Effects of Metformin on Middle Cerebral Artery Flow Velocity in Newly Diagnosed Type 2 Diabetic Patients Hassoun K

American Journal of BioMedicine AJBM 2016;4(9):364-373 DOI: 10.18081/2333-5106/016-9/364-373

Effects of metformin on middle cerebral artery flow velocity in newly diagnosed type 2 Diabetic patients Hassoun K. Hayder1, Ghazal R. Mohammed2, Mudhafar MH. Ahmed3, Hadi R. Najah3*

Abstract

Type 2 diabetes mellitus is a major cause of cerebrovascular disease. Risk of ischemic stroke is higher in diabetic patients and it is about 2-6 times that in normal population. Atherosclerotic lesions happen early in the disease and patients with type 2 diabetes mellitus. Transcranial Doppler can be used for examination of cerebral arteries and it can detect early atherosclerotic changes. Metformin an old oral anti-diabetic drug but still cornerstone in the treatment guidelines of type 2 diabetes mellitus. It improves endothelial function with preferable cardiovascular effects. Twenty patients were recruited for the study. Transcranial Doppler examination done for all patients before initiation of treatment. Patients received metformin for twelve weeks and they were re-examined with transcranial Doppler. The data of present study showed that a highly significant increase in diastolic velocity and mean flow velocity after treatment with significant reduction in pulsatility index and resistive index. In conclusion, metformin treatment increases cerebral diastolic flow velocity with reduction in vascular resistance in patients with type 2 diabetes. Keywords: Metformin; Transcranial Doppler; Middle cerebral artery (MCA); Type 2 diabetes mellitus

*Corresponding author email: [email protected] 1Department of Neurology, College of Medicine/Kufa University 2Department of Pharmacology, College of Medicine/Baghdad University 3Department of Pharmacology and Therapeutics, College of Medicine/ Kufa University Received June13, 2016; accepted August14, 2016; published September14, 2016 Copyright © 2016 NH. This is article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction

Stroke is major global health problem. asymptomatic individuals [3]. It is considered the 6th cause of death However, few and old reports from in United States but may be considered KSA and other Gulf countries recorded the second cause of death in developing annual incidence from 29 to about 60 countries [1]. There is little data per 100000 people [4]. The incidence of available about risk of stroke in Iraq stroke is increasing in these countries and even in Middle East area [2]. A and the risk is expanding, therefore, study about prevalence of silent stroke urgent strategy for prevention and in Iraqi Kurdish population was found better clinical care of stroke patients is and it was about 19% in normal needed [2]. Diabetes mellitus is a well-

Copyright © 2016AJBM 364 American Journal of BioMedicine AJBM 2016;4(9):364-373 DOI: 10.18081/2333-5106/016-9/364-373 recognized risk factor for artery and atherosclerosis [13]. Increase cerebrovascular diseases. The in pulsatility index means reduction in association between stroke risk and perfusion of cerebral tissue [14-16]. diabetic patients is well known and Metformin is the only member of the many studies concerned with this biguanide group of oral anti-diabetic concept. Previous studies have been drugs available for use today. found that the risk of stroke and Metformin is considered the drug of cerebrovascular complication was choice for the treatment of patients with greater in diabetic patients than those type 2 diabetes mellitus. American without the disease. The risk was 3 academy of endocrinology and folds greater in patients with type 2 diabetology guidelines in 2016 diabetes mellitus than in non-diabetic mentioned the use of metformin in all population. Furthermore, morbidity and stages of diabetes and combined it with mortality that happen with stroke is other agents in high HbA1c [17, 18]. greater and more severe in diabetic Metformin is regarded as an oral anti- patients than those who are non- diabetic drug because it lowers blood diabetic [5]. Also patients with glucose concentrations in T2D without metabolic syndrome and pre-diabetic causing overt hypoglycemia. have one and half fold increase in the Metformin is also frequently risk of stroke than other population [6]. described as an insulin sensitizer This is due to multiple risk factors like leading to reduction in insulin hyperlipidemia, hypertension and resistance and significant reduction of insulin resistance which manifested as plasma fasting insulin level. The glucose intolerance. improvement in insulin sensitivity by Early microangiopathic changes are metformin could be ascribed to its also attributed to cerebrovascular positive effects on insulin receptor complication and stroke in diabetic expression and tyrosine kinase activity. patients as macrovascular compl- Metformin is the only biguanide that ications [7]. Transcranial Doppler is can be used in clinical practice [18]. In useful tool for detection of cerebral addition to anti-hyperglycemic effect of vasculopathy. It can detect systolic and metformin, it also improves endothelial diastolic velocities, resistive index and function. In this regard, it does so by pulsatility index [8-10]. Diastolic flow several mechanisms; first: it decreases in cerebral arteries is important because free fatty acids and triglycerides. the perfusion of tissues occurs during Moreover, it inhibits hepatic diastole, therefore it is important to lipogenesis and increase peripheral maintain adequate diastolic flow to fatty acids utilization [19]. Second: keep adequate cerebral perfusion and metformin mitigates oxidized LDL overcome any changes in general mediated endothelial injury [20]. Third: circulation [11]. Resistive index and it activates SIRT as well as increases its pulsatility index represent vascular expression in endothelial cells. Previous resistance [12]. Increase in resistive studies showed that increase SIRT index means decrease in compliance of activity and expression is protective

Copyright © 2016AJBM 365 American Journal of BioMedicine AJBM 2016;4(9):364-373 DOI: 10.18081/2333-5106/016-9/364-373 against endothelial injury and was unique among other oral considered as anti-atherosclerotic factor hypoglycemic agents in reduction of [21]. Fourth: metformin may increase cardiovascular morbidity and mortality endothelial NO via AMPK activation that is associated with diabetes mellitus pathway. Recent studies demonstrated [28]. Besides that, metformin reduces that metformin increases the risk of retinopathy, neuropathy and bioavailability of nitric oxide and eNOS other microvascular complications [29]. through activation of AMPK pathway Metformin also prevent cerebrovascular [22]. Furthermore, AMPK pathway disease and remodeling in diabetic activation increases the activity of patient and reduces risk of ischemic peroxisome proliferator activated stroke as well as it may reverse receptor gamma which is a transcription established diabetes-related vascular factor increases lipid oxidation and structural changes [30]. Our study is utilization in skeletal muscles as well as conducted to confirm the beneficial has important role in regulation of effect of early treatment of metformin glucose metabolism [23]. Activation of on cerebral hemodynamics in patients AMPK pathway also reduces with type 2 diabetes mellitus as endoplasmic reticulum stress which is examined by transcranial Doppler. associated with endothelial dysfunction and accelerated atherosclerotic changes Subjects and methods as well as oxidative stress [24]. Fifth Twenty patients with newly diagnosed mechanism: metformin reduces type 2 diabetes mellitus were included oxidative stress [25] and finally in our study. The study started from metformin significantly reduces November 2014 and end in October inflammatory mediators of 2016. A verbal consent was taken from atherosclerosis like adhesion molecules each participant. The study was such as VCAM and ICAM [23]. approved by Kufa Medical College In previous clinical trial where Ethical Committee for clinical trials. patients with polycystic ovarian The diabetic patients were selected syndrome used metformin, there was from center of diabetes and significant reduction in vascular endocrinology in Al Sadr medical City oxidative stress, hyperinsulinemia, in Najaf City/Iraq. They were dyslipidemia and endothelial diagnosed with diabetes mellitus type 2 dysfunction [26]. The net result of according to World Health above review is that metformin Organization definition of diabetes as improves endothelial injury and may fasting plasma glucose ≥ 7.0 mmol/L preserve endothelial function. It has (126 mg/dL), 2-hour post-load plasma been found that short-duration glucose ≥ 11.1 mmol/L (200 mg/dL) or metformin treatment mitigates arterial HbA1C ≥6.5% [31]. Patients were stiffness and endothelial dysfunction in randomly selected by endocrinologist young women with polycystic ovary after diagnosis and all of them have disease [27]. In the United Kingdom newly diagnosed type 2 diabetes. They Prospective Diabetes Study, metformin

Copyright © 2016AJBM 366 American Journal of BioMedicine AJBM 2016;4(9):364-373 DOI: 10.18081/2333-5106/016-9/364-373 underwent investigation regarding localization of middle cerebral artery fasting blood sugar and glycated spectral waveform [32, 33]. To hemoglobin. Then transcranial Doppler recognize the waveform of middle examination and measurements were cerebral artery, the waves are above under taken at TCD department/ Middle zero line in spectral wave display Euphrates Neuroscience center/ Al Sadr screen. After localization of middle Medical city/Najaf. Studies were cerebral artery waveform and getting conducted in the morning (9:00 am) the optimal signal of middle cerebral after overnight fasting and subjects artery. The means of peak systolic refrained from products containing velocity, diastolic velocity, resistive caffeine 24-hours before study sessions. index and pulsatility index of 10 The time required for every subject to cardiac cycles were automatically complete study sessions was recorded by specific TCD software of approximately 30 minutes. Digital the device. Then, patients were treated transcranial Doppler with M-mode with metformin (Glucophage) 1000mg WAKIe with continuous monitoring daily for twelve weeks. After twelve and physiological test software weeks, glycated hemoglobin level with (Atysmedical, France) and EZ-Dop transcranial Doppler examination were DWL, COMPUMEDICS, GmbH, repeated.Version 20 SPSS statistical Germany. These instruments are program was used for analysis of data. provided with head-band as probe Paired t-test was used for comparison holder for pulse-wave 2 MHz phase between means of before and after array transducer. To study the MCA treatment analysis for the same patients. blood flow velocities, the subject was asked to tilt his head to a side and to Results breath normal quiet breathing, the Mean age of patients was 44.55±1.18 MCA was first identified by Doppler years. Patients consist of seven women probe through trans-temporal window, with a ratio of 35% and 13 men with a usually M1 segment. For identification ratio of 65%. Metformin group also of middle cerebral artery, spectral wave showed a significant decrease in FBS form window was started at 20mm and from 159.25±6.24 mg/dL to then decreased gradually to 12mm to 129.1±5.37mg/dL after twelve weeks of get rid of ultrasound noise and obtain treatment with metformin 1 g/day (P accurate measure. The depth of Doppler <0.000). For metformin group HbA1c beam that was adjusted at 45-55mm, decreased from 7.76±0.26% to utilizing a trans-temporal window 6.86±0.16% (P <0.000). There was no above zygomatic arch in the pre- statistical difference in peak systolic auricular area. To obtain MCA spectral velocity between baseline reading wave form, probe is directed backward (71.35±1.84cm/sec) and post-treatment and slightly upward. The pulse wave one (72.1±1.1cm/sec) (P=0.517). On Doppler sample volume was adjusted to the hand, there was statistical maximum level in the device and the significant increase in diastolic velocity power 75 MW for identification and

Copyright © 2016AJBM 367 American Journal of BioMedicine AJBM 2016;4(9):364-373 DOI: 10.18081/2333-5106/016-9/364-373 and mean flow velocity from pulsatility index and resistive index (25.35±0.96cm/sec, 40.68±1.02 cm/sec) after treatment. Pulsatility index to (28.6±0.5 cm/sec, 43.11±0.51cm/sec) deceased from 1.14±0.04 to 1.01±0.025 respectively and p values as follow (P=0.001) and resistive index also (P<0.000 and 0.001). Metformin group decreased from 0.64±0.0134 to showed significant decrease in 0.61±0.009 (P=0.007).

Table 1. Effect of metformin on glycemic control and Doppler indices

Figure 1.

Bar charts explain the effect of metformin on systolic, diastolic and mean velocities of middle cerebral artery by TCD examination in newly diagnosed patients with type 2 DM. ** means P<0.05.

Figure 2.

Spectral wave form of right middle cerebral artery of patient with newly diagnosed type 2 DM before treatment. The yellow arrow referred to diastolic wave.

Figure 3.

Spectral waveform of right middle cerebral artery of the same patient above in Figure 2 after treatment with metformin for 12 weeks. The yellow arrow referred to diastolic velocity. There was increase in both systolic and diastolic but the latter is more with decrease in both RI and PI.

Discussion Therefore, improvement in diastolic velocity may protect the patient from Nowadays, there is clear and sufficient ischemic stroke as it keeps adequate evidence that type 2 diabetes mellitus is blood flow during diastole. Pulsatility associated with accelerated athero- index and resistive index may reflect sclerosis, therefore an increased risk of the compliance of the vessel and stroke and other vascular disease exists. therefore, high PI and/or RI may These vascular complications are indicate increase vascular resistance associated with high morbidity and and increase in arterial stiffness [15, mortality. From this point, it is of 16]. Previous studies showed that paramount importance to predict any diabetic patients have higher resistive evidence of vasculopathy and manage it index than normal population and this earlier [34]. may increase micro-and macro-vascular In our study, metformin exerted complications [32]. significant reduction in blood glucose Furthermore, it may predict the risk and HbA1c. It is well known that of cerebrovascular disease. It is clear metformin decreases insulin resistance fact that early diagnosis and treatment in all tissues especially the liver [35]. It of vascular complications in diabetic also decreases hepatic output of glucose patients is prompt and it is highly [36]. Moreover, metformin decreases β- recommended. In our study, metformin cells apoptosis and slows diabetes not only improve diastolic blood flow disease progression [37-39]. Many of velocity but it also lower resistive and these effects are mediated through pulsatility indices. No previous study AMP-kinase pathway [22, 23, 30]. was found regarding the effect of Nowadays, metformin use is metformin on cerebrovascular recommended in the onset of diabetes hemodynamics by transcranial Doppler. type 2 [17]. Furthermore, it is highly This finding further ensures the positive recommended in pre-diabetic patients cardiovascular effects of metformin. and metabolic syndrome [40]. Early use of metformin with regular Localized baseline increase in systolic exercises and dietary control delays the velocity may indicate stenosis of onset of cardiovascular complications cerebral vessel [41]. In our study, we of diabetes [42]. In a large randomized did not record abnormally high systolic clinical trial, metformin decreases the velocity and patients with high systolic risk of stroke in diabetic patients [43]. velocity that indicate variable degree of Moreover, chronic metformin treatment stenosis were excluded from our study. significantly reduces infarct size in On the other hand, diastolic velocity is animal model [44]. The mechanism important as diastolic flow is vital for beyond that is chronic metformin brain perfusion as cerebral perfusion therapy down-regulate AMPK in occurs during diastole [11, 12]. Patients cerebral vessels and decreases lactate with impaired diastolic flow have high accumulation during ischemia [42-45]. risk of developing cerebrovascular However, acute metformin treatment accident [13, 14]. during ischemic stroke may cause

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