Loss of Malat1 does not modify age- or diet-induced adipose tissue accretion and insulin resistance in mice

The transcript level of long non-coding RNAs; MALAT1 and TUG1, and the association with metabolic syndrome-related parameters in women with overweight and obesity

Background

Recent studies have addressed the possible role of long non-coding RNAs (lnc-RNAs), Metastasis-Associated Lung Adenocarcinoma Transcript 1 (MALAT1), and Taurine Upregulated Gene 1 (TUG1), in modulating the underlying mechanisms of obesity-related metabolic abnormalities. However, studies are limited and contradictory. Hence, we sought to investigate the relationship of the transcript level of these two lnc-RNAs with metabolic syndrome (MetS)-related parameters in women with obesity and overweight.

Method

This cross-sectional study was conducted on 342 women with obese and overweight. We conducted assessments encompassing anthropometric measurements, body composition analysis, fasting blood sugar (FBS) levels, lipid profile analysis, insulin levels, HOMA-IR index, and liver enzyme profiling. A quantitative real-time polymerase chain reaction (PCR) was used to evaluate transcript levels of MALAT1 and TUG1. Also, a 147-question semi-quantitative food frequency questionnaire (FFQ) and the International Physical Activity Questionnaire (IPAQ) were used to evaluate food intake and physical activity, respectively.

Results

There was a significant association between FBS and MALAT1 transcript level (β: 0.382; 95% CI: 0.124, 0.640; P = 0.004). Also, there was a significant association between triglyceride (TG) and MALAT1 transcript level (β: 4.767; 95% CI: 2.803, 6.731; P < 0.0001). After adjusting for age, BMI, energy intake, and physical activity, an inverse significant association was observed between high-density lipoprotein cholesterol (HDL-c) and MALAT1 transcript level (β: -0.325; 95% CI: -0.644, -0.006; P = 0.046).

Conclusions

Our findings indicated positive associations between mRNA levels of MALAT1 and MetS-related parameters, including FBG, TG, HDL, and systolic blood pressure in overweight and obese women. However, large prospective studies are needed to further establish this concept.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01367-2.

MALAT1: A Long Non-Coding RNA with Multiple Functions and Its Role in Processes Associated with Fat Deposition

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) belongs to the lncRNA molecules, which are involved in transcriptional and epigenetic regulation and the control of gene expression, including the mechanism of chromatin remodeling. MALAT1 was first discovered during carcinogenesis in lung adenocarcinoma, hence its name. In humans, 66 of its isoforms have been identified, and in pigs, only 2 are predicted, for which information is available in Ensembl databases (Ensembl Release 111). MALAT1 is expressed in numerous tissues, including adipose, adrenal gland, heart, kidney, liver, ovary, pancreas, sigmoid colon, small intestine, spleen, and testis. MALAT1, as an lncRNA, shows a wide range of functions. It is involved in the regulation of the cell cycle, where it has pro-proliferative effects and high cellular levels during the G1/S and mitotic (M) phases. Moreover, it is involved in invasion, metastasis, and angiogenesis, and it has a crucial function in alternative splicing during carcinogenesis. In addition, MALAT1 plays a significant role in the processes of fat deposition and adipogenesis. The human adipose tissue stem cells, during differentiation into adipocytes, secrete MALAT1 as one the most abundant lncRNAs in the exosomes. MALAT1 expression in fat tissue is positively correlated with adipogenic FABP4 and LPL. This lncRNA is involved in the regulation of PPARγ at the transcription stage, fatty acid metabolism, and insulin signaling. The wide range of MALAT1 functions makes it an interesting target in studies searching for drugs to prevent obesity development in humans. In turn, in farm animals, it can be a source of selection markers to control the fat tissue content.

The interaction between MALAT1 and TUG1 with dietary fatty acid quality indices on visceral adiposity index and body adiposity index

We aimed to investigate the interaction between the transcript levels of taurine-upregulated gene 1 (TUG1) and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and the Cholesterol-Saturated Fat Index (CSI) in relation to the visceral adiposity index (VAI) and body adiposity index (BAI). This cross-sectional study involved 346 women classified as obese and overweight, aged between 18 and 48 years. Dietary intake and the quality of dietary fat were assessed using a validated and reliable 147-item semi-quantitative food frequency questionnaire, with the Cholesterol-Saturated Fat Index (CSI) used as an indicator. Transcription levels of MALAT1 and TUG1 were evaluated through real-time polymerase chain reaction following the criteria outlined in the Minimum Information for Publication of Quantitative standards. Serum profiles were measured using standard protocols. We observed a positive association between transcription level of MALAT1 and VAI in both crude (β = 3.646, 95% CI 1.950-5.341, p < 0.001) and adjusted (β = 8.338, 95% CI 6.110-10.566, p < 0.001) models. Furthermore, after adjusting for confounders, a significant positive interaction was noted between MALAT1 expression and CSI on BAI (β: 0.130, 95% CI 0.019, 0.240, p = 0.022), with a marginal positive interaction observed on VAI (β: 0.718, 95% CI - 0.028, 1.463, p = 0.059). It seems that there may be a positive interaction between MALAT1 transcription level and CSI on VAI and BAI among overweight and obese women. However, no associations were seen between TUG1 mRNA level and the above-mentioned outcomes. Further functional studies are still required to elucidate this concept.

Malat1 deficiency prevents hypoxia-induced lung dysfunction by protecting the access to alveoli

Hypoxia is common in lung diseases and a potent stimulator of the long non-coding RNA Metastasis-Associated Lung Adenocarcinoma Transcript 1 (MALAT1). Herein, we investigated the impact of Malat1 on hypoxia-induced lung dysfunction in mice. Malat1-deficient mice and their wild-type littermates were tested after 8 days of normoxia or hypoxia (10% oxygen). Hypoxia decreased elastance of the lung by increasing lung volume and caused in vivo hyperresponsiveness to methacholine without altering the contraction of airway smooth muscle. Malat1 deficiency also modestly decreased lung elastance but only when tested at low lung volumes and without altering lung volume and airway smooth muscle contraction. The in vivo responsiveness to methacholine was also attenuated by Malat1 deficiency, at least when elastance, a readout sensitive to small airway closure, was used to assess the response. More impressively, in vivo hyperresponsiveness to methacholine caused by hypoxia was virtually absent in Malat1-deficient mice, especially when hysteresivity, a readout sensitive to small airway narrowing heterogeneity, was used to assess the response. Malat1 deficiency also increased the coefficient of oxygen extraction and decreased ventilation in conscious mice, suggesting improvements in gas exchange and in clinical signs of respiratory distress during natural breathing. Combined with a lower elastance at low lung volumes at baseline, as well as a decreased propensity for small airway closure and narrowing heterogeneity during a methacholine challenge, these findings represent compelling evidence suggesting that the lack of Malat1 protects the access to alveoli for air entering the lung.

New long-non coding RNAs related to fat deposition based on pig model

Obesity is a problem in the last decades since the development of certain technologies has forced submission to a faster pace of life, resulting in nutritional changes. Domestic pigs are an excellent animal model in recognition of adiposity-related processes, corresponding to the size of individual organs, the distribution of body fat in the organism, and similar metabolism. The present study applied next-generation sequencing to identify adipose tissue (AT) transcriptomic signals related to increased fat content by identifying differentially expressed genes (DEGs), including long-non coding RNAs in Złotnicka White pigs (n=16). Moreover, besides commonly used functional analysis, we applied the Freiburg RNA tool to predict DE lncRNA targets based on calculation hybridisation energy. And in addition, DE lncRNAs were recognized based on information available in databases. The obtained results show that closely 230 gene expression was found to be dependent on fat content, included 8 lncRNAs. The most interesting was that among identified DE lncRNAs was transcript corresponding to human MALAT1, which was previously considered in the obesity-related context. Moreover, it was identified that in ENSSSCG00000048394, ENSSSCG00000047210, ENSSSCG00000047442 and ENSSSCG00000041577 lncRNAs are contained repeat insertion domains of LncRNAs (RIDLs) considered as important gene expression regulatory elements, and ENSSSCG00000041577 seems to be the host for mir1247(NR_031649.1). The analysis of energy hybridisation between DE lncRNAs and DEGs using the Freiburg IntaRNAv2 tool, including isoforms expressed in AT, showed that ENSSSCG00000047210 lncRNA interacted with the highest number of DEGs and ENSSSCG00000047210 expression was only correlated with positive fat-related DEGs. The functional analysis showed that down-regulated DEGs involved in ECM proteoglycan pathways could be under control of both positive and negative fat-related lncRNAs. The present study, using pigs as an animal model, expands our current knowledge of possible gene expression regulation by lncRNAs in fat tissue and indicates for MALAT1 role in the fat deposition determination, which function is still often questioned or doubtful.

A comprehensive review on high fat diet-induced diabetes mellitus: An epigenetic view

Modern lifestyle, genetics, nutritional overload through high-fat diet attributed prevalence and diabetes outcomes with various complications primarily due to obesity in which energy-dense diets frequently affect metabolic health. One possible issue usually associated with elevated chronic fat intake is insulin resistance, and hyperglycaemia constitutes an important function in altering the carbohydrates and lipids metabolism. Similarly, in assessing human susceptibility to weight gain and obesity, genetic variations play a central role, contributing to keen interest in identifying the possible role of epigenetics as a mediator of gene-environmental interactions influencing the production of type 2 diabetes mellitus and its related concerns. Epigenetic modifications associated with the acceptance of a sedentary lifestyle and environmental stress factors in response to energy intake and expenditure imbalances complement genetic alterations and lead to the production and advancement of metabolic disorders such as diabetes and obesity. Methylation of DNA, histone modifications and increases in the expression of non-coding RNAs can result in reduced transcriptional activity of key β-cell genes thus creating insulin resistance. Epigenetics contribute to changes in the expression of the underlying insulin resistance and insufficiency gene networks, along with low-grade obesity-related inflammation, increased ROS generation and DNA damage in multi organs. This review focused on epigenetic mechanisms and metabolic regulations associated with high fat diet (HFD)-induced diabetes mellitus.

The role of long noncoding RNA in lipid, cholesterol, and glucose metabolism and treatment of obesity syndrome

Obesity syndromes, characterized by abnormal lipid, cholesterol, and glucose metabolism, are detrimental to human health and cause many diseases, including obesity and type II diabetes. Increasing evidence has shown that long noncoding RNA (lncRNA), transcripts longer than 200 nucleotides that are not translated into proteins, play an important role in regulating abnormal metabolism in obesity syndromes. For the first time, we systematically summarize how lncRNA is involved in complex obesity metabolic syndromes, including the regulation of lipid, cholesterol, and glucose metabolism. Moreover, we discuss lncRNA involvement in food intake that mediates obesity syndromes. Furthermore, this review might shed new light on a lncRNA-based strategy for the prevention and treatment of obesity syndromes. Recent investigations support that lncRNA is a novel molecular target of obesity syndromes and should be emphasized. Namely, lncRNA plays a crucial role in the development of obesity syndrome process. Various lncRNAs are involved in the process of lipid, cholesterol, and glucose metabolism by regulating gene transcription, signaling pathway, and epigenetic modification of metabolism-related genes, proteins, and enzymes. Food intake could also induce abnormal expression of lncRNA associated with obesity syndrome, especially high-fat diet. Notably, some nanomolecules and natural extracts may target lncRNAs, associated with obesity syndrome, as a potential treatment for obesity syndromes.

Adipose tissue gene expression of long non-coding RNAs; MALAT1, TUG1 in obesity: is it associated with metabolic profile and lipid homeostasis-related genes expression?

BACKGROUND

Recent studies point toward the possible regulatory roles of two lncRNAs; metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and taurine upregulated gene 1 (TUG1) in the pathogenesis of obesity-related disorders and regulation of lipogenesis and adipogenesis. In an attempt to understand the molecules involved in human obesity pathogenesis, we aimed to evaluate the expression of MALAT1 and TUG1 in visceral adipose tissues (VAT) and subcutaneous adipose tissues (SAT) of obese women, as compared to normal-weight women. The mRNA expression of possible target genes including peroxisome proliferator-activated receptor gamma (PPARγ), PPARγ coactivator-1 alpha (PGC1α), sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) which are involved in adipogenesis and lipogenesis were also examined.

METHODS

This study was conducted on 20 obese [body mass index (BMI) ≥ 30 kg/m 2] female participants and 19 normal-weight (BMI < 25 kg/m 2) female participants. Real-time PCR was performed to investigate the mRNA expression of the above-mentioned genes in VAT and SAT from all participants.

RESULTS

The results showed lower mRNA levels of TUG1 in both the VAT and SAT of obese women, compared to normal-weight women. Furthermore, TUG1 expression in SAT positively correlated with BMI, waist circumference (WC), hip circumference, HOMA-IR, and insulin levels, eGFR value, creatinine levels, and hs-CRP in all participants independent of age and HOMA-IR. However, VAT mRNA expression of TUG1 had a positive correlation with obesity indices and HOMA-IR and insulin levels in the whole population. Moreover, SAT mRNA level of TUG1 was positively correlated with SAT gene expression of PGC1α, SREBP-1c, FAS, and ACC independent of age and HOMA-IR. Although mRNA expression of MALAT1 did not differ between two groups for any tissue, it was positively correlated with SAT mRNA levels of SREBP-1c, PPARγ, and their targets; FAS and ACC, as well as with VAT mRNA levels of PGC1α.

CONCLUSIONS

It seems likely that TUG1 with distinct expression pattern in VAT and SAT are involved in the regulation of lipogenic and adipogenic genes and obesity-related parameters. However, more studies are necessary to establish this concept.

Function and Mechanism of Long Noncoding RNAs in Adipocyte Biology

The last two decades have witnessed an explosion of interest in adipocyte biology, coinciding with the upsurge of obesity and metabolic syndrome. Now we have new perspectives on the distinct developmental origins of white, brown, and beige adipocytes and their role in metabolic physiology and disease. Beyond fuel metabolism, adipocytes communicate with the immune system and other tissues by releasing diverse paracrine and endocrine factors to orchestrate adipose tissue remodeling and maintain systemic homeostasis. Significant progress has been made in delineating the regulatory networks that govern different aspects of adipocyte biology. Here we provide an overview on the emerging role of long noncoding RNAs (lncRNAs) in the regulation of adipocyte development and metabolism and discuss the implications of the RNA-protein regulatory interface in metabolic control.

Role of epigenomic mechanisms in the onset and management of insulin resistance

The prevalence of insulin resistance (IR) is increasing rapidly worldwide and it is a relevant health problem because it is associated with several diseases, such as type 2 diabetes, cardiovascular disorders and cancer. Understanding the mechanisms involved in IR onset and progression will open new avenues for identifying biomarkers for preventing and treating IR and its co-diseases. Epigenetic mechanisms such as DNA methylation are important factors that mediate the environmental effect in the genome by regulating gene expression and consequently its effect on the phenotype and the development of disease. Taking into account that IR results from a complex interplay between genes and the environment and that epigenetic marks are reversible, disentangling the relationship between IR and epigenetics will provide new tools to improve the management and prevention of IR. Here, we review the current scientific evidence regarding the association between IR and epigenetic markers as mechanisms involved in IR development and potential management.