[The clinical impact of gestational diabetes mellitus]

In Denmark, gestational diabetes mellitus (GDM) develops in about 2% of all pregnant women. The discussion of GDM is complicated by lack of consensus regarding screening methods, diagnosis and treatment. Observational studies indicate that untreated GDM is associated with an increased risk of maternal and perinatal morbidity, and that the offspring of GDM mothers tend to be at increased risk of developing diabetes and adiposity as a result of an abnormal intrauterine environment. Several follow-up studies have shown that women with previous GDM run a considerable risk of developing diabetes (especially type 2 diabetes) later in life. Intervention strategies for this high risk group are suggested.

No association between birth weight and Type 1 diabetes mellitus--a twin-control study

AIMS

To investigate, by means of a twin-control study, whether there is a relationship between birth weight and Type 1 diabetes mellitus.

METHODS

In the youngest part (n = 20 888 pairs) of the Danish Twin Register, 95 twin pairs (26 monozygotic and 69 dizygotic) with Type 1 diabetes were identified. Information about birth weight and birth length, prematurity, maternal age and parity was obtained from midwives' records and from the Danish Medical Birth Registry and analysed using Student's two-sided t-test, Chi-square test and logistic regression.

RESULTS

Birth data were available for 83 diabetic and 51 healthy twin individuals, altogether 67 twin pairs (20 monozygotic and 47 dizygotic). Mean birth weight was 2537 g and 2565 g (NS) in monozygotic and dizygotic pairs and the corresponding length at birth 47.6 cm and 48.2 cm (NS). In pairs discordant for diabetes, the mean birth weight was 2538 g in twins with diabetes and 2549 g in twins without diabetes (NS). Logistic regression in discordant pairs showed no relationship between diabetes status and birth weight, birth length, birth order, sex or prematurity. Logistic regression in concordant vs. discordant pairs showed no effect of mean birth weight and birth length, maternal age, parity or weeks of prematurity.

CONCLUSIONS

There is no association between Type 1 diabetes mellitus and birth weight in this study. Furthermore, variables related to birth weight and length cannot explain why some pairs are concordant while other remain discordant.

Correlations between insulin sensitivity and bone mineral density in non-diabetic men

AIMS

To investigate relationships between bone mineral density (BMD), insulin secretion and insulin sensitivity, controlling for body composition, in view of data suggesting that hyperglycaemia [corrected] leads to decreased osteoblast proliferation and a negative calcium balance and that insulin stimulates osteoblast differentiation and collagen synthesis, with no clear evidence if this response in impaired in insulin resistance.

METHODS

Femur and whole body (WB) BMD was measured in 55 male patients with ischaemic heart disease and 40 healthy men, using a Hologic QDR-2000 densitometer. Insulin sensitivity (Si) was estimated as the rate of glucose disappearance divided by the area under the insulin curve during an intravenous glucose tolerance test.

RESULTS

Insulin and C-peptide levels were not correlated with BMD, but Si was a significant predictor of femur (log, r = 0.35) and WB BMD (log r = 0.29, both P<0.01), even after controlling for weight and age. Fat mass (FM) was a predictor of BMD (femur: r = 0.33 P<0.01, WB: r = 0.43 P<0.001). In the femur the association with FM disappeared when log(Si) was entered in the regression. Lean body mass (LBM) contributed significantly to BMD (r = 0.50 and r = 0.66, both P<0.001).

CONCLUSIONS

These results are compatible with a direct influence of lean body mass on bone, while the impact of fat mass may consist of insulin resistance with increased insulin exposure of bone. It is hypothesized that patients with insulin resistance in the metabolic pathway do not exhibit resistance to the skeletal actions of insulin.

Cytokine RNA levels in transiliac bone biopsies from healthy early postmenopausal women

The cytokines interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6 induce osteoclast formation and may contribute to the development of postmenopausal osteoporosis. Cross-sectional studies have suggested that both IL-1 and IL-1ra secretion increase on estrogen withdrawal, and that postmenopausal osteoporosis is associated with an inadequate increase in monocyte IL-1ra secretion with age. We measured cytokine mRNA (IL-1beta, IL-1ra, IL-6, and TNF-alpha) directly in bone biopsies from early postmenopausal women to determine if a lower compensatory increase in IL-1ra mRNA could be demonstrated in women with rapid bone loss after the menopause. Biopsies were obtained from 23 early postmenopausal women (mean age 53.9 years) who participated in a randomized study of hormone replacement therapy (HRT) and risk factors for osteoporosis. Bone mineral density was assessed by duel energy X-ray absorptiometry at 0, 1, 2, and 5 years. Women in the control group were recruited to the biopsy study based on their observed rate of bone loss (upper or lower tertile). Consent was also obtained from 11 participants receiving HRT. Biopsies were taken at 2 years, frozen in nitrogen, and homogenized. Cytokine mRNA was measured by competitive reverse transcriptase polymerase chain reaction. The IL-1ra/IL-1beta mRNA slope for the slow-loss group was steeper (deltaF = 23.3, p < 0.01) than that observed in the fast-loss group, indicating that slower bone loss was associated with higher IL-1ra mRNA levels relative to IL-1beta. During HRT, the IL-1beta mRNA level was inversely correlated with serum estradiol (log r2 = 0.77, p < 0.01), and women with a serum estradiol below 200 pmol/L during HRT had IL-1beta, mRNA levels identical to the control group. In contrast, IL-1ra mRNA was independent of serum estradiol. Histomorphometric analysis revealed weak correlations between IL-1beta mRNA and activation frequency (r2 = 0.26, p = 0.06) and between IL-1ra and volume referent bone resorption rate (r2 = 0.19, p = 0.11). TNF-alpha was not associated with the bone loss rates or with serum estradiol, and only three samples were positive for IL-6 mRNA. The findings support the hypothesis that IL-1beta production within bone increases with declining estrogen levels, and that an increase in II-1ra protects against accelerated bone loss.

Lumbar vertebral body compressive strength evaluated by dual-energy X-ray absorptiometry, quantitative computed tomography, and ashing

Bone densitometry with DXA (dual energy X-ray absorptiometry) and QCT (quantitative computed tomography) techniques are used for in vivo assessment of bone strength and thereby prediction of fracture risk. However, only few in vitro studies have investigated and compared these techniques' ability to determine vertebral compressive strength. The aim of the present study was to (1) assess the predictive value of DXA, QCT, and pQCT (peripheral QCT) for vertebral bone compressive strength assessed by mechanical testing; (2) describe both linear and power relationship between density and strength; and (3) evaluate whether gender-related differences in the above relations were present. The material comprised human lumbar vertebrae L3 from 51 women and 50 men (age range: 18 to 96 years). The study showed that both DXA and CT techniques (QCT and pQCT) have a high predictive value for vertebral strength. The DXA BMD had a high correlation with maximum compressive load (r2 = 0.86). The QCT and pQCT had high correlations with maximum compressive stress (r2 = 0.75 and r2 = 0.86, respectively). The correlation between ash density of the biomechanically tested specimen and maximum compressive stress was r2 = 0.88. There were no differences between linear and power fit in the degree of determination between density and strength. There was no gender-related difference in the relationship between volumetric density and maximum compressive stress. In conclusion, it was demonstrated that DXA, QCT, and pQCT are ex situ equally capable of predicting vertebral compressive strength with a degree of determination (r2) between 75% and 86%. No differences were found between linear and power analysis of the relationship between density and strength, and no difference was found in the density strength relationship between women and men.

General characteristics of the insulin resistance syndrome: prevalence and heritability. European Group for the study of Insulin Resistance (EGIR)

It has recently been recommended by a WHO expert committee that the insulin resistance syndrome, a cluster of cardiovascular risk factors linked to insulin resistance, should be termed 'the metabolic syndrome'. Characterisation with data from 2 large databases [the European Group for the study of Insulin Resistance (EGIR) and the Danish Twin Register] has shown that insulin resistance correlates closely with the various components of the metabolic syndrome, and that the prevalence of the syndrome is approximately 16% among Caucasians. Both genetically determined and environmentally induced insulin resistance may precipitate onset of the metabolic syndrome, and increased levels of abdominal fat may be of primary importance in its development.

The Trp64Arg mutation of the adrenergic beta-3 receptor gene impairs insulin secretion: a twin study

AIMS

The physiological role of the adrenergic beta-3 receptor is poorly understood in man but the Trp64Arg mutation of the receptor gene has been related to the insulin resistance syndrome, an earlier onset of diabetes and rapid weight gain. This study set out to examine the effects of the mutation on glycaemic responses after an oral glucose tolerance test.

METHODS

A standard oral glucose tolerance test (75 g glucose) was performed in 196 dizygotic twins. Serum insulin and glucose responses were measured at 0, 30 and 120 min.

RESULTS

In the twins discordant for the mutation (21 pairs), no effects of the mutation were found on the plasma glucose responses. The insulin response given as incremental area under curve (iAUC) (median 13.8 (25-75th percentile 9.3-21.0) vs. 23.3 (14.2-29.2) mmol x l(-1) x min, P<0.021) and the insulinogenic index ((insulin30min - insulin0min)/ (glucose30min - glucose0min)), a measure of the insulin secretory capacity (44 (34-58) vs. 75 (42-124), P<0.006), were considerably lower in the variant type. The results were confirmed when using non-paired statistics on all subjects.

CONCLUSION

It was concluded that the adrenergic beta-3 receptor, in addition to its already known effects, may be involved in the regulation of insulin secretion and that patients with the Trp64Arg mutation present an impaired insulin secretion.

[The clinical impact of gestational diabetes mellitus]

In Denmark, gestational diabetes mellitus (GDM) develops in about 2% of all pregnant women. The discussion of GDM is complicated by lack of consensus regarding screening methods, diagnosis and treatment. Observational studies indicate that untreated GDM is associated with an increased risk of maternal and perinatal morbidity, and that the offspring of GDM mothers tend to be at increased risk of developing diabetes and adiposity as a result of an abnormal intrauterine environment. Several follow-up studies have shown that women with previous GDM run a considerable risk of developing diabetes (especially type 2 diabetes) later in life. Intervention strategies for this high risk group are suggested.

Intracellular skeletal muscle glucose metabolism is differentially altered by dexamethasone treatment of normoglycemic relatives of type 2 diabetic patients

Young first-degree relatives of type 2 diabetic patients are insulin-resistant, with the insulin resistance mainly located in skeletal muscle due to decreased insulin-induced nonoxidative glucose metabolism and muscle glycogen synthase activation. We investigated whether the mechanism differs for dexamethasone (dex)-induced insulin resistance in first-degree relatives of type 2 diabetics versus healthy control subjects by quantifying intracellular glucose processing in muscle biopsies taken before and after 5 days of dex treatment (4 mg/d) in 20 normal glucose-tolerant relatives of type 2 diabetic patients and 20 matched controls (age, 29.4 +/- 1.7 v 29.4 +/- 1.6 years; body mass index, 25.1 +/- 1.0 v 25.1 +/- 0.9 kg/m2). In addition, an intravenous glucose tolerance test (IVGTT) combined with continuous indirect calorimetry was performed. Following 5 days of dex treatment, glucose tolerance deteriorated in both the relatives and the control subjects. Fasting dry-weight muscle glucose and fasting intracellular muscle glucose concentrations increased in response to dex only in the relatives (2.43 +/- 0.21 v 2.97 +/- 0.26 mmol/kg dry weight, P < .05; 0.28 +/- 0.07 v 0.45 +/- 0.08 mmol/L intracellular water, P < .05); no increases were observed in the control subjects. Fasting dry-weight muscle lactate also increased post-dex only in the relatives (7.37 +/- 0.40 v 10.77 +/- 1.22 mmol/kg dry weight, P < .001). Both basal muscle glucose and lactate concentrations from the IVGTT study correlated with the 2-hour post-dex glucose value obtained during the OGTT study in the relatives (R = .76 and R = .74, respectively, both P < .0001) but not in the control subjects. Basal intramuscular glycogen synthase activity decreased approximately 25% in both the relatives and control subjects post-dex; the decrement was significant (P < .01) only in control subjects. Indirect calorimetry during the post-dex IVGTT demonstrated increased glucose oxidation (P < .03) and reduced lipid oxidation (P < .03) in the relatives only. We postulate that the insulin resistance induced by dex in first-degree relatives of type 2 diabetic patients is associated with a preferential channeling of glucose into the glycolytic pathway (increased glucose oxidation and lactate production), probably associated with a preexisting downregulation of the glycosen synthase pathway.

Age- and gender-related differences in vertebral bone mass, density, and strength

This study was designed to evaluate age- and gender-related differences in vertebral bone mass, density, and strength by dual-energy X-ray absorptiometry (DXA), quantitative computed tomography (QCT), peripheral QCT (pQCT), ash measurements, and biomechanical testing. The material comprised human lumbar vertebral bodies (L3) from 51 females and 50 males (age-range: 18-96 years). The results showed that females had significantly lower vertebral body bone mass (ash weight) than males at any given age. The decline in bone mass with age was parallel for females and males. The different bone density measurements-cancellous ash density, total vertebral body ash density, DXA bone mineral density, QCT, and pQCT-showed no gender-related difference concerning numeric value or changes with age. Morphometrical measurements showed that females had smaller vertebral bodies (volumes) than males. Hence the females had significantly smaller cross-sectional area (CSA) of L3 than males (11.6 cm2 and 14.4 cm2, respectively). This led to females having lower maximum compressive load (N) than males at all ages, whereas maximum compressive stress (load/CSA) showed no gender-related difference. In conclusion, females have lower vertebral body bone mass than males at any given age, due to smaller vertebral bodies. Hence, maximum compressive load (strength not corrected for size) was lower in females. Vertebral body cancellous bone density and total-vertebral body density were equal when comparing genders, and no gender differences were found in the size-corrected strength: maximum compressive stress. The decrease with age in vertebral body compressive strength decrease was twice as large as the age decrease in density.

Does zygosity influence the metabolic profile of twins? A population based cross sectional study

OBJECTIVE

To study the influence of zygosity on the metabolic variables involved in the pathophysiology of type 2 diabetes.

DESIGN

Population based cross sectional study.

SETTING

Odense University Hospital, Denmark.

PARTICIPANTS

125 monozygotic twin pairs and 178 dizygotic twin pairs of the same sex born between 1921 and 1940.

MAIN OUTCOME MEASURES

Clinical characteristics of monozygotic and dizygotic twins with or without a family history of type 2 diabetes.

RESULTS

Absolute prevalences of type 2 diabetes and impaired glucose tolerance according to the World Health Organisation criteria were similar in both the monozygotic and the dizygotic twins as were measurements of height, weight, body mass index, waist to hip ratio, and fasting plasma glucose and insulin concentrations. During the oral glucose tolerance test, monozygotic twins had a higher incremental plasma insulin area under the curve than dizygotic twins (10.05 (SD 0.68) v 9.89 (0.72) pmol/lxminutes, P<0.01) indicating insulin resistance. In twins with normal glucose tolerance and without first degree relatives or co-twins with type 2 diabetes or impaired glucose tolerance, both the glucose and insulin areas under the curve were higher among monozygotic twins (glucose 214.4 (88.3) v 189.8 (78.4) mmol/lxminutes, P<0.05; insulin 20 040 (14 865-32 554) v 17 625 (12 330-23 640) pmol/lxminutes, P=0.08).

CONCLUSION

Zygosity influences both plasma glucose and plasma insulin concentrations during an oral glucose tolerance test. This supports an intrauterine influence on glucose homeostasis and perhaps on insulin resistance in humans.

Triglyceride-induced diabetes associated with familial lipoprotein lipase deficiency

Raised plasma triglycerides (TGs) and nonesterified fatty acid (NEFA) concentrations are thought to play a role in the pathogenesis of insulin-resistant diabetes. We report on two sisters with extreme hypertriglyceridemia and overt diabetes, in whom surgical normalization of TGs cured the diabetes. In all of the family members (parents, two affected sisters, ages 18 and 15 years, and an 11-year-old unaffected sister), we measured oral glucose tolerance, insulin sensitivity (by the euglycemic-hyperinsulinemic clamp technique), substrate oxidation (indirect calorimetry), endogenous glucose production (by the [6,6-2H2]glucose technique), and postheparin plasma lipoprotein lipase (LPL) activity. In addition, GC-clamped polymerase chain reaction-amplified DNA from the promoter region and the 10 coding LPL gene exons were screened for nucleotide substitution. Two silent mutations were found in the father's exon 4 (Glu118 Glu) and in the mother's exon 8 (Thr361 Thr), while a nonsense mutation (Ser447 Ter) was detected in the mother's exon 9. Mutations in exons 4 and 8 were inherited by the two affected girls. At 1-2 years after the appearance of hyperchylomicronemia, both sisters developed hyperglycemia with severe insulin resistance. Because medical therapy (including high-dose insulin) failed to reduce plasma TGs or control glycemia, lipid malabsorption was surgically induced by a modified biliopancreatic diversion. Within 3 weeks of surgery, plasma TGs and NEFA and cholesterol levels were drastically lowered. Concurrently, fasting plasma glucose levels fell from 17 to 5 mmol/l (with no therapy), while insulin-stimulated glucose uptake, oxidation, and storage were all markedly improved. Throughout the observation period, plasma TG levels were closely correlated with both plasma glucose and insulin concentrations, as measured during the oral glucose tolerance test. These cases provide evidence that insulin-resistant diabetes can be caused by extremely high levels of TGs.

Mechanisms of insulin resistance in non-oxidative glucose metabolism: the role of glycogen synthase

Insulin-mediated non-oxidative glucose metabolism is more or less identical to glycogen synthesis in skeletal muscle and that is why this pathway is specifically discussed in this paper. All three major steps in non-oxidative glucose processing--glucose transport, phosphorylation and glycogen synthesis--are found to be reduced in response to insulin in insulin-resistant type 2 diabetic subjects compared with controls. The insulin-signalling cascade from the insulin receptor to PI-3-K was also found to be abnormal, resulting in a severely reduced phosphorylation degree of the IRS-1 (IRS-2?)-PI-3-K complex, which can explain both reduced glucose transport and glycogen synthesis. The most pronounced finding in our studies is reduced glycogen synthase activation by insulin which is found in prediabetic subjects with normal glucose tolerance as well as in type 2 diabetics, but more severely. This defect was not reversible after treatment (normalization of blood glucose) and is therefore a candidate for the primary defect which is likely to be of genetic origin, but also could be caused by genetic imprinting, intrauterine malnutrition and social inheritance (obesity). Most of the abnormalities in non-oxidative glucose metabolism may be of secondary origin due to hyperglycemia itself or obesity. Both events may stimulate production of glucosamine, malonyl CoA and intramuscular triglyceride accumulation. These metabolites can theoretically induce most of the defects in glucose processing and furthermore impair insulin signalling. Whether the primary defect in activation of glycogen synthase is due to an abnormality in the enzyme complex itself or in the insulin signalling cascade still has to be investigated.

Effect of moderate improvement in metabolic control on magnesium and lipid concentrations in patients with type 1 diabetes

OBJECTIVE

To evaluate the effect of clinically obtainable improvements in metabolic control in patients with type 1 diabetes on biochemical cardiovascular risk factors.

RESEARCH DESIGN AND METHODS

Blood and 24-h urinary samples were obtained from 49 patients with type 1 diabetes before and after a run-in period and after 3 months of intervention, with frequent adjustment of insulin dosage according to measured blood glucose concentrations.

RESULTS

The intervention caused a mean insulin dosage increment of 10%, a 20% decrease in fasting plasma glucose concentration, a 10% decrease in albumin corrected serum fructosamine, and a somewhat lesser decrease in HbAlc.A 14% decrease in the renal excretion of magnesium (Mg) was observed, but without a change in average serum Mg concentration. Serum HDL cholesterol increased 4%, and serum triglycerides decreased 10% as an average. Looking at individual patients, the decrease in serum triglycerides correlated with both the change in serum total Mg concentration and with the increase in insulin dosage. Using the change in serum total Mg concentration and in insulin dosage as independent variables in a multiple regression analysis, the coefficient of correlation with the decrease in serum triglycerides was 0.52.

CONCLUSIONS

Moderate but clinically obtainable improvement of metabolic control in patients with type 1 diabetes seems to reduce the loss of Mg, increase serum HDL cholesterol, and decrease serum triglycerides. The decrease in serum triglycerides was associated with the change in serum total Mg concentration. These reductions in Mg loss and serum triglycerides might reduce the risk of developing cardiovascular disease in patients with type 1 diabetes.

Impact of ubiquinone (coenzyme Q10) treatment on glycaemic control, insulin requirement and well-being in patients with Type 1 diabetes mellitus

AIM

To investigate the effect of ubiquinone (coenzyme Q10) on glycaemic control and insulin requirement in patients with Type 1 diabetes mellitus (DM).

METHODS

We investigated 34 patients with Type 1 DM in a randomized, double-blind, placebo-controlled study. Patients received either 100 mg Q10 or placebo daily for 3 months. The insulin doses were adjusted according to patients' home measurements of blood glucose concentrations and reported experience of hypoglycaemia.

RESULTS

At randomization no differences existed between the Q10 and the placebo groups in age, body mass index (BMI), HbA1c, daily insulin dose or mean daily blood glucose concentration. Serum Q10 concentration increased in the Q10 group (mean +/- SD: 0.9+/-0.2 vs. 2.0+/-1.0 microg/ml, P<0.005), with no change in the placebo group (0.9+/-0.3 vs. 0.9+/-0.3 microg/ml, not significant (NS)). Following intervention no differences existed between the Q10 and the placebo groups regarding HbA1c (7.86+/-0.88 vs. 7.84+/-0.84%), mean daily blood glucose concentrations (8.06+/-1.86 vs. 8.53+/-1.88 mM), mean insulin dose (52.1+/-13.2 vs. 52.6+/-21.4 U), hypoglycaemic episodes (2.0+/-1.8 vs. 2.5+/-2.1 episodes/week), or cholesterol concentrations (4.81+/-0.91 vs. 4.78+/-1.07 mM). Furthermore, no differences existed in the well-being of the patients reported from a visual analogue scale (physical: 0.67+/-0.21 vs. 0.71+/-0.18, psychological: 0.70+/-0.25 vs. 0.73+/-0.24).

CONCLUSION

Q10 treatment does not improve glycaemic control, nor does it reduce insulin requirement, and it can therefore be taken by patients with Type 1 DM without any obvious risk of hypoglycaemia. No major beneficial or unfavourable effects on the investigated parameters could be demonstrated and no major changes in the sense of well-being occurred in the patients.

The Danish Osteoporosis Prevention Study (DOPS): project design and inclusion of 2000 normal perimenopausal women

OBJECTIVE

In 1990 we initiated a 20 year, partly randomised study (Danish Osteoporosis Prevention Study, DOPS) in order to (a) evaluate clinical, biochemical and osteodensitometric variables as predictors of low bone mass and future osteoporotic fractures, and (b) test the hypothesis, that hormone replacement therapy (HRT) initiated shortly after menopause reduces the risk of later osteoporotic fractures. This report describes study design and baseline characteristics of the DOPS-cohort.

METHODS

The study design is pragmatic, attempting to mimic the normal clinical situation. Several HRT alternatives are available according to clinical need. It was considered futile, impractical and unethical to use placebo for 20 years. Instead the study focus on hard endpoints (fractures) confirmed by independent persons (peripheral fractures) or by methods which allow investigator blinding (spinal X-rays). Statistical evaluation will focus on intention to treat analyses evaluating the decision of HRT and it's feasibility. With a compliance of 60% we will have sufficient statistical power (88%) to detect a fracture reduction of 40% in the treatments group. Clinical risk factors, current daily intakes of macronutrients, vitamins and minerals, anthropometric variables, biochemical variables (including bone markers and 25-hydroxyvitamin D), regional bone mineral density (BMD) and total body composition were assessed in all participants at entry and at various follow up intervals.

RESULTS

2016 study participants were recruited by direct mailing to a random sample of 45-58 years old women. In the randomised arm 501 were allocated to HRT and 505 to no treatment. In the non-randomised arm 219 preferred HRT and 791 preferred no treatment. Post-randomisation analysis revealed a slight but significant difference in age (50.01 versus 50.44 years) but no difference in menopausal age, prevalence of hysterectomy, educational level, BMI, serum bone alkaline phosphatase, serum osteocalcin, urine hydroxyproline or serum 25-hydroxyvitamin D. In the non-randomised arm women preferring HRT were closer to menopause, had a higher prevalence of hysterectomy, were better educated, were leaner, and had lower bone turnover than the women, who refused HRT.

CONCLUSION

It is possible to include a sufficient number of perimenopausal women in a randomised 20 year study on the antifracture effect of HRT.

Independent influence of age on basal insulin secretion in nondiabetic humans. European Group for the Study of Insulin Resistance

Glucose tolerance deteriorates with aging. To test whether age per se impairs basal beta-cell function, we analyzed retrospective clamp data from a large group (n = 957) of nondiabetic Europeans over the 18-85 yr age range (the European Group for the Study of Insulin Resistance database). In this cohort, the fasting posthepatic insulin delivery rate [IDR, obtained as the product of clamp-derived posthepatic insulin MCR and fasting plasma insulin concentration] was 8.9 (6.6) mU/min (median and interquartile range), and it gradually increased with age. In univariate association, IDR was positively related to body mass index (P < 0.0001), fasting plasma glucose (P < 0.01), and waist-to-hip ratio (P < 0.001), and negatively related to insulin sensitivity (P < 0.0001). After controlling for these factors in a multivariate model, IDR declined significantly with age (P < 0.0001). This intrinsic effect of age on IDR was similar in men and women, and it averaged 25% between 18-85 yr. In the same statistical model, insulin MCR (but not fasting plasma insulin concentration) showed a significant (P < 0.0001) inverse relation to age. We conclude that, in nondiabetic Caucasian subjects of either sex, senescence per se is associated with a progressive decline in both insulin clearance and basal insulin release.

Independent influence of age on basal insulin secretion in nondiabetic humans. European Group for the Study of Insulin Resistance

Glucose tolerance deteriorates with aging. To test whether age per se impairs basal beta-cell function, we analyzed retrospective clamp data from a large group (n = 957) of nondiabetic Europeans over the 18-85 yr age range (the European Group for the Study of Insulin Resistance database). In this cohort, the fasting posthepatic insulin delivery rate [IDR, obtained as the product of clamp-derived posthepatic insulin MCR and fasting plasma insulin concentration] was 8.9 (6.6) mU/min (median and interquartile range), and it gradually increased with age. In univariate association, IDR was positively related to body mass index (P < 0.0001), fasting plasma glucose (P < 0.01), and waist-to-hip ratio (P < 0.001), and negatively related to insulin sensitivity (P < 0.0001). After controlling for these factors in a multivariate model, IDR declined significantly with age (P < 0.0001). This intrinsic effect of age on IDR was similar in men and women, and it averaged 25% between 18-85 yr. In the same statistical model, insulin MCR (but not fasting plasma insulin concentration) showed a significant (P < 0.0001) inverse relation to age. We conclude that, in nondiabetic Caucasian subjects of either sex, senescence per se is associated with a progressive decline in both insulin clearance and basal insulin release.

Heritability of type II (non-insulin-dependent) diabetes mellitus and abnormal glucose tolerance--a population-based twin study

To elucidate the relative importance of genetic and environmental factors on the development of Type II (non-insulin dependent) diabetes mellitus, we examined a sample of twins (n = 606) ascertained from the population-based Danish Twin Register. Based on a standard 75 g oral glucose tolerance test and current WHO criteria we identified 62 pairs in which one or both had Type II diabetes. The probandwise concordance (monozygotic: 0.50; dizygotic: 0.37) for Type II diabetes per se was not very different. When including the twins with impaired glucose tolerance (IGT), however, the probandwise concordance for abnormal glucose tolerance was significantly different between monozygotic (0.63) and dizygotic (0.43) twin pairs, (p < 0.01). These findings were supported by the heritability estimates for Type II diabetes per se (26%) and for abnormal glucose tolerance (61%). The metabolic variables, insulin resistance and insulin secretion, and anthropometric variables, body mass index and waist to hip ratio, known to be associated with the development of glucose intolerance had a heritability of 26, 50, 80 and 6% respectively. This study confirms the notion of a multifactorial aetiology of Type II diabetes. It supports the contribution of non-genetic aetiological components in the development of Type II diabetes per se. The study also indicates a role for genes in the aetiology of abnormal glucose tolerance. We therefore propose that genetic predisposition is important for the development of abnormal glucose tolerance. Non-genetic factors, however, might play a predominant role in controlling whether a genetically predisposed individual progresses to overt Type II diabetes.

Vertebral bone density evaluated by dual-energy X-ray absorptiometry and quantitative computed tomography in vitro

Vertebral bone density is evaluated mainly by dual-energy X-ray absorptiometry (DXA) or quantitative computed tomography (QCT). Densitometry is used as an estimator of bone strength and forms the basis for choice of treatment. DXA expresses bone density in grams per square centimeter (area density) and QCT expresses bone density in milligrams per cubic centimeter (volumetric density). The aim of this study was to identify the differences between the two techniques, DXA and QCT, when applied to a group of female and male subjects over a wide age range. The data consisted of 221 lumbar vertebral bodies (L3 and L4) excised at autopsy. There were 90 females with a mean age of 65.6 (range 18-94) years and 131 males with a mean age of 62.0 (range 21-94) years. The vertebrae were scanned en bloc in demineralized water in Plexiglas containers with both DXA and QCT. DXA was performed using posteroanterior (PA) and lateral projection. QCT was performed in the center of each vertebra with 1 cm slice thickness. Both methods showed decreasing bone density with age. Lateral DXA showed a decrease in bone density with age from approximately 0.8 g/cm2 to approximately 0.4 g/cm2. QCT showed a decrease in bone density with age from approximately 180 mg/cm3 to approximately 30 mg/cm3. Lateral DXA bone mineral densities (BMD) were correlated with QCT densities in both females (r2 = 0.68, p < 0.00001) and males (r2 = 0.53, p < 0.00001), but females had constantly lower DXA BMDs than males at a given QCT density. QCT and width-adjusted midlateral DXA (g/cm3) were significantly correlated, with r2 = 0.64 (p < 0.00001) for females and r2 = 0.61 (p < 0.00001) for males. In conclusion, age- and gender-related differences in human vertebral bone density were shown to be dependent on the scanning method used. DXA bone mineral content (BMC) and BMD showed that females had lower values than males at all ages. When the "volumetric" DXA measurements and QCT were used, the females had the highest densities in the younger decades and males had the highest densities in the oldest decades. Finally, the area density (BMD) measured by DXA was lower in females than in males with identical QCT volumetric bone densities.

Irreversibility of the defect in glycogen synthase activity in skeletal muscle from obese patients with NIDDM treated with diet and metformin

OBJECTIVE

To assess the reversibility of the defect in glycogen synthase (GS) activity in skeletal muscle from obese patients with NIDDM treated with a hypocaloric diet and metformin.

RESEARCH DESIGN AND METHODS

Eighteen obese patients newly diagnosed with NIDDM were included in a randomized placebo-controlled double-blind parallel group trial and followed for 3 months. Euglycemic-hyperinsulinemic clamp including indirect calorimetry and biopsy of m. vastus lateralis was performed before and after treatment with a hypocaloric diet plus metformin or placebo. The patients were studied at basal, low, and high insulin concentrations.

RESULTS

The impaired GS activity in muscle biopsies was not reversed either by acute normalization of glycemia (for 8 h) or by chronic reduction of hyperglycemia by diet plus metformin. In both treatment groups, comparable effects on glycemic control and weight loss were found together with marked insulin suppression of nonesterified fatty acids and increased glucose oxidation. Total glucose disposal at euglycemic-hyperinsulinemic clamp increased significantly in the metformin group by 25% at high insulin level (259 +/- 31 vs. 207 +/- 21 mg x m(-2) x min(-1), P < 0.05). An insignificant increase by 13% was found in the placebo group. There were no significant changes in nonoxidative glucose metabolism. GS activity and glucose utilization showed no significant differences between the two treatment groups when regression coefficients, expressed as incremental changes by increments of insulin, were compared.

CONCLUSIONS

Defective GS activity in obese NIDDM patients is not secondary to hyperglycemia. Metformin and diet had no significant influence on GS activity. The added effect of metformin to that of a hypocaloric diet in improving insulin-stimulated glucose utilization is marginal when blood glucose reduction is obtained by weight loss.

Methodological aspects of measuring human skeletal muscle electrolyte content and ouabain binding capacity

The aim of the study was to evaluate the use of freeze-dried and dissected small muscle biopsy specimens ("dry") for the determination of human muscle electrolyte content and ouabain binding capacity, compared with an easier method, without this freeze-drying step ("wet"). Freeze-drying and dissection of muscle biopsy specimens reduced the variation in the determination of muscle potassium and magnesium content. The total coefficient of variation was 8.6% in the dry determination of muscle potassium content and 13.5% in the wet determination (P < 0.05). In the determination of muscle magnesium content, the total coefficient of variation was 7.4% in the dry determination and 13.7% when determined wet (P < 0.005). Muscle sodium content had a very large coefficient of variation, independent of the method used. The content of dry solids was too high in biopsies which were incubated in Tris-vanadate buffer (31.9%), compared to biopsies which were not incubated in Tris-vanadate buffer (24.9%, P < 0.001). Hereby, the measured ouabain binding capacity became too high when measured wet. In conclusion, muscle electrolyte content and ouabain binding capacity should be determined after drying and microdissection of the biopsies, because this method confers the least variation and the highest accuracy.