A short story of Klotho and FGF23: a deuce of dark side or the savior?

Correlation between soluble klotho and chronic kidney disease-mineral and bone disorder in chronic kidney disease: a meta-analysis

We conducted a systematic search across medical databases, including PubMed, Web of Science, EMBASE, and Cochrane Library, up to March 2023. A total of 1944 subjects or individuals from 17 studies were included in our final analysis. The correlation coefficient (r) between sKlotho and calcium was [0.14, (0.02, 0.26)], and a moderate heterogeneity was observed (I2 = 66%, P < 0.05). The correlation coefficient (r) between Klotho and serum phosphate was [- 0.21, (- 0.37, - 0.04)], with apparent heterogeneity (I2 = 84%, P < 0.05). The correlation coefficient (r) between sKlotho and parathyroid hormone and vascular calcification was [- 0.23,(- 0.29, - 0.17); - 0.15, (- 0.23, - 0.08)], with no significant heterogeneity among the studies. (I2 = 40%, P < 0.05; I2 = 30%, P < 0.05). A significant correlation exists between low sKlotho levels and an increased risk of CKD-MBD in patients with CKD. According to the findings, sKlotho may play a role in alleviating CKD-MBD by lowering phosphorus and parathyroid hormone levels, regulating calcium levels, and suppressing vascular calcification. As analysis showed that sKlotho has an important impact on the pathogenesis and progression of CKD-MBD in CKD patients. Nonetheless, further comprehensive and high-quality studies are needed to validate our conclusions.

The Role of the FGF19 Family in the Pathogenesis of Gestational Diabetes: A Narrative Review

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications. Understanding the pathogenesis and appropriate diagnosis of GDM enables the implementation of early interventions during pregnancy that reduce the risk of maternal and fetal complications. At the same time, it provides opportunities to prevent diabetes, metabolic syndrome, and cardiovascular diseases in women with GDM and their offspring in the future. Fibroblast growth factors (FGFs) represent a heterogeneous family of signaling proteins which play a vital role in cell proliferation and differentiation, repair of damaged tissues, wound healing, angiogenesis, and mitogenesis and also affect the regulation of carbohydrate, lipid, and hormone metabolism. Abnormalities in the signaling function of FGFs may lead to numerous pathological conditions, including metabolic diseases. The FGF19 subfamily, also known as atypical FGFs, which includes FGF19, FGF21, and FGF23, is essential in regulating metabolic homeostasis and acts as a hormone while entering the systemic circulation. Many studies have pointed to the involvement of the FGF19 subfamily in the pathogenesis of metabolic diseases, including GDM, although the results are inconclusive. FGF19 and FGF21 are thought to be associated with insulin resistance, an essential element in the pathogenesis of GDM. FGF21 may influence placental metabolism and thus contribute to fetal growth and metabolism regulation. The observed relationship between FGF21 and increased birth weight could suggest a potential role for FGF21 in predicting future metabolic abnormalities in children born to women with GDM. In this group of patients, different mechanisms may contribute to an increased risk of cardiovascular diseases in women in later life, and FGF23 appears to be their promising early predictor. This study aims to present a comprehensive review of the FGF19 subfamily, emphasizing its role in GDM and predicting its long-term metabolic consequences for mothers and their offspring.

Mechanism of the Fibroblast Growth Factor 23/α-Klotho Axis in Peripheral Blood Mononuclear Cell Inflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a prevalent type of dementia and threatens the health of most elderly people and poses a huge burden to families and society. The fibroblast growth factor 23 (FGF23)/α-Klotho axis is associated with multiple aging-related diseases. Hence, this study explored the mechanism of the FGF23/α-Klotho axis in AD. FGF23/α-Klotho protein contents and levels of inflammatory cytokines in AD patients were measured, and the correlation between FGF23/α-Klotho protein contents and inflammatory cytokines was analyzed. FGF23 and α-Klotho expressions were blocked in peripheral blood mononuclear cells (PBMCs) in AD patients (AD-PBMCs) to assess the effects on cell inflammation and the Wnt/β-catenin pathway activation. The Wnt/β-catenin pathway was inhibited to evaluate cell inflammation. Combined treatments of the cells were conducted to verify the role of the FGF23/α-Klotho axis and the Wnt/β-catenin pathway in inflammation in AD-PBMCs. Increased FGF23 protein concentration and reduced α-Klotho protein concentration were observed in AD patients and correlated with inflammatory cytokine levels. FGF23 inhibition or α-Klotho overexpression reduced the production of inflammatory cytokines and activated the Wnt/β-catenin pathway in AD-PBMCs. Blocking the Wnt/β-catenin pathway increased inflammatory cytokine production in AD-PBMCs and annulled the effects of the FGF23/α-Klotho axis on AD-induced cell inflammation. We concluded that the FGF23/α-Klotho axis can regulate the AD-induced cell inflammation through the Wnt/β-catenin pathway.

Advances of Fibroblast Growth Factor/Receptor Signaling Pathway in Hepatocellular Carcinoma and its Pharmacotherapeutic Targets

Hepatocellular carcinoma (HCC) is a type of primary liver cancer with poor prognosis, and its incidence and mortality rate are increasing worldwide. It is refractory to conventional chemotherapy and radiotherapy owing to its high tumor heterogeneity. Accumulated genetic alterations and aberrant cell signaling pathway have been characterized in HCC. The fibroblast growth factor (FGF) family and their receptors (FGFRs) are involved in diverse biological activities, including embryonic development, proliferation, differentiation, survival, angiogenesis, and migration, etc. Data mining results of The Cancer Genome Atlas demonstrate high levels of FGF and/or FGFR expression in HCC tumors compared with normal tissues. Moreover, substantial evidence indicates that the FGF/FGFR signaling axis plays an important role in various mechanisms that contribute to HCC development. At present, several inhibitors targeting FGF/FGFR, such as multikinase inhibitors, specific FGFR4 inhibitors, and FGF ligand traps, exhibit antitumor activity in preclinical or early development phases in HCC. In this review, we summarize the research progress regarding the molecular implications of FGF/FGFR-mediated signaling and the development of FGFR-targeted therapeutics in hepatocarcinogenesis.

Klotho dysfunction: A pathway linking the aging process to bipolar disorder?

AIM

Although accelerated aging profile has been described in bipolar disorder (BD), the biology linking BD and aging is still largely unknown. Reduced levels and/or activity of a protein named Klotho is associated with decreased life span, premature aging and occurrence of age-related diseases. Therefore, this study was designed to evaluate plasma levels of Klotho in BD patients and controls.

METHODS

Forty patients with type 1 BD and 30 controls were enrolled in this study. After clinical evaluation, peripheral blood samples were drawn and plasma levels of Klotho were measured using enzyme-linked immunosorbent assay.

RESULTS

Patients with BD and controls presented similar age and sex distribution. The mean ± SD length of illness was 24.00 ± 12.75 years. BD patients presented increased frequency of clinical comorbidities in comparison with controls, mainly arterial hypertension, diabetes mellitus, and hypothyroidism. Both patients with BD in remission and in mania exhibited increased plasma levels of Klotho in comparison with controls. There was no significant difference between patients in mania and patients in remission regarding the levels of Klotho.

CONCLUSION

Klotho-related pathway is altered in BD. Contrary to our original hypothesis, our sample of patients with BD presented increased plasma levels of Klotho in comparison with controls. Elevated levels of Klotho in long-term BD patients may be associated with the disorder progression. Further studies are needed to better understand the role of Klotho in BD and other mood disorders.

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.

Metabolic roles of endocrine fibroblast growth factors

Considerable effort is currently being devoted to understanding the physiological and pharmacological action of the endocrine fibroblast growth factors (FGFs). These three proteins (FGF15/19, FGF21 and FGF23) act in a tissue-specific manner through a membrane-complex consisting of an FGF-receptor and α/βKlotho. FGF15/19 is produced in the intestine and regulates postprandial liver metabolism and gallbladder filling. FGF21 is largely liver-derived and co-ordinates adaptive changes in response to nutritional and physiological stresses. FGF23 signals from the bone to the kidney to maintain phosphate homeostasis. In pharmacological settings, FGF15/19, FGF21, and the prototypical FGF1, potentially represent novel treatments for obesity and diabetes. This review summarises the recent advances in our understanding of the biology of these important metabolic regulators.

Is Klotho F352V Polymorphism the Missing Piece of the Bone Loss Puzzle in Renal Transplant Recipients?

BACKGROUND

Bone disorders are next to cardiovascular problems in frequency in renal transplant (RT) recipients. Reduction in 1,25-dihydroxycholecalciferol (1,25D) levels is among the reasons causing bone loss in these patients. Klotho (KL) serves as a co-receptor for fibroblast growth factor 23 (FGF23), and functions in vitamin D metabolism. KL polymorphisms have been identified in several studies, and phenylalanine to valine substitution at amino acid position 352 seemed to be important to KL function. We investigated KL F352V polymorphism and its relation with 1,25D levels in RT recipients.

METHODS

The study included 25 RT recipients (8 female, 17 male) and 26 (14 female, 12 male) healthy control subjects who were wild (FF) phenotypes in terms of KL F352V polymorphism. RT recipients with (FV, n = 11) and without (FF, n = 14) a heterozygote polymorphism were determined with high resolution DNA melting analysis of KL F352V polymorphism. Serum 1,25D levels were measured using the RIA method.

RESULTS

RT recipients with FV phenotype had significantly lower 1,25D levels (17.58 ± 18.38 pg/ml) compared to recipients with FF phenotype (44.91 ± 24.68 pg/ml) and control subjects (28.24 ± 12.13 pg/ml). 1,25D levels in RT recipients with FF phenotype were significantly higher than control subjects.

CONCLUSIONS

KL F352V polymorphism may increase the expression of FGF23 co-receptor, KL protein and thus may decrease renal expression of 1α-hydroxylase, and/or stimulate 24-hydroxylase in RT recipients. The resultant decrease 1,25D levels may participate in bone loss in these patients.