The emerging role of fibroblast growth factor 21 in diabetic nephropathy

Therapeutic effect and mechanism of combined use of FGF21 and insulin on diabetic nephropathy

Although FGF21 ameliorates diabetic nephropathy (DN), the efficacy is not satisfactory. Studies demonstrate that FGF21 combined with Insulin exhibits reciprocal sensitization on glucose and lipid metabolism in mice with type 2 diabetes. However, therapeutic effect of combined use of FGF21 and Insulin on DN has not been reported. Therefore, this study explored therapeutic effect and mechanism of combined use of FGF21 and Insulin on DN. Our results showed that compared with Insulin or FGF21 alone, FGF21 combined with Insulin further ameliorated blood glucose, HbAlc, OGTT, renal function, liver function, blood lipid, histopathological changes, oxidative stress and AGEs in the mice of DN (BKS-Lepr^em2Cd479/Gpt). Moreover, FGF21 combined with Insulin further reduced expressions of IL-1β, IL-6, TNF-α via promoting M1 type macrophage into M2 type macrophage. Results of real-time PCR and Western blot showed that FGF21 combined with Insulin upregulated the expressions of autophagy related genes LC3-Ⅱ and BCL-1. Mesangial cells play an important role in the pathological changes of DN mice. However, the effect of FGF21 on mesangial cells has not been reported. In this study, d-glucose was used in high glucose (HG) model in mesangial cells. The results showed that FGF21 significantly reduced the levels of OS, AGEs and cell overproliferation. Meanwhile, FGF21 significantly ameliorated autophagy level via upregulating the phosphorylation of AMPK and downregulating phosphorylation of mTOR. These effects were reversed in siRNA-β-klotho transfected mesangial cells. In conclusion, our results demonstrate that combination FGF21 with Insulin exhibits a better therapeutic effect on DN compared with FGF21 or Insulin alone. This study provides a theoretical basis for combined used of FGF21 and Insulin as a new treatment for DN and further provides theoretical support for application of FGF21 in treatment of DN.

Therapeutic Effects of Fibroblast Growth Factor-21 on Diabetic Nephropathy and the Possible Mechanism in Type 1 Diabetes Mellitus Mice

BACKGROUND

Fibroblast growth factor 21 (FGF21) has been only reported to prevent type 1 diabetic nephropathy (DN) in the streptozotocin-induced type 1 diabetes mellitus (T1DM) mouse model. However, the FVB (Cg)-Tg (Cryaa-Tag, Ins2-CALM1) 26OVE/PneJ (OVE26) transgenic mouse is a widely recommended mouse model to recapture the most important features of T1DM nephropathy that often occurs in diabetic patients. In addition, most previous studies focused on exploring the preventive effect of FGF21 on the development of DN. However, in clinic, development of therapeutic strategy has much more realistic value compared with preventive strategy since the onset time of DN is difficult to be accurately predicted. Therefore, in the present study OVE26 mice were used to investigate the potential therapeutic effects of FGF21 on DN.

METHODS

Four-month-old female OVE26 mice were intraperitoneally treated with recombinant FGF21 at a dose of 100 μg/kg/day for 3 months. The diabetic and non-diabetic control mice were treated with phosphate-buffered saline at the same volume. Renal functions, pathological changes, inflammation, apoptosis, oxidative stress and fibrosis were examined in mice of all groups.

RESULTS

The results showed that severe renal dysfunction, morphological changes, inflammation, apoptosis, and fibrosis were observed in OVE26 mice. However, all the renal abnormalities above in OVE26 mice were significantly attenuated by 3-month FGF21 treatment associated with improvement of renal adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) activity and sirtuin 1 (SIRT1) expression.

CONCLUSION

Therefore, this study demonstrated that FGF21 might exert therapeutic effects on DN through AMPK-SIRT1 pathway.

Fibroblast growth factor 21 in lipid metabolism and non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in several developed countries, ranging from simple non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH) and cirrhosis. Currently, NAFLD has been confirmed to be associated with dyslipidemia, insulin resistance, and pre-diabetes, which are always grouped together as metabolic syndrome. Fibroblast growth factor 21 (FGF21) plays an important role in liver pathophysiology with multiple metabolic functions. Accumulating evidence has shown that FGF21 could directly modulate lipid metabolism and reduce lipid accumulation in hepatocytes through an insulin-independent pathway, thus suppressing the pathogenesis of NAFLD. Furthermore, treatment with FGF21 could obviously reverse NAFLD and synergistically alleviate obesity and counteract insulin resistance. In this review, we summarize the current knowledge of FGF21 and the evidence of FGF21 as an important regulator in hepatic lipid metabolism. The mechanisms by which FGF21 affects the pathogenesis of NAFLD would also be proposed for the further understanding of FGF21.

Association of OSAHS Hypoxia Indicators with Early Renal Injury and Serum Fibroblast Growth Factor 21 in Obese Type 2 Diabetic Patients

OBJECTIVE

This study aimed to explore the association of obstructive sleep apnea-hypopnea syndrome (OSAHS) hypoxia indicators with early renal injury and serum fibroblast growth factor 21 (FGF21) in obese type 2 diabetic patients.

METHODS

A total of 109 obese patients with type 2 diabetes mellitus (T2DM) were recruited, including 70 males and 39 females, with an average age of 52.77 ± 13.57 years and average BMI of 29.08 ± 4.36 kg/m2. Overnight sleep monitoring was performed with a portable monitor to record respiratory parameters [apnea-hypopnea index (AHI), oxygen desaturation index (ODI), lowest oxygen saturation (LSaO2), mean oxygen saturation (MSaO2/MPO2) and cumulative time of oxygen saturation < 90% (CT < 90%)]. Ultrasonography was done to detect the quantitative liver fat content (LFC). The urine microalbumin and creatinine ratio (ACR) were determined by immunoturbidimetry. FGF21 was measured at baseline by enzyme-linked immunosorbent assay. Patients were divided into the proteinuria group (n = 42) and non-proteinuria group (n = 67). Correlation analysis and multivariate linear regression analysis were used to analyze the related data. In addition, patients were divided into the T2DM without OSAHS group (n = 16) and T2DM with OSAHS group (n = 93) according to the AHI value. The correlation analysis was used to assess the relationship between FGF21 and clinical variables.

RESULTS

(1) ACR positively correlated with waist circumference (WC), AHI, ODI, CT < 90% and LFC, but negatively with MSaO2 and LSaO2. (2) AHI, ODI, CT < 90% and LFC were independent risk factors for ACR, LSaO2 and MSaO2 was a protective factor. (3) Serum FGF21 decreased in the OSAHS group compared with the non-OSAHS group. After adjustment for age, WC and TG, FGF21 correlated negatively with AHI, but positively with MSaO2.

CONCLUSIONS

AHI, ODI, CT < 90% and LFC are independent risk factors for ACR. FGF21 is associated with hypoxia indicators, and improving OSAHS status and reducing liver fat content may be helpful for the prevention and treatment of early diabetic nephropathy (DN).

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR-IOR-15006225.