Assessment of the Effects of Dietary Vitamin D Levels on Olanzapine-Induced Metabolic Side Effects: Focus on the Endocannabinoidome-Gut Microbiome Axis.

Vitamin D deficiency is associated with poor mental health and dysmetabolism. Several metabolic abnormalities are associated with psychotic diseases, which can be compounded by atypical antipsychotics that induce weight gain and insulin resistance. These side-effects may be affected by vitamin D levels. The gut microbiota and endocannabinoidome (eCBome) are significant regulators of both metabolism and mental health, but their role in the development of atypical antipsychotic drug metabolic side-effects and their interaction with vitamin D status is unknown. We studied the effects of different combinations of vitamin D levels and atypical antipsychotic drug (olanzapine) exposure on whole-body metabolism and the eCBome-gut microbiota axis in female C57BL/6J mice under a high fat/high sucrose (HFHS) diet in an attempt to identify a link between the latter and the different metabolic outputs induced by the treatments. Olanzapine exerted a protective effect against diet-induced obesity and insulin resistance, largely independent of dietary vitamin D status. These changes were concomitant with olanzapine-mediated decreases in Trpv1 expression and increases in the levels of its agonists, including various N-acylethanolamines and 2-monoacylglycerols, which are consistent with the observed improvement in adiposity and metabolic status. Furthermore, while global gut bacteria community architecture was not altered by olanzapine, we identified changes in the relative abundances of various commensal bacterial families. Taken together, changes of eCBome and gut microbiota families under our experimental conditions might contribute to olanzapine and vitamin D-mediated inhibition of weight gain in mice on a HFHS diet.

Three of a Kind: Control of the Expression of Liver-Expressed Antimicrobial Peptide 2 (LEAP2) by the Endocannabinoidome and the Gut Microbiome.

The endocannabinoidome (expanded endocannabinoid system, eCBome)-gut microbiome (mBIome) axis plays a fundamental role in the control of energy intake and processing. The liver-expressed antimicrobial peptide 2 (LEAP2) is a recently identified molecule acting as an antagonist of the ghrelin receptor and hence a potential effector of energy metabolism, also at the level of the gastrointestinal system. Here we investigated the role of the eCBome-gut mBIome axis in the control of the expression of LEAP2 in the liver and, particularly, the intestine. We confirm that the small intestine is a strong contributor to the circulating levels of LEAP2 in mice, and show that: (1) intestinal Leap2 expression is profoundly altered in the liver and small intestine of 13 week-old germ-free (GF) male mice, which also exhibit strong alterations in eCBome signaling; fecal microbiota transfer (FMT) from conventionally raised to GF mice completely restored normal Leap2 expression after 7 days from this procedure; in 13 week-old female GF mice no significant change was observed; (2) Leap2 expression in organoids prepared from the mouse duodenum is elevated by the endocannabinoid noladin ether, whereas in human Caco-2/15 epithelial intestinal cells it is elevated by PPARγ activation by rosiglitazone; (3) Leap2 expression is elevated in the ileum of mice with either high-fat diet-or genetic leptin signaling deficiency-(i.e., ob/ob and db/db mice) induced obesity. Based on these results, we propose that LEAP2 originating from the small intestine may represent a player in eCBome- and/or gut mBIome-mediated effects on food intake and energy metabolism.

Alterations of brain endocannabinoidome signaling in germ-free mice.

We investigated the hypothesis that the endocannabinoidome (eCBome), an extension of the endocannabinoid (eCB) signaling system with important functions in the CNS, may play a role in the microbiota-gut-brain axis. Using LC-MS/MS and qPCR arrays we profiled the brain eCBome of juvenile (4 weeks) and adult (13 weeks) male and female germ-free (GF) mice, which are raised in sterile conditions and virtually devoid of microbiota, present neurophysiological deficits, and were found recently to exhibit a strongly altered gut eCBome in comparison to conventionally raised age/sex-matched controls. The causal effect of the gut microbiome on the eCBome was investigated through the re-introduction into adult male GF mice of a functional gut microbiota by fecal microbiota transfer (FMT). The concentrations of the eCB, 2-arachidonoylglycerol (2-AG), and its 2-monoacylglycerol congeners, were significantly reduced in the brain, but not in the hypothalamus, of both juvenile and adult male and adult female GF mice. FMT rendered these decreases non-statistically significant. The eCB, anandamide (AEA), and its congener N-acylethanolamines (NAEs), were instead increased in the brain of adult female GF mice. Saturated fatty acid-containing NAEs were decreased in adult male GF mouse hypothalamus in a manner not reversed by FMT. Only few changes were observed in the expression of eCBome enzymes and receptors. Our data open the possibility that altered eCBome signaling may underlie some of the brain dysfunctions typical of GF mice.