Project Summary South Asian individuals (SAs) (individuals from India, Pakistan, Bangladesh, Sri Lanka, and Nepal) have markedly increased risk of atherosclerotic cardiovascular disease (ASCVD), premature insulin resistance, and higher risk of type 2 diabetes compared with non-Hispanic White individuals and other groups. The global cardiovascular community has officially recognized SA ethnicity as a “risk-enhancing factor” in the 2018 ACC/AHA Prevention Guidelines2 as well as in the QRISK2/3 risk calculator used in the U.K. Reducing ASCVD risk and mortality from ASCVD in SAs is a clear priority and unmet need. Our team has demonstrated that advanced measures of lipid metabolism (protective and adverse) are superior to traditional risk factors and conventional lipids (non-HDL-C, HDL-C, and triglycerides) in predicting ASCVD risk. These advanced measures have been studied primarily in those of European and African descent but not among SAs. Our overall goal is to improve cardiometabolic risk in SAs. The specific objective of this project is to determine whether advanced measures of lipoprotein metabolism explain the excess cardiometabolic risk in SAs. We will leverage the NHLBI-supported Mediators of Atherosclerosis in SAs Living in America (MASALA), the largest longitudinal cohort of U.S. SAs with extensive cardiometabolic phenotyping (N=1,164) and compare these findings to similarly phenotyped White, Black, Hispanic, and Chinese participants in the Multi-Ethnic Study of Atherosclerosis (MESA, N=6814). We will utilize the UK Biobank to ascertain metabolomic signatures of SAs and incident ASCVD and diabetes (N=8,762 SAs vs. 472,780 Europeans). Aim 1: Determine the association between advanced measures of lipoprotein metabolism and metabolic phenotypes in SAs. Aim 2: Determine the association between advanced measures of lipoprotein metabolism and subclinical plaque prevalence and progression and incident ASCVD in SAs. Specific Aim 3: Determine the metabolomic signatures of South Asians compared to non-SAs with respect to cardiometabolic phenotypes. The proposed studies are expected to provide critical insights into the link between advanced protective and adverse measures of lipoprotein metabolism and excess cardiometabolic risk in SAs and may eventually lead to better clinical biomarkers specific to SAs as well as to novel interventions targeting these lipoprotein markers in SAs. Given the excessive burden of ASCVD and diabetes in SAs, this proposal may have a large public health benefit to this less studied but high-risk ethnic group.