(09-09-09) High protein intake reduces intrahepatocellular lipid deposition in humans.

Bortolotti M, Kreis R, Debard C, Cariou B, Faeh D, Chetiveaux M, Ith M,
Vermathen P, Stefanoni N, L? KA, Schneiter P, Krempf M, Vidal H, Boesch C, Tappy L.
Department of Physiology, University of Lausanne, Lausanne, Switzerland.

BACKGROUND: High sugar and fat intakes are known to increase
intrahepatocellular lipids (IHCLs) and to cause insulin resistance. High
protein intake may facilitate weight loss and improve glucose homeostasis in insulin-resistant patients, but its effects on IHCLs remain unknown.
OBJECTIVE:
The aim was to assess the effect of high protein intake on high-fat diet-
induced IHCL accumulation and insulin sensitivity in healthy young men. DESIGN:
Ten volunteers were studied in a crossover design after 4 d of either a
hypercaloric high-fat (HF) diet; a hypercaloric high-fat, high-protein (HFHP) diet; or a control, isocaloric (control) diet. IHCLs were measured by (1)H-magnetic resonance spectroscopy, fasting metabolism was measuredby indirect calorimetry, insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp, and plasma concentrations were measured by enzyme-linked immunosorbent assay and gas chromatography-mass spectrometry; expression of key lipogenic
genes was assessed in subcutaneous adipose tissue biopsy specimens. RESULTS:
The HF diet increased IHCLs by 90 +/- 26% and plasma tissue-type plasminogen activator inhibitor-1 (tPAI-1) by 54 +/- 11% (P < 0.02 for both) and inhibited plasma free fatty acids by 26 +/- 11% and beta-hydroxybutyrate by 61 +/- 27% (P < 0.05 for both). The HFHP diet blunted the increase in IHCLs and normalized
plasma beta-hydroxybutyrate and tPAI-1 concentrations. Insulin sensitivity was not altered, whereas the expression of sterol regulatory element-binding protein-1c and key lipogenic genes increased with the HF and HFHP diets (P < 0.02). Bile acid concentrations remained unchanged after the HF diet but increased by 50 +/- 24% after the HFHP diet (P = 0.14).
CONCLUSIONS:
Protein intake significantly blunts the effects of an HF diet on IHCLs and tPAI-1 through effects presumably exerted at the level of the liver. Protein-induced increases in BA concentrations may be involved. This trial was registered at www.clinicaltrials.gov as NCT00523562.

Source: Am J Clin Nutr. 2009 Aug 26.

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