Insulin production rate following glucose ingestion estimated by splanchnic C-peptide output in normal man

Abstract

Insulin production rate has been estimated in healthy male volunteers (n = 16), and evaluated with respect to splanchnic glucose exchange. Insulin production rate was calculated from splanchnic immunoreactive C-peptide output. C-peptide secretion was estimated by the hepatic venous catheter technique both in the basal state and for 2 h following ingestion of various glucose loads (0, 12.5, 25, 50, 75, and 100 g). The results demonstrate a basal insulin production rate of 0.017 +/- 0.002 U/min (mean +/- SEM) or 2.04 U/2 h. Values rose in a dose dependent manner from 2.6 +/- 1.1 U/2 h after ingestion of 12.5 g of glucose to 10.8 +/- 1.1 U/2 h following a glucose load of 100 g. Insulin retention by the liver was estimated at 0.012 +/- 0.001 U/min in the basal state, and ranged from 47-85% (70 +/- 2%) of production following an oral glucose load. It was also demonstrated 1) that the relative splanchnic glucose output was inversely related to the amount of ingested glucose, and reached a minimum when glucose in excess of 50 g was ingested; and 2) that hepatic glucose retention was directly proportional to insulin production rate (r = 0.83; p less than 0.001; n = 15). It is suggested that the adaptive capacity of the splanchnic bed to retain glucose depending on the amount of ingested glucose guarantees that splanchnic glucose output fluctuates in healthy man only within a narrow range.

Pulsatile Insulin Secretion Dictates Systemic Insulin Delivery by Regulating Hepatic Insulin Extraction In Humans

“…The calculated fractional hepatic insulin extraction reported in the present study is higher than the estimated ϳ50% in the dog (2,4) but consistent with values reported in most human studies (5)(6)(7)44). In particular, based on a similar hepatic-vein sampling technique, hepatic first-pass extraction of insulin has been estimated as 70 -85% by different groups (7,45,46).…”

“…Five nondiabetic subjects (two men and three women, mean age 32 years [range 25 F ollowing insulin secretion, the first organ of impact is the liver, where a proportion of secreted insulin is cleared through a receptormediated process (1)(2)(3). The proportion of insulin cleared has been estimated as ϳ50% in dogs (2,4) and ϳ40 -80% in humans (5)(6)(7)(8). Insulin is secreted in discrete secretory bursts occurring approximately every 4 min (9,10).…”

High Plasma Free Fatty Acids Decrease Splanchnic Glucose Uptake in Patients with Non-Insulin-Dependent Diabetes Mellitus.

“…Although it was possible that a small oral glucose load caused a bigger error than a larger one, 0.2 g/kg glucose was administered orally to prevent a temporary increase in plasma glucose after oral glucose load. It has been reported that absorption of oral loading glucose (12.5 25 g), which is a similar amount to the glucose load in the present study, from the gut is completed within 2 h in healthy subjects [27] and dogs [28]. The rate of absorption of the oral glucose load in NIDDM subjects was shown to be comparable to that in normal subjects [29].…”

The role of ?diabetogenic? hormones on carbohydrate and lipid metabolism following oral glucose loading in insulin dependent diabetics: Effects of acute hormone administration

“…However, high serum concentrations of free insulin are to be anticipated as most diabetic subjects were receiving an insulin infusion of 100 mU/min, and some even of 200 mU/min. Thus the insulin dose administered by the glucose controlled insulin infusion system for assimilation of 50g of glucose was considerably greater than the 6.8_ 1.4 U (SEM) of insulin released by healthy man after ingestion of the same glucose load [37]. This implies that the induced over-insulinization of the diabetic patients might have reduced any expected effects of the weaker counter-regulatory hormones, glucagon and cortisol on glucose assimilation.…”