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blueoaknx · 7 days ago

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The Impact of High Fructose Corn Syrup on Mitochondrial Function

The Impact of High Fructose Corn Syrup on Mitochondrial Function:

Analysis

High fructose corn syrup (HFCS), a widely used sweetener derived from corn, has become a major component of the modern diet, especially in processed foods and sugary beverages. HFCS is composed of glucose and fructose in varying proportions, with HFCS-55 (55% fructose, 45% glucose) and HFCS-42 (42% fructose, 58% glucose) being the most common formulations. While the impact of HFCS on metabolic health has been widely discussed, recent studies have shown that it can also exert a detrimental effect on mitochondrial function. This technical analysis explores the biochemical mechanisms by which HFCS damages mitochondria, contributing to cellular dysfunction and a range of metabolic diseases.

Mitochondrial Physiology and Biochemical Function

Mitochondria are highly specialized organelles responsible for producing adenosine triphosphate (ATP), the primary energy currency of the cell, through oxidative phosphorylation (OXPHOS). This process occurs in the inner mitochondrial membrane and involves the electron transport chain (ETC) and ATP synthase. The mitochondria are also involved in regulating cellular metabolism, maintaining redox balance, calcium homeostasis, and apoptosis (programmed cell death). Mitochondrial dysfunction, characterized by impaired ATP production, altered mitochondrial dynamics (fusion/fission), and excessive reactive oxygen species (ROS) production, is a key factor in the pathogenesis of many chronic diseases, including obesity, insulin resistance, cardiovascular diseases, and neurodegenerative disorders.

Fructose Metabolism and Its Divergence from Glucose

The metabolism of fructose, particularly in the liver, diverges significantly from that of glucose, and it is this divergence that underpins much of the mitochondrial dysfunction associated with HFCS consumption. Unlike glucose, which is predominantly metabolized via glycolysis and the citric acid cycle (TCA cycle), fructose bypasses the rate-limiting step of glycolysis, catalyzed by phosphofructokinase-1 (PFK-1), and is instead phosphorylated by fructokinase to form fructose-1-phosphate. This rapid metabolism of fructose in the liver can overwhelm metabolic pathways and lead to the accumulation of intermediate metabolites such as dihydroxyacetone phosphate (DHAP) and glyceraldehyde, which can be further converted to fatty acids and triglycerides through de novo lipogenesis (DNL).

Excessive fructose consumption leads to the accumulation of triglycerides, particularly within hepatocytes, which is a hallmark of non-alcoholic fatty liver disease (NAFLD). The lipid accumulation in the liver, in turn, exacerbates mitochondrial dysfunction and oxidative stress, contributing to insulin resistance and a cascade of metabolic disorders.

Mechanisms of Mitochondrial Damage Induced by HFCS

Increased ROS Production

One of the most significant consequences of excess fructose metabolism is the elevated production of reactive oxygen species (ROS). ROS are byproducts of cellular respiration, primarily generated at complexes I and III of the electron transport chain. Under normal conditions, mitochondria have a robust antioxidant defense system, including enzymes like superoxide dismutase (SOD), catalase, and glutathione peroxidase, which help neutralize ROS. However, when cells are exposed to an overload of fructose, the liver mitochondria become overwhelmed, leading to excessive ROS generation.

Fructose metabolism increases the NADPH/NADP+ ratio, enhancing the activity of nicotinamide adenine dinucleotide phosphate (NADPH)-dependent oxidases such as NADPH oxidase (NOX), which further amplifies ROS production. These ROS cause oxidative damage to mitochondrial DNA (mtDNA), lipids in the mitochondrial membranes, and mitochondrial proteins. Such damage impairs mitochondrial function by decreasing mitochondrial membrane potential, disrupting the electron transport chain, and promoting mitochondrial fragmentation. Furthermore, mtDNA is particularly vulnerable to ROS due to its proximity to the electron transport chain and the lack of histone protection, leading to mutations that impair mitochondrial replication and protein synthesis.

Disruption of Mitochondrial Biogenesis

Mitochondrial biogenesis refers to the process by which new mitochondria are synthesized within a cell to meet the energy demands. This process is tightly regulated by several transcription factors, most notably peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α). PGC-1α activates the transcription of nuclear and mitochondrial genes involved in energy metabolism, mitochondrial dynamics, and antioxidant defenses.

Fructose consumption has been shown to inhibit PGC-1α expression in both liver and skeletal muscle cells. Reduced PGC-1α levels lead to impaired mitochondrial biogenesis, which limits the ability of cells to adapt to increased energy demands. This is particularly concerning in tissues with high metabolic demands, such as muscle, heart, and liver, where impaired mitochondrial function can exacerbate energy deficits and lead to insulin resistance, fatty liver disease, and other metabolic disorders.

Mitochondrial Permeability Transition and Apoptosis

Chronic exposure to high levels of fructose can lead to mitochondrial permeability transition (MPT), a process in which the mitochondrial inner membrane becomes permeable to ions and small molecules, disrupting mitochondrial function. MPT is typically induced by excessive ROS production, calcium overload, or changes in the mitochondrial membrane potential. The opening of the mitochondrial permeability transition pore (MPTP) leads to the loss of mitochondrial membrane potential, uncoupling of oxidative phosphorylation, and the release of pro-apoptotic factors such as cytochrome c into the cytoplasm. This, in turn, activates the caspase cascade, promoting apoptosis.

In the context of HFCS-induced mitochondrial dysfunction, increased ROS and altered metabolic intermediates, such as ceramides, may trigger MPT and apoptotic pathways, leading to cell death and tissue damage. In tissues such as the liver and pancreas, this can exacerbate the pathological progression of fatty liver disease and insulin resistance.

Fatty Acid Accumulation and Impaired Beta-Oxidation

Excessive fructose consumption induces de novo lipogenesis (DNL) in the liver, leading to an increase in the synthesis of fatty acids, which are esterified into triglycerides and stored within hepatocytes. This accumulation of lipids can overwhelm the capacity of mitochondria to oxidize these fatty acids via beta-oxidation, leading to mitochondrial dysfunction. The accumulation of lipotoxic intermediates such as ceramides and diacylglycerols further impairs mitochondrial function by inhibiting key enzymes involved in mitochondrial energy production.

Moreover, the excess fatty acids can impair mitochondrial membrane fluidity, reducing the efficiency of oxidative phosphorylation. The lipid-induced mitochondrial dysfunction leads to further oxidative stress, creating a feedback loop that exacerbates the metabolic disturbances caused by high fructose intake.

Clinical Implications of HFCS-Induced Mitochondrial Dysfunction

The long-term consumption of HFCS has profound implications for human health, particularly in the context of metabolic diseases:

Insulin Resistance and Type 2 Diabetes: HFCS-induced mitochondrial dysfunction, particularly in liver and muscle cells, contributes to impaired insulin signaling and glucose homeostasis. As mitochondrial function declines, cells become less responsive to insulin, leading to insulin resistance, a precursor to type 2 diabetes.

Non-Alcoholic Fatty Liver Disease (NAFLD): The accumulation of fat in the liver, driven by increased fructose metabolism, leads to mitochondrial damage and dysfunction, which exacerbates the progression of NAFLD to non-alcoholic steatohepatitis (NASH), a more severe form of liver disease.

Cardiovascular Disease: Mitochondrial dysfunction in cardiomyocytes can impair ATP production, leading to reduced contractile function and the progression of cardiovascular disease. The increased oxidative stress and inflammatory mediators associated with mitochondrial damage also contribute to vascular injury and atherosclerosis.

Neurodegenerative Diseases: Impaired mitochondrial function in neurons, driven by high fructose intake, may contribute to neurodegenerative diseases such as Alzheimer's and Parkinson's disease, as mitochondria play a critical role in maintaining neuronal health.

Conclusion

High fructose corn syrup exerts a significant impact on mitochondrial function through several interconnected mechanisms. These include the increased production of reactive oxygen species (ROS), inhibition of mitochondrial biogenesis, induction of mitochondrial permeability transition, and the accumulation of toxic lipid intermediates. These disruptions in mitochondrial homeostasis contribute to the development of insulin resistance, non-alcoholic fatty liver disease, and other chronic metabolic diseases. Addressing the widespread consumption of HFCS and reducing dietary fructose intake could be crucial in mitigating mitochondrial dysfunction and preventing associated metabolic disease

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healthtimetaylor · 5 years ago

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Aged garlic extract and its constituent, S-allyl-L-cysteine, induce the apoptosis of neuroblastoma cancer cells

PMID: Exp Ther Med. 2020 Feb ;19(2):1511-1521. Epub 2019 Dec 27. PMID: 32010332 Abstract Title: Aged garlic extract and its constituent, S-allyl-L-cysteine, induce the apoptosis of neuroblastoma cancer cells due to mitochondrial membrane depolarization. Abstract: Aged garlic extract (AGE) has been demonstrated to have therapeutic properties in tumors; however its mechanisms of action have not yet been fully elucidated. A previous study revealed that AGE exerts an anti-proliferative effect on a panel of both sensitive [wild-type (WT)] and multidrug-resistant (MDR) human cancer cells. Following treatment of the cells with AGE, cytofluorimetric analysis revealed the occurrence of dose-dependent mitochondrial membrane depolarization (MMD). In this study, in order to further clarify the mechanisms of action of AGE, the effects of AGE on mitochondria isolated from rat liver mitochondria (RLM) were also examined. AGE induced an effect on the components of the electrochemical gradient (Δµ), mitochondrial membrane potential (ΔΨ) and mitochondrial electrochemical gradient (ΔpH). The mitochondrial membrane dysfunctions of RLM induced by AGE, namely the decrease in both membrane potential and chemical gradient were associated with a higher oxidation of both the endogenous glutathione and pyridine nucleotide content. To confirm the anti-proliferative effects of AGE, experiments were performed on the human neuroblastoma (NB) cancer cells, SJ-N-KP and the MYCN-amplified IMR5 cells, using its derivative S-allyl-L-cysteine (SAC), with the aim of providing evidence of the anticancer activity of this compound and its possible molecular mechanism as regards the induction of cytotoxicity. Following treatment of the cells with SAC at 20 mM, cell viability was determined by MTT assay and apoptosis was detected by flow cytometry, using Annexin V-FITC labeling. The percentages of cells undergoing apoptosis was found to be 48.0% in the SJ-N-KP and 50.1% in the IMR5 cells. By cytofluorimetric analysis, it was suggested that the target of SAC are the mitochondria. Mitochondrial activity was examined by labeling the cells with the probe, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylimidacarbocyanine iodide (JC-1). Following treatment with SAC at 50 mM, both NB cell lines exhibited a marked increase in MMD. On the whole, the findings of this study indicate that both natural products, AGE and SAC, cause cytotoxicity to tumor cells via the induction of mitochondrial permeability transition (MPT).

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lopezdorothy70-blog · 6 years ago

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Blue light exposure can induce damages to human retinal pigment epithelium cells in vitro

PMID: Zhonghua Yan Ke Za Zhi. 2006 Dec ;42(12):1095-102. PMID: 17415967 Abstract Title: [Relationship between blue light-induced apoptosis and mitochondrial membrane potential and cytochrome C in cultured human retinal pigment epithelium cells]. Abstract: OBJECTIVE: To investigate the effect of blue light on apoptosis and mitochondrial permeability transition (MPT) of cultured human retinal pigment epithelium (RPE) cells in vitro.METHODS: Human RPE cells were exposed to blue light (wave length 470 -490 nm). The present study consisted of three parts. Part one studied the effect of various intensities of blue light on the RPE cells. Cells were irradiated with (500+/-100) lx (group 1) , (2000+/-500) lx (group 2) and (3000+/-500)lx ( group 3) blue light, and followed by 24 hours observation. Part two studied the effect of various duration of blue light at identical intensity on the RPE cells. For the study on various subtypes of RPE cells, cells were irradiated by blue light at (2000+/-500) x for 6, 12, and 24 hours. For the study of mitochondrial membrane potential, cells were irradiated for 3, 6, and 12 hours. Part three studied cells irradiated with blue light at identical intensity and duration, but with various prolongation of post-exposure culture. The prolongation of post-exposure culture was 6, 12, 24, and 36 hours. Phototoxicity was quantified at various periods after exposure by staining of the nuclei of membrane-compromised cells, by TdT-dUTP terminal nick-end labeling (TUNEL) of apoptotic cells and by Annexin V labeling for phosphatidylserine exposure. Transmission electronmicroscopy was used to determine the ultrastructure changes of RPE cells. Mitochondrial membrane potential ( deltaPsim ) was measured by rhodamine 123 staining and subsequent flow cytometry. Cytochrome C activity was assayed by ELISA. Caspase-3 was detected by colorimetric assay.RESULTS: TUNEL-positive labeling cells in first group of part two study showed cell shrinkage, membrane blebbing, apoptotic body, condensation and fragmentation of chromatin. Mitochondrial swelling, extinction of inner mitochondrial membrane ridge, dilation of rough endoplasmic reticulum and increase of the lysosome were also observed in transmission electronmicroscopy. Blue light at (500 +/- 100) x intensity did not induce damage to RPE cells, but decrease of delta Psim was observed. A significant increase of apoptotic, apoptotic necrotic and necrotic percentages, as well as significant decrease of deltaPsim were observed at higher light intensity in part one study. Increase of apoptotic percentage was the main response to shorter exposure of blue light. Increase of apoptotic necrotic and necrotic percentage and pronounced decrease of deltaPsim occurred in cells irradiated by longer exposure in part two study. In part 3 study, apoptotic response was increased gradually during 6 and 12 hours prolongation of post-exposure culture, more apoptotic necrosis or necrosis were found after post-exposure 24 hours. Decrease of deltaPsim was observed in 6 hours prolongation of post-exposure culture and lasting for 48 hours. The concentration of cytochrome C was significantly increased in post-exposure 24 and 36 hours, without any changes of Caspase-3 activity.CONCLUSIONS: Blue light exposure can induce damages to human RPE cells in vitro, which include apoptosis, apoptotic necrosis and necrosis. These changes are caused by triggering the mitochondrial permeability transition, which results in decrease of deltaPsim and release of cytochrome C. deltaPsim can be used as a earlier parameter of blue light-induced apoptosis.

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battybat-boss · 6 years ago

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Blue light exposure can induce damages to human retinal pigment epithelium cells in vitro

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