Adipocyte expression of glucose transporter 1 and 4 in PCOS: Relationship to insulin-mediated and non-insulin-mediated whole-body glucose uptake.

backgroundPolycystic ovary syndrome (PCOS) is a highly prevalent endocrine-metabolic disorder associated with insulin resistance (IR). In IR states, non-insulin-mediated glucose uptake (NIMGU) may increase to compensate for declining insulin-mediated glucose uptake (IMGU), although this does not appear to be the case in PCOS. The underlying molecular mechanisms for this deficiency remain unclear.

objectivesTo compare adipocyte glucose transporter 1 and 4 (GLUT-1 and GLUT-4) gene expression in PCOS women and matched controls, and to determine whether changes in GLUT-1 and GLUT-4 are associated with concomitant alterations in whole-body glucose uptake. RESEARCH DESIGN AND

methodsIn this prospective cross-sectional study, 23 women with PCOS (by NIH 1990 criteria) and 23 matched controls were studied for subcutaneous abdominal adipocyte GLUT-1 and GLUT-4 mRNA expression (by real-time PCR), and basal whole-body IR (by HOMA-IR) and insulin secretion (by HOMA-β%). A subset of six PCOS women and six matched controls also underwent a mFSIVGTT to determine dynamic state glucose uptake (by insulin sensitivity index [Si] and glucose effectiveness [Sg]) and insulin secretion (by the acute insulin response to glucose [AIRg] and the disposition index [Di]).

resultsFor similar adiposity (BMI and waist-hip ratio), PCOS women tended to have higher HOMA-IR and lower Di and Si, and higher HOMA-β% and lower GLUT-4 than controls, while GLUT-1 was similar. GLUT-1 was positively associated with Sg (reflecting NIMGU) and GLUT-4 positively with Si (reflecting IMGU). GLUT-4 was associated negatively with HOMA-IR and HOMA-β% and positively with Di for the entire cohort but not with AIRg. Both GLUT-1 and GLU-4 were negatively associated with BMI, but not with each other.

conclusionOur results suggest that IR secondary to a lower IMGU and enhanced insulin secretion in PCOS is in part attributable to a reduction in adipocyte GLUT-4 expression that is not accompanied by a compensatory increase in GLUT-1 expression.