Metabolism

ObjectiveMaternal obesity is usually associated with placental hypovascularity. This study aimed to challenge this paradigm by investigating the immediate vascular adaptations in the placental labyrinth zone in response to short-term, diet-induced obesity. The study hypothesised that there would be an initial compensatory hypervascularisation before the onset of systemic metabolic disease. MethodsFemale Wistar rats were fed either a standard control diet (CG, n = 9) or an ultra-processed, hypercaloric cafeteria diet (EG, n = 9) for eight weeks to induce obesity. On gestational day 16.5, maternal morphometric and biochemical analyses were performed alongside detailed placental histomorphometry and immunohistochemistry for CD31/-actin, in order to quantify foetal vessel density in the labyrinth zone using ImageJ. ResultsThe cafeteria diet successfully induced a significant obese phenotype (mean weight gain: 62.73 g in the experimental group (EG) versus 32.26 g in the control group (CG); P < 0.0001), but did not induce significant hyperglycaemia or dyslipidaemia (P > 0.05). Although there were no significant differences in foetal or placental weights, the labyrinth zone of the EG showed a significant increase in foetal vessel density (29.08 {+/-} 1.91 vessels/field) compared to the CG (26.06 {+/-} 1.80 vessels/field; P = 0.014), indicating robust vascular remodelling. ConclusionShort-term exposure to an obesogenic diet triggers significant compensatory hypervascularisation in the placenta of rats, which is an adaptive response that precedes systemic metabolic dysfunction. This finding contrasts with the hypovascularity observed in chronic obesity. The discrepancy between increased vascular density and foetal growth underscores the importance of evaluating not only the quantity but also the quality and function of blood vessels when assessing placental health in cases of maternal obesity. HighlightsO_LIAcute cafeteria diet-induced obesity causes placental hypervascularity. C_LIO_LIIncreased placental vasculature does not correlate with enhanced foetal growth. C_LIO_LIRapid obesity develops without major pre-gestational metabolic disruption. C_LIO_LIA biphasic model of vascular adaptation to maternal obesity is proposed. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/664837v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@1090dfaorg.highwire.dtl.DTLVardef@174c7cdorg.highwire.dtl.DTLVardef@1e9a413org.highwire.dtl.DTLVardef@131bf9_HPS_FORMAT_FIGEXP M_FIG C_FIG

Obesity is a global health crisis, with its prevalence particularly severe in the United States, where over 42% of adults are classified as obese. Obesity is driven by complex molecular and tissue-level mechanisms that remain poorly understood. Among these, angiogenesis--primarily mediated by vascular endothelial growth factor (VEGF-A)--is critical for adipose tissue expansion but presents unique challenges for therapeutic targeting due to its intricate regulation. Systems biology approaches have advanced our understanding of VEGF-A signaling in vascular diseases, but their application to obesity is limited by scattered and sometimes contradictory data. To address this gap, we performed a comprehensive analysis of the existing literature to synthesize key findings, standardize data, and provide a holistic perspective on the adipose vascular microenvironment. The data mining revealed five key findings: (1) obesity increases adipocyte size by 78%; (2) vessel density in adipose tissue decreases by 51% in obese mice, with vessels being 47-58% smaller and 4-9 times denser in comparison with tumor vessels; (3) capillary basement membrane thickness remains similar regardless of obesity; (4) VEGF-A shows the strongest binding affinity for VEGFR1, with four times stronger affinity for VEGFR2 than for NRP1; and (5) binding affinities measured by radioligand binding assay and surface plasmon resonance (SPR) are significantly different. These consolidated findings provide essential parameters for systems biology modeling, new insights into obesity-induced changes in adipose tissue, and a foundation for developing angiogenesis-targeting therapies for obesity.

BackgroundVisceral obesity is a critical determinant of severe coronavirus disease-2019 (COVID-19). Methods: In this study, we performed a comprehensive histomorphologic analysis of autoptic visceral adipose tissues (VAT), lungs and livers of 19 COVID-19 and 23 non-COVID-19 subjects. ResultsAlthough there were no between-groups differences in body-mass-index and adipocytes size, higher prevalence of CD68+ macrophages in COVID-19 subjects VAT was detected (p=0.005) and accompanied by crown-like structures presence, signs of adipocytes stress and death. Consistently, human adipocytes were successfully infected by SARS-CoV2 in vitro and displayed lower cell viability. Being VAT inflammation associated with lipids spill-over from dead adipocytes, we studied lipids distribution employing Oil-Red-O staining (ORO). Lipids were observed within lungs and livers interstitial spaces, macrophages, endothelial cells, and vessels lumen, features suggestive of fat embolism syndrome, more prevalent among COVID-19 individuals (p<0.001). Notably, signs of fat embolism were more prevalent among obese (p=0.03) independently of COVID-19 diagnosis, suggesting that such condition may be an obesity complication, exacerbated by SARS-CoV2 infection. Importantly, all infected subjects lungs presented lipids-rich (ORO+) hyaline membranes, formations associated with COVID-19-related pneumonia, present only in one control with non-COVID-19 pneumonia. ConclusionsThis study describes for the first time novel COVID-19-related features possibly underlying the unfavorable prognosis in obese SARS-CoV2-infected-subjects.

BackgroundThe global prevalence of obesity, an established risk and progression factor for colon cancer, is high and rising. Unfortunately, the mechanisms underlying the obesity-colon cancer association are incompletely understood, and new molecular targets enabling more effective intervention strategies to break the obesity-colon cancer link are urgently needed. ObjectiveThis study integrated RNA sequencing data from mouse and human colon tumor samples, as well as human adipose samples, to rigorously establish obesity-associated transcriptomic signatures conserved between the two species. MethodsWe employed a mouse colon cancer model with colonoscopy-guided orthotopic transplantation of syngeneic Apc-null;KrasG12D/+;Trp53-null;Smad4-null;tdTomato colon tumor organoids. Epithelial cell adhesion molecule (EpCAM)-positive cells from murine tumors, and 193 human colon tumors and 188 human mesenteric adipose tissue samples from the ColoCare cohort underwent transcriptomic analyses. ResultsDiet-induced obesity reduced survival in the mouse model of colon cancer. Integrated transcriptomic analyses of EpCAM-positive murine tumor cells and bulk human tumors revealed obesity-driven enrichment of inflammation and metabolic pathways, including upregulation of genes involved in innate immune sensing (TLR2, MYD88, IRF4) and tumor microenvironment remodeling (MMP9, TGFB1, SERPINE1). Analysis of paired mesenteric visceral adipose tissue and tumor samples from the ColoCare cohort indicated that obesity amplifies inflammatory signaling pathways through unique adipose ligand-tumor receptor interactions. ConclusionsThese results establish obesity-associated adipose tissue dysregulation as a key inter-tissue modulator of biology, with concordant cross-species effects on tumor cell-intrinsic inflammatory and metabolic programs.

Obesity strongly increases the risk of cardiometabolic diseases, yet the underlying mediators of this relationship are not fully understood. Given that obesity has broad effects on circulating protein levels, we investigated circulating proteins that mediate the effects of obesity on coronary artery disease (CAD), stroke, and type 2 diabetes--since doing so may prioritize targets for therapeutic intervention. By integrating proteome-wide Mendelian randomization (MR) screening 4,907 plasma proteins, colocalization, and mediation analyses, we identified seven plasma proteins, including collagen type VI 3 (COL6A3). COL6A3 was strongly increased by body mass index (BMI) ({beta} = 0.32, 95% CI: 0.26-0.38, P = 3.7 x 10-8 per s.d. increase in BMI) and increased the risk of CAD (OR = 1.47, 95% CI:1.26-1.70, P = 4.5 x 10-7 per s.d. increase in COL6A3). Notably, COL6A3 is cleaved at its C-terminus to produce endotrophin, which was found to mediate this effect on CAD. In single-cell RNA sequencing of adipose tissues and coronary arteries, COL6A3 was highly expressed in cell types involved in metabolic dysfunction and fibrosis. Finally, we found that body fat reduction can reduce plasma levels of COL6A3-derived endotrophin, thereby highlighting a tractable way to modify endotrophin levels. In summary, we provide actionable insights into how circulating proteins mediate the effect of obesity on cardiometabolic diseases and prioritize endotrophin as a potential therapeutic target.

Obesity associates with a reduction in cold-induced glucose tracer uptake in brown adipose tissue in humans, suggesting loss of thermogenic capacity. We therefore hypothesized that a whitening of BAT occurs in obesity and assessed the molecular characteristics of deep neck BAT in a cohort of 24 normal weight, 24 overweight and 22 obese individuals in comparison with subcutaneous abdominal white adipose tissue (WAT). We found that the major marker of BAT thermogenesis, UCP1, was associated with central but not general obesity. We performed transcriptomic analysis of BAT in a cohort of 27 individuals classified as normal weight, over-weight or obese, and additionally four subjects with type 2 diabetes (T2DM), dispersed among the 3 BMI groups. We identified 3204 differentially expressed genes between BAT and WAT in samples from normal weight individuals, including genes involved in thermogenesis, but also revealing differences in developmental and immune system related genes. In BAT from individuals with overweight or obesity, 202 genes were downregulated and 66 of these were involved in cellular respiratory pathways, likely reflecting previously observed reduction in thermogenic function with obesity. Importantly, most BAT selective genes were not affected, and isolated adipose progenitors differentiated into thermogenic adipocytes with equal frequency regardless of BMI group. In conclusion, our data suggest a retained BAT identity, with a selective reduction of thermogenic genes, in human obesity.

ObjectiveSARS-CoV-2 infection is associated with impaired glucose metabolism. Although the mechanisms are not fully understood, insulin resistance (IR) appears to be a central factor. Patients who had a severe acute phase, but even asymptomatic or with mild COVID-19, have an increased risk of T2DM. After the acute phase, post-COVID-19 syndrome (PCS) also seems to be related to this metabolic disturbance, but there is a paucity of studies. This study aims to evaluate a possible relationship between PCS and IR after mild COVID-19 and, if confirmed, whether there are differences by sex. Subjects and methodsRetrospective observational cohort study including subjects who had mild COVID-19 between April and September 2020 in a community setting. None had been vaccinated against SARS-CoV-2 at inclusion, and previous T2DM and liver disease were exclusion criteria. Patients who met NICE criteria were classified as PCS+. Epidemiological and laboratory data were analysed. Three assessments were performed: 1E (pre-COVID-19, considered baseline and reference for comparisons), 2E (approximately 3 months after the acute phase), and 3E (approximately 20 months after the acute phase). A triglyceride-to-glucose (TyG) index [&ge;]8.74 was considered IR. Albumin-to-globulin ratio (AGR) and lactate dehydrogenase (LDH) were assessed as inflammatory markers. Bivariate analyses were performed, using nonparametric and repeated measures tests. A subsample without metabolic disorder or CVD (age<median, BMI<25 kg/m2, elevated AGR, TyG index=7.80 [0.5]) was generated to reasonably rule out prior baseline IR that could bias the results. The relationships between PCS and TyG in 3E (TyG3) were modeled in 8 multiple regressions, stratifying by sex and BMI combinations. ResultsA total of 112 subjects (median [IQR] of age= 44 [20] years; 65 women) were analysed. Up to 14.3% was obese and 17% was hypertensive. Significant increases between 1E and 3E were registered regarding (i) basal glycemia (BG), 87 [14] mg/dL vs. 89 [14]; p=0.014, (ii) TyG index (8.25 [0.8] vs. 8.32 [0.7]; p=0.002), and (iii) LDH in 3rd tertile (16.1% vs 32.1%; p=0.007). A total of 8 previously normoglycemic subjects, showed BG2 or BG3 >126 mg/dL. The subgroups with IR highest prevalence at 3E were those of BMI [&ge;]25 kg/m2 and PCS+. The subgroup without CVD presented a significant increase in the TyG index (TyG1=7.80 [0.1] vs. TyG3= 8.28 [0.1]; p=0.017). LDH1 was significantly correlated with TyG3 in both sexes (rho=0.214 in women, rho=0.298 in men); in contrast, LDH2 and LDH3 did not present such an association. In multivariable analysis, PCS has shown to be an independent and predictive variable of TyG index in women with BMI<25 kg/m2, after adjustment for age, hypertension, BMI, Charlson comorbidity index, AGR1, AGR2, LDH1, number of symptoms of acute COVID-19, and number of days of the acute episode ({beta}=0.350; p=0.039). ConclusionsPCS has played a secondary role in predicting IR, showing a modest effect compared to BMI or prior hypertension. A significant increase in IR has been noted 20 months after mild COVID-19, both in cases of previous baseline IR and in those without previous IR. Basal serum LDH has shown to be predictive of current TyG, regardless of elevated LDH after SARS-CoV-2 infection. There were profound differences between women and men, confirming the need for a sex-stratified analysis when addressing the relation between PCS and glycemic alterations.

Obesity increases significantly cancer risk in various organs. Although this has been recognized for decades, the mechanism through which this happens has never been explained. Here, we show that obese people (BMI [&ge;]30) have on average 55% (95%CI: 46%-66%), 68% (95%CI: 59%-76%), and 39% (95%CI: 29%-49%) larger kidneys, liver, and pancreas, respectively. We also find a significant linear relationship between the increase in organ volume and the increase in cancer risk (P-value<10-12). These results provide a mechanism explaining why obese individuals have higher cancer risk in several organs: the larger the organ volume the more cells at risk of becoming cancerous. These findings are important for a better understanding of the effects that obesity has on cancer risk and, more generally, for the development of better preventive strategies to limit the mortality caused by obesity.

Gastric bypass surgery results in long-term weight loss due to re-routing of the gastro-intestinal anatomy and dietary intake alterations. Studies have examined protein change during rapid weight loss (up to 1 year post-surgery), but whether protein changes are maintained long-term after weight stabilization is unknown. To identify proteins and pathways involved with the long-term beneficial effects of weight loss, abundances of 1297 blood-circulating proteins were measured at baseline, 2 and 12 years after Roux-en-Y gastric bypass surgery. Protein changes were compared between 234 surgery and 144 non-surgery subjects with severe obesity, with discovery and replication subgroups. Seventy-one protein changes were associated with 12-year BMI changes and 58 (7 unique) with surgical status. Protein changes, including ApoM, were most strongly associated with long-term changes in lipids (HDL-C and triglycerides). Inflammation, adipogenesis, cellular signaling, and complement pathways were implicated. Short-term improvements in protein levels were maintained long-term, even after some weight regain.

Obesity is a complex chronic disease characterized by excessive adiposity and associations with numerous co-morbidities, including cancer. Despite extensive research, we have limited understanding of the mechanisms coupling obesity to cancer risk, and separately, of the contexts where obesity does or does not exacerbate disease. Here, we show that chronic high-fat diet induced obesity has no significant effect on the Trp53R270H/+ mouse, a model of human Li-Fraumeni multi-cancer syndrome. Surprisingly, despite inducing rapid and highly penetrant obesity and long-term differences in adiposity, greater than one year of HFD had no significant effect on survival or tumor burden. These findings were replicated in two separate cohorts totaling 359 mice and thus provide important negative data for the field. Given strong publication bias against negative data in the literature, this large murine cohort study represents a clear case where chronic diet-induced obesity does not accelerate or aggravate cancer outcomes. The data thus carry high impact for researchers, funders, and policymakers alike.

Protein tyrosine phosphatases are crucial regulators of metabolism with specific roles in different tissues. To investigate hepatocyte-specific function of protein tyrosine phosphatase receptor type K (PTPRK), we generated mice carrying floxed Ptprk alleles and crossed them with Alb-Cre mice (Ptprk{Delta}Hep mice). Under chow feeding, Ptprk{Delta}Hepmice were largely comparable to littermate controls. In contrast, Ptprk{Delta}Hepmice fed a high-fat, high-fructose, high-cholesterol diet exhibited reduced steatosis, lower hepatic PPAR{gamma}, and blunted hepatocyte hypertrophy, accompanied by improved systemic insulin sensitivity, as assessed by hyperinsulinemic-euglycemic clamps. We identified PTPRK-interacting proteins enriched for metabolic functions associated with glycolysis and lipid biosynthesis using pull downs from primary hepatocyte lysates. In line with these findings, Ptprk{Delta}Hep mice developed fewer tumours than controls in an obesity and carcinogen-induced hepatocellular carcinoma (HCC) model. Our data show that under nutrient excess PTPRK is functionally engaged in hepatocytes to support PPAR{gamma}-linked steatotic growth, insulin resistance, and tumour initiation, highlighting PTPRK as a potential therapeutic target in MASLD-associated HCC.

Obesity is a life-threatening condition characterized by a maladaptive remodeling of the visceral white adipose tissue (vWAT), including fibrosis, that drives vWAT metabolic alterations. We previously identified CD9hi adipose tissue progenitors as the main drivers of vWAT fibrosis in mice and humans. However, how their functions are controlled, especially by macrophages, remains largely unknown. We found that obesity-elicited monocyte-derived macrophages (obeMac) accumulation was considerably elevated in mice prone to obesity-induced vWAT fibrosis. Limiting obeMac build-up decreased the numbers and fibrogenic activation of CD9hi progenitors, leading to decreased vWAT fibrosis and improved glucose homeostasis. In patients with obesity, we identified macrophages similar to mouse obeMacs that were associated with accumulation of CD9hi progenitors in the vWAT and loss of glycemic control. Finally, intercellular communication analysis identified mediators produced by obeMacs that control the fibrogenic potential of CD9hi progenitors. Together, we uncovered an obeMac-CD9hi progenitors axis controlling vWAT fibrosis and dysfunction.

Hypercalcemia, caused by tumor secretion of parathyroid hormone-related protein (PTHrP), is associated with anorexia and weight loss. We demonstrate that overexpression of PTHrP by tumor cells in a transgenic model of breast cancer causes anorexia and rapid weight loss. These changes are accompanied by activation of neurons in the area postrema (AP), the nucleus tractus solitarius (NTS) and the parabrachial nucleus (PBN), a hindbrain circuit regulating food intake. Blocking hypercalcemia prevents anorexia and activation of these brain centers in tumor bearing mice, whereas injecting calcium activates the same circuit in wild-type mice. Neurons in the AP express the calcium-sensing receptor (CaSR) and the same AP/NTS/PBN circuit is stimulated by treating WT mice with cinacalcet, an allosteric activator of the CaSR. Finally, treating diet-induced obese mice with cinacalcet reduces food intake and causes weight loss. These results suggest that CaSR-expressing neurons in the AP might be a pharmacologic target for obesity.

Despite considerable advances in identifying risk factors for obesity development, there remains substantial gaps in our knowledge about its etiology. Variation in obesity (defined by BMI) is thought to be due in part to heritable factors; however, obesity-associated genetic variants only account for a small portion of heritability. Epigenetic regulation defined by genetic and/or environmental factors with changes in gene expression, may account for some of this "missing heritability". Epigenetic studies of obesity have largely been conducted in populations of European ancestry, despite the disproportionate burden of obesity in African Americans (AAs). To address race/ethnic (RE)-differences in obesity, we conducted a BMI epigenome-wide association study (EWAS) meta-analysis using AA participants from the Jackson Heart Study (JHS, n=1604) and the Multi-Ethnic Study of Atherosclerosis (MESA, n=179). Analyses using a linear regression model with methylation as the outcome and continuous BMI as the predictor were stratified by study and sex, then meta-analyzed. There were 208 methylation sites (CpGs) that reached epigenome-wide significance (p< 8.72x10-8); 151 of these were novel. Of the novel CpGs, 29 CpGs were available for replication testing in a separate sample of AA and 20 replicated. Differentially methylated region (DMR) analysis resulted in 54 DMRs significantly associated with BMI. Several regions are proximal to, or include, genes previously associated with obesity traits (e.g., SOCS3, ABCG1, and TGFB1) in GWAS. Gene and trait enrichment and pathway analysis showed enrichment for genes in immune system and inflammation related pathways (e.g., the IL-6/JAK/STAT pathway). In conclusion, EWAS of BMI in AAs replicated previously known associations identified in European and multi-ethnic EWAS and identified novel obesity-associated CpGs.

Severe (class III) obesity is a chronic, relapsing condition, with a high burden of co-morbidity and mortality. Previous evidence has established genetics as an important contributing factor. We therefore designed a custom genotyping array to screen a cohort of UK patients seeking treatment for severe obesity. 1,714 participants were genotyped using a custom AXIOM array, focusing on rare (minor allele frequency <0.01) variants, with CADD-PHRED [&ge;]15 in 78 genes known/suspected to cause Mendelian forms of obesity. Concordance analyses of 22 duplicate samples and 66 samples with whole exome sequence data revealed good genotyping reliability. We identified the proportion of study participants who carried, or were homozygous for, rare, predicted-deleterious variants in genes with dominant and recessive modes of inheritance (MOI), respectively. 27% of patients carried relevant mutations consistent with the expected MOI, which was very similar to the rate observed in the UKB 50K whole exome sequencing dataset. However, the clinical obesity cohort were more likely to carry two or more such variants, in separate genes, than UK Biobank participants (p = 0.018). In conclusion, our results provide evidence: that (i) custom genotyping arrays, used with improved algorithms can allow reliable, cost-effective screening for rare genetic variants; (ii) rare mutations in "obesity genes" may be at high prevalence among bariatric patients, as well as in the general population; and (iii) that severe obesity may have an oligogenic pattern of inheritance in some cases.

Emerging evidence that circulating levels of key metabolic intermediates are sensed by a range of G-Protein Coupled receptors (GPCRs) is providing critical new insights into the control of systemic metabolic homeostasis, and how disturbances in such sensing may contribute to metabolic disease. The hydroxycarboxylic acid receptors for lactate (HCAR1), {beta}-hydroxybutyrate (HCAR2), and octanoate (HCAR3) are encoded by three closely homologous GPCR genes co-located in a region where common genetic variation has been reportedly associated with lipid levels and body fat distribution. By resolving sequence homology in this region, we were able to refine this signal to a coding variant (R311C) in HCAR2. Using corrected genotypes from [~]500K participants from UK Biobank and direct genotyping of four other studies, we found that carriage of the HCAR2 p.R311C variant was significantly associated with type 2 diabetes risk, reduced gynoid fat mass, increased waist-hip ratio, higher circulating triglycerides, glucose and alanine aminotransferase levels, lower levels of HDL cholesterol and adiponectin and impaired suppression of circulating levels of non-esterified fatty acids after oral glucose. Adipose tissue explants from mice engineered to express the equivalent mutation variant (p.R308C) in the mouse ortholog showed increased lipolytic activity, basally and after {beta}-hydroxybutyrate (BHB) treatment. In vivo, the mice were insulin resistant and had increased liver fat and impaired post-prandial suppression of NEFAs. The variant alters an amino acid located in the intracellular C-terminal tail of HCAR2, increasing recruitment of {beta}-arrestin and resulting in enhanced internalisation and reduced cell surface expression. In conclusion, a common variant in the human ketone body receptor results in impaired control of adipocyte lipolysis and adversely impacts systemic lipid and glucose metabolism. These findings highlight the importance of anti-lipolytic ketone body signalling in adipocytes for the maintenance of metabolic health Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/25336995v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@1dd7e54org.highwire.dtl.DTLVardef@90ca10org.highwire.dtl.DTLVardef@1c1ef16org.highwire.dtl.DTLVardef@137c18b_HPS_FORMAT_FIGEXP M_FIG C_FIG

Fat accumulation, de novo lipogenesis, and glycolysis are key drivers of hepatocyte reprogramming and the consequent metabolic dysfunction-associated steatotic liver disease (MASLD). Here we report that obesity leads to dysregulated expression of hepatic protein-tyrosine phosphatases (PTPs). PTPRK was found to be increased in steatotic hepatocytes in both humans and mice, and positively correlated with PPAR{gamma}-induced lipogenic signalling. High-fat-fed PTPRK knockout mice displayed reduced weight gain and hepatic fat accumulation. Phosphoproteomic analysis in primary hepatocytes and hepatic metabolomics identified fructose-1,6-bisphosphatase 1 and glycolysis as PTPRK targets in metabolic reprogramming. Silencing PTPRK in hepatoma cell lines resulted in reduced colony-forming ability and PTPRK knockout mice developed smaller tumours after diethylnitrosamine-induced hepatocarcinogenesis. Our study defines a novel role for PTPRK in regulating hepatic glycolysis, lipid metabolism, and tumour development. PTPRK inhibition may provide therapeutic possibilities in obesity-associated liver diseases. HighlightsO_LIHepatic receptor-type PTPs are increased in MASLD C_LIO_LIPTPRK is expressed in hepatocytes and upregulated in obesity C_LIO_LIPTPRK deficiency reduces body fat mass and liver steatosis in diet-induced obesity C_LIO_LIPTPRK regulates hepatic glycolysis and lipogenesis, promoting tumorigenesis C_LI

BackgroundCoronavirus disease 2019 (COVID-19), is more severe in individuals with obesity. Furthermore, a cytokine storm was observed in many critically ill patients with COVID-19. Since adipose tissue secretes cytokines, we investigated whether cytokines mediate the effect of obesity on COVID-19 severity. MethodsUsing two-sample Mendelian randomization analyses we assessed the causal effect of body mass index (BMI) on COVID-19 severity. We then evaluated the BMI effect on 41 inflammatory cytokines, as well as on JAK-2, lymphocyte percentage and leptin. We also tested the relationship between these immunological factors and COVID-19 severity. The estimates obtained were used in a mediation analysis to understand the immunological factors linking BMI to COVID-19 severity. ResultsHigher BMI increased the risk of COVID-19 severity. BMI was also causally associated with 5 of the 41 inflammatory cytokines, HGF, TRAIL, IL 13, IL6, and IL 7. We identified TNF- and IL-8 as the only two inflammatory cytokines associated with COVID-19 severity. Leptin-related genetic variation was associated with COVID-19 severity, but JAK-2 and lymphocyte percentage were not. We found no statistical evidence of mediation of immunological factors tested on the relationship between BMI and COVID-19 severity, although our estimate was 52.8%. ConclusionsWe replicated the previously reported association between BMI and COVID-19 severity. We identified the inflammatory cytokines elevated due to higher BMI. Other inflammatory cytokines showed evidence for increasing COVID-19 severity. However, we were unable to find statistical evidence of baseline levels of circulating cytokines, or additional factors involved in a cytokine storm i.e. JAK-2, lymphocyte percentage, and leptin, mediating the link between BMI and severe COVID-19. Although targeting specific cytokines will be of benefit in the general population, further work on cytokine levels during early phases of COVID-19 infection is needed to provide new approaches to decrease the risk of severe COVID-19 with higher BMI.

The translocator protein (TSPO) is a mitochondrial outer membrane protein with high expression in cells specialized for lipid metabolism, including white adipose tissue (WAT), where its physiological function remains poorly defined. Our previous work demonstrated a role for TSPO in mitochondrial fatty acid oxidation, prompting us to investigate its contribution to adipocyte lipid homeostasis under metabolic stress. We employed a combination of in vivo and in vitro approaches using global Tspo knockout (Tspo-/-) mice, primary adipocyte cultures, and pharmacological TSPO-binding drugs to examine TSPO function. We show that Tspo-/- mice exhibited increased WAT mass and adipocyte hypertrophy following high-fat diet feeding, with no changes in caloric intake. These changes were accompanied by suppression of key lipolytic genes, reduced circulating NEFA and glycerol levels, and altered expression of fatty acid oxidation genes. Lipidomic profiling showed no genotype-dependent changes, indicating impaired mobilization rather than altered lipid composition. In vitro, TSPO deficiency enhanced lipid accumulation during adipocyte diberentiation and impaired expression of lipolytic genes. TSPO-binding drugs phenocopied this response in TSPO-expressing cells. Mechanistically, we identify protoporphyrin IX (PPIX), an endogenous TSPO ligand, as a suppressor of adipogenic and lipolytic programs. PPIX levels increase during adipogenesis, and its accrual inhibits both lipid accumulation and lipolytic response, whereas hemin does not elicit these ebects. Our findings identify TSPO as a regulator of adipocyte lipid metabolism through a previously unrecognized TSPO-PPIX axis that influences lipid mobilization in adipocytes. This mechanism provides insight into TSPOs role in metabolic adaptation and highlights its potential as a therapeutic target in obesity-associated adipose dysfunction.

ObjectiveThis research aims to uncover the factors associated with circulating FGF21 levels in a cohort mimicking metabolic disease progression, examining its relationship with adipose tissue (AT) morphology and function. It also investigates FGF21 level changes post-metabolic surgery, predictive factors, and their links to metabolic adjustments. DesignIn this observational study, serum FGF21 was measured in 678 individuals cross-sectionally and longitudinally in 189 undergoing metabolic surgery. We explored links between FGF21, AT histology, cardiometabolic risk factors, weight loss, glucose metabolism changes using feature selection algorithms, univariate/multivariate models, and transcriptome/proteome network analyses in subcutaneous and visceral AT. ResultsFGF21 levels track closely with central adiposity, subclinical inflammation, insulin resistance, and cardiometabolic risk, with circulating leptin emerging as the top predictor. Visceral AT inflammation was associated with liver dysfunction and FGF21 elevation. Post-surgery, FGF21 peaked transitorily at 3 months and predicted fat mass loss at 12 months but not HOMA-IR improvements. Mediation analysis indicated an increased catabolic and AT-lipolytic state associated with higher liver enzyme and FGF21 levels (total effect 0.38, p<0.01; proportion mediation 32%, p<0.01). AT fibrosis was related to a blunted transitory FGF21 increase, and lower fat loss, and hence linked with a reduced surgical effect (FFA and visceral AT fibrosis: rho=-0.31, p=0.030; FFA and fat-mass loss: rho=0.17, p=0.020). ConclusionFGF21 reflects the livers metabolic response to AT characteristics in both central adiposity and after metabolic surgery, with its dynamics reflecting AT-liver crosstalk.