Abstract

   The global obesity epidemic particularly affects women of reproductive
   age. Offspring of obese mothers suffer from an increased risk of liver
   disease but the molecular mechanisms involved remain unknown. We
   performed an integrative genomic analysis of datasets that investigated
   the impact of maternal obesity on the hepatic gene expression profile
   of the offspring in mice. Furthermore, we developed a murine model of
   maternal obesity and studied the development of liver disease and the
   gene expression profile of the top dysregulated genes by quantitative
   real-time polymerase chain reaction (qPCR). Our data are available for
   interactive exploration on our companion webpage. We identified five
   publicly available datasets relevant to our research question. Pathways
   involved in metabolism, the innate immune system, the clotting cascade,
   and the cell cycle were consistently dysregulated in the offspring of
   obese mothers. Concerning genes involved in the development of liver
   disease, Egfr, Vegfb, Wnt2, Pparg and six other genes were dysregulated
   in multiple independent datasets. In our own model, we observed a
   higher tendency towards the development of non-alcoholic liver disease
   (60 vs. 20%) and higher levels of alanine aminotransferase (41.0 vs.
   12.5 IU/l, p = 0.008) in female offspring of obese mothers. Male
   offspring presented higher levels of liver fibrosis (2.4 vs. 0.6%
   relative surface area, p = 0.045). In a qPCR gene expression analysis
   of our own samples, we found Fgf21, Pparg, Ppard, and Casp6 to be
   dysregulated by maternal obesity. Maternal obesity represents a looming
   threat to the liver health of future generations. Our comprehensive
   transcriptomic analysis will help to better understand the mechanisms
   of the development of liver disease in the offspring of obese mothers
   and can give rise to further explorations.

   Keywords: maternal obesity, liver disease, whole-genome expression
   analysis, transcriptomics, non-alcoholic fatty liver disease,
   developmental origins of health and disease

1. Introduction

   We are living in a time of a global obesity epidemic with a global
   obesity rate that has doubled over the past 40 years and is predicted
   to reach 50% in the USA by 2030 [[48]1,[49]2]. Obesity is also
   associated with an elevated risk for several major chronic diseases
   such as type 2 diabetes, cardiovascular disease, some cancers, and
   chronic liver disease [[50]3,[51]4]. Women of reproductive age are
   particularly affected by obesity and close to one-third of children in
   the USA are born to obese mothers with a rising trend [[52]5,[53]6].

   Besides increased perinatal complications, maternal obesity also leads
   to increased morbidity in the children of obese mothers
   [[54]6,[55]7,[56]8]. In particular, maternal obesity is a risk factor
   for compromised cognitive development, metabolic syndrome, and even
   childhood cancers [[57]9,[58]10,[59]11]. Additionally, murine studies
   have shown that pups born to obese mothers exhibit an increased risk of
   developing liver diseases such as steatosis and signs of hepatitis such
   as increased inflammatory markers and fibrosis [[60]12,[61]13]. A
   recent epidemiological study confirmed these results and demonstrated
   that the offspring of obese mothers had a threefold higher risk of
   developing non-alcoholic liver disease (NAFLD) in adulthood [[62]14].

   Several studies have explored the expression of selected genes, and a
   number of groups have performed whole-genome expression profiling
   [[63]13,[64]15,[65]16,[66]17,[67]18,[68]19,[69]20,[70]21,[71]22] in the
   offspring of obese mothers. Study heterogeneity, the multifactorial
   etiology of the disease, and the comparatively small impact on gene
   expression by maternal obesity have not allowed clear identification of
   the molecular pathways involved in the development of chronic liver
   disease. The aim of this study is to identify the major pathways and
   genes associated with the development of liver disease in the offspring
   of obese mothers.

   Due to the heterogeneity of the available data, we chose to perform an
   integrative genomic analysis of all available datasets studying the
   transcriptional impact of maternal obesity. This allowed us to identify
   genes and pathways that were dysregulated most consistently among the
   different studies. In the next step, we developed our own model of
   maternal obesity and characterized the offspring. We then used the
   information that we obtained from the integrative genomic analysis to
   study the most consistently dysregulated genes in our own samples. The
   raw results of our analysis are publicly available for different
   analyses by other groups combined with a web-based tool for the
   analysis of specific genes
   ([72]http://www.genebrowser.unige.ch/maternalobesity/, accessed on 29
   November 2021).

2. Materials and Methods

2.1. Database Search

   We performed a search of the Gene Expression Omnibus (GEO) [[73]23]
   from the National Center for Biotechnology Information for gene
   expression datasets using the following search term ((“obesity”[MeSH
   Terms] OR obese[All Fields]) OR fat[All Fields] OR western[All Fields])
   AND (F1[All Fields] OR offspring[All Fields]) AND ((“liver”[MeSH Terms]
   OR liver[All Fields]) OR hepatic[All Fields]). Only mouse studies were
   included in our analysis. Additionally, the Center for Information
   Biology Gene Expression database (CIBEX) [[74]24] and ArrayExpress
   [[75]25] were searched with similar search terms but no additional hits
   were retrieved ([76]Figure S1).

2.2. Qualtitative Literature Search to Identify Pathways and Genes Relevant
for the Progression of Liver Disease

   We performed a qualitative literature search to identify genes and
   pathways that have been identified previously as relevant for the
   development or the progression of non-alcoholic fatty liver disease
   (NAFLD) or non-alcoholic steatohepatitis (NASH). Additionally, we
   included genes that were identified by other groups to play a role in
   the development of liver disease in the offspring of obese mothers. A
   full list of pathways and genes with references is available under