Total Western Diet Alters Mechanical and Thermal Sensitivity and Prolongs Hypersensitivity Following Complete Freund's Adjuvant in Mice.

UNLABELLED: Obesity and chronic pain are often comorbid and their rates are increasing. It is unknown whether increased pain is caused by greater weight or poor diet quality or both. Therefore, we utilized a Total Western Diet (TWD) to investigate the functional and physiologic consequences of nutritionally poor diet in mice. For 13 weeks on the commercially available TWD, based on the National Health and Nutrition Examination Survey, thresholds of TWD-fed mice significantly increased in both thermal and mechanical tests. Quantitative magnetic resonance imaging revealed a significant increase in fat mass with a concomitant decrease in lean mass in the TWD-fed mice. In addition, there were significant increases in levels of serum leptin and inflammatory cytokines. After chronic pain induction using complete Freund's adjuvant, hypersensitivity was more pronounced and significantly prolonged in the TWD-fed mice. Therefore, prolonged exposure to poor diet quality resulted in altered acute nociceptive sensitivity, systemic inflammation, and persistent pain after inflammatory pain induction. PERSPECTIVE: These results highlight the negative effects of poor diet quality with respect to recovery from hypersensitivity and susceptibility to chronic pain. A complete understanding of the impact of diet can aid in treatment and recovery dynamics in human clinical patients.

Language and motor cortex response to comprehending accidental and intentional action sentences.

Understanding the meaning of others' actions involves mentally simulating those actions by oneself. Embodied theories of language espouse a prominent role for motor simulation in reading comprehension, especially when words, sentences, or narratives portray everyday actions. Inherent in these actions is the level of agency of the actor. Motor cortex activity in response to processing action verbs has been relatively well-established. What has been less explored, however, are: (1) the neural bases of determining whether an action is intentional or accidental (agency); and (2) whether agency influences level of motor simulation. This functional MRI study investigated how language and motor areas of the brain respond to sentences depicting intentional versus accidental action. 25 healthy adults read a series of sentences in the MRI scanner and determined whether the actions described were accidental or intentional. The main results include: (1) left hemisphere language areas (left inferior frontal gyrus, LIFG; left superior temporal gyrus, LSTG), premotor cortex (PM), and presupplementary motor area (pSMA) were strongly activated by both sentence types; (2) processing accidental action, relative to intentional action, elicited greater activity in LIFG, medial prefrontal cortex (MPFC), and left amygdala; no statistically significant activity was found in the opposite contrast; and (3) greater percent signal change was observed in LIFG while processing accidental action and in right precentral gyrus for intentional action. The results of this study support language and motor region involvement in action sentence comprehension in accordance with embodiment theories. Additionally, it provides new insight into the linguistic, integrative, and emotional demands of comprehending accidental action, its underlying neural circuitry, and its relationship to intentionality bias: the predisposition to ascribe purpose to action.

Efficacy of Common Analgesics for Postsurgical Pain in Rats.

Each year, millions of rats undergo surgery for research purposes and receive analgesics to alleviate pain. We sought to evaluate the efficacy of common analgesics in tests of hot-plate nociception and postsurgical pain by using the Rat Grimace Scale. Rats received a single dose of one of several drug-dose combinations and were tested by using the hot-plate test (acute pain) or after laparotomy (with either prophylactic or intraoperative analgesic). The efficacy of analgesics for hot-plate pain was generally not predictive of efficacy for surgical pain. Carprofen and ketoprofen were rarely effective in any of the conditions tested. With the exception of the opioid buprenorphine, several of the drugs we tested required higher-than-recommended doses to alleviate pain. Taken together, our data suggest that current analgesic use frequently is insufficient, and many rats may experience significant postsurgical pain even when analgesics are used in commonly recommended doses.

Dietary influence on pain via the immune system.

Obesity rates are approaching epidemic proportions and are a significant factor in annual health care costs. In addition to cardiovascular comorbidities, the presence of diabetes and/or chronic pain is extremely high in this population of individuals. It is now well accepted that the cells of the innate (and adaptive) immune system mediate both acute and chronic pain through release of cytokines into the system. In this chapter, we outline the ways in which poor food choices and elevated adipose tissue (body fat) are likely to activate the immune system and increase inflammation and pain. In addition, we explore the ways in which a variety of foods (e.g., broccoli, ginger, grapes, and fish oils) may have anti-inflammatory effects via their direct action on cells in the immune system and on the subsequent release of inflammatory cytokines. Some foods (green tea, ginger, and broccoli) have been found to antagonize specific cell surface receptors, whereas others (grapes, soy proteins, tomatoes and ginseng) appear to reduce nuclear translocation of the major transcription factor NFκB, thereby reducing production of inflammatory cytokines. Together, we provide data in support of the use of diet interventions to reduce pain and inflammation in patients suffering from chronic pain or other inflammation-mediated disorders.