Protein diet reduces energy efficiency?

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Despite the higher energy density of the higher protein meals, animals were fed

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lib, but the higher protein predisposed less weight. Yet, caloric intakes were

higher with the high-protein, it seemed. Energy was lost due to inefficient use

of

the calories. This apparently occurred especially at night.

Petzke KJ, Friedrich M, Metges CC, Klaus S.

Long-term dietary high protein intake up-regulates tissue specific gene

expression

of uncoupling proteins 1 and 2 in rats.

Eur J Nutr. 2005 Oct;44(7):414-21. Epub 2004 Dec 28.

PMID: 15602629

Summary

Background The consequences of chronic high protein (HP) diets are discussed

controversially and are not well understood. Rats adapted to HP exposure show an

increased amino acid and fat oxidation and lower feed energy efficiency. We

hypothesized that the dietary protein level can affect gene expression of

uncoupling

protein (UCP) homologues which is suggested to be involved in thermogenesis,

substrate oxidation, and energy expenditure.

Aim of the study To assess the mRNA expression of UCP homologues in various

tissues of rats fed HP diets and to relate UCP gene expression to various

parameters

of substrate and energy metabolism. To obtain further indications for the

possible

involvement of UCP in reducing feed energy efficiency under conditions of HP

exposure.

Methods Adult rats were adapted to casein based diets containing either 13.8%

(adequate, AP), 25.7% (medium, MP), or 51.3 % (high, HP) crude protein. Rats

were

fed for 8 wk and killed in the postabsorptive state. Energy expenditure and mRNA

expression were measured using indirect calorimetry and Northern blot analysis,

respectively. Pearson correlation coefficients were calculated to determine

relationships between UCP mRNA expression and metabolic parameters.

Results Hepatic UCP2 mRNA expression was increased by MP and HP diets compared

to

AP diet. In skeletal muscle UCP2 mRNA expression was lowest under MP conditions.

UCP1 mRNA expression in brown adipose tissue (BAT) was significantly increased

by HP

exposure. The values were inversely associated with feed energy efficiency and

positively with energy expenditure and oxygen consumption in the dark period.

Skeletal muscle UCP2 and UCP3 mRNA expression strongly correlated with the

plasma

free fatty acid concentration, whereas BAT UCP1 and hepatic UCP2 gene expression

did

not.

Conclusions Our results indicate that hepatic UCP2 and BAT UCP1 mRNA

expression is

related to the level of dietary protein intake. This suggests a role of UCPs in

substrate oxidation and in thermogenesis under conditions of HP exposure.

Table 1 Composition of purified test diets containing different protein

concentrations (AP adequate protein;MP medium protein;HP high protein)

===================

Diet----AP MP HP

----g/100 g g/100 g g/100 g

==================

Casein 15 30 60

Wheat starch 58 43 13

Saccharose 10 10 10

Palm kernel fat 3 3 3

Soy bean oil 2 2 2

Cellulose 5 5 5

Mineral mixture 5 5 5

Vitamin mixture 2 2 2

Crude protein 13.8 25.7 51.3

Gross energy,kJ/g 16.8 17.9 19.9

Table 2 Body weight,fat weights and plasma

metabolites of rats fed for 8 wk diets with different

protein concentrations (AP adequate,13.8 %;MP

medium,25.7 %;HP high,51.3 %).Rats were in the

postabsorptive state,1–2 h after removal of food offered overnight 1–3

=============================

Diet AP MP HP

============================

Body weight

Final body weight (g)445±12 b 415±10 a 409±8 a

Body weight increase (g/8 wk)209±11 b 182±9 a,b 177±9 a

Total epididymal fat pad weight (g)14.7±1.7 b 11.0±1.0 a 10.0±0.9 a

Plasma metabolites

FFA (mmol/l)0.95±0.08 a 0.95±0.10 a,b 1.27±0.13 b

fT3 (pg/ml)3.63±0.11 3.61±0.11 3.46±0.25

Urea (µmol/ml)5.60±0.23 a 8.96±0.47 b 11.25±0.57 c

============================

1 Values are means±SEM,n =10.

Within a row,values without a common superscript differ,P <0.05

2 For diet compositions and more details see Material and Methods.

3 FFA free fatty acids;fT3 free triiodothyronine

Table 3 Nutrient intake,energy expenditure,and

net oxidation of macronutrients of rats fed for 8 wk

diets with different protein concentrations (AP adequate,13.8 %;MP medium,25.7

%;HP

high, 51.3 %)1–3

============================

Diet AP MP HP

============================

Nutrient intake

Total gross energy intake (MJ)20.7±0.5 a 20.7±0.5 a 23.0±0.4 b

Total N intake (g)22.5±0.5 a 52.0±1.3 b 100.0±1.9 c

Mean feed energy efficiency (g/MJ)4 9.62±0.25 c 8.90±0.21 b 7.73±0.32 a

Overall daily energy expenditure (d 56)

TEE (kJ/h)10.6±0.2 10.8±0.4 10.4±0.4

TEE (kJ/(h kg))23.8±0.6 25.9±0.7 24.9±0.7

RMR (kJ/h)7.58±0.19 7.15±0.22 7.13±0.33

RMR (kJ/(h kg))17.0±0.6 17.2±0.4 17.1±0.7

VO2 (lO2/h)0.51±0.01 0.52±0.02 0.52±0.02

VO2 (lO2/(h kg))1.14±0.03 1.26±0.03 1.24±0.04

RQ 0.97±0.01 c 0.92±0.01 b 0.86±0.01 a

Dark phase energy expenditure (d 56,1900 h– 0600 h))

EEdark (kJ/h)11.3±0.2 11.6±0.4 11.1±0.5

EEdark (kJ/(h kg))25.4±0.7 28.0±0.8 26.7±0.9

VO2,dark (lO2/h)0.54±0.01 0.57±0.02 0.56±0.02

VO2,dark (lO2/(h kg))1.21±0.03 a 1.37±0.04 b 1.33±0.05 b

Net oxidation of macronutrients

FO (g/d)0.35±0.12 a 0.77±0.15 a,b 1.16±0.23 b

CO (g/d)12.14±0.26 c 9.06±0.68 b 4.98±0.50 a

PO (g/d)1.46±0.08 a 3.64±0.30 b 6.19±0.57 c

===========================

1 Values are means±SEM,n =10.

Within a row,values without a common superscript differ,P <0.05.

2 For diet compositions and more details see Material and Methods.

3 CO carbohydrate oxidation;EE energy expenditure;FO fat oxidation;PO protein

oxidation;RMR resting metabolic rate;RQ respiratory quotient;TEE total energy

expenditure;VO2 oxygen consumption.

4 Body weight gain (g)divided by energy intake (MJ)

Table 4 Gene expression of UCP homologues and

leptin in various tissues of rats fed diets with different

protein concentrations (AP adequate,13.8 %;MP

medium,25.7 %;HP high,51.3 %).Rats were in the

postabsorptive state,1–2 h after removal of food offered overnight 1–3

===========================

Diet AP MP HP

===========================

UCP1,BAT (AU)0.95±0.08 a 0.94±0.12 a 1.44±0.11 b

UCP2 (AU)

Liver 0.76±0.12 a 1.03±0.04 b 1.09±0.04 b

Spleen 1.08±0.10 0.92±0.06 1.13±0.07

Mucosa (proximal jejunum,30 cm)0.72±0.08 0.65±0.05 0.74±0.04

WAT 0.83±0.06 0.82±0.09 0.74±0.06

Skeletal muscle 0.71±0.10 a,b 0.45±0.05 a 0.90±0.12 b

UCP3,skeletal muscle (AU)0.77±0.12 0.57±0.11 0.86±0.07

Leptin (AU)

BAT 1.02±0.11 0.92±0.13 1.04±0.07

WAT 0.99±0.20 0.92±0.13 1.04±0.07

==========================

1 Values are means±SEM,n =10.

Within a row,values without a common superscript differ,P <0.05.

2 For diet compositions and more details see Material and Methods.

3 AU arbitrary units;BAT interscapular brown adipose tissue;UCP uncoupling

protein;WAT white adipose tissue

Table 5 Pearson correlation coefficients between

UCP1,UCP2,and UCP3 mRNA expression in BAT,liver

and skeletal muscle (m.biceps femoris)and parameters of postabsorptive

circulating

metabolites in rats

fed diets with different protein concentrations 1–4

============================

Parameter UCP2,UCP2,UCP3,UCP1

Liver Skeletal muscle Skeletal muscle BAT

============================

Body weight–0.346 ns ns–0.273 2

Epididymal fat pad weight–0.270 2 ns ns–0.358

VO2,dark,lO2/(h kg)0.274 2 ns ns 0.444

EEdark ns ns ns 0.347

FEE,g body weight gain/MJ EI ns–0.306–0.270 2–0.365

Urea concentration,plasma 0.524 ns ns 0.367

FFA concentration,plasma ns 0.586 0.368 ns

fT3 concentration,plasma–0.272 2 ns ns 0.355

=============================

n=30

correlation coefficients were significant (P <0.05)if not otherwise

stated;one-sided

test;correlation

coefficients not significant (P >0.1)are labeled ns.

2 Correlation coefficient of borderline significance 0.1 >P >0.05).3 For diet

compositions and more details see Material and Methods.

4 BAT interscapular brown adipose tissue;EEdark energy expenditure in dark

cycle;EI

energy intake;FEE feed energy efficiency;FFA free fatty acids;fT3 free

triiodothyronine;VO2,dark dark phase oxygen consumption in;UCP uncoupling

protein

Al Pater, PhD; email: old542000@...

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