Administration of alpha klotho reduces liver and adipose lipid accumulation in obese mice

Therapeutic potential of AAV-FL-Klotho in obesity: Impact on weight loss and lipid metabolism in mice

Klotho, an anti-aging protein, has gained attention for its protective effects against various diseases, including metabolic disorders, through recombinant Klotho administration. However, the potential of Klotho as a target for gene therapy requires further exploration, as it remains relatively understudied in the context of metabolic disorders. In this study, we demonstrate that AAV-full length(FL)-Klotho administration induces weight loss in mice and provides protection against high-fat diet (HFD)-induced obesity and hepatic steatosis, concurrently reducing the weights of white adipose tissue and liver. AAV-FL-Klotho administration also enhanced thermogenic gene expression in brown adipose tissue (BAT) and improved the morphology of interscapular BAT. The weight loss effect of AAV-FL-Klotho was found to be, at least in part, mediated by UCP1-dependent thermogenesis in brown adipocytes, potentially influenced by hepatokines secreted from AAV-FL-Klotho-transduced hepatocytes. These findings suggest that AAV-FL-Klotho is an attractive candidate for gene therapy to combat obesity. Nevertheless, unbiased experiments have also revealed disturbances in lipid metabolism due to AAV-FL-Klotho, as evidenced by the emergence of lipomas and increased expression of hepatic lipogenic proteins.

Serum α-Klotho and fibroblast growth factor 23 levels are not associated with non-proliferative diabetic retinopathy in type 1 diabetes mellitus

Diabetic retinopathy is a commonly observed cause of blindness and is a common problem in individuals with diabetes. Recent investigations have showed the capability of serum α-Klotho and FGF 23 in mitigating the effects of diabetic retinopathy. This study aimed to discover the correlation between FGF 23, α-Klotho, and diabetic retinopathy in type 1 diabetics. This case-control study included 63 diabetic patients and 66 healthy controls. Following an overnight duration of fasting, morning blood samples were taken from both the patient and the control groups. The serum concentrations of α-Klotho and FGF 23 were quantified. An experienced ophthalmologist inspected the retinopathy. All participants in this study have moderate non-proliferative retinopathy. A p value under 0.05 was considered statistically significant. The mean α-Klotho level for retinopathic diabetic patients was 501.7 ± 172.2 pg/mL and 579.6 ± 312.1 pg/mL for non-retinopathic diabetic patients. In comparison, α-Klotho level of the control group was 523.2 ± 265.4 pg/mL (p = 0.531). The mean of FGF 23 level did not demonstrate a significant difference (p = 0.259). The mean FGF 23 level were 75.7 ± 14.0 pg/mL, 74.0 ± 14.8 pg/mL and 79.3 ± 14.4 pg/mL in groups, respectively. In conclusion, there was no significant difference in FGF 23 and α-Klotho levels between type 1 diabetics with and without retinopathy when compared to the control group.

Klotho regulates the myogenic response of muscle to mechanical loading and exercise

NEW FINDINGS

What is the central question of this study? Does the hormone Klotho affect the myogenic response of muscle cells to mechanical loading or exercise? What is the main finding and its importance? Klotho prevents direct, mechanical activation of genes that regulate muscle differentiation, including genes that encode the myogenic regulatory factor myogenin and proteins in the canonical Wnt signalling pathway. Similarly, elevated levels of klotho expression in vivo prevent the exercise-induced increase in myogenin-expressing cells and reduce exercise-induced activation of the Wnt pathway. These findings demonstrate a new mechanism through which the responses of muscle to the mechanical environment are regulated.

ABSTRACT

Muscle growth is influenced by changes in the mechanical environment that affect the expression of genes that regulate myogenesis. We tested whether the hormone Klotho could influence the response of muscle to mechanical loading. Applying mechanical loads to myoblasts in vitro increased RNA encoding transcription factors that are expressed in activated myoblasts (Myod) and in myogenic cells that have initiated terminal differentiation (Myog). However, application of Klotho to myoblasts prevented the loading-induced activation of Myog without affecting loading-induced activation of Myod. This indicates that elevated Klotho inhibits mechanically-induced differentiation of myogenic cells. Elevated Klotho also reduced the transcription of genes encoding proteins involved in the canonical Wnt pathway or their target genes (Wnt9a, Wnt10a, Ccnd1). Because the canonical Wnt pathway promotes differentiation of myogenic cells, these findings indicate that Klotho inhibits the differentiation of myogenic cells experiencing mechanical loading. We then tested whether these effects of Klotho occurred in muscles of mice experiencing high-intensity interval training (HIIT) by comparing wild-type mice and klotho transgenic mice. The expression of a klotho transgene combined with HIIT synergized to tremendously elevate numbers of Pax7+ satellite cells and activated MyoD+ cells. However, transgene expression prevented the increase in myogenin+ cells caused by HIIT in wild-type mice. Furthermore, transgene expression diminished the HIIT-induced activation of the canonical Wnt pathway in Pax7+ satellite cells. Collectively, these findings show that Klotho inhibits loading- or exercise-induced activation of muscle differentiation and indicate a new mechanism through which the responses of muscle to the mechanical environment are regulated.

Relationship between klotho and physical function in healthy aging

Epidemiological studies have reported a strong association between circulating Klotho and physical function; however, the cohorts were comprised of older adults with multiple comorbidities. Herein, we examined the relationship between Klotho and physical function in a community-based cohort of healthy adults. In this cross-sectional study, serum Klotho was measured in 80 adults who visited the Musculoskeletal Function, Imaging, and Tissue Resource Core of the Indiana Center for Musculoskeletal Health. Participants (n = 20, 10 [50%] men per group) were chosen into four age groups: 20-34, 35-49, 50-64, and ≥ 65 years, and were further grouped based on performance (low vs. high) on grip strength and chair stand tests. Klotho levels were lower in the ≥ 65 years group (703.0 [189.3] pg/mL; p = 0.022) and the 50-64 years group (722.6 [190.5] pg/mL; p = 0.045) compared to 20-34 years (916.1 [284.8] pg/mL). No differences were observed in Klotho between the low and high performers. The ≥ 65 years group walked a shorter distance during the 6-min walk test (6MWT) compared to 20-34 years (p = 0.005). Klotho was correlated with age (p < 0.001), body fat (p = 0.037), and 6MWT distance (p = 0.022). Klotho levels decline as early as the fifth decade of life, potentially before the onset of age-related impairment in exercise capacity.

Emerging role of α-Klotho in energy metabolism and cardiometabolic diseases

BACKGROUND AND AIM

Klotho was first identified as a gene associated with aging and longevity in 1997. α-Klotho is an anti-aging protein and its role in energy metabolism, various cardiovascular diseases (CVDs), and metabolic disorders is increasingly being recognized. In this review, we aimed to outline the potential protective role and therapeutic prospects of α-Klotho in energy metabolism and cardiometabolic diseases (CMDs).

METHODS

We comprehensively reviewed the relevant literature in PubMed using the keywords 'Klotho', 'metabolism', 'cardiovascular', 'diabetes', 'obesity', 'metabolic syndrome', and 'nonalcoholic fatty liver disease'.

RESULTS

α-Klotho can be divided into membrane-bound Klotho, secreted Klotho, and the most studied circulating soluble Klotho that can act as a hormone. Klotho gene polymorphisms have been implicated in energy metabolism and CMDs. α-Klotho can inhibit insulin/insulin growth factor-1 signaling and its overexpression can lead to a 'healthy insulin resistance' and may exert beneficial effects on the regulation of glycolipid metabolism and central energy homeostasis. α-Klotho, mainly serum Klotho, has been revealed to be protective against CVDs, diabetes and its complications, obesity, and nonalcoholic fatty liver disease. Human recombinant Klotho protein/Klotho gene delivery, multiple drugs, or natural products, and exercise can increase α-Klotho expression.

CONCLUSION

Overall, α-Klotho has demonstrated its potential as a promising target for modulating energy metabolism and CMDs, and further research is needed to explore its utilization in clinical practice in the future.

Association between klotho and non-alcoholic fatty liver disease and liver fibrosis based on the NHANES 2007-2016

INTRODUCTION AND OBJECTIVES

This study aims to explore the association between Klotho and Non-Alcoholic Fatty Liver Disease (NAFLD), a condition affecting millions worldwide. Klotho may have a protective effect against NAFLD mechanisms like inflammation, oxidative stress, and fibrosis. The study will use FLI and FIB-4 score to diagnose NAFLD in a large population for investigating the link between Klotho and NAFLD.

MATERIALS AND METHODS

The study aimed to explore the association between Klotho and NAFLD by measuring the α-Klotho protein levels in the participants' blood using ELISA. Patients with underlying chronic liver diseases were excluded. The severity of NAFLD was evaluated using FLI and FIB-4, and logistic regression models were used to analyze the data obtained from NHANES. Subgroup analyses were conducted to study Klotho's effect on hepatic steatosis and fibrosis in diverse subpopulations.

RESULTS

The study found that low levels of α-Klotho were associated with NAFLD, with ORs ranging from 0.72 to 0.83. However, high levels of α-Klotho were associated with NAFLD-related fibrosis. The Q4 group showed significant results in individuals aged 51 years or younger and in females. Non-Hispanic White ethnicity, education level of high school or above, non-smoking, non-hypertension, and non-diabetic groups showed negative correlations.

CONCLUSIONS

Our study suggests a potential correlation between α-Klotho levels in the blood and NAFLD in adult patients, especially among younger individuals, females and Non-Hispanic Whites. Elevated α-Klotho levels may have therapeutic benefits in treating NAFLD. Further research is required to validate these findings, but they provide new insights for managing this condition.

The association of serum Klotho concentrations with hyperlipidemia prevalence and lipid levels among US adults: a cross-sectional study

BACKGROUND

Klotho has anti-oxidative and anti-inflammatory properties. However, little is known about whether high Klotho concentrations were associated with reduced hyperlipidemia risk and improved plasma lipid levels.

METHODS

Participants with complete data on serum Klotho and plasma lipid concentrations from the 2007-2016 National Health and Nutrition Examination Survey were included. Weighted regression models were fitted to explore the association of Klotho concentrations with hyperlipidemia risk and plasma lipid levels while restricted cubic spline models were applied to explore the dose-response relationship. Additionally, we assessed the mediating effects of C-reaction protein (CRP) on the foregoing association.

RESULTS

Individuals in the fourth and fifth quintile of serum Klotho had an adjusted odds ratio (OR) of 0.77 (95%CI: 0.65, 0.93) and 0.67 (95%CI: 0.65, 0.93) for hyperlipidemia. Doubling of serum Klotho concentrations was associated with decreased hyperlipidemia risk (OR = 0.81; 95%CI: 0.68, 0.95) and triglyceride levels (13.25 mg/dL; 95%CI: 4.02, 22.47), with a monotonic dose-response relationship. Individuals in the fourth and fifth quintile of serum Klotho had a 0.07 (95%CI: 0.002, 0.13), 0.08 (95%CI: 0.02, 0.15) and 0.05 (95%CI: -0.03, 0.12) mg/dL decreased CRP levels, with a marginally significant trend (Ptrend = 0.05).

CONCLUSIONS

Higher Klotho concentrations were associated with reduced hyperlipidemia risk and triglyceride levels. Klotho supplementation maybe a promising method to intervene and prevent hyperlipidemia, but the underlying mechanism should be further explored.

Higher levels of serum α-Klotho are longitudinally associated with less central obesity in girls experiencing weight gain

Introduction

Klotho is an anti-aging protein that reduces adiposity and increases caloric expenditure, among others. Although associations between secreted α-Klotho levels and obesity have been described, its relationship with central obesity and visceral fat accumulation during childhood is poorly understood. Our objective was to study the longitudinal associations between serum α-Klotho concentrations and obesity-related parameters in apparently healthy children.

Subjects and methods

We studied a cohort of 208 apparently healthy school-age children (107 girls and 101 boys) assessed at baseline (mean age 8.5 ± 1.8 years) and at follow-up 4 years later. Serum α-Klotho concentrations were measured at baseline in all subjects. Obesity-related parameters, such as BMI, waist circumference, body fat, visceral fat, triglyceride levels, HOMA-IR index, and C-reactive protein were studied. Boys and girls were classified into 3 groups according to weight change between baseline and follow-up visits: weight loss, stable weight, or weight gain (based on a BMI-SDS change cut-off > 0.35 SD).

Results

In girls (N=107), but not in boys, we observed negative associations of serum α-Klotho protein with BMI, waist circumference, body fat, visceral fat, HOMA IR index, and C-reactive protein at baseline and also at follow-up. The associations of α-Klotho and obesity-related parameters were more evident in girls who exhibited weight gain. In such girls, multivariate regression analyses (adjusting for age, puberty and baseline weight/height ratio) showed that α-Klotho protein was negatively associated with follow-up BMI, waist circumference, and visceral fat (p = 0.003 to 0.028). For each 1 SD-increase in baseline α-Klotho, follow-up waist circumference decreased by 4.15 cm and visceral fat by 1.38 mm.

Conclusions

In school-age girls, serum α-Klotho concentrations are longitudinally related to a more favorable metabolic profile. In girls experiencing weight gain, α-Klotho may prove to be a protective factor against the accumulation of visceral fat.

Reduced Klotho expression and its prognostic significance in canine hepatocellular carcinoma

Klotho is an anti-ageing gene and is known to act as a tumour suppressor in human hepatocellular carcinoma (HCC). According to a previous study, Klotho is present in normal canine mammary glands, and down-expression in tumours is positively associated with negative prognosis. However, the presence and significance of Klotho in canine HCC has not yet been reported. This study aimed to confirm Klotho expression in normal canine liver tissues using western blotting and immunohistochemistry, and whether the expression differed in non-neoplastic liver disease and HCC. Furthermore, correlation between clinicopathologic features and expression of Klotho was evaluated. All of the normal liver tissues showed the presence of Klotho, and Klotho expression was significantly decreased in the HCC tissue as compared to the non-neoplastic hepatic tissue. Additionally, Klotho expression was significantly associated with tumour size (P = .045), liver enzyme (alanine aminotransferase (ALT)) (P = .018), and metastasis (P = .024). Analysis of the survival curve revealed that reduced Klotho expression was significantly associated with poor disease-free survival (P = .041) in HCC. These results show that Klotho expression is present in normal canine liver tissue and that reduced Klotho expression is associated with poor prognosis in canine HCC. Thus, Klotho was presumed to be a potential clinical prognostic marker for canine HCC.

Association between serum klotho levels and cardiovascular disease risk factors in older adults

Background

Klotho deficiency is a significant predictor of cardiovascular disease (CVD)-related mortality and morbidity. However, research assessing the association between klotho and individual risk factors of CVD is limited. This study aimed to explore the association between circulating serum klotho levels and risk factors for CVD in adults.

Methods

We used the 2007–2016 National Health and Nutrition Examination Survey and included 13,154 participants for whom serum klotho levels were available. Body mass index (BMI), exercise, smoking status, alcohol consumption, hypertension, dyslipidemia, serum lipid parameters, and blood pressure were considered as CVD risk factors.

Results

Circulating klotho levels were negatively associated with being overweight (beta coefficient: − 22.609, p = 0.0025), obesity (beta coefficient: − 23.716, p = 0.0011), current smoking (beta coefficient: − 46.412, p < 0.0001), and alcohol consumption (beta coefficient: − 51.194, p < 0.0001). There was a positive association between serum klotho levels and no history of dyslipidemia (beta coefficient: 15.474, p = 0.0053). Serum klotho levels were significantly decreased by a unit increase in triglycerides (beta coefficient: − 0.117, p = 0.0006) and total cholesterol (beta coefficient: − 0.249, p = 0.0002). There was a significant non-linear relationship between serum klotho levels, triglycerides, and total cholesterol.

Conclusions

Lower serum klotho levels are associated with certain CVD risk factors, including high BMI, smoking, alcohol consumption, and lipid parameters (triglycerides and total cholesterol). This study suggests that the soluble klotho level may be a potential marker for CVD risk.

Klotho Levels and Their Relationship with Inflammation and Survival among Alcoholic Patients

α-Klotho (Klotho) is an antiaging hormone with anti-inflammatory and antioxidative properties. Some studies suggest that Klotho increases in response to enhanced oxidative damage and inflammation. Alcoholism is a proinflammatory condition. The aim of this study was to analyze the relationship between Klotho and the serum levels of the inflammatory markers in alcoholic liver disease and to assess its prognostic value. We included 184 alcoholics and 35 age- and sex-matched controls. We determined the serum levels of Klotho, the tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-8, and malondialdehyde (MDA), and routine laboratory variables. Patients were followed-up with during 16 ± 18 months; 67 patients died. Klotho levels were higher among cirrhotics (with KW = 37.00 and p < 0.001) and were related to the Child−Pugh score (with KW = 15.96 and p < 0.001) and to the TNF-α (ρ = 0.28; p < 0.001) and MDA (ρ = 0.21; p = 0.006). The child’s groups were associated with mortality, both in the univariate (with the log-rank = 13.56, p = 0.001, Breslow = 12.33, and p = 0.002) and multivariate (with β = 0.43, p = 0.02, and OR = 1.53 (1.07−2.15)) analyses, also introducing Klotho and the TNF-α as dichotomic variables. However, the independent prognostic value of the Child’s groups was displaced by Klotho when only cirrhotics were considered; Klotho, over the median (574.4 pg/mL), was associated with higher mortality (with p = 0.04 and OR = 2.68 (1.06−6.84)). We conclude that Klotho is increased in liver cirrhosis. It is directly related to TNF-α, MDA, and to mortality in cirrhotics.

Pathobiology of the Klotho Antiaging Protein and Therapeutic Considerations

The α-Klotho protein (henceforth denoted Klotho) has antiaging properties, as first observed in mice homozygous for a hypomorphic Klotho gene (kl/kl). These mice have a shortened lifespan, stunted growth, renal disease, hyperphosphatemia, hypercalcemia, vascular calcification, cardiac hypertrophy, hypertension, pulmonary disease, cognitive impairment, multi-organ atrophy and fibrosis. Overexpression of Klotho has opposite effects, extending lifespan. In humans, Klotho levels decline with age, chronic kidney disease, diabetes, Alzheimer’s disease and other conditions. Low Klotho levels correlate with an increase in the death rate from all causes. Klotho acts either as an obligate coreceptor for fibroblast growth factor 23 (FGF23), or as a soluble pleiotropic endocrine hormone (s-Klotho). It is mainly produced in the kidneys, but also in the brain, pancreas and other tissues. On renal tubular-cell membranes, it associates with FGF receptors to bind FGF23. Produced in bones, FGF23 regulates renal excretion of phosphate (phosphaturic effect) and vitamin D metabolism. Lack of Klotho or FGF23 results in hyperphosphatemia and hypervitaminosis D. With age, human renal function often deteriorates, lowering Klotho levels. This appears to promote age-related pathology. Remarkably, Klotho inhibits four pathways that have been linked to aging in various ways: Transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), Wnt and NF-κB. These can induce cellular senescence, apoptosis, inflammation, immune dysfunction, fibrosis and neoplasia. Furthermore, Klotho increases cell-protective antioxidant enzymes through Nrf2 and FoxO. In accord, preclinical Klotho therapy ameliorated renal, cardiovascular, diabetes-related and neurodegenerative diseases, as well as cancer. s-Klotho protein injection was effective, but requires further investigation. Several drugs enhance circulating Klotho levels, and some cross the blood-brain barrier to potentially act in the brain. In clinical trials, increased Klotho was noted with renin-angiotensin system inhibitors (losartan, valsartan), a statin (fluvastatin), mTOR inhibitors (rapamycin, everolimus), vitamin D and pentoxifylline. In preclinical work, antidiabetic drugs (metformin, GLP-1-based, GABA, PPAR-γ agonists) also enhanced Klotho. Several traditional medicines and/or nutraceuticals increased Klotho in rodents, including astaxanthin, curcumin, ginseng, ligustilide and resveratrol. Notably, exercise and sport activity increased Klotho. This review addresses molecular, physiological and therapeutic aspects of Klotho.

Association between Soluble α-Klotho Protein and Metabolic Syndrome in the Adult Population

Klotho protein is an anti-aging protein and plays multiple roles in ion-regulation, anti-oxidative stress, and energy metabolism through various pathways. Metabolic syndrome is a combination of multiple conditions that compose of multiple risk factors of cardiovascular disease and type 2 diabetes. Gene regulation and protein expression are discovered associated with metabolic syndrome. We aimed to figure out the correlation between Klotho protein and metabolic syndrome in generally healthy adults. A cross-sectional study of 9976 respondents ≥ 18 years old from the US National Health and Nutrition Examination Survey (2007-2012) by utilizing their soluble Klotho protein concentrations. Multivariate linear regression models were used to analyze the effect of soluble Klotho protein on the prevalence of metabolic syndrome. Soluble Klotho protein concentration was inversely correlated with the presence of metabolic syndromes (p = 0.013) and numbers of components that met the definition of metabolic syndrome (p < 0.05). The concentration of Soluble Klotho protein was negatively associated with abdominal obesity and high triglyceride (TG) in the adjusted model (p < 0.05). Soluble Klotho protein is correlated with changing metabolic syndrome components in adults, especially central obesity and high TG levels. Despite conventional function as co-factor with fibroblast growth factor-23 (FGF23) that regulates phosphate and vitamin D homeostasis, FGF23-independent soluble Klotho protein may act on multiple signal pathways in different organs and tissue in roles of anti-aging and protection from metabolic syndrome.

Protective association of Klotho rs495392 gene polymorphism against hepatic steatosis in non-alcoholic fatty liver disease patients

Background/Aims

Non-alcoholic fatty liver disease (NAFLD) is closely associated with metabolic dysfunction. Among the multiple factors, genetic variation acts as important modifiers. Klotho, an enzyme encoded by the klotho (KL) gene in human, has been implicated in the pathogenesis of metabolic dysfunctions. However, the impact of variants in KL on NAFLD risk remains poorly understood. The aim of this study was to investigate the impact of KL rs495392 C>A polymorphism on the histological severity of NAFLD.

Methods

We evaluated the impact of the KL rs495392 polymorphism on liver histology in 531 Chinese with NAFLD and replicated that in the population-based Rotterdam Study cohort. The interactions between the rs495392, vitamin D, and patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 polymorphism were also analyzed.

Results

Carriage of the rs495392 A allele had a protective effect on steatosis severity (odds ratio [OR], 0.61; 95% confidence interval [CI], 0.42–0.89; P=0.010) in Chinese patients. After adjustment for potential confounders, the A allele remained significant with a protective effect (OR, 0.66; 95% CI, 0.45–0.98; P=0.040). The effect on hepatic steatosis was confirmed in the Rotterdam Study cohort. Additional analysis showed the association between serum vitamin D levels and NAFLD specifically in rs495392 A allele carriers, but not in non-carriers. Moreover, we found that the rs495392 A allele attenuated the detrimental impact of PNPLA3 rs738409 G allele on the risk of severe hepatic steatosis.

Conclusions

The KL rs495392 polymorphism has a protective effect against hepatic steatosis in patients with NAFLD.

Association of bone biomarkers with advanced atherosclerotic disease in people with overweight/obesity

BACKGROUND

A growing body of evidence suggests a potential link between bone metabolism and cardiovascular disease. Aim of this study was to investigate the relationship between levels of circulating bone turnover biomarkers and advanced atherosclerosis.

METHODS

Klotho (KL), sclerostin (SOST), osteopontin (OPN) and osteoprotegerin (OPG) were measured in patients undergoing elective coronary angiography and carotid Doppler ultrasound. The primary outcome was the difference in bone biomarkers levels between participants with and without advanced atherosclerosis, defined as the presence of a critical coronary (≥70%) and/or carotid (≥50%) stenosis.

RESULTS

A total of 80 subjects (32.5% females) with a mean age of 68 ± 10 years were included. Advanced atherosclerosis was detected in 55 (68.8%) patients. Subjects with advanced atherosclerosis showed higher serum levels of OPG (p = 0.0015) and SOST (p = 0.017) and similar levels of KL (p = 0.62) and OPN (p = 0.06) compared to patients without. After adjustment for age and sex, only elevated levels of OPG remained significantly associated with advanced atherosclerosis (p = 0.011).

CONCLUSIONS

Higher serum levels of OPG are independently associated with advanced atherosclerosis confirming a common bond between bone metabolism and vascular disease. Further investigations on the role of selected bone biomarkers in the pathogenesis of cardiovascular disease are needed.

Circulating α-klotho regulates metabolism via distinct central and peripheral mechanisms

Emerging evidence implicates the circulating α-klotho protein as a prominent regulator of energy balance and substrate metabolism, with diverse, tissue-specific functions. Despite its well-documented ubiquitous role inhibiting insulin signaling, α-klotho elicits potent antidiabetic and anti-obesogenic effects. α-Klotho facilitates insulin release and promotes β cell health in the pancreas, stimulates lipid oxidation in liver and adipose tissue, attenuates hepatic gluconeogenesis, and increases whole-body energy expenditure. The mechanisms underlying α-klotho's peripheral functions are multifaceted, including hydrolyzing transient receptor potential channels, stimulating integrin β1➔focal adhesion kinase signaling, and activating PPARα via inhibition of insulin-like growth factor receptor 1. Moreover, until recently, potential metabolic roles of α-klotho in the central nervous system remained unexplored; however, a novel α-klotho➔fibroblast growth factor receptor➔PI3kinase signaling axis in the arcuate nucleus of the hypothalamus has been identified as a critical regulator of energy balance and glucose metabolism. Overall, the role of circulating α-klotho in the regulation of metabolism is a new focus of research, but accumulating evidence identifies this protein as an encouraging therapeutic target for Type 1 and 2 Diabetes and obesity. This review analyzes the new literature investigating α-klotho-mediated regulation of metabolism and proposes impactful future directions to progress our understanding of this complex metabolic protein.

Effects of thyroxine and propylthiouracil on feeding behavior and the expression of hypothalamic appetite-regulating peptides and thyroid function in goldfish (Carassius auratus)

There is poor evidence for an association between thyroidal state, feeding and appetite regulation in fish. We assessed how an altered thyroid state influences feeding behavior, food intake and expression of hypothalamic appetite-regulating peptides (Klotho-α and Klotho-β; orexin, OX; cholecystokinin, CCK; agouti-related peptide, AgRP; cannabinoid receptor 1, CB1) in goldfish. We also measured the expressions of hypothalamic, pituitary and liver transcripts that regulate the thyroid [thyrotropin-releasing hormone (TRH), thyrotropin-releasing hormone receptor (TRH-R) type 1, thyroid stimulating hormone beta (TSHβ), deiodinases (DIO2, DIO3), UDP-glucuronosyltransferase (UGT1A1), thyroid receptor alpha and beta (TRα, TRβ)], and circulating levels of total thyroxine (tT₄) and total triiodothyronine (tT₃). Goldfish were implanted with propylthiouracil (PTU) or T₄ osmotic pumps for 12 days. T₄- treatment increased feeding behavior but not food intake, increased central TSHβ and DIO2, and hepatic DIO2 transcript expression and increased central DIO3 mRNA. Under hyperthyroid conditions, hypothalamic Klotho and CCK expressions were downregulated, suggesting an increased metabolic state and a hypothalamic response to regulate energy balance. AgRP, OX and CB1 were not affected by T₄ treatment. PTU had no effect on any of the parameters examined, suggesting it is not a sensitive thyroid inhibitor in fish. Overall, we show that unlike in mammals, hyperthyroid conditions in goldfish do not lead to an increased desire or need to consume food, furthering evidence for a weak link between the thyroid and appetite.

Extrarenal expression of α-klotho, the kidney related longevity gene, in Heterocephalus glaber, the long living Naked Mole Rat

The Naked Mole Rat (NMR), Heterocephalus glaber, provides an interesting model for studying biomarkers of longevity due to its long lifespan of more than 30 years, almost ten times longer than that of mice and rats. α-Klotho (klotho) is an aging-suppressor gene, and overexpression of klotho is associated with extended lifespan in mice. Klotho is predominantly expressed in the kidney. The expression profile of klotho in the NMR has not previously been reported. The present investigation studied the expression of klotho in the kidney of NMR with that of Rattus Norvegicus (RN) and demonstrated that klotho was expressed in the kidney of NMR at the same level as found in RN. Besides, a significant expression of Kl mRNA was found in the liver of NMR, in contrast to RN, where no hepatic expression was detected. The Klotho expression was further confirmed at the protein level. Thus, the results of the present comparative study indicate a differential tissue expression of klotho between different species. Besides its important function in the kidney, Klotho might also be of significance in the liver of NMR. It is suggested that the hepatic extrarenal expression of klotho may function as a further longevity-related factor in supplement to the Klotho in the kidney.

Neuroprotective action of Cortexin, Cerebrolysin and Actovegin in acute or chronic brain ischemia in rats

This study was the first to compare the neuroprotective activity of Cerebrolysin^®, Actovegin^® and Cortexin^® in rodent models of acute and chronic brain ischemia. The neuroprotective action was evaluated in animals with acute (middle cerebral artery occlusion) or chronic (common carotid artery stenosis) brain ischemia models in male rats. Cortexin^® (1 or 3 mg/kg/day), Cerebrolysin^® (538 or 1614 mg/kg/day) and Actovegin^® (200 mg/kg/day) were administered for 10 days. To assess the neurological and motor impairments, open field test, adhesive removal test, rotarod performance test and Morris water maze test were performed. Brain damage was assessed macro- and microscopically, and antioxidant system activity was measured in brain homogenates. In separate experiments in vitro binding of Cortexin^® to a wide panel of receptors was assessed, and blood-brain barrier permeability of Cortexin^® was assessed in mice in vivo. Cortexin^® or Cerebrolysin^® and, to a lesser extent, Actovegin^® improved the recovery of neurological functions, reduced the severity of sensorimotor and cognitive impairments in rats. Cortexin^® reduced the size of necrosis of brain tissue in acute ischemia, improved functioning of the antioxidant system and prevented the development of severe neurodegenerative changes in chronic ischemia model. Radioactively labeled Cortexin^® crossed the blood-brain barrier in mice in vivo with concentrations equal to 6–8% of concentrations found in whole blood. During in vitro binding assay Cortexin^® (10 μg/ml) demonstrated high or moderate binding to AMPA-receptors (80.1%), kainate receptors (73.5%), mGluR1 (49.0%), GABAA1 (44.0%) and mGluR5 (39.7%), which means that effects observed in vivo could be related on the glutamatergic and GABAergic actions of Cortexin^®. Thus, Cortexin, 1 or 3 mg/kg, or Cerebrolysin^®, 538 or 1614 mg/kg, were effective in models acute and chronic brain ischemia in rats. Cortexin^® contains compounds acting on AMPA, kainate, mGluR1, GABAA1 and mGluR5 receptors in vitro, and readily crosses the blood-brain barrier in mice.

Cisplatin decreases HOXA13 and alphaVBeta3 integrin levels in the uterus

OBJECTIVE

To examine the effects of cisplatin on uterine histology and implantation molecules and the possible protective role of recombinant Klotho administration on uterine histology and uterine receptivity in mice exposed to cisplatin.

MATERIALS AND METHODS

This study was conducted using thirty-two adult female mice assigned to four groups with 8 mice in each group. Saline was given to the 1st group, cisplatin to the 2nd group, recombinant mouse Klotho to the 3rd group and recombinant mouse Klotho plus cisplatin to the 4th group. Uterine tissues were examined for damage histologically and immunobiologically for the uterine receptivity markers HOXA13 and alphaVBeta3 integrin.

RESULTS

Apoptosis, degeneration, decrease in uterine thickness and uterine absence of gland scores were higher in the cisplatin group (3rd group) compared to the saline group (1st group) (cisplatin vs. saline p < 0.0001 for all parameters). In the recombinant Klotho plus cisplatin group (4th group), scores of apoptosis, degeneration, reduction in uterine thickness and uterine absence of gland were lower than the group receiving only cisplatin (cisplatin plus recombinant Klotho vs cisplatin, p = 0.006 for apoptosis; p = 0.017 for degeneration; p = 0.011 for the reduction in uterine thickness; p = 0.002 for the absence of gland). However, HOXA13 and alphaVBeta3 integrin staining levels were not different between the cisplatin group (group 3) and the cisplatin plus recombinant Klotho group (group 4) (p = 0.980 and p = 0.762, respectively.) CONCLUSION: Cisplatin has adverse effects on the uterus. Administration of recombinant Klotho was found to attenuate the cisplatin-induced damage but failed to preserve levels of the implantation molecules HOXA13 and alphaVbeta3. Further studies examining the effect of cisplatin toxicity using other implantation markers along with functional studies are needed.

The effects of recombinant klotho in cisplatin-induced ovarian failure in mice

AIM

To investigate whether recombinant klotho given concomitantly with cisplatin is effective in preventing cisplatin-induced ovarian damage.

METHODS

Thirty-two adult female mice were divided into four groups. Saline was given to the first group, cisplatin to the second group, recombinant mouse klotho to the third group, and recombinant mouse klotho + cisplatin to the fourth group. The removed ovarian tissues were examined and groups were compared histologically and immunohistochemical examination for antimullerian hormone (AMH), superoxide dismutase (SOD) and catalase expression were done. Glutathione peroxidase (GPx) and glutathione reductase (GR) activities were measured by ELISA.

RESULTS

Ovarian tissue weight, primary and secondary follicle counts were higher in cisplatin + recombinant klotho group compared to cisplatin group in our study (respectively p < 0.0001, p < 0.0001, and p = 0.010). Injury scores (stromal congestion, edema and infiltration, follicular degeneration scores and edema in corpus luteum scores) were similar between cisplatin and cisplatin + recombinant klotho groups (all p > 0.05). AMH staining intensities were similar between cisplatin and cisplatin + recombinant klotho groups (p = 0.925). There was no difference between the groups in terms of SOD, GPx, and GR (p > 0.05).

CONCLUSIONS

The recombinant klotho administered before cisplatin could partially protect the ovarian tissue from cisplatin-induced ovarian damage considering that there was no difference in histologic injury score parameters, AMH staining intensity and oxidative stress markers between cisplatin and cisplatin plus klotho groups except that klotho preserved follicules to some extent. The antioxidant mechanism of action of klotho may not be the primary protection mechanism in cisplatin induced ovarian injury.

Update on the Crosstalk Between Adipose Tissue and Mineral Balance in General Population and Chronic Kidney Disease

Adipose tissue is nowadays considered as a major endocrine organ, which apart from controlling lipid metabolism, displays a significant role in energy expenditure, food intake and in the regulation of various systemic physiological processes. Adipose derived pro-inflammatory cytokines and adipokines, particularly leptin and adiponectin, provide inter-communication of adipose tissue with various metabolic pathways, ultimately resulting in a complex network of interconnected organ systems. Recent clinical and experimental research has been focused on exploring the direct interaction between adipokine profile and elements of mineral metabolism, including parathormone (PTH), fibroblast growth factor-23 (FGF23) and calcitriol. The emerging crosstalk between adipose tissue and calcium and phosphorus homeostasis suggests that metabolic disorders from one system may directly affect the other and vice versa. It is current knowledge that fat metabolism disturbance, commonly encountered in obese individuals, influences the expression of calciotriopic hormones in general population, while various clinical trials attempting to successfully achieve body fat loss by modulating mineral profile have been published. In chronic kidney disease (CKD) state, there is an increasing evidence suggesting that mineral disorders, influence adipose tissue and linked endocrine function. On the contrary, the impact of disturbed fat metabolism on CKD related mineral disorders has been also evocated in clinical studies. Recognizing the pathogenetic mechanisms of communication between adipose tissue and mineral balance is critical for understanding the effects of metabolic perturbations from the one system to the other and for identifying possible therapeutic targets in case of disrupted homeostasis in one of the two connected systems. To that end, this review aims to enlighten the recent advances regarding the interplay between mineral metabolism, fat mass and adipokine profile, based on in vitro, in vivo and clinical studies, in general population and in the course of CKD.

Centrally circulating α-klotho inversely correlates with human obesity and modulates arcuate cell populations in mice

Objective

Our laboratory recently identified the centrally circulating α-klotho protein as a novel hypothalamic regulator of food intake and glucose metabolism in mice. The current study aimed to investigate novel molecular effectors of central α-klotho in the arcuate nucleus of the hypothalamus (ARC), while further deciphering its role regulating energy balance in both humans and mice.

Methods

Cerebrospinal fluid (CSF) was collected from 22 adults undergoing lower limb orthopedic surgeries, and correlations between body weight and α-klotho were determined using an α-klotho enzyme-linked immunosorbent assay (ELISA) kit. To investigate the effects of α-klotho on energy expenditure (EE), 2-day intracerebroventricular (ICV) treatment was performed in diet-induced obesity (DIO) mice housed in TSE Phenomaster indirect calorimetry metabolic cages. Immunohistochemical staining for cFOS and patch clamp electrophysiology were used to determine the effects of central α-klotho on proopiomelanocortin (POMC) and tyrosine hydroxylase (TH) neurons. Additional stainings were performed to determine novel roles for central α-klotho to regulate non-neuronal cell populations in the ARC. Lastly, ICV pretreatment with fibroblast growth factor receptor (FGFR) or PI3kinase inhibitors was performed to determine the intracellular signaling involved in α-klotho-mediated regulation of ARC nuclei.

Results

Obese/overweight human subjects had significantly lower CSF α-klotho concentrations compared to lean counterparts (1,044 ± 251 vs. 1616 ± 218 pmol/L, respectively). Additionally, 2 days of ICV α-klotho treatment increased EE in DIO mice. α-Klotho had no effects on TH neuron activity but elicited varied responses in POMC neurons, with 44% experiencing excitatory and 56% experiencing inhibitory effects. Inhibitor experiments identified an α-klotho→FGFR→PI3kinase signaling mechanism in the regulation of ARC POMC and NPY/AgRP neurons. Acute ICV α-klotho treatment also increased phosphorylated ERK in ARC astrocytes via FGFR signaling.

Conclusion

Our human CSF data provide the first evidence that impaired central α-klotho function may be involved in the pathophysiology of obesity. Furthermore, results in mouse models identify ARC POMC neurons and astrocytes as novel molecular effectors of central α-klotho. Overall, the current study highlights prominent roles of α-klotho→FGFR→PI3kinase signaling in the homeostatic regulation of ARC neurons and whole-body energy balance.

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Human CSF α-klotho concentrations exhibit a strong, inverse correlation with body weight and BMI.

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ICV α-klotho treatment increases energy expenditure in DIO mice.

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α-Klotho.→FGFR→PI3kinase signaling modulates ARC NPY/AgRP and POMC neurons.

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α-Klotho.→FGFR→ERK signaling regulates ARC astrocytes.

Distinct utilization of biotin in and between adipose and brain during aging is associated with a lipogenic shift in Wistar rat brain

Tissue-specific metabolism determines their functions that collectively sense and respond to numerous stress cues to achieve systemic homeostasis. Chronic stress skews such metabolic profiles and leads to failure of organs as evidenced by a bias towards lipid synthesis and storage in the aging brain, muscle, and liver under Alzheimer's disease, sarcopenia, and non-alcoholic fatty liver disease, respectively. In contrast, the tissue destined for lipid synthesis and storage, such as adipose, limits its threshold and develops diabetes mellitus. However, the underlying factors that contribute to this lipogenic shift between organs are unknown. From this perspective, differential biotin utilization between lipid-rich tissues such as adipose and brain during aging was hypothesized owing to the established role of biotin in lipogenesis. The same was tested using young and aged Wistar rats. We found that adipose-specific biotin content was much higher than the brain irrespective of aging status, as well as its associated cues. However, within tissues, the adipose fails to maintain its biotinylation levels during aging whereas the brain seizes more biotin and exhibits lipid accumulation. Furthermore, mimicking the age-related stress cues in vitro such as high glucose and endoplasmic reticulum stress deprive the astroglial biotin content, but not that of adipocytes. Lipid accumulation in the aging brain was also correlated with increased S-adenosylmethionine levels and biotin utilization by astrocytes. In summary, differential biotin utilization between adipose and brain under aging and their respective cell types like adipocytes and astrocytes under age-associated stress cues connects well with the lipogenic shift in rat brain.

Central α-Klotho Suppresses NPY/AgRP Neuron Activity and Regulates Metabolism in Mice

α-Klotho is a circulating factor with well-documented antiaging properties. However, the central role of α-klotho in metabolism remains largely unexplored. The current study investigated the potential role of central α-klotho to modulate neuropeptide Y/agouti-related peptide (NPY/AgRP)-expressing neurons, energy balance, and glucose homeostasis. Intracerebroventricular administration of α-klotho suppressed food intake, improved glucose profiles, and reduced body weight in mouse models of type 1 and 2 diabetes. Furthermore, central α-klotho inhibition via an anti-α-klotho antibody impaired glucose tolerance. Ex vivo patch clamp electrophysiology and immunohistochemical analysis revealed that α-klotho suppresses NPY/AgRP neuron activity, at least in part, by enhancing miniature inhibitory postsynaptic currents. Experiments in hypothalamic GT1-7 cells observed that α-klotho induces phosphorylation of AKT^ser473, ERK^{thr202/tyr204}, and FOXO1^ser256 as well as blunts AgRP gene transcription. Mechanistically, fibroblast growth factor receptor 1 (FGFR1) inhibition abolished the downstream signaling of α-klotho, negated its ability to modulate NPY/AgRP neurons, and blunted its therapeutic effects. Phosphatidylinositol 3 kinase (PI3K) inhibition also abolished α-klotho's ability to suppress food intake and improve glucose clearance. These results indicate a prominent role of hypothalamic α-klotho/FGFR1/PI3K signaling in the modulation of NPY/AgRP neuron activity and maintenance of energy homeostasis, thus providing new insight into the pathophysiology of metabolic disease.

Therapeutic implications of shared mechanisms in non-alcoholic fatty liver disease and chronic kidney disease

The most common cause of liver disease worldwide is now non-alcoholic fatty liver disease (NAFLD). NAFLD refers to a spectrum of disease ranging from steatosis to non-alcoholic steatohepatitis, causing cirrhosis, and ultimately hepatocellular carcinoma. However, the impact of NAFLD is not limited to the liver. NAFLD has extra-hepatic consequences, most notably, cardiovascular and renal disease. NAFLD and chronic kidney disease share pathogenic mechanisms including insulin resistance, lipotoxicity, inflammation and oxidative stress. Not surprisingly, there has been a recent surge in efforts to manage NAFLD in an integrated way that not only protects the liver but also delays comorbidities such as chronic kidney disease. This concept of simultaneously addressing the main disease target and comorbidities is key to improve outcomes, as recently demonstrated by clinical trials of SGLT2 inhibitors and GLP1 receptor agonists in diabetes. HIF activators, already marketed in China, also have the potential to protect both liver and kidney, as suggested by preclinical data. This review concisely discusses efforts at identifying common pathogenic pathways between NAFLD and chronic kidney disease with an emphasis on potential paradigm shifts in diagnostic workup and therapeutic management.

Klotho Pathways, Myelination Disorders, Neurodegenerative Diseases, and Epigenetic Drugs

In this review we outline a rationale for identifying neuroprotectants aimed at inducing endogenous Klotho activity and expression, which is epigenetic action, by definition. Such an approach should promote remyelination and/or stimulate myelin repair by acting on mitochondrial function, thereby heralding a life-saving path forward for patients suffering from neuroinflammatory diseases. Disorders of myelin in the nervous system damage the transmission of signals, resulting in loss of vision, motion, sensation, and other functions depending on the affected nerves, currently with no effective treatment. Klotho genes and their single-pass transmembrane Klotho proteins are powerful governors of the threads of life and death, true to the origin of their name, Fates, in Greek mythology. Among its many important functions, Klotho is an obligatory co-receptor that binds, activates, and/or potentiates critical fibroblast growth factor activity. Since the discovery of Klotho a little over two decades ago, it has become ever more apparent that when Klotho pathways go awry, oxidative stress and mitochondrial dysfunction take over, and age-related chronic disorders are likely to follow. The physiological consequences can be wide ranging, potentially wreaking havoc on the brain, eye, kidney, muscle, and more. Central nervous system disorders, neurodegenerative in nature, and especially those affecting the myelin sheath, represent worthy targets for advancing therapies that act upon Klotho pathways. Current drugs for these diseases, even therapeutics that are disease modifying rather than treating only the symptoms, leave much room for improvement. It is thus no wonder that this topic has caught the attention of biomedical researchers around the world.

Klotho/FGF23 and Wnt Signaling as Important Players in the Comorbidities Associated with Chronic Kidney Disease

Fibroblast Growth Factor 23 (FGF23) and Klotho play an essential role in the regulation of mineral metabolism, and both are altered as a consequence of renal failure. FGF23 increases to augment phosphaturia, which prevents phosphate accumulation at the early stages of chronic kidney disease (CKD). This effect of FGF23 requires the presence of Klotho in the renal tubules. However, Klotho expression is reduced as soon as renal function is starting to fail to generate a state of FGF23 resistance. Changes in these proteins directly affect to other mineral metabolism parameters; they may affect renal function and can produce damage in other organs such as bone, heart, or vessels. Some of the mechanisms responsible for the changes in FGF23 and Klotho levels are related to modifications in the Wnt signaling. This review examines the link between FGF23/Klotho and Wnt/β-catenin in different organs: kidney, heart, and bone. Activation of the canonical Wnt signaling produces changes in FGF23 and Klotho and vice versa; therefore, this pathway emerges as a potential therapeutic target that may help to prevent CKD-associated complications.

Systemic Klotho therapy protects against insulitis and enhances beta-cell mass in NOD mice

The levels of the anti-aging protein α-Klotho, in its soluble form (s-Klotho), are depressed in the circulation of patients with type 1 diabetes (T1D) or type 2 diabetes (T2D). Gene transfer experiments have suggested a protective role for β-cell specific expression of α-Klotho in murine models of T1D and T1D, but these approaches are not easily translatable to clinical therapy. It is unknown whether systemic s-Klotho protein treatment ameliorates disease in T1D, which is characterized by autoimmune destruction of β cells. We previously reported from in vitro experiments with β cells that s-Klotho increases insulin secretion, reduces cells death and promotes β-cell replication. Here, we investigated s-Klotho protein therapy in NOD mice, which have autoimmune T1D. We observed that diabetic NOD mice have significantly lower plasma levels of s-Klotho, compared to their non-diabetic counterparts. To examine in vivo effects of Klotho, we treated NOD mice with s-Klotho protein, or with a Klotho blocking antibody. Systemic treatment with s-Klotho ameliorated diabetes; notably increasing β-cell replication and total β-cell mass. Klotho expression was increased locally in the islets. s-Klotho also markedly reduced immune-cell infiltration of islets (insulitis). In contrast, administration of the Klotho antibody was detrimental, and aggravated the loss of β-cell mass. Thus, s-Klotho has protective effects in this model of T1D, and this appears to depend on a combination of increased β-cell replication and reduced insulitis. These findings suggest that s-Klotho might be effective as a new therapeutic agent for T1D.

High-Intensity Interval Training Restores Glycolipid Metabolism and Mitochondrial Function in Skeletal Muscle of Mice With Type 2 Diabetes

High-intensity interval training has been reported to lower fasting blood glucose and improve insulin resistance of type 2 diabetes without clear underlying mechanisms. The purpose of this study was to investigate the effect of high-intensity interval training on the glycolipid metabolism and mitochondrial dynamics in skeletal muscle of high-fat diet (HFD) and one-time 100 mg/kg streptozocin intraperitoneal injection-induced type 2 diabetes mellitus (T2DM) mice. Our results confirmed that high-intensity interval training reduced the body weight, fat mass, fasting blood glucose, and serum insulin of the T2DM mice. High-intensity interval training also improved glucose tolerance and insulin tolerance of the T2DM mice. Moreover, we found that high-intensity interval training also decreased lipid accumulation and increased glycogen synthesis in skeletal muscle of the T2DM mice. Ultrastructural analysis of the mitochondria showed that mitochondrial morphology and quantity were improved after 8 weeks of high-intensity interval training. Western blot analysis showed that the expression of mitochondrial biosynthesis related proteins and mitochondrial dynamics related proteins in high-intensity interval trained mice in skeletal muscle were enhanced. Taken together, these data suggest high-intensity interval training improved fasting blood glucose and glucose homeostasis possibly by ameliorating glycolipid metabolism and mitochondrial dynamics in skeletal muscle of the T2DM mice.

α-Klotho Expression in Mouse Tissues Following Acute Exhaustive Exercise

α-Klotho, a multifunctional protein, has been demonstrated to protect tissues from injury via anti-oxidation and anti-inflammatory effects. The expression of α-klotho is regulated by several physiological and pathological factors, including acute inflammatory stress, oxidative stress, hypertension, and chronic renal failure. Exhaustive exercise has been reported to result in tissue damage, which is induced by inflammation, oxidative stress, and energy metabolism disturbance. However, little is known about the effects of exhaustive exercise on the expression of α-klotho in various tissues. To determine the effects, the treadmill exhaustion test in mice was performed and the mice were sacrificed at different time points following exhaustive exercise. Our results confirmed that the full-length (130 kDa) and shorter-form (65 kDa) α-klotho were primarily expressed in the kidneys. Moreover, we found that, except for the kidneys and brain, other tissues primarily expressed the shorter-form α-klotho, including liver, which was in contrast to previous reports. Furthermore, the shorter-form α-klotho was decreased immediately following the acute exhaustive exercise and was then restored to the pre-exercise level or even higher levels in the next few days. Our results indicate that α-klotho may play a key role in the body exhaustion and recovery following exhaustive exercise.

Impaired function of fibroblast growth factor 23 / Klotho protein axis in prediabetes and diabetes mellitus: Promising predictor of cardiovascular risk

The discovery of clear molecular mechanisms of early cardiac and vascular complications in patients with prediabetes and known diabetes mellitus are core element of stratification at risk with predictive model creation further. Previous clinical studies have shown a pivotal role of impaired signaling axis of fibroblast growth factor 23 (FGF23), FGF23 receptor isoforms and its co-factor Klotho protein in cardiovascular (CV) complications in prediabetes and diabetes. Although there were data received in clinical studies, which confirmed a causative role of altered function of FGF-23/Klotho protein axis in manifestation of CV disease in prediabetes and type 2 diabetes mellitus (T2DM), the target therapy of these diseases directing on improvement of metabolic profiles, systemic and adipokine-relating inflammation by beneficial restoring of dysregulation in FGF-23/Klotho protein axis remain to be not fully clear. The aim of the review was to summarize findings regarding the role of impaired FGF-23/Klotho protein axis in developing CV complications in patients with prediabetes and type 2 diabetes mellitus. It has been elucidated that elevated levels of FGF-23 and deficiency of Klotho protein in peripheral blood are predictors of CV disease and CV outcomes in patients with (pre) diabetes, while predictive values of dynamic changes of the concentrations of these biomarkers require to be elucidated in detail in the future.