Effect of central administration of interleukin-1 receptor antagonist on protein synthesis in skeletal muscle, kidney, and liver during sepsis

Identifying and Managing Malnutrition Stemming from Different Causes

Protein–energy malnutrition (PEM) is highly prevalent among peritoneal dialysis (PD) patients and is a strong predictor of morbidity and mortality. A wide range of factors can lead to PEM and associated wasting (PEM/W) in PD patients, but persistent inflammation and the presence of diabetes have been identified as the two main reasons. An important body of literature has been reporting studies of methods suitable for detecting malnutrition in its early phase so that appropriate intervention can be provided. Although assessment of nutrition status has been substantially improved, no definitive single method of assessing nutrition status has been decided. Rather, several different markers of nutrition should be evaluated together. Because of the complexity of treating malnutrition in PD patients, nontraditional strategies such as appetite stimulants, anti-inflammatory diets, and anti-inflammatory pharmacologic agents are recommended to be combined with more traditional forms of nutritional support, so as to provide a better chance of recovery. The present review briefly discusses the causes of PEM/W, the methods most commonly used to identify the condition, and the new management strategies available.

Androgen Action via the Androgen Receptor in Neurons Within the Brain Positively Regulates Muscle Mass in Male Mice

Although it is well established that exogenous androgens have anabolic effects on skeletal muscle mass in humans and mice, data from muscle-specific androgen receptor (AR) knockout (ARKO) mice indicate that myocytic expression of the AR is dispensable for hind-limb muscle mass accrual in males. To identify possible indirect actions of androgens via the AR in neurons to regulate muscle, we generated neuron-ARKO mice in which the dominant DNA binding-dependent actions of the AR are deleted in neurons of the cortex, forebrain, hypothalamus, and olfactory bulb. Serum testosterone and luteinizing hormone levels were elevated twofold in neuron-ARKO males compared with wild-type littermates due to disruption of negative feedback to the hypothalamic-pituitary-gonadal axis. Despite this increase in serum testosterone levels, which was expected to increase muscle mass, the mass of the mixed-fiber gastrocnemius (Gast) and the fast-twitch fiber extensor digitorum longus hind-limb muscles was decreased by 10% in neuron-ARKOs at 12 weeks of age, whereas muscle strength and fatigue of the Gast were unaffected. The mass of the soleus muscle, however, which consists of a high proportion of slow-twitch fibers, was unaffected in neuron-ARKOs, demonstrating a stimulatory action of androgens via the AR in neurons to increase the mass of fast-twitch hind-limb muscles. Furthermore, neuron-ARKOs displayed reductions in voluntary and involuntary physical activity by up to 60%. These data provide evidence for a role of androgens via the AR in neurons to positively regulate fast-twitch hind-limb muscle mass and physical activity in male mice.

Expression of myeloid differentiation factor 88 in neurons is not requisite for the induction of sickness behavior by interleukin-1β

Background

Animals respond to inflammation by suppressing normal high-energy activities, including feeding and locomotion, in favor of diverting resources to the immune response. The cytokine interleukin-1 beta (IL-1β) inhibits normal feeding and locomotor activity (LMA) via its actions in the central nervous system (CNS). Behavioral changes in response to IL-1β are mediated by myeloid differentiation factor 88 (MyD88) in non-hematopoietic cells. It is unknown whether IL-1β acts directly on neurons or requires transduction by non-neuronal cells.

Methods

The Nestin-cre mouse was crossed with MyD88^lox mice to delete MyD88 from neurons and glia in the CNS (MyD88^ΔCNS). These mice were compared to total body MyD88KO and wild type (WT) mice. Mice had cannulae stereotactically placed in the lateral ventricle and telemetry transponders implanted into the peritoneum. Mice were treated with either intracerebroventricular (i.c.v.) IL-1β (10 ng) or vehicle. Food intake, body weight and LMA were continuously monitored for 24 h after treatment. I.c.v. tumor necrosis factor (TNF), a MyD88-independent cytokine, was used to control for normal immune development. Peripheral inflammation was modeled using intraperitoneal lipopolysaccharide (LPS). Groups were compared using two-way ANOVA with Bonferroni post-test. Efficacy of recombination was evaluated using tdTomato reporter mice crossed with the Nestin-cre mouse. MyD88 deletion was confirmed by Western blot.

Results

I.c.v. IL-1β treatment caused a significant reduction in feeding, body weight and LMA in WT mice. MyD88KO mice were protected from these changes in response to i.c.v. IL-1β despite having intact behavioral responses to TNF. Cre-mediated recombination was observed in neurons and astrocytes, but not microglia or endothelial cells. In contrast to MyD88KO mice, the behavioral responses of MyD88^ΔCNS mice to i.c.v. IL-1β or intraperitoneal (i.p.) LPS were indistinguishable from those of WT mice.

Conclusion

Sickness behavior is mediated by MyD88 and is dependent on the activity of cytokines within the brain. Our results demonstrate that MyD88 is not required in neurons or astrocytes to induce this behavioral response to IL-1β or LPS. This suggests that a non-Nestin expressing cell population responds to IL-1β in the CNS and transduces the signal to neurons controlling feeding and activity.

Central nervous system inflammation induces muscle atrophy via activation of the hypothalamic-pituitary-adrenal axis

Systemic and CNS-delimited inflammation triggers skeletal muscle catabolism in a manner dependent on glucocorticoid signaling.

Skeletal muscle catabolism is a co-morbidity of many chronic diseases and is the result of systemic inflammation. Although direct inflammatory cytokine action on muscle promotes atrophy, nonmuscle sites of action for inflammatory mediators are less well described. We demonstrate that central nervous system (CNS)–delimited interleukin 1β (IL-1β) signaling alone can evoke a catabolic program in muscle, rapidly inducing atrophy. This effect is dependent on hypothalamic–pituitary–adrenal (HPA) axis activation, as CNS IL-1β–induced atrophy is abrogated by adrenalectomy. Furthermore, we identified a glucocorticoid-responsive gene expression pattern conserved in models of acute and chronic inflammatory muscle atrophy. In contrast with studies suggesting that the direct action of inflammatory cytokines on muscle is sufficient to induce catabolism, adrenalectomy also blocks the atrophy program in response to systemic inflammation, demonstrating that glucocorticoids are requisite for this process. Additionally, circulating levels of glucocorticoids equivalent to those produced under inflammatory conditions are sufficient to cause profound muscle wasting. Together, these data suggest that a significant component of inflammation-induced muscle catabolism occurs indirectly via a relay in the CNS.

Chronic intracerebroventricular TLQP-21 delivery does not modulate the GH/IGF-1-axis and muscle strength in mice

OBJECTIVE

Biallelic ablation of VGF determines a dwarf phenotype. VGF precursor protein encodes for different biologically active peptides none of which has been related to growth or muscular abnormalities. Here we present the first attempt to fill this gap. We tested the hypothesis that a recently identified VGF-derived peptide, TLQP-21, shown to centrally modulate metabolic functions, could also modulate growth hormone (GH)-axis and muscle strength.

DESIGN

Adult male mice were chronically icv injected with TLQP-21 (15 microg/day for 14 days). Physiological, molecular and behavioral parameters related to the GH/IGF-1-axis were investigated.

RESULTS

Except for a reduction in the soleus weight, TLQP-21 did not affect GH/IGF-1-axis mediators, muscle strength and muscle weight.

CONCLUSIONS

Results collected exclude a role for TLQP-21 in modulating the GH/IGF1-axis and muscle functions. VGF-derived peptides involved in the dwarf phenotype of VGF-/- mice have to be identified yet.

The Effects of Perioperative Pain Management Techniques on Food Consumption and Body Weight After Laparotomy in Rats

We examined the effects of two perioperative pain management techniques on recovery after laparotomy, as assessed by body weight (BW) and food consumption (FC). All rats received a preoperative intrathecal mixture of morphine plus bupivacaine combined with one of two treatments: (a) injection of slow-release morphine at the end of the surgery or (b) an antiinflammatory drug, interleukin-1 receptor antagonist (IL-1ra), combined with the preoperative mixture. Laparotomy significantly decreased FC and BW. Both analgesic treatments resulted in a faster recovery of FC and BW. This beneficial effect was more pronounced in the group receiving preoperative analgesics combined with IL-1ra.

IMPLICATIONS

Effective perioperative pain management can improve postoperative recovery. We studied the effects of two preoperative pain management techniques on recovery after laparotomy in rats. Both analgesic treatments resulted in a faster recovery, especially preoperative analgesics combined with interleukin-1 receptor antagonist.

IL-10, IL-6, and TNF-alpha: central factors in the altered cytokine network of uremia--the good, the bad, and the ugly

It has been increasingly apparent that wasting and cardiovascular disease (CVD) is associated with a persistent systemic inflammatory response in end-stage renal disease (ESRD) patients. The reasons for the increased risk of inflammation in ESRD patients appear to be complex, including non-dialysis as well as dialysis-related factors. The combination of an impaired immune response coupled with persistent immune stimulation may have a role in the low-grade systemic inflammation and altered cytokine balance that characterizes the uremic state and which may translate into increased risk for vascular disease. The accelerated atherosclerotic process of ESRD may involve several interrelated processes, such as oxidative stress, endothelial dysfunction, and vascular calcification, in a milieu of constant low-grade inflammation with impaired function of neutrophils and T cells, as well as a dysregulated cytokine network. Although a large number of pro- and anti-inflammatory cytokines are of importance, available data suggest that the anti-inflammatory cytokine interleukin (IL)-10 and the mainly proinflammatory cytokines IL-6 and tumor necrosis factor-alpha (TNF-alpha) may play important roles in the development of Th imbalance, CVD and wasting in the uremic milieu. Given the strong association between proinflammatory cytokines and complications common in ESRD, such as vascular calcification and wasting, the potential role of both general and targeted anticytokine treatment strategies in ESRD patients needs further evaluation.

POOR NUTRITIONAL STATUS AND INFLAMMATION: Novel Approaches in an Integrated Therapy of Inflammatory-Associated Wasting in End-Stage Renal Disease

It is increasingly apparent that end-stage renal disease (ESRD) patients carry an inflammatory burden, which may play a pivotal role in the evolution of not only wasting, but also the massive increase in the relative risk of cardiovascular disease (CVD). Thus wasting is strongly associated with a persistent systemic inflammatory response, CVD, and impaired patient survival in end-stage renal disease (ESRD), as well as in other chronic diseases. Evidence suggests that a facilitative interaction between inflammatory cytokines and other factors such as poor appetite, comorbidity, acidosis, anemia, and hormonal derangements may cause wasting in this patient group. Clearly, isolated interventions in the form of nutritional energy and protein supplementation have seldom proven to be very effective in improving nutritional status and outcome in ESRD patients, presumably because of the need to attack other causative factors. Therefore, new treatment strategies must be evaluated. Strategies such as multiple appetite stimulants, various "anti-inflammatory diets," and new potentially useful anti-inflammatory pharmacologic agents may be tested alone, or in combination, to evaluate if these new therapeutic modalities can improve the outcome of ESRD patients. As the etiology of wasting in ESRD is multifactorial, we propose that its treatment must include not one, but a number of concomitant measures to provide an integrated therapy against this devastating complication.