Timing matters: The contribution of running during different periods of the light/dark cycle to susceptibility to activity-based anorexia in rats.

Individuals with anorexia nervosa (AN) exhibit dangerous weight loss due to restricted eating and hyperactivity. Those with AN are predominantly women and most cases have an age of onset during adolescence. Activity-based anorexia (ABA) is a rodent behavioral paradigm that recapitulates many of the features of AN including restricted food intake and hyperactivity, resulting in precipitous weight loss. In addition, there is enhanced sensitivity to the paradigm during adolescence. In ABA, animals are given time-restricted access to food and unlimited access to a running wheel. Under these conditions, most animals increase their running and decrease their food intake resulting in precipitous weight loss until they either die or researchers discontinue the paradigm. Some animals learn to balance their food intake and energy expenditure and are able to stabilize and eventually reverse their weight loss. For these studies, adolescent (postnatal day 33-42), female Sprague Dawley (n = 68) rats were placed under ABA conditions (unlimited access to a running wheel and 1.5 hrs access to food) until they either reached 25% body weight loss or for 7 days. 70.6% of subjects reached 25% body weight loss before 7 days and were designated susceptible to ABA while 29.4% animals were resistant to the paradigm and did not achieve the weight loss criterion. We used discrete time survival analysis to investigate the contribution of food intake and running behavior during distinct time periods both prior to and during ABA to the likelihood of reaching the weight loss criterion and dropping out of ABA. Our analyses revealed risk factors, including total running and dark cycle running, that increased the likelihood of dropping out of the paradigm, as well as protective factors, including age at the start of ABA, the percent of total running exhibited as food anticipatory activity (FAA), and food intake, that reduced the likelihood of dropping out. These measures had predictive value whether taken before or during exposure to ABA conditions. Our findings suggest that certain running and food intake behaviors may be indicative of a phenotype that predisposes animals to susceptibility to ABA. They also provide evidence that running during distinct time periods may reflect functioning of distinct neural circuitry and differentially influence susceptibility and resistance to the paradigm.

Single-nucleus RNA sequencing in ischemic cardiomyopathy reveals common transcriptional profile underlying end-stage heart failure.

Ischemic cardiomyopathy (ICM) is the leading cause of heart failure worldwide, yet the cellular and molecular signature of this disease is largely unclear. Using single-nucleus RNA sequencing (snRNA-seq) and integrated computational analyses, we profile the transcriptomes of over 99,000 human cardiac nuclei from the non-infarct region of the left ventricle of 7 ICM transplant recipients and 8 non-failing (NF) controls. We find the cellular composition of the ischemic heart is significantly altered, with decreased cardiomyocytes and increased proportions of lymphatic, angiogenic, and arterial endothelial cells in patients with ICM. We show that there is increased LAMININ signaling from endothelial cells to other cell types in ICM compared with NF. Finally, we find that the transcriptional changes that occur in ICM are similar to those in hypertrophic and dilated cardiomyopathies and that the mining of these combined datasets can identify druggable genes that could be used to target end-stage heart failure.

Activity-based anorexia in adolescent female rats causes changes in brain mitochondrial dynamics.

Anorexia Nervosa (AN) is associated with a high rate of morbidity and mortality as well as a high rate of relapse. The molecular mechanisms underlying the progression of the disorder or the relapses are largely unknown. Patients with AN have been shown to have increased oxidative stress, but its involvement in the development in the disease is unknown. We have previously shown that adolescent female rats undergoing the activity-based anorexia (ABA) paradigm also show signs of oxidative stress. Due to their role in the release of reactive oxygen species (ROS), mitochondria are of high interest in diseases exhibiting oxidative stress. In this study, the impact of ABA on brain mitochondrial dynamics was examined. We found transient changes in the medial prefrontal cortex, hypothalamus, and hippocampus following 25% weight loss and changes in the amygdala at a 10-day weight recovery timepoint. These changes point towards damage in the mitochondria contributing to the oxidative stress.

Discovery of Orally Bioavailable and Brain-Penetrable Prodrugs of the Potent nSMase2 Inhibitor DPTIP.

Extracellular vesicles (EVs) can carry pathological cargo and play an active role in disease progression. Neutral sphingomyelinase-2 (nSMase2) is a critical regulator of EV biogenesis, and its inhibition has shown protective effects in multiple disease states. 2,6-Dimethoxy-4-(5-phenyl-4-thiophen-2-yl-1H-imidazol-2-yl)phenol (DPTIP) is one of the most potent (IC50 = 30 nM) inhibitors of nSMase2 discovered to date. However, DPTIP exhibits poor oral pharmacokinetics (PK), limiting its clinical development. To overcome DPTIP's PK limitations, we synthesized a series of prodrugs by masking its phenolic hydroxyl group. When administered orally, the best prodrug (P18) with a 2',6'-diethyl-1,4'-bipiperidinyl promoiety exhibited >fourfold higher plasma (AUC0-t = 1047 pmol·h/mL) and brain exposures (AUC0-t = 247 pmol·h/g) versus DPTIP and a significant enhancement of DPTIP half-life (2 h vs ∼0.5 h). In a mouse model of acute brain injury, DPTIP released from P18 significantly inhibited IL-1ß-induced EV release into plasma and attenuated nSMase2 activity. These studies report the discovery of a DPTIP prodrug with potential for clinical translation.

Adolescent female rats prone to the activity based anorexia (ABA) paradigm have altered hedonic responses and cortical astrocyte density compared to resistant animals.

OBJECTIVE: Anhedonia, which in part involves the lack of pleasure in consuming palatable food, is a long-lasting symptom observed in patients both when acutely ill and when long term recovered from Anorexia Nervosa. The neurocircuitry underlying this phenomenon is not well understood. Here we use the preclinical activity-based anorexia (ABA) model in adolescent female rats to assess the impact of excessive exercise, limited food intake and acute weight loss, on adolescent female rat orofacial responding to intraoral sucrose, as measured by the taste reactivity test (TRT). Animals were identified as either prone or resistant to this paradigm based on a weight loss criterion. Measures of food intake, running wheel activity, taste reactivity and medial prefrontal cortex astrocyte expression were compared across groups. METHODS: Adolescent female rats implanted with an intraoral catheter were given a TRT using 1 M (M) sucrose at baseline, max weight loss (25% weight loss from start of ABA or 7 full days on the paradigm) or 10 days recovered from the ABA paradigm. Animals were sacrificed after the final TRT and astrocyte density was measured via immunohistochemistry. RESULTS: Animals resistant to the ABA paradigm ran less than prone animals during the ABA period. Additionally, we found that resistant animals displayed more cumulative 'liking' responses to sucrose compared to prone animals at maximum weight loss. Finally, we found prone animals 10-days recovered from ABA had reduced medial prefrontal cortex astrocyte density compared to levels in resistant animals. DISCUSSION: Rats presented with the physiological challenge of the ABA paradigm either adapt their behavior to stabilize their body weight (i.e. resistant), or rapidly lose weight (i.e. prone). Furthermore, we found that prone animals have reduced orofacial responding to 1 M sucrose at maximum weight loss compared to responses in resistant animals, and this anhedonia-like behavior may be a result of reduced astrocyte density that affects cortical function.

Activity-based anorexia disrupts systemic oxidative state and induces cortical mitochondrial fission in adolescent female rats.

OBJECTIVE: Patients with Anorexia Nervosa (AN) display increased levels of oxidative stress that correlates with disease severity. Unfortunately, the biological ramifications of AN-induced oxidative stress on the brain are largely unknown. Our lab uses the preclinical activity-based anorexia (ABA) paradigm to model symptoms of AN. The goal of the present study was to determine how ABA experience affects oxidative state and its consequences in adolescent female rats. METHOD: We compared systemic glutathione and cysteine plasma concentrations and medial prefrontal cortex (mPFC) mitochondrial fission in ABA animals at maximum weight loss or following 10-days of weight recovery to levels in age-matched sedentary (SED) control rats. RESULTS: ABA animals at maximum weight loss had significantly lower plasma levels of cysteine and glutathione compared to SED controls. Additionally, ABA animals at max weight loss have significantly more mPFC mitochondrial fission. There were no significant differences in plasma analyte levels or mitochondrial fission between weight recovered ABA animals and SED controls. DISCUSSION: These data suggest that ABA experience results in oxidative stress that is remedied after weight restoration. The long-lasting ramifications of transient periods of increased oxidative stress are unknown and can lead to significant consequences on brain function and behavior.