8 Macrovascular disease and hyperinsulinaemia

Abstract

The evidence that hyperinsulinaemia represents an independent risk factor for cardiovascular disease is tantalizing but the hypothesis cannot be said to be proven. The inconsistencies arising from the major prospective studies require that further work be done. Hyperinsulinaemia may not carry the same implications in all subjects and its interactions with other risk factors and with blood glucose are not well described. Possible further research has been discussed and outlined at a recent meeting (Colwell, 1985). The suggestions include delineating the action of growth factors and insulin in defined serum-free tissue culture, and the use of more sophisticated culture models, such as smooth muscle covered by vascular endothelium. The choice of human or primate tissue is desirable because of the species specificity of the atherosclerotic lesions. Prospective trials of modifying peripheral insulin levels in treated diabetic patients are probably still impracticable. The case for attempting to achieve normoglycaemia in diabetes to avoid microvascular complications is strong, and current insulin treatment regimens accept peripheral hyperinsulinaemia as a consequence of achieving portal insulin concentrations sufficient to suppress hepatic glucose output. It is hard to envisage a trial to examine reduced peripheral insulin concentrations which would not give unacceptably poor blood glucose control. Current studies of different methods and degrees of control of blood glucose might be used to provide some indication of whether such a trial could ever be justified. The Diabetes Control and Complication Trial (DCCT) is a prospective multicentre study of intensive versus conventional insulin treatment in insulin-dependent diabetic patients in the USA, and the UK Prospective Study of therapies of maturity onset diabetes (UKPS) is following patients not satisfactorily controlled on diet, randomized to different treatment modalities. These may produce some evidence within the next few years, on insulin concentrations and complications (Tattersall and Scott, 1987). Should any of this change current management of non-insulin-dependent diabetes? Despite claims of enthusiasts, special treatment regimens with intensive exercise, a particular oral agent or the addition of sulphonylureas to insulin therapy are either not generally applicable or have little theoretical basis (Martin, 1986). Current 'good practice' in Europe as put forth in a consensus document (Alberti and Gries, 1988), recognizes the need to address risk factors other than diabetes in the management of the non-insulin-dependent diabetic patient.(ABSTRACT TRUNCATED AT 400 WORDS)