Fibroblast Growth Factor 21 Mimetics for Treating Atherosclerosis

Higher fasting fibroblast growth factor 21 was associated with a greater decline in postprandial blood pressure

BACKGROUND

A fall in blood pressure (BP) following a meal is well known and is usually a transient phenomenon, due to appropriate cardiovascular adjustments. Older individuals and those with high BP experience a greater postprandial fall that can manifest as postprandial hypotension (PPH). Fibroblast growth factor 21 (FGF21) is positively associated with BP, and is known to increase after meal ingestion. We explored whether fasting FGF21 or its postprandial change would be associated with meal induced BP change, after accounting for several covariates.

METHODS

Eighty-three Western Australian adults were studied. Supine resting BP was recorded and an oral glucose test was administered. Serial measurements of systolic BP (SBP) and diastolic BP (DBP) were then made in duplicate every 30 min up to 120 min. Fasting and 120 min blood samples were analysed for FGF21 and clinical chemistry. Multiple linear regression analyses of the incremental area under curve of postprandial SBP and DBP was conducted on 12 known determinants.

RESULTS

The final parsimonious model based on backward regression of postprandial SBP included fasting SBP, gender, fasting insulin and fasting FGF21 (β = -0.009 (95% confidence interval (CI): 0.017, -0.002, P = 0.015)). For postprandial DBP these included fasting DBP, gender, fasting glucose, fasting insulin and fasting FGF21 (β = -0.005; 95% CI: 0.010, -0.001, P = 0.021).

CONCLUSIONS

A higher fasting FGF21, independent of glucose and insulin, was associated with a greater postprandial decline in SBP and in DBP.

Potential role of fibroblast growth factor 21 in the deterioration of bone quality in impaired glucose tolerance

PURPOSE

Findings on trabecular bone score (TBS), an index of bone quality, have been reported in prediabetes defined by impaired fasting glucose or HbA1c. Here, we assessed the bone mineral density (BMD) and TBS in prediabetes individuals with impaired glucose tolerance (IGT), and investigated the association of these bone parameters with serum levels of fibroblast growth factor 21 (FGF21), a hormone implicated in bone metabolism and with higher levels in IGT.

METHODS

Chinese postmenopausal women aged 55-80 years, without diabetes, were recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study in 2016-2018. Normal glucose tolerance (NGT) was defined by fasting glucose < 5.6 mmol/L and 2-h plasma glucose (2hG) < 7.8 mmol/L, and IGT by 2hG 7.8-11 mmol/L. Serum levels of FGF21 and other bone metabolism regulators were measured. Insulin sensitivity was assessed by the Matsuda index. Independent determinants of TBS were evaluated using multivariable stepwise linear regression.

RESULTS

173 individuals with NGT and 73 with IGT were included. TBS was lower in those with IGT compared to those with NGT, while BMD was comparable. Individuals with IGT had significantly higher serum FGF21 levels, which in turn showed an independent inverse relationship with TBS, attenuated after inclusion of the Matsuda index. Serum FGF21 levels, however, did not correlate with BMD.

CONCLUSION

Among Chinese postmenopausal women, bone quality was worse in IGT, despite comparable bone density. FGF21 levels showed a significant independent inverse relationship with TBS, partly attributed to insulin resistance. Whether FGF21 contributes to the impaired bone quality in IGT remains speculative.

FGF21 induces autophagy-mediated cholesterol efflux to inhibit atherogenesis via RACK1 up-regulation

Fibroblast growth factor 21 (FGF21) acts as an anti‐atherosclerotic agent. However, the specific mechanisms governing this regulatory activity are unclear. Autophagy is a highly conserved cell stress response which regulates atherosclerosis (AS) by reducing lipid droplet degradation in foam cells. We sought to assess whether FGF21 could inhibit AS by regulating cholesterol metabolism in foam cells via autophagy and to elucidate the underlying molecular mechanisms. In this study, ApoE^−/− mice were fed a high‐fat diet (HFD) with or without FGF21 and FGF21 + 3‐Methyladenine (3MA) for 12 weeks. Our results showed that FGF21 inhibited AS in HFD‐fed ApoE^−/− mice, which was reversed by 3MA treatment. Moreover, FGF21 increased plaque RACK1 and autophagy‐related protein (LC3 and beclin‐1) expression in ApoE^−/− mice, thus preventing AS. However, these proteins were inhibited by LV‐RACK1 shRNA injection. Foam cell development is a crucial determinant of AS, and cholesterol efflux from foam cells represents an important defensive measure of AS. In this study, foam cells were treated with FGF21 for 24 hours after a pre‐treatment with 3MA, ATG5 siRNA or RACK1 siRNA. Our results indicated that FGF21‐induced autophagy promoted cholesterol efflux to reduce cholesterol accumulation in foam cells by up‐regulating RACK1 expression. Interestingly, immunoprecipitation results showed that RACK1 was able to activate AMPK and interact with ATG5. Taken together, our results indicated that FGF21 induces autophagy to promote cholesterol efflux and reduce cholesterol accumulation in foam cells through RACK1‐mediated AMPK activation and ATG5 interaction. These results provided new insights into the molecular mechanisms of FGF21 in the treatment of AS.

Ethyl acetate extract of sappanwood alleviates experimental atherosclerosis in rats through changes in FGF21 and SREBP-2 expression

Sappanwood extract shows promising effects against atherosclerosis. The fibroblast growth factor 21 (FGF21) and sterol regulatory element-binding protein 2 (SREBP2) are involved in atherosclerosis development. This study aimed to examine whether sappanwood ethyl acetate extract (SEAE) alleviates experimental atherosclerosis in rats through FGF21/SREBP-2 signaling. Rats were randomized to six groups (n=10/group): blank control, model, simvastatin (positive control, 4.2 mg/kg/d), and SEAE high-, medium-, and low-dose (2.30, 1.15, and 0.575 g/kg/d, respectively). The high-fat- and vitamin D3-induced rodent model of atherosclerosis was created (except in the blank control group). Aorta and liver underwent histopathologic examination. SREPB-2 and FGF21 expression levels were examined by real-time RT-PCR and western blot. Compared with the blank control group, the model group showed aortic and hepatic histopathology compatible with the development of atherosclerosis due to a high-fat diet. In addition, total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-C) were elevated (all P<0.05). SREBP2 expression was high, and FGF21 expression was low (both P<0.05). Compared with the model group, SEAE alleviated the changes in liver and aorta by histopathology and decreased total cholesterol, triglycerides, and LDL-C (all P<0.05), especially in the medium-, and high-dose groups. In addition, medium-dose SEAE increased FGF21 levels (mRNA: +296%; protein: +69%; P<0.05) and decreased SREBP2 levels (mRNA: -44%; protein: -77%; P<0.05). Simvastatin, as the positive control, had similar effects to those of SEAE. In conclusion, SEAE improves lipid metabolism and alleviates atherosclerosis through changes in FGF21 and SREBP-2 expression levels.

Two-hundred-liter scale fermentation, purification of recombinant human fibroblast growth factor-21, and its anti-diabetic effects on ob/ob mice

Fibroblast growth factor-21 (FGF-21) is a potential cytokine for type II diabetes mellitus. This study aimed to optimize recombinant human FGF-21 (rhFGF-21) production in Escherichia coli BL21 (DE3) employing high cell density fermentation at a 200-L scale and pilot-scale purification. FGF-21 was eventually expressed in E. coli BL21 (DE3) using human FGF-21 synthetic DNA sequence via the introduction of vector pET-3c; the product is used as seed strain during the fermentation of rhFGF-21. Fermentation of rhFGF-21 was performed in a 30-L and 200-L fermenters. rhFGF-21 was primarily expressed in the form of inclusion bodies after IPTG induction. At the 200-L scale, the bacterial production and expression levels of rhFGF-21 were 38.8 ± 0.6 g/L and 30.9 ± 0.7%, respectively. Additionally, the high purification (98%) of rhFGF-21 was tested with HPLC analysis and reducing & non-reducing SDS-PAGE analysis. The final yield of purified rhFGF-21 was 71.1 ± 13.9 mg/L. The activity of rhFGF-21 stock solution reached at 68.67 ± 8.74 IU/mg. Blood glucose controlling and insulin sensitization were improved with treatment of rhFGF-21 in type II diabetic ob/ob mice. Our results showed that the relatively stable and time-saving pilot-scale production process was successfully established, providing an efficient and cost-effective strategy for large-scale and industrial production of rhFGF-21.

Protection Effect of Exogenous Fibroblast Growth Factor 21 on the Kidney Injury in Vascular Calcification Rats

Background:

Chronic kidney disease (CKD) is closely related to the cardiovascular events in vascular calcification (VC). However, little has known about the characteristics of kidney injury caused by VC. Fibroblast growth factor 21 (FGF21) is an endocrine factor, which takes part in various metabolic actions with the potential to alleviate metabolic disorder diseases. Even FGF21 has been regarded as a biomarker in CKD, the role of FGF21 in CKD remains unclear. Therefore, in this study, we evaluate the FGF21 on the kidney injury in VC rats.

Methods:

The male Sprague-Dawley rats were divided into three groups: (1) control group, (2) Vitamin D3 plus nicotine (VDN)-induced VC group, (3) FGF21-treated VDN group. After 4 weeks, the rats were killed and the blood was collected for serum creatinine, urea nitrogen, calcium, and phosphate measurement. Moreover, the renal tissues were homogenized for alkaline phosphatases (ALPs) activity and calcium content. The levels of FGF21 protein were measured by radioimmunoassay. The levels of β-Klotho and FGF receptor 1 (FGFR1) protein were measured by enzyme-linked immunosorbent assay (ELISA). The structural damage and calcifications in aortas were stained by Alizarin-red S. Moreover, the structure of kidney was observed by hematoxylin and eosin staining.

Results:

The renal function impairment caused by VDN modeling was ameliorated by FGF21 treatment, inhibited the elevated serum creatinine and urea level by 20.5% (34.750 ± 4.334 μmol/L vs. 27.630 ± 2.387 μmol/L) and 4.0% (7.038 ± 0.590 mmol/L vs. 6.763 ± 0.374 mmol/L; P < 0.01), respectively, together with the structural damages of glomerular atrophy and renal interstitial fibrosis. FGF21 treatment downregulated the ALP activity, calcium content in the kidney of VC rats by 42.1% (P < 0.01) and 11.7% (P < 0.05) as well as ameliorated the aortic injury and calcification as compared with VDN treatment alone group, indicating an ameliorative effect on VC. ELISA assays showed that the expression of β-Klotho, a component of FGF21 receptor system, was increased in VDN-treated VC rats by 37.4% (6.588 ± 0.957 pg/mg vs. 9.054 ± 0.963 pg/mg; P < 0.01), indicating an FGF21-resistant state. Moreover, FGF21 treatment downregulated the level of β-Klotho in renal tissue by 16.7% (9.054 ± 0.963 pg/mg vs. 7.544 ± 1.362 pg/mg; P < 0.05). However, the level of FGFR1, the receptor of FGF21, kept unchanged under VDN and VDN plus FGF21 administration (0.191 ± 0.0376 ng/mg vs. 0.189 ± 0.032 ng/mg vs. 0.181 ± 0.034 ng/mg; P > 0.05).

Conclusions:

In the present study, FGF21 was observed to ameliorate the kidney injury in VDN-induced VC rats. FGF21 might be a potential therapeutic factor in CKD by cutting off the vicious circle between VC and kidney injury.