The importance of free fatty acids in the development of Type 2 diabetes

Novel Model Predicts Type 2 Diabetes Mellitus Patients Complicated With Metabolic Syndrome Using Retrospective Dataset From First Affiliated Hospital of Shenzhen University, China

Objective: Metabolic syndrome (MS) is the most important risk factor for Type 2 diabetes mellitus (T2DM) and cardiovascular disease. This study used a retrospective dataset from the First Affiliated Hospital of Shenzhen University and aimed to develop and validate a novel model nomogram based on clinical parameters to predict MS in patients with T2DM. Methods: A total of 2854 patients with T2DM between January 2014 and May 2022 were selected and divided into a training dataset (n = 2114) and a validation dataset (n = 740). This study used multivariate logistic regression analysis to develop a nomogram for predicting MS in patients with T2DM that included candidates selected in the LASSO regression model. The data were set standardized before LASSO regression. The area under the receiver operating characteristic curve (AUC-ROC) was used to assess discrimination in the prediction model. The calibration curve is used to evaluate the calibration of the calibration nomogram, and the clinical decision curve is used to determine the clinical utility of the calibration diagram. The validation dataset is used to evaluate the performance of predictive models. Results: A total of 2854 patients were eligible for this study. There were 1941 (68.01%) patients with MS. The training dataset included 20 potential risk factors of the patient's demographic, clinical, and laboratory indexes in the LASSO regression analysis. Gender, hypertension, BMI, WC, HbA1c, TG, LDL, and HDL were multivariate models. We obtained a model for estimating MS in patients with T2DM. The AUC-ROC of the training dataset in our model is 0.886, and the 95% CI is 0.871-0.901. Similar to the results obtained from the training dataset, the AUC-ROC of the validation dataset in our model is 0.859, and the 95% CI is 0.831-0.887, thus proving the robustness of the model. The prediction model is as follows: logit (MS) = -9.18209 + 0.14406 ∗ BMI (kg/m2) + 0.09218 ∗ WC (cm) + 1.05761 ∗ TG (mmol/L)-3.30013 ∗ HDL (mmol/L). The calibration plots of the predicted probabilities show excellent agreement with the observed MS rates. Decision curve analysis demonstrated that the new nomogram provided significant net benefits in clinical applications. Conclusion: The prediction model of this study covers four clinically easily obtained parameters: BMI, WC, TG, and HDL, and shows a high accuracy rate in the validation dataset. Our predictive model may provide an effective method for large-scale epidemiological studies of T2DM patients with MS and offer a practical tool for the early detection of MS in clinical work.

Circulating non-esterified fatty acids, risk of dementia and cognitive decline: The cardiovascular health study and multi-ethnic study of atherosclerosis

Circulating non-esterified fatty acids (NEFAs) have toxic effects on a variety of organs central to cardiometabolic disease and can cross the blood-brain barrier. Whether NEFAs associate with cognitive decline or dementia remains unknown. Circulating total NEFA levels were measured in 3242 participants without dementia among older adults of the Cardiovascular Health Study (CHS) and related to adjudicated dementia over 6 years (n = 456 cases) and annually assessed cognitive decline. For confirmation, we related circulating NEFAs to cognition assessed 10 years later among 4361 participants in the Multi-Ethnic Study of Atherosclerosis (MESA). In CHS participants, each SD higher NEFA levels were associated with a hazard ratio (HR) for all-cause dementia of 1.11 (95 % CI: 1.01; 1.22). Baseline NEFA levels were also associated with more rapid decline in cognition over 6 years of follow-up. In MESA, circulating NEFA measurements were associated with lower cognitive scores measured 10 years later.'

Caveolin-1 deficiency alleviates palmitate-induced intracellular lipid accumulation and inflammation in pancreatic β cells

Lipotoxicity-induced pancreatic β cell damage is a strong predictor of type 2 diabetes mellitus (T2DM). Our previous work showed that Caveolin-1 (Cav-1) depletion decreased β-cell apoptosis and improved β-cell viability. Further microarray analysis indicated significant changes in the expression of genes related to fatty acid metabolism and inflammation. The objective of this study was to explore the role of Cav-1 in intracellular lipid accumulation and inflammation in β cells under lipotoxic conditions. Here, we established a β-cell-specific Cav-1 knockout (β-Cav-1 KO) mouse model and a CAV-1 depleted β cell line (NIT-1). We found that Cav-1 silencing significantly reduced palmitate (PA)-induced intracellular triglyceride (TG) accumulation and decreased proinflammatory factor expression in both the mouse and cell models. Further mechanistic investigation revealed that amelioration of lipid metabolism was achieved through the downregulation of lipogenic markers (SREBP-1c, FAS and ACC) and upregulation of a fatty acid oxidation marker (CPT-1). Meanwhile, decrease of inflammatory cytokines (IL-6, TNF-α, and IL-1β) secretion was found with the involvement of the IKKβ/NF-κB signaling pathways. Our findings suggest that Cav-1 is of considerable importance in regulating lipotoxicity-induced β-cell intracellular lipid accumulation and inflammation.

Skipping breakfast does not accelerate the hyperglycemia-induced endothelial dysfunction but reduces blood flow of the brachial artery in young men

PURPOSE

Postprandial hyperglycemia is assumed to have a negative impact on flow-mediated dilation (FMD), an index of endothelial function, and blood flow of the peripheral conduit arteries. This study aimed to determine whether the enhancement of postprandial hyperglycemia by skipping breakfast accelerates endothelial dysfunction and reduces the blood flow in the brachial artery in young men.

METHODS

Using a randomized cross-over design, ten healthy men completed two trials: with and without breakfast (Eating and Fasting trials, respectively). Venous blood sampling and brachial FMD tests were conducted before, 30, 60, 90, and 120 min after a 75-g oral glucose tolerance test (OGTT).

RESULTS

Skipping breakfast boosted post-OGTT glucose levels than having breakfast (P = 0.01). The magnitude of the decrease in FMD via OGTT did not vary between trials (main effect of trial P = 0.55). Although brachial blood flow tended to decrease after OGTT in both trials (interaction and main effect of time P = 0.61 and P = 0.054, respectively), the decrease in blood flow following OGTT was greater in the Fasting trial than in the Eating trial (main effect of trial, mean difference =  - 15.8 mL/min [95%CI =  - 25.6 to - 6.0 mL/min], P < 0.01).

CONCLUSION

Skipping breakfast did not enhance the magnitude of the decrease in FMD following glucose loading, but did accelerate hyperglycemia-induced reduction in brachial blood flow. Current findings suggest that even missing one breakfast has negative impacts on the blood flow regulation of the peripheral conduit arteries in young men who habitually eat breakfast.

Association of cluster determinant 36, scavenger receptor class B type 1, and major facilitator superfamily domain containing the 2a genetic polymorphism with serum lipid profile in aging population with type 2 diabetes mellitus

Background

Lipid metabolism disorder commonly happens in subjects with Type 2 diabetes mellitus (T2DM) which may be linked to genetic variants of lipid metabolism-related genes. However, few studies have explored the relationship between lipid metabolism-related gene polymorphism and serum lipid profile in aging subjects with T2DM. The present study was designed to explore the impact of genetic polymorphism of cluster determinant 36 (CD36) (rs1049673, rs1054516, rs2151916), scavenger receptor class B type 1 (SCARB1) (rs5888), and major facilitator superfamily domain containing the 2a (MFSD2A) (rs12083239, rs4233508, rs12072037) on the relationship between circulating lipids in aging subjects with T2DM.

Methods

205 T2DM patients and 205 age and gender matched control subjects were recruited. Information on demographic characteristics was collected by using a self-administered questionnaire. Fasting venous blood samples were taken for lipid-related gene genotyping and serum lipid profile measurement. The Chi-square test was used to compare percentage differences and to calculate P-value for Hardy-Weinberg equilibrium. Logistic regression and multiple linear regression were used to explore the risk or correlation between variables, and general linear model (GLM) was used to compare the means of serum lipids between the groups.

Results

In T2DM group, CD36 rs1054516 and MFSD2A rs12072037 were correlated with serum TC level. In control group, CD36 rs1049673 was correlated with serum HDL-C level. Meanwhile, T2DM subjects with MFSD2A rs12083239 (CG), MFSD2A rs4233508 (TT), and MFSD2A rs12072037 (AA) had higher TG level than control subjects. T2DM subjects with CD36 rs1049673 (CG, GG), CD36 rs1054516 (CT), CD36 rs2151916 (TT, CT), SCARB1 rs5888 (GG), MFSD2A rs12083239 (GG, CG), MFSD2A rs4233508 (TT), and MFSD2A rs12072037 (CA, AA) had lower HDL-C level than control subjects. T2DM subjects with MFSD2A rs12072037 (AA) had lower LDL-C level than control subjects. In dominant model, major genotype (GG) of SCARB1 gene was associated with the risk of T2DM (OR = 0.636, P = 0.032).

Conclusion

The genetic polymorphism of CD36 (rs1049673, rs1054516, rs2151916), SCARB1 (rs5888), and MFSD2A (rs12083239, rs4233508, rs12072037) were associated with serum lipids in T2DM subjects. The SCARB1 rs5888 major genotype (GG) was a protective factor for T2DM. Large scale cohort study is required to determine the relationship between lipid metabolism-related gene polymorphism, serum lipid profile and T2DM in aging subjects.

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.

Lipidomics Analysis of Free Fatty Acids in Human Plasma of Healthy and Diabetic Subjects by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS)

Targeted analytical methods for the determination of free fatty acids (FFAs) in human plasma are of high interest because they may help in identifying biomarkers for diseases and in monitoring the progress of a disease. The determination of FFAs is of particular importance in the case of metabolic disorders because FFAs have been associated with diabetes. We present a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method, which allows the simultaneous determination of 74 FFAs in human plasma. The method is fast (10-min run) and straightforward, avoiding any derivatization step and tedious sample preparation. A total of 35 standard saturated and unsaturated FFAs, as well as 39 oxygenated (either hydroxy or oxo) saturated FFAs, were simultaneously detected and quantified in plasma samples from 29 subjects with type 2 diabetes mellitus (T2D), 14 with type 1 diabetes mellitus (T1D), and 28 healthy subjects. Alterations in the levels of medium-chain FFAs (C6:0 to C10:0) were observed between the control group and T2D and T1D patients.

Homocysteine inhibits pro-insulin receptor cleavage and causes insulin resistance via protein cysteine-homocysteinylation

Elevation in homocysteine (Hcy) level is associated with insulin resistance; however, the causality between them and the underlying mechanism remain elusive. Here, we show that Hcy induces insulin resistance and causes diabetic phenotypes by protein cysteine-homocysteinylation (C-Hcy) of the pro-insulin receptor (pro-IR). Mechanistically, Hcy reacts and modifies cysteine-825 of pro-IR in the endoplasmic reticulum (ER) and abrogates the formation of the original disulfide bond. C-Hcy impairs the interaction between pro-IR and the Furin protease in the Golgi apparatus, thereby hindering the cleavage of pro-IR. In mice, an increase in Hcy level decreases the mature IR level in various tissues, thereby inducing insulin resistance and the type 2 diabetes phenotype. Furthermore, inhibition of C-Hcy in vivo and in vitro by overexpressing protein disulfide isomerase rescues the Hcy-induced phenotypes. In conclusion, C-Hcy in the ER can serve as a potential pharmacological target for developing drugs to prevent insulin resistance and increase insulin sensitivity.

Changes in the gut microbiome influence the hypoglycemic effect of metformin through the altered metabolism of branched-chain and nonessential amino acids

AIMS

Although metformin has been reported to affect the gut microbiome, the mechanism has not been fully determined. We explained the potential underlying mechanisms of metformin through a multiomics approach.

METHODS

An open-label and single-arm clinical trial involving 20 healthy Korean was conducted. Serum glucose and insulin concentrations were measured, and stool samples were collected to analyze the microbiome. Untargeted metabolomic profiling of plasma, urine, and stool samples was performed by GC-TOF-MS. Network analysis was applied to infer the mechanism of the hypoglycemic effect of metformin.

RESULTS

The relative abundances of Escherichia, Romboutsia, Intestinibacter, and Clostridium were changed by metformin treatment. Additionally, the relative abundances of metabolites, including carbohydrates, amino acids, and fatty acids, were changed. These changes were correlated with energy metabolism, gluconeogenesis, and branched-chain amino acid metabolism, which are major metabolic pathways related to the hypoglycemic effect.

CONCLUSIONS

We observed that specific changes in metabolites may affect hypoglycemic effects through both pathways related to AMPK activation and microbial changes. Energy metabolism was mainly related to hypoglycemic effects. In particular, branched-chain amino acid metabolism and gluconeogenesis were related to microbial metabolites. Our results will help uncover the potential underlying mechanisms of metformin through AMPK and the microbiome.

A Preliminary Study Showing the Impact of Genetic and Dietary Factors on GC-MS-Based Plasma Metabolome of Patients with and without PROX1-Genetic Predisposition to T2DM up to 5 Years Prior to Prediabetes Appearance

Risk factors for type 2 diabetes mellitus (T2DM) consist of a combination of an unhealthy, imbalanced diet and genetic factors that may interact with each other. Single nucleotide polymorphism (SNP) in the prospero homeobox 1 (PROX1) gene is a strong genetic susceptibility factor for this metabolic disorder and impaired β-cell function. As the role of this gene in T2DM development remains unclear, novel approaches are needed to advance the understanding of the mechanisms of T2DM development. Therefore, in this study, for the first time, postprandial changes in plasma metabolites were analysed by GC–MS in nondiabetic men with different PROX1 genotypes up to 5 years prior to prediabetes appearance. Eighteen contestants (12 with high risk (HR) and 6 with low risk (LR) genotype) participated in high-carbohydrate (HC) and normo-carbohydrate (NC) meal-challenge tests. Our study concluded that both meal-challenge tests provoked changes in 15 plasma metabolites (amino acids, carbohydrates, fatty acids and others) in HR, but not LR genotype carriers. Postprandial changes in the levels of some of the detected metabolites may be a source of potential specific early disturbances possibly associated with the future development of T2DM. Thus, accurate determination of these metabolites can be important for the early diagnosis of this metabolic disease.

Potential biomarker in serum for predicting susceptibility to type 2 diabetes mellitus: Free fatty acid 22:6

AIMS/INTRODUCTION

Type 2 diabetes mellitus is closely linked to increased levels of free fatty acids (FFAs) in obese individuals, although which FFA is most associated with type 2 diabetes mellitus is unclear. This study aimed to identify the specific FFAs that best predict the occurrence of type 2 diabetes mellitus in obese individuals, and assess their potential application value.

MATERIALS AND METHODS

Participants were divided into three groups: a normal weight group (n = 20), an obese group (n = 10) and a type 2 diabetes mellitus group (n = 10). FFAs in serum samples were determined by ultra-high-pressure liquid chromatography-mass spectrometry, and orthogonal partial least squares discriminant analysis models were used to study the FFA profile among the three groups.

RESULTS

Compared with the normal weight group, 14 FFAs (C8:0/10:0/14:0/16:1/18:1/20:2/ 20:3 /20:4/ 20:5/ 22:6/7:0/9:0/11:0 and C13:0) were significantly increased in the obese group, and nine FFAs (C14:0, C18:1, C20:1, C 18:2, C20:2, C20:3, C18:3, C20:5 and C22:6) were significantly increased in the type 2 diabetes mellitus group. Subsequently, the Venn diagram results showed that six FFAs (C14:0, C18:1, C20:2, C20:3, C20:5 and C22:6) were significantly increased in both the obese and type 2 diabetes mellitus groups. Among these six, C22:6 was finally identified as an independent risk factor for type 2 diabetes mellitus, and had a great potential to predict the susceptibility to type 2 diabetes mellitus (area under the curve 0.803).

CONCLUSIONS

C22:6 can be an independent risk factor for type 2 diabetes mellitus, and it has a great potential to predict the susceptibility to type 2 diabetes mellitus.

Impact of curcumin on fatty acid metabolism

Free fatty acids (FFAs) and fatty acid synthesis (FAS) activity have significantly contributed to disease states such as insulin resistance, obesity, type 2 diabetes, myocardial infarction, blood pressure, and several types of cancer. Currently, several treatment options are available for patients with these conditions. Due to safety concerns, adverse effects, limited efficacy, and low tolerability associated with many medications, the identification of novel agents with less toxicity and a more favorable outcome is warranted. Curcumin is a phenolic compound derived from the turmeric plant with various biological activities, including anticarcinogenic, antioxidant, antiinflammatory, and hypolipidemic properties. PubMed, Scopus, and Web of Science were searched up to February 2020 for studies that demonstrated the efficacy and mechanisms of curcumin action on FFAs, FAS, and β-oxidation activity, as well as the desaturation system. Most of the evidence is in-vivo and in-vitro studies that demonstrate that curcumin possesses regulatory properties on FFAs levels through its effects on FAS and β-oxidation activity as well as desaturation system, which could improve insulin resistance, obesity, and other FFAs-related disorders. The present study provides a review of the existing in-vitro, in-vivo, and clinical evidence on the effect of curcumin on FFAs and FAS activity, β-oxidation, and desaturation system.

Nonesterified Fatty Acids and Kidney Function Decline in Older Adults: Findings From the Cardiovascular Health Study

RATIONALE & OBJECTIVE

Circulating nonesterified fatty acids (NEFAs) make up a small portion of circulating lipids but are a metabolically important energy source. Excessive circulating NEFAs may contribute to lipotoxicity in many tissues, including the kidneys. We investigated the relationship between total circulating NEFA concentration and kidney outcomes in older, community-dwelling adults.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

4,698 participants≥65 years of age in the Cardiovascular Health Study who underwent total fasting serum NEFA concentration measurements in 1992-1993.

EXPOSURE

Fasting serum NEFA concentration at one time point.

OUTCOME

Three primary outcomes: estimated glomerular filtration rate (eGFR) decline of≥30%, the composite of eGFR decline≥30% or kidney failure with replacement therapy, and change in eGFR. These outcomes were assessed over 4- and 13-year periods.

ANALYTICAL APPROACH

Logistic regression for the dichotomous outcomes and mixed effects models for the continuous outcome, with sequential adjustment for baseline covariates. Inverse probability of attrition weighting was implemented to account for informative attrition during the follow-up periods.

RESULTS

Serum NEFA concentrations were not independently associated with kidney outcomes. In unadjusted and partially adjusted analyses, the highest quartile of serum NEFA concentration (compared with lowest) was associated with a higher risk of≥30% eGFR decline at 4 years and faster rate of decline of eGFR. No associations were evident after adjustment for comorbidities, lipid levels, insulin sensitivity, medications, and vital signs: the odds ratio for the eGFR decline outcome was 1.33 (95% CI, 0.83-2.13), and the difference in eGFR slope in the highest versus lowest quartile of serum NEFA concentration was-0.15 (95% CI, -0.36 to 0.06) mL/min/1.73m² per year.

LIMITATIONS

Single NEFA measurements, no measurements of post-glucose load NEFA concentrations or individual NEFA species, no measurement of baseline urine albumin.

CONCLUSIONS

A single fasting serum NEFA concentration was not independently associated with long-term adverse kidney outcomes in a cohort of older community-living adults.

Associations Between Serum Free Fatty Acid Levels and Incident Diabetes in a 3-Year Cohort Study

PURPOSE

High circulating free fatty acid (FFA) is associated with the development of diabetes. This study was designed to evaluate longitudinal associations between FFA levels, changes in FFA levels, and mean FFA levels and incident diabetes.

PARTICIPANTS AND METHODS

This 3-year cohort study was conducted in Ningyang between 2011 and 2014. Serum FFA, fasting blood glucose (FPG), 2-hour postprandial blood glucose (2hPG), and glycosylated hemoglobin (HbA1c) levels were measured at baseline and at the end of follow-up. A multivariate stepwise logistic regression model was used to evaluate associations between serum FFA levels in various groups and the risk of incident diabetes.

RESULTS

Of the 2905 individuals without baseline diabetes, 290 developed diabetes by the 3-year follow-up. With increasing baseline FFA levels, the mean FPG, 2hPG, and HbA1c levels, and the prevalence of diabetes at the end of follow-up increased. The trend of FPG and HbA1c increase was not statistically significant. Higher baseline FFA levels were not significantly associated with greater risk of incident diabetes. However, longitudinal changes in serum FFA levels showed that individuals with serum FFA levels from normal to high (OR = 2.956, 95% CI: 2.089-4.184) or from high to high (OR = 3.343, 95% CI: 2.300-4.857) had greater risk of incident diabetes compared with those with normal to normal FFA levels. Similarly, individuals with ΔFFA ≥ 0 mmol/L (OR = 1.762, 95% CI: 1.373-2.262) or high mean serum FFA levels (OR = 2.120, 95% CI: 1.620-2.775) were at higher risk of incident diabetes than those with ΔFFA < 0 mmol/L or normal mean serum FFA levels.

CONCLUSION

The longitudinal status of serum FFA levels, including chronic increases and sustained high levels, was more closely associated with high risk of incident diabetes than was high baseline FFA levels.

Link between serum uric acid and pancreatic beta-cell function in drug naïve subjects with type 2 diabetes treated with sitagliptin

Aim: The objective of this study is to investigate the changes of UA with sitagliptin in relation to its glycemic/non-glycemic efficacies.Methods: Drug naïve subjects with T2DM (n = 62) were administered 25-50 mg/day sitagliptin monotherapy for 3 months. The subjects were divided into two subgroups according to the changes in (Δ) UA (above the median [group A, n = 31]: ΔUA = 23.3%, p < 0.00001, and below the median [group B, n = 31]: ΔUA = -0.9%, n.s.). Changes in glycemic/non-glycemic parameters were compared between these two groups, which acted as a control for each other.Results: In the overall subjects, UA significantly increased (10.8%, p < 0.00001). Significant correlations between ΔUA and ΔBMI (R = 0.252), ΔHOMA-B (R = 0.309) or ΔCPR-index (R = 0.258), and significant negative correlations between ΔUA and ΔHbA1c (R = -0.290) or ΔFFA (R = -0.271) were seen. Between group A and group B, some parameters displayed distinct regulatory patterns. HbA1c significantly decreased in both groups (group A: from 9.97% to 7.65%, group B: from 10.41% to 8.85%) with significant inter-group differences (higher reductions in group A, p < 0.05). C-peptide (+10.6%) and BMI (+1.7%) significantly increased, and FFA (-20.5%) decreased in group A. HOMA-R or 20/(C-peptide x FBG) had no changes in either group, while HOMA-B (group A: +85.1%, group B: +38.8%) or CPR-index (group A: +37.7%, group B: +20.5%) increased in both groups with significant inter-group differences (both p < 0.01). TG (-18.8%) significantly decreased, and T-C (-3.5%) and non-HDL-C (-4%) had a tendency to decrease in group B.Conclusions: These results suggest that UA and beta-cell functions/glycemic efficacy are closely linked during sitagliptin therapy. Those with elevated UA had better beta-cell enhancing and glyemic efficacies. Body weights increased and FFA decreased in these populations. By contrast, those without changes in UA had favorable profiles in atherogenic lipids.

A high fat diet with a high C18:0/C16:0 ratio induced worse metabolic and transcriptomic profiles in C57BL/6 mice

BACKGROUND

Differential effects of individual saturated fatty acids (SFAs), particularly stearic acid (C18:0), relative to the shorter-chain SFAs have drawn interest for more accurate nutritional guidelines. However, specific biologic and pathologic functions that can be assigned to particular SFAs are very limited. The present study was designed to compare changes in metabolic and transcriptomic profiles in mice caused by a high C18:0 diet and high palmitic acid (C16:0) diet.

METHODS

Male C57BL/6 mice were assigned to a normal fat diet (NFD), a high fat diet with high C18:0/C16:0 ratio (HSF) or an isocaloric high fat diet with a low C18:0/C16:0 ratio (LSF) for 10 weeks. An oral glucose tolerance test, 72-h energy expenditure measurement and CT scan of body fat were done before sacrifice. Fasting glucose and lipids were determined by an autobiochemical analyzer. Blood insulin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels were measured by enzyme-linked immunosorbent assay methods. Free fatty acids (FFAs) profiles in blood and liver were determined by using gas chromatography-mass spectrometry. Microarray analysis was applied to investigate changes in transcriptomic profiles in the liver. Pathway analysis and gene ontology analysis were applied to describe the roles of differentially expressed mRNAs.

RESULTS

Compared with the NFD group, body weight, body fat ratio, fasting blood glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), triglyceride, IL-6, serum and liver FFAs including total FFAs, C16:0 and C18:0 were increased in both high fat diet groups and were much higher in the HSF group than those in the LSF group. Both HSF and LSF mice exhibited distinguishable long non-coding RNA (lncRNA), microRNA and mRNA expression profiles when compared with those of NFD mice. Additionally, more differentially expressed lncRNAs and mRNAs were observed in the HSF group than in the LSF group. Some biological functions and pathways, other than energy metabolism regulation, were identified as differentially expressed mRNAs between the HSF group and the LSF group.

CONCLUSION

The high fat diet with a high C18:0/C16:0 ratio induced more severe glucose and lipid metabolic disorders and inflammation and affected expression of more lncRNAs and mRNAs than an isocaloric low C18:0/C16:0 ratio diet in mice. These results provide new insights into the differences in biological functions and related mechanisms, other than glucose and lipid metabolism, between C16:0 and C18:0.

Transcriptomic comparison of liver tissue between Anqing six-end-white pigs and Yorkshire pigs based on RNA sequencing

Chinese indigenous pig and Western commercial pig breeds show different patterns of lipid metabolism, fat deposition, and fatty acid composition; for these reasons, they have become vitally important models of energy metabolism and obesity in humans. To compare the mechanisms underlying lipid metabolism between Yorkshire pigs (lean type) and Anqing six-end-white pigs (obese type), the liver transcriptomes of six castrated boars with a body weight of approximately 100 kg (three Yorkshire and three Anqing) were analyzed by RNA-seq. The total number of reads produced for each liver sample ranged from 47.05 to 62.6 million. Among 362 differentially expressed genes, 142 were up-regulated and 220 were down-regulated in Anqing six-end-white pigs. Based on these data, 79 GO terms were significantly enriched. The top 10 (the 10 with lowest corrected P-value) significantly enriched GO terms were identified, including lipid metabolic process and carboxylic acid metabolic process. Pathway analysis revealed three significantly enriched KEGG pathways including PPAR signaling pathway, steroid hormone biosynthesis, and retinol metabolism. Based on protein–protein interaction networks, multiple genes responsible for lipid metabolism were identified, such as PCK1, PPARA, and CYP7A1, and these were considered promising candidate genes that could affect porcine liver lipid metabolism and fat deposition. Our results provide abundant transcriptomic information that will be useful for animal breeding and biomedical research.

Nonesterified fatty acids, cognitive decline, and dementia

PURPOSE OF REVIEW

Dementia is rapidly growing as sources of morbidity and mortality as the US population ages, but its pathophysiology remains poorly understood. As a result, no disease-modifying treatments currently exist. We review the evidence that nonesterified fatty acids may play a key role in this condition.

RECENT FINDINGS

Nonesterified fatty acids appear to influence several pathways leading to dementia. In addition to their vascular effects, these moieties cross the blood-brain barrier, where they are toxic to several cell types. They may also influence insulin metabolism in the brain directly and indirectly, and some drugs that lower circulating levels appear to slow cognitive decline and brain atrophy in diabetes.

SUMMARY

Nonesterified fatty acids may contribute to dementia, much as they do to diabetes and cardiovascular disease. Several therapeutic agents lower circulating levels of nonesterified fatty acids and should be tested for their potential preventive effects on cognitive decline in healthy populations before irreversible neuronal attrition occurs.

Hepatic FATP5 expression is associated with histological progression and loss of hepatic fat in NAFLD patients

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are characterized by the accumulation of excess hepatic fat. However, in the progression from NASH to cirrhosis, hepatic fat is often lost. Our aim was to elucidate the mechanism underlying hepatic fat loss during NASH progression.

METHODS

Liver biopsies were performed at The University of Tokyo Hospital between November 2011 and March 2016 on 146 patients with NAFLD and 14 patients with cryptogenic cirrhosis who were not being treated with any diabetes or dyslipidemia drugs. Among them, 70 patients underwent liver biopsy after an overnight fast, and 90 patients were biopsied 5 h after an oral glucose tolerance test. Expression differences in genes encoding several fatty acid metabolism-related factors were examined and correlated with hepatic histological changes based on NAFLD activity scores. Prospective patient follow-up continued until June 2018.

RESULTS

The level of fatty acid transport protein 5 (FATP5), which is associated with free fatty acid intake, was significantly and inversely correlated with features of histological progression, including ballooning and fibrosis. This was confirmed by immunohistochemical analysis. Transcript levels of genes encoding fatty acid metabolism-related proteins were comparable between NASH with severe fibrosis and cryptogenic cirrhosis. Furthermore, a prospective cohort study demonstrated that low FATP5 expression was the most significant risk factor for hepatic fat loss.

CONCLUSIONS

Decreased hepatic FATP5 expression in NAFLD is linked to histological progression, and may be associated with hepatic fat loss during NASH progression to cirrhosis.

The Role of PPARδ Agosnist GW501516 in Rats with Gestational Diabetes Mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a disorder of glucose metabolism that occurs or is found for the first time during pregnancy. GDM is very harmful and urgently needs drug treatment to improve pregnancy outcome. PPARδ is involved in a variety of biological processes related to glycolipid metabolism in the body, suggesting that it may be closely related to insulin resistance and impaired glucose tolerance. The role of PPARδ agonist GW501516 in gestational diabetes has not been studied.

METHODS

Firstly, the rat model of GDM was established. Then, fasting blood-glucose (FGB), fasting insulin (FINS), HOMA-islet resistance index (HOMA-IR) and insulin sensitivity index (ISI) of GDM rats treated with GW501516 were measured on day 3, day 10 and day 17. Glucose tolerance test was performed on the 20th day of gestation to measure glucose tolerance in rats. The expression of PPARδ and Angptl8 in islet tissues of rats was detected by Western blot and immunohistochemistry (IHC). Histopathological changes of islet were detected by HE stain; apoptosis rate of islet cells was detected by Tunel; and expression of apoptosis-related proteins in the cells was detected by Western blot. The biochemical kits were used to detect the expression of lipid metabolism-related factors in blood of GDM rats after the PPARδ agonist GW501516 treatment. Finally, the expression of SREBP-1c and GLUT2 in islet tissues was detected by RT-qPCR and IHC.

RESULTS

The PPARδ agonist GW501516 decreased the expression of FGB, FINS and HOMA-IR in GDM rats, and we found that GW501516 decreased ISI in GDM rats. GW501516 increased glucose tolerance in GDM rats too. In GDM rats, the expression of PPARδ in islet decreased and the expression of Angptl8 increased, which was reversed by GW501516. In addition, we also found that GW501516 can improve the damaged islet tissue of GDM rats, reduce the apoptosis rate of islet cells and inhibit the expression of lipid metabolism-related factors in the blood. Finally, we found that GW501516 inhibited the expression of SREBP-1c and promoted the expression of GLUT2 in the islet tissue.

CONCLUSION

The PPARδ agonist GW501516 could improve the blood glucose level, damaged islet tissue and increase the insulin content in the rats with GDM, possibly by regulating the SREBP-1c/GLUT2 pathway. Our study provided a new basis for clinical treatment of GDM in pregnant women with PPARδ agonist GW501516.

Palmitic Acid Induces MicroRNA-221 Expression to Decrease Glucose Uptake in HepG2 Cells via the PI3K/AKT/GLUT4 Pathway

Obesity-related insulin resistance and high fatty acid concentrations occur during the development of type 2 diabetes mellitus. The role of high concentrations of plasma-free fatty acids is not fully understood. In this study, palmitic acid (PA, 0.8 mM for 24 h) induced the expression of miR-221 that bound to phosphoinositide 3-kinases (PI3K) mRNA to inhibit glucose uptake by HepG2 cells. Compared with controls, PA significantly decreased glucose uptake, increased insulin receptor substrate-2 (IRS-2) and miR-221 expression, and decreased phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and glucose transporter type 4 (GLUT4) mRNA expression. Luciferase reporter assay revealed that miR-221 binding inhibited PI3K expression. Transfection of HepG2 cells with an miR-221 mimic induced miR-221 expression and inhibited the PI3K/AKT pathway. PA decreased glucose uptake in HepG2 cells by inducing the expression of miR-221, which bound to PI3K mRNA and suppressed PI3K/AKT signaling. miR-221 may be a novel target for preventing and treating obesity-induced insulin resistance.

Interactive association of lipopolysaccharide and free fatty acid with the prevalence of type 2 diabetes: A community-based cross-sectional study

AIMS/INTRODUCTION

Increased blood lipopolysaccharide (LPS) or free fatty acid (FFA) levels correlate with an increased risk of type 2 diabetes. The purpose of the present study was to evaluate the interactive effect of serum LPS and FFA levels on the prevalence of type 2 diabetes.

MATERIALS AND METHODS

This cross-sectional study included 2,553 community-dwelling Chinese adults. Fasting serum LPS levels were determined using the Limulus Amebocyte Lysate Chromogenic Endpoint assay, and FFA levels were determined using an enzymatic method. The participants were divided into three groups according to the tertiles of LPS or FFA levels or nine groups according to the tertiles of LPS and FFA levels. The odd ratios (ORs) for type 2 diabetes were estimated using logistic regression analysis.

RESULTS

We found that higher serum LPS or FFA levels were associated with higher high-sensitivity C-reactive protein levels (P < 0.001), homeostatic model assessment of insulin resistance levels (P < 0.001) and ORs for type 2 diabetes (P < 0.01). Meanwhile, there were significant interactions between LPS and FFA in terms of the high-sensitivity C-reactive protein level (P < 0.001), homeostatic model assessment of insulin resistance level (P < 0.001) and ORs for type 2 diabetes (P < 0.001). In the fully adjusted logistic regression model, the OR for participants with type 2 diabetes in the higher LPS and FFA level group were 6.58 (95% confidence interval 3.05-14.18, P < 0.001) compared with that in participants in the lower LPS and FFA level group.

CONCLUSIONS

The interaction between LPS and FFA was associated with an increased risk of type 2 diabetes in community-dwelling Chinese adults.

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

Therapeutic Potential of Lespedeza bicolor to Prevent Methylglyoxal-Induced Glucotoxicity in Familiar Diabetic Nephropathy

Lespedeza bicolor (LB) is often used in traditional medicine to remove toxins, replenish energy stores, and regulate various symptoms of diabetes. This study aimed to explore the use of LB as a therapeutic to prevent diabetic nephropathy in methylglyoxal (MGO)-treated models in vitro and in vivo. Western blotting, immunostaining, and biochemical assays were used to obtain several experimental readouts in renal epithelial cells (LLC-PK1) and BALB/c mice. These include: production of reactive oxygen species (ROS), formation of advanced glycation end-products (AGEs), expression of receptor for advanced glycation end-products (RAGE), apoptotic cell death, glucose levels, fatty acid and triglyceride levels, expression of pro-inflammatory cytokines IL-1β and TNF-α, glyoxalase 1 (Glo1), and nuclear factor erythroid 2-related factor 2 (Nrf2). Pretreatment with LB significantly reduced MGO-induced cellular apoptosis, intracellular production of ROS, and formation of AGEs to ameliorate renal dysfunction in vitro and in vivo. Interestingly, administering LB in MGO-treated cells and mice upregulated the expression of Nrf2 and Glo1, and downregulated the expression of IL-1β and TNF-α. Moreover, LB reduced MGO-induced AGE accumulation and RAGE expression in the kidneys, which subsequently reduced AGE-RAGE interactions. Overall, LB ameliorates renal cell apoptosis and corrects renal dysfunction in MGO-treated mice. These findings extend our understanding of the pathogenic mechanism of MGO-induced nephrotoxicity and regulation of the AGE/RAGE axis by Lespedeza bicolor.

Propionate suppresses hepatic gluconeogenesis via GPR43/AMPK signaling pathway

Short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate are generated by gut microbial fermentation of dietary fiber. SCFAs may exert multiple beneficial effects on human lipid and glucose metabolism. However, their actions and underlying mechanisms are not fully elucidated. In this study, we examined the direct effects of propionate on hepatic glucose and lipid metabolism using human HepG2 hepatocytes. Here, we demonstrate that propionate at a physiologically-relevant concentration effectively suppresses palmitate-enhanced glucose production in HepG2 cells but does not affect intracellular neutral lipid levels. Our results indicated that propionate can decline in gluconeogenesis by down-regulation of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) through activation of AMP-activated protein kinase (AMPK), which is a major regulator of the hepatic glucose metabolism. Mechanistic studies also revealed that propionate-stimulated AMPK phosphorylation can be ascribed to Ca²⁺/calmodulin-dependent protein kinase kinase β (CaMKKβ) activation in response to an increase in intracellular Ca²⁺ concentration. Moreover, siRNA-mediated knockdown of the propionate receptor GPR43 prevented propionate-inducible activation of AMPK and abrogates the gluconeogenesis-inhibitory action. Thus, our data indicate that the binding of propionate to hepatic GPR43 elicits CaMKKβ-dependent activation of AMPK through intracellular Ca²⁺ increase, leading to suppression of gluconeogenesis. The present study suggests the potential efficacy of propionate in preventive and therapeutic management of diabetes.

Impact of obesity on longitudinal changes to cardiac structure and function in patients with Type 2 diabetes mellitus

AIMS

Few prospective studies have evaluated the natural progression of left ventricular (LV) remodelling in patients with Type 2 diabetes mellitus (T2DM). The aim of this study was to evaluate the impact of obesity on longitudinal cardiac structural and functional changes in patients with T2DM.

METHODS AND RESULTS

This study comprised of 274 patients with T2DM (mean age, 62.2 ± 11.4 years; male, 51.5%). Echocardiographic parameters including LV geometry, systolic, and diastolic functions were measured at baseline and follow-up. The median follow-up was 24 months (from 12 months to 48 months). The entire cohort showed a significant increase in LV wall thickness, LV mass (LVM), and prevalence of concentric hypertrophy (19.6-27.3%). Further, systolic function and diastolic function had deteriorated at follow-up assessment. Multivariable adjusted linear regression demonstrated that baseline body mass index (BMI) predicted longitudinal change to LVM (β  = 0.29, P < 0.01) and LV ejection fraction (β  = -0.15, P < 0.05). Patients were divided into three groups according to their BMI: normal weight (BMI <23 kg/m2), overweight (BMI between 23 kg/m2 and 27.5 kg/m2), or obese (BMI ≥27.5 kg/m2). Importantly, obesity at baseline predicted a greater longitudinal increase in LVM and decrease in LV ejection fraction compared with overweight and normal weight patients.

CONCLUSION

Being obese at baseline was associated with greater longitudinal increase in LV mass and greater deterioration in LV systolic function.

Protective effect of docosahexaenoic acid on lipotoxicity-mediated cell death in Schwann cells: Implication of PI3K/AKT and mTORC2 pathways

BACKGROUND AND AIM

Docosahexaenoic acid (DHA) exhibits neuroprotective properties and has been shown to preserve nerve cells following trauma and ischemic injury. Recently, we showed that DHA pretreatment improved locomotion and reduced neuropathic pain after acute spinal cord injury in adult rats. These improvements were associated with an increase in the levels of AKT in spinal cord injury neurons. In this study, we investigate the implication of PI3K/AKT and mTOR pathway in DHA-mediated protection of primary cultured Schwann cells (pSC) undergoing palmitic acid-induced lipotoxicity (PA-LTx).

METHODS

Primary cultured Schwann cells were treated with PA (PA:BSA, 2:1) in the presence or absence of DHA (1-200 µM) for 24-48 hr. Cell viability was determined by crystal violet staining and nuclear morphology was examined using Hoechst staining.

RESULTS

We found that pSC cultures exposed to palmitic acid (PA) overload showed chromatin condensation, a decrease in cell viability and an inhibition of AKT phosphorylation in a time-dependent manner. Next, pSC exposed to PA overload were treated with DHA. The data show that co-treatment with DHA inhibited the loss of cell viability and apoptosis caused by PA. Moreover, treatment with DHA inhibited chromatin condensation, significantly stimulated p-AKT phosphorylation under PA-LTx condition, and DHA alone increased AKT phosphorylation. Additionally, when these pSC cultures were treated with PI3K inhibitors LY294002 and, BKM120 and mTOR inhibitors Torin 1 (mTORC1/mTORC2), but not rapamycin (mTORC1), the protective effects of DHA were not observed.

CONCLUSION

These findings suggest PI3K/AKT and mTORC2 kinase pathways are involved in the protective function (s) of DHA in PA-induced Schwann cell death.

The Role of Insulin-like Growth Factor (IGF) Axis in Early Diagnosis of Pancreatic Adenocarcinoma (PDAC)

New-onset diabetes mellitus (DM) is one of the first symptoms of pancreatic adenocarcinoma (PDAC). The frequency of endocrine disorders is estimated between 40% and 80% in patients with pancreatic cancer. DM is a risk factor for cancer development but it may also be a consequence of the tumor growth. Data confirming the existence of a relationship between long standing type 2 DM and an increased risk of PDAC comes from numerous clinical studies. Insulin resistance phenomenon and hyperinsulinemia may result in the increased proliferation of pancreatic islets which in turn may cause a predisposition to cancer development. In contrast, it is proved that new-onset DM among patients over 50 years old significantly increases the risk of PDAC recognition. Insulin-like growth factor 1 (IGF-1) and their complex proteins, IGF binding proteins, which comprise the IGF axis play a crucial role in carbohydrate metabolism disorders and, studies have shown that they may contribute to PDAC growth. Some studies confirm that IGF-1 is connected with early carcinogenesis in animals and humans. Assessing the levels of these proteins may thus be helpful in early recognition of PDAC in patients with recently detected endocrine disorders, especially pancreatic DM.

Stevioside modulates oxidative damage in the liver and kidney of high fat/low streptozocin diabetic rats

This study investigated the potential of stevioside to prevent oxidative DNA damage in the liver and kidney of type 2 diabetes mellitus (T2DM) using high fat-low streptozocin rat model. Rats were treated daily with 12.5, 25 and 50 mg/kg stevioside orally for 21 days. Levels of biomarkers of T2DM, lipid profile and oxidative stress were assayed spectrophotometrically. The DNA ladder assay method was used to assess DNA fragmentation in the liver and kidney while computational analysis was used to predict the mechanisms of antidiabetic properties of stevioside. Stevioside significantly (p < 0.05) decreased the levels of plasma glucose, insulin, dipeptidyl peptidase IV and activities of kidney angiotensin converting enzyme. Stevioside significantly reduced oxidative stress by decreasing the levels of lipid peroxidation and nitric oxide in the liver and kidney; thereby, reducing the extent of DNA fragmentation in the liver and kidney of the diabetic rats. The in silico analysis showed that the ability of stevioside to exert these effects is linked to its inhibition of beta-adrenergic receptor kinase and G-protein-coupled receptor kinase. The results of this study suggest that the prevention of DNA fragmentation may be an additional benefit of the use of stevioside in the management of T2DM.

Liraglutide suppresses non-esterified free fatty acids and soluble vascular cell adhesion molecule-1 compared with metformin in patients with recent-onset type 2 diabetes

Background

It has been suggested that liraglutide could have an impact on glucose and lipid metabolism disorder and adhesion molecule activation, which may play important roles in the vascular damage of diabetes. In this study, we examined the effects of liraglutide versus metformin on non-esterified free fatty acids, beta-cell insulin secretion, and adhesion molecule levels in patients with recent-onset type 2 diabetes mellitus.

Methods

In this study, 60 patients newly diagnosed with type 2 diabetes mellitus (mean age 33.97 ± 5.67 years) were randomly assigned to receive once-daily subcutaneous liraglutide or oral metformin. Before the study and after the 8-week treatment period, a 75 g oral glucose tolerance test was performed. Plasma glucose, lipids and lipoprotein, plasma insulin, glycaemic and insulin responses, non-esterified free fatty acids (NEFA), and soluble vascular cell adhesion molecule-1 (sVCAM-1) levels were evaluated.

Results

After 8 weeks, 120 min of NEFA (155 ± 125 vs 99 ± 73 µmol/L, P = 0.026) and the levels of sVCAM-1 (465 ± 136 vs 382 ± 131 ng/ml, P = 0.013) significantly decreased, while the early phase insulin secretion index (24.94 [7.78, 38.89] vs. 31.13 [17.67, 59.09], P = 0.031), fasting plasma insulin (104 [51, 123] vs 113 [54, 171] mIU/L, P = 0.015), 60 min plasma insulin (326 [165, 441] vs 471 [334, 717] mIU/L, P = 0.005), 120 min plasma insulin (401 [193, 560] vs 500 [367, 960] mIU/L, P = 0.047), and insulin area under the curve (AUCins) (648 [321, 742] vs 738 [451, 1118] mIU/L, P = 0.005) remarkably increased for patients in the liraglutide treatment group. The levels of sVCAM-1 dramatically decreased after 8 weeks of liraglutide treatment (503 ± 182 vs 382 ± 131 ng/ml, P = 0.046) compared to that of the metformin treatment group. At the same time, the differences before and after liraglutide treatment in 120 min of NEFA (− 32 [− 96, − 5] vs 5 [− 35, 38] µmol/L, P = 0.033) and AUCins (738 [451, 1118] vs 594 [357, 1216] mIU/L, P = 0.014) were remarkably enhanced compared to that of the metformin therapy. Nevertheless, there were no significant differences in fasting NEFA after liraglutide or metformin treatment. The reduction of 120 min NEFA (ΔNEFA) was positively correlated with the decrease of sVCAM-1 (ΔsVCAM-1) after 8 weeks of liraglutide treatment (r = 0.523, P = 0.003).

Conclusions

Our results demonstrate that liraglutide administration is more effective than metformin in reducing 120 min NEFA and suppressing sVCAM-1 levels for recent-onset type 2 diabetes mellitus. We suggest that this outcome may be because liraglutide is associated with potentiating insulin secretion capacity, inhibiting vascular inflammatory cytokines, and antagonizing atherosclerosis.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0701-4) contains supplementary material, which is available to authorized users.

The Effect of Hypoxia and Metformin on Fatty Acid Uptake, Storage, and Oxidation in L6 Differentiated Myotubes

Metabolic impairments associated with obstructive sleep apnea syndrome (OSA) are linked to tissue hypoxia, however, the explanatory molecular and endocrine mechanisms remain unknown. Using gas-permeable cultureware, we studied the chronic effects of mild and severe hypoxia on free fatty acid (FFA) uptake, storage, and oxidation in L6 myotubes under 20, 4, or 1% O₂. Additionally, the impact of metformin and the peroxisome proliferator-activated receptor (PPAR) β/δ agonist, called GW501516, were investigated. Exposure to mild and severe hypoxia reduced FFA uptake by 37 and 32%, respectively, while metformin treatment increased FFA uptake by 39% under mild hypoxia. GW501516 reduced FFA uptake under all conditions. Protein expressions of CD36 (cluster of differentiation 36) and SCL27A4 (solute carrier family 27 fatty acid transporter, member 4) were reduced by 17 and 23% under severe hypoxia. Gene expression of UCP2 (uncoupling protein 2) was reduced by severe hypoxia by 81%. Metformin increased CD36 protein levels by 28% under control conditions and SCL27A4 levels by 56% under mild hypoxia. Intracellular lipids were reduced by mild hypoxia by 18%, while in controls only, metformin administration further reduced intracellular lipids (20% O₂) by 36%. Finally, palmitate oxidation was reduced by severe hypoxia, while metformin treatment reduced non-mitochondrial O₂ consumption, palmitate oxidation, and proton leak at all O₂ levels. Hypoxia directly reduced FFA uptake and intracellular lipids uptake in myotubes, at least partially, due to the reduction in CD36 transporters. Metformin, but not GW501516, can increase FFA uptake and SCL27A4 expression under mild hypoxia. Described effects might contribute to elevated plasma FFA levels and metabolic derangements in OSA.

Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men

The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.

Molecular Mechanisms of Antipsychotic Drug-Induced Diabetes

Antipsychotic drugs (APDs) are widely prescribed to control various mental disorders. As mental disorders are chronic diseases, these drugs are often used over a life-time. However, APDs can cause serious glucometabolic side-effects including type 2 diabetes and hyperglycaemic emergency, leading to medication non-compliance. At present, there is no effective approach to overcome these side-effects. Understanding the mechanisms for APD-induced diabetes should be helpful in prevention and treatment of these side-effects of APDs and thus improve the clinical outcomes of APDs. In this review, the potential mechanisms for APD-induced diabetes are summarized so that novel approaches can be considered to relieve APD-induced diabetes. APD-induced diabetes could be mediated by multiple mechanisms: (1) APDs can inhibit the insulin signaling pathway in the target cells such as muscle cells, hepatocytes and adipocytes to cause insulin resistance; (2) APD-induced obesity can result in high levels of free fatty acids (FFA) and inflammation, which can also cause insulin resistance. (3) APDs can cause direct damage to β-cells, leading to dysfunction and apoptosis of β-cells. A recent theory considers that both β-cell damage and insulin resistance are necessary factors for the development of diabetes. In high-fat diet-induced diabetes, the compensatory ability of β-cells is gradually damaged, while APDs cause direct β-cell damage, accounting for the severe form of APD-induced diabetes. Based on these mechanisms, effective prevention of APD-induced diabetes may need an integrated approach to combat various effects of APDs on multiple pathways.

Differential proteomic analysis of white adipose tissues from T2D KKAy mice by LC-ESI-QTOF

Type 2 diabetes (T2D) has become a worldwide increasingly social health burden for its high morbidity and heightened prevalence. As one of the main tissues involved in uptake of glucose under the stimulation of insulin, WAT plays very important role in metabolic and homeostasis regulation. We performed a differential proteomics study to investigate alterations in epididymis fat pad of high fat diet fed T2D KKAy mice compared to normal fed C57BL/6J mice, by ¹⁸ O-labeling relative quantitative technique. Among 329 confidently identified proteins, 121 proteins showed significant changes with CV ≤ 20% (fold changes of >2 or <0.5 as threshold). According to GO classification, we found that altered proteins contained members of biological processes of metabolic process, oxidative stress, ion homeostasis, apoptosis and cell division. In metabolic, proteins assigned to fatty acid biosynthesis (FAS etc.) were decreased, the key enzyme (ACOX3) in β-oxidation process was increased. Increased glycolysis enzymes (ENOB etc.) and decreased TCA cycle related enzymes (SCOT1 etc.) suggested that glucose metabolism in mitochondria of T2D mice might be impaired. Elevated oxidative stress was observed with alterations of a series of oxidordeuctase (QSOX1 etc.). Besides, alterations of ion homeostasis (AT2C1 etc.) proteins were also observed. The enhancement of cell proliferation associated proteins (ELYS etc.) and inhibition of apoptosis associated proteins (RASF6 etc.) in WAT might contributed to the fat pad and body weight gain. Overall, these changes in WAT may serve as a reference for understanding the functional mechanism of T2D.

Association between subclinical left ventricular systolic dysfunction and glycemic control in asymptomatic type 2 diabetic patients with preserved left ventricular function

BACKGROUND

Type 2 diabetes is strongly associated with the occurrence of cardiovascular diseases, especially heart failure. Some studies have suggested that subclinical systolic dysfunction as assessed by tissue Doppler imaging (TDI) is already present in uncomplicated diabetic patients with normal left ventricular ejection fraction (LVEF). Considering the importance of this aspect, the aim of this cross-sectional study was to examine the relationship between glycated hemoglobin and mean s' wave velocity (a reliable measure of early LV systolic dysfunction) in a cohort of type 2 diabetic outpatients with preserved LVEF and without ischemic heart disease.

METHODS

Forty-four male patients with newly diagnosed and 172 male patients with established type 2 diabetes were recruited for this cross-sectional study. All patients were evaluated with a transthoracic echocardiographic Doppler. The statistical analysis was conducted by a linear multivariate regression analysis, including several potential confounders.

RESULTS

The mean values of mean s' wave velocity were lower in patients with a worse glycemic control and progressively decreased across the quartiles of glycated hemoglobin. The multivariate linear regression analysis showed that mean s' wave velocity was inversely and independently associated with glycated hemoglobin (standardized beta coefficient -0.178; p = 0.043) after adjustment for age, duration of diabetes, body mass index, pulse pressure, estimated glomerular filtration rate, microvascular complication status, and indexed cardiac mass.

CONCLUSIONS

These results suggest that s' wave velocity, as evaluated by TDI echocardiography, was an early marker of systolic dysfunction in type 2 diabetic patients with preserved LVEF and without prior ischemic heart disease. Moreover, early systolic dysfunction was independently associated with poor glycemic control in these patients. Future studies are needed to elucidate the pathogenic role of chronic hyperglycemia in the development of early LV systolic dysfunction.

Glucagon-like peptide-1 effects lipotoxic oxidative stress by regulating the expression of microRNAs

Aim to confirm whether the treatment of GLP-1 can modulated body weight, lipid metabolism, insulin content, pancreas oxidative stress, improved T-AOC, MDA levels related to FFA-Induced oxidative stress in C57BL/6 mice and INS-1 cells. In this study, GLP-1 makes the expression of AMPK, PPARα, CPT1A and SIRT1 increased, and the expression of SREBP1c, miR-33 and miR-370 decreased. Interestingly, the effects of GLP-1 were less dose dependent as GLP-1 regulated the FFA, which related to gene expression at much lower doses (3 μg/kg, 10 mM, mice and INS-1 respectively) and effects were relatively maintained at higher dose (30 μg/kg, 100 mM, mice and INS-1 respectively) as well. Subsequently, the analysis showed that inhibited expression of miR-33 and miR-370 upregulated the expression of CPT1A and SIRT1, reversely mimics. These results demonstrated for the first time that GLP-1 improve lipotoxic oxidative stress of pancreas by regulate expression of microRNAs.

Protective Role of PPARdelta in Lipoapoptosis of Pancreatic β Cells

Lipoapoptosis plays an important role in the pathogenesis of type 2 diabetes. Peroxisome proliferator-activated receptor delta (PPARdelta), a vital regulator of glucose and lipid metabolism, may reduce fatty acid-induced pancreatic β cell lipotoxicity in diabetes. However, the detailed molecular mechanisms underlying this process are not fully understood. In this study, we investigated the effect of activation of PPARdelta on palmitate-induced β cell apoptosis, and we explored the potential mechanism of the antiapoptotic effect. The cell apoptosis was determined by DNA fragmentation analysis and Hoechst 33342 staining. The expressing of glucagon-like peptide-1 receptor (GLP-1R) in INS-1 cells was assessed by Western blotting, quantification of PCR, and was further confirmed by immunofluorescence staining. The potential of PPARdelta to interact with homologous PPRE in the GLP-1R gene was determined by Chromatin immunoprecipitation (ChIP). Our results showed that exposure of INS-1 cells to palmitate for 24 h caused a significant increase in cell apoptosis, which was inhibited by GW501516. PPARdelta exerted anti-apoptotic effects in pancreatic β cells via the PI3 K/PKB/FoxO1 signaling pathway. Moreover, PPARdelta upregulated the GLP-1R expression under lipotoxic conditions. The ChIP assay revealed a direct binding of PPARdelta to a noncanonical PPRE motif of the GLP-1R gene in INS-1 cells. Our study suggested that the anti-apoptotic action of PPARdelta may involve its transcriptional regulation of GLP-1R and PI3 K/PKB/FoxO1 signaling. GW501516 and possible other GW-based strategies may confer additional benefit beyond improved glycemic control.

Biomechanism of chlorogenic acid complex mediated plasma free fatty acid metabolism in rat liver

Background

Plasma free fatty acids (FFA) are involved in blood lipid metabolism as well as many health complications. The present study was conducted to evaluate the potential role of chlorogenic acid complex from green coffee bean (CGA7) on FFA metabolism in high fat diet fed rats.

Methods

Hyperlipidemia was induced in Wistar rats using high-fat diet. The animals were given CGA7/orlistat concurrently for 42 days. The parameters analysed during the study include plasma and liver total cholesterol (TC), Triglycerides (TG) and FFA. AMPK activation in the liver was analysed through ELISA. The multiple factors involved in AMPK mediated FFA metabolism were analysed using western blotting.

Results

CGA7 (50, 100, 150 mg/kg BW) decreased triglycerides (TG) and FFA levels in plasma and liver. CGA7 administration led to the activation of AMP-activated protein kinase (AMPK) and a subsequent increase in the levels of carnitine palmitoyltransferase 1 (CPT-1). There was a decrease in acetyl-CoA carboxylase (ACC) activity as evident by the increase in its phosphorylation level.

Conclusion

Chlorogenic acids improved the blood lipid metabolism in rats by alleviating the levels of FFA and TG, modulating the multiple factors in liver through AMPK pathway. The study concludes that CGA7 complex can be promoted as an active ingredient in nutrition for obesity management.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1258-y) contains supplementary material, which is available to authorized users.

β-Caryophyllene attenuates palmitate-induced lipid accumulation through AMPK signaling by activating CB2 receptor in human HepG2 hepatocytes

SCOPE

Nonalcoholic fatty liver disease is currently the most common chronic liver disease worldwide, characterized by excessive hepatic lipid accumulation without significant ethanol consumption. We have performed a screening for medicinal foods that inhibit hepatocytic lipid accumulation through activation of AMP-activated protein kinase (AMPK), which is a critical regulator of the hepatic lipid metabolism.

METHODS AND RESULTS

We found that clove (Syzygium aromaticum), which is commonly used as a spice, markedly inhibits palmitate-inducible lipid accumulation in human HepG2 hepatocytes. Analyses of the clove extracts found that β-caryophyllene, an orally-active cannabinoid, is the principal suppressor of the lipid accumulation, and stimulates the phosphorylation of AMPK and acetyl-CoA carboxylase 1 (ACC1). Our data also showed that β-caryophyllene prevents the translocation of sterol regulatory element-binding protein-1c (SREBP-1c) into the nucleus and forkhead box protein O1 (FoxO1) into the cytoplasm through AMPK signaling, and consequently, induces a significant downregulation of fatty acid synthase (FAS) and upregulation of adipose triglyceride lipase, respectively. Moreover, we demonstrated that the β-caryophyllene-induced activation of AMPK could be mediated by the cannabinoid type 2 receptor-dependent Ca²⁺ signaling pathway.

CONCLUSION

Our results suggest that β-caryophyllene has the potential efficacy in preventing and ameliorating nonalcoholic fatty liver disease and its associated metabolic disorders.

Fucoidan from Acaudina molpadioides protects pancreatic islet against cell apoptosis via inhibition of inflammation in type 2 diabetic mice

Inflammation induces pancreatic islet cell apoptosis. Effects of fucoidan from Acaudina molpadioides (Am-FUC) on inhibition of pancreatic islet cell apoptosis and inflammation in type 2 diabetic mice were investigated. Am-FUC repaired pancreatic islet cells, decreased serum C-reactive protein (CRP), macrophage inflammatory protein 1 (MIP-1), interleukin 1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) levels, and increased the IL-10 level. Am-FUC also reduced TNF-α, CRP, MIP-1, IL-1β, and IL-6 mRNA expressions, and increased IL-10 mRNA expression in epididymal adipose tissues. Am-FUC reduced Bid, Bax, cytochrome c, caspase 9, and caspase 3 mRNA expressions, and increased Bcl-2 and Bcl-xL mRNA expressions. Am-FUC down-regulated t-Bid, Bax, cytochrome c, and caspase 9 activities, cleaved caspase 3 proteins, and up-regulated Bcl-2 and Bcl-xL proteins. Thus, an Am-FUCblocked mitochondrial pathway was the suppression mechanism in pancreatic islet cell apoptosis via regulation of inflammatory cytokines providing dietary intervention in type 2 diabetes and inflammation-induced pancreatic islet apoptosis.

Serotonin- and Dopamine-Related Gene Expression in db/db Mice Islets and in MIN6 β-Cells Treated with Palmitate and Oleate

High circulating nonesterified fatty acids (NEFAs) concentration, often reported in diabetes, leads to impaired glucose-stimulated insulin secretion (GSIS) through not yet well-defined mechanisms. Serotonin and dopamine might contribute to NEFA-dependent β-cell dysfunction, since extracellular signal of these monoamines decreases GSIS. Moreover, palmitate-treated β-cells may enhance the expression of the serotonin receptor Htr2c, affecting insulin secretion. Additionally, the expression of monoamine-oxidase type B (Maob) seems to be lower in islets from humans and mice with diabetes compared to nondiabetic islets, which may lead to increased monoamine concentrations. We assessed the expression of serotonin- and dopamine-related genes in islets from db/db and wild-type (WT) mice. In addition, the effect of palmitate and oleate on the expression of such genes, 5HT content, and GSIS in MIN6 β-cell was determined. Lower Maob expression was found in islets from db/db versus WT mice and in MIN6 β-cells in response to palmitate and oleate treatment compared to vehicle. Reduced 5HT content and impaired GSIS in response to palmitate (-25%; p < 0.0001) and oleate (-43%; p < 0.0001) were detected in MIN6 β-cells. In conclusion, known defects of GSIS in islets from db/db mice and MIN6 β-cells treated with NEFAs are accompanied by reduced Maob expression and reduced 5HT content.

Functional and association studies of the cholesteryl ester transfer protein (CETP) gene in a Wannan Black pig model

Some polymorphisms of the human CETP gene are causally and significantly associated with serum lipids levels; however, the information regarding this gene in pigs is sparse. To evaluate the effects of CETP on blood lipid traits and fat deposition in pig, porcine CETP tissue expression patterns were observed by quantitative real-time polymerase chain reaction (qPCR) first. High expression was detected in liver, spleen, gluteus medius (GM) muscle and backfat. A de novo polymorphism (AF333037:g.795C>T) in the intron 1 region of porcine CETP was identified. This polymorphism was further genotyped by direct sequencing of the PCR products of 390 Wannan Black pigs, a Chinese native breed population. Association analyses at 45 and 300 days of age revealed highly significant associations between CETP genotypes and serum lipid traits. Furthermore, this polymorphism was proved to be associated with differences in liver CETP mRNA levels: pigs at 300 days of age with the TT genotype had higher levels than did those with other genotypes (P = 0.021). Additionally, analysis at 300 days of age showed that GM CETP mRNA expression correlated positively with serum lipids levels as well as with carcass backfat thickness and intramuscular fat content in GM. These results indicate that CETP is involved in serum, adipose and muscle lipid metabolism in pigs. The mechanisms underlying such relationships and their functional implications are worthy of further research.

Assessment of left ventricular function by three-dimensional speckle-tracking echocardiography in well-treated type 2 diabetes patients with or without hypertension

PURPOSE

The aims of this study were to investigate the myocardial deformation in well-treated type 2 diabetes patients with or without hypertension using three-dimensional speckle-tracking echocardiography and to explore variables that could affect myocardial deformation.

METHODS

We studied 82 patients with type 2 diabetes and controlled blood glucose, including 46 subjects with diabetes alone and 36 subjects with diabetes and well-controlled hypertension, and 40 age- and gender-matched controls. Left ventricular real-time three-dimensional (3D) full-volume images were recorded and analyzed using online software. The left ventricular ejection fraction, global longitudinal strain (GLS), global circumferential strain, global area strain, and global radial strain were measured and compared.

RESULTS

Despite a similar three-dimensional left ventricular ejection fraction, GLS was significantly lower in patients with diabetes only than in controls (p < 0.001). Patients with diabetes and hypertension showed significantly lower systolic strains in all directions than controls and patients with diabetes only (p < 0.001 and p < 0.05, respectively). Multiple regression analysis revealed that fasting plasma glucose and left ventricular end-diastolic volume were significant factors influencing GLS in both diabetic groups.

CONCLUSIONS

Early-stage diabetic patients showed an impaired left ventricular strain that was worsened by coexistent hypertension, although blood glucose and blood pressure were well controlled. Three-dimensional speckle-tracking echocardiography was able to detect these subclinical changes.

The p66(Shc) redox adaptor protein is induced by saturated fatty acids and mediates lipotoxicity-induced apoptosis in pancreatic beta cells

AIMS/HYPOTHESIS

The role of the redox adaptor protein p66(Shc) as a potential mediator of saturated fatty acid (FA)-induced beta cell death was investigated.

METHODS

The effects of the FA palmitate on p66(Shc) expression were evaluated in human and murine islets and in rat insulin-secreting INS-1E cells. p66(Shc) expression was also measured in islets from mice fed a high-fat diet (HFD) and from human donors with different BMIs. Cell apoptosis was quantified by two independent assays. The role of p66(Shc) was investigated using pancreatic islets from p66 (Shc-/-) mice and in INS-1E cells with knockdown of p66(Shc) or overexpression of wild-type and phosphorylation-defective p66(Shc). Production of reactive oxygen species (ROS) was evaluated by the dihydroethidium oxidation method.

RESULTS

Palmitate induced a selective increase in p66(Shc) protein expression and phosphorylation on Ser(36) and augmented apoptosis in human and mouse islets and in INS-1E cells. Inhibiting the tumour suppressor protein p53 prevented both the palmitate-induced increase in p66(Shc) expression and beta cell apoptosis. Palmitate-induced apoptosis was abrogated in islets from p66 (Shc-/-) mice and following p66 (Shc) knockdown in INS-1E cells; by contrast, overexpression of p66(Shc), but not that of the phosphorylation-defective p66(Shc) mutant, enhanced palmitate-induced apoptosis. The pro-apoptotic effects of p66(Shc) were dependent upon its c-Jun N-terminal kinase-mediated phosphorylation on Ser(36) and associated with generation of ROS. p66(Shc) protein expression and function were also elevated in islets from HFD-fed mice and from obese/overweight cadaveric human donors.

CONCLUSIONS/INTERPRETATION

p53-dependent augmentation of p66(Shc) expression and function represents a key signalling response contributing to beta cell apoptosis under conditions of lipotoxicity.