Abnormal fatty acid composition of lymphocytes of biotin-deficient rats

ELOVL5 Is a Critical and Targetable Fatty Acid Elongase in Prostate Cancer

The androgen receptor (AR) is the key oncogenic driver of prostate cancer, and despite implementation of novel AR targeting therapies, outcomes for metastatic disease remain dismal. There is an urgent need to better understand androgen-regulated cellular processes to more effectively target the AR dependence of prostate cancer cells through new therapeutic vulnerabilities. Transcriptomic studies have consistently identified lipid metabolism as a hallmark of enhanced AR signaling in prostate cancer, yet the relationship between AR and the lipidome remains undefined. Using mass spectrometry-based lipidomics, this study reveals increased fatty acyl chain length in phospholipids from prostate cancer cells and patient-derived explants as one of the most striking androgen-regulated changes to lipid metabolism. Potent and direct AR-mediated induction of ELOVL fatty acid elongase 5 (ELOVL5), an enzyme that catalyzes fatty acid elongation, was demonstrated in prostate cancer cells, xenografts, and clinical tumors. Assessment of mRNA and protein in large-scale data sets revealed ELOVL5 as the predominant ELOVL expressed and upregulated in prostate cancer compared with nonmalignant prostate. ELOVL5 depletion markedly altered mitochondrial morphology and function, leading to excess generation of reactive oxygen species and resulting in suppression of prostate cancer cell proliferation, 3D growth, and in vivo tumor growth and metastasis. Supplementation with the monounsaturated fatty acid cis-vaccenic acid, a direct product of ELOVL5 elongation, reversed the oxidative stress and associated cell proliferation and migration effects of ELOVL5 knockdown. Collectively, these results identify lipid elongation as a protumorigenic metabolic pathway in prostate cancer that is androgen-regulated, critical for metastasis, and targetable via ELOVL5. SIGNIFICANCE: This study identifies phospholipid elongation as a new metabolic target of androgen action that is critical for prostate tumor metastasis.

Structure and regulation of acetyl-CoA carboxylase genes of metazoa

Acetyl-CoA carboxylase (ACC) plays a fundamental role in fatty acid metabolism. The reaction product, malonyl-CoA, is both an intermediate in the de novo synthesis of long-chain fatty acids and also a substrate for distinct fatty acyl-CoA elongation enzymes. In metazoans, which have evolved energy storage tissues to fuel locomotion and to survive periods of starvation, energy charge sensing at the level of the individual cell plays a role in fuel selection and metabolic orchestration between tissues. In mammals, and probably other metazoans, ACC forms a component of an energy sensor with malonyl-CoA, acting as a signal to reciprocally control the mitochondrial transport step of long-chain fatty acid oxidation through the inhibition of carnitine palmitoyltransferase I (CPT I). To reflect this pivotal role in cell function, ACC is subject to complex regulation. Higher metazoan evolution is associated with the duplication of an ancestral ACC gene, and with organismal complexity, there is an increasing diversity of transcripts from the ACC paraloges with the potential for the existence of several isozymes. This review focuses on the structure of ACC genes and the putative individual roles of their gene products in fatty acid metabolism, taking an evolutionary viewpoint provided by data in genome databases.

The abundance and function of biotin-dependent enzymes are reduced in rats chronically administered carbamazepine

The effect of dietary antiepileptic drug administration on the metabolism and function of the water-soluble vitamin biotin was analyzed in a physiologically relevant rat model of biotin nutriture. Administration of carbamazepine (CBZ) in semipurified rat diet at 1.5 and 2.9 g/kg for 19 d did not reduce growth rate or food intake. After this dietary treatment, brain lactic acid and ammonia concentrations were significantly elevated, but no changes in these metabolites occurred in the liver. Urinary biotin excretion was altered and the concentrations of biotin sulfoxides and biocytin in the serum were elevated. Brain biotin was unaffected, but concentrations of bisnorbiotin and biocytin were significantly reduced by dietary administration of CBZ. The relative abundance of hepatic acetyl CoA carboxylase 1 and 2, pyruvate carboxylase (PC), methylcrotonyl CoA carboxylase and propionyl CoA carboxylase was significantly reduced by CBZ, whereas the relative abundance of biotinylated PC was significantly reduced in the brain. In agreement with the carboxylase abundance data, the activity of hepatic PC was significantly reduced in rats consuming CBZ-containing diets. These data demonstrate that administration of the antiepileptic medication CBZ, even with food, reduces the abundance and function of biotin-dependent enzymes in the liver and brain, partially accounting for the metabolic alterations, including organic acidemia, that are observed clinically.

Dietary biotin intake modulates the pool of free and protein-bound biotin in rat liver

The current studies were undertaken to analyze the relationships among dietary biotin intake, hepatic free biotin and hepatic protein-bound biotin in rats. The biotin status of rats was manipulated through dietary intervention to model moderate biotin deficiency, adequacy, supplementation and pharmacologic biotin supplementation (0, 0.06, 0.6 and 100 mg/kg, respectively). Urinary biotin excretion was directly related to biotin intake, but no difference between biotin-adequate and biotin-supplemented rats was detected. In contrast, plasma biotin was directly and significantly regulated by biotin intake at every intake level. A hepatic free biotin pool was directly demonstrated in these studies, and like plasma, its size was directly related to dietary biotin intake. The relationship between dietary biotin intake and protein-bound biotin was also analyzed. Moderate biotin deficiency markedly decreased the abundance of each biotinylated polypeptide in rat liver. Biotin supplementation did not significantly elevate the abundance of biotinylated pyruvate, propionyl CoA, methylcrotonyl CoA or acetyl CoA carboxylase 1. The abundance of biotinylated acetyl CoA carboxylase 2, however, was significantly higher in biotin-supplemented rats. Pharmacologic biotin intake significantly reduced the abundance of biotinylated propionyl CoA and methylcrotonyl CoA carboxylase. These results indicate the following: 1) moderate biotin deficiency reduces free and protein bound biotin; 2) biotin intakes in rats that mimic the currently recommended daily value (DV) do not result in full protein biotinylation; and 3) pharmacologic supplementation may reduce the abundance of functional carboxylases.