Metformin increases liver accumulation of vitamin B12 – An experimental study in rats

Aims/hypothesis

Patients treated with metformin exhibit low levels of plasma vitamin B₁₂ (B₁₂), and are considered at risk for developing B₁₂ deficiency. In this study, we investigated the effect of metformin treatment on B₁₂ uptake and distribution in rats.

Methods

Sprague Dawley rats (n = 18) were divided into two groups and given daily subcutaneous injections with metformin or saline (control) for three weeks. Following this, the animals received an oral dose of radio-labeled B₁₂ (⁵⁷[Co]-B₁₂), and urine and feces were collected for 24 h. Plasma, bowel content, liver, and kidneys were collected and analyzed for B₁₂, unsaturated B₁₂-binding capacity, and ⁵⁷[Co]-B₁₂.

Results

Three weeks of metformin treatment reduced plasma B₁₂ by 22% or 289 [47-383] pmol/L (median and [range]) (p = 0.001), while no effect was observed on unsaturated B₁₂-binding capacity. Compared with controls, the amount of B₁₂ in the liver was 36% (p = 0.007) higher in metformin-treated rats, while the B₁₂ content in the kidney was 34% (p = 0.013) lower. No difference in the total amount of absorbed ⁵⁷[Co]-B₁₂ present in the tissues and organs studied was found, suggesting that metformin has no decreasing effect on the B₁₂ absorption.

Conclusions/interpretation

These results show that metformin treatment increases liver accumulation of B₁₂, thereby resulting in decreases in circulating B₁₂ and kidney accumulation of the vitamin. Our data questions whether the low plasma B₁₂ observed in patients treated with metformin reflects impaired B₁₂ status, and rather suggests altered tissue distribution and metabolism of the vitamin.     

Involvement of mercury methylation in microbial mercury detoxication

A vitamin B₁₂ requiring strain was isolated fromChlostridium cochlearium T-2 C which is known to synthesize various types of vitamin B₁₂ including methylcobalamin and has an ability to methylate inorganic mercury. The vitamin B₁₂ auxotroph lacking the mercury-methylating activity showed higher sensitivity to inorganic mercury than its original strain, while the sensitivity of both strains to methylmercury was relatively low and essentially the same. These data seem to present affirmative evidence to postulate the physiological role of methylcobalamin-dependent methylation of mercury to be a process of detoxication.Abbreviation MNNG N-methyl-N-nitro-N-nitrosoguanidine     

Microbiological activities of nucleotide loop-modified analogues of vitamin B12

Novel vitamin B₁₂ analogues in which the D-ribose moiety of the nucleotide loop was replaced by an oligomethylene group and a trimethylene analogue containing imidazole instead of 5,6-dimethylbenzimidazole as well as cobinamide methyl phosphate were tested for biological activities with Escherichia coli 215, a B₁₂- or methionine-auxotroph, and Lactobacillus leichmannii ATCC 7830 as test organisms. A cyano form of 5,6-dimethylbenzimidazolyl tetramethylene, trimethylene and hexamethylene analogues supported the growth of L. leichmannii in this order. 5.6-Dimethylbenzimidazolyl dimethylene and imidazolyl trimethylene analogues did not show B₁₂ activity and behaved as weak B₁₂ antagonists when added together with cyanocobalamin. An adenosyl form of the biologically active analogues served as coenzymes for ribonucleotide reductase of this bacterium, whereas that of the inactive analogues did not. The latter acted as weak competitive inhibitors against adenosylcobalamin. ON the contrary, all the analogues did not support the growth of E. coli 215 at all by themselves and inhibited the growth when added with a suboptimum level of cyanocobalamin. A methyl form of the analogues also did not support the growth of E. coli 215, although they served as active coenzymes for methionine synthase of the bacterium. Since unlabeled analogues strongly inhibited the uptake of [³H]cyanocobalamin by this bacterium, it seems likely that the analogues exert their anti-B₁₂ activity toward E. coli 215 by blocking the B₁₂-transport systemAbbreviations AdoCbl adenosylcobalamin - MeCbl methylcobalamin - CN-Cbl cyanocobalamin or vitamin B₁₂ - Cbl cobalamin - (CN, aq)Cbi cyanoaquacobinamide - MeCbi methylcobinamide - Cbi cobinamide - (CN, aq)Cbi-PMe cyanoaquacobinamide methyl phosphate - Cbi-PMe cobinamide methyl phosphate - DBI 5,6-dimethylbenzimidazole - DBIyl 5,6-dimethylbenzimidazolyl - FMNH₂ fully reduced form of riboflavin 5-phosphate     

Vitamin B12, homocysteine and carotid plaque in the era of folic acid fortification of enriched cereal grain products

Background

Carotid plaque area is a strong predictor of cardiovascular events. High homocysteine levels, which are associated with plaque formation, can result from inadequate intake of folate and vitamin B₁₂. Now that folic acid fortification is widespread in North America, vitamin B₁₂ has become an important determinant of homocysteine levels. We sought to determine the prevalence of low serum levels of vitamin B₁₂, and their relation to homocysteine levels and carotid plaque area among patients referred for treatment of vascular disease since folic acid fortification of enriched grain products.

Methods

We evaluated 421 consecutive new patients with complete data whom we saw in our vascular disease prevention clinics between January 1998 and January 2002. We measured total carotid plaque area by ultrasound and determined homocysteine and serum vitamin B₁₂ levels in all patients.

Results

The patients, 215 men and 206 women, ranged in age from 37 to 90 years (mean 66 years). Most were taking medications for hypertension (67%) and dyslipidemia (62%). Seventy-three patients (17%) had vitamin B₁₂ deficiency (vitamin B₁₂ level < 258 pmol/L with homocysteine level > 14 μmol/L or methylmalonic acid level > 271 nmol/L). The mean area of carotid plaque was significantly larger among the group of patients whose vitamin B₁₂ level was below the median of 253 pmol/L than among those whose vitamin B₁₂ level was above the median: 1.36 (standard deviation [SD] 1.27) cm² v. 1.09 (SD 1.0) cm²; p = 0.016.

Conclusions

Vitamin B₁₂ deficiency is surprisingly common among patients with vascular disease, and, in the setting of folic acid fortification, low serum vitamin B₁₂ levels are a major determinant of elevated homocysteine levels and increased carotid plaque area.Elevated plasma total homocysteine levels are a strong, graded independent risk factor for stroke and myocardial infarction.^1,2 Mechanisms by which homocysteine may cause vascular disease include a propensity for thrombosis and impaired thrombolysis, increased production of hydrogen peroxide, endothelial dysfunction and increased oxidation of low-density lipoproteins and Lp(a) lipoproteins.³ Folic acid fortification of enriched cereal grain products began in North America in March 1996 and was made mandatory in 1998. Fortification has reduced the number of neural tube defects by half,⁴ which is clearly a beneficial outcome, but so far it has had little impact on cardiovascular mortality.⁵Carotid plaque area is a strong predictor of cardiovascular events.⁶ High homocysteine levels, which are associated with plaque formation, can result from inadequate intake of folate and vitamin B₁₂. Now that folic acid fortification is widespread, vitamin B₁₂ has become an important determinant of homocysteine levels.⁷ We sought to determine the prevalence of low serum levels of vitamin B₁₂, and their relation to homocysteine levels and carotid plaque area among patients referred for treatment of vascular disease since folic acid fortification of enriched grain products.     

Aquaporins and membrane diffusion of CO2 in living organisms

Background

Determination of CO₂ diffusion rates in living cells revealed inconsistencies with existing models about the mechanisms of membrane gas transport. Mainly, these discrepancies exist in the determined CO₂ diffusion rates of bio-membranes, which were orders of magnitudes below those for pure lipid bilayers or theoretical considerations as well as in the observation that membrane insertion of specific aquaporins was rescuing high CO₂ transport rates. This effect was confirmed by functional aquaporin protein analysis in heterologous expression systems as well as in bacteria, plants and partly in mammals.

Scope of Review

This review summarizes the arguments in favor of and against aquaporin facilitated membrane diffusion of CO₂ and reports about its importance for the physiology of living organisms.

Major Conclusions

Most likely, the aquaporin tetramer forming an additional fifth pore is required for CO₂ diffusion facilitation. Aquaporin tetramer formation, membrane integration and disintegration could provide a mechanism for regulation of cellular CO₂ exchange. The physiological importance of aquaporin mediated CO₂ membrane diffusion could be shown for plants and cyanobacteria and partly for mammals.

General Significance

Taking the mentioned results into account, consequences for our current picture of cell membrane transport emerge. It appears that in some or many instances, membranes might not be as permeable as it was suggested by current bio-membrane models, opening an additional way of controlling the cellular influx or efflux of volatile substances like CO₂. This article is part of a Special Issue entitled Aquaporins.     

Allosteric modulators of human A2B adenosine receptor

Background

Among adenosine receptors (ARs) the A_2B subtype exhibits low affinity for the endogenous agonist compared with the A₁, A_2A, and A₃ subtypes and is therefore activated when concentrations of adenosine increase to a large extent following tissue damages (e.g. ischemia, inflammation). For this reason, A_2B AR represents an important pharmacological target.

Methods

We evaluated seven 1-benzyl-3-ketoindole derivatives (7–9) for their ability to act as positive or negative allosteric modulators of human A_2B AR through binding and functional assays using CHO cells expressing human A₁, A_2A, A_2B, and A₃ ARs.

Results

The investigated compounds behaved as specific positive or negative allosteric modulators of human A_2B AR depending on small differences in their structures. The positive allosteric modulators 7a,b and 8a increased agonist efficacy without any effect on agonist potency. The negative allosteric modulators 8b,c and 9a,b reduced agonist potency and efficacy.

Conclusions

A number of 1-benzyl-3-ketoindole derivatives were pharmacologically characterized as selective positive (7a,b) or negative (8c, 9a,b) allosteric modulators of human A_2B AR.

General significance

The 1-benzyl-3-ketoindole derivatives 7–9 acting as positive or negative allosteric modulators of human A_2B AR represent new pharmacological tools useful for the development of therapeutic agents to treat pathological conditions related to an altered functionality of A_2B AR.     

DNA-maleimide: An improved maleimide compound for electrophoresis-based titration of reactive thiols in a specific protein

Background

Thiol-mediated redox regulation of proteins plays a key role in many cellular processes.

Methods

To understand the redox status of cysteinyl thiol groups of the desired proteins, we developed a new maleimide reagent: a maleimide-conjugated single strand DNA, DNA-maleimide (DNA-Mal).

Results

DNA-Mal labelled proteins run as a distinct band on SDS-PAGE, with a discrete 9.32 kDa mobility shift per label regardless of the protein species or electrophoretic conditions.

Conclusions

DNA-Mal labels free thiols like standard maleimide reagents, but possesses practical advantages in titration of the number and relative content of free thiols in a protein.

General significance

The versatility of DNA molecule enhances the application of DNA-Mal in a broader range of cysteine containing proteins.     

Identification and characterization of retinoid-active short-chain dehydrogenases/reductases in Drosophila melanogaster

Background

In chordates, retinoid metabolism is an important target of short-chain dehydrogenases/reductases (SDRs). It is not known whether SDRs play a role in retinoid metabolism of protostomes, such as Drosophila melanogaster.

Methods

Drosophila genome was searched for genes encoding proteins with ∼ 50% identity to human retinol dehydrogenase 12 (RDH12). The corresponding proteins were expressed in Sf9 cells and biochemically characterized. Their phylogenetic relationships were analyzed using PHYLIP software.

Results

A total of six Drosophila SDR genes were identified. Five of these genes are clustered on chromosome 2 and one is located on chromosome X. The deduced proteins are 300 to 406 amino acids long and are associated with microsomal membranes. They recognize all-trans-retinaldehyde and all-trans-3-hydroxyretinaldehyde as substrates and prefer NADPH as a cofactor. Phylogenetically, Drosophila SDRs belong to the same branch of the SDR superfamily as human RDH12, indicating a common ancestry early in bilaterian evolution, before a protostome–deuterostome split.

Conclusions

Similarities in the substrate and cofactor specificities of Drosophila versus human SDRs suggest conservation of their function in retinoid metabolism throughout protostome and deuterostome phyla.

General significance

The discovery of Drosophila retinaldehyde reductases sheds new light on the conversion of β-carotene and zeaxantine to visual pigment and provides a better understanding of the evolutionary roots of retinoid-active SDRs.     

El déficit de vitamina B12 y ácido fólico en la población mayor de 65 años: estudio descriptivo

Introduction

The aim of this study is to establish the prevalence of vitamin B12 and folic acid deficiency in the population of 65 years and over in semi-urban and rural area, as well as investigating the risk factors, and the determining factors of this deficiency in this population and its relationship with the prevalence of concomitant cardiovascular and cognitive diseases.

Materials and methods

A cross-sectrionall study conducted in the Geriatrics Outpatients in the period between 2008 and 2010. Demographic, clinical and laboratory were collected at 3 different times.A bivariate analysis was performed with lack of vitamin B12 and folic acid, as the outcome variables.

Results

Vitamin B12 defieciency was found in 16.5% of the sample, and no folic acid deficiency. A strong association was found with vitamin B12 deficiency and cardiac and cerebrovascular diseases, vascular risk factors and drugs administered in prevention of cardiac events and ischaemic stroke.

Conclusions

There was a higher prevalence of vitamin B12 deficiency in the elderly population in the catchment area of Medina del Campo compared to that found in the literature, but not so with the isolated deficiency of folic acid.     

Methionine oxidation and reduction in proteins

Background

Cysteine and methionine are the two sulfur containing amino acids in proteins. While the roles of protein-bound cysteinyl residues as endogenous antioxidants are well appreciated, those of methionine remain largely unexplored.

Scope

We summarize the key roles of methionine residues in proteins.

Major conclusion

Recent studies establish that cysteine and methionine have remarkably similar functions.

General significance

Both cysteine and methionine serve as important cellular antioxidants, stabilize the structure of proteins, and can act as regulatory switches through reversible oxidation and reduction. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.     

Azoxystrobin,a mitochondrial complex III Qo site inhibitor,exerts beneficial metabolic effects in vivo and in vitro

Background

Several anti-diabetes drugs exert beneficial effects against metabolic syndrome by inhibiting mitochondrial function. Although much progress has been made toward understanding the role of mitochondrial function inhibitors in treating metabolic diseases, the potential effects of these inhibitors on mitochondrial respiratory chain complex III remain unclear.

Methods

We investigated the metabolic effects of azoxystrobin (AZOX), a Q_o inhibitor of complex III, in a high-fat diet-fed mouse model with insulin resistance in order to elucidate the mechanism by which AZOX improves glucose and lipid metabolism at the metabolic cellular level.

Results

Acute administration of AZOX in mice increased the respiratory exchange ratio. Chronic treatment with AZOX reduced body weight and significantly improved glucose tolerance and insulin sensitivity in high-fat diet-fed mice. AZOX treatment resulted in decreased triacylglycerol accumulation and down-regulated the expression of genes involved in liver lipogenesis. AZOX increased glucose uptake in L6 myotubes and 3T3-L1 adipocytes and inhibited de novo lipogenesis in HepG2 cells. The findings indicate that AZOX-mediated alterations to lipid and glucose metabolism may depend on AMP-activated protein kinase (AMPK) signaling.

Conclusions

AZOX, a Q_o inhibitor of mitochondrial respiratory complex III, exerts whole-body beneficial effects on the regulation of glucose and lipid homeostasis in high-fat diet-fed mice.

General significance

These findings provide evidence that a Q_o inhibitor of mitochondrial respiratory complex III could represent a novel approach for the treatment of obesity.     

A Combined Supplementation of Omega-3 Fatty Acids and Micronutrients (Folic Acid,Vitamin B12) Reduces Oxidative Stress Markers in a Rat Model of Pregnancy Induced Hypertension

Objectives

Our earlier studies have highlighted that an altered one carbon metabolism (vitamin B₁₂, folic acid, and docosahexaenoic acid) is associated with preeclampsia. Preeclampsia is also known to be associated with oxidative stress and inflammation. The current study examines whether maternal folic acid, vitamin B₁₂ and omega-3 fatty acid supplementation given either individually or in combination can ameliorate the oxidative stress markers in a rat model of pregnancy induced hypertension (PIH).

Materials and Methods

Pregnant Wistar rats were assigned to control and five treatment groups: PIH; PIH + vitamin B₁₂; PIH + folic acid; PIH + Omega-3 fatty acids and PIH + combined micronutrient supplementation (vitamin B₁₂ + folic acid + omega-3 fatty acids). L-Nitroarginine methylester (L-NAME; 50 mg/kg body weight/day) was used to induce hypertension during pregnancy. Blood Pressure (BP) was recorded during pregnancy and dams were dissected at d20 of gestation.

Results

Animals from the PIH group demonstrated higher (p<0.01 for both) systolic and diastolic BP; lower (p<0.01) pup weight; higher dam plasma homocysteine (p<0.05) and dam and offspring malondialdehyde (MDA) (p<0.01), lower (p<0.05) placental and offspring liver DHA and higher (p<0.01) tumor necrosis factor–alpha (TNF–ά) levels as compared to control. Individual micronutrient supplementation did not offer much benefit. In contrast, combined supplementation lowered systolic BP, homocysteine, MDA and placental TNF-ά levels in dams and liver MDA and protein carbonyl in the offspring as compared to PIH group.

Conclusion

Key constituents of one carbon cycle (folic acid, vitamin B₁₂ and DHA) may play a role in reducing oxidative stress and inflammation in preeclampsia.     

Prostaglandin E2 produced by inducible COX-2 and mPGES-1 promoting cancer cell proliferation in vitro and in vivo

Aim

Many cancers originate and flourish in a prolonged inflammatory environment. Our aim is to understand the mechanisms of how the pathway of prostaglandin E₂ (PGE₂) biosynthesis and signaling can promote cancer growth in inflammatory environment at cellular and animal model levels.

Main methods

In this study, a chronic inflammation pathway was mimicked with a stable cell line that over-expressed a novel human enzyme consisting of cyclooxygenase isoform-2 (COX-2) linked to microsomal (PGE₂ synthase-1 (mPGES-1)) for the overproduction of pathogenic PGE₂. This PGE₂-producing cell line was co-cultured and co-implanted with three human cancer cell lines including prostate, lung, and colon cancers in vitro and in vivo, respectively.

Key findings

Increases in cell doubling rates for the three cancer cell types in the presence of the PGE₂-producing cell line were clearly observed. In addition, one of the four human PGE₂ subtype receptors, EP₁, was used as a model to identify PGE₂-signaling involved in promoting the cancer cell growth. This finding was further proven in vivo by co-implanting the PGE₂-producing cells line and the EP₁-positive cancer cells into the immune deficient mice, after that, it was observed that the PGE₂-producing cells promoted all three types of cancer formation in the mice.

Significance

This study clearly demonstrated that the human COX-2 linked to mPGES-1 is a pathway that, when mediated by the EP, is linked to promoting cancer growth in a chronic inflammatory environment. The identified pathway could be used as a novel target for developing and advancing anti-inflammation and anti-cancer interventions.     

Double-tailed lipid modification as a promising candidate for oligonucleotide delivery in mammalian cells

Background

The potential use of nucleic acids as therapeutic drugs has triggered the quest for oligonucleotide conjugates with enhanced cellular permeability. To this end, the biophysical aspects of previously reported potential lipid oligodeoxyribonucleotide conjugates were studied including its membrane-binding properties and cellular uptake.

Methods

These conjugates were fully characterized by MALDI-TOF mass spectrometry and HPLC chromatography. Their ability to insert into lipid model membrane systems was evaluated by Langmuir balance and confocal microscopy followed by the study of the internalization of a lipid oligodeoxyribonucleotide conjugate bearing a double-tail lipid modification (C₂₈) into different cell lines by confocal microscopy and flow cytometry. This compound was also compared with other lipid containing conjugates and with the classical lipoplex formulation using Transfectin as transfection reagent.

Results

This double-tail lipid modification showed better incorporation into both lipid model membranes and cell systems. Indeed, this lipid conjugation was capable of inserting the oligodeoxyribonucleotide into both liquid-disordered and liquid-ordered domains of model lipid bilayer systems and produced an enhancement of oligodeoxyribonucleotide uptake in cells, even better than the effect caused by lipoplexes. In addition, in β₂ integrin (CR3) expressing cells this receptor was directly involved in the enhanced internalization of this compound.

Conclusions

All these features confirm that the dual lipid modification (C₂₈) is an excellent modification for enhancing nucleic acid delivery without altering their binding properties.

General significance

Compared to the commercial lipoplex approach, oligodeoxyribonucleotide conjugation with C₂₈ dual lipid modification seems to be promising to improve oligonucleotide delivery in mammalian cells.     

A rubber transfer gasket to improve the throughput of liquid–liquid extraction in 96-well plates: Application to vitamin D testing

Background

The unmitigated rise in demand for the assessment of vitamin D status has taxed the ability of clinical mass spectrometry laboratories to preserve turn-around times. We aimed to improve the throughput of liquid–liquid extraction of plasma/serum for the assay of 25-hydroxy vitamin D.

Methods

We designed and fabricated a flexible rubber gasket that seals two 96-well plates together to quantitatively transfer the contents of one plate to another. Using the transfer gasket and a dry-ice acetone bath to freeze the aqueous infranatant, we developed a novel liquid–liquid extraction workflow in a 96-well plate format. We applied the technology to the mass spectrometric quantification of 25-hydroxy vitamin D.

Results

Cross-contamination between wells was ≤0.13%. The interassay imprecision over 132 days of clinical implementation was less than 10%. The method compared favorably to a standard liquid–liquid extraction in glass tubes (Deming slope = 1.018, S_x|y = 0.022). The accuracy of the assay was 102–105% as assessed with the recently released control materials from NIST.

Conclusions

The development of a plate-sealing gasket permits the liquid–liquid extraction of clinical specimens in a moderate-throughput workflow and the reliable assay of vitamin D status. In the future, the gasket may also prove useful in other sample preparation techniques for HPLC or mass spectrometry.     

Novel vitamin B<Subscript>12</Subscript>-producing <Emphasis Type="Italic">Enterococcus</Emphasis> spp. and preliminary in vitro evaluation of probiotic potentials

Vitamin B₁₂ is an essential nutrient required for crucial metabolic processes in humans. Vitamin B₁₂-producing lactic acid bacteria (LAB) have been attracting increased attentions currently because of the generally recognized as safe (GRAS) status. Most of recent studies focused on Lactobacillus, and little is known about B₁₂-producing Enterococcus. In the present study, five Enterococcus strains isolated from infant feces were identified as vitamin B₁₂ producers. Among them, Enterococcus faecium LZ86 had the highest B₁₂ production (499.8 ± 83.7 μg/L), and the B₁₂ compound from LZ86 was identified as the biological active adenosylcobalamin, using reversed phase high-performance liquid (RP-HPLC) chromatogram. We examined basic probiotic and safety properties of E. faecium LZ86 and found that it was able to survive harsh environmental conditions (hot temperature, cold temperature, ethanol and osmotic stresses), tolerate gastric acid (pH 2.0, 3 h) and bile salts (0.3%), and adhere to Caco-2 cells. We also showed that E. faecium LZ86 is devoid of transferable antibiotic resistance and potential virulence factors. Together, here we report a B₁₂-producing E. faecium strain LZ86 firstly, which has desirable probiotic properties and may serve as a good candidate for vitamin B₁₂ fortification in food industry.     

Chronic hypoxia leads to a glycolytic phenotype and suppressed HIF-2 signaling in PC12 cells

Background

Along with other regulators of cell metabolism, hypoxia-inducible factors HIF-1 and HIF-2 differentially regulate cell adaptation to hypoxia. Switches in HIF-1/HIF-2 signaling in chronic hypoxia have not been fully investigated.

Methods

Proliferation, viability, apoptosis, neuronal and bioenergetic markers, mitochondrial function, respiration, glycolysis, HIF signalling, responses to O₂ and glucose deprivation (OGD) were examined using tumor PC12 and SH-SY5Y cells continuously grown at 3% O₂.

Results

Hypoxic PC12 cells (H-cells) exhibit reduced proliferation and histone H4 acetylation, NGF-independent differentiation, activation of AMPK, inhibition of Akt, altered mitochondria and response to NGF. Cellular cytochrome c is increased with no effect on apoptosis. Reduction in respiration has minor effect on cellular ATP which is maintained through activated uptake (GLUT1) and utilization (HK2, PFK2) of glucose. H-cells exhibit resistance to OGD linked to increased glycogen stores. HIF-2alpha protein is decreased without changes in mRNA. Unlike HIF-1alpha, HIF-2alpha is not stabilized pharmacologically or by O₂ deprivation. Capacity for HIF-2alpha stabilization is partly restored when H-cells are cultured at normoxia. In low-respiring SH-SY5Y cells cultured under the same conditions HIF-2alpha stabilization and energy budget are not affected.

Conclusions

In chronically hypoxic PC12 cells glycolytic energy budget, increased energy preservation and low susceptibility to OGD are observed. HIF-2alpha no longer orchestrates adaptive responses to anoxia.

General significance

Demonstrated switch in HIF-1/HIF-2 signaling upon chronic hypoxia can facilitate cell survival in energy crisis, by regulating balance between energy saving and decrease in proliferation, on one hand and active cell growth and tumor expansion, on the other.     

Pregnancy,delivery, and breastfeeding after total gastrectomy for gastric cancer: a case report

Background

The reports of pregnancy after total gastrectomy for gastric cancer are rare.

Case presentation

We report a case of a 35-year-old woman, gravida 0, para 0, who became pregnant and delivered a baby 2?years and 6?months after laparoscopic-assisted total gastrectomy for early gastric cancer. Postoperatively, she showed a good progress during the follow-up and was continuously taking oral iron supplement and administered with methylcobalamin intramuscular injection. Two years after gastrectomy, she became pregnant. During the pregnancy, she kept taking iron and vitamin B₁₂ supplementation and had a good course of pregnancy and a normal delivery. However, 2?months after the delivery, liver dysfunction was detected via blood examination. The patient switched from exclusive breastfeeding to combined feeding with formula, and her laboratory results returned to normal. During 10?years of follow-up after the delivery, the patient was in good condition without any recurrence and nutritional deficiencies, and her child had thrived.

Conclusions

Careful monitoring and management of iron and vitamin deficiencies are essential during pregnancy and the lactation periods for patients who previously underwent total gastrectomy. During the lactation period, a combination of formula and breastfeeding provides maternal and fetal nutritional support.