Oral supplementations with GLN+ALA or DIP are effective in attenuating oxidative stress and the proinflammatory responses induced by endotoxemia in mice.

In trained rats, oral supplementation with DIP or GLN+ALA solution increased the expression of muscle HSP70, favored muscle l-glutamine/GSH status and improved redox defenses, which attenuate markers of muscle damage, thus improving the beneficial effects of high-intensity exercise training.

We evaluated the effects of chronic oral supplementation with L-glutamine and L-alanine in their free form or as the dipeptide L-alanyl-L-glutamine (DIP) on muscle damage, inflammation and cytoprotection, in rats submitted to progressive resistance exercise (RE). Wistar rats (n 8/group) were submitted to 8-week RE, which consisted of climbing a ladder with progressive loads. In the final 21 d before euthanasia, supplements were delivered in a 4 % solution in drinking water. Glutamine, creatine kinase (CK), lactate dehydrogenase (LDH), TNF-α, specific IL (IL-1β, IL-6 and IL-10) and monocyte chemoattractant protein-1 (MCP-1) levels were evaluated in plasma. The concentrations of glutamine, TNF-α, IL-6 and IL-10, as well as NF-κB activation, were determined in extensor digitorum longus (EDL) skeletal muscle. HSP70 level was assayed in EDL and peripheral blood mononuclear cells (PBMC). RE reduced glutamine concentration in plasma and EDL (P < 0·05 v. sedentary group). However, L-glutamine supplements (L-alanine plus L-glutamine (GLN + ALA) and DIP groups) restored glutamine levels in plasma (by 40 and 58 %, respectively) and muscle (by 93 and 105 %, respectively). GLN + ALA and DIP groups also exhibited increased level of HSP70 in EDL and PBMC, consistent with the reduction of NF-κB p65 activation and cytokines in EDL. Muscle protection was also indicated by attenuation in plasma levels of CK, LDH, TNF-α and IL-1β, as well as an increase in IL-6, IL-10 and MCP-1. Our study demonstrates that chronic oral L-glutamine treatment (given with L-alanine or as dipeptide) following progressive RE induces cyprotective effects mediated by HSP70-associated responses to muscle damage and inflammation.

Aging is an intricate process modulated by different molecular and cellular events, such as genome instability, epigenetic and transcriptional changes, molecular damage, cell death and senescence, inflammation, and metabolic dysfunction. Particularly, protein quality control (chaperone systems) tends to be negatively affected by aging, thus leading to cellular senescence in metabolic tissues and, as a consequence, to the increasing dissemination of inflammation throughout the body. The heat shock (HS) response and its associated expression of the 70 kDa family of heat shock proteins (HSP70), which are anti-inflammatory molecular chaperones, are found to be markedly decreased during muscle inactivity and aging, while evidence supports the loss of HSP70 as a key mechanism which may drive muscle atrophy, contractile dysfunction, and reduced regenerative capacity. In addition, abnormal stress response is linked with higher incidence of neurodegenerative diseases as well as low-grade inflammatory diseases that are associated with physical inactivity and obesity. Therefore, strategies to increase or, at least, to maintain the levels of HSP70, and its accompanying HS response to stress, are key to reduce biological cell dysfunctions that occur in aging. In this sense, physical exercise is of note as it is the most powerful inducer of the HS response, comparable only to heat stress and fever-like conditions. On the other hand, the amino acid L-glutamine, whose production within the skeletal muscle and liberation into the blood stream is dependent on muscle activity, is a potentializer of HSP70 expression and HS response, particularly via its entering in hexosamine biosynthetic pathway (HBP). Herein, we discuss the collaborative role of glutamine (and its donors/precursors) and physical exercise (mostly responsible for glutamine release into the circulation) as potential tools to increase HSP70 expression and the HS response in the elderly.

In this study we investigated the chronic effects of oral l-glutamine and l-alanine supplementation, either in their free or dipeptide form, on glutamine-glutathione (GLN-GSH) axis and cytoprotection mediated by HSP-27 in rats submitted to resistance exercise (RE). Forty Wistar rats were distributed into 5 groups: sedentary; trained (CTRL); and trained supplemented with l-alanyl-l-glutamine, l-glutamine and l-alanine in their free form (GLN+ALA), or free l-alanine (ALA). All trained animals were submitted to a 6-week ladder-climbing protocol. Supplementations were offered in a 4% drinking water solution for 21 days prior to euthanasia. Plasma glutamine, creatine kinase (CK), myoglobin (MYO), and erythrocyte concentration of reduced GSH and glutathione disulfide (GSSG) were measured. In tibialis anterior skeletal muscle, GLN-GSH axis, thiobarbituric acid reactive substances (TBARS), and the expression of heat shock factor 1 (HSF-1), 27-kDa heat shock protein (HSP-27), and glutamine synthetase were determined. In CRTL animals, high-intensity RE reduced muscle glutamine levels and increased GSSG/GSH rate and TBARS, as well as augmented plasma CK and MYO levels. Conversely, l-glutamine-supplemented animals showed an increase in plasma and muscle levels of glutamine, with a reduction in GSSG/GSH rate, TBARS, and CK. Free l-alanine administration increased plasma glutamine concentration and lowered muscle TBARS. HSF-1 and HSP-27 were high in all supplemented groups when compared with CTRL (p < 0.05). The results presented herein demonstrate that l-glutamine supplemented with l-alanine, in both a free or dipeptide form, improve the GLN-GSH axis and promote cytoprotective effects in rats submitted to high-intensity RE training.

Fasting is known to cause physiological changes in the endocrine pancreas, including decreased insulin secretion and increased reactive oxygen species (ROS) production. However, there is no consensus about the long-term effects of intermittent fasting (IF), which can involve up to 24 hours of fasting interspersed with normal feeding days. In the present study, we analyzed the effects of alternate-day IF for 12 weeks in a developing and healthy organism. Female 30-day-old Wistar rats were randomly divided into two groups: control, with free access to standard rodent chow; and IF, subjected to 24-hour fasts intercalated with 24-hours of free access to the same chow. Alternate-day IF decreased weight gain and food intake. Surprisingly, IF also elevated plasma insulin concentrations, both at baseline and after glucose administration collected during oGTT. After 12 weeks of dietary intervention, pancreatic islets displayed increased ROS production and apoptosis. Despite their lower body weight, IF animals had increased fat reserves and decreased muscle mass. Taken together, these findings suggest that alternate-day IF promote β -cell dysfunction, especially in developing animals. More long-term research is necessary to define the best IF protocol to reduce side effects.

AimsChronic high fat consumption has been shown to modulate nutrient transporter content in the intestine of obese mice; however it is unclear if this regulation occurs before or after the establishment of obesity, and the underlying molecular mechanism requires elucidation.Main methodsTowards this goal C57BL/6 mice were fed a low fat diet (LFD) or high fat diet (HFD), and specific protein and gene expression levels were assessed for up to 12 weeks. Similar experiments were also performed with leptin-deficient (Ob/Ob) mice.Key findingsThe results showed that the HFD group presented decreased GLUT2, PEPT1, FAT/CD36 and NPC1L1, and increased NHE3, MTTP and L-FABP content. Animals fed an HFD also presented enhanced lipid transporter gene expression of Slc27a4, Npc1l1, Cd36, Mttp and L-Fabp. Additionally, FAT/CD36 and NPC1L1 protein levels were reduced in both HFD-induced obese and Ob/Ob mice. Ob/Ob mice also exhibited increased Slc2a2 and Slc15a1 mRNAs expression, but the protein expression levels remained unchanged. The HFD also attenuated PKA and PKC activities. The inhibition of PKA was associated with decreased FAT/CD36 content, whereas increased L-FABP levels likely depend on CREB activation, independent of PKA. It is plausible that the HFD-induced changes in NPC1L1, MTTP and L-FABP protein content involve regulation at the level of transcription. Moreover, the changes in GLUT2 and PEPT1 content might be associated with low PKC activity.SignificanceThe results indicated that an HFD is capable of reducing nutrient transporter content, possibly attenuating nutrient uptake into the intestine, and may represent a feedback mechanism for regulating body weight. Furthermore, the elevated levels of NHE3, L-FABP and MTTP may account for the increased prevalence of hypertension and dyslipidemia in obese individuals. All of these changes are potentially linked to reduced PKA or PKC activities.

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