Diets high in calories can be used to model metabolic diseases, including obesity and its associated comorbidities, in animals. Drosophila melanogaster fed high-sugar diets (HSDs) exhibit complications of human obesity including hyperglycemia, hyperlipidemia, insulin resistance, cardiomyopathy, increased susceptibility to infection, and reduced longevity. We hypothesize that lipid storage in the high-sugar-fed fly’s fat body (FB) reaches a maximum capacity, resulting in the accumulation of toxic lipids in other tissues or lipotoxicity. We took two approaches to characterize tissue-specific lipotoxicity. Ultra-HPLC-MS/MS and MALDI-MS imaging enabled spatial and temporal localization of lipid species in the FB, heart, and hemolymph. Substituent chain length was diet dependent, with fewer odd chain esterified FAs on HSDs in all sample types. By contrast, dietary effects on double bond content differed among organs, consistent with a model where some substituent pools are shared and others are spatially restricted. Both di- and triglycerides increased on HSDs in all sample types, similar to observations in obese humans. Interestingly, there were dramatic effects of sugar feeding on lipid ethers, which have not been previously associated with lipotoxicity. Taken together, we have identified candidate endocrine mechanisms and molecular targets that may be involved in metabolic disease and lipotoxicity.

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Hypertension may develop before or after the onset of diabetes and it is known to increase the risk of developing diabetic nephropathy. Alpha-1 antitrypsin (AAT) is a multi-functional protein with beneficial effects in various diseases but its role in reducing blood pressure in the diabetic kidney has not been thoroughly studied. Like blood pressure, epithelial sodium channels (ENaC) and its adaptor protein myristoylated alanine-rich C-kinase substrate (MARCKS) are regulated by circadian rhythms. Our hypothesis is that administration of human AAT (hAAT) reduces blood pressure in hypertensive diabetic mice by attenuating membrane expression of ENaC and its association with the actin cytoskeleton. First, we show hAAT administration results in reduced blood pressure in diabetic db/db mice compared to vehicle treatment in both the inactive and active cycles. Western blotting and immunohistochemistry analyses showed a reduction of ENaC and the actin cytoskeleton protein, MARCKS in the kidneys of diabetic db/db mice treated with hAAT compared to vehicle. hAAT treatment resulted in elevated amounts of extracellular vesicles present in the urine of diabetic db/db mice compared to vehicle treatment both in the inactive and active cycles. Multiple hexosylceramides, among other lipid classes increased in urinary EVs released from hAAT treated hypertensive diabetic mice compared to vehicle treated mice. Taken together, these data suggest hAAT treatment could normalize blood pressure in the diabetic kidney in a mechanism involving attenuation of renal ENaC and MARCKS protein expression and possibly ceramide metabolism to hexosylceramide in kidney cells.

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