Apparent folate deficiency in iron-deficiency anaemia

Heavy chain ferritin enhances serine hydroxymethyltransferase expression and de novo thymidine biosynthesis

We have elucidated a biochemical mechanism whereby changes in iron metabolism cause changes in folate-dependent one-carbon metabolism. Although animal and clinical studies have demonstrated that perturbations in iron status and metabolism alter folate metabolism, the biochemical mechanisms underlying these associations have yet to be identified. The effect of altered ferritin expression on folate metabolism was determined in human MCF-7 cells and SH-SY5Y neuroblastoma. Cells expressing rat heavy chain ferritin (HCF) exhibited markedly increased expression of the folate-dependent enzyme cytoplasmic serine hydroxymethyltransferase (cSHMT). These effects were not seen when rat light chain ferritin was expressed. Additionally, cSHMT expression was not altered when HCF expression was induced in MCF-7 cells cultured with supplemental ferric citrate. This indicates that cSHMT expression is increased by elevated HCF concentrations, independent of increased iron availability, suggesting that cSHMT expression may respond to HCF-induced chelation of the regulatory iron pool. Increased HCF expression did not alter cSHMT mRNA levels, but did increase translation rates of cSHMT mRNA. The increase in translation was mediated, at least in part, through the cSHMT 5'-untranslated region of the transcript. MCF-7 cells with increased expression of cSHMT displayed increased efficiency of de novo thymidylate biosynthesis, indicating that thymidylate synthesis is normally limited by cSHMT activity in MCF-7 cells. Our data suggest that the iron regulatory pool may play an important role in regulating folate metabolism and thereby thymidine biosynthesis.

Neutrophil hypersegmentation in iron deficiency anaemia: a case-control study

Neutrophil hypersegmentation (NH) is an important haematological feature of cobalamin or folate deficiency. As iron deficiency and folate deficiency often occur in the same target groups it is important to establish whether iron deficiency alone is a cause of NH. We report a case-control study which addresses this issue. Two groups of hospital patients were studied. Group 1 comprised 50 patients with iron deficiency anaemia (IDA). Group II comprised 50 control age- and sex-matched patients who were haematologically normal without evidence of iron deficiency from the iron studies. Patients with other factors which could affect the degree of neutrophil segmentation (cobalamin/folate deficiency, renal failure, infection and drug exposures) were excluded from the study. A total of 10 000 neutrophils were examined, 100 from each patient. NH was defined as the presence of five or more five-lobed neutrophils per 100, or any neutrophils with six or more lobes. The results were as follows: IDA, mean neutrophil lobe count 3.36; number of patients with NH 31/50 (62%): controls, mean neutrophil lobe count 2.96, number of patients with NH 2/50 (4%). These differences were statistically significant. We conclude that NH is common in IDA. The mechanism whereby iron deficiency results in NH is not clear.

Low serum B12 levels in a hematologically normal elderly subpopulation

Serum Vitamin B12 levels were determined on 378 patients ranging in age from 56 to 104 years with a median age of 77 for both males and females. A radiodilution method was employed for these determinations. This screening procedure identified 26 patients with low serum B12 levels. Nineteen of these patients had no other symptoms and were hematologically normal. The B12 binding proteins, transcobalamins (TC) I, II, and III were quantitated employing QUSO and DEAE cellulose batch separations. The total number of TC II binding/affinity sites for B12 were elevated in both the normal and low B12 elderly groups. About 17% of the total serum B12 was carried by TC II in the control group while only 4% of the total was carried on TC II in both the normal and low B12 elderly. This was accompanied by an increase in unsaturation in TC II for these two groups. The findings suggest that an alteration in the TC II-B12 delivery system has occurred in the elderly.

Folate deficiency and neurological disorders in adults

The restless legs syndrome could represent a folate responsive disorder in both patients with acquired-folate deficiency and those with familial symptomatology. Patients with acquired folate-deficiency could be divided into two subgroups. (i) those with minor neurological signs (restless legs syndrome, vibration sense impairment and tactile hypoesthesia in both legs with diminished ankle jerks and a prolonged or assymetrical Achilles-reflex time) and (ii) those with major neurological signs (subacute combined degeneration with or without neuropathies). In some of these patients the classical triad of the malabsorption syndrome is replaced by another triad, constipation, abnormal jejunal biopsy and abnormal d-xylose absorption. A low folic serum acid level could induce minor neuropsychiatric symptoms while an additional low CSF folate could induce major neurological symptoms in spite of the presence of a normal erythrocyte folate level and in the absence of frank anemia. Possible further studies are described.