in several human neoplasms. A growing body of evidence has suggested that DNA methylation can be altered by dietary manipulation of methyl group donors. This study investigated whether moderate depletion of folate, a dietary component needed for the synthesis of methyl groups, would cause decreased hepatic and colonic S-adenosylmethionine concentrations, and thereby lead to global and/or protooncogene-specific DNA hypomethylation. Weanling rats were fed an amino acid-defined diet containing either 0 or 8 mg folate/kg diet for 15 or 24 wk. Significantly lower systemic, hepatic and colonic folate concentrations were observed in the moderately folate-depleted rats than in controls at both 15 and 24 wk (P < 0.005). Although hepatic S-adenosylmethionine was significantly lower in the moderately folate-depleted rats than in controls at the two time points (P < 0.03), colonic S-adenosylmethionine concentrations were not significantly different between the two groups at either time point. No significant differences between the folate-depleted and control animals could be detected with regard to global DNA methylation in the liver or colonic mucosa. Furthermore, c-myc protooncogene-specific DNA methylation in the colonic mucosa was not significantly different between these two groups of animals. These results indicate that moderate folate depletion does not cause a significant reduction in global DNA methylation in liver or colonic mucosa or in c-myc-specific colonic mucosal DNA methylation in this rat model.

DNA methylation as an intermediate biomarker in colorectal cancer: modulation by folic acid supplementation

Several studies have suggested that DNA hypomethylation is an early step in colorectal carcinogenesis. However, it is not clear at which stage in carcinogenesis this hypomethylation occurs, what promotes it, the extent to which it can be reversed and the consequences of such reversal in affecting tumour development. In an attempt to address some of these questions, we studied three groups of subjects with similar age and gender distributions: a group of 12 patients with colorectal carcinomas; a group of 12 patients with colorectal adenomas; and a group of eight healthy control subjects. Two experimental protocols were employed. In the first protocol, intrinsic DNA methylation was evaluated in neoplastic and in normal-appearing rectal mucosa of patients with colonic carcinomas or adenomas, compared with a group of healthy controls. In the second protocol, we examined, in a prospective and controlled fashion, the effect of folic acid supplementation (10 mg/day) on the degree of DNA methylation of rectal mucosa from those same patients after removal of the neoplasms. The degree of intrinsic DNA methylation was assessed on the basis of the capacity of the DNA isolates to serve as methyl acceptors in in vitro incubations that contained DNA methylase and [3H-methyl] S-adenosylmethionine. Intrinsic DNA methylation was significantly lower in carcinomas than in adenomas (P < 0.005). In addition, normal-appearing rectal mucosa from patients with carcinomas was significantly less methylated than in healthy controls (P < 0.005); the mean value found in the latter was also greater than the value observed in patients with adenomas, but not significantly so (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Severe folate deficiency causes secondary depletion of choline and phosphocholine in rat liver

It has previously been shown that choline deficiency causes depletion of hepatic folate concentration in rats. Two separate experiments were undertaken to investigate the converse phenomenon: whether folate deficiency would lead to depletion of hepatic choline. In Experiment 1, severe folate deficiency was induced in rats by feeding an amino acid-defined diet containing (per kg diet) 1.4 g choline, 0 mg folate and 10 g succinylsulfathiazole. Control rats were fed the same diet containing 8 mg folate/kg. After 4 wk, plasma and hepatic folate concentrations were significantly depleted in the severely folate-deficient rats compared with controls (P < 0.001), and hepatic choline and phosphocholine concentrations were 65 and 80% lower, respectively (P < 0.001). In Experiment 2, moderate folate deficiency was induced in rats by feeding the same diet as described above, but with the succinylsulfathiazole omitted. After 24 wk, significant systemic folate deficiency was present in the moderately folate-deficient rats compared with controls (P < 0.001). A modest reduction (36%, P = 0.087) in hepatic choline concentration was observed in the moderately folate-deficient rats compared with controls. No significant differences in hepatic phosphocholine concentrations were detected between the two groups. These results indicate that severe folate deficiency causes secondary hepatic choline deficiency in rats.

Global DNA hypomethylation increases progressively in cervical dysplasia and carcinoma

BACKGROUND

Global DNA hypomethylation has been observed in some human neoplasms and has been implicated as an important factor in carcinogenesis. The current study was designed to assess whether DNA hypomethylation occurs in cervical dysplasia and cancer, and to determine the relationship between the degree of DNA hypomethylation and the grade of neoplasia.

METHODS

Cervical biopsy specimens were obtained from colposcopically identifiable lesions in 41 patients with abnormal Pap smear results. The extent of global DNA methylation was assessed by incubating the extracted DNA with [3H]-S-adenosylmethionine and Sss1 methyltransferase, an enzyme that specifically catalyzes the transfer of methyl groups to cytosine residues in the cytosine-guanine doublet. The degree of exogenous 3H-methyl group incorporation into the DNA therefore is related reciprocally to the extent of endogenous DNA methylation. These data were compared with the histopathologic classification of the lesions.

RESULTS

The extent of 3H-methyl group incorporation was increased threefold and sevenfold in the DNA from cervical dysplasia and cancer, respectively, compared with the DNA from normal cervical tissue (P = 0.006, analysis of variance). Significant incremental increases in DNA hypomethylation were observed in the progression from normal and low grade squamous intraepithelial lesions (SIL) to high grade SIL and to cancer (P < 0.0001, trend).

CONCLUSIONS

These data show that global DNA hypomethylation is a significant epigenetic event in cervical carcinogenesis and that the degree of DNA hypomethylation increases with the grade of cervical neoplasia. These data suggest that global DNA methylation may serve as a biochemical marker of cervical neoplasia.

Measurement of zinc bioavailability from beef and a ready-to-eat high-fiber breakfast cereal in humans: application of a whole-gut lavage technique

We measured zinc absorption in humans from two different foods, using a whole-gut lavage technique. Healthy adults (n = 8) were given test foods containing approximately 4 mg (61.2 mumol) Zn as either beef or a high-fiber, ready-to-eat breakfast cereal. Basal zinc loss in the gut was measured after giving only 200 mL water alone after an overnight fast. Mean polyethylene glycol (PEG) recovery, a nonabsorbable fecal marker, was 95 +/- 2% (mean +/- SE). There was no significant difference of PEG recoveries with the various treatments. True absorption of zinc was 11.0 +/- 5.4 mumol (716.3 +/- 355.9 micrograms) for breakfast cereal and 34.8 +/- 3.5 mumol (2274.1 +/- 230.2 micrograms) for beef. Fractional zinc absorption was significantly lower for breakfast cereal compared with beef, 14.7 +/- 6.7% vs 55.1 +/- 4.6%, respectively. Our findings demonstrate that zinc absorption can be measured in humans from single foods containing a physiological dose of zinc by using the whole-gut lavage absorption technique and that zinc bioavailability from beef is about fourfold greater than from a high-fiber breakfast cereal.

The vitamin K content of intravenous lipid emulsions

Commercially available intravenous lipid emulsions are largely derived from vegetable oils, a natural source of phylloquinone (vitamin K1). We therefore examined the concentration of vitamin K1 in two widely used intravenous lipid emulsions by using a previously validated high performance liquid chromatography technique. The vitamin K1 concentrations of 10% emulsions of Intralipid and Liposyn II were 30.8 and 13.2 micrograms/dL, respectively. The concentration of vitamin K1 in the 20% emulsions of these products was essentially double that in the 10% emulsions. The coefficients of variation between the vitamin K1 content in three different lots of each product were consistently less than 7.0%. The observed concentrations of the vitamin in these lipid emulsions paralleled the predicted content on the basis of the type of vegetable oil(s) used to make the product. The type of vegetable oil used for production therefore seems to be a major determinant of the final vitamin K1 content. The vitamin K1 contained in these intravenous lipid emulsions is substantial and may have great impact on the vitamin K status of the recipient.

The effects of vitamins B12, B6, and folate on blood homocysteine levels

The interaction between plasma homocysteine levels and vitamins B6, B12, and folate is an exciting field and one that has gathered great momentum over the past few years, with the recognition that homocysteine probably plays an important role in occlusive vascular disease. Our understanding in this field is greatly advanced compared to just a few years ago. There are a number of important issues, however, that will need to be addressed in the future if we are to develop a sufficient knowledge base to effectively minimize the risk of occlusive vascular disease ascribable to hyperhomocysteinemia. These include (1) definitive evidence that homocysteine is the actual agent that mediates accelerated occlusive vascular disease and the mechanism by which this occurs; (2) an understanding of what constitutes a pathologic elevation in homocysteine (is there a threshold concentration in the plasma below which no vascular injury occurs? is the peak concentration achieved the critical determinant of injury, or is the area under the curve, or some other feature, more important?); (3) understanding what synergies might exist by adding B6 or B12 to a regimen of folate supplementation (what doses are most appropriate? will toxologic issues limit the utility of supplementation?); and (4) determining the circumstances where reduction of plasma homocysteine will retard or reverse the process of occlusive vascular disease.