title: Insulin insensitivity is associated with a decrease in postprandial thermogenesis in normal pregnancy.
abstract: Insulin sensitivity and postprandial thermogenesis were investigated at various stages of pregnancy to assess if changes in insulin sensitivity contribute to energy conservation during pregnancy. Cross-sectional and longitudinal studies were undertaken. Sixteen control non-pregnant women were compared with 10 women in the second trimester (2nd) and thirteen women in the third trimester (3rd) of uncomplicated pregnancy. Six women were studied at all three time points. The slope of plasma glucose decline following a bolus of intravenous insulin was used as an index of insulin sensitivity. Resting energy expenditure was measured with continuous indirect calorimetry. Postprandial thermogenesis was measured as the change in energy expenditure for the 2 h after a mixed meal. Results are expressed as mean +/- SEM or median (interquartile range). Insulin sensitivity was lower as pregnancy progressed (non-pregnant control 181 (177-205) vs 2nd 111 (100-112) vs 3rd 96 (80-109) mumol l-1 min-1, p < 0.001). Fasting insulin levels were significantly higher in the third trimester but not in the second trimester (non-pregnant control 1.9 (1.5-6.0) vs 2nd 3.1 (2.8-5.2) vs 3rd 8.6 (4.8-9.7) mU l-1, p < 0.05). Meal stimulated insulin levels were higher in the second and third trimesters compared to non-pregnant women (insulin area over 2 h, postmeal, non-pregnant control 78 +/- 10 vs 2nd 92 +/- 14 vs 3rd 145 +/- 14 mU l-1 h-1, p < 0.005). Postprandial thermogenesis was lowest in the third trimester (non-pregnant control 103 +/- 5 vs 2nd 74 +/- 8 vs 3rd 48 +/- 8 kJ, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Unit of Metabolic Medicine, St Mary's Hospital Medical School, Paddington, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Robinson
authors.forename: J
authors.initials: J
authors.lastname: Viira
authors.forename: J
authors.initials: J
authors.lastname: Learner
authors.forename: S P
authors.initials: SP
authors.lastname: Chan
authors.forename: V
authors.initials: V
authors.lastname: Anyaoku
authors.forename: R W
authors.initials: RW
authors.lastname: Beard
authors.forename: D G
authors.initials: DG
authors.lastname: Johnston
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D001786:Blood Glucose / Q000378:metabolism*; D002151:Calorimetry; D004435:Eating / Q000502:physiology*; D004734:Energy Metabolism; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D010101:Oxygen Consumption; D010928:Placental Lactogen / Q000097:blood; D011247:Pregnancy / Q000502:physiology*; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011388:Prolactin / Q000097:blood; D012016:Reference Values; D013997:Time Factors; D014280:Triglycerides / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D014284:Triiodothyronine; D011388:Prolactin; D010928:Placental Lactogen