Endocrine Abstracts

Irisin is a myokine correlated with lean body mass, despite its association with cardiovascular events (Mantzoros 2014). Increased muscle volume and lipoatrophy have been reported in female FPLD (Ji JCEM 214). Our aim was to determine whether irisin could help to distinguish certain lipodystrophic obesities from FPLD.

Methods and patients: Circulating irisin levels (EIA Phoenix) were measured in 20 LMNA-related FPLD, 19 normal-weighed controls (H) and 13 obese non-diabetic (OND) patients, and correlated with body composition (DEXA/MRI), and metabolic and inflammatory (CRP, leukocytes CD4) parameters (Clin.gov2009-AO-1169-48).

Results: Irisin medians differed between the three groups (P: 0.0076) and were higher in OND (P: 0.0099) and FPLD (P: 0.047) than in H groups, without difference between FPLD and OND. Irisinaemia, similar between male and female, was positively correlated to lean mass (g)/height² (r=0.51; P<0.0001), BMI, triglycerides (r=0.45–0.49; P< 0.001) and to a lesser extent to insulin, body weight, MRI-intra-abdominal fat mass, MRI-intra-abdominal/MRI-total fat mass, FBG, A1c, cholesterol, and ASAT (r=0.42–0.33; P<0.01). The ratio ‘lean mass/height²’ differed significantly between the three groups (P<0.0001) with higher values in OND (P<0.0001) and FPLD (P=0.03) compared to H groups, without difference between FPLD and OND. Leptinaemia was higher in OND compared to H and FPLD (P<0.0001), without difference between these two groups. The ratio «irisin/leptin» differed between the three groups (P<0.0001) with higher values in FPLD and H (both P<0.0001) compared to OND, without difference between FPLD and H. Irisin was not correlated with leptin and inflammatory parameters.

Conclusion: FPLD is characterized by high irisinemia and low leptinemia, OND by both high leptinaemia and irisinaemia. Irisin is increased in diseases characterised by higher lean mass whatever the amount of fat mass. Irisin/leptin ratio, a biological marker of lean/fat mass, may help to identify FPLD.