Advancing metabolism research to overcome low litter survival in metabolically stressed mice

A High-Fat and High-Fructose Diet Exacerbates Liver Dysfunction by Regulating Sirtuins in a Murine Model

Metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly emerging as the most prevalent chronic liver disease, closely linked to the escalating rates of diabesity. The Western diet's abundance of fat and fructose significantly contributes to MASLD, disrupting hepatic glucose metabolism. We previously demonstrated that a high-fat and high-fructose diet (HFHFD) led to increased body and liver weight compared to the low-fat diet (LFD) group, accompanied by glucose intolerance and liver abnormalities, indicating an intermediate state between fatty liver and liver fibrosis in the HFHFD group. Sirtuins are crucial epigenetic regulators associated with energy homeostasis and play a pivotal role in these hepatic dysregulations. Our investigation revealed that HFHFD significantly decreased Sirt1 and Sirt7 gene and protein expression levels, while other sirtuins remained unchanged. Additionally, glucose 6-phosphatase (G6Pase) gene expression was reduced in the HFHFD group, suggesting a potential pathway contributing to fibrosis progression. Chromatin immunoprecipitation analysis demonstrated a significant increase in histone H3 lysine 18 acetylation within the G6Pase promoter in HFHFD livers, potentially inhibiting G6Pase transcription. In summary, HFHFD may inhibit liver gluconeogenesis, potentially promoting liver fibrosis by regulating Sirt7 expression. This study offers an epigenetic perspective on the detrimental impact of fructose on MASLD progression.

Parent-offspring cannibalism throughout the animal kingdom: a review of adaptive hypotheses

Parents that kill and consume their offspring often appear to be acting against their own reproductive interests. Yet parent-offspring cannibalism is common and taxonomically widespread across the animal kingdom. In this review, I provide an overview of our current understanding of parent-offspring cannibalism, which has seen a proliferation in adaptive hypotheses over the past 20 years for why parents consume their own young. I review over four decades of research into this perplexing behaviour, drawing from work conducted on fishes, reptiles, insects, birds, and mammals among other taxa. Many factors have been hypothesised to explain parent-offspring cannibalism in nature, including poor parental energy reserves, small or large brood sizes, low or uncertain parentage, and high brood densities, and additional factors are still being uncovered. Parent-offspring cannibalism does not appear to have a single predominant explanation; rather, the factor, or set of factors, that govern its expression is largely taxon specific. Parents may either consume all offspring under their care (full-brood cannibalism) or consume a fraction of their offspring (partial brood cannibalism). These forms of cannibalism are thought to provide adaptive benefits to cannibals under a range of circumstances, primarily by allowing parents to allocate parental efforts more optimally - energy from eating (some of) one's current offspring can be redirected to other offspring, or to parental growth, survival, and ultimately to other future reproductive endeavours. Thus, parent-offspring cannibalism is a phenotypically plastic trait that responds to changing environmental, social, and physiological conditions. The expression of parent-offspring cannibalism in any given system is intimately linked to the reproductive value of current young relative to parents' expectations for future reproduction, and also to whether parental care is predominantly depreciable or non-depreciable. Furthermore, parent-offspring cannibalism has the potential to generate conflict between the sexes, and I briefly discuss some consequences of this conflict on patterns of mate choice. Finally, there still remain many aspects of this behaviour where our understanding is poor, and I highlight these topics to help guide future research.

Switching to a Standard Chow Diet at Weaning Improves the Effects of Maternal and Postnatal High-Fat and High-Sucrose Diet on Cardiometabolic Health in Adult Male Mouse Offspring

Cardiac mitochondrial dysfunction contributes to obesity-associated heart disease. Maternal and postnatal diet plays an important role in cardiac function, yet the impacts of a mismatch between prenatal and postweaning diet on cardiometabolic function are not well understood. We tested the hypothesis that switching to a standard chow diet after weaning would attenuate systemic metabolic disorders and cardiac and mitochondrial dysfunction associated with maternal and postnatal high-fat/high-sucrose (HFHS) diet in mice. Six-month-old male CD1 offspring from dams fed a HFHS diet and weaned to the same HFHS diet (HH) or switched to a standard chow diet (HC) were compared to offspring from dams fed a low-fat/low-sucrose diet and maintained on the same diet (LL). HC did not decrease body weight (BW) but normalized glucose tolerance, plasma cholesterol, LDL, and insulin levels compared to the HH. Systolic function indicated by the percent fractional shortening was not altered by diet. In freshly isolated cardiac mitochondria, maximal oxidative phosphorylation-linked respiratory capacity and coupling efficiency were significantly higher in the HC in the presence of fatty acid substrate compared to LL and HH, with modification of genes associated with metabolism and mitochondrial function. Switching to a standard chow diet at weaning can attenuate the deleterious effects of long-term HFHS in adult male mouse offspring.

Effects of non-aversive versus tail-lift handling on breeding productivity in a C57BL/6J mouse colony

Non-aversive handling is a well-documented refinement measure for improving rodent welfare. Because maternal stress is related to reduced productivity, we hypothesized that welfare benefits associated with non-aversive handling would translate to higher production and fewer litters lost in a laboratory mouse breeding colony. We performed a randomized controlled trial to examine the effects of a standard method of handling (tail-lift with forceps) versus non-aversive handling with transfer tunnels ('tunnel-handled') on breeding performance in 59 C57BL/6J mouse pairs. Intervention assignments could not be concealed from technicians, but were concealed from assessors and data analyst. An operationally significant effect of tunnel-handling (large enough differences to warrant programmatic change) was defined before study initiation as a 5% increase in productivity, or one extra pup over the reproductive lifetime of each pair. Pairs were randomly allocated to handling intervention and cage rack location, and monitored over an entire 6-month breeding cycle. For each group, we measured number of pups born and weaned, and number of entire litters lost prior to weaning. Differences between transfer methods were estimated by two-level hierarchical mixed models adjusted for parental effects and parity. Compared to tail-lift mice, tunnel-handled mice averaged one extra pup per pair born (+1.0; 95% CI 0.9, 1.1; P = 0.41) and weaned (+1.1, 95% CI 0.9, 1.2; P = 0.33). More tunnel-handled pairs successfully weaned all litters produced (13/29 pairs, 45% vs 4/30 pairs, 13%; P = 0.015), averaged fewer litter losses prior to weaning (11/29 pairs [38%] vs 26/30 pairs [87%]; P <0.001), and had a 20% lower risk of recurrent litter loss. The increase in numbers of pups produced and weaned with tunnel handling met threshold requirement for operational significance. These data and projected cost savings persuaded management to incorporate tunnel handling as standard of care across the institution. These data also suggest that overlooked husbandry practices such as cage transfer may be major confounders in studies of mouse models.

Obesity, not a high fat, high sucrose diet alone, induced glucose intolerance and cardiac dysfunction during pregnancy and postpartum

Cardiovascular disease is the leading cause of death in women during pregnancy and the postpartum period. Obesity is an independent risk factor for cardiovascular diseases. Nearly 60% of women of reproductive age are considered overweight or obese, cardiovascular disease morbidity and mortality continue to be pervasive. The objective of this study was to determine the effects of an obesogenic diet on the cardiometabolic health of dams during pregnancy and postpartum. Female mice were fed either a high-fat, high-sucrose diet (HFHS) or a refined control diet (CON) for 8 weeks before initiation of pregnancy and throughout the study period. Mice in the HFHS showed two distinct phenotypes, obesity-prone (HFHS/OP) and obesity resistance (HFHS/OR). Pre-pregnancy obesity (HFHS/OP) induced glucose intolerance before pregnancy and during postpartum. Systolic function indicated by the percent fractional shortening (%FS) was significantly decreased in the HFHS/OP at late pregnancy (vs. HFHS/OR) and weaning (vs. CON), but no differences were found at 6 weeks of postpartum among groups. No induction of pathological cardiac hypertrophy markers was found during postpartum. Plasma adiponectin was decreased while total cholesterol was increased in the HFHS/OP. Our results suggested that obesity, not the diet alone, negatively affected cardiac adaptation during pregnancy and postpartum.

Effect of Chronic Western Diets on Non-Alcoholic Fatty Liver of Male Mice Modifying the PPAR-γ Pathway via miR-27b-5p Regulation

Western diets contribute to metabolic diseases. However, the effects of various diets and epigenetic mechanisms are mostly unknown. Here, six week-old C57BL/6J male and female mice were fed with a low-fat diet (LFD), high-fat diet (HFD), and high-fat high-fructose diet (HFD-HF) for 20 weeks. We determined that HFD-HF or HFD mice experienced significant metabolic dysregulation compared to the LFD. HFD-HF and HFD-fed male mice showed significantly increased body weight, liver size, and fasting glucose levels with downregulated PPARγ, SCD1, and FAS protein expression. In contrast, female mice were less affected by HFD and HFD-HF. As miR-27b contains a seed sequence in PPARγ, it was discovered that these changes are accompanied by male-specific upregulation of miR-27b-5p, which is even more pronounced in the HFD-HF group (p < 0.01 vs. LFD) compared to the HFD group (p < 0.05 vs. LFD). Other miR-27 subtypes were increased but not significantly. HFD-HF showed insignificant changes in fibrosis markers when compared to LFD. Interestingly, fat ballooning in hepatocytes was increased in HFD-fed mice compared to HFD-HF fed mice, however, the HFD-HF liver showed an increase in the number of small cells. Here, we concluded that chronic Western diet-composition administered for 20 weeks may surpass the non-alcoholic fatty liver (NAFL) stage but may be at an intermediate stage between fatty liver and fibrosis via miR-27b-5p-induced PPARγ downregulation.