Lucia Perego

Type 2 diabetes is characterized by insulin resistance and inadequate insulin secretion. In the advanced stages of the disease, beta-cell dysfunction worsens and insulin therapy may be necessary to achieve satisfactory metabolic control. Studies in autopsies found decreased beta-cell mass in pancreas of people with type 2 diabetes. Apoptosis, a constitutive program of cell death modulated by the Bcl family genes, has been implicated in loss of beta-cells in animal models of type 2 diabetes. In this study, we compared the effect of 5 days' culture in high glucose concentration (16.7 mmol/l) versus normal glucose levels (5.5 mmol/l) or hyperosmolar control (mannitol 11 mmol/l plus glucose 5 mmol/l) on the survival of human pancreatic islets. Apoptosis, analyzed by flow cytometry and electron and immunofluorescence microscopy, was increased in islets cultured in high glucose (HG5) as compared with normal glucose (NG5) or hyperosmolar control (NG5+MAN5). We also analyzed by reverse transcriptase-polymerase chain reaction and Western blotting the expression of the Bcl family genes in human islets cultured in normal glucose or high glucose. The antiapoptotic gene Bcl-2 was unaffected by glucose change, whereas Bcl-xl was reduced upon treatment with HG5. On the other hand, proapoptotic genes Bad, Bid, and Bik were overexpressed in the islets maintained in HG5. To define the pancreatic localization of Bcl proteins, we performed confocal immunofluorescence analysis on human pancreas. Bad and Bid were specifically expressed in beta-cells, and Bid was also expressed, although at low levels, in the exocrine pancreas. Bik and Bcl-xl were expressed in other endocrine islet cells as well as in the exocrine pancreas. These data suggest that in human islets, high glucose may modulate the balance of proapoptotic and antiapoptotic Bcl proteins toward apoptosis, thus favoring beta-cell death.

Insulin and insulin-like growth factor (IGF-1) are mitogenic for fibroblasts and smooth muscle cells. IGF-1 increases in inflamed and fibrotic tissues and induces proliferation of rat hepatic stellate cells (HSC). This study evaluates the potential roles of these hormones in the development of liver fibrosis. Insulin and IGF-1 receptor expression was evaluated by immunohistochemistry in both cultured human HSC and human liver tissue. Phosphorylation of both 70-kd S6 kinase and extracellular-regulated kinase (ERK), cell proliferation, type I collagen gene expression, and accumulation in HSC culture media were evaluated by Western blot, immunohistochemistry for bromodeoxyuridine (BrdU), Northern blot, and enzyme-linked immunosorbent assay, respectively. Insulin and IGF-1 receptors were detected in HSC in vitro and in liver sections from patients with chronic active hepatitis. Insulin and IGF-1 induced 70-kd S6 kinase phosphorylation in HSC, whereas IGF-1 only induced ERK phosphorylation. Insulin and IGF-1 stimulated HSC proliferation in a dose-dependent fashion, with IGF-1 being four to five times more potent than insulin. Cell exposure to specific inhibitors showed that both phosphatidylinositol 3-kinase (PI3-K) and ERK are involved in IGF-1-induced mitogenesis, whereas insulin stimulated mitogenesis through a PI3-K-dependent ERK-independent pathway. IGF-1 increased type I collagen gene expression and accumulation in HSC culture media through a PI3-K- and ERK-dependent mechanism. In conclusion, insulin and IGF-1, which stimulate HSC mitogenesis and collagen synthesis, may act in concert to promote liver fibrosis in vivo by a differential activation of PI3-K- and ERK1-dependent pathways.

OBJECTIVE: Lifestyle modifications and pharmacological interventions can prevent type 2 diabetes in obese subjects with impaired glucose tolerance. The aim of this study was to compare laparoscopic adjustable gastric banding (LAGB) and conventional diet (No-LAGB) in the prevention (primary intervention study; 56 vs. 29 patients) and remission (secondary intervention study; 17 vs. 20 patients) of type 2 diabetes and hypertension in grade 3 obesity in a 4-year study. RESEARCH DESIGN AND METHODS: The subjects (n = 122; age 48.5 +/- 1.05 years; BMI 45.7 +/- 0.67 kg/m2) underwent a diagnostic workup, including psychological and psychiatric assessments, in preparation for the LAGB procedure. Of the 122 subjects, 73 had the surgery (LAGB group). The control group (No-LAGB group) consisted of the 49 subjects who refused the surgery but agreed to be followed up; 6 of these subjects dropped out by the 2nd year of the study, so that the final number of patients was 73 and 43 in the LAGB and No-LAGB groups, respectively. All patients had a yearly visit and oral glucose tolerance test. RESULTS: From baseline to the end of the 4-year follow-up, BMI decreased from 45.9 +/- 0.89 at baseline to 37.7 +/- 0.71 kg/m2 in the LAGB group and remained steady in the No-LAGB group (from 45.2 +/- 1.04 to 46.5 +/- 1.37 kg/m2), with no significant differences between the primary and secondary intervention groups. In the primary intervention study, five of the No-LAGB subjects (17.2%) and none of the LAGB subjects (0.0%; P = 0.0001) progressed to type 2 diabetes; in the secondary intervention study, type 2 diabetes remitted in one No-LAGB patient (4.0%) and seven LAGB patients (45.0%; P = 0.0052). Hypertension occurred in 11 No-LAGB patients (25.6%) and 1 LAGB patient (1.4%; P = 0.0001) and remitted in 1 No-LAGB (2.3%) and 15 LAGB patients (20.5%; P = 0.0001). A study of body mass composition revealed a significant reduction of fat mass and a transitory, but not significant, decrease of fat-free mass in LAGB patients. CONCLUSIONS: In morbid obesity, sustained and long-lasting weight loss obtained through LAGB prevents the occurrence of type 2 diabetes and hypertension and decreases the prevalence of these disorders.

CONTEXT: Obesity is frequently associated with left ventricular hypertrophy, even when uncomplicated by hypertension or diabetes mellitus. Left ventricular hypertrophy is an important risk factor for congestive heart failure. OBJECTIVE: The objective of this study was to evaluate the relationship between leptin and left ventricular mass in uncomplicated, morbid (grade 3) obesity and the existence of leptin receptors and intracellular signaling proteins in the human heart. DESIGN: Left ventricular mass (LVM) was calculated through electrocardiogram reading in normotensive grade III obese patients (World Health Organization classification) undergoing bariatric surgery [laparoscopic adjustable gastric banding (LAGB)] at baseline and 1 yr later. The control group was composed of healthy lean normotensive subjects. Leptin receptors were detected by PCR and immunocytochemistry in human heart biopsies. SETTING: This study was performed at university hospitals. PATIENTS: Thirty-one grade 3 obese patients and 30 healthy nonobese normotensive, age- and sex-matched control subjects were studied. INTERVENTION: Obese subjects underwent LAGB to induce weight loss and were evaluated at baseline and after 1 yr. RESULTS: LVM, plasma leptin, glucose, insulin levels, and homeostasis model assessment index were higher in obese than in lean controls (P < 0.01); at univariate regression analysis, LVM correlated with body mass index, leptin, and homeostasis model assessment index; at multiple regression analysis, LVM only correlated with leptin levels (P = 0.001). Obese subjects were reevaluated 1 yr after LAGB, when their body mass index changed from 46.2 +/- 1.24 to 36.6 +/- 1.05 kg/m(2) (P < 0.01); the decrease in LVM correlated only with the decrease in leptin levels (P < 0.01). We demonstrated that long and short isoforms of the leptin receptor and intracellular proteins mediating leptin signaling were expressed in human heart by RT-PCR, immunocytochemistry, or both methods. CONCLUSIONS: These data suggest that leptin could contribute to the left ventricular hypertrophy in humans.