Impact of family history of diabetes on the assessment of beta-cell function.

Numerous factors impinge on beta-cell function, and include the genetic background and insulin sensitivity of the individual. The aim of the present study was to evaluate the impact of a family history of non-insulin-dependent diabetes mellitus (NIDDM) on beta-cell function and to determine whether the relationships between beta-cell function and insulin sensitivity and age are influenced by a family history of diabetes. Thirty-three healthy control subjects (CON), 20 normal glucose-tolerant first-degree relatives of known NIDDM patients (REL), and 12 nondiabetic identical twins with an identical twin with known NIDDM were studied. Insulin and C-peptide responses to an acute intravenous glucose (AIRg) and glucagon bolus (at euglycemia [AIR[G.GON]]) were measured, as well as each individual's insulin sensitivity. Fasting insulin and C-peptide levels were similar in all groups. AIRg was significantly reduced by 65% in the nondiabetic twins compared with the CON and REL groups, with the latter group being similar to CON, whereas for the AIR[G.GON], the insulin responses in the twin subjects were reduced only by 35% compared with CON. Following stepwise (default) multiple regression analysis, three independent variables (insulin sensitivity, 23%; family history of NIDDM, 20%; and fasting glucose, 7%) were identified, and these combined to fit a model for prediction of acute beta-cell responses to glucose that yielded an R2 (adjusted) value of 50%. Following analysis of covariance (ANCOVA), a positive family history of NIDDM and insulin sensitivity but not the age of the subject were confirmed as separate factors affecting AIRg. In conclusion, in subjects with normal or mild glucose intolerance, the individual's genetic background and insulin sensitivity are important determinants of insulin secretion.

Practical application of methods for in vivo assessment of insulin secretion and action.

In vivo measurement of insulin sensitivity can be made using the glucose clamp technique or the intravenous glucose tolerance test (IVGTT) with minimal model analysis. The glucose clamp provides a direct, readily understandable measure of insulin action but is more demanding for investigators and subjects. Assessment of insulin secretion must be made by a separate test. The IVGTT is easier to perform but the data are more difficult to analyse and the value for insulin sensitivity is a derived rather than direct measure. As well as insulin sensitivity, glucose mediated glucose disposal and insulin secretion are measured by the IVGTT. In fact the IVGTT technique relies on adequate endogenous insulin secretion whereas the glucose clamp does not. The choice between these two techniques depends on the study to be performed and the available laboratory facilities.

Assessment of milk transfer coefficients for use in prediction models of radioactivity transport.

The transfer coefficient (Fm) which is widely used to predict the fraction of ingested radionuclides found in milk is an important parameter for modelling. The accuracy of estimates can be improved by considering the following factors that influence the Fm; (1) the physical-chemical form of the radionuclide in the feed of cows, (2) the hay to concentrate ratio of cows diets and (3) correcting for a steady state situation for feed intake and milk concentrations. Factors such as stable element intake, soil intake, milk production rate, metabolic rate and inhalation do not appear to have significant effects upon the transfer coefficient.

Beef production options and requirements for fossil fuel.

A large percentage of the feed resources used in beef production cannot be used by man or most other animals. These noncompetitive feeds could be used in different ways to increase beef production, but fossil fuel consumption by the beef industry would not be greatly reduced.