Endocrine Abstracts

Background: We and others have shown that ectopic lipids are flexible fuel stores in healthy subjects, in patients with type 1 diabetes or with GHD. IMCL are depleted by exercise and repleted by diet, whereas intrahepatocellular lipids (IHCL) are increased immediately after exercise. It is unclear whether the exercise-induced flexibility of IMCL and IHCL persists until 24 h and whether healthy subjects and patients with GHD behave differently.

Methods: Male patients with GHD and sedentary CS were included. VO_2max was assessed by spiroergometry, visceral and subcutaneous fat by whole body MRI. ¹H-MR-spectroscopy was performed in the M. vastus intermedius (IMCL) and the liver (IHCL) before and after 2 h of exercise at 50–60% VO_2max and 24 h thereafter, while diet and physical activity were standardized.

Results: 14 men (seven GHD and seven CS) were recruited. Mean (±S.D.) age was 46.9±11.7 and 39±12.6 years in GHD and CS, respectively (p=NS). BMI was 26.7±3.8 and 27±4.1 kg/m² (p=NS), waist circumference 93.3±12.8 cm and 91.3±13.8 cm (p=NS), VO_2max 30.5±6.2 and 42.8±10.9 ml/kg per min in GHD and CS, respectively (P=0.03). Visceral fat content (of total body mass) was 4.2±1.4% and 2.4±1.5% (P=0.04) and subcutaneous fat content was 16.7±3.0% and 15.8±4.0% (p=NS) in GHD and CS.

IMCL were decreased during aerobic exercise in both groups (−11.5±21.9% in CS and −8.9%±19.1% in GHD) and repleted after 24 h in CS (−5.5±26.6% compared to baseline) but not in GHD (−17.9±15.3%), (P=0.048 for interaction). IHCL increased immediately after exercise and decreased to baseline after 24 h (p=NS for interaction).

Conclusion: These findings suggest that IMCL’s flexibility differs in patients with GHD 24 h after exercise whereas the kinetics of IHCL are similar. Apart from lower VO_2max and higher visceral fat in GHD, the lack of lipolytic action of GH could explain the findings: the reduced fat availability following exercise may have led to a decreased repletion of IMCL at 24 h.