Menoufia Medical Journal

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 33  |  Issue : 3  |  Page : 920--925

Role of tumor necrosis factor alpha in type 2 diabetic nephropathy


Rawhia H El-Edel1, Waleed M Fathy1, Dalia H Abou-Elela1, Mahmoud M Emara2, Noran T Abo El-Khair1,  
1 Department of Clinical Pathology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Internal Medicine, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Correspondence Address:
Noran T Abo El-Khair
Faculty of Medicine, Yaseen Abdelghafar Street, Shebin Elkom 32511
Egypt

Abstract

Objectives To study the role of tumor necrosis factor alpha (TNF-α) in type 2 diabetic nephropathy (DN). Background DN, a long-term major microvascular complication of uncontrolled hyperglycemia, affects a large population worldwide. It is considered the driving cause of end-stage kidney disease. TNF-α is a proinflammatory cytokine and plays an important role in the pathogenesis and clinical outcome of DN. Patients and methods The present case–control study was conducted on three groups: group I included 20 healthy controls, group II [diabetes mellitus (DM)] included 38 patients with type 2 DM without nephropathy, and group III comprised diabetes with chronic kidney disease (DM-CKD) and included 40 patients with type 2 DM with nephropathy. TNF-α level was determined using enzyme-linked immunosorbent assay. Routine chemical tests were done using chemistry autoanalyzer, and glycated hemoglobin was measured using ion-exchange resin chromatography. Correlations were tested by Pearson's correlation analysis. Logistic regression was used to detect the most independent/affecting factor for development of the DN. Results Serum level of TNF-α in DM group was significantly higher than controls (P < 0.001); in addition, the level in DM-CKD was significantly higher than controls and DM (P < 0.001). Moreover, there was a significant positive correlation between serum levels of TNF-α and fasting blood glucose, creatinine, total cholesterol, low-density lipoprotein-cholesterol, glycated hemoglobin, and microalbumin/creatinine ratio among DM-CKD group (r = 0.042, <0.001, <0.001, <0.001, 0.027, and 0.043, respectively). Conclusion Serum TNF-α was significantly increased in patients with DM and DM-CKD but was higher in patients with DM-CKD, which designates that TNF-α can participate in progression of DM to DN and might play an important role in mediating DN.



How to cite this article:
El-Edel RH, Fathy WM, Abou-Elela DH, Emara MM, Abo El-Khair NT. Role of tumor necrosis factor alpha in type 2 diabetic nephropathy.Menoufia Med J 2020;33:920-925


How to cite this URL:
El-Edel RH, Fathy WM, Abou-Elela DH, Emara MM, Abo El-Khair NT. Role of tumor necrosis factor alpha in type 2 diabetic nephropathy. Menoufia Med J [serial online] 2020 [cited 2021 Apr 21 ];33:920-925
Available from: http://www.mmj.eg.net/text.asp?2020/33/3/920/296693


Full Text



 Introduction



Type 2 diabetes mellitus (T2DM) is one of the most prevalent chronic diseases. Prolonged hyperglycemia in patients with T2DM is the major cause of all microvascular and macrovascular complications including diabetic nephropathy (DN) which may develop at a later stage of the disease [1]. DN, the most common chronic microvascular complication of diabetes mellitus (DM), seriously affects living quality of the patients. Inflammation, cell hypertrophy, and dedifferentiation contribute to the progression of DN. The occurrence of DN is related to various factors including oxidative stress, high glucose, hemodynamics changes, and inflammatory processes [2]. DN has traditionally been considered as a nonimmune disease; however, evidence demonstrates an increase in macrophage infiltration and overproduction of leukocyte adhesion molecules in kidneys [1].

Tumor necrosis factor alpha (TNF-α) is a cell signaling protein related to systemic inflammation and is one of the cytokines that institute the acute-phase reaction. The primary role of TNF-α is in regulation of immune cells [3]. TNF-α is synthesized primarily by monocytes/macrophages, although intrinsic resident renal cells can also synthesize this cytokine. The actions of TNF-α are mediated by specific cell surface receptors. Binding of TNF-α to its receptors activates a number pathways that result in the expression of a variety of transcription factors, cytokines, growth factors, receptors, cell adhesion molecules, mediators of inflammatory processes, and acute-phase proteins; in addition, it could mediate apoptotic and necrotic cell death [4] Consequently, TNF-α accelerates the release and synthesis of inflammatory cytokines and could participate in the progression of DN. Thus, the aim of this work is to study the role of serum level of TNF-α in type 2 DN.

 Patients and Methods



The present study included 98 patients attending Internal Medicine Outpatient Clinics and Inpatient Departments of Menoufia University Hospitals, Shebin Elkom, Egypt, between September 2016 and December 2018.

They were divided into three groups: group I represented healthy controls and included 20 apparently healthy individuals, age, and sex matched with patients groups (15 males and five females), with age ranged between 36 and 65 years. The patients were divided according to their microalbumin/creatinine ratio (ACR) into two groups: ACR less than 30 mg/g as group II (DM group), which included 38 patients with DM (28 males and 10 females), with age ranged between 36 and 63 years, and ACR more than 30 mg/g as group III [DM-chronic kidney disease (CKD) group], which included 40 patients with T2DM with nephropathy (30 males and 10 females), with age ranged between 36 and 65 years. The exclusion criteria include patients with: urinary tract infection or other known renal disease, uncontrolled hypertension or congestive heart failure, fever, inflammatory, infectious, autoimmune, rheumatic, hematological, neoplastic, or other endocrine diseases.

This study was approved by the Research Ethics Committee. Written informed consent was obtained from all participants.

The following assessments were done for all participants: history taking, clinical examination, and assessment of anthropometric measurements. Overall, 10 ml of fasting venous blood sample was taken to determine fasting blood glucose (FBG), glycated hemoglobin (HbA1c), blood urea nitrogen (BUN), creatinine, total cholesterol, triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C). An aliquot of serum was stored at − 80°C till further use for the estimation of TNF-α level. Another venous sample was taken after 2 h of eating to measure 2-h postprandial (2 h PP) glucose level. Urine samples were collected to estimate microalbumin and creatinine in urine, and then ACR was calculated.

Routine biochemical investigations such as FBG and 2 h PP [5], BUN [6], serum and urine creatinine [7], total cholesterol [8], TG [8], and HDL-C [9] were carried out using Beckman coulter (Au 680) chemistry autoanalyzer using kit supplied by Beckman (Beckman, Miami, USA). LDL-C was calculated by Friedwald's and Fredrickson's formula [10]. HbA1c was measured by ion-exchange resin chromatography [11] using commercially available kits (Biotec, Church Ln, Bisley, UK). Microalbumin in urine [12] was measured using a fluorescence sandwich immunodetection method (Boditech Med Inc, Ichroma, South Korea). TNF-α was measured by enzyme-linked immunosorbent assay method [13] as per manufactures protocol (SunRed Bio, Shanghai, China).

Statistical analysis

All statistical tests were performed using SPSS, version 20 (IBM Corp., Armonk, New York, USA). For comparisons of demographic data and biochemical investigations between the studied groups, the following tests were used: χ2 test, analysis of variance test followed by Tukey, Kruskal–Wallis test followed by Dunn's, Student t test, and Mann–Whitney test. Spearman's coefficient was used for correlation. Receiver operating characteristic (ROC) curve was used to get best cutoff for TNF-α. Odds ratio and confidence interval were calculated by logistic regression analysis. The significance level was set at 0.05 or less.

 Results



The demographic data and duration of diabetes are shown in [Table 1]. The duration of diabetes was longer in DM-CKD than DM. BMI and HbA1c were significantly higher in patient groups compared with the control group (P < 0.001), whereas HbA1c was significantly higher in DM-CKD than DM (P = 0.013). ACR, BUN, creatinine, and lipid profile (total cholesterol, TG, and LDL-C) were significantly higher in DM-CKD than DM (P < 0.001). Moreover, LDL-C level was significantly higher in DM than controls (P < 0.001), whereas BUN and creatinine did not reach significant level between DM and controls (P = 490, 0.319). HDL-C levels are significantly lower in DM-CKD than DM and controls (P < 0.001), and similarly lower in DM than controls (P < 0.001) [Table 2].{Table 1}{Table 2}

Regarding serum level of TNF-α [Table 3], both patient groups had significantly higher TNF-α concentrations than controls (P < 0.001); moreover, the level in DM-CKD was higher than DM (P < 0.001). ROC curve [Figure 1] revealed that the best cutoff level of TNF-α was 155 ng/l, where sensitivity was 90.62%, specificity was 94.12%, positive predictive value was 93.5%, negative predictive value was 91.4%, and diagnostic accuracy was 92.42%. The area under the ROC curve was 0.962 (P < 0.001) (confidence interval, 0.921–1.003). TNF-α level showed a significant positive correlation with FBG, creatinine, total cholesterol, LDL-C, HbA1c, and ACR in DM-CKD (r = 0.042, <0.001, <0.001, <0.001, 0.027, and 0.043, respectively) [Table 4]. Multivariate logistic regression revealed that there was no independent risk factor for DN as the disease is multifactorial [Table 5].{Figure 1}{Table 3}{Table 4}{Table 5}

 Discussion



DN is one of the common diabetic microvascular complications that may lead to end-stage renal disease. TNF-α is a proinflammatory cytokine that plays an important role in the pathogenesis and clinical outcome of DN[1]. Both patient groups were significantly higher in BMI than the control group, with no significant difference between DM and DM-CKD. These results agreed with Doghish et al. [14], who reported that BMI did not differ between patients with DM and those with DM-CKD. However, Gupta et al. [1] reported that there was no significant difference observed in BMI between DM and DM-CKD groups compared with controls. Maric-Bilkan [15] stated that both obesity- and diabetes-related renal diseases share common initiating events, which include interactions among multiple factors which activate intracellular signaling that trigger production of cytokines and growth factors, leading to renal disease.

It was found that the duration of diabetes was longer in DM-CKD than DM. This agreed with Mahfouz et al. [16], who found that there was a significant difference regarding the duration of diabetes between DM and DM-CKD. Meanwhile, Ochodnicky et al. [17] and Motawi et al. [18] reported that there was no significant difference in the duration of diabetes between DM and DM-CKD. The relation between DN and duration of diabetes was explained by Gallagher and Suckling[19], who reported that prolonged exposure to hyperglycemia causes damage to kidney structures, either directly or through hemodynamic changes. Anders et al. [20] stated that hyperglycemia lowers sodium exposure at the macula densa, which inhibits tubuloglomerular feedback, dilates the afferent arteriole, and induces glomerular hyperfiltration, triggering podocyte barotrauma and resulting in podocyte and nephron loss.

In the present study, FBG, 2 h PP, and HbA1c were significantly higher in DM-CKD and DM compared with controls. The obtained results agreed with Motawi et al. [18], whereas Alnaggar et al. [21] and Gupta et al. [1] found that FBS and 2 h PP were significantly higher in T2DM with microalbuminuria compared with normoalbuminuria group. Saulnier-Blache et al. [2] reported that HbA1c did not differ between DM and DM-CKD. Hyperglycemia has been considered as the key initiator of kidney damage associated with DN by dysregulation of several metabolic pathways. Bedard and Krause [22] informed that hyperglycemia leads to an increase in oxidative stress by exacerbating mitochondrial generation of reactive oxygen species which cause DNA damage and contributes to apoptosis. As well, TNF-α as an inflammatory cytokine activates both cell-survival and cell-death mechanisms. Binding of TNF-α to TNF receptor-1 induces recruitment of death domain protein, which activates more additional protein mediators and transmits an activating signal from the activated receptor to signaling caspase cascade with subsequent apoptosis [23].

BUN and creatinine did not reach significance level between DM and controls; however, BUN, creatinine, and ACR in DM-CKD were higher than both DM and controls in. These results were consistent with that of Doghish et al. [14] and Dabhi and Mistry [24]. Regarding lipid profile, total cholesterol, TG, and LDL-C were significantly higher in DM-CKD as compared with DM and controls, without significant difference between DM and controls regarding total cholesterol and TG. However, HDL-C was lower in DM-CKD than DM and controls; moreover, HDL-C was lower in DM than controls. The obtained results agreed with Mahfouz et al. [16]. Moreover, Motawi et al. [18] reported that TG was higher in DM-CKD than DM and controls, but there was no significant difference between patient groups in total cholesterol, LDL-C, and HDL-C. Meanwhile, Alnaggar et al. [21] reported that there was no significant difference between DM and DM-CKD regarding lipid profile. Dyslipidemia increase macrophage activation and extracellular matrix expression in the glomeruli under diabetic conditions, leading to DN. Doghish et al. [14] reported that dyslipidemia is noted in diabetic patients with early stage of kidney injury. It is owing to impaired function of lipoprotein lipase which is localized in the endothelial cells, leading to increase in TG and decrease in HDL-C.

Both patient groups had significantly higher TNF-α concentrations than controls; in addition, DM-CKD was higher than DM. TNF-α level showed a significant positive correlation with FBG, creatinine, total cholesterol, LDL-C, HbA1c, and ACR in DM-CKD group. These results agreed with Chen et al. [3], who found that TNF-α was increased in DM-CKD and DM, but higher in DM-CKD, suggesting an elevated inflammatory burden in DN. However, Gupta et al. [1] reported that TNF-α in their studied groups did not reach statistical significance. Awad et al. [25] indicated that the cytokine TNF-α plays a vital function in the course of DN, which was primarily produced by macrophages and monocytes and had effects on peripheral insulin resistance in addition to insulin secretion, and this cytokine was cytotoxic to mesangial, epithelial, and glomerular cells that could lead to direct renal injury. Chen et al. [3] stated that TNF-α was a pleiotropic cytokine that played a critical role in mediating inflammatory processes, which was implicated in tubulointerstitial and glomerular damage.

 Conclusion



Serum level of TNF-α was significantly increased in patients with DM and DM-CKD but was higher in patients with DM-CKD, which designates that TNF-α can participate in the progression of DM to DN and might play an important role in mediating DN changes. However, owing to the complexity of DN mechanisms, the association of TNF-α in the pathogenesis needs further research and clinical confirmation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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