Mapping of the fibroblast growth factors in human white adipose tissue

Ceramide-induced FGF13 impairs systemic metabolic health

Ceramide accumulation impairs adipocytes' ability to efficiently store and utilize nutrients, leading to energy and glucose homeostasis deterioration. Using a comparative transcriptomic screen, we identified the non-canonical, non-secreted fibroblast growth factor FGF13 as a ceramide-regulated factor that impairs adipocyte function. Obesity robustly induces FGF13 expression in adipose tissue in mice and humans and is positively associated with glycemic indices of type 2 diabetes. Pharmacological or genetic inhibition of ceramide biosynthesis reduces FGF13 expression. Using mice with loss and gain of function of FGF13, we demonstrate that FGF13 is both necessary and sufficient to impair energy and glucose homeostasis independent of ceramides. Mechanistically, FGF13 exerts these effects by inhibiting mitochondrial content and function, metabolic elasticity, and caveolae formation, which cumulatively impairs glucose utilization and thermogenesis. These studies suggest the therapeutic potential of targeting FGF13 to prevent and treat metabolic diseases.

Selection signature analysis reveals genes associated with tail phenotype in sheep

Tail type of sheep, which may be affected by many genes with a complex mechanism, is an important economic trait concerned by both raiser and consumers. Here, we employed two sheep breeds with extreme phenotypes - Mongolian sheep (short-fat-tailed) and Bamei Mutton sheep (long-thin-tailed) to analyze the genetic differences at the genomic level and find candidate genes associated with tail phenotype. The results of population structure analysis showed that the LD decay rate of Mongolian sheep was greater than that of Bamai Mutton sheep. When K = 2, the two populations were obviously separated with a certain degree of mixing. From 49 sheep individuals, 20,270,930 and 2,479,474 SNPs and Indels were identified, respectively. Selection signals were detected based on F ST , π-Ratio, and XP-EHH. These three methods identified 85 candidate genes, of which PDGFD, GLIS1, AR, and FGF9 were reported to be associated with tail fat deposition, while VRTN associated with tail length in sheep tail phenotype; the others were novel genes that may play important roles in sheep tail phenotype formation. Gene annotation revealed that these candidate genes mainly participate in pathways associated with fat deposition or lipid metabolism. This study provided insight into sheep tail type development and a guide for molecular breeding.

A novel 22-bp InDel within FGF7 gene is significantly associated with growth traits in goat

Fibroblast growth factor 7 (FGF7) is involved in lipid metabolism, which is considered as a candidate gene with close relation with muscle development by eGWAs and RNA-Seq analyses. To date, limited research has been conducted on the relationship between FGF7 gene and growth traits. The main objective of this work was to further investigate the association between novel InDel within FGF7 gene and growth traits in goat. Herein, FGF7 mRNA expression levels were investigated in various Fuqing goat tissues. We found that FGF7 gene was expressed in six adult goat tissues with the highest mRNA levels in adipose tissue. This result suggested that FGF7 gene might play a critical role in fat deposition. We also detected potential polymorphisms in Fuqing, Nubian and Jianyang Daer breeds. A 22-bp InDel polymorphism in FGF7 gene was detected in 396 goats and the three genotypes were designated as II, ID, and DD. Correlation analysis revealed that InDel polymorphism was significantly associated with growth traits (P < 0.05). Goats with genotypes ID and/or II had superior growth traits compared to those with genotype DD. In summary, our findings suggested that the 22-bp InDel within FGF7 gene could act as a molecular marker to improve the growth traits of goats in breeding programs.

FGFR1 Signaling Facilitates Obesity-Driven Pulmonary Outgrowth in Metastatic Breast Cancer

Survival of dormant, disseminated breast cancer cells contributes to tumor relapse and metastasis. Women with a body mass index greater than 35 have an increased risk of developing metastatic recurrence. Herein, we investigated the effect of diet-induced obesity (DIO) on primary tumor growth and metastatic progression using both metastatic and systemically dormant mouse models of breast cancer. This approach led to increased PT growth and pulmonary metastasis. We developed a novel protocol to induce obesity in Balb/c mice by combining dietary and hormonal interventions with a thermoneutral housing strategy. In contrast to standard housing conditions, ovariectomized Balb/c mice fed a high-fat diet under thermoneutral conditions became obese over a period of 10 weeks, resulting in a 250% gain in fat mass. Obese mice injected with the D2.OR model developed macroscopic pulmonary nodules compared with the dormant phenotype of these cells in mice fed a control diet. Analysis of the serum from obese Balb/c mice revealed increased levels of FGF2 as compared with lean mice. We demonstrate that serum from obese animals, exogenous FGF stimulation, or constitutive stimulation through autocrine and paracrine FGF2 is sufficient to break dormancy and drive pulmonary outgrowth. Blockade of FGFR signaling or specific depletion of FGFR1 prevented obesity-associated outgrowth of the D2.OR model.

IMPLICATIONS

Overall, this study developed a novel DIO model that allowed for demonstration of FGF2:FGFR1 signaling as a key molecular mechanism connecting obesity to breakage of systemic tumor dormancy and metastatic progression.

Fibroblast growth factors induce hepatic tumorigenesis post radiofrequency ablation

Image-guided radiofrequency ablation (RFA) is used to treat focal tumors in the liver and other organs. Despite potential advantages over surgery, hepatic RFA can promote local and distant tumor growth by activating pro-tumorigenic growth factor and cytokines. Thus, strategies to identify and suppress pro-oncogenic effects of RFA are urgently required to further improve the therapeutic effect. Here, the proliferative effect of plasma of Hepatocellular carcinoma or colorectal carcinoma patients 90 min post-RFA was tested on HCC cell lines, demonstrating significant cellular proliferation compared to baseline plasma. Multiplex ELISA screening demonstrated increased plasma pro-tumorigenic growth factors and cytokines including the FGF protein family which uniquely and selectively activated HepG2. Primary mouse and immortalized human hepatocytes were then subjected to moderate hyperthermia in-vitro, mimicking thermal stress induced during ablation in the peri-ablational normal tissue. Resultant culture medium induced proliferation of multiple cancer cell lines. Subsequent non-biased protein array revealed that these hepatocytes subjected to moderate hyperthermia also excrete a similar wide spectrum of growth factors. Recombinant FGF-2 activated multiple cell lines. FGFR inhibitor significantly reduced liver tumor load post-RFA in MDR2-KO inflammation-induced HCC mouse model. Thus, Liver RFA can induce tumorigenesis via the FGF signaling pathway, and its inhibition suppresses HCC development.

Serum fibroblast growth factor 1 and its association with pancreatic beta cell function and insulin sensitivity in adults with glucose intolerance

Background

Beneficial role of fibroblast growth factor 1 (FGF1) in the regulation of glucose metabolism and adipose tissue remodeling was suggested in rodents. This study aimed to investigate the association between serum FGF1 levels and metabolic parameters in adults with glucose intolerance.

Methods

Serum FGF1 levels were examined using an enzyme-linked immunosorbent assay in 153 individuals with glucose intolerance. Associations between serum FGF1 levels and metabolic parameters, including body mass index (BMI), glycated hemoglobin (HbA1c), and 75 g oral glucose tolerance test-derived parameters, including insulinogenic index (IGI), Matsuda insulin sensitivity index (ISI), and disposition index (DI), were examined.

Results

Serum FGF1 was detected in 35 individuals (22.9%), possibly due to the autocrine/paracrine nature of the peptide. IGI and DI levels were significantly lower in individuals with higher FGF1 levels than in those with lower FGF1 levels or undetectable FGF1 (p=0.006 and 0.005 for IGI and DI, respectively, after adjustment for age, sex, and BMI). Univariable and multivariable analyses using the Tobit regression model also revealed a negative association between FGF1 levels and IGI and DI. The regression coefficients per 1-SD of log-transformed IGI and DI were -0.461 (p=0.013) and -0.467 (p=0.012), respectively, after adjustment for age, sex, and BMI. In contrast, serum FGF1 levels were not significantly associated with ISI, BMI, or HbA1c.

Conclusions

The serum concentration of FGF1 was significantly elevated in individuals with low insulin secretion, suggesting a possible interaction between FGF1 and beta cell function in humans.

Integrated bioinformatics approach reveals methylation-regulated differentially expressed genes in obesity

Objective

To identify DNA methylation and gene expression profiles involved in obesity by implementing an integrated bioinformatics approach.

Materials and methods

Gene expression (GSE94752, GSE55200, and GSE48964) and DNA methylation (GSE67024 and GSE111632) datasets were obtained from the GEO database. Differentially expressed genes (DEGs) and differentially methylated genes (DMGs) in subcutaneous adipose tissue of patients with obesity were identified using GEO2R. Methylation-regulated DEGs (MeDEGs) were identified by overlapping DEGs and DMGs. The protein-protein interaction (PPI) network was constructed with the STRING database and analyzed using Cytoscape. Functional modules and hub-bottleneck genes were identified by using MCODE and CytoHubba plugins. Functional enrichment analyses were performed based on Gene Ontology terms and KEGG pathways. To prioritize and identify candidate genes for obesity, MeDEGs were compared with obesity-related genes available at the DisGeNET database.

Results

A total of 54 MeDEGs were identified after overlapping the lists of significant 274 DEGs and 11,556 DMGs. Of these, 25 were hypermethylated-low expression genes and 29 were hypomethylated-high expression genes. The PPI network showed three hub-bottleneck genes (PTGS2, TNFAIP3, and FBXL20) and one functional module. The 54 MeDEGs were mainly involved in the regulation of fibroblast growth factor production, the molecular function of arachidonic acid, and ubiquitin-protein transferase activity. Data collected from DisGeNET showed that 11 of the 54 MeDEGs were involved in obesity.

Conclusion

This study identifies new MeDEGs involved in obesity and assessed their related pathways and functions. These results data may provide a deeper understanding of methylation-mediated regulatory mechanisms of obesity.

Autocrine FGF1 signaling promotes glucose uptake in adipocytes

Fibroblast growth factor 1 (FGF1) is an autocrine growth factor released from adipose tissue during over-nutrition or fasting to feeding transition. While local actions underlie the majority of FGF1's anti-diabetic functions, the molecular mechanisms downstream of adipose FGF receptor signaling are unclear. We investigated the effects of FGF1 on glucose uptake and its underlying mechanism in murine 3T3-L1 adipocytes and in ex vivo adipose explants from mice. FGF1 increased glucose uptake in 3T3-L1 adipocytes and epididymal WAT (eWAT) and inguinal WAT (iWAT). Conversely, glucose uptake was reduced in eWAT and iWAT of FGF1 knockout mice. We show that FGF1 acutely increased adipocyte glucose uptake via activation of the insulin-sensitive glucose transporter GLUT4, involving dynamic crosstalk between the MEK1/2 and Akt signaling proteins. Prolonged exposure to FGF1 stimulated adipocyte glucose uptake by MEK1/2-dependent transcription of the basal glucose transporter GLUT1. We have thus identified an alternative pathway to stimulate glucose uptake in adipocytes, independent from insulin, which could open new avenues for treating patients with type 2 diabetes.

Severe iatrogenic hypoglycaemia modulates the fibroblast growth factor protein response

INTRODUCTION

There is evidence that fibroblast growth factor (FGF) levels may be implicated in hypoglycaemia, with FGF19 being a potential contributor to insulin-independent pathways driving postprandial hypoglycaemia following bariatric surgery and basic FGF (FGF2) being elevated following mild hypoglycaemia occurring after the glucose tolerance test. However, their response following severe iatrogenic hypoglycaemia is unknown and therefore this pilot exploratory study was undertaken.

METHODS

A case-control study of aged-matched type 2 diabetes (T2D; n = 23) and control (n = 23) subjects who underwent a hyperinsulinaemic clamp, initially to euglycaemia in T2D (5 mmol/L; 90 mg/dl), and then to hypoglycaemia (<2 mmol/L; <36 mg/dl) with subsequent follow-up time course to 24 h. FGF and FGF receptor proteins were determined by Slow Off-rate Modified Aptamer (SOMA)-scan plasma protein measurement.

RESULTS

At baseline, FGF12 (p = .006) was higher and FGF20 (p = .004) was lower in T2D versus controls. At hypoglycaemia, FGF7 was lower in T2D. Post-hypoglycaemic levels of FGF18, FGF19, FGF20 and FGF23 were lower while FGF12 and FGF16 were higher in T2D versus control at different time points. No differences between T2D and controls were seen for FGF1, FGF2, FGF4, FGF6, FGF8, FGF9, FGF10, FGF21 or any of the FGF receptors. At 24 h post-hypoglycaemia, FGF20 (p = .01) differed between controls and T2D, while the levels for the other proteins measured returned to baseline. None of the FGF proteins altered from baseline to euglycaemia when clamped in T2D subjects. FGF23 negatively correlated with fasting blood glucose, but no FGFs correlated with body mass index in T2D.

CONCLUSION

Severe transient hypoglycaemia modulated FGF7, 16, 19, 20 and 23 (known to be associated with diabetes), together with FGF18 and 12, not previously reported to be associated with diabetes but that may be important in the pathophysiology of hypoglycaemia; FGF20 remained low at 24 h. Taken together, these data suggest that recurrent hypoglycaemia may contribute to the development of complications through changes in FGF proteins.

Metabolic Messengers: fibroblast growth factor 1

While fibroblast growth factor (FGF) 1 is expressed in multiple tissues, only adipose-derived and brain FGF1 have been implicated in the regulation of metabolism. Adipose FGF1 production is upregulated in response to dietary stress and is essential for adipose tissue plasticity in these conditions. Similarly, in the brain, FGF1 secretion into the ventricular space and the adjacent parenchyma is increased after a hypercaloric challenge induced by either feeding or glucose infusion. Potent anorexigenic properties have been ascribed to both peripheral and centrally injected FGF1. The ability of recombinant FGF1 and variants with reduced mitogenicity to lower glucose, suppress adipose lipolysis and promote insulin sensitization elevates their potential as candidates in the treatment of type 2 diabetes mellitus and associated comorbidities. Here, we provide an overview of the known metabolic functions of endogenous FGF1 and discuss its therapeutic potential, distinguishing between peripherally or centrally administered FGF1.

The Use of Human Serum Samples to Study Malignant Transformation: A Pilot Study

Obesity and excess adiposity account for approximately 20% of all cancer cases; however, biomarkers of risk remain to be elucidated. While fibroblast growth factor-2 (FGF2) is emerging as an attractive candidate biomarker for visceral adipose tissue mass, the role of circulating FGF2 in malignant transformation remains unknown. Moreover, functional assays for biomarker discovery are limited. We sought to determine if human serum could stimulate the 3D growth of a non-tumorigenic cell line. This type of anchorage-independent 3D growth in soft agar is a surrogate marker for acquired tumorigenicity of cell lines. We found that human serum from cancer-free men and women has the potential to stimulate growth in soft agar of non-tumorigenic epithelial JB6 P+ cells. We examined circulating levels of FGF2 in humans in malignant transformation in vitro in a pilot study of n = 33 men and women. Serum FGF2 levels were not associated with colony formation in epithelial cells (r = 0.05, p = 0.80); however, a fibroblast growth factor receptor-1 (FGFR1) selective inhibitor significantly blocked serum-stimulated transformation, suggesting that FGF2 activation of FGFR1 may be necessary, but not sufficient for the transforming effects of human serum. This pilot study indicates that the FGF2/FGFR1 axis plays a role in JB6 P+ malignant transformation and describes an assay to determine critical serum factors that have the potential to promote tumorigenesis.

Hepatokines and adipokines in NASH-related hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) is increasing in industrialised societies; this is likely secondary to the increasing burden of non-alcoholic fatty liver disease (NAFLD), its progressive form non-alcoholic steatohepatitis (NASH), and the metabolic syndrome. Cumulative studies suggest that NAFLD-related HCC may also develop in non-cirrhotic livers. However, prognosis and survival do not differ between NAFLD- or virus-associated HCC. Thus, research has increasingly focused on NAFLD-related risk factors to better understand the biology of hepatocarcinogenesis and to develop new diagnostic, preventive, and therapeutic strategies. One important aspect thereof is the role of hepatokines and adipokines in NAFLD/NASH-related HCC. In this review, we compile current data supporting the use of hepatokines and adipokines as potential markers of disease progression in NAFLD or as early markers of NAFLD-related HCC. While much work must be done to elucidate the mechanisms and interactions underlying alterations to hepatokines and adipokines, current data support the possible utility of these factors - in particular, angiopoietin-like proteins, fibroblast growth factors, and apelin - for detection or even as therapeutic targets in NAFLD-related HCC.

Adipocyte Piezo1 mediates obesogenic adipogenesis through the FGF1/FGFR1 signaling pathway in mice

White adipose tissue (WAT) expansion in obesity occurs through enlargement of preexisting adipocytes (hypertrophy) and through formation of new adipocytes (adipogenesis). Adipogenesis results in WAT hyperplasia, smaller adipocytes and a metabolically more favourable form of obesity. How obesogenic WAT hyperplasia is induced remains, however, poorly understood. Here, we show that the mechanosensitive cationic channel Piezo1 mediates diet-induced adipogenesis. Mice lacking Piezo1 in mature adipocytes demonstrated defective differentiation of preadipocyte into mature adipocytes when fed a high fat diet (HFD) resulting in larger adipocytes, increased WAT inflammation and reduced insulin sensitivity. Opening of Piezo1 in mature adipocytes causes the release of the adipogenic fibroblast growth factor 1 (FGF1), which induces adipocyte precursor differentiation through activation of the FGF-receptor-1. These data identify a central feed-back mechanism by which mature adipocytes control adipogenesis during the development of obesity and suggest Piezo1-mediated adipocyte mechano-signalling as a mechanism to modulate obesity and its metabolic consequences.

Adipose tissue expansion occurs via enlargement of adipocytes as well as the generation of new fat cells, the latter being associated with more favorable metabolic outcomes. Here, the authors show that activation of adipocyte Piezo1 results in release of FGF1 and stimulates the differentiation of adipocyte precursor cells.

A combination of genetics and microbiota influences the severity of the obesity phenotype in diet-induced obesity

Obesity has emerged as a major global health problem and is associated with various diseases, such as metabolic syndrome, type 2 diabetes mellitus, and cardiovascular diseases. The inbred C57BL/6 mouse strain is often used for various experimental investigations, such as metabolic research. However, over time, genetically distinguishable C57BL/6 substrains have evolved. The manifestation of genetic alterations has resulted in behavioral and metabolic differences. In this study, a comparison of diet-induced obesity in C57BL/6JHanZtm, C57BL/6NCrl and C57BL/6 J mice revealed several metabolic and immunological differences such as blood glucose level and cytokine expression, respectively, among these C57BL/6 substrains. For example, C57BL/6NCrl mice developed the most pronounced adiposity, whereas C57BL/6 J mice showed the highest impairment in glucose tolerance. Moreover, our results indicated that the immunological phenotype depends on the intestinal microbiota, as the cell subset composition of the colon was similar in obese ex-GF B6NRj^B6JHanZtm and obese B6JHanZtm mice. Phenotypic differences between C57BL/6 substrains are caused by a complex combination of genetic and microbial alterations. Therefore, in performing metabolic research, considering substrain-specific characteristics, which can influence the course of study, is important. Moreover, for unbiased comparison of data, the entire strain name should be shared with the scientific community.

Adipose-Derived Molecules-Untouched Horizons in Alzheimer's Disease Biology

The global incidence of Alzheimer's disease (AD) is on the rise with the increase in obesity and metabolic disease epidemic. Obesity is co-morbid with the increase in mass of adipose tissue, which secretes numerous molecules that are biologically important. Obesity and its associated conditions are perhaps involved in the causative pathway of AD. Immunologically important cytokines such as IL-1β, IL-10, and IL-18, which are released by adipose tissue, are also found to be associated with AD. Besides, the expression of IL-6, IFNγ, and TNF alpha are also associated with AD. Ang-I and Ang-II are found to mediate the progression of AD. Complement factors B, C4b, and H are differentially expressed in AD. Overall, several adipocyte-derived cytokines are found to be dysregulated in AD, and their role in AD remains to be studied. The induction of autophagy is a very promising strategy in the treatment of AD. A variety of adipose-derived molecules have been shown to modulate autophagy. However, very little literature is available on the role of adipose-derived molecules in inducing autophagy in microglial cells of AD. Understanding the role of adipose-derived molecules in the development of AD, especially in the induction of autophagy, would open up new avenues in devising strategies for the treatment of AD.

Fibroblast growth factors in control of lipid metabolism: from biological function to clinical application

PURPOSE OF REVIEW

Several members of the fibroblast growth factor (FGF) family have been identified as key regulators of energy metabolism in rodents and nonhuman primates. Translational studies show that their metabolic actions are largely conserved in humans, which led to the development of various FGF-based drugs, including FGF21-mimetics LY2405319, PF-05231023, and pegbelfermin, and the FGF19-mimetic NGM282. Recently, a number of clinical trials have been published that examined the safety and efficacy of these novel therapeutic proteins in the treatment of obesity, type 2 diabetes (T2D), nonalcoholic steatohepatitis (NASH), and cholestatic liver disease. In this review, we discuss the current understanding of FGFs in metabolic regulation and their clinical potential.

RECENT FINDINGS

FGF21-based drugs induce weight loss and improve dyslipidemia in patients with obesity and T2D, and reduce steatosis in patients with NASH. FGF19-based drugs reduce steatosis in patients with NASH, and ameliorate bile acid-induced liver damage in patients with cholestasis. In contrast to their potent antidiabetic effects in rodents and nonhuman primates, FGF-based drugs do not appear to improve glycemia in humans. In addition, various safety concerns, including elevation of low-density lipoprotein cholesterol, modulation of bone homeostasis, and increased blood pressure, have been reported as well.

SUMMARY

Clinical trials with FGF-based drugs report beneficial effects in lipid and bile acid metabolism, with clinical improvements in dyslipidemia, steatosis, weight loss, and liver damage. In contrast, glucose-lowering effects, as observed in preclinical models, are currently lacking.

Loss of growth hormone-mediated signal transducer and activator of transcription 5 (STAT5) signaling in mice results in insulin sensitivity with obesity

Growth hormone (GH) has an important function as an insulin antagonist with elevated insulin sensitivity evident in humans and mice lacking a functional GH receptor (GHR). We sought the molecular basis for this sensitivity by utilizing a panel of mice possessing specific deletions of GHR signaling pathways. Metabolic clamps and glucose homeostasis tests were undertaken in these obese adult C57BL/6 male mice, which indicated impaired hepatic gluconeogenesis. Insulin sensitivity and glucose disappearance rate were enhanced in muscle and adipose of mice lacking the ability to activate the signal transducer and activator of transcription (STAT)5 via the GHR (Ghr-391^-/-) as for GHR-null (GHR^-/-) mice. These changes were associated with a striking inhibition of hepatic glucose output associated with altered glycogen metabolism and elevated hepatic glycogen content during unfed state. The enhanced hepatic insulin sensitivity was associated with increased insulin receptor β and insulin receptor substrate 1 activation along with activated downstream protein kinase B signaling cascades. Although phosphoenolpyruvate carboxykinase (Pck)-1 expression was unchanged, its inhibitory acetylation was elevated because of decreased sirtuin-2 expression, thereby promoting loss of PCK1. Loss of STAT5 signaling to defined chromatin immunoprecipitation targets would further increase lipogenesis, supporting hepatosteatosis while lowering glucose output. Finally, up-regulation of IL-15 expression in muscle, with increased secretion of adiponectin and fibroblast growth factor 1 from adipose tissue, is expected to promote insulin sensitivity.-Chhabra, Y., Nelson, C. N., Plescher, M., Barclay, J. L., Smith, A. G., Andrikopoulos, S., Mangiafico, S., Waxman, D. J., Brooks, A. J., Waters, M. J. Loss of growth hormone-mediated signal transducer and activator of transcription 5 (STAT5) signaling in mice results in insulin sensitivity with obesity.

Resistance to visceral obesity is associated with increased locomotion in mice expressing an endothelial cell-specific fibroblast growth factor 1 transgene

Overdevelopment of visceral adipose is positively correlated with the etiology of obesity-associated pathologies including cardiovascular disease and insulin resistance. However, identification of genetic, molecular, and physiological factors regulating adipose development and function in response to nutritional stress is incomplete. Fibroblast Growth Factor 1 (FGF1) is a cytokine expressed and released by both adipocytes and endothelial cells under hypoxia, thermal, and oxidative stress. Expression of Fibroblast Growth Factor 1 (FGF1) in adipose is required for normal depot development and remodeling. Loss of FGF1 leads to deleterious changes in adipose morphology, metabolism, and insulin resistance. Conversely, diabetic and obese mice injected with recombinant FGF1 display improvements in insulin sensitivity and a reduction in adiposity. We report in this novel, in vivo study that transgenic mice expressing an endothelial-specific FGF1 transgene (FGF1-Tek) are resistant to high-fat diet-induced abdominal adipose accretion and are more glucose-tolerant than wild-type control animals. Metabolic chamber analyses indicate that suppression of the development of visceral adiposity and insulin resistance was not associated with alterations in appetite or resting metabolic rate in the FGF1-Tek strain. Instead, FGF1-Tek mice display increased locomotor activity that likely promotes the utilization of dietary fatty acids before they can accumulate in adipose and liver. This study provides insight into the impact that genetic differences dictating the production of FGF1 has on the risk for developing obesity-related metabolic disease in response to nutritional stress.

Characterization of fibroblast growth factor 1 in obese children and adolescents

BACKGROUND

Fibroblast growth factor 1 (FGF1) can regulate glucose and lipid metabolism in obese mice. Serum FGF1 has increased in type 2 diabetes mellitus adults and correlated with BMI. This study aimed to indicate conventional weight loss effects on FGF1 in obese children and adolescents.

MATERIALS AND METHODS

Clinical and metabolic parameters of 88 lean and obese individuals (ages 5–15 years) and 39 obese individuals followed with 6 months of lifestyle intervention were collected. Serum FGF1 levels were detected through enzyme-linked immunosorbent assays.

RESULTS

FGF1 levels were increased in obese individuals. Serum FGF1 levels were significantly correlated with BMI and waist circumferences (r = 0.377, P = 0.012; r = 0.301, P = 0.047, respectively). Multivariate stepwise linear regression analyses showed that FGF1 levels were significantly correlated with HbA1c and HOMA-IR (β = 0.371, P = 0.008; β = 0.323, P = 0.021, respectively). Weight loss (2.3 ± 0.1 kg) was accompanied by a significant reduction of circulating FGF1 levels (7.2 ± 0.4 pg/mL). Changes in FGF1 were significantly correlated with changes in fasting glucose, HOMA-IR and low-density lipoprotein cholesterol (β = 0.277, P = 0.020; β = 0.474, P < 0.001; β = 0.320, P = 0.008, respectively).

CONCLUSION

FGF1 levels were increased in obese individuals. Serum FGF1 levels were significantly correlated with BMI and waist circumferences (r = 0.377, P = 0.012; r = 0.301, P = 0.047, respectively). Multivariate stepwise linear regression analyses showed that FGF1 levels were significantly correlated with HbA1c and HOMA-IR (β = 0.371, P = 0.008; β = 0.323, P = 0.021, respectively). Weight loss (2.3 ± 0.1 kg) was accompanied by a significant reduction of circulating FGF1 levels (7.2 ± 0.4 pg/mL). Changes in FGF1 were significantly correlated with changes in fasting glucose, HOMA-IR and low-density lipoprotein cholesterol (β = 0.277, P = 0.020; β = 0.474, P < 0.001; β = 0.320, P = 0.008, respectively).

Upregulated TNF Expression 1 Year After Bariatric Surgery Reflects a Cachexia-Like State in Subcutaneous Adipose Tissue

Background

Adipose tissue dysfunction contributes to obesity-associated chronic diseases. In the first year after bariatric surgery, obese patients significantly improve their metabolic status upon losing weight. We aimed to investigate whether changes in subcutaneous adipose tissue gene expression reflect a restoration of a healthy lean phenotype after bariatric surgery.

Methods

Thirty-one severely obese patients (BMI ≥ 40 kg/m²) were examined before and after surgery. subcutaneous adipose tissue (SAT) was collected during and 1 year after bariatric surgery. SAT from 20 matched lean and overweight patients (BMI < 30 kg/m²) was collected during elective abdominal surgery. Baseline characteristics and SAT gene expression relevant to glucose and lipid metabolism, inflammation, and apoptosis were analyzed.

Results

After surgery, mean BMI decreased from 46.1 ± 6.3 to 31.1 ± 5.7 kg/m² and homeostasis model assessment of insulin resistance from 5.4 ± 5.3 to 0.8 ± 0.8. SAT expression of most analyzed inflammatory cytokines, growth factors, and metabolic and cell surface markers was greatly downregulated even compared to the lean cohort. In contrast, gene expression of TNF and CASP3 was significantly upregulated. Elastic net regression analysis showed that fasting glucose levels and CASP3 predicted increased TNF expression in the post-obese group.

Conclusions

Gene expression patterns in SAT 1 year after bariatric surgery point to a reduced inflammation. The unexpected high TNF expression in SAT of post-obese subjects is most likely not an indicator for inflammation, but rather an indicator for increased lipolysis and adipose tissue catabolism. Notably, after bariatric surgery SAT gene expression reflects a cachexia-like phenotype and differs from the lean state.

Electronic supplementary material

The online version of this article (doi:10.1007/s11695-016-2477-5) contains supplementary material, which is available to authorized users.

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.

Fibroblast growth factor 1 levels are elevated in newly diagnosed type 2 diabetes compared to normal glucose tolerance controls

Fibroblast growth factor 1 (FGF1) has been recently characterized as a potent insulin sensitizer that regulates adipose tissue remodeling, but the physiological role of FGF1 remains unclear. This study measured serum FGF1 levels for the first time in patients with newly diagnosed type 2 diabetes mellitus (T2DM), and further explored the correlations between FGF1 levels and various metabolic parameters in T2DM. Serum FGF1 levels were determined using ELISA in age-, sex- and BMI- matched subjects with normal glucose tolerance (NGT) (n=80) and newly diagnosed T2DM (n=80). Oral glucose tolerance test (OGTT), glycosylated hemoglobin (HbA1C), blood lipids, and insulin secretion were also measured. Insulin resistance and pancreatic β-cell function were assessed by homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of beta cell function (HOMA-β), respectively. Serum FGF1 levels were significantly higher in T2DM patients than in normal glucose tolerance subjects (74.52 [55.91∼101.34] vs. 60.31 [48.99∼83.91] pg/mL; P<0.05). In addition, serum FGF1 level positively correlated with body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), fasting plasma glucose (FPG), 2-h post-OGTT glucose (2h PG), and HbA1C (all P values <0.05) in T2DM subjects. Multivariate regression analyses showed that BMI and HbA1C were the independent factors influencing serum FGF1 levels. Logistic regression analyses demonstrated that serum FGF1 was significantly associated with type 2 diabetes (P<0.01). Circulating concentrations of FGF1 are significantly increased in T2DM patients. Our results suggest that FGF1 may play a role in the pathogenesis of T2DM.

Estrogens increase expression of bone morphogenetic protein 8b in brown adipose tissue of mice

Background

In mammals, white adipose tissue (WAT) stores fat and brown adipose tissue (BAT) dissipates fat to produce heat. Several studies showed that females have more active BAT. Members of the bone morphogenetic protein (BMP) and fibroblast growth factor (FGF) families are expressed in BAT and are involved in BAT activity. We hypothesized that differential expression of BMPs and FGFs might contribute to sex differences in BAT activity.

Methods

We investigated the expression of BMPs and FGFs in BAT of male and female C57BL/6J mice upon gonadectomy, cold exposure, and exposure to sex steroids.

Results

Of the FGF family, BAT Fgf1, Fgf9, Fgf18, and Fgf21 expression was induced upon cold exposure, but only Fgf1 expression was obviously different between the sexes: females had 2.5-fold lower BAT Fgf1 than males. Cold exposure induced BAT Bmp4 and Bmp8b expression, but only Bmp8b differed between the sexes: females had 35-fold higher BAT Bmp8b than males. Ovariectomy almost completely blunted BAT Bmp8b expression, while orchidectomy had no effect. Male mice and ovariectomized female mice treated with diethylstilbestrol (DES) had approximately 350-fold and approximately 36-fold higher BAT Bmp8b expression, respectively. Ninety-day and 7-day treatment of female mice with dihydrotestosterone (DHT) decreased BAT Bmp8b expression by approximately fivefold and approximately fourfold, respectively. Finally, treatment of primary murine brown adipocytes with DES did not result in changes in Bmp8b expression.

Conclusions

BAT Bmp8b expression in mice is positively regulated by presence of ovaries and estrogens such as DES.

Fibroblast Growth Factor Signaling in Metabolic Regulation

The prevalence of obesity is a growing health problem. Obesity is strongly associated with several comorbidities, such as non-alcoholic fatty liver disease, certain cancers, insulin resistance, and type 2 diabetes, which all reduce life expectancy and life quality. Several drugs have been put forward in order to treat these diseases, but many of them have detrimental side effects. The unexpected role of the family of fibroblast growth factors in the regulation of energy metabolism provides new approaches to the treatment of metabolic diseases and offers a valuable tool to gain more insight into metabolic regulation. The known beneficial effects of FGF19 and FGF21 on metabolism, together with recently discovered similar effects of FGF1 suggest that FGFs and their derivatives carry great potential as novel therapeutics to treat metabolic conditions. To facilitate the development of new therapies with improved targeting and minimal side effects, a better understanding of the molecular mechanism of action of FGFs is needed. In this review, we will discuss what is currently known about the physiological roles of FGF signaling in tissues important for metabolic homeostasis. In addition, we will discuss current concepts regarding their pharmacological properties and effector tissues in the context of metabolic disease. Also, the recent progress in the development of FGF variants will be reviewed. Our goal is to provide a comprehensive overview of the current concepts and consensuses regarding FGF signaling in metabolic health and disease and to provide starting points for the development of FGF-based therapies against metabolic conditions.

Identification of novel putative adipomyokines by a cross-species annotation of secretomes and expression profiles

Adipose tissue and skeletal muscle are organs that respond strongly to obesity and physical activity exhibiting high secretory activity. To identify novel putative adipomyokines, comparative expression studies of skeletal muscle and adipose tissue of lean (C57BL/6J) and obese (C57BL/6J on a high-fat diet and NZO) mice, of sedentary and endurance trained C57BL/6J mice and of cattle characterized by different amounts of intramuscular fat were combined with human secretome data and scored. In highly regulated transcripts, we identified 119 myokines, 79 adipokines and 22 adipomyokines. Network analysis of these candidates revealed remodelling of extracellular matrix and tissue fibrosis as relevant functions of several of these candidates. Given the pathophysiogical relevance of fibrosis for adipose-muscle-cross-talk in obesity and type 2 diabetes and its physiological role in exercise adaptation and meat quality of farm animals, they represent interesting candidates for further investigations in different research areas and species.

Adipose tissue, diet and aging

Age related increase in body fat mass, visceral adipose tissue (AT), and ectopic fat deposition are strongly related to worse health conditions in the elderly. Moreover, with aging higher inflammation in adipose tissue may be observed and may contribute to inflammaging. Aging may significantly affect AT function by modifying the profile of adipokines produced by adipose cells, reducing preadipocytes number and their function and increasing AT macrophages infiltration. The initiating events of the inflammatory cascade promoting a greater AT inflammatory profile are not completely understood. Nutrients may determine changes in the amount of body fat, in its distribution as well as in AT function with some nutrients showing a pro-inflammatory effect on AT. Evidences are sparse and quite controversial with only a few studies performed in older subjects. Different dietary patterns are the result of the complex interaction of foods and nutrients, thus more studies are needed to evaluate the association between dietary patterns and changes in adipose tissue structure, distribution and function in the elderly.

Semaphorin 3C is a novel adipokine linked to extracellular matrix composition

AIMS/HYPOTHESIS

Alterations in white adipose tissue (WAT) function, including changes in protein (adipokine) secretion and extracellular matrix (ECM) composition, promote an insulin-resistant state. We set out to identify novel adipokines regulated by body fat mass in human subcutaneous WAT with potential roles in adipose function.

METHODS

Adipose transcriptome data and secretome profiles from conditions with increased/decreased WAT mass were combined. WAT donors were predominantly women. In vitro effects were assessed using recombinant protein. Results were confirmed by quantitative PCR/ELISA, metabolic assays and immunochemistry in human WAT and adipocytes.

RESULTS

We identified a hitherto uncharacterised adipokine, semaphorin 3C (SEMA3C), the expression of which correlated significantly with body weight, insulin resistance (HOMA of insulin resistance [HOMAIR], and the rate constant for the insulin tolerance test [KITT]) and adipose tissue morphology (hypertrophy vs hyperplasia). SEMA3C was primarily found in mature adipocytes and had no direct effect on human adipocyte differentiation, lipolysis, glucose transport or the expression of β-oxidation genes. This could in part be explained by the significant downregulation of its cognate receptors during adipogenesis. In contrast, in pre-adipocytes, SEMA3C increased the production/secretion of several ECM components (fibronectin, elastin and collagen I) and matricellular factors (connective tissue growth factor, IL6 and transforming growth factor-β1). Furthermore, the expression of SEMA3C in human WAT correlated positively with the degree of fibrosis in WAT.

CONCLUSIONS/INTERPRETATION

SEMA3C is a novel adipokine regulated by weight changes. The correlation with WAT hypertrophy and fibrosis in vivo, as well as its effects on ECM production in human pre-adipocytes in vitro, together suggest that SEMA3C constitutes an adipocyte-derived paracrine signal that influences ECM composition and may play a pathophysiological role in human WAT.

Novel aspects of brown adipose tissue biology

During the last decades, obesity research has focused on food intake regulation, whereas energy expenditure has been mainly measured based on whole-body oxygen consumption. With the renaissance of brown adipose tissue (BAT) thermogenesis as a potential drug target in humans, more thought is put into alternative heat-producing mechanisms. Also, the interaction of peripheral and central components to regulate thermogenesis requires further studies. Certainly, several of the novel molecular genetic tools available now, compared with 40 years ago, will be helpful to gain new insights in BAT-controlled energy homeostasis and promises new approaches to pharmacologically control body weight.

Stability of human mesenchymal stem cells during in vitro culture: considerations for cell therapy

Ex vivo expansion and manipulation of human mesenchymal stem cells are important approaches to immunoregulatory and regenerative cell therapies. Although these cells show great potential for use, issues relating to their overall nature emerge as problems in the field. The need for extensive cell quantity amplification in vitro to obtain sufficient cell numbers for use, poses a risk of accumulating genetic and epigenetic abnormalities that could lead to sporadic malignant cell transformation. In this study, we have examined human mesenchymal stem cells derived from bone marrow, over extended culture time, using cytogenetic analyses, mixed lymphocyte reactions, proteomics and gene expression assays to determine whether the cultures would retain their potential for use in subsequent passages. Results indicate that in vitro cultures of these cells demonstrated chromosome variability after passage 4, but their immunomodulatory functions and differentiation capacity were maintained. At the molecular level, changes were observed from passage 5 on, indicating initiation of differentiation. Together, these results lead to the hypothesis that human mesenchymal stem cells cultures can be used successfully in cell therapy up to passage 4. However, use of cells from higher passages would have to be analysed case by case.

Adipose zinc-α2-glycoprotein is a catabolic marker in cancer and noncancerous states

OBJECTIVE

Zinc-α2-glycoprotein (ZAG) has been proposed as a tumour-derived cancer cachexia factor. However, ZAG is produced by some normal tissues, including white adipose tissue (WAT), and high serum ZAG levels are present in nonmalignant conditions. We determined whether human WAT contributes to serum ZAG levels and how serum and WAT-secreted ZAG levels correlate with catabolism in patients with cancer and in obese subjects undergoing a very low-calorie diet (VLCD) for 11 days.

DESIGN/SUBJECTS

ZAG levels in serum and in conditioned medium from WAT/adipocytes were determined by enzyme-linked immunosorbent assay. ZAG release from WAT in vivo was determined in 10 healthy subjects. The correlation between ZAG and cachexia was studied in 34 patients with newly diagnosed gastrointestinal cancer. The impact of a VLCD on ZAG release and serum levels was assessed in 10 obese women.

RESULTS

ZAG was released from abdominal WAT and adipocytes in vitro. However, the arteriovenous differences in vivo showed that there was no significant contribution of WAT to the circulating levels. WAT-secreted but not serum ZAG correlated positively with poor nutritional status but not with fat mass (or body mass index) in patients with gastrointestinal cancer. In obese subjects on a VLCD, ZAG secretion from WAT increased significantly whereas serum levels remained unaltered.

CONCLUSIONS

 ZAG is released from human WAT, but this tissue does not contribute significantly to the circulating levels. WAT-secreted ZAG correlates with nutritional status but not with fat mass in both cancer and nonmalignant conditions. Adipose ZAG is therefore a local factor activated primarily by the catabolic state per se.

ITIH-5 expression in human adipose tissue is increased in obesity

Adipocytes secrete many proteins that regulate metabolic functions. The gene inter-α (globulin) inhibitor H5 (ITIH-5) encodes a secreted protein and is known to be expressed abundantly in the placenta. However, using gene expression profiles data we observed high expression of ITIH-5 in adipose tissue. The aim of this study was to test the hypothesis that ITIH-5 is strongly expressed in human adipocytes and adipose tissue, and is related to obesity and clinical metabolic variables. ITIH-5 adipose tissue mRNA expression was analyzed with DNA microarray and real-time PCR, and its association with clinical variables was examined. ITIH-5 protein expression was analyzed using western blot. ITIH-5 mRNA expression was abundant in human adipose tissue, adipocytes, and placenta, and higher in subcutaneous (sc) compared to omental adipose tissue (P < 0.0001). ITIH-5 mRNA and protein expression in sc adipose tissue were higher in obese compared to lean subjects (P < 0.0001 and P < 0.001, respectively). ITIH-5 mRNA expression was reduced after diet-induced weight loss (P < 0.0001). ITIH-5 mRNA expression was associated with anthropometry and clinical metabolic variables. In conclusion, ITIH-5 is highly expressed in sc adipose tissue, increased in obesity, down regulated after weight loss, and associated with measures of body size and metabolism. Together, this indicates that ITIH-5 merits further investigation as a regulator of human metabolism.

The serum level of fibroblast growth factor-23 and calcium-phosphate homeostasis in obese perimenopausal women

Plasma FGF-23 concentrations and its relationship with calcium-phosphate homeostasis were evaluated in 48 perimenopausal obese women and in 29 nonobese controls. Serum parathyroid hormone, 25-hydroxyvitamin D(3), CTX1, osteocalcin, total calcium, phosphorus, creatinine, and plasma intact FGF-23 concentrations were assessed. DXA of lumbar spine and femoral neck was performed to determine bone mineral density (BMD). Plasma iFGF-23 concentration was significantly higher in obese patients (by 42%) and correlated with age and BMD of proximal femur (R = -0.346; R = 0.285, resp.) but not with markers of bone turnover. However, serum phosphorus level in obese subjects was significantly lower. iFGF-23 concentration correlated significantly with body mass index (R = 0.292) and fat content (R = 0.259) in all study subjects. Moreover, a significant correlation between iFGF-23 and iPTH (R = 0.254) was found. No correlation between serum phosphorus or eGFR and plasma iFGF-23 and between eGFR and serum phosphorus was found. Elevated serum iFGF-23 concentration may partially explain lower phosphorus levels in the obese and seems not to reflect bone turnover.

A stratified transcriptomics analysis of polygenic fat and lean mouse adipose tissues identifies novel candidate obesity genes

Background

Obesity and metabolic syndrome results from a complex interaction between genetic and environmental factors. In addition to brain-regulated processes, recent genome wide association studies have indicated that genes highly expressed in adipose tissue affect the distribution and function of fat and thus contribute to obesity. Using a stratified transcriptome gene enrichment approach we attempted to identify adipose tissue-specific obesity genes in the unique polygenic Fat (F) mouse strain generated by selective breeding over 60 generations for divergent adiposity from a comparator Lean (L) strain.

Results

To enrich for adipose tissue obesity genes a ‘snap-shot’ pooled-sample transcriptome comparison of key fat depots and non adipose tissues (muscle, liver, kidney) was performed. Known obesity quantitative trait loci (QTL) information for the model allowed us to further filter genes for increased likelihood of being causal or secondary for obesity. This successfully identified several genes previously linked to obesity (C1qr1, and Np3r) as positional QTL candidate genes elevated specifically in F line adipose tissue. A number of novel obesity candidate genes were also identified (Thbs1, Ppp1r3d, Tmepai, Trp53inp2, Ttc7b, Tuba1a, Fgf13, Fmr) that have inferred roles in fat cell function. Quantitative microarray analysis was then applied to the most phenotypically divergent adipose depot after exaggerating F and L strain differences with chronic high fat feeding which revealed a distinct gene expression profile of line, fat depot and diet-responsive inflammatory, angiogenic and metabolic pathways. Selected candidate genes Npr3 and Thbs1, as well as Gys2, a non-QTL gene that otherwise passed our enrichment criteria were characterised, revealing novel functional effects consistent with a contribution to obesity.

Conclusions

A focussed candidate gene enrichment strategy in the unique F and L model has identified novel adipose tissue-enriched genes contributing to obesity.

A putative role for endogenous FGF-2 in FGF-1 mediated differentiation of human preadipocytes

The defining characteristic of obesity is increased adipose tissue (AT) mass following chronic positive energy supply. AT mass is determined by adipocyte number and size, which reflect proliferation and differentiation of preadipocytes and hypertrophy of pre-existing adipocytes. The molecular pathways governing AT expansion are incompletely defined. We previously reported that FGF-1 primes proliferating primary human preadipocytes (phPA), thereby increasing adipogenesis. Here we examined whether FGF-1's adipogenic actions were due to modulation of other FGFs. Treatment of phPA with FGF-1 reduced FGF-2 mRNA/protein by 80%. To examine a putative functional role we performed siRNA knockdown studies. Following FGF-2 knockdown preadipocyte proliferation was decreased and expression of adipogenic genes (PPARγ, G3PDH and adiponectin) was increased at day 1 of differentiation. These results suggest that changes in endogenous FGF-2 levels contribute to FGF-1's early adipogenic effects and highlight the complexity of the paracrine interplay between FGFs within human AT.