Heterogeneous effects of individual high-fat diet compositions on phenotype, metabolic outcome, and hepatic proteome signature in BL/6 male mice.

The multitude of obesogenic diets used in rodent studies can hardly be overviewed. Since standardization is missing and assuming that individual compositions provoke individual effects, the choice of quality, quantity and combination of diet ingredients seems to be crucial for the outcome and interpretation of obesity studies. Therefore, the present study was conducted to compare the individual effects of three commonly used obesogenic diets, mainly differing in sugar and fat content. Besides basic phenotypic and metabolic characterization, one main aspect was a comparative liver proteome analysis. As expected, the obtained results picture differentiated consequences mainly depending on fat source and/or fat- and sugar quantity. By confirming the general presumption that the choice of nutritional composition is a pivotal factor, the present findings demonstrate that a conscious selection is indispensable for obtaining reliable and sound results in obesity research. In conclusion, we strongly recommend a careful selection of the appropriate diet in advance of a new experiment, taking into account the specific research question.

Metformin Prevents Key Mechanisms of Obesity-Related Complications in Visceral White Adipose Tissue of Obese Pregnant Mice.

With the gaining prevalence of obesity, related risks during pregnancy are rising. Inflammation and oxidative stress are considered key mechanisms arising in white adipose tissue (WAT) sparking obesity-associated complications and diseases. The established anti-diabetic drug metformin reduces both on a systemic level, but only little is known about such effects on WAT. Because inhibiting these mechanisms in WAT might prevent obesity-related adverse effects, we investigated metformin treatment during pregnancy using a mouse model of diet-induced maternal obesity. After mating, obese mice were randomised to metformin administration. On gestational day G15.5, phenotypic data were collected and perigonadal WAT (pgWAT) morphology and proteome were examined. Metformin treatment reduced weight gain and visceral fat accumulation. We detected downregulation of perilipin-1 as a correlate and observed indications of recovering respiratory capacity and adipocyte metabolism under metformin treatment. By regulating four newly discovered potential adipokines (alpha-1 antitrypsin, Apoa4, Lrg1 and Selenbp1), metformin could mediate anti-diabetic, anti-inflammatory and oxidative stress-modulating effects on local and systemic levels. Our study provides an insight into obesity-specific proteome alterations and shows novel modulating effects of metformin in pgWAT of obese dams. Accordingly, metformin therapy appears suitable to prevent some of obesity's key mechanisms in WAT.

Treatment of high fat diet-induced obese pregnant mice with IL-6 receptor antibody does not ameliorate placental function and fetal growth restriction.

PROBLEM: Pregnancy complications and adverse birth outcomes are in part fueled by the rise in obesity and its associated co-morbidities in western societies. Fetal healthy development and placental function are disturbed by an obese, inflammatory environment associated with cytokines, such as interleukin-6, causing inadequate supply of nutrients to the fetus and perinatal programming with severe health consequences. METHOD OF STUDY: Mice received high fat diet (HFD) before and during gestation to induce obesity. We performed an IL-6 receptor antibody (MR16-1) treatment in pregnant obese mice at embryonic days E0.5, E7.5 and E14.5 to investigate whether this could ameliorate HFD-induced and obesity-associated placental dysfunction, evaluated by stereology and western blot, and improve offspring outcome at E15.5 in obese dams. RESULTS: We observed fewer fetuses below the 10th percentile and placental vascularization was less aggravated following MR16-1 treatment of obese dams, showing slight improvements in labyrinth zone (Lz) vascularization. However, placental dysfunction and fetal growth restriction were still apparent in MR16-1 dams compared to lean control dams. Molecular analysis showed significantly elevated IL-6 level in placentas of MR16-1 treated dams. CONCLUSION: Treatment with MR16-1 blocks IL-6 signaling in the placenta, but has only limited effects on preventing HFD-associated placental dysfunction and offspring outcomes in mice, suggesting further mechanisms in the deterioration of placental vascularization and fetal nutrient supply as a consequence of maternal obesity.

Maternal high fat diet-induced obesity affects trophoblast differentiation and placental function in mice†.

Evidence suggests that maternal obesity (MO) can aggravate placental function causing severe pathologies during the perinatal window. However, molecular changes and mechanisms of placental dysfunction remain largely unknown. This work aimed to decipher structural and molecular alterations of the placental transfer zone associated with MO. To this end, mice were fed a high fat diet (HFD) to induce obesity before mating, and pregnant dams were sacrificed at E15.5 to receive placentas for molecular, histological, and ultrastructural analysis and to assess unidirectional materno-fetal transfer capacity. Laser-capture microdissection was used to collect specifically placental cells of the labyrinth zone for proteomics profiling. Using BeWo cells, fatty acid-mediated mechanisms of adherens junction stability, cell layer permeability, and lipid accumulation were deciphered. Proteomics profiling revealed downregulation of cell adhesion markers in the labyrinth zone of obese dams, and disturbed syncytial fusion and detachment of the basement membrane (BM) within this zone was observed, next to an increase in materno-fetal transfer in vivo across the placenta. We found that fetuses of obese dams develop a growth restriction and in those placentas, labyrinth zone volume-fraction was significantly reduced. Linoleic acid was shown to mediate beta-catenin level and increase cell layer permeability in vitro. Thus, MO causes fetal growth restriction, molecular and structural changes in the transfer zone leading to impaired trophoblast differentiation, BM disruption, and placental dysfunction despite increased materno-fetal transfer capacity. These adverse effects are probably mediated by fatty acids found in HFD demonstrating the need for obesity treatment to mitigate placental dysfunction and prevent offspring pathologies.

Effect of Maternal Obesity in Mice on IL-6 Levels and Placental Endothelial Cell Homeostasis.

Obesity during pregnancy is a known health risk for mother and child. Since obesity is associated with increased inflammatory markers, our objectives were to determine interleukin-6 (IL-6) levels in obese mice and to examine the effect of IL-6 on placental endothelial cells. Placentas, blood, and adipose tissue of C57BL/6N mice, kept on high fat diet before and during pregnancy, were harvested at E15.5. Serum IL-6 levels were determined and endothelial cell markers and IL-6 expression were measured by qRT-PCR and western blot. Immunostaining was used to determine surface and length densities of fetal capillary profiles and placental endothelial cell homeostasis. Human placental vein endothelial cells were cultured and subjected to proliferation, apoptosis, senescence, and tube formation assays after stimulation with hyperIL-6. Placental endothelial cell markers were downregulated and the percentage of senescent endothelial cells was higher in the placental exchange zone of obese dams and placental vascularization was strongly reduced. Additionally, maternal IL-6 serum levels and IL-6 protein levels in adipose tissue were increased. Stimulation with hyperIL-6 provoked a dose dependent increase of senescence in cultured endothelial cells without any effects on proliferation or apoptosis. Diet-induced maternal obesity led to an IUGR phenotype accompanied by increased maternal IL-6 serum levels. In the placenta of obese dams, this may result in a disturbed endothelial cell homeostasis and impaired fetal vasculature. Cell culture experiments confirmed that IL-6 is capable of inducing endothelial cell senescence.

Maternal High Fat Diet and in-Utero Metformin Exposure Significantly Impact upon the Fetal Renal Proteome of Male Mice.

There is accumulating evidence for fetal programming of later kidney disease by maternal obesity or associated conditions. We performed a hypothesis-generating study to identify potentially underlying mechanisms. Female mice were randomly split in two groups and fed either a standard diet (SD) or high fat diet (HFD) from weaning until mating and during pregnancy. Half of the dams from both groups were treated with metformin ((M), 380 mg/kg), resulting in four experimental groups (SD, SD-M, HFD, HFD-M). Caesarean section was performed on gestational day 18.5. Fetal kidney tissue was isolated from cryo-slices using laser microdissection methods and a proteomic screen was performed. For single proteins, a fold change ≥1.5 and q-value <0.05 were considered to be statistically significant. Interestingly, HFD versus SD had a larger effect on the proteome of fetal kidneys (56 proteins affected; interaction clusters shown for proteins concerning transcription/translation, mitochondrial processes, eicosanoid metabolism, H2S-synthesis and membrane remodeling) than metformin exposure in either SD (29 proteins affected; clusters shown for proteins involved in transcription/translation) or HFD (6 proteins affected; no cluster). By further analysis, ATP6V1G1, THY1, PRKCA and NDUFB3 were identified as the most promising candidates potentially mediating reprogramming effects of metformin in a maternal high fat diet.

A Potential Role for GSK3ß in Glucose-Driven Intrauterine Catch-Up Growth in Maternal Obesity.

Obesity and unhealthy nutrition are increasing and affect women of childbearing age and hence during pregnancy. Despite normal or even high birth weight, the offspring suffers from long-term metabolic risks. We hypothesized that fetal growth is disturbed during different intrauterine phases. Underlying molecular events remain elusive. Female mice were fed either a standard diet (SD) or a high-fat diet (HFD) after weaning until mating and during pregnancy. Pregnant mice were euthanized at gestational day (G)15.5 and G18.5, and fetuses and placentas were removed for analysis. HFD fetuses displayed intrauterine growth restriction (IUGR) at G15.5, which disappeared until G18.5, indicating intrauterine catch-up growth during that time period. Main placental findings indicate decreased canonical Wnt-GSK3ß signaling and lower proliferation rates at G18.5, which goes along with a smaller placental transfer zone. On the other hand, glucose depots (glycogen cluster) in HFD placentas decreased more strongly between G15.5 and G18.5 compared with placentas from SD mothers, and the glucose transporter protein GLUT-1 was increased at G18.5 in the HFD group. Maternal diet-induced obesity causes an IUGR phenotype at the beginning of the third week (G15.5) in our mouse model. This phenotype is reversed by the end of the third week (G18.5) despite a smaller placental transfer zone, probably based on GSK3ß-mediated increased glucose mobilization in the placenta and hence an increased glucose supply to the fetus.

Hippocampal insulin resistance links maternal obesity with impaired neuronal plasticity in adult offspring.

OBJECTIVE: Maternal obesity and a disturbed metabolic environment during pregnancy and lactation have been shown to result in many long-term health consequences for the offspring. Among them, impairments in neurocognitive development and performance belong to the most dreaded ones. So far, very few mechanistic approaches have aimed to determine the responsible molecular events. METHODS: In a mouse model of maternal diet-induced obesity and perinatal hyperinsulinemia, we assessed adult offspring's hippocampal insulin signaling as well as concurrent effects on markers of hippocampal neurogenesis, synaptic plasticity and function using western blotting and immunohistochemistry. In search for a potential link between neuronal insulin resistance and hippocampal plasticity, we additionally quantified protein expression of key molecules of synaptic plasticity in an in vitro model of acute neuronal insulin resistance. RESULTS: Maternal obesity and perinatal hyperinsulinemia result in adult hippocampal insulin resistance with subsequently reduced hippocampal mTor signaling and altered expression of markers of neurogenesis (doublecortin), synaptic plasticity (FoxO1, pSynapsin) and function (vGlut, vGAT) in the offspring. The observed effects are independent of the offspring's adult metabolic phenotype and can be associated with multiple previously reported behavioral abnormalities. Additionally, we demonstrate that induction of insulin resistance in cultured hippocampal neurons reduces mTor signaling, doublecortin and vGAT protein expression. CONCLUSIONS: Hippocampal insulin resistance might play a key role in mediating the long-term effects of maternal obesity and perinatal hyperinsulinemia on hippocampal plasticity and the offspring's neurocognitive outcome.

Maternal obesity attenuates predelivery inflammatory reaction in C57BL/6N mice.

Inflammation and oxidative stress are known to increase before labour. Whether gonadal white adipose tissue (gWAT) participates in this process and whether labour-related processes in placental and adipose tissue are altered in obese women is unknown. In our mouse model, lean mice display elevated placental inflammation and oxidative stress towards the end of pregnancy, accompanied by an increased expression of pro-inflammatory factors in gWAT. Obese mice also display elevated levels of pro-inflammatory factors and oxidative stress in placentas shortly before birth. However, placental infiltration with leukocytes and an increase in gWAT pro-inflammatory factor expression in obese dams are lacking.