Lipoprotein insulin resistance index: a lipoprotein particle-derived measure of insulin resistance

Abstract

Abstract Background: Lipoprotein particle sizes and concentrations are characteristically altered in patients with insulin resistance (IR) or type 2 diabetes mellitus (T2DM). This study assessed the ability of an IR score, based on nuclear magnetic resonance (NMR)-derived lipoprotein information, to detect IR in otherwise healthy individuals.

Methods: Lipoprotein subclass and size information were evaluated for strength of association with IR, as measured by homeostasis model assessment of insulin resistance (HOMA-IR) in the Multi-Ethnic Study of Atherosclerosis (MESA). To increase the likelihood of identifying subjects with IR, six lipoprotein measures were combined into a single algorithm. The resulting assay [Lipoprotein Insulin Resistance Index (LP-IR)] was developed using HOMA-IR in 4972 nondiabetic subjects from MESA and verified independently using glucose disposal rates (GDRs) measured during hyperinsulinemic-euglycemic clamps in 56 insulin-sensitive, 46 insulin-resistant, and 46 untreated subjects with T2DM.

Results: LP-IR exhibited stronger associations with HOMA-IR (r=0.51) and GDR (r=-0.53) than each of the individual lipoprotein parameters as well as the triglycerides/high-density lipoprotein cholesterol (TGs/HDL-C) ratio (r=0.41 and -0.44, respectively). In MESA, associations between the LP-IR score and HOMA-IR were strong in men (r=0.51), women (r=0.52), European Americans (r=0.58), African Americans (r=0.48), Chinese Americans (r=0.49), and Hispanic Americans (r=0.45). When LP-IR was categorized by HOMA-IR and either body mass index (BMI) or fasting plasma glucose (FPG), subgroups were revealed whose LP-IR scores were high (≥ 50), despite having normal BMIs (<24 kg/m(2)) or FPG (<100 mg/dL).

Conclusions: LP-IR scores had strong associations with multiple measures, HOMA-IR, and GDR, the former being more reflective of hepatic and the latter of peripheral insulin sensitivity, and may represent a simple means to identify individuals with IR.

FIG. 1.

Distribution of Lipoprotein Insulin Resistance Index (LP-IR) scores in Multi-Ethnic Study of Atherosclerosis (MESA) participants.

FIG. 2.

Relationship between insulin resistance (IR) and Lipoprotein Insulin Resistance Index (LP-IR) score in Multi-Ethnic Study of Atherosclerosis (MESA) and Medical University of South Carolina (MUSC) participants. (A) Least-squares mean and 95% confidence intervals of log-transformed homeostasis model assessment of insulin resistance (HOMA-IR) in MESA participants adjusted for age, sex, and race in subgroups based on LP-IR score decile. Mean LP-IR scores in deciles 1 to 10 were 5, 16, 27, 34, 42, 50, 57, 64, 71, and 83, respectively. (B) Scatterplot of glucose disposal rate (GDR) values versus LP-IR scores for MUSC study participants (n=148).

FIG. 3.

Insulin resistance as a function of Lipoprotein Insulin Resistance Index (LP-IR) and body mass index (BMI) or glucose in Multi-Ethnic Study of Atherosclerosis (MESA). Least squares mean homeostasis model assessment of insulin resistance (HOMA-IR), adjusted for age, sex, and race, by LP-IR category and body mass index (BMI) (A) and fasting plasma glucose (FPG) (B).