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Non-human primates are most suitable for generating cervical experimental models, and it is necessary to study the anatomy of the cervical spine in non-human primates when generating the models. The purpose of this study was to provide the anatomical parameters of the cervical spine and spinal cord in long-tailed macaques (Macaca fascicularis) as a basis for cervical spine-related experimental studies. Cervical spine specimens from 8 male adult subjects were scanned by micro-computed tomography, and an additional 10 live male subjects were scanned by magnetic resonance imaging. The measurements and parameters from them were compared to those of 12 male adult human subjects. Additionally, 10 live male subjects were scanned by magnetic resonance imaging, and the width and depth of the spinal cord and spinal canal and the thickness of the anterior and posterior cerebrospinal fluid were measured and compared to the relevant parameters of 10 male adult human subjects. The tendency of cervical parameters to change with segmental changes was similar between species. The vertebral body, spinal canal, and spinal cord were significantly flatter in the human subjects than in the long-tailed macaques. The cerebrospinal fluid space in the long-tailed macaques was smaller than that in the human subjects. The anatomical features of the cervical vertebrae of long-tailed macaques provide a reference for establishing a preclinical model of cervical spinal cord injury.

Ketogenic diet (KD) has been used in epilepsy for decades, but previous studies found it may cause severe bone loss. Every-other-day ketogenic diet (EODKD), the combination of KD with intermittent fasting, showed better potential for seizure control recently, while its effects on bone remain unknown. This study aims to establish different ketogenic rat models and compare the influence of EODKD with KD on bone microstructure and metabolism. Thirty male Sprague-Dawley rats were divided into Control, KD and EODKD groups, fed with standard diet, continuous and intermittent ketogenic diet respectively. After 12 weeks, bone mineral density (BMD) and body fat percentage were obtained by dual energy X-ray absorptiometry. Micro-CT and three-point bending test were used to evaluate the bone microstructure and mechanical properties. Activities of serum alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) were measured, together with the osteogenic capabilities of bone marrow stromal cells (BMSCs) tested by ALP activities and alizarin red stain in different osteogenic stage. Both EODKD and KD induced higher ketone and more fat percentage, but led to lower body weight compared with Control group. They both compromised bone mass and mechanical properties. Compared with KD, EODKD demonstrated higher ketone levels, but it also inhibited osteoclastic process as well as early osteogenic differentiation. In general, EODKD accelerated ketosis, but may not deteriorate bone microstructure and strength than KD.

A high-fat, low–carbohydrate diet (KD) or calorie restriction in the form of every-other-day fasting (EODF) results in ketone body metabolism with an increasing β-hydroxybutyrate (βOHB) level. Previous studies have supported that a KD and EODF have a neuroprotective effect. However, the βOHB levels in the cerebrospinal fluid (CSF) resulting from a KD and EODF remain unknown. The aim of this study was to detect βOHB levels in rats fed a KD, EODF diet, and every-other-day ketogenic diet (EODKD) and to compare the serum βOHB level with the CSF βOHB level. Twenty-four male Sprague-Dawley rats were randomly divided into KD, EODF, EODKD, and standard diet (SD) groups. A customized food with a ratio of carbohydrates to fats of 1:4 was used in the KD and EODKD groups. The βOHB level was measured using ELISA kits in 200 µl serum and 100 µl CSF samples for each rat after feeding for 2 weeks. The KD, EODF, and EODKD resulted in a significant increase in βOHB levels in both the serum and CSF. The βOHB levels in the EODKD group were the highest. The CSF βOHB level was, on average, 69% of the serum βOHB level. There was a positive correlation between the overall βOHB levels in serum and that in cerebrospinal fluid. This study demonstrated that the KD, EODF, and EODKD resulted in ketone body metabolism, as the βOHB levels increased significantly compared with those resulting from the standard diet. Our results suggested that the serum βOHB level was an indicator of the CSF βOHB level, and that the EODKD was an effective diet to enhance ketogenic metabolism.