Biomedical subjects

X Q Zhao

Publications and source records attributed to X Q Zhao.

At least 19 recordsLinked to original sources

PubMed2006

Hypoxia-inducible factor 1alpha cDNA cloning and its mRNA and protein tissue specific expression in domestic yak (Bos grunniens) from Qinghai-Tibetan plateau.

Adaptation to hypoxia is regulated by hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor consisting of an oxygen-regulated alpha-subunit and a constitutively expressed beta-subunit. How animals living on Qinghai-Tibetan plateau adapt to the extreme hypoxia environment is known indistinctly. In this study, the Qinghai yak, which has been living at 3000-5000 m altitude for at least two millions of years, was selected as the model of high hypoxia-tolerant adaptation species. The HIF-1alpha ORFs (open reading frames) encoding for two isoforms of HIF-1alpha have been cloned from the brain of the domestic yak. Its expression of HIF-1alpha was analyzed at both mRNA and protein levels in various tissues. Both its HIF-1alpha mRNA and protein are tissue specific expression. Its HIF-1alpha protein's high expression in the brain, lung, and kidney showed us that HIF-1alpha protein may play an important role in the adaptation to hypoxia environment.

Amino Acid Sequence↗

PubMed2006

Leptin cDNA cloning and its mRNA expression in plateau pikas (Ochotona curzoniae) from different altitudes on Qinghai-Tibet Plateau.

Leptin, an adipocyte-derived hormone, plays an important role in body energy homeostasis. Plateau pika (Ochotona curzoniae), an endemic and keystone species living only at 3000-5000 m above sea level on Qinghai-Tibet Plateau, is a typically high hypoxia and low temperature tolerant mammal with high resting metabolic rate (RMR), non-shivering thermogenesis (NST), and high ratio of oxygen utilization to cope with harsh plateau environment. To explore the molecular mechanism of ecological acclimation in plateau pika, we first cloned pika leptin cDNA and compared its mRNA expression in different altitudes (3200 and 3900 m) using real-time RT-PCR (Taqman probe) technology. The full-length pika leptin cDNA was 3015 with 504 bp open-reading frame encoding the precursor peptide of 167 amino acids including 21 residues of signal peptide. Pika leptin was 70-72% homologous to that of other species and was of similarly structural characteristics with other species. The pika-specific genetic diversity in leptin sequence occurred at twenty sites. With the increase in altitude, there were larger fat store and high level of ob gene expression in plateau pika. Our results indicated that leptin is sensitive to cold and hypoxia plateau environment and may play one of important roles in pika's ecological adaptation to harsh plateau environment.

Altitude↗

PubMed2005

Online monitoring and characterization of flocculating yeast cell flocs during continuous ethanol fermentation.

Both intrinsic and observed kinetic investigations for those ethanol fermentations using self-flocculated yeast strains have been hindered by the lack of real online monitoring techniques and proper characterization methods for the flocs. An optical detecting technique, the focused beam reflectance measurement probe developed by Lasentec (Redmond, WA) was inserted into a fermentor to monitor the floc chord length distributions. Using a simulating system composed of the floc-buffer suspensions, the total floc chord length counts per second were directly correlated with the floc biomass concentrations so that the floc biomass concentrations can be in situ detected. Furthermore, a characterization method of the flocs was established by properly weighted treatments of the detected floc chord length distributions. When a real yeast floc ethanol fermentation system was detected during its intrinsic kinetic investigations in which the floc size needed to be controlled at a level of micrometer scale to eliminate inner mass transfer limitations, it was found and validated that CO(2) produced during fermentation exerted significant disturbances. By applying 1/length-weighted treatment, these disturbances were effectively overcome.

Bioreactors↗

PubMed2005

Seasonal changes in weight and body composition of yak grazing on alpine-meadow grassland in the Qinghai-Tibetan plateau of China.

Forty-five male yaks (born April 2001) were studied to determine how seasonal changes on the Qinghai-Tibetan plateau affected BW and body composition. Thirty yaks were weighed monthly from birth to 26 mo of age to determine seasonal changes in BW. The remaining 15 yaks were allocated randomly to five groups (three yaks per group), designated for slaughter at 13, 15, 18, 22, and 25 mo to measure seasonal effects on body chemical composition. All yaks were grazed on the alpine-meadow grassland of the plateau without any supplementation. All BW and body composition data were calculated on an individual basis. Body weight and body composition data were both compared across seven growth periods spanning 2 yr and defined by season. From April (birth) to December 2001 of the first growing season, yak BW increased (P < 0.01); however, during the subsequent cold season (December 2001 to May 2002), BW decreased (P < 0.01). The second growing season ran from May 2002 (13 mo of age) to October 2002 (18 mo of age), and the second live weight-loss season ran from October 2002 until May 2003. The weight loss experienced by yaks during the first weight-loss season was 25.64% of the total weight gain in the first growing season. The weight loss experienced by yaks during the second weight-loss season was 29.73% of the total weight gain in the second growing season. Energy retention in the second growing season was 291.07 MJ, 50.8% of which was consumed during the subsequent cold season. Energy accumulation in the summer (from May to July) and fall (from July to October) of the second growing season did not differ (5.01 and 6.30 MJ/kg of EBW gain, respectively; P = 0.63). The energy mobilized during the second winter (from October 2002 to February 2003) was 16.49 MJ/kg of EBW, and in the second spring (from February to May 2003), it was 9.06 MJ/kg of EBW. These data suggest that the decrease in grazing yak BW during the first cold season is much less than during the second cold season, and that the energy content per unit of BW mobilized is greater (P = 0.02) in winter than in spring. Results from this study demonstrate highly efficient compensatory growth in grazing yaks following the first weight loss period during the first cold season. This benefit could be exploited by herders to improve yak production. Yaks may have developed a type of self-protection mechanism to overcome the long cold seasons in the Qinghai-Tibetan plateau.

Adaptation, Physiological↗

PubMed2004

Cloning of hypoxia-inducible factor 1alpha cDNA from a high hypoxia tolerant mammal-plateau pika (Ochotona curzoniae).

Hypoxia-inducible factor 1 is a transcription factor composed of HIF-1alpha and HIF-1beta. It plays an important role in the signal transduction of cell response to hypoxia. Plateau pika (Ochotona curzoniae) is a high hypoxia-tolerant and cold adaptation species living only at 3000-5000 m above sea level on the Qinghai-Tibet Plateau. In this study, HIF-1alpha cDNA of plateau pika was cloned and its expression in various tissues was studied. The results indicated that plateau pika HIF-1alpha cDNA was highly identical to those of the human (82%), bovine (89%), mouse (82%), and Norway rat (77%). The deduced amino acid sequence (822bp) showed 90%, 92%, 86%, and 86% identities with those of the human, bovine, house mouse, and Norway rat, respectively. Northern blot analyses detected two isoforms named pLHIF-1alpha and pSHIF-1alpha. The HIF-1alpha mRNA was highly expressed in the brain and kidney, and much less in the heart, lung, liver, muscle, and spleen, which was quite different from the expression pattern of mouse mRNA. Meanwhile, a new variant of plateau pika HIF-1alpha mRNA was identified by RT-PCR and characterized. The deduced protein, composed of 536 amino acids, lacks a part of the oxygen-dependent degradation domain (ODD), both transactivation domains (TADs), and the nuclear localization signal motif (NLS). Our results suggest that HIF-1alpha may play an important role in the pika's adaptation to hypoxia, especially in brain and kidney, and pika HIF-1alpha function pattern may be different from that of mouse HIF-1alpha. Furthermore, for the high ratio of HIF-1alpha homology among the animals, the HIF-1alpha gene may be a good phylogenetic performer in recovering the true phylogenetic relationships among taxa.

Adaptation, Physiological↗

PubMed2003

Energy metabolism and protein balance in growing rats fed different levels of dietary fibre and protein.

A study was performed to investigate the effect of different levels of dietary fibre (DF) and dietary protein on visceral organ size, digestibility, nitrogen balance and energy metabolism in rats. Thirty-six male Wistar rats, initial body weight about 76 g were used in a factorial design consisting of three levels of DF (low, 100 g/kg DM: medium, 250 g/kg DM and high, 290 g/kg DM) and two levels of dietary protein (low, 120 g/kg DM and high, 223 g/kg DM). The added fibre source was soybean hulls and Danish fish meal was used as sole source of dietary protein. Measurements of gas-exchange were done on six rats (one group) while urine and faeces were collected individually. The ratio of food/empty body gain increased (P<0.05) with increasing DF and decreasing levels of dietary protein. The weight of the digestive tract was larger (P<0.05) in rats fed the high fibre diet than in those fed the low fibre diet. The digestibility of nutrients and energy decreased linearly with increasing level of soybean fibre (P<0.05). An increased intake of DF was associated with a concomitant loss of protein and energy to faeces. The microbial degradation of NSP and other unabsorbed carbohydrates caused considerably changes in N metabolism of the colon. In rats fed the low protein diets increased levels of DF decreased N excretion in urine and increased N excretion in faeces, while the ratio of retained/digested protein remained constant. When rats were fed the high protein diet protein retention dropped in response to DF both absolute and relative to digested amount, indicating that energy intake could be a limiting factor. Heat production as a percentage of metabolizable energy (HP/ME) was higher (P<0.05) in rats fed the low protein diet than in rats fed the high protein diet, but no significant difference was found among DF levels.

Animals↗

PubMed2001

Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease.

BACKGROUND: Both lipid-modifying therapy and antioxidant vitamins are thought to have benefit in patients with coronary disease. We studied simvastatin-niacin and antioxidant-vitamin therapy, alone and together, for cardiovascular protection in patients with coronary disease and low plasma levels of HDL. METHODS: In a three-year, double-blind trial, 160 patients with coronary disease, low HDL cholesterol levels and normal LDL cholesterol levels were randomly assigned to receive one of four regimens: simvastatin plus niacin, vitamins, simvastatin-niacin plus antioxidants; or placebos. The end points were arteriographic evidence of a change in coronary stenosis and the occurrence of a first cardiovascular event (death, myocardial infarction, stroke, or revascularization). RESULTS: The mean levels of LDL and HDL cholesterol were unaltered in the antioxidant group and the placebo group; these levels changed substantially (by -42 percent and +26 percent, respectively) in the simvastatin-niacin group. The protective increase in HDL2 with simvastatin plus niacin was attenuated by concurrent therapy with antioxidants. The average stenosis progressed by 3.9 percent with placebos, 1.8 percent with antioxidants (P=0.16 for the comparison with the placebo group), and 0.7 percent with simvastatin-niacin plus antioxidants (P=0.004) and regressed by 0.4 percent with simvastatin-niacin alone (P<0.001). The frequency of the clinical end point was 24 percent with placebos; 3 percent with simvastatin-niacin alone; 21 percent in the antioxidant-therapy group; and 14 percent in the simvastatin-niacin-plus-antioxidants group. CONCLUSIONS: Simvastatin plus niacin provides marked clinical and angiographically measurable benefits in patients with coronary disease and low HDL levels. The use of antioxidant vitamins in this setting must be questioned.

Antioxidants↗

PubMed2001

Electron-beam tomography coronary calcium scores are superior to Framingham risk variables for predicting the measured proximal stenosis burden.

Previous studies of electron-beam tomography (EBT) have correlated coronary calcium scores with simplistic visual estimates of disease severity. In a clinical trial designed to evaluate 2 treatment strategies in coronary artery disease (CAD) patients with low levels of high-density lipoprotein cholesterol, we used quantitative coronary angiography to measure composite proximal stenosis burden from the baseline coronary angiogram and assessed the traditional Framingham risk variables in 146 patients. Stenosis burden is the sum, per patient, of percent stenosis for the worst lesion found in each of 9 standard proximal coronary segments. EBT estimates of coronary calcium (Agatston score, calcium volume score) were obtained for 115 of these patients. Stenosis burden was correlated with the calcium scores and risk variables. The best traditional correlates of stenosis burden were smoking status (r = 0.31, p = 0.001), prior myocardial infarction (r = 0.24, p = 0.005), body mass index (r = 0.23, p = 0.005), pack-years smoking (r = 0.20, p = 0.05), and age (r = 0.17, p = 0.04). With adjustment for age, all these correlations improved (eg, body mass index x age [r = 0.28, p = 0.001]). In addition, total cholesterol x age (r = 0.22, p = 0.008), fibrinogen x age (r = 0.19, p = 0.03), and systolic blood pressure x age (r = 0.18, p = 0.03) became significant correlates. Spearman correlations of the calcium scores with stenosis burden were considerably greater (Agatston: r = 0.62, p <0.0001; calcium volume: r = 0.63, p <0.0001). In multivariate regression analysis, calcium score, body mass index, and history of myocardial infarction were independent correlates of stenosis burden (R(2) = 0.45). At a given point in time, the EBT coronary calcium scores are greatly superior to the Framingham risk factors in predicting the measured proximal stenosis burden. Agatston and calcium volume scores are comparably predictive of stenosis burden.

Body Burden↗

PubMed2001

Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL.

One strategy for treating coronary artery disease (CAD) patients with low HDL cholesterol (HDL-C) is to maximally increase the HDL-C to LDL-C ratio by combining lifestyle changes with niacin (N) plus a statin. Because HDL can prevent LDL oxidation, the low-HDL state also may benefit clinically from supplemental antioxidants. Lipoprotein changes over 12 months were studied in 153 CAD subjects with low HDL-C randomized to take simvastatin and niacin (S-N), antioxidants (vitamins E and C, beta-carotene, and selenium), S-N plus antioxidants (S-N+A), or placebo. Mean baseline plasma cholesterol, triglyceride, LDL-C, and HDL-C levels of the 153 subjects were 196, 207, 127, and 32 mg/dL, respectively. Without S-N, lipid changes were minor. The S-N and S-N+A groups had comparably significant reductions (P</=0.001) in plasma cholesterol, triglyceride, and LDL-C. However, increases in HDL-C, especially HDL(2)-C, were consistently higher in the S-N group than in the S-N+A group (25% vs 18% and 42% vs 0%, respectively). With S-N, but not with S-N+A, there was a selective increase in apolipoprotein (apo) A-I (64%) in HDL particles containing apo A-I but not A-II [Lp(A-I)] and their particle size. Thus, in CAD patients with low HDL-C, S-N substantially increased HDL(2)-C, Lp(A-I), and HDL particle size. These favorable responses were blunted by the antioxidants used owing to a striking selective effect on Lp(A-I). This unexpected adverse interaction between antioxidants and lipid therapy may have important implications for the management of CAD.

Adult↗

PubMed2001

Effects of prolonged intensive lipid-lowering therapy on the characteristics of carotid atherosclerotic plaques in vivo by MRI: a case-control study.

High-resolution magnetic resonance imaging (MRI) with flow suppression not only provides useful information on luminal and wall areas of the carotid artery but also can identify the principal tissue components of the carotid atherosclerotic plaque. The effects of intensive lipid-lowering therapy on these MRI tissue characteristics were examined in patients with coronary disease (CAD). Eight CAD patients who have been receiving intensive lipid-lowering treatment (niacin 2.5 g/d, lovastatin 40 mg/d, and colestipol 20 g/d) for 10 years in the Familial Atherosclerosis Treatment Study (FATS) follow-up were randomly selected from among 60 such treated patients. Eight CAD patients who were matched to the treated patients for age (+/-3 years), baseline low density lipoprotein (+/-5 mg/dL), and triglycerides (+/-50 mg/dL) but who had never been treated with lipid-lowering drugs were selected as controls. For each of these 32 carotid arteries, luminal and plaque areas were measured by planimetry, in a blinded protocol, from the magnetic resonance image that showed most plaque. Fibrous tissue, calcium, and lipid deposits were identified on the basis of established criteria. Plaque composition was estimated as a fraction of total planimetered area. Patients treated with 10-year intensive lipid-lowering therapy, compared with control subjects, had significantly lower low density lipoprotein cholesterol levels (84 versus 158 mg/dL, respectively; P<0.001) and higher high density lipoprotein cholesterol levels (51 versus 37 mg/dL, respectively; P<0.001). As a group, treated patients, compared with untreated control subjects, had a smaller core lipid area (0.7 versus 10.2 mm(2), respectively; P=0.01) and lipid composition (1% versus 17%, respectively). Group differences in luminal area (55 [treated] versus 44 [control] mm(2), P=NS) and plaque area (58 [treated] versus 64 [control] mm(2), P=NS) tended to favor treatment. MRI appears useful for estimating carotid plaque size and composition. Hyperlipidemic CAD patients frequently (97%) have at least moderate (>/=40% area stenosis) carotid plaque. In this case-control study, prolonged intensive lipid-lowering therapy is associated with a markedly decreased lipid content, a characteristic of clinically stable plaques.

Calcinosis↗

PubMed2000

Ca(2+)-dependent inhibition of actin-activated myosin ATPase activity by S100C (S100A11), a novel member of the S100 protein family.

S100C (S100A11, calgizzarin) inhibits the actin-activated myosin Mg(2+)-ATPase activity of smooth muscle in a dose-dependent manner: its half-maximal effect occurs at a S100C/actin molar ratio of 0.05 and its maximal effect occurs at a ratio of 0.20. Furthermore, S100C was found to bind to actin with a stoichiometry of 1:6-7 in the presence of Ca(2+), with an affinity of 1 x 10(-6) M determined by cosedimentation assays. Other Ca(2+)-binding proteins such as S100A1, S100A2, S100B, and calmodulin did not inhibit actin-activated myosin Mg(2+)-ATPase activity. Calmodulin, S100A1, and S100B reversed the inhibitory effect of calponin in a Ca(2+)-dependent manner, S100A2 had no effect, and S100C had additional inhibitory effects. The results suggest that S100C might be involved in the regulation of actin-activated myosin Mg(2+)-ATPase activity through its Ca(2+)-dependent interaction with actin filaments.

Actins↗

PubMed1999

Intracoronary thrombus and platelet glycoprotein IIb/IIIa receptor blockade with tirofiban in unstable angina or non-Q-wave myocardial infarction. Angiographic results from the PRISM-PLUS trial (Platelet receptor inhibition for ischemic syndrome management in patients limited by unstable signs and symptoms). PRISM-PLUS Investigators.

BACKGROUND: The present study describes the effects of tirofiban, a nonpeptide platelet glycoprotein (GP) IIb/IIIa receptor blocker, on the characteristics of culprit lesions in patients with unstable angina (UA) or non-Q-wave myocardial infarction (NQWMI). METHODS AND RESULTS: Of 1915 patients enrolled in PRISM-PLUS, 1491 had a readable film obtained a median of 65 hours after randomization. A core laboratory examined the culprit lesions for intracoronary thrombus burden (primary end point) and for TIMI flow grade distribution and severity of the obstruction and of underlying coronary artery disease (secondary end points). The combination of tirofiban plus heparin compared with heparin alone significantly reduced the intracoronary thrombus burden of the culprit lesions (OR=0.77, P=0.022), improved the perfusion grade (OR=0.65, P=0.002), and decreased the severity of the obstruction (P=0.037), but it did not influence the severity of the underlying plaque. Persistence of a thrombus in 45% of patients was associated with a 2.4-fold increase in the odds of death at 30 days (P=0.005) and a 2-fold increase in the odds of myocardial infarction (P=0.002). CONCLUSIONS: The addition of tirofiban to heparin reduced the thrombus burden of the culprit lesion and improved distal perfusion in patients with UA or NQWMI, which supports the clinical benefit observed with the combination treatment.

Aged↗

PubMed1998

Importance of endothelial function in mediating the benefits of lipid-lowering therapy.

Trials of lipid lowering by various methods have clearly demonstrated the benefits, clinically and angiographically. Evidence of slowed arterial disease progression and even regression has been convincing but modest, at best. For example, among those treated intensively in the Familial Atherosclerosis Treatment Study (FATS), the mean improvement in proximal stenosis severity was <1% per patient, and only 12% of all lesions showed convincing regression. Despite these modest arterial benefits, the associated reductions in major cardiovascular events have been surprisingly great (24-35% in 3 recent large trials and > or =50% in angiographic trials using combination therapies). The process of plaque disruption helps explain this discrepancy. Disruption can be predicted by a large accumulation of core lipid in the plaque and a high density of lipid-laden macrophages in its thinned fibrous cap. Lesions with these characteristics comprise only 10-20% of the overall lesion population but account for 60-90% of the acute clinical events. Lipid-lowering therapy has beneficial effects on these "high-risk" features of plaque morphology. The composite of data presented here supports the hypothesis that lipid-lowering therapy selectively depletes lipids from this relatively small but dangerous subgroup of fatty lesions, effectively stabilizing them.

Coronary Artery Disease↗

PubMed1998

Lipid altering or antioxidant vitamins for patients with coronary disease and very low HDL cholesterol? The HDL-Atherosclerosis Treatment Study Design.

Evidence supports the idea that substantial benefits may derive from treatments that increase high density lipoprotein (HDL) cholesterol (HDL-C), apolipoprotein (apo) A-I, HDL2 (or 2b) or the size of HDL particles with, or without, apo A-II. HDL3 appears to be neutral in terms of coronary artery disease risk, and apo A-II appears to be adverse. Because HDL particles serve as antioxidants in vitro, the hypothesis that low HDL-C reflects an antioxidant deficiency state appears tenable. Based on these observations, a three-year angiographic study was proposed and received funding. Enrollment began in January 1995 and was completed in January 1997.

Adult↗

PubMed1997

Moderate dose, three-drug therapy with niacin, lovastatin, and colestipol to reduce low-density lipoprotein cholesterol <100 mg/dl in patients with hyperlipidemia and coronary artery disease.

The efficacy, safety, and tolerability of a moderate dose, 3-drug lipid-lowering regimen were evaluated among 29 male patients with hyperlipidemia and coronary artery disease. In an initial 12-month phase, regular niacin, 500 mg qid, lovastatin, 20 mg bid, and colestipol, 10 g/bid, were given with dose adjustment for lipid targets and side effects. This was followed by 2 random sequence crossover phases (8 months each) alternating regular niacin with a polygel controlled-release formulation of niacin for use in this regimen. Lipid, lipoprotein, apoprotein, and clinical chemistry determinations were obtained at baseline, during the initial phase, at the 2 crossover phases, and at 6 weeks after therapy. A final questionnaire queried specific side effects and overall preferences. Low-/high-density lipoprotein (LDL/HDL) changed from means of 215/46 mg/dl at baseline, to 94/59 mg/dl after run-in, to 85/52 mg/dl after 8 months of controlled-release niacin, and to 98/56 mg/dl after 8 months of regular niacin (regular niacin vs controlled-release niacin, p <0.005/<0.05). The target of LDL < or = 100 mg/dl was achieved at 8 months by 83% of these patients with controlled-release niacin and by 52% with regular niacin (p <0.01). Compliance was 95% with controlled-release niacin versus 85% with regular niacin (p <0.001). The controlled-release niacin and regular niacin regimens did not differ in terms of uric acid, glucose, insulin, or asparate aminotransferase levels. Overall, 21% of patients called the 3 drugs "very easy" and 72% "fairly easy" to take. The controlled-release niacin-containing regimen was preferred by 21 patients and the regular niacin by 4. In conclusion, these regimens achieve striking lipid changes among hyperlipidemic patients. Controlled release is the preferred niacin preparation in terms of LDL reduction, compliance, patient preference, and achieving the National Cholesterol Education Program guideline of LDL < or = 100 mg/dl. The 2 niacin preparations did not differ in evidence of toxicity.

Cholesterol, LDL↗

PubMed1997

Influence of environmental temperature on in vivo energy expenditure in vitro ouabain-sensitive respiration in duodenal mucosa and liver in rats fed different levels of dietary fiber or protein.

Seventy two Wistar rats were used in two repeat studies to investigate the effect of environmental temperature (18 degrees C or 28 degrees C) and increasing levels of dietary fibre (low, 68 g/kg DM; medium 110 g/kg DM; high, 157 g/kg DM) or protein (low, 91 g/kg DM; medium, 171 g/kg DM; high, 262 g/kg DM) on digestive tract, visceral organ size, energy metabolism, and respiration attributable to Na+,K(+)-ATPase activity in duodenal mucosa and liver. Total and ouabain-sensitive (a measure of Na+,K(+)-ATPase activity) O2 consumption in vitro of tissues were measured polarographically using a Clark-style YSI biological O2 monitor. Whole body heat production (in vivo) was measured using open-circuit respiration chambers. The weight of the visceral organs was higher in rats housed at 18 degrees C than at 28 degrees C. The empty weight of the small intestine, caecum, and colon increased as the level of dietary fibre increased (P 0.05). Heat production as a proportion of metabolizable energy was higher (P < 0.05) at 18 degrees C than at 28 degrees C in the first experiment but this difference was significant in the second experiment. Rats fed the low protein diet had significantly higher (P > 0.05) heat production than those fed medium or high protein diets. Compared to 28 degrees C, environmental temperature of 18 degrees C caused an increased total and ouabain-sensitive O2 consumption in duodenal mucosa. There was no significant effect of environmental temperature on total and ouabain-sensitive O2 consumption in the liver. However, ouabain-sensitive O2 consumption in liver was significantly higher (P 0.05) when rats were fed a low protein diet compared to the medium or high protein diet. Total and ouabain-sensitive O2 consumption increased in duodenal mucosa of rats fed low level of dietary fibre compared to the medium or high dietary fibre diets. The in vitro results corresponded with the whole animal energy expenditure and O2 consumption in vivo.

Animals↗

PubMed1997

Energy expenditure and quantitative oxidation of nutrients in rats (Rattus norvegicus) kept in different thermal environments and given two levels of dietary fiber.

A study was performed to investigate the effect of environmental temperature (16 degrees C, 24 degrees C or 32 degrees C) and dietary fiber (DF) on energy expenditure and quantitative oxidation of nutrients in rats. Forty-eight male rats, initial body weight 90-105 g, were allocated to eight groups in two series. The rats kept at 24 degrees C was repeated in both series. Low and high fiber diets (56 vs. 257 g DF/kg dry matter) were studied in 6-week balance experiments. The rats in all groups were offered the same amount of air-dried food. Indirect calorimetry was used to measure the energy metabolism. The difference in heat production (HP) calculated by RQ and CN methods was < 2% and was not affected by environmental temperature and DF. The relation between fat and protein oxidation changed from 1.54 to 1.00 when the ambient temperature changed from 16 degrees C to 32 degrees C. The contribution of carbohydrate oxidation to total HP was lowest at 16 degrees C, whereas the fat and protein oxidation was highest at 16 degrees C. The oxidation of nutrients was not influenced by DF. The additional energy retained at the higher temperatures had a constant ratio between fat and protein, i.e., 70:30. At an energy retention of 65.8 kJ/kg0.75 d or less, body fat is mobilized and only protein deposited. Because of higher HP, rats living in the cold environment used more fat as substrate for HP than rats kept in warmer environments. The cold environment results in an increase in the amount of interscapular brown adipose tissue, but no significant difference was found between DF levels.

Adipose Tissue, Brown↗

PubMed1997

Secondary prevention of heart disease amongst patients with lipid abnormalities: practice and trends in the United States.

Patients with established coronary disease and abnormalities of lipid metabolism represent a particularly important subgroup, since their mortality risk is typically 10 times greater than that amongst-subjects with comparable risk factors but no clinical history. Such patients are commonly treated initially with anti-anginal therapy; if ischaemic symptoms persist they often undergo revascularization (bypass or angioplasty). While invasive procedures restore blood flow and relieve ischemia, they do not, in most cases, reduce risk of subsequent MI or death, or alter the underlying atherogenic process(es). Despite this, there has been a progressive 54% decline in age-adjusted cardiac mortality over the period 1960-1995, which appears best attributable to US lifestyle changes. In particular, the past decade has provided compelling evidence for the merits of a fourth approach: comprehensive risk factor management. Clinical outcome studies have confirmed the substantial merit of aspirin prophyllaxis and of intensive lipid-lowering therapy in secondary prevention. Prospective angiographic trials and evidence from studies of vascular biology have provided insight into mechanisms of benefit. As a consequence, lipid therapy and aspirin use have increased greatly among middle aged and older US citizens, especially those with CAD. The growth of comprehensive medical management now rivals that of invasive revascularization in secondary prevention.

Aspirin↗