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UDK 616.379-008.64:615.065-252.349.7;616.833:616.839-07-08 DOI: http://doi.org/10.30978/CEES-2019-4-45
Vitamin B12 levels in metformin-treated type 2 diabetes patients
INTRODUCTION
Metformin is a first-line drug in the pharmacotherapy of type 2 diabetes mellitus (DM). Apart from the low cost, good efficacy, and beneficial effects on body weight, the relatively safe adverse effect profile has justified the widespread use of metformin [1, 2]. Several studies have reported association of vitamin B12 deficiency in type 2 diabetes patients treated with metformin [3—5]. Metformin does, however, induce vitamin B12 malabsorption, which may increase the risk of developing vitamin B12 deficiency — a clinically important and treatable condition. In addition, metformin treatment has been reported to be associated with decreased folate concentration, although the mechanism of this effect has not been elucidated. Finally, decreases in both folate and vitamin B12 concentrations might, in turn, result in an increase in homocysteine concentrations, an independent risk factor for cardiovascular disease, especially among individuals with type 2 DM [6, 7].
All current evidence on vitamin B12 deficiency in metformin treatment comes from short term studies [8—10]. No long term, placebo controlled data on the effects of metformin on concentrations of vitamin B12 in patients with type 2 DM have been reported. In addition, placebo controlled data on the effects of metformin on homocysteine concentrations in type 2 diabetes are sparse, and again no long term data are available.
Clinically, vitamin B12 deficiency could lead to altered mental status, megaloblastic anemia, and neurological
damage [11]. Peripheral neuropathy due to vitamin B12 deficiency may be confused with diabetic peripheral neuropathy or may contribute to the aggravation of diabetic peripheral neuropathy [12]. The progression of neurologic damage due to vitamin B12 deficiency can be stopped by early detection and treatment with cobalamin supplementation [13]. However, if this occurrence is misdiagnosed as diabetic neuropathy, permanent neurological damage may occur [14]. This study was done to further explore this question.
Aim of the study — to study the prevalence of vitamin B12 deficiency and the factors associated with it in patients with type 2 diabetes mellitus who were treated with metformin.
MATERIALS AND METHODS
The patients were recruited from the endocrinology outpatient department of a tertiary care center from August 2018 to December 2018, after taking informed consent.
Patients were defined as type 2 DM with an age at diagnosis above 30 years. Pregnancy, pernicious anemia, malabsorption syndrome, gastrointestinal surgery, autoimmune thyroid disease, chronic hepatitis, chronic kidney disease stage 4 and above, chronic alcohol abuse, and the use of oral/parenteral vitamin B12 or multivitamin supplements were exclusion criteria.
An observational study was conducted from August 2018 to December 2018. The study was approved by the Univetsity Ethical Committee.
Паньш 1ван Володимирович, доцент кафедри шшчно! ¡мунологи, алергологи та ендокринологи. 58002, м. Чершвщ, Театральна площа, 2. E-mail: ip@bsmu.edu.ua
Table 1
Baseline characteristics of patients with type 2 DM
Variable Group 1, n = 35 Group 2, n = 25 P
Age, years 52.7 ± 3.4 49.4 ± 3.1 0.47
Sex, n (%)
Male 16 (45.7) 11 (44.0) 0.34
Female 19 (54.3) 14 (56.0)
Duration of DM, years 6.7 ± 1.1 1.9 ± 0.6 < 0.01
BMI, kg/m2 29.3 ± 2.4 29.3 ± 2.4 0.23
HbAlc, % 7.9 ± 1.5 7.8 ± 1.4 0.30
DM — diabetes mellitus, BMI — body mass index, HbAlc — glycated hemoglobin
A total of 53 patients with type 2 DM (group 1, n = 35, receiving metformin and group 2, n = 25, never treated with metformin) from the endocrinology clinic in Chernivtsi were studied.
Group 1 consisted of patients with type 2 DM with ongoing treatment with metformin with duration of metformin use > 6 months while second group consisted of patients with type 2 DM who had never received metformin.
History about diabetes onset, dose, and duration of metformin usage as well as recent (within 3 months) glycated hemoglobin (HbAlc) was obtained from Centre records. The Centre records, patient's prescriptions, and medicines were also searched for prescription of any vitamin B12-containing supplements and patients were shown a list of commonly available multivitamins containing vitamin B12 and were asked about their use at any time in the past.
Vitamin B12 estimation was done by competitive chemiluminescent enzyme immunoassay on Immulite analyzer using commercial kits from Siemens Healthcare Diagnostics Inc., New York, USA. The calibration range of this assay was 197—771 pg/ml. Vitamin B12 deficiency was defined as levels below 190 pg/ml.
Statistical analysis was performed using Statistical Package for Social Sciences SPSS version 14 (SPSS Inc., Chicago, IL, USA). Continuous variables were described as mean and standard deviation. The categorical variables were stated as proportions or percentages. The comparison between the first group and second group was done with Student's t-test for continuous variables and Chi-square test for categorical variables. Linear regression analyses were carried out to study the effect of duration since the diagnosis of diabetes, use of metformin, and duration of metformin use on
serum vitamin B12 levels. P < 0.05 was considered statistically significant.
RESULTS
A total of 60 patients with type 2 DM (group 1, n = 35, receiving metformin and group 2, n = 25, never treated with metformin) from the endocrinology clinic in Chernivtsi were studied. Serum Vitamin B12 levels were measured in all patients. The mean age of the study population was 51.9 ± 9.3 years. Table 1 shows the baseline characteristics of patients with type 2 DM. The two groups were comparable except for duration of DM which was significantly greater in the first group. Duration of metformin use was 26.2 ± 5.4 months (range 6—140 months). Daily dose of metformin was 839.2 ± 53.1 mg (range 500—2500 mg). The cumulative dose of metformin was 970.8 ± 517.2 g (range 85—10,590 g).
The serum mean unadjusted vitamin B12 levels were 239.6 ± 37.4 pg/ml in the first group and 293.6 ± 42.3 pg/ml in the second group (p = 0.37).
The mean duration of DM was longer in the first group as compared to the second group (6.7 ± 1.1 years vs. 1.9 ± 0.6 years, p < 0.01). Vitamin B12 deficiency was present in 16 (45.7 %) of the first group and in 6 (24.0 % of the second group (p = 0.04).
On univariate linear regression analysis with vitamin B12 levels as the dependent variable and metformin use (no and yes) as the predictor variable, metformin use was associated with a 8.7 ± 3.9 pg/ml (p = 0.73) lower vitamin B12 level. On univariate linear regression analysis with vitamin B12 levels as the dependent variable and duration of DM as the predictor variable, vitamin B12 levels were 12.2 ± 3.0 pg/ml (95 % CI 6.4—18.0, p < 0.001) higher for every 1 year increase in the duration of DM.
To further study the association of vitamin B12 levels and duration of DM, we performed a stratified analysis. Figure 1 shows the box plot of serum vitamin B12 with duration of DM categorized into newly diagnosed (0—1 year), 1—5 years, and > 5 years. Serum vitamin B12 levels were higher by 41.4 pg/ml in patients with DM of 1—5 years compared to those with recently diagnosed diabetes (p = 0.41). Serum vitamin B12 levels were higher by 119.4 pg/ml in patients with duration of DM > 5 years compared to those with recently diagnosed diabetes (p < 0.02). Similarly, serum vitamin B12 levels were 77.1 pg/ml higher in > 5 years DM duration group compared to 1 —5 year duration of DM group (p = 0.03).
On univariate linear regression analysis with vitamin B12 levels as the dependent variable and duration of
metformin use as the predictor variable, duration of metformin use predicted a 0.8 ± 0.4 pg/ml (p = 0.05) lower Vitamin B12 levels for every 1 month increase in the duration of metformin use. On stratifying duration of metformin use into no metformin use, 0—1 years, 1—5 years, and more than 5 years, it was found that a 20.1 pg/ml (p = 0.64) and 37.3 pg/ml lower serum vitamin B12 concentration was observed in individuals with a 0—1 years and 1 —5 year duration of metformin use, respectively, compared with the group which had not received metformin.
In contrast, the serum concentration of vitamin B12 was higher by 45.4 pg/ml (p = 0.27) in individuals who had received metformin for more than 5 years compared to those who had never received metformin. To understand the interplay of duration of DM and metformin use on serum Vitamin B12 levels, a stratified analysis was carried out. A multivariate linear regression analysis with serum vitamin B12 levels as the dependent variable and metformin use (no/yes) and duration of DM (stratified as 1—5 years and > 5 years) as predictor variables were done to adjust for the duration of DM. In this analysis, metformin use group was associated with a 87.3 ± 37.1 pg/ml (p = 0.03) lower serum vitamin B12 levels. The serum vitamin B12 levels were 104.9 ± 42.0 pg/ml (p = 0.02) higher in the 1—5 year duration of DM group while they were 192.3 ± 48.9 pg/ml (p < 0.01) higher in > 5 year duration of DM group.
DISCUSSION
The present study involving 60 patients with type 2 DM (35 metformin and 25 without metformin) showed lower vitamin B12 levels with metformin use, when adjusted for duration since diagnosis of diabetes, which is consistent with other studies published earlier [1—7]. Without adjusting for duration of DM, there was neither a significant difference in serum vitamin B12 levels nor in the prevalence of vitamin B12 deficiency. However, the prevalence of vitamin B12 deficiency in patients on metformin in our study is higher than that reported in literature [4—6, 15].
An interesting finding from our study is the statistically significant rise in vitamin B12 with increasing duration of DM. In a cross-sectional study from the US comprising 1621 patients with type 2 DM (575 on metformin and 1046 not on metformin) and 6867 persons without diabetes, the DM without metformin group had the lowest prevalence of vitamin B12 deficiency (2.4 %) as compared to 5.8 % in the diabetes on metformin group and the 3.3 % in the group without
0—1 yrs 1 —5 yrs > 5 yrs
Figure 1. Vitamin B12 levels and duration of type 2 DM (0—1, 0—5 years and > 5 years)
diabetes [3]. We did make an active effort to exclude patients who had been given vitamin B12-containing supplements for any indication (review of available medical records was done, and patients were asked about the use of vitamin B12-containing multivitamin supplements), but these preparations are available over the counter, and we cannot be sure that patients had never taken these medications earlier. In addition, the higher vitamin B12 levels with greater duration of DM were seen in the second group also who were not at the risk of metformin-related vitamin B12 deficiency (as they never received metformin) and hence are less likely to have received vitamin B12 treatment.
The limitation of our study is that we did not measure functional markers of vitamin B12 deficiency (serum homocysteine and serum methylmalonic acid levels) which may better reflect the status of vitamin B12 levels in the body as compared to serum vitamin B12 levels. In addition, our sample size was small. The strength of this study is that the second group included only those patients who had never taken metformin. The reason for choosing such a group was to exclude a possible long-term effect of metformin use on vitamin B12 status. Vitamin B12 is stored in the liver and several years may pass before the stores are depleted and detectable vitamin B12 deficiency manifests. Thus, including patients with a history of metformin use in the no metformin group is a potential confounder which we excluded in this study.
CONCLUSIONS
Metformin use was associated with a significantly lower serum vitamin B12 levels when adjusted for duration of diabetes.
Serum vitamin B12 levels were higher by 41.4 pg/ml in patients with DM of 1—5 years compared to those with recently diagnosed diabetes (p = 0.41). Serum vitamin B12 levels were higher by 119.4 pg/ml in patients with duration of DM > 5 years compared to those with recently diagnosed diabetes (p < 0.02). Similarly, serum vitamin B12 levels were 77.1 pg/ml higher in > 5 years DM duration group compared to 1—5 year duration of DM group (p = 0.03).
Further study of the impact of duration of diabetes on serum vitamin B12 levels and of functional markers of vitamin B12 deficiency on hematological and neurological parameters will be interesting.
Джврвла фнансування — eidcymHi. Гонорар за написания рукопису eid комерцшних орга^зацш чи iHwux за^каелених сторн аетор не отримуеае. Конфл1кт ¡нтврвав — eidcym^ü. Етичн1 аспвкти. Доcлiдження розглянуто КоMime-том з етики ВДНЗУ «Букоеинський держаений медич-нийyнieeрcumem» (протокол № 8 eiд 17.09.2018 р.).
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15. Паныш B.I. Вплив метилкобаламшу на вмкт впамшу В12 i прояви нейропати у хворих на цукровий д1абет 2-го типу з метформЫ-асоцмованим дефщитом впа-MiHy В]2. Miжнародний ендокринолопчний журнал. 2019;15(4):45-49. doi: 10/22141/2224-0721.15.4. 2019.174818.
ABSTRACT Vitamin B12 levels in metformin-treated type 2 diabetes patients I. V. Pankiv
Bukovinian State Medical University, Chernivtsi
Background. Metformin is the most widely used oral antihyperglycaemic drug, but it may lower B12 status, which could have important clinical implications. There are limited data about the effect of metformin use on serum vitamin B12 levels in type 2 diabetes mellitus (DM) patients.
Aim. To study serum Vitamin B12 levels in patients with type 2 diabetes mellitus who were receiving metformin and compared them to those never treated with metformin.
Materials and methods. A total of 60 patients with type 2 DM (group 1, n = 35, receiving metformin and group 2, n = 25, never treated with metformin) from the endocrinology clinic in Chernivtsi were studied. Serum vitamin B12 levels were measured in all patients.
Results and discussion. The serum vitamin B12 levels were 239.6 ± 37.4 pg/ml in metformin group and 293.6 ± 42.3 pg/ml in the no metformin group (p = 0.37). When adjusted for duration of DM, metformin use was associated with a 57.2 ± 7.3 pg/ml (p = 0.03) lower serum vitamin B12 levels. Serum vitamin B12 levels were higher by 41.4 pg/ml in patients with DM of 1 —5 years compared to those with recently diagnosed diabetes (p = 0.41). Serum vitamin B12 levels were higher by 119.4 pg/ml in patients with duration of DM > 5 years compared to those with recently diagnosed diabetes (p < 0.02). Similarly, serum vitamin B12 levels were 77.1 pg/ml higher in > 5 years DM duration group compared to 1—5 year duration of DM group (p =
0.03). Serum vitamin B12 levels for the entire cohort were higher by 11.8 ± 1.7 pg/ml (p < 0.01) for every
1 year increase in the DM duration.
Conclusions. Metformin use was associated with a lower serum vitamin B12 levels when adjusted for duration of DM. Increasing duration of DM was associated with higher serum vitamin B12 levels.
Key words: type 2 diabetes mellitus, metformin, vitamin B12 levels.
РЕЗЮМЕ Вм1ст в1там1ну B12 у хворих на цукровий д1абет 2-го типу
1. В. Паньк'в
Буковинський державний медичний yHieepcumem, Черн1вц1
Вступ. Метформш залишаеться найбтьш вико-ристовуваним пероральним антиппергл^емтним препаратом, однак при цьому вш може знижувати ртень вп"ам1ну B12, що може мати важлив1 клшты наслщки. Наявн обмежен дан про вплив застосу-вання метформшу на р1вень вп"амшу B12 у сироватц кров1 у хворих на цукровий д1абет 2-го типу (ЦД2).
Мета роботи — вивчити ртень в^амшу B12 у сироватц кров1 у пащентш ¡з цукровим дебетом
2 типу, як отримували метформ¡н, та портняти Тх ¡з пац¡ентами, як н¡коли не л¡кувалися метформ¡ном.
Матер1али та методи. Пщ спостереженням перебували 60 пащентш ¡з ЦД2 (група 1, п = 35, як отримували метформ¡н, та група 2, п = 25, як¡ ыколи не л¡кувались метформ¡ном) з Чершвецького обласного ендокринолог¡чного центру. P¡вень вгга-м¡ну В12 у сироватц¡ кров¡ вим¡рювали у вс¡x пащен-тт. Результати. P¡вень в¡там¡ну В12 у сироватц кров¡ становив (239,6 ± 37,4) пг/мл у перш¡й груп та (293,6 ± 42,3) пг/мл у другш груп¡ (р = 0,37). Пкля скоригування за тривалктю ЦД2, використання метформ¡ну було пов'язано з нижчим ртнем в^ами ну В12 у сироватц¡ кров¡ на (57,2 ± 7,3) пг/мл (р = 0,03). Ртень в¡там¡ну В12 у сироватц¡ кров¡ був бть-шим на 41,4 пг/мл у пащентш ¡з тривал¡стю ЦД2 вщ одного до п'яти рок¡в портняно з тими, у кого д^-бет був нещодавно д¡агностований (р = 0,41). Ртень в¡там¡ну В12 у сироватц¡ кров¡ був б¡льшим на 119,4 пг/мл у пащентш ¡з тривал¡стю ЦД2 > 5 рокв порт-няно з патентами з недавно д¡агностованим д^-бетом (р < 0,02). Аналопчно, ртень в¡там¡ну В12 у сироватц¡ кров¡ був на 77,1 пг/мл вище при трива-лост¡ ЦД2 понад 5 рокв пор¡вняно з хворими з тривал¡стю ЦД2 1—5 рокв (р = 0,03). Ртень в¡там¡-ну В12 у сироватф кров¡ для вс¡еí когорти був вищим на (11,8 ± 1,7) пг/мл (95 % Д| 6,3—17,0, р < 0,01) за кожен рк зб¡льшення тривалост¡ ЦД2. Висновки. Застосування метформ¡ну пов'язано з нижчим рт-нем в¡там¡ну В12 у сироватц¡ кров¡, що залежало в¡д тривалост¡ цукрового д¡абету.
Ключов1 слова: цукровий д¡абет 2-го типу, метформш, вп"амш В12.
РЕЗЮМЕ Содержание витамина В12 у больных сахарным диабетом 2-го типа И. В. Панькив
Буковинский государственный медицинский университет, Черновцы
Вступление. Метформин остается наиболее используемым пероральным антигипергликемичес-ким препаратом, однако при этом он может снижать уровень витамина В12, что может иметь важные клинические последствия. Имеются ограниченные данные о влиянии применения метформина на уровень витамина В12 в сыворотке крови у больных сахарным диабетом 2-го типа (СД2).
Цель работы — изучить уровень витамина В12 в сыворотке крови у пациентов с сахарным диабетом 2-го типа, получавших метформин, и сравнить
их с пациентами, которые никогда не лечились мет-формином.
Материалы и методы. Под наблюдением находились 60 пациентов с СД2 (группа 1, п = 35, получавших метформин и группа 2, п = 25, которые никогда не лечились метформином) из Черновицкого областного эндокринологического центра. Уровень витамина В12 в сыворотке крови измеряли у всех пациентов. Результаты. Уровень витамина В12 в сыворотке крови составил (239,6 ± 37,4) пг/мл в первой группе и (293,6 ± 42,3) пг/мл во второй группе (р = 0,37). После коррекции по продолжительности СД2 использование метформина было связано с более низким уровнем витамина В12 в сыворотке крови на (57,2 ± 7,3) пг/мл (р = 0,03). Уровень витамина В12 в сыворотке крови был больше на 41,4 пг/мл у пациентов с длительностью СД2 от одного до пяти лет по сравнению с теми,
у кого диабет был недавно диагностирован (р = 0,41). Уровень витамина В12 в сыворотке крови был больше на 119,4 пг/мл у пациентов с длительностью СД2 свыше 5 лет по сравнению с пациентами с недавно диагностированным диабетом (р < 0,02). Аналогично, уровень витамина В12 в сыворотке крови был на 77,1 пг/мл выше при продолжительности СД2 более 5 лет по сравнению с больными с длительностью СД2 1 —5 лет (р = 0,03). Уровень витамина В12 в сыворотке крови для всей когорты был выше на (11,8 ± 1,7) пг/ мл (95 % ДИ 6,3—17,0, р < 0,01) на каждый год увеличения продолжительности СД2. Выводы. Применение метформина связано с низким уровнем витамина В12 в сыворотке крови, что зависело от продолжительности сахарного диабета.
Ключевые слова: сахарный диабет 2-го типа, метформин, витамин В12.
Дата надходження до редакцп 27.11.2019 р.
