Effets directs et aigus de médicaments insulinosensibilisateurs sur la cellule bêta des îlots pancréatiques : de l’outil de recherche à l’identification de la décélération métabolique comme mode d’action

Le diabète de type 2 (DT2) apparaît lorsque la sécrétion d’insuline par les cellules β des îlots du pancréas ne parvient plus à compenser la résistance à l’insuline des organes cibles. Parmi les médicaments disponibles pour traiter le DT2, deux classes agissent en améliorant la sensibilité à l’insuline : les biguanides (metformine) et les thiazolidinediones (pioglitazone et rosiglitazone). Des études suggèrent que ces médicaments protègent également la fonction des cellules β. Dans le but d’identifier des mécanismes par lesquels les médicaments insulinosensibilisateurs protègent les cellules β, nous avons étudié les effets aigus de la metformine et de la pioglitazone sur le métabolisme et la fonction des cellules INS 832/13, sécrétrices d’insuline et des îlots pancréatiques isolés de rats. Nous avons aussi validé in vivo avec des rats Wistar les principales observations obtenues en présence de pioglitazone grâce à des clamps glucidiques et par calorimétrie indirecte. Le traitement aigu des cellules β avec de la pioglitazone ou de la metformine inhibe la sécrétion d’insuline induite par le glucose en diminuant la sensibilité des cellules au glucose (inhibition en présence de concentrations intermédiaires de glucose seulement). Dans les mêmes conditions, les traitements inhibent aussi plusieurs paramètres du métabolisme mitochondrial des nutriments et, pour la pioglitazone, du métabolisme des lipides. Les composés affectent le métabolisme en suivant un patron d’inhibition similaire à celui observé pour la sécrétion d’insuline, que nous avons nommé « décélération métabolique ». La capacité de la pioglitazone à inhiber la sécrétion d’insuline et à ralentir le métabolisme mitochondrial de façon aigüe se confirme in vivo. En conclusion, nous avons identifié la décélération métabolique de la cellule β comme nouveau mode d’action pour les médicaments insulinosensibilisateurs. La décélération métabolique causée par les agents insulinosensibilisateurs les plus utilisés semble provenir d’une inhibition du métabolisme mitochondrial et pourrait être impliquée dans les bienfaits de ceux-ci dans un contexte de stress métabolique. Le fait que les deux agents insulinosensibilisateurs étudiés agissent à la fois sur la sensibilité à l’insuline et sur la sécrétion d’insuline, les deux composantes majeures du DT2, pourrait expliquer pourquoi ils sont parmi les agents antidiabétiques les plus efficaces. La décélération métabolique est une approche thérapeutique à considérer pour le traitement du DT2 et d’autres maladies métaboliques.

Mesure de l’activité physique par accélérométrie : validation et précision de la mesure

Introduction : Les accéléromètres sont actuellement les appareils les plus utilisés pour mesurer le niveau d’activité physique, et ce, parce qu'ils évaluent les niveaux d'activité physique de façon objective. Toutefois, les mouvements humains sont difficiles à mesurer, et de nombreuses limitations doivent être prises en considération pour la bonne utilisation des accéléromètres. Les études présentées s’intéressent donc à la validité de la fonction podomètre des accéléromètres ainsi qu’à la validation de la composante accéléromètre d’un nouvel appareil multicapteur (SenseDoc). Méthode : Les sujets ayant participé à la première étude, qui consistait en la validation de la fonction podomètre des accéléromètres, ont marché sur un tapis roulant à trois vitesses différentes (2,5 km/h, 3,5 km/h et 4,8 km/h) pendant 5 minutes par palier. Un accéléromètre (ActiGraph GT3X) porté à la ceinture a enregistré le nombre de pas tandis qu'une caméra a enregistré la marche des participants. Pour la seconde étude, les participants portaient un accéléromètre Actigraph et un SenseDoc à la hanche. Les données brutes des accéléromètres et la mesure de la consommation d’oxygène par calorimétrie indirecte ont été mesurées lors de 14 activités réalisées en laboratoire allant de sédentaires à vigoureuses. Résultats : La première étude indique que les accéléromètres ont détecté seulement 53 % des pas à 2,5 km/h, 82 % à 3,5 km/h et 91 % à 4,8 km/h pour les personnes non obèses. Pour les personnes obèses, l'accéléromètre a détecté 47 % des pas à 2.5 km/h, 67 % à 3.5 km/h et 100 % à 4.8 km/h, des résultats significativement différents des personnes non obèses. La seconde étude confirme pour sa part que le SenseDoc est un outil valide de mesure du niveau d’activité physique. Les accéléromètres possèdent une bonne capacité prédictive de la dépense énergétique avec des valeurs de R carré de 0,84 et 0,80 respectivement pour l'Actigraph et le SenseDoc. Conclusion : À vitesse de marche lente, les accéléromètres sous-estiment le nombre de pas, et ce, dans une plus large mesure chez les personnes obèses que chez les personnes non obèses. Également, une méthode valide et transparente de transformation de données brutes d’accélérométrie a été divulguée dans l’étude avec le SenseDoc. Les travaux présentés dans ce mémoire visent à améliorer l’utilisation en milieu clinique et en recherche des accéléromètres et ouvrent la voie à une plus grande uniformité entre les études utilisant différents types d’accéléromètres.

Calorimetría indirecta versus Harris-Benedict para determinar gasto energético basal en pacientes ventilados

El inadecuado aporte nutricional en los pacientes con enfermedades criticas, ha llevado al desarrollo de complicaciones que incrementan la mortalidad y los costos de la atención en salud. Muchos factores están involucrados en el consumo de los nutrientes por el organismo, como: los traslados, las intervenciones quirúrgicas, el uso de vasopresores, la ventilación mecánica, entre otros. Si se presenta imprecisión en la de-terminación del gasto energético, puede conllevar a un sobre aporte alimenticio en el paciente el cual puede afectar la evolución y pronosti-co del individuo. Es de conocimiento universal que los costos en salud cada día se in-crementan, en especial cuando se presenta requerimiento del manejo de un paciente en la unidad de cuidados intensivos. Para predecir el gasto energético basal de los paciente en las UCI se cuentan con herramientas de evaluación sencillas, de fácil uso y económicas, como la ecuación de Harris-Benedict, o herramientas complejas y de difícil manejo como la Calorimetría Indirecta. El incremento en la demanda de servicios con mayor tecnología en el tratamiento de los pacientes, enfrenta al personal de salud para ser más crítico en el uso de la nueva tecnología, por tal motivo, se evaluó la presencia de correlación entre las ecuaciones de Harris-Benedict y Calorimetría Indirecta, encontrando que se presenta una buena correlación entre las ecuaciones, con un valor de Pearson de 0,700 y una p = 0.002. Por lo que se puede concluir que las ecuaciones pueden ser utilizadas para estimar el gasto energético basal de los pacientes en la UCI.

Simulating the effects of grassland management and grass ensiling on methane emission from lactating cows

A dynamic, mechanistic model of enteric fermentation was used to investigate the effect of type and quality of grass forage, dry matter intake (DMI) and proportion of concentrates in dietary dry matter (DM) on variation in methane (CH(4)) emission from enteric fermentation in dairy cows. The model represents substrate degradation and microbial fermentation processes in rumen and hindgut and, in particular, the effects of type of substrate fermented and of pH oil the production of individual volatile fatty acids and CH, as end-products of fermentation. Effects of type and quality of fresh and ensiled grass were evaluated by distinguishing two N fertilization rates of grassland and two stages of grass maturity. Simulation results indicated a strong impact of the amount and type of grass consumed oil CH(4) emission, with a maximum difference (across all forage types and all levels of DM 1) of 49 and 77% in g CH(4)/kg fat and protein corrected milk (FCM) for diets with a proportion of concentrates in dietary DM of 0.1 and 0.4, respectively (values ranging from 10.2 to 19.5 g CH(4)/kg FCM). The lowest emission was established for early Cut, high fertilized grass silage (GS) and high fertilized grass herbage (GH). The highest emission was found for late cut, low-fertilized GS. The N fertilization rate had the largest impact, followed by stage of grass maturity at harvesting and by the distinction between GH and GS. Emission expressed in g CH(4)/kg FCM declined oil average 14% with an increase of DMI from 14 to 18 kg/day for grass forage diets with a proportion of concentrates of 0.1, and on average 29% with an increase of DMI from 14 to 23 kg/day for diets with a proportion of concentrates of 0.4. Simulation results indicated that a high proportion of concentrates in dietary DM may lead to a further reduction of CH, emission per kg FCM mainly as a result of a higher DM I and milk yield, in comparison to low concentrate diets. Simulation results were evaluated against independent data obtained at three different laboratories in indirect calorimetry trials with COWS consuming GH mainly. The model predicted the average of observed values reasonably, but systematic deviations remained between individual laboratories and root mean squared prediction error was a proportion of 0.12 of the observed mean. Both observed and predicted emission expressed in g CH(4)/kg DM intake decreased upon an increase in dietary N:organic matter (OM) ratio. The model reproduced reasonably well the variation in measured CH, emission in cattle sheds oil Dutch dairy farms and indicated that oil average a fraction of 0.28 of the total emissions must have originated from manure under these circumstances.

Effects of beacon administration on energy expenditure and substrate utilisation in Psammomys obesus (Israeli sand rats)

Objective: To investigate whether beacon administration affects substrate utilisation, physical activity levels or energy expenditure in Psammomys obesus. Design: Pairs of age- and sex-matched Psammomys obesus were randomly assigned to either beacon-treated (15 µg/day for 7 days (i.c.v.)) or control (i.c.v. saline) groups. Measurements: Indirect calorimetry on day 0 and day 7 to measure oxygen consumption and carbon dioxide production, which were used to calculate fat oxidation, carbohydrate oxidation and total energy expenditure. Physical activity in the calorimeter was measured using an infrared beam system. Food intake and body weight were measured daily. Results: The administration of beacon significantly increased body weight compared to saline-treated control animals. This body weight gain was primarily due to increased body fat content. Average daily food intake tended to be higher in beacon-treated Psammomys obesus, but no effect of beacon administration on substrate oxidation, activity or energy expenditure was detected. Conclusion: The effects of beacon on body weight are due to increased food intake, with no detectable effect on nutrient partitioning, physical activity or energy expenditure.

Calpain 3 gene expression in skeletal muscle is associated with body fat content and measures of insulin resistance

OBJECTIVE: To investigate whether skeletal muscle gene expression of calpain 3 is related to obesity and insulin resistance.

DESIGN: Cross-sectional studies in 27 non-diabetic human subjects and in Psammomys obesus, a polygenic animal model of obesity and type 2 diabetes.

MEASUREMENTS: Expression of CAPN3 in skeletal muscle was measured using Taqman fluorogenic PCR. In the human subjects, body composition was assessed by DEXA and insulin sensitivity was measured by euglycemic-hyperinsulinemic clamp. In Psammomys obesus, body composition was determined by carcass analysis, and substrate oxidation rates, physical activity and energy expenditure were measured by whole-body indirect calorimetry.

RESULTS: In human subjects, calpain 3 gene expression was negatively correlated with total (P=0.022) and central abdominal fat mass (P=0.034), and with blood glucose concentration in non-obese subjects (P=0.017). In Psammomys obesus, calpain 3 gene expression was negatively correlated with circulating glucose (P=0.013) and insulin (P=0.034), and with body fat mass (P=0.049). Indirect calorimetry revealed associations between calpain 3 gene expression and carbohydrate oxidation (P=0.009) and energy expenditure (P=0.013).

CONCLUSION/INTERPRETATION: Lower levels of expression of calpain 3 in skeletal muscle were associated with reduced carbohydrate oxidation and elevated circulating glucose and insulin concentrations, and also with increased body fat and in particular abdominal fat. Therefore, reduced expression of calpain 3 in both humans and Psammomys obesus was associated with phenotypes related to obesity and insulin resistance.

Glucose ingestion during exercise blunts exercise-induced gene expression of skeletal muscle fat oxidative genes.

Ingestion of carbohydrate during exercise may blunt the stimulation of fat oxidative pathways by raising plasma insulin and glucose concentrations and lowering plasma free fatty acid (FFA) levels, thereby causing a marked shift in substrate oxidation. We investigated the effects of a single 2-h bout of moderate-intensity exercise on the expression of key genes involved in fat and carbohydrate metabolism with or without glucose ingestion in seven healthy untrained men (22.7 ± 0.6 yr; body mass index: 23.8 ± 1.0 kg/m²; maximal O2 consumption: 3.85 ± 0.21 l/min). Plasma FFA concentration increased during exercise (P < 0.01) in the fasted state but remained unchanged after glucose ingestion, whereas fat oxidation (indirect calorimetry) was higher in the fasted state vs. glucose feeding (P < 0.05). Except for a significant decrease in the expression of pyruvate dehydrogenase kinase-4 (P < 0.05), glucose ingestion during exercise produced minimal effects on the expression of genes involved in carbohydrate utilization. However, glucose ingestion resulted in a decrease in the expression of genes involved in fatty acid transport and oxidation (CD36, carnitine palmitoyltransferase-1, uncoupling protein 3, and 5'-AMP-activated protein kinase-α2; P < 0.05). In conclusion, glucose ingestion during exercise decreases the expression of genes involved in lipid metabolism rather than increasing genes involved in carbohydrate metabolism.

Improved skeletal muscle oxidative enzyme activity and restoration of PGC-1α and PPARß/δ gene expression upon rosiglitazone treatment in obese patients with type 2 diabetes mellitus

Objective: To examine whether rosiglitazone alters gene expression of some key genes involved in mitochondrial biogenesis and oxidative capacity in skeletal muscle of type 2 diabetic patients, and whether this is associated with alterations in skeletal muscle oxidative capacity and lipid content.

Design: Skeletal muscle gene expression, mitochondrial protein content, oxidative capacity and lipid accumulation were measured in muscle biopsies obtained from diabetic patients, before and after 8 weeks of rosiglitazone treatment, and matched controls. Furthermore, whole-body insulin sensitivity and substrate utilization were assessed.

Subjects: Ten obese type 2 diabetic patients and 10 obese normoglycemic controls matched for age and BMI.

Methods: Gene expression and mitochondrial protein content of complexes I–V of the respiratory chain were measured by quantitative polymerase chain reaction and Western blotting, respectively. Histochemical staining was used to quantify lipid accumulation and complex II succinate dehydrogenase (SDH) activity. Insulin sensitivity and substrate utilization were measured during a hyperinsulinemic–euglycemic clamp with indirect calorimetry.

Results: Skeletal-muscle mRNA of PGC-1a and PPARb/d – but not of other genes involved in glucose, fat and oxidative metabolism – was significantly lower in diabetic patients (Po0.01). Rosiglitazone significantly increased PGC-1a (B2.2-fold, Po0.01) and PPARb/d (B2.6-fold, Po0.01), in parallel with an increase in insulin sensitivity, SDH activity and metabolic flexibility (Po0.01). Surprisingly, none of the measured mitochondrial proteins was reduced in type 2 diabetic patients, nor affected by rosiglitazone treatment. No alterations were seen in muscular fat accumulation upon treatment.

Conclusion: These results suggest that the insulin-sensitizing effect of rosiglitazone may involve an effect on muscular oxidative capacity, via PGC-1a and PPARb/d, independent of mitochondrial protein content and/or changes in intramyocellular lipid.

Upregulation of peroxisome proliferator-activated receptor gamma coactivator gene (PGC1A) during weight loss is related to insulin sensitivity but not to energy expenditure

Aims/hypothesis We investigated whether skeletal muscle peroxisome proliferator-activated receptor gamma coactivator-1 (PGC1A; also known as PPARGC1A) and its target mitofusin-2 (MFN2), as well as carnitine palmitoyltransferase-1 (CPT1; also known as carnitine palmitoyltransferase 1A [liver] [CPT1A]) and uncoupling protein (UCP)3, are involved in the improvement of insulin resistance and/or in the modification of energy expenditure during surgically induced massive weight loss.
Materials and methods Seventeen morbidly obese women (mean BMI: 45.9 ± 4 kg/m2) were investigated before, and 3 and 12 months after, Roux-en-Y gastric bypass (RYGB). We evaluated insulin sensitivity by the euglycaemic–hyperinsulinaemic clamp, energy expenditure and substrate oxidation by indirect calorimetry, and muscle mRNA expression by PCR.
Results Post-operatively, PGC1A was enhanced at 3 (p = 0.02) and 12 months (p = 0.03) as was MFN2 (p = 0.008 and p = 0.03 at 3 and 12 months respectively), whereas UCP3 was reduced (p = 0.03) at 12 months. CPT1 did not change. The expression of PGC1A and MFN2 were strongly (p < 0.0001) related. Insulin sensitivity, which increased after surgery (p = 0.002 at 3, p = 0.003 at 12 months), was significantly related to PGC1A and MFN2, but only MFN2 showed an independent influence in a multiple regression analysis. Energy expenditure was reduced at 3 months post-operatively (p = 0.001 vs before RYGB), remaining unchanged thereafter until 12 months. CPT1 and UCP3 were not significantly related to the modifications of energy expenditure or of lipid oxidation rate.
Conclusions/interpretation Weight loss upregulates PGC1A, which in turn stimulates MFN2 expression. MFN2 expression significantly and independently contributes to the improvement of insulin sensitivity. UCP3 and CPT1 do not seem to influence energy expenditure after RYGB.

Effect of carbohydrate ingestion on metabolism during running and cycling

The effects of carbohydrate or water ingestion on metabolism were investigated in seven male subjects during two running and two cycling trials lasting 60 min at individual lactate threshold using indirect calorimetry, U-¹⁴C-labeled tracer-derived measures of the rates of oxidation of plasma glucose, and direct determination of mixed muscle glycogen content from the vastus lateralis before and after exercise. Subjects ingested 8 ml/kg body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or water 10 min before exercise and an additional 2 ml/kg body mass of the same fluid after 20 and 40 min of exercise. Plasma glucose oxidation was greater with CHO than with water during both running (65 ± 20 vs. 42 ± 16 g/h; P < 0.01) and cycling (57 ± 16 vs. 35 ± 12 g/h; P < 0.01). Accordingly, the contribution from plasma glucose oxidation to total carbohydrate oxidation was greater during both running (33 ± 4 vs. 23 ± 3%; P < 0.01) and cycling (36 ± 5 vs. 22 ± 3%; P < 0.01) with CHO ingestion. However, muscle glycogen utilization was not reduced by the ingestion of CHO compared with water during either running (112 ± 32 vs. 141 ± 34 mmol/kg dry mass) or cycling (227 ± 36 vs. 216 ± 39 mmol/kg dry mass). We conclude that, compared with water, 1) the ingestion of carbohydrate during running and cycling enhanced the contribution of plasma glucose oxidation to total carbohydrate oxidation but 2) did not attenuate mixed muscle glycogen utilization during 1 h of continuous submaximal exercise at individual lactate threshold.

The effects of exercise and adipose tissue lipolysis on plasma adiponectin concentration and adiponectin receptor expression in human skeletal muscle

Objective: It has been suggested that adiponectin regulates plasma free fatty acid (FFA) clearance by stimulating FFA uptake and/or oxidation in muscle. We aimed to determine changes in plasma adiponectin concentration and adiponectin receptor 1 and 2 mRNA expression in skeletal muscle during and after prolonged exercise under normal, fasting conditions (high FFA trial; HFA) and following pharmacological inhibition of adipose tissue lipolysis (low FFA trial; LFA). Furthermore, we aimed to detect and locate adiponectin in skeletal muscle tissue. Methods: Ten subjects performed two exercise trials (120 min at 50% VO2max). Indirect calorimetry was used to determine total fat oxidation rate. Plasma samples were collected at rest, during exercise and during post-exercise recovery to determine adiponectin, FFA and glycerol concentrations. Muscle biopsies were taken to determine adiponectin protein and adiponectin receptor 1 and 2 mRNA expression and to localise intramyocellular adiponectin. Results: Basal plasma adiponectin concentrations averaged 6.57±0.7 and 6.63±0.8 mg/l in the HFA and LFA trials respectively, and did not change significantly during or after exercise. In the LFA trial, plasma FFA concentrations and total fat oxidation rates were substantially reduced. However, plasma adiponectin and muscle adiponectin receptor 1 and 2 mRNA expression did not differ between trials. Immunohistochemical staining of muscle cross-sections showed the presence of adiponectin in the sarcolemma of individual muscle fibres and within the interfibrillar arterioles. Conclusion: Plasma adiponectin concentrations and adiponectin receptor 1 and 2 mRNA expression in muscle are not acutely regulated by changes in adipose tissue lipolysis and/or plasma FFA concentrations. Adiponectin is abundantly expressed in muscle, and, for the first time, it has been shown to be present in/on the sarcolemma of individual muscle fibres.

Energy expenditure and the body cell mass in Cystic Fibrosis

Poor nutritional status in patients with cystic fibrosis (CF) is associated with severe lung disease, and possible causative factors include inadequate intake, malabsorption, and increased energy requirements. Body cell mass (which can be quantified by measurement of total body potassium) provides an ideal standard for measurements of energy expenditure. The aim of this study was to compare resting energy expenditure (REE) in patients with CF with both predicted values and age-matched healthy children and to    determine whether REE was related to either nutritional status or pulmonary function. REE was measured by indirect calorimetry and body cell mass by scanning with total body potassium in 30 patients with CF (12 male, mean AGE = 13.07 ± 0.55 y) and 18 healthy children (six male, mean AGE = 12.56 ± 1.25 y). Nutritional status was expressed as a percentage of predicted total body potassium. Lung function was measured in the CF group by spirometry and expressed as the percentage of predicted forced expiratory volume in 1 s. Mean REE was significantly increased in the patients with CF compared with healthy children (119.3 ± 3.1% predicted versus 103.6 ± 5% predicted, P < 0.001) and, using multiple regression techniques, REE for total body potassium was significantly increased in patients with CF (P = 0.0001). There was no relation between REE and nutritional status or pulmonary disease status in the CF group. In conclusion, REE is increased in children and adolescents with CF but is not directly related to nutritional status or pulmonary disease.

Novel genes in the liver of diabetic Psammomys obesus

Type 2 diabetes mellitus is a metabolic disease characterised by defects in insulin secretion and insulin action and disturbances in carbohydrate, fat and protein metabolism. Hepatic insulin resistance contributes to hyperglycemia and also leads to disturbances in fat metabolism in type 2 diabetes. Psammomys obesus is a unique poly genie animal model of type 2 diabetes and obesity, ideally suited for studies examining physiological and genetic aspects of these diseases. To identify metabolic abnormalities potentially contributing to the obesity and diabetes phenotype in P. obesus, indirect calorimetry was used to characterise whole body energy expenditure and substrate utilisation. Lean-NGT, obese-IGT and obese-diabetic animals were examined in fed and fasted states and following 14 days of dietary energy restriction. Energy expenditure and fat oxidation were elevated in the obese-IGT and obese-diabetic groups in proportion to body weight. Glucose oxidation was not different between groups. Obese-diabetic P. obesus displayed elevated nocturnal blood glucose levels and fat oxidation. Following 14 days of dietary energy restriction, body weight was reduced and plasma insulin and blood glucose levels were normalised in all groups. Glucose oxidation was reduced and fat oxidation was increased. After 24 hours of fasting, plasma insulin and blood glucose levels were normalised in all groups. Energy expenditure and glucose oxidation were greatly reduced and fat oxidation was increased. Following either dietary energy restriction or fasting, energy expenditure, glucose oxidation and fat oxidation were not different between groups of P. obesus. Energy expenditure and whole body substrate utilisation in P. obesus was similar to that seen in humans. P. obesus responded normally to short term fasting and dietary energy restriction. Elevated nocturnal fat oxidation rates and plasma glucose levels in obese-diabetic P. obesus may be an important factor in the pathogenesis of obesity and type 2 diabetes in these animals. These studies have further validated P. obesus as an ideal animal model of type 2 diabetes and obesity. It was hypothesised that many genes in the liver of P. obesus involved in glucose and fat metabolism would be differentially expressed between lean-NGT and obese-diabetic animals. These genes may represent significant factors in the pathophysiology of type 2 diabetes. Two gene discovery experiments were conducted using suppression subtractive hybridisation (SSH) to enrich a cDNA library for differentially expressed genes. Experiment 1 used cDNA dot blots to screen 576 clones with cDNA derived from lean-NGT and obese-diabetic animals. 6 clones were identified as overexpressed in lean-NGT animals and 6 were overexpressed in obese-diabetic animals. These 12 clones were sequenced and SYBR-Green PCR was used to confirm differential gene expression. 4 genes were overexpressed (≥1.5 fold) in lean-NGT animals and 4 genes were overexpressed (≥1.5 fold) in obese-diabetic animals. To explore the physiological role of these genes, hepatic gene expression was examined in several physiological conditions. One gene, encoding thyroxine binding globulin (TBG), was confirmed as overexpressed in lean-NGT P. obesus with ad libitum access to food, relative to both obese-IGT and obese-diabetic animals. TBG expression decreased with fasting in all animals. Fasting TBG expression remained greater in lean-NGT animals than obese-IGT and obese-diabetic animals. TBG expression was not significantly affected by dietary energy restriction. TBG is involved in thyroid metabolism and is potentially involved in the regulation of energy expenditure. Fasting increased hepatic site 1 protease (SIP) expression in lean-NGT animals but was not significantly affected in obese-IGT and obese-diabetic animals. SIP expression was not significantly affected by dietary energy restriction. SIP is involved in the proteolytic processing of steroid response element binding proteins (SREBP). SREBPs are insulin responsive and are known to be involved in lipid metabolism. Gene expression studies found TBG and SIP were associated with obesity and diabetes. Future research will determine whether TBG and SIP are important in the pathogenesis of these diseases. Experiment 2 used SSH and cDNA microarray to screen 8064 clones. 223 clones were identified as overexpressed in lean-NGT P. obesus and 274 clones were overexpressed in obese-diabetic P. obesus (p ≤0.05). The 9 most significantly differentially expressed clones identified from the microarray screen were sequenced (p ≤0.01). 7 novel genes were identified as well as; sulfotransferase related protein and albumin. These 2 genes have not previously been associated with either type 2 diabetes or obesity. It is unclear why hepatic expression of these genes may differ between lean-NGT and obese-diabetic groups of P. obesus. Subsequent studies will explore the potential role of these novel and known genes in the pathophysiology of type 2 diabetes.

IUGR in the absence of postnatal 'catch-up' growth leads to improved whole body insulin sensitivity in rat offspring

A suboptimal in utero environment leads to fetal adaptations to ensure short-term survival but in the long-term may lead to disease when the postnatal growth does not reflect that in utero. This study examined the effect of IUGR on whole body insulin sensitivity and metabolic activity in adult rats. Female Wistar-Kyoto rats were fed either a normal protein diet (NPD 20% casein) or a low protein diet (LPD; 8.7% casein) during pregnancy and 2 wk of lactation. In offspring at 32 wk of age, indirect calorimetry and dual energy x-ray absorptiometry (DEXA) were performed to assess metabolic activity and body composition. Insulin sensitivity was assessed using a euglycemic-hyperinsulinemic clamp. At 3 d of age, male and female LPD offspring were 23 and 27% smaller than controls, respectively. They remained significantly smaller throughout the experimental period (~10% smaller at 32 wk). Importantly, there was increased insulin sensitivity in LPD offspring (47% increase in males and 38% increase in females); pancreatic insulin content was normal. Body composition, O2 consumption, respiratory exchange ratio (RER), and locomotor activity were not different to controls. These findings suggest that in the absence of “catch-up” growth IUGR programs for improved insulin sensitivity.