(HealthDay News) – Gastric bypass surgery alters the hormones and amino acids produced during digestion, possibly elucidating the mechanisms through which the surgery eliminates symptoms of type 2 diabetes, according to a study published in the May issue of the Journal of Clinical Endocrinology and Metabolism.

Andreas Lindqvist, PhD, from Lund University in Malmö, Sweden, and colleagues first gave four patients a mixed meal test (MMT) orally, preceded by overnight fast, and then gave it to them via the gastrostomy tube, preceded by two-hour fasting. Hormones and metabolites were assessed from blood samples.

The researchers found that the oral MMT produced a 4.6-fold increase in plasma insulin, a 9.3-fold increase in glucagon-like peptide-1, and a 2.5-fold increase in glucose-dependent insulinotropic peptide plasma levels (P<0.05 for all), compared to the gastrostomy MMT. Elevated branched-chain amino acid levels (1.4 to 2-fold; P<0.05) and suppressed fatty acid levels (approximately 50%; P<0.05) accompanied the changes in hormone levels.

“These data, comparing identical nutrient delivery, demonstrate markedly higher incretin and insulin responses after oral MMT than after gastric MMT, thereby providing a potential explanation for the rapid remission of type 2 diabetes observed after gastric bypass surgery,” the authors write.

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