Chronic inflammation is a key player in metabolic dysfunction-associated fatty liver disease (MAFLD) progression. Necroptosis, an inflammatory cell death pathway, is elevated in MAFLD patients and mouse models, yet its role is unclear due to the diverse mouse models and inhibition strategies. In our study, we inhibited necroptosis by targeting mixed lineage kinase domain-like pseudokinase (MLKL), the terminal effector of necroptosis, in a high-fat, high-fructose, high-cholesterol (HFHFrHC) mouse model of diet-induced MAFLD. Despite the HFHFrHC diet upregulating MLKL (2.5-fold), WT mice livers showed no increase in necroptosis markers or associated proinflammatory cytokines. Surprisingly, Mlkl^−/− mice experienced exacerbated liver inflammation without protection from diet-induced liver damage, steatosis, or fibrosis. In contrast, Mlkl^+/− mice showed a significant reduction in these parameters that was associated with elevated Pparα and Pparγ levels. Both Mlkl^−/− and Mlkl^+/− mice on the HFHFrHC diet resisted diet-induced obesity, attributed to the increased beiging, enhanced oxygen consumption, and energy expenditure due to adipose tissue, and exhibited improved insulin sensitivity. These findings highlight the tissue-specific effects of MLKL on the liver and adipose tissue, and they suggest a dose-dependent effect of MLKL on liver pathology.

The prevalence of childhood obesity has increased nearly ten times over the last 40 years, influenced by early life nutrients that have persistent effects on life-long metabolism. During the first six months, infants undergo accelerated adipose accumulation, but little is known regarding infant fatty acid status and its relationship to infant body composition. We tested the hypothesis that a low arachidonic to docosahexaenoic acid ratio (AA/DHA) in infant red blood cells (RBCs), a long-term indicator of fatty acid intake, would associate with more infant fat-free mass (FFM) and/or less adipose accumulation over the first 4 months of life. The fatty acid and composition of breastmilk and infant RBCs, as well as the phospholipid composition of infant RBCs, were quantified using targeted and unbiased lipid mass spectrometry from infants predominantly breastfed or predominantly formula-fed. Regardless of feeding type, FFM accumulation was inversely associated with the infant’s RBC AA/DHA ratio (p = 0.029, R² = 0.216). Infants in the lowest AA/DHA ratio tertile had significantly greater FFM when controlling for infant sex, adiposity at 2 weeks, and feeding type (p < 0.0001). Infant RBC phospholipid analyses revealed greater peroxisome-derived ether lipids in the low AA/DHA group, primarily within the phosphatidylethanolamines. Our findings support a role for a low AA/DHA ratio in promoting FFM accrual and identify peroxisomal activity as a target of DHA in the growing infant. Both FFM abundance and peroxisomal activity may be important determinants of infant metabolism during development.

During the last century, the range of the American burying beetle (Nicrophorus americanus Olivier) has been reduced by >90%. Only isolated, extant populations of this federally threatened species now exist, primarily in the Great Plains. Although the primary reason for this decline remains unclear, anthropogenic changes to habitat and vertebrate food sources used for reproduction have played a significant role. Other factors may be contributing to the decline, but little research has been conducted on understanding predators of N. americanus and how the beetle avoids them. Herein, we document a new predatory species for N. americanus, the northern short-tailed shrew (Blarina brevicauda Say), and report anecdotal evidence that beetles may avoid the musky scent of this predator. In June 2019, we observed the death of at least 2 N. americanus in the presence of a male B. brevicauda in a baited pitfall trap in Tripp County, South Dakota. In August 2020, we observed predation of carrion beetles by a female B. brevicauda that did not produce any noticeable scent. In 2019, after predation and with the presence of the male's musky scent, we noted avoidance of the baited trap by carrion beetles (Silphidae) for the remainder of the 5-day sampling period. Understanding potential predators of and predator avoidance by N. americanus will help aid recovery efforts and improve trapping protocols.

Nicrophorusis a genus of beetles that bury and transform small vertebrate carcasses into a brood ball coated with their oral and anal secretions to prevent decay and that will serve as a food source for their young.Nicrophorus pustulatusis an unusual species with the ability to overtake brood of other burying beetles and whose secretions, unlike otherNicrophorusspecies, has been reported not to exhibit antimicrobial properties. This work aims to better understand how the presence or absence of a food source influences the expression of genes involved in the feeding process ofN.pustulatus. To achieve that, total RNA was extracted from pooled samples of salivary gland tissue fromN.pustulatusand sequenced using an Illumina platform. The resulting reads were used to assemble ade novotranscriptome using Trinity. Duplicates with more than 95% similarity were removed to obtain a “unigene” set. Annotation of the unigene set was done using the Trinotate pipeline. Transcript abundance was determined using Kallisto and differential gene expression analysis was performed using edgeR. A total of 651 genes were found to be differentially expressed, including 390 upregulated and 261 downregulated genes in fed insects compared to starved. Several genes upregulated in fed beetles are associated with the insect immune response and detoxification processes with only one transcript encoding for the antimicrobial peptide (AMP) defensin. These results confirm thatN.pustulatusdoes not upregulate the production of genes encoding AMPs during feeding. This study provides a snapshot of the changes in gene expression in the salivary glands ofN.pustulatusfollowing feeding while providing a well described transcriptome for the further analysis of this unique burying beetle.

The largest North American Silphidae, the American burying beetle (ABB), Nicrophorus americanus Olivier, has been extirpated from ∼90% of its historic range and is federally threatened. Two distinct populations in the Southern (Oklahoma and Arkansas) and North-Central United States (Nebraska and South Dakota) persist at the western edge of the ABB's former range. In Nebraska, the western limits of occurrence are associated with Merritt Reservoir and linked irrigation canals. ABBs are also found at the nearby hand-planted McKelvie National Forest. While habitat alteration and fragmentation are likely the primary reasons for ABB decline, few studies have examined their response to human habitat modifications unrelated to urbanization or agricultural conversion. Through five-day sampling periods with carrion-baited pitfall traps, ABB were captured and recorded in June and August from 2015 to 2017 at Merritt Reservoir and McKelvie National Forest in Cherry County, Nebraska. Traps were placed in transects (N = 4) at each location with reservoir traps set at the shoreline, transition, and upland habitats and forest traps set in the prairie, transition zone, and pine forest. At Merritt Reservoir, 651 ABB were captured, with significantly more collected at the shoreline. Concurrently, 23 ABB were captured at McKelvie Forest, with more ABB found within the forest compared to nearby prairie. These findings support previous suggestions that the western distribution of ABB is limited by moisture. Further investigation may indicate that reliable soil moisture associated with altered habitats in Nebraska could support ABB and potentially allow western range expansion.