SHLP2

The Sun 2023 paper (Nature Communications, independent Chinese group) documented that SHLP2 administration — both systemic and intracerebroventricular — protected male mice from high-fat diet-induced obesity over a treatment period. Body weight gain was significantly reduced compared to vehicle controls. Insulin sensitivity improved by euglycemic clamp measurement. Energy expenditure increased — consistent with thermogenesis promotion through POMC neuron activation. Food intake was reduced. The 2016 Cobb paper from the Cohen group established the in vivo insulin sensitization through clamp studies. Together these papers, from independent groups, establish SHLP2 as a metabolically active compound in mouse models of obesity and insulin resistance. Grade B: two independent groups; animal models; mechanistic pathway identified.

SHLP2 improves glucose homeostasis through two demonstrated mechanisms: centrally, via POMC neuron activation in the arcuate nucleus suppressing hepatic glucose production; peripherally, via direct effects on insulin signaling in muscle and adipose tissue. Of all six SHLPs, only SHLP2 produced in vivo insulin sensitization in the Cobb 2016 study. This selectivity — SHLP3 and others did not replicate the in vivo effect despite similar in vitro profiles — suggests SHLP2 has specific properties related to receptor engagement or bioavailability that make it uniquely effective for whole-body insulin action. The in vitro adipocyte differentiation enhancement (which SHLP2 and SHLP3 both showed) is a separate mechanism from the in vivo insulin sensitization, suggesting multiple complementary pathways contribute. Grade B: in vivo clamp data (Cohen group); CXCR7/POMC mechanism (independent Sun 2023 group).

THE PROSTATE CANCER FINDING — IMPORTANT BUT OBSERVATIONAL

Xiao et al. (Oncotarget, 2017; Cohen group + Freedland group at Duke/Cedars-Sinai): 200 men undergoing prostate biopsy — 100 negative biopsies and 100 prostate cancer cases; 100 Black and 100 white men. Serum SHLP2 measured by ELISA before biopsy. Results: SHLP2 was significantly higher in white controls versus white PCa cases. SHLP2 levels >350 pg/mL ruled out prostate cancer with ≥95% accuracy in both racial groups. A racial disparity was also observed — mean SHLP2 levels were significantly higher in white controls versus Black controls, a finding with potential implications for disparities in prostate cancer risk. WHAT THIS MEANS AND DOESN'T MEAN: Lower SHLP2 is associated with higher prostate cancer risk. This is observational — it does not prove that SHLP2 prevents prostate cancer, and it does not prove that raising SHLP2 through exogenous injection reduces prostate cancer risk. The association could reflect a shared underlying biology (mitochondrial dysfunction driving both SHLP2 decline and cancer risk), not a direct protective mechanism. This distinction matters. The finding is compelling and warrants further investigation. It does not establish SHLP2 as a cancer prevention therapeutic.

SHLP2 improved mitochondrial oxygen consumption rate and reduced mitochondrial ROS in NIT-1 beta cells and 22RV1 prostate epithelial cells in culture. Age-related decline in circulating SHLP2 levels — documented across multiple species by Cohen's group — is consistent with the hypothesis that SHLP2 decline contributes to aging-related mitochondrial dysfunction and metabolic disease. Whether restoring SHLP2 levels reverses age-related mitochondrial functional decline in a way that produces measurable healthspan benefit — analogous to Humanin's centenarian correlation — has not been tested in an aging-specific animal study or human cohort. Grade C: cell culture mitochondrial data; age decline correlation.

The metabolomic data (Mehta 2019) showing reduced ceramides and lysophosphatidylcholines in SHLP2-treated mice implies cardiovascular benefit, as these sphingolipids are markers of cardiovascular risk. Humanin has more directly characterized cardiovascular effects (Mayo Clinic observational data). SHLP2's cardiovascular effects are inferred from metabolomic surrogate markers rather than directly measured endpoints. Grade D: metabolomic inference; no direct cardiovascular study.

SHLP2 treatment increases circulating leptin levels in mice — an unusual finding. Leptin is the satiety hormone produced by adipose tissue; it is generally reduced with fat loss and elevated in obesity (where leptin resistance develops). The SHLP2-driven leptin elevation, in the context of reduced fat mass and improved insulin sensitivity, may reflect increased adipose tissue leptin production in a more metabolically healthy state — or it may reflect a complexity in SHLP2's endocrine interactions that requires further characterization. SHLP3, in contrast, elevated both metabolic and inflammatory markers, suggesting the SHLPs have meaningfully different endocrine profiles. Grade C: animal data; mechanistic significance of leptin elevation not fully characterized.

SHLP2 is approximately 20-21 amino acids in length, encoded within the mitochondrial 16S rRNA gene (MT-RNR2) — the same gene that encodes Humanin. The sequence begins at a different start position within the 16S rRNA region, producing a distinct amino acid sequence from Humanin despite overlapping genomic origin. Like the other SHLP family members and Humanin, SHLP2 is a secreted peptide — it is produced inside cells and released into circulation, where it can act as an endocrine signal. Molecular weight: approximately 2,000-2,200 Da depending on the exact sequence terminus.

The SHLP family's shared genomic location in the 16S rRNA gene means all six peptides are encoded in overlapping reading frames within the same region — an extraordinary compression of biological information in the mitochondrial genome, which is under extreme evolutionary pressure to remain compact. This location also means SHLP2's expression is linked to mitochondrial transcriptional activity — conditions that affect mitochondrial gene expression (aging, metabolic stress, exercise, dietary restriction) affect SHLP2 expression alongside Humanin and the other MDPs.

SHLP1-6 ARE DIFFERENT PEPTIDES WITH DIFFERENT PROFILES — NOT INTERCHANGEABLE

SHLP1, SHLP2, SHLP3, SHLP4, SHLP5, and SHLP6 are six distinct peptides with distinct sequences and distinct biological effects. In the 2016 characterization: SHLP2 and SHLP3 were most Humanin-like in vitro; only SHLP2 improved insulin action in vivo; SHLP3 elevated both metabolic and inflammatory markers (suggesting it may have a more complex and potentially less favorable profile); SHLP4 was associated with reduced cell viability (potentially apoptotic at certain concentrations). When purchasing 'SHLP2' from a research vendor, verify via mass spectrometry that you have SHLP2 specifically and not SHLP3 or another family member — the sequences differ and their effects in cell culture and animals are measurably different. COA identity confirmation is not optional for SHLP peptides.

SHLP2: lyophilized powder reconstituted with bacteriostatic water. Standard peptide storage: -20C for long-term; 2-8C after reconstitution; use within 30 days. SHLP2's relatively short amino acid sequence (20-21 AA) makes it sensitive to peptidase degradation after reconstitution — standard cold-chain handling is important. Mass spectrometry confirmation at ~2,000-2,200 Da is the identity check. HPLC purity 98%+. Pricing 2026: research vendor, 1-5 mg SHLP2: $40-120 depending on quantity and vendor.

Pinchas Cohen is listed as a consultant and stockholder of CohBar Inc., a biotechnology company focused on developing MDP-based therapeutics for age-related diseases. This commercial relationship is disclosed in multiple Cohen group publications including the SHLP2 metabolomic study (Mehta 2019). CohBar's pipeline includes MDP analogs derived from the same family as SHLP2 and Humanin. This relationship should be noted when evaluating Cohen group publications on MDPs — it does not invalidate the research but is relevant provenance context consistent with the assessment applied to Sinclair/NMN and Brenner/NR in the NAD+ chapter.

CXCR7 (chemokine receptor 7, also called ACKR3) is an atypical chemokine receptor expressed in the brain, heart, kidney, and immune tissues. It is unusual among chemokine receptors in that it acts primarily as a signaling receptor rather than a canonical GPCR — it couples to β-arrestin pathways and activates downstream MAP kinase and PI3K/Akt cascades without classic G-protein signaling. Sun et al. (Nature Communications, 2023) identified CXCR7 through high-throughput structural complementation screening — a systematic approach to identifying receptor-ligand pairs — and confirmed SHLP2 binding and activation in multiple cell systems. This identification came from an independent Chinese academic group with no affiliation to Cohen's USC lab. Grade B: receptor identification via validated screening approach; independent lab; published in peer-reviewed journal; not yet replicated by a third group.

Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus are a critical hub of energy balance regulation. They receive metabolic signals (leptin, insulin, glucose, GLP-1) and integrate them to suppress food intake and increase energy expenditure. SHLP2, both systemically injected and delivered directly into the brain (ICV), activated POMC neurons in the arcuate nucleus — measured by c-Fos expression (a marker of neuronal activation). This POMC activation was associated with reduced food intake and increased thermogenesis. The Sun 2023 paper specifically demonstrated that CXCR7 mediates this POMC activation. Grade B: clear mechanistic pathway identified; independent group; animal model.

The POMC neuron connection places SHLP2 in a mechanistic category shared with GLP-1 receptor agonists — both activate the same hypothalamic neuronal population. This is mechanistically significant: it suggests SHLP2 acts as a natural GLP-1-like satiety signal of mitochondrial origin, potentially explaining the metabolic protection effects through a central appetite and thermogenesis mechanism rather than only peripheral insulin signaling.

Cobb et al. (Aging, 2016): in hyperinsulinemic-euglycemic clamp studies (the gold standard for measuring insulin sensitivity in vivo), intracerebral infusion of SHLP2 increased glucose uptake in peripheral tissues and suppressed hepatic glucose production — demonstrating insulin sensitization both peripherally (muscle/fat take up more glucose) and centrally (liver produces less glucose). This is a mechanistically important finding: SHLP2 improves insulin sensitivity through at least two mechanisms simultaneously — direct peripheral effects and central hypothalamic effects mediated through POMC activation. Among the six SHLPs, only SHLP2 produced this in vivo insulin sensitization — SHLP3 and others did not. Grade B: clamp study data (the methodological gold standard for insulin sensitivity); Cohen group primary; animal model.

In cell culture, SHLP2 treatment increased oxygen consumption rate (OCR) — a direct measure of mitochondrial oxidative phosphorylation — and reduced reactive oxygen species production in pancreatic beta cells (NIT-1) and prostate cancer cells (22RV1). These mitochondrial effects are consistent with the broader MDP theme of improving mitochondrial bioenergetics, and mechanistically complement the CXCR7/POMC central mechanism by suggesting direct cellular effects in metabolically important tissues. Grade C: cell culture; Cohen group; consistent with MDP class effects.

Similar to Humanin, SHLP2 reduces apoptosis in cell culture systems. In NIT-1 (pancreatic beta cells) and 22RV1 (prostate epithelial cells), SHLP2 treatment reduced cell death from metabolic stress insults. The anti-apoptotic effects, combined with improved mitochondrial function, suggest SHLP2 protects vulnerable cell populations that are important in aging-related diseases. Grade C: cell culture; Cohen group; mechanistically coherent.

Mehta et al. (Metabolomics, 2019) performed untargeted plasma metabolomics in diet-induced obesity mice treated with HNG (Humanin analog) or SHLP2. Both peptides lowered sphingolipids — a class of bioactive lipids associated with insulin resistance, inflammation, and cardiovascular disease when elevated. SHLP2 specifically reduced ceramides and lysophosphatidylcholines — metabolites strongly associated with age-related metabolic disorders. This metabolomic profile provides a molecular window into how SHLP2 improves metabolic health beyond simple insulin sensitization, implicating lipid metabolism pathways that are independent of the CXCR7/POMC mechanism. Grade C: animal metabolomics; Cohen group; metabolite changes are directionally appropriate for metabolic health improvement.

SHLP2's pharmacokinetics are uncharacterized in any published study. Plasma half-life: unknown. Tissue distribution: unknown. CNS penetration after peripheral injection: unknown (though the Sun 2023 paper showed that SYSTEMIC injection produced hypothalamic POMC activation in mice, suggesting some degree of brain access). The animal studies used intraperitoneal injection at relatively high doses; community users employ subcutaneous injection at much lower doses. Whether the community's SubQ protocol achieves hypothalamic concentrations relevant to CXCR7/POMC signaling — the most mechanistically characterized pathway — is not established.

SHLP2: lyophilized powder reconstituted with bacteriostatic water. Solution is clear and colorless. Refrigerate at 2-8C after reconstitution; use within 30 days. Mass spectrometry confirming ~2,000-2,200 Da is the identity check — and critically, the mass spec must identify SHLP2 specifically and not another SHLP family member, which would have a different molecular weight. HPLC purity 98%+. Pricing 2026: research vendor, 2-5 mg SHLP2: $50-120.

Protocol

Dose

Frequency

Notes

Conservative / entry

0.5-1 mg SubQ

Weekly

Very conservative; potentially sub-threshold; assess response

Standard community

1-2 mg SubQ

Weekly or 2-3x per week

Most reported community protocol

Animal study reference (Cobb 2016)

2.5 mg/kg IP

Twice daily x 3 days

HNG or SHLP2; allometric human equivalent ~12-20 mg/day — far above community doses

The dose gap between animal research protocols and community dosing is even larger for SHLP2 than for most compounds in this book. The Cobb 2016 DIO study used 2.5 mg/kg IP twice daily — for a 70 kg human, allometrically equivalent to roughly 12-20 mg daily by the SubQ route (accounting for route differences and species scaling). Community protocols of 1-2 mg weekly are orders of magnitude below this. Whether any CXCR7 receptor activation occurs in humans at community doses is genuinely unknown.

No established timing requirement. Community users typically inject in the morning. The hypothalamic POMC activation mechanism suggests timing relative to meals could matter — POMC neurons integrate meal-related signals — but this has not been studied for SHLP2. Morning injection is the community default, consistent with other metabolic peptide protocols.

SHLP2 has no published human safety study and no long-term animal toxicology study. The published animal studies were short-term (3 days for Cobb 2016; course of HFD treatment for Sun 2023). Community self-reports form the primary safety signal, and the community using SHLP2 is very small. No serious adverse events have been reported in the very limited community use.

• Injection site reactions: standard for SubQ injection; mild.
• No significant systemic adverse effects reported in community use: the very small community provides minimal signal — absence of reports is not safety confirmation.
• Leptin elevation: observed in animal studies; physiological significance in humans unknown; potential for altered appetite regulation.

SHLP3 — SHLP2's closest structural relative — elevated both metabolic AND inflammatory markers in the Cobb 2016 characterization. The SHLPs look similar but have meaningfully different biological profiles. This variability within the family underscores why identity verification (mass spec confirming SHLP2 specifically at ~2,000-2,200 Da) is critical. A batch of SHLP3 sold as SHLP2 would not be pharmacologically equivalent and may have different adverse effect potential.

The prostate cancer biomarker finding (lower SHLP2 = higher cancer risk) is an important context for the anti-apoptotic effects documented in cell culture. SHLP2 reduces apoptosis in 22RV1 cells (prostate epithelial cells). In cancer cells, anti-apoptotic compounds could theoretically support tumor cell survival. However, the observational data shows the opposite association — higher SHLP2 correlates with lower prostate cancer risk, not higher. The probable interpretation: endogenously elevated SHLP2 is part of a healthy mitochondrial signaling environment that is protective against cancer development. Whether exogenous SHLP2 in a cancer-present environment has the same protective association is unknown — this is the same theoretical question raised for Humanin. Active malignancy caution applies.

• Active malignancy: the anti-apoptotic cell culture data creates a theoretical concern regardless of the observational association. Discuss with oncologist before use in any cancer context.
• Pregnancy: no safety data; avoid.
• Diabetic medications: SHLP2's insulin sensitization could interact with diabetes drugs causing hypoglycemia; monitor blood glucose if diabetic.

Not FDA-approved. Not PCAC-reviewed. Research chemical only. Not a controlled substance. Not listed on the 2026 WADA Prohibited List — unlike MOTS-c (S4.4 explicitly named), SHLP2 has not attracted WADA regulatory attention. Athletes can currently use SHLP2 without known WADA violation. CohBar Inc. (Cohen commercial relationship) may have proprietary interests in SHLP analogs — the research chemical SHLP2 available from vendors is not a CohBar product and does not carry pharmaceutical quality oversight.

Each MDP in this cluster addresses a distinct mechanistic dimension: MOTS-c drives AMPK/metabolic signaling and exercise adaptation; Humanin drives neuroprotection and cytoprotection via GP130/STAT3; SHLP2 drives metabolic protection via CXCR7/POMC hypothalamic signaling and peripheral insulin sensitization. Three different receptors, three different downstream pathways, three different primary applications — genuinely non-redundant. The complete MDP stack is mechanistically coherent. Note: MOTS-c is WADA S4.4 banned; Humanin and SHLP2 are not. Athletes cannot include MOTS-c without WADA violation.

SHLP2 activates POMC neurons via CXCR7. GLP-1 receptor agonists (semaglutide, tirzepatide, retatrutide) also activate POMC neurons, through a different receptor but convergent downstream pathways. Combining SHLP2 with GLP-1 class drugs at the POMC level could produce additive appetite suppression — or could produce redundant POMC activation without additional benefit. The community combination of SHLP2 with GLP-1 drugs is not pharmacologically well-characterized. Users on retatrutide or tirzepatide who add SHLP2 should monitor for amplified appetite suppression that could cause excessive caloric restriction.

NAD+ supports mitochondrial energy production; SHLP2 improves mitochondrial function and peripheral insulin sensitivity. Both address metabolic aging from different angles. Non-redundant. No pharmacological conflicts. The combination addresses both cofactor availability (NAD+) and cellular mitochondrial signaling (SHLP2's CXCR7/metabolic pathways).

The SHLP2 user community is extremely small. Community reports are too sparse for meaningful consensus. What exists suggests the compound is subtle in effect — consistent with a mechanism that operates on metabolic homeostasis rather than acute pharmacological stimulation. Some users report appetite reduction, consistent with the POMC mechanism if community doses are sufficient to activate CXCR7. Most users report nothing perceptible at 1-2 mg weekly.

SHLP2 is the most frontier-level compound in this book's MDP section. The appropriate user profile is narrow: adults who have already used and responded to Humanin, MOTS-c, or other MDPs; who understand the evidence limitation (animal models, one human observational study); who are specifically motivated by the metabolic/obesity/insulin resistance application where SHLP2 has the most specific mechanistic justification; and who have access to reliable COA verification for the correct peptide identity. General anti-aging users who haven't established an MDP foundation are better served by MOTS-c or Humanin, which have more developed evidence bases.

Men concerned about prostate cancer risk — particularly those with family history or PSA concerns — represent a theoretically motivated SHLP2 user population based on the biomarker association. The critical framing: the Xiao 2017 finding suggests lower SHLP2 is a marker of higher prostate cancer risk. It does not prove that exogenous SHLP2 reduces prostate cancer risk. Until an intervention trial tests this hypothesis, the most the biomarker finding supports is: measure your SHLP2 level; if low, consider what that means as part of a broader health picture. It does not straightforwardly support 'inject SHLP2 to prevent prostate cancer.'

• Using SHLP2 without confirming identity via mass spec: the SHLPs look similar by name but differ in sequence and biological effect. SHLP3 elevated inflammatory markers in characterization studies. Verify ~2,000-2,200 Da via COA mass spec.
• Treating the prostate cancer biomarker finding as proof of anti-cancer efficacy: lower SHLP2 correlates with higher PCa risk. Raising SHLP2 via injection has not been shown to reduce PCa risk. Observational correlation ≠ intervention evidence.
• Assuming community doses reach the CXCR7/POMC mechanism: the dose gap between animal research (2.5 mg/kg) and community use (1-2 mg weekly) is very large. Whether CXCR7 activation in the human hypothalamus occurs at community doses is unknown.
• Combining with GLP-1 drugs without monitoring for excess appetite suppression: both SHLP2 (CXCR7/POMC) and GLP-1 agonists activate POMC neurons. Additive appetite suppression at the same neuronal target is a plausible combination effect.

SHLP2 is among the least commonly available research peptides. Very few vendors carry it. Batch quality variation is high. The identity verification challenge (SHLP2 vs other SHLPs) makes mass spectrometry essential — this is not optional given the multiple-sequence SHLP family. Endotoxin testing below 0.1 EU/mg for injectable use. The rarity and small community creates a market where vendor accountability is lower than for high-volume peptides like BPC-157 or GHK-Cu.

Cobb LJ, Lee C, Xiao J, Yen K, Wong RG, Nakamura HK, Mehta HH, Gao Q, Ashur C, Huffman DM, Wan J, Muzumdar R, Barzilai N, Cohen P. (2016). Naturally occurring mitochondrial-derived peptides are age-dependent regulators of apoptosis, insulin sensitivity, and inflammatory markers. Aging (Albany NY). 8(4):796-809. PMC4925829. [THE discovery paper: in silico identification of SHLP1-6 within MT-RNR2; cell culture characterization of all six; only SHLP2 improved insulin action in vivo by clamp study; SHLP2 and SHLP3 most Humanin-like in vitro; SHLP3 elevated inflammatory markers. Cohen group USC.]

Sun S, Yang X, Liu X, et al. (Nature Communications, 2023). Mitochondria-derived peptide SHLP2 regulates energy homeostasis through the activation of hypothalamic neurons. PMC10356901. [INDEPENDENT Chinese academic group — no USC affiliation. CXCR7 identified as SHLP2 receptor via high-throughput structural complementation screening. POMC neuron activation in arcuate nucleus. HFD obesity protection. Improved insulin sensitivity. Thermogenesis promotion. THE most important independent replication in SHLP2 literature.]

Xiao J, Howard L, Wan J, Wiggins E, Vidal A, Cohen P, Freedland SJ. (Oncotarget, 2017). Low circulating levels of the mitochondrial-peptide hormone SHLP2: novel biomarker for prostate cancer risk. PMC5706922. [Cohen group + Freedland group (Duke/Cedars-Sinai) INDEPENDENT collaboration. n=200 men (100 PCa, 100 negative; 100 Black, 100 white). Lower SHLP2 associated with PCa risk in white men. >350 pg/mL rules out PCa with 95% accuracy both races. Racial disparity in SHLP2 levels documented. OBSERVATIONAL — not an intervention study.]

Mehta HH, Xiao J, Ramirez R, Miller B, Kim SJ, Cohen P, Yen K. (Metabolomics, 2019). Metabolomic profile of diet-induced obesity mice in response to humanin and small humanin-like peptide 2 treatment. PMC6554247. [Cohen group USC. SHLP2 and HNG lower sphingolipids, ceramides, lysophosphatidylcholines in DIO mice. Molecular mechanism of metabolic improvement characterized. CohBar Inc. conflict of interest disclosed.]

Merry TL, et al. (Am J Physiol Endocrinol Metab, 2020). Mitochondrial-derived peptides in energy metabolism. PMC5663826. [Comprehensive MDP review including SHLP2's metabolic role; positions SHLP2 alongside MOTS-c and Humanin in the MDP energy regulation framework; independent review authors]

MDP

Gene Location

Primary Mechanism

Primary Application

Evidence Base

WADA

MOTS-c

MT-RNR1 (12S rRNA)

AMPK via AICAR

Exercise mimicry; metabolic flexibility

B — multiple animal + human observational

S4.4 banned

Humanin (HNG)

MT-RNR2 (16S rRNA)

GP130/STAT3/Akt; Bax/IGFBP-3

Neuroprotection; longevity biomarker

B — 24 years, multiple independent labs

Not listed

SHLP2

MT-RNR2 (16S rRNA)

CXCR7/POMC; insulin sensitization

Metabolic health; obesity; PCa biomarker

B-C — 8 years; partial independent replication

Not listed

SHLP3

MT-RNR2 (16S rRNA)

Similar to SHLP2 in vitro; elevated inflammation in vivo

Not recommended — inflammatory signal

C — caution warranted

Not listed

SS-31 (not MDP)

N/A — synthetic

Cardiolipin stabilization

Mitochondrial structure; energy efficiency

A-B — Phase 2/3 + FDA approval

Not listed

• Lower SHLP2 = higher cancer risk means SHLP2 prevents cancer: the observational biomarker finding is a correlation. It does not establish a therapeutic effect. Restoring SHLP2 through injection has not been shown to reduce cancer risk.
• SHLP2 is similar to SHLP3 and the other SHLPs: the six SHLPs have meaningfully different biological profiles. SHLP3 elevated inflammatory markers. SHLP4 may have pro-apoptotic activity. Verify via mass spec that your product is specifically SHLP2.
• CXCR7 receptor identification = mechanism fully understood: identifying the receptor is a major step. How SHLP2 modulates CXCR7 signaling across different tissues, at different ages, and in humans requires substantially more characterization.
• SHLP2 is as evidence-supported as Humanin: Humanin has 24 years of research history with multiple independent labs across multiple countries. SHLP2 has 8 years, one primary research group, and one significant independent replication (the 2023 CXCR7 paper). These are different evidence positions.

— End of SHLP2 —

THE PEPTIDE BIBLE | SHLP2 | For Research & Educational Purposes Only