Elimination of Contrast Agent Gadobutrol with Sustained Low Efficiency Daily Dialysis Compared to Intermittent Hemodialysis.

BACKGROUND: In patients with renal failure, gadolinium-based contrast agents (GBCA) can be removed by intermittent hemodialysis (iHD) to prevent possible toxic effects. There is no data on the efficacy of GBCA removal via sustained low efficiency daily dialysis (SLEDD) which is mainly used in intensive care unit (ICU) patients. METHODS: We compared the elimination of the GBCA gadobutrol in 6 ICU patients treated with SLEDD (6-12 h, 90 L dialysate) with 7 normal ward inpatients treated with iHD (4 h, dialysate flow 500 mL/min). Both groups received 3 dialysis sessions on 3 consecutive days starting after the application of gadobutrol. Blood samples were drawn before and after each session and total dialysate, as well as urine was collected. Gadolinium (Gd) concentrations were measured using mass spectrometry and eliminated Gd was calculated from dialysate and urine. RESULTS: The initial mean plasma Gd concentration was 385 ± 183 µM for the iHD and 270 ± 97 µM for the SLEDD group, respectively (p > 0.05). The Gd-reduction rate after the first dialysis session was 83 ± 9 and 67 ± 9% for the iHD and the SLEDD groups, respectively (p = 0.0083). The Gd-reduction rate after the second and third dialysis was 94-98 and 89-96% for the iHD and the SLEDD groups (p > 0.05). The total eliminated Gd was 89 ± 14 and 91 ± 4% of the dose in the iHD and the SLEDD groups, respectively (p > 0.05). Gd dialyzer clearance was 95 ± 22 mL/min and 79 ± 19 mL/min for iHD and SLEDD, respectively (p > 0.05). CONCLUSIONS: Gd-elimination with SLEDD is equally effective as iHD and can be safely used to remove GBCA in ICU patients.

Urinary Neutrophil Gelatinase-Associated Lipocalin (NGAL) and proteinuria predict severity of acute kidney injury in Puumala virus infection.

BACKGROUND: Nephropathia epidemica (NE) is a mild form of hemorrhagic fever with renal syndrome (HFRS) that is caused by the Puumala virus. Periodic outbreaks have been described in endemic areas, with a substantial number of previously healthy individuals developing acute kidney injury (AKI). There is a considerable diversity in the clinical course of the disease, and few patients require renal replacement therapy. METHODS: We tested whether urinary neutrophil gelatinase associated lipocalin (uNGAL), urine albumin/creatinine ratio (uACR), urine protein/creatinine ratio (uPCR), urine dipstick protein, C-reactive protein, procalcitonin, leukocyte and platelet count, determined on admission to the hospital, can predict the severity of AKI. Sixty-one patients were analyzed during admission in the emergency department. RESULTS: The variables most strongly associated with peak plasma creatinine concentration were uNGAL (ß = 0.70, p <0.0001), uPCR (ß = 0.64, p = 0.001), uACR (ß = 0.61, p = 0.002), and dipstick proteinuria (ß = 0.34, p = 0.008). The highest AUC-ROC to predict stage 3 AKI according to the acute kidney injury network's (AKIN) classification was seen for uNGAL (0.81, p = 0.001). CONCLUSION: uNGAL accurately predicts the severity of AKI in NE. This could help emergency room physicians predict disease severity and allow for initial risk stratification.

Leptin affects insulin action in astrocytes and impairs insulin-mediated physical activity.

BACKGROUND/AIMS: Impaired insulin action is an early event in the pathogenesis of obesity and type 2-diabetes, and among the metabolic confounders in obese, hyperleptinaemia is constantly present; however its impact on insulin action in the brain and locomotor activity is unknown. METHODS: We examined insulin action by Western Blot analysis and glycogen synthesis in primary astrocytes and brain tissue and detected locomotion in C57BL/6 mice. The insulin-mediated desire to move was evaluated in healthy volunteers and correlated to leptin levels. RESULTS: Leptin treatment led to a significant decrease in insulin-mediated phosphorylation of the insulin receptor and Akt473 which was accompanied by a decline in glycogen synthesis in primary astrocytes and significantly decreased insulin-induced phosphorylation of the insulin receptor and insulin receptor substrate-2 in brain tissues of mice. Intracerebroventricular insulin failed to promote locomotion in the presence of elevated leptin levels. Lean human subjects reported an increase in the desire to move following insulin which failed in obese and there was an inverse correlation between the insulin-mediated desire to move and leptin levels. CONCLUSIONS: Our data suggest a crosstalk of leptin and insulin in the brain which leads to a decline in locomotor activity. This might represent a molecular mechanism in obese to inhibit physical activity.

Metformin Associated Lactic Acidosis in Clinical Practice - A Case Series.

AIMS: The aim of this case report is to specify the frequency and mortality of Metformin-Associated Lactic Acidosis (MALA) in emergency medicine, as the diagnosis seems to occur more often than estimated. METHODS: To identify the subjects, we developed screening criteria for MALA. We measured the serum metformin concentration to confirm the diagnosis in all patients fulfilling these criteria. Retrospectively the patients were grouped according to individual risk (according to a defined risk score) and the application of renal replacement therapy. RESULTS: From 2013 until 2018 we were able to identify 11 MALA patients revealing a frequency of 1:4,000 emergency patients. Six patients survived and five died in the follow-up. All three patients in the high-risk group died although all of them received renal replacement therapy. In the low-risk group (three patients, one with renal replacement therapy), all patients survived, while in the intermediate-risk group (five patients, one with renal replacement therapy) three patients survived and two died. Additional severe comorbidities also contributed to mortality. CONCLUSIONS: Every patient matching the screening criteria of acute renal failure, lactic acidosis and continued intake of metformin can be considered a potential MALA case. A risk score assessment which includes severe comorbidities may help to identify high-risk individuals and should be evaluated in larger studies.To prevent MALA, patients should be trained to immediately interrupt their own metformin use when showing signs of volume depletion. Physicians should be aware of the additional risk factors such as co-medication with diuretics, ACE (angiotensin converting enzyme) ACE inhibitors and NSAIDs (non steroidal anti inflammatory drugs).

The temporal sequence of magnetic brain activity for food categorization and memorization--an exploratory study.

The importance of food stimuli for all living organisms is defined by their relevance for survival. Therefore, visual processing of food stimuli is influenced by many factors, such as cultural and societal background. In this magnetoencephalography (MEG) study, we examined the categorization and memorization of visual food and non-food stimuli in lean subjects, using a one-back working memory task. We found an increase in neural activity in several different regions of the brain elicited by food stimuli in comparison to non-food stimuli. The first observed significant difference was found in low-level visual areas as early as 120 ms after stimulus onset. The stimulus category of the previous picture did not influence this effect. However, preceding stimuli modulated behavioral measures (reaction time and accuracy of responses) and later components of the evoked responses around 350 ms. The evoked magnetic field of this late component showed a significant increase inactivity in the temporal cortex for food versus non-food objects. This late component exhibited a significant correlation with the reaction time. The difference of category-specific effects in the early components and the behavioral modulation of late components could be useful for further investigations of the cortical activity in response to food stimuli, e.g. in subjects with eating disorders or obesity.

Brain insulin sensitivity is linked to adiposity and body fat distribution.

Brain insulin action regulates eating behavior and energy fluxes throughout the body. However, numerous people are brain insulin resistant. How brain insulin responsiveness affects long-term weight and body fat composition in humans is still unknown. Here we show that high brain insulin sensitivity before lifestyle intervention associates with a more pronounced reduction in total and visceral fat during the program. High brain insulin sensitivity is also associated with less regain of fat mass during a nine year follow-up. Cross-sectionally, strong insulin responsiveness of the hypothalamus associates with less visceral fat, while subcutaneous fat is unrelated. Our results demonstrate that high brain insulin sensitivity is linked to weight loss during lifestyle intervention and associates with a favorable body fat distribution. Since visceral fat is strongly linked to diabetes, cardiovascular risk and cancer, these findings have implications beyond metabolic diseases and indicate the necessity of strategies to resolve brain insulin resistance.

Effect of genetic variation in Kv1.3 on olfactory function.

BACKGROUND: Olfactory function is reduced in aged humans and diabetes mellitus patients. However, little is known about the pathogenic mechanisms leading to olfactory dysfunction. Recently, it has been shown that the voltage-gated potassium channel Kv1.3 is regulated by insulin and is highly expressed in the olfactory bulb. Furthermore, the function of this channel is associated with olfaction in mice and with glucose metabolism in mice and men. We therefore hypothesized that a functionally relevant polymorphism in Kv1.3 might alter olfactory function. METHODS: We investigated a group of 94 healthy subjects (male: n = 58, female: n = 36) for olfactory function and genotyped them for rs2821557 in the human Kv1.3 gene. Olfactory function was tested using standardised sniffing sticks, and parameters of glucose metabolism were assessed. RESULTS: We found a significant olfactory impairment in male homozygous carriers of the Kv1.3 polymorphism rs2821557 (recessive model, p = 0.018, adjusted for age) that could not be determined in female subjects due to the very small number of homozygous minor allele carriers (n = 1). In addition, we found a significant correlation of olfactory dysfunction with higher HbA1c and fasting plasma glucose (p = 0.004 and p = 0.001, both adjusted for age). We also found a loss of olfactory function with age (p = 0.006). Gender, body mass index and insulin sensitivity did not alter smelling function. CONCLUSIONS: The presence of genetic variation in Kv1.3 is associated with decreased olfactory function in healthy subjects. As olfactory function, glucose metabolism and genetic variation in Kv1.3 seem to be associated, further studies are needed to clarify the underlying mechanisms.

SIRT1 genetic variants associate with the metabolic response of Caucasians to a controlled lifestyle intervention--the TULIP Study.

BACKGROUND: Sirtuin1 (SIRT1) regulates gene expression in distinct metabolic pathways and mediates beneficial effects of caloric restriction in animal models. In humans, SIRT1 genetic variants associate with fasting energy expenditure. To investigate the relevance of SIRT1 for human metabolism and caloric restriction, we analyzed SIRT1 genetic variants in respect to the outcome of a controlled lifestyle intervention in Caucasians at risk for type 2 diabetes. METHODS: A total of 1013 non-diabetic Caucasians from the Tuebingen Family Study (TUEF) were genotyped for four tagging SIRT1 SNPs (rs730821, rs12413112, rs7069102, rs2273773) for cross-sectional association analyses with prediabetic traits. SNPs that associated with basal energy expenditure in the TUEF cohort were additionally analyzed in 196 individuals who underwent a controlled lifestyle intervention (Tuebingen Lifestyle Intervention Program; TULIP). Multivariate regressions analyses with adjustment for relevant covariates were performed to detect associations of SIRT1 variants with the changes in anthropometrics, weight, body fat or metabolic characteristics (blood glucose, insulin sensitivity, insulin secretion and liver fat, measured by magnetic resonance techniques) after the 9-month follow-up test in the TULIP study. RESULTS: Minor allele (X/A) carriers of rs12413112 (G/A) had a significantly lower basal energy expenditure (p = 0.04) and an increased respiratory quotient (p = 0.02). This group (rs12413112: X/A) was resistant against lifestyle-induced improvement of fasting plasma glucose (GG: -2.01%, X/A: 0.53%; p = 0.04), had less increase in insulin sensitivity (GG: 17.3%, X/A: 9.6%; p = 0.05) and an attenuated decline in liver fat (GG: -38.4%, X/A: -7.5%; p = 0.01). CONCLUSION: SIRT1 plays a role for the individual lifestyle intervention response, possibly owing to decreased basal energy expenditure and a lower lipid-oxidation rate in rs12413112 X/A allele carriers. SIRT1 genetic variants may, therefore, represent a relevant determinant for the response rate of individuals undergoing caloric restriction and increased physical activity.

A new variant in the human Kv1.3 gene is associated with low insulin sensitivity and impaired glucose tolerance.

CONTEXT: The voltage-gated potassium channel Kv1.3 (KCNA3) is expressed in a variety of tissues including liver and skeletal muscle. In animal models, knockout of Kv1.3 has been found to improve insulin sensitivity and glucose tolerance. OBJECTIVE: We examined whether mutations in the Kv1.3 gene exist in humans and whether they are associated with alterations of glucose homeostasis. DESIGN AND SETTING: We conducted a genotype-phenotype association study at a university hospital. PARTICIPANTS AND METHODS: In 50 nondiabetic subjects, we screened approximately 4.5 kb of chromosome 1 comprising the single exon, the promoter/5'-untranslated region, and the 3'-untranslated region of the human Kv1.3 gene for mutations by direct sequencing. Subsequently, all identified single-nucleotide polymorphisms were analyzed in 552 nondiabetic subjects who underwent an oral glucose tolerance test (OGTT). Of these, 304 had undergone an additional hyperinsulinemic euglycemic clamp. MAIN OUTCOME MEASURES: We assessed postprandial blood glucose during OGTT and insulin sensitivity measured by hyperinsulinemic euglycemic clamp. RESULTS: We identified five single-nucleotide polymorphisms in the promoter region (T-548C, G-697T, A-845G, T-1645C, and G-2069A) with allelic frequencies of the minor allele of 26, 23, 9, 41, and 16%, respectively. The -1645C allele was associated with higher plasma glucose concentrations in the 2-h OGTT (P = 0.03) even after adjustment for sex, age, and body mass index (P = 0.002). In addition, it was associated with lower insulin sensitivity (P = 0.01, adjusted for sex, age, and body mass index). Functional in vitro analysis using EMSA showed differential transcription factor binding to the T-1645C polymorphism. CONCLUSIONS: We show that a variant in the promoter of the Kv1.3 gene is associated with impaired glucose tolerance and lower insulin sensitivity. Therefore, the Kv1.3 channel represents a candidate gene for type 2 diabetes.

Association of the T-G polymorphism in adiponectin (exon 2) with obesity and insulin sensitivity: interaction with family history of type 2 diabetes.

The adipocyte-derived hormone adiponectin seems to protect from insulin resistance, a key factor in the pathogenesis of type 2 diabetes. Genome-wide scans have mapped a susceptibility locus for type 2 diabetes and the metabolic syndrome to chromosome 3q27, where the adiponectin gene is located. A common silent T-G exchange in nucleotide 94 (exon 2) of the adiponectin gene has been associated with increased circulating adiponectin levels. Metabolic abnormalities associated with the G allele have not been reported. We therefore assessed whether this polymorphism alters insulin sensitivity and/or measures of obesity using the Tübingen Family Study database (prevalence of the G allele, 28%). In 371 nondiabetic individuals, we found a significantly greater BMI in GG + GT (25.5 +/- 0.7 kg/m(2)) compared with TT (24.1 +/- 0.3 kg/m(2); P = 0.02). Insulin sensitivity (determined by euglycemic clamp, n = 209) was significantly lower in GG + GT (0.089 +/- 0.007 units) compared with TT (0.112 +/- 0.005 units; P = 0.02). This difference disappeared completely on adjustment for BMI. Because our population contains a relatively high proportion of first-degree relatives of patients with type 2 diabetes, we stratified by family history (FHD). Much to our surprise, the genotype differences in BMI and insulin sensitivity in the whole population were attributable entirely to differences in the subgroup without FHD, whereas in the subgroup with FHD, the G allele had absolutely no effect. Moreover, individuals without FHD had a significantly lower BMI than individuals with FHD (25.2 +/- 0.4 vs. 26.2 +/- 0.5 kg/m(2); P = 0.01), which was not the case for the GG + GT subgroup without FHD (27.0 +/- 0.9 kg/m(2); NS). This suggests that in individuals without familial predisposition for type 2 diabetes, the adiponectin polymorphism may mildly increase the obesity risk (and secondarily insulin resistance). In contrast, in individuals who are already burdened by other genetic factors, this small effect may be very hard to detect.

Relationships among age, proinsulin conversion, and beta-cell function in nondiabetic humans.

The aim of the present study was to examine the relationships among beta-cell function, proinsulin conversion to insulin, and age. We studied insulin and proinsulin secretion in nondiabetic subjects during an oral glucose tolerance test (OGTT) using published indexes of beta-cell function (n = 379, age 16--68 years) and a modified hyperglycemic clamp (10 mmol/l, additional glucagon-like peptide [GLP-1] infusion, final arginine bolus; n = 50, age 19--68 years). Proinsulin conversion to insulin was assessed using proinsulin/insulin (PI/I) ratios immediately after an acute stimulus (OGTT, 30 min; hyperglycemic clamp, 2.5-5.0 min after glucose and arginine). There was a negative correlation between age and beta-cell function (adjusted for insulin sensitivity, BMI, and fasting glucose) in the OGTT (r = -0.21, P < 0.001) and first phase of the hyperglycemic clamp (r = -0.30, P = 0.03), but not second phase (r = -0.08, P = 0.6) or arginine-induced insulin secretion (r = 0.06, P = 0.7). There was a positive correlation between age and the PI/I ratio in the OGTT (r = 0.24, P < 0.001). Analogously, there was also a positive correlation between age and the PI/I ratio during first phase (r = 0.37, P = 0.009) and arginine stimulation (r = 0.33, P = 0.01) of the hyperglycemic clamp. First-phase insulin secretion of the hyperglycemic clamp was inversely correlated with the PI/I ratio (r = -0.60, P < 0.001). Interestingly, adjusting first-phase secretion rate for the PI/I ratio abolished the linear relationship with age (r = -0.06, P = 0.7). In conclusion, aging is associated with deteriorating beta-cell function and deteriorating proinsulin conversion to insulin. The age effect on insulin secretion appears to be attributable at least in part to an impairment of proinsulin conversion to insulin.

Plasma adiponectin concentrations predict insulin sensitivity of both glucose and lipid metabolism.

In animals, the adipocyte-derived hormone adiponectin has been shown to improve insulin sensitivity, a key factor in the pathogenesis of type 2 diabetes. In Pima Indians, high plasma adiponectin levels are associated with increased insulin sensitivity and reduced risk of type 2 diabetes. It is unclear whether this is also the case in white individuals and whether an additional beneficial effect on lipid metabolism exists. We therefore analyzed in nondiabetic individuals the associations between plasma adiponectin concentrations and insulin sensitivity measured by a euglycemic-hyperinsulinemic clamp (n = 262) and estimated by an oral glucose tolerance test (OGTT; n = 636) and serum lipid parameters using correlational analysis. Plasma adiponectin concentrations were positively correlated with insulin sensitivity, both measured with the clamp (r = 0.28, P = 0.0015 in women; r = 0.42, P < 0.0001 in men) and estimated from the OGTT (r = 0.37, P < 0.0001 in women; r = 0.41, P < 0.0001 in men) before and after adjusting for sex and percentage of body fat (all P < 0.001). Fasting triglycerides and the free fatty acid (FFA) concentrations during the OGTT (area under the curve) and at 120 min were negatively correlated in both women and men, whereas HDL was positively correlated with plasma adiponectin concentrations (all P < 0.004). Most notable, these relationships remained significant after adjusting for insulin sensitivity of glucose disposal in addition to sex and percentage of body fat (all P < 0.05). In conclusion, high adiponectin predicts increased insulin sensitivity. This relationship is independent of low body fat mass and affects not only insulin-stimulated glucose disposal but also lipoprotein metabolism and insulin-mediated suppression of postprandial FFA release. This suggests pleiotropic insulin sensitizing effects of adiponectin in humans.

The prevalent Glu23Lys polymorphism in the potassium inward rectifier 6.2 (KIR6.2) gene is associated with impaired glucagon suppression in response to hyperglycemia.

Genetic factors play an important role in the pathogenesis of type 2 diabetes. The relevance to type 2 diabetes of the common polymorphism Glu23Lys in the potassium inward rectifier 6.2 (KIR6.2) gene is still controversial. The aim of this study was to assess whether this polymorphism influences beta-cell function, alpha-cell function, or insulin action. We therefore studied 298 nondiabetic subjects using an oral glucose tolerance test (OGTT) and 75 nondiabetic subjects using a hyperglycemic clamp (10 mmol/l) with additional glucagon-like peptide (GLP)-1 and arginine stimulation. The prevalence of the Lys allele was approximately 37%, and the Lys allele was associated with higher incremental plasma glucose during the OGTT (P = 0.03, ANOVA). Neither first- nor second-phase glucose-stimulated C-peptide secretion was affected by the presence of the polymorphism; nor were maximal glucose-, GLP-1-, or arginine-induced C-peptide secretion rates; nor was insulin sensitivity (all P > 0.7). However, the relative decrease in plasma glucagon concentrations during the 10 min after the glucose challenge was reduced in carriers of the Lys allele (10 +/- 3% decrease from baseline in Lys/Lys, 18 +/- 2% in Glu/Lys, and 20 +/- 2% in Glu/Glu; P = 0.01, ANOVA). In conclusion, our findings suggest that the common Glu23Lys polymorphism in KIR6.2 is not necessarily associated with beta-cell dysfunction or insulin resistance but with diminished suppression of glucagon secretion in response to hyperglycemia. Our findings thus confirm its functional relevance for glucose metabolism in humans.

Interaction effect between common polymorphisms in PPARgamma2 (Pro12Ala) and insulin receptor substrate 1 (Gly972Arg) on insulin sensitivity.

The Pro12Ala polymorphism in the peroxisome proliferator-activated receptor (PPAR) gamma2 gene is associated with a reduced risk of type 2 diabetes. A beneficial effect on insulin sensitivity is reported in some but not all populations. It is possible that this genetic variant produces a characteristic phenotype only against a certain genetic background. We therefore tested the hypothesis that carriers of the Ala allele of PPARgamma2 exhibit a different phenotype against the background of the Gly972Arg polymorphism in the insulin receptor substrate (IRS) 1. We determined insulin sensitivity in the four combinations defined by the absence or presence of the polymorphic allele (healthy, glucose tolerant subjects), by the oral glucose tolerance test (OGTT; using a validated index, n=318) and hyperinsulinemic clamp ( n=201). Insulin sensitivity was not or was only marginally different between Pro/Pro and X/Ala in the overall population. Interestingly, using the OGTT index, insulin sensitivity was significantly greater in X/Ala (PPARgamma2) + X/Arg (IRS-1) than in Pro/Pro (PPARgamma2) + X/Arg (IRS-1). On the other hand, insulin sensitivity was similar in the X/Ala (PPARgamma2) + Gly/Gly (IRS-1 972) and the Pro/Pro (PPARgamma2) + Gly/Gly (IRS-1). The results were practically identical using insulin sensitivity from the clamp. In conclusion, the Arg972 (IRS-1) background produced a marked difference in insulin sensitivity between X/Ala and Pro/Pro (PPARgamma) which was not present in the whole population or against the Gly972 (IRS-1) background. This suggests that the Ala allele of PPARgamma2 becomes particularly advantageous against the background of an additional, possibly disadvantageous genetic polymorphism. Allowing for gene-gene interaction effects may reveal novel information regarding metabolic effects of genetic variants.

Assessing the shape of the glucose curve during an oral glucose tolerance test.

OBJECTIVE: The oral glucose tolerance test (OGTT) is used to define the status of glucose tolerance based on the plasma glucose level at 120 min. The purpose of the present study was to identify parameters that determine the shape of the plasma glucose course measured at 0, 30, 60, 90, and 120 min during an OGTT. RESEARCH DESIGN AND METHODS: OGTT data from 551 subjects (485 with normal glucose tolerance [NGT] and 66 with impaired glucose tolerance [IGT]) were analyzed. We distinguished between "monophasic," "biphasic," and unclassified glucose shapes. A "shape" index based on the extent and the direction of the plasma glucose change in the second hour allowed us to treat shape as a continuous variable. RESULTS: In the biphasic group, the NGT-to-IGT ratio was slightly higher (173/20 vs. 209/40, P = 0.08) and the male-to-female ratio was lower (60/133 vs. 120/129, P = 0.0003). Subjects with a biphasic shape had significantly lower age, BMI, waist-to-hip ratio (WHR), HbA(1c), plasma glucose, and area under the insulin curve (insulin(AUC)) and a better estimated insulin sensitivity and secretion (using validated indexes) than monophasic subjects (all P < 0.05). By adjusting this shape index for glucose(AUC) (as continuous measure of glucose tolerance), correlations with age, BMI, WHR, HbA(1c), and insulin(AUC) were completely abolished. The adjusted shape index was still higher in female than in male subjects but lower in IGT than in NGT subjects (both P = 0.0003). Finally, we tested common polymorphisms in insulin receptor substrate (IRS)-1, IRS-2, calpain-10, hepatic lipase, and peroxisome proliferator-activated receptor-gamma for association with the shape index. CONCLUSIONS: We conclude that the plasma glucose shape during an OGTT depends on glucose tolerance and sex. In addition, genetic factors seem to play a role. The shape index may be a useful metabolic screening parameter in epidemiological and genetic association studies.

Reduced skeletal muscle oxygen uptake and reduced beta-cell function: two early abnormalities in normal glucose-tolerant offspring of patients with type 2 diabetes.

OBJECTIVE: Studies on insulin sensitivity and insulin secretion in subjects with a familial predisposition for type 2 diabetes mellitus (T2DM) traditionally produce inconsistent results. This may be due to small sample size, subject selection, matching procedures, and perhaps lack of a measure of physical fitness. RESEARCH DESIGN AND METHODS: In the present study, we specifically tested the hypothesis that a family history of T2DM is associated with reduced VO(2max), measured by incremental bicycle ergometry, independent of insulin sensitivity estimated from an oral glucose tolerance test (OGTT; n = 424) and measured by a euglycemic-hyperinsulinemic clamp (n = 185). Subjects included in the study were young (34 +/- 10 years), healthy, and normal glucose tolerant with either a first-degree relative (FDR) with T2DM (n = 183), a second-degree relative with T2DM (n = 94), or no family history of T2DM (control subjects, n = 147). BMI, percent body fat, waist-to-hip ratio (WHR), and habitual physical activity (HPA; standard questionnaire) were comparable among groups. FDRs had significantly lower VO(2max) than control subjects: 40.5 +/- 0.6 vs. 45.2 +/- 0.9 ml O(2)/kg lean body mass, P = 0.01 after adjusting for sex, age, BMI, HPA, and insulin sensitivity (euglycemic-hyperinsulinemic clamp). RESULTS: BMI, percent body fat, waist-to-hip ratio (WHR), and habitual physical activity (HPA; standard questionnaire) were comparable among groups. FDRs had significantly lower VO(2max) than control subjects: 40.5 +/- 0.6 vs. 45.2 +/- 0.9 ml O(2)/kg lean body mass, P = 0.01 after adjusting for sex, age, BMI, HPA, and insulin sensitivity (euglycemic-hyperinsulinemic clamp). Insulin sensitivity per se was not affected by family history of T2DM after adjusting for age, sex, BMI, and percent body fat (P = 0.76). The appropriateness of beta-cell function for the individual insulin sensitivity (disposition index: product of a validated secretion parameter [OGTT] and sensitivity [clamp]) was significantly lower in FDRs (87 +/- 4 units) versus control subjects (104 +/- 6 units, P = 0.02 after adjusting for sex, age, and BMI). Analyses of the larger OGTT group produced essentially the same results. CONCLUSIONS: In conclusion, these data are compatible with the hypothesis that familial predisposition for T2DM impairs maximal oxygen consumption in skeletal muscle. Because habitual physical activity was not different, genetic factors may be involved. Conceivably, reduced VO(2max) precedes skeletal muscle insulin resistance, providing a partial explanation for discrepancies in the literature.

Metabolic characterization of a woman homozygous for the Ser113Leu missense mutation in carnitine palmitoyl transferase II.

Carnitine palmitoyl transferase (CPT) II is a key enzyme in transporting FFA into the mitochondrial matrix for beta oxidation. The clinical manifestation of CPT II deficiency is characterized mainly by myopathic symptoms. Conceivably, the inability of skeletal muscle to oxidize (long-chain) FFAs could also have far-reaching metabolic consequences, such as insulin resistance secondary to increased muscle lipids, about which relatively little is known. We therefore performed a series of metabolic studies in a 43-yr-old woman homozygous for the Ser113Leu mutation in the CPT II gene, the single most common genetic cause of CPT II deficiency, and compared the results with data from a male and female control group taken from the Tübingen family study database. The metabolic studies included oral glucose tolerance test (OGTT), euglycemic hyperinsulinemic clamp to measure insulin sensitivity, indirect calorimetry to measure substrate oxidation, stable isotopes for determination of glycerol turnover, and magnetic resonance spectroscopy for measurement of intramyocellular lipids. Compared with the female control group, the patient was normal glucose tolerant but severely insulin resistant, basal lipolysis was markedly reduced, and carbohydrate oxidation was maximally increased in the basal state and did not increase further during insulin stimulation. Conversely, lipid oxidation was virtually absent and did not decrease during insulin stimulation. Surprisingly, intramyocellular lipids were well within the range of the control group. In conclusion, genetic CPT II deficiency is characterized by insulin resistance, which is not explained by increased intramyomellular lipids. However, it may be partially explained by glucose oxidation already maximally increased in the basal state, which cannot be increased any further by insulin. Reduced basal lipolysis may represent a compensatory mechanism for the reduced oxidative FFA disposal characteristic for this disease.

Intramyocellular lipids: anthropometric determinants and relationships with maximal aerobic capacity and insulin sensitivity.

The existence of metabolically relevant intramyocellular lipids (IMCL) as assessed by the noninvasive (1)H-magnetic resonance spectroscopy (MRS) has been established. In the present studies, we analyzed the relationships between IMCL in two muscle types [the predominantly nonoxidative tibialis muscle (tib) and the predominantly oxidative soleus muscle (sol)] and anthropometric data, aerobic capacity (VO(2)max, bicycle ergometry, n = 77) and insulin sensitivity (hyperinsulinemic euglycemic clamp, n = 105) using regression analysis. In univariate regression, IMCL (tib) was weakly but significantly correlated with percentage of body fat (r = 0.28, P = 0.01), whereas IMCL (sol) was better correlated with waist-to-hip ratio (r = 0.41, P < 0.0001). No significant univariate correlation with age or maximal aerobic power was observed. After adjusting for adiposity, IMCL (tib) was positively correlated with measures of aerobic fitness. A significant interaction term between VO(2)max and percentage of body fat on IMCL (tib) (P = 0.04) existed (whole model r(2) = 0.26, P = 0.001). In contrast, aerobic fitness did not influence IMCL (sol). No correlation between insulin sensitivity as such and IMCL (tib) (r = -0.13, P = 0.2) or IMCL (sol) (r = 0.03, P = 0.72) was observed. Nethertheless, a significant interaction term between VO(2)max and IMCL on insulin sensitivity existed [P = 0.04 (tib) and P = 0.02 (sol)]; [whole model (sol) r(2) = 0.61, P < 0.0001, (tib) r(2) = 0.60, P < 0.0001]. In conclusion, obesity and aerobic fitness are important determinants of IMCL. IMCL and insulin sensitivity are negatively correlated in untrained subjects. The correlation between the two parameters is modified by the extent of aerobic fitness and cannot be found in endurance trained subjects. Thus, measurements of aerobic fitness and body fat are indispensable for the interpretation of IMCL and its relationship with insulin sensitivity.

Increased insulin clearance in peroxisome proliferator-activated receptor gamma2 Pro12Ala.

The Pro12Ala polymorphism of the peroxisome proliferator-activated receptor (PPARgamma(2)) is associated with reduced risk for type 2 diabetes. Although increased insulin sensitivity of glucose disposal and lipolysis has been reported, the exact mechanism by which the risk reduction is conferred is not clear. Because the conclusion of greater insulin sensitivity hinged upon lower insulin levels in some studies, it is possible that more efficient insulin clearance is involved. We therefore estimated insulin clearance during a euglycemic hyperinsulinemic clamp (insulin infusion rate divided by steady-state insulin concentration, 229 normal glucose tolerant [NGT] subjects), an oral glucose tolerance test (OGTT) (mean C-peptide divided by mean insulin concentrations, 406 NGT, 54 impaired glucose tolerant or mildly diabetic subjects), and a hyperglycemic clamp (120 minutes, 10 mmol/L, C-peptide divided by insulin in the steady-state, 56 NGT subjects). In the carriers of the Ala allele (prevalence approximately 24%), insulin clearance in all 3 protocols was significantly greater ( approximately 10%), than in controls. While the results from the euglycemic clamp reflect both hepatic and peripheral insulin clearance, those from the OGTT and the hyperglycemic clamp reflect mainly hepatic insulin extraction. Free fatty acids (FFA) during the steady state of the euglycemic hyperinsulinemic clamp were significantly lower in carriers of the Ala allele (26 +/- 5 micromol/L) than in controls (46 +/- 3 micromol/L, P =.02). In conclusion, the Pro12Ala polymorphism is associated with increased insulin clearance. This could be the result of reduced FFA delivery, which has been shown to improve hepatic insulin removal and sensitivity. Because PPARgamma(2) is mainly expressed in adipose tissue, one of the main regulatory effects of the polymorphism may well be the more efficient suppression of (possibly intra-abdominal) lipolysis.

Polymorphism rs3123554 in CNR2 reveals gender-specific effects on body weight and affects loss of body weight and cerebral insulin action.

OBJECTIVE: The cannabinoid-receptor system is involved in the regulation of food intake. Here, we test whether single nucleotide polymorphisms (SNPs) in CNR2, encoding the cannabinoid-receptor 2, are associated with weight in a cross-sectional cohort. Furthermore, we wanted to investigate if the identified hits influence weight loss during lifestyle intervention; and study a potential involvement of cerebral insulin action. METHODS: 2006 subjects at increased risk for type 2 diabetes mellitus were genotyped for 5 tagging SNPs in the CNR2 locus. All subjects underwent a 75-g OGTT. 345 subjects participated in a lifestyle intervention (TUebingen Lifestyle Intervention Programme). Cerebrocortical insulin sensitivity was measured by magnetoencephalography after intranasal insulin application in 43 subjects. RESULTS: In the cross-sectional cohort, the minor allele of rs3123554 was associated with lower BMI (Padd = 0.01, Prec = 0.004), and this was attributable to its effect in women only. Interestingly, during lifestyle intervention, carriers of the same allele lost less body weight (Padd = 0.03, Prec = 0.008). Moreover, carriers of this minor allele showed lower cerebral insulin sensitivity (Prec = 0.0402). CONCLUSIONS: The minor allele of rs3123554 is associated cross-sectionally with lower body weight, whereas during intervention the same allele led to less reduction of body weight. Reduced cerebral insulin sensitivity in carriers of this allele might contribute to these disadvantageous effects during lifestyle intervention.