The liver metabolizes ethanol through three enzymatic pathways: alcohol dehydrogenase (ADH), cytochrome p450 (also called MEOS), and catalase. Alcohol dehydrogenase class I (ADH1) is considered the most important enzyme for the metabolism of ethanol, MEOS and catalase (CAT) are considered minor alternative pathways. However, contradicting experiments suggest that the non-ADH1 pathway may have a greater relevance for the metabolism of ethanol than previously thought. In some conditions, ethanol is predominately metabolized to acetaldehyde via cytochrome P450 family 2 (CYP2E1), which is involved in the generation of reactive oxygen species (ROS), mainly through electron leakage to oxygen to form the superoxide (O₂^•−) radical or in catalyzed lipid peroxidation. The CAT activity can also participate in the ethanol metabolism that produces ROS via ethanol directly reacting with the CAT-H₂O₂ complex, producing acetaldehyde and water and depending on the H₂O₂ availability, which is the rate-limiting component in ethanol peroxidation. We have shown that CAT actively participates in lactate-stimulated liver ethanol oxidation, where the addition of lactate generates H₂O₂, which is used by CAT to oxidize ethanol to acetaldehyde. Therefore, besides its known role as a catalytic antioxidant component, the primary role of CAT could be to function in the metabolism of xenobiotics in the liver.

To study the differences in the levels of nitrogen metabolites, such as ammonia and nitric oxide and the correlations existing among them in both red blood cells (RBCs) and serum, as well as the possible differences by gender in healthy subjects and patients with type 2 Diabetes Mellitus (DM). This cross-sectional study included 80 patients diagnosed with type 2 DM (40 female and 40 male patients) and their corresponding controls paired by gender (40 female and 40 male). We separated serum and RBC and determined metabolites mainly through colorimetric and spectrophotometric assays. We evaluated changes in the levels of the main catabolic by-products of blood nitrogen metabolism, nitric oxide (NO), and malondialdehyde (MDA). Healthy female and male controls showed a differential distribution of blood metabolites involved in NO metabolism and arginine metabolism for the ornithine and urea formation. Patients with DM had increased ammonia, citrulline, urea, uric acid, and ornithine, mainly in the RBCs, whereas the level of arginine was significantly lower in men with type 2 DM. These findings were associated with hyperglycemia, glycosylated hemoglobin (Hb A_1C), and levels of RBC’s MDA. Furthermore, most of the DM-induced alterations in nitrogen-related metabolites appear to be associated with a difference in the RBC capacity for the release of these metabolites, thereby causing an abrogation of the gender-related differential management of nitrogen metabolites in healthy subjects. We found evidence of a putative role of RBC as an extra-hepatic mechanism for controlling serum levels of nitrogen-related metabolites, which differs according to gender in healthy subjects. Type 2 DM promotes higher ammonia, citrulline, and MDA blood levels, which culminate in a loss of the differential management of nitrogen-related metabolites seen in healthy women and men.

Gluconacetobacter diazotrophicus is a N₂-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2–C6) and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.

The number of patients afflicted by type 2 diabetes and its morbidities has increased alarmingly, becoming the cause of many deaths. Normally, during nutrient intake, insulin secretion is increased and glucagon secretion is repressed, but when plasma glucose concentration increases, a state of prediabetes occurs. High concentration of plasma glucose breaks the redox balance, inducing an oxidative stress that promotes chronic inflammation, insulin resistance, and impaired insulin secretion. In the same context, obesity is one of the most crucial factors inducing insulin resistance, inflammation, and contributing to the onset of type 2 diabetes. Measurements of metabolites like glucose, fructose, amino acids, and lipids exhibit significant predictive associations with type 2 diabetes or a prediabetes state and lead to changes in plasma metabolites that could be selectively affected by gender and age. In terms of gender, women and men have biological dissimilarities that might have an important role for the development, diagnosis, therapy, and prevention of type 2 diabetes, obesity, and relevant hazards in both genders, for type 2 diabetes. Therefore, the present review attempts to analyze the influence of gender on the relationships among inflammatory events, oxidative stress, and metabolic alterations in patients undergoing obesity and/or type 2 diabetes.

Metabolic dysfunction–associated fatty liver disease (MASLD) is associated with severe forms of liver injury, including fibrosis and cirrhosis. The main risk factors for MASLD—obesity, type 2 diabetes mellitus (T2DM), dyslipidemia, and insulin resistance (IR)—contribute to metabolic disturbances that initiate hepatic steatosis. Metabolic and alcohol-related liver disease (MetALD) describes patients with MASLD who also present alcohol-associated hepatic injury. Chronic oxidative and inflammatory stress promotes the progression of steatosis in both conditions. T2DM and chronic alcohol consumption are independent lifestyle-related risk factors for cirrhosis within the spectrum of metabolic dysfunction–related liver disease (MASLD and MetALD). The coexistence of both conditions may exacerbate hepatic pathological alterations. IR, which is frequently observed in patients with cirrhosis, can lead to the development of a condition known as hepatogenic diabetes (HD). HD is characterized by hyperinsulinemia, IR, and β-cell dysfunction occurring during the onset of cirrhosis and is associated with hepatic inflammation even in the absence of traditional metabolic risk factors such as obesity or a prior history of T2DM. In this context, alcohol intake enhances lipolysis in peripheral tissues, promotes hepatic steatosis, and aggravates metabolic dysfunction, ultimately contributing to excessive mitochondrial production of reactive oxygen species (ROS). Therefore, the present review examines the role of oxidative stress—both alcohol-related and non-alcohol–related—in the pathogenesis of HD, with particular emphasis on ethanol metabolism, oxidative stress, and their interactions in conditions such as T2DM and MetALD.

Zidovudine (AZT) has significantly reduced the mortality and morbidity rates among AIDS patients, but it has been associated with hepatotoxicity. AZT treatment has been linked to disrupted lipid and glucose metabolism, and the enhancement of pro-inflammatory chemokines and other mediators, which can lead to liver steatosis. In contrast, the administration of adenosine (ADO) has proven to be an effective hepatoprotector against both acute and chronic liver damage. Therefore, present study was aimed to investigate the harmful effects of chronic AZT administration and the beneficial effects of the co-administered ADO. Chronic oral AZT administration did not induce hyperglycemia or dyslipidemia, but serum liver marker enzyme activities were increased, as well as evidence of liver steatosis and inflammation. These findings were associated with low insulin and glucagon levels, elevated serum levels of pro-inflammatory cytokines and disruptions in cell redox states in these animals. ADO co-administration attenuated the deleterious effects induced by AZT: blocking the production of inflammatory molecules, increasing serum insulin and glucagon levels, and restoring liver cellular redox state. Then, blood insulin levels seemed to be greatly influenced by the cellular redox state, which was altered by AZT administration. This alteration is likely to be connected to mitochondrial integrity and metabolism.