Vitamin E prevents the age-dependent and palmitate-induced disturbances of sphingolipid turnover in liver cells

Analyzing free fatty acids in seminal plasma from asthenozoospermia patients undergoing antioxidant therapy

OBJECTIVE

Different aspects of the functions of free fatty acid (FFA) in seminal plasma and their implications on male fertility are known. However, the profile of FFA in seminal plasma in asthenozoospermic patients following antioxidant therapy has not been studied.

METHODS

In this case-control study, the total antioxidant capacity (TAC) and FFA profile of the seminal plasma were determined in 80 patients (29 normozoospermic volunteers and 51 asthenozoospermic men) who were treated with antioxidants for three months.

RESULTS

The TAC level in normozoospermic men was significantly higher than in asthenozoospermic men before and after antioxidant therapy with even lower values after the treatment (p=0.0001). The most abundant identified FFAs in seminal plasma were palmitic acid, vaccenic acid, eicosatrienoic acid, stearic acid, and myristoleic acid. Palmitic acid was lower in asthenozoospermic patients (p=0.0001), and antioxidant treatment restored its level to near-control levels. Compared to normozoospermic controls, the level of eicosatrienoic acid is significantly lower in asthenozoospermia patients before (p=0.01) and after treatment (p=0.0001). Additionally, following oral antioxidant supplementation, the FFA pattern in asthenozoospermic patients changes to the pattern observed in normozoospermic men. However, these changes are not statistically significant.

CONCLUSIONS

The TAC level in asthenozoospermic patients after antioxidant treatment did not change to the levels in the control group; it even dropped to a lower level following three months of treatment. Antioxidant treatment can change the level of the FFA compositions of seminal plasma.

Potential Vitamin E Signaling Mediators in Skeletal Muscle

Vitamin E (Vit E) deficiency studies underline the relevance of this vitamin in skeletal muscle (SkM) homeostasis. The knowledge of the effectors and modulators of Vit E action in SkM cells is limited, especially in aging and chronic diseases characterized by a decline in musculoskeletal health. Vit E comprises eight fat-soluble compounds grouped into tocopherols and tocotrienols, which share the basic chemical structure but show different biological properties and potentials to prevent diseases. Vit E has antioxidant and non-antioxidant activities and both favorable and adverse effects depending on the specific conditions and tissues. In this review, we focus on the actual knowledge of Vit E forms in SkM functions and new potential signaling effectors (i.e., bioactive sphingolipids and myokines). The possible advantages of Vit E supplementation in counteracting SkM dysfunctions in sarcopenia and under microgravity will also be discussed.

Sex Differences in Cardiovascular Diseases: A Matter of Estrogens, Ceramides, and Sphingosine 1-Phosphate

The medical community recognizes sex-related differences in pathophysiology and cardiovascular disease outcomes (CVD), culminating with heart failure. In general, pre-menopausal women tend to have a better prognosis than men. Explaining why this occurs is not a simple matter. For decades, sex hormones like estrogens (Es) have been identified as one of the leading factors driving these sex differences. Indeed, Es seem protective in women as their decline, during and after menopause, coincides with an increased CV risk and HF development. However, clinical trials demonstrated that E replacement in post-menopause women results in adverse cardiac events and increased risk of breast cancer. Thus, a deeper understanding of E-related mechanisms is needed to provide a vital gateway toward better CVD prevention and treatment in women. Of note, sphingolipids (SLs) and their metabolism are strictly related to E activities. Among the SLs, ceramide and sphingosine 1-phosphate play essential roles in mammalian physiology, particularly in the CV system, and appear differently modulated in males and females. In keeping with this view, here we explore the most recent experimental and clinical observations about the role of E and SL metabolism, emphasizing how these factors impact the CV system.

Tocotrienol-Rich Fraction of Palm Oil Improves Behavioral Impairments and Regulates Metabolic Pathways in AβPP/PS1 Mice

We have recently shown that the tocotrienol-rich fraction (TRF) of palm oil, a mixture of vitamin E analogs, improves amyloid pathology in vitro and in vivo. However, precise mechanisms remain unknown. In this study, we examined the effects of long-term (10 months) TRF treatment on behavioral impairments and brain metabolites in (15 months old) AβPP/PS1 double transgenic (Tg) Alzheimer’s disease (AD) mice. The open field test, Morris water maze, and novel object recognition tasks revealed improved exploratory activity, spatial learning, and recognition memory, respectively, in TRF-treated Tg mice. Brain metabolite profiling of wild-type and Tg mice treated with and without TRF was performed using ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution accurate mass (HRAM)-orbitrap tandem mass spectrometry (MS/MS). Metabolic pathway analysis found perturbed metabolic pathways that linked to AD. TRF treatment partly ameliorated metabolic perturbations in Tg mouse hippocampus. The mechanism of this pre-emptive activity may occur via modulation of metabolic pathways dependent on Aβ interaction or independent of Aβ interaction.

Novel role of PKR in palmitate-induced Sirt1 inactivation and endothelial cell senescence

Endothelial cell senescence is regarded as a vital characteristic of cardiovascular diseases. Elevated palmitate (PA) is an independent risk factor of cardiovascular diseases, but its role in endothelial cell senescence is currently unknown. During the course of studying the prosenescent role of PA, we discovered a key role of dsRNA-dependent protein kinase [protein kinase R (PKR)] in endothelial senescence. Exposure of human umbilical vein endothelial cells (HUVECs) to PA-induced cell senescence is characterized by increased levels of senescence-associated β-galactose glucosidase activity, excessive production of reactive oxygen species production, impaired cellular proliferation, and G1 phase arrest. This phenomenon is associated with an increase of PKR autophosphorylation and decreased activity of sirtuin 1 (Sirt1), a pivotal antisenescent factor. PKR inactivation by PKR siRNA or its phosphorylation inhibitor 2-aminopurine significantly attenuated PA-induced HUVEC senescence by reversing Sirt1 activity and its downstream signaling. Moreover, to study the regulatory mechanism between PKR and Sirt1, we found that PKR promotes JNK activation to inhibit Sirt1 activity and that this effect could be reversed by the JNK inhibitor SP600125. These findings provide evidence that PKR mediates PA-induced HUVEC senescence by inhibiting Sirt1 signaling. Our study provides novel insights into the actions and mechanisms of PKR in endothelial senescence.

NEW & NOTEWORTHY This study first provides a novel observation that dsRNA-dependent protein kinase (PKR) mediates palmitate-induced sirtuin 1 inactivation and subsequent human umbilical vein endothelial cell senescence. Most importantly, these new findings will provide a potential therapeutic strategy to improve free fatty acid-induced endothelial senescence by targeting PKR in cardiovascular diseases.

Effects of inhibitors of key enzymes of sphingolipid metabolism on insulin-induced glucose uptake and glycogen synthesis in liver cells of old rats

Sphingolipids play an important role in the development of insulin resistance. Ceramides are the most potent inhibitors of insulin signal transduction. Ceramides are generated in response to stress stimuli and in old age. In this work, we studied the possible contribution of different pathways of sphingolipid metabolism in age-dependent insulin resistance development in liver cells. Inhibition of key enzymes of sphingolipid synthesis (serine palmitoyl transferase, ceramide synthase) and degradation (neutral and acidic SMases) by means of specific inhibitors (myriocin, fumonisin B1, imipramine, and GW4869) was followed with the reduction of ceramide level and partly improved insulin regulation of glucose metabolism in "old" hepatocytes. Imipramine and GW4869 decreased significantly the acidic and neutral SMase activities, respectively. Treatment of "old" cells with myriocin or fumonisin B1 reduced the elevated in old age ceramide and SM synthesis. Ceramide and SM levels and glucose metabolism regulation by insulin could be improved with concerted action of all tested inhibitors of sphingolipid turnover on hepatocytes. The data demonstrate that not only newly synthesized ceramide and SM but also neutral and acidic SMase-dependent ceramide accumulation plays an important role in development of age-dependent insulin resistance.

Spinal cord injury causes chronic liver pathology in rats

Traumatic spinal cord injury (SCI) causes major disruption to peripheral organ innervation and regulation. Relatively little work has investigated these post-SCI systemic changes, however, despite considerable evidence that multiple organ system dysfunction contributes to chronic impairments in health. Because metabolic dysfunction is common after SCI and the liver is a pivotal site for metabolic homeostasis, we sought to determine if liver pathology occurs as a result of SCI in a rat spinal contusion model. Histologic evidence showed excess lipid accumulation in the liver for at least 21 days post-injury after cervical or midthoracic SCI. Lipidomic analysis revealed an acute increase in hepatic ceramides as well as chronically elevated lactosylceramide. Post-SCI hepatic changes also included increased proinflammatory gene expression, including interleukin (IL)-1α, IL-1β, chemokine ligand-2, and tumor necrosis factor-α mRNA. These were coincident with increased CD68+ macrophages in the liver through 21 days post-injury. Serum alanine transaminase, used clinically to detect liver damage, was significantly increased at 21 days post-injury, suggesting that early metabolic and inflammatory damage preceded overt liver pathology. Surprisingly, liver inflammation was even detected after lumbar SCI. Collectively, these results suggest that SCI produces chronic liver injury with symptoms strikingly similar to those of nonalcoholic steatohepatitis (fatty liver disease). These clinically significant hepatic changes after SCI are known to contribute to systemic inflammation, cardiovascular disease, and metabolic syndrome, all of which are more prevalent in persons with SCI. Targeting acute and prolonged hepatic pathology may improve recovery and reduce long-term complications after SCI.

Long-term food restriction prevents aging-associated sphingolipid turnover dysregulation in the brain

Abnormalities of sphingolipid turnover in the brain during normal aging and age-related neurological disorders were associated with the neurons loss and cognitive malfunction. Calorie restriction (CR) prevented age-related deficits in hippocampal long-term potentiation and improved cognitive function at old age. In the paper we investigated the ceramide and sphingomyelin (SM) levels in the brain regions, which are critical for learning and memory of 3- and 24-month-old rats, as well as the correction of sphingolipid turnover in the brain of old rats, by means of the CR diet and modulators of SM turnover. Using the [methyl-(14)C-choline]SM, the neutral, but not the acid SMase activity has been observed to increase in both the hippocampus and brain cortex of 24-month-old rats with respect to 3-month-old animals. Age-dependent changes of neutral SMase activities were associated with ceramide accumulation and SM level drop in the brain structures studied. Treatment of the rats with the CR diet or N-acetylcysteine (NAC) or α-tocopherol acetate, but not an inhibitor of acid SMase imipramine, reduced the ceramide content and neutral SMase activity in the hippocampus of 24-month-old animals with respect to control rats of the same age. These results suggest that redox-sensitive neutral SMase plays important role in SM turnover dysregulation in both the hippocampus and neocortex at old age and that the CR diet can prevent the age-dependent accumulation of ceramide mainly via neutral SMase targeting.