Background Bariatric surgery is an effective long-term weight loss strategy yielding improvements in neurocognitive function; however, the mechanism(s) responsible for these improvements remains unclear. Here, we assessed the feasibility of using magnetic resonance imaging (MRI) to evaluate whether cerebral vascular reactivity (CVR) is impaired in severely obese bariatric surgery candidates compared with normal weight healthy controls and whether CVR improves following bariatric surgery. We also investigated whether changes in CVR were associated with changes in cognitive function. Methods Bariatric surgery candidates (n = 6) were compared with normal weight healthy controls of a similar age (n = 10) at baseline, and then reassessed 2 weeks and 14 weeks following sleeve gastrectomy bariatric surgery. Young reference controls (n = 7) were also studied at baseline to establish the range of normal for each outcome measure. Microvascular and macrovascular CVR to hypercapnia (5% CO2) were assessed using blood-oxygen-level-dependent (BOLD) MRI, and changes in the middle cerebral artery (MCA) cross-sectional area, respectively. Cognitive function was assessed using a validated neurocognitive software. Results Compliance with the CVR protocol was high. Both macro- and micro-cerebrovascular function were highest in the young reference controls. Cognitive function was lower in obese bariatric surgery candidates compared with normal weight controls, and improved by 17% at 2 weeks and 21% by 14 weeks following bariatric surgery. To our surprise, whole-brain CVR BOLD did not differ between obese bariatric surgery candidates and normal weight controls of similar age (0.184 ± 0.101 vs. 0.192 ± 0.034 %BOLD/mmHgCO2), and did not change after bariatric surgery. In contrast, we observed vasoconstriction of the MCA during hypercapnia in 60% of the obese patients prior to surgery, which appeared to be abolished following bariatric surgery. Improvements in cognitive function were not associated with improvements in either CVR BOLD or MCA vasodilation after bariatric surgery. Conclusions Assessing CVR responses to a hypercapnic challenge with MRI was feasible in severely obese bariatric patients. However, no changes in whole-brain BOLD CVR were observed following bariatric surgery despite improvements in cognitive function. We recommend that future large trials assess CVR responses to cognitive tasks (rather than hypercapnia) to better define the mechanisms responsible for cognitive function improvements following bariatric surgery.

中文翻译：

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减肥手术对脑血管反应性和认知功能的影响：一项非随机试验研究。

背景减肥手术是一种有效的长期减肥策略，可改善神经认知功能。然而，导致这些改进的机制仍不清楚。在这里，我们评估了使用磁共振成像 (MRI) 来评估与正常体重的健康对照组相比，严重肥胖的减肥手术候选人的脑血管反应性 (CVR) 是否受损以及减肥手术后 CVR 是否改善的可行性。我们还调查了 CVR 的变化是否与认知功能的变化有关。方法 减肥手术候选人 (n = 6) 与基线时相似年龄的正常体重健康对照 (n = 10) 进行比较，然后在袖状胃切除减肥手术后 2 周和 14 周重新评估。还在基线研究了年轻的参考对照（n = 7），以确定每个结果测量的正常范围。使用血氧水平依赖性 (BOLD) MRI 和大脑中动脉 (MCA) 横截面积的变化分别评估微血管和大血管 CVR 对高碳酸血症 (5% CO2) 的影响。使用经过验证的神经认知软件评估认知功能。结果 对 CVR 协议的依从性很高。在年轻的参考对照中，宏观和微观脑血管功能均最高。与正常体重对照组相比，肥胖减肥手术候选人的认知功能较低，减肥手术后 2 周和 14 周分别提高了 17% 和 21%。令我们惊讶的是，全脑 CVR BOLD 在肥胖减肥手术候选者和相似年龄的正常体重对照之间没有差异（0.184 ± 0.101 对 0.192 ± 0.034 %BOLD/mmHgCO2），并且在减肥手术后没有变化。相比之下，我们在手术前观察到 60% 的肥胖患者在高碳酸血症期间 MCA 的血管收缩，这在减肥手术后似乎被消除了。认知功能的改善与减肥手术后 CVR BOLD 或 MCA 血管舒张的改善无关。结论 使用 MRI 评估 CVR 对高碳酸血症挑战的反应在严重肥胖的减肥患者中是可行的。然而，尽管认知功能有所改善，但在减肥手术后没有观察到全脑 BOLD CVR 的变化。