Review: State of the knowledge on the importance of folates and cobalamin for dairy cow metabolism

Synthesis of B vitamins by the rumen microbiota is usually sufficient to avoid the appearance of clinical deficiency symptoms in dairy cows under normal feeding conditions. Nevertheless, it is now generally accepted that vitamin deficiency is much more than the appearance of major functional and morphological symptoms. Subclinical deficiency, which is present as soon as the supply is lower than the need, causes cellular metabolic changes leading to a loss of metabolic efficiency. Folates and cobalamin, two B vitamins, share close metabolic relationships. Folates act as co-substrates in one-carbon metabolism, providing one-carbon unit for DNA synthesis and de novo synthesis of methyl groups for the methylation cycle. Cobalamin acts as a coenzyme for reactions in the metabolism of amino acids, odd-numbered chain fatty acids including propionate and de novo synthesis of methyl groups. Both vitamins are involved in reactions to support lipid and protein metabolism, nucleotide synthesis, methylation reactions and possibly, maintenance of redox status. Over the last decades, several studies have reported the beneficial effects of folic acid and vitamin B12 supplements on lactation performance of dairy cows. These observations indicate that, even when cows are fed diets adequately balanced for energy and major nutrients, B-vitamin subclinical deficiency could be present. This condition reduces casein synthesis in the mammary gland and milk and milk component yields. Folic acid and vitamin B12 supplements, especially when given together, may alter energy partitioning in dairy cows during early and mid-lactation as indicated by increased milk, energy-corrected milk, or milk component yields without affecting DM intake and BW or even with reductions in BW or body condition loss. Folate and cobalamin subclinical deficiency interferes with efficiency of gluconeogenesis and fatty acid oxidation and possibly alters responses to oxidative conditions. The present review aims to describe the metabolic pathways affected by folate and cobalamin supply and the consequences of a suboptimal supply on metabolic efficiency. The state of knowledge on the estimation of folate and cobalamin supply is also briefly mentioned.

Combined biotin, folic acid, and vitamin B12 supplementation given during the transition period to dairy cows: Part I. Effects on lactation performance, energy and protein metabolism, and hormones

Biotin (B₈), folates (B₉), and vitamin B₁₂ (B₁₂) are involved and interrelated in several metabolic reactions related to energy and protein metabolism. We hypothesized that a low supply of one of the latter vitamins during the transition period would impair metabolic status. The purpose of this study was to evaluate the effect of B₈ supplementation on the response of lactation performance and selected energy and protein metabolites and hormones to a combined supplementation of B₉ and B₁₂ given to periparturient dairy cows, from d -21 to 21 relative to calving. A total of 32 multiparous Holstein cows housed in tie stalls were randomly assigned, according to their previous 305-d milk yield, to 8 incomplete blocks of 4 treatments: (1) a 2-mL weekly i.m. injection of saline (0.9% NaCl; B₈-/B₉B₁₂-); (2) 20 mg/d of dietary B₈ (unprotected from ruminal degradation) and 2-mL weekly i.m. injection of 0.9% NaCl (B₈+/B₉B₁₂-); (3) 2.6 g/d of dietary B₉ (unprotected) and 2-mL weekly i.m. injection of 10 mg of B₁₂ (B₈-/B₉B₁₂+); and (4) 20 mg/d of dietary B₈, 2.6 g/d of dietary B₉, and weekly i.m. injection of 10 mg of B₁₂ (B₈+/B₉B₁₂+) in a 2 × 2 factorial arrangement. Milk yield and dry matter intake were obtained daily and milk components weekly. Blood samples were taken weekly from d -21 to calving and 3 times per week from calving to 21 d following parturition. Prepartum plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), and adiponectin were unaffected by treatments. Biotin, B₉, and B₁₂ supplements increased their respective concentrations in plasma and milk. Cows fed the B₈ supplement tended to have lower dry matter intake, but only cows in B₈+/B₉B₁₂- had greater plasma concentrations of NEFA compared with B₈-/B₉B₁₂-. Milk and total solid yields were greater by 13.5 and 13.9%, respectively, for B₈-/B₉B₁₂+ [45.5 (standard error, SE: 1.8) and 5.81 (0.22) kg/d, respectively] compared with B₈-/B₉B₁₂- [40.1 (1.9) and 5.10 (0.23) kg/d, respectively], but these effects were suppressed when combined with the B₈ supplement. Cows in the B₈-/B₉B₁₂+ group had decreased plasma insulin and tended to have increased NEFA concentrations, but postpartum plasma concentrations of glucose, BHB, leptin, and adiponectin were not affected. These cows also mobilized more body fat reserves, as suggested by a tendency to increased plasma NEFA and more milk total solids compared with B₈-/B₉B₁₂- cows. However, plasma concentrations of BHB and adiponectin were similar among treatments. This suggests that the B₉ and B₁₂ supplements enhanced efficiency of energy metabolism in early lactation cows. Folic acid and B₁₂ supplementation increased postpartum plasma Cys and homocysteine concentrations but did not affect plasma Met concentration, suggesting an upregulation of the transsulfuration pathway. In summary, our results showed that, under the current experimental conditions, increasing B₈ supply did not improve responses to the B₉ and B₁₂ supplementation.

Combined biotin, folic acid, and vitamin B12 supplementation given during the transition period to dairy cows: Part II. Effects on energy balance and fatty acid composition of colostrum and milk

Biotin (B₈), folate (B₉), and vitamin B₁₂ (B₁₂) are involved in several metabolic reactions related to energy metabolism. We hypothesized that a low supply of one of these vitamins during the transition period would impair metabolic status. This study was undertaken to assess the interaction between B₈ supplement and a supplementation of B₉ and B₁₂ regarding body weight (BW) change, dry matter intake, energy balance, and fatty acid (FA) compositions of colostrum and milk fat from d -21 to 21 relative to calving. Thirty-two multiparous Holstein cows housed in tie stalls were randomly assigned, according to their previous 305-d milk yield, to 8 incomplete blocks in 4 treatments: (1) a 2-mL weekly i.m. injection of saline (0.9% NaCl; B₈-/B₉B₁₂-); (2) 20 mg/d of dietary B₈ (unprotected from ruminal degradation) and 2-mL weekly i.m. injection of 0.9% NaCl (B₈+/B₉B₁₂-); (3) 2.6 g/d of dietary B₉ (unprotected) and 2-mL weekly i.m. injection of 10 mg of B₁₂ (B₈-/B₉B₁₂+); (4) 20 mg/d of dietary B₈, 2.6 g/d of dietary B₉, and 2-mL weekly i.m. injection of 10 mg of B₁₂ (B₈+/B₉B₁₂+) in a 2 × 2 factorial arrangement. Colostrum was sampled at first milking. and milk samples were collected weekly on 2 consecutive milkings and analyzed for FA composition. Body condition score and BW were recorded every week throughout the trial. Within the first 21 d of lactation, B₈-/B₉B₁₂+ cows had an increased milk yield by 13.5% [45.5 (standard error, SE: 1.8) kg/d] compared with B₈-/B₉B₁₂- cows [40.1 (SE: 1.9)], whereas B₈ supplement had no effect. Even though body condition score was not affected by treatment, B₈-/B₉B₁₂+ cows had greater BW loss by 24 kg, suggesting higher mobilization of body reserves. Accordingly, milk de novo FA decreased and preformed FA concentration increased in B₈-/B₉B₁₂+ cows compared with B₈-/B₉B₁₂- cows. In addition, cows in the B₈+/B₉B₁₂- group had decreased milk de novo FA and increased preformed FA concentration compared with B₈-/B₉B₁₂- cows. Treatment had no effect on colostrum preformed FA concentration. Supplemental B₈ decreased concentrations of ruminal biohydrogenation intermediates and odd- and branched-chain FA in colostrum and milk fat. Moreover, postpartum dry matter intake for B₈+ cows tended to be lower by 1.6 kg/d. These results could indicate ruminal perturbation caused by the B₈ supplement, which was not protected from rumen degradation. Under the conditions of the current study, in contrast to B₈+/B₉B₁₂- cows, B₈-/B₉B₁₂+ cows produced more milk without increasing dry matter intake, although these cows had greater body fat mobilization in early lactation as suggested by the FA profile and BW loss.

Abstract 3375: Molecular subtyping of circulating tumor cells in patients with small cell lung cancer

Background: Recently, a new molecular classification of small cell lung cancer (SCLC), defined by expression of four key transcription regulators - ASCL1, NEUROD1, YAP1 and POU2F3 - has been proposed. These molecular subtypes may confer differential biology and therapeutic vulnerabilities, however, studies to date have been constrained by the paucity of available longitudinal tumor biopsy samples obtained from patients with SCLC. Herein, we utilized circulating tumor cells (CTCs) to characterize subtype marker heterogeneity at the time of diagnosis and evaluate the dynamic nature of marker expression during treatment in patients with SCLC.

Methods: Informed consent was obtained from patients with SCLC using an IRB approved protocol (IRB#030763). We have collected blood samples from 32 patients, including treatment naïve samples from the entire cohort as well as on-treatment samples (median of 4 collections per patient). We utilized the RareCyte rare-cell analysis platform to isolate and quantify CTCs, which were defined as CK/EpCAM positive and CD45 negative. Each sample was also evaluated for expression of neuroendocrine markers (ASCL1, NEUROD1) and non-neuroendocrine markers (YAP1, POU2F3). Each set of neuroendocrine and non-neuroendocrine markers were co-stained along with the CTC markers. Mean fluorescence intensity of each marker was extracted using a python program.

Results: To date, we have analyzed 22/32 (69%) treatment naïve samples, including n=6 patients with early stage disease and n=16 patients with advanced/metastatic disease. We detected CTCs from 16/22 (73%) patients, with quantities ranging from 1 - 3406 (median = 66) per 7.5ml of blood. CTCs were positive for the neuroendocrine markers ASCL1 in 16/16 (100%) and NEUROD1 in 10/16 (62%); all NEUROD1 positive CTCs were also positive for ASCL1. The non-neuroendocrine markers YAP1 and POU2F3 were detected in 6/16 (37%) and 11/16 (69%) samples, respectively, including YAP1/POU2F3 double positives in 6/16 (37%). Analysis of on-treatment samples is ongoing.

Conclusion: We have developed a protocol for monitoring expression of subtype markers on CTCs isolated from patients with SCLC. We found CTCs expressing both neuroendocrine and non-neuroendocrine markers at the time of diagnosis. Ongoing work will attempt to delineate the dynamic nature of subtype marker expression during therapy, to correlate with clinical outcomes. These studies have the potential to offer critical insights regarding the heterogeneity and evolution of SCLC, a tumor type in which novel disease insights and innovative treatment strategies are urgently needed to improve patient survival.

Citation Format: Prasad R. Kopparapu, Melinda Duplessis, Edward Lo, Yingjun Yan, Wade T. Iams, Josh Nordberg, Arturo Ramirez, Tad George, Christine Lovly. Molecular subtyping of circulating tumor cells in patients with small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3375.

Clinical Validation of a Circulating Tumor Cell Assay Using Density Centrifugation and Automated Immunofluorescence Microscopy

OBJECTIVES

The US Food and Drug Administration (FDA)-approved CELLSEARCH assay (Menarini Silicon Biosystems) for circulating tumor cells (CTCs) relies on expression of an epithelial cell adhesion molecule to enrich for CTCs. We sought to validate a CTC assay (RareCyte) for clinical use that instead collects a buffy coat preparation enriched for CTCs.

METHODS

Normal peripheral blood specimens spiked with cultured breast and prostate cancer cells and 47 clinical samples were used to validate assay performance. Specimens were enriched for buffy coat cells and applied onto 8 glass slides. The slides were immunofluorescently stained and imaged by automated microscopy and computer-aided image analysis.

RESULTS

The assay was 100% specific for detecting spiked tumor cells. For samples spiked with 25, 50, and 125 cells, the percentage coefficients of variation were 42%, 21%, and 3.7%, respectively. Linearity studies demonstrated a slope of 0.99, an intercept of 1.6, and R2 of 0.96. Recoveries at the 25-, 50-, and 125-cell levels were 92%, 111%, and 100%, respectively. Clinical samples run on both CELLSEARCH and RareCyte correlated with an R2 of 0.8 after log-transformation and demonstrated 87.5% concordance using the CELLSEARCH criteria for predicting adverse outcomes.

CONCLUSIONS

The RareCyte CTC assay has comparable performance to the FDA-cleared method and is ready for further clinical validation studies.

Performance perception of Canadian dairy producers when transitioning to an automatic milking system

Adoption of automated milking systems (AMS) has increased exponentially around the world in recent years. The objective of this observational study was to evaluate how producer perception of changes in cow-average milk yield and somatic cell count (SCC) compared with the actual changes in their herds after the introduction of AMS in Canadian commercial dairy herds. Data were collected (in 2014 and 2015) through a survey of 97 Canadian dairy herds that shifted to AMS from 2000 to 2014. Producers were asked their perception about milk yield and SCC changes (increase, decrease, or no change) after AMS introduction. Actual herd performance data were obtained from dairy herd improvement organizations. Differences between the 12-mo rolling herd-average milk yield (kg/cow per year) and SCC (cells/mL) at the closest test 2 yr after transitioning to AMS and at the last test before the transition were calculated and compared with the producer perception answers. After AMS adoption, milking herd size, milk yield, SCC, and number of AMS units per herd averaged (± standard deviation) 99.8 ± 54.4 cows, 9,619 ± 1,354 kg/cow per year, 248,825 ± 97,286 cells/mL, and 1.9 ± 1.1 units, respectively. On average, after AMS introduction, herd size, milk yield, and culling rate increased by 11.3 cows, 441 kg/cow per year, and 1.3%, respectively, and calving interval decreased by 7 d. For producers who perceived an increase, actual milk yield and SCC increases averaged (mean ± standard deviation) +534 ± 1,003 kg/cow per year and +56,679 ± 66,662 cells/mL, respectively. Alternatively, for producers who perceived a decrease, actual milk yield and SCC decreases averaged -984 ± 658 kg/cow per year and -26,976 ± 94,099 cells/mL, respectively. An actual milk yield change of +83.1 ± 1,113.3 kg/cow per year and an SCC change of +6,135 ± 72,609 cells/mL were observed in the herds in which the dairy producers perceived no change with the AMS introduction. Hence, dairy producers were, on average, able to discern their actual milk yield and SCC changes after AMS adoption. However, the proportions of dairy producers who accurately perceived their actual milk yield and SCC changes after AMS introduction were 39.4% for milk yield (increase: 36.3%; decrease: 100.0%; and no change: 45.5%) and 46.7% for SCC (increase: 50.0%; decrease: 39.0%; and no change: 54.1%). From these results, we concluded that several dairy producers distorted their actual milk yield and SCC changes or were not fully aware of those changes.

Response to a glucose tolerance test in early-lactation Holstein cows receiving a supplementation of biotin, folic acid, and vitamin B12

The aim of the study was to evaluate glucose and insulin metabolism of cows receiving a supplementation of biotin (B₈), folic acid (B₉), and vitamin B₁₂ (B₁₂) during the transition period. According to a 2 × 2 factorial arrangement, 32 cows were randomly assigned to 9 incomplete blocks according to their previous 305-d milk yield. Within each block, cows were randomly assigned to 1 of the following levels of biotin from -27 to 28 d relative to the parturition: (1) no biotin supplement (B₈-) or (2) 20 mg/d of dietary biotin (B₈+). Within each level of biotin, the cows received either (1) 2-mL weekly intramuscular injections of saline 0.9% NaCl (B₉B₁₂-) or (2) 2.6 g/d of dietary folic acid and 2-mL weekly intramuscular injections of 10 mg of vitamin B₁₂ (B₉B₁₂+). An intravenous glucose tolerance test was performed at 25 d in milk. Baseline plasma glucagon, glucose, and nonesterified fatty acid concentrations did not differ among treatments. For B₉B₁₂+ cows, baseline plasma insulin concentration and maximal glucose concentration after glucose administration were greater when also combined with biotin compared with no biotin combination, whereas there was no effect in B₉B₁₂- cows. There was no treatment effect on time to reach half-maximal glucose and insulin concentrations, glucose positive incremental area under the curve, and glucose and insulin clearance rates. Regarding insulin results, maximal plasma concentration and positive incremental area under the curve were respectively 51 and 74% greater for cows receiving the B₈ supplement than for cows who did not. Moreover, plasma nonesterified fatty acid concentration nadir tended to be reached later for B₈ cows. Insulin peak was reached earlier for cows in the group B₉B₁₂+ than cows in B₉B₁₂-, regardless of B₈ supplementation. Under the current conditions, our results suggested that cows receiving a B₈ supplement had a reduced insulin sensitivity in early lactation. Insulin response was faster for B₉B₁₂+ cows, but this was not translated into further improvements following the glucose administration challenge.

Short communication: Potential prediction of vitamin B12 concentration based on mid-infrared spectral data using Holstein Dairy Herd Improvement milk samples

The purpose of this study was (1) to predict the quantitative concentration of vitamin B₁₂ in milk using mid-infrared (MIR) spectrometry, and (2) to evaluate the potential of MIR spectra to discriminate different clusters of records based on their B₁₂ concentration. Milk samples were collected from 4,340 Holstein cows between 3 and 592 d in milk and located in 100 herds. Samples were taken using in-line milk meters and divided into 2 aliquots: one for MIR spectrometry and the other for B₁₂ concentration reference analyses by radioassay. Analyses were performed on 311 selected spectral wavelengths. A partial least squares regression model was built to quantify B₁₂ concentration. Discriminant analysis was used to isolate B₁₂ concentration clusters. A B₁₂ concentration threshold was set at 442 ng/dL, because this represents the cutoff value for a 250-mL glass of milk to fulfill 46% of the daily vitamin B₁₂ recommended dietary allowance for individuals 14 yr or older. For each analysis, records coming from two-thirds of herds were used to calibrate prediction equations, and the remaining records (one-third of herds for validation) were used to assess the prediction performance. In the case of discriminant analysis, validation sets were divided into evaluation sets (one-third of herds) to obtain alternate probability cutoffs and in test sets (two-thirds of herds) to validate equations. Spectral and B₁₂ concentration outliers were identified by calculating standardized Mahalanobis distance and with a residual analysis, respectively (n = 3,154). Regarding quantitative B₁₂ concentration, cross-validation and validation coefficients of determination averaged 0.51 and 0.46, respectively, which are relatively low, which would limit the potential use of the developed quantitative equations. In addition, root mean square errors of prediction of cross validation and validation sets averaged 88.9 and 94.7 ng/dL, respectively. Area under the receiver operating characteristic curve of test sets averaged 0.81 based on the 442 ng/dL threshold, which could be considered to represent good accuracy of classification. However, the false discovery rate averaged 36%. In summary, models predicting quantitative B₁₂ concentration had low cross-validation and validation coefficients of determination, limiting their use, but the proposed discriminant models could be used to identify milk samples with naturally high B12.

Symposium review: One-carbon metabolism and methyl donor nutrition in the dairy cow

The present review focuses on methyl donor metabolism and nutrition in the periparturient and lactating dairy cow. Methyl donors are involved in one-carbon metabolism, which includes the folate and Met cycles. These cycles work in unison to support lipid, nucleotide, and protein synthesis, as well as methylation reactions and the maintenance of redox status. A key feature of one-carbon metabolism is the multi-step conversion of tetrahydrofolate to 5-methyltetrahyrofolate. Homocysteine and 5-methyltetrahyrofolate are utilized by vitamin B₁₂-dependent Met synthase to couple the folate and Met cycles and generate Met. Methionine may also be remethylated from choline-derived betaine under the action of betaine hydroxymethyltransferase. Regardless, Met is converted within the Met cycle to S-adenosylmethionine, which is universally utilized in methyl-group transfer reactions including the synthesis of phosphatidylcholine. Homocysteine may also enter the transsulfuration pathway to generate glutathione or taurine for scavenging of reactive oxygen metabolites. In the transition cow, a high demand exists for compounds with a labile methyl group. Limited methyl group supply may contribute to inadequate hepatic phosphatidylcholine synthesis and hepatic triglyceride export, systemic oxidative stress, and compromised milk production. To minimize the perils associated with methyl donor deficiency, the peripartum cow relies on de novo methylneogenesis from tetrahydrofolate. In addition, dietary supplementation of rumen-protected folic acid, vitamin B₁₂, Met, choline, and betaine are potential nutritional approaches to target one-carbon pools and improve methyl donor balance in transition cows. Such strategies have merit considering research demonstrating their ability to improve milk production efficiency, milk protein synthesis, hepatic health, and immune response. This review aims to summarize the current understanding of folic acid, vitamin B₁₂, Met, choline, and betaine utilization in the dairy cow. Methyl donor co-supplementation, fatty acid feeding strategies that may optimize methyl donor supplementation efficacy, and potential epigenetic mechanisms are also considered.

Technical note: Extrapolation of hepatic glycogen concentration of the whole organ by performing a liver biopsy

Glycogen, a complex polysaccharide, is the form of storage of glucose in mammals that can be released rapidly when needed. Recent studies have mainly reported hepatic glycogen concentration for early-lactating cows, when the energy demand is higher than the energy supply from dry matter intake, driving the cow to use the energy stored as hepatic glycogen. Generally, liver samples are obtained through percutaneous needle biopsies in the right lobe of the liver. Our objective was to analyze the variation of glycogen concentration in the livers of Holstein and Jersey cows among different liver locations representing all lobes, to evaluate whether samples obtained by liver biopsies are representative of the whole organ. Liver from 10 culled lactating cows (5 Holstein and 5 Jersey cows) from 30 to 113 mo of age at slaughter were obtained. Each liver was sampled no more than 3 h after death on the following sites: 3 sites in the right lobe (1 to 3), 2 in the diaphragmatic surface of the left lobe (4 and 5), 3 in the visceral surface of the left lobe (6 to 8), 1 in the quadrate lobe (9), and 1 in the caudate lobe (10). Samples were snap frozen in liquid N₂ and were then analyzed for glucose concentration after conversion of glycogen to glucose using amyloglucosidase (EC 3.2.1.3). Glycogen results are reported as grams of glucose per 100 g of wet weight of liver (i.e., percent of wet weight of liver). Liver weights averaged 5.1 [standard deviation (SD) 1.2, minimum 3.3, maximum 6.2] kg for Holstein and 6.0 (SD 1.8, minimum 4.7, maximum 8.9) kg for Jersey cows. Holstein cows [1.31, standard error of the mean (SEM) 0.05% of wet weight] had greater liver glycogen concentration than did Jersey cows (0.75, SEM 0.05% of wet weight). No significant difference was noted among the 10 liver locations regarding glycogen concentration and averaged, for both breeds, 1.03% of wet weight (SEM 0.10). These results suggest that, in dairy cows, percutaneous needle liver biopsy in the right lobe is an accurate technique to fairly extrapolate glycogen concentration of the whole organ.

Cross-sectional study of the effect of diet composition on plasma folate and vitamin B12 concentrations in Holstein cows in the United States and Canada

The objective of this cross-sectional study was to assess the variability of plasma folate and vitamin B₁₂ concentrations in lactating Holstein cows across the United States and Canada. We also evaluated the effect of diet composition and cow characteristics on folate and vitamin B₁₂ plasma vitamin concentrations. A total of 22 and 24 US and Canadian dairy herds were enrolled, totaling 427 and 476 cows at 10 to 197 days in milk across all US and Canadian herds, respectively. Blood samples were taken to analyze plasma folate and vitamin B₁₂ concentrations, and ingredients of the diet were collected to determine nutrient composition. To reduce the number of interdependent variables in the analysis of the association of diet composition with plasma vitamin concentrations, we conducted a principal component analysis. Plasma folate concentrations were lower for US cows [13.4 ng/mL, 95% confidence interval (CI): 12.7-14.2] than for Canadian cows (14.5 ng/mL, 95% CI: 13.7-15.2), and the opposite was observed for plasma vitamin B₁₂ concentrations (US 206 pg/mL, 95% CI: 192-221; Canada 170 pg/mL, 95% CI: 159-181). The highest plasma concentrations of both vitamins were observed in the Northwest region of the United States (Oregon and Washington). Cows in California had the lowest plasma folate concentrations, and cows in Québec and New York State had the lowest plasma vitamin B₁₂ concentrations. Plasma folate concentrations were higher for multiparous than for primiparous cows and plasma vitamin B₁₂ concentrations progressively increased from parity 1 to 3 and higher. For both studied vitamins, plasma concentrations were lower at 0 to 55 than at 56 to 200 days in milk. Of 3 principal components, the one associated with dietary carbohydrates was significantly correlated with plasma folate and vitamin B₁₂ concentrations. Indeed, plasma folate concentrations decreased with dietary fiber concentrations (i.e., neutral and acid detergent fibers and lignin) and increased with dietary nonfiber carbohydrate concentrations. We obtained the opposite results for plasma vitamin B₁₂ concentrations. Both multivariable models explained 41% (pseudo-R²) of the variation in plasma folate and vitamin B₁₂ concentrations. Information gathered in this study is the first step toward determining sources of variation in plasma folate and vitamin B₁₂ concentrations, as well as the vitamin status of cows.

Glucose and insulin responses to an intravenous glucose tolerance test administered to feed-restricted dairy cows receiving folic acid and vitamin B12 supplements

The present experiment was conducted to determine whether, during periods of negative energy balance, the increase in glucose availability, despite similar DMI and greater milk production, induced by a combined supplement of folic acid and vitamin B₁₂ was related to effects of insulin on metabolism. Sixteen multiparous Holstein cows averaging 45 days in milk (standard deviation: 3) were assigned to 8 blocks of 2 animals each according to their milk production (45 kg/d; standard deviation: 6) during the week preceding the beginning of the experiment. Within each block, they received weekly intramuscular injections of either saline (CON) or folic acid and vitamin B₁₂ (VIT) during 5 consecutive weeks. During the last week, the cows were fed 75% of their ad libitum intake during 4 d. Blood samples were taken the morning before starting the feed restriction and on the third day of feed restriction. On the fourth day of feed restriction, the daily meal was not served and an intravenous glucose tolerance test was performed. During the 4 wk preceding the feed restriction, milk production and DMI were not affected by treatments. During the feed restriction, the vitamin supplement tended to decrease milk fat concentration and increase milk concentration of lactose. Plasma concentrations of homocysteine, Ile, Leu, Val, and branched-chain AA increased in VIT cows during the restriction but not in CON cows. During the glucose tolerance test, insulin peak height was lower and insulin incremental positive area under the curve tended to be lower for VIT than for CON [83 (95% confidence interval, CI: 64-108) vs. 123 (95% CI: 84-180) µg·180 min/L, respectively]. Free fatty acid nadir was reached earlier for VIT than for CON [34 (95% CI: 26-43) vs. 46 (95% CI: 31-57) min, respectively]. Glucose area under the curve, clearance rate and peak height, insulin time to reach the peak and clearance rate, and free fatty acid nadir did not differ between VIT and CON. The reduction in insulin release during a glucose tolerance test without changes in glucose clearance rate or area under the curve suggests that the vitamin supplement improved insulin sensitivity in feed-restricted lactating dairy cows.

Abstract 750: Detection of mutations in single circulating tumor cells using MALDI-TOF mass spectrometry

Background: As cancer therapeutics are increasingly selected based upon molecular genetic information, having reliable, accurate, rapid and inexpensive methods for mutational analysis are extremely desirable. Circulating tumor cells (CTCs) allow non-invasive “liquid biopsy” access to intact cells for molecular analysis. Here we demonstrate the successful detection of mutations in model CTCs individually isolated from blood (AccuCyte® - CyteFinder® system, RareCyte) using MALDI-TOF Mass Spectrometry (MassARRAY, Agena Bioscience).

Methods: Breast (MDA-MD-231) and lung (NCI-H1975) cancer cells with a set of known mutations were spiked into blood and processed by AccuCyte onto microscope slides and stained on an automated immunostainer. Slides were imaged using the CyteFinder digital fluorescence scanning microscope and mCTCs were identified by positive nuclear, EpCAM, and cytokeratin staining, and negative CD45 staining. mCTCs and white blood cell (WBC) negative controls were picked from the slides and put into PCR tubes using the CytePicker® module. DNA from individual or small pools of cells (3-5) was amplified using the PicoPLEX® (Rubicon) whole genome amplification (WGA) kit; alternatively cells were lysed and directly entered into the ensuing iPLEX® Pro workflow. Specific regions surrounding 5 different mutations in each of the mCTC lines were amplified from the WGA product or the lysed cells and the products were detected and scored for the mutations using a single PCR reaction iPLEX® Pro panel that includes a combination of 10 common lung and breast cancer mutations using the MassARRAY® platform.

Results: Five point mutations in four different genes (CDKN2A, EGFR, PIK3CA, and TP3) were measured in the NCI-H1975 lines and four point mutations in four genes (BRAF, KRAS, NF2, and TP53) and a deletion in one gene (CDKN2A) were measured in the MDA-MB-231 cells by iPLEX® Pro chemistry on the MassARRAY® system. All mutations were accurately detected in the WGA single and pooled cell samples and most were also detected in cells that did not undergo WGA before PCR with with iPLEX Pro panel. Allelic frequency observed was consistent with known zygosity of the mutation.

Conclusions: MassARRAY successfully detected mutations in single model CTCs that were individually picked from a blood sample processed by the AccuCyte - CyteFinder system. Integrating CTC isolation with MassARRAY may be a practical way to identify and monitor known cancer mutations non-invasively.

Citation Format: Jackie L. Stilwell, Ryan T. Birse, Arturo Ramirez, Melinda Duplessis, Brennan Enright, Darryl Irwin, Eric Kaldjian. Detection of mutations in single circulating tumor cells using MALDI-TOF mass spectrometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 750. doi:10.1158/1538-7445.AM2017-750

Short communication: Factors affecting vitamin B12 concentration in milk of commercial dairy herds: An exploratory study

Only bacteria can synthesize vitamin B12, and this requires adequate Co supply. The natural source of vitamin B12 in human diets comes from animal products, especially those from ruminants. This study aimed to describe variability regarding vitamin B12 concentration in milk among and within commercial dairy herds in early lactation. A secondary objective was to explore potential causes for this variability such as genetic variation and diet characteristics. In total, 399 dairy cows (135 primiparous and 264 multiparous; 386 Holstein and 13 Jersey cows) in 15 commercial herds were involved. Milk samples were taken at 27.4±4.1 and 55.4±4.1d in milk. Neither parity (primiparous vs. multiparous) nor sampling time affected milk concentrations of vitamin B12. Nevertheless, vitamin B12 concentration in milk was highly variable among and within dairy herds. The lowest vitamin B12 concentration in milk of cows was observed in the Jersey herd. Among herds, vitamin B12 concentration in milk ranged from 2,309 to 3,878 pg/mL; one glass (250mL) of milk from those herds would provide between 23 and 40% of the vitamin B12 recommended daily allowance. Among individual cows, however, this provision varied between 16 and 57% of the recommendation. In spite of the limited size of the studied population, the heritability value was 0.23, suggesting that genetic selection could modify milk vitamin B12 concentration. We observed a positive relationship between milk vitamin B12 concentration and dietary acid detergent fiber content and a negative relationship between milk concentration of vitamin B12 and dietary crude protein content.

An economic model evaluating the supplementation of folic acid and vitamin B12 given around parturition and in early lactation on dairy farms in Québec, Canada

Duplessis, M., Girard, C. L., Santschi, D. E. and Pellerin, D. 2014. An economic model evaluating the supplementation of folic acid and vitamin B12 given around parturition and in early lactation on dairy farms in Québec, Canada. Can. J. Anim. Sci. 94: 737–747. The aim of this study was to estimate the potential profitability of a combined supplement of folic acid and vitamin B12 given around parturition and in early lactation in commercial dairy herds in Québec. A total of 791 dairy cows from 14 herds were enrolled. Cows were assigned to weekly intramuscular injections of saline or 320 mg of folic acid and 10 mg of vitamin B12. Treatments began 3 wk before the expected calving date and lasted until 8 wk of lactation. Within each herd, data on production, reproduction, and incidence of metabolic disorders and other diseases were recorded. With regard to the Canadian dairy industry, which operates under a supply management system, two scenarios were studied: (1) quota kept constant and (2) number of cows kept constant. For scenarios 1 and 2, eight and seven herds out of 14, respectively, obtained a positive annual net margin per cow following the vitamin supplement. The average net margins were Can$31.18 and Can$–4.86 N cow−1 yr−1 for scenarios 1 and 2, respectively. The variability of the response highlights that supplies of these vitamins by ruminal synthesis were probably different among herds and actual knowledge does not allow predicting supplies according to the diet.

Chloroplast genome sequencing analysis of Heterosigma akashiwo CCMP452 (West Atlantic) and NIES293 (West Pacific) strains

BACKGROUND

Heterokont algae form a monophyletic group within the stramenopile branch of the tree of life. These organisms display wide morphological diversity, ranging from minute unicells to massive, bladed forms. Surprisingly, chloroplast genome sequences are available only for diatoms, representing two (Coscinodiscophyceae and Bacillariophyceae) of approximately 18 classes of algae that comprise this taxonomic cluster. A universal challenge to chloroplast genome sequencing studies is the retrieval of highly purified DNA in quantities sufficient for analytical processing. To circumvent this problem, we have developed a simplified method for sequencing chloroplast genomes, using fosmids selected from a total cellular DNA library. The technique has been used to sequence chloroplast DNA of two Heterosigma akashiwo strains. This raphidophyte has served as a model system for studies of stramenopile chloroplast biogenesis and evolution.

RESULTS

H. akashiwo strain CCMP452 (West Atlantic) chloroplast DNA is 160,149 bp in size with a 21,822-bp inverted repeat, whereas NIES293 (West Pacific) chloroplast DNA is 159,370 bp in size and has an inverted repeat of 21,665 bp. The fosmid cloning technique reveals that both strains contain an isomeric chloroplast DNA population resulting from an inversion of their single copy domains. Both strains contain multiple small inverted and tandem repeats, non-randomly distributed within the genomes. Although both CCMP452 and NIES293 chloroplast DNAs contains 197 genes, multiple nucleotide polymorphisms are present in both coding and intergenic regions. Several protein-coding genes contain large, in-frame inserts relative to orthologous genes in other plastids. These inserts are maintained in mRNA products. Two genes of interest in H. akashiwo, not previously reported in any chloroplast genome, include tyrC, a tyrosine recombinase, which we hypothesize may be a result of a lateral gene transfer event, and an unidentified 456 amino acid protein, which we hypothesize serves as a G-protein-coupled receptor. The H. akashiwo chloroplast genomes share little synteny with other algal chloroplast genomes sequenced to date.

CONCLUSION

The fosmid cloning technique eliminates chloroplast isolation, does not require chloroplast DNA purification, and reduces sequencing processing time. Application of this method has provided new insights into chloroplast genome architecture, gene content and evolution within the stramenopile cluster.

Identification of a genetic determinant responsible for host specificity in Streptococcus thermophilus bacteriophages

Phage-host interactions remain poorly understood in lactic acid bacteria and essentially in all Gram-positive bacteria. The aim of this study was to identify the phage genetic determinant (anti-receptor) involved in the recognition of Streptococcus thermophilus hosts. The complete genomic sequence of the lytic S. thermophilus phage DT1 was determined previously, and bioinformatic analysis indicated that orf18 might be the anti-receptor gene. The orf18 of six additional S. thermophilus phages was determined (DT2, DT4, MD1, MD2, MD4 and Q5) and compared with the orf18 of DT1. The deduced ORF18 was divided into three domains. The first domain, which contains the N-terminal part of the protein, was conserved in all seven phages. The second domain was detected in only two phages and flanked by a motif called collagen-like repeats. The second domain also contained a variable region (VR1). All seven phages had a third domain that consisted of the C-terminal section of the protein as well as another variable region (VR2). Chimeric DT1 phages were constructed by recombination; a portion of its orf18 was replaced by the corresponding section in orf18 of the phage MD4. All DT1 chimeric phages acquired the host range of phage MD4. Analysis of the orf18 in the chimeric phages revealed that host specificity in phages DT1 and MD4 resulted from VR2. This is the first report on the identification and characterization of a phage gene involved in the host recognition process of Gram-positive bacteria.