The Effect of Hyperglycemic Hyperinsulinemia on Small‐Intestinal Mucosal Protein Synthesis in Patients After Surgical Stress

Abstract

Hyperglycemic hyperinsulinemia cannot stimulate intestinal protein synthesis in healthy individuals but does so in conditions characterized by an altered somatotropic axis such as diabetes. Only in a state of growth hormone resistance (high growth hormone but low insulin like growth factor [IGF‐1] concentrations), extra insulin may acutely reverse the impaired, growth‐hormone‐induced IGF‐1 release, thereby exerting anabolic actions at the intestinal tract. Growth hormone resistance can be also found in patients after surgical stress. Therefore, we wanted to test the hypothesis whether hyperglycemic hyperinsulinemia would stimulate ileal protein synthesis in the latter condition. Mass spectrometry techniques (capillary gas chromatography/combustion isotope ratio mass spectrometry) were used to directly determine the incorporation rate of 1‐[13C]‐leucine into ileal mucosal protein. All subjects had an ileostomy, which allowed easy access to the ileal mucosa, and consecutive sampling from the same tissue was performed during continuous isotope infusion (0.16 μmol/kg min). Isotopic enrichments and fractional protein synthesis were determined at baseline (period I) and after a 4‐hour glucose infusion (170 mg/kg/h) or after infusion of saline (control group) (period II). In controls, ileal protein synthesis declined significantly during prolonged isotope infusion (period I: 1.11± 0.14%/h, period II: 0.39 ± 0.13%/h, p < .01). In contrast, ileal protein synthesis remained constant during glucose infusion (period I: 1.32 ± 0.35%/h, period II: 1.33 ± 0.21%/h, n.s. vs period I, but p < .005 vs the corresponding value at the end of period II in the control group). Using the continuous tracer infusion technique, ileal protein synthesis seemingly declines over a short time in control subjects. We found evidence that this artificial decline was due to mass effects of a rapidly turning over mucosa protein pool in which an isotopic plateau was reached during the experiment and of which the size amounted to approximately 4% of the total mixed protein pool. Maintenance of ileal protein synthesis during glucose infusion therefore indicates a rise of ileal protein synthesis in a slowly turning over protein pool. This effect in postsurgical patients would be compatible with the concept of intestinal insulin action to depend on the specific clinical state (eg, growth hormone resistance).

Influence of leucine on protein metabolism, phosphokinase expression, and cell proliferation in human duodenum

“…Insulin may be responsible for the effect of maltodextrins, because insulinemia was similarly increased in both arms in the current study. However, previous studies reported that insulin did not influence the intestinal protein synthesis rate in healthy conditions (25,36), in contrast with observations made in surgical patients (37).…”

Metabolic cross talk between the colon and the periphery: implications for insulin sensitivity

“…In addition to effects on motility, elevated glucose-dependent insulinotropic polypeptide secretion could stimulate pancreatic insulin secretion. Hyperinsulinaemia can have anabolic actions on the intestinal tract, with a demonstrated stimulation of ileal protein synthesis following ileostomy (Rittler et al 2006) and specific reduction of urinary Na + excretion (Quinones-Galvan & Ferrannini, 1997), so addressing the underlying issue of Na + depletion. Thus, although the exact 'trigger' for intestinal adaptation remains to be determined, adaptation does indeed take place, enabling the remaining absorptive surface of the GI tract and transit time to increase, both of which enhance the process of absorption and Na-water balance.…”