Insulin Status and Vascular Responses to Weight Loss in Obesity
Are the effects of weight loss on arterial function differentially modified by insulin status?
The study was conducted in 208 overweight or obese patients receiving medical/dietary (48%) or bariatric surgical (52%) weight loss treatment during a median period of 11.7 months. Measured plasma metabolic parameters and vascular endothelial function using ultrasound was performed at baseline and following weight loss intervention, and stratified analyses by median plasma insulin levels.
Subjects ages 45 ± 1 years and a mean body mass index (BMI) of 45 ± 9 kg/m2 experienced 14 ± 14% weight loss during the study period. Nearly 90% of those with a ≥10% loss in weight had bariatric surgery. Higher insulin levels were significantly associated with coronary disease, diabetes, and hypertension; greater weight, BMI, and triglycerides, and lower high-density lipoprotein. Both groups had a significant improvement in each of the metabolic parameters, but improvements in insulin and homeostasis model of assessment (HOMA) were greater despite a similar loss in weight in those with higher insulin. In individuals with baseline plasma insulin levels above the median >12 uIU/ml (n = 99), ≥10% weight loss (compared to <10%) significantly improved brachial artery flow-mediated vasodilation and microvascular reactive hyperemia (p < 0.05 for all). In contrast, vascular function did not change significantly in the lower insulin group (12 uIU/ml, n = 109) despite similar degree of weight loss. In analyses using a 5% weight loss cut-point, only microvascular responses improved in the higher insulin group (p = 0.02).
The authors concluded that insulin status is an important determinant of the positive effect of weight reduction on vascular function, with hyperinsulinemic patients deriving the greatest benefit. They also found that integrated improvement in both microvascular and macrovascular function is associated with ≥10% weight loss.
The findings support the general recommendation that a target of ≥10% weight loss should be considered in patients with the metabolic syndrome, who are very likely to have a fasting insulin >12 uIU/ml. While assessment of vascular endothelial function is a useful tool for this and other scientific studies, the reproducibility is not adequate for clinical purposes in individuals.
Keywords: Hormones, Bariatric Surgery, Vasodilation, Weight Loss, Overweight, Body Weight, Coronary Disease, Diet, Reducing, Insulin Resistance, Metabolic Syndrome X, Hyperinsulinism, Body Mass Index, Biological Markers, Troponin I, Obesity, Homeostasis, Triglycerides, Lipoproteins, HDL, Diabetes Mellitus
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