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Context: Glucose-dependent insulinotropic polypeptide (GIP) may increase lipid clearance by stimulating lipid uptake. However, given that GIP promotes release of insulin by the pancreas and insulin is anti-lipolytic, the effect may be indirect. Objective: In this study we examined the association between GIP and lipid metabolism in individuals with low to high risk of type 2 diabetes and assessed whether the associations were modified by or mediated through insulin. Design, Setting, and Participants: Analyses were based on the Danish cross-sectional ADDITIONPRO study (n 1405). Lipid metabolism was measured by fasting plasma lipids and obesity incluDing abdominal fat distribution assessed by ultrasonography. GIP and insulin were measured during an oral glucose tolerance test (0, 30 and 120 min). Linear regression analysis was used to study the associations between GIP, plasma lipids, and obesity measures. Results: A doubling in fasting GIP levels was associated with lower low-density lipoprotein in both men (mean [95% CI]0.10 mmol/l [0.18-0.03]) and women (0.14 mmol/l [0.23-0.04]) and with higher high-density lipoprotein in women (0.06 mmol/l [0.02-0.10]). In men, a doubling in stimulated GIP was associated with 0.13 cm less 0.01-0.25 sc fat but with more visceral abdominal fat (0.45 cm [0.12-0.78]) and higher waist-hip ratio (0.011 [0.004-0.019]). Conclusions: Contrary to what was previously thought, GIP may be associated with improved low-density lipoprotein clearance but with an unhealthy fat distribution independent of insulin. The effect of GIP on obesity measures was substantially different between men and women. The potential effect of GIP on visceral and sc adipose tissue physiology warrants further examination.

Fetal exposure to maternal diabetes is associated with increased risk of type 2 diabetes mellitus (T2DM) later in life. The pathogenesis of T2DM involves dysfunction of the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), as well as hyperglucagonemia.Our aim was to investigate circulating plasma levels of GLP-1, GIP, and glucagon during the oral glucose tolerance test (OGTT) in adult offspring of women with diabetes in pregnancy.We conducted a follow-up study of 567 offspring, aged 18-27 years. We included two groups exposed to maternal diabetes in utero: offspring of women with diet-treated gestational diabetes mellitus (O-GDM; n = 163) or type 1 diabetes (O-T1DM; n = 146). Two reference groups were included: offspring of women with risk factors for GDM, but normoglycemia during pregnancy (O-NoGDM; n = 133) and offspring from the background population (O-BP; n = 125). The subjects underwent a 75-g OGTT with venous samples at 0, 30, and 120 minutes.Fasting plasma levels of GLP-1 were lower in the two diabetes-exposed groups compared to O-BP (O-GDM, P = .040; O-T1DM, P = .008). Increasing maternal blood glucose during OGTT in pregnancy was associated with reduced postprandial suppression of glucagon in the offspring. Lower levels of GLP-1 and higher levels of glucagon during the OGTT were present in offspring characterized by overweight or prediabetes/T2DM at follow-up, irrespective of exposure status.Lower levels of fasting GLP-1 and impaired glucagon suppression in adult offspring exposed to maternal diabetes during pregnancy are diabetogenic traits that may contribute to glucose intolerance in these persons, but further investigations are needed.

Food ingestion decreases bone resorption, and glucose-dependent insulinotropic polypeptide (GIP) may mediate this effect. Mice overexpressing GIP have increased osteoblast activity and are rescued from age-related bone loss, whereas GIPR knockout mice have decreased cortical bone mass and compromised bone quality. Carriers of the functional variant GIPR Glu354Gln (rs1800437) have higher plasma glucose 2 hours after glucose ingestion, suggesting that the variant encoding GIPR 354Gln decreases the effect of GIP.The objective of the study was to investigate the effect of GIPR Glu354Gln on bone mineral density (BMD) and fracture risk.This was a prospective, comprehensive, cohort study (number NCT00252408).A total of 1686 perimenopausal women were included.Dual-energy X-ray absorptiometry was performed at baseline and after 10 years. Incident fractures were recorded during the follow-up and were obtained from the Danish National Patient Registry, giving a total follow-up time of a minimum 16 years.After 10 years, women with the minor frequency C allele of rs1800437 (354Gln) had significantly lower BMD at the femoral neck compared with carriers of the major G-allele (CC: 0.755 ± 0.015 g/cm(2) vs CG: 747 ± 0.005 g/cm(2); GG: 0.766 ± 0.004 g/cm(2), P.001). Correspondingly, total hip BMD was significantly lower among C allele carriers (CC: 0.881 ± 0.016 g/cm(2); CG: 0.884 ± 0.005 g/cm(2); and GG: 0.906 ± 0.004 g/cm(2), P.001). Finally, women homozygous for the variant C allele had an increased risk (hazard ratio 1.6, confidence interval 1.0-2.6, P.05) of nonvertebral fractures.This study demonstrates an association between a functional GIPR polymorphism Glu354Gln (rs1800437) and BMD and fracture risk. These findings further establish GIP to be involved in the regulation of bone density.

Offspring of women with diabetes during pregnancy have an increased risk of glucose intolerance in adulthood, but the underlying mechanisms are unknown.We aimed to investigate the effects of intrauterine hyperglycemia on insulin secretion and action in adult offspring of mothers with diabetes.A cohort of 587 Caucasian offspring, without known diabetes, was followed up at the age of 18-27 years. We included 2 groups exposed to maternal diabetes in utero: offspring of women with gestational diabetes mellitus (n = 167) or type 1 diabetes (n = 153). Two reference groups were included: offspring of women with risk factors for gestational diabetes mellitus but normoglycemia during pregnancy (n = 139) and offspring from the background population (n = 128).Indices of insulin sensitivity and insulin release were calculated using insulin and glucose values from a standard oral glucose tolerance test (120 minutes, 75 g glucose). Pancreatic β-cell function taking the prevailing insulin sensitivity into account was estimated by disposition indices.Both groups of offspring exposed during pregnancy to either maternal gestational diabetes or type 1 diabetes had reduced insulin sensitivity compared with offspring from the background population (both P.005). We did not find any significant difference in absolute measures of insulin release. However, the disposition index was significantly reduced in both the diabetes-exposed groups (both P.005).Reduced insulin sensitivity as well as impaired pancreatic β-cell function may contribute to the increased risk of glucose intolerance among adult offspring born to women with diabetes during pregnancy.

Recently, 10 novel type 2 diabetes (T2D) susceptibility single nucleotide polymorphisms (SNPs) in ZMIZ1, ANK1, KLHDC5, TLE1, ANKRD55, CILP2, MC4R, BCAR1, HMG20A, and GRB14 loci were discovered in MetaboChip-genotyped populations of European ancestry.The aim of the present study was to characterize prediabetic quantitative traits underlying these SNP associations and to calculate the amount of interindividual variation in glycemic traits explained by these and previous T2D susceptibility variants.A total of 5739 Danish individuals naive to glucose-lowering medication were included in quantitative trait studies, and case-control analyses were performed in 1892 patients with T2D and 6603 normoglycemic control subjects. Participants without known T2D underwent an oral glucose tolerance test, and measures of insulin release and sensitivity were estimated from insulinogenic, disposition, BIGTT, and Matsuda indexes.We confirmed associations of ZMIZ1, KLHDC5, CILP2, HMG20A, ANK1, ANKRD55, and BCAR1 with T2D. The risk T allele of BCAR1 rs7202877 associated with decreased disposition index (P = .02). The C allele of ANK1 rs516946 associated with decreased insulinogenic (P = .005) and disposition (P = .002) indexes. The G allele of ANKRD55 rs459193 associated with decreased Matsuda index (P = .02) adjusted for waist circumference. The C allele of GRB14 rs13389219 associated with both increased insulinogenic (P = .04) and decreased Matsuda (P = .05) indexes. All validated European T2D variants still only explained a few percentage points of glycemic trait variation.BCAR1 rs7202877 may mediate its diabetogenic impact through impaired β-cell function, but this finding needs to be replicated in independent studies. In addition, we substantiated previous evidence that ANK1 rs516946 confers impaired insulin release and that ANKRD55 rs459193 and GRB14 rs13389219 associate with insulin resistance.

The minor G-allele of FOXO3A rs2802292 has been associated with longevity. We aimed to investigate whether a phenotype related to healthy metabolic aging could be identified in individuals carrying the longevity-associated FOXO3A rs2802292 G-allele.rs2802292 was genotyped in a phenotypically well-characterized population of young and elderly twins (n = 190) and in the population-based Inter99 cohort (n = 5768). All participants underwent oral glucose tolerance tests, and the twin population was additionally examined with an iv glucose tolerance test and a hyperinsulinemic, euglycemic clamp. Basal and insulin-stimulated FOXO3A mRNA expression was assessed in skeletal muscle biopsies from the twin population.In the twin sample, carriers of the minor G-allele of rs2802292 showed reduced fasting plasma insulin [per allele effect (β) = -13% (-24; -1) (95% confidence interval), P = 0.03] and lower incremental area under the curve 0-120 min for insulin after an oral glucose load [β = -14% (-23; -5), P = 0.005]. The G-allele was associated with increased peripheral insulin action [glucose disposal rate clamp, β = 0.85 mg · kg(fat-free mass)(-1) · min(-1)() (0.049; 1.64), P = 0.04] and lower hepatic insulin resistance index [β = -13% (-25; -1), P = 0.03]. Furthermore, carriers of the G-allele had increased basal FOXO3A mRNA expression in skeletal muscle compared with T-allele carriers [β = 16% (0; 33), P = 0.047]. In the Inter99 sample, we found an association with reduced incremental area under the curve 0-120 min for insulin after an oral glucose load [β = -3% (-5; -0.07), P = 0.04], but this association was not significant after adjustment for body mass index.Our data indicate that the minor G-allele of FOXO3A rs2802292 is associated with enhanced peripheral and hepatic insulin sensitivity in our small twin cohort, which may be mediated through increased FOXO3A mRNA expression, although no major metabolic impact of rs2802292 was found in the large Inter99 cohort.

Udgivelsesdato: 2009-Jul CONTEXT: In animal studies, exposure to intrauterine hyperglycemia increases the risk of cardiovascular disease through only partly understood epigenetic mechanisms. Human long-term follow-up studies on the same topic are few. OBJECTIVE: The aim was to study the risk of overweight and the metabolic syndrome in adult offspring of women with diet-treated gestational diabetes mellitus (GDM) or type 1 diabetes, and additionally to study associations between estimates of maternal hyperglycemia and outcome in the offspring. DESIGN AND SETTING: We conducted a follow-up study of 1066 primarily Caucasian women aged 18-27 yr in the Center for Pregnant Women with Diabetes, Rigshospitalet, Copenhagen, Denmark. PARTICIPANTS: Offspring of women with diet-treated GDM (n = 168) and an unexposed reference group (n = 141) participated, as well as offspring of women with type 1 diabetes (n = 160) and offspring from the background population representing an unexposed reference group (n = 128). The follow-up rate was 56% (597 of 1066). MAIN OUTCOME MEASURES: Women with body mass index of at least 25 kg/m(2) were considered overweight. The metabolic syndrome was determined by the International Diabetes Federation 2006 criteria. Results: The risk of overweight was doubled in offspring of women with diet-treated GDM or type 1 diabetes compared with offspring from the background population, whereas the risk of the metabolic syndrome was 4- and 2.5-fold increased, respectively. Offspring risk of the metabolic syndrome increased significantly with increasing maternal fasting blood glucose as well as 2-h blood glucose (during oral glucose tolerance test). CONCLUSIONS: Adult offspring of women with diet-treated GDM or type 1 diabetes are risk groups for overweight and the metabolic syndrome. Intrauterine hyperglycemia may in addition to genetics and other factors contribute to the pathogenesis of overweight and the metabolic syndrome.

Udgivelsesdato: 2009-Feb OBJECTIVE: Recent studies identified the rs9939609 A-allele of the FTO (fat mass and obesity associated) gene as being associated with obesity and type 2 diabetes. We studied the role of the A-allele in the regulation of peripheral organ functions involved in the pathogenesis of obesity and type 2 diabetes. METHODS: Forty-six young men underwent a hyperinsulinemic euglycemic clamp with excision of skeletal muscle biopsies, an iv glucose tolerance test, 31phosphorous magnetic resonance spectroscopy, and 24-h whole body metabolism was measured in a respiratory chamber. RESULTS: The FTO rs9939609 A-allele was associated with elevated fasting blood glucose and plasma insulin, hepatic insulin resistance, and shorter recovery half-times of phosphocreatine and inorganic phosphate after exercise in a primarily type I muscle. These relationships--except for fasting insulin--remained significant after correction for body fat percentage. The risk allele was not associated with fat distribution, peripheral insulin sensitivity, insulin secretion, 24-h energy expenditure, or glucose and fat oxidation. The FTO genotype did not influence the mRNA expression of FTO or a set of key nuclear or mitochondrially encoded genes in skeletal muscle during rest. CONCLUSION: Increased energy efficiency--and potentially increased mitochondrial coupling--as suggested by faster recovery rates of phosphocreatine and inorganic phosphate in oxidative muscle fibers may contribute to the increased risk of obesity and type 2 diabetes in homozygous carriers of the FTO A-risk allele. Hepatic insulin resistance may represent the key metabolic defect responsible for mild elevations of fasting blood glucose associated with the FTO phenotype.

Objective: We aimed to examine the association between gestational diabetes mellitus (GDM) and 11 recently identified type 2 diabetes susceptibility loci. Research Design and Methods: Type 2 diabetes risk variants in TCF7L2, CDKAL1, SLC30A8, HHEX/IDE, CDKN2A/2B, IGF2BP2, FTO, TCF2, PPARG, KCNJ11, and WFS1 loci were genotyped in a cohort of women with a history of GDM (n = 283) and glucose-tolerant women of the population-based Inter99 cohort (n = 2446). Results: All the risk alleles in the 11 examined type 2 diabetes risk variants showed an odds ratio (OR) greater than 1 for the GDM group compared with the control group ranging from 1.13 [95% confidence interval (CI) 0.88–1.46] to 1.44 (95% CI 1.19–1.74) except for the WFS1 rs10010131 variant with OR 0.87 (95% CI 0.73–1.05). Combined analysis of all 11 variants showed a highly significant additive effect of multiple risk alleles on risk of GDM [OR 1.18 (95% CI 1.10–1.27)] per risk allele, P = 3.2 × 10−6). Applying receiver-operating characteristic showed an area under the receiver-operating characteristic curve of 0.62 for the genetic test alone and 0.73 when combining information on age, body mass index, and genotypes of the 11 gene variants. Conclusions: The prevalence in a prior GDM group of several previously proven type 2 diabetes risk alleles equals the findings from association studies on type 2 diabetes. This supports the hypothesis that GDM and type 2 diabetes are two of the same entity.

Context: Fat redistribution, insulin resistance, and low-grade inflammation characterize HIV-infected patients with lipodystrophy. Currently, no effective therapies exist for the combined treatment of fat redistribution and insulin resistance. Objective: Our objective was to evaluate the effects of strength and endurance training on insulin sensitivity and fat distribution in HIV-infected patients with lipodystrophy. Subjects and Methods: Twenty sedentary HIV-infected men with lipodystrophy were randomly assigned to supervised strength or endurance training three times a week for 16 wk. The primary endpoints were improved peripheral insulin sensitivity (euglycemic-hyperinsulinemic clamp combined with isotope-tracer infusion) and body fat composition (dual-energy x-ray absorptiometry scan). Secondary endpoints included fasting lipids and inflammatory markers. Results: Insulin-mediated glucose uptake increased with both endurance training (55.7 ± 11 to 63.0 ± 11 μmol glucose/kg lean mass·min, P = 0.02) and strength training (49.0 ± 12 to 57.8 ± 18 μmol glucose/kg lean mass·min, P = 0.005), irrespective of training modality (P = 0.24). Only strength training increased total lean mass 2.1 kg [95% confidence interval (CI), 0.8–3.3], decreased total fat 3.3 kg (95% CI, −4.6 to −2.0), trunk fat 2.5 kg (95% CI, −3.5 to −1.5), and limb fat 0.75 kg (95% CI, −1.1 to −0.4). Strength training significantly decreased total and limb fat mass to a larger extent than endurance training (P < 0.05). Endurance training reduced total cholesterol, low-density lipoprotein cholesterol, free fatty acids, high-sensitivity C-reactive protein, IL-6, IL-18, and TNF-α and increased high-density lipoprotein cholesterol, whereas strength training decreased triglycerides, free fatty acids, and IL-18 and increased high-density lipoprotein cholesterol (P < 0.05 for all measurements). Conclusion: This study demonstrates that both strength and endurance training improve peripheral insulin sensitivity, whereas only strength training reduces total body fat in HIV-infected patients with lipodystrophy.

We investigated the regulation and metabolic effects of TCF7L2 gene expression in human sc fat and skeletal muscle and the impact of the TCF7L2, rs7903146, T-allele on gene expression and measures of glucose metabolism including insulin secretion and peripheral and hepatic insulin action.The rs7903146 was genotyped in 1) a population-based sample of 587 twins (55-64 yr) with glucose tolerance ranging from normal to type 2 diabetes and 2) a population of 196 nondiabetic young (22-31 yr) and elderly (57-66 yr) twins. All subjects underwent oral glucose tolerance tests, and population 2 was additionally examined with iv glucose tolerance tests and hyperinsulinemic, euglycemic clamps.Elderly T-allele carriers had decreased plasma insulin responses and lower disposition index, whereas insulinogenic index was similar between genotype groups. Elderly nondiabetic T-allele carriers had increased peripheral insulin sensitivity (P = 0.03). Young T-allele carriers had impaired hepatic insulin sensitivity (P = 0.04) independent of plasma insulin levels. TCF7L2 gene expression in skeletal muscle and adipose tissue was not explained by genotype, sex, aerobic capacity, birth, or adult anthropometry and was not associated with in vivo glucose metabolism.The rs7903146 T-allele associates with hepatic insulin resistance and diminished glucose-stimulated plasma insulin secretion. Our study does not provide evidence of a role of TCF7L2 gene expression in sc fat tissue and muscle tissue in the regulation of glucose homeostasis. This suggests that the primary defect of rs7903146 T-allele carriers is impairment of insulin secretion rather than a defect in insulin action in peripheral tissues.

Context: CDKAL1 is a recently discovered susceptibility gene for type 2 diabetes. Objective: Our objective was to investigate the impact of rs7754840 of CDKAL1 on insulin secretion, insulin sensitivity, and risk of type 2 diabetes. Design and settings: Study 1 (the EUGENE2 study) was a cross-sectional study including subjects from five white populations in Europe (Denmark, Finland, Germany, Italy, and Sweden). Study 2 is an ongoing prospective study of Finnish men. Participants: In study 1, 846 nondiabetic offspring of type 2 diabetic patients (age 40 +/- 10 yr; body mass index 26.7 +/- 5.0 kg/m(2)) participated. In study 2, subjects included 3900 middle-aged men (533 type 2 diabetic and 3367 nondiabetic subjects). Interventions: INTERVENTIONS included iv glucose-tolerance test (IVGTT), oral glucose-tolerance test (OGTT), and euglycemic-hyperinsulinemic clamp in study 1 and OGTT in study 2. Main outcome measures: Parameters of insulin secretion, insulin resistance, and glucose tolerance status were assessed. Results: In study 1, carriers of the GC and CC genotypes of rs7754840 had 11 and 24% lower first-phase insulin release in an IVGTT compared with that in carriers of the GG genotype (P = 0.002). The C allele was also associated with higher glucose area under the curve in an OGTT (P = 0.016). In study 2, rs7754840 was significantly associated with type 2 diabetes (P = 0.022) and markers of impaired insulin release [insulinogenic index (IGI), P = 0.012] in 2405 men with normal glucose tolerance. Conclusions: rs7754840 of CDKAL1 was associated with markers of impaired insulin secretion in two independent studies. Furthermore, rs7754840 was associated with type 2 diabetes in Finnish men (study 2). Therefore, CDKAL1 is likely to increase the risk of type 2 diabetes by impairing insulin secretion.

The separate and combined effects of the PPARG Pro(12)Ala polymorphism and the KCNJ11 Glu(23)Lys polymorphisms on risk of type 2 diabetes were investigated in relatively large-scale, case-control studies. Separate effects of the variants were examined among 1187/1461 type 2 diabetic patients and 4791/4986 middle-aged, glucose-tolerant subjects. The combined analysis involved 1164 type 2 diabetic patients and 4733 middle-aged, glucose-tolerant subjects. In the separate analyses, the K allele of the KCNJ11 Glu(23)Lys associated with type 2 diabetes (odds ratio, 1.19; P = 0.0002), whereas the PPARG Pro(12)Ala showed no significant association with type 2 diabetes. The combined analysis indicated that the two polymorphisms acted in an additive manner to increase the risk of type 2 diabetes, and we found no evidence for a synergistic interaction between them. Analysis of a model with equal additive effects of the two variants showed that the odds ratio for type 2 diabetes increased with 1.14/risk allele (P = 0.003). Together, the two polymorphisms conferred a population-attributable risk for type 2 diabetes of 28%. In conclusion, our results showed no evidence of a synergistic interaction between the KCNJ11 Glu(23)Lys and PPARG Pro(12)Ala polymorphisms, but indicated that they may act in an additive manner to increase the risk of type 2 diabetes.

This study was performed to test the hypothesis that genetic variation in the promoter of the glucose transporter 2 (GLUT2) might predispose to prediabetic phenotypes or type 2 diabetes. A total of 1611 bp comprising the minimal promoter region of the GLUT2 gene were examined by combined single-strand conformational polymorphism and heteroduplex analysis followed by direct sequencing of identified variants on genomic DNA from 96 randomly recruited Danish type 2 diabetic patients. We identified 4 nucleotide variants, -447g--a, -149c--a, -122t--c, and -44g--a. None of the variants were positioned in known or presumed transcription factor binding sites, TATA-box, or transcriptional start site. Association studies of the -149c--a, -122t--c, and -44g--a variants revealed that the variants were as prevalent in 320 type 2 diabetic patients [11.0% (95% confidence interval, 8.4-13.6), 9.8% (7.4-12.2), and 29.0% (24.4-33.6), respectively] as in 241 age-matched glucose-tolerant subjects [13.1% (9.8-16.4), 11.2% (8.3-14.1), and 33.4% (28.8-38.0), respectively]. The -447g--a mutation was only identified in a single diabetic patient and did not show cosegregation with diabetes in the family of the proband. The three common variants showed in a primary genotype-phenotype study comprising 241 glucose-tolerant middle-aged subjects association to increased plasma glucose levels during an oral glucose tolerance test. However, this result could not be replicated in a second sample of 298 60-yr-old glucose-tolerant subjects. In conclusion, we found no evidence supporting the hypothesis that genetic variability in the minimal promoter of the GLUT2 is associated with type 2 diabetes or prediabetic phenotypes in the Danish population.

The third form of maturity-onset diabetes of the young is caused by mutations in the hepatocyte nuclear factor-1alpha gene. Recently, we demonstrated an association between a prevalent polymorphism at codon 98, Ala/Val98, of this gene and a 20% decreased insulin release during an oral glucose tolerance test (OGTT) in middle-aged glucose-tolerant Danish Caucasian subjects. The major objective of the present study was to replicate this finding among glucose-tolerant first degree relatives of type 2 diabetic patients of the same ethnic origin. All participants, 231 glucose-tolerant offspring of 62 type 2 diabetic probands, underwent an OGTT with measurements of plasma glucose, serum insulin, and serum C peptide during the test. Thirty-three heterozygous carriers of the Ala/Val variant were identified, whereas no subjects had the variant in its homozygous form. Ala/Val carriers had a 20% reduction in serum C peptide at 30 min during the OGTT (1225+/-636 vs. 1507+/-624 pmol/L; P=0.02) compared to wild-type carriers. No significant differences in serum insulin levels during the OGTT were observed between carriers of the variant and Ala/Ala homozygotes. In conclusion, among Danish glucose-tolerant first degree relatives of type 2 diabetic patients the Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene is associated with a decreased serum C-peptide secretion during an OGTT. This finding confirms our previously reported observation of the functional importance of the variant to insulin secretion during an OGTT among middle-aged healthy subjects.

The effects of GH substitution on skeletal mass, bone turnover, and calcium metabolism were investigated in 29 patients with GH deficiency who were randomized to sc injections with GH (2 IU/m2 day) or placebo for 12 months. During GH treatment, serum insulin-like growth factor I increased 263 +/- 98% (P0.001). Serum osteocalcin, bone a alkaline phosphatase, and procollagen type I C-terminal propeptide increased by 376 +/- 78% (P0.005), 128 +/- 17% (P0.005), and 100 +/- 17% (P0.005), respectively. Serum type I collagen telopeptide and urinary levels of pyridinoline, deoxypyridinoline, and hydroxyproline rose by 158 +/- 39% (P0.005), 170 +/- 48% (P0.005), 156 +/- 78% (P0.005), and 161 +/- 50% (P0.005), respectively. Serum ionized calcium rose by 1.7 +/- 0.6% (P0.05), whereas serum PTH decreased insignificantly. Vitamin D metabolites remained unaltered. Urinary calcium/creatinine increased and phosphate/creatinine decreased transiently, returning to baseline values at 9 months. When measured by dual energy x-ray absorptiometry, whole body bone mineral density (BMD) and (BMD) of the radius decreased 2.4 +/- 0.6% (P0.05) and 3.5 +/- 1.0% (P0.005), respectively, whereas no significant changes were observed in BMD of the femur or spine. Our results indicate that long term GH treatment activates bone remodeling in patients with GH deficiency. The observed slight decrease in BMD may be explained by expansion of the remodeling space and reduced mean age of bone tissue. IT remains unclear whether long term treatment with GH will lead to an increase in bone mass and improved skeletal biomechanical competence.

Due to alternative splicing of exon 11 of the receptor gene, the human insulin receptor exists in two forms, that have distinct tissue-specific expression and are functionally different. Needle biopsies obtained from vastus lateralis muscle from 20 patients with noninsulin-dependent diabetes mellitus (NIDDM) and 20 normal control subjects were analyzed for the relative expression of insulin receptor mRNA variants in a novel assay using fluorescence-labeled primers and subsequent analysis on an automated DNA sequencer. In subgroups of patients and control subjects, insulin binding and tyrosine kinase activity were examined in wheat germ agglutinin-purified insulin receptors isolated from muscle biopsies. Moreover, insulin-stimulated glucose disposal was studied by means of the euglycemic hyperinsulinemic clamp technique. No difference in the relative expression of spliced variants of the insulin receptor mRNA was observed (control subjects, 71.4 +/- 1.3% insulin receptor mRNA with exon 11; NIDDM patients, 71.5 +/- 1.3% insulin receptor mRNA with exon 11). No significant interrelationships were demonstrated among the relative expression of insulin receptor mRNA variants, insulin binding, and tyrosine kinase activity toward the exogenous substrate poly(Glu-Tyr(4:1)). Furthermore, no significant relationship was demonstrated between the glucose disposal rate and the relative expression of insulin receptor splice variants. In conclusion, in skeletal muscle from both normal control subjects and NIDDM patients, the proportion of insulin receptor mRNA with exon 11 is about 70%. In addition, no significant correlations exist among insulin binding, insulin receptor tyrosine kinase activity, glucose disposal rate, and expression of alternative spliced insulin receptors in human skeletal muscle.