Food Restriction Affects Inflammatory Response and Nutritional State in Tuco-tucos (Ctenomys talarum)

Abstract

Insufficient or unbalanced food intake typically has a negative impact on immune responses. The understanding of this effect is, however, hampered by the effect that food has on general condition, which, in turn, affects immunity, and the interaction among general condition, immunocompetence, and concurrent infections. The goal of this study was to determine the effects of food restriction and methionine supplementation on immunity in tuco-tucos (Ctenomys talarum). Effects of diet manipulations on nutritional state, inflammatory response to phytohemagglutinin (PHA), and other immune parameters (bacterial killing capacity, natural antibodies, and leukocyte profile) were evaluated. Health and stress parameters and endoparasite loads were assessed to understand more deeply potential effects of treatments on immune status. Individuals under food restriction presented an altered nutritional state as well as increased stress levels (higher N: L ratios) compared with individuals fed ad libitum, and a marked reduction in the inflammatory response to PHA. Supplementation with methionine did not affect any of the parameters analyzed. Endoparasite loads were not affected by treatments. Our results support the idea that food insufficiency can modulate the individual's immune responsiveness through the lack of adequate essential nutrients, metabolic fuel and energetic reserves, or by a detrimental effect of the stress caused by nutrient limitation. We show that the response to PHA previously reported as nonenergetically costly for C. talarum, implies a nutritional cost; an opposite pattern to that previously found for the adaptive antibody response to sheep red blood cells in the same species.

Individual condition and inflammatory response to PHA in the subterranean rodent Ctenomys talarum (Talas tuco-tuco): A multivariate approach

“…Given that this immune response is not energetically costly (Merlo et al, 2014b), the magnitude of this response could be independent of the general individual condition when environmental conditions are benign. The variability observed in the inflammatory response is more likely to be a consequence of different levels of infection among individuals (which is also supported by previous experiments conducted with Talas tuco-tucos in captivity; Merlo et al, 2016b), nutrition (Merlo et al, 2016a) and potentially other factors still unexplored (e.g. genetics).…”

“…There is a clear synergism between infection and poor condition (Beldomenico et al, 2008a,b), in which parasites have detrimental effects on their host condition through reduction of hostís energy reserves and nutrients (Brown and Brown, 1989;Richner et al, 1993), and, in turn, poor condition predisposes to host infections, given that immunocompetence is impaired. For C. talarum, it is known that the energetic cost of the PHA response is low (Merlo et al, 2014a), but nevertheless, a reduction of˜10% of body weight (induced by a low-calorie diet in captivity) reduces the inflammatory response to PHA in a5 4% (Merlo et al, 2016a). Also, it has been proposed that parasites trigger the activation of energy-consuming immune mechanisms (Beldomenico et al, 2008a,b;Sheldon and Verhulst, 1996), and can modulate, up-regulating or suppressing, the host resistance to other pathogens (Boughton et al, 2011;Cox, 2001).…”

Different regulation of cortisol and corticosterone in the subterranean rodent Ctenomys talarum: Responses to dexamethasone, angiotensin II, potassium, and diet

“…Nonetheless, GCs and N: L ratios might show different sensitivities in their responses to stressors and also the direction of change might vary depending on the duration of a given stressor (i.e., acute or chronic). An increase in N: L ratios, but not in cortisol levels, was reported in C. talarum subjected to a chronic restriction in food intake (though these animals were fed with limited amounts of vegetables, instead of grasses) producing a 25% decrease (Schleich et al, 2015) or 13% decrease in body mass (Merlo et al, 2016). In the last case, decreased levels of glucose, triglycerides and an inflammatory response to phytohemagglutinin also accompanied food restriction (Merlo et al 2016).…”

Prenatal predatory stress in a wild species of subterranean rodent: Do ecological stressors always have a negative effect on the offspring?

“…The leukocyte profile was used to evaluate the innate immune defenses in the juveniles (Figure b), in a similar way to that previously performed in adults of C. talarum (Cutrera et al, ; Merlo et al, ; Merlo, Cutrera, & Zenuto, ; Merlo, Cutrera, & Zenuto, ; Schleich, Zenuto, & Cutrera, ). Relative counts of each leukocyte type in blood provide information about different processes that could be occurring in the individual, such as stress (increased neutrophils: lymphocytes ratio), virus (increased lymphocyte count), bacteria and microparasites (increased neutrophil counts), allergies and parasitism (eosinophilia), infection or endocrine disorders (increased basophil count), chronic infection or inflammation (increased monocyte count; Voigt, ).…”