Novel measures of inflammation and insulin resistance are related to obesity and fitness in a diverse sample of 11-14 year olds: The HEALTHY Study.

BACKGROUND: GlycA is a novel serum marker of systemic inflammation. There is no information on GlycA in pediatric populations, how it differs by gender or its association with body mass index (BMI) or fitness. Lipoprotein insulin resistance index (LP-IR) is a serum measure of insulin resistance, which is related to changes in BMI group in adolescents, but its relationship with fitness is unknown. The current study examined the independent associations between fitness and BMI with GlycA and LP-IR among US adolescents. METHODS: Participants were 1664 US adolescents from the HEALTHY study with complete 6th and 8th grade BMI, fitness and blood data. GlycA and LP-IR were measured by nuclear magnetic resonance spectroscopy. Three BMI groups and three fitness groups were created. Linear mixed models examined associations between GlycA, LP-IR, fitness and BMI. RESULTS: LP-IR decreased between 6th and 8th grade. GlycA increased among girls but decreased among boys. At 8th grade, median GlycA values were 27 (7.6%) µmol l(-1) higher (381 versus 354) for girls than boys. Median GlycA 6th grade values were 9% higher in obese girls than healthy weight girls. Overall, there was strong evidence (P<0.001) that GlycA was higher in higher BMI groups. Fitness was negatively associated with GlycA (r=-0.37 and -0.35) and LP-IR (r=-0.34 and -0.18) at the 6th and 8th grade assessments. As BMI category increased and fitness category decreased, GlycA and LP-IR levels increased. Lowest GlycA was found in the low BMI/high fitness group. CONCLUSIONS: GlycA was associated with BMI and fitness among in US adolescents. These findings suggest that there are independent effects for BMI and fitness group with both GlycA and LP-IR. Future studies should validate the role of GlycA and LP-IR to evaluate the effects of interventions to modify obesity and fitness to improve systemic inflammation and insulin resistance.

Benefits of combination of insulin degludec and liraglutide are independent of baseline glycated haemoglobin level and duration of type 2 diabetes.

AIM: To evaluate, using post hoc analyses, whether the novel combination of a basal insulin, insulin degludec, and a glucagon-like peptide-1 receptor agonist, liraglutide (IDegLira), was consistently effective in patients with type 2 diabetes (T2D), regardless of the stage of T2D progression. METHODS: Using data from the DUAL I extension [insulin-naïve patients uncontrolled on oral antidiabetic drugs (OADs), n = 1660, 52 weeks] and DUAL II (patients uncontrolled on basal insulin plus OADs, n = 398, 26 weeks) randomized trials, the efficacy of IDegLira was investigated with regard to measures of disease progression stage including baseline glycated haemoglobin (HbA1c), disease duration and previous insulin dose. RESULTS: Across four categories of baseline HbA1c (≤7.5-9.0%), HbA1c reductions were significantly greater with IDegLira (1.1-2.5%) compared with IDeg or liraglutide alone in DUAL I. In DUAL II, HbA1c reductions were significantly greater with IDegLira (0.9-2.5%) than with IDeg in all but the lowest HbA1c category. In DUAL I, insulin dose and hypoglycaemia rate were lower across all baseline HbA1c categories for IDegLira versus IDeg, while hypoglycaemia was higher with IDegLira than liraglutide, irrespective of baseline HbA1c. In DUAL II, insulin dose and hypoglycaemia rate were similar with IDegLira and IDeg (maximum dose limited to 50 U) independent of baseline HbA1c. The reduction in HbA1c with IDegLira was independent of disease duration and previous insulin dose but varied depending on pre-trial OAD treatment. CONCLUSIONS: IDegLira effectively lowered HbA1c across a range of measures, implying suitability for patients with either early or advanced T2D.

One-year efficacy and safety of a fixed combination of insulin degludec and liraglutide in patients with type 2 diabetes: results of a 26-week extension to a 26-week main trial.

AIMS: To confirm, in a 26-week extension study, the sustained efficacy and safety of a fixed combination of insulin degludec and liraglutide (IDegLira) compared with either insulin degludec or liraglutide alone, in patients with type 2 diabetes. METHODS: Insulin-naïve adults with type 2 diabetes randomized to once-daily IDegLira, insulin degludec or liraglutide, in addition to metformin ± pioglitazone, continued their allocated treatment in this preplanned 26-week extension of the DUAL I trial. RESULTS: A total of 78.8% of patients (1311/1663) continued into the extension phase. The mean glycated haemoglobin (HbA1c) concentration at 52 weeks was reduced from baseline by 1.84% (20.2 mmol/mol) for the IDegLira group, 1.40% (15.3 mmol/mol) for the insulin degludec group and 1.21% (13.2 mmol/mol) for the liraglutide group. Of the patients on IDegLira, 78% achieved an HbA1c of <7% (53 mmol/mol) versus 63% of the patients on insulin degludec and 57% of those on liraglutide. The mean fasting plasma glucose concentration at the end of the trial was similar for IDegLira (5.7 mmol/l) and insulin degludec (6.0 mmol/l), but higher for liraglutide (7.3 mmol/l). At 52 weeks, the daily insulin dose was 37% lower with IDegLira (39 units) than with insulin degludec (62 units). IDegLira was associated with a significantly greater decrease in body weight (estimated treatment difference, -2.80 kg, p < 0.0001) and a 37% lower rate of hypoglycaemia compared with insulin degludec. Overall, all treatments were well tolerated and no new adverse events or tolerability issues were observed for IDegLira. CONCLUSIONS: These 12-month data, derived from a 26-week extension of the DUAL I trial, confirm the initial 26-week main phase results and the sustainability of the benefits of IDegLira compared with its components in glycaemic efficacy, safety and tolerability.

Is insulin the most effective injectable antihyperglycaemic therapy?

AIMS: The recent type 2 diabetes American Diabetes Association/European Association for the Study of Diabetes (ADA/EASD) position statement suggested insulin is the most effective glucose-lowering therapy, especially when glycated haemoglobin (HbA1c) is very high. However, randomized studies comparing glucagon-like peptide-1 receptor agonists (GLP-1RAs) exenatide once-weekly [OW; DURATION-3 (Diabetes therapy Utilization: Researching changes in A1c, weight, and other factors Through Intervention with exenatide ONce-Weekly)] and liraglutide once-daily [OD; LEAD-5 (Liraglutide Effect and Action in Diabetes)] with insulin glargine documented greater HbA1c reduction with GLP-1RAs, from baseline HbA1c ∼8.3% (67 mmol/mol). This post hoc analysis of DURATION-3 and LEAD-5 examined changes in HbA1c, fasting glucose and weight with exenatide OW or liraglutide and glargine, by baseline HbA1c quartile. METHODS: Descriptive statistics were provided for change in HbA1c, fasting glucose, weight, and insulin dose, and subjects (%) achieving HbA1c <7.0%, by baseline HbA1c quartile. Inferential statistical analysis on the effect of baseline HbA1c quartile was performed for change in HbA1c. An analysis of covariance (ANCOVA) model was used to evaluate similarity in change in HbA1c across HbA1c quartiles. RESULTS: At 26 weeks, in both studies, HbA1c reduction, and proportion of subjects reaching HbA1c <7.0%, were similar or numerically greater with the GLP-1RAs than glargine for all baseline HbA1c quartiles. Fasting glucose reduction was similar or numerically greater with glargine. Weight decreased with both GLP-1RAs across all quartiles; subjects taking glargine gained weight, more at higher baseline HbA1c. Adverse events were uncommon although gastrointestinal events occurred more frequently with GLP-1RAs. CONCLUSIONS: HbA1c reduction with the GLP-1RAs appears at least equivalent to that with basal insulin, irrespective of baseline HbA1c. This suggests that liraglutide and exenatide OW may be appropriate alternatives to basal insulin in type 2 diabetes, including when baseline HbA1c is very high (≥9.0%).

Cardiovascular safety of the glucagon-like peptide-1 receptor agonist taspoglutide in people with type 2 diabetes: an individual participant data meta-analysis of randomized controlled trials.

AIMS: To study the short-term cardiovascular effects of the once-weekly glucagon-like peptide-1 receptor agonist taspoglutide. METHODS: We conducted a meta-analysis of individual-participant data from nine randomized controlled trials in the T-Emerge programme, which assessed the efficacy and safety of taspoglutide in type 2 diabetes. Our primary outcome was a composite of death from cardiovascular disease (CVD) and acute myocardial infarction, stroke and hospitalization for unstable angina. RESULTS: Overall, 7056 individuals were included in the analysis, and there were 67 primary endpoint events during 7478 person-years of follow-up (40 vs 27 events in the intervention vs control groups, respectively). The odds ratio for the composite endpoint among people randomized to taspoglutide was 0.94 (95% confidence interval 0.57-1.56), which was robust across multiple subgroups. Longer-term data were not available as the development of taspoglutide was stopped because of gastrointestinal intolerance and serious hypersensitivity reactions. CONCLUSIONS: The available data suggest that short-term, once-weekly administration of taspoglutide was not associated with an excess risk of CVD, and provide insights relevant to the development of other novel once-weekly incretin mimetics.

Efficacy, safety and tolerability of aleglitazar in patients with type 2 diabetes: pooled findings from three randomized phase III trials.

AIMS: To evaluate the potential efficacy, safety and tolerability of aleglitazar as monotherapy or add-on therapy to metformin or to a sulphonylurea (either alone or in combination with metformin). METHODS: We conducted a pooled analysis of data from three randomized phase III clinical trials of aleglitazar in patients with type 2 diabetes (n = 591). The three studies focused on: (i) aleglitazar alone; (ii) aleglitazar and metformin; and (iii) aleglitazar and sulphonylurea with or without metformin. Patients were randomized to 26 weeks' treatment with aleglitazar 150 µg/day or placebo. The primary endpoint was change in glycated haemoglobin (HbA1c) concentration from baseline to week 26. Secondary endpoints included changes in lipids, fasting plasma glucose and homeostatic model assessment of insulin resistance (HOMA-IR) at week 26. RESULTS: Reductions in HbA1c concentration from baseline to week 26 were statistically significantly greater with aleglitazar than with placebo. Aleglitazar treatment was associated with more beneficial changes in lipid profiles and HOMA-IR values than was placebo. Aleglitazar was generally well tolerated, with no reports of congestive heart failure. The incidence of peripheral oedema was similar in both groups. Change in body weight was +1.37 kg with aleglitazar and -0.53 kg with placebo. Hypoglycaemia was more frequently reported with aleglitazar (7.8%) than with placebo (1.7%), a result probably driven by the type of background medication. CONCLUSIONS: Development of aleglitazar was halted because of a lack of cardiovascular efficacy and peroxisome proliferator-activated receptor-related side effects in patients with type 2 diabetes post-acute coronary syndrome; however, in the present studies, aleglitazar was well tolerated and effective in improving HbA1c, insulin resistance and lipid variables.

LEADER 2: baseline calcitonin in 9340 people with type 2 diabetes enrolled in the Liraglutide Effect and Action in Diabetes: Evaluation of cardiovascular outcome Results (LEADER) trial: preliminary observations.

AIMS: To report preliminary data on baseline serum calcitonin concentrations and associated clinical characteristics in a global population with type 2 diabetes before liraglutide or placebo randomization. METHODS: The ongoing LEADER trial has enrolled 9340 people with type 2 diabetes and at high risk of cardiovascular disease at 410 centres worldwide. People with baseline serum calcitonin ≤ 50 ng/l were randomized to liraglutide once daily or placebo and will be followed for up to 5 years. Serum calcitonin was measured at baseline and will be measured annually thereafter. An independent committee of thyroid experts will oversee calcitonin monitoring throughout the trial and will review all calcitonin concentrations ≥ 20 ng/l. RESULTS: The mean age of participants was 64.3 ± 7.2 years, 64.3% were men, and mean the body mass index was 32.5 ± 6.3 kg/m(2). The median (interquartile range) baseline serum calcitonin values were 3.9 (1.0 to >7.6) ng/l in men and 1.0 (1.0 to >1) ng/l in women. Serum calcitonin was >10 ng/l in 14.6% of men and in 0.96% of women. In sex-specific multivariable linear analysis of covariance models, a reduced glomerular filtration rate (GFR) was associated with higher serum calcitonin concentrations that were statistically significant. A 20 ml/min/1.73 m(2) decrease in estimated GFR (eGFR) was associated with a 14% increase in serum calcitonin in women and an 11% increase in men. CONCLUSIONS: In the LEADER population, the prevalence of elevated serum calcitonin concentrations at baseline was high, and there was an inverse association between eGFR and serum calcitonin concentrations.

Subcutaneous injection of hyaluronidase with recombinant human insulin compared with insulin lispro in type 1 diabetes.

AIMS: Prandial treatment with human regular insulin for diabetes may result in early postprandial hyperglycaemia and late hypoglycaemia due to its slow onset and long duration of action. This study compared injections of recombinant human insulin (rHI) formulated with recombinant human hyaluronidase [rHuPH20] (INSULIN-PH20) to insulin lispro for prandial treatment in subjects with type 1 diabetes (T1D). METHODS: After a 1-month run-in period using twice-daily insulin glargine (or usual basal insulin therapy for pump users) with prandial lispro, 46 subjects with T1D (42 ± 13 years; body mass index: 26 ± 4 kg/m(2); A1c: 6.8 ± 0.5%) were assigned to INSULIN-PH20 or lispro in a random sequence for two consecutive, 12-week periods as the prandial insulin in an intensive treatment regimen. RESULTS: The mean glycaemic excursion for INSULIN-PH20 (0.96 ± 2.00 mmol/l) was comparable (p = 0.322) to lispro (0.80 ± 1.95 mmol/l). The 8-point self-monitored blood glucose profiles were also comparable in the two groups. Good glycaemic control (A1c) was maintained for both treatments at 12 weeks (INSULIN-PH20: 7.0 ± 0.5%; lispro: 6.9 ± 0.6%). Overall rates of hypoglycaemia (≤ 3.9 mmol/l) were 24 events per patient per 4 weeks for INSULIN-PH20 and 22 events for lispro. There were no significant differences in adverse events or immunogenicity between treatments and both treatments were well tolerated. CONCLUSIONS: Unlike commercially available formulations of regular human insulin, a formulation of rHI with rHuPH20 was comparable to lispro for postprandial glucose excursions in a basal-bolus treatment regimen for T1D patients. Glycaemic control, safety and tolerability profiles were comparable for both treatments.

Dipeptidyl-peptidase-4 inhibitors and pancreatic cancer: a cohort study.

AIM: To compare pancreatic cancer incidence and diagnostic evaluation among patients initiating dipeptidyl-peptidase-4 (DPP-4) inhibitor treatment with those initiating sulfonylureas (SU) and thiazolidinediones (TZD). METHODS: Medicare claims data were examined in a new-user active-comparator cohort study. Patients >65 years with no prescriptions for DPP-4 inhibitors, SU or TZD at baseline were included if they had at least two claims for the same drug within 180 days. Using an as-treated approach and propensity score-adjusted Cox models, we estimated the hazard ratios (HRs) and 95% confidence intervals (CIs) for pancreatic cancer. Diagnostic evaluations were compared using risk ratios. RESULTS: In the DPP-4 inhibitor versus SU comparison, there were 18 179 patients who initiated treatment with DPP-4 inhibitors, of whom 26 developed pancreatic cancer (interquartile range follow-up 5-18 months). In the DPP-4 inhibitor versus TZD comparison there were 29 366 people initiating DPP-4 inhibitor treatment and 52 of these developed pancreatic cancer. The risk of pancreatic cancer with DPP-4 inhibitor treatment was lower relative to SU treatment (HR: 0.6, CI: 0.4-0.9) and similar to TZD treatment (HR: 1.0, 95% CI: 0.7-1.4). After the first 6 months of follow-up were excluded to reduce the potential for reverse causality, the results were not altered. The probability of diagnostic evaluation after commencing DPP-4 inhibitor treatment (79.3%) was similar to that for TZD (74.1%, risk ratio 1.06, 95% CI: 1.05-1.07) and SU (74.6%) (risk ratio 1.06, 95% CI: 1.05-1.07). The probability of diagnostic evaluation before the index date (date of initiating treatment) was ∼80% for all cohorts. CONCLUSION: Although the present study was limited by sample size and the observed duration of treatment in the USA, our well-controlled population-based study suggests there is no higher short-term pancreatic cancer risk with DPP-4 inhibitor treatment relative to SU or TZD treatment.

Options for prandial glucose management in type 2 diabetes patients using basal insulin: addition of a short-acting GLP-1 analogue versus progression to basal-bolus therapy.

Integrating patient-centered diabetes care and algorithmic medicine poses particular challenges when optimized basal insulin fails to maintain glycaemic control in patients with type 2 diabetes. Multiple entwined physiological, psychosocial and systems barriers to insulin adherence are not easily studied and are not adequately considered in most treatment algorithms. Moreover, the limited number of alternatives to add-on prandial insulin therapy has hindered shared decision-making, a central feature of patient-centered care. This article considers how the addition of a glucagon-like peptide 1 (GLP-1) analogue to basal insulin may provide new opportunities at this stage of treatment, especially for patients concerned about weight gain and risk of hypoglycaemia. A flexible framework for patient-clinician discussions is presented to encourage development of decision-support tools applicable to both specialty and primary care practice.

Insulin degludec improves glycaemic control with lower nocturnal hypoglycaemia risk than insulin glargine in basal-bolus treatment with mealtime insulin aspart in Type 1 diabetes (BEGIN(®) Basal-Bolus Type 1): 2-year results of a randomized clinical trial.

AIMS: The goal of this study was to compare the long-term safety and efficacy of the basal insulin analogue, insulin degludec with insulin glargine (both with insulin aspart) in Type 1 diabetes, over a 2-year time period. METHODS: This open-label trial comprised a 1-year main trial and a 1-year extension. Patients were randomized to once-daily insulin degludec or insulin glargine and titrated to pre-breakfast plasma glucose values of 3.9-4.9 mmol/l. RESULTS: The rate of nocturnal confirmed hypoglycaemia was 25% lower with insulin degludec than with insulin glargine (P = 0.02). Rates of confirmed hypoglycaemia, severe hypoglycaemia and adverse events, and reductions in glycated haemoglobin and fasting plasma glucose were similar between groups. Despite achieving similar glycaemic control, insulin degludec-treated patients used 12% less basal and 9% less total daily insulin than did insulin glargine-treated patients (P < 0.01). CONCLUSIONS: Long-term basal therapy using insulin degludec in Type 1 diabetes required lower doses and was associated with a 25% lower risk for nocturnal hypoglycaemia than insulin glargine.

Patient-reported outcomes are superior in patients with Type 2 diabetes treated with liraglutide as compared with exenatide, when added to metformin, sulphonylurea or both: results from a randomized, open-label study.

AIMS: The Liraglutide Effect and Action in Diabetes 6 trial was an open-label trial comparing liraglutide with exenatide as an 'add-on' to metformin and/or sulphonylurea. METHODS: Patients with Type 2 diabetes were randomized to liraglutide 1.8 mg once daily or exenatide 10 µg twice daily for 26 weeks. This was followed by a 14-week extension phase, in which all patients received liraglutide 1.8 mg once daily. RESULTS: Patient-reported outcomes were measured in 379 patients using Diabetes Treatment Satisfaction Questionnaire status (DTSQs) and DTSQ change (DTSQc). The change in overall treatment satisfaction (DTSQs score) from baseline at week 26 with liraglutide was 4.71 and with exentaide was 1.66 [difference between groups 3.04 (95% CI 1.73-4.35), P<0.0001]. Five of the six items on the DTSQs improved significantly more with liraglutide than with exenatide (differences: current treatment 0.37, P=0.0093; convenience 0.68, P<0.0001; flexibility 0.57, P=0.0002; recommend 0.49, P=0.0003; continue 0.66, P=0.0001). Patients perceived a greater reduction in hypoglycaemia at week 26 with liraglutide than with exenatide [difference in DTSQc score 0.48 (0.08-0.89), P=0.0193] and a greater reduction in perceived hyperglycaemia [difference 0.74 (0.31-1.17), P=0.0007]. During the extension phase, when all patients received liraglutide, DTSQs scores remained stable in patients who continued on liraglutide and increased significantly (P=0.0026) in those switching from exenatide. CONCLUSIONS: These results demonstrate significant improvements in patients' treatment satisfaction with liraglutide compared with exenatide.

Major histocompatibility complex restriction fragment length polymorphisms define three diabetogenic haplotypes in BB and BBN rats.

Class I and II major histocompatibility complex (MHC) probes can be used to subdivide diabetes-prone BB rats and their BBN control strain, coderived from the same outbred colony by selection against diabetes. Class II probes (A-alpha in particular) distinguish four restriction fragment length polymorphisms (RFLP), termed 1a, 1b, 2a, and 2b, in the BBN population, only one of which (2a) is found in BB rats. The degree of class II RFLP in the population studied is RT1.B-alpha greater than or equal to RT1.B-beta greater than RT1.D-alpha greater than or equal to RT1.D-beta, suggesting that intra-class II region dynamics may be different in rats compared with mice. A class I probe (S16) absolutely distinguished BB from BBN rats, since all BB rats exhibit an RFLP pattern termed 2a0, while 2a BBN rats can be subdivided into 2a1 and 2a2 forms. Serologic evaluation has shown that 2a0, 2a1, and 2a2 rats express RT1.AuBu, 1a rats express RT1.AaDa, and 1b rats express neither RT1a nor RT1u at the loci tested. A breeding study was carried out to determine the diabetogenicity of the MHC-defined RFLP's. As expected, the BB-derived 2a0 is diabetogenic. The BBN-derived 2a1 and 2a2 RFLPs are also diabetogenic, while 1a and 1b rats do not carry MHC-linked diabetogenic genes. The MHC-linked diabetes gene acts in a functionally recessive manner, since there is a 10-fold higher incidence in homozygotes than in heterozygotes. Analysis of the RFLP patterns leads us to hypothesize that the 2a1 RFLP results from a crossover between 1a and 2a0 MHCs and that the diabetogenic MHC-linked gene is on the class II side of Qa and T1. The availability of three diabetogenic MHC haplotypes should help localize the MHC-linked diabetogenic gene of rats.

Two genes required for diabetes in BB rats. Evidence from cyclical intercrosses and backcrosses.

The BB rat develops a syndrome of autoimmune diabetes similar to Type I diabetes of man. It also has a severe T cell lymphopenia. As part of an ongoing breeding program to transfer the diabetogenic genes of the BB rat onto inbred rat strain backgrounds, diabetic animals were used in a backcross (BC)- intercross (IC)-backcross breeding scheme with Brown Norway (BN), Lewis (L), and Wistar-Furth (WF) inbred rats. We have used monoclonal antibodies to analyze both lymphopenia and major histocompatibility (MHC) antigens (the RT1 locus in the rat) in relation to the development of diabetes. To examine T cell subsets we used a panel of monoclonal antibodies, in particular W3/25 and OX19 , which discriminate the abnormal phenotype better than W3/13. In our breeding program, at least two independent genes or gene complexes are required for the expression of diabetes. One gene determines the lymphopenia, is inherited by simple autosomal recessive genetics and is not linked to the MHC. The second gene is linked to the MHC. Both genes are necessary, but neither gene is sufficient by itself for the development of diabetes.

Medical management of hyperglycaemia in type 2 diabetes mellitus: a consensus algorithm for the initiation and adjustment of therapy: a consensus statement from the American Diabetes Association and the European Association for the Study of Diabetes.

The consensus algorithm for the medical management of type 2 diabetes was published in August 2006 with the expectation that it would be updated, based on the availability of new interventions and new evidence to establish their clinical role. The authors continue to endorse the principles used to develop the algorithm and its major features. We are sensitive to the risks of changing the algorithm cavalierly or too frequently, without compelling new information. An update to the consensus algorithm published in January 2008 specifically addressed safety issues surrounding the thiazolidinediones. In this revision, we focus on the new classes of medications that now have more clinical data and experience.

The NOD mouse: recessive diabetogenic gene in the major histocompatibility complex.

Examination of the histocompatibility region of the nonobese diabetic (NOD) mouse with antibodies against class II glycoproteins (products of immune response genes of the major histocompatibility complex I-A and I-E), hybrid T-cell clones, and mixed-lymphocyte cultures and analysis of restriction fragment length polymorphisms indicate that the NOD mouse has a unique class II major histocompatibility complex with no expression of surface I-E, no messenger RNA for I-E alpha, and an I-A not recognized by any monoclonal antibodies or hybrid T-cell clones studied. In crosses of NOD mice with control C3H mice, the development of diabetes was dependent on homozygosity for the NOD mouse's unique major histocompatibility region.

Analysis of the gene sequences of the insulin receptor and the insulin-sensitive glucose transporter (GLUT-4) in patients with common-type non-insulin-dependent diabetes mellitus.

Insulin resistance is a common feature of non-insulin-dependent diabetes mellitus (NIDDM) and "diabetes susceptibility genes" may be involved in this abnormality. Two potential candidate genes are the insulin receptor (IR) and the insulin-sensitive glucose transporter (GLUT-4). To elucidate whether structural defects in the IR and/or GLUT-4 could be a primary cause of insulin resistance in NIDDM, we have sequenced the entire coding region of the GLUT-4 gene from DNA of six NIDDM patients. Since binding properties of the IRs from NIDDM subjects are normal, we also analyzed the sequence of exons 16-22 (encoding the entire cytoplasmic domain of the IR) of the IR gene from the same six patients. When compared with the normal IR sequence, no difference was found in the predicted amino acid sequence of the IR cytoplasmic domain derived from the NIDDM patients. Sequence analysis of the GLUT-4 gene revealed that one patient was heterozygous for a mutation in which isoleucine (ATC) was substituted for valine (GTC) at position 383. Consequently, the GLUT-4 sequence at position 383 was determined in 24 additional NIDDM patients and 30 nondiabetic controls and all showed only the normal sequence. From these studies, we conclude that the insulin resistance seen in the great majority of subjects with the common form of NIDDM is not due to genetic variation in the coding sequence of the IR beta subunit, nor to any single mutation in the GLUT-4 gene. Possibly, a subpopulation of NIDDM patients exists displaying variation in the GLUT-4 gene.

Small intestine hexose transport in experimental diabetes. Increased transporter mRNA and protein expression in enterocytes.

The effect of insulinopenic diabetes on the expression of glucose transporters in the small intestine was investigated. Enterocytes were sequentially isolated from jejunum and ileum of normal fed rats, streptozotocin-diabetic rats, and diabetic rats treated with insulin. Facilitative glucose transporter (GLUT) 2, GLUT5, and sodium-dependent glucose transporter 1 protein content was increased from 1.5- to 6-fold in enterocytes isolated from diabetic animals in both jejunum and ileum. Insulin was able to reverse the increase in transporter protein expression seen after induction of diabetes. There was a four- to eightfold increase in the amount of enterocyte glucose transporter mRNA after diabetes with greater changes in sodium-dependent glucose transporter 1 and GLUT2 than in GLUT5 levels. In situ hybridization showed that after the induction of diabetes there was new hybridization in lower villus and crypt enterocytes that was reversed by insulin treatment. Thus, the increase in total hexose transport caused by diabetes is due to a premature expression of hexose transporters by enterocytes along the crypt-villus axis, causing a cumulative increase in enterocyte transporter protein during maturation. These changes are likely to represent an adaptive response by the organism to increase nutrient absorption in a perceived state of tissue starvation. These adaptive changes may lead to exacerbation of hyperglycemia in uncontrolled diabetes.

Specific class II histocompatibility gene polymorphism in BB rats.

The BB rat spontaneously develops insulin-dependent diabetes mellitus of autoimmune etiology. From breeding studies, one of the genes necessary for the development of diabetes in these animals is linked to RT1, the rat major histocompatibility complex. To better define the BB rat's RT1-linked diabetogenic gene (RT1-DM), we have used restriction endonucleases BamH1 and EcoR1 in conjunction with an I-A alpha (class II mouse major histocompatibility complex) gene probe to study RT1 class II gene polymorphisms among diabetes-prone BB rats and the related non-diabetes-prone BBN rats. Both BB and BBN rats are indistinguishable RT1u by serologic methods. Four polymorphic chromosome types (la, lb, lla, and llb) were recognized among the control BBN rats. In contrast, all BB rats were homozygous (lla/lla). From the multiple breeding programs involved, we hypothesize that the BB rat's RT1-linked diabetogenic gene is linked to an l-A alpha-defined gene of the type lla chromosome. The ability to split the RT1u of BB rats will provide a powerful tool to localize and characterize RT1-DM.