Adolescent exposure to low-dose THC disrupts energy balance and adipose organ homeostasis in adulthood.

One of cannabis' most iconic effects is the stimulation of hedonic high-calorie eating-the "munchies"-yet habitual cannabis users are, on average, leaner than non-users. We asked whether this phenotype might result from lasting changes in energy balance established during adolescence, when use of the drug often begins. We found that daily low-dose administration of cannabis' intoxicating constituent, Δ9-tetrahydrocannabinol (THC), to adolescent male mice causes an adult metabolic phenotype characterized by reduced fat mass, increased lean mass and utilization of fat as fuel, partial resistance to diet-induced obesity and dyslipidemia, enhanced thermogenesis, and impaired cold- and ß-adrenergic receptor-stimulated lipolysis. Further analyses revealed that this phenotype is associated with molecular anomalies in the adipose organ, including ectopic overexpression of muscle-associated proteins and heightened anabolic processing. Thus, adolescent exposure to THC may promote an enduring "pseudo-lean" state that superficially resembles healthy leanness but might in fact be rooted in adipose organ dysfunction.

Diet-Induced Obesity Disrupts Histamine-Dependent Oleoylethanolamide Signaling in the Mouse Liver.

INTRODUCTION: Previous work suggests the existence of a paracrine signaling mechanism in which histamine released from visceral mast cells into the portal circulation contributes to fasting-induced ketogenesis by stimulating biosynthesis of the endogenous high-affinity PPAR-α agonist oleoylethanolamide (OEA). METHODS: Male C57Bl/6J mice were rendered obese by exposure to a high-fat diet (HFD; 60% fat). We measured histamine, OEA, and other fatty-acid ethanolamides by liquid-chromatography/mass spectrometry, gene transcription by RT-PCR, protein expression by ELISA, neutral lipid accumulation in the liver using Red Oil O and BODIPY staining, and collagen levels using picrosirius red staining. RESULTS: Long-term exposure to HFD suppressed both fasting-induced histamine release into portal blood and histamine-dependent OEA production in the liver. Additionally, subchronic OEA administration reduced lipid accumulation, inflammatory responses, and fibrosis in the liver of HFD-exposed mice. DISCUSSION: The results suggest that disruption of histamine-dependent OEA signaling in the liver might contribute to pathology in obesity-associated liver steatosis.

Frequent Low-Dose Δ9-Tetrahydrocannabinol in Adolescence Disrupts Microglia Homeostasis and Disables Responses to Microbial Infection and Social Stress in Young Adulthood.

BACKGROUND: During adolescence, microglia are actively involved in neocortical maturation while concomitantly undergoing profound phenotypic changes. Because the teenage years are also a time of experimentation with cannabis, we evaluated whether adolescent exposure to the drug's psychotropic constituent, Δ9-tetrahydrocannabinol (THC), might persistently alter microglia function. METHODS: We administered THC (5 mg/kg, intraperitoneal) once daily to male and female mice from postnatal day (PND) 30 to PND44 and examined the transcriptome of purified microglia in adult animals (PND70 and PND120) under baseline conditions or following either of two interventions known to recruit microglia: lipopolysaccharide injection and repeated social defeat. We used high-dimensional mass cytometry by time-of-flight to map brain immune cell populations after lipopolysaccharide challenge. RESULTS: Adolescent THC exposure produced in mice of both sexes a state of microglial dyshomeostasis that persisted until young adulthood (PND70) but receded with further aging (PND120). Key features of this state included broad alterations in genes involved in microglia homeostasis and innate immunity along with marked impairments in the responses to lipopolysaccharide- and repeated social defeat-induced psychosocial stress. The endocannabinoid system was also dysfunctional. The effects of THC were prevented by coadministration of either a global CB1 receptor inverse agonist or a peripheral CB1 neutral antagonist and were not replicated when THC was administered in young adulthood (PND70-84). CONCLUSIONS: Daily low-intensity CB1 receptor activation by THC during adolescence may disable critical functions served by microglia until young adulthood with potentially wide-ranging consequences for brain and mental health.

NAAA-regulated lipid signaling governs the transition from acute to chronic pain.

Chronic pain affects 1.5 billion people worldwide but remains woefully undertreated. Understanding the molecular events leading to its emergence is necessary to discover disease-modifying therapies. Here we show that N-acylethanolamine acid amidase (NAAA) is a critical control point in the progression to pain chronicity, which can be effectively targeted by small-molecule therapeutics that inhibit this enzyme. NAAA catalyzes the deactivating hydrolysis of palmitoylethanolamide, a lipid-derived agonist of the transcriptional regulator of cellular metabolism, peroxisome proliferator-activated receptor-α (PPAR-α). Our results show that disabling NAAA in spinal cord during a 72-h time window following peripheral tissue injury halts chronic pain development in male and female mice by triggering a PPAR-α-dependent reprogramming of local core metabolism from aerobic glycolysis, which is transiently enhanced after end-organ damage, to mitochondrial respiration. The results identify NAAA as a crucial control node in the transition to chronic pain and a molecular target for disease-modifying medicines.