Effects of soy diet on inflammation-induced primary and secondary hyperalgesia in rat

Diet can exert both analgesic and pronociceptive effects in acute and chronic pain models: a systematic review of preclinical studies

BACKGROUND

Although diet is an essential aspect of human health, the link between diet and pain is still not well understood. Preclinical animal research provides information to understand underlying mechanisms that allow identifying the needs for human research.

OBJECTIVES

This study aims to give a systematic overview of the current evidence from preclinical studies regarding the analgesic and pronociceptive effects of various diets in non-neuropathic, non-cancer, or non-visceral acute and chronic pain models.

STUDY DESIGN

A systematic Review.

SETTING

This study examined studies that investigate the analgesic and pronociceptive effects of various diets in non-neuropathic, non-cancer, or non-visceral acute and chronic pain models.

METHODS

This review was conducted following the PRISMA guidelines and was registered in PROSPERO with the registration number CRD42019133473. The certainty of evidence was examined by a modified GRADE approach.

RESULTS

After the screening process twenty-four eligible papers were included in this review. Nineteen studies examined acute pain, nine studies chronic inflammatory pain, and four studies assessed both acute and chronic pain models.

LIMITATIONS

Due to the heterogeneity of the included studies, a meta-analysis was not included in this study.

CONCLUSIONS

In animal models, excessive saturated, monounsaturated or omega-6 polyunsaturated fat ingestion and diets rich in fats and carbohydrates can decrease pain sensitivity in acute nociceptive pain, whereas it can induce mechanical allodynia and heat hyperalgesia in chronic inflammatory pain. Additionally, diets rich in anti-inflammatory ingredients, as well as a calorie-restricted diet can promote recovery from primary mechanical allodynia and heat hyperalgesia in chronic inflammatory pain.

Reduction of inflammation in chronic pancreatitis using a soy bread intervention: A feasibility study

INTRODUCTION

Chronic pancreatitis is a chronic inflammatory disease, which progresses to fibrosis. Currently there are no interventions to delay or stop the progression to irreversible organ damage. In this study, we assessed the tolerability and feasibility of administering soy bread to reduce circulating inflammatory mediators.

METHODS

Subjects with chronic pancreatitis diagnosed using the American Pancreatic Association diagnostic guidelines were enrolled. During the dose escalation (DE) phase, subjects received one week of soy bread based using a 3 + 3 dose-escalation design, which was then followed by a maximally tolerated dose (MTD) phase with four weeks of intervention. Dose-limiting toxicities (DLTs) were monitored. Plasma cytokine levels were measured using a Meso Scale Discovery multiplex assay kit. Isoflavonoid excretion in 24-h urine collection was used to measure soy bread compliance.

RESULTS

Nine subjects completed the DE phase, and one subject completed the MTD phase without any DLTs at a maximum dosage of three slices (99 mg of isoflavones) per day. Reported compliance to soy bread intervention was 98%, and this was confirmed with urinary isoflavones and their metabolites detected in all subjects. There was a significant decline in the TNF-α level during the DE phase (2.667 vs 2.382 pg/mL, p = 0.039); other levels were similar.

CONCLUSIONS

In this feasibility study, there was excellent compliance with a short-term intervention using soy bread in chronic pancreatitis. Reduction was seen in at least one pro-inflammatory cytokine with short-term intervention. Larger cohorts and longer interventions with soy are warranted to assess the efficacy of reducing pro-inflammatory mediators of disease.

Evaluation of the antirheumatic effects of isoflavone-free soy protein isolate and etanercept in rats with adjuvant-induced arthritis

IMPACT STATEMENT

In view of the partial clinical benefit and significant toxicity of traditional rheumatoid arthritis (RA) treatments, there is a growing trend to use complementary therapy. The antiarthritic activity of soy is related to the effect of soy isoflavones. However, little is known about the antiarthritic activity of soy protein itself. This study demonstrates that soy protein isolate (SPI) and etanercept (ETN), a tumor necrosis factor-α (TNF-α) inhibitor, protect rats against the effects of adjuvant-induced arthritis (AIA) by reducing inflammation (TNF-α and matrix metalloproteinase-3), autoantibody production (anticyclic citrullinated peptide), and lipid peroxidation (malondialdehyde). Only SPI improved dyslipidemia accompanied by RA, giving it the advantage of reducing cardiovascular risk. Additionally, the severity of arthritis-induced pathology, including inflammatory infiltrates, synovial hyperplasia, pannus formation, synovial vascularity, and cartilage erosions, was reduced by both SPI and ETN. This research ascertains the possible antiarthritic effect of SPI, making it a recommended alternative therapy for RA.

Laboratory environmental factors and pain behavior: the relevance of unknown unknowns to reproducibility and translation

The poor record of basic-to-clinical translation in recent decades has led to speculation that preclinical research is "irreproducible", and this irreproducibility in turn has largely been attributed to deficiencies in reporting and statistical practices. There are, however, a number of other reasonable explanations of both poor translation and difficulties in one laboratory replicating the results of another. This article examines these explanations as they pertain to preclinical pain research. I submit that many instances of apparent irreproducibility are actually attributable to interactions between the phenomena and interventions under study and "latent" environmental factors affecting the rodent subjects. These environmental variables-often causing stress, and related to both animal husbandry and the specific testing context-differ greatly between labs, and continue to be identified, suggesting that our knowledge of their existence is far from complete. In pain research in particular, laboratory stressors can produce great variability of unpredictable direction, as stress is known to produce increases (stress-induced hyperalgesia) or decreases (stress-induced analgesia) in pain depending on its parameters. Much greater attention needs to be paid to the study of the laboratory environment if replication and translation are to be improved.

Daily oral intake of β-cryptoxanthin ameliorates neuropathic pain

β-cryptoxanthin, a xanthophyll carotenoid, exerts preventive effects on various lifestyle-related diseases. Here, we found that daily oral administration of β-cryptoxanthin significantly ameliorated the development of tactile allodynia following spinal nerve injury but was ineffective in mechanical allodynia in an inflammatory pain model in mice. Our results suggest that β-cryptoxanthin supplementation would be beneficial for the prophylaxis of neuropathic pain.

Breast cancer pain management - a review of current & novel therapies

Breast cancer is one of the most prevalent cancers amongst women in the world. Unfortunately, even after adequate treatment, some patients experience severe pain either due to disease progression or due to treatment related side effects. The persistent pain causes a negative physical and psychosocial impact on patients' lives. Current rational pain management is patient-centred and requires a thorough psychological assessment. Usually adequate analgesia is achieved by adopting the WHO's three step analgesic ladder. As the disease progresses, the pain experienced by the patient also increases. This necessitates the administration of opioids and adjuvant analgesics to the breast cancer patients experiencing severe pain. However, opioid use is associated with intolerable side effects like constipation, nausea, vomiting, fear of dependence, and tolerance. Concomitant medications are required to combat these unacceptable side effects. Adjuvant analgesics need to be added to provide adequate and satisfactory analgesia. These factors worsen the psychological state of patients and deteriorate their quality of life. Hence, there is a need to develop therapeutic modalities to provide adequate analgesia with minimum side effects. This review article focuses on the current treatments available for cancer pain management, their limitations, and novel targets and non-pharmacological measures under investigation which have the potential to produce a radical change in pain management measures for the breast cancer patients.