Surplus fat rapidly increases fat oxidation and insulin resistance in lipodystrophic mice

Differential expression of microRNAs in serum exosomes of obese and non-obese mice and analysis of their function

OBJECTIVE

To extract exosomes from obese and non-obese mice, screen specifically expressed microRNAs by high-throughput sequencing and explore their roles.

METHODS

An animal obesity model was constructed, and the successful construction of the obesity model was verified by HE staining, Western Blot and RT-qPCR. In addition, exosomes were extracted and verified by Western Blot. High-throughput sequencing was performed on the extracted serum exosomes to screen for differentially expressed microRNAs. fluorescence quantitative RT-PCR (RT-qPCR) was used to validate the differentially expressed miRNAs and explore their functions.

RESULTS

8 microRNAs were up-regulated and 11 microRNAs were down-regulated. mmu-miR-674-5p and X_28316 were significantly down-regulated and had the greatest impact on protein pathways. 8_13258 was significantly up-regulated and affected multiple protein pathways. GO enrichment analysis suggested that the differentially expressed microRNAs were mainly involved in the cleavage of microtubule activity, transferase activity/transferase pentameric acid. GO enrichment analysis suggested that differentially expressed microRNAs were mainly involved in the processes of cleavage microtubule activity, transferase activity/transfer pentamer, and threonine phosphatase/threonine kinase activity.KEGG pathway enrichment analysis showed that differentially expressed microRNAs were mainly involved in the processes of regulating the phosphorylation of TP53 activity, the G2/M DNA damage checkpoint, and the processing of the ends of DNA double-strand breaks. Protein interaction networks were enriched for Stat3, Fgr, Camk2b, Rac1, Asb6, and Ankfy1. Suggesting that they may be mediated by differential genes to participate in the process of insulin resistance. qRT-PCR results showed that the expression trend of mmu-miR-674-5p was consistent with the sequencing results. It suggests that it may be able to participate in the regulation of insulin resistance as a target gene.

CONCLUSION

microRNAs were differentially expressed in serum exosomes of obese and non-obese mice and might be involved in the specific regulation of insulin resistance. mmu-miR-674-5p was differentially expressed significantly and the validation trend was consistent with it, suggesting that it might be able to participate in the regulation of insulin resistance as a target gene.

Compound probiotics producing cellulase could replace cellulase preparations during solid-state fermentation of millet bran

Low-value agricultural by-products can be converted into high-value biological products by fermentation with probiotic strains or by enzymatic hydrolysis. However, the high costs of enzyme preparations significantly limit their applications in fermentation. In this study, the solid-state fermentation of millet bran was performed using a cellulase preparation and compound probiotics producing cellulase (CPPC), respectively. The results showed that both factors effectively destroyed the fiber structure, reduced the crude fiber content by 23.78% and 28.32%, respectively, and significantly increased the contents of beneficial metabolites and microorganisms. Moreover, CPPC could more effectively reduce the anti-nutrient factors and increase the content of anti-inflammatory metabolites. The correlation analysis revealed that Lactiplantibacillus and Issatchenkia had synergistic growth during fermentation. Overall, these results suggested that CPPC could replace cellulase preparation and improve antioxidant properties while reducing anti-nutrient factors of millet bran, thus providing a theoretical reference for the efficient utilization of agricultural by-products.

Resting and exercise metabolic characteristics in obese children with insulin resistance

Purpose: This study aimed to explore the characteristics of resting energy expenditure (REE) and lipid metabolism during incremental load exercise in obese children and adolescents with insulin resistance (IR) to provide evidence for exercise intervention in obese children and adolescents with IR.

Method: From July 2019 to August 2021, 195 obese children and adolescents aged 13–17 were recruited through a summer camp. The participants were divided into IR (n = 67) and no-IR (without insulin resistance, n = 128) groups and underwent morphology, blood indicators, body composition, and resting energy consumption gas metabolism tests. Thirty participants each were randomly selected from the IR and no-IR groups to carry out the incremental treadmill test.

Results: Significant metabolic differences in resting and exercise duration were found between the IR and no-IR groups. In the resting state, the resting metabolic equivalents (4.33 ± 0.94 ml/min/kg vs. 3.91 ± 0.73 ml/min/kg, p = 0.001) and REE (2464.03 ± 462.29 kcal/d vs. 2143.88 ± 380.07 kcal/d, p < 0.001) in the IR group were significantly higher than in the no-IR group. During exercise, the absolute maximal fat oxidation (0.33 ± 0.07 g/min vs. 0.36 ± 0.09 g/min, p = 0.002) in the IR group was significantly lower than in the no-IR group; maximal fat oxidation intensity (130.9 ± 8.9 bpm vs. 139.9 ± 7.4 bpm, p = 0.040) was significantly lower in the IR group.

Conclusion: Significant resting and exercise metabolic differences were found between obese IR and no-IR children and adolescents. Obese IR children and adolescents have higher REE and lower maximal fat oxidation intensity than obese no-IR children and adolescents.

Pasteurized Akkermansia muciniphila Reduces Fat Accumulation via nhr-49-Mediated Nuclear Hormone Signaling Pathway in Caenorhabditis elegans

Pasteurized Akkermansia muciniphila (p-AKK) is related to lipid metabolism and helps control obesity. The main goal of this study was to investigate the role and mechanism of p-AKK in lipid metabolism using Caenorhabditis elegans. The results showed that p-AKK increased the healthy lifespan of nematodes and helped maintain exercise ability in aging, suggesting a potential increase in energy expenditure. The overall fat deposition and triglyceride level were significantly decreased and the p-AKK anti-oxidative stress helped to regulate fatty acid composition. Additionally, the transcriptome results showed that p-AKK increased the expression of lipo-hydrolase and fatty acid β-oxidation-related genes, including lipl-4, nhr-49, acs-2 and acdh-8, while it decreased the expression of fat synthesis-related genes, including fat-7, elo-2 and men-1. These results partially explain the mechanisms underlying the fact that p-AKK decreases fat accumulation of C. elegans via nhr-49/acs-2-mediated signaling involved in fatty acid β-oxidation and synthesis.

Exercise as an Aging Mimetic: A New Perspective on the Mechanisms Behind Exercise as Preventive Medicine Against Age-Related Chronic Disease

Age-related chronic diseases are among the most common causes of mortality and account for a majority of global disease burden. Preventative lifestyle behaviors, such as regular exercise, play a critical role in attenuating chronic disease burden. However, the exact mechanism behind exercise as a form of preventative medicine remains poorly defined. Interestingly, many of the physiological responses to exercise are comparable to aging. This paper explores an overarching hypothesis that exercise protects against aging/age-related chronic disease because the physiological stress of exercise mimics aging. Acute exercise transiently disrupts cardiovascular, musculoskeletal, and brain function and triggers a substantial inflammatory response in a manner that mimics aging/age-related chronic disease. Data indicate that select acute exercise responses may be similar in magnitude to changes seen with +10–50 years of aging. The initial insult of the age-mimicking effects of exercise induces beneficial adaptations that serve to attenuate disruption to successive “aging” stimuli (i.e., exercise). Ultimately, these exercise-induced adaptations reduce the subsequent physiological stress incurred from aging and protect against age-related chronic disease. To further examine this hypothesis, future work should more intricately describe the physiological signature of different types/intensities of acute exercise in order to better predict the subsequent adaptation and chronic disease prevention with exercise training in healthy and at-risk populations.

Regulation of lipoprotein metabolism by ANGPTL3, ANGPTL4, and ANGPTL8

Triglyceride-rich lipoproteins deliver fatty acids to tissues for oxidation and for storage. Release of fatty acids from circulating lipoprotein triglycerides is carried out by lipoprotein lipase (LPL), thus LPL serves as a critical gatekeeper of fatty acid uptake into tissues. LPL activity is regulated by a number of extracellular proteins including three members of the angiopoietin-like family of proteins. In this review, we discuss our current understanding of how, where, and when ANGPTL3, ANGPTL4, and ANGPTL8 regulate lipoprotein lipase activity, with a particular emphasis on how these proteins interact with each other to coordinate triglyceride metabolism and fat partitioning.

Adipocyte-Specific Deletion of Lamin A/C Largely Models Human Familial Partial Lipodystrophy Type 2

Mechanisms by which autosomal recessive mutations in Lmna cause familial partial lipodystrophy type 2 (FPLD2) are poorly understood. To investigate the function of lamin A/C in adipose tissue, we created mice with an adipocyte-specific loss of Lmna (Lmna ^ADKO). Although Lmna ^ADKO mice develop and maintain adipose tissues in early postnatal life, they show a striking and progressive loss of white and brown adipose tissues as they approach sexual maturity. Lmna ^ADKO mice exhibit surprisingly mild metabolic dysfunction on a chow diet, but on a high-fat diet they share many characteristics of FPLD2 including hyperglycemia, hepatic steatosis, hyperinsulinemia, and almost undetectable circulating adiponectin and leptin. Whereas Lmna ^ADKO mice have reduced regulated and constitutive bone marrow adipose tissue with a concomitant increase in cortical bone, FPLD2 patients have reduced bone mass and bone mineral density compared with controls. In cell culture models of Lmna deficiency, mesenchymal precursors undergo adipogenesis without impairment, whereas fully differentiated adipocytes have increased lipolytic responses to adrenergic stimuli. Lmna ^ADKO mice faithfully reproduce many characteristics of FPLD2 and thus provide a unique animal model to investigate mechanisms underlying Lmna-dependent loss of adipose tissues.

PI3K/Akt pathway expression in children with different obesity degrees and its relationship with glucolipid metabolism and insulin resistance

OBJECTIVE

This study investigated and analyzed the expression of PI3K/Akt pathway in children with different degree of obesity and its connection with glucolipid metabolism and insulin resistance (IR).

METHODS

157 children with simple obesity, who admitted to our hospital from March 2020 to September 2020, were enrolled as obesity group. These children were divided into mild-group (n=67), moderate-group (n=55) and severe-group (n=35) referring to their body mass index (BMI). Another 60 healthy children admitted to hospitalized were randomly chosen as control group. The expression of PI3K mRNA and Akt mRNA in peripheral blood mononuclear cells (PBMCs) of each group were detected by RT-PCR, and its connection with glucose and lipid metabolism, as well as IR was analyzed.

RESULTS

Each group of children had insignificant difference in FBG (Fasting blood glucose) level (P>0.05). The triglyceride (TG), total cholesterol (TC), Low-density lipoprotein (LDL), Fasting insulin (FINS) and Homeostasis model assessment insulin resistance (HOMA-IR) levels in each obesity group were substantially higher than those in control group (P<0.05), and these levels decreased remarkably with the increase of obesity severity (P<0.05). The high-density lipoprotein (HDL) level of children in each obesity group was notably lower than that of the control group (P<0.05), and the level decreased remarkably with the ascending degree of obesity (P<0.05). The levels of PI3K mRNA and Akt mRNA in PBMCs of children in each obesity group were obviously lower than those in control group (P<0.05), and these index levels decreased much with the increasing worsen of children's obesity degree (P<0.05). The relative expression of PI3K mRNA and Akt mRNA in children with simple obesity was negatively correlated with TG, TC, LDL, FINS and HOMA-IR (P<0.05), positively correlated with HDL (P<0.05), and was not associated with FBG level (P>0.05).

CONCLUSION

The inhibition of PI3K/Akt signaling pathway in children with simple obesity is associated with the abnormal glucolipid metabolism and IR, which affects the occurrence and progression of obesity.

Pathophysiological role of metabolic flexibility on metabolic health

Glucose, fatty acids, and amino acids among others are oxidized to generate adenosine triphosphate (ATP). These fuels are supplied from the environment (through food intake) and internal depots (through lipolysis, glycogenolysis, and proteolysis) at different rates throughout the day. Complex adaptive systems permit to accommodate fuel oxidation according to fuel availability. This capacity of a cell, tissue, or organism to adapt fuel oxidation to fuel availability is defined as metabolic flexibility (MetF). There are conditions, such as insulin resistance, diabetes, and obesity, in which MetF seems to be impaired. The observation that those conditions are accompanied by mitochondrial dysfunction has set the basis to propose a link between mitochondrial dysfunction, metabolic inflexibility, and metabolic health. We here highlight the evidence about the notion that MetF influences metabolic health.

Combination Usage of AdipoCount and Image-Pro Plus/ImageJ Software for Quantification of Adipocyte Sizes

In recent decades, the prevalence of obesity has been rising. One of the major characteristics of obesity is fat accumulation, including hyperplasia (increase in number) and hypertrophy (increase in size). After histological staining, it is critical to accurately measure the number and size of adipocytes for assessing the severity of obesity in a timely fashion. Manual measurement is accurate but time-consuming. Although commercially available adipocyte counting tools, including AdipoCount, Image-Pro Plus, and ImageJ were helpful, limitations still exist in accuracy and time consuming. In the present study, we introduced the protocol of combined usage of these tools and illustrated the process with histological staining slides from adipose tissues of lean and obese mice. We found that the adipocyte sizes quantified by the tool combination were comparable as manual measurement, whereas the combined methods were more efficient. Besides, the recognition effect of monochrome segmentation image is better than that of color segmentation image. Overall, we developed a combination method to measure adipocyte sizes accurately and efficiently, which may be helpful for experimental process in laboratory and also for clinic diagnosis.

Aging and plasma triglyceride metabolism

The risk for metabolic disease, including metabolic syndrome, insulin resistance, and diabetes, increases with age. Altered plasma TG metabolism and changes in fatty acid partitioning are also major contributors to metabolic disease. Plasma TG metabolism itself is altered by age in humans and rodents. As discussed in this review, the age-induced changes in human TG metabolism include increased plasma TG levels, reduced postprandial plasma TG clearance rates, reduced postheparin LPL activity, decreased adipose tissue lipolysis, and elevated ectopic fat deposition, all of which could potentially contribute to age-associated metabolic diseases. Similar observations have been made in aged rats. We highlight the limitations of currently available data and propose that mechanistic studies are needed to understand the extent to which age-induced alterations in TG metabolism contribute to metabolic disease. Such mechanistic insights could aid in therapeutic strategies for preventing or managing metabolic disease in older individuals.

Lipodystrophic syndromes: From diagnosis to treatment

Lipodystrophic syndromes are acquired or genetic rare diseases, characterised by a generalised or partial lack of adipose tissue leading to metabolic alterations linked to strong insulin resistance. They encompass a variety of clinical entities due to primary defects in adipose differentiation, in the structure and/or regulation of the adipocyte lipid droplet, or due to immune-inflammatory aggressions, chromatin deregulations and/or mitochondrial dysfunctions affecting adipose tissue. Diagnosis is based on clinical examination, pathological context and comorbidities, and on results of metabolic investigations and genetic analyses, which together determine management and genetic counselling. Early lifestyle and dietary measures focusing on regular physical activity and avoiding excess energy intake are crucial. They are accompanied by multidisciplinary follow-up adapted to each clinical form. In case of hyperglycemia, antidiabetic medications, with metformin as a first-line therapy in adults, are used in addition to lifestyle and dietary modifications. When standard treatments have failed to control metabolic disorders, the orphan drug metreleptin, an analog of leptin, can be effective in certain forms of lipodystrophy syndrome. Metreleptin therapy indications, prescription and monitoring were recently defined in France, representing a major improvement in patient care.

Deficiency of T cell CD40L has minor beneficial effects on obesity-induced metabolic dysfunction

OBJECTIVE

Obesity-associated metabolic dysfunction increases the risk of multiple diseases such as type 2 diabetes and cardiovascular disease. The importance of the co-stimulatory CD40-CD40L dyad in diet-induced obesity (DIO), with opposing phenotypes arising when either the receptor (aggravating) or the ligand (protective) is deleted, has been described previously. The functions of CD40 and CD40L are cell type dependent. As co-stimulation via T cell-mediated CD40L is essential for driving inflammation, we here investigate the role of T cell CD40L in DIO.

RESEARCH DESIGN AND METHODS

CD4CreCD40L^fl/fl mice on a C57BL/6 background were generated and subjected to DIO by administration of 15 weeks of high fat diet (HFD).

RESULTS

HFD-fed CD4CreCD40L^fl/fl mice had similar weight gain, adipocyte sizes, plasma cholesterol and triglyceride levels as their wild-type (WT) counterparts. Insulin and glucose tolerance were comparable, although CD4CreCD40L^fl/fl mice did have a decreased plasma insulin concentration, suggesting a minor improvement of insulin resistance. Furthermore, although the degree of hepatosteatosis was similar in both genotypes, the gene expression of fatty acid synthase 1 and ATP-citrate lyase had decreased, whereas expression of peroxisome proliferator-activated receptor-α had increased in livers of CD4CreCD40L^fl/fl mice, suggesting decreased hepatic lipid uptake in absence of T cell CD40L.Moreover, CD4CreCD40L^fl/fl mice displayed significantly lower numbers of effector memory CD4⁺ T cells and regulatory T cells in blood and lymphoid organs compared with WT. However, immune cell composition and inflammatory status of the adipose tissue was similar in CD4CreCD40L^fl/fl and WT mice.

CONCLUSIONS

T cell CD40L deficiency results in a minor improvement of insulin sensitivity and hepatic steatosis in DIO, despite the strong decrease in effector T cells and regulatory T cells in blood and lymphoid organs. Our data indicate that other CD40L-expressing cell types are more relevant in the pathogenesis of obesity-associated metabolic dysfunction.

Phenotypic and Genetic Characteristics of Lipodystrophy: Pathophysiology, Metabolic Abnormalities, and Comorbidities

PURPOSE OF REVIEW

This article focuses on recent progress in understanding the genetics of lipodystrophy syndromes, the pathophysiology of severe metabolic abnormalities caused by these syndromes, and causes of severe morbidity and a possible signal of increased mortality associated with lipodystrophy. An updated classification scheme is also presented.

RECENT FINDINGS

Lipodystrophy encompasses a group of heterogeneous rare diseases characterized by generalized or partial lack of adipose tissue and associated metabolic abnormalities including altered lipid metabolism and insulin resistance. Recent advances in the field have led to the discovery of new genes associated with lipodystrophy and have also improved our understanding of adipose biology, including differentiation, lipid droplet assembly, and metabolism. Several registries have documented the natural history of the disease and the serious comorbidities that patients with lipodystrophy face. There is also evolving evidence for increased mortality rates associated with lipodystrophy. Lipodystrophy syndromes represent a challenging cluster of diseases that lead to severe insulin resistance, a myriad of metabolic abnormalities, and serious morbidity. The understanding of these syndromes is evolving in parallel with the identification of novel disease-causing mechanisms.

Muscle and adipose tissue insulin resistance: malady without mechanism?

Insulin resistance is a major risk factor for numerous diseases, including type 2 diabetes and cardiovascular disease. These disorders have dramatically increased in incidence with modern life, suggesting that excess nutrients and obesity are major causes of "common" insulin resistance. Despite considerable effort, the mechanisms that contribute to common insulin resistance are not resolved. There is universal agreement that extracellular perturbations, such as nutrient excess, hyperinsulinemia, glucocorticoids, or inflammation, trigger intracellular stress in key metabolic target tissues, such as muscle and adipose tissue, and this impairs the ability of insulin to initiate its normal metabolic actions in these cells. Here, we present evidence that the impairment in insulin action is independent of proximal elements of the insulin signaling pathway and is likely specific to the glucoregulatory branch of insulin signaling. We propose that many intracellular stress pathways act in concert to increase mitochondrial reactive oxygen species to trigger insulin resistance. We speculate that this may be a physiological pathway to conserve glucose during specific states, such as fasting, and that, in the presence of chronic nutrient excess, this pathway ultimately leads to disease. This review highlights key points in this pathway that require further research effort.