Effects of sulfur amino acids on porcine preadipocyte differentiation in culture

Adipogenesis is characterized by two temporally distinct processes: (1) proliferation during which pre-adipocytes replicate and increase in number and (2) differentiation during which pre-adipocytes change in morphology and accumulate lipids. Deregulation of the intracellular glutathione, the most important non-enzymatic intracellular anti-oxidant, has recently been shown to affect murine preadipocyte differentiation. Methionine (Met) is the essential precursor of Cysteine (Cys), which is the rate-limiting factor in glutathione synthesis. Here, we investigated whether low levels of Met+Cys may alter porcine adipogenesis. Preadipocytes were isolated from a subcutaneous fat depot of growing piglets and cultured with different doses of Met (0, 40, 70 and 100 μM (adequate physiological dose) in a media deprived of Cys. Very low levels of Met (0 or 40 μM) in the culture media dramatically lowered preadipocyte proliferation and reduced lipid accumulation in differentiating cells. Preadipocyte proliferation was similar at doses of 70 μM and 100 μM of Met, but lipid droplets in differentiating cells after 13, 21 and 24 days (d) of culture were more numerous at a dose of 70 μM than at a dose of 100 μM. At d13 of differentiation, the expression levels of CEBPalfa PPARgamma, two genes regulating the transcription of adipocyte-specific genes, and of LPL and HSL, two enzymes of lipid metabolism, were higher at a dose of 70 μM than at a dose of 100 μM. At d24 of differentiation, expression levels of these genes were much higher at a dose of 100 μM. These results suggest a delay between time-related changes in gene expressions and lipid accumulation in cells. They show that very strong defficiency in Met decreases both proliferation and differentiation, whereas a mild defficiency of Met alters only differentiation of porcine preadipocytes