Insulin stimulation of adipose tissue lipoprotein lipase. Use of the euglycemic clamp technique.
Key result
Insulin infusion significantly stimulated adipose tissue lipoprotein lipase activity by 6 hours compared to saline control (P < 0.01), with the increase inversely related to basal enzyme activity.
Why the study?
Does insulin infusion stimulate adipose tissue lipoprotein lipase activity in normal human subjects?
Population
16 normal human subjects (11 in the insulin group, 5 in the control group)
Comparison
Insulin infusion to achieve and maintain serum… vs 0.9% saline infusion
Design
Other
Follow-up
6 hours
Authors
Discussion
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Implication
May affect postprandial lipid handling differently from antilipolysis; leaves open clinical relevance in metabolic disease pending confirmation.
Key Points
- To evaluate the role and time course of insulin in regulating human adipose tissue lipoprotein lipase activity under euglycemic conditions.
- Infused insulin to maintain serum levels of ~70 µU/ml while maintaining basal plasma glucose in 11 normal subjects, comparing them to 5 control subjects receiving 0.9% saline.
- Obtained baseline and serial adipose tissue biopsies to measure lipoprotein lipase activity over a 6-hour period alongside serum free fatty acids and triglycerides.
- Serum free fatty acids decreased to 27 ± 3% of basal levels by 20 min (t = 5.19, P < 0.001) and serum triglycerides fell to 77 ± 3% by 80 min (t = 3.76, P < 0.01).
- Adipose tissue lipoprotein lipase activity did not increase significantly above control levels in the first 3 hours, but showed significant stimulation by 6 hours of insulin infusion (t = 3.94, P < 0.01).
- The 6-hour increase in lipoprotein lipase activity was inversely correlated with basal enzyme activity (r = -0.690, P < 0.02) and was unrelated to the amount of glucose infused.
Structured PICO
Does insulin infusion stimulate adipose tissue lipoprotein lipase activity in normal human subjects?
P
Population
16 normal human subjects (11 in the insulin group, 5 in the control group)
I
Intervention
Insulin infusion to achieve and maintain serum levels of approximately 70 microunits/ml while plasma glucose was kept at basal concentrations (euglycemic clamp) for 6 hours
C
Comparator
0.9% saline infusion
O
Outcome
Adipose tissue lipoprotein lipase activitysurrogate
Main Result
p-value: p=<0.01
Insulin stimulates adipose tissue lipoprotein lipase activity in humans, though this effect is delayed compared to its antilipolytic effects.
Limitations
- Feeding was not part of the protocol, limiting conclusions about the role of insulin-stimulated ATLPL in chylomicron removal.
- Hepatic glucose output was not measured, so glucose utilization could only be approximated by the amount of glucose infused.
Cite This Study
Sadur et al. (1982) studied Healthy volunteers (n=16). Insulin vs. 0.9% saline was evaluated on Adipose tissue lipoprotein lipase (ATLPL) activity at 6 hours (p=<0.01). Insulin infusion significantly stimulated adipose tissue lipoprotein lipase activity by 6 hours compared to saline control (P < 0.01), with the increase inversely related to basal enzyme activity.