Effect of Paraplegia on the Time Course of Exogenous Fatty Acid Incorporation Into the Plasma Triacylglycerol Pool in the Postprandial State

The Physiology of Neurogenic Obesity: Lessons from Spinal Cord Injury Research

BACKGROUND

A spinal cord injury (SCI) from trauma or disease impairs sensorimotor pathways in somatic and autonomic divisions of the nervous system, affecting multiple body systems. Improved medical practices have increased survivability and life expectancy after SCI, allowing for the development of extensive metabolic comorbidities and profound changes in body composition that culminate in prevalent obesity.

SUMMARY

Obesity is the most common cardiometabolic component risk in people living with SCI, with a diagnostic body mass index cutoff of 22 kg/m2 to account for a phenotype of high adiposity and low lean mass. The metameric organization of specific divisions of the nervous system results in level-dependent pathology, with resulting sympathetic decentralization altering physiological functions such as lipolysis, hepatic lipoprotein metabolism, dietary fat absorption, and neuroendocrine signaling. In this manner, SCI provides a unique opportunity to study in vivo the "neurogenic" components of certain pathologies that otherwise are not readily observable in other populations. We discuss the unique physiology of neurogenic obesity after SCI, including the altered functions mentioned above as well as structural changes such as reduced skeletal muscle and bone mass and increased lipid deposition in the adipose tissue, skeletal muscle, bone marrow, and liver.

KEY MESSAGE

The study of neurogenic obesity after SCI gives us a unique neurological perspective on the physiology of obesity. The lessons learned from this field can guide future research and advancements to inform the study of obesity in persons with and without SCI.

Optical Coherence Tomography Angiography and Attenuation Imaging for Label-Free Observation of Functional Changes in the Intestine after Sympathectomy: A Pilot Study

We present in this study optical coherence tomography angiography (OCTA) and OCT attenuation imaging (OCTAI) for in vivo non-destructive visualization of intramural blood and lymphatic vessels of the intestine wall. Rabbit small intestine in the norm and after thoracolumbar sympathectomy served as the object of the intraoperative study. Compared to OCTA real-time imaging, OCTAI takes several minutes and can be termed as “nearly real time”. OCTAI signal processing was modified to take into account the signal-to-noise ratio and the final thickness of the intestine wall. The results showed that, after sympathectomy, changes in functioning of intramural blood and lymphatic vessels were observed with a high statistical significance. The occurrence of trauma-induced constriction of the blood and lymphatic vessels led to an especially pronounced decrease in the length of small-caliber (<30 µm) blood vessels (p < 10−5), as well as in the volumetric density of lymphatic vessels (on average by ~50%) compared to their initial state. Remarkably, OCTA/OCTAI modalities provide the unique ability for “nearly-instant detection” of changes in functional status of the tissues, long before they become visible on histology. The proposed approach can be used in further experiments to clarify the mechanisms of changes in intestinal blood and lymph flows in response to trauma of the nervous system. Furthermore, potentially it can be used intraoperatively in patients requiring express diagnosis of the state of intramural blood and lymph circulation.