Insulin responses to glucose and isoproterenol decrease with age

Area of Science:

• Endocrinology
• Gerontology
• Physiology

Background:

• Older trauma patients exhibit impaired glucose tolerance, partly due to diminished insulin response.
• This study investigated if reduced pancreatic sensitivity to beta-adrenergic stimulation underlies these diminished insulin responses in older individuals.

Purpose of the Study:

• To compare the effects of beta-adrenergic stimulation and glucose loading on insulin response in young versus older healthy adults.
• To determine if diminished beta-adrenergic sensitivity contributes to age-related glucose intolerance.

Main Methods:

• Prospective study involving healthy young and older adults undergoing isoproterenol infusion.
• Paired studies included isoproterenol infusion alone and with a hyperglycemic glucose clamp.
• Measurements included heart rate, serum insulin, and hemodynamic and physiological variables.

Main Results:

• Older adults had a less pronounced heart rate increase in response to isoproterenol (p < 0.01).
• Serum insulin levels during combined infusion and clamp were lower in older adults (467 pmol/L) than in young adults (755 pmol/L) (p < 0.05).
• Whole-body glucose disposal was significantly lower in older adults (5.8 mg/kg/min) compared to younger adults (9.6 mg/kg/min) (p < 0.05).

Conclusions:

• Healthy older adults exhibit lower heart rate and serum insulin responses to combined isoproterenol and glucose loading compared to younger individuals.
• Diminished tissue sensitivity to beta-adrenergic signals may explain the impaired insulin response and glucose intolerance seen in older individuals post-injury or illness.