Human milk and infant formula can induce in vitro adipocyte differentiation in murine 3T3-L1 preadipocytes

Breast Milk from Non-Obese Women with a High Omega-6 to Omega-3 Fatty Acid Ratio, but Not from Women with Obesity, Increases Lipogenic Gene Expression in 3T3-L1 Preadipocytes, Suggesting Adipocyte Dysfunction

Maternal body mass index is associated with breast milk (BM) fatty acid composition. This study investigated the effects of BM omega (n)-6:n-3 polyunsaturated fatty acids (PUFAs) from non-obese women and women with obesity on the process of adipogenesis in 3T3-L1 preadipocytes. BM samples were collected from non-obese women (BMNO) and women with obesity (BMO) at one month postpartum. The fatty acid composition was measured, and BMNO and BMO groups with the lowest (Q1) and highest (Q4) quartiles of n-6:n-3 PUFA ratios were identified. 3T3-L1 preadipocytes were differentiated in the presence or absence of BM. Lipid accumulation and the expression of genes involved in lipogenesis and lipolysis were measured. Treatment with BMNO containing high (vs. low) n-6:n-3 PUFA ratios significantly increased the mRNA expression of lipogenic genes (acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase); however, there was no effect when cells were treated with BMO (with either low or high n-6:n-3 PUFA ratios). Treatment with BMO (high n-6:n-3 PUFA ratio) caused larger lipid droplets. Our findings demonstrated that BMNO with a high n-6:n-3 PUFA ratio was associated with a higher expression of lipogenic genes, while BMO with a high n-6:n-3 PUFA ratio showed larger lipid droplets, suggesting adipocyte dysfunction. These findings may have implications in the BM-mediated programming of childhood obesity.

Assessment of adipogenic, antioxidant, and anti-inflammatory properties of whole and whey bovine colostrum

Bovine colostrum (BC) has been used for nutraceutical purposes for animals and humans. Bovine colostrum is a complex heterogeneous product and its antimicrobial activity, antioxidant potential, and growth factors can vary depending on age and species of the cow as well as their environment. Bovine colostrum preparation in skimmed or whey fractions can also alter properties of BC. Our goal was to compare cumulative anti-inflammatory, antioxidant, and adipogenic properties of natural (whole) versus whey BC. We compared properties of whole and whey BC in 3T3-L1 preadipocytes permanently transfected with reporters responding to changes in inflammatory (NfκbRE/green fluorescent protein), anti-inflammatory (Nrf2/YFP), and adipogenic (Fabp4/cyan fluorescent protein) status in cells. Interleukin-6 secretion in these cells was measured by ELISA. Whole and whey BC induce IL-6 secretion from 3T3-L1 fibroblasts; however, whey preparation stimulated less IL-6 secretion. Cumulative inflammatory nuclear factor (NF)κB activation in the presence of lipopolysaccharide was reduced by both whole (-27%) and whey BC (-22%) compared with lipopolysaccharide-treated cells (100%). Treatment with whole BC was more effective in the reduction of NFκB activation compared with whey BC and occurred in a dose-dependent manner. In consonance with decreased NFκB activation, the Nrf2 promoter activity was also reduced in response to whole (-27%) and whey (-13%) treatments compared with nontreated cells (100%). Whole and whey BC suppressed adipogenesis, measured as induction of Fabp4, by -27 and -13%, respectively, compared with nontreated 3T3-L1 fibroblasts (100%). Our results showed distinct differences in properties of whey and whole BC that could be used to attain reduced adipogenic or cumulative inflammatory responses.

Modulation of brown adipocyte activity by milk by-products: Stimulation of brown adipogenesis by buttermilk

Brown adipocytes dissipate chemical energy in the form of heat through the expression of mitochondrial uncoupling protein 1 (Ucp1); Ucp1 expression is further upregulated by the stimulation of β-adrenergic receptors in brown adipocytes. An increase in energy expenditure by activated brown adipocytes potentially contributes to the prevention of or therapeutics for obesity. The present study examined the effects of milk by-products, buttermilk and butter oil, on brown adipogenesis and the function of brown adipocytes. The treatment with buttermilk modulated brown adipogenesis, depending on the product tested; during brown adipogenesis, buttermilk 1 inhibited the differentiation of HB2 brown preadipocytes. In contrast, buttermilk 3 and 5 increased the expression of Ucp1 in the absence of isoproterenol (Iso), a β-adrenergic receptor agonist, suggesting the stimulation of brown adipogenesis. In addition, the Iso-induced expression of Ucp1 was enhanced by buttermilk 2 and 3. The treatment with buttermilk did not affect the basal or induced expression of Ucp1 by Iso in HB2 brown adipocytes, except for buttermilk 5, which increased the basal expression of Ucp1. Conversely, butter oil did not significantly affect the expression of Ucp1, irrespective of the cell phase of HB2 cells, ie, treatment during brown adipogenesis or of brown adipocytes. The results of the present study indicate that buttermilk is a regulator of brown adipogenesis and suggest its usefulness as a potential food material for antiobesity.

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.

Infant formula alters surfactant protein A (SP-A) and SP-B expression in pulmonary epithelial cells

Surfactant proteins A (SP-A) and SP-B are critical in the ability of pulmonary surfactant to reduce alveolar surface tension and provide innate immunity. Aspiration of infant milk formula can lead to lung dysfunction, but direct effects of aspirated formula on surfactant protein expression in pulmonary cells have not been described. The hypothesis that infant formula alters surfactant protein homeostasis was tested in vitro by assessing surfactant protein gene expression in cultured pulmonary epithelial cell lines expressing SP-A and SP-B that were transiently exposed (6 hr) to infant formula. Steady-state levels of SP-A protein and mRNA and SP-B mRNA in human bronchiolar (NCI-H441) and mouse alveolar (MLE15) epithelial cells were reduced in a dose-dependent manner 18 hr after exposure to infant formula. SP-A mRNA levels remained reduced 42 hr after exposure, but SP-B mRNA levels increased 10-fold. Neither soy formula nor non-fat dry milk affected steady-state SP-A and SP-B mRNA levels; suggesting a role of a component of infant formula derived from cow milk. These results indicate that infant formula has a direct, dose-dependent effect to reduce surfactant protein gene expression. Ultimately, milk aspiration may potentially result in a reduced capacity of the lung to defend against environmental insults.

Proliferation and differentiation of stromal-vascular cells in primary culture differ between neonatal pigs consuming maternal or formula milk

Proliferation and differentiation of preadipocytes from 7-d-old pigs consuming maternal or formula milk were examined in primary culture of stromal-vascular (s-v) cells derived from subcutaneous adipose tissue. Unsuckled pigs were bottle-fed isoenergetically with colostrum and then sow's milk (SM) or with formula milk alone (F) from birth to 7 d. Isolated cells were exposed to serum-supplemented medium and serum-free medium to determine proliferation and differentiation, respectively. Proliferation estimated between d 3 and 4 of culture was higher (P<0.05) in cells from F than SM pigs. In addition, the number of s-v cells isolated from 1 g of adipose tissue was higher (P<0.01) in F than SM pigs. Variables assessing differentiation were also affected. The percentage of differentiating cells and lipoprotein lipase (LPL) activity were lower (P<0.05) in F than SM pigs, whereas malic enzyme (ME) activity did not differ significantly between the two groups. In conclusion, formula milk increased the number of s-v cells and their capacity for proliferation, whereas the potential for cell differentiation was lower compared with cells from the maternal milk group. Further studies are required to identify the growth and/or nutritional factors that are implicated in the observed differences and to determine whether subsequent development of adipose tissue is affected.