The Circulating Lipidome In Severe Obesity.

Background: Severe obesity (SevO; BMI ≥40 kg/m²) is rapidly increasing globally and disproportionately affects minority populations. However, it remains understudied in mechanistic and omics literature. Lipid metabolism plays a central role in obesity-related cardiometabolic disease (CMD), but the relationship between molecular lipid species and SevO is poorly understood, particularly in high-risk groups.

Methods: We analyzed 578 participants from the Cameron County Hispanic Cohort (CCHC) with fasting plasma lipidomic and genetic data, comparing those living with SevO (n=185) to non-obese controls (n=393). A total of 830 circulating lipid species across 49 classes were quantified. Associations between individual lipids and SevO were assessed using logistic regression and orthogonal projections to latent structures discriminant analysis (OPLS-DA). Potential causal links were assessed using network deconvolution mendelian randomization (NDMR), and influential lipids were correlated with CMD traits and DXA-derived body composition.

Results: Participants with SevO exhibited statistically significantly more adverse cardiometabolic risk factors than controls. Lipidomic profiling revealed broad alterations: shorter, saturated, and monounsaturated triacylglycerols were markedly elevated, while lysophospholipids, plasmalogens, cholesteryl esters, and long-chain lipids were reduced in individuals with SevO when compared to controls (BMI ≥ 18.5 and > 25 kg/m²). OPLS-DA identified over 300 influential lipid species predictive of SevO status. NDMR analyses implicated specific triacylglycerol species as potentially causally linked with SevO status. Influential lipids correlated with insulin resistance, liver steatosis, body fat measures, and HDL-C (absolute value ranges 0.2-0.4).

Conclusions: Our findings reveal that SevO is marked by extensive and lipid class-specific dysregulation of the circulating lipidome, with strong links to cardiometabolic risk. Notably, triacylglycerols containing shorter length acyl chains emerged as a distinctive lipid signature of SevO-consistently elevated, strongly discriminative of SevO status, and uniquely exhibiting a consistent causal relationship. Our results provide compelling evidence for a novel lipidomic pathway underpinning severe obesity and underscore critical avenues for future research into its genetic, dietary, and mechanistic determinants.