Leptin and adiponectin synthesis and secretion in mature 3T3-L1 adipocytes are differentially down-regulated by arsenic and palmitic acid exposure throughout different stages of adipogenesis

AIMS

Arsenic is a risk factor for type 2 diabetes and cardiovascular disease. However, little is known about arsenic effects over adipocyte endocrine functionality, particularly for leptin and adiponectin, and about its interaction with dietary components, which are the main environmental regulators of adipose tissue functionality. The aim of this work was to evaluate leptin and adiponectin in mature 3T3-L1 adipocytes exposed to palmitate (simulating excess fat intake), arsenite, or both throughout two different stages of adipogenesis.

MATERIAL AND METHODS

3T3-L1 adipocytes were exposed starting from the beginning of its differentiation process during 11 d or once adipocytes were mature for 72 h. Adipokines secretion was evaluated by ELISA, intracellular protein levels and secreted adiponectin multimers by Western blot and mRNA abundance by qPCR.

KEY FINDINGS

Leptin and adiponectin secretion decreased by arsenite alone or in combination with palmitate due to reduced gene and protein expression of both adipokines. However, leptin was impaired more at the transcriptional level, whereas affections to adiponectin were more relevant at the intracellular protein amount level with changes in the multimers proportion. The gene expression of several of their transcription factors was altered. Additionally, the magnitude of the effects depends on the adipocyte cell stage at which exposure began; adiponectin was more affected when exposure started from differentiation and leptin once adipocytes were mature.

SIGNIFICANCE

These results in an in vivo model could be translated into less satiety and reduced insulin sensitivity.

Therapeutic Effect of Curcumin on 5/6Nx Hypertriglyceridemia: Association with the Improvement of Renal Mitochondrial β-Oxidation and Lipid Metabolism in Kidney and Liver

Chronic kidney disease (CKD) prevalence is constantly increasing, and dyslipidemia in this disease is characteristic, favoring cardiovascular events. However, the mechanisms of CKD dyslipidemia are not fully understood. The use of curcumin (CUR) in CKD models such as 5/6 nephrectomy (5/6Nx) has shown multiple beneficial effects, so it has been proposed to correct dyslipidemia without side effects. This work aimed to characterize CUR's potential therapeutic effect on dyslipidemia and alterations in lipid metabolism and mitochondrial ß-oxidation in the liver and kidney in 5/6Nx. Male Wistar rats were subjected to 5/6Nx and progressed by 4 weeks; meanwhile, CUR (120 mg/kg) was administered for weeks 5 to 8. Our results showed that CUR reversed the increase in liver and kidney damage and hypertriglyceridemia induced by 5/6Nx. CUR also reversed mitochondrial membrane depolarization and β-oxidation disorders in the kidney and the increased lipid uptake and the high levels of proteins involved in fatty acid synthesis in the liver and kidney. CUR also decreased lipogenesis and increased mitochondrial biogenesis markers in the liver. Therefore, we concluded that the therapeutic effect of curcumin on 5/6Nx hypertriglyceridemia is associated with the restoration of renal mitochondrial ß-oxidation and the reduction in lipid synthesis and uptake in the kidneys and liver.

Protection Strategies Against Palmitic Acid-Induced Lipotoxicity in Metabolic Syndrome and Related Diseases

Diets rich in carbohydrate and saturated fat contents, when combined with a sedentary lifestyle, contribute to the development of obesity and metabolic syndrome (MetS), which subsequently increase palmitic acid (PA) levels. At high concentrations, PA induces lipotoxicity through several mechanisms involving endoplasmic reticulum (ER) stress, mitochondrial dysfunction, inflammation and cell death. Nevertheless, there are endogenous strategies to mitigate PA-induced lipotoxicity through its unsaturation and elongation and its channeling and storage in lipid droplets (LDs), which plays a crucial role in sequestering oxidized lipids, thereby reducing oxidative damage to lipid membranes. While extended exposure to PA promotes mitochondrial reactive oxygen species (ROS) generation leading to cell damage, acute exposure of ß-cells to PA increases glucose-stimulated insulin secretion (GSIS), through the activation of free fatty acid receptors (FFARs). Subsequently, the activation of FFARs by exogenous agonists has been suggested as a potential therapeutic strategy to prevent PA-induced lipotoxicity in ß cells. Moreover, some saturated fatty acids, including oleic acid, can counteract the negative impact of PA on cellular health, suggesting a complex interaction between different dietary fats and cellular outcomes. Therefore, the challenge is to prevent the lipid peroxidation of dietary unsaturated fatty acids through the utilization of natural antioxidants. This complexity indicates the necessity for further research into the function of palmitic acid in diverse pathological conditions and to find the main therapeutic target against its lipotoxicity. The aim of this review is, therefore, to examine recent data regarding the mechanism underlying PA-induced lipotoxicity in order to identify strategies that can promote protection mechanisms against lipotoxicity, dysfunction and apoptosis in MetS and obesity.

Effect of N-Acetylcysteine in Mitochondrial Function, Redox Signaling, and Sirtuin 3 Levels in the Heart During Cardiorenal Syndrome Type 4 Development

Type 4 cardiorenal syndrome (CRS-4) is a pathology in which chronic kidney disease (CKD) triggers the development of cardiovascular disease. CKD pathophysiology produces alterations that can affect the bioenergetics of heart mitochondria, causing oxidative stress and reducing antioxidant glutathione (GSH) levels. GSH depletion alters protein function by affecting post-translational modifications such as S-glutathionylation (RS-SG), exacerbating oxidative stress, and mitochondrial dysfunction. On the other hand, N-acetylcysteine (NAC) is an antioxidant GSH precursor that modulates oxidative stress and RS-SG. Moreover, recent studies have found that NAC can activate the Sirtuin 3 (SIRT3) deacetylase in diseases. However, the role of NAC and its effects on mitochondrial function, redox signaling, and SIRT3 modifications in the heart during CRS-4 have not been studied. This study aimed to investigate the role of NAC in mitochondrial function, redox signaling, and SIRT3 in the hearts of animals with CRS-4 at two months of follow-up. Our results showed that the oral administration of NAC (600 mg/kg/day) improved blood pressure and reduced cardiac fibrosis. NACs' protective effect was associated with preserving cardiac mitochondrial bioenergetics and decreasing these organelles' hydrogen peroxide (H2O2) production. Additionally, NAC increased GSH levels in heart mitochondria and regulated the redox state, which coincided with an increase in nicotinamide adenine dinucleotide oxidized (NAD+) levels and a decrease in mitochondrial acetylated lysines. Finally, NAC increased SIRT3 levels and the activity of superoxide dismutase 2 (SOD-2) in the heart. Thus, treatment with NAC decreases mitochondrial alterations, restores redox signaling, and decreases SIRT3 disturbances during CRS-4 through an antioxidant defense mechanism.