搜索结果：American journal of physiology. Endocrinology and metabolism

We are only beginning to understand the extent and reasons for the individual variation in postprandial response dynamics in key hormones and metabolites such as insulin, glucose, and triacylglycerols (TAGs). More nuanced statistical approaches for postprandial curve analyses, coupled with phenotyping of curve-associated factors, may help uncover the underlying physiology and possible associations with disease risk. In a clinical trial of 190 adults (90 males and 100 females) with abdominal obesity (age: 21-56 yr, BMI: 26-54), we used functional principal component analysis (FPCA) to examine postprandial serum glucose, C-peptide, and TAGs after a 4-h standardized mixed meal test. Correlations were explored between identified curve patterns and more than 100 anthropometric and fasting biochemistry traits. Postprandial curve levels, peaks, and dips varied substantially. Although the primary patterns in postprandial glucose, C-peptide, and TAGs uncovered by FPCA corresponded with area under the curve (AUC), the presence and timing of curve peaks and dips were uncorrelated with AUC. Males had higher postprandial levels and larger variation than females. Over 40% of the participants had nonsynchronized postprandial glucose and C-peptide curves. A postprandial phenotype characterized by elevated and delayed postprandial peaks in glucose and C-peptide, and a high postprandial TAG level and peak, was strongly associated with multiple blood biomarkers and anthropometric traits linked to insulin resistance and liver pathologies (correlation range: -0.49, 0.63). Although our findings support the general usefulness of postprandial AUC, FPCA provided detailed insight into individual postprandial glucose and insulin dynamics, which may inform improved diagnostics and personalized dietary advice.NEW & NOTEWORTHY Functional principal component analysis (FPCA) revealed large individual and sex-specific differences in postprandial glucose, C-peptide, and triacylglycerol dynamics in obesity. Although the primary postprandial patterns correlated strongly with the area under the curve (AUC), the presence and timing of peaks varied independently of AUC. Over 40% of participants showed nonsynchronized postprandial glucose and C-peptide curves. High and delayed peaks were associated with markers of insulin resistance, altered amino acid metabolism, visceral adiposity, and liver dysfunction.

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.

Metformin and exercise are often coprescribed in adults with prediabetes and type 2 diabetes mellitus. However, metformin may alter metabolic responses to exercise. This systematic review and meta-analysis evaluated the impact of metformin on exercise metabolism, including lactate, glucose, insulin, and free fatty acids, along with exercise capacity. Electronic databases (Web of Science, PubMed/Medline, Embase, and SPORTDiscus) were searched through January 2025. Twenty-one studies that involved acute (single dose), nonacute (multiple doses), and habitual metformin (prescribed) intake were included in the systematic review. Study quality and risk of bias were assessed using the Cochrane Risk of Bias 2 tool. Random-effects meta-analyses were conducted on lactate, glucose, insulin, and exercise capacity during acute and nonacute studies, and effects are reported as standardized mean differences (SMDs) with 95% confidence intervals. Across 325 participants (female, n = 125), metformin doses ranged from 500 to 3,000 mg/day and interventions ranged from 1 dose to 12 wk. Acute studies were primarily in young, healthy males, whereas habitual studies involved older adults (predominantly female) on long-term metformin treatment. Metformin was associated with greater lactate concentrations during exercise (SMD = 0.98, 95% CI: 0.36, 1.60, P = 0.002). Metformin modulates exercise metabolism, with the largest impact being on lactate accumulation during exercise. The direction of these interactions may depend on dose, duration, and participant characteristics. This review provides the first critical synthesis of available literature combining metformin and exercise metabolism, capacity, and training adaptations, offering insights to clinicians and exercise practitioners on potential implications of coprescribing metformin and exercise.

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.

The association of perturbed skeletal muscle metabolism with intensive care unit (ICU)-acquired weakness (ICUAW) is not clear. The objective of the present study was to characterize temporal changes in skeletal muscle mitochondrial function, ATP concentration, and substrate utilization during and up to 6 mo 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 utilization in the critically ill patients to control groups that had either undergone elective surgery or leg immobilization (i.e., muscle disuse). The study design was a randomized controlled trial of functional electrical stimulation-assisted cycle ergometry (FESCE) versus standard care, with skeletal muscle mitochondrial respirometry defined a priori in a nested subgroup of patients as the primary outcome. Mitochondrial respirometry did not change 7 days or 6 mo 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 mo 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 with elective surgery patients. These changes reflected expression of genes related to glycogen metabolism when disuse was accounted for, and 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.NEW & NOTEWORTHY The association of skeletal muscle metabolism with intensive care unit (ICU)-acquired weakness (ICUAW) is not clear. We report for the first time that reduced muscle ATP content by day 7 of ICU stay persisted after 6 mo and tended to be associated with ICUAW. Moreover, lower muscle glycogen and greater muscle lactate were observed earlier at day 1 compared with elective surgery patients. These changes reflected the expression of genes related to glycogen metabolism, which were predictive of mortality.

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 alleviate fetal hypoxemia and hypoglycemia and improve 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 with 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 versus 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 with 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.NEW & NOTEWORTHY Using a sheep model of placental insufficiency, we showed that prenatal oxygen and glucose supplementation improved mitochondrial respiration and partially normalized mitochondrial proteomic profiles in growth-restricted fetal skeletal muscle. These findings highlight that targeted prenatal correction of hypoxemia and hypoglycemia can mitigate mitochondrial deficits associated with fetal growth restriction.

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.

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.

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.

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.

Fatty acid oxidation (FAO) is a critical bioenergetic source for skeletal muscle, with FAO impairments being linked to metabolic and contractile dysfunction. FAO is regulated by the carnitine shuttle, in which FAO-eligible fatty acids, in the form of acylcarnitines, are transported into the mitochondrial matrix by carnitine-acylcarnitine translocase (CACT); however, the role of CACT in muscle in vivo has remained unexplored. To determine the requirement of CACT in muscle FAO and its influence on muscle mitochondrial bioenergetics, lipid profile, and muscle contractility, a novel conditional skeletal muscle-specific CACT knockout mouse (CactSk-/-) was generated. The requirement of CACT for long-chain FAO was confirmed by the complete abrogation of FAO flux in CactSk-/- muscle mitochondria. CACT was also required for the oxidative flux of medium-chain octanoyl-carnitine and acetyl-carnitine. CACT loss disrupted the lipid profile of skeletal muscle, with long-chain acylcarnitine accumulation and a shift in the saturation profile of phospholipids away from saturated and highly unsaturated and toward di- and tri-saturated phospholipids. Elevated mitochondrial content was demonstrated by increased phospholipid content and mitochondrial staining in CactSk-/- muscles, occurring to a greater extent in oxidative muscles. Loss of CACT reduced muscle-specific force production by &#x223c;70% in oxidative soleus muscle despite increased fiber size and compensatory mitochondrial accumulation that preserved muscle metabolic capacity. These findings demonstrate the crucial role of CACT in muscle FAO and show that oxidative muscles, in particular, undergo extensive lipid compositional, metabolic, and structural remodeling that coincides with impaired contractile function.NEW & NOTEWORTHY Novel model of CACT loss in muscle to demonstrate that CACT is required for long, medium, and short-chain fatty acid oxidation in skeletal muscle. Deletion of CACT drives oxidative and glycolytic muscle lipid remodeling and impairs oxidative, but not glycolytic, muscle contractile capacity. Oxidative soleus muscle mitochondria compensate for CACT loss by increasing mitochondrial content and muscle capacity for oxidation of nonfatty acid substrates.

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.

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.

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.

This study investigated the efficacy of thiazolidinediones in mitigating diet-induced obesity and associated glucose intolerance in canines in vivo. We used a multitechnique approach and compared the results related to 1) fasting metabolites, hormones, and lipides; 2) oral glucose tolerance test (OGTT), and 3) hyperinsulinemic euglycemic (HIEG) clamps in 24 healthy dogs that were then fed a high-fat diet and assigned to a placebo group (n = 8) or received a daily dose of pioglitazone group (n = 16) for 56 days. The animals were studied before and after treatment, acting as their own controls, and we used a principal component analysis to combine the results obtained for the three different techniques. Both groups experienced weight gain, with 12% and 14% increases in the placebo and pioglitazone groups, respectively. The fasting level of free fatty acids was increased in both placebo (+17.5%) and pioglitazone groups (+7.7%), as were the insulin levels (+27% and 35%, respectively, in placebo and pioglitazone), but fasting glucose levels were reduced slightly in both (-2.7 and -2.9 mg/dL, respectively). Pioglitazone increased fasting adiponectin levels by 54% between day -1 and day 56. OGTTs revealed a significantly better glucose tolerance in the pioglitazone treatment group compared with the placebo group, as the level of insulin secreted during the OGTT was normalized. HIEG clamps demonstrated that, in the placebo group, glucose infusion rate and glucose utilization decreased in response to the diet, but this effect was prevented by pioglitazone. In conclusion, these findings show that pioglitazone is beneficial in preventing the consequences of dietary metabolic stress and overfeeding in canines.NEW & NOTEWORTHY This study validates the efficacy of the thiazolidinediones (TZD) drug pioglitazone in a fat-fed canine model. Using a novel principal component analysis integrating multimodal data (fasting metabolites, OGTT, and clamp results), we demonstrate that pioglitazone effectively reverses diet-induced glucose intolerance and significantly improves insulin sensitivity. Mechanistically, this improvement is driven by adiponectin action. These findings provide strong evidence supporting TZD use as a prophylactic tool for mitigating metabolic syndrome.

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.

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&#xb0;C), standard (22&#xb0;C), and cold (10&#xb0;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 (V&#x307;o2) at 22&#xb0;C and an attenuation of thermogenic demand at 10&#xb0;C, whereas nesting has minimal effects at 30&#xb0;C. In contrast, the type of nesting material did not differentially affect V&#x307;o2, 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.

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 &#x3b2;3, &#x3b2;2, and &#x3b1;1a, 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 &#x3b1;1a, &#x3b2;2, and &#x3b2;3 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 &#x3b1;1a 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 &#x3b1;1a'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.

Pancreatic &#x3b1;-cells secrete glucagon. The glucagon secretion rate (GSR) increases when plasma glucose decreases; conversely, GSR decreases when glucose rises. In addition, amino acids (AAs) stimulate GSR. Impaired GSR suppression by glucose contributes to postprandial hyperglycemia in individuals with impaired glucose tolerance, obesity, and type 2 diabetes (T2D). However, the current method to assess &#x3b1;-cell responsivity to glucose ignores the contribution of AAs and is a two-step approach with some limitations. To address this, we developed a model-based method to quantify &#x3b1;-cell responsivity to glucose during a graded glucose infusion, in the presence and absence of AAs. A total of 52 subjects were studied. Thirty-seven subjects from study 1 [13 M, age = 54&#x2009;&#xb1;&#x2009;10 yr, body mass index (BMI) = 30&#x2009;&#xb1;&#x2009;5 kg/m2] were studied once. Fifteen subjects (4 M, age = 47&#x2009;&#xb1;&#x2009;11 yr, BMI = 28&#x2009;&#xb1;&#x2009;4 kg/m2) from study 2 were studied twice: once with saline and once with an AA infusion (Clinisol 15%, 0.003 mL/kg/min). Plasma glucagon, glucose, and AA concentrations were measured over 240 min. We tested several mathematical models of GSR, and the best one was selected using standard criteria. The optimal model describes GSR as an exponential decay driven by delayed plasma glucose concentration and modulated by AAs. The model provides an index of &#x3b1;-cell responsivity, G50, i.e., the glucose increase required to suppress GSR by 50%. AA infusion increased G50 compared with the saline infusion. This model-based approach provides an index of &#x3b1;-cell responsiveness under both physiological and AA-stimulated conditions. Its use may help in the early detection of &#x3b1;-cell dysfunction in people at risk of developing T2D.NEW & NOTEWORTHY In this study, we propose two new mathematical models able to quantify glucagon secretion during a graded glucose infusion, in the presence and absence of amino acids. The models provide an index of &#x3b1;-cell responsivity, G50, i.e., the glucose increase required to suppress glucose secretion rate (GSR) by 50%. Results show that the presence of amino acids reduced &#x3b1;-cell responsivity to glucose.