Improved insulin sensitivity and adipose tissue dysregulation after short-term treatment with pioglitazone in non-diabetic, insulin-resistant subjects.
OBJECTIVE
We examined whether short-term treatment with a thiazolidinedione improves insulin sensitivity in non-obese but insulin-resistant subjects and whether this is associated with an improvement in dysregulated adipose tissue (reduced expression of IRS-1, GLUT4, PPARgamma co-activator 1 and markers of terminal differentiation) that we have previously documented to be associated with insulin resistance.


METHODS
Ten non-diabetic subjects, identified as having low IRS-1 and GLUT-4 protein in adipose cells as markers of insulin resistance, underwent 3 weeks of treatment with pioglitazone. The euglycaemic-hyperinsulinaemic clamp technique was used to measure insulin sensitivity before and after treatment. Serum samples were analysed for glucose, insulin, lipids, total and high-molecular-weight (HMW) adiponectin levels. Biopsies from abdominal subcutaneous adipose tissue were taken, cell size measured, mRNA and protein extracted and quantified using real-time RT-PCR and Western blot.


RESULTS
Insulin sensitivity was improved after 3 weeks treatment and circulating total as well as HMW adiponectin increased in all subjects, while no effect was seen on serum lipids. In the adipose cells, gene and protein expression of IRS-1 and PPARgamma co-activator 1 remained unchanged, while adiponectin, adipocyte P 2, uncoupling protein 2, GLUT4 and liver X receptor-alpha increased. Insulin-stimulated tyrosine phosphorylation and p-ser-PKB/Akt increased, while no significant effect of thiazolidinedione treatment was seen on the inflammatory status of the adipose tissue in these non-obese subjects.


CONCLUSIONS
Short-term treatment with pioglitazone improved insulin sensitivity in the absence of any changes in circulating NEFA or lipid levels. Several markers of adipose cell differentiation, previously shown to be reduced in insulin resistance, were augmented, supporting the concept that insulin resistance in these individuals is associated with impaired terminal differentiation of the adipose cells.
Hammarstedt
A
A
The Lundberg Laboratory for Diabetes Research, Department of Internal Medicine, The Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
Sopasakis
V Rotter
VR
Gogg
S
S
Jansson
P-A
PA
Smith
U
U
D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D052242:Adiponectin; D000273:Adipose Tissue / Q000187:drug effects / Q000502:physiology*; D000328:Adult; D015992:Body Mass Index; D049628:Body Size; D005786:Gene Expression Regulation / Q000187:drug effects; D051275:Glucose Transporter Type 4; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood / Q000235:genetics; D009004:Monosaccharide Transport Proteins / Q000172:deficiency / Q000235:genetics; D009124:Muscle Proteins / Q000172:deficiency / Q000235:genetics; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics; D000077205:Pioglitazone; D045162:Thiazolidinediones / Q000494:pharmacology*
D052242:Adiponectin; D051275:Glucose Transporter Type 4; D007004:Hypoglycemic Agents; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; C495692:SLC2A4 protein, human; D045162:Thiazolidinediones; D000077205:Pioglitazone