Delta-6 desaturase (Fads2) deficiency alters triacylglycerol/fatty acid cycling in murine white adipose tissue.

The Δ-6 desaturase (D6D) enzyme is not only critical for the synthesis of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from α-linolenic acid (ALA), but recent evidence suggests that it also plays a role in adipocyte lipid metabolism and body weight; however, the mechanisms remain largely unexplored. The goal of this study was to investigate if a D6D deficiency would inhibit triacylglycerol storage and alter lipolytic and lipogenic pathways in mouse white adipose tissue (WAT) depots due to a disruption in EPA and DHA production. Male C57BL/6J D6D knockout (KO) and wild-type (WT) mice were fed either a 7% w/w lard or flax (ALA rich) diet for 21 weeks. Energy expenditure, physical activity, and substrate utilization were measured with metabolic caging. Inguinal and epididymal WAT depots were analyzed for changes in tissue weight, fatty acid composition, adipocyte size, and markers of lipogenesis, lipolysis, and insulin signaling. KO mice had lower body weight, higher serum nonesterified fatty acids, smaller WAT depots, and reduced adipocyte size compared to WT mice without altered food intake, energy expenditure, or physical activity, regardless of the diet. Markers of lipogenesis and lipolysis were more highly expressed in KO mice compared to WT mice in both depots, regardless of the diet. These changes were concomitant with lower basal insulin signaling in WAT. Collectively, a D6D deficiency alters triacylglycerol/fatty acid cycling in WAT by promoting lipolysis and reducing fatty acid re-esterification, which may be partially attributed to a reduction in WAT insulin signaling.

A reduction of skeletal muscle DHA content does not result in impaired whole body glucose tolerance or skeletal muscle basal insulin signaling in otherwise healthy mice.

Delta-6 desaturase (D6D), encoded by the Fads2 gene, catalyzes the first step in the conversion of α-linolenic acid to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The ablation of D6D in whole body Fads2-/- knockout (KO) mice results in an inability to endogenously produce EPA and DHA. Evidence supports a beneficial role for EPA and DHA on insulin-stimulated glucose disposal in skeletal muscle in the context of a metabolic challenge; however, it is unknown how low EPA and DHA levels impact skeletal muscle fatty acid composition and insulin signaling in a healthy context. The objective of this study was to examine the impact of ablating the endogenous production of EPA and DHA on skeletal muscle fatty acid composition, whole body glucose and insulin tolerance, and a key marker of skeletal muscle insulin signaling (pAkt). Male C57BL/6J wild-type (WT), Fads2+/- heterozygous, and Fads2-/- KO mice were fed a low-fat diet (16% kcal from fat) modified to contain either 7% w/w lard or 7% w/w flaxseed for 21 wk. No differences in total phospholipid (PL), triacylglycerol, or reactive lipid content were observed between genotypes. As expected, KO mice on both diets had significantly less DHA content in skeletal muscle PL. Despite this, KO mice did not have significantly different glucose or insulin tolerance compared with WT mice on either diet. Basal pAktSer473 was not significantly different between the genotypes within each diet. Ultimately, this study shows for the first time, to our knowledge, that the reduction of DHA in skeletal muscle is not necessarily detrimental to glucose homeostasis in otherwise healthy animals.NEW & NOTEWORTHY Skeletal muscle is the primary location of insulin-stimulated glucose uptake. EPA and DHA supplementation has been observed to improve skeletal muscle insulin-stimulated glucose uptake in models of metabolic dysfunction. Fads2-/- knockout mice cannot endogenously produce long-chain n-3 polyunsaturated fatty acids. Our results show that the absence of DHA in skeletal muscle is not detrimental to whole body glucose homeostasis in healthy mice.

Inhibition of Δ-6 desaturase reduces fatty acid re-esterification in 3T3-L1 adipocytes independent of changes in n3-PUFA cellular content.

Δ-6 desaturase (D6D) is a key enzyme in the synthesis of long-chain polyunsaturated fatty acids (LC-PUFA). Evidence suggests that reduced D6D activity not only disrupts LC-PUFA production, but also impacts whole body lipid handling and body weight; however, the mechanisms remain largely unexplored. Therefore, we investigated the effect of D6D inhibition on the regulation of lipid accumulation in 3T3-L1 adipocytes with and without changes in n-3 PUFA content. 3T3-L1 cells were treated with a D6D inhibitor (SC-26196) in the presence or absence of α-linolenic acid (ALA) throughout differentiation. We found that D6D inhibition blocked the conversion of ALA to eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPAn-3) when ALA was supplemented, while no changes in n-3 PUFA content were observed in cells treated with the D6D inhibitor alone. D6D inhibited cells had reduced triacylglycerol (TAG) accumulation despite an EPA/DPA deficiency. In addition, analyses of cellular protein markers, as well as non-esterified fatty acids and glycerol release in medium, suggested an increase in lipolysis and a decrease in fatty acid re-esterification in D6D-inhibited cells, independent of n-3 PUFA changes. To provide further evidence, we treated cells with the D6D inhibitor in the presence or absence of EPA and compared them with ALA-treated cells. Although EPA further reduced TAG content, the reduced markers of fatty acid re-esterification were not affected by ALA or EPA. Collectively, this study provides new insight showing that D6D inhibition reduces TAG accumulation and fatty acid re-esterification in adipocytes independent of changes in n-3 PUFA cellular content.

Erratum to: Herbal decoctosome is a novel form of medicine.

Following the published article, we noticed an error duplication in Figure 5G "control" and "PGY-6" that was introduced during the revised process, with an attempt to replace it with higher-resolution images. Here we provide the original data in the first submitted manuscript (Figure 5G).

Herbal decoctosome is a novel form of medicine.

Traditionally, herbal medicine is consumed by drinking decoctions produced by boiling herbs with water. The functional components of the decoction are heat stable. Small RNAs (sRNAs) were reported as a new class of functional components in decoctions. However, the mechanisms by which sRNAs survive heat treatment of the decoction and enter cells are unclear. Previous studies showed that plant-derived exosome-like nanoparticles (ELNs), which we call botanosomes, could deliver therapeutic reagents in vivo. Here, we report that heat-stable decoctosomes (ELNs) from decoctions have more therapeutic effects than the decoctions in vitro and demonstrate therapeutic efficacy in vivo. Furthermore, sRNAs, such as HJT-sRNA-m7 and PGY-sRNA-6, in the decoctosome exhibit potent anti-fibrosis and anti-inflammatory effects, respectively. Decoctosome is comprised of lipids, chemical compounds, proteins, and sRNAs. A medical decoctosome mimic is called bencaosome. A single lipid sphinganine (d22:0) identified in the decoctosome was mixed and heated with the synthesized sRNAs to form the simplest bencaosome. This simple bencaosome structure was identified by critical micelle concentration (cmc) assay that sRNAs coassembled with sphinganine (d22:0) to form the lipid layers of vesicles. The heating process facilitates co-assembly of sRNAs and sphinganine (d22:0) until a steady state is reached. The artificially produced sphinganine-HJT-sRNA-m7 and sphinganine- PGY-sRNA-6 bencaosomes could ameliorate bleomycin-induced lung fibrosis and poly(I:C)-induced lung inflammation, respectively, following oral administration in mice. Our study not only demonstrates that the herbal decoctosome may represent a combinatory remedy in precision medicine but also provides an effective oral delivery route for nucleic acid therapy.

Multifunctional aptamer-based nanoparticles for targeted drug delivery to circumvent cancer resistance.

By its unique advantages over traditional medicine, nanomedicine has offered new strategies for cancer treatment. In particular, the development of drug delivery strategies has focused on nanoscale particles to improve bioavailability. However, many of these nanoparticles are unable to overcome tumor resistance to chemotherapeutic agents. Recently, new opportunities for drug delivery have been provided by oligonucleotides that can self-assemble into three-dimensional nanostructures. In this work, we have designed and developed functional DNA nanostructures to deliver the chemotherapy drug doxorubicin (Dox) to resistant cancer cells. These nanostructures have two components. The first component is a DNA aptamer, which forms a dimeric G-quadruplex nanostructure to target cancer cells by binding with nucleolin. The second component is double-stranded DNA (dsDNA), which is rich in -GC- base pairs that can be applied for Dox delivery. We demonstrated that Dox was able to efficiently intercalate into dsDNA and this intercalation did not affect the aptamer's three-dimensional structure. In addition, the Aptamer-dsDNA (ApS) nanoparticle showed good stability and protected the dsDNA from degradation in bovine serum. More importantly, the ApS&Dox nanoparticle efficiently reversed the resistance of human breast cancer cells to Dox. The mechanism circumventing doxorubicin resistance by ApS&Dox nanoparticles may be predominantly by cell cycle arrest in S phase, effectively increased cell uptake and decreased cell efflux of doxorubicin. Furthermore, the ApS&Dox nanoparticles could effectively inhibit tumor growth, while less cardiotoxicity was observed. Overall, this functional DNA nanostructure provides new insights into the design of nanocarriers to overcome multidrug resistance through targeted drug delivery.