Insulin patterns prior to and after onset of diabetes

The genetic basis of type 2 diabetes mellitus: impaired insulin secretion versus impaired insulin sensitivity

Despite the fact that it is the prevalent view that insulin resistance is the main genetic factor predisposing to development of type 2 diabetes, review of several lines of evidence in the literature indicates a lack of overwhelming support for this concept. In fact, the literature better supports the case of impaired insulin secretion being the initial and main genetic factor predisposing to type 2 diabetes, especially 1) the studies in people at high risk to subsequently develop type 2 diabetes (discordant monozygotic twins and women with previous gestational diabetes), 2) the studies demonstrating compete alleviation of insulin resistance with weight loss, and 3) the studies finding that people with type 2 diabetes or IGT can have impaired insulin secretion and no insulin resistance compared with well matched NGT subjects. The fact that insulin resistance may be largely an acquired problem in no way lessens its importance in the pathogenesis of type 2 diabetes. Life style changes (exercise, weight reduction) and pharmacological agents (e.g., biguanides and thiazolidendiones) that reduce insulin resistance or increase insulin sensitivity clearly have major beneficial effects (122, 144-146, 153-155).

Diabetes, blood lipids, lipoproteins, and change of environment: restudy of the "new immigrant Yemenites" in Israel

Restudy of 306 "new immigrant Yemenite" Jews, an ethnic group in which, upon their arrival in Israel, no diabetes was detected, revealed, 25 yr after their immigration, an increased incidence of diabetes and higher plasma and lipoprotein-lipid levels. The prevalence of diabetes (defined as "glucose intolerance") rose to 11.8% (13.2% males and 9.7% females). Obesity in females resulted in increased prevalence of diabetes in all age groups, while in males it affected the older age group only. The male/female diabetic ratio was affected by weight status--in the underweight, diabetes was more prevalent in males, in the overweight, the rate of diabetes in females equaled that of males. In nondiabetics (those with normal glucose tolerance), neither the glucose tolerance nor the insulin response deteriorated with aging. Most diabetics had a delayed insulin response. However, about 50% of nondiabetics and diabetics had insulin response peak at 60 min and similar insulin levels. It appears that in newly discovered adult-onset diabetics in this population there is no shortage of insulin, but rather shortage of insulin action. In nondiabetics, the levels of plasma cholesterol and triglycerides (TG) were higher than levels upon their arrival. In diabetics, the plasma TG, cholesterol, and LDL-cholesterol levels were higher when compared to those of nondiabetics, especially in the group of overweight males. Hyperlipoproteinemia was diagnosed in 27.7% of diabetics and 11.0% of nondiabetics. In diabetics, the HDL/LDL cholesterol ratio was found to be reduced, significantly so in overweight diabetics.

Insulin and proinsulin in normal and chemical diabetic children

Plasma levels of total immunoreactive insulin and immunoreactive proinsulin were studied in 10 normal children and 15 children with chemical diabetes ranging in age from 5 to 13 years. Eleven of the children with chemical diabetes demonstrated significantly elevated TIRI during fasting and following glucose administration. There was a delay in the increment of plasma TIRI in four children with chemical diabetes, but otherwise their TIRI levels were normal. In these four children IRP was not significantly different from normal; however, in the remaining children with chemical diabetes, those with elevated TIRI, the IRP was elevated following glucose administration. Although the IRP was significantly elevated in the hyperinsulinemic group, the TIRI was also increased to such an extent that the glucose intolerance demonstrated in these patients could not be attributed to the elevated IRP.

The evolution of diabetes from prediabetes

Temporary stress-induced undue hyperglycaemia following an oral carbohydrate load taken during hospitalization is being tested as a possible indicator of prediabetes.

Observations in patients 15 months after hospitalization have permitted us to compare the blood sugar, insulin and growth hormone patterns evoked by an oral glucose load before and after glucose intolerance has appeared, viz. to speculate upon the evolution of diabetes from prediabetes. Though the numbers of such instances are as yet limited, they already suggest several possible sequences. Thus, our data support the concept that glucose intolerance, in addition to stemming from a decrease in insulin levels, can develop with true increases or with no evident decrease in the insulin responses to oral glucose.

The simplified in-hospital carbohydrate tolerance test employed in assembling groups of possibly prediabetic individuals is also an efficient means of detecting permanent glucose intolerance of the diabetes mellitus type.