Role of decreased plasma tryptophan in memory deficits observed in type-I diabetes

To investigate the relationship between plasma tryptophan and the occurrence of memory dysfunctions in male and female type 1 diabetics.

The case-control study was conducted at two urban healthcare facilities in Karachi from January to June 2009, and comprised 100 diabetic subjects of among whom were 50 men and 50 women. The controls were also similar in number and gender. A questionnaire was used to evaluate the memory impairment in the subjects. Plasma tryptophan was determined by high performance liquid chromatography with ultra-violet method. Students' t test was used to analyse tryptophan data.

There was considerable memory impairment in the cases (n = 40) compared to the controls (n = 5). Results also showed a significant (p < 0.01) decrease in plasma tryptophan levels in both male and female diabetic patients.

Diabetic subjects exhibited occurrence of memory impairment with concomitant decline in plasma tryptophan levels. The findings indicate that decreased brain uptake of tryptophan and lowered brain 5-hydroxytryptamine levels may be responsible for the memory deficits seen in diabetics.