Delta aminolevulinate dehydratase (ALA-D) activity in human and experimental diabetes mellitus

The haem pathway is impaired in porphyrias and a frequent coexistence of di abetes mellitus and porphyria disease has been reported. We have therefore decided to investigate delta-aminolevulinate dehydratase, one of the more sensitive enzymes in the haem pathway: in both human diabe tic patients and diabetic rats. We have studied 131 diabetes mellitus patie nts, 32 insulin dependent and 99 non-insulin dependent. The latter group wa s further subdivided according to treatment: diet alone (n = 24), diet plus oral hypoglycemic agents (n = 28) and diet plus insulin (n = 47). We have also performed similar studies in the rat model of diabetes mellitus, induc ed in 11 Wistar rats by streptozotocin. Control groups of both humans and a nimals were used. Erythrocytic aminolevulinate dehydratase activity was reduced in both insul in dependent and non-insulin dependent diabetic patients as compared to the ir controls (p < 0.001). This activity was only partially restored by addit ion of zinc and thiols to the incubation media. In insulin-dependent diabet es mellitus, reduction of enzyme activity was related to the glycosilated h emoglobin concentration (p < 0.05) and in non-insulin dependent diabetes me llitus to the glycemia (p < 0.01). In the diabetic rat, aminolevulinate deh ydratase activity was diminished on both erythrocytes (p < 0.01) and hepati c tissue (p < 0.01) when compared to the control group. The decrease in activity of erythrocyte aminolevulinate dehydratase observe d in diabetic patients, may represent an additional and useful parameter fo r the assessment of the severity of carbohydrate metabolism impairment. (C) 1999 Elsevier Science Ltd. All rights reserved.