How protein protects against fatty liver

Date:
August 18, 2020
Source:
Deutsches Zentrum fuer Diabetesforschung DZD
Summary:
Non-alcoholic fatty liver disease is the most common chronic
liver disease in the world, with sometimes life-threatening
consequences. A high-protein, calorie-reduced diet can cause
the harmful liver fat to melt away -- more effectively than
a low-protein diet. A new study shows which molecular and
physiological processes are potentially involved.



FULL STORY ========================================================================== Non-alcoholic fatty liver disease is the most common chronic liver
disease in the world, with sometimes life-threatening consequences. A high-protein, calorie-reduced diet can cause the harmful liver fat to
melt away -- more effectively than a low-protein diet. A new study by
DIfE/DZD researchers published in the journal Liver International shows
which molecular and physiological processes are potentially involved.


========================================================================== Causes and consequences of a non-alcoholic fatty liver Non-alcoholic
fatty liver disease is characterized by a build-up of fat in the
liver and is often associated with obesity, type 2 diabetes, high blood pressure and lipid disorders. If left untreated, fatty liver can lead to cirrhosis with life-threatening consequences. The causes of the disease
range from an unhealthy lifestyle -- that is, eating too many high-fat, high-sugar foods and lack of exercise -- to genetic components. Already
in previous studies, the research team led by PD Dr. Olga Ramich and
Professor Andreas Pfeiffer from the German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE) observed a positive effect of a high-protein
diet on liver fat content. "The new results now give us deeper insights
into how the high-protein diet works," said Ramich, head of the research
group Molecular Nutritional Medicine at DIfE.

High-protein diet is more effective than low-protein diet For the current study, the research team led by Ramich and Pfeiffer investigated how
the protein content of food influences the amount of liver fat in obese
people with a non-alcoholic fatty liver. For this, the 19 participants
were to follow either a diet with a high or low protein content for
three weeks. Subsequently, surgery to treat obesity (bariatric surgery)
was carried out and liver samples were collected.

Analysis of the samples showed that a calorie-reduced, high-protein
diet decreased liver fat more effectively than a calorie-reduced,
low-protein diet: while the liver-fat content in the high-protein group decreased by around 40 percent, the amount of fat in the liver samples
of the low-protein group remained unchanged. The study participants
in both groups lost a total of around five kilograms. "If the results
continue to be confirmed in larger studies, the recommendation for an
increased intake of protein together with a healthy low-fat diet as part
of an effective fatty liver therapy could find its way into medical
practice," said Andreas Pfeiffer, head of the Research Group Clinical Nutrition/DZD at DIfE and the Clinic for Endocrinology in the Charite'
-- Universita"tsmedizin Berlin, Campus Benjamin Franklin.

Molecular fat absorption mechanisms The researchers assume that the
positive effect of the high-protein diet is mainly due to the fact that
the uptake, storage and synthesis of fat is suppressed. This is indicated
by extensive genetic analyses of the liver samples that Professor Stephan Herzig and his team at Helmholtz Zentrum Mu"nchen conducted. According to
these analyses, numerous genes that are responsible for the absorption,
storage and synthesis of fat in the liver were less active after the high-protein diet than after the low-protein diet.

Unexpected results In addition, Olga Ramich's research group, together
with the Department of Physiology of Energy Metabolism at DIfE, also investigated the functions of the mitochondria. "Mitochondrial activity
was very similar in both groups. That surprised us. We originally assumed
that the high-protein diet would increase mitochondrial activity and
thus contribute to the degradation of liver fat," said Department Head Professor Susanne Klaus. The researchers were also surprised that the
serum levels of Fibroblast Growth Factor 21 (FGF21) were lower after
the high-protein diet which reduced liver fat than after the low-
protein diet. "FGF21 is known to have beneficial effects on metabolic regulation. Further studies will be necessary to show why the factor was reduced in the actually positively acting high-protein diet," said Ramich.

Furthermore, autophagy activity was lower in liver tissue after the high- protein diet compared to the low-protein diet. "Lipid degradation via 'lipophagy', as a special form of autophagy, therefore does not appear
to be involved in the breakdown of liver fat in the high-protein diet."
As a next step, Ramich and Pfeiffer intend to follow up their findings
about the mechanisms involved and thus gain new insights into the mode
of action of targeted dietary intervention strategies.


========================================================================== Story Source: Materials provided by Deutsches_Zentrum_fuer_Diabetesforschung_DZD. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Chenchen Xu, Mariya Markova, Nicole Seebeck, Anne Loft, Silke
Hornemann,
Thomas Gantert, Stefan Kabisch, Kathleen Herz, Jennifer
Loske, Mario Ost, Verena Coleman, Frederick Klauschen, Anke
Rosenthal, Volker Lange, Ju"rgen Machann, Susanne Klaus, Tilman
Grune, Stephan Herzig, Olga Pivovarova‐Ramich, Andreas
F. H. Pfeiffer. High‐protein diet more effectively reduces
hepatic fat than low‐protein diet despite lower autophagy
and FGF21 levels. Liver International, 2020; DOI: 10.1111/liv.14596 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200818103815.htm

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