Transgenic mice overexpressing SREBP-1a under the control of the PEPCK promoter exhibit insulin resistance, but not diabetes

AbstractSterol regulatory element-binding protein-1 (SREBP-1) is a transcription factor which regulates genes involved in the synthesis of fatty acids and triglycerides. The overexpression of nuclear SREBP-1a in transgenic mice under the control of the PEPCK promoter (TgSREBP-1a) caused a massively enlarged fatty liver and disappearance of peripheral white adipose tissue. In the current study, we estimated the impact of this lipid transcription factor on plasma glucose/insulin metabolism in vivo. TgSREBP-1a exhibited mild peripheral insulin resistance as evidenced by hyperinsulinemia both at fasting and after intravenous glucose loading, and retarded glucose reduction after insulin injection due to decreased plasma leptin levels. Intriguingly, hyperinsulinemia in TgSREBP-1a mice was markedly exacerbated in a fed state and sustained after intravenous glucose loading, and paradoxically decreased after the portal injection of glucose. TgSREBP-1a mice consistently showed very small plasma glucose increases after portal glucose loading because of a large capacity for hepatic glucose uptake. These data suggested that hepatic insulin resistance emerges postprandially. In addition, pancreatic islets from TgSREBP-1a were enlarged. These data demonstrate that SREBP-1a activation in the liver has a strong impact on plasma insulin levels, implicating the potential role of SREBPs in hepatic insulin metabolism relating to insulin resistance

Octacosanol and policosanol prevent high-fat diet-induced obesity and metabolic disorders by activating brown adipose tissue and improving liver metabolism

Brown adipose tissue (BAT) is an attractive therapeutic target for treating obesity and metabolic diseases. Octacosanol is the main component of policosanol, a mixture of very long chain aliphatic alcohols obtained from plants. The current study aimed to investigate the effect of octacosanol and policosanol on high-fat diet (HFD)-induced obesity. Mice were fed on chow, or HFD, with or without octacosanol or policosanol treatment for four weeks. HFD-fed mice showed significantly higher body weight and body fat compared with chow-fed mice. However, mice fed on HFD treated with octacosanol or policosanol (HFDo/p) showed lower body weight gain, body fat gain, insulin resistance and hepatic lipid content. Lower body fat gain after octacosanol or policosanol was associated with increased BAT activity, reduced expression of genes involved in lipogenesis and cholesterol uptake in the liver, and amelioration of white adipose tissue (WAT) inflammation. Moreover, octacosanol and policosanol significantly increased the expression of Ffar4, a gene encoding polyunsaturated fatty acid receptor, which activates BAT thermogenesis. Together, these results suggest that octacosanol and policosanol ameliorate diet-induced obesity and metabolic disorders by increasing BAT activity and improving hepatic lipid metabolism. Thus, these lipids represent promising therapeutic targets for the prevention and treatment of obesity and obesity-related metabolic disorders

Carrot Consumption Frequency Associated with Reduced BMI and Obesity through the SNP Intermediary rs4445711

It is unclear whether genetic interactions are involved in the association between vegetable intake and reduced body mass index (BMI) or obesity. We conducted a comprehensive search for single nucleotide polymorphisms (SNPs) which are associated with the interaction between vegetable intake frequency and BMI or obesity. We performed a genome-wide association analysis to evaluate the genetic interactions between self-reported intake of vegetables such as carrot, broccoli, spinach, other green vegetables (green pepper and green beans), pumpkin, and cabbage with BMI and obesity, which is defined as a BMI ≥ 25.0 kg/m2 in the Japanese population (n = 12,225). The mean BMI and prevalence of obesity was 23.9 ± 3.4 kg/m2 and 32.3% in men and 22.1 ± 3.8 kg/m2 and 17.3% in in women, respectively. A significant interaction was observed between rs4445711 and frequency of carrot intake on BMI (p = 4.5 × 10−8). This interaction was slightly attenuated after adjustment for age, sex, alcohol intake, smoking, physical activity and the frequency of total vegetable intake (p = 2.1 × 10−7). A significant interaction was also observed between rs4445711 and frequency of carrot intake on obesity (p = 2.5 × 10−8). No significant interactions that were the same as the interaction between frequency of carrot intake and rs4445711 were observed between the intake frequency of broccoli, spinach, other green vegetables, pumpkin or cabbage and BMI or obesity. The frequency of carrot consumption is implicated in reducing BMI by the intermediary of rs4445711. This novel genetic association may provide new clues to clarify the association between vegetable intake and BMI or obesity

Identification of key microRNAs regulating ELOVL6 and glioblastoma tumorigenesis

ELOVL fatty acid elongase 6 (ELOVL6) controls cellular fatty acid (FA) composition by catalyzing the elongation of palmitate (C16:0) to stearate (C18:0) and palmitoleate (C16:1n-7) to vaccinate (C18:1n-7). Although the transcriptional regulation of ELOVL6 has been well studied, the post-transcriptional regulation of ELOVL6 is not fully understood. Therefore, this study aims to evaluate the role of microRNAs (miRNAs) in regulating human ELOVL6. Bioinformatic analysis identified five putative miRNAs: miR-135b-5p, miR-135a-5p, miR-125a-5p, miR-125b-5p, and miR-22–3p, which potentially bind ELOVL6 3′-untranslated region (UTR). Results from dual-luciferase assays revealed that these miRNAs downregulate ELOVL6 by directly interacting with the 3′-UTR of ELOVL6 mRNA. Moreover, miR-135b-5p and miR-135a-5p suppress cell proliferation and migration in glioblastoma multiforme cells by inhibiting ELOVL6 at the mRNA and protein levels. Taken together, our results provide novel regulatory mechanisms for ELOVL6 at the post-transcriptional level and identify potential candidates for the treatment of patients with glioblastoma multiforme