Omega-3 fatty acids induce Ca2+ mobilization responses in human colon epithelial cell lines endogenously expressing FFA4

Aim:

Free fatty acid receptor 4 (FFA4; formerly known as GPR120) is the G protein-coupled receptor (GPCR) for omega-3 polyunsaturated fatty acids. FFA4 has been found to express in the small intestines and colons of mice and humans. In this study we investigate the effects of omega-3 polyunsaturated fatty acids on FFA4 in human colon epithelial cells in vitro.

Methods:

HCT116 and HT-29 human colon epithelial cell lines endogenously expressing FFA4 were used. Intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured in fura 2-AM-loaded cells with fluorescence spectrophotometry. RT-PCR and immunohistochemistry were used to detect FFA4.

Results:

Ten to 100 μmol/L of omega-3 polyunsaturated fatty acids α-linolenic acid (αLA) or eicosapentaenoic acid (EPA) induced dose-dependent [Ca²⁺]_i increase in HCT116 and HT-29 cells, whereas docosahexaenoic acid (DHA) had no effect. In addition, the omega-6 fatty acids linoleic acid and γ-linoleic acid also dose-dependently increase [Ca²⁺]_i, but the mono-unsaturated fatty acid oleic acid and saturated fatty acids such as stearic acid and palmitic acid had no effect. In HCT116 and HT-29 cells, the αLA-induced [Ca²⁺]_i increase was partially inhibited by pretreatment with EGTA, phospholipase C inhibitor edelfosine, cADPR inhibitors 8-bro-cADPR or DAB, and abolished by pretreatment with Ca²⁺ATPase inhibitor thapsigargin, but was not affected by G_i/o protein inhibitor PTX or IP₃R inhibitor 2-APB.

Conclusion:

Omega-3 and omega-6 long-chain polyunsaturated fatty acids (C18-20) induce Ca²⁺ mobilization responses in human colonic epithelial cells in vitro through activation of FFA4 and PTX-insensitive G_i/o protein, followed by Ca²⁺ release from thapsigargin-sensitive Ca²⁺ stores and Ca²⁺ influx across the plasma membrane.     

Mass fragmentographic determination of myocardial free fatty acids

In contrast to plasma free fatty acids (FFA) remarkably little work has been carried out on myocardial FFA content directly. Reported values of normal FFA content vary so widely (29.0 to 25 000 nmol/g wet wt) that clearly the usual methods for the determination of FFA are difficult or not at all applicable to myocardial tissue. A method has been developed for the mass fragmentographic determination of myocardial FFA content and distribution and has been validated for sensitivity, reproducibility, specificity, recovery, cross-reaction with other lipids and reliability.The FFA content of normoxic canine myocardium was found to be 55.6 ± 20.2 nmol/g wet wt. This value is considerably below most of the previously reported values and much of the reported work on myocardial FFA content and changes must be re-examined.     

Growth hormone secretion in diabetic retinopathy

Summary The plasma HGH response to insulin-induced hypoglycemia (0.2 U/kg) and the 24-h plasma HGH pattern during a normal day have been studied in 14 non obese long-term insulin-dependent diabetics with proliferative retinopathy, mean age 39 ± 2 (ranging between 24 and 50 years). Plasma glucose and FFA were also determined. The results were compared with those of 18 normal subjects of similar age and weight. The mean plasma HGH response to insulin in retinopathic diabetics was slightly lower (with no significant differences) than in controls in whom hypoglycemia was induced with a smaller dose of insulin (0.1 U/kg). This pattern of plasma HGH could be related to the delayed plasma glucose fall observed in retinopathic diabetics in comparison to normal subjects, even if the HGH peak after insulin in both groups (18.61 ± 4.32 ng/ml in retinopathic diabetics, 27.43 ± 4.19 in controls) did not seem to be correlated to the degree of hypoglycemia, but rather to the age of the subjects. Plasma HGH pattern, studied with blood samples taken every three hrs during a normal day, did not reveal differences between the diabetics and controls. Plasma glucose, however, was higher in retinopathic diabetics than in controls in spite of the insulin treatment. These results show that in diabetic patients with retinopathy, increased HGH secretion does not occur in conditions of ordinary life or after insulin-induced hypoglycemia, although the HGH plasma levels observed in retinopathic diabetics could be considered too high in relation to the elevated blood glucose levels. Traduzione a cura degli AA.     

Metabolic clues regarding the enhanced performance of elite endurance athletes from orchiectomy-induced hormonal changes

This article examines the metabolic performance of an elite cyclist, Lance Armstrong, before and after his diagnosis with testicular cancer. Although a champion cyclist in 1-day events prior to his diagnosis of testicular cancer at age 25, he was not a contender in multi-day endurance cycle races such as the 3-week Tour de France. His genetic makeup and physiology (high VO2max, long femur, strong heavy build) coupled with his ambition and motivation enabled him at an early age to become one of the best 1-day cyclists in the world. Following his cancer diagnosis, he underwent a unilateral orchiectomy, brain surgery and four cycles of chemotherapy. After recovering, he returned to cycling and surprisingly excelled in the Tour de France, winning this hardest of endurance events 7 years running. This dramatic transformation from a 1-day to a 3-week endurance champion has led many to query how this is possible, and under the current climate, has led to suggestions of doping as to the answer to this metamorphosis. Physiological tests following his recovery indicated that physiological parameters such as VO2max were not affected by the unilateral orchiectomy and chemotherapy. We propose that his dramatic improvement in recovery between stages, the most important factor in winning multi-day stage races, is due to his unilateral orchiectomy, a procedure that results in permanent changes in serum hormones. These hormonal changes, specifically an increase in gonadotropins (and prolactin) required to maintain serum testosterone levels, alter fuel metabolism; increasing hormone sensitive lipase expression and activity, promoting increased free fatty acid (FFA) mobilization to, and utilization by, muscles, thereby decreasing the requirement to expend limiting glycogen stores before, during and after exercise. Such hormonal changes also have been associated with ketone body production, improvements in muscle repair and haematocrit levels and may facilitate the loss of body weight, thereby increasing power to weight ratio. Taken together, these hormonal changes act to limit glycogen utilization, delay fatigue and enhance recovery thereby allowing for optimal performances on a day-to-day basis. These insights provide the foundation for future studies on the endocrinology of exercise metabolism, and suggest that Lance Armstrong's athletic advantage was not due to drug use.     

Accumulation of lipids and oxidatively damaged DNA in hepatocytes exposed to particles

Exposure to particles has been suggested to generate hepatosteatosis by oxidative stress mechanisms. We investigated lipid accumulation in cultured human hepatocytes (HepG2) and rat liver after exposure to four different carbon-based particles. HepG2 cells were exposed to particles for 3 h and subsequently incubated for another 18 h to manifest lipid accumulation. In an animal model of metabolic syndrome we investigated the association between intake of carbon black (CB, 14 nm) particles and hepatic lipid accumulation, inflammation and gene expression of Srebp-1, Fasn and Scd-1 involved in lipid synthesis. There was a concentration-dependent increase in intracellular lipid content after exposure to CB in HepG2 cells, which was only observed after co-exposure to oleic/palmitic acid. Similar results were observed in HepG2 cells after exposure to diesel exhaust particles, fullerenes C₆₀ or pristine single-walled carbon nanotubes. All four types of particles also generated oxidatively damaged DNA, assessed as formamidopyrimidine DNA glycosylase (FPG) sensitive sites, in HepG2 cells after 3 h exposure. The animal model of metabolic syndrome showed increased lipid load in the liver after one oral exposure to 6.4 mg/kg of CB in lean Zucker rats. This was not associated with increased iNOS staining in the liver, indicating that the oral CB exposure was associated with hepatic steatosis rather than steatohepatitis. The lipid accumulation did not seem to be related to increased lipogenesis because there were unaltered gene expression levels in both the HepG2 cells and rat livers. Collectively, exposure to particles is associated with oxidative stress and steatosis in hepatocytes.     

Effect of insulin on glucagon enhanced lipolysis in vitro

Summary Glucagon in concentrations similar to those found in human plasma markedly stimulates lipolysis in rat adipose tissuein vitro. The effects of these physiological concentrations of glucagon are reduced or abolished by insulin at concentrations of 25 and 100U/ml. Considering the marked insulinogenic effect of glucagon these observations may provide an explanation for the delayed increase of blood FFA observed after glucagon injectionin vivo.This work was supported by the Fonds National de la Recherche Scientifique and the Fonds de la Recherche Scientifique Médicale, Belgium.     

Metabolic syndrome and associated factors among psychiatric patients in Jimma University Specialized Hospital,South West Ethiopia

Background

Metabolic syndrome is a multisystem disorder which coined to describe the recognized clustering of metabolic and cardiovascular abnormalities including obesity, hypertension, dyslipidemia, and abnormalities of glucose homeostasis.