Low-Fat Diet Designed for Weight Loss But Not Weight Maintenance Improves Nitric Oxide-Dependent Arteriolar Vasodilation in Obese Adults

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.

The Effect of Low-Carbohydrate Diet on Macrovascular and Microvascular Endothelial Function Is Not Affected by the Provision of Caloric Restriction in Women with Obesity: A Randomized Study

“…We did not measure oxidative stress and inflammation, both of which are known as the underlying mechanisms of reduced NO bioavailability. On the other hand, enhanced vasoconstriction, e.g., due to increased generation of cyclo-oxygenase (COX-1)-derived vasoconstrictor metabolites, may also contribute to impaired FID [ 36 , 37 ]. Future studies to further dissect the mechanisms by which LC diet improves microvascular endothelial function in obesity appear warranted.…”

“…We defined CR diet as a caloric deficit by 500 calories/day less than the planned caloric intake. We calculated the planned caloric intake for each participant using the Mifflin equation, which considers individual body weight, height, age, and physical activity levels, and has been used in different diet interventions [ 26 , 37 ]. The planned caloric intake should match individual metabolic needs, be similar as their baseline caloric intake, and not induce any body weight changes.…”

Hyperhomocysteinemia and Low Folate and Vitamin B12 Are Associated with Vascular Dysfunction and Impaired Nitric Oxide Sensitivity in Morbidly Obese Patients

“…Adipose tissues were cleaned of excess connective tissue and carefully dissected to isolate visceral and subcutaneous resistance arterioles. Isolated arterioles were used to measure microvascular reactivity as we previously described [ 9 , 10 , 11 ]. Briefly, both SAT and VAT arterioles were cannulated and mounted in an organ perfusion chamber where arteriolar ends were secured using 10-0 nylon Ethilon monofilament suture.…”

“…Endothelin-1 (Peninsula, San Carlos, CA, USA) was used to pre-constrict cannulated arterioles and those that demonstrated less than 30% constriction compared to baseline were excluded from the study since they are mostly damaged during processing [ 9 , 10 , 11 , 13 , 14 , 15 ]. Internal diameters of cannulated arterioles were measured at baseline conditions and during continuing increases of the intraluminal pressure gradient (10–100 cmH 2 O), acetylcholine concentration (ACh; 10 −9 –10 −4 M) [ 10 ], or the NO donor, sodium nitroprusside (SNP; 10 −9 –10 −4 M).…”

Vitamin D Improves Nitric Oxide-Dependent Vasodilation in Adipose Tissue Arterioles from Bariatric Surgery Patients

“…Adipose tissues were dissected, and resistance arterioles were isolated and cleaned of excess fat and connective tissues. Arterioles were then washed and prepared for measuring changes in the internal diameter in response to flow and acetylcholine (Ach) as previously described [26,28,29]. In summary, isolated arterioles were cannulated using glass micropipettes in an organ perfusion chamber, and both ends were secured using a 10-0 nylon Ethilon monofilament suture.…”