Metabolic diseases such as type 2 diabetes mellitus and obesity are associated with compositional and functional changes in the intestinal microbiota. After more than 10 years of intense research, evidence is emerging for a causal role of the intestinal microbiota in initiation and progression of these adverse metabolic conditions. However, underlying mechanisms are still unknown. Presumably, microorganisms alone or in consortia (dysbiosis) regulate energy metabolism and insulin sensitivity, energy extraction from diet, and intestinal barrier and immune function. In this context, microbial treatment options including fecal microbiota transplantation are discussed for metabolic disease. Nevertheless, inconclusive and incomplete study results require further clinical and experimental validation.

Purpose of review Lipid metabolism presents a targetable metabolic vulnerability in colorectal cancer (CRC). Lipid signatures and cancer-cell lipid requirements may serve as noninvasive diagnostic and prognostic biomarkers and as a therapeutic target, respectively. Recent findings A growing body of new studies highlight the complexity of lipid metabolism in CRC. Cancer cells are able to utilize an alternative fatty acid desaturation pathway, underlining the metabolic plasticity of tumors. CRC tissue shows a robust triglyceride-species signature with prognostic value in CRC patients. Lipidomic analyses in germfree and colonized mice identify a unique lipid signature and suggest that bacteria inhibit metabolism of polyunsaturated fatty acids by blocking desaturase and elongase activities. Cellular stress responses, particularly the well characterized unfolded protein response, are involved in regulating lipid synthesis and homeostasis, and contribute to adaptation of the lipid environment. Together, lipid metabolism, the intestinal microbiota and cellular stress responses unarguably play crucial roles in CRC. Summary A number of recent advances in our understanding of dysregulated lipid metabolism in CRC underline the importance of this research field. An improved knowledge of the complex interplay between lipid metabolism, cellular stress and the intestinal microbiota in the context of CRC may lead to novel therapeutic strategies.

Metabolische Erkrankungen wie Diabetes mellitus Typ 2 und Adipositas führen zu Veränderungen im mikrobiellen Ökosystem des Darms, sowohl auf kompositioneller als auch funktioneller Ebene. Nach über 10 Jahren intensiver Forschung scheint eine kausale Beteiligung der Mikrobiota an der Entstehung und Progression von Diabetes mellitus Typ 2 und Adipositas möglich, wobei die zugrunde liegenden Mechanismen noch immer unklar sind. Vermutet wird, dass Mikroorganismen allein oder in Gemeinschaften (Dysbiose) den Insulin- und Glukosestoffwechsel, die Energieextraktion aus der Nahrung sowie die Barriere- und Immunfunktion des Darms beeinflussen. Auf dieser Grundlage werden derzeit mikrobielle Therapien wie Stuhltransplantationen bei metabolischen Erkrankungen erprobt. Allerdings ist die Studienlage noch lückenhaft und widersprüchlich, sodass es weiterer klinischer Validierung bedarf.