7718 Dysregulated BCAA catabolism and insulin secretory response in the early stages of insulin resistance in mature adolescents
Authors: Basin A , Wang Q , Hong H , Ilkayeva O , Muehlbauer M , Hsia D , D’Alessio D A , Newgard C B , Freemark M , Gumus Balikcioglu P 
Published: October 2024

Abstract
Disclosure: A. Basin: None. Q. Wang: None. H. Hong: None. O. Ilkayeva: None. M. Muehlbauer: None. D. Hsia: None. D.A. D'Alessio: None. C.B. Newgard: None. M. Freemark: None. P. Gumus Balikcioglu: None.
Objective: We recently showed that surrogate markers of insulin resistance (IR) and insulin secretion are differentially associated with branched-chain amino acids (BCAAs) and their catabolites the branched-chain ketoacids (BCKAs). In this longitudinal study, we determined if baseline levels of BCAAs, BCKAs or the BCKA/BCAA ratio are associated with changes in IR, insulin secretion, and insulin secretion adjusted for IR after a one year follow up in adolescents aged 18-21 yr without Type 2 diabetes. Methods: We performed frequently sampled oral glucose tolerance tests (OGTT) at baseline and one year follow up in 10 adolescents with normal weight and 10 adolescents without Type 2 diabetes but with overweight/obesity and mild IR. After an overnight fast of 8-12 hours, participants had fasting blood samples drawn and consumed 1.75 g/kg, to a maximum of 75 g glucose solution as the initiation of an OGTT. Glucose (G) and insulin (I) were measured at times -15, 0, 10, 15, 30, 45, 60, 90, 120, and 180 minutes. Plasma metabolomic profiles were obtained at time 0. HOMA-IR, Matsuda Index, AUC glucose, AUC insulin, insulinogenic index (IGI) and disposition index (DI) at 15 and 30 min were calculated. % Body fat was measured by TANITA. Results: At one year follow up groups were comparable in age, sex, race, ethnicity and pubertal status. Participants with overweight/obesity had higher BMI (22.5±1.3 vs 36.2±9.7), BF% (16.8±8.4 vs 37.9±10.2), leptin, and diastolic blood pressure than lean participants. They were also more insulin resistant as evidenced by higher HOMA-IR . AUC glucose,AUC insulin, and IGI were comparable across groups, as were fasting BCAA levels and BCKA/BCAA ratio. As with baseline levels, follow-up BCAA levels correlated positively with AUC insulin, HOMA-IR, and IGI at 30 min and negatively with totaland HMW-adiponectin, and Matsuda Index, but did not correlate with BMI or % body fat. Likewise at follow up, BCKAs correlated negatively with total and HMW-adiponectin and did not correlate with Matsuda Index, or HOMA-IR. In association models adjusted for baseline age, sex, and BMI, higher baseline levels of the BCKA, α-keto-β-methylvalerate (KMV, isoleucine catabolite), and a higher BCKA/BCAA ratio were associated with a relative reduction in acute insulin secretion as reflected in a reduction in 15 min IGI at 1 year follow up. Conclusions: In this cohort of adolescents without Type 2 diabetes and with varying degrees of adiposity and insulin sensitivity, we identified KMV as a marker associated with a subsequent reduction in acute glucose-stimulated insulin secretion at one year follow up.These findings suggest that dysregulated BCAA catabolism is associated with loss of compensatory insulin secretion in the face of IR and may play a role in progression to impaired glucose tolerance and development of Type 2 diabetes.
Presentation: 6/1/2024