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Biomedical subjects

E T Li

Publications and source records attributed to E T Li.

At least 19 recordsLinked to original sources
PubMed2001

Body fat determination by dual energy X-ray absorptiometry and its relation to body mass index and waist circumference in Hong Kong Chinese.

OBJECTIVE: To determine the relationship between percent body fat and body mass index (BMI) in the Chinese population of Hong Kong and to investigate whether the newly proposed lower BMI cut-offs for obesity in the Asia-Pacific Region recommended jointly by the International Association for the Study of Obesity, the International Obesity Task Force and the WHO are appropriate for Hong Kong Chinese. METHODS: A total of 190 female and 140 male healthy subjects were recruited from the community. BMI was calculated as weight/height(2). Body fat content (%BF) was measured by dual-energy X-ray absorptiometry (DEXA). RESULTS: Comparing %BF measured by DEXA with predicted %BF derived from BMI using a prediction formula developed in Caucasian population showed that the formula significantly under-predicted %BF by 1.1% in males and 3.4% in females. A predicted BMI of 25 and 30 kg/m(2) using a Caucasian-based formula corresponds to an actual BMI of 23 and 25 kg/m(2), respectively. On linear regression analysis, 25% BF corresponds to a BMI of 24.6 kg/m(2) in males and a waist circumference of 86 cm; 35% BF corresponds to a BMI of 22.6 kg/m(2) and a waist circumference of 73.5 cm in females. CONCLUSION: Hong Kong Chinese population have a higher %BF for a given BMI which would partly explain why the health risks associated with obesity occur at a lower BMI. Our results would support the recommendations of using lower BMI cut-offs to define obesity in the Asia Region.

Absorptiometry, Photon↗
PubMed2000

Isolation of leptin-binding peptides from a random peptide phage library.

Leptin plays a role in regulating the body weight in mice. Injection of recombinant mouse leptin expressed in Escherichia coli reduced the food intake and body weight in normal, ob/ob and diet-induced obesity mice. Hyperglycemia, hyperinsulinemia and hypothermia can also be corrected in ob/ob mice after leptin injection. Leptin is a 16-kDa secretory protein comprising 167 amino acids produced in adipose tissue and is secreted to blood stream. In this study, a recombinant mouse leptin was generated and purified from a baculovirus expression system. This protein was used to identify putative ligands using a phage library of random peptides. Three leptin-binding phage clones were found, which were characterized by DNA sequencing and ELISA methods. The amino acid sequences of the reactive peptides are: LAYCSDPVRCLVWWY, MFWISAVSFVDHALV and LVLVLSAFLCCGVG. All three clones bound to recombinant human and mouse leptins. These peptides may be useful tools to study leptin-receptor interaction, food intake and body weight regulation.

Amino Acid Sequence↗
PubMed1999

Menstrual cycle and voluntary food intake in young Chinese women.

The effect of menstrual cycle phase on energy and macronutrients intakes was assessed in 20 university students (21.2+/-1.3 years) all of whom experienced ovulatory cycle as documented by a surge in urinary luteinizing hormone. Three-day food intake records, which consisted of one weekend day, were kept in both mid-follicular and mid-luteal phases. Mean daily energy intake was higher (p=0.02) in the luteal phase (6978+/-1847 kJ) than in the follicular phase (6095+/-1174 kJ). Intakes of carbohydrate and fat were also significantly elevated (by 15 and 21%, respectively) in the luteal phase. The menstrual phase effect on energy intake was attributed to the substantially higher intakes from Thursday through Sunday in the luteal phase. The proportion of energy from the three macronutrients was not affected by menstrual phase nor day of the week.

Adult↗
PubMed1999

Dual-energy X-ray absorptiometry for body composition estimation in Chinese women.

OBJECTIVE: To determine whether dual-energy X-ray absorptiometry (DXA) is a valid method for body composition assessment of obese and non-obese subjects. DESIGN: Cross-sectional study. SUBJECTS: Chinese women living in Hong Kong; 66 of 91 subjects had body mass index (BMI) of >25 kg/m2. MEASUREMENTS: Anthropometrics, including body weight, body height, waist and hip girth. Percentage body fat (%BF) and fat-free mass (FFM) from DXA (Hologic 2000 plus, Enhanced Array Whole Body Version 5.63) were compared with that based on a tracer dose of deuterium oxide for the determination of total body water (TBW). RESULTS: In both obese and non-obese subjects, FFMDXA was similar to FFMTBW. The Bland and Altman-type analysis indicated that comparable between-methods differences (mean bias) and limits of agreement were obtained in obese and non-obese subjects for FFM (0.4, between -4.4 and 5.2 kg vs 0.5, between -3.1 and 4.1 kg) and %BF (-0.6, between -7.6 and 6.4% vs -1.2, between -8.6 and 6.2%). The %BF bias was independent of age, BMI, hip circumference, and waist-to-hip ratio, but correlated with waist girth (r=0.24, P=0. 021). CONCLUSION: The sources of bias are methodological and anthropometric in nature. The between-methods differences, however, are small and clinically insignificant. DXA is a valid method for assessing the body composition of obese patients. SPONSORSHIP: This study was supported by a HKU-CRCG grant.

Absorptiometry, Photon↗
PubMed1999

Resting metabolic rate and thermic effects of a sucrose-sweetened soft drink during the menstrual cycle in young Chinese women.

The resting metabolic rate (RMR) and thermic effects (TEF) of a sucrose-sweetened soft drink in a group (n = 19) of ovulating young Chinese women were determined by indirect calorimetry in the midfollicular and midluteal phases of the menstrual cycle. Urinary luteinizing hormone surge was used to confirm ovulation. The RMR was measured twice in each phase and found to be similar (F(1,18) = 0.863) across the follicular (5018 kJ/24 h) and the luteal (5098 kJ/24 h) phases. Within each phase and on separate days, subjects were given water (280 mL) or sucrose-sweetened soft drink (539 kJ). Soft drink, but not water, consumption increased energy expenditure over a period of 45 min. Compared with the follicular phase, a small but significant increase in TEF (kJ/45 min) was observed in the luteal phase (t = 2.434, p < 0.05). Energy expenditure after drinking the soft drink, however, was similar in the two phases. RMR was positively correlated with TEF (r = 0.613, p < 0.01) and net TEF (r = 0.648, p < 0.005) in the luteal but not the follicular phase. In ovulating women, the thermic effect of sucrose is influenced by the phase of the menstrual cycle.

Adult↗
PubMed1994

Effects of essential amino acids on food and water intake of rats.

This study examined the effects of selected groups of essential amino acids (EAAs), given by gavage, on short-term food and water intake. Amino acid groups were selected on the basis of their common physiologic functions in relation to current hypotheses on the role of amino acids in food intake control, and the quantities given were based on the proportions in 1.5 g of the EAA content of albumin. The complete EAA mixture (1.5 g) suppressed food intake by an average of 60 and 37% during the 1st and 2nd h of feeding, respectively, but had no influence on feeding in the subsequent 12 h. Total daily (14 h) intake was decreased by 9%. With the exception of the aromatic amino acid (Phe + Tyr + Trp, 0.34 g) group, all groups significantly decreased food intake by a comparable magnitude (32%) during the 1st h. In this time period, rats given the EAAs, Arg + Met + Val (0.38 g), and Arg + His + Lys (0.44 g) mixtures increased their water intake, whereas intake by rats given the Phe + Tyr + Trp + Thr (0.46 g) and Ile + Leu + Val (0.45 g) mixtures was unchanged. Thus, the food intake suppression caused by EAAs was not accounted for by an equal effect of its component amino acid groups. As well, food intake suppression by amino acid groups was not explained by increased water consumption, nor was it simply related to the quantity of nitrogen provided by the treatment.

Amino Acids, Essential↗
PubMed1994

Dissociation between plasma and brain amino acid profiles and short-term food intake in the rat.

The relationship between plasma and brain amino acids and short-term food intake after administration of albumin, or its constituent amino acids, was examined. Rats given protein (0.85 g chicken egg albumin) or an amino acid mixture patterned after egg albumin reduced their food intake during 1 h of feeding beginning 30 min after gavage. Similarly, when given separately, the essential (EAA) and nonessential amino acid (NEAA) fractions of egg albumin caused comparable decreases in food intake. As the dose increased from 0.5 to 1.5 g the duration of anorexia prolonged to 12 h. Little change occurred in plasma amino acids at 30 and 60 min after albumin at 0.85 g, although many increased by 25-50% at 60 min after 1.5 g. Marked changes in plasma occurred after gavage with the total mixture of constituent free amino acids and after either EAA or NEAA fractions. Brain amino acid concentrations were little affected by albumin and did not show consistent changes after the amino acid treatments. Thus the reductions in food intake after ingestion of albumin or of its constituent amino acids were not predicted from the resulting changes in either plasma or brain concentrations of amino acids.

Administration, Oral↗
PubMed1993

Buspirone-induced carbohydrate feeding is not influenced by route of administration and nutritional status.

Rats were habituated to ad lib food intake from two isoenergetic diets that differed in carbohydrate and protein content. To examine the route of administration effect, buspirone (0.6, 1.0, and 1.4 mg/kg) was injected into satiated rats either subcutaneously or intraperitoneally. Overall, no route of administration effect was observed; however, when results of the lowest dose were analyzed separately, the subcutaneous route was more effective than the intraperitoneal route. Regardless of route of administration, buspirone increased food intake over the first 2 h of food presentation in a dose-dependent manner. Moreover, the increase was entirely attributed to increases in intake from the high carbohydrate diet. In the subsequent experiment, the effect of buspirone (0.6 mg/kg) was examined in both satiated (early light period) and nonsatiated rats (early dark period). Both groups responded to buspirone with an increase in carbohydrate intake. Despite differences in baseline intake, the absolute increase was similar between satiated and nonsatiated rats. These data suggest that both sensitivity and selectively of buspirone-induced feeding are neither influenced by route of administration nor nutritional status of rats.

Animals↗
PubMed1992

Effect of 5-HT agonists on rats fed single diets with varying proportions of carbohydrate and protein.

Low doses of 5-HT agonists have been shown to selectively suppress carbohydrate intake in rats given dietary choices. To investigate further the relationship between dietary macronutrient composition and 5-HT-induced anorexia, the present study examined the effects of three 5-HT agonists on rats fed single isocaloric diets containing varying proportions of carbohydrate (CHO) and protein (PRO). Rats were habituated to eat one of the three diets (73.5% CHO--10% PRO, 58.5% CHO--25% PRO or 43.5% CHO--40% PRO) during the dark period (1900-0700 h). Saline or 5-HT agonists (fluoxetine, RU 24969 and dexfenfluramine) were administered intraperitoneally at 1845 hours, 15 min prior to food access. At the doses used, food intake was significantly affected only during the first hour of eating. All 5-HT agonists caused dose-dependent decreases in food intake (P < 0.01). The magnitude of decrease, however, was significantly influenced by diet composition. Reduction in intake was greatest in rats fed the 73.5% CHO--10% PRO diet. Thus, rats chronically fed a diet high in carbohydrate content were more sensitive to the anorectic effect of 5-HT agonists than rats fed diets containing moderate to low levels of carbohydrate.

Animals↗
PubMed1991

Effects of repeated administration of serotonergic agonists on diet selection and body weight in rats.

Food intake, diet selection and body weight gain were examined in three separate experiments in which rats received saline or one of three serotonergic agonists, dexfenfluramine, RU 24969 and fluoxetine. In all experiments, food was available only in the dark period during which time rats were given simultaneous access to two isoenergetic diets which differed in their protein and carbohydrate content. After habituation to this feeding paradigm and intraperitoneal injections, rats were assigned to control or drug group. Saline or a serotonergic agonist was given to the same rat once daily, 15 min prior to feeding, for six consecutive days. All three agonists (1.5 mg/kg for dexfenfluramine and RU 24969; 3 mg/kg for fluoxetine) caused immediate (first two h of feeding) hypophagia which was accounted for by the selective suppression in intake of the high-carbohydrate-low-protein diet. This selective shift in diet choice was sustained upon repeated exposure. Although the effects of these agonists on daily (12-h) feeding was less pronounced, appetite suppression was due entirely to reduced intake of the high-carbohydrate-low-protein diet. Of the three agonists tested, partial tolerance was observed only after dexfenfluramine. Nevertheless, all three agonists caused comparable declines in weight gain. These results suggest that repeated administration of serotonergic agonists has sustained impacts on food intake, diet choice and weight gain.

Animals↗
PubMed1990

Selective increase in carbohydrate intake by rats treated with 8-hydroxy-2-(di-n-propylamino)-tetraline or buspirone.

Both 8-hydroxy-2-(di-n-propylamino)-tetraline (8-OH-DPAT) and buspirone (BUSP) were found to induce food intake in free-feeding, self-selecting young rats. The hyperphagia was macronutrient specific. In rats given simultaneous access to two diets which differed in carbohydrate and protein content, 8-OH-DPAT and BUSP selectively increased intake from the diet with high carbohydrate content during a two hour test. This specific behavioral effect is dose-dependent and is opposite to that induced by serotonin releasers or reuptake inhibitors. In a separate experiment, the selective decrease in carbohydrate intake after fluoxetine (FLX) was blocked by 8-OH-DPAT co-administration. These results further support a role for the serotonergic system in the control of feeding and macronutrient specific appetites.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1990

Food intake and selection pattern of rats treated with dexfenfluramine, fluoxetine and RU 24969.

The effects of two indirect (dexfenfluramine and fluoxetine) and one direct (RU 24969) serotonergic agonists on diet selection over a 12-hr period were examined. Rats were habituated to eat, during the dark period, from two isoenergetic diets that differed in carbohydrate and protein content. Drugs were injected intraperitoneally at 1845 hr, 15 min prior to food access. The drugs exerted their effects mainly during the first hour of feeding (1900-2000 hr). At this time, a selective suppression in intake of the high carbohydrate-low protein diet was the most prominent characteristic of all three serotonergic agonists. This macronutrient specific effect was particularly strong at low dosages (dexfenfluramine, fluoxetine and RU 24969: 0.5, 2.0 and 1.0 mg/kg, respectively). With time, as the effect of drugs wore off, diet selection pattern became more variable. The fact that both indirect 5-HT agonists and a direct selective 5-HT receptor agonist share a specific behavioral effect provides additional support for the role of serotonin in the control of macronutrient specific appetites.

Animals↗
PubMed1990

Food intake and choice in lean and obese Zucker rats after intragastric carbohydrate preloads.

Feeding behavior in response to a carbohydrate preload was determined in lean and obese Zucker rats. Rats were adapted to a schedule of feeding during a 12-h daily dark period. Carbohydrate preloads (cornstarch in water) were given by intragastric intubation 30 min before rats had access to a choice of two diets that differed in their protein and carbohydrate contents. Behavioral responses of lean rats to carbohydrate preloads were prompt and selective. In the first hour of feeding, reduction in intake, mainly of the high carbohydrate-low protein diet, more than compensated for the energy content of the preload. In contrast, obese rats failed to achieve a similar degree of compensation to the energy surplus from the carbohydrate preload during the first hour of feeding. Also, their decreases in food intake were nonselective. In general, it took obese rats two or more hours to adjust their feeding behavior in response to a carbohydrate preload. Increasing the size of the preload did not improve the overall response of obese rats, but an extra 30-min lapse between preload and food access led to selective suppression in first-hour intake from the high carbohydrate-low protein diet. These findings suggest that altered food intake and selection behavior of the obese Zucker rat may be, in part, due to a delay in response to physiologic and metabolic changes arising from carbohydrate ingestion.

Analysis of Variance↗
PubMed1989

Route of delivery of phenylalanine influences its effect on short-term food intake in adult male rats.

The effect of phenylalanine (Phe) on plasma and brain Phe and tyrosine (Tyr) levels and on short-term food intake in male rats was measured after intragastric (i.g.), subcutaneous (s.c.) and intraperitoneal (i.p.) administration. Compared to equimolar alanine (Ala), which served as the control, Phe significantly suppressed feeding at a dose of 90 mg/kg body wt when given i.p., but doses up to 720 mg/kg body wt had no effect when given i.g. or s.c. The high doses of Phe given by the i.g. or s.c. route resulted in higher levels of Phe in both plasma and brain than those following i.p. injection (90 mg/kg body wt). Furthermore, brain Tyr levels after i.g. Phe (720 mg/kg body wt) were equal to or higher than after i.p. Phe (90 mg/kg body wt). We conclude that the route of administration is an important variable influencing the effects of Phe on feeding behavior, and that these effects are not readily explained by plasma or brain Phe and Tyr concentrations.

Alanine↗
PubMed1987

Food intake and selection after peripheral tryptophan.

Two studies investigated the effects of peripheral (IP) administration of the dietary indispensible amino acid tryptophan, on food intake and macronutrient selection in rats adapted to a 12 hr nocturnal feeding period and a choice of 10% and 60% casein diets. In a dose-response study (35, 55, 75, 95, 115 mg/kg), the threshold dose of 75 mg/kg produced a significant reduction in total food intake (3.6 to 2.3 g, p less than 0.05) during the first hour of feeding. The reduction in carbohydrate intake (2.1 vs. 1.2 g, p less than 0.05) was greater than that for protein intake (1.6 vs. 1.1 g, p less than 0.05). Twelve hr total food intake was also decreased (20.9 to 19.5 g, p less than 0.05) and this was attributable to decreased carbohydrate intake (13.2 to 11.8 g, p less than 0.05). In a second study designed to determine if tryptophan's effects were mediated by the central nervous system, brain tryptophan uptake was blocked by co-injecting valine with tryptophan. The significant reduction in first hour total food intake by tryptophan was not prevented by co-injection of an equal quantity of valine (3.5 to 1.8 g, p less than 0.05). Again the suppression of carbohydrate intake (2.0 to 0.9 g p less than 0.05) was greater than that for protein intake (1.5 to 0.9 g, p less than 0.05). This dose of valine significantly reduced brain tryptophan uptake by 16% (21.3 to 17.8 micrograms/g, p less than 0.05) and when administered alone did not affect first hour total food intake (3.1 vs 3.2 g).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗