The Significance of Basal Insulin Levels in the Evaluation of the Insulin Response to Glucose in Diabetic and Nondiabetic Subjects*

Abstract

Abstract. The level of insulin after an overnight fast (basal) in 37 obese and nonobese male subjects with normal and abnormal carbohydrate tolerance was directly related to the increase in insulin concentration during a 3 hr 100 g oral glucose tolerance test. Obesity, but not diabetes, was associated with an elevation of this basal insulin level. Thus obesity predicted with the magnitude of the insulin response to glucose ingestion. When the individual insulin values were expressed as per cent change from the basal level, this effect of obesity was excluded. The insulin levels of all subjects with normal carbohydrate tolerance promptly rose 5-7-fold, and reached peak values 1 hr after oral glucose. In contrast, the diabetic response (as per cent increase) was markedly reduced during the 1st hr, and maximal (but still subnormal) insulin levels were not attained until 2 hr. In all subjects the insulin response (quantitated by calculation of the area circumscribed by a plot of the per cent change in insulin with time) showed a significant inverse correlation with the glucose response. Thus increasing degrees of carbohydrate intolerance were associated with decreasing insulin responses. Elevated levels of insulin, in both the basal state and in response to glucose, were related to obesity.

Hyperinsulinaemia in obesity is not accompanied by an increase in serum proinsulin/insulin ratio in groups of human subjects with and without glucose intolerance

“…These results remind us of the study by Bagdade and Porte [9] on the effect of Type 2 diabetes and obesity on insulin-secretory response during OGTT. The basal insulin level increased in obese subjects whether or not they had diabetes.…”

“…Obesity is known to be associated with hyperinsulinaemia [9,10] and thought insulin secretion is to increase to compensate for insulin resistance in obesity. The Beta-cell mass is known to increase with obesity both in experimental animal models [19] and in man [20].…”

“…Diabetes, as described here is that defined by World Health Organisation (WHO) criteria [14], but the normal type was defined more strictly than the WHO recommendation. Therefore, the borderline type included not only impaired glucose tolerance by WHO standard, but also a selection of subjects who would have been regarded as 'norreal' by WHO criteria 9 Obesity was defined by the body mass index (weight/height 2 in kg/m z) exceeding 25.0.…”

“…Obesity is usually accompanied by hyperinsulinaemia both at fasting and after glucose challenge [9,10]. It is considered to result from increased insulin secretion produced as a compensatory response to the Beta cells.…”

Hyperglucagonemia of the isolated perfused pancreas of diabetic mice (db/db)

“…As shown in the present experiments, diabetic hyperinsulinemie mice appeared to have alpha cell function insensitive to hyperglycemia, while arginine induced an exaggerated rise in glueagon secretion. Simultaneously, there was an excessive and somewhat delayed hyperinsulinism, as previously described [3] and similar to the obese, maturity onset human diabetic (2,20).…”