Advantages of dynamic "closed loop" stable isotope flux phenotyping over static "open loop" clamps in detecting silent genetic and dietary phenotypes

作者：Vaitheesvaran Bhavapriya; Chueh Fu Yu; Xu Jun; Trujillo Chuck; Saad M F; Lee W N P; McGuinness Owen P; Kurland Irwin J^*

来源：Metabolomics, 2010, 6(2): 180-190.

DOI：10.1007/s11306-009-0190-2

• Orphan nuclear receptor action
• Stable isotope flux phenotyping
• Metabolic flexibility

In vivo insulin sensitivity can be assessed using "open loop" clamp or "closed loop" methods. Open loop clamp methods are static, and fix plasma glucose independently from plasma insulin. Closed loop methods are dynamic, and assess glucose disposal in response to a stable isotope labeled glucose tolerance test. Using PPAR alpha(-/-) mice, open and closed loop assessments of insulin sensitivity/glucose disposal were compared. Indirect calorimetry done for the assessment of diurnal substrate utilization/metabolic flexibility showed that chow fed PPAR alpha(-/-) mice had increased glucose utilization during the light (starved) cycle. Euglycemic clamps showed no differences in insulin stimulated glucose disposal, whether for chow or high fat diets, but did show differences in basal glucose clearance for chow fed PPAR alpha(-/-) versus SV129J-wt mice. In contrast, the dynamic stable isotope labeled glucose tolerance tests reveal enhanced glucose disposal for PPAR alpha(-/-) versus SV129J-wt, for chow and high fat diets. Area under the curve for plasma labeled and unlabeled glucose for PPAR alpha(-/-) was a parts per thousand 1.7-fold lower, P < 0.01 during the stable isotope labeled glucose tolerance test for both diets. Area under the curve for plasma insulin was 5-fold less for the chow fed SV129J-wt (P < 0.01) but showed no difference on a high fat diet (0.30 +/- A 0.1 for SV129J-wt vs. 0.13 +/- A 0.10 for PPAR alpha(-/-), P = 0.28). This study demonstrates that dynamic stable isotope labeled glucose tolerance test can assess "silent" metabolic phenotypes, not detectable by the static, "open loop", euglycemic or hyperglycemic clamps. Both open loop and closed loop methods may describe different aspects of metabolic inflexibility and insulin sensitivity.

• 出版日期2010-6