Propionate functions as a feeding state-dependent regulatory metabolite to counter proinflammatory signaling linked to nutrient load and obesity

Generally, fasting and refeeding confer anti- and proinflammatory effects, respectively. In humans, these caloric-load interventions function, in part, via regulation of CD4+ T cell biology. However, mechanisms orchestrating this regulation remain incomplete. We employed integrative bioinformatics of RNA sequencing and high-performance liquid chromatography-mass spectrometry data to measure serum metabolites and gene expression of peripheral blood mononuclear cells isolated from fasting and refeeding in volunteers to identify nutrient-load metabolite-driven immunoregulation. Propionate, a short chain fatty acid (SCFA), and the SCFA-sensing G protein-coupled receptor 43 (ffar2) were coordinately and inversely regulated by fasting and refeeding. Propionate and free fatty acid receptor agonists decreased interferon-γ and interleukin-17 and significantly blunted histone deacetylase activity in CD4+ T cells. Furthermore, propionate blunted nuclear factor κB activity and diminished interleukin-6 release. In parallel, propionate reduced phosphorylation of canonical T helper 1 (TH1) and TH17 regulators, STAT1 and STAT3, respectively. Conversely, knockdown of free fatty acid receptors significantly attenuated the anti-inflammatory role of propionate. Interestingly, propionate recapitulated the blunting of CD4+ TH cell activation in primary cells from obese individuals, extending the role of this metabolite to a disease associated with low-grade inflammation. Together, these data identify a nutrient-load responsive SCFA-G protein-coupled receptor linked pathway to regulate CD4+ TH cell immune responsiveness.

Changes in striatal dopamine metabolism during the development of morphine physical dependence in rats: observations using in vivo microdialysis

The present study examined the effect of prolonged morphine treatment on striatal dopamine (DA) release and metabolism, during the initial phase of the development of morphine dependence. Sprague-Dawley rats were implanted with chronic guides for microdialysis of the striatum. Morphine (two 75-mg pellets, subcutaneous implant) or placebo was given (12 hr) to pentobarbital anesthetized animals. Following recovery from anesthesia, morphine physical dependence was verified by the naloxone-evoked abstinence syndrome. Morphine produced significant increases in the dialysate level of DA nad its metabolites (DOPAC and HVA) above baseline compared to placebo treatment. HVA levels began to increase immediately following morphine administration, whereas DA and DOPAC levels began to increase after a latency of one and three hr, respectively. Morphine effects on striatal DA metabolism included changes in the metabolic disposition of DA. Increases in HVA concentration accompanied increases in DOPAC concentration up to a threshold value of DOPAC efflux; further increases in DOPAC level were associated with decreases in HVA level. These in vivo data suggest that morphine-induced changes in the regulation of striatal dopaminergic function may be an important component of the development of physical dependence.

Circadian rhythms of plasma corticosterone binding activity in the rat and the mouse

Corticosterone binding activity (CBA) and corticosteroids were measured by competitive protein binding techniques in plasma samples drawn from rats and mice at different times of day. Circacian rhythms of plasma CBA were found in both rats (onset of 14-h daily photoperiod: 0600) and mice (onset of 14-h daily photoperiod: 0700). The plasma CBA rhythm was bimodal in rats with peaks at 1000 and 1800 and unimodal in mice with peak level from 0100 to 0500. Circadian rhythms of plasma corticosteroid concentration with peaks during the late afternoon were confirmed in both rats and mice. The plasma CBA rhythms appear to be related to the circadian rhythms of both locomotor activity and plasma corticosteroid concentration.