Excess energy intake, without a compensatory increase of energy expenditure, leads to obesity. Several molecules are involved in energy homeostasis regulation and new ones are being discovered constantly. Appetite regulating hormones such as ghrelin, peptide tyrosine-tyrosine and amylin or incretins such as the gastric inhibitory polypeptide have been studied extensively while other molecules such as fibroblast growth factor 21, chemerin, irisin, secreted frizzle-related protein-4, total bile acids, and heme oxygenase-1 have been linked to energy homeostasis regulation more recently and the specific role of each one of them has not been fully elucidated. This mini review focuses on the above mentioned molecules and discusses them in relation to their regulation by the macronutrient composition of the diet as well as diet-induced weight loss.
Appetite ; Bile Acids and Salts ; Diet ; Energy Intake ; Energy Metabolism ; Fibroblast Growth Factors ; Gastric Inhibitory Polypeptide ; Ghrelin ; Heme Oxygenase-1 ; Homeostasis* ; Incretins ; Islet Amyloid Polypeptide ; Obesity ; Physiology* ; Weight Loss*

Adrenocorticotropin (ACTH) independent bilateral macronodular adrenal hyperplasia (AIMAH) is a rare form of Cushing's syndrome, in which unique endocrinological, clinical and histopathological features have been described. In AIMAH, cortisol secretion is autonomous and independent of ACTH, thus plasma ACTH levels are persistently suppressed. Various etiological mechanisms have been proposed to explain the development of AIMAH, the development of aberrant adrenal sensitivity to gastric inhibitory polypeptide (GIP), vasopressin, beta-adrenergic receptor agonists or the presence of circulating adrenal stimulating immunoglobulins have been suggested. We report on a 46-year-old female who had Cushing's syndrome, due to AIMAH, with a positive response to vasopressin.
Adrenergic beta-Agonists ; Adrenocorticotropic Hormone ; Cushing Syndrome ; Female ; Gastric Inhibitory Polypeptide ; Humans ; Hydrocortisone ; Hyperplasia* ; Immunoglobulins ; Middle Aged ; Plasma ; Vasopressins

This study aimed to elucidate the effect of tryptophan (Trp) on gut hormone secretion as well as the roles of the calcium-sensing receptor (CaSR) and its downstream signaling pathway in gut hormone secretion by assessing swine duodenal perfusion in vitro. Swine duodenum was perfused with Krebs-Henseleit buffer as a basal solution. Various concentrations (0, 10, and 20 mM) of Trp were applied to investigate its effect on gut hormone secretion. A CaSR antagonist was used to detect the involvement of CaSR and its signal molecules. The 20 mM Trp concentration promoted the secretion of cholecystokinin (CCK) and glucose-dependent insulinotropic peptide (GIP), elevated the mRNA level of CaSR, and upregulated the protein levels of CaSR, protein kinase C (PKC), and inositol trisphosphate receptor (IP3R). However, NPS 2143, an inhibitor of CaSR, attenuated the CCK and GIP release, reduced the mRNA level of CaSR, and decreased the protein levels of CaSR, PKC, and IP3R with 20 mM Trp perfusion. The results indicate that CCK and GIP secretion can be induced by Trp in swine duodenum in vitro, and the effect is mediated by CaSR and its downstream signal molecules PKC and IP3R.
Cholecystokinin ; Duodenum ; Gastric Inhibitory Polypeptide ; In Vitro Techniques ; Inositol ; Perfusion ; Protein Kinase C ; Receptors, Calcium-Sensing ; RNA, Messenger ; Swine ; Tryptophan

OBJECTIVETo observe postoperative glucose tolerance, gastric inhibitory polypeptide (GIP) , and glucogan-like peptide-1 (GLP-1) in normal glucose level dogs after undergoing gastric bypass procedures, and to explore the mechanism of gastric bypass procedures to treat type 2 diabetes.

METHODSThe 6 dogs with normal glucose tolerance had undergone gastric bypass procedures, and measure preoperative and postoperative oral and intravenous glucose tolerance (at time points 1, 2, and 4 weeks) through changes in blood glucose, insulin, gastric inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and measure preoperative and postoperative week 4 pancreatic tissue morphology.

RESULTSSecond weeks after operation, the fasting blood sugar was (3.58 ± 0.33) mmol/L, and significantly lower than preoperative (t = 3.571, P < 0.05). The GLP-1 level before oral glucose tolerance test (OGTT) and 30 minutes after OGTT were (0.90 ± 0.21) and (0.91 ± 0.19) pmol/L respectively, and significantly higher than preoperative (t value were -3.660 and -2.971, P < 0.05). GLP-1 levels began to decrease in the second week after surgery. After 4 weeks, the index recovered to the preoperative level. Four weeks after surgery when compared with preoperative, islet morphology, islet number (6.8 ± 0.8 and 7.1 ± 0.8 respectively) and islet cells (16.7 ± 2.5 and 16.3 ± 3.1 respectively) did not change significantly (P > 0.05).

CONCLUSIONGastric bypass procedures could be briefly affect normal glucose tolerance in dogs' blood glucose, insulin and diabetes-related gastrointestinal hormones.

Animals ; Blood Glucose ; Diabetes Mellitus, Type 2 ; Dogs ; Gastric Bypass ; Gastric Inhibitory Polypeptide ; Glucagon ; Glucagon-Like Peptide 1 ; blood ; Glucose ; Insulin ; blood

Glucose-dependent insulinotropic peptide (GIP), the incretins, is synthesized and released from the duodenum and proximal jejunum. Continual high-fat diet powerfully stimulated GIP secretion, leading to obesity and harmful lipid deposition in islet cells and peripheral tissues, and giving rise to insulin resistance and major disturbances in the secretion of insulin. We can improve Type 2 diabetes by compromising GIP action. The exclusion of proximal small intestine and reduction of GIP secretion may be the important reasons for Type 2 diabetes after gastric bypass surgery.
Animals ; Diabetes Mellitus, Type 2 ; complications ; surgery ; Diet, High-Fat ; adverse effects ; Gastric Bypass ; Gastric Inhibitory Polypeptide ; metabolism ; Humans ; Insulin ; metabolism ; Insulin Secretion ; Obesity ; surgery

BACKGROUND: Incretin hormone levels as a predictor of type 2 diabetes mellitus have not been fully investigated. Therefore, we measured incretin hormone levels to examine the relationship between circulating incretin hormones, diabetes, and future diabetes development in this study. METHODS: A nested case-control study was conducted in a Korean cohort. The study included the following two groups: the control group (n=149), the incident diabetes group (n=65). Fasting total glucagon-like peptide-1 (GLP-1) and total glucose-dependent insulinotropic peptide (GIP) levels were measured and compared between these groups. RESULTS: Fasting total GIP levels were higher in the incident diabetes group than in the control group (32.64±22.68 pmol/L vs. 25.54±18.37 pmol/L, P=0.034). There was no statistically significant difference in fasting total GLP-1 levels between groups (1.14±1.43 pmol/L vs. 1.39±2.13 pmol/L, P=0.199). In multivariate analysis, fasting total GIP levels were associated with an increased risk of diabetes (odds ratio, 1.005; P=0.012) independent of other risk factors. CONCLUSION: Fasting total GIP levels may be a risk factor for the development of type 2 diabetes mellitus. This association persisted even after adjusting for other metabolic parameters such as elevated fasting glucose, hemoglobin A1c, and obesity in the pre-diabetic period.
Case-Control Studies ; Cohort Studies ; Diabetes Mellitus, Type 2* ; Fasting ; Gastric Inhibitory Polypeptide* ; Glucagon-Like Peptide 1 ; Glucose ; Incretins ; Multivariate Analysis ; Obesity ; Risk Factors

OBJECTIVETo investigate the secretion patterns of glucose-dependent insulinotropic polypeptide (GIP) after different dietary loads in subjects with normal glucose tolerance (NGT) and their relation to insulin secretion and plasma glucose levels.

METHODSFourteen subjects with normal glucose tolerance underwent 75 g glucose tolerance test(OGTT) followed by mixed meal tolerance test(MMT) one week later. Blood glucose, insulin, and GIP were measured in the fasting state and at 0, 15, 30, 60, 90 and 120 min after glucose load or mixed meal load.

RESULTSThe first peak value of GIP after glucose load occurred at 15 min (45.09∓4.67 pmol/L). After a brief decline, GIP continued to increase till reaching 59.66∓11.73 pmol/L at 120 min after the load. After the mixed meal load, GIP secretion presented with two peaks: the first peak appeared at 15 min (71.69∓14.19 pmol/L) with a level significantly higher than that at 15 min following glucose load (P<0.05), and the second occurred at 90 min (55.35∓13.19 pmol/L). The area under curve of GIP showed no significant difference between the two loads (P>0.05). Compared with glucose load, mixed meal load resulted in an increase of the first GIP peak and an earlier insulin peak (30 min vs 60 min), but a significant decrease of blood glucose at 15 min (P<0.05).

CONCLUSIONCompared with glucose load, mixed meal (containing fat) can strongly stimulate GIP release and cause earlier occurrence of the insulin peak, which might be an important reason for the lower blood glucose after mixed meal.

Adult ; Blood Glucose ; metabolism ; China ; ethnology ; Diet ; Energy Intake ; Female ; Gastric Inhibitory Polypeptide ; secretion ; Glucose Tolerance Test ; Humans ; Insulin ; secretion ; Male ; Middle Aged ; Young Adult

The sweet taste receptor is expressed in taste cells located in taste buds of the tongue. This receptor senses sweet substances in the oral cavity, activates taste cells, and transmits the taste signals to adjacent neurons. The sweet taste receptor is a heterodimer of two G protein-coupled receptors, T1R2 and T1R3. Recent studies have shown that this receptor is also expressed in the extragustatory system, including the gastrointestinal tract, pancreatic beta-cells, and glucose-responsive neurons in the brain. In the intestine, the sweet taste receptor regulates secretion of incretin hormones and glucose uptake from the lumen. In beta-cells, activation of the sweet taste receptor leads to stimulation of insulin secretion. Collectively, the sweet taste receptor plays an important role in recognition and metabolism of energy sources in the body.
Brain ; Calcium ; Cyclic AMP ; Enteroendocrine Cells ; Gastric Inhibitory Polypeptide ; Gastrointestinal Tract ; Glucagon-Like Peptide 1 ; Glucose ; Glucose Transport Proteins, Facilitative ; Incretins ; Insulin ; Intestines ; Mouth ; Neurons ; Taste Buds ; Tongue

BACKGROUND: Previous studies have reported that glypican-4 (GPC4) regulates insulin signaling by interacting with insulin receptor and through adipocyte differentiation. However, GPC4 has not been studied with regard to its effects on clinical factors in patients with type 2 diabetes mellitus (T2DM). We aimed to identify factors associated with GPC4 level in T2DM. METHODS: Between January 2010 and December 2013, we selected 152 subjects with T2DM and collected serum and plasma into tubes pretreated with aprotinin and dipeptidyl peptidase-4 inhibitor to preserve active gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). GPC4, active GLP-1, active GIP, and other factors were measured in these plasma samples. We performed a linear regression analysis to identify factors associated with GPC4 level. RESULTS: The subjects had a mean age of 58.1 years, were mildly obese (mean body mass index [BMI], 26.1 kg/m2), had T2DM of long-duration (mean, 101.3 months), glycated hemoglobin 7.5%, low insulin secretion, and low insulin resistance (mean homeostatic model assessment of insulin resistance [HOMA-IR], 1.2). Their mean GPC4 was 2.0±0.2 ng/mL. In multivariate analysis, GPC4 was independently associated with age (β=0.224, P=0.009), and levels of active GLP-1 (β=0.171, P=0.049) and aspartate aminotransferase (AST; β=–0.176, P=0.043) after being adjusted for other clinical factors. CONCLUSION: GPC4 was independently associated with age, active GLP-1, and AST in T2DM patients, but was not associated with HOMA-IR and BMI, which are well known factors related to GPC4. Further study is needed to identify the mechanisms of the association between GPC4 and basal active GLP-1 levels.
Adipocytes ; Aprotinin ; Aspartate Aminotransferases ; Body Mass Index ; Diabetes Mellitus ; Diabetes Mellitus, Type 2* ; Gastric Inhibitory Polypeptide ; Glucagon-Like Peptide 1* ; Glypicans* ; Hemoglobin A, Glycosylated ; Humans ; Insulin ; Insulin Resistance ; Linear Models ; Multivariate Analysis ; Plasma ; Receptor, Insulin

BACKGROUND: K-cells function as targets for insulin gene therapy. In a previous study, we constructed EBV-based plasmids expressing rat preproinsulin controlled by glucose-dependent insulinotropic polypeptide promoters. In the present study, we attempted to correct hyperglycemia in vivo using genetically engineered K-cells in a mouse model of type 1 diabetes. METHODS: K-cells expressing insulin were transplanted under the kidney capsules of STZ-induced diabetic mice. The blood glucose levels and body weights of the experimental animals were measured daily. After four weeks, the mice were injected intra-peritoneally with 2 g/kg glucose following a 6 hr fast. Blood glucose levels were measured immediately following glucose injections. All animals were sacrificed at the end of the glucose tolerance study, and pancreas and graft-bearing kidney tissue samples were stained with antibodies against insulin, glucagon, and C-peptide. RESULTS: The body weights of K-cell-transplanted diabetic mice increased after transplantation, whereas those of untreated diabetic control mice continued to decline. The blood glucose levels of K-cell-transplanted diabetic mice decreased gradually during the two weeks following transplantation. After intra-peritoneal injection of glucose into K-cell-transplanted diabetic mice, blood glucose levels increased at 30 minutes, and were restored to the normal range between 60 and 90 minutes, while untreated control diabetic mice continued to experience hyperglycemia. Kidney capsules containing transplanted K-cells were removed, and sections were stained with anti-insulin antibodies. We detected insulin-positive cells in the kidney capsules of K-cell-transplanted diabetic mice, but not in untreated control mice. CONCLUSION: We detected glucose-dependent insulin secretion in genetically engineered K-cells in a mouse model of type 1 diabetes. Our results suggest that genetically modified insulin producing K-cells may act as surrogate beta-cells to effectively treat type 1 diabetes.
Animals ; Antibodies ; Blood Glucose ; Body Weight ; C-Peptide ; Capsules ; Gastric Inhibitory Polypeptide ; Genetic Therapy ; Glucagon ; Glucose ; Herpesvirus 4, Human ; Hyperglycemia ; Insulin ; Kidney ; Mice ; Pancreas ; Plasmids ; Protein Precursors ; Rats ; Reference Values ; Transplants