Plasma-based approach to measure target engagement for liver-targeting stearoyl-CoA desaturase 1 inhibitors

Role of omega-3 and omega-6 endocannabinoids in cardiopulmonary pharmacology

Endocannabinoids are derived from dietary omega-3 and omega-6 fatty acids and play an important role in regulation of inflammation, development, neurodegenerative diseases, cancer, and cardiovascular diseases. They elicit this effect via interactions with cannabinoid receptors 1 and 2 which are also targeted by plant derived cannabinoid from cannabis. The evidence of the involvement of the endocannabinoid system in cardiopulmonary function comes from studies that show that cannabis consumption leads to cardiovascular effect such as arrythmia and is beneficial in lung cancer patients. Moreover, omega-3 and omega-6 endocannabinoids play several important roles in cardiopulmonary system such as causing airway relaxation, suppressing atherosclerosis and hypertension. These effects are mediated via the cannabinoids receptors that are abundant in the cardiopulmonary system. Overall, this chapter reviews the known role of phytocannabinoids and endocannabinoids in the cardiopulmonary context.

NF-κB pathway play a role in SCD1 deficiency-induced ceramide de novo synthesis

Stearoyl-CoA-desaturase 1 (SCD1) deficiency mediates apoptosis in colorectal cancer cells by promoting ceramide de novo synthesis. The mechanisms underlying the cross-talk between SCD1 and ceramide synthesis have not been explored. We treated colorectal cancer cells with an SCD1 inhibitor and examined the effects on gene expression, cell growth, and cellular lipid contents. The main effect of SCD1 inhibition on the fatty acid contents of colorectal cancer cells was a decrease in monounsaturated fatty acids (MUFAs). RNA sequencing (RNA-seq) showed that the most intense alteration of gene expression after SCD1 inhibition occurred in the NF-κB signaling pathway. Further experiments revealed that SCD1 inhibition resulted in increased levels of phosphorylated NF-κB p65 and increased nuclear translocation of NF-κB p65. Treatment with an NF-κB inhibitor eliminated several effects of SCD1 inhibition, mainly including overexpression of serine palmitoyltransferase1 (SPT1), elevation of dihydroceramide contents, and suppression of cell growth. Furthermore, treatment with supplemental oleate counteracted the SCD1-induced NF-κB activation and downstream effects. In summary, our data demonstrate that the NF-κB pathway plays a role in SCD1 deficiency-induced ceramide de novo synthesis in colorectal cancer cells, and that reduced MUFA levels contribute to the course.

One-night sleep deprivation induces changes in the DNA methylation and serum activity indices of stearoyl-CoA desaturase in young healthy men

Background

Sleep deprivation has been associated with obesity among adults, and accumulating data suggests that stearoyl-CoA desaturase 1 (SCD1) expression has a relevant impact on fatty acid (FA) composition of lipid pools and obesity. The aim of this study was to investigate the effect of one-night total sleep deprivation (TSD) on DNA methylation in the 5’-prime region of SCD1, and whether detected changes in DNA methylation are associated with SCD activity indices (product to precursor FA ratios; 16:1n-7/16:0 and 18:1n-9/18:0) derived from serum phospholipids (PL).

Methods

Sixteen young, normal-weight, healthy men completed two study sessions, one with one-night TSD and one with one-night normal sleep (NS). Sleep quality and length was assessed by polysomnography, and consisted of electroencephalography, electrooculography, and electromyography. Fasting whole blood samples were collected on the subsequent morning for analysis of DNA methylation and FAs in serum PL. Linear regression analyses were performed to assess the association between changes in DNA methylation and SCD activity indices.

Results

Three CpG sites close to the transcription start site (TSS) of SCD1 (cg00954566, cg24503796, cg14089512) were significantly differentially methylated in dependency of sleep duration (−log₁₀P-value > 1.3). Both SCD-16 and SCD-18 activity indices were significantly elevated (P < 0.05) following one-night TSD, and significantly associated with DNA methylation changes of the three mentioned probes in the 5’ region of SCD1.

Conclusion

Our results suggest a relevant link between TSD, hepatic SCD1 expression and de-novo fatty acid synthesis via epigenetically driven regulatory mechanisms.

Changes in fatty acid composition in tissue and serum of obese cats fed a high fat diet

Background

Obesity and overweight have been frequently observed in dogs and cats in recent years as in humans. The compositions of fatty acids (FAs) in the accumulated lipids in tissues of obese animals may have important roles in the process and mechanisms related to the onset of metabolic disorders. The purpose of this study was to evaluate the effects of a high fat (HF) diet, which contained a higher proportion of saturated FAs, on FA metabolism and distribution in obese cats.

Cats (N = 12) were divided into control diet group (crude fat; 16.0 %) (n = 4) or a high fat (HF) diet group (crude fat; 23.9 %) (n = 8). The HF diet contained up to 60 % of calories from fat and was rich in stearic acid. Blood samples were collected at 0, 2, 4 and 6 weeks after the feeding. Adipose and liver tissues were collected at the 6^th week after feeding. We performed analysis of histological findings and fatty acid composition in serum and tissues.

Results

Body weights of the cats significantly increased in the HF group. The increased activities of hepatic enzymes and the accumulation of lipid droplets were found in hepatocytes in the HF group at the 6^th week after feeding.

In this study, the stearic acid (C18:0)-rich HF diet contained less oleic acid (C18:1n-9) and more linoleic acid (C18:2n-6) than the control. However, the composition of oleic acid in the liver was higher, and those of stearic acid and linoleic acid were lower in the HF group at the 6^th week after feeding. The higher oleic acid:stearic acid ratio suggests an increase in the conversion from saturated FA to mono-unsaturated FAs, which may reflect the hepatic storage of FAs as a relatively harmless form.

Conclusion

The stearic acid-rich HF diet increased hepatic lipid accumulation accompanied by the increased of hepatic oleic acid, increased serum oleic acid and activation of hepatic enzymes. These findings could be an important sign of early stages of dyslipidemia and hepatic damage. Also, the higher oleic acid:stearic acid ratio might be related to the increased activity of SCD-1, which suggests that the stearic acid-rich HF diet evoked hepatic lipogenesis in the feline liver.

An overview of patented small molecule stearoyl coenzyme-A desaturase inhibitors (2009 - 2013)

INTRODUCTION

Stearoyl coenzyme-A desaturase (SCD) is a critical lipogenic enzyme that converts a range of unsaturated lipids to their corresponding monounsaturated fatty acids. Genetic and enzyme-knockdown experiments have suggested an important role of SCD1 in the regulation of various metabolic disorders. With the prognostication that SCD-inhibition may serve to remediate various metabolic diseases, several pharmaceutical companies have embarked on the development of small-molecule SCD-inhibitors, with over 100 patent applications by 17 companies being reported to date.

AREAS COVERED

Recent progress on the development of SCD-inhibitors, including preclinical efficacy and safety are reviewed. Strategies toward overcoming systemic adverse events and the establishment of a suitable therapeutic margin for clinical studies are discussed.

EXPERT OPINION

Preclinically, SCD-inhibition leads to reductions in body-weight gain, improvements in glucose clearance and improved liver-lipid profile. However, chronic SCD inhibition in skin and eye-lubricating glands results in undesirable adverse events. Several strategies to overcome these findings have been described, including alternative administration routes for acne or oncology applications, use of potent and rapidly cleared compounds and SCD-inhibitors with a liver-targeted tissue distribution profile. The attainment of sufficient therapeutic margin and robust efficacy for therapeutic applications in humans remains a major frontier for SCD-inhibitors.

Lipoic Acid prevents the changes of intracellular lipid partitioning by free Fatty Acid

Background/Aims

It is suggested that the hepatic lipid composition is more important than lipid quantity in the pathogenesis of non-alcoholic steatohepatitis. We examined whether lipoic acid (LA) could alter intrahepatic lipid composition and free cholesterol distribution.

Methods

HepG2 cells were cultured with palmitic acid (PA) with and without LA. Apoptosis, changes of the mitochondrial structure, intracellular lipid partitioning, and reactive oxygen species (ROS) activity were measured.

Results

Free fatty acid (FA) increased apoptosis, and LA co-treatment prevented this lipotoxicity (apoptosis in controls vs PA vs PA+LA, 0.5% vs 19.5% vs 1.6%, p<0.05). LA also restored the intracellular mitochondrial DNA copy number (553±33.8 copies vs 291±14.55 copies vs 421±21.05 copies, p<0.05) and reversed the morphological changes induced by PA. In addition, ROS was increased in response to PA and was decreased in response to LA co-treatment (41,382 relative fluorescence unit [RFU] vs 43,646 RFU vs 41,935 RFU, p<0.05). LA co-treatment increased the monounsaturated and polyunsaturated FA concentrations and decreased the total saturated FA fraction. It also prevented the movement of intracellular free cholesterol from the cell membrane to the cytoplasm.

Conclusions

LA opposes free FA-generated lipotoxicity by altering the intracellular lipid composition and free cholesterol distribution.