Effects of dietary glutamine supplementation on immune cell polarization and muscle regeneration in diabetic mice with limb ischemia.

PURPOSE: Diabetes is a chronic inflammatory disorder resulting in endothelial dysfunction which contributes to peripheral arterial disease and limb ischemia. Leukocytes play critical roles in vascular and tissue remodelling after ischemia. This study investigated the effects of dietary glutamine (GLN) supplementation on immune cell polarization in diabetic mice subjected to limb ischemia. METHODS: Diabetes was induced by an intraperitoneal injection of streptozotocin for 5 consecutive days in C57BL/6J mice. Diabetic mice were fed the AIN-93 diet or an AIN-93 diet in which a part of the casein was replaced by GLN. After 3 weeks of the dietary intervention, mice were subjected to unilateral femoral artery ligation to induce limb ischemia. RESULTS: GLN supplementation enhanced the proportion of anti-inflammatory monocytes and regulatory T cells in the blood. Expression of C-C motif chemokine receptor 5 by activated CD4+ T cells was promoted and prolonged in the GLN-supplemented group. GLN downregulated the percentage of M1 macrophages in muscle tissues which was correlated with lower levels of C-C motif chemokine ligand 2 in plasma. The muscle M1/M2 ratio was also reduced in the GLN group. Gene expression of interleukin-6 was suppressed by GLN supplementation, while expression levels of the peroxisome proliferator-activated receptor γ and myogenic differentiation 1 genes were elevated in post-ischemic muscles. Histological findings also indicated that muscle regeneration was accelerated in the GLN group. CONCLUSIONS: GLN supplementation in diabetic mice may exert more-balanced polarization of CD4+ T cells, monocytes, and macrophages, thus attenuating inflammatory responses and contributing to muscle regeneration after limb ischemia.

Dietary glutamine supplementation enhances endothelial progenitor cell mobilization in streptozotocin-induced diabetic mice subjected to limb ischemia.

Diabetes is a metabolic disorder with increased risk of vascular diseases. Tissue ischemia may occur with diabetic vascular complications. Bone marrow-derived endothelial progenitor cells (EPCs) constitute a reparative response to ischemic injury. This study investigated the effects of oral glutamine (GLN) supplementation on circulating EPC mobilization and expression of tissue EPC-releasing markers in diabetic mice subjected to limb ischemia. Diabetes was induced by a daily intraperitoneal injection of streptozotocin for 5 days. Diabetic mice were divided into 2 nonischemic groups and 6 ischemic groups. One of the nonischemic and 3 ischemic groups were fed the control diet, while the remaining 4 groups received diets with identical components except that part of the casein was replaced by GLN. The respective diets were fed to the mice for 3 weeks, and then the nonischemic mice were sacrificed. Unilateral hindlimb ischemia was created in the ischemic groups, and mice were sacrificed at 1, 7 or 21 days after ischemia. Their blood and ischemic muscle tissues were collected for further analyses. Results showed that plasma matrix metallopeptidase (MMP)-9 and the circulating EPC percentage increased after limb ischemia in a diabetic condition. Compared to groups without GLN, GLN supplementation up-regulated plasma stromal cell-derived factor (SDF)-1 and muscle MMP-9, SDF-1, hypoxia-inducible factor-1 and vascular endothelial growth factor gene expression. The CD31-immunoreactive intensities were also higher in the ischemic limb. These findings suggest that GLN supplementation enhanced circulating EPC mobilization that may promote endothelium repair at ischemic tissue in diabetic mice subjected to limb ischemia.

Temporal changes in hepatic antioxidant enzyme activities after ischemia and reperfusion in a rat liver ischemia model: effect of dietary fish oil.

This study investigated the hypothesis that administration of tilapia fish oil diet would attenuate warm liver ischemia/reperfusion injury (IRI) and whether fish oil modulates prooxidant/antioxidant status. Male Wistar rats were subjected to 30 min of approximately 70% hepatic ischemia followed by 1, 12, and 24 h reperfusion. Rats were randomly divided into three groups: sham-operated group (SO), control-warm hepatic ischemia (WI) group, and Oil-WI group given tilapia oil for 3 weeks followed by liver IRI. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured in the plasma. Levels of thiobarbituric acid reactive substances (TBARS) and antioxidant enzymes as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were measured in liver fractions. In the sham group, there was no enzymatic or histological change. I/R caused significant increase in serum AST, ALT, and tissue TBARS levels. As compared to the control group, animals treated with tilapia oil experienced a significant decrease (p < 0.05) in AST and ALT levels in reperfusion periods. Tissue TBARS levels in Oil-WI group were significantly (p < 0.05) reduced as compared to control group at 60 min after reperfusion. After ischemia, 1, 12, and 24 h of reperfusion, CAT, SOD, and GPx values were the lowest in the Oil-WI group and highest in the control group and were statistically significant (p < 0.05). Histological analysis also revealed that fish oil provided some protection compared with the control group. Tilapia oil exerts a protective effect during the early phase of reperfusion, and it modulates prooxidant/antioxidant status of rat liver subjected to warm IRI.

Fish oil-enriched diet protects against ischemia by improving angiogenesis, endothelial progenitor cell function and postnatal neovascularization.

BACKGROUND: Fish oil consumption has been associated with a reduced incidence of cardiovascular diseases. However, the precise mechanisms involved are not completely understood. Here we tested the hypothesis that a fish oil-enriched diet improves neovascularization in response to ischemia. METHODS AND RESULTS: C57Bl/6 mice were fed a diet containing either 20% fish oil, rich in long-chain n-3 polyunsaturated fatty acids (PUFAs), or 20% corn oil, rich in n-6 PUFAs. After 4 weeks, hindlimb ischemia was surgically induced by femoral artery removal. We found that blood flow recovery was significantly improved in mice fed a fish oil diet compared to those fed a corn oil diet (Doppler flow ratio (DFR) at day 21 after surgery 78 ± 5 vs. 56 ± 4; p < 0.01). Clinically, this was associated with a significant reduction of ambulatory impairment and ischemic damage in the fish oil group. At the microvascular level, capillary density was significantly improved in ischemic muscles of mice fed a fish oil diet. This correlated with increased expression of VEGF and eNOS in ischemic muscles, and higher NO concentration in the plasma. Endothelial progenitor cells (EPCs) have been shown to have an important role for postnatal neovascularization. We found that the number of EPCs was significantly increased in mice fed a fish oil diet. In addition, oxidative stress levels (DCF-DA, DHE) were reduced in EPCs isolated from mice exposed to fish oil, and this was associated with improved EPC functional activities (migration and integration into tubules). In vitro, treatment of EPCs with fish oil resulted in a significant increase of cellular migration. In addition, the secretion of angiogenic growth factors including IL6 and leptin was significantly increased in EPCs exposed to fish oil. CONCLUSION: Fish oil-enriched diet is associated with improved neovascularization in response to ischemia. Potential mechanisms involved include activation of VEGF/NO pathway in ischemic tissues together with an increase in the number and the functional activities of EPCs.

Dietary nitrate supplementation improves revascularization in chronic ischemia.

BACKGROUND: Revascularization is an adaptive repair mechanism that restores blood flow to undersupplied ischemic tissue. Nitric oxide plays an important role in this process. Whether dietary nitrate, serially reduced to nitrite by commensal bacteria in the oral cavity and subsequently to nitric oxide and other nitrogen oxides, enhances ischemia-induced remodeling of the vascular network is not known. METHODS AND RESULTS: Mice were treated with either nitrate (1 g/L sodium nitrate in drinking water) or sodium chloride (control) for 14 days. At day 7, unilateral hind-limb surgery with excision of the left femoral artery was conducted. Blood flow was determined by laser Doppler. Capillary density, myoblast apoptosis, mobilization of CD34(+)/Flk-1(+), migration of bone marrow-derived CD31(+)/CD45(-), plasma S-nitrosothiols, nitrite, and skeletal tissue cGMP levels were assessed. Enhanced green fluorescence protein transgenic mice were used for bone marrow transplantation. Dietary nitrate increased plasma S-nitrosothiols and nitrite, enhanced revascularization, increased mobilization of CD34(+)/Flk-1(+) and migration of bone marrow-derived CD31(+)/CD45(-) cells to the site of ischemia, and attenuated apoptosis of potentially regenerative myoblasts in chronically ischemic tissue. The regenerative effects of nitrate treatment were abolished by eradication of the nitrate-reducing bacteria in the oral cavity through the use of an antiseptic mouthwash. CONCLUSIONS: Long-term dietary nitrate supplementation may represent a novel nutrition-based strategy to enhance ischemia-induced revascularization.

Role of enteral nutrition and pharmaconutrients in conditions of splanchnic hypoperfusion.

In critically ill patients there is consistent evidence that significant benefits are achieved if nutrients are delivered within the gut compared with the parenteral route. However, in conditions related to gut hypoflux, enteral nutrition may play a double role in counterbalancing the installed low-flow state. On the one hand, enteral-induced postprandial hyperemia may preserve the mucosal barrier and ameliorate immune competence; on the other hand, feeding by the gut may pose a theoretical risk of intestinal ischemia. Despite limited investigation, a strategic temporary minimal enteral nutrition with hypocaloric content has been recommended recently aiming to avoid the overfeeding syndrome and the menace of gut hypoperfusion. Under these conditions, the early luminal delivery of key nutrients such as arginine, glutamine dipeptides, antioxidants, and butyrate are an attractive option for this subset of patients. Arginine may prevent intestinal injury due to hypoperfusion but may harm the gut if ischemia is established. In contrast, glutamine may promote benefits in both conditions. Further investigations by randomized trials in this field are necessary.

Phenolic content of virgin olive oil improves ischemic reactive hyperemia in hypercholesterolemic patients.

OBJECTIVES: The goal of this study was to evaluate the effects of the phenolic content of virgin olive oil on endothelial reactivity. BACKGROUND: Endothelial-dependent vasodilatation is impaired during the postprandial state, and oxidative stress could play a key role in its development. METHODS: Twenty-one hypercholesterolemic volunteers received two breakfasts, using a randomized sequential crossover design. Both arms received the same olive oil, but one had its phenolic acid content reduced from 400 to 80 ppm. Ischemic reactive hyperemia (IRH) was measured with a laser-Doppler procedure at baseline and 2 h and 4 h after oil intake. Postprandial plasma concentrations of lipid fractions, lipoperoxides (LPO), 8-epi prostaglandin-F(2alpha), and nitrates/nitrites (NO(x)) were obtained at baseline and after 2 h of the fat meal. RESULTS: The intake of the polyphenol-rich breakfast was associated with an improvement in endothelial function, as well as a greater increase in concentrations of NO(x) (p < 0.001) and a lower increase in LPO (p < 0.005) and 8-epi prostaglandin-F2alpha (p < 0.001) than the ones induced by the low polyphenol fat meal. A positive correlation was found to exist between NO(x) and enhanced endothelial function at the second hour (r = 0.669; p < 0.01). Furthermore, a negative correlation was found between IRH and LPO (r = -0.203; p < 0.05) and 8-epi prostaglandin-F2alpha levels (r = -0.440; p < 0.05). CONCLUSIONS: A meal containing high-phenolic virgin olive oil improves ischemic reactive hyperemia during the postprandial state. This phenomenon might be mediated via reduction in oxidative stress and the increase of nitric oxide metabolites.