Long-term methionine-diet induced mild hyperhomocysteinemia associated cardiac metabolic dysfunction in multiparous rats

The Role of Methionine-Rich Diet in Unhealthy Cerebrovascular and Brain Aging: Mechanisms and Implications for Cognitive Impairment

As aging societies in the western world face a growing prevalence of vascular cognitive impairment and Alzheimer's disease (AD), understanding their underlying causes and associated risk factors becomes increasingly critical. A salient concern in the western dietary context is the high consumption of methionine-rich foods such as red meat. The present review delves into the impact of this methionine-heavy diet and the resultant hyperhomocysteinemia on accelerated cerebrovascular and brain aging, emphasizing their potential roles in cognitive impairment. Through a comprehensive exploration of existing evidence, a link between high methionine intake and hyperhomocysteinemia and oxidative stress, mitochondrial dysfunction, inflammation, and accelerated epigenetic aging is drawn. Moreover, the microvascular determinants of cognitive deterioration, including endothelial dysfunction, reduced cerebral blood flow, microvascular rarefaction, impaired neurovascular coupling, and blood-brain barrier (BBB) disruption, are explored. The mechanisms by which excessive methionine consumption and hyperhomocysteinemia might drive cerebromicrovascular and brain aging processes are elucidated. By presenting an intricate understanding of the relationships among methionine-rich diets, hyperhomocysteinemia, cerebrovascular and brain aging, and cognitive impairment, avenues for future research and potential therapeutic interventions are suggested.

Effect of Methionine Diet on Time-Related Metabolic and Histopathological Changes of Rat Hippocampus in the Model of Global Brain Ischemia

Hyperhomocysteinemia (hHcy) represents a strong risk factor for atherosclerosis-associated diseases, like stroke, dementia or Alzheimer's disease. A methionine (Met)-rich diet leads to an elevated level of homocysteine in plasma and might cause pathological alterations across the brain. The hippocampus is being constantly studied for its selective vulnerability linked with neurodegeneration. This study explores metabolic and histo-morphological changes in the rat hippocampus after global ischemia in the hHcy conditions using a combination of proton magnetic resonance spectroscopy and magnetic resonance-volumetry as well as immunohistochemical analysis. After 4 weeks of a Met-enriched diet at a dose of 2 g/kg of animal weight/day, adult male Wistar rats underwent 4-vessel occlusion lasting for 15 min, followed by a reperfusion period varying from 3 to 7 days. Histo-morphological analyses showed that the subsequent ischemia-reperfusion insult (IRI) aggravates the extent of the sole hHcy-induced degeneration of the hippocampal neurons. Decreased volume in the grey matter, extensive changes in the metabolic ratio, deeper alterations in the number and morphology of neurons, astrocytes and their processes were demonstrated in the hippocampus 7 days post-ischemia in the hHcy animals. Our results suggest that the combination of the two risk factors (hHcy and IRI) endorses and exacerbates the rat hippocampal neurodegenerative processes.

Putative Nox2 inhibitors worsen homocysteine-induced impaired acetylcholine-mediated relaxation

BACKGROUND AND AIM

Increased homocysteine (Hcy) is associated with coronary artery disease (CAD). Hcy increases reactive oxygen species (ROS) via NADPH oxidases (Nox), reducing acetylcholine-mediated vasorelaxation. We aimed to determine if putative Nox2 inhibitors prevent Hcy-impaired acetylcholine-mediated vasorelaxation.

METHODS AND RESULTS

New Zealand White rabbit and wild-type (C57BL/6) and Nox2^-/- (NOX) mice aortic rings were mounted in organ baths. Rabbit rings were incubated with either apocynin (10 μM), gp91ds-tat (GP, 1 μM) or PhoxI2 (1 μM) and mice rings GP (1 μM) only. Some rabbit rings were incubated with 3 mM Hcy, before pre-contraction, followed by dose-response relaxation to acetylcholine (ACh; 0.01μM-10μM). In rabbit rings treated with Hcy and GP, O₂‾ donor pyrogallol (1 μM) or Akt activator SC79 (1 μM) was added 5 min before ACh. Mice rings were used to compare Nox2 deletion to normal acetylcholine-mediated relaxation. In rabbits, Hcy reduced acetylcholine-mediated relaxation vs. control (p < 0.0001). Treatment + Hcy reduced relaxation compared with treatment alone (p < 0.0001). Pyrogallol and SC79 reversed the response of GP + Hcy (p = 0.0001). In mice, Nox2 deletion reduced acetylcholine-mediated vasorelaxation. Rabbit tissue analysis revealed that Hcy reduced eNOS phosphorylation at Thr⁴⁹⁵ and increased eNOS phosphorylation at Ser¹¹⁷⁷; no further alteration at Thr⁴⁹⁵ was observed with GP. In contrast, GP prevented increased phosphorylation at Ser¹¹⁷⁷.

CONCLUSIONS

Apocynin, GP and PhoxI2 worsens acetylcholine-mediated vascular relaxation in rabbit aorta, which is supported by results from mouse Nox2 deletion data. These inhibitors worsen Hcy-induced vascular dysfunction, suggesting that current putative Nox2 inhibitors might not be useful in treating HHcy.

Echinocystic acid ameliorates hyperhomocysteinemia-induced vascular endothelial cell injury through regulating NF-κB and CYP1A1

The present study investigated the role of echinocystic acid (EA) on the expression of nuclear factor (NF)-κB and cytochrome P450 1A1 (CYP1A1), and aortic morphology, in a rat model of hyperhomocysteinemia (Hhcy). A total of 50 Sprague Dawley rats were randomly divided into five groups as follows: Normal control (NC), model control (MC), vitamin control (VC; folic acid 1 mg/kg + vitamin B2 2 mg/kg + vitamin B12 10u g/kg), EA1 (20 mg/kg EA) and EA2 (40 mg/kg EA). Plasma homocysteine (Hcy) levels were determined via high performance liquid chromatography, and the morphology of the aorta was investigated using hematoxylin and eosin staining. Furthermore, aortic mRNA and protein levels of NF-κB and CYP1A1 were measured using reverse transcription-quantitative polymerase chain reaction analysis and western blotting, respectively. Plasma Hcy levels, and aortic mRNA and protein levels of NF-κB and CYP1A1, were significantly lower in the EA-treated group compared with the MC group (all P<0.05). However, the aortic morphology remained normal, including the endothelial cells of the inner layer, and smooth muscle cells of the media layer and adventitia. In conclusion, the results of the present study indicate that EA has a protective role on vascular endothelial cells in Hhcy through decreasing plasma Hcy, and thus NF-κB and CYP1A1 expression.

Divergent outcomes of fructose consumption on exercise capacity of rats: friend or foe

To test the hypothesis that high fructose (HF) consumption divergently affects exercise capability as a function of feeding duration, rats were fed a normal (as control) diet or a normal caloric diet with HF for 3, 6, 10, and 30 days, respectively, and then were run on a treadmill. Results show that running distance and work were significantly increased, which was associated with greater exercise oxygen consumption in rats fed HF for 3 (HF-3D) and 6 days, but were decreased in rats fed HF for 30 days (HF-30D) compared with rats in their respective control groups. Shear stress-induced vasodilation (SSID) in isolated plantaris muscle arterioles was significantly greater in the HF-3D group than the control group. The difference in SSID between the two groups was abolished by N^ω-nitro-l-arginine methyl ester (L-NAME), suggesting a nitric oxide (NO)-mediated response. Expression of phosphorylated/activated endothelial NO synthase (eNOS) and release of nitrite/NO were significantly increased in vessels of animals in the HF-3D group than controls. In contrast, arterioles isolated from the hypertensive rats in the HF-30D group displayed significantly attenuated NO-mediated SSID accompanied with greater production of superoxide compared with vessels of control animals. Additionally, the NO-dependent modulation of myocardial oxygen consumption (MV̇o₂) was also impaired in the HF-30D group, and was prevented by blocking superoxide production with apocynin, an inhibitor that also normalized the reduced SSID in the HF-30D group. In conclusion, short-term (3-6 days) HF feeding enhances exercise potential via an increase in endothelial sensitivity to shear stress, which stimulates eNOS to release NO, leading to better tissue perfusion and utilization of oxygen. However, long-term (30 days) HF feeding initiates endothelial dysfunction by superoxide-dependent mechanisms to compromise exercise performance.NEW & NOTEWORTHY The evidence that short-term fructose intake potentiates exercise capacity by nitric oxide-mediated mechanisms yields an optimal fructose feeding frame in which beneficial effects of fructose have been acquired while detrimental effects have not yet been manifested. This highlights the significance of exercise physiology in providing constructive regimens to improve physical performance.