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

Double promoter and tandem gene strategy for efficiently expressing recombinant FGF21

BACKGROUND

Fibroblast growth factor 21 (FGF21) is a promising candidate for treating metabolic disorder diseases and has been used in phase II clinical trials. Currently, metabolic diseases are prevalent worldwide, underscoring the significant market potential of FGF21. Therefore, the production of FGF21 must be effectively improved to meet market demand.

RESULTS

Herein, to investigate the impact of vectors and host cells on FGF21 expression, we successfully engineered strains that exhibit a high yield of FGF21. Surprisingly, the data revealed that vectors with various copy numbers significantly impact the expression of FGF21, and the results showed a 4.35-fold increase in expression levels. Furthermore, the performance of the double promoter and tandem gene expression construction design surpassed that of the conventional construction method, with a maximum difference of 2.67 times.

CONCLUSION

By exploring engineered vectors and host cells, we successfully achieved high-yield production of the FGF21 strain. This breakthrough lays a solid foundation for the future industrialization of FGF21. Additionally, FGF21 can be easily, quickly and efficiently expressed, providing a better tool and platform for the research and application of more recombinant proteins.

Scaling up production of recombinant human basic fibroblast growth factor in an Escherichia coli BL21(DE3) plysS strain and evaluation of its pro-wound healing efficacy

Introduction: Human basic fibroblast growth factor (hbFGF) is a highly valuable multifunctional protein that plays a crucial role in various biological processes. In this study, we aim to accomplish the scaling-up production of mature hbFGF (146aa) by implementing a high cell-density fermentation and purification process on a 500-L scale, thereby satisfying the escalating demands for both experimental research and clinical applications. Methods: The hbFGF DNA fragment was cloned into a mpET-3c vector containing a kanamycin resistance gene and then inserted into Escherichia coli BL21 (DE3) plysS strain. To optimize the yield of hbFGF protein, various fermentation parameters were systematically optimized using BOX-Behnken design and further validated in large-scale fermentation (500-L). Additionally, a three-step purification protocol involving CM-Sepharose, heparin affinity, and SP-Sepharose column chromatography was developed to separate and purify the hbFGF protein. Isoelectric focusing electrophoresis, MALDI-TOF/MS analysis, amino acid sequencing, CD spectroscopy, and Western blotting were performed to authenticate its identity. The biological efficacy of purified hbFGF was evaluated using an MTT assay as well as in a diabetic deep second-degree scald model. Results: The engineered strain was successfully constructed, exhibiting high expression of hbFGF and excellent stability. Under the optimized fermentation conditions, an impressive bacterial yield of 46.8 ± 0.3 g/L culture with an expression level of hbFGF reaching 28.2% ± 0.2% was achieved in 500-L scale fermentation. Subsequently, during pilot-scale purification, the final yield of purified hbFGF protein was 114.6 ± 5.9 mg/L culture with RP-HPLC, SEC-HPLC, and SDS-PAGE purity exceeding 98%. The properties of purified hbFGF including its molecular weight, isoelectric point (pI), amino sequence, and secondary structure were found to be consistent with theoretical values. Furthermore, the purified hbFGF exhibited potent mitogenic activity with a specific value of 1.05 ± 0.94 × 106 AU/mg and significantly enhanced wound healing in a deep second-degree scald wound diabetic rat model. Conclusion: This study successfully established a stable and efficient large-scale production process of hbFGF, providing a solid foundation for future industrial production.

Hyper-expression of GFP-fused active hFGF21 in tobacco chloroplasts

Human fibroblast growth factor 21 (hFGF21) is a promising candidate for metabolic diseases. In this study, a tobacco chloroplast transformation vector, pWYP21406, was constructed that consisted of codon-optimized encoding gene hFGF21 fused with GFP at its 5' terminal; it was driven by the promoter of plastid rRNA operon (Prrn) and terminated by the terminator of plastid rps16 gene (Trps16). Spectinomycin-resistant gene (aadA) was the marker and placed in the same cistron between hFGF21 and the terminator Trps16. Transplastomic plants were generated by the biolistic bombardment method and proven to be homoplastic by Southern blotting analysis. The expression of GFP was detected under ultraviolet light and a laser confocal microscope. The expression of GFP-hFGF21 was confirmed by immunoblotting and quantified by enzyme-linked immunosorbnent assay (ELISA). The accumulation of GFP-hFGF21 was confirmed to be 12.44 ± 0.45% of the total soluble protein (i.e., 1.9232 ± 0.0673 g kg^-1 of fresh weight). GFP-hFGF21 promoted the proliferation of hepatoma cell line HepG2, inducing the expression of glucose transporter 1 in hepatoma HepG2 cells and improving glucose uptake. These results suggested that a chloroplast expression is a promising approach for the production of bioactive recombinant hFGF21.

Hepatic PTEN Signaling Regulates Systemic Metabolic Homeostasis through Hepatokines-Mediated Liver-to-Peripheral Organs Crosstalk

Liver-derived circulating factors deeply affect the metabolism of distal organs. Herein, we took advantage of the hepatocyte-specific PTEN knockout mice (LPTENKO), a model of hepatic steatosis associated with increased muscle insulin sensitivity and decreased adiposity, to identify potential secreted hepatic factors improving metabolic homeostasis. Our results indicated that protein factors, rather than specific metabolites, released by PTEN-deficient hepatocytes trigger an improved muscle insulin sensitivity and a decreased adiposity in LPTENKO. In this regard, a proteomic analysis of conditioned media from PTEN-deficient primary hepatocytes identified seven hepatokines whose expression/secretion was deregulated. Distinct expression patterns of these hepatokines were observed in hepatic tissues from human/mouse with NAFLD. The expression of specific factors was regulated by the PTEN/PI3K, PPAR or AMPK signaling pathways and/or modulated by classical antidiabetic drugs. Finally, loss-of-function studies identified FGF21 and the triad AHSG, ANGPTL4 and LECT2 as key regulators of insulin sensitivity in muscle cells and in adipocytes biogenesis, respectively. These data indicate that hepatic PTEN deficiency and steatosis alter the expression/secretion of hepatokines regulating insulin sensitivity in muscles and the lipid metabolism in adipose tissue. These hepatokines could represent potential therapeutic targets to treat obesity and insulin resistance.

FGF21 promotes migration and differentiation of epidermal cells during wound healing via SIRT1-dependent autophagy

BACKGROUND AND PURPOSE

Migration and differentiation of epidermal cells are essential for epidermal regeneration during wound healing. Fibroblast growth factor 21 (FGF21) plays key roles in mediating a variety of biological activities. However, its role in skin wound healing remains unknown.

EXPERIMENTAL APPROACH

Fgf21 knockout (Fgf21 KO) mice were used to determine the effect of FGF21 on wound healing. The source of FGF21 and its target cells were determined by immunohistochemistry, immunoblotting, and ELISA assay. Moreover, Sirt1^flox/flox and Atg7^flox/flox mice were constructed and injected with the epidermal-specific Cre virus to elucidate the underlying mechanisms. Migration and differentiation of keratinocytes were evaluated in vitro by cell scratch assays, immunofluorescence, and qRT-RCR. The effects were further assessed when SIRT1, ATG7, ATG5, BECN1, and P53 were silenced. Interactions between SIRT1 and autophagy-related genes were assessed using immunoprecipitation assays.

KEY RESULTS

FGF21 was active in fibroblasts and promoted migration and differentiation of keratinocytes following injury. After wounding, SIRT1 expression and autophagosome synthesis were lower in Fgf21 KO mice. Depletion of ATG7 in keratinocytes counteracted the FGF21-induced increases in migration and differentiation, suggesting that autophagy is required for the FGF21-mediated pro-healing effects. Furthermore, epithelial-specific Sirt1 knockout abolished the FGF21-mediated improvements of autophagy and wound healing. Silencing of SIRT1 in keratinocytes, which decreased deacetylation of p53 and autophagy-related proteins, revealed that FGF21-induced autophagy during wound healing was SIRT1-dependent.

CONCLUSIONS AND IMPLICATIONS

FGF21 is a key regulator of keratinocyte migration and differentiation during wound healing. FGF21 may be a novel therapeutic target to accelerate would healing.

Production of active human FGF21 using tobacco mosaic virus-based transient expression system

Fibroblast growth factor (FGF) family has a wide range of metabolic processes. FGF21 exerts critical physiological functions in clinical application. This study aimed to explore a convenient and highly efficient approach for rhFGF21 expression using TMV-TES. Firstly, the vector pTTEV-GFP was constructed, followed by optimisation of the expression parameters in Nicotiana benthamiana. Then, the rhFGF21 encoding gene harbouring vector pTTEV-rhFGF21 was constructed. Agrobacterium-mediated vacuum infiltration was performed with the optimised parameters and the expression of rhFGF21 was confirmed by the immunoblotting analysis. ELISA revealed that the protein accumulation of rhFGF21 accounts for 0.11% of total soluble proteins. The biological activity was evaluated and the results suggested that tobacco-expressed rhFGF21 could stimulate the glucose uptake in swiss 3T3-L1 adipocytes, which was similar to the activity of commercial products, suggesting its native biological activity. Therefore, using TMV-TES to express rhFGF21 will be a feasible approach for the mass production of rhFGF21.

Maternal dietary resistant starch does not improve piglet's gut and liver metabolism when challenged with a high fat diet

Background

In the past several years, the use of resistant starch (RS) as prebiotic has extensively been studied in pigs, and this mostly in the critical period around weaning. RS is believed to exert beneficial effects on the gastrointestinal tract mainly due to higher levels of short chain fatty acids (SCFAs) and an improved microbiota profile. In this study, sows were fed digestible starch (DS) or RS during late gestation and lactation and the possible maternal effect of RS on the overall health of the progeny was assessed. Since RS is also described to have a positive effect on metabolism, and to investigate a metabolic programming of the progeny, half of the piglets per maternal diet were assigned to a high fat diet from weaning on to 10 weeks after.

Results

No bodyweight differences were found between the four experimental piglet groups. The high fat diet did however impact back fat thickness and meat percentage whereas maternal diet did not influence these parameters. The impact of the high fat diet was also reflected in higher levels of serum cholesterol. No major differences in microbiota could be distinguished, although higher levels of SCFA were seen in the colon of piglets born from RS fed sows, and some differences in SCFA production were observed in the caecum, mainly due to piglet diet. RNA-sequencing on liver and colon scrapings revealed minor differences between the maternal diet groups. Merely a handful of genes was differentially expressed between piglets from DS and RS sows, and network analysis showed only one significant cluster of genes in the liver due to the maternal diet that did not point to meaningful biological pathways. However, the high fat diet resulted in liver gene clusters that were significantly correlated with piglet diet, of which one is annotated for lipid metabolic processes. These clusters were not correlated with maternal diet.

Conclusions

There is only a minor impact of maternal dietary RS on the progeny, reflected in SCFA changes. A high fat diet given to the progeny directly evokes metabolic changes in the liver, without any maternal programming by a RS diet.