Mechanisms of fatty acid-induced inhibition of glucose uptake

Nanocellulose dysregulated glucose homeostasis in female mice on a Western diet: The role of gut microbiome

There is currently increased interest in nanocellulose as a food emulsifier and dietary supplement. It was hypothesized that nanocellulose could modulate behaviors and glucose homeostasis in female mice using mechanisms of altered gut microbiome and immune modulation. An initial experiment was conducted with the objective of examining whether three common types of nanocellulose affected the gut microbiome of female C57BL/6 mice on a Western diet. Cellulose nanofibrils (CNF), TEMPO-CNF and cellulose nanocrystals were administered at the physiologically relevant dose of 30 mg/kg/day for 30 days by gavage, with cellulose and water groups as the positive and negative controls, respectively. Findings suggested that CNF had the strongest effect on the gut microbiome. CNF was therefore selected for a chronic 6-month study on the gut microbiome, immune system and behaviors in female NOD mice, a model for type 1 diabetes. Gut microbiome analysis suggested that there might be some beneficial changes following subchronic exposure (e.g., at the two-month timepoint), however, this effect was no longer seen after chronic consumption (e.g., at the six-month timepoint). CNF treatment also altered the immune homeostasis, including decreases in the splenic Mac-3+ population and serum level of proinflammatory chemokine LIX. Additionally, CNF consumption decreased diabetic incidences but had no effect on the depressive-like behavior and grip strength. However, further analysis, e.g., the insulin tolerance test, indicated that CNF-treated NOD mice might exhibit signs of insulin resistance. Taken together, nanocellulose dysregulated glucose homeostasis in female mice on a Western diet involving mechanisms related to alteration of the gut microbiome.

Longitudinal Trajectory of Free Fatty Acids in Pregnancy According to First-Trimester Maternal Metabolic Status and the Presence of Gestational Diabetes

BACKGROUND/OBJECTIVES

Maternal free fatty acids (FFAs) play a critical role in maternal metabolism, fetal growth, and pregnancy outcomes. However, their relationship with maternal metabolic status in early pregnancy and the subsequent development of gestational diabetes mellitus (GDM) remains unclear.

AIM

Assess the trajectory of FFA concentrations during pregnancy, considering first-trimester metabolic status (obesity, insulin resistance-IR) and the development of GDM, and evaluate whether first-trimester FFA is a relevant risk factor for GDM.

METHODS

A case-control study nested within the OBESO cohort (Mexico City, pregnant women and their children), classified women according to first-trimester metabolic status (pregestational body mass index-pBMI, insulin resistance homeostasis model assessment-HOMA-IR > 1.6), as well as the presence of GDM: Group 1 (normal weight without IR, n = 60), Group 2 (obesity without IR, no GDM, n = 20), Group 3 (obesity with IR, no GDM, n = 20), and Group 4 (obesity with IR, with GDM, n = 9). FFA concentrations were measured each trimester. Statistical analyses included repeated measures ANOVA and logistic regression models.

RESULTS

FFA concentrations were the highest in Group 4 across all trimesters (p < 0.05). FFAs decreased throughout pregnancy in all groups (p = 0.023), with the most significant decline from the first to the third trimester (p < 0.001). The greatest reduction occurred in Group 4 (p < 0.001), followed by Group 3. Multivariate logistic regression showed no association between first-trimester FFAs and the development of GDM. Higher gestational weight gain was associated with a higher GDM risk (OR: 1.22, 95%CI: 1.01-1.48), when the FFAs difference was accounted for.

CONCLUSIONS

FFA levels are higher in women with GDM compared with women with obesity or a normal weight. However, FFAs progressively decline from the first to the third trimester, with the most pronounced decrease in women with obesity, IR, and GDM.

Advancing Diabetes Management and Glycemic Control While Exploring CagriSema's Impact on Obesity Management

Diabetes is a complex metabolic disorder affecting over 37 million people in the United States. Without proper management, diabetes can lead to a myriad of complications, including cardiovascular disease, kidney failure, and vision loss. Obesity is a major contributor to type 2 diabetes, but genetic and physiological factors make weight loss difficult, necessitating medication management for both conditions. Government-approved weight loss medications, including glucagon-like peptide-1 agonists and amylin analogs, have proven to be effective for both conditions. However, intensive glycemic control involving antidiabetic medications, while beneficial for reducing diabetic complications, can often precipitate hypoglycemic events, which are characterized by cardiac arrhythmias, coma, confusion, and even mortality. A new drug under investigation, CagriSema, combines cagrilintide, an amylin analog, with semaglutide, a glucagon-like peptide-1 agonist. This drug is being marketed as a safe and potentially superior medication to lower both Hemoglobin A1c and body weight. In this article, the pathophysiology, current guidelines, and management of diabetes will be reviewed, with an emphasis on the clinical evidence for tight glucose control and avoiding hypoglycemic events. Following this, an overview of recent trials on antidiabetic medications, including those involving CagriSema, will be presented, along with prospects for future trials in this promising area of research.

Human Adipose Tissue Metabolism in Obesity

The scientific understanding of adipose tissue has advanced tremendously during the past decade. Once thought to be an inert fat storage organ, we now know that adipose tissue serves important functions in energy balance and endocrinology, as well as playing a central role in the development of metabolic diseases. Adipose tissue lipid storage and lipolysis are tightly controlled by hormones, such as insulin, in response to the body's energy needs. Adipose insulin sensitivity can be measured in vivo in humans using isotopic fatty acid tracers and the insulin clamp technique. These data allow investigators to calculate the plasma insulin concentration that results in a 50% suppression of lipolysis. In obesity, insulin's action on adipose tissue lipolysis is clearly impaired, resulting in excess free fatty acids in circulation, which can lead to metabolic dysfunction. However, the cause of this impairment is unclear. The chronic, low-grade adipose tissue inflammation seen in obesity was thought to be the cause of adipose tissue insulin resistance. In this review, we discuss the structure of adipose tissue, how normal and abnormal adipose tissue metabolism contributes to metabolic diseases, and how inflammation might or might not play a role in adipose tissue insulin resistance.

Impact of breakfast consumption timing v. breakfast omission on post-lunch glycaemia and insulinaemia in adolescent girls: a randomised crossover trial

Adolescent girls often skip breakfast due to time constraints and reduced morning appetite. This study examined the acute impact of breakfast consumption timing v. breakfast omission (BO) on glycaemic and insulinaemic responses to lunch in infrequent breakfast-consuming girls. Fifteen girls (13·1 (sd 0·8) years) completed three conditions in a randomised crossover design: early-morning breakfast consumption (EM-BC; 08.30), mid-morning breakfast consumption (MM-BC; 10.30) and BO. A standardised lunch was provided at 12.30, followed by a 2-h post-lunch observation period. Blood and expired gas samples were collected periodically. Linear mixed models with Cohen's d effect sizes compared outcomes between conditions. Pre-lunch glucose and insulin incremental AUC (iAUC) were higher in the breakfast conditions v. BO (P ≤ 0·009), with no differences between breakfast conditions. MM-BC reduced post-lunch glucose iAUC by 36 % and 25 % compared with BO and EM-BC, respectively (P < 0·001, d = 0·92-1·44). A moderate, non-significant 15 % reduction in post-lunch glucose iAUC was seen with EM-BC v. BO (P = 0·077, d = 0·52). These reductions occurred without changes in post-lunch insulinemia (P ≥ 0·323) and were accompanied by increased post-lunch carbohydrate oxidation compared with BO (P ≤ 0·018, d = 0·58-0·75); with no differences between EM-BC and MM-BC. MM-BC lowered glycaemic response over the experimental period compared with BO (P = 0·033, d = 0·98) and EM-BC (P = 0·123, d = 0·93), with no difference between EM-BC and BO. Compared with BO, both breakfast conditions lowered post-lunch glycaemic responses with mid-morning breakfast eliciting a greater second-meal effect than early-morning breakfast. These findings indicate the breakfast-to-lunch meal interval may be a crucial factor affecting postprandial glycaemia in infrequent breakfast-consuming girls.

Effects of Hypertriglyceridemia With or Without NEFA Elevation on β-cell Function and Insulin Clearance and Sensitivity

CONTEXT

Hypertriglyceridemia is a risk factor for developing type 2 diabetes (T2D) and might contribute to its pathogenesis either directly or through elevation of nonesterified fatty acids (NEFAs).

OBJECTIVE

This study aimed at comparing the glucometabolic effects of acute hypertriglyceridemia alone or combined with NEFA elevation in subjects without diabetes.

METHODS

Twenty-two healthy lean volunteers underwent 5-hour intravenous infusions of either saline or Intralipid, without (n = 12) or with heparin (I + H; n = 10) to activate the release of NEFAs. Oral glucose tolerance tests (OGTTs) were performed during the last 3 hours of infusion. Insulin sensitivity, insulin secretion rate (ISR), model-derived β-cell function, and insulin clearance were measured after 2 hours of lipid infusion and during the OGTTs.

RESULTS

In fasting conditions, both lipid infusions increased plasma insulin and ISR and reduced insulin clearance without affecting plasma glucose and insulin sensitivity. These effects on insulin and ISR were more pronounced for I + H than Intralipid alone. During the OGTT, the lipid infusions markedly impaired glucose tolerance, increased plasma insulin and ISR, and decreased insulin sensitivity and clearance, without significant group differences. Intralipid alone inhibited glucose-stimulated insulin secretion (ie, β-cell glucose sensitivity) and increased β-cell potentiation, whereas I + H had neutral effects on these β-cell functions.

CONCLUSION

In healthy nonobese subjects, mild acute hypertriglyceridemia directly reduces glucose tolerance and insulin sensitivity and clearance, and has selective and opposite effects on β-cell function that are neutralized by NEFAs. These findings provide new insight into plausible biological signals that generate and sustain insulin resistance and chronic hyperinsulinemia in the development of T2D.

Association between the new TyG indicator-TyHGB and gestational diabetes mellitus: results from the case-control and prospective cohort studies

BACKGROUND

Given the close relationship between lipids and gestational diabetes mellitus(GDM), the present study sought to examine the association between the triglyceride high-density cholesterol-glucose body index(TyHGB) and the risk of developing GDM.

METHODS

In order to investigate the relationship between TyHGB and GDM, a retrospective case-control study and a prospective cohort study were conducted involving 1862 individuals. A multifactorial logistic regression model was employed to assess the relationship between TyHGB and GDM, and to reduce potential bias and confounding variables, the association between TyHGB and GDM was evaluated using 1:1 propensity score further matching (PSM) multivariate logistic regression of post-PSM data. The restricted cubic splines(RCS) was used to observe the dose-response relationship between TyHGB and GDM. Receiver operating characteristic (ROC) curves were employed to evaluate the predictive accuracy of GDM. Subsequently, likelihood ratio tests were utilized to investigate the correlation between TyHGB and GDM in specific subgroups.

RESULTS

After adjustment for all confounders, multivariate logistic regression analysis showed that TyHGB was significantly associated with the risk of developing GDM.The ROC curve shows the excellent predictive performance of the TyHGB index.TyHGB was better than other indices in predicting GDM in the first and second trimester.

CONCLUSIONS

This study demonstrates that TyHGB is independently associated with GDM risk. TyHGB may be used as a screening and monitoring tool for pregnant women at high risk of GDM rather than other lipid indicators.

Interplay of fatty acids, insulin and exercise in vascular health

Fatty acid metabolism, exercise, and insulin action play critical roles in maintaining vascular health, especially relevant in metabolic disorders such as obesity, type 2 diabetes, and cardiovascular disease. Insulin, a vasoactive hormone, induces arterial vasodilation throughout the arterial tree, increasing arterial compliance and enhancing tissue perfusion. These effects, however, are impaired in individuals with obesity and type 2 diabetes, and evidence suggests that vascular insulin resistance contributes to the pathogenesis of type 2 diabetes and its cardiovascular complications. Elevated plasma levels of free fatty acids in people with insulin resistance engender vascular inflammation, endothelial dysfunction, and vascular insulin resistance. Importantly, these effects are both functionally and structurally dependent, with saturated fatty acids as the primary culprits, while polyunsaturated fatty acids may support insulin sensitivity and endothelial function. Exercise enhances fatty acid oxidation, reduces circulating free fatty acids, and improves insulin sensitivity, thereby mitigating lipotoxicity and promoting endothelial function. Additionally, exercise induces beneficial vascular adaptations. This review examines the complex interplay among fatty acid metabolism, exercise training-induced vascular adaptations, and insulin-mediated vascular changes, highlighting their collective impact on vascular health and underlying mechanisms in both healthy and insulin-resistant states. It also explores the therapeutic potential of targeted exercise prescriptions and fatty acid-focused dietary strategies for enhancing vascular health, emphasizing tailored interventions to maximize metabolic benefits. Future research should investigate the pathways linking fatty acid metabolism to vascular insulin resistance, with a focus on how exercise and dietary modifications can be personalized to enhance vascular insulin sensitivity, optimize vascular health, and reduce the risks of type 2 diabetes and associated cardiovascular complications.

Non-linear dose-response relationship between the visceral adiposity index and diabetes in adults with normoglycemia: a cohort study

Objective

Previous studies have identified a positive link between the visceral adiposity index (VAI) and diabetes in specific populations. Our investigation focused on examining this association in normoglycemic adults in Japan.

Methods

A cohort study of NAGALA (NAfld in the Gifu Area Longitudinal Analysis) was undertaken from 2004 to 2015 in Japan. The link between VAI and diabetes was evaluated using multivariate Cox proportional hazards regression and restricted cubic spline (RCS) regression models. Receiver operating characteristic (ROC) curve analysis was performed to assess the predictive value of the VAI for incident diabetes.

Results

Our study included 15,452 participants, with 8,418 men (54.48%) and 7,034 women (45.52%). The average age was 43.71 ± 8.90, and 373 participants (2.41%) developed diabetes. VAI was positively related to diabetes (HR=1.13, 95% CI 1.08-1.18). The inflection point of the non-linear relationship was observed at a VAI value of 4.67. For the VAI values up to 4.67, one unit increase in the VAI related to a 24% increase in new-onset diabetes (HR=1.24, 95% CI 1.12-1.37, p<0.0001). Subgroup analysis detected a more robust relationship in women (HR=1.40, 95% CI 1.14-1.70, p=0.0010). ROC analysis indicated that VAI, with an AUC of 0.7479 (95% CI: 0.7237-0.7720), had good predictive power.

Conclusion

Our cohort study validated the positive and non-linear relationship between the VAI and diabetes in normoglycemic adults in Japan. The relevance was more marked in women than in men. For those with a VAI below 4.67, a further reduction in the VAI could potentially lead to a significant decrease in diabetes risk.

Association between serum free fatty acids and gestational diabetes mellitus

Background

Pregnant women with gestational diabetes mellitus (GDM) are at an increased risk of adverse pregnancy outcomes (APO). Early understanding of risk factors affecting these outcomes may facilitate preventive interventions for women at high risk. Blood samples from GDM and control pregnant women were collected for Free fatty acid (FFA) profiling to determine the relationship with the occurrence of APO in GDM pregnant women.

Methods

The study comprised 144 women diagnosed with GDM and 52 normal control pregnancy (NC). Venous fasting serum samples were collected during the second trimester. The serum FFA levels were detected by liquid chromatography-mass spectrometry (LC-MS). The primary outcome consisted of serious maternal and neonatal adverse events ( hypertensive disorder complicating pregnancy (HDCP), emergency cesarean section, large for gestational age (LGA), small for gestational age (SGA), macrosomia, low birth weight (LBW), preterm birth, and stillbirth). The association of metrics with outcomes was assessed, and receiver operating characteristic (ROC) curve analysis was employed to evaluate clinical utility.

Results

Differences in fatty acid profiles were observed between GDM patients and controls. Stearic acid (C18:0) levels differed between the normal pregnancy outcome (NPO) and APO groups, potentially correlating with fetal sex. Logistic regression models indicated that moderate and high levels of C18:0 were negatively associated with APO relative to the NPO group. ROC analysis demonstrated that C18:0 had a certain predictive ability for APO, and predictive efficiency was enhanced when combined with general clinical data.

Conclusion

The level of C18:0 was associated with the occurrence of APO in pregnant women with GDM and exhibited a certain predictive value. When C18:0 was combined with general clinical data, the predictive power for APO was improved.

Aging delays the suppression of lipolysis and fatty acid oxidation in the postprandial period

Plasma glycerol and free fatty acid concentrations decrease following oral glucose consumption, but changes in the rate of lipolysis during an oral glucose tolerance test (OGTT) have not been documented in conjunction with changes in fatty acid (FA) oxidation or reesterification rates in healthy individuals. After a 12-h overnight fast, 15 young (21-35 yr; 7 men and 8 women) and 14 older (60-80 yr; 7 men and 7 women) participants had the forearm vein catheterized for primed continuous infusion of [1,1,2,3,3-2H]glycerol. A contralateral hand vein was catheterized for arterialized blood sampling. Indirect calorimetry was performed simultaneously to determine total FA and carbohydrate (CHO) oxidation rates (Rox). Total FA reesterification rates (Rs) were estimated from tracer-measured lipolytic and FA oxidation rates. After a 90-min equilibration period, participants underwent a 120-min, 75-g OGTT. Glycerol rate of appearance (Ra), an index of lipolysis, decreased significantly from baseline 5 min postchallenge in young participants and 30 min in older participants. At 60 min, FA Rox decreased in both groups, but was significantly higher in older participants. Between 5 and 90 min, CHO Rox was significantly lower in older participants. In addition, FA Rs was significantly lower in older participants at 60 and 90 min. The area under the curve (AUC) for FA Rox was greater than that for FA Rs in older, but not in young participants. Our results indicate that, in aging, the postprandial suppression of lipolysis and FA oxidation are delayed such that FA oxidation is favored over CHO oxidation and FA reesterification.NEW & NOTEWORTHY To our knowledge, our investigation is the first to demonstrate changes in lipolysis during an oral glucose tolerance test (OGTT) in healthy young and older individuals. Plasma glycerol and free fatty acid concentrations changed after glycerol rate of appearance (Ra), indicating that plasma concentrations are incomplete surrogates of the lipolytic rate. Moreover, simultaneous determinations of substrate oxidation rates are interpreted to indicate that metabolic inflexibility in aging is characterized by delayed changes in postprandial substrate utilization related to the lipolytic rate.

Investigation of serum Metrnl levels in pregnant women with gestational diabetes mellitus: a prospective non-interventional cohort study

OBJECTIVE

The objective of this study was to investigate serum Metrnl levels in pregnant women with gestational diabetes mellitus and compare them with pregnant women without gestational diabetes mellitus.

METHODS

The gestational diabetes mellitus group consisted of 87 pregnant women diagnosed with gestational diabetes mellitus, and the control group consisted of 93 healthy pregnant women without gestational diabetes mellitus. Serum Metrnl levels were determined by the enzyme-linked immunosorbent assay method.

RESULTS

The two groups were similar in terms of demographic features. The median serum Metrnl level was found to be 1.16 ng/mL in the gestational diabetes mellitus group, while it was determined as 2.2 ng/mL in the control group (p=0.001). The two groups were divided into two subgroups based on participants' body mass index, normal weight and overweight. The lowest median Metrnl level was detected in the normal weight gestational diabetes mellitus group, followed by the overweight gestational diabetes mellitus group, normal weight control group, and overweight control group (1.1, 1.2, 2, and 2.4 ng/mL, respectively). Receiver operating curve analysis was performed to determine the value of the serum Metrnl level in terms of predicting gestational diabetes mellitus. The area under the curve analysis of serum Metrnl for gestational diabetes mellitus estimation was 0.768 (p=0.000, 95%CI 0.698-0.839). The optimal cutoff value for serum Metrnl level was determined as 1.53 ng/mL with 69% sensitivity and 70% specificity.

CONCLUSION

Serum Metrnl levels in pregnant women with gestational diabetes mellitus were found to be significantly lower than in pregnant women without gestational diabetes mellitus. The mechanisms underlying the decrease in serum Metrnl levels in gestational diabetes mellitus remain unclear for now, and future studies will reveal the role of Metrnl in the pathophysiology of gestational diabetes mellitus.

Adipose tissue insulin resistance in young Japanese women is associated with metabolic abnormalities and dehydroepiandrosterone-sulfate

Objective

The proportion of young Japanese women who are underweight is exceptionally high. We previously showed that the prevalence of impaired glucose tolerance (IGT) was high in underweight young Japanese women, and that IGT was characterized by high free fatty acid levels and adipose tissue insulin resistance (ATIR). As the next step, this study aimed to explore factors associated with elevated ATIR in this population.

Participants

Ninety-eight young, healthy, underweight women participated in this study.

Design

To investigate the relationship between ATIR and metabolic parameters, participants were divided into three groups (Low, Medium, and High) according to ATIR level. Body composition examination, oral glucose tolerance testing, and blood biochemical analysis were performed; Adipo-IR and the Matsuda index were used as indices of ATIR and systemic insulin sensitivity, respectively.

Results

Participants in the High ATIR group had the highest prevalence of IGT (25%), and significantly higher body fat percentage, whole-body insulin resistance, and levels of insulin-like growth factor-1 and dehydroepiandrosterone sulfate (DHEA-S) than the other two groups. They were also significantly younger and had higher systolic blood pressure than the Low ATIR group. Multiple regression analysis showed that DHEA-S, which is known to enhance lipolysis in adipose tissue, was an independent correlate of ATIR.

Conclusions

Underweight Japanese women with high ATIR had impaired metabolism, a higher prevalence of IGT, higher systemic insulin resistance, and higher systolic blood pressure. DHEA-S was a determinant of high ATIR levels.

Mitochondrial dysfunction in the pathogenesis of endothelial dysfunction

Cardiovascular diseases (CVDs) are a matter of concern worldwide, and mitochondrial dysfunction is one of the major contributing factors. Vascular endothelial dysfunction has a major role in the development of atherosclerosis because of the abnormal chemokine secretion, inflammatory mediators, enhancement of LDL oxidation, cytokine elevation, and smooth muscle cell proliferation. Endothelial cells transfer oxygen from the pulmonary circulatory system to the tissue surrounding the blood vessels, and a majority of oxygen is transferred to the myocardium by endothelial cells, which utilise a small amount of oxygen to generate ATP. Free radicals of oxide are produced by mitochondria, which are responsible for cellular oxygen uptake. Increased mitochondrial ROS generation and reduction in agonist-stimulated eNOS activation and nitric oxide bioavailability were directly linked to the observed change in mitochondrial dynamics, resulting in various CVDs and endothelial dysfunction. Presently, the manuscript mainly focuses on endothelial dysfunction, providing a deep understanding of the various features of mitochondrial mechanisms that are used to modulate endothelial dysfunction. We talk about recent findings and approaches that may make it possible to detect mitochondrial dysfunction as a potential biomarker for risk assessment and diagnosis of endothelial dysfunction. In the end, we cover several targets that may reduce mitochondrial dysfunction through both direct and indirect processes and assess the impact of several different classes of drugs in the context of endothelial dysfunction.

Effect of physical activity on free fatty acids, insulin resistance, and blood pressure in obese older women

PURPOSE

Obesity is characterized by a progressive increase in body fat accompanied by insulin resistance (IR) and elevated blood pressure (BP), and presents significant health risks, particularly in aged individuals. This study aimed to evaluate the effects of physical activity (PA) on free fatty acid (FFA) levels, IR, and BP in obese older women.

METHODS

Twenty-three participants were randomly assigned to either the control group (CON, n = 11) or the physical activity group (PA, n = 12). The PA group was provided with a target of achieving >7,000 steps/day for 5 days each week. Body composition, FFA levels, IR, and BP were measured at pre- and post- of the 12-week intervention.

RESULTS

The analysis revealed a statistically significant interaction between FFA (p < 0.01), IR (p < 0.01), and SBP (p < 0.001). FFA (p < 0.5), IR (p < 0.5), and systolic blood pressure (SBP) (p < 0.01) were significantly decreased in the PA group compared to those in the CON group, which showed no significant changes in FFA, IR, and SBP.

CONCLUSION

PA significantly decreased FFA, IR, and SBP in older women with obesity. Therefore, PA is an effective intervention for the prevention and management of obesity and cardiovascular diseases in obese older women.

Machine Learning Prediction of Prediabetes in a Young Male Chinese Cohort with 5.8-Year Follow-Up

The identification of risk factors for future prediabetes in young men remains largely unexamined. This study enrolled 6247 young ethnic Chinese men with normal fasting plasma glucose at the baseline (FPGbase), and used machine learning (Mach-L) methods to predict prediabetes after 5.8 years. The study seeks to achieve the following: 1. Evaluate whether Mach-L outperformed traditional multiple linear regression (MLR). 2. Identify the most important risk factors. The baseline data included demographic, biochemistry, and lifestyle information. Two models were built, where Model 1 included all variables and Model 2 excluded FPGbase, since it had the most profound effect on prediction. Random forest, stochastic gradient boosting, eXtreme gradient boosting, and elastic net were used, and the model performance was compared using different error metrics. All the Mach-L errors were smaller than those for MLR, thus Mach-L provided the most accurate results. In descending order of importance, the key factors for Model 1 were FPGbase, body fat (BF), creatinine (Cr), thyroid stimulating hormone (TSH), WBC, and age, while those for Model 2 were BF, white blood cell, age, TSH, TG, and LDL-C. We concluded that FPGbase was the most important factor to predict future prediabetes. However, after removing FPGbase, WBC, TSH, BF, HDL-C, and age were the key factors after 5.8 years.

Association of quality and quantity of macronutrients intake with obesity, new anthropometric indices, lipid accumulation, and blood lipid risk index in Tehranian women

Background

This study examines the association between micronutrient intake, anthropometric indices, lipid accumulation, and blood lipid risk index among Tehranian women.

Methods

A cross-sectional study was conducted on 556 Tehranian women. Dietary intake was measured using a Food Frequency Questionnaire. Biochemical assessment and anthropometric indices were measured, and demographic information and physical activity were collected.

Results

Participants with the highest intake of carbohydrates were more prone to obesity. Conversely, those in the top tertile for protein intake had a lower likelihood of obesity and higher levels of lipid accumulation product (LAP). The highest fat consumers had a 63% decreased chance of having a high Castelli's Risk Index 1 (CRI-1). A higher glycemic index (GI) and glycemic load (GL) were linked to an increased probability of a high atherogenic coefficient (AC). Women in the top tertile of GL were significantly more likely to be obese and had lower odds for high LAP. Participants in the top tertile of aromatic amino acids/branched chain amino acids (AAA/BCAA) had significantly lower chances of high CRI-1 and a high atherogenic index of plasma (AIP). Those in the highest tertile of monounsaturated fatty acids/polyunsaturated fatty acids (MUFA/PUFA) had lower odds of obesity and high AIP.

Conclusions

The amount of carbohydrate (g) and protein intake (%), dietary GL, and the ratio of MUFA to PUFA were associated with obesity. The amount of fat intake (g) and AAA/BCAA indices were associated with CRI-1. LAP decreased with an increase in GL. AC increased with an increase in GI and GL. AAA/BCAA and MUFA/PUFA were associated with AIP.

Gestational Diabetes Mellitus: What Can Medical Nutrition Therapy Do?

Gestational diabetes mellitus (GDM) is one of the common complications during pregnancy. Numerous studies have shown that GDM is associated with a series of adverse effects on both mothers and offspring. Due to the particularity of pregnancy, medical nutrition treatment is considered to be the first choice for the treatment of GDM. This contribution reviews the research progress of medical nutrition treatment in GDM, summarizes the international recommendations on the intake of various nutrients and the influence of nutrients on the prevalence of GDM, and the improvement effect of nutritional intervention on it, in order to provide references for research in related fields of GDM and the targeted development of enteral nutrition.

GLUT4 localisation with the plasma membrane is unaffected by an increase in plasma free fatty acid availability

BACKGROUND

Insulin-stimulated glucose uptake into skeletal muscle occurs via translocation of GLUT4 from intracellular storage vesicles to the plasma membrane. Elevated free fatty acid (FFA) availability via a lipid infusion reduces glucose disposal, but this occurs in the absence of impaired proximal insulin signalling. Whether GLUT4 localisation to the plasma membrane is subsequently affected by elevated FFA availability is not known.

METHODS

Trained (n = 11) and sedentary (n = 10) individuals, matched for age, sex and body mass index, received either a 6 h lipid or glycerol infusion in the setting of a concurrent hyperinsulinaemic-euglycaemic clamp. Sequential muscle biopsies (0, 2 and 6 h) were analysed for GLUT4 membrane localisation and microvesicle size and distribution using immunofluorescence microscopy.

RESULTS

At baseline, trained individuals had more small GLUT4 spots at the plasma membrane, whereas sedentary individuals had larger GLUT4 spots. GLUT4 localisation with the plasma membrane increased at 2 h (P = 0.04) of the hyperinsulinemic-euglycemic clamp, and remained elevated until 6 h, with no differences between groups or infusion type. The number of GLUT4 spots was unchanged at 2 h of infusion. However, from 2 to 6 h there was a decrease in the number of small GLUT4 spots at the plasma membrane (P = 0.047), with no differences between groups or infusion type.

CONCLUSION

GLUT4 localisation with the plasma membrane increases during a hyperinsulinemic-euglycemic clamp, but this is not altered by elevated FFA availability. GLUT4 appears to disperse from small GLUT4 clusters located at the plasma membrane to support glucose uptake during a hyperinsulinaemic-euglycaemic clamp.

In vivo techniques for assessment of insulin sensitivity and glucose metabolism

Metabolic tests are vital to determine in vivo insulin sensitivity and glucose metabolism in preclinical models, usually rodents. Such tests include glucose tolerance tests, insulin tolerance tests, and glucose clamps. Although these tests are not standardized, there are general guidelines for their completion and analysis that are constantly being refined. In this review, we describe metabolic tests in rodents as well as factors to consider when designing and performing these tests.

Contractile and Genetic Characterization of Cardiac Constructs Engineered from Human Induced Pluripotent Stem Cells: Modeling of Tuberous Sclerosis Complex and the Effects of Rapamycin

The implementation of three-dimensional tissue engineering concurrently with stem cell technology holds great promise for in vitro research in pharmacology and toxicology and modeling cardiac diseases, particularly for rare genetic and pediatric diseases for which animal models, immortal cell lines, and biopsy samples are unavailable. It also allows for a rapid assessment of phenotype-genotype relationships and tissue response to pharmacological manipulation. Mutations in the TSC1 and TSC2 genes lead to dysfunctional mTOR signaling and cause tuberous sclerosis complex (TSC), a genetic disorder that affects multiple organ systems, principally the brain, heart, skin, and kidneys. Here we differentiated healthy (CC3) and tuberous sclerosis (TSP8-15) human induced pluripotent stem cells (hiPSCs) into cardiomyocytes to create engineered cardiac tissue constructs (ECTCs). We investigated and compared their mechano-elastic properties and gene expression and assessed the effects of rapamycin, a potent inhibitor of the mechanistic target of rapamycin (mTOR). The TSP8-15 ECTCs had increased chronotropy compared to healthy ECTCs. Rapamycin induced positive inotropic and chronotropic effects (i.e., increased contractility and beating frequency, respectively) in the CC3 ECTCs but did not cause significant changes in the TSP8-15 ECTCs. A differential gene expression analysis revealed 926 up- and 439 down-regulated genes in the TSP8-15 ECTCs compared to their healthy counterparts. The application of rapamycin initiated the differential expression of 101 and 31 genes in the CC3 and TSP8-15 ECTCs, respectively. A gene ontology analysis showed that in the CC3 ECTCs, the positive inotropic and chronotropic effects of rapamycin correlated with positively regulated biological processes, which were primarily related to the metabolism of lipids and fatty and amino acids, and with negatively regulated processes, which were predominantly associated with cell proliferation and muscle and tissue development. In conclusion, this study describes for the first time an in vitro TSC cardiac tissue model, illustrates the response of normal and TSC ECTCs to rapamycin, and provides new insights into the mechanisms of TSC.

Advances in free fatty acid profiles in gestational diabetes mellitus

The morbidity of gestational diabetes mellitus (GDM) is increasing and is associated with adverse perinatal outcomes and long-term maternal and infant health. The exact mechanism underlying changes in plasma free fatty acid (FFA) profiles in patients with GDM is unknown. However, it is believed that changes in diet and lipid metabolism may play a role. Fatty acids contain many specific FFAs, and the type of FFA has different impacts on physiological processes; hence, determining changes in FFAs in individual plasma is essential. Alterations in FFA concentration or profile may facilitate insulin resistance. Additionally, some FFAs show potential to predict GDM in early pregnancy and are strongly associated with the growth and development of the fetus and occurrence of macrosomia. Here, we aimed to review changes in FFAs in women with GDM and discuss the relationship of FFAs with GDM incidence and adverse outcomes.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Delayed dinnertime impairs glucose tolerance in healthy young adults

To explore the relationship between mealtime delays of up to 3 h and subsequent glucose fluctuations, healthy young adults were allocated to three delayed dinnertimes in randomized order. Participants consumed test meals for lunch and dinner. After assessing the glucose responses using intermittently scanned continuous glucose monitoring devices (isCGM), the peak glucose elevation, and incremental area under the curve (iAUC) of postprandial glucose during certain intervals increased significantly when the time between lunch and dinner was delayed by 1 h or more. Our results support the importance of improving irregular mealtime habits, such as late eating.

Effects of Japanese Diet on Post-Exercise Glycogen Recovery in Mice Skeletal Muscle and Liver

The diet consumed by most Japanese people, which contains high amounts of carbohydrate and low levels of fat compared with the Western-style diet (WD), has been considered an effective diet for promoting glycogen recovery after exercise. However, there is no direct evidence to support this general belief, because no studies have examined the effect of whole, actually cooked Japanese-style diet (JD) on post-exercise glycogen replenishment. In this study, we comparatively examined the effects of a cooked typical JD and WD on glycogen accumulation in mouse skeletal muscle and liver after acute exercise. One-week menus (total 21 meals) of the JD and WD were reproduced based on national nutrition surveys in Japan and the U.S. All the meals were cooked, mixed and then fed to mice after acute 60-min running exercise. After the 4-h recovery period, mice given the JD had significantly higher muscle and liver glycogen concentrations than those fed the isoenergetic WD. Furthermore, even after the 24-h recovery period, the JD-fed mice also had significantly higher muscle glycogen concentration than the isoenergetic WD-fed group. Compared with the mice fed a WD, the JD-fed mice showed significantly higher plasma insulin level during the 4-h but not the 24-h recovery period. These results suggest that both short- and long-term feeding of the JD promote post-exercise muscle glycogen recovery compared to the WD, possibly through an insulin-dependent mechanism and non-insulin-dependent mechanism, respectively.

Triglycerides, Obesity and Education Status Are Associated with the Risk of Developing Type 2 Diabetes in Young Adults, Cohort Study

BACKGROUND

It is important to determine the influence of traditional risk factors on the development of type 2 diabetes mellitus (T2DM) in young adults. Goal of the research: To study the incidence of T2DM and factors that increase the risk of its occurrence during the observation of a cohort of young adults.

MATERIALS AND METHODS

1341 people aged 25-44 were included in the study from 2013 to 2017, of whom 622 were men (46.4%). The examination included anamnesis, anthropometric data, and a blood test. Cases of developed T2DM were identified by comparing the Diabetes Mellitus Register, medical records of patients, and the database of examined individuals from 2019 to 2023. T2DM Results: In the examined population, 11 participants (0.82%) developed T2DM. The prevalence of T2DM was 0.96% in men and 0.69% in women. Patients with T2DM had a higher waist circumference, BMI, SBP, TG, and lower HDL than patients without T2DM, and were also less likely to have a higher education. The risk of developing T2DM increases 6.5 times at a BMI of ≥30 kg/m2, and 5.2 times at a TG level of ≥1.7 mmol/L, regardless of other risk factors. In the absence of a higher education, the risk of developing T2DM is increased by 5.6 times.

CONCLUSION

In young people, high triglyceride levels, obesity, and a low level of education are associated with the risk of developing type 2 diabetes, regardless of other factors.

Effect of fenofibrate and selective PPARα modulator (SPPARMα), pemafibrate on KATP channel activity and insulin secretion

OBJECTIVE

Insulin secretion is regulated by ATP-sensitive potassium (KATP) channels in pancreatic beta-cells. Peroxisome proliferator-activated receptors (PPAR) α ligands are clinically used to treat dyslipidemia. A PPARα ligand, fenofibrate, and PPARγ ligands troglitazone and 15-deoxy-∆12,14-prostaglandin J2 are known to close KATP channels and induce insulin secretion. The recently developed PPARα ligand, pemafibrate, became a new entry for treating dyslipidemia. Because pemafibrate is reported to improve glucose intolerance in mice treated with a high fat diet and a novel selective PPARα modulator, it may affect KATP channels or insulin secretion.

RESULTS

The effect of fenofibrate (100 µM) and pemafibrate (100 µM) on insulin secretion from MIN6 cells was measured by using batch incubation for 10 and 60 min in low (2 mM) and high (10 mM) glucose conditions. The application of fenofibrate for 10 min significantly increased insulin secretion in low glucose conditions. Pemafibrate failed to increase insulin secretion in all of the conditions experimented in this study. The KATP channel activity was measured by using whole-cell patch clamp technique. Although fenofibrate (100 µM) reduced the KATP channel current, the same concentration of pemafibrate had no effect. Both fenofibrate and pemafibrate had no effect on insulin mRNA expression.

The Associations of Individual and Subclasses of Nonesterified Fatty Acids With Disability, and Mobility Limitation in Older Adults: The Cardiovascular Health Study

BACKGROUND

We sought to determine the associations between individual nonesterified fatty acids (NEFAs) and disability and mobility limitation.

METHODS

We studied 1 734 participants in the Cardiovascular Health Study (CHS), an ongoing population-based cohort study of community-living older American adults. We measured 35 individual NEFA species in fasting serum samples obtained at the 1996-1997 clinic visit. Using yearly assessments of activities of daily living and self-reported mobility, we identified participants with incident disability or mobility limitation during 15 years of follow-up. Cox proportional hazards regression models were used to determine the associations between per SD increment in the individual NEFAs and incident disability and mobility limitations with adjustment for potential confounding factors.

RESULTS

Higher concentrations of total and a broad range of individual NEFA species were associated with risk of disability and mobility limitation (disability: HR per SD of total NEFA [SD = 174.70] = 1.11, 95% CI = 1.04-1.18, p = .001; mobility limitation: HR per SD of total NEFA = 1.09, 95% CI = 1.02-1.16, p = .01). Among individual saturated NEFAs (SFAs), myristic (14:0) and palmitic (16:0) acids were significantly associated with higher risk of both disability and mobility limitations, but longer-chain FAs were not. Most individual monounsaturated (MUFA), n-6 polyunsaturated fatty acids (PUFAs), and trans FAs were positively significantly associated with higher risks of both disability and mobility limitation. In contrast, most n-3 PUFA species were not associated with disability or mobility limitation.

CONCLUSIONS

Higher risks of disability and mobility limitation were observed for proinflammatory intermediate-chain SFAs, MUFAs, n-6 PUFAs, and trans FAs. Our findings indicated no significant association for anti-inflammatory n-3 PUFAs.

Dietary fat quantity and quality in early pregnancy and risk of gestational diabetes mellitus in Chinese women: a prospective cohort study

We aimed to examine the association between the quantity and quality of dietary fat in early pregnancy and gestational diabetes mellitus (GDM) risk. In total, 1477 singleton pregnant women were included from Sichuan Provincial Hospital for Women and Children, Southwest China. Dietary information was collected by a 3-d 24-h dietary recall. GDM was diagnosed based on the results of a 75-g, 2-h oral glucose tolerance test at 24-28 gestational weeks. Log-binomial models were used to estimate relative risks (RR) and 95% CI. The results showed that total fat intake was positively associated with GDM risk (Q4 v. Q1: RR = 1·40; 95 % CI 1·11, 1·76; Ptrend = 0·001). This association was also observed for the intakes of animal fat and vegetable fat. After stratified by total fat intake (< 30 %E v. ≥ 30 %E), the higher animal fat intake was associated with higher GDM risk in the high-fat group, but the moderate animal fat intake was associated with reduced risk of GDM (T2 v. T1: RR = 0·65; 95 % CI 0·45, 0·96) in the normal-fat group. Vegetable fat intake was positively associated with GDM risk in the high-fat group but not in the normal-fat group. No association between fatty acids intakes and GDM risk was found. In conclusion, total fat, animal and vegetable fat intakes were positively associated with GDM risk, respectively. Whereas when total fat intake was not excessive, higher intakes of animal and vegetable fat were likely irrelevant with increased GDM risk, even the moderate animal fat intake could be linked to lower GDM risk.

Tcf7l2 in hepatocytes regulates de novo lipogenesis in diet-induced non-alcoholic fatty liver disease in mice

AIMS/HYPOTHESIS

Non-alcoholic fatty liver disease (NAFLD) associated with type 2 diabetes may more easily progress towards severe forms of non-alcoholic steatohepatitis (NASH) and cirrhosis. Although the Wnt effector transcription factor 7-like 2 (TCF7L2) is closely associated with type 2 diabetes risk, the role of TCF7L2 in NAFLD development remains unclear. Here, we investigated how changes in TCF7L2 expression in the liver affects hepatic lipid metabolism based on the major risk factors of NAFLD development.

METHODS

Tcf7l2 was selectively ablated in the liver of C57BL/6N mice by inducing the albumin (Alb) promoter to recombine Tcf7l2 alleles floxed at exon 5 (liver-specific Tcf7l2-knockout [KO] mice: Alb-Cre;Tcf7l2f/f). Alb-Cre;Tcf7l2f/f and their wild-type (Tcf7l2f/f) littermates were fed a high-fat diet (HFD) or a high-carbohydrate diet (HCD) for 22 weeks to reproduce NAFLD/NASH. Mice were refed a standard chow diet or an HCD to stimulate de novo lipogenesis (DNL) or fed an HFD to provide exogenous fatty acids. We analysed glucose and insulin sensitivity, metabolic respiration, mRNA expression profiles, hepatic triglyceride (TG), hepatic DNL, selected hepatic metabolites, selected plasma metabolites and liver histology.

RESULTS

Alb-Cre;Tcf7l2f/f essentially exhibited increased lipogenic genes, but there were no changes in hepatic lipid content in mice fed a normal chow diet. However, following 22 weeks of diet-induced NAFLD/NASH conditions, liver steatosis was exacerbated owing to preferential metabolism of carbohydrate over fat. Indeed, hepatic Tcf7l2 deficiency enhanced liver lipid content in a manner that was dependent on the duration and amount of exposure to carbohydrates, owing to cell-autonomous increases in hepatic DNL. Mechanistically, TCF7L2 regulated the transcriptional activity of Mlxipl (also known as ChREBP) by modulating O-GlcNAcylation and protein content of carbohydrate response element binding protein (ChREBP), and targeted Srebf1 (also called SREBP1) via miRNA (miR)-33-5p in hepatocytes. Eventually, restoring TCF7L2 expression at the physiological level in the liver of Alb-Cre;Tcf7l2f/f mice alleviated liver steatosis without altering body composition under both acute and chronic HCD conditions.

CONCLUSIONS/INTERPRETATION

In mice, loss of hepatic Tcf7l2 contributes to liver steatosis by inducing preferential metabolism of carbohydrates via DNL activation. Therefore, TCF7L2 could be a promising regulator of the NAFLD associated with high-carbohydrate diets and diabetes since TCF7L2 deficiency may lead to development of NAFLD by promoting utilisation of excess glucose pools through activating DNL.

DATA AVAILABILITY

RNA-sequencing data have been deposited into the NCBI GEO under the accession number GSE162449 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE162449 ).

Cerebrospinal Fluid Metabolomics: Pilot Study of Using Metabolomics to Assess Diet and Metabolic Interventions in Alzheimer's Disease and Mild Cognitive Impairment

Brain glucose hypometabolism is an early sign of Alzheimer's disease (AD), and interventions which offset this deficit, such as ketogenic diets, show promise as AD therapeutics. Conversely, high-fat feeding may exacerbate AD risk. We analyzed the metabolomic profile of cerebrospinal fluid (CSF) in a pilot study of older adults who underwent saline and triglyceride (TG) infusions. Older adults (12 cognitively normal (CN), age 65.3 ± 8.1, and 9 with cognitive impairment (CI), age 70.9 ± 8.6) underwent a 5 h TG or saline infusion on different days using a random crossover design; CSF was collected at the end of infusion. Aqueous metabolites were measured using a targeted mass spectroscopy (MS) platform focusing on 215 metabolites from over 35 different metabolic pathways. Data were analyzed using MetaboAnalyst 4.0 and SAS. Of the 215 targeted metabolites, 99 were detectable in CSF. Only one metabolite significantly differed by treatment: the ketone body 3-hydroxybutyrate (HBA). Post hoc analyses showed that HBA levels were associated with age and markers of metabolic syndrome and demonstrated different correlation patterns for the two treatments. When analyzed by cognitive diagnosis group, TG-induced increases in HBA were over 3 times higher for those with cognitive impairment (change score CN +9.8 uM ± 8.3, CI +32.4 ± 7.4, p = 0.0191). Interestingly, individuals with cognitive impairment had higher HBA levels after TG infusion than those with normal cognition. These results suggest that interventions that increase plasma ketones may lead to higher brain ketones in groups at risk for AD and should be confirmed in larger intervention studies.

Insulin Resistance Is Associated with an Unfavorable Serum Lipoprotein Lipid Profile in Women with Newly Diagnosed Gestational Diabetes

Background: Gestational diabetes (GDM) is associated with various degrees of insulin resistance—a feature related to increased risk of adverse perinatal outcomes. We aimed to determine the previously poorly investigated associations between maternal insulin resistance and serum fasting metabolome at the time of GDM diagnosis. Methods: Serum lipoprotein and amino acid profile was analyzed in 300 subjects with newly diagnosed GDM using a validated nuclear magnetic resonance spectroscopy protocol. Associations between insulin resistance (homeostasis model assessment of insulin resistance, HOMA2-IR) and serum metabolites were examined with linear regression. Results: We found insulin resistance to be associated with a distinct lipid pattern: increased concentration of VLDL triglycerides and phospholipids and total triglycerides. VLDL size was positively related and LDL and HDL sizes were inversely related to insulin resistance. Of fatty acids, increased total fatty acids, relative increase in saturated and monounsaturated fatty acids, and relative decrease in polyunsaturated and omega fatty acids were related to maternal insulin resistance. Conclusions: In newly diagnosed GDM, the association between maternal insulin resistance and serum lipoprotein profile was largely as described in type 2 diabetes. Lifestyle interventions aiming to decrease insulin resistance from early pregnancy could benefit pregnancy outcomes via more advantageous lipid metabolism.

Enhanced protein acetylation initiates fatty acid-mediated inhibition of cardiac glucose transport

Fatty acids (FAs) rapidly and efficiently reduce cardiac glucose uptake in the Randle cycle or glucose-FA cycle. This fine-tuned physiological regulation is critical to allow optimal substrate allocation during fasted and fed states. However, the mechanisms involved in the direct FA-mediated control of glucose transport have not been totally elucidated yet. We previously reported that leucine and ketone bodies, other cardiac substrates, impair glucose uptake by increasing global protein acetylation from acetyl-CoA. As FAs generate acetyl-CoA as well, we postulated that protein acetylation is enhanced by FAs and participates in their inhibitory action on cardiac glucose uptake. Here, we demonstrated that both palmitate and oleate promoted a rapid increase in protein acetylation in primary cultured adult rat cardiomyocytes, which correlated with an inhibition of insulin-stimulated glucose uptake. This glucose absorption deficit was caused by an impairment in the translocation of vesicles containing the glucose transporter GLUT4 to the plasma membrane, although insulin signaling remained unaffected. Interestingly, pharmacological inhibition of lysine acetyltransferases (KATs) prevented this increase in protein acetylation and glucose uptake inhibition induced by FAs. Similarly, FA-mediated inhibition of insulin-stimulated glucose uptake could be prevented by KAT inhibitors in perfused hearts. To summarize, enhanced protein acetylation can be considered as an early event in the FA-induced inhibition of glucose transport in the heart, explaining part of the Randle cycle.NEW & NOTEWORTHY Our results show that cardiac metabolic overload by oleate or palmitate leads to increased protein acetylation inhibiting GLUT4 translocation to the plasma membrane and glucose uptake. This observation suggests an additional regulation mechanism in the physiological glucose-FA cycle originally discovered by Randle.

The role of exercise and hypoxia on glucose transport and regulation

Muscle glucose transport activity increases with an acute bout of exercise, a process that is accomplished by the translocation of glucose transporters to the plasma membrane. This process remains intact in the skeletal muscle of individuals with insulin resistance and type 2 diabetes mellitus (T2DM). Exercise training is, therefore, an important cornerstone in the management of individuals with T2DM. However, the acute systemic glucose responses to carbohydrate ingestion are often augmented during the early recovery period from exercise, despite increased glucose uptake into skeletal muscle. Accordingly, the first aim of this review is to summarize the knowledge associated with insulin action and glucose uptake in skeletal muscle and apply these to explain the disparate responses between systemic and localized glucose responses post-exercise. Herein, the importance of muscle glycogen depletion and the key glucoregulatory hormones will be discussed. Glucose uptake can also be stimulated independently by hypoxia; therefore, hypoxic training presents as an emerging method for enhancing the effects of exercise on glucose regulation. Thus, the second aim of this review is to discuss the potential for systemic hypoxia to enhance the effects of exercise on glucose regulation.

Insights into the development of insulin resistance: Unraveling the interaction of physical inactivity, lipid metabolism and mitochondrial biology

While impairments in peripheral tissue insulin signalling have a well-characterized role in the development of insulin resistance and type 2 diabetes (T2D), the specific mechanisms that contribute to these impairments remain debatable. Nonetheless, a prominent hypothesis implicates the presence of a high-lipid environment, resulting in both reactive lipid accumulation and increased mitochondrial reactive oxygen species (ROS) production in the induction of peripheral tissue insulin resistance. While the etiology of insulin resistance in a high lipid environment is rapid and well documented, physical inactivity promotes insulin resistance in the absence of redox stress/lipid-mediated mechanisms, suggesting alternative mechanisms-of-action. One possible mechanism is a reduction in protein synthesis and the resultant decrease in key metabolic proteins, including canonical insulin signaling and mitochondrial proteins. While reductions in mitochondrial content associated with physical inactivity are not required for the induction of insulin resistance, this could predispose individuals to the detrimental effects of a high-lipid environment. Conversely, exercise-training induced mitochondrial biogenesis has been implicated in the protective effects of exercise. Given mitochondrial biology may represent a point of convergence linking impaired insulin sensitivity in both scenarios of chronic overfeeding and physical inactivity, this review aims to describe the interaction between mitochondrial biology, physical (in)activity and lipid metabolism within the context of insulin signalling.

Opposing Actions of TLR2 and TLR4 in Adipocyte Differentiation and Mature-Onset Obesity

Understanding the signaling cascades that govern adipocyte metabolism and differentiation is necessary for the development of therapies for obesity. Toll-like receptors (TLRs) are key mediators in adipogenesis, but their specific role is not completely understood. In this study, siRNA knockdown of Tlr2 in 3T3-L1 cells allowed them to differentiate more efficiently into adipocytes, whereas the opposite was observed for the knockdown of Tlr4. At the same time, we show that TLR2 knock-out mice spontaneously developed mature-onset obesity and insulin resistance. Besides a higher incidence of hyperplasia and hypertrophy in white adipose tissue (WAT), we found a significantly increased number of adipocyte precursor cells in TLR2^-/- mice compared to TLR4^-/- mice. Interestingly, genetic inactivation of Tlr4 in TLR2^-/- mice reverted their increased adiposity, insulin resistance, and restored normal levels of adipocyte precursor cells. These findings provide evidence that TLR2 and TLR4 play opposing roles in WAT homeostasis and point to the existence of cross-regulation among TLR2 and TLR4 during adipocyte differentiation both in vitro and in vivo.

Dehydrocostus lactone ameliorates lipid accumulation, insulin resistance, and endoplasmic reticulum stress in palmitate-treated hepatocytes

Fatty liver disease is caused by lipid accumulation in the liver, insulin resistance (IR), reactive oxygen species (ROS), and endoplasmic reticulum (ER) stress. Dehydrocostus lactone (DHE) has anticancer, anti-inflammatory, and anti-ulcer effects. However, its effects on hepatic steatosis and IR remain unclear. In this study, we investigated whether DHE has antisteatotic effect on fatty liver in vitro. Hepatocytes HepG2 and SNU-449 cells were exposed to 0.25 mM palmitate (PA), and then antisteatotic effect was evaluated by treatment with 10 μM DHE. DHE treatment reduced lipid accumulation and lipogenesis factor protein levels, compared with PA-treated hepatocytes. DHE treatment also decreased gluconeogenesis marker expression and recovered IR in PA-treated hepatocytes, and promoted glucose uptake in PA-treated HepG2 cells. Additionally, the levels of ROS and ER stress factors in PA-treated HepG2 cells were reduced by DHE treatment, compared with PA-treated HepG2 cells. Overall, DHE decreased lipid accumulation and lipogenesis factors as well as recovered IR, gluconeogenesis, and glucose uptake by reducing ER stress and ROS levels in PA-treated hepatocytes. Thus, DHE is a potential antisteatotic agent.

A Clinical Update on Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) traditionally refers to abnormal glucose tolerance with onset or first recognition during pregnancy. GDM has long been associated with obstetric and neonatal complications primarily relating to higher infant birthweight and is increasingly recognized as a risk factor for future maternal and offspring cardiometabolic disease. The prevalence of GDM continues to rise internationally due to epidemiological factors including the increase in background rates of obesity in women of reproductive age and rising maternal age and the implementation of the revised International Association of the Diabetes and Pregnancy Study Groups' criteria and diagnostic procedures for GDM. The current lack of international consensus for the diagnosis of GDM reflects its complex historical evolution and pragmatic antenatal resource considerations given GDM is now 1 of the most common complications of pregnancy. Regardless, the contemporary clinical approach to GDM should be informed not only by its short-term complications but also by its longer term prognosis. Recent data demonstrate the effect of early in utero exposure to maternal hyperglycemia, with evidence for fetal overgrowth present prior to the traditional diagnosis of GDM from 24 weeks' gestation, as well as the durable adverse impact of maternal hyperglycemia on child and adolescent metabolism. The major contribution of GDM to the global epidemic of intergenerational cardiometabolic disease highlights the importance of identifying GDM as an early risk factor for type 2 diabetes and cardiovascular disease, broadening the prevailing clinical approach to address longer term maternal and offspring complications following a diagnosis of GDM.

In vitro skeletal muscle models for type 2 diabetes

Type 2 diabetes mellitus, a metabolic disorder characterized by abnormally elevated blood sugar, poses a growing social, economic, and medical burden worldwide. The skeletal muscle is the largest metabolic organ responsible for glucose homeostasis in the body, and its inability to properly uptake sugar often precedes type 2 diabetes. Although exercise is known to have preventative and therapeutic effects on type 2 diabetes, the underlying mechanism of these beneficial effects is largely unknown. Animal studies have been conducted to better understand the pathophysiology of type 2 diabetes and the positive effects of exercise on type 2 diabetes. However, the complexity of in vivo systems and the inability of animal models to fully capture human type 2 diabetes genetics and pathophysiology are two major limitations in these animal studies. Fortunately, in vitro models capable of recapitulating human genetics and physiology provide promising avenues to overcome these obstacles. This review summarizes current in vitro type 2 diabetes models with focuses on the skeletal muscle, interorgan crosstalk, and exercise. We discuss diabetes, its pathophysiology, common in vitro type 2 diabetes skeletal muscle models, interorgan crosstalk type 2 diabetes models, exercise benefits on type 2 diabetes, and in vitro type 2 diabetes models with exercise.

Palmitate Potentiates Lipopolysaccharide-Induced IL-6 Production via Coordinated Acetylation of H3K9/H3K18, p300, and RNA Polymerase II

IL-6 is elevated in obese individuals and participates in the metabolic dysfunction associated with that condition. However, the mechanisms that promote IL-6 expression in obesity are incompletely understood. Because elevated levels of palmitate and LPS have been reported in obesity, we investigated whether these agents interact to potentiate IL-6 production. In this study, we report that LPS induces higher levels of IL-6 in human monocytes in the presence of palmitate. Notably, the priming effect of palmitate is associated with enhanced p300 binding and transcription factor recruitment to Il6 promoter regions. Gene silencing of p300 blocks this action of palmitate. RNA polymerase II recruitment was also enhanced at the Il6 promoter in palmitate/LPS-exposed cells. Acetylation levels of H3K9 and H3K18 were increased in monocytes treated with palmitate. Moreover, LPS stimulation of palmitate-treated cells led to increased levels of the transcriptionally permissive acetylation marks H3K9/H3K18 in the Il6 promoter compared with LPS alone. The effect of palmitate on LPS-induced IL-6 production was suppressed by the inhibition of histone acetyltransferases. Conversely, histone deacetylase inhibitors trichostatin A or sodium butyrate can substitute for palmitate in IL-6 production. Esterification of palmitate with CoA was involved, whereas β-oxidation and ceramide biosynthesis were not required, for the induction of IL-6 and H3K9/H3K18 acetylation. Monocytes of obese individuals showed significantly higher H3K9/H3K18 acetylation and Il6 expression. Overall, our findings support a model in which increased levels of palmitate in obesity create a setting for LPS to potentiate IL-6 production via chromatin remodeling, enabling palmitate to contribute to metabolic inflammation.

The Exocyst Is Required for CD36 Fatty Acid Translocase Trafficking and Free Fatty Acid Uptake in Skeletal Muscle Cells

In obesity, chronic membrane-localization of CD36 free fatty acid (FFA) translocase, but not other FFA transporters, enhances FFA uptake and intracellular lipid accumulation. This ectopic lipid accumulation promotes insulin resistance by inhibiting insulin-induced GLUT4 glucose transporter trafficking and glucose uptake. GLUT4 and CD36 cell surface delivery is triggered by insulin- and contraction-induced signaling, which share conserved downstream effectors. While we have gathered detailed knowledge on GLUT4 trafficking, the mechanisms regulating CD36 membrane delivery and subsequent FFA uptake in skeletal muscle are not fully understood. The exocyst trafficking complex facilitates the docking of membrane-bound vesicles, a process underlying the controlled surface delivery of fuel transporters. The exocyst regulates insulin-induced glucose uptake via GLUT4 membrane trafficking in adipocytes and skeletal muscle cells and plays a role in lipid uptake in adipocytes. Based on the high degree of conservation of the GLUT4 and CD36 trafficking mechanisms in adipose and skeletal muscle tissue, we hypothesized that the exocyst also contributes to lipid uptake in skeletal muscle and acts through the targeted plasma membrane delivery of CD36 in response to insulin and contraction. Here, we show that the exocyst complex is necessary for insulin- and contraction-induced CD36 membrane trafficking and FFA uptake in muscle cells.

Fasting and Postload Nonesterified Fatty Acids and Glucose Dysregulation in Older Adults

To evaluate the association of nonesterified fatty acids (NEFA) with dysglycemia in older adults, NEFA levels were measured among participants in the Cardiovascular Health Study (United States; enrolled 1989-1993). Associations with insulin sensitivity and pancreatic β-cell function, and with incident type 2 diabetes mellitus (DM), were examined. The sample comprised 2,144 participants (aged 77.9 (standard deviation, 4.5) years). Participant data from the Cardiovascular Health Study visit in 1996-1997 was used with prospective follow-up through 2010. Fasting and postload NEFA showed significant associations with lower insulin sensitivity and pancreatic β-cell function, individually and on concurrent adjustment. Over median follow-up of 9.7 years, 236 cases of DM occurred. Postload NEFA were associated with risk of DM (per standard deviation, hazard ratio = 1.18, 95% confidence interval: 1.08, 1.29), but fasting NEFA were not (hazard ratio = 1.12, 95% confidence interval: 0.97, 1.29). The association for postload NEFA persisted after adjustment for putative intermediates, and after adjustment for fasting NEFA. Sex and body mass index modified these associations, which were stronger for fasting NEFA with DM in men but were accentuated for postload NEFA in women and among leaner individuals. Fasting and postload NEFA were related to lower insulin sensitivity and pancreatic β-cell function, but only postload NEFA were associated with increased DM. Additional study into NEFA metabolism could uncover novel potential targets for diabetes prevention in elders.

Obesity as a premature aging phenotype - implications for sarcopenic obesity

Obesity and aging have both seen dramatic increases in prevalence throughout society. This review seeks to highlight common pathologies that present with obesity, along with the underlying risk factors, that have remarkable similarity to what is observed in the aged. These include skeletal muscle dysfunction (loss of quantity and quality), significant increases in adiposity, systemic alterations to autonomic dysfunction, reduction in nitric oxide bioavailability, increases in oxidant stress and inflammation, dysregulation of glucose homeostasis, and mitochondrial dysfunction. This review is organized by the aforementioned indices and succinctly highlights literature that demonstrates similarities between the aged and obese phenotypes in both human and animal models. As aging is an inevitability and obesity prevalence is unlikely to significantly decrease in the near future, these two phenotypes will ultimately combine as a multidimensional syndrome (a pathology termed sarcopenic obesity). Whether the pre-mature aging indices accompanying obesity are additive or synergistic upon entering aging is not yet well defined, but the goal of this review is to illustrate the potential consequences of a double aged phenotype in sarcopenic obesity. Clinically, the modifiable risk factors could be targeted specifically in obesity to allow for increased health span in the aged and sarcopenic obese populations.

Circulating metabolite profile in young adulthood identifies long-term diabetes susceptibility: the Coronary Artery Risk Development in Young Adults (CARDIA) study

AIMS/HYPOTHESIS

The aim of this work was to define metabolic correlates and pathways of diabetes pathogenesis in young adults during a subclinical latent phase of diabetes development.

METHODS

We studied 2083 young adults of Black and White ethnicity in the prospective observational cohort Coronary Artery Risk Development in Young Adults (CARDIA) study (mean ± SD age 32.1 ± 3.6 years; 43.9% women; 42.7% Black; mean ± SD BMI 25.6 ± 4.9 kg/m2) and 1797 Framingham Heart Study (FHS) participants (mean ± SD age 54.7 ± 9.7 years; 52.1% women; mean ± SD BMI 27.4 ± 4.8 kg/m2), examining the association of comprehensive metabolite profiles with endophenotypes of diabetes susceptibility (adipose and muscle tissue phenotypes and systemic inflammation). Statistical learning techniques and Cox regression were used to identify metabolite signatures of incident diabetes over a median of nearly two decades of follow-up across both cohorts.

RESULTS

We identified known and novel metabolites associated with endophenotypes that delineate the complex pathophysiological architecture of diabetes, spanning mechanisms of muscle insulin resistance, inflammatory lipid signalling and beta cell metabolism (e.g. bioactive lipids, amino acids and microbe- and diet-derived metabolites). Integrating endophenotypes of diabetes susceptibility with the metabolome generated two multi-parametric metabolite scores, one of which (a proinflammatory adiposity score) was associated with incident diabetes across the life course in participants from both the CARDIA study (young adults; HR in a fully adjusted model 2.10 [95% CI 1.72, 2.55], p<0.0001) and FHS (middle-aged and older adults; HR 1.33 [95% CI 1.14, 1.56], p=0.0004). A metabolite score based on the outcome of diabetes was strongly related to diabetes in CARDIA study participants (fully adjusted HR 3.41 [95% CI 2.85, 4.07], p<0.0001) but not in the older FHS population (HR 1.15 [95% CI 0.99, 1.33], p=0.07).

CONCLUSIONS/INTERPRETATION

Selected metabolic abnormalities in young adulthood identify individuals with heightened diabetes risk independent of race, sex and traditional diabetes risk factors. These signatures replicate across the life course.

Serine Palmitoyltransferase Gene Silencing Prevents Ceramide Accumulation and Insulin Resistance in Muscles in Mice Fed a High-Fat Diet

Skeletal muscles account for ~80% of insulin-stimulated glucose uptake and play a key role in lipid metabolism. Consumption of a high-fat diet (HFD) contributes to metabolic changes in muscles, including the development of insulin resistance. The studies carried out to date indicate that the accumulation of biologically active lipids, such as long-chain acyl-CoA, diacylglycerols and ceramides, play an important role in the development of insulin resistance in skeletal muscles. Unfortunately, it has not yet been clarified which of these lipid groups plays the dominant role in inducing these disorders. In order to explore this topic further, we locally silenced the gene encoding serine palmitoyltransferase (SPT) in the gastrocnemius muscle of animals with HFD-induced insulin resistance. This enzyme is primarily responsible for the first step of de novo ceramide biosynthesis. The obtained results confirm that the HFD induces the development of whole-body insulin resistance, which results in inhibition of the insulin pathway. This is associated with an increased level of biologically active lipids in the muscles. Our results also demonstrate that silencing the SPT gene with the shRNA plasmid reduces the accumulation of ceramides in gastrocnemius muscle, which, in turn, boosts the activity of the insulin signaling pathway. Furthermore, inhibition of ceramide synthesis does not significantly affect the content of other lipids, which suggests the leading role of ceramide in the lipid-related induction of skeletal muscle insulin resistance.

Glycation Alters the Fatty Acid Binding Capacity of Human Serum Albumin

Glycation significantly alters the physicochemical and biofunctional properties of proteins in foods and in vivo. In the present study, human serum albumin (HSA) as the major transporter of fatty acids was modified with glyoxal under physiological conditions. Reversibly albumin-bound glyoxal was removed, and advanced glycation end products were quantitated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The total modification of protein-bound lysine and arginine residues reached up to 4.2 and 9.6%, respectively. The impact of these modifications on the transport capacity of long-chain fatty acids was characterized by spin-labeled fatty acid probes via electron paramagnetic resonance spectroscopy. With increasing degree of glycation, the equivalence of the seven binding sites of native HSA with a dissociation constant of 0.74 ± 0.09 μM was set off with only the three high-affinity sites 2, 4, and 5 remaining (0.46 ± 0.07 μM). The other four sites were shifted to low affinities with significantly higher dissociation constants (1.32 ± 0.35 μM). Tryptic peptide mapping enabled us to relate these findings to molecular changes at specific binding sites. Modification hotspots identified were lysine 351, 286, 159 and arginine 144, 485, 117. Further investigation of plasma protein samples of uremic patients vs healthy controls gave first insights into the in vivo situation.

A mouse model of gestational diabetes shows dysregulated lipid metabolism post-weaning, after return to euglycaemia

BACKGROUND

Gestational diabetes is associated with increased risk of type 2 diabetes mellitus and cardiovascular disease for the mother in the decade after delivery. However, the molecular mechanisms that drive these effects are unknown. Recent studies in humans have shown that lipid metabolism is dysregulated before diagnosis of and during gestational diabetes and we have shown previously that lipid metabolism is also altered in obese female mice before, during and after pregnancy. These observations led us to the hypothesis that this persistent dysregulation reflects an altered control of lipid distribution throughout the organism.

METHODS

We tested this in post-weaning (PW) dams using our established mouse model of obese GDM (high fat, high sugar, obesogenic diet) and an updated purpose-built computational tool for plotting the distribution of lipid variables throughout the maternal system (Lipid Traffic Analysis v2.3).

RESULTS

This network analysis showed that unlike hyperglycaemia, lipid distribution and traffic do not return to normal after pregnancy in obese mouse dams. A greater range of phosphatidylcholines was found throughout the lean compared to obese post-weaning dams. A range of triglycerides that were found in the hearts of lean post-weaning dams were only found in the livers of obese post-weaning dams and the abundance of odd-chain FA-containing lipids differed locally in the two groups. We have therefore shown that the control of lipid distribution changed for several metabolic pathways, with evidence for changes to the regulation of phospholipid biosynthesis and FA distribution, in a number of tissues.

CONCLUSIONS

We conclude that the control of lipid metabolism is altered following an obese pregnancy. These results support the hypothesis that obese dams that developed GDM maintain dysregulated lipid metabolism after pregnancy even when glycaemia returned to normal, and that these alterations could contribute to the increased risk of later type 2 diabetes and cardiovascular disease.

Ghrelin is a signal to facilitate the utilization of fatty acids and save glucose by the liver, skeletal muscle, and adipose tissues in chicks

Ghrelin, classically known as a central appetite-stimulating hormone, has recently been recognized to play an important role in peripheral tissue energy metabolism. In chicken, contrary to mammal, ghrelin acts as an anorexia signal, increased by fasting and further elevated after refed. In the present study, the effect of ghrelin on glucose/lipid utilization by peripheral tissues was investigated. Injection of exogenous acyl ghrelin reduced plasma triglyceride and glucose levels of chickens at both fasting and fed status. In the in vitro cultured chicken primary hepatocytes, adipocytes, and myoblasts, ghrelin suppressed glucose uptake, stimulated fatty acids uptake and oxidation, and decreased TG content. In hepatocyte, ghrelin increased the activities of LPL and HL, and upregulated the expression levels of gene ACC, CPT1, and PPARα. Ghrelin treatment markedly increased the protein level of p-ACC, PPARγ, PGC1α, and CPT1 in hepatocytes, adipocytes and myoblasts. Inhibition of AMPK activity by Compound C had no influence on glucose uptake by hepatocyte, adipocyte, and myoblast, but further amplified the stimulated fatty acid uptake of adipocyte by ghrelin. The present result demonstrates that ghrelin facilitates the uptake and oxidation of fatty acid and cut down the utilization of glucose by the liver, muscle, and adipose tissues. The result suggests that ghrelin functions as a signal of fatty acid oxidation. The study provides a vital framework for understanding the intrinsic role of ghrelin as a crucial factor in the concerted regulation of metabolic substrate of hepatocytes, adipocytes, and myoblasts.