Toward noninvasive quantification of adipose tissue oxygenation with MRI.,International Journal of Obesity

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Toward noninvasive quantification of adipose tissue oxygenation with MRI.
International Journal of Obesity ( IF 4.2 ) Pub Date : 2020-03-30 , DOI: 10.1038/s41366-020-0567-x
Darya Morozov ₁ , James D Quirk ₁ , Scott C Beeman ₂

Affiliation

Background

Molecular oxygen (O₂) plays a key role in normal and pathological adipose tissue function, yet technologies to measure its role in adipose tissue function are limited. O₂ is paramagnetic and, in principle, directly influences the magnetic resonance (MR) ¹H longitudinal relaxation rate constant of lipids, R₁; thus, we hypothesize that MR imaging (MRI) can directly measure adipose O₂ via a simple measure of R₁.

Methods

R₁ was measured in a 4.7T preclinical MRI system at discrete oxygen partial pressure (pO₂) levels. These measures were made in vitro in an idealized system and in vivo in subcutaneous and visceral white adipose of rodents. pO₂ was determined using an invasive fiber-optic oxygen monitor. From the MRI and fiber optic data we determined the “relaxivity” of O₂ in lipid, a critical parameter in converting the MRI-based R₁ measurement into pO₂. We used breathing gas challenge to estimate the changes in lipid pO₂ (ΔpO₂).

Results

The relaxivity of O₂ in lipid was determined to be 1.7·10⁻³ ± 4·10⁻⁴ mmHg⁻¹s⁻¹ at 4.7T and 37 °C, and was consistent between in vitro and in vivo adipose tissue. There was a strong, significant correlation between MRI- and gold standard OxyLite-based measurements of lipid ΔpO₂ for in vivo visceral and subcutaneous fat depots in rodents.

Conclusion

This study lays the foundation for a direct, noninvasive measure of adipose pO₂ using MRI and will allow for noninvasive measurement of O₂ flux in adipose tissue. The proposed approach would be of particular importance in the interrogation of the pathogenesis of type 2 diabetes, where it has been suggested that adipose tissue hypoxia is an independent driver of insulin resistance pathway.

中文翻译：

使用 MRI 对脂肪组织氧合进行无创量化。

背景

分子氧 (O ₂ ) 在正常和病理性脂肪组织功能中起关键作用，但测量其在脂肪组织功能中的作用的技术有限。O ₂是顺磁性的，原则上直接影响脂质的磁共振 (MR) ¹ H 纵向弛豫速率常数R ₁；因此，我们假设 MR 成像 (MRI) 可以通过简单的R _{1测量直接测量脂肪 O}₂。

方法

R ₁是在 4.7T 临床前 MRI 系统中以离散氧分压 (pO ₂ ) 水平测量的。这些措施是在体外在理想化的系统中进行的，在体内是在啮齿动物的皮下和内脏白色脂肪中进行的。使用侵入式光纤氧监测仪测定pO _{2 。}根据 MRI 和光纤数据，我们确定了脂质中 O _{2的“松弛性”，这是将基于 MRI 的}R ₁测量值转换为 pO ₂的关键参数。我们使用呼吸气体挑战来估计脂质 pO ₂ (ΔpO ₂ ) 的变化。