A brief historical presentation of the hypothesis on receptor–receptor interactions as an important integrative mechanism taking place at plasma membrane level is given. Some concepts derived from this integrative mechanism especially the possible assemblage of receptors in receptor mosaics (high-order receptor oligomers) and their relevance for the molecular networks associated with the plasma membrane are discussed. In particular, the Rodbell's disaggregation theory for G-proteins is revisited in the frame of receptor mosaic model. 相似文献
Betaine homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to homocysteine (Hcy), forming dimethylglycine and methionine. We previously showed that inhibiting BHMT in mice by intraperitoneal injection of S-(α-carboxybutyl)-dl-homocysteine (CBHcy) results in hyperhomocysteinemia. In the present study, CBHcy was fed to rats to determine whether it could be absorbed and cause hyperhomocysteinemia as observed in the intraperitoneal administration of the compound in mice. We hypothesized that dietary administered CBHcy will be absorbed and will result in the inhibition of BHMT and cause hyperhomocysteinemia. Rats were meal-fed every 8 hours an l-amino acid–defined diet either containing or devoid of CBHcy (5 mg per meal) for 3 days. The treatment decreased liver BHMT activity by 90% and had no effect on methionine synthase, methylenetetrahydrofolate reductase, phosphatidylethanolamine N-methyltransferase, and CTP:phosphocholine cytidylyltransferase activities. In contrast, cystathionine β-synthase activity and immunodetectable protein decreased (56% and 26%, respectively) and glycine N-methyltransferase activity increased (52%) in CBHcy-treated rats. Liver S-adenosylmethionine levels decreased by 25% in CBHcy-treated rats, and S-adenosylhomocysteine levels did not change. Furthermore, plasma choline decreased (22%) and plasma betaine increased (15-fold) in CBHcy-treated rats. The treatment had no effect on global DNA and CpG island methylation, liver histology, and plasma markers of liver damage. We conclude that CBHcy-mediated BHMT inhibition causes an elevation in total plasma Hcy that is not normalized by the folate-dependent conversion of Hcy to methionine. Furthermore, metabolic changes caused by BHMT inhibition affect cystathionine β-synthase and glycine N-methyltransferase activities, which further deteriorate plasma Hcy levels. 相似文献
Objectives: The present study investigated the effects of dl-3-n-butylphthalide on cognitive function of patients with acute ischemic stroke (AIS).
Methods: A total of 104 patients with AIS admitted between October 2012 and June 2013 were assigned to either the Treatment (standardized treatment plus dl-3-n-butylphthalide) or Control (standardized treatment alone) groups. Cognitive function was assessed by the Beijing version of the Montreal Cognitive Assessment (MoCA-BJ) and Mini-Mental State Examination (MMSE) before and 1 month after treatment, when high-sensitivity C-reactive protein (hs-CRP) and homocysteine (Hcy) were also detected. A multivariate logistic regression analysis was done for explore the independent risk factors for vascular dementia (VD).
Results: The proportion of cognitive impairment was significantly lower after treatment than before in both the Treatment (88% vs. 64%, P = 0.023) and Control (87% vs. 70%, P = 0.047) groups. Vascular dementia dropped from 30 to 10% in the Treatment (P = 0.035) and from 25.9 to 16.7% in the Control (P = 0.027) groups. Total cognitive improvement was more significant in the Treatment Group (P = 0.018); naming, memory, attention, and linguistic abilities were significantly improved (all P < 0.05). Serum Hcy and hs-CRP levels were significantly lower in the Treatment Group than in the Control Group 1 month after treatment (P < 0.05).
Discussion: Dl-3-n-butylphthalide could significantly improve the cognitive function of AIS patients 1 month after stroke. Hcy was involved in the incidence of VD 1 month after AIS. However, further studies are necessary because of differences between groups at baseline. 相似文献
Hyperhomocysteinemia and the activation of kynurenine (KYN) pathway have been reported as the factors participated in atherosclerosis in uraemic patients. The objective of this study was to verify whether hyperhomocysteinemia may be involved in atherosclerotic cardiovascular disease (CVD) in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).
Materials and methods
We determined the plasma concentrations of KYN, KYNA, KYNA/KYN ratio, homocysteine (Hcy) and intima-media thickness (IMT) - an early reflection of the systemic atherosclerosis in CAPD patients both with and without CVD and healthy controls.
Results
KYNA concentrations and KYNA/KYN ratio were about 3 times higher in the patients with hyperhomocysteinemia (Hcy > 15 μM) compared to those with normal Hcy levels (< 15 μM), and they were significantly lower in CVD[+] than in CVD[−] patients in these studied groups. The presence of CVD was associated with higher Hcy levels only in the patients with Hcy > 15 μM. The positive association was between Hcy and KYNA, KYNA/KYN ratio in all CAPD patients and in CVD[+] patients with hyperhomocysteinemia. IMT was positively associated with Hcy levels in patients with hyperhomocysteinemia, whereas there was no relationship between IMT and KYNA concentrations in the studied groups.
Conclusions
These results showed the association between hyperhomocysteinemia and carotid atherosclerosis as well as the possible role of hyperhomocysteinemia in the activation of KYNA production in CAPD patients. The elevated KYNA levels observed in patients with hyperhomocysteinemia seem to be protective against Hcy-mediated atherosclerosis in these patients. 相似文献