Acta Physiologica

BackgroundCarnitine plays an obligatory role in energetics owing to its role in the translocation of long-chain fatty acids into the mitochondrion for oxidation. Here, we determined the metabolic and behavioral consequences of systemic carnitine deficiency (SCD) in mice. MethodsFemale C57BL/6J mice were randomized to receive normal drinking water (control, n = 8) or drinking water supplemented with mildronate 4g.L-1 (mildronate, n = 8) for 21 days. Body composition was assessed at baseline and post treatment. Metabolic and behavioral phenotyping was performed continuously over 72 hours following 14 days of control or mildronate treatment. Stable isotope were used to assess whole-body substrate oxidation. Carnitine subfractions were quantified in skeletal muscle and liver, as was mitochondrial respiratory function. Liver and muscle samples also underwent proteomic analysis. ResultsMildronate treatment depleted total carnitine in muscle and liver by [~]97% (P < 0.001) and [~]90% (P < 0.001), respectively. Carnitine depletion was accompanied by lower total energy expenditure (P = 0.01), attributable to lower voluntary wheel running (P = 0.01). Oxidation rates of palmitate (P < 0.01) but not octanoate were lower whereas rates of glucose oxidation were greater in carnitine depleted mice (P < 0.01). Mitochondrial respiratory capacity was unaltered by carnitine deficiency. Carnitine deficiency remodeled muscle and liver proteomes to support lipid oxidation and energy production. SummaryIn mice, carnitine deficiency is characterized by decreased long-chain fatty acid oxidation despite preserved mitochondrial respiratory capacity. Carnitine deficiency resulted in lower voluntary exercise and a concomitant reduction in energy expenditure.

Metabolic dysfunction-associated steatotic liver disease (MASLD) afflicts more than one-third of adults globally, contributing significantly to an increased cardiovascular disease risk. Further, patients with severe liver disease experience muscle weakness (sarcopenic obesity) and fatigue. Hypoxia-inducible factor 2 (HIF2) accumulates in the livers of MASLD patients and has been implicated in disease progression. Here we sought to understand the role of hepatic HIF2 in mediating hepatic and extra-hepatic features of MASLD. Using a well-validated obese mouse model of MASLD, we investigated the impact of hepatocyte-specific HIF2 deletion (hHIF2-/-) on hepatic, cardiac and skeletal muscle metabolism, and cardiac function. Over 28 weeks, mice were exposed to a high-fat, high-fructose, high-cholesterol (GAN) diet, which induced obesity alongside hepatic steatosis, fibrosis and inflammation. In contrast to observations in lean mouse models of liver disease, hHIF2-/- did not protect against MASLD, despite greater hepatic NADH-supported mitochondrial respiration and higher intracellular sphingomyelin levels. Instead, in the hearts of GAN-fed mice, hHIF2-/- caused diacylglycerol accumulation independent of diet, accumulation of long-chain acyl-carnitines and exacerbation of ceramide accumulation. Langendorff-perfused hearts from hHIF2-/- mice showed systolic and diastolic dysfunction, including 24% lower left ventricular developed pressure and 34% lower maximal rate of relaxation (dP/dtmin). However, isolated hearts from hHIF2-/- mice were protected against MASLD-associated sympathetic dominance, determined using autonomic receptor agonist stimulation. Both GAN-feeding and hHIF2-/- were associated with lower lean mass (14% and 5.4% lower than respective controls), whilst hHIF2-/- enhanced OXPHOS-associated protein levels in gastrocnemius muscle. Overall, hHIF2-/- resulted in detrimental extra-hepatic effects, including myocardial lipid accumulation, impaired cardiac function, and loss of whole-body lean mass, with no apparent protection against MASLD disease progression.

Metabolic syndrome (MetS), characterized by abdominal obesity, insulin resistance, dyslipidemia, and hypertension, affects a substantial proportion of the global population and increases the risk for cardiovascular disease, diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). Despite its prevalence, there are currently no effective pharmacological therapies targeting MetS, highlighting the need to identify novel etiological mechanisms, particularly within the gastrointestinal (GI) tract. Using a mouse model of MetS and healthy lean controls, we assessed the colonic microenvironment through metabolomic, transcriptomic, and microbiome analyses. Colonic organoids were cultured to further explore epithelial alterations. Additionally, human MetS fecal metabolomics data were cross-compared with the mouse model to validate translational relevance. MetS mice exhibited upregulation of colonic anabolic pathways, including glycolysis, the pentose phosphate pathway, and the tryptophan/kynurenine pathway, without evidence of intestinal inflammation. Microbiome analysis revealed an increased abundance of the genus Lactobacillus in MS NASH mice. Colonic organoids from MetS mice showed altered goblet cell differentiation. Comparative analysis with human MetS fecal metabolomics demonstrated similar dysregulated pathways, underscoring the translational relevance of these findings. Our study reveals significant metabolic and microbial alterations in the colon of MS NASH mice, implicating a dysfunctional GI tract as a potential etiological factor in MetS. These findings highlight specific metabolic pathways and microbial signatures that could serve as future therapeutic targets for MetS. NEW & NOTEWORTHYThis study identifies the colon as a metabolically active tissue affected in metabolic syndrome. Despite the absence of intestinal inflammation, MS NASH mice displayed altered colonic metabolism and microbiota composition, with conserved metabolite changes matching those seen in humans with metabolic syndrome. These findings highlight colonic metabolic dysfunction as a potential driver of gut dysbiosis and disease progression in metabolic syndrome and MASLD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/716131v1_ufig1.gif" ALT="Figure 1"> View larger version (77K): org.highwire.dtl.DTLVardef@1b7c685org.highwire.dtl.DTLVardef@4a832aorg.highwire.dtl.DTLVardef@1e95c66org.highwire.dtl.DTLVardef@1b14209_HPS_FORMAT_FIGEXP M_FIG C_FIG

{beta}2-Adrenergic receptor (Adr{beta}2) is the most abundant form of adrenergic receptors in skeletal muscle. Our previous studies have shown that the ventromedial hypothalamic nucleus (VMH) regulates metabolic benefits of exercise, potentially by skeletal muscle Adr{beta}2. Although a large body of literature has shown the importance of Adr{beta}2 on skeletal muscle physiology, it remains unexplored whether skeletal muscle Adr{beta}2 contributes to metabolic benefits of exercise, such as prevention of diet-induced obesity (DIO). Here, we generated mice lacking Adr{beta}2 in skeletal muscle cells (SKMAdr{beta}2) and tested whether SKMAdr{beta}2 is required for metabolic benefits of exercise on DIO. Deletion of SKMAdr{beta}2 completely abolished the induction of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc-1) in skeletal muscle by {beta}2-agonist, which is a potent activator of Pgc-1. Exercise upregulates Pgc-1, which regulates a broad range of skeletal muscle physiology, including hypertrophy and mitochondrial function. Deletion of SKMAdr{beta}2 hampers augmented Pgc-1 in skeletal muscle by a single bout of exercise. Intriguingly, we found that deletion of SKMAdr{beta}2 increased endurance capacity. Further, our data showed that body weight in DIO mice lacking SKMAdr{beta}2 is comparable to that of control DIO mice during exercise training, suggesting that deletion of SKMAdr{beta}2 did not affect the metabolic benefits of exercise in DIO. Collectively, our data indicate that SKMAdr{beta}2 contributes to exercise-induced transcriptional changes and endurance capacity, however, it is not required for exercise benefits on bodyweight in DIO mice.

Exercise is a cornerstone therapy for diabetes because working skeletal muscles take up glucose at dramatically greater rates than postprandial insulin-stimulated glucose uptake and, notably, do so without a requirement for insulin. This remarkable ability of working muscles is preserved in diabetes, when muscles become resistant to insulin. However, the mechanism of insulin-independent glucose uptake by working muscles is not fully understood. Here we describe a previously unrecognized glucose uptake pathway in muscle, which we refer to as "mSGLT" based on shared properties with the Sodium Glucose Linked Transporter family. In contrast to the abundant GLUT4 transporter, mSGLT is not regulated by insulin, requires Na,K-ATPase-2 activity, and transports the hexose -methyl-D-glucoside (MDG), a glucose derivative that is handled by SGLTs but not GLUT4. The mSGLT pathway and GLUT transport pathways are independent and additive. In addition to exercise, mSGLT imports glucose under other conditions of adrenergic stimulation, which inhibits pancreatic insulin release and reduces the insulin sensitivity of muscle. SGLT2-specific antibodies recognize a protein in muscle of similar size to the kidney SGLT2; this protein localizes to the muscle t-tubules, together with Na,K-ATPase-2 and MAP17, the regulatory subunit of SGLT2. However, skeletal muscles do not express a full-length transcript of Slc5a2 (SGLT2), and SGLT2-specific inhibitors do not inhibit mSGLT with high affinity. The novel transporter may be a muscle variant of Slc5a2 that results from post-transcriptional or post-translational mechanisms. mSGLT and its regulation offer potential muscle-specific therapeutic targets for treating hyperglycemia and other conditions when insulin-stimulated glucose disposal into muscle is impaired.

General anesthetics enable invasive experimentation but can affect cardiovascular and respiratory physiology, biasing preclinical outcomes. We compared five anesthetic regimens in adult male Wistar rats, tribromoethanol (TBE, 250 mg/kg i.p.), chloral hydrate (CH, 400 mg/kg i.p.), ketamine-xylazine (KX, 80/10 mg/kg i.p.), thiopental (TP, 80 mg/kg i.p.), and isoflurane (ISO, 4% induction, 2% maintenance), to investigate integrated cardiorespiratory and biochemical markers. Femoral arterial catheterization allowed continuous blood pressure (BP) and derived heart rate (HR) recordings, while ventilation was assessed through pletysmography at baseline (awake), during induction, and recovery phases of anesthesia. Variability was evaluated in the time and frequency domains, including HR, systolic blood pressure (SBP), and spontaneous baroreflex sensitivity. In an independent cohort of rats, butyrylcholinesterase (BChE), CK-MB, cTnI, and LDH were measured. Baseline BP was unchanged by TBE and TP, whereas all anesthetics affected HR. Minute ventilation and breathing frequency were reduced with all agents, while tidal volume decreased with KX and TBE only. LDH and cTnI were unaffected, BChE was reduced by KX, TBE, and ISO, and CK-MB increased with CH and KX. Variability analysis showed that all anesthetics depressed pulse-interval and SBP variability and shifted spectral power toward higher frequencies, while baroreflex sensitivity and effectiveness were consistently reduced. During recovery, KX and TP restored most variability indices, whereas CH, TBE, and ISO showed persistent suppression. These findings highlight distinct profiles of cardiovascular depression and biomarker responses across anesthetics and underscore the importance of accounting for autonomic variability when selecting different anesthetics in experimental protocols. HighlightsO_LIFive anesthetic regimens were tested in rats. C_LIO_LIAll anesthetics reduced ventilation, and KX and TBE also reduced tidal volume. C_LIO_LICH and KX increased CKMB, while KX, TBE and ISO reduced BChE. C_LIO_LIAll anesthetics reduced blood pressure variability and baroreflex sensitivity. C_LIO_LIVariability recovered with TP and KX, whereas CH, TBE and ISO showed persistent suppression. C_LI

This study aimed to determine the impact of inborn metabolic fitness and early life exercise training on whole body and brown adipose tissue (BAT) energetics. We carried out comprehensive metabolic phenotyping on 4-week old rats bred for high (high-capacity runner, HCR) and low (low-capacity runner, LCR) running capacity following randomization to voluntary wheel running (VWR) or control (CRTL) for 6-weeks. High-resolution respirometry and untargeted proteomics were then employed to determine the impact of inborn fitness and early life exercise on BAT function. When accounting for differences in body mass, early life exercise (VWR) resulted in greater basal and total energy expenditure, irrespective of strain (P < 0.0001 for both). Both leak and uncoupling protein 1 (UCP1) dependent respiratory capacities in isolated BAT mitochondria were greater in rats randomized to VWR compared to CTRL in both HCR (P < 0.01) and LCR (P < 0.05) strains. Similarly, mitochondrial sensitivity to the UCP1 inhibitor GDP was greater in both HCR (P < 0.01) and LCR (P < 0.05) rats randomized to VWR versus control. The BAT proteome differed in CTRL HCR and LCR rats, were there was enrichment in proteins related to branched chain oxidation and mitochondrial fatty acid oxidation in HCR rats. VWR remodeled the BAT proteome, where 151 proteins were differentially expressed in LCR BAT and 209 differentially expressed in LCR BAT following VWR. In both stains, there was an enrichment in proteins related to metabolism mitochondrial function in response to VWR. However, when comparing strains, 39 proteins were differentially expressed in BAT in HCR rats compared to LCR rats in response to VWR. These proteins were related to carboxylic acid and amino acid metabolism. Collectively, inborn fitness impacts body mass and composition, exercise behaviors, and the BAT proteome in early life. Early life exercise alters whole body and BAT energetics irrespective of inborn fitness, augmenting basal and total energy expenditure and BAT thermogenic capacity and function.

Right ventricular failure (RVF) is a serious disease with a high mortality but no effective pharmacologic treatments. We reported RVF was reversed by chronic treatment with an 1A-adrenergic receptor (1A-AR) agonist. Recent studies suggest mitochondrial dysfunction contributes to RVF. Therefore, we investigated if reversal of RVF by chronic 1A-AR agonist treatment involved improved mitochondrial function. A mouse model of RVF caused by pulmonary artery constriction (PAC) for 2 wk was chronically treated for a further 2 wk. with a low dose of the 1A-AR agonist A61603 (10 ng/kg/day) or vehicle (no drug control). RV dysfunction was assessed from the fractional shortening of the RV outflow tract (RVOT FS). RVOT FS for sham controls (46.5 {+/-} 1.3 %, n = 9) was reduced 4 wk after PAC (27.6 {+/-} 1.5 %, n = 13, P < 0.0001), but was higher after PAC plus 2 wk A61603 treatment (34.5 {+/-} 0.6 %, n = 14, P < 0.001). RV myocardial respiration rate (O2 consumption) for sham controls (776 {+/-} 51 pM/s/mg, n = 9) was reduced 4 wk after PAC (493 {+/-} 28 pM/s/mg, n = 15, P <0.0001), but was higher after PAC plus 2 wk A61603 treatment (634 {+/-} 30 pM/s/mg, n = 11, P <0.05). RV myocardial ATP level for sham controls (3.3 {+/-} 0.1 mM, n = 10) was reduced 4 wk after PAC (1.9 {+/-} 0.1 mM, n = 6, P < 0.0001), but was higher after PAC plus 2 wk A61603 treatment (2.6 {+/-} 0.13 mM, n = 7, P < 0.01). In conclusion, reversal of RVF after chronic A61603 treatment involved reversal of mitochondrial dysfunction. Consistent with our previous studies, this study suggests that the 1A-AR is a therapeutic target to treat RVF. HighlightsRV failure is reported to involve mitochondrial dysfunction which might impair RV contraction by decreasing cardiomyocyte ATP level. Using the pulmonary artery constriction model of RV failure, we found that chronic treatment with an 1A-adrenergic receptor agonist increased RV myocardial respiration rate, increased RV myocardial ATP level, and increased RV function. These findings suggest that the 1A-adrenergic receptor is a therapeutic target for treating RV failure, and that the mechanism involves improved RV cardiomyocyte bioenergetic status.

BackgroundCoronary autoregulation is the ability of the normal heart to maintain constant coronary blood flow (CBF) over a wide range of coronary driving pressures (CDP). Despite being vital for survival, the mechanism of coronary autoregulation is unknown. We hypothesized that GPR39, present in vascular smooth muscle cells, together with its endogenous agonist 15-hydroxyeicosatetraenoic acid (15-HETE) orchestrate coronary autoregulation. MethodsWe created coronary stenoses of varying degrees in open-chest, anesthetized dogs where we measured CBF and CDP. In a subset of animals, coronary venous blood was sampled for eicosanoid, adenosine, endothelin-1, polyunsaturated fatty acids, and prostaglandins levels. Stenoses were recreated during intravenous administration of VC108, a specific GPR39 antagonist and systemic, pulmonary, and coronary hemodynamics measured. ResultsGPR39 was identified in coronary arterioles by immunohistochemistry and in heart tissue by western blot. In-vivo, 15-HETE correlated linearly with CDP over the autoregulatory range (r2=0.47, p=0.0024). Apart from 6-keto PGF1 no other metabolite had any relation with CDP. Prior to administration of VC108, CBF did not change within the autoregulatory range. VC108 had no effect of systemic and pulmonary hemodynamics but increased CBF (p=0.02 versus vehicle) by decreasing coronary microvascular resistance (p=0.01 versus vehicle), indicating that GPR39 participates in control of normal coronary vascular tone. With VC108, coronary autoregulation was abolished and CBF became CDP dependent (r2=0.96, p=0.004). ConclusionGPR39 and its endogenous agonist 15-HETE together orchestrate coronary autoregulation when CDP is reduced. These novel findings provide a mechanism for coronary autoregulation and could direct pharmacological treatment of various coronary syndromes in humans.

Pregnant women are particularly susceptible to adverse outcomes from environmental heat, yet the physiological effects of acute heat exposure during pregnancy remain poorly understood. Some physiological changes are monitored in humans; however, investigation of underlying molecular mechanisms requires invasive methods that can only be ethically applied in mammalian models. Moreover, research with animal models has largely focused on early and lethal teratogenic effects of heat exposure and lacks longitudinal physiological monitoring, detailed parameterisation of heating regimes and in-depth investigation of underlying mechanisms. Here we used a mouse model to investigate the impact of a controlled acute heat exposure at mid-gestation (E12{middle dot}5), slowly elevating core body temperature (CBT) over 210mins to raise CBT by [~]1{degrees}C. Using high-frequency ultrasound and morphological analyses, we observed delayed alterations in placental and foetal cerebral blood flow indicative of a brain-sparing response, alongside reduced placental labyrinth zone size. Additionally, maternal cardiac function was impaired, accompanied by cardiac and renal fibrosis and elevated circulating soluble Flt-1 levels, an anti-angiogenic biomarker of gestational hypertension. These findings demonstrate that brief heat stress at mid-gestation can induce lasting effects on placental function and maternal cardiovascular health in a mammalian model, highlighting potential risks for pregnancy outcomes under increasing global temperatures. Together this data suggests that an acute exposure to heat elevating core body temperature by 1{middle dot}2{degrees}C can induce a long-term impact on both placenta and maternal health in a mouse model. It will be important to understand the molecular changes which underpin the pathophysiology and whether this is translated to humans.

BackgroundPersistent neurohormonal activation is a key driver of maladaptive remodeling and disease progression in heart failure (HF). Sodium-glucose cotransporter 2 inhibitors (SGLT2is) confer robust renoprotective effects in HF; however, the extent to which these benefits involve modulation of renal neurohormonal activity remains unclear. We hypothesized that SGLT2i-mediated renoprotection in HF is associated with attenuation of excessive renal neurohormonal activation. MethodsMale rats with myocardial infarction-induced HF and sham controls were fed standard chow or chow containing empagliflozin (EMPA, 300 mg/kg) for four weeks, followed by assessment of renal inflammatory and neurohormonal markers. Parallel in vitro studies in THP-1 macrophages and HK-2 proximal tubule cells evaluated the direct effects of EMPA on norepinephrine (NE)-dependent tubular inflammatory signaling. ResultsHF rats displayed higher renal cortical renin gene expression and angiotensin II concentrations, which remained unaffected by EMPA. Conversely, EMPA normalized the elevated urinary NE excretion and renal cortical NE content observed in HF rats. Given the inflammatory role of sympathetic hyperactivity, we assessed renal macrophage polarization. EMPA-treated HF rats showed reduced expression of pro-inflammatory markers (Tnf, Ccr2, Nos2, Il-6) and increased expression of markers associated with a reparative macrophage profile (Arg1, Mrc1, CD163), supported by higher CD206 macrophages in kidney sections. While EMPA did not directly alter THP-1 macrophage activation in vitro, it significantly reduced NE-induced SGLT2 expression and interleukin-6 (IL-6) release by HK-2 human proximal tubule epithelial cells. ConclusionThese findings support a model in which SGLT2 inhibitors confer renoprotection in HF by suppressing renal sympathetic hyperactivity, independently of the intrarenal renin-angiotensin system, thereby disrupting a maladaptive renal neuro-epithelial-immune axis and promoting a reparative macrophage phenotype. CLINICAL PERSPECTIVE Whats new?O_LIThis study identifies a renal neuro-epithelial-immune axis underlying empagliflozin-mediated renoprotection in heart failure. C_LIO_LIEmpagliflozin reduces renal cortical and urinary norepinephrine levels in heart failure without altering intrarenal renin-angiotensin system activity, revealing a distinct neurohumoral target of SGLT2 inhibition. C_LIO_LIThis sympatholytic effect is associated with a shift in renal macrophages toward a reparative (M2) phenotype, without changes in total macrophage abundance. C_LIO_LIEmpagliflozin blocks norepinephrine-induced SGLT2 upregulation, limiting proximal tubular glucose reabsorption and IL-6 production, and linking sympathetic signaling to renal inflammation. C_LI What are the clinical implications?O_LIOur findings provide a mechanistic basis for the additive cardiorenal benefits of SGLT2 inhibitors in heart failure, beyond conventional RAS-directed therapies. C_LIO_LITargeting renal sympathetic-driven inflammation may help preserve kidney function and attenuate the progression of cardiorenal syndrome. C_LIO_LISuppression of a renal neuroinflammatory pathway may help explain the early and sustained benefits of SGLT2 inhibitors across heart failure phenotypes, including nondiabetic patients. C_LI

Background & AimsDiabetes mellitus has been associated with both intestinal barrier dysfunction and peripheral neuropathy leading to increased risk of infection. The mucus layer forms a physical barrier against pathogens and is a critical component of the intestinal barrier that may be impaired in diabetes. This study aimed to assess how diabetes impacts goblet cells (GCs), mucus layer integrity, and innervation in the colon. MethodsFluorescence microscopy was used to investigate GCs, the mucus layer, and innervation in the colon of db/db mice. Custom open-access image analysis pipelines were developed to quantify GC numbers, location and content, mucus thickness, bacterial colonization, and innervation density in intestinal tissue sections. We also treated mice with the clinically used glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide to assess its capacity to reverse pathological changes to GCs and the mucus layer in a model of established type 2 diabetes (T2DM). ResultsThe mucus layer was significantly thinner in the colon of db/db mice with established diabetes and bacteria more readily colonized the epithelium and crypts. Intercrypt GC numbers were significantly reduced in db/db mice. However, there were significantly more GCs per crypt, and crypts were elongated in the db/db colon. Innervation was reduced in the mucosa and external muscle of the colon, consistent with diabetic neuropathic changes. Liraglutide treatment increased the size of GCs but had no effect on GC numbers, mucus thickness, or innervation in this model of established T2DM. ConclusionsMucus barrier dysfunction and GC hyperplasia is evident in the db/db colon. Increased microbial penetrability through the mucus layer suggests potential implications for the increased risk of gastrointestinal infection in diabetes.

Metabolic dysfunction-associated steatohepatitis (MASH) is associated with increased expression of peroxisome proliferator-activated receptor gamma (PPAR{gamma}, Pparg) and reduced expression of genes involved in methionine metabolism in the liver. The nuclear receptor PPAR{gamma} is activated by fatty acids, and the knockout of Pparg in hepatocytes (Pparg{Delta}Hep) reduced the negative effects of MASH on methionine metabolism. Here, we sought to determine whether hepatocyte Pparg is required for the transcriptional regulation of genes involved in hepatic methionine metabolism in conditions with altered fatty acid flux to the liver: fasting, refeeding, and high-fat diet (HFD)-induced obesity/steatosis. Fasting induced liver steatosis and increased the expression of key genes involved in the methionine metabolism in the liver, while 6h-refeeding reversed these effects and reduced the expression of phosphatidylethanolamine N-methyltransferase (Pemt) and cystathionine beta synthase (Cbs). Overall, fasting and refeeding did not alter hepatocyte Pparg expression nor Pparg{Delta}Hep affected fasting and refeeding-mediated regulation of methionine metabolism gene expression. Diet-induced steatosis reduced hepatic Pemt expression in control (Pparg-intact) mice, and the thiazolidinedione (TZD)-mediated activation of PPAR{gamma} in diet-induced obese control (Pparg-intact) mice reduced the expression of betaine homocysteine S-methyltransferase (Bhmt) and Cbs. However, diet-induced steatosis increased hepatocyte Pparg expression, and Pparg{Delta}Hep blocked the negative effects of HFD and TZD on hepatic methionine metabolism. The PPAR{gamma}-dependent reduction of hepatic Bhmt and Cbs expression was confirmed in mouse primary hepatocytes. Taken together, hepatocyte Pparg may serve as a negative regulator of hepatic methionine metabolism in diet-induced obese mice and these actions could contribute to promoting the onset of MASH.

Spinal muscular atrophy (SMA) is characterized by motor neuron degeneration caused by deficiency of the survival motor neuron (SMN) protein. However, evidence increasingly supports broader systemic involvement. This study aimed to examine cardiac pathology in SMA patients and to investigate how reduced SMN levels impact cardiomyocyte homeostasis. We analyzed postmortem data from 14 SMA type I patients from the pre-treatment era, integrating gross anatomical, histopathological, and clinical findings. To investigate cardiomyocyte-intrinsic effects of SMN deficiency, healthy human cardiomyocytes were subjected to SMN knockdown and assessed using metabolic assays and transcriptomic profiling. Key findings were further investigated in vivo using the Smn2B/- mouse model of SMA. We found heterogeneous cardiac involvement in SMA patients, including cardiomegaly, variable fat deposition and interstitial fibrosis. SMN knockdown in human cardiomyocytes induced a metabolic shift and widespread transcriptional dysregulation, with pathway analyses identifying selective upregulation of PTEN signaling. Elevated PTEN protein levels were observed in a subset of human SMA hearts and in early postnatal hearts of Smn2B/- mice. Our results demonstrate that the heart remains a biologically relevant target of SMN deficiency and highlights cardiomyocyte-specific metabolic and PTEN signaling alterations as potential contributors to cardiac involvement in SMA.

Kidneys play an essential role in balancing fluid and electrolyte levels. Two mouse strains, C57Bl/6 and 129S2/SV, are routinely used to study renal physiology in laboratory settings, and prior observations suggest that significant differences in salt and water handling exist between them. This study aims to further establish the sources of these observed differences at both expressional and functional levels, in male and female mice. At baseline, male 129S2/SV mice displayed decreased Na+ and increased K+ plasma concentrations compared to C57Bl/6 males, while no statistical differences were observed between female mice. Interestingly, 129S2/SV male mice had lower glomerular density than C57Bl/6 males. Immunoblotting shows that 129S2/SV mice of both sexes had increased expression of NHE3 and NKCC2 compared to their C57Bl/6 counterparts. Both total and phosphorylated NCC were more abundant in female mice as compared to males, indicating sexual dimorphism. Furthermore, 129S2/SV females had higher expression of total and phosphorylated NCC compared to C57Bl/6 females. In contrast, the expression of SGLT2, ENaC subunits, and Na+/K+-ATPase were comparable between C57Bl/6 and 129S2/SV mice of both sexes. When challenged with diuretics intended to block NKCC2, NCC or ENaC, 129S2/SV male mice responded with a smaller diuresis and natriuresis than their C57Bl/6 counterparts. Taken together, our data suggest that differential expression of key Na+ transporters along the nephron contributes to differences in Na+/K+ homeostasis between these two mouse strains. NEW & NOTEWORTHYWe assessed the influence of genetic background on the expression of key Na+ transporters along the nephron in two commonly used inbred mouse strains, C57Bl/6 and 129S2/SV. We found that the kidney expression of NHE3, NKCC2, and NCC are strain dependent. Additionally, murine strain significantly contributes to the diuretic responses induced by hydrochlorothiazide, amiloride, and furosemide.

Background Intracranial aneurysm rupture is the leading cause of spontaneous subarachnoid hemorrhage and is associated with substantial mortality and long term neurological disability. Emerging evidence suggests that the gut microbiome may influence vascular inflammation and endothelial integrity through immune and metabolic pathways, yet human evidence linking gut microbial alterations to intracranial aneurysm remains fragmented and inconsistent. Objective This systematic review and meta analysis aimed to synthesize available human evidence on the association between gut microbiome alterations and intracranial aneurysm formation or rupture, with a primary focus on microbial dysbiosis and differences in gut microbial alpha diversity. Methods This study was conducted according to PRISMA 2020 guidelines and the protocol was prospectively registered in PROSPERO (CRD420261360785). A comprehensive search of PubMed, Scopus, Web of Science, Embase, and Cochrane CENTRAL was performed from database inception until April 1, 2026, with additional screening of grey literature sources. Observational human studies evaluating gut microbiome characteristics in patients with intracranial aneurysm were included. Mendelian randomization (MR) studies investigating genetically predicted microbial taxa and aneurysm outcomes were also reviewed. Random effects meta analysis using standardized mean differences (SMD) was performed for alpha diversity outcomes. MR taxa reported in at least two independent studies were quantitatively synthesized using inverse variance weighting of log odds ratios. Results The systematic search identified 396 records. After removal of duplicates and eligibility screening, 20 studies met inclusion criteria, including 12 observational clinical studies and 8 Mendelian randomization analyses. Meta analysis of three microbiome sequencing studies demonstrated significantly reduced gut microbial alpha diversity in patients with ruptured intracranial aneurysms compared with controls. Sensitivity analyses confirmed the robustness of pooled estimates. In addition, MR evidence identified several microbial taxa, including Ruminococcus1, Bilophila, Fusicatenibacter, and Porphyromonadaceae, as potentially protective factors against aneurysm related outcomes. Across observational studies, gut dysbiosis was frequently associated with inflammatory pathways and alterations in microbial metabolites implicated in vascular dysfunction. Conclusion Current human evidence suggests a potential association between gut microbiome dysbiosis and intracranial aneurysm pathophysiology, particularly in relation to aneurysm rupture. Reduced microbial diversity and specific microbial taxa may influence vascular inflammation and aneurysm wall stability. However, existing evidence remains limited and heterogeneous. Large prospective cohorts and mechanistic studies are required to clarify causal relationships and evaluate whether microbiome targeted interventions could contribute to aneurysm risk stratification or prevention strategies.

Selectively bred diet-induced obesity-prone (DIO-P) rats have defective nutrient sensing prior to obesity onset. We hypothesized that glial inflammation in the arcuate nucleus (ARC) impairs hypothalamic responses to dietary clues, thereby promoting obesity development in genetically susceptible animals. This study established a timeline of inflammatory events in male and female DIO-P and diet-resistant (DR) rats fed either a low fat chow or exposed to a high energy diet (HED; 32% fat, 25% sucrose) for three days or four weeks. On chow diet, DIO-P rats of both sexes displayed elevated astrocyte density and increased expression of pro-inflammatory markers in the ARC, alongside reduced microglial content, compared to DR rats. Three days of HED transiently amplified most MBH pro-inflammatory markers in DIO-P rats. Four weeks of HED decreased GFAP expression in DIO-P rats while Iba1 density remained unchanged, whereas, DR rats showed a reduction in Iba1with no change in GFAP or cytokine expression. To determine whether mediobasal hypothalamus (MBH) astrocyte inflammation contributes to the development and maintenance of an obesity, astrocytic IKK{beta} was depleted before or after HED exposure. Prophylactic MBH astrocyte-specific IKK{beta} knockdown prevented subsequent body weight gain, improved glucose tolerance and decreased leptin levels in DIO-P rats to levels comparable to DR rats, with no effect in the latter. In contrast, MBH IKK{beta} astrocytic depletion in already obese DIO-P rats had no effect on energy homeostasis. Together, these findings validate the DIO-P rat as a polygenic model of obesity predisposition and demonstrate that preventing ARC astrogliosis is sufficient to HED-induced body weight gain and obesity development in genetically susceptible animals, highlighting MBH inflammation as a marker and driver of obesity predisposition. HighlightsO_LIChow-fed DIO-P rats present heightened ARC astrogliosis and cytokine expression preceding HED-induced obesity. C_LIO_LIInhibition of IKK{beta} in MBH astrocytes prevents DIO-P rats from becoming obese. C_LIO_LIOnce obese, inhibition of IKK{beta} in MBH astrocytes is not sufficient to reverse the obese phenotype. C_LI

Endurance (END) or resistance exercise (RE) training results in adaptations that give rise to distinct skeletal muscle phenotypes. Hallmarks of RE include increases in muscle fibre and muscle cross-sectional area and strength, whereas END increases mitochondrial content. Such distinct phenotypes arise from differential metabolic and mechanical signal transduction, transcriptional, and protein translation pathways, culminating in exercise mode-specific adaptations in the muscle proteome. However, little empirical data exist on the protein-specific dynamic responses underlying training-mode-specific adaptations in humans. Using a model of unilateral exercise combined with stable isotope labelling with deuterium oxide, we measured changes in synthesis and abundance from baseline and during early (week 1) and later (week 10) periods of adaptation to END and RE training in young healthy adults (n = 14; 8 female, 6 male; 20 {+/-} 1 y, 70 {+/-} 10 kg). We quantified changes in the abundance (n = 1146 proteins) and synthesis (n = 247 proteins) profiles of skeletal muscle across a 5-day pre-training baseline period and during early and later adaptation to RE and END. Abundance profiling revealed mode-specific proteome remodelling, whereby RE increased ribosomal and contractile protein networks, whereas END increased mitochondrial inner membrane proteins after 10 weeks of training. The protein-specific synthesis rates of 119 proteins showed training-induced differences (P < 0.1 and log2 fold change > 1), including subsets of structural proteins that responded differently to RE and END training modes. Notably, distinct Z-disc proteins, such as XIRP1 (RE-specific) and LDB3 (END-specific), exhibited mode-specific regulation despite sharing a similar subcellular localisation. We report, for the first time, that divergent phenotypic adaptations to RE and END extend beyond changes in bulk fraction-specific synthesis rates and are regulated by training-mode-specific adaptations in distinct protein subsets within similar subcellular protein locations.

Pathologic cardiac hypertrophy requires increased protein synthesis, but the mechanosensors that link membrane stretch to translational control remain poorly understood. Polycystin-1 (PC1), encoded by PKD1, has been proposed as a cardiac mechanosensor, with its C-terminal tail (PC1-CT) promoting hypertrophy in rodent cardiomyocytes. However, its subcellular localization and downstream signaling remain incompletely defined, especially in human cardiomyocytes. Here, we examined endogenous PC1 C-terminus localization and the effects of adenoviral PC1-CT overexpression in human iPSC-derived ventricular cardiomyocytes (hiPSC-CMs) and adult mouse ventricular myocytes. Immunofluorescence revealed a striking striated pattern for both endogenous PC1 C-terminus (detected with a PC1-CT antibody) and the overexpressed PC1-CT fragment. In hiPSC-CMs, the PC1 C-terminus localized between the -actinin bands. In contrast, in adult cardiomyocytes, the overexpressed protein colocalized with -actinin and desmin, suggesting that PC1-CT sarcomeric distribution depends on cardiomyocyte maturation. We performed RNA-seq to assess transcriptional responses downstream of PC1-CT overexpression in hiPSC-CMs relative to LacZ controls. Gene Set Enrichment Analysis (GSEA) revealed enrichment of gene sets related to ribosome biogenesis, RNA processing, and protein synthesis, while classical hypertrophic markers remained unchanged. Pathway analysis suggested increased PI3K activity. PC1-CT overexpression increased phosphorylation of Akt, ERK, S6K1, and ribosomal protein S6 without altering 4EBP1 phosphorylation, suggesting preferential activation of the mTOR-S6K1-S6 branch. Pharmacological studies showed that pan-PI3K inhibition abolished S6 phosphorylation, whereas MEK blockade did not affect it; pertussis toxin and PI3K{gamma}-selective inhibitors also did not affect S6, suggesting a Gi/o-independent PI3K/Akt signaling driving mTOR-S6K1-S6 activation. Collectively, these data identify a sarcomere-associated pool of PC1-CT that engages PI3K-Akt-mTOR-S6K1-S6 signaling to enhance transcriptional programs related to ribosome biogenesis and protein synthesis, without activating a canonical hypertrophic gene program. These findings reveal a mechanistic link between PC1-CT and cardiomyocyte growth.

The autosomal dominant p.Ala165Val mutation in LIM Domain Binding Protein 3 (LDB3) causes myofibrillar myopathy marked by Z-disc disruption, accumulation of filamin-C (FLNc) and chaperone proteins, and progressive muscle weakness. We previously showed that this mutation interferes with the LDB3-protein kinase C alpha (PKC)-FLNc mechanosensing axis and impairs chaperone-assisted selective autophagy (CASA), establishing a gain-of-function mechanism. In this study, we examined whether mutant allele-specific knockdown could reverse the disease or mitigate disease progression in-vivo. A single intramuscular-injection of an AAV9-delivered microRNA-based shRNA produced substantial knockdown of mutant Ldb3 transcripts and protein in Ldb3Ala165Val/+ knock-in mice treated either before or after the onset of pathology. Treatment after disease onset reduced filamin-C and CASA protein aggregates and improved muscle strength, whereas early intervention prevented development of molecular and histological features of myopathy. Phosphoproteomic profiling further showed broad remodeling of dysregulated phosphorylation networks, including restoration of PKC-responsive sites and normalization of altered sarcomeric and cytoskeletal signaling observed in Ldb3Ala165Val/+ mice. These findings identify disruption of the LDB3-PKC-FLNc mechanosensing pathway as a central disease driver and suggest that restoring this signaling axis may complement mutant allelespecific RNA interference (RNAi). Overall, our results support RNAi as a promising therapeutic strategy for dominant LDB3-related myofibrillar myopathy.