Serum Levels of Follistatin Are Positively Associated With Serum-Free Thyroxine Levels in Patients With Hyperthyroidism or Euthyroidism

Serum myokines as potential biomarkers of myostatin inhibition in sport doping: a preliminary study on their baseline levels in elite athletes

We considered in this study the possibility of developing an indirect procedure for detecting myostatin inhibition/suppression, a practice that is prohibited as doping in sport. We have specifically considered the potential diagnostic utility of human serum myokines as indirect markers of myostatin inhibition. Myostatin, its main antagonist follistatin, and other myokines (follistatin-like 1, musclin, oncostatin, osteonectin, irisin, brain derived neurotrophic factor, and insulin-like growth factor-1) were selected as a panel of potential biomarkers whose levels may be altered following myostatine suppression. The serum levels of myostatin and of the nine myokines were measured in elite athletes of different age, sex, and sport discipline, and their cross correlation assessed by multivariate analysis. All myokines resulted to be measurable in human serum, except for musclin and irisine, whose levels were below the limits of quantitation in a reduced number of samples. Serum concentrations varied of different orders in magnitude (musclin and osteonectin < 1 ng/mL; follistatin, myostatine and irisine 1-5 ng/mL; brainderived neurotrophic factor, follistatin-like 1 and iinsulin-like growth factor-1 > 10 ng/mL), while no significant differences were found between female and male subjects, with the exceptions of follistatin-like 1 and musclin, showing a higher concentrations in females (p < 0.05). Levels of insulin-like growth factor 1 and brain derived neurotrophic factor were significantly higher in power athletes than in endurance ones. Multivariate statistics showed that musclin, follistatin-like 1 and oncostatin are more clustered and correlated to myostatin than other myokines, suggesting they could be considered as potential biomarkers of doping by myostatin inhibitors.

Serum Follistatin Is Increased in Thyroid Cancer and Is Associated With Adverse Tumor Characteristics in Humans

CONTEXT

Obesity and classical growth factors are associated with thyroid cancer (TC). However, less is known regarding novel hormones such as follistatins and activins. We hypothesized that serum follistatin but not activins would be increased in TC.

OBJECTIVE

This work aimed to assess circulating levels of follistatins, activins, and growth factors in patients with a history of TC vs patients with nonmalignant thyroid diseases.

METHODS

A hospital-based, unmatched case-control study was conducted with 170 thyroidectomized patients due to well-differentiated TC and 106 thyroidectomized patients without history of malignancy. Anthropometric, biochemical, and histological parameters were recorded. Serum samples were collected in the steady state 45 days after surgery. Multivariate models were used to adjust for baseline differences of the unmatched variables. Serum levels of follistatin (FST), follistatin like-3, activin A, activin B, bioactive insulin-like growth factor-1, and stanniocalcin-2 were assayed with novel, highly specific ELISA kits.

RESULTS

In unmatched univariate models, TC patients had higher FST serum levels compared to cancer-free individuals, independently of histological subtype. In multivariate models adjusting for covariates, individuals in the highest tertile of FST levels were associated with an increased risk for the presence of any type of TC or specific histological subtypes, including papillary, follicular and Hürthle-cell carcinoma, and medullary TC. Higher postoperative FST concentrations were found in patients with vascular invasion and distant metastases and associated with TNM staging at diagnosis.

CONCLUSION

FST serum levels are increased in TC patients and correlate with advanced tumor aggressiveness. Future longitudinal studies are needed to confirm and extend our observations.

Serum levels of fetuin-A are negatively associated with log transformation levels of thyroid-stimulating hormone in patients with hyperthyroidism or euthyroidism: An observational study at a medical center in Taiwan

Fetuin-A is a protein with various biological functions. It plays a role in insulin resistance and arterial calcium deposition. Thyroid dysfunction may affect energy expenditure, glucose metabolism, and the risk of cardiovascular diseases. In the present study, we compared the serum fetuin-A concentrations in hyperthyroid patients with those in euthyroid patients.We recruited 30 newly-diagnosed hyperthyroid patients (the HY group) and treated them with anti-thyroid regimens as clinically indicated. We recruited 30 euthyroid individuals (the EU group) as controls. We compared laboratory parameters at the baseline and at 6 months. We then determined the associations between the levels of fetuin-A and free thyroxine (fT4), thyroid-stimulating hormone (TSH), or log transformation of TSH (logTSH).At the baseline, the HY patients had significantly higher serum fetuin-A levels than the EU patients (median [Q1, Q3]: 735.4 [537.9, 843.4] ng/mL vs 561.1[449.2, 670.5] ng/mL, P = .010). At 6 months, the serum fetuin-A levels of the HY patients decreased but were still higher than those of the EU patients (698.4 [627.6, 924.3] ng/mL vs 616.5 [498.2, 727.7] ng/mL, P = .002). At baseline, the serum levels of fetuin-A were negatively associated with logTSH (β = -53.79, P = .010). At 6 months, the levels of fetuin-A were positively associated with fT4 (β = 86.91, P = .039), and negatively associated with logTSH (β = -104.28, P < .001). Changes to the levels of fetuin-A within 6 months were negatively associated with changes to logTSH (β = -57.80, P = .019). The negative associations between fetuin-A levels and logTSH at baseline and at 6 months, and the changes during the 6 months remained significant after adjustment for sex and age (β = -51.72, P = .016; β = -103.11, P < .001; and β = -59.36, P = .020, respectively).The patients with hyperthyroidism had higher serum fetuin-A levels than the patients with euthyroidism. In patients with hyperthyroidism, the serum fetuin-A concentrations decreased after the anti-thyroid treatment. In the present study, serum fetuin-A concentrations were negatively associated with logTSH.

Circulating follistatin displays a day-night rhythm and is associated with muscle mass and circulating leptin levels in healthy, young humans

PURPOSE

Follistatin may affect lean and fat mass and be implicated in metabolic diseases. We aimed to elucidate physiological predictors of circulating follistatin variation in healthy young humans.

PROCEDURES

This was an observational, cross-sectional study with two additional prospective observational arms (circadian, seasonal sub-studies) and one prospective interventional arm (mixed meal sub-study). Healthy, young individuals of both sexes (n=122) were subjected to anthropometric and body composition measurements and their eating and exercise behavior profiles were assessed by validated questionnaires. Sub-groups were subjected to standardized meal ingestion (n=36), day-night rhythm (n=20) and seasonal variation (n=20) studies. Main outcome of the study were circulating follistatin levels.

RESULTS

At baseline follistatin levels were correlated with creatinine (r=0.24; p=0.01), creatine phosphokinase (rs=0.22; p=0.02), and with lean body mass (rs=0.19; p=0.04) and were higher in males than females (p=0.004) after adjustment for leptin, which was its major predictor. Follistatin levels showed a circadian (p<0.001), but not a seasonal, variation, and were also affected by the phase of menstrual cycle in females (p=0.034). Follistatin levels were not affected by dietary or exercise habits but levels increased after a standardized meal ingestion (250kcal) (p=0.002).

CONCLUSIONS

In healthy young individuals circulating follistatin levels are correlated with muscle mass. Follistatin levels are associated with circulating leptin levels and display a day-night rhythm and a menstrual cycle, but not a seasonal, variation.