Adipocyte-specific deletion of PIP5K1c reduces diet-induced obesity and insulin resistance by increasing energy expenditure

Pip5k1γ promotes anabolism of nucleus pulposus cells and intervertebral disc homeostasis by activating CaMKII-Ampk pathway in aged mice

Degenerative disc disease (DDD) represents a significant global health challenge, yet its underlying molecular mechanisms remain elusive. This study aimed to investigate the role of type 1 phosphatidylinositol 4-phosphate 5-kinase (Pip5k1) in intervertebral disc (IVD) homeostasis and disease. All three Pip5k1 isoforms, namely Pip5k1α, Pip5k1β, and Pip5k1γ, were detectable in mouse and human IVD tissues, with Pip5k1γ displaying a highest expression in nucleus pulposus (NP) cells. The expression of Pip5k1γ was significantly down-regulated in the NP cells of aged mice and patients with severe DDD. To determine whether Pip5k1γ expression is required for disc homeostasis, we generated a Pip5k1γfl/fl; AggrecanCreERT2 mouse model for the conditional knockout of the Pip5k1γ gene in aggrecan-expressing IVD cells. Our findings revealed that the conditional deletion of Pip5k1γ did not affect the disc structure or cellular composition in 5-month-old adult mice. However, in aged (15-month-old) mice, this deletion led to several severe degenerative disc defects, including decreased NP cellularity, spontaneous fibrosis and cleft formation, and a loss of the boundary between NP and annulus fibrosus. At the molecular level, the absence of Pip5k1γ reduced the anabolism of NP cells without markedly affecting their catabolic or anti-catabolic activities. Moreover, the loss of Pip5k1γ significantly dampened the activation of the protective Ampk pathway in NP cells, thereby accelerating NP cell senescence. Notably, Pip5k1γ deficiency blunted the effectiveness of metformin, a potent Ampk activator, in activating the Ampk pathway and mitigating lumbar spine instability (LSI)-induced disc lesions in mice. Overall, our study unveils a novel role for Pip5k1γ in promoting anabolism and maintaining disc homeostasis, suggesting it as a potential therapeutic target for DDD.

Pip5k1c expression in osteocytes regulates bone remodeling in mice

Research background

The role of osteocytes in maintaining bone mass has been progressively emphasized. Pip5k1c is the most critical isoform among PIP5KIs, which can regulate cytoskeleton, biomembrane, and Ca2+ release of cells and participate in many processes, such as cell adhesion, differentiation, and apoptosis. However, its expression and function in osteocytes are still unclear.

Materials and methods

To determine the function of Pip5k1c in osteocytes, the expression of Pip5k1c in osteocytes was deleted by breeding the 10-kb mouse Dmp1-Cre transgenic mice with the Pip5k1cfl/fl mice. Bone histomorphometry, micro-computerized tomography analysis, immunofluorescence staining and western blotting were used to determine the effects of Pip5k1c loss on bone mass. In vitro, we explored the mechanism by siRNA knockdown of Pip5k1c in MLO-Y4 cells.

Results

Pip5k1c expression was decreased in osteocytes in senescent and osteoporotic tissues both in humans and mice. Loss of Pip5k1c in osteocytes led to a low bone mass in long bones and spines and impaired biomechanical properties in femur, without changes in calvariae. The loss of Pip5k1c resulted in the reduction of the protein level of type 1 collagen in tibiae and MLO-Y4 cells. Osteocyte Pip5k1c loss reduced the osteoblast and bone formation rate with high expression of sclerostin, impacting the osteoclast activities at the same time. Moreover, Pip5k1c loss in osteocytes reduced expression of focal adhesion proteins and promoted apoptosis.

Conclusion

Our studies demonstrate the critical role and mechanism of Pip5k1c in osteocytes in regulating bone remodeling.

The translational potential of this article

Osteocyte has been considered to a key role in regulating bone homeostasis. The present study has demonstrated that the significance of Pip5k1c in bone homeostasis by regulating the expression of collagen, sclerostin and focal adhesion expression, which provided a possible therapeutic target against human metabolic bone disease.

Identification of candidate SNPs and genes associated with resistance to nervous necrosis virus in leopard coral grouper (Plectropomus leopardus) using GWAS

The leopard coral grouper (Plectropomus leopardus), which has become increasingly popular in consumption due to its bright body color and great nutritional, holds a high economic and breeding potential. However, in recent years, the P.leopardus aquaculture industry has been impeded by the nervous necrosis virus (NNV) outbreak, leading to widespread mortality among fry and juvenile grouper. However, the genetic basis of resistance to NNV in P. leopardus remains to be investigated. In the present study, we conducted a genome-wide association analysis (GWAS) on 100 resistant and 100 susceptible samples to discover variants and potential genes linked with NNV resistance. For this study, 157,926 high-quality single nucleotide polymorphisms (SNPs) based on whole genome resequencing were discovered, and eighteen SNPs loci linked to disease resistance were discovered. We annotated six relevant candidate genes, including sik2, herc2, pip5k1c, npr1, mybpc3, and arhgap9, which showed important roles in lipid metabolism, oxidative stress, and neuronal survival. In the brain tissues of resistant and susceptible groups, candidate genes against NNV infection showed significant differential expression. The results indicate that regulating neuronal survival or pathways involved in lipid metabolism may result in increased resistance to NNV. Understanding the molecular mechanisms that lead to NNV resistance will be beneficial for the growth of the P. leopardus breeding sector. Additionally, the identified SNPs could be employed as biomarkers of disease resistance in P. leopardus, which will facilitate the selective breeding of grouper.

Global research trends on the links between insulin resistance and obesity: a visualization analysis

Background

Obesity increases the chance of developing insulin resistance. Numerous inflammatory markers have been linked to an increased risk of insulin resistance in obese individuals. Therefore, we performed a bibliometric analysis to determine global research activity and current trends in the field of obesity and insulin resistance.

Methods

Scopus was used between 2002 and 2021 to retrieve publications related to terms related to obesity and insulin resistance. Data were exported to Microsoft Excel. Additionally, we use VOSviewer software to create visualization maps that describe international collaborations and research hotspots.

Results

We identified 6626 publications, including 5754 journal articles, 498 review articles, and 109 letters to the editor. The most productive countries were the United States (n = 995, 30.11%), followed by China (n = 650, 9.81%), Italy (n = 412, 6.22%) and Spain (n = 386, 5.83%). Previously to 2012, this field was mainly focused on ‘adipocyte dysfunctions that link obesity with insulin resistance”; and ‘relationship between obesity, insulin resistance, and risk of cardiovascular disease’. ‘Supplements improve insulin sensitivity‘, and ‘obesity-induced inflammation and insulin resistance’ were found more recently (after 2014), indicating that research in this field has acquired significant interest and emphasis in recent years.

Conclusions

This is the first bibliometric study to focus on publications related to insulin resistance and obesity at the global level. Our reporting of quantifiable knowledge in this field may be useful in providing evidence and direction for future research, clinical practice, and educational initiatives.

Construction and Comprehensive Analysis of miRNAs and Target mRNAs in Longissimus dorsi Muscle of Queshan Black and Large White Pigs

A miRNA-mRNA combination analysis was performed on the longissimus dorsi muscle of adult Queshan Black and Large White pigs by RNA-seq technology to reveal the molecular mechanism affecting pork quality traits. The sequencing results showed that 39 miRNAs were differentially expressed between Queshan Black and Large White pigs, which targeted 5234 mRNAs, and 15 differentially expressed miRNAs targeted 86 differentially expressed mRNAs. The qRT-PCR results showed that miRNAs showed similar expression patterns to RNA-seq. The GO analysis indicated that differentially expressed miRNAs with differential target mRNAs were primarily involved in biological processes such as phospholipase activity, MAP-kinase scaffold activity, lipase activity, and regulation of the extent of cell growth. The KEGG analysis also revealed that such mRNAs were significantly enriched in the ECM-receptor interaction, sphingolipid metabolism, apoptosis, PI3K-Akt signaling pathway, and AMPK signaling pathway. In addition, software predictions showed that 17 (13 of which were upregulated and four were downregulated) of 39 differentially expressed miRNAs targeted 118 negatively correlated expression mRNAs. The upregulated miRNAs contained 103 negatively correlated target mRNAs, whereas the downregulated miRNAs contained 15 negatively correlated target mRNAs. The GO analysis showed that such mRNAs were primarily involved in MAP-kinase scaffold activity, myoblast development, and peptidyl-lysine methylation, and the KEGG analysis showed significant enrichment in ECM-receptor interaction and focal adhesion. The functional enrichment analysis of miRNA target genes revealed that miR-328 was screened out as a key miRNA, and preliminary functional validation was performed. Moreover, the overexpressed miR-328 could affect the expression of proliferation-related genes, such as CDK2, CDK4, CCNB1, CCND1, CCNE1, and PCNA. These results indicated that miR-328 may regulate fat deposition and affect meat quality by influencing related pathways. This study revealed that the miRNA−mRNA regulatory axis affects fat deposition and skeletal muscle development, which provides a theoretical basis for further study on the molecular mechanism of meat quality.

Recent Advances in the Treatment of Insulin Resistance Targeting Molecular and Metabolic Pathways: Fighting a Losing Battle?

Diabetes Mellitus (DM) is amongst the most notable causes of years of life lost worldwide and its prevalence increases perpetually. The disease is characterized as multisystemic dysfunctions attributed to hyperglycemia resulting directly from insulin resistance (IR), inadequate insulin secretion, or enormous glucagon secretion. Insulin is a highly anabolic peptide hormone that regulates blood glucose levels by hastening cellular glucose uptake as well as controlling carbohydrate, protein, and lipid metabolism. In the course of Type 2 Diabetes Mellitus (T2DM), which accounts for nearly 90% of all cases of diabetes, the insulin response is inadequate, and this condition is defined as Insulin Resistance. IR sequela include, but are not limited to, hyperglycemia, cardiovascular system impairment, chronic inflammation, disbalance in oxidative stress status, and metabolic syndrome occurrence. Despite the substantial progress in understanding the molecular and metabolic pathways accounting for injurious effects of IR towards multiple body organs, IR still is recognized as a ferocious enigma. The number of widely available therapeutic approaches is growing, however, the demand for precise, safe, and effective therapy is also increasing. A literature search was carried out using the MEDLINE/PubMed, Google Scholar, SCOPUS and Clinical Trials Registry databases with a combination of keywords and MeSH terms, and papers published from February 2021 to March 2022 were selected as recently published papers. This review paper aims to provide critical, concise, but comprehensive insights into the advances in the treatment of IR that were achieved in the last months.

Pip5k1c Loss in Chondrocytes Causes Spontaneous Osteoarthritic Lesions in Aged Mice

Osteoarthritis (OA) is the most common degenerative joint disease affecting the older populations globally. Phosphatidylinositol-4-phosphate 5-kinase type-1 gamma (Pip5k1c), a lipid kinase catalyzing the synthesis of phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2), is involved in various cellular processes, such as focal adhesion (FA) formation, cell migration, and cellular signal transduction. However, whether Pip5k1c plays a role in the pathogenesis of OA remains unclear. Here we show that inducible deletion of Pip5k1c in aggrecan-expressing chondrocytes (cKO) causes multiple spontaneous OA-like lesions, including cartilage degradation, surface fissures, subchondral sclerosis, meniscus deformation, synovial hyperplasia, and osteophyte formation in aged (15-month-old) mice, but not in adult (7-month-old) mice. Pip5k1c loss promotes extracellular matrix (ECM) degradation, chondrocyte hypertrophy and apoptosis, and inhibits chondrocyte proliferation in the articular cartilage of aged mice. Pip5k1c loss dramatically downregulates the expressions of several key FA proteins, including activated integrin β1, talin, and vinculin, and thus impairs the chondrocyte adhesion and spreading on ECM. Collectively, these findings suggest that Pip5k1c expression in chondrocytes plays a critical role in maintaining articular cartilage homeostasis and protecting against age-related OA.