Age-related changes in amylin secretion

Amylin (islet amyloid polypeptide) is a recently identified pancreatic peptide. It has been shown to affect glucose metabolism both in vitro and in vivo. A cross sectional analysis of the effects of age on amylin secretion following a 75 g glucose tolerance test in a young (20-40 years), middle aged (41-60 years) and older (61-90 years) group was performed. Thirty lean (BMI less than 25) non-diabetic individuals were studied. Amylin secretion exhibited a U-shaped curve with greater secretion in young and old subjects than in middle aged persons. Baseline levels were 7.2 +/- 1, 4.7 +/- 1, and 5.3 +/- 0.75 pM respectively, at 60 min 9.5 +/- 0.9 (y), 5.5 +/- 1 (m), 8.6 +/- 1 (o) pM; and at 120 min 10.3 +/- 2 (y), 4.4 +/- 0.5 (m), 10.9 +/- 1.5 (o) pM. Amylin production (area under the curve) was 1102 +/- 131, 619.5 +/- 79 and 1043 +/- 120 pM per min respectively (P < 0.05). Amylin secretion was similar in both sexes. Variability in the insulin to amylin ratio for each of the age groups at different time points following a glucose load was found, suggesting that insulin and amylin are not co-secreted in a fixed ratio. A significant association was found between both maximum amylin and rise in amylin (delta) and a glucose greater than 120 mg/dl at 2 h. (P < 0.001, P < 0.001). This correlation of glucose and amylin may be interpreted as suggestive of a counterregulatory role for amylin. However, aging is also associated with changes in glucose metabolism and amylin may merely be acting as a marker of impaired glucose metabolism.