Abstract
Obesity is associated with microvascular dysfunction. While low-fat diet improves cardiovascular risk, its contributions on microvascular function, independent of weight loss, is unknown. We tested the hypothesis that nitric oxide (NO)-dependent vasodilation in microvessels is improved by low-fat diets designed for weight loss (LFWL) compared to low-fat weight maintenance (LFWM) diet. Obese adults were randomly assigned to either a LFWL diet (n = 11) or LFWM diet (n = 10) for six weeks. Microvessels were obtained from gluteal subcutaneous fat biopsies before and after the intervention for vascular reactivity measurements to acetylcholine (Ach) and flow, with and without L-NAME or indomethacin. Vascular and serum NO and C-reactive protein (CRP) were also measured. LFWL diet increased flow-induced (FID) and ACh-induced dilation (AChID); an effect that was inhibited by L-NAME. Conversely, LFWM diet did not affect FID or AChID. Indomethacin improved FID and AChID in the baseline and this effect was minimized in response to both diets. Serum NO or CRP did not change in response to either diet. In conclusion, LFWL diet improves microvascular reactivity compared to LFWM diet and increased vascular NO contribution to the improved microvascular dilation. These data suggest that weight reduction on low fat diet is critical for microvascular health.
Highlights
Obesity is a common and serious disease that affects more than one-third (36.5%) of the U.S adults and over 650 million adults worldwide [1]
While Phillips et al [6] have shown that low-fat diet improved arterial flow-mediated dilation (FMD), contradictory results have been reported by Volek et al [7], who reported FMD decreases with a low-fat diet and Keogh et al [8] who demonstrated no effect of low-fat diet on vascular function
Lipid profile changed significantly in both groups; total cholesterol decreased by an average of 6% in both groups and low density lipoproteins (LDLs) decreased by 4% in the low-fat diets designed for weight loss (LFWL) group and 10% in the low-fat weight maintenance (LFWM) group
Summary
Obesity is a common and serious disease that affects more than one-third (36.5%) of the U.S adults and over 650 million adults worldwide [1]. While in most of the studies that implemented low-fat diet, improvements in some cardiovascular risk factors such as lipid metabolism and oxidative stress were reported, findings that are related to actual vascular measurements have been lacking or conflicting. While Phillips et al [6] have shown that low-fat diet improved arterial flow-mediated dilation (FMD), contradictory results have been reported by Volek et al [7], who reported FMD decreases with a low-fat diet and Keogh et al [8] who demonstrated no effect of low-fat diet on vascular function Considering these conflicting reports, it is easy to conclude that some additional factors must play a key role in vascular outcomes of the low-fat diet and may reveal contributing mechanisms
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