Biology subjects

DeMambro, V.

Publications and source records attributed to DeMambro, V..

5 recordsLinked to original sources

bioRxiv2025

Exosome Trafficking Is a Key Regulator of Adipocyte Thermogenesis

Activation of beige adipocytes enhances energy expenditure and promotes metabolic health, presenting a promising approach for combating obesity and diabetes. As part of this process, thermogenesis, fueled in part by uncoupled mitochondrial respiration, plays a central role in converting calories into thermal energy, thereby preventing their storage as fat. Here, we identify a role for exosome trafficking as an intrinsic regulator of beige adipocyte thermogenesis. Exosomes are small extracellular vesicles that mediate cell-cell and intracellular communication by transporting regulatory cargo, including microRNAs, proteins, and lipids. Using both human cells and mouse models, we show that thermogenic activation of beige adipocytes promotes the rapid release of exosomes enriched in microRNAs known to suppress thermogenic programs. Genetic or pharmacological blockade of exosome secretion attenuates thermogenesis, whereas enhancing exosome release amplifies thermogenic output. Mice deficient in the exosome secretion regulator Rab27a exhibit reduced energy expenditure in response to both cold exposure and {beta}3-adrenergic stimulation. These findings establish exosome trafficking as a key contributor to beige adipocyte thermogenic capacity, highlighting an intracellular mechanism that may be leveraged to enhance energy expenditure and treat obesity-related metabolic diseases. Significance StatementThermogenic adipocytes, including beige fat cells, help maintain energy balance by converting excess nutrients into heat, thereby reducing fat storage and supporting metabolic function. Although these cells are known to promote energy expenditure, the intracellular processes that enable their full thermogenic response are not well defined. Here, we show that exosome secretion is required for beige adipocytes to reach their full thermogenic potential. Blocking exosome release dampens this response, while boosting it amplifies thermogenic output. These findings point to exosome release as an essential part of thermogenic regulation and a potential target for improving metabolic health.

cell biology↗

bioRxiv2025

In C57Bl6 Mice, Obesity and Subsequent Weight Loss Negatively Affected the Skeleton and Shifted the Cortical Bone Metabolome

Obesity and calorie restriction each negatively affect skeletal health. Despite the negative effects of weight loss on the skeleton, obese patients are advised to lose weight via calorie restriction. Additionally, obesity and weight loss individually alter both whole-body and local metabolism. Little is known about bone quality and changes to the cortical metabolome following calorie restriction in obese preclinical models. We hypothesized that caloric restriction would worsen bone quality in obese mice by shifting the cortical bone metabolome. To induce obesity, 8-week-old male and female C57BL6/J mice received 60% high-fat diet for 12 weeks. From 20 to 30 weeks of age, mice either remained obese or lost weight through 30% caloric restriction. Control animals received a 10% low-fat diet. Bodyweight and fat mass were increased by obesity and decreased with calorie restriction. Similarly, glucose and insulin tolerance were worsened with obesity but improved by weight loss. Compared to obesity, calorie restriction elicited more bone loss in both cortical and trabecular compartments. Weight loss also reduced bone formation. Both obesity and subsequent calorie restriction altered the cortical bone metabolome in a sex-dependent manner. Metabolic pathways altered with diet generally mapped to amino acid or fatty acid metabolism. In males, weight loss was associated with a downregulation of pathways related to tryptophan, tyrosine, ubiquinone, and fatty acids. In females, calorie restriction downregulated taurine and hypotaurine metabolism but upregulated pyrimidine metabolism, nicotinate and nicotinamide metabolism, and pantothenate and CoA biosynthesis. Our findings highlight the negative effects of obesity and subsequent caloric restriction on the skeleton. Despite improvements in components of systemic metabolism, caloric restriction in obese preclinical models did not restore bone morphology or the cortical metabolome to control conditions.

cell biology↗

bioRxiv2022

The Fatty Acid Binding Protein Family Represents a Novel Target in Multiple Myeloma

BackgroundMultiple myeloma is an incurable plasma cell malignancy with only a 53% 5-year survival rate, highlighting a critical need for new multiple myeloma vulnerabilities and therapeutic avenues. Herein, we explored a novel multiple myeloma target: the fatty acid binding protein (FABP) family. MethodsMyeloma cells treated with FABP inhibitors (BMS3094013 and SBFI-26) were examined in vivo and in vitro for cell cycle, proliferation, apoptosis, mitochondrial membrane potential, cellular metabolism (oxygen consumption rates and fatty acid oxidation), and DNA methylation. Myeloma cell responses to BMS309403 and/or SBFI-26 were assessed with RNA-sequencing and proteomic analysis, and confirmed with western blotting and qRT-PCR. Myeloma cell dependency on FABPs was assessed using DepMap. Finally, MM patient datasets (CoMMpass and GEO) were mined for FABP expression correlations with clinical outcomes. ResultsMyeloma cells treated with FABPi or with FABP5 knockout (generated via CRISPR/Cas9 editing) exhibited diminished proliferation in vitro. FABPi had potent anti- tumor effects both in vitro and in vivo in two pre-clinical MM mouse models where increased mouse survival was observed. FABPi negatively impacted mitochondrial respiration and reduced expression of MYC and other key signaling pathways in MM cells. Clinical data demonstrated worse overall and progression-free survival in patients with high FABP5. ConclusionsThis study establishes the FABP family as a therapeutically actionable dependency in multiple myeloma with a multitude of actions and cellular roles that result in the support of myeloma progression. Statement of translational relevanceMultiple myeloma (MM) is an incurable disease of the plasma cell and MM patients require better treatments as soon as possible. The fatty acid binding protein (FABP) family plays a number of roles in cells, including supporting fatty acid oxidation, lipid shuttling and signal transduction. Here, we demonstrate with CoMMpass and other clinical data that FABPs represent a biomarker for aggressive disease in MM, and are a novel, targetable protein family expressed by myeloma cells. Pharmacologically inhibiting FABPs kills tumor cells and induces cell cycle arrest in vitro and in pre-clinical models. Mechanisms of action are multitudinous, as we discovered with RNA-sequencing, proteomic analysis, and phenotyping assays. Cell metabolism, cell signaling, cell stress, and epigenetic signatures were altered in MM cells when FABPs were inhibited. In summary, targeting FABP5 holds great therapeutic potential for killing diseased cells, with few negative off-target effects on healthy cells.

cancer biology↗

bioRxiv2022

A Single Multipurpose FSH-Blocking Therapeutic for Osteoporosis and Obesity

Pharmacological and genetic studies over the past decade have established FSH as an actionable target for diseases affecting millions, notably osteoporosis, obesity and Alzheimers disease (AD). Blocking FSH action prevents bone loss, fat gain and AD-like features in mice. We recently developed a first-in-class, humanized, epitope-specific FSH blocking antibody, MS-Hu6, with a KD of 7.52 nM. Using a GLP-compliant platform, we now report the efficacy of MS-Hu6 in preventing obesity and osteoporosis in mice, and parameters of acute safety in monkeys. Biodistribution studies using 89Zr-labelled, biotinylated or unconjugated MS-Hu6 in mice and monkeys showed localization to bone, bone marrow and fat depots. MS-Hu6 displayed a {beta} phase t[1/2] of 13 days (316 hours) in humanized Tg32 mice, and bound endogenous FSH. We tested 215 variations of excipients using the protein thermal shift assay to generate a final formulation that rendered MS-Hu6 stable in solution upon freeze-thaw and at different temperatures, with minimal aggregation, and without self-, cross-, or hydrophobic interactions or appreciable binding to relevant human antigens. MS-Hu6 showed the same level of "humanness" as human IgG1 in silico, and was non-immunogenic in ELISPOT assays for IL-2 and IFN{gamma} in human peripheral blood mononuclear cell cultures. We conclude that MS-Hu6 is efficacious, durable and manufacturable, and is therefore poised for future human testing as a multipurpose therapeutic.

pharmacology and toxicology↗

bioRxiv2018

Re-Evaluating One-step Generation of Mice Carrying Conditional Alleles by CRISPR-Cas9-Mediated Genome Editing Technology

CRISPR-Cas9 gene editing technology has considerably facilitated the generation of mouse knockout alleles, relieving many of the cumbersome and time-consuming steps of traditional mouse embryonic stem cell technology. However, the generation of conditional knockout alleles remains an important challenge. An earlier study reported up to 16% efficiency in generating conditional knockout alleles in mice using 2 single guide RNAs (sgRNA) and 2 single-stranded oligonucleotides (ssODN) (2sgRNA-2ssODN). We re-evaluated this method from a large data set generated from a consortium consisting of 17 transgenic core facilities or laboratories or programs across the world. The dataset constituted 17,887 microinjected or electroporated zygotes and 1,718 live born mice, of which only 15 (0.87%) mice harbored 2 correct LoxP insertions in cis configuration indicating a very low efficiency of the method. To determine the factors required to successfully generate conditional alleles using the 2sgRNA-2ssODN approach, we performed a generalized linear regression model. We show that factors such as the concentration of the sgRNA, Cas9 protein or the distance between the placement of LoxP insertions were not predictive for the success of this technique. The major predictor affecting the methods success was the probability of simultaneously inserting intact proximal and distal LoxP sequences, without the loss of the DNA segment between the two sgRNA cleavage sites. Our analysis of a large data set indicates that the 2sgRNA-2ssODN method generates a large number of undesired alleles (>99%), and a very small number of desired alleles (<1%) requiring, on average 1,192 zygotes.

genetics↗