Dietary Supplemental Glutamine Enhances the Percentage of Circulating Endothelial Progenitor Cells in Mice with High-Fat Diet-Induced Obesity Subjected to Hind Limb Ischemia.

This study investigated whether glutamine (GLN) pretreatment can enhance circulating endothelial progenitor cells (EPCs) and attenuate inflammatory reaction in high-fat diet-induced obese mice with limb ischemia. Mice were assigned to a normal control (NC), high-fat control (HC), limb ischemia (HI), and GLN limb ischemia (HG) groups. The NC group provided chow diet and treated as a negative control. Mice in the HC and HI groups were fed a high-fat diet which 60% energy provided by fat for 8 weeks. Mice in the HG group were fed the same diet for 4 weeks and then transferred to a high-fat diet with 25% of total protein nitrogen provided as GLN to replace part of the casein for the subsequent 4 weeks. After feeding 8 weeks, mice in the HC group were sham-operated, while the HI and HG groups underwent an operation to induce limb ischemia. All mice except the NC group were euthanized on either day 1 or 7 after the operation. The results showed that the 8 weeks' high-fat diet feeding resulted in obesity. The HG group had higher circulating EPCs on day 1 while muscle vascular endothelial growth factor, matrix metalloproteinase-9, and hypoxia-inducible factor-1 gene expressions were higher on day 7 postischemia than those of the HI group. The superoxide dismutase activity and reduced glutathione content in affected muscles were higher, whereas mRNA expressions of interleukin-6 and tumor necrosis factor-α were lower in the HG than those in the HI group. These findings suggest that obese mice pretreated with GLN-supplemented high-fat diet increased circulating EPC percentage, enhanced the antioxidant capacity, and attenuated inflammatory reactions in response to limb ischemia.

Glutamine administration promotes hepatic glucose homeostasis through regulating the PI3K/Akt pathway in high-fat diet-induced obese mice with limb ischemia.

High-fat diet-induced obesity can lead to hepatic insulin resistance (IR) and alter glucose metabolism. The decreased protein expression involved in the PI3K-Akt pathway may enhance hepatic glycogenolysis and gluconeogenesis. Obesity-associated glucose dysregulation and IR are risk factors for the development of peripheral arterial disease. Glutamine (Gln) has immunomodulatory properties and was found to attenuate IR and hyperglycemia in diabetic condition. Thus, in this study we hypothesized that Gln administration modulates hepatic glucose metabolism and improve IR via PI3K-Akt pathway in obese mice with limb ischemia. Mice were divided into a high-fat group (HC), and a high-fat Gln group (HG). Mice in the HC group were fed the high-fat diet for 8 weeks, while the HG group was initially fed the high-fat diet for 4 weeks followed by a high-fat diet with Gln for an additional 4 weeks. Part of the mice in the HC and HG groups were subjected to a limb ischemic operation and were euthanized after the operation. Liver tissues and blood samples were collected for analysis. The results showed that high-fat diet-induced obesity resulted in increased plasma glucose and insulin levels. Also, impairment of hepatic insulin signaling by downregulating PI3K-Akt pathway-associated protein expression was observed. Administration of Gln increased protein expression associated with PI3K-Akt signaling pathway, while reducing G6PC and FOXO1 expression in the hepatocytes that may promote glycogen synthesis and inhibit gluconeogenesis. These findings suggest that obese mice treated with Gln-containing high-fat diet may normalize blood glucose and improve IR in response to limb ischemia.