Effects of a physiological GH pulse on interstitial glycerol in abdominal and femoral adipose tissue.
Physiologically, growth hormone (GH) is secreted in pulses with episodic bursts shortly after the onset of sleep and postprandially. Such pulses increase circulating levels of free fatty acid and glycerol. We tested whether small GH pulses have detectable effects on intercellular glycerol concentrations in adipose tissue, and whether there would be regional differences between femoral and abdominal subcutaneous fat, by employing microdialysis for 6 h after administration of GH (200 microgram) or saline intravenously. Subcutaneous adipose tissue blood flow (ATBF) was measured by the local Xenon washout method. Baseline of interstitial glycerol was higher in adipose tissue than in blood [220 +/- 12 (abdominal) vs. 38 +/- 2 (blood) micromol/l, P < 0.0005; 149 +/- 9 (femoral) vs. 38 +/- 2 (blood) micromol/l, P < 0.0005] and higher in abdominal adipose tissue compared with femoral adipose tissue (P < 0.0005). Administration of GH induced an increase in interstitial glycerol in both abdominal and femoral adipose tissue (ANOVA: abdominal, P = 0. 04; femoral, P = 0.03). There was no overall difference in the response to GH in the two regions during the study period as a whole (ANOVA: P = 0.5), but during peak stimulation of lipolysis abdominal adipose tissue was, in absolute but not in relative terms, stimulated more markedly than femoral adipose tissue (ANOVA: P = 0. 03 from 45 to 225 min). Peak interstitial glycerol values of 253 +/- 37 and 336 +/- 74 micromol/l were seen after 135 and 165 min in femoral and abdominal adipose tissue, respectively. ATBF was not statistically different in the two situations (ANOVA: P = 0.7). In conclusion, we have shown that a physiological pulse of GH increases interstitial glycerol concentrations in both femoral and abdominal adipose tissue, indicating activated lipolysis. The peak glycerol increments after GH were higher in abdominal adipose tissue, perhaps due to a higher basal rate of lipolysis in this region.
Gravhølt
C H
CH
Department of Endocrinology M and Medical Research Laboratories, Arhus University Hospital, DK-8000 Aarhus C, Denmark. ch.gravholt@dadlnet.dk
Schmitz
O
O
Simonsen
L
L
Bülow
J
J
Christiansen
J S
JS
Møller
N
N
D000005:Abdomen; D000273:Adipose Tissue / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D000328:Adult; D000409:Alanine / Q000097:blood; D001786:Blood Glucose; D004734:Energy Metabolism / Q000187:drug effects; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005269:Femur; D005990:Glycerol / Q000032:analysis / Q000378:metabolism*; D019382:Human Growth Hormone / Q000008:administration & dosage* / Q000097:blood; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D020551:Pulse Therapy, Drug; D013848:Thigh
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D019382:Human Growth Hormone; D019344:Lactic Acid; D000409:Alanine; D005990:Glycerol