Dietary supplementation of gingerols- and shogaols-enriched ginger root extract attenuate pain-associated behaviors while modulating gut microbiota and metabolites in rats with spinal nerve ligation

Neuroinflammation is a central factor in neuropathic pain (NP). Ginger is a promising bioactive compound in NP management due to its anti-inflammatory property. Emerging evidence suggests that gut microbiome and gut-derived metabolites play a key role in NP. We evaluated the effects of two ginger root extracts rich in gingerols (GEG) and shogaols (SEG) on pain sensitivity, anxiety-like behaviors, circulating cell-free mitochondrial DNA (ccf-mtDNA), gut microbiome composition, and fecal metabolites in rats with NP. Sixteen male rats were divided into four groups: sham, spinal nerve ligation (SNL), SNL+0.75%GEG in diet, and SNL+0.75%SEG in diet groups for 30 days. Compared to SNL group, both SNL+GEG and SNL+SEG groups showed a significant reduction in pain- and anxiety-like behaviors, and ccf-mtDNA level. Relative to the SNL group, both SNL+GEG and SNL+SEG groups increased the relative abundance of Lactococcus, Sellimonas, Blautia, Erysipelatoclostridiaceae, and Anaerovoracaceae, but decreased that of Prevotellaceae UCG-001, Rikenellaceae RC9 gut group, Mucispirillum and Desulfovibrio, Desulfovibrio, Anaerofilum, Eubacterium siraeum group, RF39, UCG-005, Lachnospiraceae NK4A136 group, Acetatifactor, Eubacterium ruminantium group, Clostridia UCG-014, and an uncultured Anaerovoracaceae. GEG and SEG had differential effects on gut-derived metabolites. Compared to SNL group, SNL+GEG group had higher level of 1'-acetoxychavicol acetate, (4E)-1,7-Bis(4-hydroxyphenyl)-4-hepten-3-one, NP-000629, 7,8-Dimethoxy-3-(2-methyl-3-buten-2-yl)-2H-chromen-2-one, 3-{[4-(2-Pyrimidinyl)piperazino]carbonyl}-2-pyrazinecarboxylic acid, 920863, and (1R,3R,7R,13S)-13-Methyl-6-methylene-4,14,16-trioxatetracyclo[11.2.1.0∼1,10∼.0∼3,7∼]hexadec-9-en-5-one, while SNL+SEG group had higher level for (±)-5-[(tert-Butylamino)-2'-hydroxypropoxy]-1_2_3_4-tetrahydro-1-naphthol and dehydroepiandrosteronesulfate. In conclusion, ginger is a promising functional food in the management of NP, and further investigations are necessary to assess the role of ginger on gut-brain axis in pain management.

Response of exercise-onset vasodilator kinetics to L-citrulline supplementation during different phases of the menstrual cycle

The purpose of this study was to determine whether L-citrulline (CIT) supplementation during the follicular and luteal phases of the menstrual cycle would present differential effects on vasodilator kinetics in dynamically contracting muscle. Twenty-four women were studied during the follicular (day 15 after onset of menses, n = 13) or the luteal phase (day 25 after onset of menses, n = 11). Supplementation with CIT (6g/day) or placebo occurred 7-days prior to testing in a crossover design across two menstrual cycles. Forearm vascular conductance (FVC) was calculated from blood flow and mean arterial pressure measured continuously during handgrip exercise performed at 10% maximal grip strength. FVC was calculated for each duty cycle (contract:relax, 1:2s) and expressed as a change from baseline (ΔFVC) before being fit with a monoexponential model. Amplitude of the ΔFVC response and the number of duty cycles for ΔFVC to reach 63% of steady-state amplitude (τΔFVC) were derived from the model. Analysis of variance showed no difference in the amplitude of ΔFVC between CIT and placebo (p = .45) or between menstrual cycle phases (p = .11). Additionally, τΔFVC was not different (p = .35) between CIT and placebo in women tested during the follicular (6 ± 3 versus 5 ± 3 duty cycles) or luteal phase (9 ± 1 versus 8 ± 1 duty cycles) although τΔFVC was found to be slower for women tested during the luteal as compared to the follicular phase (8 ± 4 versus 5 ± 3 duty cycles, p = .02). These results indicate that exercise-onset vasodilator kinetics is unaltered with CIT supplementation in young healthy women irrespective of menstrual cycle phase.

Dietary Supplementation of Gingerols- and Shogaols-Enriched Ginger Root Extracts Attenuate Pain-Associated Behaviors in Animals with Spinal Nerve Ligation

Objectives

Neuropathic pain (NP), arising from damage to the nervous system, could be a consequence of the imbalance between reactive oxygen species (ROS) and endogenous antioxidants after nerve injury, leading to neuroinflammation. Therefore, this study was to evaluate the effects of two ginger root extracts rich in gingerols and shogoals, respectively, on pain sensitivity and anxiety-like behaviors in neuropathic animals. We also assessed the plasma circulating cell-free mitochondrial DNA (ccf-mtDNA) damage, a biomarker of excessive mitochondria-derived ROS linked to inflammation.

Methods

Sixteen male rats were randomly divided into 4 groups: sham group, spinal nerve ligation (SNL) group as the pain control group, SNL+ gingerols-enriched ginger (GEG) extract group, and SNL+ shogoals-enriched ginger (SEG) extract group. Animals in GEG and SEG groups were fed with their respective diets on the day of SNL surgery for 30 days. At 1 day before and 10, 20, and 30 days post operation, (i) paw withdrawal mechanical thresholds were measured using von Frey filaments for pain sensory assessment; and (ii) center frequency and center duration in the open field test (OFT) were measured to assess anxiety-like behavior. At Day 30, plasma was obtained for ccf-mtDNA concentration measurement. Data were analyzed by one-way ANOVA or one-way repeated measures analysis of variance follow by post-hoc analysis.

Results

Compared to the sham group, the SNL group had significant greater pain sensitivity to mechanical stimuli. When compared to the SNL group, both GEG and SEG groups showed significantly (50%) reduced pain sensitivity (increased thresholds) as early as at 10 days and sustained at 30 days. Relative to the SNL group, both GEG and SEG groups also had less anxiety-like behavior (as indicated by the elongated center duration and increased center frequency in OFT). The SNL group had significantly higher plasma ccf-mtDNA levels relative to the sham group. When SNL-animals were fed a diet supplemented with either gingerols or shogaols, both groups showed reduction in plasma ccf-mtDNA.

Conclusions

Both gingerols and shogaols supplementation decreased pain sensitivity and improved anxiety-like behavior mediated in part through the suppression of mitochondrial damage.

Funding Sources

Texas Tech University Health Sciences Center.