Patterns of Decrease of Free Fatty Acids During Glucose Tolerance Tests

In normal subjects the decrease of serum FFA levels after an oral glucose load was prompt and persistent with a drop to below 200 μEq./L. at one hour. Among patients with mild diabetes about 40 per cent showed FFA response similar to normal despite abnormal GT. Another 40 per cent diabetic patients had a delayed FFA decrease with a drop to minimum levels only after two hours and about 15 per cent of the patients had a deficient response with only a small decrease in FFA after glucose ingestion. In the two latter groups the slopes of FFA decrease (—log FFA/t) were less steep, indicating that the failure to reach the minimum level of normal subjects was not related to the higher initial serum FFA concentration. The occurrence of normal pattern of FFA decrease among a large proportion of diabetics was taken as an indication of normal function of adipose tissue. The tissue remained sensitive to ILA even when available in diminished amounts as assessed by comparisons of rises in the glucose uptake of rat diaphragm. A delayed FFA decrease appeared associated with late appearance of ILA, whereas the inability of adipose tissue to arrest the outflow of FFA was consistent with scarcity of ILA. The differential effectiveness of insulin as a result of selective antagonism toward its action on tissues is discussed.