Supplementary Material for: Effects of Weight Loss on Adipose and Muscular Neuropilin 1 mRNA Expression in Obesity: Potential Implication in SARS-CoV-2 Infections?

Introduction: Neuropilin 1 (NRP-1) is a novel co-receptor promoting SARS-CoV-2 infectivity. Animal data indicate a role in trans-endothelial lipid transport and storage. As human data are sparse, we aimed to assess the role of NRP-1 in 2 metabolic active tissues in human obesity and in the context of weight loss-induced short- and long-term metabolic changes. Methods: After a standardized 12-week weight reduction program, 143 subjects (age >18; body mass index ≥27 kg/m2, 78% female) were randomized to a 12-month lifestyle intervention or a control group using a stratified randomization scheme. This was followed by 6-month follow-up without any intervention. Phenotyping was performed before and after weight loss, after 12-month intervention and after subsequent 6 months of follow-up. Tissue-specific insulin sensitivity was estimated by HOMA-IR (whole body and mostly driven by liver), insulin sensitivity index (ISI)Clamp (predominantly skeletal muscle), and free fatty acid (FFA) suppression during hyperinsulinemic-euglycemic clamp (FFASupp) (predominantly adipose tissue). NRP-1 mRNA expression was measured in subcutaneous adipose tissue (NRP-1AT) and skeletal muscle (NRP-1SM) before and after weight loss. Results: NRP-1 was highly expressed in adipose tissue (7,893 [7,303–8,536] counts), but neither NRP-1AT nor NRP-1SM were related to estimates of obesity. Higher NRP-1AT was associated with stronger FFASupp (r = −0.343, p = 0.003) and a tendency to higher ISIClamp (r = 0.202, p = 0.085). Weight loss induced a decline of NRP-1AT but not NRP-1SM. This was more pronounced in subjects with stronger reduction of adipose ACE-2 mRNA expression (r = 0.250; p = 0.032) but was not associated with short- and long-term improvement of FFASupp and ISIClamp. Conclusion: NRP-1AT is related to adipose insulin sensitivity in obesity. Weight loss-induced decline of NRP-1AT seems not to be involved in metabolic short- and long-term improvements after weight loss. However, weight loss-induced reduction of both NRP-1AT and ACE-2AT indicates a lower susceptibility of adipose tissue for SARS-CoV-2 after body weight reduction.

引言：神经纤毛蛋白1（Neuropilin 1, NRP-1）是一种新型共受体，可促进严重急性呼吸综合征冠状病毒2（SARS-CoV-2）的感染能力。已有动物研究数据显示其在跨内皮脂质转运与储存中发挥作用。鉴于相关人类研究数据较为匮乏，本研究旨在探讨NRP-1在人类肥胖状态下两种代谢活跃组织中的作用，以及其在体重减轻诱导的短期和长期代谢变化中的意义。
方法：本研究纳入143名受试者（年龄＞18岁，体重指数≥27 kg/m²，女性占78%），在完成标准化12周减重方案后，采用分层随机化方案将其随机分为12个月生活方式干预组与对照组。后续再进行6个月无任何干预的随访。分别在减重前、减重后、12个月干预结束时以及后续6个月随访结束时对受试者进行表型分析。采用稳态模型评估胰岛素抵抗指数（HOMA-IR，评估全身胰岛素敏感性，主要反映肝脏胰岛素敏感性）、胰岛素敏感性指数（ISI）钳夹试验（主要反映骨骼肌胰岛素敏感性）以及高胰岛素正糖钳夹试验中的游离脂肪酸（FFA）抑制率（FFASupp，主要反映脂肪组织胰岛素敏感性）来估算组织特异性胰岛素敏感性。分别在减重前后采集皮下脂肪组织（NRP-1AT）与骨骼肌（NRP-1SM）样本，检测其中NRP-1 mRNA的表达水平。
结果：NRP-1在脂肪组织中呈高表达[7893（7303~8536）计数]，但皮下脂肪组织NRP-1表达（NRP-1AT）与骨骼肌NRP-1表达（NRP-1SM）均与肥胖评估指标无显著关联。较高的NRP-1AT水平与更强的FFASupp呈负相关（r=-0.343，p=0.003），同时存在与更高ISI钳夹试验结果相关的趋势（r=0.202，p=0.085）。体重减轻可导致NRP-1AT水平下降，但对NRP-1SM无显著影响。这种NRP-1AT水平的下降在脂肪组织血管紧张素转换酶2（Angiotensin-converting enzyme 2, ACE-2）mRNA表达降幅更大的受试者中更为显著（r=0.250；p=0.032），但与FFASupp和ISI钳夹试验结果的短期及长期代谢改善无关联。
结论：肥胖状态下，皮下脂肪组织NRP-1表达与脂肪组织胰岛素敏感性相关。体重减轻诱导的NRP-1AT水平下降似乎并未参与体重减轻后代谢指标的短期与长期改善。然而，体重减轻同时导致NRP-1AT与脂肪组织ACE-2（ACE-2AT）水平下降，提示体重降低后脂肪组织对SARS-CoV-2的易感性有所降低。