Inhibition of mitochondrial function by metformin increases glucose uptake, glycolysis and GDF-15 release from intestinal cells

Even though metformin is widely used to treat type2 diabetes, reducing glycaemia and body weight, the mechanisms of action are still elusive. Recent studies have identified the gastrointestinal tract as an important site of action. Here we used intestinal organoids to explore the effects of metformin on intestinal cell physiology. Bulk RNA-sequencing analysis identified changes in hexose metabolism pathways, particularly glycolytic genes. Metformin increased expression of Slc2a1 (GLUT1), decreased expression of Slc2a2 (GLUT2) and Slc5a1 (SGLT1) whilst increasing GLUT-dependent glucose uptake and glycolytic rate as observed by live cell imaging of genetically encoded metabolite sensors and measurement of oxygen consumption and extracellular acidification rates. Metformin caused mitochondrial dysfunction and metformin’s effects on 2D-cultures were phenocopied by treatment with rotenone and antimycin-A, including upregulation of GDF15 expression, previously linked to metformin dependent weight loss. Gene expression changes elicited by metformin were replicated in 3D apical-out organoids and distal small intestines of metformin treated mice. We conclude that metformin affects glucose uptake, glycolysis and GDF-15 secretion, likely downstream of the observed mitochondrial dysfunction. This may explain the effects of metformin on intestinal glucose utilisation and food balance.

Application of a duplex PCR approach for the specific and simultaneous detection of Bifidobacterium spp. and lactobacillus spp. in duodenum, jejunum, ileum and cecum of broilers

Bifidobacterium spp. and Lactobacillus spp genera are useful and important microbiota which affect poultry performance. These bacteria are natural inhabitants of the intestine of broilers. These bacteria have a unique hexose metabolism that occurs via the phosphoketolase pathway. Bifidobacterium spp. produces the vitamins B1, B2, B6, B12, nicotinic acid and folic acid. Enzymatic hydrolysis by Bifidobacterium spp. increases bioaccessibility of lipids and proteins. Lactobacillus spp. exhibit properties which include the ability to adhere to cells, persist and multiply and produce acids, hydrogen peroxide and bacteriocidal and bacteriostatic agents. The ability of Lactobacillus to inhibit bacterial pathogens including E. coli and Salmonella species and to influence parasitic infection including Cryptosporidium parvum, Eimeria acervulina, and Giardia intestinalis (Seidavi et al. 2008). The aim of this study was to develop a method for the direct and simultaneous detection of Bifidobacterium spp. and Lactobacillus spp.in the intestine by multiplex PCR.

Differential effects of glucose and fructose on hexose metabolism in dog spermatozoa

Incubation of dog spermatozoa with 10 mmol l(-1) glucose or fructose rapidly increased the intracellular content of glucose 6-phosphate and fructose 6-phosphate, although the effect of fructose was greater. These effects were correlated with increases in ATP, ribose 5-phosphate and glycogen contents, and in the rates of formation of L-lactate and CO2. In all cases, except for ATP and glycogen, the effect of fructose was greater than that of glucose. The total hexokinase activity of the crude extracts of dog spermatozoa was more sensitive to fructose than to glucose at lower concentrations (0.1-3.0 mmol l(-1)). Both monosaccharides induced a fast and intense increase in the overall tyrosine phosphorylation of dog spermatozoa, although their specific induced-phosphorylation patterns differed slightly. Glut 3 and Glut 5 hexose transporters were the main hexose transporters in dog spermatozoa; however, other possible SGLT family-related hexose transporters were also localized. These data indicate that, at concentrations from 1 mmol l(-1) to 10 mmol l(-1), fructose has a stronger effect than glucose on hexose metabolism of dog spermatozoa. These differences appear to be related to variations in the sensitivity of hexokinase activity. Moreover, the differential hexose metabolism induced by the two sugars had distinct effects on the function of dog spermatozoa, as revealed by the diverse patterns of tyrosine phosphorylation.