Extrapancreatic tumor hypoglycemia (EPTH) is associated with increased amounts of high-molecular-weight precursor forms of insulin-like growth factor (IGF)-II ('big-IGF-II') that have a primary role in the pathophysiology of hypoglycemia. In the present study, using Western ligand and immunoblotting methods, we investigated IGF-binding proteins (IGFBPs), IGFBP-3 proteolysis and big-IGF-II in pre- and postoperative serum from two patients with EPTH due to benign pleural fibroma. In the preoperative serum, IGFBP-3 was reduced and IGFBP-2 was increased compared with that from an age-matched healthy control. IGFBP-3 proteolysis was dramatically reduced in one patient, whereas no major alteration was observed in the other (9% and 120% of control serum, respectively). IGFBPs progressively returned to a subnormal pattern in postoperative serum, whereas IGFBP- 3 proteolysis remained greater than in preoperative serum in both patients at days 14 and 90 after surgery. High-molecular-weight forms of IGF-II predominate in EPTH serum (65% and 57% of total IGF-II immunoreactivity in patients 1 and 2, respectively, compared with 2 5% in control serum). Two forms, of molecular mass 10 and 12 kDa ('standard big-IGF-II') were present in both EPTH and control sera, whereas two additional forms, of molecular mass 15 and 18 kDa ('big big-IGF-II') were observed in EPTH sera only. Big big-IGF-II represented 72% and 55% of total high-molecular-weight forms of IGF-II in the two EPTH sera, respectively. All big forms of IGF-II disappeared from the serum as early as 6 h after surgery. This study shows that combination of simple Western blotting methods, available routinely in most laboratories, should prove useful in providing reliable physiopathological information in EPTH.
MA Christofilis, M Remacle-Bonnet, C Atlan-Gepner, F Garrouste, B Vialettes, P Fuentes, R Guidicelli and G Pommier
F Bonnet, B Balkau, J M Malécot, P Picard, C Lange, F Fumeron, R Aubert, V Raverot, H Déchaud, J Tichet, P Lecomte, M Pugeat and for the DESIR Study Group
Previous evidence has suggested that a low sex hormone-binding globulin (SHBG) concentration is associated with insulin-resistance and a low adiponectin concentration. We investigated the association between SHBG and the risk of hyperglycemia in each sex and we determined potential interactions between SHBG and adiponectin levels in the development of dysglycemia.
We used a nested case–control design in the large prospective study, Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR). We studied 227 men and women who were normoglycemic at baseline but hyperglycemic at 3 years (glycemia≥6.1 mmol/l or type 2 diabetes). They were matched for sex, age, and body mass index with 227 subjects who remained normoglycemic at 3 years.
At baseline, the concentration of SHBG was significantly lower in women who subsequently developed hyperglycemia than in those who remained normoglycemic, with no difference for men. In multiple regression, SHBG at baseline was as an independent determinant of plasma adiponectin levels, in both women (P<0.0001) and men (P=0.002). In multivariate conditional logistic regression taking into account physical activity and changes in waist circumference over the follow-up, plasma SHBG remained significantly associated with the development of hyperglycemia in women but not in men. These associations persisted after adjustment for fasting insulinemia, high fasting glucose, and adiponectin levels.
These findings suggest that a low SHBG level is a strong risk marker for dysglycemia in women, independently of both adiponectinemia and insulinemia. SHBG may therefore improve the identification of women at risk of diabetes.