Association of ghrelin dynamics with beta cell function in Japanese subjects with normal glucose tolerance

Body Roundness Index Is Better Correlated with Insulin Sensitivity than Body Shape Index in Young and Middle-Aged Japanese Persons

Aims: The present study aimed to clarify the relationships between novel and traditional anthropometric indices and insulin sensitivity (SI) in young and middle-aged Japanese persons with normal glucose tolerance (NGT), and middle-aged Japanese persons with NGT and glucose intolerance. Methods: Plasma glucose and insulin levels were measured in 1270 young (age <40 years) and 2153 middle-aged persons with NGT (n = 1531) and glucose intolerance (n = 622) during a 75-g oral glucose tolerance test. Height (Ht), weight, and waist circumference (WC) were measured. The body mass index (BMI), WC, and the WC/Ht ratio were used as traditional anthropometric indices. A body shape index (ABSI) and the body roundness index (BRI) were calculated as novel indices. Indices of SI (Matsuda index and 1/homeostasis model assessment of insulin resistance) were calculated and compared with anthropometric indices. Results: The ABSI showed a weak correlation with SI indices in all groups. The BRI showed almost the same correlation with SI indices as the BMI, WC, and WC/Ht in all groups. The inverse correlation between each of the anthropometric indices other than ABSI and SI indices was weak in young persons, at 0.16-0.27 (Spearman's ρ values), but strong in middle-aged persons, at 0.38-1.00. On receiver-operating characteristic (ROC) curve analysis for detection of insulin resistance, the ABSI had a lower area under the ROC curve (AUC) than the other anthropometric indices, and the BRI and the WC/Ht ratio showed similar AUCs. The AUCs for the BRI and WC/Ht ratio were the highest in middle-aged men with NGT and glucose intolerance. Conclusions: The BRI, not the ABSI, was better correlated with SI in young and middle-aged Japanese persons. The BRI and WC/Ht ratio were comparable in their correlations with SI and the detection of insulin resistance in the participants of the present study.

Diabetic family history in young Japanese persons with normal glucose tolerance associates with k-means clustering of glucose response to oral glucose load, insulinogenic index and Matsuda index

Aims

The present study aimed to clarify the relationships between diabetic family history (FH), and dysglycemic response to the oral glucose tolerance test (OGTT), insulin secretion, and insulin sensitivity in young Japanese persons with normal glucose tolerance (NGT).

Methods

We measured plasma glucose (PG) and immunoreactive insulin levels in 1,309 young Japanese persons (age <40 years) with NGT before and at 30, 60, and 120 min during a 75-g OGTT. Dysglycemia during OGTT was analyzed by k-means clustering analysis. Body mass index (BMI), blood pressure (BP), and lipids were measured. Insulin secretion and sensitivity indices were calculated.

Results

PG levels during OGTT were classified by k-means clustering analysis into three groups with stepwise decreases in glucose tolerance even among individuals with NGT. In these clusters, proportion of males, BMI, BP and frequency of FH were higher, and lipid levels were worse, together with decreasing glucose tolerance. Subjects with a diabetic FH showed increases in PG after glucose loading and decreases in insulinogenic index and Matsuda index.

Conclusions

Dysglycemic response to OGTT by k-means clustering analysis was associated with FH in young Japanese persons with NGT. FH was also associated with post-loading glucose, insulinogenic index, and Matsuda index.

Glucose Effectiveness Decreases in Relationship to a Subtle Worsening of Metabolic Parameters in Young Japanese with Normal Glucose Tolerance

Background: The aim of the study was to investigate the relationship between glucose effectiveness (Sg) and some metabolic parameters in male and female young Japanese. Methods: We measured plasma glucose and immunoreactive insulin levels in 1309 young Japanese persons (age <40 years) with normal glucose tolerance (NGT) before and at 30, 60, and 120 min during a 75 gram oral glucose tolerance test. We also measured serum adiponectin and high-sensitivity C-reactive protein (hsCRP) levels and oral glucose effectiveness (SgI_O), and investigated factors related to SgI_O. Results: The results of Spearman correlation analysis revealed that high-density lipoprotein cholesterol (HDL) and adiponectin were positively correlated with SgI_O, whereas the proportion of males, body mass index, waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure, triglycerides (TG), and hsCRP were inversely correlated with SgI_O. The results of multiple regression analysis indicated negative correlations between SgI_O and the proportion of males, WC, and SBP and a positive correlation with HDL. The results of multiple regression analysis excluding WC indicated negative correlations between SgI_O and the proportion of males, SBP, and TG and positive correlations with HDL and adiponectin. Conclusions: Sg decreased with a subtle worsening of metabolic parameters, even in young persons with NGT. Decreased Sg may be involved in the development of glucose intolerance in individuals with worse metabolic parameters.

Swimming exercise improves gene expression of PPAR-γ and downregulates the overexpression of TLR4, MyD88, IL-6, and TNF-α after high-fat diet in rat skeletal muscle cells

Exercise training with anti-inflammatory effects can improve insulin sensitivity in muscle tissue. This study investigated the effects of eight-week swimming exercises on lipid profile, toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and peroxisome proliferator-activated receptor gamma (PPAR-γ) in gastrocnemius muscle of rats fed with high-fat diet (HFD). Thirty-two healthy male Wistar rats (8 weeks, 200 ± 20 g) were randomly divided into four groups (n = 8 each group): the control (C), aerobic exercise (E), HFD, and HFD + aerobic exercise (HFD & E). The exercise training protocol consisted of swimming 60 min/day, 5 days/week for eight weeks. Serum levels of glucose, insulin, and lipid profile were measured at end of the study. Protein expressions of TLR4, TNF-α, and IL-6 were determined by immunohistochemical method. Gene expression of TLR4/MyD88, TNF-α, IL-6, and PPAR-γ was evaluated by a real-time polymerase chain reaction in gastrocnemius muscle. HFD fed rats showed higher levels of cholesterol and LDL-c that were similar in weight gain. Meanwhile, the HFD group had a higher gene expression of TLR4, MyD88, TNF-α, IL-6, and lower gene expression of PPAR-γ compared to the control group (p < 0.05). Muscle protein expression of TLR4, TNF-α, IL-6 was lower in the E and HFD&E groups (especially when compared to HFD group, P < 0.05). We also showed a decrease in TLR4/MyD88 mRNA and an increase in PPAR-γ mRNA in gastrocnemius of E and HFD&E groups (compared to HFD group, p < 0.05). Insulin resistance in HFD&E groups show a significant decrease compared to the HFD group (p < 0.05). It seems that swimming aerobic exercise for eight weeks controlled the destructive effects of HFD on muscle inflammatory pathways along with the down-regulation of the TLR4/MyD88, inflammatory cytokine, and up-regulation PPAR-γ mRNA. It appears that the down-regulation in the expression of TLR4/MyD88 mRNA reduces the muscle pro-inflammatory cytokines, such as IL-6 and TNF-α, whose action may be caused by the adaptation of swimming aerobic exercise (an increase of PPAR-γ). Therefore, local and systemic inflammatory changes due to HFD and obesity may be affected by metabolic adaptations of aerobic exercise training, which requires further studies.

Postloading insulinemia is independently associated with arterial stiffness in young Japanese persons

Associations of arterial stiffness with glucose, insulin, and proinsulin dynamics during the oral glucose tolerance test (OGTT) remain under debate. The aim of this study was to investigate whether plasma glucose (PG), insulin, and proinsulin (Pro) contribute to arterial stiffness, measured by pulse wave velocity (PWV), in young Japanese persons. PG, immunoreactive insulin (IRI), and Pro levels were determined in 1193 young Japanese subjects (<40 years of age) with normal glucose tolerance or nondiabetic hyperglycemia before and at 30, 60, and 120 min during a 75-g OGTT. Participants were divided into two groups according to the median PWV. Background factors, PG, IRI, and Pro levels during the OGTT, and insulin sensitivity (SI) indices in each group were compared. Several multiple regression analysis models were used to evaluate factors contributing to PWV. All IRI and Pro levels before and after glucose loading and the area under the curve (AUC) values for IRI and Pro increased with higher PWV. 1/HOMA-IR and ISI-Matsuda as measures of SI decreased with higher PWV. The IRI AUC and Pro level before glucose loading (Pro0) were independently associated with PWV, in addition to male sex, heart rate, and mean blood pressure. The IRI AUC had a stronger relationship with PWV than Pro0. The IRI AUC had an independent relationship with PWV, whereas both SI indices did not. Postloading insulinemia, but not reduced SI, was independently associated with arterial stiffness in young Japanese persons.

Insulin and Proinsulin Dynamics Progressively Deteriorate From Within the Normal Range Toward Impaired Glucose Tolerance

Context

Slight elevations in plasma glucose (PG) manifest in advance of diabetes onset, but abnormalities in immunoreactive insulin (IRI), proinsulin (Pro), and adiponectin dynamics during this stage remain poorly understood.

Objective

The objective of this work is to investigate whether IRI and Pro dynamics become abnormal as glucose tolerance deteriorates from within the normal range toward impaired glucose tolerance (IGT), as well as the relationship between PG, and these dynamics and serum adiponectin levels.

Design

A cross-sectional study was designed.

Setting

This study took place at Jichi Medical University in Japan.

Participants and Measurements

PG, IRI, and Pro levels were determined in 1311 young Japanese individuals (age < 40 years) with normal or IGT before and at 30, 60, and 120 minutes during a 75-g oral glucose tolerance test. Participants were assigned to 4 groups according to glucose tolerance, and then background factors, adiponectin levels, insulin sensitivity (SI), and insulin secretion (β) indexes were determined.

Results

PG levels as well as IRI and Pro levels 60 and 120 minutes after glucose-loading increased incrementally with deteriorating glucose tolerance. All measures of β and the SI measure index of insulin sensitivity (ISI)-Matsuda decreased incrementally. Serum adiponectin levels were not significantly different among the glucose tolerance groups, but were independently and negatively correlated with fasting glucose.

Conclusions

Early β decreased and postloading Pro levels became excessive in a progressive manner as glucose tolerance deteriorated from within the normal range toward IGT.