Use of FGF21 analogs for the treatment of metabolic disorders: a systematic review and meta-analysis

FGF21 is a hormone produced primarily by the liver with several metabolic functions, such as induction of heat production, control of glucose homeostasis, and regulation of blood lipid levels. Due to these actions, several laboratories have developed FGF21 analogs to treat patients with metabolic disorders such as obesity and diabetes. Here, we performed a systematic review and meta-analysis of randomized controlled trials that used FGF21 analogs and analyzed metabolic outcomes. Our search yielded 236 articles, and we included eight randomized clinical trials in the meta-analysis. The use of FGF21 analogs exhibited no effect on fasting blood glucose, glycated hemoglobin, HOMA index, blood free fatty acids or systolic blood pressure. However, the treatment significantly reduced fasting insulinemia, body weight and total cholesterolemia. None of the included studies were at high risk of bias. The quality of the evidence ranged from moderate to very low, especially due to imprecision and indirection issues. These results indicate that FGF21 analogs can potentially treat metabolic syndrome. However, more clinical trials are needed to increase the quality of evidence and confirm the effects seen thus far.

ATP synthase affects lipid metabolism in the kissing bug Rhodnius prolixus beyond its role in energy metabolism

ATP synthase plays an essential role in mitochondrial metabolism, being responsible for the production of ATP in oxidative phosphorylation. However, recent results have shown that it may also be present in the cell membrane, involved in lipophorin binding to its receptors. Here, we used a functional genetics approach to investigate the roles of ATP synthase in lipid metabolism in the kissing bug Rhodnius prolixus. The genome of R. prolixus encodes five nucleotide-binding domain genes of the ATP synthase alpha and beta family, including the alpha and beta subunits of ATP synthase (RpATPSynA and RpATPSynB), and the catalytic and non-catalytic subunits of the vacuolar ATPase (RpVha68 and RpVha55). These genes were expressed in all analyzed organs, being their expression highest in the ovaries, fat body and flight muscle. Feeding did not regulate the expression of ATP synthases in the posterior midgut or fat body. Furthermore, ATP synthase is present in the fat body's mitochondrial and membrane fractions. RpATPSynB knockdown by RNAi impaired ovarian development and reduced egg-laying by approximately 85%. Furthermore, the lack of RpATPSynB increased the amount of triacylglycerol in the fat body due to increased de novo fatty acid synthesis and reduced transfer of lipids to lipophorin. RpATPSynA knockdown had similar effects, with altered ovarian development, reduced oviposition, and triacylglycerol accumulation in the fat body. However, ATP synthases knockdown had only a slight effect on the amount of ATP in the fat body. These results support the hypothesis that ATP synthase has a direct role in lipid metabolism and lipophorin physiology, which are not directly due to changes in energy metabolism.

Diet supplementation with egg yolk powder fattens the beetle Tribolium castaneum

Insects have become essential models in studying human metabolic diseases, mainly due to their low maintenance cost and available tools. Both mutations and modified diets induce metabolic states similar to human obesity and diabetes. Here, we explore the effect of a high-calorie, high-fat diet on the metabolism of the beetle Tribolium castaneum. Supplementation of the wheat flour diet with powdered egg yolk for 3 weeks increased the total triacylglycerol and accelerated larval development. In addition, this diet increased the triacylglycerol levels of adult beetles. However, this egg yolk supplementation did not alter the larvae's total glucose levels or lipogenic capacity and ATP citrate lyase activity. The diet also did not change the expression profile of several lipid and carbohydrate metabolism genes and insulin-like peptides. Thus, we conclude that the diet supplemented with egg yolk induces increased fat without causing diabetes phenotypes, as seen in other hypercaloric diets in insects.

Gene annotation of nuclear receptor superfamily genes in the kissing bug Rhodnius prolixus and the effects of 20-hydroxyecdysone on lipid metabolism

The hormone 20-hydroxyecdysone is fundamental for regulating moulting and metamorphosis in immature insects, and it plays a role in physiological regulation in adult insects. This hormone acts by binding and activating a receptor, the ecdysone receptor, which is part of the nuclear receptor gene superfamily. Here, we analyse the genome of the kissing bug Rhodnius prolixus to annotate the nuclear receptor superfamily genes. The R. prolixus genome displays a possible duplication of the HNF4 gene. All the analysed insect organs express most nuclear receptor genes as shown by RT-PCR. The quantitative PCR analysis showed that the RpEcR and RpUSP genes are highly expressed in the testis, while the RpHNF4-1 and RpHNF4-2 genes are more active in the fat body and ovaries and in the anterior midgut, respectively. Feeding does not induce detectable changes in the expression of these genes in the fat body. However, the expression of the RpHNF4-2 gene is always higher than that of RpHNF4-1. Treating adult females with 20-hydroxyecdysone increased the amount of triacylglycerol stored in the fat bodies by increasing their lipogenic capacity. These results indicate that 20-hydroxyecdysone acts on the lipid metabolism of adult insects, although the underlying mechanism is not clear.

dHNF4 regulates lipid homeostasis and oogenesis in Drosophila melanogaster

The fly genome contains a single ortholog of the evolutionarily conserved transcription factor hepatocyte nuclear factor 4 (HNF4), a broadly and constitutively expressed member of the nuclear receptor superfamily. Like its mammalian orthologs, Drosophila HNF4 (dHNF4) acts as a critical regulator of fatty acid and glucose homeostasis. Because of its role in energy storage and catabolism, the insect fat body controls non-autonomous organs including the ovaries, where lipid metabolism is essential for oogenesis. The present paper used dHNF4 overexpression (OE) in the fat bodies and ovaries to investigate its potential roles in lipid homeostasis and oogenesis. When the developing fat body overexpressed dHNF4, animals exhibited reduced size and failed to pupariate, but no changes in body composition were observed. Conditional OE of dHNF4 in the adult fat body produced a reduction in triacylglycerol content and reduced oogenesis. Ovary-specific dHNF4 OE increased oogenesis and egg-laying, but reduced the number of adult offspring. The phenotypic effects on oogenesis that arise upon dHNF4 OE in the fat body or ovary may be due to its function in controlling lipid utilization.