Biochemistry, function, and deficiency of vitamin B12 in Caenorhabditis elegans

An improved medium for in vitro studies of female reproduction and oviposition in Schistosoma japonicum

BACKGROUND

Schistosomiasis is a disease primarily caused by eggs laid by pathogens called schistosomes. Among the schistosome species infecting humans, Schistosoma japonicum possesses the largest fecundity; each adult female produces an average of 3500 eggs per day. The lack of proper culture conditions supporting continuous oviposition in vitro has precluded detailed investigation of mechanisms regulating sexual maturation and egg production in Schistosoma japonicum.

METHODS

We optimized in vitro culture conditions by replacing reagents that are part of the classical ABC169 medium. Fast Blue BB staining and 4',6-diamidino-2-phenylindole (DAPI) labeling were applied to observe the sexual development status of the females. In vitro RNA interference (RNAi) technology was used to validate the capability of the modified medium. The detection of male β-alanyl-tryptamine (BATT) was conducted using liquid chromatography-mass spectrometry (LC-MS).

RESULTS

Both m-AB169 (1640) and AB169 (1640) media are capable of facilitating the sexual development of paired virgin female S. japonicum, as well as sustaining the mature reproductive organs and egg production of adult S. japonicum for at least 22 days in vitro. M-AB169 (1640) provided a more stable condition for supporting the sexual maturity of female S. japonicum, as evidenced by the consistent initiation of egg production compared with AB169 (1640). Through a comparative analysis of S. japonicum and S. mansoni in diverse media, we demonstrated that these closely related species display distinct demands for their sexual development and egg production, suggesting a potential influence of nutritional factors on the observed variations in host ranges among different schistosome species. Importantly, we successfully identified the presence of the pheromone β-alanyl-tryptamine (BATT) in S. japonicum, previously identified in S. mansoni, highlighting its conserved role in schistosome reproductive development. Through the employment of double-stranded RNA (dsRNA) treatment to silence two genes that are involved in either the male (gli1, glioma-associated oncogene homolog 1) or female (vf1, vitellogenic factor 1) side in male-induced female reproductive development of S. mansoni, we confirmed that the combination of m-AB169 (1640) and RNAi technology has the capacity to facilitate in vitro studies of S. japonicum's reproductive and oviposition processes.

CONCLUSIONS

We developed a novel medium, m-AB169 (1640), that not only maintains the mature reproductive organs and continuous oviposition of adult female Schistosoma japonicum for up to 22 days but also supports the reproductive development and subsequent egg-laying of virgin females after pairing with male worms. This study provides a valuable in vitro platform for functional studies of the mechanisms underlying the fascinating biology of the female sexual development and egg production of S. japonicum, which may accelerate the development of new strategies targeting schistosome egg production.

Enhancing the biomass and docosahexaenoic acid-rich lipid accumulation of Schizochytrium sp. in propionate wastewater

In order to find a more effective way to obtain docosahexaenoic acid (DHA) rich lipid from Schizochytrium sp., a widespread propionate wastewater (PW) is used. PW is a common industrial and domestic wastewater, and transforming it into valuable products is a potential treatment method. Schizochytrium sp. is a rapidly growing oleaginous organism, which has been used commercially for DHA production. Herein, PW is completely used for DHA production by Schizochytrium sp. by genetic engineering and fermentation optimization, which can alleviate the increasingly tense demand for water resources and environmental pollution caused by industrial wastewater. Firstly, the methylmalonyl-CoA mutase (MCM) was overexpressed in Schizochytrium sp. to enhance the metabolism of propionate, then the engineered strain of overexpressed MCM (OMCM) can effectively use propionate. Then, the effects of PW with different concentration of propionate were investigated, and results showed that OMCM can completely replace clean water with PW containing 5 g L-1 propionate. Furthermore, in the fed-batch fermentation, the OMCM obtained the highest biomass of 113.4 g L-1 and lipid yield of 64.4 g L-1 in PW condition, which is 26.8% and 51.7% higher than that of wild type (WT) in PW condition. Moreover, to verify why overexpression of MCM can promote DHA and lipid accumulation, the comparative metabolomics, ATP production level, the antioxidant system, and the transcription of key genes were investigated. Results showed that ATP induced by PW condition could drive the synthesis of DHA, and remarkably improve the antioxidant capacity of cells by enhancing the carotenoids production. Therefore, PW can be used as an effective and economical substrate and water source for Schizochytrium sp. to accumulate biomass and DHA.

Determination of Vitamin B12 in Milk and Dairy Products by Isotope-Dilution Liquid Chromatography Tandem Mass Spectrometry

An isotope-dilution liquid chromatography tandem mass spectrometry method was established for the determination of vitamin B12 in milk and dairy products. The samples were spiked with stable isotope-labeled vitamin B12 and digested by pepsin and amylase. The various forms of cobalamin were transformed to cyanocobalamin by potassium cyanide after they were released from the enzymatically digested samples. Cyanocobalamin was extracted and purified by an immunoaffinity SPE cartridge and then measured in multiple reaction monitoring mode (MRM). The linear correlation coefficient (R2) of this method was greater than 0.999 in the range of 2–100 ng/mL. The detection limit and the quantification limit were 0.5 μg/kg and 1.0 μg/kg, respectively. The spiked recoveries ranged from 92.0% to 99.4% at the three spiked levels with the relative standard deviation (RSD) between 1.89% and 4.51%. The measured results of NIST SRM1849a and NIST SRM1869a by the current method are all within the reference value range. The Z value was 0.8 during participating in the FAPAS proficiency test using the developed method in 2021. The method is simple, rapid, accurate, and sensitive, and it is suitable for the determination of vitamin B12 in different types of milk and dairy products such as whey powder, whole milk powder, pure milk, fermented milk, infant formula, and prescription food for special medical purposes.

Adaptive capacity to dietary Vitamin B12 levels is maintained by a gene-diet interaction that ensures optimal life span

Diet regulates complex life-history traits such as longevity. For optimal lifespan, organisms employ intricate adaptive mechanisms whose molecular underpinnings are less known. We show that Caenorhabditis elegans FLR-4 kinase prevents lifespan differentials on the bacterial diet having higher Vitamin B12 levels. The flr-4 mutants are more responsive to the higher B12 levels of Escherichia coli HT115 diet, and consequently, have enhanced flux through the one-carbon cycle. Mechanistically, a higher level of B12 transcriptionally downregulates the phosphoethanolamine methyltransferase pmt-2 gene, which modulates phosphatidylcholine (PC) levels. Pmt-2 downregulation activates cytoprotective gene expression through the p38-MAPK pathway, leading to increased lifespan only in the mutant. Evidently, preventing bacterial B12 uptake or inhibiting one-carbon metabolism reverses all the above phenotypes. Conversely, supplementation of B12 to E. coli OP50 or genetically reducing PC levels in the OP50-fed mutant extends lifespan. Together, we reveal how worms maintain adaptive capacity to diets having varying micronutrient content to ensure a normal lifespan.

Lysosomal activity regulates Caenorhabditis elegans mitochondrial dynamics through vitamin B12 metabolism

Mitochondrial fission and fusion are highly regulated by energy demand and physiological conditions to control the production, activity, and movement of these organelles. Mitochondria are arrayed in a periodic pattern in Caenorhabditis elegans muscle, but this pattern is disrupted by mutations in the mitochondrial fission component dynamin DRP-1. Here we show that the dramatically disorganized mitochondria caused by a mitochondrial fission-defective dynamin mutation is strongly suppressed to a more periodic pattern by a second mutation in lysosomal biogenesis or acidification. Vitamin B12 is normally imported from the bacterial diet via lysosomal degradation of B12-binding proteins and transport of vitamin B12 to the mitochondrion and cytoplasm. We show that the lysosomal dysfunction induced by gene inactivations of lysosomal biogenesis or acidification factors causes vitamin B12 deficiency. Growth of the C. elegans dynamin mutant on an Escherichia coli strain with low vitamin B12 also strongly suppressed the mitochondrial fission defect. Of the two C. elegans enzymes that require B12, gene inactivation of methionine synthase suppressed the mitochondrial fission defect of a dynamin mutation. We show that lysosomal dysfunction induced mitochondrial biogenesis, which is mediated by vitamin B12 deficiency and methionine restriction. S-adenosylmethionine, the methyl donor of many methylation reactions, including histones, is synthesized from methionine by S-adenosylmethionine synthase; inactivation of the sams-1 S-adenosylmethionine synthase also suppresses the drp-1 fission defect, suggesting that vitamin B12 regulates mitochondrial biogenesis and then affects mitochondrial fission via chromatin pathways.

Synthesis, spectroscopic properties, crystal structures, DFT studies, and the antibacterial and enzyme inhibitory properties of a complex of Co(II) 3,5-difluorobenzoate with 3-pyridinol

A new complex, [Co(DFB)2(3-Pyr)2(H2O)2] (where DFB = 3,5-difluorobenzoate, 3-Pyr = 3-pyridinol), is synthesized and characterized using different techniques (elemental analysis, Fourier transform infrared spectroscopy, and single-crystal X-ray diffraction). Looking at the crystal structure of the complexes, the cobalt atom is coordinated by two nitrogen atoms from two 3-Pyr ligands, two carboxylate oxygen atoms from two DFB anions, and two oxygen atoms from two water molecules. The complex has distorted octahedral geometry around the cobalt atom center complex and crystallizes in the P21/n space group (monoclinic system). Geometry optimization, frequency analysis, and energy quantum chemical calculations on the complex are performed by Density Functional Theory [B3LYP/6-31G (d,p) basis set] to predict the molecular properties. The novel complex is tested against the metabolic isoenzymes human carbonic anhydrases I and II. The novel complex shows Ki values of 317.26 ± 23.25 µM against hCA I and 255.41 ± 48.05 µM against hCA II; the IC50 values for these isoenzymes are 274.37 and 204.33 µM.

Bacteria increase host micronutrient availability: mechanisms revealed by studies in C. elegans

Micronutrients cannot be synthesized by humans and are obtained from three different sources: diet, gut microbiota, and oral supplements. The microbiota generates significant quantities of micronutrients, but the contribution of these compounds to total uptake is unclear. The role of bacteria in the synthesis and uptake of micronutrients and supplements is widely unexplored and may have important implications for human health. The efficacy and safety of several micronutrient supplements, including folic acid, have been questioned due to some evidence of adverse effects on health. The use of the simplified animal-microbe model, Caenorhabditis elegans, and its bacterial food source, Escherichia coli, provides a controllable system to explore the underlying mechanisms by which bacterial metabolism impacts host micronutrient status. These studies have revealed mechanisms by which bacteria may increase the bioavailability of folic acid, B12, and iron. These routes of uptake interact with bacterial metabolism, with the potential to increase bacterial pathogenesis, and thus may be both beneficial and detrimental to host health.

Metabolism of Dietary and Microbial Vitamin B Family in the Regulation of Host Immunity

Vitamins are micronutrients that have physiological effects on various biological responses, including host immunity. Therefore, vitamin deficiency leads to increased risk of developing infectious, allergic, and inflammatory diseases. Since B vitamins are synthesized by plants, yeasts, and bacteria, but not by mammals, mammals must acquire B vitamins from dietary or microbial sources, such as the intestinal microbiota. Similarly, some intestinal bacteria are unable to synthesize B vitamins and must acquire them from the host diet or from other intestinal bacteria for their growth and survival. This suggests that the composition and function of the intestinal microbiota may affect host B vitamin usage and, by extension, host immunity. Here, we review the immunological functions of B vitamins and their metabolism by intestinal bacteria with respect to the control of host immunity.

Betaine-rich sugar beet molasses protects from homocysteine-induced reduction of survival in Caenorhabditis elegans

PURPOSE

Homocysteine (Hcy) in humans represents a blood-borne biomarker which predicts the risk of age-related diseases and mortality. Using the nematode Caenorhabditis elegans, we tested whether feeding betaine-rich sugar beet molasses affects the survival under heat stress in the presence of Hcy, in spite of a gene loss in betaine-homocysteine methyltransferase.

METHODS

Knockdown of the genes relevant for remethylation or transsulfuration of Hcy was achieved by RNA interference (RNAi). Survival assay was conducted under heat stress at 37 °C and Hcy levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Addition of 500 mg/l betaine-rich sugar beet molasses (SBM) prevented the survival reduction that was caused by exposure to Hcy at 37 °C. Although SBM was no longer capable of reducing Hcy levels under RNAi versus homologues for 5, 10-methylenetetrahydrofolate reductase or cystathionine-β-synthase, it still enabled the survival extension by SBM under exposure to Hcy. In contrast, RNAi for the small heat shock protein hsp-16.2 or the foxo transcription factor daf-16 both prevented the extension of survival by betaine-rich molasses in the presence of Hcy.

CONCLUSIONS

Our studies demonstrate that betaine-rich SBM is able to prevent survival reduction caused by Hcy in C. elegans in dependence on hsp-16.2 and daf-16 but independent of the remethylation pathway.

Betaine reduces β-amyloid-induced paralysis through activation of cystathionine-β-synthase in an Alzheimer model of Caenorhabditis elegans

BACKGROUND

The neurodegenerative disorder Alzheimer's disease is caused by the accumulation of toxic aggregates of β-amyloid in the human brain. On the one hand, hyperhomocysteinemia has been shown to be a risk factor for cognitive decline in Alzheimer's disease. On the other hand, betaine has been demonstrated to attenuate Alzheimer-like pathological changes induced by homocysteine. It is reasonable to conclude that this is due to triggering the remethylation pathway mediated by betaine-homocysteine-methyltransferase. In the present study, we used the transgenic Caenorhabditis elegans strain CL2006, to test whether betaine is able to reduce β-amyloid-induced paralysis in C. elegans. This model expresses human β-amyloid 1-42 under control of a muscle-specific promoter that leads to progressive, age-dependent paralysis in the nematodes.

RESULTS

Betaine at a concentration of 100 μM was able to reduce homocysteine levels in the presence and absence of 1 mM homocysteine. Simultaneously, betaine both reduced normal paralysis rates in the absence of homocysteine and increased paralysis rates triggered by addition of homocysteine. Knockdown of cystathionine-β-synthase using RNA interference both increased homocysteine levels and paralysis. Additionally, it prevented the reducing effects of betaine on homocysteine levels and paralysis.

CONCLUSION

Our studies show that betaine is able to reduce homocysteine levels and β-amyloid-induced toxicity in a C. elegans model for Alzheimer's disease. This effect is independent of the remethylation pathway but requires the transsulfuration pathway mediated by cystathionine-β-synthase.

Bi-directional effects of vitamin B12 and methotrexate on Daphnia magna fitness and genomic methylation

Here we interrogated, using three separate but complementary experimental approaches, the impact of vitamin B12 availability and methotrexate exposure on Daphnia magna, which we hypothesised should have an opposite effect on One carbon metabolism (OCM). OCM is a vital biological process supporting a variety of physiological processes, including DNA methylation. Contrary to mammalian models, this process remains largely unexplored in invertebrates. The purpose of this study was to elucidate the impact of OCM short-term alteration on the fitness and epigenome of the keystone species, Daphnia. We used maternal age at reproduction, brood size and survival rates in combination with DNA methylation sensitive comet assay to determine the effects of vitamin B12 or MTX on fitness and the epigenome. Vitamin B12 had a positive influence on Daphnia fitness and we provide evidence demonstrating that this may be associated with an increased level of genome-wide DNA methylation. Conversely, exposing D. magna to MTX negatively influenced the fitness of the animals and was associated with loss of global DNA methylation, translating in decreased fitness. These results highlight the potential importance of OCM in invertebrates, providing novel evidence supporting a potential role for epigenetic modifications to the genome in D. magna environmental adaptability.

Coenzyme B12 synthesis as a baseline to study metabolite contribution of animal microbiota

Microbial communities thrive in a number of environments. Exploration of their microbiomes – their global genome – may reveal metabolic features that contribute to the development and welfare of their hosts, or chemical cleansing of environments. Yet we often lack final demonstration of their causal role in features of interest. The reason is that we do not have proper baselines that we could use to monitor how microbiota cope with key metabolites in the hosting environment. Here, focusing on animal gut microbiota, we describe the fate of cobalamins – metabolites of the B12 coenzyme family – that are essential for animals but synthesized only by prokaryotes. Microbiota produce the vitamin used in a variety of animals (and in algae). Coprophagy plays a role in its management. For coprophobic man, preliminary observations suggest that the gut microbial production of vitamin B12 plays only a limited role. By contrast, the vitamin is key for structuring microbiota. This implies that it is freely available in the environment. This can only result from lysis of the microbes that make it. A consequence for biotechnology applications is that, if valuable for their host, B12‐producing microbes should be sensitive to bacteriophages and colicins, or make spores.