Increased disorderliness of basal insulin release, attenuated insulin secretory burst mass, and reduced ultradian rhythmicity of insulin secretion in older individuals.
Insulin is secreted in a pulsatile fashion. Rapid pulses are considered to be important for inhibiting hepatic glucose output, and ultradian pulses for stimulating peripheral glucose disposal. Aging is characterized by a progressive impairment in carbohydrate tolerance. We undertook the current studies to determine whether alterations in pulsatile insulin release accompany the age-related changes in carbohydrate metabolism. Healthy young (n = 8; body mass index, 21 +/- 1 kg/m2; age, 24 +/- 1 yr) and old (n = 9; body mass index, 24 +/- 1 kg/m2; age, 77 +/- 2 yr) volunteers underwent two studies. In the first study, insulin was sampled every 1 min for 150 min, and pulse analysis was conducted using a recently validated multiparameter deconvolution technique. In the second study, insulin was sampled every 10 min for 600 min, and insulin release was evaluated by Cluster analysis. In the 150-min studies, insulin secretory burst mass (P < 0.05) and amplitude (P < 0.01) were reduced in the elderly. In addition, approximate entropy, a measure of irregularity or disorderliness of insulin release, was increased in the aged (P < 0.01). In the 600-min studies, interpulse interval was greater in the aged (P < 0.05), and burst number was less (P < 0.05). We conclude that normal aging is characterized by more disorderly insulin release, a reduction in the amplitude and mass of rapid insulin pulses, and a decreased frequency of ultradian pulses. Whether these alterations in insulin pulsatility contribute directly to the age-related changes in carbohydrate metabolism will require further study.
Meneilly
G S
GS
Department of Medicine, University of British Columbia, Vancouver, Canada.
Ryan
A S
AS
Veldhuis
J D
JD
Elahi
D
D
D000204:Activity Cycles / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D001824:Body Constitution; D016000:Cluster Analysis; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D009994:Osmolar Concentration
D001786:Blood Glucose; D007328:Insulin