scholarly journals Carnitine metabolism in the vitamin B-12-deficient rat

1988 ◽  
Vol 255 (1) ◽  
pp. 153-159 ◽  
Author(s):  
E P Brass ◽  
S P Stabler
Keyword(s):  
Methylmalonic Acid ◽  
Methylmalonic Aciduria ◽  
Model System ◽  
Cobalamin Deficiency ◽  
Vitamin B ◽  
Carnitine Metabolism ◽  
Vitamin B 12 ◽  
Total Carnitine ◽  
The Relationship ◽  
Deficient Group

In vitamin B-12 (cobalamin) deficiency the metabolism of propionyl-CoA and methylmalonyl-CoA are inhibited secondarily to decreased L-methylmalonyl-CoA mutase activity. Production of acylcarnitines provides a mechanism for removing acyl groups and liberating CoA under conditions of impaired acyl-CoA utilization. Carnitine metabolism was studied in the vitamin B-12-deficient rat to define the relationship between alterations in acylcarnitine generation and the development of methylmalonic aciduria. Urinary excretion of methylmalonic acid was increased 200-fold in vitamin B-12-deficient rats as compared with controls. Urinary acylcarnitine excretion was increased in the vitamin B-12-deficient animals by 70%. This increase in urinary acylcarnitine excretion correlated with the degree of metabolic impairment as measured by the urinary methylmalonic acid elimination. Urinary propionylcarnitine excretion averaged 11 nmol/day in control rats and 120 nmol/day in the vitamin B-12-deficient group. The fraction of total carnitine present as short-chain acylcarnitines in the plasma and liver of vitamin B-12-deficient rats was increased as compared with controls. When the rats were fasted for 48 h, relative or absolute increases were seen in the urine, plasma, liver and skeletal-muscle acylcarnitine content of the vitamin B-12-deficient rats as compared with controls. Thus vitamin B-12 deficiency was associated with a redistribution of carnitine towards acylcarnitines. Propionylcarnitine was a significant constituent of the acylcarnitine pool in the vitamin B-12-deficient animals. The changes in carnitine metabolism were consistent with the changes in CoA metabolism known to occur with vitamin B-12 deficiency. The vitamin B-12-deficient rat provides a model system for studying carnitine metabolism in the methylmalonic acidurias.

scholarly journals Plasma and Red Cell Reference Intervals of 5-Methyltetrahydrofolate of Healthy Adults in Whom Biochemical Functional Deficiencies of Folate and Vitamin B12Had Been Excluded

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Agata Sobczyńska-Malefora ◽  
Dominic J. Harrington ◽  
Kieran Voong ◽  
Martin J. Shearer
Keyword(s):  
Methylmalonic Acid ◽  
Reference Intervals ◽  
Healthy Adults ◽  
Molecular Forms ◽  
Vitamin B ◽  
Red Cell ◽  
Relationship Of ◽  
The Relationship ◽  
Plasma Measurements ◽  
Functional Deficiency

5-Methyltetrahydrofolate (5-MTHF) is the predominant form of folate and a strong determinant of homocysteine concentrations. There is evidence that suboptimal 5-MTHF availability is a risk factor for cardiovascular disease independent of homocysteine. The analysis of folates remains challenging and is almost exclusively limited to the reporting of “total” folate rather than individual molecular forms. The purpose of this study was to establish the reference intervals of 5-MTHF in plasma and red cells of healthy adults who had been prescreened to exclude biochemical evidence of functional deficiency of folate and/or vitamin B12. Functional folate and vitamin B12status was assessed by respective plasma measurements of homocysteine and methylmalonic acid in 144 healthy volunteers, aged 19–64 years. After the exclusion of 10 individuals, values for 134 subjects were used to establish the upper reference limits for homocysteine (13 μmol/L females and 15 μmol/L males) and methylmalonic acid (430 nmol/L). Subjects with values below these cutoffs were designated as folate and vitamin B12replete and their plasma and red cell 5-MTHF reference intervals determined,N=126: 6.6–39.9 nmol/L and 223–1041 nmol/L, respectively. The application of these intervals will assist in the evaluation of folate status and facilitate studies to evaluate the relationship of 5-MTHF to disease.

scholarly journals Improved testing for vitamin B12 deficiency: correcting MMA for eGFR reduces the number of patients classified as vitamin B12 deficient

2018 ◽  
Vol 55 (6) ◽  
pp. 685-692 ◽  
Author(s):  
Saskia LM van Loon ◽  
Anna M Wilbik ◽  
Uzay Kaymak ◽  
Edwin R van den Heuvel ◽  
Volkher Scharnhorst ◽  
...  
Keyword(s):  
Data Mining ◽  
Vitamin B12 ◽  
Methylmalonic Acid ◽  
Vitamin B12 Deficiency ◽  
The Elderly ◽  
Vitamin B ◽  
Data Mining Approach ◽  
Number Of Patients ◽  
B12 Deficiency ◽  
The Relationship

Background Methylmalonic acid (MMA) can detect functional vitamin B12 deficiencies as it accumulates early when intracellular deficits arise. However, impaired clearance of MMA from blood due to decreased glomerular filtration rate (eGFR) also results in elevated plasma MMA concentrations. Alternative to clinical trials, a data mining approach was chosen to quantify and compensate for the effect of decreased eGFR on MMA concentration. Methods Comprehensive data on patient’s vitamin B12, eGFR and MMA concentrations were collected ( n = 2906). The relationship between vitamin B12, renal function (eGFR) and MMA was modelled using weighted multiple linear regression. The obtained model was used to estimate the influence of decreased eGFR on MMA. Clinical impact was examined by comparing the number of patients labelled vitamin B12 deficient with and without adjustment in MMA. Results Adjusting measured MMA concentrations for eGFR in the group of patients with low-normal vitamin B12 concentrations (90–300 pmol/L) showed that the use of unadjusted MMA concentrations overestimates vitamin B12 deficiency by 40%. Conclusions Through a data mining approach, the influence of eGFR on the relation between MMA and vitamin B12 can be quantified and used to correct the measured MMA concentration for decreased eGFR. Especially in the elderly, eGFR-based correction of MMA may prevent over-diagnosis of vitamin B12 deficiency and corresponding treatment.

Increased plasma homocysteine levels without signs of vitamin B12 deficiency in patients with multiple sclerosis assessed by blood and cerebrospinal fluid homocysteine and methylmalonic acid

2003 ◽  
Vol 9 (3) ◽  
pp. 239-245 ◽  
Author(s):  
M Vrethem ◽  
E Mattsson ◽  
H Hebelka ◽  
K Leerbeck ◽  
A Österberg ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Cerebrospinal Fluid ◽  
Methylmalonic Acid ◽  
Haemoglobin Concentration ◽  
Serum Vitamin ◽  
High Serum ◽  
Plasma Homocysteine ◽  
Cobalamin Deficiency ◽  
Vitamin B ◽  
Plasma Thcy

Objective: The aim of this study was to evaluate if multiple sclerosis (MS) is associated with vitamin B12 (cobalamin) deficiency. Methods: We measured serum vitamin B12, plasma folate, serum methylmalonic acid (MMA), plasma homocysteine (tHcy) and also cerebrospinal fluid (C SF) MMA and tHcy in 72 patients with MS and 23 controls. Results: The mean plasma tHcy level was significantly increased in MS patients (11.6 mmol/L) compared with controls (7.4 mmol/L) (P =4-0.002). Seven patients showed low serum vitamin B12levels but only one of them had concomitant high plasma tHcy. None of them showed high serum MMA. Plasma or blood folate levels did not differ between MS patients and controls. We found no significant differences in mean values or frequency of pathological tests of serum B12, serum MMA, mean corpuscular volume (MC V), haemoglobin concentration, C SF tHcy or C SF MMA between patients and healthy subjects. There were no correlations between C SF and serum/plasma levels of MMA or tHcy. Serum vitamin B12, serum MMA, plasma tHcy, C SF Hcy or C SF MMA were not correlated to disability status, activity of disease, duration of disease or age. Conclusions:The relevance of the increased mean value of plasma tHcy thus seems uncertain and does not indicate functional vitamin B12 deficiency. We can not, however, exclude the possibility of a genetically induced dysfunction of the homocysteine metabolism relevant for the development of neuroinflammation/degeneration. O ur findings indicate that, regardless of a significant increase in plasma tHcy in MS patients, the MS disease is not generally associated with vitamin B12 deficiency since we did not find any other factors indicating vitamin B12 deficiency. A nalysis of C SF MMA and C SF tHcy, which probably reflects the brain vitamin B12 status better than serum, are not warranted in MS. We conclude that B12 deficiency, in general, is not associated with MS.

scholarly journals Monitoring of vitamin B-12 nutritional status in the United States by using plasma methylmalonic acid and serum vitamin B-12

2011 ◽  
Vol 94 (2) ◽  
pp. 552-561 ◽  
Author(s):  
Regan L Bailey ◽  
Ralph Carmel ◽  
Ralph Green ◽  
Christine M Pfeiffer ◽  
Mary E Cogswell ◽  
...  
Keyword(s):  
United States ◽  
Nutritional Status ◽  
Methylmalonic Acid ◽  
Serum Vitamin ◽  
The United States ◽  
Vitamin B ◽  
Vitamin B 12
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