Serum low density lipoprotein of alcoholic patients is chemically modified in vivo and induces apolipoprotein E synthesis by macrophages

Diabetic Complications and Associated Factors: A 5-Year Facility-Based Retrospective Study at a Tertiary Hospital in Rwanda

INTRODUCTION

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from defects in insulin production, insulin action, or both. Despite advances in DM diagnosis and management, the incidence of DM-related complications remains high. This study aimed to determine patterns of common complications and associated factors among hospitalized patients in Rwanda.

METHODS

A cross-sectional study, with retrospective chart review, was conducted at CHUK from July to August, 2021. Charts for DM patients admitted from January 2016 to December 2020 were considered while those inaccessible at the time of data collection were excluded. Linear regression model was used to assess the relationship between dependent and independent variables with a p < 0.05 considered statistically significant.

RESULTS

A total of 246 charts were reviewed. The median age was 56 years (IQR: 14-90). More than half of participants (n = 135; 54.9%) were females; majority from the Central region (n = 138; 56.7%). Recorded DM risk factors included alcohol intake (n = 81; 48.5%); smoking (n = 40; 24.2%), obesity (n = 43; 52.4%), and family history of DM (n = 27; 56.3%). Majority (n = 153; 84.5%) had type 2 DM and (n = 147; 69%) had known their diagnosis for at least 6 years. Hypertension (n = 124, 50.4%), acute hyperglycemic state (n = 59, 24%), nephropathy (n = 58, 23.6%), and stroke (n = 38, 15.4%) were frequently reported complications. Nearly all participants (n = 81, 95.2%) with complications had poor glycemic control. Alcohol intake, age ≥45 years, and T1DM were associated with higher odds of DM complications (aOR = 8, 95% CI = 2-32.6, p = 0.003, aOR = 6.2, 95% CI = 1.4-27.6, p = 0.016 and aOR = 14.1, 95% CI = 1.2-161.5, p = 0.034, respectively). Duration of DM (p = 0.001) was significant at bivariate analysis.

CONCLUSION

DM complications were prevalent among the studied population with poor glycemic control mainly influenced by alcohol consumption and duration of DM. Expansion of integrated DM and hypertension screening services to lower-level centers is needed to reduce the associated morbidity and mortality.

Alcoholic macrocytosis--is there a role for acetaldehyde and adducts?

Although alcohol abuse is known to cause a wide array of adverse effects on blood cell formation, the molecular mechanisms by which alcohol exerts its toxic actions have remained poorly defined. Elevated mean corpuscular volume (MCV), macrocytosis, is the most typical morphological abnormality induced by excessive ethanol consumption. This paper reviews recent data indicating that acetaldehyde, the first metabolite of ethanol, may play a role in the haematological derangements in peripheral blood cells and in bone marrow of alcoholic patients. Studies in experimental animals and in human alcoholics have shown that acetaldehyde can bind to proteins and cellular constituents forming stable adducts. Elevated adduct levels have been found from the erythrocytes of alcohol abusers, which may also be associated with ethanol-induced effects in haematopoiesis and adverse consequences in cellular functions.

Role of naringin supplement in regulation of lipid and ethanol metabolism in rats

The current study was performed to investigate the effect of naringin supplements on the alcohol, lipid, and antioxidant metabolism in ethanol-treated rats. Male Sprague-Dawley rats were randomly divided into six groups (n = 10) based on six dietary categories: ethanol and naringin-free, ethanol (50 g/L) plus low-naringin (0.05 g/L), ethanol plus high-naringin (0.125 g/L), and three corresponding pair-fed groups. The pair-fed control rats received an isocaloric diet containing dextrin-maltose instead of ethanol for 5 wks. Among the ethanol treated groups, the naringin supplements significantly lowered the plasma ethanol concentration with a simultaneous increase in the ADH and/or ALDH activities. However, among the ethanol-treated groups, naringin supplementation resulted in a significant decrease in the hepatic triglycerides and plasma and hepatic total cholesterol compared to that in the naringin-free group. Naringin supplementation significantly increased the HDL-cholesterol and HDL-C/total-C ratio, while lowering the AI value among the ethanol-treated groups. Hepatic lipid accumulation was also significantly reduced in the naringin-supplemented groups compared to the naringin-free group among the ethanol-treated groups, while no differences were found among the pair-fed groups. Among the ethanol-treated groups, the low-naringin supplementation resulted in a significant decrease in the levels of plasma and hepatic TBARS, whereas it resulted in higher SOD and GSH-Px activities and gluthathion levels in the liver. Accordingly, naringin would appear to contribute to alleviating the adverse effect of ethanol ingestion by enhancing the ethanol and lipid metabolism as well as the hepatic antioxidant defense system.

Effect of alcohol on lipids and lipoproteins in relation to atherosclerosis

Several studies indicate that light-to-moderate alcohol consumption is associated with a low prevalence of coronary heart disease. An increase in high-density lipoprotein (HDL) cholesterol is associated with alcohol intake and appears to account for approximately half of alcohol's cardioprotective effect. In addition to changes in the concentration and composition of lipoproteins, alcohol consumption may alter the activities of plasma proteins and enzymes involved in lipoprotein metabolism: cholesteryl ester transfer protein, phospholipid transfer protein, lecithin:cholesterol acyltransferase, lipoprotein lipase, hepatic lipase, paraoxonase-1 and phospholipases. Alcohol intake also results in modifications of lipoprotein particles: low sialic acid content in apolipoprotein components of lipoprotein particles (e.g., HDL apo E and apo J) and acetaldehyde modification of apolipoproteins. In addition, "abnormal" lipids, phosphatidylethanol, and fatty acid ethyl esters formed in the presence of ethanol are associated with lipoproteins in plasma. The effects of lipoproteins on the vascular wall cells (endothelial cells, smooth muscle cells, and monocyte/macrophages) may be modulated by ethanol and the alterations further enhanced by modified lipids. The present review discusses the effects of alcohol on lipoproteins in cholesterol transport, as well as the novel effects of lipoproteins on vascular wall cells.

Uptake of acetaldehyde-modified (ethylated) low-density lipoproteins by mouse peritoneal macrophages

The uptake of acetaldehyde-modified (ethylated) low-density lipoproteins (LDLs) by murine peritoneal macrophages is described and compared with the uptake of acetylated LDLs. The fluorescent marker DiI was used. No competition between ethylated and acetylated LDLs was observed. Ethylated LDL uptake was not inhibited by polyinosinic acid or fucoidin. Our conclusion is that uptake of ethylated and acetylated LDLs can be done by two different receptors.

Oxidative stress, metabolism of ethanol and alcohol-related diseases

Alcohol-induced oxidative stress is linked to the metabolism of ethanol. Three metabolic pathways of ethanol have been described in the human body so far. They involve the following enzymes: alcohol dehydrogenase, microsomal ethanol oxidation system (MEOS) and catalase. Each of these pathways could produce free radicals which affect the antioxidant system. Ethanol per se, hyperlactacidemia and elevated NADH increase xanthine oxidase activity, which results in the production of superoxide. Lipid peroxidation and superoxide production correlate with the amount of cytochrome P450 2E1. MEOS aggravates the oxidative stress directly as well as indirectly by impairing the defense systems. Hydroxyethyl radicals are probably involved in the alkylation of hepatic proteins. Nitric oxide (NO) is one of the key factors contributing to the vessel wall homeostasis, an important mediator of the vascular tone and neuronal transduction, and has cytotoxic effects. Stable metabolites--nitrites and nitrates--were increased in alcoholics (34.3 +/- 2.6 vs. 22.7 +/- 1.2 micromol/l, p < 0.001). High NO concentration could be discussed for its excitotoxicity and may be linked to cytotoxicity in neurons, glia and myelin. Formation of NO has been linked to an increased preference for and tolerance to alcohol in recent studies. Increased NO biosynthesis also via inducible NO synthase (NOS, chronic stimulation) may contribute to platelet and endothelial dysfunctions. Comparison of chronically ethanol-fed rats and controls demonstrates that exposure to ethanol causes a decrease in NADPH diaphorase activity (neuronal NOS) in neurons and fibers of the cerebellar cortex and superior colliculus (stratum griseum superficiale and intermedium) in rats. These changes in the highly organized structure contribute to the motor disturbances, which are associated with alcohol abuse. Antiphospholipid antibodies (APA) in alcoholic patients seem to reflect membrane lesions, impairment of immunological reactivity, liver disease progression, and they correlate significantly with the disease severity. The low-density lipoprotein (LDL) oxidation is supposed to be one of the most important pathogenic mechanisms of atherogenesis, and antibodies against oxidized LDL (oxLDL) are some kind of epiphenomenon of this process. We studied IgG oxLDL and four APA (anticardiolipin, antiphosphatidylserine, antiphosphatidylethanolamine and antiphosphatidylcholine antibodies). The IgG oxLDL (406.4 +/- 52.5 vs. 499.9 +/- 52.5 mU/ml) was not affected in alcoholic patients, but oxLDL was higher (71.6 +/- 4.1 vs. 44.2 +/- 2.7 micromol/l, p < 0.001). The prevalence of studied APA in alcoholics with mildly affected liver function was higher than in controls, but not significantly. On the contrary, changes of autoantibodies to IgG oxLDL revealed a wide range of IgG oxLDL titers in a healthy population. These parameters do not appear to be very promising for the evaluation of the risk of atherosclerosis. Free radicals increase the oxidative modification of LDL. This is one of the most important mechanisms, which increases cardiovascular risk in chronic alcoholic patients. Important enzymatic antioxidant systems - superoxide dismutase and glutathione peroxidase - are decreased in alcoholics. We did not find any changes of serum retinol and tocopherol concentrations in alcoholics, and blood and plasma selenium and copper levels were unchanged as well. Only the zinc concentration was decreased in plasma. It could be related to the impairment of the immune system in alcoholics. Measurement of these parameters in blood compartments does not seem to indicate a possible organ, e.g. liver deficiency.

Covalent adducts of proteins with acetaldehyde in the liver as a result of acetaldehyde administration in drinking water

BACKGROUND/AIMS

Acetaldehyde, the first metabolic product of ethanol, has been suggested to be responsible for several adverse effects of ethanol through its ability to form covalent adducts with proteins and cellular constituents. It has recently been suggested that acetaldehyde derived from microbial ethanol oxidation in the gut could also contribute to the effects of ethanol in the liver. The present work aimed to examine whether modification of proteins by acetaldehyde occurs in rat liver as a result of acetaldehyde administration in drinking water.

METHODS

Rats were fed with either 0.7% acetaldehyde (n=10) or water (n=10) for 11 weeks. At the end of the feeding period, liver specimens were processed for immunohistochemistry for protein adducts with acetaldehyde and for hepatic cell type-specific protein markers.

RESULTS

Mild fatty change was found in the liver of the acetaldehyde-treated animals but not in the control animals. Immunohistochemical stainings for acetaldehyde adducts revealed intensive positive staining for acetaldehyde adducts in eight (80%) of the animals fed with acetaldehyde. The adducts were predominantly perivenular, although positive staining also occurred along the sinusoids and in the periportal area. Double immunofluorescence staining experiments revealed that hepatocytes were the primary targets of acetaldehyde adduct deposition, although stellate cells and Kupffer cells also showed weak positive reactions.

CONCLUSIONS

The present data indicate that acetaldehyde-protein adducts are formed in the liver of animals following acetaldehyde administration in drinking water, which may contribute to the hepatotoxicity of extrahepatic acetaldehyde. These findings should be implicated in studies on the extrahepatic pathways of ethanol oxidation.

Cytochromes P450 2A6, 2E1, and 3A and production of protein-aldehyde adducts in the liver of patients with alcoholic and non-alcoholic liver diseases

BACKGROUND/AIMS

Interaction between CYP2E1, ethanol metabolites, and enhanced lipid peroxidation is linked to the pathogenesis of alcoholic liver disease. This study was conducted to compare the expression of various cytochrome enzymes and the appearance of aldehyde adducts in humans.

METHODS

Acetaldehyde- and lipid peroxidation-derived protein adducts and CYP2A6, 2E1, and 3A4/5 were examined immunohistochemically from liver specimens of 12 alcohol abusers with either mild (n=7) or severe (n=5) liver disease, and from nine non-drinking patients with non-alcoholic steatosis (n=4), or hepatitis (n=5).

RESULTS

Ethanol-inducible CYP2E1 was present in all alcoholic livers. While CYP2A6 in zone 3 hepatocytes was also abundant in the alcoholic patients with various degrees of liver disease, CYP3A415 was most prominent in alcoholic cirrhosis. The sites of CYP2E1 and CYP2A6 immunoreactivity co-localized with fatty deposits, and with the sites of acetaldehyde and lipid peroxidation-derived protein adducts. The CYP enzymes were also abundant in the centrilobular hepatocytes of patients with fatty liver due to obesity or diabetes.

CONCLUSIONS

Alcohol-induced liver damage is associated with a generalized induction of CYP2A6, CYP2E1 and CYP3A4 and generation of acetaldehyde and lipid peroxidation-derived protein-aldehyde adducts. However, CYP induction also occurred in patients with non-alcoholic steatosis.

Induction of cytochrome P450 enzymes and generation of protein-aldehyde adducts are associated with sex-dependent sensitivity to alcohol-induced liver disease in micropigs

To assess possible links between ethanol-induced oxidant stress, expression of hepatic cytochrome P450 (CYP) enzymes, and sex steroid status, we used immunohistochemical methods to compare the generation of protein adducts of acetaldehyde (AA), malondialdehyde (MDA), and 4-hydroxynonenal (4-HNE) with the amounts of CYP2E1, CYP2A, and CYP3A in the livers of castrated and noncastrated male micropigs fed ethanol for 12 months. In castrated micropigs, ethanol feeding resulted in accumulation of fat, hepatocellular necrosis, inflammation, and centrilobular fibrosis, whereas only minimal histopathology was observed in their noncastrated counterparts. CYP2A and CYP3A were more prominent in the castrated animals than in the noncastrated micropigs. Ethanol feeding increased the hepatic content of all CYP forms. The most significant increases occurred in CYP2E1 and CYP3A in the noncastrated animals and in CYP2E1 and CYP2A in the castrated animals. Ethanol-fed castrated animals also showed the greatest abundance of perivenular adducts of AA, MDA, and HNE. In the noncastrated ethanol-fed micropigs a low expression of each CYP form was associated with scant evidence of aldehyde-protein adducts. Significant correlations emerged between the levels of different CYP forms, protein adducts, and plasma levels of sex steroids. The present findings indicate that the generation of protein-aldehyde adducts is associated with the induction of several cytochrome enzymes in a sex steroid-dependent manner. It appears that the premature, juvenile, metabolic phenotype, as induced by castration, favors liver damage. The present findings should be implicated in studies on the gender differences on the adverse effects of ethanol in the liver.

Paclitaxel analogues from Taxus x media cv. Hicksii

The roots of T. x media Rehd. cv. Hicksii gave three novel analogues of paclitaxel modified at the N-acyl residue (N-debenzoyl-N-alpha-methylbutyryl paclitaxel and N-debenzoyl-N-cinnamoyl paclitaxel, 1b and 1c, respectively) or at the ester group at C-2 (2-debenzoyl-2-tigloyl paclitaxel, 1d). Compounds 1b and 1d showed reduced cytotoxicity and tubulin binding compared to paclitaxel, while 1c retained substantial activity in these assays.

Early alcoholic liver injury: formation of protein adducts with acetaldehyde and lipid peroxidation products, and expression of CYP2E1 and CYP3A

The formation of protein adducts with reactive aldehydes resulting from ethanol metabolism and lipid peroxidation has been suggested to play a role in the pathogenesis of alcoholic liver injury. To gain further insight on the contribution of such aldehydes in alcoholic liver disease, we have compared the appearance of acetaldehyde, malondialdehyde, and 4-hydroxynonenal adducts with the expression of cytochrome P-450IIE1, and cytochrome P-4503A enzymes in the liver of rats fed alcohol with a high-fat diet for 2 to 4 weeks according to the Tsukamoto-French procedure and in control rats (high-fat liquid diet or no treatment). Urine alcohol and serum aminotransferase levels were recorded, and the liver pathology was scored from 0 to 10 according to the presence of steatosis, inflammation, necrosis, and fibrosis. The ethanol treatment resulted in the accumulation of fat, mild necrosis and inflammation, and a mean liver pathology score of 3 (range: 1 to 5). Liver specimens from the ethanol-fed animals with early alcohol-induced liver injury were found to contain perivenular, hepatocellular acetaldehyde adducts. Malondialdehyde and 4-hydroxynonenal adducts were also present showing a more diffuse staining pattern with occasional sinusoidal reactions. In the control animals, a faint positive reaction for the hydroxynonenal adduct occurred in some of the animals fed the high fat diet, whereas no specific staining was observed in the livers from the animals receiving no treatment. Expression of both CYP2E1 and CYP3A correlated with the amount of protein adducts in the liver of alcohol-treated rats. Distinct CYP2E1-positive immunohistochemistry was seen in 3 of 7 of the ethanol-fed animals. In 5 of 7 of the ethanol-fed animals, the staining intensities for CYP3A markedly exceeded those obtained from the controls. The present findings indicate that acetaldehyde and lipid peroxidation-derived adducts are generated in the early phase of alcohol-induced liver disease. The formation of protein adducts appears to be accompanied by induction of both CYP2E1 and CYP3A.

Alcohol and lipids

Alcoholic fatty liver and hyperlipemia result from the interaction of ethanol and its oxidation products with hepatic lipid metabolism. An early target of ethanol toxicity is mitochondrial fatty acid oxidation. Acetaldehyde and reactive oxygen species have been incriminated in the pathogenesis of the mitochondrial injury. Microsomal changes offset deleterious accumulation of fatty acids, leading to enhanced formation of triacylglycerols, which are partly secreted into the plasma and partly accumulate in the liver. However, this compensatory mechanism fades with progression of the liver injury, whereas the production of toxic metabolites increases, exacerbating the lesions and promoting fibrogenesis. The early presence of these changes confers to the fatty liver a worse prognosis than previously thought. Alcoholic hyperlipemia results primarily from increased hepatic secretion of very-low-density lipoprotein and secondarily from impairment in the removal of triacylglycerol-rich lipoproteins from the plasma. Hyperlipemia tends to disappear because of enhanced lipolytic activity and aggravation of the liver injury. With moderate alcohol consumption, the increase in high-density lipoprotein becomes the predominant feature. Its mechanism is multifactorial (increased hepatic secretion and increased extrahepatic formation as well as decreased removal) and explains part of the enhanced cholesterol transport from tissues to bile. These changes contribute to, but do not fully account for, the effects on atherosclerosis and/or coronary heart disease attributed to moderate drinking.

Consequences of alcohol use in diabetics

The hormone insulin, which is produced in the pancreas, is an important regulator of blood sugar levels. In people with diabetes, the pancreas does not produce sufficient insulin (type 1 diabetes) or the body does not respond appropriately to the insulin (type 2 diabetes). Alcohol consumption by diabetics can worsen blood sugar control in those patients. For example, long-term alcohol use in well-nourished diabetics can result in excessive blood sugar levels. Conversely, long-term alcohol ingestion in diabetics who are not adequately nourished can lead to dangerously low blood sugar levels. Heavy drinking, particularly in diabetics, also can cause the accumulation of certain acids in the blood that may result in severe health consequences. Finally, alcohol consumption can worsen diabetes-related medical complications, such as disturbances in fat metabolism, nerve damage, and eye disease.

Beneficial effects of alcohol withdrawal on LDL particle size distribution and oxidative susceptibility in subjects with alcohol-induced hypertriglyceridemia

LDL subclass pattern B, reported to have a higher prevalence in hypertriglyceridemics (HTGs), is considered to be associated with an increased risk for coronary artery disease, and the small dense LDL characteristic of this pattern is susceptible to oxidative modification. Alcohol is considered one of the most frequent causes of increases in plasma triglyceride (TG) levels. We investigated the effects of alcohol withdrawal on LDL subclass distribution and oxidizability in drinkers with different plasma TG levels. Thirty-seven male subjects with relatively heavy alcohol-consumption habits were divided into four groups; normotriglyceridemic (NTG)/withdrawal (n = 11), NTG/control (n = 8), hypertriglyceridemic (HTG)/withdrawal (n = 10), and HTG/control (n = 8). Both withdrawal groups abstained form alcohol for 4 weeks, while the control subjects maintained their usual intake of alcohol. Peak LDL particle diameter (PPD) was smaller in the combined HTG groups than in the combined NTG groups before abstinence, although PPD increased significantly (P < .01) from 25.5 to 26.1 nm in the HTG/withdrawal group. Before abstinence, lag times preceding LDL oxidation in the combined HTG groups were shorter than in the combined NTG groups; after withdrawal, lag time was prolonged significantly (P < .01) from 49.9 to 57.3 minutes in the HTG-withdrawal group. No significant changes in PPD and lag time were observed in the other three groups. Significant correlations (P < .05) were observed between the change (delta) in the lag time and delta TG and between delta lag time and delta PPD. We conclude that in alcohol-induced HTG subjects, alcohol withdrawal has beneficial effects on the LDL profile by shifting the particle size from smaller to larger and decreasing its susceptibility to oxidation.