Nigerian Journal of Clinical Practice

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 22  |  Issue : 6  |  Page : 750--753

Up-regulation of hypoxia inducible Factor-1α in patients with diabetic nephropathy


J Wang, S Ye 
 Department of Endocrinology, Anhui Provincial Hospital, Hefei, China

Correspondence Address:
Dr. S Ye
Department of Endocrinology, Anhui Provincial Hospital, Hefei 230001
China

Abstract

Objective: To study the role of hypoxia inducible factor-1α (HIF-1α) in patients with diabetic nephropathy (DN). Methods: In total, 133 participants were selected to conduct the investigation, parameters such as fasting blood sugar (FBS), blood urea nitrogen (BUN), and urine albumin-creatinine ratio (UACR) were tested and recorded. The biopsy assessment was conducted when renal function or urinary abnormalities. Western blotting was used to test the expression of serum HIF-1α in all patients and control group. Results: The values of FBS, BUN, and UACR were higher in DN and diabetes groups than in the healthy control. The values of FBG, BUN, and UACR were higher in DN patients than in the diabetes patients with no nephropathy. eGFR in DN patients was lower than the other two groups. The expression of HIF-1α was higher than both diabetes patients with no nephropathy and healthy control, P < 0.05. Patients with lots of albuminuria showed the highest expression of HIF-1α than the other groups. HIF-1α in normoalbuminuria and microalbuminuria groups showed no significant difference. Conclusions: HIF-1α was up-regulated in DN patients, which might give clinical basis to the role of HIF-1α in the development of DN.



How to cite this article:
Wang J, Ye S. Up-regulation of hypoxia inducible Factor-1α in patients with diabetic nephropathy.Niger J Clin Pract 2019;22:750-753


How to cite this URL:
Wang J, Ye S. Up-regulation of hypoxia inducible Factor-1α in patients with diabetic nephropathy. Niger J Clin Pract [serial online] 2019 [cited 2019 Sep 16 ];22:750-753
Available from: http://www.njcponline.com/text.asp?2019/22/6/750/260037


Full Text



 Introduction



Diabetic nephropathy (DN) is one of the various complications of diabetes mellitus, it is also the main causes of morbidity and mortality for diabetic patients, which is characterized as features such as high urinary albumin excretion rate, abnormal plasma creatinine level, abnormal glomerular filtration rate (eGFR), and calculated creatinine clearance.[1] DN will induce renal failure or other renal diseases in western countries affecting 20–40% patients requiring dialysis or transplantation.[2] In developing countries, the incidence of DN is also increasing rapidly.[3] Studies showed that diabetes with proteinuria is a high-risk factor of end-stage renal disease (ESRD) for diabetic patients[4],[5] and the incipient DN, which is recognized as a common characteristics of microalbuminuria remission/regression for both type 1 and type 2 diabetes mellitus.[6] Research for progression of DN demonstrate that DN has a close relationship with lots of biological progresses such as oxidative stress,[7] inflammation,[8] and hypoxia.[9] However, a deeper understanding for mechanisms of DN is still insignificant.

It has been proved that hypoxia is an acknowledged pathway for nephropathy and is related to the mechanism of DN development.[9] Hypoxia-inducible factor-1 (HIF-1) is the primary moderator in process of intracellular redox balance.[10] It allows the adaptive responses to hypoxia by participating in the progress of energy metabolism in cells, alimentation, glucose transport, angiogenesis, and so on. HIF-1 can also regulate particular genes, for instance, erythropoietin and vascular endothelial growth factor A or enzymes, which are involved in hypoxia or glucose metabolism.[11] HIF-1α is one of the two subunits of HIF-1 that has been proved to play an important role in process of cellular hypoxia. The degradation of HIF-1α is critically relied on the regulation of HIF-1 activity.[12] Recently, several studies showed that HIF-1α is up-regulated in DN animals.[13],[14] However, to our best knowledge, HIF-1α in DN patients has not been reported yet. In the current research, our group investigated the expression condition of HIF-1α in DN patients and studied the relationship between HIF-1α and DN risk factors.

 Subjects and Method



Subjects

This study selected a total of 133 participants including 61 patients with type 2 diabetes without nephropathy, 49 patients with DN, and 23 healthy individuals as a control at Anhui provincial hospital during January 2012 to December 2016. The type 2 diabetes mellitus was diagnosed according to the WHO diagnostic standard in 1999.[15] Nephropathy was identified according to the historical eGFR, which is estimated in diabetes patients:[16] diabetic but no nephropathy, historical eGFR >90; DN, historical eGFR <60; healthy, no diabetes, and eGFR >90. Historical eGFR was according to the patients' medical records and was confirmed again before the study. Among the DN patients, patients were further divided into normoalbuminuria, urine albumin-creatinine ratio (UACR) <30 mg/g; micro-albuminuria, UACR within 30–300 mg albumin/g creatinine) and large amount of albuminuria, UACR >300 mg/g.[17] Other parameters such as fasting blood sugar (FBS) and blood urea nitrogen (BUN) were also tested and recorded.

Patients who had other kidney or urinary system diseases, severe cardiovascular or hepatic diseases, severe infection, pregnant, surgery, cancer, and patients who had used drugs that might affect level of serum HIF-1α such as rapamycin or had used agents that might affect urinary albumin excretion rate such as ACE inhibitor 1 month before the study were excluded. Detailed clinical data for all patients' inflammation were showed in

[Table 1]. The research was agreed with Ethic committee of Anhui provincial hospital. Informed consents were acquired from all participants involved in this study.{Table 1}

Biopsy assessment

The biopsy assessment was conducted when renal function or urinary abnormalities was not consistent with the clinical expression or the natural history of DN. Tissue samples were fixed in buffered formalin and then deal with paraffin blocks and to tested by using light microscopy. Sections were treated by Masson's staining.

Evaluation of HIF-1α

Western blotting experiment was conducted to test serum HIF-1α expression in all patients and the control. GAPDH was used as a control. Proteins were extracted from the serum samples by the following standard method which is described elsewhere.[18] Then samples were loaded on SDS-PAGE and transferred to PVDF membranes. The membranes were then incubated with a main antibody following a conjugated secondary antibody. The films were scanned by using the EasySee Western Blot Kit (Beijing TransGen Biotech, Beijing, China).

Statistical analysis

Measurements were presented as the mean ± SD, and comparisons were conducted or using student's t test and one-way analysis of variance with SPSS version 19.00 (SPSS Inc., Chicago, IL, USA). Prognostic factors for the overall and disease-free survival of DN were analyzed using the Cox regression model. Probability values < 0.05 were considered statistically significant.

 Results



Clinical information of all patients

The present study involved a total of 133 participants including 61 patients with type 2 diabetes but no nephropathy, 49 patients with DN, and 23 healthy individuals. As shown in [Table 1], the clinical characteristics of all participants showed that no significant difference was observed in age, gender, and body mass index among different groups. However, the values of FBS, BUN, and UACR were all significantly higher in DN and diabetes groups than in the healthy control. Meanwhile, the values of FBG, BUN, and UACR were also all significantly higher in DN patients compared with the diabetes patients with no nephropathy. There was a significant lower of eGFR in DN than other two groups.

Histological analysis

To confirm the injury of renal tissues in DN patients, the biopsy assessment was conducted when the renal function or urinary abnormalities was inconsistent with the clinical expression or the natural history of DN. As shown in [Figure 1], no obvious lesion was observed in diabetes patients with no nephropathy. However, in DN patients, pathological changes of degeneration atrophy and fibrosis appeared in tubulointerstitial, indicating apparent renal injury of the DN patients.{Figure 1}

Expression of HIF-1α in different group of patients

To further investigate different HIF-1α expression in DN patients, DN patients were further divided into normoalbuminuria (n = 8), microalbuminuria (n = 12), and large amount of albuminuria (n = 29) groups according to UACR. The HIF-1α expression was detected by using Western blotting. Results showed that in DN patients, HIF-1α expression was obviously higher than both diabetes patients with no nephropathy and healthy control, P < 0.05 [Figure 2]. In addition, HIF-1α expression in large amount of albuminuria group was significantly higher than other groups. However, HIF-1α in normoalbuminuria and micro-albuminuria groups showed no significant difference. There is also no obvious difference in diabetes patients with no nephropathy compared with the healthy control. These results showed that HIF-1α was obviously up-regulated in the patients who had DN, and the abnormal expression could be correlated with nephropathy induced by diabetes.{Figure 2}

 Discussion



Although studies have demonstrated the pathological process of DN, molecular mechanisms of DN remained unclear. Hypoxia has been proposed to play a central pathogenic role in process of renal diseases. The reducing of oxygen delivery and increasing of oxygen consumption were considered to be the cause of renal hypoxia in diabetes. Recently, the role of HIF-1α in the process of DN has attracted scholars' attention. Studies showed that diabetes has a complicated inhibitory effect on HIF-1α and can preclude its optimal reaction to hypoxia.[10],[19] Ries et al. showed that HIF-1 could be determined by magnetic resonance imaging in the outer medulla of diabetic animals at the early stage.[20] Gu et al. also showed that HIF-1α pro582Ser polymorphism had a protective association with DN in male subjects.[21] However, up to now, no studies focused on clinical HIF-1α expression in the patients who had DN. In the current research, we determined HIF-1α expression in DN patients and found that HIF-1α was obviously up-regulated.

The present study involved a total of 53 participants including 21 patients with type 2 diabetes but no nephropathy, 19 patients with DN, and 13 healthy individuals. A comparison was made among different groups to see different HIF-1α expression. Results showed that HIF-1α was obviously up-regulated in DN patients. Patients with a large amount of albuminuria showed the highest expression of HIF-1α. In addition, histological analysis demonstrated renal injury was obvious in DN patients. Some similar studies that used animal models have been reported before. Ortega et al. studied the function of HIF-1α in serious renal injury in diabetic mice with experimental endotoxemia, results showed that the high expression of both HIF-1 and VEGF.[22] Matoba et al. demonstrated that down-regulating the expression of HIF-1α could inhibit the development of type 2 DN mice.[13] Gao et al. found that by reducing the expression of HIF-1α, the levels of pro-inflammatory IL-6 and TNF-α could be decreased in streptozotocin induced rats with diabetic retinopathy.[14] All these results were inconsistent with the present study and can illuminate the possible relationship between HIF-1α and DN.

In conclusion, we determined that HIF-1α was up-regulated in DN patients. This study may give a clinical basis to the function of HIF-1α in the progression of DN, and further studies are needed to make deeper insights.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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