Vitamin-B12 Status of Patients on Long-term Metformin Therapy

Vitamin-B₁₂ malabsorption has been found in 21 (30%) of 71 diabetic patients taking long-term metformin therapy in addition to dietary management. The patients with evidence of B₁₂ malabsorption had significantly lower haemoglobin levels (and significantly higher serum folic acid levels) than those with normal B₁₂ absorption. Steatorrhoea was found in only one patient. Stopping metformin therapy resulted in reversion of B₁₂ absorption to normal in most patients examined. Four patients with B₁₂ malabsorption were found to have pathologically low serum B₁₂ levels. The causes and implications of these findings are discussed and it is concluded that all patients on long-term metformin therapy should have annual serum B₁₂ estimations.     

Nutrition-Related Vitamin B12 Deficiency in Patients in Pakistan with Type 2 Diabetes Mellitus not Taking Metformin

ObjectiveTo estimate the frequency of undiagnosed vitamin B₁₂ deficiency among patients with type 2 diabetes mellitus who had not taken metformin during at least the prior 5 years and to ascertain whether vitamin B₁₂ deficiency among the patients with type 2 diabetes was due to nutritional deficiency or malabsorption.MethodsSerum vitamin B₁₂ levels were measured in 44 subjects with diabetes and a mean age of 51 years (range, 40 to 70), 21 (48%) of whom had low levels (< 200 pg/mL). Of those 21 patients, 10 agreed to enroll in an intervention phase consisting of oral supplementation with mecobalamin, 1,500 μg daily for 3 months. Those patients in whom vitamin B₁₂ levels failed to normalize after oral supplementation alone would be presumed to have vitamin B₁₂ deficiency attributable to malabsorption.ResultsAlmost half of the subjects with type 2 diabetes not taking metformin had biochemically proven vitamin B₁₂ deficiency. All 10 subjects who enrolled in the intervention phase had normalization of their vitamin B₁₂ levels after 3 months of oral supplementation with mecobalamin.ConclusionWe conclude that vitamin B₁₂ deficiency is common among patients with type 2 diabetes and was related to nutrition in our study group. In addition to intensive glycemic control, vitamin B₁₂ supplementation should be considered for treatment of diabetic neuropathy. In almost 50% of patients with low vitamin B₁₂ levels, the deficiency was corrected with oral supplementation only. This, indeed, is an important finding, inasmuch as oralvitamin B₁₂ supplementation is easy, convenient, and readily accepted by patients. This finding highlights the need for aggressive and early diagnosis and treatment to avoid complications of vitamin B₁₂ deficiency. (Endocr Pract. 2010;16:205-208)     

Vitamin B12 Excretion in Patients with Various Skin Diseases

The excretion in the urine of ⁵⁸Co after an oral dose of ⁵⁸Co vitamin B₁₂ given together with intrinsic factor has been found to be reduced in a number of patients with psoriasis, eczema, and other less common dermatoses. There is a correlation between the abnormality and the extent of the rash. A reduced glomerular filtration rate was found in a few of the patients in whom it was measured, and this must have been responsible, at least in part, for the reduced excretion of vitamin B₁₂ in these patients, but abnormal vitamin B₁₂ excretion also occurred in the absence of impaired renal function. Our evidence is insufficient to show whether malabsorption or increased tissue utilization of vitamin B₁₂ was the explanation in other cases. Certainly a number of patients had steatorrhoea, and in these it is most likely that malabsorption was the major factor. In patients without steatorrhoea a lone malabsorption of vitamin B₁₂ cannot be excluded. A decreased serum concentration of vitamin B₁₂ was found in only one of the patients.     

Systemic lupus erythematosus

Imerslund-Gräsbeck syndrome (IGS) or selective vitamin B₁₂ (cobalamin) malabsorption with proteinuria is a rare autosomal recessive disorder characterized by vitamin B₁₂ deficiency commonly resulting in megaloblastic anemia, which is responsive to parenteral vitamin B₁₂ therapy and appears in childhood. Other manifestations include failure to thrive and grow, infections and neurological damage. Mild proteinuria (with no signs of kidney disease) is present in about half of the patients. Anatomical anomalies in the urinary tract were observed in some Norwegian patients. Vitamin B₁₂ absorption tests show low absorption, not corrected by administration of intrinsic factor. The symptoms appear from 4 months (not immediately after birth as in transcobalamin deficiency) up to several years after birth. The syndrome was first described in Finland and Norway where the prevalence is about 1:200,000. The cause is a defect in the receptor of the vitamin B₁₂-intrinsic factor complex of the ileal enterocyte. In most cases, the molecular basis of the selective malabsorption and proteinuria involves a mutation in one of two genes, cubilin (CUBN) on chromosome 10 or amnionless (AMN) on chromosome 14. Both proteins are components of the intestinal receptor for the vitamin B₁₂-intrinsic factor complex and the receptor mediating the tubular reabsorption of protein from the primary urine. Management includes life-long vitamin B₁₂ injections, and with this regimen, the patients stay healthy for decades. However, the proteinuria persists. In diagnosing this disease, it is important to be aware that cobalamin deficiency affects enterocyte function; therefore, all tests suggesting general and cobalamin malabsorption should be repeated after abolishment of the deficiency.     

Higher Prevalence of Metformin-Induced Vitamin B12 Deficiency in Sulfonylurea Combination Compared with Insulin Combination in Patients with Type 2 Diabetes: A Cross-Sectional Study

Long-term and high-dose treatment with metformin is known to be associated with vitamin B₁₂ deficiency in patients with type 2 diabetes. We investigated whether the prevalence of B₁₂ deficiency was different in patients treated with different combination of hypoglycemic agents with metformin during the same time period. A total of 394 patients with type 2 diabetes treated with metformin and sulfonylurea (S+M group, n = 299) or metformin and insulin (I+M group, n = 95) were consecutively recruited. The vitamin B₁₂ and folate levels were quantified using the chemiluminescent enzyme immunoassay. Vitamin B₁₂ deficiency was defined as vitamin B₁₂≤300 pg/mL without folate deficiency (folate>4 ng/mL). The mean age of and duration of diabetes in the subjects were 59.4±10.5 years and 12.2±6.7 years, respectively. The mean vitamin B₁₂ level of the total population was 638.0±279.6 pg/mL. The mean serum B₁₂ levels were significantly lower in the S+M group compared with the I+M group (600.0±266.5 vs. 757.7±287.6 pg/mL, P<0.001). The prevalence of vitamin B₁₂ deficiency in the metformin-treated patients was significantly higher in the S+M group compared with the I+M group (17.4% vs. 4.2%, P = 0.001). After adjustment for various factors, such as age, sex, diabetic duration, duration or daily dose of metformin, diabetic complications, and presence of anemia, sulfonylurea use was a significant independent risk factor for B₁₂ deficiency (OR = 4.74, 95% CI 1.41–15.99, P = 0.012). In conclusion, our study demonstrated that patients with type 2 diabetes who were treated with metformin combined with sulfonylurea require clinical attention for vitamin B₁₂ deficiency and regular monitoring of their vitamin B₁₂ levels.     

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.     

Vitamina B12 en pacientes diabéticos tipo 2 en tratamiento con metformina

ObjectiveTo test vitamin B12 plasma levels in type 2 diabetic patients treated with metformin in our area.MethodsA cross-sectional, observational study of consecutive type 2 diabetic patients on drug treatment attending an internal medicine outpatient clinic.ResultsOne hundred and nine patients (81 treated with metformin) were enrolled into the study. Mean time on metformin treatment was 43.5 months and mean drug dose was 1,779 mg/day. Patients treated with metformin had significantly lower vitamin B₁₂ plasma levels (393.5 vs. 509 pg/mL, P = .0008). Seven (8.6%) of 81 patients treated with metformin and none of the 28 patients not treated with the drug had vitamin B₁₂ plasma levels lower than 197 pg/mL. No correlation was found between vitamin B12 plasma levles and metformin treatment time or dosage.ConclusionsIn type 2 diabetic patients, treatment with metformin is associated to lower vitamin B12 plasma levels. Vitamin B12 deficiency associated with metformin is relatively common in our area.     

Idiopathic hypoparathyroidism with impaired vitamin B12 absorption and neuropathy

A 68-year-old man presenting with chronic intermittent diarrhea and progressive ataxia was found to have idiopathic hypoparathyroidism. Intrinsic factor-resistant vitamin B₁₂ malabsorption was demonstrated. Both the diarrhea and vitamin malabsorption were reversed by correction of hypocalcemia.His neurological profile was a combination of peripheral nerve, posterior column and cerebellar deficits. He had calcifications in the dentate nuclei of the cerebellum. Possible etiological factors such as vitamin B₁₂ deficiency, folic acid deficiency and steatorrhea have been excluded. Posterior column and cerebellar abnormalities improved with treatment. It is postulated that hypocalcemia causes functional, reversible spinal cord and cerebellar dysfunction.     

Selective vitamin B12 malabsorption in two siblings

Two siblings with megaloblastic anemia responsive to parenteral vitamin B₁₂ were studied to elucidate the cause of the B₁₂ deficiency. Gastric juice from both contained acid and functional intrinsic factor. Serum contained transcobalamin II and lacked antibodies to intrinsic factor. Schilling tests showed vitamin B₁₂ malabsorption uncorrected by hog intrinsic factor or pancreatic extract. Other parameters of small intestinal function were normal. Proteinuria was initially present in both but cleared in one following treatment with B₁₂. These patients with “familial selective vitamin B₁₂ malabsorption” are the first reported from Canada. Only 37 cases have been reported in the world literature to date.     

Vitamin B12 Malabsorption after Cobalt Teletherapy for Carcinoma of the Bladder

After cobalt teletherapy for carcinoma of the bladder, eight out of 14 consecutively admitted patients were shown to have malabsorption of vitamin B₁₂, though none had developed a megaloblastic anaemia. Despite lack of symptoms this group of patients is at risk after radiotherapy.     

Malabsorption in Overland Travellers to India

Thirty-four cases of malabsorption are described in young adults after brief periods of overland travel to India. Symptoms included diarrhoea, abdominal distension, and weight loss. Investigation revealed fat, xylose, and vitamin B₁₂ malabsorption with marked morphological changes in the mucosa. Lower levels of serum folate and vitamin B₁₂ were observed in those with protracted diarrhoea, but no anaemia developed. Malabsorption may persist for many months after return to the U.K. Most patients responded initially to antibiotics, but some subsequently relapsed. The reasons why these patients developed tropical sprue are discussed.     

Effect of Metformin Therapy on Vitamin D and Vitamin B12 Levels in Patients with Type 2 Diabetes Mellitus

ObjectiveTo determine the effect of metformin on 25-hydroxyvitamin D [25(OH)D] and vitamin B₁₂ levels in patients with type 2 diabetes mellitus.MethodsWe performed a retrospective review of medical records of patients treated between 2003 and 2009 at Loyola University Medical Center, Maywood, Illinois, in both ambulatory primary care and endocrinology clinics. The study cohort consisted of 706 patients with type 2 diabetes mellitus who were 20 to 93 years old (mean age, 63 ± 13) and had a mean body mass index of 33.1 kg/m². Of these patients, 42% were treated with metformin, and 34% had been diagnosed with osteoporosis or osteopenia.ResultsPatients taking metformin had statistically significant lower vitamin B₁₂ levels than those not receiving metformin (P < .0001; 95% confidence interval [CI] = − 220 to − 84 pg/mL). No statistically significant difference was found between users and nonusers of metformin in regard to 25(OH)D levels when adjusted for variables (P = .297; 95% CI for mean difference = − 0.7 to 2.2 ng/mL). Metformin use did not adversely affect successful treatment of vitamin D deficiency in this patient population as a whole, nor did it affect the subgroup with osteoporosis (P = .956). The patients with osteoporosis had statistically significant lower baseline 25(OH)D levels in comparison with those without osteoporosis, when adjustments were made for all variables (P = .003; 95% CI = 0.7 to 3.5 ng/ mL).ConclusionThis study confirms the higher prevalence of vitamin B₁₂ deficiency in metformin-treated patients with type 2 diabetes than in those not treated with metformin. This study also suggests that vitamin D deficiency is not a clinical concern among metformin-treated patients with type 2 diabetes and that metformin does not negatively affect treatment of vitamin D deficiency in these patients. (Endocr Pract. 2012;18:179–184)     

Steatorrhea in patients with liver disease

Intestinal function was studied in 26 patients with seven types of acute and chronic liver disease, documented by liver biopsy. Steatorrhea, defined by a stool fat higher than 6 g. per day, was present in 18 of 23 consecutive patients studied, an incidence of 78.3%. Two patients with infectious hepatitis associated with steatorrhea studied previously were added and the 20 cases were analyzed. The malabsorption found was confined to fat and fat-soluble vitamins; stool excretion varied from 6.1 to 22 g. per day in the seven groups studied. No histological abnormality was seen on jejunal biopsy, serum vitamin B₁₂, D-xylose and Schilling tests were normal, and no radiological findings associated with malabsorption were detected in the small bowel. It is concluded that steatorrhea is a common finding in a wide variety of acute and chronic liver diseases and cannot be attributed to a primary defect of the small bowel.     

Metformin and phenformin block the peripheral antinociception induced by diclofenac and indomethacin on the formalin test

AimsRecent evidence has shown that systemic administration of sulfonylureas and biguanides block the diclofenac-induced antinociception, but not the effect produced by indomethacin. However, there are no reports about the peripheral interaction between analgesics and the biguanides metformin and phenformin. Therefore, this work was undertaken to determine whether glibenclamide and glipizide and the biguanides metformin and phenformin have any effect on the peripheral antinociception induced by diclofenac and indomethacin.Main methodsDiclofenac and indomethacin were administered locally in the formalin-injured rat paw, and the antinociceptive effect was evaluated using the 1% formalin test. To determine whether peripheral antinociception induced by diclofenac or indomethacin was mediated by either the ATP-sensitive K⁺ channels or biguanides-induced mechanisms, the effect of pretreatment with the appropriates vehicles or glibenclamide, glipizide, metformin and phenformin on the antinociceptive effect induced by local peripheral diclofenac and indomethacin was assessed.Key findingsLocal peripheral injections of diclofenac (50–200 μg/paw) and indomethacin (200–800 μg/paw) produced a dose-dependent antinociception during the second phase of the test. Local pretreatment with glibenclamide, glipizide, metformin and phenformin blocked the diclofenac-induced antinociception. On the other hand, the pretreatment with glibenclamide and glipizide did not prevent the local antinociception produced by indomethacin. Nonetheless, metformin and phenformin reversed the local antinociception induced by indomethacin.SignificanceData suggest that diclofenac could activate the K⁺ channels and biguanides-dependent mechanisms to produce its peripheral antinociceptive effects in the formalin test. Likewise, a biguanides-dependent mechanism could be activated by indomethacin consecutively to generate its peripheral antinociceptive effect.     

Megaloblastic Anemia Associated with Surgically Produced Gastrointestinal Abnormalities

Two of the mechanisms for vitamin B₁₂ deficiency, leading to megaloblastic anemia, are the result of surgically produced abnormalities of the gastrointestinal tract. The basic mechanism is different for each lesion.Total gastrectomy results in complete lack of intrinsic factor which is necessary for vitamin B₁₂ absorption. It is believed that if patients survive long enough and are not given prophylactic vitamin B₁₂ therapy, all would develop megaloblastic anemia.Intestinal anastomosis leading to stasis of intestinal contents, with overgrowth of bacteria may cause vitamin B₁₂ deficiency through bacterial interference with the utilization of vitamin B₁₂.Use of radioactive vitamin B₁₂ (cobalt⁶⁰-labeled B₁₂) has led to a better understanding of the pathogenesis of both types of megaloblastic anemia. The radioactive vitamin provides a useful tool for study of its absorption from the gastrointestinal tract.     

Synergistic Anti-Cancer Effect of Phenformin and Oxamate

Phenformin (phenethylbiguanide; an anti-diabetic agent) plus oxamate [lactate dehydrogenase (LDH) inhibitor] was tested as a potential anti-cancer therapeutic combination. In in vitro studies, phenformin was more potent than metformin, another biguanide, recently recognized to have anti-cancer effects, in promoting cancer cell death in the range of 25 times to 15 million times in various cancer cell lines. The anti-cancer effect of phenformin was related to complex I inhibition in the mitochondria and subsequent overproduction of reactive oxygen species (ROS). Addition of oxamate inhibited LDH activity and lactate production by cells, which is a major side effect of biguanides, and induced more rapid cancer cell death by decreasing ATP production and accelerating ROS production. Phenformin plus oxamate was more effective than phenformin combined with LDH knockdown. In a syngeneic mouse model, phenformin with oxamate increased tumor apoptosis, reduced tumor size and ¹⁸F-fluorodeoxyglucose (FDG) uptake on positron emission tomography/computed tomography compared to control. We conclude that phenformin is more cytotoxic towards cancer cells than metformin. Furthermore, phenformin and oxamate have synergistic anti-cancer effects through simultaneous inhibition of complex I in the mitochondria and LDH in the cytosol, respectively.     

Impact of Helicobacter pylori on the development of vitamin B12 deficiency in the absence of gastric atrophy

Background. Cobalamin (vitamin B₁₂) deficiency is associated with Helicobacter pylori infection. This study examined how serum vitamin B₁₂ levels relate to gastric mucosa H. pylori density and histology, and to hematological findings in patients with minimal or no gastric atrophy. A second aim was to confirm that H. pylori eradication therapy increases serum B₁₂. Materials and Methods. Biopsies of the gastric mucosa from a population of dyspeptic patients were graded for level of chronic inflammation, neutrophil activity, atrophy, and H. pylori density. A total of 145 H. pylori‐infected patients with minimal or no atrophy were included in the study. Serum cobalamin level, hemoglobin level, and mean corpuscular volume were measured in the 145 patients before eradication therapy, and in 65 of the subjects after treatment. The hematologic findings before and after eradication therapy and correlations between serum vitamin B₁₂ level and histologic parameters, hematologic findings, and patient age were statistically analyzed. Results. There was no significant correlation between serum cobalamin level and patient age. Before treatment all the histopathological scores were inversely correlated with serum vitamin B₁₂ level (p < .01) on univariate analysis. Only H. pylori density was significantly associated with B₁₂ level on multivariate analysis. Serum hemoglobin and cobalamin levels were significantly increased after treatment, regardless of H. pylori eradication status (p < .001). Conclusion. The findings provide strong evidence that H. pylori infection is associated with cobalamin deficiency, and show that this is true even in patients with nonulcer dyspepsia and minimal or no gastric atrophy.     

Effect of adjunct metformin treatment in patients with type-1 diabetes and persistent inadequate glycaemic control. A randomized study

Background

Despite intensive insulin treatment, many patients with type-1 diabetes (T1DM) have longstanding inadequate glycaemic control. Metformin is an oral hypoglycaemic agent that improves insulin action in patients with type-2 diabetes. We investigated the effect of a one-year treatment with metformin versus placebo in patients with T1DM and persistent poor glycaemic control.

Methodology/Principal Findings

One hundred patients with T1DM, preserved hypoglycaemic awareness and HaemoglobinA_1c (HbA_1c) ≥8.5% during the year before enrolment entered a one-month run-in on placebo treatment. Thereafter, patients were randomized (baseline) to treatment with either metformin (1 g twice daily) or placebo for 12 months (double-masked). Patients continued ongoing insulin therapy and their usual outpatient clinical care. The primary outcome measure was change in HbA_1c after one year of treatment. At enrolment, mean (standard deviation) HbA_1c was 9.48% (0.99) for the metformin group (n = 49) and 9.60% (0.86) for the placebo group (n = 51). Mean (95% confidence interval) baseline-adjusted differences after 12 months with metformin (n = 48) versus placebo (n = 50) were: HbA_1c, 0.13% (−0.19; 0.44), p = 0.422; Total daily insulin dose, −5.7 U/day (−8.6; −2.9), p<0.001; body weight, −1.74 kg (−3.32; −0.17), p = 0.030. Minor and overall major hypoglycaemia was not significantly different between treatments. Treatments were well tolerated.

Conclusions/Significance

In patients with poorly controlled T1DM, adjunct metformin therapy did not provide any improvement of glycaemic control after one year. Nevertheless, adjunct metformin treatment was associated with sustained reductions of insulin dose and body weight. Further investigations into the potential cardiovascular-protective effects of metformin therapy in patients with T1DM are warranted.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00118937","term_id":"NCT00118937"}}NCT00118937