Pentoxifylline: a new armamentarium in diabetic foot ulcers

Australian guideline on wound healing interventions to enhance healing of foot ulcers: part of the 2021 Australian evidence-based guidelines for diabetes-related foot disease

BACKGROUND

Diabetes-related foot ulceration (DFU) has a substantial burden on both individuals and healthcare systems both globally and in Australia. There is a pressing need for updated guidelines on wound healing interventions to improve outcomes for people living with DFU. A national expert panel was convened to develop new Australian evidence-based guidelines on wound healing interventions for people with DFU by adapting suitable international guidelines to the Australian context.

METHODS

The panel followed National Health and Medical Research Council (NHMRC) procedures to adapt suitable international guidelines by the International Working Group of the Diabetic Foot (IWGDF) to the Australian context. The panel systematically screened, assessed and judged all IWGDF wound healing recommendations using ADAPTE and GRADE frameworks for adapting guidelines to decide which recommendations should be adopted, adapted or excluded in the Australian context. Each recommendation had their wording, quality of evidence, and strength of recommendation re-evaluated, plus rationale, justifications and implementation considerations provided for the Australian context. This guideline underwent public consultation, further revision and approval by ten national peak bodies.

RESULTS

Thirteen IWGDF wound healing recommendations were evaluated in this process. After screening, nine recommendations were adopted and four were adapted after full assessment. Two recommendations had their strength of recommendations downgraded, one intervention was not currently approved for use in Australia, one intervention specified the need to obtain informed consent to be acceptable in Australia, and another was reworded to clarify best standard of care. Overall, five wound healing interventions have been recommended as having the evidence-based potential to improve wound healing in specific types of DFU when used in conjunction with other best standards of DFU care, including sucrose-octasulfate impregnated dressing, systemic hyperbaric oxygen therapy, negative pressure wound therapy, placental-derived products, and the autologous combined leucocyte, platelet and fibrin dressing. The six new guidelines and the full protocol can be found at: https://diabetesfeetaustralia.org/new-guidelines/ CONCLUSIONS: The IWGDF guideline for wound healing interventions has been adapted to suit the Australian context, and in particular for geographically remote and Aboriginal and Torres Strait Islander people. This new national wound healing guideline, endorsed by ten national peak bodies, also highlights important considerations for implementation, monitoring, and future research priorities in Australia.

Are the Protean Effects of Pentoxifylline in the Therapy of Diabetes and Its Complications Still Relevant?

Pentoxifylline (Px) has protean effects that can be utilized in the therapy of diabetes and its complications. There have been well-documented but often inconclusive improvements in peripheral arterial disease, foot ulcers, peripheral neuropathy, nephropathy, retinopathy, ischemic heart disease and cerebrovascular disease. In addition, non-alcoholic steatosis and steatohepatitis, which are closely associated with insulin resistance and type 2 diabetes, have been shown to improve with pentoxifylline. Surprisingly, pentoxifylline modestly improves insulin resistance through improvements in capillary blood flow as well as beta cell function and decreased hepatic glucose production. The therapeutic effects of pentoxifylline are complementary to the effects of drugs such as blockers of the renin-angiotensin-aldosterone system when utilized in the therapy of diabetic nephropathy.

Involvement of cAMP/EPAC/Akt signaling in the antiproteolytic effects of pentoxifylline on skeletal muscles of diabetic rats

Advances in the knowledge of the mechanisms controlling protein breakdown in skeletal muscles have allowed the exploration of new options for treating muscle-wasting conditions. Pentoxifylline (PTX), a nonselective phosphodiesterase (PDE) inhibitor, attenuates the loss of muscle mass during catabolic conditions, mainly via inhibiting protein breakdown. The aim of this study was to explore the mechanisms by which PTX inhibits proteolysis in the soleus and extensor digitorum longus (EDL) muscles of streptozotocin-induced diabetic rats. The levels of atrogin-1 and muscle RING finger-1 were decreased, as were the activities of caspase-3 (EDL) and calpains (soleus and EDL), in diabetic rats treated with PTX, which at least partly explains the drop in the ubiquitin conjugate (EDL) levels and in proteasome activity (soleus and EDL). Treatment with PTX decreased PDE activity and increased cAMP content in muscles of diabetic rats; moreover, it also increased both the protein levels of exchange protein directly activated by cAMP (EPAC, a cAMP effector) and the phosphorylation of Akt. The loss of muscle mass was practically prevented in diabetic rats treated with PTX. These findings advance our understanding of the mechanisms underlying the antiproteolytic effects of PTX and suggest the use of PDE inhibitors as a strategy to activate cAMP signaling, which is emerging as a promising target for treating muscle mass loss during atrophic conditions. NEW & NOTEWORTHY cAMP signaling has been explored as a strategy to attenuate skeletal muscle atrophies. Therefore, in addition to β₂AR agonists, phosphodiesterase inhibitors such as pentoxifylline (PTX) can be an interesting option. This study advances the understanding of the mechanisms related to the antiproteolytic effects of PTX on skeletal muscles of diabetic rats, which involve the activation of both exchange protein directly activated by cAMP and Akt effectors, inhibiting the expression of atrogenes and calpain/caspase-3-proteolytic machinery.