Tucker Wesley J, Thomas Binu P, Puzziferri Nancy, Samuel T Jake, Zaha Vlad G, Lingvay Ildiko, Almandoz Jaime, Wang Jing, Gonzales Edward A, Brothers R Matthew, Nelson Michael D
1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.
2Department of Nutrition & Food Sciences, Texas Woman's University, Houston, TX USA.
Pilot Feasibility Stud. 2020 Feb 13;6:21. doi: 10.1186/s40814-020-00569-2. eCollection 2020.
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.
Bariatric surgery candidates ( = 6) were compared with normal weight healthy controls of a similar age ( = 10) at baseline, and then reassessed 2 weeks and 14 weeks following sleeve gastrectomy bariatric surgery. Young reference controls ( = 7) were also studied at baseline to establish the range of normal for each outcome measure. Microvascular and macrovascular CVR to hypercapnia (5% CO) 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.
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/mmHgCO), 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.
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.
减肥手术是一种有效的长期减肥策略，能改善神经认知功能；然而，导致这些改善的机制仍不清楚。在此，我们评估了使用磁共振成像（MRI）来评估与正常体重健康对照相比，严重肥胖的减肥手术候选者的脑血管反应性（CVR）是否受损，以及减肥手术后CVR是否改善。我们还研究了CVR的变化是否与认知功能的变化相关。
在基线时，将减肥手术候选者（n = 6）与年龄相似的正常体重健康对照者（n = 10）进行比较，然后在袖状胃切除术减肥手术后2周和14周重新评估。还在基线时研究了年轻对照者（n = 7），以确定每个结局指标的正常范围。使用血氧水平依赖（BOLD）MRI评估对高碳酸血症（5% CO₂）的微血管和大血管CVR，以及大脑中动脉（MCA）横截面积的变化。使用经过验证的神经认知软件评估认知功能。
对CVR方案的依从性很高。年轻对照者的大、小脑血管功能均最高。与正常体重对照者相比，肥胖的减肥手术候选者的认知功能较低，减肥手术后2周时改善了17%，14周时改善了21%。令我们惊讶的是，肥胖的减肥手术候选者与年龄相似的正常体重对照者之间的全脑CVR BOLD无差异（0.184 ± 0.101 vs. 0.192 ± 0.034 %BOLD/mmHg CO₂），且减肥手术后未发生变化。相反，我们观察到60%的肥胖患者在手术前高碳酸血症期间MCA出现血管收缩，减肥手术后这种收缩似乎消失了。减肥手术后认知功能的改善与CVR BOLD或MCA血管舒张的改善均无关。
在严重肥胖的减肥患者中，使用MRI评估对高碳酸血症挑战的CVR反应是可行的。然而，尽管认知功能有所改善，但减肥手术后全脑BOLD CVR未观察到变化。我们建议未来的大型试验评估对认知任务（而非高碳酸血症）的CVR反应，以更好地确定减肥手术后认知功能改善的机制。
