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

Differential effects of milk, yogurt, and cheese on energy homeostasis and brown adipose tissue phenotype in high-fat diet-induced obese mice

Aim: We hypothesized that milk, yogurt, and cheese have differential impacts on energy expenditure (EE) and obesity in mice fed a high-fat diet (HFD). Methods: C57BL/6 mice (n = 16 per group) were fed a HFD or a HFD supplemented with fat-free milk (MILK), fat-free plain yogurt (YOG), or reduced-fat cheddar cheese (CHE; 19 kcal% fat), each provided at 10% of the daily energy intake, for 8 weeks. EE was quantified using a metabolic chamber. Metabolic pathways related to BAT mitochondrial function and uncoupling protein 1 (UCP1) abundance were assessed. Serum lipidomic profiles were analyzed to identify potential mediators of the observed effects. Results: MILK supplementation lowered weight gain and fat accumulation and enhanced EE and BAT thermogenesis, perhaps via the SIRT1-AMPK-PGC1α axis in BAT. This led to elevated UCP1 abundance and enhanced the abundance of hormone-sensitive lipase (HSL). MILK also altered serum lipid species, indicating enhanced energy use, and promoted BAT thermogenesis and mitochondrial function pathways. YOG exhibited a similar pattern but a lower magnitude of effects than MILK on reducing weight gain and fat mass, increasing EE, and BAT thermogenic proteins, including AMPK-PGC1α-UCP1. Both MILK and YOG showed a relative increase in serum PC 15:0_15:0 and LPC 15:0. In contrast, CHE reduced weight gain and increased EE without impacting BAT thermogenesis proteins or serum lipid species. Conclusion: Our study showed that MILK, YOG, and CHE reduced weight gain in mice on a HFD by increasing EE. MILK and YOG also up-regulated BAT thermogenesis, while both additionally altered lipids involved in fat metabolism and inflammation. CHE did not affect BAT thermogenesis and lipid species compared to HFD.

Milk fat globule membrane and its component phosphatidylcholine induce adipose browning both in vivo and in vitro

The functional induction of brown-like adipocytes in white adipose tissue (WAT) provides a defense against obesity. The aim of this study was to analyze the effects of milk fat globule membrane (MFGM) and its component phosphatidylcholine (PC) on the brown remodeling of WAT. Male C57BL/6 J mice were fed a high-fat diet (HFD) for 8 weeks and then fed HFD for another 8 weeks with MFGM. In vitro studies were performed in C3H10T1/2 pluripotent stem cells, 3T3-L1 pre-adipocytes and differentiated inguinal WAT stromal vascular cells (SVCs) to determine the role of MFGM and PC on the formation of brown-like adipocytes. MFGM decreased fasting glucose and serum insulin levels in HFD-fed mice. MFGM improved glucose tolerance and insulin sensitivity, and induced browning of inguinal WAT. MFGM and its component PC stimulated transformation of brown-like adipocytes in C3H10T1/2 pluripotent stem cells, 3T3-L1 adipocytes and SVCs by increasing the protein expression of UCP1, PGC-1α, PRDM16 as well as the mRNA expression of other thermogenic genes and beige cell markers. MFGM and PC also increased mitochondrial DNA (mtDNA) copy number, mitochondrial density and oxygen consumption rate and up-regulated the mRNA expression of mitochondria-biogenesis-related genes in vitro. PPARα inhibitor GW6471 treatment or knockdown of PPARα using lentivirus-expressing shRNA inhibited the PC-induced increase in the protein expression of UCP1, PGC-1α and PRDM16 in C3H10T1/2 pluripotent stem cells and 3T3-L1 adipocytes, indicating the potential role of PPARα in PC-mediated brown-like adipocyte formation. In conclusion, MFGM and milk PC induced adipose browning, which has major protective effects against obesity and metabolic dysfunction.