A rare mutation in ABCC8/SUR1 leading to altered ATP-sensitive K+ channel activity and beta-cell glucose sensing is associated with type 2 diabetes in adults

OBJECTIVE

ATP-sensitive K(+) channels (K(ATP) channels) link glucose metabolism to the electrical activity of the pancreatic beta-cell to regulate insulin secretion. Mutations in either the Kir6.2 or sulfonylurea receptor (SUR) 1 subunit of the channel have previously been shown to cause neonatal diabetes. We describe here an activating mutation in the ABCC8 gene, encoding SUR1, that is associated with the development of type 2 diabetes only in adults.

RESEARCH DESIGN AND METHODS

Recombinant K(ATP) channel subunits were expressed using pIRES2-based vectors in human embryonic kidney (HEK) 293 or INS1(832/13) cells and the subcellular distribution of c-myc-tagged SUR1 channels analyzed by confocal microscopy. K(ATP) channel activity was measured in inside-out patches and plasma membrane potential in perforated whole-cell patches. Cytoplasmic [Ca(2+)] was imaged using Fura-Red.

RESULTS

A mutation in ABCC8/SUR1, leading to a Y356C substitution in the seventh membrane-spanning alpha-helix, was observed in a patient diagnosed with hyperglycemia at age 39 years and in two adult offspring with impaired insulin secretion. Single K(ATP) channels incorporating SUR1-Y356C displayed lower sensitivity to MgATP (IC(50) = 24 and 95 micromol/l for wild-type and mutant channels, respectively). Similar effects were observed in the absence of Mg(2+), suggesting an allosteric effect via associated Kir6.2 subunits. Overexpression of SUR1-Y356C in INS1(832/13) cells impaired glucose-induced cell depolarization and increased in intracellular free Ca(2+) concentration, albeit more weakly than neonatal diabetes-associated SUR1 mutants.

CONCLUSIONS

An ABCC8/SUR1 mutation with relatively minor effects on K(ATP) channel activity and beta-cell glucose sensing causes diabetes in adulthood. These data suggest a close correlation between altered SUR1 properties and clinical phenotype.

The type and the position of HNF1A mutation modulate age at diagnosis of diabetes in patients with maturity-onset diabetes of the young (MODY)-3

OBJECTIVE

The clinical expression of maturity-onset diabetes of the young (MODY)-3 is highly variable. This may be due to environmental and/or genetic factors, including molecular characteristics of the hepatocyte nuclear factor 1-alpha (HNF1A) gene mutation.

RESEARCH DESIGN AND METHODS

We analyzed the mutations identified in 356 unrelated MODY3 patients, including 118 novel mutations, and searched for correlations between the genotype and age at diagnosis of diabetes.

RESULTS

Missense mutations prevailed in the dimerization and DNA-binding domains (74%), while truncating mutations were predominant in the transactivation domain (62%). The majority (83%) of the mutations were located in exons 1- 6, thus affecting the three HNF1A isoforms. Age at diagnosis of diabetes was lower in patients with truncating mutations than in those with missense mutations (18 vs. 22 years, P = 0.005). Missense mutations affecting the dimerization/DNA-binding domains were associated with a lower age at diagnosis than those affecting the transactivation domain (20 vs. 30 years, P = 10(-4)). Patients with missense mutations affecting the three isoforms were younger at diagnosis than those with missense mutations involving one or two isoforms (P = 0.03).

CONCLUSIONS

These data show that part of the variability of the clinical expression in MODY3 patients may be explained by the type and the location of HNF1A mutations. These findings should be considered in studies for the search of additional modifier genetic factors.

Waist circumference does not predict circulating adiponectin levels in sub-Saharan women

Background

Because of previously reported ethnic differences in determinants and markers of obesity and related metabolic disorders, we sought to investigate circulating levels of adiponectin and their correlates in a sub-Saharan African (sSA) population.

Subjects and Methods

We studied 70 non-diabetic volunteers (33M/37F) living in Yaoundé, Cameroon, aged 24–69 yr, with BMI 20–42 kg/m². In all participants we measured waist circumference and total body fat by bioimpedance, and obtained a fasting venous blood sample for measurement of plasma glucose, serum insulin and adiponectin concentrations. We performed a euglycaemic hyperinsulinaemic clamp in 1/4 subjects, and HOMA_IR was used as surrogate of fasting insulin sensitivity index since it best correlates to clamp measurements.

Results

Males had lower adiponectin levels than females (8.8 ± 4.3 vs. 11.8 ± 5.5 μg/L). There was no significant correlation between adiponectin and total body fat (r_s = -0.03; NS), whereas adiponectin was inversely correlated with waist circumference (r_s = -0.39; p = 0.001). Adiponectin correlated negatively with insulin resistance (r_s = -0.35; p = 0.01). In a regression analysis using fasting adiponectin concentration as the dependent variable, and age, HOMA_IR, waist circumference, and fat mass as predictors, waist circumference (β = -3.30; p = 0.002), fat mass (β = -2.68; p = 0.01), and insulin resistance (β = -2.38; p = 0.02) but not age (β = 1.11; p = 0.27) were independent predictors of adiponectin. When considering gender, these relations persisted with the exception of waist circumference in females.

Conclusion

Adiponectin correlates in this study population are comparable to those observed in Caucasians with the exception of waist circumference in women. The metabolic significance of waist circumference is therefore questioned in sSA women.

Effect of raloxifene -- a selective oestrogen receptor modulator -- on kidney function in post-menopausal women with Type 2 diabetes: results from a randomized, placebo-controlled pilot trial

AIMS

Epidemiological and experimental data suggest that activation of the oestrogen receptor pathway limits the incidence and the progression of diabetic nephropathy. We tested the hypothesis that raloxifene protects against increasing urinary albumin excretion in post-menopausal women with Type 2 diabetes in a randomized pilot clinical trial.

METHODS

We included 39 post-menopausal women with Type 2 diabetes and micro- or macro-albuminuria in a 6-month, double-blind, placebo-controlled trial: 20 received placebo and 19 received 60 mg raloxifene per day. The albumin : creatinine ratio (ACR) in urine was determined on three consecutive days during the week before randomization and during the week before the final visit.

RESULTS

One patient in each group dropped out in the first 3 weeks, leaving 37 patients for the analysis (19 on placebo and 18 on raloxifene). From randomization to the final visit, mean ACR was unchanged in the placebo group {277 microg/mg (67; 651) [median (interquartile range)] vs. 284 microg/mg (79; 1508)} but decreased slightly in the raloxifene group [376 microg/mg (67; 615) vs. 243 microg/mg (103; 549)]. This corresponds to a change of +24 (-37; +517) for the placebo group vs. -10 microg/mg (-36; +16) for the raloxifene group (P = 0.11). In multivariate analysis, raloxifene treatment (P(adjusted) = 0.013), baseline low-density lipoprotein (LDL) cholesterol (P(adjusted) = 0.023) and change in LDL cholesterol (P(adjusted) = 0.008) were related to the absolute change in ACR. Adverse effects were similar in the two groups.

CONCLUSIONS

These results suggest that raloxifene may limit the progression of albuminuria in post-menopausal women with diabetes; further studies in a larger population are warranted.

How do different GLP-1 mimetics differ in their actions?

Glucagon-like peptide-1 (GLP-1) mimetics have been developed to overcome the pharmacokinetic limitations of GLP-1 for the treatment of type 2 diabetes. Their mechanisms of action and clinical effects appear particularly interesting because they target the main pathophysiologic mechanisms involved in type 2 diabetes. GLP-1 receptor agonists are more powerful and are particularly advantageous by their weight loss-inducing capacity, whereas dipeptidyl peptidase IV inhibitors exhibit a better tolerance profile. However, their ultimate role is still to be defined in the therapeutic strategy of type 2 diabetes.

Consequences of fetal exposure to maternal diabetes in offspring

CONTEXT

Type 2 diabetes is the result of both genetic and environmental factors. Fetal exposure to maternal diabetes is associated with a higher risk of abnormal glucose homeostasis in offspring beyond that attributable to genetic factors, and therefore, may participate in the excess of maternal transmission of type 2 diabetes.

EVIDENCE ACQUISITION

A MEDLINE search covered the period from 1960-2005.

EVIDENCE SYNTHESIS

Human studies performed in children and adolescents suggest that offspring who had been exposed to maternal diabetes during fetal life exhibit higher prevalence of impaired glucose tolerance and markers of insulin resistance. Recent studies that directly measured insulin sensitivity and insulin secretion have shown an insulin secretory defect even in the absence of impaired glucose tolerance in adult offspring. In animal models, exposure to a hyperglycemic intrauterine environment also led to the impairment of glucose tolerance in the adult offspring. These metabolic abnormalities were transmitted to the next generations, suggesting that in utero exposure to maternal diabetes has an epigenetic impact. At the cellular level, some findings suggest an impaired pancreatic beta-cell mass and function. Several mechanisms such as defects in pancreatic angiogenesis and innervation, or modification of parental imprinting, may be implicated, acting either independently or in combination.

CONCLUSION

Thus, fetal exposure to maternal diabetes may contribute to the worldwide diabetes epidemic. Public health interventions targeting high-risk populations should focus on long-term follow-up of subjects who have been exposed in utero to a diabetic environment and on a better glycemic control during pregnancy.

Large genomic rearrangements in the hepatocyte nuclear factor-1beta (TCF2) gene are the most frequent cause of maturity-onset diabetes of the young type 5

Maturity-onset diabetes of the young (MODY) 5 is caused by mutations in the TCF2 gene encoding the transcription factor hepatocyte nuclear factor-1beta. However, in 60% of the patients with a phenotype suggesting MODY5, no point mutation is detected in TCF2. We have hypothesized that large genomic rearrangements of TCF2 that are missed by conventional screening methods may account for this observation. In 40 unrelated patients presenting with MODY5 phenotype, TCF2 was screened for mutations by sequencing. Patients without mutations were then screened for TCF2 rearrangements by the quantitative multiplex PCR of short fluorescent fragments (QMPSF). Among the 40 patients, the overall detection rate was 70%: 18 had point mutations, 9 had whole-gene deletions, and 1 had a deletion of a single exon. Similar phenotypes were observed in patients with mutations and in subjects with large deletions. These results suggest that MODY5 is more prevalent than previously reported, with one-third of the cases resulting from large deletions of TCF2. Because QMPSF is more rapid and cost effective than sequencing, we propose that patients whose phenotype is consistent with MODY5 should be screened first with the QMPSF assay. In addition, other MODY genes should be screened for large genomic rearrangements.

Subcutaneous insulin resistance successfully circumvented on long term by peritoneal insulin delivery from an implantable pump in four diabetic patients

Extreme subcutaneous insulin resistance is a rare syndrome characterized by a severe resistance to subcutaneous (S/C) insulin together with persistence of normal or near normal intravenous (IV) insulin sensitivity. Its pathophysiology is unknown, although increased insulin degrading activity has been reported in the S/C adipose tissue fraction in some cases. Until now, proposed treatments have been disappointing. We report 4 cases who were successfully treated by intraperitoneal (IP) route.

METHODS

The diagnosis of subcutaneous insulin resistance was based upon following combined conditions: resistance to hypoglycaemic action of subcutaneous insulin but normal or near normal sensitivity to IV or IP insulin.

RESULTS

4 patients among those followed by EVADIAC group met these criteria: 3 with type 1 diabetes (C peptide=0), the last one with unexplained non insulin-deficient diabetes (no anti-GAD antibodies, C peptide=5 ng/ml). All of them had been treated with subcutaneous insulin therapy without success despite huge doses (up to 4000 IU/day in two patients). The 3 type 1 diabetic patients presented with a history of repeated ketoacidosis episodes. A treatment of insulin mixed with aprotinin had been proposed to 2 patients without success. The IV insulin sensitivity was proved to be normal in two patients by euglycaemic clamp data. A skin biopsy was performed in 1 patient. An accumulation of insulin in the derma was revealed with no increase of degradation products of insulin. In these 4 patients, a dramatic improvement of diabetes control was obtained by IP insulin delivery from an implantable pump (HbA1c decrease by at least 3%).

CONCLUSION

Although pathophysiology of the subcutaneous insulin resistance syndrome remains unexplained, our data show that intra-peritoneal insulin therapy from an implantable pump allows diabetes control in patients affected by this uncommon but severely disabling condition.

High prevalence of glucose-6-phosphate dehydrogenase deficiency without gene mutation suggests a novel genetic mechanism predisposing to ketosis-prone diabetes

CONTEXT

Ketosis-prone diabetes (KPD) is mostly observed in males of West African descent and is characterized by phasic or permanent insulin dependence without apparent autoimmune process.

OBJECTIVE

KPD subjects display a propensity to hyperglycemia-induced acute insulin deficiency, suggesting that they exhibit a propensity to oxidative stress in beta-cells. The enzyme glucose-6-phosphate dehydrogenase (G6PD) is a defense mechanism against oxidative stress, and G6PD deficiency, an X-linked genetic disorder with male predominance, is frequent in West Africans. We hypothesized that mutations in the G6PD gene could predispose to KPD.

DESIGN

We studied G6PD erythrocyte enzyme activity and the insulin secretory reserve (glucagon-stimulated C peptide) in a cohort of hospitalized West Africans with KPD (n = 59) or type 2 diabetes (T2DM; n = 59) and in normoglycemic controls (n = 55). We also studied the G6PD gene in an extended population of KPD patients (n = 100), T2DM patients (n = 59), and controls (n = 85).

RESULTS

The prevalence of G6PD deficiency was higher in KPD than in T2DM and controls (42.3%; 16.9%; 16.4%; P = 0.01). In KPD, but not in T2DM, insulin deficiency was proportional to the decreased G6PD activity (r = 0.33; P = 0.04). We found no increase in the prevalence of G6PD gene mutations in KPD compared with T2DM and controls. Rather, we found a 20.3% prevalence of G6PD deficiency in KPD without gene mutation.

CONCLUSIONS

This study suggests that 1) G6PD deficiency alone is not causative of KPD; and 2) alterations in genes controlling both insulin secretion and G6PD-mediated antioxidant defenses may contribute to the predisposition to KPD in West Africans.

Is capillary ketone determination useful in clinical practice? In which circumstances?

A new method is now available to measure capillary levels of 3-hydroxybutyrate (3HB), one of the three ketone bodies. It is a quantitative and enzymatic test that uses the same equipment as for home capillary blood glucose determination but with specific strips. In comparison to urine ketone test, there is no false negative or false positive results, it is highly correlate to standard automate assays and patients find it more acceptable. Clinical implementations of this new test begin to be reported. Some studies showed an advantage of ketonemia versus ketonuria measurement to detect and to treat diabetic ketoacidosis in the emergency room. In diabetic patients treated with continuous subcutaneous insulin infusion, ketonemia seems to be more relevant to detect lack of insulin. In the current care of patient with type 1 diabetes and especially in children blood ketone test is more effective than urine ketone test to prevent hospitalisation during sick days. For other situations such as diabetic pregnancy or type 2 diabetes, more data are needed to determine if capillary measurement of 3HB is really useful. This new test is easier and less unpleasant than doing urinary test but it is still far more expensive. Further clinical studies are needed to define whether self 3HB monitoring should substitute urinary test in outpatient care.

Biological actions of the incretins GIP and GLP-1 and therapeutic perspectives in patients with type 2 diabetes

Incretin hormones are defined as intestinal hormones released in response to nutrient ingestion, which potentiate the glucose-induced insulin response. In humans, the incretin effect is mainly caused by two peptide hormones, glucose-dependent insulin releasing polypeptide GIP, and glucagon-like peptide-1 GLP-1. GIP is secreted by K cells from the upper small intestine while GLP-1 is mainly produced in the enteroendocrine L cells located in the distal intestine. Their effect is mediated through their binding with specific receptors, though part of their biological action may also involve neural modulation. GIP and GLP-1 are both rapidly degraded into inactive metabolites by the enzyme dipeptidyl-peptidase-IV (DPP-IV). In addition to its effects on insulin secretion, GLP-1 exerts other significant actions, including stimulation of insulin biosynthesis, inhibition of glucagon secretion, inhibition of gastric emptying and acid secretion, reduction of food intake, and trophic effects on the pancreas. As the insulinotropic action of GLP-1 is preserved in type 2 diabetic patients, this peptide was a candidate as a therapeutic agent for this disease. A number of pharmacological strategies have been developed to provide continuous delivery of GLP-1 and to prevent degradation of GLP-1, including continuous administration of GLP-1, DPP-IV inhibitors and DPP-IV resistant GLP-1 analogues. Recent results of the most clinically advanced incretin mimetics confirmed their efficacy to improve glycemic control in type 2 diabetic patients. Further results are expected to confirm the efficacy/safety profile of these compounds, and to find their place in the therapeutic strategy of type 2 diabetes.

[Physical activity and type 2 diabetes]

Muscular exercise promotes glucose utilisation by the skeletal muscle, independently of insulin action, by activating the AMP-activated protein kinase (AMPK). This process is not altered in patients with obesity and/or type 2 diabetes, despite the presence of insulin resistance. Thus, exercise should play a key role in the management of type 2 diabetic patients. Regular physical activity enhances insulin sensitivity, improves glucose control and corrects some cardiovascular risk factors. This paper briefly presents some practical recommendations about physical activity in obese and/or type 2 diabetic patients.

PAX4 gene variations predispose to ketosis-prone diabetes

Ketosis-prone diabetes (KPD) is a rare form of type 2 diabetes, mostly observed in subjects of west African origin (west Africans and African-Americans), characterized by fulminant and phasic insulin dependence, but lacking markers of autoimmunity observed in type 1 diabetes. PAX4 is a transcription factor essential for the development of insulin-producing pancreatic beta-cells. Recently, a missense mutation (Arg121Trp) of PAX4 has been implicated in early and insulin deficient type 2 diabetes in Japanese subjects. The phenotype similarities between KPD and Japanese carriers of Arg121Trp have prompted us to investigate the role of PAX4 in KPD. We have screened 101 KPD subjects and we have found a new variant in the PAX4 gene (Arg133Trp), specific to the population of west African ancestry, and which predisposes to KPD under a recessive model. Homozygous Arg133Trp PAX4 carriers were found in 4% of subjects with KPD but not in 355 controls or 147 subjects with common type 2 or type 1 diabetes. In vitro, the Arg133Trp variant showed a decreased transcriptional repression of target gene promoters in an alpha-TC1.6 cell line. In addition, one KPD patient was heterozygous for a rare PAX4 variant (Arg37Trp) that was not found in controls and that showed a more severe biochemical phenotype than Arg133Trp. Clinical investigation of the homozygous Arg133Trp carriers and of the Arg37Trp carrier demonstrated a more severe alteration in insulin secretory reserve, during a glucagon-stimulation test, compared to other KPD subjects. Together these data provide the first evidence that ethnic-specific gene variants may contribute to the predisposition to this particular form of diabetes and suggest that KPD, like maturity onset diabetes of the young, is a rare, phenotypically defined but genetically heterogeneous form of type 2 diabetes.

Clinical spectrum associated with hepatocyte nuclear factor-1beta mutations

BACKGROUND

Maturity-onset diabetes of the young type 5 (MODY5), a type of dominantly inherited diabetes mellitus and nephropathy, has been associated with mutations of the hepatocyte nuclear factor-1beta (HNF-1beta) gene, mostly generating truncated protein. Various phenotypes, including urogenital malformations, are related to HNF-1beta mutations.

OBJECTIVE

To describe clinical and genetic findings in 13 patients with 8 novel HNF-1beta mutations.

DESIGN

Multicenter, descriptive study.

SETTING

2 departments of diabetes, 1 department of internal medicine, and 1 department of nephrology.

PARTICIPANTS

8 probands with diabetes diagnosed before 40 years of age and nondiabetic kidney disease who were selected independent of their family history of diabetes, and 5 offspring.

MEASUREMENTS

Characteristics of diabetes, renal function and structure, genital tract abnormalities, pancreas structure, insulin secretion, exocrine pancreas function, and liver test results.

RESULTS

All mutations, including 5 missense changes, were found in the DNA-binding domain. Cosegregation of the mutation and MODY5 phenotype was observed in 4 families. Occurrence of a de novo mutation was demonstrated in 2 families. Diabetes was present in 10 of 13 mutation carriers. It was clinically overt in 5 participants and found by screening at age 19 to 38 years in 5 participants. Pancreas atrophy was observed in 5 of 6 probands, and pancreas exocrine insufficiency was observed in 6 of 7 probands. Renal involvement, consisting of structural changes and slowly progressive renal failure, was recognized in 9 patients at 18 to 41 years of age. Dysplastic kidneys were found by ultrasonography in 3 fetuses who subsequently showed transient neonatal renal failure. Genital tract abnormalities were present in 5 probands and liver enzyme levels were abnormal in 11 of 13 patients.

LIMITATIONS

Since the study was small and not population-based, it could not estimate the prevalence of MODY5. Other phenotypes might be associated with HNF-1beta mutations.

CONCLUSIONS

Maturity-onset diabetes of the young type 5 encompasses a wide clinical spectrum. Analysis for mutations of HNF-1beta is warranted, even without a family history of diabetes, in nonobese patients with diabetes and slowly progressive nondiabetic nephropathy, particularly when pancreatic atrophy or genital abnormalities are present.

Ketosis-prone type 2 diabetes in patients of sub-Saharan African origin: clinical pathophysiology and natural history of beta-cell dysfunction and insulin resistance

Nonautoimmune ketosis-prone diabetic syndromes are increasingly frequent in nonwhite populations. We have characterized a cohort of patients of sub-Saharan African origin who had ketosis-prone type 2 diabetes (n = 111), type 1 diabetes (n = 21), and type 2 diabetes (n = 88) and were admitted to a hospital for management of uncontrolled diabetes. We compared epidemiological, clinical, and metabolic features at diabetes onset and measured insulin secretion (glucagon-stimulated C-peptide) and insulin action (short intravenous insulin tolerance test) during a 10-year follow-up. Ketosis-prone type 2 diabetes shows a strong male predominance, stronger family history, higher age and BMI, and more severe metabolic decompensation than type 1 diabetes. In ketosis-prone type 2 diabetes, discontinuation of insulin therapy with development of remission of insulin dependence is achieved in 76% of patients (non-insulin dependent), whereas only 24% of patients remain insulin dependent. During evolution, ketosis-prone type 2 diabetes exhibit specific beta-cell dysfunction features that distinguish it from type 1 and type 2 diabetes. The clinical course of non-insulin-dependent ketosis-prone type 2 diabetes is characterized by ketotic relapses followed or not by a new remission. Progressive hyperglycemia precedes and is a strong risk factor for ketotic relapses (hazard ratio 38). The probability for non-insulin-dependent ketosis-prone type 2 diabetes to relapse is 90% within 10 years, of whom approximately 50% will become definitively insulin dependent. Insulin sensitivity is decreased in equal proportion in both ketosis-prone type 2 diabetes and type 2 diabetes, but improves significantly in non-insulin-dependent ketosis-prone type 2 diabetes, only after correction of hyperglycemia. In conclusion, ketosis-prone type 2 diabetes can be distinguished from type 1 diabetes and classical type 2 diabetes by specific features of clinical pathophysiology and also by the natural history of beta-cell dysfunction and insulin resistance reflecting a propensity to glucose toxicity.

L’activité physique comme moyen de traitement du diabète de type 2 : le rationnel

Physical exercise is an important component of type 2 diabetes mellitus management. Acute physical exercise, on a day by day basis, has a clear hypoglycaemic effect. Physical exercise, on a regular basis at a sufficient level, has numerous favourable effects: improvement of glycaemic control (HbA1c) and insulin sensitivity, decrease of visceral fat mass, increase of skeletal muscle mass, favourable effects on various cardiovascular risk factors (arterial pressure, HDL-cholesterol, triglycerides, etc.). However, precise characteristics of physical exercise to be advised in type 2 diabetic patients (type of exercise, frequency, intensity, etc.) are still a matter of debates, as well as lack of practical guidance in/or differences between the various current recommendations. The crucial point, however, remains their feasibility, as well as the lack of long term patient's motivation and compliance which may partly explain the current low level of physical exercise observed in type 2 diabetic patients.

Effect of a diabetic environment in utero on predisposition to type 2 diabetes

BACKGROUND

Type 2 diabetes is affected by genetics and environmental factors. We aimed to assess the effect of an in-utero diabetic environment independently of the genetic background for type 2 diabetes.

METHODS

We measured insulin sensitivity and insulin secretion in response to oral and intravenous glucose in 15 non-diabetic adult offspring of mothers with type 1 diabetes (exposed participants) and 16 offspring of type 1 diabetic fathers (controls). No participants had type 1 diabetes-associated autoantibodies. We also measured pancreatic polypeptide, a marker of parasympathetic drive to the pancreas.

FINDINGS

There was no difference between the groups with respect to percent body fat and insulin sensitivity. Five of the 15 exposed participants, but none of the controls had impaired glucose tolerance (p=0.02). Early insulin secretion after an oral glucose tolerance test was lower in exposed participants than in controls: 8.6 IU/mmol (SD 5.4) in exposed participants with impaired glucose tolerance, 14.2 IU/mmol (6.5) in those with normal glucose tolerance and 17.7 IU/mmol (10.9) in controls (p=0.04). Mean insulin secretion rate during glucose infusion study was 4.7 pmol/kg per min (3.6) in people with impaired glucose tolerance, 5.5 pmol/kg per min (4.5) in exposed participants with normal glucose tolerance and 7.5 pmol/kg per min (6.1) in controls (p<0.0001). The area under the curve of pancreatic polypeptide 120 min after oral glucose ingestion was 1007 (429) in people with impaired glucose tolerance, 2829 (1701) in those with normal glucose tolerance, and 3224 (1352) in controls (p=0.04).

INTERPRETATION

Exposure to a diabetic environment in utero is associated with increased occurrence of impaired glucose tolerance and a defective insulin secretory response in adult offspring, independent of genetic predisposition to type 2 diabetes. This insulin secretory defect could be related to low parasympathetic tone. Epidemiological studies are needed to confirm our observations before therapeutic strategies can be devised.

Marital status and family size of type 1 diabetic patients in a French cohort

OBJECTIVE

To compare the marital status, the number of offspring and the cumulative incidence of type 1 diabetes in offspring of type 1 diabetic men and women.

METHODS

From the database of patients attending our department, we reviewed the files of all the 352 subjects aged >=40 years with type 1 diabetes and compared male and female patients for whom age, age at diagnosis of diabetes, marital status, socio-economic status, number and age of offspring, diagnosed type 1 diabetes in the offspring could be obtained from patient's record and/or direct interview (86 males and 78 females).

RESULTS

In this population, 73% of women and 81% of men were married or living a marital life (NS), and 35% of women versus 8% of men had no offspring (P<0.0001). The proportion of parents with 2 offspring or more was 43% in females and 61% in males (p=0.03) and was not related to the socio-economic status. The number of offspring with diagnosed type 1 diabetes was small (8/229) and did not show significant association with gender of the parent, with a cumulative incidence of 3.2 and 3.7% in offspring of type 1 diabetic mothers and fathers respectively.

CONCLUSION

Type 1 diabetic women born before 1960 had fewer children than men. In this cohort, there was no difference in the cumulative incidence of type 1 diabetes in offspring of type 1 diabetic men and women despite reduced family size in women.

[Cushing's syndrome during pregnancy]

The rare association of Cushing's syndrome and pregnancy is explained by the amenorrhea and sterility inherent to the syndrome. In the literature, 125 cases have been reported: 30 cases of early diagnosis and 95 others diagnosed in the second half of pregnancy.

AT THE START OF PREGNANCY

When hypercorticism exists before pregnancy it is hardly secretory. Its diagnosis, at an early stage, is not hindered by the hormone modifications of pregnancy. Its aetiological treatment raises the problem of the compatibility in pursuing the latter.

IN THE SECOND HALF OF PREGNANCY

The positive and aetiological diagnoses of Cushing's syndrome are difficult and its prevalence may therefore be underestimated. The evocative clinical signs are unspecific: excessive weight gain, hypertension of pregnancy and gestational diabetes. The 24-hour free hypercortisoluria and the absence of dexamethasone inhibition are of little diagnostic value after the 14th week of amenorrhea. The positive diagnosis therefore relies essentially on the abolition of the circadian rhythm of cortisol. The biological hyperandrogenia commonly observed is not discriminating. Adrenal aetiologies are frequent. Imaging must be performed to eliminate an adrenocortical tumor.

PROGNOSIS

The maternal prognosis depends on the hypertension, preeclampsia, diabetes and the complications of Cushing's syndrome. It depends on the activity of the hypercorticism and its early aetiological treatment, which must not be delayed after pregnancy. The foetal prognosis depends on the maternal prognosis. It is represented by preterm delivery, hypotrophy and death of the foetus in utero. The therapeutic management must be symptomatic and aetiologic, maternal and obstetrical.

Metabolic and immunogenetic prediction of long-term insulin remission in African patients with atypical diabetes

AIMS

We aimed to characterize a cohort of 'atypical' diabetic patients of sub-Saharan African origin and to analyse possible determinants of long-term remission.

METHODS

Over 6 years, we studied the clinical and therapeutic profile of 42 consecutive patients undiagnosed or untreated prior to inclusion presenting with cardinal features of diabetes mellitus. We measured insulin secretion and sensitivity at inclusion. Immunogenetic (anti-GAD, anti-ICA and HLA class II) markers of Type 1 diabetes were compared with a 90-non-diabetic unrelated adult African population.

RESULTS

Twenty-one ketonuric patients (age 42 +/- 9 (sd) years; body mass index (BMI) 26 +/- 3 kg/m2) were initially insulin-treated (IT), and 21 non-ketonuric patients (age 38 +/- 8 years; BMI 26 +/- 5 kg/m2) had oral and/or diet therapy (NIT). Insulin could be discontinued in 47.6% (10/21) IT with adequate glycaemic control (HbA1c 6.7 +/- 1.3%), while insulin was secondarily started in 38.1% (8/21) NIT in expectation of better control. The initial basal (odds ratio (OR) 9.1, 95% confidence interval (CI) 1.3-64.4) and stimulated C-peptide (OR 8.17, 95% CI 1.5-44.1) were independently associated with remission. Insulin resistance was present in all the groups, more marked in the insulin-treated NIT. Anti-GAD antibodies and ICA were rare, but 38.1% IT vs. 1.1% controls had Type 1 diabetes HLA susceptibility haplotypes (P < 0.001) without significant difference between the subgroups.

CONCLUSION

Prolonged discontinuation of insulin is frequent in African diabetic patients initially presenting with signs of insulinopenia. In our patients, long-term insulin therapy was not associated with immunogenetic markers of Type 1 diabetes. The initial measure of insulin secretion seemed a good predictor of long-term remission.

Tasting a liquid meal after a prolonged fast is associated with preferential activation of the left hemisphere

We used positron emission tomographic scanning of the brain and measures of regional cerebral blood flow to investigate the response of 44 right-handed people to the oral administration of 2 ml of a liquid formula meal after a 36 h fast (and shortly before the administration of a satiating amount of the same meal). Several areas of the left hemisphere were significantly more activated than the contralateral, including the frontal operculum, ventral insula, and piriform cortex. In contrast with reports of right-hemisphere dominance in chemosensory perception in non-hungry individuals, our study reveals a preferential activation of the left hemisphere when people who are very hungry are briefly exposed to the chemical and physical properties of a liquid meal. This raises the possibility that the physiological context in which perception takes place (i.e. extreme vs moderate vs no hunger) may importantly affect the brain representation of chemosensory stimuli.

Sex differences in the human brain's response to hunger and satiation

BACKGROUND

Sex differences in eating behavior are well documented, but it is not known whether these differences have neuroanatomical correlates. Recent neuroimaging studies have provided functional maps of the human cerebral areas activated in response to hunger and satiation.

OBJECTIVE

The objective of this study was to assess whether the brain's response to a meal is sex-specific.

DESIGN

Using positron emission tomography, we measured regional cerebral blood flow, a marker of neuronal activity, to investigate the functional neuroanatomy of hunger (36-h fast) and satiation (in response to a liquid meal) in 22 women and 22 men.

RESULTS

We observed extensive similarities, as well as some differences, between the sexes. In response to hunger, the men tended to have greater activation in the frontotemporal and paralimbic areas than did the women (P < 0.005). In response to satiation, the women tended to have greater activation in the occipital and parietal sensory association areas and in the dorsolateral prefrontal cortex than did the men (P < 0.005); in contrast, the men tended to have greater activation in the ventromedial prefrontal cortex than did the women (P < 0.005).

CONCLUSIONS

Despite extensive similarities in the brain responses to hunger and satiation between the men and women, our study showed sex-specific brain responses to a meal that indicate possible differences between men and women in the cognitive and emotional processing of hunger and satiation. This study provides a foundation for investigating the brain regions and cognitive processes that distinguish normal and abnormal eating behavior in men and women.

[Determinants and control of energy expenditure]

Obesity is a risk factor for many diseases including cardio-vascular disease, type 2 diabetes, and certain forms of cancer, among others. Obesity results from a chronic imbalance between calorie intake and energy expenditure. Genetic factors obviously play an important role in weight gain, but only in certain environments. The principal cause of the obesity epidemic is not clear: is obesity due to excessive food intake, a dynamic reduction in energy expenditure, or an association of these two factors? However, most obese subjects gain weight because of an inaptitude to adjust energy expenditure in response to excessive food intake. In this article, we review briefly the respective role of genes and environment in the development of obesity, then describe metabolic risk factors involved. Longitudinal studies conducted in Pima Indians have demonstrated that a relative decrease in basal metabolism, weak lipid oxidation in the fasting state, reduced spontaneous physical activity, and lower sympathetic nervous system activity are risk factors for obesity. Unlike our growing knowledge of food intake regulation, little is known about the control of energy expenditure. New discoveries should provide information on obesity susceptibility genes and increase the chances of developing new anti-obesity treatments.

Diabetes in Africans. Part 2: Ketosis-prone atypical diabetes mellitus

Diabetes is increasing with ageing and changes in lifestyle in populations of African ancestry as described in the first part of this review. Apart from classical type 1 and Type 2 diabetes, atypical presentations are observed in these populations, especially "tropical" and "ketosis-prone" atypical diabetes. Ketosis-prone atypical diabetes that has been classified by ADA as idiopathic Type 1 diabetes or Type 1b is the most common atypical form. It is characterised by an acute initial presentation with severe hyperglycaemia and ketosis, as classical Type 1 diabetes. In the subsequent clinical course after initiation of insulin therapy, prolonged remission is often possible with cessation of insulin therapy and maintenance of appropriate metabolic control. Metabolic studies showed a markedly blunted insulin secretory response to glucose, partially reversible with the improvement of blood glucose control. Variable levels of insulin resistance are observed, especially in obese patients. Pancreatic B-cell autoimmunity is an exceptional finding. Association with type 1 susceptibility HLA alleles is variable. The molecular mechanisms underlining the insulin secretory dysfunction are still to be understood and may involve gluco-lipotoxicity processes, glucagon dysregulation, effect of stress, or may be genetically determined. The present review summarises the available clinical and metabolic features and suggests some pathogenetic hypotheses and principles of management for the ketosis-prone atypical diabetes of the Africans.

Diabetes in Africans. Part 1: epidemiology and clinical specificities

The prevalence of diabetes in African communities is increasing with ageing of the population and lifestyle changes associated with rapid urbanisation and westernisation. Traditional rural communities still have very low prevalence, at most 1-2%, except in some specific high-risk groups, whereas 1-13% or more adults in urban communities have diabetes. Type 2 diabetes is the predominant form (70-90%), the rest being represented by typical type 1 patients and patients with atypical presentations that require more pathophysiological insight. Due to the high urban growth rate, dietary changes, reduction in physical activity, and increasing obesity, it is estimated that the prevalence of diabetes is due to triple within the next 25 years. In addition, long-term complications occur early in the course of diabetes and concern a high proportion of patients, probably higher than in other ethnic groups, and that could be partly explained by uncontrolled hypertension, poor metabolic control and possible ethnic predisposition. The combination of the rising prevalence of diabetes and the high rate of long-term complications in Africans will lead to a drastic increase of the burden of diabetes on health systems of African countries. The design and implementation of appropriate strategy for early diagnosis and treatment, and population-based primary prevention of diabetes in these high-risk populations is therefore a public health priority.

Effect of satiation on brain activity in obese and lean women

OBJECTIVE

To investigate the response of the brains of women to the ingestion of a meal.

RESEARCH METHODS AND PROCEDURES

We used measures of regional cerebral blood flow (rCBF), a marker of neuronal activity, by positron emission tomography to describe the functional anatomy of satiation, i.e., the response to a liquid meal in the context of extreme hunger (36-hour fast) in 10 lean (BMI < or = 25 kg/m(2); 32 +/- 10 years old, 61 +/- 7 kg; mean +/- SD) and 12 obese (BMI > or = 35 kg/m(2); 30 +/- 7 years old, 110 +/- 14 kg) women.

RESULTS

In lean and obese women, satiation produced significant increases in rCBF in the vicinity of the prefrontal cortex (p < 0.005). Satiation also produced significant decreases in rCBF in several regions including the thalamus, insular cortex, parahippocampal gyrus, temporal cortex, and cerebellum (in lean and obese women), and hypothalamus, cingulate, nucleus accumbens, and amygdala (in obese women only; all p < 0.005). Compared with lean women, obese women had significantly greater increases in rCBF in the ventral prefrontal cortex and had significantly greater decreases in the paralimbic areas and in areas of the frontal and temporal cortex.

DISCUSSION

This study indicates that satiation elicits differential brain responses in obese and lean women. It also lends additional support to the hypothesis that the paralimbic areas participate in a central orexigenic network modulated by the prefrontal cortex through feedback loops.

Exercise training-induced triglyceride lowering negatively correlates with DHEA levels in men with type 2 diabetes

OBJECTIVE

To investigate the effect of an exercise training program on lipid profile in correlation with DHEA level and body weight and body composition in type 2 diabetic men.

DESIGN

Longitudinal, controlled clinical intervention study with exercise training consisting of an 8 week supervised program of aerobic exercise (75% VO(2) peak, 45 min), twice a week and intermittent exercise, once a week, on a bicycle ergometer.

SUBJECTS

Sixteen men (age 45.4+/-7.2 y (mean+/-s.d.), HbA1c 8.15+/-1.7%, body mass index (BMI) 29.6+/-4.6 kg/m(2)) were randomly divided into two groups: trained group (n=8) and control group (n=8).

MEASUREMENTS

Lipid, apo- and lipoprotein and DHEA concentrations. Cross-sectional areas of subcutaneous and visceral adipose tissue and mid-thigh muscle by magnetic resonance imaging.

RESULTS

Training decreased visceral (153.25+/-38.55 vs 84.20+/-21.30 cm(2), P<0.001), subcutaneous (241.55+/-49.55 vs 198.00+/-39.99 cm(2), P<0.001) adipose tissue area and triglyceride levels (2.59+/-1.90 vs 1.79+/-1.08 nmol/l, P<0.05) and increased mid-thigh muscle cross-sectional area (148.30+/-36.10 vs 184.35+/-35.85 cm(2), P<0.001), and DHEA levels (11.00+/-3.10 vs 14.25+/-4.10 nmol/l, P<0.05) with no modification in body weight. Changes in triglycerides were negatively correlated with changes in DHEA (r=-0.81, P=0.03). This correlation was independent of changes in abdominal fat distribution.

CONCLUSION

Training decreases abdominal fat depots, improves muscular mass and affects favourably triglyceride and DHEA levels. Changes in triglycerides and DHEA were inversely related.

Low acute insulin secretory responses in adult offspring of people with early onset type 2 diabetes

The offspring of Pima Indians with early onset type 2 diabetes are at high risk for developing diabetes at an early age. This risk is greater among those whose mothers were diabetic during pregnancy. To define the metabolic abnormalities predisposing individuals in these high-risk groups to diabetes, we conducted a series of studies to measure insulin secretion and insulin action in healthy adult Pima Indians. In 104 normal glucose-tolerant subjects, acute insulin secretory response (AIR) to a 25-g intravenous glucose challenge correlated with the age at onset of diabetes in the mother (r = 0.23, P = 0.03) and, in multiple regression analyses, the age at onset of diabetes in the father (P = 0.02), after adjusting for maternal age at onset and after allowing for an interaction between these terms. In contrast, insulin action (hyperinsulinemic glucose clamp) did not correlate with the age at onset of diabetes in the parents. To determine whether early onset diabetes in the parents affected insulin secretion in the offspring across a range of glucose concentrations, responses to a stepped glucose infusion were measured in 23 subjects. Insulin secretion rates were lower in individuals whose mothers had developed diabetes before 35 years of age (n = 8) compared with those whose parents remained nondiabetic until at least 49 years of age (n = 15) (average insulin secretory rates: geometric mean [95% CI] 369 [209-652] vs. 571 [418-780] pmol/min, P = 0.007). Finally, the AIR was lower in individuals whose mothers were diabetic during pregnancy (n = 8) than in those whose mothers developed diabetes at an early age but after the birth of the subject (n = 41) (740 [510-1,310] vs. 1,255 [1,045-1,505] pmol/l, P < 0.02). Thus, insulin secretion is lower in normal glucose tolerant offspring of people with early onset type 2 diabetes. This impairment may be worsened by exposure to a diabetic environment in utero.

[Physical exercise and insulin sensitivity]

Physical exercise is known to be essential in the treatment of type 2 diabetes. An increased glucose uptake is evidenced during acute muscular exercise, over the post-exercise period, and following physical training. In this paper, we review metabolic and molecular aspects of physical exercise. We emphasize on the non-insulin dependent glucose transport induced by muscular contraction, which involves AMP-activated protein kinase. The discovery of this pathway is likely to open new therapeutic targets for type 2 diabetes.

Differential brain responses to satiation in obese and lean men

Knowledge of how the brain contributes to the regulation of food intake in humans is limited. We used positron emission tomography and measures of regional cerebral blood flow (rCBF) (a marker of neuronal activity) to describe the functional anatomy of satiation (i.e., the response to a liquid meal) in the context of extreme hunger (36-h fast) in 11 obese (BMI > or =35 kg/m2, age 27+/-5 years, weight 115+/-11 kg, 38+/-7% body fat; mean +/- SD) and 11 lean (BMI < or =25 kg/m2, age 35+/-8 years, weight 73+/-9 kg, 19+/-6% body fat) men. As in lean men, satiation in obese men produced significant increases in rCBF in the vicinity of the ventromedial and dorsolateral prefrontal cortex and significant decreases in rCBF in the vicinity of the limbic/paralimbic areas (i.e., hippocampal formation, temporal pole), striatum (i.e., caudate, putamen), precuneus, and cerebellum. However, rCBF increases in the prefrontal cortex were significantly greater in obese men than in lean men (P < 0.005). rCBF decreases in limbic/paralimbic areas, temporal and occipital cortex, and cerebellum were also significantly greater in obese men than in lean men (P < 0.005), whereas rCBF decreases in the hypothalamus and thalamus were attenuated in obese men compared with lean men (P < 0.05). This study raises the possibility that the brain responses to a meal in the prefrontal areas (which may be involved in the inhibition of inappropriate response tendencies) and limbic/paralimbic areas (commonly associated with the regulation of emotion) may be different in obese and lean men. Additional studies are required to investigate how these differential responses are related to the pathophysiology of obesity.

Regions of the human brain affected during a liquid-meal taste perception in the fasting state: a positron emission tomography study

BACKGROUND

The sensation of taste provides reinforcement for eating and is of possible relevance to the clinical problem of obesity.

OBJECTIVE

Positron emission tomography (PET) was used to explore regions of the brain that were preferentially affected during the taste perception of a liquid meal by 11 right-handed, lean men in the fasting state.

DESIGN

After subjects had fasted for 36 h, 2 measurements of regional cerebral blood flow (rCBF) obtained immediately after subjects retained and swallowed 2 mL of a flavored liquid meal (the taste condition) were compared with 2 measurements of rCBF obtained immediately after subjects retained and swallowed 2 mL of water (the baseline condition).

RESULTS

Compared with the baseline condition, taste was associated with increased rCBF (P < 0.005) in the left dorsolateral prefrontal cortex and superior temporal gyrus; the right ventrolateral prefrontal cortex, supramarginal gyrus, and anterior thalamus; and bilaterally in the hippocampal formation, posterior cingulate, midbrain, occipital cortex, and cerebellum. Taste was also associated with decreased rCBF (P < 0.005) in the right dorsolateral prefrontal cortex, superior temporal gyrus, and supplementary motor area, and bilaterally in the medial prefrontal cortex and inferior parietal lobule.

CONCLUSIONS

This exploratory study provides additional evidence that the temporal cortex, thalamus, cingulate cortex, caudate, and hippocampal formation are preferentially affected by taste stimulation. The asymmetric pattern of activity in the dorsolateral prefrontal cortex and superior temporal gyrus may contribute to the taste perception of a liquid meal perceived as pleasant. Additional studies are required to determine how these regions are affected in patients with obesity or anorexia.

Neuroanatomical correlates of hunger and satiation in humans using positron emission tomography

The central role of the hypothalamus in the origination and/or processing of feeding-related stimuli may be modulated by the activity of other functional areas of the brain including the insular cortex (involved in enteroceptive monitoring) and the prefrontal cortex (involved in the inhibition of inappropriate response tendencies). Regional cerebral blood flow (rCBF), a marker of neuronal activity, was measured in 11 healthy, normal-weight men by using positron emission tomography in a state of hunger (after 36-h fast) and a state of satiation (after a liquid meal). Hunger was associated with significantly increased rCBF in the vicinity of the hypothalamus and insular cortex and in additional paralimbic and limbic areas (orbitofrontal cortex, anterior cingulate cortex, and parahippocampal and hippocampal formation), thalamus, caudate, precuneus, putamen, and cerebellum. Satiation was associated with increased rCBF in the vicinity of the ventromedial prefrontal cortex, dorsolateral prefrontal cortex, and inferior parietal lobule. Changes in plasma insulin concentrations in response to the meal were negatively correlated with changes in rCBF in the insular and orbitofrontal cortex. Changes in plasma free fatty acid concentrations in response to the meal were negatively correlated with changes in rCBF in the anterior cingulate and positively correlated with changes in rCBF in the dorsolateral prefrontal cortex. In conclusion, these findings raise the possibility that several regions of the brain participate in the regulation of hunger and satiation and that insulin and free fatty acids may be metabolic modulators of postprandial brain neuronal events. Although exploratory, the present study provides a foundation for investigating the human brain regions and cognitive operations that respond to nutritional stimuli.

Development of beta 3-adrenoceptor agonists for the treatment of obesity and diabetes--an update

Beta 3-adrenoceptor (beta 3-AR) agonists were found to have remarkable anti-obesity and anti-diabetic effects in rodents shortly after their discovery in the early 1980s. Despite these promising qualities, several pharmaceutical problems and theoretical concerns have slowed the development of these products as therapeutic agents in humans during the last 15 years. To date, the pharmaceutical industry has not been successful in developing a beta 3-AR agonist for use in the treatment of human obesity and type 2 diabetes. Pharmaceutical problems in this area concern important differences between rodent and human beta 3-AR and the difficulty in finding a compound with sufficient bioavailability that is a highly selective and full agonist at the human receptor. Some of these problems seem to have been solved with the cloning of the human beta 3-AR, which has made it possible to develop novel compounds directly and specifically against the human receptor. However, several theoretical concerns still remain. These include the major question as to whether the number of biologically active beta 3-ARs in adult humans is sufficient to produce relevant metabolic effects and, if so, whether their long-term stimulation is safe and free of unwarranted side effects. In addition, the mechanisms of action of beta 3-AR agonists remain poorly understood. Recent studies using CL 316,243, a highly selective beta 3-adrenergic compound, have provided new insights into the potential mechanisms of action of these drugs in rodents as well as the first evidence that treatment with a highly selective beta 3-AR agonist exerts relevant metabolic effects in humans. It appears that chronic beta 3-adrenergic stimulation in white adipose tissue increases the expression of newly discovered mitochondrial uncoupling proteins (UCP 2 and 3) and a "reawakening" of dormant brown adipocytes. In addition, beta 3-ARs may be present in skeletal muscle where ectopic expression of UCP-1 has been reported. If these findings are confirmed, tissues other than brown fat may play an important role in mediating beta 3-adrenergic effects on thermogenesis and substrate oxidation. In humans, treatment with CL 316,243 for 8 weeks, in spite of limited bioavailability, induced marked plasma concentration-dependent increases in insulin sensitivity, lipolysis, and fat oxidation in lean volunteers, without causing beta 1-, or beta 2-mediated side effects. These results clearly indicate that favourable metabolic effects can be achieved by selective beta 3-AR stimulation in humans. The compounds of the next generation currently emerging from preclinical development are full agonists at the human beta 3-AR. These agents have demonstrated promising results in non-human primates. It will be interesting to see whether their efficacy in clinical trials is superior to that achieved with previous (rodent) beta 3-AR agonists and, if so, whether their effects will eventually translate into weight loss and improved metabolic control that could facilitate their use as effective drugs for the treatment of obesity and Type 2 diabetes in humans.

Metabolic predictors of weight gain

Human obesity is the result of both environmental and genetic factors. In this manuscript, we briefly review the metabolic factors predicting body weight gain in Pima Indians, a population prone to obesity. The metabolic predictors of weight gain are: 1) a low metabolic rate, 2) low levels of physical activity, 3) low rates of fat oxidation, 4) insulin sensitivity, 5) low sympathetic nervous system activity, and 6) low plasma leptin concentrations. In contrast, obesity is associated with high metabolic rate, high fat oxidation, low insulin sensitivity and high plasma leptin concentration. This observation emphasizes the need to conduct prospective studies to obtain a better understanding of the etiology of obesity. In addition, genetic studies will help to identify new pathways involved in the pathophysiology of obesity.

Visceral adipose tissue is not increased in Pima Indians compared with equally obese Caucasians and is not related to insulin action or secretion

Pima Indians are insulin resistant and hyperinsulinaemic compared with Caucasians. We investigated whether abdominal fat distribution was different between Pimas and Caucasians and whether differences in the amount of visceral fat explained metabolic differences between the groups. Total body fat (absorptiometry) and abdominal fat distribution at L4-L5 (magnetic resonance imaging) were compared in 20 Pima Indians (10 men/10 women) and 20 age-, sex- and BMI-matched Caucasians. Insulin action was measured as glucose disposal during a two-step hyperinsulinaemic-euglycaemic glucose clamp and insulin secretion was assessed in response to oral and intravenous glucose tolerance tests. By design, percent body fat was similar in Pimas and Caucasians. Abdominal visceral and subcutaneous adipose tissue areas were also similar in the two groups (151+/-16 vs 139+/-15 cm2 and 489+/-61 vs 441+/-7 cm2 respectively). Plasma insulin concentrations were higher in Pimas than Caucasians in the fasting state (27+/-6 vs 11+/-2 mU/ml; p < 0.01) and after a 75-g oral glucose load (area under the curve 19975+/-2626 vs 9293+/-1847 mU x l(-1) x 180 min(-1); p < 0.005). Glucose disposal was lower in Pimas than Caucasians during both steps of the clamp and negatively correlated (after adjustment for percent body fat and sex) with visceral adipose tissue in Caucasians (partial r = -0.51, p = 0.03), but not in Pima Indians (r = -0.03, p = 0.92). Insulin secretion was not related to visceral fat independently of percent body fat in either group. We conclude that a relative increase in visceral fat does not explain insulin resistance and hyperinsulinaemia in Pima Indians.

Evaluation of abdominal fat distribution in noninsulin-dependent diabetes mellitus: relationship to insulin resistance

Accumulation of visceral adipose tissue is associated with metabolic complications such as noninsulin-dependent diabetes mellitus. The aim of this study was to evaluate the effect of abdominal adipose tissue on insulin sensitivity in subjects with noninsulin-dependent diabetes mellitus (NIDDM). Areas of abdominal fat were calculated from axial magnetic resonance images obtained at the level of the umbilicus in 21 men with NIDDM [age, 45.6 +/- 8.3 (+/-SD) yr; body mass index, 29.3 +/- 4.5 kg/m(-2); total body fat (skinfold thickness), 26.8 +/- 5.4%; waist to hip ratio, 0.97 +/- 0.07; duration of diabetes, 59 +/- 47 months; hemoglobin A1c, 8.1 +/- 1.5%]. Insulin sensitivity was evaluated by an insulin tolerance test. The areas of deep abdominal fat and sc abdominal fat were, respectively, 135.3 +/- 55.1 and 211.8 +/- 99.1 cm2. The blood glucose disappearance rate was 2.11 +/- 0.87%/min and was negatively related to deep abdominal fat (r = 0.72; P = 0.0025). In contrast, areas of sc abdominal fat, total body fat, body mass index, and waist to hip ratio were not related to the blood glucose disappearance rate. Plasma triglyceride concentrations averaged 1.8 +/- 0.8 mmol/L and were positively related to deep abdominal fat (r = 0.69; P = 0.0018). We conclude that insulin sensitivity is strongly related to visceral adipose tissue accumulation in NIDDM.