Distribution of membrane cholesterol of adrenal cortical cells after corticotropin stimulation.
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ABSTRACT:
SUBMITTER: Conneely OM
PROVIDER: S-EPMC1152281 | biostudies-other | 1983 Aug
REPOSITORIES: biostudies-other
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Project description:Rat adrenal 105,000 g supernatant contains two lipid moieties, 'lipid-I' and 'lipid-II' which contain non-esterified cholesterol and stimulate cholesterol side-chain cleavage in soluble or mitochondrial enzyme systems. Lipid-I contains relatively large low-density heat-stable particles, whereas lipid-II particles are smaller, more dense and heat-labile. Lipid-I and lipid-II can be separated from clear cytosol by ultracentrifugation and gel filtration respectively. Corticotropin plus cycloheximide treatment increases the non-esterified cholesterol concentrations in the lipid fractions, and stimulatory effects of lipids on cholesterol side-chain cleavage appear to correlate with non-esterified cholesterol concentrations therein. On addition of saturating amounts of cholesterol-rich lipid, pregnenolone synthesis and cholesterol binding to cytochrome P-450 are stimulated more in mitochondria from corticotropin-stimulated adrenals than in mitochondria from control or corticotropin-plus cycloheximide-stimulated adrenals. These results support the contention that the corticotropin-induced increase in mitochondrial cholesterol side-chain cleavage involves an increase in cholesterol utilization as well as an increase in cholesterol availability.
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Project description:The type 1 and type 2 cannabinoid receptors (CB1 and CB2 receptors) are class A G protein-coupled receptors (GPCRs) that are activated by endogenous lipids called endocannabinoids to modulate neuronal excitability and synaptic transmission in neurons throughout the central nervous system (CNS), and inflammatory processes throughout the body. CB1 receptor is one of the most abundant GPCRs in the CNS and is involved in many physiological and pathophysiological processes, including mood, appetite, and nociception. CB2 receptor is primarily found on immunomodulatory cells of both the CNS and the peripheral immune system. In this study, we isolated lipid raft and non-lipid raft fractions of plasma membrane (PM) from mouse cortical tissue by using cold non-ionic detergent and sucrose gradient centrifugation to study the localization of CB1 receptor and CB2 receptor. Lipid raft and non-lipid raft fractions were confirmed by flotillin-1, caveolin-1 and transferrin receptor as their protein biomarkers. Both CB1 receptor and CB2 receptor were found in non-raft compartments that is inconsistent with previous findings in cultured cell lines. This study demonstrates compartmentalization of both CB1 receptor and CB2 receptor in cortical tissue and warrants further investigation of CB1 receptor and CB2 receptor compartmental distribution in various brain regions and cell types.
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Project description:OBJECTIVE:To identify predictors of hypothalamic-pituitary-adrenal (HPA) axis recovery interval and severity of glucocorticoid withdrawal symptoms (GWS) in patients undergoing adrenalectomy for corticotropin-independent cortisol excess. DESIGN:This is a retrospective study of patients with mild autonomous cortisol excess (MACE), moderate and severe Cushing syndrome (CS) who developed adrenal insufficiency after unilateral adrenalectomy between 1998 and 2017. RESULTS:Adrenalectomy was performed in 81 patients (79% women, median age 52 years [IQR 42-62]). HPA axis recovery occurred at a median of 4.3 months (IQR 1.6-11.4) after adrenalectomy (severe CS vs moderate CS vs MACE: median 11.4 vs 2.8 vs 2.1 months, P < 0.01). Main predictors of HPA axis recovery interval included: preoperative serum cortisol concentration after 1-mg overnight dexamethasone suppression test >10 ?g/dL or >276 nmol/L (9.7 vs 1.3 months if cortisol ?10 ?g/dL or ?276 nmol/L, P < 0.01); body mass index (for every 3 kg/m2 decrease, glucocorticoid taper increased by 1 month, P < 0.05); age <45 (11.4 vs 2.3 months if ?45 years, P < 0.05); duration of symptoms prior to diagnosis >1 year (11.4 vs 2.8 months if ?1 year); moon facies (11.4 vs 2.2 months if no rounding of the face); and myopathy (13.1 vs 2.7 months if no myopathy, P < 0.05). Patients with severe CS had a higher incidence of GWS compared to patients with MACE (66.7% vs 40.0%, P < 0.05) with a median of 1 and 0 events/patient, respectively. CONCLUSIONS:The HPA axis recovery interval was the longest for patients with severe CS. Surprisingly, patients with moderate CS recovered their HPA axis as quickly as those with MACE. Glucocorticoid withdrawal symptoms were observed in all groups, with more events in patients with severe CS. This study emphasizes the need to counsel patients on expectations for HPA axis recovery and address intervention for GWS based on individual preoperative parameters.
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Project description:Aims/hypothesisDiminished cortical filamentous actin (F-actin) has been implicated in skeletal muscle insulin resistance, yet the mechanism(s) is unknown. Here we tested the hypothesis that changes in membrane cholesterol could be a causative factor, as organised F-actin structure emanates from cholesterol-enriched raft microdomains at the plasma membrane.MethodsSkeletal muscle samples from high-fat-fed animals and insulin-sensitive and insulin-resistant human participants were evaluated. The study also used L6 myotubes to directly determine the impact of fatty acids (FAs) on membrane/cytoskeletal variables and insulin action.ResultsHigh-fat-fed insulin-resistant animals displayed elevated levels of membrane cholesterol and reduced F-actin structure compared with normal chow-fed animals. Moreover, human muscle biopsies revealed an inverse correlation between membrane cholesterol and whole-body glucose disposal. Palmitate-induced insulin-resistant myotubes displayed membrane cholesterol accrual and F-actin loss. Cholesterol lowering protected against the palmitate-induced defects, whereas characteristically measured defects in insulin signalling were not corrected. Conversely, cholesterol loading of L6 myotube membranes provoked a palmitate-like cytoskeletal/GLUT4 derangement. Mechanistically, we observed a palmitate-induced increase in O-linked glycosylation, an end-product of the hexosamine biosynthesis pathway (HBP). Consistent with HBP activity affecting the transcription of various genes, we observed an increase in Hmgcr, a gene that encodes 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. In line with increased HBP activity transcriptionally provoking a membrane cholesterol-based insulin-resistant state, HBP inhibition attenuated Hmgcr expression and prevented membrane cholesterol accrual, F-actin loss and GLUT4/glucose transport dysfunction.Conclusions/interpretationOur results suggest a novel cholesterolgenic-based mechanism of FA-induced membrane/cytoskeletal disorder and insulin resistance.
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2023-09-05 | GSE242081 | GEO
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