Reabsorption of betaine in Henle's loops of rat kidney in vivo

Vitamin B Supplementation and Nutritional Intake of Methyl Donors in Patients with Chronic Kidney Disease: A Critical Review of the Impact on Epigenetic Machinery

Cardiovascular morbidity and mortality are several-fold higher in patients with advanced chronic kidney disease (CKD) and end-stage renal disease (ESRD) than in the general population. Hyperhomocysteinemia has undoubtedly a central role in such a prominent cardiovascular burden. The levels of homocysteine are regulated by methyl donors (folate, methionine, choline, betaine), and cofactors (vitamin B6, vitamin B12,). Uremia-induced hyperhomocysteinemia has as its main targets DNA methyltransferases, and this leads to an altered epigenetic control of genes regulated through methylation. In renal patients, the epigenetic landscape is strictly correlated with the uremic phenotype and dependent on dietary intake of micronutrients, inflammation, gut microbiome, inflammatory status, oxidative stress, and lifestyle habits. All these factors are key contributors in methylome maintenance and in the modulation of gene transcription through DNA hypo- or hypermethylation in CKD. This is an overview of the epigenetic changes related to DNA methylation in patients with advanced CKD and ESRD. We explored the currently available data on the molecular dysregulations resulting from altered gene expression in uremia. Special attention was paid to the efficacy of B-vitamins supplementation and dietary intake of methyl donors on homocysteine lowering and cardiovascular protection.

Urinary metabolites predict prolonged duration of delayed graft function in DCD kidney transplant recipients

Extending kidney donor criteria, including donation after circulatory death (DCD), has resulted in increased rates of delayed graft function (DGF) and primary nonfunction. Here, we used Nuclear Magnetic Resonance (NMR) spectroscopy to analyze the urinary metabolome of DCD transplant recipients at multiple time points (days 10, 42, 180, and 360 after transplantation). The aim was to identify markers that predict prolonged duration of functional DGF (fDGF). Forty-seven metabolites were quantified and their levels were evaluated in relation to fDGF. Samples obtained at day 10 had a different profile than samples obtained at the other time points. Furthermore, at day 10 there was a statistically significant increase in eight metabolites and a decrease in six metabolites in the group with fDGF (N = 53) vis-à-vis the group without fDGF (N = 22). In those with prolonged fDGF (≥21 days) (N = 17) urine lactate was significantly higher and pyroglutamate lower than in those with limited fDGF (<21 days) (N = 36). In order to further distinguish prolonged fDGF from limited fDGF, the ratios of all metabolites were analyzed. In a logistic regression analysis, the sum of branched-chain amino acids (BCAAs) over pyroglutamate and lactate over fumarate, predicted prolonged fDGF with an AUC of 0.85. In conclusion, kidney transplant recipients with fDGF can be identified based on their altered urinary metabolome. Furthermore, two ratios of urinary metabolites, lactate/fumarate and BCAAs/pyroglutamate, adequately predict prolonged duration of fDGF.

Betaine chemistry, roles, and potential use in liver disease

BACKGROUND

Betaine is the trimethyl derivative of glycine and is normally present in human plasma due to dietary intake and endogenous synthesis in liver and kidney. Betaine is utilized in the kidney primarily as an osmoprotectant, whereas in the liver its primary role is in metabolism as a methyl group donor. In both organs, a specific betaine transporter mediates cellular uptake of betaine from plasma. The abundance of both betaine and the betaine transporter in liver greatly exceeds that of other organs.

SCOPE OF REVIEW

The remarkable contributions of betaine to normal human and animal health are summarized together with a discussion of the mechanisms and potential beneficial effects of dietary betaine supplements on liver disease.

MAJOR CONCLUSIONS

A significant amount of data from animal models of liver disease indicates that administration of betaine can halt and even reverse progression of the disruption of liver function. Betaine is well-tolerated, inexpensive, effective over a wide range of doses, and is already used in livestock feeding practices.

GENERAL SIGNIFICANCE

The accumulated data indicate that carefully controlled additional investigations in humans are merited. The focus should be on the long-term use of betaine in large patient populations with liver diseases characterized by development of fatty liver, especially non-alcoholic fatty liver disease and alcoholic liver disease.

OMICS Technologies and Applications in Sugar Beet

Sugar beet is a species of the Chenopodiaceae family. It is an important sugar crop that supplies approximately 35% of the sugar in the world. Sugar beet M14 line is a unique germplasm that contains genetic materials from Beta vulgaris L. and Beta corolliflora Zoss. And exhibits tolerance to salt stress. In this review, we have summarized OMICS technologies and applications in sugar beet including M14 for identification of novel genes, proteins related to biotic and abiotic stresses, apomixes and metabolites related to energy and food. An OMICS overview for the discovery of novel genes, proteins and metabolites in sugar beet has helped us understand the complex mechanisms underlying many processes such as apomixes, tolerance to biotic and abiotic stresses. The knowledge gained is valuable for improving the tolerance of sugar beet and other crops to biotic and abiotic stresses as well as for enhancing the yield of sugar beet for energy and food production.

Beetroot-Carrot Juice Intake either Alone or in Combination with Antileukemic Drug 'Chlorambucil' As A Potential Treatment for Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is one of the chronic lymphoproliferative disorders (lymphoid neoplasms). It is characterized by a progressive accumulation of functionally incompetent lymphocytes. Patients with leukemia often seek unconventional treatments not prescribed by hematologist in order to improve their cancer treatment outcome or to manage symptoms. In the present report, a 76-year-old patient was diagnosed with B-cell chronic lymphocytic leukemia (B-CLL). Beetroot-carrot juice is used as a complementary and or/alternative therapy used in conjunction with conventional leukemic treatment (chlorambucil) that has been a standard first-line chemotherapeutic agent for patients with CLL and known to have serious and undesirable side-effects. After one month and 15 days of administration of beetroot-carrot juice therapy, the patient had improved appetite, a sense of general well-being and increased vigor daily activities. Furthermore, beetroot-carrot juice was used as an adjuvant to chlorambucil resulted in a substantial reduction in leukocytes and lymphocytes count in peripheral blood and improvement in the relevant biochemical parameters. Beetroot-carrot juice can be used as an effective treatment for CLL alone or in combination with chlorambucil when taken orally with regular diet on daily basis.

The betaine/GABA transporter and betaine: roles in brain, kidney, and liver

The physiological roles of the betaine/GABA transporter (BGT1; slc6a12) are still being debated. BGT1 is a member of the solute carrier family 6 (the neurotransmitter, sodium symporter transporter family) and mediates cellular uptake of betaine and GABA in a sodium- and chloride-dependent process. Most of the studies of BGT1 concern its function and regulation in the kidney medulla where its role is best understood. The conditions here are hostile due to hyperosmolarity and significant concentrations of NH₄Cl and urea. To withstand the hyperosmolarity, cells trigger osmotic adaptation, involving concentration of a transcriptional factor TonEBP/NFAT5 in the nucleus, and accumulate betaine and other osmolytes. Data from renal cells in culture, primarily MDCK, revealed that transcriptional regulation of BGT1 by TonEBP/NFAT5 is relatively slow. To allow more acute control of the abundance of BGT1 protein in the plasma membrane, there is also post-translation regulation of BGT1 protein trafficking which is dependent on intracellular calcium and ATP. Further, betaine may be important in liver metabolism as a methyl donor. In fact, in the mouse the liver is the organ with the highest content of BGT1. Hepatocytes express high levels of both BGT1 and the only enzyme that can metabolize betaine, namely betaine:homocysteine –S-methyltransferase (BHMT1). The BHMT1 enzyme removes a methyl group from betaine and transfers it to homocysteine, a potential risk factor for cardiovascular disease. Finally, BGT1 has been proposed to play a role in controlling brain excitability and thereby represents a target for anticonvulsive drug development. The latter hypothesis is controversial due to very low expression levels of BGT1 relative to other GABA transporters in brain, and also the primary location of BGT1 at the surface of the brain in the leptomeninges. These issues are discussed in detail.

Biodistribution and radiation dosimetry of deuterium-substituted 18F-fluoromethyl-[1, 2-2H4]choline in healthy volunteers

(11)C-choline and (18)F-fluoromethylcholine ((18)F-FCH) have been used in patients to study tumor metabolic activity in vivo; however, both radiotracers are readily oxidized to respective betaine analogs, with metabolites detectable in plasma soon after injection of the radiotracer. A more metabolically stable FCH analog, (18)F-fluoromethyl-[1,2-(2)H4]choline ((18)F-D4-FCH), based on the deuterium isotope effect, has been developed. We report the safety, biodistribution, and internal radiation dosimetry profiles of (18)F-D4-FCH in 8 healthy human volunteers.

METHODS

(18)F-D4-FCH was intravenously administered as a bolus injection (mean ± SD, 161 ± 2.17 MBq; range, 156-163 MBq) to 8 healthy volunteers (4 men, 4 women). Whole-body (vertex to mid thigh) PET/CT scans were acquired at 6 time points, up to 4 h after tracer injection. Serial whole-blood, plasma, and urine samples were collected for radioactivity measurement and plasma radiotracer metabolites. Tissue (18)F radioactivities were determined from quantitative analysis of the images, and time-activity curves were generated. The total numbers of disintegrations in each organ normalized to injected activity (residence times) were calculated as the area under the curve of the time-activity curve normalized to injected activities and standard organ volumes. Dosimetry calculations were performed using OLINDA/EXM 1.1.

RESULTS

The injection of (18)F-D4-FCH was well tolerated in all subjects, with no radiotracer-related serious adverse event reported. The mean effective dose averaged over both men and women (± SD) was estimated to be 0.025 ± 0.004 (men, 0.022 ± 0.002; women, 0.027 ± 0.002) mSv/MBq. The 5 organs receiving the highest absorbed dose (mGy/MBq) were the kidneys (0.106 ± 0.03), liver (0.094 ± 0.03), pancreas (0.066 ± 0.01), urinary bladder wall (0.047 ± 0.02), and adrenals (0.046 ± 0.01). Elimination was through the renal and hepatic systems.

CONCLUSION

(18)F-D4-FCH is a safe PET radiotracer with a dosimetry profile comparable to other common (18)F PET tracers. These data support the further development of (18)F-D4-FCH for clinical imaging of choline metabolism.

Assessment of urinary betaine as a marker of diabetes mellitus in cardiovascular patients

Abnormal urinary excretion of betaine has been demonstrated in patients with diabetes or metabolic syndrome. We aimed to identify the main predictors of excretion in cardiovascular patients and to make initial assessment of its feasibility as a risk marker of future diabetes development. We used data from 2396 patients participating in the Western Norway B-vitamin Intervention Trial, who delivered urine and blood samples at baseline, and in the majority at two visits during follow-up of median 39 months. Betaine in urine and plasma were measured by liquid-chromatography-tandem mass spectrometry. The strongest determinants of urinary betaine excretion by multiple regression were diabetes mellitus, age and estimated glomerular filtration rate; all p<0.001. Patients with diabetes mellitus (n = 264) had a median excretion more than three times higher than those without. We found a distinct non-linear association between urinary betaine excretion and glycated hemoglobin, with a break-point at 6.5%, and glycated hemoglobin was the strongest determinant of betaine excretion in patients with diabetes mellitus. The discriminatory power for diabetes mellitus corresponded to an area under the curve by receiver-operating characteristics of 0.82, and betaine excretion had a coefficient of reliability of 0.73. We also found a significant, independent log-linear relation between baseline betaine excretion and the risk of developing new diabetes during follow-up. The good discriminatory power for diabetes, high test-retest stability and independent association with future risk of new diabetes should motivate further investigation on the role of betaine excretion in risk assessment and long-term follow-up of diabetes mellitus.

NMR-based metabonomic approach on the toxicological effects of a Cimicifuga triterpenoid

Cimicifugae Rhizoma, a well-known botanical dietary supplement, has been the subject of intense interest due to its potential application for alleviating menopausal symptom. Although there are clinic data that the Cimicifuga extract should have hepatotoxicity, no evidence on the main chemical components has been reported. Cimicidol-3-O-β -d-xyloside (CX) is one of the main triterpenoids of the rhizome. This work studies the toxicological effects of CX after oral administration (50 mg kg(-1) per day) over a 7-day period in female SD rats using metabonomic analyses of (1) H NMR spectra of urine, serum and liver tissue extracts. Histopathological studies of liver and analyses of blood biochemical parameter, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, blood urea nitrogen and creatinine revealed that CX had no negative impacts on liver and kidney. However, the metabolic signature of (1) H NMR-based urinalysis of daily samples displayed an increment in the levels of taurine, trimethylamine-N-oxide (TMAO), betaine and acetate. Elevated serum levels of creatinine, glucose, alanine, TMAO and betaine and lower levels of lactate were observed. Metabolic profiling on aqueous soluble extracts of liver showed simultaneously increases in succinate, glycogen, choline, glycerophosphorylcholine, TMAO and betaine levels and reduction in valine, glucose and lactate levels. Nevertheless, no changes in any metabonomic level were found in lipid-soluble extracts of liver. These findings indicate that CX has a slight toxicity in liver and kidney via disturbance of the metabolisms of energy and amino acids. The present study provides a reasonable explanation for the clinical hepatotoxicity of Cimicifuga extract.

[18F]fluoromethyl-[1,2-2H4]-choline: a novel radiotracer for imaging choline metabolism in tumors by positron emission tomography

Current radiotracers for positron emission tomography imaging of choline metabolism have poor systemic metabolic stability in vivo. We describe a novel radiotracer, [(18)F]fluoromethyl-[1,2-(2)H(4)]-choline (D4-FCH), that employs deuterium isotope effect to improve metabolic stability. D4-FCH proved more resistant to oxidation than its nondeuterated analogue, [(18)F]fluoromethylcholine, in plasma, kidneys, liver, and tumor, while retaining phosphorylation potential. Tumor radiotracer levels, a determinant of sensitivity in imaging studies, were improved by deuterium substitution; tumor uptake values expressed as percent injected dose per voxel at 60 min were 7.43 +/- 0.47 and 5.50 +/- 0.49 for D4-FCH and [(18)F]fluoromethylcholine, respectively (P = 0.04). D4-FCH was also found to be a useful response biomarker. Treatment with the mitogenic extracellular kinase inhibitor PD0325901 resulted in a reduction in tumor radiotracer uptake that occurred in parallel with reductions in choline kinase A expression. In conclusion, D4-FCH is a very promising metabolically stable radiotracer for imaging choline metabolism in tumors.

Urea promotes TonEBP expression and cellular adaptation in extreme hypertonicity

The transcriptional activator TonEBP is a central regulator of osmolality in the renal medulla and whole body water homeostasis. In order to understand the regulation of TonEBP in the renal medulla, we examined MDCK cells, a kidney-derived epithelial cell line, under conditions mimicking the renal medulla. Moderate changes in ambient tonicity, which was tolerated without prior adaptation, displayed lasting effects on TonEBP in bidirectional manner-stimulated by hypertonicity and inhibited by hypotonicity. TonEBP expression was further enhanced by extreme hypertonicity observed in the inner medullae of antidiuretic animals. Urea stimulated TonEBP expression and promoted cellular proliferation under the conditions of extreme hypertonicity. On the other hand, the TonEBP activity was negatively modulated under these conditions presumably to temper the highly abundant TonEBP. We conclude that urea is critical to the cellular adaptation to extreme hypertonicity and the high level of TonEBP expression in the inner medulla.

1H-NMR metabolic profiling of human neonatal urine

OBJECT

The measurement of different urine components and their changes over time may provide comprehensive and early information about perinatal metabolic processes and physiological changes. We hypothesized that (1) H-NMR-spectroscopy generating a complex spectral profile without pre-selection of urinary metabolites could identify metabolites determining the neonatal physiological status and discriminating between different metabolic states.

MATERIALS AND METHODS

We studied spot urine of three groups of neonates (healthy term-born, term-born with non-specific bacterial infections, and preterm neonates) for the first 6 days of life using (1) H-NMR-spectroscopy. In the group of healthy neonates metabolites changing were identified and their excretion patterns compared between groups.

RESULTS

Six metabolites indicating physiological changes were identified: N-methylnicotinamide (NAD (+)-pathway), formate, hippurate, betaine (kidney development), taurine (neuronal development), and bile acids (hepatic clearance). While the dynamic changes over the first 6 days were the same for all metabolites in both groups of term-born neonates, the excretion of N-methylnicotinamide and taurine was significantly higher in preterm neonates compared to healthy term neonates and neonates with bacterial infections from the third day after birth (P < 0.05).

CONCLUSION

Urine analysis using (1) H-NMR-spectroscopy could identify markers for perinatal metabolic changes. Further studies have to clarify if the proposed physiological interpretation will correlate with long-term physiological development.

High sodium chloride intake decreases betaine-homocysteine S-methyltransferase expression in guinea pig liver and kidney

Betaine-homocysteine S-methyltransferase (BHMT) is the only enzyme known to catabolize betaine. In addition to being a substrate for BHMT, betaine also functions as an osmoprotectant that accumulates in the kidney medulla under conditions of high extracellular osmolarity. The mechanisms that regulate the partitioning of betaine between its use as a methyl donor and its accumulation as an osmoprotectant are not completely understood. The aim of this study was to determine whether BHMT expression is regulated by salt intake. This report shows that guinea pigs express BHMT in the liver, kidney, and pancreas and that the steady-state levels of BHMT mRNA in kidney and liver decrease 68% and 93% in guinea pigs consuming tap water containing high levels of salt compared with animals provided untreated tap water. The animals consuming the salt water also had approximately 50% less BHMT activity in the liver and kidney, and steady-state protein levels decreased approximately 30% in both organs. Pancreatic BHMT activity and protein levels were unaffected by the high salt treatment. The complex mechanisms involved in the downregulation of hepatic and renal BHMT expression in guinea pigs drinking salt water remain to be clarified, but the physiological significance of this downregulation may be to expedite the transport and accumulation of betaine into the kidney medulla under conditions of high extracellular osmolarity.

Polarized function of thick ascending limbs of Henle cells in osmoregulation

BACKGROUND

Organic osmolytes are necessary for osmoregulation in mammalian kidney. Since renal epithelial cells in many cases possess specific mechanisms both for uptake and osmotically regulated release, we investigated their localization in polarized cells.

METHODS

An immortalized epithelial cell line derived from the thick ascending limb of Henle's loop (TALH) was used to examine the transport characteristics of the apical and basolateral plasma membranes for osmotic regulation of organic osmolytes. Cells were cultured on filters in a two-compartment chamber.

RESULTS

In culture under hypertonic conditions the TALH cells accumulated in the following balance: sorbitoverline> betaine = myo-inositoverline> glycerophosphoryl choline (GPC). When extracellular osmolarity was decreased, then sorbitol was released on the apical side, whereas betaine and myo-inositol efflux occurred on the basolateral side. GPC release showed no preference of either side. Taurine did not seem to be necessary for osmoregulation under these conditions. Osmotically regulated myo-inositol and betaine uptake was located on the apical side, and choline uptake took place on both sides equally.

CONCLUSION

These results show that in renal epithelial cells, both osmotically induced release and the uptake of organic osmolytes are divided between the apical and the basolateral sides. This might be important for volume regulation.

Amino acids and their transporters in the retina

This review provides an overview of the distributions, properties and roles of amino acid transport systems in normal and pathological retinal tissues and discusses the roles of specific identified transporters in the mammalian retina. The retina is used in this context as a vehicle for describing neuronal and glial properties, which are in some, but not all cases comparable to those found elsewhere an the brain. Where significant departures are noted, these are discussed in the context of functional specialisations of the retina and its relationship to adjacent supporting tissues such as the retinal pigment epithelium. Specific examples are given where immunocytochemical labelling for amino acid transporters may yield inaccurate results, possibly because of activity-dependent conformation changes of epitopes in these proteins which render the epitopes more or less accessible to antibodies.