Breast cancer is a leading cause of mortality and morbidity among females worldwide. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2023, we provided an updated comprehensive assessment of the epidemiological trends, disease burden, and risk factors associated with breast cancer globally, regionally, and nationally from 1990 to 2023. Breast cancer incidence, mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs) were estimated by age and sex for 204 countries and territories from 1990 to 2023. Mortality estimates were generated using GBD Cause of Death Ensemble models, leveraging data from population-based cancer registration systems, vital registration systems, and verbal autopsies. Mortality-to-incidence ratios were calculated to derive both mortality and incidence estimates. Prevalence was calculated by combining incidence and modelled survival estimates. YLLs were established by multiplying age-specific deaths with the GBD standard life expectancy at the age of death. YLDs were estimated by applying disability weights to prevalence estimates. The sum of YLLs and YLDs equalled the number of DALYs. Breast cancer burden attributable to seven risk factors was examined through the comparative risk assessment framework. The GBD forecasting framework was used to forecast breast cancer incidence and mortality from 2024 to 2050. Age-standardised rates were calculated for each metric using the GBD 2023 world standard population. In 2023, there were an estimated 2·30 million (95% uncertainty interval [UI] 2·01 to 2·61) breast cancer incident cases, 764 000 deaths (672 000 to 854 000), and 24·1 million (21·3 to 27·5) DALYs among females globally. In the World Bank low-income group, where a low age-standardised incidence rate (ASIR) was estimated (44·2 per 100 000 person-years [31·2 to 58·4]), the age-standardised mortality rate (ASMR) was the highest (24·1 per 100 000 [16·8 to 31·9]). The highest ASIR was in the high-income group (75·7 per 100 000 [67·1 to 84·0]), and the lowest ASMR was in the upper-middle-income group (11·2 per 100 000 [10·2 to 12·3]). Between 1990 and 2023, the ASIR in the low-income group increased by 147·2% (38·1 to 271·7), compared with a 1·2% (-11·5 to 17·2) change in the high-income group. The ASMR decreased in the high-income group, changing by -29·9% (-33·6 to -25·9), but increased by 99·3% (12·5 to 202·9) in the low-income group. The increase in age-standardised DALY rates followed that of ASMRs. Risk factors such as dietary risks, tobacco use, and high fasting plasma glucose contributed to 28·3% (16·6 to 38·9) of breast cancer DALYs in 2023. The risk factors with a decrease in attributable DALYs between 1990 and 2023 were high alcohol use and tobacco. By 2050, the global incident cases of breast cancer among females were forecast to reach 3·56 million (2·29 to 4·83), with 1·37 million (0·841 to 2·02) deaths. The stable incidence and declining mortality rates of female breast cancer in high-income nations reflect success in screening, diagnosis, and treatment. In contrast, the concurrent rise in incidence and mortality in other regions signals health system deficits. Without effective interventions, many countries will fall short of the WHO Global Breast Cancer Initiative's ambitious target of achieving an annual reduction of 2·5% in age-standardised mortality rates by 2040. The mounting breast cancer burden, disproportionately affecting some of the world's most vulnerable populations, will further exacerbate health inequalities across the globe without decisive immediate action. Gates Foundation, St Jude Children's Research Hospital.
Interferon regulatory factor 4 (IRF4) connects immunity and metabolism in immune cells and parenchymal cells of metabolic tissues. In immune cells, IRF4 is a metabolic rheostat that promotes glycolysis to support macrophage polarization and increase oxidative phosphorylation to enable T cell proliferation and memory, while limiting transcription of pro-inflammatory programs. IRF4 also dictates cell-autonomous responses in adipocytes and muscle cells, including transcriptional regulation of lipolysis in white adipocytes, thermogenesis in brown adipocytes, and glucose and amino acid metabolism in muscle cells. IRF4 responds to nutritional status and hormonal signals involved in obesity pathogenesis and mediates interorgan communication involved in liver steatosis during metabolic dysfunction-associated steatotic liver disease (MASLD). This review summarizes how IRF4 participates in metabolic and immune responses in adipose tissue, skeletal muscle, liver, and tissue-resident immune cells during obesity. IRF4 immunometabolism is relevant to obesity and MASLD because of its bidirectional role in immune cells and metabolic cells. Obesity alters inflammatory and nutritional activators of IRF4, which modify immune and parenchymal cell metabolism to produce local and systemic metabolic inflammation, which can alter endocrine control of metabolism. Therefore, the cell-specific functions of IRF4 in immune cells and metabolic cells position IRF4 as a transcriptional node connecting changes in immunity and metabolism during metabolic disease.
Obesity is a chronic disease, representing a significant health problem worldwide. Unhealthy eating habits and sedentarism are key contributors to the development of obesity. Dietary and exercise strategies are the first-line therapies for weight loss or maintenance and have proven effective in controlling weight. However, long-term adherence is challenging, and rapid weight regain often follows intervention cessation. In mice, time-restricted feeding (TRF) and exercise (EXE) independently prevent weight gain and maintain metabolic health, yet weight regain is observed upon cessation. Whether combining TRF and EXE provides longer-lasting benefits remains unclear. Here, we assessed weight and metabolic parameters in Swiss male mice fed with a high-fat diet (HFD) during an 8-wk intervention of TRF (8-h food access in the active phase) or TRF combined with EXE (60-min treadmill running daily) and after cessation and transfer to ad libitum feeding. TRF and EXE interventions successfully mitigate weight gain, improve glycemic homeostasis, and attenuate lipid accumulation in the liver and adipose tissue hypertrophy compared to mice fed HFD ad libitum. However, cessation of both strategies led to rapid weight regain, impaired glycemic control, and increased circulating lipid levels. Although the combination of TRF and EXE led to the lowest body weight and best metabolic health, this group showed no protection against the metabolic impairments observed after TRF cessation alone. In conclusion, TRF and EXE are complementary strategies for managing metabolic health, but cessation of these interventions leads to rapid weight regain and metabolic deterioration, with only partial preservation of select metabolic adaptations. These findings underscore the critical need for sustained adherence to lifestyle interventions in obesity management.NEW & NOTEWORTHY This study demonstrates that combining time-restricted feeding with aerobic training improves weight and metabolic health in Swiss mice fed a high-fat diet. Importantly, we show that most metabolic benefits are lost after intervention cessation. However, insulin sensitivity and aspects of hepatic lipid metabolism are partially maintained after cessation of the intervention. These findings provide new insight into the durability of metabolic improvements induced by lifestyle interventions and highlight the potential of combined dietary and exercise strategies to counteract diet-induced obesity and metabolic dysfunction.
Gestational diabetes mellitus (GDM) is a form of glucose intolerance that develops during pregnancy, affecting approximately 14% of pregnancies worldwide. GDM leads to an excess supply of nutrients to the fetus, influencing fetal metabolism and potentially stimulating metabolic inflammation (metaflammation), which may impact liver function. In fact, increased fetal liver size has been reported in GDM pregnancies. This study investigated the impact of GDM on fetal metaflammation and its potential association with the liver function parameters γ-glutamyl transferase (GGT), alanine transaminase (ALT), and bilirubin, in umbilical cord plasma (UCP). UCP samples were collected following healthy (n = 57) and GDM pregnancies (n = 25). Glucometabolic and lipid profiles, inflammatory markers, and liver function parameters were analyzed and the impact of GDM and the interrelation of liver biomarkers with maternal and neonatal parameters were assessed. UCP from GDM pregnancies exhibited increased levels of metaflammation-associated markers, including triglycerides, interleukin-6 and C-reactive protein (CRP). Among liver parameters, the detoxification and antioxidant defense enzyme GGT was elevated, whereas ALT and bilirubin species remained unchanged. Correlation analysis revealed that although GGT was increased in GDM, it was associated with improved metabolic characteristics, including reduced insulin resistance, insulin, C-peptide, and leptin, and increased high-density lipoprotein. Overall, these findings indicate that the GDM environment shifts fetal metabolism toward metaflammation and elevates GGT, an enzyme involved in detoxification and protection against oxidative stress. The inverse association of GGT with insulin resistance suggests a compensatory role of GGT, potentially mitigating fetal metabolic and inflammatory disturbances in GDM through its antioxidant activity.NEW & NOTEWORTHY Excess fetal nutrient supply in gestational diabetes mellitus (GDM) results in signs of fetal metabolic inflammation (metaflammation) in umbilical cord plasma, and higher levels of γ-glutamyl transferase (GGT), a liver enzyme involved in defense against oxidative stress. The correlations of GGT levels with reduced insulin resistance, C-peptide, and leptin suggest that GGT has a positive effect on fetal metabolic health.
Adipose tissue androgen turnover, dictated at least in part by the enzymes aldo-keto reductase 1 C type 2 (AKR1C2) and aldo-keto reductase 1 C type 3 (AKR1C3), has been linked to abdominal obesity. Recently, we investigated a single-nucleotide polymorphism (SNP) named rs28571858, that might increase AKR1C2 and AKR1C3 expression in human adipose tissue. Here, we studied the impact of rs28571848 on adipose tissue function and cardiometabolic health in bariatric surgery candidates. We genotyped a sample of 2,776 bariatric surgery candidates and retrospectively obtained anthropometry, blood lipid and glucose profiles, menopausal status, and medication use. In a subsample of 135 individuals (62% women, age 42 yr, body mass index of 51 kg/m2), we additionally assessed AKR1C2 and AKR1C3 expression in whole tissue by RT-qPCR. Features of adipose tissue dysfunction, such as mean adipocyte diameter and pericellular fibrosis, were assessed by histological staining and semiautomated image analysis. Finally, adipose tissue AKR1C family enzyme activity was measured by fluorimetry. The rs28571848 SNP affected AKR1C3 expression in both subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) in women only, while not altering AKR1C2 expression in either men or women. Individuals carrying the minor allele exhibited increased VAT AKR1C activity compared to those with the wildtype genotype. Analysis of blood lipid profile in the whole cohort revealed that "TT" carriers had elevated total cholesterol, low-density lipoprotein-cholesterol, and indices of insulin resistance. The rs28571858 SNP increased adipose tissue AKR1C3 expression and activity in women. Increased AKR1C3 may contribute to an adipose tissue milieu that prompts lipogenesis, adversely affecting cardiometabolic health by disrupting lipid homeostasis and insulin sensitivity.NEW & NOTEWORTHY rs28571858 has a minor allele frequency of 18.7% in a cohort of 2,776 residents of Quebec, Canada. rs28571858 is associated with adipose tissue AKR1C3 expression and activity in women. Minor allele homozygote carriers have increased total cholesterol, LDL-cholesterol, and indices of insulin resistance.
Bone marrow adipose tissue (BMAT) has been linked to negative bone health outcomes, and a high level of bone marrow adipocyte accumulation is observed during aging and in individuals with diabetes and obesity. This study explores the relationships between BMAT, age, metabolic health, and the impact of their interactions on bone turnover in a cross-sectional cohort of healthy women and men. Levels of bone turnover biomarkers, procollagen type 1 N-terminal propeptide (P1NP) and β-CrossLaps, were determined alongside dipeptidyl peptidase-4 (DPP4) concentration and activity as biomarkers of metabolic health. We used magnetic resonance imaging to assess proton density fat fraction to quantify BMAT mass in healthy individuals and correlated results to sex, age, body mass index (BMI), and glycated hemoglobin A1c (HbA1c), which represents long-term glycemic control. Age was the strongest determinant of increased BMAT mass, explaining more than a third of its overall variation, as well as a robust determinant of bone turnover. A sex-specific correlation pattern was observed between BMAT and bone turnover: women displayed a trend for a positive correlation of BMAT, which depended on age. In men, BMAT mass correlated significantly, but inversely, with both biomarkers, which was also age-dependent. DPP4 concentration and activity were positively associated with P1NP in both sexes, and these relationships were independent of age, BMI, or HbA1c. These findings indicate that the impact of BMAT on bone turnover may be age-dependent, whereas metabolic regulator DPP4 is linked to bone turnover independently of metabolic health or aging.NEW & NOTEWORTHY Our findings highlight the central role of bone marrow adipose tissue in the relationship between bone health, age, and metabolism. Increased marrow adipocytes produce endocrine signals, such as dipeptidyl peptidase-4, which modulate these associations. We show that women and men have distinct associations between bone turnover, age, and bone marrow adipocytes.
Irritable bowel syndrome (IBS), a common disorder of gut-brain interaction, has been increasingly associated with metabolic dysfunction and cardiometabolic risk. This study aimed to comprehensively assess cardiometabolic risk factors in individuals with IBS and to characterize their metabolic profiles in comparison with those of healthy and diabetic cohorts. First, in a retrospective database analysis, cardiometabolic risk factors of patients with IBS (n = 582,377) were compared with healthy controls (HCs) (n = 1,492,376). Following propensity score matching (n = 492,468), cardiometabolic parameters were analyzed during a follow-up period of 1-24 mo postindex. Second, a total of 234 individuals underwent comprehensive metabolic phenotyping using state-of-the-art nuclear magnetic resonance spectroscopy, comparing blood profiles of patients diagnosed with type 2 diabetes (T2D), IBS, and HC. We observed an increased cardiometabolic risk profile in patients with IBS compared with HC, characterized by higher mean body mass index, higher triglyceride levels, lower high-density lipoprotein cholesterol, and higher hemoglobin A1c levels. Odds ratios (ORs) were significantly increased in IBS, particularly for chronic hyperglycemia (OR = 16.32; P < 0.001). Results were confirmed by deep metabolic phenotyping, revealing a metabolic tendency in patients with IBS toward profiles characteristic of T2D by alterations in amino acid (glycine, histidine, and phenylalanine), glucose (glucose, lactate, and pyruvate), and lipid metabolism (parameters related to very low-density lipoproteins). Our findings confirm that IBS is linked to a distinct cardiometabolic risk profile and reveal metabolic associations relevant to T2D.NEW & NOTEWORTHY We identified a distinct cardiometabolic risk profile in patients with IBS, characterized by elevated BMI, triglycerides, HbA1c, and reduced HDL-C levels. Metabolic phenotyping reveals a pattern in patients with IBS comparable with T2D profiles, including altered amino acid, glucose, and lipid metabolism.
Hypocholesterolemia hallmarks sepsis, though its pathophysiology and tissue-specific consequences are unclear. As low circulating cholesterol may reflect impaired endogenous cholesterol synthesis, we hypothesized that infusion of the cholesterol precursor mevalonate can reverse sepsis-induced hypocholesterolemia, whereby beneficially affecting adrenal and muscle integrity. In a catheterized mouse model of cecal ligation and puncture-induced sepsis (male 24-wk-old C57BL/6J mice), septic mice received either 5-day mevalonate infusion (78 mg/day) or placebo versus healthy controls (n = 50). Plasma high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, corticosterone, total bile acids, adrenocortical lipids, myofiber cholesterol, and muscle force were quantified. Expression markers of cholesterol homeostasis and structural integrity were investigated in adrenal, muscle and liver tissue. Liver mevalonate metabolites were quantified with liquid chromatography-mass spectrometry (LC-MS). Next, a secondary analysis on a prospective observational human study on the time course of adrenal function in the intensive care unit was performed to assess the association between plasma cholesterol and cortisol (n = 47). Also, plasma mevalonate was quantified with LC-MS. In septic mice, 5-day mevalonate infusion worsened HDL and LDL hypocholesterolemia versus placebo (P < 0.05). Decreased hepatic cholesterol synthesis expression markers, apolipoproteins, and hepatic cholesterol concentrations were observed in mevalonate-infused septic mice versus placebo (P < 0.05). No additional effect on plasma corticosterone, bile acids, myofiber cholesterol, and loss of muscle force and adrenocortical lipid depletion was observed. In prolonged sepsis patients, plasma mevalonate was increased, whereas plasma HDL- and LDL-cholesterol were low (P < 0.05) but did not correlate with plasma cortisol. To conclude, mevalonate infusion worsened sepsis-induced hypocholesterolemia, possibly due to increased feedback on hepatic cholesterol synthesis, without aggravating the adrenal or muscle sepsis phenotype.NEW & NOTEWORTHY Prolonged infusion with the cholesterol precursor, mevalonate, worsened hypocholesterolemia in a mouse model of sepsis-induced critical illness, likely due to increased feedback on hepatic cholesterol synthesis. Loss of muscle force and mass was not further affected, nor did mevalonate affect adrenal gland steroidogenic markers and the loss of adrenocortical lipids. In prolonged sepsis patients, sustained HDL and LDL hypocholesterolemia was observed in the face of high plasma mevalonate concentrations, but did not correlate with plasma cortisol.
Maternal obesity alters breast milk composition in ways that may predispose infants to excess adiposity. Although maternal exercise during lactation has been associated with favorable shifts in milk metabolites in humans, the mechanisms by which exercise remodels the mammary gland and milk lipid profile to influence offspring metabolism remain unclear. We developed a mouse model incorporating daily moderate treadmill exercise only during lactation, using lean (LN) and diet-induced obese (OB) dams, and leveraged indirect calorimetry, stable isotope tracer respirometry, and mammary epithelial cell (MEC) proteomics assays. Maternal obesity broadly remodeled the MEC proteome, decreasing enzymes of de novo fatty acid synthesis and altering lipid transport and oxidative pathways. These molecular adaptations in OB dams corresponded to higher milk triglyceride content and shifts in fatty acid composition, including suppressed medium-chain fatty acids (MCFAs). The exercise (EX) intervention during lactation reset MEC protein networks, enhancing protein translation and vesicle transport pathways, whereas decreasing fatty acid desaturation, relative to the sedentary (SED) group. In OB dams, the exercise intervention increased milk MCFA levels and partially corrected the proinflammatory omega-6 fatty acid bias. Offspring suckling OB-EX dams exhibited enhanced in vivo fatty acid oxidation, partially rescuing obesity-associated impairments in metabolic fuel preference. Together, maternal exercise during lactation remodels mammary metabolism and milk fatty acid composition in obese dams, which in turn, enhances postnatal lipid oxidation. These findings highlight lactation as a modifiable window, wherein maternal activity influences milk composition and early life metabolism.NEW & NOTEWORTHY Maternal obesity alters milk fatty acid composition, with consequences for postnatal metabolism. Maternal exercise during lactation in obese dams remodeled the mammary epithelial cell proteome, increasing medium-chain fatty acids in milk and enhancing offspring lipid oxidation.
SLC30A10 mediates manganese (Mn) efflux in both the intestine and liver, protecting against Mn toxicity. In previous studies, we found that Slc30a10 is one of the genes most induced by 1,25(OH)2D3 in mouse intestine and human enteroids. In addition, in Slc30a10 knockout mice, we noted a significant decrease in Trpv6, a vitamin D target gene involved in intestinal calcium transport, indicating a link between Mn efflux transport in the intestine, calcium, and the vitamin D endocrine system. In this study, we examined the effect of varying levels of Mn in 3-wk-old male and female mice fed diets either low, adequate, or high in calcium for 4 wk. Mn levels were markedly elevated in the mice fed the low calcium diets (0.02%, 0.1%) in tissues and blood. Under low calcium conditions, serum 1,25(OH)2D3 and intestinal Slc30a10 were induced as possible compensatory mechanisms to manage Mn toxicity. However, when older mice were similarly fed a high Mn low calcium diet for 4 wk, there was a decrease in serum 1,25(OH)2D3, in renal Cyp27b1 and either no effect or a decreased Mn response to low calcium in tissues and blood. Our findings indicate that low dietary calcium may contribute to the pathogenesis of Mn-induced toxicity, that the interactions between Mn and calcium are mediated in part by 1,25(OH)2D3 and that there is a protective mechanism of control of Mn homeostasis by vitamin D and calcium with potential therapeutic relevance for the prevention or management of Mn-induced disease.NEW & NOTEWORTHY This study demonstrates that low calcium levels in growing mice markedly elevate Mn in blood and other tissues thus contributing to the pathogenesis of Mn-induced toxicity, that interaction between Mn and calcium are mediated in part by 1,25(OH)2D3 and that there is a protective mechanism of control of Mn homeostasis by vitamin D and calcium with potential therapeutic relevance for prevention or management of Mn induced diseases.
Circulating sphingolipids have been associated with diabetes risk and chronic complications. This study characterized the sphingolipidome in a subset of the CA.ME.LI.A. cohort to identify lipid signatures related to sex, body mass index (BMI), and fasting glucose levels. Three hundred sixty-seven subjects (217 men) were stratified into six groups based on BMI (normal weight or overweight/obese) and fasting glucose levels (normal, impaired, or diabetes). Circulating sphingolipids were measured by LC-MS/MS. The effects of BMI, glucose levels, and their interaction on the sphingolipidome were analyzed using a two-way ANOVA model. Women showed higher circulating sphingolipid levels than men, except for ganglioside GM3. Glucose levels produced relevant changes on hexosyl- and lactosylceramides, which were significantly reduced in subjects with diabetes, independently of BMI. Some ceramide and sphingomyelin species also varied only according to glucose levels. Dihydroceramide 18:0 and 24:1 were higher in overweight/obese subjects, whereas sphingomyelin 18:1 and GM3 24:0 were higher in normal-weight individuals. Gangliosides GM3 were higher in normal body weight with normal glucose levels and impaired fasting glucose as compared with overweight obese individuals of the same categories. Sphingomyelin 18:1, GM3 24:1, sphingosine, and dihydrosphingosine-1-phosphate levels were significantly regulated by both BMI and glucose. In overweight/obese individuals, sphingosine-1-phosphate and dihydrosphingosine-1P levels were reduced in impaired fasting glucose and diabetes. The circulating sphingolipidome differs in men and women, being modulated by BMI and glucose levels. These data support the concept that sphingolipids could be novel biomarkers for obesity, diabetes, and associated complications.NEW & NOTEWORTHY Sphingolipid glycosylation is an enzymatic process that does not follow the pattern of nonenzymatic hemoglobin glycosylation. Unexpectedly, hexosyl- and lactosylceramides decreased in impaired fasting glucose and diabetes, with and without obesity. On the other hand, dihydroceramides increased in overweight/obesity with prediabetes/diabetes. The circulating sphingolipidome is differentially regulated in humans according to sex, glucose, and BMI.
Handgrip strength is a proxy for muscular fitness, an indicator for general health status, and is associated with cardiometabolic health. The mechanisms connecting handgrip strength to skeletal muscle function are incompletely understood. We applied integrated linkage-disequilibrium-adjusted colocalization analysis of genome-wide association study summary statistics for handgrip strength, combined with expression and splicing quantitative trait loci from skeletal muscle, and identified glycogen branching enzyme 1 (GBE1) as a candidate gene for handgrip strength. CRISPR-interference knockdown of GBE1 in immortalized human skeletal muscle cells (HMCL-7304) demonstrated decreased glycogen content and accumulation of polyglucosan bodies. Knockdown of GBE1 led to increased oxygen consumption rate, oxidative stress, and changes in mitochondrial morphology. Transcriptomic profiling of GBE1 knockdown cells identified upregulation of the human superoxide dismutase 2 and enrichment of pathways related to muscle contraction and oxidative stress responses. These functional genomic analyses prioritize GBE1 as a muscle-relevant candidate gene for handgrip strength and provide mechanistic insights to muscle fitness.NEW & NOTEWORTHY Colocalization of genome-wide association study (GWAS) loci with quantitative trait loci (QTL) in skeletal muscle tissue identified GBE1 as a candidate for handgrip strength. Cellular phenotypes with GBE1 knockdown in immortalized human skeletal muscle cells include decreased glycogen content, accumulation of polyglucosan bodies, changes in mitochondrial function and morphology, and increased expression of reactive oxygen species (ROS) scavengers. Transcriptomic changes suggest a role for GBE1 in muscle contraction and oxidative stress-mediated responses.
Placental insufficiency causes fetal hypoxemia and hypoglycemia and is a major driver of fetal growth restriction (FGR). In FGR skeletal muscle, mitochondrial respiration is reduced, partially due to altered mitochondrial protein abundance. We have shown that maternal oxygen and fetal glucose supplementation alleviates fetal hypoxemia and hypoglycemia and improves skeletal muscle satellite cell proliferation. However, its effects on muscle mitochondrial respiratory function and proteomic profiles remain unknown. Here, we tested whether correcting fetal hypoxemia and hypoglycemia restores mitochondrial oxidative phosphorylation and normalizes mitochondrial proteomic profiles in FGR sheep skeletal muscle. Placental insufficiency and FGR were induced by maternal hyperthermia during gestation. Near-term fetuses were chronically catheterized and received 7-10 days of maternal tracheal oxygen insufflation and fetal intravenous (IV) glucose infusion (FOG) or maternal air insufflation and fetal IV saline infusion (FAS). Both were compared to normally-grown control fetuses without supplementation (CON). Principal component analysis of the mitochondrial proteome indicated that FOG clustered closer to CON than to FAS. Abundances of 48 of 80 proteins that were differentially expressed in FAS vs CON returned to CON levels with FOG supplementation. Mitochondria isolated from CON and FOG muscle had similar glutamate/malate-driven state 3 (ADP stimulated) respiration, and both rates were greater than FAS mitochondria. Mitochondrial complex I activity was lower in FAS compared to CON, and FOG showed an intermediate level that was not different from either group. Together, these findings indicate that prenatal oxygen and glucose supplementation rescued mitochondrial respiratory dysfunction and partially normalized mitochondrial proteome in FGR skeletal muscle.
Glucagon-like peptide 1 (GLP-1) is generally safe against hypoglycemia, although it stimulates insulin and inhibits glucagon secretion. One explanation is that glucagon secretion is not inhibited by GLP-1 during hypoglycemia. We aimed at understanding the lack of suppression of glucagon secretion by GLP-1 by exploring the paracrine and neural regulation of pancreatic hormone secretion during hypoglycemia. Isolated rat pancreas (A) and an organ block comprising pancreas and stomach (B) were perfused. We performed 1) dose-response studies with GLP-1 (7-36) at hypoglycemia; 2) studies with GLP-1 (7-36) with and without blockage of somatostatin (SST) activity (with SST receptor antagonists); 3) and 4) dose-response experiments with acetylcholine at euglycemia and studies under hypoglycemia; and 5) finally, we studied the role of cholinergic signaling for modulation of GLP-1 activity under hypoglycemia. We measured glucagon, SST, and insulin levels. The secretion of SST was dependent on surgical preparation (A or B, P = 0.0006) and on cholinergic stimulation (P < 0.0001), rather than on glucose levels (P > 0.05). The infusion of SSTR antagonists in the isolated perfused rat pancreas blocked the paracrine effects of SST (P = 0.0041) and stimulated glucagon secretion (P = 0.0023). Cholinergic activity stimulated glucagon secretion during hypoglycemia through suppression of SST secretion. Cholinergic signaling delivered through the gastric intramural autonomic ganglia and/or vagus nerve efferents to the pancreas appears to be crucial for preventing GLP-1-induced inhibition of glucagon secretion during hypoglycemia.NEW & NOTEWORTHY Autonomic signaling suppresses somatostatin secretion, crucial for paracrine stimulation of glucagon secretion. SST mediates GLP-1-induced inhibition of glucagon secretion, but autonomic signaling may interfere with this mechanism. Activation of cholinergic pathways in a preparation with prepancreatic parasympathetic structures suppresses SST secretion in response to GLP-1 and potentiates glucagon secretion during hypoglycemia. These findings support the clinical importance of autonomic signaling in regulating pancreatic hormone secretion and hypoglycemia risk in some patients on GLP-1 receptor agonists.
The association of perturbed skeletal muscle metabolism with ICU acquired weakness (ICUAW) is not clear. The objective of the present study was to characterise temporal changes in skeletal muscle mitochondrial function, ATP concentration, and substrate utilisation during and up to 6 months post ICU admission in critically ill patients, and to delineate mechanisms underpinning ICUAW by comparing the expression of genes involved in skeletal muscle mitochondrial function and substrate utilisation in the critically ill patients to control groups that had either undergone elective surgery or leg immobilisation (i.e. muscle disuse). The study design was a randomised controlled trial of functional electrical stimulation-assisted cycle ergometry (FESCE) vs. standard care, with skeletal muscle mitochondrial respirometry defined a priori in a nested sub-group of patients as the primary outcome. Mitochondrial respirometry did not change 7 days or 6 months after ICU admission and was not impacted by FESCE. However, a 20% reduction in muscle ATP content by day 7 of ICU stay persisted after 6 months and tended to associate with ICUAW (P=0.078, R2=0.582). Moreover, a 40% lower muscle glycogen and 2.5-fold greater muscle lactate were observed earlier at day 1 compared to elective surgery patients. These changes reflected expression of genes related to glycogen metabolism when disuse was accounted for, and of which a greater expression of the gene encoding glycogen phosphorylase (PYGM) was predictive of mortality. We conclude that muscle glycogen metabolism is rapidly dysregulated in critical illness, which may have implications for muscle ATP resynthesis and ICUAW.
Structural changes in microcirculation are often considered the first signs of vascular damage due to hypertension. A key tissue type emerging as a regulator of vascular tone is perivascular adipose tissue (PVAT). PVAT is a complex collection of adipocytes, immune cells, nerves, collagen fibers, and capillaries that surround most blood vessels. Norepinephrine (NE) is an important catecholamine that has emerged as a key driver of PVAT anticontractile factors. The release of anticontractile factors such as nitric oxide (NO) and adiponectin counteract smooth muscle contraction and limit vasoconstriction. NE stimulates adrenergic receptors such as β3, β2, and α1a, leading to the activation of Gs and Gq signal transduction cascades. Despite the importance of NE in promoting PVAT vasoactive functions, the cellular signal transduction mechanisms that underlie this effect remain unknown. Here, we used Ca2+ and NO imaging, selective drugs, and immunofluorescence to investigate mechanisms of NE-induced Ca2+ responses in PVAT. Our findings demonstrate that NE-induced Ca2+ signaling in PVAT is mediated by α1a, β2, and β3 adrenergic receptors, with depot-specific differences. Ca2+ responses in mesenteric PVAT, aortic PVAT, and white adipose tissue originate largely from internal stores. Selective agonism used in Ca2+ and NO imaging supports the role of adrenergic receptors as major mediators of NE-induced responses with depot-specific differences. Immunofluorescence confirmed that all three receptor subtypes are present on the adipocyte membrane and the vasculature. Together, these results highlight the complexity of adrenergic signaling in PVAT.NEW & NOTEWORTHY Norepinephrine (NE)-induced Ca2+ signaling in PVAT is mediated by adrenergic receptors with depot-specific roles. All three receptor subtypes contribute in mPVAT and aPVAT, whereas α1a predominates in white adipose tissue. Internal Ca2+ stores are the primary Ca2+ source for NE-induced signaling across depots. Ca2+ imaging with selective agonists supports α1a's role, and NO imaging highlights depot diversity. Immunofluorescence data confirm receptor expression on adipocytes and vasculature, indicating complex signaling pathways in adipose tissues studied here across depots.
Nesting materials are used to enhance animal welfare in laboratory settings, yet their physiological impact, particularly on energy metabolism, remains undercharacterized. Here, we investigated the effect of three commonly used nesting materials (nestlet, Enrich-n'Nest, and Bed-r'Nest) and the presence versus absence of nesting on metabolic parameters in male mice housed at thermoneutral (30°C), standard (22°C), and cold (10°C) temperatures. Using indirect calorimetry, we continuously monitored respiratory exchange ratio (RER), food intake, and water intake. Within each thermal condition, the presence of nesting compared with no nesting was associated with reduced oxygen consumption (V̇o2) at 22°C and an attenuation of thermogenic demand at 10°C, whereas nesting has minimal effects at 30°C. In contrast, the type of nesting material did not differentially affect V̇o2, RER, or ingestive behavior at any temperature. Environmental variables, including temperature stability and relative humidity, were closely monitored and remained within standard ranges throughout the experiments. Together, these findings demonstrate that although nesting availability modulates metabolic demand in a temperature-dependent manner, commonly used nesting materials do not introduce meaningful variability in metabolic cage studies. These findings support the continued use of these three nesting materials in metabolic phenotyping and highlight the importance of transparent reporting of housing and enrichment conditions to improve reproducibility in preclinical metabolic research.NEW & NOTEWORTHY Nesting availability, but not nesting material type, modulates energy metabolism in individually housed male mice in a temperature-dependent manner. Nesting reduces metabolic demand at standard housing temperature, with minimal impact at thermoneutrality. These findings support the use of common nesting materials and highlight the importance of reporting environmental enrichment to improve rigor and reproducibility in metabolic studies.
The enzyme selenocysteine (Sec) lyase (SCLY) decomposes Sec, releasing selenide for the synthesis of selenoproteins, which contain Sec in their primary structure and participate in strong redox reactions, maintaining redox balance. We previously showed that global disruption of the Scly gene (Scly KO) in mice leads to obesity. Targeted deletion of Scly in agouti-related peptide neurons enhances energy expenditure and brown adipose tissue (BAT) activation, augmenting leanness. We hypothesized that Scly KO mice develop obesity due to failure of BAT-controlled mechanisms of energy expenditure due to redirection of Sec to an alternative pathway. We analyzed BAT from male Scly KO mice on selenium (Se)-adequate [0.25 parts per million (ppm)] and Se-deficient (0.08 ppm) diets for morphology, Se content, selenoprotein expression, thyroid hormones, and additional Sec-using pathways. We found that the BAT of Scly KO mice was enlarged, with lower Se levels, and substantial whitening on a Se-adequate diet. This phenotype worsened on low Se and coincided with a mild impairment in adapting to cold exposure. BAT whitening coincided with an increase in triglycerides and reduced 3-hydroxy-3-methylglutaryl coenzyme A and cholesterol. BAT selenoproteins regulating energy metabolism, type 2 iodothyronine deiodinase (DIO2), glutathione peroxidase 1 (GPX1), and glutathione peroxidase 1 (GPX4), were significantly decreased. DIO2 reduction corresponded with an increase in thyroxine and thyroid-stimulating hormone and a reduction in heat-producing uncoupling protein 1. Downregulation of GPX4 did not affect ferroptosis in the BAT. Therefore, the whitened BAT of the Scly KO mouse is a multifactorial process involving the disruption of BAT function through changes to selenoproteins involved in energy metabolism.NEW & NOTEWORTHY Global loss of the selenocysteine-decomposing enzyme selenocysteine lyase in mice leads to lipid accumulation and whitening of the brown adipose tissue, with consequent obesity development. Selenocysteine lyase modulates selenium levels and selenoprotein expression, specifically GPX1, GPX4, and DIO2, in brown adipocytes. Selenocysteine metabolic fate hinges on the actions of selenocysteine lyase.
The objective of this is to compare the effects of diet restriction and semaglutide treatment on body composition (BC), energy expenditure (EE), and metabolic adaptation (MA) in Göttingen Minipigs as a model for human obesity. Diet-induced obese Göttingen Minipigs were divided into three groups (n = 8): a control group receiving vehicle and fed ad libitum, a group treated with the GLP-1 receptor agonist (GLP-1RA) semaglutide and fed ad libitum, and a diet-restricted group receiving vehicle and weight-matched the semaglutide group. BC, EE, and plasma parameters were measured at baseline and after 10 wk; tissue mitochondrial respiration and myosin conformation were measured after 10 wk. Diet-restricted minipigs gained 6.8% (P < 0.01) more body fat compared with semaglutide, mediated by a greater loss of fat-free mass (4.3 kg, P < 0.05) and a tendency for a higher fat mass gain (P = ns). Diet restriction led to significantly decreased EE compared with the control group (-273 kcal/day, P < 0.05), but no differences between groups were observed when adjusting EE for changes in BC. Energy balance modeling revealed significant MA in the diet-restricted animals (P < 0.01) compared with both control and semaglutide groups. Diet restriction was further associated with decreased proton leak and resting myosin ATP consumption in muscle. Semaglutide treatment improved BC and EE outcomes compared with diet restriction despite similar weight trajectories. Furthermore, semaglutide treatment prevented specific energy-conserving changes in tissues, thus highlighting novel mechanisms regulating energy balance during GLP-1RA treatment.NEW & NOTEWORTHY Specific energy-conserving mechanisms and metabolic adaptation challenge weight loss efficiency and maintenance, and promote weight regain after diet restriction. Less is known about these mechanisms after pharmacologically induced weight loss. For the first time in a minipig model of obesity, the research demonstrated how GLP-1 receptor agonist (GLP-1RA) treatment, compared with a weight-matched diet-restricted group, positively influenced body composition, energy expenditure, mitochondrial thermogenesis, and myosin ATPase activity. These novel mechanisms of energy expenditure may have potential as future drug targets.
Deuterated water (2H2O) can be used to measure de novo lipogenesis (DNL) with minimal participant burden, but implications of tracer washout on repeated measures in humans are unclear. This study is an exploratory analysis of data from a crossover trial to determine the impact of duration between repeated 2H2O dosing for sequential assessments of DNL, alongside day-to-day variability in DNL. A total of 22 nonobese adults (11 men and 11 women) completed three laboratory visits in a randomized, crossover design (35 ± 13-day washout). Participants consumed 3 g·kg-1 body water of 2H2O the evening before laboratory visits. Blood was sampled before 2H2O ingestion, and the following morning in a fasted state. Deuterium (2H) enrichment of plasma water and very-low-density lipoprotein-triacylglycerol (VLDL-TG)-palmitate were used to determine DNL. Although predosing plasma water 2H enrichments (mole percent) increased across visits from 0.017 ± 0.003% to 0.022 ± 0.008% and 0.027 ± 0.014%, respectively (P < 0.05), postdose enrichments did not display a systematic bias, and nor did 2H enrichments of VLDL-TG-palmitate or measures of DNL [largest mean difference = -1.2%; 95% confidence interval (95% CI) = -12.7% to 9.1%, P = 0.45]. The day-to-day standard deviation and coefficient of variation of fractional hepatic DNL was 2.39% (95% CI = 1.35%-3.42%) and 27% (95% CI = 19%-35%), respectively. Repeated 2H2O dosing does not systematically bias measures of fasting hepatic DNL when using a washout duration of ∼4 wk. We also found no evidence that DNL is biased by washout durations of 3 wk. Therefore, 2H2O can be used to reliably assess human hepatic DNL in repeated measures designs with at least 3 wk between sequential measures.NEW & NOTEWORTHY Repeated deuterated water dosing in humans does not systematically bias measures of fasting hepatic DNL when using a washout duration of ∼4 wk. Fasting fractional hepatic DNL can be reliably assessed using deuterated water over sequential visits with as little as 3 wk washout between measures. At the group level, the within-participant variability in fasting hepatic DNL was relatively small and permits efficient detection of minimal clinically important differences in hepatic DNL with crossover studies.