Iwar Klimes

Insulin Therapy in Obese, Non-insulin-dependent Diabetes Induces Improvements in Insulin Action and Secretion that Are Maintained for Two Weeks After Insulin Withdrawal

The effects of rigorous insulin treatment on insulin action (insulin clamp) and secretion (plasma insulin response to glucose) were studied in 13 obese patients with non-insulin-dependent diabetes mellitus (NIDDM). Improvements were documented in fasting (P < 0.0001) and postprandial (P < 0.0001) plasma glucose concentrations, insulin secretion after oral glucose (P < 0.001), and insulin action (P < 0.005) after 30 days of therapy. Mean integrated plasma insulin response to glucose increased 2.5-fold after insulin therapy, but this improvement varied considerably from patient to patient. Insulin action also increased with insulin treatment and the resulting values were no longer significantly different from a weight- and age-matched group of subjects with normal glucose tolerance. However, there was considerable patient-to-patient variation in the degree to which insulin action was enhanced. The insulin-induced improvements in glucose tolerance persisted for at least 2 wk after insulin withdrawal, and were associated with continued increased insulin secretion and insulin action. In conclusion, control of hyperglycemie for 1 mo led to improvements in both insulin secretion and action in a series of obese patients with NIDDM that persisted for at least 2 wk after cessation of therapy.

Effects of obesity, diabetes and exercise on Fndc5 gene expression and irisin release in human skeletal muscle and adipose tissue: in vivo and in vitro studies

Considerable controversy exists regarding the role of irisin, a putative exercise‐induced myokine, in human metabolism. We therefore studied irisin and its precursor Fndc5 in obesity, type 2 diabetes and exercise. Complex clinical studies combined with cell culture work revealed that Fndc5/irisin was decreased in type 2 diabetes in vivo, but not in muscle cells in vitro, indicating that diabetes‐related factor(s) regulate Fndc5/irisin in vivo. Several attributes of type 2 diabetes, such as hyperglycaemia, triglyceridaemia, visceral adiposity and extramyocellular lipid deposition were negatively associated with adipose tissue Fndc5 mRNA and circulating irisin. Moreover, mimicking diabetic status in vitro by treating muscle cells with palmitate and glucose lowered Fndc5 mRNA. Neither exercise training nor an acute exercise bout modulated circulating irisin or muscle Fndc5 expression. However, the associations between intensity of habitual physical activity, muscle volume, strength, contractility and circulating irisin provide a link between irisin and positive outcomes of increased physical activity.

Improvement of Glucose Homeostasis After Exercise Training in Non-insulin-dependent Diabetes

Six obese patients with recent-onset, non-insulin-dependent diabetes underwent assessment of glucose tolerance, insulin secretory capacity, and insulin-induced glucose disposal before and after 6–10 wk of intensive aerobic training while maintaining body weight. Fasting plasma glucose declined in every subject (average = −33 mg/dl), and oral glucose tolerance (3 h integrated plasma glucose) improved in five of the six (average = −74 mg × 3 h/dl) after training. Individual improvement in control of plasma glucose was directly proportional to degree of hyperglycemia before training and correlated well with an observed improvement in the early (30-min) plasma insulin response to oral glucose (all six subjects). The response of insulin action to training was highly variable; although the observed increase in average insulin-induced glucose disposal rate (M) during the euglycemic clamp did not reach statistical significance in our small cohort, the relative change in M was directly related to reduction in fasting insulin levels after training. Our results show that regular endurance exercise is effective in improving glucose homeostasis and may serve as an adjunct to other modes of treatment in recent-onset, non-insulin-dependent diabetic individuals.

The hypotriglyceridemic effect of dietary n−3 FA is associated with increased β-oxidation and reduced leptin expression

To study the mechanisms responsible for the hypotriglyceridemic effect of marine oils, we monitored the effects of high dietary intake of n−3 PUFA on hepatic and muscular β-oxidation, plasma leptin concentration, leptin receptor gene expression, and in vivo insulin action. Two groups of male Wistar rats were fed either a high-fat diet [28% (w/w) of saturated fat] or a high-fat diet containing 10% n−3 PUFA and 18% saturated fat for 3 wk. The hypotriglyceridemic effect of n−3 PUFA was accompanied by increased hepatic oxidation of palmitoyl-CoA (125%, P<0.005) and palmitoyl-l-carnitine (480%, P<0.005). These findings were corroborated by raised carnitine palmitoyltransferase-2 activity (154%, P<0.001) and mRNA levels (91%, P<0.01) as well as by simultaneous elevation of hepatic peroxisomal acyl-CoA oxidase activity (144%, P<0.01) and mRNA content (82%, P<0.05). In contrast, hepatic carnitine palmitoyltransferase-1 activity remained unchanged despite a twofold increased mRNA level after n−3 PUFA feeding. Skeletal muscle FA oxidation was less affected by dietary n−3 PUFA, and the stimulatory effect was found only in peroxisomes. Dietary intake of n−3 PUFA was followed by increased acyl-CoA oxidase activity (48%, P<0.05) and mRNA level (83%, P<0.05) in skeletal muscle. The increased FA oxidation after n−3 PUFA supplementation of the high-fat diet was accompanied by lower plasma leptin concentration (−38%, P<0.05) and leptin mRNA expression (−66%, P<0.05) in retroperitoneal adipose tissue, and elevated hepatic mRNA level for the leptin receptor Ob-Ra (140%, P<0.05). Supplementation of the high-fat diet with n−3 PUFA enhanced in vivo insulin sensitivity, as shown by normalization of the glucose infusion rate during euglycemic hyperinsulinemic clamp.Our results indicate that the hypotriglyceridemic effect of dietary n−3 PUFA is associated with stimulation of FA oxidation in the liver and to a smaller extent in skeletal muscle. This may ameliorate dyslipidemia, tissue lipid accumulation, and insulin action, in spite of decreased plasma leptin level and leptin mRNA in adipose tissue.

High prevalence of prediabetes and diabetes in a population exposed to high levels of an organochlorine cocktail

Aims/hypothesisA heavily polluted area of Eastern Slovakia was targeted by the PCBRISK cross-sectional survey to search for possible links between environmental pollution and both prediabetes and diabetes.MethodsAssociations of serum levels of five persistent organic pollutants (POPs), namely polychlorinated biphenyls (PCBs), 2,2′-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p′-DDE), 2,2′-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (p,p′-DDT), hexachlorobenzene (HCB) and β-hexachlorocyclohexane (β-HCH), with prediabetes and diabetes were investigated in 2,047 adults. Diabetes and prediabetes were diagnosed by fasting plasma glucose in all participants and by OGTT in 1,220 compliant participants.ResultsOur population was stratified in terms of individual POPs quintiles and associations between environmental pollution, prediabetes and diabetes were investigated. Prevalence of prediabetes and diabetes increased in a dose-dependent manner, with individuals in upper quintiles of individual POPs showing striking increases in prevalence of prediabetes as shown by OR and 95% CI for PCBs (2.74; 1.92–3.90), DDE (1.86; 1.17–2.95), DDT (2.48; 1.77–3.48), HCB (1.86; 1.7–2.95) and β-HCH (1.97; 1.28–3.04). Interestingly, unlike PCBs, DDT and DDE, increased levels of HCB and β-HCH seemed not to be associated with increased prevalence of diabetes. Nevertheless, individuals in the 5th quintile of the variable expressing the cumulative effect of all five POPs (sum of orders) had a more than tripled prevalence of prediabetes and more than six times higher prevalence of diabetes when compared with the 1st referent quintile.Conclusions/interpretationIncreasing serum concentrations of individual POPs considerably increased prevalence of prediabetes and diabetes in a dose-dependent manner. Interaction of industrial and agricultural pollutants in increasing prevalence of prediabetes or diabetes is likely.

Cytosolic citrate and malonyl-CoA regulation in rat muscle in vivo

In liver, insulin and glucose acutely increase the concentration of malonyl-CoA by dephosphorylating and activating acetyl-CoA carboxylase (ACC). In contrast, in incubated rat skeletal muscle, they appear to act by increasing the cytosolic concentration of citrate, an allosteric activator of ACC, as reflected by increases in the whole cell concentrations of citrate and malate [Saha, A. K., D. Vavvas, T. G. Kurowski, A. Apazidis, L. A. Witters, E. Shafrir, and N. B. Ruderman. Am. J. Physiol. 272 ( Endocrinol. Metab. 35): E641-E648, 1997]. We report here that sustained increases in plasma insulin and glucose may also increase the concentration of malonyl-CoA in rat skeletal muscle in vivo by this mechanism. Thus 70 and 125% increases in malonyl-CoA induced in skeletal muscle by infusions of glucose for 1 and 4 days, respectively, and a twofold increase in its concentration during a 90-min euglycemic-hyperinsulinemic clamp were all associated with significant increases in the sum of whole cell concentrations of citrate and/or malate. Similar correlations were observed in muscle of the hyperinsulinemic fa/fa rat, in denervated muscle, and in muscle of rats infused with insulin for 5 h. In muscle of 48-h-starved rats 3 and 24 h after refeeding, increases in malonyl-CoA were not accompanied by consistent increases in the concentrations of malate or citrate. However, they were associated with a decrease in the whole cell concentration of long-chain fatty acyl-CoA (LCFA-CoA), an allosteric inhibitor of ACC. The results suggest that increases in the concentration of malonyl-CoA, caused in rat muscle in vivo by sustained increases in plasma insulin and glucose or denervation, may be due to increases in the cytosolic concentration of citrate. In contrast, during refeeding after starvation, the increase in malonyl-CoA in muscle is probably due to another mechanism.In liver, insulin and glucose acutely increase the concentration of malonyl-CoA by dephosphorylating and activating acetyl-CoA carboxylase (ACC). In contrast, in incubated rat skeletal muscle, they appear to act by increasing the cytosolic concentration of citrate, an allosteric activator of ACC, as reflected by increases in the whole cell concentrations of citrate and malate [Saha, A. K., D. Vavvas, T. G. Kurowski, A. Apazidis, L. A. Witters, E. Shafrir, and N. B. Ruderman. Am. J. Physiol. 272 (Endocrinol. Metab. 35): E641-E648, 1997]. We report here that sustained increases in plasma insulin and glucose may also increase the concentration of malonyl-CoA in rat skeletal muscle in vivo by this mechanism. Thus 70 and 125% increases in malonyl-CoA induced in skeletal muscle by infusions of glucose for 1 and 4 days, respectively, and a twofold increase in its concentration during a 90-min euglycemic-hyperinsulinemic clamp were all associated with significant increases in the sum of whole cell concentrations of citrate and/or malate. Similar correlations were observed in muscle of the hyperinsulinemic fa/fa rat, in denervated muscle, and in muscle of rats infused with insulin for 5 h. In muscle of 48-h-starved rats 3 and 24 h after refeeding, increases in malonyl-CoA were not accompanied by consistent increases in the concentrations of malate or citrate. However, they were associated with a decrease in the whole cell concentration of long-chain fatty acyl-CoA (LCFA-CoA), an allosteric inhibitor of ACC. The results suggest that increases in the concentration of malonyl-CoA, caused in rat muscle in vivo by sustained increases in plasma insulin and glucose or denervation, may be due to increases in the cytosolic concentration of citrate. In contrast, during refeeding after starvation, the increase in malonyl-CoA in muscle is probably due to another mechanism.

Mutations in HNF1A Result in Marked Alterations of Plasma Glycan Profile

A recent genome-wide association study identified hepatocyte nuclear factor 1-α (HNF1A) as a key regulator of fucosylation. We hypothesized that loss-of-function HNF1A mutations causal for maturity-onset diabetes of the young (MODY) would display altered fucosylation of N-linked glycans on plasma proteins and that glycan biomarkers could improve the efficiency of a diagnosis of HNF1A-MODY. In a pilot comparison of 33 subjects with HNF1A-MODY and 41 subjects with type 2 diabetes, 15 of 29 glycan measurements differed between the two groups. The DG9-glycan index, which is the ratio of fucosylated to nonfucosylated triantennary glycans, provided optimum discrimination in the pilot study and was examined further among additional subjects with HNF1A-MODY (n = 188), glucokinase (GCK)-MODY (n = 118), hepatocyte nuclear factor 4-α (HNF4A)-MODY (n = 40), type 1 diabetes (n = 98), type 2 diabetes (n = 167), and nondiabetic controls (n = 98). The DG9-glycan index was markedly lower in HNF1A-MODY than in controls or other diabetes subtypes, offered good discrimination between HNF1A-MODY and both type 1 and type 2 diabetes (C statistic ≥0.90), and enabled us to detect three previously undetected HNF1A mutations in patients with diabetes. In conclusion, glycan profiles are altered substantially in HNF1A-MODY, and the DG9-glycan index has potential clinical value as a diagnostic biomarker of HNF1A dysfunction.

Genetic variation in the Sorbs of eastern Germany in the context of broader European genetic diversity.

Population isolates have long been of interest to genetic epidemiologists because of their potential to increase power to detect disease-causing genetic variants. The Sorbs of Germany are considered as cultural and linguistic isolates and have recently been the focus of disease association mapping efforts. They are thought to have settled in their present location in eastern Germany after a westward migration from a largely Slavic-speaking territory during the Middle Ages. To examine Sorbian genetic diversity within the context of other European populations, we analyzed genotype data for over 30 000 autosomal single-nucleotide polymorphisms from over 200 Sorbs individuals. We compare the Sorbs with other European individuals, including samples from population isolates. Despite their geographical proximity to German speakers, the Sorbs showed greatest genetic similarity to Polish and Czech individuals, consistent with the linguistic proximity of Sorbian to other West Slavic languages. The Sorbs also showed evidence of subtle levels of genetic isolation in comparison with samples from non-isolated European populations. The level of genetic isolation was less than that observed for the Sardinians and French Basque, who were clear outliers on multiple measures of isolation. The finding of the Sorbs as only a minor genetic isolate demonstrates the need to genetically characterize putative population isolates, as they possess a wide range of levels of isolation because of their different demographic histories.

Hereditary Hypertriglyceridemic Rat: A New Animal Model of Metabolic Alterations in Hypertension

Hereditary hypertriglyceridemic rats (hHTg) were developed as a new genetic model for the study of relationships between blood pressure (BP) and metabolic abnormalities. This strain has been produced by selective inbreeding from Wistar rats according to the rise of plasma triglycerides induced by a high-sucrose diet. Though hHTg rats display hypertriglyceridemia, impaired glucose tolerance, hyperinsulinemia, insulin resistance and increased BP even without nutritional stimuli, high sucrose feeding further aggravates these symptoms. High plasma triglycerides levels in hHTg rats seem to be a consequence of their hyperproduction. Impaired insulin action is responsible for the defective glucoregulation in this strain. The loss of insulin responsiveness might be due to a reduction in the number of glucose transporters. Highly significant relationships among plasma triglycerides, ouabain-resistant Na+ transport and BP were demonstrated in the hHTg rats. Segregating populations (F2 hybrids) should be used for genetic analysis of the primary role of lipid and/or ion transport abnormalities in the pathogenesis of this form of genetic hypertension.

Protein array reveals differentially expressed proteins in subcutaneous adipose tissue in obesity.

Objective: Many adipokines, inflammatory cytokines, and other proteins produced by adipose tissue have been shown to be involved in the development of obesity‐related insulin resistance. Nevertheless, new factors that play an important role in these processes are still emerging. Therefore, we screened the level of 120 different proteins in biopsies of subcutaneous adipose tissue (ScAT) of lean and obese subjects.