👤 Grace Back

An acute increase of lipids in the upper small intestine (USI) of rodents and humans triggers lipid-sensing pathways to reduce food intake. However, USI lipid sensing does not reduce feeding in high-fat (HF) fed conditions, and the underlying mechanism remains elusive. Here, we report that HF feeding in male rats impaired USI lipid infusion to stimulate glucose-dependent insulinotropic polypeptide (GIP) secretion and decrease refeeding, and the defects of USI lipid sensing were restored by metformin. Next, we found that infusion of GIP receptor (GIPR) agonist in the nucleus of the solitary tract (NTS), but not mediobasal hypothalamus or area postrema, resulted in decreased refeeding in chow-fed rats. The anorectic effect of NTS GIPR agonist remained intact in HF rats and was inhibited by a genetic knockdown of GIPR. Finally, an inhibition of NTS GIPR also negated the ability of USI lipid sensing with metformin to decrease refeeding despite an increase in plasma GIP levels in HF rats. Thus, USI lipid sensing in HF rats is enhanced by metformin to trigger an endocrine GIP to NTS GIPR axis to reduce food intake, thereby unveiling small intestinal lipid-sensing pathways as potential targets to enhance GIP action and reduce weight in obesity. High-fat (HF) feeding in rats impairs upper small intestine (USI) lipid sensing to increase plasma glucose-dependent insulinotropic polypeptide (GIP) levels and reduce feeding. Metformin enhances USI lipids to increase GIP and reduce feeding in HF-fed rats. GIP activates the GIP receptor (GIPR) in the nucleus of the solitary tract (NTS), which reduces food intake in HF-fed rats. GIPR in the NTS is required for small intestinal lipids with metformin to reduce feeding. Show less

Obesity and overweight are worldwide public health problems with an evident genetic predisposition that is still poorly understood. In addition, great variability has been described across populations. In this work, we analyzed the association of variants in four genes: PPARG (rs1801282), PPARGC1A (rs8192678), FTO (rs9939609) and MC4R (rs17782313) with overweight and obesity in a large sample of the Brazilian population. The case-control study involved 4084 individuals (1844 with overweight or obesity; and 2240 with normal BMI). Genotyping was performed by quantitative PCR. MC4R rs17782313-C was associated with obesity (OR = 1.27, p = 0.038) and when stratifying by sex associated only in women (OR = 1.36, p = 0.030). FTO rs9939609-A allele was associated with overweight however for women it represented a risk factor (OR = 1.24, p = 0.034) and for men, a protective factor (OR = 0.68, p = 0.033). PPARG was the strongest associated gene, with both overweight and obesity, and this association was also restricted to women (rs1801282-GG OR = 1.46, p = 0.027). The combined effect of the three risk alleles on overweight and obesity had an OR of 1.65 (p = 0.008) and when stratifying by sex again it was significant only in females (OR = 1.95, p = 0.0028). Our findings indicate that the three genes play a significant role in predisposing to overweight and/or obesity in the Brazilian population, reaching together a relatively high impact on these traits. Interestingly our results also suggest a strong sex-specific genetic effect of these variants. Show less

The ATP-binding cassette transporters ABCG5 and ABCG8 form heterodimers that limit absorption of dietary sterols in the intestine and promote cholesterol elimination from the body through hepatobiliary secretion. To identify cis-regulatory elements of the two genes, we have cloned and analyzed twenty-three evolutionary conserved region (ECR) fragments using the CMV-luciferase reporter system in HepG2 cells. Two ECRs were found to be responsive to the Liver-X-Receptor (LXR). Through elaborate deletion studies, regions containing putative LXREs were identified and the binding of LXRα was demonstrated by EMSA and ChIP assay. When the LXREs were inserted upstream of the intergenic promoter, synergistic activation by LXRα/RXRα in combination with GATA4, HNF4α, and LRH-1, which had been shown to bind to the intergenic region, was observed. In conclusion, we have identified two LXREs in ABCG5/ABCG8 genes for the first time and propose that these LXREs, especially in the ECR20, play major roles in regulating these genes. Show less