Key Points
- To determine the true frequency and amplitude of pulsatile insulin release in humans by sampling directly from the portal vein during fasting and hyperglycemic conditions.
- Assessed human subjects with indwelling transjugular intrahepatic portasystemic stent shunts (TIPSS) placed to decompress portal hypertension.
- Quantitated insulin secretion kinetics in the overnight fasted state and during an 8 mmol/L hyperglycemic clamp using high-frequency blood sampling.
- Direct portal vein sampling demonstrated a distinct insulin secretion periodicity with an interpulse interval of approximately 5 minutes.
- Oscillation amplitude and mass of insulin pulses in the portal vein were approximately 5-fold greater than those detected in the arterialized systemic circulation.
- Elevated insulin output during hyperglycemia was driven primarily by the amplification of individual pulse mass rather than changes in pulse frequency.
Structured PICO
PPopulationHuman subjects who had indwelling transjugular intrahepatic portasystemic stent shunts (TIPSS) to decompress portal hypertension
IInterventionDirect portal vein sampling of pulsatile insulin release in both the overnight fasted state and during a hyperglycemic clamp (8 mmol/L)
CComparatorSampling from the systemic circulation (arterialized vein)
OOutcomeFrequency (interpulse interval) and amplitude of pulsatile insulin secretionsurrogate
Direct measurement in the portal vein confirms that human insulin secretion occurs in high-frequency pulses every 5 minutes, and hyperglycemia increases insulin release by amplifying pulse mass rather than frequency.