Myokines in Acromegaly: An Altered Irisin Profile

Effect of a GH Secretagogue, Anamorelin, on Serum Irisin and Inflammation Levels in Osteosarcopenic Adults

Background

Data suggest an association between GH secretion and circulating levels of the myokine irisin and inflammatory cytokinesIL-6 and high-sensitivity C-reactive protein (hsCRP). The impact of GH secretagogues on these markers is unknown.

Objectives

To determine the effect of treatment with the GH secretagogue anamorelin on 12-month changes in serum irisin, IL-6, and hsCRP levels and to assess whether baseline irisin levels modulate the glycemic response to treatment with anamorelin.

Methods

This is an ancillary study in 26 older adults with osteosarcopenia who participated in a 12-month trial examining the effect of anamorelin 100 mg/day vs placebo on musculoskeletal outcomes. Serum irisin, IL-6, and hsCRP were measured at baseline and 12 months.

Results

Treatment with anamorelin, compared with placebo, did not significantly alter irisin levels [12-month change = 0.50 ± 1.2 (SD) ng/mL in anamorelin group and -0.08 ± 2.3 ng/mL in placebo; P = .191]. Baseline irisin levels were not significantly correlated with 2-month change in fasting glucose levels in the anamorelin group (r = -0.222, P = .46) or the placebo group (r = 0.30, P = .34); however, the slopes of the 2 regression lines describing the relationship by group tended to differ (P = .0547). Anamorelin treatment for 12 months had no significant effect on serum IL-6 or hsCRP levels.

Conclusion

In this small sample of older adults with osteosarcopenia, treatment with the GH secretagogue anamorelin did not significantly alter levels of irisin, IL-6, or hsCRP. Higher baseline irisin levels may attenuate the glycemic response to anamorelin treatment; however, a larger study is needed to confirm this possibility.

Reduced irisin levels in patients with acromegaly

Objectives

Several metabolic disturbances are seen in acromegaly however, data regarding the contribution of irisin to these disturbances is currently insufficient. In a cohort of patients with acromegaly, we measured serum irisin levels in active and controlled cases and determined independent factors that effect serum irisin including fibronectin type III domain-containing protein 5 (FNDC5) genotyping.

Methods

A cross-sectional case-control study including 46 patients with acromegaly (28 F/18 M, age: 50.3 ± 12.1 year, BMI: 30.7 ± 5.1 kg/m2) and 81 age-, gender-, body mass index- and body composition-matched healthy controls was conducted. 15 acromegalic patients (33%) had active disease. Irisin levels were measured by enzyme-linked immunosorbent assay. Three different regions (rs3480, rs1746661, and rs16835198) of FNDC5 were subjected to polymorphism analyses.

Results

Both groups were overweight and had similar body composition. Irisin levels were lower in patients with acromegaly than controls (median [IQR]: 44.8 [41.7–46.7] ng/mL vs. 51.7 [45.5–60.1] ng/mL, p≤0.001, respectively). Active and controlled patients had similar irisin levels. Irisin was not correlated with growth hormone (GH), insulin-like growth factor 1 (IGF-1), and IGF-1 index. In multiple linear regression model, somatostatin receptor ligand use (β=−20.30, 95% CI [−34]–[−6], p=0.006) was determined as the only independent factor that affect serum irisin.

Conclusions

Serum irisin levels are low in patients with acromegaly who are on somatostatin receptor ligand therapy. Single nucleotide polymorphisms (SNPs) of FNDC5 have no independent effects on circulating irisin levels under somatostatin ligand action. Endocrine muscle functions also seem to be regulated by somatostatin action, which requires further studies.

Osteosarcopenia—The Role of Dual-Energy X-ray Absorptiometry (DXA) in Diagnostics

Osteoporosis and sarcopenia lead to increased mortality, but their early diagnosis allows preventive measures and treatment to be implemented. The dual-energy X-ray absorptiometry (DXA) method enables the assessment of both bone mineral density (BMD) and bone quality based on the trabecular bone score (TBS), the Bone Strain Index (BSI), hip structure analysis (HSA), and comprehensive hip axis length (HAL). The main complications of osteoporosis are fractures, and a BMD value or T-score together with TBS can be also applied in fracture risk calculation using the Fracture Risk Assessment Tool (FRAX). In recent years, the interest in sarcopenia has increased. There are many methods for assessing the quality, quantity and function of muscles. Total body DXA provides information not only about the BMD of the whole skeleton or the amount of lean tissue (identified as fat-free mass), but also about the amount and distribution of adipose tissue. Some parameters obtained from DXA measurements related to muscle and/or fat mass are used in the assessment of osteosarcopenia. The following article presents a wide range of possibilities for the use of the DXA method in the diagnosis of osteosarcopenia because DXA is a useful technique for the diagnosis of bone density and body composition together.