Intracellular hyperinsulinism: a metabolic characteristic of obesity with and without Type 2 diabetes: intracellular insulin in obesity and Type 2 diabetes

Intracellular insulin in human tumors: examples and implications

Insulin is one of the major metabolic hormones regulating glucose homeostasis in the organism and a key growth factor for normal and neoplastic cells. Work conducted primarily over the past 3 decades has unravelled the presence of insulin in human breast cancer tissues and, more recently, in human non-small cell lung carcinomas (NSCLC). These findings have suggested that intracellular insulin is involved in the development of these highly prevalent human tumors. A potential mechanism for such involvement is insulin's binding and inactivation of the retinoblastoma tumor suppressor protein (RB) which in turn is likely controlled by insulin-degrading enzyme (IDE). This model and its supporting data are collectively covered in this survey in order to provide further insight into insulin-driven oncogenesis and its reversal through future anticancer therapeutics.

Body weight reduction in rats by oral treatment with zinc plus cyclo-(His-Pro)

BACKGROUND AND PURPOSE

We have previously shown that treatment with zinc plus cyclo-(His-Pro) (CHP) significantly stimulated synthesis of the insulin degrading enzyme and lowered plasma insulin and blood glucose levels, alongside improving oral glucose tolerance in genetically type 2 diabetic Goto-Kakizaki (G-K) rats and in aged obese Sprague-Dawley (S-D) rats. Thus, we postulated that zinc plus CHP (ZC) treatment might also improve body weight control in these rats. We therefore determined the effects of ZC treatment on body weights in both genetically diabetic, mature G-K rats and non-diabetic, obese S-D rats.

EXPERIMENTAL APPROACH

G-K rats aged 1.5-10 months and non-diabetic overweight or obese S-D rats aged 6-18 months were treated with 0-6 mg CHP plus 0-10 mg zinc L(-1) drinking water for 2-4 weeks, and changes in weight, serum leptin and adiponectin levels, food and water intakes were measured.

KEY RESULTS

The optimal dose of CHP (in combination with zinc) to reduce weight and plasma leptin levels and to increase plasma adiponectin levels was close to 0.1 mg kg(-1) day(-1), in either mature G-K rats and aged overweight or obese S-D rats. Food and water intake significantly decreased in ZC treated rats in both aged S-D rats and mature G-K rats, but not in young S-D and G-K rats.

CONCLUSIONS AND IMPLICATIONS

ZC treatment improved weight control and may be a possible treatment for overweight and obesity.

Impact of large-volume liposuction on serum lipids in orientals: a pilot study

Recent advances in liposuction techniques now make it possible to remove considerable amounts of subcutaneous adipose tissue. However, the metabolic consequences of this procedure are not well documented. The aim of this study was to identify the effects from the surgical removal of subcutaneous fat on the body weights and serum lipids of patients who have undergone large-volume liposuction. In this study, eleven consecutive patients with a minimum aspirate volume of 5,000 ml were evaluated, and their serum lipids were measured at a postoperative 2-month follow-up assessment. Tumescent fluid was infiltrated using the superwet technique. The liposuction device used was a Liposlim power-assisted liposuction system. The amount of solution infiltrated and the volume of aspirate were measured. Pre- and postoperative serum lipids, body weights, and body mass indices were compared. Statistical analysis was performed on lipid profile changes and aspirate volumes using Spearman's correlations. The average volumes of infiltrate and aspirate were 7,241 and 6,790 ml, respectively. Mean body weight decreased from 64.5 +/- 18.8 to 59.9 s +/- 17.8 kg (p < 0.01). The change in body weight per 1 l of aspirate volume was 0.67 +/- 0.10 kg/l. The mean body mass index dropped from 23.8 +/- 4.4 to 22.0 +/- 4.2 kg/m(2) (p < 0.01), and the mean total serum cholesterol levels from 168.2 +/- 23.6 to 162.9 +/- 26.5 mg/dl, an average of 3.2%. The mean low-density lipoprotein (LDL) decreased from 94.3 +/- 20.5 to 89.5 +/- 19.0 mg/dl, a 5.1% drop, and the mean high-density lipoprotein (HDL) decreased from 55.8 +/- 9.5 to 53.7 +/- 10.7 mg/dl, a 3,8% drop. The mean HDL/LDL proportion increased from 62.6 +/- 20.9% to 63.5 +/- 22.4%, averaging 1.4%. However, no significant correlation was found between the aspirated volume of fat and lipid profile change. In conclusion, over a 2-month period, large-volume liposuction reduced weight and total cholesterol level and increased the HDL/LDL ratio. The authors hope to discover whether the therapeutic impact of liposuction is long-lasting, and to determine whether it reduces the morbidity and mortality associated with obesity.

Insulin secretion, peripheral insulin sensitivity and insulin-receptor binding in subjects with different degrees of obesity

OBJECTIVES

The aim of the present study was to investigate insulin secretion, insulin-receptor binding and peripheral insulin sensitivity in subjects with different degrees of obesity.

METHODS

36 obese subjects with normal glucose tolerance and different degrees of obesity and 40 healthy normal-weight subjects participated in the study. Peripheral insulin sensitivity was measured by using the euglycaemic hyperinsulinaemic clamp technique, and insulin-receptor binding-on circulating mononuclear blood cells. Insulin secretion was studied during intravenous tolbutamide test.

RESULTS

The subjects with I degree of obesity demonstrated a significant decrease in the number of total (p<0.0001) and high-affinity (p<0.01) insulin receptors per cell, as well as significantly higher insulin receptor affinity (p<0.01) as compared to the normal-weight subjects. The subjects with II degree of obesity also demonstrated a significant decrease in the number of total (p<0.0001) and high-affinity receptors (p<0.001) per cell as well as an increase (p<0.001) in insulin-receptor affinity as compared to the controls. The significantly decreased receptor number in the subjects with I and II degree of obesity was accompanied by an increase in insulin receptor affinity; thus their insulin-receptor binding being maintained similar to the controls. The subjects with III degree obesity presented a significant decrease (p<0.0001) in the number of both the total and high-affinity insulin receptors as well as a reduction in insulin receptor affinity as compared to the controls. Therefore the percentage of specifically bound insulin was significantly lower (p<0.01) as compared to that of the control group. Insulin resistance in the obese subjects is associated with secondary hyperinsulinaemia, which is present in subjects with I and II degree of obesity; while in severely obese subjects exhaustion of beta-cell secretory capacity is observed.

CONCLUSION

We consider that III degree of obesity appears to be a risk factor for type 2 diabetes mellitus as the alterations in insulin sensitivity, insulin-receptor binding and beta-cell secretion are quite similar to the reported in diabetic patients.

Insulin permeability across an in vitro dynamic model of endothelium

PURPOSE

Endothelium insulin permeability was investigated using in vitro, dynamic culture of endothelial cells.

METHODS

Endothelial cells were cultured in a hollow fiber apparatus and continuously exposed to a flow. Transendothelial electrical resistance and permeability to [14C]sucrose and [14C]inulin were used to monitor the integrity of the endothelial monolayer.

RESULTS

Under these experimental conditions, measurements of insulin permeability, investigated at increasing hormone concentrations, suggested that the predominant transendothelial insulin fluxes were attributable to bidirectional convective transport rather than to a saturable transport mechanism, in agreement with in vivo experiment results published earlier. Analytical determinations of insulin catabolism demonstrated a low percent of insulin degradation by the endothelium, leading to production of insulin metabolites qualitatively identical to those produced by human monocytes.

CONCLUSIONS

The findings of this paper indicated that (a) insulin crosses the endothelial monolayer by paracellular "leak" and endothelial insulin receptors have a minor (if any) role in insulin transport; (b) degradation of the hormone by BAEC is minimal; (c) the in vitro, dynamic culture of endothelial cells presented here should represent a valuable transport model system to study permeability mechanisms of insulin and many other drugs.

Improvements in cardiovascular risk profile with large-volume liposuction: a pilot study

In this study, the authors investigated the physiologic effects of the altered body composition that results from surgical removal of large amounts of subcutaneous adipose tissue. Fourteen women with body mass indexes of greater than > 27 kg/m2 underwent measurements of fasting plasma insulin, triglycerides, cholesterol, body composition by dual-energy x-ray absorptiometry (DXA), resting energy expenditure, and blood pressure before and after undergoing large-volume ultrasound-assisted liposuction. There were no significant intraoperative complications. Body weight had decreased by 5.1 kg (p < 0.0001) by 6 weeks after liposuction, with an additional 1.3-kg weight loss (p < 0.05) observed between 6 weeks and 4 months after surgery, for a total weight loss of 6.5 kg (p < 0.00006). Body mass index decreased from (mean +/- SEM) 28.8 +/- 2.3 to 26.8 +/- 1.5 kg/m2 (p < 0.0001). This change in body weight was primarily the result of decreases in body fat mass: as assessed by DXA, lean body mass did not change (43.8 +/- 3.1 kg to 43.4 +/- 3.6 kg, p = 0.80), whereas DXA total body fat mass decreased from 35.7 +/- 6.3 to 30.1 +/- 6.5 kg (p < 0.0001). There were significant decreases in fasting plasma insulin levels (14.9 +/- 6.5 mIU/ml before liposuction versus 7.2 +/- 3.2 mIU/ml 4 months after liposuction, p < 0.007), and systolic blood pressure (132.1 +/- 7.2 versus 120.5 +/- 7.8 mmHg, p < 0.0002). Total cholesterol, high-density lipoprotein cholesterol, plasma triglycerides, and resting energy expenditure values were not significantly altered after liposuction. In conclusion, over a 4-month period, large-volume liposuction decreased weight, body fat mass, systolic blood pressure, and fasting insulin levels without detrimental effects on lean body mass, bone mass, resting energy expenditure, or lipid profiles. Should these improvements be maintained over time, liposuction may prove to be a valuable tool for reducing the comorbid conditions associated with obesity.