Hyperlipoproteinemia, diabetes, and oxygen affinity of hemoglobin

Oxyhemoglobin dissociation curves (ODC) were performed on blood from diabetic and nondiabetic subjects with and without hypertriglyceridemia. P50 at in vivo pH was slightly lower than normal in normolipemic diabetics (25.7 versus 26.6 mmHg, p less than 0.05), in spite of increased red cell 2,3-diphosphoglycerate concentration (15.4 versus 14.4 mumole/g Hg, p less than 0.025). P50 at in vivo pH in diabetics with moderately elevated very low density lipoproteins (VLDL)--Type IV hyperlipoproteinemia (HLP)--was likewise found to be slightly lower than normal (25.5 versus 26.6 mmHg, p less than 0.05). In contrast, diabetics with pronounced hyperlipemia due to accumulation of chylomicrons (type I HLP) or due to accumulation of chylomicrons (type I HLP) or due to accumulation of chylomicrons as well as VLDL (type V HLP) showed markedly increased hemoglobin--oxygen affinity (P50:21.1 versus 26.6 mmHg, p less than 0.001). The change in the ODC of normolipemic diabetics is considered to be an expresssion of the presence of an increased proportion of a hemoglobin fraction (Hb Alc) with increased oxygen affinity. The additional change in the ODC of the hyperlipemic patients is thought to be secondary to accumulation of triglyceride-rich particles for the following reasons: (1) a similar increase in oxygen affinity of hemoglobin was demonstrated in familial type I HLP of nondiabetic subjects; (2) normal red cells increased their oxygen affinity when incubated in lactescent plasma; (3) in both acquired types I and V HLP the disappearance of HLP was followed by a normalization of the ODC.