Here we make the case that wildlife declines of the last 40, and notably the last 20 years, are the result of pesticide induced epigenetic disruption, that has induced genetic malformations, mineral deficiencies, and metabolic disruption specifically thyroid disorders diabetes. We have laid out the individual geographical cases, and the similarities between them. This includes the close correlation between the marked decline of wildlife populations with the increase of herbicide use in association with these animals’ ecology; as well as the malformations and mineral deficiencies that accompany these declines. and the increase in pesticide use.
To begin, we will look at the association of herbicides and endocrine disruption. Specifically the role of herbicides in inducing diabetes and thyroid disorders. It has been shown through studies of pesticide applicators, and their spouses, that pesticide application is correlated with increases in thyroid disorders(1) and the development of diabetes(3). In these studies of applicators and/or their spouse it was determined there was an increased risk from the application of many pesticides. These did not cover the ingestion of these pesticides, as has been documented with wildlife, or in human consumption of treated food. These studies also did cover the mechanisms by which these metabolic disruptions occur.
“Pesticide use has increased dramatically worldwide and the effects of pesticides on glucose metabolism are too significant for a possible diabetogenic link to be dismissed.”(2)
The development of diabetes has been associated with the disruption of GliS3(4). GliS3 is a member of the Gli-similar zinc finger protein family and encodes a nuclear protein with five C2H2-type zinc finger domains. This protein functions as both a repressor and activator of transcription and is specifically involved in the development of pancreatic beta cells, the thyroid, eye, liver and kidneys. Mutations in this gene have been associated with neonatal diabetes and congenital hypothyroidism(5). A primary cause of underbite observed in pesticide exposed wildlife populations is congenital hypothyroidism.
Gli-similar 3, zinc finger protein(GLIS3) is a novel transcription factor, that shows high homology to the proteins of the Gli and Zic families(6) All of these are closely related zinc finger proteins that interact with Sonic Hedgehog(SHh). GliS3 has both repressor and activation functions within these interactions. There is evidence for cross-talk between the GliS and Gli signaling pathways.
While disruption of GliS3 is involved in the development of diabetes, diabetes is also shown to disrupt and suppress SHh function(13). While Sonic Hedgehog is a mediator of Gli1, 2, and 3 with GliS3 being homologous and cross talking with GLI1, 2, and 3, the reverse holds true as well. Gli and GliS mediate SHh function. This works as an open loop feedback system that responds to input from external sources.
Below is the feedback and functional association of SHh and Gli
a | Sonic Hedgehog (SHh) can induce Gli1 and Gli2 transcription, whereas it represses Gli3. Gli2 might mediate the induction of Gli1 by SHH. Fibroblast growth factor (FGF) signaling can induce the transcription of Gli2 and Gli3, and all three Gli proteins can induce Wnt transcription. Gli1/SHh and Gli3 antagonize each other.
b | SHh affects the choice of repressor or activator Gli function. SHh signaling can repress the formation of Gli3 repressors, and influence the formation of Gli2 and perhaps Gli1 activators.
Sonic Hedgehog(SHh) plays a key role in regulating vertebrate organogenesis, such as in the growth of digits on limbs and organization of the brain. SHh is a morphogen that is involved in patterning many systems including the teeth, specifically the incisors, and craniofacial development(7). With underbites, a result of congenital hypothyroidism, we see malformed incisors, in combination with the disruption of the upper face (craniofacial region of the skull). Despite the term underbite, the lower jaw is not longer, but rather the premaxillary bone is underdeveloped, thus shorter and narrower than normal, and the incisors are malformed.
The herbicide glyphosate has been shown to suppress SHh function via endogenous retinoid activity, which led to craniofacial malformations(19).
SHh(8) and Foxe1 are associated with congenital hypothyroidism and thyroid dysgenesis(9). Foxe1 is a target of Gli2, and therefore mediated through Gli-SHh repression and expression(10)(11). Foxe1 is also responsible for the development and orientation of feathers and hair. Foxe1-null skin displays aberrant hair formation with the production of thinner and curly pelage hairs. Although the hair follicle internal structure is conserved and several lineage markers are properly expressed, the orderly down-growth of follicles is strikingly disrupted, causing disorientation, misalignment and aberrantly shaped hair follicles(11). These disruptions have been observed in animals with congenital hypothyroidism and other associated malformations (Judy Hoy).
SHh-Gli mediation has also been shown to play a role in sexual dymorphism during early development, along with the masculinization processes of male external genitalia. SHh expressed in the UPE regulates GT mesenchymal differentiation through Gli2. Genetic disruption of Hedgehog signal led to a hypospadias-like phenotype(12). Hypospadias and the disruption of external male genitalia has been observed in wildlife exposed to pesticides. Along with the disruption of external genitalia, such as short penis sheaths and malformed scotums, testicles are many times monorchid, cryptorchid, or otherwise asymmetrically developed, as in the forward misplacement of the left inguinal lymph node and thus also the forward misplacement of the left spermatic cord resulting in the scrotum being formed with the left hemiscrota directly forward of the right hemiscrota, 90 degrees out of proper alignment. “Transgenic double homozygous Gli1-/- and Gli2-/- knockout mice display serious central nervous system and lung defects have small lungs, undescended testes”(26) As with copper and selenium deficiencies, other mineral deficiencies have been associated with these malformations. Zinc deficiencies have been correalated with some of these reproductive malformations, while also playing a role in not only the zinc finger proteins, but in SHh signalling as well(35).
We see similar left/right asymmetry in antler morphogenesis in association with deer, elk, and moose populations expressing testicular malformations, and congenital hypothyroidism. Zic (another zinc finger protein) and Gli proteins regulate various aspects of neural and skeletal development. Deficiencies in Zic3 result in disturbance of the left to right body axis (heterotaxy)(6). Zic2 has been shown to be critical for establishment of the left-right axis, thus loss of Zic2 function can result in defects in heart formation. The enlarged right heart ventricle reported on multiple ungulate species is an example(Hoy, et al. 2015). Another member of the Zic family, Zic3, has previously been linked to establishment of the left-right axis(14). Zic and Gli family proteins are transcription factors that share similar zinc finger domains. Recent studies indicate that Zic and Gli collaborate in neural and skeletal development with SHh(15).
The growth, and annual regrowth of deer antlers is very similar to embryonic limb development. In embryonic limb development we see both SHh and Indian Hedgehog(IHh)(23) play a mediating role role in the morphogenesis. In antler development and growth we see Indian Hedgehog(IHh) play a mediating role in development(21) while other Hh genes surely play a role as well. Indian Hedgehog(IHH) is one of three proteins in the mammalian signaling pathway family called hedgehog, the others being desert hedgehog (DHH) and Sonic Hedgehog(SHH)(20). IHh like SHh can be expressed or repressed via retinoic acid, with retinoic acid and it’s receptors expressed in antler tissue. Like SHH, IHH and DHH both also mediate Gli zinc finger family proteins, which then interact with Zic family proteins that control left/right axial development(heterotaxy). This is why glyphosate induced retinoic acid disruption of Hh proteins and genes, results in not only underbites, and reproductive malformations, but malformed antlers and their asymmetry as well. The Gli proteins are the effectors of Hedgehog (Hh) signaling and have been shown to be involved in cell fate determination, proliferation and patterning in many cell types and most organs during embryo development.(22) The underbites, reproductive malformations, and antler dysgenesis seen in pesticide exposed wildlife populations are all patterning malformations associated with Gli.
Below is an example of IHH’s influence on GLi2 and Gli3.
Also seen in association with the before mentioned malformations in pesticide exposed wildlife populations is laminitis in the hooves of ungulates. Laminitis is a painful inflammatory condition of the tissues (laminae) that bond the hoof wall to the pedal (coffin) bone in the horse hoof. It is characterized by the disruption of the laminae which are made up of many layers of keratin, keratin is made up of keratinocyte cells. It has been shown that laminitis is accompanied by the loss of laminar keratinocytes.(27) The bones of the hoof are suspended within the axial hooves of ungulates by layers of modified skin cells, known as laminae or lamellae, which act as shock absorbers during locomotion.(24) Laminitis in ungulates is many times expressed as not only a disruption of laminae growth, but also an associatied over growth or the laminae structure. GLi1 as found in keratoncytes is responsible for the up and down regulation of associated genes, which mediates proliferation of these cells(22). So loss of laminar keratinocytes as seen in laminitis may be due to the down regulating affect of Gli1 by upstream influences, as is seen in other associated malformations. Laminitis is also closely associated with metabolic disorders such as diabetes, and other associated issues related to insulin resistance. This is also the case with copper deficiencies seen in moose. that have been determined to be a part of their environmentally induced diabetes.
We also see fibromas in wildlife populations, specifically deer that have been exposed to pesticide use. These are described as “cutaneous deer fibromas”(28) They have been diagnosed as fibroma, ossifying fibroma, fibrosarcoma, multiple neurofibromatosis, fibropapilloma, papilloma, and warts(29). The association of the papilloma virus has been made in some of these tumors, which is why they are sometimes called fibromapapilloma. In humans these are seen in association with metabolic disorders like diabetes(30)(32), In much the same way we see the association with laminitis and diabetes in horses. And as with these cases in deer, the papilloma virus has also been found in association with them in humans(31). Like with laminitis these tumors involve the disruption of keratinocyte skin cells. These tumors vary from keratinized, to fibrovascular, to squamous(34). In both keratinized and squamous cell proliferation we see Hh and Gli expression in the proliferation of these cells(33).
Laminitis and malformed beaks in birds, as seen in association with the other malformations in animals exposed to pesticides, is associated with biotin deficiencies and diabetes(16). Biotin supplementation is used to treat horses with laminitis(17), which has been shown to be associated with disrupted insulin resistance and diabetes(18).