Date of Graduation
Bachelor of Science
Impaired glucose tolerance is the key defining characteristic of diabetes, a condition which affects nearly 30% of Americans. Hydration status and the physiological effects of poor hydration have been linked to compromised glucose tolerance in animal models, but have not been thoroughly investigated in humans. PURPOSE: The purpose of this investigation was to observe the effect of altered hydration status on a healthy male adult’s response to an oral glucose tolerance test (OGTT). METHODS: Four healthy adult men (28.4±1 y, 23.6±1.2 kg/m2, HbA1C 5.6±0.2%, non-smoking, non-athletes) participated. Subjects took OGTT’s in both a hypohydrated and euhydrated state. The euhydrated state was achieved by infusing an isotonic solution of 0.9% NaCl at a rate of 0.1 mL/min/kg for 120 minutes via venous catheter, while the hypohydrated state was achieved by infusing a hypertonic solution of 3% NaCl at the same rate. Blood samples of 15 mL each were taken before infusion and every 30 minutes during infusion. The OGTT commenced after 120 minutes of infusion and blood samples were taken after 5, 30, 60, 90, and 120 minutes. RESULTS: Plasma osmolality increased during the hypertonic infusion (to maximum 300 mmol/kg) and remained normal during the isotonic infusion (284-288 mmol/kg). Plasma volume increased during infusion in both conditions, though more significantly in the hypertonic condition (maximum 16.5% increase from baseline) than in the isotonic condition (maximum 5.6% increase from baseline). Both insulin and glycemic responses to the OGTT showed a greater increase in the hypertonic condition (insulin peak 56.0 μU/mL; glucose peak 138 mg/dL) than in the isotonic condition (insulin peak 41.7 μU/mL; glucose peak 133 mg/dL). Three measures of insulin response–homeostatic model assessment for insulin resistance (HOMA IR), Matsuda index for insulin sensitivity, and quantitative insulin sensitivity check index (QUICKI)–indicated decreased insulin sensitivity and increased insulin resistance in the hypertonic condition (HOMA IR 0.93; Matsuda 12.4; QUICKI 0.8) compared to the isotonic condition (HOMA IR 0.85; Matsuda 12.67; QUICKI 0.9). However, none of the measured results reached the thresholds for diagnosis of diabetes. CONCLUSION: Infusion of hypertonic saline solution is a valid means of simulating hypohydration. Acute hypertonicity elicits an acute, negative effect on glucose tolerance and insulin sensitivity in healthy men. Though these results were only measured in an acute sense, there may be implications that chronic proper hydration could be an effective and inexpensive means of delaying or preventing the onset of type II diabetes in those with a high risk of developing the condition.
Schroeder, Alison L., "The Effect of Hypertonicity on Glucose Regulation in Healthy Adults" (2016). Biological Sciences Undergraduate Honors Theses. 16.