BACKGROUND. Activation of the NLRP3 inflammasome is associated with metabolic dysfunction, and intermittent fasting has been shown to improve clinical presentation of NLRP3 inflammasome-linked diseases. As mitochondrial perturbations, which function as a damage-associated molecular pattern, exacerbate NLRP3 inflammasome activation, we investigated whether fasting blunts inflammasome activation via sirtuin-mediated augmentation of mitochondrial integrity. METHODS.We performed a clinical study of 19 healthy volunteers. Each subject underwent a 24-hour fast and then was fed a fixed-calorie meal. Blood was drawn during the fasted and fed states and analyzed for NRLP3 inflammasome activation. We enrolled an additional group of 8 healthy volunteers to assess the effects of the sirtuin activator, nicotinamide riboside, on NLRP3 inflammasome activation. RESULTS.In the fasting/refeeding study, individuals showed less NLRP3 inflammasome activation in the fasted state compared with that in refed conditions. In a human macrophage line, depletion of the mitochondrial-enriched sirtuin deacetylase SIRT3 increased NLRP3 inflammasome activation in association with excessive mitochondrial ROS production. Furthermore, genetic and pharmacologic SIRT3 activation blunted NLRP3 activity in parallel with enhanced mitochondrial function in cultured cells and in leukocytes extracted from healthy volunteers and from refed individuals but not in those collected during fasting. CONCLUSIONS.Together, our data indicate that nutrient levels regulate the NLRP3 inflammasome, in part through SIRT3-mediated mitochondrial homeostatic control. Moreover, these results suggest that deacetylase-dependent inflammasome attenuation may be amenable to targeting in human disease. TRIAL REGISTRATION. ClinicalTrials.gov NCT02122575 and NCT00442195.

Twenty-four hours of fasting is known to blunt activation of the human NLRP3 inflammasome. This effect might be mediated by SIRT3 activation, controlling mitochondrial reactive oxygen species. To characterize the molecular underpinnings of this fasting effect, we comparatively analyzed the NLRP3 inflammasome response to nutrient deprivation in wild-type and SIRT3 knock-out mice. Consistent with previous findings for human NLRP3, prolonged fasting blunted the inflammasome in wild-type mice but not in SIRT3 knock-out mice. In SIRT3 knock-out bone marrow-derived macrophages, NLRP3 activation promoted excess cytosolic extrusion of mitochondrial DNA along with increased reactive oxygen species and reduced superoxide dismutase 2 (SOD2) activity. Interestingly, the negative regulatory effect of SIRT3 on NLRP3 was not due to transcriptional control or priming of canonical inflammasome components but, rather, occurred via SIRT3-mediated deacetylation of mitochondrial SOD2, leading to SOD2 activation. We also found that siRNA knockdown of SIRT3 or SOD2 increased NLRP3 supercomplex formation and activation. Moreover, overexpression of wild-type and constitutively active SOD2 similarly blunted inflammasome assembly and activation, effects that were abrogated by acetylation mimic-modified SOD2. Finally, administration of lipopolysaccharide increased liver injury and the levels of peritoneal macrophage cytokines, including IL-1β, in SIRT3 KO mice. These results support the emerging concept that enhancing mitochondrial resilience against damage-associated molecular patterns may play a pivotal role in preventing inflammation and that the anti-inflammatory effect of fasting-mimetic diets may be mediated, in part, through SIRT3-directed blunting of NLRP3 inflammasome assembly and activation.

Many people of African ancestry have lower absolute neutrophil counts (ANC) without increased risk for infection. This is associated with the Duffy null phenotype (non-expression of the Duffy antigen on red blood cells), which is commonly found in those of African descent. Currently, there are no studies that compare the ANC of individuals with Duffy null phenotype to those with Duffy non-null phenotypes within a self-identified Black population. This study aimed to assess the impact of Duffy status on ANC in a healthy population of self-identified Black individuals by adding on a complete blood count with differential as well as a Duffy testing to individuals at a single primary care center. This study found that 66.7% (80/120) of Black individuals have the Duffy null phenotype, and there is a significant difference in ANC between Duffy null and Duffy non-null individuals (Median: 2,820 cells/uL vs 5,005 cells/uL; p<0.001). Additionally, 23.8% (19/80) of Duffy null individuals had an ANC<2,000 cells/uL compared to no Duffy non-null individuals. The Duffy null phenotype is clinically insignificant, but inappropriate reference ranges can propagate systemic racism. Thus, we advocate for development of Duffy null specific ANC reference ranges as well as replacing the term "benign ethnic neutropenia" with Duffy-null associated neutrophil count (DANC).

AIMSickle Cell Disease (SCD) is associated with high child mortality and birth incidence in sub-Saharan Africa. Improved SCD medical services in Ghana aims to enhance survival into adulthood, creating emerging need for transition from pediatric to adult care. Anticipating transition for adolescents with SCD, we sought to understand patient and caretaker perspectives on transition to adult care within Ghana.MATERIALS AND METHODSStructured interviews were conducted with a sample of patients ages 12–15 years and accompanying adults at Ghana’s Komfo Anokye Teaching Hospital Sickle Cell Clinic (KATH SCC) covering four areas: SCD medical knowledge, symptom self-management, psychosocial impact, and transition preparation.RESULTSIn total, 46 children (mean age 13 years) paired with 46 adults were interviewed. Most children and caretakers had some knowledge about SCD and disease management. At least one-third lacked knowledge about SCD as an inherited condition. Youth were significantly more concerned about family burden and social stigmatization than adults. Most were unaware that patients are expected to switch care to adult medical providers by age 15 years, but were willing to transfer if needed.CONCLUSIONSOur clinic-based assessment at KATH SCC identified needs of adolescents and caretakers for education and counseling about disease, self-management, transition, family burden, and stigmatization. These findings provide insights into perspectives and educational gaps of families treated for SCD. Results suggest consideration of transition planning for adolescents with SCD and their caretakers in Ghana. Generalizability of our findings and practical methods to address needs for transition within Africa remain to be tested.