Search

The fact that hyperinsulinemia occurs in simple obesity and mild glucose intolerance has been well established. Altered hepatic insulin extraction may influence the levels of circulating hormone. The simultaneous measurement of insulin and C-peptide concentrations in peripheral blood enables an in vivo estimation of hepatic insulin removal. To evaluate hepatic insulin extraction, insulin and C-peptide responses to oral glucose were studied in 176 obese and nonobese subjects with normal, impaired, or diabetic glucose tolerance. Insulin levels as well as insulin incremental areas in glucose intolerant subjects were significantly higher than in weight-matched controls. The levels of C-peptide as well as C-peptide incremental areas were only slightly enhanced in subjects with impaired glucose tolerance, whereas they were reduced in subjects with diabetic tolerance. The molar ratios of C-peptide to insulin, both in the fasting state and after ingestion of glucose, as well as the relationship between the incremental areas of the two peptides were used as measures of hepatic insulin extraction. They were significantly reduced in glucose intolerant subjects and, to a lesser extent, in nondiabetic obese subjects. These results indicate that peripheral hyperinsulinemia in subjects with simple obesity or impaired glucose tolerance is a result of both pancreatic hypersecretion and diminished hepatic insulin extraction. In subjects with a more severe degree of glucose intolerance, decreased hepatic insulin removal is the primary cause of hyperinsulinemia.

In the present study insulin and C-peptide responses to oral glucose as well as C-peptide to insulin ratios and relations were evaluated in 10 nondiabetic obese female subjects with reactive hypoglycemia and in 10 age- and weight-matched controls. Insulin levels and incremental areas did not differ significantly in the two groups, whereas C-peptide concentrations and incremental areas were significantly higher in the obese group with reactive hypoglycemia. C-peptide to insulin molar ratio increments after glucose load as well as relations between incremental areas of the two peptides were significantly higher in obese subjects with reactive hypoglycemia than in controls. Our results suggest that B-cell response to oral glucose as well as insulin uptake by the liver in obese subjects with reactive hypoglycemia are greater than in controls.

The aim of the present study was to investigate the secretion and the hepatic removal of insulin in a group of 14 unaffected offspring of 14 type 2 (noninsulin-dependent) diabetic couples compared to 14 healthy subjects without family history of diabetes mellitus. The two groups, each consisting of 5 obese and 9 nonobese subjects, were carefully matched for sex, age, and body weight. We examined glucose, insulin, and C-peptide levels, as well as C-peptide to insulin ratios and relations during the oral glucose tolerance test. Glucose concentrations and incremental areas were similar in the two groups, as well as insulin and C-peptide levels and areas. C-peptide to insulin molar ratios, both in fasting state and after glucose load, as well as relations between C-peptide and insulin incremental areas were not different. Our results suggest that the healthy offspring of type 2 diabetic couples have a normal response of beta-cell to oral glucose as well as a normal removal of insulin by the liver.

The aim of the present study was to investigate the secretion and hepatic removal of insulin in the healthy offspring of type 2 (non-insulin-dependent) diabetic subjects. For this purpose, we examined the insulin and C-peptide responses to a 75 g oral glucose tolerance test in a group of 55 healthy subjects each having one parent with type 2 diabetes mellitus, and in a group of 55 individuals without a family history of diabetes. All the 110 subjects in the study were ambulatory volunteers, in good general health, and with normal glucose tolerance. The two groups were carefully matched for sex, age, and body weight. Glucose and insulin concentrations as well as incremental areas were similar in the two groups. C-peptide levels and incremental areas were almost identical. C-peptide to insulin molar ratios both in fasting state and after glucose load, as well as relations between C-peptide and insulin incremental areas did not differ in the two groups. In conclusion, the healthy offspring of only one non-insulin-dependent diabetic parent show a normal beta-cell response to glucose, and normal removal of insulin by the liver.

The present study was designed to compare insulin extraction by the liver following oral glucose administrations of different size, in order to evaluate insulin removal by the liver in relation to the insulin exposure, and to the amount of ingested glucose. Insulin secretion by the pancreas was estimated by the measurement of peripheral C-peptide levels, and insulin extraction by the liver by the analysis of peripheral C-peptide to insulin ratios and relations. Ten healthy subjects (5 males and 5 females), aged 16 to 66 yr, with normal bw, and without family history of diabetes mellitus were investigated by means of the administration, on alternate days, of 50 and 150 g oral glucose loads. After the 150 g oral glucose load plasma glucose levels were significantly higher than after the 50 g oral glucose administration: glucose incremental areas of 1.45 +/- 0.12 vs. 0.55 +/- 0.04 mmol/l X min, respectively (p less than 0.001). Similarly, insulin concentrations were significantly higher following 150 g than after 50 g glucose ingestion: insulin incremental areas of 0.52 +/- 0.09 vs. 0.20 +/- 0.04 nmol/l X min (p less than 0.001). Also C-peptide levels were higher after 150 vs. 50 g oral glucose load: C-peptide incremental areas of 1.85 +/- 0.41 vs. 0.64 +/- 0.13 nmol/l X min (p less than 0.01). C-peptide to insulin molar ratios were similar during the two glucose challenge, and averaged 5.25 +/- 0.42 vs. 5.08 +/- 0.50 after 50 and 150 g oral glucose loads, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)