Pioglitazone increases gallbladder volume in insulin-resistant obese mice.
BACKGROUND
Both obesity and diabetes are associated with an increased incidence of gallstones. Recent animal and human data from our laboratory suggest that insulin resistance is associated with increased gallbladder volume and/or impaired gallbladder emptying. Pioglitazone is a thiazolidinedione that has been shown to improve insulin resistance. Therefore, we tested the hypothesis that pioglitazone would improve insulin resistance, decrease resting gallbladder volume and improve gallbladder response to neurotransmitters in insulin-resistant obese mice fed a 25% carbohydrate diet.


METHODS
Twenty eight-week-old insulin-resistant obese (Lep(ob)) mice fed a 25% carbohydrate diet for 4 weeks. Half of the animals had 0.3 g/kg pioglitazone added to their diet. At 12 weeks all animals were fasted and underwent cholecystectomy. Gallbladder volume and weight were measured, and fresh gallbladders were placed in a muscle bath to assess response to acetylcholine (ACh 10(-5)M), neuropeptide Y (NPY 10(-8,-7,-6)M) and cholecystokinin (CCK 10(-10,-9,-8,-7)M). Serum glucose and insulin were measured, and HOMA Index, a measure of insulin resistance, was calculated.


RESULTS
Fasting serum insulin and HOMA Index were significantly decreased (P < 0.03), but gallbladder volume was significantly increased (P < 0.03) in the pioglitazone treated group. Pioglitazone did not alter gallbladder weight or response to ACh, NPY, or CCK.


CONCLUSIONS
These data suggest that in insulin-resistant obese mice pioglitazone 1) lowers insulin-resistance, 2) increases resting gallbladder volume, and 3) does not alter gallbladder response to neurotransmitters. Therefore, we conclude that pioglitazone, while improving insulin resistance, paradoxically increases gallbladder volume and, thereby, may increase the propensity for gallstone formation by enhancing gallbladder stasis.
Al-Azzawi
Hayder H
HH
Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Mathur
Abhishek
A
Lu
Debao
D
Swartz-Basile
Deborah A
DA
Nakeeb
Attila
A
Pitt
Henry A
HA
D000109:Acetylcholine / Q000494:pharmacology; D000367:Age Factors; D000818:Animals; D001786:Blood Glucose; D002766:Cholecystokinin / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology; D004040:Dietary Carbohydrates / Q000494:pharmacology; D005260:Female; D005704:Gallbladder / Q000187:drug effects / Q000473:pathology*; D042882:Gallstones / Q000209:etiology / Q000473:pathology; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D020738:Leptin / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009478:Neuropeptide Y / Q000494:pharmacology; D009765:Obesity / Q000188:drug therapy* / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D010446:Peptide Fragments / Q000494:pharmacology; D000077205:Pioglitazone; D045162:Thiazolidinediones / Q000494:pharmacology*
D001786:Blood Glucose; D018678:Cholinergic Agents; D004040:Dietary Carbohydrates; D007004:Hypoglycemic Agents; D007328:Insulin; D020738:Leptin; D009478:Neuropeptide Y; D010446:Peptide Fragments; D045162:Thiazolidinediones; C050803:cholecystokinin 10 C-terminal fragment; D002766:Cholecystokinin; D000109:Acetylcholine; D000077205:Pioglitazone