High-Fat Diet Induces Pre-Diabetes and Distinct Sex-Specific Metabolic Alterations in Negr1-Deficient Mice

The Interplay of Genetic Predisposition, Circadian Misalignment, and Metabolic Regulation in Obesity

PURPOSE OF REVIEW

This review explores the complex interplay between genetic predispositions to obesity, circadian rhythms, metabolic regulation, and sleep. It highlights how genetic factors underlying obesity exacerbate metabolic dysfunction through circadian misalignment and examines promising interventions to mitigate these effects.

RECENT FINDINGS

Genome-wide association Studies (GWAS) have identified numerous Single Nucleotide Polymorphisms (SNPs) associated with obesity traits, attributing 40-75% heritability to body mass index (BMI). These findings illuminate critical links between genetic obesity, circadian clocks, and metabolic processes. SNPs in clock-related genes influence metabolic pathways, with disruptions in circadian rhythms-driven by poor sleep hygiene or erratic eating patterns-amplifying metabolic dysfunction. Circadian clocks, synchronized with the 24-h light-dark cycle, regulate key metabolic activities, including glucose metabolism, lipid storage, and energy utilization. Genetic mutations or external disruptions, such as irregular sleep or eating habits, can destabilize circadian rhythms, promoting weight gain and metabolic disorders. Circadian misalignment in individuals with genetic predispositions to obesity disrupts the release of key metabolic hormones, such as leptin and insulin, impairing hunger regulation and fat storage. Interventions like time-restricted feeding (TRF) and structured physical activity offer promising strategies to restore circadian harmony, improve metabolic health, and mitigate obesity-related risks.

Proline exacerbates hepatic gluconeogenesis via paraspeckle-dependent mRNA retention

Type 2 diabetes (T2D) is a global health issue characterized by abnormal blood glucose levels and is often associated with excessive hepatic gluconeogenesis. Increased circulating non-essential amino acids (NEAAs) are consistently observed in individuals with T2D; however, the specific contribution of each amino acid to T2D pathogenesis remains less understood. Here, we report an unexpected role of the NEAA proline in coordinating hepatic glucose metabolism by modulating paraspeckle, a nuclear structure scaffolded by the long non-coding RNA Neat1. Mechanistically, proline diminished paraspeckles in hepatocytes, liberating the retained mRNA species into cytoplasm for translation, including the mRNAs of Ppargc1a and Foxo1, contributing to enhanced gluconeogenesis and hyperglycaemia. We further demonstrated that the proline-paraspeckle-mRNA retention axis existed in diabetic liver samples, and intervening in this axis via paraspeckle restoration substantially alleviated hyperglycaemia in both female and male diabetic mouse models. Collectively, our results not only delineated a previously unappreciated proline-instigated, paraspeckle-dependent mRNA-retention mechanism regulating gluconeogenesis, but also spotlighted proline and paraspeckle as potential targets for managing hyperglycaemia.

Unraveling the genetic links between depression and type 2 diabetes

BACKGROUND

Type 2 diabetes (T2D) is a chronic metabolic disorder that has high comorbidity with mental disorders. The genetic relationships between T2D and depression are far from being well understood.

METHODS

We performed genetic correlation, polygenic overlap, Mendelian randomization (MR) analyses, cross-trait meta-analysis, and Bayesian colocalization analysis to assess genetic relationships between T2D and depression, in the forms of major depressive disorder (MDD) and depressed affect (DAF). Then, the summary data-based MR (SMR) analysis was performed to prioritize genes contributing to MDD and to T2D from functional perspective. MDD-driven signaling pathways were constructed to understand the influence of MDD on T2D at the molecular level.

RESULTS

T2D has positive genetic correlations both with MDD (rg = 0.14) and with DAF (rg = 0.19). The polygenic overlap analysis showed that about 60 % of causal variants for T2D are shared with MDD and DAF. The MR analysis indicated that genetic liabilities to both MDD (OR: 1.24, 95 % CI: 1.11-1.38) and DAF (OR: 1.48, 95 % CI: 1.23-1.78) are associated with an increased risk for T2D, while genetic liability to T2D is not associated with the risk for MDD (OR: 1.00, 95 % CI: 0.99-1.01) or DAF (OR: 1.01, 95 % CI: 1.00-1.02). The cross-trait meta-analysis identified 271 genomic loci, of which 29 were novel. Genetic predisposition to MDD and T2D shares six overlapping loci, involving some well-characterized genes, such as TCF4 and NEGR1. Colocalization analysis revealed three shared chromosome regions between MDD and T2D, which covers mediator genes including SCYL1, DENND1A, and MAD1L1. Molecular pathway analysis suggests mechanisms that promote the development of T2D through inflammatory pathways overactive in patients with MDD. The SMR analysis and the meta-analysis highlighted seven genes with functional implications for both MDD and T2D, including TNKS2, CCDC92, FADS1, ERI1, THUMPD3, NUCKS1, and PM20D1.

CONCLUSIONS

Our study points out that depression, in the forms of MDD and DAF, may increase the risk of T2D. Analysis of underlying genetic variation and the molecular pathways, connecting depression and T2D, indicate that the pathophysiological foundations of these two conditions have a notable overlap.

Transcriptomics of Subcutaneous Tissue of Lipedema Identified Differentially Expressed Genes Involved in Adipogenesis, Inflammation, and Pain

Background

Lipedema is a disease typically affecting women with a symmetrical, painful fat distribution disorder, which is hypothesized to be caused by impaired adipogenesis, inflammation, and extracellular matrix remodeling, leading to fibrosis and the development of edema in lipedema subcutaneous adipose tissue. The pathogenesis and molecular processes leading to lipedema have not yet been clarified.

Methods

A whole transcriptome analysis of subcutaneous tissue of lipedema stages I (n = 12), II (n = 9), and III (n = 8) compared with hypertrophied subcutaneous tissue (n = 4) was performed. Further data about hormonal substitution and body morphology were collected. The study is registered at ClinicalTrials.gov (NCT05861583).

Results

We identified several differentially expressed genes involved in mechanisms leading to the development of lipedema. Some genes, such as PRKG2, MEDAG, CSF1R, BICC1, ERBB4, and ACP5, are involved in adipogenesis, regulating the development of mature adipocytes from mesenchymal stem cells. Other genes, such as MAFB, C1Q, C2, CD68, CD209, CD163, CD84, BCAT1, and TREM2, are predicted to be involved in lipid accumulation, hypertrophy, and the inflammation process. Further genes such as SHTN1, SCN7A, and SCL12A2 are predicted to be involved in the regulation and transmission of pain.

Conclusions

In summary, the pathogenesis and development of lipedema might be caused by alterations in adipogenesis, inflammation, and extracellular matrix remodeling, leading to fibrosis and the formation of edema resulting in this painful disease. These processes differ from hypertrophied adipose tissue and may therefore play a main role in the formation of lipedema.

The IgLON family of cell adhesion molecules expressed in developing neural circuits ensure the proper functioning of the sensory system in mice

Deletions and malfunctions of the IgLON family of cell adhesion molecules are associated with anatomical, behavioral, and metabolic manifestations of neuropsychiatric disorders. We have previously shown that IgLON genes are expressed in sensory nuclei/pathways and that IgLON proteins modulate sensory processing. Here, we examined the expression of IgLON alternative promoter-specific isoforms during embryonic development and studied the sensory consequences of the anatomical changes when one of the IgLON genes, Negr1, is knocked out. At the embryonal age of E12.5 and E13.5, various IgLONs were distributed differentially and dynamically in the developing sensory areas within the central and peripheral nervous system, as well as in limbs and mammary glands. Sensory tests showed that Negr1 deficiency causes differences in vestibular function and temperature sensitivity in the knockout mice. Sex-specific differences were noted across olfaction, vestibular functioning, temperature regulation, and mechanical sensitivity. Our findings highlight the involvement of IgLON molecules during sensory circuit formation and suggest Negr1's critical role in somatosensory processing.

Depression-Associated Negr1 Gene-Deficiency Induces Alterations in the Monoaminergic Neurotransmission Enhancing Time-Dependent Sensitization to Amphetamine in Male Mice

In GWAS studies, the neural adhesion molecule encoding the neuronal growth regulator 1 (NEGR1) gene has been consistently linked with both depression and obesity. Although the linkage between NEGR1 and depression is the strongest, evidence also suggests the involvement of NEGR1 in a wide spectrum of psychiatric conditions. Here we show the expression of NEGR1 both in tyrosine- and tryptophan hydroxylase-positive cells. Negr1-/- mice show a time-dependent increase in behavioral sensitization to amphetamine associated with increased dopamine release in both the dorsal and ventral striatum. Upregulation of transcripts encoding dopamine and serotonin transporters and higher levels of several monoamines and their metabolites was evident in distinct brain areas of Negr1-/- mice. Chronic (23 days) escitalopram-induced reduction of serotonin and dopamine turnover is enhanced in Negr1-/- mice, and escitalopram rescued reduced weight of hippocampi in Negr1-/- mice. The current study is the first to show alterations in the brain monoaminergic systems in Negr1-deficient mice, suggesting that monoaminergic neural circuits contribute to both depressive and obesity-related phenotypes linked to the human NEGR1 gene.

Impact of a High-Fat Diet on the Metabolomics Profile of 129S6 and C57BL6 Mouse Strains

Different inbred mouse strains vary substantially in their behavior and metabolic phenotype under physiological and pathological conditions. The purpose of this study was to extend the knowledge of distinct coping strategies under challenging events in two differently adapting mouse strains: C57BL/6NTac (Bl6) and 129S6/SvEvTac (129Sv). Thus, we aimed to investigate possible similarities and differences in the body weight change, behavior, and several metabolic variables in Bl6 and 129Sv strains in response to high-fat diet (HFD) using the AbsoluteIDQ p180 kit. We found that 9 weeks of HFD induced a significant body weight gain in 129Sv, but not in Bl6 mice. Besides that, 129Sv mice displayed anxiety-like behavior in the open-field test. Metabolite profiling revealed that 129Sv mice had higher levels of circulating branched-chain amino acids, which were even more amplified by HFD. HFD also induced a decrease in glycine, spermidine, and t4-OH-proline levels in 129Sv mice. Although acylcarnitines (ACs) dominated in baseline conditions in 129Sv strain, this strain had a significantly stronger AC-reducing effect of HFD. Moreover, 129Sv mice had higher levels of lipids in baseline conditions, but HFD caused more pronounced alterations in lipid profile in Bl6 mice. Taken together, our results show that the Bl6 line is better adapted to abundant fat intake.

Special Issue: Emerging Paradigms in Insulin Resistance

This Biomedicines Special Issue was designed to attract articles that focused on different facets of biology relating to insulin resistance, defined as reduced cellular and organismal response to the insulin hormone, and its underlying mechanisms [...]

Anti-Obesity and Anti-Adipogenic Effects of Administration of Arginyl-Fructose-Enriched Jeju Barley (Hordeum vulgare L.) Extract in C57BL/6 Mice and in 3T3-L1 Preadipocytes Models

In our previous study, we reported that arginyl-fructose (AF), one of the Amadori rearrangement compounds (ARCs) produced by the heat processing of Korean ginseng can reduce carbohydrate absorption by inhibiting intestinal carbohydrate hydrolyzing enzymes in both in vitro and in vivo animal models. This reduced absorption of carbohydrate might be helpful to control body weight gain due to excessive carbohydrate consumption and support induced calorie restriction. However, the weight management effect, except for the effect due to anti-hyperglycemic action, along with the potential mechanism of action have not yet been determined. Therefore, the efforts of this study are to investigate and understand the possible weight management effect and mechanism action of AF-enriched barley extracts (BEE). More specifically, the effect of BEE on lipid accumulation and adipogenic gene expression, body weight gain, body weight, plasma lipids, body fat mass, and lipid deposition were evaluated using C57BL/6 mice and 3T3-L1 preadipocytes models. The formation of lipid droplets in the 3T3-L1 treated with BEE (500 and 750 µg/mL) was significantly blocked (p < 0.05 and p < 0.01, respectively). Male C57BL/6 mice were fed a high-fat diet (30% fat) for 8 weeks with BEE (0.3 g/kg-body weight). Compared to the high fat diet control (HFD) group, the cells treated with BEE significantly decreased in intracellular lipid accumulation with concomitant decreases in the expression of key transcription factors, peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer-binding protein alpha (CEBP/α), the mRNA expression of downstream lipogenic target genes such as fatty acid binding protein 4 (FABP4), fatty acid synthase (FAS), and sterol regulatory element-binding protein 1c (SREBP-1c). Supplementation of BEE effectively lowered the body weight gain, visceral fat accumulation, and plasma lipid concentrations. Compared to the HFD group, BEE significantly suppressed body weight gain (16.06 ± 2.44 g vs. 9.40 ± 1.39 g, p < 0.01) and increased serum adiponectin levels, significantly, 1.6-folder higher than the control group. These results indicate that AF-enriched barley extracts may prevent diet-induced weight gain and the anti-obesity effect is mediated in part by inhibiting adipogenesis and increasing adiponectin level.

Risk prediction of diabetes and pre-diabetes based on physical examination data

Diabetes is a metabolic disorder caused by insufficient insulin secretion and insulin secretion disorders. From health to diabetes, there are generally three stages: health, pre-diabetes and type 2 diabetes. Early diagnosis of diabetes is the most effective way to prevent and control diabetes and its complications. In this work, we collected the physical examination data from Beijing Physical Examination Center from January 2006 to December 2017, and divided the population into three groups according to the WHO (1999) Diabetes Diagnostic Standards: normal fasting plasma glucose (NFG) (FPG < 6.1 mmol/L), mildly impaired fasting plasma glucose (IFG) (6.1 mmol/L ≤ FPG < 7.0 mmol/L) and type 2 diabetes (T2DM) (FPG > 7.0 mmol/L). Finally, we obtained1,221,598 NFG samples, 285,965 IFG samples and 387,076 T2DM samples, with a total of 15 physical examination indexes. Furthermore, taking eXtreme Gradient Boosting (XGBoost), random forest (RF), Logistic Regression (LR), and Fully connected neural network (FCN) as classifiers, four models were constructed to distinguish NFG, IFG and T2DM. The comparison results show that XGBoost has the best performance, with AUC (macro) of 0.7874 and AUC (micro) of 0.8633. In addition, based on the XGBoost classifier, three binary classification models were also established to discriminate NFG from IFG, NFG from T2DM, IFG from T2DM. On the independent dataset, the AUCs were 0.7808, 0.8687, 0.7067, respectively. Finally, we analyzed the importance of the features and identified the risk factors associated with diabetes.