High-protein diets prevent steatosis and induce hepatic accumulation of monomethyl branched-chain fatty acids

The hallmark of nonalcoholic fatty liver disease is steatosis of unknown etiology. To test how dietary protein decreases steatosis, we fed female C57BL/6 J mice low-fat (8 en%) or high-fat (42 en%) combined with low-protein (11 en%), high-protein (HP; 35 en%) or extra-high-protein (HPX; 58 en%) diets for 3 weeks. The 35 en% protein diets reduced hepatic triglyceride, free fatty acid, cholesterol and phospholipid contents to ~50% of that in 11 en% protein diets. Every additional 10 en% protein reduced hepatic fat content ~1.5 g%. HP diets had no effect on lipogenic or fatty acid-oxidizing genes except Ppargc1alpha (+30%), increased hepatic PCK1 content 3- to 5-fold, left plasma glucose and hepatic glycogen concentration unchanged, and decreased inflammation and cell stress (decreased Fgf21 and increased Gsta expression). The HP-mediated decrease in steatosis correlated inversely with plasma branched-chain amino-acid (BCAA) concentrations and hepatic content of BCAA-derived monomethyl branched-chain fatty acids (mmBCFAs) 14-methylpentadecanoic (14-MPDA; valine-derived) and, to a lesser extent, 14-methylhexadecanoic acid (isoleucine-derived). Liver lipid content was 1.6- to 1.8-fold higher in females than in males, but the anti-steatotic effect of HP diets was equally strong. The strong up-regulation of PCK1 and literature data showing an increase in phosphoenolpyruvate and a decline in tricarboxylic acid cycle intermediates in liver reveal that an increased efflux of these intermediates from mitochondria represents an important effect of an HP diet. The HP diet-induced increase in 14-MPDA and the dietary response in gene expression were more pronounced in females than males. Our findings are compatible with a facilitating role of valine-derived mmBCFAs in the antisteatotic effect of HP diets

Prevention and reversal of hepatic steatosis with a high-protein diet in mice

The hallmark of NAFLD is steatosis of unknown etiology. We tested the high-protein (HP)(2) diet on diet-induced steatosis in male C57BL/6 mice without pre-existing fatty liver. Mice were fed all combinations of low-fat (LF) or high-fat (HF) and low-protein (LP) or HP diets for control for reduced energy intake by HF/HP-fed mice, a pair-fed HF/LP included. Reversibility of pre-existing steatosis was investigated by sequentially feeding HF/LP and HF/HP diets. HP-containing diets lipids to ~40% of corresponding LP-containing diets, were more efficient respect than reducing energy intake to 80%, and reversed pre-existing diet-induced steatosis. Compared to LP-containing diets, mice fed HP- diets showed increased mitochondrial oxidative capacity (elevated mAco, and Cpt1 mRNAs, complex-V protein, and decreased plasma free and short-chain acyl-carnitines, and [C0]/[C16+C18] carnitine ratio); gluconeogenesis and pyruvate cycling (increased PCK1 protein and fed plasma-glucose concentration without increased G6pase mRNA); reduced desaturation (decreased Scd1 expression and [C16:1n-7]/[C16:0] ratio) increased long-chain PUFA elongation; a selective increase in plasma branched-chain amino acids; a decrease in cell stress (reduced eIF2alpha, and Fgf21 and Chop expression); and a trend toward less (lower Mcp1 and Cd11b expression and less phosphorylated NFkappaB). HP diets prevent and reverse steatosis independently of fat and intake more efficiently than a 20% reduction in energy intake. The to result from fuel-generated, highly distributed small, synergistic lipid and BCAA catabolism, and a decrease in cell stress