Proinsulin C-peptide shows beneficial effects on microvascular complications of Type 1 diabetes. However, the possible occurrence of membrane C-peptide receptor(s) has not been elucidated. The aim of this study was to identify and characterize membrane proteins to which C-peptide binds. The enzyme α-enolase was co-immunoprecipitated with C-peptide after chemical cross-linking to HL-60 cell surface proteins and identified by mass spectrometry. Recombinant α-enolase activity was modulated by C-peptide, with a significant decrease in Km for 2-phosphoglycerate without affecting Vmax. The enzyme modulation by C-peptide was abolished when C-terminal basic lysine residue (K434) of the enzyme was replaced by neutral alanine or acidic glutamate, but not with basic arginine. The enzyme modulation by C-peptide was reproduced with the C-peptide fragments containing glutamate corresponding to position 27 (E27) of the full-length C-peptide. Addition of a lysine analogue to the assay and A31 cell culture abrogated the enzyme modulation and MAP kinase activation by C-peptide, respectively. The results indicate that C-peptide has the capacity to activate α-enolase through a specific interaction between E27 of the peptide and K434 of the enzyme. Since α-enolase plays a role as a cell surface receptor for plasminogen, it may conceivably also serve as a receptor for C-peptide in vivo.
1. In the present study, we conducted the first randomized, double-blind, placebo-controlled study of bofu-tsusho-san (BF), an oriental herbal medicine (24 mg/day ephedrine in Ephedrae Herba and an efficacy equivalent of 280 mg caffeine, judging from the phosphodiesterase-inhibitory effect of Glycyrrhizae Radix, Forsythiae Fructus and Schizonepetae Spica and another 14 crude drugs) in obese women with impaired glucose tolerance (IGT). 2. The aim of the present study was to determine whether BF was effective in decreasing visceral adiposity and insulin resistance. Eighty-one Japanese women (body mass index (BMI) 36.5 ± 4.8 kg/m2) with IGT and insulin resistance (IR), who had been treated with a low-calorie diet (5016 kj/day: 1200 kcal) and an exercise regimen (1254 kj/day: 300 kcal), were randomized to receive either placebo (n = 40) or BF treatment (n = 41) three times a day. 3. After 24 weeks treatment, the BF group lost significantly (P < 0.01) more bodyweight and abdominal visceral fat without a decrease in the adjusted resting metabolic rate (RMR), whereas the placebo group lost bodyweight (P < 0.05) and had no significant change in abdominal visceral fat. The BF group had a lower fasting serum insulin level (P < 0.05), a lower insulin area under the curve (P < 0.05) and a lower level of the homeostasis model assessment of insulin resistance (P < 0.01) compared with values before treatment. 4. We conclude that BF could be a useful herbal medicine in treating obesity with IGT.
To clarify whether cigarette smoke stimulates the sympathetic nervous system (SNS) and thermogenesis in interscapular brown adipose tissue (IBAT), we measured norepinephrine (NE) turnover, an indicator of SNS activity, guanosine-5'-diphosphate (GDP) binding, a thermogenic indicator, and oxygen consumption in IBAT in monosodium-L-glutamate (MSG)-induced obese and saline control mice following a two-week exposure to cigarette smoke. Cigarette smoke significantly increased NE turnover, GDP binding and oxygen consumption in IBAT, and significantly reduced body weight in MSG obese mice as well as in control mice. However, food intake was unchanged in the MSG group. These results suggest that cigarette smoke stimulates NE turnover and thermogenesis in BAT, which contribute to the mitigation of obesity.
SUMMARY 1. The anti‐obesity and anti‐diabetic effects of mazindol were evaluated in obese diabetic yellow KK mice and C57B1 control mice. 2. The study compound was fed through a gastric tube at a rate of 1 or 2 mg/kg per day (0.01 mol/L HC1 as control) for 2 weeks. The following parameters were compared in treated and control animals: bodyweight, food intake, white adipose tissue (WAT) weight, brown adipose tissue (BAT) weight and its thermogenesis, noradrenaline (NA) turnover, blood glucose and serum insulin levels and glucose transporter 4 (GLUT4). 3. Furthermore, bodyweight loss of mice pair‐fed the same amount of food as the mazindol‐treated mice for 2 weeks was measured. 4. Mazindol significantly decreased food intake and significantly increased guanosine‐5′‐diphosphate‐binding in BAT mitochondria and NA turnover in BAT in both yellow KK and C57B1 groups. The amounts of WAT in subcutaneous, mesenteric and retroperitoneal regions and bodyweights were significantly decreased in both groups. Bodyweight loss in mice pair fed with the mazindol‐treated groups was approximately 70% compared with that in the mazindol‐treated groups. Furthermore, mazindol decreased the levels of blood glucose and serum insulin during the glucose overloading test in yellow KK mice, but it did not influence the GLUT4 protein concentration in WAT and muscle. 5. These observations suggest that mazindol possesses both an anti‐obesity action, due to the inhibition of appetite as well as the activation of BAT thermogenesis via increased NA turnover in BAT, and an anti‐diabetic action. Consequently, mazindol may be useful for the treatment of obesity as well as non‐insulin‐dependent diabetes mellitus in obese persons.
The minced pancreas of the neonatal rat was cultured for 35 days in a pancreatic chamber which was constructed of a plastic tube and an ultrafiltration membrane. Insulin and amylase secreted from this pancreatic chamber into the culture medium were measured. During the experiment, the concentration of glucose in the culture medium was changed between 5.5 and 16.5 mM at 2-3 day intervals in order to determine the insulin secretory response of the pancreatic tissue. Insulin secretion was markedly increased in response to 16.5 mM glucose. The ratio of insulin secretion to amylase secretion in the culture medium increased with the advance of culture days although secretions of both insulin and amylase decreased individually. On the 7th culture day, short term incubations were performed to test with various insulin secretagogues; obvious insulin release into the incubation medium was observed. These results show that the pancreatic chamber also in vitro secretes insulin rapidly and significantly in response to various stimuli; that by longer culture of a neonatal rat pancreas in this device, insulin secretory cells without exocrine tissue would be obtained without using digestive enzymes; that application of a pancreatic chamber for a pancreatic transplantation may be feasible.
Resumen en: We conducted a randomized, double-blind placebo controlled study of bofu-tsusho-san (BF), in obese women with impaired glucose tolerance (IGT). The Kampo...
