Accumulating evidence shows a strong correlation between type 2 diabetes mellitus, mitochondrial dysfunction, and oxidative stress. We evaluated the effects of dietary peanut shell extract (PSE) supplementation on mitochondrial function and antioxidative stress/inflammation markers in diabetic mice. Fourteen db/db mice were randomly assigned to a diabetic group (DM in AIN-93G diet) and a PSE group (1% wt/wt PSE in AIN-93G diet) for 5 weeks. Six C57BL/6J mice were fed with an AIN-93G diet for 5 weeks (control group). Gene and protein expression in the liver, brain, and white adipose tissue (WAT) were determined using qRT-PCR and Immunoblot, respectively. Compared to the control group, the DM group had (i) increased gene and protein expression levels of DRP1 (fission), PINK1 (mitophagy), and TNFα (inflammation) and (ii) decreased gene and protein expression levels of MFN1, MFN2, OPA1 (fusion), TFAM, PGC-1α (biogenesis), NRF2 (antioxidative stress) and IBA1 (microglial activation) in the liver, brain, and WAT of db/db mice. Supplementation of PSE into the diet restored the DM-induced changes in the gene and protein expression of DRP1, PINK1, TNFα, MFN1, MFN2, OPA1, TFAM, PGC-1α, NRF2, and IBA1 in the liver, brain, and WAT of db/db mice. This study demonstrates that PSE supplementation improved mitochondrial function in the brain, liver, and WAT of db/db mice, in part due to suppression of oxidative stress and inflammation.

Background: Neuroinflammation and mitochondrial dysfunction have been implicated in the progression of neuropathic pain (NP) but can be mitigated by supplementation with gingerol-enriched ginger (GEG). However, the exact benefits of GEG for each sex in treating neuroinflammation and mitochondrial homeostasis in different brain regions and the colon remain to be determined. Objective: Evaluate the effects of GEG on emotional/affective pain and spontaneous pain behaviors, neuroinflammation, as well as mitochondria homeostasis in the amygdala, frontal cortex, hippocampus, and colon of male and female rats in the spinal nerve ligation (SNL) NP model. Methods: One hundred rats (fifty males and fifty females) were randomly assigned to five groups: sham + vehicle, SNL + vehicle, and SNL with three different GEG doses (200, 400, and 600 mg/kg BW) for 5 weeks. A rat grimace scale and vocalizations were used to assess spontaneous and emotional/affective pain behaviors, respectively. mRNA gene and protein expression levels for tight junction protein, neuroinflammation, mitochondria homeostasis, and oxidative stress were measured in the amygdala, frontal cortex, hippocampus, and colon using qRT-PCR and Western blot (colon). Results: GEG supplementation mitigated spontaneous pain in both male and female rats with NP while decreasing emotional/affective responses only in male NP rats. GEG supplementation increased intestinal integrity (claudin 3) and suppressed neuroinflammation [glial activation (GFAP, CD11b, IBA1) and inflammation (TNFα, NFκB, IL1β)] in the selected brain regions and colon of male and female NP rats. GEG supplementation improved mitochondrial homeostasis [increased biogenesis (TFAM, PGC1α), increased fission (FIS, DRP1), decreased fusion (MFN2, MFN1) and mitophagy (PINK1), and increased Complex III] in the selected brain regions and colon in both sexes. Some GEG dose–response effects in gene expression were observed in NP rats of both sexes. Conclusions: GEG supplementation decreased emotional/affective pain behaviors of males and females via improving gut integrity, suppressing neuroinflammation, and improving mitochondrial homeostasis in the amygdala, frontal cortex, hippocampus, and colon in both male and female SNL rats in an NP model, implicating the gut–brain axis in NP. Sex differences observed in the vocalizations assay may suggest different mechanisms of evoked NP responses in females.

Objectives. The relationships among neuropathic pain, gut microbiota, microbiome-derived metabolites, and neuropathology have received increasing attention. This study examined the effects of two dosages of gingerol-enriched ginger (GEG) on mechanical hypersensitivity, anxiety-like behavior, gut microbiome composition and its metabolites, and neuropathology markers in female rats in the spinal nerve ligation (SNL) model of neuropathic pain. Methods. Forty female rats were assigned to 4 groups: sham-vehicle, SNL-vehicle, SNL+GEG at 200 mg/kg BW, and SNL+GEG at 600 mg/kg BW via oral gavage. All animals were given an AIN-93G diet for 5 weeks. Mechanical hypersensitivity was assessed by the von Frey test. Anxiety-like behavior was assessed by the open field test. Fecal microbiota composition and metabolites were determined using 16S rRNA gene sequencing and GC-MS, respectively. Neuropathology gene expression profiling of the amygdala was assessed by an nCounter^® Neuropathology pathway panel. Results. Both GEG-treated groups showed decreased mechanical hypersensitivity and anxiety-like behavior in the SNL model. Gut microbiome diversity in both GEG groups was decreased compared with untreated SNL rats. In the SNL model, phyla such as Bacteroidota, Proteobacteria and Verrucomicrobiota were decreased. Compared with the untreated SNL group, both GEG groups exhibited increased abundance of the phyla Bacteroidota (i.e., Rikenella, Alistipes, Muribaculaceae, Odoribacter), Firmicutes (i.e., UBA1819, Ruminococcaceae, Oscillospiraceae, Roseburia), and Verrucomicrobiota (i.e., Victivallis). GEG groups had higher levels of nine hydrophilic positive metabolites [val-glu, urocanic acid, oxazolidinone, L-threonine, L-norleucine, indole, imino-tryptophan, 2,3-octadiene-5,7-diyn-1-ol, and (2E)-3-(3-hydroxyphenyl) acrylaldehyde] and two hydrophilic negative metabolites [methylmalonic acid and metaphosphoric acid], as well as lower levels of five hydrophilic metabolites [xanthine, N-acetylmuramic acid, doxaprost, adenine, and 1-myristoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine]. Among the 770 neuropathology genes, 1 gene (PLA2G4A) was upregulated and 2 genes (CDK5R1 and SHH) were downregulated in SNL rats. GEG caused the upregulation of nine genes (APC, CCNH, EFNA5, GRN, HEXB, ITPR1, PCSK2, TAF9, and WFS1) and downregulation of three genes (AVP, C4A, and TSPO) in the amygdala. Conclusions. GEG supplementation mitigated pain-associated behaviors in female rats with neuropathic pain, in part by reversing the molecular neuropathology signature of the amygdala. This was associated with changes in the gut microbiome composition and fecal metabolites, which could play a role in mediating the effects of GEG on neuropathic pain.

Emerging evidence shows that the gut microbiota plays an important role in neuropathic pain (NP) via the gut–brain axis. Male rats were divided into sham, spinal nerve ligation (SNL), SNL + 200 mg GEG/kg BW (GEG200), and SNL + 600 mg GEG/kg BW (GEG600) for 5 weeks. The dosages of 200 and 600 mg GEG/kg BW for rats correspond to 45 g and 135 g raw ginger for human daily consumption, respectively. Both GEG groups mitigated SNL-induced NP behavior. GEG-supplemented animals had a decreased abundance of Rikenella, Muribaculaceae, Clostridia UCG-014, Mucispirillum schaedleri, RF39, Acetatifactor, and Clostridia UCG-009, while they had an increased abundance of Flavonifactor, Hungatella, Anaerofustis stercorihominis, and Clostridium innocuum group. Relative to sham rats, Fos and Gadd45g genes were upregulated, while Igf1, Ccl2, Hadc2, Rtn4rl1, Nfkb2, Gpr84, Pik3cg, and Abcc8 genes were downregulated in SNL rats. Compared to the SNL group, the GEG200 group and GEG600 group had increases/decreases in 16 (10/6) genes and 11 (1/10) genes, respectively. GEG downregulated Fos and Gadd45g genes and upregulated Hdac2 genes in the amygdala. In summary, GEG alleviates NP by modulating the gut microbiome and reversing a molecular neuroimmune signature.

Background: Metabolic syndrome (MetS) is characterized by chronic inflammation, oxidative stress, and mitochondrial dysfunction. MetS is associated with increased intestinal permeability and dysbiosis. The objective of this study was to investigate the effects of peanut shell extract (PSE) and luteolin (LUT) on the kidneys, colon, and ileum in a MetS-like murine model. Methods: Thirty-six male Slc6a14^y/− mice were divided into four groups: low-fat diet (LFD), high-fat diet (HFD), HFD + 200 mg PSE/kg BW (PSE, p.o.), and HFD + 100 mg LUT/kg BW (LUT, p.o.) for 4 months. Outcome measures included glucose homeostasis, intestinal permeability, gut microbiome composition, and mRNA gene expression of mitochondrial homeostasis and inflammation/oxidative stress in the kidneys, colon, and ileum. Results: HFD resulted in glucose dysregulation with hyperglycemia and insulin resistance. PSE and LUT improved insulin tolerance and beta-cell function. PSE and LUT mitigated HFD-increased serum lipopolysaccharide-binding protein concentration. Perturbations in the gut microbiome were associated with HFD, and PSE or LUT reversed some of these changes. Specifically, Phocaeicola vulgatus was depleted by HFD and reverted by PSE or LUT. Relative to the LFD group, the HFD group (1) upregulated mitochondrial fusion (MFN1, MFN2, OPA1), mitophagy (TLR4, PINK1, LC3B), and inflammation (NFκB, TNFα, IL6), and (2) downregulated mitochondrial fission (FIS1, DRP1), biosynthesis (PGC1α, NRF1, NRF2, TFAM), electron transport chain (complex I), and antioxidant enzyme (SOD1) in the kidneys, colon, and ileum. Conclusions: PSE and LUT reversed such HFD-induced changes in the aforementioned gene expression levels.

Background/Objective: There is strong evidence that the tripartite interaction between glucose homeostasis, gut microbiota, and the host immune system plays a critical role in the pathophysiology of type 2 diabetes mellitus (T2DM). We reported previously that peanut shell extract (PSE) improves mitochondrial function in db/db mice by suppressing oxidative stress and inflammation in the liver, brain, and white adipose tissue. This study evaluated the impacts of PSE supplementation on glucose homeostasis, liver histology, intestinal microbiome composition, and the innate immune response in diabetic mice. Methods: Fourteen db/db mice were randomly assigned to a diabetic group (DM, AIN-93G diet) and a PSE group (1% wt/wt PSE in the AIN-93G diet) for 5 weeks. Six C57BL/6J mice received the AIN-93G diet for 5 weeks (control group). Parameters of glucose homeostasis included serum insulin, HOMA-IR, HOMA-B, and the analysis of pancreatic tissues for insulin and glucagon. We assessed the innate immune response in the colon and liver using a microarray. Gut microbiome composition of cecal contents was analyzed using 16S rRNA gene amplicon sequencing. Results: PSE supplementation improved glucose homeostasis (decreased serum insulin concentration, HOMA-IR, and HOMA-B) and reduced hepatic lipidosis in diabetic mice. PSE supplementation reversed DM-induced shifts in the relative abundance of amplicon sequence variants of Enterorhabdus, Staphylococcus, Anaerotruncus, and Akkermansia. Relative to the DM mice, the PSE group had suppressed gene expression levels of Cd8α, Csf2, and Irf23 and increased expression levels of Tyk2, Myd88, and Gusb in the liver. Conclusions: This study demonstrates that PSE supplementation improves T2DM-associated disorders of diabetic mice, in part due to the suppression of innate immune inflammation.