A novel index of whole body antilipolytic insulin action

Objective:

Assessment of antilipolytic insulin action is important in obesity research, but extensive isotopic tracer studies are not always feasible. We evaluated whether an index of antilipolytic insulin action could be derived from readily available insulin and glycerol concentrations obtained during clamps or oral glucose tolerance tests (OGTT).

Design and Methods:

We evaluated data collected from 29 subjects who had undergone a 3‐stage hyperinsulinemic‐euglycemic clamp (4, 8, and 40 mU/m²/min) with infusion of ²H₅]glycerol to calculate the glycerol rate of appearance (GLY_RA). Exponential decay curves for GLY_RA across insulin concentrations were generated for each individual and suppression of lipolysis was calculated as the insulin concentration needed to half‐maximally suppress GLY_RA (GLY_RA EC₅₀). Areas under the curve for glycerol (GLY_AUC) and insulin (INS_AUC) were calculated and their products (INS_AUC × GLY_AUC) were calculated as an index of insulin suppression of lipolysis.

Results:

The clamp index was highly correlated with GLY_RA EC₅₀ (r = 0.862, P < 0.001), as was an OGTT‐derived index (r = 0.720, P < 0.01).

Conclusions:

These findings suggest that the products of the insulin and glycerol AUC from either a clamp or an OGTT are good biomarkers of the antilipolytic action of insulin and are comparable with direct measurement by isotopic tracer methods.