Role of EGFR but not HER2 or HER3 gene copy number in predicting sensitivity of head and neck squamous cell carcinoma (SCCHN) cell lines to EGFR tyrosine kinase inhibitors

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Background: EGFR gene copy number has previously been reported to predict for improved overall survival in NSCLC patients treated with gefitinib (IRESSA) or erlotinib compared with placebo [JCO 2006;24:5034–42 & N Engl J Med 2005;353:133–44]. The utility of EGFR gene copy number as a predictive biomarker in other tumour types such as squamous cell carcinoma of the head and neck (SCCHN) is currently under clinical investigation. The present study examined a panel of 20 SCCHN cell lines to identify potential biomarkers predicting in vitro sensitivity to EGFR tyrosine kinase inhibitors (TKIs). Methods: A panel of 20 SCCHN cell lines was screened for sensitivity to gefitinib, vandetanib or erlotinib using a viable cell number endpoint, with G150 values determined for each cell line (inhibitor concentration required to give 50% growth inhibition). Cell lines were blinded and assessed for EGFR, HER2 and HER3 protein expression by ELISA, mutation status by dye-terminator sequencing, and gene copy number by fluorescence in situ hybridisation (FISH). Results: A broad range in sensitivity was observed for all compounds across the panel of 20 SCCHN cell lines (G150 ranging from 0.001uM to =10uM). 12 cell lines were positive for EGFR genomic gain. Sensitivity (GI50 <1uM) to all EGFR TKIs was seen in 11 lines and resistance (GI50 >8uM) in 5 lines. Of the sensitive cell lines, 9 were positive for EGFR genomic gain compared with only 1 of the resistant lines. Furthermore, EGFR protein expression also had a direct association with EGFR TKI sensitivity. In contrast, only 4 cell lines were positive for HER2 or HER3 genomic gain and there was no correlation with sensitivity. The most sensitive cell line was positive for EGFR genomic gain and was the only line to have an EGFR TK mutation (S768I in exon 20). Conclusions: EGFR gene copy number and protein expression appeared to have predictive value in identifying SCCHN cell lines sensitive to EGFR TKIs.

No significant financial relationships to disclose.

Effect of carbohydrate overfeeding on whole body macronutrient metabolism and expression of lipogenic enzymes in adipose tissue of lean and overweight humans

OBJECTIVE

Lipids stored in adipose tissue can originate from dietary lipids or from de novo lipogenesis (DNL) from carbohydrates. Whether DNL is abnormal in adipose tissue of overweight individuals remains unknown. The present study was undertaken to assess the effect of carbohydrate overfeeding on glucose-induced whole body DNL and adipose tissue lipogenic gene expression in lean and overweight humans.

DESIGN

Prospective, cross-over study.

SUBJECTS AND METHODS

A total of 11 lean (five male, six female, mean BMI 21.0+/-0.5 kg/m(2)) and eight overweight (four males, four females, mean BMI 30.1+/-0.6 kg/m(2)) volunteers were studied on two occasions. On one occasion, they received an isoenergetic diet containing 50% carbohydrate for 4 days prior to testing; on the other, they received a hyperenergetic diet (175% energy requirements) containing 71% carbohydrates. After each period of 4 days of controlled diet, they were studied over 6 h after having received 3.25 g glucose/kg fat free mass. Whole body glucose oxidation and net DNL were monitored by means of indirect calorimetry. An adipose tissue biopsy was obtained at the end of this 6-h period and the levels of SREBP-1c, acetyl CoA carboxylase, and fatty acid synthase mRNA were measured by real-time PCR.

RESULTS

After isocaloric feeding, whole body net DNL amounted to 35+/-9 mg/kg fat free mass/5 h in lean subjects and to 49+/-3 mg/kg fat free mass/5 h in overweight subjects over the 5 h following glucose ingestion. These figures increased (P<0.001) to 156+/-21 mg/kg fat free mass/5 h in lean and 64+/-11 mg/kg fat free mass/5 h (P<0.05 vs lean) in overweight subjects after carbohydrate overfeeding. Whole body DNL after overfeeding was lower (P<0.001) and glycogen synthesis was higher (P<0.001) in overweight than in normal subjects. Adipose tissue SREBP-1c mRNA increased by 25% in overweight and by 43% in lean subjects (P<0.05) after carbohydrate overfeeding, whereas fatty acid synthase mRNA increased by 66 and 84% (P<0.05).

CONCLUSION

Whole body net DNL is not increased during carbohydrate overfeeding in overweight individuals. Stimulation of adipose lipogenic enzymes is also not higher in overweight subjects. Carbohydrate overfeeding does not stimulate whole body net DNL nor expression of lipogenic enzymes in adipose tissue to a larger extent in overweight than lean subjects.

Mechanisms of action of beta-glucan in postprandial glucose metabolism in healthy men

OBJECTIVE

To assess whether beta-glucan (which is fermented in the colon) lowers postprandial glucose concentrations through mechanisms distinct from a delayed carbohydrate absorption and inhibits de novo lipogenesis.

DESIGN

Administration of frequent small meals each hour over 9 h allows a rate of intestinal absorption to be reached which is independent of a delayed absorption. A group of 10 healthy men received either an isoenergetic diet containing 8.9 g/day beta-glucan or without beta-glucan for 3 days. On the third day, the diet was administered as fractioned meals ingested every hour for 9 h.

SETTING

Laboratory for human metabolic investigations.

SUBJECTS

Ten healthy male volunteers.

MAIN OUTCOME MEASURES

Plasma glucose and insulin concentrations, glucose kinetics, glucose oxidation, de novo lipogenesis.

RESULTS

On the third day, plasma glucose and free fatty acid concentrations, carbohydrate and lipid oxidation, and energy expenditure were identical with beta-glucan and cellulose. Plasma insulin concentrations were, however, 26% lower with beta-glucan during the last 2 h of the 9 h meal ingestion. Glucose rate of appearance at steady state was 12% lower with beta-glucan. This corresponded to a 21% reduction in the systemic appearance rate of exogenous carbohydrate with beta-glucan, while endogenous glucose production was similar with both diets. De novo lipogenesis was similar with and without beta-glucan.

CONCLUSION

Administration of frequent meals with or without beta-glucan results in similar carbohydrate and lipid metabolism. This suggests that the lowered postprandial glucose concentrations which are observed after ingestion of a single meal containing beta-glucan are essentially due to a delayed and somewhat reduced carbohydrate absorption from the gut and do not result from the effects of fermentation products in the colon.

Calcium supplementation of chocolate: effect on cocoa butter digestibility and blood lipids in humans

BACKGROUND

The digestibility of cocoa butter was reported in animal but not human studies to be low (60-70% and 89-94%, respectively). These differences could be due to the much higher ratio of calcium to fat (by wt) in the diet of rats (0.04-0.18) than in that of humans (0.01).

OBJECTIVE

We investigated whether supplementation of chocolate with 0.9% calcium (by wt), as an integral part of a Western diet, reduces absorption of cocoa butter and hence the digestible energy value of chocolate. We also assessed the effect of calcium supplementation on the blood lipid profile.

DESIGN

Ten men were fed control diets containing 98-101 g chocolate/d with or without a 0.9%-Ca supplement (0.9 g Ca/d) for 2 periods of 2 wk each. The study was conducted with use of a randomized, double-blind crossover design under free-living conditions but with strict control of food intake.

RESULTS

Calcium supplementation of chocolate increased fecal fat 2-fold (from 4.4 to 8.4 g/d; P < 0.0001) and reduced the absorption of cocoa butter by 13.0%. This was due mainly to an increase in the excretion of palmitic and stearic acids (3.4 g/d), which reduced the absorbable energy value of the chocolate by approximately 9%. This supplementation also reduced plasma LDL cholesterol by 15% (P < 0.02); HDL cholesterol was unchanged.

CONCLUSIONS

Calcium supplementation can be used as a means of reducing the absorbable energy value of chocolate. Supplementation with 2.25% CaCO3 had no effect on the taste of chocolate, was well tolerated by the subjects, and reduced LDL cholesterol in a short-term study.

Digestibility of cocoa butter from chocolate in humans: a comparison with corn-oil

OBJECTIVE

To compare, in humans, the digestibility of moderate amounts of cocoa butter (30.7 g/d) consumed in the form of chocolate as part of a normal western diet with that of a well-absorbed fat (corn oil); and hence determine whether, by virtue of its apparent low absorption, cocoa butter can be considered to be a low calorie fat.

DESIGN

Randomised, two-period crossover metabolic study, conducted under free-living conditions, but with strict control over food intake.

SETTING

Metabolic Unit, Nestlé Research Center Lausanne.

SUBJECTS

Twelve healthy men were selected from volunteers at the Nestlé Research Center and all subjects completed the study.

INTERVENTION

Two treatment periods of two weeks each: cocoa butter and control periods, with strict dietary control separated by a two week wash out period.

RESULTS

No differences (P>0.05) were observed in faecal weight (wet or dry), faecal fat nor in defecation frequency between treatments (cocoa butter and corn oil). Cocoa butter at a dose of 30.7 g/d in the form of black chocolate, consumed between two meals, was found to have a similar digestibility to that of corn oil (99 % of corn oil digestibility).

CONCLUSION

Cocoa butter, consumed as back chocolate within a normal mixed diet, has a high digestibility, similar to that of corn oil, and a digestible energy value of 37 kJ/g in man. Thus, cocoa butter cannot be considered to be a low-calorie fat.

SPONSORSHIP

Nestec Ltd, Switzerland. European Journal of Clinical Nutrition (2000) 54, 120-125

Overnight glucose metabolism in obese non-insulin-dependent diabetic patients and in healthy lean individuals

Increased fasting hepatic glucose production is present in NIDDM patients, and has been shown to be due to increased gluconeogenesis. In order to determine the contribution of the cycling between glucose and three-carbon compounds (Cori and glucose-alanine cycles) to the increased hepatic glucose production, glucose kinetics measured overnight in seven obese NIDDM patients and six lean healthy subjects with both 6.6 2H glucose and U-13C glucose were determined. At 0500 h obese NIDDM subjects showed a 40% increase in glucose appearance calculated from 6.6 2H glucose, whereas glucose appearance calculated from U-13C glucose was similar compared to lean subjects, indicating increased glucose cycling. Non-oxidative glucose disposal was also increased three-fold in NIDDM patients. Glucose cycling was increased by 111% in NIDDM patients (118 +/- 18 mumole min-1 vs. 56 +/- 11 in controls, P < 0.05) and was positively correlated with plasma glucose concentration (r = 0.831, P < 0.001) and with non-oxidative glucose disposal (r = 0.714, P < 0.01). Four NIDDM patients were studied again after 3 days of insulin therapy. Insulin restored near-normoglycaemia (7.4 +/- 0.8 mmole l-1) and normalized rates of glucose appearance and glucose cycling. It is concluded that increased glucose cycling in obese NIDDM patients accounts for a major part of the increased fasting hepatic glucose production and non-oxidative glucose disposal in obese NIDDM subjects.

Effects of glucose and amino acid infusion on glucose turnover in insulin-resistant obese and type II diabetic patients

Glucose turnover was assessed from [6,6-2H]glucose and [U-13C]glucose dilution analysis in six lean nondiabetic subjects, six obese patients with normal glucose tolerance, and six obese patients with non-insulin-dependent diabetes mellitus (NIDDM) during sequential infusions of glucose (13.9 mumol/kg fat-free mass [FFM]/min) and glucose+amino acid (4.2 mg/kg FFM/min). Cori cycle activity was assessed from the difference between glucose turnover obtained from [6,6-2H]glucose and [U-13C]glucose. During infusion of glucose alone, total glucose turnover was increased by 70% in obese NIDDM patients. Amino acid infusion decreased glucose concentrations by 0.8, 0.5, and 1.8 mmol/L in controls, obese patients, and NIDDM patients, respectively. This decrease in glycemia occurred despite an increase in glucose turnover in lean and obese nondiabetic subjects, and was due to an increased metabolic clearance rate (MCR) of glucose. In NIDDM patients the MCR of glucose was unchanged, and the decrease in glycemia was explained by a diminution in hepatic glucose output. Glucose turnover obtained by [6.6-2H] dilution analysis exceeded significantly the values obtained by dilution analysis in obese subjects and obese NIDDM patients, but not in controls. This indicates an increased Cori cycle activity in these patients.

Effect of L-carnitine on submaximal exercise metabolism after depletion of muscle glycogen

The effect of L-carnitine on energy metabolism at a high lipolytic flux was studied. Nine healthy male subjects received L-carnitine (CARN) (3 g.d-1) for 7 d, or a placebo (CONT), both with Ca pentothenate. The treatment increased resting nitrogen excretion slightly (+15%, P < 0.02). After an overnight fast, the subjects were submitted successively to 20 min bicycle exercise at 43 +/- 2 (SEM) %VO2max, a glycogen depletion routine involving high intensity bouts to exhaustion, 1-2 h of rest, again 20 min at the initial load, and finally 20 min at 57 +/- 3 %VO2max. After glycogen depletion, blood short-chain acylcarnitine concentrations increased 5 times as much in CARN as in CONT (P < 0.02). Fat oxidation estimated from respiratory gas exchange doubled after glycogen depletion for the same exercise intensity. However, there were no treatment differences in nonprotein RQ, heart rate, perceived fatigue, and blood parameters. It is concluded that during submaximal exercise after glycogen depletion (i.e., at a high lipid flux) substrate metabolism is not influenced by L-carnitine supplementation.

Thermic effect of infused amino acids in healthy humans and in subjects with insulin resistance

The thermic effect of food has been observed to be decreased in subgroups of obese nondiabetic and obese diabetic subjects. The mechanisms responsible for this decrease have not been fully elucidated. Although protein elicits the largest thermic effect among the various nutrients, most studies have addressed carbohydrate- or fat-induced thermogenesis in insulin resistance. To determine whether the decreased thermic effect of nutrients in insulin-resistant patients could be related to a decrease in protein-induced thermogenesis, glucose [13.9 mumol.kg fat-free mass (FFM)-1.min-1] with or without amino acids (4.2 mg.kg FFM-1.min-1) was infused into a group of six obese nondiabetic subjects (Ob), six obese subjects with non-insulin-dependent diabetes mellitus (NIDDM), and six lean subjects. The thermic effect of infused amino acid (% of infused energy) measured by indirect calorimetry was 21.1 +/- 3.2%, 23.8 +/- 1.8%, and 20.0 +/- 2.9% in lean, Ob, and NIDDM subjects, respectively (NS). It is concluded that the thermic effect of protein is not altered in insulin-resistant patients.

Protein absorption and energy digestibility at high altitude

To test the hypothesis that malabsorption of dietary protein is partly responsible for the weight loss observed during prolonged altitude exposure, six healthy male subjects [31.8 +/- 4.5 (SD) yr] received 15N-labeled soya protein by mouth and [15N]glycine intravenously at 122 and 5,000 m. From the subsequent 4-day total urine and fecal pools, the different fractions of the administered 15N were determined by mass spectrometry. Weight and skinfold thickness were measured at the beginning and end of the altitude exposure. In addition, the overall digestible energy of the diet at altitude was assessed by a 3-day diet control and adiabatic bomb calorimetric assessment of the energy content of the corresponding fecal pool. The average decrease of the subjects' weight during altitude exposure was 3%. Loss of fat mass at altitude estimated from the skinfold measurements was 9%. Protein absorption, calculated as 100--[fecal excretion of 15N after ingestion of 15N soya protein (% of dose given)--fecal excretion of 15N after injection of 15N glycine (% of dose given)], was not significantly impaired at altitude compared with sea level (96 vs. 97%, respectively), and overall digestible energy at altitude, calculated as 100--percent undigested gross energy in the feces, amounted to 96%. It is concluded that, at least up to an altitude of 5,000 m, malabsorption does not play a role in altitude-related weight loss.

Effects of infused amino acids on glucose production and utilization in healthy human subjects

Amino acids have been reported to increase endogenous glucose production in normal human subjects during hyperinsulinemia: however, controversy exists as to whether insulin-mediated glucose disposal is inhibited under these conditions. The effect of an amino acid infusion on glucose oxidation rate has so far not been determined. Substrate oxidation rates, endogenous glucose production, and [13C]glucose synthesis from [13C]bicarbonate were measured in six normal human subjects during sequential infusions of exogenous glucose and exogenous glucose with (n = 5) or without (n = 5) exogenous amino acids. Amino acids increased endogenous glucose production by 84% and [13C]glucose synthesis by 235%. Glucose oxidation estimated from indirect calorimetry decreased slightly after amino acids, but glucose oxidation estimated from [13C]glucose-13CO2 data was increased by 14%. It is concluded that gluconeogenesis is the major pathway of amino acid degradation. During amino acid administration, indirect calorimetry underestimates the true rate of glucose oxidation, whereas glucose oxidation calculated from the 13C enrichment of expired CO2 during [U-13C]glucose infusion does not. A slight stimulation of glucose oxidation during amino acid infusion, concomitant with an increased plasma insulin concentration, indicates that amino acids do not inhibit glucose oxidation.

Metabolic effects of instant bean and potato over 6 hours

For 7 d six volunteers consumed at breakfast a 50-g starch meal prepared from either potato-flakes bran or instant bean flakes. These meals were isocaloric and had the same analytical composition. The metabolic effect of the meals on plasma glucose and insulin levels and on energy expenditure were assessed over 6 h on days 1 and 7 of each diet period. No significant differences in the shape and magnitude of plasma glucose and insulin responses were observed between days 1 and 7 of the same diet. Maximum glucose and insulin responses were significantly lower after the bean meal than after the potato meal. Although each meal tested was digested at a different rate, substrate oxidation and energy expenditure over 6 h were very similar.

Oxidative and non-oxidative glucose metabolism in non-obese type 2 (non-insulin-dependent) diabetic patients

Insulin resistance is a common feature of Type 2 (non-insulin-dependent) diabetes mellitus. This defect in insulin-mediated glucose metabolism could result from a defect in either glucose oxidation or non-oxidative glucose disposal. To examine this question, euglycaemic insulin clamp studies were performed in 16 normal weight Type 2 and 11 age-matched control subjects. In Type 2 diabetic patients the fasting plasma glucose concentration, 8.39 +/- 0.50 mmol/l, was allowed to decline (over 54 +/- 6 min) to 5.33 +/- 0.11 mmol/l before starting the insulin clamp. Total body glucose uptake was significantly decreased in Type 2 diabetic patients vs control subjects (148 +/- 15 vs 264 +/- 25 mg/min.m2, p less than 0.001). Both total glucose oxidation (59 +/- 6 vs 89 +/- 6 mg/min.m2, p less than 0.005) and non-oxidative glucose disposal (89 +/- 15 vs 179 +/- 24 mg/min.m2, p less than 0.005) were significantly reduced in the Type 2 diabetic patients. Basal glucose oxidation was also reduced in the Type 2 diabetic patients (22 +/- 3 vs 38 +/- 5 mg/min.m2, p less than 0.01). In conclusion, during the postabsorptive state and under conditions of euglycaemic hyperinsulinaemia, impairment of glucose oxidation and non-oxidative glucose disposal both contribute to the insulin resistance observed in normal weight Type 2 diabetic patients. Since lipid oxidation was normal in this group of diabetic patients, excessive non-esterified fatty acid oxidation cannot explain the defects in glucose disposal.

Thyroid hormones and thermogenesis: the metabolic cost of food and exercise

To mimic plasma T3 levels observed in a previous overfeeding study, six lean healthy men received replacement amounts of L-thyroxine (200 micrograms/d) to block endogenous thyroid hormone production while consuming their habitual diet. After 4 weeks equilibration on T4, L-triiodothyronine (T3) was given (45 micrograms/d) in addition to T4, to produce mild T3-thyrotoxicosis, for another 2 weeks. At the end of this period T3 was discontinued but the subjects continued to receive T4 for another 2 weeks. Resting metabolic rate, exercise efficiency, and the thermic effect of food were measured using a ventilated hood, open circuit indirect calorimeter at the end of each phase of the experiment. There was a significant increase in the resting metabolic rate of 6% (P less than 0.01) while the subjects were mildly T3-thyrotoxic. The increase in energy expenditure however, during exercise on a bicycle ergometer or following a 500 kcal liquid-formula meal remained unaltered in the same situation. Thus, mild T3-toxicosis does not alter the efficiency of exercise or the thermic effect of food. These results suggest that the increased plasma T3 levels, observed in overfeeding, could explain corresponding increases in resting metabolic rate but not changes in the efficiency of exercise or the utilization of food.

Influence of beta-adrenergic blockade on glucose-induced thermogenesis in man

The role of beta-adrenergically mediated sympathetic nervous activity in the regulation of glucose-induced thermogenesis was examined in healthy male subjects. Respiratory gas exchange was measured continuously, using the ventilated hood technique, under conditions of hyperinsulinemia and hyperglycemia (glucose clamp technique, insulin infusion 1 mU/kg per min, glucose levels 125 mg/dl above basal) before and after beta-adrenergic blockade (i.v. propranolol, 3-mg bolus plus 0.1 mg/min for 2 h). After 2 h of insulin and glucose infusion in series 1, glucose uptake had increased to 23.5 +/- 2.3 mg/kg per min and insulin concentration to 199 +/- 21 microU/ml. Simultaneously, the energy expenditure had risen by 0.39 +/- 0.05 kcal/min above basal. After propranolol administration, glucose uptake did not change, while energy expenditure fell significantly, to a level 0.28 +/- 0.04 kcal/min above basal. The glucose-induced thermogenesis (GIT) was 6.5 +/- 0.3% before and 4.6 +/- 0.5% (P less than 0.02) after propranolol. In series 2, insulin and glucose infusion was continued for 4 h without propranolol administration. Glucose uptake rose (+12%) and insulin levels increased (+40%) between the 2nd and 4th h but energy expenditure and GIT remained unchanged. Subjects in series 3 received saline infusion alone for 3 h, at which time propranolol administration as in series 1 was added during a further 2-h period. No changes in energy expenditure were seen during saline or propranolol infusion. These data demonstrate the presence of a beta-adrenergically mediated sympathetic nervous component in glucose-induced thermogenesis in healthy human subjects. This factor may be of importance in the regulation of normal body weight in man.

Stimulation of thermogenesis in men after combined glucose-long-chain triglyceride infusion

The effect of combined long-chain triglyceride infusion (Intralipid 20%) with graded doses of insulin/glucose on energy expenditure was examined in 17 healthy young male volunteers by using the euglycemic insulin clamp technique in combination with indirect calorimetry. Intralipid was infused for 90 min at a constant rate of 0.23 g/min; plasma free fatty acids increased from base-line values of 380 +/- 8 mumol/l to steady state levels of 650 +/- 12 mumol/l. After 90 min the Intralipid was continued and insulin was infused at three rates (0.5, 2, and 4 mU/kg . min) to achieve steady state hyperinsulinemic plateaus of 63 +/- 4, 167 +/- 10, and 410 +/- 15 microU/ml. Plasma glucose concentration was maintained constant at basal euglycemic levels (insulin clamp technique) by infusing glucose at 0.24, 0.48, and 0.59 g/min, respectively. Glucose storage during the insulin clamp (ie, glucose uptake minus glucose oxidation) was 0.13, 0.33, and 0.40 g/min for each group and exogenous lipid storage was 0.17, 0.18, and 0.19 g/min, respectively. The net increment in energy expenditure was 0.15, 0.24, and 0.26 kcal/min, respectively, which represents 8.5% of the energy content of the total amount of glucose and lipid stored. The experimentally determined value (approximately 9%) for the cost of storing both glucose and lipid was found to be significantly greater than predicted by stoichiometric calculations. However, the experimental value for the combined infusion was less than that observed for glucose storage alone (12%). This finding provides support for the use of combined glucose/fat infusions in parenteral nutrition as it is used more economically than when glucose is infused alone.

Energy cost of glucose storage in human subjects during glucose-insulin infusions

The effect of graded levels of hyperinsulinemia on energy expenditure, while euglycemia was maintained by glucose infusion, was examined in 22 healthy young male volunteers by using the euglycemic insulin clamp technique in combination with indirect calorimetry. Insulin was infused at five rates to achieve steady-state hyperinsulinemic plateaus of 62 +/- 4, 103 +/- 5, 170 +/- 10, 423 +/- 16, and 1,132 +/- 47 microU/ml. Total body glucose uptake during each of the five insulin clamp studies was 0.41, 0.50, 0.66, 0.74, and 0.77 g/min, respectively. Glucose storage (calculated from the difference between total body glucose uptake minus total glucose oxidation) was 0.25, 0.29, 0.43, 0.49, and 0.52 g/min for each group, respectively, and represented over 60-70% of total glucose uptake. The net increment in energy expenditure after intravenous glucose was 0.08, 0.10, 0.14, 0.17, and 0.23 kcal/min, respectively. Throughout the physiological and supraphysiological range of insulinemia, there was a significant relationship (r = 0.95, P less than 0.001) between the increment in energy expenditure and glucose storage, indicating an energy cost of 0.45 kcal/g glucose stored. However, at each level of hyperinsulinemia, the theoretical value for the energy cost of glucose storage (assuming that all of the glucose is stored in the form of glycogen) could account for only 45-63% of the actual increase in energy expenditure that was measured by indirect calorimetry. These results indicate that factors in addition to glucose storage as glycogen must be responsible for the increase in energy expenditure that accompanies glucose infusion.

The comparative oxidation of glucose, fructose, sorbitol and xylitol in normal man

The aim of the study was to compare the effects of fructose, sorbitol and xylitol with those of glucose on blood glucose and insulin levels and carbohydrate utilization in man. The experiment was performed by means of continuous indirect calorimetry in five groups of five to six normal volunteers during infusion of either glucose, fructose, sorbitol, xylitol or a mixture of fructose, glucose and xylitol in the proportion of 2:1:1. Glucose and insulin did not present any important variations during the fructose, sorbitol and xylitol infusiosns. However, carbohydrate oxidation rose significantly during administration of these substrates. Carbohydrate oxidation rose 80 mg/min for fructose, 27 mg/min for sorbitol, 39 mg/min for xylitol and 75 mg/min for the carbohydrate mixture, in comparison to 101 mg/min for glucose. It is concluded that fructose, sorbitol and xylitol provoke an increase in carbohydrate utilization without a corresponding rise in glycemia and insulinemia.

Thermic effect of glucose in obese subjects studied by direct and indirect calorimetry

1. The thermic effect of a glucose load (50 g) was studied in ten control and eleven obese female subjects, using both direct and indirect calorimetry simultaneously. Experiments were done under conditions of thermal equilbrium (28 degrees and 30% relative humidity). 2. Thermal balance (heat production measured by indirect calorimetry minus heat losses measured directly) was negative in the control group during the fasting period (heat deficit -14-2 +/- 5-0 kJ/m2 per h), whereas that of the obese group was in equilibrium (+ 1-4 +/- 4-8 kJ/m2 per h). 3. After the glucose load, metabolic rate increased 13-0 +/- 1-5 and 1-3% in the control and obese groups respectively. 4. In contrast to the metabolic rate, total heat losses were not significantly altered in either group after the glucose load. Total heat losses of the obese group were significantly lower than those of the control group throughout the experimental period. 5. During the experiments the amount of heat stored was increased in both groups. Thermal balance in the control group became positive while that of the obese group remained positive. 6. During the fasting period, the control subjects oxidized more carbohydrates (90-4 mg/min) than lipids (68-8 mg/min), whereas obese subjects oxidized more lipids (103-7 mg/min) than carbohydrates (50.2 mg/min). After the glucose load, the oxidation rate of carbohydrates was increased in both groups to 158-1 mg/min in control subjects and 95-6 mg/min in obese subjects. 7. The mean skin temperature of the control subjects was significantly higher than that of the obese subjects and remained higher throughout the postprandial period. 8. These results indicate that: (a) during the fasting period, the energy sources utilized and the thermal balance of the two groups were different; (b) the thermic effect of glucose was less in the obese subjects and, therefore, might be a factor contributing to their low energy expenditure.