Bariatric surgery helps to reduce blood pressure - insights from GATEWAY trial

While there is much observational evidence that weight loss and bariatric surgery lead to a sustained reduction in blood pressure, until the Gastric Bypass to Treat Obese Patients With Steady Hypertension (GATEWAY) trial, there has been no randomized bariatric surgery study in hypertensive subjects where hypertension remission and/or reduction of antihypertensive medications were used as primary outcomes. The GATEWAY trial prospectively randomized 100 obese individuals with established but controlled hypertension to either Roux-en-Y gastric bypass (RYGB) or conventional medical therapy. At the 12-month follow-up >80% of the subjects in the surgery group had been able to stop or reduce their antihypertensive medication compared with only 13% in the medication group. This conclusively shows that RYGB surgery is an effective treatment of hypertension. While GATEWAY is a well-designed study, a few caveats limit the generalizability of the results. It will be of great interest to see what the planned 5-year follow-up data will show given that hypertension has been shown to relapse in >20% of the subjects within the first 3 years after bariatric surgery. Furthermore, GATEWAY did not include individuals with extreme forms of obesity (BMI >_ 40 kg/m), current smokers and the majority were females ( 70%). Ethnic considerations are also important as the majority were white and it is possible that race impacts on hypertension and sensitivity to different drugs and/or surgery. In any case, with the results from GATEWAY as well as previous studies, the scientific community can now shift its focus to understanding how bariatric surgery improves blood pressure. Given the multifactorial causes of hypertension, the beneficial effects are most probably dependent on several different mechanisms. As discussed, these may include increased physical activity, reduced sleep apnea, changes in diet (and microbiota?), altered activity in the sympathetic nervous system and improved insulin sensitivity. The most dramatic change following bariatric surgery is in white adipose tissue (WAT) mass and phenotype. It has therefore been proposed that WAT may play a causal role in explaining the improvements in blood pressure. WAT expresses and secretes a large number of polypeptides (collectively termed adipokines) and non-peptide factors, which may exert both local and systemic effects. Obese WAT is characterized by chronic low-grade inflammation, fibrosis, oxidative stress and an altered balance between vasoconstrictors/-dilators (e.g. endothelin and nitric oxide), all of which may impact on vascular phenotype and thereby Mikael Rydén is a senior consultant in Endocrinology, Diabetology and Internal Medicine and Professor of Clinical and Experimental Adipose Tissue Research. Prof Rydén has over 20 years of experience in the research file spanning over experimental and clinical studies with a particular focus on the links between adipocytes and cardiometabolic complications. He has published almost 200 peer-reviewed original articles and reviews and has been engaged in several regulatory authorities setting up guidelines for type 2 diabetes treatment. Jesper Bäckdahl is a resident in Endocrinology and PhD student under the supervision of Mikael Rydén. Dr Bäckdahl holds a master degree in Public Health from the London School of Hygiene and Tropical Medicine. His research revolves around adipose tissue and its link to arterial stiffness and hypertension.