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Background <p>Diabetic neuropathic pain (DNP) is a debilitating complication affecting up to 50% of diabetic patients and severely impairing their quality of life. Current treatments provide limited relief and carry considerable side effects, underscoring the urgent need for novel, mechanism-based analgesics. Recent studies have identified tetrahydrobiopterin (BH4) as a crucial modulator of pain sensitivity. After nerve injury, its levels surge in injured neurons and infiltrating immune cells, amplifying pain signals via nitric oxide (NO) production, neuroinflammation, and ion channel sensitisation.</p> Main text <p>This review addresses the critical translational challenge posed by the BH4 paradox in DNP: although systemic BH4 is essential for vascular and metabolic integrity and is depleted under chronic hyperglycaemia, its localised overproduction in the nervous system drives neuropathic hypersensitivity. Non-selective inhibition of the key upstream enzyme, GTP cyclohydrolase-1 (GCH1), risks systemic BH4 deficiency, impairing neurotransmitter biosynthesis and causing severe vascular and metabolic side effects. Attention has therefore turned to sepiapterin reductase (SPR), the terminal enzyme in BH4 <i>de novo</i> biosynthesis, as a more selective and safer target. SPR inhibition suppresses pathological BH4 overproduction in nociceptive and immune tissues while preserving physiological levels through the dihydrofolate reductase (DHFR)-mediated salvage pathway. Preclinical studies of SPR inhibitors such as sulfasalazine show analgesia with limited central nervous system side effects due to their restricted blood-brain barrier (BBB) permeability. To guide clinical application, we synthesise the biochemical, genetic, and physiological roles of BH4 in DNP, and propose a translational biomarker framework for monitoring target engagement and systemic safety in future clinical trials.</p> Conclusion <p>We outline the mechanistic rationale and translational considerations for developing highly selective SPR inhibitors as a potentially better-tolerated, more selective approach for DNP and other BH4-driven chronic pain conditions. This rationale currently rests largely on genetic, preclinical, and surrogate-biomarker evidence, and no completed human trial has evaluated SPR inhibition for chronic pain. The proposed biomarker framework is therefore intended to inform trial design and dose optimisation rather than to imply current clinical readiness, as one step toward a future precision-medicine strategy for pain.</p>

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Targeting tetrahydrobiopterin metabolism in diabetic neuropathic pain: mechanisms, implications, and therapeutic strategies

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月31日

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  • Zhaoyinling Wei,
  • Dey Amarthya,
  • Solomon Tesfaye,
  • Ling Gao

摘要

Background

Diabetic neuropathic pain (DNP) is a debilitating complication affecting up to 50% of diabetic patients and severely impairing their quality of life. Current treatments provide limited relief and carry considerable side effects, underscoring the urgent need for novel, mechanism-based analgesics. Recent studies have identified tetrahydrobiopterin (BH4) as a crucial modulator of pain sensitivity. After nerve injury, its levels surge in injured neurons and infiltrating immune cells, amplifying pain signals via nitric oxide (NO) production, neuroinflammation, and ion channel sensitisation.

Main text

This review addresses the critical translational challenge posed by the BH4 paradox in DNP: although systemic BH4 is essential for vascular and metabolic integrity and is depleted under chronic hyperglycaemia, its localised overproduction in the nervous system drives neuropathic hypersensitivity. Non-selective inhibition of the key upstream enzyme, GTP cyclohydrolase-1 (GCH1), risks systemic BH4 deficiency, impairing neurotransmitter biosynthesis and causing severe vascular and metabolic side effects. Attention has therefore turned to sepiapterin reductase (SPR), the terminal enzyme in BH4 de novo biosynthesis, as a more selective and safer target. SPR inhibition suppresses pathological BH4 overproduction in nociceptive and immune tissues while preserving physiological levels through the dihydrofolate reductase (DHFR)-mediated salvage pathway. Preclinical studies of SPR inhibitors such as sulfasalazine show analgesia with limited central nervous system side effects due to their restricted blood-brain barrier (BBB) permeability. To guide clinical application, we synthesise the biochemical, genetic, and physiological roles of BH4 in DNP, and propose a translational biomarker framework for monitoring target engagement and systemic safety in future clinical trials.

Conclusion

We outline the mechanistic rationale and translational considerations for developing highly selective SPR inhibitors as a potentially better-tolerated, more selective approach for DNP and other BH4-driven chronic pain conditions. This rationale currently rests largely on genetic, preclinical, and surrogate-biomarker evidence, and no completed human trial has evaluated SPR inhibition for chronic pain. The proposed biomarker framework is therefore intended to inform trial design and dose optimisation rather than to imply current clinical readiness, as one step toward a future precision-medicine strategy for pain.