Adipokine Human Resistin Promotes Obesity-associated Inflammatory Intervertebral Disc Degeneration via Pro-inflammatory Cytokine Cascade Activation

Adipokine human Resistin (hResistin), is known to be associated with insulin resistance and secrete low-grade pro-inflammatory cytokines in obesity. Although studies on low-grade inflammation of adipokine hResistin are known, studies on the effects and mechanisms of intervertebral disc degeneration (IVDD) are still lacking. Thus, we investigated the adipokine hResistin with or without pro-inflammatory cytokine IL-1β in intervertebral disc (IVD) cells such as human annulus fibrosus (hAF) and nucleus pulposus (hNP). The mean optical density changes in IL-1β, IL-6, IL-8, MMP-1, MMP-3, and MMP-13, induced by the combined-hResistin and IL-1β stimulation on hAF cells, was significantly greater than that of the same induced by mono-IL-1β stimulation. Similarly, in the case of the mean optical density change of inflammatory mediators induced by the combined-hResistin and IL-1β stimulation on hNP cells was also significantly greater than that of the same induced by mono-IL-1β stimulation. These results improve understanding of hResistin on inflammatory IVDD but also with other obesity-related inflammatory diseases.

Fetal circulating human resistin increases in diabetes during pregnancy and impairs placental mitochondrial biogenesis

Background: Diabetes during pregnancy affects placental mitochondrial content and function, which has the potential to impact fetal development and the long-term health of offspring. Resistin is a peptide hormone originally discovered in mice as an adipocyte-derived factor that induced insulin resistance. In humans, resistin is primarily secreted by monocytes or macrophages. The regulation and roles of human resistin in diabetes during pregnancy remain unclear. Methods: Fetal resistin levels were measured in cord blood from pregnancies with (n=42) and without maternal diabetes (n=81). Secretion of resistin from cord blood mononuclear cells (CBMCs) was measured. The actions of human resistin in mitochondrial biogenesis were determined in placental trophoblastic cells (BeWo cells) or human placental explant.Results: Concentrations of human resistin in cord sera were higher in diabetic pregnancies (67 ng/ml) compared to healthy controls (50 ng/ml, P< 0.05), and correlated (r=0.4, P=0.002) with a measure of maternal glycemia (glucose concentration 2 h post challenge). Resistin mRNA was most abundant in cord blood mononuclear cells (CBMCs) compared with placenta and mesenchymal stem cells (MSCs). Secretion of resistin from cultured CBMCs was increased in response to high glucose (25 mM). Exposing BeWo cells or human placental explant to resistin decreased expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), mitochondrial abundance, and ATP production. Conclusions: Resistin is increased in fetal circulation of infants exposed to the diabetic milieu, potentially reflecting a response of monocytes/macrophages to hyperglycemia and metabolic stresses associated with diabetes during pregnancy. Increased exposure to resistin may contribute to mitochondrial dysfunction and aberrant energy metabolism characteristic of offspring exposed to diabetes in utero.

Fetal circulating human resistin increases in diabetes during pregnancy and impairs placental mitochondrial biogenesis

Background Diabetes during pregnancy affects placental mitochondrial content and function, which can impact fetal development and the long-term health of offspring. Resistin is a peptide hormone originally discovered in mice as an adipocyte-derived factor that induced insulin resistance. Unlike rodents, human resistin is primarily secreted by monocytes or macrophages. The regulation and roles of human resistin in diabetes during pregnancy remain unclear. Methods Human resistin levels were measured in cord blood of women with diabetes during pregnancy (n=42) and healthy controls (n=81). Secretion of resistin from cord blood mononuclear cells (CBMCs) were measured. The actions of human resistin in mitochondrial biogenesis were determined on placental trophoblastic cells (BeWo cells) or human placental explant. Results Concentrations of human resistin in cord sera were higher in diabetic pregnancies (67 ng/ml) compared to healthy controls (50 ng/ml, P< 0.05), and correlated (r=0.4, P=0.002) with a measure of maternal glycemia (glucose concentration 2 h post challenge). Resistin mRNA was most abundant in cord blood mononuclear cells (CBMCs). Secretion of resistin from cultured CBMCs was increased in response to high glucose (25 mM). Exposing BeWo cells or human placental explant to resistin decreased expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), mitochondrial abundance, and ATP production. Conclusions In summary, we have shown that resistin is increased in fetal circulation of infants exposed to the diabetic milieu potentially reflecting the response of monocytes/macrophages to hyperglycemia and metabolic stresses associated with diabetes during pregnancy. Increased exposure to resistin may contribute to mitochondrial dysfunction and aberrant energy metabolism characteristic of offspring exposed to diabetes in utero .

In Silico Analysis of Coding/Noncoding SNPs of Human RETN Gene and Characterization of Their Impact on Resistin Stability and Structure

Resistin (RETN) is a gene coding for proinflammatory adipokine called resistin secreted by macrophages in humans. Single nucleotide polymorphisms (SNPs) in RETN are linked to obesity and insulin resistance in various populations. Using dbSNP, 78 nonsynonymous SNPs (nsSNPs) were retrieved and tested on a PredictSNP 1.0 megaserver. Among these, 15 nsSNPs were predicted as highly deleterious and thus subjected to further analyses, such as conservation, posttranscriptional modifications, and stability. The 3D structure of human resistin was generated by homology modeling using Swiss model. Root-mean-square deviation (RMSD), hydrogen bonds (h-bonds), and interactions were estimated. Furthermore, UTRscan served to identify UTR functional SNPs. Among the 15 most deleterious nsSNPs, 13 were predicted to be highly conserved including variants in posttranslational modification sites. Stability analysis predicted 9 nsSNPs (I32S, C51Y, G58E, G58R, C78S, G79C, W98C, C103G, and C104Y) which can decrease protein stability with at least three out of the four algorithms used in this study. These nsSNPs were chosen for structural analysis. Both variants C51Y and C104Y showed the highest RMS deviations (1.137 Å and 1.308 Å, respectively) which were confirmed by the important decrease in total h-bonds. The analysis of hydrophobic and hydrophilic interactions showed important differences between the native protein and the 9 mutants, particularly I32S, G79C, and C104Y. Six SNPs in the 3′UTR (rs920569876, rs74176247, rs1447199134, rs943234785, rs76346269, and rs78048640) were predicted to be implicated in polyadenylation signal. This study revealed 9 highly deleterious SNPs located in the human RETN gene coding region and 6 SNPs within the 3′UTR that may alter the protein structure. Interestingly, these SNPs are worth to be analyzed in functional studies to further elucidate their effect on metabolic phenotype occurrence.

Human resistin protects against endotoxic shock by blocking LPS–TLR4 interaction

Helminths trigger multiple immunomodulatory pathways that can protect from sepsis. Human resistin (hRetn) is an immune cell-derived protein that is highly elevated in helminth infection and sepsis. However, the function of hRetn in sepsis, or whether hRetn influences helminth protection against sepsis, is unknown. Employing hRetn-expressing transgenic mice (hRETNTg+) and recombinant hRetn, we identify a therapeutic function for hRetn in lipopolysaccharide (LPS)-induced septic shock. hRetn promoted helminth-induced immunomodulation, with increased survival of Nippostrongylus brasiliensis (Nb)-infected hRETNTg+ mice after a fatal LPS dose compared with naive mice or Nb-infected hRETNTg− mice. Employing immunoprecipitation assays, hRETNTg+Tlr4−/− mice, and human immune cell culture, we demonstrate that hRetn binds the LPS receptor Toll-like receptor 4 (TLR4) through its N terminal and modulates STAT3 and TBK1 signaling, triggering a switch from proinflammatory to anti-inflammatory responses. Further, we generate hRetn N-terminal peptides that are able to block LPS proinflammatory function. Together, our studies identify a critical role for hRetn in blocking LPS function with important clinical significance in helminth-induced immunomodulation and sepsis.