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Endocan in prediabetes, diabetes, and diabetes-related complications: a systematic review and meta-analysis

Diabetology & Metabolic Syndrome volume 15, Article number: 102 (2023) Cite this article

Abstract

Background

Diabetes is one of the chronic conditions with a high burden all around the world. Macrovascular and microvascular involvement are among the common mechanisms by which diabetes can impact patients’ lives. Endocan as an inflammatory endothelial biomarker has been shown to increase in several communicable and non-communicable diseases. Herein, we aim to investigate the role of endocan as a biomarker in diabetes as a systematic review and meta-analysis.

Methods

International databases, including PubMed, Web of Science, Scopus, and Embase were searched for relevant studies assessing blood endocan in diabetic patients. Estimation of the standardized mean difference (SMD) and 95% confidence interval (CI) for comparison of circulating endocan levels between diabetic patients and non-diabetic controls were conducted through random-effect meta-analysis.

Results

Totally, 24 studies were included, assessing 3354 cases with a mean age of 57.4 ± 8.4 years. Meta-analysis indicated that serum endocan levels were significantly higher in diabetic patients in comparison with healthy controls (SMD 1.00, 95% CI 0.81 to 1.19, p-value < 0.01). Moreover, in the analysis of studies with only type-2 diabetes, the same result showing higher endocan was obtained (SMD 1.01, 95% CI 0.78 to 1.24, p-value < 0.01). Higher endocan levels were also reported in chronic diabetes complications such as diabetic retinopathy, diabetic kidney disease, and peripheral neuropathy.

Conclusion

Based on our study’s findings, endocan levels are increased in diabetes, however, further studies are needed for assessing this association. In addition, higher endocan levels were detected in chronic complications of diabetes. This can help researchers and clinicians in recognizing disease endothelial dysfunction and potential complications.

Introduction

Diabetes mellitus is one of the leading health concerns worldwide with a profound impact on public health and socioeconomic development. Despite the decrease in incidence in recent years, diabetes’s prevalence is still increasing in developed countries as well as developing countries [1, 2]. Globally, type 2 diabetes mellitus (T2DM) accounts for almost 90% of the 537 million diabetes cases worldwide [3]. Based on International Diabetes Federation’s reports, 10.5% of adults aged 20–79 had diabetes in 2021, which is expected to grow to 12.2% by 2030 [4].

In addition to being a prevalent chronic disease, diabetes poses microvascular and macrovascular complications [5]. By early diagnosis and treatment, healthcare systems can reduce microvascular and macrovascular complications of diabetes which can lead to improvement in the disease’s outcome [3, 6, 7]. Moreover, in light of the high prevalence of T2DM, non-specific or only partial symptoms in the early stages, early diagnosis is particularly essential, leading to intensive studies on identifying a novel biomarker for T2DM such as endocan [5].

While T1DM is a result of autoimmune destruction and T2DM is mainly driven by β-cell dysfunction and insulin resistance [8, 9], an association is observed between diabetes mellitus and endothelial dysfunction [10]. Recent researches suggest that the endothelial and insulin signaling pathways interact, resulting in impaired vascular response and nitric oxide-dependent vasodilation, reduced cellular uptake of glucose, enhanced oxidative stress, and inflammation. As a result of all these pathophysiologic mechanisms, atherosclerosis could develop [11]. In addition to being a key factor in the development of atherosclerosis [12], endothelial dysfunction plays a critical role in its progression. In addition, it is an early indicator of diabetic vascular disease that can independently predict the cardiovascular risk [10, 13].

Previously called endothelial cell-specific molecule-1 (ESM1), endocan may be indicative of endothelial dysfunction [14]. It is a soluble dermatan sulfate proteoglycan secreted and expressed predominantly by vascular endothelial cells but can also be found in serum and plasma [15, 16]. Endocan regulates endothelium activation, permeability, and proliferation [17, 18]. Since endocan affects inflammatory and vasculoprotective signals, it might be effective in atherosclerosis and is an endothelial dysfunction marker [17]. Endocan levels have been reported to be higher in patients with endothelial damage and neovascularization, whereas normal levels are found in patients with functioning endothelial tissue [19, 20].

In this article, we reviewed the role of endocan as an endothelial marker in prediabetes, diabetes, and diabetes-related complications (retinopathy, nephropathy, and neuropathy) in addition to its diagnostic utility in special populations of diabetes (e.g., cardiovascular diseases and obstructive sleep apnea). Moreover, we compared the serum levels of endocan in diabetics with non-diabetic subjects and T2DM with non-diabetics using meta-analysis.

Methods

Search strategy

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analysis) statement was used for the conduction of the current systematic review and meta-analysis [21]. The following databases were searched from inception through February 13, 2023, with no restrictions or any filters: PubMed, Embase, Scopus, and the Web of Science. The search terms used in our study were: “diabetes” OR “diabetic” OR “pre-diabetes” OR “prediabetic” AND “Endocan” OR “ESM-1” OR “endothelial cell-specific molecule 1”. The search strategy and all the used keywords are explained in detail in Supplementary Table 1. Two independent reviewers (AK and AHB) systematically reviewed all studies with title and abstract for inclusion and the full text for the primary review. In cases of disagreements, the conclusion was finalized by a discussion with the third reviewer (BS).

Study selection

The applied inclusion criteria were (1) clinical studies that measured the blood level of endocan in patients with diabetes and compared them with the control group; (2) studies that evaluated the blood level of endocan in pre-diabetic patients and compared them with the control group. Exclusion criteria were as follows: (1) not reported endocan levels or exact endocan levels; (2) reported endocan levels in mediums other than blood (such as vitreous or gingival crevicular fluid); (3) conference abstracts, letters, or review articles.

We defined the PICO (population, intervention, control, and outcome) for selecting studies as:

(P): patients with diabetes, prediabetes, or diabetes-related complications.

(I): measuring circulating endocan levels as a biomarker in patients and controls.

(C): healthy individuals or diabetic patients without chronic comorbidities.

(O): could the peripheral endocan level significantly differentiate patients with prediabetes and diabetes from healthy individuals or the cases with diabetes-related complications from the ones without chronic complications.

Data extraction

Data extraction of the included studies was carried out by one of the reviewers (BS) and cross-checked by a second reviewer (AK). We extracted the following data: (1) first author name, publication year, publication country, and design of the study; (2) study population, the definition of diabetic and control groups; (3) type of diabetes in diabetic groups, existing diabetes complications, and comorbidities; (4) the number of participants in each group, age mean ± standard deviation (SD), sex proportions, and HbA1c mean and SD in total population; (5) main findings; and (6) plasma and/or serum endocan levels.

Quality assessment

The methodological quality of the studies was assessed by two reviewers (AK and AHB), applying the “Newcastle–Ottawa Quality Assessment Scale” (NOS) checklist [22] for cohort and case-control studies and Downs and Black guidelines for cross-sectional studies [23]. According to NOS, selection, comparability, and outcome were assessed as potential sources of bias. Each of them was categorized as “very good,” “good,” “satisfactory,” or “unsatisfactory” based on the scores of 9–10, 7–8, 5–6, and < 5, respectively. Regarding the Downs and Black system, we used the checklist customized for our included studies which are observational in nature. Hence, we only assessed items 1, 2, 3, 6, 7, 10, 11, 12, 18, 20, 21, and 22. Each item can be scored as 1 for a “Yes” answer and 0 for a “No”/”unable to determine” answer. As suggested by Ratcliffe and collaborators [24], the overall qualities of the studies were graded as “high quality” by achieving a score of > 66.8% (> 8), “medium quality” with a score of 33.4–66.7% [4,5,6,7,8], and “low quality” by a total score of < 33.3% (< 4). Quality assessment was performed by two independent reviewers (AK and AHB) and the third reviewer (BS) solved any disagreements between the two reviewers. Kappa Cohen’s [25] was also calculated for the assessment of agreement between the two independent reviewers.

Statistical analysis

Random-effect model was used for the conduction of meta-analysis. We calculated the estimation of standardized mean difference (SMD) in addition to 95% confidence interval (CI) for comparison between endocan levels in diabetic patients and controls. All the analyses were done using STATA (version 17.0, Stata Corp), and a p-value < 0.05 was considered statistically significant. We also assessed the quality of evidence and strength of recommendations based on the GRADE approach with incorporates five domains: risk of bias, inconsistency, indirectness, imprecision, and publication bias [26].

In cases of endocan levels reported in median and interquartile range or median and range, we used Luo et al. [27] and Wan et al. [28] methods to convert those data into median and SD. Using Cochrane’s Q and Higgin’s I2 test, the heterogeneity of studies was calculated. The considered heterogeneity thresholds were: ≤ 25% for low, 26–75% for moderate, and > 75% for high [29]. We conducted meta-regression based on mean age, publication year, sample size, male percentage, and HbA1c Supplementary Figs. 2–6, and subgroup analysis in regard to diabetes type and comorbidities, both in diabetic patient groups. Finally, statistical tests of Egger’s [30] and Begg’s [31] in addition to the funnel plot visual assessment were utilized to recognize publication bias.

Results

Literature search and included studies characteristics

The initial search yielded 303 results: 53 from PubMed, 66 from Web of Science, 91 from Scopus, and 93 from Embase. After the removal of the duplicates (n = 131), 172 studies remained. Title/abstract screening resulted in 56 remaining studies and full-text screening led to the exclusion of 33 studies. Manual searching also resulted in 5 studies from websites and 8 from citation searching, among which one was finally included. The most frequent reason for exclusion both in database searches screening and manual search was not reporting endocan levels. Details and flowchart of searching and exclusion reasons are shown in Fig. 1.

Fig. 1
figure 1

PRISMA flowchart summarizing the selection process of eligible studies based on inclusion/exclusion criteria

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Finally, 24 studies were included and their characteristics are described in Table 1 [32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55]. A total of 3354 patients with a mean age of 57.35 ± 8.35 years and 52.56% were male. Other than five studies in which “plasma” endocan was reported, most studies measured “serum” endocan levels [39, 40, 46, 50, 52]. One study included T1DM patients [32]; however, the majority of studies had only T2DM as their included population [33, 35, 36, 38, 39, 42, 44, 45, 47, 48, 51,52,53, 55]. All cohort and case-control studies were of high quality based on the NOS scoring system (Supplementary Table 2). Cross-sectional studies also had high qualities based on our customized Downs and Black criteria, except for Bilir et al. [36] that had a score of 7 in the overall quality assessment (Supplementary Table 3). The agreement percentage was 87.5% and Cohen’s k was 0.75 for independent quality assessments by two authors.

Table 1 Characteristics of studies evaluating endocan levels in diabetic patients
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Meta-analysis

Meta-analysis of endocan levels in serum in diabetic patients vs. healthy controls

Thirteen studies reported exact endocan levels in diabetic patients and non-diabetic ones and were included in the meta-analysis. Meta-analysis of endocan levels in diabetic patients vs. non-diabetic cases showed that there is a significantly increased level of endocan in diabetes (SMD 1.00, 95% CI 0.81 to 1.19, p-value < 0.01). The heterogeneity was moderate in this meta-analysis (I2: 62.19%). The forest plot showing this meta-analysis is illustrated in Fig. 2.

Fig. 2
figure 2

Forest plot showing meta-analysis and subgroup analysis of serum endocan levels in diabetic patients vs. healthy controls

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Four studies investigated patients with other diseases than diabetes, including obstructive sleep apnea [37], erectile dysfunction [45], coronary artery disease [49], and cirrhosis [55]. A subgroup analysis was performed for other studies without comorbidities and as shown in Fig. 2, there were increased serum endocan levels in these patients in comparison with healthy controls (SMD 1.03, 95% CI 0.79 to 1.28, p-value < 0.01, I2: 62.19%).

Publication bias assessment, meta-regression, and quality of evidence

Visual assessment of the funnel plot showed no significant source of publication bias (Supplementary Fig. 1). Similarly, Begg’s and Egger’s tests also did not indicate any sign of publication bias (p-value = 0.246 and p-value = 0.604, respectively). Meta-regression showed that none of the mean age, publication year, male percentage, sample size, and HbA1C levels had an association with the SMD of meta-analysis. Moreover, the publication year accounted for 23.01% of heterogeneity, and levels of HbA1C had R2 of 4.91% (Table 2). The bubble plots for these analyzes are illustrated in Supplementary Figs. 2–6. GRADE approach also revealed a moderate quality of analyses, due to high inconsistency which stems from the high heterogeneity observed (Table 3).

Table 2 Meta-regression of endocan levels in patients with diabetes mellitus vs. controls
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Table 3 Summary of the GRADE quality of evidence assessment
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Meta-analysis of serum endocan levels in type 2 diabetes vs. healthy control

Meta-analysis showed that endocan is statistically higher in type 2 diabetic patients (SMD 1.01, 95% CI 0.78 to 1.24, p-value < 0.01) (Fig. 3) in spite of the fact that this was associated with moderate heterogeneity (I2: 70.35%). Analysis in a subgroup of studies including patients without comorbidity resulted in the same result (SMD 1.02, 95% CI 0.74 to 1.31, p-value < 0.01). Table 3 shows that the evidence assessment of these two analyses had moderate quality.

Fig. 3
figure 3

Forest plot showing meta-analysis and subgroup analysis of serum endocan levels in type 2 diabetic patients vs. healthy controls

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Endocan in pre-diabetic patients vs. controls

Two studies investigated circulatory endocan levels in pre-diabetic patients [34, 47]. Arman et al. [34] compared endocan levels between 42 pre-diabetic and 42 healthy controls and found significantly decreased levels of endocan in patients with pre-diabetes (120 [65–185] ng/l vs. 138 [84–300] ng/l, p-value = 0.042). However, Klisic et al. [47] found comparable endocan levels between pre-diabetic patients and healthy controls (pre-diabetes: 0.308 [0.248–0.383] ng/ml vs. control: 0.282 [0.246–0.323] ng/ml; p-value > 0.05). Patients with T2DM had higher levels of endocan compared to both pre-diabetic patients and healthy controls (P < 0.01).

Endocan levels in complications of diabetes

Kidney diseases

Chen et al. [41] measured peripheral endocan in patients with diabetic kidney disease (DKD) and divided them into three groups based on proteinuria and estimated glomerularfiltration rate (eGFR): early DKD, established DKD, and advanced DKD. The early DKD group had significantly lower endocan levels (688.76 ± 274.71 pg/ml) compared to both established (691.62 ± 293.39 pg/ml) and advanced DKD groups (739.78 ± 325.70 pg/ml) (p-value < 0.05). In addition, advanced DKD was associated with statistically higher levels of endocan in comparison with established DKD (p-value < 0.05). A study conducted by Chang et al. [40] compared renal events between tertiles of endocan levels in patients with T2DM. They found no association between the occurrence of renal events and endocan levels in this prospective cohort.

The relation between albuminuria and levels of endocan in diabetic patients was investigated in two studies [42, 44]. Cikrikcioglu et al. [42] divided patients with T2DM into normo-albuminuria, microalbuminuria, and macroalbuminuria groups. They found significantly lower endocan in patients with macroalbuminuria in comparison with normo-albuminuric ones (379.96 ± 189.95 ng/l vs. 495.45 ± 344.82 ng/l; p-value = 0.039). Other comparisons between these groups resulted in insignificant differences (p-value > 0.05). In another study, Ekiz-Bilir et al. [44] found significantly higher endocan levels in patients with normo-albuminuria (1011.4 [429.9–1681.8] ng/l) and nephropathy (1175.3 [564.5–1637.5] ng/l) compared to healthy controls (680.77 [213.3–1433.1] ng/l) (p-value = 0.001 and p-value < 0.001, respectively). Moreover, patients with nephropathy had higher levels of endocan than normo-albuminuric patients (p-value = 0.011).

Retinopathy

Bozkurt et al. [38] compared endocan levels between T2DM patients without retinopathy (G2, n = 21), non-proliferative T2DM retinopathy patients (G3, n = 24), proliferative T2DM retinopathy (G4, n = 27), and healthy controls (G1, n = 28). Endocan levels were meaningfully higher in diabetic patients in comparison with non-diabetic ones and the levels were also higher in proliferative retinopathy than in non-proliferative retinopathy (G1: 170.05 ± 85.67 ng/l, G2: 333.91 ± 13.41, G3: 340.42 ± 105, G4: 472.83 ± 147; p-value < 0.05 in One Way Anova). In a study conducted by Celik et al. [39], they found significantly higher levels of endocan in diabetic patients with retinopathy and cataract compared to diabetic patients with cataracts and without retinopathy (7.69 ± 0.39 ng/ml vs. 6.58 ± 0.50 ng/ml, p-value < 0.01).

Neuropathy

In a single-blind controlled trial conducted by Bilir et al. [36], diabetic patients with peripheral neuropathy had significantly higher, compared to diabetic patients without neuropathy (1227.1 [575.9–1862.3] vs. 1043.0 [429.9–1678], p-value < 0.001) and healthy controls (1227.1 [575.9–1862.3] vs. 781.8 [213.3–1433.1], p-value < 0.001). Moreover, diabetic patients without neuropathy had significantly higher levels of endocan compared to healthy controls (1043.0 [429.9–1678] vs. 781.8 [213.3–1433.1], p-value < 0.001).

Endocan in special populations of diabetic patients

Cardiovascular diseases

Four studies evaluated circulatory endocan in diabetic patients with or without cardiovascular comorbidity [35, 49, 51, 53]. Kose et al. [49] found significantly higher levels of endocan in patients presenting with acute coronary syndrome (ACS) with diabetes compared to ACS patients without diabetes (1.02 ± 0.33 ng/ml vs. 0.81 ± 0.21 ng/ml, p-value = 0.016). A study by Lv et al. [51] compared endocan levels between diabetic patients (with or without subclinical atherosclerosis) and healthy controls. They found higher endocan concentrations in diabetic patients with subclinical atherosclerosis (1.20 ± 0.33 ng/ml) compared to diabetic patients without subclinical atherosclerosis (0.89 ± 0.28 ng/ml, p-value < 0.05) and healthy controls (0.68 ± 0.24 ng/ml). In another study by Qiu et al. [53], diabetic patients presented with ST-elevation myocardial infarction (STEMI) had higher endocan levels compared to diabetic patients without STEMI (1.25 ± 0.50 ng/ml vs. 1.09 ± 0.16, p-value < 0.05) and healthy controls without cardiovascular complications (1.03 ± 0.03 ng/ml, p-value < 0.05). Finally, Balamir et al. [35], investigated endocan levels in diabetic patients with or without endothelial dysfunction (defined by carotid intima-media thickness) and healthy controls. They found significantly higher endocan levels in diabetic patients with endothelial dysfunction compared to diabetic patients without endothelial dysfunction (475.1 [123.7–1274.6] pg/ml vs. 216.4 [60–731.6] pg/ml, p-value < 0.001).

Obstructive sleep apnea

Bingol et al. [37] evaluated endocan in patients with obstructive sleep apnea (OSA) with and without diabetes. They found comparable levels of endocan between OSA patients with and without diabetes (1.48 ± 0.86 ng/ml vs. 1.19 ± 0.3 ng/ml, p-value = 0.489).

Liver diseases

Dallio et al. [43] evaluated endocan levels in patients with non-alcoholic fatty liver disease (NAFLD) patients, diabetic patients, and healthy controls. Among patients with NAFLD, diabetic patients had significantly higher endocan levels compared to non-diabetic ones (1.56 ± 0.81 ng/ml vs. 0.72 ± 0.58 ng/ml, p-value = 0.001). Moreover, in another study by Zuwala-Jagiello et al. [55], patients with cirrhosis and diabetes had significantly higher endocan levels compared to non-diabetic patients with cirrhosis (4.08 [3.1–5.2] ng/ml vs. 2.6 [0.7–3.6], p-value < 0.01).

Erectile dysfunction

Elkamshoushi et al. [45] evaluated endocan levels in patients with erectile dysfunction (with or without T2DM) and healthy controls. Endocan levels were significantly higher in diabetic patients with erectile dysfunction compared to non-diabetic patients with erectile dysfunction (2600.83 ± 208.22 ng/ml vs. 2390.65 ± 228.72 ng/ml, p-value = 0.013).

Discussion

In the current study, we compared the level of endocan in diabetic patients and non-diabetic cases. Our meta-analysis showed that the level of serum endocan is significantly increased in patients with diabetes compared to non-diabetic controls. Patients with T2DM also have increased levels of endocan compared with healthy controls. Besides, endocan levels in neuropathy, retinopathy, or cardiovascular diseases are higher than in diabetic patients without these complications. Overall, it seems that endocan might be a possible suitable candidate for the assessment of endothelial dysfunction in diabetic patients.

At the molecular level, endocan is a soluble proteoglycan primarily released by endothelial cells. Its expression is up-regulated by inflammatory markers, including tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β, which in turn leads to the higher expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1); leukocyte migration and inflammatory response are the result of the higher expression of these cell adhesion molecules. In line, endocan levels are also elevated in other conditions, such as malignancies, inflammatory diseases, hypertension, atherosclerosis, carotid artery disease, peripheral artery disease, and sepsis [56]. Therefore, it is not surprising that it is increased in diabetes due to its inflammatory role same as other diseases.

Another rationale by which endocan might be increased is endothelial dysfunction observed in diabetes as well as other diseases. Increased plasma levels of endocan are thought to be a possible immuno-inflammatory marker that may represent endothelial activation and dysfunction and may be linked to diseases causing endothelial damage like diabetes [14, 57]. Based on experimental and clinical studies, there is a link between insulin resistance and endothelial dysfunction, for which newer anti-diabetic agents are modified to target it [58]. Moreover, since atherosclerotic events are one of the main pathways diabetes can affect health, considering the highlighted role of the endothelium in its progression [59], endocan could be suggested as a prognostic biomarker. Interestingly, endothelial dysfunction has been also reported in prediabetic conditions like impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) [60].

Based on our study’s findings, endocan is raised in diabetes-related complications such as diabetic retinopathy, neuropathy, and kidney disease. Vascular and endothelial damage in diabetic patients is correlated with many complications, such as retinopathy [61], neuropathy [62], and cardiovascular diseases [63]. As our results showed that the increased endocan levels are associated with the complications mentioned above, endocan could be used as a predictive factor for complications in diabetic patients. The association of retinopathy, neuropathy, and cardiovascular diseases with endocan levels could be explained by its role in endothelial activation, permeability, and proliferation, as well as its association with endothelial dysfunction [56]. Moreover, it has been recommended that the mechanism by which diabetes can affect macro- and microvasculature, and hence these complications, is through the release of pro-inflammatory cytokines and free radicals [64] as mentioned earlier. In the study by Abu El-Asrar et al., vitreous fluids of diabetic patients with active proliferative retinopathy were compared with those of controls. It was shown that vitreous endocan levels were higher in retinopathic patients [65]. In addition to retinopathy, diabetic macular edema, one of the most important causes of visual impairment, is also reported to be associated with an increase in blood endocan [38].

Several studies have shown a diagnostic role for endocan in kidney diseases, such as acute kidney injury (AKI), chronic kidney disease (CKD), and renal replacement therapy (hemodialysis or kidney transplantation); however, the results are conflicting, and the exact mechanism of endocan in kidney function has not fully determined [66]. Results regarding the association of endocan levels with albuminuria and DKD in diabetic patients were controversial, and more studies are required to determine the association of endocan levels with kidney diseases and their progression in patients with diabetes.

The fact that endocan was mostly increased in diabetic patients with other diseases compared with controls shows that endocan is more severely related to diabetes rather than these diseases. So, endocan is still a useful biomarker of diabetes in these patients. For sure, other studies with larger sample sizes are needed to confirm these findings.

Considering all these findings, a point of caution is that increased endocan levels could not be the only determining marker in the diagnosis of diabetes and predicting its future complications. Certainly, future studies assessing endocan levels in microvascular complications are needed to provide better insight into the use of endocan as a prognostic biomarker in diabetes. Poor glycemic control in diabetic patients is also related to more complications, and it seems that endocan levels decrease with improvement in glycemic control [14]. This finding suggests endocan as a potentially useful marker for monitoring glycemic control along with other traditional markers such as HgA1c.

Our study is the first systematic review and meta-analysis comparing the levels of endocan in diabetic patients with non-diabetic controls and investigating the correlation of endocan levels with complications in diabetic patients. While this systematic review can provide useful information about the role of endocan in diabetes and its complications, it has some limitations. The heterogenicity between the studies was high and was not reduced after excluding the studies with comorbidities other than diabetes. Besides, endocan levels could be elevated in many other diseases, and more studies are required to investigate its diagnostic ability in diabetes. Moreover, due to the low number of studies, we were unable to conduct a meta-analysis on the association of endocan levels with complications in diabetic patients.

Conclusion

In general, endocan is a biomarker that is overexpressed in diabetes, regardless of the presence of other comorbidities. Additionally, our review revealed that endocan can be associated with complications of diabetes such as diabetic nephropathy and neuropathy. As endocan is a factor of endothelial dysfunction, further studies are warranted to assess its role in the pathophysiology of diabetic complications and investigate its diagnostic and prognostic role in diabetes.

Data availability

Not applicable.

References

  1. Patterson CC, Harjutsalo V, Rosenbauer J, Neu A, Cinek O, Skrivarhaug T, et al. Trends and cyclical variation in the incidence of childhood type 1 diabetes in 26 european centres in the 25 year period 1989–2013: a multicentre prospective registration study. Diabetologia. 2019;62(3):408–17.

    Article  PubMed  Google Scholar 

  2. Dwyer-Lindgren L, Mackenbach JP, van Lenthe FJ, Flaxman AD, Mokdad AH. Diagnosed and undiagnosed diabetes prevalence by County in the U.S., 1999–2012. Diabetes Care. 2016;39(9):1556–62.

    Article  PubMed  Google Scholar 

  3. Ahmad E, Lim S, Lamptey R, Webb DR, Davies MJ. Type 2 diabetes. Lancet. 2022;400(10365):1803–20.

    Article  PubMed  Google Scholar 

  4. Sun H, Saeedi P, Karuranga S, Pinkepank M, Ogurtsova K, Duncan BB, et al. IDF Diabetes Atlas: Global, regional and country-level diabetes prevalence estimates for 2021 and projections for 2045. Diabetes Res Clin Pract. 2022;183:109119.

    Article  PubMed  Google Scholar 

  5. Long J, Yang Z, Wang L, Han Y, Peng C, Yan C, et al. Metabolite biomarkers of type 2 diabetes mellitus and pre-diabetes: a systematic review and meta-analysis. BMC Endocr Disord. 2020;20(1):174.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Hu FB. Globalization of diabetes: the role of diet, lifestyle, and genes. Diabetes Care. 2011;34(6):1249–57.

    Article  PubMed  PubMed Central  Google Scholar 

  7. Xu Y, Wang L, He J, Bi Y, Li M, Wang T, et al. Prevalence and control of diabetes in chinese adults. JAMA. 2013;310(9):948–59.

    Article  CAS  PubMed  Google Scholar 

  8. Taylor R. Type 2 diabetes: etiology and reversibility. Diabetes Care. 2013;36(4):1047–55.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  9. Paschou SA, Papadopoulou-Marketou N, Chrousos GP, Kanaka-Gantenbein C. On type 1 diabetes mellitus pathogenesis. Endocr Connect. 2018;7(1):R38–r46.

    Article  CAS  PubMed  Google Scholar 

  10. Maruhashi T, Higashi Y. Pathophysiological Association between Diabetes Mellitus and Endothelial Dysfunction. Antioxid (Basel). 2021;10(8).

  11. Zhang J. Biomarkers of endothelial activation and dysfunction in cardiovascular diseases. Rev Cardiovasc Med. 2022;23(2):73.

    Article  PubMed  Google Scholar 

  12. Balta S, Demirkol S, Celik T, Kucuk U, Unlu M, Arslan Z, et al. Association between coronary artery ectasia and neutrophil–lymphocyte ratio. Angiology. 2013;64(8):627–32.

    Article  PubMed  Google Scholar 

  13. Hamilton SJ, Watts GF. Endothelial dysfunction in diabetes: pathogenesis, significance, and treatment. Rev Diabet Stud. 2013;10(2–3):133–56.

    Article  PubMed  PubMed Central  Google Scholar 

  14. Arman Y, Akpinar TS, Kose M, Emet S, Yuruyen G, Akarsu M, et al. Effect of glycemic regulation on endocan levels in patients with diabetes: a preliminary study. Angiology. 2016;67(3):239–44.

    Article  CAS  PubMed  Google Scholar 

  15. Huang X, Chen C, Wang X, Zhang JY, Ren BH, Ma DW, et al. Prognostic value of endocan expression in cancers: evidence from meta-analysis. Onco Targets Ther. 2016;9:6297–304.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Li C, Geng H, Ji L, Ma X, Yin Q, Xiong H. ESM-1: a Novel Tumor Biomaker and its research advances. Anticancer Agents Med Chem. 2019;19(14):1687–94.

    Article  CAS  PubMed  Google Scholar 

  17. Leite AR, Borges-Canha M, Cardoso R, Neves JS, Castro-Ferreira R, Leite-Moreira A. Novel biomarkers for evaluation of endothelial dysfunction. Angiology. 2020;71(5):397–410.

    Article  CAS  PubMed  Google Scholar 

  18. Balta S, Mikhailidis DP, Demirkol S, Ozturk C, Celik T, Iyisoy A. Endocan: a novel inflammatory indicator in cardiovascular disease? Atherosclerosis. 2015;243(1):339–43.

    Article  CAS  PubMed  Google Scholar 

  19. Icli A, Cure E, Cure MC, Uslu AU, Balta S, Mikhailidis DP, et al. Endocan levels and subclinical atherosclerosis in patients with systemic Lupus Erythematosus. Angiology. 2016;67(8):749–55.

    Article  CAS  PubMed  Google Scholar 

  20. Khalaji A, Amirkhani N, Sharifkashani S, Peiman S, Behnoush AH. Systematic Review of Endocan as a Potential Biomarker of COVID-19. Angiology. 2023:00033197231152941.

  21. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. Syst Rev. 2021;10(1):89.

    Article  PubMed  PubMed Central  Google Scholar 

  22. Wells GA, Shea B, O’Connell D, Peterson J, Welch V, Losos M et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. Oxford; 2000.

  23. Downs SH, Black N. The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions. J Epidemiol Community Health. 1998;52(6):377–84.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  24. Ratcliffe E, Pickering S, McLean S, Lewis J. Is there a relationship between subacromial impingement syndrome and scapular orientation? A systematic review. Br J Sports Med. 2014;48(16):1251–6.

    Article  PubMed  Google Scholar 

  25. Viera AJ, Garrett JM. Understanding interobserver agreement: the kappa statistic. Fam Med. 2005;37(5):360–3.

    PubMed  Google Scholar 

  26. Guyatt GH, Oxman AD, Vist GE, Kunz R, Falck-Ytter Y, Alonso-Coello P, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336(7650):924–6.

    Article  PubMed  PubMed Central  Google Scholar 

  27. Luo D, Wan X, Liu J, Tong T. Optimally estimating the sample mean from the sample size, median, mid-range, and/or mid-quartile range. Stat Methods Med Res. 2018;27(6):1785–805.

    Article  PubMed  Google Scholar 

  28. Wan X, Wang W, Liu J, Tong T. Estimating the sample mean and standard deviation from the sample size, median, range and/or interquartile range. BMC Med Res Methodol. 2014;14:135.

    Article  PubMed  PubMed Central  Google Scholar 

  29. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ. 2003;327(7414):557–60.

    Article  PubMed  PubMed Central  Google Scholar 

  30. Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ. 1997;315(7109):629–34.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  31. Begg CB, Mazumdar M. Operating characteristics of a rank correlation test for publication bias. Biometrics. 1994;50(4):1088–101.

    Article  CAS  PubMed  Google Scholar 

  32. Anlk A, Çelik E, Çevik Ö, Ünüvar T, Anlk A. The relation of serum endocan and soluble endoglin levels with metabolic control in children and adolescents with type 1 diabetes mellitus. J Pediatr Endocrinol Metab. 2020;33(8):1013–8.

    Article  Google Scholar 

  33. Arman Y, Akpinar TS, Kose M, Emet S, Yuruyen G, Akarsu M, et al. Effect of glycemic regulation on endocan levels in patients with diabetes. Angiology. 2016;67(3):239–44.

    Article  CAS  PubMed  Google Scholar 

  34. Arman Y, Atici A, Altun O, Sarikaya R, Yoldemir SA, Akarsu M, et al. Can the serum Endocan Level be used as a Biomarker to predict subclinical atherosclerosis in patients with Prediabetes? Arq Bras Cardiol. 2022;119(4):544–50.

    CAS  PubMed  PubMed Central  Google Scholar 

  35. Balamir I, Ates I, Topcuoglu C, Turhan T. Association of Endocan, Ischemia-Modified albumin, and hsCRP levels with endothelial dysfunction in type 2 diabetes Mellitus. Angiology. 2018;69(7):609–16.

    Article  CAS  PubMed  Google Scholar 

  36. Bilir B, Ekiz Bilir B, Yilmaz I, Soysal Atile N, Yildirim T, Kara SP, et al. Association of apelin, endoglin and endocan with diabetic peripheral neuropathy in type 2 diabetic patients. Eur Rev Med Pharmacol Sci. 2016;20(5):892–8.

    CAS  PubMed  Google Scholar 

  37. Bingol Z, Kose M, Pihtili A, Akpinar T, Tukek T, Kiyan E. Serum endothelial cell specific molecule-1 (endocan) levels in patients with obstructive sleep apnea. Biomarkers Med. 2016;10(2):177–84.

    Article  CAS  Google Scholar 

  38. Bozkurt E, Gumus A, Koban Y. Can serum endocan level predict stage of diabetic retinopathy? Retina-Vitreus. 2020;29(4):318–23.

    Article  Google Scholar 

  39. Celik F, Aydin S. Blood and aqueous humor phoenixin, endocan and spexin in patients with diabetes mellitus and cataract with and without diabetic retinopathy. Peptides. 2022;150.

  40. Chang LH, Hwu CM, Chu CH, Lin YC, Huang CC, You JY, et al. The combination of soluble tumor necrosis factor receptor type 1 and fibroblast growth factor 21 exhibits better prediction of renal outcomes in patients with type 2 diabetes mellitus. J Endocrinol Invest. 2021;44(12):2609–19.

    Article  CAS  PubMed  Google Scholar 

  41. Chen Z, Yuan K, Yan R, Yang H, Wang X, Wang Y, et al. The role of endothelial biomarkers in predicting damp-heat syndrome in diabetic kidney disease. J Tradit Chin Med Sci. 2022;9(1):34–9.

    Google Scholar 

  42. Cikrikcioglu MA, Erturk Z, Kilic E, Celik K, Ekinci I, Yasin Cetin AI, et al. Endocan and albuminuria in type 2 diabetes mellitus. Ren Fail. 2016;38(10):1647–53.

    Article  CAS  PubMed  Google Scholar 

  43. Dallio M, Masarone M, Caprio GG, Di Sarno R, Tuccillo C, Sasso FC, et al. Endocan serum levels in patients with non-alcoholic fatty liver disease with or without type 2 diabetes mellitus: a pilot study. J Gastrointest Liver Dis. 2017;26(3):261–8.

    Article  Google Scholar 

  44. Ekiz-Bilir B, Bilir B, Aydın M, Soysal-Atile N. Evaluation of endocan and endoglin levels in chronic kidney disease due to diabetes mellitus. Archives of Medical Science. 2019;15(1):86–91.

    Article  CAS  PubMed  Google Scholar 

  45. Elkamshoushi AAM, Hassan EM, El Abd AM, Hassan SZ, Maher AA. Serum endocan as a predictive biomarker of cardiovascular risk in erectile dysfunction patients. Andrologia. 2018;50(10).

  46. Kim JS, Ko GJ, Kim YG, Lee SY, Lee DY, Jeong KH, et al. Plasma endocan as a predictor of cardiovascular event in patients with end-stage renal disease on hemodialysis. J Clin Med. 2020;9(12):1–10.

    Article  Google Scholar 

  47. Klisic A, Kavaric N, Stanisic V, Vujcic S, Spasojevic-Kalimanovska V, Ninic A, et al. Endocan and a novel score for dyslipidemia, oxidative stress and inflammation (DOI score) are independently correlated with glycated hemoglobin (HbA1c) in patients with prediabetes and type 2 diabetes. Archives of Medical Science. 2020;16(1):42–50.

    Article  CAS  PubMed  Google Scholar 

  48. Klisic A, Kavaric N, Vujcic S, Mihajlovic M, Zeljkovic A, Ivanisevic J, et al. Inverse association between serum endocan levels and small LDL and HDL particles in patients with type 2 diabetes mellitus. Eur Rev Med Pharmacol Sci. 2020;24(15):8127–35.

    CAS  PubMed  Google Scholar 

  49. Kose M, Emet S, Akpinar TS, Kocaaga M, Cakmak R, Akarsu M, et al. Serum Endocan Level and the severity of coronary artery disease. Angiology. 2015;66(8):727–31.

    Article  CAS  PubMed  Google Scholar 

  50. Kosir G, Jug B, Novakovic M, Mijovski MB, Ksela J. Endocan is an independent predictor of heart failure-related mortality and hospitalizations in patients with chronic stable heart failure. Dis Markers. 2019;2019.

  51. Lv YY, Zhang YQ, Shi WY, Liu JX, Li YH, Zhou ZB, et al. The Association between Endocan levels and subclinical atherosclerosis in patients with type 2 diabetes Mellitus. Am J Med Sci. 2017;353(5):433–8.

    Article  PubMed  Google Scholar 

  52. Moin ASM, Sathyapalan T, Atkin SL, Butler AE. Diagnostic and Prognostic Protein Biomarkers of β-Cell Function in Type 2 Diabetes and Their Modulation with Glucose Normalization. Metabolites. 2022;12(3).

  53. Qiu CR, Fu Q, Sui J, Zhang Q, Wei P, Wu Y, et al. Analysis of serum endothelial cell-specific molecule 1 (endocan) level in type 2 diabetes Mellitus with Acute ST-Segment Elevation myocardial infarction and its correlation. Angiology. 2017;68(1):74–8.

    Article  CAS  PubMed  Google Scholar 

  54. Singh R, Goyal S, Aggarwal N, Mehta S, Kumari P, Singh V, et al. Study on dengue severity in diabetic and non-diabetic population of tertiary care hospital by assessing inflammatory indicators. Ann Med Surg (Lond). 2022;82:104710.

    PubMed  Google Scholar 

  55. Zuwala-Jagiello J, Pazgan-Simon M, Simon K, Kukla M, Murawska-Cialowicz E, Grzebyk E. Serum endocan level in diabetes mellitus of patients with cirrhosis and risk of subsequent development of spontaneous bacterial peritonitis. J Physiol Pharmacol. 2019;70(3):399–405.

    CAS  Google Scholar 

  56. Balta S, Balta I, Mikhailidis DP. Endocan: a new marker of endothelial function. Curr Opin Cardiol. 2021;36(4):462–8.

    Article  PubMed  Google Scholar 

  57. Chen J, Jiang L, Yu XH, Hu M, Zhang YK, Liu X, et al. Endocan: a key player of Cardiovascular Disease. Front Cardiovasc Med. 2021;8:798699.

    Article  CAS  PubMed  Google Scholar 

  58. Takeda Y, Matoba K, Sekiguchi K, Nagai Y, Yokota T, Utsunomiya K et al. Endothelial Dysfunction in Diabetes. Biomedicines. 2020;8(7).

  59. Davignon J, Ganz P. Role of endothelial dysfunction in atherosclerosis. Circulation. 2004;109(23 Suppl 1):Iii27–32.

    PubMed  Google Scholar 

  60. Kirpichnikov D, Sowers JR. Diabetes mellitus and diabetes-associated vascular disease. Trends Endocrinol Metab. 2001;12(5):225–30.

    Article  CAS  PubMed  Google Scholar 

  61. Gui F, You Z, Fu S, Wu H, Zhang Y. Endothelial dysfunction in Diabetic Retinopathy. Front Endocrinol (Lausanne). 2020;11:591.

    Article  PubMed  Google Scholar 

  62. Maiuolo J, Gliozzi M, Musolino V, Carresi C, Nucera S, Macrì R et al. The Role of Endothelial Dysfunction in Peripheral Blood Nerve Barrier: Molecular Mechanisms and Pathophysiological Implications. Int J Mol Sci. 2019;20(12).

  63. Hadi HA, Suwaidi JA. Endothelial dysfunction in diabetes mellitus. Vasc Health Risk Manag. 2007;3(6):853–76.

    CAS  PubMed  PubMed Central  Google Scholar 

  64. Bozkurt E, Çakır B, Çelik E, Doğan E, Uçak T, Alagöz G. Correlation of the aqueous humor total antioxidant capacity, total oxidant status, and levels of IL-6 and VEGF with diabetic retinopathy status. Arq Bras Oftalmol. 2019;82(2):136–40.

    Article  PubMed  Google Scholar 

  65. Abu El-Asrar AM, Nawaz MI, De Hertogh G, Al-Kharashi AS, Van Den Eynde K, Mohammad G, et al. The angiogenic biomarker endocan is upregulated in proliferative diabetic retinopathy and correlates with vascular endothelial growth factor. Curr Eye Res. 2015;40(3):321–31.

    Article  CAS  PubMed  Google Scholar 

  66. Nalewajska M, Gurazda K, Marchelek-Myśliwiec M, Pawlik A, Dziedziejko V. The role of Endocan in selected kidney Diseases. Int J Mol Sci. 2020;21:17.

    Article  Google Scholar 

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Authors and Affiliations

  1. School of Medicine, Tehran University of Medical Sciences, Tehran, Iran

    Amirmohammad Khalaji, Amir Hossein Behnoush, Behrad Saeedian & Shaghayegh Khanmohammadi

  2. Non-Communicable Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran

    Amirmohammad Khalaji, Amir Hossein Behnoush, Shaghayegh Khanmohammadi & Zahra Shokri Varniab

  3. Pediatric Urology and Regenerative Medicine Research Center, Gene, Cell and Tissue Research Institute, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran

    Zahra Shokri Varniab

  4. Department of Internal Medicine, AdventHealth Orlando Hospital, Orlando, FL, USA

    Soheil Peiman

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AK: Writing - original draft/ Conceptualization/ Formal analysis/ Visualization, AHB: Supervision/ Writing - review & editing, BS, SK, ZSV: Writing - original draft/ Data curation, SP: Writing - review & editing. All authors read and approved the final manuscript.

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Supplementary Table 1

. Search details. Supplementary Table 2. Quality Assessment based on the Newcastle-Ottawa Scale (NOS). Supplementary Table 3. Qualities of cross-sectional studies based on Downs and Black criteria. Supplementary Figure 1. Funnel plot for the meta-analysis of endocan levels in diabetes. Supplementary Figure 2. Bubble plot for meta-regression based on mean age. Supplementary Figure 3. Bubble plot for meta-regression based on publication year. Supplementary Figure 4. Bubble plot for meta-regression based on HbA1C levels in diabetic patients. Supplementary Figure 5. Bubble plot for meta-regression based on the male percentage. Supplementary Figure 6. Bubble plot for meta-regression based on the sample size.

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Khalaji, A., Behnoush, A., Saeedian, B. et al. Endocan in prediabetes, diabetes, and diabetes-related complications: a systematic review and meta-analysis. Diabetol Metab Syndr 15, 102 (2023). https://doi.org/10.1186/s13098-023-01076-z

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Keywords

Diabetology & Metabolic Syndrome

ISSN: 1758-5996

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