Biology subjects

Doucette, C.

Publications and source records attributed to Doucette, C..

3 recordsLinked to original sources

bioRxiv2025

Combined Deletion of miR-27a and miR-27b Enhances Protection Against Diet-Induced Obesity

MicroRNAs (miRNAs) are frequently encoded within polycistronic clusters thought to function as coherent regulatory units, yet whether individual cluster members act cooperatively or exert distinct physiological effects remains unclear. miR-27a and miR-27b are closely related miRNAs located within separate paralogous miR-23/27/24 clusters, but their in vivo relationship is unresolved. Using isoform-specific knockout models generated by precise CRISPR-based excision of individual miRNA hairpins, we defined how miR-27a and miR-27b regulate adipose thermogenesis and systemic metabolism. High-fat feeding increased miR-27a/b expression and suppressed thermogenic gene programs in subcutaneous white adipose tissue. In primary beige and brown adipocytes, loss of either isoform produced modest activation of thermogenic programs, whereas combined deletion caused additive increases in Ucp1 expression and mitochondrial DNA content. Ex vivo heat production was significantly elevated in double-knockout adipose explants relative to wild-type and single-knockout controls. In vivo, double-knockout mice exhibited increased energy expenditure and, under high-fat diet conditions, reduced adiposity with improved glucose homeostasis compared with wild-type and single-knockout mice. In contrast to metabolic dysfunction reported following whole-cluster deletion, selective miR-27 loss reveals a protective thermogenic program. These findings demonstrate that miRNA clusters need not act as coherent regulatory modules and identify miR-27a/b as a cooperative thermogenic checkpoint with therapeutic implications. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/666011v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@7d6b74org.highwire.dtl.DTLVardef@199d56org.highwire.dtl.DTLVardef@1a87e48org.highwire.dtl.DTLVardef@fab51a_HPS_FORMAT_FIGEXP M_FIG C_FIG * CRISPR isoform-specific knockouts isolate miR-27a/b contributions to metabolism. *Dual miR-27a/b loss drives cooperative thermogenic activation. *Double knockouts enhance energy expenditure and metabolic fitness in diet-induced obesity. *miR-27a/b deletion reveals that clustered miRNAs can exert non-coherent regulatory roles.

physiology↗

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↗

bioRxiv2021

The Cardiolipin Transacylase Tafazzin Regulates Basal Insulin Secretion and Mitochondrial Function in Pancreatic Islets from Mice

ObjectiveTafazzin (TAZ) is a cardiolipin (CL) biosynthetic enzyme important for maintaining mitochondrial function. TAZ impacts both the species and content of CL in the inner mitochondrial membrane which are essential for normal cellular respiration. In pancreatic {beta}-cells, mitochondrial function is closely associated with insulin secretion. However, the role of TAZ and CL in the secretion of insulin from pancreatic islets remains unknown. MethodsMale 4-month-old doxycycline-inducible TAZ knock-down (TAZ KD) mice and wild-type littermate controls were utilized. Immunohistochemistry was used to assess {beta}-cell morphology in whole pancreas sections, while ex vivo insulin secretion, CL content, RNA-Seq analysis and mitochondrial oxygen consumption were measured from isolated islet preparations. ResultsEx vivo insulin secretion under non-stimulatory low-glucose concentrations was reduced [~]52% from islets isolated from TAZ KD mice. Mitochondrial oxygen consumption under low-glucose conditions was also reduced [~]58% in islets from TAZ KD animals. TAZ-deficiency in pancreatic islets was associated with significant alteration in CL molecular species and reduced oxidized CL content. In addition, RNA-Seq of isolated islets showed that TAZ KD increased expression of extracellular matrix genes which are linked to pancreatic fibrosis, activated stellate cells and impaired {beta}-cell function. ConclusionThese data indicate a novel role for TAZ in regulating normal {beta}-cell function, particularly under low-glucose conditions.

physiology↗