Insulin sensitivity in non-diabetic relatives of patients with non-insulin-dependent diabetes from two ethnic groups

Significance of Ethnic Factors in Immunosuppressive Therapy Management After Organ Transplantation

Clinical outcomes after organ transplantation have greatly improved in the past 2 decades with the discovery and development of immunosuppressive drugs such as calcineurin inhibitors, antiproliferative agents, and mammalian target of rapamycin inhibitors. However, individualized dosage regimens have not yet been fully established for these drugs except for therapeutic drug monitoring-based dosage modification because of extensive interindividual variations in immunosuppressive drug pharmacokinetics. The variations in immunosuppressive drug pharmacokinetics are attributed to interindividual variations in the functional activity of cytochrome P450 enzymes, UDP-glucuronosyltransferases, and ATP-binding cassette subfamily B member 1 (known as P-glycoprotein or multidrug resistance 1) in the liver and small intestine. Some genetic variations have been found to be involved to at least some degree in pharmacokinetic variations in post-transplant immunosuppressive therapy. It is well known that the frequencies and effect size of minor alleles vary greatly between different races. Thus, ethnic considerations might provide useful information for optimizing individualized immunosuppressive therapy after organ transplantation. Here, we review ethnic factors affecting the pharmacokinetics of immunosuppressive drugs requiring therapeutic drug monitoring, including tacrolimus, cyclosporine, mycophenolate mofetil, sirolimus, and everolimus.

The influence of ethnicity and glucose tolerance status on subjective hunger sensations and prospective food intake in overweight and obese Asian and European Australians

AIMS

To examine the influence of ethnicity and glucose tolerance status on subjective sensations and food intake in overweight/obese Asian and European Australians.

METHODS

18 Asians and 26 Europids were classified as normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) based on serial measures of finger-prick glucose following an oral glucose tolerance test (OGTT). Subjective sensations of hunger and satiety were measured before and every 15min after the OGTT using a visual analogue scale (VAS). Food intake was measured covertly from consumption of a buffet style lunch and from self-maintained 24h food records. All serial measurements were converted into total area under the curve (TAUC) and comparisons adjusted for age, fat and fat-free mass.

RESULTS

There was a significant difference interaction between ethnicity (ETH) and glucose tolerance (GTT) for subjective fullness, desire for food and prospective food intake. IGT Asians had significantly greater sensations of fullness, but lesser prospective food and desire to eat, as compared to other groups. However there were no differences in calorie and macronutrient intake at buffet lunch or over 24-h.

CONCLUSION

Interactions between ethnicity and glucose tolerance status in subjective sensations did not transcribe to differences in prospective food intake.

Insulin resistance syndrome in South Asians

Although South Asians express increased features (conventional) of insulin resistance syndrome, these do not fully explain the increased mortality both from ischaemic heart disease and ischaemic stroke in South Asians compared to Whites. Thrombotic risk factors for vascular disease, as a part of insulin resistance syndrome in South Asians, are being investigated and are an important moiety. The management of the epidemic of ischaemic vascular disease in South Asians is a major global endeavour.

Construction of adiponectin-encoding plasmid DNA and gene therapy of non-obese type 2 diabetes mellitus

Adiponectin (ADN), an insulin-sensitizing adipokine, stimulates glucose uptake, inhibits gluconeogenesis, and plays an important role in improving insulin sensitivity. Since blood levels of ADN are low in type 2 diabetes mellitus (DM), this study was designed to investigate the therapeutic effectiveness of increasing the ADN level through injection of plasmid DNA encoding ADN in type 2 DM. A non-obese type 2 DM mouse model was established via combined administration of streptozotocin with nicotinamide and exhibited significantly higher plasma glucose concentration and insulin resistance compared with normal controls according to oral glucose tolerance and insulin challenge tests. Plasmid DNA encoding mouse ADN from differentiated NIH3T3 adipocytes was constructed in pVAX1 (pVAX/ADN). Transfection of pVAX/ADN into various cell lines including HeLa, HT22, HEK293, HepG2, and SK-Hep1 cells, increased ADN mRNA expression levels in a dose-dependent manner. The administration of pVAX/ADN into non-obese type 2 DM mice via tail vein significantly increased the blood level of ADN and decreased the plasma glucose concentration. Moreover, the parameters related to insulin resistance (HOMA-IR) and insulin sensitivity (QUICKI) were significantly improved. These results suggest that ADN gene therapy could be a clinically effective tool for the treatment of type 2 DM.

Establishment and Pathophysiological Characterization of Type 2 Diabetic Mouse Model Produced by Streptozotocin and Nicotinamide

This study was performed in order to establish a mouse model that represents the non-obese type 2 diabetes reflecting a majority of diabetic patients among Asian races and to show its pathophysiological profiles. Streptozotocin (STZ) was administered to C57BL/6J mice with or without nicotinamide (120 or 240 mg/kg, STZ/NA120 or STZ/NA240), twice with an interval of 2 d, and plasma glucose concentration, body weight, water intake, insulin contents and insulin signal-related proteins were monitored. STZ-induced hyperglycemia (fasting and non-fasting), body weight loss and polyposia were significantly depressed by NA dose-dependently. In STZ/NA120 and STZ/NA240 mice, pancreatic insulin content was retained by 28 and 43% of normal control (10.5+/-0.93 microU/ml), respectively, and histological damage of pancreatic beta cells was also less severe than that observed in STZ mice. When given the calorie-controlled high fat diet, the STZ/NA mice caused hyperlipidemia, and significantly increased insulin resistance. These observations suggest that the combined administration of STZ and NA causes partial depletion of pancreatic insulin and that the high fat constituents lead to insulin resistance in this model. The present mouse model, therefore, well exhibits the recent diabetic pathophysiological characteristics of a majority of Asian patients.

Beta-cell dysfunction and glucose intolerance: results from the San Antonio metabolism (SAM) study

AIMS/HYPOTHESIS

Both insulin resistance and beta-cell dysfunction play a role in the transition from normal glucose tolerance (NGT) to Type 2 diabetes (T2DM) through impaired glucose tolerance (IGT). The aim of the study was to define the level of glycaemia at which beta-cell dysfunction becomes evident in the context of existing insulin resistance.

METHODS

Insulin response (OGTT) and insulin sensitivity (euglycaemic insulin clamp) were evaluated in 388 subjects in the San Antonio Metabolism (SAM) study (138 NGT, 49 IGT and 201 T2DM). In all subjects the insulin secretion/insulin resistance index (DeltaI/DeltaG/IR) was calculated as the ratio of the increment in plasma insulin to the increment in plasma glucose during the OGTT divided by insulin resistance, as measured during the clamp.

RESULTS

In lean NGTs with a 2-h plasma glucose concentration (2-h PG) between 5.6 and 6.6 and between 6.7 and 7.7 mmol/l, there was a progressive decline in DeltaI/DeltaG/IR compared with NGTs with a 2-h PG less than 5.6 mmol/l. There was a further decline in DeltaI/DeltaG/IR in IGTs with a 2-h PG between 7.8 and 9.3 and between 9.4 and 11.0 mmol/l, and in Type 2 diabetic patients with a 2-h PG greater than 11.1 mmol/l. Lean and obese subjects showed coincident patterns of relation of 2-h PG to DeltaI/DeltaG/IR.

CONCLUSION/INTERPRETATION

When the plasma insulin response to oral glucose is related to the glycaemic stimulus and severity of insulin resistance, there is a progressive decline in beta-cell function that begins in "normal" glucose tolerant individuals.

Insulin action and secretion in healthy Hispanic-Mexican first-degree relatives of subjects with type 2 diabetes

The aim of this study was to assess the early insulin secretion and insulin action of healthy non-diabetic Hispanic-Mexican subjects with and without family history of Type 2 diabetes (FHD). One hundred and twenty non-relative subjects were compared against 115 first-degree relatives of individuals with Type 2 diabetes. To assign the subjects to the correspondent group, the FHD was carefully ascertained by clinical examination of the participants' parents. Age and gender were matched criteria. Incomplete or unclear data about FHD, previous diagnosis of diabetes or chronic diseases were exclusion criteria. Subjects in both groups were required to have fasting glucose <6.1 mmol/l, and 2-h PG<7.7 mmol/l. Insulin action and secretion were estimated by HOMA (homeostasis model insulin analysis resistance index) and insulinogenic index, respectively. Logistic regression analysis showed an independent relationship between BMI and insulin resistance (HOMA score >5.0) (odds ratio, OR, 1.42, p=0.03), and between FHD and insulin resistance (OR 1.27, p=0.04). On the other hand, there was a strong and independent relationship between FHD and high early insulin secretion (insulinogenic index >0.72) (OR 1.64, p=0.01) but not between BMI and high early insulin secretion (OR 0.93, p=0.3). Healthy Mexican first-degree relatives of subjects with Type 2 diabetes show an independent relationship between FHD and both high early insulin response and decreased insulin action, whereas BMI was only related to insulin resistance.

Diet-induced change in fatty acid composition of plasma triacylglycerols is not associated with change in glucagon-like peptide 1 or insulin sensitivity in people with type 2 diabetes

BACKGROUND

Polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs) have been shown to positively affect blood lipids; however, their comparative effects on insulin sensitivity are unclear.

OBJECTIVE

Our objective was to investigate whether chronic intake of MUFAs or PUFAs improves insulin sensitivity in people with type 2 diabetes via stimulation of the endogenous gut hormone glucagon-like peptide 1 [7-36] amide (GLP-1).

DESIGN

Nine overweight people with type 2 diabetes received isoenergetic high-MUFA (20.3 +/- 3.5% of total energy) or high-PUFA (13.4 +/- 1. 3%) diets for 24 d in a randomized, double-blind crossover design.

RESULTS

Weight and glycemic control remained stable throughout the study. Despite a significant change in the plasma triacylglycerol linoleic-oleic acid ratio (L:O) with both diets (MUFA: from 0.46 +/- 0.03 to 0.29 +/- 0.02, P: < 0.005; PUFA: from 0.36 +/- 0.04 to 0.56 +/- 0.05, P: < 0.05) and the phospholipid L:O (1.7 +/- 0.1 to 2.0 +/- 0.3; P: = 0.04) during consumption of the PUFA diet, this change was not associated with a change in insulin sensitivity, measured by the short-insulin-tolerance test. There was a significant reduction in the ratio of total to HDL cholesterol during consumption of the PUFA diet (5.2 +/- 0.4 compared with 4.7 +/- 0.3; P: = 0.005) but no change with the MUFA diet. There was no change in the fasting or postprandial incremental area under the curve in response to an identical standard test meal for glucose, insulin, triacylglycerol, nonesterified fatty acids, or GLP-1.

CONCLUSIONS

Over the 3-wk intervention period, diet-induced change in the triacylglycerol or phospholipid L:O was not associated with either increased stimulation of GLP-1 or a change in insulin sensitivity in people with type 2 diabetes.

Specific insulin and proinsulin in normal glucose tolerant first-degree relatives of NIDDM patients

In order to identify early abnormalities in non-insulin-dependent diabetes mellitus (NIDDM) we determined insulin (using an assay that does not cross-react with proinsulin) and proinsulin concentrations. The proinsulin/insulin ratio was used as an indicator of abnormal beta-cell function. The ratio of the first 30-min increase in insulin to glucose concentrations following the oral glucose tolerance test (OGTT; I30-0/G30-0) was taken as an indicator of insulin secretion. Insulin resistance (R) was evaluated by the homeostasis model assessment (HOMA) method. True insulin and proinsulin were measured during a 75-g OGTT in 35 individuals: 20 with normal glucose tolerance (NGT) and without diabetes among their first-degree relatives (FDR) served as controls, and 15 with NGT who were FDR of patients with NIDDM. The FDR group presented higher insulin (414 pmol/l vs 195 pmol/l; P = 0.04) and proinsulin levels (19.6 pmol/l vs 12.3 pmol/l; P = 0.03) post-glucose load than the control group. When these groups were stratified according to BMI, the obese FDR (N = 8) showed higher fasting and post-glucose insulin levels than the obese NGT (N = 9) (fasting: 64.8 pmol/l vs 7.8 pmol/l: P = 0.04, and 60 min post-glucose: 480.6 pmol/l vs 192 pmol/l: P = 0.01). Also, values for HOMA (R) were higher in the obese FDR compared to obese NGT (2.53 vs 0.30; P = 0.075). These results show that FDR of NIDDM patients have true hyperinsulinemia (which is not a consequence of cross-reactivity with proinsulin) and hyperproinsulinemia and no dysfunction of a qualitative nature in beta-cells.

Treatment with protease inhibitors associated with peripheral insulin resistance and impaired oral glucose tolerance in HIV-1-infected patients

BACKGROUND

The use of protease inhibitors in the treatment of HIV-1 infection is associated with the new onset of diabetes mellitus, hyperlipidaemia and lipodystrophy. It is unclear whether these findings are coincidental or whether they reflect a causative effect of protease inhibitors.

OBJECTIVE

To evaluate the effect of treatment with protease inhibitors on insulin sensitivity, oral glucose tolerance and serum lipids in HIV-infected patients in order to determine whether treatment with protease inhibitors can cause peripheral insulin resistance.

DESIGN

Cross-sectional controlled study in HIV-infected patients treated with protease inhibitors to assess insulin sensitivity, oral glucose tolerance and changes in serum lipids.

METHODS

Sixty-seven patients treated with protease inhibitors, 13 therapy-naive patients and 18 HIV-negative control subjects were tested for insulin sensitivity (intravenous insulin tolerance test). In a subgroup of 24 treated patients, oral glucose tolerance was determined. Serum lipids prior to and under treatment with protease inhibitors were compared.

RESULTS

Patients on protease inhibitors had a significantly decreased insulin sensitivity when compared with therapy-naive patients (median, 75 and 156 micromol/l/min, respectively; P < 0.001). All treated patients with impaired (n=4) or diabetic (n=9) oral glucose tolerance, and four out of 11 patients with normal glucose tolerance showed peripheral insulin resistance; all therapy-naive patients had normal insulin sensitivity. Treatment with protease inhibitors led to a significant increase in total triglycerides and cholesterol in the 67 treated patients (median increase, 113 and 37 mg/ml, respectively).

CONCLUSION

Treatment with protease inhibitors is associated with peripheral insulin resistance, leading to impaired or diabetic oral glucose tolerance in some of the patients, and with hyperlipidaemia. Overall, there is a large variation in the severity and clinical presentation of protease inhibitor-associated metabolic side-effects.

The genetic basis of type 2 diabetes mellitus: impaired insulin secretion versus impaired insulin sensitivity

Despite the fact that it is the prevalent view that insulin resistance is the main genetic factor predisposing to development of type 2 diabetes, review of several lines of evidence in the literature indicates a lack of overwhelming support for this concept. In fact, the literature better supports the case of impaired insulin secretion being the initial and main genetic factor predisposing to type 2 diabetes, especially 1) the studies in people at high risk to subsequently develop type 2 diabetes (discordant monozygotic twins and women with previous gestational diabetes), 2) the studies demonstrating compete alleviation of insulin resistance with weight loss, and 3) the studies finding that people with type 2 diabetes or IGT can have impaired insulin secretion and no insulin resistance compared with well matched NGT subjects. The fact that insulin resistance may be largely an acquired problem in no way lessens its importance in the pathogenesis of type 2 diabetes. Life style changes (exercise, weight reduction) and pharmacological agents (e.g., biguanides and thiazolidendiones) that reduce insulin resistance or increase insulin sensitivity clearly have major beneficial effects (122, 144-146, 153-155).

Insulin sensitivity indices calculated from basal and OGTT-induced insulin, glucose, and FFA levels

Insulin Sensitivity Indices for glycemia [ISI(gly)] and blood FFA [ISI(ffa)] can be calculated with the formulas: ISI(gly) = 2/[(INSp x GLYp) + 1], and ISI(ffa) = 2/[(INSp x FFAp) + 1], where INSp, GLYp and FFAp = insulinemic, glycemic, and FFA areas during OGTT (75 g glucose) of the person under study, simplified by considering only data at 0 and 2 h (0-2 h areas), according to WHO criteria or, better, at 0, 1 and 2 h (0-1-2 h areas). Expressed as unit/ volume.h-1, 0-1-2 h area is equal to 1/2 value at 0 min + value at 1 h + 1/2 value at 2 h, while 0-2 h area is equal to value at 0 + value at 2 h. Instead of areas, basal levels can also be used. Basal levels and areas are expressed taking the mean normal value as unit, so that in normal subjects ISI(gly) and ISI(ffa) are always around 1, with maximal variations between 0 and 2. Each laboratory should have its normal reference values for basal levels and OGTT areas. However, reliable mean normal values were selected from literature. Based on meta-analysis of published data, ISI(gly) and ISI(ffa) were reduced in subjects who were overweight and/or IGT and in NIDDM patients and their relatives. Moreover, correlation of ISI(gly) with the euglycemic clamp data was significant. However, it should be stressed that the clamp procedure is performed under artificially induced steady-state whereas ISI(gly) and ISI(ffa) are obtained under rather physiological conditions, with hormonal and metabolic variables unmodified, thus being suitable to assess whole-body insulin sensitivity in the clinical setting.

Decreased glucose tolerance, not decreased insulin sensitivity, is a maturational abnormality in the male offspring of a parent with early coronary artery disease

We investigated whether the male offspring of a parent with early coronary artery disease (before the age of 60; n = 61) exhibit decreased insulin sensitivity compared with controls matched for age and body mass index (BMI) (n = 39). The insulin sensitivity index (S[I]) was determined by the minimal modeling method of Bergman from a frequently sampled intravenous glucose tolerance test with intravenous tolbutamide. Offspring and controls had a similar S[I], insulin-independent glucose utilization (S[G]), first-phase insulin response (AIR[G]), and area under the glucose curve. When subjects were separated into two age groups, younger subjects aged 15 to 30 years and older subjects aged 31 to 45 years, important differences were seen. S[G] was significantly increased in younger offspring compared with controls (22.8 +/- 2.3 v 16.8 +/- 2.3 x 10(-3) x min(-1), P < .05). Older offspring had a significantly increased area under the glucose curve compared with controls (18,250 +/- 322 v 17,225 +/- 347 mg/dL x min(-1), P < .05). Older offspring also had decreased S[I] compared with younger offspring (5.0 +/- 0.4 v 6.6 +/- 0.9 x 10(-4) x min(-1) x micro U/mL, P < .05), but this difference was eliminated after adjusting for BMI and waist to hip ratio (5.5 +/- 0.4 v5.8 +/- 0.9 x 10(-3) x min(-1), nonsignificant). This study does not support the concept that insulin resistance is an early atherogenic risk factor in offspring at risk for coronary disease because of their family history. However, it does point to the importance of maturational changes in glucose homeostasis in these offspring.

Insulin receptor substrate-1 gene mutations in NIDDM; implications for the study of polygenic disease

Variations in the coding regions of the insulin receptor substrate-1 (IRS-1) gene have recently been suggested to contribute to the susceptibility of non-insulin-dependent diabetes mellitus (NIDDM). The purpose of this study was to examine the role of the IRS-1 missense mutations at codons 972 (glycine to arginine) and 513 (alanine to proline) in two diverse populations from South India and Finland at high risk for NIDDM. DNA was amplified and digested with restriction enzymes BstN1 to detect the codon 972 mutation and Dra III to detect the codon 513 mutation. The codon 513 mutation was not found in the study subjects. The codon 972 mutation was present in 10.3% of 126 middle-aged NIDDM subjects and 5.3% of 95 matched control subjects in the South Indians (p = 0.17). In elderly Finnish subjects the frequency of the mutation was 7.5% in 40 NIDDM subjects and 7% in 42 matched control subjects. The frequency of codon 972 mutation in the South Indian NIDDM subjects was very similar to the two previously published studies in Danish and French subjects although each study individually fails to reach conventional levels of significance. The data from all four ethnic groups were analysed together after ascertaining that significant heterogeneity did not exist between the studies. Overall, the frequency of the codon 972 mutation is found in 10.7% NIDDM subjects and 5.8% control subjects (p = 0.02). These studies suggest that the codon 972 mutation of the IRS-1 gene might act as a susceptibility gene predisposing to NIDDM in certain ethnic groups.

Increased secretion of 32,33 split proinsulin after intravenous glucose in glucose-tolerant first-degree relatives of patients with non-insulin dependent diabetes of European, but not Asian, origin

OBJECTIVE

The aetiology of non-insulin dependent diabetes is unknown, but defective insulin secretion is a feature. The disease also has a strong genetic basis and first-degree relatives of patients have an increased risk of future diabetes. To investigate whether beta-cell dysfunction is an early feature of the disease, we studied insulin secretion in healthy first-degree relatives of patients with non-insulin dependent diabetes.

DESIGN

Each subject underwent a 1-hour intravenous glucose tolerance test (0.3 g/kg).

PATIENTS

Seventeen first-degree relatives of patients (10 of European and 7 of Asian (Indian subcontinent) origin) with normal glucose tolerance were compared with 17 matched control subjects with no family history of diabetes.

MEASUREMENTS

Plasma immunoreactive insulin (IRI) was measured by radioimmunoassay, and specific insulin, intact and 32,33 split proinsulin were measured by specific immunoradiometric assays (IRMA) for the 1st phase (0-10 minutes) and 2nd phase (10-60 minutes) responses. Glucose and intermediary metabolites were measured enzymatically.

RESULTS

Fasting concentrations of IRI, IRMA insulin, intact and 32,33 split proinsulin were similar in relatives and controls in each group. Fasting glucose levels were similar in European relatives and controls but lower in Asian relatives compared to their controls (mean +/- SE 4.9 +/- 0.2 vs 5.5 +/- 0.2 mmol/l, P < 0.05). Following intravenous glucose, European relatives had similar IRI and glucose levels to their controls. Secretion of 32,33 split proinsulin was increased in European relatives compared to their controls, significantly so for 2nd phase secretion (1st phase median (range): 71 (7-352) vs 55 (17-118) pmol/l min, NS; 2nd phase: 433 (115-1459) vs 234 (55-745) pmol/l min, P < 0.05). Secretion of IRMA insulin and intact proinsulin were similar in European relatives and controls (IRMA insulin: 1st phase 2757 (700-10,969) vs 2830 (632-4682) pmol/l min; 2nd phase 6387 (3006-15,865) vs 5284 (2060-18,605) pmol/l min; intact proinsulin: 1st phase 31 (13-113) vs 32 (16-72) pmol/l min; 2nd phase: 174 (87-737) vs 159 (97-298) pmol/l min). European relatives had a greater percentage of proinsulin-like molecules (intact + 32,33 split proinsulin) to total insulin (sum of IRMA insulin + intact + 32,33 split proinsulin) during the 2nd phase of secretion (9.1 (5.0-11.8) vs 5.9 (4.3-12.6)%, P < 0.05). In contrast, Asian relatives had similar secretion of IRI, IRMA insulin, intact and 32,33 split proinsulin to their controls. Glucose disappearance (KG) was similar in relatives and controls within each ethnic group (Europeans: relatives 725 +/- 101 vs controls 668 +/- 47/min; Asian: relatives 610 +/- 97 vs controls 783 +/- 936/min). Asian relatives had higher fasting circulating glycerol (65 +/- 7 vs 44 +/- 4 mumol/l, P < 0.05), non-esterified fatty acid (569 +/- 59 vs 375 +/- 64 mumol/l, P < 0.05) and 3-hydroxybutyrate levels (147 (44-187) vs 35 (21-57) mumol/l, P < 0.01) than their controls and this persisted following intravenous glucose. This difference was not observed in the European group.

CONCLUSION

First-degree relatives of European patients with NIDDM possess early signs of beta-cell dysfunction, with increased and disproportionate secretion of 32,33 split proinsulin after intravenous glucose, whilst glucose tolerance is still normal.

Insulin resistance with respect to lipolysis in non-diabetic relatives of European patients with type 2 diabetes

Type 2 diabetes is characterized by resistance to insulin action of glucose metabolism and lipolysis. First-degree relatives of diabetic patients are at increased risk of developing diabetes themselves and early metabolic abnormalities in these relatives may represent primary defects in the pathogenesis of diabetes. Our previous work has demonstrated impaired suppression of lipolysis after an oral glucose load in glucose-tolerant relatives of Asian origin, but not in European relatives. To investigate whether a more subtle defect exists in the European population we studied 8 first-degree relatives of European patients and 9 matched control subjects. All had normal glucose tolerance. Glycerol and glucose turnovers were measured using a primed constant infusion of the stable isotopic tracers [1,1,1,2,3(2)H5] glycerol and [6,6(2)H] glucose, basally and in response to a very low dose insulin infusion (0.005 units kg-1 h-1). The relatives had higher basal insulin concentrations (median (range): 49 (30 to 113) vs 28 (18 to 66) pmol 1(-1), p < 0.05) compared to controls, but basal glycerol and glucose turnovers and plasma concentrations of glycerol, glucose, and non-esterifed fatty acids (NEFA) were similar. Following insulin, the suppression of glycerol appearance in the circulation measured isotopically was significantly less complete in the relatives compared with controls (mean change +/- SEM: + 0.06 +/- 0.21 vs - 0.51 +/- 0.16 mumol kg-1 min-1, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic analysis of glucokinase and the chromosome 20 diabetes susceptibility locus in families with type 2 diabetes

Mutations of the glucokinase gene (chromosome 7p) have been shown to cause some cases of familial maturity onset diabetes of youth (MODY) but few, if any, cases of late onset familial Type 2 diabetes. A further single large pedigree with MODY has shown linkage to a marker for the adenosine deaminase gene (ADA, chromosome 20q), although the diabetes susceptibility gene at this locus has not been identified. We have studied members of 19 families with familial Type 2 diabetes (including 10 European families, 6 families from the Indian subcontinent, and 3 families of Afro-Caribbean origin), 2 of which were of MODY type (and both European), with a glucokinase marker and a marker linked to ADA, to examine whether glucokinase, or the unknown defect on chromosome 20, are implicated in diabetes in our pedigrees. Several models were constructed for standard two-point linkage analysis. Glucokinase is not the cause of diabetes in all of these families but was excluded in only one MODY family. It was possible to exclude both loci in the second MODY pedigree. No evidence was found of linkage to either marker in this multi-ethnic population under the models used. At least one further locus is involved in determining susceptibility to MODY.

Serum lipoprotein levels and plasma concentrations of insulin, intact and 32, 33 split proinsulin in normoglycaemic relatives of patients with type 2 diabetes

Type 2 diabetes is associated with abnormal lipoprotein levels and altered plasma concentrations of insulin, intact and 32, 33 split proinsulin. To investigate whether these are early features of the disease, we studied 36 normoglycaemic first-degree relatives of patients with Type 2 diabetes (13 European, 15 of Asian (Indian-subcontinent), and 8 of Afro-Caribbean origin) and 36 control subjects with no family history of diabetes. Relatives and controls were matched for age (mean +/- S.E. 33 +/- 2 vs 34 +/- 2 years), body mass index (23.7 +/- 0.5 vs 23.7 +/- 0.6 kg m-2), sex (17 M, 19 F) and ethnic origin. After an overnight fast, blood was sampled for measurement of serum lipids, plasma glucose and insulin, intact and 32, 33 split proinsulin by specific immunoradiometric assays. Relatives and controls had similar fasting concentrations of glucose (5.0 +/- 0.1 vs 4.9 +/- 0.1 mmol l-1), total cholesterol (4.51 +/- 0.13 vs 4.54 +/- 0.17 mmol l-1), HDL-cholesterol (1.21 +/- 0.06 vs 1.10 +/- 0.05 mmol l-1), LDL-cholesterol (2.84 +/- 0.14 vs 2.96 +/- 0.14 mmol l-1) and triglyceride (median (range) 0.78 (0.44-2.45) vs 0.83 (0.41-4.03) mmol l-1). Fasting levels of insulin (50.4 (18.9-174.0) vs 51.6 (10.0-118.0) pmol l-1, intact proinsulin (2.8 (0.1-15.0) vs 2.1 (0.6-6.4) pmol l-1 and 32, 33 split proinsulin (2.0(0-23.7) vs 1.6 (0.3-6.0) pmol l-1) were not significantly different between relatives and controls.(ABSTRACT TRUNCATED AT 250 WORDS)