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(1994) O'Sullivan, Anthony J; Kelly, John J.; Hoffman, David M.; Freund, Judith; Ho, Ken K.Y.Journal Article
(1995) O'Sullivan, Anthony; Kelly, John; Hoffman, David; Baxter, R; Ho, K.K.Y.Journal ArticleShort term GH administration increases lipid breakdown and oxidation (lipidox) and reduces glucose uptake and carbohydrate oxidation (CHOox). It is not clear whether similar shifts in substrate oxidation occur in acromegaly, and our aim was to investigate this. Using indirect calorimetry, we compared energy expenditure, CHOox, and lipidox in 20 acromegalic patients and 20 normal subjects pair-matched for sex, age, height, and weight. Investigations were performed in the basal state (12-h fast) and during a 75-g oral glucose tolerance test (OGTT). Acromegalic patients had significantly higher fasting glucose levels and greater glucose and insulin responses during an OGTT than normal subjects. Fasting nonesterified free fatty acid and insulin-like growth factor (IGF)-binding protein-1 levels were similar in the two groups, and both were acutely suppressed by oral glucose to the same degree. Basal energy expenditure was significantly greater in the acromegalic patients (1682 +/- 49 vs. 1540 +/- 45 Cal/24 h; P < 0.05), who showed a trend toward higher basal CHOox. Oral glucose resulted in a significantly higher rise in energy expenditure in the normal compared to the acromegalic subjects. During the OGTT, CHOox significantly increased in both groups, but rose to a higher level in the acromegalic patients (177 +/- 10 vs. 138 +/- 9 mg/min; P = 0.004). Oral glucose significantly reduced lipidox in both groups, but lipidox was reduced to a significantly lower level in the acromegalic patients (32 +/- 4 vs. 46 +/- 3 mg/min; P = 0.004). In acromegaly, basal CHOox (r = 0.56; P = 0.01) and postglucose CHOox (r = 0.79; P = 0.0001) were both positively correlated to IGF-I, but not to insulin and/or glucose. In normal subjects, postglucose CHOox was positively correlated to IGF- I. In summary, hyperinsulinemia in acromegaly was associated with higher glucose levels and a blunted thermogenic response to glucose, and displayed no relationship to the pattern of substrate oxidation. CHOox was increased, and lipidox was reduced in acromegaly, and the extent of IGF-I elevation was related to CHOox in the basal and postglucose states. We conclude that 1) the chronic effects of GH excess on substrate oxidation differ from the short term effects of GH administration; 2) impaired insulin action in acromegaly extends to effects on energy expenditure; and 3) IGF-I may be an important regulator of substrate oxidation in acromegaly.
A comparison of the effects of oral and transdermal estrogen replacement on insulin sensitivity in postmenopausal women(1995) O'Sullivan, Anthony J.; Ho, Ken K.Y.Journal ArticlePrevious studies have shown that oral, but not transdermal, administration of estrogen stimulates GH secretion in postmenopausal women. Because GH impairs insulin action, the impact of estrogen replacement therapy on carbohydrate metabolism may be influenced by the route of administration. The aim of this study was to prospectively compare the effects of oral and transdermal estrogen replacement on glucose tolerance and insulin sensitivity in postmenopausal women. In an open label, randomized, cross-over study, nine postmenopausal women were randomized to transdermal estrogen patches (Estraderm-TTS 100) or oral conjugated estrogen (Premarin, 1.25 mg) daily for 12 weeks and then crossed over to receive the alternative treatment for a further 12 weeks. An oral glucose tolerance test and hyperinsulinemic euglycemic clamp (HEC) were performed before treatment and at the end of 10 weeks of treatment. Oral and transdermal estrogen both significantly reduced LH to the same degree. Mean GH did not significantly change with transdermal estrogen, but rose significantly during oral estrogen therapy. Peak and mean glucose and insulin levels during the oral glucose tolerance test were not altered by estrogen therapy and were not significantly different between treatments. Mean glucose and insulin levels were maintained at an identical level during the HEC performed at pretreatment and during estrogen therapy. The mean glucose infusion rate required to maintain euglycemia during the HEC (mean +/- SEM, pretreatment, 40.4 +/- 4.8 mumol/kg.min) was unaltered by oral (39.8 +/- 4.6 mumol/kg.min) or transdermal estrogen treatment (42.1 +/- 4.2 mumol/kg.min). However, during the transdermal estrogen phase (60 +/- 10 mumol/L), the mean nonesterified free fatty acid concentration was suppressed to a significantly lower level during the HEC than during the oral estrogen phase (120 +/- 20 mumol/L; P < 0.05). We conclude that compared to the oral route, transdermal estrogen therapy is associated with a slight, but significant, improvement of insulin action on lipid metabolism. However, in the short term, the route of estrogen replacement therapy does not have a major impact on glucose metabolism in postmenopausal women.