Differences in insulin sensitivity, pancreatic beta cell function and circulating adiponectin across glucose tolerance status in Thai obese and non-obese women

Association Between Bone Mineral Density and Pancreatic β-Cell Function in Elderly Men and Postmenopausal Women

Purpose:

To explore the association between bone mineral density (BMD) and β-cell function.

Methods:

A cross-sectional study was performed in Fujian, China, from 2011 to 2012. The study included 572 elderly men older than age 60 years and 1558 postmenopausal women aged 45 to 86 years, excluding those with diabetes and insulin resistance. Fasting glucose and insulin concentrations were measured. Pancreatic β-cell function was estimated by using the homeostasis model assessment (HOMA-β). Calcaneus BMD was measured by using quantitative ultrasonography. Multiple regression analyses were applied to explore the association.

Results:

Participants with decreased BMD had lower fasting glucose (P < 0.001 in postmenopausal women; P = 0.007 in elderly men) and greater HOMA-β (P = 0.001 in postmenopausal women; P = 0.008 in elderly men) than those with normal BMD, whereas no statistical differences in insulin were seen among categories of BMD. After adjustment for all confounders, HOMA-β was still significantly negatively related to BMD in both groups (all P < 0.001), and remarkable positive relationships were found between BMD and fasting glucose. Furthermore, binary logistic regression presented fully adjusted odds ratios for diabetes in those with osteoporosis vs those with normal BMD: 0.60 [95% confidence interval (CI), 0.38 to 0.94] and 0.66 (95% CI, 0.49 to 0.91) in the original selected population of elderly men (n = 1070) and postmenopausal women (n = 2825), respectively.

Conclusions:

BMD was independently inversely associated with HOMA-β and positively associated with fasting glucose in both elderly men and postmenopausal women, suggesting that bone mass may be a predictor of glucose metabolism. Further research is needed to verify the associations and determine the exact mechanism underlying them.

Associations Between Serum 25-Hydroxyvitamin D, Insulin Sensitivity, Insulin Secretion, and β-Cell Function According to Glucose Tolerance Status

BACKGROUND

The objective of this study was to determine whether glucose tolerance status influences the associations between serum 25-hydroxyvitamin D [25(OH)D], insulin sensitivity, insulin secretion, and β-cell function.

METHODS

This cross-sectional study included 112 French Canadian postmenopausal women with normal glucose tolerance (NGT; n = 65) or abnormal glucose tolerance (AGT; n = 47). Estimates of insulin sensitivity [homeostasis model assessment of insulin sensitivity (HOMA %S) and glucose disposal rate (GDR)], insulin secretion [area under the curve of C-peptide (AUC C-peptide)], and β-cell function (GDR × AUC C-peptide) were derived from a 2-hr euglycemic-hyperinsulinemic clamp and a 75-gram 3-hr oral glucose tolerance test (OGTT). Measures of adiposity were taken (waist circumference, body mass index, fat mass by the hydrostatic weighting technique, and computed tomography (CT)-derived total and visceral adiposity), questionnaires on physical activity, dietary calcium, and vitamin D intake were administered, and blood was sampled for measurement of parathyroid hormone, interleukin-6, and adiponectin.

RESULTS

AGT status was significantly associated with lower insulin sensitivity and β-cell function (P ≤ 0.01 for all) but not with insulin secretion. Lower serum 25(OH)D concentrations were significantly associated with lower insulin sensitivity and secretion (P ≤ 0.01 for all) but not with β-cell function. The interaction between glucose tolerance status and serum 25(OH)D concentration was not significant for either insulin sensitivity, insulin secretion, or β-cell function, even after adjustment for potential confounders.

CONCLUSION

Vitamin D and glucose tolerance status are both independently associated with measures of insulin sensitivity, insulin secretion, and β-cell function. However, the association between serum 25(OH)D and these surrogate markers of type 2 diabetes mellitus risk is not influenced by glucose tolerance status.

Different associations of diabetes with β-cell dysfunction and insulin resistance among obese and nonobese Chinese women with prior gestational diabetes mellitus

OBJECTIVE

To examine the relative contributions of β-cell dysfunction and insulin resistance to postpartum diabetes risk among obese and nonobese women with prior gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

We performed a cross-sectional survey 1-5 years after 1,263 women who had GDM gave birth. Polytomous logistic regression models were used to assess the associations of β-cell dysfunction (the lower quartile of HOMA-%β), insulin resistance (the upper quartile of HOMA-IR), decreased insulin sensitivity (the lower quartile of HOMA-%S), and different categories of BMI with prediabetes and diabetes risk.

RESULTS

β-Cell dysfunction, insulin resistance, and decreased insulin sensitivity all were significantly associated with hyperglycemic status across normal weight, overweight, and obese groups, and the patterns of insulin resistance and decreased insulin sensitivity were similar. BMI was inversely associated with β-cell dysfunction and positively associated with insulin resistance across normal glucose, prediabetes, and diabetes categories. Compared with women with normal glucose and weight, obese women with normal glucose had increased β-cell secretory function (odds ratio [OR] 0.09 [95% CI 0.02-0.37]) and insulin resistance (OR 17.4 [95% CI 9.47-31.9]). Normal weight diabetic women displayed the most β-cell dysfunction (OR 13.6 [95% CI 4.06-45.3]), whereas obese diabetic women displayed the highest insulin resistance (OR 45.8 [95% CI 18.5-113]).

CONCLUSIONS

For women with prior GDM, β-cell dysfunction had more pronounced contribution to postpartum diabetes among nonobese subjects, whereas insulin resistance contributed more to postpartum hyperglycemia among obese subjects.

Effects of leptin and adiponectin on pancreatic β-cell function

Leptin and adiponectin are hormones secreted from adipocytes that have important roles in metabolism and energy homeostasis. This review evaluates the effects of leptin and adiponectin on β-cell function by analyzing and compiling results from human clinical trials and epidemiologic studies as well as in vitro and in vivo experiments. Leptin has been shown to inhibit ectopic fat accumulation and thereby prevent β-cell dysfunction and protect the β-cell from cytokine- and fatty acid-induced apoptosis. However, leptin suppresses insulin gene expression and secretion as well as glucose transport into the β-cell. Adiponectin stimulates insulin secretion by enhancing exocytosis of insulin granules and upregulating the expression of the insulin gene; however, this effect depends on the prevailing glucose concentration and status of insulin resistance. In addition, adiponectin has antiapoptotic properties in β-cells. Available evidence concerning the role of these adipokines on insulin secretion, insulin gene expression, and apoptosis is not always entirely consistent; and many fundamental questions remain to be answered by future studies.

Rice intake and type 2 diabetes in Japanese men and women: the Japan Public Health Center-based Prospective Study

BACKGROUND

Refined carbohydrates have been suggested to deteriorate glucose metabolism; however, whether persons with elevated intakes of white rice, which is a major staple food for the Japanese, experience increased risk of developing type 2 diabetes remains unclear.

OBJECTIVE

We prospectively investigated the association between white rice intake and risk of type 2 diabetes.

DESIGN

Participants were 25,666 men and 33,622 women aged 45-75 y who participated in the second survey of the Japan Public Health Center-based Prospective Study and who had no prior history of diabetes. We ascertained food intake by using a validated 147-item food-frequency questionnaire. Odds ratios of self-reported, physician-diagnosed type 2 diabetes over 5 y were estimated by using logistic regressions.

RESULTS

A total of 1103 new cases of type 2 diabetes were self-reported. There was a significant association between rice intake and an increased risk of type 2 diabetes in women; the multivariate-adjusted odds ratio for the highest compared with lowest quartiles of rice intake was 1.65 (95% CI: 1.06, 2.57; P for trend = 0.005). In men, the association was unclear, although there was a suggestion of a positive association in persons who were not engaged in strenuous physical activity (P for trend = 0.08).

CONCLUSIONS

Elevated intake of white rice is associated with an increased risk of type 2 diabetes in Japanese women. The finding that is suggestive of a positive association of rice intake in physically inactive men deserves further investigation.

Dietary glycemic load, glycemic index, and refined grains intake are associated with reduced β-cell function in prediabetic Japanese migrants

OBJECTIVE: To investigate the association between carbohydrate intakes and β-cell function (HOMA-β) in Japanese-Brazilians with impaired glucose tolerance (IGT). METHODS: Dietary intakes were assessed by a validated food frequency questionnaire in a cross-sectional survey carried out in 2000. The associations between diet and HOMA-β were verified in 270 newly diagnosed IGT in multiple linear regression models. RESULTS: The mean (SD) age was 58 (11) years and the mean HOMA-β was 65 (47). The glycemic load was inversely associated with HOMA-β, β1 -0.140 (95%CI = -1.044; -0.078), p = 0.023. The inverse association was also observed for refined grains intakes: -0.186 (95%CI = -0.4862; -0.058), p = 0.012. After adjustments for body mass index, the glycemic index was inversely associated with HOMA-β: -0.1246 (95%CI = -2.2482, -0.0257), p < 0.001. CONCLUSIONS: These data suggested that dietary glycemic load, glycemic index, and refined grains intakes are associated with reduced β-cell function, and the quality of dietary carbohydrates may be relevant for maintaining β-cell function among individuals with IGT.