Different effects of IGF-I on insulin-stimulated glucose uptake in adipose tissue and skeletal muscle.

• The effect of insulin-like growth factor I (IGF-I) on insulin-stimulated glucose uptake was studied in adipose and muscle tissues of hypophysectomized female rats. IGF-I was given as a subcutaneous infusion via osmotic minipumps for 6 or 20 days. All hypophysectomized rats received L-thyroxine and cortisol replacement therapy. IGF-I treatment increased body weight gain but had no effect on serum glucose or free fatty acid levels. Serum insulin and C-peptide concentrations decreased. Basal and insulin-stimulated glucose incorporation into lipids was reduced in adipose tissue segments and isolated adipocytes from the IGF-I-treated rats. In contrast, insulin treatment of hypophysectomized rats for 7 days increased basal and insulin-stimulated glucose incorporation into lipids in isolated adipocytes. Pretreatment of isolated adipocytes in vitro with IGF-I increased basal and insulin-stimulated glucose incorporation into lipids. These results indicate that the effect of IGF-I on lipogenesis in adipose tissue is not direct but via decreased serum insulin levels, which reduce the capacity of adipocytes to metabolize glucose. Isoproterenol-stimulated lipolysis, but not basal lipolysis, was enhanced in adipocytes from IGF-I-treated animals. In the soleus muscle, the glycogen content and insulin-stimulated glucose incorporation into glycogen were increased in IGF-I-treated rats. In summary, IGF-I has opposite effects on glucose uptake in adipose tissue and skeletal muscle, findings which at least partly explain previous reports of reduced body fat mass, increased body cell mass, and increased insulin responsiveness after IGF-I treatment.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

Nyckelord

Adipocytes

drug effects

metabolism

Adipose Tissue

drug effects

metabolism

Animals

Blood Glucose

metabolism

C-Peptide

blood

Female

Glucose

metabolism

Glycogen

metabolism

Hypoglycemic Agents

pharmacology

Hypophysectomy

Insulin

blood

pharmacology

Insulin-Like Growth Factor I

metabolism

pharmacology

Lipid Metabolism

Lipolysis

drug effects

Muscle

Skeletal

drug effects

metabolism

Organ Size

drug effects

Rats

Rats

Sprague-Dawley

Spleen

drug effects

growth & development

Weight Gain

drug effects

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)