Excessive folic acid supplementation in pregnant mice impairs insulin secretion and induces the expression of genes associated with fatty liver in their offspring

Objective

Previous human and animal studies have shown that excessive maternal intake of folic acid (FA) predisposes to impaired glucose tolerance in the offspring. However, the underlying mechanism is unknown. Therefore, we aimed to determine whether excessive supplementation with FA during pregnancy affects the glucose tolerance of mouse offspring.

Research methods & procedures

Pregnant C57BL/6J mice were fed AIN93G diet containing either 2 mg [control group (CN)] or 40 mg [high FA group (HFA)] FA/kg diet throughout their pregnancies. On postnatal days (PD)22 and 50, fasting blood glucose was measured in the offspring of both groups, and an oral glucose tolerance test (OGTT) was performed on PD50. On PD53, tissues were collected, and the tissue masses, area of insulin expression in the pancreas, liver triglyceride content, and gene expression were determined.

Results

The blood glucose concentrations at 60 and 120 min of the OGTT were higher in female HFA than CN offspring. The serum fasting and non-fasting insulin concentrations and the area of insulin expression in the pancreas were lower in HFA than CN offspring. The liver triglyceride content was higher in female, and tended to be higher in male (P < 0.05), HFA offspring than CN offspring (P < 0.05). The liver mRNA expression of fat synthesis genes, such as Pparγ2 (male and female) and Cidec (male), was higher in HFA than CN offspring (P < 0.05).

Conclusion

Excessive maternal supplementation of FA in mice leads to lower insulin synthesis and an impairment in hepatic fat metabolism in the offspring.

Pgc1a is responsible for the sex differences in hepatic Cidec/Fsp27β mRNA expression in hepatic steatosis of mice fed a Western diet

Hepatic fat-specific protein 27 [cell death-inducing DNA fragmentation effector protein C (Cidec)/Fsp27] mRNA levels have been associated with hepatic lipid droplet extent under certain circumstances. To address its hepatic expression under different dietary conditions and in both sexes, apolipoprotein E (Apoe)-deficient mice were subjected to different experimental conditions for 11 wk to test the influence of cholesterol, Western diet, squalene, oleanolic acid, sex, and surgical castration on Cidec/Fsp27 mRNA expression. Dietary cholesterol increased hepatic Cidec/Fsp27β expression, an effect that was suppressed when cholesterol was combined with saturated fat as represented by Western diet feeding. Using the latter diet, neither oleanolic acid nor squalene modified its expression. Females showed lower levels of hepatic Cidec/Fsp27β expression than males when they were fed Western diets, a result that was translated into a lesser amount of CIDEC/FSP27 protein in lipid droplets and microsomes. This was also confirmed in low-density lipoprotein receptor (Ldlr)-deficient mice. Incubation with estradiol resulted in decreased Cidec/Fsp27β expression in AML12 cells. Whereas male surgical castration did not modify the expression, ovariectomized females did show increased levels compared with control females. Females also showed increased expression of peroxisome proliferator-activated receptor-γ coactivator 1-α (Pgc1a), suppressed by ovariectomy, and the values were significantly and inversely associated with those of Cidec/Fsp27β. When Pgc1a-deficient mice were used, the sex differences in Cidec/Fsp27β expression disappeared. Therefore, hepatic Cidec/Fsp27β expression has a complex regulation influenced by diet and sex hormonal milieu. The mRNA sex differences are controlled by Pgc1a.

Microstructural features of lyophilized adipose - A new concept to estimate the metabolic symptoms for obese patients

The aim of this study was to investigate the distribution of different morphological features in different layers of lyophilized adipose tissue. In this work the scanning electron microscopy (SEM) was adopted for investigation of lyophilized adipose tissue taken from obese patients. The adipose tissue was taken from subcutaneous (SAT), preperitoneal (PAT) and visceral (VAT) layers of adipose tissue. The obtained results of the main microstructural features provided information about morphological features of subcutaneous, preperitoneal and visceral layers in obese people. The obtained SEM results possibly could be used for the estimation of metabolic symptoms and prediction different diseases. The SEM method was never used before to investigate morphology of SAT, PAT and VAT layers of lyophilized human adipose tissue.

What lipodystrophies teach us about the metabolic syndrome

Lipodystrophies are the result of a range of inherited and acquired causes, but all are characterized by perturbations in white adipose tissue function and, in many instances, its mass or distribution. Though patients are often nonobese, they typically manifest a severe form of the metabolic syndrome, highlighting the importance of white fat in the "safe" storage of surplus energy. Understanding the molecular pathophysiology of congenital lipodystrophies has yielded useful insights into the biology of adipocytes and informed therapeutic strategies. More recently, genome-wide association studies focused on insulin resistance have linked common variants to genes implicated in adipose biology and suggested that subtle forms of lipodystrophy contribute to cardiometabolic disease risk at a population level. These observations underpin the use of aligned treatment strategies in insulin-resistant obese and lipodystrophic patients, the major goal being to alleviate the energetic burden on adipose tissue.

Betaine increases mitochondrial content and improves hepatic lipid metabolism

The liver plays a critical role in lipid metabolism. Hepatic dysfunction is not only the direct cause of fatty liver disease, but the main risk factor for obesity, diabetes, and other metabolic diseases. So far, therapeutic strategies against fatty liver disease are very limited. Betaine is a methyl donor. Current studies reported that the intake of betaine decreases body fat and is beneficial for treatment of fatty liver disease and metabolic syndrome. However, the underlying mechanisms remain largely unknown. In this study, to investigate the role of betaine on hepatic lipid metabolism and explore the underlying mechanism, HepG2 cells were cultured with fatty acids and betaine. The data indicated that betaine inhibited hepatic fat accumulation and promoted mitochondrial content and activity, suggesting that betaine is involved in the regulation of lipid and energy metabolism. Gene expression analysis implied that betaine inhibits fatty acid synthesis, but stimulates fatty acid oxidation and lipid secretion. Further, to study the mechanism of betaine, FTO (RNA demethylase) and its mutant (loss of demethylase activity) were used. The results showed that FTO blocked the ability of betaine to regulate lipid metabolism and mitochondrial content, but the FTO mutant had no effect, suggesting that betaine influences RNA methylation. This work links betaine administration with mitochondrial activity and RNA methylation, and provides a potential target for the development of new therapeutic strategies for the treatment of fatty liver disease.

Cidec differentially regulates lipid deposition and secretion through two tissue-specific isoforms

Lipid metabolism has important roles in animal growth, development, and reproduction. As a regulator of lipid metabolism, CIDEc promotes unilocular development of lipid droplets and stimulates intracellular lipid deposition, and has two isoforms, CIDEc-l and CIDEc-s. CIDEc-l has ten more N-terminal amino acids than CIDEc-s. However, the functions of two isoforms are largely unknown. In this study, the expression profiles of two isoforms in Bama pigs differed, with cidec-l dominant in the liver and small intestine, and cidec-s dominant in muscle and adipose tissue. Fasting and consuming a high-fat diet resulted in changes in the expression of the two isoforms that were closely related to changes in blood and muscle triglyceride (TG) concentrations. Comparison of gene expression and TG concentration suggested that CIDEc-l accelerated lipid secretion and that CIDEc-s promoted lipid deposition, implying that the two isoforms had different functions. Study In vitro confirmed that CIDEc-s stimulated lipid deposition in C2C12 muscle cells and CIDEc-l promoted lipid secretion in HepG2 liver cells. The results showed that two tissue-specific CIDEc isoforms had different roles in lipid deposition and secretion. They may be potential targets for regulation of fat content.