Amino Acid Ingestion Strongly Enhances Insulin Secretion in Patients With Long-Term Type 2 Diabetes

  1. Luc J.C. van Loon, PHD1,
  2. Margriet Kruijshoop, MSC1,
  3. Paul P.C.A. Menheere, PHD2,
  4. Anton J.M. Wagenmakers, PHD1,
  5. Wim H.M. Saris, MD, PHD1 and
  6. Hans A. Keizer, MD, PHD1
  1. 1Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, Maastricht, the Netherlands
  2. 2Department of Clinical Chemistry, University Hospital Maastricht, Maastricht, the Netherlands

    Abstract

    OBJECTIVE—Insulin secretion in response to carbohydrate intake is blunted in type 2 diabetic patients. However, it is not clear whether the insulin response to other stimuli, such as amino acids, is also diminished. Recently, we defined an optimal insulinoptropic mixture containing free leucine, phenylalanine, and a protein hydrolysate that substantially enhances the insulin response in healthy young subjects when coingested with carbohydrate. In this study, we aimed to investigate the insulinotropic capacity of this mixture in long-term type 2 diabetic patients.

    RESEARCH DESIGN AND METHODS—Ten type 2 diabetic patients (aged 59.1 ± 2.0 years, BMI 26.5 ± 0.7 kg/m2) and 10 healthy control subjects (58.8 ± 2.1 years, 26.5 ± 0.7 kg/m2) visited our lab twice, during which insulin responses were determined following ingestion of carbohydrate only (CHO) or carbohydrate with the free amino acid/protein mixture (CHO+PRO). All subjects received 0.7 g · kg−1 · h−1 carbohydrate with or without 0.35 g · kg−1 · h−1 of the amino acid/protein mixture.

    RESULTS—Insulin responses were dramatically increased in the CHO+PRO trial in both the type 2 diabetic and control groups (189 and 114%, respectively) compared with the CHO trial (P < 0.01). Plasma glucose, glucagon, growth hormone, cortisol, IGF-I, and IGF binding protein 3 responses were not different between trials within the 2-h time frame.

    CONCLUSIONS—The insulin secretory capacity in long-term type 2 diabetic patients is substantially underestimated, as the insulin response following carbohydrate intake can be nearly tripled by coingestion of a free amino acid/protein mixture. Future research should be performed to investigate whether such nutritional interventions can improve postprandial glucose disposal.

    Footnotes

    • Address correspondence and reprint requests to Dr. L.J.C. van Loon, Department of Human Biology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. E-mail: l.vanloon{at}hb.unimaas.nl.

      Received for publication 21 August 2002 and accepted in revised form 24 November 2002.

      A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

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