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DETECTION OF AUTONOMIC NERVOUS SYSTEM CHANGES DURING DUODENAL GLUCOSE INFUSION IN HUMANS: A PILOT STUDY
Florina Corpodean
*, Michael Kachmar, Adam Lowe, Vance L. Albaugh
Louisiana State University Pennington Biomedical Research Center, Baton Rouge, LA
Introduction: Classical physiologic teaching demonstrates that intestinal nutrient delivery stimulates the parasympathetic nervous system (PNS), which dominates during the "rest-and-digest" phase of feeding. Notably, the most effective anti-obesity treatments, GLP-1 agonists and bariatric surgery, either directly or indirectly mimic rapid nutrient delivery, suggesting that autonomic nervous system (ANS) balance may be involved in the underlying mechanisms of these treatments. The aim of this pilot study was to explore the feasibility of monitoring ANS flow during variable rate glucose infusions, using heart rate variability (HRV) as a surrogate marker for PNS and sympathetic nervous system (SNS) activity.
Methods: Ten healthy, non-diabetic participants underwent 2, 125kcal bolus infusions (33kcal/min FAST vs. 10kcal/min SLOW) into the proximal duodenum (D1/D2) in a crossover fashion on separate study days separated by a minimum of 1 week. HRV was collected continuously during the study. PNS activity was assessed using multiple HRV indices: high-frequency (HF) power, HF log, HF ms2, and the root mean square of successive differences (RMSSD). Additionally, the standard deviation of normal-to-normal intervals (SDNN) provided an overall measure of ANS activity. Paired t-tests compared HRV changes across the three phases, while a standard regression model was used to assess changes in ANS activity.
Results: PNS activity decreased following duodenal glucose infusion, though this change was not statistically significant. Notably, a greater reduction in PNS activity was observed during the slower infusion rate. The normalized percent change (NPC) in HRV was more pronounced during the slow infusion, with significant reductions in SDNN, RMSSD, HF log, and HF ms2 respectively. Specifically, the slow infusion resulted in a larger decrease in HF log (p=0.006) and HF ms2 (p=0.05) compared to the fast infusion rate.
Conclusion: This pilot study demonstrates that monitoring of ANS activity is feasible during nutrient infusion and suggests that duodenal glucose may be associated with transiently decreased PNS activity. While these changes appear paradoxical with classical teaching, they nonetheless provide valuable insights into the relationship between nutrient delivery rate and ANS modulation that warrants further study.
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