INPP4B protects from metabolic syndrome and associated disorders

A high fat diet and obesity have been linked to the development of metabolic dysfunction and the promotion of multiple cancers. The causative cellular signals are multifactorial and not yet completely understood. In this report, we show that Inositol Polyphosphate-4-Phosphatase Type II B (INPP4B) signaling protects mice from diet-induced metabolic dysfunction. INPP4B suppresses AKT and PKC signaling in the liver thereby improving insulin sensitivity. INPP4B loss results in the proteolytic cleavage and activation of a key regulator in de novo lipogenesis and lipid storage, SREBP1. In mice fed with the high fat diet, SREBP1 increases expression and activity of PPARG and other lipogenic pathways, leading to obesity and non-alcoholic fatty liver disease (NAFLD). Inpp4b−/− male mice have reduced energy expenditure and respiratory exchange ratio leading to increased adiposity and insulin resistance. When treated with high fat diet, Inpp4b−/− males develop type II diabetes and inflammation of adipose tissue and prostate. In turn, inflammation drives the development of high-grade prostatic intraepithelial neoplasia (PIN). Thus, INPP4B plays a crucial role in maintenance of overall metabolic health and protects from prostate neoplasms associated with metabolic dysfunction.


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02/10/2021
For RNA sequencing, the libraries were generated using the NEBNext® Ultra™ RNA Library Prep Kit and used for Illumina 150-bp pairedend sequencing. Quality control assessment was done using Illumina RNA-seq pipeline to estimate genomic coverage, percent alignment and nucleotide quality.
Raw reads were mapped to the reference mouse genome using HISAT2 and STAR software. For the differential analysis of known genes, the reads for each gene aligned by HISAT2 were counted using HTSeq software. Alignment by STAR was run with the option "quantMode TranscriptomeSAM" that allowed counting of reads aligned to each gene. Raw counts from HTSeq and STAR were imported into Bioconductor/R package DESeq2. Field-specific reporting Please select the one below that is the best fit for your research. If you are not sure, read the appropriate sections before making your selection.

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All studies must disclose on these points even when the disclosure is negative. The gene expression differences were analyzed using 2 way ANOVA. All data are presented as mean ± SEM. A sample size of 9 in each group has a 95% power to detect an effect size of 0.75 with a significance level (alpha) of 0.05. P-values less than 0.05 were considered statistically significant.
For RNA seq, we used the published data set for our estimation of samples size, and it is from AJPGI with comparisons of NAFLD vs CTRL. Prior data (from AJPGI) indicates that the average read count among the prognostic genes is about 400, the average dispersion is 0.1, and the ratio of the geometric mean of normalization factors is 1. We assumed that the total number of genes for testing will be 10,000, and the top 700 genes are prognostic. If the desired minimum fold change is 2.5, we estimated that we will need to study 4 subjects in each group to be able to reject the null hypothesis that the population means of the two groups are equal with probability (power) 0.8 using exact test. The FDR associated with this test of this null hypothesis is 0.1. For western blotting 4-6 samples per variable were used to achieve statistical significance of p<0.05 using 2-way ANOVA. The glucose tolerance test was performed with at least 7 mice in each group. The measurements were analyzed 2-way ANOVA.
No data were excluded from the analysis Three or more independent experiments were used for comparisons of mRNA and protein levels. Two independent groups spaced one year apart were analyzed for each of the following groups: WT/LFD, WT/HFD, Inpp4b-/-/LFD, and Inpp4b-/-/HFD to ensure reproducibility of the phenotypes.
Both wild-type or mutant female breeders were distributed randomly between low fat diet or high fat diet groups. All available pups were used for analyses.
Investigators for histological analyses were blinded to the animal's group allocation.