title: Disparate effects of weight loss on insulin sensitivity and erythrocyte sodium-lithium countertransport activity.
abstract: Previous investigations have demonstrated an association between impaired insulin sensitivity and elevated erythrocyte sodium-lithium countertransport (Na(+)-Li+ CT) activity. It has been speculated that insulin resistance and endogenous hyperinsulinemia are causally related to the development of elevated Na(+)-Li+ CT activity. To test this hypothesis, we measured insulin sensitivity (euglycemic insulin clamp technique) and Na(+)-Li+ CT activity in eight obese women before (weight = 102 +/- 5 kg) and after (weight = 88 +/- 5 kg; P < .001) a 10 week weight reduction program. Maximal velocity of Na(+)-Li+ CT activity did not change (0.50 +/- 0.09 v 0.49 +/- 0.10 mmol/L red blood cells/h; P = NS) despite the significant improvement in insulin sensitivity (73 +/- 12 vs 110 +/- 7 mg/m2/min; P < .0025) and reduction in fasting insulin levels (17 +/- 2 v 10 +/- 2 microU/mL; P < .05) that accompanied weight loss. These results suggest that insulin resistance and hyperinsulinemia are not linked pathophysiologically to the development of elevated Na(+)-Li+ CT activity.
authors.affiliation: Department of Internal Medicine, Joslin Diabetes Center, New England Deaconess Hospital, Boston, Massachusetts.
authors.forename: H A
authors.initials: HA
authors.lastname: Wolpert
authors.forename: S N
authors.initials: SN
authors.lastname: Steen
authors.forename: N W
authors.initials: NW
authors.lastname: Istfan
authors.forename: D C
authors.initials: DC
authors.lastname: Simonson
mesh_terms: D000328:Adult; D017920:Antiporters; D002352:Carrier Proteins / Q000097:blood*; D015331:Cohort Studies; D004038:Diet, Reducing; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D009765:Obesity / Q000097:blood / Q000178:diet therapy / Q000503:physiopathology*; D015431:Weight Loss
chemical_list: D017920:Antiporters; D002352:Carrier Proteins; D007328:Insulin; C045885:sodium-lithium countertransporter