Physiological parameters regulating circulating levels of the IGFBP-4/Stanniocalcin-2/PAPP-A axis.

Background: Insulin Growth Factor Binding Protein 4 (IGFBP-4), Stanniocalcin-2 (STC-2) and Pregnancy-Associated Plasma Protein-A (PAPP-A) have a well-documented involvement in several physiological functions in humans but predictors of their circulating levels remain largely unknown. We aimed to identify anthropometric and biochemical parameters associated with circulating levels of IGFBP-4/STC-2/PAPP-A axis (ISPa) cross-sectionally and to study their day-night variation and their regulation in response to mixed meal and exercise.

Methods: One hundred twenty two healthy individuals were evaluated cross-sectionally.

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).

Circulating irisin in healthy, young individuals: day-night rhythm, effects of food intake and exercise, and associations with gender, physical activity, diet, and body composition.

Context: The myokine irisin may increase energy expenditure and affect metabolism.

Objective: The objective of the study was to elucidate predictors of irisin and study whether circulating irisin may have day-night rhythm in humans.

Design: This was an observational, cross-sectional study with an additional 24-hour prospective observational arm (day-night rhythm substudy) and two prospective interventional arms (mixed meal substudy and exercise substudy).