Early macrophage response to obesity encompasses Interferon Regulatory Factor 5 regulated mitochondrial architecture remodelling

Adipose tissue macrophages (ATM) adapt to changes in their energetic microenvironment. Caloric excess, in a range from transient to diet-induced obesity, could result in the transition of ATMs from highly oxidative and protective to highly inflammatory and metabolically deleterious. Here, we demonstrate that Interferon Regulatory Factor 5 (IRF5) is a key regulator of macrophage oxidative capacity in response to caloric excess. ATMs from mice with genetic-deficiency of Irf5 are characterised by increased oxidative respiration and mitochondrial membrane potential. Transient inhibition of IRF5 activity leads to a similar respiratory phenotype as genomic deletion, and is reversible by reconstitution of IRF5 expression. We find that the highly oxidative nature of Irf5-deficient macrophages results from transcriptional de-repression of the mitochondrial matrix component Growth Hormone Inducible Transmembrane Protein (GHITM) gene. The Irf5-deficiency-associated high oxygen consumption could be alleviated by experimental suppression of Ghitm expression. ATMs and monocytes from patients with obesity or with type-2 diabetes retain the reciprocal regulatory relationship between Irf5 and Ghitm. Thus, our study provides insights into the mechanism of how the inflammatory transcription factor IRF5 controls physiological adaptation to diet-induced obesity via regulating mitochondrial architecture in macrophages.

Interferon Regulatory Factor 5 levels have been shown to increase in adipose tissue macrophages in diet-induced obesity. Here authors show that IRF5 transcriptionally represses the Growth Hormone Inducible Transmembrane Protein gene encoding a mitochondrial protein important for oxidative respiration in macrophages, thus driving the detrimental metabolic changes observed in obesity.

Cardiac troponin I and BNP for predicting zero Agatston score in patients with diabetes mellitus

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

Coronary artery calcifications (CAC) scoring assessed by the Agatston score has shown an excellent prognostic value in large studies, particularly in diabetic patients, with a very low rate of cardiovascular events in patients with a zero Agatston score. Moreover, recent studies have suggested that high-sensitive cardiac troponin I (hs-cTnI) and brain natriuretic peptide (BNP) may be useful for detecting subclinical atherosclerosis, especially in diabetic patients. However, the link between hs-cTnI/BNP and the Agatston score has not been investigated in this population.

PURPOSE

The aim of this study was to investigate if hs-cTnI and BNP can bring additional value to predict zero Agatston score in patients with diabetes mellitus in addition to usual risk factors.

METHODS

Between 2015 and 2019, CAC score was prospectively performed in consecutive patients with diabetes mellitus with high cardiovascular risk. Patients with symptoms or known coronary artery disease were excluded. Within 24h from CT exam, peripheral blood samples were taken to measure hs-cTnI and BNP. The relationship between serum hs-cTnI/BNP concentrations and zero Agatston score was evaluated using univariate and multivariate binomial models. 77 variables have been used to build the model. The implication of hs-cTnI and BNP in this multivariate model was evaluated using nested models associated with Chi-squared test of independence.

RESULTS

A total of 844 patients with diabetes were enrolled (61 ± 7 years, 57% men, mean diabetes duration 18 years). In this population, 294 (35%) had a zero Agatston score, 253 (30%) an Agatston score from 1 to 100, 161 (19%) from 101 to 400, and 136 (16%) higher than 400. In univariate analysis, hs-cTnI and BNP concentrations were associated with a zero Agatston score (respectively OR, 2.63 [95% CI, 1.51-5.01]; p < 0.001 and OR, 1.09 [95% CI, 1.01-1.22]; p = 0.03). In multivariate analysis, hs-cTnI and BNP concentrations were associated with a zero Agatston score (respectively OR, 2.38 [95% CI, 1.51-4.76]; p = 0.009 and OR, 1.18 [95% CI, 1.07-1.32]; p = 0.001). Among the 77 variables, the multivariate model including age, gender, smoking, dyslipidaemia, duration of the diabetes, arterial hypertension, presence of diabetic neuropathy, hs-cTnI and BNP concentrations, significantly discriminated the zero Agatston score (AUC = 0.81; p < 0.001). The most discriminant threshold was ≤ 3ng/l for hs-cTnI and <17ng/l for BNP. In nested models, both hs-cTnI and BNP brought information to this multivariate model to predict a zero Agatston score (respectively p = 0.003 and p < 0.001 to the Chi-squared test). Moreover, removing hs-cTnI and BNP from the model results in a significant reduction in model performance (AUC = 0.79; p = 0.004).

CONCLUSIONS

Cardiac biomarkers hs-cTnI and BNP are associated with a zero Agatston score, which is correlated with a very low risk of cardiovascular events in asymptomatic patients with diabetes mellitus.

Abstract Figure. ROC curve to predict zero Agatston score

P2489What are the main determinants of an increase in bnp level in asymptomatic diabetic patients without known cardiac disease?

Background

Diabetes mellitus is associated with a high risk of heart failure. The predictors of futures heart failure events in diabetic patients are not clearly understood. BNP measurement can be used as a surrogate endpoint for the diagnosis of heart failure. We investigated the determinants of an increase in BNP level in a large cohort of asymptomatic diabetic patients without known cardiac disease

Methods

This prospective study included consecutive stable diabetic (type 1 or 2) patients coming for yearly check-up between March 2015 and July 2018 in the university center for the study of diabetes and its complications. Patients with an history of cardiac disease (coronary artery disease, atrial fibrillation, cardiomyopathy, previous heart failure ...) were excluded. All patients had a complete clinical exam, blood pressure measurement (3 consecutive times – mean of 2 lasts measurements), ECG, and blood sample including HbA1C, risk factors assessment, renal function (CKD-EPI) and BNP measurement. Data are presented as mean±SD or median - Spearman's rank and multivariate regression were used for analysis.

Results

3743 patients (mean age 57±14 y.o. – 57% male – 78% / 18% / 4% of type 2, type 1 or other type of diabetes respectively – Mean duration of diabetes 17 [1–63] y. – 44% treated with insulin) were studied. Mean±SD / median [min-max] BNP level was 25±39 / 12 [4–737] ng/L. BNP was <20 / 21–35 / 36–50 / 51–100 / 101–400 / >400 ng/L in 69 / 15 / 6 / 7 / 3 / 0.1% of the population respectively. The parameters most correlated with BNP level in type 1 and type 2 diabetes were age, duration of diabetes, renal function, HbA1C, and pulsed pressure. For multivariate analysis, renal function was removed of the model as it was highly correlated with age (r=−0.68). Multivariate analysis demonstrated that in type 1 diabetes, high BNP level was linked to age (p<0.001), pulsed pressure (p<0.001), duration of diabetes (p=0.003) and HbA1C (p=0.02). In type 2 diabetes, high BNP level was linked to age (p<0.0001), pulsed pressure (p<0.0001), duration of diabetes (p=0.005) but not HbA1C (p=0.09). Interestingly the type of treatment (mainly insulin treatment) was not independently related to an increase in BNP level.

Conclusion

Age, pulsed pressure and duration of diabetes are the main determinants of an increased level of BNP in asymptomatic diabetic patients without any history of cardiac disease. This result could help to select a population who could benefit to a more extensive follow up concerning heart failure.

Ketosis-prone atypical diabetes in Cameroonian people with hyperglycaemic crisis: frequency, clinical and metabolic phenotypes

AIM

It is unclear whether ketosis-prone diabetes is a specific type or a subtype of Type 2 diabetes. We aimed to describe the clinical and metabolic features of ketosis-prone diabetes in a sub-Saharan population.

METHODS

We consecutively enrolled and characterized 173 people with non-autoimmune diabetes admitted for hyperglycaemic crisis at the Yaoundé Central Hospital, Cameroon. Blood samples were collected for fasting glucose, HbA_1c , lipid profile and C-peptide assays with insulin resistance and secretion estimation by homeostasis model assessment. People were classified as having Type 2 diabetes (n = 124) or ketosis-prone diabetes (n = 49). Ketosis-prone diabetes was sub-classified as new-onset ketotic phase (n = 34) or non-ketotic phase (n = 15).

RESULTS

Ketosis-prone diabetes was found in 28.3% of the hyperglycaemic crises. Age at diabetes diagnosis was comparable in Type 2 and ketosis-prone diabetes [48 ± 14 vs 47 ± 11 years; P = 0.13] with a similar sex distribution. Overall BMI was 27.7 ± 13.4 kg/m² and was ≥ 25 kg/m² in 55.8% of those taking part, however, 73.5% of those with ketosis-prone diabetes reported weight loss of > 5% at diagnosis. Blood pressure and lipid profile were comparable in both types. Ketosis-prone diabetes in the ketotic phase was characterized by lower insulin secretion and higher serum triglycerides compared with non-ketotic ketosis prone and Type 2 diabetes. Type 2 and ketosis prone diabetes in the non-ketotic phase were comparable in terms of lipid profile, blood pressure, waist-to-hip ratio, BMI and fat mass, insulin secretion and insulin resistance indices.

CONCLUSIONS

Ketosis-prone diabetes is likely to be a subtype of Type 2 diabetes with the potential to develop acute insulinopenic episodes.

Which oral antidiabetic drug to combine with metformin to minimize the risk of hypoglycemia when initiating basal insulin?: A randomized controlled trial of a DPP4 inhibitor versus insulin secretagogues

We conducted a pilot study to evaluate two therapeutic strategies at the time of insulin initiation in type 2 diabetic patients insufficiently controlled with metformin+insulin-secretagogues (IS, sulfonylureas or glinides). Patients were randomized to remain under the same dual therapy or to receive metformin+DPP4 inhibitors while starting insulin. Similar glycemic control was achieved in both groups. However less hypoglycemia was observed with DPP4 inhibitors despite higher doses of insulin.

Biguanides and thiazolidinediones inhibit stimulated lipolysis in human adipocytes through activation of AMP-activated protein kinase

AIMS/HYPOTHESIS

In rodent adipocytes, activated AMP-activated protein kinase reduces the lipolytic rate. As the hypoglycaemic drugs metformin and thiazolidinediones activate this enzyme in rodents, we tested the hypothesis that in addition to their known actions they could have an anti-lipolytic effect in human adipocytes.

METHODS

Adipose tissue was obtained from individuals undergoing plastic surgery. Adipocytes were isolated and incubated with lipolytic agents (isoprenaline, atrial natriuretic peptide) and biguanides or thiazolidinediones. Lipolysis was quantified by the glycerol released in the medium. AMP-activated protein kinase activity and phosphorylation state were determined using standard procedures.

RESULTS

In human adipocytes, isoprenaline and atrial natriuretic peptide stimulated the lipolytic rate three- to fourfold. Biguanides and thiazolidinediones activated AMP-activated protein kinase and inhibited lipolysis by 30-40%, at least in part by inhibiting hormone-sensitive lipase translocation to the lipid droplet. Inhibition of AMP-activated protein kinase by compound C precluded this inhibitory effect on lipolysis. Stimulation of lipolysis also induced an activation of AMP-activated protein kinase concomitant with a drop in ATP concentration.

CONCLUSIONS/INTERPRETATION

We show for the first time in human adipocytes that biguanides and thiazolidinediones activate AMP-activated protein kinase, thus counteracting lipolysis induced by lipolytic agents. In addition, beta-agonist- or ANP-stimulated lipolysis increases AMP-activated protein kinase activity. This is because of an increase in the AMP/ATP ratio, linked to activation of some of the released fatty acids into acyl-CoA. AMP-activated protein kinase activation could represent a physiological means of avoiding a deleterious drain of energy during lipolysis but could be used to restrain pharmacological release of fatty acids.

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.

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.

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.

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.

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.

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.

[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.

[Insulin sensitivity and hepatic glucose production: nycthemeral variations]

Glucose tolerance is subject to circadian variations and has been found to be better in the morning or afternoon. An increase in plasma glucose and insulin concentrations has recently been observed between 5 and 9 a.m. These physiological changes correspond to an increase in insulin requirements in patients with insulin-dependent diabetes mellitus (the "dawn phenomenon"). In patients with non-insulin-dependent diabetes mellitus, the circadian rhythm of insulin secretion is suppressed. Studies of insulin sensitivity during a hyperinsulinaemic hyperglycaemic clamp (a supraphysiological experimental condition) indicated that: i) insulin-induced glucose utilization is decreased in the morning according to a circadian rhythm; ii) this change results from an increase in hepatic glucose production but not from a decrease in glucose uptake; and iii) a circadian rhythm is also observed for plasma free fatty acids and cortisol concentrations, which could account in part for the circadian changes in insulin sensitivity. Recognition of these circadian changes has implications for the treatment of non-insulin-dependent diabetes mellitus.

Glucose turnover in humans in the basal state and after intravenous glucose: a comparison of two models

This study investigated the ability of two models to represent glucose kinetics in the basal steady state and during an intravenous glucose tolerance test (IVGTT). Six young nonobese male subjects were studied after an overnight fast. Two bolus injections of [U-13C]glucose were given 150 min apart, the first without and the second together with concomitant injection of unlabeled glucose. [3-3H]glucose was constantly infused throughout the study and served to provide an independent means for evaluation of system responses. A linear time-invariant three-compartmental model and the two-compartment time-variant model proposed by Caumo and Cobelli were used to interpret measured time courses of [U-13C]glucose and to reconstruct endogenous glucose production and glucose removal. The ability of the two models to describe the glucose tracer time course was comparable. Simulation studies showed that the two-compartmental time-variant system better predicted measured [3-3H]glucose concentration profiles than did the three-compartmental time-invariant model. However, endogenous glucose production and the integral of excess glucose removal over basal during the IVGTT derived from the two models were almost identical.

Mobilization of visceral adipose tissue related to the improvement in insulin sensitivity in response to physical training in NIDDM. Effects of branched-chain amino acid supplements

OBJECTIVE

To evaluate the effects of an intense physical training program on abdominal fat distribution, glycemic control, and insulin sensitivity in patients with NIDDM and to determine whether branched-chain amino acid (BCAA) supplements influence these effects.

RESEARCH DESIGN AND METHODS

Twenty-four patients (ages 45 +/- 2 [mean +/- SE] years, BMI 30.2 +/- 0.9 kg/m2, HbA1c 7.9 +/- 0.3%) were randomly assigned to four groups: training plus BCAA supplement (n = 6), training plus placebo (n = 6), sedentary plus BCAA supplement (n = 6), and sedentary plus placebo (n = 6). Physical training consisted of a supervised 45-min cycling exercise at 75% of their oxygen uptake peak (VO2 peak) two times per week and an intermittent exercise one time per week for 2 months.

RESULTS

Patients who exercised increased their VO2 peak by 41% and their insulin sensitivity by 46%. Physical training significantly decreased abdominal fat evaluated by magnetic resonance imaging (umbilicus), with a greater loss of visceral adipose tissue (VAT) (48%) in comparison with the loss of subcutaneous adipose tissue (18%), but did not significantly affect body weight. The change in visceral abdominal fat was associated with the improvement in insulin sensitivity (r = 0.84, P = 0.001). BCAA supplementation had no effect on abdominal fat and glucose metabolism.

CONCLUSIONS

Physical training resulted in an improvement in insulin sensitivity with concomitant loss of VAT and should be included in the treatment program for patients with NIDDM.

Influence of simulated altitude on the performance of five blood glucose meters

OBJECTIVE

To determine the reliability of five blood glucose meters (BGMs) at various simulated altitudes using a hypobaric chamber.

RESEARCH DESIGN AND METHODS

Blood glucose levels (ranged from 1.5 to 26.3 mmol/l, according to the reference method) were measured in 18 venous blood samples by each BGM at 200, 1,000, and every 500 m up to 4,000 m in a hypobaric chamber, where temperature and humidity were held constant.

RESULTS

Four BGMs underestimated and one overestimated blood glucose concentration while barometric pressure decreased. The average percent error varied in relation to simulated altitude from 0.26 +/- 4.8% (SD) at 200 m to -28.9 +/- 4.5% at 4,000 m (Glucometer 3; P < 0.05), from 28.4 +/- 5.7 to 49.3 +/- 5.9% (Accu-Chek Easy; P < 0.05), from -10.5 +/- 2.6 to 19.8 +/- 4.3% (Tracer, P < 0.05), from -5.5 +/- 2.6 to -11.2 +/- 3.0% (Reflolux; NS), and from 17.8 +/- 4.3 to 14.8 +/- 3.6% (One Touch; NS). The most accurate seemed to be the Reflolux, except for high blood glucose levels at simulated high altitudes. The One Touch II showed a good agreement, whatever the barometric pressure and the range of blood glucose concentrations. The highest underestimation was seen with the Glucometer 3.

CONCLUSIONS

Except for the Accu-Chek Easy, low barometric pressure underestimated the BGM results in comparison with measurements taken at simulated low altitudes. The lack of accuracy and consistency of performance > 2,000 m should be known by diabetic patients practicing sports activities, such as trekking or skiing at high altitudes.