Exosomes are a subtype of membrane-contained vesicles 40–200 nm in diameter that are secreted by cells into their surroundings. By transporting proteins, lipids, mRNA, miRNA, lncRNA, and DNA, exosomes are able to perform such vital functions as maintaining cellular homeostasis, removing cellular debris, and facilitating intercellular and interorgan communication. Exosomes travel in all body fluids and deliver their molecular messages in autocrine, paracrine as well as endocrine manners. In recent years, there has been an increased interest in studying exosomes as diagnostic markers and therapeutic targets, since in many disease conditions this machinery becomes dysregulated or hijacked by pathological processes. Additionally, delivery of exosomes and exosomal miRNA has already been shown to improve systemic metabolism and inhibit progression of cancer development in mice. However, the subcellular machinery of exosomes, including their biogenesis, release and uptake, remains largely unknown. This review will bring molecular details of these processes up to date with the goal of expanding the knowledge basis for designing impactful exosome experiments in the future.

Aging, chronic high-fat diet feeding, or housing at thermoneutrality induces brown adipose tissue (BAT) involution, a process characterized by reduction of BAT mass and function with increased lipid droplet size. Single nuclei RNA sequencing of aged mice identifies a specific brown adipocyte population of Ucp1-low cells that are pyroptotic and display a reduction in the longevity gene syntaxin 4 (Stx4a). Similar to aged brown adipocytes, Ucp1-STX4KO mice display loss of brown adipose tissue mass and thermogenic dysfunction concomitant with increased pyroptosis. Restoration of STX4 expression or suppression of pyroptosis activation protects against the decline in both mass and thermogenic activity in the aged and Ucp1-STX4KO mice. Mechanistically, STX4 deficiency reduces oxidative phosphorylation, glucose uptake, and glycolysis leading to reduced ATP levels, a known triggering signal for pyroptosis. Together, these data demonstrate an understanding of rapid brown adipocyte involution and that physiologic aging and thermogenic dysfunction result from pyroptotic signaling activation.

The challenges of achieving optimal glycemic control in type 2 diabetes highlight the need for new therapies. Inappropriately elevated endogenous glucose production (EGP) is the main source of hyperglycemia in type 2 diabetes. Since activation of central K_ATP channels suppresses EGP in non-diabetic rodents and humans, this study examined whether type 2 diabetic humans and rodents retain central regulation of EGP. The K_ATP channel activator diazoxide was administered in a randomized, placebo-controlled crossover design to eight type 2 diabetes subjects and seven age- and BMI-matched healthy controls. Comprehensive measures of glucose turnover and insulin sensitivity were performed during euglycemic ‘pancreatic’ clamp studies following diazoxide and placebo administration. Complementary rodent clamp studies were performed in Zucker Diabetic Fatty rats. In type 2 diabetes subjects, extrapancreatic K_ATP channel activation with diazoxide under fixed hormonal conditions failed to suppress EGP, while matched controls demonstrated a 27% reduction in EGP (p=0.002) with diazoxide. Diazoxide also failed to suppress EGP in diabetic rats. These results suggest that suppression of EGP by central K_ATP channel activation may be lost in type 2 diabetes. Restoration of central regulation of glucose metabolism could be a promising therapeutic target to reduce hyperglycemia in type 2 diabetes.

Mitochondrial dysfunction devastates the heart in major cardiovascular diseases, yet the mechanisms governing mitochondrial quality control remain elusive. We discovered that TIGAR (TP53-induced glycolysis and apoptosis regulator) deficiency established profound cardiac protection through developmental epigenetic programming of Parkin expression. Using mice with whole-body and cardiomyocyte-specific TIGAR knockout, we demonstrated remarkable cardioprotection following myocardial infarction with maintained ejection fraction, and complete resistance to diet-induced cardiac hypertrophy despite comparable weight gain. TIGAR deficiency triggered dramatic increases in Parkin expression across all somatic tissues except testes, where Parkin levels remained extraordinarily high (100-fold greater than cardiac levels) regardless of TIGAR status, revealing tissue-specific regulatory mechanisms. This protection was entirely Parkin dependent, as double-knockout mice lost all cardioprotective benefits. Crucially, adult TIGAR manipulation failed to alter Parkin levels, demonstrating that this pathway operated exclusively during critical developmental windows to program lifelong cardiac resilience. Whole-genome bisulfite sequencing identified reduced DNA methylation in Prkn intron 10 as the key regulatory mechanism, with CRISPR deletion dramatically increasing Parkin expression in multiple cell lines. Our findings reveal how early cardiac metabolism programs lifelong cardiac function through epigenetic mechanisms, and identify developmental metabolic programming as a potential therapeutic target for preventing both ischemic heart disease and metabolic cardiomyopathy.

Summary: Soluble NSF Attachment protein REceptor (SNARE)-mediated membrane fusion plays a crucial role not only in presynaptic vesicle exocytosis but also in postsynaptic receptor delivery. The latter is considered particularly important for long-term synaptic plasticity and learning and memory, yet underlying mechanisms including the identity of the key SNARE proteins remain elusive. Here, we investigate the role of neuronal Synaptosomal-Associated Protein-23 (SNAP-23) by analyzing pyramidal-neuron specific SNAP-23 conditional knockout (cKO) mice. SNAP-23 immunostaining in postsynaptic spines was effectively decreased in the SNAP-23 cKO hippocampus. Electrophysiological analysis of SNAP-23 deficient neurons using acute hippocampal slices showed normal basal neurotransmission in CA3-CA1 synapses with unchanged AMPA and NMDA currents. Nevertheless, we found theta-burst stimulation induced long-term potentiation (LTP) was vastly diminished in SNAP-23 cKO. Moreover, unlike syntaxin-4 cKO mice in which both basal neurotransmission and LTP decrease manifested changes in a broad set of behavioral tasks, deficits of SNAP-23 cKO is more limited to spatial memory. Our data reveal that neuronal SNAP-23 is selectively crucial for synaptic plasticity and spatial memory without affecting basal glutamate receptor function.

Adipocytes are increasingly recognized as active endocrine cells that secrete substantial quantities of EVs enriched in proteins, lipids, and nucleic acids. However, the mechanisms governing EV secretion and the dynamics of EV release in different biological contexts are not fully understood. To address this gap, we generated a novel adipocyte-specific CD63-GFP reporter mouse line, in which expression of GFP-tagged CD63 is driven by the Adiponectin promoter, enabling selective labeling and tracking of AdEVs in vivo. Using this reporter model, we examined secretion of AdEVs and their delivery to APCs within adipose tissues. Confocal imaging and flow cytometry revealed that AdEVs are actively taken up by APCs, highlighting a previously underappreciated mechanism of paracrine communication within the adipose microenvironment. To complement the in vivo studies, an in vitro system was established, allowing for the direct monitoring of EV secretion from differentiated adipocytes. APCs were isolated from subcutaneous white adipose tissues of the reporter mice and induced to differentiate into mature adipocytes. In these cells, CD63-GFP signals were observed as discrete puncta and became enriched at the plasma membrane when EV secretion was inhibited, consistent with vesicle accumulation upon blocked release. Under normal growth conditions, EVs secreted into the culture medium were concentrated and subsequently purified using size exclusion chromatography, enabling downstream functional and biochemical analyses. This platform can be applied to APCs derived from other adipose depots, such as epididymal white and brown adipose tissue, or by differentiating them into depot-specific adipocytes, thereby enabling comparisons of EV secretion among different adipocyte types. Together, these approaches introduce a robust genetic tool and a complementary in vitro system to dissect the dynamics of AdEV secretion and targeting. These advances shed light on intra-adipose cellular communication and lay the groundwork for understanding the broader metabolic influence of AdEVs in health and disease.