Euglycemic hyperinsulinemic clamp to assess posthepatic glucose appearanceafter carbohydrate loading. 1. Validation in pigs

Background: Precise knowledge of the rate of glucose absorption after meal feeding requires invasive methods in humans. Objective: This study aimed to validate in an animal model a technique combining the euglycemic hyperinsu linemic clamp and oral carbohydrate loading (OC-Clamp) as a noninvasive pro cedure to quantify the posthepatic appearance of glucose after oral carbohy drate loading. Design: Twenty-one pigs were fitted with arterial, jugular, portal, and duo denal catheters and a portal blood flow probe. At glucose clamp steady stat e, duodenal glucose (0.9 g/kg; DG-Clamp) and oral carbohydrate (140 g corn or mung bean starch as part of a mixed meal; OC-Clamp) were administered wh ile the glucose infusion was progressively reduced to compensate for the in cremental posthepatic appearance of glucose. [3-H-3]glucose was used to ass ess the glucose turnover rate. Results: Hepatic glucose production was totally suppressed by insulin infus ion, and the whole-body glucose turnover rate remained stable during glucos e absorption. The incremental portal appearance of glucose after the DG loa d was not altered by hyperinsulinemia, and the cumulative posthepatic appea rance of glucose was 63 +/- 3% ((x) over bar + SEM) of the DG load. The net hepatic portal appearance of glucose remained constant during absorption ( 34 +/- 3% of the load). After the OC load, the respective portal appearance rates of glucose were significantly different between carbohydrate sources ; however, the rates paralleled those of the posthepatic appearance of gluc ose. Again, net hepatic glucose uptake expressed as portal appearance was s imilar for both carbohydrates. Conclusions: The results validate the OC-Clamp method to monitor the posthe patic appearance of glucose after carbohydrate ingestion and to discriminat e between different carbohydrate sources. The results suggest that the tech nique be used in humans.