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Review Article Effectiveness of Coenzyme Q10 Supplementation for Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis Shi-ying Zhang , 1,2 Kai-lin Yang , 1 Liu-ting Zeng , 1 Xiao-he Wu , 2 and Hui-yong Huang 1 1 Hunan University of Chinese Medicine, Changsha 410208, China 2 Jiangxi Provincial Peoples Hospital, Nanchang 330006, China Correspondence should be addressed to Xiao-he Wu; [email protected] and Hui-yong Huang; [email protected] Received 15 March 2018; Accepted 26 July 2018; Published 16 September 2018 Academic Editor: Alberto Ferlin Copyright © 2018 Shi-ying Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objective. To evaluate the eectiveness and safety of coenzyme Q10 for patients with type 2 diabetes mellitus (T2DM). Methods. Data from randomized controlled trials were obtained to assess the eects of coenzyme Q10 versus placebo or western medicine on patients with T2DM. The studys registration number is CRD42018088474. The primary outcomes included glycosylated hemoglobin, fasting blood glucose, and fasting insulin. Result. Thirteen trials involving 765 patients were included. Compared with the control group, coenzyme Q10 may decrease the HbA1c (WMD 0.29; 95% CI 0.54, 0.03; P =0 03) and the fasting blood glucose (WMD 11.21; 95% CI 18.99, 3.43; P =0 005). For fasting insulin, there is also not strong evidence that conrms which one is better because there was no statistical dierence (WMD 0.48; 95% CI 2.54, 1.57; P =0 65). Conclusion. Based on current evidence, coenzyme Q10 may assist glycemic control, decrease TG, and improve HDL-C in patients with T2DM. 1. Introduction Diabetes is one of the major global health issues. According to the World Health Organization, in 2014, about 422 million adults were suering from diabetes. In the US, more than 9% of the US population were aected by diabetes [13]. In the global population of diabetes, 90%95% are with type 2 dia- betes mellitus (T2DM). Since 1980, the global prevalence of diabetes in adults has nearly doubled. Diabetes caused 1.5 million deaths in 2012 as it relates to increased risk of cardio- vascular and other diseases [4, 5]. And according to estimates of the Diabetes Federation Diabetes Atlas, the number of patients with diabetes in 2035 will reach 592 million [6]. Patients with T2DM are at high risk of developing hyperglycemia-related cardiovascular complications such as heart disease, hypertension, stroke, retinopathy, and nephropathy. In the US, disability, loss of work, and prema- ture death caused by diabetes have resulted in a huge direct and indirect medical costs [2]. Without eective prevention and management programs, a further signicant increase in diabetes will have grave consequences on the health and lifespan of the world population [6]. At present, the treat- ment of diabetes is still lacking etiological treatment; the treatment of diabetes is mainly achieved through diabetes management including healthy eating, weight control, appropriate physical activity, antiglycemic medications, and multifactorial risk reduction [7]. T2DM occurs when the organism fails to respond to the increased blood glucose caused by the impaired β cell secre- tion and/or insulin resistance [1, 8]. Therefore, T2DM is a complex chronic disease. Oxidative stress and insulin resis- tance are recognized pathogenic mechanisms in the develop- ment and progression of T2DM and its complications [1, 9]. Insulin, secreted by β cells, plays crucial roles in many meta- bolic processes such as regulating the glucose uptake [1, 10]. Therefore, when insulin secretion is impaired, glucose uptake will also be aected. Persistent hyperglycemia will lead to the overproduction of reactive oxygen species, which can cause oxidative damage to deoxyribonucleic acid (DNA), proteins, and lipids [1, 10, 11]. Because the mitochondria are in prox- imity to the sources of reactive oxygen species, oxidative stress often leads to mitochondrial damage, resulting in Hindawi International Journal of Endocrinology Volume 2018, Article ID 6484839, 11 pages https://doi.org/10.1155/2018/6484839

Effectiveness of Coenzyme Q10 Supplementation for Type 2

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Page 1: Effectiveness of Coenzyme Q10 Supplementation for Type 2

Review ArticleEffectiveness of Coenzyme Q10 Supplementation for Type 2Diabetes Mellitus: A Systematic Review and Meta-Analysis

Shi-ying Zhang ,1,2 Kai-lin Yang ,1 Liu-ting Zeng ,1 Xiao-he Wu ,2

and Hui-yong Huang 1

1Hunan University of Chinese Medicine, Changsha 410208, China2Jiangxi Provincial People’s Hospital, Nanchang 330006, China

Correspondence should be addressed to Xiao-he Wu; [email protected] and Hui-yong Huang; [email protected]

Received 15 March 2018; Accepted 26 July 2018; Published 16 September 2018

Academic Editor: Alberto Ferlin

Copyright © 2018 Shi-ying Zhang et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Objective. To evaluate the effectiveness and safety of coenzyme Q10 for patients with type 2 diabetes mellitus (T2DM). Methods.Data from randomized controlled trials were obtained to assess the effects of coenzyme Q10 versus placebo or western medicineon patients with T2DM. The study’s registration number is CRD42018088474. The primary outcomes included glycosylatedhemoglobin, fasting blood glucose, and fasting insulin. Result. Thirteen trials involving 765 patients were included. Comparedwith the control group, coenzyme Q10 may decrease the HbA1c (WMD −0.29; 95% CI −0.54, −0.03; P = 0 03) and the fastingblood glucose (WMD −11.21; 95% CI −18.99, −3.43; P = 0 005). For fasting insulin, there is also not strong evidence thatconfirms which one is better because there was no statistical difference (WMD −0.48; 95% CI −2.54, 1.57; P = 0 65). Conclusion.Based on current evidence, coenzyme Q10 may assist glycemic control, decrease TG, and improve HDL-C in patients with T2DM.

1. Introduction

Diabetes is one of the major global health issues. Accordingto theWorld Health Organization, in 2014, about 422millionadults were suffering from diabetes. In the US, more than 9%of the US population were affected by diabetes [1–3]. In theglobal population of diabetes, 90%–95% are with type 2 dia-betes mellitus (T2DM). Since 1980, the global prevalence ofdiabetes in adults has nearly doubled. Diabetes caused 1.5million deaths in 2012 as it relates to increased risk of cardio-vascular and other diseases [4, 5]. And according to estimatesof the Diabetes Federation Diabetes Atlas, the number ofpatients with diabetes in 2035 will reach 592 million [6].Patients with T2DM are at high risk of developinghyperglycemia-related cardiovascular complications such asheart disease, hypertension, stroke, retinopathy, andnephropathy. In the US, disability, loss of work, and prema-ture death caused by diabetes have resulted in a huge directand indirect medical costs [2]. Without effective preventionand management programs, a further significant increase indiabetes will have grave consequences on the health and

lifespan of the world population [6]. At present, the treat-ment of diabetes is still lacking etiological treatment; thetreatment of diabetes is mainly achieved through diabetesmanagement including healthy eating, weight control,appropriate physical activity, antiglycemic medications, andmultifactorial risk reduction [7].

T2DM occurs when the organism fails to respond to theincreased blood glucose caused by the impaired β cell secre-tion and/or insulin resistance [1, 8]. Therefore, T2DM is acomplex chronic disease. Oxidative stress and insulin resis-tance are recognized pathogenic mechanisms in the develop-ment and progression of T2DM and its complications [1, 9].Insulin, secreted by β cells, plays crucial roles in many meta-bolic processes such as regulating the glucose uptake [1, 10].Therefore, when insulin secretion is impaired, glucose uptakewill also be affected. Persistent hyperglycemia will lead to theoverproduction of reactive oxygen species, which can causeoxidative damage to deoxyribonucleic acid (DNA), proteins,and lipids [1, 10, 11]. Because the mitochondria are in prox-imity to the sources of reactive oxygen species, oxidativestress often leads to mitochondrial damage, resulting in

HindawiInternational Journal of EndocrinologyVolume 2018, Article ID 6484839, 11 pageshttps://doi.org/10.1155/2018/6484839

Page 2: Effectiveness of Coenzyme Q10 Supplementation for Type 2

mitochondrial dysfunction. An increasing number of studieshave shown that in obese and T2DM patients, reactive oxy-gen species can aggravate the insulin resistance status andinterfere with the insulin signaling pathway through impair-ing the mitochondrial ability to oxidize fat [12, 13]. Mean-while, the abnormality in mitochondrial functionssecondary to oxidative stress is one of the mechanisms lead-ing to T2DM and T2DM-related complications [11].

Coenzyme Q10 is a lipid-soluble nutrient widely presentin living cells. Coenzyme Q10, as an effective antioxidant, canscavenge free radicals and protect cells from oxidation.Recent studies have found that T2DM patients have signifi-cantly lower levels of coenzyme Q10 than healthy people[1, 14–16], which indicates that coenzyme Q10 deficiencymay reduce the organism’s ability to counter hyperglycemia-induced oxidative stress in T2DM [17, 18]. This suggeststhat coenzyme Q10 plays an important role in the patho-genesis of T2DM [19]. Therefore, exogenous coenzymeQ10 supplements may improve the oxidative stress-induced abnormalities in mitochondrial functions, therebybettering glycemic control in patients with T2DM [20].

Therefore, the purpose of this paper is to review theavailable randomized controlled trials (RCTs) to evaluatethe effectiveness of coenzyme Q10 for T2DM. Althoughsystematic reviews and meta-analyses of the effects ofcoenzyme Q10 on the metabolic profile of diabetes melli-tus [21] and diabetes-related biomarkers [22] have beenperformed, the analysis in 2015 only showed that coen-zyme Q10 may reduce triglyceride levels, while the analy-sis in 2016 only included RCTs before 2014. Over time,more RCTs about coenzyme Q10 were published between2014 and 2018. Therefore, the results of systematic reviewsand meta-analyses need to be updated. This systematicreview and meta-analysis is a registered review with proto-col (CRD42018088474) in PROSPERO, which is aimed atevaluating the effects of coenzyme Q10 on T2DM.

2. Materials and Methods

2.1. Protocol. Study selection, assessment of eligibility criteria,data extraction, and statistical analyses were performed basedon a predefined protocol registered on PROSPERO(CRD42018088474) (see Supplementary Materials avail-able here).

2.2. Search Strategy and Study Selection. Records of coenzymeQ10 supplementation in T2DM were identified through asystematic literature search from the China National Knowl-edge Infrastructure (CNKI) Databases, Chinese BiomedicalDatabase (CBM), Cochrane Library (until Issue 2, 2018),Web of Science, Embase, Wan Fang Database (ChineseMinistry of Science and Technology), PubMed, MEDLINEComplete, ClinicalTrials.gov, and Chinese Science andTechnology Periodical Database (VIP), from their inceptionto February 2018. The search terms included CoenzymeQ10, CoQ 10, CoQ10, ubidecarenone, co-enzyme Q10,ubiquinone Q10, Bio-Quinone Q10, ubiquinone 50, ubisemi-quinone radical, ubisemiquinone, ketosis-resistant diabetesmellitus, non-insulin-dependent diabetes mellitus, stablediabetes mellitus, and type 2 diabetes mellitus. For example,the search strategy for PubMed is presented in Table 1.

Studies meeting the inclusion criteria were included inthis review (see Box 1).

2.3. Data Extraction. Three reviewers (Shi-ying Zhang,Kai-lin Yang, and Liu-ting Zeng) independently selectedthe studies and extracted the data from the studies. Disagree-ments were resolved by discussion of five reviewers (Shi-yingZhang, Kai-lin Yang, Liu-ting Zeng, Xiao-he Wu, and Hui-yong Huang). We first reviewed the titles and abstracts ofeach of the studies and excluded the articles that do not meetthe eligibility criteria. Then, we assessed the full texts of stud-ies that meet the criteria. A customized form was used to

Table 1: Search strategy for PubMed.

Database Search strategy

PubMed

(Coenzyme Q10 OR CoQ 10 OR CoQ10 OR ubidecarenone OR co-enzyme Q10 OR ubiquinone Q10 OR Bio-Quinone Q10 OR2,3-dimethoxy-5-methyl-6-decaprenylbenzoquinone OR ubiquinone 50 OR ubisemiquinone radical OR Q-ter OR

ubisemiquinone OR coenzyme Q10, (Z,Z,Z,Z,Z,Z,E,E,E)-isomer OR coenzyme Q10, ion (1-), (all-E)-isomer)AND

(Type 2 diabetes mellitus OR Diabetes Mellitus, Noninsulin-Dependent OR Diabetes Mellitus, Ketosis-Resistant OR DiabetesMellitus, Ketosis Resistant OR Ketosis-Resistant Diabetes Mellitus OR Diabetes Mellitus, Non Insulin Dependent OR Diabetes

Mellitus, Non-Insulin-Dependent OR Non-Insulin-Dependent Diabetes Mellitus OR Diabetes Mellitus, Stable OR StableDiabetes Mellitus ORDiabetes Mellitus, Type II ORNIDDMORDiabetes Mellitus, Noninsulin Dependent ORDiabetes Mellitus,

Maturity-Onset OR Diabetes Mellitus, Maturity Onset OR Maturity-Onset Diabetes Mellitus OR Maturity Onset DiabetesMellitus OR MODY OR Diabetes Mellitus, Slow-Onset OR Diabetes Mellitus, Slow Onset OR Slow-Onset Diabetes Mellitus OR

Type 2 Diabetes Mellitus OR Noninsulin-Dependent Diabetes Mellitus OR Noninsulin Dependent Diabetes Mellitus ORMaturity-Onset Diabetes OR Diabetes, Maturity-Onset OR Maturity Onset Diabetes OR Type 2 Diabetes OR Diabetes, Type 2

OR Diabetes Mellitus, Adult-Onset OR Adult-Onset Diabetes Mellitus OR Diabetes Mellitus, Adult Onset)AND

(randomized controlled trial [pt] OR controlled clinical trial [pt] OR placebo [tiab] OR drug therapy [sh] OR trial [tiab] ORgroups [tiab] OR clinical trials as topic [mesh: noexp] OR Clinical Trial OR random∗ [tiab] OR random allocation [mh] OR

single-blind method [mh] OR double-blind method [mh] OR cross-over studies)NOT

(animals [mh] NOT humans [mh])

2 International Journal of Endocrinology

Page 3: Effectiveness of Coenzyme Q10 Supplementation for Type 2

record authors, year of publication, intervention, controlgroup, outcomes, AEs, and duration.

If there is missing information in the article, reviewerswould attempt to contact the authors to obtain the data orimpute the missing data according to the Cochrane Hand-book 5.1.0 [23]. If P < 0 05, the missing standard deviationswould be imputed by a P value; if P > 0 05 or P = NS, it wouldbe imputed by using the average of candidate standarddeviations [23].

2.4. Study Quality Assessment.We assessed the risk of bias byusing the risk of a bias assessment tool based on theCochrane Handbook [24]. The criteria consist of 7 items:random sequence generation, allocation concealment, blind-ing of participants and personnel, blinding of outcomeassessment, incomplete outcome data, selective outcomereporting, and other sources of bias. The study quality assess-ment was performed by three reviewers (Shi-ying Zhang,Kai-lin Yang, and Liu-ting Zeng) independently. Disagree-ments were resolved by consensus among all five reviewers(Shi-ying Zhang, Kai-lin Yang, Liu-ting Zeng, Xiao-he Wu,and Hui-yong Huang).

2.5. Statistical Analysis. The data were analyzed by RevMan5.3 software. The dichotomous variable measure was sum-marized by risk ratio (RR) with a 95% confidence interval(CI). The continuous outcomes underwent meta-analysisusing mean differences (MD) and 95% CI. Heterogeneityamong studies was assessed using Cochrane’s Q and I2 statis-tic [25]. The fixed effect model would be used when P > 0 1and I2 < 50%. We would explore the reasons for heterogene-ity, perform the subgroup analysis, or use the random effectsmodel when P < 0 1 and I2 > 50%.

3. Results

3.1. Results of the Search. Two hundred ninety-seven articleswere found in the initial search; two hundred eighty of themwere excluded based on the title and abstract and seventeenof them were retrieved for more detailed evaluation. Finally,thirteen studies were included in this systematic review andmeta-analysis, and four were excluded (Figure 1).

3.2. Description of Included Trials and Risk of Bias in IncludedStudies. Thirteen RCTs with 765 participants met theinclusion criteria. All of them were parallel-group RCTs. In

Playford et al.’s [26] and Chew et al.’s research [27], therewere two trial groups and two control groups. According tothe Cochrane Handbook 5.1.0, we split the shared trial andcontrol groups into two groups with a smaller sample size[23] and include the four reasonably independent compari-sons [Playford 2002a (coenzyme Q10 vs. placebo), Playford2002b (coenzyme Q10 vs. Fenofibrate), Playford 2002c(coenzyme Q10+ fenofibrate vs. placebo), and Playford2002d (coenzyme Q10+ fenofibrate vs. fenofibrate) andChew 2008a (coenzyme Q10 vs. placebo), Chew 2008b(coenzyme Q10 vs. fenofibrate), Chew 2008c (coenzymeQ10+ fenofibrate vs. placebo), and Chew 2008d (coenzymeQ10+ fenofibrate vs. fenofibrate)]. Study characteristics arepresented in Table 2.

With regard to the selection bias, eight RCTs [19, 26–32]did not describe the randomization procedures, and twelveRCTs [19, 26–28, 30–37] did not describe an acceptablemethod of allocation concealment; thus, we thought thattheir risk of bias is unclear. One RCT [33] used block ran-domization, three RCTs [34, 36, 37] utilized permuted ran-dom block allocation, and one RCT used a website [35] toconduct randomization; we therefore rated them as havinga low risk of bias. One RCT [29] describes an acceptablemethod of allocation concealment, and it was rated as havinga low risk of bias. As for the performance bias and detectionbias, two trials were unclear [32, 33], but they used objectivemeasures (e.g., HbA1c, fasting insulin, and fasting glucose)and the outcome is not likely to be influenced by the lack ofblinding, while the remaining three studies used blinding;thus, we gave a low risk of bias for all. None of trials misseddata and incompletely reported the outcomes; therefore, wegave a low risk of bias. Other sources of bias were at low riskin all of the included studies. A graphical summary of therisks of bias assessment is presented in Figure 2.

3.3. Primary Outcomes

3.3.1. Glycosylated Hemoglobin. All of the RCTs reported theHbA1c at the end of treatment. Due to the high heterogeneity(τ2 = 0 20, I2 = 88%, P < 0 00001), the random effects modelwas used. As shown in Figure 3, coenzyme Q10 may decreasethe HbA1c compared with the control group (WMD −0.29;95% CI −0.54, −0.03; P = 0 03).

3.3.2. Fasting Blood Glucose. Ten RCTs [19, 27, 29–37]reported the fasting blood glucose. The random effects model

P (Participants) Patient with type 2 diabetes mellitusI (Intervention) Coenzyme Q10 with no limits on the type, dose, frequency and so onC (Comparisons) Western medicine, blanks or placeboO (Outcomes) Primary: glycosylated hemoglobin, fasting blood glucose, fasting insulin, adverse events

Secondary: HOMA-IR, blood lipids, adiponectinS (Study type) Randomized controlled trials (RCTs) assessing the effects of coenzyme Q10 for the treatment of type 2 diabetes

mellitus (with no limits on the manner by which randomization has been achieved, on blinding or on thelanguage of publication)

Box 1: Inclusion criteria.

3International Journal of Endocrinology

Page 4: Effectiveness of Coenzyme Q10 Supplementation for Type 2

was utilized because of the high heterogeneity (τ2 = 140 45,I2 = 85%, P < 0 00001). As shown in Figure 4, coenzymeQ10may decrease the fasting blood glucose compared withthe control group (WMD −11.21; 95% CI −18.99, −3.43;P = 0 005).

3.3.3. Fasting Insulin. Four RCTs [29–31, 36] reported thefasting insulin. The random effects model was used dueto the high heterogeneity (τ2 = 2 60, I2 = 77%, P = 0 005).The result showed that there is no statistically significantdifference between the coenzyme Q10 group and controlgroup in adjusting insulin (WMD −0.48; 95% CI −2.54,1.57; P = 0 65) (Figure 5).

3.4. Secondary Outcomes

3.4.1. Homeostasis Model Assessment of Insulin Resistance.Four RCTs [29–31, 36] reported HOMA-IR. Due to the highheterogeneity (τ2 = 1 56, I2 = 92%, P < 0 00001), the randomeffects model was utilized. The results showed that in impro-ving the HOMA-IR, the difference between the coenzymeQ10 group and the control group was not statistically signifi-cant (MD −0.89; 95% CI −2.25, 0.48; P = 0 20) (Figure 6).

3.4.2. Blood Lipids. Nine RCTs [19, 26, 27, 29–32, 34, 37]reported TC. The random effects model was utilizedbecause of the high heterogeneity (τ2 = 189 73, I2 = 87%,P < 0 00001). In this index, there is also not strong

evidence that confirms which one is better because therewas no statistical difference (WMD −3.53; 95% CI −12.11,5.08; P = 0 42) (Figure 7).

Seven RCTs [19, 26, 27, 30, 31, 34, 37] reported TG. Therandom effects model was utilized due to the high heteroge-neity (τ2 = 854 44, I2 = 90%, P < 0 00001). In this index,there is also not strong evidence that confirms which one isbetter (WMD −16.50; 95% CI −35.66, 2.65; P = 0 09)(Figure 8).

Eight RCTs [26, 27, 29–32, 34, 37] reported LDL-C.Due to the high heterogeneity (τ2 = 120 20, I2 = 95%, P <0 00001), the random effects model was used. The resultsshowed that in decreasing the LDL-C, the differencebetween the coenzyme Q10 group and the control groupwas not statistically significant (WMD −3.84; 95% CI−10.70, 3.03; P = 0 27) (Figure 9).

Nine RCTs [19, 26, 27, 29–32, 34, 37] reported HDL-C.The random effects model was used due to the high heteroge-neity (τ2 = 28 76, I2 = 86%, P < 0 00001). As shown inFigure 10, coenzyme Q10 may increase HDL-C levelscompared to the control group (WMD 3.53; 95% CI 0.35,6.71; P = 0 03).

3.4.3. Adiponectin. Two RCTs [33, 36] reported adiponectin.Due to the high heterogeneity (τ2 = 57 71, I2 = 92%,P = 0 0003), we used the random effects model. The resultsshowed that there was no statistically significant differencebetween the coenzyme Q10 group and the control group in

297 of records identifiedthrough database searching:

-CNKI: 2

-Cohrane Library: 1-Web of Science: 48-MEDLINE Complete: 96-ClinicalTrials.gov: 3

Total records: 297

Records a�er screening: 17Records excluded based on the title andabstract: 280

Records excluded according toinclusion/exclusion criteria: 4

Records included according toinclusion/exclusion criteria: 13

Records eventually included: 13

-Embase: 45-PubMed: 72-Wan Fang: 21

Figure 1: Flow diagram of searching and article selection.

4 International Journal of Endocrinology

Page 5: Effectiveness of Coenzyme Q10 Supplementation for Type 2

Table2:The

characteristicsof

theinclud

edstud

ies.

Stud

ySamplesize

Intervention

Relevantou

tcom

esMeanage(years)

Duration

Trial

grou

pCon

trol

grou

pTrialgrou

pCon

trol

grou

pTrialgrou

pCon

trol

grou

p

Hod

gson

etal.[28]

3836

Coenzym

eQ10

200mgor

coenzymeQ10

200mg

+feno

fibrate200mg

Placebo

orfeno

fibrate200mg

HbA

1c52

±6.41

54.4±9.88

12weeks

Playfordetal.[26]

3835

Coenzym

eQ10

200mgor

coenzymeQ10

200mg

+feno

fibrate200mg

Placebo

orfeno

fibrate200mg

HbA

1c,T

G,T

C,H

DL-C,L

DL-C

52.7±9.80

54.1±13.7

12weeks

Moazenetal.[33]

2626

Coenzym

eQ10

200mg

Microcrystalline

cellu

lose

(placebo)

Fastingbloodglucose,HbA

1c,adipo

nectin

50.67±7.01

52.79±7.66

8weeks

AkbariF

akhrabadi

etal.[29]

3230

Coenzym

eQ10

200mg

Microcrystalline

cellu

lose

(placebo)

Fastingbloodglucose,fastinginsulin

,HbA

1c,

HOMA-IR,T

C,H

DL-C,L

DL-C

56.7±6.4

54.8±6.7

12weeks

Gho

lamietal.[30]

3535

Coenzym

eQ10

100mg

Cellulose

acetate

100mg

Fastingbloodglucose,fastinginsulin

,HbA

1c,

HOMA-IR,T

C,T

G,H

DL-C,L

DL-C

52.97±1.04

53.68±1.14

12weeks

Zahedietal.[31]

2020

Coenzym

eQ10

150mg

Maize

starch

150mg

Fastingbloodglucose,fastinginsulin

,HbA

1c,

HOMA-IR,T

C,T

G,H

DL-C,L

DL-C

53.5±9.7

58.8±9.6

12weeks

Chewetal.[27]

3633

Coenzym

eQ10

200mgor

coenzymeQ10

200mg

+feno

fibrate160mg

Placebo

orfeno

fibrate160mg

Fastingbloodglucose,HbA

1c,T

C,T

G,H

DL-C,

LDL-C

62.22±7.41

63.57±8.09

24weeks

Hosseinzadeh-Attar

etal.[34]

3133

Coenzym

eQ10

200mg

Maize

starch

200mg

Fastingbloodglucose,HbA

1c,T

C,T

G,H

DL-C,

LDL-C

45.2±7.6

47.1±8.3

12weeks

Moh

ammed-Jaw

adetal.[32]

1919

Coenzym

eQ10

200mg

+antidiabeticdrugs

Antidiabeticdrugs

Fastingbloodglucose,HbA

1c,T

C,H

DL-C,LDL-

C49.37±6.65

51.63±8.13

8weeks

Erikssonetal.[19]

1211

Coenzym

eQ10

200mg

Placebo

200mg

Fastingbloodglucose,HbA

1c,T

C,T

G,H

DL-C

65±17.32

64±23.22

24weeks

Lim

etal.[35]

4040

Coenzym

eQ10

200mg

Placebo

200mg

Fastingbloodglucose,HbA

1c54

±9

53±9

12weeks

Mehrdadietal.[36]

2630

Coenzym

eQ10

200mg

Placebo

200mg

Fastingbloodglucose,fastinginsulin

,HbA

1c,

adipolin,H

OMA-IR

46±7

48±8

12weeks

Kolahdo

uzMoh

ammadietal.

[37]

3133

Coenzym

eQ10

200mg

Placebo

200mg

Fastingbloodglucose,HbA

1c,T

G,T

C,H

DL-C,

LDL-C

45.23±7.64

47.18±8.31

12weeks

5International Journal of Endocrinology

Page 6: Effectiveness of Coenzyme Q10 Supplementation for Type 2

improving the adiponectin (WMD −4.32; 95% CI −15.27,6.62; P = 0 44) (Figure 11).

3.5. Adverse Events. None of RCTs reported AEs.

4. Discussions

This study is a systematic review and meta-analysis thatregards the effects of coenzyme Q10 on T2DM patients. Itsynthesizes the results from 13 RCTs (including the newestRCTs [29–34, 36] after 2014) involving 765 participants todraw an overall conclusion. Although significant differencesbetween groups were found for some outcomes, the availableevidence shows that coenzyme Q10 may improve the glyce-mic control (decreasing the HbA1c and fasting blood glu-cose) and blood lipids (decreasing TG and increasing HDL-C), suggesting that coenzyme Q10 may assist glycemic con-trol and protect the cardiovascular system. However, thesefindings should be interpreted with caution although it seemslike that they are prospective. The unclear risk of bias for

selection bias (random sequence generation and allocationconcealment), the small number of patients, and the highheterogeneity limited the promotion of the results. In addi-tion, the lack of statistical significance of fasting insulin,HOMA-IR, TC, LDL-C, and adiponectin does not equate tono medical significance. Instead, it may mean that coenzymeQ10 may be the safer or cheaper treatment options.

Coenzyme Q10 deficiency, particularly ubiquinol (thereduced form of coenzyme Q10) deficiency, is often observedamong patients with T2DM. The ubiquinol/ubiquinone ratiois often utilized as an indicator to react to the body’s oxida-tive stress [38]. Decreased ubiquinol levels are often accom-panied by increased ubiquinone levels, suggesting that thereis an ineffective conversion between ubiquinone and ubiqui-nol. It also indicates that the body’s ability to scavenge freeradicals is reduced. Meanwhile, the impaired conversion ofubiquinone to ubiquinol is often found in many diseases[39]. Román-Pintos et al. [15] found that coenzyme Q10levels in T2DM patients were significantly lower than thosein healthy people, while their MDA levels were significantly

Random sequence generation (selection bias)

Allocation concealment (selection bias)

Blinding of outcome assessment (detection bias)

Incomplete outcome data (attrition bias)

Selective reporting (reporting bias)

Other biases

Yes (low risk)

Unclear

No (high risk)

0% 25% 50% 75% 100%

Blinding of participants and personnel (performance bias)

(a)

Zahe

di 2

014

Play

ford

200

3

Moh

amm

ed-Ja

wad

201

4

Moa

zen

2015

Meh

rdad

i 201

7

Lim

200

8

Kola

hdou

z Moh

amm

adi 2

013

Hos

sein

zade

h-At

tar 2

015

Hod

gson

200

2

Gho

lam

i 201

8

Erik

sson

199

9

Chew

200

8

Akb

ari F

akhr

abad

i 201

4

Random sequence generation (selection bias)

Allocation concealment (selection bias)

Blinding of outcome assessment (detection bias)

Incomplete outcome data (attrition bias)

Selective reporting (reporting bias)

Other biases

Blinding of participants and personnel (performance bias)

(b)

Figure 2: (a, b) The risk of bias.

6 International Journal of Endocrinology

Page 7: Effectiveness of Coenzyme Q10 Supplementation for Type 2

higher than those in healthy one. Furthermore, the ubiqui-none/ubiquinol ratio in T2DM patients was continuouslyhigher than that in normal heathy people throughout theday after breakfast, which indicates that postprandial hyper-glycemia is associated with increased oxidative stress [16].Meanwhile, exogenous coenzyme Q10 supplementation can

increase over 31% of the activity of succinate dehydrogenasein patients with T2DM [15]. The mitochondrial succinatedehydrogenase is a flavoprotein in the mitochondrial innermembrane which can donate electrons to coenzyme Q10.Since the Krebs cycle relies on succinate dehydrogenase andNADH dehydrogenase, it can be inferred that appropriate

Moazen 2015Akbari Fakhrabadi 2014Gholami 2018Zahedi 2014Chew 2008aChew 2008bChew 2008cChew 2008dHosseinzadeh-Attar 2015Mohammed-Jawad 2014Erikson 1999Lim 2008Mehrdadi 2017Kolahdouz Mohammadi 2013

Favours [coenzyme Q10] Favours [control]2001000−100−200

Total (95% CI)Heterogeneity: 𝜏2 = 140.45; χ2 = 88.46, df = 13 (P < 0.00001); I2 = 85%Test for overall effect: Z = 2.82 (P = 0.005)

Study or subgroup−3.83−9.2−16.2−15.5

1.81.8−9−9

−0.22−39.66−12.60

2.27−0.23

41.5253.816.4831.547.27.28.288.2826.8255.74181.0837.827.9334.46

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CISD263235208899311912402631

306

Total6.756.7

12.4219.83.65.43.65.42.189.64−12.6−1.81.432.18

Mean85.1648.5610.9856.746.485.46.485.432.7348.29119.8836.9334.2731.14

SD26303520108108331911403033

313

Total3.2%5.1%

10.9%4.5%10.4%10.5%10.3%10.4%8.0%3.7%0.4%7.5%7.5%7.6%

100.0%

Weight−10.58 [−47.00, 25.84]−15.90 [−41.39, 9.59]

−28.62 [−32.84, −24.40]−35.30 [−63.75, −6.85]−1.80 [−8.20, 0.76]−3.60 [−9.84, 2.64]

−12.60 [−19.34, −5.86]−14.40[−20.98, −7.82]−2.40 [−17.02, 12.22]

−49.30 [−82.46, −16.14]0.00 [−124.56, 124.56]1.80 [−14.58, 18.18]0.84 [−15.46, 17.14]−2.41 [−18.54, 13.72]−11.21 [−18.99, −3.43]

Mean differenceIV, random, 95% CI

Figure 4: Fasting blood glucose.

Akbari Fakhrabadi 2014Gholami 2018Zahedi 2014Mehrdadi 2017

Favours [coenzyme Q10] Favours [control]20100−10−20

Total (95% CI)Heterogeneity: 𝜏2 = 2.60; χ2 = 12.85, df = 13 (P < 0.005); I2 = 77%Test for overall effect: Z = 0.46 (P = 0.65)

Study or subgroup−0.47−1.93−0.650.23

17.830.736.62.1

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CISD32352026

113

Total3.12−0.42−0.22−1.06

Mean13.140.715.193.63

SD30352030

115

Total6.0%

41.8%17.9%34.3%

100.0%

Weight−3.59 [−11.35, 4.17]−1.51 [−1.85, −1.17]−0.43 [−4.11, 3.25]1.29 [−0.24, 2.82]

−0.481 [−2.54, 1.57]

Mean differenceIV, random, 95% CI

Figure 5: Fasting insulin.

Hodgson 2002Playford 2003aPlayford 2003bPlayford 2003cPlayford 2003dMoazen 2015Akbari Fakhrabadi 2014Gholami 2018Zahedi 2014Chew 2008aChew 2008bChew 2008cChew 2008dHosseinzadeh-Attar 2015Mohammed-Jawad 2014Erikson 1999Lim 2008Mehrdadi 2017Kolahdouz Mohammadi 2013

Favours [coenzyme Q10] Favours [control]420−2−4

Total (95% CI)Heterogeneity: 𝜏2 = 0.20; χ2 = 147.16, df = 18 (P < 0.00001); I2 = 88%Test for overall effect: Z = 2.22 (P = 0.03)

Study or subgroup−0.13

0.10.1−0.3−0.3−0.07−0.35−1.2−0.39−0.1−0.1−0.1−0.1−0.61−1.10.10.2

−0.62−0.61

0.741.341.341.121.120.131.850.330.850.20.20.20.20.621.96

1.20.62.38

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CIMean difference

IV, random, 95% CISD38101099263235208899311912403631

382

Total0.340.30.30.30.30.05−0.2−0.150.23−0.1−0.3−0.1−0.3−0.160.40.20

−0.2−0.17

Mean0.651.121.651.121.6521.60.441.10.20.170.20.170.911.6

2.831

0.962.08

SD36999826303520108108331911403033

384

Total7.3%3.2%2.5%3.5%2.5%4.7%4.3%7.9%5.6%7.9%7.9%7.9%7.9%7.0%3.2%0.4%6.3%6.8%3.3%

100.0%

Weight−0.47 [−0.79, −0.15]−0.20 [−1.31, 0.91]−0.20 [−1.56, 1.16]−0.60 [−1.63, 0.43]−0.60 [−1.96, 0.76]−0.12 [−0.89, 0.65]−0.15 [−1.01, 0.71]−1.05 [−1.23, −0.87]−0.62 [−1.23, −0.01]0.00 [−0.19, 0.19]0.20 [0.02, 0.38]0.00 [−0.18, 0.18]0.20 [0.02, 0.38]

−0.45 [−0.83, −0.07]−1.50 [−2.62, −0.38]0.20 [−3.58, 3.98]0.20 [−0.28, 0.68]

−0.42 [−0.83, −0.01]−0.44 [−1.54, −0.66]

−0.29 [−0.54, −0.03]

Figure 3: Glycosylated hemoglobin.

7International Journal of Endocrinology

Page 8: Effectiveness of Coenzyme Q10 Supplementation for Type 2

coenzyme Q10 level is beneficial for this cycle [40]. There-fore, based on the evidence above, the abnormalities in mito-chondrial functions secondary to oxidative stress in T2DMpatients may be potentially relieved by restoring the coen-zyme Q10 level through exogenous coenzyme Q10 supple-mentation, ultimately improving the glycemic control.

None of RCTs reported information about AEs, whichmeans that there is currently a lack of reports on AEs. How-ever, this does not mean that the intervention of coenzyme

Q10 is safe [41]. Thus, although, based on current evidences,we consider that coenzyme Q10 is a relatively safe treatment,we cannot assure it. Future clinical trials are required toreport AEs with more explanations [42].

Compared with previous reviews [21, 22], the strengthsof this systematic review and meta-analysis are that it isstrictly conducted in accordance with the protocol registeredon PROSPERO and it assesses more outcomes. It alsoincluded seven new RCTs [29–34, 37] after 2014. Of course,

Playford 2003aPlayford 2003bPlayford 2003cPlayford 2003dAkbari Fakhrabadi 2014Gholami 2018Zahedi 2014Chew 2008aChew 2008bChew 2008cChew 2008dHosseinzadeh-Attar 2015Mohammed-Jawad 2014Erikson 1999Kolahdouz Mohammadi 2013

Favours [coenzyme Q10] Favours [control]2001000−100−200

Total (95% CI)Heterogeneity: 𝜏2 = 189.73; χ2 = 107.21, df = 14 (P < 0.00001); I2 = 88%Test for overall effect: Z = 0.80 (P = 0.42)

Study or subgroup00

−19.34−19.344.9

−20.228.13.873.87

−15.47−15.47−10.32−29.22

0−10.32

34.4234.4232.8732.8733.166.8421.857.737.737.737.7326.1666.51107.1240.28

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CIMean difference

IV, random, 95% CISD101099323520889931191231

252

Total3.87

−30.943.87

−30.945

−0.8−7.5−3.87−7.73−3.87−7.732.911.4311.62.97

Mean32.4831.7132.4831.7136.157.3523.410.237.7310.237.7320.3449.6126.4537.15

SD999830352010810833191133

252

Total4.5%4.6%4.5%4.4%7.2%10.0%8.0%9.2%9.4%9.3%9.4%8.6%3.5%0.7%6.8%

100.0%

Weight−3.87 [−33.96, 26.22]30.94 [1.20, 60.68]

−23.21 [−53.40, 6.68]11.60 [−19.12, 42.32]

−40.65 [−77.96, −3.34]

−0.10 [−17.40, 17.20]−19.42 [−22.75, −16.09]

15.60 [1.57, 29.63]7.74 [−0.56, 16.04]11.60 [4.02, 19.18]

−11.60 [−19.71, −3.49]−7.74 [−15.10, −0.38]−13.22 [−24.75, −1.69]

−11.60 [−77.96, −3.34]−13.29 [−32.31, 5.73]−3.53 [−12.11, 5.06]

Figure 7: Total cholesterol.

Playford 2003aPlayford 2003bPlayford 2003cPlayford 2003dGholami 2018Zahedi 2014Chew 2008aChew 2008bChew 2008cChew 2008dHosseinzadeh-Attar 2015Erikson 1999Kolahdouz Mohammadi 2013

Favours [coenzyme Q10] Favours [control]5002500−250−500

Total (95% CI)Heterogeneity: 𝜏2 = 854.44; χ2 = 116.36, df = 12 (P < 0.00001); I2 = 90%Test for overall effect: Z = 1.69 (P = 0.09)

Study or subgroup−8.85−8.85−106.25−106.25−30.17−23.8−8.85−8.85−53.13−53.13−3.9−17.71−3.91

72.6172.6174.3874.3814.1251.7615.3715.3715.3715.3741.07302.0969.76

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CIMean difference

IV, random, 95% CISD1010

99

35208899

311231

201

Total8.85−93.48.85−93.42.28−6.417.71−35.4217.71−35.426.24

−61.986.25

Mean88.5521.2488.5521.2414.8565.217.7115.3417.7115.3448.03516.2383.21

SD99983520108108331133

203

Total4.2%6.7%4.1%6.3%11.0%8.0%10.4%10.5%10.5%10.5%9.8%0.3%7.8%

100.0%

Weight−17.70 [−90.99, 55.59]84.55 [37.46, 131.64]

−115.10 [−190.65, −39.55]−12.85 [−63.62, 37.92]

−10.16 [−47.70, 27.38]

−32.45 [−39.24, −25.66]−17.40 [−53.88, 19.08]−26.56 [−41.85, −11.27]26.57 [11.52, 41.62]

−70.84 [−85.72, −55.96]−17.71 [−32.33, −3.09]−10.14 [−31.99, 11.71]44.27 [−305.41, 393.95]

−16.50 [−35.66, 2.65]

Figure 8: Triglyceride.

Akbari Fakhrabadi 2014Gholami 2018Zahedi 2014Mehrdadi 2017

Favours [coenzyme Q10] Favours [control]1050−5−10

Total (95% CI)Heterogeneity: 𝜏2 = 1.56; χ2 = 38.17, df = 3 (P < 0.00001); I2 = 92%Test for overall effect: Z = 1.27 (P = 0.20)

Study or subgroup−0.13−1.11−0.550.15

2.110.372.690.91

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CISD32352026

113

Total1.180.480.83−0.34

Mean3.360.484.281.46

SD30352030

115

Total23.3%30.7%17.0%29.0%

100.0%

Weight−1.31 [−2.72, 0.10]−1.59 [−3.60, −1.39]−1.38 [−3.60, 0.84]0.49 [−0.14, 1.12]

−0.89 [−2.25, 0.48]

Mean differenceIV, random, 95% CI

Figure 6: Homeostasis model assessment of insulin resistance.

8 International Journal of Endocrinology

Page 9: Effectiveness of Coenzyme Q10 Supplementation for Type 2

this systematic review and meta-analysis also has limitations,including but not limited to the number of patients partici-pated which is only 765 and the heterogeneity of some out-comes. Such heterogeneity confounds the interpretation ofstatistical findings. The heterogeneity may come from thepotential discrepancies in the pharmacological effects of var-ious coenzyme Q10 preparations which may result from dif-ferent standardizations of the coenzyme Q10 manufacturing

process, dosage, duration of treatment, units of laboratorytests, and races of the selected patients or other places. There-fore, the random effects model was adopted, although it can-not completely eliminate heterogeneity.Meanwhile, the studyduration is generally short-to-medium term (mostly 12weeks), and the long-term efficacy of coenzyme Q10 is tem-porarily uncertain. Furthermore, in the included studies, thedose of CoQ10 in the experimental group was not necessarily

Playford 2003aPlayford 2003bPlayford 2003cPlayford 2003d

Gholami 2018Zahedi 2014Chew 2008aChew 2008bChew 2008cChew 2008dHosseinzadeh-Attar 2015Mohammed-Jawad 2014Kolahdouz Mohammadi 2013

Favours [coenzyme Q10] Favours [control]100500−50−100

Total (95% CI)Heterogeneity: 𝜏2 = 120.20; χ2 = 265.74, df = 13 (P < 0.00001); I2 = 95%Test for overall effect: Z = 1.10 (P = 0.27)

Study or subgroup7.727.72−3.86−3.86

−14.7916.1−0.39−0.39−1.16−1.16−6.77−22.95−6.78

34.3534.3532.8132.81

5.0617.252.542.543.693.6919.338.431.32

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CIMean difference

IV, random, 95% CISD101099

35208899311931

240

Total0

−15.440

−15.44

−15.440.58.95−5.25−0.773.873.514.783.58

Mean32.81

31.65232.8131.652

5.8820.982.323.872.323.8719.8529.2428.08

SD9998

3520108108331933

241

Total3.4%3.5%3.4%3.4%

10.1%7.8%10.1%10.0%10.0%9.9%8.5%5.1%7.0%

100.0%

Weight7.72 [−22.49, 37.93]23.16 [−6.52, 52.84]−3.86 [−34.17, 26.45]11.58 [−19.09, −39.55]

−10.36 [−24.97, 4.25]

−23.74 [−26.31, −21.17]Akbari Fakhrabadi 2014 0.2 23.6 32 0.5 23.57 35 7.9% −0.30 [−12.05, 11.45]

21.35 [9.45, 33.25]0.38 [−1.89, 2.65]

−4.26 [−7.47, −1.05]−0.39 [−3.20, 2.42]−5.03 [−8.64, −1.42]−10.27 [−19.86, −0.68]−37.73 [−59.43, −16.03]

−3.84 [−10.70, 3.03]

Figure 9: LDL-C.

Playford 2003aPlayford 2003bPlayford 2003cPlayford 2003d

Gholami 2018Zahedi 2014Chew 2008aChew 2008bChew 2008cChew 2008dHosseinzadeh-Attar 2015Mohammed-Jawad 2014Eriksson 1999

Favours [coenzyme Q10] Favours [control]100500−50−100

Total (95% CI)Heterogeneity: 𝜏2 = 28.76; χ2 = 98.43, df = 14 (P < 0.00001); I2 = 86%Test for overall effect: Z = 2.17 (P = 0.03)

Study or subgroup1.161.165.45.4

3.77−5.253.873.87−3.87−3.87−1.32−0.633.48

6.186.187.337.33

1.449.857.737.737.737.737.317.1437

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CIMean difference

IV, random, 95% CISD101099

35208899311912

252

Total−1.546.56−1.546.56

0.66−1.4−7.73−3.87−7.73−3.87−20.3−3.863.48

Mean5.796.565.796.56

1.4710.457.737.737.737.737.837.3535.29

SD9998

3520108108331911

252

Total7.3%7.1%6.9%6.6%

9.1%6.7%6.2%6.0%6.4%6.2%8.2%7.7%1.0%

100.0%

Weight2.70 [−2.68, 8.08]

−5.40 [−11.15, 0.35]6.94 [0.84, 13.04]−1.16 [−7.76, 5.44]

0.00 [−29.55, 29.55]Kolahdouz Mohammadi 2013 −1.33 13.19 31 −4.04 12.12 33 6.8% 2.71 [−3.51, 8.93]

3.11 [2.43, 3.79]Akbari Fakhrabadi 2014 −2.2 8.58 32 −0.6 8.23 30 7.9% −1.60 [−5.78, 2.58]

−3.85 [−10.14, 2.44]11.60 [4.41, 18.79]7.74 [0.16, 15.32]3.86 [−3.10, 10.82]0.00 [−7.36, 7.36]18.98 [15.27, 22.69]3.23 [−1.38, 7.84]

3.53 [0.35, 6.71]

Figure 10: HDL-C.

Moazen 2015Mehrdadi 2017

Favours [coenzyme Q10] Favours [control]50250−25−50

Total (95% CI)Heterogeneity: 𝜏2 = 57.71; χ2 = 13.05, df = 1 (P < 0.0003); I2 = 92%Test for overall effect: Z = 0.77 (P = 0.44)

Study or subgroup0.44−9.16

4.2512.52

MeanCoenzyme Q10 Control Mean difference

IV, random, 95% CIMean difference

IV, random, 95% CISD2626

52

Total−0.551.03

Mean5.157.42

SD2630

56

Total52.5%47.5%

100.0%

Weight0.99 [−1.58, 3.56]

−10.19 [−15.69, −4.69]

−4.32 [−15.27 6.62]

Figure 11: Adiponectin.

9International Journal of Endocrinology

Page 10: Effectiveness of Coenzyme Q10 Supplementation for Type 2

the same, which could lead to differences in the effect oflowering blood glucose; the difference in dosage makes itdifficult to determine the minimum effective dose of coen-zyme Q10. Finally, due to the fact that none of the trialsreported AEs, the safety of coenzyme Q10 should be inter-preted with caution. In the future, more similar high-quality randomized controlled trials are needed to amendthe results of this systematic review and meta-analysis.

5. Conclusion

Coenzyme Q10 may assist glycemic control, decrease TG,and improve HDL-C in patients with T2DM. However, thelimitations in RCTs, including small sample sizes and shortduration, make the result be interpreted cautiously. The ben-efits from long-term treatment of coenzyme Q10 beyond 6months remain to be defined by future studies. Meanwhile,more randomized, double-blind, large-sample-size trials ofcoenzyme Q10 for T2DM are needed in the future to validateor revise the result of this work.

Conflicts of Interest

We declare no competing interests.

Authors’ Contributions

Shi-ying Zhang, Kai-lin Yang, Liu-ting Zeng, Xiao-he Wu,and Hui-yong Huang are responsible for the study conceptand design. Shi-ying Zhang, Kai-lin Yang, and Liu-ting Zengare responsible for the literature searching. Shi-ying Zhang,Kai-lin Yang, Liu-ting Zeng, Xiao-he Wu, and Hui-yongHuang are responsible for the data analysis and interpreta-tion. Shi-ying Zhang, Kai-lin Yang, and Liu-ting Zengdrafted the paper. Xiao-he Wu and Hui-yong Huang super-vised the study. All authors participated in the analysis andinterpretation of data and approved the final paper.

Acknowledgments

This work is supported by the National Natural ScienceFoundation of China (no. 81373551), the Doctoral Fund ofMinistry of Education of China (no. 20134323110001), thekey projects of Hunan Department of Science and Technol-ogy (no. S2014S2032).

Supplementary Materials

CRD42018088474.pdf is the protocol of this systematicreview and meta-analysis; PRISMA 2009 checklist.doc isthe PRISMA checklist. (Supplementary Materials)

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