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Decreased insulin sensitivity and muscle enzyme activity in elderly subjects

Decreased insulin sensitivity and muscle enzyme activity in elderly subjects
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  European Journal of Clinical Investigation 1 988) 18,493-498 ecreased insulin sensitivity and muscle enzyme activity in elderly subjects Y. T. KKUSZYNSKA, G. PETRANYI K. G. M. M. ALBERTI, Department of Medicine, University of Newcastle upon Tyne, Newcastle upon Tyne, U.K. Received 30 December 1987 and in revised form 25 April 1988 Abstract. Skeletal muscle glycogen deposition, and the activation of muscle glycogen synthase and pyruvate deh y drogenase during a hyerinsulinaemic euglycaemic clamp have been measured in six young and six elderly males matched for body mass index, physical activity and diet. Clamp glucose requirement (insulin, 0.1 U kg-' h-') was significantly lower in the older subjects (8.0f0.4 mg kg-' min-I) than in younger subjects (10.5f0.6 mg kg-' min-I, P<0.02). Although the older subjects had a 6.5 decrease in lean body mass, clamp glucose requirement expressed per unit of lean body mass was also significantly decreased in the older subjects (10.2f0.5 vs. 12.4f0.6 mg kg-* min-I, P<O.O5). The increase in muscle glycogen with the clamp was decreased by 33 in the older subjects (elderly: 13.1 1.3 mg g-' protein, young: 19.6f2.2 mg g-' protein; P < 0.05), and was strongly correlated with clamp glucose requirement r =0*72, P< 0.01 . Glucose-6-phosphate independent glycogen synthase activity increased significantly between fasting and the end of the clamps in both groups (P< 0.001), but was lower at the end of the clamp in the older subjects P 0.05). Glycogen synthase activity at the end of the clamp correlated with both clamp glucose requirement r =0.83, P< .01 and muscle glycogen deposition r 0.73, P < 0.01 . Skeletal muscle pyruvate dehydro- genase activity increased significantly between fasting and end of clamp in the young subjects P 0.05 but not in the elderly males. Pyruvate dehydrogenase activity at the end of the clamp, however, did not differ between the two groups and was not related to clamp glucose requirement. Thus the impaired glucose hand- ling of the elderly may be related to decreased insulin action on muscle and muscle enzymes. Keywords. Ageing, insulin insensitivity, glucose clamp, skeletal muscle, glycogen, glycogen synthase, pyruvate dehydrogenase. Introduction The progressive deterioration of glucose tolerance with age is well recognized [1,2] but its mechanism is uncertain. In most studies, serum insulin concentra- tions have been found to be normal or increased during Correspondence: Dr Y. T. Kruszynska Department of Medicine Royal Free Hospital Pond Street London NW3 2QG U.K. oral or intravenous glucose challenge [I 31, although there is some controversy over whether first-phase insulin release is normal [4, 51. The combination of impaired glucose tolerance and normal or elevated serum insulin levels has led to the concept that insulin resistance is the major factor involved in the age- related deterioration of glucose tolerance [2, 31. This concept is supported by a number of studies showing a decline in insulin-stimulated glucose disposal during a euglycaemic clamp [6-81. The tissue responsible for insulin insensitivity at the doses used for the euglycae- mic clamp is likely to be skeletal muscle [9]. Consistent with this is the finding of Jackson and colleagues [3] of decreased glucose uptake by forearm muscle during oral glucose loading in elderly subjects. Although skeletal muscle would appear to be the tissue responsible for the insulin insensitivity in elderly subjects, the biochemical site of the metabolic defect remains to be determined. We have therefore examined the relationship between clamp glucose disposal, muscle glycogen formation and the activities of muscle glycogen synthase and pyruvate dehydrogenase. These two insulin-regulated enzymes are on the specific pathways of glucose storage and glucose oxidation, respectively. Patients and methods Twelve normal male subjects were recruited and divided into young [21-37 years (mean SD, 27 ] and elderly [53-75 years (mean SD, 64 )] groups. The two groups were matched for body mass index (BMI). Their clinical characteristics are summarized in Table 1. Lean body mass was estimated from the sum of skin-fold thickness at four sites (biceps, triceps, suprailiac and subscapular) [lo]. Approval for the study was given by the local ethical committee, and informed consent was given by each subject. All subjects were healthy and taking no medications. They were all leading active lives but did not regularly undertake strenuous occupational or recreational exercise. On questioning they appeared well matched for physical activity. No subject had a family history of diabetes. Subjects were asked to maintain their regular diet pattern before study. Daily carbohydrate, fat and total calorie intake in the week prior to study were estimated by dietary histories. All subjects consumed a 493  494 Y. T KRUSZYNSKA, G. PETRANYI & K. G. M. M. ALBERT1 Table 1. Clinical characteristics of the subjects studied Young Elderly Subjects n) 6 6 Age 21k7 64 9 BMI kg m-*) 24k2 25k Weight kg) 71+5 71 k4 Lean body mass kg) 60k4 56k2 Per cent adiposity ( ) 15f2 21f3 Ratio of subscapular to triceps skin-fold thickness 1.7k0.4 2.3 .7 Mean SD. diet containing at least 180 g carbohydrate, and the diets were similar in the two groups. Study protocol Subjects were admitted to hospital on the evening before study and fasted from 21.00 h. On the morning of study two i.v. cannulae were inserted into forearm veins. One cannula was used for infusion of insulin (Human Actrapid, Novo, Basingstoke, U.K.) diluted in Haemaccel (Hoechst, Frankfurt am Main, FRG). The second cannula was inserted retrogradely in a distal vein, the hand being maintained in a hand- warmer at 60°C This cannula was used for intermit- tent blood sampling, being flushed after use with 0.15 moll-' saline. A basal blood sample was taken at 07.00 h for estimation of blood glucose, serum insulin and HbAI. A needle biopsy of the vastus lateralis muscle (- 250 mg) was then performed using a UCH-type needle [ under local lignocaine anaesthesia. The tissue was frozen immediately in liquid nitrogen. After the basal biopsy an i.v. insulin infusion (0.1 U kg-' h-') was begun from a Harvard syringe pump. Blood glucose concentration was measured at 5-min intervals by the glucose oxidase method (Yellow Springs Glucose Analyser, Clandon Scientific, Lon- don, U.K.), and clamped at 4.0 mmol 1-' for 4 h by adjustment of the rate of infusion of a solution of 20 (w/v) glucose in water [12]. Glucose turnover was not measured as hepatic glucose output is effectively supressed in normal subjects at the insulin dose used [7]. Samples for serum insulin determination were taken at 30-min intervals throughout the clamp. A second biopsy was performed on the contralateral vastus lateralis during the last 30 min of the clamp, metabolic data therefore being gathered in the preced- ing 30 min from 180 to +210 min. uscle glycogen synthase activity Muscle glycogen synthase activity was measured by the method of Golden et al [13] within 24 h of obtaining the tissue. Samples of muscle ( - 05 g) were homogenized (Polytron Kinematica, Lucerne, Swit- zerland) in 800 pl of Tris/HCl buffer, pH 7.8, contain- ing 10 mmol 1-' EDTA, 5 mmol 1- NaF and 2.5 g 1- rabbit liver glycogen type 111 (Sigma, Poole, Dorset, U.K.). The homogenate was centrifuged at 10 000 x g for 30 sin a micro-centrifuge, and the supernatant used for glycogen synthase assay by measuring the incor- poration of UDP-UI4C glucose into glycogen at 30°C. The final concentration of UDP-glucose in the assay was 6.7 mmol 1- . Total glycogen synthase activity was measured in the presence of 10 mmol I- glucose-6- phosphate. One unit of enzyme is the amount of enzyme catalysing the transfer of 1 pmol of glucose from UDP-glucose into glycogen per min at 30°C. uscle pyruvate dehydrogenase activity Skeletal muscle pyruvate dehydrogenase was measured spectrophotometrically [ 141 by coupling the acetyl CoA generated in the assay to p-aminophenyla- zobenzene sulphonic acid by arylamine acetyl transfer- ase prepared from pigeon liver [ 151. Muscle ( - .1 g) was homogenized at 0°C (Polytron Kinematica, set- ting No4, 30 s) in 8 pl of 100 mmol I- Tris/HCl buffer, pH 7.3, containing dithiothreitol (2.0 mmol 1-I), EDTA (2.0 mmol 1-I), 0.1 (v/v) Triton X 100 and 50 ml I- rat serum. Samples were freeze-thawed three times and centrifuged at 1 xg or 5 s. The final composition of the buffer in the assay was 100 mmol l-'Tris/HCl, 0-7 mmol l-I EDTA, 1.2 mmol l-' dithiothreitol, 1.0 mmol 1-' MgC12, 2.0 mmol 1- NAD, 1.0 mmol 1 I thiamine pyrophosphate, 1.0 mmol I-'pyruvate and 0.2 mmol I- coenzyme A. The decrease in absorbance was followed at 460 nm. For determination of total pyruvate dehydrogenase acti- vity, extracts were incubated with purified bovine kidney PDH phosphatase for 25 min at 30°C in the presence of 10 mmol 1-' MgCL and 10 mmol 1- dichloroacetate. One unit of enzyme is defined as the activity converting 1 pmol min-' of pyruvate at 30°C. Other analyses For determination of skeletal muscle glycogen ap- proximately 100 mg of muscle were extracted with perchloric acid. Glycogen was hydrolysed by the amyloglucosidase method [ 161 and the resulting glu- cose assayed by an automated enzymic fluorimetric method [ 171. The intra-assay coefficient of variation for muscle glycogen determination in rat skeletal muscle was 6.8%. Protein was determined by the method of Lowry et al [ 181. Serum insulin was assayed by a double antibody technique [19] using a human insulin standard. Glycosylated haemoglobin was measured by isoelectric focussing [20]. Statistical analysis Results are expressed as means & SE unless otherwise indicated. The significance of differences was tested by Student's paired or unpaired t-test as appropriate.  MUSCLE ENZYMES AND INSULIN SENSITIVITY IN AGEING 495 Correlations were sought by Pearson's least squares method. Results Table 2 Skeletal muscle glycogen content, glycogen synthase activity and pyruvate dehydrogenase activity in the two groups of normal subjects Fasting End ofclamp* Glucose clamp studies and insulin pharmacokinetics No differences were found between the young and old subjects in fasting blood glucose concentration (4.4 -t. 0.1 vs. 4 5 f .1 mmol 1-I), fasting serum insulin (6.0 .8 vs. 6.6 f .7 mU 1-I) or glycosylated haemo- globin (young: 5.6 0.2, elderly: 5.9 f .2 ). Steady- state serum insulin concentrations during the clamp from + 90 to + 210 min were not different between the two groups (young: 77 5, elderly: 86 + 4 mU 1-I). The blood glucose concentration from + 180 to + 2 10 min was 4.0 f .1 mmol I- ( SD) in the young subjects and 4.0+0.1 mmol I- in the older group. The coefficient of variation of blood glucose calculated for each subject was 2.6f0.9 f SD) and 3.1 1.0 , respectively. Glucose requirement to maintain the clamp calculated for the interval + 180 to +210 min was significantly decreased in the elderly subjects, 8.0k0.4 mg kg-' min-' compared with the younger subjects, 10.5f0.6 mg kg-' min-I; P<0-02. Clamp glucose requirement was also significantly decreased when expressed per unit of lean body mass (elderly: 10.2+0-5 mg kg-I min-I, young: 12.4f0-6 mg kg-' min- ; P < 0.05). Clamp glucose requirement was negatively correlated with age (r = .65, P < 0.05) but more strongly negatively correlated with per cent adiposity (r= -0.82, P<O.Ol). Skeletal muscle glycogen concentration and glycogen synthase activity After an overnight fast no difference was found in muscle glycogen concentration, total glycogen syn- thase activity or expressed glycogen synthase activity between the two groups of subjects (Table 2). The increase in muscle glycogen concentration between the basal and clamp biopsies was significantly greater in the younger subjects than in the older subjects (young: 19.6k2.2 mg g-' protein, elderly: 13.1 f 1.3 mg g-' protein; P < 0.05 , although total glycogen concentra- tions at the end of the clamp were not significantly different (Table 2, t = 1.824). Glycogen deposition was correlated with clamp glucose requirement when the study groups were combined (Fig. 1, r = 0.72, P < 0.01 but failed to reach statistical significance when the two groups were analysed separately (young: r = 0.42, elderly: r = 0.52). The correlation was not improved by expressing clamp glucose requirement in terms of lean body mass (r =0*73). Glucose-6-phosphate-stimulated (total) glycogen synthase activity did not change during the clamp in either group of subjects and was not different between the two groups at the end of the clamp. No relationship was found between total glycogen synthase activity Glycogen content (rngg- protein) Young subjects Elderly subjects Glycogen synthase Total (U g- wet weight) Young subjects Elderly subjects Per cent active ( ) Young subjects Elderly subjects Pyruvate dehydrogenase Total U g- wet weight) Young subjects Elderly subjects Per cent active ( ) Young subjects Elderly subjects 59 5 1.4 59.7 .5 2.32 fO.15 2.16k0.05 15.4k 1 5 14.2k0.7 0.89k0.10 0.90 f .08 12.8k 1 1 14.2f 1.4 79 0 .3 72.8k2.5 2.32 10 2.17 k0.04 36.9 Ifr 2.2 28.8 .7t 0.89 - O. 10 0.89 0 09 19.6f 1 8 17.8 .2 Mean f SE, n =6 in both groups. * The increase rom fasting to clamp was significant for glycogen content, per cent active glycogen synthase P< 0 001 for both) and per cent active pyruvate dehydrogenase in young subjects P< 0.02). t P < 0 05 ompared with young subjects. and glucose requirement or muscle glycogen concen- tration. At the end of the clamp, expressed activity of skeletal muscle glycogen synthase was significatly increased compared with the basal state, P < 0.001 for both groups (Table 2). The expressed glycogen syn- thase activity at the end of the clamp was, however, decreased in the older subjects compared with the younger group, P<O O5 (Table 2). At the end of the clamp, expressed glycogen synthase activity was corre- lated with clamp glucose requirement when the study groups were combined (Fig, 1; r =0.83, P<O.OI , but not within the groups (young: r = 0.78, elderly: r = 0.75; both NS). Correlation was also found between glyco- gen synthase activity and glycogen increment (r = 0.73, P < 0.01; young: r = 0.62, NS; elderly: r = 039, NS). Skeletal muscle pyruvate dehydrogenase Total pyruvate dehydrogenase activity did not differ between the two groups of subjects and was not stimulated by the clamp (Table 2). Expressed activity of pyruvate dehydrogenase increased 58 f 9 SD) during the clamp in the younger subjects (Table 2, P .02) but not in the older group (24.4 f 1 (SD) t = 1.993; Table 2). However, expressed enzyme acti- vity at the end of the clamp was not significantly different between the two groups and no relationship was found with clamp glucose requirement.  496 Y. T. KRUSZYNSKA, G PETRANYI K. G M. M. ALBERT1 0 0 O 0 0. 0 0 OO 5 - 0 00 0 0 25 0 0 1 1 16   1 16   Glucose requirement (mg kg- min- ) Figure 1 The relationships between glucose requirement to maintain a glucose clamp and the increment in glycogen content of skeletal muscle during the clamp left-hand panel), and between glucose requirement and glycogen synthase activity right-hand panel) in six young 0) nd six elderly 0) ormal males. Calculated correlation coefficients n 12) were: glycogen increment vs. glucose requirement, I 0.72, P < 0.01; glycogen synthase vs. glucose requirement, r=043 P < 0 01 Discussion The decrease in clamp glucose requirement in our elderly subjects is consistent with previous studies [6-81. Although the elderly group had a 6.5 decrease in lean body mass (Table 1) compared with the younger subjects, clamp glucose requirement was still decreased by 18 P<O.O5) when expressed per unit of lean body mass. Per cent adiposity was correlated positively with age and negatively with clamp glucose requirement. Nonetheless, factors other than the in- crease in adiposity with age must also be responsible for the impairment of insulin action. Precautions were taken to match the subjects for physical activity and diet, but as these assessments were subjective it is not possible to rule out physical activity as a contributory factor to the differences in insulin action observed. Although we did not measure glucose turnover isotopically, it can be assumed that at the insulin concentrations attained during the clamps, hepatic glucose production is effectively suppressed in both the young and elderly subjects [6, 71. It is also well recognized that during a euglycaemic clamp there is little uptake of glucose by the liver [9 211. Further- more, since adipose tissue disposes of less than 5 of an intravenous glucose load [22], the site of the age- related decrease in insulin sensitivity most likely resides in muscle. The skeletal muscle biopsies suggest that this insensitivity is in part related to a failure to store administered glucose as glycogen in muscle. Thus, the elderly subjects increased their muscle glycogen stores by significantly less than the younger subjects (Table 2) and a strong relationship was found between glycogen deposition and clamp glucose requirement (Fig 1). Insulin sensitivity and glycogen deposition were also closely related to the expressed activity of skeletal muscle glycogen synthase (Fig. l), which was stimu- lated by the clamp in both groups of subjects (Table 2). A similar if poorer relationship between clamp glucose requirement, glycogen deposition and glycogen syn- thase activity was found by Bogardus and colleagues in a mixed group of normal and mildly glucose-intolerant American Indians [23]. Assuming the muscle biopsies to be representative, and muscle to be 40 of body mass [24], skeletal muscle glycogen would account for 71 and 59 of the glucose infused in the young and elderly subjects, respectively. Oxidative pathways would thus account for approximately one-third of total glucose disposal, a figure in close agreement with that determined by indirect calorimetry for normal subjects under similar glucose clamp conditions [25]. Our findings suggest that at the insulin concentrations attained during the study, the peripheral insulin insensitivity in elderly males is determined primarily by the metabolic path- way between plasma glucose and muscle glycogen. These results are consistent with observations that insulin-mediated glucose uptake by muscle is mainly into non-oxidative pathways, and thus into glycogen [26]. It is not possible, however, to exclude a concomi- tant impairment of glucose oxidation in our elderly subjects. We were able to show a 58 stimulation of expressed pyruvate dehydrogenase during the clamp in the younger subjects but not in the older men. In view of the small number of subjects studied it is possible that this may represent a statistical type-2 error. Expressed pyruvate dehydrogenase activity at the end of the clamp, however, did not differ between the two groups, and no relationship with insulin sensitivity was found. A possible explanation for this poor correlation is that pyruvate dehydrogenase activity might not be rate limiting for the metabolism of pyruvate to acetyl CoA in the muscle studied. As intra-mitochondria1 pyruvate concentrations are very much lower than those in the cytosol, either production of pyruvate via glycolysis or its transport into the mitochondria may be the important determinants of the flux through pyruvate dehydrogenase. Total assayable activities of both glycogen synthase and pyruvate dehydrogenase were similar in the two  MUSCLE ENZYMES AND INSULIN SENSITIVITY IN AGEING 497 groups of subjects and were unrelated to insulin sensitivity. Thus, decreased synthesis of these key enzymes of glucose metabolism is unlikely to explain the age-related decrease in insulin sensitivity. Although glycogen synthase activity was strongly related to insulin sensitivity, it cannot be assumed that abnormalities in the regulation of this enzyme are directly responsible for the measured changes in insulin sensitivity. The demonstration of defects in the pathways of glucose transport [27, 281, glucose oxi- dation [29] and lipogenesis [30] in isolated adipocytes from elderly subjects suggests a more proximal defect in the pathway of insulin action. However, as studies of insulin binding to receptors on isolated adipocytes have yielded conflicting data [6 8 29-31], and as defects in adipocyte metabolism have been demon- strated independently of binding abnormalities [3 I], a post-binding abnormality would seem likely. Decreased muscle glucose transport might contri- bute to the decrease in clamp glycogen deposition in the elderly subjects. It does not, however, explain the decreased activation of glycogen synthase as this enzyme in skeletal muscle of both man and rat is regulated by insulin but not by ambient glucose concentration or glucose flux [21 321. The effect of insulin on this enzyme will be mediated by the biochemical events occurring after its binding to the membrane receptor, and it is possible that any defect in this pathway could be quantitatively similar when expressed at another site such as the stimulation of glucose transport. Studies of body fat topography have shown that, in the majority of men, adiposity is largely confined to the upper parts of the body [33] and this localization is more strongly associated with metabolic disturbance [34-361. In the current study the ratio of subscapular to triceps skin-fold thickness was not statistically signifi- cantly different between the two groups Table ; t 1.943). However, as this is a less sensitive indicator of central obesity than the waist-hip ratio, it remains possible that a more central distribution of the slightly increased adipose tissue mass in the elderly subjects Table 1) could contribute to the impairment of insulin action found [37]. The observation that a central distribution of body fat correlates both with a decrease in muscle fibre capillary density and with an increase in the proportion of fast-twitch glycoiytic fibres in muscle [37] suggests a possible mechanism for the decrease in insulin action. As fast-twitch glycolytic fibres are less insulin responsive than more oxidative fibres [38,39], it will be of interest to examine the effects of age on muscle fibre composition. Acknowledgments We thank Dr J. McCormack for kindly providing the pyruvate dehydrogenase phosphatase and Dr R. Den- ton for providing the coupling agent. The study was supported by the British Diabetic Association. References Davidson MB. the effect ofaging in carbohydrate metabolism: a review of the English literature and a practical approach to the diagnosis of diabetes mellitus in the elderly. Metabolism 2 Silverstone FA Branfonbrener M Shock NW Yiengst MJ. Age differences in the intravenous glucose tolerance tests and the response to insulin. J Clin Invest 1957;36:504-14. 3 Jackson RA Blix PM Mathews JA el al. Influence of aging on glucose homeostasis. J Clin Endocrinol Metab 1982;55:840-8. 4 Kalant N, Leibovici D Leibovici T Fukushima N. Effect of age on glucose utilisation and responsiveness to insulin in forearm muscle. J Am Geriatr SOC 1980;28:204-7. 5 Chen M, Bergman RN Pacini G Porte D. Pathogenesis of age- related glucose intolerance in man. Insulin resistance and decreased B-cell function. J Clin Endocrinol Metab 1985;60: 13- 20. 6 Fink RI Kolterman OG Griffin J Olefsky JM. Mechanism of insulin resistance in aging. J Clin Invest 1983;71:1523-35 7 DeFronzo RA. Glucose intolerance and aging. Evidence for tissue insensitivity to insulin. Diabetes 1979;28:1095-101. 8 Rowe JW Minaker KL Pallota JA Flier JS. Characterisation of the insulin resistance of aging. J Clin Invest 1983;71:1581-7. 9 DeFronzo RA Ferrannini E Hendler R Felig P Wahren J. Regulation of splanchnic and peripheral glucose uptake by insulin and hyperglycaemia in man. Diabetes 1983;32:35-45. 10 Womersley J Boddy K King PC Durning JVGA. A compari- son of fat free mass of young adults estimated by anthropometry body density and total body potassium content. Clin Sci Edwards RHT Round JM Jones DA. Needle biopsy of skeletal muscle: a review of 1 years experience. Muscle Nerve 12 DeFronzo RA Tobin JD Andres R. Glucose clamp technique: a method for quantifying insulin secretion and resistance. Am J Physiol 1979;237:E214-23. 13 Golden S Wals PA Katz J. An improved procedure for the assay of glycogen synthase and phosphorylase in rat liver homo- genates. Anal Biochem 1977;77:43645. 14 Coore HG Denton RM Martin BR Randle PJ. Regulation of adipose tissue pyruvate dehydrogenase by insulin and other hormones. Biochem J 1971;125:115-27. 5 Tabor H Mehler AH Stedtman ER. The enzymatic acetylation of amines. J Biol Chem 1953;204:127-38. 16 Keppler D Decker K. GIycogen determination with amyloglu- cosidase. In: Bergmeyer HK ed. Methods of Enzymatic Analy- sis. New York: Academic Press 1974 1127-31. 17 Lloyd B Burrin J Smythe P Alberti KGMM. Enzymic fluorimetric continuous flow assays for blood glucose lactate pyruvate alanine glycerol and 3-hydroxybutyrate. Clin Chem 18 Lowry OH Rosenborough NJ Farr AL Randall RJ. Protein measurement with the Fohn phenol reagent. J Biol Chem 19 Soeldner JS Slone D. Critical variables in the radioimmunoas- say of serum insulin using the double antibody technique. Diabetes 1965;14:771-9. 20 Stickland MH Perkins CM Wales JK. The measurement of haemoglobin Alc by isoelectric focussing in diabetic patients. Diabetologia 1982;22:3 15-7. 21 Kruszynska YT Home PD Alberti KGMM. In vivo regulation of liver and skeletal muscle glycogen synthase activity by glucose and insulin. Diabetes 1986;35:662-7. 22 Bjorntorp P Berchtold P Larson B. The glucose uptake of human adipose tissue in obesity. Eur J Clin Invest 1971;1:480-5. 23 Bogardus C Lillioja S, Stone K Mott D. Correlation between muscle glycogen synthase activity and in vivo insulin action in man. J Clin Invest 1984;73:1185-90. 24 Yki-Jarvinen H Koivisto VA. Effects of body composition on insulin sensitivity. Diabetes 1983;342:965-9. 25 Thiebaud D Jacot E DeFronzo RA Maeder E Jequier E Felber JP. The effect of graded doses of insulin on total glucose 1979;28:688-705. 1972;43:469-75. 1983;6:676-83. 1978;24: 1724-9. 195 93:256-75.
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