Cellular Bioenergetics: Experimental Evidence for Alcohol-induced Adaptations

Alcohol-induced gut permeability defect through dysbiosis and enterocytic mitochondrial interference causing pro-inflammatory macrophages in a dose dependent manner

Although toxicity of alcohol toward the intestines and immunity is mentioned, there might be different effect of alcohol in a low and a high dose and the rodent model development using a simple SHIRPA binary score night be useful. Hence, a low and high dose of alcohol (6.30 and 1.26 g/kg/day) were administered in might for 16 weeks before determination of several parameters. As such, the peak blood alcohol concentration (BAC) of low and high dose of alcohol were approximately at 0.05 and 0.15%, respectively, at 1 h post-administration, which correlated with SHIRPA score at 1.8 ± 0.8 and 7.2 ± 0.6, respectively. After 16 wk of administration, a significant liver injury in high-dose alcohol was indicated by liver enzymes, liver weight, histology score, apoptosis, and hepatic accumulation of triglyceride (TG) and oxidative stress (malondialdehyde; MDA) with reduced anti-oxidant (glutathione). Meanwhile, low-dose alcohol demonstrated only elevated apoptosis with increased TG and MDA in liver tissue. Leaky gut from both dose of alcohol was also demonstrated by FITC-dextran, endotoxemia, serum beta glucan, and reduced occludin. However, bacterial abundance (microbiome analysis) of the feces from small bowel of high-dose alcohol, but not the low dose, was different from the control (increased Alitipes spp. with reduced Lachnospiraceae). In conclusion, both low- and high-dose alcohol induced leaky gut, while only the high-dose caused gut dysbiosis and alcohol damaged mitochondria but enhanced glycolysis in enterocytes and macrophages. Leaky gut might be more sensitive than dysbiosis to determine alcohol-induced intestinal injury.

Young Age and Concomitant Cannabis (THC) and Ethanol (EtOH) Exposure Enhances Rat Brain Damage Through Decreased Cerebral Mitochondrial Respiration

The reason why young people taking concomitantly cannabis (THC) and ethanol (EtOH) are more prone to stroke is underresearched. To investigate whether an underlying mechanism of increased brain damage could be an impaired mitochondrial function, this experiment determined the acute effects of EtOH, both alone and associated with THC, on mitochondrial respiration and oxidative stress (hydrogen peroxide H2O2) on young (11 weeks) and middle-aged (45 weeks) brain in rats, using a high-resolution oxygraph (Oxygraph-2K, Oroboros instruments). In young brains, EtOH decreased mitochondrial respiration by -51.76 ± 2.60% (from 32.76 ± 3.82 to 17.41 ± 1.42 pmol/s/mL, p < 0.0001). In 45-week-old brains, the decrease was lesser, but still significant -36.0 ± 2.80% (from 30.73 ± 7.72 to 20.59 ± 5.48 pmol/s/mL, p < 0.0001). Concomitant THC aggravated brain mitochondrial respiration decreases at 11 weeks (-86.86 ± 1.74%, p < 0.0001) and at 45 weeks (-73.95 ± 3.69%, p < 0.0001). Such additional injury was enhanced in young brains (p < 0.01). H2O2 production was similar in both age groups (1.0 ± 0.2 versus 1.1 ± 0.08 pmol O2/s/mL) and was not modified by THC addition. In conclusion, EtOH alone significantly impairs brain mitochondrial respiration and concomitant THC further aggravates such damage, particularly in young brains. These data support the hypothesis that enhanced mitochondrial dysfunction might participate in the increased occurrence of stroke in the young and urge for better prevention against EtOH and THC addictions in adolescents.

Acetylation of proximal cysteine-lysine pairs by alcohol metabolism

Alcohol consumption induces hepatocyte damage through complex processes involving oxidative stress and disrupted metabolism. These factors alter proteomic and epigenetic marks, including alcohol-induced protein acetylation, which is a key post-translational modification (PTM) that regulates hepatic metabolism and is associated with the pathogenesis of alcohol-associated liver disease (ALD). Recent evidence suggests lysine acetylation occurs when a proximal cysteine residue is within ∼15 Å of a lysine residue, referred to as a cysteine-lysine (Cys-Lys) pair. Here, acetylation can occur through the transfer of an acetyl moiety via an S → N transfer reaction. Alcohol-mediated redox stress is known to occur coincidentally with lysine acetylation, yet the biochemical mechanisms related to cysteine and lysine crosstalk within ALD remain unexplored. A murine model of ALD was employed to quantify hepatic cysteine redox changes and lysine acetylation, revealing that alcohol metabolism significantly reduced the cysteine thiol proteome and increased protein acetylation. Interrogating both cysteine redox and lysine acetylation datasets, 1280 protein structures generated by AlphaFold2 represented by a 3D spatial matrix were used to quantify the distances between 557,815 cysteine and lysine residues. Our analysis revealed that alcohol metabolism induces redox changes and acetylation selectively on proximal Cys-Lys pairs with an odds ratio of 1.88 (p < 0.0001). Key Cys-Lys redox signaling hubs were impacted in metabolic pathways associated with ALD, including lipid metabolism and the electron transport chain. Proximal Cys-Lys pairs exist as sets with four major motifs represented by the number of Cys and Lys residues that are pairing (Cys1:Lys1, Cysx:Lys1, Cys1:Lysx and Cysx:Lysx) each with a unique microenvironment. The motifs are composed of functionally relevant Cys-Ly altered within ALD, identifying potential therapeutic targets. Furthermore, these unique Cys-Lys redox signatures are translationally relevant as revealed by orthologous comparison with severe alcohol-associated hepatitis (SAH) explants, revealing numerous pathogenic thiol redox signals in these patients.

Alpinetin Exhibits Antioxidant and Anti-Inflammatory Effects in C57BL/6 Mice with Alcoholic Liver Disease Induced by the Lieber-DeCarli Ethanol Liquid Diet

Alcohol-associated liver disease (ALD) is a common non-communicable chronic liver disease characterized by a spectrum of conditions ranging from steatosis and alcohol-associated steatohepatitis (AH) to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). The pathogenesis of ALD involves a complex interplay of various molecular, biochemical, genetic, epigenetic, and environmental factors. While the mechanisms are well studied, therapeutic options remain limited. Alpinetin, a natural flavonoid with antioxidant and anti-inflammatory properties, has shown potential hepatoprotective effects, though its efficacy in ALD remains unexplored. This study investigated the hepatoprotective effects of alpinetin using a Lieber-DeCarli ethanol liquid diet model of ALD in C57BL/6 mice. Mice were divided into three groups: the control group, the ethanol group, and the ethanol group treated with alpinetin. Serum activity of ALT, AST, γ-GT, and ALP was measured to assess liver function, along with antioxidative and oxidative/nitrosative stress markers in liver tissue. Pro-inflammatory cytokines and endoplasmic reticulum (ER) stress parameters in liver tissue were also evaluated. Histological assessment of disease activity was performed using the SALVE grading and staging system. Treatment with alpinetin significantly reduced serum levels of ALT, AST, γ-GT, and oxidative/nitrosative stress markers while increasing antioxidative markers. The levels of pro-inflammatory cytokines and ER stress parameters were significantly decreased. Histological analysis demonstrated reduced steatosis, hepatocyte ballooning, and inflammation. These findings suggest that alpinetin holds promise as a potential therapeutic agent for managing ALD.

Cannabis (THC) Aggravates the Deleterious Effects of Alcohol (EtOH) on Skeletal Muscles' Mitochondrial Respiration: Modulation by Age and Metabolic Phenotypes

The anti-inflammatory and analgesic properties of cannabis might be useful to treat muscle diseases, including those linked or not to alcohol. Nevertheless, delta 9 tetrahydrocannabinol (THC) and ethanol (EtOH), often used concomitantly, can have deleterious effects on cardiac mitochondria. We therefore determined whether EtOH, alone and associated with THC, impairs skeletal muscle mitochondrial respiration. Further, we investigated potential modulation by metabolic phenotype and age by analyzing predominantly glycolytic gastrocnemius and oxidative soleus muscles in young and middle-aged rats (12 and 49 weeks). Considering the gastrocnemius, EtOH impaired mitochondrial respiration in a similar manner in young- and middle-aged muscles (-34.97 ± 2.97% vs. -37.50 ± 6.03% at 2.1 × 10-5 M; p < 0.05). Interestingly, concomitant THC aggravated EtOH-related mitochondrial impairment in young gastrocnemius (-49.92 ± 1.69%, vs. -34.97 ± 2.97 p < 0.05). Concerning the soleus, EtOH alone mainly decreased young muscle mitochondrial respiration (-42.39 ± 2.42% vs. -17.09 ± 7.61% at 2.1 × 10-5 M, p < 0.001, at 12 and 49 weeks). The soleus was less impaired at 12 weeks by THC and EtOH association than the gastrocnemius (-49.92 ±1.69 vs. -27.22 ± 8.96% in gastrocnemius and soleus, respectively, p < 0.05). In conclusion, EtOH, alone and associated with THC, significantly impairs skeletal muscle mitochondrial respiration and THC aggravates EtOH-induced effects on young glycolytic muscle. Age and metabolic phenotypes modulate these deleterious effects, with the glycolytic muscles of young rats being more prone to impairments than oxidative muscles.

Alcohol Alters Skeletal Muscle Bioenergetic Function: A Scoping Review

Bioenergetic pathways uniquely support sarcomere function which, in turn, helps to maintain functional skeletal muscle (SKM) mass. Emerging evidence supports alcohol (EtOH)-induced bioenergetic impairments in SKM and muscle precursor cells. We performed a scoping review to synthesize existing evidence regarding the effects of EtOH on SKM bioenergetics. Eligible articles from six databases were identified, and titles, abstracts, and full texts for potentially relevant articles were screened against inclusion criteria. Through the search, we identified 555 unique articles, and 21 met inclusion criteria. Three studies investigated EtOH effects on the adenosine triphosphate (ATP)-phosphocreatine (PCr) system, twelve investigated EtOH effects on glycolytic metabolism, and seventeen investigated EtOH effects on mitochondrial metabolism. Despite increased ATP-PCr system reliance, EtOH led to an overall decrease in bioenergetic function through decreased expression and activity of glycolytic and mitochondrial pathway components. However, effects varied depending on the EtOH dose and duration, model system, and sample type. The results detail the EtOH-induced shifts in energy metabolism, which may adversely affect sarcomere function and contribute to myopathy. These findings should be used to develop targeted interventions that improve SKM bioenergetic function, and thus sarcomere function, in people with Alcohol Use Disorder (AUD). Key areas in need of further investigation are also identified.

Mitochondrial quality control in alcohol-associated liver disease

Excessive alcohol consumption is a leading cause of alcohol-associated liver disease (ALD), a significant global health concern with limited therapeutic options. Understanding the key factors contributing to ALD pathogenesis is crucial for identifying potential therapeutic targets. Central to ALD pathogenesis is the intricate interplay between alcohol metabolism and cellular processes, particularly involving mitochondria. Mitochondria are essential organelles in the liver, critical for energy production and metabolic functions. However, they are particularly vulnerable to alcohol-induced damage due to their involvement in alcohol metabolism. Alcohol disrupts mitochondrial function, impairing ATP production and triggering oxidative stress, which leads to cellular damage and inflammation. Mitochondrial quality control mechanisms, including biogenesis, dynamics, and mitophagy, are crucial for maintaining optimal mitochondrial function. Chronic alcohol consumption disrupts mitochondrial quality control checkpoints, leading to mitochondrial dysfunction that impairs fatty acid oxidation and contributes to hepatic steatosis in ALD. Moreover, alcohol promotes the accumulation of damaged mitochondria and the release of proinflammatory components, exacerbating liver damage and inflammation. Preserving mitochondrial health presents a promising therapeutic approach to mitigate ALD progression. In this review, we provide a comprehensive overview of the effects of alcohol on mitochondrial function and quality control mechanisms, highlighting their role in ALD pathogenesis. Understanding these mechanisms may pave the way for the development of novel therapeutic interventions for ALD.

Phosphoglycerate mutase 5 exacerbates alcoholic cardiomyopathy in male mice by inducing prohibitin-2 dephosphorylation and impairing mitochondrial quality control

BACKGROUND

The induction of mitochondrial quality control (MQC) mechanisms is essential for the re-establishment of mitochondrial homeostasis and cellular bioenergetics during periods of stress. Although MQC activation has cardioprotective effects in various cardiovascular diseases, its precise role and regulatory mechanisms in alcoholic cardiomyopathy (ACM) remain incompletely understood.

METHODS

We explored whether two mitochondria-related proteins, phosphoglycerate mutase 5 (Pgam5) and prohibitin 2 (Phb2), influence MQC in male mice during ACM.

RESULTS

Myocardial Pgam5 expression was upregulated in a male mouse model of ACM. Notably, following ACM induction, heart dysfunction was markedly reversed in male cardiomyocyte-specific Pgam5 knockout (Pgam5cKO) mice. Meanwhile, in alcohol-treated male mouse-derived neonatal cardiomyocytes, Pgam5 depletion preserved cell survival and restored mitochondrial dynamics, mitophagy, mitochondrial biogenesis and the mitochondrial unfolded protein response (mtUPR). We further found that in alcohol-treated cardiomyocyte, Pgam5 binds Phb2 and induces its dephosphorylation at Ser91. Alternative transduction of phospho-mimetic (Phb2S91D) and phospho-defective (Phb2S9A) Phb2 mutants attenuated and enhanced, respectively, alcohol-related mitochondrial dysfunction in cardiomyocytes. Moreover, transgenic male mice expressing Phb2S91D were resistant to alcohol-induced heart dysfunction.

CONCLUSIONS

We conclude that ACM-induced Pgam5 upregulation results in Pgam5-dependent Phb2S91 dephosphorylation, leading to MQC destabilisation and mitochondrial dysfunction in heart. Therefore, modulating the Pgam5/Phb2 interaction could potentially offer a novel therapeutic strategy for ACM in male mice.

HIGHLIGHTS

Pgam5 knockout attenuates alcohol-induced cardiac histopathology and heart dysfunction in male mice. Pgam5 KO reduces alcohol-induced myocardial inflammation, lipid peroxidation and metabolic dysfunction in male mice. Pgam5 depletion protects mitochondrial function in alcohol-exposed male mouse cardiomyocytes. Pgam5 depletion normalises MQC in ACM. EtOH impairs MQC through inducing Phb2 dephosphorylation at Ser91. Pgam5 interacts with Phb2 and induces Phb2 dephosphorylation. Transgenic mice expressing a Ser91 phospho-mimetic Phb2 mutant are resistant to ACM.

Chronic binge alcohol mediated hepatic metabolic adaptations in SIV-infected female rhesus macaques

AIMS

As the interactions of alcohol and HIV/SIV infection and their impact on liver metabolic homeostasis remain to be fully elucidated, this study aimed to determine alcohol-mediated hepatic adaptations of metabolic pathways in SIV/ART-treated female rhesus macaques fed a nutritionally balanced diet.

METHODS

Macaques were administered chronic binge alcohol (CBA; 13-14 g ethanol/kg/week for 14.5 months; n = 7) or vehicle (VEH; n = 8) for 14.5 months. Livers were excised following an overnight fast. Gene and protein expression, enzymatic activity, and lipid content were determined using frozen tissue and histological staining was performed using paraffin-embedded tissue.

RESULTS

CBA/SIV macaques showed increased hepatic protein expression of electron transport Complex III and increased gene expression of glycolytic (phosphofructokinase and aldolase) and gluconeogenic (pyruvate carboxylase) enzymes and of genes involved in lipid turnover homeostasis (perilipin 1, peroxisome proliferator-activated receptor gamma, carbohydrate responsive binding protein, and acetyl-CoA carboxylase B) as compared to that of livers from the VEH/SIV group. Plasma triglyceride concentration had a significant positive association with liver triglyceride content in the CBA/SIV group.

CONCLUSIONS

These results reflect CBA-associated alterations in expression of proteins and genes involved in glucose and lipid metabolism homeostasis without significant evidence of steatosis or dysglycemia. Whether these changes predispose to greater liver pathology upon consumption of a high fat/high sugar diet that is more aligned with dietary intake of PWH and/or exposure to additional environmental factors warrants further investigation.

A critical review of ethanol effects on neuronal firing: A metabolic perspective

Ethanol metabolism is relatively understudied in neurons, even though changes in neuronal metabolism are known to affect their activity. Recent work demonstrates that ethanol is preferentially metabolized over glucose as a source of carbon and energy, and it reprograms neurons to a state of reduced energy potential and diminished capacity to utilize glucose once ethanol is exhausted. Ethanol intake has been associated with changes in neuronal firing and specific brain activity (EEG) patterns have been linked with risk for alcohol use disorder (AUD). Furthermore, a haplotype of the inwardly rectifying potassium channel subunit, GIRK2, which plays a critical role in regulating excitability of neurons, has been linked with AUD and shown to be directly regulated by ethanol. At the same time, overexpression of GIRK2 prevents ethanol-induced metabolic changes. Based on the available evidence, we conclude that the mechanisms underlying the effects of ethanol on neuronal metabolism are a novel target for developing therapies for AUD.

Cumulative Deleterious Effects of Tetrahydrocannabinoid (THC) and Ethanol on Mitochondrial Respiration and Reactive Oxygen Species Production Are Enhanced in Old Isolated Cardiac Mitochondria

Delta 9 tetrahydrocannabinol (THC), the main component of cannabis, has adverse effects on the cardiovascular system, but whether concomitant ethanol (EtOH) and aging modulate its toxicity is unknown. We investigated dose responses of THC and its vehicle, EtOH, on mitochondrial respiration and reactive oxygen production in both young and old rat cardiac mitochondria (12 and 90 weeks). THC dose-dependently impaired mitochondrial respiration in both groups, and such impairment was enhanced in aged rats (-97.5 ± 1.4% vs. -75.6 ± 4.0% at 2 × 10-5 M, and IC50: 0.7 ± 0.05 vs. 1.3 ± 0.1 × 10-5 M, p < 0.01, for old and young rats, respectively). The EtOH-induced decrease in mitochondrial respiration was greater in old rats (-50.1 ± 2.4% vs. -19.8 ± 4.4% at 0.9 × 10-5 M, p < 0.0001). Further, mitochondrial hydrogen peroxide (H2O2) production was enhanced in old rats after THC injection (+46.6 ± 5.3 vs. + 17.9 ± 7.8%, p < 0.01, at 2 × 10-5 M). In conclusion, the deleterious cardiac effects of THC were enhanced with concomitant EtOH, particularly in old cardiac mitochondria, showing greater mitochondrial respiration impairment and ROS production. These data improve our knowledge of the mechanisms potentially involved in cannabis toxicity, and likely support additional caution when THC is used by elderly people who consume alcohol.

Differential Lipidomics, Metabolomics and Immunological Analysis of Alcoholic and Non-Alcoholic Steatohepatitis in Mice

Non-alcoholic steatohepatitis (NASH) and alcoholic steatohepatitis (ASH) are the leading causes of liver disease worldwide. To identify disease-specific pathomechanisms, we analyzed the lipidome, metabolome and immune cell recruitment in livers in both diseases. Mice harboring ASH or NASH had comparable disease severities regarding mortality rate, neurological behavior, expression of fibrosis marker and albumin levels. Lipid droplet size was higher in NASH than ASH and qualitative differences in the lipidome were mainly based on incorporation of diet-specific fatty acids into triglycerides, phosphatidylcholines and lysophosphatidylcholines. Metabolomic analysis showed downregulated nucleoside levels in both models. Here, the corresponding uremic metabolites were only upregulated in NASH suggesting stronger cellular senescence, which was supported by lower antioxidant levels in NASH as compared to ASH. While altered urea cycle metabolites suggest increased nitric oxide synthesis in both models, in ASH, this depended on increased L-homoarginine levels indicating a cardiovascular response mechanism. Interestingly, only in NASH were the levels of tryptophan and its anti-inflammatory metabolite kynurenine upregulated. Fittingly, high-content immunohistochemistry showed a decreased macrophage recruitment and an increased polarization towards M2-like macrophages in NASH. In conclusion, with comparable disease severity in both models, higher lipid storage, oxidative stress and tryptophan/kynurenine levels were seen in NASH, leading to distinct immune responses.

Effects of Antioxidants in Fermented Beverages in Tissue Transcriptomics: Effect of Beer Intake on Myocardial Tissue after Oxidative Injury

Fermented beverages, such as wine and beer, are rich in polyphenols that have been shown to have protective effects against oxidative stress. Oxidative stress plays a central role in the pathogenesis and progression of cardiovascular disease. However, the potential benefits of fermented beverages on cardiovascular health need to be fully investigated at a molecular level. In this study, we aimed at analyzing the effects of beer consumption in modulating the transcriptomic response of the heart to an oxidative stress challenge induced by myocardial ischemia (MI) in the presence of hypercholesterolemia in a pre-clinical swine model. Previous studies have shown that the same intervention induces organ protective benefits. We report a dose-dependent up-regulation of electron transport chain members and the down-regulation of spliceosome-associated genes linked to beer consumption. Additionally, low-dose beer consumption resulted in a down-regulation of genes associated with the immune response, that was not shown for moderate-dose beer consumption. These findings, observed in animals having demonstrated beneficial effects at the organ-level, indicate that the antioxidants in beer differentially affect the myocardial transcriptome in a dose-dependent manner.

Mitochondrial Dysfunction: At the Nexus between Alcohol-Associated Immunometabolic Dysregulation and Tissue Injury

Alcohol misuse, directly or indirectly as a result of its metabolism, negatively impacts most tissues, including four with critical roles in energy metabolism regulation: the liver, pancreas, adipose, and skeletal muscle. Mitochondria have long been studied for their biosynthetic roles, such as ATP synthesis and initiation of apoptosis. However, current research has provided evidence that mitochondria participate in myriad cellular processes, including immune activation, nutrient sensing in pancreatic β-cells, and skeletal muscle stem and progenitor cell differentiation. The literature indicates that alcohol impairs mitochondrial respiratory capacity, promoting reactive oxygen species (ROS) generation and disrupting mitochondrial dynamics, leading to dysfunctional mitochondria accumulation. As discussed in this review, mitochondrial dyshomeostasis emerges at a nexus between alcohol-disrupted cellular energy metabolism and tissue injury. Here, we highlight this link and focus on alcohol-mediated disruption of immunometabolism, which refers to two distinct, yet interrelated processes. Extrinsic immunometabolism involves processes whereby immune cells and their products influence cellular and/or tissue metabolism. Intrinsic immunometabolism describes immune cell fuel utilization and bioenergetics that affect intracellular processes. Alcohol-induced mitochondrial dysregulation negatively impacts immunometabolism in immune cells, contributing to tissue injury. This review will present the current state of literature, describing alcohol-mediated metabolic and immunometabolic dysregulation from a mitochondrial perspective.