Relationships between body weight, fasting blood glucose concentration, sex and age in tree shrews (Tupaia belangeri chinensis).

The tree shrew (Tupaia belangeri chinensis) is a squirrel-like lower primate or a close relative of primates, commonly used as an animal model in biomedical research. Despite more than three decades of usage in research, the clear relationships between body weight, fasting blood glucose concentration, sex and age among tree shrews remain unclear. Based on an investigation of 992 tree shrews (454 males and 538 females) aged between 4 months and 4 years old, we found that male tree shrews have significantly higher body weight and fasting blood glucose concentration than female tree shrews (p < 0.001). The concentration of fasting blood glucose slightly increased with body weight in males (r = 0.152, p < 0.001). Meanwhile, in females, the body weight, concentration of fasting blood glucose and waist circumference positively increased with age (p < 0.001). Additionally, 17 tree shrews with Lee index [body weight (g)0.331000/body length (cm)] above 290 had significantly higher body weight, waist circumference and glycated haemoglobin A1c (HbA1c) than non-obese tree shrews with a Lee index score below 290 (p < 0.001). Interestingly, 6 of 992 tree shrews (three males and three females, 2-4 years old) displayed impaired plasma triglycerides, HbA1c, low-density lipoprotein and oral glucose tolerance test, suggestive of the early symptoms of metabolic syndrome. This study provides the first clear relationships between body weight, fasting blood glucose concentration, sex and age in tree shrews, further improving our understanding of this relationship in metabolic syndrome (MetS). Given the similarity of tree shrews to humans and non-human primates, this finding supports their potential use as an animal model in the research of MetS.