Obesity is associated with an increased risk of all-cause mortality. Mortality related to excess body weight occurred mostly due to coronary artery disease. Compared to subjects with normal weight or overweight, obesity is an independent risk factor for CAD. In this study, it was HOMA-IR not BMI that was associated with presence of CAD, independent of the presence of DM and hypertension, age, sex, smoking, BMI and HbA1C. The prevalence of CAD in was 26.72% among the studied young-middle obese adults.Data from other studies ranged from 4.5–52%[15–17], owing to differences of race, age, sex ratio, radiology examination methods (CTA or angiography) or definitions of CAD.
However, the relationship between BMI, other cardiovascular risk factors, and the risk of CAD are complex. There is an ongoing debate in light of this conflicting result. In subgroup analysis by region or ethnicity, significant differences in all of the ethnic groups and regions was not observed[16]. In this study, it was HOMA-IR not BMI that associated with CAD in obese adults with a BMI of 28 to 60 Kg/m2. Obesity and/or an increased BMI are independently associated with greater risk of insulin resistance, metabolic syndrome, diabetes, hypertension, and dyslipidemia, and these complications may be more important markers of CAD risk than obesity/BMI alone. Another possible reason may be attributed to the inherent limitations of BMI as a marker of obesity or severe obesity, without exactly reflecting body fatness and lean body mass. For example, a person with increased muscle mass would have the same BMI as a person with increased fat percentage. Thirdly, we suppose that once a person’s BMI༞28(Chinese guideline) or 30 Kg/m2, his/her risk for CAD may be higher, irrespective of the different degrees of obesity, and the risks should be determined by HOMA-IR and other insulin resistance factors. Finally, the sample of this study was a limitation, which weak the strength of the association. And associations of BMI with extent of coronary stenosis hadn’t been studied.
Insulin resistance is a major component of obesity, metabolic syndrome, T2DM and CAD. HOMA-IR is a commonly used marker of insulin resistance which incorporates both glucose and insulin concentrations. An meta-analysis of 65 studies published in 2012, which included 516,325 participants, also revealed that insulin resistance, evaluated by HOMA-IR, was a good predictor for cardiovascular disease[8].In this study, HOMA-IR was independently associated with having coronary stenosis in obese patients. While the Pearson analysis showed no association between HOMA-IR and BMI. It illustrates why the two factors did not relate to the risks of CAD simultaneously. This indicates that maybe we should pay more attention to insulin resistance than BMI alone to evaluate the CAD risks in obese patients.
Currently, statins are generally considered as important drugs that can improve the condition of coronary plaque. According to a study published by JACC in 2018 involving more than 3,500 patients who used coronary CTA to evaluate coronary artery plaques, statins can delay the progression of coronary artery plaques and facilitate the transformation of plaques to stable plaques but cannot reverse the degree of coronary artery stenosis[18]. As shown in Table 3, metabolic surgery has significant remission effect on various risk factors of CAD. This could be the cause of remission in coronary stenosis. As is proved by other studies[19], the mechanism might be: a) By limiting food intake (all types of metabolic surgery) and nutrient intake (gastric bypass surgery), thereby promoting the remission of metabolic syndrome and improving cardiovascular conditions, b) Studies have shown that metabolic surgery simultaneously improves gastrointestinal hormones, intestinal flora, central nervous system and other systemic factors, thus improving metabolic syndrome. Metabolic surgery is likely to be a promising therapeutic approach for obese patients with CAD except weight loss. However, the number of follow-up cases was too few, which needs multi-centered large sample studies to yield stronger findings.
Limitation of our study: a) There was a bias in sex ratio(male,32.76%vs 19.50% respectively),owing to the women had more willing to visit Bariatric Clinics. While men were more susceptible to CAD. As we know, men usually have higher BMI and weight, so the strength of the association might be weakened; b) Another shortage was the small sample size, especially in the postoperative cases, and the limited sample size of our study did not allow for subgroup analysis