Palmitate enhances the differentiation of mouse embryonic stem cells towards white adipocyte lineages

Nicotinamide Promotes Adipogenesis in Umbilical Cord-Derived Mesenchymal Stem Cells and Is Associated with Neonatal Adiposity: The Healthy Start BabyBUMP Project

The cellular mechanisms whereby excess maternal nutrition during pregnancy increases adiposity of the offspring are not well understood. However, nicotinamide (NAM), a fundamental micronutrient that is important in energy metabolism, has been shown to regulate adipogenesis through inhibition of SIRT1. Here we tested three novel hypotheses: 1) NAM increases the adipogenic response of human umbilical cord tissue-derived mesenchymal stem cells (MSCs) through a SIRT1 and PPARγ pathway; 2) lipid potentiates the NAM-enhanced adipogenic response; and 3) the adipogenic response to NAM is associated with increased percent fat mass (%FM) among neonates. MSCs were derived from the umbilical cord of 46 neonates born to non-obese mothers enrolled in the Healthy Start study. Neonatal %FM was measured using air displacement plethysmography (Pea Pod) shortly after birth. Adipogenic differentiation was induced for 21 days in the 46 MSC sets under four conditions, +NAM (3mM)/-lipid (200 μM oleate/palmitate mix), +NAM/+lipid, -NAM/+lipid, and vehicle-control (-NAM/-lipid). Cells incubated in the presence of NAM had significantly higher PPARγ protein (+24%, p <0.01), FABP4 protein (+57%, p <0.01), and intracellular lipid content (+51%, p <0.01). Lipid did not significantly increase either PPARγ protein (p = 0.98) or FABP4 protein content (p = 0.82). There was no evidence of an interaction between NAM and lipid on adipogenic response of PPARγ or FABP4 protein (p = 0.99 and p = 0.09). In a subset of 9 MSC, SIRT1 activity was measured in the +NAM/-lipid and vehicle control conditions. SIRT1 enzymatic activity was significantly lower (-70%, p <0.05) in the +NAM/-lipid condition than in vehicle-control. In a linear model with neonatal %FM as the outcome, the percent increase in PPARγ protein in the +NAM/-lipid condition compared to vehicle-control was a significant predictor (β = 0.04, 95% CI 0.01-0.06, p <0.001). These are the first data to support that chronic NAM exposure potentiates adipogenesis in human MSCs in-vitro, and that this process involves PPARγ and SIRT1.

In utero growth restriction and catch-up adipogenesis after developmental di (2-ethylhexyl) phthalate exposure cause glucose intolerance in adult male rats following a high-fat dietary challenge

Phthalates impact adipocyte morphology in vitro, but the sex-specific adipogenic signature immediately after perinatal di(2-ethylhexyl) phthalate (DEHP) exposure and adulthood physiology following a high-fat (HF) dietary challenge are unknown. In the current study, pregnant and lactating dams received DEHP (300 mg/kg body weight) or oil. At weaning [postnatal day (PND) 21], adipose tissue was sampled for real-time polymerase chain reaction. The remaining offspring consumed a control or HF diet. DEHP decreased % fat in males at birth from 13.9%±0.2 to 11.8%±0.6 (mean±S.E.M.), representing a 15.1% decrease in fat by DEHP, and these males caught up in adiposity to controls by PND21. Adult DEHP-exposed males had a 27.5% increase in fat (12.5%±0.9% in controls vs. 15.9%±1.5% in the DEHP group); adipocyte perimeter was increased as well, with fewer small/medium-sized adipocytes, and decreased cell number compared to oil controls. HF diet intake in DEHP-exposed males further increased male energy intake and body weight and led to glucose intolerance. In PND21 males, DEHP increased the expression of adipogenic markers (Pparg1, Cebpa, Adipoq, Ppard, Fabp4, Fasn, Igf1), decreased Lep, and decreased markers of mesenchymal stem cell commitment to the adipogenic lineage (Bmp2, Bmp4, Stat1, Stat5a) compared to oil controls. These data suggest that DEHP may decrease the adipocyte pool at birth, which initially increases adaptive adipocyte maturation and lipid accumulation, but leads to adipose tissue dysfunction in adulthood, decreasing the capacity to adapt to a HF diet, and leading to systemic glucose intolerance.

PLIN2 inhibits insulin-induced glucose uptake in myoblasts through the activation of the NLRP3 inflammasome

Impaired lipid metabolism and inflammatory pathways have individually been implicated in the development of insulin resistance in skeletal muscle; however, little evidence is available to date linking the two in this context. In this study, we explored a potential molecular mechanism underlying insulin resistance in myoblasts mediated by the crosstalk between lipid accumulation and inflammatory pathways. We examined the influence of perilipin 2 (PLIN2), one of the most highly expressed lipid droplet-associated proteins in skeletal muscle, on glucose uptake and on the nucleotide‑binding domain, leucine‑rich repeat containing protein 3 (NLRP3) inflammasome in vitro. PLIN2 overexpression in C2C12 cells led to an increased expression of NLRP3, caspase‑1 and interleukin (IL)‑1β, along with an impaired insulin‑induced glucose uptake. This defect was remedied by the RNAi‑mediated knockdown of NLRP3 expression. We also found that insulin receptor substrate‑1 (IRS‑1), a component of insulin signaling, was negatively regulated by NLRP3 and IL‑1β, and that IL‑1β inhibited insulin‑induced glucose uptake in myoblasts. These results suggest that PLIN2 inhibits insulin‑induced glucose uptake by activating NLRP3, caspase‑1 and IL‑1β, leading to a decreased IRS‑1 expression. This study provides in vitro evidence supporting an association between lipid metabolism and inflammatory pathways in the pathogenesis of insulin resistance in skeletal muscle, and suggests potential therapeutic targets that warrant further investigation.

The lipid fraction of human milk initiates adipocyte differentiation in 3T3-L1 cells

BACKGROUND

The prevalence of childhood obesity has increased worldwide over the past decade. Despite evidence that human milk lowers the risk of childhood obesity, the mechanism is not fully understood.

AIMS

We investigated the direct effect of human milk on differentiation of 3T3-L1 preadipocytes.

STUDY DESIGN AND SUBJECTS

3T3-L1 preadipocytes were treated with donated human milk only or the combination of the standard hormone mixture; insulin, dexamethasone (DEX), and 3-isobututyl-1-methylxanthine (IBMX). Furthermore, the induction of preadipocyte differentiation by extracted lipids from human milk was tested in comparison to the cells treated with lipid extracts from infant formula. Adipocyte differentiation, specific genes as well as formation of lipid droplets were examined.

RESULTS

We clearly show that lipids present in human milk initiate 3T3-L1 preadipocyte differentiation. In contrast, this effect was not observed in response to lipids present in infant formula. The initiation of preadipocyte differentiation by human milk was enhanced by adding the adipogenic hormone, DEX or insulin. The expression of late adipocyte markers in Day 7 adipocytes that have been induced into differentiation with human milk lipid extracts was comparable to those in control cells initiated by a standard adipogenic hormone cocktail.

CONCLUSIONS

These results demonstrate that human milk contains bioactive lipids that can initiate preadipocyte differentiation in the absence of the standard adipogenic compounds via a unique pathway.