Glucosamine (GlcN) is a popular nutritional supplement used to treat osteoarthritis in postmenopausal women. Postmenopausal women are at higher risk of type 2 diabetes mellitus and metabolic syndrome because of ovarian hormone deficiency. We used ovariectomized (OVX) rats as the model to investigate whether GlcN would induce insulin resistance (IR) in OVX rats and the underlying mechanisms.
The rats were divided into four groups: (1) sham-operated group (SHAM), (2) SHAM with GlcN treatment (SHAM + GlcN), (3) OVX group, (4) OVX with GlcN treatment (OVX + GlcN). Intraperitoneal (IP) GlcN was given at 12 weeks after the surgical procedure for 2 weeks. The IP glucose tolerance test (IPGTT) was performed to measure plasma glucose and insulin and to calculate the clinical homeostasis model assessment–IR (HOMA-IR) and glucose-insulin index. Western blot analysis for the detection of glucose transport protein subtype 4 expression in the skeletal muscle and histopathological examination of the changes in pancreatic islets were also performed.
Fasting plasma glucose increased in the OVX + GlcN group, and fasting plasma insulin and HOMA-IR were elevated more significantly in this group. In addition, plasma glucose, plasma insulin, HOMA-IR, and glucose-insulin index were significantly elevated only in the OVX with GlcN group after IP glucose injection, implying that IR was induced by GlcN only in female rats without the protection of ovarian hormone. In addition, we found that treatment with GlcN decreased the expression of glucose transport protein subtype 4 in the skeletal muscle and induced pancreatic islet hyperplasia only in OVX rats.
The results demonstrate that female rats do not develop IR upon GlcN treatment except after ovariectomy. Those who take GlcN after menopause or bilateral oophorectomy should watch their blood glucose level closely, especially after meals.