Insulin sensitivity, glucose effectiveness, and insulin secretion in nondiabetic offspring of patients with non-insulin-dependent diabetes mellitus: a cross-sectional study

Effect of physical training on insulin secretion and action in skeletal muscle and adipose tissue of first-degree relatives of type 2 diabetic patients

Physical training affects insulin secretion and action, but there is a paucity of data on the direct effects in skeletal muscle and adipose tissue and on the effect of training in first-degree relatives (FDR) of patients with type 2 diabetes. We studied insulin action at the whole body level and peripherally in skeletal muscle and adipose tissue as well as insulin-secretory capacity in seven FDR and eight control (CON) subjects before and after 12 wk of endurance training. Training improved physical fitness. Insulin-mediated glucose uptake (GU) increased (whole body and leg; P < 0.05) after training in CON but not in FDR, whereas glucose-mediated GU increased (P < 0.05) in both groups. Adipose tissue GU was not affected by training, but it was higher (abdominal, P < 0.05; femoral, P = 0.09) in FDR compared with CON. Training increased skeletal muscle lipolysis (P < 0.05), and it was markedly higher (P < 0.05) in subcutaneous abdominal than in femoral adipose tissue and quadriceps muscle with no difference between FDR and CON. Glucose-stimulated insulin secretion was lower in FDR compared with CON, but no effect of training was seen. Glucagon-like peptide-1 stimulated insulin secretion five- to sevenfold. We conclude that insulin-secretory capacity is lower in FDR than in CON and that there is dissociation between training-induced changes in insulin secretion and insulin-mediated GU. Maximal GU rates are similar between groups and increases with physical training.

Genetics of type 2 diabetes mellitus: status and perspectives

Throughout the last decade, molecular genetic studies of non-autoimmune diabetes mellitus have contributed significantly to our present understanding of this disease's complex aetiopathogenesis. Monogenic forms of diabetes (maturity-onset diabetes of the young, MODY) have been identified and classified into MODY1-6 according to the mutated genes that by being expressed in the pancreatic beta-cells confirm at the molecular level the clinical presentation of MODY as a predominantly insulin secretory deficient form of diabetes mellitus. Genomewide linkage studies of presumed polygenic type 2 diabetic populations indicate that loci on chromosomes 1q, 5q, 8p, 10q, 12q and 20q contain susceptibility genes. Yet, so far, the only susceptibility gene, calpain-10 (CAPN10), which has been identified using genomewide linkage studies, is located on chromosome 2q37. Mutation analyses of selected 'candidate' susceptibility genes in various populations have also identified the widespread Pro12Ala variant of the peroxisome proliferator-activated receptor-gamma and the common Glu23Lys variant of the ATP-sensitive potassium channel, Kir6.2 (KCNJ11). These variants may contribute significantly to the risk type 2 diabetes conferring insulin resistance of liver, muscle and fat (Pro12Ala) and a relative insulin secretory deficiency (Glu23Lys). It is likely that, in the near future, the recent more detailed knowledge of the human genome and insights into its haploblocks together with the developments of high-throughput and cheap genotyping will facilitate the discovery of many more type 2 diabetes gene variants in study materials, which are statistically powered and phenotypically well characterized. The results of these efforts are likely to be the platform for major progress in the development of personalized antidiabetic drugs with higher efficacy and few side effects.

Analysis of the relationship between body mass index, insulin resistance, and beta-cell function: a cross-sectional study using the minimal model

The objective of our research was to identify the mathematical model that would best define the relationship between obesity, insulin resistance (IR), and beta-cell function. Eighty-seven healthy subjects with a wide range of body mass index (BMI) were studied. Insulin sensitivity (IS) was calculated using Bergman's minimal model. Acute insulin response (AIRg) was calculated as the secretion of insulin during the first 10 minutes following a glucose bolus. IS x AIRg was used as an index of insulin-mediated glucose uptake (IMGU). The relationships among BMI, IS, fasting plasma insulin (FPI), and AIRg were studied in linear relationship terms and in terms of the hyperbolic function. Where the best fit was linear, the Jones and Molitoris method was used to investigate whether the 2-line fit was significantly better. The division of the population into BMI quartiles shows that from the third quartile, IS (12.4 +/- 6.0 v 11.0 +/- 6.4 v 4.8 +/- 1.8 v 3.2 +/- 2.0 E-5 min(-1)[pmol/L](-1), P < .01) diminishes. Nevertheless, a plateau was established between the last 3 quartiles for IS x AIRg. AIRg related to BMI via a breakpoint of 29.3 kg . m(-2). The best fits for both the BMI/IS and BMI/FPI relationships were hyperbolic. Our data indicate that obesity represents a continuum of IR, with severity increasing as BMI increases. Nevertheless, above a value of 29 kg . m(-2) and despite great increases in adiposity, IS tends to descend slowly. Moreover, there seems to be an IMGU threshold at a BMI value of approximately 27 kg . m(-2), above which an increase in adiposity leads to a greater fall in IS x AIRg. Furthermore, this threshold also appears to affect pancreatic response to a glucose stimulus.

[Glucose effectiveness and components of the metabolic syndrome in recently diagnosed hypertensive patients]

BACKGROUND

Glucose effectiveness (SG) is a parameter that indicates the glucose ability to clearing itself from the plasma independently of insulin's action. Our purpose was to analyze the cluster characteristics associated with the metabolic syndrome in a group of non-obese, recent-onset hypertensives and to test if there was a correlation with SG and the effectiveness of glucose at basal insulin point (GEZI).

PATIENTS AND METHOD

We studied 36 patients with mild hypertension with normal basal glucose levels. We determined plasma lipid subfractions, apolipoproteins and urate levels. An intravenous glucose tolerance test (TTGI) and minimal model analysis according to Bergman was performed and SG, GEZI and insulin sensitivity (SI) were calculated.

RESULTS

Patients with lower SG and GEZI had higher levels of total triglycerides (Tg) (r = 0.42; p = 0.01 and r = 0.48; p = 0.002, respectively) and triglycerides bind to VLDL (Tg-VLDL) (r = 0.40; p < 0.01 and r = 0.49; p = 0.002, respectively). When the cluster of metabolic syndrome was analyzed, SG was inversely related to uric acid levels and to the waist-hip index. However, SI was only related to the uric acid levels (r = 0.38; p = 0.01).

CONCLUSIONS

In non-obese, recently diagnosed hypertensive patients, the SG parameter seems to be an early marker for the development of metabolic syndrome.