Metabolic adaptation to feeding and fasting during lactation in humans

J Clin Endocrinol Metab. 2002 Jan;87(1):302-7. doi: 10.1210/jcem.87.1.8178.

Abstract

The aim of these studies was to determine the metabolic adaptation to fasting and feeding during lactation. Normal lactating (L) and nonlactating (NL) women (n = 6 each) were studied using infusions of [U-13C]glucose and [2-13C]glycerol during: 1) a 24-h fast, and 2) ingestion of Sustacal (protocol 1). In addition, 8 L and 6 NL women were studied during infusion of [6,6-2H2]glucose and ingestion of a glucose meal containing [1-13C]glucose (protocol 2). Protocol 1: Glucose production rate (GPR) during fasting was 33% higher in the L women (12.5 +/- 1.0 vs. 9.4 +/- 0.5 micromol x kg(-1) x min(-1); P < 0.03). Fractional gluconeogenesis (GNG), GNG rate, glucose, lactate, beta- hydroxybutyrate, FFA, insulin, and C-peptide were similar in both groups during feeding and fasting, but glycogenolysis was 50% higher in fasting L women. Protocol 2: Although GPR was slightly increased in the L group (L, 1.8 +/- 0.2 micromol x kg(-1) x min(-1); NL, 1.2 +/- 0.2 micromol x kg(-1) x min(-1); P < 0.04), no other differences were observed in splanchnic and systemic metabolism of ingested glucose between L and NL women. Insulin concentrations were lower in L women compared with controls (L, 15 +/- 3 microU/ml; NL, 28 +/- 6 microU/ml; P = 0.05). In conclusion, the increased glucose demands of lactation are met by increased GPR as a result of increased glycogenolysis but not GNG or by increased use of FFA. During feeding, lactating women handle oral carbohydrates normally but have increased insulin sensitivity.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3-Hydroxybutyric Acid / blood
  • Adaptation, Physiological
  • Adult
  • Blood Glucose / analysis
  • C-Peptide / blood
  • Carbon Isotopes
  • Eating*
  • Fasting*
  • Fatty Acids / blood
  • Female
  • Glucagon / blood
  • Glucose / administration & dosage
  • Glucose / metabolism
  • Glycerol / metabolism
  • Humans
  • Insulin / blood
  • Lactation*
  • Lactic Acid / biosynthesis
  • Lactic Acid / blood
  • Milk, Human / metabolism
  • Postpartum Period
  • Time Factors

Substances

  • Blood Glucose
  • C-Peptide
  • Carbon Isotopes
  • Fatty Acids
  • Insulin
  • Lactic Acid
  • Glucagon
  • Glucose
  • Glycerol
  • 3-Hydroxybutyric Acid