Biology subjects

Whitfield, P. D.

Publications and source records attributed to Whitfield, P. D..

9 recordsLinked to original sources

bioRxiv2026

Comparative lipidomic profiling of the livestock pathogens Trypanosoma congolense and Trypanosoma brucei

African Animal Trypanosomosis (AAT) is a disease affecting domestic animals, in particular cattle, in sub-Saharan Africa, resulting in billion-dollar losses annually. New drugs to combat and control AAT are urgently required, yet few treatment candidates are currently on the horizon. This can be attributed, in part, to the relative challenges associated with culturing the clinically relevant parasite species in a laboratory environment. Particularly, effective culture of bloodstream form Trypanosoma congolense, the trypanosome species responsible for a large proportion of AAT disease in cattle, requires the use of goat serum, whilst T. brucei is typically cultured in FBS-supplemented culture. This constrains in vitro studies on biology, especially comparative analyses between AAT-causing species. The differing serum supplementation requirements of these two trypanosome species point to metabolic distinctions, which may be important considerations in developing experimental systems to enable the identification and design of novel, pan-species therapies. In this study, untargeted LC-MS lipidomics analyses were conducted to determine the relative lipidomic profiles of T. congolense and T. brucei bloodstream form parasites. Employing a new media formulation that permits effective in vitro culture of both species, it was possible to establish that their global lipidomic profiles are distinct. Notably, T. congolense exhibits a relatively low abundance of ether phospholipids compared to T. brucei, whilst also possessing an enrichment of long-chain polyunsaturated fatty acids (PUFAs). These observations indicate that there are significant differences in the ways these parasites synthesise and remodel their lipid complement, highlighting an evolutionary divergence between the species that likely carries implications for host-pathogen interactions as well as trypanosome membrane biology. Furthermore, this study demonstrates that fine-tuning fatty acid supplementation may aid in optimising a universal medium suited for multiple species of AAT parasites. SummaryMultiple species of protozoan parasites can cause African Animal Trypanosomosis (AAT) in livestock and other animals. However, AAT research has largely centred on a single species, Trypanosoma brucei, partially due to the comparative difficulties in sustaining the other economically important parasite species - Trypanosoma congolense and Trypanosoma vivax - in laboratory culture. In this work, we aimed to determine whether distinctions in use of lipids between T. brucei and T. congolense explains their differing in vitro culture requirements. Using a newly designed media formulation, it was possible to culture mammalian-infective forms of both parasite species under identical conditions, enabling direct comparison of their lipidome - a complete inventory of the different fats and lipids the cells contain. We demonstrate that the T. congolense lipidome significantly differs from that of T. brucei, and that T. congolense shows a preference for longer, more unsaturated lipids. These differences are likely to underlie species-specific differences observed during host infections. Furthermore, our work demonstrates that understanding the lipid biology of protozoan parasites aids in optimisation of laboratory culturing conditions, thereby facilitating further research into these understudied pathogens, including the development of new therapies.

microbiology↗

bioRxiv2026

Spermidine enhances metabolic flexibility and attenuates inflammation associated with ageing in farmed Atlantic salmon

Metabolic ageing and associated changes in lipid mobilisation have been most heavily studied in humans and model taxa, yet remain poorly understood in farmed animals, with potentially important uncharacterised implications for health and welfare outcomes in food production systems. Here, we study both processes in domesticated Atlantic salmon (Salmo salar), the worlds most commercially valuable farmed fish, comparing three stages of aquaculture production. Our sampling captures a key life-cycle change where juvenile fish transition from freshwater into seawater (smoltification), followed by the ongoing ageing process during a final period of growth in seawater. Integrating lipidomics and proteomics of visceral adipose and skeletal muscle tissue, we firstly identified a metabolic-ageing profile akin to that observed in humans, which was distinct from lipid-associated remodelling associated with earlier smoltification. This was marked by impaired triglyceride storage, dysfunctional autophagy-lysosomal pathways, inflammation, fibrosis and reduced pathogen clearance pathways in visceral adipose tissue. In skeletal muscle, ageing was accompanied by reduced metabolic flexibility together with triglyceride and fatty acid accumulation, depletion of phospholipids, and a reduction in free fatty acids required for ATP production. We go on to provide experimental in vivo evidence that dietary spermidine supplementation suppresses adipose inflammation and reverses age-associated metabolic flexibility by re-establishing the buffering role of adipose tissue and enhancing fatty acid metabolism in skeletal muscle. Importantly, spermidine appears to reprogram lipid flux to counter metabolic ageing. As farmed Atlantic salmon exhibit key features of metabolic ageing observed in humans that appear linked to its recent domestication history, this species offers a novel model for ageing related studies of vertebrate metabolism.

molecular biology↗

bioRxiv2025

Adiponectin exerts sex-dependent effects on lipid, amino acid, and glucose metabolism during caloric restriction

Adiponectin is the most abundant hormone in the circulation. Plasma adiponectin decreases in obesity but increases in leanness, including during caloric restriction (CR) in animals and humans. In obesity, adiponectin deficiency promotes cardiometabolic dysfunction. In contrast, the roles of adiponectin in CR, when it is at its highest, are largely unknown. To address this, we studied global adiponectin knockout (KO) in male and female mice fed either ad libitum (AL) or a 30% CR diet from 9-13 weeks of age. We show that adiponectin KO did not alter CR effects on body mass, body composition, or energy expenditure. However, KO unexpectedly decreased blood glucose levels during CR, both on fasting and following an oral glucose challenge. This is opposite to the effects of adiponectin deficiency in the context of ad libitum diet (AL) or obesity, and occurred without changes in insulin secretion or sensitivity. Moreover, adiponectin KO augmented CR-induced increases in plasma fatty acids in both sexes and, in males only, impaired systemic triglyceride clearance under CR. Indirect calorimetry further revealed that adiponectin KO alters the shifts between carbohydrate and lipid utilisation that occur during transitions between fed and fasted states. To determine potential molecular mechanisms, we investigated effects of adiponectin KO on the liver, a major adiponectin target that plays key roles entraining metabolism to nutritional state. Hepatic transcriptomics revealed that, in both sexes, adiponectin KO upregulates sterol and fatty acid synthesis genes under AL while increasing amino acid catabolic genes during CR. Together, our findings suggest that adiponectin tunes glucose, lipid, and amino acid metabolism during CR, in whole or in part through effects on the liver. The widely reported functions of adiponectin in pathological states, including obesity and insulin resistance, thus differ sharply from its roles during CR, with marked sexual dimorphism apparent for many of these functions.

physiology↗

bioRxiv2024

Rapamycin induced autophagy enhances lipid breakdown and ameliorates lipotoxicity in Atlantic salmon cells.

Autophagy is a highly conserved cellular recycling process essential for homeostasis in all eukaryotic cells. Lipid accumulation and its regulation by autophagy are key areas of research for understanding metabolic disorders in human and model mammals. However, the role of autophagy in lipid regulation remains poorly characterised in non-model fish species of importance to food production, which could be important for managing health and welfare in aquaculture. Addressing this knowledge gap, we investigate the role of autophagy in lipid regulation using a macrophage-like cell line (SHK-1) from Atlantic salmon (Salmo salar L.), the worlds most commercially valuable farmed finfish. Multiple lines of experimental evidence reveal that the autophagic pathway responsible for lipid droplet breakdown is conserved in Atlantic salmon cells. We employed global lipidomics and proteomics analyses on SHK-1 cells subjected to lipid overload, followed by treatment with rapamycin to induce autophagy. This revealed that activating autophagy via rapamycin enhances storage of unsaturated triacylglycerols and suppresses key lipogenic proteins, including fatty acid elongase 6 and acid sphingomyelinase. Moreover, fatty acid elongase 6 was identified as cargo for autophagosomes, suggesting a critical role for autophagy in lipid metabolism in fish. Together, this study establishes a novel model of lipotoxicity and advances understanding of lipid autophagy in fish cells, with significant implications for addressing fish health issues in aquaculture.

cell biology↗

bioRxiv2024

Hydroxysteroid 17-beta dehydrogenase 13 (Hsd17b13) knockdown attenuates liver steatosis in high-fat diet obese mice

Hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13) loss-of-function gene variants are associated with decreased risk of metabolic dysfunction-associated steatotic liver disease (MASLD). Our RNA-seq analysis of steatotic liver from obese mice -/+ Fenretinide treatment identified major beneficial effects of Fenretinide on hepatic gene expression including Hsd17b13. We sought to determine the relationship between Hsd17b13 expression and MASLD and to validate it as a therapeutic target by liver-specific knockdown. Hsd17b13 expression, which is unique to hepatocytes and associated with the lipid-droplet, was elevated in multiple models of MASLD and normalised with prevention of obesity and steatotic liver. Direct, liver- specific, shRNA-mediated knockdown of Hsd17b13 (shHsd17b13) in high-fat diet (HFD)-obese mice, markedly improved hepatic steatosis with no effect on body weight, adiposity or glycaemia. shHsd17b13 decreased elevated serum ALT, serum FGF21 levels and markers of liver fibrosis e.g. Timp2. shHsd17b13 knockdown in HFD-obese mice and Hsd17b13 overexpression in cells reciprocally regulated expression of lipid metabolism genes e.g. Cd36. Global lipidomic analysis of liver tissue revealed a major decrease in diacylglycerols (e.g. DAG 34:3) with shHsd17b13 and an increase in phosphatidylcholines containing polyunsaturated fatty acids (PUFA) e.g. PC 34:3 and PC 42:10. Expression of key genes involved in phospholipid and PUFA metabolism e.g. Cept1, were also reciprocally regulated suggesting a potential mechanism of Hsd17b13 biological function and role in MASLD. In conclusion, Hsd17b13 knockdown in HFD-obese adult mice was able to alleviate MASLD via regulation of fatty acid and phospholipid metabolism, thereby confirming HSD17B13 as a genuine therapeutic target for MASLD and development of liver fibrosis. KEY POINTSO_LIHSD17B13 loss-of-function gene variants are associated with decreased risk of metabolic dysfunction-associated (MA) steatotic liver disease and steatohepatitis (MASLD and MASH). C_LIO_LIRNA-seq analysis of steatotic liver identified beneficial effects of Fenretinide on hepatic gene expression including downregulation of Hsd17b13. C_LIO_LILiver-specific shRNA knockdown of Hsd17b13 in obese mice markedly improved hepatic steatosis and markers of liver health e.g. serum ALT, serum Fgf21 levels. C_LIO_LIHsd17b13 influenced expression of lipid/phospholipid metabolism genes e.g. Cd36 and Cept1 and phosphatidylcholines PC 34:3 and PC 42:10. C_LIO_LIOur study suggests a mechanism of HSD17B13s biological function and the strong rationale behind targeting HSD17B13 for MASLD/MASH. C_LI

physiology↗

bioRxiv2022

Fenretinide inhibits obesity and fatty liver disease but induces Smpd3 to increase serum ceramides and worsen atherosclerosis in LDLR-/- mice.

Fenretinide is a synthetic retinoid that can prevent obesity and improve insulin sensitivity in mice by directly altering retinol/retinoic acid homeostasis and inhibiting excess ceramide biosynthesis. We determined the effects of Fenretinide on LDLR-/- mice fed high-fat/high-cholesterol diet +/- Fenretinide, a model of atherosclerosis and non-alcoholic fatty liver disease (NAFLD). Fenretinide prevented obesity, improved insulin sensitivity and completely inhibited hepatic triglyceride accumulation, ballooning and steatosis. Moreover, Fenretinide decreased the expression of hepatic genes driving NAFLD, inflammation and fibrosis e.g. Hsd17b13, Cd68 and Col1a1. The mechanisms of Fenretinides beneficial effects in association with decreased adiposity were mediated by inhibition of ceramide synthesis, via hepatic DES1 protein, leading to increased dihydroceramide precursors. However, Fenretinide treatment in LDLR-/- mice enhanced circulating triglycerides and worsened aortic plaque formation. Interestingly, Fenretinide led to a 4-fold increase in hepatic sphingomyelinase Smpd3 expression, via a retinoic acid-mediated mechanism and a further increase in circulating ceramide levels, linking induction of ceramide generation via sphingomyelin hydrolysis to a novel mechanism of increased atherosclerosis. Thus, despite beneficial metabolic effects, Fenretinide treatment may under certain circumstances enhance the development of atherosclerosis. However, targeting both DES1 and Smpd3 may be a novel, more potent therapeutic approach for the treatment of metabolic syndrome.

physiology↗

bioRxiv2022

The effects of caloric restriction on adipose tissue and metabolic health are sex- and age-dependent

Caloric restriction (CR) is a nutritional intervention that reduces the risk of age-related diseases in numerous species, including humans. CRs metabolic effects, including decreased fat mass and improved insulin sensitivity, play an important role in its broader health benefits. However, the extent and basis of sex differences in CRs health benefits are unknown. We found that 30% CR in young (3-month-old) male mice decreased fat mass and improved glucose tolerance and insulin sensitivity, whereas these effects were blunted or absent in young female mice. Females resistance to fat and weight loss was associated with decreased lipolysis, lower systemic energy expenditure and fatty acid oxidation, and increased postprandial lipogenesis compared to males. Positron emission tomography-computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) showed that peripheral glucose uptake was comparable between sexes. Instead, the sex differences in glucose homeostasis were associated with altered hepatic ceramide content and substrate metabolism: compared to CR males, CR females had lower TCA cycle activity but higher blood ketone concentrations, a marker of hepatic acetyl-CoA content. This suggests that males use hepatic acetyl-CoA for the TCA cycle whereas in females it accumulates, thereby stimulating gluconeogenesis and limiting hypoglycaemia during CR. In aged mice (18-months old), when females are anoestrus, CR decreased fat mass and improved glucose homeostasis to a similar extent in both sexes. Finally, in a cohort of overweight and obese humans CR-induced fat loss was also sex- and age-dependent: younger females (<45 years) resisted fat loss compared to younger males while in older subjects (>45 years) this sex difference was absent. Collectively, these studies identify age-dependent sex differences in the metabolic effects of CR and highlight adipose tissue, the liver and oestrogen as key determinants of CRs metabolic benefits. These findings have important implications for understanding the interplay between diet and health and for maximising the benefits of CR in humans. HIGHLIGHTSO_LICaloric restriction (CR) decreases fat mass and improves glucose homeostasis in young male mice, but young females resist these effects. C_LIO_LICR females resist lipolysis, decrease energy expenditure and increase postprandial lipogenesis more than CR males, explaining how females resist fat loss. C_LIO_LISex differences in glucose homeostasis are associated with altered hepatic metabolism and gluconeogenesis, without marked differences in peripheral glucose uptake. C_LIO_LICRs effects on fat loss and glucose homeostasis are comparable in aged male and female mice, implicating oestrogen as the driver of the sexually dimorphic effects in young mice. C_LIO_LIIn humans, females resist CR-induced fat loss in an age-dependent manner, further supporting the role of oestrogen in the sexually dimorphic effects of CR. C_LI

physiology↗

bioRxiv2019

Lipidomics analysis of juveniles blue mussels (Mytilus edulis L. 1758), a key economic and ecological species.

Blue mussels (Mytilus edulis L.) are important components of coastal ecosystems functioning through benthopelagic coupling and ecosystem engineering. At the same time, mussel production is central in the economy of coastal areas. Therefore, understanding their nutritional, physiological and metabolic processes at key life stages is important for their management, both within food production systems and in wild populations.\n\nLipids are crucial molecules for bivalve growth, but their diversity and roles have been considered from fatty acid (FA) perspective. In this paper, we applied lipidomics to bivalve nutrition. Lipidomics provides a holistic perspective on lipid patterns; by examining the lipidome, important physiological information can be acquired. Here, we use controlled laboratory experiments to elucidate the responses to changes in the diet of newly settled mussels juveniles, one of the most critical life stages. The diets considered in this study are single strains diet of Cylindrotheca fusiformis CCAP 1017/2 - CYL, Isochrysis galbana CCAP 927/1- ISO, Monodopsis subterranean CCAP 848/1 - MONO, Nannochloropsis oceanica CCAP 849/10- NANNO and a commercial algae paste -SP.\n\nThe diets had a significant effect on spat GR and WI, and according to their efficacy resulted ranked as follows: ISO>NANNO/CYL>SP>MONO. Spat FA composition and neutral lipid content (principally triacylglycerols - TG), were influenced by the diets. Furthermore, untargeted lipidomics also showed shifts in several phospholipid species, with changes related to the essential PUFA available from the diet. TG content, neutral lipids and several TG and FA species were correlated (Spearman R2>0.8 FDR p<0.05) with spat WI, suggesting their possible application as markers of mussel juvenile condition. The availability of dietary essential PUFA deeply modified the spat lipidome both for neutral and for polar lipids. This change in the lipidome could have major impacts on their ecology and their production for food.

biochemistry↗

bioRxiv2018

Characterization of the role of glycine lipids in Bacteroides thetaiotaomicron

Acylated amino acids function as important components of the cellular membrane in some bacteria. Biosynthesis is initiated by the N-acylation of the amino acid and this is followed by subsequent O-acylation of the acylated molecule resulting in the production of the mature diacylated amino acid lipid. In this study we use both genetics and liquid chromatography-mass spectrometry (LC-MS) to characterize the biosynthesis and function of novel diacylated glycine lipid (GL) species in Bacteroides thetaiotaomicron. We, and others, have previously reported the identification of a gene, named glsB in this study, that encodes a N-acyltransferase activity responsible for the production of a monoacylated glycine called N-acyl-3-hydroxy-palmitoyl glycine (or commendamide). In all of the Bacteroidales genomes so far sequenced the glsB gene is located immediately downstream from a gene, named glsA, also predicted to encode a protein with acyltransferase activity. We use LC-MS to show that co-expression of glsB and glsA results in the production of GL in Escherichia coli. We constructed a deletion mutant of the glsB gene in B. thetaiotaomicron and we confirm that glsB is required for the production of GL in B. thetaiotaomicron. Moreover, we show that glsB is important for the ability of B. thetaiotaomicron to adapt to stress and colonize the mammalian gut. Therefore, this report is the first to describe the genetic requirements for the biosynthesis of GL, a novel diacylated amino acids species that contributes to fitness in the human gut bacterium, B. thetaiotaomicron.

microbiology↗