Fibroblast growth factor (FGF21) protects mouse liver against D-galactose-induced oxidative stress and apoptosis via activating Nrf2 and PI3K/Akt pathways

The role of FGF21 in type 1 diabetes and its complications

Data from the International Diabetes Federation show that 347 million people worldwide have diabetes, and the incidence is still rising. Although the treatment of diabetes has been advanced, the current therapeutic options and outcomes, e.g. complications, are yet far from ideal. Therefore, an urgent need exists for the development of more effective therapies. Numerous studies have been conducted to establish and confirm whether FGF21 exerts beneficial effects on obesity and diabetes along with its complications. However, most of the studies associated with FGF21 were conducted in the patients with type 2 diabetes. Subsequently, the effect of FGF21 in the prevention or treatment of type 1 diabetes and its complications were also increasingly reported. In this review, we summarize the findings available on the function of FGF21 and the status of FGF21's treatment for type 1 diabetes. Based on the available information, we found that FGF21 exerts a hypoglycemic effect, restores the function of brown fat, and inhibits various complications in type 1 diabetes patients. Although these features are predominantly similar to those observed in the studies that showed the beneficial impact of FGF21 on type 2 diabetes and its complications, there are also certain distinct features and findings that may be of provide important and instructive for us to understand mechanistic insights and further promote the prevention and treatment of type 1 diabetes.

Fibroblast growth factors 19 and 21 in acute liver damage

Currently there are very few pharmacological options available to treat acute liver injury. Because its natural exposure to noxious stimuli the liver has developed a strong endogenous hepatoprotective capacity. Indeed, experimental evidence exposed a variety of endogenous hepatic and systemic responses naturally activated to protect the hepatic parenchyma and to foster liver regeneration, therefore preserving individual's survival. The fibroblast growth factor (FGF) family encompasses a range of polypeptides with important effects on cellular differentiation, growth survival and metabolic regulation in adult organisms. Among these FGFs, FGF19 and FGF21 are endocrine hormones that profoundly influence systemic metabolism but also exert important hepatoprotective activities. In this review, we revisit the biology of these factors and highlight their potential application for the clinical management of acute liver injury.

Hypoxia induces senescence of bone marrow mesenchymal stem cells via altered gut microbiota

Systemic chronic hypoxia is a feature of many diseases and may influence the communication between bone marrow (BM) and gut microbiota. Here we analyse patients with cyanotic congenital heart disease (CCHD) who are experiencing chronic hypoxia and characterize the association between bone marrow mesenchymal stem cells (BMSCs) and gut microbiome under systemic hypoxia. We observe premature senescence of BMSCs and abnormal d-galactose accumulation in patients with CCHD. The hypoxia that these patients experience results in an altered diversity of gut microbial communities, with a remarkable decrease in the number of Lactobacilli and a noticeable reduction in the amount of enzyme-degraded d-galactose. Replenishing chronic hypoxic rats with Lactobacillus reduced the accumulation of d-galactose and restored the deficient BMSCs. Together, our findings show that chronic hypoxia predisposes BMSCs to premature senescence, which may be due to gut dysbiosis and thus induced d-galactose accumulation.

Systemic chronic hypoxia is a feature of many diseases and may influence the communication between bone marrow and gut microbiota. Here, the authors show that chronic hypoxia predisposes bone marrow stem cells to premature senescence, which may be due to gut dysbiosis and gut microbiota-derived d-galactose accumulation.

Fibroblast growth factor-21 prevents diabetic cardiomyopathy via AMPK-mediated antioxidation and lipid-lowering effects in the heart

Our previous studies showed that both exogenous and endogenous FGF21 inhibited cardiac apoptosis at the early stage of type 1 diabetes. Whether FGF21 induces preventive effect on type 2 diabetes-induced cardiomyopathy was investigated in the present study. High-fat-diet/streptozotocin-induced type 2 diabetes was established in both wild-type (WT) and FGF21-knockout (FGF21-KO) mice followed by treating with FGF21 for 4 months. Diabetic cardiomyopathy (DCM) was diagnosed by significant cardiac dysfunction, remodeling, and cardiac lipid accumulation associated with increased apoptosis, inflammation, and oxidative stress, which was aggravated in FGF21-KO mice. However, the cardiac damage above was prevented by administration of FGF21. Further studies demonstrated that the metabolic regulating effect of FGF21 is not enough, contributing to FGF21-induced significant cardiac protection under diabetic conditions. Therefore, other protective mechanisms must exist. The in vivo cardiac damage was mimicked in primary neonatal or adult mouse cardiomyocytes treated with HG/Pal, which was inhibited by FGF21 treatment. Knockdown of AMPKα1/2, AKT2, or NRF2 with their siRNAs revealed that FGF21 protected cardiomyocytes from HG/Pal partially via upregulating AMPK–AKT2–NRF2-mediated antioxidative pathway. Additionally, knockdown of AMPK suppressed fatty acid β-oxidation via inhibition of ACC–CPT-1 pathway. And, inhibition of fatty acid β-oxidation partially blocked FGF21-induced protection in cardiomyocytes. Further, in vitro and in vivo studies indicated that FGF21-induced cardiac protection against type 2 diabetes was mainly attributed to lipotoxicity rather than glucose toxicity. These results demonstrate that FGF21 functions physiologically and pharmacologically to prevent type 2 diabetic lipotoxicity-induced cardiomyopathy through activation of both AMPK–AKT2–NRF2-mediated antioxidative pathway and AMPK–ACC–CPT-1-mediated lipid-lowering effect in the heart.

FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury

Cisplatin, a widely used cancer therapy drug, induces nephrotoxicity or acute kidney injury (AKI), but the underlying mechanism remains unclear, and renal protective approaches are not available. Fibroblast growth factor (FGF)21 is an endocrine factor that regulates glucose uptake, metabolism, and energy expenditure. However, recent work has also implicated FGF21 in cellular stress response under pathogenic conditions. The role and regulation of FGF21 in AKI are unclear. Here, we show that FGF21 was dramatically induced during cisplatin treatment of renal tubular cells in vitro and mouse kidneys in vivo. The inductive response was suppressed by pifithrin (a pharmacological inhibitor of P53), suggesting a role of P53 in FGF21 induction. In cultured renal tubular cells, knockdown of FGF21 aggravated cisplatin-induced apoptosis, whereas supplementation of recombinant FGF21 was protective. Consistently, recombinant FGF21 alleviated cisplatin-induced kidney dysfunction, tissue damage, and tubular apoptosis in mice. Mechanistically, FGF21 suppressed P53 induction and activation during cisplatin treatment. Together, these results indicate that FGF21 is induced during cisplatin nephrotoxicity to protect renal tubules, and recombinant FGF21 may have therapeutic potential.-Li, F., Liu, Z., Tang, C., Cai, J., Dong, Z. FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury.

The Role and Potential Therapeutic Implications of the Fibroblast Growth Factors in Energy Balance and Type 2 Diabetes

PURPOSE OF REVIEW

Obesity and its associated metabolic diseases have reached epidemic proportions worldwide, reducing life expectancy and quality of life. Several drugs have been tested to treat these diseases but many of them have damaging side effects. Consequently, there is an urgent need to develop more effective therapies. Recently, endocrine fibroblast growth factors (FGFs) have become attractive targets in the treatment of metabolic diseases. This review summarizes their most important functions as well as FGF-based therapies for the treatment of obesity and type 2 diabetes (T2D).

RECENT FINDINGS

Recent studies demonstrate that circulating levels of FGF19 are reduced in obesity. In fact, exogenous FGF19 administration is associated with a reduction in food intake as well as with improvements in glycaemia. In contrast, FGF21 levels are elevated in subjects with abdominal obesity, insulin resistance and T2D, probably representing a compensatory response. Additionally, elevated levels of circulating FGF23 in individuals with obesity and T2D are reported in most clinical studies. Finally, increased FGF1 levels in obese patients associated with adipogenesis have been described. FGFs constitute important molecules in the treatment of metabolic diseases due to their beneficial effects on glucose and lipid metabolism. Among all members, FGF19 and FGF21 have demonstrated the ability to improve glucose, lipid and energy homeostasis, along with FGF1, which was recently discovered to have beneficial effects on metabolic homeostasis. Additionally, FGF23 may also play a role in insulin resistance or energy homeostasis beyond mineral metabolism control. These results highlight the relevant use of FGFs as potential biomarkers for the early diagnosis of metabolic diseases. In this regard, notable progress has been made in the development of FGF-based therapies and different approaches are being tested in different clinical trials. However, further studies are needed to determine their potential therapeutic use in the treatment of obesity and obesity-related comorbidities.

Total Flavonoid Extract from Abelmoschus manihot (L.) Medic Flowers Attenuates d-Galactose-Induced Oxidative Stress in Mouse Liver Through the Nrf2 Pathway

Abelmoschus manihot (L.) Medic is an edible hibiscus that is rich in flavonoids, and its use as Chinese herbal medicine for the treatment of diseases and health maintenance dates back to ancient times. The chemical compositions of total flavonoid of A. manihot (L.) Medic flower extract (TFAE) were identified and determined by high performance liquid chromatography (HPLC). The effects of TFAE on antioxidative activities in a d-galactose (d-gal)-induced mouse model and Nrf2-mediated antioxidant responses were evaluated. Male Kunming mice were randomly divided into normal control group, d-gal aging model group, d-gal+ascorbic acid group that served as a positive control, and d-gal+TFAE (40, 80, and 160 mg TFAE/kg) group. After 42 days, the antioxidant effects of these treatments were determined by biochemical studies, Western blotting, quantitative real-time polymerase chain reaction, and histological analysis. The results showed that the groups administered TFAE exhibited significant elevation in liver activities of antioxidant enzymes, including catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC), and decreased malondialdehyde (MDA) production in a dose-dependent manner compared with the d-gal-induced model group. Expression of Nrf2 and its target antioxidants (HO-1 and NQO1) was manifestly increased by TFAE treatment. TFAE also increased mRNA expression of GPx, SOD, and CAT and decreased tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). Furthermore, the microstructure of livers in TFAE-administered mice was obviously improved as compared with the d-gal model group. These results suggest that TFAE protects mice against d-gal-induced oxidative stress, and the effect is related to the activation of Nrf2 signaling.

Effect of mild hypothermia preconditioning against low temperature (4°C) induced rat liver cell injury in vitro

Bioartificial liver holds special position in the field of regenerative medicine, and cold environment at 4℃ is widely used for the short storage of both organ and liver cell for later application. However, the disadvantages of such cold storage could influence cell viability and lead to cell apoptosis in different degrees. In this study, we mainly explore the pre-protective effect of mild hypothermia against low temperature (4℃)-induced rat liver cell injury in vitro. Our results indicated that the precondition with mild hypothermia could increase cell viability, such as cell proliferation, LDH regulation and glycogen synthesis ability of liver cell. The precondition also decreased the ROS production and relieved cell apoptosis in liver cells. Compared with the model group, the mitochondrial membrane potential was restored in the mild hypothermia group, as well as the mitochondrial membrane permeability transition pore opening, indicating that the therapeutic mechanism was related to mitochondrial protection. Further analysis showed that PI3K-Akt-GSK3β signal pathway might be associated with the pre-protective effect of mild hypothermia. Thus, our study suggested that the precondition with mild hypothermia hold the protective effect for liver cell in cold environment, and further developed a novel strategy for the storage of liver seed cells, even bioartificial liver.

Vildagliptin and caloric restriction for cardioprotection in pre-diabetic rats

Long-term high-fat diet (HFD) consumption causes cardiac dysfunction. Although calorie restriction (CR) has been shown to be useful in obesity, we hypothesized that combined CR with dipeptidyl peptidase-4 (DPP-4) inhibitor provides greater efficacy than monotherapy in attenuating cardiac dysfunction and metabolic impairment in HFD-induced obese-insulin resistant rats. Thirty male Wistar rats were divided into 2 groups to be fed on either a normal diet (ND, n = 6) or a HFD (n = 24) for 12 weeks. Then, HFD rats were divided into 4 subgroups (n = 6/subgroup) to receive just the vehicle, CR diet (60% of mean energy intake and changed to ND), vildagliptin (3 mg/kg/day) or combined CR and vildagliptin for 4 weeks. Metabolic parameters, heart rate variability (HRV), cardiac mitochondrial function, left ventricular (LV) and fibroblast growth factor (FGF) 21 signaling pathway were determined. Rats on a HFD developed insulin and FGF21 resistance, oxidative stress, cardiac mitochondrial dysfunction and impaired LV function. Rats on CR alone showed both decreased body weight and visceral fat accumulation, whereas vildagliptin did not alter these parameters. Rats in CR, vildagliptin and CR plus vildagliptin subgroups had improved insulin sensitivity and oxidative stress. However, vildagliptin improved heart rate variability (HRV), cardiac mitochondrial function and LV function better than the CR. Chronic HFD consumption leads to obese-insulin resistance and FGF21 resistance. Although CR is effective in improving metabolic regulation, vildagliptin provides greater efficacy in preventing cardiac dysfunction by improving anti-apoptosis and FGF21 signaling pathways and attenuating cardiac mitochondrial dysfunction in obese-insulin-resistant rats.

Glaucarubulone glucoside from Castela macrophylla suppresses MCF-7 breast cancer cell growth and attenuates benzo[a]pyrene-mediated CYP1A gene induction

Quassinoids often exhibit antioxidant and antiproliferative activity. Emerging evidence suggests that these natural metabolites also display chemopreventive actions. In this study, we investigated the potential for the quassinoid glaucarubulone glucoside (Gg), isolated from the endemic Jamaican plant Castela macrophylla (Simaroubaceae), to display potent cytotoxicity and inhibit human cytochrome P450s (CYPs), particularly CYP1A enzymes, known to convert polyaromatic hydrocarbons into carcinogenic metabolites. Gg reduced the viability of MCF-7 breast adenocarcinoma cells (IC₅₀ = 121 nm) to a greater extent than standard of care anticancer agents 5-fluorouracil, tamoxifen (IC₅₀ >10 μm) and the tamoxifen metabolite 4-hydroxytamoxifen (IC₅₀ = 2.6 μm), yet was not cytotoxic to non-tumorigenic MCF-10A breast epithelial cells. Additionally, Gg induced MCF-7 breast cancer cell death. Gg blocked increases in reactive oxygen species in MCF-10A cells mediated by the polyaromatic hydrocarbon benzo[a]pyrene (B[a]P) metabolite B[a]P 1,6-quinone, yet downregulated the expression of genes that promote antioxidant activity in MCF-7 cells. This implies that Gg exhibits antioxidant and cytoprotective actions in non-tumorigenic breast epithelial cells and pro-oxidant, cytotoxic actions in breast cancer cells. Furthermore, Gg inhibited the activities of human CYP1A according to non-competitive kinetics and attenuated the ability of B[a]P to induce CYP1A gene expression in MCF-7 cells. These data indicate that Gg selectively suppresses MCF-7 breast cancer cell growth without impacting non-tumorigenic breast epithelial cells and blocks B[a]P-mediated CYP1A induction. Taken together, our data provide a rationale for further investigations of Gg and similar plant isolates as potential agents to treat and prevent breast cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Evidence of oxidative stress in brain and liver of young rats submitted to experimental galactosemia

Galactosemia is a disorder of galactose metabolism, leading to the accumulation of this carbohydrate. Galactosemic patients present brain and liver damage. For evaluated oxidative stress, 30-day-old males Wistar rats were divided into two groups: galactose group, that received a single injection of this carbohydrate (5 μmol/g), and control group, that received saline 0.9 % in the same conditions. One, twelve or twenty-four hours after the administration, animals were euthanized and cerebral cortex, cerebellum, and liver were isolated. After one hour, it was found a significant increase in TBA-RS levels, nitrate and nitrite and protein carbonyl contents in cerebral cortex, as well as protein carbonyl content in the cerebellum and in hepatic level of TBA-RS, and a significant decrease in nitrate and nitrite contents in cerebellum. TBA-RS levels were also found increased in all studied tissues, as well as nitrate and nitrite contents in cerebral cortex and cerebellum, that also present increased protein carbonyl content and impairments in the activity of antioxidant enzymes of rats euthanized at twelve hours. Finally, animals euthanized after twenty-four hours present an increase of TBA-RS levels in studied tissues, as well as the protein carbonyl content in cerebellum and liver. These animals also present an increased nitrate and nitrite content and impairment of antioxidant enzymes activities. Taken together, our data suggest that acute galactose administration impairs redox homeostasis in brain and liver of rats.

Fibroblast growth factor 21 (FGF21) therapy attenuates left ventricular dysfunction and metabolic disturbance by improving FGF21 sensitivity, cardiac mitochondrial redox homoeostasis and structural changes in pre-diabetic rats

AIMS

Fibroblast growth factor 21 (FGF21) acts as a metabolic regulator and exerts cardioprotective effects. However, the effects of long-term FGF21 administration on the heart under the FGF21-resistant condition in obese, insulin-resistant rats have not been investigated. We hypothesized that long-term FGF21 administration reduces FGF21 resistance and insulin resistance and attenuates cardiac dysfunction in obese, insulin-resistant rats.

METHODS

Eighteen rats were fed on either a normal diet (n = 6) or a high-fat diet (HFD; n = 12) for 12 weeks. Then, rats in the HFD group were divided into two subgroups (n = 6 per subgroup) and received either the vehicle (HFV) or recombinant human FGF21 (rhFGF21, 0.1 mg kg(-1)  day(-1) ; HFF) injected intraperitoneally for 28 days. The metabolic parameters, inflammation, malondialdehyde (MDA), heart rate variability (HRV), left ventricular (LV) function, cardiac mitochondrial redox homoeostasis, cardiac mitochondrial fatty acid β-oxidation (FAO) and anti-apoptotic signalling pathways were determined.

RESULTS

HFV rats had increased dyslipidaemia, insulin resistance, plasma FGF21 levels, TNF-α, adiponectin and MDA, depressed HRV, and impaired LV and mitochondrial function. HFV rats also had decreased cardiac Bcl-2, cardiac PGC-1α and CPT-1 protein expression. However, FGF21 restored metabolic parameters, decreased TNF-α and MDA, increased serum adiponectin, and improved HRV, cardiac mitochondrial and LV function in HFF rats. Moreover, HFF rats had increased cardiac Bcl-2, cardiac PGC-1α and CPT-1 protein expression.

CONCLUSION

Long-term FGF21 therapy attenuates FGF21 resistance and insulin resistance and exerts cardioprotection by improving cardiometabolic regulation via activating anti-apoptotic and cardiac mitochondrial FAO signalling pathways in obese, insulin-resistant rats.

Cerebralcare Granule(®), a Chinese Herb Compound Preparation, Attenuates D-Galactose Induced Memory Impairment in Mice

Cerebralcare granule(®) (CG) is a preparation of Traditional Chinese Medicine that widely used in China. It was approved by the China State Food and Drug Administration for treatment of headache and dizziness associated with cerebrovascular diseases. In the present study, we aimed to investigate whether CG had protective effect against D-galactose (gal)-induced memory impairment and to explore the mechanism of its action. D-gal was administered (100 mg/kg, subcutaneously) once daily for 8 weeks to induced memory deficit and neurotoxicity in the brain of aging mouse and CG (7.5, 15, and 30 g/kg) were simultaneously administered orally. The present study demonstrates that CG can alleviate aging in the mouse brain induced by D-gal through improving behavioral performance and reducing brain cell damage in the hippocampus. CG prevents aging mainly via suppression of oxidative stress response, such as decreasing NO and MDA levels, renewing activities of SOD, CAT, and GPx, as well as decreasing AChE activity in the brain of D-gal-treated mice. In addition, CG prevents aging through inhibiting NF-κB-mediated inflammatory response and caspase-3-medicated neurodegeneration in the brain of D-gal treated mice. Taken together, these data clearly demonstrates that subcutaneous injection of D-gal produced memory deficit, meanwhile CG can protect neuron from D-gal insults and improve memory ability.

Up-regulation of Nrf2 is involved in FGF21-mediated fenofibrate protection against type 1 diabetic nephropathy

The lipid lowering medication, fenofibrate (FF), is a peroxisome proliferator-activated receptor-alpha (PPARα) agonist, possessing beneficial effects for type 2 diabetic nephropathy (DN). We investigated whether FF can prevent the development of type 1 DN, and the underlying mechanisms. Diabetes was induced by a single intraperitoneal injection of streptozotocin in C57BL/6J mice. Mice were treated with oral gavage of FF at 100mg/kg every other day for 3 and 6 months. Diabetes-induced renal oxidative stress, inflammation, apoptosis, lipid and collagen accumulation, and renal dysfunction were accompanied by significant decrease in PI3K, Akt, and GSK-3β phosphorylation as well as an increase in the nuclear accumulation of Fyn [a negative regulator of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)]. All these adverse effects were significantly attenuated by FF treatment. FF also significantly increased fibroblast growth factor 21 (FGF21) expression and enhanced Nrf2 function in diabetic and non-diabetic kidneys. Moreover, FF-induced amelioration of diabetic renal damage, including the stimulation of PI3K/Akt/GSK-3β/Fyn pathway and the enhancement of Nrf2 function were abolished in FGF21-null mice, confirming the critical role of FGF21 in FF-induced renal protection. These results suggest for the first time that FF prevents the development of DN via up-regulating FGF21 and stimulating PI3K/Akt/GSK-3β/Fyn-mediated activation of the Nrf2 pathway.

Chlorogenic acid protects D-galactose-induced liver and kidney injury via antioxidation and anti-inflammation effects in mice

CONTEXT

Oxidative stress and inflammation are implicated in the aging process and its related hepatic and renal function decline. Chlorogenic acid (CGA) is one of the most abundant polyphenol compounds in the human diet. Recently, CGA has shown in vivo and in vitro antioxidant properties.

OBJECTIVE

The current study investigates the effects of protective effects of chlorogenic acid (CGA) on D-galactose-induced liver and kidney injury.

MATERIALS AND METHODS

Hepatic and renal injuries were induced in a mouse model by subcutaneously injection of D-galactose (D-gal; 100 mg/kg) once a day for 8 consecutive weeks and orally administered simultaneously with CGA included in the food (200 mg/kg of diet). The liver and renal functions were examined. Histological analyses of liver and kidney were done by haematoxylin and eosin staining. The oxidative stress markers and pro-inflammatory cytokines in the liver and the kidney were measured. Results CGA significantly reduced the serum aminotransferase, serum creatinine (SCr) and blood urea nitrogen (BUN) levels in D-gal mice (p <0.05). CGA also restored superoxide dismutase, catalase, and malondialdehyde levels and decreased glutathione content in the liver and kidney in D-gal mice (p <0.05). Improvements in liver and kidney were also noted in histopathological studies. CGA reduced tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) protein levels in the liver and kidney in D-gal mice (p <0.05).

DISCUSSION AND CONCLUSION

These findings suggest that CGA attenuates D-gal-induced chronic liver and kidney injury and that this protection may be due to its antioxidative and anti-inflammatory activities.

Effects of fibroblast growth factor 21 on the heart

Fibroblast growth factor 21 (FGF21) is a novel polypeptide ligand that has been shown to be involved in several physiological and pathological processes including regulation of glucose and lipids as well as reduction of arteriosclerotic plaque formation in the great vessels. It has also been shown to exert cardioprotective effects in myocardial infarction, cardiac ischemia-reperfusion injury, cardiac hypertrophy and diabetic cardiomyopathy. Moreover, FGF21 protects the myocardium and great arteries by attenuating remodeling, inflammation, oxidative stress and also promoting the energy supply to the heart through fatty acid β-oxidation. This growing evidence emphasizes the important roles of FGF21 in cardioprotection. This review comprehensively summarizes and discusses the consistent and inconsistent findings regarding the beneficial effects of FGF21 on the heart available from both basic research and clinical reports. The details of the signaling, biological and pharmacological effects of FGF21 with regard to its protection of the heart are also presented and discussed in this review.

Minireview: Roles of Fibroblast Growth Factors 19 and 21 in Metabolic Regulation and Chronic Diseases

Fibroblast growth factor (FGF)19 and FGF21 are hormones that regulate metabolic processes particularly during feeding or starvation, thus ultimately influencing energy production. FGF19 is secreted by the intestines during feeding and negatively regulates bile acid synthesis and secretion, whereas FGF21 is produced in the liver during fasting and plays a crucial role in regulating glucose and lipid metabolism, as well as maintaining energy homeostasis. FGF19 and FGF21 are regarded as late-acting hormones because their functions are only used after insulin and glucagon have completed their actions. Although FGF19 and FGF21 are activated under different conditions, they show extensively functional overlap in terms of improving glucose tolerance, insulin sensitivity, weight loss, and lipid, and energy metabolism, particularly in pathological conditions such as diabetes, obesity, metabolic syndrome, and cardiovascular and renal diseases. Most patients with these metabolic diseases exhibit reduced serum FGF19 levels, which might contribute to its etiology. In addition, the simultaneous increase in serum FGF21 levels is likely a compensatory response to reduced FGF19 levels, and the 2 proteins concertedly maintain metabolic homeostasis. Here, we review the physiological and pharmacological cross talk between FGF19 and FGF21 in relation to the regulation of endocrine metabolism and various chronic diseases.

Additive protection by LDR and FGF21 treatment against diabetic nephropathy in type 2 diabetes model

The onset of diabetic nephropathy (DN) is associated with both systemic and renal changes. Fibroblast growth factor (FGF)-21 prevents diabetic complications mainly by improving systemic metabolism. In addition, low-dose radiation (LDR) protects mice from DN directly by preventing renal oxidative stress and inflammation. In the present study, we tried to define whether the combination of FGF21 and LDR could further prevent DN by blocking its systemic and renal pathogeneses. To this end, type 2 diabetes was induced by feeding a high-fat diet for 12 wk followed by a single dose injection of streptozotocin. Diabetic mice were exposed to 50 mGy LDR every other day for 4 wk with and without 1.5 mg/kg FGF21 daily for 8 wk. The changes in systemic parameters, including blood glucose levels, lipid profiles, and insulin resistance, as well as renal pathology, were examined. Diabetic mice exhibited renal dysfunction and pathological abnormalities, all of which were prevented significantly by LDR and/or FGF21; the best effects were observed in the group that received the combination treatment. Our studies revealed that the additive renal protection conferred by the combined treatment against diabetes-induced renal fibrosis, inflammation, and oxidative damage was associated with the systemic improvement of hyperglycemia, hyperlipidemia, and insulin resistance. These results suggest that the combination treatment with LDR and FGF21 prevented DN more efficiently than did either treatment alone. The mechanism behind these protective effects could be attributed to the suppression of both systemic and renal pathways.

The role of Nrf2 in oxidative stress-induced endothelial injuries

Endothelial dysfunction is an important risk factor for cardiovascular disease, and it represents the initial step in the pathogenesis of atherosclerosis. Failure to protect against oxidative stress-induced cellular damage accounts for endothelial dysfunction in the majority of pathophysiological conditions. Numerous antioxidant pathways are involved in cellular redox homeostasis, among which the nuclear factor-E2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1)-antioxidant response element (ARE) signaling pathway is perhaps the most prominent. Nrf2, a transcription factor with a high sensitivity to oxidative stress, binds to AREs in the nucleus and promotes the transcription of a wide variety of antioxidant genes. Nrf2 is located in the cytoskeleton, adjacent to Keap1. Keap1 acts as an adapter for cullin 3/ring-box 1-mediated ubiquitination and degradation of Nrf2, which decreases the activity of Nrf2 under physiological conditions. Oxidative stress causes Nrf2 to dissociate from Keap1 and to subsequently translocate into the nucleus, which results in its binding to ARE and the transcription of downstream target genes. Experimental evidence has established that Nrf2-driven free radical detoxification pathways are important endogenous homeostatic mechanisms that are associated with vasoprotection in the setting of aging, atherosclerosis, hypertension, ischemia, and cardiovascular diseases. The aim of the present review is to briefly summarize the mechanisms that regulate the Nrf2/Keap1-ARE signaling pathway and the latest advances in understanding how Nrf2 protects against oxidative stress-induced endothelial injuries. Further studies regarding the precise mechanisms by which Nrf2-regulated endothelial protection occurs are necessary for determining whether Nrf2 can serve as a therapeutic target in the treatment of cardiovascular diseases.