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Orally administered tryptophan and experimental type 2 diabetes
M A Tormo1, A Romero de Tejada, I Morales
1Departamento Fisiología, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain. matormo@unex.es
Molecular and Cellular Biochemistry
|September 15, 2004
Summary
Oral L-tryptophan supplementation did not alter blood sugar or insulin in diabetic rats. However, it increased melatonin at 2 AM in diabetic rats and affected antioxidant enzyme activity, impacting oxidative stress markers.
Area of Science:
- Biochemistry
- Endocrinology
- Nutritional Science
Background:
- Diabetes mellitus is characterized by hyperglycemia, leading to increased oxidative stress and altered antioxidant defenses.
- L-tryptophan (TRP), a precursor to melatonin, is an endogenous antioxidant with potential modulatory effects on metabolic and oxidative processes.
- Understanding the interplay between TRP, melatonin, and oxidative stress in diabetes is crucial for developing novel therapeutic strategies.
Purpose of the Study:
- To investigate the effects of oral L-tryptophan (TRP) administration on glycemic control, insulin, melatonin levels, and antioxidant enzyme activity (catalase and superoxide dismutase).
- To evaluate these effects in both non-diabetic (ND) and type 2 diabetic (n5-STZ) male Wistar rats.
- To assess TRP's impact on food and water intake as indicators of metabolic changes.
Main Methods:
- Rats received daily oral administration of L-tryptophan (125 mg/kg body weight) for 15 days.
- Glycemia was measured every two days, while food and water intake were recorded daily.
- Plasma insulin and melatonin levels were measured at specific time points, alongside erythrocyte catalase and superoxide dismutase (SOD) activities.
Main Results:
- Diabetic rats exhibited higher glycemia and lower insulin levels compared to non-diabetic rats; TRP did not alter these parameters.
- TRP administration increased melatonin levels at 02:00 in diabetic rats but did not affect non-diabetic rats.
- Catalase activity decreased in non-diabetic rats and increased in diabetic rats following TRP treatment; SOD activity remained unchanged. Food intake increased in treated diabetic rats.
Conclusions:
- Oral L-tryptophan supplementation does not influence glycemic or insulin levels in type 2 diabetic rats.
- TRP administration enhances melatonin production at 02:00 in diabetic rats and modulates catalase activity differently between diabetic and non-diabetic states.
- The observed increase in food intake in diabetic rats suggests potential metabolic effects of TRP beyond direct glycemic control.