Clinical Observation Of The Relationship Between The Change Of Serum Vitamin B12 By Metformin And Diabetic Peripheral Neuropathy

Diabetes is a global public health problem. Diabetic PeripheralNeuropathy (DPN) is a common chronic complication of diabetes with highincidence, and it is the risk factor of diabetic foot ulcer and limb amputation.Metformin is the first line hypoglycemic agent for type 2 diabetes. Howeverlong-term treatment with metformin may influence the absorption of VitaminB12 (VitB12), leading to the decrease of serum VitB12 levels. But VitB12 isessential for complete structure and function of nervous system, its deficiencycan cause or worsen DPN. Therefore, under medication with metformin, theearly diagnosis and treatment for VitB12 deficiency and DPN of diabeticpatients be of great importance. VitB12 can translate homocysteine (Hcy) intomethionine. VitB12 deficiency may increase Hcy level and also influence theuse of folic acid which will cause megaloblastic anemia. Therefore, serumHcy and mean corpuscular volume (MCV) are common indicators of VitB12deficiency. Clinical manifestation of DPN is subtle, the inspection anddiagnosis need multi-layered integrated consideration. Toronto ClinicalScoring System (TCSS), l0g monofilament and vibration perception threshold(VPT) inspections are commonly used for the diagnosis of DPN. They areeconomic, simple, noninvasive, and proves be of high clinical value. Diabeticperipheral arterial disease (PAD) plays an important role in the occurrenceand development of DPN. Vascular ultrasound and ankle brachial index (ABI)are important examinations for PAD. Objective:1) To analyze the effects of metformin on VitB12 levels and DPN.2) To investigate the correlation between VitB12 levels and other clinicaldata. To evaluate the diagnostic value of MCV、Hcy on VitB12 deficiency.3) To discuss the risk factors of DPN and PAD.4) To evaluate the clinical value of TCSS, VPT and l0g monofilament inthe diagnosis of DPN and their correlation.5) To evaluate the effectiveness of vascular ultrasound and ABI in thediagnosis of PAD.Methods:1) Designing a case-control study: the diabetic patients were randomlydivided into group A and B. Group A included 32 patients who had takenmetformin for more than 6 months. Group B included 42 patients without thetreatment of metformin during the past 6 months. Metformin application andother laboratory indexes were recorded.2) The examinations of TCSS, VPT, l0g monofilament, vascularultrasound and ABI were applied to all the patients.3) The experimental results of the two groups were compared andanalyzed.4) The correlation between VitB12 levels and the dosage and duration ofmetformin application was analyzed in group A.5) The correlation between VitB12 levels and other clinical data wasanalyzed to screen influencing elements.6) Screening risk factors of DPN by the results of TCSS as criteria forthe diagnosis of DPN.7) Analysing the correlation of diabetic PAD with DPN. 8) Screening risk factors of PAD by the results of vascular ultrasound ascriteria for the diagnosis of PAD.Results:1) In group A, the serum VitB12 levels is lower than group B, meanwhilethe abnormality rates of TCSS, VPT and l0g monofilament were higher thangroup B. But the two groups compared with no significance difference. Thelevels of MCV and Hcy between the two groups had no significant differenceas well.2) The dosage and course of metformin treatment had no correlation withVitB12 levels.3) VitB12 levels had negative relationship with the body mass index(BMI) but had no significant relationship with Hcy, MCV and other clinicaldata.4) TCSS, VPT and l0g monofilament were consistent in the diagnosisof DPN. The detection rate of DPN: TCSS>VPT>10g monofilament.5) The duration of diabetes and glycated hemoglobin A1c (HBAlc) werethe main factors for DPN.6) DPN was associated with diabetic PAD. Vascular ultrasound hadhigher diagnostic effectiveness in the diagnosis of diabetic PAD than ABI.7) Age and HBAlc were the most powerful factors for PAD.Conclusions:1) Metformin exposure has the risk of decreasing VitB12 levels andincreasing the morbidity of DPN, but whether these changes clinically were ofreal statistical significance deserves further confirmation. The purpose ofmetformin as the first line hypoglycemic agent is to control hyperglycemiaand delay the occurrence of diabetic complications. But for the risk of increasing the morbidity of DPN compared with its total benefits ofhypoglycemic effect, cardiovascular protection and so on, clinician how tochoose needs further observation. Whether patients with the application ofmetformin require conventionally additionally supply of VitB12 or calciumneeds further research. On the basis of this experiment, we should furtherincrease the sample size or make large sample prospective case-controlstudies to find iatrogenic cause of VitB12 deficiency. Interval tests and timelytherapy may prevent neuropathy occurrence and aggravation.2) The role of Hcy and MCV as the assistant diagnosis of VitB12deficiency needs further research.3) The duration of diabetes and HBAlc were correlated with DPN. Itindicates that the long-term hyperglycemia is a risk factor for DPN.4) TCSS、VPT、l0g monofilament are important examinations for theevaluation of DPN, and TCSS has the most advantages on the diagnosispotency.5) Vascular ultrasound and ABI are important examinations forscreening diabetic PAD, and the former is more sensitive to early vascularlesions.6) DPN was correlated with diabetic PAD. It indicates that vascularlesions can cause ischemic and anoxic damages to nerves which willaggravate DPN.7) Age and HBAlc were correlated with diabetic PAD. It demonstratesthat age increasing and the long-term hyperglycemia are risk factors for PAD.