Dysglycemia and liver lipid content determine the relationship of insulin resistance with hepatic OXPHOS capacity in obesity.

BACKGROUND & AIMS: Hepatic mitochondrial respiration is higher in steatosis, but lower in overt type 2 diabetes. We hypothesized that hepatic OXPHOS capacity increases with a greater degree of insulin resistance in obesity, independent of other metabolic diseases. METHODS: We analysed 65 humans without diabetes (BMI 50±7 kg/m2, HbA1c 5.5±0.4%) undergoing bariatric surgery. MASLD stages were assessed by histology, whole-body insulin sensitivity (PREDIcted-M index) by oral glucose tolerance tests, and maximal ADP-stimulated mitochondrial OXPHOS capacity by high-resolution respirometry of liver samples. RESULTS: Prediabetes was present in 30 participants, and MASLD in 46 participants. Thereof, 25 had metabolic dysfunction-associated steatohepatitis (MASH), and seven had F2-F3 fibrosis. While simple regression did not detect an association of insulin sensitivity with hepatic OXPHOS capacity, interaction analyses revealed that the regression coefficient of OXPHOS capacity depended on fasting plasma glucose (FPG) and liver lipid content. Interestingly, the respective slopes were negative for FPG ≤100 mg/dl, but positive for FPG >100 mg/dl. Liver lipid content displayed similar behavior, with a threshold value of 24%. Post-challenge glycemia affected the association between insulin sensitivity and OXPHOS capacity normalized for citrate synthase activity. Presence of prediabetes affected hepatic insulin signaling, mitochondrial dynamics and fibrosis prevalence, while the presence of MASLD related to higher biomarkers of hepatic inflammation, cell damage and lipid peroxidation in people with normal glucose tolerance. CONCLUSIONS: Rising liver lipid contents and plasma glucose concentrations, even in the non-diabetic range, are associated with a progressive decline of hepatic mitochondrial adaptation in people with obesity and insulin resistance. CLINTRIALS. GOV IDENTIFIER: NCT01477957.

Persistence of remission after lengthening of golimumab in inflammatory joint diseases.

OBJECTIVES: In refractory inflammatory joint diseases (IJDs) biological disease-modifying anti-rheumatic drugs (bDMARDs) may achieve remission. EULAR recommends bDMARD tapering when remission persists. However, guidelines on tapering modalities and criteria for patient selection are lacking. We aimed to evaluate remission persistency after lengthening the time between injections of golimumab in patients affected by IJD and to identify any patient or disease characteristics associated to flare after lengthening. METHODS: Patients affected by rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and juvenile idiopathic arthritis (JIA) treated with golimumab were enrolled in a retrospective observational study. Demographic data, ESR, cRP, DAS28/ BASDAI, were collected at baseline and during the follow-up (T1- defined as a medical check-up after 1 year of treatment or, for patients with longerg exposure, the first medical check-up in 2016, when at our unit we began to experience drug tapering- and T2- 12 months after the lengthening was started). In 22/80 patients in remission at T1, injection time was lengthened. RESULTS: Eighty patients were enrolled, 34 AS, 33 PsA, 9RA and 4 JIA. At baseline, all had an active disease. At T1, 60/80 patients reached remission and 22/60 patients started tapering. At T2, 20/22 pts (91%) were in remission. At T1 BASDAI was higher (2.2, SD 0.28 vs. 0.58, SD 0.47; p<0.001) in patients who lost remission at T2.Patients who flared recovered remission once taken back to a 28-day interval. 4/38 patients maintained at the standard dose flared up and switched/swapped bDMARD. The difference in retention rate toward patients on reduced dose was not significant. CONCLUSIONS: Results show that golimumab lengthening is safe and successfully maintains remission. In patients who experienced a flare after lengthening, the standard regimen promptly restored remission.

Rheumatology residency in a European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases centre: opportunities and challenges.

Rheumatology is a growing medical speciality with many attractive points to young doctors. Residency is a demanding period of a physician's life, and choosing the right hospital for one's residency may not be easy. We report on our personal experience as Rheumatology residents in European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases (ERN-ReCONNET) centres.

Persistent whole day meal effects of three dipeptidyl peptidase-4 inhibitors on glycaemia and hormonal responses in metformin-treated type 2 diabetes.

AIM: Dipeptidyl peptidase-4 (DPP-4) inhibition has effects on both fasting and postprandial glucose. However, the extent of this effect over the whole day and whether different DPP-4 inhibitors have the same effects have not been established. We therefore explored the whole day effects of three different DPP-4 inhibitors versus placebo on glucose, islet and incretin hormones after ingestion of breakfast, lunch and dinner in subjects with metformin-treated and well-controlled type 2 diabetes. METHODS: The study was single-centre and crossover designed, involving 24 subjects [12 men, 12 women, mean age 63 years, body mass index 31.0 kg/m2 , glycated haemoglobin 44.7 mmol/mol (6.2%)], who underwent four test days in random order. Each whole day test included ingestion of standardized breakfast (525 kcal), lunch (780 kcal) and dinner (560 kcal) after intake of sitagliptin (100 mg) or vildagliptin (50 mg twice), or saxagliptin (5 mg) or placebo. RESULTS: Compared with placebo, DPP-4 inhibition reduced glucose levels, increased beta-cell function (insulin secretory rate in relation to glucose), suppressed glucagon, increased intact glucagon-like-peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) but suppressed total GLP-1 and GIP after all three meals. The effects were sustained throughout the daytime period with similar changes after each meal and did not differ between the DPP-4 inhibitors. CONCLUSIONS: DPP-4 inhibition has persistent daytime effects on glucose, islet and incretin hormones with no difference between three different DPP-4 inhibitors.

Cardiometabolic risk factor clustering in patients with deficient branched-chain amino acid catabolism: A case-control study.

Classical organic acidemias (OAs) result from defective mitochondrial catabolism of branched-chain amino acids (BCAAs). Abnormal mitochondrial function relates to oxidative stress, ectopic lipids and insulin resistance (IR). We investigated whether genetically impaired function of mitochondrial BCAA catabolism associates with cardiometabolic risk factors, altered liver and muscle energy metabolism, and IR. In this case-control study, 31 children and young adults with propionic acidemia (PA), methylmalonic acidemia (MMA) or isovaleric acidemia (IVA) were compared with 30 healthy young humans using comprehensive metabolic phenotyping including in vivo 31 P/1 H magnetic resonance spectroscopy of liver and skeletal muscle. Among all OAs, patients with PA exhibited abdominal adiposity, IR, fasting hyperglycaemia and hypertriglyceridemia as well as increased liver fat accumulation, despite dietary energy intake within recommendations for age and sex. In contrast, patients with MMA more frequently featured higher energy intake than recommended and had a different phenotype including hepatomegaly and mildly lower skeletal muscle ATP content. In skeletal muscle of patients with PA, slightly lower inorganic phosphate levels were found. However, hepatic ATP and inorganic phosphate concentrations were not different between all OA patients and controls. In patients with IVA, no abnormalities were detected. Impaired BCAA catabolism in PA, but not in MMA or IVA, was associated with a previously unrecognised, metabolic syndrome-like phenotype with abdominal adiposity potentially resulting from ectopic lipid storage. These findings suggest the need for early cardiometabolic risk factor screening in PA.

Insulin clearance is altered in women with a history of gestational diabetes progressing to type 2 diabetes.

BACKGROUND AND AIMS: Insulin clearance is a relevant process in glucose homeostasis. In this observational study, we aimed to assess insulin clearance (ClINS) in women with former gestational diabetes (fGDM) both early after delivery and after a follow-up. METHODS AND RESULTS: We analysed 59 fGDM women, and 16 women not developing GDM (CNT). All women underwent an oral glucose tolerance test (OGTT) yearly, and an insulin-modified intravenous glucose tolerance test (IVGTT) at baseline and at follow-up end (until 7 years). Both IVGTT and OGTT ClINS was assessed as insulin secretion to plasma insulin ratio. We also defined IVGTT first (0-10 min) and second phase (10-180 min) ClINS. We found that 14 fGDM women progressed to type 2 diabetes (PROG), whereas 45 women remained diabetes-free (NONPROG). At baseline, IVGTT ClINS showed alterations in PROG, especially in second phase (0.88 ± 0.10 l·min-1 in PROG, 0.60 ± 0.06 in NONPROG, 0.54 ± 0.07 in CNT, p ≤ 0.03). Differences in ClINS were not found from OGTT. Cox regression analysis showed second phase ClINS as significant type 2 diabetes predictor (hazard ratio = 1.90, 95% confidence interval 1.09-3.30, p = 0.02). CONCLUSION: This study showed that insulin clearance derived from an insulin-modified IVGTT is notably altered in women with history of GDM progressing towards type 2 diabetes.

Empagliflozin in posttransplantation diabetes mellitus: A prospective, interventional pilot study on glucose metabolism, fluid volume, and patient safety.

The safety and efficacy of sodium-glucose cotransporter 2 inhibitors in posttransplantation diabetes mellitus is unknown. We converted stable kidney transplant patients to 10 mg empagliflozin, aiming at replacing their insulin therapy (<40 IU/d). N = 14 participants (the required sample size) completed the study visits through 4 weeks and N = 8 through 12 months. Oral glucose tolerance test (OGTT)-derived 2-hour glucose (primary end point) increased from 232 ± 82 mg/dL (baseline) to 273 ± 116 mg/dL (4 weeks, P = .06) and to 251 ± 71 mg/dL (12 months, P = .41). Self-monitored blood glucose and hemoglobin A1c were also clinically inferior with empagliflozin monotherapy, such that insulin was reinstituted in 3 of 8 remaining participants. Five participants (2 of them dropouts) vs nine of 24 matched reference patients developed bacterial urinary tract infections (P = .81). In empagliflozin-treated participants, oral glucose insulin sensitivity decreased and beta-cell glucose sensitivity increased at the 4-week and 12-month OGTTs. Estimated glomerular filtration rate and bioimpedance spectroscopy-derived extracellular and total body fluid volumes decreased by 4 weeks, but recovered. All participants lost body weight. No participant developed ketoacidosis; 1 patient developed balanitis. In conclusion, although limited by sample size and therefore preliminary, these results suggest that empagliflozin can safely be used as add-on therapy, if posttransplant diabetes patients are monitored closely (NCT03113110).

Glucagon and insulin secretion, insulin clearance, and fasting glucose in GIP receptor and GLP-1 receptor knockout mice.

It is not known whether GIP receptor and GLP-1 receptor knockout (KO) mice have perturbations in glucagon secretion or insulin clearance, and studies on impact on fasting glycemia have previously been inconsistent in these mice. We therefore studied glucagon secretion after oral whey protein (60 mg) and intravenous arginine (6.25 mg), insulin clearance after intravenous glucose (0.35 g/kg) and fasting glucose, insulin, and glucagon levels after standardized 5-h fasting in female GIP receptor and GLP-1 receptor KO mice and their wild-type (WT) littermates. Compared with WT controls, GIP receptor KO mice had normal glucagon responses to oral protein and intravenous arginine, except for an enhanced 1-min response to arginine, whereas glucagon levels after oral protein and intravenous arginine were enhanced in GLP-1 receptor KO mice. Furthermore, the intravenous glucose test revealed normal insulin clearance in both GIP receptor and GLP-1 receptor KO mice, whereas ß-cell glucose sensitivity was enhanced in GIP receptor KO mice and reduced in GLP-1 receptor KO mice. Finally, GIP receptor KO mice had reduced fasting glucose (6.7 ± 0.1, n = 56, vs. 7.4 ± 0.1 mmol/l, n = 59, P = 0.001), whereas GLP-1 receptor KO mice had increased fasting glucose (9.1 ± 0.2, n = 44, vs. 7.7 ± 0.1 mmol/l, n = 41, P < 0.001). We therefore suggest that GIP has a limited role for glucagon secretion in mice, whereas GLP-1 is of importance for glucagon regulation, that GIP and GLP-1 are of importance for the regulation of ß-cell function beyond their role as incretin hormones, and that they are both of importance for fasting glucose.

Glucose effectiveness and its components in relation to body mass index.

BACKGROUND: Obesity is known to induce a deterioration of insulin sensitivity (SI ), one of the insulin-dependent components of glucose tolerance. However, few studies investigated whether obesity affects also the insulin-independent component, that is glucose effectiveness (SG ). This cross-sectional study aimed to analyse SG and its components in different body mass index (BMI) categories. MATERIALS AND METHODS: Three groups of subjects spanning different BMI (kg m-2 ) categories underwent a 3-h frequently sampled intravenous glucose tolerance test: Lean (LE; 18.5 ≤ BMI < 25, n = 73), Overweight (OW; 25 ≤ BMI < 30, n = 90), and Obese (OB; BMI ≥ 30, n = 41). OB has been further divided into two subgroups, namely Obese I (OB-I; 30 ≤ BMI < 35, n = 27) and Morbidly Obese (OB-M; BMI ≥ 35, n = 14). Minimal model analysis provided SG and its components at zero (GEZI) and at basal (BIE) insulin. RESULTS: Values for SG were 1.98 ± 1.30 × 10-2 ·min-1 in all subjects grouped and 2.38 ± 1.23, 1.84 ± 0.82, 1.59 ± 0.61 10-2 ·min-1 in LE, OW and OB, respectively. In all subjects grouped, a significant inverse linear correlation was found between the log-transformed values of SG and BMI (r = -0.3, P < 0.0001). SG was significantly reduced in OW and OB with respect to LE (P < 0.001) but no significant difference was detected between OB and OW (P = 0.35) and between OB-I and OB-M (P = 0.25). Similar results were found for GEZI. BIE was not significantly different among NW, OW and OB (P = 0.11) and between OB-I and OB-M (P ≥ 0.07). CONCLUSIONS: SG and its major component GEZI deteriorate in overweight individuals compared to those in the normal BMI range, without further deterioration when BMI increases above 30 kg m-2 .

MARKEDLY DELAYED INSULIN SECRETION AND A HIGH RATE OF UNDETECTED OVERT DIABETES CHARACTERIZE GLUCOSE METABOLISM IN ADULT PATIENTS WITH CYSTIC FIBROSIS AFTER LUNG TRANSPLANTATION.

OBJECTIVE: Cystic fibrosis-related diabetes (CFRD) is associated with adverse clinical outcomes and should be screened for by an annual oral glucose tolerance test (OGTT). Since pathophysiologic studies have mainly been performed in a pediatric/adolescent, nontransplanted collective, we aimed to assess parameters of insulin secretion and sensitivity in adult cystic fibrosis (CF) patients after lung transplantation (LT). METHODS: Twelve adult CF patients after LT without known diabetes (33.3 ± 11.5 years; body mass index [BMI] 21.5 ± 3.3 kg/m2) and 8 control subjects matched by age (36.0 ± 6.6 years; P>.05), BMI (22.3 ± 1.5 kg/m2; P>.05), and gender (CON group) underwent a 3-hour OGTT with glucose, insulin, and C-peptide measurements. Parameters of insulin secretion and sensitivity as well as lipid profiles were assessed. RESULTS: In the CF group, 4 patients were diagnosed with overt diabetes (CFRD) compared to CF patients without diabetes (CF-noDM), of whom 6 had indeterminate glycemia with 1-h glucose values >200 mg/dL. The insulin peak after glucose load occurred after 30 minutes in CON, after 90 minutes in CF-noDM, and was missing in CFRD. Insulin sensitivity was comparable between the groups. Beta-cell glucose sensitivity was markedly reduced in CFRD (10.7 ± 5.8 pmol/min*m2*mM), higher in CF-noDM (39.9 ± 23.4 pmol/min*m2*mM), but still significantly lower compared to CON (108.3 ± 53.9 pmol/min*m2*mM; P = .0008). CFRD patients exhibited increased triglyceride levels and decreased high-density lipoprotein levels. CONCLUSION: Adult CF patients after LT have profound disturbances in glucose metabolism, with a high rate of undetected diabetes and markedly delayed insulin secretion. Curbed beta-cell glucose sensitivity rather than insulin resistance explains postprandial hyperglycemia and is accompanied by abnormalities in lipid metabolism. ABBREVIATIONS: AUC = area under the curve; BMI = body mass index; CF = cystic fibrosis; CFRD = cystic fibrosis-related diabetes; CFTR = cystic fibrosis transmembrane-conductance regulator; CF-TX = cystic fibrosis patients who underwent lung transplantation; CGM = continuous glucose monitoring; HbA1c = glycated hemoglobin; HDL = high-density lipoprotein; INDET = indeterminate glycemia; LDL = low-density lipoprotein; LT = lung transplantation; OGIS = oral glucose sensitivity index; OGTT = oral glucose tolerance test; QUICKI = quantitative insulin sensitivity check index.

Prediction of clamp-derived insulin sensitivity from the oral glucose insulin sensitivity index.

AIMS/HYPOTHESIS: The euglycaemic-hyperinsulinaemic clamp is the gold-standard method for measuring insulin sensitivity, but is less suitable for large clinical trials. Thus, several indices have been developed for evaluating insulin sensitivity from the oral glucose tolerance test (OGTT). However, most of them yield values different from those obtained by the clamp method. The aim of this study was to develop a new index to predict clamp-derived insulin sensitivity (M value) from the OGTT-derived oral glucose insulin sensitivity index (OGIS). METHODS: We analysed datasets of people that underwent both a clamp and an OGTT or meal test, thereby allowing calculation of both the M value and OGIS. The population was divided into a training and a validation cohort (n = 359 and n = 154, respectively). After a stepwise selection approach, the best model for M value prediction was applied to the validation cohort. This cohort was also divided into subgroups according to glucose tolerance, obesity category and age. RESULTS: The new index, called PREDIcted M (PREDIM), was based on OGIS, BMI, 2 h glucose during OGTT and fasting insulin. Bland-Altman analysis revealed a good relationship between the M value and PREDIM in the validation dataset (only 9 of 154 observations outside limits of agreement). Also, no significant differences were found between the M value and PREDIM (equivalence test: p < 0.0063). Subgroup stratification showed that measured M value and PREDIM have a similar ability to detect intergroup differences (p < 0.02, both M value and PREDIM). CONCLUSIONS/INTERPRETATION: The new index PREDIM provides excellent prediction of M values from OGTT or meal data, thereby allowing comparison of insulin sensitivity between studies using different tests.

Increased insulin clearance in mice with double deletion of glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide receptors.

To establish whether incretin hormones affect insulin clearance, the aim of this study was to assess insulin clearance in mice with genetic deletion of receptors for both glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), so called double incretin receptor knockout mice (DIRKO). DIRKO ( n = 31) and wild-type (WT) C57BL6J mice ( n = 45) were intravenously injected with d-glucose (0.35 g/kg). Blood was sampled for 50 min and assayed for glucose, insulin, and C-peptide. Data were modeled to calculate insulin clearance; C-peptide kinetics was established after human C-peptide injection. Assessment of C-peptide kinetics revealed that C-peptide clearance was 1.66 ± 0.10 10-3 1/min. After intravenous glucose administration, insulin clearance during first phase insulin secretion was markedly higher in DIRKO than in WT mice (0.68 ± 0.06 10-3 l/min in DIRKO mice vs. 0.54 ± 0.03 10-3 1/min in WT mice, P = 0.02). In contrast, there was no difference between the two groups in insulin clearance during second phase insulin secretion ( P = 0.18). In conclusion, this study evaluated C-peptide kinetics in the mouse and exploited a mathematical model to estimate insulin clearance. Results showed that DIRKO mice have higher insulin clearance than WT mice, following intravenous injection of glucose. This suggests that incretin hormones reduce insulin clearance at physiological, nonstimulated levels.

Effect of single-dose DPP-4 inhibitor sitagliptin on ß-cell function and incretin hormone secretion after meal ingestion in healthy volunteers and drug-naïve, well-controlled type 2 diabetes subjects.

To explore the effects of a single dose of the DPP-4 inhibitor sitagliptin on glucose-standardized insulin secretion and ß-cell glucose sensitivity after meal ingestion, 12 healthy and 12 drug-naïve, well-controlled type 2 diabetes (T2D) subjects (mean HbA1c 43 mmol/mol, 6.2%) received sitagliptin (100 mg) or placebo before a meal (525 kcal). ß-cell function was measured as the insulin secretory rate at a standardized glucose concentration and the ß-cell glucose sensitivity (the slope between glucose and insulin secretory rate). Incretin levels were also monitored. Sitagliptin increased standardized insulin secretion, in both healthy and T2D subjects, compared to placebo, but without increasing ß-cell glucose sensitivity. Sitagliptin also increased active glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) and reduced total (reflecting the secretion) GIP, but not total GLP-1 levels. We conclude that a single dose of DPP-4 inhibition induces dissociated effects on different aspects of ß-cell function and incretin hormones after meal ingestion in both healthy and well-controlled T2D subjects.

The Fatty Liver Index (FLI) Relates to Diabetes-Specific Parameters and an Adverse Lipid Profile in a Cohort of Nondiabetic, Dyslipidemic Patients.

BACKGROUND: Patients with hyperlipidemia are at high risk for developing a fatty liver. The fatty liver index (FLI) is a noninvasive and well-established method for the estimation of a fatty liver. However, little is known about the metabolic characterization of nondiabetic treated patients with hyperlipidemia who have different risk levels for a fatty liver. METHODS: In this study, 74 nondiabetic patients with hyperlipidemia were divided into 3 groups according to their fatty liver index. A comparison of metabolic characteristics was done. These characteristics included intima media thickness (IMT) and nutritional habits, which were further divided into FLI subgroups with low, intermediate, and high risk for a fatty liver. RESULTS: Patients with hyperlipidemia, with a high risk for a fatty liver (FLI ≥ 60), had subclinical elevations in parameters of carbohydrate metabolism (insulin, fasting plasma glucose, C-peptide) including a higher insulin resistance (quantitative insulin sensitivity check index, QUICKI) compared to lower FLI groups. These patients also presented a higher risk for a metabolic syndrome (p = 0.018), as well as an adverse lipid profile (e.g., high-density lipoprotein [HDL] cholesterol, triglycerides [TG]-HDL ratio). FLI group 3 was characterized by significantly lower levels of omega-3 fatty acids (p = 0.048). CONCLUSION: The fatty liver index relates to diabetes-specific parameters and an adverse lipid profile and is an appropriate index for risk evaluation of metabolic syndrome.

Insulin resistance and beta-cell dysfunction in people with prediabetes according to criteria based on glycemia and glycosylated hemoglobin.

Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are well-known conditions of risk for diabetes. Recently, 1h-hyperglycemia (1h-HG), i.e., glycemia > 8.6 mmol/L, has been suggested as further condition of diabetes risk. Moreover, in 2010 the American Diabetes Association included the measurement of glycosylated hemoglobin (HbA1c) among the criteria of diabetes risk (5.7-6.4%). Aim of this study was investigating all these different conditions of diabetes risk, with specific focus on possible insulin sensitivity and beta-cell function changes, when 1h-HG, and further HbA1c-prediabetes, are added to the already deeply studied condition of IFG/IGT. In this study, we retrospectively analysed 744 participants that underwent 2h-OGTT and HbA1c measurement. Participants were stratified into groups: (i) normal glucose tolerance, NGT (n=178); (ii) IFG and/or IGT (n=88); (iii) IFG/IGT plus 1h-HG (n=342); (iv) IFG/IGT plus 1h-HG plus HbA1c-prediabetes (n=136). We calculated several indices of insulin sensitivity and beta-cell function, as well as an index considering both aspects (disposition index). We found that progressing from group (i) to group (iv) both insulin sensitivity and beta-cell function tended to further deteriorate; the parameter providing more evidence was the disposition index (p<0.008 in any group comparison). In conclusion, for appropriate assessment of the level of diabetes risk (especially in people already known to be at high risk), it may be convenient to measure all the indicated parameters, that is, glycemia at fasting, at one hour and two hours during OGTT, and glycosylated hemoglobin.

Human insulin dynamics in women: a physiologically based model.

Currently available models of insulin dynamics are mostly based on the classical compartmental structure and, thus, their physiological utility is limited. In this work, we describe the development of a physiologically based model and its application to data from 154 patients who underwent an insulin-modified intravenous glucose tolerance test (IM-IVGTT). To determine the time profile of endogenous insulin delivery without using C-peptide data and to evaluate the transcapillary transport of insulin, the hepatosplanchnic, renal, and peripheral beds were incorporated into the circulatory model as separate subsystems. Physiologically reasonable population mean estimates were obtained for all estimated model parameters, including plasma volume, interstitial volume of the peripheral circulation (mainly skeletal muscle), uptake clearance into the interstitial space, hepatic and renal clearance, as well as total insulin delivery into plasma. The results indicate that, at a population level, the proposed physiologically based model provides a useful description of insulin disposition, which allows for the assessment of muscle insulin uptake.

Sfrp5 associates with beta-cell function in humans.

BACKGROUND: Secreted frizzled-related protein (Sfrp)5 improves insulin sensitivity, but impairs beta-cell function in rodents. However, the relationship between Sfrp5, insulin sensitivity and secretion in humans is currently unclear. Therefore, the aim of the study was to characterize the associations between serum Sfrp5 and indices of insulin sensitivity and beta-cell function from dynamic measurements using oral glucose tolerance tests (OGTT) in humans. MATERIAL AND METHODS: This study enrolled 194 individuals with nonalcoholic fatty liver disease (NAFLD), who were diagnosed based on ultrasound and liver transaminases and underwent a frequent sampling 75-g OGTT. Fasting serum Sfrp5 was measured by ELISA. Associations were assessed with several indices of insulin sensitivity and beta-cell function derived from glucose, insulin and C-peptide concentrations during the OGTT. RESULTS: Circulating Sfrp5 associated inversely with the insulinogenic index based on C-peptide (rs = -0·244, P = 0·001), but not with the insulinogenic index based on insulin levels (rs = -0·007, P = 0·926) after adjustment for age, sex and body mass index. Sfrp5 inversely correlated only with QUICKI as a marker of insulin sensitivity in the model adjusted for age and sex (rs = -0·149, P = 0·039). These associations were not influenced by the additional adjustment for hepatic steatosis index. CONCLUSIONS: The inverse association of serum Sfrp5 with beta-cell function suggests a detrimental role of Sfrp5 for insulin secretion also in humans. The severity of NAFLD does not appear to affect this relationship. The weak association between serum Sfrp5 and insulin sensitivity was partially explained by body mass.

Pancreatic adipose tissue infiltration, parenchymal steatosis and beta cell function in humans.

AIMS/HYPOTHESIS: This study aimed to perform a comprehensive analysis of interlobular, intralobular and parenchymal pancreatic fat in order to assess their respective effects on beta cell function. METHODS: Fifty-six participants (normal glucose tolerance [NGT] (n = 28), impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) (n = 14) and patients with type 2 diabetes (n = 14)) underwent a frequent-sampling OGTT and non-invasive magnetic resonance imaging (MRI; whole-body and pancreatic) and proton magnetic resonance spectroscopy ((1)H-MRS; liver and pancreatic fat). Total pancreatic fat was assessed by a standard 2 cm(3) (1)H-MRS method, intralobular fat by 1 cm(3) (1)H-MRS that avoided interlobular fat within modified DIXON (mDIXON) water images, and parenchymal fat by a validated mDIXON-MRI fat-fraction method. RESULTS: Comparison of (1)H-MRS techniques revealed an inhomogeneous distribution of interlobular and intralobular adipose tissue, which increased with decreasing glucose tolerance. mDIXON-MRI measurements provided evidence against uniform steatosis, revealing regions of parenchymal tissue void of lipid accumulation in all participants. Total (r = 0.385, p < 0.01) and intralobular pancreas adipose tissue infiltration (r = 0.310, p < 0.05) positively associated with age, but not with fasting or 2 h glucose levels, BMI or visceral fat content (all p > 0.5). Furthermore, no associations were found between total and intralobular pancreatic adipose tissue infiltration and insulin secretion or beta cell function within NGT, IFG/IGT or patients with type 2 diabetes (all p > 0.2). CONCLUSIONS/INTERPRETATION: The pancreas does not appear to be another target organ for abnormal endocrine function because of ectopic parenchymal fat storage. No relationship was found between pancreatic adipose tissue infiltration and beta cell function, regardless of glucose tolerance status.