Synthesis of hepatic secretory proteins in normal adults consuming a diet marginally adequate in protein

The plasma concentration and hepatic synthesis rates of albumin, transthyretin, very low-density lipoprotein apolipoprotein B-100 (VLDL-apoB-100), high-density lipoprotein apolipoprotein A-1, fibrinogen, alpha1-antitrypsin, and haptoglobin were measured in six normal adults before and after consuming a protein intake of 0.6 g. kg body wt(-1). day(-1) for 7 days. The synthesis of hepatic proteins was measured from the incorporation of [(2)H(5)]- phenylalanine, following prime/continuous infusion, using plasma VLDL-apoB-100 isotopic enrichment to represent the precursor pool. Synthesis of albumin declined by 50% (P < 0.001) following the lower-protein diet, VLDL-apoB-100 declined by 20% (P < 0.001), and apoA-1 declined by 16% (P < 0.05). By contrast, synthesis increased for fibrinogen (50%, P < 0.05) and haptoglobin (90%, P < 0.001). This pattern of change, with decreased synthesis of nutrient transport proteins and increased formation of acute-phase proteins, suggestive of a low-grade inflammatory response, was accompanied by increased plasma concentration of the inflammatory cytokine interleukin 6 (30%, P < 0.05). The pattern of change in the synthesis of hepatic secretory proteins following 7 days on the low-protein diet may be of functional relevance for lipid transport and the capacity to cope with stress.     

Combined effect of salinomycin and feeding on whole body glucose kinetics in sheep fed a high-concentrate diet

The aim of this study was to investigate the effects of salinomycin (SL) and feeding on whole body glucose kinetics in sheep fed a high-concentrate diet (25% orchardgrass hay and 75% commercial concentrate). Four adult sheep were fed the diet with or without 20 mg x kg(-1) diet of SL once daily for each 3 wk. The rates of glucose entry and utilization were determined before and during 3 h after feeding using a [ (13)C(6)] glucose dilution approach. Ruminal characteristics and concentrations of blood volatile fatty acids (VFA) and plasma glucose and insulin were also measured. Metabolizable energy intake was unaffected (P = 0.22) with SL. Salinomycin decreased (P = 0.06) the ratio of acetate to propionate in rumen fluid. Salinomycin increased (P = 0.01) both rates of entry and utilization of glucose, but did not affect (P > 0.10) concentrations of blood VFA or plasma glucose or insulin. Feeding caused gradual increases in concentrations of blood acetate (P < 0.01) and propionate (P = 0.01), a transient increase in plasma insulin concentration (P = 0.05), a transient decrease in plasma glucose concentration (P < 0.01), and persistent increases in both rates of glucose entry (P < 0.01) and utilization (P < 0.01). No SL x feeding interaction was observed (P > 0.10) on any measurements. We conclude that SL and feeding would have an additive effect on both rates of glucose entry and utilization without modifications with SL to feeding responses of peripheral concentrations of blood VFA, plasma glucose and insulin.     

The nature of the ingested protein has no effect on lean body mass during energy restriction in overweight rats

Severe energy restriction in obesity not only leads to fat mass loss but also to lean mass loss. The aim of this study was to compare the capacity of casein, a slowly digested protein, and milk soluble proteins (MSP; rapidly digested) to limit the loss of lean mass induced by energy restriction. Obesity was first induced in male Wistar rats by a 5-week feeding with a high-fat high-sucrose diet. The impact of energy restriction was then studied with high-protein (32%) diets containing either casein, MSP, or a 50/50 mixture of both proteins for 3 weeks (n = 10 per group). Food intake, body weight, nitrogen balance, creatinine, and 3-methyl-histidine excretion were measured during energy restriction. Then, tissue weights, plasma metabolic parameters (amino acids, glucose, insulin, cholesterol, triglycerides), and in vivo liver and extensor digitorum longus (EDL) muscle protein synthesis rates were measured in postabsorptive state at the end of the experimental period. Although significant differences relevant to protein metabolism were observed between groups (protein intake, plasma amino acid concentrations, fecal nitrogen excretion, muscle protein synthesis rates), week per week, there were no significant differences in nitrogen balance whatever the protein used. In conclusion, our results show that in young overweight energy restricted rats, using a high-protein diet, the nature of protein intake has no influence on body protein retention.     

Effect of protein starvation on protein turnover in liver, oviduct and whole body of laying hens

1. Whole body protein turnover rates in White Leghorn laying hens were reduced by protein starvation for 7 days, followed by complete restoration by protein repletion for 7 days. 2. Protein starvation considerably reduced fractional and absolute rates of protein synthesis both in the liver and, to a greater extent, in the oviduct. 3. It was suggested that a considerable portion of the reduced whole body protein synthesis could be accounted for by the reduced protein synthesis in these organs when laying hens were subjected to protein starvation.     

The effect of starvation on energy turnover and protein metabolism in Ophiocephalus punctatus bloch

1. At 20°C, fish starved for various durations took less food than unstarved fish. At 28°C, 20-day starved fish alone consumed more food.
2. The maximum feeding was during the second ten days at 28°C but in the first ten days at 20°C.
3. Absorption efficiency was unaffected by temperature and starvation.
4. Absorption rate reflected feeding rate.
5. At 28°C the conversion efficiency was high for the ten-day starved fish but at 20°C the 30-day starved fish showe high conversion efficiency.
6. Conversion rate is governed not only by feeding rate but also by conversion efficiency.
7. At 28°C the 20-day starved fish alone compensated for loss of energy, total and protein nitrogen. At 20°C the loss was compensated for by all fish.

     

Active muscle and whole body lactate kinetics after endurance training in men.

We evaluated the hypotheses that endurance training decreases arterial lactate concentration ([lactate](a)) during continuous exercise by decreasing net lactate release () and appearance rates (R(a)) and increasing metabolic clearance rate (MCR). Measurements were made at two intensities before [45 and 65% peak O(2) consumption (VO(2 peak))] and after training [65% pretraining VO(2 peak), same absolute workload (ABT), and 65% posttraining VO(2 peak), same relative intensity (RLT)]. Nine men (27.4 +/- 2.0 yr) trained for 9 wk on a cycle ergometer, 5 times/wk at 75% VO(2 peak). Compared with the 65% VO(2 peak) pretraining condition (4.75 +/- 0.4 mM), [lactate](a) decreased at ABT (41%) and RLT (21%) (P < 0.05). decreased at ABT but not at RLT. Leg lactate uptake and oxidation were unchanged at ABT but increased at RLT. MCR was unchanged at ABT but increased at RLT. We conclude that 1) active skeletal muscle is not solely responsible for elevated [lactate](a); and 2) training increases leg lactate clearance, decreases whole body and leg lactate production at a given moderate-intensity power output, and increases both whole body and leg lactate clearance at a high relative power output.     

Effect of very low calorie diet on body composition and exercise response in sedentary women.

The effect of very low calorie diet (VLCD) on fat-free mass (FFM) and physiological response to exercise is a topic of current interest. Ten moderately obese women (aged 23-57 years) received VLCD (1695 kJ.day-1) for 6 weeks. FFM, estimated by four conventional techniques, and heart rate (fc), blood lactate (la(b)), mean arterial pressure (MAP), respiratory exchange ratio (R) and rating of perceived exertion (RPE) were measured during a submaximal cycle ergometry test 1 week before, in the 2nd and 6th week, and 1 week after VLCD treatment. Strength and muscular endurance of the quadriceps and hamstrings were tested by isokinetic dynamometry. The 11.5-kg reduction in body mass was approximately 63% fat and 37% FFM. The latter was attributed largely to the loss of water associated with glycogen. Whilst exercise fc increased by 9-14 beats.min-1 (P < 0.01), there were substantial decreases (P < 0.01) in submaximal MAP (1.07-1.73 kPa), la(b) (0.75-1.00 mmol.l-1 and R (0.07-0.09) during VLCD. R and fc returned to normal levels after VLCD. Gross strength decreased (P < 0.01) by 9 and 13% at 1.05 rad.s-1 and 3.14 rad.s-1, respectively. Strength expressed relative to body mass (Nm.kg-1) increased (P < 0.01) at the lower contraction velocity, but there was no change at the faster velocity. Muscular endurance also decreased (P < 0.01) by 62 and 82% for the hamstrings and quadriceps, respectively. We concluded that the strength decrease was a natural adaptation to the reduction in body mass as the ratio of strength to FFM was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of cytokines and testosterone in regulating lean body mass and resting energy expenditure in HIV-infected men

Although catastrophic weight loss is no longer common in HIV-infected men, we hypothesized that a more gradual process of cachexia [loss of lean body mass (LBM) without severe weight loss, often accompanied by elevated resting energy expenditure (REE)] is still common and is driven by excessive production of the catabolic cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta). We performed a longitudinal analysis of an ongoing cohort study of nutritional status in 172 men with HIV infection. LBM loss of >1 kg occurred in 35% of the cohort, and LBM loss of >5% occurred in 12.2% over 8 mo of observation, but classical wasting (loss of approximately 10% of weight) was rare (2%). Both TNF-alpha (-150 g LBM. ng(-1) x ml(-1), P < 0.02) and IL-1 beta production (-130 g LBM x ng(-1) x ml(-1), P < 0.01) by peripheral blood mononuclear cells predicted loss of LBM. A rise in REE of >200 kcal/day was found in 17.7% of the subjects regardless of weight change. IL-1 beta (+9 kcal/day per ng/ml, P < 0.002) and TNF-alpha (+10 kcal/day per ng/ml, P < 0.02) production predicted Delta REE. Serum free testosterone was inversely associated with TNF-alpha production and was not an independent predictor of either Delta LBM or Delta REE after adjustment for cytokine production. Even though weight loss was rare in this cohort of patients treated with highly active antiretroviral therapy, loss of LBM was common and was driven by catabolic cytokines and not by inadequate dietary intake or hypogonadism.     

Role of adipose specific lipid droplet proteins in maintaining whole body energy homeostasis

Excess or insufficient lipid storage in white adipose tissue lipid droplets is associated with dyslipidemia, insulin resistance and increased risk for diabetes type 2. Thus, maintenance of adipose lipid droplet growth and function is critical to preserve whole body insulin sensitivity and energy homeostasis. Progress in understanding biology of lipid droplets has underscored the role of proteins that interact with lipid droplets. Here, we review the current knowledge of adipose specific lipid droplet proteins, which share unique functions controlling adipocyte lipid storage, limiting lipid spill-over and lipotoxic effects thought to contribute to disease. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.     

Effect of low protein and low energy diet on physiological status and digestibility of F344 rats.

A long-term raising study was carried out on male F344/DuCrj rats with three low protein (Crude Protein (CP); 14.5, 11.5, 8.5%) and low energy (Digestible Energy (DE); 2.0 kcal/g) diets from 4 to 104 weeks of age. In rats fed the 8.5% CP diet, body weight and digestible crude protein (DCP) consumption at 10 weeks of age were lower (P < 0.05) but the body weight at 50 weeks of age was higher (P < 0.05) than in the other groups. In rats fed the 8.5% CP diet the crude fat digestibility was higher (P < 0.05), and the CP/nitrogen-corrected metabolizable energy (MEn) ratio was low. On the other hand, the mean survival time at 80 weeks of age was shorter in rats fed the 8.5% CP diet (P < 0.05).     

The role of degradation of fetal haemoglobin in the energy supply of very low body weight pre-term babies

Low body weight premature babies born before the 32nd gestational week were studied to analyse the postnatal fall in plasma haemoglobin and in quantitative changes in amino acid levels. Red blood cells of premature low body weight infants were found to disintegrate more rapidly than those of mature newborns. Thin-layer ion-exchange chromatographic studies showed that amino acids originating from the degrading haemoglobin-F lead to rise in plasma amino acids. These amino acids might play a role as substrates for gluconeogenesis in the energy supply of low body weight premature babies during the special fasting state just after birth.     

Effects of fasting on insulin action and glucose kinetics in lean and obese men and women

The development of insulin resistance in the obese individual could impair the ability to appropriately adjust metabolism to perturbations in energy balance. We investigated a 12- vs. 48-h fast on hepatic glucose production (R(a)), peripheral glucose uptake (R(d)), and skeletal muscle insulin signaling in lean and obese subjects. Healthy lean [n = 14; age = 28.0 +/- 1.4 yr; body mass index (BMI) = 22.8 +/- 0.42] and nondiabetic obese (n = 11; age = 34.6 +/- 2.3 yr; BMI = 36.1 +/- 1.5) subjects were studied following a 12- and 48-h fast during 2 h of rest and a 3-h 40 mUxm(-2)xmin(-1) hyperinsulinemic-euglycemic clamp (HEC). Basal glucose R(a) decreased significantly from the 12- to 48-h fast (lean 1.96 +/- 0.23 to 1.63 +/- 0.15; obese 1.23 +/- 0.07 to 1.07 +/- 0.07 mgxkg(-1)xmin(-1); P = 0.004) and was equally suppressed during the HEC after both fasts. The increase in glucose R(d) during the HEC after the 12-h fast was significantly decreased in lean and obese subjects after the 48-h fast (lean 9.03 +/- 1.17 to 4.16 +/- 0.34, obese 6.10 +/- 0.77 to 3.56 +/- 0.30 mgxkg FFM(-1)xmin(-1); P < 0.001). After the 12- but not the 48-h fast, insulin-stimulated AKT Ser(473) phosphorylation was greater in lean than obese subjects. We conclude that 1) 48 h of fasting produces a marked decline in peripheral insulin action, while suppression of hepatic glucose production is maintained in lean and obese men and women; and 2) the magnitude of this decline is greater in lean vs. obese subjects.     

The effect of extreme temperatures and starvation on the body proportions of the rat

The effects of extremely cold and hot environments on body proportions of rats were studied. These effects included changes in the length of the tail, trunk, extremities, cranio-facial and nasal dimensions, in bone robusticity and bone shape, in the size of the ear and in some characteristics of the skin and hair. Since animals in both extreme temperatures fail to gain normal body weight, all changes were also studied in a group of starving rats. Because of the lower body weight and its concomitant reduction of body measurements, absolute values were avoided for analysis and all parameters were related to neurocranial length and trunk length. Such a triple experimental approach (response to cold, heat, and starvation) combined with a two-fold frame of reference (neurocranial length and trunk length), as well as statistical corrections for body weight loss, made it possible to differentiate between nutrition-specific and temperature-specific responses under conditions of extreme temperature exposure. Moreover, some attention was given to endocrine pathways involved in some morphological changes. The methodological advantages of a multi-experimental approach over a single-experimental technique were demonstrated.