Fatty acid amide hydrolase is lower in young cannabis users.

We have recently shown that levels of fatty acid amide hydrolase (FAAH), the enzyme that metabolizes the endocannabinoid anandamide, are lower in the brains of adult cannabis users (CUs) (34 ± 11 years of age), tested during early abstinence. Here, we examine replication of the lower FAAH levels in a separate, younger cohort (23 ± 5 years of age). Eighteen healthy volunteers (HVs) and fourteen CUs underwent a positron emission tomography scan using the FAAH radioligand [11 C]CURB. Regional [11 C]CURB binding was calculated using an irreversible two-tissue compartment model with a metabolite-corrected arterial plasma input function. The FAAH C385A genetic polymorphism (rs324420) was included as a covariate. All CUs underwent a urine screen to confirm recent cannabis use and had serum cannabinoids measured. One CU screened negative for cannabinoids via serum and was removed from analysis. All HVs reported less than five lifetime cannabis exposures more than a month prior to study initiation. There was a significant effect of group (F1,26 = 4.31; P = .048) when two A/A (rs324420) HVs were removed from analysis to match the genotype of the CU group (n = 16 HVs, n = 13 CUs). Overall, [11 C]CURB λk3 was 12% lower in CU compared with HV. Exploratory correlations showed that lower brain [11 C]CURB binding was related to greater use of cannabis throughout the past year. We confirmed our previous report and extended these findings by detecting lower [11 C]CURB binding in a younger cohort with less cumulative cannabis exposure.

Imaging Brain Fatty Acid Amide Hydrolase in Untreated Patients With Psychosis.

BACKGROUND: The brain's endocannabinoid system, the primary target of cannabis, has been implicated in psychosis. The endocannabinoid anandamide is elevated in cerebrospinal fluid of patients with schizophrenia. Fatty acid amide hydrolase (FAAH) controls brain anandamide levels; however, it is unknown if FAAH is altered in vivo in psychosis or related to positive psychotic symptoms. METHODS: Twenty-seven patients with schizophrenia spectrum disorders and 36 healthy control subjects completed high-resolution positron emission tomography scans with the novel FAAH radioligand [11C]CURB and structural magnetic resonance imaging. Data were analyzed using the validated irreversible 2-tissue compartment model with a metabolite-corrected arterial input function. RESULTS: FAAH did not differ significantly between patients with psychotic disorders and healthy control subjects (F1,62.85 = 0.48, p = .49). In contrast, lower FAAH predicted greater positive psychotic symptom severity, with the strongest effect observed for the positive symptom dimension, which includes suspiciousness, delusions, unusual thought content, and hallucinations (F1,26.69 = 12.42, p = .002; Cohen's f = 0.42, large effect). Shorter duration of illness (F1,26.95 = 13.78, p = .001; Cohen's f = 0.39, medium to large effect) and duration of untreated psychosis predicted lower FAAH (F1,26.95 = 6.03, p = .021, Cohen's f = 0.27, medium effect). These results were not explained by past cannabis exposure or current intake of antipsychotic medications. FAAH exhibited marked differences across brain regions (F7,112.62 = 175.85, p < 1 × 10-56; Cohen's f > 1). Overall, FAAH was higher in female subjects than in male subjects (F1,62.84 = 10.05, p = .002; Cohen's f = 0.37). CONCLUSIONS: This first study of brain FAAH in psychosis indicates that FAAH may represent a biomarker of disease state of potential utility for clinical studies targeting psychotic symptoms or as a novel target for interventions to treat psychotic symptoms.

A systematic review of phytocannabinoid exposure on the endocannabinoid system: Implications for psychosis.

Cannabis, the most widely used illicit drug worldwide, produces psychoactive effects through its component cannabinoids, which act on the endocannabinoid system. Research on how cannabinoid exposure affects the endocannabinoid system is limited. Substantial evidence indicates cannabis use as a risk factor for psychosis, and the mechanism(s) by which this is occurring is/are currently unknown. Here, we conduct the first review of the effects of exogenous cannabinoids on the endocannabinoid system in humans with and without psychotic disorders. The most well established finding is the down-regulation of cannabinoid CB1 receptors (CB1R) after chronic and recent cannabis exposure, but it remains uncertain whether this effect is present in cannabis users with schizophrenia. We highlight where cannabis exposure affects the endocannabinoid system in a pattern that may mirror what is seen in psychosis, and how further research can push this field forward. In these times of changing cannabis legislation, research highlighting the biological effects of cannabinoids is greatly needed.

Sphingolipid changes do not underlie fatty acid-evoked GLUT4 insulin resistance nor inflammation signals in muscle cells.

Ceramides contribute to obesity-linked insulin resistance and inflammation in vivo, but whether this is a cell-autonomous phenomenon is debated, particularly in muscle, which dictates whole-body glucose uptake. We comprehensively analyzed lipid species produced in response to fatty acids and examined the consequence to insulin resistance and pro-inflammatory pathways. L6 myotubes were incubated with BSA-adsorbed palmitate or palmitoleate in the presence of myriocin, fenretinide, or fumonisin B1. Lipid species were determined by lipidomic analysis. Insulin sensitivity was scored by Akt phosphorylation and glucose transporter 4 (GLUT4) translocation, while pro-inflammatory indices were estimated by IκBα degradation and cytokine expression. Palmitate, but not palmitoleate, had mild effects on Akt phosphorylation but significantly inhibited insulin-stimulated GLUT4 translocation and increased expression of pro-inflammatory cytokines Il6 and Ccl2 Ceramides, hexosylceramides, and sphingosine-1-phosphate significantly heightened by palmitate correlated negatively with insulin sensitivity and positively with pro-inflammatory indices. Inhibition of sphingolipid pathways led to marked changes in cellular lipids, but did not prevent palmitate-induced impairment of insulin-stimulated GLUT4 translocation, suggesting that palmitate-induced accumulation of deleterious lipids and insulin resistance are correlated but independent events in myotubes. We propose that muscle cell-endogenous ceramide production does not evoke insulin resistance and that deleterious effects of ceramides in vivo may arise through ancillary cell communication.

Saturated fatty acids activate caspase-4/5 in human monocytes, triggering IL-1ß and IL-18 release.

Obesity is associated with metabolic tissue infiltration by monocyte-derived macrophages. Saturated fatty acids contribute to proinflammatory gene induction in tissue-embedded immune cells. However, it is unknown how circulating monocytes, the macrophage precursors, react to high-fat environments. In macrophages, saturated fatty acids activate inflammatory pathways and, notably, prime caspase-associated inflammasomes. Inflammasome-activated IL-1ß contributes to type 2 diabetes. We hypothesized that 1) human monocytes from obese patients show caspase activation, and 2) fatty acids trigger this response and consequent release of IL-1ß/IL-18. Human peripheral blood monocytes were sorted by flow cytometry, and caspase activity was measured with a FLICA dye-based assay. Blood monocytes from obese individuals exhibited elevated caspase activity. To explore the nature and consequence of this activity, human THP1 monocytes were exposed to saturated or unsaturated fatty acids. Caspase activity was revealed by isoform-specific cleavage and enzymatic activity; cytokine expression/release was measured by qPCR and ELISA. Palmitate, but not palmitoleate, increased caspase activity in parallel to the release of IL-1ß and IL-18. Palmitate induced eventual monocyte cell death with features of pyroptosis (an inflammation-linked cell death program involving caspase-4/5), scored through LDH release, vital dye influx, cell volume changes, and nuclear morphology. Notably, selective gene silencing or inhibition of caspase-4/5 reduced palmitate-induced release of IL-1ß and IL-18. In summary, monocytes from obese individuals present elevated caspase activity. Mechanistically, palmitate activates a pyroptotic program in monocytes through caspase-4/5, causing inflammatory cytokine release, additional to inflammasomes. These caspases represent potential, novel, therapeutic targets to taper obesity-associated inflammation.