1. Weight loss surgery was associated with significant improvement in both macrovascular and microvascular function across subgroups of sex, race, and metabolic syndrome in addition to effective weight loss.
2. Variation in vascular response to bariatric intervention across subgroups underscores heterogeneity in physiological responses to weight loss and potential activation of specific pathological pathways among clinical subgroups.
Evidence Rating Level: 2 (Good)
Study Rundown: The obesity epidemic has resulted in an increasing number of related deaths primarily driven by cardiovascular diseases. In recent years, bariatric surgery has emerged as one of the most effective and sustainable, albeit invasive, weight loss strategy that has also been shown to reduce cardiovascular mortality. Despite these clear benefits, the underlying mechanisms of this association are not well understood. This population-based longitudinal cohort study sought to identify variables associated with vascular improvement after bariatric surgery and examine the effects of sex, race, and metabolic status on postsurgical microvascular and macrovascular outcomes. The main outcomes and measures of the analysis were flow-mediated dilation (FMD) and reactive hyperemia (RH) used as measures of macrovascular and microvascular function respectively. In addition, clinical variables were assessed preoperatively at baseline and postoperatively within 12 months of bariatric surgery. Among 307 individuals with obesity who received bariatric surgery, the intervention was associated with significant improvement in both macrovascular and microvascular function across subgroups of sex, race, and traditional metabolic syndrome in addition to effective weight loss. Although the study did not observe changes in macrovascular function among individuals with metabolically healthy obesity, the use of high-sensitivity C-reactive protein plasma levels greater than 2 mg/dL as a non-specific biomarker identified participants with seemingly metabolically healthy obesity who had low-grade inflammation that also achieved microvascular benefit from bariatric surgery. These findings suggest that bariatric surgery was associated with significant improvement of cardiovascular risk factors and vascular endothelial phenotype in addition to a healthy reduction in weight. In particular, improvements in microvascular function were observed across all subgroups of sex, race, and metabolic syndrome while macrovascular changes displayed more variability across subgroups. A limitation of this study was that the majority of study participants were women. Although this accurately reflects the general clinical practice and known sex differences in populations that seek weight loss interventions, it limits the generalizability of the study findings in the future as bariatric surgery emerges as an effective weight loss strategy in both sexes.
In-Depth [prospective cohort]: This population-based longitudinal cohort study enrolled 307 individuals with obesity who underwent bariatric surgery (mean [SD] age, 42  years; 246 [80%] women; 199 [65%] White; mean [SD] body mass index, 46 ) at Boston Medical Center, a large, multi-ethnic urban academic center with presurgical and postsurgical assessments (minimum 1 assessment). Data was collected from December 2001 to August 2019 with data analysis completed in September 2019. Overall, bariatric surgery in patients with obesity was associated with significant weight loss and improved macrovascular and microvascular function across subgroups of sex, race, and traditional metabolic syndrome (mean [SD] pre- vs postsurgery weight: 126  kg vs 104  kg; P < .001; mean [SD] pre- vs postsurgery FMD: 9.1% [5.3] vs 10.2% [5.1]; P < .001; mean [SD] pre- vs postsurgery RH: 764%  vs 923% ; P < .001). The strongest factors associated with change in vascular phenotype correlated with adiposity markers and several metabolic variables depending on vascular territory (e.g., association of weight change with change in RH: estimate, −3.2; 95%CI, −4.7 to −1.8; association of hemoglobin A1c with change in FMD: estimate, −0.5; 95%CI, −0.95 to −0.05). Biomarker assessment using high-sensitivity C-reactive protein plasma levels of greater than 2mg/dL as a non-specific biomarker identified individuals with seemingly metabolically healthy obesity and low-grade inflammation who also derived microvascular benefit from bariatric surgery.
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